Short range UHF telemetry system using passive transponders for vehicle ID and status information

An electronic tag and reader system using modulated backscatter at 915 MHz or 2450 MHz is described which has a reading range from several centimeters to tens of meters, reads a 128 bit message in 30 ms, can read tags in motion, and discriminates between tags in the field of view by proximity. It is concluded that this electronic ID system can now be used for the automatic identification of vehicles. This system uses high-frequency RF signals to read remotely an electronically coded ID or other message from a tag mounted to the vehicle (or any other object to be identified), whether the vehicle is stationary or moving. It has been tested on trucks, railway cars, intermodal containers, and automobiles to perform quickly, inexpensively, and reliably tasks that until now were done by human operators.