design of a compact band notched communication by …
TRANSCRIPT
DESIGN OF A COMPACT BAND NOTCHED
ANTENNA FOR ULTRAWIDEBAND
COMMUNICATION
BY
NUURUL HUDAA BINTI MOHD SOBLI
A dissertation submitted in partial fulfilment of the
requirements for the degree of Master of Science
(Communication Engineering)
Kulliyyah of Engineering
International Islamic University Malaysia
OCTOBER 2009
ii
ABSTRACT
This research work focuses on analysis and design of a compact printed band-notched
antenna for UWB communications. The proposed antenna is designed to cover the
FCC bandwidth for UWB applications (3.1–10.6GHz) with band-notched at frequency
band (5.15–5.825GHz). The proposed antenna is fed by microstrip line, and it consists
of square radiating patch with three steps and a W-shaped slot on the top layer with a
slotted-parasitic patch on the bottom layer of the antenna. The slotted-parasitic patch
acts as a notch filtering element to reject the frequency band (5.15–5.825GHz) which
is used by IEEE 802.11a and HIPERLAN/2. The proposed antenna structure is
simulated in order to obtain the return loss, the gain, and the radiation efficiency of the
antenna, using the commercial electromagnetic (EM) simulators; CST Microwave
Studio and HFSS. Furthermore, parametric studies on the return loss have been carried
out in order to obtain the optimal dimensions for the proposed antenna. The
performances of the proposed antenna are investigated in both frequency domain and
time domain. Moreover, the pulse distortions of different input pulses are investigated
based on S21 parameters for two different orientations (face to face and side by side).
There is a small acceptable influence on the matching between the input and the
output pulses and it is found that the pulse distortion is low. The studies also show that
high signal fidelity is achieved for all input signals. In order to verify the simulated
results, the proposed antenna had been fabricated. The measured result for the return
loss of the proposed antenna shows that the antenna has operating frequency
bandwidth from 2.92–10.75GHz and notched frequency at 5.16–5.95GHz. Therefore,
it is demonstrated numerically and experimentally that the antenna is a good candidate
for UWB applications.
iii
ملخص البحث
صمم الهوائي ليعمل ضمن الحزمة العريضة , تناقش هذه الرسالة تحليل وتصميم هوائي مدمج ذو حزمة مفصولة
ويتألف ,الهوائي المقترحة يغذيه خط رقيق. جيجاهيرتز )5.825–5.15(وفصلت الحزمة , جيجاهيرتز )3.1-10.6(
وهذا الشق يلعب , وشق اخر تحت الهوائي, الطبقة العلياوشق على شكل حرف دبليو في, من رقعة مربعة الشكل
وال HFSS تمت عملية محاكاة الهوائي باستخدام برنامج ال. جيجاهيرتز )5.825–5.15(دور الفلتر لرفض الحزمة
CSTاكات تم اختبار الهوائي في مح. للحصول على الابعاد المثلى لهذا لهوائي, وقد تم تسجيل ربح الهوائي وكفاءته
بالاضافة الى ذلك تم التحقق من النبضات الغير طبيعية من عدة مدخلات استنادا . في اال الزمنى ومجال الترددي
للتحقق من النتائج صنع الهوائي واجريت عليه .هناك تأثير مقبول بين المدخلات والمخرجات .S21 الى معاملات
)5.95–5.16(ولايعمل في الحزمة , جيجاهيرتز )10.75–2.92(اختبار وقد ثبت ان الهوائي يعمل ضمن الحزمة
.مما يبرهن ان الهوائي يصلح للعمل في الترد ذو النطاق العريض جدا ,جيجاهيرتز
iv
APPROVAL PAGE
I certify that I have supervised and read this study and that in my opinion, it conforms
to acceptable standards of scholarly presentation and is fully adequate, in scope and
quality, as a dissertation for the degree of Master of Science (Communication
Engineering).
….....……….....…………...
Hany Essam Abd-El-Raouf
Supervisor
I certify that I have read this study and that in my opinion, it conforms to acceptable
standards of scholarly presentation and is fully adequate, in scope and quality, as a
dissertation for the degree of Master of Science (Communication Engineering).
.....…..…...…….…………..
Md. Rafiqul Islam
Internal Examiner
I certify that I have read this study and that in my opinion, it conforms to acceptable
standards of scholarly presentation and is fully adequate, in scope and quality, as a
dissertation for the degree of Master of Science (Communication Engineering).
…......………………....……
Zaiki Awang
External Examiner
This dissertation was submitted to the Department of Electrical and Computer
Engineering and is accepted as a partial fulfilment of the requirements for the degree
of Master of Science (Communication Engineering).
…….....……..……………..
Othman O. Khalifa
Head, Department of
Electrical and Computer
Engineering
This dissertation was submitted to the Kulliyyah of Engineering and is accepted as a
partial fulfillment of the requirements for the degree of Master of Science
(Communication Engineering).
…........……………...…..…
Amir Akramin Shafie
Dean, Kulliyyah of
Engineering
v
DECLARATION
I hereby declare that this dissertation is the result of my own investigations, except
where otherwise stated. I also declare that it has not been previously or concurrently
submitted as a whole for any other degrees at IIUM or other institutions.
Nuurul Hudaa Binti Mohd Sobli
Signature………………………………………… Date…………………….
vi
INTERNATIONAL ISLAMIC UNIVERSITY MALAYSIA
DECLARATION OF COPYRIGHT AND AFFIRMATION
OF FAIR USE OF UNPUBLISHED RESEARCH
Copyright © 2009 by Nuurul Hudaa Binti Mohd Sobli. All rights reserved.
DESIGN OF A COMPACT BAND-NOTCHED ANTENNA FOR
ULTRAWIDEBAND COMMUNICATION
No part of this unpublished research may be reproduced, stored in a retrieval
system, or transmitted, in any form or by any means, electronic, mechanical,
photocopying, recording or otherwise without prior written permission of the
copyright holder except as provided below.
1. Any material contained in or derived from this unpublished research
may only be used by others in their writing with due acknowledgement.
2. IIUM or its arbitrary will have the right to make and transmit copies
(print or electronic) for institutional or academic purposes.
3. The IIUM library will have the right to make, store in a retrieval system
and supply copies of this unpublished research if requested by other
universities and research libraries.
Affirmed by Nuurul Hudaa Binti Mohd Sobli.
…………………………… ………………………..
Signature Date
vii
I dedicated this humble work of mine to my parents Mohd Sobli Ismail and Radiah
Latiff, my heart Riza Abd. Rahman and all my teachers who have guided me
throughout my life.
Thank you for your love, patience and guidance, Jazakumullahu Khairan.
viii
ACKNOWLEDGEMENT
All the gratitude is due to Allah. Thence, I would like to express my sincere gratitude
to my supervisor, Associate Professor Dr. Hany Essam Abd-El-Raouf for the
opportunity to work on this project, and also for his guidance, and support in my
work. His patient and encouragement were invaluable to me throughout the course of
this research. He pushed me to perform to the best of my abilities and gave me
opportunities and exposure that I would never have had. For that, I am extremely
grateful.
I also would like to thank Bro. Mohd Shukur (the technical assistant of IIUM Radio
Frequency (RF) Design Lab) for his sincere help and invaluable assistance. In
addition, my sincere thanks also go to Bro. Mohd Fahmi Alias (the technical assistant
of IIUM Printed Circuit Board (PCB) Lab) for his help, co-operation, and instructions
in the antenna fabrication’s processes.
The author expresses her gratefulness to Professor Zaiki Awang, Bro. Hisham and all
staffs of UITM Microwave Technology Center (MTC), Shah Alam for their
permission and help during part of my measurement work.
Next, I would like to say a lot of thanks from the bottom of my heart to my family
especially my parents, Mohd Sobli Ismail and Radiah Latiff for their constant support,
motivation, and encouragement throughout all these years. Furthermore, I wish to
express my special thanks to Riza Abd. Rahman who is very special to me for his
endless help, support, and motivation in putting this research to the end. Without
them, I would never have gotten this far.
Last but not least, I am grateful to all of my friends for their time that we spent
together when doing our different projects in one lab.
viii
TABLE OF CONTENTS
Abstract……………………………………………….……………………..……… ...ii
Approval Page………………………………………..…………………………….… iv
Declaration Page……………………………………………….………………..……. v
Copyright Page………………………………………………………..…………....... vi
Dedication …………………………………………………………………………....vii
Acknowledgements………………………………………………………..…......…. viii
List of Tables…………………………………………………………………...……. xi
List of Figures…………………………………………………………………..….... xii
List of Abbreviations………………………………………………………....…….. xvi
CHAPTER ONE: INTRODUCTION………………………………………….…. 1
1.1 Introduction………………………………………………………….…… 1
1.2 Problem Statement…………………………………………………..…… 3
1.3 Objectives…………………………………………………………...…… 4
1.4 Research Methodology…………………………………………..………. 5
1.5 Organization of Thesis…………………………………………………… 6
CHAPTER TWO: UWB TECHNOLOGY….…................................................…7
2.1 Introduction…………………………….……...…………….………...… 7
2.2 Background of UWB………………………………………….………… 7
2.2.1 UWB Signal Modulation Schemes……...…………………....…. 11
2.2.1.1 Pulse Amplitude Modulation (PAM) …...………….…... 11
2.2.1.2 Pulse Position Modulation (PPM)…...………………..... 12
2.2.1.3 Binary Phase Shift Keying (BPSK) ...………………..… 13
2.2.2 Single Band and Multiband Schemes of UWB System...…….… 13
2.3 Advantages of UWB………...…………………………………….…… 15
2.4 Regulations Issues………………………………….........……..………. 18
2.4.1 FCC Rules in United States……………………………………... 18
2.4.2 Regulations Worldwide…………………………......................... 21
2.5 UWB Standards……...………………………………………………… 26
2.5.1 Direct Sequence UWB (DS-UWB)……………………………... 26
2.5.2 Multiband OFDM (MB-OFDM)…………………………...…… 28
2.6 UWB Applications……………………………………………………... 29
2.7 Summary……………………………………………………………..… 31
CHAPTER THREE: UWB ANTENNAS – THEORY AND DESIGN……….... 33
3.1 Introduction………………...………………………………………...… 33
3.2 Antenna Parameters…………...…………………………………..…… 33
3.2.1 Return Loss………...……………………………………….…… 34
3.2.2 Frequency Bandwidth ……………………...……………...…… 34
3.2.3 Co-Polarization and Cross-Polarization………...…………...….. 35
ix
3.3 Requirements for UWB Antennas……………...……………………… 36
3.4 Approaches to Achieve Wide Operating Frequency Bandwidth…….... 37
3.4.1 Resonant Antenna…………………..………...…...…………….. 38
3.4.1.1 Quality Factor and Bandwidth……………………......... 39
3.4.1.2 Fundamental Limitations for Electrically
Small Antennas…………………………………………..41
3.4.2 Traveling Wave Antennas……………….…...………...……….. 43
3.4.3 Resonance Overlapping of Antennas……...…………………..... 45
3.4.4 “Fat” Monopole Antennas ………………...……………..….….. 46
3.4.5 Bandwidth Enhancement for Patch Antennas ………...….…….. 49
3.5 Selected Previous Work on UWB Antenna…………………...……..... 51
3.5.1 Planar UWB Antennas…………………………….......………... 51
3.5.1.1 Ultra-wideband Antenna for UWB Applications…......... 51
3.5.1.2 UWB Printed Monopole Antenna with Rectangular
Slitted Ground Plane ……………………………...….... 52
3.5.1.3 Tuning Fork Type of UWB Patch Antenna ……..…...... 53
3.5.1.4 UWB Planar Antenna with Improve Cut-Off
at the Out of Band Frequencies ....................................... 54
3.5.1.5 Printed Slot Planar Inverted Cone Antenna for
Ultrawideband Applications. ……......….……...…......... 55
3.5.2 UWB Antennas with Band-Notched ……………...…..……….. 55
3.5.2.1 Small Band-Rejected Antenna with the Parasitic
Strip for UWB ……...…..…………………...……......... 55
3.5.2.2 Planar Ultrawideband Antenna with T-Stubs
Band-Notched Structure ……………………...……...… 56
3.5.2.3 UWB Slot Band-Notched Antennas ……...……………. 57
3.5.2.4 Modified UWB Planar Monopole Antenna with Variable
Frequency Band-Notched Function ……........…............ 58
3.5.2.5 UWB Planar Band-Notched Antenna Using Parasitic
Elements …………….………..……………...……......... 58
3.6 Summary………………...……………………...………...................... 59
CHAPTER FOUR: DESIGN AND DEVELOPMENT OF A COMPACT
BANDNOTCHED UWB ANTENNA…...….…………….. 61
4.1 Introduction……………..………………..……………………...…..… 61
4.2 Antenna Design…………………………..….………………...……….. 62
4.3 Return Loss – Parametric Study…………………...…..…...………….. 65
4.3.1 Effect of the Step Widths………..………...……...…………….. 66
4.3.2 Effect of the Ground Plane Length…………......…....………….. 67
4.3.3 Effect of the Ground Plane Slit Width……......…….….……….. 69
4.3.4 Effect of the Ground Plane Slit Length…...…...…………….….. 71
4.3.5 Effect of the Parasitic Element Length………......………..…….. 72
4.3.6 Effect of the Parasitic Element Width…………......…..………... 74
4.3.7 Effect of the Parasitic Element Slot Dimensions…….………..... 75
4.4 Far-Field Simulation Results……………………...………...……...….. 79
4.4.1 Radiation Patterns……………………..………………......…….. 79
4.4.2 Antenna Gain and Directivity versus the Frequency…….......….. 83
4.5 Current Distributions………………………...……...……………...….. 85
x
4.6 Experimental Results……………………...………………….….....….. 89
4.7 Summary…………………………….......………….……...................... 92
CHAPTER FIVE: TIME DOMAIN RESPONSE OF A COMPACT BAND-
NOTCHED UWB ANTENNA…………...……..………….. 93
5.1 Introduction………………………………...…..……..……………….. 93
5.2 Performance of the Band-Notched UWB Antenna in the
Communication System………………...…………..………………….. 94
5.3 Pulse Shapes………………………...…………….……..…...……….. 101
5.3.1 Rayleigh Pulse………………………………………..…………101
5.3.2 Fourth Order Rayleigh Pulse…………………………...……….102
5.3.3 Modulated Gaussian Pulse………………………………...……104
5.3.4 Fifth Derivative Gaussian Pulse……………………………...…105
5.4 Correlation between the Transmitting and the Receiving Antennas......106
5.4.1 Received Signal Waveforms…………………………….....….. 107
5.4.2 Fidelity……………………………………………….…..…….. 117
5.5 Summary………………………………………………........................ 120
CHAPTER SIX: CONCLUSION AND SUGGESTIONS FOR FUTURE
WORK…………………………………….………………….. 122
6.1 Conclusion……………...…….……………….……..…………....….. 122
6.2 Suggestions for Future Work…………………………..……..……..... 124
BIBLIOGRAPHY………...……...…………….………………….…………..….. 125
APPENDIX A: ELECTROMAGNETIC NUMERICAL MODELING
TECHNIQUES………………...…..………..…………..…….. 135
A.1 Maxwell’s Equations…….……………...…...……………………….. 135
A.2 Finite Integration Technique……...….……………………….............. 136
A.2.1 Maxwell’s Grid Equations……………...………..…..……....... 138
A.2.2 Advanced Techniques in CST Microwave Studio®….……….. 140
A.3 Finite Element Method…………………….………………....……..... 141
A.3.1 Representation of Field Quantity……………......…………….. 141
A.3.2 Basis Functions……………………………...……..….……..... 142
A.3.3 Size of Mesh versus Accuracy………...…….………..……….. 143
APPENDIX B: LIST OF PUBLICATIONS………………….…………..…….144
xi
LIST OF TABLES
Table No. Page No.
2.1 FCC emission limits for indoor and hand-held systems 20
2.2 Summary of a comparison of the United States, Japan, and Korea,
Europe, and Singapore UWB regulations 25
2.3 Operating frequency ranges for different classes of UWB devices 31
4.1 Optimal dimensions of the proposed band-notched UWB antenna 89
5.1 Fidelity for proposed band-notched UWB antenna pair without
slotted-parasitic patch 119
5.2 Fidelity for proposed band-notched UWB antenna pair with
slotted-parasitic patch 119
xii
LIST OF FIGURES
Figure No. Page No.
2.1 PAM 12
2.2 PPM 12
2.3 BPSK 13
2.4 Ultra-wideband communications spread transmitting energy across
a wide spectrum of frequency (Cravotta, 2002) 16
2.5 FCC indoor and outdoor emission masks 20
2.6 ECC proposed spectral mask 22
2.7 Proposed spectral mask in Asia 24
2.8 Example of direct sequence spread spectrum 27
2.9 Band plan for MB-OFDM UWB system (Siriwongpairat et al., 2005) 28
3.1 Impedance of an antenna with frequency 38
3.2 Equivalent circuit of an antenna 39
3.3 Antenna within a sphere of radius r 41
3.4 Calculated antenna quality factor Q versus kr 42
3.5 Plate monopole antennas with various configurations 47
3.6 UWB dipoles with various configurations 48
3.7 Circular monopole antenna printed on PCB 49
3.8 Antenna with a parasitic patch and co-planar coupling scheme 50
3.9 Aperture coupled fed stacked patch antenna 50
3.10 A simple patch antenna with partial ground plane 51
3.11 Ultrawideband antenna for UWB applications (a) top layer,
(b) bottom layer 52
xiii
4.1 Geometry and configurations of the proposed antenna 62
4.2 Effect of step widths, Wst1, Wst2, and Wst3 on the return loss of the
proposed antenna 67
4.3 Effect of ground plane length, Lg on the return loss of the proposed
antenna 69
4.4 Effect of ground plane slit widths, Wt on the return loss of the proposed
antenna 70
4.5 Effect of ground plane slit length, Lt on the return loss of the proposed
antenna 72
4.6 Effect of parasitic element length, Lr on the return loss of the proposed
antenna 73
4.7 Effect of parasitic element width, Wr on the return loss of the proposed
antenna 75
4.8 Effect of parasitic element slot width, Wps on the return loss of the
proposed antenna 76
4.9 Effect of parasitic element slot length, Lps on the return loss of the
proposed antenna 77
4.10 Simulated return loss of the proposed antenna without slotted parasitic
element 78
4.11 Simulated return loss of the proposed antenna with slotted parasitic
element patch 79
4.12 Radiation patterns of the proposed antenna in the XZ-plane (φ = 0°)
and the YZ-plane (φ = 90°) at 3.1GHz, 6.5GHz, and 10GHz 80
4.13 Simulated 3D radiation patterns showing the directivity in dBi for the
proposed antenna at 3.1GHz, 6.5GHz, and 10GHz 83
4.14 Simulated gain versus frequency of the proposed antenna 84
4.15 Simulated directivity versus frequency of the proposed antenna 84
4.16 Simulated efficiency versus frequency of the proposed antenna 85
4.17 Simulated current distributions of the proposed antenna 86
4.18 Prototype of the final design of the compact band-notched UWB antenna 90
xiv
4.19 Measured and simulated return loss of the proposed antenna;
(a) from 2GHz to 12GHz,
(b) from 2GHz to 30GHz 91
5.1 Transmitting and receiving antennas in two different orientations 95
5.2 Magnitude of the transfer function for the face to face case with and
without slotted-parasitic patch 96
5.3 Magnitude of the transfer function for the side by side case with and
without slotted-parasitic patch 97
5.4 Phase of the transfer function for the face to face case with and
without slotted-parasitic patch 98
5.5 Phase of the transfer function for the side by side case with and
without slotted-parasitic patch 99
5.6 Group delay of the transfer function for the face to face case with and
without slotted-parasitic patch 100
5.7 Group delay of the transfer function for the side by side case with
and without slotted-parasitic patch 100
5.8 Normalized first order Rayleigh pulses with different values of a 102
5.9 FFT of the first order Rayleigh pulses with different values of a 102
5.10 Normalized fourth order Rayleigh pulse 103
5.11 FFT of the fourth order Rayleigh pulse 103
5.12 Normalized modulated Gaussian pulse 104
5.13 FFT of the modulated Gaussian pulse 105
5.14 Normalized fifth derivative Gaussian pulse 106
5.15 FFT of the fifth derivative Gaussian pulse 106
5.16 Received signal waveforms of the first order Rayleigh pulse
with a = 30ps 108
5.17 Received signal waveforms of the first order Rayleigh pulse
with a = 45ps 110
5.18 Received signal waveforms of the first order Rayleigh pulse
with a = 80ps 112
xv
5.19 Received signal waveforms of the fourth order Rayleigh pulse
with a = 67ps 113
5.20 Received signal waveforms of modulated Gaussian pulse
with a = 350ps, fc = 4GHz 115
5.21 Received signal waveforms of the fifth derivative Gaussian pulse
with a = 51ps 116
A.1 FIT discretization 137
A.2 A cell V of the grid G with the electric grid voltage e on the edges of
An and the magnetic facet flux bn through this surface 138
A.3 The field inside each tetrahedron 142
xvi
LIST OF ABBREVIATIONS
1G First-Generation
2D Two-Dimensional
2G Second-Generation
3D Three-Dimensional
3G Third-Generation
4G Fourth-Generation
ABW Absolute BandWidth
AWGN Additive White Gaussian Noise
BPSK Binary Phase Shift Keying
BW BandWidth
CEPT Conference of European Posts and Telecommunications
CSMA/CA Carrier Sense Multiple Access with Collision Avoidance
CST™ Computer Simulation Tool
DAA Detect and Avoid
DC Direct Current
DSSS Direct Sequence Spread Spectrum
DS-UWB Direct Sequence Ultra Wideband
DVD Digital Video Disc
ECC Electronic Communications Committee
EM ElectroMagnetic
ETRI Electronics and Telecommunications Research Institute
ETSI European Telecommunications Standards Institute
FBW Fractional BandWidth
FCC Federal Communications Commission
FEM Finite Element Method
FFT Fast Fourier Transform
FIT Finite Integration Technique
FM Frequency Modulated
FR4 Flame Resistant 4
GPR Ground Penetrating Radar
GPS Global Positioning System
GSM Global System for Mobile Communications
HDTV High-Definition TV
HFSS™ High Frequency Structure Simulator
IDA Infocomm Development Authority
IEEE Institute of Electrical and Electronics Engineers
IFFT Inverse Fast Fourier Transform
ISM Industrial Scientific and Medicine
ITU International Telecommunication Union
LCD Liquid Crystal Display
LH Left-Hand
MBOA MultiBand OFDM Alliance
MB-OFDM Multiband Orthogonal Frequency Division Multiplexing
xvii
MIC Ministry of Internal Affairs & Communications
MIT Massachusetts Institute of Technology
MPEG Moving Picture Experts Group
NF Noise Figure or Noise Factor
NICT National Institute of Information and Communications Technology
OFDM Orthogonal Frequency Division Multiplexing
PAM Pulse Amplitude Modulation
PBA® Perfect Boundary Approximation
PC Personal Computer
PCB Printed Circuit Board
PDA Personal Digital Assistant
PN Pseudo-Noise
PPM Pulse Position Modulation
PSD Power Spectral Density
PVP Personal Video Player
RF Radio Frequency
RH Right-Hand
SMA SubMiniature version A
SINR Signal-to-Interference Ratio
SNR Signal-to-Noise Ratio
TEM Transverse Electromagnetic
TM-UWB Time Modulated Ultra Wideband
TST Thin Sheet Technology™
U-NII Unlicensed National Information Infrastructure
UFZ UWB Friendly Zone
UHF Ultra High Frequency
USB Universal Serial Bus
UWB Ultra Wideband
VHF Very High Frequency
VSWR Voltage Standing Wave Ratio
Wi-Fi Wireless Fidelity
WLAN Wireless Local Area Network
WPAN Wireless Personal Area Network
1
CHAPTER ONE
INTRODUCTION
1.1 INTRODUCTION
Wireless communication technology has a great impact on our life today. Its
contribution to connecting people has changed our lives during the past two decades.
The emerging of cell phone gives us opportunity and even more freedom to
communicate with each other at any time and in any place. In addition, wireless local
area network (WLAN) technology provides an unlimited access to the internet without
suffering from managing yards of unsightly and expensive cables.
The technical improvements on the existing wireless communication
technology have also contributed to the emerging of a large number of new services.
The first-generation (1G) mobile communication technology only allowed analogue
voice communication while the second-generation (2G) technology realized digital
voice communication. Today, the third-generation (3G) technology can provide video
telephony, internet access, video/music download services as well as digital voice
services. In the near future, the fourth-generation (4G) technology will be able to
provide on-demand high quality audio and video services, and other advanced
services.
In the past few years, more interests have been emphasized on Wireless
Personal Area Network (WPAN) technology worldwide. The future WPAN aims to
provide reliable wireless connections between computers, portable devices, and
consumer electronics within a short range. Furthermore, fast data storage and
exchange between these devices will also be accomplished. This requires data rate
2
which is much higher than what can be achieved through currently existing wireless
technologies.
The increase in the demand on both data rate and bandwidth has forced Federal
Communications Commission (FCC) to allocate a specific bandwidth for commercial
use of ultra wide band (UWB) technology. Therefore, in April 2002, FCC gave formal
approval for unlicensed use of UWB technology devices with the allocation of
frequency band from 3.1 to 10.6 GHz which is 7.5 GHz of spectrum (Federal
Communications Commission [FCC], 2002). The first approved rules from FCC were
started in February 2002 and the formal approval was made into reality only in April
2002 (FCC, 2002). The allocation of frequency band for UWB technology has
presented the opportunity and the challenge for all antenna designers.
In addition, this allocation of spectrum for commercial use also contributes to
the competitive study in designing UWB system among both academy and industry
communities of telecommunications. Thus, after setting the FCC regulations clearly
for the ultra wideband transmissions, the development of ultra wideband will be
speeded up. It is expected within few years, to find UWB replacing many of the
existing narrow band techniques. The advantages of the UWB technology are
explained in more details in Chapter 2.
However, for the best of our knowledge the formal standard for UWB
communications is not finalized completely until this moment. The regulatory bodies
around the world are currently working on the UWB regulations and the Institute of
Electrical and Electronics Engineers (IEEE) is currently trying to finalize the UWB
standards. It is expected that when this work is finalized, a lot of UWB products will
be available to the customers in the market.
3
The various types of UWB antennas, such as the planar volcano-smoke slot
antenna, bowtie patch antenna, and the modified bowtie antenna with a triangular
shape, have been developed for UWB systems. In particular, the planar patch antenna
is extensively used in wireless communications because of its light weight, low cost,
and ease of fabrication. It is well known, however, that its bandwidth is inherently
narrow (Mihai, 2002). Thus, many researches have been attempted to widen the
bandwidth of the conventional printed antennas. Thus, various structures have been
proposed to overcome the narrow bandwidth. For example, parasitic elements around
the antenna bring about broad bandwidth operation, but increase the size of the
antenna (Rogers and Butler, 1999; Chung et al., 2004) Broadband performance can be
obtained by using a monopole antenna with a modified shape (Smith et al., 2004).
1.2 PROBLEM STATEMENT
In accordance with the regulations released by the FCC, UWB systems have been
allocated to the bandwidth from 3.1 to 10.6 GHz. However, the use of the 5.15–5.825
GHz band is limited by IEEE 802.11a and HIPERLAN/2. A band rejection
characteristic must be introduced on the UWB antennas. These antennas are called
band-notched UWB antennas. This is due to the fact that UWB transmitters should not
cause any electro-magnetic interference on nearby communication system such as
Wireless LAN (WLAN) systems. Therefore UWB antennas with notched
characteristics in WLAN frequency band are desired.
Moreover, the designed antenna should have a planar structure with small size.
The electrical characteristics and physical shape and dimensions of the proposed
antenna should make it suitable and attractive to be used in UWB systems.
4
Furthermore, study on the time domain characteristics of band-notched UWB
antenna is another important issue. A good time domain response with low distortion
is a primary requirement for the UWB antenna. This is because UWB systems
transmit narrow pulses rather than employing continuous wave carrier to convey
information. The effect of the antenna on the transmitted pulse becomes a crucial issue
in such that the antenna behaves like a bandpass filter and reshapes the spectra of the
pulses (Ma and Jeng, 2005).
In addition, the signal waveforms arriving at the receiver are usually not as
same as the source pulses excited at the transmitter. The received waveforms usually
have some distortion in which it differs from the input signal. The distortion in the
received signal is due to the non-uniform magnitude and/or non-linear phase of the
transfer function of the antenna system. In other words, the magnitude of S21 and/or
the group delay between transmitting and receiving antennas are not constant.
Therefore, the antenna should be designed with extra care in order to avoid undesired
distortions in the received signal.
1.3 OBJECTIVES
There are several objectives that have been specified for this research.
1. To design a printed antenna that will be operating in the UWB
frequency band as well as acting as a band-notched antenna to reject
WLAN frequency band (5.15 GHz to 5.825 GHz) and avoid any
interference due to other wireless communication systems within this
frequency band such as IEEE 802.11(a) and HIPERLAN/2.
2. To design the antenna with a particular shape on a specific material
which has low cost and easy to fabricate.
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3. To optimize the antenna shape and dimensions based on the evaluation
of the antenna parameters such as the return loss, radiation efficiency,
radiation pattern and the antenna gain. Based on a parametric study of
the effect of different dimensions on the antenna performance, the final
antenna structure will be produced with its optimum dimensions which
satisfy both of the required UWB frequency response and the band-
notched characteristics.
4. To fabricate the designed antenna with its optimum dimensions and to
measure the antenna parameters. The performance of the antenna will
be validated by comparing the experimental results with the simulated
results.
5. To perform a time domain analysis for the band-notched UWB antenna
system in order to investigate the effect of the undesired distortion
(between the transmitting and the receiving antennas) on the received
signal at the receiving antenna.
1.4 RESEARCH METHODOLOGY
The following were the milestones in the realization of this research work:
1. Literature review:
a. Understanding ultrawideband technology
b. Understanding the theory and designs of ultrawideband antennas
c. Review and analysis of different structure for band-notched UWB
antennas
2. Designing the band-notched UWB antenna by using available
electromagnetic simulator which is CST Microwave Studio
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3. Optimizing the antenna structure
4. Analysis for the time domain response of the designed antenna
5. Fabricating the final structure of the antenna
6. Measuring the return loss of the fabricated antenna
1.5 ORGANIZATION OF THESIS
This thesis is organized in six chapters as follows:
Chapter 2: “UWB Technology” discusses a brief introduction to UWB
technology. The history of UWB technology and its advantages are discussed. In
addition, current regulation state and standards are also addressed.
Chapter 3: “UWB Antennas – Theory and Designs” includes a brief review for
the antenna parameters which will be used in this thesis. The primary requirements for
a suitable UWB antenna are discussed. In addition, some general approaches to
achieve wide operating frequency bandwidth of antenna are also introduced.
In Chapter 4, design and developing of band-notched UWB antenna are
discussed. The operation principle of the antenna in frequency domain is addressed
based on the performances and characteristics of the antenna. The simulated and
measured results are compared.
In Chapter 5, time domain performances of band-notched UWB antenna
system are analyzed. The response of the receiving antenna to the transmitting antenna
is investigated. Furthermore, the received signal waveforms are assessed by the
fidelity (the correlation between the transmitting and receiving antennas).
Chapter 6 concludes the researches that have been done in this thesis. In
addition, suggestions for future work are also discussed.