A CIRCULARLY POLARIZED COMPACT ANTENNA FOR UHF BAND RFID READER

This paper presents a circularly polarized compact antenna based on the concept of Yagi-Uda antenna. By properly arranging three ring resonators operating at the fundamental mode, a compact Yagi-Uda like antenna is proposed to form directional pattern. This proposed antenna has comparable size with the ring resonator of quarter-wavelength, while the performances are comparable with the conventional microstrip antenna of half-wavelength. To validate the proposed design methodology, an antenna working at UHF radio- frequency identiflcation (RFID) band is benchmarked. Both simulated and measured results are shown for comparison.