Sub-Aperture Polar Format Algorithm for Curved Trajectory Millimeter Wave Radar Imaging

With the development of smart driving technology, Millimeter Wave (MMW) radar has become increasingly crucial in the automotive environmental sensing system. However, limited by the vehicle size, the MMW radar antenna length cannot meet the requirements of high-resolution imaging. Synthetic Aperture Radar (SAR) can solve this problem to some extent. But unlike airborne and spaceborne SAR, the near-field and curved trajectories in automotive MMW radar imaging are unavoidable. In this paper, we propose an imaging method based on sub-aperture Polar Format Algorithm (PFA) for curved trajectory imaging. Firstly, the beam width is narrowed by filtering. This technique can lower the system Pulse Repetition Frequency (PRF) requirement. Subsequently, the whole aperture is divided into several sub-apertures where PFA achieves high-resolution imaging in each sub-aperture. Finally, by rotating the sub-images and mosaicking them together, the whole scene imaging is completed. Besides, the paper also analyzes the factors affecting sub-image mosaicking. Based on the imaging results, we can conclude that the proposed method is effective in curved trajectory imaging.