A high-gain 58-GHz box-horn array antenna with suppressed grating lobes

A low-profile high-gain antenna array of box horns for the frequency band 5 7.2-58.2 GHz is presented. The antenna consists of 256 radiating elements d ivided into two subgroups of 128 elements fed by a rectangular waveguide fe ed network. The radiating elements are fed in parallel and the waveguides a re connected with T-junctions, The matching of the T-junctions is improved with a matching pin and a splitter, Because of the waveguide feed network, the element spacing is larger than one wavelength, which causes grating lob es, The grating lobes and sidelobes in the H-plane have been suppressed by the use of a combination of subarrays, a special characteristic of the box horn, and an array amplitude tapering. The measured sidelobe levels in the H-plane are below -30 dB at angles larger than 8 degrees from boresight, A gain higher than 35.7 dBi and a return loss higher than 14.4 dB have been-m easured for the antenna over the band 57.2-58.2 GHz.