[time-nuts] GPS signal simulator
Tom Van Baak
tvb at LeapSecond.com
Thu Dec 11 06:33:36 UTC 2008
> In my quest to keep improving my GPSDO, a simple test tool
> that I find indispensable is a GPS 1PPS (or 100Hz) signal simulator
> reference. Others may also find this useful because it allows testing the
> PLL & DO in their GPSDO to Cs type accuracy using a standard OCXO.
Warren,
There's been some discussion about a GPS simulator for the
purpose of playing with GPSDO algorithms a couple of times
on the list over the years.
But since you're making more progress than most have, here
is a nice pair of 400,000 (!) sample data sets for you to use:
http://www.leapsecond.com/pages/gpsdo-sim/
For playing with GPSDO, the character of the typical 1PPS is
very easy to model (it's basically a few ns of noise that nicely
averages down at 1 over tau out past a day) so going all the way
back to RF simulation of the GPS SV signal(s) might be overkill.
In any event, I found it much easier to just take real GPS 1PPS
data, and real OCXO data, and then simulate a GPSDO from
those two raw data sets. You can plot phase, frequency, ADEV
of both inputs and one output and see the GPSDO humps we
always talk about, etc.
/tvb
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