# US 2014/0194055 A1 · Near Field Communication Apparatus

> Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt

- Number: US 2014/0194055 A1
- Document ID: US20140194055A1
- Status: Published application
- Kind: A1
- Application number: 13/734,849
- Filed: 2013-01-04
- Published: 2014-07-10
- Earliest claimed: 2013-01-04
- Assignees: Cambridge Silicon Radio Limited
- Inventors: Steve Jones
- Web page: https://patentgrep.com/patent/US20140194055A1

## CPC

- H04B 5/77: for interrogation
- H04B 5/70: specially adapted for specific purposes
- H04W 4/80: Services using short range communication, e.g. near-field communication [NFC], radio-frequency identification [RFID] or low energy communication
- H04W 52/0254: {detecting a user operation or a tactile contact or a motion of the device}
- Y02D 30/70: in wireless communication networks
- H04B: TRANSMISSION
- H04W: WIRELESS COMMUNICATION NETWORKS (broadcast communication H04H; communication systems using wireless links for non-selective communication, e.g. wireless extensions H04M1/72)
- Y02D: CLIMATE CHANGE MITIGATION TECHNOLOGIES IN INFORMATION AND COMMUNICATION TECHNOLOGIES [ICT], I.E. INFORMATION AND COMMUNICATION TECHNOLOGIES AIMING AT THE REDUCTION OF THEIR OWN ENERGY USE

## 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

### Claim 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.

### Claim 2 (depends on 1)

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.

### Claim 3 (depends on 1)

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

### Claim 4 (depends on 1)

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

### Claim 5 (depends on 4)

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

### Claim 6 (depends on 1)

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

### Claim 7 (depends on 6)

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

### Claim 8 (depends on 1)

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

### Claim 9 (depends on 1)

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

### Claim 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.

### Claim 11 (depends on 10)

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

### Claim 12 (depends on 10)

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.