While waiting for the TAPR TICC to be delivered and the various PCBs to arrive, I decided picking up the GPS simulator from Leapsecond.com again.
I reimplemented the simulation engine in Octave to have an integrated solution and tweaked it so that it matches my own STM32 code so that the parameters and results can be shared and compared between the simulator and the real hardware. Also, I'll use it as an experimentation platform for Kalman filtering.
Here's some interesting results from the simulator.
TIC filtering:
Red: short timeconstant (40s)
Blue: long timeconstant (1000s)
Interestingly, with a longer filter constant you don't get a lot of advantage, for tau=300 you get a slightly lower sigma but you pay for it with a significant bulge at tau=3000
Next, PI loop gain:
Higher gain gives a quicker decline above tau=2000s, but degrades sigma for tau < 2000s significantly. The red curve is probably optimal.
Next, OCXO vs. RB:
Yellow trace is the PRS10 dataset I got from TVB with a PI integrator timeconstant of 2000s, blue is the OCXO dataset from leapsecond.com. Red is the same OCXO with timeconstant 200s.