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					Capstone Project                                         Lew Chia Yong Mervin
ENG 499 – Final Report                                   U751316X



                            SIM UNIVERSITY
         SCHOOL OF SCIENCE AND TECHNOLOGY




  INTELLIGENT TAG FOR FIRE-FIGHTER AND
                           LAW ENFORCER




         STUDENT: LEW CHIA YONG MERVIN (U751316X)
                   SUPERVISOR: DR LUM KUM MENG




               A project report submitted to SIM University
       In partial fulfillment of the requirements for the degree of
                     Bachelor of Engineering (Electronics)


                                  May 2010




                                                                            1
Capstone Project                                                     Lew Chia Yong Mervin
ENG 499 – Final Report                                               U751316X



ABSTRACT

Radio Frequency Identification (RFID) is a technology that uses radio frequency
communication to identify, track locations and manage objects, people or animals.
The technology is getting popular due to its advantages and low implementation cost
plays a critical role as well. It is widely used to track assets and their stock level and
at the same time able to track their location on the shelves or warehouse as well. Since
it is able to track their location, this also able to find assets which are tagged but have
went missing. Other than tracking items, it is also used to track people movement or
crowd control through proximity cards and door card readers.


As it seems that RFID technology is being implemented across many different
industries, this project looks into the possibility of using the same technology in the
military and security industry, exploring the location tracking or positioning
capability especially for those who are involved in life threatening missions. The main
idea is to embed RFID tags in their uniforms, which able to transmit the information
back to the command centre, specifying the wearer’s location, hence people in the
command centre is able to have a full picture and have better deployment plan.


The main objective of this project is to design and simulate a UWB microstrip
antenna which is capable of operating in the range of 3GHz to 5GHz and show a
return loss of less than -15dB in the operating range, using the Agilent - Advance
Design System.




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Capstone Project                                                    Lew Chia Yong Mervin
ENG 499 – Final Report                                              U751316X



ACKNOWLEDGEMENT

I would like to give thanks to UNISIM for allowing me to work on this project.


I would like to extend my sincere appreciation to my project tutor, Dr Lum Kum
Meng, for his continuous support and kind understanding shown throughout this
period of time. To ensure on my progress of my project, Dr Lum had been providing
his own time and effort on checking my progress of my report and assisting in answer
my queries. His assistance and comments were most valuable to help me to achieve
what I have completed in this project.


I would like also like to give thanks to my family, friends and classmates for their
kind support and understanding through this period.




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Capstone Project                                                                                                                Lew Chia Yong Mervin
ENG 499 – Final Report                                                                                                          U751316X


TABLE OF CONTENTS

ABSTRACT ............................................................................................................................................ 2

ACKNOWLEDGEMENT ..................................................................................................................... 3

CHAPTER 1.               INTRODUCTION ...................................................................................................... 6
        1.1.      Background........................................................................................................................... 6
        1.2.      Project Objective .................................................................................................................. 7
        1.3.      Overall Objective .................................................................................................................. 7
CHAPTER 2.               RFID SYSTEM ........................................................................................................... 9
   2.     Introduction of RFID .................................................................................................................... 9
        2.1. RFID Technology: What is RFID? ....................................................................................... 9
        2.2.   RFID Hardware Components ............................................................................................. 10
           2.2.1.        RFID Tag .................................................................................................................................. 10
           2.2.2.        RFID Reader ............................................................................................................................. 13
           2.2.3.        Antenna ..................................................................................................................................... 14
        2.3.      RFID Advantages and Limitations ..................................................................................... 15
           2.3.1.        Advantages of using RFID ........................................................................................................ 15
           2.3.2.        Limitations of using RFID ........................................................................................................ 16
        2.4.      RFID Applications (Case Studies)...................................................................................... 17
           2.4.1.        Payment System ........................................................................................................................ 17
           2.4.2.        Human Tracking........................................................................................................................ 18
           2.4.3.        Animals Identification ............................................................................................................... 18
           2.4.4.        Intelligent Book Shelves ........................................................................................................... 19
        2.5.      RFID System Operating Range and Standards ................................................................... 19
CHAPTER 3.               PROJECT PLAN ...................................................................................................... 21

CHAPTER 4.               LITERATURE REVIEW – ULTRA WIDE BAND .............................................. 23
   4.1     Ultra Wide Band (UWB) Basics............................................................................................. 23
   4.2     Classification of UWB antenna .............................................................................................. 24
      4.2.1     Frequency-independent antennas .................................................................................... 24
      4.2.2     Small-element antennas .................................................................................................. 24
      4.2.3     Horn antennas ................................................................................................................. 24
      4.2.4     Reflectors antennas ......................................................................................................... 24
CHAPTER 5.               LITERATURE REVIEW – ANTENNA ................................................................. 25
   5.1     Antenna Basics ....................................................................................................................... 25
   5.2     Antenna Parameters ................................................................................................................ 26
      5.2.1    Resonant Frequency ....................................................................................................... 26
      5.2.2    Field Regions .................................................................................................................. 26
      5.2.3    Directivity and Gain ....................................................................................................... 27
      5.2.4    Radiation pattern............................................................................................................. 28
      5.2.5    Impedance ....................................................................................................................... 28
      5.2.6    Efficiency ....................................................................................................................... 28
      5.2.7    Bandwidth....................................................................................................................... 28
      5.2.8    Polarization ..................................................................................................................... 29
CHAPTER 6.               LITERATURE REVIEW – MICROSTRIP ANTENNA ...................................... 30
   6.1     Microstrip Antenna ................................................................................................................. 30
   6.2     Advantages and Limitations of Microstrip ............................................................................. 31
   6.3     Radiation Pattern .................................................................................................................... 32
   6.4     Microstrip Antenna Configurations ........................................................................................ 32
      6.4.1    Microstrip Patch Antenna ............................................................................................... 33
      6.4.2    Microstrip Dipole Antenna ............................................................................................. 33
      6.4.3    Printed Slot Antenna ....................................................................................................... 34
      6.4.4    Microstrip Travelling-Wave Antenna ............................................................................. 34


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Capstone Project                                                                                                  Lew Chia Yong Mervin
ENG 499 – Final Report                                                                                            U751316X



CHAPTER 7.              LITERATURE REVIEW – SUBSTRATE ............................................................. 36
   7.1     Types of Substrates ................................................................................................................. 36
      7.1.1    Ceramic Substrates ......................................................................................................... 36
      7.1.2    Semiconductor Substrates ............................................................................................... 37
      7.1.3    Ferrimagnetic Substrates ................................................................................................ 37
      7.1.4    Synthetic Substrates ........................................................................................................ 37
      7.1.5    Composite Material Substrates ....................................................................................... 37
   7.2     Substrate Parameters ............................................................................................................... 38
      7.2.1    Relative Permittivity ....................................................................................................... 38
      7.2.2    Dielectric Thickness ....................................................................................................... 38
      7.2.3    Loss Tangent................................................................................................................... 39
CHAPTER 8.              LITERATURE REVIEW – ADVANCE DESIGN SYSTEM (ADS) ................... 40
   8.1        Introduction to Advance Design System (ADS) ..................................................................... 40
   8.2        ADS Momentum Circuit Design ............................................................................................ 40
CHAPTER 9.              ANTENNA DESIGN AND SIMULATION RESULTS......................................... 44
   9.1     Design Specifications ............................................................................................................. 44
   9.2     Design Reference .................................................................................................................... 44
   9.3     Main Design ........................................................................................................................... 45
      9.3.1     Simulation Setting .......................................................................................................... 50
      9.3.2     Results and Observation ................................................................................................. 51
   9.4     Alternative design ................................................................................................................... 53
      9.4.1     Simulation Setting .......................................................................................................... 53
      9.4.2     Results and Observation ................................................................................................. 53
CHAPTER 10.                 CONCLUSION ..................................................................................................... 55

CHAPTER 11.                 RECOMMENDATION ........................................................................................ 56

REFERENCES ..................................................................................................................................... 57

APPENDICES ...................................................................................................................................... 59




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Capstone Project                                                    Lew Chia Yong Mervin
ENG 499 – Final Report                                              U751316X



CHAPTER 1. INTRODUCTION


This chapter gives an overview of this project which will give a brief background of
the project and outline the project’s objective and the approach.


1.1.    Background


RFID technology is a new technology that is fast becoming a popular choice for many
different uses all around the world, ranging from passports to inventory systems.
Many RFID initiatives had been launched in Singapore as well. In May 2004,
Infocomm Development Authority of Singapore had launch a three-year, S$10
million plan to develop Radio Frequency Identification or RFID technology to
augment Singapore's position as a key logistics hub.


The plan aims to build RFID-enabled supply chain clusters by bringing together
manufacturers, logistics service providers, retailers, infrastructure providers and
solutions providers across various industry sectors in Singapore. As of February 2006,
industry has committed to invest more than S$30million towards RFID projects.
Some of the current RFID uses are as follows:


    a. Inventory control
    b. Access control
    c. Laboratory analysis
    d. Lap-counting e.g. the number of laps runners have completed are recorded
        automatically
    e. Time and place data-logging e.g. security guards on patrol can automatically
        log their patrolling route and shift
    f. Vehicle identification e.g. Singapore’s Electronic Road Pricing (ERP) System
    g. Ticketing e.g. some theme parks issue wrist-bands to customers for rides
    h. Building security
    i. Asset tracking




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Capstone Project                                                     Lew Chia Yong Mervin
ENG 499 – Final Report                                               U751316X


Using the current RFID technology, it would be a logical approach to implement the
system to tag law enforcers’ uniforms and able to monitor their movement and
location. During emergency situations, they can be easily located and be evacuated
out of danger areas when required.


1.2.    Project Objective


The objective of this project is to design and implement a system utilizing Radio
Frequency Identification (RFID) technology to enable real-time tracking of personnel
location. The target audiences of this project are the policeman (law-enforcers) and
the fire-fighters when they are carrying out their daily or operational duties.


The implementation of intelligent tags for law-enforcers and fire-fighters hopes to
benefit the local forces mainly Singapore Civil Defence Force (SCDF) and Singapore
Police Force (SPF). This project will enable the forces to have better planning in
operations and deployment of manpower as it will enable them to remotely monitor
the location of the personnel. The RFID tags could also have additional features
which can monitor the temperature and the heartbeat of the personnel. The
information could be relayed to the command centre in real time for monitoring
purpose.

The main objective of this project is to design and simulate a UWB microstrip
antenna which is capable of operating in the range of 3GHz to 5GHz using the
Agilent - Advance Design System. The proposed antenna should show a return loss of
less than -15dB in the operating range.


1.3.    Overall Objective


For this project, the focus is on the location tracking capability which can be used in
the government uniformed organization that involves in dangerous missions. With the
use of RFID technology, RFID tags can be embedded as part of the firemen and
policemen’s uniform. Other than containing the personal details of the wearer for
identification, the tag can be used to specify the wearer’s exact location which can be
useful when it comes to making rescue or to decide if reinforcement is required.

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Capstone Project                                                 Lew Chia Yong Mervin
ENG 499 – Final Report                                           U751316X




Each RFID tag consists of an active RFID microchip, an antenna and a battery. Each
chip is programmed with a unique ID number that is associated to a specific wearer
and the information is kept in the database. As the tag is an active tag, it will
constantly broadcast its wearer’s information as well as other information like the
wearer’s heart beat and temperature to its surrounding. The information will be
transmitted to the receiver and in turn will be sent to a laptop or PC in the command
central via a central monitoring system.


The objective of this project is to design and implement a system to enable real-time
tracking of personnel location by utilizing RFID technology and software integration.




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Capstone Project                                                   Lew Chia Yong Mervin
ENG 499 – Final Report                                             U751316X



CHAPTER 2. RFID SYSTEM


This chapter gives a background study of the technology behind Radio Frequency
Identification (RFID). It also explains the basic functions of a typical RFID system.


2. Introduction of RFID


RFID is fast becoming one of the major and most important technologies around the
world. It is currently being used in different areas ranging from product inventory
tracking, passports, transportation payment to animal identification and human
implants. To embark on this project, an understanding of RFID technology is required
and the following points shall be discussed in detail:


        a. RFID Technology
        b. RFID Hardware Components
        c. RFID Advantages and Disadvantages
        d. RFID Applications
        e. RFID System Operating Range and Standards


2.1.    RFID Technology: What is RFID?


RFID is a generic term used to describe a system that transmits the identity (in the
form of a unique serial number) of an object or person wirelessly using radio waves. It
is grouped under the category of automatic identification technologies which include
bar codes etc. RFID is designed to be fully automated where the readers will extract
information, which is stored in the tag, through the transmission of radio waves. After
which, the information was sent to a central computer system for processing or
monitoring. RFID is also contactless which means it can be detected anywhere as long
as the RFID tags and readers are within range.




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Capstone Project                                                 Lew Chia Yong Mervin
ENG 499 – Final Report                                           U751316X


A typical RFID system consists of a transceiver (RFID Reader) and a transponder
(RFID Tag). The transceiver or RF Reader is a device which reads the radio
frequency and receives information from a RF tag. It also transfers information to a
processing device. The transponder or RF Tag which consists of a microchip attached
to a radio antenna mounted on a substrate. Each chip can hold information of a
product or shipment information, etc.




                             Figure 2.1 How RFID Works?


2.2.    RFID Hardware Components


RFID involves detecting and identifying a tagged object through the information it
transmits There are three common hardware components which is used in all RFID
system which are, RFID Tags, RFID Readers and Antenna.


2.2.1. RFID Tag


An RFID Tag is a device that can store and transmit information to a reader through
transmission of radio waves. The tags are classified based on whether the tag contains
a power supply and provides support for specialized tasks. They are Passive, Active
and Semi-active (or known as semi-passive). They also come in various forms like
tags, labels, smart cards, watches, mobile phones and many more. Figure 2.2 shows
some of RFID tags.




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Capstone Project                                                   Lew Chia Yong Mervin
ENG 499 – Final Report                                             U751316X




                             Figure 2.2 Typical RFID Tag


    a. Passive Tag


    Passive tag does not have an integrated power supply and instead it uses the power
    emitted from the reader to power itself and transmit the stored information to the
    reader. The passive tag consists of a microchip and antenna as main components.
    It has a long life and it is generally resistant to environment conditions. The size
    of the tag is typically smaller as compared to other tags.


    For this type of tag, the reader always starts the communication first, followed by
    the tag. The presence of a reader is compulsory for such a tag to transmit its data.
    The price of a passive tag is generally cheaper as compared to other tags due to
    the simple construction of the tag and no power supply required.




                                   Figure 2.3 Passive Tag




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Capstone Project                                                   Lew Chia Yong Mervin
ENG 499 – Final Report                                             U751316X


     Advantages of Passive Tag                  Limitations of Passive Tag
        Function without battery; Long life       Only can be read within limited
        Cheaper to manufacture                     distance
        Smaller in size                           Not able to include sensors or other
                                                    electronics due to lack of power
                   Table 1 Advantages and Limitations of Passive tag


    b. Active Tag


    Active tag has a power supply and electronics for performing specialized tasks. It
    uses its on-board power supply to transmit its stored information to the reader.
    The tag does not need the reader’s emitted power for data transmission. The active
    tag consists of a microchip, antenna, on-board power supply and electronics as
    main components. For this tag, the on-board electronics can contain
    microprocessors, sensors and input / output ports which are powered by the on-
    board power supply. For example, the components can be used to measure
    temperature. The information can be transmitted to a reader.


    For this type of tag, the tag always starts the communication first. As the presence
    of a reader is not required for data transmission, the tag can broadcast its data to
    the surrounding even in the absence of a reader. Therefore the tags are also called
    transmitter. Another form of the active tag enters to a hibernation mode in the
    absence of a reader. The reader wakes up the tag by issuing an appropriate
    command. This state saves the battery power and has a longer life as compared to
    an active transmitter tag.


    c. Semi-Active (Semi-Passive) Tags


    A semi-active tag is the same as active tags where they have power supply and
    electronics. The power supply provides power to the tag for its operation.
    However, for transmitting the data, the tag uses the reader’s emitted power.
    Therefore, it is also known as battery-assisted tag.



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Capstone Project                                                       Lew Chia Yong Mervin
ENG 499 – Final Report                                                 U751316X


    For this type of tag, a reader always starts the communication first, followed by
    the tag. As the semi-active tag does not use the reader’s signal to excite itself, it
    can be read from a longer distance as compared to a passive tag. The tag also
    needs less time for its proper reading as no time is needed to energize the tag. So
    if the tag is moving at high speed, its information still can be read. A semi-active
    tag might offer better readability for tagging of RF-opaque and RF-absorbent
    materials.




                             Figure 2.4 Active Tag / Semi-Active Tag


    Advantages of Active/Semi-Active Tags         Limitations    of    Active/Semi-Active
                                                  Tags
       Can be read at distances of 100 feet         Limited lifetime due to limited
        or more                                       battery power
       Able      to      include   sensors   or     More expensive
        electronics as power is available in         Larger in size which might limit
        tag                                           its applications.
                                                     Long term maintenance cost for an
                                                      active RFID tags
                       Table 2 Advantages and Limitations of Active tag


        2.2.2. RFID Reader

        An RFID reader also known as interrogator is a device that can read from and
        write data to compatible RFID tags. Thus, it also works as a writer as well.
        The reader is the considered as the central system of the RFID system, from


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Capstone Project                                                    Lew Chia Yong Mervin
ENG 499 – Final Report                                              U751316X


        establishing communication with and control of this component is the most
        important task of any entity which seeks integration with this hardware.


        The reader transmits RF energy through one or more antennas. An antenna in
        the tag picks up this energy and the tag then converts it into electrical energy
        via induction. This electrical energy is sufficient to power the chip attached to
        the tag antenna which stores the tag information. The tag then sends back the
        information.


        A reader consists of the following main components:
                 a. Transmitter
                 b. Receiver
                 c. Microprocessor
                 d. Memory
                 e. Input / Output channels for external sensors, actuators
                 f. Controller
                 g. Communication interface
                 h. Power
        A number of factors can affect the distance at which a tag can be read or
        detected which have an impact on the RFID system’s read range. They are
        frequency used for identification, antenna gain, orientation and polarization of
        the reader antenna and transponder antenna, and placement of tag on the
        object


        2.2.3. Antenna

        In an RFID system, antenna is the critical link for data communication
        between the tag and the reader. It controls the system’s data acquisition and
        communication. Antenna design and placement plays a significant factor in
        determining the coverage zone, range and accuracy of communication. Most
        of the RFID antennas need to be tuned to the resonance of the operating
        frequency which results to be affected by external factors such as RF
        variations, losses due to metal proximity, signal fading, environmental


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Capstone Project                                                    Lew Chia Yong Mervin
ENG 499 – Final Report                                              U751316X


        variations, signal reflection, antenna cabling losses and interference from other
        RF sources


        The selection of which antenna to use for the RFID tag is usually determined
        by the operating frequency and the application required. For antennas which
        operate in low-frequency (LF) passive tags, many coils turns are required to
        power the circuit as the voltage induced is proportional to frequency. For
        example, such tags are used for tracking animals which required multilayer
        coil wrapped around a core.


        Antennas which operate in high-frequency (HF) have a spiral with a few turns
        and can provide a transmission range up to a few meters. As compared to LF
        tags, HF tags cost less to produce. However, HF tags need two metal layers
        and an insulator layer for crossover connection from the most outer layer to
        the inner spiral.


        Ultra-high frequency (UHF) antennas only required one metal sheet which
        reduced the production cost. There are many types of dipoles antennas which
        are used by these tags, for example like dipole antenna and folded dipole
        antenna.

2.3.    RFID Advantages and Limitations


2.3.1. Advantages of using RFID


    a. Ease of use


        Once implemented, the whole system is automated and there is no need for
        any human interference to capture the data. All information will be
        automatically captured and sent to the computer database.




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Capstone Project                                                   Lew Chia Yong Mervin
ENG 499 – Final Report                                             U751316X


    b. Speed


        Several tags can be scanned simultaneously and this speeds up the scanning
        process.


    c. Memory size


        Using RFID tags, the memory size is bigger than current means (e.g.
        Barcode). This enables more information to be saved or extracted from it.


    d. Absence of line of sight


        A line of sight is generally not required for an RFID reader to read a RFID tag.


2.3.2. Limitations of using RFID


    a. Poor performance with RF-opaque and RF-absorbent objects


        This is a frequency-dependent behavior. The current technology does not work
        well with these materials and, in some cases, fail completely.


    b. Security concerns


        Currently the tags are world-readable which means this pose a risk to the
        information leak. It is currently still under research to find a way to achieve
        privacy from unauthorized readers.


    c. Proximity issues


        Tags cannot be read well when placed on metal or liquid objects or when these
        objects are between the reader and the tag. Nearly any object that is between
        the reader and the tag reduces the distance the tag can be read from.




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Capstone Project                                                 Lew Chia Yong Mervin
ENG 499 – Final Report                                           U751316X


2.4.    RFID Applications (Case Studies)


As RFID is getting more popular, more industries are using RFID applications to do
many different things. Below are some of the applications which are currently used in
Singapore:


2.4.1. Payment System


It is getting more popular to use RFID as a payment method. One of it is to collect
road tolls without the cars stopping. An example is Singapore’s ERP (Electronic Road
Pricing) system works using active RFID units in vehicles. Singapore public transport
services (buses and trains) also uses RFID cards or known as EZ Link cards for
payment.


The ez-link card is a think, compact card which is made of PET material that is
environmental friendly. A tamper-proof IC chip and antenna are built into the card.
Both the card and the reader communicate using radio wave via wireless
communication. The sensing distance between the card and the reader is up to 10cm.
The card itself contains no battery but operates from electromagnetic energy received
from the reader. Both the card and the reader ensure secure, fast and reliable
transmission of data between them. The strong encryption techniques prevent
eavesdropping and fraudulent use. This helps to ensure the integrity of transaction
information captured.




                          Figure 2.5 Ez-Link Contactless Card




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Capstone Project                                                     Lew Chia Yong Mervin
ENG 499 – Final Report                                               U751316X


2.4.2. Human Tracking


Hospital wide deployment of SmartSense Admission-Discharge-Transfer (ADT)
module took place in Tan Tock Seng Hospital (TTSH) on 16 January 2007. By using
RFID technology, patients' locations were monitored to better manage bed allocation.
Patients only have to wear a wrist identification tag, also known as SmartTAG, to
transmit location information to the central server, which will decode and send data to
an online dashboard system indicating bed availability. As a result, hospital staff can
obtain the real-time status of bed availability in the wards and thus reduce in-patient
registration and admission processing time significantly.




                             Figure 2.6 SmartTAG on patients


2.4.3. Animals Identification


On 22 May 07, Underwater World Singapore integrated aquatic science and
technology of RFID together. The RFID tag implanted in each fish will enable it to be
sensed by antennas that are fitted on the front of the exhibition tank. When the fish
swims within detectable range, the RFID tag sends a signal to the antenna, which then
relays a signal to a touch screen computer. The computer will then display the name
of the fish such as Tiny the Arapaima. Visitors will also be able to navigate through
all the detailed information about the fish such as its origin, diet and characteristics by
clicking on the appropriate icon on the computer screen.




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Capstone Project                                                      Lew Chia Yong Mervin
ENG 499 – Final Report                                                U751316X


2.4.4. Intelligent Book Shelves


In March 2008, the National Library Board collaborated with the Agency for Science,
Technology and Research (A*STAR)'s Exploit Technologies Pte Ltd (Exploit
Technologies) and the Institute for Infocomm Research (I2R) to develop and test the
Smart Shelf system at the Lee Kong Chian Reference Library in the National Library
building. It is currently in a trial period for 6 months. The Smart Shelf system is
deployed to track 46,000 books on 275 shelves in the Social Sciences and Applied
Sciences Reference sections, making this a large-scale trial of the prototype. The new
system offers benefits to both library users and NLB staff by providing real-time book
location on shelf, tracking readership patterns, allowing real-time inventory checks to
facilitate library staff in performing quick and accurate shelving.


2.5.    RFID System Operating Range and Standards


RFID system operating range and performance depends on the following factors:


    a. Operating frequency
    b. RF power output of the reader
    c. Size of the tag
    d. Material composition of the item to which the tag is attached
    e. Whether the tag had battery assistance


RFID tags operate under different frequencies on different applications. Each
particular frequency is usually chosen to suit the desired system characteristics. There
are four major frequency ranges that RFID systems operate at. As a rule of thumb,
low-frequency systems are distinguished by short reading ranges, slow read speeds,
and lower cost. It generally provide better penetration through non-metallic materials
which have a high moisture content but relatively short operating range and more
expensive tags. Higher-frequency RFID systems are used where longer read ranges
and fast reading speeds are required, such as for vehicle tracking and automated toll
collection. Microwave requires the use of active RFID tags.



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Capstone Project                                                    Lew Chia Yong Mervin
ENG 499 – Final Report                                              U751316X


Frequency                    Range                Applications
Low-frequency                3 feet               Pet and ranch animal identification;
(125 - 148 KHz)                                   car key locks
High-frequency               3 feet               library book identification;
(13.56 MHz)                                       clothing identification; smart cards
Ultra-high freq              25 feet              Supply chain tracking:
(860 - 960 MHz)                                   Box,    pallet,    container,   trailer
                                                  tracking
Microwave:                   100 feet             Highway toll collection;
(2.45GHz and 5.8GHz)                              vehicle fleet identification
                           Table 3 Frequency and Ranges


The read range will depend on whether the tag is a passive tag or an active tag.
Passive tags have short ranges and active tags have a much longer read ranges.


At the moment, there is no global public body that governs the frequencies used for
RFID and each country is able to set its own rules. The international organization for
Standardization, ISO, has published the 18000 family of RFID standards covering a
range frequency and application requirements. EAN International and UCC
established EPCglobal to produce a standard for consumer product tagging.


For this project, the focus will be for the RFID technology to operate in the Ultra
Wide Band (UWB) of 3 GHz to 5 GHz as this is found to be suitable due to the
following reasons:


        a. Ability to operate in a GPS denied environment
        b. Able to overcome the communicate barrier (walls)
        c. Spectrum sharing allows little or no interferences with other wireless
            systems
        d. Multi-path
        e. Low power consumption




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Capstone Project                                                     Lew Chia Yong Mervin
ENG 499 – Final Report                                               U751316X



CHAPTER 3. PROJECT PLAN
This chapter describes the project management plan and the different stages which are
used to carry out this project.


The project requires proper planning and execution to ensure success. It shall adopt a
structure system analysis and design methodology to achieve the project objectives.
The project is planned with 3 phases, split into 5 different stages, which are designed
to guide and carry out successful management of the project. To ensure a successful
completion of the project, it involves careful planning, proper management and good
organization.


They are as follows:


     Phase                Stage                               Task
                            1          Background study of the project requirement
     Initial
                            2          Literature review
                            3          Technical design and modeling RF antenna
   Execution
                            4          Simulation of design
    Closure                 5          Project review




The initial phase of the project, which is Stage 1 and 2, offers the initial planning and
study on the feasibility of the project. For this stage, the project is analyzed to
determine the feasibility of the project. The function and requirements are identified
and processes are being set to ensure a smooth execution of the project. It is important
to have a good and clear understanding of the project background and objectives.
With a clear understanding of the background will assist in making suitable decisions
when it comes to technical specifications for the project.


The execution phase, which is Stage 3 and 4, provides the execution plan and
achieving the project with the desired result. During this phase, logical designs are
produced based on the function and requirements of the project which are determined

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Capstone Project                                                    Lew Chia Yong Mervin
ENG 499 – Final Report                                              U751316X


in the first phase. At the simulation and testing process, a set of acceptance test
criteria will be set to measure the results of the integration test and the RF antenna
modeling gain test. The test would have taken placed with a set of dummy data which
will be used as part of the tracking algorithm for testing. This will include testing and
debugging. Any improvement or amendments to the design will be done at this stage
as well.


The closure phase which is Stage 5 involves the closure of the project with a project
review. This is to review on the project as the solution which was implemented and
compared the final results to the objectives that are set in the initial stage of the
project to determine if it was successful. The review shall also include any difficulties
during the project phase, technical bugs, and limitations of the RF solution. After the
review is completed, any improvement on the design or a better solution can be
presented for future development.




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Capstone Project                                                 Lew Chia Yong Mervin
ENG 499 – Final Report                                           U751316X



CHAPTER 4. LITERATURE REVIEW – ULTRA WIDE
                         BAND
This chapter discusses about the Ultra-Wide Band frequency range and the reason
why the designed antenna is selected to operate in this range.


4.1     Ultra Wide Band (UWB) Basics


Ultra Wide Band (UWB) is a radio technology that can be used at very low energy
levels for short range high-bandwidth communications by using a large portion of a
radio spectrum. UWB transmission does not interfere with other older narrowband
and continuous carrier waves which is in the same frequency band. However, studies
have shown that the rise of noise level by a number of UWB transmitters affects on
existing communications services.


UWB transmission transmits information by generating radio energy at specific time
instants and occupying large bandwidth thus enabling a pulse-position or time-
modulation. UWB radio technology is able to determine “time of flight” of the direct
path of the radio transmission between the transmitter and receiver at various
frequencies. This will overcome multi path propagation. Hence, UWB is suitable for
short-distance applications, high data transfer and real time location and tracking
system.




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Capstone Project                                                  Lew Chia Yong Mervin
ENG 499 – Final Report                                            U751316X


4.2     Classification of UWB antenna


UWB antennas can be categorized into four different groups based on form and
function.



4.2.1 Frequency-independent antennas


It relies on a variation in geometry from a small-scale portion, which contributed to a
higher frequency, to a large-scale portion, which contributed to a lower frequency.
Some examples of the antenna will be spiral, log periodic and conical spiral antennas.



4.2.2 Small-element antennas


These antennas are usually small in size and omni-directional. Some examples of the
antenna will be bow tie and ellipsoidal antennas.



4.2.3 Horn antennas


This type of antennas functions like an electromagnetic tunnel concentrating energy in
a particular direction. It usually has high gain but is being compensated with a
relatively narrow beam. It is suitable for point-to-point links or applications which
requires a narrow field of view.



4.2.4 Reflectors antennas


A reflector antenna, like a horn antenna, concentrates its energy towards a specific
direction. It also tend to have high gain and large in size. However, the structure of
reflector antenna is simpler compared to horn antenna and is easier for any
modification by changing the antenna feed.




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Capstone Project                                                   Lew Chia Yong Mervin
ENG 499 – Final Report                                             U751316X



CHAPTER 5. LITERATURE REVIEW – ANTENNA


This chapter gives an introduction of an antenna and the parameters which determines
the antenna’s performance.


5.1      Antenna Basics

An antenna is a transducer which is designed to radiate and receive electromagnetic
waves. Since a single antenna is able to serve as a receiving or transmitting device, it
is also known to be a reciprocal device. They are structures that provide transactions
between guided and free-space waves.


Antenna is a key component in any wireless system. The RF signal is first transmitted
to free space through the antenna. The signal propagates in space and is picked up by
the receiving antenna, which then amplified and processed the signal to recover the
information.


There are many different types of antennas, classified in different ways. Some
examples like:


      a. Shape or geometries – Wire / Aperture / Printed;
      b. Gain – High / Medium / Low;
      c. Beam shapes – Omni-directional / Pencil / Fan;
      d. Bandwidth – Wide / Narrow.




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Capstone Project                                                      Lew Chia Yong Mervin
ENG 499 – Final Report                                                U751316X




                          Figure 5.1 Various types of antennas


5.2     Antenna Parameters


An antenna’s performance is based on several key parameters, which can be taken
into consideration during the design process to design an antenna with optimal
performance. They are resonant frequency, field regions, impedance, directivity and
gain, radiation pattern, polarization, efficiency and bandwidth.

5.2.1   Resonant Frequency


The resonant frequency refers to the electrical length of an antenna, which is usually
the physical length of the wire divided by the velocity factor. A typical antenna is
tuned for a specific frequency and is able to receive a range of frequencies that are
centered on the resonant frequency. Some properties of an antenna, like radiation
pattern and impedance, change with frequency, hence the antenna’s resonant
frequency maybe close to the centre frequency as to accommodate more important
properties.



5.2.2   Field Regions


There are three principle regions to differentiate the fields surrounding an antenna.
They are reactive near field, radiating near field and far field. The far field region is
the most critical as it determines the antenna’s radiation pattern. Antennas are used to

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Capstone Project                                                     Lew Chia Yong Mervin
ENG 499 – Final Report                                               U751316X


communicate wirelessly in long distance and hence this is the region of operation for
most antennas.


The far field region is the region furthest from the antenna. The radiation pattern does
not change shape with distance in this region. This region is dominated by radiated
fields. This region is dominated by radiated fields with the E- fields and H- fields
perpendicular to each other and the direction of the propagation as the plane waves.


The reactive near field is in the immediate vicinity of the antenna. The fields are
predominately reactive fields, which means the E-fields and H-fields are out of phase
by 90 degrees to each other.


The radiating near field is the region in between the near and far fields. The reactive
fields are not dominating in this region and the radiating fields begin to merge. In this
region, the shape of the radiation pattern may vary with distance.



5.2.3   Directivity and Gain


Directivity of an antenna is a measure of the antenna ability to focus energy in a
particular direction during transmission or to receive energy better from a particular
direction. It is a measure of how 'directional' an antenna's radiation pattern is.
Directivity is defined by direction to the radiation intensity averaged over all
directions.


Gain measures the antenna’s ability to direct the input power radiated in a particular
direction and being measured at the peak radiation intensity. An antenna with a low
gain emits radiation with about the same power in all directions, whereas a high-gain
antenna will preferentially radiate in particular directions.




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Capstone Project                                                     Lew Chia Yong Mervin
ENG 499 – Final Report                                               U751316X


5.2.4   Radiation pattern


A radiation pattern defines the variation of the power radiated by an antenna as a
function of the direction away from the antenna. For example, an ideal isotropic
antenna, it will be a sphere. The radiation pattern of an antenna is typically
represented by a three dimensional graph, or polar plots of the horizontal and vertical
cross sections. It shows the relative field strength transmitted from or received by the
antenna. The graph will also show side lobes and back lobes, where the antenna’s gain
is at a minima or maxima.



5.2.5   Impedance


Impedance relates the voltage to the current at the input to the antenna. The real part
of an antenna's impedance represents power that is either radiated away or absorbed
within the antenna. The imaginary part of the impedance represents power that is
stored in the near field of the antenna (non-radiated power).



5.2.6   Efficiency


Efficiency is the ratio of power actually radiated to the power put into the antenna
terminals. It also can be calculated as radiation resistance divided by total resistance.
A high efficiency antenna has the most power present at the antenna’s input radiated
away whereas a low efficiency antenna has most of the power absorbed as losses
within the antenna. The losses within an antenna are usually the conduction losses and
dielectric losses.



5.2.7   Bandwidth


Bandwidth describes the range of frequencies over which the antenna can properly
radiate or receive energy. It is usually quoted in terms of Voltage Standing Wave
Ratio (VSWR) which is a measure of how well matched an antenna is (in terms of


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Capstone Project                                                       Lew Chia Yong Mervin
ENG 499 – Final Report                                                 U751316X


impedance) to the transmission line it connects to. It is determined from the voltage
measured along a transmission line leading to an antenna. It is the ratio of the peak
amplitude of a standing wave to the minimum amplitude of a standing wave.


The bandwidth of an antenna can be increased by using thicker wires, tapering
antenna components and combining multiple antennas into a single assembly and
allowing natural impedance to select the correct antenna.



5.2.8   Polarization


Polarization is defined as the orientation of the electric field of an electromagnetic
wave by the antenna which radiated into the free space. If the polarization of a wave
is in a desired direction, maximum power can be achieved at the antenna terminal. It
can be generally be classified into linear or circular polarization.


In linear polarization, the electric field vector stays in the same plane containing the
direction of the propagation. It can be classified into vertically and horizontally
polarized wave. The antenna is considered as vertically polarized when its electric
field is perpendicular to the Earth’s surface. A horizontally polarized happens when
its electric field is parallel to the Earth’s surface.


In circular polarization the electric field vector appears to be rotating with circular
motion about the direction of propagation. This involves two linearly polarized
electric field components with equal amplitude and their planes ate at right angles to
each other, rotates in a circle making one revolution during one period of wave. The
circular polarized wave can be right-hand circular polarized (clockwise) or left-hand
circular polarized (anti-clockwise) depending on the direction of the rotation.




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Capstone Project                                                    Lew Chia Yong Mervin
ENG 499 – Final Report                                              U751316X



CHAPTER 6. LITERATURE REVIEW – MICROSTRIP
                         ANTENNA


This chapter introduces the basic functions and various configurations of microstrip
antenna.


6.1     Microstrip Antenna

Microstrip antenna comprises of a thin metallic strip (patch) that placed a small
fraction of a wavelength above the ground plane. The design aims to achieve to the
have maximum antenna’s pattern being normal to the patch.




                    Figure 6.1 Configuration of Microstrip Antenna


In its simplest configuration, the antenna consists of a radiating patch on one side of a
dielectric substrate (εr < 10), which has a ground plane on the other side. The patch
conductors, usually made of copper or gold, are used to simplify analysis and
performance prediction. The maximum pattern can be achieved by selecting a suitable
configuration of the excitation beneath the patch.


The use of microstrip antenna is recommended because of its reduced size, high
impedance bandwidth, high total gain in spite of small size and ease of fabrication. It
is also generally inexpensive to manufacture and design microstrip antenna.




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Capstone Project                                                     Lew Chia Yong Mervin
ENG 499 – Final Report                                               U751316X




                              Figure 6.2 Microstrip Cross-Section


6.2      Advantages and Limitations of Microstrip


As compared to conventional antenna, microstrip antennas do have several
advantages. Many of the applications of the antenna are able to cover the wide range
of frequency from 100MHz to 100GHz. Some of the advantages of microstrip
antennas compared to conventional antennas are:


      a. The antenna is usually light weight, low volume and thin profile;
      b. The fabrication cost is low which means lower cost for mass productions;
      c. Linear and circular polarizations are possible with simple feed;
      d. Dual-frequency and dual-polarization antennas which can be produced easily;
      e. No cavity backing is required;
      f. It can be easily integrated with microwave integrated circuits;
      g. Feed lines and matching networks can be fabricated simultaneously with
         antenna structure.


Microstrip antennas do have its limitations as well. They are:


      a. Narrow bandwidth and associate tolerance problems;
      b. Lower gain;
      c. Large ohmic loss in the feed structure of arrays;
      d. Most microstrip antennas radiate into half-space;
      e. Lower power handling capability;
      f. Poor efficiency due to use of high dielectric constant substrate.


The effects limitations can be overcome or minimize by some of the following
methods. For example, for the limitations of lower gain and power handling can be

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Capstone Project                                                  Lew Chia Yong Mervin
ENG 499 – Final Report                                            U751316X


overcome through an array configuration. The use of photonic bandgap structures can
be used to improve the poor efficiency, reduced gain and radiation pattern
degradations.


6.3     Radiation Pattern

Radiation of a microstrip antenna can be achieved by connecting the antenna to a
microwave source. Upon energizing the patch, a charge distribution will be
established on the surrounding surfaces of the patch.




                   Figure 6.3 Charge distribution and current density


As the repulsive forces of the positive and the negative charges causes some of the
charges from the bottom surface of the patch to be push towards the surface of the
patch. This movement of the charges created current density at the bottom and the top
surfaces of the patch. As the force between the charges dominates, most of the charge
concentration and current flow will remain below the patch.


A small amount of the current will flow around the edges of the patch to its top
surface which creates a weak magnetic field tangential to the edges. Subsequently, the
patch can be modeled as a cavity with electric walls at the top and below and four
magnetic walls along the edges of the patch. As the four sidewalls of the cavity
represent four narrow apertures or slots through which radiation takes place.


6.4     Microstrip Antenna Configurations

Microstrip antenna is generally divided into four categories: Microstrip patch
antennas, Microstrip dipoles antenna, Printed slot antennas and Microstrip travelling
wave antenna. They are categorized by different physical parameters and can be
designed to have many geometrical shapes and dimensions.

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Capstone Project                                                  Lew Chia Yong Mervin
ENG 499 – Final Report                                            U751316X


6.4.1 Microstrip Patch Antenna


Microstrip patch antenna has the simplest configuration of the four categories. It
consists of a conducting patch of any size on one side of the substrate with a ground
plane on the other side. Even though the antenna comes in different shape and sizes,
they behave like a dipole due to their radiation characteristics is similar. The most
common shape used would be rectangular and circular shaped. A typical patch
antenna usually has a gain between 5 to 6dB.




             Figure 6.4 Examples of some basic microstrip patch antenna

6.4.2 Microstrip Dipole Antenna


Microstrip dipole antenna is different from rectangular patch antenna in terms of
geometry with their length-to width ration. Both radiation patterns are similar due to
similar longitudinal current distributions. However, both types of antennas differed in
radiation resistance, bandwidth and cross-polar radiation. The advantages of dipole
antenna are small size, linear polarization, suitable for higher frequencies which are
able to attain significant bandwidth.




                    Figure 6.5 Microstrip center-fed dipole antenna

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Capstone Project                                                    Lew Chia Yong Mervin
ENG 499 – Final Report                                              U751316X


6.4.3 Printed Slot Antenna


Printed slot antenna has a slot in the ground plane of a grounded substrate. Some of
the basic slot shapes include a rectangular slot, annular slot, rectangular ring slot and
tapered slot. The slot antennas, similar like microstrip patch antennas, the feeding
mechanism can be by a microstrip line or a coplanar waveguide.


Slot antennas are bidirectional radiators, as they radiate on both sides of the slot.
Unidirectional radiation can be obtained by using a reflector plate on one side of the
slot. With a combination of strip and slot antennas, allows desired polarization like
circular or linear polarization to be produced.




                          Figure 6.6 Rectangular slot antenna


6.4.4 Microstrip Travelling-Wave Antenna


Microstrip travelling-wave antenna consists of chain-shaped periodic conductors to
form a long microstrip line. To avoid the standing waves on the antenna, the other end
of the travelling-wave antenna is terminated in a matched resistive load. The design of
microstrip travelling-wave antenna is a main beam lies in any direction from
broadside to end fire. For circular polarization, travelling-wave antenna such as
rampart-line antenna, chain antenna, square-loop antenna and crank-type antenna are
being used.




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Capstone Project                                                 Lew Chia Yong Mervin
ENG 499 – Final Report                                           U751316X




         Figure 6.7 Examples of configurations of microstrip travelling wave




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Capstone Project                                                   Lew Chia Yong Mervin
ENG 499 – Final Report                                             U751316X



CHAPTER 7. LITERATURE REVIEW – SUBSTRATE

This chapter discusses the different substrate characteristics and material parameters
for substrate which will affect the performance of the antenna.


The choice of choosing a material for the antenna substrate is an important factor in
the process of designing the antenna as this affects the electrical performance of the
antenna, circuits and transmission line. A substrate must be able to satisfy the
electrical and mechanical requirements which can be difficult at times.


There are many substrate properties to be considered in the design process. For
example, such as dielectric constant, loss tangent and their variation with temperature
range, dimensional stability with processing, temperature and humidity. There are
also other physical properties such as resistance to chemicals, tensile and structural
strengths, flexibility, strain relief and many more, which are important during the
fabrication process.


The choice of substrate much depends on the application. For instance, to keep the
size small, low-frequency applications require high dielectric constants, microstrip
patch antennas use low dielectric constant substrates and slot antennas require high
dielectric constant materials.


7.1     Types of Substrates


The various substrates can be categorized in five groups: ceramic, semiconductor,
ferrimagnetic, synthetic and composite.


7.1.1 Ceramic Substrates

The most commonly used ceramic substrate for microstrip is alumina. Its electrical
characteristics like low loss and less dispersion with frequency makes it desirable.
The limitations are it is hard and brittle, making it difficult to process mechanically.



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Capstone Project                                                    Lew Chia Yong Mervin
ENG 499 – Final Report                                              U751316X


The size is also limited by the fabrication process, which maximum size is about four
inches by four inches.



7.1.2   Semiconductor Substrates


This type of substrate is used for passive circuits and antennas. However, the size of
the available semiconductor substrates is too small to be used at microwave
frequencies for antennas.



7.1.3 Ferrimagnetic Substrates


The use of ferrite substrates has been popular, as they are anisotropic in nature. The
relative permittivity values are in the range of 9 to 16 and usually have low dielectric
loss. The resonant frequency of a microstrip patch deposited on a ferrite substrate
depends on the biasing magnetic field. By varying the bias, the frequency can be
tuned, without affecting the radiation characteristics of the antenna.



7.1.4 Synthetic Substrates


These pure organic materials possess low loss and low permittivity which are suitable
for microstrip antennas. However these materials are soft and unstable with
temperature hence making it less desirable.



7.1.5 Composite Material Substrates


The composite substrates are a combination of different materials to obtain the desired
electrical and mechanical properties. A wide variety of materials with permittivity
range of 2.1 to 10 are available. They are also come in large sizes with good
mechanical properties for fabrication.




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Capstone Project                                                     Lew Chia Yong Mervin
ENG 499 – Final Report                                               U751316X


7.2     Substrate Parameters


There are two main concerns of energy losses and they are signal reflections, due to
impedance mismatch or changes, and loss of signal energy into the dielectric of the
material. Hence parameters such as relative permittivity, dielectric thickness and loss
tangent are controlled tightly.



7.2.1 Relative Permittivity


Relative permittivity, or dielectric constant, is a measure of the ability of an insulating
material to store a charge from an applied electromagnetic field before the energy is
being transmitted. It is also a measure of the ability to slow down the electromagnetic
wave as it travels through the insulating material.


Relative permittivity differs in different material: The lower the relative permittivity,
the higher the impedance of an antenna, the faster a signal propagate through the
material of antenna and the smaller the stray capacitance along the transmission line.
Hence it is better to have a low relative permittivity.



7.2.2 Dielectric Thickness


Dielectric thickness is an important factor for impedance in transmission line. The
control of the thickness is necessary during fabrication, especially for high frequency
antenna. However, the thickness can be controlled by the selection of the substrate
material as well. The impedance increases as the dielectric thickness increases.
Therefore, controlling the thickness is important for very thin dielectric layers.


Thick substrates dielectric constant usually is in the lower range and therefore is more
desirable for having better antenna performance. The reason being they are able to
generate better efficiency, larger bandwidth and loosely bound fields for radiation into
space. However, it will cause the antenna to lose its compactness (increase in weight)
due to the thicker substrate. The substrate thickness will also determine the range of


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Capstone Project                                                    Lew Chia Yong Mervin
ENG 499 – Final Report                                              U751316X


the operating frequency as shown in the chart below. As a rule of thumb, the thickness
of the microstrip substrate should be limited to 10% of a wavelength.




            Figure 7.1: Chart on Substrate Thickness and Operating Frequency

7.2.3 Loss Tangent


The loss tangent is a parameter of a dielectric material that quantifies its inherent
dissipation of electromagnetic energy. It also measures the loss attenuation as signal
wave propagating down the microstrip transmission line. As the loss tangent
decreases, more of the output signal is able to transmit to its destination. It will also
cause a reduction in signal amplitude as the signal travels through the substrate.




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Capstone Project                                                     Lew Chia Yong Mervin
ENG 499 – Final Report                                               U751316X



CHAPTER 8. LITERATURE REVIEW – ADVANCE
           DESIGN SYSTEM (ADS)

This chapter introduces the Advance Design System (ADS) software which is used to
simulate the antenna design for this project.

8.1     Introduction to Advance Design System (ADS)

Agilent – Advanced Design Software (ADS) is a powerful electronic design
automation software system which is able to provide comprehensive design
integration for product design. Some examples of the design applications would be
mobile phones, wireless networks, radar and satellite communications systems and
high-speed digital serial links.


ADS is the industry leader in high-frequency design. It supports system and RF
design engineers developing all types of RF designs, from simple to the most
complex, from RF microwave modules to integrated MMICs for communications and
aerospace / defense applications.


The integrated design environment provides system and circuit simulators with
schematic capture, layout and verification capability thus removing the starts and
stops associated with design tools. Hence, ADS is selected to perform the modeling
and simulation of various suitable antenna designs for the purpose of this project.


8.2     ADS Momentum Circuit Design

ADS Momentum Circuit design is used to build and simulate on the antenna design.
The main window is where all the projects are created and managed. Each project
folder consisted of all the design files and generated results after the simulation.




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Capstone Project                                                    Lew Chia Yong Mervin
ENG 499 – Final Report                                              U751316X




                               Figure 8.1 Main Window


The schematic window is where the design is being created and edited. This window
shows the design in a form of a block diagram and how different blocks are being
linked together. It also shows the dimensions of the design.




                             Figure 8.2 Schematic Window


The layout window is where the user is able to place objects on a layer. It also allows
the user to draw the desired shapes for the design. This is also where the user will set
the preferred layer definitions and specify the design layers as well.




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Capstone Project                                                 Lew Chia Yong Mervin
ENG 499 – Final Report                                           U751316X




                             Figure 8.3 Layout Window


Once the design is ready, the simulator can be used. The simulation parameters are
keyed in. During the simulation, a message window will appears and displays
messages of the current process or any warning messages.




                         Figure 8.4 Simulation Input Window




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Capstone Project                                                   Lew Chia Yong Mervin
ENG 499 – Final Report                                             U751316X


After the simulation is completed, the data is generated and stored in a dataset. The
data display window can be viewed and analyzed on the dataset. The user is able to
measurements, change the scale of the graph or add captions.




                         Figure 8.5 Simulation Result Window




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Capstone Project                                                      Lew Chia Yong Mervin
ENG 499 – Final Report                                                U751316X



CHAPTER 9. ANTENNA DESIGN AND SIMULATION
           RESULTS

This chapter describes the design process and the factors taken into consideration
when designing the UWB microstrip antenna. All the designs and the simulation of
the antenna will be done using ADS Momentum.


9.1     Design Specifications

The initial design will be based on an UWB microstrip antenna that is capable of
operating at a frequency range of GHz. A set of factors were taken into consideration
before deciding on the initial antenna design. They are as follows:



            a. Size of the antenna is small and light;
            b. Operates between 3 GHz to 5 GHz;
            c. Able to be implemented on a microstrip;
            d. Ease of fabrication.


9.2     Design Reference
A design of a stacked patch antenna was proposed from A.A. Serra P. Nepa, G.
Manara, G. Tribellini and S. Cioci (A Wide-Band Dual-Polarized Stacked Patch
Antenna, IEEE Antennas and Wireless Propagation Letters, Vol 6, 2007). The wide-
band dual-polarized slot-coupled stacked antenna was designed to operation at UTMS
(1920MHz – 2170 MHz) and WLAN (2.4 GHz).




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Capstone Project                                                 Lew Chia Yong Mervin
ENG 499 – Final Report                                           U751316X




                    Figure 9.1 Side and Bottom view of the antenna


The proposed antenna is composed of two square aluminum patched fed by two
microstrip lines through a couple of crossed slots opened in a copper ground plane
separating two substrates. The upper patch is separated from the lower one by 18mm
foam (low dielectric constant substrate); the lower patch is placed at a distance of
11mm over the dielectric laminate by means of a foam spacer. The square patched are
2mm thick, the upper and lower patch has a width of 31mm and 45mm respectively.


The results showed that the antenna is able to operate in both UTMS and WLAN
band. The measured gain is between 7.5dB and 9dB and the radiation pattern are
characterized by a -3dB beamwidth. The cross-polarization level is always less than
-25 dB.


9.3       Main Design

The initial design is to be based on an UWB microstrip antenna that is capable of
operating at a frequency range of GHz.


For this design, dual feed mechanism will be used to achieve circular polarization for
the UWB antenna and excite the antenna patch with a 90o time phase with the feed,
with aperture coupled. A square patch microstrip antenna is selected as it simplifies
the analysis and its performance predication.      In order to achieve the desired
bandwidth of 3 GHz to 5 GHz, 4 stubs with varying dimensions of feeding strips are
used.

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Capstone Project                                                    Lew Chia Yong Mervin
ENG 499 – Final Report                                              U751316X




A three-layer structure will be used to achieve the antenna design. The proposed
design as follows:


        a. Layer 1: Antenna Patch
        b. Layer 2: Aperture Slots
        c. Layer 3: 4-Stub Feeding Mechanism


The cross-sectional view of the antenna design is shown in Figure 9.1.




                Figure 9.2 Cross-Sectional View of the Antenna Design


Figure 9.2 displays the design of the antenna on the ADS software. It shows the actual
scale of the antenna based on the initial design. The top layer is the square antenna
patch; the middle layer with the aperture slot and the bottom layer consist of the 4
tuning stubs.




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Capstone Project                                                Lew Chia Yong Mervin
ENG 499 – Final Report                                          U751316X




                           Figure 9.3 Layout of the antenna


Figure 9.3 shows a 3D version of the designed antenna.




                         Figure 9.4 3D drawing of the antenna




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Capstone Project                                                        Lew Chia Yong Mervin
ENG 499 – Final Report                                                  U751316X


The configurations for the different substrate layers are shown in Figures 9.5 to 9.8.
In Figure 9.5 and 9.6, the thickness of the substrate and the relative permittivity of
FR4 and Foam are keyed in. The loss tangent of the substrate is assumed to be zero to
provide an ideal environment.


The metallization layer is shown in Figure 9.8. It shows the different layers of the
antenna and in what order they are being stacked together.




      Figure 9.5 FR4 layer configuration           Figure 9.6 Foam layer configuration




       Figure 9.7 Free Space layer configuration     Figure 9.8 Metallization layers




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Capstone Project                                                                                   Lew Chia Yong Mervin
ENG 499 – Final Report                                                                             U751316X


Frequency tuning can be accomplished by varying the length of a printed or coaxial
transmission line stub attached to the antenna. Narrow stubs allow fine tuning, and
wide stubs are useful for larger tuning range. Hence, different shapes of tuning stubs
and different slots shapes are being used with appropriate tuning stubs, to get the
desired results. Table 4 shows the dimensions of the main design.



                                                                                                    Strip 6



           Strip 1             Strip 2            Strip 3            Strip 4             Strip 5




                     Stub 8
                     Strip 8             Stub 9             Stub 9              Stub 8

                                                                                                              Strip 7




           Figure 9.9 Stub aperture feeding mechanisms with strip indicator


                               Microstrip                       Dimension (L x B) mm
                                    1                                  11.438 x 1.859
                                    2                                   11.48 x 1.706
                                    3                                  11.558 x 1.450
                                    4                                   11.48 x 1.706
                                    5                                  11.438 x 1.859
                                    6                                   14.43 x 1.859
                                    7                                 8.0922 x 1.0349
                                    8                                  0.045 x 12.269
                                    9                                  0.085 x 12.269
                          Square Patch                                         35 x 35
                                  Table 4 Dimensions for the antenna




                                                                                                                        49
Capstone Project                                                    Lew Chia Yong Mervin
ENG 499 – Final Report                                              U751316X


9.3.1   Simulation Setting


Before the simulation can be performed, simulation settings need to be entered. Figure
9.10 shows that the simulation will run on a frequency from 3GHz to 5 GHz. The
sample points taken for the plot is set at 999 as the more sample points will result in a
more accurate plot.




                         Figure 9.10 Simulation Setting Window




                                                                                       50
Capstone Project                                                  Lew Chia Yong Mervin
ENG 499 – Final Report                                            U751316X


9.3.2   Results and Observation


Figure 9.11 shows the result of the S parameter of the signal travelling from port 1 to
port 2 and back to port 1. The marker, m1, shows that the magnitude of the signal at
the first notch of 3.74GHz is -21.24dB. For m2, the magnitude at the second notch at
4.91GHz is -37.2dB.


Based on industrial standard, a functional antenna design should have a magnitude of
-20dB and below. Hence based on the above result, the antenna is considered
functional.




                               Figure 9.11 S11 Result




                                                                                    51
Capstone Project                                                   Lew Chia Yong Mervin
ENG 499 – Final Report                                             U751316X


Figure 9.12 shows the S parameter of the signal travelling from port 1 to port 2. The
desired result will be the difference between marker m1 and m2 is 3dB. However for
this design, the difference between m1 and m2 is -1.08dB. It is slightly off but still
within acceptable limits. Both are at the resonant frequency of 4GHz.




                                                          m3
                                                          freq=4.038GHz
                                                          dB (S(2,1))==2.962




                            Figure 9.12 S21 and S31 Results


From the 3D radiation pattern, a table was created to show on the antenna parameters
in the frequency band of 3GHz to 5GHz.


Frequency Band           Power Radiated      Effective        Directivity      Gain
      (GHz)                 (Watts)            Angle             (dB)          (dB)
         3                 0.000081           229.89             4.96           4.84
       3.78                0.000091           153.13             6.72           4.18
         4                 0.000054           159.06             6.55           5.10
       4.67                0.000043           158.35             6.58           6.46
         5                  0.0001            123.09             7.67           4.76
                              Table 5 Antenna Parameter




                                                                                       52
Capstone Project                                                 Lew Chia Yong Mervin
ENG 499 – Final Report                                           U751316X


9.4     Alternative design

The main design is slightly modified with the size of square patch increased to 45mm
x 45mm.


9.4.1   Simulation Setting
The settings is the same as the first design.



9.4.2 Results and Observation


As shown in Figure 9.13, the marker, m1, shows that the magnitude of the signal at
the first notch of 3.7GHz is -20.9dB. For m2, the magnitude at the second notch at
4.9GHz is -37.7dB.




                                 Figure 9.13 S11 Result




                                                                                   53
Capstone Project                                                   Lew Chia Yong Mervin
ENG 499 – Final Report                                             U751316X


The difference between m1 and m2 is -1.07dB as shown in Figure 9.14. It is slightly
off but still within acceptable limits. Both are at the resonant frequency of 4GHz.




                            Figure 9.14 S21 and S31 Results


From the 3D radiation pattern, a table was created to show on the antenna parameters
in the frequency band of 3GHz to 5GHz.


Frequency Band           Power Radiated       Effective       Directivity       Gain
      (GHz)                 (Watts)             Angle            (dB)            (dB)
         3                  0.0001             182.22            5.97            3.73
       3.78                 0.0001             182.12            5.96            3.73
         4                 0.000067            188.52            5.82            5.19
       4.67                0.000043            160.46            6.52            6.51
         5                  0.0001             120.60            7.76            4.81
                              Table 6 Antenna Parameter


Comparing both designs antenna parameters, the design with 45mm x 45mm square
patch antenna offers a slightly higher gain from 4 GHz onwards.




                                                                                        54
Capstone Project                                                      Lew Chia Yong Mervin
ENG 499 – Final Report                                                U751316X



CHAPTER 10. CONCLUSION

A detailed background study was done of the topic of RFID technology for this
project. This provided an introduction and basic knowledge which is required in order
to achieve success for this project. This process of reading and understanding the
basic of RFID did assist me in having a better understanding of this topic especially I
have little knowledge prior to this project.


Understanding RFID technology is not enough as my objective is to design an UWB
antenna operating in the range of 3GHz to 5GHz and achieve a return loss of less than
-15dB. Hence, other than understanding RFID technology, I will need to read and
understand in details of antenna and their parameters. I also need to understand on the
different types of substrates and their characteristics before I am to start on the
microstrip design. Therefore, I spent quite some time on doing the research and at the
same time trying to understand and coming out with the design.


This is the first time that I am using Advance Design System software for this project.
I would try to learn how to use the different functions which would assist me in this
project and also understanding the theory behind the software so that I am able to
relate to the simulation results which was generated.


The antenna design was modified from a proposed design. This enables me to speed
up my design process to get reach my objective. However, it was during the
simulation process and understanding the results that took up much of my time. The
design needs to be revisited at times to make minor adjustments in order to get the
desired results.


Above all, this project also requires me to use my soft skills like project management,
organisation skills. Through the project process, I am able to realize my own strength
and weakness even though there was assistance provided by my tutor. The skills that
were learnt and used played a critical part to complete this project and making it a
success.


                                                                                        55
Capstone Project                                                 Lew Chia Yong Mervin
ENG 499 – Final Report                                           U751316X



CHAPTER 11. RECOMMENDATION

There are areas to be improved on for this project. The antenna design could be
improved further and modified to make it commercially feasible. Some of the
recommendations to achieve it are as follows:


    a. Another square patch antenna can be added on to improve the antenna gain.
    b. The size of the antenna needs to be reduced further to be embedded in the
        uniform;
    c. The range of operating frequency of the antenna needs to be increased;
    d. The actual fabricated antenna design need to go through more detailed testing;
    e. The antenna to be integrated and tested with a complete RFID system.




                                                                                   56
Capstone Project                                                  Lew Chia Yong Mervin
ENG 499 – Final Report                                            U751316X




REFERENCES

    1. Sandip Lahiri, 2006, RFID Sourcebook


    2. Bill Glover and Himanshu Bhatt, 2006, RFID Essentials

    3. R. Garg, P. Bhartia, I. Bahl and A. Ittiptboon, 2001, Microstrip Antenna
        Design Handbook

    4. K.C. Gupta, R. Garg, I.Bahl and P. Bhartia, 1996, Microstrip Lines and
        Slotlines


    5. RFID - Fundamentals & Future
        (http://www.ida.gov.sg/Infocomm%20Adoption/20061002182723.aspx)


    6. RFID Identified as Next Growth Area for Singapore ICT Industry
        (http://www.ida.gov.sg/News%20and%20Events/20060822143050.aspx?getP
        agetype=20)


    7. RFID Journal (2002-2007): What is RFID?
        (http://www.rfidjournal.com/article/articleprint/1339/-1/129)


    8. News Article (http://www.cadi.com.sg/news0107TTSH.htm)


    9. Press Release
        (http://www.underwaterworld.com.sg/pdf/media%20releases/rfid-
        med%20rel.pdf)


    10. Press Release
        (http://www.nlb.gov.sg/Corporate.portal?_nfpb=true&_windowLabel=PRHan
        dler_1&PRHandler_1_actionOverride=%2FIBMS%2FcorpHomePR%2Fcorp
        PRHandler%2Fdetail&PRHandler_1detailId=422&PRHandler_1mediaType=
        1&_pageLabel=Corporate_page_ne_pressreleases)

                                                                                    57
Capstone Project                                                  Lew Chia Yong Mervin
ENG 499 – Final Report                                            U751316X




    11. RFID Journal (2002-2007): The Basics of RFID Technology
        (http://www.rfidjournal.com/article/articleprint/1337/-1/129)


    12. RFID Journal (2002-2007): RFID Business Applications
        (http://www.rfidjournal.com/article/articleprint/1334/-1/129)


    13. Antenna (Radio) (http://en.wikipedia.org/wiki/Antenna_(radio))


    14. Antenna Theory (http://www.antenna-theory.com/)


    15. Microstrip antenna (http://en.wikipedia.org/wiki/Microstrip_antenna)


    16. Microstrip (http://www.microwaves101.com/encyclopedia/microstrip.cfm)


    17. Advanced Design System (ADS) Software
        (http://www.home.agilent.com/agilent/product.jspx?nid=-
        34346.0.00&cc=US&lc=eng)


    18. A Wide-Band Dual-Polarized Stacked Patch Antenna, IEEE Antennas and
        Wireless Propagation Letters, Vol 6, 2007 by A.A. Serra P. Nepa, G. Manara,
        G. Tribellini and S. Cioci




                                                                                    58
Capstone Project                                                Lew Chia Yong Mervin
ENG 499 – Final Report                                          U751316X



APPENDICES

Antenna feeding stubs with no square patch antenna


                         Microstrip       Dimension (L x B) mm
                             1                11.438 x 1.859
                             2                 11.48 x 1.706
                             3                11.558 x 1.450
                             4                 11.48 x 1.706
                             5                11.438 x 1.859
                             6                 14.43 x 1.859
                             7                8.0922 x 1.0349
                             8                0.045 x 12.269
                             9                0.085 x 12.269




                                                                                  59
Capstone Project                                                      Lew Chia Yong Mervin
ENG 499 – Final Report                                                U751316X


                                  All Stubs length is 0.085mm


                          Microstrip            Dimension (L x B) mm
                              1                     11.438 x 1.859
                              2                      11.48 x 1.706
                              3                     11.558 x 1.450
                              4                      11.48 x 1.706
                              5                     11.438 x 1.859
                              6                      14.43 x 1.859
                              7                     8.0922 x 1.0349
                              8                     0.085 x 12.269
                              9                     0.085 x 12.269
                         Square Patch                   45 x 45




                                                                                        60
Capstone Project                                                Lew Chia Yong Mervin
ENG 499 – Final Report                                          U751316X


Parameters – All Stubs length is 0.045mm


                          Microstrip       Dimension (L x B) mm
                              1               11.438 x 1.859
                              2                11.48 x 1.706
                              3               11.558 x 1.450
                              4                11.48 x 1.706
                              5               11.438 x 1.859
                              6                14.43 x 1.859
                              7               8.0922 x 1.0349
                              8               0.045 x 12.269
                              9               0.045 x 12.269
                         Square Patch             45 x 45




                                                                                  61
Capstone Project         Lew Chia Yong Mervin
ENG 499 – Final Report   U751316X




                                           62
Capstone Project         Lew Chia Yong Mervin
ENG 499 – Final Report   U751316X




                                           63
Capstone Project         Lew Chia Yong Mervin
ENG 499 – Final Report   U751316X




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