Originally posted by: highwire
<div class="FTQUOTE"><begin quote>Originally posted by: Born2bwire
The holes in the door's screen are cylindrical waveguides. You can sit down and solve for the wave solutions of the waveguide and notice that only evanescent solutions will propagate and thus have an estimation of the amount of power that will leak through. Waveguide is a rather general term, it's a structure the confines and guides the propagation of electromagnetic waves or sound waves. It does not need to be the classical rectangular or cylindrical PEC waveguide as coaxial cables are waveguides, traces on a PCB are waveguides, etc.</end quote></div>
The fact that evanescent energy is present on the outer surface of a perforated EM shield is not a sign of "leakage". It should be thought of as being bound to the surface or the wave within. The very rapid decrease in intensity of this energy at even very small distances is a clue that energy lost to radiation not a necessary condition.
While, as was mentioned, everything in this realm can be reduced to Maxwell's Equations, this does not mean that everything can be called anything. I think it is a good thing to respect technology and keep in mind functional descriptions of components. Thus, the box in which I heat my coffee with radio frequency energy in the morning is not a waveguide. It is just a cavity with a lot of standing waves, and hopefully not very leaky. On the other hand, since the functional attribute of "waveguide" generally means conveyance of energy, I very much endorse that in circuits where EM fields are important, that twisted pair, coax cable, circuit traces, really really are waveguides as well.