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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
April 2009
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
Date :
iv
“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
Date :
v
Dedicated, in thankful appreciation for support, encouragement and understandings
to my beloved mother, father, and friends for give me support to get through this
journey in my project and further studies.
vi
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.
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.
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.
ix
TABLE OF CONTENT
CHAP.
I
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
1.1 Project Background
1.2 Objectives
1.3 Problem Statement
PAGE
i
ii
iii
iv
v
vi
vii
viii
ix
xii
xiii
xvi
xviii
1
2
2
x
II
III
IV
1.4 Scope Of Work
LITERATURE REVIEW
2.1 Surface Wave
2.2 Introduction EBG Structure
2.3 Method 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
3.1 Microstrip Patch Design
3.2 EBG structure Design
3.2.1 Circular EBG structure design
3.2.2 Square EBG structure design
3.2.3 Triangular EBG structure design
3.3 Fabrication
RESULT ANALYSIS AND DISCUSSION
4.1 MIcrostrip Patch Antenna
4.2 Different 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
xi
V
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
4.3 Comparison for three types of EBG structure
CONCLUSIONS AND RECOMMENDATIONS
5.1 Conclusions
5.2 Recommendation
REFERENCES
APPENDIX A
43
52
53
57
58
60
62
63
64
67
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
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
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
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29
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31
32
33
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34
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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
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49
50
51
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53
54
55
55
56
57
57
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59
60
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
Width
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
Radius of lattice
xviii
LIST OF APPENDICES
NO TITLE PAGE
A Radiation Pattern for EBG structure 67
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.
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].
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.
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.
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
6
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].
7
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
