Hi to all.
I want to test if the block Correlate and Sync improves my GFSK receiver, so I started modifying ./gr-digital/examples/demod/test_corr_and_sync.grc .
1) I replaced the BPSK modulator (with rrc filter) by a Chunks to Symbols [-1,+1] followed by a Interpolating FIR with gaussian taps.
2) I replaced the matched filter taps for Correlate and Sync and Polyphase Clock Sync with the ones I think are correct BUT OBVIOUSLY ARE NOT [<-- help needed here].
3) I eliminated frequency offset and Costas Loop because I believe they are not applicable after a FM demodulation (which I did not included in this first exploration).
(Flowgraph attached)
Things I observe:
* Correlate and Sync detects preamble start, but the clock recovery looks wrong (this can be seen zooming in or in the constellation plot).
* QT GUI Time sink showing correlation does not triggers with the hardcoded value (200). I had to change it to 45.
I'm having a hard time figuring out from the c++ code and documentation the right way to design the taps to put into Correlate and Sync and PFB Clock Sync blocks.
I always find myself feeling I get contradictory clues from code, examples and documentation when choosing the taps for blocks that depend on PFB.
test_corr_and_sync_for_square_waves.grc