High gain Fabry-Pérot circular polarization cavity antenna for UHF RFID applications

A Fabry-Pérot cavity antenna for UHF RFID application is presented. First, a circularly polarized antenna is designed to obtain a high gain of 9.82 dB at 868 MHz. Then a hexagonal patch type frequency selective surface is designed and placed above the primary antenna to be used as partially reflective surface (PRS) to enhance its gain. The overall dimension of the structure is about (1.73 λ₀ * 1.5 λ₀ * 0.53 λ₀), where λ₀ is the free-space operating wavelength. The simulation results yield a 13.12 dB realized gain, 1.61 % 3 dB gain bandwidth and an axial ratio less than 3 dB with a ±33° beamwidth at 868 MHz. The cavity reflex antenna exhibits a good efficiency of 96.13% and side lobe level (SLL) less than -14 dB.