[SI-LIST] : Eye diagram displays from HSPICE simulations

Chris.H.Simon@gd-is.com
Mon, 19 Jul 1999 13:33:06 -0500

Mike,

You mention that you run many randomly switching bits in an HSPICE simulation
and view the resulting eye diagram. Is there a way to view eye diagrams in
Avanti Avanwaves or do you use some other waveform viewer with this capability?
I have tried to do this in Avanwaves but couldn't find the right combination to
get the overlayed waveforms.

Chris Simon
General Dynamics Information Systems

From: "Mike Degerstrom" <degerstrom.michael@mayo.edu> on 07/19/99 02:33 PM GMT

Please respond to si-list@silab.eng.sun.com

To: si-list@silab.eng.sun.com
cc: (bcc: Chris H Simon/GDIS/GDYN)
Subject: Re: [SI-LIST] : even-odd mode influence

John,

Are you refering to the W-element model instead of the T-element model?
If so then, WRT the W-element inaccuracies: did you try to adjust the
.options RISETIME parameter? We've looked at the w-element
model in some detail and we totally agree that the AC models
give a very different response than that predicted with the
transient w-element model. By adjusting the RISETIME parameter
you can get the transient loss correct at one or two frequencies.
In general, I think the w-element model can be used with
good results for modeling of wide-band digital signals. The
trick is knowing whether you are getting good results or not!

However, this is getting way off the subject of the original
posting. I suspect the original post was not concerned with losses.
If that is the case then the w-element does a great job with
multiple coupled conductors. We often run at least 3 coupled
conductors together and run many randomly switching bits in
the simulation. Then we view the resulting eye diagram to
see the effects of the crosstalk, i.e., coupling modes. It took
us some time to develop these capabilities. You can, of course,
use the approach suggested by Dima which is to use convert
the coupled lines to decoupled lines. In fact, it is probably
best to start with Dima's approach so you better understand
the theory instead of just trusting that some fully coupled
EM result is correctly translated to a fully coupled transmission
line model.

Mike

On Jul 16, 8:57am, John Williamson wrote:
> Subject: RE: [SI-LIST] : even-odd mode influence
> Folks,
>
> A comment on HSPICE lossy coupled T-line accuracy. Be careful when using the
> W-element.
> We've found that the time and frequency domains do not agree. For example, a
> set of extracted
> RLGC parameters resulted in a frequency domain attenuation of -25dB at
> 10GHz. However when
> the same model was used in the time domain driven by a 10GHz sine wave, the
> attenuation was
> only -8dB. We've found that this can be corrected by dividing the model up
> into several shorter
> ones. It's not computationally efficient, but it works fairly well.
>
> Regards,
>
> jw
>
> John M. Williamson, 0V30, Electromagnetic & interconnect technology
> Nortel Networks
> (613) 763 3198, ESN 393-3198 E-mail: williamj@nortel.ca
>
> > -----Original Message-----
> > From: jaydiep@us.ibm.com [SMTP:jaydiep@us.ibm.com]
> > Sent: Thursday, July 15, 1999 4:49 PM
> > To: si-list@silab.eng.sun.com
> > Subject: [SI-LIST] : even-odd mode influence
> >
> >
> >
> > Weber,
> >
> > To be able to simulate even-odd mode effects, you'll have to model the
> > conductors as a system of coupled transmission lines. There are not many
> > simulators that can do it, and even the ones that can are pretty limited
> > to the
> > number of conductors they can handle. Many of them can only handle lumped
> > models, where what you really need to see what's going on is a true
> > distributed
> > model. You'll need a field solver to extract the coupled transmission
> > line
> > matrices - it's not easily done analytically. Take a look at Ansoft,
> > Applied
> > Simulation Technology, and Pacific Numerix. HSPICE can model coupled
> > lines
> > using geometric input (conductor size, spacing, etc.), but I can't vouch
> > for its
> > accuracy.
> >
> > Jay Diepenbrock
> >
> > Senior Engineer
> > Interconnect Technology & Qualification
> > IBM Global Procurement, B8UA/061, RTP, NC
> > Phone: 919-543-8804 Fax: 919-543-3642
> > Email: jaydiep@us.ibm.com
> >
> >
> >
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>
>-- End of excerpt from John Williamson

--
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Mike Degerstrom         Email:    degerstrom.michael@mayo.edu
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