In this paper, a new ultrahigh frequency circularly polarized microstrip antenna using in RFID reader is proposed. The proposed antenna has a simple structure, it has non-symmetrical rectangular corner truncated square patch, ground plane and a probe feed. To achieve good circular polarization(CP) radiation characteristics, it uses air as the dielectric layer. Simulation results of a constructed prototype with the center operating frequency at 923 MHz showed that the antenna has a return loss S11 of about −24 dB, a gain level of about 9.48 dBi. The antenna has good impedance and radiation characteristics over the required bandwidth, 920-925 MHz (Chinese UHF RFID band).
Dual-Band Dual-Sense Circularly Polarized Stacked Patch Antenna With a Small Frequency Ratio for UHF RFID Reader Applications