Hi Wojciech, Thanks for sharing your TICC plot. Yes, the periodic peaks show the ~55 ps quantization, which is the limiting factor of the TICC's single-shot resolution. The TICC is based on the TDC7200 Time-to-Digital Converter (TDC) chip, which uses a digital ring oscillator, which a mobius strip-like closed loop of an odd number of gates. So this quantization is expected and readily measurable with any pair of stable sources. But I'm not sure why your plot is so ragged. Either you have too few samples, or one of your sources is unstable, or maybe the 1PPS is itself quantized, or perhaps some low order digits from the TICC are truncated before you made your plot. If you use cleaner sources and longer runs you can get textbook-pretty results. The attached plot is the result of a 30 hour run on a TICC (beta, Nov 2016): http://leapsecond.com/pages/ticc/ticc-log5342-hist-1.gif Also attached is what happens if you zoom in a bit: http://leapsecond.com/pages/ticc/ticc-log5342-hist-3.gif In that second plot both the 1 ps granularity of the TICC ascii output and the ~55 ps quantization of the TDC7200 chip are visible. A TICC tends to have slightly better resolution than a hp 53132A but the "character" of their resolution is quite different: the TICC has strong quantization peaks and the 53132 is more Gaussian; the TICC outputs with 1 ps resolution (overly optimistic) and the hp rounds to 0.1 ns (probably conservative). If you try to push the envelope with better-than-spec performance out of a TICC or try to automate channel-channel-reference calibration, these details start to matter. /tvb ----- Original Message ----- From: "Wojciech Owczarek" <wojciech@owczarek.co.uk> To: "Discussion of precise time and frequency measurement" <time-nuts@febo.com> Sent: Tuesday, April 04, 2017 9:20 AM Subject: [time-nuts] TICC resolution... > _______________________________________________ > 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.

Tom, Thanks for your comments - the plot was really a quick example only. Yes, I am aware of the TDC7200 method of operation, all I meant to say was that the 55 ps clusters can be clearly seen, and I was expecting the jitter to blur the lines somewhat more. It was a combination of a histogram with a low number of bins, few samples, and judging by the phase plot I am also suspecting quantisation of the 1PPS output. The source is quite stable, although it is being actively GPS+GLN disciplined. While the 10 MHz and the 1PPS come from the same unit, they do not come directly from the PRS10, they hit some CMOS->LVDS->distribution->CMOS and some 74xxx, across different paths, so all that takes a toll. I have some less complex systems available where this should be cleaner. Anyhow, the TICC is proving an invaluable tool for field testing, calibration, and even cable delay measurement.. ...One reaches a whole new level of anal retentiveness once in the sub-100 ps range. Thanks, Wojciech On 4 April 2017 at 23:03, Tom Van Baak <tvb@leapsecond.com> wrote: > Hi Wojciech, > > Thanks for sharing your TICC plot. Yes, the periodic peaks show the ~55 ps > quantization, which is the limiting factor of the TICC's single-shot > resolution. The TICC is based on the TDC7200 Time-to-Digital Converter > (TDC) chip, which uses a digital ring oscillator, which a mobius strip-like > closed loop of an odd number of gates. So this quantization is expected and > readily measurable with any pair of stable sources. > > But I'm not sure why your plot is so ragged. Either you have too few > samples, or one of your sources is unstable, or maybe the 1PPS is itself > quantized, or perhaps some low order digits from the TICC are truncated > before you made your plot. > > If you use cleaner sources and longer runs you can get textbook-pretty > results. > > The attached plot is the result of a 30 hour run on a TICC (beta, Nov > 2016): > http://leapsecond.com/pages/ticc/ticc-log5342-hist-1.gif > > Also attached is what happens if you zoom in a bit: > http://leapsecond.com/pages/ticc/ticc-log5342-hist-3.gif > > In that second plot both the 1 ps granularity of the TICC ascii output and > the ~55 ps quantization of the TDC7200 chip are visible. > > A TICC tends to have slightly better resolution than a hp 53132A but the > "character" of their resolution is quite different: the TICC has strong > quantization peaks and the 53132 is more Gaussian; the TICC outputs with 1 > ps resolution (overly optimistic) and the hp rounds to 0.1 ns (probably > conservative). If you try to push the envelope with better-than-spec > performance out of a TICC or try to automate channel-channel-reference > calibration, these details start to matter. > > /tvb > > > ----- Original Message ----- > From: "Wojciech Owczarek" <wojciech@owczarek.co.uk> > To: "Discussion of precise time and frequency measurement" < > time-nuts@febo.com> > Sent: Tuesday, April 04, 2017 9:20 AM > Subject: [time-nuts] TICC resolution... > > > > _______________________________________________ > > time-nuts mailing list -- time-nuts@febo.com > > To unsubscribe, go to https://www.febo.com/cgi-bin/m > ailman/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/m > ailman/listinfo/time-nuts > and follow the instructions there. > -- - Wojciech Owczarek