[time-nuts] crunching numbers from XOR phase detector

[Tom Van Baak]

> 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?

John,

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.

/tvb