A New Kind of Radar for Collision Avoidance

An experimental automobile radar has been demonstrated which is designed to avoid rear end collisions on highways. A completely passive reflector, mounted on the back of vehicles, returns the second harmonic of the frequency transmitted from the trailing vehicle. The radar is immune to clutter since its receiver is tuned to the second harmonic frequency only. It is also immune to blinding by cars traveling in the opposite direction, as well as to other interference problems inherent in a dense environment.