Single-fed single-patch broadband circularly polarized antenna for UHF RFID reader applications

A single-fed single-patch broadband circularly polarized (CP) antenna is proposed for radio frequency identification (RFID) reader operating at 865-928 MHz. The antenna comprises a novel probe-fed meandered strip and a corner truncated square patch. Broadband CP operation is achieved by selecting an optimal size of the truncated corners and using a thick air-layer substrate (about 0.12λ₀). To obtain good impedance matching (VSWR<;1.5) within the 3 dB axial ratio bandwidth, the probe-fed meandered strip feed technique is proposed and adopted. In addition, the commercial software called HFSS was also used to simulate the antenna performance. Simulation results show that the proposed antenna has an impedance bandwidth (VSWR<;1.5) of about 74 MHz (858-932 MHz), a 3dB axial ratio bandwidth of about 71 MHz (860-931 MHz), and a gain level of 8.6 dBi or larger within the operating bandwidth.