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[Discuss-gnuradio] Using a MPSK Demodulator or 4QAM for oQPSK

From: Marius
Subject: [Discuss-gnuradio] Using a MPSK Demodulator or 4QAM for oQPSK
Date: Sat, 26 May 2012 18:08:04 +0200


I found a comment in the source code of the MPSK block, that it could
be used for oQPSK demodulation. I think this block is very interesting
implementation, however I'm not sure which parameters I should use for
oQPSK. In the gr-ieee802_15_4 implementation from Thomas Schmid he
uses a Quadrature Demod with an MM Clock Recovery where the parameters

omega = self.sps
gain_omega = .25*gain_mu*gain_mu        # critically damped

This works just fine - with a Quadrature Demodulator.

Can somebody suggest parameters for the MPSK Block, or give me some
hints how I can calculate/test them at least? The MPSK block uses a
Costas Loop for Demodulation, so the approach is quite different here.
Also I wonder whether it's possible to use a 4QAM Demod, because
practically a 4QAM mod produces the same wave-form like a QPSK.
Practically at least ,)


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