An Alternative N-Port Characteristic-Mode Formulation for Lossy Structures

In this letter, a novel N-port characteristic mode (CM) formulation is proposed. By developing the weighting matrix appropriately and solving the proposed generalized eigenvalue equation, the obtained eigenvalues possess significant physical interpretation. Most importantly, the contributions of the radiated, dissipated, and reactive powers can be separated by the obtained eigenvalues. Numerical results of several antennas in lossy environments validate that the proposed N-port CM formulation not only reveals the resonant CMs within the considered frequency band but also further identifies the modal radiation efficiency of each CM.