Forum: GNU Radio Quick Costas Loop question

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53e914bcf9093cbd67202d1bed80d8cf?d=identicon&s=25 Steven Clark (Guest)
on 2007-02-02 22:17
(Received via mailing list)
Is there any reason why the Costas carrier recovery loop used in the
dqpsk.py example would not be suitable for similar use in a gmsk
receiver?

TIA
-Steven
8cc60441dc67b4e59421ebe95dc63c23?d=identicon&s=25 Tom Rondeau (Guest)
on 2007-02-03 14:41
(Received via mailing list)
> From: discuss-gnuradio-bounces+trondeau=vt.edu@gnu.org
[mailto:discuss-gnuradio-bounces+trondeau=vt.edu@gnu.org] On Behalf Of >
Steven Clark
> Sent: Friday, February 02, 2007 4:16 PM
> To: Discuss-gnuradio@gnu.org
> Subject: [Discuss-gnuradio] Quick Costas Loop question
>
> Is there any reason why the Costas carrier recovery loop used in the
dqpsk.py example would not be suitable for similar use
> in a gmsk receiver?
>
> TIA
> -Steven

Steven,

You should be able to. I've used it in an AM receiver before to get
better
carrier lock. The GMSK is fairly tolerant of frequency offsets, though,
so
the Costas loop would increase the computational complexity and it
shouldn't
be necessary (except under exceptional circumstances) that a change in
frequency wouldn't correct. The FM receiver and the M&M do a bit of
carrier
correction themselves. Top of my head, I think about +-4 kHz max.

Tom
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