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Re: [Discuss-gnuradio] frequent phase slip with the new digital.costas_l
Re: [Discuss-gnuradio] frequent phase slip with the new digital.costas_loop_cc
Thu, 20 Sep 2012 10:45:53 -0400
On Thu, Sep 20, 2012 at 9:56 AM, Kyle Zhou <address@hidden> wrote:
> I adapted my codes from gnuradio-3.3 to the new 3.6 version.
> One of the changes is the new digital.costas_loop_cc is now implemented based
> on control_loop.
> The costas loop is used for phase recovery of a QPSK signal.
> But I noticed that with the new version, the output experiences a lot of
> phase slips.
> To be exact, the phase at the output rotate 90 degree from time to time.
> I changed it back to the old gr.costas_loop_cc and this did not happen.
> The setting for the old loop is alpha=0.01, beta=alpha*alpha/4,
> max_freq=2*pi*0.1, min_freq=-max_freq.
> The setting for the new loop is loop bandwidth = 2*pi/100
> The new version is only good when SNR is very high, say 13dB+
> Any has encountered the same problem? or am I doing something wrong?
I was using this just last week in a demonstration and hadn't noticed
any problems. If you can pin-point what's going wrong, though, I'll be
sure to fix it.