NFC Technology and Conformance Testing

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Agenda

l NFC Basicsl Standard Evolutionl Physical Layer Compliance Tests

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NFC Introduction

l Contactless data exchangel Passive – activel Active – active

l Close proximity ~ 10 cml Data transfer using the “near

field”l Low carrier frequency of 13.56 MHzl Magnetic coupling between

transmitter and receiver similar to transformer principle

l Standard developed jointly by NXP and Sony

l Backward compatible with smart card technologyl ISO/IEC 14443 A/Bl JIS X 6319-4

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NFC Coupling Method

Information is coupled between the polling and listening devices using the near field – equivalent to transformer principle

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Frequency Spectrum of NFC Signal

l Auxiliary carriers transfer information from passive listener (target) to poller (initiator) through load modulation on poller antenna

l Auxiliary carriers are not used in peer to peer communicationl Carrier is used as a power source in active-passive communications

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Modulation Types

l Poller (initiator) uses ASK modulation on 13.56 MHz carrier

l Passive devices communicate on auxiliary carrier via load modulationl ASK for 14443A and PSK for 14443Bl ASK directly on carrier for JIS X

6319-4

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Coding Types Used in NFC

l NRZ-L: logical 1 and 0 coded as high and low level and signal level is maintained throughout a bit period

l Manchester: first half bit is high for a logical 1 and second half is high for logical 0

l Modified Miller: negative going pulse after half a bit interval for a 1 and at the start of a bit interval for a 0. For a 1 followed by a zero, no pulse

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Frequency and Time Representation

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Evolution of NFC Air Interface

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NFC Operating Modes

l Card emulation mode (passive mode): behaves like existing contactless card and conforms to one of the legacy standards

l Peer to Peer mode: both devices are active and exchange datal Reader/Writer mode (active mode): the NFC device is active and

reads or writes a passive legacy RFID tag

Each mode canUse any of 3 technologies

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Poll Mode Resolution

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NFC Standards Overview

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NFC Tag Types

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NFC RF Measurements – Listening Device

l NFC Forum Reference Polling Devicel Sends commands to listening devicel Received response from listening device (load modulation)

l Command generator – modulated 13.56 MHz carrierl Load modulation measuring tool – oscilloscope or signal anlyzer

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NFC RF Measurements – Polling Device

l NFC Forum reference listening devicel Receives polling signal from device under testl Transmits appropriate response via load modulation

l Listening device response generator – arbitrary waveform generator (AWG)

l Measuring waveform tool – analyzes the polling signal and generates a trigger for the response generator

l Measuring Field tool – measures the carrier power from the poller

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NFC Reference Polling and Listening Devices

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RF Tests for NFC Devices in Polling Mode

l Carrier frequency accuracyl Power level measurementl Sufficient power to drive passive devicesl Measured within the specified volume above the coupling device

l Waveform characteristicsl Rise time, fall time, etc.

l Load modulation sensitivityl Correct reception at minimum specified level

l Threshold level testl Polling device must switch off its RF field when exposed to an RF field f

a certain strength

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RF Tests for NFC Devices in Listening Mode

l Load modulation measurementl The signal strength of the load modulation must be within required limits

l Power receptionl The listening device must answer correctly even in bad conditions

l Frame delay timel Response time from the end of the polling command to the start of

transmission from the phone in card emulation model Important in NFC-A mode for anti-collision

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Test Setup for Polling Mode

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Test Setup for Listening Mode

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Carrier Power and Frequency Measurement

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Load Modulation

Polling command

Load modulation

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Automated Measurement Software

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Poller Timing Values

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Poller Signal vs. Time

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Listener Values

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Listener Signal vs. Time

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Summary

l NFC technology is an evolution of contactless data exchangel Addition of peer to peer and read/write to passive smart card model Backward compatible with legacy smart card

l The NFC forum has established both RF and protocol compliance tests l Guarantees interoperability

l RF testing verifies the air interface for polling and listening devicesl Reference poller and listener l Command and response generator (AWG and vector signal generator)l Waveform analysis tool (oscilloscope with NFC trigger and I/Q

demodulation)l Automation software controls acquisition and analyzes waveform data

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About Rohde & Schwarz

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