The Designer's Guide Community Forum

The Designer's Guide Community Forum
https://designers-guide.org/forum/YaBB.pl
Simulators >> RF Simulators >> PXF analysis on Oscillators
https://designers-guide.org/forum/YaBB.pl?num=1129575745

Message started by ganesh on Oct 17^th, 2005, 12:02pm

Title: PXF analysis on Oscillators
Post by ganesh on Oct 17^th, 2005, 12:02pm

Hello ppl.,
I am running PXF analysis on oscillators. In order to verify my understanding of the PXF analysis, I am running a simple experiment. I injected resistor noise through a controlled source to specific nodes of the oscillator. I manually calculated the resistor noise contribution from the output of the PXF analysis.
Manual calculation:

rn - resistor noise
sn - transfer function from sideband n (output of PXF analysis)

total resistor noise contribution = rn*(s0^2+s1^2+..)

I tried verifying the same by the noise contribution summary that spectre spits out. They don't seem to match. Am I doing something wrong here? Let me get your inputs/suggestions.

Thanks,
Ganesh.

Title: Re: PXF analysis on Oscillators
Post by Ken Kundert on Oct 17^th, 2005, 2:07pm

Did you include the negative sidebands?

-Ken

Title: Re: PXF analysis on Oscillators
Post by ganesh on Oct 18^th, 2005, 6:12pm

Hi Ken,
Thanks for your reply. There is some subtlety in PXF which I think I understood better. In the VCO actually I was looking at k=-1,0, 1 sidebands for the PNOISE analysis. While the corresponding sidebands in the PXF analysis was k=0,-1,-2. This is because my fout in the pxf analysis was (Fundpss + offset frequency). Correspondingly the fin is offset by 1 harmonic.

Does this sound alright?

-Ganesh.

Title: Re: PXF analysis on Oscillators
Post by Ken Kundert on Oct 18^th, 2005, 10:00pm

Given the same options (sweeptype=relative or absolute) and the same output frequency range, PXF and PNoise will treat sidebands identically.

-Ken

Title: Re: PXF analysis on Oscillators
Post by ganesh on Oct 19^th, 2005, 10:09am

Got it! Thanks a lot, Ken.

-Ganesh.