Planar antenna array design considerations for RFID electronic toll collection system

This paper deals with the design of a radio-frequency identification (RFID) reader for electronic toll collection (ETC) systems. The ETC scheme herein considered comprises a planar antenna array as radiating element of the RFID reader. This reader is required to be capable of alternatively illuminating three (or more) road surface portions called coverage areas, where a transponder (tag) might be present. Coverage areas have to be well-defined in order to avoid collision. This paper treats with the design of the RFID reader, with special emphasis on the coverage area synthesis in the practical case of a limited size antenna array.