Hi all!
I need a clue where to start.
I have a signal that is BPSK that is modulated not by applying the filtered baseband to the in-phase component, but instead doing literal analog phase shifting.
The result is that the signal transitions between the -1 and 1 symbols not through zero, but instead along the unit circle.
The transmitted baseband is RRC-filtered.
My questions:
1. Is Raised Cosine even a valid Nyquist filter for such a signal? After all, the actual In-phase transition occurs not according to the RRC response, but according to the sine OF the RRC.
2. The response of such a modulator to a unit impulse is necessarily complex. From what I gather, the matched filter is then, also complex (time reversed and conjugated). How should I go about this in GnuRadio, given that the PFB Clock sync only takes real taps?
3. Or can I just take the real part of the matched filter and feed that to PFB Clock sync? The constellation will have a weird spread (see picture). Will that affect either Costas or PFB?
PS: The positioning of the constellation plots was not planned.
All the best,
Laur