Radio frequency identification device

Abstract

A radio frequency identification device includes a transceiver having a resonant circuit, a rectifier, a charge pump, a state machine, and a transmitter. The resonant circuit includes an antenna and has a resonant frequency. The rectifier is coupled to the resonant circuit to provide a rectified signal in response to energy from the antenna. The charge pump is enabled in response to the rectified signal to provide a first logic signal. The state machine provides a second logic signal in response to the first logic signal. The transmitter includes an amplifier coupled to the resonant circuit to form a Colpitts oscillator that is enabled by the second logic signal to transmit a response signal for identifying the radio frequency identification device.

1 - 27 . (canceled)  
     
     
         28 . A transceiver comprising: 
 a. a resonant circuit having a resonant frequency, the resonant circuit comprising an antenna;    b. a rectifier coupled to the resonant circuit to provide a rectified signal in response to energy from the antenna;    c. a charge pump enabled in response to the rectified signal to provide a first logic signal;    d. a state machine that provides a second logic signal in response to the first logic signal; and    e. a transmitter comprising an amplifier coupled to the resonant circuit to form a Colpitts oscillator that is enabled by the second logic signal.    
     
     
         29 . The transceiver of  claim 28  wherein the charge pump comprises a capacitor and a transistor, the transistor passing a current to the capacitor in response to the first logic signal, the second logic signal being provided in accordance with a voltage across the capacitor.  
     
     
         30 . The transceiver of  claim 28  wherein the amplifier is coupled to the resonant circuit through an analog switch, the analog switch operative to facilitate oscillation in accordance with the second logic signal.  
     
     
         31 . A transceiver comprising: 
 a. means for receiving radio frequency energy via an antenna to provide a rectified signal;    b. means for accumulating a charge from the rectified signal to provide a first logic signal;    c. means for providing a second logic signal a time after receipt of the first logic signal; and    d. a Colpitts oscillator enabled by the second logic signal for transmitting a response signal via the antenna.    
     
     
         32 - 40 . (canceled)