Method and device for modulating an active load

• US 10,560,156 B2
• Filed: 04/06/2018
• Issued: 02/11/2020
• Est. Priority Date: 09/21/2010
• Status: Active Grant

• Current Assignee: Verimatrix Incorporated (Verimatrix SA)
• Original Assignee: Verimatrix Incorporated (Verimatrix SA)
• Inventors: Bernard, Frederic, Cordier, Nicolas, Pernisek, Florian, Charrat, Bruno
• Primary Examiner(s): Tsvey, Gennadiy
• Application Number:
  US15/947,384
• Publication Number:
  US 20180227016A1
• Time in Patent Office: 676 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 of a data frame by sequentially and repetitively;

applying, with the oscillator circuit operating in a free oscillation mode, the second periodic signal to the inductive antenna circuit to transmit a portion of the data frame, the second periodic signal being applied to the inductive antenna circuit in response to the data-carrying modulation signal having a first logic value;

after transmitting the portion of the data frame, inhibiting application of the second periodic signal to the inductive antenna circuit, application of the second periodic signal to the inductive antenna circuit being inhibited in response to the data-carrying modulation signal having a second logic value, the second logic value being opposite the first logic value; and

during at least a portion of a period of time that application of the second periodic signal to the inductive antenna circuit is inhibited, placing the oscillator circuit in a synchronous oscillation mode, the placing the oscillator circuit in the synchronous oscillation mode resulting in the second periodic signal being synchronized to the first periodic signal.

2. 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,

the applying and inhibiting application of the first periodic signal to the synchronization input of the oscillator circuit including applying and inhibiting application of the first periodic signal to the synchronization input of the oscillator circuit responsive to a masking signal.

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

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

5. 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 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.

6. 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 that is configured to produce a second periodic signal that is based on the first periodic signal;

the device being configured to;

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

applying, with the oscillator circuit operating in a free oscillation mode, the second periodic signal to the inductive antenna circuit to transmit a portion of the data frame, the second periodic signal being applied to the inductive antenna circuit in response to the data-carrying modulation signal having a first logic value;

after transmitting the portion of the data frame, inhibiting application of the second periodic signal to the inductive antenna circuit, application of the second periodic signal to the inductive antenna circuit being inhibited in response to the data-carrying modulation signal having a second logic value, the second logic value being opposite the first logic value; and

during at least a portion of a period of time that application of the second periodic signal to the inductive antenna circuit is inhibited, placing the oscillator circuit in a synchronous oscillation mode, the placing the oscillator circuit in the synchronous oscillation mode resulting in the second periodic signal being synchronized to the first periodic signal.

7. The device of claim 6, 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, the device being 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.

8. The device of claim 6, 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,

the phase comparator being inhibited from supplying the phase signal when the oscillator circuit is in the free oscillation mode, such that a value of the control voltage at an input of the voltage-controlled oscillator is maintained.

9. The device of claim 6, further comprising a phase shifting circuit configured to phase shift the second periodic signal relative to the first periodic signal.

10. The device of claim 6, further comprising:

at least one host processor configured to supply the device with data to be sent;

an active load modulation circuit configured to provide the data-carrying modulation signal based on the data to be sent.

11. The device of claim 6, wherein the device is mounted in or on a portable medium.

12. The device of claim 6, wherein the device is included in a smart card.

13. 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 of a data frame by sequentially and repetitively;

applying, with the oscillator circuit operating in a free oscillation mode, the second periodic signal to the inductive antenna circuit to transmit a portion of the data frame, the second periodic signal being applied to the inductive antenna circuit in response to the data-carrying modulation signal having a first logic value;

after transmitting the portion of the data frame, inhibiting application of the second periodic signal to the inductive antenna circuit, application of the second periodic signal to the inductive antenna circuit being inhibited in response to the data-carrying modulation signal having a second logic value, the second logic value being opposite the first logic value; and

a period of time after inhibiting application of the second periodic signal to the inductive antenna circuit and while continuing to inhibit application of the second periodic signal to the inductive antenna circuit, placing the oscillator circuit in a synchronous oscillation mode, the placing the oscillator circuit in the synchronous oscillation mode resulting in the second periodic signal being synchronized to the first periodic signal.

14. The method of claim 13, 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,

the applying and inhibiting application of the first periodic signal to the synchronization input of the oscillator circuit including applying and inhibiting application of the first periodic signal to the synchronization input of the oscillator circuit responsive to a masking signal.

15. The method of claim 13, further comprising phase shifting the second periodic signal relative to the first periodic signal.

16. The method of claim 13, wherein the sequence of data bits includes a sequence of encoded data bits.

17. The method of claim 13, further comprising:

supplying a control voltage based on a phase signal;

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

inhibiting 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.

18. 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 that is configured to produce a second periodic signal that is based on the first periodic signal;

the device being configured to;

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

applying, with the oscillator circuit operating in a free oscillation mode, the second periodic signal to the inductive antenna circuit to transmit a portion of the data frame, the second periodic signal being applied to the inductive antenna circuit in response to the data-carrying modulation signal having a first logic value;

after transmitting the portion of the data frame, inhibiting application of the second periodic signal to the inductive antenna circuit, application of the second periodic signal to the inductive antenna circuit being inhibited in response to the data-carrying modulation signal having a second logic value, the second logic value being opposite the first logic value; and

a period of time after inhibiting application of the second periodic signal to the inductive antenna circuit and while continuing to inhibit application of the second periodic signal to the inductive antenna circuit, placing the oscillator circuit in a synchronous oscillation mode, the placing the oscillator circuit in the synchronous oscillation mode resulting in the second periodic signal being synchronized to the first periodic signal.

19. The device of claim 18, 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,

the phase comparator being inhibited from supplying the phase signal when the oscillator circuit is in the free oscillation mode, such that a value of the control voltage at an input of the voltage-controlled oscillator is maintained.

20. The device of claim 18, further comprising a phase shifting circuit configured to phase shift the second periodic signal relative to the first periodic signal.

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