Single-layer circularly polarized patch antenna for RFID reader application

In this letter, a novel and single-layer proximity-fed square patch antenna has been proposed to obtain circularly polarized radiation. However, the single-layer proximity-fed square patch antenna with circular polarization has a few studied up to now. The proposed antenna consists of a pair of square radiating patches coupled in close proximity to a microstrip line in the same side and a coupling arrow-shaped slot fed by the microstrip line in the other side. The excitation mechanism of the proposed antenna is the radiating patches directly fed and from the coupling slot fed by the microstrip line. The antenna operates at its fundamental orthogonal modes (TMoi and TMio) for the UHF band (902-928 MHz). The two near-degenerated resonant modes for circularly polarization of a square patch antenna are generated by etching diagonal unequal cross-slot to the patch. Details of the antenna design and the obtained experimental results of the antenna performance are presented and discussed.