An X-band system using semipassive signpost reflectors for automatic location and tracking of vehicles

A system for determining the location of a moving vehicle with the aid of semipassive signpost reflectors deployed throughout an urban area is presented. The signpost reflectors allow a viable system to be configured since access to electric utility power is not required, thereby permitting a particularly simple and inexpensive installation. Signpost emplacement, data rates, and other system parameters are described. The interrogator, mounted at the vehicle, "reads" the electronic signpost reflector to ascertain basic position information. This information is sent via the vehicle's two-way radio to a central location for control purposes. By using microwave energy at X-band for the interrogation signal, the antennas can utilize a beam shaping pattern although still being physically small. Appropriate antenna patterns can be used to define a very narrow (ribbon-like) reception area allowing very precise location information to be ascertained. The results of actual field tests in urban and suburban environments are presented for this new system.