A circularly polarized slits loaded UHF RFID antenna with parasitic element

An eccentric annular slot patch antenna is initially studied for UHF (ultrahigh frequency) RFID (radio frequency identification) reader antenna application that can operate within the North America RFID band (902–928 MHz). Circular polarization (CP) radiation is achieved in this band by loading two narrow open-ended slots (slits) into the slot patch. To further enhance the CP bandwidth, a parasitic element is loaded beside the patch antenna that forms the proposed antenna. From the experimental results, the proposed antenna can yield an impedance bandwidth (10-dB return loss) between 618 to 1105 MHz, while good CP bandwidth (3-dB axial ratio, AR) from 886 to 942 MHz is also attained. In addition to that, gain level and efficiency of more than 7.6 dBic and 91%, respectively, were also measured.