A novel slot-coupling feeding technique for circularly polarized patch antennas

In this paper a novel slot-coupling feeding technique is used to feed a circularly polarized patch antenna. The antenna is fed through two microstrip lines which are excited 90° out-of-phase and coupled to a square patch by means of a square ring slot realized in the feeding network ground plane. Design procedure and simulation results are shown for a 2×2 array working in the WiMax 3.3-3.8 GHz frequency band. Due to both the symmetry properties of the novel slot-coupling feeding technique and the implementation of a sequential rotation technique, excellent axial ratio performance is achieved in a wide frequency band where return loss is greater than 10dB and axial ratio is less than 3dB for any direction in the antenna main beam.