3-Sample Report(Without Certificates)

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SIMULATING AND MODELING OF MICROSTRIP

ANTENNA

A PROJECT REPORT

Submitted by

MINHAZ VAYADA (110770111022)

ARTI PATEL (110770111004)

I n partial ful f ilment for the award of the degree

of

BACHELOR OF ENGINEERING

in

ELECTRONICS AND COMMUNICATION ENGINEERING

SILVER OAK COLLEGE OF ENGINEERING & TECHNOLOGY

Gujarat Technological University, Ahmedabad

November, 2014


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Project ID – 4034

Department of Electronics & Communication Engineering Page III

Silver Oak College of Engineering & Technology

Electronics & Communication department

November, 2014

CERTIFICATE

Date:

This is to certify that the dissertation entitled "SIMULATING AND

MODELING OF MICROSTRIP ANTENNA” has been carried out by

MINHAZ VAYADA (110770111022), ARTI PATEL (110770111004).

under my guidance in fulfilment of the degree of Bachelor of Engineering

in Electronics and Communication, 7th

Semester of Gujarat Technological

University, Ahmadabad during the academic year 2014-15.

Guide: Mr. Raj Hakani

Asst. Professor, EC Dept

SOCET, Ahmadabad

Mr. Amit Agrawal

Head of the Department


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Project ID – 4034

Department of Electronics & Communication Engineering Page IV

ACKNOWLEDGEMENT

Project work is something that cannot be completed by the blind efforts of an individual but it

is a constant inspiration and help of the people you work around.

We are heartily thankful to Mr. Raj Hakani whose encouragement, guidance and support

from the initial to this level enabled us for developing and understanding of the Project work.

We deeply acknowledge support of our respected Head of Electronics and Communication

Department Mr. Amit Agrawal gave us the constant and humble guidance throughout the

project work.

We owe our deepest gratitude to Dr. Saurin Shah, Principal, SOCET who became our

constant source of inspiration throughout the work.

We would like to thank from the bottom of our heart to Mr. Raj Hakani, who lead us

in the field of Antenna Design, and gave us right direction in HFSS software and design

pattern.

Finally, we deeply acknowledge the backbone support of our family.

Minhaz Vayada (110770111022)

Arti Patel (110770111004)


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Project ID – 4034

Department of Electronics & Communication Engineering Page V

ABSTRACT

Microstrip patch antenna is widely used due to its many advantages, but its

main drawback is its narrow bandwidth. Using software like HFSS 13, CAD-

FEKO and design parameters we can design patch and ground plane

dimensions. We can also design an antenna used in ISM band which works on

the frequency of 2.4GHz. Antenna’s performance also depends on substrate

material so here we can have an analysis for different substrate material and

we can get better bandwidth by analysing the performance of various

substrates. We can also get better VSWR and S11 with appropriate selecting

dimensions of Superstrate. This dimension of Superstrate is selected by iteration

method. We can achieve more (60%) bandwidth with slots into Microstrip

antenna.


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Project ID – 4034

Department of Electronics & Communication Engineering Page VI

LIST OF FIGURES

Figure 1 Antenna Radiation Pattern ........................................................................................... 5

Figure 2 Radiation Pattern of a Directional Antenna ................................................................. 6

Figure 3 A Vertically Polarized Wave ....................................................................................... 7

Figure 4 Commonly Used Polarization Schemes ...................................................................... 7

Figure 5 Measurement of Bandwidth ........................................................................................ 8

Figure 6 Geometry of Commonly known Microstrip Patch Antenna ........................................ 9

Figure 7 Operation of Microstrip patch Antenna ..................................................................... 10

Figure 8

Analysis of Efficiency, Bandwidth and Substrate Height ......................................... 11

Figure 9 Probe fed microstrip patch antenna ........................................................................... 12

Figure 10 Direct contact microstrip feed line .......................................................................... 12

Figure 11 Aperture coupled Microstrip patch antenna ............................................................ 13

Figure 12 Proximity coupled patch .......................................................................................... 14

Figure 13 Microstrip line with Electric field ........................................................................... 15

Figure 14 Top view and Side view of antenna ........................................................................ 16

Figure 15 Charge distribution and current density creation on the microstrip patch ............... 17

Figure 16 Flowchart for designing microstrip antenna parameter ........................................... 21

Figure 17 Snapshot of MPA Calculator ................................................................................... 22

Figure 18 Top view of Microstrip Antenna with Rectangular Plane ..................................... 24

Figure 19 Graph of S11 for rectangular plane ......................................................................... 24

Figure 20 Top view of MPA with FR-4 Material .................................................................... 25

Figure 21 Result of S11 with FR-4 Material ........................................................................... 25

Figure 22 Result of S11 with PTFE Material .......................................................................... 26

Figure 23 Result of S11 with RT/Duroid Material .................................................................. 26

Figure 24 Result of Radiation Pattern ...................................................................................... 26

http://f/Project/Report_Antenna.docx%23_Toc403207929http://f/Project/Report_Antenna.docx%23_Toc403207929http://f/Project/Report_Antenna.docx%23_Toc403207929


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Project ID – 4034

Department of Electronics & Communication Engineering Page VII

LIST OF ABBREVATIONS

Symbol Name Abbreviations

MSA Microstrip Antenna

HFSS High Frequency Standard Simulator

ISM Industrial, Scientific and Medical

NFC Near Field Communication

VSWR Voltage Standing Wave Ratio

PTFE Poly Tetra Fluoro Ethylene

EmC Electromagnetic Compatibility

TEM Transverse-Electric-Magnetic

FEM Finite Element Method

FEKO Field Calculation for Bodies with Arbitrary Surface

FR4 Flame Retardancies 4

WLAN Wireless Local Area Network

HPBW Half Power Beam Width

MoM Moment Method


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Project ID – 4034

Department of Electronics & Communication Engineering Page VIII

TABLE OF CONTENTS

TITLE PAGE ........................................................................................................................... II

CERTIFICATE ........................................................................................................................ III

ABSTRACT .............................................................................................................................. V

LIST OF FIGURES ................................................................................................................. VI

LIST OF ABBREVATIONS ................................................................................................. VII

TABLE OF CONTENTS .................................................................................................... VIII

CHAPTER 1

INTRODUCTION ............................................................................................ 1

1.1

Overview ..................................................................................................................... 1

1.2

Problem Statement ...................................................................................................... 1

1.3

Motivation ................................................................................................................... 1

CHAPTER 2

LITERATURE SURVEY ............................................................................... 3

2.1. Microstrip Antenna Technology ..................................................................................... 3

2.2. Recent Advances on Data Networks, Communications, Computers .............................. 3

2.3. Broadband Microstrip patch Antenna ............................................................................. 3

2.4. Design of a Stacked Microstrip Patch Antenna Using HFSS ......................................... 4

2.5. Design and Modeling of Microstrip Patch Antenna Used for S-Band Communication. 4

CHAPTER 3

ANTENNA FUNDAMENTALS ..................................................................... 5

3.1 Antenna Performance Parameters .................................................................................... 5

3.1.1 Radiation Pattern ....................................................................................................... 6

3.1.2 Directivity ................................................................................................................. 6

3.1.3 Gain ........................................................................................................................... 6

3.1.4 Radiation Resistance ................................................................................................. 7

3.1.5 Polarizations .............................................................................................................. 7

3.1.6 Voltage Standing Wave Ratio (VSWR) ................................................................... 7

3.1.7 Bandwidth ................................................................................................................. 8

CHAPTER 4 MICROSTRIP ANTENNA .......................................................................... 9

4.1 Basic Principle of Operation ............................................................................................ 9

4.2 Material Consideration................................................................................................... 10

4.3 Feeding Techniques ....................................................................................................... 11

4.4 Methods of Analysis ...................................................................................................... 14

4.4.1 Transmission Line Model ....................................................................................... 14

4.4.2 Cavity Model .......................................................................................................... 16


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Department of Electronics & Communication Engineering Page IX

4.4 Advantages of Microstrip Antenna ................................................................................ 18

4.5 Disadvantages of Microstrip Antenna ........................................................................... 18

CHAPTER 5 MICROSTRIP ANTENNA DESIGN ........................................................ 20

5.1 Design Procedure ........................................................................................................... 20

5.2 Microstrip patch antenna calculator ............................................................................... 22

5.3 Antenna Simulation ....................................................................................................... 23

5.3.1 Steps for Antenna analysis using HFSS.................................................................. 23

5.4 MPA with Changing Ground plane design .................................................................... 23

5.5 MPA with different Material ......................................................................................... 24

CONCLUSION AND FUTURESCOPE ................................................................................. 27

REFERENCES ........................................................................................................................ 28


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Project ID – 4034 Chapter 1 Introduction

Department of Electronics & Communication Engineering Page 1

CHAPTER 1 INTRODUCTION

1.1 Overview

In high-performance aircraft, spacecraft, satellite, and missile applications, where size,

weight, cost, performance, ease of installation, and aerodynamic profile are constraints, low-

profile antennas may be required. Presently there are many other government and commercial

applications, such as mobile radio and wireless communications that have similar

specifications. To meet these requirements, microstrip antennas can be used. These antennas

are low profile, conformable to planar and non-planar surfaces, simple and inexpensive to

manufacture using modern printed-circuit technology, mechanically robust when mounted on

rigid surfaces, compatible with MMIC designs, and when the particular patch shape and

mode are selected, they are very versatile in terms of resonant frequency, polarization,

pattern, and impedance.

1.2 Problem Statement

Microstrip patch antenna is used due to its many advantages like small in size, easilyinstallable and light in weight but a main disadvantage of microstrip antenna is its bandwidth.

To overcome the bandwidth problem, different bandwidth enhancement techniques have been

adopted. Here I am going to make a microstrip patch antenna for ISM band which is widely

used for Cordless phones, Bluetooth devices, NFC devices and wireless computer networks.

Antenna is simulated in HFSS 13.

1.3 Motivation

Despite the many advantages of patch antennas, One of the main limitations with patch

antennas is their inherently narrowband performance due to its resonant nature. With

bandwidths as low as a few percent, broadband applications using conventional patch designs

are limited. Other characteristics of patch antennas include low efficiencies, limited power

capacity, spurious feed radiation, poor polarization purity, and manufacturing tolerance

problems. For over two decades, research scientists have developed several methods to

increase the bandwidth of a patch antenna. Many of these techniques involve adjusting the

http://en.wikipedia.org/wiki/Bluetoothhttp://en.wikipedia.org/wiki/Bluetooth


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Project ID – 4034 Chapter 1 Introduction


placement and/or type of element used to feed (or excite) the antenna. The first, simplest and

most direct, approach is to increase the thickness of the substrate, while using a low dielectric

substrate. Using thick dielectric substrate material on the other hand has the ability to produce

undesired surface wave which likely reduces the antenna efficiency, gain, bandwidth,

increases the side-lobes and antenna loss in general. In recent years the fastest-growing uses

of ISM bands have been for short-range, low power communications systems and Microstrip

patch antenna is best suitable for low power application.


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Project ID – 4034 Chapter 2 Literature Survey


CHAPTER 2 LITERATURE SURVEY

In this section some related works on Microstrip Patch antenna has been explained.

2.1. Microstrip Antenna Technology

Author: Keith R. carver, James W. Mink, Member IEEE [7]

Published Year: IEEE Transactions on Antennas and Propagation, Vol.29, No. 1,

January 1981

Conclusion: After reviewing this paper I have understood basics of microstrip antenna and

methods for analysis Microstrip antenna. Also they have explain various geometry of

microstrip antenna.

2.2. Recent Advances on Data Networks, Communications, Computers

Author: Bazeyi Hategekimana ,Jeyasingh Nithianandam.[1]

Published Year: Recent Advances on Data Networks, Communications, Computers "ISBN:

978-960-474-134-2,June 1999

Conclusion: This paper is for multilayer microstrip patch antenna. They used concept of

multilayer for broadband application. In their design they have use coaxial probe feeding

method with square patches and they obtained return loss (RL) better than -20dB at 1.8GHz ,

bandwidth (BW) greater than 10% at 10dB 1.8GHz.

2.3. Broadband Microstrip patch Antenna

Author: Mohammad Tariqul Islam,Mohammed Nazmus Shakib,Norbahiah Misran [2]

Published Year: European Journal of Scientific Research ISSN 1450-216X Vol.27 No.2

(2009)

Conclusion: The wideband characteristic of the antenna is achieved by using the L-shaped

probe feeding techniques, the use of series slots (H-shaped) and use of another pair of parallel

slots (E-shaped) lead to the patch size reduction. Better radiation performance is achieved by


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Project ID – 4034 Chapter 2 Literature Survey


embedding parallel slots onto the patch (E-shaped) while the use of inverted patch improves

the gain of the antenna. The composite effects of integrating these techniques offer a low

profile, broadband, high gain, and compact antenna element suitable for array applications.

The proposed microstrip patch antenna achieves a fractional bandwidth of 21.79% (1.84 to

2.29 GHz) at 10 dB return loss. The maximum achievable gain of the antenna is 9.5 dBi with

gain variation of 0.9dB.

2.4. Design of a Stacked Microstrip Patch Antenna Using HFSS

Author: Mark S. Reese, Constantine A. Balanis, and Craig R. Birtcher[3]

Published Year: IEEE 2009

Conclusion : Impedance matching across wideband can be achieved using stacked aperture

coupled microstrip patch antenna and using this method -10 dB return loss bandwidth, and

consequently the 2:1 SWR bandwidth, is 23% having obtained satisfactory results in the S

band.

2.5. Design and Modeling of Microstrip Patch Antenna Used for S-Band

Communication

Author: Kashmira Vaghela, Ved Vyas Dwivedi, Balvant Makwana[4]

Published Year: Proceedings of an International Conference on Optoelectronics, ICT — 2009

Conclusion: From this paper I have got idea about design parameters of microstrip patch

antenna. Also I got idea about two substrates microstrip antenna. Here they have design

antenna for s-band (3GHZ).


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Project ID – 4034 Chapter 3 Antenna Fundamentals


CHAPTER 3 ANTENNA FUNDAMENTALS

An antenna is defined by Webster’s Dictionary as ―a usually metallic device (as a rod or

wire) for radiating or receiving radio waves.‖ In the IEEE Standard Definitions of Terms for

Antennas (IEEE Std 145 – 1983) is defined as the structure associated with the region oftransition between a guided wave and a free-space wave, or vice versa.

In some applications a large antenna element is unsuitable for size. This requires the designer

to use a high operational frequency or create a unique antenna solution. The radiation from an

antenna can be explained with the help of Figure which shows a voltage source connected to

a two conductor transmission line. When a sinusoidal voltage is applied across the

transmission line, an electric field is created which is sinusoidal in nature and these results in

the creation of electric lines of force which are tangential to the electric field. Due to the time

varying electric and magnetic fields, electromagnetic waves are created and these travel

between the conductors. As these waves approach open space, free space waves are formed

by connecting the open ends of the electric lines. Since the sinusoidal source continuously

creates the electric disturbance, electromagnetic waves are created continuously and these

travel through the transmission line, through the antenna and are radiated into the free space.

Figure 1 Antenna Radiation Pattern

[8]

3.1 Antenna Performance Parameters

The important parameters that are used to specify the properties of an antenna are as

explained below


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3.1.1 Radiation Pattern

It is a plot of the power radiated from an antenna per unit solid angle which is nothing but the

radiation intensity. Let us consider the case of an isotropic antenna. An isotropic antenna is

one which radiates equally in all directions. If the total power radiated by the isotropic

antenna is P, then the power is spread over a sphere of radius r, so that the power density S at

this distance in any direction is given as:

HPBW: The half power beam width (HPBW) can be defined as the angle subtended

by the half power points of the main lobe.

Main Lobe: This is the radiation lobe containing the direction of maximum radiation.

Figure 2 Radiation Pattern of a Directional Antenna

[8]

3.1.2 Directivity

The directivity of an antenna has been defined as ―the ratio of the radiation intensity in a

given direction from the antenna to the radiation intensity averaged over all directions‖. The

directivity is fairly insensitive to the substrate thickness. In a Microstrip patch antenna

directivity is higher for lower permittivity because of the larger patch.

3.1.3 Gain

The gain is a basic property which is used as a figure of merit. It is defined as the ratio of

maximum radiation intensity in given direction to maximum radiation intensity from a

reference antenna produced in the same direction with the same power.

2

P PS = =

area 4 r

int t an

int .

Maximum radiation ensity from tes tennaGain G

Maximum radiation ensity from a ref antenna with same power input


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3.1.4 Radiation Resistance

It is defined as that fictitious resistance which, when substituted in series with the antenna,

will consume the same power as is actually radiated.

3.1.5 PolarizationsPolarization or plane of polarization of a radio wave can be defined by the direction in which

the electric vector E is aligned during the passage of at least one full cycle. Electric field

vector E is vertical or lies in the vertical place, the wave is said to be vertically polarized. If E

is in horizontal plane, the wave is said to horizontally polarize. Further, the undesired

radiation from an antenna is called as cross Polarization. The cross polarization, for linearly

polarized antennas, is perpendicular to the intended radiation.

Figure 3 A Vertically Polarized Wave

[8]

Figure 4 Commonly Used Polarization Schemes

[8]

3.1.6 Voltage Standing Wave Ratio (VSWR)

In order for the antenna to operate efficiently, maximum transfer of power must take place

between the transmitter and the antenna. If the condition for matching is not satisfied, then


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some of the power may be reflected back and this leads to the creation of standing waves,

which can be characterized by a parameter called as the Voltage Standing Wave Ratio.

3.1.7 Bandwidth

The bandwidth of an antenna is defined as ―the range of usable frequencies within which the

performance of the antenna, with respect to some characteristic, conforms to a specified

standard.‖ The bandwidth of a broadband antenna can be defined as the ratio of the upper tolower frequencies of acceptable operation. The bandwidth of a narrowband antenna can be

defined as the percentage of the frequency difference over the center frequency. These

definitions can be written in terms of equations as follows:

[7]

1

1

VSWR

in sr

i in s

Z Z V

V Z Z

H broadband

L

f BW

f (%) 100 H Lnarrowband

C

f f BW

f

Figure 5 Measurement of Bandwidth


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Project ID – 4034 Chapter 4 Microstrip Antenna


CHAPTER 4 MICROSTRIP ANTENNA

Microstrip antennas are one of the most widely used types of antenna. A microstrip antenna

consists of a radiating metallic patch or an array of patches situated on one side of a thin,

non-conducting, substrate panel with a metallic ground plane situated on the other side of the

panel. The metallic patch is normally made up of thin copper foil or is copper-foil-plated with

a corrosion resistive metal, such as gold, tin, or nickel. Each patch can be designed with a

variety of shapes, with the most popular shapes being rectangular or circular. The dielectric

substrate is used primarily to provide proper spacing and mechanical support between the

patch and its ground plane. It is also often used with high dielectric-constant material to load

the patch and reduce its size. The substrate material should be low in insertion loss with a loss

tangent of less than 0.005, in particular for large array application.

Figure 6 Geometry of Commonly known Microstrip Patch Antenna

[8]

Generally, substrate materials can be separated into three categories in accordance with their

dielectric constant:

1. Having a relative dielectric constant εr in the range of 1.0 to 2.0. This type of material can

be air, polystyrene foam, or dielectric honeycomb.

2. Having εr in the range of 2.0 to 4.0 with material consisting mostly of fiberglass reinforced

Teflon.

3. With εr between 4 and 10. The material can consist of ceramic, quartz, or alumina.

4.1 Basic Principle of Operation


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The primary source of this radiation is the electric fringing fields between the edges of the

conductor element and the ground-plane behind it. By analyzing this we discovered that the

Q (quality factor) of the dielectric cavity formed by two short circuit walls and four open

circuit walls depends on several parameters. The parameters are dielectric constant (εr),height (h) of the Substrate, patch dimensions and the frequency. Results showed that at high

frequency, radiation loss is the main source of energy dissipation as shown in figure.

Figure 7 Operation of Microstrip patch Antenna

[8]

The metallic patch essentially creates a resonant cavity, where the patch is the top of the

cavity, the ground plane is the bottom of the cavity, and the edges of the patch form the sides

of the cavity. The edges of the patch act approximately as an open-circuit boundary

condition. Hence, the patch acts approximately as a cavity with perfect electric conductor on

the top and bottom surfaces, and a perfect ―magnetic conductor‖ on the sides. This point of

view is very useful in analyzing the patch antenna, as well as in understanding its behaviour.

Inside the patch cavity the electric field is essentially z directed and independent of the z-

coordinate. Hence, the patch cavity modes are described by a double index (m, n). For the

(m, n) cavity mode of the rectangular patch, the electric field has the form.

4.2 Material Consideration

The purpose of the substrate material of a microstrip antenna is primarily to provide

mechanical support for the radiating patch elements and to maintain the required precision

spacing between the patch and its ground plane. With higher dielectric constant of the

substrate material, the patch size can also be reduced due to loading effect. Certainly, with

reduced antenna volume, higher dielectric constant also reduces bandwidth. There is a variety

of types of substrate materials. The relative dielectric constant of these materials can be


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anywhere from 1 to 10.Materials with dielectric constants higher than 10 should be used with

care. They can significantly reduce the radiation efficiency by having small antenna volumes.

The most popular type of material is Teflon-based with a relative dielectric constant between

2 and 3. This Teflon-based material, also named PTFE (poly tetra fluoro ethylene), has a

structure form very similar to the fiberglass material used for digital circuit boards, but it has

a much lower loss tangent or insertion loss.

Figure 8 Analysis of Efficiency, Bandwidth and Substrate Height

[6]

The selection of the appropriate material for a microstrip antenna should be based on the

desired patch size, bandwidth, insertion loss, thermal stability, cost, etc. For commercial

application, cost is one of the most important criteria in determining the substrate type. For

example, a single patch or an array of a few elements may be fabricated on a low-cost

fiberglass material at the L-band frequency, while a 20-element array at 30 GHz may have to

use higher-cost, but lower loss, Teflon-based material. For a large number of array elements

at lower microwave frequencies (below 15 GHz), a dielectric honeycomb or foam panel may

be used as substrate to minimize insertion loss, antenna mass, and material cost with

increased bandwidth performance.

4.3 Feeding Techniques

There are many configurations that can be used to feed microstrip antennas. The four most

popular are the microstrip line, coaxial probe, aperture coupling, and proximity coupling. The

most common type of feeding technique is the direct probe feed, shown in Figure for a


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rectangular patch, where the center conductor of a coaxial feed line penetrates the substrate to

make direct contact with the patch. For linear polarization, the patch is usually fed along the

centreline, y = W /2. The feed point location at x =Xf controls the resonant input resistance.

The input resistance is highest when the patch is fed at the edge, and smallest when the patch

is fed at the center (x = L /2). It has narrow bandwidth and it is more difficult to model,

especially for thick substrates (h > 0.02λ).

Figure 9 Probe fed microstrip patch antenna

[8]

Another common feeding technique, preferred for planar fabrication, is the direct-contact

microstrip feed line, shown in Figure. An inset notch is used to control the resonant input

resistance at the contact point. The input impedance seen by the microstrip line is

approximately the same as that seen by a probe at the contact point, provided the notch does

not disturb the modal field significantly.

The microstrip-line feed is easy to fabricate, simple to match by controlling the inset position

and rather simple to model. However as the substrate thickness increases, surface waves and

spurious feed radiation increase, which for practical designs limit the bandwidth (typically 2 –

5%).

Figure 10 Direct contact microstrip feed line

[8]

Both the microstrip feed line and the probes possess inherent asymmetries which generate

higher order modes which produce cross-polarized radiation. To overcome some of these


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problems, no contacting aperture-coupling feeds Aperture Coupling is another type of EMC

feed. David M. Pozar first proposed this type of feed to increase the bandwidth of the MSA.

The RF energy from the feed line is coupled to the radiating element through a common

aperture in the form of a rectangular slot. It mainly consists of two substrates separated by a

ground plane. Top substrate is for the radiating element and the bottom substrate is for the

feed-line. A slot is made in the ground plane to provide coupling between the feed line and

patch.

Figure 11 Aperture coupled Microstrip patch antenna

[8]

For the sake of maximum coupling the slot is usually placed at the center and it is

perpendicular to the feed line, as a result the patch and the slot may share common center.

The length of the slot should be kept somehow larger than the width of the slot. The

diagrammatic setup for aperture coupling is shown in figure. This scheme has the advantage

of isolating the feeding network from the radiating patch element. It also overcomes the

limitation on substrate thickness imposed by the feed inductance of a coaxial probe, so that

thicker substrates and hence higher bandwidths can be obtained but it suffers from high back

radiation.

Proximity coupling is a type of EMC feed, this has many advantages over edge fed and

coaxial fed antenna. Proximity-coupled microstrip antenna is also known as non-contacting

feeds. Some advantages are:

No physical contact between feed line and radiating element.

No drilling required.

Less spurious radiation.

Better for array configurations.


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Good suppression of higher order modes

Better high frequency performance

Figure 12 Proximity coupled patch

[8]

Matching can be achieved by controlling the length of the feed line and the width-to-line ratio

of the patch. The major disadvantage of this feed scheme is that it is difficult to fabricate

because of the two dielectric layers which need proper alignment. Also, there is an increase in

the overall thickness of the antenna.

4.4 Methods of Analysis

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 but it is less accurate. The cavity model is more accurate and gives

good physical insight but is complex in nature. The full wave models are extremely accurate,

versatile and can treat single elements, finite and infinite arrays, stacked elements, arbitrary

shaped elements and coupling. These give less insight as compared to the two models

mentioned above and are far more complex in nature.

4.4.1 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 non-homogeneous line of

two dielectrics, typically the substrate and air.


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Figure 13 Microstrip line with Electric field

[8]

Hence, as seen from Figure, 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 (εreff ) must be obtained in order to account for

the fringing and the wave propagation in the line. The value of εreff is slightly less than εr

because the fringing fields around the periphery of the patch are not confined in the dielectric

substrate but are also spread in the air as shown in Figure above. The expression for εreff is

given by Balanis as:

Where εreff = Effective dielectric constant

εr = Dielectric constant of substrate

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. In order to operate in the fundamental

TM10 mode, the length of the patch must be slightly less than λ/2 where λ is the wavelength

in the dielectric medium and is equal to λ0/√εreff where λ0 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 Figure 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.

1

2( 1) ( 1)1 12

2 2r r

reff

h

W


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Figure 14 Top view and Side view of antenna

[2]

It is seen from above Figure that the normal components of the electric field at the two edges

along the width are in opposite directions and thus out of phase since the patch is λ/2 long

and hence they cancel each other in the broadside direction. The tangential components

which are in phase, means that the resulting fields combine to give maximum radiated field

normal to the surface of the structure. Hence the edges along the width can be represented as

two radiating slots, which 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 modelled 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. The designing parameters of microstrip patch antenna is described in next

chapter.

4.4.2 Cavity Model

Although the transmission line model discussed in the previous section is easy to use, it has

some inherent disadvantages. Specifically, it is useful for patches of rectangular design and it

ignores field variations along the radiating edges. These disadvantages can be overcome by

using the cavity model. A brief overview of this model is given below. In this model, the

interior region of the dielectric substrate is modelled as a cavity bounded by electric walls on

the top and bottom. The basis for this assumption is the following observations for thin

substrates (h


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The electric field is z directed only, and the magnetic field has only the transverse

components Hx and Hy in the region bounded by the patch metallization and the ground

plane. This observation provides for the electric walls at the top and the bottom.

Figure 15 Charge distribution and current density creation on the microstrip patch

[4]

Consider Figure 15, when the microstrip patch is provided power, a charge distribution is

seen on the upper and lower surfaces of the patch and at the bottom of the ground plane.

When the microstrip patch is provided power, a charge distribution is seen on the upper and

lower surfaces of the patch and at the bottom of the ground plane. This charge distribution is

controlled by two mechanisms-an attractive mechanism and a repulsive mechanism as

discussed by Richards. The attractive mechanism is between the opposite charges on the

bottom side of the patch and the ground plane, which helps in keeping the charge

concentration intact at the bottom of the patch. The repulsive mechanism is between the like

charges on the bottom surface of the patch, which causes pushing of some charges from the

bottom, to the top of the patch. As a result of this charge movement, currents flow at the top

and bottom surface of the patch. The cavity model assumes that the height to width ratio (i.e.

height of substrate and width of the patch) is very small and as a result of this the attractive

mechanism dominates and causes most of the charge concentration and the current to be below the patch surface. Much less current would flow on the top surface of the patch and as

the height to width ratio further decreases, the current on the top surface of the patch would

be almost equal to zero, which would not allow the creation of any tangential magnetic field

components to the patch edges. Hence, the four sidewalls could be modelled as perfectly

magnetic conducting surfaces. This implies that the magnetic fields and the electric field

distribution beneath the patch would not be disturbed. However, in practice, a finite width to

height ratio would be there and this would not make the tangential magnetic fields to be

completely zero, but they being very small, the side walls could be approximated to be


26/36



perfectly magnetic conducting. Since the walls of the cavity, as well as the material within it

are lossless, the cavity would not radiate and its input impedance would be purely reactive.

Hence, in order to account for radiation and a loss mechanism, one must introduce a radiation

resistance R R and a loss resistance R L. A lossy cavity would now represent an antenna and the

loss is taken into account by the effective loss tangent δeff .

4.4 Advantages of Microstrip Antenna

Microstrip antennas have several advantages compared to conventional microwave antennas,

and therefore many applications cover the broad frequency range from ~ 100 MHz to ~ 100

GHz. Some of the principal advantages of microstrip antennas compared to conventional

microwave antennas are:

Light weight, low profile planar configurations, which can be made conformal.

Low fabrication cost; readily amenable to mass production.

The antennas may be easily mounted on missiles, rockets and satellites without major

alterations.

Linear, circular (left hand or right hand) polarizations are possible with simple

modification of patch geometry and changes in feed position.

Dual frequency antennas can be easily made.

Feed lines and matching networks are fabricated simultaneously with antenna

structure.

4.5 Disadvantages of Microstrip Antenna

The microstrip antennas also have some disadvantages compared to conventional microwave

antennas including:

Narrow bandwidth.

Loss, hence somewhat lower gain.

Practical limitations on the maximum gain

Poor end fire radiation performance

Poor isolation between the feed and the radiating elements

Possibility of excitation of surface waves & Lower power Handling Capability


27/36



There are ways to minimize the effect of some of these limitations. For example, bandwidth

can be increased to more than 60% by using special techniques; lower gain and lower power

handling limitations can be overcome thorough an array configuration. Surface wave

associated limitations such as poor efficiency, increased mutual coupling, reduced gain and

radiation pattern degradation can be overcome by the use of photonic band gap structures.


28/36

Project ID – 4034 Chapter 5 Microstrip Antenna Design


CHAPTER 5 MICROSTRIP ANTENNA DESIGN

The main factors involved in the design of a single patch antenna are:

Selection of substrate material

Feed position & its location

Patch dimensions.

For the selection of substrate, the major electrical properties to consider are relative dielectric

constant and loss tangent. The selection of substrate material plays a very important role in

patch antenna design. A higher loss tangent reduces antenna efficiency and increases feed

losses. A higher dielectric constant results in smaller patch but generally reduces bandwidth

resulting in tighter fabrication tolerance. The substrate thickness should be chosen as large as

possible to maximize bandwidth and efficiency, but not so large to risk surface wave.

5.1 Design Procedure

The design procedure used throughout thesis is applicable for antennas that work in the

frequency range of ISM band. The frequency band is used in Cordless phones, Bluetooth

devices, NFC devices, and wireless computer networks etc. The design techniques are also

applicable to any frequency ranges, which can be selected according to the designer’s wish.

Step 1: Width Calculation (W): The width of a micro strip patch is given by,

( 1)2

2r

a

cW

f

(5.1)

Step 2: Calculation Of Effective Dielectric Constant (εreff

): The effective dielectric

constant is given by,

(5.2)

1

2( 1) ( 1)1 12

2 2

r r reff

h

W

http://en.wikipedia.org/wiki/Bluetoothhttp://en.wikipedia.org/wiki/Near_field_communicationhttp://en.wikipedia.org/wiki/Wireless_networkhttp://en.wikipedia.org/wiki/Wireless_networkhttp://en.wikipedia.org/wiki/Near_field_communicationhttp://en.wikipedia.org/wiki/Bluetooth


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Figure 16 Flowchart for designing microstrip antenna parameter

[3]

Step 3: Calculation of the Effective Length (Leff ): The effective length is given by,

(5.3)

Step 4: Calculation of the Length Extension (ΔL):

(5.4)

Step 5: Calculation Of Actual Length Of Patch (L): The actual length is obtained by

rewriting equation as:

(5.5)

2eff

o reff

c L

f

0.412 ( 0.3)( 0.264)

( 0.258)( 0.8)

reff

reff

W h

h LW

h

2eff L L L


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Substituting = 3.0068cm and ΔL = 0.073852cm we get L= 2.8591cm. The width to

length ratio of the patch is 1, Sometimes is known as aspect ratio of the patch. Typically the

width of patch is taken to be W≤ 2L for wideband design.

Step 6: Determination Of Feed Point Location

A coaxial probe type feed is to be used in this design. The feed point must be located at that

point on the patch, where the input impedance is 50 ohms for the resonant frequency. Hence,

a trial and error method is used to locate the feed point. For different locations of the feed

point, the return loss (R L) is compared and that feed point is selected where the R L is most

negative.

5.2 Microstrip patch antenna calculator

Figure 17 Snapshot of MPA Calculator

Microstrip patch antenna calculator is made for avoiding manually calculation of

antenna design parameters. Snapshot of MPA is shown in figure 17. Here transmission line

model is used for designing MPA calculator. In this program we have to enter only resonant

frequency of antenna(f 0), Height of the substrate(h) and the permittivity of the substrate than

eff L


31/36



it will carry out all the necessary mathematical calculations, Please note that the values are in

millimetre.

5.3 Antenna Simulation

In order to calculate the full three-dimensional electromagnetic field inside a structure and the

corresponding S-parameters, HFSS employs the finite element method (FEM). FEM is a very

powerful tool for solving complex engineering problems, the mathematical formulation of

which is not only challenging but also tedious. The basic approach of this method is to divide

a complex structure into smaller sections of finite dimensions known as elements. These

elements are connected to each other via joints called nodes. Each unique element is then

solved independently of the others thereby drastically reducing the solution complexity. The

final solution is then computed by reconnecting all the elements and combining their

solutions. These processes are named assembly and solution respectively in the FEM. FEM

finds applications not only in electromagnetic but also in other branches of engineering such

as plane stress problems in mechanical engineering, vehicle aerodynamics and heat transfer.

FEM is the basis of simulation in HFSS.

5.3.1 Steps for Antenna analysis using HFSS

1.

Create a parametric solid model for geometry.

2. Specify material property.

3. Specify boundary condition and excitations

4.

Specify analysis and frequency sweep setup information

5.

Perform the analysis

6. Examine the results.

7. Examine the fields

5.4 MPA with Changing Ground plane design

For getting better S11 and bandwidth we need to change in microstrip antenna design. In

design we can change in shape of ground plane or patch. So first analysis with change in

ground plane design. An antenna design and simulation result for rectangular ground plane

and regular polyhedron plane is shown in figures. Patch Size: L=4 cm, W=3 cm, Ground

plane Size: L=10 cm, W =9 cm, Substrate height: 0.32 cm.


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Figure 18 Top view of Microstrip Antenna with Rectangular Plane

Figure 19 Graph of S11 for rectangular plane

5.5 MPA with different Material

We are changing material in MPA and find out suitable material for wider bandwidth and

better S11.

Figure 20 is top view of MPA with material FR-4 which has εr = 4.4 and substrate height=

1.7 mm. we get another design parameters by keeping this values into design equations. For

better S11 we need to find out feeding location by taking no. of iteration. Here we get best

feeding location (from starting point of substrate) Patch Dimensions: L=27.45 mm, Width =

37.1 mm, Ground Plane Dimensions: Length= 39mm and Width = 47.46 mm.


33/36



Figure 20 Top view of MPA with FR-4 Material

Figure 21 Result of S11 with FR-4 Material

Patch Dimension for PTFE material MPA: εr = 2.5, height=1.7 mm, Patch dimensions = 33

mm, W=37 mm, ground Plane dimensions= L=44.2 mm, W=48.2 mm. We got S11= -30db at

2.48 GHZ.

2.00 2.20 2.40 2.60 2.80 3.00Freq [GHz]

-30.00

-25.00

-20.00

-15.00

-10.00

-5.00

0.00

d B ( S t ( c o

a x p i n_

T 1 , c o a x p i n_

T 1 ) )

Ansoft Corporation FR_2.45XY Plot 1

m2

m3 m4

BW:0.14 GHZ5.7 %

Curve Info

dB(St(coaxpin_T1,coaxpin_T1))

Setup1 : Sweep1

Name X Y

m2 2.4500 -29.1383

m3 2.3900 -10.2684

m4 2.5200 -10.1882


34/36



Figure 22 Result of S11 with PTFE Material

Figure 23 Result of S11 with RT/Duroid Material

Figure 24 Result of Radiation Pattern

Patch Dimension for RT/duroid material MPA: εr = 2.2, height: 1.7 mm, Patch dimensions=

31.4 mm, W=39.15 mm, ground Plane dimensions: L=43.02 mm, W=49.72 mm. We got

S11=-31.4402db at 2.45 GHZ.

2.00 2.20 2.40 2.60 2.80 3.00Freq [GHz]

-30.00

-25.00

-20.00

-15.00

-10.00

-5.00

0.00

d B ( S t ( c o a x p i n_

T 1 , c

o a x p i n_

T 1 ) )

Ansoft Corporation PTFE_oldXY Plot 1

m1

m2m3

Curve Info

dB(St(coaxpin_T1,coaxpin_T1))

Setup1 : Sw eep1

Name X Y

m1 2.4800 -29.5922

m2 2.7400 -9.7985

m3 2.3900 -10.2900


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CONCLUSION AND FUTURESCOPE

Microstrip antenna is widely used due to its various advantages but main drawback isits bandwidth. As we have to make an antenna that works on ISM band so we have

to change the design accordingly. By changing in ground plane design we are not

getting efficient frequency but by changing substrate material we can get better

bandwidth. Also by increasing the thickness of substrate, we can get better output.


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Project ID – 4034 References

REFERENCES

[1] Bazeyi Hategekimana ,Jeyasingh Nithianandam "Recent Advances on Data Networks,

Communications, Computers "ISBN: 978-960-474-134-2

[2] Mohammad Tariqul Islam,Mohammed Nazmus Shakib,Norbahiah Misran

"Broadband Microstrip patch Antenna "European Journal of Scientific Research ISSN

1450-216X Vol.27 No.2 (2009), pp.174-180

[3] Mark S. Reese*, Constantine A. Balanis, and Craig R. Birtcher "Design of a Stacked

Microstrip Patch Antenna Using HFSS" IEEE 2009

[4] Amish Kumar Jha, Bharti Gupta "Performance of Microstrip Antenna of Different

Substrates and Geometries for S-Band" IJCSET | June 2011 | Vol 1.

[5] H. F. Shaban, H. A. Elmikaty, and A. A. Shaalan "Study The Effect of

Electromagnetics Band-Gap(EBG) Substrate on Two Patches Microstrip

Antenna"Progress In Electromagnetics Research B, Vol. 10, 55 – 74, 2008

[6] Design and Modeling of Microstrip Patch Antenna Used For S band Communication,

Ved Vyas Dwivedi & Balvant Makwana , Proceedings of an International Conference

on Optoelectronics, ICT — (ICOICT 2009)

[7] Microstrip Antenna Technology ,Keith R.carver , James W. Mink, Member

IEEE,IEEE transactions on Antennas And Propogation, VOL.AP "-29, NO. 1,

JANUARY 1981

[8] Antenna Theory Analysis And Design by Constantine A. Balanis, A John Willy

publication sons,Inc.

[9] Compact And Broadband Microstrip Antenna by kin-Lu Wong , A John Willy

publication sons,Inc.

[10] Getting Started with HFSSv13 for Antenna Design v0.pdf

Documents

3-Sample Report(Without Certificates)