Microstrip Leaky Wave Antenna Design For WLAN Application.

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MICROSTRIP LEAKY WAVE ANTENNA DESIGN FOR WLAN

APPLICATION

NURLIYANA BT ABD MALIK

This report is submitted in partial fulfillment of requirements for the award of Bachelor of Electronic Engineering (Telecommunication Electronics) With Honours

Faculty of Electronic Engineering and Computer Engineering Universiti Teknikal Malaysia Melaka

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UNIVERSTI TEKNIKAL MALAYSIA MELAKA

FAKULTI KEJURUTERAAN ELEKTRONIK DAN KEJURUTERAAN KOMPUTER

BORANG PENGESAHAN STATUS LAPORAN

PROJEK SARJANA MUDA II

Tajuk Projek : MICROSTRIP LEAKY WAVE ANTENNA DESIGN FOR WLAN APPLICATION

Sesi

Pengajian : 2008/2009

Saya NURLIYANA BT ABD MALIK

mengaku membenarkan Laporan Projek Sarjana Muda ini disimpan di Perpustakaan dengan syarat-syarat kegunaan seperti berikut:

1. Laporan adalah hakmilik Universiti Teknikal Malaysia Melaka.

2. Perpustakaan dibenarkan membuat salinan untuk tujuan pengajian sahaja.

3. Perpustakaan dibenarkan membuat salinan laporan ini sebagai bahan pertukaran antara institusi pengajian tinggi.

4. Sila tandakan ( √ ) :

SULIT*

(Mengandungi maklumat yang berdarjah keselamatan atau kepentingan Malaysia seperti yang termaktub di dalam AKTA RAHSIA RASMI 1972)

TERHAD* (Mengandungi maklumat terhad yang telah ditentukan oleh

organisasi/badan di mana penyelidikan dijalankan)

TIDAK TERHAD

Disahkan oleh:

__________________________ ___________________________________

(TANDATANGAN PENULIS) (COP DAN TANDATANGAN PENYELIA)

Alamat Tetap:

NO 317 JLN TKP 6, TAMAN KANTAN PERMAI, 43000 KAJANG,

SELANGOR.

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“I hereby declare that this report is the result of my own work except for quotes as cited in the references.”

Signature : ………

Author : ………

Date : ………

NURLIYANA BT ABD MALIK 6TH APRIL 2009

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“I hereby declare that I have read this report and in my opinion this report is sufficient in terms of the scope and quality for the award of Bachelor of Electronic Engineering

(Telecommunication Electronics) With Honours.”

Signature : ………...

Supervisor’s Name : ………..

Date : ………...

MOHAMAD ZOINOL ABIDIN BIN ABD AZIZ 6TH APRIL 2009

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DEDICATION

M y Beloved Parents,

En Abd M alik Hj M ahfudz & Pn Sabariah I smail, M y Brother and Sister,

M y kind hearted supervisor, M r M ohamad Zoinol Abidin Abd Aziz

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ACKNOWLEDGEMENT

First of all, I would like to thank to Allah the Almighty who always beside me guiding and giving me blessing to finish my Project Sarjana Muda II successfully.

My sincere appreciation and gratitude are dedicated to my honorable supervisor, En Mohamad Zoinol Abidin Bin Abd Aziz for his encouragement, guidance and critics. Without his continued support and interest, this thesis would not have been the same as presentd here.

I would like to extend my sincere appreciation to all my dearest friends especially Shela, Hajar, Kak Iwan and Wani for their friendship, encouragement and always being beside me in every condition. Not to forget, all students under the same supervisor thank you for sharing the similar knowledge.

Last but not least, I would like to thank my beloved family especially my loving parents, En Abd Malik Mahfudz and Pn Sabariah Ismail. Their loves, supports and prayers have given me the strength to finish what I have started. Finally, to everybody that has been involved in my project directly or indirectly, thank you very much.

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ABSTRACT

This project presents an overview of design of Microstrip Leaky-Wave Antenna for Wireless Local Area Network Application. WLAN and wireless information network requires low-cost, low profiles and efficiency smart antenna. Microstrip leaky-wave antenna (MLWA) can be a candidate for its simple construction, low profiles, easy to match and frequency-scanning ability. The circuit was designed by using CST Microwave Studio and the circuit was simulated to obtain the return loss, radiation pattern, gain, directivity, bandwidth, FNBW and HPBW. Design process of MLWA starts with designing the single patch and followed by designing the array antenna by varied the number of elements, N and value of phase different, β. Array Factor equation is used to plot the MLWA radiation pattern and the plot was compared with the simulation result. Minimum resonant frequency occurred when the number of elements is greater. When the number of β increase, the value for directivity and bandwidth will slightly increase. As the number of elements is increase, the multiple beam appear on the radiation pattern will also increase. FR4 photo-resist board is used for the fabrication of the selected design antenna by using chemical etching technique. Finally, the fabricated antenna was measured by using network analyzer and antenna trainer to measure the return loss, directivity, bandwidth, FNBW, HPBW and radiation pattern. The measurement result was compared with the simulation result.

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ABSTRAK

Projek ini berkenaan dengan rekaan antena jalur-mikro kebocoran gelombang (MLWA) untuk aplikasi WLAN. Aplikasi WLAN ini memerlukan antena yang mempunyai ciri-ciri seperti kos pembinaan yang rendah serta mempunyai kecekapan yg tinggi. MLWA boleh dijadikan sebagai antenna yang terbaik untuk digunakan kerana ia mudah dari segi pembinaan serta mempunyai keupayaan pengesanan frekuensi yang tinggi. Penyediaan dan simulasi litar bagi antena ini akan menggunakan perisian CST Microwave Studio dan litar ini di simulasi untuk mendapatkan nilai kehilangan penghantaran, corak radiasi, nilai dapatan, nilai arah, lebar jalur, HPBW, dan FNBW. Proses merekabentuk antenna ini bermula dengan rekaan bagi satu elemen diikuti dengan membuat rekaan bagi rangkaian antenna dimana nilai elemen, N dan beza fasa β akan di variasikan . Rumus factor rangkaian, AF alkan digunakan untuk memplot corak radiasi dan plot tersebut akan dibandingkan dengan corak radiasi hasil daripada simulai. Nilai kehilangan penghantaran yang minimum terhasil apabila nilai elemen adalah banyak. Apabila nilai β dinaikkan, nilai arah dan jalur lebar akan meningkat. Apabila nilai elemen semakin besar, nilai alang yang terhasil pada corak radiasi akan menjadi semakin banyak. Fabrikasi bagi antenna ini telah menggunakan papan FR4 dengan menggunakan teknik chemical etching. Kemudian, antenna yang telah difabrikasi akan di ukur dengan menggunakan penganalisa rangkaian dan set antenna untuk mendapatkan nilai kehilangan penghantaran, nilai arah, jalur lebar, FNBW, HPBW dan corak radiasi. Nilai-nilai tersebut akan dibandingkan dengan nilai yang terhasil daripada simulasi.

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CONTENTS

CHAP TITLE PAGES

PROJECT TITLE i

STATUS REPORT FORM ii

STUDENT DECLARATION iii

SUPERVISOR DECLARATION iv

DEDICATION v

ACKNOWLEDGEMENT vi

ABSTRACT vii

ABSTRAK viii

CONTENTS ix

LIST OF TABLES xiii

LIST OF FIGURES xv

LIST OF ABBREVIATIONS xviii

LIST OF APPENDICES xx

I INTRODUCTION

1.1 Project Introduction 1

1.2 Objective of Project 1

1.3 Problem Statement 2

1.4 Scope of Project 2

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II LITERATURE REVIEW

2.1 Introduction 4

2.2 Basic Antenna Parameter 4

2.2.1 Radiation Pattern 5

2.2.2 Directivity 8

2.1.3 Input Impedance 9

2.1.4 Return Loss & Voltage Standing Wave Ratio (VSWR) 10

2.1.5Antenna Efficiency 12

2.1.6 Antenna Gain 12

2.1.7 Polarization 13

2.1.8 Bandwidth 15

2.3 Types of Antenna 16

2.4 Microstrip Antenna 16

2.5 Rectangular Patch and Transmission Line 19

2.5.1 Single Patch Antenna Design 19

2.5.2 Transmission Line Design 20

2.6 Antenna Array 21

2.6.1 Array Factor 22

2.6.2 Antenna Array and Beamforming 22

2.6.3 Feed Network 23

2.7 Leaky Wave Antenna (LWA) 24

2.7.1 Slit-Coupled LWA 25

2.7.2 Single Conductor Strip LWA 25

2.7.3 Flat Slotted Waveguide (FSW) 26

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III MICROSTRIP LEAKY WAVE ANTENNA DESIGN

3.1 Introduction 29

3.2 Design Methodology 29

3.3 Design Specification 32

3.4 CST Microwave Studio 33

3.5 Single Patch Antenna Design and Simulation 37 3.6 Design of 12 elements with different value of β 40 3.7 Design for different number of elements N with fixed value

of β

3.8 Design of 6 elements with variation arrangement ofβ 42

3.9 Array Factor of MLWA 44

3.10 Fabrication Process 44

3.11 Measurement 48

3.11.1 Return Loss Measurement 48

3.11.2 Radiation Pattern Measurement 48

IV RESULT ANALYSIS AND DISCUSSION

4.1 Result Analysis for Single Patch Antenna 50 4.2 Design Analysis of 12 Elements with Different Value of β 51 4.3 Design Analysis for Different Number of Elements, N with 53 Fixed Value of β = 45˚

4.4 Design Analysis of 6 Elements with Variation of β 57

4.5 Analysis for Design I and II 59

4.6 Analysis for Design III and Design IV 62

4.7 Array Factor Plot of 6 Elements with Different Value of β 64 4.8 Array Factor Plot for β = 45º with different number of

elements, N

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V CONCLUSION AND RECOMMENDATION

5.1 Conclusion 73

5.2 Recommendation 74

REFERENCES 75

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LIST OF TABLES

NO TITLE PAGES

2.1 Advantages and Disadvantages of Microstrip Antenna 18

3.1 MLWA Design Specifications 32

3.2 Parameter Setup in CST 34

3.3 Calculated Dimensions for Single Patch 37

3.4 Calculated Dimensions for Transmission Line 38 3.5 Calculated and Optimized dimension for single patch 39

3.6 Value of d with respect to β 40

3.7 Value of β for each design 43

4.1 Difference of Original and Normalized Patch in terms of Return Loss

4.2 Variation of Phase Difference (β°) for 12 element patches 52

4.3 Variation Number of Elements, N 54

4.4 Beam Angle for Different Number of Elements 56 4.5 Variation of Phase Difference (β˚) for 6 Elements Patches 57

4.6 Beam Angle for Different value of β 59

4.7 Simulation Result for Design I and Design II 60 4.8 Simulation Result for Design III and Design IV 62 4.9 Comparison of Beam Angles between Simulation and array

Factor for Variation of β

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for different number of elements, N

4.11 Comparison of simulation and measured return loss for Design 1 69 4.12 Comparison of simulation and measured return loss for Design I

and II

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LIST OF FIGURES

NO TITLE PAGES

2.1 Antenna Radiation Pattern 5

2.2 Radiation pattern for isotropic antenna and omni directional antenna

2.3 Radiation Pattern of an omni directional antenna 7

2.4 Antenna Directivity 9

2.5 Equivalent circuit of transmitting antenna 11

2.6 Vertical and circular polarization in 3-D 13

2.7 Common antenna polarizations 14

2.8 Definition of antenna bandwidth in respect to return loss measurement

2.9 Types of Antennas 16

2.10 Microstrip Antenna 17

2.11 Microstrip Antenna Radiation 18

2.12 Structure of a Microstrip Patch Antenna 19

2.13 Microstrip Transmission Line 20

2.14 Types of Array Feed Network 23

2.15 Types of Leaky Wave Antenna 24

2.16 Reduced equivalent circuit for slit-coupled MLWA 25

2.17 Single-conductor strip structure 26

2.18 Flat Slotted Waveguide (FSW) 27

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3.1 Design Process 30

3.2 Project Methodology 31

3.3 Design Environment 33

3.4 Workspace Window 34

3.5 Brick parameter Window 35

3.6 Steps and Parameter Setup 35

3.7 Single Patch Antenna 37

3.8 Structure and Simulation for Single Patch Antenna (a) 2-D View, (b) 3-D View

3.9 Response of return loss for single element 39 3.10 Structure for MLWA with 12 Elements in 2-D View 40 3.11 Figure 3.11 Simulation of MLWA for (a) 12 Elements, (b) 6

Elements

3.12 Simulation of MLWA for 3 elements 42

3.13 Design II (a) Structure, (b) Simulation 44

3.14 Example of Layout (a) CST Microwave Studio, (b) CorelDraw Suite 12

3.15 Flow Chart for Fabrication Process 46

3.16 UV Exposure Unit 47

3.17 Return Loss Measurement Setup 48

3.18 Radiation Pattern Measurement Setup 49

4.1 Return Loss for Original and Optimized Single Patch 51

4.2 Structure for 12 Elements with β= 45° 51

4.3 Response of Return Loss for variation of β 52

4.4 Structure for 3 Elements with β = 45˚ 53

4.5 3-D plot of radiation pattern 55

4.6 2-D Radiation Pattern Plot 56

4.7 Structure for 6 Elements 57

4.8 2-D plot of radiation pattern for β = 15º, 30º and 45º 58

4.9 Structure for Design I 59

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4.11 2-D plot of radiation pattern for increasing Design I and II 61

4.12 Structure for Design III 62

4.13 Response of S11 for Design III and Design IV 63 4.14 2-D plot of radiation pattern for Design III and Design IV 63 4.15 Array Factor Plot versus Simulation Plot with β = 60º 64 4.16 Array Factor Plot versus Simulation Plot for 9 Elements 66

4.17 Fabricated MLWA 68

4.18 Radiation pattern for simulation and measurement result for Design 1

4.19 Radiation pattern for simulation and measurement result for Design I

4.20 Radiation pattern for simulation and measurement result for Design II

4.21 Radiation pattern for simulation and measurement result for Design III

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LIST OF ABBREVIATIONS

LWA - Leaky-Wave Antenna

FPC - Fabry Perot Cavities

FSS - Frequency Selective Surface FSW - Flat Slotted Waveguide

MLWA - Microstrip Leaky-Wave Antenna MOS - Microwave Office Sotware PRS - Partially Reflective Surface

RL - Return Loss

VSWR - Voltage Standing Wave Ration WLAN - Wireless Local Area Network

P - Total Power Radiated

S - Power Density

Ui - Radiation intensity for isotropic antenna HPBW - Half power beam-width

FNBW - First Null Beamwidth

D - Directivity of Antenna

Zin - Antenna impedance at the terminals

Rin - Antenna resistance at the terminals

Xin - Antenna reactance at the terminals

RL - Return Loss

L - Length of Patch

W - Width of Patch

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w - Width of Transmission Line

ΔL - Length extension

h - Height of Substrate

β - Phase different between two radiating elements

N - Number of elements

d - Distance between elements

θ - Polar Angle

AF - Array Factor

φ - Phase Shift

dB - Decibel

dBi - Isotropic Decibel

C - Speed of light in vacuum

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LIST OF APPENDICES

APPENDIX TITLE PAGES

A Types of Antenna Review 77

B MLWA Design 81

C Simulation Result 83

D SigmaPlot Result 86

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CHAPTER I

INTRODUCTION

1.1 Project Introduction

In recent years, the microstrip leaky-wave antenna (MLWA) has got more and more attention for its simple feeding construction, easily coupling and frequency scanning. MLWA works in the first high mode TE10. These antennas are intrinsically non-resonant and so are capable of wide band performance and, in addition, the main beam can be scanned by changing frequency. For these reasons, of late, they have attracted a lot of attention, especially for airborne applications. A microstrip leaky wave antenna with first higher-order mode excitation radiates power in the narrow frequency regime before cutoff. The radiation main-beam depends on the operating frequency. Therefore it can be used as a frequency-scanning antenna.

1.2 Objective of Project

The objective of this project is to design, simulate and fabricate Microstrip Leaky-Wave Antenna for WLAN application operating at frequency of 2.4 GHz. The

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designed antenna should have return loss of ≤ -10 dB and maximum value of directivity and gain.

1.3 Problem Statement

Wireless local area network and wireless information network requires low-cost, low profiles and efficiency smart antenna. Besides that, the demand of antenna which has the ability to frequency-scan leads to the development of new design of microstrip antenna. Since that conventional design of microstrip antenna doesn’t have the frequency-scanning ability, Microstrip Leaky-Wave Antenna (MLWA) can be the best candidate for its simple construction, low profiles, easy to match and frequency-scanning ability.

1.4 Scope of Project

This project will focus on 4 areas and the main focus is to design Microstrip Leaky-Wave Antenna operates at frequency of 2.4 GHz. Then, CST Microwave Studio was used to simulate the return loss, radiation pattern, directivity, gain, HPBW and FNBW of the design. Next, the design of leaky wave antenna was fabricated on FR4 board using the chemical etching technique. Finally, the return loss, directivity, gain, HPBW, FNBW and radiation pattern of the leaky wave antenna were measured.

1.5 Report Organization

The organization of this report is followed by Chapter 2 discusses the literature review of this project. This chapter contains research and information on several important concepts and types of antenna. It will follow by the design rules and calculations use in designing the antenna. Chapter 3 discusses and explains the methodology in completing this project. The calculation and simulation results will be

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include in Chapter 4. Finally, the conclusion from the study and extension progress in order to complete this project is stated in Chapter 5.

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CHAPTER II

LITERATURE REVIEW

2.1 Introduction

Antennas are metallic structures designed for radiating and receiving electromagnetic energy. An antenna acts as a transitional structure between the guiding device (e.g. waveguide, transmission line) and the free space. The official IEEE definition of an antenna as given by Stutzman and Thiele follows the concept: “That part of a transmitting or receiving system that is designed to radiate or receive electromagnetic waves”. The performance of an antenna can be gauged from a number of parameters [1].

2.2 Basic Antenna Parameter

There are several important antenna parameters that should be considered when choosing an antenna for certain application. Some important parameters of the antenna are return loss, radiation pattern, polarization, directivity and bandwidth.

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