From: D. C. Sessions ([email protected])
Date: Mon Jan 10 2000 - 14:19:36 PST
Kim Helliwell wrote:
> Chris Heard wrote:
> > Here's another...
> > Use a ground trace in between signal traces to reduce crosstalk....
> I'm curious why this is screwy. Is it because:
> 1. The separation of the signal traces alone (because of the ground trace)
> would be enough to reduce the crosstalk, so the ground trace is not needed, or
> 2. The ground trace actually contributes more crosstalk.
#2. The reason is that for nontrivial frequencies the "ground trace"
is really floating metal and takes up space. So if you have room for
a 6 mil track between two other 6 mil tracks, you COULD have 18 mils
of space instead. 18 mils of space has 2/3 the capacitance of 12
mils (6 mils of copper is close to a dead short) and thus more coupling.
-- D. C. Sessions [email protected]
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