[SI-LIST] Re: Slot Antenna

If I understand the original question correctly, 
simply putting dc potentials across a slot won't 
make it radiate.  If the supplies are necesarily 
noisy, there *may be* radiation.  

Strictly speaking, a slot antenna is a hole punched 
in one sheet of metal around which current circulates 
that sets up a potential across the hole. With that 
current remaining constant and thus the potential 
across the hole remaining constant, the other main 
parameter that decides how strongly the slot radiates 
is the area of the hole.  This mechanism cannot happen 
with two power planes which are unconnected to each 
other and in close proximity. 

And strictly speaking, two unconnected power planes 
in close proximity to each other in a printed circuit board 
are not a slot antenna.  More like a two dimensional 
version of a folded dipole.  Think of the old rabbitt ears 
antenna with a piece of aluminum foil on each arm.  That's 
a version of a folded dipole. And that's the model for two 
power planes in close proximity. 

If the power supply noise is acceptably low, construction is 
done attention to proper stackup, and traces are reasonably 
routed mindful of the slots, I doubt the slot will be a cause 
of detrimental radiation.  

All strictly my opinion, of course.  

Regards, Doug McKean 


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