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Interrogator-responder communication system

  • US 4,912,471 A
  • Filed: 11/03/1983
  • Issued: 03/27/1990
  • Est. Priority Date: 11/03/1983
  • Status: Expired due to Fees
First Claim
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1. An interrogator-responder communication system comprising at least one interrogating station adapted to be located along a route taken by vehicles, and at least one passive responder having no power-producing source of its own, said interrogating station comprising (a) means for radiating a power signal to develop a power signal field located along said route and (b) further means for radiating at least one interrogating signal to develop an interrogating signal field located along said route in such a manner that the peak power level of said interrogating signal field lies behind the peak power level of said power signal field as viewed from a preselected direction of vehicle travel along said route, said responder being adapted to be carried by one of the vehicles intended for travel along said route such that said responder passes, in sequence through said power and interrogating signal fields upon travel of the responder-carrying vehicle along said route, said responder having (a) first means for receiving said power signal as the responder passes through said power signal field, (b) second means powered by energy derived from the received power signal for supplying an electrical information-bearing signal, and (c) third means for re-radiating said interrogating signal as the responder passes through said interrogating signal field and for modulating the interrogating signal with said information-bearing- signal to provide the re-radiated signal with a modulated signal component, and said interrogating station having receiver means for receiving and demodulating the re-radiation of said interrogating signal.

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