We've been building Zdiff boards at Viasystems for over a year now. When I
researched the available prediction tools available at the time, there was
nothing available that was even remotely accurate. So... like every good pwb
manufacturer, we developed our own, using a comprehensive DOE that validated
each of the design and/or fabrication variables. Specifically this included,
line width, differential line spacing, dielectric spacing and dielectric
constant (ie different glass/resin contents). The resulting mathematical
model is performing very well and wev'e since refined it's accuracy as
additional data is obtained.

For elements for consideration, refer to "Transmission Line Design Handbook"
by Brian C. Wadell (ISBN0-89006-436-9).

Our testing unit is the CITS system from Polar. After comparison to
alternative units, we felt that it was the best system for our needs.

Hope this helps.

Dave Rooke
Circo Craft - Pointe Claire
A division of Viasystems
[log in to unmask]

= = = = =
>     Looking for some information regarding differential impedance: The
>     design rule, calculation and the testing of differential values.
>     Thanks,
>
>     Teik M. Ng
>     PC World
>

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