A Novel CP Antenna for UHF RFID Handheld Reader

A novel antenna for UHF radio-frequency identification (RFID) readers with circular polarization (CP) operation is proposed in this paper. The antenna consists of a 50 Ω microstrip feed line, two resonant paths on the upper surface of the substrate, and a system ground on the lower surface of the substrate. By adjusting the parameters of the two resonant paths, a circularly polarized reader antenna with good impedance matching can be obtained. Experimental results show that the proposed design exhibits good performance in term of circularly polarized radiation, and both the impedance bandwidth (931 MHz to 960 MHz) and the 3 dB axial-ratio bandwidth (948 MHz to 954 MHz) meet the Japanese RFID requirement (950 MHz to 954 MHz). Furthermore, the proposed antenna offers the following advantages: compact size (60 mm × 60 mm × 0.8 mm), simple structure, ease of fabrication, and low cost.