Re: [SI-LIST] : Upper limit of interplane capacitance

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From: Doug (dmckean@gte.net)
Date: Fri Jun 09 2000 - 09:35:55 PDT


> Larry Miller wrote:
>
> Dr Howie Johnson did an article on this sometime back.
>
> Here is an excerpt. See what you think:

What would people expect the characteristic impedance
to be of a 4" x 6" x 4mil FR-4 structure?

Parallel plates are just two dimensional transmission
lines with L and C being in units of H/area and F/area.
The equations pop out pretty much the same as a one
dimensional transmission line, i.e.

 vprop = 1/sqrt(LC)
 Z0 = sqrt(L/C)

In fact, there's some pretty neat derivations
for parallel plates such as

 Z0 = sqrt(mu/epsilon)*d/w

 d = distance of separation
 w = width

ignoring fringing effects.

Just was wondering if anyone has done any
research into correlating pure theory
versus reality.

- Doug McKean

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