**From:** Ted Mido (*mido@avanticorp.com*)

**Date:** Tue Nov 28 2000 - 10:13:44 PST

**Next message:**Haller, Robert: "RE: [SI-LIST] : Accuracy of HSPICE W-element transmission lines"**Previous message:**William Baldwin: "Re: FWD: Re: [SI-LIST] : Eye pattern with differencial signals."**In reply to:**Chan, Michael: "RE: [SI-LIST] : Accuracy of HSPICE W-element transmission lines"**Next in thread:**David Kaiser: "RE: [SI-LIST] : Accuracy of HSPICE W-element transmission lines"

Right it should be 2000.4. Because I've just past old draft, the last paragraph

looks meaningless. Thank you for pointing it out.

ted

From: "Chan, Michael" <Michael.Chan@compaq.com>

Subject: RE: [SI-LIST] : Accuracy of HSPICE W-element transmission lines

Date: Tue, 28 Nov 2000 08:17:41 -0600

*> Ted:
*

*> In your second last paragraph below, is it a typo error? Is it supposed
*

*> to be 2000.4 instead of 99.4? Thanks.
*

*>
*

*> Michael Chan
*

*>
*

*>
*

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

*> From: Ted Mido [mailto:mido@avanticorp.com]
*

*> Sent: Monday, November 27, 2000 7:59 PM
*

*> To: david.kaiser@mcdata.com
*

*> Cc: ldmiller@nortelnetworks.com; keskinen@nortelnetworks.com;
*

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

*> Subject: RE: [SI-LIST] : Accuracy of HSPICE W-element transmission lines
*

*>
*

*>
*

*>
*

*> Dear SIers,
*

*>
*

*> I am a developper of hspice and currently taking in charge of W-element.
*

*> You may have seen following information on W element feature from
*

*> the person who had been taking in charge of W element. But for those who
*

*> haven't read seen it I would like to resend this by adding up to date
*

*> information. Please take a look at this.
*

*>
*

*> ---
*

*>
*

*> I would like to clarify the four Hspice issues which have been
*

*> actively discussed:
*

*>
*

*> 1) Accuracy of the field solver for computing the skin-effect
*

*> matrix Rs.
*

*> 2) Discussion of the inclusion of the imaginary term for Rs:
*

*> SQRT(f)*Rs [eq1] vs. SQRT(f)*Rs*(1+j) [eq2].
*

*> 3) Discrepancy between the transient and ac analysis results for
*

*> the cases with non-zero Gd values.
*

*> 4) Discrepancy between the transient analysis results using
*

*> a single long line versus several short lines.
*

*>
*

*> (1) It is clearly stated in the Hspice manual that the computation
*

*> of Rs does NOT account for any proximity or edge effects; hence,
*

*> the resulting value is significantly smaller than the actual value.
*

*> This is consistent with the computed data by Richard Mellitz.
*

*> We are currently working on implementing a new solver which
*

*> accurately models the skin, proximity and edge effects.
*

*> For 2000.4 release, we have implemented a new field solver which
*

*> is for skin effect resistance and inductance which have following
*

*> features.
*

*>
*

*> Advantage:
*

*>
*

*> 1. Effects due to magnetic coupling such as skin effect
*

*> and proximity effect can be modeled.
*

*> 2. Resistive ground plane is taken into account (but not in C and G).
*

*>
*

*> Side Effect: (*important*)
*

*>
*

*> 1. Rs has off diagonal components due to magnetic coupling
*

*> 2. Lo becomes bigger than previous extraction because of
*

*> proximity effect especially under the condition of high
*

*> resistive ground plane.
*

*>
*

*> Limitation:
*

*>
*

*> 1. due to the limitation of "RLGC" model input (only real value),
*

*> imaginary part of Rs is ignored. this may cause error in
*

*> high frequency R,L value. In fact Rs is computed to fit
*

*> the formula [eq.2] which models skin effect resistance.
*

*> (in future release, this will be solved by changing the
*

*> output to "frequency tabular RLGC model" which is
*

*> implemented in 2000.4 described below.)
*

*>
*

*>
*

*> (2) The main issue for this second problem is that while including
*

*> the imaginary term [eq2] models the skin effect (marginally) better
*

*> at high frequencies, it may introduce a significant error at low
*

*> frequencies. Some people, especially those working on high
*

*> frequency applications, are accustomed to use [eq2] while others
*

*> prefer [eq1].
*

*>
*

*> I prefer to use [eq2] since it is mathematically more valid solution
*

*> at the high frequency range where the SQRT(f) dependency is valid,
*

*> and furthermore, both equations are not accurate at low frequencies
*

*> anyway. I ran some test cases using both equations and observed no
*

*> significant differences in ac analysis. However, the accuracy of
*

*> the transient analysis is slightly degraded when [eq1] is used.
*

*>
*

*> Nonetheless, we will change the implementation so that you can
*

*> optionally exclude the imaginary term.
*

*>
*

*> (The ultimate solution to this Rs problem, as it has been pointed
*

*> out by Michael Tsuk, could be to use a better modeling equation
*

*> or even tabular data.)
*

*>
*

*> (3) The difference in attenuation between transient and ac analyses
*

*> with non-zero Gd values is a rather subtle problem. The cause of
*

*> this problem is mainly due to the limitation of the dielectric
*

*> model equation based on f*Gd as has been pointed out by Dmitri.
*

*>
*

*> (4) The discrepancy between the transient results using a single
*

*> line versus several cascaded short lines is mainly due to the
*

*> limitations on the difference approximation routine used in
*

*> W-element for the frequency-dependent cases. Recently, we have
*

*> significantly improved the difference approximation routine, and
*

*> and this discrepancy has been eliminated. (No risetime parameter
*

*> setting is necessary anymore.)
*

*>
*

*>
*

*> All of these improvements will be available for the next release
*

*> of Hspice (version 99.4). We will soon make a beta version available
*

*> (approximately 1 month); however, the new solver mentioned in (1)
*

*> won't be implemented in this beta version.
*

*>
*

*> I hope this note clarifies all the issues related to the W-element
*

*> and field solver in Hspice.
*

*> I apologize for a somewhat late response.
*

*>
*

*> Regards,
*

*>
*

*>
*

*>
*

*> : Ted Mido
*

*> : Avant! Corporation (Oregon R&D)
*

*> : 9205 SW Gemini Drive
*

*> : Beaverton, Oregon 97008
*

*>
*

*>
*

*> From: David Kaiser <david.kaiser@mcdata.com>
*

*> Subject: RE: [SI-LIST] : Accuracy of HSPICE W-element transmission lines
*

*> Date: Mon, 27 Nov 2000 17:28:12 -0700
*

*>
*

*> > Nope. This is conjecture based on my expectations and experience. But
*

*> > when I confronted a support person at Avanti, he addmitted that there
*

*> > may be limitations above 1GHz.
*

*> >
*

*> > David
*

*> >
*

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

*> > From: Larry Miller [mailto:ldmiller@nortelnetworks.com]
*

*> > Sent: Monday, November 27, 2000 11:53 AM
*

*> > To: David Kaiser; Kai Keskinen; si-list@silab.eng.sun.com
*

*> > Subject: RE: [SI-LIST] : Accuracy of HSPICE W-element transmission lines
*

*> >
*

*> >
*

*> >
*

*> > Yes, but have you compared your results (either) with real hardware?
*

*> >
*

*> > Inquiring minds want to know....
*

*> >
*

*> > Thanks,
*

*> >
*

*> > Larry Miller
*

*> >
*

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

*> > From: David Kaiser [SMTP:david.kaiser@mcdata.com]
*

*> > Sent: Monday, November 27, 2000 10:17 AM
*

*> > To: Keskinen, Kai [KAN:0G15:EXCH]; si-list@silab.eng.sun.com
*

*> > Subject: RE: [SI-LIST] : Accuracy of HSPICE W-element
*

*> > transmission lines
*

*> >
*

*> > I have compared the W-element with the RLGC matrix from running
*

*> > APSIM on 100 Ohm diff'l pairs). With a 30ps pulse and 10ps rise times,
*

*> > the reflected pulse was very symetrical for the W-element, but showed
*

*> > and RC roll off with APSIM. The APSIM seemed to shown a more realistic
*

*> > reflection pulse.
*

*> >
*

*> >
*

*> > David Kaiser
*

*> > McDATA Corp.
*

*> > 310 Interlocken Pkwy.
*

*> > Broomfield, CO 80021
*

*> > (303) 460-4431
*

*> > davidk@mcdata.com
*

*> >
*

*> >
*

*> >
*

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

*> > From: Kai Keskinen [ mailto:keskinen@nortelnetworks.com
*

*> > <mailto:keskinen@nortelnetworks.com> ]
*

*> > Sent: Thursday, November 23, 2000 11:19 AM
*

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

*> > Subject: [SI-LIST] : Accuracy of HSPICE W-element transmission lines
*

*> >
*

*> >
*

*> >
*

*> > Hello SI-People:
*

*> >
*

*> > We have now several times encountered differences in results
*

*> > from other modelling packages and results from HSPICE w-element models
*

*> > for applications involving fairly long striplines > 30cm on FR4 and
*

*> > GETEK with 2.5Gbps signals with ~100ps edge rates. The W-element model
*

*> > appears to give lower loss than the other techniques. Typical track
*

*> > widths are 6-8 mils with 100Ohm loosely coupled differential pairs.
*

*> >
*

*> > Avant! claims the W-element method is accurate without providing
*

*> > a paper showing how it was validated.
*

*> >
*

*> > How does the rest of the SI community feel about the accuracy of
*

*> > the W-element model?
*

*> >
*

*> > Thanks in advance,
*

*> >
*

*> > Kai Keskinen
*

*> > Equipment and Network Interconnect
*

*> > Nortel Subsystems and Performance Networks (NSPaN)
*

*> > (613)-765-3506 (ESN 395)
*

*> > keskinen@nortelnetworks.com
*

*> >
*

*> >
*

*>
*

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

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*

*>
*

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**Next message:**Haller, Robert: "RE: [SI-LIST] : Accuracy of HSPICE W-element transmission lines"**Previous message:**William Baldwin: "Re: FWD: Re: [SI-LIST] : Eye pattern with differencial signals."**In reply to:**Chan, Michael: "RE: [SI-LIST] : Accuracy of HSPICE W-element transmission lines"**Next in thread:**David Kaiser: "RE: [SI-LIST] : Accuracy of HSPICE W-element transmission lines"

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