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Transponder arrangement

  • US 5,451,959 A
  • Filed: 06/22/1994
  • Issued: 09/19/1995
  • Est. Priority Date: 07/08/1988
  • Status: Expired due to Term
First Claim
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1. A transponder system comprising:

  • an interrogation unit for communicating with cooperating responder units comprising;

    a microprocessor;

    a transmitter for transmission of at least one RF interrogation signal of a first frequency and terminating after a duration predetermined by the microprocessor, anda receiver for receiving signal information at least at said first frequency and at the termination of the interrogation signal; and

    a responder unit located in spaced relation with respect to said interrogation unit for receiving said at least one RF interrogation signal transmitted from the transmitter of said interrogation unit and returning data present in said responder as signal information to the receiver of said interrogation unit in response to the reception of said at least on interrogation signal, said responder unit comprising;

    a single antenna for receiving said interrogation signal and transmitting said data present in said responder unit;

    an energy accumulator for storing energy contained in said at least one interrogation signal and received by said antenna;

    a carrier wave generator operable for providing a FSK modulated carrier wave having at least two frequencies, one of said two frequencies being said first frequency of said at least one interrogation signal and a second frequency selectively shifted from said first frequency;

    a memory for storing identification data and other data;

    circuitry operably connected to the output of said carrier wave generator for producing control signals for maintaining and modulating the carrier wave;

    said antenna transmitting the FSK modulated carrier wave with said data contained in said memory from said responder unit back to the receiver of said interrogation unit as signal information;

    circuitry for initiating operation of said carrier wave generator in response to the power level of the RF interrogation signal received by said responder unit decreasing and the presence of a predetermined energy amount stored in said energy accumulator; and

    a sensor sensitive to predetermined physical parameters in the environmental area of said responder unit for providing at least some of said data stored in said memory.

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