METHOD AND DEVICE FOR MODULATING AN ACTIVE LOAD

• US 20170180008A1
• Filed: 02/15/2017
• Published: 06/22/2017
• Est. Priority Date: 09/21/2010
• Status: Active Grant

• Current Assignee: Verimatrix Incorporated (Verimatrix SA)
• Original Assignee: Inside Secure SA
• Inventors: BERNARD, Frdric, CHARRAT, Bruno, PERNISEK, Florian, CORDIER, Nicolas
• Granted Patent: US 9,941,934 B2
• Time in Patent Office: Days
• 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: H04B 1/3816 Mechanical arrangements for accommodating identification devices, e.g. cards or chips; with connectors for programming identification devices
• CPC Class Codes: H04B 5/72 for local intradevice communication
• CPC Class Codes: H04L 7/08 the synchronisation signals recurring cyclically

Abstract

In a general aspect, a method can include producing, by an inductive antenna circuit, a first periodic signal that is based on an alternating external magnetic field; producing, by an oscillator circuit, a second periodic signal that is based on the first periodic signal; and transmitting, in correspondence with a data-carrying modulation signal, a sequence of data bits. The transmitting can include sequentially and repetitively: applying, with the oscillator circuit operating in a free oscillation mode, the second periodic signal to the inductive antenna circuit; and inhibiting, with the oscillator circuit operating in a synchronous oscillation mode, application of the second periodic signal to the inductive antenna circuit. The synchronous oscillation mode of the oscillator circuit can cause the second periodic signal to be synchronized to the first periodic signal.

Claims

1. A method comprising:

producing, by an inductive antenna circuit, a first periodic signal that is based on an alternating external magnetic field;

producing, by an oscillator circuit, a second periodic signal that is based on the first periodic signal;

transmitting, in correspondence with a data-carrying modulation signal, a sequence of data bits by sequentially and repetitively;

applying, with the oscillator circuit operating in a free oscillation mode, the second periodic signal to the inductive antenna circuit; and

inhibiting, with the oscillator circuit operating in a synchronous oscillation mode,

application of the second periodic signal to the inductive antenna circuit,

the synchronous oscillation mode of the oscillator circuit causing the second periodic signal to be synchronized to the first periodic signal.

2. The method of claim 1, wherein:

applying the second periodic signal to the inductive antenna circuit includes applying the second periodic signal to the inductive antenna circuit when the data-carrying modulation signal has a first logic value; and

inhibiting application of the second periodic signal to the inductive antenna circuit includes inhibiting application of the second periodic signal to the inductive antenna circuit when the data-carrying modulation signal has a second logic value, the second logic value being opposite the first logic value.

3. The method of claim 1, further comprising:

inhibiting application of the first periodic signal to a synchronization input of the oscillator circuit when the oscillator circuit is placed in the free oscillation mode; and

applying the first periodic signal to the synchronization input of the oscillator circuit when the oscillator circuit is placed in the synchronous oscillation mode.

4. The method of claim 3, wherein applying and inhibiting application of the first periodic signal to the synchronization input of the oscillator circuit includes applying and inhibiting application of the first periodic signal to the synchronization input of the oscillator circuit responsive to a masking signal.

5. The method of claim 1, further comprising phase shifting the second periodic signal relative to the first periodic signal.

6. The method of claim 1, wherein the sequence of data bits includes a sequence of encoded data bits.

7. The method of claim 1, further comprising:

supplying a control voltage based on a phase signal;

generating the second periodic signal responsive to the control voltage; and

inhibiting the supplying of the phase signal when placing the oscillator circuit in the free oscillation mode, so as to maintain a value of the control voltage.

8. A device for sending a data frame, the device comprising:

an inductive antenna circuit configured to produce a first periodic signal that is based on an alternating external magnetic field;

an oscillator circuit configured to produce a second periodic signal that is based on the first periodic signal; and

an active load modulation circuit configured to provide a data-carrying modulation signal,

the device being configured to;

transmit, in correspondence with the data-carrying modulation signal, a sequence of data bits by sequentially and repetitively;

applying, with the oscillator circuit operating in a free oscillation mode, the second periodic signal to the inductive antenna circuit; and

inhibiting, with the oscillator circuit operating in a synchronous oscillation mode, application of the second periodic signal to the inductive antenna circuit,

the synchronous oscillation mode of the oscillator circuit causing the second periodic signal to be synchronized to the first periodic signal.

9. The device of claim 8, wherein:

the active load modulation circuit applies the second periodic signal to the inductive antenna circuit when a data-carrying modulation signal has a first logic value; and

the active load modulation circuit is inhibited from applying the second periodic signal to the inductive antenna circuit when the data-carrying modulation signal has a second logic value, the second logic value being opposite the first logic value.

10. The device of claim 8, wherein:

application of the first periodic signal to a synchronization input of the oscillator circuit is inhibited when the oscillator circuit is placed in the free oscillation mode; and

the first periodic signal is applied to the synchronization input of the oscillator circuit when the oscillator circuit is placed in the synchronous oscillation mode.

11. The device of claim 10, wherein the device is configured to selectively apply and inhibit application of the first periodic signal to the synchronization input of the oscillator circuit responsive to a masking signal.

12. The device of claim 8, wherein the oscillator circuit includes an astable oscillator having a specific self-oscillation frequency determined by components of the astable oscillator.

13. The device of claim 8, wherein the oscillator circuit further includes a phase locked loop including:

a phase comparator configured to provide a phase signal;

an active low-pass filter configured to receive the phase signal and supply a control voltage based on the phase signal; and

a voltage-controlled oscillator configured to receive the control voltage and generate the second periodic signal responsive to the control voltage,

wherein the phase comparator is inhibited from supplying the phase signal when switching into the free oscillation mode, so as to maintain a value of the control voltage at an input of the voltage-controlled oscillator.

14. The device of claim 8, further comprising a phase shifting circuit configured to phase shift the second periodic signal relative to the first periodic signal.

15. The device of claim 8, further comprising at least one host processor configured to supply the device with data to be sent.

16. The device of claim 8, wherein the device is mounted in or on a portable medium.

17. The device of claim 8, wherein the device is included in a smart card.

18. The device of claim 8, wherein the data frame includes a plurality of encoded data bits.