Performance Analysis of EPC Tags

Introduction

Recent mandates by the U.S. Department of Defense and major retailers have made RFID important to a large number of people who were previously unfamiliar with the technology. The speed at which the market and technology are moving has created demand for good quality information. In particular, there is a lot of marketing hype and competing claims, which leaves end users to try to sort everything out for themselves.

The RFID Alliance Lab was created to provide credible, high-quality information about RFID products on behalf of end users. (For more information about who we are, see Appendix A.) The Lab will produce regular reports on tags, readers and other critical components. In this first report, we measured the fundamental performance characteristics of UHF tags based on EPCglobal's Class 0 and Class 1 specification. (We describe Class 0 and Class 1 tags in Section 2.) We examined four basic characteristics:

• How a tag performs at varying distances
• How a tag performs at varying orientation
• How a tag performs near water and metal
• How a tag performs on 5 different products on a "real world" conveyor system.

Our aim is to provide information that end users can use to make decisions about which tags are likely to perform best on particular product types. The report is divided into four sections, described below. Each section has subsection in which we describe the tests we performed, present our findings, and summarize our interpretation of those findings. Sidebars in boxes explain some of the technical issues and terminology end users need to get the full value of the report.

Section 2: Description of tags tested. We selected 10 tags that manufacturers said were currently available in commercial quantities. These include tags from Alien Technology, Avery Dennison, Matrics (now owned by Symbol), and UPM Rafsec. All the tags that we tested were donated by tag vendors. In Section 2, we also give a description of the readers and antennas used in this report.

Section 3: Free air testing. This section describes how, in an ideal setting, tag performance varies with distance and with orientation. We define performance by the percentage of successful tag reads. Tags were tested in a controlled environment with ideal conditions. This is important to understanding tag performance because it removes any external variables, and it means that the difference in performance is completely due to the difference in the tags.

Section 4: Tags Near Materials. This section describes how tags perform near metal and water, two materials that have a high impact on the performance of RFID tags. As in Section 3, we tested the tags in a controlled environment with ideal conditions to remove external variables that could affect the results.

Section 5: Conveyor Testing. For these tests, we took the 10 RFID tags out of the laboratory and into an operational distribution center, placed the tags on products, and tested them on a production conveyor system. These results are less scientific because we could not control external conditions. But these conditions more closely approximate the conditions under which end users will use the tags. It was therefore important to provide a comparison of how the tags perform under scientifically controlled ideal conditions and real-world conditions. (For more details, see How the Tests Were Conducted.)

Section 6: Conclusion: Highlights from the report.

Appendix: A description of future test reports and more about the RFID Alliance Lab

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How the Tests Were Conducted

Table of Contents

1.  Introduction............................................ 1

2.  The Tags ................................................  2

2.1 Description of .......................................  2

2.2 The Readers .........................................  3

3.  Free Air Testing ....................................  5

3.1  Performance vs. Distance ...................  5

3.1.1  The Test .............................................  5

3.1.2  The Data ............................................  6

3.1.3  Summary of Findings......................... 8

3.2  Orientation Sensitivity .......................  9

3.2.1  The Test ............................................  9

3.2.2  The Data ...........................................  9

3.2.3  Summary of Findings .......................  13

3.2.4  Discussion of Free Air Tests ............  14

3.3  Summary ...........................................  15


Sidebars:

Multipath .....................................................  5

How to Read a Radiation Pattern ................  5

Dipole Antenna ...........................................  9

What Is dB? ................................................  13

What Are dBi, dBd, and dBm? ..................  15

Why Use Attenuators? ...............................  16


4.  Tags Near Materials ............................  17

4.1  Tags Near Conductors ......................  17

4.1.1  The Test ............................................  17

4.1.2  The Data ...........................................  18

4.1.3  Summary and Findings .....................  19

4.2  Tags Near Water .................................  19

4.2.1  The Test ............................................  20

4.2.2  The Data ...........................................  20

4.2.3  Summary and Findings .....................  21

4.3  Summary ............................................  21


Sidebar:

The Effect of Conductors and Dielectrics....  17


5.  Conveyor Testing .................................  22

5.1  The Test ..............................................  22

5.2  The Data .............................................  22

5.3  Summary and Findings .....................  25

6.  Conclusions ..........................................  26

6.1  Recommendations .............................  26

6.2  Summary of Important Results ........  26

Appendix A:  Who We Are ........................  28


Tables

2.1  Tested RFID Tag Descriptions ..............  2

6.1  Summary of Results for Class 0 Tags ....  27

6.2  Summary of Results for Class 1 Tags .....  27

A.1  Future RFID Alliance Lab Reports .......  28

Figures

2.1  Images of tested RFID tags .....................  3

2.2  Readers and antennas .............................  4

3.1  Angles ? and ?.......................................... 5

3.2  Distribution of fractional reads vs.
         attenuation/distance ................................ 7

Sidebar:  Dipole Antenna .............................  9

3.3  Radiation pattern .....................................  10

4.1  Class 0 tags in front of metal ...................  18

4.2  Class 1 tags in front of metal ...................  19

4.3  Material long dipole ................................  19

Sidebar:  Constructive interference ...............  19

Sidebar:  Destructive interference .................  19

4.4  Class 0 near water ...................................  20

4.5  Class 1 near water ...................................  20

5.1  Individual tag performance results from
            conveyor testings..................................  23

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