[SI-LIST] Re: SPLIT PLANE GAP

In my opinion and with regard to signal integrity, 
25mil to 100 mil split widths are relatively small 
when compared to the wavelengths involved. 

With regard to EMI, splits (or better slots) are 
the electrical dual to a wire antenna.  Where 
current makes a wire antenna work, a voltage 
potential makes the slot work as an antenna. 
This would be accomplished with the return 
current following the trace to the point of the 
split, then attempting to go around it. 

I've seen some bench measurements that show 
the greatest point of radiation is at the furthest 
ends of split where the current abruptly changes 
directions, i.e. the point of greatest acceleration 
of charge. 

This is one of couple of instances where one 
can have perfectly acceptable signal integrity 
but bad EMI. 

Regards, Doug McKean 

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