Passive RFID tag that retains state after temporary loss of power

CAFC
  • US 6,812,841 B2
  • Filed: 01/23/2002
  • Issued: 11/02/2004
  • Est. Priority Date: 01/23/2002
  • Status: Active Grant
First Claim
Patent Images

1. An RFID transponder, comprising:

  • an RF front end adapted to receive an interrogating RF signal;

    an analog circuit coupled to said RF front end and adapted to recover analog signals from said received interrogating RF signal, said analog circuit providing state information defining a desired state of said RFID transponder corresponding to said analog signals;

    a digital state machine coupled to said analog circuit and adapted to execute at least one command in accordance with said state information;

    a memory coupled to said digital state machine and adapted to store and retrieve digital data responsive to said at least one command executed by said digital state machine a power capacitor coupled to said analog circuit and deriving a voltage rectified from said interrogating RF signal to charge said power capacitor, said power capacitor thereby providing electrical power for said analog circuit, said digital state machine and said memory; and

    a state holding cell coupled to said digital state machine and being adapted to maintain said state information during a loss in power provided by said power capacitor due to lapse in receipt of said interrogating RF signal by said RF front end.

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