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QPSK and QAM examples not working properly

Question asked by F.Shahin on Dec 4, 2017
Latest reply on Dec 8, 2017 by F.Shahin
I have a ZedBoard and an ADI FMCOMMS 3, and I’m trying to follow the examples mentioned in the “AD-FMCOMMS2/3/4 Datafiles” document:
I have worked on both QPSK and 16-QAM examples. However, I’m not getting any correct results when viewing the constellations using the ADI IIO Oscilloscope. For the QPSK, the results look more like a very noisy 16-QAM constellation as seen in the next screenshot:
I tried changing the parameters of the FMCOMMS using ADI IIO Oscilloscope to make the output clearer, but without any success. However, when I use the data file mentioned in the documentation (qpskwithfilt_txt.zip), I get a clean result:
If I’m not mistaken, this indicates that there aren’t any configuration errors in my FMCOMMS3 board. I would also like to note that the output data from the simulation “qpskwithfilt.slx” is completely different from the data in “qpskwithfilt_txt.zip”
I then tried the 16-QAM example to see if it will work. The constellation isn’t clear at all, and the output looks more like a noise than a signal as seen in the next screenshot:
The only difference in settings I made for the QAM is changing the sampling rate to 20 MHz. The output data from the simulation has some differences to the file uploaded in the documentation (qam16_20mdata.zip).
My question is, what is the cause of this behavior? Take into consideration that one of the data files uploaded in the documentation works without any problem.

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