I'm not sure this went out right the first time!!

At 12:54 PM 8/26/96 -0400, you wrote:
>
>
>
>> Point 6. Has anybody measured a difference in radiation using 90 degree
>> angles? Or is this based on heresay (an electronics "Urban Myth")?
>
>
>>> 6. Eliminate ALL 90 degree angles on traces, and planes.  All 90 degree 
>>>    angles radiate, it is important to run your clean up utilities if you
>>>    haven't already.  Also consider the planes as capable of radiation
>>>    especially at higher frequecies, so 45 all the corners.
>
>
>I am not a Phd, but have taken some classes and hope my response is adequate.  
>
>
>The radiation at a 90 degree bend is based on theory.  ----

          <  clip  >

I know of high speed and EMI specialists who have taken such measurements, but
have done so for their own use, not for publication. Their position is that
EMI emissions are higher at 90 degree corners than at 45 degree. The reason
is not for obscure transmission line issues or impedance mismatch, etc. There
is too much mis-information written about this. The reason is that 90 degree
corners begin to look antennas. THIS IS AN ANTENNA ISSUE, NOT A TRANSMISSION
LINE ISSUE. The reason you don't see much definitively written about it is that
antenna design is a black magic art!!

There is a technical note on this issue available at
ftp.eskimo.com/u/u/ultra/notes
Download file t004.exe.
It is a self extracting .prn file in HP Laserjet II format, suitable for sending
to a pc-based HP printer. 

Alternatively, send a request to [log in to unmask] and they will snail
mail a copy to you.

Doug Brooks

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