An Antenna with a Modulated Self-Complementary Metasurface Ground Plane for GPS Applications

Global Positioning System (GPS) base station antennas should have a quasi-isotropic radiation pattern in the upper hemisphere and provide almost zero radiation in the bottom hemisphere for positioning error reduction. Usually, a base station GPS antenna consists of an omnidirectional antenna element and a ground plane, which suppresses the back radiation. However, along with the back radiation suppression, a ground plane makes the radiation pattern in the upper hemisphere narrower. To avoid this negative effect of a ground plane, we propose the use of a modulated self-complementary metasurface ground plane. As an antenna element, we use a three-dipole antenna with quasi-isotropic radiation and circular polarization patterns. We demonstrate that the antenna with a modulated self-complementary metasurface ground plane provides quasi-isotropic radiation and polarization patterns in a required angular sector. For back radiation suppression, we use a semitransparent cylindrical surface located near the ground plane's edge. We demonstrate that effective back radiation suppression is possible by using a fully resistive semitransparent edge.