Electromagnetic transponder read terminal operating in very close coupling
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 cooperating with at least one transponder when the latter enters its field, the terminal including an oscillating circuit adapted to receiving a high frequency A.C. excitation voltage, and circuitry for detuning this oscillating circuit with respect to a determined transmission frequency when a transponder is very close to the terminal.
Claims14
A terminal for generating an electromagnetic field adapted to cooperate with at least one transponder when the transponder enters in the electromagnetic field of the terminal, the terminal including:
- an oscillating circuit adapted to receiving a high frequency A.C. excitation voltage;
- and
- means for detuning the oscillating circuit to a detuned mode with respect to a determined transmission frequency when the at least one transponder is very close to the terminal;
- wherein the terminal provides power to the at least one transponder via the electromagnetic field when the terminal is in the detuned mode.
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 including a resistive element and a variable capacitive element;
- a controller, coupled to the oscillating circuit, that switches the oscillating circuit between a tuned mode and a detuned mode;
- and
- a first comparator that provides a comparison bit, a value of the comparison bit indicating a distance between the terminal and the remote transponder relative to a critical coupling point;
- wherein the controller switches the oscillating circuit between the tuned mode and the detuned mode in response to the value of the comparison bit.
A wireless data transmission system comprising:
- at least one transponder that does not have an independent power source;
- and
- a terminal that generates an electromagnetic field, the terminal including:
- an oscillating circuit having resistive element and a variable capacitive element and adapted to receive an AC excitation voltage;
- and
- a controller that switches the oscillating circuit between a tuned mode and a detuned mode based on a distance between the transponder and the terminal;
- wherein the transponder receives operating power from the terminal via the electromagnetic field when the terminal is in the detuned mode.
Dependencies are inferred from the claim text.