79 GHz Band Ultra-Low Profile Radar Module Using End-Fire Antenna and Lens

This paper proposes a 79 GHz band ultra-low profile radar module which has a new antenna structure that combines an end-fire antenna (EFA) with a lens, and the EFA radiates radio waves in the horizontal direction to the substrate. Both electromagnetic simulation and actual measurements demonstrate that the new antenna structure combining the EFA with a lens enables 3 dB improved antenna gain and beam angle adjustment in the desired direction. In general, automotive use case, where radars are mounted behind a bumper, multiple reflections between the bumper and the radar surface can pose an issue. The multiple reflections degrade radar performance, resulting in maximum detection range reduction and angle estimation errors. Compared to the conventional radar which uses a broadside antenna (BSA) that radiates radio waves in the vertical direction to the substrate, the proposed radar has a smaller facing area to the bumper so that it can reduce the multiple reflections. Under such mounting conditions, both simulation and measurements show that the proposed radar can improve the variation of transmission loss through the bumper by 3 dB when the distance between the bumper and the radar surface changes, compared to the conventional radar using a BSA. Furthermore, by reducing multiple reflections, the proposed radar improves the accuracy of the direction of arrival (DOA) estimation. These results prove the effectiveness of the proposed radar.