Detection of an electric signature of an electromagnetic transponder

• US 7,046,121 B2
• Filed: 08/09/2001
• Issued: 05/16/2006
• Est. Priority Date: 08/09/2000
• Status: Active Grant

• Current Assignee: STMicroelectronics SA (STMicroelectronics NV)
• Original Assignee: STMicroelectronics SA (STMicroelectronics NV)
• Inventors: Wuidart, Luc
• Primary Examiner(s): Zimmerman, Brian
• Assistant Examiner(s): Yang, Clara
• Application Number:
  US10/343,775
• Publication Number:
  US 20030164742A1
• Time in Patent Office: 1,741 Days
• Field of Search: 340/10.1, 340/10.4, 340/10.41, 340/572.5, 455/67.11, 455/106, 455/107
• US Class Current: 340/10.1
• CPC Class Codes: G06K 7/0008 General problems related to the reading of electronic memory record carriers, independent of its reading method, e.g. power transfer

Abstract

The invention concerns a terminal generating a high-frequency electromagnetic field by means of an oscillating circuit, adapted to co-operate with at least a transponder when the latter enters said field, comprising means (37) for regulating the phase of the signal in the oscillating circuit with respect to a reference value, and means for detecting, on the basis of a current measurement in the oscillating circuit and a voltage measurement at the terminals of a capacitive element (31) of said oscillating circuit, an electric signature of a transponder.

Claims

1. A terminal for generating a high-frequency electromagnetic field by means of an oscillating circuit, adapted to cooperating with at least one transponder when said transponder enters this field, and including:

means for regulating the signal phase in the oscillating circuit with respect to a reference value; and

means for detecting, based on a measurement of a current in the oscillating circuit and on a measurement of a voltage across a capacitive element of the oscillating circuit, an electric signature of a transponder.

2. The terminal of claim 1, wherein the electric signature enables determining a type to which the transponder belongs from among a set of types identified by characteristic manufacturing parameters.

3. The terminal of claim 1 including means for comparing the signature of a transponder having entered its field with at least one signature sample memorized during a learning phase.

4. The terminal of claim 1, including means for determining and storing characteristic information relative to the voltages across the capacitive element of its oscillating circuit and to the currents in this oscillating circuit, in several determined configurations of the distance separating a reference transponder from the terminal, and for taking into account this characteristic information to determine the transponder'"'"'s signature.

5. The terminal of claim 4, wherein said characteristic information includes:

the voltage across the capacitive element when no transponder is present in the field of the terminal;

the voltage across the capacitive element when a transponder is in a relation of maximum closeness with the terminal;

the current in the oscillating circuit when no transponder is present in the terminal'"'"'s field; and

the current in the oscillating circuit when a transponder is in a relation of maximum closeness with the terminal.

6. The terminal of claim 1 wherein the signature detection is performed without interpreting any data message carried by the high-frequency field.

7. The terminal of claim 1, including means for evaluating, based on the measurement of the current in the oscillating circuit, the minimum number of transponders present in the field.

8. The terminal of claim 7, further including means for, based on the measurement of the voltage across the capacitive element of the oscillating circuit, evaluating the maximum number of transponders present in the terminal'"'"'s field.

9. A method for establishing at least one communication between a terminal of generation of a high-frequency magnetic field and an electromagnetic transponder comprising determining a type of a transponder from among a set of types identified by characteristic electric parameters of the transponders linked to a sizing of an inductive resistor and/or a capacitor of oscillating circuits of the transponders, before exchanging any data message between the transponder and the terminal.

10. The method of claim 9, wherein said determination includes comparing the current measured in an oscillating circuit of the terminal and a voltage across a capacitive element of the oscillating circuit with previously calculated and stored values to establish the set of identified types.

11. The method of claim 9 including periodically sending a request sequence until at least one transponder entering the field sends an acknowledgement, and evaluating based on the current measurement a minimum number of transponders likely to be present in the field.

12. The method of claim 11, further including, based on the evaluation of the minimum number and on a measurement of the voltage, evaluating the maximum number of transponders likely to be present in the terminal'"'"'s field.

13. The method of any of claim 9, wherein the method is applied to a terminal for generating a high-frequency electromagnetic field by means of an oscillating circuit, adapted to cooperating with at least one transponder when said transponder enters the electromagnetic field, the terminal including means for regulating the signal phase in the oscillating circuit with respect to a reference value and means for detecting, based on a measurement of a current in the oscillating circuit and on a measurement of a voltage across a capacitive element of the oscillating circuit, and electric signature of a transponder.

14. A terminal for operation with at least one electromagnetic transponder, comprising:

an oscillating circuit for generating a high-frequency electromagnetic field; and

a circuit configured to detect an electrical signature of a transponder in the electromagnetic fields,

wherein the electrical signature is indicative of one or more electrical characteristics linked to a sizing of an inductive resistor and/or a capacitor of an oscillating circuit of the transponder.

15. A terminal as defined in claim 14, wherein the circuit is configured to detect the electrical signature based on a measurement of a current in the oscillating circuit and on a measurement of a voltage across a capacitive element of the oscillating circuit.

16. A terminal as defined in claim 15, wherein the circuit is configured for comparing the electrical signature of the transponder in the electromagnetic field with at least one stored signature.

17. A terminal as defined in claim 15, further comprising means for regulating the signal phase in the oscillating circuit with respect to a reference value.

18. A terminal as defined in claim 15, further comprising means for determining and storing characteristic values of voltages across the capacitive element and currents in the oscillating circuit in at least two configurations of distance separating a reference transponder from the terminal, and for using the stored characteristic values to determine the electrical signature of the transponder.

19. A terminal as defined in claim 18, wherein the characteristic values include:

a voltage across the capacitive element when no transponder is present in the electromagnetic field of the terminal;

a voltage across the capacitive element when the reference transponder is in a relation of maximum closeness to the terminal;

a current in the oscillating circuit when no transponder is present in the electromagnetic field of the terminal; and

a current in the oscillating circuit when the reference transponder is in a relation of maximum closeness to the terminal.

20. A terminal as defined in claim 15, further including means for evaluating a minimum number of transponders present in the electromagnetic field, based on measurement of the current in the oscillating circuit.

21. A terminal as defined in claim 22, further including means for evaluating a maximum number of transponders present in the electromagnetic field, based on measurement of the voltage across the capacitive element of the oscillating circuit.

22. A terminal as defined in claim 14, wherein the circuit is configured to determine, based on the detected electrical signature, a transponder type to which the transponder belongs from a set of transponder types identified by characteristic manufacturing parameters.

23. A terminal as defined in claim 14, wherein the electrical signature of the transponder is detected without interpreting any data message carried by the high-frequency electromagnetic field.

24. A method for operating a terminal with at least one transponder, comprising:

generating a high-frequency electromagnetic field with an oscillating circuit; and

detecting an electrical signature of a transponder in the electromagnetic field,

wherein the electrical signature is indicative of one or more electrical characteristics linked to a sizing of an inductive resistor and/or a capacitor of an oscillating circuit of the transponder.

25. A method as defined in claim 24, wherein detecting the electrical signature of the transponder comprises measuring a current in the oscillating circuit and measuring a voltage across a capacitive element of the oscillating circuit.

26. A method as defined in claim 24, wherein detecting the electrical signature of the transponder includes determining a transponder type to which the transponder belongs from a set of transponder types identified by characteristic manufacturing parameters.

27. A method as defined in claim 24, wherein detecting the electrical signature of the transponder includes comparing the detected electrical signature with at least one stored signature.

28. A method as defined in claim 24, further comprising regulating the signal phase in the oscillating circuit with respect to a reference value.

29. A method as defined in claim 24, further comprising determining and storing characteristic values of voltages across the capacitive element of the oscillating circuit and currents in the oscillating circuit in at least two configurations of distance separating a reference transponder from the terminal and using the stored characteristic values to determine the electrical signature of the transponder.

30. A method as defined in claim 29, wherein determining and storing characteristic values includes:

determining and storing a voltage across the capacitive element when no transponder is present in the electromagnetic field;

determining and storing a voltage across the capacitive element when the reference transponder is in a relation of maximum closeness to the terminal;

determining and storing a current in the oscillating circuit when no transponder is present in the electromagnetic field; and

determining and storing a current in the oscillating circuit when the reference transponder is in a relation of maximum closeness to the terminal.

31. A method as defined in claim 24, wherein detecting the electrical signature of the transponder is performed without interpreting any data message carried by the electromagnetic field.

32. A method as defined in claim 24, further including evaluating the minimum number of transponders present in the electromagnetic field, based on measurement of the current in the oscillating circuit.

33. A method as defined in claim 32, further including evaluating the maximum number of transponders present in the electromagnetic field, based on measurement of the voltage across the capacitive element of the oscillating circuit.

34. An apparatus for establishing communication between a terminal and an electromagnetic transponder, comprising:

an oscillating circuit for generating a high-frequency electromagnetic field; and

a circuit configured to determine a type of transponder in the electromagnetic field from a set of transponder types identified by characteristic electric parameters of the transponders linked to a sizing of an inductive resistor and/or a capacitor of oscillating circuits of the transponders, before exchanging any data message between the transponder and the terminal.