Re: [Discuss-gnuradio] Carrier leakage on transmit

[Charles Brain]

Well I have had another look at the offset stuff.

What seems to be happening is that when you apply an offset 
you have to scale back the max IQ values being sent to the USRP2.

I get this situation.

No LO offset, great raised cosine shaped QPSK signal
Add LO offset, QPSK signal looks awful.

Reduce IQ signal amplitude QPSK signal again looks good 
and I can see the LO offset on the spectrum analyser.

I have also noticed that when I try OFDM the unwanted rubbish 
on either side of my OFDM signal changes with LO offset.

There seems to be an interaction in there somewhere probably
to do with the complex mixer in the FPGA. I have not ruled out my 
own code yet but it seems unlikely.

- Charles

http://www.g4guo.blogspot.com/