UHF RFID Reader Antenna for Near-Field and Far-Field Operations

This paper presents a radio frequency identification (RFID) reader antenna designed for near-field and far-field operation. The reader antenna consists of a segmented loop antenna on the periphery and a patch antenna placed inside the loop antenna. The far field of the antenna is circularly polarized (CP), which is achieved by adjusting the patch antenna perturbation and antenna feed position. The simulation results show that the antenna works from 906 to 923 MHz with reflection coefficient less than −10dB, and the axial-ratio bandwidth of less than 3dB is 12MHz (907MHz-919MHz).