[SI-LIST] Re: 90 degree bend

Kanakaraj wrote:

>Hi,
>The simplest thing is that when you make 90 degree turns on the pcb track,
>the electron moving in it cannot make sudden turns..( remember inertia of
>direction in physics and a bus making a 90 degree turn at full speed)... so
>some of the electrons will jump out of the pcb track and will cause emi
>issues..
>
>and Andy, Andrew, Ray anderson and the seniors will give you more inputs on
>that.
>Well I am too like you. a beginner :-)
>Kanak
>
>  
>
Nice story, unfortunately not a very good analogy. The crux of the 
problem (if you consider it a problem in your application) is that a 
sharp right angle bend will introduce an impedance discontinuity in the 
trace due to a bit of excess C at the bend. You can miter the bend by 45 
degrees to mitigate the excess C. (the microwave guys have developed 
what is called an 'optimal' miter [whose details I don't have handy at 
the moment] that is even better than a simple 45 degree miter at dealing 
with the problem. The problem of excess C at the turn isn't very 
problematic until you get to really high frequencies or very fast 
risetimes. As far as electrons missing the turn and hurtling off the 
road............

This story reminds me of the one that related by a US Navy instructor to 
a class of new aviation electronics techs at the Naval Air Technical 
Training Command at NAS Millington back in the early 70's. He explained 
(with a straight face) that one could understand how a capacitor worked 
if you looked at the schematic symbol. He explained that it blocked DC 
because there was a gap between the parallel lines in the symbol, and 
that it passed AC because the sine wave would "go from the connecting 
wire, up over the first line, down through the gap, around the second 
line and eventually reach the second wire"

-Ray

------------------------------------------------------------------
To unsubscribe from si-list:
si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field

or to administer your membership from a web page, go to:
http://www.freelists.org/webpage/si-list

For help:
si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field

List FAQ wiki page is located at:
                http://si-list.org/wiki/wiki.pl?Si-List_FAQ

List technical documents are available at:
                http://www.si-list.org

List archives are viewable at:     
                http://www.freelists.org/archives/si-list
or at our remote archives:
                http://groups.yahoo.com/group/si-list/messages
Old (prior to June 6, 2001) list archives are viewable at:
                http://www.qsl.net/wb6tpu

Other related posts: