High isolation circularly polarized (CP) antennas using compact soft surface

A compact soft surface is proposed to improve an isolation of circularly polarized patch antennas in this article. The soft surface is generally made up of a periodically alternating perfect electric conductor and perfect magnetic conductor. The perfect magnetic conductor is implemented by the corrugation with a depth of quarter wavelength. The proposed compact soft surface is designed by a folded corrugation with a length of a quarter wavelength and the folded part is located below perfect electric conductor plane. Thus, the compact soft surface can be designed without any additional area above the ground plane. To verify its feasibility, mutual coupling and axial ratio of two circularly polarized antenna elements without and with the compact soft surface have been compared. This improved isolation results in small active reflection coefficient and wide beamwidth of active element pattern which would help to design wide scanning angle array.