A Novel 24-GHz Air-Filled Cavity-Backed Slot Antenna Array with Out-of-Phase Power Divider for Automotive Radar System

A novel 24-GHz cavity backed slot antenna with out-of-phase power divider based on multilayer air-filled print circuit board (PCB) for automotive radar is presented. By etching the bow-tie slot and rectangular slot on the antenna element, the two resonant frequencies at 23.45GHz and 24.15GHz are stimulated. For the antenna element, the measured operating frequency band is 23–25.01GHz and the maximum measured gain is 7.08dBi. And then, the antenna array with 16 antenna elements is proposed. The microstrip-to-slotline power divider with 180° phase difference is designed to compose the feeding network. According to the measured results of the antenna array, the impedance bandwidth is from 23.22–25.03GHz and the maximum gain is 14.83dBi. In addition, the front-back ratio (F/B) is larger than 25dB.