Circularly polarised square patch antenna with asymmetrical Y-shaped feed structure

A novel single-feed structure for circularly polarised square patch antennas is proposed and theoretically studied. The proposed antenna has a simple structure, consisting of a square radiating patch and an asymmetrical Y-shaped microstrip feed line. The two orthogonal modes with equal amplitude and ±90° out of phase are simultaneously excited by the suggested feed structure with two different branch lengths. It is shown that the proposed antenna has good circular polarisation characteristic.