Contents I. Introduction
The analysis of the interaction between an electromagnetic (EM) field and a metallic enclosure is a classical shielding problem [1]. Metallic enclosures are usually adopted to reduce the EM coupling between their inner volume and the outer world. However, important couplings are often caused by the unavoidable presence of apertures, necessary for many practical purposes, such as ventilation. Also in the presence of apertures the aperture-cavity system is resonant, although its resonant frequencies move slightly from those of the corresponding closed cavity, and the quality factor is no more infinite. In any case, at the resonant frequencies the shielding effectiveness (SE) of the system deteriorates dramatically. The SE of enclosures is strongly dependent on the number, shape, and thickness of the apertures, on the presence of internal loads, and on the type of the radiating EM source, which can be modeled as an impinging uniform plane wave or a dipole.
