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 <t...@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" <wojci...@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 _______________________________________________ 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.