Transient electromagnetic fields coupled into a conducting cavity through a slot aperture

The problem of an incident transient electromagnetic wave coupled into a conducting cavity through a slot aperture is solved with the aid of the equivalence theorem. Application of the method of moments and definition of generalized admittances lead to a network formulation. The singularity expansion method is used to determine the transient fields. Methods for finding the natural frequencies, the natural-mode vectors, and the coupling coefficients are discussed. Natural-mode distributions are obtained for the more important system singularities, and coupling coefficients are computed as functions of the angle of incidence. Typical time responses of the magnetic current over the slot aperture and of the electric and magnetic fields inside the cavity for a step-function incident wave are included.