Transmission of an EM wave through the aperture of a cylindrical cavity

The penetration of an electromagnetic wave through an aperture in a cylindrical structure is investigated. By using the moment method, the electrical and magnetic fields in a cavity behind the aperture are determined as a function of frequency of the incident field. The accuracy of the numerical solution is established through tests of satisfaction of the boundary condition, edge condition, and convergence with respect to the number of modes in the aperture. Depending on the frequency and location inside the cavity, the stored electromagnetic energy density varies very rapidly. Its peak value can be two orders of magnitude greater than the incident energy density. The frequencies where the peaks occur can be identified approximately as the resonance frequencies of the cavity when the aperture is closed.