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DESIGN OF TRIPLE-BAND MICROSTRIP ANTENNA FOR MOBILE PHONE JAMMER

BY

OMAR NOORI DHAKIR

A dissertation submitted in fulfilment of the requirement for the degree of Master of Science in Communication

Engineering

Kulliyyah of Engineering International Islamic University

Malaysia

FEBRUARY 2013

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ii

ABSTRACT

The new developments in wireless technology required the use of microstrip antenna in many applications and necessitated the use of a smaller size antenna with higher gain, lighter weight and lower cost. In this study a h-shaped patch antenna with a small size is designed as a new shape to produce a triple-band frequency that works with a mobile phone jammer. These bands are 0.9, 1.8 and 2.45 GHz. The triple-band is achieved using three slots inside a rectangular patch antenna. Each slot is dedicated to a specific frequency based on relationship between the length of the slot and the wavelength of the frequency. The commercial software, CST Microwave Studio, is used for the antenna design and optimization. In CST software there are five types to optimize the h-shape patch antenna to accomplish the triple-band with a good resonant frequency and return loss. One of these types is called genetic algorithm that is used here. The bandwidth is increased by using a short pin method. The h-shape slot single patch antenna is fabricated and the measured results are shown improvement in terms of return loss, resonant frequency and bandwidth when compared with previous works. Finally, the h-shaped single patch antenna is arranged in a linear array and the mutual coupling between elements is decreased.

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iii

صخلم ثحبلا

ABSTRACT IN ARABIC

تاروطتلا ةديدلجا

في ايجولونكت يكلسلاا

تبلطت مادختسأ

يئاوه بترسوركيالما ديدعلا في

يئاوه مادختسأ تبجوتساو تاقيبطتلا نم تا

يغص ة مجلحا و

يلاع ة بسكلا نزولا ةفيفخو

نمثلا ةصيخرو .

في اذه ثحبلا ميمصت تم

يئاوه مجلحا يغص نم

عون يئاوه ةعقرلا تاذ

لكشلا لكشب لثمتلما ديدلجا

( )

h

توحنلما ةعقرلا فصتنم في

لمعيو ىلع

ثلاث تاددرت

ليابولما ىلع شيوشتلا ةزهجا عم لمعت تيلا .

يه ثلاثلا تاددترلا هذه

0.9 , و 8.1 5..2

زترهاجيج .

ه هذ تاددترلا تم

لوصلحا اهيلع

نع قيرط تنح فصتنم في قوقش ثلاث يئاوه

ةعقرلا ليطتسلما لكشلا تاذ .

ينب ةقلاعلا ىلع ادامتعأ ينعم ددترل صصمخ قش لك ثيح

لوط قشلا لوطلاو جولما

ي لكل ددرت . في اذه ثحبلا تم مادختسأ جمانبرلا

يراجتلا (

CST

software

) ميمصتل ةاكامحو

يئاولها . في اذه جمانبرلا دجوي

سخم عاونا نم عاونا ينسحتلا

اهمدحأ وه

(

Genetic algorithms

) يذلا تم همادختسأ عم

(

parameter sweep

) ينسحتل

ميمصتلا اذه .

امك تم ينستح ضرع

ةمزلحا هذله تاددترلا جاردا قيرط نع

(

short pin

) في

ةفاح ةعقرلا . ىلع اهذيفنت للاخ نم ةيددرت مزح ثلاث ىلع لوصلحا تم نا دعب جمانرب

ةاكالمحا يئاولها اذه عينصت كلذ دعب تم

سايقو تدادترلا اهضرعو

رادقمو (

return loss

)

ةاكالمحا جئاتن عم اهتنراقمو نمو

ثم اهتنراقم عم

جئاتن لمعلا اذله ةبهاشلما ةقباسلا لامعلاا .

فيو ةياهنلا تم عضو اذه يئاولها في

ةفوفصم ةيطخ

نوكتت نم عبرأ تايئاوه ةنيعم تافاسبم

ةيددترلا مزلحا ةحازا ةليمع ليلقتل

.

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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 thesis for the degree of Master of Science in Communication Engineering.

_____________________________

Jalel Chebil Supervisor

_____________________________

Sheroz Khan Co. 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 thesis for the degree of Master of Science in Communication Engineering.

___________________

Khaizuran Bin Abdullah Internal Examiner

This dissertation was submitted to the Department of communication Engineering and is accepted as fullfilment of the requirement for the degree of Master of Science in 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 fulfilment of the requirement for degree of Master of Science in Communication Engineering.

_____________________________

Md Noor Bin Salleh

Dean, Kulliyyah of Engineering

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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.

Omar Noori Dhakir

Signature ... Date ...

COPYRIGHT PAGE

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vi

INTERNATIONAL ISLAMIC UNIVERSITY MALAYSIA

DECLARATION OF COPYRIGHT AND AFFIRMATION OF FAIR USE OF UNPUBLISHED RESEARCH

Copyright ©5082by Omar Noori Dhakir. All rights reserved.

COPYRIGHT PAGE

DESIGN OF TRIPLE-BAND MICROSTRIP ANTENNA FOR MOBILE PHONE JAMMER

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 library will have the right to make and transmit copies (print or electronic) for institutional and 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 Omar Noori Dhakir

... ...

Signature Date

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vii

ACKNOWLEDGEMENTS

All praise to Almighty Allah (SWT) for His endless blessing and granting me patience to complete my thesis and master degree and salutation upon the Prophet Muhammad (PBUH).

I wish to thank my family for their help and support. Special thanks to my mother, my father and my uncle as an example of hard work and aspiration; I have always been overwhelmed by their wise advices, care, kindness, and love since I was child until now. There are no words that can show my gratitude to them, for all thank you so much.

Also I would like to thank my heart I mean my wife for her care, kindness, and love and for standing by me throughout my arduous academic journey and for enduring the hardship of being away from our home country, so thanks a lot my beloved.

In addition, I would like to express my gratitude to my brothers, my sisters and my wife's family for standing by me throughout my arduous academic journey. Thank you so much for all.

I never forget to show my sincere gratitude to a special person. This thesis would never have been possible without his insightful observations and advice, my supervisor, Associate Prof. Dr. Jalel Chebil, and thanks to my co-supervisor Associate Prof. Dr. Sheroz Khan and thanks a lot to Dr. Mohammed Hade Habiba and Dr. Rafiq alislam so thanks a lot for all.

I would like to thank also to all of my friends in my country and at the faculty of engineering and others whom presented somehow perpetually refreshed, helpful, and memorable.

Finally, I would like to thank everybody who was important to the successful realization of this thesis, as well as expressing my apology that I could not mention the names personally one by one.

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viii

TABLE OF CONTENTS

Abstract ... ii

Abstract in arabic ... iii

Approval page ... iv

Declaration ... v

Copyright page ... vi

Acknowledgements ... vii

Table of contents ... viii

List of tables ... xi

List of figures ... xii

List of abbreviations ... xv

CHAPTER ONE: INTRODUCTION ... 1

1.1 Motivation ... 1

1.2 the Mobile Phone Jammer ... 1

1.3 Statement Of The Problem ... 3

1.4 Research Objectives ... 3

1.5 Research Methodology ... 4

1.6 Scope ... 5

1.7 Thesis Organization ... 5

CHAPTER TWO: MICROSTRIP PATCH ANTENNA ... 6

2.1 Introduction ... 6

2.2 Antenna Design Parameters ... 8

2.2.1 Gain ... 8

2.2.2 Radiation Pattern ... 8

2.2.3 Return Losses and Standing Wave Ratio ... 8

2.2.4 Input Impedance ... 9

2.2.5 Bandwidth ... 9

2.3 Microstrip Antenna Configurations ... 10

2.3.1 Microstrip Patch Antenna ... 10

2.3.2 Microstrip or Printed Dipole Antenna ... 11

2.3.3 Printed Slot Antenna ... 12

2.3.4 Microstrip Traveling-Wave Antenna ... 14

2.4 Methods Of Analysis ... 15

2.4.1 Transmission Line Model ... 17

2.4.2 Cavity Model ... 19

2.4.3 Full Wave... 21

2.4.4 Finite-Difference Time-Domain (FDTD) Method ... 21

2.4.5 Finite-Element Method (FEM) ... 22

2.5 Feeding Techniques ... 22

2.5.1 Microstrip Line Feed ... 23

2.5.2 Coaxial Feed/probe coupling ... 24

2.5.3 Aperture-Coupled Microstrip Feed ... 25

2.5.4 Proximity Coupled Feed ... 26

2.6 Rectangular Patch Antenna Using Transmission Line Model ... 27

2.6.1 Patch Antenna Parameters ... 27

2.6.2 Losses and Quality Factor ... 28

2.6.3 Radiation Loss ... 30

2.6.4 Surface Waves Loss ... 30

2.6.5 Conduction Loss ... 30

2.6.6 Dielectric Loss ... 31

2.7 Multi-band Frequency Microstrip Antenna... 31

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ix

2.8 Multi-Band Techniques For Patch Antenna ... 31

2.8.1 Orthogonal-Mode Dual-Frequency Patch Antennas ... 33

2.8.2 Multi-patch dual-frequency antennas ... 34

2.8.3 Reactively-loaded patch antennas ... 35

2.9 Previous Studies On The Multi-Band Frequency... 37

2.10 Bandwidth Enhancement Techniques Using Short Pin ... 39

2.11 Array Antenna Fundamentals ... 40

2.11.1 N-Element Array With Uniform Amplitude And Spacing ... 41

2.11.2 Coupling ... 42

2.14 SUMMARY ... 43

CHAPTER THREE: RESEARCH METHODOLOGY ... 44

3.0 Introduction ... 44

3.1. ANALYSIS TECHNIQUE: TRANSMISSION LINE MODEL... 46

3.1.1 Fringing Effect ... 46

3.1.2 Effective Length and Width ... 47

3.2 ANTENNA DIMENSIONS ... 47

3.2.1 Microstrip Line Feed Dimension Calculation ... 47

3.3 Design Of A SIngle Element Patch Antenna At 1.8 Ghz ... 49

3.4 Design approach Of The Triple-Band Antenna ... 50

3.5 Slots Insertion ... 51

3.5.1 Insertion of first slot ... 51

3.5.2 Insertion of second slot ... 51

3.5.3 Insertion of third slot ... 51

3.5.4 Insertion of two slots ... 52

3.5.5 Insertion of three slots ... 52

3.6 Genetic Algorithms And Parameter Sweep Optimization... 52

3.7 Bandwidth Increase Using Short Pin ... 55

3.8 Fabrication Of The h- Slot Patch Antenna ... 56

3.8.1 Antenna fabrication and measurements ... 56

3.8.2 Layout of the Microstrip antenna ... 56

3.8.3 Cutting up-to-scale ... 57

3.8.4 Lamination, Scanning and film creation ... 57

3.8.5 Removing the copper ... 59

3.9 THE ARRAY ANTENNA DESIGN ... 60

3.10 SUMMARY ... 61

CHAPTER FOUR: SIMULATION AND PERFORMANCE EVALUATION OF THE DESIGNED ANTENNA ... 62

4.0 Introduction ... 62

4.1 Simulation And Optimization Of One Resonant Frequency For A Single Element Rectangular Patch Antenna ... 62

4.2 Simulation Results For The Insertion Of Slots Inside The Patch ... 64

4.3 Triple-Band Optimization ... 69

4.4 Triple-Band Bandwidth Optimization Using Short Pin ... 75

4.5 The Fabrication Result ... 77

4.6 Comparison With Previous Works ... 80

4.7 Triple-Band Simulation For the Array Antenna... 83

4.8 Summary ... 86

CHAPTER FIVE: CONCLUSION AND FUTURE WORK ... 87

5.1 Conclusion ... 87

5.2 Future Work ... 88

BIBLIOGRAPHY ... 89

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x

APPENDIX A ... 95

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xi

LIST OF TABLES

Table No. Page No.

4.1 Parameters for the single element patch antenna design 63 4.2 Parameters for the single element patch antenna design after

enhanced single element rectangular patch antenna

64

4.3 Parameters Dimensions for h Slot patch antenna 72

4.4 Gain, return losses and line impedance 74

4.5 Return Losses for Triple-Band 79

4.6 Bandwidth Comparison for the Triple-Band Patch Antennas 80 4.7 Size Comparison for the Triple-Band Patch Antennas 81 4.8 Gain Comparison for the Triple-Band Patch Antennas 81 4.9 Fabrication Comparison for the Triple-Band Patch Antennas 82 4.10 Feeding Technique Comparison for the Triple-Band Patch

Antennas

82

4.11 Comparison between one, two and four elements in term of gain values

86

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xii

LIST OF FIGURES

Figure No. Page No.

2.1 Microstrip Antennas 7

2.2 printed dipole antenna (dipole element) 12

2.3 Symmetrical folded printed dipole 12

2.4 Basic slot antenna shapes with feed structure 13

2.5 Various printed microstrip traveling-wave antenna shapes 15

2.6 Four –slot model 18

2.7 Equivalent circuit of a microstrip patch element 18 2.8 Microstrip antenna geometry (a) Effective dielectric constant (b)

Microstrip line (c) Electric field lines

20 2.9 Charge distribution and current density creation on microstrip

patch

20 2.10 the geometry of a direct microstrip feed microstrip antenna

Quarter-wave transformer and inst-fed respectively

24 2.11 Coaxial probe feeding of a microstrip antenna 25

2.12 Aperture-Coupled Microstrip Feed 27

2.13 the geometry of a proximity coupled microstrip feed microstrip patch antenna (a) top view and (b) side view

27 2.14 (a)Transmitting antenna and (b) its equivalent circuits 29

2.15 multi-band techniques 33

2.16 The geometry of the slotted antenna (a) slotted rectangular-patch antenna (b) slotted square-patch antenna (c) cross-subarray patch antenna (d) slotted cross-patch antenna (e) U slot and C Slot around patch centre

37

2.17 Short pin at the edge patch 40

2.18 N-element linear arrays 41

3.1 Methodology flowchart 45

3.2 Width of the feed, W0, and the inset depth, Y0 48

3.3 variables with each slot edge 53

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xiii

3.4 parameter sweep dialog box 54

3.5 resulting dialog box for parameter sweep 55

3.6 CNC drilling machine: (a) Control PC and the robotic arm; (b) the robotic arm

57

3.7 Laminating machine 58

3.8 Ultraviolet Machine 59

3.9 Bench Module machine 59

4.1 The S-parameters as a function of frequency (a) before enhanced single element rectangular patch antenna, (b) after enhanced single element rectangular patch antenna

63

4.2 Patch antennas with slots for (a) 0.9 GHz (b) 1.8 GHz (c) 2.45 GHZ respectively

65 4.3 Plot of S11 in (dB) for an antenna with resonant frequency at

0.9GHz with the use of parameter sweeping

66 4.4 Plot of S11 in (dB) for an antenna with resonant frequency at

1.8GHz with the use of parameter sweeping

67 4.5 Plot of S11 in (dB) for an antenna with resonant frequency at

2.45GHz with the use of parameter sweeping

67

4.6 Patch antenna with slots for 0.9 and 1.8 GHz 68

4.7 Plot of S11 (in dB) for an antenna with resonant frequency at 1.9 and 1.8 GHz

68 4.8 Patch antenna with slots for 0.9, 1.8 and 2.45 GHz 69 4.9 Plot of S11 (in dB) for an antenna with resonant frequency at 0.9,

1.8 and 2.45 GHz

69

4.10 antenna shape after using genetic algorithms 70

4.11 Plot of S11 (in dB) for an antenna after genetic algorithms was used

71 4.12 Optimized Patch antenna with three slots with resonant

frequencies at 0.9, 1.8 and 2.45 GHz using parameter sweep

71 4.13 Plot of S11 (in dB) for an optimized antenna with resonant

frequency at 0.9, 1.8 and 2.45 GHz

72 4.14 simulation gain radiation pattern in 2D for (a) 0.9 GHz (b) 1.8

GHz (c) 2.4 GHZ respectively

73 4.15 Current distributions of antenna. (a) 0.9, (b) 1.8 GHz and (c) 2.54

GHz

74

4.16 short pin in the edge of the patch antenna 75

4.17 The triple bands frequencies with one short pin in the edge of patch antenna

75

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xiv

4.18 the triple bands frequencies with two short pin in the edge of patch antenna

76

4.19 Network Analyzer 77

4.20 geometry of antenna fabrication 78

4.21 patch antenna fabrication results 78

4.22 simulation and fabrication results 79

4.23 Two-Element Array (a) Array Geometry (b) S11 parameter 84 4.24 Return losses for two-element array with space 0.341.8 between

patches

84 4.25 four element Array (a) Array Geometry (b) S11 parameter 85

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xv

LIST OF ABBREVIATIONS

MPA Microstrip Patch Antenna BTS Base Transceiver Station

dB Decibels

SWR Standing Wave Ratio

BW Bandwidth

MSA Microstrip Slot Antennas GSM Global System Mobile

FDTD Finite-Difference Time-Domain FEM Finite-Element Method

GHz Giga Hertz

PCS Personal Communication System

UMTS Universal Mobile Telecommunication System WLAN Wireless Local Area Network

DCS Digital Cellular System

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CHAPTER ONE INTRODUCTION

1.1 MOTIVATION

The continuous boom and boost of wireless communication have been leading to more and more demands for small sizes of antennas, light-weight and high gain; these are supposed to be with omni-directional radiation (Elsadek, 2010; Mohammed M. Y.

Yousef, 2010). A microstrip antenna is one of the types of antenna that is chosen by researchers to be used in wireless applications due to the characteristics that distinguish these antennas in terms of small size, low profile, good integration, low cost. The microstrip patch antennas which function via multiple frequency bands are necessary to use with some wireless applications like mobile phones and the mobile phone jammer. Over the recent past years, great effort has been focusing on the designs of microstrip antennas and enhancing their characteristic. This type of antenna is better used in the applications that require very narrow band properties, like security applications. The principle drawback of the microstrip patch antenna is the restricted bandwidth which is an important parameter in the antenna design (Maci & Gentili, 1997). However, there are some techniques that are used to improve bandwidth.

1.2 THE MOBILE PHONE JAMMER

Considering the increase in the number of users over the last twenty years there has been a significant rise in the popularity of mobile communication devices. The mobile networks have already started to cause annoyance by the mobile ringing in inappropriate places or times. Some places such as mosques, lecture rooms, libraries,

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2

concert halls, meeting rooms, demand for strict silence. The cell phone jammer is the tool for addressing this problem. The use of intentional RF blockage (Communication jamming devices) as a warfare technique dates from World War II (Araujo, Santos, &

Dias, 2007). The mobile jammer devices which were once limited to electronic warfare use are now becoming civilian products. We can define the cell phone jammer as a device which attempts to obstruct the physical transmission and reception of mobile wireless communication, thus prohibiting cellular phones from continuing the process of sending/receiving signals from/to Base Transceiver Station (BTS). Mobile jammers have been thus becoming a vital necessity over the past few years, and their importance as civilian electronic products/gadgets is gradually realized more and more. In a more cultured society the necessity for restricting the use of cellular phones is on the rise in communal settings such as places of worship, educational institutions, theatres, and others where silence is greatly appreciated.

There are two major types of jammers, non-intelligent and intelligent jammers.

The non-intelligent jammer is used in a restricted area and it is designed to block all mobile phones operating in a certain frequency band such as the downlink frequency band of the global system for mobile communication. This type of jammers is not fit for civilian use as they are specifically used for military applications; because they block all mobile phones transmission operation in the area. In addition, the system will keep on transmit jamming signals, whether there is a mobile user in that restricted area or not. Moreover, a non-intelligent system jams the whole downlink frequency band even though the intruder mobile phone uses only a small portion of the band.

The intelligent jammer is developed to solve problems such as those appearing in non- intelligent jammers; therefore this jammer is the most powerful jamming system that can be used in military and civilian places. Typically, the intelligent jammer functions

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3

as a detection device. When it locates a mobile station receiving a signal from the base station, it signals the base station, preventing it from establishing communication. This series of steps which includes the detection and obstruction of call establishment takes place during the period of time normally occupied by signaling and hand shaking. The study in this project will focus on the antenna design as part of smart antenna system that will be used in a mobile phone jammer.

1.3 STATEMENT OF THE PROBLEM

The cost, power consumption, design complexity, robustness, size, gain, multi-band, components availability, performance, and selectivity pose a challenge to researchers to invent new means and techniques to design an efficient microstrip antenna that considers all these factors. In this study, an array of triple-band antennas will be designed as part of a smart antenna for the mobile phone jammer and the design should reduce these problems.

1.4 RESEARCH OBJECTIVES In this project the main objectives are:

1. To design a triple-band patch antenna using h-slots inside patch antenna as a new shape, capable of working on finely tuned frequencies of 0.9, 1.8 and 2.45 GHz. The designed antenna should also be of smaller size, easy to fabricate with a lower cost, a wider bandwidth and higher gain compared with previous work.

2. To design an array antenna as of a smart antenna for a mobile phone jammer.

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4

3. To evaluate the performance of the designed antenna.

1.5 RESEARCH METHODOLOGY

In this research, the following steps are taken in order to achieve the desired objectives:

· Conduct a comprehensive study on the fundamental concepts of patch antenna designs, considered being part of smart antennas.

· Design and simulate a patch antenna for a single resonant frequency.

· Investigate and analyses the multi-band patch antenna methods in the light of the results from recent reports of such works.

· Design and simulate a patch antenna for a multi-band resonant frequency.

· Investigate and analyses the short pin methods aimed at improving the band width of the patch.

· Investigate the spacing between the elements to design an array antenna considered part of smart antennas.

· Design and simulate an array antenna using CST Microwave studio software.

· Develop a prototype multi-band microstrip patch antenna based on the design specification parameters.

· Obtain experimental results for validating the performance of the designed antenna by comparing them with those from the simulation.

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5 1.6 SCOPE

The main contributions of this project are to investigate the multi-band frequency using a microstrip patch antenna and try to improve one of the best designs in term of size, gain and return loss. This scope is limited to the design and fabrication of microstrip patch triple-band slotted antenna that is better than the previous design in the same bands. This antenna is part of a smart array antenna that is used with mobile phone jammer.

1.7 THESIS ORGANIZATION

Chapter two provides an overview of microstrip patch antenna design with regards to the parameters of a microstrip patch antenna which has one resonant frequency and a multi-band frequency. The bandwidth improvement and the array antenna are also discussed in this chapter. Chapter three presents the methodology of this study. The slots insertion inside the patch to achieve a triple-band displayed in detail. In addition the fabrication procedure is reported. Moreover, chapter four presents the results of the triple-band patch antenna, bandwidth improvement, comparison between fabrication and simulation results and array antenna with a best distance between elements are shown. Chapter five is the conclusion and suggestions for future work of the research.

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CHAPTER TWO:

MICROSTRIP PATCH ANTENNA

2.1 INTRODUCTION

The main goal of this research is to design a microstrip patch antenna operating at multiple frequency bands. It is necessary to have an overview of this topic. This chapter discusses the antenna design parameters in general, and presents an overview about the microstrip patch antenna with special focus on the techniques used for multi-band patch antenna, enhancement of bandwidth and array antenna.

The microstrip antenna name was raised in 1953 by (Deschamps). Gutton and Baissinot received patent in France (Baissinot, 1955). In 1970 the growth in this device was evidenced by the access to good substrates with attractive thermal, efficient tangent and mechanical properties (Garg, 2001).

Because of the many advantages it offers, such as affordability, being lightweight, having low volume, conformal configuration, and compatibility with integrated circuits. Researchers were keen to develop microstrip patch antennas and arrays of patch antenna, and used it in various applications (Bahl & Bhartia, 1980).

However, microstrip antennas also have some limitation like somewhat lower gain (almost 6 dB), low power, large ohmic loss in the feed structure of arrays, low efficiency, poor polarization purity, and significantly narrow frequency bandwidth (Balanis, 2005; Garg, 2001). Nevertheless, there are some methods to overcome these problems for example the efficiency can be extended (to as large as 90 percent if

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surface waves are not included) and bandwidth (up to about 35 percent) by increasing the height of the substrate (D. M. Pozar, 1992).

A microstrip patch antenna in its most basic form consists of three parts:

ground plane, dielectric substrate and the radiating patch printed on one face of the a dielectric substrate as shown in Figure 2.1 (Balanis, 2005). Numerous substrates are suitable for the design and the range of their dielectric constants is typically 2.2 ≤ r ≤ 12 (Balanis, 2005).

A microstrip patch antenna performance will supply large bandwidth, good efficiency and loosely field’s radiation into space, when substrate is thick in this case the value of dielectric constant is small and the size of patch antenna is large. The microstrip patch antenna with high value for dielectric constants and thin substrate requires tightly bound fields to reduce unrequired coupling and radiation. The size of patch antenna in this case will be smaller and suitable for microwave circuitry (D. M.

Pozar, 1992).

Figure 2.1: Microstrip Antennas

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8 2.2 ANTENNA DESIGN PARAMETERS

The essential characteristics of an antenna like radiation pattern, gain, return losses, and impedance require description because the antenna is the focal point of communication systems and they are basically dependent on the characteristics of the antenna used in the system (Au, Bakshi, 2009).

2.2.1 Gain

Gain of antenna is described as the ratio of the amount of power conveyed toward peak radiation to that of an isotropic source (Balanis, 2005). Antenna gain is written in a real antenna's specification sheet because it takes into account the actual losses that occur. An antenna with a gain of 3 dB means that the power received far from the antenna will be 3 dB higher (twice as much) than what would be received from a lossless isotropic antenna with the same input power.

2.2.2 Radiation Pattern

A radiation pattern represents the variance of the power radiated by an antenna as a function of space coordinates. This power difference is evident in the antenna's far field due to the variation of the arrival angle (Balanis, 2005).

2.2.3 Return Losses and Standing Wave Ratio

S-parameters illustrate the input-output relationship between terminals in an electrical system, or it is the loss of signal power which follows the reflection caused by a discontinuity in a transmission line or optical fiber. This discontinuity can be the result of a failure to correspond with the terminating load or with a device inserted in the

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9

line. It is normally depicted as a ratio in decibels (dB). Return loss has a relationship with standing wave ratio (SWR). Increasing return loss corresponds to lower SWR.

Return loss is an indication of how well devices or lines are matched. A high return loss represents a good match. Return loss is more preferable to SWR in modern practice due to its finer resolution for small values of reflected wave (Bird, 2009).

2.2.4 Input Impedance

Input impedance pertains to “the impedance presented by an antenna at its terminals or the ratio of the voltage to current at a pair of terminals or the ratio of the appropriate.

components of the electric to magnetic fields at a point.” (Balanis, 2005). The real part of the antenna 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. This is non-radiated power. An antenna with a real input impedance (zero imaginary part) is said to be resonant and the voltage and current are exactly in time-phase. Note that the impedance of an antenna will vary with frequency.

2.2.5 Bandwidth

The bandwidth of an antenna represents “the range of frequencies within which the Performance of the antenna, with respect to some characteristic, conforms to a specified standard.”(Balanis, 2005). Bandwidth is typically quoted in terms of VSWR.

For instance, an antenna may be described as operating at 100-400 MHz with a VSWR<1.5. This statement implies that the reflection coefficient is less than 0.2 and

Rujukan

DOKUMEN BERKAITAN

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Hence, this study was designed to investigate the methods employed by pre-school teachers to prepare and present their lesson to promote the acquisition of vocabulary meaning..

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DISSERTATION SUBMITTED IN FULFILLMENT OF THE REQUIREMENT FOR THE DEGREE MASTER OF SCIENCE.. INSTITUTE OF BIOLOGICAL SCIENCE FACULTY