This maybe my code but…
Has anyone seen low level spikes that walk across the spectrum on transmit?
I know it is not sample drop-outs because they look completely different.
Unfortunately I don’t have a realtime spectrum analyser (just a conventional one)
so they are difficult to capture.
I have seen this issue before on different hardware and that was down to rapid phase changes
in an OFDM signal between symbols.
What I am seeing is very similar but in a RRC filtered QPSK signal.
I am also seeing a constellation diagram with what looks like unexpected phase jitter.
Are there any known issues with the FPGA code (metastability, lack of timing closure etc)
that could account for this?
- Charles