Detection of the distance between an electromagnetic transponder and a terminal
First Claim
1. A method of determining a distance separating an electromagnetic transponder from a terminal generating a magnetic field via a first oscillating circuit, the transponder including a second oscillating circuit, upstream of a rectifier adapted to provide a D.C. voltage having a level, the method comprising the steps of:
- storing a first information relative to the level of the D.C. voltage when the second oscillating circuit is tuned on a determined frequency;
storing a second information relative to the level of the D.C. voltage after having caused a frequency detuning of the second oscillating circuit; and
comparing the first and second information.
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Accused Products
Abstract
A method and apparatus for determining the distance separating an electromagnetic transponder from a terminal generating a magnetic field by a first oscillating circuit, the transponder including a second oscillating circuit, upstream of a rectifying circuit adapted to providing a D.C. voltage. The method includes storing a first information relative to the level of the D.C. voltage when the second oscillating circuit is tuned on a determined frequency; storing a second information relative to the level of the D.C. voltage after having caused a frequency detuning of the second oscillating circuit; and comparing the two stored pieces of information.
256 Citations
38 Claims
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1. A method of determining a distance separating an electromagnetic transponder from a terminal generating a magnetic field via a first oscillating circuit, the transponder including a second oscillating circuit, upstream of a rectifier adapted to provide a D.C. voltage having a level, the method comprising the steps of:
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storing a first information relative to the level of the D.C. voltage when the second oscillating circuit is tuned on a determined frequency;
storing a second information relative to the level of the D.C. voltage after having caused a frequency detuning of the second oscillating circuit; and
comparing the first and second information. - View Dependent Claims (3, 5)
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2. A method of determining a distance separating an electromagnetic transponder from a terminal generating a magnetic field via a first oscillating circuit, the transponder including a second oscillating circuit, upstream of a rectifier adapted to provide a D.C. voltage having a level, the method comprising steps of:
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storing a first information relative to the level of the D.C. voltage when the second oscillating circuit is tuned on a determined frequency;
storing a second information relative to the level of the D.C. voltage after having caused a frequency detuning of the second oscillating circuit; and
periodically measuring said levels and comparing the variation of the stored information for two successive measurements in the same tuning conditions.
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4. A method of determining a distance separating an electromagnetic transponder from a terminal generating a magnetic field via a first oscillating circuit, the transponder including a second oscillating circuit, upstream of a rectifier adapted to provide a D.C. voltage having a level, the method comprising steps of:
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storing a first information relative to the level of the D.C. voltage when the second oscillating circuit is tuned on a determined frequency;
storing a second information relative to the level of the D.C. voltage after having caused a frequency detuning of the second oscillating circuit; and
comparing the first and second information, wherein the comparison between the first and second information is used to determine the position of the transponder with respect to a critical coupling position of the respective oscillating circuits of the transponder and of the terminal.
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6. A method of determining a distance separating an electromagnetic transponder from a terminal generating a magnetic field via a first oscillating circuit, the transponder including a second oscillating circuit, upstream of a rectifier adapted to provide a D.C. voltage having a level, the method comprising steps of:
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storing a first information relative to the level of the D.C. voltage when the second oscillating circuit is tuned on a determined frequency;
storing a second information relative to the level of the D.C. voltage after having caused a frequency detuning of the second oscillating circuit;
comparing the first and second information and determining an operating mode of the transponder among two modes respectively corresponding to a tight coupling or loose coupling position.
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7. An electromagnetic transponder capable of determining a distance separating the electromagnetic transponder from a terminal generating a magnetic field via a first oscillating circuit, the transponder comprising:
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a second oscillating circuit that includes at least one switched capacitor and is tuned at a first frequency when the at least one switched capacitor is in a first state and is detuned from the first frequency when the at least one switched capacitor is in a second state;
a rectifier, coupled to the second oscillating circuit, that produces a D.C. voltage at a first level when the second oscillating circuit is tuned to the first frequency and at a second level when the second oscillating circuit is detuned from the first frequency;
a storage element for storing first and second information respectively relative to the first and second levels of the D.C. voltage; and
a comparator that compares the first and second information. - View Dependent Claims (8)
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9. An electromagnetic transponder capable of determining a distance separating the electromagnetic transponder from a terminal generating a magnetic field via a first oscillating circuit, the transponder comprising:
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a second oscillating circuit that includes at least one switched capacitor and is tuned at a first frequency when the at least one switched capacitor is in a first state and is detuned from the first frequency when the at least one switched capacitor is in a second state;
a rectifier, coupled to the second oscillating circuit, that produces a D.C. voltage at a first level when the second oscillating circuit is tuned to the first frequency and at a second level when the second oscillating circuit is detuned from the first frequency;
a comparator that compares the first and second information; and
two capacitors, respectively associated with each end terminal of an inductive element of the second oscillating circuit, each capacitor being connected in series with a switch, a reference terminal of which is connected to a reference supply potential downstream of the rectifier. - View Dependent Claims (10)
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11. A method of determining a distance separating a transponder and a terminal generating an electromagnetic field oscillating at a first oscillation frequency, wherein the transponder includes an oscillating circuit, the method comprising acts of:
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(A) detecting the electromagnetic field with the oscillating circuit tuned to the first oscillation frequency;
(B) producing a first signal corresponding to the detected electromagnetic field when the oscillating circuit is tuned to the first oscillation frequency;
(C) detuning the oscillating circuit to a second oscillation frequency;
(D) detecting the electromagnetic field with the oscillating circuit detuned to the second oscillation frequency;
(E) producing a second signal corresponding to the detected electromagnetic field when the oscillating circuit is detuned to the second oscillation frequency; and
(F) comparing the first and second signals to yield an output corresponding to the distance between the transponder and the terminal. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24)
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25. An apparatus that determines a distance between a transponder and a terminal generating electromagnetic radiation, the apparatus comprising:
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an oscillating circuit, tunable to a first oscillation frequency and to a second oscillation frequency, that generates an output varying with the distance when the oscillating circuit is located adjacent the transponder; and
a processor that receives the output of the oscillating circuit when tuned to both the first and second oscillating frequencies and generates a signal corresponding to the distance between the transponder and the terminal. - View Dependent Claims (26, 27, 28, 29, 30, 31, 32, 33, 34)
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35. An apparatus for determining a distance between first and second objects, comprising:
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a first oscillating circuit, coupled to the first object, having a first oscillation frequency and producing a first signal that varies with a distance of the first object from the second object;
a second oscillating circuit, coupled to the first object, having a second oscillation frequency, and producing a second signal that varies with the distance between the first and second objects; and
a processor that receives information representative of the first and second signals and, based thereon, produces an output signal corresponding to the distance between the two objects. - View Dependent Claims (36, 37)
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38. A method for determining a distance separating a first object and a second object, wherein the first object generates an electromagnetic field having a first oscillation frequency, and wherein the second object is coupled to a second oscillating circuit;
- the method comprising acts of;
(A) generating a first signal from the second oscillating circuit when tuned to a first frequency, the first signal representative of a detection of the electromagnetic field;
(B) generating a second signal from the second oscillating circuit when tuned to a second frequency, the second signal representative of a detection of the electromagnetic field; and
(C) determining the distance separating the first and second objects based on the first and second signals.
- the method comprising acts of;
Specification