Detection, by an electromagnetic transponder reader, of the distance separating it from a transponder
AssigneeSTMicroelectronics S.r.l.
InventorsLuc Wuidart, Michel Bardouillet, Jean-Pierre Enguent
Life of this patent
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Abstract
A terminal for generating an electromagnetic field adapted to cooperate with at least one transponder when the transponder enters the electromagnetic field, the terminal including circuitry for determining the distance separating the at least one transponder from the terminal without requiring any transmission from the transponder to the terminal. In one example, the terminal also includes a phase regulation loop that regulates the phase of a signal in an oscillating circuit of the terminal with respect to a reference value.
Claims20
A terminal for generating an electromagnetic field adapted to cooperate with at least one transponder when said transponder enters in the field, and comprising an oscillating circuit adapted to receive a high frequency A.C. drive voltage, the terminal including means for determining a distance separating the transponder from the terminal without requiring any transmission from the transponder to the terminal and means for regulating a phase of a signal in the oscillating circuit with respect to a reference value.
A terminal that generates an electromagnetic field, the terminal being adapted to communicate with a transponder when the transponder enters the electromagnetic field, the terminal comprising:
- an oscillating circuit;
- a phase-regulation loop that regulates a phase of a signal in the oscillating circuit with respect to a reference value;
- and
- a distance detector that determines a distance between the terminal and the transponder based on a value of a real part of an impedance of the oscillating circuit.
A method for determining a distance between a terminal that generates an electromagnetic field, the terminal being adapted to communicate with a transponder when the transponder enters the electromagnetic field, and the transponder that enters the electromagnetic field, independent of the transponder transmitting any signal, the method comprising acts of:
- regulating a phase of a current in an oscillating circuit of the terminal;
- determining a value of a real part of an impedance of the oscillating circuit;
- and
- determining the distance between the terminal and the transponder based on the value of the real part of the impedance of the oscillating circuit.
Dependencies are inferred from the claim text.