Re: [time-nuts] crunching numbers from XOR phase detector
Neat. Thanks for sharing. With a XOR, you can't tell which input is higher frequency. I think you can fix that with a second XOR and a delay line. I think 90 degrees of delay will provide the most information. At 10 MHz, that's 25 ns. I think that's about 15 feet of good coax. -- 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] crunching numbers from XOR phase detector
Le 04/01/2012 09:58, Hal Murray a écrit : Neat. Thanks for sharing. With a XOR, you can't tell which input is higher frequency. I think you can fix that with a second XOR and a delay line. I think 90 degrees of delay will provide the most information. At 10 MHz, that's 25 ns. I think that's about 15 feet of good coax. all that spaghetti made me wonder if you can get it on a chip . yes, it seems. ex EP8034, 200ns in tenths. there are others of course. ___ 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] crunching numbers from XOR phase detector (mike cook)
Neat. Thanks for sharing. With a XOR, you can't tell which input is higher frequency. I think you can fix that with a second XOR and a delay line. I think 90 degrees of delay will provide the most information. At 10 MHz, that's 25 ns. I think that's about 15 feet of good coax. all that spaghetti made me wonder if you can get it on a chip . yes, it seems. ex EP8034, 200ns in tenths. there are others of course. http://www.minicircuits.com/pdfs/JSPHS-12.pdf It's not digital. It is an alalog adjustable voltage controlled phase shifter. If you want to shift a relatively clean 10Mhz sine... ___ 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] crunching numbers from XOR phase detector
On Wed, 04 Jan 2012 00:58:24 -0800, Hal Murray hmur...@megapathdsl.net wrote: With a XOR, you can't tell which input is higher frequency. I think you can fix that with a second XOR and a delay line. I think 90 degrees of delay will provide the most information. At 10 MHz, that's 25 ns. I think that's about 15 feet of good coax. I was thinking of an added D flip-flop, D latch, or a 330 ohm 100 pF RC delay in front of a second XOR gate. ___ 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] crunching numbers from XOR phase detector
At 10:16 AM + 1/4/12, time-nuts-requ...@febo.com wrote: Date: Wed, 04 Jan 2012 00:58:24 -0800 From: Hal Murray hmur...@megapathdsl.net To: Discussion of precise time and frequency measurement time-nuts@febo.com Subject: Re: [time-nuts] crunching numbers from XOR phase detector Message-ID: 20120104085824.8426e800...@ip-64-139-1-69.sjc.megapath.net Content-Type: text/plain; charset=us-ascii Neat. Thanks for sharing. With a XOR, you can't tell which input is higher frequency. I think you can fix that with a second XOR and a delay line. I think 90 degrees of delay will provide the most information. At 10 MHz, that's 25 ns. I think that's about 15 feet of good coax. Beware of teflon dielectric cable, as the teflon knee is centered around room temperature, making delay cables of teflon quite sensitive to slight changes in temperature. http://www.micro-coax.com/pages/technicalinfo/applications/27.asp Joe Gwinn ___ 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] crunching numbers from XOR phase detector
On Wed, Jan 4, 2012 at 12:58 AM, Hal Murray hmur...@megapathdsl.net wrote: Neat. Thanks for sharing. With a XOR, you can't tell which input is higher frequency. I think you can fix that with a second XOR and a delay line. I think you can build a PFD or Phase Frequency Detector with three or four flip flops. This avoid using the delay line and works over a wide range. If I'm not mistaken there is a PFD inside the 74HC4046. It uses flip flops. Be sure to look at the 74HC type not the cd4046. The 75hc type works up to 18MHz. Chris Albertson Redondo Beach, California ___ 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] crunching numbers from XOR phase detector
You're right there are 3 phase detectors in the 4046: RS and JK flip-flops and and XOR gate. On Wed, Jan 4, 2012 at 6:21 PM, Chris Albertson albertson.ch...@gmail.comwrote: On Wed, Jan 4, 2012 at 12:58 AM, Hal Murray hmur...@megapathdsl.net wrote: Neat. Thanks for sharing. With a XOR, you can't tell which input is higher frequency. I think you can fix that with a second XOR and a delay line. I think you can build a PFD or Phase Frequency Detector with three or four flip flops. This avoid using the delay line and works over a wide range. If I'm not mistaken there is a PFD inside the 74HC4046. It uses flip flops. Be sure to look at the 74HC type not the cd4046. The 75hc type works up to 18MHz. Chris Albertson Redondo Beach, California ___ 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] crunching numbers from XOR phase detector
Be very careful of the FPD in the 4046. It has a dead-zone when the phase error is at or very close to zero. Some versions of the chip claim to have improved that dead-zone. But it's still there to some degree, at least in all the versions I have tried. -Brian, WA1ZMS - Original Message From: Chris Albertson albertson.ch...@gmail.com To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Wed, January 4, 2012 12:21:06 PM Subject: Re: [time-nuts] crunching numbers from XOR phase detector On Wed, Jan 4, 2012 at 12:58 AM, Hal Murray hmur...@megapathdsl.net wrote: Neat. Thanks for sharing. With a XOR, you can't tell which input is higher frequency. I think you can fix that with a second XOR and a delay line. I think you can build a PFD or Phase Frequency Detector with three or four flip flops. This avoid using the delay line and works over a wide range. If I'm not mistaken there is a PFD inside the 74HC4046. It uses flip flops. Be sure to look at the 74HC type not the cd4046. The 75hc type works up to 18MHz. Chris Albertson Redondo Beach, California ___ 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] crunching numbers from XOR phase detector
Have you tried the 74HCT9046? They claim no dead zone. Note - seems to be HCT only. Orin. On Wed, Jan 4, 2012 at 9:32 AM, Brian Justin wa1...@att.net wrote: Be very careful of the FPD in the 4046. It has a dead-zone when the phase error is at or very close to zero. Some versions of the chip claim to have improved that dead-zone. But it's still there to some degree, at least in all the versions I have tried. -Brian, WA1ZMS ___ 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] crunching numbers from XOR phase detector
Not yet, but I guess I will now! Thanks! -Brian - Original Message From: Orin Eman orin.e...@gmail.com To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Wed, January 4, 2012 12:59:12 PM Subject: Re: [time-nuts] crunching numbers from XOR phase detector Have you tried the 74HCT9046? They claim no dead zone. Note - seems to be HCT only. Orin. On Wed, Jan 4, 2012 at 9:32 AM, Brian Justin wa1...@att.net wrote: Be very careful of the FPD in the 4046. It has a dead-zone when the phase error is at or very close to zero. Some versions of the chip claim to have improved that dead-zone. But it's still there to some degree, at least in all the versions I have tried. -Brian, WA1ZMS ___ 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] crunching numbers from XOR phase detector
On 1/4/12 8:14 AM, Joe Gwinn wrote: At 10:16 AM + 1/4/12, time-nuts-requ...@febo.com wrote: Date: Wed, 04 Jan 2012 00:58:24 -0800 From: Hal Murray hmur...@megapathdsl.net To: Discussion of precise time and frequency measurement time-nuts@febo.com Subject: Re: [time-nuts] crunching numbers from XOR phase detector Message-ID: 20120104085824.8426e800...@ip-64-139-1-69.sjc.megapath.net Content-Type: text/plain; charset=us-ascii Neat. Thanks for sharing. With a XOR, you can't tell which input is higher frequency. I think you can fix that with a second XOR and a delay line. I think 90 degrees of delay will provide the most information. At 10 MHz, that's 25 ns. I think that's about 15 feet of good coax. Beware of teflon dielectric cable, as the teflon knee is centered around room temperature, making delay cables of teflon quite sensitive to slight changes in temperature. http://www.micro-coax.com/pages/technicalinfo/applications/27.asp See also http://www.gore.com/en_xx/products/cables/microwave/phase-stability-whitepaper.html http://www.gore.com/en_xx/products/cables/microwave/changes-insertion-loss-phase.html Yeah, but the change is pretty small, (a few hundred ppm) and overall, those cables have fairly low temperature coefficient. The latter Gore writeup shows 0.2 deg/GHz/ft across the knee For the 10 MHz scenario at 15ft, that's .03 degrees, 83 ppm You sort of have a choice between a cable that has low overall variation, but a step in the curve OR a cable that has a smooth characteristic and no bumps. Interestingly, other dielectrics don't show this effect. In particular, the silica dielectric stuff is very stable. ___ 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] crunching numbers from XOR phase detector
The XOR phase comparator is without feed-back and that simply means no dead-zone. This is consistent with literature on XOR PDs. It will of course have non-linearity which is improving with speed of the process technology. A 74HC4046 will be better than a CD4046. BUT the low-frequency noise is inversely proportional to channel-length of the used MOSFETs. So for time-nuts interests a slower CD4046 can be better. The other 4046 phase comparators are made of flip-flops where the dead-zone is proportional to gate-delay. For ultimate performance one have to use a classical DRM. - Henry Brian Justin schrieb: Not yet, but I guess I will now! Thanks! -Brian - Original Message From: Orin Eman orin.e...@gmail.com To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Wed, January 4, 2012 12:59:12 PM Subject: Re: [time-nuts] crunching numbers from XOR phase detector Have you tried the 74HCT9046? They claim no dead zone. Note - seems to be HCT only. Orin. On Wed, Jan 4, 2012 at 9:32 AM, Brian Justin wa1...@att.net wrote: Be very careful of the FPD in the 4046. It has a dead-zone when the phase error is at or very close to zero. Some versions of the chip claim to have improved that dead-zone. But it's still there to some degree, at least in all the versions I have tried. -Brian, WA1ZMS -- ehydra.dyndns.info ___ 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] crunching numbers from XOR phase detector
Previously I have been comparing 10 MHz frequencies using TvB's picPET device plus a picDIV divider to get a 1 PPS signal, but I wanted more resolution for comparing relative drift of two Rb references. I got square wave outputs from my references (see my previous posts) and I made a simple XOR phase detector from a single XOR gate (74LVC1G86) : https://picasaweb.google.com/lh/photo/ofFwP8Eo1qFAzNObq69iCtMTjNZETYmyPJy0liipFm0 I have read about how nonlinear the XOR PD becomes at the endpoints (0 and 180 phase shift) although this one seems to work pretty well, and the output looks reasonably triangular: https://picasaweb.google.com/lh/photo/swKVhhP7NerRvMKdnW8rjtMTjNZETYmyPJy0liipFm0 There is some nonlinearity but it seems consistent from cycle to cycle. I might be able to reduce the bumps with better circuit layout, shorter wires, terminated lines etc. But just for playing around with my initial data, I think I can model the shape of the response and get a more accurate reading of instantaneous phase angle vs time. I could write some code for this, but I suspect this wheel has been invented before... is there any reference I should consult? I think something similar is done inside the PIC-TIC to calibrate its response? ___ 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] crunching numbers from XOR phase detector
There is some nonlinearity but it seems consistent from cycle to cycle. I might be able to reduce the bumps with better circuit layout, shorter wires, terminated lines etc. But just for playing around with my initial data, I think I can model the shape of the response and get a more accurate reading of instantaneous phase angle vs time. I could write some code for this, but I suspect this wheel has been invented before... is there any reference I should consult? I think something similar is done inside the PIC-TIC to calibrate its response? John, Very nice plot. Thanks for sharing that. The next step is simply to differentiate and then re-plot the data (you know that's just one line of code: x[i+1] - x[i]). You should see two lines, +slope and -slope. Then take the absolute value. You should now see one line and the auto-scaled plot will show in much greater detail the variations of Rb performance and/or XOR non-linearity. Make these two plots and then I'll walk you through the next step. /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] crunching numbers from XOR phase detector
Having access to two Rb sources and looking at phase shift and jitter is something I find interesting. Has anyone fed two Rb sourced 10mhz signals in to a high-z an op-amp and looked at the output on a SA ? Should probably have at least 100mhz bw on the SA in order to see the events. A few tests to run with this experiment are 1) From cold: phase spectra to lock 2) From hot(power cycle) phase spectral to lock -- both power down/up at the same time. then vice versa 3) phase spectra relative to heat( forced air heat sinking, thermal blanketing ,etc) Obviously this test is geared for short term phase events, where as you are looking for long term. I find both equally interesting. When i get some extra time and hardware, I'm going to end up performing this very test. 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.
