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Measurements >> Phase Noise and Jitter Measurements >> Verilog-A model of VCO for PSS/PNOISE simulation
https://designers-guide.org/forum/YaBB.pl?num=1213382491

Message started by pholm on Jun 13^th, 2008, 11:41am

Title: Verilog-A model of VCO for PSS/PNOISE simulation
Post by pholm on Jun 13^th, 2008, 11:41am

Hello,

I'm looking for a Verilog-A model of a VCO with frequency dependent phase noise that runs in pss/pnoise. The model needs to output a voltage waveform to drive the PFD/CP circuit in my top level PLL. All I can find in the various references here are models designed for transient analysis or use in a linearized PLL model. The end goal is to make a VCO/divider combination so I can run a full pss/pnoise sim of my PLL with transistor level models of everything except the VCO. The frequency dependent noise is achievable, I think, through use of the flicker_noise function.

Would very much appreciate some help.

Thanks!
Peter

Title: Re: Verilog-A model of VCO for PSS/PNOISE simulati
Post by Ryan Cheung on Jun 13^th, 2008, 9:15pm

It seems that the Verilog-A model cannot be run in pss/pnoise simulation.

Title: Re: Verilog-A model of VCO for PSS/PNOISE simulati
Post by Ken Kundert on Jun 13^th, 2008, 11:12pm

Perhaps Listing 1 in http://www.designers-guide.org/Analysis/rf-sim.pdf is what you are looking for.

-Ken

Title: Re: Verilog-A model of VCO for PSS/PNOISE simulation
Post by sandman on Jul 8^th, 2008, 8:54am

Please correct me if I'm wrong, but from what I understand the PSS simulations cannot be performed with hidden state variables in the verilog-a code/model, that come from using the PRN generators in the noise functions. Apparently when such PRN generators are used, the PSS simulation cannot find a steady state (SS) solution to define the VCO's waveform.

Cheers.

Title: Re: Verilog-A model of VCO for PSS/PNOISE simulation
Post by Ken Kundert on Jul 8^th, 2008, 9:38am

Using random number generators to model phase noise in an oscillator is fundamentally incompatible with PSS not because of hidden state, but because the result is not periodic.

However, the question originally involved using the flicker_noise function. In this case the noise is confined to the small-signal PNoise analysis and is not present during the PSS analysis.

-Ken