[SI-LIST] Re: 20H rule explanation from W. Michael King
- From: "Douglas C. Smith" <doug@xxxxxxxxxx>
- To: Raymond.Anderson@xxxxxxx, si-list@xxxxxxxxxxxxx
- Date: Mon, 08 Oct 2001 18:26:51 -0700 (PST)
Hi Ray and the group,
The pdf paper has an error in it that makes Acrobat (V4, full version) have
some viewing problems,
but from what I can see, I think the author made an error in his starting
assumptions. First it seems
to be a simulation with a very simple set of conditions (current paths and
component placement) as
opposed to real measurements. Simulations are a good starting point, but I need
to see them
backed up by real measurements of something similar that is easily constructed
as a check. This
is especially important for me since the result is conterintuitive here.
It has been a long time, but I recall the 20H rule involved component placement
as well and cannot
be taken out of context just as a set of planes (Time permitting, I plan to
check on this after stocking
up on Ginko Biloba [memory enhancer] :-). Many designers have had excellent
results laying out
planes in this way as part of an overall plan.
This would be a very simple experiment to run at home for about about a day or
two's total work. If I
do this in the future, I will make the results available in this forum.
Doug
---- Ray Anderson <Raymond.Anderson@xxxxxxx> wrote:
>
> I don't want to add fuel to the 20H "rule" debate, but
> just noticed this short paper from EPEP2000 on the web at:
>
> http://www.sigrity.com/papers/epep2000/epep_20h.pdf
>
> Paper is by Chen (of ucsc.edu) and Fang (of ucsc.edu and sigrity.com).
>
> The conclusion states:
>
> "This paper investigates the effects of 20-H rule and shielding vias on the
> radiation from the printed circuit board. For the two-plane structure, 20-H
> rule yields much more radiation than the normal structure. For the multiple
> plane case, no significant change in radiation is found if the 20-H rule is
> applied to the internal planes. Also the numerical result shows that the
> usage of shielding vias would cut down the radiation effectively."
>
>
> Kind of what I've suspected all along.....
>
>
> -Ray
> Sun Microsystems Inc.
>
> >
> >
> >RJS,
> >
> >No, I'm pretty sure there's no good information in that
> >explanation. It appears to be a parody of the type of
> >nonsense that appears on this list from time to time.
> >My guess is that it is a hoax of some kind.
> >
> >Mary
> >
>
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>
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