**From:** *RMELLISON@aol.com*

**Date:** Sun Jun 03 2001 - 20:04:41 PDT

**Next message:**Carlos Moll: "Re: [SI-LIST] : Serpentine delays"**Previous message:**Daniel, Erik S.: "RE: [SI-LIST] : Re: Antenna Problem on the Board"**Maybe in reply to:**subramanya C K: "[SI-LIST] : Antenna Problem on the Board"**Next in thread:**Charles Grasso: "RE: [SI-LIST] : Antenna Problem on the Board"**Reply:**Charles Grasso: "RE: [SI-LIST] : Antenna Problem on the Board"**Reply:**Chris Rokusek: "RE: [SI-LIST] : Antenna Problem on the Board"

To Chris Rokusek, Jian-X. Zheng, Jason Leung, Andrew Martwick and others.

Thanks for the feedback.

The replies got me to really thinking about radiation and impedance. I went

to my ARRL handbook to check out the quarterwave transformer reasoning, and

this seems valid for a special case. But after reading a new book

(Controlling Radiated Emissions by Design by Michel Mardiguian), I'm more

convinced than ever that it is not the higher impedance that gives rise to

greater EMI--it's the height of the trace above the ground plane that is the

governing factor. The common assumption of the replies was that a higher

impedance was caused by a larger height above the ground plane. Obviously

you can get higher or lower Zo by varying the width of the trace while

holding h constant. In this instance, I would say that for a given voltage

across the transmission line, the lower impedance line would produce more EMI

due to higher line current. This is stated various places in Mardiguian's

book, also.

Nobody replied to my question about the radiation comparison of source

terminated lines to end terminated lines. It seems to me that since you have

half as much current in a source terminated line, the EMI should be half as

much as a parallel terminated line would produce. Does anyone agree with

me?

I appreciate the help.

Richard Ellison

972-569-8317

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**Next message:**Carlos Moll: "Re: [SI-LIST] : Serpentine delays"**Previous message:**Daniel, Erik S.: "RE: [SI-LIST] : Re: Antenna Problem on the Board"**Maybe in reply to:**subramanya C K: "[SI-LIST] : Antenna Problem on the Board"**Next in thread:**Charles Grasso: "RE: [SI-LIST] : Antenna Problem on the Board"**Reply:**Charles Grasso: "RE: [SI-LIST] : Antenna Problem on the Board"**Reply:**Chris Rokusek: "RE: [SI-LIST] : Antenna Problem on the Board"

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