RE: [SI-LIST] : differential impedance calculations

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From: Dan Swanson (DSWANSON@BartleyRF.com)
Date: Fri Nov 03 2000 - 08:15:16 PST


Since you asked ....

Linecalc in general is pretty good. Microstrip uses Jansen equations,
coupled microstrip uses Kirschning and Jansen equations. These are
complicated,
pages and pages of code, equations that were developed by fitting to
field-solver data.
Some geometries like symmetrical stripline will have an exact analytical
equation inside Linecalc.
Other geometries will be the best they could find in the literature.

Loss is an interesting problem. Linecalc asks for trace thickness, relative
conductivity and
loss tangent of the substrate. But we know there are other mechanisms,
roughness,
metal porosity, etc. So I always recommend a test board that matches the
geometry you
will be using. Use the test board data to "fudge" the input parameters to
the software so
you get the right loss. Then future calculations with similar geometry
should be pretty good.

As far as field-solvers, it is hard to beat FlexPDE for the money ($495).
Text mode input
that is really a macro language. Once you get your geometry going you can do
lots of
"what ifs" very quickly. Can include trace thickness, trapezoidal
cross-section, etc. If
you want some sample files I would be willing to share.

Dan

Dan Swanson EMAIL: d.swanson@ieee.org
Bartley RF Systems, Inc. TEL: 978-834-4085
37 South Hunt Road FAX: 978-388-7077
Amesbury, MA 01913

> -----Original Message-----
> From: Jason Xiao [SMTP:jxiao@riverdelta.com]
> Sent: Friday, November 03, 2000 9:50 AM
> To: 'Eric Bogatin'; Larry Miller; chasgra; Charles Grasso; Gary
> Peterson; si-list
> Subject: RE: [SI-LIST] : differential impedance calculations
>
> What about HP (Agilent) ADS Lincalc (eesof stuff)?
> Anybody would like to share your experience on impedance/loss calculation
> with Lincalc?
>
>

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