Compact GNSS antenna with circular polarization and low axial ratio

The investigation and development of a compact antenna for GNSS high-performance applications over a high-DK substrate are presented. In order to reduce multipath and achieve best performances, a very good polarization purity over a possibly wide bandwidth is needed. Therefore, a substrate which has both high DK and high thickness is used. However, because of the use of such substrate, the performance of the antenna may severely degrade when the total footprint (i.e. substrate and ground plane dimensions) change or when the antenna is used in array configurations. The reason for that are mainly waves excited into the substrate itself, producing spurious radiation and a high coupling between adjacent antennas. To overcome this drawback, a soft/hard surface (SHS) is employed, resulting in an antenna which has lower coupling with adjacent elements, as well as a relatively broad axial-ratio bandwidth.