Electromagnetic reflectivity characteristics of road surfaces

Advances in the design, development, and fabrication of key microwave components along with those in electronics have resulted in growing optimism about the application of radar technology to solving the automotive highway collision problem. However, before an automotive radar system can be fully realized, a major effort will be required to define the environment in which the system must operate, and to obtain a fundamental understanding of the influence of these RF parameters. One such parameter which will have a considerable effect on the design of automobile radars is that due to the presence of natural and man-made surfaces within the beamwidth of the antenna. Generally, the presence of such a surface will result in incident RF energy being reflected off the surface in a forward direction and some portion being scattered in a backward direction. This paper presents the results of a program which was designed to measure this type of reflectivity characteristic for common road surfaces. Measured data are presented along with a theoretical study demonstrating the influence that this phenomenon can have on highway collision radar systems.