Single-Folded Leaky-Wave Antennas for Automotive Radars at 77 GHz

Low-cost multilayer antennas are proposed for the next-generation automotive radar systems at millimeter waves. The antennas consist of a multilayer pillbox leaky-wave antenna structure where the feeding (integrated horn) and radiating parts are connected by a quasi-optical system made by an integrated parabola and several coupling slots (pillbox transition). In addition, a scanning capability is obtained by displacing the feeding part in the focal plane of the pillbox transition. Three prototypes with different feed locations have been manufactured and tested. The antenna stack-up consists of two Rogers 5880 substrates piled up by a diffusion bonding process. The integrated horn and pillbox transition are synthesized by perfect vertical metallic walls and closely spaced metallic pins, respectively. The E- and H-plane radiation patterns measured in the 74-78-GHz band show an average half-power beamwidth of about 11.5° and 5.5°, respectively, and sidelobe levels better than -15 dB up to a scan angle of 18°. The measured gains are about 24 dB around 77 GHz, resulting in a total efficiency higher than 50%.