Effect of radar polarizations on detectability of debris on roads at millimeter-wave frequencies

Numerous automotive accidents are reported each year. Many of these are attributed to road surface conditions and objects or obstacles on road surfaces. A desirable feature of automotive radar sensors is the ability to detect debris on the highway environment and the provision of an advance warning to drivers. Debris may be detected by comparing the radar cross section (RCS) values of the targets on the road surface with the RCS threshold level defined in terms of the backscatter from the road surface alone, the radar antenna parameters, and a prescribed false alarm rate. Since the RCS of a point target is influenced by many physical parameters such as material, size, shape, and target orientation, a complete polarimetric characterization of radar backscatter of debris on road surfaces may be done analytically. A physical optics model is developed for predicting scattering from solid objects with perpendicular facets such as bricks and right-angled iron. The validity of the theoretical models was verified by comparing the simulation results with the backscatter measurements of a brick and a piece of right-angled iron on an asphalt surface at 94 GHz.