[time-nuts] TICC resolution...
wojciech at owczarek.co.uk
Tue Apr 4 20:04:00 EDT 2017
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
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
On 4 April 2017 at 23:03, Tom Van Baak <tvb at 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
> The attached plot is the result of a 30 hour run on a TICC (beta, Nov
> Also attached is what happens if you zoom in a bit:
> 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.
> ----- Original Message -----
> From: "Wojciech Owczarek" <wojciech at owczarek.co.uk>
> To: "Discussion of precise time and frequency measurement" <
> time-nuts at febo.com>
> Sent: Tuesday, April 04, 2017 9:20 AM
> Subject: [time-nuts] TICC resolution...
> > _______________________________________________
> > time-nuts mailing list -- time-nuts at febo.com
> > To unsubscribe, go to https://www.febo.com/cgi-bin/m
> > and follow the instructions there.
> time-nuts mailing list -- time-nuts at febo.com
> To unsubscribe, go to https://www.febo.com/cgi-bin/m
> and follow the instructions there.
More information about the time-nuts