Re: [SI-LIST] : Frequency dependence and all that jazz

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From: Erik Daniel (Daniel.Erik@mayo.edu)
Date: Thu Dec 23 1999 - 05:52:11 PST


Nilesh-

The HSPICE W-element can handle limited (but common) frequency dependence of
just the R and G matrices (not L and C) describing a transmission line. This
is accounted for in the time domain as well as frequency domain, but it does
have limitations. Perhaps Dmitri Kuznetsov can comment further.

HP-EEsof's MDS or ADS tools can handle a much wider range of
frequency-dependent parameters, but while time-domain simulations can be
performed, they are a bit contrived as the tool was really designed to perform
frequency domain analysis.

                                        - Erik

On Dec 22, 3:10pm, Shah, Nilesh N wrote:
> Subject: RE: [SI-LIST] : Frequency dependence and all that jazz
> Hi:
> I have a question:
> It's all well and fine to build frequency dependent MODELS,
> but what about the simulator(ex Hspice) itself?
> For example, if I feed the output of a simple inverter to an
> L,C, R network, (and I'm doing a simple time domain transient analysis)
>
> INVERTER------LRC NETWORK----OUTPUT
>
> does the simulator decompose the output waveform of the inverter
> into it's frequency components before feeding it into the LC network?(i
> don't think so)
> For example, if the output of my buffer looks like a repeating square pulse
> running at 400Mhz 50% duty cycle with a finite rise time, does the LRC
> network "see"
> the input wave as
> Asin(w1t)+Bsin(w2t)+..... etc
> where w1=400Mhz and w2,w3 etc are the harmonics?Or does one have to
> explicitly
> take the output of the waveform, decompose it and then feed it artificially
> to the LRC network?
>
> or does the LRC network "see" as it's input,a bunch of dc points for
> which the simulator solves the nodal matrix using difference or differential
> equations? i.e. does the LRC network "see" only 1 frequency coming in which
> is the fundamental?
>
> How does this work?How is the frequency content of the output waveform of
> the buffer conveyed to the LCR network?
> I was planning to investigate this but I thought some of
> you experts out there might have the answer at the top of your head...
>
> Also, tools like Ansoft Q3d extract models only at 1 frequency(I think), so
> unless you use HFSS, how do you get a true frequency dependent model?
> I've generated R,L versus frequency and other parameter versus frequency
> curves, but this is with 2 d models using TEM assumptions.what about 3-d
> models?
> is ther ANY way at all except for using a full wave solver like HFSS to
> generate true frequency
> dependent models and simulate in the time domain?
>
> Thanks for your ideas in advance.
> Nilesh
>
>
> Nilesh N Shah,
> Package Electrical Design Engineer,
> PCG, Folsom, CA.
> Intel Corporation.
> tel:916-356 1129.
>
>
>
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>
>-- End of excerpt from Shah, Nilesh N

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Erik Daniel, Ph.D.                         Mayo Foundation
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