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...
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