Design of Millimeter-Wave Circularly-Polarized Antenna Array with Aperture-Coupled Feed for Axial-Ratio Bandwidth Enhancement

In the project, a circularly-polarized aperture-coupled rectangular patch antenna array with 5 elements operated from 26.5～29.5 GHz(10.7%) will be designed and manufactured. Also it is expected to achieve 3-dB axial-ratio bandwidth > 13%, RHCP peak gain > 11 dBic, (left-hand cpl)/(right-hand cpl) > 25 dB, and front-to-back ratio > 15 dB.The presented design will easily have much wider axial-ratio bandwidth than the impedance bandwidth. Therefore, the main task of the project will be the adjustment of the impedance bandwidth to the desired value. Most aperture-coupled circularly polarized patch antennas in the literatures are of square or circular shapes. The configuration of the aperture is often of a cross or L shapes which excite two orthogonal modes in the patch. In the project, the presented aperture will not only excite the rectangular patch, it also participates the radiation. Moreover, the shape of the presented aperture will have insignificant radiation right below the ground plane. In addition to the simulation, antenna measurements using facilities in CIC will be conducted for design validation. The measurements will including S-parameters, peak gain, radiation patterns, and axial ratio.