High gain and wideband circularly polarized S-shaped patch antenna with reactive impedance surface and frequency-selective surface configuration for Wi-Fi and Wi-Max applications

In this paper, broadband circularly polarized S-shaped patch antenna is designed with a reactive impedance surface (RIS). Besides the RIS structure, the frequency-selective surface (FSS) superstrate is deployed to enrich the antenna gain. The S-shaped patch is modeled on an FR4 glass epoxy and its feed position is set to resonate at 5.3 GHz. The 6 x 6 array size of square patches forms the RIS structure which is inserted in the middle of the S-shaped patch and ground plane to enhance -10 dB impedance bandwidth and 3 dB axial ratio bandwidth. The 6 x 6 array of unit cells forms the FSS superstrate which is deployed approximately half-wavelength (approximate to lambda/2) height above the ground plane to act like a Fabry Perot cavity (FPC) resonator antenna for improving the antenna gain. The combination of RIS and FSS with an S-shaped patch antenna improves the -10 dB impedance bandwidth, 3 dB axial ratio bandwidth, and the gain simultaneously. The proposed antenna resonates over a wide frequency range with a -10 dB impedance bandwidth of 31.8% (4.81-6.63 GHz) and the antenna has a good 3 dB axial ratio bandwidth of 18.9% (4.99-6.03 GHz). The antenna peak gain is around 10 dBi. The proposed antenna prototype is measured in the anechoic chamber and the measured results mimic the simulation results.