A Wideband Circularly Polarized Corporate-Fed Waveguide Aperture Array in the 60 GHz Band

A wideband circularly polarized planar antenna with hexagonal apertures arrayed over a plate-laminated waveguide slot array is developed in the 60 GHz band. The 2×2-element subarray functioning as the principal component is precisely and efficiently analyzed by the method of moments using numerical eigenmode expansion. This numerical approach is particularly applied to the regions of both the X-shaped cavity and hexagonal radiating aperture for circular polarization. Moreover, the bandwidths of both axial ratio (AR) and impedance matching in the subarray are significantly widened by applying the genetic algorithm in two steps. The bandwidths for both AR <; 3 dB and VSWR <; 1.5 are improved from 4.8% to 14.5% compared with the previous design. Their mechanisms are investigated in detail as well. A 32×32-element array with a uniform illumination is designed and fabricated by the diffusion bonding of thin copper plates. The wideband antenna performance is verified by the experimental evaluation.