RE: [SI-LIST] : Skin effect Modeling and Verification

Mellitz, Richard (mellitz@xgate.columbiasc.ncr.com)
Sun, 7 Sep 1997 20:53:10 -0400

Agreed, W models do well. The trick is to determine good values for the
Maxwell matrix. For example, traces less than 1/2 oz and less than 4
mils wide (i.e. PWB not cables) have significantly greater Rac than you
calculate from using a simple quadrangle geometry. What this does is
make ringing dampen are rate very similar to measurements.

I use W models when I get spice decks for I/O ring electronics from chip
mfgs to determine SSO effects. I don't like using lumped models for SSO
analysis which many vendors default to. We've got good agreement with
lab measurement here to.

Richard Mellitz, NCR

>----------
>From: Dr. Edward P. Sayre[SMTP:esayre@nesa.com]
>Sent: Saturday, September 06, 1997 11:47 AM
>To: Ray Anderson; simon@mcc.com
>Cc: si-list@silab.Eng.Sun.COM; Edward Sayre; chen@nesa.com; baxter@nesa.com;
>Elcora@aol.com; Elco, Richard ; vdm@avanticorp.com;
>hamed_emami@avanticorp.com; cangel@decwa.ece.uiuc.edu
>Subject: [SI-LIST] : Skin effect Modeling and Verification
>
>Dear SI/IBIS colleagues:
>
>As some of you may know, I and my colleagues Mike Baxter, Jinhua Chen, Tom
>Savarino and one of our client researchers, Dick Elco have been addressing
>the questions that Chris Simon posed in his recent message.
>
>The issue of time domain skin effects is at once one of the oldest questions
>in signal transfer going back to signalling in Morse code across the
>Atlantic, leading directly to the use of inductive loading coils and the
>theory of the distortionless line. At the same time, it is one of the
>newest and most important due to the clear emergence of differential
>signalling and Gigabit transfers desired in the HIPPI-64 and copper Fibre
>Channel contexts.
>
>Over the past year, we have been asking ourselves exactly how does one
>address the problems of skin effects in the time domain with arbitrary
>risetimes and non-linear sources and receivers. The frequency domain
>expanations for finite lines are not easily analytically specified from
>first principles, and a variety of conformal mapping and numerical methods
>have been applied successfully. The most readily studied is the round wire
>where anlaytic solutions are possible. Many authors, this one included, have
>developed concentric ring analogs for skin effects. We at NESA have
>extended these to finite elements for transmission line segmentation.
>(Design SuperCon'97)
>
>Recently, in investigations involving cabling and 1.0625 Gbps Fibre Channel
>signalling, we have had the opportunity to compare the .W model in
>Avanti/HSPICE to the NESA segmented model in both the time and frequency
>domain for long cables. To date, calculations have been made for both the
>NESA and .W model. Both the .W model and NESA models have proven to allow
>excellent modeling of real cable attenuation vs. frequency response (defined
>in the frequency domain from measurements). The issue for time domain
>simulations is the phase response, for it is the phase vs. frequency
>response which determines the dispersive characteristics of the transmission
>system. We have performed numerous time domain (.TRAN) simulations using
>both matched lab generators and realistic semiconductors, ECL and CMOS,
>driving these cable models. Variations in wire gauge are being considered
>as well as dielectric losses. As soon as we have experimental verifications
>of the simulation models, we will be publishing the results. Suffice to say
>so far that to date, the .W model seems to be holding up pretty well. [We
>refer the readers to Dr. Kuznetzov's notes on the .W model, avaliable from
>Avanti, for more details concerning the frequency modeling of Rs and G]. The
>trick is learning to relate the .W parameters to the actual interconnect you
>are working with. For best use of the .W model, (that to avoid a SWAG), you
>have to have frequenxy domain results for a sample of the interconnect.
>(The NESA model comes from first principles, but is limited in shunt loss
>considerations.)
>
>Lastly, I wish to note that NESA has no affiliation with any simulation tool
>company and respects all trademarks, and other proprietary marking for
>product manes and features. We will keep the community informed as results
>develop.
>
>Ed Sayre
>
>PS: If you are planning to come to the IBIS meeting we aresponsoring on
>September 18th, please let us know ASAP by e-mail so we can plan properly.
>
>
>
>
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>| "High Performance Engineering & Design" |
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>| Dr. Ed Sayre e-mail: esayre@nesa.com |
>| NESA, Inc. http://www.nesa.com/ |
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>| Stow, MA 01775 USA Fax +1.508.897-5359 |
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