LO phase noise + QAM64

Hello all.
I have some task. I need to trasmit and receive one digital package of QAM 64 modulation. What the phase noise must LO have for trasmitting and receiving?
LO trans. = 7.3 Ghz
LO receiv. = 5.5

if i have 90dBc/Hz offset 100kHz it will be ok?

i think it is hard to tell , and u need to run a system level simulation and try to check the phase noise effect on ur QAM signal

u can do this with VSS from AWR

khouly

I agree that you need to run a system analysis, but from my experience dealing with 64QAM, -90dBc/Hz @ 100kHz should be fine for your circuit.

Thank yoг for answer. Is it important to have a good dBc @1kHz, @10khz? For a exapmle, i have - 90dBc/Hz @100kHz and it's fine, but what dBc/Hz@10KHz needs for transmitting?

At these VCO frequencies and spacing from the carrier probably the PN slope is approximately 10dB/decade. So, the phase noise should be better than -80dBc/Hz @ 10kHz.
You need an RF system analysis to see other phase noise contributors.

Thanks. if I undestood right the PN slope of the LO should be 10dB/decade to transmit and receive QAM signal without problem? What other sources of phase noise do you know? Can an amplifier make worse the phase noise if it's used after LO?