Phase glitches on transmit?

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

Looks like it was in my GPU code.

Ah, good to know!

I didn’t want any of the Lime developers wasting their time looking into it.

On some forums you can mark a thread when an issue is closed.
I am not sure what the protocol is on here.

  • Charles

Good point and since this was a support question, I will do that.