Re: [Discuss-gnuradio] QAM, carrier tracking and clock recovery

[Martin Dvh]

Tom Rondeau wrote:
>>-----Original Message-----
>>From: address@hidden [mailto:discuss-
>>address@hidden On Behalf Of Martin Dvh
>>Sent: Wednesday, January 31, 2007 10:24 PM
>>To: gnuradio mailing list
>>Subject: Re: [Discuss-gnuradio] QAM, carrier tracking and clock recovery
>>
>>You might find my benchmark_rx_oscopy.py and kinda working qam16 code
>>interesting.
>>they are in branches/developers/nldudok1/digital-wip3 which is a branched
>>version of your digital-wip2
>>look in
>>branches/developers/nldudok1/digital-wip3/gnuradio-
>>examples/python/digital/
>>and
>>branches/developers/nldudok1/digital-wip3/gnuradio-
>>core/src/lib/general/gr_mpsk_receiver_cc
>>and
>>branches/developers/nldudok1/digital-wip3/gnuradio-
>>core/src/python/blksimpl
>>
>>benchmark_rx_oscopy.py gives you a live constellation view (put it at X-Y
>>mode manually with the rightmost pulldown)
>>and live tweaking of parameters
>>
>>greetings,
>>Martin
> 
> 
> 
> I just saw the commit now. I'll check it out tomorrow and see what it looks
> like. You guys are my new heroes; I wouldn't have been able to touch this
> for a while yet ;)
> 
> How's it working with the AGC loop?
The  agc2 seems to work.
The feedforward agc only works when manually compensating for the noise (1.0 + 
noise as reference)
This would need an error loopback from the gr_mspk receiver

I think my main problem now is detecting of which quadrant we are in.
Or use the right kind of differential coding.
(I just used the gr.diff_decoder_bb and gr.diff_encoder_bb)

I have also strugled with the right formulation for the phase_detector error 
signal.
(conj or not, pos or neg sign) But I think I got it now.

I send the complete constellation as list from python to the mpsk_receiver as 
vector.
For some reason I had to reverse this list to get it to work.
This could also mean I needed to solve this in a different way and it just 
accidently now sometimes works. (mirror the constellation, add pi,
something like that)

Greetings,
Martin



> Tom
> 
> 
> 
> 
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