[time-nuts] GPS signal simulator

[WarrenS]

>    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

****************** 
Tom

Thanks that should be very useful for software simulations.

The use I had in mind for the tool I described where for the next stage of testing. 
It can be used to test at the REAL Hardware level, using a 'perfect' GPS signal with 
no noise or with any type of desired controlled noise.
For example it is hard and time consuming to see how many ps of error 
your phase detector is adding or what the phase margin or noise gain is of the H/W PLL.
Is the power supply good enough or is it causing errors, etc 
When using real GPS data, the random noise will hide the advanced 
type of information you may want to take.
The other use of the Hardware simulator is for someone that wants to know how 
accurate their GPSDO is but does not have access to a source accurate enough 
to test their GPSDO.

WarrenS