A TM(21) MODE ANNULAR-RING MICROSTRIP ANTENNA FOR PERSONAL SATELLITE COMMUNICATION USE

This paper presents a configuration of circularly polarized annular-ri ng microstrip antenna (ARMSA) and its design method to obtain high gai n and low axial ratio including the analysis of finite ground plane ef fect using G.T.D. for personal satellite communication use. The ARMSA excited at TM(21) mode through co-planar branch-line hybrid coupler fo r circular polarization produces a conical pattern which has high gain in low elevation angle. The relation of gain and axial ratio versus t he dielectric constant of substrate are shown and the existence of the dielectric constant which satisfies two requirements, that is, high g ain and low axial ratio are clarified. For car-top application, experi mental results in the L-band showed satisfactory characteristics for v ehicle antenna.