Low-Frequency Electromagnetic Penetration of Loaded Apertures

Low-frequency (quasi-static) electromagnetic penetration of an aperture can be reduced by loading the aperture with a conductive film or a bonded-junction wire mesh. A quantitative analysis of this phenomenon is carried out in this paper for a loaded circular aperture in a perfectly conducting ground plane of infinite transverse extent. Contact resistance between the aperture loading and the rim is taken into account. The quasi-static magnetic-field problem and the electrostatic field problem from which the aperture polarizabilities and penetrant fluxes are determined are shown to reduce to the problem of solving a single Fredholm integral equation. Exact (numerical) and approximate (variational) solutions to this integral equation are obtained, and the latter are used to represent the polarizabilities and penetrant fluxes by simple analytical formulas and equivalent circuits. These representations are found to be quite accurate when the contact resistance is not too large