RADIO TAG AND SYSTEM

  • US 20070096875A1
  • Filed: 05/22/2006
  • Published: 05/03/2007
  • Est. Priority Date: 10/02/2005
  • Status: Active Grant
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First Claim
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1. A method for use with a base station and with a plurality of tags, each tag lacking a battery, each tag having a respective unique identifier, each tag having digital logic, each tag defining a first state internal thereto, the method comprising the steps of:

  • at the base station, transmitting a radio-frequency power signal at a first frequency, the first frequency being below 1 MHz;

    at each tag among the plurality of tags, receiving the radio-frequency power signal by means of a first antenna, the first antenna comprising a high-Q circuit;

    at each tag among the plurality of tags, deriving DC power from the radio-frequency power signal;

    at each tag among the plurality of tags, developing a power-on-reset signal from the radio-frequency power signal;

    at each tag among the plurality of tags, deriving a first clock signal from the radio-frequency power signal, the first clock signal being higher than the first frequency, the derivation of the first clock signal from the radio-frequency power signal being performed without use of a crystal and without use of a phase-locked loop and without use of a resonator;

    at each tag among the plurality of tags, resetting the digital logic by the power-on-reset signal, and resetting the first state;

    at the base station, transmitting a data signal at a second frequency, the data signal comprising a start signal followed by a serial digital message;

    at each tag among the plurality of tags, receiving the data signal by means of a second antenna, the second antenna comprising a low-Q circuit;

    at each tag among the plurality of tags, detecting the start signal of the data signal;

    at each tag among the plurality of tags, comparing the serial digital message of the data signal with the respective unique identifier;

    at each tag among the plurality of tags, in the event of a match between the serial digital message of the data signal and the respective unique identifier, transmitting a first message by means of the second antenna if the first state was not set, and transmitting a second message by means of the second antenna if the first state was set;

    at each tag among the plurality of tags, in the event of a match between the serial digital message of the data signal and the respective unique identifier, setting the first state.

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