A New Collision Avoidance System using Baseband Reflectometry

This paper describes a guided wave, baseband radar-type sensor for protecting automated rapid transit vehicles traveling in dedicated guideways. The system has been given the acronym CASBAR for Collision Avoidance System using BAseband Reflectometry. A baseband pulse signal, 2 nanoseconds wide, is transmitted through a surface waveguide (Goubau line) supported alongside the guideway. Reflections from a passive target located on an adjacent vehicle down the track are processed in a receiver. One output of the receiver controls the brakes which can be applied in dangerous situations. The maximum range of the system is 300 feet and its range and range rate resolutions are 1 foot and 0.5 feet/sec. respectively. A demonstration model of the system has been successfully tested on a vehicle developed by the Boeing Aerospace Co. The intrinsic low cost and high degree of range resolution of baseband radar technology makes this approach attractive for this application.