David,

one way to estimate the rate is to raise the CPM signal to an

appropriate power in order to generate spectral lines that can be easily

tracked.

The precise power is a function of the modulation index of your CPM

modulation. Eg, if you are using full-response CPFSK with h=N/D

(where N,D are relative primes) then you can raise your signal to the

power D in order to generate spectral lines. I don’t remember off the

top off my head the exact frequency of these spectral lines but you can

easily find out the relationship by simple experimentation.

BTW, are you using the cpm.py hierarchical block that is

on the trunk? If yes, I attach a simple python code that

demonstrates the spectral line generation for a 4-CPFSK

with h=1/2.

Achilleas