Generalised hybrid-network parameters for electromagnetic coupling between dissimilar regions through a small aperture

A generalised network representation for electromagnetic coupling between dissimilar regions through a small aperture is developed. Hybrid-network parameters are defined. The parameters for one region are independent of the characteristics of the other coupled region. By properly combining the parameters of some canonical regions, various complex problems of small-aperture coupling can be solved. Examples are included for coupling between two dissimilar halfspaces and for coupling between a rectangular waveguide and a halfspace through an elliptic hole.