Re: [time-nuts] Advantages Disadvantages of the TPLL Method
can no longer claim fs timing. What you can claim is a long term frequency stability in ppm. OK, so your smart, well done, congratulations! Let's forget about femtoseconds and shove them firmly in the bin, so no one talk about them again, OK. Now, if you look at Warren's block diagram you will see that the reference (device given) and DUT oscillators are feed via pads (values given) into a mixer. The output of this mixer is fed via a 100kHz LPF to remove the sum product and then via a simple op-amp with 100 gain. The rest of the loop is just a way to add the necessary DC offset such that when the reference and DUT oscillators match, IE. the average DC out of the mixer is 0V, the EFC on the reference oscillator is biased correctly. So you can look up the output of a 10811 ocxo and also see the specs to work out the EFC F/V and I'm sure this information is probably very easily available via the resources in this list. To be honest, I expect that the EFC voltage deviation is going to be small relative to the full range. You know that there is a 100kHz R/C filter in the loop so perhaps you can scribble some numbers down on a piece of paper with your pencil. If you can't, what more do you need to be able to do this, thanks for your help. This is my simple understanding of phase detectors and mixers. You might get there by dividing down a bunch of numbers but I don't think the method supports the claim (of fs timing). Let's kill the fs thing please! Steve Bob - Original Message - From: Steve Rooke To: Discussion of precise time and frequency measurement Sent: Sunday, June 20, 2010 2:00 AM Subject: Re: [time-nuts] Advantages Disadvantages of the TPLL Method Bob, Can I answer this one. On 20 June 2010 04:36, Robert Benward rbenw...@verizon.net wrote: Warren, I was responding to ke5fx comment using a 12-bit, 480-Hz serial DAQ in place of the voltage-to-frequency converter in the diagram above. A DAQ is a multifaceted data acquisition system, where as in your annotated diagram you showed an ADC. The DAQ that Warren is referring to to has a 12bit ADC input capable of performing up to 480 samples per second. I understand it's analog, but you said: Say you have a nice logic gate with 1 ns delay . So back to the analog loop, do you have an analysis that gets you from EFC to femtosecond stability? PLLs are notorious for phase noise, the phase noise actually representing the error term that brings the loop back into lock. I personally think the 1fs issue has become way out of hand and people are now focussing on that instead of the big picture. Whilst I understand that the professional engineers on this list wish to pounce on every t that is not crossed, every i that is not dotted, and requiring a complete mathematical breakdown of everything, it is not going to happen here. If those professional engineers would like to assist with the process of understanding and documenting this idea in a way that pulls their chain, that would be great, but if it's down to pointing the finger at the amateur engineers and laughing, then perhaps they need more education in etiquette. Remember the golden rule, do unto others as you would wish to be done. Sure, some of us do not have the correct technical engineering banter, so when we call the World a sort of round ball shape, please don't play deaf until we say it's an oblate spheroid. Try to help us communicate with you, we are trying to describe things in the best way we can and we have something useful to contribute, IE. just take Warren's TPLL implementation which seems to be producing good results. So why don't we try to understand exactly how it is doing this instead of ripping it apart and saying you shouldn't do it that way, you have to do it this way. Remember that geezer who invented the lightbulb, he didn't work it all out mathematically on paper before he chose tungsten, no he did it experimentally and everyone seems to think highly of him. Steve For your second email: You are now averaging the repeatable jitter? YES I was not questioning the procedure, I was questioning the conclusion; Are you using a digital phase detector or a mixer as shown? Analog Phase detector Why the digital analogy if it's all analog? Do you have an analysis of the loop sensitivity/resolution? No analysis, No limit it is analog I don't agree with you about the limit, and without an analysis or even a simple calculation, how do arrive at femtosecond lock? if there is no limit, why not a hundred times less? Why do you say the results are repeatable in the short term vs the long term? Long term includes other factors such as non random drift, not just random Noise Maybe so, but using the short term , is not a license to better jitter figures by a factor of 100. Since you are not using digital, I don't know where
Re: [time-nuts] Advantages Disadvantages of the TPLL Method
Nigel, Thanks for letting us have your name. On 21 June 2010 10:05, gandal...@aol.com wrote: Warren Your stock answer of claiming that everyone and his granny is missing the point is wearing a bit thin, and despite your suggestion I have not missed anything either and that includes John's results. But have you looked at the block schematic and understood how it works from that? Those results, as far as they go, look very good, and I have no doubt you deserve credit for what you've achieved, but what YOU seem to have missed, or conveniently continue to ignore, is the need to be able to prove, or provide sufficient information so that someone else can prove, that your results are applicable to a more general case, and at least to the accuracy that you claim. So the only way to prove this for you is not empirically, it has to be numerically! Enjoy your wait! There will always be empirical design methods, so called rules of thumb for example, and these can be very valuable tools but the results from such methods, indeed the results from any design method, still need to be evaluated and confirmed in practice. And what part of confirmed in practice have you not understood so far. Your saying one thing and then something different. I am totally confused by your use of the English language despite coming from somewhere that teaches the Queen's English. In a similar fashion your measurement technique, again as with all others, needs validation and proper analysis of its limitations before you can truly come to rely upon it as a stand alone tool. It may well be good enough for everything you need but despite John's measurements, and however good his results, what you haven't demonstrated so far is the ability to evaluate those limitations so you can be sure of that. The only way at the moment that you can be really sure of your measurements each and every time is to have someone like John check your results each and every time. John spent a month testing LOTS of different devices with thei TPLL against a TSC trying to see if it would fail but he could not. He did come to some conclusions as to the limited range that the TPLL can be used over and we accept that. So, you want to be pedantic and say that if you can only prove it empirically, then you have to test it in an infinite number of ways. It's a bloody good job that the guy who invented the lightbulb only had to do it 14,000 times and not an infinite number of times as we would all be in the dark now, wouldn't we. It doesn't matter how many times your results are checked and confirmed, and it doesn't matter that your technique might be perfect and your results might be perfect every time, what you've demonstrated very clearly so far is that you just don't know whether or not that's true. Do you believe in God? Go ahead and prove it! I've wondered sometimes if you're just frightened that somebody might prove you wrong but I don't recall anyone suggesting you're actually wrong, all I've seen is folks trying to help you and offer well meant and useful advice that could assist you properly evaluate the limitations of what you're proposing. Actually, over the whole period that the TPLL has been discussed on this list it's my observation that a lot of the input from others has NOT been well meant and useful advice and your just proving it here and now. However, there must be a definite blockage somewhere because you seem to have gone into auto repeat mode, and for someone who claims not to have time to produce any documentation you must have wasted hours and hours churning out the same old smokescreens. And your still asking the same old questions over and over again when you should have realised that your not talking to someone who can give you the answers you need to satisfy YOU. It's no good trying to get blood out of a stone, perhaps it's your turn to donate some of the red stuff and try to understand this thing without someone being able to describe it your language. OK, I hear you say, so let's have a full schematic for us to work with. Well, I'll tell you exactly what will happen if that gets put on the table shall I. There will be a flood of posts from certain quarters who will say, you shouldn't do it like that, you should do it like this, what a stupid design, this is all wrong, what a stupid chap this is! Get the idea. If you haven't already spotted this, this list is a TOUGH ROOM and there is no sympathy for anyone who is unable to show they are top of the class. Well, it's for time-nuts, so I agree it's a bleeding edge technical group but there are a lot of people on this list who are really fascinated by this area and really want to learn and contribute. I've thrown up a good deal of stupid ideas since I joined this group but have learnt a great deal on the subject, perhaps you should learn some humility. Refusing to share your recipe so to speak, with all the
Re: [time-nuts] Advantages Disadvantages of the TPLL Method
On 21 June 2010 10:49, Chuck Harris cfhar...@erols.com wrote: No disrespect to you or John intended, but that is a data set of one experiment. We used to call that a High School Proof. What is not said here is that John spent a month testing the TPLL with a variety of different sources just to see if he could make it fail but he could not. Just because you only see one set of results, does not show the whole picture here.. It takes an infinite number of experiments of that sort to prove a conjecture. Agreed but statistics would suggest you don't have to go to those lengths. Cheers, Steve -Chuck Harris ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. -- Steve Rooke - ZL3TUV G8KVD The only reason for time is so that everything doesn't happen at once. - Einstein ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Advantages Disadvantages of the TPLL Method
On 21 June 2010 11:49, Chuck Harris cfhar...@erols.com wrote: If there have been an infinite number of tests done, and all are verified as correct, we have a pretty fair idea that the next test done will also be correct... but the verification is important... without it we cannot know for sure. The infinite + 1st test could be the exception that disproves the conjecture. Surely that is impossible! Cheers, Steve -- Steve Rooke - ZL3TUV G8KVD The only reason for time is so that everything doesn't happen at once. - Einstein ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Advantages Disadvantages of the TPLL Method
There is a fairly detailed block schematic that has been posted, even a photo of the proto BB just to show how simple it is. Perhaps a full component level schematic will surface sometime. I think that the math that is needed to describe this TPLL will have to come from a third-party if that is what is required anyway. Steve On 21 June 2010 12:37, Bob Camp li...@rtty.us wrote: Hi Schematics of each of the various implementations tired would be nice. That would allow others to implement duplicates and see what happened. Without schematics only approximations can be implemented and analyzed. That generally opens up more issues than it addresses. The nature of the conversation so far is not one that encourages participation or shared experimentation. Details of the various experiments attempted would be helpful. The rabbit out o the hat approach to data gets pretty old pretty fast. It's apparent from various oblique references that far more than the run off against the Symmetricom box has been done. A more rigorous approach to the math is needed if this is ever going to be accepted. This is after all an area where hair splitting issues over the math have been a very big deal for at least 40 years. Bob On Jun 20, 2010, at 7:17 PM, Magnus Danielson wrote: On 06/21/2010 12:49 AM, Chuck Harris wrote: WarrenS wrote: GandalfG8 Posted: Snake Oil anyone? I nice short response, but it shows missed the MAJOR difference. You need to see: http://www.thegleam.com/ke5fx/tpll.htm ws No disrespect to you or John intended, but that is a data set of one experiment. We used to call that a High School Proof. It takes an infinite number of experiments of that sort to prove a conjecture. It doesn't prove it, just makes it fairly likely correct. But then again, correct is not available here. Sufficiently accurate within some bounds is. These bounds can be of a myriad of types. As for the Warren style TPLL, a particular implementation needs to be referred to, both in form of analogue design and digital processing. From that limiting properties may be established. Some of these may be compensated for enhanced performance. Cheers, Magnus ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. -- Steve Rooke - ZL3TUV G8KVD The only reason for time is so that everything doesn't happen at once. - Einstein ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Advantages Disadvantages of the TPLL Method
Bob, Can I answer this one. On 20 June 2010 04:36, Robert Benward rbenw...@verizon.net wrote: Warren, I was responding to ke5fx comment using a 12-bit, 480-Hz serial DAQ in place of the voltage-to-frequency converter in the diagram above. A DAQ is a multifaceted data acquisition system, where as in your annotated diagram you showed an ADC. The DAQ that Warren is referring to to has a 12bit ADC input capable of performing up to 480 samples per second. I understand it's analog, but you said: Say you have a nice logic gate with 1 ns delay . So back to the analog loop, do you have an analysis that gets you from EFC to femtosecond stability? PLLs are notorious for phase noise, the phase noise actually representing the error term that brings the loop back into lock. I personally think the 1fs issue has become way out of hand and people are now focussing on that instead of the big picture. Whilst I understand that the professional engineers on this list wish to pounce on every t that is not crossed, every i that is not dotted, and requiring a complete mathematical breakdown of everything, it is not going to happen here. If those professional engineers would like to assist with the process of understanding and documenting this idea in a way that pulls their chain, that would be great, but if it's down to pointing the finger at the amateur engineers and laughing, then perhaps they need more education in etiquette. Remember the golden rule, do unto others as you would wish to be done. Sure, some of us do not have the correct technical engineering banter, so when we call the World a sort of round ball shape, please don't play deaf until we say it's an oblate spheroid. Try to help us communicate with you, we are trying to describe things in the best way we can and we have something useful to contribute, IE. just take Warren's TPLL implementation which seems to be producing good results. So why don't we try to understand exactly how it is doing this instead of ripping it apart and saying you shouldn't do it that way, you have to do it this way. Remember that geezer who invented the lightbulb, he didn't work it all out mathematically on paper before he chose tungsten, no he did it experimentally and everyone seems to think highly of him. Steve For your second email: You are now averaging the repeatable jitter? YES I was not questioning the procedure, I was questioning the conclusion; Are you using a digital phase detector or a mixer as shown? Analog Phase detector Why the digital analogy if it's all analog? Do you have an analysis of the loop sensitivity/resolution? No analysis, No limit it is analog I don't agree with you about the limit, and without an analysis or even a simple calculation, how do arrive at femtosecond lock? if there is no limit, why not a hundred times less? Why do you say the results are repeatable in the short term vs the long term? Long term includes other factors such as non random drift, not just random Noise Maybe so, but using the short term , is not a license to better jitter figures by a factor of 100. Since you are not using digital, I don't know where this example came from or why it is relevant. Is there not a lower limit to how much you can average? Depends or everything, but not up to 1 sec of averaging when the conditions are made right I don't understand how you arrive at this conclusion For your last email: What attracted me to the TPLL question now was that you comment that you are maintaining a femtosecond lock. Please don't dumb it down for me. I may not understand all the statistical stuff, but I can understand an analysis. Bob - Original Message - From: WarrenS warrensjmail-...@yahoo.com To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Saturday, June 19, 2010 3:27 AM Subject: Re: [time-nuts] Advantages Disadvantages of the TPLL Method Bob Don't know if I can explain it to you, I'm not so good at explaining, I'll give it *ONE* try. Example with some random picked numbers (JUST TO SHOW THE MAIN POINTS). I tried, All information and test that are available on the TPLL is on JOHN'S KE5FX site or in past postings. http://www.thegleam.com/ke5fx/tpll.htm One other thing I may not of made clear, The analog averaging thing does not help at low freq like at 1 PPS The TPLL works great because it is at a high freq like 5 or 10 MHz. DAQ == DataQ == ADC I don't think 10ps is achievable under any dynamic conditions IMHO OK, I don't really care, use whatever number you want, you'll still end up below the Ref osc noise. but You may be surprised then by what the single shot Aperture uncertainty specs are for the kind of devices that really care about this sort of thing. But then none of that really maters AT ALL, because there is NO Digital anything in the simple TPLL before the ADC where a 10 Hz device would work fine for most. I
Re: [time-nuts] Advantages Disadvantages of the TPLL Method
Steve, I am a professional engineer, but in this arena I am an amateur. That is why I'm asking the questions, not to put down, but to understand some of the claims made. And as I said in one of my previous emails, I've seen amateurs run circles around the professionals, and those professional admitting utter astonishment at those amateur accomplishments (this is in the area of amateur astrophotography). What I have heard throughout this thread is a lot of bashing of those asking the questions, surfacing as derogatory and berating comments on other's understanding. I have also heard much claims to a certain procedure without one iota of numerical mumbo-jumbo to back it up. The issue here is an inability to describe a simple claim. Pete has attempted to put things in simple numbers, and I see where he is going, and I concur with some of his calculations. If one can not describe what appears to be a simple procedure, then I must question the basic understanding behind the explanation. If you make a wild claim, and then you can't even get the bullet on the paper, then I must question the shooter's understanding. I guess I am not comfortable with the use of femtoseconds to describe frequency accuracy. Technically, a locked PLL is at the exact frequency as the reference, as measured in the long term. The phase between the two may not be at zero, that depends on the type of phase detector and the DC offsets in the system. On the short term, phase noise of the reference will cause the loop to generate error terms which will change the phase of the DUT. Oscillators are also specified using phase noise, e.g. 135dB down @ 100Hz. That specifies how much energy is not in the bandwidth of the carrier. It also implies the phase is constantly changing! If the phase is changing, the error term is changing, and so forth and so on.Your measurement can only be as good as your reference oscillator. A DVM can only average this error, it can't give you the instantaneous value of the peak deviation of the error signal, which is what you would need to claim fs cycle to cycle timing. Fs units are appropriate for cycle to cycle variation, not long term or multicycle assements. Even the best HP DVM is only good to 3ppm on the 100mV scale and the shortest reading is 167us. That's 10 orders of magnitude greater that the deviation you are trying to measure. If you average the mixer output, you can no longer claim fs timing. What you can claim is a long term frequency stability in ppm. This is my simple understanding of phase detectors and mixers. You might get there by dividing down a bunch of numbers but I don't think the method supports the claim (of fs timing). Bob - Original Message - From: Steve Rooke To: Discussion of precise time and frequency measurement Sent: Sunday, June 20, 2010 2:00 AM Subject: Re: [time-nuts] Advantages Disadvantages of the TPLL Method Bob, Can I answer this one. On 20 June 2010 04:36, Robert Benward rbenw...@verizon.net wrote: Warren, I was responding to ke5fx comment using a 12-bit, 480-Hz serial DAQ in place of the voltage-to-frequency converter in the diagram above. A DAQ is a multifaceted data acquisition system, where as in your annotated diagram you showed an ADC. The DAQ that Warren is referring to to has a 12bit ADC input capable of performing up to 480 samples per second. I understand it's analog, but you said: Say you have a nice logic gate with 1 ns delay . So back to the analog loop, do you have an analysis that gets you from EFC to femtosecond stability? PLLs are notorious for phase noise, the phase noise actually representing the error term that brings the loop back into lock. I personally think the 1fs issue has become way out of hand and people are now focussing on that instead of the big picture. Whilst I understand that the professional engineers on this list wish to pounce on every t that is not crossed, every i that is not dotted, and requiring a complete mathematical breakdown of everything, it is not going to happen here. If those professional engineers would like to assist with the process of understanding and documenting this idea in a way that pulls their chain, that would be great, but if it's down to pointing the finger at the amateur engineers and laughing, then perhaps they need more education in etiquette. Remember the golden rule, do unto others as you would wish to be done. Sure, some of us do not have the correct technical engineering banter, so when we call the World a sort of round ball shape, please don't play deaf until we say it's an oblate spheroid. Try to help us communicate with you, we are trying to describe things in the best way we can and we have something useful to contribute, IE. just take Warren's TPLL implementation which seems to be producing good results. So why don't we try
Re: [time-nuts] Advantages Disadvantages of the TPLL Method
the simple TPLL works, then you are Greatly underestimating my abilities. (It's not Luck that it works as good as it does) and concerning your latest question, The answers is yes, a noise floor resolution of 1e-12 at 100Hz does mean it must have useful resolution down to at least 10 fs, 1e-14 seconds and no I'm not going to explain why that is so either. ws *** ** [time-nuts] Advantages Disadvantages of the TPLL Method Robert Benward rbenward at verizon.net Sun Jun 20 14:46:09 UTC 2010 Steve, I am a professional engineer, but in this arena I am an amateur. That is why I'm asking the questions, not to put down, but to understand some of the claims made. And as I said in one of my previous emails, I've seen amateurs run circles around the professionals, and those professional admitting utter astonishment at those amateur accomplishments (this is in the area of amateur astrophotography). What I have heard throughout this thread is a lot of bashing of those asking the questions, surfacing as derogatory and berating comments on other's understanding. I have also heard much claims to a certain procedure without one iota of numerical mumbo-jumbo to back it up. The issue here is an inability to describe a simple claim. Pete has attempted to put things in simple numbers, and I see where he is going, and I concur with some of his calculations. If one can not describe what appears to be a simple procedure, then I must question the basic understanding behind the explanation. If you make a wild claim, and then you can't even get the bullet on the paper, then I must question the shooter's understanding. I guess I am not comfortable with the use of femtoseconds to describe frequency accuracy. Technically, a locked PLL is at the exact frequency as the reference, as measured in the long term. The phase between the two may not be at zero, that depends on the type of phase detector and the DC offsets in the system. On the short term, phase noise of the reference will cause the loop to generate error terms which will change the phase of the DUT. Oscillators are also specified using phase noise, e.g. 135dB down @ 100Hz. That specifies how much energy is not in the bandwidth of the carrier. It also implies the phase is constantly changing! If the phase is changing, the error term is changing, and so forth and so on.Your measurement can only be as good as your reference oscillator. A DVM can only average this error, it can't give you the instantaneous value of the peak deviation of the error signal, which is what you would need to claim fs cycle to cycle timing. Fs units are appropriate for cycle to cycle variation, not long term or multicycle assements. Even the best HP DVM is only good to 3ppm on the 100mV scale and the shortest reading is 167us. That's 10 orders of magnitude greater that the deviation you are trying to measure. If you average the mixer output, you can no longer claim fs timing. What you can claim is a long term frequency stability in ppm. This is my simple understanding of phase detectors and mixers. You might get there by dividing down a bunch of numbers but I don't think the method supports the claim (of fs timing). Bob - Original Message - From: Steve Rooke To: Discussion of precise time and frequency measurement Sent: Sunday, June 20, 2010 2:00 AM Subject: Re: [time-nuts] Advantages Disadvantages of the TPLL Method Bob, Can I answer this one. On 20 June 2010 04:36, Robert Benward rbenward at verizon.net wrote: Warren, I was responding to ke5fx comment using a 12-bit, 480-Hz serial DAQ in place of the voltage-to-frequency converter in the diagram above. A DAQ is a multifaceted data acquisition system, where as in your annotated diagram you showed an ADC. The DAQ that Warren is referring to to has a 12bit ADC input capable of performing up to 480 samples per second. I understand it's analog, but you said: Say you have a nice logic gate with 1 ns delay . So back to the analog loop, do you have an analysis that gets you from EFC to femtosecond stability? PLLs are notorious for phase noise, the phase noise actually representing the error term that brings the loop back into lock. I personally think the 1fs issue has become way out of hand and people are now focussing on that instead of the big picture. Whilst I understand that the professional engineers on this list wish to pounce on every t that is not crossed, every i that is not dotted, and requiring a complete mathematical breakdown of everything, it is not going to happen here. If those professional engineers would like to assist with the process of understanding and documenting this idea in a way that pulls their chain, that would be great, but if it's down to pointing the finger at the amateur engineers and laughing, then perhaps they need more education in etiquette. Remember the golden rule, do unto others
Re: [time-nuts] Advantages Disadvantages of the TPLL Method
GandalfG8 Posted: Snake Oil anyone? I nice short response, but it shows missed the MAJOR difference. You need to see: http://www.thegleam.com/ke5fx/tpll.htm ws ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Advantages Disadvantages of the TPLL Method
In a message dated 20/06/2010 22:11:51 GMT Daylight Time, warrensjmail-...@yahoo.com writes: I nice short response, but it shows missed the MAJOR difference. You need to see: http://www.thegleam.com/ke5fx/tpll.htm - Warren Your stock answer of claiming that everyone and his granny is missing the point is wearing a bit thin, and despite your suggestion I have not missed anything either and that includes John's results. Those results, as far as they go, look very good, and I have no doubt you deserve credit for what you've achieved, but what YOU seem to have missed, or conveniently continue to ignore, is the need to be able to prove, or provide sufficient information so that someone else can prove, that your results are applicable to a more general case, and at least to the accuracy that you claim. There will always be empirical design methods, so called rules of thumb for example, and these can be very valuable tools but the results from such methods, indeed the results from any design method, still need to be evaluated and confirmed in practice. In a similar fashion your measurement technique, again as with all others, needs validation and proper analysis of its limitations before you can truly come to rely upon it as a stand alone tool. It may well be good enough for everything you need but despite John's measurements, and however good his results, what you haven't demonstrated so far is the ability to evaluate those limitations so you can be sure of that. The only way at the moment that you can be really sure of your measurements each and every time is to have someone like John check your results each and every time. It doesn't matter how many times your results are checked and confirmed, and it doesn't matter that your technique might be perfect and your results might be perfect every time, what you've demonstrated very clearly so far is that you just don't know whether or not that's true. I've wondered sometimes if you're just frightened that somebody might prove you wrong but I don't recall anyone suggesting you're actually wrong, all I've seen is folks trying to help you and offer well meant and useful advice that could assist you properly evaluate the limitations of what you're proposing. However, there must be a definite blockage somewhere because you seem to have gone into auto repeat mode, and for someone who claims not to have time to produce any documentation you must have wasted hours and hours churning out the same old smokescreens. Refusing to share your recipe so to speak, with all the bullshit you've come up with as to why that shouldn't be necessary, and to insult and attempt to belittle those who have tried to advise you, with all that crap about the experts who just don't understand how it works etc etc, well, sorry mate but that really is the mark of a true snake oil salesman and, if nothing else, you've certainly got that off to perfection. regards Nigel GM8PZR ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Advantages Disadvantages of the TPLL Method
WarrenS wrote: GandalfG8 Posted: Snake Oil anyone? I nice short response, but it shows missed the MAJOR difference. You need to see: http://www.thegleam.com/ke5fx/tpll.htm ws No disrespect to you or John intended, but that is a data set of one experiment. We used to call that a High School Proof. It takes an infinite number of experiments of that sort to prove a conjecture. -Chuck Harris ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Advantages Disadvantages of the TPLL Method
On 06/21/2010 12:49 AM, Chuck Harris wrote: WarrenS wrote: GandalfG8 Posted: Snake Oil anyone? I nice short response, but it shows missed the MAJOR difference. You need to see: http://www.thegleam.com/ke5fx/tpll.htm ws No disrespect to you or John intended, but that is a data set of one experiment. We used to call that a High School Proof. It takes an infinite number of experiments of that sort to prove a conjecture. It doesn't prove it, just makes it fairly likely correct. But then again, correct is not available here. Sufficiently accurate within some bounds is. These bounds can be of a myriad of types. As for the Warren style TPLL, a particular implementation needs to be referred to, both in form of analogue design and digital processing. From that limiting properties may be established. Some of these may be compensated for enhanced performance. Cheers, Magnus ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Advantages Disadvantages of the TPLL Method
Magnus Danielson wrote: On 06/21/2010 12:49 AM, Chuck Harris wrote: WarrenS wrote: GandalfG8 Posted: Snake Oil anyone? I nice short response, but it shows missed the MAJOR difference. You need to see: http://www.thegleam.com/ke5fx/tpll.htm ws No disrespect to you or John intended, but that is a data set of one experiment. We used to call that a High School Proof. It takes an infinite number of experiments of that sort to prove a conjecture. It doesn't prove it, just makes it fairly likely correct. Notice the quotation marks around the word prove in the above sentence. That is an English language construct that is meant to show that something is not quite right about the thing in the quotes. In this case, I am indicating a looser version of prove than would usually be expected. If there have been an infinite number of tests done, and all are verified as correct, we have a pretty fair idea that the next test done will also be correct... but the verification is important... without it we cannot know for sure. The infinite + 1st test could be the exception that disproves the conjecture. But then again, correct is not available here. Sufficiently accurate within some bounds is. These bounds can be of a myriad of types. Absolutely! But because of our lack of information about the plan of the device we will never know if Warren's a genius, or just another fool. (I notice by your use of correct that you already know about that quote thingy I mentioned above ;-) As for the Warren style TPLL, a particular implementation needs to be referred to, both in form of analogue design and digital processing. From that limiting properties may be established. Some of these may be compensated for enhanced performance. Yep! That is the scientific method. -Chuck Harris ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Advantages Disadvantages of the TPLL Method
Hi Schematics of each of the various implementations tired would be nice. That would allow others to implement duplicates and see what happened. Without schematics only approximations can be implemented and analyzed. That generally opens up more issues than it addresses. The nature of the conversation so far is not one that encourages participation or shared experimentation. Details of the various experiments attempted would be helpful. The rabbit out o the hat approach to data gets pretty old pretty fast. It's apparent from various oblique references that far more than the run off against the Symmetricom box has been done. A more rigorous approach to the math is needed if this is ever going to be accepted. This is after all an area where hair splitting issues over the math have been a very big deal for at least 40 years. Bob On Jun 20, 2010, at 7:17 PM, Magnus Danielson wrote: On 06/21/2010 12:49 AM, Chuck Harris wrote: WarrenS wrote: GandalfG8 Posted: Snake Oil anyone? I nice short response, but it shows missed the MAJOR difference. You need to see: http://www.thegleam.com/ke5fx/tpll.htm ws No disrespect to you or John intended, but that is a data set of one experiment. We used to call that a High School Proof. It takes an infinite number of experiments of that sort to prove a conjecture. It doesn't prove it, just makes it fairly likely correct. But then again, correct is not available here. Sufficiently accurate within some bounds is. These bounds can be of a myriad of types. As for the Warren style TPLL, a particular implementation needs to be referred to, both in form of analogue design and digital processing. From that limiting properties may be established. Some of these may be compensated for enhanced performance. Cheers, Magnus ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Advantages Disadvantages of the TPLL Method
Well so much for my short 'berry' answers, that did not last long, sorry berry readers. You think you are tired of hearing the same ol repeated stuff over and over and over ..., Think about how tired I am of needing to repeat it. The simple TPLL works good enough to measure any OCXO that I'm aware of. (Oh yea, I said that already about a hundred times, and tested it more than that) To me and some others that has now been proven well enough to make this method useful. What else do you and most others need to know to use it? Do you need to know exactly why mine works so good or how to make it better or how good one could make it with 'new' parts?? When was the last time anyone needed to fully understand the inter workings and details and limitations of their cell phone or TV or their TSC 5120A before they were able to make use of it? I don't need to understand it better, remember I'm the one with the working unit. I'm not looking to make mine better than I already know how to do. What I have made more than clear by now, is that they should not rely on me to tell them exactly how I did it, If someone wants to understand it better, then they should build their own. If they are not able to do that or at the VERY least come up with their own schematic with the information given on John's report, then they certainly are not going to be able to improve on it or analyze it. What I have missed the point of and do not understand, is why any real expert would ever need to know exactly how I did it, before they are able to analyze it. It is so simple that they can do it any number of different ways. Why do they ONLY want to analyze mine? They need to make their own schematic and analyze it. If they find it works worse than I've said, sent me a copy and I'll tell them what they did wrong. Likely theirs will work and analyze much better that what I've done and said, because most will not make the KISS compromises that I have, and will not want to use the same 6 or so parts I had in my parts bin. what you've demonstrated very clearly so far is that you just don't know whether or not that's true. (how good the results are) That is close to right. It is others that do not know, I do agree to that much. I know the limitations of what I've built and that it is not perfect and I know how to make it even better. But it is good enough and I do already know how good that is. And the reason some say that I must now prove this to others is what I don't yet get. I'm not trying to get anyone to believe I know what I'm doing, I'm just trying to convince others that the TPLL method can work and is a viable alternative sometimes. Now it would seem that has already been done by all of John's test. Some have suggested that I should just stop responding to these post, it is going nowhere, and they are right, but I have to admit, I'm having too much fun. And if this can bring a little joy or education to others or make the TPLL better understood then it is worth it, even when it is at my expense. wow OK, I must concede that JUST because this TPLL BB has ALWAYS worked in the past for every condition and for hundreds of test, this is not conclusive prove that it will not be completely wrong any or every time in the future. If this is the point that is now trying to be made with one of the later post, Then at least ONE of us, is on the wrong SITE. OH, and here is the real topper for all this. Because I have made something that is so very basic and simple and obvious and cheap and with so few parts and using a method that some so called expert(s) did not seem to know about or understand because it is so old, then I must be a fool or a genius. SO Why is it OR? did you ever consider maybe it is both. :-) It is pretty obvious with the hindsight that I've gained about some Nut experts, that only a real fool would of ever started this project, let alone try and tell ANYONE about it. Have fun and do try and do what you enjoy or at least enjoy what you're doing. I am. ws ** [time-nuts] Advantages Disadvantages of the TPLL Method GandalfG8 at aol.com GandalfG8 at aol.com Sun Jun 20 22:05:14 UTC 2010 In a message dated 20/06/2010 22:11:51 GMT Daylight Time, warrensjmail-one at yahoo.com writes: I nice short response, but it shows missed the MAJOR difference. You need to see: http://www.thegleam.com/ke5fx/tpll.htm - Warren Your stock answer of claiming that everyone and his granny is missing the point is wearing a bit thin, and despite your suggestion I have not missed anything either and that includes John's results. Those results, as far as they go, look very good, and I have no doubt you deserve credit for what you've achieved, but what YOU seem to have missed, or conveniently continue to ignore, is the need to be able to prove, or provide sufficient information so that someone else can prove, that your results are applicable to a
Re: [time-nuts] Advantages Disadvantages of the TPLL Method
IMHO, this comment is totally uncalled for, regardless... Also, it is unsigned - poor etiquette. John Allen - -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of gandal...@aol.com Sent: Sunday, June 20, 2010 4:07 PM To: time-nuts@febo.com Subject: Re: [time-nuts] Advantages Disadvantages of the TPLL Method In a message dated 20/06/2010 18:47:41 GMT Daylight Time, warrensjmail-...@yahoo.com writes: Short summery for the Berry readers: The simple TPLL BB works fine and is better than any OXCO that it has been used with. The fact that some so called experts do not believe or understand why, does not change that proven fact. * and the longer story for those that have nothing better to do all day long. For others that have been around for a while and have endured reading the silly exchanges here, I do apologize for yet another round of the same NS. But it would seem that some have missed a few important points about this subject. I do not apologize for the fact that I can not /or will not explain every detail of the simple TPLL BB that I've built in a way that satisfies all. but -- Snake Oil anyone? ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Advantages Disadvantages of the TPLL Method
On 21 June 2010 08:07, gandal...@aol.com wrote: In a message dated 20/06/2010 18:47:41 GMT Daylight Time, warrensjmail-...@yahoo.com writes: Short summery for the Berry readers: The simple TPLL BB works fine and is better than any OXCO that it has been used with. The fact that some so called experts do not believe or understand why, does not change that proven fact. * and the longer story for those that have nothing better to do all day long. For others that have been around for a while and have endured reading the silly exchanges here, I do apologize for yet another round of the same NS. But it would seem that some have missed a few important points about this subject. I do not apologize for the fact that I can not /or will not explain every detail of the simple TPLL BB that I've built in a way that satisfies all. but -- Snake Oil anyone? Well, Mr. Smartypants, the difference here is that his Snake Oil has been proven to work. I don't particularly care how the thing works mathematically, I'm more interested in the results. If you want to get bogged down in the nitty gritty instead of looking at the big picture then you are the one loosing out here. A respected member of this list carried out tests of this TPLL implementation against a expensive piece of equipment and found it produced very similar results over an expected range of usability with a lot of different DUT and spending a month doing it. Stop trying to extract stuff out of Warren that he has already said he is unable to give you. He is an amateur experimental engineer (no offence intended Warren) and as such doesn't have, or need, to understand this stuff mathematically or in the secret special language that only the professional engineering gods know. He has something you don't have, he has a $10 gadgit that produces results that are easily good enough for many on this list. So it looks like your the looser here! Steve -- Steve Rooke - ZL3TUV G8KVD The only reason for time is so that everything doesn't happen at once. - Einstein ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Advantages Disadvantages of the TPLL Method
Bob Don't know if I can explain it to you, I'm not so good at explaining, I'll give it *ONE* try. Example with some random picked numbers (JUST TO SHOW THE MAIN POINTS). I tried, All information and test that are available on the TPLL is on JOHN'S KE5FX site or in past postings. http://www.thegleam.com/ke5fx/tpll.htm One other thing I may not of made clear, The analog averaging thing does not help at low freq like at 1 PPS The TPLL works great because it is at a high freq like 5 or 10 MHz. DAQ == DataQ == ADC I don't think 10ps is achievable under any dynamic conditions IMHO OK, I don't really care, use whatever number you want, you'll still end up below the Ref osc noise. but You may be surprised then by what the single shot Aperture uncertainty specs are for the kind of devices that really care about this sort of thing. But then none of that really maters AT ALL, because there is NO Digital anything in the simple TPLL before the ADC where a 10 Hz device would work fine for most. I just gave you an example to try and answer your question on digital logic which was: How do you do fs when most digital logic has jitter several of orders of magnitude greater? ws *** [time-nuts] Advantages Disadvantages of the TPLL Method Robert Benward rbenward at verizon.net Sat Jun 19 03:18:05 UTC 2010 Warren, Is there not a lower limit to how much you can average? Yes, it's the sqrt of the number of samples, but doesn't noise, hardware, and other perturbations limit the usefulness of this method? Then one can get repeatable results say 100 times better from cycle to cycle in the short term. so down to 10ps repeatable. Why do you say the results are repeatable in the short term vs the long term? Isn't what you defined above (repeatability) the opposite of jitter? Jitter I thought was cycle to cycle variation in prop delay. On 1ns prop devices, I don't think 50-100ps jitter is unreasonable under the most optimum conditions, the most careful circuit layout, and constant repeatable inputs. I don't think 10ps is achievable under any dynamic conditions IMHO. One can average 1,000,000 readings of the 10 ps jitter If they are truly random, that can give you a 1e-3 improvement (square root of number of samples averaged) You are now averaging the repeatable jitter. KE5FX's website shows a diagram and a link to your diagram as well. Are you using a digital phase detector or a mixer as shown? BTW, KE5FX refers to DAQ as your update to the design, where I believe he meant an ADC. You have my curiosity peaked. Do you have an analysis of the loop sensitivity/resolution? Bob - Original Message - From: WarrenS warrensjmail-one at yahoo.com To: Discussion of precise time and frequency measurement time-nuts at febo.com Sent: Friday, June 18, 2010 6:49 PM Subject: Re: [time-nuts] Advantages Disadvantages of the TPLL Method Bob posted can you explain it to me? Don't know, I'll give it ONE try. I'm not so good at explaining, but it is pretty basic if one does not start assuming that it can not be done at the start. It is mostly about averaging lots of those transitions, and the real trick is that it is not Digital. Analog has no lower limits except manly for Johnson noise type effects (mostly). Example with some random picked numbers. and assuming all analog that has no digital steps in it to limit resolution or add noise. Say you have a nice logic gate with 1 ns delay If you make it all nice and clean, and repeatable such as constant PS, rise time etc. Then one can get repeatable results say 100 times better from cycle to cycle in the short term. so down to 10ps repeatable. Now make things even more clean with no variations and assuming random noise. Now if one is doing this at 10 MHz and only cares about the average over 0.1 sec (10 Hz) One can average 1,000,000 readings of the 10 ps jitter If they are truly random, that can give you a 1e-3 improvement (square root of number of samples averaged) so now down to 10 fs of average jitter at 10 Hz for a 10 MHZ gate starting with a 1ns initial delay. OF course if Anything changes at all, it will drift much more than that, which may or may not mater much depending on what one is doing. If you only really care about the difference between any two consecutive 100 ms reading that are next to each other, as is (mostly) the case in ADEV, then not a big deal. IF it does matter or you want to do better, the next step is to do it all differential, so you are looking at only the different of two separate independent but equal circuits. Differential can give, say a 1000 to one or better improvement in drift due to common things such as temperature etc. If that helps explain the basics, good, if not you need to ask others to explain it better. And yes there all kinds of things that can do go wrong and many ways to screw it up. so as easy as it sounds, it does take a bit
Re: [time-nuts] Advantages Disadvantages of the TPLL Method
On 06/19/2010 12:49 AM, WarrenS wrote: Say you have a nice logic gate with 1 ns delay If you make it all nice and clean, and repeatable such as constant PS, rise time etc. Then one can get repeatable results say 100 times better from cycle to cycle in the short term. so down to 10ps repeatable. Now make things even more clean with no variations and assuming random noise. Now if one is doing this at 10 MHz and only cares about the average over 0.1 sec (10 Hz) One can average 1,000,000 readings of the 10 ps jitter If they are truly random, that can give you a 1e-3 improvement (square root of number of samples averaged) so now down to 10 fs of average jitter at 10 Hz for a 10 MHZ gate starting with a 1ns initial delay. The square root improvement assumes white noise, and will work when white noise dominates. A logical gate or any other amplifier will also have flicker noise, which doesn't average out like that. The meaningful length of averaging thus depends on the cut-off frequency between white and flicker noise. To analyse it, Allan variance and friends needs to be applied. Thus, only for short-term stability may straight averaging work for estimation. Cheers, Magnus ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Advantages Disadvantages of the TPLL Method
Hi Since ADEV is a measurement of noise, you want to be very careful about just which noise you keep and which noise you throw away. Bob On Jun 19, 2010, at 7:06 AM, Magnus Danielson wrote: On 06/19/2010 12:49 AM, WarrenS wrote: Say you have a nice logic gate with 1 ns delay If you make it all nice and clean, and repeatable such as constant PS, rise time etc. Then one can get repeatable results say 100 times better from cycle to cycle in the short term. so down to 10ps repeatable. Now make things even more clean with no variations and assuming random noise. Now if one is doing this at 10 MHz and only cares about the average over 0.1 sec (10 Hz) One can average 1,000,000 readings of the 10 ps jitter If they are truly random, that can give you a 1e-3 improvement (square root of number of samples averaged) so now down to 10 fs of average jitter at 10 Hz for a 10 MHZ gate starting with a 1ns initial delay. The square root improvement assumes white noise, and will work when white noise dominates. A logical gate or any other amplifier will also have flicker noise, which doesn't average out like that. The meaningful length of averaging thus depends on the cut-off frequency between white and flicker noise. To analyse it, Allan variance and friends needs to be applied. Thus, only for short-term stability may straight averaging work for estimation. Cheers, Magnus ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Advantages Disadvantages of the TPLL Method
Warren, I was responding to ke5fx comment using a 12-bit, 480-Hz serial DAQ in place of the voltage-to-frequency converter in the diagram above. A DAQ is a multifaceted data acquisition system, where as in your annotated diagram you showed an ADC. I understand it's analog, but you said: Say you have a nice logic gate with 1 ns delay . So back to the analog loop, do you have an analysis that gets you from EFC to femtosecond stability? PLLs are notorious for phase noise, the phase noise actually representing the error term that brings the loop back into lock. For your second email: You are now averaging the repeatable jitter? YES I was not questioning the procedure, I was questioning the conclusion; Are you using a digital phase detector or a mixer as shown? Analog Phase detector Why the digital analogy if it's all analog? Do you have an analysis of the loop sensitivity/resolution?No analysis, No limit it is analog I don't agree with you about the limit, and without an analysis or even a simple calculation, how do arrive at femtosecond lock? if there is no limit, why not a hundred times less? Why do you say the results are repeatable in the short term vs the long term?Long term includes other factors such as non random drift, not just random Noise Maybe so, but using the short term , is not a license to better jitter figures by a factor of 100. Since you are not using digital, I don't know where this example came from or why it is relevant. Is there not a lower limit to how much you can average? Depends or everything, but not up to 1 sec of averaging when the conditions are made right I don't understand how you arrive at this conclusion For your last email: What attracted me to the TPLL question now was that you comment that you are maintaining a femtosecond lock. Please don't dumb it down for me. I may not understand all the statistical stuff, but I can understand an analysis. Bob - Original Message - From: WarrenS warrensjmail-...@yahoo.com To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Saturday, June 19, 2010 3:27 AM Subject: Re: [time-nuts] Advantages Disadvantages of the TPLL Method Bob Don't know if I can explain it to you, I'm not so good at explaining, I'll give it *ONE* try. Example with some random picked numbers (JUST TO SHOW THE MAIN POINTS). I tried, All information and test that are available on the TPLL is on JOHN'S KE5FX site or in past postings. http://www.thegleam.com/ke5fx/tpll.htm One other thing I may not of made clear, The analog averaging thing does not help at low freq like at 1 PPS The TPLL works great because it is at a high freq like 5 or 10 MHz. DAQ == DataQ == ADC I don't think 10ps is achievable under any dynamic conditions IMHO OK, I don't really care, use whatever number you want, you'll still end up below the Ref osc noise. but You may be surprised then by what the single shot Aperture uncertainty specs are for the kind of devices that really care about this sort of thing. But then none of that really maters AT ALL, because there is NO Digital anything in the simple TPLL before the ADC where a 10 Hz device would work fine for most. I just gave you an example to try and answer your question on digital logic which was: How do you do fs when most digital logic has jitter several of orders of magnitude greater? ws *** [time-nuts] Advantages Disadvantages of the TPLL Method Robert Benward rbenward at verizon.net Sat Jun 19 03:18:05 UTC 2010 Warren, Is there not a lower limit to how much you can average? Yes, it's the sqrt of the number of samples, but doesn't noise, hardware, and other perturbations limit the usefulness of this method? Then one can get repeatable results say 100 times better from cycle to cycle in the short term. so down to 10ps repeatable. Why do you say the results are repeatable in the short term vs the long term? Isn't what you defined above (repeatability) the opposite of jitter? Jitter I thought was cycle to cycle variation in prop delay. On 1ns prop devices, I don't think 50-100ps jitter is unreasonable under the most optimum conditions, the most careful circuit layout, and constant repeatable inputs. I don't think 10ps is achievable under any dynamic conditions IMHO. One can average 1,000,000 readings of the 10 ps jitter If they are truly random, that can give you a 1e-3 improvement (square root of number of samples averaged) You are now averaging the repeatable jitter. KE5FX's website shows a diagram and a link to your diagram as well. Are you using a digital phase detector or a mixer as shown? BTW, KE5FX refers to DAQ as your update to the design, where I believe he meant an ADC. You have my curiosity peaked. Do you have an analysis of the loop sensitivity/resolution? Bob - Original Message - From: WarrenS
Re: [time-nuts] Advantages Disadvantages of the TPLL Method
Magnus posted: The square root improvement assumes white noise A logical gate or any other amplifier will also have flicker noise, To analyze it, Allan variance and friends needs to be applied. No disagreements What some may be missing is that this side tracked discussion and has little at all do directly with the Simple TPLL method or it's limitations when doing ADEV. What the above has to do with is the effect of high speed averaging on different frequencies If the noise is high freq then averaging works great as stated (or even better) BUT say the frequency of the noise_signal is at a low frequency such as 10 Hz and under (a typical flicker or 1/F noise) Does anyone need to have a detailed explanation or fancy math paper on why averaging a Noise_signal for under 100ms (no mater samples are used) would NOT get rid of the longer that 100ms (10 Hz) noise? If they do not know why, then I can not or well not help with that. Back to the TPLL Adev is used to show the effect of all the noise signals aftering they have been averaged (integrated) over tau0. Integrating all signal noises, be it white, pink, black and blue, and yes even flicker noise over Tau0 like the TPLL does, then gives the correct raw data to be able do ADEV for any and all noise types. This is something that the Phase type methods do not do as easy or as well. Maybe it would help to think of it as the Averaging (and intigrating) is getting rid of all the unwanted High freq noise above Tau0 that are not suppose to be include in or contribute to ADEV, so that the system can measure all the noises at and below Tau0 freq which are suppose to be included in ADEV. So the fact that averaging does not get rid of flicker noise, IS NOT A BAD THING for finding the correct Adev, IT IS A GOOD THING. And the fact that averaging by intigration at tau0 to get rid of the noise_Frequencies above Tau0 is not as bad thing as some have clamed in the past but a GOOD thing ws * [time-nuts] Advantages Disadvantages of the TPLL Method Magnus Danielson magnus at rubidium.dyndns.org Sat Jun 19 11:06:41 UTC 2010 On 06/19/2010 12:49 AM, WarrenS wrote: Say you have a nice logic gate with 1 ns delay If you make it all nice and clean, and repeatable such as constant PS, rise time etc. Then one can get repeatable results say 100 times better from cycle to cycle in the short term. so down to 10ps repeatable. Now make things even more clean with no variations and assuming random noise. Now if one is doing this at 10 MHz and only cares about the average over 0.1 sec (10 Hz) One can average 1,000,000 readings of the 10 ps jitter If they are truly random, that can give you a 1e-3 improvement (square root of number of samples averaged) so now down to 10 fs of average jitter at 10 Hz for a 10 MHZ gate starting with a 1ns initial delay. The square root improvement assumes white noise, and will work when white noise dominates. A logical gate or any other amplifier will also have flicker noise, which doesn't average out like that. The meaningful length of averaging thus depends on the cut-off frequency between white and flicker noise. To analyse it, Allan variance and friends needs to be applied. Thus, only for short-term stability may straight averaging work for estimation. Cheers, Magnus ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Advantages Disadvantages of the TPLL Method
Bob I tried, (more than once), and now we are heading way off subject. I should of known better and learned by my past mistakers and stuck to the TPLL performance issues. Which TPLL graph or plot do you not understand? You need to ask the experts about the rest. ws [time-nuts] Advantages Disadvantages of the TPLL Method Robert Benward rbenward at verizon.net Sat Jun 19 16:36:50 UTC 2010 Warren, I was responding to ke5fx comment using a 12-bit, 480-Hz serial DAQ in place of the voltage-to-frequency converter in the diagram above. A DAQ is a multifaceted data acquisition system, where as in your annotated diagram you showed an ADC. I understand it's analog, but you said: Say you have a nice logic gate with 1 ns delay . So back to the analog loop, do you have an analysis that gets you from EFC to femtosecond stability? PLLs are notorious for phase noise, the phase noise actually representing the error term that brings the loop back into lock. For your second email: You are now averaging the repeatable jitter? YES I was not questioning the procedure, I was questioning the conclusion; Are you using a digital phase detector or a mixer as shown? Analog Phase detector Why the digital analogy if it's all analog? Do you have an analysis of the loop sensitivity/resolution?No analysis, No limit it is analog I don't agree with you about the limit, and without an analysis or even a simple calculation, how do arrive at femtosecond lock? if there is no limit, why not a hundred times less? Why do you say the results are repeatable in the short term vs the long term?Long term includes other factors such as non random drift, not just random Noise Maybe so, but using the short term , is not a license to better jitter figures by a factor of 100. Since you are not using digital, I don't know where this example came from or why it is relevant. Is there not a lower limit to how much you can average? Depends or everything, but not up to 1 sec of averaging when the conditions are made right I don't understand how you arrive at this conclusion For your last email: What attracted me to the TPLL question now was that you comment that you are maintaining a femtosecond lock. Please don't dumb it down for me. I may not understand all the statistical stuff, but I can understand an analysis. Bob ** - Original Message - From: WarrenS warrensjmail-one at yahoo.com To: Discussion of precise time and frequency measurement time-nuts at febo.com Sent: Saturday, June 19, 2010 3:27 AM Subject: Re: [time-nuts] Advantages Disadvantages of the TPLL Method Bob Don't know if I can explain it to you, I'm not so good at explaining, I'll give it *ONE* try. Example with some random picked numbers (JUST TO SHOW THE MAIN POINTS). I tried, All information and test that are available on the TPLL is on JOHN'S KE5FX site or in past postings. http://www.thegleam.com/ke5fx/tpll.htm One other thing I may not of made clear, The analog averaging thing does not help at low freq like at 1 PPS The TPLL works great because it is at a high freq like 5 or 10 MHz. DAQ == DataQ == ADC I don't think 10ps is achievable under any dynamic conditions IMHO OK, I don't really care, use whatever number you want, you'll still end up below the Ref osc noise. but You may be surprised then by what the single shot Aperture uncertainty specs are for the kind of devices that really care about this sort of thing. But then none of that really maters AT ALL, because there is NO Digital anything in the simple TPLL before the ADC where a 10 Hz device would work fine for most. I just gave you an example to try and answer your question on digital logic which was: How do you do fs when most digital logic has jitter several of orders of magnitude greater? ws *** [time-nuts] Advantages Disadvantages of the TPLL Method Robert Benward rbenward at verizon.net Sat Jun 19 03:18:05 UTC 2010 Warren, Is there not a lower limit to how much you can average? Yes, it's the sqrt of the number of samples, but doesn't noise, hardware, and other perturbations limit the usefulness of this method? Then one can get repeatable results say 100 times better from cycle to cycle in the short term. so down to 10ps repeatable. Why do you say the results are repeatable in the short term vs the long term? Isn't what you defined above (repeatability) the opposite of jitter? Jitter I thought was cycle to cycle variation in prop delay. On 1ns prop devices, I don't think 50-100ps jitter is unreasonable under the most optimum conditions, the most careful circuit layout, and constant repeatable inputs. I don't think 10ps is achievable under any dynamic conditions IMHO. One can average 1,000,000 readings of the 10 ps jitter If they are truly random, that can give you a 1e-3 improvement (square root of number of samples averaged) You are now averaging
Re: [time-nuts] Advantages Disadvantages of the TPLL Method
Warren, All I wanted was an explanation of how you arrived at femtosecond timing. You gave me analogies instead. Since you cannot explain it, I ask anyone else on this listbot if they can put it in proper context for me. Thank you for your effort regardless. Bob - Original Message - From: WarrenS To: Discussion of precise time and frequency measurement Sent: Saturday, June 19, 2010 2:07 PM Subject: Re: [time-nuts] Advantages Disadvantages of the TPLL Method Bob I tried, (more than once), and now we are heading way off subject. I should of known better and learned by my past mistakers and stuck to the TPLL performance issues. Which TPLL graph or plot do you not understand? You need to ask the experts about the rest. ws [time-nuts] Advantages Disadvantages of the TPLL Method Robert Benward rbenward at verizon.net Sat Jun 19 16:36:50 UTC 2010 Warren, I was responding to ke5fx comment using a 12-bit, 480-Hz serial DAQ in place of the voltage-to-frequency converter in the diagram above. A DAQ is a multifaceted data acquisition system, where as in your annotated diagram you showed an ADC. I understand it's analog, but you said: Say you have a nice logic gate with 1 ns delay . So back to the analog loop, do you have an analysis that gets you from EFC to femtosecond stability? PLLs are notorious for phase noise, the phase noise actually representing the error term that brings the loop back into lock. For your second email: You are now averaging the repeatable jitter? YES I was not questioning the procedure, I was questioning the conclusion; Are you using a digital phase detector or a mixer as shown? Analog Phase detector Why the digital analogy if it's all analog? Do you have an analysis of the loop sensitivity/resolution?No analysis, No limit it is analog I don't agree with you about the limit, and without an analysis or even a simple calculation, how do arrive at femtosecond lock? if there is no limit, why not a hundred times less? Why do you say the results are repeatable in the short term vs the long term?Long term includes other factors such as non random drift, not just random Noise Maybe so, but using the short term , is not a license to better jitter figures by a factor of 100. Since you are not using digital, I don't know where this example came from or why it is relevant. Is there not a lower limit to how much you can average? Depends or everything, but not up to 1 sec of averaging when the conditions are made right I don't understand how you arrive at this conclusion For your last email: What attracted me to the TPLL question now was that you comment that you are maintaining a femtosecond lock. Please don't dumb it down for me. I may not understand all the statistical stuff, but I can understand an analysis. Bob ** - Original Message - From: WarrenS warrensjmail-one at yahoo.com To: Discussion of precise time and frequency measurement time-nuts at febo.com Sent: Saturday, June 19, 2010 3:27 AM Subject: Re: [time-nuts] Advantages Disadvantages of the TPLL Method Bob Don't know if I can explain it to you, I'm not so good at explaining, I'll give it *ONE* try. Example with some random picked numbers (JUST TO SHOW THE MAIN POINTS). I tried, All information and test that are available on the TPLL is on JOHN'S KE5FX site or in past postings. http://www.thegleam.com/ke5fx/tpll.htm One other thing I may not of made clear, The analog averaging thing does not help at low freq like at 1 PPS The TPLL works great because it is at a high freq like 5 or 10 MHz. DAQ == DataQ == ADC I don't think 10ps is achievable under any dynamic conditions IMHO OK, I don't really care, use whatever number you want, you'll still end up below the Ref osc noise. but You may be surprised then by what the single shot Aperture uncertainty specs are for the kind of devices that really care about this sort of thing. But then none of that really maters AT ALL, because there is NO Digital anything in the simple TPLL before the ADC where a 10 Hz device would work fine for most. I just gave you an example to try and answer your question on digital logic which was: How do you do fs when most digital logic has jitter several of orders of magnitude greater? ws *** [time-nuts] Advantages Disadvantages of the TPLL Method Robert Benward rbenward at verizon.net Sat Jun 19 03:18:05 UTC 2010 Warren, Is there not a lower limit to how much you can average? Yes, it's the sqrt of the number of samples, but doesn't noise, hardware, and other perturbations limit the usefulness of this method? Then one can get repeatable results say 100
Re: [time-nuts] Advantages Disadvantages of the TPLL Method
Bob, I might shed some light on this topic, but my comments apply only to a few measurements made in my shop, not part of any PLL scheme. My intent was to determine the apparent noise floor of a Minicircuits SYPD-2 phase detector; a low offset, low conversion loss, DBM. The SYPD-2 IF port was terminated in 600 ohms in parallel with 0.1uF. The SYPD-2 was first characterized for DC output sensitivity with 10MHz @+7dBm on RF 10.0001MHz @+7dBm on LO. At this drive level, the IF output is triangular the gain was found to be 800 mV/Rad at 0VDC. I did not perform a tolerance analysis on this measurement can only estimate the error at +/- 40mV/Rad. The 90 deg offset of the SYPD-2 was measured at 500uV using +7dBm input power to both RF LO ports. This measurement was performed to monitor the 90 deg offset DC for any obvious instability which might make lower level readings useless; the offset was stable to +/- 2uV over several minutes. Finally, the mixer was driven with +7dBm at both ports, but the LO port signal was delayed by a 90 deg hybrid splitter + a 500ps, DC to 2GHz, adjustable phase shifter. This configuration allows very fine (5K part settable resolution) adjustment to reach 0VDC output from the SYPD-2. The DC output stability was +/- 4uV/ minute after allowing an hour to reach thermal mechanical equilibrium ( having no room temperature transients from my heating system). If the phase sensitivity can be assumed to scale down linearly, then 4uV resolution = 5uRad (80fs) @ 10MHz. With more care, or better equipment, 10fs resolution might be possible; but it will be difficult. Without knowing the noise type involved, it's unclear what benefit might be provided by averaging. More work needs to be done. Pete Rawson ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Advantages Disadvantages of the TPLL Method
Hi Pete, I calculated about 0.5uV/V for 10fs, so we are on the same page. I will need to read this several times for it to sink in, but I much appreciate the calculations and technical reply! Thanks! Bob - Original Message - From: Pete Rawson To: Discussion of precise time and frequency measurement Sent: Saturday, June 19, 2010 5:08 PM Subject: Re: [time-nuts] Advantages Disadvantages of the TPLL Method Bob, I might shed some light on this topic, but my comments apply only to a few measurements made in my shop, not part of any PLL scheme. My intent was to determine the apparent noise floor of a Minicircuits SYPD-2 phase detector; a low offset, low conversion loss, DBM. The SYPD-2 IF port was terminated in 600 ohms in parallel with 0.1uF. The SYPD-2 was first characterized for DC output sensitivity with 10MHz @+7dBm on RF 10.0001MHz @+7dBm on LO. At this drive level, the IF output is triangular the gain was found to be 800 mV/Rad at 0VDC. I did not perform a tolerance analysis on this measurement can only estimate the error at +/- 40mV/Rad. The 90 deg offset of the SYPD-2 was measured at 500uV using +7dBm input power to both RF LO ports. This measurement was performed to monitor the 90 deg offset DC for any obvious instability which might make lower level readings useless; the offset was stable to +/- 2uV over several minutes. Finally, the mixer was driven with +7dBm at both ports, but the LO port signal was delayed by a 90 deg hybrid splitter + a 500ps, DC to 2GHz, adjustable phase shifter. This configuration allows very fine (5K part settable resolution) adjustment to reach 0VDC output from the SYPD-2. The DC output stability was +/- 4uV/ minute after allowing an hour to reach thermal mechanical equilibrium ( having no room temperature transients from my heating system). If the phase sensitivity can be assumed to scale down linearly, then 4uV resolution = 5uRad (80fs) @ 10MHz. With more care, or better equipment, 10fs resolution might be possible; but it will be difficult. Without knowing the noise type involved, it's unclear what benefit might be provided by averaging. More work needs to be done. Pete Rawson ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Advantages Disadvantages of the TPLL Method
Charles posted its operation needs to be characterized if technically oriented folks are to be expected to take you seriously. If a simple BB that works as well as that one, does not already do that, then nothing else I'm able or willing to do or say is going to change much. It is a good thing that people can accept things when shown that they work, even when they do not fully understand how. Or else there would no acceptance of much of anything including gravity, computers, email, women or Windows. So your point is? and why do you think I care? Maybe you are missing the point of my intended audience. After all, I'm not the one that is lost or the one that does not know now it works. I have a working unit that, I know how it works and how to test it. how you determined phase locking down to femtosecond levels, ... You do indeed have many valid technical questions that I'd try and explain in a way that you could understand, IF my goal was still to try and educate you, or if I thought there was ANY chance I'd be able to do so. You seem to again of missed the point of my last answer, One with enough technical ability can see what John's data says from his noise floor measurements. But If you do not understand that or how I'm doing it by measuring the PD output, then I can not teach or show you how, even if I still wanted to try. My past failed attempts prove that. So I'll just continue to do what I do best, and that is to make and test TPLL BBs for myself. If you were thinking that I am one that can or am willing to try and teach you basic or advanced anything, then you are greatly over estimating my abilities and/or my patience. You need to look else where if you want to read a fancy math paper on how and why this all works or how to measure it. If you can't find one to your liking and still want to know how to measure fs stuff, I'm sure if you ask nicely in a new thread, others would be more than willing to help you out with something that you could understand and accept. Then again if I missed your point and your only goal is to verify if I now how to do it, then I can save you some trouble, Yes the TPLL and I know how to measure fs phase differences, and we both know how to integrate along with a lot of other basic things including even adding two plus two. (and I doubt that you understand that last point either, Don't take it so personal, It is likely not just your problem) BTW, one of the other points you seem to be missing in how I can measure test things so easy that others can find so hard to do. After all I do have a big advantages over most, I can use another one of my GP PLL BB as a tester. As I've point out before, they can do much more than just ADEV. But then you would not be expected to know that without an advantage list. Seems like it is again 'Time to Push the Reset.Button' on this thread's subject, cause this has got way off the subject. As long as it is so far off the subject of advantages disadvantages, I'll add, in response to what others have said both on and off line. IF others want to build a TPLL using buffer amps, or VFC, or difference Ref Osc, or multiple Ref osc, or a digital version or with cross correlation, or using different software, or different algorithms, or different connectors, or more parts, or more expensive parts or cheaper parts, or that works better with some imaginary unreal data set, or over a wider freq range, or over a longer tau, or at a lower level, or with less injection locking, or any of the other thing's that have been brought up, by all means, Go for it. I've tried to encourage others to do it their your own way. No single solution is best for all situations. What several of the suggestions show is that many do not yet know how simple a TPLL can be made or do they even understand exactly how the 3 basic parts work together. I have consider all the suggestions and tried many of them and so far have found the variations unnecessary for my applications. Also I have not heard about any H/W that others have built, only a lot of criticism from some about what I've done or said or not said. No problem, If others do not like what I've done or the way I've done it or tested it, even when many of them do not know what it is or how it works, by all means they should do it there own way. What I've done is to test one of my simple TPLL versions and show that it's performance is good enough to be limited by the OCXO. That is all, Don't read more into my comments than that. The simple TPLL does not go down to 1e-15. What I said is that is the limit of the low cost AMP that I choose, and it insures the amp has no significant negative effect. Of course all is not perfect, nor is this is the best that a TPLL can be made, not even close. But it is good enough for me. I know how to made it better, much better, with lower noise, more resolution, faster, lower tau, smaller or bigger, more
Re: [time-nuts] Advantages Disadvantages of the TPLL Method
Warren, I'm a newbie, so can you explain it to me? Femto anything is something mostly reserved for a well equipped lab. How do you do it when most digital logic has jitter several of orders of magnitude greater? Bob - Original Message - From: WarrenS warrensjmail-...@yahoo.com To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Friday, June 18, 2010 3:58 PM Subject: Re: [time-nuts] Advantages Disadvantages of the TPLL Method Charles posted its operation needs to be characterized if technically oriented folks are to be expected to take you seriously. If a simple BB that works as well as that one, does not already do that, then nothing else I'm able or willing to do or say is going to change much. It is a good thing that people can accept things when shown that they work, even when they do not fully understand how. Or else there would no acceptance of much of anything including gravity, computers, email, women or Windows. So your point is? and why do you think I care? Maybe you are missing the point of my intended audience. After all, I'm not the one that is lost or the one that does not know now it works. I have a working unit that, I know how it works and how to test it. how you determined phase locking down to femtosecond levels, ... You do indeed have many valid technical questions that I'd try and explain in a way that you could understand, IF my goal was still to try and educate you, or if I thought there was ANY chance I'd be able to do so. You seem to again of missed the point of my last answer, One with enough technical ability can see what John's data says from his noise floor measurements. But If you do not understand that or how I'm doing it by measuring the PD output, then I can not teach or show you how, even if I still wanted to try. My past failed attempts prove that. So I'll just continue to do what I do best, and that is to make and test TPLL BBs for myself. If you were thinking that I am one that can or am willing to try and teach you basic or advanced anything, then you are greatly over estimating my abilities and/or my patience. You need to look else where if you want to read a fancy math paper on how and why this all works or how to measure it. If you can't find one to your liking and still want to know how to measure fs stuff, I'm sure if you ask nicely in a new thread, others would be more than willing to help you out with something that you could understand and accept. Then again if I missed your point and your only goal is to verify if I now how to do it, then I can save you some trouble, Yes the TPLL and I know how to measure fs phase differences, and we both know how to integrate along with a lot of other basic things including even adding two plus two. (and I doubt that you understand that last point either, Don't take it so personal, It is likely not just your problem) BTW, one of the other points you seem to be missing in how I can measure test things so easy that others can find so hard to do. After all I do have a big advantages over most, I can use another one of my GP PLL BB as a tester. As I've point out before, they can do much more than just ADEV. But then you would not be expected to know that without an advantage list. Seems like it is again 'Time to Push the Reset.Button' on this thread's subject, cause this has got way off the subject. As long as it is so far off the subject of advantages disadvantages, I'll add, in response to what others have said both on and off line. IF others want to build a TPLL using buffer amps, or VFC, or difference Ref Osc, or multiple Ref osc, or a digital version or with cross correlation, or using different software, or different algorithms, or different connectors, or more parts, or more expensive parts or cheaper parts, or that works better with some imaginary unreal data set, or over a wider freq range, or over a longer tau, or at a lower level, or with less injection locking, or any of the other thing's that have been brought up, by all means, Go for it. I've tried to encourage others to do it their your own way. No single solution is best for all situations. What several of the suggestions show is that many do not yet know how simple a TPLL can be made or do they even understand exactly how the 3 basic parts work together. I have consider all the suggestions and tried many of them and so far have found the variations unnecessary for my applications. Also I have not heard about any H/W that others have built, only a lot of criticism from some about what I've done or said or not said. No problem, If others do not like what I've done or the way I've done it or tested it, even when many of them do not know what it is or how it works, by all means they should do it there own way. What I've done is to test one of my simple TPLL versions and show that it's performance is good enough to be limited by the OCXO. That is all, Don't
Re: [time-nuts] Advantages Disadvantages of the TPLL Method
Bob posted can you explain it to me? Don't know, I'll give it ONE try. I'm not so good at explaining, but it is pretty basic if one does not start assuming that it can not be done at the start. It is mostly about averaging lots of those transitions, and the real trick is that it is not Digital. Analog has no lower limits except manly for Johnson noise type effects (mostly). Example with some random picked numbers. and assuming all analog that has no digital steps in it to limit resolution or add noise. Say you have a nice logic gate with 1 ns delay If you make it all nice and clean, and repeatable such as constant PS, rise time etc. Then one can get repeatable results say 100 times better from cycle to cycle in the short term. so down to 10ps repeatable. Now make things even more clean with no variations and assuming random noise. Now if one is doing this at 10 MHz and only cares about the average over 0.1 sec (10 Hz) One can average 1,000,000 readings of the 10 ps jitter If they are truly random, that can give you a 1e-3 improvement (square root of number of samples averaged) so now down to 10 fs of average jitter at 10 Hz for a 10 MHZ gate starting with a 1ns initial delay. OF course if Anything changes at all, it will drift much more than that, which may or may not mater much depending on what one is doing. If you only really care about the difference between any two consecutive 100 ms reading that are next to each other, as is (mostly) the case in ADEV, then not a big deal. IF it does matter or you want to do better, the next step is to do it all differential, so you are looking at only the different of two separate independent but equal circuits. Differential can give, say a 1000 to one or better improvement in drift due to common things such as temperature etc. If that helps explain the basics, good, if not you need to ask others to explain it better. And yes there all kinds of things that can do go wrong and many ways to screw it up. so as easy as it sounds, it does take a bit of skill and art to do it. Especially when one realizes that you are measuring things 0.001 in of distance change will have major effects on because of the speed of light. (approx 1ft /ns, 0.01 in/ps, 1 micron/4fs) Now if one starts out, not with a gate but a phase detector that is made for such things, and averages enough (but not to long) and is real careful, 1fs resolution is possible in the 100 Hz range with 10 MHz 10 MHz 1fs at 100 Hz gives 1e-13 freq variation resolution at tau 10ms The simple BB TPLL is only getting about a tenth of that, (as shown on John's test plots) so it can be made much better with enough care, if anyone has a ref osc that needs it. But as I am always so quick to point out, the BB tester was not optimized for any one thing, It's performance was selected as a compromise for 'KISS' reasons. (KISS = Keep It Simple so the experts can understand.) please let me know on or off line if I'm wasting my time trying to explain this to the non nut experts without the help of the fancy math papers. ws * Warren, I'm a newbie, so can you explain it to me? Femto anything is something mostly reserved for a well equipped lab. How do you do it when most digital logic has jitter several of orders of magnitude greater? Bob * [time-nuts] Advantages Disadvantages of the TPLL Method Robert Benward rbenward at verizon.net Fri Jun 18 20:23:40 UTC 2010 Previous message: [time-nuts] Advantages Disadvantages of the TPLL Method Messages sorted by: [ date ] [ thread ] [ subject ] [ author ] Warren, I'm a newbie, so can you explain it to me? Femto anything is something mostly reserved for a well equipped lab. How do you do it when most digital logic has jitter several of orders of magnitude greater? Bob * - Original Message - From: WarrenS warrensjmail-one at yahoo.com To: Discussion of precise time and frequency measurement time-nuts at febo.com Sent: Friday, June 18, 2010 3:58 PM Subject: Re: [time-nuts] Advantages Disadvantages of the TPLL Method Charles posted its operation needs to be characterized if technically oriented folks are to be expected to take you seriously. If a simple BB that works as well as that one, does not already do that, then nothing else I'm able or willing to do or say is going to change much. It is a good thing that people can accept things when shown that they work, even when they do not fully understand how. Or else there would no acceptance of much of anything including gravity, computers, email, women or Windows. So your point is? and why do you think I care? Maybe you are missing the point of my intended audience. After all, I'm not the one that is lost or the one that does not know now it works. I have a working unit that, I know how it works and how to test it. how you determined phase locking down to femtosecond levels, ... You do
Re: [time-nuts] Advantages Disadvantages of the TPLL Method
Warren wrote: you are greatly over estimating my abilities Probably true, even of my estimation. Best regards, Charles == Better to remain silent and be thought a fool, than to speak up and remove all doubt. Attributed to Mark Twain, though not verified ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Advantages Disadvantages of the TPLL Method
Warren, Is there not a lower limit to how much you can average? Yes, it's the sqrt of the number of samples, but doesn't noise, hardware, and other perturbations limit the usefulness of this method? Then one can get repeatable results say 100 times better from cycle to cycle in the short term. so down to 10ps repeatable. Why do you say the results are repeatable in the short term vs the long term? Isn't what you defined above (repeatability) the opposite of jitter? Jitter I thought was cycle to cycle variation in prop delay. On 1ns prop devices, I don't think 50-100ps jitter is unreasonable under the most optimum conditions, the most careful circuit layout, and constant repeatable inputs. I don't think 10ps is achievable under any dynamic conditions IMHO. One can average 1,000,000 readings of the 10 ps jitter If they are truly random, that can give you a 1e-3 improvement (square root of number of samples averaged) You are now averaging the repeatable jitter. KE5FX's website shows a diagram and a link to your diagram as well. Are you using a digital phase detector or a mixer as shown? BTW, KE5FX refers to DAQ as your update to the design, where I believe he meant an ADC. You have my curiosity peaked. Do you have an analysis of the loop sensitivity/resolution? Bob - Original Message - From: WarrenS warrensjmail-...@yahoo.com To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Friday, June 18, 2010 6:49 PM Subject: Re: [time-nuts] Advantages Disadvantages of the TPLL Method Bob posted can you explain it to me? Don't know, I'll give it ONE try. I'm not so good at explaining, but it is pretty basic if one does not start assuming that it can not be done at the start. It is mostly about averaging lots of those transitions, and the real trick is that it is not Digital. Analog has no lower limits except manly for Johnson noise type effects (mostly). Example with some random picked numbers. and assuming all analog that has no digital steps in it to limit resolution or add noise. Say you have a nice logic gate with 1 ns delay If you make it all nice and clean, and repeatable such as constant PS, rise time etc. Then one can get repeatable results say 100 times better from cycle to cycle in the short term. so down to 10ps repeatable. Now make things even more clean with no variations and assuming random noise. Now if one is doing this at 10 MHz and only cares about the average over 0.1 sec (10 Hz) One can average 1,000,000 readings of the 10 ps jitter If they are truly random, that can give you a 1e-3 improvement (square root of number of samples averaged) so now down to 10 fs of average jitter at 10 Hz for a 10 MHZ gate starting with a 1ns initial delay. OF course if Anything changes at all, it will drift much more than that, which may or may not mater much depending on what one is doing. If you only really care about the difference between any two consecutive 100 ms reading that are next to each other, as is (mostly) the case in ADEV, then not a big deal. IF it does matter or you want to do better, the next step is to do it all differential, so you are looking at only the different of two separate independent but equal circuits. Differential can give, say a 1000 to one or better improvement in drift due to common things such as temperature etc. If that helps explain the basics, good, if not you need to ask others to explain it better. And yes there all kinds of things that can do go wrong and many ways to screw it up. so as easy as it sounds, it does take a bit of skill and art to do it. Especially when one realizes that you are measuring things 0.001 in of distance change will have major effects on because of the speed of light. (approx 1ft /ns, 0.01 in/ps, 1 micron/4fs) Now if one starts out, not with a gate but a phase detector that is made for such things, and averages enough (but not to long) and is real careful, 1fs resolution is possible in the 100 Hz range with 10 MHz 10 MHz 1fs at 100 Hz gives 1e-13 freq variation resolution at tau 10ms The simple BB TPLL is only getting about a tenth of that, (as shown on John's test plots) so it can be made much better with enough care, if anyone has a ref osc that needs it. But as I am always so quick to point out, the BB tester was not optimized for any one thing, It's performance was selected as a compromise for 'KISS' reasons. (KISS = Keep It Simple so the experts can understand.) please let me know on or off line if I'm wasting my time trying to explain this to the non nut experts without the help of the fancy math papers. ws * Warren, I'm a newbie, so can you explain it to me? Femto anything is something mostly reserved for a well equipped lab. How do you do it when most digital logic has jitter several of orders of magnitude greater? Bob * [time-nuts] Advantages Disadvantages of the TPLL Method
Re: [time-nuts] Advantages Disadvantages of the TPLL Method
Hi Warren, how do I change the com port in Lady Heather software. Thank You Best regards, Sal C. Cornacchia Electronic RF Microwave Engineer (Ret.) From: WarrenS warrensjmail-...@yahoo.com To: Discussion of precise time and frequency time-nuts@febo.com Sent: Thu, June 17, 2010 1:29:57 AM Subject: Re: [time-nuts] Advantages Disadvantages of the TPLL Method Charles I'm curious how you determined that the oscillators are being held to within femtoseconds of each other. I done it several ways including measuring the PD output. You seem to be missing how insignificant an 1-e6 injection locking to EFC gain ratio is. I can't detail, to your satisfaction, all the hundreds of test that show no significant effect of so many different things. For an independent test that may help you with things you missed see: http://www.ke5fx.com/tpll.htm ws *** [time-nuts] Advantages Disadvantages of the TPLL Method Charles P. Steinmetz charles_steinmetz at lavabit.com Thu Jun 17 02:10:31 UTC 2010 Warren wrote: Charles Posted: How much EFC is required depends, in part, on the strength of the pulling. There are three varying inputs. NOT at ALL what my test have shown so I guess we do NOT agree on this. The point you missed, is only the EFC is changing significantly because of the high gain and BW. It insures the two Oscillators are held to within femtoseconds of each other, to at least out to the e-16 at large taus. So other things are held constant enough that their effects are kept below any ref Osc effects. Why must everything be a matter of other people missing something? I understand how oscillators behave with respect to injection pulling/locking, and how that might affect the operation and accuracy of a system such as you are using. I myself noted that Magnus had suggested the effect may not be significant in such a system, but that drawing that conclusion for any particular design would require careful experiments and, hopefully, backup by mathematical analysis. How is that missing anything? The carefully constructed experiments, that show it works as advertised have been done, and the most important ones have been posted. Forgive me if I missed something, but all I saw regarding the relative gains of the error loop and the injection loop were (i) that you increased the coupling by a factor of 1000 and (ii) that you used a variable attenuator. If you did carefully designed experiments, nothing I saw posted suggested it. This is a potentially important point because some oscillators one might want to test (or use as a reference) may be very much more sensitive to injection locking (pulling, actually) than the ones you are using. Therefore, the behavior should be characterized so users can determine whether it might affect their results. It didn't seem to have any effect using the oscillators I had is not really a very useful characterization of the behavior. [I do see that in a subsequent message you asked for suggestions for further tests.] I'm curious how you determined that the oscillators are being held to within femtoseconds of each other. And, how many femtoseconds? Best regards, Charles ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Advantages Disadvantages of the TPLL Method
Hi A handy reference on Lady Heather is here: http://www.thegleam.com/ke5fx/heather/readme.htm To change the com to port 3 you launch it with a /3 on the command line. In my case the Target line under properties is: C:\Program Files\Heather\heather.exe /3 You get to that particular properties page by right clicking on the LH icon on the desktop in Windows. Bob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of SAL CORNACCHIA Sent: Thursday, June 17, 2010 11:25 AM To: WarrenS; Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Advantages Disadvantages of the TPLL Method Hi Warren, how do I change the com port in Lady Heather software. Thank You Best regards, Sal C. Cornacchia Electronic RF Microwave Engineer (Ret.) From: WarrenS warrensjmail-...@yahoo.com To: Discussion of precise time and frequency time-nuts@febo.com Sent: Thu, June 17, 2010 1:29:57 AM Subject: Re: [time-nuts] Advantages Disadvantages of the TPLL Method Charles I'm curious how you determined that the oscillators are being held to within femtoseconds of each other. I done it several ways including measuring the PD output. You seem to be missing how insignificant an 1-e6 injection locking to EFC gain ratio is. I can't detail, to your satisfaction, all the hundreds of test that show no significant effect of so many different things. For an independent test that may help you with things you missed see: http://www.ke5fx.com/tpll.htm ws *** [time-nuts] Advantages Disadvantages of the TPLL Method Charles P. Steinmetz charles_steinmetz at lavabit.com Thu Jun 17 02:10:31 UTC 2010 Warren wrote: Charles Posted: How much EFC is required depends, in part, on the strength of the pulling. There are three varying inputs. NOT at ALL what my test have shown so I guess we do NOT agree on this. The point you missed, is only the EFC is changing significantly because of the high gain and BW. It insures the two Oscillators are held to within femtoseconds of each other, to at least out to the e-16 at large taus. So other things are held constant enough that their effects are kept below any ref Osc effects. Why must everything be a matter of other people missing something? I understand how oscillators behave with respect to injection pulling/locking, and how that might affect the operation and accuracy of a system such as you are using. I myself noted that Magnus had suggested the effect may not be significant in such a system, but that drawing that conclusion for any particular design would require careful experiments and, hopefully, backup by mathematical analysis. How is that missing anything? The carefully constructed experiments, that show it works as advertised have been done, and the most important ones have been posted. Forgive me if I missed something, but all I saw regarding the relative gains of the error loop and the injection loop were (i) that you increased the coupling by a factor of 1000 and (ii) that you used a variable attenuator. If you did carefully designed experiments, nothing I saw posted suggested it. This is a potentially important point because some oscillators one might want to test (or use as a reference) may be very much more sensitive to injection locking (pulling, actually) than the ones you are using. Therefore, the behavior should be characterized so users can determine whether it might affect their results. It didn't seem to have any effect using the oscillators I had is not really a very useful characterization of the behavior. [I do see that in a subsequent message you asked for suggestions for further tests.] I'm curious how you determined that the oscillators are being held to within femtoseconds of each other. And, how many femtoseconds? Best regards, Charles ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Advantages Disadvantages of the TPLL Method
Thank You Bob, I will try it and will advise it it works for me. Best regards, Sal C. Cornacchia Electronic RF Microwave Engineer (Ret.) From: Bob Camp li...@rtty.us To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Thu, June 17, 2010 12:10:03 PM Subject: Re: [time-nuts] Advantages Disadvantages of the TPLL Method Hi A handy reference on Lady Heather is here: http://www.thegleam.com/ke5fx/heather/readme.htm To change the com to port 3 you launch it with a /3 on the command line. In my case the Target line under properties is: C:\Program Files\Heather\heather.exe /3 You get to that particular properties page by right clicking on the LH icon on the desktop in Windows. Bob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of SAL CORNACCHIA Sent: Thursday, June 17, 2010 11:25 AM To: WarrenS; Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Advantages Disadvantages of the TPLL Method Hi Warren, how do I change the com port in Lady Heather software. Thank You Best regards, Sal C. Cornacchia Electronic RF Microwave Engineer (Ret.) From: WarrenS warrensjmail-...@yahoo.com To: Discussion of precise time and frequency time-nuts@febo.com Sent: Thu, June 17, 2010 1:29:57 AM Subject: Re: [time-nuts] Advantages Disadvantages of the TPLL Method Charles I'm curious how you determined that the oscillators are being held to within femtoseconds of each other. I done it several ways including measuring the PD output. You seem to be missing how insignificant an 1-e6 injection locking to EFC gain ratio is. I can't detail, to your satisfaction, all the hundreds of test that show no significant effect of so many different things. For an independent test that may help you with things you missed see: http://www.ke5fx.com/tpll.htm ws *** [time-nuts] Advantages Disadvantages of the TPLL Method Charles P. Steinmetz charles_steinmetz at lavabit.com Thu Jun 17 02:10:31 UTC 2010 Warren wrote: Charles Posted: How much EFC is required depends, in part, on the strength of the pulling. There are three varying inputs. NOT at ALL what my test have shown so I guess we do NOT agree on this. The point you missed, is only the EFC is changing significantly because of the high gain and BW. It insures the two Oscillators are held to within femtoseconds of each other, to at least out to the e-16 at large taus. So other things are held constant enough that their effects are kept below any ref Osc effects. Why must everything be a matter of other people missing something? I understand how oscillators behave with respect to injection pulling/locking, and how that might affect the operation and accuracy of a system such as you are using. I myself noted that Magnus had suggested the effect may not be significant in such a system, but that drawing that conclusion for any particular design would require careful experiments and, hopefully, backup by mathematical analysis. How is that missing anything? The carefully constructed experiments, that show it works as advertised have been done, and the most important ones have been posted. Forgive me if I missed something, but all I saw regarding the relative gains of the error loop and the injection loop were (i) that you increased the coupling by a factor of 1000 and (ii) that you used a variable attenuator. If you did carefully designed experiments, nothing I saw posted suggested it. This is a potentially important point because some oscillators one might want to test (or use as a reference) may be very much more sensitive to injection locking (pulling, actually) than the ones you are using. Therefore, the behavior should be characterized so users can determine whether it might affect their results. It didn't seem to have any effect using the oscillators I had is not really a very useful characterization of the behavior. [I do see that in a subsequent message you asked for suggestions for further tests.] I'm curious how you determined that the oscillators are being held to within femtoseconds of each other. And, how many femtoseconds? Best regards, Charles ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts
Re: [time-nuts] Advantages Disadvantages of the TPLL Method
Hi The gotcha is that the injection gain is phase angle dependent. Bob On Jun 16, 2010, at 1:57 AM, Magnus Danielson wrote: On 06/16/2010 05:45 AM, Charles P. Steinmetz wrote: Warren wrote: Charles posted: but the locked frequency will be different from both oscillators' free-running frequency and the EFC will not correctly indicate the test oscillator deviation because it isn't the only control input in the system. Good point and No argument (except for the deviation part) Because the EFC is the only control input THAT IS VARYING. No, it's not. The strength with which each oscillator pulls on the other also varies as the equilibrium frequency (the result of all three recursive control inputs) moves around relative to the two instantaneous free-running frequencies. How much EFC is required depends, in part, on the strength of the pulling. There are three varying inputs. Magnus suggested that the effect of injection locking may be enough smaller than the EFC input that it has little practical significance. That may be so, but when dealing with measurement accuracy in the hundreds or tens ot ppt, this needs to be verified by the results of carefully constructed experiments and hopefully also supported by mathematical analysis. What you get is a scale error. Consider that you have an amplifier gain of 1000 and the injection locking provide a gain of 1, that will result in actual gain of 1001 and the gain error on the EFC will become 1000/1001. Considering that Allan deviation estimation has problem of its own, this scale error is not significant. What you do need to check is that the relationship between intended gain and injection gain is sufficiently different. Since oscillator frequency from EFC may not be completely correct, we already want calibration of that scale factor (K_O) and the gain error due to injection locking would be included into that correction factor. So, sufficiently small amount of injection locking gain will change the apparent EFC coefficient K_O [Rad/sV] on which the scale of TPLL frequency measurements depends. The fractional frequency observed is y(t) = 2*pi*f_0 / K_O,eff EFC(t) Cheers, Magnus ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Advantages Disadvantages of the TPLL Method
In my world, successive gains multiply, not add. A series of three gains of 10 gives a gain of 1000, not 30. What am I missing? Bill Hawkins -Original Message- From: Magnus Danielson Sent: Wednesday, June 16, 2010 12:58 AM What you get is a scale error. Consider that you have an amplifier gain of 1000 and the injection locking provide a gain of 1, that will result in actual gain of 1001 and the gain error on the EFC will become 1000/1001. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Advantages Disadvantages of the TPLL Method
Bob posted The gotcha is that the injection gain is phase angle dependent. So what? and it is also dependant on a whole bunch of other stuff, amplitude being a major one. And the gotcha you to your gotcha is that the phase difference in the TPLL is fixed at very close at 90 deg. (zero on the PD with in uv, a few femtoseconds variation) Just to put this subject to rest, I tried to measure the ratio of EFC gain to injection lock gain at near zero PD output at the nominal signal levels I'm using. The problem is this is analog. Analog unlike digital has some limits of about 1 PPM (1e-6) and 50 nv (5e-8) The IL ratio seems to be below 1e-6 so I have been unable to measure the ratio. The effect seems to be below the noise level of the reference Osc so that also makes it a bit hard to get a good number. Anyone have any suggestion how to go about measuring an effect this low? Until I can measure the IL effect more accurately, I'm just going to have go with the more general statement that the TPLL method is limited by the Reference Osc. If the reference osc or DUT Injection Lock sensitivity is more than say around 1e5 times the 10811, It is best to add an external buffer to be save to keep the gain errors below 10%. ws ** [time-nuts] Advantages Disadvantages of the TPLL Method Bob Camp lists at rtty.us Wed Jun 16 11:34:27 UTC 2010 Hi The gotcha is that the injection gain is phase angle dependent. Bob ** On Jun 16, 2010, at 1:57 AM, Magnus Danielson wrote: On 06/16/2010 05:45 AM, Charles P. Steinmetz wrote: Warren wrote: Charles posted: but the locked frequency will be different from both oscillators' free-running frequency and the EFC will not correctly indicate the test oscillator deviation because it isn't the only control input in the system. Good point and No argument (except for the deviation part) Because the EFC is the only control input THAT IS VARYING. No, it's not. The strength with which each oscillator pulls on the other also varies as the equilibrium frequency (the result of all three recursive control inputs) moves around relative to the two instantaneous free-running frequencies. How much EFC is required depends, in part, on the strength of the pulling. There are three varying inputs. Magnus suggested that the effect of injection locking may be enough smaller than the EFC input that it has little practical significance. That may be so, but when dealing with measurement accuracy in the hundreds or tens ot ppt, this needs to be verified by the results of carefully constructed experiments and hopefully also supported by mathematical analysis. What you get is a scale error. Consider that you have an amplifier gain of 1000 and the injection locking provide a gain of 1, that will result in actual gain of 1001 and the gain error on the EFC will become 1000/1001. Considering that Allan deviation estimation has problem of its own, this scale error is not significant. What you do need to check is that the relationship between intended gain and injection gain is sufficiently different. Since oscillator frequency from EFC may not be completely correct, we already want calibration of that scale factor (K_O) and the gain error due to injection locking would be included into that correction factor. So, sufficiently small amount of injection locking gain will change the apparent EFC coefficient K_O [Rad/sV] on which the scale of TPLL frequency measurements depends. The fractional frequency observed is y(t) = 2*pi*f_0 / K_O,eff EFC(t) Cheers, Magnus ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Advantages Disadvantages of the TPLL Method
Hi If the oscillator you have happens to injection lock at 90 degrees, or quite near it, then that's not going to help. If the oscillator you have likes to lock at 21 degrees then it will help you out. The angle varies device to device. Bob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of WarrenS Sent: Wednesday, June 16, 2010 11:46 AM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Advantages Disadvantages of the TPLL Method Bob posted The gotcha is that the injection gain is phase angle dependent. So what? and it is also dependant on a whole bunch of other stuff, amplitude being a major one. And the gotcha you to your gotcha is that the phase difference in the TPLL is fixed at very close at 90 deg. (zero on the PD with in uv, a few femtoseconds variation) Just to put this subject to rest, I tried to measure the ratio of EFC gain to injection lock gain at near zero PD output at the nominal signal levels I'm using. The problem is this is analog. Analog unlike digital has some limits of about 1 PPM (1e-6) and 50 nv (5e-8) The IL ratio seems to be below 1e-6 so I have been unable to measure the ratio. The effect seems to be below the noise level of the reference Osc so that also makes it a bit hard to get a good number. Anyone have any suggestion how to go about measuring an effect this low? Until I can measure the IL effect more accurately, I'm just going to have go with the more general statement that the TPLL method is limited by the Reference Osc. If the reference osc or DUT Injection Lock sensitivity is more than say around 1e5 times the 10811, It is best to add an external buffer to be save to keep the gain errors below 10%. ws ** [time-nuts] Advantages Disadvantages of the TPLL Method Bob Camp lists at rtty.us Wed Jun 16 11:34:27 UTC 2010 Hi The gotcha is that the injection gain is phase angle dependent. Bob ** On Jun 16, 2010, at 1:57 AM, Magnus Danielson wrote: On 06/16/2010 05:45 AM, Charles P. Steinmetz wrote: Warren wrote: Charles posted: but the locked frequency will be different from both oscillators' free-running frequency and the EFC will not correctly indicate the test oscillator deviation because it isn't the only control input in the system. Good point and No argument (except for the deviation part) Because the EFC is the only control input THAT IS VARYING. No, it's not. The strength with which each oscillator pulls on the other also varies as the equilibrium frequency (the result of all three recursive control inputs) moves around relative to the two instantaneous free-running frequencies. How much EFC is required depends, in part, on the strength of the pulling. There are three varying inputs. Magnus suggested that the effect of injection locking may be enough smaller than the EFC input that it has little practical significance. That may be so, but when dealing with measurement accuracy in the hundreds or tens ot ppt, this needs to be verified by the results of carefully constructed experiments and hopefully also supported by mathematical analysis. What you get is a scale error. Consider that you have an amplifier gain of 1000 and the injection locking provide a gain of 1, that will result in actual gain of 1001 and the gain error on the EFC will become 1000/1001. Considering that Allan deviation estimation has problem of its own, this scale error is not significant. What you do need to check is that the relationship between intended gain and injection gain is sufficiently different. Since oscillator frequency from EFC may not be completely correct, we already want calibration of that scale factor (K_O) and the gain error due to injection locking would be included into that correction factor. So, sufficiently small amount of injection locking gain will change the apparent EFC coefficient K_O [Rad/sV] on which the scale of TPLL frequency measurements depends. The fractional frequency observed is y(t) = 2*pi*f_0 / K_O,eff EFC(t) Cheers, Magnus ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Advantages Disadvantages of the TPLL Method
On 06/16/2010 04:30 PM, Bill Hawkins wrote: In my world, successive gains multiply, not add. A series of three gains of 10 gives a gain of 1000, not 30. What am I missing? They are parallel. Cheers, Magnus ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Advantages Disadvantages of the TPLL Method
On 06/16/2010 06:16 PM, Bob Camp wrote: Hi If the oscillator you have happens to injection lock at 90 degrees, or quite near it, then that's not going to help. If the oscillator you have likes to lock at 21 degrees then it will help you out. The angle varies device to device. If the injection lock gain is significantly less than the intended loop gain, then it may have any angle without significant influence. If these gains is close, it matters and if the injection lock gain is larger, it will dominate and care much be taken to ensure stable phase in order to have a stable gain. A tight PLL has a fairly high gain, so if the injection lock gain is sufficiently low (should always be verified!) then the effect should be low enought. The Wolaver analysis assumes a phase angle, so the model includes the angle-effect. Cheers, Magnus ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Advantages Disadvantages of the TPLL Method
Warren wrote: Charles Posted: How much EFC is required depends, in part, on the strength of the pulling. There are three varying inputs. NOT at ALL what my test have shown so I guess we do NOT agree on this. The point you missed, is only the EFC is changing significantly because of the high gain and BW. It insures the two Oscillators are held to within femtoseconds of each other, to at least out to the e-16 at large taus. So other things are held constant enough that their effects are kept below any ref Osc effects. Why must everything be a matter of other people missing something? I understand how oscillators behave with respect to injection pulling/locking, and how that might affect the operation and accuracy of a system such as you are using. I myself noted that Magnus had suggested the effect may not be significant in such a system, but that drawing that conclusion for any particular design would require careful experiments and, hopefully, backup by mathematical analysis. How is that missing anything? The carefully constructed experiments, that show it works as advertised have been done, and the most important ones have been posted. Forgive me if I missed something, but all I saw regarding the relative gains of the error loop and the injection loop were (i) that you increased the coupling by a factor of 1000 and (ii) that you used a variable attenuator. If you did carefully designed experiments, nothing I saw posted suggested it. This is a potentially important point because some oscillators one might want to test (or use as a reference) may be very much more sensitive to injection locking (pulling, actually) than the ones you are using. Therefore, the behavior should be characterized so users can determine whether it might affect their results. It didn't seem to have any effect using the oscillators I had is not really a very useful characterization of the behavior. [I do see that in a subsequent message you asked for suggestions for further tests.] I'm curious how you determined that the oscillators are being held to within femtoseconds of each other. And, how many femtoseconds? Best regards, Charles ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Advantages Disadvantages of the TPLL Method
Charles I'm curious how you determined that the oscillators are being held to within femtoseconds of each other. I done it several ways including measuring the PD output. You seem to be missing how insignificant an 1-e6 injection locking to EFC gain ratio is. I can't detail, to your satisfaction, all the hundreds of test that show no significant effect of so many different things. For an independent test that may help you with things you missed see: http://www.ke5fx.com/tpll.htm ws *** [time-nuts] Advantages Disadvantages of the TPLL Method Charles P. Steinmetz charles_steinmetz at lavabit.com Thu Jun 17 02:10:31 UTC 2010 Warren wrote: Charles Posted: How much EFC is required depends, in part, on the strength of the pulling. There are three varying inputs. NOT at ALL what my test have shown so I guess we do NOT agree on this. The point you missed, is only the EFC is changing significantly because of the high gain and BW. It insures the two Oscillators are held to within femtoseconds of each other, to at least out to the e-16 at large taus. So other things are held constant enough that their effects are kept below any ref Osc effects. Why must everything be a matter of other people missing something? I understand how oscillators behave with respect to injection pulling/locking, and how that might affect the operation and accuracy of a system such as you are using. I myself noted that Magnus had suggested the effect may not be significant in such a system, but that drawing that conclusion for any particular design would require careful experiments and, hopefully, backup by mathematical analysis. How is that missing anything? The carefully constructed experiments, that show it works as advertised have been done, and the most important ones have been posted. Forgive me if I missed something, but all I saw regarding the relative gains of the error loop and the injection loop were (i) that you increased the coupling by a factor of 1000 and (ii) that you used a variable attenuator. If you did carefully designed experiments, nothing I saw posted suggested it. This is a potentially important point because some oscillators one might want to test (or use as a reference) may be very much more sensitive to injection locking (pulling, actually) than the ones you are using. Therefore, the behavior should be characterized so users can determine whether it might affect their results. It didn't seem to have any effect using the oscillators I had is not really a very useful characterization of the behavior. [I do see that in a subsequent message you asked for suggestions for further tests.] I'm curious how you determined that the oscillators are being held to within femtoseconds of each other. And, how many femtoseconds? Best regards, Charles ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Advantages Disadvantages of the TPLL Method
Hi With any phase lock system injection locking can indeed be a problem. Since it's dependent both on frequency offset and phase angle, checking for it can be tricky. I've seen an unfortunately large amount of data where injection locking was the issue. There are a number of ways of checking for it, each with their own issues (and hardware requirements). Bob On Jun 15, 2010, at 1:39 AM, Bruce Griffiths wrote: WarrenS wrote: Bruce posted If and only if injection locking isn't significant. No problem then, because it is not significant. For each and every oscillator pair someone may try? Can place this one under the 'ADVANTAGE' side. That's descending into the murky realms of pseudoscience. At best you've only shown this to be true for the particular oscillator pair being compared. Not only must the effect of injection locking be insignificant for the reference, it has to be insignificant for the test oscillator as well. If injection locking is an issue the efc gain with the loop open will differ from the efc gain with the loop closed. I have tested this thoroughly in many ways. I do understand the concerns and doubts, especially with an unbuffered HP 10811 as the reference. The 10811s are pretty sensitive to injection locking and phase pulling. Unlike most other methods, one of the many unique properties that the TPLL method has is that injection locking is normally not a problem with it. It will change the loop parameters in particular the efc gain. Its just a matter of how much it affects the efc gain. I find it is generally unnecessary to buffer either the Ref Osc or the DUT. This is one of the many features that helps make the simple TPLL so simple. (also it does not hurt or change anything to add a proper buffer) The lack of injection locking is one of the advantages that contributes to its exceptional and unbelievable performance. But Adler's equation indicates that an oscillator is much more to susceptible to injection effects when the injected signal frequency is very close to the oscillator frequency. I did not leave the buffers out of the simple TPLL BB that was tested because of my lack of knowledge, but because of my extra knowledge on the subject that showed that they were unnecessary. More than once, I have tried to explain the reason why injection locking is not a problem with my version of the TPLL method, but until one proves it for their self, more words from me will not help. I do understand the skepticism and doubt, and I know why it is so hard to believe this for those that have not worked with is this type of method before. I guess someone should write one of those fancy math papers, if it has not already been done, that explains it in more convincing terms than I've been able to. It is hard for me to believe that paper has not already been written, But then it is hard for me to believe that the TPLL is not used more often. There are plenty of places that one of the TPLL methods well give the best overall solution. ws *** Bruce [time-nuts] Advantages Disadvantages of the TPLL Method Bruce Griffiths bruce.griffiths at xtra.co.nz WarrenS wrote: Long explanations, cause I try to explain, the best I can, when I say something is WRONG or misleading Magnus Posted: EFC linearity will remain an issue for analog oscillators. The oscillator gain will differ depending on offset voltage and temperature. TRUE it is an issue, but somewhat misleading because it need NOT be a problem or limitation (mostly) EFC Linearity can be an issue because the TPLL is limited by the performance of the reference oscillator in lots of ways. BUT Oscillator EFC gain or linearity are not likely to be of much concern or a limitation for high end performance. The gain nonlinearity I've measured can vary two to one over the full range of a good Oscillator but it is more like 10% over the normally used range, if one stays well away from the end points. NOT so good but livable if you are not making something real accurate. BUT For all my accurate stuff, when using a HP 10811, I limit the full-scale change to 1e-9 or 1e-8 at most. This uses such a small part of the total EFC range, that the nonlinearity effects are generally below the noise level and of little concern at all. The fact that Oscillator gain does differ with the EFC voltage (offset voltage), means if you want to get max accuracy out of the TPLL, it will need to be calibrated at the EFC offset voltage it is being used at. One simple solution, if the OSC also has a independent manual Freq adjustment like the single oven 10811, is to use it always set the EFC voltage to be near zero volts. BTW calibration need not be much of a problem, because it can be a static calibration. If and only if injection locking isn't significant. This needs to be established for each setup. The simplest way to take
Re: [time-nuts] Advantages Disadvantages of the TPLL Method
Bruce posted But Adler's equation indicates that an oscillator is much more susceptible to injection effects when the injected signal frequency is very close to the oscillator frequency. No argument, BUT The thing that you (and maybe Adler?) are missing is that effect goes away when the two frequencies ARE exactly the same. I'm not talking close, I'm talking the exact same freq with phase held in quadrature within single digit femtoseconds. BIG difference, Once that is understood, then that sort of answers your other comments. For each and every oscillator pair someone may try? Can't say for sure, I've only tried the ones I've tried, but even the ones that are highly susceptible were OK. At best you've only shown this to be true for the particular oscillator pair being compared. Yep, maybe I'm just real lucking again and it only applies to all the ones I've tested. That's descending into the murky realms of pseudoscience. OR as I see it, it is using just a little common sense. When is the last time you heard of a problem with an oscillator injection locking to it's self? Not only must the effect of injection locking be insignificant for the reference, it has to be insignificant for the test oscillator as well. NO argument, If you are testing a DUT what this does effect, then one should buffer it or take other precaution. If you want to make sure the tester is not effecting the osc there is another choice besides the Buffer. DON'T connected it. The tester will work at better than -60 dB signal levels and if one just gets a couple of small wires close that is enough signal coupling that one can made 1 sec and slower tau readings. OR you do both the buffer and antennas you can test the OSC from across the room. Which side of the list do you think that should go on, advantages or disadvantages? If injection locking is an issue the efc gain with the loop open will differ from the efc gain with the loop closed. It will change the loop parameters in particular the efc gain. Its just a matter of how much it affects the efc gain. NO argument, The PLL loop is never opened. THAT will screw up everything and cause the injection, delta gain, etc. Sounds like it is time for someone to find or write another one of the fancy math papers that covers this case. ws * [time-nuts] Advantages Disadvantages of the TPLL Method Bruce Griffiths bruce.griffiths at xtra.co.nz Tue Jun 15 05:39:31 UTC 2010 WarrenS wrote: Bruce posted If and only if injection locking isn't significant. No problem then, because it is not significant. For each and every oscillator pair someone may try? Can place this one under the 'ADVANTAGE' side. That's descending into the murky realms of pseudoscience. At best you've only shown this to be true for the particular oscillator pair being compared. Not only must the effect of injection locking be insignificant for the reference, it has to be insignificant for the test oscillator as well. If injection locking is an issue the efc gain with the loop open will differ from the efc gain with the loop closed. I have tested this thoroughly in many ways. I do understand the concerns and doubts, especially with an unbuffered HP 10811 as the reference. The 10811s are pretty sensitive to injection locking and phase pulling. Unlike most other methods, one of the many unique properties that the TPLL method has is that injection locking is normally not a problem with it. It will change the loop parameters in particular the efc gain. Its just a matter of how much it affects the efc gain. I find it is generally unnecessary to buffer either the Ref Osc or the DUT. This is one of the many features that helps make the simple TPLL so simple. (also it does not hurt or change anything to add a proper buffer) The lack of injection locking is one of the advantages that contributes to its exceptional and unbelievable performance. But Adler's equation indicates that an oscillator is much more to susceptible to injection effects when the injected signal frequency is very close to the oscillator frequency. I did not leave the buffers out of the simple TPLL BB that was tested because of my lack of knowledge, but because of my extra knowledge on the subject that showed that they were unnecessary. More than once, I have tried to explain the reason why injection locking is not a problem with my version of the TPLL method, but until one proves it for their self, more words from me will not help. I do understand the skepticism and doubt, and I know why it is so hard to believe this for those that have not worked with is this type of method before. I guess someone should write one of those fancy math papers, if it has not already been done, that explains it in more convincing terms than I've been able to. It is hard for me to believe that paper has not already been written, But then it is hard for me to believe that the TPLL is not used more often.
Re: [time-nuts] Advantages Disadvantages of the TPLL Method
Bob posted Since it's dependent both on frequency offset and phase angle, When there is no freq offset as in the wsTPLL and no changing of phase angle, I'm saying that injection locking no longer applies. The thing that some may be missing is that the DUT Osc is cloned by the reference Osc. There is no significant difference between them. (within the PLL bandwidth which is than tau0) An oscillator is not going to injection to its self (as far as I know) NOW, Frequency offset due to loading effects, that is another issue and a possible problem, so I'm surprised it has not yet been brought up. I've seen an unfortunately large amount of data where injection locking was the issue. No argument, me too. That is why the lack of injection locking problems with the wsTPLL goes high on the advantage side. checking for it can be tricky. There are a number of ways of checking for it, No argument, and I do know how to test for it, I also know how to do integrate and I know how to add 2 + 2. What I do not know how to do is to get a simple, basic, obvious point across. ws ** [time-nuts] Advantages Disadvantages of the TPLL Method Bob Camp lists at rtty.us Tue Jun 15 11:48:10 UTC 2010 Hi With any phase lock system injection locking can indeed be a problem. Since it's dependent both on frequency offset and phase angle, checking for it can be tricky. I've seen an unfortunately large amount of data where injection locking was the issue. There are a number of ways of checking for it, each with their own issues (and hardware requirements). Bob * On Jun 15, 2010, at 1:39 AM, Bruce Griffiths wrote: WarrenS wrote: Bruce posted If and only if injection locking isn't significant. No problem then, because it is not significant. For each and every oscillator pair someone may try? Can place this one under the 'ADVANTAGE' side. That's descending into the murky realms of pseudoscience. At best you've only shown this to be true for the particular oscillator pair being compared. Not only must the effect of injection locking be insignificant for the reference, it has to be insignificant for the test oscillator as well. If injection locking is an issue the efc gain with the loop open will differ from the efc gain with the loop closed. I have tested this thoroughly in many ways. I do understand the concerns and doubts, especially with an unbuffered HP 10811 as the reference. The 10811s are pretty sensitive to injection locking and phase pulling. Unlike most other methods, one of the many unique properties that the TPLL method has is that injection locking is normally not a problem with it. It will change the loop parameters in particular the efc gain. Its just a matter of how much it affects the efc gain. I find it is generally unnecessary to buffer either the Ref Osc or the DUT. This is one of the many features that helps make the simple TPLL so simple. (also it does not hurt or change anything to add a proper buffer) The lack of injection locking is one of the advantages that contributes to its exceptional and unbelievable performance. But Adler's equation indicates that an oscillator is much more to susceptible to injection effects when the injected signal frequency is very close to the oscillator frequency. I did not leave the buffers out of the simple TPLL BB that was tested because of my lack of knowledge, but because of my extra knowledge on the subject that showed that they were unnecessary. More than once, I have tried to explain the reason why injection locking is not a problem with my version of the TPLL method, but until one proves it for their self, more words from me will not help. I do understand the skepticism and doubt, and I know why it is so hard to believe this for those that have not worked with is this type of method before. I guess someone should write one of those fancy math papers, if it has not already been done, that explains it in more convincing terms than I've been able to. It is hard for me to believe that paper has not already been written, But then it is hard for me to believe that the TPLL is not used more often. There are plenty of places that one of the TPLL methods well give the best overall solution. ws *** Bruce [time-nuts] Advantages Disadvantages of the TPLL Method Bruce Griffiths bruce.griffiths at xtra.co.nz WarrenS wrote: Long explanations, cause I try to explain, the best I can, when I say something is WRONG or misleading Magnus Posted: EFC linearity will remain an issue for analog oscillators. The oscillator gain will differ depending on offset voltage and temperature. TRUE it is an issue, but somewhat misleading because it need NOT be a problem or limitation (mostly) EFC Linearity can be an issue because the TPLL is limited by the performance of the reference oscillator in lots of ways. BUT Oscillator EFC gain or linearity are not likely to be of much
Re: [time-nuts] Advantages Disadvantages of the TPLL Method
Warren wrote: The thing that you (and maybe Adler?) are missing is that effect goes away when the two frequencies ARE exactly the same. I'm not talking close, I'm talking the exact same freq with phase held in quadrature within single digit femtoseconds. BIG difference, Once that is understood, then that sort of answers your other comments. Actually, this is not true. If either or both oscillators are affected by injection locking (and they pretty much all are, to some degree -- in this connection, note that you want to make measurements down to E-12 or better [I thought you mentioned E-14 somewhere early on], so even the least bit of IL will affect the results), what you have is two control inputs to the controlled oscillator (the EFC and the reference oscillator) and one control input to the reference oscillator (the oscillator under test, which is itself controlled by both EFC and the reference oscillator). They will reach equilibrium (unless the recursive feedback is unstable), but the locked frequency will be different from both oscillators' free-running frequency and the EFC will not correctly indicate the test oscillator deviation because it isn't the only control input in the system. Best regards, Charles ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Advantages Disadvantages of the TPLL Method
Hi If the two oscillators are locked by input to the EFC then the EFC voltage will reproduce the phase / frequency of the DUT on the reference (they are phase locked via the PLL). If the two oscillators are locked by injection locking, small changes in the EFC is no longer needed to keep them in phase / frequency alignment. The injection lock bypasses the pll within the injection lock bandwidth. It's a second control loop in parallel with the PLL. Since the two oscillators are already locked (by injection) the EFC information is suppressed within the injection lock bandwidth, but not outside it. It's not a brick wall filter, the normal stuff applies to exactly how much you have lost on the EFC from the injection lock. This is not some sort of math mumbo jumbo. I've physically seen it happen multiple times on real hardware on the bench in the lab. It happens on breadboards built from scratch. It happens with HP 3048's. It's a very real limit when doing any at output frequency PLL's. Bob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of WarrenS Sent: Tuesday, June 15, 2010 10:04 AM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Advantages Disadvantages of the TPLL Method Bob posted Since it's dependent both on frequency offset and phase angle, When there is no freq offset as in the wsTPLL and no changing of phase angle, I'm saying that injection locking no longer applies. The thing that some may be missing is that the DUT Osc is cloned by the reference Osc. There is no significant difference between them. (within the PLL bandwidth which is than tau0) An oscillator is not going to injection to its self (as far as I know) NOW, Frequency offset due to loading effects, that is another issue and a possible problem, so I'm surprised it has not yet been brought up. I've seen an unfortunately large amount of data where injection locking was the issue. No argument, me too. That is why the lack of injection locking problems with the wsTPLL goes high on the advantage side. checking for it can be tricky. There are a number of ways of checking for it, No argument, and I do know how to test for it, I also know how to do integrate and I know how to add 2 + 2. What I do not know how to do is to get a simple, basic, obvious point across. ws ** [time-nuts] Advantages Disadvantages of the TPLL Method Bob Camp lists at rtty.us Tue Jun 15 11:48:10 UTC 2010 Hi With any phase lock system injection locking can indeed be a problem. Since it's dependent both on frequency offset and phase angle, checking for it can be tricky. I've seen an unfortunately large amount of data where injection locking was the issue. There are a number of ways of checking for it, each with their own issues (and hardware requirements). Bob * On Jun 15, 2010, at 1:39 AM, Bruce Griffiths wrote: WarrenS wrote: Bruce posted If and only if injection locking isn't significant. No problem then, because it is not significant. For each and every oscillator pair someone may try? Can place this one under the 'ADVANTAGE' side. That's descending into the murky realms of pseudoscience. At best you've only shown this to be true for the particular oscillator pair being compared. Not only must the effect of injection locking be insignificant for the reference, it has to be insignificant for the test oscillator as well. If injection locking is an issue the efc gain with the loop open will differ from the efc gain with the loop closed. I have tested this thoroughly in many ways. I do understand the concerns and doubts, especially with an unbuffered HP 10811 as the reference. The 10811s are pretty sensitive to injection locking and phase pulling. Unlike most other methods, one of the many unique properties that the TPLL method has is that injection locking is normally not a problem with it. It will change the loop parameters in particular the efc gain. Its just a matter of how much it affects the efc gain. I find it is generally unnecessary to buffer either the Ref Osc or the DUT. This is one of the many features that helps make the simple TPLL so simple. (also it does not hurt or change anything to add a proper buffer) The lack of injection locking is one of the advantages that contributes to its exceptional and unbelievable performance. But Adler's equation indicates that an oscillator is much more to susceptible to injection effects when the injected signal frequency is very close to the oscillator frequency. I did not leave the buffers out of the simple TPLL BB that was tested because of my lack of knowledge, but because of my extra knowledge on the subject that showed that they were unnecessary. More than once, I have tried to explain the reason why injection locking is not a problem with my version of the TPLL method, but until one proves it for their self
Re: [time-nuts] Advantages Disadvantages of the TPLL Method
Charles posted: but the locked frequency will be different from both oscillators' free-running frequency and the EFC will not correctly indicate the test oscillator deviation because it isn't the only control input in the system. Good point and No argument (except for the deviation part) Because the EFC is the only control input THAT IS VARYING. Also what I have said in the past, maybe unclearly: NOW, Frequency offset due to loading effects, that is another issue and a possible problem, so I'm surprised it has not yet been brought up. The effects you are talking about are there and can be significant and are easy to measure (with a second TPLL tester) but the BIG IMPORTANT point is they are a fixed type of offset error and constant and do not effect the Delta EFC with delta freq change. The effect you state is a limit for the absolute accuracy of the DUT's frequency measurment that the tester can make but it does not limit the delta freq accuracy.(which is all that is really required for ADEV.) BTW the way I reduce that effect you are talking about so that it also becomes significant, compared to the accuracy of the Ref osc, is to add attenuator pads in both osc paths. This does raise the noise floor some, but the noise floor is so low that it can be raised and still not be significant compared to the Ref osc, so it allows a good compromise to be made. simple Example: Take an osc that has some IL, buffer up its output real good at 90 deg and now couple just a little of that buffered signal into the osc output. The 1e-11 to e-12 freq shift that will cause does not cause the osc to become unstable or have some other significant different EFC shape, It just causes the freq to change a little (offset) about the same as any other fixed and constant load would have. In any case there are lots of little subtle things that are going on that I can not address in a single email, so that is why all I clam is that the simple TPLL is better than the reference Osc, so it is good enough. And YES it can be made MUCH better, if one uses more than a single active part, but so what? for most things it is good enough as is. ** Charles posted: Warren wrote: The thing that you (and maybe Adler?) are missing is that effect goes away when the two frequencies ARE exactly the same. I'm not talking close, I'm talking the exact same freq with phase held in quadrature within single digit femtoseconds. BIG difference, Once that is understood, then that sort of answers your other comments. Actually, this is not true. If either or both oscillators are affected by injection locking (and they pretty much all are, to some degree -- in this connection, note that you want to make measurements down to E-12 or better [I thought you mentioned E-14 somewhere early on], so even the least bit of IL will affect the results), what you have is two control inputs to the controlled oscillator (the EFC and the reference oscillator) and one control input to the reference oscillator (the oscillator under test, which is itself controlled by both EFC and the reference oscillator). They will reach equilibrium (unless the recursive feedback is unstable), but the locked frequency will be different from both oscillators' free-running frequency and the EFC will not correctly indicate the test oscillator deviation because it isn't the only control input in the system. Best regards, Charles ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Advantages Disadvantages of the TPLL Method
I was surprised at the lack of it in this case. The 10811s are usually fairly vulnerable to it; you certainly can't feed two of them into the mixer on a 3048A without using isolation amps. But then, the loop BW is about a thousand times wider in the TPLL than in a traditional loose-PLL phase noise test set. -- john, KE5FX -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com]on Behalf Of Bob Camp Sent: Tuesday, June 15, 2010 4:48 AM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Advantages Disadvantages of the TPLL Method Hi With any phase lock system injection locking can indeed be a problem. Since it's dependent both on frequency offset and phase angle, checking for it can be tricky. I've seen an unfortunately large amount of data where injection locking was the issue. There are a number of ways of checking for it, each with their own issues (and hardware requirements). Bob ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Advantages Disadvantages of the TPLL Method
Bob posted: If the two oscillators are locked by injection locking, small changes in the EFC is no longer needed to keep them in phase / frequency alignment. No disagreement I guess the thing you may be missing is that there is so much gain and BW in the TPLL EFC feedback loop that it complexly overpowers any injection locking tendency and makes its effect insignificant This I have tested for in many ways, one way was to increase the cross coupling between the oscillators by 1000. If you can not believe that I know how to test for this or add 2 numbers, I'd suggest you try it for yourself with a TPLL and stop speculating how I'm wrong. Injection locking and its friends is not a problem with the simple TPLL tester using 10811 ref osc, and the 3db 5 db pads shown in my block diagram. ws Hi If the two oscillators are locked by input to the EFC then the EFC voltage will reproduce the phase / frequency of the DUT on the reference (they are phase locked via the PLL). If the two oscillators are locked by injection locking, small changes in the EFC is no longer needed to keep them in phase / frequency alignment. The injection lock bypasses the pll within the injection lock bandwidth. It's a second control loop in parallel with the PLL. Since the two oscillators are already locked (by injection) the EFC information is suppressed within the injection lock bandwidth, but not outside it. It's not a brick wall filter, the normal stuff applies to exactly how much you have lost on the EFC from the injection lock. This is not some sort of math mumbo jumbo. I've physically seen it happen multiple times on real hardware on the bench in the lab. It happens on breadboards built from scratch. It happens with HP 3048's. It's a very real limit when doing any at output frequency PLL's. Bob -Original Message- From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On Behalf Of WarrenS Sent: Tuesday, June 15, 2010 10:04 AM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Advantages Disadvantages of the TPLL Method Bob posted Since it's dependent both on frequency offset and phase angle, When there is no freq offset as in the wsTPLL and no changing of phase angle, I'm saying that injection locking no longer applies. The thing that some may be missing is that the DUT Osc is cloned by the reference Osc. There is no significant difference between them. (within the PLL bandwidth which is than tau0) An oscillator is not going to injection to its self (as far as I know) NOW, Frequency offset due to loading effects, that is another issue and a possible problem, so I'm surprised it has not yet been brought up. I've seen an unfortunately large amount of data where injection locking was the issue. No argument, me too. That is why the lack of injection locking problems with the wsTPLL goes high on the advantage side. checking for it can be tricky. There are a number of ways of checking for it, No argument, and I do know how to test for it, I also know how to do integrate and I know how to add 2 + 2. What I do not know how to do is to get a simple, basic, obvious point across. ws ** [time-nuts] Advantages Disadvantages of the TPLL Method Bob Camp lists at rtty.us Tue Jun 15 11:48:10 UTC 2010 Hi With any phase lock system injection locking can indeed be a problem. Since it's dependent both on frequency offset and phase angle, checking for it can be tricky. I've seen an unfortunately large amount of data where injection locking was the issue. There are a number of ways of checking for it, each with their own issues (and hardware requirements). Bob * On Jun 15, 2010, at 1:39 AM, Bruce Griffiths wrote: WarrenS wrote: Bruce posted If and only if injection locking isn't significant. No problem then, because it is not significant. For each and every oscillator pair someone may try? Can place this one under the 'ADVANTAGE' side. That's descending into the murky realms of pseudoscience. At best you've only shown this to be true for the particular oscillator pair being compared. Not only must the effect of injection locking be insignificant for the reference, it has to be insignificant for the test oscillator as well. If injection locking is an issue the efc gain with the loop open will differ from the efc gain with the loop closed. I have tested this thoroughly in many ways. I do understand the concerns and doubts, especially with an unbuffered HP 10811 as the reference. The 10811s are pretty sensitive to injection locking and phase pulling. Unlike most other methods, one of the many unique properties that the TPLL method has is that injection locking is normally not a problem with it. It will change the loop parameters in particular the efc gain. Its just a matter of how much it affects the efc gain. I find it is generally unnecessary to buffer either the Ref Osc or the DUT
Re: [time-nuts] Advantages Disadvantages of the TPLL Method
On 06/15/2010 03:28 PM, WarrenS wrote: Bruce posted But Adler's equation indicates that an oscillator is much more susceptible to injection effects when the injected signal frequency is very close to the oscillator frequency. No argument, BUT The thing that you (and maybe Adler?) are missing is that effect goes away when the two frequencies ARE exactly the same. I'm not talking close, I'm talking the exact same freq with phase held in quadrature within single digit femtoseconds. BIG difference, Once that is understood, then that sort of answers your other comments. Actually, as we have this in a PLL, it doesn't work out quite like that. Wolaver shows how the PLL is modified with an additional proportional path (his analysis is on active PI loop, but the additional proportional path also applies to active lag loops). For the active PI loop, the injection locking will modulate the PLL bandwidth. I would need to analyse the details for an active lag filter, but since the gain increases in the loop, so will the loop frequency. The implication for the EFC is that not all the gain goes through the amplifier, so the EFC deviations will become less. However, a tight PLL has high gain for starters, so unless there is very high injection gain the effect will be very modest. If the gain is calibrated during closed loop conditions and the injection is relatively stable, then the effect is essentially cancelled anyway. I would assume that the gain-change of typical injection is a small fraction of loop gain, so then it is a small effect that should not affect the results to much. It may be good to measure the injection gain and compare it to the loop gain. For a loose PLL, as being used for phase noise measurements, injection locking is a much bigger concern. But, the effect is there even when the frequency is the same. It is just that the application in tight PLL makes it very small. For each and every oscillator pair someone may try? Can't say for sure, I've only tried the ones I've tried, but even the ones that are highly susceptible were OK. At best you've only shown this to be true for the particular oscillator pair being compared. Yep, maybe I'm just real lucking again and it only applies to all the ones I've tested. That's descending into the murky realms of pseudoscience. OR as I see it, it is using just a little common sense. When is the last time you heard of a problem with an oscillator injection locking to it's self? I think these can be answered by much better arguments than pseudoscience or pure luck. The loop gain dominates over the injection gain and thus makes it a minor effect. and that by applying analysis. Not only must the effect of injection locking be insignificant for the reference, it has to be insignificant for the test oscillator as well. NO argument, If you are testing a DUT what this does effect, then one should buffer it or take other precaution. If you want to make sure the tester is not effecting the osc there is another choice besides the Buffer. DON'T connected it. The tester will work at better than -60 dB signal levels and if one just gets a couple of small wires close that is enough signal coupling that one can made 1 sec and slower tau readings. OR you do both the buffer and antennas you can test the OSC from across the room. Which side of the list do you think that should go on, advantages or disadvantages? Neither. It's a characteristic, it needs to be analyzed. If the DUT is very sensitive, then additional care may be taken or maybe it just isn't a very good solution. If injection locking is an issue the efc gain with the loop open will differ from the efc gain with the loop closed. It will change the loop parameters in particular the efc gain. Its just a matter of how much it affects the efc gain. NO argument, The PLL loop is never opened. THAT will screw up everything and cause the injection, delta gain, etc. Sounds like it is time for someone to find or write another one of the fancy math papers that covers this case. Page 102-104 in Dan Wolavers book covers this with sufficiently clarity that I could answer this. I have been trying to hint to this before. Anyway, page 103 is a very instructive conversion from different representations of a PI-loop with injection into a simpler form. The math follows up and remaining analysis becomes very easy to do. Cheers, Magnus ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Advantages Disadvantages of the TPLL Method
Bob posted The injection lock gain rises at 1/f. At some point it's going to be greater than the gain through the EFC. It would seem to me with that argument then nothing works, everything in the universal will all be at the same frequency sooner or later. fortunately The PLL feedback gain also rises due to the 'PI' integrator at the same 1/f rate, and starts out way ahead. Don't think the injection lock is ever going to catch up, at least not in OUR life times. The offset cause by the effect of Loading is a different subject, and has also been taken care of (good enough). ws * Hi The injection lock gain rises at 1/f. At some point it's going to be greater than the gain through the EFC. Bob -Original Message- From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On Behalf Of WarrenS Sent: Tuesday, June 15, 2010 1:37 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Advantages Disadvantages of the TPLL Method Bob posted: If the two oscillators are locked by injection locking, small changes in the EFC is no longer needed to keep them in phase / frequency alignment. No disagreement I guess the thing you may be missing is that there is so much gain and BW in the TPLL EFC feedback loop that it complexly overpowers any injection locking tendency and makes its effect insignificant This I have tested for in many ways, one way was to increase the cross coupling between the oscillators by 1000. If you can not believe that I know how to test for this or add 2 numbers, I'd suggest you try it for yourself with a TPLL and stop speculating how I'm wrong. Injection locking and its friends is not a problem with the simple TPLL tester using 10811 ref osc, and the 3db 5 db pads shown in my block diagram. ws Hi If the two oscillators are locked by input to the EFC then the EFC voltage will reproduce the phase / frequency of the DUT on the reference (they are phase locked via the PLL). If the two oscillators are locked by injection locking, small changes in the EFC is no longer needed to keep them in phase / frequency alignment. The injection lock bypasses the pll within the injection lock bandwidth. It's a second control loop in parallel with the PLL. Since the two oscillators are already locked (by injection) the EFC information is suppressed within the injection lock bandwidth, but not outside it. It's not a brick wall filter, the normal stuff applies to exactly how much you have lost on the EFC from the injection lock. This is not some sort of math mumbo jumbo. I've physically seen it happen multiple times on real hardware on the bench in the lab. It happens on breadboards built from scratch. It happens with HP 3048's. It's a very real limit when doing any at output frequency PLL's. Bob -Original Message- From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On Behalf Of WarrenS Sent: Tuesday, June 15, 2010 10:04 AM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Advantages Disadvantages of the TPLL Method Bob posted Since it's dependent both on frequency offset and phase angle, When there is no freq offset as in the wsTPLL and no changing of phase angle, I'm saying that injection locking no longer applies. The thing that some may be missing is that the DUT Osc is cloned by the reference Osc. There is no significant difference between them. (within the PLL bandwidth which is than tau0) An oscillator is not going to injection to its self (as far as I know) NOW, Frequency offset due to loading effects, that is another issue and a possible problem, so I'm surprised it has not yet been brought up. I've seen an unfortunately large amount of data where injection locking was the issue. No argument, me too. That is why the lack of injection locking problems with the wsTPLL goes high on the advantage side. checking for it can be tricky. There are a number of ways of checking for it, No argument, and I do know how to test for it, I also know how to do integrate and I know how to add 2 + 2. What I do not know how to do is to get a simple, basic, obvious point across. ws ** [time-nuts] Advantages Disadvantages of the TPLL Method Bob Camp lists at rtty.us Tue Jun 15 11:48:10 UTC 2010 Hi With any phase lock system injection locking can indeed be a problem. Since it's dependent both on frequency offset and phase angle, checking for it can be tricky. I've seen an unfortunately large amount of data where injection locking was the issue. There are a number of ways of checking for it, each with their own issues (and hardware requirements). Bob * On Jun 15, 2010, at 1:39 AM, Bruce Griffiths wrote: WarrenS wrote: Bruce posted If and only if injection locking isn't significant. No problem then, because it is not significant. For each and every oscillator pair someone may try? Can place
Re: [time-nuts] Advantages Disadvantages of the TPLL Method
Magnus posted a bunch of good stuff, Neither. It's a characteristic, it needs to be analyzed. If the DUT is very sensitive, then additional care may be taken or maybe it just isn't a very good solution. We have little disagreements for the most part. Except maybe for if it should be on 'the list'. The characteristics are what makes the advantages and disadvantages, so they belong on the list. The high natural rejection that the TPLL has to injection locking makes it much less sensitive than any other system, so it lets one keep it simple. TO me that is an advantage. I did test for the effect by connecting the REF osc to the DUT osc with a variable attenuator, and could not make the TPLL system start to fail until I the coupling got so low that it started to short out the two signals, and still it was working, just got a bit noisier I called the results of that test good enough and moved on to other ways of testing. All of which it also passed with flying colors Another subtle side effect of that advantages is that the cables do not to be shielded so well. example: If I bring a third osc's that is connect to a RG58 BNC shielded cable and is offset in freq by 1 to 10 Hz The effect of coupling (and or Injection locking) between to BNC shielded cables can be seem at the Tester output. What I have found is if I want to get the full accuracy of the TPLL, I can not have an offset osc cable on the same table, unless it is fully enclosed in a RF proof box. ws ** [time-nuts] Advantages Disadvantages of the TPLL Method Magnus Danielson magnus at rubidium.dyndns.org Tue Jun 15 17:53:49 UTC 2010 On 06/15/2010 03:28 PM, WarrenS wrote: Bruce posted But Adler's equation indicates that an oscillator is much more susceptible to injection effects when the injected signal frequency is very close to the oscillator frequency. No argument, BUT The thing that you (and maybe Adler?) are missing is that effect goes away when the two frequencies ARE exactly the same. I'm not talking close, I'm talking the exact same freq with phase held in quadrature within single digit femtoseconds. BIG difference, Once that is understood, then that sort of answers your other comments. Actually, as we have this in a PLL, it doesn't work out quite like that. Wolaver shows how the PLL is modified with an additional proportional path (his analysis is on active PI loop, but the additional proportional path also applies to active lag loops). For the active PI loop, the injection locking will modulate the PLL bandwidth. I would need to analyse the details for an active lag filter, but since the gain increases in the loop, so will the loop frequency. The implication for the EFC is that not all the gain goes through the amplifier, so the EFC deviations will become less. However, a tight PLL has high gain for starters, so unless there is very high injection gain the effect will be very modest. If the gain is calibrated during closed loop conditions and the injection is relatively stable, then the effect is essentially cancelled anyway. I would assume that the gain-change of typical injection is a small fraction of loop gain, so then it is a small effect that should not affect the results to much. It may be good to measure the injection gain and compare it to the loop gain. For a loose PLL, as being used for phase noise measurements, injection locking is a much bigger concern. But, the effect is there even when the frequency is the same. It is just that the application in tight PLL makes it very small. For each and every oscillator pair someone may try? Can't say for sure, I've only tried the ones I've tried, but even the ones that are highly susceptible were OK. At best you've only shown this to be true for the particular oscillator pair being compared. Yep, maybe I'm just real lucking again and it only applies to all the ones I've tested. That's descending into the murky realms of pseudoscience. OR as I see it, it is using just a little common sense. When is the last time you heard of a problem with an oscillator injection locking to it's self? I think these can be answered by much better arguments than pseudoscience or pure luck. The loop gain dominates over the injection gain and thus makes it a minor effect. and that by applying analysis. Not only must the effect of injection locking be insignificant for the reference, it has to be insignificant for the test oscillator as well. NO argument, If you are testing a DUT what this does effect, then one should buffer it or take other precaution. If you want to make sure the tester is not effecting the osc there is another choice besides the Buffer. DON'T connected it. The tester will work at better than -60 dB signal levels and if one just gets a couple of small wires close that is enough signal coupling that one can made 1 sec and slower tau readings. OR you do both the buffer and antennas you can test the OSC from across the
Re: [time-nuts] Advantages Disadvantages of the TPLL Method
Hi Warren, On 06/15/2010 08:49 PM, WarrenS wrote: Magnus posted a bunch of good stuff, Neither. It's a characteristic, it needs to be analyzed. If the DUT is very sensitive, then additional care may be taken or maybe it just isn't a very good solution. We have little disagreements for the most part. Except maybe for if it should be on 'the list'. The characteristics are what makes the advantages and disadvantages, so they belong on the list. Well, it depends on the oscillators involved... so it is just not given... but assuming a fairly typical oscillator for our world, then it would end up on the advantage side. The high natural rejection that the TPLL has to injection locking makes it much less sensitive than any other system, so it lets one keep it simple. TO me that is an advantage. Hmm, yes... for the typical oscillator yes... I did test for the effect by connecting the REF osc to the DUT osc with a variable attenuator, and could not make the TPLL system start to fail until I the coupling got so low that it started to short out the two signals, and still it was working, just got a bit noisier I called the results of that test good enough and moved on to other ways of testing. All of which it also passed with flying colors Noiser as you added gain... Another subtle side effect of that advantages is that the cables do not to be shielded so well. example: If I bring a third osc's that is connect to a RG58 BNC shielded cable and is offset in freq by 1 to 10 Hz The effect of coupling (and or Injection locking) between to BNC shielded cables can be seem at the Tester output. What I have found is if I want to get the full accuracy of the TPLL, I can not have an offset osc cable on the same table, unless it is fully enclosed in a RF proof box. That would help, definitly. Cheers, Magnus ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Advantages Disadvantages of the TPLL Method
I promised myself I would not get into this any more, but here we go again... WarrenS warrensjmail-...@yahoo.com wrote: Charles posted: but the locked frequency will be different from both oscillators' free-running frequency and the EFC will not correctly indicate the test oscillator deviation because it isn't the only control input in the system. Good point and No argument (except for the deviation part) Because the EFC is the only control input THAT IS VARYING. Any parasitic control input is a problem in that system, like any other system. I thought the point of all this was to measure the noise of an oscillator? If it is noisy (and they all are, to some level, otherwise you would not need to measure it), then its frequency (or phase) is varying. If the test oscillator is coupled (via injection locking) to the reference oscillator, the test oscillator will force the ref oscillator to follow its noise without the need to move the EFC. The EFC voltage will be stable (because the oscillators move together), while you have two synchronously noisy oscillators. If you measure the EFC, you will be left to believe your oscillator is better than it is. Please note that the effect is not simply a scaling factor, because injection locking is a non-linear effect, or rather it is a mostly linear effect over a typically very limited dynamic range. Small variations will be totally coupled, where larger ones could possibly unlock the oscillators, producing steps in the EFC voltage. Said another way, you cannot eliminate the effects of injection locking by post-processing the data. Injection locking is a parasitic control input and it is a problem with ANY method that purports to measure noise. Ignore it at your own risk, but don't say it does not matter, unless you want to prove something we already know. Didier ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Advantages Disadvantages of the TPLL Method
Hi What is the configuration of your loop? Bob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of WarrenS Sent: Tuesday, June 15, 2010 2:16 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Advantages Disadvantages of the TPLL Method Bob posted The injection lock gain rises at 1/f. At some point it's going to be greater than the gain through the EFC. It would seem to me with that argument then nothing works, everything in the universal will all be at the same frequency sooner or later. fortunately The PLL feedback gain also rises due to the 'PI' integrator at the same 1/f rate, and starts out way ahead. Don't think the injection lock is ever going to catch up, at least not in OUR life times. The offset cause by the effect of Loading is a different subject, and has also been taken care of (good enough). ws * Hi The injection lock gain rises at 1/f. At some point it's going to be greater than the gain through the EFC. Bob -Original Message- From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On Behalf Of WarrenS Sent: Tuesday, June 15, 2010 1:37 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Advantages Disadvantages of the TPLL Method Bob posted: If the two oscillators are locked by injection locking, small changes in the EFC is no longer needed to keep them in phase / frequency alignment. No disagreement I guess the thing you may be missing is that there is so much gain and BW in the TPLL EFC feedback loop that it complexly overpowers any injection locking tendency and makes its effect insignificant This I have tested for in many ways, one way was to increase the cross coupling between the oscillators by 1000. If you can not believe that I know how to test for this or add 2 numbers, I'd suggest you try it for yourself with a TPLL and stop speculating how I'm wrong. Injection locking and its friends is not a problem with the simple TPLL tester using 10811 ref osc, and the 3db 5 db pads shown in my block diagram. ws Hi If the two oscillators are locked by input to the EFC then the EFC voltage will reproduce the phase / frequency of the DUT on the reference (they are phase locked via the PLL). If the two oscillators are locked by injection locking, small changes in the EFC is no longer needed to keep them in phase / frequency alignment. The injection lock bypasses the pll within the injection lock bandwidth. It's a second control loop in parallel with the PLL. Since the two oscillators are already locked (by injection) the EFC information is suppressed within the injection lock bandwidth, but not outside it. It's not a brick wall filter, the normal stuff applies to exactly how much you have lost on the EFC from the injection lock. This is not some sort of math mumbo jumbo. I've physically seen it happen multiple times on real hardware on the bench in the lab. It happens on breadboards built from scratch. It happens with HP 3048's. It's a very real limit when doing any at output frequency PLL's. Bob -Original Message- From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On Behalf Of WarrenS Sent: Tuesday, June 15, 2010 10:04 AM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Advantages Disadvantages of the TPLL Method Bob posted Since it's dependent both on frequency offset and phase angle, When there is no freq offset as in the wsTPLL and no changing of phase angle, I'm saying that injection locking no longer applies. The thing that some may be missing is that the DUT Osc is cloned by the reference Osc. There is no significant difference between them. (within the PLL bandwidth which is than tau0) An oscillator is not going to injection to its self (as far as I know) NOW, Frequency offset due to loading effects, that is another issue and a possible problem, so I'm surprised it has not yet been brought up. I've seen an unfortunately large amount of data where injection locking was the issue. No argument, me too. That is why the lack of injection locking problems with the wsTPLL goes high on the advantage side. checking for it can be tricky. There are a number of ways of checking for it, No argument, and I do know how to test for it, I also know how to do integrate and I know how to add 2 + 2. What I do not know how to do is to get a simple, basic, obvious point across. ws ** [time-nuts] Advantages Disadvantages of the TPLL Method Bob Camp lists at rtty.us Tue Jun 15 11:48:10 UTC 2010 Hi With any phase lock system injection locking can indeed be a problem. Since it's dependent both on frequency offset and phase angle, checking for it can be tricky. I've seen an unfortunately large amount of data where injection locking was the issue. There are a number of ways of checking for it, each
Re: [time-nuts] Advantages Disadvantages of the TPLL Method
Warren wrote: Charles posted: but the locked frequency will be different from both oscillators' free-running frequency and the EFC will not correctly indicate the test oscillator deviation because it isn't the only control input in the system. Good point and No argument (except for the deviation part) Because the EFC is the only control input THAT IS VARYING. No, it's not. The strength with which each oscillator pulls on the other also varies as the equilibrium frequency (the result of all three recursive control inputs) moves around relative to the two instantaneous free-running frequencies. How much EFC is required depends, in part, on the strength of the pulling. There are three varying inputs. Magnus suggested that the effect of injection locking may be enough smaller than the EFC input that it has little practical significance. That may be so, but when dealing with measurement accuracy in the hundreds or tens ot ppt, this needs to be verified by the results of carefully constructed experiments and hopefully also supported by mathematical analysis. Best regards, Charles ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Advantages Disadvantages of the TPLL Method
Charles Posted: when dealing with measurement accuracy in the hundreds or tens of ppt, this needs to be verified by the results of carefully constructed experiments and hopefully also supported by mathematical analysis. No argument, on that part. The carefully constructed experiments, that show it works as advertised have been done, and the most important ones have been posted. (unless you mean the experiments must be done by you) Still waiting for someone to do the mathematical analysis. How much EFC is required depends, in part, on the strength of the pulling. There are three varying inputs. NOT at ALL what my test have shown so I guess we do NOT agree on this. The point you missed, is only the EFC is changing significantly because of the high gain and BW. It insures the two Oscillators are held to within femtoseconds of each other, to at least out to the e-16 at large taus. So other things are held constant enough that their effects are kept below any ref Osc effects. But no mater who is correct, It does work, which is the more important thing at this stage. ws *** time-nuts] Advantages Disadvantages of the TPLL Method Charles P. Steinmetz charles_steinmetz at lavabit.com Wed Jun 16 03:45:03 UTC 2010 Warren wrote: Charles posted: but the locked frequency will be different from both oscillators' free-running frequency and the EFC will not correctly indicate the test oscillator deviation because it isn't the only control input in the system. Good point and No argument (except for the deviation part) Because the EFC is the only control input THAT IS VARYING. No, it's not. The strength with which each oscillator pulls on the other also varies as the equilibrium frequency (the result of all three recursive control inputs) moves around relative to the two instantaneous free-running frequencies. How much EFC is required depends, in part, on the strength of the pulling. There are three varying inputs. Magnus suggested that the effect of injection locking may be enough smaller than the EFC input that it has little practical significance. That may be so, but when dealing with measurement accuracy in the hundreds or tens ot ppt, this needs to be verified by the results of carefully constructed experiments and hopefully also supported by mathematical analysis. Best regards, Charles ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Advantages Disadvantages of the TPLL Method
On 06/16/2010 05:45 AM, Charles P. Steinmetz wrote: Warren wrote: Charles posted: but the locked frequency will be different from both oscillators' free-running frequency and the EFC will not correctly indicate the test oscillator deviation because it isn't the only control input in the system. Good point and No argument (except for the deviation part) Because the EFC is the only control input THAT IS VARYING. No, it's not. The strength with which each oscillator pulls on the other also varies as the equilibrium frequency (the result of all three recursive control inputs) moves around relative to the two instantaneous free-running frequencies. How much EFC is required depends, in part, on the strength of the pulling. There are three varying inputs. Magnus suggested that the effect of injection locking may be enough smaller than the EFC input that it has little practical significance. That may be so, but when dealing with measurement accuracy in the hundreds or tens ot ppt, this needs to be verified by the results of carefully constructed experiments and hopefully also supported by mathematical analysis. What you get is a scale error. Consider that you have an amplifier gain of 1000 and the injection locking provide a gain of 1, that will result in actual gain of 1001 and the gain error on the EFC will become 1000/1001. Considering that Allan deviation estimation has problem of its own, this scale error is not significant. What you do need to check is that the relationship between intended gain and injection gain is sufficiently different. Since oscillator frequency from EFC may not be completely correct, we already want calibration of that scale factor (K_O) and the gain error due to injection locking would be included into that correction factor. So, sufficiently small amount of injection locking gain will change the apparent EFC coefficient K_O [Rad/sV] on which the scale of TPLL frequency measurements depends. The fractional frequency observed is y(t) = 2*pi*f_0 / K_O,eff EFC(t) Cheers, Magnus ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Advantages Disadvantages of the TPLL Method
Steve, On 06/14/2010 04:49 AM, Steve Rooke wrote: On 14 June 2010 10:46, Magnus Danielsonmag...@rubidium.dyndns.org wrote: Still puts it in the mid-tau range as a method. The useful range and precision of a particular implementation of the method will vary. By putting a GPSDO in the usual place of the DUT and putting the 10811 in place of the reference oscillator it could work well beyond the 1000s point. CAVEAT: this only works for a DUT that has an EFC that is reasonably linear. EFC linearity will remain an issue for analog oscillators. The oscillator gain will differ depending on offset voltage and temperature. So if you are just thinking about the TPLL for taking ADEV data from 0.1 to 1000 sec, then you're are missing 90% of the other useful stuff it can do as good or better than most anything thing else out there, and all for the same $10 (my cost). The typical price-tag of a 10811 is in 100-150 USD. I think it is reasonable to assume that a TPLL weighs in at about 200 USD with all support mixers, amplifiers, ADCs etc. It's not bad, but if you don't have the parts that's about what you need to spend at least. If you really wanted to be a scrooge, you could open the case on one of those plethera of HP intruments and temporarily borrow that 10811 that is just sitting there. As for something like a ADC, you could find a DAQ on fleeBay which could do duty here and also be a useful tool for general purpose use. Heck, you can use your sound card to digitize the EFC, provided it is DC coupled. If you don't have the parts, then it will set you back with at least that number. If you have the parts, you have already invested in them and payed for them that way. You may be lucky to be given the oscillator, but honestly you can't rely on that. I just want the cost numbers to be more reasonably given. It is still a fairly cheap solution. BTW, with a couple of minor configuration changes, the TPLL BreadBoard can be transformed into a LPLL, so the usefulness of the basic Universal TPLL BB circuit has even more possibilities. In fact one could make yet another list of all the additional things it can do with no added cost, just by changing a few jumpers and values. But those things are for later discussions, one windmill at a time. Measurement of phase noise is what the LPLL is good at, especially when done in cross-correlation mode. Interferometric setups use the mixers better. Both these techniques could be used for LPLL and TPLL measures. Do you have some pointers to these setups please Magnus? Look at Enrico Rubiolas site where his publications and presentations should be inspirational. His focus is on LPLLs. but the methodology of cross-correlation and interferometric setup should be as viable in the TPLL world. Cheers, Magnus ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Advantages Disadvantages of the TPLL Method
Thanks Magnus! On 14 June 2010 20:45, Magnus Danielson mag...@rubidium.dyndns.org wrote: Steve, On 06/14/2010 04:49 AM, Steve Rooke wrote: On 14 June 2010 10:46, Magnus Danielsonmag...@rubidium.dyndns.org wrote: Still puts it in the mid-tau range as a method. The useful range and precision of a particular implementation of the method will vary. By putting a GPSDO in the usual place of the DUT and putting the 10811 in place of the reference oscillator it could work well beyond the 1000s point. CAVEAT: this only works for a DUT that has an EFC that is reasonably linear. EFC linearity will remain an issue for analog oscillators. The oscillator gain will differ depending on offset voltage and temperature. So if you are just thinking about the TPLL for taking ADEV data from 0.1 to 1000 sec, then you're are missing 90% of the other useful stuff it can do as good or better than most anything thing else out there, and all for the same $10 (my cost). The typical price-tag of a 10811 is in 100-150 USD. I think it is reasonable to assume that a TPLL weighs in at about 200 USD with all support mixers, amplifiers, ADCs etc. It's not bad, but if you don't have the parts that's about what you need to spend at least. If you really wanted to be a scrooge, you could open the case on one of those plethera of HP intruments and temporarily borrow that 10811 that is just sitting there. As for something like a ADC, you could find a DAQ on fleeBay which could do duty here and also be a useful tool for general purpose use. Heck, you can use your sound card to digitize the EFC, provided it is DC coupled. If you don't have the parts, then it will set you back with at least that number. If you have the parts, you have already invested in them and payed for them that way. You may be lucky to be given the oscillator, but honestly you can't rely on that. I just want the cost numbers to be more reasonably given. It is still a fairly cheap solution. BTW, with a couple of minor configuration changes, the TPLL BreadBoard can be transformed into a LPLL, so the usefulness of the basic Universal TPLL BB circuit has even more possibilities. In fact one could make yet another list of all the additional things it can do with no added cost, just by changing a few jumpers and values. But those things are for later discussions, one windmill at a time. Measurement of phase noise is what the LPLL is good at, especially when done in cross-correlation mode. Interferometric setups use the mixers better. Both these techniques could be used for LPLL and TPLL measures. Do you have some pointers to these setups please Magnus? Look at Enrico Rubiolas site where his publications and presentations should be inspirational. His focus is on LPLLs. but the methodology of cross-correlation and interferometric setup should be as viable in the TPLL world. Cheers, Magnus ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. -- Steve Rooke - ZL3TUV G8KVD The only reason for time is so that everything doesn't happen at once. - Einstein ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Advantages Disadvantages of the TPLL Method
Long explanations, cause I try to explain, the best I can, when I say something is WRONG or misleading Magnus Posted: EFC linearity will remain an issue for analog oscillators. The oscillator gain will differ depending on offset voltage and temperature. TRUE it is an issue, but somewhat misleading because it need NOT be a problem or limitation (mostly) EFC Linearity can be an issue because the TPLL is limited by the performance of the reference oscillator in lots of ways. BUT Oscillator EFC gain or linearity are not likely to be of much concern or a limitation for high end performance. The gain nonlinearity I've measured can vary two to one over the full range of a good Oscillator but it is more like 10% over the normally used range, if one stays well away from the end points. NOT so good but livable if you are not making something real accurate. BUT For all my accurate stuff, when using a HP 10811, I limit the full-scale change to 1e-9 or 1e-8 at most. This uses such a small part of the total EFC range, that the nonlinearity effects are generally below the noise level and of little concern at all. The fact that Oscillator gain does differ with the EFC voltage (offset voltage), means if you want to get max accuracy out of the TPLL, it will need to be calibrated at the EFC offset voltage it is being used at. One simple solution, if the OSC also has a independent manual Freq adjustment like the single oven 10811, is to use it always set the EFC voltage to be near zero volts. BTW calibration need not be much of a problem, because it can be a static calibration. What I use for a finial calibration check is the 2G turn over, which I measure very accurately by other means before hand and then use that as a known freq offset to check operation and calibration. Of course there are any number of other ways. As far as temperature having ANY effect on EFC gain, that is a total NON issue. If temperature had any effect on EFC Gain then Temperature would also effect Osc Frequency at a fixed EFC voltage, which would then effect the OSC freq drift and stability, that would then effect anything that the Osc was used for, NOT just the TPLL. The TPLL actually has a slight advantage over other methods, because the PLL will adjust the freq to be correct, even if the EFC effect should change. I think it is reasonable to assume that a TPLL weighs in at about 200 USD with all support mixers, amplifiers, ADCs etc. if you don't have the parts It is still a fairly cheap solution. Yes I think that is ONE reasonable number to use and a fair conclusion. BUT there are others. The EBAY cost of the TPLL can be easy under $10, not including the reference Osc and the ADC. Do note, NONE of items above are plural, Only one is needed per system unlike some other methods. Because the cost of the Ref Osc is so variable and depends so much on what one is doing, I have noticed that its cost is generally not included in the base price. I think even on the $20K+ TSC 5120A that the reference Osc is an extra cost option. The ADC is another BIG variable, depending on your needs and skill level and junk box, almost no limit in cost at the high end, and can be as low as $0.00 dollars if you are a student doing a science project. It can also be as low as $1.00 if one is good at programming PICS or other micros with built in ADC's. The only other major part in the TPLL with any cost over $1 is the Phase detector. The one I use most is a micro-circuits $15 single price device, but I've used all sorts of dual balanced mixers, and if one is real cheap and good at design, I have found that a PD based on a 50 cent XOR gate works fine. ws * On 14 June 2010 10:46, Magnus Danielson Posted: Steve Still puts it in the mid-tau range as a method. The useful range and precision of a particular implementation of the method will vary. By putting a GPSDO in the usual place of the DUT and putting the 10811 in place of the reference oscillator it could work well beyond the 1000s point. CAVEAT: this only works for a DUT that has an EFC that is reasonably linear. EFC linearity will remain an issue for analog oscillators. The oscillator gain will differ depending on offset voltage and temperature. So if you are just thinking about the TPLL for taking ADEV data from 0.1 to 1000 sec, then you're are missing 90% of the other useful stuff it can do as good or better than most anything thing else out there, and all for the same $10 (my cost). The typical price-tag of a 10811 is in 100-150 USD. I think it is reasonable to assume that a TPLL weighs in at about 200 USD with all support mixers, amplifiers, ADCs etc. It's not bad, but if you don't have the parts that's about what you need to spend at least. If you really wanted to be a scrooge, you could open the case on one of those plethera of HP intruments and temporarily borrow that 10811 that is just sitting there.
Re: [time-nuts] Advantages Disadvantages of the TPLL Method
Steve posted Add smilies as you see fit. But can it make a decent cup of char? Can you add a cup-holder, those are essential these days. So does it grind wheat to make flower then; by golly, this thing is versatile. Funny or sarcastic, depending where one puts the smilies, but I would not yet count anything out. :-) A major limitation for me with the simple TPLL has been it only test things that are very close in freq to it's reference Frequency, which I mistakenly considered was the same as it's controlled Ref oscillator . Necessity can be the mother of innovation I recently had a need to test an off freq Osc that was not within range of the 10811 Osc I normally use with my TPLL. Simple solution turned out to be. Use the TPLL's controlled 10811 as the reference for my freq synthesizer and use the fully adjustable synthesizer output as the reference freq of the TPLL. After a couple of minor changes in level and Bandwidth, I now have a full frequency range TPLL tester. OF course the performance is still limited by the quality and B/W of the TPLL's reference signal which now must include any synthesizer limitations, BUT being limited to a single fixed frequency is no longer one of the limitations. IN fact it is now obvious to me that ANY reference freq can be used with the simple TPLL, as long as it is derived in some way from a EFC controlled OSC. The controlled oscillator freq can be divided, multiplied, mixed up or down or used with a synthesizer, same as any PLL, and this opens up a whole new range of uses for the TPLL. (and a new set of trade offs) No longer a $10 solution, but then a had an eBay synthesizer setting around already, so it did not add any extra cost for me. ws ** [time-nuts] Advantages Disadvantages of the TPLL Method Steve Rooke sar10538 at gmail.com Mon Jun 14 02:37:32 UTC 2010 Warren, Penny dropped! On 14 June 2010 05:29, WarrenS warrensjmail-one at yahoo.com wrote: Magnus Posted The TPLL is a mid-tau stability test, since it's sweet-spot is in the 0,1 - 1000 s range. Short-term is better handled in LPLL phase-noise measurements. Mostly agree, it is a mid-tau device, but also consider: The simple TPLL can be used to find the 1ms to 10 ms ADEV as good and maybe? better than ANYthing else. AND I use it to find the drift and ADEV of my dual oven HP 10811's out to weeks, so there is no long term limit. (the trick is to control the DUT and not the Reference when doing long term testing) Of course, provided that the DUT has an EFC, you can put this in place of the reference oscillator and put a, say, GPSDO in place of where the DUT normally goes. This will certainly extend things at long Tau out as far as you wish. As for short tau, it would be better to convert the circuit to LPLL. BUT I find the TPLL method is useful for MUCH more than just getting ADEV data. As such it's sweet spot extends from below 0.004 ms (250 Hz) all the way up to weeks, when the DUT is the controlled Osc. Either 0.004 s or 4 ms methinks. You would have to make sure that the B/W from the mixer out right to the ability to control the reference oscillator is that wide. This could be verified by breaking off the EFC and injecting 250Hz into there and seeing if the original feed to the EFC follows it. ALSO the simple TPLL is very Good and useful for seeing and measuring the effects of temperature, line noise, vibration, PS, load, and just about everything else that effects the frequency stability of an oscillators below 1 KHz or so. Providing that the reference oscillator is not subjected to those effects at the same time (isolation). So if you are just thinking about the TPLL for taking ADEV data from 0.1 to 1000 sec, then you're are missing 90% of the other useful stuff it can do as good or better than most anything thing else out there, and all for the same $10 (my cost). If you have some stock items that you can borrow for this job and not just dedicate it to the TPLL. Still, that is not an unreasonable assumption for many. If still in doubt about some of the TPLL's other high end performance capabilities, try the swinging osc test with ANYthing else and see if you can match the simple TPLL's performance. If one would make a list for the non ADEV uses and advantages of the simple TPLL It would indeed be very long list, and it does not take any fancy write up to see that, just a bit of open minded thinking. But can it make a decent cup of char? BTW, with a couple of minor configuration changes, the TPLL BreadBoard can be transformed into a LPLL, so the usefulness of the basic Universal TPLL BB circuit has even more possibilities. In fact one could make yet another list of all the additional things it can do with no added cost, Can you add a cup-holder, those are essential these days. just by changing a few jumpers and values. But those things are for later discussions, one windmill at a time. So
Re: [time-nuts] Advantages Disadvantages of the TPLL Method
WarrenS wrote: Long explanations, cause I try to explain, the best I can, when I say something is WRONG or misleading Magnus Posted: EFC linearity will remain an issue for analog oscillators. The oscillator gain will differ depending on offset voltage and temperature. TRUE it is an issue, but somewhat misleading because it need NOT be a problem or limitation (mostly) EFC Linearity can be an issue because the TPLL is limited by the performance of the reference oscillator in lots of ways. BUT Oscillator EFC gain or linearity are not likely to be of much concern or a limitation for high end performance. The gain nonlinearity I've measured can vary two to one over the full range of a good Oscillator but it is more like 10% over the normally used range, if one stays well away from the end points. NOT so good but livable if you are not making something real accurate. BUT For all my accurate stuff, when using a HP 10811, I limit the full-scale change to 1e-9 or 1e-8 at most. This uses such a small part of the total EFC range, that the nonlinearity effects are generally below the noise level and of little concern at all. The fact that Oscillator gain does differ with the EFC voltage (offset voltage), means if you want to get max accuracy out of the TPLL, it will need to be calibrated at the EFC offset voltage it is being used at. One simple solution, if the OSC also has a independent manual Freq adjustment like the single oven 10811, is to use it always set the EFC voltage to be near zero volts. BTW calibration need not be much of a problem, because it can be a static calibration. If and only if injection locking isn't significant. This needs to be established for each setup. The simplest way to take the effects of injection locking into account is to measure the effective EFC gain with the loop closed. What I use for a finial calibration check is the 2G turn over, which I measure very accurately by other means before hand and then use that as a known freq offset to check operation and calibration. Of course there are any number of other ways. As far as temperature having ANY effect on EFC gain, that is a total NON issue. If temperature had any effect on EFC Gain then Temperature would also effect Osc Frequency at a fixed EFC voltage, which would then effect the OSC freq drift and stability, that would then effect anything that the Osc was used for, NOT just the TPLL. The TPLL actually has a slight advantage over other methods, because the PLL will adjust the freq to be correct, even if the EFC effect should change. I think it is reasonable to assume that a TPLL weighs in at about 200 USD with all support mixers, amplifiers, ADCs etc. if you don't have the parts It is still a fairly cheap solution. Yes I think that is ONE reasonable number to use and a fair conclusion. BUT there are others. The EBAY cost of the TPLL can be easy under $10, not including the reference Osc and the ADC. Do note, NONE of items above are plural, Only one is needed per system unlike some other methods. Because the cost of the Ref Osc is so variable and depends so much on what one is doing, I have noticed that its cost is generally not included in the base price. I think even on the $20K+ TSC 5120A that the reference Osc is an extra cost option. The ADC is another BIG variable, depending on your needs and skill level and junk box, almost no limit in cost at the high end, and can be as low as $0.00 dollars if you are a student doing a science project. It can also be as low as $1.00 if one is good at programming PICS or other micros with built in ADC's. The only other major part in the TPLL with any cost over $1 is the Phase detector. The one I use most is a micro-circuits $15 single price device, but I've used all sorts of dual balanced mixers, and if one is real cheap and good at design, I have found that a PD based on a 50 cent XOR gate works fine. ws * Bruce On 14 June 2010 10:46, Magnus Danielson Posted: Steve Still puts it in the mid-tau range as a method. The useful range and precision of a particular implementation of the method will vary. By putting a GPSDO in the usual place of the DUT and putting the 10811 in place of the reference oscillator it could work well beyond the 1000s point. CAVEAT: this only works for a DUT that has an EFC that is reasonably linear. EFC linearity will remain an issue for analog oscillators. The oscillator gain will differ depending on offset voltage and temperature. So if you are just thinking about the TPLL for taking ADEV data from 0.1 to 1000 sec, then you're are missing 90% of the other useful stuff it can do as good or better than most anything thing else out there, and all for the same $10 (my cost). The typical price-tag of a 10811 is in 100-150 USD. I think it is reasonable to assume that a TPLL weighs in at about 200 USD with all support mixers, amplifiers, ADCs etc.
Re: [time-nuts] Advantages Disadvantages of the TPLL Method
Bruce posted If and only if injection locking isn't significant. No problem then, because it is not significant. Can place this one under the 'ADVANTAGE' side. I have tested this thoroughly in many ways. I do understand the concerns and doubts, especially with an unbuffered HP 10811 as the reference. The 10811s are pretty sensitive to injection locking and phase pulling. Unlike most other methods, one of the many unique properties that the TPLL method has is that injection locking is normally not a problem with it. I find it is generally unnecessary to buffer either the Ref Osc or the DUT. This is one of the many features that helps make the simple TPLL so simple. (also it does not hurt or change anything to add a proper buffer) The lack of injection locking is one of the advantages that contributes to its exceptional and unbelievable performance. I did not leave the buffers out of the simple TPLL BB that was tested because of my lack of knowledge, but because of my extra knowledge on the subject that showed that they were unnecessary. More than once, I have tried to explain the reason why injection locking is not a problem with my version of the TPLL method, but until one proves it for their self, more words from me will not help. I do understand the skepticism and doubt, and I know why it is so hard to believe this for those that have not worked with is this type of method before. I guess someone should write one of those fancy math papers, if it has not already been done, that explains it in more convincing terms than I've been able to. It is hard for me to believe that paper has not already been written, But then it is hard for me to believe that the TPLL is not used more often. There are plenty of places that one of the TPLL methods well give the best overall solution. ws *** [time-nuts] Advantages Disadvantages of the TPLL Method Bruce Griffiths bruce.griffiths at xtra.co.nz WarrenS wrote: Long explanations, cause I try to explain, the best I can, when I say something is WRONG or misleading Magnus Posted: EFC linearity will remain an issue for analog oscillators. The oscillator gain will differ depending on offset voltage and temperature. TRUE it is an issue, but somewhat misleading because it need NOT be a problem or limitation (mostly) EFC Linearity can be an issue because the TPLL is limited by the performance of the reference oscillator in lots of ways. BUT Oscillator EFC gain or linearity are not likely to be of much concern or a limitation for high end performance. The gain nonlinearity I've measured can vary two to one over the full range of a good Oscillator but it is more like 10% over the normally used range, if one stays well away from the end points. NOT so good but livable if you are not making something real accurate. BUT For all my accurate stuff, when using a HP 10811, I limit the full-scale change to 1e-9 or 1e-8 at most. This uses such a small part of the total EFC range, that the nonlinearity effects are generally below the noise level and of little concern at all. The fact that Oscillator gain does differ with the EFC voltage (offset voltage), means if you want to get max accuracy out of the TPLL, it will need to be calibrated at the EFC offset voltage it is being used at. One simple solution, if the OSC also has a independent manual Freq adjustment like the single oven 10811, is to use it always set the EFC voltage to be near zero volts. BTW calibration need not be much of a problem, because it can be a static calibration. If and only if injection locking isn't significant. This needs to be established for each setup. The simplest way to take the effects of injection locking into account is to measure the effective EFC gain with the loop closed. What I use for a finial calibration check is the 2G turn over, which I measure very accurately by other means before hand and then use that as a known freq offset to check operation and calibration. Of course there are any number of other ways. As far as temperature having ANY effect on EFC gain, that is a total NON issue. If temperature had any effect on EFC Gain then Temperature would also effect Osc Frequency at a fixed EFC voltage, which would then effect the OSC freq drift and stability, that would then effect anything that the Osc was used for, NOT just the TPLL. The TPLL actually has a slight advantage over other methods, because the PLL will adjust the freq to be correct, even if the EFC effect should change. I think it is reasonable to assume that a TPLL weighs in at about 200 USD with all support mixers, amplifiers, ADCs etc. if you don't have the parts It is still a fairly cheap solution. Yes I think that is ONE reasonable number to use and a fair conclusion. BUT there are others. The EBAY cost of the TPLL can be easy under $10, not including the reference Osc and the ADC. Do note, NONE of items above are plural, Only one is needed per system unlike
Re: [time-nuts] Advantages Disadvantages of the TPLL Method
On 06/14/2010 06:13 PM, WarrenS wrote: Long explanations, cause I try to explain, the best I can, when I say something is WRONG or misleading Magnus Posted: EFC linearity will remain an issue for analog oscillators. The oscillator gain will differ depending on offset voltage and temperature. TRUE it is an issue, but somewhat misleading because it need NOT be a problem or limitation (mostly) EFC Linearity can be an issue because the TPLL is limited by the performance of the reference oscillator in lots of ways. BUT Oscillator EFC gain or linearity are not likely to be of much concern or a limitation for high end performance. The gain nonlinearity I've measured can vary two to one over the full range of a good Oscillator but it is more like 10% over the normally used range, if one stays well away from the end points. NOT so good but livable if you are not making something real accurate. BUT For all my accurate stuff, when using a HP 10811, I limit the full-scale change to 1e-9 or 1e-8 at most. This uses such a small part of the total EFC range, that the nonlinearity effects are generally below the noise level and of little concern at all. The fact that Oscillator gain does differ with the EFC voltage (offset voltage), means if you want to get max accuracy out of the TPLL, it will need to be calibrated at the EFC offset voltage it is being used at. One simple solution, if the OSC also has a independent manual Freq adjustment like the single oven 10811, is to use it always set the EFC voltage to be near zero volts. BTW calibration need not be much of a problem, because it can be a static calibration. What I use for a finial calibration check is the 2G turn over, which I measure very accurately by other means before hand and then use that as a known freq offset to check operation and calibration. Of course there are any number of other ways. The main point I am trying to make is that it may not be useful to read the number of the data-sheet, but calibration methods should be performed. Should not be particularly hard to do, but if you do not make provisions for it, it will become a scaling error issue. Hand-trimming the coarse offset should be done if far away. As far as temperature having ANY effect on EFC gain, that is a total NON issue. If temperature had any effect on EFC Gain then Temperature would also effect Osc Frequency at a fixed EFC voltage, which would then effect the OSC freq drift and stability, that would then effect anything that the Osc was used for, NOT just the TPLL. The TPLL actually has a slight advantage over other methods, because the PLL will adjust the freq to be correct, even if the EFC effect should change. Yes, but since we derive our measurements from that EFC our sampled data will change so it will creep into the sample-series. Hand-calibrating towards zero EFC and let it stabilize should work well enough. Identifying potential problems is the first step to finding ways to avoid or compensate for them. I think it is reasonable to assume that a TPLL weighs in at about 200 USD with all support mixers, amplifiers, ADCs etc. if you don't have the parts It is still a fairly cheap solution. Yes I think that is ONE reasonable number to use and a fair conclusion. BUT there are others. The EBAY cost of the TPLL can be easy under $10, not including the reference Osc and the ADC. The point I was trying to make that the total cost was more around 200 USD including ref oscillator and ADC. Do note, NONE of items above are plural, Only one is needed per system unlike some other methods. Because the cost of the Ref Osc is so variable and depends so much on what one is doing, I have noticed that its cost is generally not included in the base price. I think even on the $20K+ TSC 5120A that the reference Osc is an extra cost option. The reference oscillator plays a different role in that system. The ADC is another BIG variable, depending on your needs and skill level and junk box, almost no limit in cost at the high end, and can be as low as $0.00 dollars if you are a student doing a science project. It can also be as low as $1.00 if one is good at programming PICS or other micros with built in ADC's. Indeed. Cheap audio-boards could be hacked up. The only other major part in the TPLL with any cost over $1 is the Phase detector. The one I use most is a micro-circuits $15 single price device, but I've used all sorts of dual balanced mixers, and if one is real cheap and good at design, I have found that a PD based on a 50 cent XOR gate works fine. You may get very low on some of these, but what I was aiming for was a more average price for the average builder. You are usually not all that lucky when you want to. Also, recall that packaging and transport adds on top of that, including import taxes and VAT... which I did not included. Your milage may vary a lot. I just 200 USD is a more realistic value. It doesn't make it less valuable as a tool, I am
Re: [time-nuts] Advantages Disadvantages of the TPLL Method
Magnus posted: The main point I am trying to make is that it may not be useful to read the number of the data-sheet, One of my short comings, I never even considered one would do that. I guess it would be possible if one only needed say 50% accuracy for small differences. Right it needs to be calibrated, It's analog. Hand-trimming the coarse offset should be done if far away. Yes, the TPLL BB has provisions for course manual offset, med H/W offset and Software offset Can put that one under the disadvantage list also. It is not like Digital, One has to understand the differences and when to use which offset. Yes, but since we derive our measurements from that EFC our sampled data will change so it will creep into the sample-series. What I find effective is to recheck the TPLL reference by exchanging the DUT with a known freq every day or so (with my reference), or can be done as much as one needs ( 100 sec, hr etc) as long as it is properly taken into account. It takes only a second or so to place a full accuracy calibration marker on the plot or the data log, that takes into account all drifts including the TPLL ref osc, based on a separate fixed reference freq that can be CS or anything. You may get very low on some of these, but what I was aiming for was a more average price for the average builder. The point I was trying to make that the total cost was more around 200 USD including ref oscillator and ADC. I just think 200 USD is a more realistic cost (value). No disagreement, My point which is different than yours, is it all depends on how much effort design time one wants to put into it. Total parts cost can be kept under $10 in small production runs (even without eBay) including all but the Reference OSC. For the reference OSC there is all kinds of lower and higher cost devices that would be suitable for some. We seem to agree on all the major points so far. Hard to have much of a discussion when two agree. So time to bring up something that we may NOT agree on. Bandwidth and the bandwidth filter freq used with the TPLL has little effect as long as its freq is than about 2x tau0 freq, Unlike most other Phase methods, where the optimal Bandwidth is tau0 or 1/2 trau0. Before some go ballistic over the comment, consider what the effect of the Tau0 integration is on the oversampled TPLL Frequency data. Example: because most are confused by my mixed use of freq, time constant, tau0 and BW Tau0 = 0.1 sec, 100 ms, 10 sample per second (all the same) Phase methods need an optimal Bandwidth of 5Hz, or 10 Hz or 100ms or ... depending on which paper you read. The optimal wsTPLL method BW for tau0 = 20 Hz (greater BW does not change the ADEV results, like it does with Phase). and the TPLL optimal BW for tau0 of 1 sec is = than 2 Hz and the optimal BW for TPLL of tau0 of 10ms is = than 200 Hz Note that BIG difference is, unlike Phase methods, a single filter freq can be selected that works for all TPLL tau0 It does not have to be changed for each tau0 (in the above example the H/W BW filter should be = than 200 Hz for any tau0 =10ms) AND I'm suggesting that goes at the top of the advantages list, right above simple. Now I expect that will restart the name calling from some before they even think. ws ** [time-nuts] Advantages Disadvantages of the TPLL Method Magnus Danielson magnus at rubidium.dyndns.org Mon Jun 14 22:25:11 UTC 2010 On 06/14/2010 06:13 PM, WarrenS wrote: Long explanations, cause I try to explain, the best I can, when I say something is WRONG or misleading Magnus Posted: EFC linearity will remain an issue for analog oscillators. The oscillator gain will differ depending on offset voltage and temperature. TRUE it is an issue, but somewhat misleading because it need NOT be a problem or limitation (mostly) EFC Linearity can be an issue because the TPLL is limited by the performance of the reference oscillator in lots of ways. BUT Oscillator EFC gain or linearity are not likely to be of much concern or a limitation for high end performance. The gain nonlinearity I've measured can vary two to one over the full range of a good Oscillator but it is more like 10% over the normally used range, if one stays well away from the end points. NOT so good but livable if you are not making something real accurate. BUT For all my accurate stuff, when using a HP 10811, I limit the full-scale change to 1e-9 or 1e-8 at most. This uses such a small part of the total EFC range, that the nonlinearity effects are generally below the noise level and of little concern at all. The fact that Oscillator gain does differ with the EFC voltage (offset voltage), means if you want to get max accuracy out of the TPLL, it will need to be calibrated at the EFC offset voltage it is being used at. One simple solution, if the OSC also has a independent manual Freq adjustment like the single oven 10811, is to use it always set the EFC voltage to be near
Re: [time-nuts] Advantages Disadvantages of the TPLL Method
WarrenS wrote: Bruce posted If and only if injection locking isn't significant. No problem then, because it is not significant. For each and every oscillator pair someone may try? Can place this one under the 'ADVANTAGE' side. That's descending into the murky realms of pseudoscience. At best you've only shown this to be true for the particular oscillator pair being compared. Not only must the effect of injection locking be insignificant for the reference, it has to be insignificant for the test oscillator as well. If injection locking is an issue the efc gain with the loop open will differ from the efc gain with the loop closed. I have tested this thoroughly in many ways. I do understand the concerns and doubts, especially with an unbuffered HP 10811 as the reference. The 10811s are pretty sensitive to injection locking and phase pulling. Unlike most other methods, one of the many unique properties that the TPLL method has is that injection locking is normally not a problem with it. It will change the loop parameters in particular the efc gain. Its just a matter of how much it affects the efc gain. I find it is generally unnecessary to buffer either the Ref Osc or the DUT. This is one of the many features that helps make the simple TPLL so simple. (also it does not hurt or change anything to add a proper buffer) The lack of injection locking is one of the advantages that contributes to its exceptional and unbelievable performance. But Adler's equation indicates that an oscillator is much more to susceptible to injection effects when the injected signal frequency is very close to the oscillator frequency. I did not leave the buffers out of the simple TPLL BB that was tested because of my lack of knowledge, but because of my extra knowledge on the subject that showed that they were unnecessary. More than once, I have tried to explain the reason why injection locking is not a problem with my version of the TPLL method, but until one proves it for their self, more words from me will not help. I do understand the skepticism and doubt, and I know why it is so hard to believe this for those that have not worked with is this type of method before. I guess someone should write one of those fancy math papers, if it has not already been done, that explains it in more convincing terms than I've been able to. It is hard for me to believe that paper has not already been written, But then it is hard for me to believe that the TPLL is not used more often. There are plenty of places that one of the TPLL methods well give the best overall solution. ws *** Bruce [time-nuts] Advantages Disadvantages of the TPLL Method Bruce Griffiths bruce.griffiths at xtra.co.nz WarrenS wrote: Long explanations, cause I try to explain, the best I can, when I say something is WRONG or misleading Magnus Posted: EFC linearity will remain an issue for analog oscillators. The oscillator gain will differ depending on offset voltage and temperature. TRUE it is an issue, but somewhat misleading because it need NOT be a problem or limitation (mostly) EFC Linearity can be an issue because the TPLL is limited by the performance of the reference oscillator in lots of ways. BUT Oscillator EFC gain or linearity are not likely to be of much concern or a limitation for high end performance. The gain nonlinearity I've measured can vary two to one over the full range of a good Oscillator but it is more like 10% over the normally used range, if one stays well away from the end points. NOT so good but livable if you are not making something real accurate. BUT For all my accurate stuff, when using a HP 10811, I limit the full-scale change to 1e-9 or 1e-8 at most. This uses such a small part of the total EFC range, that the nonlinearity effects are generally below the noise level and of little concern at all. The fact that Oscillator gain does differ with the EFC voltage (offset voltage), means if you want to get max accuracy out of the TPLL, it will need to be calibrated at the EFC offset voltage it is being used at. One simple solution, if the OSC also has a independent manual Freq adjustment like the single oven 10811, is to use it always set the EFC voltage to be near zero volts. BTW calibration need not be much of a problem, because it can be a static calibration. If and only if injection locking isn't significant. This needs to be established for each setup. The simplest way to take the effects of injection locking into account is to measure the effective EFC gain with the loop closed. What I use for a finial calibration check is the 2G turn over, which I measure very accurately by other means before hand and then use that as a known freq offset to check operation and calibration. Of course there are any number of other ways. As far as temperature having ANY effect on EFC gain, that is a total NON issue. If temperature had any effect on EFC Gain then Temperature
Re: [time-nuts] Advantages Disadvantages of the TPLL Method
Here are a couple of really good articles that describe many methods of phase/frequency measurement, including TPLL. You'll see some nice advantage/disadvantage lists in several of these documents, which is why I'm posting the links. Warren Bruce, please look at the first five documents at least. John too. Lots of TPLL info. This is all worth reading. I don't know why I didn't find some of these papers six months ago. System Phase Noise Calculation and Measurement Techniques http://www.mpdigest.com/issue/Articles/2009/sept/spectrum/Default.asp -- short article, nice summary. PN9000 Automated Phase Noise Measurement System Application Note #1 http://www.aeroflex.com/ats/products/prodfiles/appnotes/12/app1.pdf -- see section 2; TPLL is section 2.2. Oscillator Phase Noise Measurements using the Phase Lock Method http://ravoltek.net/dippa/dippa_rajala_olli.pdf -- TPLL, equations, graphs, error analysis, photos, schematics, parts list. An investigation into the phase noise of quartz crystal oscillators http://etd.sun.ac.za/bitstream/10019/337/1/BentleyB.pdf -- see chapter 4 or at least section 4.3; TPLL is 4.3.3.2. PN9000 Automated Phase Noise Measurement System Application Note #2 http://smartdata.usbid.com/datasheets/usbid/2000/2000-q4/app2.pdf http://www.datasheetarchive.com/pdf/Datasheet-010/DSA00173368.pdf -- theory of operation, TPLL A General Theory of Phase Noise in Electrical Oscillators http://www.chic.caltech.edu/Publications/general_full.PDF -- too deep for me. Phase Noise Measurement. Using the Phase Lock Technique http://www.chem.duke.edu/~boris/datasheets/AN1639_phase_noise.pdf http://www.lansdale.com/Articles/an1639.pdf -- might be applicable. Correlation-based phase noise measurements http://www.femto-st.fr/~rubiola/pdf-others/correl-report.pdf -- for John Miles Practical Problems Involving Phase Noise Measurements http://tycho.usno.navy.mil/ptti/ptti2001/paper42.pdf -- also for John. /tvb ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Advantages Disadvantages of the TPLL Method
Warren, On 06/13/2010 05:45 AM, WarrenS wrote: Thanks for the positive contrbution, A good example of one of the TPLL's obvious disadvantages. The simple cheap analog version of the TPLL is limited by it's need to have a dedicated Ref OSC. One way I have got around that problem, which would not apply to all, is to put the DUT unit as the controlled OSC, and use a special Tbolt as the reference Oscillator. The other way around the problem is the Digital version of the TPLL that uses DSS. I think one should best break the TPLL into three different cases, as they have different characteristics. BTW that limitation is not nearly as big as one would think. This is because the long term accuracy is already limited by the reference osc, so one would not generally use this kind of system out past 1000 sec or so anyway. So If doing long term multichannel Osc, One would likely be MUCH better off with a more basic undersampled Phase system for long term testing and just go thru and cheek each Osc one at time for a short time with a low tau tester such as this type. The TPLL is a mid-tau stability test, since it's sweet-spot is in the 0,1 - 1000 s range. Short-term is better handled in LPLL phase-noise measurements. Keep the advantages and disadvantages coming in, so the Time Nuts can compare which methods work best for their application. Now if we just had some place to log the responses. Could be arranged. Best way would naturally be to whip up a draft article providing a survey. It may be useful to break up detailed analysis in separate articles. There is many details in this. Summery: If you have multi oscillators to test simultaneously that do not have EFC input, and that you want to do continuous sampling on, and do not have multiple TSC boxes, the TPLL is not the right tool for the job. Agreed... for large N. Be better off with one simple lower resolution multiplexed time stamped TI phase system and a single TPLL. Actually that might not be what you want, the articles Bruce referred to points out some interesting problems which also needs to be understood as one progresses down that path. For me, finding those articles was a good side-consequence of this discussion. Bruce posted: The poor cost scaling of the tight PLL system is another reason why it has fallen out of favour for those who have more than 2 frequency standards to compare simultaneously. Thanks for that opinion, but I don't think we should list the above as a unique disadvantage. Maybe need a new column heading for that one, Any name suggestions? It's a conditioned disadvantage, but still a disadvantage. Doesn't apply for 1 or 2 channel systems. Does not sound all that valid or unique of a reason to me. It seems the same can be said about a TSC or any new high cost system. Indeed. This is the N channel condition. The DTMT system proved much cheaper for many-channel setups. Infact, the many-channel setup situation has very few solutions even today when looking at commercial boxes. I would think a more important reason is that the simple TPLL is not a universal do all system. Because the simple analog version is Limited by it's reference Osc in many ways, This does give it some possible major disadvantages like not working so good with a CS or Rb standard. If one has more time than money, there are ways around that. Sure is. The TPLL method does not fit all needs. It's fine, we just need to quantify properly what needs it fits. The N-channel case is a limitation which may or may not apply to a particular case. For most hobbyists and many commercial usages, the N-channel case is not a serious limit. It could also be argued that for small N (say 8) the cost would still not be prohibiting. Personally I lack mixers and such to setup an 8-channel system, as I already have more than 8 10811 and an 8-channel ADC system suitable for the task. Oh, I still count myself as a hobbyist. Cheers, Magnus ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Advantages Disadvantages of the TPLL Method
Correlation-based phase noise measurements http://www.femto-st.fr/~rubiola/pdf-others/correl-report.pdf -- for John Miles Practical Problems Involving Phase Noise Measurements http://tycho.usno.navy.mil/ptti/ptti2001/paper42.pdf -- also for John. I've got these in my collection, but it never hurts to go back over them. Both these papers, of course, end their exploration of averaged correlation by saying and here a dynamic signal analyzer is typically used. :-P It turns out that the common OCXO I was using has a higher PN floor than I thought (about -154 dBc/Hz) so I'll probably switch to independent OCXOs before delving into this too much further. -- john, KE5FX ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Advantages Disadvantages of the TPLL Method
John, On 06/13/2010 10:00 AM, John Miles wrote: Correlation-based phase noise measurements http://www.femto-st.fr/~rubiola/pdf-others/correl-report.pdf -- for John Miles Practical Problems Involving Phase Noise Measurements http://tycho.usno.navy.mil/ptti/ptti2001/paper42.pdf -- also for John. I've got these in my collection, but it never hurts to go back over them. Both these papers, of course, end their exploration of averaged correlation by saying and here a dynamic signal analyzer is typically used. :-P Which is how they say problem solved by somebody else. It turns out that the common OCXO I was using has a higher PN floor than I thought (about -154 dBc/Hz) so I'll probably switch to independent OCXOs before delving into this too much further. You where kind of measuring the noise floor of your setup. Cheers, Magnus ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Advantages Disadvantages of the TPLL Method
Tom, I took the liberty of converting your post into an entry in my Time-Nuts Wiki: http://www.ko4bb.com/dokuwiki/doku.php?id=precision_timing:phase_frequency_m easurement_methods Please note anyone can edit this Wiki or create new pages. Didier -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Tom Van Baak Sent: Sunday, June 13, 2010 1:35 AM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Advantages Disadvantages of the TPLL Method Here are a couple of really good articles that describe many methods of phase/frequency measurement, including TPLL. You'll see some nice advantage/disadvantage lists in several of these documents, which is why I'm posting the links. Warren Bruce, please look at the first five documents at least. John too. Lots of TPLL info. This is all worth reading. I don't know why I didn't find some of these papers six months ago. System Phase Noise Calculation and Measurement Techniques http://www.mpdigest.com/issue/Articles/2009/sept/spectrum/Default.asp -- short article, nice summary. PN9000 Automated Phase Noise Measurement System Application Note #1 http://www.aeroflex.com/ats/products/prodfiles/appnotes/12/app1.pdf -- see section 2; TPLL is section 2.2. Oscillator Phase Noise Measurements using the Phase Lock Method http://ravoltek.net/dippa/dippa_rajala_olli.pdf -- TPLL, equations, graphs, error analysis, photos, schematics, parts list. An investigation into the phase noise of quartz crystal oscillators http://etd.sun.ac.za/bitstream/10019/337/1/BentleyB.pdf -- see chapter 4 or at least section 4.3; TPLL is 4.3.3.2. PN9000 Automated Phase Noise Measurement System Application Note #2 http://smartdata.usbid.com/datasheets/usbid/2000/2000-q4/app2.pdf http://www.datasheetarchive.com/pdf/Datasheet-010/DSA00173368.pdf -- theory of operation, TPLL A General Theory of Phase Noise in Electrical Oscillators http://www.chic.caltech.edu/Publications/general_full.PDF -- too deep for me. Phase Noise Measurement. Using the Phase Lock Technique http://www.chem.duke.edu/~boris/datasheets/AN1639_phase_noise.pdf http://www.lansdale.com/Articles/an1639.pdf -- might be applicable. Correlation-based phase noise measurements http://www.femto-st.fr/~rubiola/pdf-others/correl-report.pdf -- for John Miles Practical Problems Involving Phase Noise Measurements http://tycho.usno.navy.mil/ptti/ptti2001/paper42.pdf -- also for John. /tvb ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Advantages Disadvantages of the TPLL Method
Didier On 13 June 2010 21:51, Didier Juges did...@cox.net wrote: Tom, I took the liberty of converting your post into an entry in my Time-Nuts Wiki: http://www.ko4bb.com/dokuwiki/doku.php?id=precision_timing:phase_frequency_m easurement_methods Just to let you know that your link got busted by a line-wrap somewhere so it is not clickable and has to be cut and pasted into place. But it could be just the World hating me again :) Cheers, Steve Please note anyone can edit this Wiki or create new pages. Didier -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Tom Van Baak Sent: Sunday, June 13, 2010 1:35 AM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Advantages Disadvantages of the TPLL Method Here are a couple of really good articles that describe many methods of phase/frequency measurement, including TPLL. You'll see some nice advantage/disadvantage lists in several of these documents, which is why I'm posting the links. Warren Bruce, please look at the first five documents at least. John too. Lots of TPLL info. This is all worth reading. I don't know why I didn't find some of these papers six months ago. System Phase Noise Calculation and Measurement Techniques http://www.mpdigest.com/issue/Articles/2009/sept/spectrum/Default.asp -- short article, nice summary. PN9000 Automated Phase Noise Measurement System Application Note #1 http://www.aeroflex.com/ats/products/prodfiles/appnotes/12/app1.pdf -- see section 2; TPLL is section 2.2. Oscillator Phase Noise Measurements using the Phase Lock Method http://ravoltek.net/dippa/dippa_rajala_olli.pdf -- TPLL, equations, graphs, error analysis, photos, schematics, parts list. An investigation into the phase noise of quartz crystal oscillators http://etd.sun.ac.za/bitstream/10019/337/1/BentleyB.pdf -- see chapter 4 or at least section 4.3; TPLL is 4.3.3.2. PN9000 Automated Phase Noise Measurement System Application Note #2 http://smartdata.usbid.com/datasheets/usbid/2000/2000-q4/app2.pdf http://www.datasheetarchive.com/pdf/Datasheet-010/DSA00173368.pdf -- theory of operation, TPLL A General Theory of Phase Noise in Electrical Oscillators http://www.chic.caltech.edu/Publications/general_full.PDF -- too deep for me. Phase Noise Measurement. Using the Phase Lock Technique http://www.chem.duke.edu/~boris/datasheets/AN1639_phase_noise.pdf http://www.lansdale.com/Articles/an1639.pdf -- might be applicable. Correlation-based phase noise measurements http://www.femto-st.fr/~rubiola/pdf-others/correl-report.pdf -- for John Miles Practical Problems Involving Phase Noise Measurements http://tycho.usno.navy.mil/ptti/ptti2001/paper42.pdf -- also for John. /tvb ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. -- Steve Rooke - ZL3TUV G8KVD The only reason for time is so that everything doesn't happen at once. - Einstein ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Advantages Disadvantages of the TPLL Method
I saw that. There is nothing I can do about it other than by using a url shortener which I am reluctant to do because of the obfuscation and potential for abuse. I assume that by now everyone knows how to deal with these problems, and if someone does not, now is a good time to brush up... Didier -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Steve Rooke Sent: Sunday, June 13, 2010 5:17 AM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Advantages Disadvantages of the TPLL Method Didier On 13 June 2010 21:51, Didier Juges did...@cox.net wrote: Tom, I took the liberty of converting your post into an entry in my Time-Nuts Wiki: http://www.ko4bb.com/dokuwiki/doku.php?id=precision_timing:phase_frequ ency_m easurement_methods Just to let you know that your link got busted by a line-wrap somewhere so it is not clickable and has to be cut and pasted into place. But it could be just the World hating me again :) Cheers, Steve Please note anyone can edit this Wiki or create new pages. Didier -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Tom Van Baak Sent: Sunday, June 13, 2010 1:35 AM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Advantages Disadvantages of the TPLL Method Here are a couple of really good articles that describe many methods of phase/frequency measurement, including TPLL. You'll see some nice advantage/disadvantage lists in several of these documents, which is why I'm posting the links. Warren Bruce, please look at the first five documents at least. John too. Lots of TPLL info. This is all worth reading. I don't know why I didn't find some of these papers six months ago. System Phase Noise Calculation and Measurement Techniques http://www.mpdigest.com/issue/Articles/2009/sept/spectrum/Default.asp -- short article, nice summary. PN9000 Automated Phase Noise Measurement System Application Note #1 http://www.aeroflex.com/ats/products/prodfiles/appnotes/12/app1.pdf -- see section 2; TPLL is section 2.2. Oscillator Phase Noise Measurements using the Phase Lock Method http://ravoltek.net/dippa/dippa_rajala_olli.pdf -- TPLL, equations, graphs, error analysis, photos, schematics, parts list. An investigation into the phase noise of quartz crystal oscillators http://etd.sun.ac.za/bitstream/10019/337/1/BentleyB.pdf -- see chapter 4 or at least section 4.3; TPLL is 4.3.3.2. PN9000 Automated Phase Noise Measurement System Application Note #2 http://smartdata.usbid.com/datasheets/usbid/2000/2000-q4/app2.pdf http://www.datasheetarchive.com/pdf/Datasheet-010/DSA00173368.pdf -- theory of operation, TPLL A General Theory of Phase Noise in Electrical Oscillators http://www.chic.caltech.edu/Publications/general_full.PDF -- too deep for me. Phase Noise Measurement. Using the Phase Lock Technique http://www.chem.duke.edu/~boris/datasheets/AN1639_phase_noise.pdf http://www.lansdale.com/Articles/an1639.pdf -- might be applicable. Correlation-based phase noise measurements http://www.femto-st.fr/~rubiola/pdf-others/correl-report.pdf -- for John Miles Practical Problems Involving Phase Noise Measurements http://tycho.usno.navy.mil/ptti/ptti2001/paper42.pdf -- also for John. /tvb ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. -- Steve Rooke - ZL3TUV G8KVD The only reason for time is so that everything doesn't happen at once. - Einstein ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Advantages Disadvantages of the TPLL Method
Just to let you know that your link got busted by a line-wrap somewhere so it is not clickable and has to be cut and pasted into place. I saw that. There is nothing I can do about it other than by using a url shortener which I am reluctant to do because of the obfuscation and potential for abuse. One approach is to use a URL shortener but also include the long URL even though it will get chopped up and such. The key idea is that at least some of the target audience will be able to decrypt the line wrapping and/or other mangling and reconstruct the target URL if the url shortening service goes tits-up. Both bit.ly and tinyurl.com are reasonably on the ball about blocking spammers from using their services. There may be (many?) other anti-spam URL shorteners that I don't know about. (Some of of the shorteners seem to be run by spammers.) -- These are my opinions, not necessarily my employer's. I hate spam. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Advantages Disadvantages of the TPLL Method
On 13/06/2010, Didier Juges did...@cox.net wrote: I saw that. There is nothing I can do about it other than by using a url shortener You can hint to most email clients that you'd like lines unbroken, using angle brackets This may work... http://www.ko4bb.com/dokuwiki/doku.php?id=precision_timing:phase_frequency_measurement_methods Steve ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Advantages Disadvantages of the TPLL Method
Steve, This seems to work with your email client sending and Outlook here receiving (I received that link unbroken), but the same link I just sent was broken, so it seems Outlook is doing that on the way out, but not on the way in... I should have known, Microsoft... Bottom line, no sure way to fix it, therefore the use of brain matter is recommended... Didier -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Steve Wiseman Sent: Sunday, June 13, 2010 9:57 AM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Advantages Disadvantages of the TPLL Method On 13/06/2010, Didier Juges did...@cox.net wrote: I saw that. There is nothing I can do about it other than by using a url shortener You can hint to most email clients that you'd like lines unbroken, using angle brackets This may work... http://www.ko4bb.com/dokuwiki/doku.php?id=precision_timing:ph ase_frequency_measurement_methods Steve ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Advantages Disadvantages of the TPLL Method
Magnus Posted The TPLL is a mid-tau stability test, since it's sweet-spot is in the 0,1 - 1000 s range. Short-term is better handled in LPLL phase-noise measurements. Mostly agree, it is a mid-tau device, but also consider: The simple TPLL can be used to find the 1ms to 10 ms ADEV as good and maybe? better than ANYthing else. AND I use it to find the drift and ADEV of my dual oven HP 10811's out to weeks, so there is no long term limit. (the trick is to control the DUT and not the Reference when doing long term testing) BUT I find the TPLL method is useful for MUCH more than just getting ADEV data. As such it's sweet spot extends from below 0.004 ms (250 Hz) all the way up to weeks, when the DUT is the controlled Osc. ALSO the simple TPLL is very Good and useful for seeing and measuring the effects of temperature, line noise, vibration, PS, load, and just about everything else that effects the frequency stability of an oscillators below 1 KHz or so. So if you are just thinking about the TPLL for taking ADEV data from 0.1 to 1000 sec, then you're are missing 90% of the other useful stuff it can do as good or better than most anything thing else out there, and all for the same $10 (my cost). If still in doubt about some of the TPLL's other high end performance capabilities, try the swinging osc test with ANYthing else and see if you can match the simple TPLL's performance. If one would make a list for the non ADEV uses and advantages of the simple TPLL It would indeed be very long list, and it does not take any fancy write up to see that, just a bit of open minded thinking. BTW, with a couple of minor configuration changes, the TPLL BreadBoard can be transformed into a LPLL, so the usefulness of the basic Universal TPLL BB circuit has even more possibilities. In fact one could make yet another list of all the additional things it can do with no added cost, just by changing a few jumpers and values. But those things are for later discussions, one windmill at a time. ws ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Advantages Disadvantages of the TPLL Method
I went quickly thru Tom's reference list and was unable to fine anything that had much if anything to do directly with the NIST, the NBS, or the slightly modified ws TPLL method. All of those papers seem to be about how to measure Phase noise, NOT frequency stability, and from what I was able to find, the measurements they were making were not taken from the EFC line put from the mixer/PhaseDector output. Big Difference, makes that more like a LPLL type method. As far as the list of disadvantages that I could find, the one under what Tom said was a good TPLL example, said: The phase lock loop must be very precisely controlled, since it effects measurement results is clearly not what NBS or I'm doing. Neither does the schematic in another paper have anything to do with the simple TPLL method. Lots of good and useful stuff there, Just nothing (I could find) on the TPLL method that we have been discussing here. If anyone could point out something that I missed, it would make my search for any relevant things easier. ws * Tom, I took the liberty of converting your post into an entry in my Time-NutsWiki: http://www.ko4bb.com/dokuwiki/doku.php?id=precision_timing:phase_frequency_measurement_methodsPlease note anyone can edit this Wiki or create new pages.Didier ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Advantages Disadvantages of the TPLL Method
Warren, Penny dropped! On 14 June 2010 05:29, WarrenS warrensjmail-...@yahoo.com wrote: Magnus Posted The TPLL is a mid-tau stability test, since it's sweet-spot is in the 0,1 - 1000 s range. Short-term is better handled in LPLL phase-noise measurements. Mostly agree, it is a mid-tau device, but also consider: The simple TPLL can be used to find the 1ms to 10 ms ADEV as good and maybe? better than ANYthing else. AND I use it to find the drift and ADEV of my dual oven HP 10811's out to weeks, so there is no long term limit. (the trick is to control the DUT and not the Reference when doing long term testing) Of course, provided that the DUT has an EFC, you can put this in place of the reference oscillator and put a, say, GPSDO in place of where the DUT normally goes. This will certainly extend things at long Tau out as far as you wish. As for short tau, it would be better to convert the circuit to LPLL. BUT I find the TPLL method is useful for MUCH more than just getting ADEV data. As such it's sweet spot extends from below 0.004 ms (250 Hz) all the way up to weeks, when the DUT is the controlled Osc. Either 0.004 s or 4 ms methinks. You would have to make sure that the B/W from the mixer out right to the ability to control the reference oscillator is that wide. This could be verified by breaking off the EFC and injecting 250Hz into there and seeing if the original feed to the EFC follows it. ALSO the simple TPLL is very Good and useful for seeing and measuring the effects of temperature, line noise, vibration, PS, load, and just about everything else that effects the frequency stability of an oscillators below 1 KHz or so. Providing that the reference oscillator is not subjected to those effects at the same time (isolation). So if you are just thinking about the TPLL for taking ADEV data from 0.1 to 1000 sec, then you're are missing 90% of the other useful stuff it can do as good or better than most anything thing else out there, and all for the same $10 (my cost). If you have some stock items that you can borrow for this job and not just dedicate it to the TPLL. Still, that is not an unreasonable assumption for many. If still in doubt about some of the TPLL's other high end performance capabilities, try the swinging osc test with ANYthing else and see if you can match the simple TPLL's performance. If one would make a list for the non ADEV uses and advantages of the simple TPLL It would indeed be very long list, and it does not take any fancy write up to see that, just a bit of open minded thinking. But can it make a decent cup of char? BTW, with a couple of minor configuration changes, the TPLL BreadBoard can be transformed into a LPLL, so the usefulness of the basic Universal TPLL BB circuit has even more possibilities. In fact one could make yet another list of all the additional things it can do with no added cost, Can you add a cup-holder, those are essential these days. just by changing a few jumpers and values. But those things are for later discussions, one windmill at a time. So does it grind wheat to make flower then; by golly, this thing is versatile. Add smilies as you see fit. Cheers, Steve ws ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. -- Steve Rooke - ZL3TUV G8KVD The only reason for time is so that everything doesn't happen at once. - Einstein ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Advantages Disadvantages of the TPLL Method
On 14 June 2010 10:46, Magnus Danielson mag...@rubidium.dyndns.org wrote: Still puts it in the mid-tau range as a method. The useful range and precision of a particular implementation of the method will vary. By putting a GPSDO in the usual place of the DUT and putting the 10811 in place of the reference oscillator it could work well beyond the 1000s point. CAVEAT: this only works for a DUT that has an EFC that is reasonably linear. So if you are just thinking about the TPLL for taking ADEV data from 0.1 to 1000 sec, then you're are missing 90% of the other useful stuff it can do as good or better than most anything thing else out there, and all for the same $10 (my cost). The typical price-tag of a 10811 is in 100-150 USD. I think it is reasonable to assume that a TPLL weighs in at about 200 USD with all support mixers, amplifiers, ADCs etc. It's not bad, but if you don't have the parts that's about what you need to spend at least. If you really wanted to be a scrooge, you could open the case on one of those plethera of HP intruments and temporarily borrow that 10811 that is just sitting there. As for something like a ADC, you could find a DAQ on fleeBay which could do duty here and also be a useful tool for general purpose use. Heck, you can use your sound card to digitize the EFC, provided it is DC coupled. BTW, with a couple of minor configuration changes, the TPLL BreadBoard can be transformed into a LPLL, so the usefulness of the basic Universal TPLL BB circuit has even more possibilities. In fact one could make yet another list of all the additional things it can do with no added cost, just by changing a few jumpers and values. But those things are for later discussions, one windmill at a time. Measurement of phase noise is what the LPLL is good at, especially when done in cross-correlation mode. Interferometric setups use the mixers better. Both these techniques could be used for LPLL and TPLL measures. Do you have some pointers to these setups please Magnus? Cheers, Steve Cheers, Magnus ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. -- Steve Rooke - ZL3TUV G8KVD The only reason for time is so that everything doesn't happen at once. - Einstein ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Advantages Disadvantages of the TPLL Method
WarrenS wrote: subject: Advantages Disadvantages of the TPLL Method. Here is a new and unique Idea that may be useful for many. Rather than focusing on what some members may or may not already know, or how good or bad one specific working BB configuration is. How about focusing on what the TPLL method can and can not do well. If someone will make a place to post and compile a couple of list, I can start it off with what I've learned so far: DISADVANTAGES of the TPLL method: --- #1) The TPLL method is limited by it's reference OSC. This isn't necessarily correct, one could use a pair of tight PLL loops and use correlation techniques to reduce the contribution of the reference oscillator noise. The ref osc (or the DUT) needs to have an Analog/or Digital EFC control input with a bandwidth that is wider than the desired Tau0 #2) It basically measures Freq and not Phase differences, and few understand how and why it works so well or it's many advantages. This is not true, there is no inherent SNR advantage in measuring frequency changes as opposed to measuring phase differences. When the phase measurement system and the frequency measurement systems being compared have the same noise bandwidth then the measurement floors are comparable. For example, the TSC5120A is a narrow band system based on measuring phase differences with a comparable or lower noise floor than your implementation of the tight PLL. The common technique of using a time interval counter to measure the phase difference between 2 RF signals once ever second or so is a wideband technique with severe undersampling, consequently the system noise floor is much higher than for narrow bandwidth techniques. If the phase difference between the 2 signals were measured more frequently and digitally low pass filtered the noise will be much lower. Since one has to calculate average frequency from the frequency samples by integration/averaging this is mathematically equivalent to reconstructing the phase change between the start and end of the averaging time (Tau0). One effect of undersampling is to convert (in the sampled data) a proportion of any flicker phase noise (and other non white phase noise components) to white phase noise. The effect of this is to change the ADEV vs Tau plots from their true shape. With a single pole RC filter the required minimum sampling rate to ensure that such effects are acceptably small cannot be known unless the phase noise spectra of the 2 oscillators being compared is known. However the extra phase noise filtering due to the finite PLL bandwidth (including any EFC filtering built in to the reference oscillator) allows an estimate of the maximum sampling rate likely to be required to ensure that such phase noise whitening effects are acceptably small. #3) TBD ADVANTAGES of the TPLL method: --- 1 thru 30) same as I've posted several times before. I'm sure others will find many more if they try it or at least understand it better. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. Bruce ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Advantages Disadvantages of the TPLL Method
On 06/12/2010 11:29 PM, Bruce Griffiths wrote: WarrenS wrote: subject: Advantages Disadvantages of the TPLL Method. Here is a new and unique Idea that may be useful for many. Rather than focusing on what some members may or may not already know, or how good or bad one specific working BB configuration is. How about focusing on what the TPLL method can and can not do well. If someone will make a place to post and compile a couple of list, I can start it off with what I've learned so far: DISADVANTAGES of the TPLL method: --- #1) The TPLL method is limited by it's reference OSC. This isn't necessarily correct, one could use a pair of tight PLL loops and use correlation techniques to reduce the contribution of the reference oscillator noise. True. The same technique is being used for LPLL phase noise measurements. The reference oscillator will still be a limit, but wither you can go below the reference oscillator noise or not is what makes the difference. Such a setup costs about twice of a single-channel TPLL. Usually there is two ADC channels available. The cross-correlation processing isn't too hard to achieve and is efficiently performed using FFTs and a little support-processing. FFTW is a good tool to toss the FFT processing to. The remaining wrapping is in a few ten lines of codes or so. Going down the FFT path will give the frequency plot for free, getting it back into the time-domain cost extra. The ref osc (or the DUT) needs to have an Analog/or Digital EFC control input with a bandwidth that is wider than the desired Tau0 #2) It basically measures Freq and not Phase differences, and few understand how and why it works so well or it's many advantages. This is not true, there is no inherent SNR advantage in measuring frequency changes as opposed to measuring phase differences. When the phase measurement system and the frequency measurement systems being compared have the same noise bandwidth then the measurement floors are comparable. For example, the TSC5120A is a narrow band system based on measuring phase differences with a comparable or lower noise floor than your implementation of the tight PLL. The common technique of using a time interval counter to measure the phase difference between 2 RF signals once ever second or so is a wideband technique with severe undersampling, consequently the system noise floor is much higher than for narrow bandwidth techniques. If the phase difference between the 2 signals were measured more frequently and digitally low pass filtered the noise will be much lower. Using time-stamping counters at high rate would be possible if being able to cope with the rate of samples. You want a frontend to do that if you want to run continously. As for digital filtering. When doing measurements in the 0,1 - 1000 s range for the G.813 measurements, a 10 Hz low-pass filter is being required. Since one has to calculate average frequency from the frequency samples by integration/averaging this is mathematically equivalent to reconstructing the phase change between the start and end of the averaging time (Tau0). Depends on the details. Some counters (SR620 for instance) can have biases for frequency data which their time-difference measures do not have. A TPLL does not suffer from that particular problem, as it cranks out its frequency estimation by a different method. One effect of undersampling is to convert (in the sampled data) a proportion of any flicker phase noise (and other non white phase noise components) to white phase noise. The effect of this is to change the ADEV vs Tau plots from their true shape. Care to hand a reference or two for this statement? Regardless, care must be taken to ensure high enough bandwidth compared to the tau for the measurements not to be affected. Cheers, Magnus ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Advantages Disadvantages of the TPLL Method
Magnus Danielson wrote: On 06/12/2010 11:29 PM, Bruce Griffiths wrote: WarrenS wrote: subject: Advantages Disadvantages of the TPLL Method. Here is a new and unique Idea that may be useful for many. Rather than focusing on what some members may or may not already know, or how good or bad one specific working BB configuration is. How about focusing on what the TPLL method can and can not do well. If someone will make a place to post and compile a couple of list, I can start it off with what I've learned so far: DISADVANTAGES of the TPLL method: --- #1) The TPLL method is limited by it's reference OSC. This isn't necessarily correct, one could use a pair of tight PLL loops and use correlation techniques to reduce the contribution of the reference oscillator noise. True. The same technique is being used for LPLL phase noise measurements. The reference oscillator will still be a limit, but wither you can go below the reference oscillator noise or not is what makes the difference. Such a setup costs about twice of a single-channel TPLL. Usually there is two ADC channels available. Yes the cost of the reference oscillator dominates the system cost, the additional $10 (omitting the cost of the phase detector) to implement the tight PLL is relatively insignificant. The cross-correlation processing isn't too hard to achieve and is efficiently performed using FFTs and a little support-processing. FFTW is a good tool to toss the FFT processing to. The remaining wrapping is in a few ten lines of codes or so. Going down the FFT path will give the frequency plot for free, getting it back into the time-domain cost extra. If one is calculating the FFT then it is possible to calculate ADEV directly from the FFT (of the frequency samples) with little additional effort, for the relevant formulae see: http://hal.archives-ouvertes.fr/docs/00/37/63/05/PDF/alaa_p1_v4a.pdf Note such processing doesn't increase the cost of the system as one needs a PC to calculate frequency stability measures, unless one wants/needs to do it in real time. One disadvantage of a tight PLL system is that finite EFC range and EFC non linearity may preclude its application to noisier sources. Linearising the EFC transfer function will help but the reference oscillator EFC range will ultimately provide an upper limit to the measurable noise. The ref osc (or the DUT) needs to have an Analog/or Digital EFC control input with a bandwidth that is wider than the desired Tau0 #2) It basically measures Freq and not Phase differences, and few understand how and why it works so well or it's many advantages. This is not true, there is no inherent SNR advantage in measuring frequency changes as opposed to measuring phase differences. When the phase measurement system and the frequency measurement systems being compared have the same noise bandwidth then the measurement floors are comparable. For example, the TSC5120A is a narrow band system based on measuring phase differences with a comparable or lower noise floor than your implementation of the tight PLL. The common technique of using a time interval counter to measure the phase difference between 2 RF signals once ever second or so is a wideband technique with severe undersampling, consequently the system noise floor is much higher than for narrow bandwidth techniques. If the phase difference between the 2 signals were measured more frequently and digitally low pass filtered the noise will be much lower. Using time-stamping counters at high rate would be possible if being able to cope with the rate of samples. You want a frontend to do that if you want to run continously. As for digital filtering. When doing measurements in the 0,1 - 1000 s range for the G.813 measurements, a 10 Hz low-pass filter is being required. Since one has to calculate average frequency from the frequency samples by integration/averaging this is mathematically equivalent to reconstructing the phase change between the start and end of the averaging time (Tau0). Depends on the details. Some counters (SR620 for instance) can have biases for frequency data which their time-difference measures do not have. A TPLL does not suffer from that particular problem, as it cranks out its frequency estimation by a different method. Yes, but I thought that we were calculating the required averages from the frequency (EFC) samples by approximating the required integrals. One effect of undersampling is to convert (in the sampled data) a proportion of any flicker phase noise (and other non white phase noise components) to white phase noise. The effect of this is to change the ADEV vs Tau plots from their true shape. Care to hand a reference or two for this statement? References for the whitening effect of undersampling: http://www.obs-besancon.fr/tf/publis/metrologia98a.pdf http://www.obs-besancon.fr/tf/publis/metrologia98b.pdf The
Re: [time-nuts] Advantages Disadvantages of the TPLL Method
Another disadvantage of the Tight PLL system that only applies to multichannel systems is that a dedicated reference oscillator is required for each channel. i.e. for an N channel system N reference oscillators are required. If correlation techniques were to be employed then an N channel system requires 2N reference oscillators. N channel versions of Dual Mixer systems by contrast only need a single offset oscillator and a single reference oscillator. Similarly an N channel heterodyne system only requires a single offset oscillator. An N channel direct RF phase sampling system (like that employed by the 2 channel TSC5120A) only requires a single samplign clock source. An N channel time interval counter that periodically (eg at a 1Hz rate) measures phase differences between 2 RF signals only requires a single reference source. The above system can be regarded as an undersampled version of the direct RF phase sampling system. The poor cost scaling of the tight PLL system is another reason why it has fallen out of favour for those who have more than 2 frequency standards to compare simultaneously. Bruce WarrenS wrote: Great start Now if we just had a list that someone would add the advantages and disadvantages to, so that any non relevant stuff could be easily seen and removed or moved to a third list, It would all become much clearer. ws Magnus Danielson wrote: On 06/12/2010 11:29 PM, Bruce Griffiths wrote: WarrenS wrote: subject: Advantages Disadvantages of the TPLL Method. Here is a new and unique Idea that may be useful for many. Rather than focusing on what some members may or may not already know, or how good or bad one specific working BB configuration is. How about focusing on what the TPLL method can and can not do well. If someone will make a place to post and compile a couple of list, I can start it off with what I've learned so far: DISADVANTAGES of the TPLL method: --- #1) The TPLL method is limited by it's reference OSC. This isn't necessarily correct, one could use a pair of tight PLL loops and use correlation techniques to reduce the contribution of the reference oscillator noise. True. The same technique is being used for LPLL phase noise measurements. The reference oscillator will still be a limit, but wither you can go below the reference oscillator noise or not is what makes the difference. Such a setup costs about twice of a single-channel TPLL. Usually there is two ADC channels available. Yes the cost of the reference oscillator dominates the system cost, the additional $10 (omitting the cost of the phase detector) to implement the tight PLL is relatively insignificant. The cross-correlation processing isn't too hard to achieve and is efficiently performed using FFTs and a little support-processing. FFTW is a good tool to toss the FFT processing to. The remaining wrapping is in a few ten lines of codes or so. Going down the FFT path will give the frequency plot for free, getting it back into the time-domain cost extra. If one is calculating the FFT then it is possible to calculate ADEV directly from the FFT (of the frequency samples) with little additional effort, for the relevant formulae see: http://hal.archives-ouvertes.fr/docs/00/37/63/05/PDF/alaa_p1_v4a.pdf Note such processing doesn't increase the cost of the system as one needs a PC to calculate frequency stability measures, unless one wants/needs to do it in real time. One disadvantage of a tight PLL system is that finite EFC range and EFC non linearity may preclude its application to noisier sources. Linearising the EFC transfer function will help but the reference oscillator EFC range will ultimately provide an upper limit to the measurable noise. The ref osc (or the DUT) needs to have an Analog/or Digital EFC control input with a bandwidth that is wider than the desired Tau0 #2) It basically measures Freq and not Phase differences, and few understand how and why it works so well or it's many advantages. This is not true, there is no inherent SNR advantage in measuring frequency changes as opposed to measuring phase differences. When the phase measurement system and the frequency measurement systems being compared have the same noise bandwidth then the measurement floors are comparable. For example, the TSC5120A is a narrow band system based on measuring phase differences with a comparable or lower noise floor than your implementation of the tight PLL. The common technique of using a time interval counter to measure the phase difference between 2 RF signals once ever second or so is a wideband technique with severe undersampling, consequently the system noise floor is much higher than for narrow bandwidth techniques. If the phase difference between the 2 signals were measured more frequently and digitally low pass filtered the noise will be much lower. Using time-stamping counters at high rate
Re: [time-nuts] Advantages Disadvantages of the TPLL Method
Thanks for the positive contrbution, A good example of one of the TPLL's obvious disadvantages. The simple cheap analog version of the TPLL is limited by it's need to have a dedicated Ref OSC. One way I have got around that problem, which would not apply to all, is to put the DUT unit as the controlled OSC, and use a special Tbolt as the reference Oscillator. The other way around the problem is the Digital version of the TPLL that uses DSS. BTW that limitation is not nearly as big as one would think. This is because the long term accuracy is already limited by the reference osc, so one would not generally use this kind of system out past 1000 sec or so anyway. So If doing long term multichannel Osc, One would likely be MUCH better off with a more basic undersampled Phase system for long term testing and just go thru and cheek each Osc one at time for a short time with a low tau tester such as this type. Keep the advantages and disadvantages coming in, so the Time Nuts can compare which methods work best for their application. Now if we just had some place to log the responses. Summery: If you have multi oscillators to test simultaneously that do not have EFC input, and that you want to do continuous sampling on, and do not have multiple TSC boxes, the TPLL is not the right tool for the job. Be better off with one simple lower resolution multiplexed time stamped TI phase system and a single TPLL. Bruce posted: The poor cost scaling of the tight PLL system is another reason why it has fallen out of favour for those who have more than 2 frequency standards to compare simultaneously. Thanks for that opinion, but I don't think we should list the above as a unique disadvantage. Maybe need a new column heading for that one, Any name suggestions? Does not sound all that valid or unique of a reason to me. It seems the same can be said about a TSC or any new high cost system. I would think a more important reason is that the simple TPLL is not a universal do all system. Because the simple analog version is Limited by it's reference Osc in many ways, This does give it some possible major disadvantages like not working so good with a CS or Rb standard. If one has more time than money, there are ways around that. ws *** Bruce Griffiths bruce.griffiths at xtra.co.nz Sun Jun 13 01:25:13 UTC 2010 Another disadvantage of the Tight PLL system that only applies to multichannel systems is that a dedicated reference oscillator is required for each channel. i.e. for an N channel system N reference oscillators are required. If correlation techniques were to be employed then an N channel system requires 2N reference oscillators. N channel versions of Dual Mixer systems by contrast only need a single offset oscillator and a single reference oscillator. Similarly an N channel heterodyne system only requires a single offset oscillator. An N channel direct RF phase sampling system (like that employed by the 2 channel TSC5120A) only requires a single samplign clock source. An N channel time interval counter that periodically (eg at a 1Hz rate) measures phase differences between 2 RF signals only requires a single reference source. The above system can be regarded as an undersampled version of the direct RF phase sampling system. The poor cost scaling of the tight PLL system is another reason why it has fallen out of favour for those who have more than 2 frequency standards to compare simultaneously. Bruce WarrenS wrote: Great start Now if we just had a list that someone would add the advantages and disadvantages to, so that any non relevant stuff could be easily seen and removed or moved to a third list, It would all become much clearer. ws Magnus Danielson wrote: On 06/12/2010 11:29 PM, Bruce Griffiths wrote: WarrenS wrote: subject: Advantages Disadvantages of the TPLL Method. Here is a new and unique Idea that may be useful for many. Rather than focusing on what some members may or may not already know, or how good or bad one specific working BB configuration is. How about focusing on what the TPLL method can and can not do well. If someone will make a place to post and compile a couple of list, I can start it off with what I've learned so far: DISADVANTAGES of the TPLL method: --- #1) The TPLL method is limited by it's reference OSC. This isn't necessarily correct, one could use a pair of tight PLL loops and use correlation techniques to reduce the contribution of the reference oscillator noise. True. The same technique is being used for LPLL phase noise measurements. The reference oscillator will still be a limit, but wither you can go below the reference oscillator noise or not is what makes the difference. Such a setup costs about twice of a single-channel TPLL. Usually there is two ADC channels available. Yes the cost of the reference oscillator dominates the system cost, the
Re: [time-nuts] Advantages Disadvantages of the TPLL Method
WarrenS wrote: Thanks for the positive contrbution, A good example of one of the TPLL's obvious disadvantages. The simple cheap analog version of the TPLL is limited by it's need to have a dedicated Ref OSC. One way I have got around that problem, which would not apply to all, is to put the DUT unit as the controlled OSC, and use a special Tbolt as the reference Oscillator. The other way around the problem is the Digital version of the TPLL that uses DSS. BTW that limitation is not nearly as big as one would think. This is because the long term accuracy is already limited by the reference osc, so one would not generally use this kind of system out past 1000 sec or so anyway. So If doing long term multichannel Osc, One would likely be MUCH better off with a more basic undersampled Phase system for long term testing and just go thru and cheek each Osc one at time for a short time with a low tau tester such as this type. Keep the advantages and disadvantages coming in, so the Time Nuts can compare which methods work best for their application. Now if we just had some place to log the responses. Summery: If you have multi oscillators to test simultaneously that do not have EFC input, and that you want to do continuous sampling on, and do not have multiple TSC boxes, the TPLL is not the right tool for the job. Be better off with one simple lower resolution multiplexed time stamped TI phase system and a single TPLL. If one has a production requirement to test/compare several hundred oscillators simultaneously, the TSC5120A and its variants, being 2 channel instruments, aren't really that useful even if one could afford several hundred of them. Such a requirement may be difficult to meet within a modest budget whilst still achieving the performance requirements (eg 1E-13/tau system noise). Even with a much smaller number of oscillators (eg 8 -16) devising an affordable measurement system may be challenging. Bruce Bruce posted: The poor cost scaling of the tight PLL system is another reason why it has fallen out of favour for those who have more than 2 frequency standards to compare simultaneously. Thanks for that opinion, but I don't think we should list the above as a unique disadvantage. Maybe need a new column heading for that one, Any name suggestions? Does not sound all that valid or unique of a reason to me. It seems the same can be said about a TSC or any new high cost system. I would think a more important reason is that the simple TPLL is not a universal do all system. Because the simple analog version is Limited by it's reference Osc in many ways, This does give it some possible major disadvantages like not working so good with a CS or Rb standard. If one has more time than money, there are ways around that. ws *** Bruce Griffiths bruce.griffiths at xtra.co.nz Sun Jun 13 01:25:13 UTC 2010 Another disadvantage of the Tight PLL system that only applies to multichannel systems is that a dedicated reference oscillator is required for each channel. i.e. for an N channel system N reference oscillators are required. If correlation techniques were to be employed then an N channel system requires 2N reference oscillators. N channel versions of Dual Mixer systems by contrast only need a single offset oscillator and a single reference oscillator. Similarly an N channel heterodyne system only requires a single offset oscillator. An N channel direct RF phase sampling system (like that employed by the 2 channel TSC5120A) only requires a single samplign clock source. An N channel time interval counter that periodically (eg at a 1Hz rate) measures phase differences between 2 RF signals only requires a single reference source. The above system can be regarded as an undersampled version of the direct RF phase sampling system. The poor cost scaling of the tight PLL system is another reason why it has fallen out of favour for those who have more than 2 frequency standards to compare simultaneously. Bruce WarrenS wrote: Great start Now if we just had a list that someone would add the advantages and disadvantages to, so that any non relevant stuff could be easily seen and removed or moved to a third list, It would all become much clearer. ws Magnus Danielson wrote: On 06/12/2010 11:29 PM, Bruce Griffiths wrote: WarrenS wrote: subject: Advantages Disadvantages of the TPLL Method. Here is a new and unique Idea that may be useful for many. Rather than focusing on what some members may or may not already know, or how good or bad one specific working BB configuration is. How about focusing on what the TPLL method can and can not do well. If someone will make a place to post and compile a couple of list, I can start it off with what I've learned so far: DISADVANTAGES of the TPLL method: --- #1) The TPLL method is limited by it's reference OSC. This isn't necessarily
