Hi I sorted of had an epiphany when thinking about EMI shielding a PCB...
If the frequency of the system on a PCB was constant ( lets 20MHz digital system or something) could I take advantage of that fact and design a trace around the perimeter that will prevent that frequency from being transmitted in or out?
For example a circular trace with a diameter that is half the wavelength, an EM wave would induce a current in the loop equal and opposite to itself causing the net energy seen inside the loop to be 0. Right?
Of course this only applies if the wave is polarized in the correct direction but since all the PCB traces are also only polarized that direction it should not matter.
(I know for MHz a half wave is fairly large and impractical but just ignore that part of it)