design of multibeam antenna for …eprints.utm.my/id/eprint/11414/1/sitizuraidahibrahimmfke...antena...

25
DESIGN OF MULTIBEAM ANTENNA FOR WIRELESS LOCAL AREA NETWORK APPLICATIONS SITI ZURAIDAH IBRAHIM UNIVERSITI TEKNOLOGI MALAYSIA

Upload: phamanh

Post on 24-Mar-2019

226 views

Category:

Documents


0 download

TRANSCRIPT

DESIGN OF MULTIBEAM ANTENNA FOR WIRELESS LOCAL AREA

NETWORK APPLICATIONS

SITI ZURAIDAH IBRAHIM

UNIVERSITI TEKNOLOGI MALAYSIA

iii

ACKNOWLEDGEMENT

First of all, thanks to our creator, “Allah” for the continuous blessing and for

giving me the strength and chances in completing this project.

Special thanks to my project supervisor, Associate Prof. Dr. Mohamad Kamal

A. Rahim, for his guidance, support and helpful comments in doing this project.

My family deserves special mention for their constant support and for their

role of being the driving force towards the success of my project. My friends

deserve recognition for lending a helping hand when I need them. En. Thelaha and

En. Nazri, the closest colleagues at P18, deserves praises for their assistance in the

fabrication and testing of my project.

My sincere appreciation also goes to everyone whom I may not have

mentioned above who have helped directly or indirectly in the completion of my

project.

iv

ABSTRACT

The current trend in most access point in conventional wireless local area

network (WLAN) is to use omnidirectional antennas, which radiates and receives

power equally in all directions. This attribute however gives result of lower power

efficiency and decrease network performance due to co-channel interference that

arrived from undesired directions. One of the proposed solutions to overcome these

constraints is to use multibeam antenna on WLAN access points. Multibeam

antennas are antenna arrays that make use of beamforming networks to produce

multiple independent beams that directed to different directions. In this project,

multibeam antenna comprises of linear antenna array and beamforming network is

presented. It was designed at 2.4 GHz to suit the application of WLAN at 802.11b/g.

Butler Matrix 4 x 4 is chosen as a beamforming network which was designed to

provide four different progressive phase shifts, -45°, +135°, -135°, +45° that coupled

to antenna array. It is made up from four 90° hybrid coupler, two 0 dB crossover and

two -45° phase shifter. Each component is designed and simulated using Agilent

ADS software and fabricated on FR4 board. This network is then combined with a

linear antenna arrays with the aim to produce four independent beams at four

different directions. Three types of antenna array that having different kind of

radiation patterns have been implemented which are square patch antenna, 4 x 2

planar antenna array and dipole antenna. The obtained result shows that 4 beams are

generated by each design where square patch antenna array produce Half Power

Beamwidth, HPBW for each beams about 30° and manage to cover 120° of coverage

area, 4 x 2 antenna array has HPBW about 7° and cover 30° while dipole antenna

produce two kind of beams, broader and narrower beams. Finally, it can be

concluded that the objectives of this project are achieved.

v

ABSTRAK

Hala tuju kebanyakan titik akses pada Rangkaian Kawasan Tempatan

Wayarles (WLAN) masa kini masih menggunakan antena halaan-omni, di mana ia

menyebarkan dan menerima kuasa daripada semua arah. Keadaan ini bagaimanapun

telah menyebabkan kecekapan kuasa menjadi rendah, malah menyebabkan

penurunan prestasi rangkaian yang disebabkan oleh gangguan saluran utama

daripada arah yang tidak dikehendaki. Salah satu jalan penyelesaian kepada

kelemahan ini ialah dengan menggunakan antena pelbagai sinaran pada titik akses

WLAN. Antena pelbagai sinaran adalah tatasusun antena yang menggunakan

jaringan pembentuk alur untuk menghasilkan beberapa sinaran yang menghala pada

arah yang berlainan. Dalam projek ini, antena pelbagai sinaran yang diperbuat

daripada tatasusun antena dan jaringan pembentuk alur dibentangkan. Ia direka pada

frekuensi 2.4 GHz untuk applikasi WLAN pada 802.11b/g. 4 x 4 Butler Matrix

dipilih sebagai jaringan pembentuk alur dan direka untuk menghasilkan empat nilai

anjakan fasa progesif yang berbeza iaitu -45°, +135°, -135°, +45° yang digandingkan

dengan tatasusun antena. It diperbuat daripada empat komponen gandingan hibrid

90°, dua komponen garis silang 0 dB dan dua penganjak fasa -45°. Setiap komponen

direkabentuk dan disimulasi menggunakan perisian Agilent ADS and difabrikasi ke

atas papan FR4. Jaringan ini kemudiannya dicantumkan bersama antena bertatasusun

lurus dengan matlamat untuk menghasilkan empat sinaran yang berasingan. Tiga

jenis antena yang mempunyai corak radiasi berbeza telah digunakan iaitu antenna

tampalan segi empat sama, 4 x 2 tatasusun antena dan antena dua-kutub. Keputusan

yang diperolehi menunjukkan empat sinaran telah dihasilkan, yang mana antena

tampalan segi empat sama menghasilkan HPBW selebar 30° dan kawasan liputan

seluas 120°, 4 x 2 tatasusun antenna mempunyai HPBW selebar 7° dan kawasan

liputan seluas 30° dan antena dua-kutub menghasilkan dua jenis sinaran yang

berbeza, sempit dan lebar. Akhirnya, dapatlah disimpulkan bahawa objektif projek

telah dicapai.

vi

TABLE OF CONTENTS

CHAPTER TITLE PAGE

DECLARATION ii

ACKNOWLEDGEMENT iii

ABSTRACT iv

ABSTRAK v

TABLE OF CONTENTS vi

LIST OF TABLES ix

LIST OF FIGURES xi

LIST OF ABBREVIATIONS xv

LIST OF SYMBOLS xvii

LIST OF APPENDICES xix

1 INTRODUCTION 1

1.1 Background of the problem 1

1.2 Problem Statement 4

1.3 Objective 4

1.4 Scope of the Study 5

1.5 Project Contribution 5

1.6 Organization of the Thesis 6

2 LITERATURE REVIEW 8

2.1 Smart Antenna Technology 8

2.1.1 Motivation towards Smart Antenna 11

2.1.2 Smart Antenna Applications in WLAN 14

vii

2.1.2.1 Standard of WLAN 15

2.1.2.2 Co-channel interference on

WLAN 18

2.1.2.3 Benefits of beam switching in

WLAN 20

2.1.3 Four Beams Multibeam Antenna 23

2.2 Antenna Basic 26

2.2.1 Microstrip Antenna 26

2.2.2 Antenna properties 27

2.2.2.1 Radiation Pattern 28

2.2.2.2 Half Power Beamwidth 32

2.2.2.3 Polarization 32

2.2.2.4 Bandwidth 34

2.2.3 Antenna Array 34

2.2.3.1 Uniform Linear Antenna Array 35

2.2.3.2 Beamswitching 43

2.3 Beamforming Network 46

2.3.1 Blass Matrix 48

2.3.2 Butler Matrix 48

2.3.2.1 90° Hybrid Coupler 52

2.3.2.2 0 dB Crossover 54

2.3.2.3 Phase Shifter 56

2.4 Previous Work 56

2.4.1 Integration between conventional 4 x 4

Butler Matrix and Antenna Array 57

2.4.2 Development of 4 x 4 Butler Matrix 62

2.5 Chapter Summary 68

3 METHODOLOGY 69

3.1 Project Methodology 69

3.2 Design development and software simulation 70

3.2.1 Development of Antenna Array 71

3.2.1.1 (4 x 1) Square Patch Antenna 71

3.2.1.2 4 x (4 x 2) Antenna Array 75

viii

3.2.1.3 (4 x 1) Dipole Antenna 77

3.2.2 Development of Butler Matrix 77

3.2.2.1 The design of 90° Hybrid 78

3.2.2.2 The design of 0 dB Crossover 81

3.2.2.3 Phase Shifter 83

3.2.2.4 Construction of Butler Matrix 85

3.3 Prototype Fabrication 88

3.4 Measurement Setup 89

3.4.1 S-parameter 89

3.4.2 Radiation pattern 90

3.5 Comparison of the designed Butler Matrix with

other findings 91

3.6 Chapter Summary 95

4 EXPERIMENTAL RESULTS & DISCUSSION 96

4.1 Result of Return Loss 96

4.2 Result of Butler Matrix 99

4.3 Radiation Pattern 100

4.4 Result analysis 107

4.5 Comparison of the measured radiation pattern with

other findings 117

4.6 The comparison between commercially used

antenna with designed multibeam antenna 122

4.7 Chapter Summary 124

5 CONCLUSION & FUTURE WORK 125

5.1 Conclusion 125

5.2 Proposed Future Work 127

REFERENCES 128

Appendices A – E 133-152

ix

LIST OF TABLES

TABLE NO. TITLE PAGE

2.1 IEEE WLAN standards 16

2.2 The center frequency defined by 802.11b/g specifications 17

2.3 The operation of multibeam antenna 25

2.4 The effect of varying parameter N 39

2.5 The effect of varying parameter d 40

2.6 The effect of varying parameter β 41

2.7 An example of power divider result in ideal case 44

2.8 Progressive phase difference corresponds to each input port

of Butler 44

2.9 Numerical value for 2 x 2 Butler Matrix 50

2.10 Numerical value for 4 x 4 Butler Matrix 50

2.11 Numerical value for 8 x 8 Butler Matrix 51

2.12 S-parameter for ideal case 90°hybrid coupler 53

2.13 S-parameter for ideal case 0 dB crossover 55

2.14 Previous work on the integration between conventional

4 x 4 Butler Matrix and Antenna Array 58

2.15 Previous work on the development of 4 x 4 Butler Matrix 64

3.1 Specifications for the FR4 board 70

3.2 Simulated result analysis for 4x1 square patch antenna 74

3.3 Radiation pattern of 4 x1 square patch interpretation 75

3.4 Simulated result analysis for 4x2 antenna array 76

3.5 Width value for each impedance value in hybrid coupler 78

3.6 The numerical result of simulated hybrid coupler 80

x

3.7 The numerical result of simulated hybrid coupler 83

3.8 The numerical result of simulated 45° phase shifter 84

3.9 The numerical result of simulated 0° phase shifter 85

3.10 Design Specification of the Butler Matrix 86

3.11 The simulated output phase of Butler Matrix (schematic) 87

3.12 Computed phase error (schematic simulation) 87

3.13 The simulated output phase of Butler Matrix (momentum) 87

3.14 Computed phase error (momentum simulation) 87

3.15 The comparison between designed Butler Matrix and other

Findings 92

4.1 The numerical result of square patch antenna 98

4.2 The numerical result of 4 x 2 antenna array 98

4.3 The numerical result of dipole antenna 99

4.4 The measured output phase of Butler Matrix 100

4.5 Computed phase error (measurement) 100

4.6 Numerical result of measured radiation patterns of using

square patch 103

4.7 Numerical result of measured radiation patterns of using

4 x 2 antenna array 104

4.8 Numerical result of measured radiation patterns of using

dipole antenna 105

4.9 AF equations correspond to each β 108

4.10 The comparison between measured radiation patterns of the

design with other findings 118

4.11 The comparison between commercially used antenna with

designed multibeam antenna 122

xi

LIST OF FIGURES

FIGURE NO. TITLE PAGE

2.1 Radiation pattern of smart antenna 9

2.2 The functional block diagram of smart antenna 10

2.3 Radiation pattern of Omnidirectional Antenna (Top view) 12

2.4 Directional Antenna Coverage Pattern 12

2.5 Antenna diversity 13

2.6 The motivation towards smart antenna implementation 14

2.7 WLAN with two APs 15

2.8 3 non-overlap channels in 802.11b/g 18

2.9 Devices that cause interference to WLAN AP 18

2.10 APs with 3 non-overlap channel 19

2.11 WLAN with more than 3 APs 19

2.12 An example of multibeam antenna coverage on WLAN 20

2.13 Comparison of throughput between switched beam and traditional

AP 21

2.14 Simulation results of BER when utilizing switch-beam antenna

in AP 22

2.15 The plot of CIR (carrier to interference ratio) as a function of

the cellular frequency reuse factor, K, and the number of beams, m 23

2.16 Block diagram of 4 ports multibeam antenna 24

2.17 The generated radiation pattern by exciting current at one port at

instant 24

2.18 4 beams radiation pattern 25

2.19 Rectangular patch antenna 26

2.20 Various feeding technique 27

xii

2.21 Coordinate system for radiation pattern measurement 28

2.22 Principle and E/H pattern cuts 29

2.23 2D radiation pattern 30

2.24 Radiation pattern of omnidirectional antenna 31

2.25 E-plane linear polarized 33

2.26 Various antenna array configuration 35

2.27 An example of pattern multiplication theorem 36

2.28 N element along x axis 36

2.29 Uniform Linear Array Configuration 37

2.30 Plots of AF with2λ

=d , 0=β and N = 4, 8 and 12 39

2.31 Plots of AF with, N = 4, 0=β and d = 0.25λ, 0.5λ, λ, 1.25λ 40

2.32 Plots of AF with, N = 4, d = 0.25λ 41

2.33 Phase scanning block diagram 42

2.34 A switched line phase shifter 42

2.35 The operation of power divider in terms of S-parameter 43

2.36 4 x 4 Butler Matrix configuration 44

2.37 Progressive phase difference corresponds to each input port of

Butler Matrix (block diagram form) 45

2.38 Radiation pattern obtained 46

2.39 Flow chart of the type beamformer 47

2.40 Blass Matrix configuration 48

2.41 AF plot for 2 x 2 Butler Matrix (N = 2, β = ±90°) 49

2.42 Block Diagram of 4 x 4 Butler Matrix 50

2.43 AF plot for 4 x 4 Butler Matrix (N = 4, β = ±45°, ±135°) 50

2.44 Block Diagram of 8 x 8 Butler Matrix 51

2.45 AF plot for 8 x 8 Butler Matrix (N = 8, β = ±22.5°, ±67.5°,

±112.5°, ±157.5°,) 51

2.46 Geometry of 90° hybrid coupler 52

2.47 Geometry of 0 dB crossover 54

2.48 Illustration that represents the function of 0 dB crossover 55

3.1 The flow chart of the operational framework 69

3.2 The block diagram of the complete design configuration 70

3.3 The flow chart of the design development of the project 70

xiii

3.4 Square patch antenna configuration 72

3.5 Simulated Return Loss for 4 x 1 square patch antenna 73

3.6 Radiation pattern of 4 x 1 square patch antenna 74

3.7 Layout of 4 x 2 antenna array 75

3.8 Return Loss of 4 x 2 array patch 76

3.9 E-plane co-polarization radiation pattern of 4 x 2 array patch 76

3.10 The flow chart of the Butler Matrix implementation 78

3.11 Designed hybrid coupler 79

3.12 The simulated result of hybrid coupler 80

3.13 Designed 0 dB crossover 82

3.14 The simulated result of amplitude and phase of 0 dB crossover 83

3.15 Designed 45° phase shifter 84

3.16 Designed 0° phase shifter 85

3.17 The block structure and layout of the Butler Matrix. 86

3.18 Fabricated prototype 89

3.19 The configuration of the project 90

4.1 Measured return loss of square patch antenna correspond to

each port 97

4.2 Measured return loss of each 4 x 2 antenna array 98

4.3 Measured return loss of each dipole antenna 99

4.4 Measured radiation pattern of single antenna 101

4.5 Measured radiation patterns of using square patch 102

4.6 Measured radiation patterns of using 4 x 2 antenna 103

4.7 Measured radiation patterns of using dipole antenna 104

4.8 Overlapped radiation pattern 106

4.9 The computed radiation pattern of AF corresponds to each β 108

4.10 Computed radiation pattern of AF 109

4.11 Conversion of array pattern from linear unit to dB 110

4.12 Pattern multiplication of square patch antenna case 111

4.13 Pattern multiplication of 4 x 2 antenna array case 112

4.14 Pattern multiplication of dipole antenna case 113

4.15 Radiation pattern comparison between computed and measured

result (square patch antenna case) 114

4.16 Radiation pattern comparison between computed and measured

xiv

result (4 x 2 antenna array case) 115

4.17 Radiation pattern comparison between computed and measured

result (dipole antenna case) 116

xv

LIST OF ABBREVIATIONS

2D - Two dimensional

3D - Three dimensional

3G - Third Generation

AF - Array Factor

AP - Access Point

BER - Bit Error Rate

BPSK - Binary Phase Shift Keying

CCK - Complementary Code Keying

CIR - Carrier to Interference Ratio

CPW - Co-planar waveguide

DBPSK - Differential Binary Phase Shift Keying

DQPSK - Differential Quadrature Phase Shift Keying

DSSS - Direct Sequence Spread Spectrum

FCC - Federal Communications Commission

FR4 - Fire Retardant Type 4

FHSS - Frequency Hoping Spread Spectrum

GFSK - Gaussian Frequency Shift Keying

HPBW - Half-power beamwidth

IEEE - Institution of Electrical and Electronic Engineer

IF - Intermediate Frequency

ISM - Industrial, Scientific, Medical

LAN - Local Area Network

LOS - Line of Sight

NLOS - Non line of sight

OFDM - Orthogonal Frequency Division Multiplexing

xvi

QPSK - Quadrature Phase Shift Keying

QAM - Quadrature Amplitude Modulation

RF - Radio Frequency

SDMA - Spatial Division Multiple Access

SINR - Signal to Interference and Noise Ratio

SIR - Signal to Interference Ratio

SLL - Side lobe level

SNR - Signal to Noise Ratio

UV - Ultra Violet

VoWi-Fi - Voice over Wide Fidelity

WLAN - Wireless Local Area Network

xvii

LIST OF SYMBOLS

dB - decibel

1R - First beam on the right side of polar plot

1L - First beam on the left side of polar plot

2R - Second beam on the right side of polar plot

2L - Second beam on the left side of polar plot

W - Width of rectangular patch antenna

L - Length of rectangular patch antenna

εr - Dielectric constant

h - Substrate height

λg - Guided wavelength

(r,θ,φ) - Spherical coordinate system

E - Electric

H - Magnetic

P(θ)n - Normalized radiated power pattern

P(θ) - θ component of the radiated power as a function of angles θ

P(θ)max - The radiated power maximum value

Eθ - E field existing θ direction

Eφ - E field existing φ direction

fu - Upper cutoff frequency

fl - Lower cutoff frequency

N - Number of elements

d - distance between antenna elements

θ - phase

β - phase difference between antenna elements

k - wave number

xviii

λ0 - wavelength in free space

l - transmission line length

Zo - characteristic impedance

w - transmission line width

εeff - effective dielectric constant

c - velocity of light in free space

fr - operating frequency

tan δ - dissipation factor

Leff - Effective length

∆L - length extension

BW% - bandwidth in percentage

xix

LIST OF APPENDICES

APPENDIX TITLE PAGE

A. FR4 general technical specifications 133

B. Simulation result of Butler Matrix 134

C. H-Co measured radiation pattern for square patch 136

D. E-Co measured radiation pattern for square patch

antenna when multiple input activated simultaneously 137

E. Submitted papers for proceedings 139

CHAPTER 1

INTRODUCTION

This dissertation proposes the development of multibeam antenna that can be

implemented for WLAN application. In this first chapter, the background of the

project is discussed providing the problem statement, objective, scope of the study

and project contribution.

1.1 Project Background

In recent years, wireless networking has become a key solution to various

data communication needs. Wireless LANs are fast, flexible and cheap compared to

conventional wired LANs and they are still improving [1]. While in wireless

communications two most important restricting factors are interference and multipath

fading [2]. Multipath is a condition which arises when transmitted signal undergoes

reflection from various obstacles in the propagation environment which cause the

multiple signals arrive from different directions [3]. The result is degradation in

signal quality when they are combined at the receiver due to the phase mismatch. Co-

channel interference is the interference between signals that operate at the same

frequency.

2

Smart antenna is one of the most promising technologies that will enable

higher capacity in wireless networks by effectively reducing multipath and co-

channel interference [4]-[6]. This achieved by focusing the radiation only in the

desired direction and adjusting itself to change traffic conditions or signal

environment. The early smart antenna systems were designed for use in military

applications to suppress interfering or jamming signals from the enemy [3]. Since

interference suppression was a feature in this system, this technology was borrowed

to apply to personal wireless communications where interference was limiting the

number of users that a network could handle [3].

It has been studies [7] and tested [8], [9], that applying simple smart antenna

systems and algorithm to WLAN, would improve the performance worthily [1].

Taking into account that IEEE 802.11a WLAN the bit rate rises with an increase in

the Signal to Interference and Noise Ratio (SINR), developing a smart antenna

solution for WLAN application becomes more valuable [1]. Multiple beam antenna

array, a part of smart antenna system is known to be able to provide capacity

enhancement by means of interference reduction though spatial filtering [9]. It

provides a considerable increase in network capacity when compared to traditional

antenna systems or sector based systems [9].

The current trend in most access point in conventional WLAN is to use

omnidirectional antennas, which radiates and receives power equally in all directions

[10]. The implementation of this antenna is simple but it forms some limitations on

the performance of the network. As the direction is not specific, only small

percentage of the overall energy is reaching to the desired user which resulting the

lower power efficiency. It also suffers of co-channel interference as signals that

operate at the same frequency from undesired directions also capable to reach the

antenna. Due to the limited spectrum allocation in WLAN, co-channel interference

will become an issue which is the major problem of omnidirectional antenna

broadcast [11].

3

One of the proposed solutions to overcome these constraints is to use

multibeam antenna on WLAN access points, AP [12]. Multibeam antennas are

antenna array that make use of beamforming network to produce multiple

independent beams that directed to different directions. By offering independent

beams or channels, AP will switch between these channels to select the channel that

has the highest received power. This feature assist the antenna system to maximize

the power received in the desired directions.

The implementation of multibeam antenna is not new. In fact, it has been

implemented in Cellular Radio Systems in a few years back. It has been reported in

[6] that by having a multiple beam, the selected beam can reduce the interference,

increase the system carrier to interference level and then offer an opportunity for the

greater capacity by tighter frequency reuse. The increase in frequency reuse permits a

75% increase in the number of RF channels at the site and doubling the overall

number of the subscriber capacity [6].

As the implementation of multibeam antenna gives a tremendous result in

cellular communications, people interested to apply multiple beam antennas for

WLAN communications. So far, most studies had done on the simulation to observe

the performance in WLAN [1], [9], [12]-[15]. For example in [12], it has been

proved that the multibeam antenna is capable to reduce the value of Bit Error Rate

(BER). Compare to omni directional antenna application, the simulation results show

that utilizing switch-beam antenna in AP the BER performance improve about 2 dB

in light-of-sight (LOS) case, and 6 dB in non-light-of –sight (NLOS) case.

With the motivation gained from the simulation that has been done in

literature [1], [9], [12]-[15], this project aims to produce physical implementation of

multibeam antenna so that the actual performance of multibeam antenna in WLAN

could be observed in future.

4

1.2 Problem Statement

By applying omnidirectional antenna on the WLAN AP, it is suffering from a

number of disadvantages which can be summarized as follows:

I. Lower power efficiency

II. Capacity Limitation due to contribution of co-channel interference

These disadvantages can be overcome by using multibeam antenna on the

WLAN access point. This project will only focus on the development of the antenna

itself to meet the satisfied performance that can be used in WLAN system. Thus far,

a few studies has been done on the multibeam antenna, but most of them were

discussing more about beamforming network [16]-[23] which are in terms of

bandwidth and compactness while put less concentration on constructing the

multibeam antenna itself. The main task here is to design a multibeam antenna

system by integrating an antenna array with beamforming network so that the overall

performance of the multibeam antenna in terms of radiation pattern could be

observed.

1.3 Objective

The main objectives of this study can be divided into two goals;

I. To design an antenna system that capable to produce multiple beam of the

radiation pattern

II. To simulate and fabricate that antenna system design so that its performance

can be observed

This project is aim for WLAN application at 2.4GHz

5

1.4 Scope of Study

The first part of this study is to understand the concept of multibeam antenna.

The needed of multibeam antenna on WLAN, the function of the multibeam antenna

and implementation of the antenna system are studied.

In the second part of the study, the multibeam antenna is designed and

simulated. At this stage, the fundamental of antenna parameters, microstrip antenna

characteristics and the theory about multibeam antenna has been covered. After that,

the antenna array and Butler Matrix are designed and simulated.

The third part is the fabrication and measurement of the design. At this stage,

related equipment such as UV Light Equipment, Network Analyzer, Spectrum

Analyzer, Signal Generator, etc. are expected to be familiarized and well handled.

The last part of the study is the analysis part. It is expected that during the

study, the measured result and the theoretical should be compared and observed.

1.5 Project Contribution

The application of smart antenna is not limited to the WLAN network only,

but also can be implemented in most communication network. As provided in

Chapter 2, Section 2.4, most studies have been done on the improvement of

beamforming network [16]-[23] rather than constructing the multibeam antenna

itself. This dissertation will give a basic idea about the integration between antenna

array and beamforming network and the performance of multibeam antenna using 3

6

different types of antenna (directional antenna, omnidirectional antenna, and broader

beamwidth antenna) are observed. Previous works only show the result of using

omnidirectional antenna [24] and broader beamwidth antenna [25]-[27] which

constructed and discussed independently. The multibeam antenna produced by this

project could be integrated later with RF switch and controller part that constructed

by other parties so that a complete switched beam antenna system could be

constructed. Multibeam antenna also can be implemented in the case of Spatial

Division Multiple Access (SDMA) by injecting different signal to each input ports

[28], [29].

1.6 Organization of Thesis

The thesis is divided into five chapters. The first chapter is Introduction,

which provides information regarding the project background, objectives, scope of

project, project contribution and the layout of the thesis.

The second chapter is Literature Review. In this chapter, the concept of

smart antennas, antenna theory, beamforming network and related previous works

are thoroughly explained.

The third chapter is Methodology, in which the methods employed in this

project will be explained. The design procedures and simulation results for this

project will be presented in detail. The simulation results and subsequent analysis

will be discussed. Prototype fabrication and measurement setup are also presented.

7

Results and analysis of the fabrication and measurement are presented in

Chapter 4. The comparison between simulations, fabrication results, measurement

results, and computation result will be explained in this chapter.

The last chapter is Conclusion and Future Work. This chapter will conclude

the findings of the project and provide recommendations for future work.