testing phase noise of VCO

[Usman Hai]

Hello
I have made a differential VCO using cross.coupled logic. I wanted to test the phase noise in SpectreRF...can anybody tell me what should I do.
I know to measure phase noise of oscillator but how to measure of VCO with 75Khz variation.
Thanx in advance
/Noman

 

[BigBoss]

If your VCO is frequency modulated, how you will be able to measure PN ?? It's impossible !!
PN is essentially frequency/phase modulation with noise and how you will extract this deviation from main modulation?? I mean, when you make a frequency/phase modulation, how will you define this noise modulated signal??

The way of measurement of PN is only to measure the carrier without modulation..

 

[Mazz]

I think that Noman means that he's interested in phase noise at 75kHz offset...
If so, use PSS in spectre to get the right oscillator frequency and Pnoise to measure phase noise (there is a tab to do it in the Pnoise options if I well remember).
I hope it can help.
Mazz