A novel input impedance computation method for coaxial probe fed microstrip antennas by utilizing characteristic modes

A method to efficiently compute the input impedance of the coaxial probe fed microstrip antennas by using characteristic modes is proposed in this paper. The efficiency is achieved by defining a discontinuous source current at the feed location that models the current injected by the probe. The input impedance is simply expressed in terms of modal excitation coefficients and eigenvalues of each mode.