[time-nuts] crunching numbers from XOR phase detector
Tom Van Baak
tvb at LeapSecond.com
Wed Jan 4 02:38:07 UTC 2012
> 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?
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.
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