FRACTAL ANTENNA FOR AEROSPACE NAVIGATION

DISSERTATION
ON
DESIGN OF FRACTAL MICROSTRIP PATCH
ANTENNA FOR AEROSPACE NAVIGATION
SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENT FOR THE
AWARD OF THE DEGREE OF
MASTER OF TECHNOLOGY
ELECTRONICS AND COMMUNICATION ENGINEERING
(SPECIALIZATION IN COMMUNICATION SYSTEMS)
SUBMITTED BY
Rupleen Kaur (2013ECB1235)
(Reg. No. 2013 RG/A-277)
UNDER THE SUPERVISION OF
Er. Satbir Singh (Assistant Professor)
DEPARTMENT OF ELECTRONICS AND COMMUNICATION
ENGINEERING
GURU NANAK DEV UNIVERSITY, RC GURDASPUR
JULY, 2015

Dept.of ECE, GNDU, Regional Campus Gurdaspur i
Guru Nanak Dev University, Regional Campus, Gurdaspur
Department of Electronics & Communication Engineering
(Established by State Legislature Act No 21 of 1969)
Accredited at “A” grade level by NAAC and awarded
“University with Potential for Excellence” status by UGC
Phone: 01874-240517, Fax: 01874-242678
CERTIFICATE
Certified that the thesis entitled “Design of Fractal Microstrip Patch Antenna for
Aerospace Navigation” submitted by Rupleen Kaur (Regd. No. 2013 RG/A-277) in the
partial fulfillment of the requirements for the award of the degree of Master of
Technology (Electronics and Communication Engineering) of Guru Nanak Dev
University, is a record of student’s own work carried under my supervision and guidance.
To the best of our knowledge, this thesis has not been submitted to any University or
institute for award of any degree. It is further understood that by this certificate the
undersigned do not endorse or approve any statement made, opinion expressed or
conclusion drawn herein, but approve the thesis only for the purpose for which it is
submitted.
Supervisor
Er. Satbir Singh
Assistant Professor,
Department of Electronics and Communication
Engineering,
Guru Nanak Dev University
Regional Campus,
Gurdaspur-143521,
Punjab, India
Dated:
Co-Supervisor
Er. Naveen Kumar
(IEEE Member)
Executive Director
Elixir Publication
Chandigarh, India

Dept.of ECE, GNDU, Regional Campus Gurdaspur ii
DECLARATION
I, Rupleen Kaur, bearing University Registration Number 2013 RG/A-277, a student of
M.Tech (Regular) of Electronics & Communication Engineering Department; hereby
declare that I own the full responsibility for the information, results etc. provided in this
thesis titled “Design of Fractal Microstrip Patch Antenna for Aerospace Navigation”
submitted to Guru Nanak Dev University for the award of M.Tech (ECE) degree. I
hereby declare that this thesis is my own work and effort and that it has not been
submitted anywhere for any award. Where other sources of information have been used,
they have been acknowledged. I have taken care in all respect to honor the intellectual
property right and have acknowledged the contribution of others for using them in
academic purpose. I further declare that in case of violation of intellectual property right
or copyright, I as the candidate will be fully responsible for the same, my honorable
supervisors and Institute will not be responsible for the violation of any intellectual
property right.
Rupleen Kaur
Roll no. 2013 ECB 1235
Date:
Place: Guru Nanak Dev University, Regional Campus, Gurdaspur

Dept.of ECE, GNDU, Regional Campus Gurdaspur iii
ACKNOWLEDGEMENT
The completion of any project brings with it a sense of satisfaction, but it won’t be
complete without thanking the people who made it possible and whose constant support
crowned my efforts with success. I wish to express my deepest gratitude to Er. Satbir
Singh, Assistant Professor, Dept. of ECE, GNDU, Regional Campus Gurdaspur for his
sincere and invaluable guidance, suggestions and constant encouragement, and belief in
me, which inspired me to submit my thesis.
I am thankful to Dr. Anu Sheetal, Professor and Incharge of Dept. of ECE, GNDU,
Regional Campus Gurdaspur for providing full facilities for the execution of this thesis
work.
My sincere thanks to Er. Naveen Kumar, Director, Elixir Publications, Chandigarh for his
consistent guidance, encouragement and help in learning HFSS software. I also attribute
my sincere gratitude to NITTTR, Chandigarh for providing necessary lab facilities and
equipments.
I am grateful to all of my friends for helping me and would also like to thank all those
who have directly or indirectly contributed to the success of this work. Their intelligence
and innovation have helped me go through my every query and ended up in a huge
success.
Big thanks to my Institution and all of my faculty members for helping me in completing
my thesis and providing me with immense knowledge related to the subject.
I am extremely happy to acknowledge and express my sincere gratitude to my parents for
their constant support and encouragement.
Rupleen Kaur
Roll no. 2013 ECB 1235

Dept.of ECE, GNDU, Regional Campus Gurdaspur iv
ABSTRACT
In navigational applications antenna plays an important role in determining the location,
tracking and mapping of vehicles. In the recent years navigational antennas have
progressed rapidly and are required to perform various services like surveying, mapping
and providing geographical information without compromising size, weight and
performance. There has been a great demand for antenna designs that have multiband and
wideband properties. Hence the antenna required should be small in size, light in weight,
operates at multiband frequencies, consumes low power and provides high reliability.
Earlier Navigation was based on observations and not on scientific methods but modern
navigation determines the position by collecting the information from satellites through
the receivers. Navigational tools were initially developed for military users but with the
advent of wireless communication systems it has been adopted in civil as well. In military
applications navigational antennas are required for many applications such as
surveillance, beam steering, beam forming, tracking etc. These antennas are positioned
on aircrafts, ships or other vehicles. In aerospace navigation, antennas use radio
frequencies to communicate with air traffic control and find its destination. Therefore
different antennas are required for different purposes and hence they need a large space.
In order to overcome this problem i.e., instead of using number of antennas, a multiband
antenna that can be operated at many frequencies is the need of today.
During this thesis work a compact, mechanically robust antenna that has the capability of
operating at multiple frequencies has been designed. The antenna is a single feed fractal
microstrip patch antenna. It has two circular and two rectangular slots on the ground in
order to improve the resonance of the antenna. Moreover the antenna has conventional
Koch fractal design on the top of the patch to get multiple frequency bands. High
Frequency Structure Simulator (HFSS) software will be used for designing and obtaining
the results for the antenna. High Frequency Structure Simulator (HFSS) is an industry
standard simulation tool. It has powerful drawing capabilities to simply the antenna
design. It is seen that after simulation the antenna provides desired resonant frequencies
that have good operating bandwidth.

Dept.of ECE, GNDU, Regional Campus Gurdaspur v
TABLE OF CONTENTS
Page no.
Certificate i
Declaration ii
Acknowledgement iii
Abstract iv
Table of Contents v-ix
List of Abbreviations x
List of Figures xi-xiii
List of Tables xiv
CHAPTER 1
INTRODUCTION 1-20
1.1 Overview 1
1.2 Antenna design issues in aerospace navigation 3
1.2.1 Coverage 3
1.2.2 Space Available 3
1.3 Antenna Fundamentals 3
1.4 How an Antenna Radiates 4
1.5 Near and Far Field Regions 5
1.6 Antenna Performance Parameters 6
1.6.1 Radiation Pattern 6
1.6.2 Directivity 7
1.6.3 Input Impedance 8
1.6.4 VSWR 9
1.6.5 Return Loss 10
1.6.6 Antenna Efficiency 10
1.6.7 Antenna Gain 11
1.6.8 Polarization 11

Dept.of ECE, GNDU, Regional Campus Gurdaspur vi
1.6.9 Bandwidth 12
1.7 Types of Antennas 13
1.7.1 Half Wave Dipole 13
1.7.2 Monopole Antenna 14
1.7.3 Loop Antenna 15
1.7.4 Helical Antenna 17
1.7.5 Horn Antenna 18
1.8 Organization of Thesis 19
CHAPTER 2
FRACTAL MICROSTRIP PATCH ANTENNA 21-33
2.1 Introduction 21
2.2 Advantages and Disadvantages of Microstrip Patch
Antenna
21
2.3 Basic Principle of Operation 22
2.4 Feeding Techniques 23
2.4.1 Coaxial Probe Feed 23
2.4.2 Microstrip Line Feed 24
2.5 Parameters Determining the Performance of Microstrip
Patch Antenna
25
2.5.1 Effect of Substrate 25
2.5.2 Effect of Parasitic Patches 25
2.5.3 Effect of Multilayer Configuration 25
2.6. Fractals 26
2.6.1 Introduction 26
2.7 Dimensions of Fractal Geometry 27
2.8 Fractal Geometries 28
2.8.1 Sierpinski Gasket 28
2.8.2 Sierpinski Carpet 29
2.8.3 Koch Curve 29

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2.8.4 Hilbert Curve 30
2.8.5 Minkowski Curve 30
2.8.6 Pythagorean Tree Fractal 31
2.9 Advantages and Disadvantages of Fractal Geometries 31
2.9.1 Advantages of Fractal Geometries 31
2.9.2 Disadvantages of Fractal Geometries 31
2.10 Applications of Fractal Geometries 32
2.10.1 Astronomy 32
2.10.2 Nature 32
2.10.3 Computer Science 32
2.10.4 Telecommunication and Medicine 33
CHAPTER 3
LITERATURE SURVEY 34-42
3.1 Literature Review 34
3.2 Inferences Drawn 41
CHAPTER 4
PROPOSED RESEARCH WORK 43-50
4.1 Problem Definition 43
4.2 Objective 43
4.3 Scope of Work 44
4.4 Methodology of Proposed Research work 44
4.4.1 Design Methodology 44
4.4.2 Selection of Design Parameters 45
4.4.3 Selected Geometry 45
4.5 Design of Fractal Microstrip Patch Antennas 45
4.5.1 A Simple Microstrip Patch Antenna 45
4.5.2 A Multiband Microstrip Patch Antenna with Koch
Fractal Geometry
47

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4.5.3 A Multiband Fractal Antenna with Four Slots on the
Ground Plane
49
CHAPTER 5
SIMULATED AND MEASURED RESULTS
VALIDATION
51-67
5.1 Introduction 51
5.2 Simulated Results of Microstrip Patch Antenna 51-53
5.2.1 Return Loss Characteristics 51
5.2.3 Gain 52
5.2.4 Voltage Standing Wave Ratio 53
5.3 Simulated Results of Fractal Patch Antenna 54-56
5.3.3 Gain 55
5.4 Simulated Results of Multiband Fractal Patch Antenna
with Slots on the Ground Plane
57-60
5.4.3 Gain 59
5.5 Validation of Simulated Results 60
5.6 Hardware Implementation 62
5.6.1 Introduction 62
5.7 Fabrication Techniques 62
5.8 Hardware Testing 64
5.9 Performance Assessment of Fabricated Antenna 65

Dept.of ECE, GNDU, Regional Campus Gurdaspur ix
5.9.2 Comparison between Simulated and Measured
Results
66
CHAPTER 6
CONCLUSION AND FUTURE WORK 68-69
6.1 Conclusion 68
6.2 Future Work 69
LIST OF PUBLICATIONS xv
REFERENCES xiv-xviii

Dept.of ECE, GNDU, Regional Campus Gurdaspur x
LIST OF ABBREVIATIONS
HF High Frequency
NAVAID Navigational Aid
RMM Remote Monitoring and Management
LLWAS Low Level Wind shear Alert System
TACAN Tactical Air Navigation
DME Distance Measuring Equipment
GPS Global Positioning System
GLONASS Global Orbiting Navigational Satellite
System
RADAR Radio Detection and Ranging
ASDE Airport Service Detection Equipment
HFSS High Frequency Structure Simulator

Dept.of ECE, GNDU, Regional Campus Gurdaspur xi
LIST OF FIGURES
Figure No. Description Page No.
Figure 1.1 Radiation Pattern from an antenna 4
Figure 1.2 Field regions nearby an antenna 6
Figure 1.3 Radiation Pattern of Directional Antenna 7
Figure 1.4 Equivalent circuit of transmitting antenna 9
Figure 1.5 Various polarization schemes 11
Figure 1.6 Bandwidth from the plot of reflection coefficient 12
Figure 1.7 Half wave dipole 13
Figure 1.8 Radiation Pattern of Half wave dipole 14
Figure 1.9 Monopole Antenna 14
Figure 1.10 Radiation Pattern of Monopole Antenna 15
Figure 1.11 Loop Antennas 16
Figure 1.12 Radiation Pattern of Loop Antenna 16
Figure 1.13 Helix Antenna 17
Figure 1.14 Radiation Pattern of Helical Antenna 18
Figure 1.15 Types of Horn Antennas 18
Figure 2.1 Microstrip Antenna Structure 21
Figure 2.2 Side view of Microstrip Patch Antenna 23
Figure 2.3 Coaxial Probe Feed for Microstrip Patch Antenna 24
Figure 2.4 Microstrip Line Feed for Microstrip Patch Antenna 24
Figure 2.5 Multilayer Configuration 26
Figure 2.6 Sierpinski Gasket 29
Figure 2.7 Sierpinski Carpet 29
Figure 2.8 Koch Curve 30
Figure 2.9 Hilbert Curve 30
Figure 2.10 Minkowski Curve 31
Figure 2.11 Pythagorean Tree Fractal 31

Dept.of ECE, GNDU, Regional Campus Gurdaspur xii
Figure 4.1 Flow graph of Design Methodology of Proposed
Research Work
44
Figure 4.2 Microstrip Patch Antenna (a) Top View (b) 3D View in
HFSS
46
Figure 4.3 3D View in HFSS (a) First iteration (b) Second iteration
(c) Third iteration
48
Figure 4.4 3D View of fractal microstrip patch antenna in HFSS 48
Figure 4.5 Multiband Fractal Patch Antenna with Slotted Ground
Plane (a) Bottom View (b) 3D view
49
Figure 4.6 Detailed Dimensions of Proposed Antenna in HFSS 50
Figure 5.1 Simulated Return Loss of basic Microstrip Patch
Antenna
51
Figure 5.2 3D Radiation Pattern of Microstrip Patch Antenna 52
Figure 5.3 Simulated 3-D Gain Plot of Microstrip Patch Antenna 53
Figure 5.4 Simulated VSWR plot of microstrip patch antenna 53
Figure 5.5 Simulated Return Loss of Fractal Patch Antenna 54
Figure 5.6 Simulated 3D radiation pattern of Fractal Patch Antenna 55
Figure 5.7 Simulated 3D Gain plot of Fractal Patch Antenna 56
Figure 5.8 Simulated VSWR plot of fractal patch antenna 56
Figure 5.9 Simulated Return Loss of Multiband Fractal Antenna 57
Figure 5.10 Simulated 3D radiation pattern of Multiband Fractal
Antenna
58
Figure 5.11 Simulated 3-D Gain Plot of Multiband Fractal Antenna 59
Figure 5.12 Simulated VSWR plot of Multiband Fractal Antenna 60
Figure 5.13 Mask generated using Coral Draw (a) Fractal geometry
(b) Ground slots
63
Figure 5.14 Screens Generated in Screen Printing technique (a)
Antenna Ground Plane (b) T-shaped Top Patch
63
Figure 5.15 Final Fabricated antenna layout (a) Top View (b)
Bottom View (c) Side view
64

Dept.of ECE, GNDU, Regional Campus Gurdaspur xiii
Figure 5.16 Fractal Patch Antenna mounted on Network Analyzer 65
Figure 5.17 Measured Return Loss of Multiband Fractal Antenna 66
Figure 5.18 Measured v/s Simulated Return Loss of Multiband
Fractal Antenna
67

Dept.of ECE, GNDU, Regional Campus Gurdaspur xiv
LIST OF TABLES
Table No. Description Page No.
Table 1.1 Various Frequency Bands for Aerospace Navigation 2
Table 4.1 Detailed Dimensions of Proposed Microstrip Patch
Antenna
46
Table 4.2 Detailed Dimensions of Proposed Multiband Fractal
Antenna
50
Table 5.1 Comparison between Proposed Multiband Fractal
Antenna with the Design Proposed in [30]
60

Dept. of ECE, GNDU, Regional Campus Gurdaspur 1
CHAPTER 1
INTRODUCTION
1.1 Overview
In 1886, Henry Hertz developed a wireless communication system in which an electric
spark occurred in dipole and loop antenna. Since then antennas are being used for
television, mobile and satellite communication. In the year 1880, Nicola Tesla suggested
a radio to transmit information and described first radio communication systems in his
papers in the year 1891. At the same time, Guglielmo Marconi was the first to patent the
telegraph and signified the importance of wireless communication. In 1940, the first
standard for communication technology was introduced [1]. A large growth in wireless
technologies was seen during 1980’s and 1990’s, due to which cheap wireless services
were introduced all over the world. In 21st
century a great progress can be seen in
wireless technologies in which the devices are becoming smaller to integrate various
services.
In wireless applications antenna plays an important role as it converts electrical power
into radio waves. An antenna acts as an interface between space and transmission line.
Earlier each antenna operates at a single frequency therefore different antennas were
required for different purposes. Today’s communication requires an antenna that provides
high gain, wide bandwidth, supports multiple frequencies, is compact in size and satisfies
various requirements of the system.
Earlier Navigation was based on observations and not on scientific methods but modern
navigation determines the position by collecting the information from satellites through
the receivers. Navigational tools were initially developed for military users but with the
advent of wireless communication systems it has been adopted in civil as well. Mobile
phones, computers, laptops have GPS functionality. The GPS is a space based satellite
system that provides location information anytime and anywhere. In military applications
navigational antennas are required for many applications such as surveillance, beam
steering, beam forming, radar, tracking etc. These antennas are positioned on aircrafts,
ships or other vehicles. In aerospace navigation, antennas use radio frequencies to

communicate with air traffic control and find its destination. Various frequency bands
allocated for aerospace navigational applications are listed below in Table 1.1.
Table 1.1 Various Frequency Bands for Aerospace Navigation
Frequency Band Name
2100 - 28,000 kHz HF Communications
750 MHz NAVAID (Marker Beacons)
8-12 GHz X-band
932 – 935 & 941 – 944
MHz
RMM, LLWAS, etc.
960 – 1215 MHz NAVAID (TACAN / DME, etc.)
1215 – 1390 MHz Air Route Surveillance Radar; GPS and GLONASS L1
1545 – 1559 MHz Satellite-Based Comm (To Aircraft)
1559 – 1610 MHz Satellite Navigation; GPS and GLONASS L1
1646.5 – 1660.5 MHz Satellite-Based Comm (From Aircraft)
9000 – 9200 MHz Military Precision Approach Radar
14.4 – 15.35 GHz Microwave Link
15.7 – 16.2 GHz Radar (ASDE-3)
18-19 GHz Point to Point Radio Communication

A great improvement can be seen in aerospace navigation and various new standards are
being used throughout the world. In order to implement the new standards it is essential
to have an antenna that is low profile, supports various frequencies and provides good
transmission and reception signals. However designing such an antenna is a difficult task
because various parameters such as space, volume and presence of other objects play an
important role. Various design issues are discussed below.
1.2 Antenna Design Issues in Aerospace Navigation
Aerospace navigation requires an antenna that supports wideband/multiband frequencies
and is small in size. The major challenge in designing an antenna for aerospace
navigation is that it covers maximum frequencies while consuming less volume.
Therefore an antenna that has light weight, low cost, robust, flexible and can support
multiple frequencies is the need of today [2].
Various design issues are briefly explained below:
1.2.1 Coverage
Wireless devices should be designed in such a way that it covers maximum frequencies
that are allocated to a particular application. Earlier different antennas were used for
different purposes. The latest trend in designing an antenna for navigation purpose is that
it covers maximum frequencies. This affects in designing a complex patch antenna with
fractal shapes on its patch.
1.2.2 Space Available
Now-a-days the inclination in wireless communication is to design a compact antenna so
that it can be easily positioned even in places where volume is a major issue. While
designing a low profile antenna, complexity increases as patch is designed using fractal
geometries. Moreover bandwidth and radiation efficiency are directly proportional to the
size of the antenna. Therefore as size increases performance also increases and hence
more volume is required.

1.3 Antenna Fundamentals
Antennas are very essential part of communication systems. An antenna converts RF
signal that is travelling on a conductor into an electromagnetic wave. Antennas exhibits
reciprocity property i.e., antenna has same characteristics while transmitting or receiving.
In order to pair transmission and reception, antenna must be tuned to similar frequency
band of the radio to which it is linked.
1.4 How an Antenna Radiates
Firstly, let us consider how radiation takes place. Radiation in conducting wire takes
place mainly due to deceleration or acceleration of charge. No current flows, if there is no
motion of charge and hence no radiation occurs. However, when a charge moves along
bent or curved wire with uniform velocity, radiation is produced [3].
Figure 1.1 Radiation pattern from an antenna

To understand the concept of radiation from an antenna, let us consider a voltage source
connected to a transmission line. When a voltage is applied across the conductor, a
sinusoidal electric field is produced and thus electric lines of force are also formed. The
free electrons in the conductor are dislocated by electric lines of force which in turn
produce charge by the movement of these charge carriers and hence magnetic field is
created.
Electromagnetic waves that travel between the conductors are created due to time varying
magnetic and electric fields. When these waves come close to the open space, they form
free space waves by simply joining the open ends of electric field lines. Since electrical
disturbances are created continuously by the sinusoidal source, therefore electromagnetic
waves are also radiated continuously into the free space. The electromagnetic waves are
preserved inside the antenna and transmission lines due to the presence of charged
particles, but the moment they penetrate into the free space closed loops are formed and
are radiated.
1.5 Near and Far Field Regions
The antenna field patterns are associated with two types of energy: reactive energy and
radiating energy. Therefore space around the antenna is divided into three regions as
shown in figure 1.3.
 Reactive near field region: This region is influenced by reactive field. The energy in
reactive field appears as reactance by oscillating towards and away from the antenna.
Therefore the energy appears as reactance. In this no energy is dissipated, in fact it is
stored in the given region. The exterior most boundary is at a distance of R1=
0.62√D3
/λ where λ is the wavelength, D is the highest dimension of antenna and R1 is
the distance from the antenna.
 Radiating near field region (Fresnel region): This region resides between the far field
region and the near field region. In this field radiation fields dominate while reactive
fields are smaller. The exterior most boundary is at a distance of R2= 2D2
/λ where λ is
the wavelength and R2 is the distance from the antenna [3].
 Far-field region (Fraunhofer region): The region beyond radiating near field region is
the far field region. Here only the radiation fields are present and the reactive field

does not exist. In this region, field distribution is independent from the distance of the
antenna.
Figure 1.2 Field regions nearby an antenna
1.6 Antenna Performance Parameters
The performance of the antenna can be measured from various parameters. Some
important parameters are discussed below.
1.6.1 Radiation Pattern
Radiation Pattern or Antenna Pattern is the total strength of the radiated field in different
directions from the antenna, at a given distance. The radiation pattern also describes
receiving properties of an antenna. The radiation pattern is measured in two dimensions
i.e., the vertical or horizontal planes, although it is a three dimensional pattern [3]. The
measurements of the pattern are either presented in a polar or rectangular format. The
points in the polar coordinate graph are positioned alongside a rotating radius and they
intersect with several concentric circles. In rectangular plot it is difficult to conceptualize
the behavior of antenna at different directions.
To understand the concept if radiation pattern, let us consider a directional antenna. A
directional antenna radiates more in a particular direction while less in other directions.
An omnidirectional antenna is an exceptional case of directional antenna having constant

radiation pattern in E-plane and varies in orthogonal or H-plane. Figure 1.3 shows the
radiation pattern of a directional antenna.
Figure 1.3 Radiation Pattern of Directional Antenna
 HPBW: The angle linked by half power points of the main lobe is known as Half
Power Beam width (HPBW).
 Major Lobe: This lobe contains the maximum intensity of radiation in a particular
direction.
 Minor Lobes: These lobes contain the radiation in undesired directions. Therefore all
the lobes other than major lobe are the minor lobes.
 Back Lobe: The lobe exactly in the opposite direction of the main lobe is called back
lobe.
 Side Lobe: The lobes adjacent to main lobe are called side lobes. These lobes are
unrelated by various nulls.
1.6.2 Directivity
Directivity can be defined as an ability of an antenna to transmit more power in a specific
direction while transmitting or receive more power from a specific direction while
receiving [3]. Or we can say, the directivity of an object whose physical properties vary
in different directions, is defined as the ratio of its radiation intensity in a specific

direction, over that of an isotropic source, whose physical properties remain same
throughout all the directions. Therefore
D= U/Ui = 4πU/P (1.1)
where D = directivity of the antenna
U = the radiation strength of the antenna
Ui = the radiation strength of an isotropic source
P = the total power emitted
Directivity is the ratio of two radiation strengths; therefore it is a dimensionless quantity.
It is expressed in dBi. For the antenna to be more directive, it will have a narrow main
lobe rather than a broad one.
1.6.3 Input Impedance
The input impedance of an antenna can be defined as the ratio of the voltage to the
current at the antenna and the transmission cable connecting them [3]. The impedance of
the pair should be same for an efficient transfer of energy. The impedance of an antenna
should not be different from 50Ω. Mathematically input impedance can be represented as:
Zin = Rin + jXin (1.2)
where Zin = antenna impedance at the terminals
Rin = antenna resistance at the terminals
Xin = antenna reactance at the terminals
The imaginary part of the input impedance, Xin shows the radiation strength stored in the
near field of the antenna. Rin called the resistive part of the input impedance is composed
of two parts, loss resistance RL and radiation resistance Rr. Radiation reactance represents
the actual power transmitted by an antenna while loss resistance is the heat dissipated
from the antenna.

1.6.4 Voltage Standing Wave Ratio
For an antenna to function effectively, transfer of maximum power between the
transmitter and the antenna should take place. This can happen only when the impedance
of the transmitter (Zs) is matched to the impedance of the antenna (Zin). Maximum Power
Transfer theorem says that maximum power can be transmitted only if the impedance of
the antenna is a complex conjugate of the impedance of the transmitter and vice-versa.
Therefore, condition for impedance matching is:
Zin = Zs
*
(1.3)
If the above condition is not fulfilled, then some of the radiations are reflected back,
leading to formation of standing waves, which can be distinguished by a parameter
known as Voltage Standing Wave Ratio (VSWR). Mathematically:
VSWR =1 + |Γ| /1 − |Γ| (1.4)
ᴦ = Vr / Vi = Zin – Zs/ Zin+ Zs (1.5)
ᴦ = reflection coefficient
Vi = amplitude of incident wave
Vr = amplitude of reflected wave
Figure 1.4 Equivalent circuit of transmitting antenna

The value of VSWR should be less because higher the value, the greater is the mismatch
between the antenna and the transmitter. Ideally the value of VSWR should be unity.
1.6.5 Return Loss (RL)
Return loss can be defined as the power that is wasted to the load and is not returning as a
reflection. Return loss also indicates the mismatching between the transmitter and the
antenna. Mathematically it is represented as:
RL = -20 log |Γ| (1.6)
If impedance matching is perfect then Γ= 0 and RL = infinity, i.e., no reflected power.
Similarly when Γ= 1 and RL = 0dB, this means that all the incident power is reflected
back. The value of VSWR should not exceed 3, since this value gives RL of -10 dB.
1.6.6 Antenna Efficiency
Antenna efficiency can be defined as the amount of losses occurring within the antenna
and at various terminals of the antenna. Various losses can be defined as:
 Reflection Losses: These losses occur mainly due to impedance mismatching between
the terminals and the antenna.
 I2
R losses: These are the conduction and dielectric losses.
Hence mathematically efficiency of the antenna can be defined as:
et= er ec ed (1.7)
where et = total antenna efficiency
er = mismatch efficiency
ec = conduction efficiency
ed = dielectric efficiency

1.6.7 Antenna Gain
Antenna gain is closely associated with the directivity of the antenna. Directivity can be
defined as an ability of an antenna to transmit more power in a specific direction while
transmitting or receive more power from a specific direction while receiving. Therefore,
if the efficiency of the antenna is 100% then the antenna can act as an isotropic radiator
whose directivity is equal to the gain of the antenna. More precisely, we can define
antenna gain as an ability of an antenna to achieve more power in one direction at the
expense of lost power in other directions.
1.6.8 Polarization
Polarization is defined as the direction of electric field of an electromagnetic wave. It
describes the direction and position of electric field with respect to ground [3].
Polarization is of two types i.e., linear and circular polarization.
 Linear polarization: In linear polarization electric field path is back and forth along a
line. Figure 1.5 represents linear polarization.
Figure 1.5 Various polarization schemes

 Circular polarization: In circular polarization, electric field vector rotates in circular
path while remaining constant in height. Circular polarization is further of two types:
Right hand circular polarized wave and Left hand circular polarized wave. In Right
hand circular polarized wave, the electric field vector rotates in clockwise motion. In
Left hand circular polarized wave; the electric field vector rotates in anticlockwise
motion. Figure 1.6 represents circular polarization.
1.6.9 Bandwidth
Bandwidth can be defined as range of accessible frequencies on the sides of center
frequency where the various parameters of antenna such as input impedance,
polarization, radiation pattern, gain lie near to the values that are obtained at the center
frequency [3]. For a broad band antenna, bandwidth can be described as the ratio of the
upper frequency and the lower frequency, whereas for narrowband antenna bandwidth is
the percentage of difference between the upper and the lower frequency from the center
frequency.
Figure 1.6 Bandwidth from the plot of reflection coefficient

Therefore mathematically bandwidth can be defined as:
BW broadband =
𝑓 𝐻
𝑓𝐿
(1.8)
BW narrowband (%) = [ 𝑓𝐻 − 𝑓𝐿/ 𝑓𝐶] × 100 (1.9)
Where 𝑓𝐻 is the upper frequency.
𝑓𝐿 is the lower frequency.
𝑓𝐶 is the center frequency.
1.7 Types of Antennas
Antennas are of different sizes and shapes according to different wireless applications.
The size and shape and the material used to make an antenna determines various
characteristics of the antenna. Following are the different types of antennas used in
wireless communication.
1.7.1 Half Wave Dipole
As the name implies the length of the antenna is half of its wavelength. In order to
maintain the balance of the performance, dipoles can be longer or shorter than half the
wavelength.
Figure 1.7 Half wave dipole

Wire transmission line is used to feed the dipole antenna. In this the two sinusoidal
currents are equal in amplitude but opposite in direction [4]. Hence, no radiation occurs
from the transmission line due to cancellation effect. The gain of 2 dB can be achieved
from dipole antenna having bandwidth of 10%. The half power beamwidth of dipole
antenna is about 78degrees with directivity equals to 1.64. Figure 1.8 shows radiation
pattern of half wave dipole antenna.
Figure 1.8 Radiation Pattern of Half wave dipole
1.7.2 Monopole Antenna
The monopole antenna has been derived by applying the image theory to the dipole
antenna. According to the theory, if a conducting plate is positioned beneath a single
element of length L/2 and this length is carrying the current, then integration of the
element and its image functions in a similar manner as a dipole of length L except that
the radiations exist only in the area the plane.
Figure 1.9 Monopole Antenna

In this type of antenna, the radiation resistance is halved and the directivity is doubled to
that of a dipole antenna. This type of antennas finds its applications in mobiles where the
handset case or the car body acts as a conducting plane. It is a quarter wavelength
monopole and the gain varies from 2-6 dB. The directivity is 3.28 and the radiation
resistance is 36.5 Ω. The radiation pattern is shown in figure 1.10.
Figure 1.10 Radiation Pattern of Monopole Antenna
1.7.3 Loop Antennas
A conductor bent into the closed curve shape forming a square or a circle with a gap to
form terminals is called as loop antenna. There are basically two types of loop antennas:
electrically large loop antenna and electrically small loop antenna. If the total
circumference is approximately equal to the wavelength then it called as electrically large
loop antenna. An electrically small loop antenna has small total loop circumference as
compared to the wavelength.
As shown in figure 1.12, the radiation pattern of the dipole antennas is identical to
small circular loop antenna, regardless of the fact that the dipole is vertically polarized
and loop antennas are horizontally polarized [4].
If the core of the loop antenna is filled with ferrite, the performance can be increased
because ferrite increases the radiation resistance.

Figure 1.11 Loop Antennas
The radiation pattern of small loop antenna is different from that of large loop antenna. It
is seen that the radiation pattern of large loop antenna is maximum along the z axis. In the
loop, a null is along the z axis and a lobe along the y axis. A gain of -2dB to 3dB can be
seen in loop antennas. These antennas have bandwidth around 10% and can be used in
pagers and AM broadcast receivers.
Figure 1.12 Radiation Pattern of Loop Antenna

1.7.4 Helical Antennas
In helical antenna a wounded helical shaped conductor is connected to the ground plane.
Figure 1.13 shows a helix antenna. The antenna basically has two principal modes called
normal mode (broadside radiation) and axial mode (endfire radiation). For the helical
antenna to operate in the normal mode, the diameter of the helix should be very small as
compared to the wavelength. However, when the circumference of the helix is same as
that of the order of the wavelength, then the antenna is operating in axial mode.
Figure 1.13 Helix Antenna
In normal mode of operation, the field is minimum along the helix axis and maximum in
a plane normal to the axis. In this mode low bandwidth is obtained and can be used for
handheld devices [4]
In the axial mode of operation, the antenna radiates single beam along the axis of the
helical antenna. This mode gives high bandwidth and better gain when compared to
normal mode of operation. In this mode, as the turns on the helix increases, the beam
becomes narrower. In this mode antenna is widely used in satellite communication
because of its broadband nature. Figure 1.14 shows the different radiation patterns of
helix antenna.

Figure 1.14 Radiation Pattern of Helical Antenna
1.7.5 Horn Antenna
Horn antennas are widely used in microwave regions where waveguides are used as feed
forming a megaphone like structures.
Figure 1.15 Types of Horn Antenna

Horn antennas have many advantages such as low VSWR, low weight, wide bandwidth,
high gain and are easy to manufacture [4]. Rectangular, elliptical and circular are various
apertures of horn antennas. Various geometries of horn antennas are shown in figure
1.15. Rectangular waveguide feed having broad horizontal wall is used as feed in these
horn antennas.
 H-plane Horn Antenna: If a narrow wall of waveguide is used as feed for broad wall
dimension of horn antenna, then it is known as H-plane horn antenna.
 E-plane Horn Antenna: If the broad wall dimensions of horn antenna have a
waveguide feed in E-plane, and then it is called as E-plane horn antenna.
 Pyramidal Horn Antenna: If the broad wall dimensions of horn antenna have a
waveguide feed in E as well as H-plane then it is called as pyramidal horn antenna.
The horn antenna reduces reflected waves and increases travelling waves which results in
wide bandwidth and low VSWR [5]. The antenna is widely used in satellite tracking,
communication dishes as a feed element.
In the above section various antennas and their properties have been discussed.
Microstrip Patch antenna is another commonly used antenna. The aim of the thesis work
is to design a compact patch antenna using various fractal geometries for aerospace
navigation and is explained in the next chapters.
1.8 Organization of Thesis
A low profile antenna covering multiple frequencies of aerospace navigation is presented
in this thesis. The design of the antenna is compact, robust and simple. Organization of
thesis is explained below.
Chapter 2 covers fundamental and theory of Microstrip Patch Antenna. Various design
parameters are also discussed. Furthermore various fractal geometries and their
characteristics are also analyzed.
Chapter 3 covers literature review. Articles covering various fractal designs on
microstrip patch antenna are reviewed and inference is also drawn after studying these
articles.

Chapter 4 covers proposed work and methodology adopted to obtain results from
simulation of proposed antenna.
Chapter 5 provides the results. Simulations are performed to obtain the results. Various
parameters such as gain plot, return loss characteristics, far field patterns and Voltage
Standing Wave Ratio (VSWR) plot are discussed in this chapter. It also includes the
hardware implementation. Various steps for the fabrication of the antenna are explained
and the measured results are compared with the simulated results.
Chapter 6 includes the conclusion of the thesis work and suggestions are also presented
for future development of the antenna.

CHAPTER 2
FRACTAL MICROSTRIP PATCH ANTENNA
2.1 Microstrip Patch Antenna
Microstrip patch antenna was developed by Bob Munson in 1972. It consists of radiating
patches that are placed on the top of the dielectric substrate and a conductive layer is
present on the bottom surface of the substrate, forming a ground for the antenna. The
shape and dimensions of the patch are the important features of the antenna [6].
Microstrip patch antennas are light in weight because of absence of machined parts and
are simpler, compact and easy to manufacture with printed circuit technology.
Figure 2.1 Microstrip Patch Antenna Structure
2.2 Advantages and Disadvantages of Microstrip Patch Antenna
Microstrip antennas are widely used in wireless applications due to their compact
structure. They are used as navigational antennas in aerospace and space communication.
These antennas are thin and compact and hence are extremely suited for handheld devices
such as pagers, phones etc [7]. Some of the major pros of Microstrip Antennas are:
 Compact and light in weight.
 Low manufacturing cost.
 Supports circular as well as linear polarization.
 Supports multiple frequencies.

 Robust and can be placed on rigid surfaces.
 Can be merged with microwave integrated circuits (MICs).
Some of the major disadvantages of Microstrip Antenna when compared with
conventional antennas are:
 Limited bandwidth.
 Nearly 6dB gain.
 High ohmic losses.
 Limited power handling capacity.
 Little efficiency due to conductor and dielectric losses.
 Low impedance bandwidth.
 Artificial feed radiation from strips, surface waves, etc.
Microstrip patch antennas have high quality factor (Q). Quality Factor shows losses in the
antenna. Moreover high value of Q tends to have narrow bandwidth and low efficiency.
In order to reduce the value of Q, thick dielectric substrates should be used. But thickness
leads to unwanted power as power forwarded by the source goes into surface wave. By
array configuration, lower power handling capacity and lower gain can be overcome.
2.3 Basic Principle of Operation
Figure 2.2 shows a patch antenna in which ground is usually made of PC board. The
middle conductor of the coax represents probe feed to pair electromagnetic energy in and
out of patch.
The electric field is maximum (positive) at one side of the patch and minimum (negative)
at the other and zero at the core of the patch. The positive and negative sides changes
continuously with the phase of applied signal [8].
In a patch, the flow of electric field does not stop unexpectedly as in a cavity; rather it
expands towards the periphery. The expanding of field towards periphery is known as
fringing field and this causes the patch to radiate. This is the basic principle of a patch
antenna.

Figure 2.2 Side view of Patch Antenna
The electric field is maximum (positive) at one side of the patch and minimum (negative)
at the other and zero at the core of the patch. The positive and negative sides changes
continuously with the phase of applied signal [8].
In a patch, the flow of electric field does not stop unexpectedly as in a cavity; rather it
expands towards the periphery. The expanding of field towards periphery is known as
fringing field and this causes the patch to radiate. This is the basic principle of a patch
antenna.
2.4 Feeding Techniques
The feeding methods in Microstrip Patch antennas can be categorized as contacting and
non-contacting. In non-contacting electromagnetic field coupling is executed for the
transmission of power within the radiating patch and the microstrip line. On the other
hand in contacting, power is fed directly to the patch using bridging element. In
Microstrip Patch Antennas following are the feeding techniques:
 Coaxial probe feed
 Microstrip transmission line feed
2.4.1 Coaxial Probe Feed
Coaxial Probe Feed is the most common feeding technique used in Microstrip Patch
antennas. In this technique inner most conductor of coaxial connector expands from the

dielectric to the patch whereas, the outer conductor of the cable is joined to the ground
plane. Figure 2.3 shows a microstrip patch antenna with coaxial probe feed [7].
Figure 2.3 Coaxial Probe Feed for Microstrip Patch Antenna
The main advantage of such feeding technique is that it can be placed anywhere inside
the patch according to its input impedance. This method is easy to manufacture and
produces low artificial radiations. Nevertheless the main disadvantage is that it produces
narrow bandwidth and drilling of hole inside the substrate is somewhat difficult [9].
2.4.2 Microstrip Line Feed
In this type of technique, a strip of conductor is joined directly to the edge of microstrip
patch antenna as depicted in figure 2.4. The strip is shorter in width when compared to
the patch. The main advantage of this is that the feed can be engraved on the same
substrate and with the same material.
Figure 2.4 Microstrip Line Feed for Microstrip Patch Antenna

In this we do not need any additional matching element to match the impedance of the
patch to the feed line. This technique is easy to fabricate. However the disadvantage of
such technique as the thickness of the substrate increases, spurious waves and surface
waves also increases which in turn holds back the bandwidth of antenna.
2.5 Parameters Determining the Performance of Microstrip Patch
Antenna
A microstrip patch antenna consists of a ground plane, substrate and a patch. Various
parameters determine the performance of the antenna, some of which are explained
below:
2.5.1 Effect of Substrate
It is seen that the bandwidth of the antenna depends upon various parameters of the
substrate. The quality factor Q varies inversely with the impedance bandwidth of the
patch antenna. Therefore various parameters of substrate such as thickness and dielectric
constant can be changed to obtain different values of Q. Here Q is:
Q = Energy stored/Power lost
The bandwidth also depends upon the thickness of the substrate. As the thickness of the
substrate increases the bandwidth also increases. On the contrary when εr decreases,
bandwidth increases. However a thick substrate results in poor radiation efficiency. Also
thick substrates give rise to fictions radiation and radiation from the probe feed also
increases. Therefore this can be counted as a limitation in obtaining an octave bandwidth.
2.5.2 Effect of Parasitic Patches
A parasitic patch can be defined as a patch that is placed close to the feed patch. The
presence of parasitic patch excites the feed patch through coupling between the two
patches. If the resonance frequencies of the two patches are in close proximity to each
other, then a wide bandwidth can be obtained because the VSWR is of responses that
results in broad bandwidth.

2.5.3 Effect of Multilayer Configuration
When two or more patches of the dielectric substrate are placed together on different
layers, they form multilayer configurations. A multilayer configuration shows a decline
in radiation pattern when compared to single layer. One major drawback is the increase in
height which is not advantageous in the applications where space is a major issue. This
configuration also increases back radiation. Multilayer configuration yields broad
bandwidth [10, 11].
Figure 2.5 Multilayer Configuration
2.6 FRACTALS
2.6.1 Introduction
The word fractal was first devised by Benoit Mandelbort in the year 1975. It has been
derived from a Latin word “fractus” meaning fractured or broken. The fractal geometries
are generated from the complex structures occurring in nature. In the year 1988, Nathan
Cohen built the first fractal antenna. These antennas are designed using simple fractal
geometries which have self similar and space filling properties. Self similar property
associated with fractal geometry enables to design different parts of antenna that look
similar to each other when viewed at different scale. Space filling property reduces the
size of antenna when compared to other traditional antennas. Therefore by using fractal

geometries a compact antenna that can be operated at different frequencies can be
obtained.
Antennas with fractal geometries are quiet attractive due to their low weight, compact
size, multiband nature and easy manufacturing. The geometries of fractal antenna are
difficult to define using Euclidean geometries. The fractal antennas undergo number of
iteration forming a copy of the parent. Hence these antennas are also known as “Natural
Antennas” because their geometry resembles natural occurring phenomena such as
branches of trees, rivers, galaxies etc.
The antenna that undergoes number of iterations is called deterministic fractal antenna.
These antennas are designed using broken lines known as generators. The segments
forming broken line are substituted by the generator forming first iteration according to
the algorithm. The step is repeated infinitely resulting in fractal geometries. The iteration
function system decides the number of iterations [12].
A. Properties of Fractal Geometries
 Space Filling Properties: Fractal Geometries have space filling curves.
 Self Similarity: An object is approximately similar to a part of itself.
B. Fractal Geometry Types
Geometries are based on shapes that are self similar. There are two geometry types:
 Random: These geometries are not exactly familiar to a part of itself but are quiet
familiar.
 Deterministic: A generator is taken and is applied on successive size scales.
2.7 Dimensions of Fractal Geometry
Dimensions can be defined as the number of parameters or co-ordinates of an object.
There are different parameters for dimensions of fractal geometries such as self
similarity, topological dimension, and box counting dimension. Here self similarity
dimension is considered to define fractal geometries [14]. The self similarity dimension is
defined as:
𝐷s = log 𝑁/ log(
1
𝑠
) (2.1)

N is the number of self similar copies.
s is the scale factor.
Fractal Antennas have repeating patterns, therefore despite of using the word “repeat” we
use “iterate” and the process of repeating pattern is called iteration. The iterative function
is given by:
𝑊(𝑥) = 𝐴𝑥 + 𝑡 = [
𝑎 𝑏
𝑐 𝑑
] [
𝑥1
𝑥2
] + [
𝑒
𝑓] (2.2)
Where 𝐴 = [
(
1
𝑠
) 𝑐𝑜𝑠𝜃 − (
1
𝑠
) 𝑠𝑖𝑛𝜃
(
1
𝑠
) 𝑠𝑖𝑛𝜃 (
1
𝑠
) 𝑐𝑜𝑠𝜃
] (2.3)
Here a, b, c, d is defined by rotation and scaling of initial geometry and e and f denote the
translation.
Fractal geometries have two main components:
1. Initiator: The basic geometry of fractal antenna.
2. Generator: Shape that we get after different iterations.
Fractal antennas provide better input impedance and can be used in devices where space
is a major issue because of space filling property. These antennas can show multiband
properties due to self similar design. By using self similar property a number of copies
can be found within the whole geometry. Hence fractal geometries do not have any
characteristic size and shape. Despite of having so many advantages fractal antennas are
difficult to fabricate and sometimes provide lower gain.
2.8 Fractal Geometries
2.8.1 Sierpinski Gasket
In 1915, Waclaw Sierpinski designed Sierpinski triangle. In this the equilateral triangle is
subdivided into smaller equilateral triangles. This pattern can be generated using
mathematical equations.

In order to create this geometry an equilateral triangle is cut out from the center of main
triangle and thus resulting in three smaller triangles of equal dimensions, called first
iteration as shown in figure 2.6. This process is carried out infinitely. This geometry is
most commonly used for antenna applications. This is used for monopole and dipole
antenna configurations [6].
Figure 2.6 Sierpinski Gasket
2.8.2 Sierpinski Carpet
This geometry is similar to sierpinski gasket, but it uses squares in place of triangles. In
first order iteration a square having dimensions one third of the main square is subtracted
from the center of the square. This process is repeated infinite times in order to get next
order iterations. The pattern is repeated in a symmetrical manner such that each etched
square is one third in dimension of the sharing square. Figure 2.7 represents geometry of
Sierpinski Carpet [14].
Figure 2.7 Sierpinski Carpet

2.8.3 Koch Curve
In the year 1998, von Koch monopole antenna improved various features such as
radiation resistance, bandwidth and resonance frequency when compared to conventional
antennas.
Figure 2.8 Koch Curve
This geometry is quiet simple. It starts with a straight line as an initiator. The line is
divided into three equal parts; the segment in the middle is replaced with two other of
same length. This is the first iteration version and is called the generator. Monopole and
dipole antennas can be constructed with Koch Curve geometry. Figure 2.8 shows the
geometry of Koch Curve [15].
2.8.4 Hilbert Curve
This geometry is also known as Space Filling Curve since it fills the area it occupies.
In this geometry each consecutive iteration consists of previous four copies of iteration.
The geometry is simple as the curves can be drawn easily and the lines of the geometry
do not intersect with each other. The fractal geometry of Hilbert Curve is shown in figure
2.9 [16].
Figure 2.9 Hilbert Curve

2.8.5 Minkowski Curve
In 1907, a German mathematician, Hermann Minkowski devised a new fractal shape
called Minkowski Sausage and later known as Minkowski Curve.
Figure 2.10 Minkowski Curve
This fractal geometry reduces the size of antenna and also increases the efficiency by
occupying the volume with electrical length. The fractal geometry of the fractal design is
shown in figure 2.10 [17].
2.8.6 Pythagorean Tree Fractal
In Pythagorean Tree Fractal the geometry starts with square, called zeroth iteration.
When two other squares are placed upon the first square such that the corners coincides
with the main square then this is known as second order iteration. The process is followed
by infinite iterations accordingly. The fractal geometry of Pythagorean Tree Fractal is
shown in figure 2.11 [18].
Figure 2.11 Pythagorean Tree Fractal

2.9 Advantages and Disadvantages of Fractal Geometries
2.9.1 Advantages of Fractal Geometries
 Small in size
 Better input impedance
 Wideband/multiband support
2.9.2 Disadvantages of Fractal Geometries
 Fabrication and Design is complicated
 Numerical limitations
 Lower Gain in some cases
2.10 APPLICATIONS OF FRACTAL GEOMETRIES:
Fractals can be described as anything that appears irregular. Fractal geometries are
unique and random. Common fractal shapes found are:
 leaves of the trees
 a DNA molecule
 various veins in our hands
 irregular patterns of clouds
 an oxygen molecule
Various applications of fractal geometries are discussed below:
2.10.1 Astronomy
Fractal geometries can be seen in space as well. According to cosmologists, the matter is
spread uniformly across space. But the above assumption is not true. Astronomers
assume that the universe is not smooth at large scales but the assumptions can be true at
small scales. But various scientists claims that the structure of universe is fractal at all
scales.

2.10.2 Nature
Tree is a good example to show fractal geometry in nature. Study various branches,
leaves and structures of tree. It is seen that they all possess similarity in their fields.
Another example to show similarity in nature is weather. Weather forecasts are not
generally accurate because of minor disturbances in heating, solar etc. More examples of
fractal geometries in nature can be mountains, coastlines etc.
2.10.3 Computer Science
Fractal image compression is the most useful technique used in computer science. Using
this technique, images can be compressed much more than their usual ways. Another
advantage of fractals in computer science is image enlargement without pixelisation.
2.10.4 Telecommunication and Medicines
Fractals can be used for biosensor interactions in medical field. Fractals have found their
way in sector of telecommunications because of its small size and light in weight.
Fractals provide multiband behavior by transmitting the currents in different arms.

CHAPTER 3
LITERATURE SURVEY
In the world of wireless communication, there has been an ever increasing demand of
compact, small and low power consumption antenna designs. Therefore compromise has
to be made among bandwidth, volume or radiation pattern of an antenna while designing
a compact antenna that is capable of covering maximum frequency bands required for a
given application.
3.1 Literature Review
Tu Zhen et al. in [19] designed a Minkowski Fractal Loop yagi Antenna based on Rao-
Wilton-Glisson (RWG) and delta-feed gap model. The Minkowski loop yagi antenna is
iterated up to 1st
level. The proposed antenna operates at 880-960 MHz frequency band.
Minkowski loop reduces the size of the antenna up to 34.5% as compared to square loop
yagi antenna working on same frequency band. The size of the Minkowski loop yagi
antenna is 8.5 × 8.5 cm2
. The gain of the antenna is between 10dBi-11.2dBi. The antenna
provides good return loss over targeted frequencies.
J.B. Pereira et al. in [20] designed a simple printed fractal monopole antenna for WLAN
USB dongle applications. In this antenna a combination of fractal geometry and
meandered line is used to achieve multiband characteristics. The proposed antenna covers
a bandwidth of 2.22 to 2.52GHz and 5.03 to 5.84 GHz that covers entire band required
for various WLAN standards such as 802.11 a/b/g standards. The size of the antenna is
50 × 20 mm2
which is perfect for a USB dongle. Moreover the antenna provides good
return loss and maximum gain of 2.4dBi and 1.8 dBi over 5.2/5.8GHz and 2.4GHz band
respectively.
Joan Gemio et al. in [21] designed a triangular monopole on a fractal ground plane to
obtain a dual band antenna for WLAN applications. The design of the ground plane is
based on Sierpinski gasket. The antenna covers 2.45 and 5.4 GHz frequency bands of

WLAN. It is seen that directivity and efficiency changes significantly by using fractal
based ground plane as compared to solid ground plane of same dimensions. The
directivity of the antenna is 3.4 dB and 4.6 dB for 2.45 GHz and 5.4 GHz respectively.
This antenna can be used for indoor environments.
Y.B. Thakare et al. in [22] designed a novel star shaped fractal patch antenna for the
reduction of backscattering of radar cross section (RCS). The size of the antenna was
reduced to 50% when compared with a conventional circular microstrip patch (CCMP)
antenna. The proposed antenna operates at 0.85-4GHz frequency band. It is seen that as
the number of iterations increases, a reduction in backscattering RCS can be observed at
multiband because of frequency selective nature, when compared to other conventional
patch antennas. In addition by varying the size and thickness of the substrate
backscattering can be reduced. The size of the antenna is 110mm ×110mm. The proposed
antenna design can be used for many defense and civilian applications.
S.R. Anoop et al. in [23] designed fractal microstrip patch antenna for multiband
operation. The square patch of the antenna is iterated upto three iteration. The dimensions
of the patch are 27mm × 27mm. The proposed antenna design resonates at 2.6 GHz, 3.3
GHz, 4.5 GHz and 6.9 GHz. Due to self similarity between different parts of patch, the
antenna shows multiple frequency bands. The proposed antenna has compact structure
and is designed on FR4 substrate. It is observed that after each iteration, the antenna
resonates at more number of frequency bands. The average percentage of bandwidth is
10.92. The antenna provides good gain and radiation properties.
Atif Jamil et al. in [24] designed a compact multiband hybrid meandered Koch fractal
antenna for USB dongle. The proposed antenna is designed using Koch-meandered
fractal geometry and covers a bandwidth of 5.1406- 5.8737 GHz and 2.2909-2.553 GHz.
The minimum return loss is achieved at the lower band of 2.41GHz of -28.9dB and the
upper band shows a return loss of -20.8dB at 5.36GHz. The dimensions of the antenna
are 14.2mm × 10mm and it covers a complete band of WLAN IEEE 802.11 a/b/g
standard. The antenna provides good symmetric radiation patterns and high gain. The

antenna is compact and provides good performance and can be used in USB dongle for
WLAN applications.
A. Ismahayati et al. in [25] presents the design of Koch fractal antenna and monopole
antenna. By using fractal geometry a compact size and multiband behavior can be
obtained. Various parameters such as gain, bandwidth, reflection coefficient and radiation
pattern of monopole antenna and Koch fractal antenna are discussed. The size and
dimensions of the two antennas are kept same. The results show that Koch fractal antenna
is better than planar monopole as it covers more number of resonant frequencies,
provides larger bandwidth and is compact in size. The Koch fractal antenna operates at
three frequencies i.e., 7 GHz, 2.4GHz and 5.8GHz while planar monopole antenna
resonates at a single frequency, covering a bandwidth of 360-368 MHz. Therefore it is
seen that as the number of iterations increases in fractal design, more frequencies are
covered. Moreover size of the Koch fractal antenna reduces up to 20% when compared to
planar monopole antenna.
Yogesh Kumar Choukiker et al. in [26] designed a wideband fractal antenna with
combination of two fractal geometries. The wideband mechanism is achieved by studying
the behavior of current on the patch. The antenna is realized using cantor and Koch
fractal geometries and covers a bandwidth of 1.64GHz- 3.5 GHz. The dimension of the
antenna is 66mm × 25mm and is fed using microstrip line with a matching of 50Ω. A
gain of 2.5 dBi- 6 dBi can be observed at a wideband frequency range with
omnidirectional radiation patterns. The antenna can be used for many wireless
applications.
Hitesh Dholakiya et al. in [27] presented a single slot on the patch of the microstrip patch
antenna to enhance the bandwidth of the antenna. The antenna provides 3.5 times higher
bandwidth than conventional microstrip patch antenna. The proposed antenna covers a
frequency range of 2 to 6 GHz and obtains gain of 4dB. The size of the antenna is 75mm
× 75mm.The dimensions of the slot on the patch of the antenna is 30mm × 30mm. The

slot on the patch is iterated three times and each consecutive iteration increases the
bandwidth of the antenna. The antenna can be used for many applications.
D. Kumar et al. in [28] designed miniature fractal antenna for wireless applications. In
this design copper is used as an antenna material while FR4 is used as a substrate. The
dimension of the antenna is 36mm × 20mm × 1.6mm.The proposed antenna operates at
two frequencies i.e., 180MHz and 200MHz. It is seen that the radiation pattern of the
antenna is mainly directional radiating large amount of energy in upward direction. The
VSWR values of 1.19, 1.2, 1.26 and 1.84 are well matched with impedance values of
55Ω, 57 Ω, 36 Ω and 43 Ω respectively. Also backward radiation is low because of the
presence of separate ground plane. Radiations can be achieved in C, J and X band
regions.
Dilara Khatun et al. in [29] designed a multiband fractal square Koch antenna for
UHF/SHF application. The antenna operates 496MHz and 1430MHz after first iteration
and 460MHZ, 1248MHz, 1926MHz and 4390MHz after second iteration. The feed of the
antenna is located at the origin. The proposed antenna provides a gain of 4.9dB after first
iteration and 8dB after second iteration. It is seen that as the number of iterations
increases, operating bands also increases since the first iteration provided two frequency
bands while second iteration provided four frequency bands. Therefore the antenna can
be operated for UHF/SHF applications because of its multiband behavior.
Trushit Upadhyaya et al. in [30] designed a square patch fractal antenna to obtain
multiband behavior of patch resonator antenna. The proposed antenna operates at 2.7-
2.9GHz for aeronautical navigation and 9.0-9.3GHz for Maritime radio navigation. In
this modified conventional Koch geometry is used to design the antenna. The square
patch is iterated consecutively three times. The dimension of the antenna is 70mm ×
70mm × 3.2mm. A gain of about 8.53dB with good radiation pattern can be observed.
The antenna provides good return loss over targeted frequencies. The proposed antenna
can be used for various military and commercial applications.

Dr. S. Arivazhagan et al. in [31] designed a triangular fractal patch antenna with slit for
Indian Regional Navigational Satellite System (IRNSS) and GPS Aided and Geo
Augmented Navigation (GAGAN) applications. These systems are based on satellites and
are designed to provide support over Asian- Pacific regions. The proposed antenna
operates at 1175 MHz, 1575.2 MHz and 2492.08 MHz. Sierpinski Gasket fractal
geometry is used to design this antenna. The directivity of the antenna is 6.29723dB
while the gain is equal to 5.052dB. The antenna shows good radiation properties and
supports multiple bands. The designed antenna can be used for military applications.
S. Banu et al. in [32] designed a fractal microstrip patch antenna for Wireless Power
Transmission (WPT) systems. The patch of the microstrip antenna is iterated up to 3rd
level. The proposed antenna operates at frequency range of 1 to 5 GHz covering
1.86/2.29/3.02/4.50 GHz. The dimensions of the antenna are 54.36mm × 46.72mm. The
directivity of the antenna is 7.48 dB while gain oscillates from 2.98 to 3.01 dB. The
antenna operates at multiple frequencies and hence can be used in Wireless Power
Transmission (WPT) systems in Solar Power Satellites. The antenna operates at S-band
and C- band and has small size and light weight. Therefore authors concluded that fractal
antennas can be used to replace conventional patch antennas due to their size reduction
property.
Raj Kumar et al. in [33] designed a compact fractal monopole antenna for Ultra
Wideband (UWB) applications. The dimension of the proposed antenna is 40mm ×
40mm. The antenna operates at a bandwidth of 8.54 GHz covering frequencies from
2.8GHz to 11.4 GHz. The antenna is designed on FR4 substrate. It is observed that the
antenna is Omni-directional in H-plane and bidirectional in E-plane. The antenna
provides good return loss over targeted frequencies with peak gain of around 5dB. The
proposed antenna can be easily integrated with MMIC devices and can be useful for
navigational applications such as radar and fourth generation wireless communication
applications.

N.H.M. Sukaimi et al. in [34] designed a multilayer fractal patch antenna using Low
Temperature Co-Fired Ceramic (LTCC) Technology. In this design a Minkowski fractal
design has been used. The proposed antenna design eight layers of substrate are used.
The Ferro A6S with dielectric constant 5.9 is used as a substrate with thickness 0.096mm.
The proposed antenna covers a bandwidth from 2.33 MHz to 16.1 MHz. The dimension
of the ground plane of the proposed antenna is 35 × 25 mm2
while total thickness is
0.8mm. A gain of 10.02 dB is provided by the proposed antenna. It is observed that the
better simulation results are obtained using fractal patch antennas when compared with
convention patch antennas.
Sundaravel Elumalai Muthumani et al. in [35] designed a compact slot loaded fractal
patch antenna that provides bidirectional radiation properties. In this design Koch fractal
design has been used. Slots are introduced in the middle and corner edges of the radiating
patch to reduce the size of the antenna. The antenna resonates at 1.53 GHz and 1.27 GHz.
The antenna shows bidirectional and good radiation properties in co-polarized H-plane
and E-plane. The size of the antenna is reduced 60 % of the conventional patch antennas.
The proposed antenna can be used in handheld devices such as mobile phones.
Yuming Nie et al. in [36] designed a compact triband fractal Planar Inverted F Antenna
(PIFA) for mobile handset applications. The proposed antenna resonates at GSM (0.89-
0.96GHz), DCS (1.71 GHz- 1.88GHz) and WLAN (2.445 GHz- 2.455GHz) frequency
bands. The dimensions of the antenna are 41mm × 21mm × 1.55mm and consuming a
volume of nearly 1.51 cm3
. Because of very compact size, the antenna can be used inside
commercial mobile handsets. The reflection co-efficient of the proposed antenna is – 6dB
in GSM and DCS bands and -10dB in WLAN. It has been observed that the antenna
provides good radiation properties and return loss for all the operating bands.
T. Rama Rao et al. in [37] designed a fractal patch antenna for UWB wireless
communications. A new fractal design is proposed by the authors to design the antenna.
In this two circles are removed with center on the main patch. After this, an arc is
removed from the main patch. The same process is repeated four times. The dimensions

of the proposed antenna are 34mm ×32mm× 1.6mm. The radiation pattern of the antenna
is nearly omnidirectional with gain of 4.83dB. The antenna operates at a bandwidth of
7.90 GHz covering range of frequencies from 3.24GHz to 11.14GHz with an efficiency
of 93.55%. The antenna is quiet suitable for Ultra Wideband wireless communication
systems. Moreover the proposed antenna is small in size, low cost and is easy to
fabricate.
Sayantan Dhar et al. in [38] designed a dielectric resonator antenna that operates at
multiple frequencies. The antenna is designed using Minkowski fractal geometry to
reduce the size of the antenna and to generate multiple frequency bands. The dielectric
load improves the impedance bandwidth as well as gain of the antenna. The proposed
antenna operates at GSM (890-960 MHz), PCS (1850-1990 MHz), IEEE 802.11 b/g/n
(2.4-2.485 GHz), WiMAX (3.4-3.6 GHz) and IEEE 802.11 a/h/j/n (5.15- 5.85 GHz). The
dimension of the antenna is 100mm × 100mm × 1.6mm. The antenna provides a gain of
1.1-3.1dBi over various frequency bands. The antenna provides good return loss over
targeted frequencies.
Malathi Kanagasabai et al. in [39] designed a circularly polarized broadband antenna
using fractal geometry to achieve broad VSWR bandwidth and Axial Ratio bandwidth
(ARBW). The proposed antenna operates at 1.47 GHz- 1.83 GHz and 1.47GHz – 1.83
GHz. The dimension of the antenna is 65mm × 65mm × 1.6mm. The antenna provides a
gain of 6.6dB at 1.775GHz. A reflector at half wave distance from the radiator has been
installed to make the antenna bidirectional. The antenna provides good return loss over
targeted frequencies and an efficiency of 76% to 94% in the operating band.
V. Dinesh et al. in [40] designed a rectangular carpet fractal antenna for various wireless
applications. The dimension of the patch of the proposed antenna is 100mm × 100mm
and resonates at two frequencies i.e., 3.6GHz and 7GHz. The antenna is designed using
Sierpinski gasket carpet fractal geometry and is iterated up to 3 iterations. The antenna is
designed on FR-4 substrate with thickness of 1.6mm. The proposed antenna provides a
gain of 3.9711 dB. The antenna provides good return loss over targeted frequencies.

V. Dhana Raj et al. in [41] designed microstrip apollonian gasket fractal antenna for
multiband wireless applications. The proposed antenna operates in L-band and C-band to
X-band. The antenna has various advantages in terms of size, volume and design when
compared to other conventional antennas. The maximum gain of the antenna is 3.61dB.
The proposed antenna shows a maximum return loss of -28.97dB and VSWR of 1.09 at
8.16 GHz. The antenna can be used for vehicular Radar, PCS, imaging systems and GPS.
Shrivishal Tripathi et al. in [42] designed a compact octagonal shaped fractal antenna for
Ultra Wideband (UWB) Multiple Input Multiple Output (MIMO) applications. The
antenna is designed using Koch fractal geometry. For good isolation fractal monopoles
are placed orthogonal to each other. The dimension of the antenna is 45mm × 45mm and
shows quasi omnidirectional radiation pattern. The proposed antenna shows bandwidth
from 2- 10.6 GHz and isolation better than 17dB can be seen over entire UWB range. The
antenna shows good pulse preserving capability and hence can be used for various
wireless applications.
Tanmoy Sarkar et al. in [43] designed a microstrip patch antenna using different fractal
slot structures for bandwidth enhancement. The proposed antenna operates at 3.20 GHz,
3.37 GHz and 4.26 GHz. A gain of 4.5 dB to 5.3 dB can be achieved for the impedance
bandwidth from 3.20 GHz to 4.26 GHz. It is observed that the bandwidth of the antenna
improves by introducing fractal geometry when compared to conventional antennas.
Apollonian shaped fractal slot achieves maximum percentage of bandwidth. Moreover
gain of the antenna also improves with the introduction of fractal geometries.
3.2 Inferences Drawn
As it is clear from the literature survey of Microstrip Patch antenna and various Fractal
geometries that an antenna is required that is small in size, light in weight, operates at
multiple frequencies, consumes low power and provides high reliability. Fractal
geometries used with microstrip patch antenna reduces the size of antenna and also
enhances multiband properties by increasing the number of fractal iterations.

Today’s communication requires an antenna that provides higher gain, wider bandwidth,
supports multiple frequencies and is compact in size so that it consumes less space.
Therefore variety of approaches need to developed in order to get the desirable features
of antenna. The new approaches should be able to corporate with the existing technology.
A smaller antenna that supports multiple frequencies is the need for the aerospace
navigation applications.
Microstrip Patch Antenna with Fractal designs is used for aerospace navigation
applications. Microstrip patch antenna alone cannot provide multiband properties and in
order to get multiband properties patch antenna is coupled with fractal geometries. In
fractal antennas coupling between sharp angles produce different current paths achieving
multiband operations. Also by increasing the number of fractal iterations, perimeter of
patch increases and effective area decreases and hence size of the antenna can be
reduced. Antennas used in aerospace navigation should also exhibit Omni directional
characteristics in order to communicate with the air traffic. A microstrip patch antenna
with fractal geometries provide multiband and omni directional properties and hence can
be used for aerospace navigation.
Fractal Microstrip Patch Antenna is preferred over other conventional antennas because it
provides low profile planar configuration, has small size, supports multiband and
wideband operations and provides better input impedance. These features make fractal
antennas unique from other antennas and make them suitable for using with navigation
applications.

CHAPTER 4
PROPOSED RESEARCH WORK
4.1 Problem Definition
The latest development in aerospace navigation is to design a mechanically robust
antenna that has the capability of operating at multiple frequencies. The problem of
covering maximum navigational frequencies is the need of today and can be achieved by
using fractal designs [44]. A fractal design not only covers maximum frequencies but also
reduces the size of the antenna and can be used in places where space is a major issue.
Therefore the aim of the thesis is to design a fractal microstrip patch antenna that has
desired multiband resonance, compact profile and exhibits omni directional
characteristics.
4.2 Objectives
In this thesis, a mechanically robust and low profile antenna is designed to operate at
various frequency bands. The main objectives of the thesis work are:
• To study the recent progress and trends towards fractal microstrip patch antenna.
• To design a small microstrip patch antenna using fractal geometries.
• To design an antenna that it covers maximum navigation frequencies.
• To reduce the size of the antenna.
• To improve the gain of the antenna.
• To design an Omni directional antenna to obtain good radiation pattern.
Therefore microstrip patch antenna using various fractal geometries is designed and
optimized that has compact structure and supports multiple frequency bands mainly
7.5GHz, 9.60GHz, 12.15GHz, 13.90 GHz, 15.30 GHz and16.30 GHz.

4.3 Scope of Work
In this work, a conventional Koch fractal antenna with slots on the ground plane is
designed. The fractal designs covers maximum number of frequency bands and also
reduces the size of the antenna. The slots are well positioned and are used to cover the
desire frequency bands.
4.4 Methodology of Proposed Research Work
4.4.1 Design Methodology
The simulation of the antenna is carried out using High Frequency Structure Simulator
(HFSS) software. High Frequency Structure Simulator (HFSS) is an industry standard
simulation tool. It has powerful drawing capabilities to simply the antenna design. It is
seen that after simulation the antenna provides desired resonant frequencies that have
good operating bandwidth. Designing a multiband antenna using fractal geometries is a
complicated task because slight changes in different parameters can affect resonant
frequencies or return loss. The main design methodology is shown in figure 4.1.
Figure 4.1 Flow graph of Design Methodology of Proposed Research Work
Selection of
Design
parameters
Modeling
of
Multiband
Antenna
structure.
Optimizing
Design
Parameters
Compariso
n & Result
Validation

4.4.2 Selection of Design Parameters
The aim of this thesis work is to design an antenna that is compact in size and supports
multiple frequency bands. Moreover this antenna must be able to operate in various
frequency bands such as 7.5GHz, 9.60GHz, 12.15GHz, 13.90 GHz, 15.30 GHz and16.30
GHz. As a result various antennas were studied and their behavior and characteristics
were observed. Among these antennas Microstrip Patch Antenna (MSA) with fractal
geometry is considered as the most promising candidate. Therefore various fractal
geometries are studied and basics are learned to develop a multi-band structure.
There are many fractal geometries to design multi-band antenna. These geometries result
in dual band and tri-band operations. It is also observed that the overall sizes of the
antenna also reduces by using these designs and hence are suitable for device where less
space is required. From all the above characteristics of fractal patch antenna it is
observed that it is highly suitable for small and compact devices where space is a major
issue.
4.4.3 Selected Geometry
The geometry of the antenna is simple and robust that is commonly used in various
navigation applications. In this design FR4 is used as dielectric material with dielectric
constant, ɛr = 4.4; loss tangent, δ = 0.02 and height of substrate, h = 1.6mm. To feed the
antenna co-axial cable is used from the backside of the PCB where the ground plane lies.
4.5 Design of Fractal Microstrip Patch Antenna
In this section various levels of iterations of fractal designs will be discussed along with
proposed multiband fractal antenna with slots on the ground plane. To understand the
concept of microstrip patch antenna with conventional Koch fractal geometry, a basic
design is analyzed first.
4.5.1 A Simple Microstrip Patch Antenna
Before designing a multi-band fractal patch antenna, various designing process of simple
microstrip patch antenna and its characteristics will be discussed. By designing simple
patch antenna, various characteristics, concepts and other factors that determine the

performance of patch antenna are studied in detailed manner. The basic dimensions of
Microstrip Patch Antenna are derived using following equation.
Lp + Wp = λ/2 (4.1)
The resultant dimensions of Microstrip Patch Antenna are:
Lp = 45mm
Wp = 45mm
Figure 4.2 Microstrip Patch Antenna (a) Top View (b) 3D View in HFSS
Table 4.1 Detailed Dimensions of Proposed Microstrip Patch Antenna
Parameter Value (mm)
Lg 45
Wg 45
Lp 40
Wp 40
Ls 45
Ws 45
h 1.6

The proposed antenna consists of a ground plane, substrate and a radiating patch as
shown in figure 4.2 (a) and (b). The total volume occupied by the antenna is
approximately 3240mm3
. In this geometry the antenna structure resonates at 3.4 GHz, 7
GHz and 9 GHz. Although the antenna shows multiband behavior but these frequencies
are not desirable for aerospace navigation. In order to get desired frequencies, Koch
fractal design is deployed on patch antenna and its various effects are discussed in the
next section.
4.5.2 A Multiband Microstrip Patch Antenna with Koch Fractal Geometry
The structure of the proposed microstrip patch antenna with conventional Koch fractal
geometry and its three iteration levels is shown in figure 4.3 (a), (b), (c). The proposed
fractal antenna consists of a radiating patch, ground plane and co-axial feed. By using
fractal geometries the size of the antenna can be reduced while it still maintains its
multiband behavior.
The fractal geometry can be changed mainly by two factors: the iteration number and
iteration factor. The construction law of geometry is depicted by the iteration factor and
the number of iteration processes is represented by the iteration number. Here ¼ factors
are taken. Let us assume that the dimensions of the patch are equal to parameter A, where
A = 40. Various design steps of fractal antenna are explained below.
 Step 0: In 0th
iteration, the shape of the patch is square with an area A2 and perimeter
4A.
 Step 1: In 1st
iteration four squares with dimensions of A/4 are cut out from the
middle of the sides of the main square as shown in figure 4.3 (a). Hence Area =
0.75A2
and Perimeter = 6A.
 Step 2: In 2nd
iteration, the so formed four edges are taken as individual squares and
again four squares with dimensions 3A/32 are cut out of them as shown in figure 4.3
(b). Hence Area = 0.60 A2
and Perimeter = 9A.
 Step 3: In 3rd
iteration, the three small edges are taken as individual squares and again
the above steps are repeated and squares of dimensions 9A/256 are cut out from these
edges as shown in figure 4.3 (c). Hence Area = 0.36 A2
and Perimeter = 15.75 A.

Figure 4.3 3D View in HFSS (a) First iteration (b) Second iteration (c) Third iteration
The dimensions of the ground plane of the antenna are 45×45×1.6 mm3
and that of a
radiating patch are 40×40 mm2
. The 3D view in HFSS of the proposed antenna is shown
in figure 4.4. All the iterations are the modification of conventional Koch geometry.
Figure 4.4 3D View of fractal microstrip patch antenna in HFSS
The main objective of the thesis work is to design a compact, robust and multiband
antenna that covers maximum number of navigation frequencies and can be used in
devices where less space is available. Therefore the dimension of the antenna is 45mm ×
45mm × 1.6mm. With these dimensions the antenna resonates at 7.50 GHz, 11.5 GHz,

13.5 GHz, 15.5 GHz and 16.5 GHz with good bandwidth to serve for various navigation
applications
4.5.3 A Multiband Fractal Patch Antenna with Four Slots on the Ground Plane
The structure of the proposed fractal antenna with different slots on the ground plane is
shown in figure 4.5. Modifying the ground plane results in enhancement of operational
bandwidth and coverage of other navigation frequencies. The dimensions of the ground
plane of the proposed antenna are 45mm × 45mm × 1.6mm and that of radiating patch are
40mm × 40mm. The slots placed on the ground plane results in obtaining certain
navigational frequencies that a simple fractal patch antenna was not able to cover.
Moreover these slots also results in the improvement of operation bandwidth and
simplified the design of PCB.
Figure 4.5 Multiband Fractal Patch Antenna with Slotted Ground Plane (a) Bottom View (b) 3D view
Figure 4.6 shows the detailed dimensions of proposed antenna with two rectangular and
two circular slots on the ground plane. All the four slots are placed close to the edges of
the ground plane of the antenna. The location of feed is selected after observations and
optimization so that the antenna resonates at 2.6 GHz and 9.4 GHz.
The dimensions and the position of the four slots are so selected so as to achieve
maximum operating bandwidth at each resonating frequencies. Also a wideband of 7
GHz is obtained after introduction of slots on the ground plane. Values of dimensions are
given in table 4.3. The proposed antenna supports several frequency bands. The main
objective of the research work is to design a small, low profile multiband antenna for

aerospace navigation. The size of the antenna is very compact and can be used in places
where space is a major issue. The navigational bands covered by proposed antenna are
HF communication ( 2.6 GHz), NAVAID ( 7.5 GHz), LLWAS, RMM, LDRCL ( 9.4
GHz), Surveillance RADAR, GPS, GLONASS L1, Satellite Based Navigation, fixed
links, Military RADAR (12.6 GHz – 18.6 GHz).
Figure 4.6 Detailed Dimensions of Proposed Antenna in HFSS
Table 4.2 Detailed Dimensions of Proposed Multiband Fractal Antenna
Parameter Value (mm)
Lg 45
Wg 45
Lp 40
Wp 40
Ls 45
Ws 45
R1 03
L1 10
L2 10
h 1.6

CHAPTER 5
SIMULATED AND MEASURED RESULTS VALIDATION
5.1 Introduction
All the results presented in this chapter are produced by the simulation software called
High Frequency Structural Simulator (HFSS). High Frequency Structure Simulator
(HFSS) is an industry standard simulation tool. It has powerful drawing capabilities to
simply the antenna design. In this chapter, the various results such as radiation patterns,
3-D Gain plots, return loss and VSWR plots are discussed.
5.2 Simulated Results of Microstrip Patch Antenna
The first step is designing and simulation of microstrip patch antenna using HFSS
software. The basic microstrip patch antenna resonates at only two frequencies and a gain
of 3dBi is observed.
5.2.1 Return Loss Characteristics
The following plot in figure 5.1 shows the return loss of basic microstrip patch antenna
design.
Return Coefficient v/s Frequency
Figure 5.1 Simulated Return of basic Microstrip Patch Antenna

From the plot shown in figure 5.1, it can be observed that the antenna resonates at 3.4
GHz, 7GHz, 9 GHz, 12.6 GHz and 14.6 GHz. The return loss obtained is -11.91, -18.66, -
11.33, -11.51, and -14.24 respectively.
The simulated 3D radiation pattern at 2.5 GHz can be obtained from the simulation
results using High Frequency Structural Simulator (HFSS) software as shown in figure
5.2. It can be seen from the plot that antenna provides almost omni directional radiation
and can be used for navigation applications.
Figure 5.2 3D Radiation Pattern of Microstrip Patch Antenna
5.2.3 Gain
The gain describes the efficiency of the efficiency of the antenna. The net gain of the
antenna obtained after simulating microstrip patch antenna is shown in figure 5.3. A gain
of 2.69 dB is observed at 7GHz. The gain obtained has a moderate value and is observed
to be good according to the performance of the antenna.

Figure 5.3 Simulated 3-D Gain Plot of Microstrip Patch Antenna
5.2.4 Voltage Standing Wave Ratio (VSWR)
The value of Voltage Standing Wave Ratio (VSWR) should be 3:1 or less than 3dB at
resonate frequency. This value is advantageous for most of the applications of wireless
communication. Figure 5.4 shows the simulated results of VSWR for the frequency range
from 1 GHz to 20 GHz.
VSWR v/s Frequency
Figure 5.4 Simulated VSWR plot of microstrip patch antenna

5.3 Simulated Results of Fractal Patch Antenna
After designing and analyzing basic microstrip patch antenna, the following step is to
design fractal microstrip patch antenna using modified conventional Koch geometry.
Proposed antenna covers multiple frequencies and covers a wideband of 7 GHz.
5.3.1 Return Loss Characteristics
The following plot in figure 5.5 shows the return loss for fractal patch antenna.
Return Coefficient v/s Frequency
Figure 5.5 Simulated Return Loss of Fractal Patch Antenna
From the plot shown in figure 7.5, it can be observed that the proposed antenna resonates
at 2.6 GHz, 4.6 GHz, 7 GHz, 8.6 GHz, 11 GHz, 13.4 GHz , 14.2 GHz, 15.4GHz, 16.6
GHz and 18.2 GHz with return loss -8.27, -6.95, -10.59, -5.87, -13.59, -23.93, -13.86, -

28.69, -20.78 and -9.92 respectively. The navigational bands covered by the antenna are
HF Communication (2.1-2.8 GHz), NAVAID (7.5 GHz), Air Router Surveillance Radar,
GPS, GLONASS L1 (12.15- 13.9 GHz), Sattelite Based Communication (15.45- 15.59
GHz), Satellite Navigation (15.59- 16.10 GHz) and Fixed Links and LDRCL (17.10 –
18.50GHz).
The simulated 3 D radiation pattern is obtained from the simulated results and is shown
in figure 5.6. It can be observed from the results that the antenna is almost omni
directional and hence can be used for aerospace navigation supporting multiple standards.
Figure 5.6 Simulated 3D radiation pattern of Fractal Patch Antenna
5.3.3 Gain
The gain determines the efficiency of the antenna and is important figure of merit of
antenna. The overall gain of the proposed antenna after simulation is shown in figure 5.7.
A peak gain of 7.36 dB is obtained at frequency 13.4 GHz.

Figure 5.7 Simulated 3D Gain plot of Fractal Patch Antenna
communication. Figure 5.8 shows the simulated results of VSWR for the frequency
sweep from 1 GHz to 20 GHz. The value of VSWR is less than 3 at all the resonating
frequencies.
VSWR v/s Frequency
Figure 5.8 Simulated VSWR plot of fractal patch antenna

5.4 Simulated Results of Multiband Fractal Patch Antenna with Slots on
the Ground Plane
The antenna designed in the previous section was a wideband antenna with Koch fractal
geometry on its patch. It can be observed that the fractal geometries not only reduces the
size of the patch and allows the other components to integrate on the same substrate but
also provide multiple frequencies with good return loss peaks. It can be seen that various
navigational frequencies were not covered by the fractal patch antenna. Therefore, in
order to cover those frequencies we extend the designing of the antenna by introducing
various slots on the ground plane. These slots provided good resonance along with good
gain and impedance bandwidth. Thus, introduction of slots on the ground plane further
improves the performance of the antenna.
5.4.1 Return loss characteristics
The plot shown in figure 5.9 shows the return loss of the proposed antenna. The proposed
antenna covers multiple frequencies with wideband of 7 GHz.
Return Coefficient vs. Frequency
Figure 5.9 Simulated Return Loss of Multiband Fractal Antenna

From the plot shown in above figure, it can be observed that the proposed antenna
resonates at 2.6 GHz, 7GHz, 9.4 GHz, 11.4 GHz, 13.4 GHz, 17 GHz, 18.2 GHz
and19.4GHz with return loss of -9.15, -10.49, -22.60, -23.32, -43.76, -13.13, -11.38 and -
12.11 respectively. The navigational bands covered by the proposed antenna are HF
communication (2.1- 2.8 GHz), NAVAID (7.50 GHz), RMM, LLWAS, LDRCL (9.32-
9.4GHz), Military RADAR (9-9.2 GHz), Air route Surveillance RADAR; GPS (12.15-
13.9 GHz), Microwave Link (14.4-15.35 GHz), Satellite Based Communication to
aircraft ( 15.45- 15.59 GHz), GPS, RADAR (15.7-16.2 GHz) GLONASS L1 (15.59-
16.10GHz), Satellite based communication from aircraft (16.45-16.60 GHz) and LDRCL
(17.10-18.50 GHz).
The simulated 3 D radiation pattern is obtained from the simulated results and is shown
in figure 5.10. It can be observed from the results that the antenna is almost omni
directional and hence can be used for aerospace navigation supporting multiple standards.
Figure 5.10 Simulated 3D radiation pattern of Multiband Fractal Antenna

5.4.3 Gain
The gain determines the efficiency of the antenna and is important figure of merit of
antenna. The overall gain of the proposed antenna after simulation is shown in figure
5.11. A peak gain of 7.95 dB is obtained at frequency 11.4 GHz.
Figure 5.11 Simulated 3-D Gain Plot of Multiband Fractal Antenna
communication. Figure 5.12 shows the simulated results of VSWR for the frequency
sweep from 1 GHz to 20 GHz. The value of VSWR is less than 3 at all the resonating
frequencies. As seen VSWR at 7GHz, 9.4 GHz, 11.4 GHz, 13.4 GHz, 17 GHz, 18.2 GHz
and19.4GHz is 2.9dB, 1.25dB, 1.9dB, 0.14dB, 3dB and 3dB respectively.

VSWR vs. Frequency
Figure 5.12 Simulated VSWR plot of Multiband Fractal Antenna
5.5 VALIDATION OF SIMULATED RESULTS
Table 5.1 Comparison between Proposed Multiband Fractal Antenna with the Design
Proposed in [30]
Antenna Design/
Parameters
Volume (mm3) Return Loss(dB) Frequency Bands
Covered
Design in [33] 15,680 3GHz: -22.20
7.49GHz: -18.70
9.68GHz: -30.96
11.2GHz: -15.82
HF Communication
(2.1- 2.8 GHz),
NAVAID(7.50
GHz), & Military
RADAR (9-9.2
GHz).
Proposed Design 3,240 2.6 GHz: -9.15 HF communication

7GHz: -10.49
9.4 GHz: -22.60
11.4 GHz: -23.32
13.4 GHz: -43.76
17 GHz: -13.13
18.2 GHz: -11.38
19.4GHz: -12.11
(2.1- 2.8 GHz),
NAVAID (7.50
GHz), RMM,
LLWAS, LDRCL
(9.32- 9.4GHz),
Military RADAR (9-
9.2 GHz), Air route
Surveillance
RADAR; GPS
(12.15- 13.9 GHz),
Microwave Link
(14.4-15.35 GHz),
Satellite Based
Communication to
aircraft ( 15.45-
15.59 GHz), GPS,
RADAR (15.7-16.2
GHz) GLONASS L1
(15.59- 16.10GHz),
Satellite based
communication from
aircraft (16.45-16.60
GHz) and LDRCL
(17.10-18.50 GHz).
It is clear from the data given in table 7.1 that the proposed multiband fractal antenna
covers more frequencies and there is an overall size reduction of 79.33% as compared to
proposed design in [30].
% Size Reduction = 100 –
3240
15680
× 100 = 79.33%

5.6 HARDWARE IMPLEMENTATION
5.6.1 Introduction
Hardware implementation can be defined as designing an electronic circuit or a physical
device as modeled by a computer program. In the previous section we have designed a
fractal patch antenna using High Frequency Structure Simulator (HFSS) software. High
Frequency Structure Simulator (HFSS) is an industry standard simulation tool. It has
powerful drawing capabilities to simply the antenna design. It is seen that after simulation
the antenna provides desired resonant frequencies that have good operating bandwidth,
radiation patterns and gain.
Hardware is an essential part of wireless communication systems. Therefore in this
section various techniques adopted to design a hardware prototype of simulated antenna
and its various results will be discussed.
5.7 Fabrication Techniques
Various techniques are available to fabricate a fractal microstrip patch antenna.
Fabrication is a very complex and time consuming task where problems are faced and
dealt constantly. Therefore a simple and low cost method that has been used to design
this fractal patch antenna is discussed. Following are the various design steps adopted to
fabricate fractal microstrip patch antenna.
Step 1: The first step to fabricate an antenna is to cut out various shapes (such as ground
plane, substrate and patch) required in antenna fabrication of exact dimensions using
Vernier Caliper. The Vernier Caliper is an instrument that can be used to calculate
internal and external distances accurately.
Step 2: According to the design, mask of fractal geometry and slots on the ground plane
are designed using Coral Draw for the fabrication of fractal patch antenna. Coral Draw is
graphic designing software that is used for producing blueprints for fractal designs, slots,
computer chips etc. The mask layout so obtained is shown in figure 5.13.

Figure 5.13 Mask generated using Coral Draw (a) Fractal geometry (b) Ground slots
Step 3: In order to transfer the mask image on copper plated PCB board screen printing
lithography technique is used. In screen printing lithography an ink is forced on the metal
surface through an allready prepared screen to create a pattern.
Before coating the positive photo resist (PPR) , PCB sheets are cleaned using organic
solvent and dried with hot air gun. The PCB is pre-heated in an oven at 90 degree celcius
in order to remove impurities. Now the masks that was prepared earlier is now built onto
both the sides of the PCB .
After the mask is transferred onto the PCB, it is again placed in oven at a temperature of
130 degree celcius so that it becomes hard and rigid.
Figure 5.14 Screens Generated in Screen Printing technique (a) Antenna Ground Plane (b) Fractal
Geometry

Step 4: In order to remove unwanted parts, chemical etching is done. The exposed parts
are etched out using solution of ferric chloride (FeCl3). Then these parts are rinsed in
water and dried in air [45].
Step 5: The fabricated patch antenna is mounted accurately on predesigned mask of
copper sheet called the ground plane. The female connector is soldered at the predecided
feed location of PCB from the backside of the fabricated antenna. Hence the final
fabricated antenna is obtained through various steps. The final antenna so obtained is
shown in figure 5.15.
Figure 5.15 Final Fabricated antenna layout (a) Top View (b) Bottom View (c) Side view
5.8 Hardware Testing
The next and final step in hardware implementation is the testing of fabricated antenna
hardware. Network Analyzer measures the return loss of the fractal patch antenna. In this

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