I did recently see an article on this exact question. It was thoroughly
tested using field solvers and the field solvers confirmed the reduction of
radiation from traces designed to the 20H rule. Sorry can't look for the
article right now and have no recollection of exactly where it was,
magazine, internet or other. If I can recollect where I saw this article, I
will let you know.
        Note that this article tested the issue using traces, not power
planes. As for Ivan's comments, there is a lot of truth to which he speaks,
remember that to any moderate or high frequency AC signals there is no
difference between the GND and Power planes. They are virtually shorted
together to AC signals. Thinking about this as I am writing, I wonder if
this is a 'misplaced' theory, it belongs to traces and not power planes. I
have heard both versions but the power plane theory makes less sense the
more I think about it.

Brad Velander,
Lead PCB Designer,
Norsat International Inc.,
#300 - 4401 Still Creek Dr.,
Burnaby, B.C., V5C 6G9.
Tel. (604) 292-9089 direct
Fax (604) 292-9010
website www.norsat.com


> -----Original Message-----
> From: Bagotronix Tech Support [mailto:[EMAIL PROTECTED]]
> Sent: Wednesday, July 11, 2001 3:40 PM
> To: Protel EDA Forum
> Subject: Re: [PEDA] perimeter stitched ground vias question
> 
> 
> I don't claim to be an expert, but here's my thoughts anyway:
> 
> What if your ground plane is as noisy as your power plane?  
> If the ground
> plane and power plane cover the same areas they can (almost) 
> completely
> nullify each other's noise IFF the noise currents in each plane are
> correlated with the other plane.  An instance where the noise 
> currents would
> NOT correlate would be for non-differential (i.e. 
> ground-referenced I/O,
> power feeds, etc.) signals entering/exiting the board.  But for local
> (on-board) circuitry, the noise in each plane should correlate.
<SNIP>
> 
> Best regards,
> Ivan Baggett
> Bagotronix Inc.
> website:  www.bagotronix.com
> 

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