I. Introduction
In The past few years, 77-GHz millimeter-wave (mmWave) radar technology, as a low-cost alternative to LiDAR in advanced driver assistance systems [1], has been rapidly developed and has been applied to autonomous emergency braking, adaptive cruise control, and other functions. In addition to its reasonable costs, mmWave radar is robust to different lighting and weather conditions and can provide measurements of range, azimuth angles, and instantaneous velocity [2].