NEAR FIELD RF COMMUNICATORS AND NEAR FIELD RF COMMUNICATIONS-ENABLED DEVICES

• US 20100068999A1
• Filed: 11/27/2007
• Published: 03/18/2010
• Est. Priority Date: 11/27/2006
• Status: Active Grant

• Current Assignee: NXP USA, Inc. (NXP Semiconductors NV)
• Original Assignee: Broadcom Corporation (Broadcom, Inc.)
• Inventors: Miles, David, Bangs, Joakim
• Granted Patent: US 8,565,675 B2
• Time in Patent Office: Days
• US Class Current: 455/41.100
• 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 RF communicator comprising:

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

demodulation circuitry to extract the modulation from a received modulated radio frequency signal inductively coupled to the antenna circuit, wherein the demodulation circuitry has a virtual earth input.

2. A near field RF communicator according to claim 1, wherein the demodulation circuitry comprises a virtual earth input amplifier and a demodulator.

3. A near field RF communicator according to claim 1, wherein the demodulation circuitry comprises a single input amplifier and a demodulator, wherein the single input is a virtual earth input.

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

5. A near field RF communicator according to claim 1, wherein the demodulation circuitry comprises:

a differential amplifier having a non-inverting input coupled to receive a first modulated radio frequency signal from a first output of the antenna circuit, an inverting input coupled to receive a second modulated radio frequency signal from a second output of the antenna circuit, and an output, the non-inverting and inverting inputs being virtual earth inputs; and

a demodulator coupled to the output of the differential amplifier.

6. A 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. A near field RF communicator according to claim 1, wherein the virtual earth input comprises a current mirror.

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

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

10. A near field RF communicator according to claim 1, further comprising a modulator operable to modulate a radio frequency signal in accordance with data to enable communication of data by the near field RF communicator.

11. A near field RF communicator according to claim 1, wherein a signal generator is provided to provide a radio frequency signal and wherein the signal generator is operable to cause modulation of the radio frequency signal in accordance with data to enable communication of data by the near field RF communicator.

12. A near field RF communicator according to claim 1, further comprising a data store operable to store data, a modulator operable to modulate a radio frequency signal in accordance with data, and a controller operable both to initiate near field radio frequency communication with another near field RF communicator and to respond to near field radio frequency communication initiated by another near field RF communicator.

13. A near field RF communicator according to claim 1, further comprising a power deriver operable to derive power from a radio frequency signal inductively coupled to the coupler.

14. A near field RF communicator according to claim 1, wherein the near field RF communicator is an NFC communicator.

15. A device comprising a near field RF communicator in accordance with claim 1.

16. A near field RF communicator comprising:

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

demodulation circuitry to extract the modulation from a received modulated radio frequency signal inductively coupled to the antenna circuit, wherein the demodulation circuitry has a first modulated signal input to receive a first modulated radio frequency signal from a first output of the antenna circuit and a second modulated signal input to receive a second modulated radio frequency signal from a second output of the antenna circuit and is operable to extract modulation from a received modulated RF signal using both the first and second modulated radio frequency signals.

17. A near field RF communicator according to claim 16, wherein the demodulation circuitry comprises:

a differential amplifier having a non-inverting input, an inverting input and an output; and

a demodulator coupled to the output of the differential amplifier, the non-inverting input being coupled to the first output of the antenna circuit and the inverting input being coupled to the second output of the antenna circuit.