Date: Thu Feb 24 2000 - 11:57:54 PST
I have advocated the intelligent use of moating techniques since 1989 and
have achieved very positive results. I emphasize "intelligent use" as we are
all aware of the problems created by passing high-speed signals over split
planes, but the rationale goes much farther that just increased signal paths.
I use moating to mitigate ESD and impinging radiation effects, intercept
PCB-generated radiation, and to suppress CM resonance effects.
Two days ago I received word back on a client's respin on a deficient board
(>18 dB over FCC B) that now achieves a MAXIMUM emission level of 19 dB BELOW
FCC B. This delta of >37 dB improvement exceeds the typical 18 to 25 dB
improvement I normally achieve, but is an excellent example of the proper
implementation of moating techniques. On this board, I removed one set of
moats and added two others, along with some minor rerouting of some signal
traces to accommodate these changes.
The ability to envision the fields and waves (including resonances) in an
assembly takes a good deal of experience.
Michael L. Conn
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