STUDY ON IMPROVED RADIATION PERFORMANCE CHARACTERISTICS OF FRACTAL ANTENNA FOR WIRELESS APPLICATIONS

STUDY ON IMPROVED RADIATION PERFORMANCE CHARACTERISTICS OF FRACTAL ANTENNA FOR WIRELESS APPLICATIONS
DEPT. OF ECE, SDMIT UJIRE Page 1
CHAPTER 1
Introduction
The term “wireless” is commonly used in the telecommunications industry to refer
to telecommunications systems (e.g., radio transmitters and receivers, remote controls,
computer networks, network terminals, etc.) which use some form of energy (e.g. Radio
frequency (RF), infrared light, laser light, visible light, acoustic energy, etc.) to transfer
information without the use of wires. Information is transferred in this manner over both
short and long distances. Applications may involve point-to-point communication, point-
to-multipoint communication, broadcasting, cellular networks and other wireless
networks.
Antenna is a very important component for the wireless communication systems
using radio frequency and microwaves. By definition, an antenna is a device used to
transform an RF signal, traveling on a conductor, into an electromagnetic wave in free
space. The IEEE Standard Definitions of Terms for Antennas (IEEE Standard 145-1983)
defines the antenna or aerial as “a means for radiating or receiving radio waves”. In other
words it is a transitional structure between free space and a guiding device that is made to
efficiently radiate and receive radiated electromagnetic waves. Antennas are commonly
used in radio, television broadcasting, cell phones, radar and other systems involving the
use of electromagnetic waves. Antennas demonstrate a property known as reciprocity,
which means that an antenna will maintain the same characteristics regardless if it is
transmitting or receiving.
With Advance of wireless communication systems and increasing importance of
other wireless applications, wide band and low profile antennas are in great demand for
both commercial and military applications. For antenna design that possess the following
highly desirable attributes: i) Compact size ii) Low profile iii) Conformal iv) Multiband
and broadband, there are a variety of approaches that have been developed over years,
which can be utilized to achieve one or more of these design objectives. The use of fractal
geometry is a solution to the design of multiband antennas. In recent years several fractal
geometries have been introduced for antenna applications with varying degrees of success
in improving antenna characteristics. Fractal represents a class of geometry with very
unique properties that are useful to antenna designers. The efficient packing of this
electrically large element constitutes a miniaturization technique to produce small-size
elements suitable for installation in portable telecommunication devices. The space filling

property, when applied to an antenna element, leads to an increase of electrical length.
The more convoluted and longer surface currents results in lowering the antenna resonant
frequency for a given overall extension of resonator. Therefore given a desired resonance
frequency, the physical size of the whole structure can be reduced. Method to improve the
antenna performance is by using the electromagnetic band gap (EBG) structure on
microstrip antenna. EBG structure are periodic lattices, which can provide effective and
flexible control over the propagation of the EM waves within a particular band. It has
been shown that this structure can lower input return loss and widen the impedance
bandwidth of microstrip antenna by suppressing the unwanted surface waves. The
inclusion of EBG in microstrip antenna design allows gain enhancement, enhanced
directivity, improved bandwidth and size miniaturization. Similarly, since microstrip
antennas are very versatile and are used, among other things, to synthesize a required
pattern that cannot be achieved with a single element. In addition, they are used to scan
the beam of an antenna system, increase the directivity, and perform various other
functions which would be difficult with any one single element. The elements can be fed
by a single line or by multiple lines in a feed network arrangement, so in this paper we
also used an array to develop the performance of this antenna.
1.1 Aim and Objectives
The aim of this project is to make a detailed study on the design and to study how
will the performance of Microstrip fractal antenna is improved with the introduction of
the two elemental array and EBG structure in the fractal antenna design using IE3D
software. In addition to this we also analyze the matching of practical and simulated
results.
1.2Organization of the report
 Antenna Basics
 Microstrip Patch Antenna
 Fractals
 Design Specifications
 Simulation and Results
 Conclusion and Future Scope

CHAPTER 2
Antenna theory
2.1 Introduction
Communications has become the key to momentous changes in the organization
of businesses and industries as they themselves adjust to the shift to an information
economy. Information is indeed the lifeblood of modern economies and antennas provide
mother earth a solution to a wireless communication system.
The radio antenna is an essential component in any radio system. An antenna is a
device that provides a means for radiating or receiving radio waves. In other words, it
provides a transition from guided waves on a transmission line to a “free space” wave
(and vice versa in the receiving case). Thus information can be transferred between
different locations without any intervening structure. Furthermore, antennas are required
in situations where it is impossible, impractical or uneconomical to provide guiding
structures between the transmitter and the receiver.
A guided wave traveling along a transmission line, which opens out as in figure
2.1, will radiate as free space wave. The guided wave is a plane wave while the free space
wave is a spherically expanding wave. Along the uniform part of the line, energy is
guided, as a plane wave with little loss, provided the spacing between the wires is a small
fraction of a wavelength. At the right, as the transmission line separation approaches a
wavelength or more, the wave tends to be radiated so that the opened-out line acts like an
antenna, which launched the free space wave. The currents on the transmission line flow
out on the transmission line and end there, but the fields associated with them keep on
going. To be more explicit, the region of transition between the guided wave and the free
space wave may be defined as an antenna.
In this vast and dynamic field, the antenna technology has been an indispensable
partner of the communication revolution. Many major advances that took place over the
years are now in common use. Despite numerous challenges, the antenna technology has
grown with a fast pace to harass the electromagnetic spectrum, which is one of the
greatest gifts of nature.

Figure 2.1 Antenna as a Transition Device
2.2 Antenna Properties
An antenna is an electrical conductor or system of conductors
 Transmitter – Radiates electromagnetic energy into space
 Receiver – Collects electromagnetic energy from space
The IEEE definition of an antenna as given by Stutzman and Thiele is, “That part of a
transmitting or receiving system that is designed to radiate or receive electromagnetic
waves”.
The performance of the antenna is determined by several factors called antenna
properties are defined in following sections.
2.2.1 Antenna Gain
Gain is a measure of the ability of the antenna to direct the input power into
radiation in a particular direction and is measured at the peak radiation intensity. Consider
the power density radiated by an isotropic antenna with input power P0 at a distance R
which is given by S = P0/4πR2. An isotropic antenna radiates equally in all directions, and
it’s radiated power density S is found by dividing the radiated power by the area of the

sphere 4πR2. An isotropic radiator is considered to be 100% efficient. The gain of an
actual antenna increases the power density in the direction of the peak radiation:
Equation-2.1
Gain is achieved by directing the radiation away from other parts of the radiation sphere.
In general, gain is defined as the gain-biased pattern of the antenna.
Equation-2.2
2.2.2 Antenna directivity
Directivity is a measure of the concentration of radiation in the direction of the
maximum.
Equation-2.3
Directivity and gain differ only by the efficiency, but directivity is easily estimated from
patterns. Gain—directivity times efficiency—must be measured. The average radiation
intensity can be found from a surface integral over theradiation sphere of the radiation
intensity divided by 4π, the area of the sphere in steradians:
Equation-2.4
This is the radiated power divided by the area of a unit sphere. The radiation intensity
U(θ,φ) separates into a sum of co- and cross-polarization components:
Equation-2.5
Both co- and cross-polarization directivities can be defined:
Equation-2.6

Directivity can also be defined for an arbitrarydirection D(θ,φ) as radiation
intensitydivided by the average radiation intensity, butwhen the coordinate angles are
notspecified, we calculate directivity at Umax.
2.2.3 Antenna Efficiency
The surface integral of the radiation intensity over the radiation sphere divided by
the input power P0 is a measure of the relative power radiated by the antenna, or the
antenna efficiency.
Equation-2.7
where Pr is the radiated power. Material losses in the antenna or reflected power due to
poor impedance match reduce the radiated power.
2.2.4 Input Impedance
The input impedance of an antenna is defined as “the impedance presented by an
antenna at its terminals or the ratio of the voltage to the current at the pair of terminals or
the ratio of the appropriate components of the electric to magnetic fields at a point”.
Hence the impedance of the antenna can be written as given below.
Equation-2.8
Where,Zin is the antenna impedance at the terminals
Rin is the antenna resistance at the terminals
Xin is the antenna reactance at the terminals
The imaginary part, Xin of the input impedance represents the power stored in the
near field of the antenna. The resistive part, Rin of the input impedance consists of two
components, the radiation resistance Rr and the loss resistance RL. The power associated
with the radiation resistance is the power actually radiated by the antenna, while the
power dissipated in the loss resistance is lost as heat in the antenna itself due to dielectric
or conducting losses.
2.2.5 Polarization
The polarization of an antenna is the polarization of the wave radiated from the
antenna. Areceiving antenna has to be in the same polarization as the transmitting antenna
otherwise it will not resonate. Polarization is a property of the electromagnetic wave; it

describes the magnitude and direction of the electric field vector as a function of time,
with other words “the orientation of the electric field for a given position in space”. A
simple strait wire has one polarization when mounted vertically, and different polarization
when mounted horizontally figure (2.2). Polarization can be classified as linear, circular,
and elliptical.
In linear polarization the antenna radiates power in the plane of propagation, only
one plane, the antenna is vertically linear polarized when the electric field is
perpendicular to the earth’s surface, and horizontally linear polarized when the electric
field is parallel to the earth’s surface. Circular polarization antenna radiates power in all
planes in the direction of propagation(vertical, horizontal, and between them). The plane
of propagation rotates in circle making one complete cycle in one period of wave.
Figure 2.2 - Polarization of electromagnetic wave
2.2.6 Return Loss
It is a parameter which indicates the amount of power that is “lost” to the load and
does not return as a reflection. Hence the RL is a parameter to indicate how well the
matching between the transmitter and antenna has taken place. Simply put it is the S11 of
an antenna. A graph of S11 of an antenna vs frequency is called its return loss curve. For
optimum working such a graph must show a dip at the operating frequency and have a
minimum dB value at this frequency. This parameter was found to be of crucial
importance to our project as we sought to adjust the antenna dimensions for a fixed
operating frequency (say 1.9 GHz). A simple RL curve is shown in figure 2.1.
Figure 2.3 – RL curve of an antenna

2.2.7 Radiation Pattern
The radiation pattern of an antenna is a plot of the far-field radiation properties of
an antenna as a function of the spatial co-ordinates which are specified by the elevation
angle (θ) and the azimuth angle (φ) . More specifically it is a plot of the power radiated
from an antenna per unit solid angle which is nothing but the radiation intensity. It can be
plotted as a 3D graph or as a 2D polar or Cartesian slice of this 3D graph. It is an
extremely parameter as it shows the antenna’s directivity as well as gain at various points
in space. It serves as the signature of an antenna and one look at it is often enough to
realize the antenna that produced it.Because this parameter was so important to our
software simulations we needed to understand it completely. A general 3D radiation
pattern is also shown in figure 2.5.
Figure 2.4 – 2D Polar Plot Figure 2.5 – 3D Radiation Pattern
(Yagi antenna) (Rectangular Patch)
2.2.8 Beamwidth
Beamwidth of an antenna is easily determined from its 2D radiation pattern and is
also a very important parameter. Beamwidth is the angular separation of the half-power
points of the radiated pattern. The way in which beamwidth is determined is shown in
figure 2.6.
Figure 2.6 – Determination of HPBW from radiation pattern

2.3 Types of Antennas
Antennas can be classified in several ways. One way is the frequency band of
operation. Others include physical structure and electrical/electromagnetic design. Most
simple, non-directional antennas are basic dipoles or monopoles. More complex,
directional antennas consist of arrays of elements, such as dipoles, or use one active and
several passive elements, as in the Yagi antenna. New antenna technologies are being
developed that allow an antenna to rapidly change its pattern in response to changes in
direction of arrival of the received signal. These antennas and the supporting technology
are called adaptive or “smart” antennas and may be used for the higher frequency bands
in the future. A few commonly used antennas are described in the following sections.
2.3.1 Dipoles and Monopoles
The vertical dipole or its electromagnetic equivalent, the monopole could be
considered one of the best antennas for LMR applications. It is omni directional (in
azimuth) and, if it is a half-wavelength long, has a gain of 1.64 (or G = 2.15 dBi) in the
horizontal plane. A center- fed, vertical dipole is illustrated in figure 2.7 (a). Although
this is a simple antenna, it can be difficult to mount on a mast or vehicle. The ideal
vertical monopole is illustrated in figure 2.7 (b). It is half a dipole placed in half space,
with a perfectly conducting, infinite surface at the boundary.
Figure 2.7 - The vertical dipole and its electromagnetic equivalent, the vertical
monopole
2.3.2 Corner Reflector
An antenna comprised of one or more dipole elements in front of a corner
reflector, called the corner-reflector antenna, is illustrated in figure 2.8.

Figure 2.8 - Corner-reflector antennas
2.3.3 Yagi Antenna
Another antenna design that uses passive elements is the Yagi antenna. This
antenna, illustrated in figure 2.9, is inexpensive and effective. It can be constructed with
one or more (usually one or two) reflector elements and one or more (usually two or
more) director elements. Figure 2.10 shows a Yagi antenna with one reflector, a folded-
dipole active element, and seven directors, mounted for horizontal polarization.
Figure 2.9 - The Yagi antenna — (a) three elements and (b) multiple elements
Figure 2.10 - A Typical Yagi antenna

CHAPTER 3
Microstrip patch antennas
A microstrip antenna consists of conducting patch on a ground plane separated by
dielectric substrate. This concept was undeveloped until the revolution in electronic
circuit miniaturization and large-scale integration in 1970. After that many authors have
described the radiation from the ground plane by a dielectric substrate for different
configurations. The early work of Munson on micro strip antennas for use as a low profile
flush mounted antennas on rockets and missiles showed that this was a practical concept
for use in many antenna system problems. Various mathematical models were developed
for this antenna and its applications were extended to many other fields. The number of
papers, articles published in the journals for the last ten years, on these antennas shows
the importance gained by them. The micro strip antennas are the present day antenna
designer’s choice.
Low dielectric constant substrates are generally preferred for maximum radiation.
The conducting patch can take any shape but rectangular and circular configurations are
the most commonly used configuration. Other configurations are complex to analyze and
require heavy numerical computations. A microstrip antenna is characterized by its
Length, Width, Input impedance, and Gain and radiation patterns. Various parameters of
the microstrip antenna and its design considerations were discussed in the subsequent
chapters. The length of the antenna is nearly half wavelength in the dielectric; it is a very
critical parameter, which governs the resonant frequency of the antenna. There are no
hard and fast rules to find the width of the patch.
3.1 Waves on Microstrip
The mechanisms of transmission and radiation in a microstrip can be understood
by considering a point current source (Hertz dipole) located on top of the grounded
dielectric substrate (fig. 3.1) This source radiates electromagnetic waves. Depending on
the direction toward which waves are transmitted, they fall within three distinct
categories, each of which exhibits different behaviors.
Figure 3.1- Hertz dipole on a microstrip substrate

3.1.1 Surface Waves
The waves transmitted slightly downward, having elevation angles θ between
π/2and π -arcsin (1/√εr), meet the ground plane, which reflects them, and then meet the
dielectric-to-air boundary, which also reflects them (total reflection condition). The
magnitude of the field amplitudes builds up for some particular incidence angles that
leads to the excitation of a discrete set of surface wave modes; which are similar to the
modes in metallic waveguide.
The fields remain mostly trapped within the dielectric, decaying exponentially
above the interface (fig 3.2). The vector α, pointing upward, indicates the direction of
largest attenuation. The wave propagates horizontally along β, with little absorption in
good quality dielectric. With two directions of α and β orthogonal to each other, the wave
is a non-uniform plane wave. Surface waves spread out in cylindrical fashion around the
excitation point, with field amplitudes decreasing with distance (r), say1/r, more slowly
than space waves. The same guiding mechanism provides propagation within optical
fibers.
Surface waves take up some part of the signal’s energy, which does not reach the
intended user. The signal’s amplitude is thus reduced, contributing to an apparent
attenuation or a decrease in antenna efficiency. Additionally, surface waves also
introduce spurious coupling between different circuit or antenna elements. This effect
severely degrades the performance of microstrip filters because the parasitic interaction
reduces the isolation in the stop bands.
In large periodic phased arrays, the effect of surface wave coupling becomes
particularly obnoxious, and the array can neither transmit nor receive when it is pointed at
some particular directions (blind spots). This is due to a resonance phenomenon, when the
surface waves excite in synchronism the Floquet modes of the periodic structure. Surface
waves reaching the outer boundaries of an open microstrip structure are reflected and
diffracted by the edges. The diffracted waves provide an additional contribution to
radiation, degrading the antenna pattern by raising the side lobe and the cross polarization
levels. Surface wave effects are mostly negative, for circuits and for antennas, so their
excitation should be suppressed if possible.
Figure 3.2 – Surface waves

3.1.2 Leaky Waves
Waves directed more sharply downward, with θ angles between π - arcsin (1/√εr)
and π, are also reflected by the ground plane but only partially by the dielectric-to-air
boundary. They progressively leak from the substrate into the air (Fig 3.3), hence their
name laky waves, and eventually contribute to radiation. The leaky waves are also non-
uniform plane waves for which the attenuation direction α points downward, which may
appear to be rather odd; the amplitude of the waves increases as one moves away from the
dielectric surface. This apparent paradox is easily understood by looking at the figure 3.3;
actually, the field amplitude increases as one move away from the substrate because the
wave radiates from a point where the signal amplitude is larger. Since the structure is
finite, this apparent divergent behavior can only exist locally, and the wave vanishes
abruptly as one crosses the trajectory of the first ray in the figure.
In more complex structures made with several layers of different dielectrics, leaky
waves can be used to increase the apparent antenna size and thus provide a larger gain.
This occurs for favorable stacking arrangements and at a particular frequency.
Conversely, leaky waves are not excited in some other multilayer structures.
Figure 3.3 – Leaky waves
3.1.3 Guided Waves
When realizing printed circuits, one locally adds a metal layer on top of the
substrate, which modifies the geometry, introducing an additional reflecting boundary.
Waves directed into the dielectric located under the upper conductor bounce back and
forth on the metal boundaries, which form a parallel plate waveguide. The waves in the
metallic guide can only exist for some particular values of the angle of incidence, forming
a discrete set of waveguide modes. The guided waves provide the normal operation of all
transmission lines and circuits, in which the electromagnetic fields are mostly
concentrated in the volume below the upper conductor. On the other hand, this buildup of
electromagnetic energy is not favorable for patch antennas, which behave like resonators
with a limited frequency bandwidth.

3.2 Patch antennas
Microstrip patch antennas are the most common form of printed antennas. They
are popular for their low profile, geometry and low cost.A microstrip device in its
simplest form is a layered structure with two parallel conductors separated by a thin
dielectric substrate. The lower conductor acts as a ground plane. The device becomes a
radiating microstrip antenna when the upper conductor is a patch with a length that is an
appreciable fraction of a wavelength (λ), approximately half a wavelength (λ / 2). In other
words, a microstrip patch antenna consists of a radiating patch on one side of a dielectric
substrate which has a ground plane on the other side as shown in Fig. 3.4.
Figure 3.4 - Typical microstrip patch antenna
The patch is generally made of conducting material such as copper or gold and can take
any possible shape. Some of the typical patch shapes are shown in Fig. 3.5.
Figure 3.5 - Different shapes and sizes of patch
The radiating patch and the feed lines are usually photo etched on the dielectric
substrate. Microstrip patch antennas radiate primarily because of the fringing fields
between the patch edge and the ground plane. Microstrip patch antennas have many
advantages when compared to conventional antennas. As such, they have found usage in
a wide variety of applications ranging from embedded antennas such as in a cellular

phone, pagers etc. to telemetry and communication antennas on missiles and in satellite
communications.
Some of their principal advantages are,
 Light weight and low volume
 Low profile planar configuration which can be easily made conformal to host
surface
 Low fabrication cost, hence can be manufactured in large quantities
 Supports both, linear as well as circular polarization
 Can be easily integrated with microwave integrated circuits (MICs)
 Capable of dual and triple frequency operations
 Mechanically robust when mounted on rigid surfaces
 In spite of the many advantages, these antennas also suffer from a number of
disadvantages.
Some of these disadvantages are,
 Narrow bandwidth
 Low efficiency
 Low gain
 Extraneous radiation from feeds and junctions
 Poor end fire radiator except tapered slot antennas
 Low power handling capacity
 Surface wave excitation.
3.3 Feed Techniques for Patch Antennas
Microstrip antennas are fed by a variety of methods that are broadly classified into
two main categories, namely, contacting and non-contacting. In the contacting method,
the RF power is fed directly to the radiating patch using a connecting element such as a
microstrip line. In the non-contacting method, electromagnetic field coupling is done to
transfer power between the microstrip line and the radiating patch.
The four most popular feed techniques used are the microstrip line, coaxial probe
(both contacting schemes), aperture coupling and proximity coupling (both non-
contacting schemes). These are discussed in subsequent sections.

3.3.1 Microstrip Line Feed
This type of feed technique excitation of the antenna would be by the Microstrip
line of the same substrate as the patch that is here can be considered as an extension to the
Microstrip line, and these both can be fabricated simultaneously. This conducting strip is
directly connected to the edge of the Micro strip patch. , as known the conducting strip is
smaller than that of the patch in width. This type of structure has actually an advantage of
feeding the directly done to the same substrate to yield a planar structure as said above.
The coupling between the Microstrip line and the patch is in the form of the edge or butt-
in coupling as shown in the figure. Or it is through a gap between them.
Figure 3.6 - A Type of Microstrip feed and the corresponding equivalent circuits,
Microstrip feed at a radiating edge
Figure 3.7 - Rectangular microstrip patch antenna
3.3.2 Coaxial Feed
The coaxial feed or probe feed is a very common contacting scheme of feeding
patch antennas. The configuration of a coaxial feed is shown in Fig.3.8. As seen from Fig.
3.8, the inner conductor of the coaxial connector extends through the dielectric and is

soldered to the radiating patch, while the outer conductor is connected to the ground
plane.
Figure 3.8 – coaxial feed
The main advantage of this type of feeding scheme is that the feed can be placed
at any desired location inside the patch in order to match with its input impedance. This
feed method is easy to fabricate and has low spurious radiation
As we are using only probe feed and linefeed techniques in our design, we do not
discuss further about other remaining methods of feeding here.
3.4 Methods of Analysis for Patch Antennas
The most popular models for analysis of microstrip patch antennas are the
transmission line model, cavity model, and full wave model (which include primarily
integral equations / moment method).The transmission line model is the simplest of all
and it gives good physical insight but it is less accurate. The cavity model is more
accurate and gives good physical insight but is complex in nature. The full wave models
are extremely accurate, versatile and can treat single elements, finite and infinite arrays,
stacked elements, arbitrary shaped elements and coupling. These give less insight as
compared to the two models mentioned above and are far more complex in nature.
3.4.1 Transmission Line Model –Radiation mechanism
This model represents the microstrip antenna by two slots of width W and height
h, separated by a transmission line of length L. The microstrip is essentially a non-
homogeneous line of two dielectrics, typically the substrate and air. A typical microstrip

line is shown in Fig. 3.9 while the electric field lines associated with it are shown in Fig.
3.10.
Figure 3.9 - Physical and effective length of a microstrip patch
Figure 3.10 - Electric field lines
As seen from Fig. 3.10, most of the electric field lines reside in the substrate while
some electric field lines exist in the air. As a result, this transmission line cannot support
pure transverse-electric-magnetic (TEM) mode of transmission since the phase velocities
would be different in the air and the substrate. Instead, the dominant mode of propagation
would be the quasi-TEM mode. Hence, an effective dielectric constant (εreff) must be
obtained in order to account for the fringing and the wave propagation in the line.
The value of εreff is slightly less than εr, because the fringing fields around the
periphery of the patch are not confined in the dielectric substrate but are also spread in the
air as shown in Fig. 3.10 above. The expression for εreff is given as:
Equation - 3.1
Where εreff denotes effective dielectric constant, εr stands for dielectric constant of
substrate, h represents height of dielectric substrate, and W identifies width of the patch.

Figure 3.11 shows the transmission line model for patch antenna, where Fig.
3.11(a) is the patch antenna, Fig. 3.11(b) is the top view and Fig. 3.11(c) is the side view
of the antenna.
(a) Microstrip patch antenna
(b) Top view of antenna (c) Side view of antenna
Figure 3.11 - Transmission line model for patch antenna
In order to operate in the fundamental TM10 mode, the length of the patch must
be slightly less than λ / 2, where λ is the wavelength in the dielectric medium and is equal
to λ0 / εreff, where λ0is the free space wavelength. The TM10 model implies that the field
varies one λ / 2 cycle along the length and there is no variation along the width of the
patch. In Fig. 3.11(b) shown above, the microstrip patch antenna is represented by two
slots, separated by a transmission line of length L and open circuited at both the ends.
Along the width of the patch, the voltage is maximum and current is minimum due to the

open ends. The fields at the edges can be resolved into normal and tangential components
with respect to the ground plane.
It is seen from Fig 3.11(c) that the normal components of the electric field at the
two edges along the width are in opposite directions and thus out of phase since the patch
is λ / 2 long and hence they cancel each other in the broadside direction. The tangential
components (seen in Fig 3.11(c)), which are in phase, means that the resulting fields
combine to give maximum radiated field normal to the surface of the structure. Hence the
edges along the width can be represented as two radiating slots, which areλ / 2 apart and
excited in phase and radiating in the half space above the ground plane. The fringing
fields along the width can be modeled as radiating slots and electrically the patch of the
microstrip antenna looks greater than its physical dimensions.
3.5 Microstrip antenna arrays
An antenna array is a system of similar antennas oriented similarly to get greater
directivity in described direction. In other words, it is a radiating system consisting of
several spaced and properly phased radiators. In many microstrip antenna applications,
system requirements can be met with a single patch element. In other cases, however
systems require higher antenna gains while maintaining low profile structures, which calls
for the development of microstrip arrays. Microstrip arrays due to their extremely thin
profiles offers 3 outstanding advantages relative to other type of antennas, low weight,
low profile, with conformability and low manufacturing cost.
A microstrip array is the integration of microstrip element with a coaxial feed. It
may be classified in many ways. The spectral distribution of elements is common
classification: array may be linear planar or volume. The advantages of microstrip
antennas appear when all the elements of the array along with the feed network are
monolithically etched from one side of the printed circuit board they are,
 The process of photo etching hundred’s as even thousands of microwave
components in one process result in a low cost antenna array.
 The resulting printed circuit board is very thin. Since the array is designed to
operate from the ground place on the back of the printed board, its performance is
unaffected by mounting to a metallic surface such as an aircraft or a missile. The
resulting design is doubly conformal. It is conformal to underlying structure to

which it can be bolted or laminated and it is extremely conformal aerodynamically
because of minimum protrusion.
 Microstrip arrays have high performance because an infinite variety and quantity
of antenna elements power dividers, matching sections, phasing sections etc. can
be added to printed circuit board without any cost impact. This gives the design
engineer many components that are not commercially available in separate
packages.
 The microstrip array is very reliable since the entire array is one continuous piece
of copper.
However, microstrip antennas arrays also have some disadvantages as,
 Narrow bandwidth (by using optimization, the bandwidth can be increase).
 Poor isolation between feed and radiating elements.
 Possibility of excitation of surface waves.
 Low efficiency due to high loss mainly in feeding network
 Larger size
 Higher cost
To minimize these effects, accurate analysis techniques optimum design methods
and innovative array concepts are imperative to the successful of microstrip array
antennas.
There are various types of antenna can be design by using array technique such as
dual band microstrip antenna, multiband microstrip antenna and ultra-wide band antenna.
Below are the figures of some application of array structure:
Figure 3.12 - Dual band microstrip antenna

Figure 3.13 - Ultra wideband antenna
For the previous figures, inset feed technique is used as a feeding technique for all
elements in array. To minimize the losses at the transmission lines, quarter wave length
transformer matching technique is used together with power divider. By using power
divider, the supply current can be divided equally to each patch means that each patch can
radiates power equally. Referring to the above figures, the usage of power divider is not
needed.
3.6 Electromagnetic Band Gap (EBG) structure
In recent years, there has been growing interest in utilizing electromagnetic band-
gap (EBG) structures in the electromagnetic and antenna community. The EBG
terminology has been suggested based on the photonic band-gap (PBG) phenomena in
optics that are realized by periodical structures. There are diverse forms of EBG
structures design such as EBG structures integrated with active device and multilayer
EBG structures.
Electromagnetic Band Gap (EBG) always referred as photonic band gap (PBG)
surface or high impedance surface. This structure is compact which has good potential to
build low profile and high efficiency antenna surface. The main advantage of EBG
structure is their ability to suppress the surface wave current. The generation of surface
waves decreases the antenna efficiency and degrades the antenna pattern. Furthermore, it
increases the mutual coupling of the antenna array which causes the blind angle of a
scanning array. The feature of surface-wave suppression helps to improve antenna’s
performance such as increasing the antenna gain and less power wasted when reducing
backward direction. There are two types of EBG structure to be discussed. Firstly is
Perforated dielectric and the second one is Metallodielectric structures. Perforated
dielectric is defined as effectively suppress unwanted substrate mode commonly exist in

microstrip antenna. This structure designed by drill periodic holes on dielectric subtracts
to introduce another dielectric but in practical, this structure is difficult to implement.
Metallodielectric structure is exhibits an attractive reflection phase future where the
reflected field change continuously from 180 degrees to -180 degrees versus frequency. It
was allow a low profile wire antenna to radiate efficiently with enhance bandwidth,
radiation pattern, gain, reduce back radiation and reduce size lobe.
EBG structure can be design by various shapes and every shape will have
different frequency band gap. Something special of the EBG structure is it can be
designed which has a characteristic whether it is inductive or more capacitive.
3.6.1 Suppression of surface waves by EBG structure
Surface wave propagation is a serious problem in microstrip antennas. Surface
waves reduce antenna efficiency and gain, limit bandwidth, increase end-fire radiation,
increase cross-polarization levels, and limit the applicable frequency range of microstrip
antennas.Two solutions to the surface wave problem are available now. One of the
approaches is based on the micromachining technology in which part of the substrate
beneath the radiating element is removed to realize a low efficiency dielectric constant
environment for the antenna. In this case the power loss through surface wave excitation
is reduced and coupling of power to the space wave enhanced. The second technique
relies on photonics band gap (PBG) engineering. In this case, the substrate is periodically
loaded so that the surface wave dispersion diagram presents a forbidden frequency range
(stop band or band gap) about the antenna operating frequency. Because the surface
waves cannot propagate along the substrate, an increase amount of radiating power
couples to the space waves. Also, other surface wave coupling effects like mutual
coupling between array elements and interference with onboard systems are now absent.
The figure below shows the blocking of propagation surface wave on waveguide by using
EBG (PBG) structure.
Figure 3.14 - The blocking of propagation surface wave by EBG structure

Photonics band gap materials are new class of periodic dielectrics, which arethe
photonics analogs of semiconductors. Electromagnetic waves behave in photonics
substrates as electrons behave in semiconductors. Various type of periodic loading of
substrates has been studied to realize the PBG nature of the substrate. Early attempts
involved drilling a periodic pattern of holes in the substrate or etching a periodic pattern
of circle in the ground plane. Next, a periodic pattern of the metallic pads was shorted to
the ground plane with vias. Recently, a new loading pattern has been studied. This type of
planar or 2-D loading is simple to realize (no via are necessary) and is compatible with
standard monolithic microwaves integrated circuit fabrication technology.
The transmission coefficient of a PBG substrate is characterized by a band gap or
stop band region. The transmission and reflection coefficient of a microstrip line in PBG
substrate with circles etched in the ground plane are shown like figure 3.16.
Figure 3.15 - Square lattice of etched circles Figure 3.16 – Square lattice of small
in the ground plane metal pads with grounding vias in the
center
3.6.2 Principle of Electromagnetic Band Gap (EBG) structure
The basic design of EBG structure is shown in figure 3.17 known as mushroom
like EBG structure. This structure has frequency range where the surface impedance is
very high. The equivalent LC circuit acts as a two-dimensional electric filter in this range
of frequency to block the flow of the surface waves. The central frequency of the band
gap is shown in equation 3.2. The inductor L results from the current flowing through the
vias, and the capacitor C due to the gap effect between the adjacent patches. Thus, the
approach to increase the inductance or capacitance will naturally result in the decrease of
band-gap position.

Figure 3.17 - 2D EBG structure
Central frequency of the band gap is given by;
Equation – 3.2
Where;
Equation – 3.3
Equation – 3.4
The bandwidth of the electromagnetic band gap is given by;
Equation – 3.5
Therefore, the antenna with EBG structure operates at a lower frequency compared to the
antenna without EBG structure. Normally, when design the microstrip antenna operates at
lower frequency, the larger size of substrate needed. So, the EBG structure can reduce the
size of the antenna and the fabrication cost. Next, the EBG structure can enhance the
bandwidth of the original antenna structure.

CHAPTER 4
Fractals
“A fractal is a shape made of parts similar to the whole in some way”
4.1 Fractal’s Definition
According to Webster’s Dictionary a fractal is defined as being “derived from the
Latin fractus meaning broken, uneven: any of various extremely irregular curves or shape
that repeat themselves at any scale on which they are examined.”
4.2 Why Fractal Antennas?
The relationship of the physical size of the antenna to its operating wavelength is a
fundamental parameter in antenna design. The physical size of an antenna is generally
half or quarter of its operating free space wavelength, and the range of frequencies over
which the antenna operate satisfactorily is normally 10-40% of this center wavelength.
This range of frequencies is generally called the bandwidth of the antenna. Making the
dimensions of the antenna much smaller than its operating wavelength will reduce its
radiation resistance, efficiency and bandwidth.
Fractal geometry due to its self-similarity property can overcome this limitation of
antenna size and its operating wavelength, that is, fractal antennas can be much smaller
size than the operating wavelength without seriously affecting the other antenna
parameters. Also antennas based on fractal geometry display multiband behavior, not
easily available in conventional antenna design.
In summary, the compact size of the fractal antenna (relative to its operating
wavelength) and its multiband behavior makes it’s very useful in current
telecommunication industry.
4.3 Basics of Fractals
In the study of antennas, fractal antenna theory is a relatively new area. The term
“fractal” means broken or irregular fragments. It was originally coined by Mandelbrot
(1983) to describe a family of complex shapes that possess an inherent self-similarity or
self-affinity in their geometrical structure. Jiggered (1990) defined fractal
electrodynamics as an area in which fractal geometry was combined with electromagnetic

theory for the purpose of investigating a new class of radiation, propagation and
scattering problems. One of the most promising area fractal electrodynamics re-searches
is in its application to antenna theory and design. There are varieties of approaches that
have been developed over the years, which can be utilized to archive one or more of these
design objectives. The development of fractal geometry came largely from an in depth
study of the pattern nature, with the advance of wireless communication system and their
increasing importance wide band and low profile antennas are in great demand for both
commercial and military applications. A fractal is a rough or fragmented geometric shape
that can be split into parts, each of which is a reduced-size copy of the whole and this
property is called self -similarity. Fractal geometries are composite designs that repeat
themselves or their statistical characteristics and are thus “self-similar” fractal geometry
finds a variety of applications in engineering. Fractal geometry is space filling contours of
regular or irregular shapes, and is super imposed of too much iteration and they describe
the self-similar property of fractal geometry. Fractals are a class of shapes which have not
characteristic size. Each fractal is composed of multiple iterations of a single elementary
shape the iteration can continue infinitely, thus forming a shape within a finite boundary
but of infinite length or area.
4.4 Main features of fractals
 It has a finite structure at arbitrarily small scales
 It is too irregular to be easily described in traditional Euclidean geometric
 It is self-similar
 Simple and recursive.
Modern telecommunication systems require the antenna with wider bandwidth
and smaller dimension than conventionally possible. This has initiated antenna research in
various directions, are of which is by using fractal shaped antenna elements. In recent
years several fractal geometries have been introduced for antenna application with
varying degree of success in improving antenna characteristics. Some of these geometries
have been particularly useful in reducing the size of the antenna, while other designs aim
at incorporating multiband characteristics. These are low profile antennas with moderate
gain and can be made operative at multiple frequency bands and hence are
multifunctional. In our present work we focus on generation of multi frequency which
yields increases the bandwidth and size reduction of antenna. A plus shape patch is taken

as a base shape and in first iteration four other plus shape patches of the order of 1/3 of
base shape are placed touching the base shape. Similarly second iterations are taken by
further placing plus shaped patches at even reduced scales. It is found that as the iteration
number and iteration factor increases, the resonance frequencies become lower than those
of the zero iteration, which represents a conventional plus shape patch.
4.5 Self-similar fractals
The explosive growth of wireless systems and booming demand for a variety of
new wireless applications have renewed interest in multiband antennas. The most recent
multi-band antenna development is based upon the exploitation of the self-similarity
property of fractal shapes. A self-similar set is one that consists of scaled down copies of
itself, i.e., a contraction which reduces an image by same factors horizontally and
vertically.
(a) (b) (c)
(d)
Figure 4.1 - Self- similar Fractal structures (a) initiator (b) 1st iteration (c) 2nd
iteration (d) 3rd iteration
In mathematics, a self- similar object is exactly or approximately similar to a part of itself
(i.e. the whole has the same shape as one or more of the parts).

4.6 Self-affine fractals
This fractal is self- affine instead of self-similar because the pieces are scaled by
different amounts in the x- and y-directions. A rescaling procedure used in fractal
geometry and performed on a two variable system. For example, in a system utilizing an
x-axis and y- axis representing time and price, the x-axis could be rescaled by one ratio
and/or procedure while the y-axis is rescaled by a different ratio and/or procedure.
(a) (b)
(c) (d)
Figure 4.2 - Self- affine Fractal structures (a) initiator (b) 1st iteration (c) 2nd
iteration (d) 3rd iteration
A Self-affine set, on the other hand, is a contraction which reduces an image by
different factors, horizontally and vertically. Thus, it can provide additional flexibility in
the antenna design, since by selecting the scale factors appropriately, resonances can be
spaced by different factors.
4.7 Type of fractal antennas
4.7.1 Koch curve
The Koch fractal curve is one of the most well-known fractal shapes. It consists of
repeated application of the IFS. The Koch curve is shown in Figure 4.3. Each iteration
adds length to the total curve which results in a total length that is 4/3 the length of Koch
curve and is given by

L = (
4
3
)
k
Equation – 4.1
Here k is the iteration stage.
Figure 4.3: Koch Curve
4.7.2 Sierpinski gasket
The Sierpinski gasket or triangle is generated by using triangle as the basic
function shape. The Sierpinski Gasket fractal is generated by the IFS method and Figure
4.4 shows the step generation of Sierpinski gasket
Figure 4.4: Sierpinski gasket
4.7.3 Sierpinski carpet
The Sierpinski carpet is shown in Figure 4.5, it uses a square instead of the
triangle as the basic function shape.
Figure 4.5: Sierpinski carpet iterative constriction

4.8 Advantages and applications
4.8.1 Advantages
 Very broadband and multiband frequency response that derives from the inherent
properties of the fractal geometry of the antenna.
 Compact size compared to antennas of conventional designs, while maintaining
good to excellent efficiencies and gains.
 Mechanical simplicity and robustness.
 Design to particular multi frequency characteristics containing specified stop
bands as well as specific multiple pass bands.
 The wideband capability of fractal antennas allows smaller antennas that have
from 10:1 to 200:1 bandwidths that can handle moderate to high power.
4.8.2 Applications
 Fractal antennas provide optimal design solutions for commercial applications
like-wireless network, telematics, RFID, portable devices, automated meter
reading.
 It is used in defense applications such as electronic warfare, signal intelligence,
tactical communications.
4.8.3 Some of the Disadvantages of fractals
 Complexity in modeling the antenna
 The benefit begin to diminish after first few iterations

CHAPTER 5
Antenna design
5.1 Design Specifications
The three essential parameters for the design of a rectangular Microstrip Patch Antenna
are:
 Frequency of operation (fₒ): The resonant frequency of the antenna must be selected
according to our applications. We use the resonating frequency as 2 GHz for our
design. This frequency range is used for wireless applications.
 Dielectric constant of the substrate (εr): Glass Epoxy is used in our design with
dielectric constant of 4.4.
 Height of dielectric substrate (h): Height of dielectric substrate controls the
bandwidth. The value of h used in our design is 1.6mm.
Hence the essential parameter values for our design are:
 fₒ=2GHz
 εr=4.4
 h=1.6mm
Figure 5.1 – Microstrip Antenna
Step 1: Calculation of the Width (W):
The width of the Microstrip patch antenna is given by equation (5.1) as
Equation – 5.1
Substituting c = 3e8 m/s, εr= 4.4 and fₒ = 2GHz, we get
W=45.6mm.

Step 2: Calculation of Effective Dielectric constant (εreff):
Equation (5.2) gives the effective Dielectric constant as
Equation – 5.2
Substituting εr = 4.4, W = 45.6mm and h = 1.6mm we get
εreff = 4.126.
Step 3: Calculation of Effective length (Leff):
Equation (5.3) gives the effective length as:
Equation – 5.3
Substituting c = 3e8 m/s, εreff = 4.126 and fₒ = 2GHz, we get
Leff = 36.92mm.
Step 4: Calculation of length extension (ΔL):
Equation (5.4) gives the length extension as:
Equation – 5.4
Substituting εreff = 4.126, W= 45.6mm and h = 1.6mm we get:
ΔL = 0.0740mm.
Step 5: Calculation of actual length of patch (L):
The actual length is obtained by re-writing equation (5.5) as:
L = Leff-2ΔL Equation - 5.5
Substituting Leff = 36.92mm and ΔL = 0.0740mm we get:
L=35.44mm.
Step 6: Calculation of actual length of patch (L):
The actual length is obtained by re-writing equation (5.5) as:
L = Leff - 2ΔL Equation - 5.6
Substituting Leff = 36.92mm and ΔL = 0.0740mm we get:

L=35.44mm.
Step 7: Design of 50Ω micro strip feed line:
For Zo=50Ω, εr=4.4
W/d= 8eA/e2A-2; for w/d>2 Equation- 5.7
2/π [B-1-ln (2B-1) +εr-1/2 εr {ln (B-1)+0.39-(0.61/ εr)}; for w/d<2
Where, A= Zo (εr+1)1/2/120 + (εr-1)/ (εr+1)[0.23+0.11/ εr] and B=377π/2Zoεr
1/2
Let us assume w/d<2, &after calculation B=5.643
Therefore w/d=1.9133;
Width of feed line Wf 50=W=1.6×10-3×1.9133=0.3061cm
Step 8: Design of length of feed line:
λg = λ0/εeff
1/2; where εeff = εr-[ εr - εe/1+G(f/fp)];G=( Zo-5/60)1/2 +0.004Zo Equation-5.8
fp= Zo/2µ0h
Therefore G=1.066025 and fp=12.434GHz and εeff =4.1336 hence λg=7.37cm
Therefore Lf50= λg/4=1.8445cm
Step 9: Length of quarter wave transformer:
In this case select Zo= (Zin×Zt) 1/2=112.6131Ω where Zin=243.550Ω and Zt=50 Ω
Now G = (Zo-5/60)1/2+0.004, Zo=1.78968
For 2GHzεe=4.126, therefore using above formulas fp=2.0045GHz, εeff=4.1247,
λg=7.3823cm.Therefore Lt= λg/4=1.456cm
Step 10: Width of quarter wave transformer:
A=Zo (εr+1)1/2/120+ εr-1/ εr+1[0.23+0.11/ εr] and W/d= 8eA/e2A-2;
Substituting Zo and εr we get A= 2.3413 therefore W/d= .078413
Therefore width of quarter wave transformer Wt =W=1.6×10-3×0.78413=1.2546mm
Step 11: Calculation of the ground plane dimensions (Lg, Wg):
The transmission line model is applicable to infinite ground planes only. However, for
practical considerations, it is essential to have a finite ground plane. It has been shown in
many open literatures that similar results for finite and infinite ground planes can be
obtained if the size of the ground plane is greater than the patch dimensions by

approximately six times the substrate thickness all around the periphery. Hence, for this
design, the ground plane dimensions would be given as:
Lg = 6h + L=6 (1.6) + 72.33=81.93mm Equation – 5.9
Wg = 6h + W=6 (1.6) + 45.6=55.2mm Equation – 5.10
5.2 Software Tool Used: ZEALAND IE3D
The electromagnetic simulation software adopted is Zealand’s IE3D. IE3D is an
integrated full wave electromagnetic simulation and optimization package for the analysis
and design of 3-D Microstrip antennas, microwave and millimeter-wave integrated
circuits and high speed printed circuit board.
5.3Applications of IE3D
It is used for the design of
 Microwave circuits and MMICs.
 RF circuits and RFIDs.
 Microwave, RF and wireless antennas.
 PCB, electronic packaging and signal integrity.

5.4 Project Flow
Figure 5.1 – Flow Diagram of the Project
START
LITERATURE
Review
Dimension Calculation
Design in Zealand IE3D Software
Simulation
Analysis
Expected
Results?
Fabricate
Measurement using
Network Analyzer
Comparing simulation
And practical result
Analysis and report
Writing
END

5.5 Hardware Tool Used: Network Analyzer E5062A
The testing of antenna is done using E5062A which is a Two Port Vector Network
Analyzer from Agilent technologies. The ENA series vector network analyzer provides
the best combination of speed and accuracy for measuring multiport and balanced
components such as fibers, duplexers and RF modules up to 3GHz. A vector analyzer
provides a simple and complete vector network measurement in a compact, fully
integrated RF network. E5062A vector network analyzer offers built-in source, receiver
and s-parameter test set covering frequencies from 300 KHz to 3GHZ.
Figure 5.2 Network Analyzer

CHAPTER 6
Simulated and practical results
We have designed two antennas with 2 iterations on each antenna along with base
reference antenna. Here are our antennas with their nomenclature.
 Antenna 1 (Fig 6.1 to 6.12)
Here we have taken rectangular patch as the reference antenna and carried out
2 further iterations on it with a scale factor of 1/4 to form self – affine fractal geometry on
reference antenna along with EBG structure.
 Antenna 2 (Fig 6.13 to 6.32)
Here we have taken 2 rectangular patches as a 2-elemental reference antenna
array and carried out three further iterations on it with scaling factor of 1/3 to form plus
shaped self - similar fractal geometry from reference array. Here microstrip feed method
is used.

Reference Antenna with EBG structure
Figure 6.1 – Software design Figure 6.2 – Hardware Design
S- Parameter display of Reference antenna with EBG
Figure 6.3–Simulated Result Figure 6.4 – Practical Result
Base Antenna with EBG structure (Self-Affine Geometry)
Figure 6.5 - Software design Figure 6.6 – Hardware Design

S- Parameter Display of Base Antenna with EBG structure
(Self-Affine Geometry)
Figure 6.7 - Simulated Result Figure 6.8 -Practical Result
Antenna 1st Iteration with EBG structure (Self-Affine Geometry)
Figure 6.9–Software design Figure 6.10 – Hardware Design
S- Parameter Display of 1st
iteration with EBG structure
(Self-Affine Geometry)
Figure 6.11 - Simulated Result Figure 6.12 - Practical Result

Reference array antenna
Figure 6.13 – Software Design
Figure 6.14 – Hardware Design
S- Parameter Display of Reference Antenna array
Figure 6.15 – Simulated Result
Figure 6.16 - Practical Result

Base array antenna without slot (Self-Similar Geometry)
S- Parameter Display of Base Antenna array without slot
(Self-Similar Geometry)
Figure 6.20–Practical Result

Base array antenna with slot (1mm, 21.82mm)
(Self-similar Geometry)
Figure 6.21–Software Design
S- Parameter Display of Base Antenna array with slot (1mm, 21.82mm)

1st iteration of Antenna array with slot (1mm, 21.82mm)
S- Parameter Display of 1st
iteration with slot (1mm, 21.82mm)
Figure 6.27 - Simulated Result

2nd iteration of Antenna array with slot (1mm, 21.82mm)
S- Parameter Display of 2nd iteration with slot (1mm, 21.82mm)

Comparison of gain in single element antenna and 2 - element array
Antenna
Figure 6.33 – Gain of Single Element Figure 6.34 – Gain of Antenna Array
Comparison of gain in Antenna Reference with and without EBG
Figure 6.35 – Gain without EBG Figure 6.36 - Gain with EBG
Here we can see that by the use of 2 – Elemental array for antenna design, the gain
of the antenna has been improved by a factor of 3 compared to single element antenna
reference. Similarly, we got gain improvement with other iterations of design. Hence, we
can conclude that performance of single element antenna will improve with the increase
in the number of antenna elements used in the antenna design.
In a similar way, when we compared the gains of antenna with EBG structure and
antenna without EBG structure, gain of the antenna is been improved with the EBG
structure by a factor of around 2. Therefore we can conclude that, the use of EBG
structure in the antenna design will improve its performance in a good manner.

COMPARISION OF SIMULATED AND PRACTICAL
RESULTS
ANTENNA
NAME
SIMULATED RESULT PRACTICAL RESULT
FREQUENCY
(GHz)
RETURN
LOSS
(dB)
FREQUENCY
(GHz)
RETURN
LOSS
(dB)
ANTENNA ARRAY
Reference 1.99 -15.48 1.98 -21.79
Base antenna
without slot
2.25 -13 2.31 -13.91
Base antenna
with slot
1.26 -33.24 1.36 -12.96
1st Iteration 1.03 -23.84 1.09 -16.10
2nd Iteration 0.97 -17.60 1.03 -18.39
ANTENNA WITH EBG
Base antenna 1.98 -17.57 1.98 -15.26
1st Iteration 1.17 -17.96 1.19 -12.90
2nd Iteration 1.14 -12.14 1.17 -17.50

CONCLUSION
Rectangular microstrip antenna array and rectangular microstrip antenna with
square EBG structure are designed using the appropriate design formulae and is
fabricated using quick fabrication procedure, then it is tested using the vector network
analyzer E5062A. The antenna design is worked out at frequency 2GHz frequency. When
tested practically it was properly matching with designed frequency.
In this report, a novel electromagnetic band gap structure (EBGs) is proposed. A
fractal microstrip antenna is implemented using the EBGs as a ground plane, and the
measured results show that the reduction in the surface wave level is remarkable.
Compared with the reference antenna at improvement of the return loss is achieved, and
the back lobe is reduced. Thus considerable size reduction& a total bandwidth are
achieved. In addition to this, use of array in our design resulted in improved radiation
with enhance bandwidth and good return loss. Simulation is carried out using IE3D
software and it is found that simulated results are in good agreement with the
experimental results.
The dielectric constant plays a major role in the overall performance of a patch
antenna. It affects both the width, in turn the characteristic impedance and the length
resulting in an altered resonant frequency. We have used the fiber glass substrate (glass
epoxy) but the permittivity (εr) alters from batch to batch sometimes even between
different sheets of substrates.
As we have implemented antenna arrays using fractal geometry to improve the
performance of single element antenna, traditional wideband antennas (spiral and log –
periodic) can be analyzed with fractal geometry to shed new light on their operating
principles. In addition to this, EBG structure of different shapes (like plus shape, spiral
shape etc.) can analyzed with antenna elements with good multiband and improved
characteristics.

FUTURE SCOPE
In our project, aim of improving the performance (Ex: gain, directivity, return loss) of the
antenna is achieved.
Future challenges of a Microstrip antenna are:
 Bandwidth Extension Techniques
 Control of Radiation Patterns
 Reducing Losses/increasing efficiency
 Improving feed networks
Size reduction techniques:
The bandwidth can be increased as follows
 By increasing the thickness of the substrate
 By use of high dielectric constant of the substrate so that physical dimensions of
the parallel plate transmission line decreases.
 By increasing the inductance of the micro strip by cutting holes or slots in it.
 By adding reactive components to reduce the VSWR
 In order to increase the directivity of the micro strip antennas multiple Microstrip
radiators are used to cascade to form an array.
There are several methods to implement the antenna design with the use of
different fractal geometries like Koch curves, Hilbert structures etc., different number of
antenna elements in the design and also different types of EBG structures (Ex: plus
shaped EBG, hexagonal EBGs, circular shapes etc.).Therefore we can further improve
our design by using different implementations in our design and by using metallic vias in
our design in the future.

REFERENCES
[1] IE3D User’s Manual, Release 9, Zealand software, Inc.
[2] “Bandwidth enhancement of dual patch microstrip antenna array using dummy EBG
patterns on feedline” by MANIK GUJRAL B.Eng. (Hons.), NUS in 2007.
[3] “Design and Analysis of Microstrip Patch Antenna Arrays” – Ahmed Fatthi Alsager.
[4] “Design and Simulation of Multiband Microstrip Patch Antenna for Mobile
Communications” by Daniel Mammo.
[5] “Design of linearly polarized rectangular microstrip patch antenna using ie3d/pso” -
C. Vishnu vardhana reddy and Rahul rana.
[6] Pattern Analysis of “The Rectangular Microstrip Patch Antenna” - Vivekananda
Lanka Subrahmanya.
[7] “Development of a Self-Affine Fractal Multiband Antenna for Wireless Applications”
- Jagadeesha S., Vani R. M. & P. V. Hunagund.
[8] “A Self-Similar Fractal Antenna with Square EBG Structure” - Jagadeesha.S,
Vani.R.M, P.V. Hunagund.
[9] “Fractal geometry: what is it? And what does it do?” by B.B. Mandelbrot.
[10] “A Self-Afﬁne Fractal Multiband Antenna” - Sachendra N. Sinha, Senior Member,
IEEE, and Manish Jain.
[11] “A Self-Similar Fractal Cantor Antenna for MICS Band Wireless Applications” by
Gopalakrishnan Srivatsun, Sundaresan Subha Rani, Gangadaran Saisundara Krishnan.
[12] “Electromagnetic band gap (EBG) structure in microwave device design” by
Mohamad Kamal A. Rahim.

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