The Designer's Guide Community Forum

The Designer's Guide Community Forum
https://designers-guide.org/forum/YaBB.pl
Simulators >> RF Simulators >> PSS(Flexible Balance) & Transient are inconsis
https://designers-guide.org/forum/YaBB.pl?num=1181258876

Message started by sunghkim@usc.edu on Jun 7^th, 2007, 4:27pm

Title: PSS(Flexible Balance) & Transient are inconsis
Post by sunghkim@usc.edu on Jun 7^th, 2007, 4:27pm

I'm simulating my upconversion mixer.

After parasitic extraction, I ran PSS (Flexible Blance Method)analysis and Transient analysis. Surprisingly, Those two simulation are totally different simulation results. PSS simulation showed me reasonable (good?) result while the transient simulation showed very poor performance. I tweaked the tolerance options but the transient simulation result didn't change much. Before parasitic extraction, both analysis showed me identical result.

Does anyone know the reason of this weird behavior of the simulator?

Thanks

Title: Re: PSS(Flexible Balance) & Transient are inconsis
Post by byang on Jun 7^th, 2007, 7:26pm

It is more likely that Harmonic Balance or Flexible Balance result is "too" nice. Harmonic Balance may use a few harmonics in simulation which smooths out bad waveforms. Today's Harmonic Balance simulators seem bad at error control.

It is still possible transient has problem. But I think it is less likely.

byang

Title: Re: PSS(Flexible Balance) & Transient are inconsis
Post by Sean on Jun 7^th, 2007, 9:16pm

Thanks for your opinion.

The wave form from the two simulation differ in regard to amplitude rather than the shape of the wave. I'm not sure if it is some information which decide something, though.

Title: Re: PSS(Flexible Balance) & Transient are inconsis
Post by Ken Kundert on Jun 8^th, 2007, 12:02am

Are you sure you have reached steady state in transient?

How does shooting compare to harmonic balance?

-Ken

Title: Re: PSS(Flexible Balance) & Transient are inconsis
Post by Sean on Jun 8^th, 2007, 12:14am

I appreciate for your interest.

For transient analysis, I confirmed it is in steady state. FYI, my application is upconversion mixer(LO=44GHz). I looked at the output of the mixer in transient wave form.
For PSS (Flexible Balance) analysis, I setup tstab=20ns. After this simulation I also looked at time domain wave to compare.

I also compared Flexible Balance and Shooting method. Those two method showed identical results. As far as I know, Shooting method also rely on transient analysis. If it is right, shooting method must be the same as transient analysis. It also confused me.
Is it possible for circuit components in the extracted view work correctly only for a specific analysis type?

Before parasitic extraction, both transient and PSS analysis showed identical or very close results. With parasitic extracted view, the simulation result became significantly different. The amplitude in the wave form differ in the order of 100. The transient analysis showed very poor performance.

I will post the simulation captures soon.

Thanks

Title: Re: PSS(Flexible Balance) & Transient are inconsis
Post by byang on Jun 8^th, 2007, 7:02am

Another thing you can try is Envelope Following analysis. Envelope Following analysis should follow the transient analysis curve. You'll get more clue whether the transient waveform is right or not.

byang