60 GHz Waveguide-Fed Cavity Array Antenna by Multistepped Slot Aperture

This letter presents a center-feed high-gain and high-efficiency 4 × 4-element slot array antenna in the 60 GHz band. The antenna feed network is designed using only a single-layered square quad-ridge cavity structure, which is excited through a rectangular slot that has the same size as that of a standard WR-15 rectangular waveguide. The proposed antenna avoids any conventional power dividers in the feed network, which reduces the complexity of the design and fabrication process. To enhance the operating bandwidth of the antenna and prevent the grating lobes effects, a stepped design is used for each radiating slots of the array. Furthermore, the overall radiating aperture of the antenna is equipped with a dielectric layer, which decreases the mutual coupling among array elements. As a result, a broad bandwidth antenna with high efficiency and low sidelobes in both E- and H-planes is developed over the 60 GHz band. The antenna has been fabricated and tested. Measurement results show an operating bandwidth of 11.6% from 57.7 to 64.7 GHz. A gain of more than 23 dBi, sidelobes of less than -15.2 dB, and an antenna efficiency of better than 60% are achieved.