POWER RECOVERY BY AN ELECTROMAGNETIC TRANSPONDER

• US 20120105012A1
• Filed: 06/03/2010
• Published: 05/03/2012
• Est. Priority Date: 06/19/2009
• Status: Active Grant

• Current Assignee: STMicroelectronics SAS (STMicroelectronics NV)
• Original Assignee: STMicroelectronics SAS (STMicroelectronics NV)
• Inventors: Wuidart, Luc
• Granted Patent: US 8,988,196 B2
• Time in Patent Office: Days
• US Class Current: 320/137
• CPC Class Codes: G06K 19/0701 at least one of the integrated circuit chips comprising an arrangement for power management
• CPC Class Codes: G06K 19/0702 the arrangement including a battery
• 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
• CPC Class Codes: G06K 19/0726 the arrangement including a circuit for tuning the resonance frequency of an antenna on the record carrier

Abstract

A method of power recovery by an electromagnetic transponder in the field of a terminal, wherein: a ratio of the current coupling factor of the transponder with the terminal to an optimum coupling position with a resistive load value is evaluated; and a detuning of the oscillating circuit is caused if the ratio is greater than a first threshold greater than or equal to one.

Claims

1. A method of power recovery by an electromagnetic transponder in the field of a terminal, wherein:

a ratio (r) of the current coupling factor of the transponder to a position of optimum coupling with a value of a resistive load is evaluated; and

a detuning of the oscillating circuit is caused if the ratio is greater than a first threshold greater than or equal to one.

2. The method of claim 1, wherein a decrease in the power consumption of the transponder circuits is caused if the ratio is smaller than a second threshold smaller than or equal to one.

3. The method of claim 1, wherein an increase in an intensity of the magnetic field generated by the terminal is caused if the ratio is smaller than a second threshold smaller than or equal to one.

4. The method of claim 1, wherein the ratio is obtained from data representative of a voltage across an oscillating circuit of the transponder and obtained for two values of the resistive load.

5. The method of claim 4, wherein:

first data, relative to the level of a D.C. voltage provided by a rectifier across the oscillating circuit, are measured and stored for a first value of the resistive load; and

second data, relative to the level of said D.C. voltage, are measured and stored for a second resistive load value.

6. The method of claim 5, wherein a variation of the resistive load between the first and second values is obtained by modifying the power consumption of the processing circuits comprised by the transponder.

7. The method of claim 5, wherein a variation of the resistive load between the first and second values is obtained by switching a resistive retromodulation element comprised by the transponder.

8. The method of claim 1, wherein the recovered power is at least partially used to recharge a battery comprised by 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 in the magnetic field of a terminal; and

at least one processing unit programmed to implement the method claim 1.

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

11. The transponder of claim 9, further comprising at least one switchable capacitive element for detuning the oscillating circuit.