A 140-GHz high-gain broadband tapered box-horn array antenna

A high-gain broadband low-profile low-loss antenna array of box horn at 140 GHz frequency fed by waveguide is proposed in this study. The element spacing is larger than one wavelength, resulting from the aperture size of horn and the width of the waveguide, which causes grating lobes. The simulated grating lobes in the E- and H-plane are below -16 dB and -19 dB, suppressed by a tapered structure and a special horn type of box horn, respectively. The horn array antenna exhibits 40.7-dBi peak gain and a relative impedance bandwidth of 25.26% from 120 GHz to 155.37 GHz under the condition of voltage standing wave ratio (VSWR) less than 2.