AnsweredAssumed Answered

PSG received modulation continuously rotates

Question asked by oscar.monerris on May 31, 2012
Latest reply on Jun 1, 2012 by oscar.monerris

I'm trying to capture IQ samples from a PXA using Labview (I can download them with Labview). My source is a PSG generating a digital modulation (4QAM or BPSK). 

The point is that, if I set the PXA using Basic->IQ Waveform->Display->I/Q Waveform I'm able to distinguish the samples. I'm using an scope to monitor de Q samples form the BNC output in the  PSG. So I can actually see the bits. 

Nevertheless, the blue and yellow lines in the PXA representing I and Q are not still. They should the same be from trigger to trigger as happens in the scope given that the PN23 sequence repeats all the time. 

When I download the samples to labview and plot the IQ samples I see that the constellation spins all the time. It's never still.

Any explanation on this?

Thank you!


Edited by: oscar.monerris on May 31, 2012 8:06 AM