IZNIHUSNA IDRIS - eprints.utm.myeprints.utm.my/id/eprint/48724/25/IzniHusnaIdrisMFKE2015.pdfsegi pemalar pantulan, polaradiasi dan gandaan dianalisa dan ditunjukkan. Hasil Hasil keputusan

SWITCHABLE AND TUNABLE MULTIBAND SLOT DIPOLE ANTENNA

IZNIHUSNA IDRIS

UNIVERSITITEKNOLOGI MALAYSIA

SWITCHABLE AND TUNABLE MULTIBAND SLOT DIPOLE ANTENNA

IZNI HUSNA IDRIS

A thesis submitted in fulfilment of the requirements for the award of the degree of

Master in Engineering (Electrical)

Faculty of Electrical Engineering Universiti Teknologi Malaysia

JANUARY 2015

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Dedicated to my parents, Idris bin Ismail, Sulaihah Ab. Rashid, my only sister with brother in law, Sakinah Idris, Mohd Zaidi Zuraini

my niece, Nur W f Imani Mohd Zaidi my beloved husband, Muhammad Ubaidullah Ramlan with love for their prays, support and encouragement.

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ACKNOWLEDGEMENT

Thanks and Praise to Allah for giving me the strength and chances for completing this study.

I would like to express my appreciations to all my supervisors, Dr. Mohamad Rijal Hamid, Dr. Mohd Haizal Jamaluddin and Prof. Dr. Mohamad Kamal A. Rahim for their advice and encouragement during my research work.

I would also like to thank all my colleagues at P18 and WCC, FKE; Mr. Huda A. Majid, Mr. Muhammad Faizal Ismail, Mr. Basyir D. Bala, Mr. Osman Ayob, Mr. Muhamad Nasrun Osman, Mr. Raimi Dewan, Mr. Mohd Ezwan Jalil, Muhammad Azfar Abdullah, Mr. Muhammad Ishak Abdul Sukur, Mr. Muhammad Hazmi Mokhtar, Mr. Mohamad Afiq Abdul Majid, Mr. Mohd Hidir Salleh, Mr. Khairul Hilmi Yusof, Mrs. Kamilia Kamardin, Mrs. Rafidah Rosman, Mrs. Norfatin Akma Elias, Mrs. Nazirah Othman, Ms. Siti Fairuz Roslan, Ms. Michelle, Ms. Nurul Jannah Ramly, who had helped and supported me during my research study. They assisted me regardless of the time and places.

I would like to thank all the persons who are not mentioned here especially my classmates and juniors; they have been a great help during my period of study.

Finally, I would also like to thank the developers of the utmthesis HEX project for making the thesis writing process a lot easier for me. Thanks to them, I could focus on the content of the thesis, and not wasted time with formatting issues. Those guys are awesome.

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ABSTRACT

Developments of frequency reconfigurable antennas in the wireless communication systems have attracted a lot of attention recently. Most reported antennas have narrowband to narrowband reconfiguration and multiband to multiband reconfigurations. In this research, a slot dipole antenna has been introduced with the ability to produce a multiband to narrowband reconfiguration. This type of antenna can suppress the problem of co-site interferences. Thus, two types of frequency reconfigurable antennas are studied and discussed which are switchable and tunable multiband antennas. The switchable multiband antenna is reconfigured by using Radio Frequency (RF) switches. The proposed antenna is capable to reconfigure from multiband to dual and/or single band. By having seven configurations of switches, this antenna can operate at 2.4 GHz, 3.5 GHz and/or 5.2 GHz. The antenna is able to have three states of single-band, three states of dual-band and one state of triple­band. Meanwhile, the tunable multiband antenna is reconfigured by using variable capacitors. The proposed antenna is capable to have a wide frequency tunability range for dual or single band operation (1.5 GHz - 4.5 GHz, ratio of 3:1). Each antenna has been successfully designed, fabricated and tested. The simulation and measurement results were analysed and presented in terms of reflection coefficient, radiation pattern and gain. The simulation and measurement results have been compared and a very good agreement was achieved. The reflection coefficient average accuracies of 98% has been achieved. These proposed antennas are suitable for future multi-mode applications such as cognitive radio systems.

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ABSTRAK

Perkembangan antena konfigurasi semula frekuensi dalam sistem komunikasi tanpa wayar telah menarik banyak perhatian baru-baru ini. Kebanyakan antena yang dilaporkan mempunyai konfigurasi semula jalur sempit ke jalur sempit dan konfigurasi semula berbilang jalur ke berbilang jalur. Dalam tesis ini, antena slot dwikutub telah diperkenalkan dengan mempunyai keupayaan untuk menghasilkan konfigurasi semula berbilang jalur ke jalur sempit. Jenis antena ini boleh mengurangkan masalah gangguan kawasan sekitar. Oleh itu, dua jenis antena konfigurasi semula frekuensi dikaji dan dibincangkan iaitu antena berbilang jalur boleh ubah dan boleh tala. Antena berbilang jalur boleh ubah dibina dengan menggunakan suis radio frekuensi (RF). Antena yang dicadangkan ini berupaya untuk dikonfigurasi semula daripada berbilang jalur ke jalur dual dan/atau tunggal. Dengan adanya tujuh suis konfigurasi, antena ini boleh beroperasi pada 2.4 GHz, 3.5 GHz dan/atau 5.2 GHz. Antena ini mampu memiliki tiga keadaan jalur tunggal, tiga keadaan jalur dual dan satu keadaan berbilang jalur. Manakala, antena berbilang jalur boleh tala dibina dengan menggunakan kapasitor boleh tala. Antena yang dicadangkan berupaya mempunyai kebolehan penalaan dalam julat frekuensi yang luas bagi operasi jalur berbilang atau tunggal (1.5 GHz - 4.5 GHz, dengan nisbah 3:1). Kesemua antena telah berjaya direka bentuk, difabrikasi dan diuji. Hasil keputusan simulasi dan pengukuran dari segi pemalar pantulan, polaradiasi dan gandaan dianalisa dan ditunjukkan. Hasil keputusan simulasi dan pengukuran akan dibandingkan dan satu persetujuan yang baik telah dapat dicapai. Pemalar pantulan telah mencapai purata ketepatan sebanyak 98%. Antena yang dicadangkan sesuai untuk penggunaan berbilang-mod di masa akan datang seperti sistem kognitif radio.

CHAPTER TITLE PAGE

DECLARATION iiDEDICATION iiiACKNOWLEDGEMENT ivABSTRACT vABSTRAK viTABLE OF CONTENTS viiLIST OF TABLES xLIST OF FIGURES xiiLIST OF ABBREVIATIONS xvLIST OF SYMBOLS xviLIST OF APPENDICES xvii

1 INTRODUCTION 11.1 Introduction 11.2 Problem Statement 21.3 Research Objectives 31.4 Scope of Research 31.5 Thesis Outline 4

2 LITERATURE REVIEW 62.1 Introduction 62.2 Narrowband Reconfiguration 92.3 Multiband Reconfiguration 142.4 Narrowband-Multiband Reconfiguration 192.5 Chapter Summary 26

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TABLE OF CONTENTS

3 METHODOLOGY3.1 Introduction3.2 Methodology of the project

282828

3.3 Design and Simulation 333.4 Fabrication and Measurement 363.5 Chapter Summary 40

4 FIXED MULTIBAND ANTENNA 414.1 Introduction 414.2 Multiband Antenna Design 414.3 Parametric Study 44

4.3.1 Parameter l 444.3.2 Parameter w 454.3.3 Parameter 464.3.4 Parameter w5 474.3.5 Parameters l?, and 48

4.4 Final Result of Fixed Multiband Antenna 504.4.1 Simulation 504.4.2 Measurement 534.4.3 Simulation and Measurement 554.4.4 Antenna in [3] and Fixed Multiband

Antenna 574.5 Chapter Summary 58

5 SWITCHABLE MULTIBAND ANTENNA 605.1 Introduction 605.2 Switchable Multiband Antenna Using Ideal

Switches 605.2.1 Antenna Design 615.2.2 Measurement and Validation 635.2.3 Eliminating the Unwanted Band in State

Three 715.3 Switchable Multiband Antenna Using Pin-diode

Switches 735.3.1 Antenna Design 735.3.2 Measurement Result 77

5.4 Effect of Pin-diodes on Antenna Designs 845.5 Chapter Summary 87

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6 TUNABLE MULTIBAND ANTENNA6.1 Introduction

8888

6.2 Tunable Multiband Antenna Using Fixed Capacitor 896.2.1 Antenna Design 896.2.2 Measurement and Validation 92

6.3 Tunable Multiband Antenna Using Varactor Diode 996.3.1 Antenna Design 996.3.2 Measurement Result 102

6.4 Effect of Varactor Diodes on Antenna Design 1096.5 Chapter Summary 111

7 CONCLUSIONS 1127.1 Overall Conclusion 1127.2 Key Contributions 1137.3 Future Work 113

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REFERENCESAppendices A - E

115121- 141

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TABLE NO. TITLE PAGE

2.1 Fixed multiband antenna 72.2 Narrowband to narrowband reconfiguration 102.3 Multiband to multiband reconfiguration 172.4 Single to dual-band reconfiguration 202.5 Single to dual or triple-band reconfiguration 253.1 Radiation pattern and gain measurement process 384.1 Actual parameter value of antenna in [3] 424.2 Description of new parameters for proposed antenna 434.3 Similarity and differences of the antenna 434.4 Design specification of the proposed antenna 444.5 Result of varying l 454.6 Result of varying w 464.7 Result of varying 474.8 Final value of parameters in fixed multiband antenna 514.9 Comparison between simulated and measured result of the

fixed multiband antenna 564.10 Comparison result between antenna in [3] and fixed

multiband antenna 585.1 Design specification of the switchable multiband antenna 615.2 Ideal switches configuration 625.3 Comparison of the simulated and measured resonant

frequency, switchable multiband antenna using ideal switch 675.4 Comparison of the simulated and measured gain for ideal

switch 705.5 Value of changing parameters in pin-diode antenna design 765.6 Comparison of the simulated and measured Sn using real

switches 805.7 Comparison of the simulated and measured gain for real

switches 84

LIST OF TABLES

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6.1 Design specification of the tunable multiband antenna usingfixed capacitor 89

6.2 Description and value of changing parameters 916.3 Capacitors configuration 916.4 The tuning range for fixed capacitor 956.5 Measured radiation pattern for fixed capacitor 976.6 Simulated and measured gain for fixed capacitor 996.7 Design specification of the tunable multiband antenna using

varactor diode 996.8 Value of changing parameters in varactor diode antenna

design 1006.9 Summary of gain measurement for single-band tuning using

varactor diode 1086.10 Summary of gain measurement for dual-band tuning using

varactor diode 108

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FIGURE NO. TITLE PAGE

2.1 Geometry of the antenna design [24] 122.2 Geometry of the antenna design [25] 132.3 Geometry of the antenna design [33] 152.4 Geometry of the antenna design [34] 162.5 Patch antenna design with connecting elements [45] 212.6 Simulated and measured result of Sn [45] 212.7 Microstrip patch antenna design with shorting pins [46] 222.8 Microstrip antenna with switchable frequencies [47] 222.9 Microstrip line feed of a perturbed Sierpinski monopole

gasket antenna [48] 232.10 Simulated and measured result of Sn [48] 232.11 CPW-fed line with H-shaped radiator antenna [49] 242.12 Simulated and measured result of Sn [49] 243.1 Flow chart of the fixed multiband antenna process 293.2 Flow chart of the switchable multiband antenna process 313.3 Flow chart of the tunable multiband antenna process 323.4 Ideal switch simulation 343.5 Example of discrete port in antenna design 343.6 Real switch simulation 353.7 Fixed capacitor simulation 353.8 Varactor diode simulation 353.9 A DC power supply 363.10 Photograph of the antenna during Sn measurement 374.1 Geometry of the tri-band aperture-coupled slot dipole antenna

[3] 424.2 Geometry of the proposed antenna design, fixed multiband

antenna 424.3 Performance of Sn with varying length of substrate, l 454.4 Performance of Sn with varying width of substrate, w 46

LIST OF FIGURES

4.5 Performance of Sn with varying length of rectangular slotbox, 47

4.6 Performance of Sn with varying width of feed line, w5 484.7 Result of simulated E-field at 5.2 GHz 484.8 Performance of Sn with varying length of arm pairs 504.9 Simulated design of the fixed multiband antenna 504.10 Simulated Sn of the fixed multiband antenna 514.11 Simulated radiation patterns of the fixed multiband antenna 524.12 Simulated current distribution of fixed multiband antenna 534.13 Simulated design of the fixed multiband antenna 544.14 Measured Sn of the fixed multiband antenna 544.15 Measured radiation patterns of the fixed multiband antenna 554.16 Simulated and measured Sn of the fixed multiband antenna 564.17 Simulated and measured radiation patterns of the fixed

multiband antenna 564.18 Simulated Sn of an antenna in [3] 574.19 Measured radiation pattern at 2.38 GHz of an antenna in [3] 585.1 Geometry of the switchable multiband antenna design using

ideal switches 615.2 Prototype antenna for ideal switch 635.3 Simulated and measured of Sn for ideal switch 665.4 Simulated and measured radiation pattern for ideal switch 685.5 Measured gain for ideal switch 705.6 State three preliminary result 715.7 Sn for state three, with middle arm 715.8 Sn for state three, without middle arm 725.9 Vary length of (s3) 725.10 State three final result 735.11 Antenna design for slot dipole antenna 745.12 Simulated Sn of normal and reverse design of fixed

multiband antenna 745.13 Simulated radiation patterns of normal and reverse design of

fixed multiband antenna 745.14 Geometry of antenna design with pin-diode 755.15 An antenna prototype with pin-diode 755.16 Equivalent circuit for pin-diode in ON-state 765.17 Equivalent circuit for pin-diode in OFF-state, frequency < 4

GHz 77

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5.18 Equivalent circuit for pin-diode in OFF-state, frequency > 4GHz 77

5.19 Simulated and measured of Sn for real switch 805.20 Simulated and measured radiation pattern for real switches 825.21 Measured gain for real switches 835.22 Measured gain of ideal and real switches, switchable

multiband antenna 866.1 Geometry of the tunable amultiband antenna design using

fixed capacitor 906.2 Antenna prototype design using fixed capacitor 906.3 Simulated and measured Sn of triple-band tuning 926.4 Measured Sn of fixed capacitor, dual-band 936.5 Measured Sn of fixed capacitor, single-band 956.6 Measured of Sn for low, mid and high single-band frequency

tuning range 956.7 Measured gain for single versus triple band 986.8 Geometry of the tunable multiband antenna with varactor

diode 1006.9 Antenna prototype design using varactor diode 1016.10 Measured Sn of single-band tuning using varactor diode 1026.11 Measured Sn of low and high, single-band frequency tuning 1036.12 Measured Sn of dual-band tuning with one frequency is fixed 1046.13 Measured Sn of dual-band tuning using varactor diode 1046.14 The measured radiation pattern for varactor diode at 3.5 GHz 1056.15 The measured radiation pattern for varactor diode at 3.0 GHz 1066.16 The measured radiation pattern for varactor diode at 3.15 GHz 1066.17 Sn and gain versus frequency for single-band and dual-band

frequency tuning 1076.18 Gain measurement using varactor diode for single-band

tuning 1076.19 Gain measurement using varactor diode for dual-band tuning 1086.20 Antenna prototype of varactor diode and reference antenna A 1096.21 Antenna prototype of varactor diode and reference antenna B 1106.22 Measured Sn and gain versus frequency for varactor diode

and reference antenna A 1106.23 Measured Sn and gain versus frequency for varactor diode

and reference antenna B 111

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xv

LIST OF ABBREVIATIONS

CPW - Coplanar waveguide

CST - Computer Simulation Technology

DC - Direct current

DCS - Digital Cellular Service

EM - Electromagnetic

GPS - Global Positioning System

GSM - Global System for Mobile Communication

PIL - Planar inverted L

RF-MEMS - Radio frequency micro-electromechanical system

SMA - SubMiniature version A

UMTS - Universal Mobile Telecommunications System

UV - Ultra violet

VNA - Vector network analyzer

WiMAX - Worldwide Interoperability for Microwave Access

WLAN - Wireless Local Area Network

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LIST OF SYMBOLS

A - Wavelength

- Dielectric constant

Ao - Wavelength in free space

f - Frequency

- Slot arm total length

- capacitive reactance

n - constant approximated as 3.14159

C - capacitor value

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LIST OF APPENDICES

APPENDIX TITLE PAGE

A List of Publications 121B Glossary 122C tunable multiband antenna 125D Pin-diode Data Sheet 129E Varactor-diode Data Sheet 141

CHAPTER 1

INTRODUCTION

1.1 Introduction

Reconfigurable antenna has received much attention lately. According to [1], reconfigurable antenna has been used in many applications such as mobile and satellite communications, cellular radio system and radar application. This antenna has its own unique appearance due to the overall size, lower cost and ability to reduce the complexity of a system compared to multiple single-function antenna. There are many types of reconfigurable antennas depending on their properties such as frequency, radiation pattern, bandwidth and polarization. Tuning or switching the antennas operating frequency can filter out interfering signals. In addition, changing the antennas radiation pattern into the desired direction can result in less power consumption. Thus, based on the aforementioned criteria, reconfigurable antenna has the ability to serve in many applications due to its significant advantages [2].

This thesis presents a study on frequency reconfigurable antenna. Frequency reconfigurable antenna only change its operating band and generally will not affect the antenna's radiation pattern. Frequency reconfigurable antenna can be divided into two types which are continuous and discrete tuning. Continuous tuning has a smooth tuning between one to another operating frequency. Discrete tuning, on the other hand, switches its operating frequencies from one to another. Frequency reconfigurable antennas are known to provide transceiver flexibility by switching the operating frequency to different bands. This allows them to operate in multiple operations. It can be done by using some mechanisms that can provide the reconfigurability to the antenna, such as switching and variable reactive loading [2]. Switching can be done by using pin-diode or radio frequency micro-electromechanical system (RF-MEMS), while the variable reactive loading mechanism can be operated by using the varactor or capacitance. Generally, frequency reconfiguration can be obtained by switching in and

2

out some parts of the antenna. Another way to achieve this is by means of changing the antenna structure mechanically or adjusting the antenna matching externally. In this study, frequency reconfigurable antennas were manipulated to reconfigure either by switching in and out some parts of the antenna or changing the antennas effective length to switch and tune the operating bands, respectively.

There are three main classes of techniques for frequency reconfiguration: 1) switching between narrowband, 2) switching between wideband to narrowband, and 3) switching between multiband. An antenna that can be reconfigured from one narrowband to another narrowband is only capable of supporting one radio standard at a time, whereas an antenna that can be reconfigured from wideband to narrowband can support multiple radio standards at a time. However, the wideband operation inherently provides less interference rejection compared to narrowband operation. This limitation can be overcome by employing an antenna that can be reconfigured from one multi­band to multi-band, as proposed in this thesis.

1.2 Problem Statement

Reconfigurable antenna can provide multi-function antenna which can serve in many wireless systems applications such as cognitive radio system. Unlike multiple antennas which can increase the cost and size of the system, reconfigurable antenna is believed as a new approach or technique that can eliminate the problem towards the system. Reconfigurable antenna can operate in different frequencies, radiation pattern, polarization and others at a time. It can be classified depending on their functions which are frequency reconfigurable antenna, radiation pattern reconfigurable antenna, polarization reconfigurable antenna and bandwidth reconfigurable antenna.

Most studies on frequency reconfigurable antennas implemented frequency switching between one narrowband to another narrowband configuration. In addition, multiband to another multiband configuration has also been demonstrated. The former configuration can only support one service at a time, while the latter can support multiple services simultaneously. In recent trends, the multiband operation is more favorable and applicable. However, by having multiple operating bands, the system itself will be exposed to more co-site interferences. In order to reduce this, the antenna should have some degree of electrical flexibility which able the antenna to operate either in single, dual or multi-band modes when required. This flexibility can also

3

overcome the problem of serving only one frequency band at a time, as implemented by conventional reconfigurable antennas. Therefore, the presented antenna which can reconfigure from one narrowband to another multi narrowband is a potentially suitable antenna in cognitive radio applications.

1.3 Research Objectives

The objectives of this thesis are :-

i To design switchable multiband antenna that has the capability to switch its operating bands from triple to dual or single-band, and vice versa by means of pin-diode switches.

ii To design tunable multiband antenna that has the capability to tune its multiband operating frequency to other set of bands by means of varactor diodes.

1.4 Scope of Research

In this research, a triple band antenna was designed. The antenna in [3] was chosen as a basis structure. Two designs were developed, namely a switchable multiband antenna and a tunable multiband antenna. In the former design, pin-diode switches were used, while for the latter, varactor diodes were be employed.

As a first approximation, a prototype with ideal switches (copper strips) and a prototype with fixed capacitors were developed and tested. Later, the ideal switches and fixed capacitors in the prototypes were replaced with pin-diode switches and varactor diodes, respectively. The effect of switches toward the antenna performances was then investigated and compared in terms of reflection coefficient, gain and radiation pattern of the prototypes with ideal and real switches. Lastly, all data were compiled for thesis documentation.

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1.5 Thesis Outline

This thesis is divided into seven chapters. The first chapter consists of a brief introduction to the reconfigurable antenna, which focuses on frequency reconfigurability, problem statement, research objective and scope of the research.

In the second chapter, literature review on frequency reconfigurable antenna is discussed. Previous works on frequency reconfigurable antenna regarding continuous and discrete tuning are also presented. This chapter includes discussion on two types of antennas, which are narrowband to narrowband and multiband to multiband reconfigurations.

The third chapter presents the methodology applied in this research project. The content of this chapter consists of the flow chart of the research, overall process of designing the switchable and tunable multiband antenna, including the simulation, fabrication and measured process.

The fourth chapter discusses about fixed non-reconfigurable multiband antenna, as well as parametric studies to investigate the parameters that could affect the performance of the antenna. The final design of the fixed non-reconfigurable multiband antenna is presented here.

Chapter five presents the switchable multiband antenna. This chapter also discusses the procedure to validate the concept of reconfigurability, where ideal switches (i.e. copper strips) are used in the antenna design. This chapter also presents an attempt of applying several numbers of pin-diodes to replace the ideal switches. The proposed antenna in this research is designed capable to operate in seven different modes, which are three single-band, three dual-band and/or one triple­band of operations. It can operate at three main frequencies, 2.4 GHz, 3.5 GHz and 5.2 GHz. The effect of the pin-diode is also discussed through gain analysis.

In chapter six, tunable multiband antenna is presented. It has the capability to tune the operating frequency by means of variable capacitor. The antennas are able to tune into triple-band, dual-band and single-band operating frequency. This chapter start with the design of an antenna with fixed capacitor to validate the concept of tunability. Also included is the design of the antenna with several numbers of varactor diode. The gain analysis in this chapter discusses the effect of using varactor diode.

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Finally, the last chapter concludes the overall research work and discusses some future works.

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