High Efficiency and Small Antenna With Horn and Lens for 77 GHz Automotive Radar

An antenna with a pyramidal horn and a dielectric lens was investigated to reduce a size of long-range automotive radars in the 77-GHz band. By employing an array with two horns and lenses where a diameter of the lens was half of whole output-aperture length, a height of the antenna was reduced while keeping an antenna efficiency high. The fabricated antenna with commercially available materials had the height of 14 mm and achieved the antenna efficiency of 45.6% and a frequency bandwidth of 5 GHz where reflection coefficient S11 was below −10 dB. The antenna had a flat beam whose 3-dB beamwidth was 4.5° in elevation and 15° in azimuth, meaning that the antenna can be used for long range radar with a single beam.