Metasurface-loaded circularly-polarised slot antenna with high front-to-back ratio

A new technique to achieve high front-to-back radiation ratios of slot antennas is presented. A 0.8 mm thin metasurface is loaded onto a circularly-polarised slot antenna and backed by a metallic reflector at close distances. The antenna has an overall height of ~ 0.1 wavelengths. However, it exhibits wideband characteristics with a measured impedance bandwidth (voltage standing-wave ratio ≤ 2) of 73.3% and a 3 dB axial-ratio bandwidth of 29.1%. A broadside gain of 7 dBic with a front-to-back ratio of 23.7 dB is achieved at 2.7 GHz.