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What is the use of No of harmonics option in PSS form

RFQuery

 Hi,

In PSS form, there is one option called Number of harmonics. I am NOT able to understand what is its use as PSS is any way a Steady state DC operating point analysis ?

Of course, No of harmonics actually controls the time step for better accuracy (like to avoid Aliasing effect etc). But the time step can easily controlled by maxacfreq OPTION.

 So my doubt is:- Whether the Harmonic Option in PSS form is needed for Some other reasons ?

IS there any documents which actually explains the need/use (OTHER than controlling Time Step) of No. of Harmonics option in PSS form

Thanks

 

  • Generally speaking, increasing the number of harmonics with shooting PSS does not affect accuracy (that said, there can be benefit sometimes in very high dynamic range systems of increasing the number of timepoints) - but such scenarios are often better suited to Harmonic Balance.

    Andrew,

    Considering a basic inverter driven by clock source, I ran PSS+PNoise and to my surprise I had two degrees of control over my tdnoise (Integrated) output :

    (1) No.of time points (tstrobe)

    (2)Maxacfrequency

    I did post earlier about discrepancy in results as far as varying Maxacfrequency is concerncerned (this post), however with increase in time points I found the range for tdnoise integration is somewhat overestimated when integrated from 1Hz to PSS/2 Hz.

    Also, is there any good source for understanding maxacfrequency, tstrobe , PSSHarmonics and PNoisesidebands besides Kundert's paper on switched capacitor filters and SpectreRF Theory (while Spectre RF Theory does cover all these terms, they shed little light upon interaction of these parameters).

    Thanks.

  • maxacfreq affects the number of time points in the PSS solution - and defaults to max(maxharms,10)*4*PSSfund. 

    The number of time points in the tdnoise analysis won't affect accuracy - it simply controls which time points you produce a time-domain (strobed) noise output at. Each time in tdnoise is a separate pnoise simulation with an ideal strobe at that time point - so the results should be separate from each other.

    I'm not sure what you are saying about "the range for tdnoise integration is somewhat overestimated...". It's probably best if you contact customer support so that we can get a more detailed understanding of precisely what you're doing and hoping to achieve, and can help you understand the right settings.

    The SpectreRF Theory should cover it (certainly recent MMSIM versions) - but if not, we need to understand what's not clear so that we can see what else needs to be added to the documentation to make it clearer.

    Kind Regards,

    Andrew.

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