**From:** Chan, Michael (*Michael.Chan@compaq.com*)

**Date:** Fri Jun 09 2000 - 10:03:28 PDT

**Next message:**Ray Anderson: "Re: [SI-LIST] : Upper limit of interplane capacitance"**Previous message:**Ray Anderson: "RE: [SI-LIST] : Upper limit of interplane capacitance"**Maybe in reply to:**Barry Ma: "[SI-LIST] : Upper limit of interplane capacitance"**Next in thread:**Doug McKean: "Re: [SI-LIST] : Upper limit of interplane capacitance"**Reply:**Doug McKean: "Re: [SI-LIST] : Upper limit of interplane capacitance"**Reply:**Raymond Y. Chen: "[SI-LIST] : The impedance looking into the power/ground plane structure"

I would like to point out that what would be the impedance look like when

you looks at it from the center of the two plates viewing from the top? Can

you still qualify it as a rectangular wave guide as the wave is spread out

in

360 degree other than in one particular direction. Instead of calling it the

traditional "characteristic impedance" I would prefer to see it as " driving

point impedance". Any comment from any guru ????

Michael Chan

-----Original Message-----

From: Doug [mailto:dmckean@gte.net]

Sent: Friday, June 09, 2000 11:36 AM

To: si-list@silab.eng.sun.com

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

*> 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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**Next message:**Ray Anderson: "Re: [SI-LIST] : Upper limit of interplane capacitance"**Previous message:**Ray Anderson: "RE: [SI-LIST] : Upper limit of interplane capacitance"**Maybe in reply to:**Barry Ma: "[SI-LIST] : Upper limit of interplane capacitance"**Next in thread:**Doug McKean: "Re: [SI-LIST] : Upper limit of interplane capacitance"**Reply:**Doug McKean: "Re: [SI-LIST] : Upper limit of interplane capacitance"**Reply:**Raymond Y. Chen: "[SI-LIST] : The impedance looking into the power/ground plane structure"

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