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Re: [Discuss-gnuradio] GMSK carrier recovery

From: John Windish
Subject: Re: [Discuss-gnuradio] GMSK carrier recovery
Date: Mon, 12 Mar 2007 12:15:13 -0700 (PDT)


Thanks for your interest.  Sorry it took so long to respond, I've been rather busy.

It would be worthwhile to have a solution that works over variable bit-time products, but for starters, let's say the BT product is 0.35.  The modulation index is 0.5 (which I believe is true of all GMSK implementations).


----- Original Message ----
From: Tim Meehan <address@hidden>
To: jjw <address@hidden>
Cc: address@hidden
Sent: Monday, March 5, 2007 5:21:31 PM
Subject: Re: [Discuss-gnuradio] GMSK carrier recovery

Hi John,

I am interested in your problem.  Could you give some more details
about the GMSK signal you are looking at?  For example what is the
modulation index and what is the time bandwidth product of the pulse?


On 3/5/07, jjw <address@hidden> wrote:
> I would like to add some type of carrier recovery to the GMSK demodulator in
> GNU Radio, however I am having a bit of trouble getting something
> implemented that works properly.  I have tried using gr.costas_loop_cc to
> add a costas loop for carrier recovery, but I am not quite sure how to
> calculate the parameters (alpha, beta, fmax, fmin, costas_order).
> Can anyone offer some insight into how to calculate these numbers?
> Some nominal parameters to consider would be symbol rate of 31.25 kHz, using
> the USRP at max decimation (256) which results in 8 samples per symbol (250
> kHz) sampling.  I'm using the TVRX daughtercard.
> Thanks in advance for any help!
> Regards,
> John
> --
> View this message in context: http://www.nabble.com/GMSK-carrier-recovery-tf3351059.html#a9318437
> Sent from the GnuRadio mailing list archive at Nabble.com.
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> Discuss-gnuradio mailing list
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