04068232 is referenced by 110 patents and cites 7 patents.

A passive transponder which provides remote identification of objects including cargo and trailers, vehicles or a variety of objects which move through an interrogator beam. The passive transponder is mounted onto the vehicle or object or at the location to be identified. A transmitted beam from the interrogator is directed to the transponder. Some of the beam's energy is rectified and used to power digital electronic circuitry within the transponder which generates a signal with a serially-coded digital waveform. This signal amplitude modulates a harmonic generator in the transponder which produces and emits harmonic energy derived from the incident beam from the interrogator. This harmonic energy is readily identified by an interrogator receiver which is tuned to that harmonic of the incident signal. The transponder information from the interrogator receiver is decoded in the interrogator data processor to provide the desired identification number. An internal clock frequency is generated within the passive transponder as a result of transmitted energy from the interrogator beam, and this clock determines the read-out rate of the encoded data from a field programmable read-only memory.

Title
Passive encoding microwave transponder
Application Number
5/657467
Publication Number
4068232
Application Date
February 12, 1976
Publication Date
January 10, 1978
Inventor
Ashley P Leigh
Gaithersburg
MD, US
Thomas D Meyers
New Windsor
MD, US
Agent
Michael W York
Assignee
Fairchild
MD, US
IPC
H01R 39/00
View Original Source