# US 9,438,317 B2 · Card detect architecture for near field communications

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- Number: US 9,438,317 B2
- Document ID: US9438317B2
- Status: Granted
- Kind: B2
- Application number: 14/576,496
- Filed: 2014-12-19
- Published: 2016-06-23
- Granted: 2016-09-06
- Earliest claimed: 2014-12-19
- Assignees: Intel Corporation
- Applicants: Niranjan Karandikar; Timothy F. Cox
- Inventors: Niranjan Karandikar; Timothy F. Cox
- Web page: https://patentgrep.com/patent/US9438317B2

## CPC

- H04B 5/77: for interrogation
- G06K 7/00: Methods or arrangements for sensing record carriers, {e.g. for reading patterns} (methods or arrangements for marking the record carrier in digital fashion G06K1/00; pattern recognition G06F18/00; arrangements for image or video recognition or understanding G06V10/00; character recognition, recognising digital ink or document-oriented image-based pattern recognition G06V30/00)
- G06K 7/10297: {arrangements for handling protocols designed for non-contact record carriers such as RFIDs NFCs, e.g. ISO/IEC 14443 and 18092 (cryptographic protocols H04L9/00; network security protocols H04L63/00; real-time communication protocols in data switching networks H04L65/00; network protocols for data switching network services H04L67/00)}
- G06K 19/025: {the material being flexible or adapted for folding, e.g. paper or paper-like materials used in luggage labels, identification tags, forms or identification documents carrying RFIDs (methods for testing the genuineness of valuable papers, e.g. banknotes or passports G07D7/00; constructional features of booklets and the like B42D)}
- G06K 19/07758: {arrangements for adhering the record carrier to further objects or living beings, functioning as an identification tag}
- G06K 19/07779: {the inductive antenna being a coil}
- G06K 19/07781: {the coil being fabricated in a winding process}
- G06K 19/07783: {the coil being planar}
- H01Q 1/2216: {used in interrogator/reader equipment}
- H01Q 7/005: {with variable reactance for tuning the antenna}
- H03F 1/0233: {by using a signal derived from the output signal, e.g. bootstrapping the voltage supply}
- H03F 3/189: High-frequency amplifiers, e.g. radio frequency amplifiers
- H03F 3/20: Power amplifiers, e.g. Class B amplifiers, Class C amplifiers (H03F3/26 - H03F3/30 take precedence)
- H04B 1/0458: {Arrangements for matching and coupling between power amplifier and antenna or between amplifying stages (matching circuits in general H03H)}
- H04B 5/24: Inductive coupling
- H04B 5/26: using coils
- H04B 5/266: {One coil at each side, e.g. with primary and secondary coils}
- H04B 5/48: Transceivers
- H04B 5/79: for data transfer in combination with power transfer
- H04W 4/80: Services using short range communication, e.g. near-field communication [NFC], radio-frequency identification [RFID] or low energy communication
- H04B 2001/0416: {having gain or transmission power control}
- H04B: TRANSMISSION
- G06K: GRAPHICAL DATA READING (image or video recognition or understanding G06V); PRESENTATION OF DATA; RECORD CARRIERS; HANDLING RECORD CARRIERS
- H01Q: ANTENNAS, i.e. RADIO AERIALS (radiators or antennas for microwave heating H05B6/72)
- H03F: AMPLIFIERS
- H04W: WIRELESS COMMUNICATION NETWORKS (broadcast communication H04H; communication systems using wireless links for non-selective communication, e.g. wireless extensions H04M1/72)

## Abstract

Described herein are architectures, platforms and methods for detecting near field communication (NFC) cards/tags by a NFC enabled device, using a coupled impedance signature unique to the NFC cards/tags and the NFC enabled device.

## Claims

### Claim 1

A near field communication (NFC) device comprising:
an antenna;
an NFC controller comprising:
an impedance detector configured to detect rising impedance at the antenna if an object is placed near the antenna; and
an energy source configured to be turned on by the impedance detector if the impedance detector detects the rising impedance.

### Claim 2 (depends on 1)

The NFC device of claim 1, wherein the antenna is configured to communicate and poll the object if the energy source is turned on.

### Claim 3 (depends on 1)

The NFC device of claim 1, wherein the antenna is formed by an inductor.

### Claim 4 (depends on 1)

The NFC device of claim 1, wherein the object comprises an inductor that creates a coupling with the antenna of the NFC device.

### Claim 5 (depends on 1)

The NFC device of claim 1, wherein the rising impedance approaches a threshold coupling impedance signature value.

### Claim 6 (depends on 1)

The NFC device of claim 1, wherein the impedance detector measure input impedance Zin at the antenna to detect rising impedance.

### Claim 7 (depends on 1)

The NFC device of claim 1, wherein the energy source is a power amplifier.

### Claim 8 (depends on 1)

The NFC device of claim 1, wherein the NFC controller is part of a system on a chip.

### Claim 9 (depends on 1)

The NFC device of claim 1 further comprising an RF matching network that matches impedance of the antenna to an output impedance of the energy source.

### Claim 10

A near field communication (NFC) module comprising:
an impedance detector configured to detect impedance at an antenna of a NFC device; and
a power amplifier configured to turn on and provide power to an NFC card if the NFC card is placed in proximity of the antenna and the impedance detector detects a rising coupling impedance between the antenna and the NFC card.

### Claim 11 (depends on 10)

The NFC module of claim 10, wherein the impedance detector is configured to detect rising impedance at the antenna and compare to measured impedance to a threshold value.

### Claim 12 (depends on 10)

The NFC module of claim 10, wherein the rising coupling impedance approaches a threshold coupling impedance signature value.

### Claim 13 (depends on 10)

The NFC module of claim 10, wherein the antenna is a formed by an inductor and impedance is determined by a coupling of a second inductor at the NFC card.

### Claim 14 (depends on 10)

The NFC module of claim 10, wherein the power amplifier is configured to provide polling and communicating through the antenna.

### Claim 15 (depends on 10)

The NFC module of claim 10, wherein the NFC module is configured to an RF matching network that matches impedance of the antenna to an output impedance of power amplifier.

### Claim 16 (depends on 10)

The NFC module of claim 10, wherein the NFC module is part of a system on a chip (SOC).

### Claim 17

A method of detecting a near field communication (NFC) card comprising:
measuring impedance between an object and an NFC enabled device;
determining if the impedance is rising;
powering an energy source to transmit power to the object if the impedance is determined to be rising; and
communicating with the object.

### Claim 18 (depends on 17)

The method of claim 17, wherein the measuring is between an antenna of the object and an antenna of the NFC enabled device.

### Claim 19 (depends on 17)

The method of claim 17, wherein the determining includes determining a threshold coupling impedance.

### Claim 20 (depends on 17)

The method of claim 17, wherein the communicating includes polling the object.