Generalized Theory of Characteristic Modes for non-PEC Media

Generalized theory of characteristic modes is proposed for the PMCHWT integral equation formulation of a homogeneous penetrable body. By properly expressing the weighting operator of the generalized eigenvalue equation in terms of the external radiation-related integral operators, any symmetrization or other modifications of the equations is not needed. Numerical examples are presented to demonstrate the validity of the proposed method. The obtained characteristic modes are shown to have the desired properties of physically meaningful eigenvalues and orthogonal far field patterns.