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H-Shaped Slot for Bandwidth Enhancement of Rectangular Microstrip patch antenna 1
Department of Electronics and Communication Engineering 2016
CHAPTER 1
INTRODUCTION
The need for antennas to cover very wide bandwidth is of continuing importance, particularly in the field of
electronic warfare and wideband radar and measuring system. Although microstrip patch antennas have many
very desirable features, they generally suffer from limited bandwidth. So the most important disadvantage of
microstrip resonator antenna is their narrow bandwidth. To overcome this problem without disturbing their
principal advantage (such as simple printed circuit structure, planar profile, light weight and cheapness), a number
of methods and structures have been investigated recently. In this regard we can mention multilayer structures,
broad folded flat dipoles, curved line and spiral antennas, impedance matched resonator antennas, resonator
antennas with capacitive coupled parasitic patch element, log periodic structures, modified shaped patch antenna
(H-shaped). In this project H-shaped microstrip patch antenna is analyzed and compared with rectangular patch
antenna.
Figure 1.1: Microstrip Patch Antennas
The H-shaped patch antenna here has a size about half of the rectangular patch antenna with larger bandwidth.
The larger bandwidth is because of a reduction in the quality factor (Q). Figure 1.1 shows a rectangular microstrip
patch antenna of length L, width W resting on a substrate of height h. The co-ordinate axis is selected such that
the length is along the x direction, width is along the y direction and the height is along the z direction.
H-Shaped Slot for Bandwidth Enhancement of Rectangular Microstrip patch antenna 2
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CHAPTER 2
LITERATURE SURVEY
2.1 Bandwidth Enhancement of Probe Fed Microstrip Patch Antenna
Authors: Parminder Singh, Anjali Chandel, Divya Naina
This paper deals with different techniques for bandwidth enhancement of conventional rectangular microstrip
antenna. By increasing the height of patch, increasing the substrate thickness and decreasing the permittivity of
substrate the percentage bandwidth is increased. HFSS Software is used for the simulation and design calculation
of microstrip patch antenna. The return loss, VSWR curve, directivity and gain are evaluated. Measured
simulation results show that by increasing the height of patch bandwidth is enhanced by 50-60%, by decreasing
the substrate permittivity the bandwidth is enhanced by 5-10% and by increasing substrate thickness bandwidth
is enhanced by 15-20%.
2.2 Designing of Bandwidth Improved ‘H’ Shaped Microstrip Patch Antenna for
Bluetooth applications using Ansoft HFSS
Authors: Chaitali. J. Ingale1, Anand. K. Pathrikar
This paper represents the designing of 2.4 GHz H shaped microstrip patch antenna using electromagnetic
simulation software. The model is designed and simulated in Ansoft HFSS v.13. Microstrip is a type of electrical
transmission line which can be fabricated using PCB, which convey microwave frequency signals. For good
performance of antenna, a thick dielectric substrate with low dielectric constant is desirable. This provides larger
band width, better efficiency and better radiation. The models that are used for analysis of Microstrip patch
antenna are transmission line model, cavity model and full wave model. HFSS is a high performance full- wave
electromagnetic field simulator for arbitrary 3D volumetric passive device modeling, which takes advantage of
the familiar Microsoft Windows graphical user interface. HFSS stands for High Frequency Structure Simulator.
Ansoft pioneered the use of the Finite Element Method for EM simulation, which integrates simulation,
visualization, solid modeling and automaton in an easy-to-learn environment. Ansoft HFSS can be used to
calculate parameters such as S Parameters, Resonant Frequency and Fields.
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2.3 Design and Analysis of Dual-Band Ψ- Shaped Microstrip Patch Antenna
Authors: Diwakar Singh, Amit Kumar Gupta, R. K. Prasad
This paper considers a conventional rectangular microstrip patch antenna and ψ shape antenna designed by cutting
four notches in a rectangular microstrip patch antenna. The designed antenna structure is further simulated by
IE3D simulation software. The simulation results are obtained in terms of bandwidth, gain, directivity and
efficiency. The result shows that the designed antenna is suitable to work in two different frequency bands with
a good amount of gain and efficiency. This paper helps to study about microstrip patch antenna and how to
improve the bandwidth and gain. An antenna is generally a metallic object capable of transmitting and receiving
radio waves. Antenna acts like a resonant circuit which converts electrostatic energy into electromagnetic energy
and vice versa. An antenna is one of the basic and most important requirements of any wireless communication
system. The reduced size microstrip patch antenna is a good alternative and is widely used for scaling the devices
used in wireless communication system.
 Different patch structures such as E shaped, H shaped, W shaped etc. are used for improved bandwidth
of the antenna.
 Cutting notches and slots in conventional rectangular patch geometry also improves the antenna
bandwidth and gain.
 The usage of antenna array and the antenna having stacked configuration also provides good amount
of improvement in bandwidth and gain.
In this paper the antenna structure is designed considering FR4 type material specifically glass epoxy as a
substrate.
2.4 Design and Analysis of Dual Frequency Band E-Shaped Microstrip Patch Antenna
Authors: R. K. Prasad, Amit Kumar Gupta, Dr. J. P. Saini, Dr. D. K. Srivastava
This paper emphasizes on the designing and analysis of an E-shaped microstrip patch antenna. In multiple
applications the antenna operates in more than one frequency bands. For this purpose MoM based simulation
software IE3D simulation software ver.15.2 is used. The result shows analysis of antenna performance in terms
of S11 parameter or return loss curve, VSWR, Gain, Directivity etc.
 Analysis of S11 parameter show that antenna structure work in two different frequency bands.
 VSWR should be below 2dB for the entire frequency range in which antenna has to operate.
 Designed antenna provides a gain of 3.6024dB which is useful for many applications.
 Designed antenna structure has a directivity of 3.97701 dB.
 The designed antenna has an efficiency of about 88.4522% at 1.37528 GHz.
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Advantages of microstrip antenna are:
 Used in devices which are smaller in size and moving.
 Microstrip Antennas are simple.
 Cost effective.
The E shape is designed by cutting two notches in rectangular patch antenna. FR4 material is used for the antenna
structure. Co-axial probe feeding is used for feeding purpose.
2.5 A Parametric Study on Microstrip Patch Antenna
Authors: A. Bhattacharya, B. N. Biswas
Choice of substrate with higher dielectric constant improves both amplitude and frequency stability of the patch
though substrate with lower dielectric constant is preferred for radiation efficiency.
A microstrip patch designed with a substrate having ε =2.2 and h=3.2 mm gives 400MHz bandwidth at 5.25 GHz
while a patch having ε =2.2 and h=0.787 mm gives 212 MHz bandwidth at 9.65GHz. The patch with ε=2.2 and
h=3.2 mm designed to oscillate at 5.6 GHz oscillates at 5.25 GHz but a microstrip patch designed with a substrate
having ε =2.2 and h=0.787 mm oscillates at 9.046GHz whose design frequency was 9.0 GHz. Thus, a substrate
with greater thickness enhances bandwidth, but affects resonance frequency of oscillation. Even a patch designed
with proper choice of key parameters may resonate with a frequency different from designed one. Thus it is seen
that the percentage uncertainty in resonant frequency is less pronounced if a material of low dielectric constant
and also lower substrate thickness is chosen. Thick, low dielectric constant substrates are required to enhance
microstrip antenna efficiency but thin, high dielectric constant substrates are preferred for active antenna
operation .In an active patch, due to its low dc to RF conversion efficiency heat is produced within the patch
element.
2.6 Parametric Performance Analysis of Patch Antenna using EBG Substrate
Authors: MS. Nargis Aktar, Muhammad Shahin Uddin
Electromagnetic Band Gap (EBG) substrate is used as a part of antenna structure to improve the performance of
the patch antenna. Usually, the performance of a patch antenna depends on the parameters such as Return Loss
(RL), Bandwidth (BW), Gain, and Directivity. The return loss of the antenna with EBG structure is less compared
to the conventional antenna. It is also seen that when the EBG patch width increases than the return loss also
increases. Therefore, the antenna performance is better than the conventional antenna because the return loss is
reduced for the EBG structure the bandwidth of the antenna with EBG structure is higher than the conventional
antenna. Therefore, the performance of the antenna with EBG structure is better than the conventional antenna
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because the bandwidth is increased for the EBG structure. The gain is increasing with the EBG patch width from
0.08 to 0.1 and then the middle part the gain is almost constant. After that EBG patch width from 0.12, the gain
is decreasing in nature with the increasing EBG patch width.
2.7 Size Reduction and Bandwidth Enhancement of Rectangular Printed Antenna using
Triple Narrow Slits for Wireless Communication System and Microwave X-Band
Application
Authors: Vivekkumar Yadaw, Sudipta Das, S.M Maidur Rahman
The microstrip patch antenna is preferred for wireless system RF applications, mobile, satellite and wireless
communication system. Due to the
 Low cost and compact design.
 Small size.
 Light weight.
 Low cost on mass production.
 Low profile.
 Easy integration with other components.
This paper convey about the reduced size antenna with enhanced band width. The introduction of slits at the
edges of Rectangular patch reduce the antenna size by 44%. Bandwidth of antenna is enhanced up to 13.78%.
Resonant frequency is reduced by the method of cutting unequal narrow slits at the edges of the patch. Also the
broad band-width is achieved, about 8.44-9.69 GHz. The proposed antenna has a broad band which is used for
Microwave X-band application. Feeding is done using coaxial feeding. The simulation and design is done by the
method of moment based EM Simulator IE3D.
2.8 Parametric Study of the Rectangular Microstrip Antenna using Cavity Model.
Authors: Prof. Dr. Jamal W. Salman, Lect. Star O. Hassan
The advantage of the cavity model is that it has faster speed of computation and reasonably good accuracy.
However, the disadvantages are that the antenna should be symmetrical with respect to the feed-axis and the
variation along the width should be small. In order to design a RMSA operating at high efficiency with broader
bandwidth and higher gain, it’s desirable to use a material with lower dielectric substrate permittivity, and thicker
substrate of higher losses. In addition the width of the patch must be as large as possible for a given frequency to
increase its radiation power.
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2.9 Bandwidth improvement of Microstrip Patch Antenna Using H- shaped Patch
Authors: Sudhir Bhaskar, Sachin Kumar Gupta
This paper covers two aspects of microstrip antenna design. The first aspect is the design of typical rectangular
microstrip patch antenna. The second is the analysis and design of slot cut H shaped microstrip antenna. The
transmission line model is used for analysis. The H shaped patch antenna has got half the size of that of the typical
rectangular patch antenna. The H shaped microstrip antenna produced reduction in size and higher bandwidth in
comparison to the rectangular microstrip antenna
2.10 Parametric Study for Rectangular Microstrip Patch Antennas
Authors: S. Yavalkar, R. T. Dahatonde, Dr. S. S. Rathod, Dr. S. B. Deosrkar
It was observed that, to increase resonance frequency height loss tangent is to be increased whereas width and εr
to be decreases. For increasing bandwidth, height is to be increased whereas width, ε, loss tangent is to be
decreased. It is found that lesser the loss tangent less the loss in probe giving the wider bandwidth. With an
increase in W from 43.5 mm to 44.5 mm, the following effects are observed:
 The resonance frequency decreases from 1.64 GHz to 1.57 GHz due to the increase in ΔL and εr.
 The bandwidth of the antenna increases; however, it is not very evident from the plots, because the feed
point is not optimum for the different widths. Accordingly, a better comparison will be obtained when the
feed point is optimized for the individual widths
2.11 Performance Analysis of Rectangular Patch Antenna for Different Substrate Heights
Authors: Vivek Hanumante, Panchatapa Bhattacharjee, Sahadev Roy, Pinaki Chakraborty
Increasing the height of the dielectric substrate is advantageous in increasing the bandwidth of microstrip antenna,
which is desirable in compact antenna application. However increasing height of the dielectric substrate also
results in expansion of the size of antenna, increased return loss and VSWR. But substrate with greater height can
be used to achieve better directivity. The simulation results of this paper showed that with increase in height of
dielectric substrate the resonance frequency shifts towards the desired operating frequency. Gain increases with
the increase in the height of dielectric substrate. Increase in bandwidth could be understood with the concept that
more height acquired in space results in to increased bandwidth, but further increase in height results in decrease
in bandwidth as more height allows surface waves to travel within the substrate.
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CHAPTER 3
ANTENNA THEORY
3.1 Antenna Definition
An antenna is a transducer between a guided wave and a radiated wave, or vice versa. The structure that “guides”
the energy to the antenna is most evident as a coaxial cable attached to the antenna. The radiated energy is
characterized by the antenna’s radiation pattern. Antennas are a very important component of communication
systems. By definition, an antenna is a device used to transform an RF signal, traveling on a conductor, into an
electromagnetic wave in free space. An antenna is a device for converting electromagnetic radiation in space into
electrical currents in conductors or vice-versa, depending on whether it is being used for receiving or for
transmitting, respectively. Passive radio telescopes are receiving antennas. It is usually easier to calculate the
properties of transmitting antennas. Fortunately, most characteristics of a transmitting antenna (e.g., its radiation
pattern) are unchanged when the antenna is used for receiving. Antenna is a metallic device (as a rod or wire) for
radiating or receiving radio waves. It is a circuit element that provides a transition from a guided wave on a
transmission line to a free space wave. It also provides for the collection of electromagnetic energy. A transmitting
antenna connected to a transmitter by a transmission line, forces electromagnetic waves into free space which
travel in space with velocity of light. Similarly a receiving antenna connected to a radio receiver, receives or
intercepts a portion of electromagnetic waves travelling through space. The guiding device or transmission line
may take the form of a coaxial line or a hollow pipe (waveguide), and it is used to transport electromagnetic
energy from the transmitting source to the antenna or from the antenna to the receiver.
Figure 3.1.1:Transition region between guided wave and free space wave
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An antenna radiates by changing the flow of current inside a conduction wire. By time-varying the current in a
straight wire. If there is no motion of flow or if the flow of current is uniform, the straight wire will not radiate.
If we bend the wire, even with uniform velocity, the curve along the wire will create an acceleration in the current
flow and the wire will therefore radiate. In above figure, see a radiating antenna. Antennas are of different shapes
via, dipoles, helices, paraboloids, stubs, whips etc. The shape of an antenna is an important aspect that determines
its radiation pattern. Antennas are characterized by a number of key parameters, including bandwidth, beamwidth,
directivity, efficiency, gain, polarization, radiation pattern and voltage standing wave ratio (VSWR).
Figure 3.1.2: Schematic of an antenna system
Antenna is a passive device, it does not amplify the signals and it only directs the signal energy in a particular
direction in reference with isotropic antenna. Antennas demonstrate a property known as reciprocity, which means
that an antenna will maintain the same characteristics regardless if it is transmitting or receiving. Most antennas
are resonant devices, which operate efficiently over a relatively narrow frequency band. An antenna must be tuned
to the same frequency band of the radio system to which it is connected, otherwise the reception and the
transmission will be Impaired. When a signal is fed into an antenna, the antenna will emit radiation distributed in
space in a certain way. A graphical representation of the relative distribution of the radiated power in space is
called a radiation pattern. From circuital point of view antenna behaves as a one-port network; receives guided
wave power and convert it to radiating waves. One can estimate the characteristics and efficiency of this
conversion from radiation patterns of an antenna. On the basis of directional patterns, antenna can be classified
in to two types, namely directional and Omni-directional antenna.
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3.2 Fundamental Parameters of Antennas
In order to describe the performance of an antenna, we use various, sometimes Interrelated, parameters. They
are:
3.2.1 Radiation Pattern
An antenna radiation pattern or antenna pattern is defined as a mathematical function or a graphical representation
of the radiation properties of the antenna as a function of space coordinates. Radiation properties include power
flux density, radiation intensity, field strength, directivity, phase, or Polarization.”
Figure 3.2.1.1: Radiation pattern of a hertzian dipole.
• Defined for the far-field.
• As a function of directional coordinates.
• There can be field patterns (magnitude of the electric or magnetic field) or power patterns (square of
magnitude of the electric or magnetic field).
• Often normalized with respect to their maximum value.
• The power pattern is usually plotted on a logarithmic scale or more commonly
in decibels (dB).
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3.2.2 Radiation Pattern Lobes
A radiation lobe is a portion of the radiation pattern bounded by regions of relatively weak radiation intensity.
Various parts of a radiation pattern are referred to as lobes, which may be sub classified into major or main,
minor, side, and back lobes.
 Major Lobe (also called main beam): is defined as “the radiation lobe containing the direction of
maximum radiation.”
 Minor Lobe: is any lobe except a major lobe.
 Side Lobe: is minor lobe adjacent to major lobe. That is “a radiation lobe in any direction other than the
intended lobe.”
Figure 3.2.2.1: Radiation Pattern Lobes
 Back Lobe: is lobe just opposite to major lobe. That is “a radiation lobe whose axis makes an angle of
approximately180◦ with respect to the beam of an antenna.”
• Minor lobes usually represent radiation in undesired directions, and they should be minimized.
Side lobes are normally the largest of the minor lobes.
• The level of minor lobes is usually expressed as a ratio of the power density, often termed the side lobe
ratio or side lobe level.
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In most radar systems, low side lobe ratios are very important to minimize false target indications
through the side lobes (e.g., -30 dB).
Figure 3.2.2.2:radiation lobe
The radiation pattern of most antennas show a pattern of lobes at various angles,directions where the radiated
signal strength reaches a maximum, separated by nulls, angles at which the radiation falls to zero. In a directional
antenna in which theobjective is to emit the radio wave in one direction, the lobe in that direction is designed to
be bigger (have higher field strength) than the others, this is the main lobe. The other lobes are called side lobes,
and usually represent unwanted radiation in undesired directions. The side lobe in the opposite directions from
the main lobe is called the back lobe.the radiation pattern refered to above is usually the horizontal radiation
pattern,which is plotted as a function of azimuth about the antenna, although the vertical radiation pattern may
also have a main lobe. The beam width of the antenna is the width of the main lobe, usually specified by the half
power beamwidth,the angle encompassed between the points on the side of the lobe where the power has fallen
to half (that is -3dB of its maximum value). the concepts of main lobe and side lobe also applied to acoustics and
optics and are used to describe the radiation pattern of optical systems like telescopes and acoustic transducers
like loud speakers and microphones. The main beam is the region around the direction of maximum radiation
(usually the region that is within 3dB of the peak of the main beam).
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Planes associated with an antenna:
E Plane: Plane contains the electric field vector and direction of maximum radiation.
H Plane: Plane contains the magnetic field vector and direction of maximum radiation.
3.2.3 Beamwidth
Associated with the pattern of an antenna is a parameter designated as beamwidth. The beamwidth of a pattern
is defined as the angular separation between two identical points on opposite sides of the pattern maximum.
• The beamwidth of an antenna is a very important figure of merit and often is used as a trade-off between
it and the side lobe level; that is, as the beamwidth decreases, the side lobe increases and vice versa.
• The beamwidth of the antenna is also used to describe the resolution capabilities of the antenna to
distinguish between two adjacent radiating sources or radar targets.
Figure 3.2.3.1 beamwidths of an antenna pattern.
Half-Power Beam Width (HPBW): In a plane containing the direction of the maximum of a beam, the angle
between the two directions in which the radiation intensity is one-half value of the beam.
First-Null Beamwidth (FNBW): Angular separation between the first nulls of the pattern.
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Resolution
• The most common resolution criterion states that the resolution capability of an antenna to
distinguish between two sources is equal to half the first-null beamwidth (FNBW/2), which is usually
used to approximate the HPBW.
• That is, two sources separated by angular distances equal or greater than FNBW/2 ¼ HPBW of an
antenna with a uniform distribution can be resolved.
• If the separation is smaller, then the antenna will tend to smooth the angular separation distance.
Figure 3.2.3.2: (a) Three dimensional (b) Two dimensional
Three- and two-dimensional power patterns (in linear scale) of U (θ) =cos2 (θ) cos2 (3θ).
3.2.4 Radiation resistance
Radiation resistance is that part of an antenna's feed point resistance that is caused by the radiation of
electromagnetic waves from the antenna, as opposed to loss resistance (also called ohmic resistance) which
generally causes the antenna to heat up. Radiation resistance varies at different points on the antenna. This
resistance is always measured at a current loop. The value of radiation resistance depends on several factors:
• Configuration of antenna.
• The point where radiation resistance is considered.
• Location of antenna with respect to ground and other objects.
• Ratio of length and diameter of conductors used.
3.2.5 Voltage Standing Wave Ratio (VSWR)
VSWR (Voltage Standing Wave Ratio), is a measure of how efficiently radio-frequency power is transmitted
from a power source, through a transmission line, into a load (for example, from a power amplifier through a
transmission line, to an antenna).The parameter VSWR is a measure that numerically describes how well the
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antenna is impedance matched to the radio or transmission line it is connected to. IT is the ratio of maximum
radio frequency voltage to minimum radio frequency voltage on a transmission line. It is given by:
VSWR stands for Voltage Standing Wave Ratio, and is also referred to as Standing Wave Ratio (SWR). VSWR
is a function of the reflection coefficient, which describes the power reflected from the antenna. If the reflection
coefficient is given by , then the VSWR is defined by the following formula:
The reflection coefficient is also known as s11 or return loss.
The VSWR is always a real and positive number for antennas. The smaller the VSWR is, the better the antenna
is matched to the transmission line and the more power is delivered to the antenna. The minimum VSWR is 1.0.
In this case, no power is reflected from the antenna, which is ideal. Often antennas must satisfy a bandwidth
requirement that is given in terms of VSWR. For instance, an antenna might claim to operate from 100-200 MHz
with VSWR less than 3. This implies that the VSWR is less than 3.0 over the specified frequency range. This
VSWR specifications also implies that the reflection coefficient is less than 0.5 (i.e., <0.5) over the quoted
frequency range.
3.2.6 Input Impedance
Input impedance is defined as “the impedance presented by an antenna at its terminals or the ratio of the voltage
to current at a pair of terminals or the ratio of the appropriate components of the electric to magnetic fields at a
point. The input impedance at a pair of terminals that are the input terminals of the antenna.
ZA = RA + j XA
Where
Z A = antenna impedance at terminals a –b (ohms).
RA = antenna resistance at terminals a –b (ohms).
XA = antenna reactance at terminals a –b (ohms).
In general, the resistive part of above equation consists of two components; that is,
RA = Rr + RL
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Rr = radiation resistance of the antenna.
RL = loss resistance of the antenna.
3.2.7 Gain
Gain of an antenna (in a given direction) is defined as the ratio of the intensity, in a given direction, to the radiation
intensity that would be obtained if the power accepted by the antenna were radiated isotropically. The radiation
intensity corresponding to the isotropically radiated power is equal to the power accepted (input) by the antenna
divided by 4π.
In most cases we deal with relative gain, which is defined as the ratio of the power gain in a given direction to
the power gain of a reference antenna in its referenced direction. The power input must be the same for both
antennas. The reference antenna is usually a dipole, horn, or any other antenna whose gain can be calculated or
it is known. In most cases, however, the reference antenna is a lossless isotropic source.
Thus
When the direction is not stated, the power gain is usually taken in the direction of maximum radiation. The total
radiated power (Prad) is related to the total input power (Pin) by
Prad = ecdPin
Where ecd is the antenna radiation efficiency (dimensionless).
• The gain of the antenna is closely related to the directivity.
• In addition to the directional capabilities it accounts for the efficiency of the antenna.
• Gain does not account for losses arising from impedance mismatches (reflection losses) and
polarization mismatches (losses).
3.2.8 Directivity
Directivity is the ratio of the radiation intensity in a given direction from the antenna to the radiation intensity
averaged over all directions.
• The average radiation intensity: total power radiated by the antenna divided by 4¼.
• Stated more simply, the directivity of a non-isotropic source is equal to the ratio of its radiation
intensity in a given direction over that of an isotropic source.
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Where
D = directivity (dimensionless)
U = radiation intensity (W/unit solid angle)
Umax = maximum radiation intensity (W/unit solid angle)
Prad = total radiated power (W)
3.2.9 Efficiency
• The total antenna efficiency e0 is used to take into account losses at the input terminals and within
the structure of the antenna.
𝜂 =
𝑃𝑟𝑎𝑑
𝑃𝑖𝑛
=
𝑃𝑟𝑎𝑑
𝑃𝑟𝑎𝑑 + 𝑃𝑙𝑜𝑠𝑠
=
𝑅 𝑟𝑎𝑑
𝑅 𝑟𝑎𝑑 + 𝑅𝑙𝑜𝑠𝑠
Where: η = antenna effeciency (%)
𝑃𝑟𝑎𝑑 = radiated power (W)
𝑃𝑙𝑜𝑠𝑠 = power loss due to resistive loss (W)
𝑃𝑖𝑛 = total power available to antenna (W)
𝑅 𝑟𝑎𝑑 = radiated equivalent resistance (Ω)
𝑅𝑙𝑜𝑠𝑠 = equivalent loss resistance (Ω)
𝑒0 = 𝑒 𝑟 𝑒 𝑐 𝑒 𝑑
𝑒0 is due to the combination of number of efficiencies:
𝑒0 = total efficiency,
𝑒 𝑟 = (1 − |┌|)2
𝑒 𝑟= reflection,
𝑒 𝑐= conduction efficiency
𝑒 𝑑 = dielectric efficiency,
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,
┌ = voltage reflection coefficient at the input terminals of the antenna.
Za= antenna input impedance.
Z0 = characteristic impedance of the transmission line.
VSWR = voltage standing wave ratio.
3.2.10 Bandwidth
The bandwidth of an antenna is defined as the range of frequencies within which the performance of the antenna,
with respect to some characteristic, conforms to a specified standard. The bandwidth can be considered to be the
range of frequencies, on either side of a center frequency (usually the resonance frequency for a dipole), where
the antenna characteristics (such as input impedance, pattern, beamwidth, polarization, side lobe level, gain, beam
direction, radiation efficiency) are within an acceptable value of those at the center frequency. For broadband
antennas, the bandwidth is usually expressed as the ratio of the upper-to-lower frequencies of acceptable operation
Bandwidth can be defined in terms of radiation patterns or VSWR/reflected power. The definition used is based
on VSWR. Bandwidth is often expressed in terms of percent bandwidth, because the percent bandwidth is constant
relative to frequency. If bandwidth is expressed in absolute units of frequency, for example MHz, the bandwidth
is then different depending upon whether the frequencies in question are near 150 MHz, 450 MHz or 825 MHz
3.3 Microstrip Antenna
A microstrip patch antenna (MSA) consists of a conducting patch of any planar or non-planar geometry on one
side of a dielectric substrate with a ground plane on other side. It is a popular printed resonant antenna for narrow-
band microwave wireless links that require semi hemispherical coverage. Due to its planar configuration and ease
of integration with microstrip technology, the microstrip patch antenna has been heavily studied and is often used
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as elements for an array. A large number of microstrip patch antennas have been studied to date. An exhaustive
list of the geometries along with their salient features is available. The rectangular and circular patches are the
basic and most commonly used microstrip antennas. These patches are used for the simplest and the most
demanding applications. Rectangular geometries are separable in nature and their analysis is also simple. The
circular patch antenna has the advantage of their radiation pattern being symmetric.
Sl. No Characteristic Microstrip Patch
Antenna
Microstrip Slot
Antenna
Printed Dipole
antenna
1. Profile Thin Thin Thin
2. Fabrication Very easy Easy Easy
3. Polarization Both linear and
circular
Both linear and
circular
Linear
4. Dual Frequency
operation
Possible Possible Possible
5. Shape flexibility Any shape Mostly
rectangular and
circular shapes
Rectangular and
triangular
6. Spurious radiation Exists Exists Exists
7. Bandwidth 2-50% 5-30% -30%
Table 3.3.1 Antenna Characteristic
The Microstrip patch antennas are well known for their performance and their robust design, fabrication and their
extent usage. The advantages of this Microstrip patch antenna are to overcome their de-merits such as easy to
design, light weight etc., the applications are in the various fields such as in the medical applications, satellites
and of course even in the military systems just like in the rockets, aircrafts missiles etc. the usage of the Microstrip
antennas are spreading widely in all the fields and areas and now they are booming in the commercial aspects due
to their low cost of the substrate material and the fabrication. It is also expected that due to the increasing usage
of the patch antennas in the wide range this could take over the usage of the conventional antennas for the
maximum applications. There is a number of techniques available for analyzing microstrip patch antennas. The
analytical techniques include transmission line model and cavity model. The most common numerical techniques
used are moment method and the finite difference time domain method. The later technique is time consuming
while the former method and the analytical technique have been applied to the regular shape only like rectangular,
circular, and elliptical shapes. However, the analysis of MSA is normally difficult to handle which is primarily
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due to existence of a dielectric substrate to support the conductor. The most important disadvantage of microstrip
patch antenna is their narrow bandwidth (1-3 %)
Figure 3.3.1 Rectangular microstrip patch antenna.
3.3.1 Types of Patch Antenna
Figure 3.3.1.1: Different shapes of radiating patch
 A patch antenna is atype of radio antenna with a low profile which can mounted on flat surface
 A patch antenna is also called as rectangular microstrip antenna
 They are the original type of microstrip antenna described by Howell in 1972
 It consist of flat rectangular sheet or patch of metal, mounted over a large sheet of metal called ground
plane
 Patch antena is usually constructed on dielectric substrate
 The impedace bandwidth of patch antenna is strongly influenced by spacing between patch and ground
plane
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3.3.2 Microstrip Substrate
Microstrip lines are commonly used in microwave circuits, although their performance is subject to the type of
substrate material selected for a printed-circuit board (PCB). One of the more important material parameters for
the substrate is the relative dielectric constant, which should be known before designing a high-frequency,
microstrip-based circuit. What follows is a simple and practical method for estimating the relative dielectric
constant of a microstrip substrate based on well-known microstrip line empirical equations. The substrate layer
thickness is 0.01-0.05 of free-space wavelength. It is used primarily to provide proper spacing and mechanical
support between the patch and its ground plane. The dielectric constants of the substrate are usually in the range
2.2 ≤ εr ≥ 12.
3.3.3 Advantage and Disadvantage
Microstrip patch antenna has several advantage over conventional microwave antenna with over conventional
microwave antenna with one similarity of frequency range from 100 MHz to 100 GHz same in both type. The
various advantage and disadvantage are given in table.
Sl.No.
Advantage Disadvantage
1. Low weight Low efficiency
2. Low profile Low gain
3. Thin profile Large ohmic loss in the feed
structure of arrays
4. Required no cavity backing Low power handling capacity
5. Linear and circulation polarization Excitation of surface waves
6. Capable of dual and triple frequency
operation
Polarization purity is difficult to
achieve
7. Feed lines and matching network can be
fabricated simultaneously
Complex feed structures require
high performance arrays
Table 3.3.3.1 Advantages and Disadvantages of Microstrip Patch Antenna.
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The applications of microstrip patch antenna in various fields are tabulated as below;
System Application
Aircraft and Ship antennas Communication and navigation, altimeters, blind
landing system
Missiles Radar, proximity fuses and telemetry
Satellite communications Domestic direct broadcast TV, vehicle-based
antennas, communication
Mobile communication Pagers and hand telephones, man pack system,
mobile vehicle
Remote sensing Large light weight apertures
Bio-medical Applications in microwave hyperthermia
Others Intruder alarm, personal communication, and so
forth
Table 3.3.3.2 Applications of Microstrip Antenna.
3.4 Feeding Techniques
Microstrip patch antennas can be fed by a variety of methods. These methods can be classified into two categories-
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 scheme, 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). A feed line is used to excite to radiate by direct or indirect contact.
3.4.1 Microstrip Line Feed
Microstrip line feed is one of the easier methods to fabricate as it is a just conducting strip connecting to the patch
and therefore can be consider as extension of patch. It is easy to match by controlling the inset position. In this
type of feed technique, a conducting strip is connected directly to the edge of the Microstrip patch. The conducting
strip is smaller in width as compared to the patch and this kind of feed arrangement has the advantage that the
feed can be etched on the same substrate to provide a planar structure. However as the thickness of the dielectric
substrate being used, increases, surface waves and spurious feed radiation also increases, which hampers the
bandwidth of the antenna. The feed radiation also leads to undesired cross polarized radiation. This method is
advantageous due to its simple planar structure, allows for planar feeding, easy to obtain input match. However
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the disadvantage of this method is that as substrate thickness increases, surface wave and spurious feed radiation
increases which limit the bandwidth. Coupling formula is same as coaxial probe feed.
Figure 3.4.1.1: Circuit Diagram of Microstrip Feed
The edge-coupled microstrip feed can be modeled by means of the step in width or impedance junction. The
equivalent circuit diagram is shown in below.
.
Figure 3.4.1.2: Microstrip feed
3.4.2 Coaxial Probe Feed
The Coaxial feed or probe feed is a very common technique used for feeding Microstrip patch antennas. 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. 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. However,
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its major drawback is that it provides narrow bandwidth and is difficult to model since a hole has to be drilled in
the substrate and the connector protrudes outside the ground plane, thus not making it completely planar for thick
Figure 3.4.2.1: Circuit Diagram of Coaxial Feed
substrates. Also, for thicker substrates, the increased probe length makes the input impedance more inductive,
leading to matching problems. It is seen above that for a thick dielectric substrate, which provides broad
bandwidth, the microstrip line feed and the coaxial feed suffer from numerous disadvantages. So to reduce these
types of disadvantages, non-contacting schemes are used.
Figure 3.4.2.2: Coaxial probe feed
The microstrip antenna can be fed from underneath via a probe as shown in figure 3.4.2.2.the outer conductor of
coaxial cable is connected to the ground plane and the center conductor is extended up to the patch antenna.
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3.4.3 Proximity coupled Feed
This type of feed technique is also called as the electromagnetic coupling scheme. Two dielectric substrates are
used such that the feed line is between the two substrates and the radiating patch is on top of the upper substrate.
The main advantage of this feed technique is that it eliminates spurious feed radiation and provides very high
bandwidth (as high as 13%) due to overall increase in the thickness of the microstrip patch antenna
Figure 3.4.3.1: Circuit diagram of proximity feed
This scheme also provides choices between two different dielectric media, one for the patch and one for the feed
line to optimize the individual performances. This method is advantageous to reduce harmonic radiation of
microstrip patch antenna implemented in a multilayer substrate.
The goal of the design is the suppression of the resonances at the 2nd and 3rd harmonic frequencies to reduce
spurious radiation due to the corresponding patch modes to avoid the radiation of harmonic signals generated by
non-linear devices at the amplifying stage. The study shows the possibility of controlling the second harmonic
resonance matching by varying the length of the feeding in. On the other hand, the suppression of the third
harmonic is achieved by using a compact resonator. Length of feeding stub and width-to-length ratio of patch is
used to control the match. Its coupling mechanism is capacitive in nature.
The equivalent circuit diagram of this feed is shown in above. Coupling capacitor is in series with the parallel R-
L-C resonant circuit representing the patch. Requirement of this coupling is to match the impedance and tuning
of the bandwidth. The open end of the microstrip feed gives stud and stud parameters which help in improving
bandwidth. By using this feeding technique 13 % of Bandwidth is achieved. It is effective to use two layers as it
increase the bandwidth and reduce spurious radiation, but it is difficult to form right alignment of the patches.
Advantages are that it allows planer feeding & less line radiation than microstrip feed.
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Proximity coupled microstrip patch antenna is a non-coplanar feed structure using at least two layers. Coupling
between the patch and the microstrip feeding line is capacitive in nature.
Figure 3.4.3.2: proximity coupled feed
3.4.4 Aperture coupled feed
In this type of feed technique, the radiating patch and the microstrip feed line are separated by the ground plane.
Coupling between the patch and the feed line is made through a slot or an aperture in the ground plane and
variations in the coupling will depend upon the size i.e. length and width of the aperture to optimize the result for
wider bandwidths and better return losses.
Figure 3.4.4.1: Circuit diagram of Aperture feed
The coupling aperture is usually centered under the patch, leading to lower cross-polarization due to symmetry
of the configuration. Since the ground plane separates the patch and the feed line, spurious radiation is minimized.
Aperture coupled feeding is attractive because of advantages such as no physical contact between the feed and
radiator, wider bandwidths, and better isolation between antennas and the feed network. Furthermore, aperture-
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coupled feeding allows independent optimization of antennas and feed networks by using substrates of different
thickness or permittivity.
Figure 3.4.4.2: Aperture coupled feed
3.4.5 Coplanar waveguide Feed
In a coplanar waveguide-fed microstrip antenna, the antenna and coplanar line are placed on the opposite sides of
the same dielectric substrate and the coupling from the coplanar line to microstrip antenna is accomplished via a
slot in the ground plane connected directly to the end of the coplanar line. In general, slot coupling may involve
an electric polarisability, a magnetic polarisability, or both. In slot coupling to a microstrip antenna, the magnetic
polarisability is the dominant Mechanism for a slot near the center of the patch. Because the polarisabilities
strongly depend on the shape of the slot as well as the size, it is desirable to improve the antenna performance by
optimizing the shape and size of coupling slot for given antenna dimensions. CPW-feed Microstrip patch antenna
because it have many features such as low radiation loss, less dispersion, easy integrated circuits and simple
configuration with single metallic layer, and no via holes required. The CPW fed antennas have some more
attractive features such as wider bandwidth, better impedance matching, and easy integration with active devices
and monolithic integrated circuits.
Coplanar Waveguide Feed Structure Feed line is one of the important components of antenna structure given
below in Figure. Coplanar waveguide structure is becoming popular feed line for an antenna. The coplanar
waveguide was proposed by C.P. Wen in 1969. A coplanar waveguide structure consists of a median metallic
strip of deposited on the surface of a dielectric substrate slab with two narrow slits ground electrodes running
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adjacent and parallel to the strip on the same surface. This transmission line is uni-planar in construction, which
implies that all of the conductors are on the same side of the substrate. Etching the slot and the feed line on the
same side of the substrate eliminates the alignment problem needed in other wideband feeding techniques such
as aperture coupled and proximity feed.
Figure 3.4.5.1: Coplanar waveguide feed
3.4.6 Inset Feed
It is a type of microstrip line feeding technique, in which the width of conducting strip is small as compared to
the patch and has the advantage that the feed can provide a planar structure. The purpose of the inset cut in the
patch is to match the impedance of the feed line to the patch input impedance without the need for any additional
matching element. This can be achieved by properly adjusting the inset cut position and dimensions. The inset-
fed microstrip antenna provides a method of impedance control with a planar feed configuration. The
experimental and numerical results showed that the input impedance of an inset-fed rectangular patch varied as a
4 Cos function of the normalized inset depth. A more recent study proposed a modified shifted 2 Sin form that
well characterizes probe-fed patches with a notch. It is found that a shifted 2 Cos function works well for the
inset-fed patch. The parameters of the shifted cosine-squared function depend on the notch width for a given patch
and substrate geometry.
The inset feed introduces a physical notch, which in turn introduces a junction capacitance. The physical notch
and its corresponding junction capacitance influence the resonance frequency. As the inset feed-point moves from
the edge toward the center of the patch the resonant input impedance decreases monotonically and reaches zero
at the center. When the value of the inset feed point approaches the center of the patch, the d Lp 2 π cos varies
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very rapidly; therefore the input resistance also changes rapidly with the position of the feed point. To maintain
very accurate values, a close tolerance must be preserved
Figure 3.4.6.1: Patch antenna with inset feed
The comparison of feeding techniques shows that the Rectangular Microstrip Patch Antenna with the Inset Feed
has the highest gain, lowest VSWR and return loss for the dielectric material FR4. Thus it states that inset feed
provides better impedance matching than the co-axial feed and microstrip line feed.
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CHAPTER 4
ANALYSIS METHOD FOR MICROSTRIP ANTENNA
The preferred models for the 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.
4.1. TRANSMISSION LINE MODEL
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 nonhomogeneous line of two dielectrics, typically the substrate
and air.
Figure 4.1.1: Electric field lines between patch and ground plane.
Hence, as seen from figure 4.1.1 most of the electric field lines reside in the substrate and parts of some lines in
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 (𝜀 𝑟𝑒) must be obtained in
order to account for the fringing and the wave propagation in the line. The value of 𝜀 𝑟𝑒 is slightly less than
𝜀 𝑟because 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 Figure above. The expression for 𝜀 𝑟𝑒 is
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𝜺 𝒓𝒆 =
𝜺 𝒓+𝟏
𝟐
+
𝜺 𝒓−𝟏
𝟐
(𝟏 +
𝟏𝟐𝒉
𝑾
)−𝟎.𝟓
Where 𝜀 𝑟𝑒 = Effective dielectric constant 𝜀 𝑟 = Dielectric constant of substrate, h= Height of dielectric substrate,
W =Width of the patch 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 λo/√𝜀 𝑟𝑒𝑓𝑓where λo is the free
space wavelength. The TM10 mode implies that the field varies one λ/2 cycle along the length, and there is no
variation along the width of the patch. In the fig. shown below, 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
Figure 4.1.2: Top view of microstrip antenna
The transmission line model has been utilized to determine the input performance of a rectangular patch antenna
excited by microstrip line and inset feed.Expressions for the resonant frequency,and variours other parameters
including the feed point has been calculated.The model has also been applied to determine the resonant parameters
for a patch antenna.The transmission line model treats the rectangular patch radiator as a stripline resonator with
no transverse field variation and assumes the radiation to occur from the two transverse open edges.It is well
known the dominant mode of propagation in a stripline is the TEM or quasi-TEM mode having negligible
variations of fields in the transverse direction.
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It is seen from figure 4.1.3 that the normal components of the electric field at the two edges along the width are
cancel each other in the broadside direction. The tangential components (seen in figure 4.1.3), which are in
phase, means that the resulting fields combine to give maximum radiated field normal to the surface of the
structure.
Figure 4.1.3: Side view of patch antenna
Hence the edges along the width can be represented as two radiating slots, which are λ/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. The dimensions of the patch along its length have now been extended on each end by a distance
ΔL, which is
𝛥𝐿 = 0.412ℎ
𝜀 𝑟𝑒 + 0.30
𝜀 𝑟𝑒 − 0.258
(
𝑊
ℎ⁄ + 0.264
𝑊
ℎ⁄ + 0.813
)
The effective length of the patch Leff now becomes Leff =L+2Δ for a given resonance frequency f the width W
is
𝑊 =
𝐶
2𝑓
(
𝜀 𝑟 + 1
2
)
−0.5
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4.2 DESIGN OF RECTANGULAR MICROSTRIP PATCH ANTENNA
A single element of rectangular patch antenna, as shown in figure, can be designed for the 3.3 GHz resonant
frequency using transmission line model
Figure 4.2.1: Typical rectangular patch antennas
In the typical design procedure of the microstrip antenna, the desired resonant frequency, thickness and dielectric
constant of the substrate are known or selected initially. In this design of rectangular microstrip antenna, glass
epoxy dielectric material is selected as the substrate with 1.6 mm height. Then, a patch antenna that operates at
the specified resonant frequency (3.3 GHz) can be designed by the using transmission line model equations. As
shown in figure, microstrip line type feeding mechanism used. It is also possible to determine the length and
width of quarter wave length long line (branch line) of the patch and the main feed line’s length and width to
ensure matching. The main feed line is of 50Ω characteristic impedance. The quarter wave length long line is
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used between main feed line and patch for impedance matching. The characteristic impedance of branch line is
calculated as
 Z0 – characteristic impedance of main feed line (50Ω)
 Ze – impedance at patch edge.
So for the rectangular microstrip patch antenna the parameters are:
 Resonating frequency f= 3.3 GHz.
 Patch width W = 27.8 mm.
 Patch length L = 21.42 mm.
 Branch line length qw = 11 mm.
 Substrate height h = 1.6 mm.
 Relative permittivity 𝜀 𝑟 = 4.5.
 Width of main feed line = 3 mm
4.3 DESIGN OF AN H-SHAPED MSA
The H-shaped microstrip antenna consists of an H shaped patch; supported on a grounded dielectric sheet of
thickness h and dielectric constant𝜀 𝑟. An H-shaped microstrip patch antenna, shown in figure 4.3.1 is obtained by
cutting equal rectangular slots along both the non-radiating edges of the rectangular microstrip patch antenna.
Figure 4.3.1: H shaped patch antenna
The H-shaped patch antenna reported here has a size about half that of the rectangular patch, with larger
bandwidth. The H-shaped microstrip patch antenna, because of its considerably smaller size, could replace the
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rectangular patch at UHF frequencies. When they are applied in the frequency range below 2 GHz, the sizes of
conventional rectangular microstrip patches seem to be too large.
The parameters of H shaped MSA is as below:
 Resonating frequency f= 3.3 GHz.
 Patch width W = 27.8 mm.
 Patch length L = 21.42 mm.
 Branch line length qw = 11.92 mm.
 Substrate height h = 1.6 mm.
 Relative permittivity 𝜀 𝑟 = 4.5.
 Width of main feed line = 3 mm
 Width of slots = 5 mm
 Length of slots = 3 mm
4.4 DESIGN OF INSET FED RECTANGULAR MSA
A rectangular patch of length L and width W is designed. The patch is cut at a depth d. Then inset feed of length
l and width w is formed. The port is defined at the end of the feed line. This technique is simple to model and
easy to match by controlling the inset position.
Figure 4.4.1: Rectangular MSA with an inset feeding
The inset cut provided match the impedance of the feed line with the patch input impedance without any additional
matching elements.
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The parameters of rectangular MSA with inset feeding technique as shown in figure 4.4.1 is:
 Resonating frequency f= 3.3 GHz.
 Patch width W = 27.8 mm.
 Patch length L = 21.42 mm.
 Branch line length qw = 13.92 mm.
 Substrate height h = 1.6 mm.
 Relative permittivity 𝜀 𝑟 = 4.5.
 Width of main feed line = 3 mm
 Inset feed position = (10.96,25.92,1.6)
4.5 DESIGN OF H SHAPED MSA WITH INSET FEED
The inset fed rectangular MSA is converted to H shaped patch MSA by cutting equal rectangular slots on both
sides of radiating slot. The H shaped MSA with inset feed is shown in figure 4.5.1
Figure 4.5.1: H shaped MSA with inset feed
The parameters of H shaped MSA with inset feeding is:
 Resonating frequency f= 3.3 GHz.
 Patch width W = 27.8 mm.
 Patch length L = 21.42 mm.
 Branch line length qw = 13.92 mm.
 Substrate height h = 1.6 mm.
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 Relative permittivity 𝜀 𝑟 = 4.5.
 Width of main feed line = 3 mm
 Inset feed position = (10.96,25.92,1.6)
 Width of slots = 5.233 mm
 Length of slots = 3.25 mm
The 3.3 GHz is taken as resonant frequency of the MSA. Fr4 epoxy has been selected for the substrate with
dielectric constant 4.4. the height of substrate is kept at 1.6 mm. in inset fed microstrip patch antenna the location
of feed determines the antenna input impedance. Therefore to achieve 50 impedance the inset length is determined
using the relation
𝑅𝑖𝑛(𝑦 = 𝑦0) = 𝑅𝑖𝑛(𝑦 = 0) (cos(
𝜋
𝐿
𝑦0))
2
Where𝑅𝑖𝑛(𝑦 = 0) is the input impedance at the leading radiating edge of the patch and 𝑅𝑖𝑛(y = y0) is the desired
input impedance, y0 is the inset length.
Figure 4.5.2: proposed microstrip patch antenna
The ground plane is specified by an electrical conducting boundary condition. A chamber has to be specified as
defined in to model open space, so that the radiation from the structure is absorbed and not reflected back. The
air box should be quarter wavelength long of the wavelength of interest in the direction of radiated field. The
proposed work air box is cube of dimension 200 mm.
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CHAPTER 5
SIMULATION SOFTWARE
5.1 HFSS
HFSS is a high-performance full-wave electromagnetic (EM) field simulator for arbitrary 3D volumetric passive
device modeling that takes advantage of the familiar Microsoft Windows graphical user interface. It integrates
simulation, visualization, solid modeling, and automation in an easy-to-learn environment where solutions to the
3D EM problems are quickly and accurately obtained. Ansoft HFSS employs the Finite Element Method (FEM),
adaptive meshing, and brilliant graphics to give you unparalleled performance and insight to all of 3D EM
problems. Ansoft HFSS can be used to calculate parameters such as S Parameters, Resonant Frequency, and
Fields.
Typical uses include:
 Package Modeling – BGA, QFP, Flip-Chip
 PCB Board Modeling – Power/Ground planes, Mesh Grid Grounds,
 Backplanes
 Silicon/GaAs - Spiral Inductors, Transformers
 EMC/EMI – Shield Enclosures, Coupling, Near- or Far-Field Radiation
 Antennas/Mobile Communications – Patches, Dipoles, Horns, Conformal
 Cell Phone Antennas, Quadrafilar Helix, Specific Absorption Rate(SAR),
 Infinite Arrays, Radar Cross Section(RCS), Frequency Selective
 Surfaces(FSS)
 Connectors – Coax, SFP/XFP, Backplane, Transitions
 Waveguide – Filters, Resonators, Transitions, Couplers
 Filters – Cavity Filters, Microstrip, Dielectric
HFSS is an interactive simulation system whose basic mesh element is a tetrahedron. This allows you to solve
any arbitrary 3D geometry, especially those with complex curves and shapes, in a fraction of the time it would
take using other techniques. The name HFSS stands for High Frequency Structure Simulator. Ansoft pioneered
the use of the Finite Element Method (FEM) for EM simulation by developing/implementing technologies such
as tangential vector finite elements, adaptive meshing, and Adaptive Lanczos-Pade Sweep (ALPS). Today, HFSS
continues to lead the industry with innovations such as Modes-to-Nodes and Full wave spice.
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5.2 MATLAB
MATLAB (matrix laboratory) is a multi-paradigm numerical computing environment and fourth generation
programming language. A proprietary programming language developed by math works, MATLAB allows
matrix manipulations, plotting of functions and data, implementation of algorithms, creation of user interfaces,
and interfacing with programs written in other languages including C,C++, JAVA ,FORTRAN and python.
Although MATLAB is intended primarily for numerical computing, an optional tool box uses the MuPAD
symbolic engine, allowing access to symbolic computing capabilities. An additional package, Simulink, adds
graphical multi-domain simulation and model-design for dynamic and embedded systems.
In 2004 MATLAB had around one million users across the industry and academia. MATLAB users come from
various backgrounds of engineering science and economics. The MATLAB application is built around the
MATLAB scripting language. Common usage of the MATLAB application involves using the command window
as an interactive mathematical shell or executing test files containing MATLAB code. MATLAB has structural
data types. Since all variables in MATLAB are arrays a more adequate name is structure array, where each
element of the array has the same field names. In addition MATLAB support dynamic field names. When creating
a MATLAB function the name of file should match the name of the first function in file. Valid function names
begins with a alphabetic character and can contain letters, numbers or underscores. MATLAB support object
oriented programming includes classes, inheritance, virtual dispatch, packages .However the syntax and calling
conventions are significantly different from other languages. MATLAB supports developing applications with
graphical user interface features .MATLAB can call functions and subroutines written in c programming language
and FORTRAN.
MATLAB is a weakly typed programming language because types are implicitly converted. It is an inferred typed
language because variables can be assigned without declaring their type except if they are to be treated as symbolic
subjects.MATLAB can be used in projects such as modelling ,energy consumption ,developing control
algorithms, analyzing weather data and running millions of simulations to pin point optimal dosing for antibiotics.
It helps in exploring and visualizing ideas and collaborate across disciplines including signal and image
processing communications, control systems and computational finance.
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CHAPTER 6
RESULTS
In this project two structures of microstrip patch antenna are presented. Both antenna has basic parameters
dielectric constant 𝜀 𝑟=4.4, operating frequency 𝑓𝑟 = 3.3 GHz, thickness of substrate h = 1.6mm.
6.1 RESULTS OF RECTANGULAR MSA
The simulated result of S11 scattering parameter (return loss) of single element rectangular microstrip antenna is
presented in figure. From the figure, the antenna has almost 3.3GHz resonant frequency and it has 0.1GHz.
Bandwidth at 10 dB (the difference of 3.2 GHz and 3.3 GHz). In percentage, the bandwidth of the antenna is
1.73%
Figure 6.1.1: return loss of rectangular MSA
The reflection coefficient (s11 parameter) is plotted as a function of frequency. For any antenna structure with
good performance the return loss should be minimum. The designed antenna resonates at the frequency of 3.3GHz
with a return loss of 10.5dB.
H-Shaped Slot for Bandwidth Enhancement of Rectangular Microstrip patch antenna 40
Department of Electronics and Communication Engineering 2016
The 3 dimensional radiation pattern of microstrip patch antenna resonating at frequency of 3.3GHz is shown in
figure 6.1.2
Figure: 6.1.2: 3 Dimensional radiation pattern
Figure: 6.1.3: 2 Dimensional radiation pattern
The radiation pattern is determined in the far field region and is usually represented with spherical coordinate
system.
H-Shaped Slot for Bandwidth Enhancement of Rectangular Microstrip patch antenna 41
Department of Electronics and Communication Engineering 2016
6.2 RESULTS OF INSET FED RECTANGULAR MSA
The figure 6.2.1 shows the return loss of rectangular MSA with inset feed. The designed antenna resonates at a
frequency of 3.3 GHz with a return loss of 15.9dB.
Figure 6.2.1: Return loss of inset fed rectangular MSA
From the figure the designed antenna has a bandwidth of 0.4GHz at 10dB (difference of 3.2GHz and 3.6GHz).in
percentage the bandwidth of antenna is 12.12%.
Figure 6.2.2: 3 dimensional radiation pattern of rectangular MSA
1.00 2.00 3.00 4.00 5.00 6.00
Freq [GHz]
-16.00
-14.00
-12.00
-10.00
-8.00
-6.00
-4.00
-2.00
0.00
dB(S(1,1))
HFSSDesign1XY Plot 1 ANSOFT
m1
m2
m3
Curve Info
dB(S(1,1))
Setup1 : Sweep
Name X Y
m1 3.3889 -15.9207
m2 3.2778 -11.2545
m3 3.6667 -10.1310
H-Shaped Slot for Bandwidth Enhancement of Rectangular Microstrip patch antenna 42
Department of Electronics and Communication Engineering 2016
The radiation pattern is the representation of radiation properties of antenna in spatial coordinates. Directivity is
how much an antenna concentrates energy in one direction in preference to radiation in other directions.
Figure 6.2.3: 2 dimensional radiation pattern
6.3 RESULTS OF H-SHAPED RECTANGULAR MSA
The first important parameter which is helpful to calculate the bandwidth of the antenna structure is its s11
parameter or return loss curve. The simulated result of S11 scattering parameter of single element H-shaped
microstrip antenna is presented in figure 6.3.1. From the figure, the antenna has almost 3.3GHz resonant
frequency and it has 0.22GHz bandwidth at 10 dB (the difference of 3.444 GHz and 3.222 GHz). In percentage,
the bandwidth of the antenna is 6.7%. . So by using H-shaped MSA instead of rectangular MSA bandwidth
improvement of 5% is obtained. Return loss at different locations on the patch is compared and a point where
return loss is most (RL) negative is selected as a feed point.
H-Shaped Slot for Bandwidth Enhancement of Rectangular Microstrip patch antenna 43
Department of Electronics and Communication Engineering 2016
The return loss of H shaped MSA is as shown in figure 6.3.1
Figure 6.3.1: Return loss of H shaped rectangular MSA
Figure 6.3.2: 3 dimensional radiation pattern of H shaped rectangular MSA
H-Shaped Slot for Bandwidth Enhancement of Rectangular Microstrip patch antenna 44
Department of Electronics and Communication Engineering 2016
6.4 RESULTS OF INSET FED H-SHAPED RECTANGULAR MSA
The return loss is a parameter which indicates the amount of power that is lost to the load and does not return as
a reflection. Waves are reflected leading to the formation of standing waves, when the transmitter and the antenna
impedance do not match.
Figure 6.4.1: return loss of H shaped inset fed rectangular MSA
The simulated result of S11 scattering parameter of single element H-shaped microstrip antenna with inset feed
is presented in figure 6.4.1. From the figure, the antenna has almost 3.3GHz resonant frequency and it has 0.5GHz
bandwidth at 10 dB (the difference of 3.722 GHz and 3.222 GHz). In percentage, the bandwidth of the antenna is
15%. In last section rectangular MSA presented with FR4 epoxy substrate and thickness h=1.6mm and got return
loss bandwidth 12%. In slot cut H-shaped MSA with same substrate presented and got 15% bandwidth. So by
using H-shaped MSA instead of rectangular MSA bandwidth improvement of 20% is obtained
H-Shaped Slot for Bandwidth Enhancement of Rectangular Microstrip patch antenna 45
Department of Electronics and Communication Engineering 2016
The 3 dimensional radiation pattern of H shaped MSA with resonating frequency 3.3 GHz is as shown in figure
6.4.2.
Figure 6.4.2: 3 dimensional radiation pattern of H shaped rectangular MSA with inset feed
Figure 6.4.3: 2dimensional radiation pattern of H shaped MSA with inset feed
H-Shaped Slot for Bandwidth Enhancement of Rectangular Microstrip patch antenna 46
Department of Electronics and Communication Engineering 2016
6.5 COMPARISION OF RECTANGULAR MSA AND H-SHAPED MSA
In this project two designs of rectangular MSA is presented. The two design differ by the type of feeding
technique used. The rectangular MSA presented with FR4 epoxy substrate and thickness h=1.6mm with
microstrip feeding has got a return loss bandwidth of 1.7%. In slot cut H-shaped MSA with same substrate
presented got a return loss bandwidth of 6.7%. So by using H-shaped MSA instead of rectangular MSA the
bandwidth gets improved.
ANTENNA TYPE
PROPERTIES
RECTANGULAR MSA H SHAPED MSA
RESONANT FREQUENCY 3.3 GHz 3.311GHz
BANDWIDTH GHz 0.1 GHz 0.2 GHz
PERCENTAGE
BANDWIDTH 1.7% 6.7%
RETURN LOSS 10.58dB 11.21dB
Table 6.5.1: Comparison between rectangular and H shaped MSA with microstrip feed
In the second design inset feeding is introduced instead of microstrip feeding. The rectangular MSA presented
with FR4 epoxy substrate and thickness h=1.6mm with inset feeding has got a return loss bandwidth of 11.5%.
The same substrate with slot cut H shaped MSA will give a return loss bandwidth of 15%. It is thus inferred that
inset feeding provides enhanced bandwidth compared to that of microstrip feeding.
ANTENNA TYPE
PROPERTIES
RECTANGULAR MSA H SHAPED MSA
RESONANT FREQUENCY 3.38 GHz 3.38GHz
BANDWIDTH GHz 0.4 GHz 0.5 GHz
PERCENTAGE
BANDWIDTH 12% 15%
RETURN LOSS 15.92dB 18.76dB
Table 6.5.2: Comparison between rectangular MSA and H shaped MSA with inset feed
H-Shaped Slot for Bandwidth Enhancement of Rectangular Microstrip patch antenna 47
Department of Electronics and Communication Engineering 2016
CONCLUSION
The work presented focused on designing and simulating microstrip patch antenna operating in 3.3GHz frequency
range, which would be suitable for mobile application. , In this project basics of microstrip patch antenna and its
bandwidth improvement using h shaped patch were studied in detail. Two aspects of microstrip antennas have
been studied. The first aspect is the design of typical rectangular microstrip antenna and the second is the design
of slot cut H-shaped microstrip antenna. A simple microstrip line type feed mechanism with quarter wavelength
Long Branch line used to energized patch. In the second design inset feeding mechanism is used to energize the
patch. Bandwidth of these two designs were improved using H shaped patch. The main concern is to study the
bandwidth improvement of the microstrip antenna. Rectangular microstrip antenna and H-shaped microstrip
antenna have been designed and simulated using high frequency structure simulator (HFSS). H-shaped microstrip
antenna produced reduction in size and higher bandwidth in comparison to rectangular microstrip antenna. Inset
feeding technique has an improved bandwidth, gain and other parameters compared to that of microstrip feeding.
H-Shaped Slot for Bandwidth Enhancement of Rectangular Microstrip patch antenna 48
Department of Electronics and Communication Engineering 2016
REFERENCES
[1] “Bandwidth Enhancement of Probe Fed Microstrip Patch Antenna”. International Journal of
Electronics Communication and Computer Technology (IJECCT) Volume 3 Issue 1 (January
2013).ISSN:2249-7838. Parminder Singh, Anjali Chandel ,Divya Naina.
[2] “Designing of Bandwidth Improved ‘H’ Shaped Microstrip Patch Antenna for Bluetooth
Applications Using Ansoft HFSS”.International Journal of Science and Research
Volume 3 Issue 4 2014(IJSR) Chaitali. J. Ingale1, Anand. K. Pathrikar.
[3] “Design and Analysis of Dual-Band Ψ- Shaped Microstrip Patch Antenna”. International
Journal of Advances in Engineering & Technology. (IJAET).Volume 6 Issue 1 March 2013
ISSN: 2231-1963 Diwakar Singh, Amit Kumar Gupta, R. K. Prasad.
[4] “Design and Analysis of Dual Frequency Band E-Shaped Microstrip Patch Antenna”.
Conference on Advances in Communication and Control Systems 2013(CAC2S 2013)
R. K. Prasad, Amit Kumar Gupta, Dr. J. P. Saini, Dr. D. K. Srivastava.
[5] “A Parametric Study on Microstrip Patch Antenna”. .International journal of Electronics and
Communication Technology .Volume 6 Issue1 January 2015 ISSN: 2230-7109.
A. Bhattacharya, B.N Biswas
[6] “Parametric Performance Analysis of Patch Antenna using EBG Substrate.” International
Journal of Wireless & Mobile networks (IJWMN) Volume 4, Issue 5 October 2012
MS. Nargis Aktar, Muhammad Shahin Uddin
[7] “Size Reduction and Bandwidth Enhancement of Rectangular Printed Antenna using Triple
Narrow Slits for Wireless Communication System and Microwave X-Band Applications”.
International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622
H-Shaped Slot for Bandwidth Enhancement of Rectangular Microstrip patch antenna 49
Department of Electronics and Communication Engineering 2016
Volume 2, Issue 5, October 2012.Vivekkumar yadaw,Sudipta das,S.M maidur rahaman
[8] “Parametric Study of the Rectangular Microstrip Antenna using Cavity Model”. Journal of
Engineering and Development, Volume 10, Issue 2, June 2006 ISSN: 1813-7822 Prof. Dr.
Jamal W. Salman, Lect. Star O. Hassan
[9] “Microstrip Antennas” IEEE proceedings, Volume 80, Issue 1, 1992, pp.79-91.David M.Pozar.
[10] “Parametric Study for Rectangular Microstrip Patch Antennas”IOSR Journal of Electronics
And Communication Engineering (IOSR-JECE) ISSN: 2278-8735 Volume5, Issue 2, April
2013 S.S. Yavalkar, R. T. Dahatonde, Dr. S. S. Rathod, Dr. S. B. Deosrkar
[11] “Performance Analysis of Rectangular Patch Antenna for Different Substrate Heights”.
International Journal of Innovative Research in Electrical, Electronics, Instrumentation and
Control Engineering Volume 2, Issue 1,January 2014 ISSN:2321-5526 Vivek Hanumante,
Panchatapa Bhattacharjee, Sahadev Roy, Pinaki Chakraborty.
[12] Balanis,C.A.(2005).Antenna Theory Analysis and Design, Third edition, Johan Wiley &
Sons.ISBN 0-471-66782-X.
[13] http://www.antenna-theory.com/definitions/permitivity.php
[14] www.mathworks.com
H-Shaped Slot for Bandwidth Enhancement of Rectangular Microstrip patch antenna 50
Department of Electronics and Communication Engineering 2016
APPENDIX A
HFSS ANSOFT 13.1
A.1 Introduction
HFSS is a high-performance full-wave electromagnetic (EM) field simulator for arbitrary 3D volumetric passive
device modeling that takes advantage of the familiar Microsoft Windows graphical user interface. It integrates
simulation, visualization, solid modeling, and automation in an easy-to-learn environment where solutions to the
3D EM problems are quickly and accurately obtained. Ansoft HFSS employs the Finite Element Method (FEM),
adaptive meshing, and brilliant graphics to give you unparalleled performance and insight to all of 3D EM
problems. Ansoft HFSS can be used to calculate parameters such as S Parameters, Resonant Frequency, and
Fields. HFSS is an interactive simulation system whose basic mesh element is a tetrahedron. This allows you to
solve any arbitrary 3D geometry, especially those with complex curves and shapes,in a fraction of the time it
would take using other techniques. The name HFSS stands for High Frequency Structure Simulator. Ansoft
pioneered the use of the Finite Element Method (FEM) for EM simulation by developing/implementing
technologies such as tangential vector finite elements, adaptive meshing, and Adaptive Lanczos-Pade Sweep
(ALPS). Today, HFSS continues to lead the industry with innovations such as Modes-to-Nodes and Full wave
space.
A.1.1 Flow chart for designing in HFSS
The flow chart for designing the antenna in HFSS is as depicted below. It consists of seven steps namely
calculating dimensions of antenna using the derived formulas, creating a model in HFSS by opening a project and
the dimensions are entered and the model is created. Then the analysis of model in various parameters is done,
like the return loss, radiation pattern (both in 2D and 3D), VSWR, gain and any other required parameters are
analyzed and results are stimulated.
The return loss is a parameter which indicates the amount of power that is lost to the load and does not return as
a reflection. The VSWR is basically a measure of the impedance mismatch between the transmitter and the
antenna. Antenna gain is a parameter which is closely related to the directivity of the antenna .The radiation
pattern is the representation of radiation properties of antenna in a spatial coordinates. If the simulated results of
the parameters are as per the requirement then fabrication of antenna can be performed and testing can be done.
H-Shaped Slot for Bandwidth Enhancement of Rectangular Microstrip patch antenna 51
Department of Electronics and Communication Engineering 2016
Flow chart for designing an antenna
A.1.2 Simulation Workflow
After starting ANSOFT HFSS, choose to create a new HFSS project. Select a template for a structure which is
closest to the device of interest that is a three dimensional rectangular box in the spatial coordinate for designing
a substrate of a microstrip rectangular patch antenna
 To depict a substrate press the 3D box and drag the mouse to draw it in the spatial coordinate window
 The box is named as substrate and then select the material as FR4 epoxy by double clicking the substrate.
 Give the dimensions of the substrate by entering it in another window. The position X size (length), Y
size (width), Z size (height) is to be entered.
 The command ctrl-d can be used to fit the box in the window.
H-Shaped Slot for Bandwidth Enhancement of Rectangular Microstrip patch antenna 52
Department of Electronics and Communication Engineering 2016
Substrate in HFSS window
Designing the ground
Ground in HFSS window
 To design the ground 2D box is to be created and the name is to be changed for easy identification
 Repeats the steps as that for substrate
H-Shaped Slot for Bandwidth Enhancement of Rectangular Microstrip patch antenna 53
Department of Electronics and Communication Engineering 2016
Designing the patch and feed line
Patch and feed line
 The patch and the feed dimensions are entered and the impedance is matched of feed.
 Unite the material of both patch and the feed line using the unite option and pressing the ctrl and
selecting the both patch and the feed.
Designing the port
 To draw the port the drawing plane is changed from XY to YZ plane. Then the dimensions are
entered as above.
Defining boundary and excitations
 The patch is assigned a perfect electric boundary that is named as perfect E1.
 The port is chosen to be lumped port since it is a transmission line model.
 The impedance of the port is matched to 50Ω. The option new line is selected and then click
finish after assigning a new line in the port.
H-Shaped Slot for Bandwidth Enhancement of Rectangular Microstrip patch antenna 54
Department of Electronics and Communication Engineering 2016
Anechoic chamber
 For analysis the designed antenna is placed in a chamber so that the radiation of the antenna is confined
within the chamber.
 Set the radiation boundary for the chamber.
Analysis of the antenna
 Insert the far field radiation as infinite sphere and select the radiation range of angle from 0 to 360
degree.
 Add solution sweep and set the required solution frequency that is the central frequency at which the
antenna must be radiated.
 Select the setups 1 created and add the frequency sweep. The sweep type is set as fast and the linear
sweep is set as count.
 The validation check box should show all parameters marked right.
Results
 To obtain the results select option analyze all.
 The return loss plot is created by creating model rectangular plot.
 The radiation pattern in both 2D and 3D can be obtained using the option create far field option.
A.2 MODELS IN HFSS WINDOW
Rectangular microstrip patch antenna
H-Shaped Slot for Bandwidth Enhancement of Rectangular Microstrip patch antenna 55
Department of Electronics and Communication Engineering 2016
Microstrip patch antenna using inset feed
Rectangular microstrip patch antenna using h shaped patch
H-Shaped Slot for Bandwidth Enhancement of Rectangular Microstrip patch antenna 56
Department of Electronics and Communication Engineering 2016
Rectangular microstrip patch antenna using h shaped patch with inset feed
H-Shaped Slot for Bandwidth Enhancement of Rectangular Microstrip patch antenna 57
Department of Electronics and Communication Engineering 2016
APPENDIX B
MATLAB CODES
B.1 PROGRAM FOR FINDING LENGTH AND WIDTH OF THE PATCH
%Program to calculate the parameters to design a rectangular patch antenna
%the user have to feed the values of frequency, dielectric constant, and
%height of the dielectric.
%the program will calculate automatically the width and length of the patch
function Antcal()
%This function is to be used to calculate the different parameters of a rectangular patch
antenna
clc;
fo=input('Enter frequency of operation (fo) inGHz');
Er=input('Enter Dielectric constant (Er)');
h=input('Enter height of substrate (h) in mm');
W=(3*10^8)/(2*fo*sqrt((Er+1)/2))
Eref=(Er+1)/2+((Er-1)/2)/(sqrt(1+12*h/W))
Lef=(3*10^8)/(2*fo*sqrt(Eref))
dL=((0.412*h)*(Eref+0.3)*(W/h+0.264))/((Eref-0.258)*(W/h+0.8))
L=Lef-2*dL
Lg=6*h+L
Wg=6*h+W
end
B.2 PROGRAM TO PLOT THE RADIATION PATTERN OF MSA
clc;
close all;
clear all;
theta=0:1:360;
phi=0:1:360;
freq=3.3;
h=1.6;
w=21.42;
l=27.8;
lambda=30/freq;
k=(2*pi)/lambda;
x=(k*w*sin(theta)*sin(phi)')/2;
y=cos((k*l)/2*sin(theta)*cos(phi)');
et=(sin(x)/x)*y*cos(phi);
ep=-(sin(x)/x)*y*cos(theta);
t = 0:1:360;
polar(t,et.*ep,'--b');
H-Shaped Slot for Bandwidth Enhancement of Rectangular Microstrip patch antenna 58
Department of Electronics and Communication Engineering 2016
B.3 RESULTS OF MATLAB SIMULATION
RESULT OF PROGRAM FOR FINDING WIDTH AND LENGTH OF THE PATCH
Figure 6.5.1: matlab result for antenna parameters
RESULT OF PROGRAM FOR RADIATION PATTERN
Figure 6.5.2: matlab result for radiation pattern

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  • 1. H-Shaped Slot for Bandwidth Enhancement of Rectangular Microstrip patch antenna 1 Department of Electronics and Communication Engineering 2016 CHAPTER 1 INTRODUCTION The need for antennas to cover very wide bandwidth is of continuing importance, particularly in the field of electronic warfare and wideband radar and measuring system. Although microstrip patch antennas have many very desirable features, they generally suffer from limited bandwidth. So the most important disadvantage of microstrip resonator antenna is their narrow bandwidth. To overcome this problem without disturbing their principal advantage (such as simple printed circuit structure, planar profile, light weight and cheapness), a number of methods and structures have been investigated recently. In this regard we can mention multilayer structures, broad folded flat dipoles, curved line and spiral antennas, impedance matched resonator antennas, resonator antennas with capacitive coupled parasitic patch element, log periodic structures, modified shaped patch antenna (H-shaped). In this project H-shaped microstrip patch antenna is analyzed and compared with rectangular patch antenna. Figure 1.1: Microstrip Patch Antennas The H-shaped patch antenna here has a size about half of the rectangular patch antenna with larger bandwidth. The larger bandwidth is because of a reduction in the quality factor (Q). Figure 1.1 shows a rectangular microstrip patch antenna of length L, width W resting on a substrate of height h. The co-ordinate axis is selected such that the length is along the x direction, width is along the y direction and the height is along the z direction.
  • 2. H-Shaped Slot for Bandwidth Enhancement of Rectangular Microstrip patch antenna 2 Department of Electronics and Communication Engineering 2016 CHAPTER 2 LITERATURE SURVEY 2.1 Bandwidth Enhancement of Probe Fed Microstrip Patch Antenna Authors: Parminder Singh, Anjali Chandel, Divya Naina This paper deals with different techniques for bandwidth enhancement of conventional rectangular microstrip antenna. By increasing the height of patch, increasing the substrate thickness and decreasing the permittivity of substrate the percentage bandwidth is increased. HFSS Software is used for the simulation and design calculation of microstrip patch antenna. The return loss, VSWR curve, directivity and gain are evaluated. Measured simulation results show that by increasing the height of patch bandwidth is enhanced by 50-60%, by decreasing the substrate permittivity the bandwidth is enhanced by 5-10% and by increasing substrate thickness bandwidth is enhanced by 15-20%. 2.2 Designing of Bandwidth Improved ‘H’ Shaped Microstrip Patch Antenna for Bluetooth applications using Ansoft HFSS Authors: Chaitali. J. Ingale1, Anand. K. Pathrikar This paper represents the designing of 2.4 GHz H shaped microstrip patch antenna using electromagnetic simulation software. The model is designed and simulated in Ansoft HFSS v.13. Microstrip is a type of electrical transmission line which can be fabricated using PCB, which convey microwave frequency signals. For good performance of antenna, a thick dielectric substrate with low dielectric constant is desirable. This provides larger band width, better efficiency and better radiation. The models that are used for analysis of Microstrip patch antenna are transmission line model, cavity model and full wave model. HFSS is a high performance full- wave electromagnetic field simulator for arbitrary 3D volumetric passive device modeling, which takes advantage of the familiar Microsoft Windows graphical user interface. HFSS stands for High Frequency Structure Simulator. Ansoft pioneered the use of the Finite Element Method for EM simulation, which integrates simulation, visualization, solid modeling and automaton in an easy-to-learn environment. Ansoft HFSS can be used to calculate parameters such as S Parameters, Resonant Frequency and Fields.
  • 3. H-Shaped Slot for Bandwidth Enhancement of Rectangular Microstrip patch antenna 3 Department of Electronics and Communication Engineering 2016 2.3 Design and Analysis of Dual-Band Ψ- Shaped Microstrip Patch Antenna Authors: Diwakar Singh, Amit Kumar Gupta, R. K. Prasad This paper considers a conventional rectangular microstrip patch antenna and ψ shape antenna designed by cutting four notches in a rectangular microstrip patch antenna. The designed antenna structure is further simulated by IE3D simulation software. The simulation results are obtained in terms of bandwidth, gain, directivity and efficiency. The result shows that the designed antenna is suitable to work in two different frequency bands with a good amount of gain and efficiency. This paper helps to study about microstrip patch antenna and how to improve the bandwidth and gain. An antenna is generally a metallic object capable of transmitting and receiving radio waves. Antenna acts like a resonant circuit which converts electrostatic energy into electromagnetic energy and vice versa. An antenna is one of the basic and most important requirements of any wireless communication system. The reduced size microstrip patch antenna is a good alternative and is widely used for scaling the devices used in wireless communication system.  Different patch structures such as E shaped, H shaped, W shaped etc. are used for improved bandwidth of the antenna.  Cutting notches and slots in conventional rectangular patch geometry also improves the antenna bandwidth and gain.  The usage of antenna array and the antenna having stacked configuration also provides good amount of improvement in bandwidth and gain. In this paper the antenna structure is designed considering FR4 type material specifically glass epoxy as a substrate. 2.4 Design and Analysis of Dual Frequency Band E-Shaped Microstrip Patch Antenna Authors: R. K. Prasad, Amit Kumar Gupta, Dr. J. P. Saini, Dr. D. K. Srivastava This paper emphasizes on the designing and analysis of an E-shaped microstrip patch antenna. In multiple applications the antenna operates in more than one frequency bands. For this purpose MoM based simulation software IE3D simulation software ver.15.2 is used. The result shows analysis of antenna performance in terms of S11 parameter or return loss curve, VSWR, Gain, Directivity etc.  Analysis of S11 parameter show that antenna structure work in two different frequency bands.  VSWR should be below 2dB for the entire frequency range in which antenna has to operate.  Designed antenna provides a gain of 3.6024dB which is useful for many applications.  Designed antenna structure has a directivity of 3.97701 dB.  The designed antenna has an efficiency of about 88.4522% at 1.37528 GHz.
  • 4. H-Shaped Slot for Bandwidth Enhancement of Rectangular Microstrip patch antenna 4 Department of Electronics and Communication Engineering 2016 Advantages of microstrip antenna are:  Used in devices which are smaller in size and moving.  Microstrip Antennas are simple.  Cost effective. The E shape is designed by cutting two notches in rectangular patch antenna. FR4 material is used for the antenna structure. Co-axial probe feeding is used for feeding purpose. 2.5 A Parametric Study on Microstrip Patch Antenna Authors: A. Bhattacharya, B. N. Biswas Choice of substrate with higher dielectric constant improves both amplitude and frequency stability of the patch though substrate with lower dielectric constant is preferred for radiation efficiency. A microstrip patch designed with a substrate having ε =2.2 and h=3.2 mm gives 400MHz bandwidth at 5.25 GHz while a patch having ε =2.2 and h=0.787 mm gives 212 MHz bandwidth at 9.65GHz. The patch with ε=2.2 and h=3.2 mm designed to oscillate at 5.6 GHz oscillates at 5.25 GHz but a microstrip patch designed with a substrate having ε =2.2 and h=0.787 mm oscillates at 9.046GHz whose design frequency was 9.0 GHz. Thus, a substrate with greater thickness enhances bandwidth, but affects resonance frequency of oscillation. Even a patch designed with proper choice of key parameters may resonate with a frequency different from designed one. Thus it is seen that the percentage uncertainty in resonant frequency is less pronounced if a material of low dielectric constant and also lower substrate thickness is chosen. Thick, low dielectric constant substrates are required to enhance microstrip antenna efficiency but thin, high dielectric constant substrates are preferred for active antenna operation .In an active patch, due to its low dc to RF conversion efficiency heat is produced within the patch element. 2.6 Parametric Performance Analysis of Patch Antenna using EBG Substrate Authors: MS. Nargis Aktar, Muhammad Shahin Uddin Electromagnetic Band Gap (EBG) substrate is used as a part of antenna structure to improve the performance of the patch antenna. Usually, the performance of a patch antenna depends on the parameters such as Return Loss (RL), Bandwidth (BW), Gain, and Directivity. The return loss of the antenna with EBG structure is less compared to the conventional antenna. It is also seen that when the EBG patch width increases than the return loss also increases. Therefore, the antenna performance is better than the conventional antenna because the return loss is reduced for the EBG structure the bandwidth of the antenna with EBG structure is higher than the conventional antenna. Therefore, the performance of the antenna with EBG structure is better than the conventional antenna
  • 5. H-Shaped Slot for Bandwidth Enhancement of Rectangular Microstrip patch antenna 5 Department of Electronics and Communication Engineering 2016 because the bandwidth is increased for the EBG structure. The gain is increasing with the EBG patch width from 0.08 to 0.1 and then the middle part the gain is almost constant. After that EBG patch width from 0.12, the gain is decreasing in nature with the increasing EBG patch width. 2.7 Size Reduction and Bandwidth Enhancement of Rectangular Printed Antenna using Triple Narrow Slits for Wireless Communication System and Microwave X-Band Application Authors: Vivekkumar Yadaw, Sudipta Das, S.M Maidur Rahman The microstrip patch antenna is preferred for wireless system RF applications, mobile, satellite and wireless communication system. Due to the  Low cost and compact design.  Small size.  Light weight.  Low cost on mass production.  Low profile.  Easy integration with other components. This paper convey about the reduced size antenna with enhanced band width. The introduction of slits at the edges of Rectangular patch reduce the antenna size by 44%. Bandwidth of antenna is enhanced up to 13.78%. Resonant frequency is reduced by the method of cutting unequal narrow slits at the edges of the patch. Also the broad band-width is achieved, about 8.44-9.69 GHz. The proposed antenna has a broad band which is used for Microwave X-band application. Feeding is done using coaxial feeding. The simulation and design is done by the method of moment based EM Simulator IE3D. 2.8 Parametric Study of the Rectangular Microstrip Antenna using Cavity Model. Authors: Prof. Dr. Jamal W. Salman, Lect. Star O. Hassan The advantage of the cavity model is that it has faster speed of computation and reasonably good accuracy. However, the disadvantages are that the antenna should be symmetrical with respect to the feed-axis and the variation along the width should be small. In order to design a RMSA operating at high efficiency with broader bandwidth and higher gain, it’s desirable to use a material with lower dielectric substrate permittivity, and thicker substrate of higher losses. In addition the width of the patch must be as large as possible for a given frequency to increase its radiation power.
  • 6. H-Shaped Slot for Bandwidth Enhancement of Rectangular Microstrip patch antenna 6 Department of Electronics and Communication Engineering 2016 2.9 Bandwidth improvement of Microstrip Patch Antenna Using H- shaped Patch Authors: Sudhir Bhaskar, Sachin Kumar Gupta This paper covers two aspects of microstrip antenna design. The first aspect is the design of typical rectangular microstrip patch antenna. The second is the analysis and design of slot cut H shaped microstrip antenna. The transmission line model is used for analysis. The H shaped patch antenna has got half the size of that of the typical rectangular patch antenna. The H shaped microstrip antenna produced reduction in size and higher bandwidth in comparison to the rectangular microstrip antenna 2.10 Parametric Study for Rectangular Microstrip Patch Antennas Authors: S. Yavalkar, R. T. Dahatonde, Dr. S. S. Rathod, Dr. S. B. Deosrkar It was observed that, to increase resonance frequency height loss tangent is to be increased whereas width and εr to be decreases. For increasing bandwidth, height is to be increased whereas width, ε, loss tangent is to be decreased. It is found that lesser the loss tangent less the loss in probe giving the wider bandwidth. With an increase in W from 43.5 mm to 44.5 mm, the following effects are observed:  The resonance frequency decreases from 1.64 GHz to 1.57 GHz due to the increase in ΔL and εr.  The bandwidth of the antenna increases; however, it is not very evident from the plots, because the feed point is not optimum for the different widths. Accordingly, a better comparison will be obtained when the feed point is optimized for the individual widths 2.11 Performance Analysis of Rectangular Patch Antenna for Different Substrate Heights Authors: Vivek Hanumante, Panchatapa Bhattacharjee, Sahadev Roy, Pinaki Chakraborty Increasing the height of the dielectric substrate is advantageous in increasing the bandwidth of microstrip antenna, which is desirable in compact antenna application. However increasing height of the dielectric substrate also results in expansion of the size of antenna, increased return loss and VSWR. But substrate with greater height can be used to achieve better directivity. The simulation results of this paper showed that with increase in height of dielectric substrate the resonance frequency shifts towards the desired operating frequency. Gain increases with the increase in the height of dielectric substrate. Increase in bandwidth could be understood with the concept that more height acquired in space results in to increased bandwidth, but further increase in height results in decrease in bandwidth as more height allows surface waves to travel within the substrate.
  • 7. H-Shaped Slot for Bandwidth Enhancement of Rectangular Microstrip patch antenna 7 Department of Electronics and Communication Engineering 2016 CHAPTER 3 ANTENNA THEORY 3.1 Antenna Definition An antenna is a transducer between a guided wave and a radiated wave, or vice versa. The structure that “guides” the energy to the antenna is most evident as a coaxial cable attached to the antenna. The radiated energy is characterized by the antenna’s radiation pattern. Antennas are a very important component of communication systems. By definition, an antenna is a device used to transform an RF signal, traveling on a conductor, into an electromagnetic wave in free space. An antenna is a device for converting electromagnetic radiation in space into electrical currents in conductors or vice-versa, depending on whether it is being used for receiving or for transmitting, respectively. Passive radio telescopes are receiving antennas. It is usually easier to calculate the properties of transmitting antennas. Fortunately, most characteristics of a transmitting antenna (e.g., its radiation pattern) are unchanged when the antenna is used for receiving. Antenna is a metallic device (as a rod or wire) for radiating or receiving radio waves. It is a circuit element that provides a transition from a guided wave on a transmission line to a free space wave. It also provides for the collection of electromagnetic energy. A transmitting antenna connected to a transmitter by a transmission line, forces electromagnetic waves into free space which travel in space with velocity of light. Similarly a receiving antenna connected to a radio receiver, receives or intercepts a portion of electromagnetic waves travelling through space. The guiding device or transmission line may take the form of a coaxial line or a hollow pipe (waveguide), and it is used to transport electromagnetic energy from the transmitting source to the antenna or from the antenna to the receiver. Figure 3.1.1:Transition region between guided wave and free space wave
  • 8. H-Shaped Slot for Bandwidth Enhancement of Rectangular Microstrip patch antenna 8 Department of Electronics and Communication Engineering 2016 An antenna radiates by changing the flow of current inside a conduction wire. By time-varying the current in a straight wire. If there is no motion of flow or if the flow of current is uniform, the straight wire will not radiate. If we bend the wire, even with uniform velocity, the curve along the wire will create an acceleration in the current flow and the wire will therefore radiate. In above figure, see a radiating antenna. Antennas are of different shapes via, dipoles, helices, paraboloids, stubs, whips etc. The shape of an antenna is an important aspect that determines its radiation pattern. Antennas are characterized by a number of key parameters, including bandwidth, beamwidth, directivity, efficiency, gain, polarization, radiation pattern and voltage standing wave ratio (VSWR). Figure 3.1.2: Schematic of an antenna system Antenna is a passive device, it does not amplify the signals and it only directs the signal energy in a particular direction in reference with isotropic antenna. Antennas demonstrate a property known as reciprocity, which means that an antenna will maintain the same characteristics regardless if it is transmitting or receiving. Most antennas are resonant devices, which operate efficiently over a relatively narrow frequency band. An antenna must be tuned to the same frequency band of the radio system to which it is connected, otherwise the reception and the transmission will be Impaired. When a signal is fed into an antenna, the antenna will emit radiation distributed in space in a certain way. A graphical representation of the relative distribution of the radiated power in space is called a radiation pattern. From circuital point of view antenna behaves as a one-port network; receives guided wave power and convert it to radiating waves. One can estimate the characteristics and efficiency of this conversion from radiation patterns of an antenna. On the basis of directional patterns, antenna can be classified in to two types, namely directional and Omni-directional antenna.
  • 9. H-Shaped Slot for Bandwidth Enhancement of Rectangular Microstrip patch antenna 9 Department of Electronics and Communication Engineering 2016 3.2 Fundamental Parameters of Antennas In order to describe the performance of an antenna, we use various, sometimes Interrelated, parameters. They are: 3.2.1 Radiation Pattern An antenna radiation pattern or antenna pattern is defined as a mathematical function or a graphical representation of the radiation properties of the antenna as a function of space coordinates. Radiation properties include power flux density, radiation intensity, field strength, directivity, phase, or Polarization.” Figure 3.2.1.1: Radiation pattern of a hertzian dipole. • Defined for the far-field. • As a function of directional coordinates. • There can be field patterns (magnitude of the electric or magnetic field) or power patterns (square of magnitude of the electric or magnetic field). • Often normalized with respect to their maximum value. • The power pattern is usually plotted on a logarithmic scale or more commonly in decibels (dB).
  • 10. H-Shaped Slot for Bandwidth Enhancement of Rectangular Microstrip patch antenna 10 Department of Electronics and Communication Engineering 2016 3.2.2 Radiation Pattern Lobes A radiation lobe is a portion of the radiation pattern bounded by regions of relatively weak radiation intensity. Various parts of a radiation pattern are referred to as lobes, which may be sub classified into major or main, minor, side, and back lobes.  Major Lobe (also called main beam): is defined as “the radiation lobe containing the direction of maximum radiation.”  Minor Lobe: is any lobe except a major lobe.  Side Lobe: is minor lobe adjacent to major lobe. That is “a radiation lobe in any direction other than the intended lobe.” Figure 3.2.2.1: Radiation Pattern Lobes  Back Lobe: is lobe just opposite to major lobe. That is “a radiation lobe whose axis makes an angle of approximately180◦ with respect to the beam of an antenna.” • Minor lobes usually represent radiation in undesired directions, and they should be minimized. Side lobes are normally the largest of the minor lobes. • The level of minor lobes is usually expressed as a ratio of the power density, often termed the side lobe ratio or side lobe level.
  • 11. H-Shaped Slot for Bandwidth Enhancement of Rectangular Microstrip patch antenna 11 Department of Electronics and Communication Engineering 2016 In most radar systems, low side lobe ratios are very important to minimize false target indications through the side lobes (e.g., -30 dB). Figure 3.2.2.2:radiation lobe The radiation pattern of most antennas show a pattern of lobes at various angles,directions where the radiated signal strength reaches a maximum, separated by nulls, angles at which the radiation falls to zero. In a directional antenna in which theobjective is to emit the radio wave in one direction, the lobe in that direction is designed to be bigger (have higher field strength) than the others, this is the main lobe. The other lobes are called side lobes, and usually represent unwanted radiation in undesired directions. The side lobe in the opposite directions from the main lobe is called the back lobe.the radiation pattern refered to above is usually the horizontal radiation pattern,which is plotted as a function of azimuth about the antenna, although the vertical radiation pattern may also have a main lobe. The beam width of the antenna is the width of the main lobe, usually specified by the half power beamwidth,the angle encompassed between the points on the side of the lobe where the power has fallen to half (that is -3dB of its maximum value). the concepts of main lobe and side lobe also applied to acoustics and optics and are used to describe the radiation pattern of optical systems like telescopes and acoustic transducers like loud speakers and microphones. The main beam is the region around the direction of maximum radiation (usually the region that is within 3dB of the peak of the main beam).
  • 12. H-Shaped Slot for Bandwidth Enhancement of Rectangular Microstrip patch antenna 12 Department of Electronics and Communication Engineering 2016 Planes associated with an antenna: E Plane: Plane contains the electric field vector and direction of maximum radiation. H Plane: Plane contains the magnetic field vector and direction of maximum radiation. 3.2.3 Beamwidth Associated with the pattern of an antenna is a parameter designated as beamwidth. The beamwidth of a pattern is defined as the angular separation between two identical points on opposite sides of the pattern maximum. • The beamwidth of an antenna is a very important figure of merit and often is used as a trade-off between it and the side lobe level; that is, as the beamwidth decreases, the side lobe increases and vice versa. • The beamwidth of the antenna is also used to describe the resolution capabilities of the antenna to distinguish between two adjacent radiating sources or radar targets. Figure 3.2.3.1 beamwidths of an antenna pattern. Half-Power Beam Width (HPBW): In a plane containing the direction of the maximum of a beam, the angle between the two directions in which the radiation intensity is one-half value of the beam. First-Null Beamwidth (FNBW): Angular separation between the first nulls of the pattern.
  • 13. H-Shaped Slot for Bandwidth Enhancement of Rectangular Microstrip patch antenna 13 Department of Electronics and Communication Engineering 2016 Resolution • The most common resolution criterion states that the resolution capability of an antenna to distinguish between two sources is equal to half the first-null beamwidth (FNBW/2), which is usually used to approximate the HPBW. • That is, two sources separated by angular distances equal or greater than FNBW/2 ¼ HPBW of an antenna with a uniform distribution can be resolved. • If the separation is smaller, then the antenna will tend to smooth the angular separation distance. Figure 3.2.3.2: (a) Three dimensional (b) Two dimensional Three- and two-dimensional power patterns (in linear scale) of U (θ) =cos2 (θ) cos2 (3θ). 3.2.4 Radiation resistance Radiation resistance is that part of an antenna's feed point resistance that is caused by the radiation of electromagnetic waves from the antenna, as opposed to loss resistance (also called ohmic resistance) which generally causes the antenna to heat up. Radiation resistance varies at different points on the antenna. This resistance is always measured at a current loop. The value of radiation resistance depends on several factors: • Configuration of antenna. • The point where radiation resistance is considered. • Location of antenna with respect to ground and other objects. • Ratio of length and diameter of conductors used. 3.2.5 Voltage Standing Wave Ratio (VSWR) VSWR (Voltage Standing Wave Ratio), is a measure of how efficiently radio-frequency power is transmitted from a power source, through a transmission line, into a load (for example, from a power amplifier through a transmission line, to an antenna).The parameter VSWR is a measure that numerically describes how well the
  • 14. H-Shaped Slot for Bandwidth Enhancement of Rectangular Microstrip patch antenna 14 Department of Electronics and Communication Engineering 2016 antenna is impedance matched to the radio or transmission line it is connected to. IT is the ratio of maximum radio frequency voltage to minimum radio frequency voltage on a transmission line. It is given by: VSWR stands for Voltage Standing Wave Ratio, and is also referred to as Standing Wave Ratio (SWR). VSWR is a function of the reflection coefficient, which describes the power reflected from the antenna. If the reflection coefficient is given by , then the VSWR is defined by the following formula: The reflection coefficient is also known as s11 or return loss. The VSWR is always a real and positive number for antennas. The smaller the VSWR is, the better the antenna is matched to the transmission line and the more power is delivered to the antenna. The minimum VSWR is 1.0. In this case, no power is reflected from the antenna, which is ideal. Often antennas must satisfy a bandwidth requirement that is given in terms of VSWR. For instance, an antenna might claim to operate from 100-200 MHz with VSWR less than 3. This implies that the VSWR is less than 3.0 over the specified frequency range. This VSWR specifications also implies that the reflection coefficient is less than 0.5 (i.e., <0.5) over the quoted frequency range. 3.2.6 Input Impedance Input impedance is defined as “the impedance presented by an antenna at its terminals or the ratio of the voltage to current at a pair of terminals or the ratio of the appropriate components of the electric to magnetic fields at a point. The input impedance at a pair of terminals that are the input terminals of the antenna. ZA = RA + j XA Where Z A = antenna impedance at terminals a –b (ohms). RA = antenna resistance at terminals a –b (ohms). XA = antenna reactance at terminals a –b (ohms). In general, the resistive part of above equation consists of two components; that is, RA = Rr + RL
  • 15. H-Shaped Slot for Bandwidth Enhancement of Rectangular Microstrip patch antenna 15 Department of Electronics and Communication Engineering 2016 Rr = radiation resistance of the antenna. RL = loss resistance of the antenna. 3.2.7 Gain Gain of an antenna (in a given direction) is defined as the ratio of the intensity, in a given direction, to the radiation intensity that would be obtained if the power accepted by the antenna were radiated isotropically. The radiation intensity corresponding to the isotropically radiated power is equal to the power accepted (input) by the antenna divided by 4π. In most cases we deal with relative gain, which is defined as the ratio of the power gain in a given direction to the power gain of a reference antenna in its referenced direction. The power input must be the same for both antennas. The reference antenna is usually a dipole, horn, or any other antenna whose gain can be calculated or it is known. In most cases, however, the reference antenna is a lossless isotropic source. Thus When the direction is not stated, the power gain is usually taken in the direction of maximum radiation. The total radiated power (Prad) is related to the total input power (Pin) by Prad = ecdPin Where ecd is the antenna radiation efficiency (dimensionless). • The gain of the antenna is closely related to the directivity. • In addition to the directional capabilities it accounts for the efficiency of the antenna. • Gain does not account for losses arising from impedance mismatches (reflection losses) and polarization mismatches (losses). 3.2.8 Directivity Directivity is the ratio of the radiation intensity in a given direction from the antenna to the radiation intensity averaged over all directions. • The average radiation intensity: total power radiated by the antenna divided by 4¼. • Stated more simply, the directivity of a non-isotropic source is equal to the ratio of its radiation intensity in a given direction over that of an isotropic source.
  • 16. H-Shaped Slot for Bandwidth Enhancement of Rectangular Microstrip patch antenna 16 Department of Electronics and Communication Engineering 2016 Where D = directivity (dimensionless) U = radiation intensity (W/unit solid angle) Umax = maximum radiation intensity (W/unit solid angle) Prad = total radiated power (W) 3.2.9 Efficiency • The total antenna efficiency e0 is used to take into account losses at the input terminals and within the structure of the antenna. 𝜂 = 𝑃𝑟𝑎𝑑 𝑃𝑖𝑛 = 𝑃𝑟𝑎𝑑 𝑃𝑟𝑎𝑑 + 𝑃𝑙𝑜𝑠𝑠 = 𝑅 𝑟𝑎𝑑 𝑅 𝑟𝑎𝑑 + 𝑅𝑙𝑜𝑠𝑠 Where: η = antenna effeciency (%) 𝑃𝑟𝑎𝑑 = radiated power (W) 𝑃𝑙𝑜𝑠𝑠 = power loss due to resistive loss (W) 𝑃𝑖𝑛 = total power available to antenna (W) 𝑅 𝑟𝑎𝑑 = radiated equivalent resistance (Ω) 𝑅𝑙𝑜𝑠𝑠 = equivalent loss resistance (Ω) 𝑒0 = 𝑒 𝑟 𝑒 𝑐 𝑒 𝑑 𝑒0 is due to the combination of number of efficiencies: 𝑒0 = total efficiency, 𝑒 𝑟 = (1 − |┌|)2 𝑒 𝑟= reflection, 𝑒 𝑐= conduction efficiency 𝑒 𝑑 = dielectric efficiency,
  • 17. H-Shaped Slot for Bandwidth Enhancement of Rectangular Microstrip patch antenna 17 Department of Electronics and Communication Engineering 2016 , ┌ = voltage reflection coefficient at the input terminals of the antenna. Za= antenna input impedance. Z0 = characteristic impedance of the transmission line. VSWR = voltage standing wave ratio. 3.2.10 Bandwidth The bandwidth of an antenna is defined as the range of frequencies within which the performance of the antenna, with respect to some characteristic, conforms to a specified standard. The bandwidth can be considered to be the range of frequencies, on either side of a center frequency (usually the resonance frequency for a dipole), where the antenna characteristics (such as input impedance, pattern, beamwidth, polarization, side lobe level, gain, beam direction, radiation efficiency) are within an acceptable value of those at the center frequency. For broadband antennas, the bandwidth is usually expressed as the ratio of the upper-to-lower frequencies of acceptable operation Bandwidth can be defined in terms of radiation patterns or VSWR/reflected power. The definition used is based on VSWR. Bandwidth is often expressed in terms of percent bandwidth, because the percent bandwidth is constant relative to frequency. If bandwidth is expressed in absolute units of frequency, for example MHz, the bandwidth is then different depending upon whether the frequencies in question are near 150 MHz, 450 MHz or 825 MHz 3.3 Microstrip Antenna A microstrip patch antenna (MSA) consists of a conducting patch of any planar or non-planar geometry on one side of a dielectric substrate with a ground plane on other side. It is a popular printed resonant antenna for narrow- band microwave wireless links that require semi hemispherical coverage. Due to its planar configuration and ease of integration with microstrip technology, the microstrip patch antenna has been heavily studied and is often used
  • 18. H-Shaped Slot for Bandwidth Enhancement of Rectangular Microstrip patch antenna 18 Department of Electronics and Communication Engineering 2016 as elements for an array. A large number of microstrip patch antennas have been studied to date. An exhaustive list of the geometries along with their salient features is available. The rectangular and circular patches are the basic and most commonly used microstrip antennas. These patches are used for the simplest and the most demanding applications. Rectangular geometries are separable in nature and their analysis is also simple. The circular patch antenna has the advantage of their radiation pattern being symmetric. Sl. No Characteristic Microstrip Patch Antenna Microstrip Slot Antenna Printed Dipole antenna 1. Profile Thin Thin Thin 2. Fabrication Very easy Easy Easy 3. Polarization Both linear and circular Both linear and circular Linear 4. Dual Frequency operation Possible Possible Possible 5. Shape flexibility Any shape Mostly rectangular and circular shapes Rectangular and triangular 6. Spurious radiation Exists Exists Exists 7. Bandwidth 2-50% 5-30% -30% Table 3.3.1 Antenna Characteristic The Microstrip patch antennas are well known for their performance and their robust design, fabrication and their extent usage. The advantages of this Microstrip patch antenna are to overcome their de-merits such as easy to design, light weight etc., the applications are in the various fields such as in the medical applications, satellites and of course even in the military systems just like in the rockets, aircrafts missiles etc. the usage of the Microstrip antennas are spreading widely in all the fields and areas and now they are booming in the commercial aspects due to their low cost of the substrate material and the fabrication. It is also expected that due to the increasing usage of the patch antennas in the wide range this could take over the usage of the conventional antennas for the maximum applications. There is a number of techniques available for analyzing microstrip patch antennas. The analytical techniques include transmission line model and cavity model. The most common numerical techniques used are moment method and the finite difference time domain method. The later technique is time consuming while the former method and the analytical technique have been applied to the regular shape only like rectangular, circular, and elliptical shapes. However, the analysis of MSA is normally difficult to handle which is primarily
  • 19. H-Shaped Slot for Bandwidth Enhancement of Rectangular Microstrip patch antenna 19 Department of Electronics and Communication Engineering 2016 due to existence of a dielectric substrate to support the conductor. The most important disadvantage of microstrip patch antenna is their narrow bandwidth (1-3 %) Figure 3.3.1 Rectangular microstrip patch antenna. 3.3.1 Types of Patch Antenna Figure 3.3.1.1: Different shapes of radiating patch  A patch antenna is atype of radio antenna with a low profile which can mounted on flat surface  A patch antenna is also called as rectangular microstrip antenna  They are the original type of microstrip antenna described by Howell in 1972  It consist of flat rectangular sheet or patch of metal, mounted over a large sheet of metal called ground plane  Patch antena is usually constructed on dielectric substrate  The impedace bandwidth of patch antenna is strongly influenced by spacing between patch and ground plane
  • 20. H-Shaped Slot for Bandwidth Enhancement of Rectangular Microstrip patch antenna 20 Department of Electronics and Communication Engineering 2016 3.3.2 Microstrip Substrate Microstrip lines are commonly used in microwave circuits, although their performance is subject to the type of substrate material selected for a printed-circuit board (PCB). One of the more important material parameters for the substrate is the relative dielectric constant, which should be known before designing a high-frequency, microstrip-based circuit. What follows is a simple and practical method for estimating the relative dielectric constant of a microstrip substrate based on well-known microstrip line empirical equations. The substrate layer thickness is 0.01-0.05 of free-space wavelength. It is used primarily to provide proper spacing and mechanical support between the patch and its ground plane. The dielectric constants of the substrate are usually in the range 2.2 ≤ εr ≥ 12. 3.3.3 Advantage and Disadvantage Microstrip patch antenna has several advantage over conventional microwave antenna with over conventional microwave antenna with one similarity of frequency range from 100 MHz to 100 GHz same in both type. The various advantage and disadvantage are given in table. Sl.No. Advantage Disadvantage 1. Low weight Low efficiency 2. Low profile Low gain 3. Thin profile Large ohmic loss in the feed structure of arrays 4. Required no cavity backing Low power handling capacity 5. Linear and circulation polarization Excitation of surface waves 6. Capable of dual and triple frequency operation Polarization purity is difficult to achieve 7. Feed lines and matching network can be fabricated simultaneously Complex feed structures require high performance arrays Table 3.3.3.1 Advantages and Disadvantages of Microstrip Patch Antenna.
  • 21. H-Shaped Slot for Bandwidth Enhancement of Rectangular Microstrip patch antenna 21 Department of Electronics and Communication Engineering 2016 The applications of microstrip patch antenna in various fields are tabulated as below; System Application Aircraft and Ship antennas Communication and navigation, altimeters, blind landing system Missiles Radar, proximity fuses and telemetry Satellite communications Domestic direct broadcast TV, vehicle-based antennas, communication Mobile communication Pagers and hand telephones, man pack system, mobile vehicle Remote sensing Large light weight apertures Bio-medical Applications in microwave hyperthermia Others Intruder alarm, personal communication, and so forth Table 3.3.3.2 Applications of Microstrip Antenna. 3.4 Feeding Techniques Microstrip patch antennas can be fed by a variety of methods. These methods can be classified into two categories- 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 scheme, 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). A feed line is used to excite to radiate by direct or indirect contact. 3.4.1 Microstrip Line Feed Microstrip line feed is one of the easier methods to fabricate as it is a just conducting strip connecting to the patch and therefore can be consider as extension of patch. It is easy to match by controlling the inset position. In this type of feed technique, a conducting strip is connected directly to the edge of the Microstrip patch. The conducting strip is smaller in width as compared to the patch and this kind of feed arrangement has the advantage that the feed can be etched on the same substrate to provide a planar structure. However as the thickness of the dielectric substrate being used, increases, surface waves and spurious feed radiation also increases, which hampers the bandwidth of the antenna. The feed radiation also leads to undesired cross polarized radiation. This method is advantageous due to its simple planar structure, allows for planar feeding, easy to obtain input match. However
  • 22. H-Shaped Slot for Bandwidth Enhancement of Rectangular Microstrip patch antenna 22 Department of Electronics and Communication Engineering 2016 the disadvantage of this method is that as substrate thickness increases, surface wave and spurious feed radiation increases which limit the bandwidth. Coupling formula is same as coaxial probe feed. Figure 3.4.1.1: Circuit Diagram of Microstrip Feed The edge-coupled microstrip feed can be modeled by means of the step in width or impedance junction. The equivalent circuit diagram is shown in below. . Figure 3.4.1.2: Microstrip feed 3.4.2 Coaxial Probe Feed The Coaxial feed or probe feed is a very common technique used for feeding Microstrip patch antennas. 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. 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. However,
  • 23. H-Shaped Slot for Bandwidth Enhancement of Rectangular Microstrip patch antenna 23 Department of Electronics and Communication Engineering 2016 its major drawback is that it provides narrow bandwidth and is difficult to model since a hole has to be drilled in the substrate and the connector protrudes outside the ground plane, thus not making it completely planar for thick Figure 3.4.2.1: Circuit Diagram of Coaxial Feed substrates. Also, for thicker substrates, the increased probe length makes the input impedance more inductive, leading to matching problems. It is seen above that for a thick dielectric substrate, which provides broad bandwidth, the microstrip line feed and the coaxial feed suffer from numerous disadvantages. So to reduce these types of disadvantages, non-contacting schemes are used. Figure 3.4.2.2: Coaxial probe feed The microstrip antenna can be fed from underneath via a probe as shown in figure 3.4.2.2.the outer conductor of coaxial cable is connected to the ground plane and the center conductor is extended up to the patch antenna.
  • 24. H-Shaped Slot for Bandwidth Enhancement of Rectangular Microstrip patch antenna 24 Department of Electronics and Communication Engineering 2016 3.4.3 Proximity coupled Feed This type of feed technique is also called as the electromagnetic coupling scheme. Two dielectric substrates are used such that the feed line is between the two substrates and the radiating patch is on top of the upper substrate. The main advantage of this feed technique is that it eliminates spurious feed radiation and provides very high bandwidth (as high as 13%) due to overall increase in the thickness of the microstrip patch antenna Figure 3.4.3.1: Circuit diagram of proximity feed This scheme also provides choices between two different dielectric media, one for the patch and one for the feed line to optimize the individual performances. This method is advantageous to reduce harmonic radiation of microstrip patch antenna implemented in a multilayer substrate. The goal of the design is the suppression of the resonances at the 2nd and 3rd harmonic frequencies to reduce spurious radiation due to the corresponding patch modes to avoid the radiation of harmonic signals generated by non-linear devices at the amplifying stage. The study shows the possibility of controlling the second harmonic resonance matching by varying the length of the feeding in. On the other hand, the suppression of the third harmonic is achieved by using a compact resonator. Length of feeding stub and width-to-length ratio of patch is used to control the match. Its coupling mechanism is capacitive in nature. The equivalent circuit diagram of this feed is shown in above. Coupling capacitor is in series with the parallel R- L-C resonant circuit representing the patch. Requirement of this coupling is to match the impedance and tuning of the bandwidth. The open end of the microstrip feed gives stud and stud parameters which help in improving bandwidth. By using this feeding technique 13 % of Bandwidth is achieved. It is effective to use two layers as it increase the bandwidth and reduce spurious radiation, but it is difficult to form right alignment of the patches. Advantages are that it allows planer feeding & less line radiation than microstrip feed.
  • 25. H-Shaped Slot for Bandwidth Enhancement of Rectangular Microstrip patch antenna 25 Department of Electronics and Communication Engineering 2016 Proximity coupled microstrip patch antenna is a non-coplanar feed structure using at least two layers. Coupling between the patch and the microstrip feeding line is capacitive in nature. Figure 3.4.3.2: proximity coupled feed 3.4.4 Aperture coupled feed In this type of feed technique, the radiating patch and the microstrip feed line are separated by the ground plane. Coupling between the patch and the feed line is made through a slot or an aperture in the ground plane and variations in the coupling will depend upon the size i.e. length and width of the aperture to optimize the result for wider bandwidths and better return losses. Figure 3.4.4.1: Circuit diagram of Aperture feed The coupling aperture is usually centered under the patch, leading to lower cross-polarization due to symmetry of the configuration. Since the ground plane separates the patch and the feed line, spurious radiation is minimized. Aperture coupled feeding is attractive because of advantages such as no physical contact between the feed and radiator, wider bandwidths, and better isolation between antennas and the feed network. Furthermore, aperture-
  • 26. H-Shaped Slot for Bandwidth Enhancement of Rectangular Microstrip patch antenna 26 Department of Electronics and Communication Engineering 2016 coupled feeding allows independent optimization of antennas and feed networks by using substrates of different thickness or permittivity. Figure 3.4.4.2: Aperture coupled feed 3.4.5 Coplanar waveguide Feed In a coplanar waveguide-fed microstrip antenna, the antenna and coplanar line are placed on the opposite sides of the same dielectric substrate and the coupling from the coplanar line to microstrip antenna is accomplished via a slot in the ground plane connected directly to the end of the coplanar line. In general, slot coupling may involve an electric polarisability, a magnetic polarisability, or both. In slot coupling to a microstrip antenna, the magnetic polarisability is the dominant Mechanism for a slot near the center of the patch. Because the polarisabilities strongly depend on the shape of the slot as well as the size, it is desirable to improve the antenna performance by optimizing the shape and size of coupling slot for given antenna dimensions. CPW-feed Microstrip patch antenna because it have many features such as low radiation loss, less dispersion, easy integrated circuits and simple configuration with single metallic layer, and no via holes required. The CPW fed antennas have some more attractive features such as wider bandwidth, better impedance matching, and easy integration with active devices and monolithic integrated circuits. Coplanar Waveguide Feed Structure Feed line is one of the important components of antenna structure given below in Figure. Coplanar waveguide structure is becoming popular feed line for an antenna. The coplanar waveguide was proposed by C.P. Wen in 1969. A coplanar waveguide structure consists of a median metallic strip of deposited on the surface of a dielectric substrate slab with two narrow slits ground electrodes running
  • 27. H-Shaped Slot for Bandwidth Enhancement of Rectangular Microstrip patch antenna 27 Department of Electronics and Communication Engineering 2016 adjacent and parallel to the strip on the same surface. This transmission line is uni-planar in construction, which implies that all of the conductors are on the same side of the substrate. Etching the slot and the feed line on the same side of the substrate eliminates the alignment problem needed in other wideband feeding techniques such as aperture coupled and proximity feed. Figure 3.4.5.1: Coplanar waveguide feed 3.4.6 Inset Feed It is a type of microstrip line feeding technique, in which the width of conducting strip is small as compared to the patch and has the advantage that the feed can provide a planar structure. The purpose of the inset cut in the patch is to match the impedance of the feed line to the patch input impedance without the need for any additional matching element. This can be achieved by properly adjusting the inset cut position and dimensions. The inset- fed microstrip antenna provides a method of impedance control with a planar feed configuration. The experimental and numerical results showed that the input impedance of an inset-fed rectangular patch varied as a 4 Cos function of the normalized inset depth. A more recent study proposed a modified shifted 2 Sin form that well characterizes probe-fed patches with a notch. It is found that a shifted 2 Cos function works well for the inset-fed patch. The parameters of the shifted cosine-squared function depend on the notch width for a given patch and substrate geometry. The inset feed introduces a physical notch, which in turn introduces a junction capacitance. The physical notch and its corresponding junction capacitance influence the resonance frequency. As the inset feed-point moves from the edge toward the center of the patch the resonant input impedance decreases monotonically and reaches zero at the center. When the value of the inset feed point approaches the center of the patch, the d Lp 2 π cos varies
  • 28. H-Shaped Slot for Bandwidth Enhancement of Rectangular Microstrip patch antenna 28 Department of Electronics and Communication Engineering 2016 very rapidly; therefore the input resistance also changes rapidly with the position of the feed point. To maintain very accurate values, a close tolerance must be preserved Figure 3.4.6.1: Patch antenna with inset feed The comparison of feeding techniques shows that the Rectangular Microstrip Patch Antenna with the Inset Feed has the highest gain, lowest VSWR and return loss for the dielectric material FR4. Thus it states that inset feed provides better impedance matching than the co-axial feed and microstrip line feed.
  • 29. H-Shaped Slot for Bandwidth Enhancement of Rectangular Microstrip patch antenna 29 Department of Electronics and Communication Engineering 2016 CHAPTER 4 ANALYSIS METHOD FOR MICROSTRIP ANTENNA The preferred models for the 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. 4.1. TRANSMISSION LINE MODEL 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 nonhomogeneous line of two dielectrics, typically the substrate and air. Figure 4.1.1: Electric field lines between patch and ground plane. Hence, as seen from figure 4.1.1 most of the electric field lines reside in the substrate and parts of some lines in 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 (𝜀 𝑟𝑒) must be obtained in order to account for the fringing and the wave propagation in the line. The value of 𝜀 𝑟𝑒 is slightly less than 𝜀 𝑟because 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 Figure above. The expression for 𝜀 𝑟𝑒 is
  • 30. H-Shaped Slot for Bandwidth Enhancement of Rectangular Microstrip patch antenna 30 Department of Electronics and Communication Engineering 2016 𝜺 𝒓𝒆 = 𝜺 𝒓+𝟏 𝟐 + 𝜺 𝒓−𝟏 𝟐 (𝟏 + 𝟏𝟐𝒉 𝑾 )−𝟎.𝟓 Where 𝜀 𝑟𝑒 = Effective dielectric constant 𝜀 𝑟 = Dielectric constant of substrate, h= Height of dielectric substrate, W =Width of the patch 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 λo/√𝜀 𝑟𝑒𝑓𝑓where λo is the free space wavelength. The TM10 mode implies that the field varies one λ/2 cycle along the length, and there is no variation along the width of the patch. In the fig. shown below, 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 Figure 4.1.2: Top view of microstrip antenna The transmission line model has been utilized to determine the input performance of a rectangular patch antenna excited by microstrip line and inset feed.Expressions for the resonant frequency,and variours other parameters including the feed point has been calculated.The model has also been applied to determine the resonant parameters for a patch antenna.The transmission line model treats the rectangular patch radiator as a stripline resonator with no transverse field variation and assumes the radiation to occur from the two transverse open edges.It is well known the dominant mode of propagation in a stripline is the TEM or quasi-TEM mode having negligible variations of fields in the transverse direction.
  • 31. H-Shaped Slot for Bandwidth Enhancement of Rectangular Microstrip patch antenna 31 Department of Electronics and Communication Engineering 2016 It is seen from figure 4.1.3 that the normal components of the electric field at the two edges along the width are cancel each other in the broadside direction. The tangential components (seen in figure 4.1.3), which are in phase, means that the resulting fields combine to give maximum radiated field normal to the surface of the structure. Figure 4.1.3: Side view of patch antenna Hence the edges along the width can be represented as two radiating slots, which are λ/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. The dimensions of the patch along its length have now been extended on each end by a distance ΔL, which is 𝛥𝐿 = 0.412ℎ 𝜀 𝑟𝑒 + 0.30 𝜀 𝑟𝑒 − 0.258 ( 𝑊 ℎ⁄ + 0.264 𝑊 ℎ⁄ + 0.813 ) The effective length of the patch Leff now becomes Leff =L+2Δ for a given resonance frequency f the width W is 𝑊 = 𝐶 2𝑓 ( 𝜀 𝑟 + 1 2 ) −0.5
  • 32. H-Shaped Slot for Bandwidth Enhancement of Rectangular Microstrip patch antenna 32 Department of Electronics and Communication Engineering 2016 4.2 DESIGN OF RECTANGULAR MICROSTRIP PATCH ANTENNA A single element of rectangular patch antenna, as shown in figure, can be designed for the 3.3 GHz resonant frequency using transmission line model Figure 4.2.1: Typical rectangular patch antennas In the typical design procedure of the microstrip antenna, the desired resonant frequency, thickness and dielectric constant of the substrate are known or selected initially. In this design of rectangular microstrip antenna, glass epoxy dielectric material is selected as the substrate with 1.6 mm height. Then, a patch antenna that operates at the specified resonant frequency (3.3 GHz) can be designed by the using transmission line model equations. As shown in figure, microstrip line type feeding mechanism used. It is also possible to determine the length and width of quarter wave length long line (branch line) of the patch and the main feed line’s length and width to ensure matching. The main feed line is of 50Ω characteristic impedance. The quarter wave length long line is
  • 33. H-Shaped Slot for Bandwidth Enhancement of Rectangular Microstrip patch antenna 33 Department of Electronics and Communication Engineering 2016 used between main feed line and patch for impedance matching. The characteristic impedance of branch line is calculated as  Z0 – characteristic impedance of main feed line (50Ω)  Ze – impedance at patch edge. So for the rectangular microstrip patch antenna the parameters are:  Resonating frequency f= 3.3 GHz.  Patch width W = 27.8 mm.  Patch length L = 21.42 mm.  Branch line length qw = 11 mm.  Substrate height h = 1.6 mm.  Relative permittivity 𝜀 𝑟 = 4.5.  Width of main feed line = 3 mm 4.3 DESIGN OF AN H-SHAPED MSA The H-shaped microstrip antenna consists of an H shaped patch; supported on a grounded dielectric sheet of thickness h and dielectric constant𝜀 𝑟. An H-shaped microstrip patch antenna, shown in figure 4.3.1 is obtained by cutting equal rectangular slots along both the non-radiating edges of the rectangular microstrip patch antenna. Figure 4.3.1: H shaped patch antenna The H-shaped patch antenna reported here has a size about half that of the rectangular patch, with larger bandwidth. The H-shaped microstrip patch antenna, because of its considerably smaller size, could replace the
  • 34. H-Shaped Slot for Bandwidth Enhancement of Rectangular Microstrip patch antenna 34 Department of Electronics and Communication Engineering 2016 rectangular patch at UHF frequencies. When they are applied in the frequency range below 2 GHz, the sizes of conventional rectangular microstrip patches seem to be too large. The parameters of H shaped MSA is as below:  Resonating frequency f= 3.3 GHz.  Patch width W = 27.8 mm.  Patch length L = 21.42 mm.  Branch line length qw = 11.92 mm.  Substrate height h = 1.6 mm.  Relative permittivity 𝜀 𝑟 = 4.5.  Width of main feed line = 3 mm  Width of slots = 5 mm  Length of slots = 3 mm 4.4 DESIGN OF INSET FED RECTANGULAR MSA A rectangular patch of length L and width W is designed. The patch is cut at a depth d. Then inset feed of length l and width w is formed. The port is defined at the end of the feed line. This technique is simple to model and easy to match by controlling the inset position. Figure 4.4.1: Rectangular MSA with an inset feeding The inset cut provided match the impedance of the feed line with the patch input impedance without any additional matching elements.
  • 35. H-Shaped Slot for Bandwidth Enhancement of Rectangular Microstrip patch antenna 35 Department of Electronics and Communication Engineering 2016 The parameters of rectangular MSA with inset feeding technique as shown in figure 4.4.1 is:  Resonating frequency f= 3.3 GHz.  Patch width W = 27.8 mm.  Patch length L = 21.42 mm.  Branch line length qw = 13.92 mm.  Substrate height h = 1.6 mm.  Relative permittivity 𝜀 𝑟 = 4.5.  Width of main feed line = 3 mm  Inset feed position = (10.96,25.92,1.6) 4.5 DESIGN OF H SHAPED MSA WITH INSET FEED The inset fed rectangular MSA is converted to H shaped patch MSA by cutting equal rectangular slots on both sides of radiating slot. The H shaped MSA with inset feed is shown in figure 4.5.1 Figure 4.5.1: H shaped MSA with inset feed The parameters of H shaped MSA with inset feeding is:  Resonating frequency f= 3.3 GHz.  Patch width W = 27.8 mm.  Patch length L = 21.42 mm.  Branch line length qw = 13.92 mm.  Substrate height h = 1.6 mm.
  • 36. H-Shaped Slot for Bandwidth Enhancement of Rectangular Microstrip patch antenna 36 Department of Electronics and Communication Engineering 2016  Relative permittivity 𝜀 𝑟 = 4.5.  Width of main feed line = 3 mm  Inset feed position = (10.96,25.92,1.6)  Width of slots = 5.233 mm  Length of slots = 3.25 mm The 3.3 GHz is taken as resonant frequency of the MSA. Fr4 epoxy has been selected for the substrate with dielectric constant 4.4. the height of substrate is kept at 1.6 mm. in inset fed microstrip patch antenna the location of feed determines the antenna input impedance. Therefore to achieve 50 impedance the inset length is determined using the relation 𝑅𝑖𝑛(𝑦 = 𝑦0) = 𝑅𝑖𝑛(𝑦 = 0) (cos( 𝜋 𝐿 𝑦0)) 2 Where𝑅𝑖𝑛(𝑦 = 0) is the input impedance at the leading radiating edge of the patch and 𝑅𝑖𝑛(y = y0) is the desired input impedance, y0 is the inset length. Figure 4.5.2: proposed microstrip patch antenna The ground plane is specified by an electrical conducting boundary condition. A chamber has to be specified as defined in to model open space, so that the radiation from the structure is absorbed and not reflected back. The air box should be quarter wavelength long of the wavelength of interest in the direction of radiated field. The proposed work air box is cube of dimension 200 mm.
  • 37. H-Shaped Slot for Bandwidth Enhancement of Rectangular Microstrip patch antenna 37 Department of Electronics and Communication Engineering 2016 CHAPTER 5 SIMULATION SOFTWARE 5.1 HFSS HFSS is a high-performance full-wave electromagnetic (EM) field simulator for arbitrary 3D volumetric passive device modeling that takes advantage of the familiar Microsoft Windows graphical user interface. It integrates simulation, visualization, solid modeling, and automation in an easy-to-learn environment where solutions to the 3D EM problems are quickly and accurately obtained. Ansoft HFSS employs the Finite Element Method (FEM), adaptive meshing, and brilliant graphics to give you unparalleled performance and insight to all of 3D EM problems. Ansoft HFSS can be used to calculate parameters such as S Parameters, Resonant Frequency, and Fields. Typical uses include:  Package Modeling – BGA, QFP, Flip-Chip  PCB Board Modeling – Power/Ground planes, Mesh Grid Grounds,  Backplanes  Silicon/GaAs - Spiral Inductors, Transformers  EMC/EMI – Shield Enclosures, Coupling, Near- or Far-Field Radiation  Antennas/Mobile Communications – Patches, Dipoles, Horns, Conformal  Cell Phone Antennas, Quadrafilar Helix, Specific Absorption Rate(SAR),  Infinite Arrays, Radar Cross Section(RCS), Frequency Selective  Surfaces(FSS)  Connectors – Coax, SFP/XFP, Backplane, Transitions  Waveguide – Filters, Resonators, Transitions, Couplers  Filters – Cavity Filters, Microstrip, Dielectric HFSS is an interactive simulation system whose basic mesh element is a tetrahedron. This allows you to solve any arbitrary 3D geometry, especially those with complex curves and shapes, in a fraction of the time it would take using other techniques. The name HFSS stands for High Frequency Structure Simulator. Ansoft pioneered the use of the Finite Element Method (FEM) for EM simulation by developing/implementing technologies such as tangential vector finite elements, adaptive meshing, and Adaptive Lanczos-Pade Sweep (ALPS). Today, HFSS continues to lead the industry with innovations such as Modes-to-Nodes and Full wave spice.
  • 38. H-Shaped Slot for Bandwidth Enhancement of Rectangular Microstrip patch antenna 38 Department of Electronics and Communication Engineering 2016 5.2 MATLAB MATLAB (matrix laboratory) is a multi-paradigm numerical computing environment and fourth generation programming language. A proprietary programming language developed by math works, MATLAB allows matrix manipulations, plotting of functions and data, implementation of algorithms, creation of user interfaces, and interfacing with programs written in other languages including C,C++, JAVA ,FORTRAN and python. Although MATLAB is intended primarily for numerical computing, an optional tool box uses the MuPAD symbolic engine, allowing access to symbolic computing capabilities. An additional package, Simulink, adds graphical multi-domain simulation and model-design for dynamic and embedded systems. In 2004 MATLAB had around one million users across the industry and academia. MATLAB users come from various backgrounds of engineering science and economics. The MATLAB application is built around the MATLAB scripting language. Common usage of the MATLAB application involves using the command window as an interactive mathematical shell or executing test files containing MATLAB code. MATLAB has structural data types. Since all variables in MATLAB are arrays a more adequate name is structure array, where each element of the array has the same field names. In addition MATLAB support dynamic field names. When creating a MATLAB function the name of file should match the name of the first function in file. Valid function names begins with a alphabetic character and can contain letters, numbers or underscores. MATLAB support object oriented programming includes classes, inheritance, virtual dispatch, packages .However the syntax and calling conventions are significantly different from other languages. MATLAB supports developing applications with graphical user interface features .MATLAB can call functions and subroutines written in c programming language and FORTRAN. MATLAB is a weakly typed programming language because types are implicitly converted. It is an inferred typed language because variables can be assigned without declaring their type except if they are to be treated as symbolic subjects.MATLAB can be used in projects such as modelling ,energy consumption ,developing control algorithms, analyzing weather data and running millions of simulations to pin point optimal dosing for antibiotics. It helps in exploring and visualizing ideas and collaborate across disciplines including signal and image processing communications, control systems and computational finance.
  • 39. H-Shaped Slot for Bandwidth Enhancement of Rectangular Microstrip patch antenna 39 Department of Electronics and Communication Engineering 2016 CHAPTER 6 RESULTS In this project two structures of microstrip patch antenna are presented. Both antenna has basic parameters dielectric constant 𝜀 𝑟=4.4, operating frequency 𝑓𝑟 = 3.3 GHz, thickness of substrate h = 1.6mm. 6.1 RESULTS OF RECTANGULAR MSA The simulated result of S11 scattering parameter (return loss) of single element rectangular microstrip antenna is presented in figure. From the figure, the antenna has almost 3.3GHz resonant frequency and it has 0.1GHz. Bandwidth at 10 dB (the difference of 3.2 GHz and 3.3 GHz). In percentage, the bandwidth of the antenna is 1.73% Figure 6.1.1: return loss of rectangular MSA The reflection coefficient (s11 parameter) is plotted as a function of frequency. For any antenna structure with good performance the return loss should be minimum. The designed antenna resonates at the frequency of 3.3GHz with a return loss of 10.5dB.
  • 40. H-Shaped Slot for Bandwidth Enhancement of Rectangular Microstrip patch antenna 40 Department of Electronics and Communication Engineering 2016 The 3 dimensional radiation pattern of microstrip patch antenna resonating at frequency of 3.3GHz is shown in figure 6.1.2 Figure: 6.1.2: 3 Dimensional radiation pattern Figure: 6.1.3: 2 Dimensional radiation pattern The radiation pattern is determined in the far field region and is usually represented with spherical coordinate system.
  • 41. H-Shaped Slot for Bandwidth Enhancement of Rectangular Microstrip patch antenna 41 Department of Electronics and Communication Engineering 2016 6.2 RESULTS OF INSET FED RECTANGULAR MSA The figure 6.2.1 shows the return loss of rectangular MSA with inset feed. The designed antenna resonates at a frequency of 3.3 GHz with a return loss of 15.9dB. Figure 6.2.1: Return loss of inset fed rectangular MSA From the figure the designed antenna has a bandwidth of 0.4GHz at 10dB (difference of 3.2GHz and 3.6GHz).in percentage the bandwidth of antenna is 12.12%. Figure 6.2.2: 3 dimensional radiation pattern of rectangular MSA 1.00 2.00 3.00 4.00 5.00 6.00 Freq [GHz] -16.00 -14.00 -12.00 -10.00 -8.00 -6.00 -4.00 -2.00 0.00 dB(S(1,1)) HFSSDesign1XY Plot 1 ANSOFT m1 m2 m3 Curve Info dB(S(1,1)) Setup1 : Sweep Name X Y m1 3.3889 -15.9207 m2 3.2778 -11.2545 m3 3.6667 -10.1310
  • 42. H-Shaped Slot for Bandwidth Enhancement of Rectangular Microstrip patch antenna 42 Department of Electronics and Communication Engineering 2016 The radiation pattern is the representation of radiation properties of antenna in spatial coordinates. Directivity is how much an antenna concentrates energy in one direction in preference to radiation in other directions. Figure 6.2.3: 2 dimensional radiation pattern 6.3 RESULTS OF H-SHAPED RECTANGULAR MSA The first important parameter which is helpful to calculate the bandwidth of the antenna structure is its s11 parameter or return loss curve. The simulated result of S11 scattering parameter of single element H-shaped microstrip antenna is presented in figure 6.3.1. From the figure, the antenna has almost 3.3GHz resonant frequency and it has 0.22GHz bandwidth at 10 dB (the difference of 3.444 GHz and 3.222 GHz). In percentage, the bandwidth of the antenna is 6.7%. . So by using H-shaped MSA instead of rectangular MSA bandwidth improvement of 5% is obtained. Return loss at different locations on the patch is compared and a point where return loss is most (RL) negative is selected as a feed point.
  • 43. H-Shaped Slot for Bandwidth Enhancement of Rectangular Microstrip patch antenna 43 Department of Electronics and Communication Engineering 2016 The return loss of H shaped MSA is as shown in figure 6.3.1 Figure 6.3.1: Return loss of H shaped rectangular MSA Figure 6.3.2: 3 dimensional radiation pattern of H shaped rectangular MSA
  • 44. H-Shaped Slot for Bandwidth Enhancement of Rectangular Microstrip patch antenna 44 Department of Electronics and Communication Engineering 2016 6.4 RESULTS OF INSET FED H-SHAPED RECTANGULAR MSA The return loss is a parameter which indicates the amount of power that is lost to the load and does not return as a reflection. Waves are reflected leading to the formation of standing waves, when the transmitter and the antenna impedance do not match. Figure 6.4.1: return loss of H shaped inset fed rectangular MSA The simulated result of S11 scattering parameter of single element H-shaped microstrip antenna with inset feed is presented in figure 6.4.1. From the figure, the antenna has almost 3.3GHz resonant frequency and it has 0.5GHz bandwidth at 10 dB (the difference of 3.722 GHz and 3.222 GHz). In percentage, the bandwidth of the antenna is 15%. In last section rectangular MSA presented with FR4 epoxy substrate and thickness h=1.6mm and got return loss bandwidth 12%. In slot cut H-shaped MSA with same substrate presented and got 15% bandwidth. So by using H-shaped MSA instead of rectangular MSA bandwidth improvement of 20% is obtained
  • 45. H-Shaped Slot for Bandwidth Enhancement of Rectangular Microstrip patch antenna 45 Department of Electronics and Communication Engineering 2016 The 3 dimensional radiation pattern of H shaped MSA with resonating frequency 3.3 GHz is as shown in figure 6.4.2. Figure 6.4.2: 3 dimensional radiation pattern of H shaped rectangular MSA with inset feed Figure 6.4.3: 2dimensional radiation pattern of H shaped MSA with inset feed
  • 46. H-Shaped Slot for Bandwidth Enhancement of Rectangular Microstrip patch antenna 46 Department of Electronics and Communication Engineering 2016 6.5 COMPARISION OF RECTANGULAR MSA AND H-SHAPED MSA In this project two designs of rectangular MSA is presented. The two design differ by the type of feeding technique used. The rectangular MSA presented with FR4 epoxy substrate and thickness h=1.6mm with microstrip feeding has got a return loss bandwidth of 1.7%. In slot cut H-shaped MSA with same substrate presented got a return loss bandwidth of 6.7%. So by using H-shaped MSA instead of rectangular MSA the bandwidth gets improved. ANTENNA TYPE PROPERTIES RECTANGULAR MSA H SHAPED MSA RESONANT FREQUENCY 3.3 GHz 3.311GHz BANDWIDTH GHz 0.1 GHz 0.2 GHz PERCENTAGE BANDWIDTH 1.7% 6.7% RETURN LOSS 10.58dB 11.21dB Table 6.5.1: Comparison between rectangular and H shaped MSA with microstrip feed In the second design inset feeding is introduced instead of microstrip feeding. The rectangular MSA presented with FR4 epoxy substrate and thickness h=1.6mm with inset feeding has got a return loss bandwidth of 11.5%. The same substrate with slot cut H shaped MSA will give a return loss bandwidth of 15%. It is thus inferred that inset feeding provides enhanced bandwidth compared to that of microstrip feeding. ANTENNA TYPE PROPERTIES RECTANGULAR MSA H SHAPED MSA RESONANT FREQUENCY 3.38 GHz 3.38GHz BANDWIDTH GHz 0.4 GHz 0.5 GHz PERCENTAGE BANDWIDTH 12% 15% RETURN LOSS 15.92dB 18.76dB Table 6.5.2: Comparison between rectangular MSA and H shaped MSA with inset feed
  • 47. H-Shaped Slot for Bandwidth Enhancement of Rectangular Microstrip patch antenna 47 Department of Electronics and Communication Engineering 2016 CONCLUSION The work presented focused on designing and simulating microstrip patch antenna operating in 3.3GHz frequency range, which would be suitable for mobile application. , In this project basics of microstrip patch antenna and its bandwidth improvement using h shaped patch were studied in detail. Two aspects of microstrip antennas have been studied. The first aspect is the design of typical rectangular microstrip antenna and the second is the design of slot cut H-shaped microstrip antenna. A simple microstrip line type feed mechanism with quarter wavelength Long Branch line used to energized patch. In the second design inset feeding mechanism is used to energize the patch. Bandwidth of these two designs were improved using H shaped patch. The main concern is to study the bandwidth improvement of the microstrip antenna. Rectangular microstrip antenna and H-shaped microstrip antenna have been designed and simulated using high frequency structure simulator (HFSS). H-shaped microstrip antenna produced reduction in size and higher bandwidth in comparison to rectangular microstrip antenna. Inset feeding technique has an improved bandwidth, gain and other parameters compared to that of microstrip feeding.
  • 48. H-Shaped Slot for Bandwidth Enhancement of Rectangular Microstrip patch antenna 48 Department of Electronics and Communication Engineering 2016 REFERENCES [1] “Bandwidth Enhancement of Probe Fed Microstrip Patch Antenna”. International Journal of Electronics Communication and Computer Technology (IJECCT) Volume 3 Issue 1 (January 2013).ISSN:2249-7838. Parminder Singh, Anjali Chandel ,Divya Naina. [2] “Designing of Bandwidth Improved ‘H’ Shaped Microstrip Patch Antenna for Bluetooth Applications Using Ansoft HFSS”.International Journal of Science and Research Volume 3 Issue 4 2014(IJSR) Chaitali. J. Ingale1, Anand. K. Pathrikar. [3] “Design and Analysis of Dual-Band Ψ- Shaped Microstrip Patch Antenna”. International Journal of Advances in Engineering & Technology. (IJAET).Volume 6 Issue 1 March 2013 ISSN: 2231-1963 Diwakar Singh, Amit Kumar Gupta, R. K. Prasad. [4] “Design and Analysis of Dual Frequency Band E-Shaped Microstrip Patch Antenna”. Conference on Advances in Communication and Control Systems 2013(CAC2S 2013) R. K. Prasad, Amit Kumar Gupta, Dr. J. P. Saini, Dr. D. K. Srivastava. [5] “A Parametric Study on Microstrip Patch Antenna”. .International journal of Electronics and Communication Technology .Volume 6 Issue1 January 2015 ISSN: 2230-7109. A. Bhattacharya, B.N Biswas [6] “Parametric Performance Analysis of Patch Antenna using EBG Substrate.” International Journal of Wireless & Mobile networks (IJWMN) Volume 4, Issue 5 October 2012 MS. Nargis Aktar, Muhammad Shahin Uddin [7] “Size Reduction and Bandwidth Enhancement of Rectangular Printed Antenna using Triple Narrow Slits for Wireless Communication System and Microwave X-Band Applications”. International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622
  • 49. H-Shaped Slot for Bandwidth Enhancement of Rectangular Microstrip patch antenna 49 Department of Electronics and Communication Engineering 2016 Volume 2, Issue 5, October 2012.Vivekkumar yadaw,Sudipta das,S.M maidur rahaman [8] “Parametric Study of the Rectangular Microstrip Antenna using Cavity Model”. Journal of Engineering and Development, Volume 10, Issue 2, June 2006 ISSN: 1813-7822 Prof. Dr. Jamal W. Salman, Lect. Star O. Hassan [9] “Microstrip Antennas” IEEE proceedings, Volume 80, Issue 1, 1992, pp.79-91.David M.Pozar. [10] “Parametric Study for Rectangular Microstrip Patch Antennas”IOSR Journal of Electronics And Communication Engineering (IOSR-JECE) ISSN: 2278-8735 Volume5, Issue 2, April 2013 S.S. Yavalkar, R. T. Dahatonde, Dr. S. S. Rathod, Dr. S. B. Deosrkar [11] “Performance Analysis of Rectangular Patch Antenna for Different Substrate Heights”. International Journal of Innovative Research in Electrical, Electronics, Instrumentation and Control Engineering Volume 2, Issue 1,January 2014 ISSN:2321-5526 Vivek Hanumante, Panchatapa Bhattacharjee, Sahadev Roy, Pinaki Chakraborty. [12] Balanis,C.A.(2005).Antenna Theory Analysis and Design, Third edition, Johan Wiley & Sons.ISBN 0-471-66782-X. [13] http://www.antenna-theory.com/definitions/permitivity.php [14] www.mathworks.com
  • 50. H-Shaped Slot for Bandwidth Enhancement of Rectangular Microstrip patch antenna 50 Department of Electronics and Communication Engineering 2016 APPENDIX A HFSS ANSOFT 13.1 A.1 Introduction HFSS is a high-performance full-wave electromagnetic (EM) field simulator for arbitrary 3D volumetric passive device modeling that takes advantage of the familiar Microsoft Windows graphical user interface. It integrates simulation, visualization, solid modeling, and automation in an easy-to-learn environment where solutions to the 3D EM problems are quickly and accurately obtained. Ansoft HFSS employs the Finite Element Method (FEM), adaptive meshing, and brilliant graphics to give you unparalleled performance and insight to all of 3D EM problems. Ansoft HFSS can be used to calculate parameters such as S Parameters, Resonant Frequency, and Fields. HFSS is an interactive simulation system whose basic mesh element is a tetrahedron. This allows you to solve any arbitrary 3D geometry, especially those with complex curves and shapes,in a fraction of the time it would take using other techniques. The name HFSS stands for High Frequency Structure Simulator. Ansoft pioneered the use of the Finite Element Method (FEM) for EM simulation by developing/implementing technologies such as tangential vector finite elements, adaptive meshing, and Adaptive Lanczos-Pade Sweep (ALPS). Today, HFSS continues to lead the industry with innovations such as Modes-to-Nodes and Full wave space. A.1.1 Flow chart for designing in HFSS The flow chart for designing the antenna in HFSS is as depicted below. It consists of seven steps namely calculating dimensions of antenna using the derived formulas, creating a model in HFSS by opening a project and the dimensions are entered and the model is created. Then the analysis of model in various parameters is done, like the return loss, radiation pattern (both in 2D and 3D), VSWR, gain and any other required parameters are analyzed and results are stimulated. The return loss is a parameter which indicates the amount of power that is lost to the load and does not return as a reflection. The VSWR is basically a measure of the impedance mismatch between the transmitter and the antenna. Antenna gain is a parameter which is closely related to the directivity of the antenna .The radiation pattern is the representation of radiation properties of antenna in a spatial coordinates. If the simulated results of the parameters are as per the requirement then fabrication of antenna can be performed and testing can be done.
  • 51. H-Shaped Slot for Bandwidth Enhancement of Rectangular Microstrip patch antenna 51 Department of Electronics and Communication Engineering 2016 Flow chart for designing an antenna A.1.2 Simulation Workflow After starting ANSOFT HFSS, choose to create a new HFSS project. Select a template for a structure which is closest to the device of interest that is a three dimensional rectangular box in the spatial coordinate for designing a substrate of a microstrip rectangular patch antenna  To depict a substrate press the 3D box and drag the mouse to draw it in the spatial coordinate window  The box is named as substrate and then select the material as FR4 epoxy by double clicking the substrate.  Give the dimensions of the substrate by entering it in another window. The position X size (length), Y size (width), Z size (height) is to be entered.  The command ctrl-d can be used to fit the box in the window.
  • 52. H-Shaped Slot for Bandwidth Enhancement of Rectangular Microstrip patch antenna 52 Department of Electronics and Communication Engineering 2016 Substrate in HFSS window Designing the ground Ground in HFSS window  To design the ground 2D box is to be created and the name is to be changed for easy identification  Repeats the steps as that for substrate
  • 53. H-Shaped Slot for Bandwidth Enhancement of Rectangular Microstrip patch antenna 53 Department of Electronics and Communication Engineering 2016 Designing the patch and feed line Patch and feed line  The patch and the feed dimensions are entered and the impedance is matched of feed.  Unite the material of both patch and the feed line using the unite option and pressing the ctrl and selecting the both patch and the feed. Designing the port  To draw the port the drawing plane is changed from XY to YZ plane. Then the dimensions are entered as above. Defining boundary and excitations  The patch is assigned a perfect electric boundary that is named as perfect E1.  The port is chosen to be lumped port since it is a transmission line model.  The impedance of the port is matched to 50Ω. The option new line is selected and then click finish after assigning a new line in the port.
  • 54. H-Shaped Slot for Bandwidth Enhancement of Rectangular Microstrip patch antenna 54 Department of Electronics and Communication Engineering 2016 Anechoic chamber  For analysis the designed antenna is placed in a chamber so that the radiation of the antenna is confined within the chamber.  Set the radiation boundary for the chamber. Analysis of the antenna  Insert the far field radiation as infinite sphere and select the radiation range of angle from 0 to 360 degree.  Add solution sweep and set the required solution frequency that is the central frequency at which the antenna must be radiated.  Select the setups 1 created and add the frequency sweep. The sweep type is set as fast and the linear sweep is set as count.  The validation check box should show all parameters marked right. Results  To obtain the results select option analyze all.  The return loss plot is created by creating model rectangular plot.  The radiation pattern in both 2D and 3D can be obtained using the option create far field option. A.2 MODELS IN HFSS WINDOW Rectangular microstrip patch antenna
  • 55. H-Shaped Slot for Bandwidth Enhancement of Rectangular Microstrip patch antenna 55 Department of Electronics and Communication Engineering 2016 Microstrip patch antenna using inset feed Rectangular microstrip patch antenna using h shaped patch
  • 56. H-Shaped Slot for Bandwidth Enhancement of Rectangular Microstrip patch antenna 56 Department of Electronics and Communication Engineering 2016 Rectangular microstrip patch antenna using h shaped patch with inset feed
  • 57. H-Shaped Slot for Bandwidth Enhancement of Rectangular Microstrip patch antenna 57 Department of Electronics and Communication Engineering 2016 APPENDIX B MATLAB CODES B.1 PROGRAM FOR FINDING LENGTH AND WIDTH OF THE PATCH %Program to calculate the parameters to design a rectangular patch antenna %the user have to feed the values of frequency, dielectric constant, and %height of the dielectric. %the program will calculate automatically the width and length of the patch function Antcal() %This function is to be used to calculate the different parameters of a rectangular patch antenna clc; fo=input('Enter frequency of operation (fo) inGHz'); Er=input('Enter Dielectric constant (Er)'); h=input('Enter height of substrate (h) in mm'); W=(3*10^8)/(2*fo*sqrt((Er+1)/2)) Eref=(Er+1)/2+((Er-1)/2)/(sqrt(1+12*h/W)) Lef=(3*10^8)/(2*fo*sqrt(Eref)) dL=((0.412*h)*(Eref+0.3)*(W/h+0.264))/((Eref-0.258)*(W/h+0.8)) L=Lef-2*dL Lg=6*h+L Wg=6*h+W end B.2 PROGRAM TO PLOT THE RADIATION PATTERN OF MSA clc; close all; clear all; theta=0:1:360; phi=0:1:360; freq=3.3; h=1.6; w=21.42; l=27.8; lambda=30/freq; k=(2*pi)/lambda; x=(k*w*sin(theta)*sin(phi)')/2; y=cos((k*l)/2*sin(theta)*cos(phi)'); et=(sin(x)/x)*y*cos(phi); ep=-(sin(x)/x)*y*cos(theta); t = 0:1:360; polar(t,et.*ep,'--b');
  • 58. H-Shaped Slot for Bandwidth Enhancement of Rectangular Microstrip patch antenna 58 Department of Electronics and Communication Engineering 2016 B.3 RESULTS OF MATLAB SIMULATION RESULT OF PROGRAM FOR FINDING WIDTH AND LENGTH OF THE PATCH Figure 6.5.1: matlab result for antenna parameters RESULT OF PROGRAM FOR RADIATION PATTERN Figure 6.5.2: matlab result for radiation pattern