[SI-LIST] : Signal Dispersion

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From: Bob Perlman (bobperl@best.com)
Date: Mon Sep 04 2000 - 13:18:23 PDT


Hi -

A happy Labor Day to all.

I'm looking into effects that can distort very high frequency
waveforms. There's already been a lengthy discussion of skin
effect here, and in the past folks have discussed dielectric
absorption.

One thing I haven't heard much about is dispersion. My
understanding is that, for long signal traces or cables, slight
frequency-dependent differences in propagation delay can cause
the various frequency components in a signal transition to de-align,
causing the edge to disperse. Some of the causes to which this is
attributed seem to be:
 
 - different frequencies propagating in different transmission modes
 - changes in dielectric constant as a function of frequency.

Of course, I could be totally wrong; this is just what I've been able
to piece together from things I've read. Can anyone explain
dispersion, or point to a good text that does? Under what
conditions does dispersion become significant?

Thanks,
Bob Perlman

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