RE: [SI-LIST] : 20-H Rule for Power Planes

S. Weir (weirsp@a.crl.com)
Mon, 31 May 1999 04:40:25 -0700

Jon,

I have been using a similar technique, and it seems to work pretty well. I
have been building the "outer fence", but have not been putting a gnd trace
on the inner power plane. I tend to believe that the most benefit comes
from paying the drilling cost for a tight fence to hold the inductance
down. I don't see where the additional trace would substantially reduce
the area loop in the return current. Since, ostensibly, that is the source
of the radiated power, I don't think it will help much. However, I suppose
it might be worth modelling.

Regards,

Steve.
At 05:07 PM 5/31/99 +1000, you wrote:
>
>Another trifling contribution.
>
>In the case of a power plane enclosed by two return planes:
>How 'bout cutting back the power plane, and adding an outer ring of
>return
>plane on the same layer, stitched to the outer return layers?
>
>This would have the effect of moving the fringing field right inside the
>pcb.
>
>Jon Keeble
>
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