Screening transmissions for power level and object identifier in asset monitoring and tracking systems

  • US 7,742,744 B2
  • Filed: 01/14/2009
  • Issued: 06/22/2010
  • Est. Priority Date: 12/22/2000
  • Status: Active Grant
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First Claim
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1. An RFID monitoring device comprising:

  • a memory having unique identifying information stored therein and having codes representing at least two different transmitter power levels stored therein;

    an antenna for transmitting and receiving electromagnetic signals;

    a modulator coupled to said memory for modulating the unique identifying information and the transmitter power level codes stored in said memory; and

    a transmitter coupled to said modulator and to said antenna for transmitting at least two messages via said antenna, wherein each of the at least two messages includes the modulated unique identifying information and a modulated different one of the transmitter power level codes, wherein the power level of said transmitter is controlled responsive to the power level code to correspond to the power level represented by the power level code in each transmitted message when each message is transmitted;

    whereby the transmitter power level is different for each of the messages and corresponds to the power level code contained in each of the messages transmitted; and

    wherein the RFID monitoring device is configured to wirelessly communicate to a recipient transceiver from a plurality of transceivers, the plurality of transceivers being located within the broadcast range of the RFID monitoring device, by;

    transmitting a communication at a first power level such that only a first group of transceivers receive the broadcast, the communication including a command causing each of the first group of transceivers not to respond to a subsequent broadcast; and

    subsequent thereto transmitting a communication at a second power level greater than the first power level such that a second group of transceivers greater than and including the first group of transceivers receive the broadcast, but such that only a limited number of transceivers of the second group respond to the broadcast, the limited number of transceivers excluding the first group of transceivers;

    wherein the plurality of transceivers each are associated with a respective sensor for acquiring data and transmitting the data to the RFID monitoring device.

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