Design of the Microwave Transponder for Automatic Debiting Systems

This paper describes the specification of a digital communication link between a Road-Side Unit and a microwave trnsponder which is mounted behind the windscreen of a moving vehicle to be used in a variety of traffic applications. The design of the On-Board Unit and the sub-system for the Road-Side Unit is presented. Two arrangements for the transponder have been described. A sigle-diode arrangement which acts as both ASK detector and PSK modulator has been successfully realised. This novel desih makes the transponder simple and inexpensive which is a major consideration in the design of the microwave transponder.