[Moving to list, per Eric's request]
Right, so we are talking about implementing 8PSK and pi/4 DQPSK, the later
being more important as it shows up in implementation often. My concern with
both, though, is the phase and frequency synchronization. I'm sure someone
out there has some experience with this.
To summarize, we have a second order Costas loop for BPSK and a fourth order
Costas loop for QPSK. What is normally used for synchronization with these
modulations? For pi/4 DQPSK, I was thinking we could use the current fourth
order loop, in which we can set the desired rotation. Each symbol received
would cause the rotation variable to flip 45 degrees.
a) does this work, and
b) is there a better way to do this?