Re: [time-nuts] 1 pps sync'ing
Maybe I am missing something obvious here but after using the 1PPS/10MHz reference multiplied up to 100 MHz cant you just insert a passive L/C phase shift network at the input (or output) of the multiplier chain and tune one of the "C" legs in the phase shift network to align the edges (change the the delay slightly) of the two waveforms? Temperature stability of the phase shift network might be a problem ? What are the other drawbacks of this simple approach? -DC manu...@artekmanuals.com On Jun 29, 2018, at 9:13 AM, Martyn Smith wrote: Hello, My colleague Steve asked a question about wanting to generate a 10 MHz and 100 MHz squarewaves with both rising edges aligned to a reference 1 pps input (to within 5ns). -- Dave manu...@artekmanuals.com www.ArtekManuals.com --- This email has been checked for viruses by Avast antivirus software. https://www.avast.com/antivirus ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to https://lists.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] 1 pps sync'ing
On Fri, 29 Jun 2018 16:37:41 +0200 Attila Kinali wrote: > How about just using an FPGA then? If you clock it at 200-400MHz, > then you can built a digital phase stepper with 2.5-5ns step size. > The FPGA can also handle the synchronization to an external pulse > quite easily and do fault detection (like the pulse suddenly jumping) > etc pp. BTW: if you have local oscillators for 10MHz and 100MHz, then it's also possible to sync them up, by measuring their relative phase. But all that becomes more complicated. In the end, it depends on what the exact specs are, that you need to achieve and how much effort you want to spend. As your PPS signal is fairly stable, it should be doable to sync everything up to better than 10ps (limited by how accurately the phase can be measured). If you want to, you can contact me off-list for more in-depth discussion. Attila Kinali -- It is upon moral qualities that a society is ultimately founded. All the prosperity and technological sophistication in the world is of no use without that foundation. -- Miss Matheson, The Diamond Age, Neil Stephenson ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to https://lists.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] 1 pps sync'ing
On Fri, 29 Jun 2018 14:13:10 +0100 "Martyn Smith" wrote: > I'm not trying to achieve 1-5 ns to UTC as that's not possible as already > pointed out, just 1 to 5 ns to a reference 1 pps (from Hydrogen Maser). How about just using an FPGA then? If you clock it at 200-400MHz, then you can built a digital phase stepper with 2.5-5ns step size. The FPGA can also handle the synchronization to an external pulse quite easily and do fault detection (like the pulse suddenly jumping) etc pp. Disadvantage of this is, that the output of an FPGA is rather noisy. Ie you will not get very low phase noise/jitter, but depending on your specs, it might be actually enough. If you need lower phase noise, you'd need to add a D-flipflop outside of the FPGA to syncrhonize the output. If done right, this give a jitter in the order of 100-200fs. > We definitely need all rising edges synchronised. Of course, we will have > to be very careful with cabling lengths etc otherwise we will lose all this > synchronisation. Cable length of 1m is somewhere in the order of 6-7ns delay. You have to be careful with lengths, but not very much so. If the cables are matched up to 1-2cm, that should be enough. Attila Kinali -- It is upon moral qualities that a society is ultimately founded. All the prosperity and technological sophistication in the world is of no use without that foundation. -- Miss Matheson, The Diamond Age, Neil Stephenson ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to https://lists.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] 1 pps sync'ing
Martin: Are you with PTS in Littleton ? Lester B Veenstra K1YCM MØYCM W8YCM 6Y6Y les...@veenstras.com Physical and US Postal Addresses 5 Shrine Club Drive (Physical) HC84 452 Stable Ln (RFD USPS Mail) Keyser WV 26726 GPS: 39.336826 N 78.982287 W (Google) GPS: 39.33682 N 78.9823741 W (GPSDO) Telephones: Home: +1-304-289-6057 US cell+1-304-790-9192 Jamaica cell: +1-876-456-8898 -Original Message- From: time-nuts [mailto:time-nuts-boun...@lists.febo.com] On Behalf Of Martyn Smith Sent: Friday, June 29, 2018 9:13 AM To: time-n...@febo.com Subject: [time-nuts] 1 pps sync'ing Hello, My colleague Steve asked a question about wanting to generate a 10 MHz and 100 MHz squarewaves with both rising edges aligned to a reference 1 pps input (to within 5ns). We already have a product that can do this (at 10 MHz), but it is very complicated, and Steve's job is to fine an easier approach. I'm not trying to achieve 1-5 ns to UTC as that's not possible as already pointed out, just 1 to 5 ns to a reference 1 pps (from Hydrogen Maser). We definitely need all rising edges synchronised. Of course, we will have to be very careful with cabling lengths etc otherwise we will lose all this synchronisation. So starting at 100 MHz and dividing down is a good idea, except the 100 MHz needs to be synchronised in the first place, which brings me back to the first problem. Our existing product generates 48 bit BCD time code all synchronised to a 1 pps inputs. This was designed ages ago for a customer. So, the last bit of the 48 bit is 100ns in time or 10 MHz in frequency. So we could use this board and then lock the 100 MHz to the 10 MHz. But it's not very elegant!! Anyway, the research continues. Best Regards Martyn ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to https://lists.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to https://lists.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] 1 pps sync'ing
On Fri, June 29, 2018 8:13 am, Martyn Smith wrote: > My colleague Steve asked a question about wanting to > generate a 10 MHz and 100 MHz squarewaves with > both rising edges aligned to a reference 1 pps > input (to within 5ns). You say "both," but which edge you pick is a little bit arbitrary since there are 100 million to choose to align to the PPS. General approach could be something like this (probably not optimal, but simple to understand): 100MHz tuneable oscillator -> divide by 10 -> 10MHz 10MHz -> divide by 10M -> 1Hz So you now have 100MHz, 10MHz, and 1Hz, syntonized since they came from the same source, but the synchronization is offset by the delay through the divider chains. Take the 10MHz and 1Hz signals, and send them to the data input of a D flip-flop, clocked by the 100MHz, and now the 100MHz, 10MHz, and 1Hz edges are offset only by the delay through the flip-flop. You would still have to be careful in part selection, standard CMOS logic would have several ns of propagation delay, so you couldn't just grab any random flip-flop and guarantee 5ns edge alignment. If you want to throw a little money and layout effort at the problem Analog Devices make a device which specifically advertise as being able to synchronize clock outputs to 1PPS input: http://www.analog.com/en/products/clock-and-timing/clock-generation-distribution/clock-synchronization/ad9548.html http://www.analog.com/en/education/education-library/videos/756421501001.html That device is basically a DDS based clock generator with digital PLL all in a single package, so could be more than needed for this task. I have not used the AD part personally yet, I noticed it while looking for something else and thought the fact they specifically pointed out it was useful for synchronizing to PPS was interesting. -- Chris Caudle ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to https://lists.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] 1 pps Sync'ing
On Mon, 25 Jun 2018 10:46:54 -0400 Bob kb8tq wrote: > Does UTC exist ( real time ) at the 1 ns level? Currently, it does not. The clock comparison uncertainties are still in the order of 1-3ns for short distances (several 100km) and grow quite a bit once you go over something like 2000-3000km. Unless you are using a dedicated fiber. But very few labs can afford to have a fiber connecting them to another lab. Also consider that, even within a lab, doing sub-ns accurate time comparisons is challenging. All delays and their drifts need to be precisely measured, characterized and factored in. There is a reason why the SR-620 is still the main workhorse in metrology labs, even though we have equipment available that beats the SR-620 in terms of resolution and stability. It's just not necessary to go below 20ps as the other factors cannot be eliminated with that high precision/accuracy anyways. If only precision time comparison is required, IIRC the current limit is around 50-100fs. And even that requires a lot of work and characterization. Attila Kinali -- It is upon moral qualities that a society is ultimately founded. All the prosperity and technological sophistication in the world is of no use without that foundation. -- Miss Matheson, The Diamond Age, Neil Stephenson ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to https://lists.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] 1 pps Sync'ing
Hi On a Time Nut metaphysical note - > On Jun 25, 2018, at 10:38 AM, Tom Van Baak wrote: > > Steve, > >> I need the rising edges of both the 10 MHz and 100 MHz squarewave outputs >> to be aligned with the GPS 1 pps (UTC) to within 1 ns. > > Two comments. > > 1) If you divide 100 MHz -> 10 MHz -> 1 Hz then (with careful design, > calibrated layout / wiring) you can have all three rising edges within 1 ns > *of each other*. I assume this is your goal. If you already have a 100 MHz > GPSDO then it would surprise me if the outputs are not already synchronized > with each other. I mean, almost all GPSDO give a 1PPS output that is derived > from the LO, by design. If your goal is 1 ns, you obviously do not want to > use the raw 1PPS from the receiver. What make/model GPSDO are you using? > > 2) On the other hand, if your goal is that all the outputs are within 1 ns > *of UTC*, then you have a big problem. Not even national timing laboratories, > with a pile of cesium and H-maser references, can get their UTC(k) within 1 > ns of UTC. Perhaps you can explain a bit more what you are actually doing. It > sounds like an interesting application. Relative timing at the 1 ns level is > easy. Absolute UTC timing at the ns level is much, much harder. Does UTC exist ( real time ) at the 1 ns level? Bob > > /tvb > > - Original Message - > From: "Martyn Smith" > To: > Sent: Sunday, June 24, 2018 3:37 AM > Subject: [time-nuts] 1 pps Sync'ing > > >> Hello, >> >> I am a newbie question. >> >> I have an application where I have a 10 MHz and 100 MHz squarewave output >> from my GPS frequency standard. >> >> The frequency standard uses the PRS10 rubidium. The 100 MHz output is just >> a 100 MHz VCO locked to the 10 MHz. >> >> These outputs are disciplined by the GPS's 1 pps (as far as frequency). But >> they are not in phase with it. >> >> I need the rising edges of both the 10 MHz and 100 MHz squarewave outputs to >> be aligned with the GPS 1 pps (UTC) to within 1 ns. >> >> Anyone already done this? I'm sure I've seen a distribution amplifier that >> does this at 10 MHz. >> >> But the 100 MHz is actually the more important one that I need to align. >> >> Regards >> >> Steve >> ___ >> time-nuts mailing list -- time-nuts@lists.febo.com >> To unsubscribe, go to >> https://lists.febo.com/cgi-bin/mailman/listinfo/time-nuts >> and follow the instructions there. > > ___ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe, go to > https://lists.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to https://lists.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] 1 pps Sync'ing
Steve, > I need the rising edges of both the 10 MHz and 100 MHz squarewave outputs > to be aligned with the GPS 1 pps (UTC) to within 1 ns. Two comments. 1) If you divide 100 MHz -> 10 MHz -> 1 Hz then (with careful design, calibrated layout / wiring) you can have all three rising edges within 1 ns *of each other*. I assume this is your goal. If you already have a 100 MHz GPSDO then it would surprise me if the outputs are not already synchronized with each other. I mean, almost all GPSDO give a 1PPS output that is derived from the LO, by design. If your goal is 1 ns, you obviously do not want to use the raw 1PPS from the receiver. What make/model GPSDO are you using? 2) On the other hand, if your goal is that all the outputs are within 1 ns *of UTC*, then you have a big problem. Not even national timing laboratories, with a pile of cesium and H-maser references, can get their UTC(k) within 1 ns of UTC. Perhaps you can explain a bit more what you are actually doing. It sounds like an interesting application. Relative timing at the 1 ns level is easy. Absolute UTC timing at the ns level is much, much harder. /tvb - Original Message - From: "Martyn Smith" To: Sent: Sunday, June 24, 2018 3:37 AM Subject: [time-nuts] 1 pps Sync'ing > Hello, > > I am a newbie question. > > I have an application where I have a 10 MHz and 100 MHz squarewave output > from my GPS frequency standard. > > The frequency standard uses the PRS10 rubidium. The 100 MHz output is just a > 100 MHz VCO locked to the 10 MHz. > > These outputs are disciplined by the GPS's 1 pps (as far as frequency). But > they are not in phase with it. > > I need the rising edges of both the 10 MHz and 100 MHz squarewave outputs to > be aligned with the GPS 1 pps (UTC) to within 1 ns. > > Anyone already done this? I'm sure I've seen a distribution amplifier that > does this at 10 MHz. > > But the 100 MHz is actually the more important one that I need to align. > > Regards > > Steve > ___ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe, go to > https://lists.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to https://lists.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] 1 pps Sync'ing
Hi You can indeed do this, the question is - do you *really* want to? Depending a bit on your GPS module, the 1 pps output can jump around a few nanoseconds on a second to second basis. Keeping the 100 MH edge locked implies modulating the 100 MHz by at least a few ppb at some rate faster than 1 Hz. That will degrade the phase noise on the outputs more than a little …. A deeper issue is that the GPS module really isn’t reporting “GPS time” at the 1 second level. It’s reporting GPS Time + atmospheric noise. What you would be tracking is more the bounce in the atmosphere than anything that GPS actually is doing. Something like an L1 / L2 receiver would help some with this. Bob > On Jun 24, 2018, at 6:37 AM, Martyn Smith wrote: > > Hello, > > I am a newbie question. > > I have an application where I have a 10 MHz and 100 MHz squarewave output > from my GPS frequency standard. > > The frequency standard uses the PRS10 rubidium. The 100 MHz output is just a > 100 MHz VCO locked to the 10 MHz. > > These outputs are disciplined by the GPS's 1 pps (as far as frequency). But > they are not in phase with it. > > I need the rising edges of both the 10 MHz and 100 MHz squarewave outputs to > be aligned with the GPS 1 pps (UTC) to within 1 ns. > > Anyone already done this? I'm sure I've seen a distribution amplifier that > does this at 10 MHz. > > But the 100 MHz is actually the more important one that I need to align. > > Regards > > Steve > ___ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe, go to > https://lists.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to https://lists.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
