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Measurements >> Phase Noise and Jitter Measurements >> Phase noise simulation with two oscillators
https://designers-guide.org/forum/YaBB.pl?num=1115006223

Message started by geekyfrenchy on May 1^st, 2005, 8:57pm

Title: Phase noise simulation with two oscillators
Post by geekyfrenchy on May 1^st, 2005, 8:57pm

Hello,
I am trying to simulate two distinct oscillators running at two different frequencies (Say 3500M and 3600M). I want to see the impact on the Phase Noise (at 100M offset) as a result of having the VCOs share some common element. So in the case of the 3500M VCO, I want to check PN at 3600M to see how much this PN is degraded by having the 3600M VCO running simultaneously. At this moment I can perform a transient simulation and can see both VCOs at their respective frequencies.
Has anyone used SpectreRF to complete this?
Your help is greatly appreciated.
Regards,
Helene

Title: Re: Phase noise simulation with two oscillators
Post by August West on May 2^nd, 2005, 8:23am

SpectreRF is not capable of running on a circuit that contains two free-running oscillators. It will never converge.

A circuit with two free-running oscillators has two fundamental frequencies, so it needs QPSS, but QPSS does not work on autonomous circuits.

-August

Title: Re: Phase noise simulation with two oscillators
Post by geekyfrenchy on May 2^nd, 2005, 8:35am

Hello August,
SpectreRF PSS for autonomous ckts was recently enhanced to take in consideration frequency division occuring for VCOs containing frequency dividers. As a result, the final PSS fund would be reevaluated to take in account this frequency division. In the event you have multiple frequency divisions occurring in your design, your PSS fundamental will be set as the largest common integer of all frequency sources. So based on this, I may be able to trick SpectreRF to get convergence. What I suspect is that the resulting phase noise may not be accurate since both VCOs induce perturbations to each other. I was wondering if other users have been through the same exercise.
Thanks for your email,
Geekyfrenchy