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

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From: Haller, Robert (rhaller@cereva.com)
Date: Tue Nov 28 2000 - 14:12:16 PST


Larry,
    A while ago I did simulation versus measurement comparisons using AVANT!
W-element
and a TDR with high bandwidth FET probes.
(But I used RLGC matrixes generated by Digital's/Compaq's internal Field
solver - SIMPEST) .
I utilized various edge rates 50->500 ps edge rate, a 12 inch transmission
line, and Hspice 99.x
I also acquired and digitized the source and destination waveforms of the
transmission line,
was careful to model the probes in my simulation and use the actual
digitized waveform (PWL)
with the correct output impedance as the input stimulus to SPICE.
A few Key items was to digitize the input waveform going into the W-line and
to Cross-section the
actual Transmission Line you measured.
I was successful in getting W-line simulations to virtually overlay measured
results (far end
of the Transmission line using the W-LINE).
 
At higher edge rates (< 100ps) we began to see discrepancies. I think these
were limitations in the
Dielectric losses not modeled over frequency, Michael Tsuk, Could answer
this better.
 
I also found the the simulations were surprising affected be HSPICE OPTIONS;
METHOD, TIMESTEP
Very Long Lines (> 3 Meters had issues - I think this has been fixed)
T-lines were surprising good if you don't care about high frequency effects
and U-Lines were horrible.
 
Bob Haller
Cereva Networks
Marlboro Ma.
508-486-9660-3365

-----Original Message-----
From: Larry Miller [mailto:ldmiller@nortelnetworks.com]
Sent: Monday, November 27, 2000 1:53 PM
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

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