Electromagnetic fields coupled into a cavity with a slot-aperture under resonant conditions

The electromagnetic coupling of an incident plane wave through a slot-aperture backed by a lossy rectangular cavity is analyzed by using a generalized network formulation based on an application of the equivalence principle. Two types of aperture-cavity resonances manifest themselves. The conditions for the existence and the characteristics of such double aperture-cavity resonances are studied. General expressions for field strength in the aperture, field distributions in the cavity, and maximum power penetration are derived. Appropriate expressions for an equivalent magnetic current to replace the aperture are discussed. A numerical example is given.