Electromagnetic transponder operating in very close coupling

• US 6,547,149 B1
• Filed: 04/05/2000
• Issued: 04/15/2003
• Est. Priority Date: 04/07/1999
• Status: Expired due to Term

• Current Assignee: STMicroelectronics SA (STMicroelectronics NV)
• Original Assignee: STMicroelectronics SA (STMicroelectronics NV)
• Inventors: Enguent, Jean-Pierre, Wuidart, Luc, Bardouillet, Michel
• Primary Examiner(s): Frech, Karl D.
• Assistant Examiner(s): TAYLOR, APRIL ALICIA
• Application Number:
  US09/543,378
• Time in Patent Office: 1,105 Days
• Field of Search: 235/383, 235/385, 235/492, 340/10.1, 340/10.2, 340/10.51, 340/10.52, 340/572.3, 340/572.5, 455/41, 455/73, 333/174, 333/175, 342/42
• US Class Current: 235/492
• CPC Class Codes: G06K 19/0701 at least one of the integrated circuit chips comprising an arrangement for power management
• CPC Class Codes: G06K 19/0723 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 7/0008 General problems related to the reading of electronic memory record carriers, independent of its reading method, e.g. power transfer

Abstract

An electromagnetic transponder of the type including an oscillating circuit upstream of a rectifier adapted to providing a D.C. supply voltage to an electronic circuit, the electronic circuit including circuitry for transmitting digitally coded information, and the transponder including circuitry for detuning the oscillating circuit with respect to a determined frequency, the circuitry for detuning the oscillating circuit being used when the transponder has to transmit information while it is very close to a read/write terminal.

Claims

1. An electromagnetic transponder including:

an oscillating circuit upstream of a rectifying means adapted to provide a D.C. supply voltage to an electronic circuit including means for transmitting digitally-coded information, and

means for detuning said oscillating circuit with respect to a determined frequency when the transponder has to transmit information while the transponder is very close to a read/write terminal, the rate of transmission of said information in the detuned configuration being higher than the data transmission rate in a tuned configuration of the oscillating circuit.

2. The transponder of claim 1, wherein the determined frequency corresponds to the frequency of a carrier for remotely supplying the transponder, coming from said terminal.

3. The transponder of claim 1, wherein said means for detuning the oscillating circuit include a switched capacitor, in parallel with an inductive element of the circuit, the rectifying means being formed of a one-way conduction element.

4. The transponder of claim 1, wherein said means for detuning the oscillating circuit include two capacitors, respectively associated with each end terminal of an inductive element of the oscillating circuit, each capacitor being associated in series with a switching means, a reference terminal of which is connected to a reference supply potential of the electronic circuit, downstream the rectifying means.

5. The transponder of claim 1, wherein said means for detuning the oscillating circuit are controllable between two positions to enable a selection between an operation of the transponder tuned on the determined frequency, or detuned from this frequency.

6. The transponder of claim 1, wherein said means for detuning the transponder are also used to detect the distance separating the transponder from a read/write terminal.

7. The transponder of claim 1, further including two resistive modulation means, in parallel with a capacitor for smoothing the rectified voltage provided by the rectifying means, each modulation means being dedicated to one of the tuned or detuned operating modes of the transponder.

8. A system of wireless and contactless data transmission between a terminal of generation of an electromagnetic field and at least one transponder having no independent supply means, wherein the transponder is that of claim 1.

9. The system of claim 8, wherein the data transmission rate from the transponder to the terminal is different according to whether the oscillating circuit of the transponder is or is not tuned to the determined frequency.

10. The system of claim 8, wherein the data transmission rate from the terminal to the transponder is different according to whether the oscillating circuit of the transponder is or is not tuned to the determined frequency.

11. A transponder for use with a base station, wherein the transponder receives base station signals from the base station and transmits information to the base station, comprising:

a resonant circuit that receives base station signals;

at least one first circuit that detunes the resonant circuit; and

at least one second circuit that alters a characteristic of the resonant circuit to transmit information;

wherein a rate of transmission of information is higher when the at least one first circuit detunes the resonant circuit than a rate of transmission of information when the at least one first circuit ;

does not detune the resonant circuit.

12. The transponder of claim 11 further comprising an electronic block that controls the at least one first circuit and at least one second circuit.

13. The transponder of claim 12 wherein the electronic block controls the at least one first circuit to detune the resonant circuit when the transponder is close to the base station.

14. The transponder of claim 12, wherein the electronic block controls the at least one second circuit to transmit information.

15. The transponder of claim 11, wherein the at least one first circuit comprises a capacitive element in series with a switch.

16. The transponder of claim 11, wherein the at least one second circuit comprises a resistive element in series with a switch.

17. The transponder of claim 11, further comprising at least one third circuit that rectifies base station signals.

18. A method for transmitting data from a transponder to a base station, wherein the transponder has an oscillating circuit, comprising:

detuning the oscillating circuit with respect to a determined frequency when the transponder is close to the base station; and

transmitting data from the transponder to the base station,

wherein a rate of transmission of the data while the oscillating circuit is detuned is greater than a rate of transmission of data while the oscillating circuit is tuned.