NEAR FIELD RF COMMUNICATORS

• US 20100291869A1
• Filed: 11/14/2008
• Published: 11/18/2010
• Est. Priority Date: 11/15/2007
• Status: Active Grant

• Current Assignee: Avago Technologies General IP PTE Limited (Broadcom, Inc.)
• Original Assignee: Broadcom Europe Ltd (Broadcom, Inc.)
• Inventors: Wilson, Robin
• Granted Patent: US 8,588,682 B2
• Time in Patent Office: Days
• US Class Current: 455/41.1
• CPC Class Codes: G05F 1/46 wherein the variable actually regulated by the final control device is dc G05F1/625 takes precedence
• CPC Class Codes: G06K 19/0701 at least one of the integrated circuit chips comprising an arrangement for power management
• CPC Class Codes: G06K 19/0715 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 7/10237 the reader and the record carrier being capable of selectively switching between reader and record carrier appearance, e.g. in near field communication [NFC] devices where the NFC device may function as an RFID reader or as an RFID tag
• CPC Class Codes: H02H 7/22 for distribution gear, e.g. bus-bar systems; for switching devices detecting mechanical or electrical defects in gas-insulated switchgears H02B13/065
• CPC Class Codes: H04B 5/00 Near-field transmission systems, e.g. inductive or capacitive transmission systems
• CPC Class Codes: H04B 5/24 Inductive coupling
• CPC Class Codes: H04B 5/72 for local intradevice communication
• CPC Class Codes: H04B 5/79 for data transfer in combination with power transfer

Abstract

A near field RF communicator has an inductive coupler (223) to enable inductive coupling with a magnetic field of an RF signal; a rectifier (213,214,215,216) to rectify an AC voltage derived from an RF signal inductively coupled to the inductive coupler (223); and a regulator (209,210,211,220,221,900) to regulate a voltage derived from an RF signal inductively coupled to the inductive coupler, the regulator having a voltage-controlled impedance (210, 211) and a regulator controller (209) to provide a control voltage for the voltage controlled impedance and to vary the control voltage in dependence upon a current flowing through the voltage controlled impedance (210, 211). To prevent the voltage regulator from drawing excess current and energy from an RF field in which the communicator is present the voltage regulator is controlled to provide a chosen impedance characteristic.

Claims

1. A near field RF communicator having:

an inductive coupler to enable inductive coupling with a magnetic field of an RF signal;

a rectifier to rectify an AC voltage derived from an RF signal inductively coupled to the inductive coupler; and

a regulator to regulate a voltage derived from an RF signal inductively coupled to the inductive coupler, the regulator having a voltage-controlled impedance and a regulator controller to provide a control voltage for the voltage controlled impedance and to vary the control voltage in dependence upon a current flowing through the voltage controlled impedance.

2. A communicator according to claim 1, wherein the regulator controller comprises a feedback element coupled to cause the control voltage to vary in dependence upon a current flowing through the voltage controlled impedance.

3. A communicator according to claim 1, wherein the feedback element comprises an amplifier having positive and negative inputs, and an output coupled to control the control voltage of the amplifier, and a feedback device coupled between the amplifier negative input and output.

4. A communicator according to claim 3, wherein the feedback device comprises a voltage scaler.

5. A communicator according to claim 3, wherein the feedback device comprises a voltage scaler to scale the control voltage on the basis of a reference voltage.

6. A communicator according to claim 3, wherein the feedback device comprises a voltage scaler to multiply the control voltage by a reference voltage.

7. A communicator according to claim 3, wherein the positive input of the amplifier is coupled to a junction of a potential divider coupled across the rectifier.

8. A communicator according to claim 3, wherein the voltage controlled impedance comprises a respective voltage controlled impedance for each polarity of the AC voltage.

11. A communicator according to claim 8, wherein the regulator controller is arranged to determine the current flowing through a said voltage controlled impedance on the basis of a voltage between a control electrode and one of a first and second main electrodes of the voltage controlled impedance.

12. A communicator according to claim 1, wherein the regulator controller is arranged to determine the current flowing through a said voltage controlled impedance on the basis of a voltage across a resistance coupled in series with the voltage controlled impedance.

13. A communicator according to claim 1, wherein the regulator controller is arranged to determine the current flowing through a said voltage controlled impedance on the basis of a current mirror that is coupled to mirror the current flowing through the voltage controlled impedance.

16. A communicator according to claim 1 wherein a current extractor is coupled to the output of the rectifier to extract a portion of the rectified current and wherein a demodulator of the near field RF communicator is arranged to extract modulation from the extracted portion.

17. A communicator according to claim 16, wherein the current extractor is arranged to extract a portion that does not vary significantly with the rectified voltage provided by the rectifier.

19. A communicator according to claim 16, wherein the portion is proportional to the rectified current.

20. A communicator according to claim 16, wherein the current extractor has a first current path coupled between the rectifier and a first output of the current extractor and a second current path coupled between the rectifier and a second output of the current extractor, the first output being coupled to the demodulator and the second output being coupled to provide power to the communicator.

21. A communicator according to claim 20, wherein first and second paths include voltage controlled impedances

wherein the current extractor has a voltage stabilizer to control the voltage across the voltage controlled impedance of the second current path.

25. A communicator according to claim 21, wherein the current extractor has a further voltage stabilizer to control the voltage across the voltage controlled impedance of the first current path to match the voltage across the voltage controlled impedance of the second current path without drawing significant current from the second current path.

36. A near field RF communicator in accordance with claim 1, wherein the near field RF communicator is an NFC communicator or RFID tag.

9-10. -10. (canceled)

14-15. -15. (canceled)

18. (canceled)

22-24. -24. (canceled)

26-30. -30. (canceled)

31. A near field RF communicator having an inductive coupler to enable inductive coupling with a magnetic field of an RF signal;

a rectifier to rectify an AC voltage derived from an RF signal inductively coupled to the inductive coupler;

a regulator to regulate a voltage derived from an RF signal inductively coupled to the inductive coupler; and

a demodulator that extracts modulation on the basis of a current resulting from a received modulated signal.

32. A near field RF communicator having an inductive coupler to enable inductive coupling with a magnetic field of an RF signal;

a rectifier to rectify an AC voltage derived from an RF signal inductively coupled to the inductive coupler;

a regulator to regulate a voltage derived from an RF signal inductively coupled to the inductive coupler; and

a modulator that effects load modulation by changing a voltage threshold of a voltage regulator.

33-35. -35. (canceled)