Influences of Road Surface Characteristics on Scattering Mechanisms in Automotive Radar

In this work, the influence of different road surfaces and materials, or more precisely of different asphalt and concrete surfaces, is analyzed for the automotive 77GHz band. It comprises all roads commonly found on German highways and distinguishes in specular reflection and diffuse scattering behavior. The changeover from one to the other behavior is determined by the Rayleigh criterion resulting in corresponding critical angles. For these measurements the area of sands method, the focus beam method, a synthetic aperture radar (SAR) setup as well as a openspace FMCW radar setup with a corner reflector are applied. The characterization includes probability density functions (PDF) of the reflectance of these dielectric surfaces using normal distribution as well as Rayleigh distribution. For the evaluation of the openspace measurements, the radar equation and Fresnel's equations are used, resulting in relative permittivity and roughness values, which are provided as well in an open source material library named OpenMATERIAL. For validation purposes reference samples and measurements with different polarization of the radar sensor are used.