FMCOMMS5+ZYNQ3 unstable received baseband spectrum in qpsk Simulink example

Hello All,

I executed QPSK example(zynqRadioQPSKRxAD9361AD9364SL) provided by Mathwork in Simulink, the received baseband spectrum of the signal is changing amplitude a lot! I looked at the I and Q time domain received data, the envelope of both I and Q varying unexpected and there are many spikes on the I and Q data.

I just loopbacked the transmitter interface to receiver interface with a short coax cable, the cable is tested!

Here the retrieved data:

L` X@A0 X@A0, L` X@A0 X@A0, L` X@A0 X@A0, L` X@A0 X@A0, L` X@A0 X@A0, L` X@A0 X@A0, c<!;8UY#A<!9 `ello world 006 Hello world 007 Hello world 008 Hello world 009 Hello world 010 Hello world 011 Hello world 012 Hello world 013 Hello world 014 Hello world 015 Hello world 016 Hello world 017 Hello world 018 Hello world 019 Hello world 020 Hello world 021 Hello world 022 Hello world 023 Hello world 024 Hello world 025 Hello world 026 Hello world 027 Hello world 028 Hello world 029 Hello world 030 Hello world 031 Hello world 032 Hello world 033 Hello world 034 Hello world 035 Hello world 036 Hello world 037 Hello world 038 Hello world 039 Hello world 040 Hello world 041 Hello world 042 Hello world 043 Hello world 044 Hello world 045 Hello world 046 Hello world 047 Hello world 048 Hello world 049 Hello world 050 Hello world 051 Hello world 052 Hello world 053 Hello world 054 R1L% $b)J&I :1L% $b)J&I b1L% $b)J&I b1L% $b)J&I b1L% $b)J&I b1L% $b)J&I b1L% $b)J&I b1L% $b)J&I b1L% $b)J&I b1L% $b)J&I b1L% $b)J&I b1L% $b)J&I b1L% $b)J&I b1L% $b)J&I b1L% $b)J&I b1L% $b)J&I b1L% $b)J&I b1L% $b)J&I b1L% $b)J&I b1L% $b)J&I b1L% $b)J&I b1L% $b)J&I b1L% $b)J&I b1L% $b)J&I b1L% $b)J&I b1L% $b)J&I b1L% $b)J&I b1L% $b)J&I b1L% $b)J&I b1L% $b)J&I b1L% $b)J&I b1L% $b)J&I b1L% $b)J&I b1L% $b)J&I b1L% $b)J&I b1L% $b)J&I b1L% $b)J&I b1L% $b)J&I b1L% $b)J&I b1L% $b)J&

As can be seen only a part of transmitted data retrieved correctly!! high BER!!!!

Does anybody know what are the causes of spikes in the received IQ data?

what are the causes of I/Q envelope variations over time? Could it be from non-tuned RX interface?

Please find attached received I/Q data.

Kind Regards

Arash