Forum: GNU Radio Does USRP do phase estimation when down convertion?

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596af7df4dff49c792ef1796d3abbb20?d=identicon&s=25 isulsz (Guest)
on 2009-05-31 22:55
(Received via mailing list)
When USRP down convert the passband signal, does it perform phase
estimation?
Or in other words, does the phase of the sin wave from the local
oscillator
lock to the phase of the incoming signal?

Phase is needed in coherent demodulation. I just want to know where it
is
performed in the USRP and GNU radio. I conjecture that the USRP does not
estimate the phase and the demodulator does phase estimation, for
example,
in gr_mpsk_receiver_cc. But I am not sure.


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998dbc3ac73d5487c59c0ee0f5baeeb1?d=identicon&s=25 Sebastiaan Heunis (Guest)
on 2009-06-01 00:21
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Isulsz

The DDC on the USRP only mixes the signal down using the CORDIC
algorithm.  The CORDIC only multiplies the input signal by scale
values corresponding to cos and sine.  The phase estimation should
happen in the C++ code on the PC then.

Sebastiaan
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