MICROSTRIP LEAKY WAVE ANTENNA DESIGN FOR WLAN APPLICATION NURLIYANA BT ABD MALIK

Transcription

1 1 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 April 2009

2 2 UNIVERSTI TEKNIKAL MALAYSIA MELAKA FAKULTI KEJURUTERAAN ELEKTRONIK DAN KEJURUTERAAN KOMPUTER BORANG PENGESAHAN STATUS LAPORAN PROJEK SARJANA MUDA II Tajuk Projek : Sesi Pengajian MICROSTRIP LEAKY WAVE ANTENNA DESIGN FOR WLAN APPLICATION : 2008/2009 Saya NURLIYANA BT ABD MALIK mengaku membenarkan Laporan Projek Sarjana Muda ini disimpan di Perpustakaan dengan syaratsyarat 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, KAJANG, SELANGOR. Tarikh:. Tarikh:..

3 3 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 : : 6 TH APRIL 2009

4 4 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 :... 6 TH APRIL 2009

5 5 DEDICATION To My Beloved Parents, En Abd Malik Hj Mahfudz & Pn Sabariah Ismail, My Brother and Sister, My kind hearted supervisor, Mr Mohamad Zoinol Abidin Abd Aziz And all my dearest friends.

6 6 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.

7 7 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.

8 8 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.

9 9 CONTENTS CHAP TITLE PAGES PROJECT TITLE STATUS REPORT FORM STUDENT DECLARATION SUPERVISOR DECLARATION DEDICATION ACKNOWLEDGEMENT ABSTRACT ABSTRAK CONTENTS LIST OF TABLES LIST OF FIGURES LIST OF ABBREVIATIONS LIST OF APPENDICES i ii iii iv v vi vii viii ix xiii xv xviii xx I INTRODUCTION 1.1 Project Introduction Objective of Project Problem Statement Scope of Project Report Organization 2

10 10 II LITERATURE REVIEW 2.1 Introduction Basic Antenna Parameter Radiation Pattern Directivity Input Impedance Return Loss & Voltage Standing Wave Ratio (VSWR) Antenna Efficiency Antenna Gain Polarization Bandwidth Types of Antenna Microstrip Antenna Rectangular Patch and Transmission Line Single Patch Antenna Design Transmission Line Design Antenna Array Array Factor Antenna Array and Beamforming Feed Network Leaky Wave Antenna (LWA) Slit-Coupled LWA Single Conductor Strip LWA Flat Slotted Waveguide (FSW) Microstrip Leaky Wave Antenna (MLWA) 27

11 11 III MICROSTRIP LEAKY WAVE ANTENNA DESIGN 3.1 Introduction Design Methodology Design Specification CST Microwave Studio Single Patch Antenna Design and Simulation Design of 12 elements with different value of β Design for different number of elements N with fixed value 42 of β 3.8 Design of 6 elements with variation arrangement of β Array Factor of MLWA Fabrication Process Measurement Return Loss Measurement Radiation Pattern Measurement 48 IV RESULT ANALYSIS AND DISCUSSION 4.1 Result Analysis for Single Patch Antenna Design Analysis of 12 Elements with Different Value of β Design Analysis for Different Number of Elements, N with 53 Fixed Value of β = Design Analysis of 6 Elements with Variation of β Analysis for Design I and II Analysis for Design III and Design IV Array Factor Plot of 6 Elements with Different Value of β Array Factor Plot for β = 45º with different number of 66 elements, N 4.9 Measurement Results 68

12 12 V CONCLUSION AND RECOMMENDATION 5.1 Conclusion Recommendation 74 REFERENCES 75 APPENDIX 77

13 13 LIST OF TABLES NO TITLE PAGES 2.1 Advantages and Disadvantages of Microstrip Antenna MLWA Design Specifications Parameter Setup in CST Calculated Dimensions for Single Patch Calculated Dimensions for Transmission Line Calculated and Optimized dimension for single patch Value of d with respect to β Value of β for each design Difference of Original and Normalized Patch in terms of Return 50 Loss 4.2 Variation of Phase Difference (β ) for 12 element patches Variation Number of Elements, N Beam Angle for Different Number of Elements Variation of Phase Difference (β ) for 6 Elements Patches Beam Angle for Different value of β Simulation Result for Design I and Design II Simulation Result for Design III and Design IV Comparison of Beam Angles between Simulation and array Factor for Variation of β Comparison of Beam Angles between Simulation and array factor 67

14 14 for different number of elements, N 4.11 Comparison of simulation and measured return loss for Design Comparison of simulation and measured return loss for Design I 70 and II 4.13 Comparison of simulation and measured return loss Design III 70

15 15 LIST OF FIGURES NO TITLE PAGES 2.1 Antenna Radiation Pattern Radiation pattern for isotropic antenna and omni directional 6 antenna 2.3 Radiation Pattern of an omni directional antenna Antenna Directivity Equivalent circuit of transmitting antenna Vertical and circular polarization in 3-D Common antenna polarizations Definition of antenna bandwidth in respect to return loss 15 measurement 2.9 Types of Antennas Microstrip Antenna Microstrip Antenna Radiation Structure of a Microstrip Patch Antenna Microstrip Transmission Line Types of Array Feed Network Types of Leaky Wave Antenna Reduced equivalent circuit for slit-coupled MLWA Single-conductor strip structure Flat Slotted Waveguide (FSW) Schematic diagrams of Microstrip Leaky Wave Antenna 28

16 Design Process Project Methodology Design Environment Workspace Window Brick parameter Window Steps and Parameter Setup Single Patch Antenna Structure and Simulation for Single Patch Antenna (a) 2-D View, 38 (b) 3-D View 3.9 Response of return loss for single element Structure for MLWA with 12 Elements in 2-D View Figure 3.11 Simulation of MLWA for (a) 12 Elements, (b) 6 41 Elements 3.12 Simulation of MLWA for 3 elements Design II (a) Structure, (b) Simulation Example of Layout (a) CST Microwave Studio, (b) CorelDraw 45 Suite Flow Chart for Fabrication Process UV Exposure Unit Return Loss Measurement Setup Radiation Pattern Measurement Setup Return Loss for Original and Optimized Single Patch Structure for 12 Elements with β = Response of Return Loss for variation of β Structure for 3 Elements with β = D plot of radiation pattern D Radiation Pattern Plot Structure for 6 Elements D plot of radiation pattern for β = 15º, 30º and 45º Structure for Design I Response of S 11 for Design I and Design II 60

17 D plot of radiation pattern for increasing Design I and II Structure for Design III Response of S 11 for Design III and Design IV D plot of radiation pattern for Design III and Design IV Array Factor Plot versus Simulation Plot with β = 60º Array Factor Plot versus Simulation Plot for 9 Elements Fabricated MLWA Radiation pattern for simulation and measurement result for 71 Design Radiation pattern for simulation and measurement result for 71 Design I 4.20 Radiation pattern for simulation and measurement result for 72 Design II 4.21 Radiation pattern for simulation and measurement result for Design III 72

18 18 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 U i - Radiation intensity for isotropic antenna HPBW - Half power beam-width FNBW - First Null Beamwidth D - Directivity of Antenna Z in - Antenna impedance at the terminals R in - Antenna resistance at the terminals X in - Antenna reactance at the terminals RL - Return Loss L - Length of Patch W - Width of Patch l - Length of Transmission Line

19 19 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 λ 0 - Free-space wavelength

20 20 LIST OF APPENDICES APPENDIX TITLE PAGES A Types of Antenna Review 77 B MLWA Design 81 C Simulation Result 83 D SigmaPlot Result 86 E Return Loss Measurement 88

21 21 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 TE 10. 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

22 22 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 frequencyscanning 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

23 23 include in Chapter 4. Finally, the conclusion from the study and extension progress in order to complete this project is stated in Chapter 5.

24 24 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.