RFID Application Overview and Testing Requirements · 2009-07-28 · Franco Canestri -July 2007...

Franco Canestri -July 2007 RFID Testing Requirements

presented by:

Franco Canestri and Hiromi Matsuoka

Agilent Technologies Sales & Services

GmbH & Co.KG

Böblingen, Germany

and

Agilent Technologies Signal Analysis Division

Kobe, Japan

RFID Application Overview

and Testing Requirements

Franco Canestri – July 2007 RFID Testing Requirements

Agenda

1. RFID Communication Systems, Standards, and Applications

– What’s RFID?

– Reader/Interrogator and Tag

– Frequency bands and applications

2. RFID Signal Overview at UHF Frequency Band

– Various standards at UHF band RFID

– ASK Modulation

– Line coding

3. RFID Signal Analysis (Reader/Interrogator and Tag)

– Measurements for Reader/Interrogator

– Measurements for Tag and RFID systems

4. RFID Measurement Solutions


What’s RFID?Radio Frequency IDentification

• Definition of RFID devices

– Portable size

– Data storage memory in IC chip

– Capable of contactless communication

• RFID features

– Communicates longer distances than barcode; tolerant of dirt and interference

– Communicates more data in readable, rewriteable IC chip

• Some advantages compared with barcode

– Uses in automated check-out with lower costs

– Eliminates human error factors for improved information quality

– Enables individual item recognition for traceability and tracking


RFID Communication Definitions

Reader

(Interrogator)

Tag

Forward link:

transmission from

Reader to Tag

Return link:

transmission from Tag

to Reader(―base station‖)

(―mobile station‖)


RFID Systems Description

Readers/Interrogators

Tags

• Wireless transducer with antenna

• Tag physical design dependent on

end-use

http://www.philips.at/assets/Downloadablefile/at-ge_news05_hl_rfid_reader_boxes_l-14413.jpg

http://www2.cpttm.org.mo/cyberlab/rfid/readerInDoorFrame.jpg

http://images.google.com/imgres?imgurl=http://www.infochip.com/images/hand_reader_small_chip_175w.jpg&imgrefurl=http://www.infochip.com/prod_tire.htm&h=227&w=175&sz=6&hl=en&start=6&tbnid=nxjwAH-mEtgBZM:&tbnh=108&tbnw=83&prev=/images%3Fq%3Drfid%2Breader%26svnum%3D10%26hl%3Den%26lr%3D%26rls%3DGGLG,GGLG:2006-21,GGLG:en%26sa%3DG

http://images.google.com/imgres?imgurl=http://www.sss.lv/files/psion/rfid/uhf_rfid.jpg&imgrefurl=http://www.sss.lv/psionteklogix/rfid.html&h=200&w=161&sz=8&hl=en&start=23&tbnid=dnGyPJDd-y-svM:&tbnh=104&tbnw=84&prev=/images%3Fq%3Drfid%2Breader%26start%3D20%26ndsp%3D20%26svnum%3D10%26hl%3Den%26lr%3D%26rls%3DGGLG,GGLG:2006-21,GGLG:en%26sa%3DN

http://images.google.com/imgres?imgurl=http://www.tagproduct.com/rfid/Faq/Ressources/tags.jpg&imgrefurl=http://www.tagproduct.com/rfid/Faq/rfid_tag.php&h=149&w=194&sz=10&hl=en&start=12&tbnid=s2OWSJulzgZziM:&tbnh=79&tbnw=103&prev=/images%3Fq%3Drfid%2Btags%26svnum%3D10%26hl%3Den%26lr%3D%26rls%3DGGLG,GGLG:2006-21,GGLG:en%26sa%3DN

http://www.rfidjournal.com/ezimagecatalogue/catalogue/phpEaJN3B.jpg


RFID Readers (Interrogators)

• Includes antenna, transceiver, and

decoder

• Many usage models:– Periodic requests to inquire about any tag in

the vicinity

– activate upon detection

– activate upon request

• Read range, memory variable

• Data stored for collection, or passed to

the data processor

http://www.philips.at/assets/Downloadablefile/at-ge_news05_hl_rfid_reader_boxes_l-14413.jpg

http://www2.cpttm.org.mo/cyberlab/rfid/readerInDoorFrame.jpg

http://images.google.com/imgres?imgurl=http://www.infochip.com/images/hand_reader_small_chip_175w.jpg&imgrefurl=http://www.infochip.com/prod_tire.htm&h=227&w=175&sz=6&hl=en&start=6&tbnid=nxjwAH-mEtgBZM:&tbnh=108&tbnw=83&prev=/images%3Fq%3Drfid%2Breader%26svnum%3D10%26hl%3Den%26lr%3D%26rls%3DGGLG,GGLG:2006-21,GGLG:en%26sa%3DG

http://images.google.com/imgres?imgurl=http://www.sss.lv/files/psion/rfid/uhf_rfid.jpg&imgrefurl=http://www.sss.lv/psionteklogix/rfid.html&h=200&w=161&sz=8&hl=en&start=23&tbnid=dnGyPJDd-y-svM:&tbnh=104&tbnw=84&prev=/images%3Fq%3Drfid%2Breader%26start%3D20%26ndsp%3D20%26svnum%3D10%26hl%3Den%26lr%3D%26rls%3DGGLG,GGLG:2006-21,GGLG:en%26sa%3DN


RFID Tags - Active

• Active

• On-board power source and

transmitter

• Higher range (<100 m), but more

expensive

• More reliable in difficult RF environs

• May contain memory on-board

• Battery life to 10 years

• Transponder or Beacon

http://www.rfidjournal.com/ezimagecatalogue/catalogue/phpEaJN3B.jpg


RFID Tags - Passive

• Passive

• Use power induced by the magnetic

field of the reader, or battery-assist

(passive-assist)

• Cheaper

• Potentially unlimited life span

• Better reliability, especially in difficult

physical environs

• May contain memory on-board

• Read distance: ~10 cm to <10m

• Size: smaller than a coin, as thin as

paper


Tags—Inductive vs. Radiative (Backscatter,

Remote Propagation)

Current in tag from the reader allows the tag to radiate

• Frequencies above VHF

• Reader and tag can be read from further away

• Subject to fading, reflection, etc

• Higher data rates

Radiative

InductiveBased on Magnetic

couple principle


Tags—Inductive vs. Radiative (Backscatter)

From June 2005 High Frequency Electronics

Copyright © 2005 Summit Technical Media


The Challenges of RFID

Suppose…you are all tags• You are all blindfolded

• You are nearly deaf

• You talk by whispering

• You can’t hear each other

Suppose…I’m a reader• I’m blindfolded

• I don’t know who is in the room

• I need to yell so you can hear me

• If two of you talk at once, I can’t understand you

• I’m not allowed to say your name

• I may hear many others like me screaming in the

same room

I need to identify everybody in the room What do I do?


More Challenges of RFID

• Selecting and identifying tags – collision control.

• Multiple readers in area—how to allow for a large

number of closely spaced readers.

• Minimal interference and optimized data rate for high

noise or high speed communications.

Also :

• Sessions—how to handle multiple readers talking within

same tag population

• Variable data rates—Used to handle different needs in

varied environments

• Password, protection and security


Identifying Tags

Reader talk first (RTF)

• Multiple tags receive power

•Only the tag which is queried responds

―You talk first, then

everyone else decrement ‖

…1 3 0 7

Slotted Aloha•Tags ―roll dice‖ and

announce value

•Tag with 0 value is

allowed to talk

•All tags decrement count

•New tag with 0 is allowed

to talk

―OK tag #2, download‖

Tag talk first

(TTF)•As soon as tag is

illuminated, tag

talks

•Active tags talk all

the time, for short

periods


Frequency Bands and Applications

Wall

13.56 MHz

900 MHz Multi-path

Leakage

Wall

Reader/Interrogator

Long distance and wide

coverage

• Read multiple tags at a time

• Issues from multi-path and fading

Easier RF design

• Tolerant of influence from water and

metals

• Short distance communication

Frequency 13.56 MHz (HF) 900 MHz (UHF)

Application Item tracking, electronic payment,

building security

Item tracking

Places to use Shop shelves, cash desk, ticket gate Logistics center, warehouse

Standards ISO 18092, 14443, 15693 EPCglobal Class1 Gen2

ISO 18000-6


Agenda


– What’s RFID?





– ASK Modulation

– Line coding






RFID Standards Summary at UHF band

For standards compliance and interoperability, need to verify correct configuration of:

Modulation, Bit rate, Tari, Line CodingASK: Amplitude Shift Keying

Standard Direction Modulation Bit Rate Tari Line Coding

EPCglobal C1

Gen2

(ISO 18000-6

Type C)

Forward DSB-ASK,

SSB-ASK,

PR-ASK

6.25/

12.5/25 us

PIE

Return 40/80/120

kbps

FM0 / Miller

ISO 18000-6

Type A

Forward DSB-ASK 33 kbps PIE

Return 40/160

kbps

FM0

ISO 18000-6

Type B

Forward DSB-ASK 10/40 kbps Manchester

Return 40/160

kbps

FM0


RFID Definitions: CW/Burst/PulseASK in Reader/Tag Bursts

Interrogator Power-On

Burst

Pulse

Entire signal from reader

power turn on until turn off

A single pair of

on/off intervals

A contiguous set of

symbols from a single

transmitter

This is

actually the

envelope of

the CW signal

This is the tag

using the CW

power

transmitted to

respond


Key Challenges for UHF band RFID

Communication systems: Radio waves (potential interference

from other UHF radio services)

Places to use: Logistics center, warehouse (All over the world)

Example use cases:

US – WALMART ordered to attach RFID tags for top 300 suppliers

Hong Kong – Used in HK Airport for baggage tracking

Japan – Started in May 2006 at electric mass merchandisers

Baggage control system in April 2007

Some known issues:

– Standard compliance to communicate various Tags and Readers

– Impact from multi-path, fading

– Receiver sensitivity of tags and reader with attenuated signal in the air


Terms – Bit Rate or Symbol Rate

―Bit Rate‖ used in many standard docs.

―Bit‖ means encoded ASK modulated waveform.

―Symbol‖ means same as ―Bit‖ sometimes.

―Symbol‖ appears in the standard docs, but not as often as ―Bit.‖

bit

data-0 (s1) of Miller (M=4)


Terms – Tari (Interrogator Symbols) Tari = Type A Reference Interval (ISO / IEC 18000-6-A)

The length of a binary '0' is defined as Tari, and is used as a reference for several other times in the standard.• The data rate can vary from 27 to 128 Kbps (Tari from 25 to 6.5

microseconds)• A binary '0' is a short high level pulse followed by low pulse of equal

length • A binary '1' is a longer high pulse followed by the same low pulse width

(PW)This symbol set provides a high average RF power delivered to the tag.

Value of bit is dependent on

the length of the pulse =

Pulse Interval Encoding (PIE)


Terms – Line Coding

(Manchester, FM0)

Example 01011

0 1 0 1 1

Manchester

FM0

Represents

0 = 01

1 = 10

No superposition of DC potential

by switching voltage at bit center

Represents

0 = 01 or 10

1 = 11 or 00

(phase switch at boundary)

Advantages in signal collision and

error detection


PIE (Type C) Coding

Pulse

•Represent data 0 or 1 with pulse time length

(not with voltage level at decision points)

•Variable Tari length by data rate

data-0 data-1 data-0

PW PW PW PWPW

• Bit value determined by length of pulse, not

amplitude

• To read value, look for PW, (falling, low, rising),

then delta time

• Short length=0; long length=1


RFID Communication Systems

Operations

Interrogator transmits CW signal ON and OFF

During CW ON period, Reader sends request signal to Tag

Tag receives the CW signal power, activates IC, and responds to Interrog.

CW

Reader

(Interrogator)

Tag

Key characteristics

Quite low power level from passive Tag

Different line coding between Reader and Tag


UHF band Reader signal (Gen2 DSB-ASK)

Standard defines ripple, rise time, fall

time and pulse width


Strategies for Avoiding Interference

• Frequency multiplex (manual or auto)

• Listen before talk

• Time multiplex (duty cycle transmit)

• Frequency hopping spread spectrum (FHSS)

• Direct sequence spread spectrum (DSSS)

• Chirp pulses (SAW filters)


U.S. FCC EPCglobal Regulations

Must use either FHSS (Frequency-Hopping Spread-Spectrum) or DSSS (Direct-Sequence Spread-Spectrum)

FHSS

• Requires pseudo-random sequence to choose ordering for channel hopping

• Requires equal use of 50 channels, with average time no greater than 0.4 sec on each channel during 20 sec time period if 20dB bandwidth is less than 250 kHz ORequal use of 25 channels, with average time no greater than 0.4 sec on each channel during 10 sec time period if 20dB bandwidth is greater than or equal to 250 kHz

DSSS

• Requires 6dB bandwidth of at least 500 kHz


Summary of RFID Challenges

• ASK based modulation not that simple– Tari, bit rate, T1/T2, Trise/Tfall

• Spurious Requirements to co-exist with Cellular system– -60 to -80 dBm/100kHz

• Collision Avoidance under Multi-Reader/Dense ReaderEnvironment

• Multi-path/Fading– Especially UHF tag even w/ slow movement

• Integration into Mobile Phone; Mobile Phone as Tag or Reader (example: Near-Field Communication, NFC)– Today; 13.56MHz RFID Tag (FeliCa), QR code reader

– Future; 300MHz/900MHz/2.4GHz RFID reader

• Mobile Phone-like production– Tx Power Calibration


Agenda


– What’s RFID?





– ASK Modulation

– Line coding






Required measurements for Reader, Tag and

RFID systems

Reader/Interrogator Measurements

- Signal Analysis for standard compliance

- Modulation depth, rise/fall time, demodulated bits

- Radio Regulation Test

- For all commercial product under local regulations (FCC, ETSI, TELEC etc.)

Tag and RFID System Measurements

- Radio traffic conditions (Reader and tag response, burst measurements)

- Signal analysis for troubleshooting (burst/inter-burst timing, error analysis, demodulation)

- Tag sensitivity and operating frequency

- Transmission performance (level, distance, interoperability)


Reader/Interrogator Measurements

– in time domain

on-time

on-width

off-width

rise time fall time

off-time

on-ripple overshoot

on-ripple undershoot

off-ripple overshoot

off-ripple undershoot

Higher Threshold

Lower Threshold

50%

100%

0%

Time domain analysis is required

Pulse width, Rise/Fall time requirements

for each RFID standard need to be analyzed


950 MHz ―Spectrum Regulation Test‖

Conformance Tests

Q: What equipment is needed for Radio Regulation Tests?

A: Swept-tuned spectrum analyzer, Signal generator, Power

meter, AutoTune feature (transient signals) on Spectrum An.

Q: Can FFT-based VSA be used for Radio Regulation

Tests?

A: Not recommended because of following risks.

1. Inspection agency uses swept-tuned spectrum analyzer

2. Conformance test is described with VBW, detector mode,

sweep time, which are not applicable in FFT-based VSA

For best correlation, use a swept-tuned spectrum analyzer with

AutoTune capability



Reader/Interrogator

Tag behaviorResponding correctly to Reader signals?

How long to respond to Reader signals?

Burst amplitude, duration?

Signal analysis for troubleshootingCheck the impact from interference

Investigate null Tag response

Tag sensitivityReceived signal level required

for reliable response?

Operating frequency?

Distance of reliable communication?

Behavior due to interference (reflection,

multi-path, etc.)

Need detailed and flexible measurements during Tag/Reader

communication sessions

Tag


Measurements in Data Communications

Reader/Interrogator

Establish actual data communications and capture the signal

with antennas and probing.

> Measure tag response and communication timing

Tag


Summary of required measurements

Reader/Interrogator Tag and RFID system

- Standards

compliance

- Radio traffic

condition

- Troubleshooting

- Radio

Regulation Tests- Tag sensitivity

- Operating frequency

FFT

(VSA)

Swept

SA

Use both FFT-based VSA with Spectrogram and Swept SA

to cover all measurement needs


Agenda


– What’s RFID?





– ASK Modulation

– Line coding






Burst Summary

Demod bits

ASK Summary

VSA RFID Modulation Analysis

Traffic conditions


Signal Analysis for Standard Compliance

Easy identification of

bursts in time domain

Demodulated bits

Demodulated

waveform

Modulation depth and

time domain analysis



Detect bursts with length

and interval timing

Time length of entire CW power

Clear burst identification

with direction indicated


Tag Sensitivity

Interrogator

signal

Tag response Level difference

Check the Interrogator power level, tag response, and level difference

> Swept SA can detect lower noise power level

than FFT-based VSA


What’s the best analyzer for RFID?

Swept-tuned Spectrum Analyzer with AutoTune

Spectrum analysis with the fastest sweep up to 26.5 GHz

High dynamic range

Great level and frequency accuracy

FFT-based VSA S/W

Multiple domain analysis in time, frequency, and phase

Spectrogram, digital wireless modulation analysis

SW operates with scope/logic analyzer/simulation

Swept-tuned Signal Analyzer

with AutoTune and with

integrated VSA S/W option


Test Equipment needed in RFID Applications

(from : Canestri, F. “Radio-Frequency Identification (RFID): General Application Overview

and Testing Challenges” - 2007 – submitted Paper)

Reader with

transmitting antenna Passive or Active

RFID Tag

on object to identify

R-C circuit

to groud

Short

switch Termination

AutoTuned Spectrum Analyzers

- with integrated VSA Software

- with integrated Spectrograms

- with AutoTune functionality

EDA SW solutions

Vector Network Analyzers

Signal generators

Circuits Analyzers

Logic Analyzers

Oscilloscopes

Multi-meters

Circuit Analyzers

Logic Analyzers

R T


Summary and Conclusions on

RFID measurement requirements

• RFID Communication Systems, Standards, and Applications

– RFID tags respond to Reader/Interrogator’s signal power

– Need measurements under multi-path, attenuated signal in the air

• RFID Signal Overview at UHF Frequency Band

– Various standards with parameters like bit rate, tari, line coding

– Pulse rise time and modulation quality need to be analyzed

• RFID Signal Analysis (Reader/Interrogator and Tag)

– Reader/Interrogator : Standard compliance with FFT, Regulation test

with Swept SA

– Tag and RFID systems: Measure low level response with SA

• RFID Measurement Solutions

– Signal Analyzer with Swept-SA and AutoTune plus FFT-based VSA

Franco Canestri -July 2007 RFID Testing Requirements

Thank You for Your Attention !

RFID Application Overview and Testing Requirements · 2009-07-28 · Franco Canestri -July 2007...

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Transcript of RFID Application Overview and Testing Requirements · 2009-07-28 · Franco Canestri -July 2007...