Adam,

guarded or shielded traces can be very useful to prevent coupling into a
sensitive trace or from a trace with very short rise time, even on a multilayer
board. But make sure that you ground your ground trace every 1" or so. That way
you keep the shield from becoming an antenna itself.

Volkmar

Hawes, Adam wrote:

>         I feel sure this is probably an issue for a lot of PCB
> designers......
>
>         Recently, I have come across an increasing number of engineers who
> wish to have certain tracks on multilayer PCB's shielded by ground traces
> running adjacently. It seems to be a case of jumping on the bandwagon to me
> because we never used to do this until about 12 months ago.
>
>         I was under the impression that ground tracks only served a useful
> purpose on 1or 2 layer boards and that on a multilayer they were essentially
> a waste of space as most of the capacitive coupling would be straight to the
> ground plane.
>

 (cut)



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  Volkmar Huß                              Dräger ProTech GmbH
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