Mixed‐Potential Integral Equation‐Based Characteristic Mode Formulation for Microstrip Patch Antennas in Lossy Cases

ABSTRACT In this letter, the mixed‐potential integral equation (MPIE)‐based characteristic mode (CM) formulation is presented to identify the modal behaviors of a microstrip patch antenna with a lossy substrate and superstrate. By leveraging the electric far‐field expression of the horizontal Hertzian electric dipole, a radiated‐power‐related matrix is constructed, thereby enabling the development of the proposed formulation. The proposed technique not only refines the generalized theory of CM (GTCM) framework, but also reduces the computational burden.