Omnidirectional Hemisphere Radiation Coverage Control and Back-Radiation Suppression by Using Self-Dual Metasurface and Semitransparent Edge

The ground segment of systems for geostationary satellite applications requires antennas with a special shape of radiation pattern. For some applications, a desirable antenna radiation pattern should have a quasi-isotropic shape in the upper hemisphere and provide almost zero radiation in the bottom hemisphere to suppress the multipath effect. Usually, such a requirement is satisfied by an antenna consisting of an omnidirectional radiator and a ground plane for partially back-radiation reduction. However, a conventional metallic ground plane lacks the ability to control the radiation pattern in the upper hemisphere. This limitation can be addressed by employing a modulated self-dual metasurface and a semitransparent (ST) edge in this work, which simultaneously enables pattern shaping and back-radiation suppression. The present study demonstrates that a three-dipole antenna coupled with a modulated self-dual metasurface provides quasi-isotropic radiation patterns in an angular sector of 4°-85° with respect to broadside. This achievement is attributed to the combination of a space wave radiation pattern with a leaky wave radiated by the metasurface. To further improve the back-radiation performance, we utilize a resistive, ST cylindrical surface located near the ground plane's edge. We demonstrate that effective back-radiation suppression enhancement of 7.3 dB is obtained when compared with a PEC ground plane of the same radius.