Re: [Discuss-gnuradio] frequent phase slip with the new digital.costas_loop_cc

[Tom Rondeau]

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?
> KZ

Hi Kyle,

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.

Tom