Hi, We can output the data to a sink file, from which we load the data using Matlab. Then we use scatterplot.
Thanks! Bill ________________________________ From: yufeng wang <kthyuf...@gmail.com> To: Bill Stevenson <bill.stevenso...@yahoo.com> Sent: Friday, April 10, 2009 12:22:15 PM Subject: Re: [Discuss-gnuradio] QPSK phase noise Hi, Bill, Regarding to Paco's images, I wonder which programme did you use to display the output of the images that he had got? like the constellations? I'm using benchmark.py to transmit and receive BPSK signals. I can use usrp_fft.py to display the output of the transmitter. Thanks in advance! On Fri, Apr 10, 2009 at 12:03 PM, Bill Stevenson <bill.stevenso...@yahoo.com> wrote: > Hi, Paco > > Actually, I got the similar result as you did. I think there was something > wrong in the mpsk_receiver block. I am checking it. Thanks! > > Bill > > ________________________________ > From: Paco Garcia <sarev...@gmail.com> > To: Discuss-gnuradio@gnu.org > Sent: Wednesday, April 8, 2009 9:26:36 AM > Subject: Re: [Discuss-gnuradio] QPSK phase noise > > > Johnathan, you were right with the distortion issue at the TX, I am now > using > these parameters: > > ./benchma-m dqpsk -f 1.25G -m dqpsk --tx-amplitude=500 -r 1M -M 99999999 > --excess-bw=0.35 > ./benchmark_rx.py -r 1M -m dqpsk --log --costas-alpha=0.05 -S 4 --verbose -r > 1M --gain-mu=0.01 --excess-bw=0.35 -f 1.25G --rx-gain=45 > > But still, for a 40dB SNR ( > http://img149.imageshack.us/img149/4583/screenshot4h.png ) I think we should > get a much better constellation than this one ( > http://img149.imageshack.us/img149/7968/screenshot3t.png ) > > I am using the latest gnuradio trunk and the > ../gnuradio-examples/digital/benchmark.... > I have disabled all the data loggins but the rx_receiver.dat from the > /usr/local/lib/python2.5/site-packages/gnuradio/blks2impl/dqpsk.py to reduce > the computational requirements. > > I tried the 0.5M as eric suggested but the results are even worse ( > http://img18.imageshack.us/img18/2306/screenshot5hhm.png ) > > The 2M rate constellation is the same as 1M. > > If I go with BPSK, I get this: > http://img212.imageshack.us/img212/3010/screenshot10.png > using > ./benchmark_tx.py -m dbpsk -f 1.25G -m dbpsk --tx-amplitude=500 -r 200k -M > 99999999 --excess-bw=0.35 > ./benchmark_rx.py -m dbpsk --verbose -S 4 -r 200k --excess-bw=0.35 -f 1.25G > --rx-gain=30 > debug > > The image below shows the costas loop error: > ( http://img156.imageshack.us/img156/1521/screenshot11.png ) > (zoom frequency > http://img514.imageshack.us/img514/2173/screenshot12.png ) > blue: phase > red: phase_error > cian: Q > purple: I > green: freq > > So once the costas locks, there is still some error which is causing the > blur constellation. But I think that for an almost 40dB SNR signal ( > http://img212.imageshack.us/img212/551/screenshot13.png ) we should get much > better results. > > The M&M block influences a lot, if I change the samples per symbol to 2 I > get this: ( http://img201.imageshack.us/img201/9436/screenshot14.png ) > > I have also tried via air interface getting similar results. My question is > whether this is normal for the mpsk gnuradio block receiver implementation > or I am doing something wrong. > > What are your thoughts about this? > > Thank you for your time. > > > > > > > > > > > -- > View this message in context: > http://www.nabble.com/QPSK-phase-noise-tp22934944p22950446.html > Sent from the GnuRadio mailing list archive at Nabble.com. > > > > _______________________________________________ > Discuss-gnuradio mailing list > Discuss-gnuradio@gnu.org > http://lists.gnu.org/mailman/listinfo/discuss-gnuradio > > > _______________________________________________ > Discuss-gnuradio mailing list > Discuss-gnuradio@gnu.org > http://lists.gnu.org/mailman/listinfo/discuss-gnuradio > > -- Best wishes, Yufeng
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