Mutual coupling between spherical annular-ring and circular microstrip antennas

Mutual coupling is an important issue in estimating the performance of a microstrip array antenna. In this article, the coupling characteristics between spherical concentric annular-ring and circular microstrip antennas is studied by using full-wave analysis. Both the annular-ring and the circular patches are fed by a coaxial probe. The circular patch is excited at the TM/sub 11/ mode and the annular-ring patch is operated at the TM/sub 12/ mode. Such a coupling problem is treated as a two-port network and the coupling coefficient, S/sub 12/, can be obtained from the scattering matrix. The numerical results of E-plane and H-plane coupling coefficients are presented and discussed.