Low-Profile Wideband Circularly Polarized Patch Antenna Using Asymmetric Feeding

A low-profile wideband circularly polarized aperture stacked patch (ASP) antenna without air dielectric layers is presented. The new circular ASP antenna, which is fed by two orthogonal dual-offset lines through an asymmetric crossed slot, delivers a wide bandwidth of 80% for the 10-dB return loss and similar input impedance characteristics for the two ports. Then, a novel broadband 90◦ hybrid feed network is employed to achieve good impedance matching, balanced power splitting and consistent 90◦ (±9◦) phase shifting across the wide operating band. The two unbalanced feed lines are connected to the respective ports of the feed network comprising a three-section Wilkinson power divider and a broadband 90◦ phase shifter. It is found that the proposed antenna can achieve a measured impedance bandwidth of 91.3% (2.44–6.54 GHz), measured 3-dB axial ratio (AR) bandwidth of 86.4% (2.5–6.3GHz), and measured gain bandwidth of 60.9% from 3.2 to 6.0 GHz for the gain > 4 dBic. In addition, a comparison between the proposed wideband CP antenna and related wideband CP and ASP antennas in the literature is made.