Novel compact circularly polarized antenna with high front-to-back ratio for UHF RFID reader applications

A novel compact single feed circularly polarized disk patch antenna with high front-to-back ratio for radio frequency identification (RFID) reader in the ultra high frequency (UHF) is proposed. A perturbation is induced by two cuts for the circular polarization. Four silts on the disk are used to miniaturize the size of the antenna. Furthermore, the backward radiation is reduced by the slits and the ground with proper size. The simulated and the measured results show that good performance of the proposed design is obtained, and the proposed antenna can be used in the special situation where each of the two back to back antennas is in charge of their own positive semi sphere.