PSS shooting with s-parameter file

What version of Spectre are you using? I'm guessing it's pretty ancient because s-parameter files have been supported with PSS for many years now without needing to resort to using the (very old) rational interpolation method.

In current versions (since MMSIM13.1 I think) the recommendation is to use interpolation method "bbspice" if the s-parameters represent a passive network. Otherwise you should use "linear" or "spline" - and these can also be used for passive networks in earlier versions. However, if you're using that old a version, the recommendation would be to move to a more recent SPECTRE version.

Regards,

Andrew.

Thanks Andrew! Problem solved.

I am using Cadence version ic123_isr10. spectre-W says W is an unbound variable, so I could not get the spectre version directly. However, from the simulation log file, I see that it is loading packages from mmsim151_isr11, so I assume the spectre version is 15.1

Indeed, PSS support s-parameter if I choose harmonic balance engine and spline for interp. However, if I choose shooting engine, it gives the following error:

Error found by spectre during periodic steady state analysis `pss'.
ERROR (SPCRTRF-15160): Distributed Components are not supported directly for Autonomous PSS or Envelop Analysis with Shooting engine. 1) Firstly, it's recommend to use Harmonic Balance engine for Distributed Components; 2) Or else, for this case and with Shooting engine, try the Rational Fitting Technique(set interp=rational) for NPORT components.

Actually the component that has the s-parameter file comes from a third party tool, which chooses 'spline' for interp . I tried to change it to 'rational' following the suggestions in the error message, simulation runs but did not converge.

After your suggestion, I used bbspice, then it runs and results seem to be ok.

Thanks for the help!

Ah, you didn't mention that you were simulating an autonomous circuit (e.g. an oscillator) - that does indeed make a difference; linear and spline are not supported with autonomous shooting PSS (or shooting envelope). You shouldn't use rational these days - I've just filed a CCR to get that message improved because it should be recommending bbspice over rational.

Regards,

Andrew.