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Measurements >> Phase Noise and Jitter Measurements >> VCO + Divide-by-2 pnoise (phase noise) setup
https://designers-guide.org/forum/YaBB.pl?num=1126048951

Message started by jm1974 on Sep 6^th, 2005, 4:22pm

Title: VCO + Divide-by-2 pnoise (phase noise) setup
Post by jm1974 on Sep 6^th, 2005, 4:22pm

Dear all,

Can anyone help me with VCO + divider setup.
VCO is runnig at 2G and I'm interested in phase noise after divide by 2 at 1G.
When I setup the Pnoise Analysis for my standalone VCO, in the setup form, I ignore the item"Input Source",.

But in this case what should i do?

Thanks a lot.

JM

Title: Re: VCO + Divide-by-2 pnoise (phase noise) setup
Post by Ken Kundert on Sep 6^th, 2005, 10:19pm

Specify the output to be the output of the divider and set the fundamental frequency to be 1GHz. Be sure to start the oscillator during the tstab interval.

-Ken

Title: Re: VCO + Divide-by-2 pnoise (phase noise) setup
Post by J M on Sep 6^th, 2005, 10:48pm

Thanks Ken,
What about the input noise source? should it be set to none
in pss analysis should it be in oscillator mode with oscillation node as vco outputs?

Thanks
JM

Title: Re: VCO + Divide-by-2 pnoise (phase noise) setup
Post by Andrew Beckett on Sep 6^th, 2005, 11:07pm

The PSS should be in oscillator mode, and you should specify the output to be the output of the divider (as Ken said). If you specify it at the VCO output, you'll only be analyzing half the periodic behaviour, so it (most likely) won't converge, and (if it did converge) you'd get the wrong answer...

The input source for pnoise is only relevant if you want to calculate input referred noise or noise figure/factor - which I expect you don't. It doesn't affect the calculation of output noise or phase noise.

Regards,

Andrew.

Title: Re: VCO + Divide-by-2 pnoise (phase noise) setup
Post by J M on Sep 7^th, 2005, 12:44am

Thanks Andrew,
It is quite helpful.

J M