Unified Theory of Characteristic Modes—Part II: Tracking, Losses, and FEM Evaluation

This is the second component of a two-part article dealing with a unification of characteristic mode decomposition. This second part addresses modal tracking, interpolation, and the role of ohmic losses, and presents several numerical examples for surface-based method-of-moment (MoM) formulations. A new tracking algorithm based on the algebraic properties of the transition matrix is developed, achieving excellent precision and requiring a very low number of frequency samples when compared with procedures previously reported in the literature. The transition matrix is further used to show that characteristic mode decomposition of lossy objects fails to deliver orthogonal far-fields and to demonstrate how characteristic modes can be evaluated using the finite element method (FEM).