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BPSK Constellation Errors

Question asked by Mohamed.m on Mar 12, 2018
Latest reply on Mar 16, 2018 by travisfcollins



We are using a ZC706 board with FMCOMMS-3 and transmitting and and receiving on the same board. Using a digital BIST loopback, the constellation is fine but using the antennas provides the attached constellation. It seems like the constellation points are dispersed. My question is: visually looking at the constellation diagram attached, is it affected by frequency offset ? If not, can you tell what's causing the dispersion and rotation of points?


Also, the second picture I attached has the output of my signal that I expect to have a flat amplitude but seems to be modulated with a low frequency sinusoidal. How can I fix that?