**From:** Qu Pingyu (*pingyu@ime.org.sg*)

**Date:** Wed Dec 22 1999 - 17:02:15 PST

**Next message:**Jon Powell: "Re: [SI-LIST] : Physcially-small far-end LVDS terminations?"**Previous message:**Jian Zheng: "RE: [SI-LIST] : Frequency dependence and all that jazz"

Hi!

I have a similar question as what Nilesh asked: I'm doing a frequency domain

S parameter simulation in HSPICE. How can I include a frequency dependent

resistance which was used to represent skin effect into my SPICE model ? Can

I use a resistance varying with the sweeping frequency ? Thanks in advance.

Regards

Qu Pingyu

Engineer, Advanced Packaging Development & Support

Institute of Microelectronics

11 Science Park Road, Singapore

DID: 65-7705413

Fax: 65-7745747

*> -----Original Message-----
*

*> From: Steve Corey [SMTP:steve@tdasystems.com]
*

*> Sent: Thursday, 23 December 1999 8:04
*

*> To: si-list@silab.eng.sun.com
*

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

*>
*

*> Nilesh -- SPICE-like simulators doing time-domain analyses solve their
*

*> differential equations in the time domain, based on the charge/flux stored
*

*> in
*

*> capacitors/inductors and the derivatives of the voltage/current variables
*

*> at each node/branch. A time-domain simulator has no concept of frequency.
*

*>
*

*> It is quite possible to get frequency dependence included in a model for a
*

*> time-domain simulator, since L's and C's are frequency-dependent
*

*> impedances/admittances and can be shown, when used in conjunction with R's
*

*> (and inductance coupling coeffficients) to accurately represent any
*

*> well-behaved
*

*> function if used in the correct topology and with the correct values.
*

*> However, for certain structures (e.g., long cables used at high
*

*> frequencies) a large
*

*> number of lumped elements is required to represent the delay.
*

*>
*

*> A full wave solver is one of many approaches to getting a frequency
*

*> dependent model. Other approaches, such as 2-D solvers, may be quite
*

*> sufficient
*

*> without going to such great lengths -- you have to evaluate what
*

*> frequency-dependent effects you are trying to model. /* begin brazen
*

*> advertising */ We
*

*> offer a tool which extracts models from measured data and handles some
*

*> effects, such as non-uniform impedance and next-door coupling, quite well.
*

*> /* end
*

*> brazen advertising */ General full-wave modeling from measurement is on
*

*> the horizon, and is a current research topic in academia, but we do not
*

*> offer it at
*

*> this time.
*

*>
*

*> Hope this helps,
*

*>
*

*> -- Steve
*

*>
*

*>
*

*> -------------------------------------------
*

*> Steven D. Corey, Ph.D.
*

*> Time Domain Analysis Systems, Inc.
*

*> "The Interconnect Modeling Company."
*

*> http://www.tdasystems.com
*

*>
*

*> email: steve@tdasystems.com
*

*> phone/fax: (206) 417-3439
*

*> -------------------------------------------
*

*>
*

*>
*

*> "Shah, Nilesh N" wrote:
*

*>
*

*> > 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.
*

*> >
*

*> > **** To unsubscribe from si-list: send e-mail to
*

*> majordomo@silab.eng.sun.com. In the BODY of message put: UNSUBSCRIBE
*

*> si-list, for more help, put HELP.
*

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*

*> > ****
*

*>
*

*>
*

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**Next message:**Jon Powell: "Re: [SI-LIST] : Physcially-small far-end LVDS terminations?"**Previous message:**Jian Zheng: "RE: [SI-LIST] : Frequency dependence and all that jazz"

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