LAUSR

An ultrawideband and high-gain circularly polarized (CP) antenna fed by inclined double-Y-shape slot is proposed in this letter. The antenna structure is mainly composed of two patches, an aperture coupling-fed layer and a metallic reflector. The metal reflector is placed under the feeding layer for generating unidirectional radiation and improving the gain of the antenna. Right-hand circular polarization is achieved by adjusting the lengths of the two branches of the Y-shape slot. In order to expand the impedance bandwidth (IBW), two patches are used. By chamfering the radiation patch, good ultra axial-ratio bandwidth is obtained from 3.6 to 6.0 GHz. The measurements show that the IBW is about 71.0% (3.28–6.76 GHz) for VSWR < 2, and the bandwidth of antireflection is about 49.8% (3.61–6.05 GHz). Moreover, the antenna has a stable gain is better than 8.5 dB from 3.2 to 7 GHz. The axial ratio can be kept below 3 dB over the entire half-power beamwidth.