Far field analysis of spherical-circular microstrip antennas by electric surface current models

The far field radiation patterns of a circular disk microstrip antenna mounted on a sphere are studied theoretically. The radiator is replaced by an assumed surface current distribution. The effects of the dielectric layer and the metallic sphere are rigorously taken into account by the spectral domain Green´s function formulation. In the spectral domain represented by the vector Legendre series, the Green´s function matrix is diagonal. The results are verified by comparison with results obtained from the cavity model theory. The cavity model agrees asymptotically with the present method for the case of a thin dielectric substrate.