I would like to recognize and distinguish between FM and QPSK signal by analyzing its properties. I have a general idea about their main distinguishing feature:
- FM has continuous phase;
- PSK has phase disruptions (gaps).
I can get phase for every sample since they are complex.
But I am lost in the implementation because I have many ideas how to find the phase differences but not so much practice with gnuradio blocks.
I tried to implement some kind of phase derivative function by measuring the phase difference between consecutive samples. But the problem is the following - I do no know exactly symbol rate. Can I do this by trying variable delay between samples or are there any other better alternatives in Gnuradio?
Thank you in advance for any suggestions! Of course, some channel noise exists and impairs phase measurements.