Characteristic Mode Analysis for Antennas with Waveport Problems

Characteristic mode (CM) analysis and a waveport modeling method is combined for analyzing antenna radiation and scattering. Base on the mode matching method, a MoM waveports modeling method is presented for general metallic-dielectric structures. To analyze waveguide port fed antenna with characteristic modes analysis, a suitable weighted matrix is established based on energy relationship and the CMs can be obtained by solving the new eigenvalue problem. Once the CMs are found, modal weighted coefficients of CMs, equivalent electric and magnetic currents on the antenna can readily be obtained. Numerical results of a microstrip antenna with coaxial cable line feeding is given to validate the proposed method.