DESIGN AND OPTIMIZE OF RECTANGULAR MICROSTRIP PATCH ANTENNA ARRAYS
PERFORMANCE AT 2.4 GHz
BY
KHAMIS HASSAN ALI
A dissertation submitted in fulfilment of the requirement for the degree of Master of Science
(Communication Engineering)
Kulliyyah of Engineering
International Islamic University Malaysia
SEPTEMBER 2018
ii
ABSTRACT
The demand for small and reliable, high performance, diverse polarization, low- profile, and lightweight antennas has greatly increased. Its demand is in wireless communication, mobile communications, satellite communication, electronic warfare, biological telemetry and IoT technology. Microstrip patch antennas are examples of low profile antennas. In the current highly demanding consumer world for microstrip patch antenna enabled systems, an effective and efficient higher manufacturing processing capability is required. In this research, an investigation of patch antenna array with beamforming technology was performed in detailed. The aim is to increase the data rate and capacity in Wi-Fi applications making it ready for IoT technology. It is expected that Wi-Fi will be one of the connecting devices in IoT since it is widely used in houses, public and industrial places. The array is composed of rectangular patches with modified slot on Rogers 5880 at 2.4 GHz. There is a challenge while approximating antenna array characteristics which is mutual coupling, that can result inaccurate radiation pattern of whole antenna array. To overcome this, a technique using active element pattern from a full wave antenna software was proposed as a solution to this research. Later, the beamforming technology was performed using a combination of active element pattern and genetic algorithm techniques in order to optimize the performance of the antenna array. Hence, after results analysis, the main beam was able to be steered in the desired direction from angle 10º to 30º. However, from angle 40º to 50º, main beam was not steered to the desired direction due to limitation of linear array which is as angle of steering increasing, mutual coupling increasing. Therefore, more works are needed on lowering mutation rates and increasing crossover rates for Genetic Algorithm optimization process.
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ثحبلا ةصلاخ
ةريخلأا ةنولأا يف ريبك لكشب دادزإ ىلع بلطلا
تاذ ةريغصلا تايئاوهلا
باطقتسلإا ,يلاعلا ءادلأا .فيفخلا نزولاو ريغصلا مجحلا ، عونتملا
اذه
نم تلااصتلإا ،ةلقنتملا تلااصتلاا ،ةيكلسلالا تلااصتلإا يف لثمتي بلطلا تنرتنإو يجولويبلا سايقلا ،ةينورتكللإا برحلا ،ةيعانصلا رامقلأا للاخ (ءايشلأا ةلثمأ يه ةقيقدلا ةيطيرشلا تايئاوهلا .) IOT
لل ةريغص تايئاوه
.مجحلا تايئاوهلا معدت يتلا ةمظنلأل ايلاع ابلط دهشي يذلا يلاحلا انتقو يف
ةردق تاذ ةمظنأ داجيإو ثادحتسا مزلالا نم حبصأ ةقيقدلا ةيطيرشلا .ديازتملا بلطلا ةيبلتل ةيلاع ةيلاعفبو ةريبك ةجلاعمو ةيعينصت اذه يف
ثحبلا
ةيعاعشإ ميق عم بنج ىلإ ابنج ةقيقدلا ةيطيرشلا تايئاوهلا فص بيترت مت متي .ةيسيطانغمورهكلا مزحلا هيجوت يف مدختستو )روطلاو ةعسلا( ةفلتخم ةفوفصملا لعجل اعم ةيسيطانغمورهكلا تاراشلإا روط يف تاقورفلا عمج يئاوهلاب ةنراقم يلعأ ةيهيجوت ةردق عم دحاو يئاوهك لمعت عمو .دحاولا
عم ةلوهسب تايئاوهلا فص نم ةيسيطانغمورهكلا تاراشلإا رثأتت كلذ مت ثحبلا اذه يف .دمعتملا ريغلاو دمعتملا لخادتلاو شيوشتلا ميدقت
ةينقت
لإ ةيسيطانغمورهكلا مزحلا ليكشت ى
فيفخت لجأ نم تايئاوهلا فص
.ةءافكب تاراشلإا نيب لخادتلا لغتسي ماظن مادختسا مت اضيأ
ةيمزراوخلا
دنع .بولطملا هاجتلإا يف ةيسيطانغمورهكلا مزحلا عاعشإ هيجوتل ةينيجلا لكشب ةينيجلا ةيمزراوخلا موقت ةيسيطانغمورهكلا مزحلا هيجوت ليكشت .ةهج يأ ىلإ ةمزحلا هيجوت دنع مئلام رود لضفأ نع ثحبلاب يئاوشع و امك دابتملا نارتقلإا ريثأت ىلإ ثحبلا اذه يف رظنلا متي فص رصانع نيب ل
يسيطانغمورهكلا عاعشلإا ططخم ةقد دادزتس كلذل اةجيتنو .تايئاوهلا
.ةقيقدلا ةيطيرشلا تايئاوهلا فصل
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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 dissertation for the degree of Master of Science (Communication Engineering)
………..
Norun Farihah Bt. Abdul Malek Supervisor
………..
Sarah Yasmin Mohamad 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 dissertation for the degree of Master of Science (Communication Engineering)
………..
Md Rafiqul Islam Internal Examiner
………..
Farah Diyana Bt. Abdul Rahman Internal Examiner
This dissertation was submitted to the Department of Electrical and Computer Engineering and is accepted as a fulfilment of the requirement for the degree of Master of Science (Communication Engineering)
………..
Mohamed Hadi Habaebi Head, Department of Electrical and Computer Engineering
This dissertation was submitted to the Kulliyyah of Engineering and is accepted as a fulfilment of the requirement for the degree of Master of Science (Communication Engineering)
………..
Erry Yulian Triblas Adesta Dean, Kulliyyah of Engineering
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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.
Khamis Hassan Ali
Signature ... Date ...
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INTERNATIONAL ISLAMIC UNIVERSITY MALAYSIA
DECLARATION OF COPYRIGHT AND AFFIRMATION OF FAIR USE OF UNPUBLISHED RESEARCH
DESIGN AND OPTIMIZE OF RECTANGULAR MICROSTRIP PATCH ANTENNA ARRAYS PERFORMANCE AT 2.4 GHz
I declare that the copyright holders of this dissertation are jointly owned by the student and IIUM.
Copyright © 2018 by Khamis Hassan Ali and International Islamic University Malaysia. All rights reserved.
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 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 retrieved system and supply copies of this unpublished research if requested by other universities and research libraries.
By signing this form, I acknowledged that I have read and understand the IIUM Intellectual Property Right and Commercialization policy.
Affirmed by Khamis Hassan Ali
……..……….. ………..
Signature Date
vii
ACKNOWLEDGEMENTS
Firstly, it is my utmost pleasure to dedicate this work to my dear parents and my family, who granted me the gift of their unwavering belief in my ability to accomplish this goal: thank you for your support and patience.
I wish to express my appreciation and thanks to those who provided their time, effort and support for this project. To the members of my dissertation committee, thank you for sticking with me.
Finally, a special thanks to my supervisor Dr. Norun Farihah Bt. Abdul Malek for her patience on me and continuous support, encouragement and leadership, and for that, I will be forever grateful.
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TABLE OF CONTENTS
Abstract ... ii
Abstract in Arabic……….iii
Approval Page………...iv
Declaration ... v
Copyright Page ... vi
Acknowledgements ... vii
List of Tables ... xii
List of Figures ... xiii
List of Abbreviations……….xv
CHAPTER ONE: INTRODUCTION ... 1
1.1 Background of the Study ... 1
1.2 Problem Statement and Its Significance ... 3
1.3 Research Objectives... 5
1.4 Research Scope ... 5
1.5 Research Methodology ... 5
1.6 Thesis Organization ... 7
CHAPTER TWO: LITERATURE REVIEW ... 9
2.1 Introduction... 9
2.2 Microstrip Patch Antenna ... 9
2.2.1 Background ... 9
2.2.2 Advantages and Disadvantages ... 11
2.2.3 Feeding Techniques ... 12
2.2.3.1 Coaxial Probe Feed ... 12
2.2.3.2 Microstrip Line Feed ... 13
2.2.3.3 Aperture-Coupled Feed ... 14
2.2.3.4 Proximity-Coupled Feed ... 14
2.3 Antenna Arrays ... 16
2.3.1 Geometrical Configuration ... 17
2.3.1.1 Linear Arrays ... 17
2.3.1.2 Planar Arrays ... 18
2.3.2 Mutual Coupling ... 19
2.3.3 Active Element Pattern ... 20
2.4 Optimization Techniques ... 22
2.5 Related Works ... 25
2.6 Summary ... 33
CHAPTER THREE: DESIGN OF MICROSTRIP PATCH ANTENNA ... 34
3.1 Introduction... 34
3.2 Antenna Design ... 34
3.2.1 Single Microstrip Patch Antenna ... 34
3.2.1.1 Calculation of Patch Dimension using Transmission Line34 3.2.1.2 Calculation of Substrate and Ground Dimension using Transmission Line ... 36
ix
3.2.1.3 Calculation of Coaxial Feeding Point Position using
Transmission Line Model ... 36
3.2.2 Full Wave Model of a Slotted Ring Microstrip Patch Antenna .... 37
3.2.3 Full Wave Model of a Cross Slotted Microstrip Patch Antenna ... 38
3.3 Fabrication of The Antenna Design ... 40
3.4 Antenna Arrays Design... 43
3.4.1 Linear Arrays ... 43
3.4.2 Planar Arrays... 44
3.5 Performance Optimization of Cross Slotted Ring Microstrip Patch Antenna ... 45
3.5.1 Beam Steering of 1 By 4 Linear Array Using AEP and GA Methods ... 46
3.5.1.1 Fitness Function ... 48
3.5.1.2 Active Element Pattern ... 49
3.5.1.3 Fitness Sigma Scaling ... 50
3.5.1.4 Arithmetic Crossover ... 51
3.5.1.5 Mutation... 52
3.5.2 Beam Steering of 2 by 2 Planar Array Using CST Array Wizard ... 53
3.6 Summary ... 54
CHAPTER FOUR: SIMULATION AND MEASUREMENT RESULTS ANAYLSIS ... 55
4.1 Introduction... 55
4.2 Single Patch Antenna Results ... 55
4.2.1 Slotted Ring Patch Antenna ... 55
4.2.2 Cross Slotted Ring Patch Antenna ... 58
4.2.3 Comparison of Single Patch Antenna Results ... 61
4.3 Linear Antenna Arrays Simulation Results ... 61
4.3.1 Slotted Ring 1 by 4 Patch Antenna Array ... 61
4.3.2 Cross Slotted Ring 1 by 4 Patch Antenna Array ... 63
4.3.3 Comparison of Linear Arrays Results ... 64
4.4 Planar Arrays Simulation Results ... 65
4.4.1 Slotted Ring 2 by 2 Patch Antenna Array ... 65
4.4.3 Comparison of Planar Arrays Results ... 67
4.5 Summary ... 68
CHAPTER FIVE: PERFORMANCE OPTIMIZATION OF CROSS SLOTTED RING PATCH ANTENNA ARRAYS ... 69
5.1 Introduction... 69
5.2 Performance Optimization of 1 by 4 Linear Antenna Arrays... 69
5.2.1 Comparison of Radiation Pattern Calculated using AEP and CST ... 70
5.2.2 Steerable Main Beam at 10º ... 71
5.2.2 Steerable Main Beam at 20° ... 73
5.2.3 Steerable Main Beam at 30° ... 75
5.2.4 Steerable Main Beam at 40 ... 77
5.2.5 Steerable Main Beam at 50 ... 79
x
5.2.6 Performance Comparison of Radiation Pattern at Different
Steering Angle ... 81
5.3 Beam Steering Capability of 2 by 2 Planar Antenna Arrays ... 83
5.4 Summary ... 85
CHAPTER SIX: CONCLUSION AND FUTURE WORK ... 87
6.1 Conclusion ... 87
6.2 Contribution ... 88
6.3 Future Work ... 89
REFERENCES ... 90
APPENDIX A: ………...95
xi
LIST OF TABLES
Table 2.1 Comparison advantages and disadvantages of microstrip patch antenna 11
Table 2.2 Comparison of Different Feed Techniques 15
Table 2.3 Summary of related works 30
Table 3.1 Specification of Slotted Ring Rectangular Microstrip Patch Antenna 38 Table 3.2 Specification of Cross Slotted Ring Rectangular Microstrip Patch 39 Table 4.1 Results comparison between Slotted Ring Patch and Cross Slotted Ring
Patch Antennas 61
Table 4.2 Results comparison between linear arrays of Slotted Ring Patch and Cross
Slotted Ring Patch Antennas 64
Table 4.3 Results comparison between planar arrays of Slotted Ring Patch and Cross
Slotted Ring Patch Antennas 67
Table 5.1 Amplitude and Phase of Each Element 71
Table 5.2 Amplitude and Phase at 10° 73
Table 5.3 Amplitude and Phase at 20° 74
Table 5.4 Amplitude and Phase at 30° 76
Table 5.5 Amplitude and Phase at 40° 78
Table 5.6 Amplitude and Phase at 50° 80
Table 5.7 Main Lobe Radiation Pattern at Different Steering Angle 82 Table 5.8 Comparison of Beam Steering of 2 by 2 Cross Slotted Ring Patch Antenna
Array 85
xii
LIST OF FIGURES
Figure 1.1 Beamforming Technology 2
Figure 1.2 Flow Chart of Research Methodology 7
Figure 2.1 Microstrip Patch Antenna front view 10
Figure 2.2 Microstrip Patch Antenna Top View 10
Figure 2.3 Rectangular Microstrip Patch Antenna with and without Slot 11
Figure 2.4 Coaxial Probe Feed Technique 13
Figure 2.5 Microstrip Line Feed Technique 13
Figure 2.6 Aperture-Coupled Feed Technique 14
Figure 2.7 Proximity-Coupled Feed Technique 15
Figure 2.8 Linear array geometry for patch antennas 17
Figure 2.9 Planar Geometry for Patch Antennas 19
Figure 2.10 Geometry of a Uniform N-Element Linear Array 21 Figure 2.11 Defining Geometry for the Active Element Pattern of a Uniform Linear
Array 21
Figure 3.1 Slotted Ring Patch Antenna 37
Figure 3.2 Cross Slotted Ring Patch Antenna 39
Figure 3.3 Fabricated Slotted Ring Microstrip Patch Antenna 42 Figure 3.4 Fabricated Cross Slotted Ring Microstrip Patch Antenna 42
Figure 3.5 Vector Network Analyser 43
Figure 3.6 Slotted Ring 1 by 4 Patch Antenna Array 44
Figure 3.7 Cross Slotted Ring 1 by 4 Patch Antenna Array 44
Figure 3.8 Slotted Ring 2 by 2 Patch Antenna Array 45
Figure 3.9 Cross Slotted Ring 2 by 2 Patch Antenna Array 45
Figure 3.10 Flow Chart Optimization Process Using GA 47
xiii
Figure 3.11 The Desired Radiation Pattern Selected by User in order to Steer The
Beam at Theta=30º. 48
Figure 3.12 Geometry of a Microstrip Linear Array of N elements 49
Figure 3.13 CST Array Wizard 53
Figure 4.1 Simulated S11 parameter 56
Figure 4.2 Measured S11 parameter 56
Figure 4.3 Combination of Simulation and Measurement Result of S11 Parameters 56
Figure 4.4 Impedance Matching 57
Figure 4.5 Farfield Directivity of the Polar Radiation Pattern 57 Figure 4.6 Farfield Directivity of the 3D Radiation Pattern 57
Figure 4.7 Simulated S11 Parameter 58
Figure 4.8 Measured S11 Parameter 59
Figure 4.9 Combination of Simulation and Measurement result of S11 Parameter 59
Figure 4.10 Impedance Matching 60
Figure 4.11 Farfield Directivity of the Polar Radiation Pattern 60 Figure 4.12 Farfield Directivity of the 3D Radiation Pattern 60
Figure 4.13 S-Parameters 62
Figure 4.14 Farfield Directivity of the Radiation Pattern 63
Figure 4.15 S-Parameters 63
Figure 4.16 Farfield Directivity of the Radiation Pattern 64
Figure 4.17 S-Parameters 65
Figure 4.18 Farfield Directivity of the Radiation Pattern 66
Figure 4.19 S-Parameters 66
Figure 4.20 Farfield Directivity of the Radiation Pattern 67 Figure 5.1 Comparison between Radiation Pattern between AEP and CST 70
Figure 5.2 Fitness Function at 10º 72
xiv
Figure 5.3 Main Lobe Beam at 10º 72
Figure 5.4 Fitness Function at 20º 73
Figure 5.5 Main Lobe Beam at 20º 74
Figure 5.6 Fitness Function at 30º 75
Figure 5.7 Main Lobe Beam at 30º 76
Figure 5.8 Fitness Function at 40º 77
Figure 5.9 Main Lobe Beam at 40º 78
Figure 5.10 Fitness Function at 50º 79
Figure 5.11 Main Lobe Beam at 50º 80
Figure 5.12 Beam Steering at Theta=50º from CST Array Wizard 82
Figure 5.13 Beam steering at 45º 83
Figure 5.14 Beam steering at 90º 84
Figure 5.15 Beam steering at 135º 84
Figure 5.16 Beam steering at 180º 84
xv
LIST OF ABBREVIATIONS
2D 2Dimensions
3D 3Dimensions
4G 4th Generation
AEP Active Element Pattern BER Bit Error rate.
BW Bandwidth
BWA Broadband Wireless Access CST Computer Simulation Technology
dB Decibels
Dbi Decibels -Isotropic
EBG Electromagnetic Band Gap.
ETSI European Telecommunications Standards Institute ECC Envelope Correlation Coefficient
FC center frequency
FH highest frequency
FL lowest frequency
FR4 Flame Resistant 4.
GA Genetic Algorithm
GHz Gigahertz
LTE Long Term Evolution
MHz Megahertz
MPA Micro strip Patch Antenna PCB Printed Circuit Board
RMPA Rectangular Micro strip Patch Antenna
RX Receiver
SNR Signals to Noise Ratio
TX Transmitter
UMTS Universal Mobile Telecommunications System VSWR Voltage Standing Wave Ratio
Wi-Fi Wireless Fidelity.
WiMax Worldwide Interoperability for Microwave Access WLAN Wireless Local Area Network
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CHAPTER ONE INTRODUCTION
1.1 BACKGROUND OF THE STUDY
The continuous boom and boost of wireless communication have been leading to more and more demands for small size light-weight and high gain antennas. (Elsadek, 2010;
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 and low cost. The microstrip patch antennas which function via multiple frequency bands are necessary to use with some wireless applications simultaneously like mobile phones.
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 and Gentili, 1997).
The existing trend in development of latest communication systems and wireless technologies is to achieve better coverage and capacity with high data rates (Gross, 2005). Conventionally, the power consumption and interference increase when omni directional antennas transmit signals equally to all directions rather than focusing the main beam to the desired user (Alexiou and Haardt, 2004). Thus, the capacity and high data rates can be improved by tailoring the beam to the intended users and nulls to the unintended users (Van Veen and Buckley,1988). WLAN standards offer data rates up to 54 Mbps; while GSM, CDMA and GPRS are capable of high quality voice communications but at the expense of multipath fading so utilization of spatial domain
2
(i.e. through beamforming in smart antenna systems) ensures less interference by tracking and focusing their major beam patterns to intended user (Foschini and Gans, 1998).
Figure 1.1 Beamforming Technology
Beamforming Technology. (2018, June 24). Retrieved from
http://www.hearingreview.com/2014/10/new-binaural-strategies-enhanced-hearing/
With the growth of Internet of Things (IoT), it is expected that beamforming technology will prepare the Wi-Fi to become suitable connectivity for IoT. This is because beamforming technology is used to focus a Wi-Fi signal on a specific device, rather than spreading it across a wider area as a result it gives a better quality of signal to the intended target as shown in Figure 1.1.
The beamforming capability may be achieved by implementing an advanced and intelligent signal processing algorithm in antenna array. In this case, each of the individual element of antenna array is weighted separately (amplitude and phase) so that the beam can be dynamically adjusted and directed to the intended users and ignore all other incoming signals of the same frequency.
3
In this research, an investigation of patch antenna array with beamforming technology has been performed in detailed. The aim is to increase the data rate and capacity, making it ready for IoT technology. The array is composed of rectangular patches with modified slot on Rogers 5880 at 2.4GHz. There is a challenge while approximating antenna array characteristics which is mutual coupling, that can result inaccurate radiation pattern of whole antenna array. To overcome this, a technique using active element pattern (AEP) from a full wave antenna software will be proposed as a solution to this research. Later, the beamforming technology will be performed using an Advanced Signal Processing Algorithms. There are several algorithms that are commonly used to optimise the performance of the antennas such as simulated annealing, particle swarm optimisation and genetic algorithm techniques.
1.2 PROBLEM STATEMENT AND ITS SIGNIFICANCE
Beamforming is a concept on concentrating the RF signal and aim it to the targeted direction. Rather than broadcasting the signal to a wide area, beamforming technique can be used to increase data rates and bandwidth.
With the booming of IoT, Wi-Fi will be one of the favourable choices among other connectivity solutions such as Bluetooth, ZigBee and RFID, to name a few. The reason is that it is one of the most successful and ubiquitous standard of connectivity and is used at home, enterprise, schools, hospitals, airports etc. However, as the number of devices for IoT increase together with the demand of data rates, it is expected that beamforming technology will prepare the Wi-Fi to become a suitable connectivity for IoT.
Devices that support beamforming focus their signals toward each client, concentrating the data transmission so that more data reaches the targeted device
4
instead of radiating out into the atmosphere. If the Wi-Fi client also supports beamforming, the router and client can exchange information about their respective locations in order to determine the optimal signal path. Any device that beamforms its signals is called a beamformer, and any device that receives beamformed signals is called a beamformee.
Thus, this research will focus on designing an antenna array for beamforming capabilities for Wi-Fi technology. There are many analysis of antenna array such as pattern multiplication, Uniform Distribution, Binomial and Dolph-Chebyshev techniques to name a few. However, these techniques are conventional which does not take into account the mutual coupling effect of antenna array. This is due to the presumption that all elements have equal patterns which increase inaccuracy in antenna array design. Mutual coupling effect is an interaction of energy transferred between one element to another antenna element when they are placed closely with each other. The effect of mutual coupling can be taken into account by using the AEP method. The AEP is obtained with a single element in the array is excited while all other elements in that array are terminated with matched loads. AEP is proposed to estimate the far field pattern of the antenna array because the mutual coupling is considered and it is an accurate method to synthesize the far field pattern. The AEP method has been proposed to be used for beamforming technique. The beamforming technique can be further realized by using optimization techniques in order to steer the main beam to the desired direction and nulls to the undesired direction. Hence, an optimization of the performance of antenna array at 2.4 GHz (Wi-Fi) with beamforming capabilities has been proposed as a solution for the IoT technology.
5 1.3 RESEARCH OBJECTIVES
The focus of this research is to investigate the performance of the rectangular microstrip patch antenna array at 2.4 GHz using beamforming technique.
The specific objectives of the research are as follows:
• To design a slotted ring and cross-slotted ring of rectangular microstrip patch and arrays at 2.4 GHz using Computer Simulation Technology (CST).
• To fabricate single patch antenna in order to validate the measured results with the simulated results.
• To optimize the radiation pattern of antenna array using Active Element Pattern and Genetic Algorithm optimisation technique for beam steering purpose.
1.4 RESEARCH SCOPE
The research work will cover on designing and fabricating a rectangular microstrip patch antenna. Then, the radiation patterns of antenna array will be calculated using AEP obtained from CST MWS and combine them together by GA optimisation technique from Matlab in order to steer the main beam to the desired direction. The optimisation will be implemented to determine the best excitation values of each of the element of antenna array for beamforming application.
1.5 RESEARCH METHODOLOGY
In this research, the following steps are taken place in order to achieve the objectives of this research as shown in Figure 1.2:
Step 1: Literature review
6
In order to achieve the main objectives of this research; a complete review has been performed about the microstrip patch antenna, parameters and feeding techniques, and the previous works related to optimization techniques of radiation patterns of antenna arrays.
Step 2: Design and Simulation of Microstrip Patch Antenna
A rectangular microstrip patch antenna operates at 2.4 GHz was designed and simulated. CST Microwave Studio was used for simulation, that enables the implementation of two and three dimensions analysis of patterns.
Step 3: Fabrication of the designed antenna
Microstrip patch antenna fabricated and analyzed its performances such as return loss, operating frequency and bandwidth and compared with the simulated results.
Step 4: Simulation of Microstrip Patch Antenna Arrays using CST MWS
Here a planar array of 2 by 2 and a linear array of 1 by 4 of microstrip patch antenna were simulated using CST MWS and their results such as S-parameters and radiation pattern were analysed.
Step 5: Performance Optimization of Microstrip Antenna Array
The optimisation has been performed using a combination of active element pattern (AEP-taken from CST MWS) and Genetic Algorithm technique using Matlab software. The performance of microstrip patch antenna arrays were enhanced so as the optimisation considers mutual coupling effect and increases beamforming capability of antenna array for Wi-Fi applications.
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Figure 1.2 Flow Chart of Research Methodology
1.6 THESIS ORGANIZATION
This dissertation has been divided into six chapters. Chapter one presents an introduction of the research work, problem statement, research objectives, research methodology and scope of the research. Chapter two describes a literature review of
8
the study which includes main sections such as, microstrip patch antenna fundamentals, antenna arrays, optimization techniques and related works.
Chapter three describes the design of microstrip patch antenna at 2.4 GHz. Starting with the single patch antenna design then followed by fabrication of single patch antenna and finally the design of linear and planar microstrip patch antenna arrays.
Chapter four describes the results obtained from simulation and measurement of microstrip patch antenna. The results include S-parameters, Impedance and Radiation pattern
Chapter five presents performance analysis of the proposed design of microstrip patch antenna array. This includes performance optimisation of linear arrays of microstrip antenna and beam steering capability of planar arrays of microstrip antenna.
Chapter six reports the conclusion, contribution and future work of the research.
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CHAPTER TWO LITERATURE REVIEW
2.1 INTRODUCTION
Microstrip patch antenna was first introduced in 1950s (Srivastava, et al; 2014).
However, the research and development of microstrip antenna begin to grow after 20 years with the development of printed circuit board (PCB) technology in 1970s.
Microstrip antenna was found application in different kind of fields due to its low profile and compact size (Kumar, et al; 2013). It has widely been used for the civilian and military application, for examples, radio- frequency identification (RFID), mobile system, vehicle collision avoidance system, broadcast radio, satellite communications, surveillance system, direction finding, radar systems, remote sensing, as well as missile guidance (Srivastava, et al; 2014). However, microstrip antenna suffers losses which result in narrow bandwidth and low gain. Therefore, many researches had been done to improve bandwidth by introducing different structures within the antenna geometry.
2.2 MICROSTRIP PATCH ANTENNA 2.2.1 Background
Microstrip patch antenna is a printed type antenna with a radiating patch on one side of a dielectric substrate and a ground plane on the other side as shown in Figure 2.1 and Figure 2.2. The patch is generally made of copper. It can take any shape, with rectangular and circular configurations are the most widely used. Figure 2.3 shows the different patch shapes that can be used in microstrip antennas.
