Near field RF communicators and near field RF communications-enabled devices

• US 8,565,675 B2
• Filed: 11/27/2007
• Issued: 10/22/2013
• Est. Priority Date: 11/27/2006
• Status: Active Grant

• Current Assignee: NXP USA, Inc. (NXP Semiconductors NV)
• Original Assignee: Broadcom Innovision Limited (Broadcom, Inc.)
• Inventors: Bangs, Joakim, Miles, David
• Primary Examiner(s): Alam, Fayyaz
• Assistant Examiner(s): Rachedine, Mohammed
• Application Number:
  US12/516,233
• Publication Number:
  US 20100068999A1
• Time in Patent Office: 2,156 Days
• Field of Search: None
• US Class Current: 455/41.1
• 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
• 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: H04B 5/26 using coils
• CPC Class Codes: H04B 5/48 Transceivers
• CPC Class Codes: H04B 5/77 for interrogation

Abstract

A near field RF communicator has an antenna circuit (120) to receive a modulated radio frequency signal by inductive coupling and demodulation circuitry (130 or 131) to extract the modulation from a received modulated radio frequency signal inductively coupled to the antenna circuit. The demodulation circuitry has a virtual earth input comprising a current mirror. The demodulation circuitry may be formed by an amplifier (115 or 116) and a demodulator (114) coupled to an output of the amplifier. The amplifier may be a single input amplifier (116) coupled to an output of the antenna circuit or may be a differential amplifier (115) having first and second inputs to receive the modulated radio frequency signal from first and second outputs of the antenna circuit, with each amplifier input providing a virtual earth input.

Claims

1. A near field radio frequency (RF) communicator comprising:

an antenna circuit to receive a modulated RF signal by inductive coupling; and

demodulation circuitry to extract modulation from the received modulated RF signal inductively coupled to the antenna circuit, wherein the demodulation circuitry includes a differential amplifier having first and second virtual earth inputs formed with respective first and second current mirrors to input the received modulated RF signal.

2. The near field RF communicator according to claim 1, wherein the demodulation circuitry comprises a demodulator coupled to a single output of the differential amplifier.

3. The near field RF communicator according to claim 1, wherein the differential amplifier comprises a transimpedance amplifier.

4. The near field RF communicator according to claim 1, wherein the first virtual earth input is configured to receive a first modulated RF signal from a first output of the antenna circuit and the second virtual earth input is configured to receive a second modulated RF signal from a second output of the antenna circuit and wherein the demodulation circuitry is configured to extract the modulation from the received modulated RF signal using both the first and second modulated RF signals.

5. The near field RF communicator according to claim 4, further comprising:

a first capacitor coupled between the first output of the antenna circuit and the first virtual earth input, and a second capacitor coupled between the second output of the antenna circuit and the second virtual earth input.

6. The near field RF communicator according to claim 4, wherein a coil of the antenna circuit is coupled across the first and second outputs of the antenna circuit.

7. The near field RF communicator according to claim 1, wherein each current mirror comprises a diode-coupled transistor having a main electrode coupled to a corresponding input and a further transistor having its control gate coupled to a control gate of the diode-coupled transistor such that, in operation, a current at an input of the demodulation circuitry is mirrored by the further transistor to provide an input current to the demodulation circuitry.

8. The near field RF communicator according to claim 7, wherein the diode-coupled transistor and the further transistor are field effect transistors.

9. The near field RF communicator according to claim 1, further comprising a modulator configured to modulate a RF signal in accordance with data to enable communication of data by the near field RF communicator.

10. The near field RF communicator according to claim 1, further comprising a signal generator configured to provide a RF signal and wherein the signal generator is configured to cause modulation of the RF signal in accordance with data to enable communication of data by the near field RF communicator.

11. The near field RF communicator according to claim 1, further comprising a data store configured to store data, a modulator configured to modulate a RF signal in accordance with data, and a controller configured to initiate near field RF communication with another near field RF communicator and configured to respond to near field RF communication initiated by another near field RF communicator.

12. The near field RF communicator according to claim 1, further comprising a power deriver configured to derive power from a RF signal inductively coupled to the coupler.

13. The near field RF communicator according to claim 1, wherein the near field RF communicator is an NFC communicator.

14. A near field radio frequency (RF) communicator comprising:

an antenna circuit configured to receive a modulated RF signal by inductive coupling; and

demodulation circuitry configured to extract modulation from the received modulated RF signal inductively coupled to the antenna circuit, wherein the demodulation circuitry has a first virtual earth input formed with a first current mirror configured to receive a first modulated RF signal from a first output of the antenna circuit and a second virtual earth input formed with a second current mirror configured to receive a second modulated RF signal from a second output of the antenna circuit and is configured to extract modulation from the received modulated RF signal using, both the first and second modulated RF signals.

15. The near field RF communicator according to claim 14, wherein the demodulation circuitry comprises:

a differential amplifier having a first virtual earth circuit coupled to a non-inverting input, a second virtual earth circuit coupled to an inverting input and an output; and

a demodulator coupled to the output of the differential amplifier, the first virtual earth circuit being coupled to the first output of the antenna circuit and the second virtual earth circuit being coupled to the second output of the antenna circuit.

16. The near field RF communicator according to claim 14, further comprising a first capacitor coupled between the first virtual earth input and the first output of the antenna circuit, and a second capacitor coupled between the second virtual earth input and the second output of the antenna circuit.

17. The near field RF communicator according to claim 14, wherein the first and second current mirrors have substantially the same operating characteristics.

18. The near field RF communicator according to claim 14, wherein each current mirror comprises a diode-coupled transistor having a main electrode coupled to a corresponding input and a plurality of parallel coupled transistors, wherein a control gate of each of the plurality of parallel coupled transistors is coupled to a control gate of the diode-coupled transistor, and wherein a current at the corresponding input is mirrored by one transistor of the plurality of parallel coupled transistors selectively enabled by the near field RF communicator to provide an input current to the demodulation circuitry.