From: Charles Grasso (email@example.com)
Date: Mon Jun 04 2001 - 08:55:13 PDT
In my parallel universe as an EMC guy I have indeed run across
this.A series terminated transmission line does indeed radiated 6dB ( or
half as much) lower than an equivalent transmission line without the
[mailto:firstname.lastname@example.org]On Behalf Of RMELLISON@aol.com
Sent: Sunday, June 03, 2001 9:05 PM
To: email@example.com; firstname.lastname@example.org
Subject: 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
to my ARRL handbook to check out the quarterwave transformer reasoning,
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
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
across the transmission line, the lower impedance line would produce more
due to higher line current. This is stated various places in Mardiguian's
Nobody replied to my question about the radiation comparison of source
terminated lines to end terminated lines. It seems to me that since you
half as much current in a source terminated line, the EMI should be half
much as a parallel terminated line would produce. Does anyone agree with
I appreciate the help.
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