A theoretical study on a circular microstrip antenna in a parallel plate waveguide

The input impedance of a circular microstrip antenna in a parallel plate waveguide is theoretically formulated using the cavity model with the surface admittance at the side aperture. The surface admittance is defined by the magnetic field produced by the equivalent magnetic current at the side aperture and includes the effects of the parallel plates on the antenna. The magnetic field in the parallel plate region is formulated by the Green's function approach. Presented formulation is validated through the comparisons with measurement results.