Periodic Asymmetric Trapezoidal Perturbation Microstrip Antenna for Millimeter-Wave Automotive Radar Sensors

This article presents a new design and experimental verification of a broadband wide-beam microstrip array antenna for short-range automotive radar sensors. The antenna is designed based on a pure microstrip transmission line, by inserting short inverted trapezoidal stubs alternately on both sides of the microstrip line periodically to generate a trapezoid-cascaded electric field, which enables the proposed antenna to radiate effectively. Therefore, the proposed antenna has the advantage of a simple structure. The antenna has a larger effective radiation aperture, which leads to a smaller quality factor, so the antenna has a broad bandwidth of 13% (74.02–85.08 GHz), completely covering 76–81 GHz automotive radar frequency band. The peak gain is up to 10.4 dBi. Based on the proposed antenna, a three transmitting antennas and four receiving antennas (3T4R) multiple-input-multiple-output (MIMO) radar antenna array is designed. To reduce the influence of strong surface waves on the radiation pattern, a design conception of a dummy array with an absorbing load is introduced. The array antenna of each transmitting (TX)/receiving (RX) channel can achieve a wide half-power beamwidth (HPBW) of 120° in the azimuth plane. Besides, the MIMO array exhibits good consistency, with the absolute amplitude error of TX-RX channels less than 3 dB and the phase error less than 20° in the azimuth plane.