Abstract: A system for exchanging information by means of transmitted RF signals between a fixed location interrogator and a vehicle transponder moving in the vicinity of the interrogator. The transponder responds to a first trigger signal from the interrogator by transmitting to the interrogator a first data message derived from data stored in a transponder memory. The interrogator then remotely reprograms the transponder memory and generates a second trigger pulse. The transponder responds to the second trigger pulse by transmitting the reprogrammed data it then stores and the interrogator analyzes the last mentioned transmission to determine if the transponder properly received and responded to the reprogramming.

Abstract: Antennas designed for use in producing effective electromagnetic capture zones for transponders mounted on moving vehicles. The antenna systems disclosed are principally designed to be mounted at or near the surface of a roadway carrying the vehicle whose transponder is to be interrogated. A principal advantage of the antennas of the invention is minimal interference with normal operation of the road and greatly reduced cost of installation when used in providing vehicle identification, toll collection, or communication with the transponder carrying vehicle.

Abstract: An antenna system for mounting in a roadway comprised of an electrically lossy material. The antenna system has a reflector trough shield filled with a solid dielectric. An antenna, preferably comprised of coaxial cable, is positioned in the reflector trough, which prevents electromagnetic waves radiated by the antenna from being lost into the roadway.