Wideband and high-gain circularly polarised microstrip antenna design using sandwiched metasurfaces and partially reflecting surface

In this study, the authors propose a new type of metasurface, namely a sandwiched anisotropic metasurface, for converting a linearly polarised elliptical patch antenna into a wideband circularly polarised antenna. A partially reflecting surface (PRS) as a superstrate is further used to enhance the gain of the antenna. The design rules of the antenna are also presented. The combined metasurface and the PRS-based patch antenna is designed on a low-cost substrate FR-4. The realised 3 dB axial ratio bandwidth (ARBW) of the antenna is 1.01 GHz (3.55-4.56 GHz), its impedance matching bandwidth is 1.33 GHz (3.08-4.41 GHz), and its peak gain varies from 7 to 7.84 dB within the band. By placing the PRS superstrate above the antenna, gain further improves to 9.32 dBi without degrading the performance of the antenna. Measured results are presented to validate the antenna performance and results are compared against a large number of similarly available antenna.