Microwave automatic vehicle identification(AVI) system

A new microwave AVI system has been developed that is characterized by the fact that it utilizes ceramic resonators in the composition of a transponder identification code, and a single microwave carrier to convey an interrogation signal to, and a response signal from, that transponder. In this system, the transponder is a completely passive device that requires neither a battery nor any other power supply, and is of a compact, light-weight and slim construction. This paper describes the system structure, the operational principles of the interrogator and transponder, and the transponder circuit structure.