RE: [SI-LIST] : W-Elements

Haller, Robert (
Thu, 5 Aug 1999 00:10:45 +0800

I haven't looked at roughness (and we presently don't model it), but I have
done detailed correlation between simulation and measurement (your right it
would make a good paper). I designed some test boards, took data, then
cross-sectioned the boards. I used SIMPEST (DEC's Field Solver) to create an
RLGC matrix and also a Pi model with an RC ladder (for skin effect). I
compared the simple Pi with RC ladder model, to Hspice W-lines (98.4) ,
HSPICE U-lines (ugh) and Ideal T-lines. The W-line (for my case) was
surprisingly accurate and ran very fast. The RC ladders correlation was good
but exhibited a small discrepancy at the very top edge of the rising
waveform (dielectric losses ?) and was sensitive to hspice 'method'.
U-line's correlation was poor. T-lines were surprisingly good at predicting
delay, but as expected don't demonstrate the 'rolling over' of the waveform.
I ran HSPICE using these different models varying risetime, timestep,
method, and segment lengths. I was surprised to find significant difference
in output shape depending on method, timestep and the other variables.

I concluded that W-lines were fast and accurate utilizing HSPICE 98.4 with
my edge rates, lay-up and conductor cross-section. Use a timestep of ~ .1
times your risetime for best performance and accurate results. I recommend
W-line users designing high-speed systems perform bench correlation
especially when edge rate is critical and pay particularly close attention
to measurement techniques.


Robert J. Haller
Compaq Computer Corporation
AlphaServer Product Development
Phone: (978) 493-4112
Fax: (978) 493-0941

-----Original Message-----
From: Mellitz, Richard []
Sent: Wednesday, August 04, 1999 9:49 AM
To: ''
Subject: RE: [SI-LIST] : Proposal: Rs correlation/collaboration for
W-Elem ents

Very good point about roughness. I wonder if some these EM modeling tools
could incorporate this?

Richard Mellitz,

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