Near Field Communication Apparatus

• US 20140194055A1
• Filed: 01/04/2013
• Published: 07/10/2014
• Est. Priority Date: 01/04/2013
• Status: Active Grant

• Current Assignee: Qualcomm technologies international, ltd. (Qualcomm, Inc.)
• Original Assignee: Cambridge Silicon Radio Limited (Qualcomm, Inc.)
• Inventors: Jones, Steve
• Granted Patent: US 8,971,802 B2
• Time in Patent Office: Days
• US Class Current: 455/41.1
• CPC Class Codes: H04B 5/70 specially adapted for specific purposes
• CPC Class Codes: H04B 5/77 for interrogation
• CPC Class Codes: H04W 4/80 Services using short range communication, e.g. near-field communication [NFC], radio-frequency identification [RFID] or low energy communication
• CPC Class Codes: H04W 52/0254 detecting a user operation or a tactile contact or a motion of the device
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

A system for use in a near field communications (NFC) reader, for detecting the presence of an NFC tag, is disclosed. The NFC reader has an antenna tuned to a resonant frequency. The system comprises: a first signal generator for generating a carrier signal whose frequency varies about the resonant frequency; a second signal generator for generating a modulating signal for modulating the carrier signal; a modulator for modulating the carrier signal with the modulating signal; a driver for driving the antenna with the modulated signal; and a detection system for detecting harmonics of the modulating signal in a signal present in the antenna as a result of the modulated signal. The detector is configured to generate an output when a third or higher order harmonic is detected.

Claims

1. A system for use in a near field communications (NFC) reader for detecting the presence of an NFC tag, the NFC reader having an antenna tuned to a resonant frequency, the system comprising:

a first signal generator for generating a carrier signal whose frequency varies about the resonant frequency;

a second signal generator for generating a modulating signal for modulating the carrier signal;

a modulator for modulating the carrier signal with the modulating signal;

a driver for driving the antenna with the modulated signal; and

a detection system for detecting harmonics of the modulating signal in a signal present in the antenna as a result of the modulated signal;

wherein the detection system is configured to generate an output when a third or higher order harmonic is detected.

2. A system according to claim 1, wherein the frequency of the carrier signal varies from around 3.5 MHz below the resonant frequency to around 3.5 MHz above the resonant frequency.

3. A system according to claim 1, wherein the output comprises a signal to activate the NFC reader.

4. A system according to claim 1, wherein the detection system is configured to detect a signal representative of an input impedance of the antenna.

5. A system according to claim 4, wherein the detected signal is a voltage.

6. A system according to claim 1, wherein the detection system comprises a detector and a filter.

7. A system according to claim 6, wherein the detection system comprises a voltage detector and the filter comprises a band-pass filter.

8. A system according to claim 1, further comprising a comparator for comparing a voltage output by the detection system with a predetermined threshold voltage.

9. A system according to claim 1, wherein the detection system is configured to generate an output when a fourth harmonic is detected.

10. A method for use in a near field communications (NFC) reader for detecting the presence of an NFC tag, the NFC reader having an antenna tuned to a resonant frequency, the method comprising:

generating a carrier signal whose frequency varies about the resonant frequency;

generating a modulating signal for modulating the carrier signal;

modulating the carrier signal with the modulating signal;

driving the antenna with the modulated signal;

detecting harmonics of the modulating signal in a signal present in the antenna as a result of the modulated signal; and

generating an output when a third or higher order harmonic is detected.

11. A method according to claim 10, wherein the generated output is used to activate the NFC reader.

12. A method according to claim 10, wherein the frequency of the carrier signal varies from around 3.5 MHz below the resonant frequency to around 3.5 MHz above the resonant frequency.