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DESIGN AND CHARACTERIZATION OF RFID MODULES IN
MULTILAYER CONFIGURATIONS
A Thesis Presented to
The Academic Faculty
by
Sabri Serkan Basat
In Partial Fulfillment of the Requirements for the Degree
MASTERS OF SCIENCE IN ELECTRICAL AND COMPUTER ENGINEERING
Georgia Institute of Technology December, 2006
DESIGN AND CHARACTERIZATION OF RFID MODULES IN
MULTILAYER CONFIGURATIONS
Approved by: Dr. John Papapolymerou School of Electrical and Computer Engineering Georgia Institute of Technology
Dr. Joy Laskar School of Electrical and Computer Engineering Georgia Institute of Technology
Dr. Manos M. Tentzeris, Advisor School of Electrical and Computer Engineering Georgia Institute of Technology
Date Approved: November 20, 2006
To My parents Nurdan, H. Ihsan, and my sister Z.Destan Basat for their love, encouragement, and support
iv
ACKNOWLEDGEMENTS
The author would like to thank Prof. Manos M. Tentzeris for his guidance and
encouragement and more importantly being a friend. The author owes great debt to the
ATHENA research and especially to Dr. Symeon Nikolaou for his assistance in the
preparation of this document, Amin Rida, Li Yang, and Toni Ferrer-Vidal of the PIREAS
RFID team for providing assistance in the research activity. The author would also like to
thank Dr. Massimiliano Pezzoli, Dr. Valerio Parisi, Dr. Melih Doksanbir, Dr. Alp Engin
Can, Dr. Melissa Lee Casey, and Dr. Emre Kepenek for providing the inspiration and
support in completion of this work. Most importantly the author is eternally grateful for
the motivation to try for the best that was instilled into the author’s mind by his family
Nurdan Basat, H. Ihsan Basat, and Z. Destan Basat.
v
TABLE OF CONTENTS
Page
ACKNOWLEDGEMENTS…………………………………………………………….iv
LIST OF TABLES……………………………………………………………………..viii
LIST OF FIGURES……………………………………………………………………..ix
LIST OF SYMBOLS AND ABBREVIATIONS……………………………………...xii
SUMMARY…………………………………………………………………………….xiv
CHAPTER 1: INTRODUCTION………………………………………………………1
1.1 RFID Basics.…………………………………………………………..1
1.2 History of RFID……………………………………………………….6
1.3 Background: How Does the RFID System Work?................................9
1.3.1 Reader…………………………………………………………...9
1.3.1.1 The HF Interface……………………………………….11
1.3.1.2 The Control Group..………………….………………...11
1.3.2 Tag……………………………………………………………..14
1.3.2.1 Antenna………………………………………………..14
1.3.2.2 Integrated Circuit (IC)…………………………………22
1.3.3 Coupling Mechanisms…………………………………………24
1.3.3.1 Inductive Coupling…………………………………….26
1.3.3.2 Modulated Backscatter………………………………..27
1.3.3.3 Beacon (Transmitter) Type...………………………….28
1.3.3.4 Transponder Type……………………………………..29
1.4 Summary……………………………………………………………..30
vi
CHAPTER 2: CHALLENGES AND PROBLEMS IN RFID TAG DESIGN AND RESEARCH MOTIVATION………………………………………..31
2.1 The Cost of RFID Tag………………………………………………32
2.2 Size Limitations and Optimization…………………………….........32
2.3 Tag Performance Issues……………………………………………..33
2.3.1 Tag Characteristics……………………………………………33
2.3.2 Propagation Environment Limitations………………………...34
CHAPTER 3: 13.56 MHz HF SINGLE/DOUBLE LAYER INDUCTOR COIL RFID TAG DESIGN ………………………………………………. 36
3.1 Rectangular Planar Spiral Coil Antenna Design and Modeling…….37
3.1.1 Tag Antenna Geometry…….………………………………... 37
3.1.2 RLC Calculation………….…………………………………..41
3.1.3 RLC Circuit Modeling………….…………………………….46
3.1.4 Experimental Results and Discussion…….…………………. 49
3.2 Summary……………………………………………………………53
CHAPTER 4: 915 MHz UHF RFID TAG DESIGN FOR AUTOMOTIVE TIRE APPLICATION………………………………………………………. 54
4.1 Design Approach……......…………………………………………. 56
4.2 Antenna Design……………………………….…………………... 57
4.3 Embedding Process…...................................................................... 59
4.4 Antenna Results and Discussion……………..……………………...60
4.5 Summary……………..……………………………………………...66
CHAPTER 5: HIGH-EFFICIENCY 915 MHz UHF RFID TAG ON LIQUID CRYSTAL POLYMER (LCP) SUBSTRATE WITH HIGH READ-RANGE CAPABILITY……………………………………... 67
5.1 Antenna Structure and Design Approach………………..…………. 68
5.2 Experimental Results and Discussion…………….……………….....70
vii
5.3 Bandwidth Optimization…….……………..………………………...74
5.4 Summary………………...…………………………………………...79
CHAPTER 6: PORT OF SAVANNAH ACTIVE 915 MHz UHF RFID TAG-READER SYSTEM FOR CONTAINER TRACKING FIELD STUDY …………………………...…………………………………... 80
6.1 Introduction…………………………………………………………. 81
6.2 Brief Summary of Conducted Tests………..………………….......... 84
6.2.1 Tag-Reader Response Test on F1&F2……...………………….85
6.2.1.1 F1 & F2 Test...………………..………………………….85
6.2.1.2 Canyon (Waveguide) Effect Test.……………………….88
6.3 Summary………………..…………………………………………....90
CHAPTER 7: CONCLUSIONS…………………………………….……………..…..92
APPENDIX A: LIST OF PUBLICATIONS……………………………………….…94
APPENDIX B: PORT OF SAVANNAH FIELD TEST SET-UP AND TABULATED DATA ....………...…………………………………... 95
REFERENCES………………………………………………………………………...115
viii
LIST OF TABLES
Page
Table 1: Single and Double-layer lumped component model R, L, C values………… 49
Table 2: Simulated antenna parameters and measured read range…………………….. 64
Table 3: S-shape RFID antenna performance parameters and measured read range …. 71
Table 4: Lumped element model values for the s-shape and the bandwidth optimized
s-shape designs…………………………………………………………………77
Table 5: Active UHF RFID test set-up for container tracking and tag
positions ………………………………………………………………………. 96
Table 6: Active UHF RFID Conducted field test with the times………………………..98
Table 7: Overall active UHF RFID tags by location on the containers in the stack.….. 114
ix
LIST OF FIGURES
Page
Figure 1: Basic RFID components.……………………………………………………… 1
Figure 2: RFID Technology examples in industry (Courtesy of Phillips)………………. 2
Figure 3: Active vs. Passive Tag.………………………………………………………...3
Figure 4: Effect of Environmental conditions and RFID system performance at different RFID frequency bands (courtesy of Phillips).………………………………... 5
Figure 5: The milestones in RFID technology [1]…………………………………….…7
Figure 6: General RFID reader diagram ………………………………………………..10
Figure 7: Sub-block RFID reader diagram ……………………………………………. 10
Figure 8: Geometrical representation of the sinusoidal current filament source ……… 15
Figure 9: Field regions of an antenna.…………………………………………………..16
Figure 10: Elevation plane amplitude patterns for a thin dipole with sinusoidal current distribution ( l = λ /4, λ /2, 3λ /4,λ ) [8]. …………………………………. 18
Figure 11: Three and Two-dimensional amplitude patterns for a thin dipole of and l = 1.25λ sinusoidal current distribution [8].…………………………………... 19
Figure 12: Current distributions along the length of a linear wire antenna[8]…………. 20
Figure 13: Basic RFID IC Block Diagram [5]…………………………………………. 23
Figure 14: Near-field (LF and HF) and far-field (UHF) coupling mechanisms.………. 25
Figure 15: Calculation of magnetic field B at location P due to current I on the loop….38
Figure 16: Single-layer 13.56 MHz HF antenna structure dimensions……..…………. 39
Figure 17: Double-layer 13.56 MHz HF antenna structure dimensions.………………. 40
Figure 18: Single-layer (Left) and double-layer (Right) 13.56 MHz HF RFID tags.….. 41
Figure 19: Rectangular thin film inductor ……………………………………………...43
Figure 20: Two conductor segments for mutual inductance calculation.……………….44
Figure 21: The simple series resonance circuit model…………………………………..46
x
Figure 22: Lumped element model for single-layer and double-layer 13.56 MHz HF RFID tags.…………………………………………………………………...48
Figure 23: The single-layer and double-layer input impedance (50 Ohm normalization) and return loss (28 kOhm normalization) results for 13.56 MHz HF RFID
tag……………………………………………………………………………52
Figure 24: Current flow in UHF RFID Tag antenna …………………………………....57
Figure 25: The three different RFID antenna designs for tire application ….…………..58
Figure 26: Cross-sectional view of RFID Tag placement in tire material ……………...59
Figure 27: E-phi=0 (x-z) and E-phi=90 (y-z) planes radiation patterns (Directivity vs. elevation angle theta) for the three 915 MHz UHF antenna designs in tire material. Antennas are located in the horizontal plane.……………………..62
Figure 28: S11 input load impedance Smith chart (50-Ohm reference) plots for the three 915 MHz UHF antenna designs in tire material (range of frequency= 500-1500 MHz).………………………………………………………………… 64
Figure 29: 915 MHz UHF RFID s-shape antenna structure and double inductive stub matching network……………………………………………………....68
Figure 30: Fabricated 915 MHz UHF RFID s-shape antenna and antenna direction of current flow …………………………………………..………………………70
Figure 31: Input impedance of the simulated 915 MHz UHF RFID s-shape antenna…..72
Figure 32: Three- and two-dimensional far-field radiation plots for 915 MHz UHF s-shape antenna.……………………………………………………….……….73
Figure 33: Simulated input impedance of the 915 MHz UHF s-shape antenna………….74
Figure 34: 915 MHz UHF RFID s-shape antenna structure with optimized bandwidth showing the matching stubs.………………………………………………...75
Figure 35: Measured and simulated data of return loss for the 915 MHz UHF s-shape antenna.………………………………………………………………………76
Figure 36: Equivalent circuit for 915 MHz UHF s-shape antenna structure shown in Figure 28.……………………………………………………………………77
Figure 37: The Port of Savannah.………………….……………………………………81
Figure 38: Graphical view of tag placement on containers, container placement in stack, and reader position (Courtesy of CarrierWeb).……………………....82
xi
Figure 39: Containers in the stack positioned during the day of the measurement for the active 915 MHz UHF RFID field test .………………………………... 100
Figure 40: Canyon effect (Waveguiding) case active 915 MHz UHF RFID test set-up for container tracking.……………………………………………………... 102
Figure 41: The Canyon effect for detection of active 915 MHz UHF RFID tags in the middle container stack.………………………………………………………85
Figure 42: Radiation patterns in x-z planes with (RIGHT) and without (LEFT) metal surface.………………………………………………………………………86
Figure 43: Tag/Reader orientation sensitivity (polarization).………………………….. 87
Figure 44: Top view of the reader and reflector position for active 915 MHz UHF RFID system.……………………………………….…………………….…90
xii
LIST OF SYMBOLS AND ABBREVIATIONS
RFID Radio Frequency Identification
IC Integrated Circuit
VLF Very Low Frequency
LF Low Frequency
HF High Frequency
UHF Ultra High Frequency
ISM Industrial-Scientific-Medical
GPS Global Positioning System
IFF Identify Friend or Foe
EAS Electronic Article Surveillance
EAN European Article Number
RF Radio Frequency
EPC Electronic Product Code
ISO International Standards Organization
ROM Read Only Memory
EEPROM Electrically Erasable Programmable Read Only Memory
CRC Cyclic Redundancy Code
CW Continuous Wave
AC Alternating Current
DC Direct Current
RTLS Real-time Locating Systems
PET Poly Ethylene Terephthalate
LCP Liquid Crystal Polymer
xiii
CMOS Complementary Metal Oxide Semiconductor
MoM Method of Moments
Q Quality
BW Bandwidth
GPA Georgia Port Authority
xiv
SUMMARY
Radio Frequency IDentification (RFID) Tags have become quite widespread in
many services in the industry such as access control, parcel and document tracking,
distribution logistics, automotive systems, and livestock or pet tracking. In these
applications, a wireless communication link is provided between a remote transponder
(antenna and integrated circuit (IC)) and an interrogator or reader. A suitable antenna for
these tags must have low cost, low profile and especially small size whereas the
bandwidth requirement (few kilohertz to megahertz) is less critical.
RFID tags operate in several frequency bands. The exact frequency is controlled
by the Radio Regulatory body in each country. The generic frequencies for RFID are
125-134 kHz LF, 13.56 MHz HF, UHF (400-930 MHz), and 2.45 GHz. Although there
are other frequencies used, these are the main ones. In the UHF band, there are two areas
of interest, one around 400 MHz (e.g.433 MHz) and another around 860 – 930 MHz.
Each of the frequency bands has advantages and disadvantages for operation. There
exists no single frequency for every application.
The lower frequencies 125-134 kHz and 13.56 MHz work much better near water
or humans than do the higher frequency tags. Worldwide availability of the 13.56 MHz
tags as an Intermediate unlicensed industrial, scientific, and medical (ISM) frequency and
higher data transfer rate compared to 125-134 kHz tags maintain the popularity of 13.56
MHz as a preferred design solution in harsh environments. Another reason 13.56 MHz is
a popular frequency is that the antennas can be smaller, and in some cases printed as
paths onto substrate (i.e. inductor coil tags), rather than using thick copper wire which
125-134 kHz frequency requires. On the other hand, for passive tags, the lower
frequencies usually have less range, and they have a slower data transfer rate. Higher
frequencies are used when more information needs to be transferred for longer distances.
xv
The higher frequency ranges (i.e. 915 MHz) have more regulatory controls and
differences from country to country. 860-930 MHz RFID frequency range has also
become increasingly popular in the last years because the distortion of the propagating
electromagnetic waves due to reflection (bouncing of waves off conductive reflective
surfaces), refraction (waves passing through dissimilar dielectric media), diffraction (a
sharp edge slowing a portion of the wave front allowing some of the energy to appear
behind an otherwise solid object), and power absorption by nearby objects and materials
is worse at frequencies higher than UHF. (i.e. 2.45 GHz) Environmental conditions that
are detrimental in the overall performance of the RFID tags are less for the UHF (i.e 915
MHz) than they are for even higher frequencies.(i.e. 2.45 GHz) This is the main reason
UHF tags are very popular for higher frequency applications.
In this document, methods to reduce tag size, the performance optimization of the
tag by using novel antenna matching techniques for increased operational bandwidth and
gain/radiation pattern/radiation efficiency improvement are introduced for HF and UHF
RFID tags. Chapter 1 presents a brief introduction to understand the basic principles
behind the passive RFID technology for both the lower 13.56 MHz HF and higher 915
MHz UHF and active RFID technology for 915 MHz UHF. This chapter also discusses
the reader-tag relationship from a system point of view. The challenges in RFID tag
design and the research motivation is presented in chapter 2. In chapters 3 and 4 practical
passive RFID tag designs are discussed in detail in terms of RF design for the 13.56 MHz
and 915 MHz frequencies because of this increased interest in the industry. The 13.56
MHZ is an inductor coil type RFID tag, which utilizes the near-field radiation. For this
application, the single and miniaturized double-layer designs are presented. In chapter 4,
the 915 MHz RFID tag design is discussed. The 915 MHz application is an embedded
RFID tag in an automotive tire, which utilizes the far-field radiation. Chapter 5 focuses
on passive UHF optimized radiation efficient 915 MHz tag design for increased read
range. This chapter also explains the antenna matching techniques to increase bandwidth
xvi
to cover the upper UHF (860-930 MHz) band. Finally, an evaluation of an active 915
MHz UHF RFID field study for container tracking at the port of Savannah, GA is
presented in chapter 6 followed by the conclusions in chapter 7. This field study’s
objective is to provide solutions to the challenges in container tracking.
1
CHAPTER 1
INTRODUCTION
1.1 RFID Basics
RFID systems utilize the concept of electromagnetic radiation to detect tagged
objects from a remote transponder (tag) including an antenna and a microchip transceiver
(Integrated Circuit) using a local querying system (reader or interrogator) as shown in
Figure 1.
Figure 1. Basic RFID components.
IC Antenna
2
The simplest RFID tags as shown in Figure 1 are passive meaning the power
supply to the IC is delivered by an external source such as the reader. If the tags use an
internal power source such as a battery, then the tag is active. Since RFID tags don’t need
Figure 2. RFID Technology examples in industry (Courtesy of Phillips)
to be line-of-sight like optical barcode technology, its popularity and demand has
increased. There exists widespread usage of this technology in access control, sensors and
metering applications, payment systems, communication and transportation, parcel and
document tracking, distribution logistics, automotive systems, livestock/pet tracking, and
hospitals/pharmaceutical applications. [6,25]
3
RFID technology has brought many advantages over the existing barcode
technology. First of all, RFID tags can be embedded in an item rather than the physical
exposure requirement of barcodes and can be detected using RF signal. RF signal
generation also enhances the read range for RFID tags. Barcodes only contain
information about the manufacturer or originator of an item and basic information about
the object itself; however, RFID is particularly useful for applications in which the item
must be identified uniquely. RFIDs also can hold additional functionality which means
more bits of information.
As mentioned earlier RFID transponders are categorized into two namely passive
and active tags. For the passive the tag contains an antenna and an IC that stores data. It is
powered by the electromagnetic field generated by the antenna. The response
electromagnetic field allows the RFID tag to reflect back extremely weak signal
containing data up to 3-5 meters. These tags, if manufactured in billions will come down
in price from $0.30 to $0.05 in the next 2 years. [5,12] Active tags operate very mush
like the passive ones with added functionality. They are battery powered. Because of this,
much greater range (~100 m) can be achieved. Compared to passive tags, active tags can
hold much more information (Kbytes). In addition, the existing battery allows integration
with sensors such as temperature, pressure, biological, and Global Positioning System
(GPS). The response signal of tags can be controlled at defined times and multiple tags
can be recorded at once. Depending on the complexity of the tag module, active tags cost
between $20 to $40 per item. Battery lifetime ranges between 2-4 years. Figure 3
summarizes the operational differences of the two types of tags.
4
Figure 3. Active vs. Passive Tag.
RFID tags use various frequency bands to communicate with the interrogator.
Figure 4 shows the most commonly used bands. The main frequencies are 125 kHz LF,
13.56 MHz HF, UHF (860-930MHz), and 2.45 GHz. All these frequencies including
5
Figure 4. Effect of Environmental conditions and RFID system performance at different RFID frequency bands (courtesy of Phillips).
UHF 915 MHz are ISM frequency bands which led to the widespread usage in the world
as of now. Different frequency bands are needed for various applications in rugged
environments. For instance, metal and lossy material effects as well as water and human
body absorption are more detrimental to RFID performance at UHF and higher
frequencies than the lower frequencies. Higher data rate is also achieved with higher
frequencies and anti-collision speed is limited at lower frequencies as well. Read range is
also higher at higher frequencies (~3-5 m in free space) than at the lower frequencies
(~30 cm) That’s why there is a trade-off between higher data rate, higher anti-collision
speed, and higher read range at UHF and 2.45 GHz compared to the better performance
in rugged environments in the presence of metals, lossy materials, and humans at the
lower 125 kHz and 13.56 MHz bands.
6
1.2 History of RFID
The roots of RFID technology can be traced back to World War II. The Germans,
Japanese, Americans and British were all using radar- which had been discovered by
Scottish physicist Sir Robert Alexander Watson-Watt- to warn of approaching planes
while they were still miles away; however, it was impossible to distinguish enemy planes
from allied ones.
The Germans discovered that by just rolling planes when returning to base
changes the radio signal reflected back which would alert the radar crew on the ground.
This crude method made it possible for the Germans to identify their planes. The British
developed the first active identify friend or foe (IFF) system. By just putting a transmitter
on each British plane, it received signals from the aircrafts. This identified the planes as
friendly [1].
An early exploration of the RFID technology came in October 1948 by Harry
Stockman. [2] He stated back then that “considerable research and development work has
to be done before the remaining basic problems in reflected-power communication are
solved, and before the field of useful applications is explored”. His vision flourished until
other developments in the transistor, the integrated circuit, the microprocessor, and the
communication networks took place. RFID had to wait for a while to be realized [3].
The advances in radar and RF communications systems continued after WW II
through the 1950s and 1960s (Figure 5). In 1960s application field trials initiated. The
first commercial product came. Companies were investigating solutions for anti-theft and
this revolutionized the whole RFID industry. They investigated the anti-theft systems that
utilized RF waves to monitor if an item is paid or not. This was the start of the 1-bit
7
Electronic Article Surveillance (EAS) tags by Sensormatic, Checkpoint, and Knogo. This
is by far the most commonly used RFID application.
Figure 5. The milestones in RFID technology [1].
The electronic identification of items caught the interest of large companies as
well. In 1970s large corporations like Raytheon (RayTag 1973), RCA, and Fairchild
(Electronic Identification system 1975, electronic license plate for motor vehicles 1977)
built their own RFID modules. Thomas Meyers and Ashley Leigh of Fairchild also
developed a passive encoding microwave transponder in 1978 [3].
By 1980s there were mainstream applications all around the world. The RFID was
like a wildfire spreading without any boundaries. In the United States, RFID technology
found its place in transportation (highway tolls) and personnel access (smart ID cards). In
Europe, short-range animal tracking, industrial and business systems RFID applications
8
attracted the industry. Using RFID technology, world’s first commercial application for
collecting tolls in Norway (1987) and after in the United States by the Dallas North
Turnpike (1989) were established.
In 1990s, IBM engineers developed and patented a UHF RFID system. IBM
conducted early research with Wal-Mart, but this technology was never commercialized.
UHF offered longer read range and faster data transfer compared to the 125 kHz and
13.56 MHz applications. With these accomplishments, it led the way to the world’s first
open highway electronic tolling system in Oklahoma in 1991. This was followed by the
world’s first combined toll collection and traffic management system in Houston by the
Harris County Toll Road Authority (1992). In addition to this, GA 400 and Kansas
Turnpike Highways were the first to implement multi-protocol tags which allowed two
different standards to be read [1,3].
After IBM’s early pilot studies in 1990s with Wal-Mart, UHF RFID got a boost in
1999, when the Uniform Code Council, European Article Number (EAN) International,
Procter & Gamble and Gillette teamed up to establish the Auto-ID Center at the
Massachusetts Institute of Technology. This research focused on putting a serial number
on the tag to keep the price down using a microchip and an antenna. By storing this
information in a database, tag tracking was finally realized in this grand networking
technology. This was a crucial point in terms of business because now a stronger
communication link between the manufacturers and the business partners was established.
A business partner would now know when a shipment was leaving the dock at a
manufacturing facility or warehouse, and a retailer could automatically let the
manufacturer know when the goods arrived [1].
9
The Auto-ID Center also initiated the two air interface protocols (Class 1 and
Class 0), the Electronic Product Code (EPC) numbering scheme, and the network
architecture used to seek for the RFID tag data between 1999 and 2003. The Uniform
Code Council licensed this technology in 2003 and EPCGlobal was born as a joint
venture with EAN International, to commercialize EPC technology.
Today some of the biggest retailers in the world such as Albertsons, Metro, Target,
Tesco, Wal-Mart, and the U.S. Department of Defense stated that they plan to use EPC
technology to track their goods. The pharmaceutical (healthcare), tire (automotive),
defense and other industries are also pushing towards adaptation of this new technology.
EPCGlobal adopted a second generation (Gen-2 ISO 18000-6-C) standard in December
2004. This standard is widely used in the RFID world today [1,4].
1.3 Background: How Does the RFID System Work?
The basic components of an RFID system were presented in Figure 1. These are
mainly an interrogator (reader), a transponder (tag), and a coupling mechanism that
defines the kind of communication link between the tag and the reader. In this section,
these sub-parts of the higher level system will be explained in detail.
1.3.1 Reader
Another important part in a RFID system is the reader sub-system. It is possible to
divide an RFID reader system into two differentiated groups, namely the high frequency
interface and the control system. These groups interact among each other and with an
external host system as can be seen in Figure 6.
10
Figure 6. General RFID reader diagram.
The main functions performed by a reader are demodulating the data retrieved from
the tag, decoding the received data, and energizing in the case of passive and semi-
passive tags. A more detailed diagram of the reader can be found in Figure 7.
Figure 7. Sub-block RFID reader diagram.
11
1.3.1.1 The HF Interface
The HF interface performs the following basic functions:
• Demodulating and decoding the date retrieved from the tag.
• Energizing, in the case of passive and semi-passive tags.
Elements:
• Transmitter:
The main task of this element is to transmit power and the clock cycle to the tags.
It is part of the transceiver module.
• Receiver:
This component is responsible for receiving signals from the tag via the antenna.
Afterwards, it sends these signals to a microprocessor where the digital
information is extracted
• Power:
This module supplies the adequate power levels to all components in the reader.
1.3.1.2 The Control Group
To allow the functions of decoding, error checking and communication with an
external system the control unit makes use of a microprocessor, a controller, a
communication interface, memory and input/output channels.
• Microprocessor:
In the microprocessor the reader protocol is implemented. The microprocessor
12
will interpret the received commands, and depending on the protocol required by
the specific standard (i.e., ALOHA for HF frequencies [6], tree walking for UHF
frequencies [6]), the microprocessor will search the memory for the
corresponding program code and will execute it. It is here where error checking
is performed.
• Controller:
In order to allow joint operation with an external system, a system called the
controller, responsible for converting external orders to understandable
microprocessor binary code, is needed to enable communication. It is possible to
have a controller in either a software or hardware form.
• Communication Interface:
By using the controller, the communication interface is able to interact with an
external host system by transferring data, passing or responding to instructions.
The communication interface can be a part of the controller or an independent
entity depending on the integration level and speed requirements.
• Memory:
The memory is responsible for storing the data retrieved from the tags. The data
will be transmitted to the host system when demanded.
• Input/Output Channels for External Sensors:
When operating a reader it might happen that the tags are not in its read range,
making continuous operation a waste of energy. By using external sensors able to
detect the presence of an item nearby, for instance in a conveyor belt crossing in
13
front of the reader, it is possible to efficiently operate the reader by activating it at
the required times.
Additionally it is possible to classify the readers by the communication interface
in use or by its mobility. A brief description of each category is as follows:
Communication Interface:
• Serial Reader:
This reader uses a RS-232 (Recommended Standard 232) serial port to
communicate with the host system and transfer data or commands executed by the
user or application. These readers have a lower data transfer rate compared with
others such as a wired network reader and have a cable length limitation. On the
other hand, serial port connections are more reliable
• Network Reader:
This reader can be connected wired or wirelessly to a computer, therefore it
appears as a network device. In this case, the cable length is not a limitation, but
the connection is not as reliable as in serial readers.
Mobility of Readers:
• Stationary Reader:
These readers are mounted on a wall, portal or suitable structure in the read zone.
They can be mounted on moving objects such as trucks. These readers usually
are connected to external antennas. Agile readers are able to operate in different
14
frequencies and use different communications protocols. An RFID printer is a
type of stationary reader able to print a bar code and write on its RFID tag
• Handheld Reader:
This type of reader has an integrated antenna on it and can operate as a handheld
unit.
1.3.2 Tag
The RFID tag is the transponder unit that communicates with the reader as
mentioned earlier. It is comprised of an antenna and an IC module for passive and semi-
passive tags.
1.3.2.1 Antenna
The antenna of the tag is the main radiating element that provides the wireless
communication link between the tag and the reader. The general expression for fields
from a radiating sinusoidal current filament source is given as [7]:
)sin(114 32 θ
ωεεμωμ
πθjkro e
rjrrjdzIE −
⎥⎦
⎤⎢⎣
⎡++= (1)
)cos(112 32 θ
ωεεμ
πjkro
r erjr
dzIE −
⎥⎦
⎤⎢⎣
⎡+= (2)
)sin(14 2 θπφ
jkro err
jkdzIH −
⎥⎦⎤
⎢⎣⎡ += (3)
where
15
oI = the amplitude of the sinusoidal current filament source
dz = the sinusoidal current filament source length
k = λπ2 , λ is the wavelength
r = radial distance from the sinusoidal current filament source
ω = 2π f , f is the frequency
μ = permeability of the medium
ε = permittivity of the medium
Figure 8. Geometrical representation of the sinusoidal current filament source.
In Figure 8, the geometry of the sinusoidal current filament source is displayed. Using the
equations in (1,2,3), the 3 regions surrounding the radiating element can be identified.
These regions are namely (a) reactive near-field, (b) radiating near-field (Fresnel) and (c)
far-field (Fraunhofer) regions as shown in Figure 9 [8].
16
Figure 9. Field regions of an antenna.
Regions:
• Reactive Near-field Region:
It is the part of the field in the vicinity of the antenna (distance R <0.62 λ/3D )
is predominantly reactive and 1/r3 terms in (1,2) define this field. This field does
not radiate, but it stores energy in the form of standing waves. D is the largest
dimension of the antenna and D >> λ [7]. For a very short dipole, or equivalent
17
radiator, the outer boundary of this region is commonly taken to exist at a distance
λ /2π from the antenna surface [8].
• Radiating Near-field (Fresnel) Region:
The Fresnel region contains the standing waves and traveling waves from both
near-field and far-field regions. It exists just outside the boundary of reactive
near-field region to the far-field region boundary. These fields are dominated by
the 1/r2 term (1,2,3) and reach to λ/2 2D [7]. If the antenna has a maximum
dimension that is not large compared to the wavelength, this region may not exist
[8].
• Far-field (Fraunhofer) Region:
It is defined as the field region of an antenna where the angular field distribution
is essentially independent of the distance from the antenna. This is the region
beyond the radiating near-field boundary. The traveling waves dominate in this
region where they decay with a rate of 1/r. These traveling waves carry the
electromagnetic power.
In the far-field (Fraunhofer) region for a dipole antenna as shown in Figure 9 θE and φH
take the form of
jkro e
klkl
rIjE −
⎥⎥⎥
⎦
⎤
⎢⎢⎢
⎣
⎡ −=
)sin(
)2
cos())cos(2
cos(
2 θ
θ
πηθ (4)
jkro e
klkl
rIjEH −
⎥⎥⎥
⎦
⎤
⎢⎢⎢
⎣
⎡ −==
)sin(
)2
cos())cos(2
cos(
2 θ
θ
πηθ
φ (5)
18
where η is the intrinsic impedance (εμ =377 = 120π ohms for free space) and l is the
length of the dipole antenna. Figure 10 shows the normalized θE radiation for different
Figure 10. Elevation plane amplitude patterns for a thin dipole with sinusoidal current distribution ( l = λ /4, λ /2, 3λ /4,λ ) [8].
19
Figure 11. Three and Two-dimensional amplitude patterns for a thin dipole of l = 1.25λ and sinusoidal current distribution [8].
20
lengths. As it can be seen from the plot, the beam becomes narrower when the length of
the antenna increases. This means that the antenna becomes more directional. For some
applications in RFID such as tags on boxes in storage areas where omni-directionality is
needed the increase in directivity might be a problem. When the length is increased to l
>λ , another major problem occurs. The side lobes begin to increase as shown in Figure
11. These side lobes cause nulls which mean no electric field radiation. For instance, the
plotted pattern in Figure 11 has 6 nulls compared to only two in Figure 10.
Current distribution plays a major role in the characterization of the previously
Figure 12. Current distributions along the length of a linear wire antenna [8].
21
shown radiation patterns. The current distributions along the length of a straight wire
antenna are shown in Figure 12. It can be clearly seen from this plot that at l = λ /2
maximum current level with minimum distortion can be achieved. Because of the almost
omni-directional pattern with maximum current level and minimum amount of side lobes,
l = λ /2 is usually chosen when designing dipole antennas.
The tags that operate in the near-field region at LF and HF frequencies are mainly
loop or inductive coil antennas as discussed in detail in chapter 3. The most common
antenna for UHF far-field is printed dipole but others exist such as printed folded dipole,
printed inverted F (PIFA), meander line, slot, and patch antenna [9].
When determining the read range of a UHF RFID tag, both the distance at which
the reader will be able to detect the scattered signal and the distance at which the tag
receives enough power to operate have to be considered. Usually, the high sensitivity of
the tag limits the operating range. Using the Friis free space formula it is possible to
derive the following maximum range:
th
rtt
PGGP
rτ
πλ
4max = (6)
Or received power in decibel form
)(log20)4(log20 max1010 rGGLPP rtsystr −−+++−=λπτ (7)
22
where λ is the wavelength, Pt is the transmitted power from the reader, Gt is the gain of
the transmitter antenna, Gr is the gain of the receiver tag antenna, Pth is the minimum
threshold power at the reader and τ is the power transmission coefficient (a design factor
which takes into account the amount of energy transferred from the antenna to the reader
chip). sysL is the system losses that need to be taken into account during the measurement.
This includes the cable and connector losses, temperature differences that cause internal
losses in the instruments (i.e. antenna + transceiver of reader and tag).
1.3.2.2 Integrated Circuit (IC)
The RFID IC circuitry is basically comprised of RF front-end, some basic signal
processing blocks, logic circuitry (algorithm implementation), EEPROM for storage
(Figure 13).These components are crucial for the operational functionality of the tags [5].
Elements:
• RF Front-end:
The RF front-end typically consists of a simple circuit like resistor-inductor
circuit. The RF front-end is the main interface between the antenna and signal
processing unit. It is in charge of implementing modulators, voltage regulators,
resets and connections to the external antenna
• Signal Processing:
Signal processing handles the basic data acquisition from RF front-end.
• Control Logic:
Control logic manages functions that include the error and parity/CRC checkers,
23
Figure 13. Basic RFID IC Block Diagram [5].
data encoders, anti-collision algorithms, controllers, command decoders. Security
primitives and even tamper-proofing hardware can be included in more complex
RFID ICs.
• EEPROM Storage Memory:
Electrically Erasable and Programmable Read-only Memory (EEPROM) gives
the functionality of tags to be read/write; however, tags that cannot be
programmed use state machines or read-only memories (ROM) to store or
generate the information [6]. Because of the added programmable feature of
EEPROM, it is the memory storage unit in the new Gen 2 RFID standard.
24
1.3.3 Coupling Mechanisms
In order to understand each coupling mechanism, the differences in operation
between passive/semi-active and active tags, are introduced in this section. Passive tags
obtain power from an interrogation pulse from the reader. They use this power to send an
information message, a reply. Since the tags have no battery they essentially last forever,
and they do not wear out. A passive RFID tag is little more than a loop of antenna with
some basic circuitry. It has a read range up to about 10 meters. Active tags have an
onboard battery; hence they are able to respond with a signal that can travel perhaps as
much as 150 meters or more to a remote reader. Semi-active tags contain batteries, but
this internal power source is not used to power up the Integrated Circuit (IC). The
microchip still obtains the power from the transmitter reader signal like the passive tags.
The battery is only used to provide power for on-board electronics to perform specialized
tasks (i.e., powering a sensor module). The reading distance of a semi-active tag can be
up to 30 meters.
Depending on the tag type (passive/active/semi-active), there are four types of
coupling mechanisms between the tag (transponder) and the reader:
• Inductive Coupling
• Modulated Backscatter Coupling
• Transmitter (beacon) Type
• Transponder Type
For passive and semi-active tags, the transfer of data is achieved using inductive
or modulated backscatter coupling. Inductively coupled tags are almost always operated
25
passively. This means that the reader provides all the energy needed for the operation of
the microchip. The generation of the electromagnetic field from the reader's antenna coil
penetrates the cross-section of the coil area and the area around the coil. Since the
signal’s wavelength is several times greater than the distance between the reader's
antenna and the transponder (for example, a signal of 135 KHz in the Low Frequency
band (LF) has a wavelength of 2222 meters, and a signal of 13.56 MHz in the High
Frequency band (HF) has a wavelength of 22.1 meters), the electromagnetic field behaves
like a simple alternating magnetic field with regard to the distance between the
transponder and the antenna. This is called "near-field coupling" as discussed
mathematically earlier and shown in Figure 8. In the near-field, the electromagnetic
energy lines are formed moving outwards from the radiating element and then back into
the radiating element as shown in Figure 14. Near-field coupling occurs within roughly
Figure 14. Near-field (LF and HF) and far-field (UHF) coupling mechanisms.
26
one wavelength of a radiating element. Near-field coupling occurs for RFID applications
operating in the LF and HF bands with relatively short reading distances well within the
radian sphere, R, defined by λ/2π (λ= wavelength in free space), because of the
relationship λ = 2πR .
The occurrence of modulated backscatter coupling takes place in the “far-field
coupling” region as previously shown mathematically and displayed in Figure 14.
Beyond the near-field region, where the far-field starts, the electromagnetic energy
simply propagates outwards and the power drops off based on the inverse-square law.
The power decreases by ¼ as the distance doubles. Longer read range UHF and
microwave RFID systems utilize far-field coupling.
1.3.3.1 Inductive Coupling
The partial penetration of the emitted field from the antenna coil of the
transponder creates current on the coil of the reader. To fully explain this, it is necessary
to define the term electromagnetic induction. Electromagnetic induction is a phenomenon
through which a change in the magnetic field of a source such as a transmitter creates a
voltage level in a remote circuit such as a tag. A parallel circuit used to tune the tag’s
operating frequency to that of the reader is formed by a capacitor in parallel to the tag’s
antenna coil which behaves as an inductor. At a certain frequency, the receiver’s antenna
interchanges energy at a particular rate, called resonant frequency, which depends on
several design parameters such as size of the coil, number of turns or distance between
27
the capacitance plates, among others. At this time high currents are generated in the
reader’s antenna coil by the method known as resonance step-up.
Resonance step-up occurs when the frequency of the transmitted signal becomes
similar to the designed resonant frequency of the circuit. At this point a portion of the
energy stored as magnetic form in the inductor is transferred into electrical form in the
capacitor. Before achieving a stable state, a temporary adjustment in the energy levels at
the tag’s inductor and capacitor occurs; this whole process explains the before mentioned
resonance step-up effect. After reaching the stable state at resonant frequency, the
received energy is “stored” in the tag by transfer back and forth from the capacitance to
the inductance, in accordance with the required field strengths for the operation of the
remote transponder. A constant current is required for IC’s operations; this can be
achieved by using a rectifier, a built-in component which transforms the alternating
energy arriving at the tag into a constant current. As a general principle it is possible to
say that inductively-coupled systems are based upon a transformer-type coupling
between the primary coil in the reader and the secondary coil in the transponder. This is
true when the distance between the coils does not exceed λ/(2π) (~16% of the wavelength
λ), which defines the near-field of the transmitter antenna.
1.3.3.2 Modulated Backscatter Coupling
The interrogation pulse generated from the reader propagates outside the near-
field of the reader antenna. As this RF signal travels outwards, it may encounter the
antenna element in the tag. According to radar technology, an electromagnetic wave
bounces off an object with dimension greater than half the wavelength of the
28
electromagnetic wave. The “reflection cross-section” can then be defined as the
parameter that determines the strength of the returned signal. An electromagnetic field
propagates outwards from the reader's antenna and a small proportion of that field
(reduced by free space attenuation) reaches the transponder's antenna. Since the
incoming signal is a sinusoidal continuous wave (CW), it needs to be converted from AC
power to DC power by using a rectifier circuit with diodes. This power is then supplied to
deactivate or activate the power saving "power-down" mode.
The antenna of the transponder captures a portion of the incoming RF energy and
this energy is then reflected by the antenna of the tag and reradiated outwards. By
changing the load connected to the antenna the reflection characteristics (i.e., reflection
cross-section) of the antenna can be manipulated. A load resistor (or capacitor) connected
in parallel with the antenna is turned on and off synchronously with the data stream to be
transmitted. This generates the transmission of data from the transponder to the reader.
By varying the load of the transponder antenna, the strength of the signal reflected and
reradiated from the transponder to the reader can be modulated. In electromagnetic terms,
this is referred to as modulated backscatter. Once the modulated and encoded data
stream in the IC reaches the reader, it is then decoded and subsequently demodulated
allowing the user to retrieve the required information.
1.3.3.3 Beacon (Transmitter) Type
When the precise location of an asset needs to be tracked, beacons are used in
most real-time locating systems (RTLS). Active tags are used in this type of
communication. In an RTLS, a beacon transmits a signal with its unique identification
29
number at pre-defined intervals. The query time could be done at many different times;
could so frequent as every five seconds or once a day, depending on how often it is to
needed to know the location of an asset. At least three reader antennas positioned around
the perimeter of the area where assets are being tracked detect the beacon's signal. In this
way, the exact location of the asset can be found. RTLS are usually used in a large open
area; however, automakers use the systems in large manufacturing facilities to track
parts’ bins.
1.3.3.4 Transponder Type
Upon receiving a signal from a reader active transponders are awakened.
Transponder type active transponders are used for instance in toll payment collection,
checkpoint control and port security systems. In toll payment collection, a reader at the
booth transmits a signal that activates the transponder mounted on the car’s windshield.
When a car with an active transponder comes in close proximity of the tollbooth, the
transponder then sends out its unique ID to the reader. Battery life conservation can be
achieved by having the tag communicate with the reader only when it is within the read
range of that reader.
30
1.4 Summary
In this chapter, the basic concepts to understand the operational principles of the
RFID technology with a brief historical overview have been presented. The differences
between the two types of tags namely passive and active tags were discussed. Moreover,
the crucial elements such as the reader, the tag (antenna+IC), and the coupling
mechanisms in the overall RFID system were explained thoroughly. HF (i.e. 13.56 MHz)
and UHF (i.e. 915) band applications were also explained to lay the foundations for the
following chapters in this document.
31
CHAPTER 2
CHALLENGES AND PROBLEMS IN RFID TAG DESIGN AND
RESEARCH MOTIVATION
For a successful RFID implementation one has to possess a keen knowledge of its
standards, its technology, and how it integrates with a company’s supply-chain and
inventory data [10]. Federal Express CIO Rob Carter quoted Bill Gates’ definition of a
“two-ten technology” in a Fortune interview when he was asked about RFID. “Two-ten
technology” means for the first two years, hype reigns, followed by disappointment, until
the day 10 years later when people realize the technology has flourished and become part
of the daily life. Carter accepts after noticing some challenges and problems FedEx is
experiencing with tags and adds, “RFID might be a three-15 technology.” [10] This citing
comes from a man who is in charge of the whole activity of tracking parcels it does not
even own for up to 48 hours anywhere in the world-an activity that cries out for RFID
[10].
Apart form higher level problems in RFID applications, tag design imposes
different lower level challenges. These challenges include current high cost of tags, size
limitations and optimization, tag performance issues. From a system point of view
problems at the lower level must be resolved before moving up on the RFID system
hierarchy for an optimized overall performance. This research also proposes on how to
overcome some of these challenges.
32
2.1 The Cost of RFID Tag
In order to sell RFID tags just like any other product it has to be cheap. Mark
Roberti’s report [11] based on Auto-ID Center’s predictions on IC manufacturing cost
reduction [5] indicate that by 2007 the cost of a passive tag can reach as low as 5 cents
from 30-35 cents [12] as it is now. The prediction relies on the fact that these tags will be
sold in high volume about 30 billion a year which would in return reduce the cost the IC
to almost 1 cent. The rest of the cost will be distributed in assembly process of these ICs
[5], the antenna inlay fabrication on organic low-cost substrates such as PET, LCP,
Kapton, and paper.
There is also ongoing research at PIREAS RFID/Sensors lab headed by Dr.
Manos M. Tentzeris on metallization on paper using conductive inkjet printing. This
research focuses on using paper as a low-cost substrate and inkjet printing as a substitute
to conventional metal etching and screen printing methods. This inkjet printing method is
also investigated to embed available thin film batteries in organic substrates such as paper
to revolutionize the active tag development.
2.2 Size Limitations and Optimization
The size of the tag becomes a major issue when tags are used on items that are
limited in size. The main controlling factor for the size of a tag is the antenna size which
is governed by the operating frequency. For instance, resonance is achieved for an
optimum performing antenna length around λ/2 for various different antenna types such
as folded printed dipole, printed patch, log-spiral [15]. This means for low LF and HF
(λ/2 = 1111 m for LF 125kHz, λ/2=10.5 m for HF 13.56 Mhz) frequency applications
resonance comes with a price of increased dimensions as well as the UHF (λ/2=15 cm for
915 MHz) tags. For the lower frequencies such as the HF (13.56 MHz) printer inductive
loop antennas in the shape of a coil are used [16, 17]. For higher UHF (915 MHz) printed
33
dipole antennas size miniaturization usually achieved through meander line type
topologies [13, 14] These same folding techniques can also be applied to printed inverted
F antenna as well as slot antennas. It has to be noted that the main trade-off is between
size reduction and efficiency including gain [13]. These issues will also be addressed
later in this research document.
2.3 Tag Performance Issues
Tag performance in an RFID system is mostly evaluated how the tag read range is
in different environments. This depends mainly on the tag (IC + antenna) properties as
well as the propagation environment. The tag characteristics can be summed up in IC
sensitivity, antenna gain, antenna polarization, and impedance match [18].The
propagation environment limitations are the path loss and tag detuning. [18]
2.3.1 Tag Characteristics
• Chip Sensitivity:
It is defined by the minimum threshold power to activate the IC. It is primarily
determined by the RF Front end architecture and fabrication process [18, 22]. The
lower the threshold power (high sensitivity) results in higher read range of the tag.
• Antenna Gain and Polarization:
Antenna gain is directly controlled by how directive the antenna and if it is
radiating efficiently. The size and structural topology (array of antennas or single)
of the antenna at the frequency of operation defines how much gain can be
achieved. Polarization of the tag is important in view of RFID system level
performance. Maximum power transfer is accomplished when the polarization of
the tag is matched to the reader’s.
34
• Impedance Match:
The complex impedance (i.e 17-j350 for Phillips IC) of the IC requires a
conjugate complex impedance match at the antenna end. This becomes a real
challenge since the chip impedance varies at different power levels and
frequencies [19]. In order to maximize the tag read range impedance can be
matched at various IC power levels such as at minimum threshold power.
2.3.2 Propagation Environment Limitations
• Path Loss:
The path loss is dependent on the surrounding environment [20, 21]. The type of
scattering around the tag defines the path loss. The ideal 2)4( dπλ for free
space propagation can be changed significantly in a room, for instance, where
multiple reflections occur with the main line-of-sight signal [23].
• Tag Detuning:
When the tags are placed on or embedded in lossy materials (i.e. detergent,
automotive tire, human bodies) and in the vicinity of metal, resonant frequency of
the antenna shifts from the design frequency [15, 25]. This effect results in tag
detuning. This also affects the antenna gain and the radiation pattern and thus
results in a lower read range. Multiple tags also present this kind of problem if the
tags are very close to each other. The parasitic coupling between the antennas
causes the tags to detune because it changes the antenna impedance. Simultaneous
multiple tag identification and the position analysis of these tags are discussed in
35
[20, 21]. Antenna bending can also detune the tag by changing the radiation
pattern and impedance of the antenna [24].
As possible solutions to the challenges and problems for tag design identified in
this chapter, this research will be discussing tag size miniaturization techniques that were
presented as well as some novel techniques. In addition to this, antenna gain and radiation
efficiency, new impedance matching strategies are also explained thoroughly. These
methods will be presented for lower 13.56 MHz HF and 915 MHz UHF bands.
36
CHAPTER 3
13.56 MHz HF SINGLE/DOUBLE LAYER INDUCTOR COIL RFID
TAG DESIGN
A lot of interest has grown into the 13.56 MHz frequency in the last decade more
than the VLF, LF and UHF bands in certain applications, such as security access control.
The use of 13.56 MHz frequency has been proven to be very advantageous over these
other bands [26], [27]:
Frequency band available worldwide as an ISM frequency
Excellent Immunity to environmental noise and electrical interference
Minimal shielding effects from adjacent objects and the human body
Freedom from environmental reflections that can plague UHF systems
Good data transfer rate
On-chip capacitors for tuning transponder coil can be easily realized
Cheap ICs, disposable tags
Cost effective antenna coil manufacturing
Low RF power transmission so EM regulation compliance cause no problems
Most of the 13.56 MHz HF RFID systems employ the near-field inductive
coupling of the transponder tag with the reactive energy circulating around the reader
antenna [26]. Since these tags are passive which means no internal power supply is
needed, the necessary power required to energize and activate the tag’s microchip or low-
power CMOS IC is drawn from the localized oscillatory magnetic field created by the
37
reader unit’s antenna [26]. In order to charge up the IC with inductive coupling, the IC
should be capacitive which requires the impedance of the radiating element (antenna) to
be conjugately matched with respect to the IC’s input impedance. For this reason highly
inductive printed spiral coils are used for 13.56 MHz RFID applications as antennas.
In this section, design and modeling of a single-layer 13.56 MHz RFID tag is
presented with the development of the double-layer design to reduce size with the aid of
IE3D software, which is based on method of moments (MoM).The antenna challenges
which include port matching, efficiency, and size at 13.56 MHz as well as the
performance advantages over the UHF band are also addressed.
3.1 Rectangular Planar Spiral Coil Antenna Design and Modeling
3.1.1 Tag Antenna Geometry
RF signal can be radiated effectively if the linear dimension of the antenna is
comparable with the wavelength of the operating frequency; however, the wavelength at
13.56 MHz is 22.12 meters. For this reason, a loop antenna in the shape of a coil that is
resonating is being used. Since the operating read range of these tags is relatively small
compared to a wavelength (~20-40 cm), they operate in the near-field radiation region.
This type of antenna is called magnetic dipole antenna where the near-field magnetic
field radiation in Figure 15 falls off with r -3 and increases linearly with the
38
Figure 15. Calculation of magnetic field B at location P due to current I on the loop.
number of turns N as shown below [28,29].
(8)
Utilizing the properties of magnetic dipole antenna, single-layer and double-layer
tags were developed. The single-layer tag is shown in Figure 16. The inductor coil tag
antenna is 4.7cm by 7.9cm with 50 um aluminum metal pattern printed on top of low-cost
and easily manufactured PET (polyethylene terephalate, εr =3.2, tanδ=0.017), and
39
adhesive dielectric layer as shown in Figure 16. The IC is placed in the center where the
two extended ports 1 and 2 are located. 16 um Ag paste is used to bridge Pad1 to Pad2 in
order to connect the two ends of antenna coil structure as shown in Figure 10. 20 um SR
dielectric is embedded in between the Ag paste and the metal pattern to provide isolation.
Figure 16. Single-layer 13.56 MHz HF antenna structure dimensions.
In Figure 17 the geometry for the double-layer tag is also shown. The inductor
coil tag antenna is 4.0cm by 2.72 cm (economy in area by a factor of 3) with double-
sided 50 um aluminum metal pattern (top+bottom) printed on PET and adhesive
40
dielectric layers also displayed in Figure 11. As presented in Figure 11, the top layer pads
Pad1t and Pad2t are connected to Pad1b and Pad2b respectively with shorting pins. These
pads are connected to complete the antenna coil loop.
Figure 17. Double-layer 13.56 MHz HF antenna structure dimensions.
The fabricated single-layer and double-layer tags are displayed in Figure 18. The
center of the single and double-layers are Ports 1 and 2 where the IC is assembled. These
two tags were fabricated using the same framing process.
41
Figure 18. Single-layer (Left) and double-layer (Right) 13.56 MHz HF RFID tags.
3.1.2 RLC Calculation
In order to design spiral coil antennas, the inductance (L), the resistance (R), and
the capacitance (C) of the antennas are needed to be characterized. From these values, the
quality factor, Q, of the inductor which would give the efficiency of the tag can be also
computed. The L and R are calculated as a starting point in the design process. The C is
quite difficult to numerically calculate because of the distributed capacitance of the tag
[29]. The circuit model that is also proposed in this paper is used to find the various
different capacitances.
R is comprised of DC and AC resistances of the conductor etched on dielectric
[28]. The DC resistance is due to the even distribution of charge carriers through the
entire cross-section of the metal trace and is given by:
42
(9)
It clearly shows that a smaller cross-sectional area (9) causes higher DC resistance in the
metal trace. The resistance must be kept as small as possible to achieve higher Q inductor
coil antenna. For this reason, a larger diameter coil must be chosen for the RFID antenna.
As the frequency increases, the magnetic field is concentrated around the center
of the conductor metal trace and which in return increases the reactance near the center
that results in increased impedance [29]. This increased impedance forces the current to
flow more closely to the edges of the conductor. This phenomenon is widely known as
the skin effect. The depth into the conductor at which the current density falls to 1/e or
37% of its value along the surface is known as the skin depth.
(10)
43
The net result of the skin effect is an effective decrease in the cross-sectional area
of the conductor; therefore, a net increase in the AC resistance of the conductor occurs.
For the conductor etched on dielectric substrate the AC resistance is,
(11)
where w is the width and t is the thickness of the conductor.
Figure 19. Rectangular thin film inductor.
The inductance of a thin film inductor with a rectangular cross-section as
displayed in Figure 19 is [29],
(12)
where w is the width in cm, t is the thickness in cm, and l is the length of the conductor in
cm. When an inductor made of straight segments is considered as shown in Figure 20, the
44
L is the sum of self-inductances and mutual inductances [30] as shown below.
Figure 20. Two conductor segments for mutual inductance calculation.
(13)
Lo is calculated by adding the inductances of individual segments as shown in (12). The
mutual inductance results from the magnetic fields produced by adjacent conductors. The
mutual inductance is positive when the directions of currents on the conductors are in the
same direction and negative when they are in opposite directions.
The mutual inductance between two parallel conductors as presented in (14) is a
function of the length of the conductors and of the geometric mean distance between
them. It is calculated by,
45
(14)
where l is the length of the conductor in cm and F is the mutual inductance parameter and
computed as,
(15)
where d is the geometric mean distance between the two conductors, which is
approximately equal to the distance between the track centers of the conductors.
In Figure 20 the two conductor segments are shown as mentioned before. The j
and k in the figure are the indices for the conductor segments, and p and q are the indices
of the length for the difference in the length of the two conductors. This configuration in
Figure 20 occurs between conductors in multiple turn spiral inductor. The mutual
inductance of the conductors’ j and k is calculated using,
(16)
and if the length l1 and l2 are the same (l1= l2), then (16 d) is used. Each mutual
inductance term as shown in (14) is computed by
46
(17)
and LT is calculated based on the mutual inductances and the self inductances. It should
be again noted that for RFID coils the calculated true inductance may differ from the
resulting inductance in the final design due to the distributed capacitance and additional
conductor lengths in the fabrication process. Because of this fact, inductance calculations
are mainly used as a starting point in the final design.
3.1.3 RLC Circuit Modeling
A 13.56 MHz rectangular coil antenna can be simply modeled as a series
resonance circuit as shown in Figure 21 to understand the effect of bandwidth and quality
factor ,Q, on
Figure 21. The simple series resonance circuit model.
47
antenna performance [29]. The half power (3 dB) frequency bandwidth is calculated
using the resistance r and inductance L, and given by,
(18)
where Q is found using (18) and the resonant frequency, fo , as shown below in (19). The
series
(19)
circuit forms a voltage divider where the voltage across the inductor coil, Vo, is given by,
(20)
where XL and XC are the inductor and capacitor reactances and Vin is the input voltage.
When the circuit is resonant at the specified frequency, XL = XC and (20) becomes as
shown below.
(21)
48
(21) indicates that the output voltage is a function of the Q and the input voltage. Since
the input voltage is limited by the reader, read range can be increased by increasing the Q
[29].
The series circuit model gives a synopsis of the general behavior of inductor coil
antennas; however, this model does not give any information about the distributed
capacitance due to the substrate effects and connecting pads. A lot of research has been
conducted in RF inductor modeling [31, 32].With the helpful insight of this work, a more
complicated lumped element model is presented in Figure 22. This model includes the
Figure 22. Lumped element model for single-layer and double-layer 13.56 MHz HF RFID tags.
substrate capacitances and losses as well as the resistance, capacitance, and inductance
changes with the addition of the pads and additional metal trace lengths/widths during the
fabrication process.
Figure 22 presents the lumped element model for both the single-layer and the
double-layer tags. The model is the same for the two cases with different R, L, and C
values because the double-layer tag is merely two single-layer tags in series resulting
Ls: the series inductance of the square spiral Rs: the ohmic losses in the metal traces of the spiral Cp: capacitive coupling due to the electrical field between the spiral tracks and the pad capacitance Rp: resistance in series with Cp Cadh: the adhesive material capacitance between the coil and the PET substrate Csub: the PET substrate capacitance Rsub: the resistive loss in the PET substrate Ric: IC resistance Cic: IC capacitance
49
from the way the two inductor coils are connected to each other. Since one-port
measurement was conducted, the second port was shorted as seen in the model. This
model was run through ADS simulation software’s optimization tool to obtain the freq-
independent R, L, and C values using the input impedance results of the one-port
measurement.
3.1.4 Experimental Results and Discussion
The R, L, and C values from the single-layer and double-layer lumped element
models are presented in Table 1. The one-port measurement of the reflection coefficient
(S11) gives the input impedance of the tag for both cases as shown in Figure 17. The
lumped element model was optimized so that the measured input impedance data and the
model data align perfectly. The IC was placed and the return loss was also measured as
shown in Figure 17 again for both cases. The IC’s parallel load capacitance and
resistance (23.5 pF and 28 kOhm) with the input impedance of the tag create the resonant
circuit centered at 13.67 MHz (single-layer) and 13.94 MHz (double-layer).
Table 1. Single and Double-layer lumped component model R, L, C values.
The double-sided metal tracing creates more parasitic capacitance as seen from
the Cp, Csub, and Cadh in Table 1. The substrate resistance, Rsub, is also quite high for
both cases indicating how lossy the material is. The series inductance, Ls, and resistance,
50
Rs, characterize the inductor coil. The Ls depends on the overall length of the metal
inductor coil; meanwhile, the Rs is mainly controlled by the width of inductor coil. The
Rp is the result of pad capacitance which dominates in the single-layer case due to the use
of bridge structure to connect one end of the inductor to the other.
The performance of the coil antenna as the radiating element depends on the
efficiency which defines the read range of the tag. The efficiency is mainly characterized
for inductor coil type antennas by the Q as mentioned before. The calculated Q values for
the single-layer and the double-layer are 54.7 and 15.2 respectively. The fabricated tags
yield operational distances of 37 cm (single-layer) and 22 cm (double-layer). The
inductance of the coil plays a major role in the near-field coupling. The magnetic flux
created inside the coil due to the inductive coupling between the reader and the tag is a
function of the size and the number of turns of the coil. Another factor that limits the
efficiency of the coil antenna is the PET dielectric loss (tanδ=0.017). As seen from Table
1, the double-layer Rsub is more resistive than the single-layer which indicates the
presence of power leakage into the substrate. This also contributes to lower the efficiency
as well as the read range. The plots in Figure 23 display the relationship between read
range and return loss. The amount of power that is radiated by the double-layer tag is
about 5 dB less than the single-layer. This explains why the read range of the double-
layer tag drops to almost half of the single-layer.
In contrast to UHF (i.e. 915 MHz applications) systems, the RF field at 13.56
MHz is not absorbed by water or human tissue, which allows operation through water or
human beings with the trade-off of having a larger physical size. The influence of the air
51
Single-layer Input Impedance
0.964
0.966
0.968
0.97
0.972
0.974
0.976
0.978
12 12.5 13 13.5 14 14.5 15
freq, MHz
Rea
l (S1
1)
0.16
0.18
0.2
0.22
0.24
Imag
(S11
)
Real part (measured)Real part (simulated)
Imag part (measured)Imag part (simulated)
Imagfreq=13.56 MHzImag(S11)=0.158
Realfreq=13.56 MHzReal(S11)=0.986
Imag
Real
Double-layer Input Impedance
0.94000
0.94500
0.95000
0.95500
0.96000
0.96500
0.97000
0.97500
12 12.5 13 13.5 14 14.5 15
freq, MHz
Rea
l (S1
1)
0.15000
0.17000
0.19000
0.21000
0.23000
0.25000
0.27000
0.29000
Imag
(S11
)
Real part (measured)Real part (simulated)Imag part (measured)Imag part (simulated)
Imagfreq=13.56 MHzImag(S11)=0.220
Realfreq=13.56 MHzReal(S11)=0.959
Real
Imag
52
Single-layer and Double-layer Return Loss
-10-9-8-7-6-5-4-3-2-10
12 12.5 13 13.5 14 14.5 15
freq, MHz
dB (S
11)
Single-layer Return loss(simulated)Single-layer Return loss(measured)Double-layer Return loss(simulated)Double-layer Return loss(measured)
Single-layer
Double-layer
Double-layerfreq=13.94 MHzdB(S11)= -3.811
Single-layerfreq=13.67 MHzdB(S11)= -9.077
Figure 23. The single-layer and double-layer input impedance (50 Ohm normalization) and return loss (28 kOhm normalization) results for 13.56 MHz HF RFID tag.
moisture on the performance and efficiency is also negligible [27].As a result of the near-
field operation of 13.56 MHz RFIDs (power decreases with 6th order of distance), the
disturbing influence of adjacent systems or external noise is much lower compared to
UHF systems (power level decreases as the square of the distance) [27], something
important in RFIDs for tire/pallet inventories.
53
3.2 Summary
Designing an inductor-coil embedded antenna for 13.56 MHz RFIDs present
various challenges such as the parasitic capacitance and dielectric material (i.e. PET)
limitations. The parasitic capacitance shifts the resonant frequency, so capacitance
compensation should be considered such as adding series pad capacitance to reduce the
effect. The dielectric materials used for these applications are generally very cheap yet
lossy. This weakens the read range performance of the tag. Better performing 13.56 MHz
RFID tags could be achieved by using less lossy dielectric materials and diminishing the
ill-effect of parasitic capacitance by introducing series pad capacitance. The efficiency of
the voltage transfer, which results from the inductive coupling between the reader and the
tag coils, can be increased significantly with high Q (highly inductive yet low resistive)
circuits. The read range of 13.56 MHz is relatively longer than that of 125 kHz device
because of the fact that the antenna efficiency increases as the frequency increases. In
addition to this, the growth of the 13.56 MHz RFID market has benefited from the better
performance of 13.56 MHz RFIDs compared to UHF RFIDs in complicated
environments that get affected by factors such as air humidity or presence of human
beings and water.
54
CHAPTER 4
915 MHz UHF RFID TAG DESIGN FOR AUTOMOTIVE TIRE
APPLICATION
The recent advances in cost-effective low-power electronics and packaging have
enabled the RFID tag as a likely substitute for barcodes [33, 34].The RFID tags also
present challenges in behavioral modeling and simulation of the antenna and
module/package integration in parameters such as the pad capacitance, the estimation of
the parasitics due to the proximity of IC and antenna, and the identification of a low-cost
low-loss light material.
In this chapter, three novel miniaturized antennas are presented for 915 MHz
passive tags that are designed to be embedded inside commercial automobile tires. The
necessary power required to energize and activate the tag’s microchip is drawn from the
electromagnetic field provided by the reader unit’s antenna. The transponder IC stores the
tire's unique ID, which can be associated with the vehicle identification number. The chip
also stores information about when and where the tire was made, its maximum inflation
pressure, size and so on. The tag utilizes the low cost lead frame based IC packaging
process and the miniaturized antenna is built in the lead frame.
Passive ICs are intrinsically highly reactive because of the necessary power to
bias the IC which is delivered by charging up the IC through electromagnetic coupling.
Due to the low resistive yet high capacitive impedance of the microchip, novel design
55
approach for the RFID antennas have to be proposed comprising of antennas that are
lowly resistive (high efficiency) and highly inductive for matching to the input
impedance of the transponder IC.
One remarkable improvement to bar code systems by RFID is the possibility to
read and write on the information-carrying element on the item. The transponder can
carry several kilobytes of data that can be 1) read selectively, 2) appended with new data
elements, and 3) modified, i.e. erased and overwritten. These features depend on the type
of tag used. The tag may have its own processor capable of performing complicated tasks
with the data stored in its memory. [27] Another important feature is the capability of the
RFID reader to interact with the tag with no line-of-sight since the tag is placed inside the
tire. If a tag is in the area reached by the reader, it can be detected and communicated
with. Thus, the identification of items can be achieved without having to unpack them.
This adds to the durability of the tag as well as to the convenience of easily reading each
item, as it does not have to be outside the package protecting the item.
An RFID tag of UHF band employs far-field radiation of the real power contained
in free-space propagating electromagnetic plane waves due to its shorter wavelength,
while a 13.56 MHz HF tags is utilizing inductive coupling in the near-field region as the
wavelength is much longer. The main difference is that in UHF systems the resistive part
of the radiating power is used to communicate with the passive tag where in HF systems
the reactive part of the radiating power is used. The IE3D design tool, which is based on
method of moments (MoM), is used to optimize and analyze the tag. This tool is used as
main platform to design and come up with certain antenna performance parameters such
as gain, radiation pattern, and efficiency. Three different 7cm x 3cm (equal in area or
56
smaller) antenna designs are built to make sure maximum range is obtained. Achieving
that range has been a challenge because the lossy tire rubber makes it harder to get an
impedance matching and creates additional power loss in the tire rubber. The tested tags
in actual tires yield maximum operational distance ranging from 48.7 cm to 52.5 cm
which is well within the required range (50 cm) for the application.
4.1 Design Approach
The IC input impedance for the tire application is 17-j350 Ω, which means the
load antenna impedance should be 17+j350 Ω for maximum power transfer (conjugate
matching). This requires the antenna impedance to be low- resistive yet high-inductive.
Various antenna designs like dipole, printed patch, log-spiral, and meander-line have
been proposed as a solution in the past.[13,14,15,35] Nevertheless, a novel approach has
to be followed to keep the antenna size small and the load impedance to have a low real
part (small resistance) and a high positive imaginary part (high inductance). To achieve
this, an inductive element needs to be incorporated into the antenna. In addition to this,
the metal size is desired to be as big as possible to obtain better radiation parameters such
as directivity and efficiency through the larger radiating aperture, though it could increase
the metal loss leading to a trade-off in the antenna efficiency. Increasing the metal size
also lowers the surface resistance and increases current flow as shown in Figure 24. It is
for these above-mentioned reasons, a dipole antenna with inductive stubs and a metal
patch is used as the basis for the three antenna designs of this paper. The stubs provide
the inductive load impedance meanwhile the metal patch lowers the load resistance.
57
To accomplish maximum directivity and optimum radiation, the designs are built
to achieve half-wavelength (λr/2 ~9 cm in rubber material @ 915 MHz) resonance at first.
Figure 24. Current flow in UHF RFID Tag antenna.
In essence, the designs possess similarity to the half-wave dipole antenna; however, there
exists a trade-off between antenna-IC matching and resonance. Whenever the size is
increased to match for resonance, antenna-IC matching deteriorates. The miniaturization
of the antenna size is another issue, which requires the length of the antenna to be smaller
than the resonance length.
4.2 Antenna Design
The three RFID Tag antenna designs are shown in Figure 25. These antennas are
made of copper metal with a thickness of 200 um. The antenna is embedded inside tire
material that is basically rubber. (εr =3.0, tanδ=0.02) In addition to this, one-port
differential excitation, which is used to measure the actual antenna-IC configuration, is
employed to numerically calculate the return loss and antenna load impedance as well as
the read range measurement.
58
The single inductor stub as shown in Figure 25b is utilized to obtain the required
inductance where the triangular patch is the main radiator for Antenna#2. The other two
(a) Antenna#1 where minimum line spacing is 1.5 mm with W=14.5 mm, L=56 mm, 2 mm port separation, and trace width of 0.5 mm.
(b) Antenna#2 where minimum line spacing is 0.5 mm with W=30 mm, L=60 mm, 2 mm port separation and trace width of 0.5 mm.
(c) Antenna#3 where minimum line spacing is 0.5 mm with W=12 mm, L=67 mm, 2 mm port separation and trace width of 0.5 mm.
Figure 25. The three different RFID antenna designs for tire application.
59
designs utilize double stub configurations. Antenna#1 and Antenna#3 as shown in Figure
25a,c are also highly inductive due to the double stubs that are easily incorporated into
the radiator rectangular patches. This feature is proven to be very important to enhance
radiation because the inductive stub, which is used for antenna-IC reactance matching,
becomes more part of the radiating element by creating additional coupling with the
radiating element.
4.3 Embedding Process
The tire cross-section is displayed in Figure 26 showing the dimensions of the
tire, the rubber
Figure 26. Cross-sectional view of RFID Tag placement in tire material.
60
material, and the steel thicknesses. The position of the RFID Tag is also presented. The
tag is placed parallel to the outer steel mesh at a distance that depends on the tire size and
ranges between 4 to 8 cm above the inner steel mesh.
4.4 Antenna Results and Discussion
The radiation patterns for the three designs in tire rubber are shown in Figure 27.
All of the designs have doughnut-shaped radiation patterns in the phi=0 deg (x-z plane)
and phi=90 deg (y-z plane) planes as expected since the antennas are dipole type. The
creation of nulls in the horizontal plane (x-y plane) with dipole type of antennas is a
limiting factor. It is actually desired to achieve maximum radiation when the tag is read
in the plane (x-z or y-z planes) that is perpendicular to the RFID antenna. The horizontal
radiation is also crucial in terms of the orientation of the reader. The Interrogator (reader)
does not necessarily have to be positioned on top or bottom with respect to the RFID tag,
but the tire RFID tag should also have the functionality to be read from the sides as well.
In addition to this, the radiation pattern is suppressed and more in the horizontal plane (x-
y plane) when the tag is embedded in actual tire with the steel meshes. The steel meshes
that protect the tire from deformation act like two metal plates creating the waveguide
effect. For this reason, a second antenna tag can be placed as close as possible to the side
surface of the tire perpendicular to the parallel configuration displayed in Figure 27. The
dual polarization (horizontal and vertical) capture will improve the detection in the
direction vertical to the antenna (z-axis) where antenna is least likely to be read. Utilizing
two orthogonal tags (x-y horizontal plane and y-z/x-z vertical plane) would overcome this
obstacle in
61
(a) antenna#1
(b) antenna#2
62
(c) antenna#3
Figure 27. E-phi=0 (x-z) and E-phi=90 (y-z) planes radiation patterns (Directivity vs. elevation angle theta) for the three 915 MHz UHF antenna designs in tire material. Antennas are located in the horizontal plane.
case the application requires effective radiation characteristics in the horizontal plane.
63
(a) antenna#1
(b) antenna#2
64
(c) antenna#3
Figure 28. S11 input load impedance Smith chart (50-Ohm reference) plots for the three 915 MHz UHF antenna designs in tire material (range of frequency= 500-1500 MHz).
The antenna load impedances for the three antennas are shown in Figure 28,
verifying that they are high-inductive and low-resistive. The load impedance values are
displayed in Table 2 along with other radiation parameters namely
Table 2. Simulated antenna parameters and measured read range.
65
return loss, directivity, radiation efficiency, and read range in tire material and in actual
tire. As it can be seen from Table 2, the antenna efficiency determines how much
operational distance is needed for the tag. For example, although Antenna#2 and
Antenna#3 exhibit almost the same return loss and directivity, the read range is higher for
Antenna#3 due to higher radiation efficiency of this antenna. Still, the read range does
not only depend on the efficiency of the radiating antenna.
The first set of read ranges as presented in Table 2 are measured only with RFID
tag in tire material. When the tag is embedded in actual commercial tires, Antenna#1,#2,
and #3 yield operational distances of 52.8, 48.7, 52.0 cm respectively. The application
requires a read range of 50 cm due to anti-collision limitations, so the three designs are
acceptable including antenna#2 which requires further minor optimization. The reason
for the read range reduction is the presence of the steel meshes on the inner and outer
surfaces of the tire.
Further efficiency improvement can be accomplished in three ways: 1) Create
more coupling by surrounding the radiating patch with the inductive stub. The stubs that
enclose or join with the patch generate more current flow which enables the antenna to
radiate more. 2) Make the inductive stub more integrated with the radiating patch by
joining the stub and the patch. 3) Use a less lossy dielectric material which would
minimize excitation of substrate modes and power leakage into the dielectric.
66
4.5 Summary
Three novel antennas have been shown for 915 MHz UHF RFID applications for
tires. These antennas with low resistance and high inductance for the input impedance
provide a good example of a design procedure if the load impedance from the
transponder is unusually high in capacitance and low in resistance. The tag size plays a
major role in determining the read range: The smaller the tag, the smaller the energy
capture area, therefore the shorter the read range, especially complicated lossy media
such as tires. A proper design of the system and a thorough optimization of the
interrogator power, the antenna positioning and orientation, and an optimum tag in-tire
positioning helps to alleviate this limitation. Multiple tagging can be used to improve the
detection of the tags in both the horizontal and vertical planes. It has been observed that
the effective read range also depends on the absorption/attenuation factor of the type of
the material in which the tag is embedded.
67
CHAPTER 5
HIGH-EFFICIENCY 915 MHz UHF RFID TAG DESIGN ON LIQUID
CRYSTAL POLYMER (LCP) SUBSTRATE WITH HIGH READ-
RANGE CAPABILITY
The demand for flexible antennas with higher efficiency and more compact size
has increased in the recent years mainly due to the requirements for a higher and higher
read range performance of the increasingly used RFID tags and their almost ubiquitous
presence in the industry in security-related applications.
The passive UHF RFID tags see the widest use in supply-chain and retail
applications. One of the biggest advantages of passive UHF tags over the higher
frequency tags (i.e. 2.45 GHz RFID tags) is that they have a range, in many environments,
of over ten feet (and sometimes as much as tens of feet). Additionally, RFID readers can
scan hundreds of UHF tags simultaneously, whereas the lower frequency tags (VLF, LF,
and HF bands), already suffering from limited read range (~1-2 feet), can handle about
10% of that scanning capacity with a lower data transfer rate.
The proposed 915 MHz RFID tag employs far-field coupling of the real power
contained in free-space propagating electromagnetic plane waves due to its shorter
wavelength than, for example, the 13.56 MHz HF tags, where the inductive coupling of
the transponder tag operates in the near-field as the wavelength is much longer. The IE3D
and HFSS design tools are used to perform a system-level optimization of the tag, as well
68
as to design and come up with certain antenna performance parameters such as directivity,
radiation pattern, and efficiency.
In this chapter, the design and development of a unique high read-range high-
efficiency (95%) RFID antenna for the 915 MHZ UHF band is discussed. The RFID
exceptional characteristics are investigated in terms of antenna-IC matching and radiation
efficiency. This 915 MHz passive tag is a 3” x 3” omni-directional tag and yielded a read
range of 31 feet compared to a 4” x 4” leading commercial design of 26 feet tested range
in lab. This tag also possesses higher read power range (-7dBm to 30 dBm) than the
leading commercial design (-5dBm to 30 dBm). The proposed RFID antenna was
fabricated on 50.8 micron thick Liquid Crystal Polymer (LCP) and the read range of the
proposed RFID tags was experimentally verified.
5.1 Antenna Structure and Design Approach
The RFID antenna structure is shown in Figure 29. The single dipole antenna is
Figure 29. 915 MHz UHF RFID s-shape antenna structure and double inductive stub
matching network.
69
comprised of a resistive shorting stub with length j and width i, a double inductive stub,
and a radiating body. The 250-bit read/write chip is mounted on the 4 ports, namely RF1,
RF2, Vdd, and Vss at the feeding point as presented in Figure 29. RF1 and RF2 ports are
the RF signal terminals. Vdd is the open port to measure the IC bias voltage and Vss is the
ground port. The chip is designed to be operational with both single and dual dipole
antennas. The RF signal ports RF1 and RF2 are needed to be shorted to deliver the
information to the charge pump in the IC with the same phase. Time delay of the same
signal at the two RF ports leads to loss of information. For the single dipole antenna, RF2
port is grounded so that signal-ground (S-G) type of excitation can be created at the
feeding point.
It is crucial to achieve high radiation efficiency for high read range since most
commercial RFID antennas suffer from low efficiencies (~50-60%) [36]. In order to
accomplish maximum directivity and optimum radiation, the design is built to achieve
half-wavelength (λr /2 ~16 cm in air @ 915 MHz) resonance at first. This was taken about
to be the maximum length when the dipole antenna is stretched from one end to the other.
The tapered design is proposed to obtain a smoother transition from the connecting RF1
and RF2 pads of the IC at the interface to the single dipole antenna to reduce reflections
as much as possible. Another benefit from this tapering is used to maintain the high-
efficiency when the antenna is embedded in a dielectric material such as LCP, although
LCP’s dielectric constant (~3) is close to the free space.
The overall matching network is designed to conjugately match a chip impedance
of 73-j113 for maximum power delivery. The resistive shorting stub and the double
inductive stub make up the overall matching network to match to the chip input
70
impedance. The shorting stub mainly controls the resistive matching and the double
inductive stub controls the reactive matching. The double inductive stub structure is
composed of two inductive stubs to provide symmetry on both sides of the RFID tag [37].
In Figure 30 the fabricated 18 um thick copper antenna on flexible, low-cost, and
Figure 30. Fabricated 915 MHz UHF RFID s-shape antenna and antenna direction of current flow.
easily manufacturable LCP (εr =3.16, tanδ=0.00192) with 50.8 um thickness is shown.
The antenna can be used for sensor applications. For this reason, the antenna is also
designed to accommodate space for other surface components such as a sensor module
and a battery with minimum interference to the overall antenna performance.
5.2 Experimental Results and Discussion
The RFID antenna performance parameters are displayed in Table 3 below. The
calculated return loss [38] values at 915 MHz based on the 73-j113 Ω chip impedance for
the simulated and measured antennas are -15.97 dB and -13.78 dB respectively. One
major factor for the high efficiency is because of the way the current flow is directed as
71
presented in Figure 30. Since the direction of current flow in the top and bottom parts of
Table 3. S-shape RFID antenna performance parameters and measured read range.
the antenna always add up constructively for far-field radiation, the radiation efficiency is
maximized. The 5% loss in efficiency is mainly due to the amount of radiation loss in the
matching network. The RFID tag was also tested for read/write power levels. The read
power range was from -7 dBm to 30 dBm and the pattern generator was able to write
250-bit user data to the memory of the chip for power levels above 2 dBm. The length j
of the antenna’s shorting stub was reduced to half of the original length to observe the
performance difference. The simulated input impedance of the antenna becomes
44+j100.1 Ω. The resistance drops dramatically (higher return loss); meanwhile, the
inductance stays almost the same as expected. When this tag was tested, power levels
were from -5 to 29 dBm for reading and 3 dBm for writing. The read range was measured
to be close to 30 feet (9.14 m) in a room.This shows the effect of power transmission loss
between the antenna and the matching network. More power is needed to write on the
chip because of this loss in the matching network. Although the efficiency stays the same
(95%) compared to the original antenna in Table 3, read range is decreased due to the
lower real part of the radiated power. The input impedance resistance goes down from
Input Impedance (Simulated)
Input Impedance (Measured) Directivity Efficiency
Measured Read Range in Lab
59.7+j96.4 Ω 49 + j106 Ω 2.18 dBi 95 % 31 feet (9.45 m)
72
59.7 Ω to 44 Ω which translates as lower resistive power transfer at the antenna+IC
interface.
The input impedance of the simulated antenna design is shown in Figure 31. As it
can be observed from the plot, the phase angle between resistance and inductance of the
Input Impedance
0
50
100
150
200
250
300
350
0.7 0.8 0.9 1 1.1 1.2
freq (GHz)
Rea
l (O
hm)
0
50
100
150
200
250
300
350
Imag
(Ohm
)
real
imag
Figure 31. Input impedance of the simulated 915 MHz UHF RFID s-shape antenna.
antenna input impedance (Zant =59.7 +j96.4) is lower around 915 MHz compared to
inductively coupled feed [39] matching networks. Antennas designed using inductively
coupled feed structures yield high phase angles (i.e. Zant = 6.2 +j127). As explained in the
paper [39], at resonance the resistive part of the input impedance of the antenna Ra
depends only on the mutual coupling M; meanwhile, the inductance Xa is dependent on
the inductive loop inductance Lloop. Ra is actually not only dependent on the M but also
on the antenna resistance Rrb. High Rrb causes low input impedance resistance. Since the
antenna shape defines Rrb, low Rrb might not be achieved with some designs such as the
73
one presented in [39]. For this reason, a matching network that is composed of a shorting
stub to control input impedance resistance Ra and a double inductive stub to control
inductance Xa is proposed.
In Figure 32 the 2-D and 3-D radiation plots are shown. The 3-D radiation pattern
of the antenna is doughnut-shaped as expected for the general radiation pattern for a half-
Figure 32. 3-D and 2-D far-field radiation plots for 915 MHz UHF s-shape antenna.
74
wavelength dipole. The 2-D polar plot shows the radiation in the two different planar cuts
for the x-z plane (φ=0 deg) and the y-z plane (φ=90 deg) with angle θ that varies from 0
to 360 degrees. The pattern is almost omni-directional with two nulls in the whole 360
degree coverage area that add up to be less than 10 degrees. This pattern mimics the
radiation pattern of a half-wavelength dipole antenna as it is a tapered dipole antenna.
The nulls lay horizontal to the x-y plane where the RFID tag is least expected to
transmit/receive information from the reader.
5.3 Bandwidth Optimization
In order to realize high-bandwidth UHF RFID tags that cover the 860-930 MHz
band, one proposed idea is to operate outside the self-resonance peak resulting in a more
flat impedance response against frequency as shown in Figure 33. This yields to a
Figure 33. Simulated input impedance of the 915 MHz UHF s-shape antenna.
-2000
-1000
0
1000
2000
3000
4000
5000
0.5 0.6 0.7 0.8 0.9 1 1.1 1.2
Frequency (GHz)
Impe
danc
e (O
hm)
ResistanceReactance
UHF RFID Frequency Band
75
bandwidth of ~ 8% which is predominantly realized by the finite slope of the reactance of
the antenna in the frequency of interest. The previously shown design in Figure 29 is
modified to achieve the above-mentioned bandwidth. This is presented in Figure 34
where the resistive shorting stub and double inductive stub were tuned to accomplish the
Figure 34. 915 MHz UHF RFID s-shape antenna structure with optimized bandwidth
showing the matching stubs.
Double Inductive Stub
Resistive Stub
Terminals for IC Radiating body
76
-30
-25
-20
-15
-10
-5
0
0.85 0.87 0.89 0.91 0.93 0.95
Frequency (GHz)
Ret
urn
Loss
(dB
)
MeasurementSimulation
bandwidth of 70 MHz.
The simulated impedance at the center frequency f0= 895 MHz is 57.46+j112.1
which results in a return loss RL<-18dB. This antenna has a bandwidth of ~8% (70 MHz)
where the bandwidth is defined by a Voltage Standing Wave Ratio (VSWR) of 2
(alternatively a RL of -9.6 dB) as shown in Figure 35. The tapering of this s-shaped
antenna along with the matching techniques (resistive and inductive stubs) allow for the
first-ever 3 in x 3 in RFID antenna with such a high bandwidth (~8%).
Figure 35. Measured and simulated data of return loss for the 915 MHz UHF
s-shape antenna.
77
The circuit model of this design in Figure 34 is a lumped element equivalent circuit
model and shown in Figure 36. This model can be used to figure out the lumped component
Figure 36. Equivalent circuit for 915 MHz UHF s-shape antenna structure shown
in Figure 28.
equivalent circuit to any dipole antenna design. Table 4 presents the lumped element
Rs (Ω) Rp (Ω) Ls (nH) Cp (pF) Rs2 (Ω) Rp2 (Ω) Ls2 (nH) C p2 (pF) CE (pF)
S-shape 17.0 72.8 47.4 0.29 1.66 0.67 33.6 0.0225 0.45
Opt. BW s-shape
12.0 60.0 48.8 0.30 ~0 0.25 62.35 0.245 0.47
Table 4. Lumped element model values for the s-shape and the bandwidth optimized s-shape designs.
values for the model in Figure 36. The equivalent circuit shows how stubs can be used to
tune the impedance in order to match to any IC. Parametric sweeps can be used along
Rs: antenna series resistance (due to metal effects) Ls : antenna series inductance (due to metal effects) RP : tag parallel resistance (due to substrate + metal effects) CP : tag parallel capacitance (due to substrate + metal effects) RS2 : resistive stub series resistance LS2 : resistive stub series inductance RP2 : resistive stub parallel resistance CP2 : resistive stub parallel capacitance CTag : capacitive coupling (CE, LCP // CE ,air)
78
different stubs structures (for example loops structures can be used for adding series
inductance or parallel capacitance). The resistance of the antenna is mainly determined
by the radiating body and can be tuned by the two stubs as shown above. This model also
helps to determine the amount of loss (as parallel resistance and capacitance) due to the
substrate loss which helps in understanding radiation efficiency as a function of the
substrate.
79
5.4 Summary
Maximum read range can be achieved when the dipole RFID antenna is half-
wavelength resonant and has direction of current flow that adds up constructively. The
tag size also plays a major role in determining the read range: The larger the tag, the
larger the energy capture area, therefore the longer the read range. One major difficulty in
RFID tag design is designing the matching network since the chips come with either high
or low input impedance phase angles. (i.e. Philips EPC 1.19 ASIC Zc=16-j350, NSC
MM9647 Zc=73-j113). This requires matching networks to be easily tunable for these
different IC input impedance values. For this reason the proposed matching network
topology can be utilized. In the meantime, the serial stub matching method achieves high
bandwidth (~8%) covering the European and Asian bands (860-930 MHz) something
quite important for multiband/multistandard RFIDs. The universal operations of the
RFIDs necessitate the use of wideband antennas with optimized performance in terms of
radiation pattern, efficiency, and gain.
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CHAPTER 6
PORT OF SAVANNAH ACTIVE 915 MHZ UHF RFID TAG-
READER SYSTEM FOR CONTAINER TRACKING FIELD STUDY
Recently in the past couple months a lot of media attention has been brought on
the security issues by the Dubai Ports World deal with the ports in the U.S.A. as well as
any other port in the world. Former U.S. Customs and Border Protection Commissioner
Robert Bonner described the situation with the ports where only less than 1% of the
incoming containers can be checked as the “Trojan horse of the 21st century.” [40] Due to
large scale global economy, cargo containers carry approximately 90% of the world’s
trade. Only in the U.S.A. almost half of the incoming trade (by value) arrives in the U.S.
ports by containers onboard ships which is equivalent to nearly 11 million cargo
containers each year [41]. Detailed inspection of these containers upon arrival into the
U.S.A. is simply impossible, so active RFID technology is proposed as a solution to track
these containers.
This chapter focuses on an active RFID field test that took place in the Georgia
Port Authority’s (GPA) port of Savannah as shown in Figure 37. The Port of Savannah,
home to the largest single-terminal container facility of its kind on the U.S. East and Gulf
coasts, is comprised of two modern, deepwater terminals: Garden City Terminal and
Ocean Terminal. Together, these facilities exemplify the GPA's exacting standards of
efficiency and productivity. Garden City Terminal is one of the top five container
handling facilities in the United States, encompassing more than 1,200 acres and moving
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millions of tons of containerized cargo annually. Port of Savannah is the nation’s 3rd
largest port in terms of container handling capacity which is about 2 million a year.
Figure 37. The Port of Savannah.
6.1 Introduction
The purpose of the savannah port test was to show the feasibility of container
detection utilizing active tags instead of passive tags. In order to do this a field study was
conducted to detect the tags placed on the containers in the stack at numerous locations as
shown in Figure 38.
Passive tags have limited read ranges (max ~3-4 m ideally) since they don’t use
internal power source (i.e. battery).They depend on the external power radiated from the
reader. When these tags are placed close to metal containers, they suffer from increased
performance degradation. Radiation around the antenna gets distorted and the amount of
power received/transmitted gets really low. This causes read ranges (<1 m) that are even
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Figure 38. Graphical view of tag placement on containers, container placement in stack,
and reader position (Courtesy of CarrierWeb).
Tag Pattern 1: 4 tags on side
edges
Tag Pattern 2: 4 tags as shown
Tag Pattern 3: 4 tags on faces
Tag Pattern 4: 4 tags on faces
Tag Pattern 5: 4 tags on
vertical corners
Reader Pattern: Readings at 8’, 16’, 25’ high
& at each of: Street positions every 20’ and 40’
along street.
83
lower than the ideal case. On the other hand, active tags can handle the metal surface
reflections better. The active tags can be detected ideally up to 100 m. The reflection of
power due to the metal surface is also present with the active tags; however, the tags
utilize internal power to communicate with the reader. This will reduce the possible read
range (min ~30-40 m) but definitely not as low as the passive tag case. In addition to this,
the antenna/IC impedance matching in active tags, which regulates how much power is
transmitted/received internally from the antenna to the IC in the RFID tag module, does
not get affected as significantly as it does with the passive tags in the presence of the
metal close to the tag. For these reasons, the active tag RFID solution is definitely the
better solution compared to the passive tag.
Read range and orientation sensitivity (polarization) are the most important
Figure 38. 2-D radiation patterns for active tag or reader.
84
factors for the tracking of containers. Read range is simply how far away a standard
interrogator can read a tag. Orientation sensitivity means how much the read performance
degrades when the orientation, or angle, of the tag to the interrogator changes. ( i.e. the
presence of metal or surface reflections) An orientation-insensitive tag will work the
same way regardless of how the tag is rotated. An orientation-sensitive tag will work well
at some angles, but it may become completely invisible at other angles as presented in
Figure 38. The size of that "angle of invisibility" is called the null zone of the tag. If the
orientation of the tag can't be controlled, large null zones can be problematic because the
tag cannot be read. If multiple tagging is used so that different tag orientation can be
achieved, the problem of null zones can be mitigated.
6.2 Brief Summary of Conducted Tests
In order to prove the concept, two different types of tests were conducted as
shown in Table 6 of Appendix B. The first test was to test the detection of tags on the
containers facing F1 and F2. The layout of this test is presented in Figure 39 of Appendix
B. This test was done with different reader heights to detect tags in 4 pattern
configurations (patterns 2, 3, 4, 5). Pattern 1 test was also conducted to observe if the tags
in the vertical column in the center of the container stack can be detected (Table 5
Appendix B). This was carried out to understand what the effect of reader height and
distance on tag detection and observe the trend with these changes. The second test
(Appendix B Figure 40) was to observe the canyon (waveguide) effect (horizontal row)
where the corridors in between the container stacks cause the reader power to bounce off
from one side to the other as shown in Figure 41.
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Figure 41. The Canyon effect for detection of active 915 MHz UHF RFID tags in the middle container stack.
6.2.1 Tag-reader Response Test on F1 & F2
6.2.1.1 F1 & F2 Test
Patterns 1 (container stack in the middle at Bay 64, position 3), 3 (column at corner of
F 1 and F2), 4 (5 containers in #2 height on F1) and 5 (5 containers on vertical corners
on F 1)
The tests were conducted at three heights (8ft, 16 ft, and 25ft). Location 1 seemed
to read the most amount of tags since it is in the corner of F1 & F2. The most amount of
reads were observed at 8 ft rather than 16 ft or 25 ft. The reason is that the distance from
the reader to the stack is too short at 8 ft. This makes the reader more directive (power is
more focusing on one portion of the sweep angle).The reflection of the generated waves
are more focused on the lower stack since the reader-stack distance is short. Most of the
86
tags are also in the bottom layers. These can still be read; however, at higher reader
levels the distance of the reader from the stack needs to be also increased. This will
improve the distribution of signal power more omni-directional and enhance the
performance.
The overall performance of the pattern 5 compared to the patterns 3 and 4 is
definitely better. When the reader is moved from location 1 to 5 and 6, the readability of
tags increased. This shows that by placing the reader almost in the middle of F1,
detection of tags on that side can be optimized. The reason why pattern 5 performed
better than the other two patterns is because of the polarization of the tags and the reader.
The reader is linearly polarized (vertical or horizontal). The tags are now directional
Figure 42. Radiation patterns in x-z planes with (RIGHT) and without (LEFT) metal surface.
87
pointing outwards from the metal surface instead of being omni-directional when no
metal is present as displayed in Figure 42. This restricts the tags to only one polarization
(vertical or horizontal) depending on which side of the container they are placed. This is
very critical when the reader and the tag orientations are different. For example,
minimum detection is observed (patterns 3, 4) with reader since most of the tags on the
containers are horizontally polarized meanwhile the reader is vertically polarized.
When the incoming wave and the antenna polarization are perpendicular as shown
in Figure 42 top drawing creates no reception at the reader or tag. The traveling waves
from the reader to the active tag must arrive at an angle other than 90 degrees
(orthogonal waves). The bottom drawing in Figure 37 shows the maximum
reception/transmission case. Pattern 1 also suffered mainly because of this polarization
Figure 43. Tag/Reader orientation sensitivity (polarization).
88
loss. Pattern 2 test also showed that even if the tags are on one face and in close
proximity to each other almost each and every one of them can be read. Higher detection
can be successfully achieved by increasing the processing time.
6.2.1.2 Canyon (Waveguide) effect test
Patterns 2 (4 containers on F 2 at height 3) and 3 (column at corner of F 1 and F 2)
The last three tests that were conducted were to prove that waveguiding of the
plane waves occur by reading the tags in between containers. The reflection of the
propagating waves in between the containers creates the rectangular waveguide mode.
This channel effect as well as the instigation of surface waves (creepy waves) due to the
proximity of the traveling waves to conductive surface (containers) improves the
detection of the active tags. Even cellular phone that operates at 900 MHz was
receiving/transmitting full when tested along the corridors between the container stacks.
The height of the reader plays a major role for the detection: the higher the reader,
the further the reader can read. Although there is collision of the tags, 4 out of 5 tags
were read at 25ft and only 3 out of 5 at 8ft. This shows that the reader must be placed
higher at least 40ft or higher depending on further empirical test data. Here the trend is
important and is being proven. Canyon effect can be achieved when the reader is placed
high (i.e light posts) enough for the traveling wave to go through the container stacks.
Surface waves will also improve this. Another important point is that even if the tags
were positioned in the middle of or on the edges of the container surfaces, not much of
difference was observed. These two configurations seemed to behave the same way.
89
Anti-collision of tags in the reader processor is also a very important issue as well
as the coupling effect (electromagnetic interference of one tag on the other). It was also
observed that 5 min tests yielded better results than the 3 min tests. The reason is that the
probability of detection increases with increased time. This is intrinsic to the processor.
This is generic with all the test setups. Ample time is needed for the reader processor.
Recommended time is 7-10 min but the longer the time the better the readability of tags.
90
6.2 Summary
This conducted field study at the port of Savannah was of great benefit to realize
the challenges in such a harsh environment. Especially rugged metal containers create
increased level of difficulty for RFID tag detection. In order to improve the performance
of the active RFID system and implement it successfully, the following steps must be
taken into account:
1) The readers must be positioned higher than 30 feet. Putting the readers on the light
posts (~90 feet) could solve this problem depending how far they are from the
container stacks.
2) The readers have to be positioned pointing downwards and radiation pattern should
be changed from omni-directional to directional utilizing reflectors as shown below
in Figure 44. Beta angle can be made smaller (i.e. Beta from 60 degrees to 45
degrees) to control the directionality of the reader. The general trend is the smaller
the angle, the smaller the beamwidth, the more directional the reader becomes. If the
reader becomes more directional, more power gain is achieved. This results in higher
read range and detection probability. When two readers are positioned next to each
Figure 44. Top view of the reader and reflector position for active 915 MHz UHF RFID system.
91
other, with this configuration least amount of electromagnetic coupling between the
readers will be accomplished. This will lead to overall RFID tag system performance
enhancement.
3) Multiple readers are needed to read the tags in different orientations. For instance, 2-
3 readers positioned equally in between the edges of of F1 and F2 at a level at least
higher than the maximum stack height (5 containers stacked up on top of each other)
is one possible way of achieving maximum detection. Reader synchronization can
be utilized for readers that are close to each other.
4) Processing time of 7-10 min is required for anti-collision avoidance. If system can
handle longer time, that is more preferred.
5) The distance of the readers from the edge of the containers is also critical. By
moving the reader far away from the metal will minimize the reception of reflected
power at the reader. This needs to be tested empirically.
6) Even if the tags were placed side by side (pattern 2) or one after the other (canyon
effect), the tags were detected almost completely.
7) With this type of reader orientation, pattern 5 configuration seems to be the best
solution for the detection. When the tags are placed on the edges, canyon effect
detection will also be maximized.
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CHAPTER 7
CONCLUSIONS
The main objective of this thesis has been to develop and optimize RFID antennas
for passive 13.56 MHz HF and 915 MHz UHF tags as well as understanding the effects
of harsh environments on active 915 MHz UHF RFID technology. The popularity of
these two bands have shown that optimization techniques will be of great interest in the
various different RFID applications from inventory control to container tracking.
The miniaturization technique of using two inductors connected serially for 13.56
MHz HF tags can be utilized for even lower 125 kHz range. This technique can be used
as long as the fact that substrate material loss is not neglected. Further improvement in
near-field radiation can also be achieved with substrates that have magnetic properties by
embedding ferrite particles in the substrate. This is beneficial for both radiation
optimization and size reduction.
Passive tags that operate in the passive UHF range usually suffer from poor
impedance matching at the antenna-IC interface. The ICs come in with different
impedances. This is one of the greatest challenges when designing the antenna for such
IC. This thesis showed that the resistive stub and double inductive stub techniques can
accomplish conjugate matching to any IC input impedance. Antenna’s radiation
properties are also critical for the UHF band since the environmental interference (i.e.
metals, liquids, human body absorption) affect more this band than the HF or lower
bands. This requires the designer to enhance antenna radiation characteristics such as
radiation pattern, radiation efficiency and gain by improving the current flow on the
93
antenna. The loss in the medium sometimes cannot be controlled, so optimum
performance must be attained as discussed in previous chapters.
Even the active tags undergo similar challenges from the environment
surrounding the tag-reader system. The conducted field study at the port of Savannah,
GA has revealed that one must comprehend the obstacles from a higher system point of
view not only at the lower tag design level. The problematic interaction between the
reader and the tag presents the real complication to a successfully operating RFID
application.
In RFID technology every application comes with different and sometimes unique
challenges. In today’s world transfer of information is increasing day by day. The same
pattern is repeated with the RFID technology. The need to gather more information and
store demands higher data rates and storage capacities. Integration of tags with other
active modules such as sensors (i.e. temperature, pressure) with batteries has caught a lot
of attention lately. This means greater challenges are imminent in terms of packaging
constraints and frequency limitations.
94
APPENDIX A
LIST OF PUBLICATIONS
[1] S. S. Basat, S. Bhattacharya, Li Yang, A. Rida, M. M. Tentzeris, J. Laskar, “Design of a Novel High-Efficiency UHF RFID Antenna on Flexible LCP Substrate with High Read-Range Capability”, Proc. of the 2006 IEEE-APS Symposium Albuquerque, AZ, July 2006.
[2] S. Basat, S. Bhattacharya, A. Rida, S. Johnston, L. Yang, M.M. Tentzeris, J. Laskar, “Fabrication and Assembly of a Novel High-Efficiency UHF RFID Tag on Flexible LCP Substrate”, Proc. of the 2006 IEEE-ECTC Symposium San Diego,CA, May 2006.
[3] Li Yang, Serkan Basat, Amin Rida, M.M. Tentzeris, “Design and Development of Novel Miniaturized UHF RFID Tags on Ultra-low-cost Paper-based Substrates”, 2007 IEEE-APMC Conference Thailand, Bangkok Dec 2007.
[4] Antonio Ferrer-Vidal, Amin Rida, Serkan Basat, Li Yang, M.M. Tentzeris “Integration of Sensors and RFIDs on Ultra-low-cost Paper-based Substrates for Wireless Sensors Networks Applications”, 2006 IEEE-SECON Conference Reston,VA, Sep 2006.
[5] RongLin Li, S. Basat, J. Laskar, and M. M. Tentzeris, “Development of wideband circularly polarized square- and rectangular-loop antennas”, 2006 IEE Proc. Microwaves, Antennas & Propagation , Jan. 2006.
[6] S.S.Basat, K.Lim, J.Laskar and M.M.Tentzeris, "Design and Modeling of Embedded 13.56 MHz RFID Antennas" , Procs. of the 2005 IEEE-APS Symposium, pp.64-67, vol.4B, Washington, DC, July 2005.
[7] S.Basat, K.Lim, I.Kim, J.Laskar, M.M.Tentzeris, Y.Kim, S.Lim and B.Chung, “Design and Development of a Miniaturized Embedded UHF RFID Tag for Automotive Tire Applications”, Procs. of the 2005 IEEE-ECTC Symposium , pp.867-870, Orlando, FL, June 2005.
[8] N.Bushyager, L.Martin, S.Khushrushahi, S.Basat and M.M.Tentzeris, “Design of RF and Wireless Packages Using Fast Hybrid Electromagnetic/Statistical Methods”, Proc. of the 2003 IEEE-ECTC Symposium, pp.1546-1549, New Orleans, LA, May 2003.
95
APPENDIX B
PORT OF SAVANNAH FIELD TEST SET-UP AND TABULATED
DATA
Pattern 5 (5 containers on ground level on Face 1) TAG POSITION Container Number Bay Position Height 1 2 3 4 HLUX 221126-2 59 1 1 1814 13C9 137E 137CHLUX 316405-7 61 1 1 1832 135A 1148 136EZCSU 811148-5 64 1 1 136F 1360 138E 13B2CLHU 851935-5 68 1 1 FEC F4E 134E ECO HLXU 452424-5 72 1 1 F4B 1097 133F 13A6 See Test Plan in Figure 32 for illustration of tag positions for each pattern. Face 1 of our stack is the side where pattern 4 and 5 containers are positioned. Face 2 of our stack is the end where pattern 2 containers are positioned Face 3 of our stack is the face opposite Face 1. Face 4 of our stack is opposite Face 2. The Bay 59 is the bay where containers on Face 2 are stacked. Bay 61 is the second row of containers moving back from Face 2 Bay 64 is the third row of container moving back from Face 2 Bay 68 is the fourth row of containers moving back from Face 2 Bay 72 is the fifth row of containers moving back from Face 2 Position 1 is the first row of containers on Face 1 Position 2 is the second row of containers moving back from Face 1 Position 3 is the third row of containers moving back from Face 1 Position 4 is the fourth row of containers moving back from Face 1 Position 5 is the fifth row of containers moving back from Face 1 Height 1 is the ground level container in any stack. Height 2, 3, 4, 5, etc are respectively moving higher in any stack Container are positioned by the Bay number, the position number, and the height number. Pattern 4 (5 containers in #2 height onFace 1) TAG POSITION Container Number Bay Position Height 1 2 3 4 COPU 236440-2 59 1 2 1821 1344 1397 1813HLXU 260561-0 61 1 2 None 17FD 13BE 684 TCKU 934866-2 64 1 2 11D5 1817 F45 1346TCKU 966695-6 68 1 2 13AB 13AF 10BD 183DHLXU 457117-0 72 1 2 1809 1190 1391 1027
96
Pattern 3 (Column at corner of Face 1 and 2) TAG POSITION Container Number Bay Position Height 1 2 3 4 HLXU 221126-2 59 1 1 182D 1838 180B NONECOPU 236440-2 59 1 2 1821 1344 1397 1813NYKU 257254-0 59 1 3 1133 1833 13BF 1821TTNU 335697-1 59 1 4 1343 1820 1803 1133TTNU 198038-2 59 1 5 1021 1340 1366 1343 Pattern 2 (5 containers across Face 2 at height 3) TAG POSITION Container Number Bay Position Height 1 2 3 4 NYKU 257254-0 59 1 3 182D 182E 13A7 13C! PONU 018719-7 59 2 3 1352 ECF 1810 1369NYKU 263405-0 59 3 3 1379 1361 13B7 13A2NYKU 256927-4 59 4 3 1373 1356 17FA 1364TTNU 318245-8 59 5 3 13BO 137F 1348 13A1 Pattern 1 ( container stack in the middle at Bay 64, Position 3) TAG POSITION Container Number Bay Position Height 1 2 3 4 TTNU 583003-5 64 3 1 17F9 13A8 11A8 NONEGATU 861360-4 64 3 2 13AD 13C8 136D 13A9TCKU 931425-6 64 3 3 17FE 138D 1837 1385TCNU 954041-1 64 3 4 927 133E 6A1 13B6TRIU 968716-4 64 3 5 1384 13CB F22 1819 Containers in Yellow were moved before test. They were in the stack, but location unknown) Container COPU 236440-2 in 59,1,2 in both patterns 3 & 4 with identical tag placement (tags shown twice) Container HLXU 221126-2 in 59,1,1 in both patterns 3 & 5 with different tag placements (7 total tags) Container NYKU 257254-0 in 59,1,3 in both pattern 2 & 3 with different tag placements (8 total tags) Some tag numbers are shown twice when they represent both the top of one container and bottom of another.
Table 5. Active UHF RFID Test set-up for container tracking and tag positions.
97
First Test (Was Performed on Face F1) At 8 Feet:
1 2 3 4 5 6 7 8 9 10 0 degrees 11:17:00 2:05:00 2:13:00 2:21:00 2:28:00 2:38:00 2:46:00 2:53:00 3:01:00 3:08:00
45 deg. 11:19:00 2:06:00 2:14:00 2:22:00 2:29:00 2:39:00 2:47:00 N/A 3:02:00 N/A 90 deg. 11:20:00 2:07:00 2:15:00 2:23:00 2:30:00 2:40:00 2:48:00 2:54:00 N/A 3:09:00180 deg. 11:21:00 2:08:00 2:16:00 2:24:00 2:31:00 2:41:00 2:49:00 2:55:00 3:03:00 3:10:00270 deg. 11:22:00 2:09:00 2:17:00 2:25:00 2:32:00 2:42:00 2:50:00 2:56:00 3:04:00 3:11:00315 deg. N/A N/A N/A N/A 2:34:00 2:43:00 2:51:00 2:57:00 3:05:00 3:12:00
Note: After 2:08 the car was moved as far away from the reader as possible. At 16 Feet 7 Inches:
1 2 3 4 5 6 7 8 9 10 0 degrees 11:29:41 1:48:00 1:41:00 1:33:15 1:27:00 1:20:00 1:14:00 1:07:00 1:01:00 12:54:00
45 deg. 11:31:00 1:49:00 1:42:00 1:34:15 N/A 1:21:00 1:15:00 1:08:00 1:02:00 12:55:0090 deg. 11:32:00 1:50:00 1:43:00 1:35:15 1:29:00 1:22:00 1:16:00 1:09:00 1:03:00 12:56:00180 deg. 11:33:00 1:51:00 1:44:00 1:36:15 1:30:00 1:23:00 1:17:00 1:10:00 1:04:00 12:57:00270 deg. 11:34:00 1:52:00 1:45:00 1:37:15 1:31:00 1:24:00 1:18:00 1:11:00 1:05:00 12:58:00315 deg. N/A 1:53:00 1:46:00 1:38:15 1:28:00 N/A N/A N/A N/A N/A
At 25 Feet 1 Inch:
1 2 3 4 5 6 7 8 9 10 0 degrees 11:42:00 11:50:00 11:56:15 12:02:26 12:09:35 12:16:18 12:22:30 12:29:30 12:36:00 12:43:00
45 deg. 11:43:00 11:51:00 11:57:15 12:03:26 12:10:35 12:17:18 12:23:30 12:30:30 12:37:00 12:44:0090 deg. 11:44:00 11:52:00 11:58:15 12:04:26 12:11:35 12:18:18 12:24:30 12:31:30 12:38:00 12:45:00180 deg. 11:45:00 11:53:00 11:59:15 12:05:26 12:12:35 12:19:18 12:25:30 12:32:30 12:39:00 12:46:00270 deg. 11:46:00 11:54:00 12:00:15 12:06:26 12:13:35 12:20:18 12:26:30 12:33:30 12:40:00 12:47:00315 deg. N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A
3:30:15 measured location 5 halfway at 0 degrees, 8 feet. 3:39:50 measured location 5 at the edge at 0 degrees, 8 feet. 3:59:00 measured location 5 at the edge at 0 degrees, 16 feet. Second Test (performed on face F2) In this test, all measurements were taken on the middle gap, with three stacks of containers on each side. 40 feet away from the containers:
98
4:13 PM height was 8 feet. 20 feet away from the containers: 4:20 PM height was 8 feet. at the edge of the containers: 4:28 PM 8 feet 4:38 PM 16' 7'' 4:54:25 25' 1'' Third Test (performed on face F4) All measurements taken on the middle gap and at the edge of the containers. 5:24 PM 25' 1'' 5:34 PM 16' 7'' 5:44 PM 8 feet
Table 6. Active UHF RFID Conducted field test with the times.
99
Face F4 10
1 1 4
4 0
0
9
1 1 2
1 1
4
8
1
1 1 0
0 0
0
7 third test here
3 0 1
1 4
4
Face F1
6
Face
F3
100
2 0 3
3 3
3
5
40 fe
et
2 5 5
5 4
0
4 20
feet
2 5 5
5 2
0
3 20
feet
4 1 4
4 4
2
2 second test performed here
40 fe
et
1 0 degrees ------>
Face F2
Figure 39. Containers in the stack positioned during the day of the measurement for the active 915 MHz UHF RFID field test.
101
This test was performed at 8', 16', and 25' 4'' This test was only performed at 25' 4''
4
4 4
4
2
1 2
1
0
0 0
0
ECO was replaced by F4E
ECO
1
1 1
F4E
1
3 3 3 3
102
134E
134E
13A6
5
5 5
13A6
5
1097
5
5 5 1097
5
0F4B
4
4 4 0F4B
4
Figure 40. Canyon effect (Waveguiding) case active 915 MHz UHF RFID test set-up for container tracking.
103
Tag-ID Container Number Bay Position Height TAG POSITION Pattern Location
1 8FT Location 1 16FT
Location 1 25FT
Location 2 8FT
Location 2 16FT
Location 2 25FT
Location 3 8FT
Location 3 16FT
001814 HLUX 221126-2
59 1 1 1 5 x x x x x x x x
0013C9 HLUX 221126-2
59 1 1 2 5 x x x
00137E HLUX 221126-2
59 1 1 3 5 x x x x x x x
00137C HLUX 221126-2
59 1 1 4 5 x x x x x x x x
001832 HLUX 316405-7
61 1 1 1 5 x x x x x x x x
00135A HLUX 316405-7
61 1 1 2 5 x x x x
001148 HLUX 316405-7 61 1 1 3 5
00136E HLUX 316405-7
61 1 1 4 5 x x x x x x x x
00136F ZCSU 811148-5
64 1 1 1 5 x x x x x x
001360 ZCSU 811148-5
64 1 1 2 5 x
00138E ZCSU 811148-5
64 1 1 3 5 x x x x x
0013B2 ZCSU 811148-5
64 1 1 4 5 x x x x x x x x
000FEC CLHU 851935-5
68 1 1 1 5
000F4E CLHU 851935-5
68 1 1 2 5
00134E CLHU 851935-5
68 1 1 3 5 x x
000EC0 CLHU 851935-5
68 1 1 4 5 x x x x
000F4B HLXU 452424-5
72 1 1 1 5 x
001097 HLXU 452424-5 72 1 1 2 5
00133F HLXU 452424-5
72 1 1 3 5 x x x
0013A6 HLXU 452424-5
72 1 1 4 5 x x x x x x x
001821 COPU 236440-2 59 1 2 1 4
001344 COPU 236440-2
59 1 2 2 4 x x x
001397 COPU 236440-2
59 1 2 3 4 x x x x x x x x
001813 COPU 236440-2 59 1 2 4 4
No TAG HLXU 260561-0
61 1 2 1 4
0017FD HLXU 260561-0
61 1 2 2 4 x x x x
0013BE HLXU 260561-0
61 1 2 3 4 x x x x x x x
000684 HLXU 260561-0 61 1 2 4 4
0011D5 TCKU 934866-2
64 1 2 1 4
001817 TCKU 934866-2
64 1 2 2 4
000F45 TCKU 934866-2
64 1 2 3 4 x x
001346 TCKU 934866-2 64 1 2 4 4
0013AB TCKU 966695-6
68 1 2 1 4
0013AF TCKU 966695-6
68 1 2 2 4
104
0010BD TCKU 966695-6
68 1 2 3 4
00183D TCKU 966695-6
68 1 2 4 4 x x
001809 HLXU 457117-0 72 1 2 1 4
001190 HLXU 457117-0 72 1 2 2 4
001391 HLXU 457117-0
72 1 2 3 4 x x
001027 HLXU 457117-0 72 1 2 4 4
001821 COPU 236440-2 59 1 2 1 3
001344 COPU 236440-2
59 1 2 2 3 x x x
001397 COPU 236440-2
59 1 2 3 3 x x x x x x x x
001813 COPU 236440-2 59 1 2 4 3
00182D HLXU 221126-2
59 1 1 1 3 x x x x x
001838 HLXU 221126-2
59 1 1 2 3 x x x
00180B HLXU 221126-2
59 1 1 3 3 x x x x x x x x
No TAG HLXU 221126-2
59 1 1 4 3
001133 NYKU 257254-0 59 1 3 1 3
001833 NYKU 257254-0
59 1 3 2 3 x x x x x x
0013BF NYKU 257254-0
59 1 3 3 3 x x x x x x x x
001821 NYKU 257254-0 59 1 3 4 3
001021 TTNU 198038-2 59 1 5 1 3
001340 TTNU 198038-2 59 1 5 2 3
001366 TTNU 198038-2
59 1 5 3 3 x
001343 TTNU 198038-2 59 1 5 4 3
001343 TTNU 335697-1 59 1 4 1 3
001820 TTNU 335697-1 59 1 4 2 3
001803 TTNU 335697-1
59 1 4 3 3 x
001133 TTNU 335697-1 59 1 4 4 3
001373 NYKU 256927-4
59 4 3 1 2 x x
001356 NYKU 256927-4
59 4 3 2 2 x x x
0017FA NYKU 256927-4
59 4 3 3 2 x x x
001364 NYKU 256927-4 59 4 3 4 2
00182D NYKU 257254-0
59 1 3 1 2 x x x x x
00182E NYKU 257254-0
59 1 3 2 2 x x x x x
0013A7 NYKU 257254-0
59 1 3 3 2 x x x x x x
0013C1 NYKU 257254-0
59 1 3 4 2 x x x x x x
001379 NYKU 263405-0
59 3 3 1 2 x x
001361 NYKU 263405-0
59 3 3 2 2 x x x x
0013B7 NYKU 263405-0
59 3 3 3 2 x x x
0013A2 NYKU 263405-0
59 3 3 4 2 x x x
105
001352 PONU 018719-7
59 2 3 1 2 x x x
000ECF PONU 018719-7
59 2 3 2 2 x x
001810 PONU 018719-7
59 2 3 3 2 x x x
001369 PONU 018719-7
59 2 3 4 2 x x x x
0013B0 TTNU 318245-8
59 5 3 1 2 x
00137F TTNU 318245-8
59 5 3 2 2 x x
001348 TTNU 318245-8
59 5 3 3 2 x
0013A1 TTNU 318245-8 59 5 3 4 2 x x
0013AD GATU 861360-4 64 3 2 1 1
0013C8 GATU 861360-4 64 3 2 2 1
00136D GATU 861360-4 64 3 2 3 1
0013A9 GATU 861360-4
64 3 2 4 1
0017FE TCKU 931425-6
64 3 3 1 1 x
00138D TCKU 931425-6 64 3 3 2 1
001837 TCKU 931425-6 64 3 3 3 1
001385 TCKU 931425-6 64 3 3 4 1
000927 TCNU 954041-1 64 3 4 1 1
00133E TCNU 954041-1 64 3 4 2 1
0006A1 TCNU 954041-1 64 3 4 3 1
0013B6 TCNU 954041-1
64 3 4 4 1
001384 TRIU 968716-4 64 3 5 1 1
0013CB TRIU 968716-4 64 3 5 2 1
000F22 TRIU 968716-4 64 3 5 3 1
001819 TRIU 968716-4 64 3 5 4 1
0017F9 TTNU 583003-5 64 3 1 1 1
0013A8 TTNU 583003-5 64 3 1 2 1
0011A8 TTNU 583003-5 64 3 1 3 1
No TAG TTNU 583003-5
64 3 1 4 1
106
Tag-ID Container Number Bay Position Height TAG POSITION Pattern Location
3 25FTLocation
4 8FT Location 4 16FT
Location 4 25FT
Location 5 8FT
Location 5 16 FT
Location 5 25FT
Location 6 8FT
001814 HLUX 221126-2
59 1 1 1 5 x x x x x x x x
0013C9 HLUX 221126-2
59 1 1 2 5 x x x
00137E HLUX 221126-2
59 1 1 3 5 x x x
00137C HLUX 221126-2
59 1 1 4 5 x x x x x
001832 HLUX 316405-7
61 1 1 1 5 x x x x x x x x
00135A HLUX 316405-7
61 1 1 2 5 x x x x x x
001148 HLUX 316405-7 61 1 1 3 5
00136E HLUX 316405-7 61 1 1 4 5 x x x x x x x x
00136F ZCSU 811148-5 64 1 1 1 5 x x x x x x x x
001360 ZCSU 811148-5
64 1 1 2 5 x x x x x x x
00138E ZCSU 811148-5
64 1 1 3 5 x x x x x x x x
0013B2 ZCSU 811148-5
64 1 1 4 5 x x x x x x x x
000FEC CLHU 851935-5
68 1 1 1 5 x
000F4E CLHU 851935-5
68 1 1 2 5 x
00134E CLHU 851935-5
68 1 1 3 5 x x x x x x x
000EC0 CLHU 851935-5
68 1 1 4 5 x x x x x x x x
000F4B HLXU 452424-5
72 1 1 1 5 x x
001097 HLXU 452424-5 72 1 1 2 5
00133F HLXU 452424-5
72 1 1 3 5 x x x x x
0013A6 HLXU 452424-5
72 1 1 4 5 x x x x x x x
001821 COPU 236440-2 59 1 2 1 4
001344 COPU 236440-2
59 1 2 2 4 x
001397 COPU 236440-2
59 1 2 3 4 x x x x x x x x
001813 COPU 236440-2 59 1 2 4 4
No TAG HLXU 260561-0
61 1 2 1 4
0017FD HLXU 260561-0
61 1 2 2 4 x x
0013BE HLXU 260561-0
61 1 2 3 4 x x x x x x x x
000684 HLXU 260561-0 61 1 2 4 4
0011D5 TCKU 934866-2
64 1 2 1 4 x x x x
001817 TCKU 934866-2
64 1 2 2 4 x x x x x
000F45 TCKU 934866-2
64 1 2 3 4 x x x x x x x x
001346 TCKU 934866-2 64 1 2 4 4
0013AB TCKU 966695-6
68 1 2 1 4 x x x
0013AF TCKU 966695-6
68 1 2 2 4 x x
0010BD TCKU 966695-6
68 1 2 3 4 x x x x
00183D TCKU 966695-6
68 1 2 4 4 x x x
107
001809 HLXU 457117-0 72 1 2 1 4
001190 HLXU 457117-0 72 1 2 2 4
001391 HLXU 457117-0
72 1 2 3 4 x x x x x x
001027 HLXU 457117-0 72 1 2 4 4
001821 COPU 236440-2 59 1 2 1 3
001344 COPU 236440-2
59 1 2 2 3 x
001397 COPU 236440-2
59 1 2 3 3 x x x x x x x x
001813 COPU 236440-2 59 1 2 4 3
00182D HLXU 221126-2
59 1 1 1 3
001838 HLXU 221126-2
59 1 1 2 3 x x
00180B HLXU 221126-2
59 1 1 3 3 x x x x x x x x
No TAG HLXU 221126-2
59 1 1 4 3
001133 NYKU 257254-0 59 1 3 1 3
001833 NYKU 257254-0
59 1 3 2 3 x x x x x
0013BF NYKU 257254-0
59 1 3 3 3 x x x x x x x x
001821 NYKU 257254-0 59 1 3 4 3
001021 TTNU 198038-2 59 1 5 1 3
001340 TTNU 198038-2 59 1 5 2 3
001366 TTNU 198038-2
59 1 5 3 3
001343 TTNU 198038-2 59 1 5 4 3
001343 TTNU 335697-1 59 1 4 1 3
001820 TTNU 335697-1 59 1 4 2 3
001803 TTNU 335697-1
59 1 4 3 3
001133 TTNU 335697-1 59 1 4 4 3
001373 NYKU 256927-4
59 4 3 1 2
001356 NYKU 256927-4
59 4 3 2 2
0017FA NYKU 256927-4
59 4 3 3 2
001364 NYKU 256927-4 59 4 3 4 2
00182D NYKU 257254-0
59 1 3 1 2
00182E NYKU 257254-0
59 1 3 2 2
0013A7 NYKU 257254-0
59 1 3 3 2
0013C1 NYKU 257254-0
59 1 3 4 2
001379 NYKU 263405-0
59 3 3 1 2
001361 NYKU 263405-0
59 3 3 2 2
0013B7 NYKU 263405-0
59 3 3 3 2
0013A2 NYKU 263405-0
59 3 3 4 2
001352 PONU 018719-7
59 2 3 1 2
000ECF PONU 018719-7
59 2 3 2 2
108
001810 PONU 018719-7
59 2 3 3 2
001369 PONU 018719-7
59 2 3 4 2 x
0013B0 TTNU 318245-8
59 5 3 1 2
00137F TTNU 318245-8
59 5 3 2 2
001348 TTNU 318245-8
59 5 3 3 2
0013A1 TTNU 318245-8
59 5 3 4 2
0013AD GATU 861360-4
64 3 2 1 1 x
0013C8 GATU 861360-4 64 3 2 2 1
00136D GATU 861360-4 64 3 2 3 1
0013A9 GATU 861360-4
64 3 2 4 1 x
0017FE TCKU 931425-6
64 3 3 1 1 x x x x
00138D TCKU 931425-6 64 3 3 2 1
001837 TCKU 931425-6 64 3 3 3 1
001385 TCKU 931425-6 64 3 3 4 1
000927 TCNU 954041-1 64 3 4 1 1
00133E TCNU 954041-1 64 3 4 2 1
0006A1 TCNU 954041-1 64 3 4 3 1
0013B6 TCNU 954041-1
64 3 4 4 1 x
001384 TRIU 968716-4 64 3 5 1 1
0013CB TRIU 968716-4 64 3 5 2 1
000F22 TRIU 968716-4 64 3 5 3 1
001819 TRIU 968716-4 64 3 5 4 1
0017F9 TTNU 583003-5 64 3 1 1 1
0013A8 TTNU 583003-5 64 3 1 2 1
0011A8 TTNU 583003-5 64 3 1 3 1
No TAG TTNU 583003-5
64 3 1 4 1
109
Tag-ID Container Number Bay Position Height TAG POSITION Pattern Location
6 16FT Location 6 25FT
Location 7 8FT
Location 7 16FT
Location 7 25FT
Location 8 8FT
Location 8 16FT
Location 8 25FT
001814 HLUX 221126-2
59 1 1 1 5 x x x x
0013C9 HLUX 221126-2
59 1 1 2 5
00137E HLUX 221126-2
59 1 1 3 5 x
00137C HLUX 221126-2
59 1 1 4 5 x x
001832 HLUX 316405-7
61 1 1 1 5 x x x x x x x x
00135A HLUX 316405-7
61 1 1 2 5 x
001148 HLUX 316405-7 61 1 1 3 5
00136E HLUX 316405-7 61 1 1 4 5 x x x x x x x x
00136F ZCSU 811148-5 64 1 1 1 5 x x x x x x x x
001360 ZCSU 811148-5
64 1 1 2 5 x x x x
00138E ZCSU 811148-5
64 1 1 3 5 x
0013B2 ZCSU 811148-5
64 1 1 4 5 x x x x x x x x
000FEC CLHU 851935-5
68 1 1 1 5 x x x
000F4E CLHU 851935-5
68 1 1 2 5
00134E CLHU 851935-5
68 1 1 3 5 x x x
000EC0 CLHU 851935-5
68 1 1 4 5 x x x
000F4B HLXU 452424-5
72 1 1 1 5 x x x x x
001097 HLXU 452424-5 72 1 1 2 5
00133F HLXU 452424-5
72 1 1 3 5 x x x x x x x
0013A6 HLXU 452424-5
72 1 1 4 5 x x x x x x x
001821 COPU 236440-2 59 1 2 1 4
001344 COPU 236440-2
59 1 2 2 4 x
001397 COPU 236440-2
59 1 2 3 4 x x x x x x
001813 COPU 236440-2 59 1 2 4 4
No TAG HLXU 260561-0
61 1 2 1 4
0017FD HLXU 260561-0
61 1 2 2 4
0013BE HLXU 260561-0
61 1 2 3 4 x x x x x x
000684 HLXU 260561-0 61 1 2 4 4
0011D5 TCKU 934866-2
64 1 2 1 4 x
001817 TCKU 934866-2
64 1 2 2 4 x
000F45 TCKU 934866-2
64 1 2 3 4
001346 TCKU 934866-2 64 1 2 4 4
0013AB TCKU 966695-6
68 1 2 1 4 x x x x
0013AF TCKU 966695-6
68 1 2 2 4 x x x x x x
0010BD TCKU 966695-6
68 1 2 3 4 x x x x
00183D TCKU 966695-6
68 1 2 4 4 x x
110
001809 HLXU 457117-0 72 1 2 1 4
001190 HLXU 457117-0 72 1 2 2 4
001391 HLXU 457117-0
72 1 2 3 4 x x x x x x x x
001027 HLXU 457117-0 72 1 2 4 4
001821 COPU 236440-2 59 1 2 1 3
001344 COPU 236440-2
59 1 2 2 3 x
001397 COPU 236440-2
59 1 2 3 3 x x x x x x
001813 COPU 236440-2 59 1 2 4 3
00182D HLXU 221126-2
59 1 1 1 3
001838 HLXU 221126-2
59 1 1 2 3
00180B HLXU 221126-2
59 1 1 3 3 x x x x x x x
No TAG HLXU 221126-2
59 1 1 4 3
001133 NYKU 257254-0 59 1 3 1 3
001833 NYKU 257254-0
59 1 3 2 3
0013BF NYKU 257254-0
59 1 3 3 3 x x x
001821 NYKU 257254-0 59 1 3 4 3
001021 TTNU 198038-2 59 1 5 1 3
001340 TTNU 198038-2 59 1 5 2 3
001366 TTNU 198038-2
59 1 5 3 3
001343 TTNU 198038-2 59 1 5 4 3
001343 TTNU 335697-1 59 1 4 1 3
001820 TTNU 335697-1 59 1 4 2 3
001803 TTNU 335697-1
59 1 4 3 3
001133 TTNU 335697-1 59 1 4 4 3
001373 NYKU 256927-4
59 4 3 1 2
001356 NYKU 256927-4
59 4 3 2 2
0017FA NYKU 256927-4
59 4 3 3 2
001364 NYKU 256927-4 59 4 3 4 2
00182D NYKU 257254-0
59 1 3 1 2
00182E NYKU 257254-0
59 1 3 2 2
0013A7 NYKU 257254-0
59 1 3 3 2
0013C1 NYKU 257254-0
59 1 3 4 2
001379 NYKU 263405-0
59 3 3 1 2
001361 NYKU 263405-0
59 3 3 2 2
0013B7 NYKU 263405-0
59 3 3 3 2
0013A2 NYKU 263405-0
59 3 3 4 2
001352 PONU 018719-7
59 2 3 1 2
000ECF PONU 018719-7
59 2 3 2 2
111
001810 PONU 018719-7
59 2 3 3 2
001369 PONU 018719-7
59 2 3 4 2
0013B0 TTNU 318245-8
59 5 3 1 2
00137F TTNU 318245-8
59 5 3 2 2
001348 TTNU 318245-8
59 5 3 3 2
0013A1 TTNU 318245-8
59 5 3 4 2
0013AD GATU 861360-4
64 3 2 1 1
0013C8 GATU 861360-4 64 3 2 2 1
00136D GATU 861360-4 64 3 2 3 1
0013A9 GATU 861360-4
64 3 2 4 1
0017FE TCKU 931425-6
64 3 3 1 1 x x x
00138D TCKU 931425-6 64 3 3 2 1
001837 TCKU 931425-6 64 3 3 3 1
001385 TCKU 931425-6 64 3 3 4 1
000927 TCNU 954041-1 64 3 4 1 1
00133E TCNU 954041-1 64 3 4 2 1
0006A1 TCNU 954041-1 64 3 4 3 1
0013B6 TCNU 954041-1
64 3 4 4 1 x
001384 TRIU 968716-4 64 3 5 1 1
0013CB TRIU 968716-4 64 3 5 2 1
000F22 TRIU 968716-4 64 3 5 3 1
001819 TRIU 968716-4 64 3 5 4 1
0017F9 TTNU 583003-5 64 3 1 1 1
0013A8 TTNU 583003-5 64 3 1 2 1
0011A8 TTNU 583003-5 64 3 1 3 1
No TAG TTNU 583003-5
64 3 1 4 1
112
Tag-ID Container Number Bay Position Height TAG POSITION Pattern Location
9 8FT Location 9 16FT
Location 9 25FT
Location 10 8FT
Location 10 16FT
Location 10 25FT
001814 HLUX 221126-2
59 1 1 1 5
0013C9 HLUX 221126-2
59 1 1 2 5
00137E HLUX 221126-2
59 1 1 3 5
00137C HLUX 221126-2
59 1 1 4 5
001832 HLUX 316405-7
61 1 1 1 5 x x x x x
00135A HLUX 316405-7
61 1 1 2 5
001148 HLUX 316405-7 61 1 1 3 5
00136E HLUX 316405-7 61 1 1 4 5 x x x x x x
00136F ZCSU 811148-5 64 1 1 1 5
001360 ZCSU 811148-5
64 1 1 2 5
00138E ZCSU 811148-5
64 1 1 3 5
0013B2 ZCSU 811148-5
64 1 1 4 5 x x x x x x
000FEC CLHU 851935-5
68 1 1 1 5
000F4E CLHU 851935-5
68 1 1 2 5
00134E CLHU 851935-5
68 1 1 3 5
000EC0 CLHU 851935-5
68 1 1 4 5
000F4B HLXU 452424-5
72 1 1 1 5 x x
001097 HLXU 452424-5 72 1 1 2 5
00133F HLXU 452424-5
72 1 1 3 5 x x
0013A6 HLXU 452424-5
72 1 1 4 5 x
001821 COPU 236440-2 59 1 2 1 4
001344 COPU 236440-2
59 1 2 2 4
001397 COPU 236440-2
59 1 2 3 4
001813 COPU 236440-2 59 1 2 4 4
No TAG HLXU 260561-0
61 1 2 1 4
0017FD HLXU 260561-0
61 1 2 2 4
0013BE HLXU 260561-0
61 1 2 3 4 x
000684 HLXU 260561-0 61 1 2 4 4
0011D5 TCKU 934866-2
64 1 2 1 4
001817 TCKU 934866-2
64 1 2 2 4
000F45 TCKU 934866-2
64 1 2 3 4
001346 TCKU 934866-2 64 1 2 4 4
0013AB TCKU 966695-6
68 1 2 1 4
0013AF TCKU 966695-6
68 1 2 2 4 x x
0010BD TCKU 966695-6
68 1 2 3 4
00183D TCKU 966695-6
68 1 2 4 4
113
001809 HLXU 457117-0 72 1 2 1 4
001190 HLXU 457117-0 72 1 2 2 4
001391 HLXU 457117-0
72 1 2 3 4 x x x x x x
001027 HLXU 457117-0 72 1 2 4 4
001821 COPU 236440-2 59 1 2 1 3
001344 COPU 236440-2
59 1 2 2 3
001397 COPU 236440-2
59 1 2 3 3
001813 COPU 236440-2 59 1 2 4 3
00182D HLXU 221126-2
59 1 1 1 3
001838 HLXU 221126-2
59 1 1 2 3
00180B HLXU 221126-2
59 1 1 3 3
No TAG HLXU 221126-2
59 1 1 4 3
001133 NYKU 257254-0 59 1 3 1 3
001833 NYKU 257254-0
59 1 3 2 3
0013BF NYKU 257254-0
59 1 3 3 3
001821 NYKU 257254-0 59 1 3 4 3
001021 TTNU 198038-2 59 1 5 1 3
001340 TTNU 198038-2 59 1 5 2 3
001366 TTNU 198038-2
59 1 5 3 3
001343 TTNU 198038-2 59 1 5 4 3
001343 TTNU 335697-1 59 1 4 1 3
001820 TTNU 335697-1 59 1 4 2 3
001803 TTNU 335697-1
59 1 4 3 3
001133 TTNU 335697-1 59 1 4 4 3
001373 NYKU 256927-4
59 4 3 1 2
001356 NYKU 256927-4
59 4 3 2 2
0017FA NYKU 256927-4
59 4 3 3 2
001364 NYKU 256927-4 59 4 3 4 2
00182D NYKU 257254-0
59 1 3 1 2
00182E NYKU 257254-0
59 1 3 2 2
0013A7 NYKU 257254-0
59 1 3 3 2
0013C1 NYKU 257254-0
59 1 3 4 2
001379 NYKU 263405-0
59 3 3 1 2
001361 NYKU 263405-0
59 3 3 2 2
0013B7 NYKU 263405-0
59 3 3 3 2
0013A2 NYKU 263405-0
59 3 3 4 2
001352 PONU 018719-7
59 2 3 1 2
000ECF PONU 018719-7
59 2 3 2 2
114
001810 PONU 018719-7
59 2 3 3 2
001369 PONU 018719-7
59 2 3 4 2
0013B0 TTNU 318245-8
59 5 3 1 2
00137F TTNU 318245-8
59 5 3 2 2
001348 TTNU 318245-8
59 5 3 3 2
0013A1 TTNU 318245-8
59 5 3 4 2
0013AD GATU 861360-4
64 3 2 1 1
0013C8 GATU 861360-4 64 3 2 2 1
00136D GATU 861360-4 64 3 2 3 1
0013A9 GATU 861360-4
64 3 2 4 1
0017FE TCKU 931425-6
64 3 3 1 1
00138D TCKU 931425-6 64 3 3 2 1
001837 TCKU 931425-6 64 3 3 3 1
001385 TCKU 931425-6 64 3 3 4 1
000927 TCNU 954041-1 64 3 4 1 1
00133E TCNU 954041-1 64 3 4 2 1
0006A1 TCNU 954041-1 64 3 4 3 1
0013B6 TCNU 954041-1
64 3 4 4 1
001384 TRIU 968716-4 64 3 5 1 1
0013CB TRIU 968716-4 64 3 5 2 1
000F22 TRIU 968716-4 64 3 5 3 1
001819 TRIU 968716-4 64 3 5 4 1
0017F9 TTNU 583003-5 64 3 1 1 1
0013A8 TTNU 583003-5 64 3 1 2 1
0011A8 TTNU 583003-5 64 3 1 3 1
No TAG TTNU 583003-5
64 3 1 4 1
Table 7. Overall active UHF RFID tags by location on the containers in the stack.
115
REFERENCES
[1] http://www.rfidjournal.com/article/articleview/1338/1/129.
[2] Harry Stockman, “Communication by Means of Reflected Power,” Proceedings of the IRE, pp.1196-1204, October 1948.
[3] Jeremy Landt, “Shrouds of Time The History of RFID,” AIM Inc., ver. 1.0, October 2001.
[4] http://www.epcglobaleurope.org/.
[5] Gitanjali Swamy and Sanjay Sarma, “Manufacturing Cost Simulations for Low Cost RFID systems,” Auto-ID Center, February 2003.
[6] K. Finkenzeller, RFID Handbook: Fundamentals and Applications in Contactless Smart Cards and Identification, John Wiley and Sons Inc, New York, 2 edition, 2003.
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