GMSK carrier recovery


#1

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

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#2

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?

Tim