Target Motion Enhanced Angle Estimation for Millimeter-Wave Radar With Sparse Uniform Linear Array

A high angular resolution is crucial for refining the perception capabilities of millimeter-wave (MMW) radar for advanced driver assistant systems (ADASs). Sparse uniform linear arrays (SULAs) could serve as an effective and economical way for expanding array apertures to enhance the angular resolution. They provide analytical solutions while ensuring antenna continuity and mitigating the impact of mutual coupling. However, the presence of undesirable grating lobes in SULAs incurs angle ambiguity. Considering the movement of targets of interest in the sensed environment, this article proposes a novel angle-estimation method for MMW radar with SULA assisted by target motion information to address the above issue. The grating-lobe characteristics and target angle ambiguity are theoretically analyzed to indicate their essential consistency. Based on this, multiple collaborative measurements are introduced to deduce all ambiguous angles. In addition, their mutual-motion relationship imposes constraints on these ambiguous angles, promoting an initial angle estimation. A sequential measurement procedure and voting mechanism are applied to prevent nonunique solutions associated with target-angle shifts. These processes allow for determining the final and unambiguous estimated angle, thereby enhancing the reliability and stability of the proposed method. Finally, its effectiveness is validated through numerical simulations and experiments.