A 45 $^\circ$ Linearly Polarized Hollow-Waveguide Corporate-Feed Slot Array Antenna in the 60-GHz Band

A 45^° linearly polarized hollow-waveguide slot array antenna has been proposed to achieve low sidelobes in the E- and H-planes by a diamond-shaped array arrangement. A layer for radiating slots was added into the conventional plate-laminated antenna. The 2 × 2-element sub-array was designed to suppress grating lobes and low cross-polarization. The 16 × 16-element array in the 60-GHz band was fabricated by diffusion bonding of the laminated thin metal plates. The first sidelobe levels in the E- and H-planes were -25.5 and -26.1 dB, respectively, and the cross-polarization was - 31.5 dB in the boresight. High antenna efficiency of 70% with greater than 32 dBi gain over 5 GHz was maintained by the corporate-feed hollow waveguide structure. Quantitative amount of fabrication error due to etching and alignment was revealed by simulations.