Power management in an electromagnetic transponder

• US 8,922,338 B2
• Filed: 06/15/2010
• Issued: 12/30/2014
• Est. Priority Date: 06/19/2009
• Status: Active Grant

• Current Assignee: STMicroelectronics SAS (STMicroelectronics NV)
• Original Assignee: STMicroelectronics SAS (STMicroelectronics NV)
• Inventors: Wuidart, Luc
• Primary Examiner(s): Phan, Hai
• Assistant Examiner(s): Yu, Royit
• Application Number:
  US12/815,776
• Publication Number:
  US 20110140852A1
• Time in Patent Office: 1,659 Days
• Field of Search: 340/10.1, 340/10.4, 340/118, 340/572.1, 340/825.49, 342/118
• US Class Current: 340/5.61
• CPC Class Codes: G06K 19/0707 the arrangement being capable of collecting energy from external energy sources, e.g. thermocouples, vibration, electromagnetic radiation G06K19/0702 takes precedence
• CPC Class Codes: G06K 19/0712 the arrangement being capable of triggering distinct operating modes or functions dependent on the strength of an energy or interrogation field in the proximity of the record carrier active means for hindering electromagnetic reading or writing G06K19/07336
• CPC Class Codes: G06K 19/0715 the arrangement including means to regulate power transfer to the integrated circuit
• CPC Class Codes: G06K 19/0723 the record carrier comprising an arrangement for non-contact communication, e.g. wireless communication circuits on transponder cards, non-contact smart cards or RFIDs

Abstract

A method of evaluation, by an electromagnetic transponder in the field of a terminal generating a magnetic field, of power that can be extracted from this field, including the steps of: evaluating the current coupling between the transponder and the terminal; and deducing therefrom information relative to the power available in this coupling position.

Claims

1. A method performed by an electromagnetic transponder in a magnetic field of a terminal, the method comprising steps of:

calculating a value of a current coupling between the transponder and the terminal;

measuring a value of a first electrical quantity of the transponder, wherein the first electrical quantity is selected from a group consisting of a current and a voltage;

using the value of the current coupling and the measured value of the first electrical quantity to deduce a value of a second electrical quantity extractable by the transponder from the magnetic field of the terminal;

determining whether to perform an operation based at least in part on the deduced value of the second electrical quantity; and

after it is determined to perform the operation, starting performance of the operation.

2. The method of claim 1, wherein the transponder comprises an oscillating circuit upstream of rectifying means capable of providing a D.C. voltage, and wherein calculating the value of the current coupling comprises:

measuring and storing first data relative to a first level of said D.C. voltage for a first value of a resistive load formed by circuits of the transponder on the oscillating circuit;

measuring and storing second data relative to a second level of said D.C. voltage for a second value of the resistive load; and

deducing, based at least in part on the first and second data, a position of the current coupling with respect to an optimum coupling position, wherein the optimum coupling position corresponds to a value of the resistive load selected from a group consisting of the first value of the resistive load and the second value of the resistive load.

3. The method of claim 1, wherein the deduced value of the second electrical quantity extractable by the transponder from the magnetic field of the terminal is a maximum value of the second electrical quantity extractable by the transponder from the magnetic field of the terminal.

4. The method of claim 2, further comprising switching a resistive retromodulation element of the transponder to vary the resistive load between the first and second values of the resistive load.

5. The method of claim 1, wherein determining whether to perform the operation comprises:

determining whether the deduced value of the second electrical quantity is sufficient for the transponder to perform the operation.

6. The method of claim 5, wherein the second electrical quantity comprises a power extractable by the transponder from the magnetic field of the terminal, and wherein determining whether the deduced value of the second electrical quantity is sufficient for the transponder to perform the operation comprises:

loading, from a memory storing a plurality of amounts of power corresponding to a respective plurality of transponder operations, an amount of power corresponding to the operation; and

comparing the deduced value of the power extractable by the transponder from the magnetic field of the terminal to the amount of power corresponding to the operation.

7. The method of claim 1, further comprising:

determining whether the deduced value of the second electrical quantity is sufficient for the transponder to perform a particular operation; and

when it is determined that the deduced value of the second electrical quantity is not sufficient for the transponder to perform the particular operation, facilitating performance of the particular operation by adapting a device selected from the group consisting of the terminal and the transponder.

8. The method of claim 7, wherein facilitating performance of the operation by adapting the device selected from the group consisting of the terminal and the transponder comprises adapting the transponder by performing a second operation selected from the group consisting of:

changing a clock frequency of a component of a load circuit of the transponder, placing at least a portion of the transponder in a stand-by mode, and postponing execution of a third operation of the transponder.

9. An electromagnetic transponder comprising:

an oscillating circuit upstream of a rectifying circuit capable of providing a D.C. voltage when the transponder is present in the magnetic field of a terminal; and

at least one processing unit capable of implementing the method of claim 1.

10. The transponder of claim 9, further comprising at least one switchable resistive element capable of being functionally connected in parallel on the oscillating circuit.

33. The method of claim 1, wherein the second electrical quantity is selected from a group consisting of a current and a power.

34. The method of claim 1, wherein the first and second electrical quantities are a load current of the transponder.

35. The method of claim 7, wherein facilitating performance of the operation by adapting the device selected from the group consisting of the terminal and the transponder comprises:

adapting the terminal by transmitting, to the terminal, a request for the terminal to increase the power of the magnetic field.

11. A transponder comprising:

an oscillator configured to provide a signal in response to a magnetic field of a terminal;

a voltage conversion circuit configured to convert the signal provided by the oscillator to a D.C. signal; and

a load circuit configured to form a resistive load on the oscillator,

wherein a resistance of the resistive load is variable,

wherein the load circuit comprises at least one processing unit configured to use a value of a coupling between the transponder and the terminal, and a measured value of a first electrical quantity of the transponder, to deduce a value of a second electrical quantity extractable by the transponder from the magnetic field of the terminal,

wherein the first electrical quantity is selected from a group consisting of a current and a voltage, and

wherein the at least one processing unit is further configured to determine whether to perform an operation based at least in part on the deduced value of the second electrical quantity; and

, after it is determined to perform the operation, to start performance of the operation.

12. The method of claim 11, wherein the at least one processing unit is further configured to determine whether to perform the operation by determining whether the deduced value of the second electrical quantity is sufficient for the transponder to perform the operation.

13. The transponder of claim 12, wherein the second electrical quantity includes a power extractable by the transponder from the magnetic field of the terminal, and wherein the at least one processing unit is further configured to determine whether the deduced value of the second electrical quantity is sufficient for the transponder to perform the operation by:

loading, from a memory storing a plurality of amounts of power corresponding to a respective plurality of transponder operations, an amount of power corresponding to the operation; and

comparing the deduced value of the power extractable by the transponder from the magnetic field of the terminal to the amount of power corresponding to the operation.

14. The transponder of claim 11, wherein the at least one processing unit is further configured to:

determine whether the deduced value of the second electrical quantity is sufficient for the transponder to perform a particular operation; and

when it is determined that the deduced value of the second electrical quantity is not sufficient for the transponder to perform the particular operation, to facilitate performance of the particular operation by adapting a device selected from the group consisting of the terminal and the transponder.

15. The transponder of claim 14, wherein adapting the device selected from the group consisting of the terminal and the transponder comprises adapting the transponder by performing a second operation selected from the group consisting of:

changing a clock frequency of the at least one processing unit, placing at least a portion of the transponder in a stand-by mode, and postponing execution of a third operation of the transponder.

16. The transponder of claim 14, wherein adapting the device selected from the group consisting of the terminal and the transponder comprises adapting the terminal by transmitting, to the terminal, a request for the terminal to increase the power of the magnetic field.

17. An electronic system comprising:

a transponder; and

a terminal,

wherein the transponder includes an oscillator configured to provide a signal in response to a magnetic field of the terminal, a voltage conversion circuit configured to convert the signal provided by the oscillator to a D.C. signal, and a load circuit configured to form a resistive load on the oscillator,

wherein the terminal includes an antenna and a regulating circuit configured to regulate a phase of a signal of the antenna such that a phase relationship between the antenna signal and a reference signal is constant,

wherein a resistance of the resistive load is variable,

wherein the load circuit comprises at least one processing unit configured to use a value of a coupling between the transponder and the terminal, and a measured value of a first electrical quantity of the transponder, to deduce a value of a second electrical quantity extractable by the transponder from the magnetic field of the terminal, and

wherein the first electrical quantity is selected from a group consisting of a current and a voltage.

18. The electronic system of claim 17, wherein the at least one processing unit is further configured:

to determine whether the deduced value of the second electrical quantity is sufficient for the transponder to perform a particular operation; and

when it is determined that the deduced value of the second electrical quantity is not sufficient for the transponder to perform the particular operation, to facilitate performance of the particular operation by adapting a device selected from the group consisting of the terminal and the transponder.

19. The system of claim 18, wherein adapting the device selected from the group consisting of the terminal and the transponder comprises adapting the transponder by performing a second operation selected from the group consisting of:

changing a clock frequency of the at least one processing unit, placing at least a portion of the transponder in a stand-by mode, and postponing execution of a third operation of the transponder.

20. The system of claim 18, wherein adapting the device selected from the group consisting of the terminal and the transponder comprises adapting the terminal by transmitting, to the terminal, a request for the terminal to increase the power of the magnetic field.

21. A method performed by a transponder in a magnetic field of a terminal, the method comprising:

obtaining a value of a first electrical quantity of the transponder, wherein the first electrical quantity is selected from a group consisting of a current and a voltage;

using a value of a coupling between the transponder and the terminal, and the measured value of the first electrical quantity, to deduce a value of a second electrical quantity extractable by the transponder from the magnetic field of the terminal;

determining whether the deduced value of the second electrical quantity is sufficient for the transponder to perform a particular operation; and

when it is determined that the deduced value of the second electrical quantity is not sufficient for the transponder to perform the particular operation, facilitating performance of the particular operation by adapting a device selected from the group consisting of the terminal and the transponder.

22. The method of claim 21, further comprising starting performance of the particular operation when it is determined that the deduced value of the second electrical quantity is sufficient for the transponder to perform the particular operation.

23. The method of claim 21, wherein the second electrical quantity extractable by the transponder from the magnetic field of the terminal includes a power extractable by the transponder from the magnetic field of the terminal, and wherein determining whether the deduced value of the second electrical quantity is sufficient for the transponder to perform the particular operation comprises:

loading, from a memory storing a plurality of amounts of power corresponding to a respective plurality of transponder operations, an amount of power corresponding to the particular operation; and

comparing the deduced value of the power extractable by the transponder from the magnetic field of the terminal to the amount of power corresponding to the particular operation.

24. The method of claim 21, wherein adapting the device selected from the group consisting of the terminal and the transponder comprises adapting the transponder by changing a clock frequency of a component of a load circuit of the transponder.

25. The method of claim 21, wherein adapting the device selected from the group consisting of the terminal and the transponder comprises adapting the transponder by placing at least a portion of the transponder in a stand-by mode.

26. The method of claim 21, wherein adapting the device selected from the group consisting of the terminal and the transponder comprises adapting the transponder by postponing execution of a second operation of the transponder.

27. The method of claim 21, wherein adapting the device selected from the group consisting of the terminal and the transponder comprises adapting the terminal by transmitting, to the terminal, a request for the terminal to increase the power of the magnetic field.

28. The method of claim 21, further comprising determining the value of the coupling between the transponder and the terminal.

29. The method of claim 28, wherein determining the value of the coupling between the transponder and the terminal comprises:

obtaining data representative of first and second levels of a voltage across an oscillating circuit of the transponder for respective first and second values of a resistive load of the transponder; and

determining, based at least in part on the data representative of the first and second levels of the voltage, the value of the coupling.

30. The method of claim 21, wherein the second electrical quantity extractable by the transponder from the magnetic field is an amount of current extractable by the transponder from the magnetic field.

31. The method of claim 21, wherein the second electrical quantity extractable by the transponder from the magnetic field is an amount of power extractable by the transponder from the magnetic field.

32. The method of claim 21, further comprising, after facilitating performance of the particular operation by adapting the device selected from the group consisting of the terminal and the transponder:

deducing a second value of the second electrical quantity; and

determining whether the second value of the second electrical quantity is sufficient for the transponder to perform the particular operation.