XFX field solver (from Quad) among other parameters outputs Rs and G
- frequency dependent resistance and shunt conductance (accounting for the
skin resistance and the dielectric dipole relaxation losses, respectively).
These parameters are extracted based on assumption that
Rskin(freq)~sqrt(freq) and G(freq)~freq. Same assumption is made in HSPICE
W-elements. However, I believe, that XFX-extracted parameters Rs and G
should be scaled by the factors sqrt(4*pi) and 2*pi respectively to be used
in W-elements. These scaling coefficients DO NOT account for necessary unit
conversion (from mils to meters, etc.). I arrived to these scaling factors
by comparing the original Telegrapher equations on page 21-80 of
"Star-Hspice Manual, Release 1998.2" with those in Quad manual. My concern
there is that these equations in Hspice manual might be given there only as
an example, and thus are accurate only to some factor.
Would anyone care to comment?
Another issue... XFX provides an optional fudge factor "lambda" that
effectively accounts for copper plane/trace surface roughness. This fudge
factor effectively scales the default copper resistivity in the skin layer.
The default value of "lambda" is 1.
Has anyone of you done any study as to what this Lambda should be? How does
this value vary (if at all) from one board vendor to another ? Is there any
particular value for Lambda if one is going to use XFX' data with Hspice
W-elements?
Thank you all.
Vadim Heyfitch
Intel, High-end Sever Division
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