Electromagnetic Band Gap (EBG) Structure.

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ELECTROMAGNETIC BAND GAP (EBG) STRUCTURE

NIK NABIHAH BINTI NIK MUSA

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

Faculty of Electronic and Computer Engineering Universiti Teknikal Malaysia Melaka

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iii

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

Signature :

Author : Nik Nabihah Binti Nik Musa

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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 : Mr. Mohamad Zoinol Abidin Bin Abd. Aziz

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Dedicated, in thankful appreciation for support, encouragement and understandings to my beloved mother, father, and friends for give me support to get through this

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ACKNOWLEDGEMENT

Alhamdulillah, praise be to Allah, the Cherisher and Sustainer of world, most Gracious, most Merciful Lord. Praise be to Allah for enabling me to complete this analysis and research for Electromagnetic Band Gap (EBG) structure project and report for my final year project.

First and foremost, I would like to express my heartily gratitude to my supervisor, Mr. Mohamad Zoinol Abidin Bin Abd. Aziz for giving the guidance and enthusiasm throughout the progress of this project.

My appreciation also goes to my family who has been so tolerant and supports me all these years. Thanks for their encouragement, love and emotional supports that they had given to me.

Nevertheless, my great appreciation dedicated to my entire friend for

supporting me steadfastly and their appreciated advice through my final year project completion.

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vii

ABSTRACT

In antenna design, there are surface waves that cannot propagate along the substrate. An increase amount of radiated power couples to space waves reducing antenna losses while increasing its gain and bandwidth. The Electromagnetic Band Gap (EBG) structures are periodic structures in which propagation of electromagnetic waves is not allowed in a specified frequency band. In this project, EBG structure had been designed in order to apply in antenna design to suppress surfaces waves and improve the radiation performance of the antenna. In designing EBG structure, the method had been used is finite difference time domain (FDTD). This EBG is designed by using microstrip. Then, the simulation process is done by using Computer Simulation Technology (CST). The purpose to simulate the design is to analyze antenna parameters, such as return loss, gain, radiation pattern and others. Various types and shapes of EBG structures had been designed such as circular, square and triangular EBG structures. Each shape is designed in two different conditions, such as EBG structures on same and different layer with microstrip patch antenna. From these designs, five EBG structures circuits were fabricated with different layer with microstrip patch antenna. Simulations and measurements show that EBG structure can achieve the lower return loss (<-10dB) compared to a microstrip without EBG structure.

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viii

ABSTRAK

Projek yang akan direka ialah struktur „Electromagnetic Band Gap (EBG)‟. Struktur „EBG‟ ialah struktur yang berkala di mana penyebaran gelombang elektromagnetik tidak dibenarkan dalam jalur frekuensi yang khusus. Jadi, untuk melaksanakan projek ini, struktur „EBG‟ akan direka untuk diaplikasikan dalam reka bentuk antenna, di mana rekaan ini akan membantu menahan gelombang permukaan dan meningkatkan persembahan radiasi antena. Dalam projek ini, struktur EBG telah direka dalam perintah bagi memohon dalam reka bentuk antena untuk menumpas permukaan-permukaan gelombang-gelombang dan meningkatkan sinaran prestasi antena. Dalam mereka struktur EBG, kaedah yang telah digunakan adalah domain masa beza terhingga (FDTD). EBG ini telah direkabentuk menggunakan mikrostrip. Kemudian, untuk menjalankan projek ini, proses simulasi adalah dibuat dengan menggunakan Computer Simulation Technology (CST). Tujuan untuk mensimulasi reka bentuk adalah bagi menganalisa antena parameter, seperti kehilangan balikan, pertambahan, pola sinaran dan lain-lain. Bermacam-macam jenis dan bentuk-bentuk bagi struktur-struktur EBG telah direka seperti bulat, empat segi dan segitiga. Tiap-tiap satu rupabentuk adalah direka dalam dua keadaan yang berbeza, seperti struktur-struktur EBG pada lapisan sama dan berbeza dengan mikrostrip antena. Daripada rekaan-rekaan ini, lima struktur-struktur EBG litar-litar direka dengan lapisan berbeza dengan mikrostrip antenna. Keputusan simulasi dan pengukuran struktur EBG boleh mencapai kehilangan balikan lebih rendah (<-10dB) disamakan ke satu mikrostrip tanpa struktur EBG.

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TABLE OF CONTENT

CHAP.

TITLE

PROJECT TITLE

THESIS STATUS DECLARATION RESEARCHER’S DECLARATION SUPERVISOR’S DECLARATION DEDICATION

ACKNOWLEDGEMENT ABSTRACT

ABSTRAK

TABLE OF CONTENTS LIST OF TABLES LIST OF FIGURES

LIST OF ABBREVIATIONS LIST OF APPENDICES

INTRODUCTION

1.1Project Background 1.2Objectives

1.3Problem Statement

PAGE

i ii iii iv v vi vii viii ix xii xiii xvi xviii

1 2 2

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III

1.4Scope Of Work

LITERATURE REVIEW

2.1Surface Wave

2.2Introduction EBG Structure

2.3Method used to analyze the features of EBG structures 2.3.1 Lumped Element Model

2.3.2 Periodic Transmission Line Method 2.3.3 Full Wave Numerical Methods 2.4 Basic Parameters of Antennas

2.5 Multiperiod EBG Design 2.6 Microstrip Patch Antenna 2.6.1 Microstrip Line Feed

MULTIPERIOD EBG STRUCTURE DESIGN

3.1Microstrip Patch Design 3.2EBG structure Design

3.2.1 Circular EBG structure design 3.2.2 Square EBG structure design 3.2.3 Triangular EBG structure design 3.3Fabrication

RESULT ANALYSIS AND DISCUSSION

4.1MIcrostrip Patch Antenna 4.2Different Shapes

4.2.1 Circular EBG structure on Same Layer with Microstrip Patch Antenna

3 4 5 9 9 10 10 12 13 15 18 21 22 22 27 31 33 36 40 40

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4.2.2 Circular EBG structure on Different Layer with Microstrip Patch Antenna

4.2.3 Square EBG structure on Same Layer with Microstrip Patch Antenna

4.2.4 Square EBG structure on Different Layer with Microstrip Patch Antenna

4.2.5 Triangular EBG structure on Same Layer with Microstrip Patch Antenna

4.2.6 Triangular EBG structure on Different Layer with Microstrip Patch Antenna

4.3Comparison for three types of EBG structure

CONCLUSIONS AND RECOMMENDATIONS

5.1 Conclusions 5.2 Recommendation

REFERENCES

APPENDIX A

62 63

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xii

LIST OF TABLES

TABLE 4.1 4.2 4.3 4.4 4.5 4.6 4.7 4.8 4.9 4.10 4.11 4.12 4.13 4.14 4.15 TITLE

Parameters value for rectangular patch Optimization radius of circle lattices

Optimization radius of circle lattices with gap Optimization radius of circle lattices with via

Optimization radius of circle lattices with gap and via Optimization radius of circle lattices

Optimization radius of circle lattices with gap Optimization radius of circle lattices with via

Optimization radius of circle lattices with gap and via Optimization radius of square lattices

Optimization radius of square lattices with via Optimization radius of square lattices

Optimization radius of square lattices with via Optimization radius of triangular lattices Parameters of triangular lattices

PAGES 39 40 41 41 42 45 47 49 50 52 53 54 57 58 59

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xiii

LIST OF FIGURES

FIGURE 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 2.9 2.10 2.11 2.12 3.1 3.2 3.3 3.4 TITLE

Surface waves lead to multipath

EBG substrate for surface wave suppression: low mutual coupling microstrip array design

EBG substrate for a low profile curl antenna design Lumped LC model for EBG analysis

Periodic transmission line method for EBG analysis Full wave FDTD model for EBG analysis

1-D multiperiod EBG structure with 8 lattice cells

2-D multiperiod EBG with a longer transmission line folded back on itself

Microstrip patch antenna with 2-D multiperiod EBG structure ground plane

Structure of a microstrip patch antenna A rectangular patch

Microstrip line feed

A rectangular patch with microstrip feed line Tree diagram of circular EBG structure design EBG structure with circular lattices

EBG structure with circular lattices with gap. Gap = 0.5mm

PAGES 5 7 8 9 10 11 14 14 15 15 17 18 21 22 23 24

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xiv 3.5 3.6 3.7 3.8 3.9 3.10 3.11 3.12 3.13 3.14 3.15 3.16 3.17 3.18 4.1 4.2 4.3 4.4 4.5 4.6 4.7 4.8 4.9 4.10

EBG structure with circular lattices with via. (Via; r = 0.5mm, ℓ= 3.27mm )

EBG structure with circular lattices with gap + via. (Gap = 0.5mm, Via; r = 0.5mm, ℓ= 3.27mm )

Various types of circular EBG structure Tree diagram of square EBG structure design

EBG structure with square lattices on second substrate

EBG structure with square lattices on second substrate. (Via; r = 0.5mm, ℓ= 3.27mm )

Various types of circular EBG structure

Tree diagram of Triangular EBG structure design EBG structure with triangular lattices

A rectangular patch antenna Circular EBG structure

Circular EBG structure with gap Square EBG structure

Triangular EBG structure

A rectangular patch with microstrip feed line Return loss for rectangular patch

Simulation and measurement radiation pattern for H-H Plane of rectangular patch

Simulation and measurement radiation pattern for E-E Plane of rectangular patch

Comparison of return loss for different type of circular EBG structure

Comparison of return loss for different type of circular EBG structure with microstrip without EBG structure

EBG structure with circular lattices

Simulated and measured return losses for circular EBG structure

Simulation and measurement radiation pattern for H-H Plane of circular EBG structure. (r = 3mm)

Simulation and measurement radiation pattern for E-E Plane

24 25 26 27 28 29 30 31 32 33 34 34 35 35 37 38 38 38 42 43 44 44 45 46

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xv 4.11 4.12 4.13 4.14 4.15 4.16 4.17 4.18 4.19 4.20 4.21 4.22 4.23 4.24 4.25 4.26 4.27 4.28 4.29

of circular EBG structure. (r = 3mm)

EBG structure with circular lattices. Gap = 0.5mm Return losses for circular EBG structure with gap

Simulation and measurement radiation pattern for E-E Plane of circular EBG structure with gap (r = 3mm)

Simulation and measurement radiation pattern for H-H Plane of circular EBG structure. with gap (r = 3mm)

EBG structure with circular lattices. (Via; r = 0.5mm, ℓ= 3.27mm )

EBG structure with circular lattices on second substrate. (Gap = 0.5mm, Via; r = 0.5mm, ℓ= 3.27mm )

Comparison between microstrip without EBG and circle EBG structure with square lattices on second substrate. Return losses for square EBG structure with different size of radius

Return losses for square EBG structure

Simulation and measurement radiation pattern for E-E Plane of square lattices EBG structure

Simulation and measurement radiation pattern for H-H Plane of square lattices EBG structure

EBG structure with square lattices. (Via; r = 0.5mm, ℓ= 3.27mm )

Comparison between microstrip without EBG and square EBG structure with triangular lattices

Return loss for triangular EBG structure

Simulation and measurement radiation pattern for H-H Plane of triangular lattices EBG structure

Simulation and measurement radiation pattern for E-E Plane of triangular lattices EBG structure.

Comparison between microstrip without EBG and triangular

46 47 48 48 49 50 51 53 53 54 55 55 56 57 57 58 59 59 60

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xvi

LIST OF ABBREVIATION

EBG - Electromagnetic Band Gap

CST - Computer Simulation Technology FR4 - Flame Retardant 4

FDTD - Finite Difference Time Domain IEEE EM GPS PEC MTL MoM FEM L C Zp Xc Z0 a1 a2 L W - - - - - - - - - - - - - - - -

Electrical and Electronics Engineers Electromagnetic

Global Positioning System Potential Equalization Clamp Multi Transmission Line Method of Moments Finite Element Method Inductance

Capacitor

Impedance for each periodic element Coupling capacitor

Initial impedance Period of lattice Period of lattice Length

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xvii c

f0 ℇr ℇeff

Leff

△L h d ℓ r

- - - - - - - - - -

Speed of light Resonant frequency Dielectric substrate

Effective dielectric constant Effective length

Length extension Height

Thickness Length

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xviii

LIST OF APPENDICES

NO TITLE PAGE

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CHAPTER I

INTRODUCTION

1.1 Project Background

The Electromagnetic Band Gap (EBG) terminology has been suggested based on the photonic band-gap (PBG) phenomena in optics that are realized by periodical structures The EBG materials provide frequency bands or also can called bandgaps or stopbands inside which waves cannot propagate in the materials [1]. Electromagnetic Band Gap (EBG) structure is known as objects that prevent the propagation of the electromagnetic waves in a specified band of frequency for all angles and for all polarization state.

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2 Surface wave is a mechanical wave that propagates along the interface between differing media, usually two fluids with different densities. A surface wave can also be an electromagnetic wave guided by a refractive index gradient.

1.2 Objective

The objectives of this project are to design an EBG structure that can suppress surface waves and improve the radiation performance of the antenna. The lower return loss (S11) will be obtained by suitable lattices of EBG structure. Then the performance of the antenna will be measure based on its return loss, and radiation pattern.

1.3 Problem Statement

In antenna design, there are surface waves that cannot propagate along the substrate. An increase amount of radiated power couples to space waves reducing antenna losses while increasing its gain and bandwidth. The EBG structures are designed to suppress surface waves and improve the radiation performance of the antenna [2].

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3 1.4 Scope of Work

The EBG structure is designed for different shapes, such as circular, square and triangular by using microstrip technique and method of finite difference time domain (FDTD) for antenna application [3]. Computer Simulation Technology (CST) is used to carry out the value of return loss, radiation pattern, gain, directivity and others parameters value of EBG structure. Then, the EBG structure circuit is fabricated on flame retardant 4 (FR4) board by using chemical etching technique. After that, network analyzer is used in order to measure the value of return loss at the resonant frequency. The value of gain and radiation pattern is also measured by using spectrum analyzer.

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CHAPTER II

LITERATURE REVIEW

In this chapter, the literature reviews that had been researched are studied to understand more about Electromagnetic Band Gap (EBG) structure, and how to design it. The literature reviews that had been reviewed are closely related to the project.

2.1 Surface Wave

A surface wave is one that propagates along an interface between two different media without radiation, such radiation being construed to mean energy converted from the surface wave field to some other form [5].In surface waves, there have electric and magnetic field components, which is excited by different sources.

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5 In order to suppress surface wave propagation, there were some techniques which can be use, such as special antenna designs, micromachining the substrate and employing electromagnetic band gap structure. The lack of availability of direct methods for investigating surface waves is becomes a problem in solving the suppression surface wave [6].

Figure 2.1 Surface waves lead to multipath [4]

2.2 Introduction EBG structure

In current years, there have many researches that have been done in growing interest on (EBG) structures. In solid state physics and related applied fields, a band gap, also called an energy gap or band gap, is an energy range in a solid where no electron states exist.

In electromagnetic band gap, the electromagnetic waves (EM) are transmitted. This transmission is occurred in a frequency range, which called forbidden frequency range or stop band [7]. According to the slow wave effect, EBG

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structures have their own property of reducing the phase velocity of EM modes, based on the frequencies near their band gap [8].

These structures have paying attention on a great deal of interest among researches due to their ability to influence the propagation of electromagnetic waves. The unique electromagnetic properties of EBG structures have led to a wide range of applications in antenna engineering. This section summarizes several typical EBG applications in antenna designs in the hope of stimulating discussions and new avenues of research in this area.

Surface waves are by-products in many antenna designs. Directing electromagnetic wave propagation along the ground plane instead of radiation into free space, the surface waves reduce the antenna efficiency and gain. The diffraction of surface waves increases the back lobe radiations, which may deteriorate the signal to noise ratio in wireless communication systems such as Global Positioning System (GPS) receivers. In addition, surface waves raise the mutual coupling levels in array designs, resulting in the blind scanning angles in phased array systems. The band gap feature of EBG structures has found useful applications in suppressing the surface waves in various antenna designs. For example, an EBG structure is used to surround a microstrip antenna to increase the antenna gain and reduce the back lobe. In addition, it is used to replace the quarter-wavelength choke rings in GPS antenna designs. Many array antennas also integrate EBG structures to reduce the mutual coupling level [9].

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Figure 2.2 EBG substrate for surface wave suppressions: low mutual coupling microstrip array design [9].

Another favorable application of EBG is to design low profile wire antennas with good radiation efficiency, which is desired in modern wireless communication systems.

When an electric current is vertical to a Perfectly Electric Conducting (PEC) ground plane, the image current has the same direction and reinforces the radiation from the original current. Thus, this antenna has good radiation efficiency, but suffers from relative large antenna height due to the vertical placement of the current. To realize a low profile configuration, one may position a wire antenna horizontally close to the ground plane.

However, the problem is the poor radiation efficiency because the opposite image current cancels the radiation from the original current. In contrast, the EBG surface is capable of providing a constructive image current within a certain

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Surface wave is a mechanical wave that propagates along the interface between differing media, usually two fluids with different densities. A surface wave can also be an electromagnetic wave guided by a refractive index gradient.

1.2 Objective

the performance of the antenna will be measure based on its return loss, and radiation pattern.

1.3 Problem Statement

In antenna design, there are surface waves that cannot propagate along the substrate. An increase amount of radiated power couples to space waves reducing antenna losses while increasing its gain and bandwidth. The EBG structures are designed to suppress surface waves and improve the radiation performance of the antenna [2].

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CHAPTER II

LITERATURE REVIEW

2.1 Surface Wave

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methods for investigating surface waves is becomes a problem in solving the suppression surface wave [6].

Figure 2.1 Surface waves lead to multipath [4]

2.2 Introduction EBG structure

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structures have their own property of reducing the phase velocity of EM modes, based on the frequencies near their band gap [8].

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Figure 2.2 EBG substrate for surface wave suppressions: low mutual coupling microstrip array design [9].

Another favorable application of EBG is to design low profile wire antennas with good radiation efficiency, which is desired in modern wireless communication systems.

Electromagnetic Band Gap (EBG) Structure.

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