Slits Loaded Circularly Polarized Universal UHF RFID Reader Antenna

A simple structure circularly polarized (CP) UHF (ultrahigh frequency) RFID (radio frequency identification) reader antenna that operates within the universal RFID bands (840-960 MHz) is investigated. Here, the technique of loading a corner truncated square patch antenna into an L-shaped ground plane is initially studied to achieve good impedance matching with broad CP bandwidth. To further enhance both the impedance bandwidth and CP bandwidth, a novel technique of loading three narrow slits into the corner truncated square patch is proposed. By meticulously arranging these three slits in a certain manner, from the experimental results, besides achieving a gain level of approximately 8.6 dBic, the proposed antenna can also yield an impedance bandwidth from 685 to 1125 MHz, while good CP bandwidth between 836 and 986 MHz is also demonstrated.