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From: | Laur Joost |
Subject: | Re: [Discuss-gnuradio] matched filter for BPSK produced by phase shifting |
Date: | Sat, 16 Apr 2016 22:37:55 +0300 |
Hi Laur,
On 16.04.2016 18:30, Laur Joost wrote:
Well, that's a good thing, envelope-wise :)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.
Wait, so you got
The transmitted baseband is RRC-filtered.
BPSK symbols (-1,+1,+1,-1...) --> RRC --> analog phase shifter?
Or how do I have to read that?
That would sound like you had two pulse shapers!
Cheers,
Marcus
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
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