A novel RFID reader antenna with circular polarization operation

A novel antenna designed for the RFID reader with circular polarization (CP) operation is proposed in this paper. The antenna contains a 50-Ω microstrip feed line, two resonant paths on the top substrate, and a system ground on the bottom substrate. Experimental results show that good CP radiation performances of the proposed design are obtained, and both the impedance bandwidth and 3-dB axial-ratio bandwidth are also met the Japanese RFID requirement. The proposed antenna also has advantages of compact, simple structure, ease fabrication, and low cost.