Characteristic modes for dielectric and magnetic bodies

A theory of characteristic modes for material bodies, both with and without losses, is developed. For loss-free bodies, the modes consist of a set of real characteristic sources which diagonalize the generalized network matrix for the body, and a set of characteristic fields which diagonalize the scattering matrix. Most of the properties of these modes remain the same as those of the corresponding modes for perfectly conducting bodies. For lossy bodies, the corresponding modes have complex characteristic sources. However, in the lossy case there also exists a set of real characteristic sources which diagonalize the generalized network matrix, but their fields do not diagonalize the scattering matrix.