SIM UNIVERSITY
SCHOOL OF SCIENCE AND TECHNOLOGY
DEVELOPMENT OF MINIATURIZED
MULTI-BAND ANTENNAS FOR MOBILE
DEVICES
STUDENT NAME : ZHANG TAO
STUDENT PI
: K0706404
SUPERVISOR
: DR SHEN ZHONG XIANG
PROJECT CODE : JAN2009/BEHE/49
Submitted to the School of Science and Technology
in partial fulfilment of the requirements for the degree of
Bachelor of Engineering in Electronics
November 2009
ABSTRACT
All of today's wireless communication systems contain one key element, an antenna of some
form. This antenna serves as the transducer between the controlled energy residing within the
system and the radiated energy existing in free space. In designing wireless systems,
engineers must choose an antenna that meets the system's requirements to firmly close the
link between the remote points of the communications system.
This project is to develop of miniaturized multi-band antennas for mobile devices
mainly design of square microstrip patch antenna. Basically the square microstrip patch
antennas are analyzed and detailed exploration is conducted to determine the antenna's
properties. The current distributions, bandwidth, radiation patterns and gain of the antenna
are discussed.
In addition, the time domain performance of the proposed antenna is also evaluated in
simulations. The research results show that this kind of square microstrip patch antenna can
radiate and receive short pulse signals without distortion.
The result of study indicates that the improved antenna can realize good bandwidth
performance as the square microstrip patch antenna, and it has low-cost, simple structural
characteristics. The miniature square microstrip patch antenna and the improved type are
suitable for the wireless communication systems, satellite communication systems and
mobile communications systems with good prospects.
I will summarise the accomplishment, performances of the design and the problems
encountered during the whole project. Further improvements and recommendations to the
project were also proposed.
ENG499 CAPSTONE PROJECT REPORT
2
TABLE OF CONTENTS
1.Introduction
1.1 Overview of Microstrip Antenna
9
9
1.2 Project Objective
10
1.3 Proposed Approach
10
1.4 Organization of the Thesis
10
2.Literature Review
11
2.1 Introduction Microstrip Patch Antenna
11
2.2 Advantages and Disadvantages
12
2.3 Feeding Methods
13
2.3.1 Microstrip Line Feed
13
2.3.2 Coaxial Feed
14
2.3.3 Aperture Coupled Feed
15
2.3.4 Proximity Coupled Feed
15
2.4 Method of Analysis
16
2.4.1 Transmission Line Model
16
2.4.2 Cavity Model
19
2.5 Multi-Band Antenna
20
2.5.1 Definition of Multi-Band Antenna
20
2.5.2 Design of Multi-Band Antenna
21
2.6 Antenna Miniaturization Techniques
22
3.Square Microstrip Patch Antenna
25
3.1 Introduction
25
3.2 Design Specifications
25
3.3 Design of Square Microstrip Antenna Using Theory Calculation
25
3.3.1 Design Procedure
3.4 Design of Square Microstrip Antenna Using IE3D Simulator
3.4.1 Results of Simulation
4.Miniaturization Antenna Design
26
28
29
33
4.1 Introduction
33
4.2 Design Description
33
4.2.1 Reduce Dielectric Constant Technique
33
4.2.2 Square Patch with Shorting GND Technique
33
ENG499 CAPSTONE PROJECT REPORT
3
4.2.3 Increase of Substrate Thickness Technique
34
4.2.4 Double Layer Half Wave Patch Technique
34
4.2.5 Combination of Shorting GND and Substrate Thickness Increase Technique
34
4.3 Results of Simulation Using IE3D Simulator
5.Conclusions
35
50
5.1 Thesis Contributions
50
5.2 Future Work
50
Reflections
52
Acknowledgements
54
References
55
ENG499 CAPSTONE PROJECT REPORT
4
List of Figures
2-1
Structure of a microstrip patch antenna
11
2-2
Common shapes of microstrip patch elements
11
2-3
Microstrip line feed
13
2-4
Probes fed rectangular microstrip patch antenna
14
2-5
Aperture-coupled feed
15
2-6
Proximity-coupled feed
16
2-7
Microstrip line
16
2-8
Electric field lines
16
2-9
Microstrip patch antennas
17
2-10 Top view of antenna
18
2-11 Side view of antenna
18
2-12 Charge distribution and current density creation on the microstrip patch
19
2-13 Patch with slots yields longer patch length
22
2-14 Circular patch with slots and high dielectric constant substrate
22
2-15 Folding of a half- wave path
23
2-16 Folding of a quarter-wave patch
23
2-17 Inverted-F patch antenna post
23
2-18 Circular patch with shorting
23
2-19 Circular polarized wire antenna
24
2-20 Antenna height reduction utilizing photonic hand-gap material
24
3-1
(a) Top view of microstrip patch antenna (b) Side view of microstrip
patch antenna (c) Overall design of microstrip patch antenna
27
3-2
Patch designed in IE3D software
29
3-3
S-parameter display for S (1, 1)
29
3-4
S-parameter displays for S (2, 2)
29
3-5
Smith Chart display for S (1, 1)
30
3-6
Smith Chart display for S (2, 2)
30
3-7
VSWR for port 1
30
3-8
VSWR for port 2
30
3-9
3D current distribution
31
3-10 Antenna and radiation efficiency vs frequency
31
3-11 Gain vs frequency
32
3-12 Total field directivity vs. frequency
32
ENG499 CAPSTONE PROJECT REPORT
5
4-1 Shorted GND patch drawing
33
4-2 Shorted GND patch Omit substrate view
33
4-3 Double layer or folded patch drawing
34
4-4 S-parameters for S (1, 1) comparison: (a) Original patch (b) Reduce dielectric
constant patch (c) Shorting GND patch (d) Increase substrate thickness patch
(e) Double layer half-wave patch (f) Combine methods patch
35
4-5 S-parameters for S (2, 2) comparison: (a) Original patch (b) Reduce dielectric
constant patch (c) Shorting GND patch (d) Increase substrate thickness patch
(e) Double layer half-wave patch (f) Combine methods patch
36
4-6 VSWR for port 1 comparison: (a) Original patch (b) Reduce dielectric
constant patch (c) Shorting GND patch (d) Increase substrate thickness
patch (e) Double layer half-wave patch (f) Combine methods patch
38
4-7 VSWR for port 2 comparison: (a) Original patch (b) Reduce dielectric
constant patch (c) Shorting GND patch (d) Increase substrate thickness
patch (e) Double layer half-wave patch (f) Combine methods patch
39
4-8 Smith Chart S (1, 1) comparison: (a) Original patch (b) Reduce dielectric
constant patch (c) Shorting GND patch (d) Increase substrate thickness
patch (e) Double layer half-wave patch (f) Combine methods patch
40
4-9 Smith Chart S (2, 2) comparison: (a) Original patch (b) Reduce dielectric
constant patch (c) Shorting GND patch (d) Increase substrate thickness
patch (e) Double layer half-wave patch (f) Combine methods patch
41
4-10 Total field gain vs frequency comparison: (a) Original patch (b) Reduce
dielectric constant patch (c) Shorting GND patch (d) Increase substrate
thickness patch (e) Double layer half-wave patch (f) Combine methods
patch
43
4-11 Total voltage field gain vs frquency comparison: (a) Original patch (b)
Reduce dielectric constant patch (c) Shorting GND patch (d) Increase
substrate thickness patch (e) Double layer half-wave patch (f) Combine
methods patch
45
4-12 Total field directivity vs frequency comparison: (a) Original patch (b)
Reduce dielectric constant patch (c) Shorting GND patch (d) Increase
substrate thickness patch (e) Double layer half-wave patch (f) Combine
methods patch
46
4-13 Antenna and radiation efficiency vs frequency comparison: (a) Original
patch (b) Reduce dielectric constant patch (c) Shorting GND patch (d)
ENG499 CAPSTONE PROJECT REPORT
6
Increase substrate thickness patch (e) Double layer half-wave patch (f)
Combine methods patch
ENG499 CAPSTONE PROJECT REPORT
48
7
List of Tables
4.1 Comparison result of S-parameter
35
4.2 Comparison result of VSWR
38
4.3 Comparison result of total field gain
43
4.4 Comparison result of total voltage field gain
44
4.5 Comparison result of total field directivity
46
4.6 Comparison result of antenna and radiation efficiency
47
4.7 Comparison of each technique overall performance
49
ENG499 CAPSTONE PROJECT REPORT
8
Chapter 1
Introduction
Modern and future wireless systems are placing greater demands on antenna designs. Many
systems now operate in two or more frequency bands, requiring dual or triple band operation
of fundamentally narrow band antennas. These include, satellite navigation systems, cellular
systems, wireless LAN and combination of these systems.
One of the most popular antennas employed in mobile communication systems is the
monopole antenna and its family. The monopole antennas are convenient to match to 50
ohms, and are unbalanced. The square microstrip patch antenna reported for multi-bands for
handsets is only about 0.05 times the wavelength of the lowest operating frequency.
This antenna is not only capable of multiband operations, but also possesses
omnidirectional radiation patterns for all operation bands. The impedance BW covers almost
all the present wireless systems of GSM (880-960MHz), including Digital Communication
Systems (DCS, 1720-1880MHz), Personal Communication Systems (PCS, 1850-1990MHz)
Universal Mobile communication systems (UMTS, 1920-2170MHz) and Industrial Science
Band (ISM, 2400-2484MHz). Its desired characteristics, such as low cost, ease of
manufacture, compact size, very wide BW, acceptable radiation efficiency, and
omnidirectional radiation patterns, makes the proposed antenna very attractive for mobile
communications.
1.1 Overview of Microstrip Antenna
A microstrip antenna consists of conducting patch on a ground plane separated by
dielectric substrate. This concept was undeveloped until the revolution in electronic
circuit miniaturization and large-scale integration in 1970[1]. After that many authors have
described the radiation from the ground plane by a dielectric substrate for different
configurations. The early work of Munson on micro strip antennas for use as a low profile
flush mounted antennas on rockets and missiles showed that this was a practical concept for
use in many antenna system problems. Various mathematical models were developed for this
antenna and its applications were extended to many other fields. The number of papers,
articles published in the journals for the last ten years, on these antennas shows the
importance gained by them. The micro strip antennas are the present day antenna designer’s
choice. Low dielectric constant substrates are generally preferred for maximum radiation.
The conducting patch can take any shape but rectangular and circular configurations are the
most commonly used configuration. Other configurations are complex to analyze and require
ENG499 CAPSTONE PROJECT REPORT
9
heavy numerical computations. A microstrip antenna is characterized by its length, width,
input impedance, and gain and radiation patterns.
Various parameters of the microstrip antenna and its design considerations were
discussed in the subsequent chapters. The length of the antenna is nearly half wavelength in
the dielectric; it is a very critical parameter, which governs the resonant frequency of the
antenna. There are no hard and fast rules to find the width of the patch.
1.2 Project Objective
The project objective is to develop a miniaturized multi-band antenna with a smaller
dimension and get better performance. Not only desired for GSM 900, 1800, 1900, UMTS
and WLAN applications to contribute effectively to standards for 3rd generation mobile
devices but also required in modern personal wireless communication devices.
1.3 Proposed Approach
The main approach would be to conduct at the SIM University Electronics laboratory. The
course required to re-design a smaller multi-band antenna. Existing miniaturization multiband antennas technique will be analyzed and see their performances from data.
The requirements of this project will be from literature review, and the guidance from
the project supervisor. The project will involve software which is available in the internet. A
systematic procedure of tests and measurement will have to be carrying out to ensure
accuracy of the test result. Assistant and guidance will be provided by Nanyang
Technological University. This project is scheduled for one year.
1.4 Organization of the Thesis
An introduction to microstrip antennas was given in Chapter 2.Apart from the advantages and
disadvantages, the various feeding techniques and models of analysis were listed.
Chapter 3 deals with design of square microstrip patch antenna and provides
Information about ID3E Software for simulation of square microstrip patch antenna which will
be used for cross verification of results for designed antennas.
Chapter 4 provides the design and development of miniaturization square microstrip
patch antenna and verification of the results for designed antennas.
Finally, Chapter 5 summarizes the contribution of this thesis and suggests areas for
future work.
ENG499 CAPSTONE PROJECT REPORT
10
Chapter 2
Literature Review
2.1 Introduction Microstrip Patch Antenna
Fundamentally, a microstrip patch antenna consists of a radiating patch on one side of a
dielectric substrate, and a ground plane on the other side as shown in Figure 2-1. The patch is
generally made of high conducting material such as copper or gold and no restriction on the
shape. The radiating patch and the feed lines are usually photo etched on the dielectric
substrate.
Figure 2-1 Structure of a microstrip patch antenna
In order to simplify analysis and performance prediction, the patch is generally square,
rectangular, circular, triangular, and elliptical or some other common shape as shown in
Figure 2-2. For a rectangular patch, the length L of the patch is usually 0.3333λo< L < 0.5 λo,
where λo is the free-space wavelength. The patch is selected to be very thin such that t << λo
(where t is the patch thickness). The height h of the dielectric substrate is usually 0.003 λo ≤ h
≤ 0.05 λo. The dielectric constant of the substrate (εr) is typically in the range 2.2 ≤ εr ≤ 12.
Figure 2-2 Common shapes of microstrip patch elements
ENG499 CAPSTONE PROJECT REPORT
11
Microstrip patch antennas radiate primarily because of the fringing fields between the patch
edge and the ground plane. For good antenna performance, a thick dielectric substrate having
a low dielectric constant is desirable since this provides better efficiency, larger bandwidth
and better radiation. However, such a configuration leads to a larger antenna size. In order to
design a compact Microstrip patch antenna, substrates with higher dielectric constants must
be used which are less efficient and result in narrower bandwidth. Hence a trade-off must be
realized between the antenna dimensions and antenna performance.
2.2 Advantages and Disadvantages
Microstrip patch antennas are increasing in popularity for use in wireless applications due to
their low-profile structure. Therefore they are extremely compatible for embedded antennas
in handheld wireless devices such as cellular phones, pagers etc.
The telemetry and communication antennas on missiles need to be thin and conformal and are
often in the form of microstrip patch antennas. Another area where they have been used
successfully is in Satellite communication. Some of their principal advantages discussed by
Kumar and Ray are given below:
• Light weight and low volume.
• Low profile planar configuration which can be easily made conformal to
host surface.
• Low fabrication cost, hence can be manufactured in large quantities.
• Supports both, linear as well as circular polarization.
• Can be easily integrated with microwave integrated circuits (MICs).
• Capable of dual and triple frequency operations.
• Mechanically robust when mounted on rigid surfaces.
Microstrip patch antennas suffer from more drawbacks as compared to conventional
antennas. Some of their major disadvantages discussed by and Garg et al are given below:
• Narrow bandwidth.
• Low efficiency.
• Low Gain.
• Extraneous radiation from feeds and junctions.
• Poor end fire radiator except tapered slot antennas.
• Low power handling capacity.
• Surface wave excitation.
Microstrip patch antennas have a very high antenna quality factor (Q). It represents the losses
associated with the antenna where a large Q leads to narrow bandwidth and low efficiency. Q
ENG499 CAPSTONE PROJECT REPORT
12
can be reduced by increasing the thickness of the dielectric substrate. However, as the
thickness increases, an increasing fraction of the total power delivered by the source goes into
a surface wave. This surface wave contribution can be counted as an unwanted power loss
because it is ultimately scattered at the dielectric bends. That causes degradation of the
antenna characteristics. Other problems like lower gain and lower power handling capacity
can be overcome by using an array configuration for the elements.
2.3 Feeding Methods
Feeding of the microstrip patch antennas can be used 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.
2.3.1 Microstrip Line Feed
In this type of feed technique, a conducting strip is connected directly to the edge of the
Microstrip patch as shown in Figure 2-3. The conducting strip is smaller in width compared
to the patch. This kind of arrangement has the advantage of the feed can be etched on the
same substrate to provide a planar structure.
Figure 2-3 Microstrip line feed
The purpose of the inset cut in the patch is to match the impedance of the feed line to the
patch without the need for any additional matching element. This can be achieved by
properly controlling the inset position. Hence this is an easy feeding scheme, since it provides
ENG499 CAPSTONE PROJECT REPORT
13
ease of fabrication and simplicity in modeling as well as impedance matching. 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.
2.3.2 Coaxial Feed
The Coaxial feed or probe feed is a very common technique used for feeding microstrip patch
antennas. As seen from Figure 2-4, the inner conductor of the coaxial connector extends
through the dielectric and is soldered to the radiating patch, while the outer conductor is
connected to the ground plane.
Figure 2-4 Probe fed rectangular microstrip patch antenna
The main advantage of this type of feeding scheme is that the feed can be placed at any
desired location inside the patch in order to match with its input impedance. This feed method
is easy to fabricate and has low spurious radiation. However, a major disadvantage 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 substrates (h > 0.02λo). 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. The non-contacting feed
techniques which have been discussed below, solve these issues.
ENG499 CAPSTONE PROJECT REPORT
14
2.3.3 Aperture Coupled Feed
In this type of feed technique, the radiating patch and the microstrip feed line are separated
by the ground plane as shown in Figure 2-5. Coupling between the patch and the feed line is
made through a slot or an aperture in the ground plane.
Figure 2-5 Aperture-coupled feed
The coupling aperture is usually centered under the patch, leading to lower cross
polarization due to symmetry of the configuration. The amount of coupling from the feed line
to the patch is determined by the shape, size and location of the aperture. Since the ground
plane separates the patch and the feed line, spurious radiation is minimized. Generally, a high
dielectric material is used for bottom substrate and a thick, low dielectric constant material is
used for the top substrate to optimize radiation from the patch. The major disadvantage of this
feed technique is that it is difficult to fabricate due to multiple layers, which also increases
the antenna thickness. This feeding scheme also provides narrow bandwidth.
2.3.4 Proximity Coupled Feed
This type of feed technique is also called as the electromagnetic coupling scheme. As shown
in Figure 2-6, 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.
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.
ENG499 CAPSTONE PROJECT REPORT
15
Figure 2-6 Proximity-coupled Feed
Matching can be achieved by controlling the length of the feed line and the width toline 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.
2.4 Method 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.
2.4.1 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.
Figure 2-7 Microstrip Line
ENG499 CAPSTONE PROJECT REPORT
Figure 2-8 Electric Field Lines
16
Hence, as seen from Figure 2-7, 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 transverseelectric-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 quasiTEM mode. Hence, an effective dielectric constant (  reff ) must be obtained in order to
account for the fringing and the wave propagation in the line. The value of  reff is slightly
less than  r 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 2-8 above. The
expression for  reff is given by Balanis [2] as:
(2.1)
 reff = Effective dielectric constant
Where
 r = Dielectric constant of substrate
h = Height of dielectric substrate
W = Width of the patch
Consider Figure 2-9 below, which 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.
Figure 2-9 Microstrip Patch Antennas
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/√  reff
where λo is the free space wavelength. The TM10 mode implies that the field varies one λ/2
ENG499 CAPSTONE PROJECT REPORT
17
cycle along the length, and there is no variation along the width of the patch. In the Figure 210 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 2-10 Top View of Antenna
Figure 2-11 Side View of Antenna
It is seen from Figure 2-11 that the normal components of the electric field at the two
edges along the width are in opposite directions and thus out of phase since the patch is λ/2
long and hence they cancel each other in the broadside direction. The tangential components
(seen in Figure 2-11), 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
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 given empirically by Hammers tad [3] as:
(2.2)
The effective length of the patch Leff now becomes:
(2.3)
ENG499 CAPSTONE PROJECT REPORT
18
For a given resonance frequency f 0 , the effective length is given by:
(2.4)
For a rectangular microstrip patch antenna. The resonance frequency for any TM mode is
given by James and Hall [4] as:
(2.5)
Where m and n are modes along L and W respectively.
For efficient radiation, the width W is given by Bahl and Bhartia [4].
(2.6)
2.4.2 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 modeled 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 << λ).
• Since the substrate is thin, the fields in the interior region do not vary much in the z
direction, i.e. normal to the patch.
• 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 2-12 Charge distribution and current density creation on the microstrip patch
ENG499 CAPSTONE PROJECT REPORT
19
Consider Figure 2-12 shown above. 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 modeled 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 perfectly magnetic conducting.
2.5 Multi-Band Antenna
2.5.1 Definition of Multi-Band Antenna
An antenna designed to operate on several bands. It is used design one part of the antenna is
active for one band, and another part is active for a different band. A multi-band antenna may
have lower than average gain or may be physically larger in compensation.
A multi-band antenna adapted to a portable electrical device capable of operating in
various wireless communication bands includes a first radiating conductor having opposite
elongated sides, a second radiating conductor extending from one end of the first radiating
conductor, a third radiating conductor arranging about a central area of the first radiating.
Both the second radiating conductor and the third radiating conductor extend from the same
elongated side of the first radiating conductor. A feeding body is curved from the third
radiating conductor. According to a position that the feeding body connecting to the third
radiating conductor and designed the feeding body, operation of the multi-band antenna has a
preferred range of a low frequency bandwidth and a high frequency harmonic bandwidth.
ENG499 CAPSTONE PROJECT REPORT
20
2.5.2 Design of Multi-Band Antenna
 Compact antenna
To efficiently radiate an electromagnetic wave into the free space, the size of an antenna
should be something in the order of the wavelength radiated, which is inversely proportional
to the frequency.
 Complete built-in antenna
As the handsets saturate in their proliferation and they diversify in functions, the design has
emerged as a major element of driving the customers to buy; In contrast to whip antennas that
protrude from the casing, built-in antennas that are installed within the casing for proper
operation can give a high degree of freedom of design. Not only because of this, but also
from the standpoints of reinforcing shock resistance, improvement of specific absorption rate
on the human body, reduction of manufacturing costs, the requirement for complete built-in
antennas for handsets is always growing.
 Multi-band Operation
The application of multi-band systems with a variety of frequency band combinations is
accelerating, whereby the international roaming is progressing globally, the communications
capacity is increasing and new functions are being added including GPS and Bluetooth. It s
expected, therefore, that all the handsets will probably become compatible with multi-band in
the near further.
 Isolation Characteristics
The isolation characteristics of an antenna indicate whether its performance is stabilized or
not against the environmental changes. Much importance has been placed on the isolation
characteristics of a mobile phone antenna from the two viewpoints as show below.
The first relates to the foldable casing consisting of the main circuit board and
display. More specifically, whether or not the same level of communication sensitivity can be
maintained between the two conditions where the casing is folded or unfolded.
The second is concerned with the performance stability against the influence of the
human hand and head. This is a problem specific to handsets such that the equipment is used
near the head while being held by the hand. Since human body is a lousy dielectric, the
electromagnetic waves radiated during the communication are absorbed by the human body
thus considerably degrading the radiation efficiency.
ENG499 CAPSTONE PROJECT REPORT
21
2.6 Antenna Miniaturization Techniques
Below is several miniaturization techniques have been identified:
 The use of high dielectric-constant material
The most popular technique in reducing the size of a printed antenna is to use high-dielectricconstant material for its substrate. In doing so, the guided-wavelength underneath the patch is
reduced and, hence the resonating patch size is also reduced. To further reduce the size, slot
can be introduced onto the resonating patch. In doing so, the current on the patch or the filed
underneath the patch will resonate from one edge as illustrated in Fig 2-13.
 Slots on the resonating patch
For the longer path, reduces the resonant frequency or the physical size of the antenna.
Depending on the length of the slots, a 10% to 20% size reduction can be achieved. Show in
Fig 2-14.
 The folding of a single-layer patch into a two-layer structure
This technique is to fold the complete single-layer patch antenna (including substrate and
ground plane) to form a two-layer structure and hence reduce the planar dimension by half.
The configuration of the folded half-wave patch is illustrated in Fig 2-15 and the folding of a
quarter-wave patch is shown in Fig 2-16.
ENG499 CAPSTONE PROJECT REPORT
22
 The inverted-F configuration
This technique is to use the planar inverted-F configuration as shown in Fig 2-17. Where the
width dimension of the short-circuited plate is significantly smaller than L1 and the
dimensions L1 and L2 are each on the order of 1/8.
 The use of a shorting post
This technique is very similar to the inverted-F method, is the use of a circular patch with a
shorting post as illustrated in Fig 2-18.
 The quarter-wave-patch approach
The antenna operates as a quarter wave patch antenna and is constructed from a rectangular
metal patch separated from a larger metallic plane. This metallic plane serves as the reference
ground plane for a circuit attached to the antenna, with a direct short between the patch and
the ground plane along one edge of the patch.
 The genetic algorithm
This technique is used to minimize the size of wire type or printed antennas, while optimize
their RF performance. This antenna optimization is very similar to human’s biological
ENG499 CAPSTONE PROJECT REPORT
23
genetic evolution where biological configurations adapt to optimal fitness to the natural
environment by a huge number of chromosome sets with binary type of genetic decisions.
For example, by using this technique, an odd-shaped small wire antenna as shown in Fig 219, achieved circular polarization with hemispherical radiation coverage.
 The use of photonic band-gap material
This emerging techniques show the “photonic band-gap” material. In the case of
electromagnetic application, it is also best called the “electromagnetic band gap” material. It
acts very similar to a frequency selective surface, will reflect or transmit through only a
certain band of electromagnetic energy. This material comes in various forms. One uses a
thin slab of dielectric material with many equally spaced holes as shown in Fig 2-20.
ENG499 CAPSTONE PROJECT REPORT
24
Chapter 3
Square Microstrip Patch Antenna
3.1 Introduction
In this chapter, the procedure for designing a square microstrip patch will be discussed. By
using theory to calculate design antenna, the dimension of the antenna is achieved. Follow by
the simulation of the design using IE3D application. The results obtained from the
simulations are demonstrated and analyzed.
3.2 Design Specifications
The three essential parameters for the design of a square microstrip patch antenna are:
• Frequency of operation ( f 0 ): The resonant frequency of the antenna must be
selected appropriately. The Mobile Communication Systems uses the frequency range from
850-3000 MHz Hence the antenna designed must be able to operate in this frequency range.
The resonant frequency selected for my design is 3.0 GHz.
• Dielectric constant of the substrate (  r ): The dielectric material selected for my
design is silicon with a constant of 2.5. A substrate with a high dielectric constant has been
selected since it reduces the dimensions of the antenna.
• Height of dielectric substrate (h): For the square microstrip patch antenna to be used
in cellular phones, it is essential that the antenna is not bulky. Hence, the height of the
dielectric substrate is selected as 1.5 mm.
Hence, the essential parameters for the design are:
• f 0 = 3.0 GHz
•  r = 2.5
• h = 1.5 mm
3.3 Design of Square Microstrip Antenna Using Theory Calculation
The propagation of the electromagnetic field is usually considered in free space, where it
travels at the speed of light. vo  3  108 m / s .  , lambda is the wavelength, expressed in
meters.
Wavelength of the GSM band
In GSM band, the following expression is used:

ENG499 CAPSTONE PROJECT REPORT
vo
f (GHz)
(3.1)
25
Hence, the wavelength of the antenna when operating at 3 GHz is 0.1 m.
3.3.1 Design Procedure
From the above, the essential parameters for the design are:
a. f o = 3 GHz, b.  r = 2.5, c. h = 1.5 mm
a) Calculation of the Width (W):
The width of the microstrip patch antenna is given by equation:
W
vo
2 fo
2
r 1
(3.2)
Substituting vo =3x10 8 m/s,  r =2.5 and f o =3 GHz,
W= 38 mm
b) Calculation of Effective dielectric constant (  reff ):
 r 1  r 1 

1
h 2
 reff 

1  12 

2
2 
W
Substituting  r =2.5, W= 38 mm and h= 1.5 mm,
 reff =2.36
(3.3)
c) Calculation of the Effective length ( Leff ):
Leff 
vo
2 f o  reff
(3.4)
Substituting vo =3x10 8 m/s,  reff =2.36 and f o =3 GHz
Leff =32.5 mm
d) Calculation of the length extension (ΔL):
W
 0.264)
h
L  0.412h
W
( reff  0.258)(  0.8)
h
8
Substituting vo =3x10 m/s,  reff =2.36 and f o =3 GHz
( reff  0.3)(
(3.5)
L =1.24 mm
e) Calculation of actual length of patch (L):
L  Leff  2L
(3.6)
Substituting Leff =33.95 mm, L =1.24 mm
L  30.01mm
ENG499 CAPSTONE PROJECT REPORT
26
f) Calculation of the ground plane dimensions (Lg and Wg):
The transmission line model is applicable to infinite ground planes only. However, for
practical considerations, it is essential to have a finite ground plane. The finite ground can be
obtained if the size of the ground plane is greater than the patch dimensions by approximately
six times the substrate thickness all around the periphery. Hence, for this design, the ground
plane dimensions would be given as:
Lg = 6h + L, Wg = 6h + W
(3.7)
Hence, the calculated Lg and Wg are 39 mm and 47 mm respectively.
g Microstrip Patch Antenna Dimensions
Figure 3-1 (a) Top view of microstrip patch antenna
Figure 3-1 (b) Side view of microstrip patch antenna
Figure 3-1 (c) Overall design of microstrip patch antenna.
ENG499 CAPSTONE PROJECT REPORT
27
Based on the calculation above, the L and W derived are 30 mm and 38 mm .The design of
the microstrip antenna array starts from microstrip antenna. The microstrip antenna is feed
using microstrip feed line, the design dimensions for this project is as follows:
Frequency, f o = 3GHz
Dielectric constant,  r = 2.5
Substrate thickness, h = 1.5 mm
Metallic strip thickness, t = 0.02 mm
Conductivity of ground plane (Copper), g = 5.8 x 10 7 S/m
Effective dielectric constant,  reff = 2.3
Resonant input impedance, Rin = 50 
h) Using bandwidth equation:



BW=3.77  r  1 /  r2 W / L h /  
(3.8)
Substituting  r = 2.5, W= 38mm, h = 1.5 mm L= 30 mm
BW=0.167 GHz
3.4 Design of Square Microstrip Antenna using IE3D Simulator
Given specifications were,
1. Dielectric constant (  r ) = 2.5
2. Frequency ( f r ) = 3.0 GHz.
3. Height (h) = 1/16 Inch = 1.59 mm.
4. Velocity of light (c) = 3×10 8 ms 1 .
5. Practical width (W) W = 38 mm.
6. Loss Tangent (tan δ) = 0.001.
7. Practical Length (L) L = 30 mm.
8. Metallic strip thickness, t = 0.02 mm
ENG499 CAPSTONE PROJECT REPORT
28
3.4.1 Results of Simulation
The Figure 3-2 shown the square microstrip patch design shape using IE3D simulator.
Figure 3-2 Patch designed in IE3D software
S-Parameters
S-parameters are mostly used for networks operating at radio frequency and microwave
frequencies where signal power and energy considerations are more easily quantified than
currents and voltages. Below Figure 3-3, 3-4 show that S-Parameter Displays for S (1.1) and
S (2.2). From the graphs, the bandwidth is about 0.16 GHz and closed to the calculation
result.0.167 GHz at frequency 3 GHz.
Figure 3-3 S-Parameter display for S (1, 1)
ENG499 CAPSTONE PROJECT REPORT
Figure 3-4 S-Parameter displays for S (2, 2)
29
Smith Charts
From the graph Figure 3-5, 3-6 as shown that the system impedance R1 is 50  .
Figure 3-5 Smith Chart display for S (1, 1) Figure 3-6 Smith Chart display for S (2, 2)
Voltage Standing Wave Ratio (VSWR)
From the graph Figure 3-7, 3-8 shown that the ratio of the amplitude of a partial standing
wave at an antinodes (maximum) to the amplitude at an adjacent node (minimum) for the
design patch antenna. Therefore VSWR estimate is 3 at frequency 3 GHz.
Figure 3-7 VSWR for Port 1
Figure 3-8 VSWR for Port 2
3D Current Distribution
From Figure 3-9 graph is shown the design patch current distribution condition.
ENG499 CAPSTONE PROJECT REPORT
30
Figure 3-9 3D Current distribution
Antenna and Radiation Efficiency Display
From Figure 3-10 shown that the design of square microstrip patch antenna has 80% antenna
efficiency and 85% radiation efficiency at frequency 3 GHz.
Figure 3-10 Antenna and radiation efficiency vs frequency
Total Gain vs. Frequency Graph
The Figure 3-11 is shown that the total field gain is about 6.5 dBi at frequency 3 GHz.
ENG499 CAPSTONE PROJECT REPORT
31
Figure 3-11 Gain vs frequency
Total Field Directivity vs. Frequency Graph
The Figure 3-12 is shown that total field directivity has 7.2 dBi at frequency 3 GHz.
Figure 3-12 Total field directivity vs. frequency
ENG499 CAPSTONE PROJECT REPORT
32
Chapter 4
Miniaturization Antenna Design
4.1 Introduction
In this chapter, 5 types of miniaturization antenna techniques are analyzed and simulated
using IE3D application and the each type of results are compared. Consequence of
miniaturization the physical dimension can be result in undesirable changes of bandwidth,
efficiency and so on. Applying of technique could cover back such condition, depend on the
techniques that applied, there may be different outcome. In this Section, these techniques or
of miniaturization are tested out by applying on the original antenna patch and follow by,
analyzed how much the antenna simulated results are different.
4.2 Design Description
4.2.1 Reduce dielectric constant technique
Changing the dielectric constant could vary the antenna performance. In this design, the
dielectric constant is lowed and specifications are as follows:
Dielectric constant (  r ) = 1.5
Height of substrate (h) = 1/16 Inch = 1.5 mm.
Thickness of patch = 0.002 mm
Loss Tangent (tan δ) = 0.001.
Practical width (W) W = 38 mm.
Practical Length (L) L = 30 mm.
The specification is same as the original design. The only change is on reducing of dielectric
constant 2.5mm to 1.5mm.
4.2.2 Square patch with shorting GND technique
This method is widely used in some of the monopole planar antenna. Antenna patch and
ground will be shorted directly near the feeding probe. Finite ground have used for this
design. Design is as follows:
Figure 4-1 Shorted GND patch drawing
ENG499 CAPSTONE PROJECT REPORT
Figure 4-2 Shorted GND patch omit substrate view
33
4.2.3 Increase of substrate thickness technique
In the microstrip antenna type, the thickness and dielectric constant of the substrate are
playing a major role. Changing those will result in alteration of the original design. Any
techniques could have advantages and disadvantages. In this part, the substrate thickness will
be doubled compare to the original design.
Dielectric constant (  r ) = 2.5
Height of substrate (h) = 1/16 Inch = 3.0 mm.
Thickness of patch = 0.002 mm
Loss Tangent (tan δ) = 0.001.
Practical width (W) W = 38 mm.
Practical Length (L) L = 30 mm.
4.2.4 Double layer half wave patch technique
Normally, when one is thinking of miniaturization on the object, example an A4 paper sheet,
folding it would be a first instinct idea. Folding the object into smaller part is the most
obvious in physical appearance in smaller. Therefore, the experiment on folding the square
patch is carried out in this section and the specification is as follows:
Figure 4-3 Double layer or folded patch drawing
4.2.5 Combination of shorting GND and increase substrate thickness technique
After trying out the above techniques and analyzing the data from the simulation, combining
the two techniques into one is considered. From the result, shorting the GND and increasing
the substrate is desirable.
ENG499 CAPSTONE PROJECT REPORT
34
4.3 Results of Simulation using IE3D Simulator
4.3.1 S-parameter- S (1, 1)
After analyses the S-parameter simulation result from Table 4.1.the result has shown that:
a) Reduce dielectric constant technique will be get more than 50% bandwidth compare the
original design bandwidth.
b) Square patch with shorting GND technique get more than 112% bandwidth compare the
original design bandwidth.
c) Double sizes of thickness substrate technique get same bandwidth result compare the
original design bandwidth.
d) Half wave square patch technique get more than 400% bandwidth compare the original
design bandwidth.
e) Combination of square patch with shorting GND and increase substrate thickness
technique get more than 180% bandwidth compare the original design bandwidth.
S-parameter Comparison Results
1.Original Design
2.Dielectric Constant Reduce 1.5 mm
3.Square Patch With Shorting GND
4.Thickness Substrate Increase from 1.5 to 3mm
5.Half Wave Square Patch (double layer substrate)
6.Square Patch with Shorting GND + Increase Substrate Thickness
(Bandwidth(dBi)
0.16 GHZ
0.24 GHZ
0.34 GHZ
0.15 GHZ
0.78 GHz
0.31 GHZ
Table 4.1 Comparison results of S-parameter
Below Figure 4-4 and Figure 4-5 are each technique simulation result graph for S-parameter
using IE3D simulator.
Figure 4-4 (a) Original patch
ENG499 CAPSTONE PROJECT REPORT
Figure 4-4 (b) Reduce dielectric constant patch
35
Figure 4-4 (c) Shorting GND patch
Figure 4-4 (d) Increase substrate thickness patch
Figure 4-4 (e) Double layer half-wave patch
Figure 4-4 (f) Combine methods patch
4.3.2 S-parameter – s( 2,2 )
Figure 4-5(a) Original patch
ENG499 CAPSTONE PROJECT REPORT
Figure 4-5(b) Reduce dielectric constant patch
36
Figure 4-5 (c) Shorting GND patch
Figure 4-5 (d) Increase substrate thickness patch
Figure 4-5(e) Double layer half-wave patch
Figure 4-5 (f) Combine methods patch
4.3.3 VSWR – Port 1
After analyses the VSWR simulation result from Table 4.2.the result has shown that:
a) Reduce dielectric constant technique will be get 71.3. It is more worst than original
design VSWR.
b) Square patch with shorting GND technique get same result compare the original design
patch.
c) Double size of thickness substrate technique get slightly larger VSWR than the original
design patch.
d) Half wave square patch technique get 2 times larger VSWR than the original design
patch.
e) Combination of square patch with shorting GND and increase substrate thickness
technique get more than 2 times larger VSWR than the original design patch antenna.
ENG499 CAPSTONE PROJECT REPORT
37
VSWR Comparison Results
VSWR
1.Original Design
2.Dielectric Constant Reduce 1.5 mm
3.Square Patch With Shorting GND
4.Thickness Substrate Increase from 1.5 to 3mm
5.Half Wave Square Patch (double layer substrate)
6. Square Patch with Shorting GND + Increase Substrate Thickness
Table 4.2 Comparison results of VSWR
3
71.3
3.1
4.85
6
6.32
Below Figure 4-6 and Figure 4-7 are each technique simulation result graph for VSWR using
IE3D simulator.
Figure 4-6 (a) Original patch
Figure 4-6 (c) Shorting GND patch
ENG499 CAPSTONE PROJECT REPORT
Figure 4-6 (b) Reduce dielectric constant patch
Figure 4-6 (d) Increase substrate thickness patch
38
Figure 4-6(e) Double layer half-wave patch
Figure 4-6 (f) Combine methods patch
4.3.4 VSWR – Port 2
Figure 4-7 (a) Original patch
Figure 4-7 (b) Reduce dielectric constant patch
Figure 4-7 (c) Shorting GND patch Figure 4-7 (d) Increase substrate thickness patch
ENG499 CAPSTONE PROJECT REPORT
39
Figure 4-7(e) Double layer half-wave patch
Figure 4-7 (f) Combine methods patch
4.3.5 Smith Chart – S( 1,1 )
After analyses the Smith Chart simulation result from graph. I can say that only the increase
substrate thickness patch technique given same result and the rest techniques are worse than
the original patch antenna design. Below Figure 4-8 and Figure 4-9 are each technique
simulation result graph for Smith Chart using IE3D simulator.
Figure 4-8 (a) Original patch
ENG499 CAPSTONE PROJECT REPORT
Figure 4-8 (b) Reduce dielectric constant patch
40
Figure 4-8 (c) Shorting GND patch
Figure 4-8 (d) Increase substrate thickness patch
Figure 4-8(e) Double layer half-wave patch
Figure 4-8 (f) Combine methods patch
4.3.6 Smith Chart – S( 2,2 )
Figure 4-9 (a) Original patch
ENG499 CAPSTONE PROJECT REPORT
Figure 4-9 (b) Reduce dielectric constant patch
41
Figure 4-9 (c) Shorting GND patch
Figure 4-9 (d) Increase substrate thickness patch
Figure 4-9(e) Double layer half-wave patch
Figure 4-9 (f) Combine methods patch
4.3.7 Total Field Gain Vs Frequency
After analyses the total field gain simulation result from Table 4.3. The result has shown that:
a) Reduce dielectric constant technique will be get -9.47 dBi. It is more worst than original
design gain.
b) Square patch with shorting GND technique get lower gain compare the original design
patch.
c) Double sizes of thickness substrate technique get slightly higher than shorting GND
technique but still not good enough than the original design patch.
d) Half wave square patch technique get -7.6 dBi. It is better than reduce dielectric constant
technique but it is worst than original design gain.
e) Combination of square patch with shorting GND and increase substrate thickness
technique only get 2.07 dBi power gains. It is not better than original design patch
antenna.
ENG499 CAPSTONE PROJECT REPORT
42
Total Field Gain Comparison Results
Power Gain(dBi)
1.Original Design
2.Dielectric Constant Reduce 1.5 mm
3.Square Patch With Shorting GND
4.Thickness Substrate Increase from 1.5 to 3mm
5.Half Wave Square Patch (double layer substrate)
6. Square Patch with Shorting GND + Increase Substrate Thickness
6.5
-9.47
2.92
3.77
-7.6
2.07
Table 4.3 Comparison results of total field gain
Below Figure 4-10 are each technique simulation result graph for total field gain vs frequency
using IE3D simulator.
Figure 4-10 (a) Original patch
Figure 4-10 (b) Reduce dielectric constant patch
Figure 4-10 (c) Shorting GND patch Figure 4-10 (d) Increase substrate thickness patch
ENG499 CAPSTONE PROJECT REPORT
43
Figure 4-10(e) Double layer half-wave patch
Figure 4-10 (f) Combine methods patch
4.3.8 Total Voltage Field Gain Vs Frquency
After analyses the total voltage field gain simulation result from Table 4.4. The result has
shown that:
a) Reduce dielectric constant technique will be get -15 dBi. It is more worst than original
design gain.
b) Square patch with shorting GND technique get lower gain compare the original design
patch.
c) Double sizes of thickness substrate technique get slightly higher than shorting GND
technique but still not good enough than the original design patch.
d) Half wave square patch technique get -12.56 dBi. It is better than reduce dielectric
constant technique but it is worst than original design gain.
e) Combination of square patch with shorting GND and increase substrate thickness
technique get -0.64 dBi power gain. It is not better than original design patch antenna.
Total Voltage Field Gain Comparison Results
Voltage Field Gain(dBi)
1.Original Design
3.85
2.Dielectric Constant Reduce 1.5 mm
-15
3.Square Patch With Shorting GND
-1.13
4.Thickness Substrate Increase from 1.5 to 3mm
-1.11
5.Half Wave Square Patch (double layer substrate)
-12.56
6. Square Patch with Shorting GND + Increase Substrate Thickness
-0.64
Table 4.4 Comparison results of total voltage field gain
Below Figure 4-11 are each technique simulation result graph for total field gain vs frequency
using IE3D simulator.
ENG499 CAPSTONE PROJECT REPORT
44
Figure 4-11 (a) Original patch
Figure 4-11 (b) Reduce dielectric constant patch
Figure 4-11 (c) Shorting GND patch Figure 4-11 (d) Increase substrate thickness patch
Figure 4-11(e) Double layer half-wave patch
Figure 4-11 (f) Combine methods patch
4.3.9 Total Field Directivity Vs Frequency
After analyses the total voltage field directivity simulation result from Table 4.5. The result
has shown that:
a) Reduce dielectric constant technique will be get 5.24 dBi. It is lower than original design
gain.
b) Square patch with shorting GND technique get slightly lower compare the original design
patch.
ENG499 CAPSTONE PROJECT REPORT
45
c) Double sizes of thickness substrate technique get slightly higher than the original design
patch.
d) Half wave square patch techniques get 6.4 dBi and lower than original design gain.
e) Combination of square patch with shorting GND and increase substrate thickness
technique get 7.05 dBi. It is not better than original design patch antenna.
Total Field Directivity Comparison Results
Directivity(dBi)
1.Original Design
7.20
2.Dielectric Constant Reduce 1.5 mm
5.24
3.Square Patch With Shorting GND
6.86
4.Thickness Substrate Increase from 1.5 to 3mm
7.4
5.Half Wave Square Patch (double layer substrate)
6.4
6. Square Patch with Shorting GND + Increase Substrate Thickness
7.05
Table 4.5 Comparison results of total field directivity
Below Figure 4-12 are each technique simulation result graph for total field directivity vs
frequency using IE3D simulator.
Figure 4-12 (a) Original patch
Figure 4-12 (b) Reduce dielectric constant patch
Figure 4-12 (c) Shorting GND patch Figure 4-12 (d) Increase substrate thickness patch
ENG499 CAPSTONE PROJECT REPORT
46
Figure 4-12(e) Double layer half-wave patch
Figure 4-12 (f) Combine methods patch
4.3.10 Antenna and Radiation Efficiency Vs Frequency
After analyses the antenna and radiation efficiency simulation result from Table 4.6. The
results have shown that:
a) Reduce dielectric constant technique is given 68.3% lower radiation efficiency and only
4.93% antenna efficiency compare the original patch antenna result.
b) Square patch with shorting GND technique get slightly higher radiation efficiency and
only 40.5 % antenna efficiency compare the original patch antenna result.
c) Double size of thickness substrate technique get slightly lower radiation efficiency and
50% antenna efficiency compare the original patch antenna result.
d) Half wave square patch technique get only 20.27% radiation efficiency and only 4.34%
antenna efficiency compare the original patch antenna result.
e) Combination of square patch with shorting GND and increase substrate thickness
technique given same radiation efficiency but the antenna efficiency result is not better
than original patch antenna result.
Radiation
Efficiency
Antenna
Efficiency
1.Original Design
84.80%
78%
2.Dielectric Constant Reduce 1.5 mm
68.30%
4.93%
3.Square Patch With Shorting GND
85.50%
40.50%
4.Thickness Substrate Increase from 1.5 to 3mm
75.59%
50%
5.Half Wave Square Patch (double layer substrate)
20.27%
4.34%
Antenna and Radiation Efficiency Comparison Results
6. Square Patch with Shorting GND + Increase
84.50%
33.30%
Substrate Thickness
Table 4.6 Comparison result of antenna and radiation efficiency
ENG499 CAPSTONE PROJECT REPORT
47
Below Figure 4-13 are each technique simulation result graph for antenna and radiation
efficiency using IE3D simulator.
Figure 4-13 (a) Original patch
Figure 4-13 (c) Shorting GND patch
Figure 4-13 (b) Reduce dielectric constant patch
Figure 4-13 (d) Increase substrate thickness patch
Figure 4-13(e) Double layer half-wave patch
ENG499 CAPSTONE PROJECT REPORT
Figure 4-13 (f) Combine methods patch
48
4.3.11 Each Technique Overall Performance
From above data come out the overall simulation performance. The Table 4.7 is shown that
original design is still the best overall performance. The rest miniaturization techniques can
only achieved individual best performance.
Overall Performance
Results
Bandwidth
(dBi)
Power
Gain
(dBi)
VSWR
Radiation
Efficiency
Antenna
Efficiency
Voltage Field
Gain(dBi)
Directivity(dBi)
1. Original Design
0.16 GHz
6.5
3
84.80%
78.00%
3.85
7.2
2. Dielectric Constant
Reduce to 1.5mm
0.24GHz
-9.47
71.3
68.30%
4.93%
-15
5.24
3. Square Patch with
Shorting GND
0.34 GHz
2.92
3.1
85.50%
40.50%
-1.13
6.86
4. Thickness Substrate
Increase from 1.5 to 3
mm
0.15 GHz
3.77
4.85
75.59%
50.00%
-1.11
7.4
5. Half Wave Square
Patch
0.78 GHz
-7.6
6
20.27%
4.34%
-12.56
6.4
6. Square Patch with
Shorting GND +
Increase Substrate
Thickness
0.31 GHz
2.07
6.32
84.50%
33.30%
-0.64
7.05
Table 4.7 Comparison of each technique overall performance
ENG499 CAPSTONE PROJECT REPORT
49
Chapter 5
Conclusions
5.1 Thesis Contributions
The design of square microstrip patch antenna for mobile device has been completed using
IE3D software. The simulation results are good enough to satisfy our requirements to
fabricate it on hardware which can be used wherever needed, especially for the frequency
3GHz. Although the simulation was carried out for the frequency of 3GHz, the design can be
adjusted to the desired frequency according to the formulae state in the section 3, since the
result have been proof that formula is reliable to be used.
Each simulation results have stated in the section 4 is for the techniques of miniature
for the square microstrip patch antenna.
Difference techniques have given different
advantages. The idea of the section 4 is to show clear statement between the original patch
and the patch that have applied the miniature techniques. From them, one can choose which
method is suitable for the application. Although, the results are good enough, the size
adjustment should be carried out in the future work.
Above all, this report can be a good starting point for the person, who is planning to
use the square type microstrip antenna. Formulae are given, and good enough to design.
However, one must be take note that investigation in this report has been limited, mostly to
theoretical studies and simulations due to lack of fabrication facilities.
5.2 Future Work
Firstly, since this project is mainly reference on the theory and research paper. All the results
that have been collected are based on the simulation, which is nearly closer to the actual
result. In order to use it in the real time system, actually hardware should be fabricated and
tested out, which can be given accurate and reliable answer.Detailed experimental studies can
be taken up at a later stage to fabricate the antenna. Before going for fabrication we can
optimize the parameters of antenna using one of the soft computing techniques known as
Particle Swarm Optimization (PSO).
Secondly, during the software simulation, using the origin design, there are some
difference in simulation result, when the probe feed different position on the patch will given
out the different answer. Importance of the probe position doesn’t explain much in the book
that referred. Therefore, different probe location on the same patch and number of probe
using may differ. This should be carried out in the future work and find out the best location
for the probe feed.
ENG499 CAPSTONE PROJECT REPORT
50
Thirdly, dielectric constant for the substrate has been simulated using 1.5 which is less
than the original design. Constant of material greater than original design are worth for trying.
It can be given different answer.
Finally, miniatures techniques that have mention in this report are individual result of
adjusting the original design, without changing the original dimension. Actual size should be
changed to smaller dimension from the original and applying all the methods on the newly
designed patch. The result of the same methods original and new design should be compared
and analyzed. This can lead to importance of the technique.
ENG499 CAPSTONE PROJECT REPORT
51
Reflections
Finally, come to the end of the report. I have put all my effort on this. All my energy and
strength are putting in for the completion the report before deadline. Moreover, final year
report is the core of the degree course it is like a turning point of my life. Struggling such
important thing is not an easy job indeed. Any mistake or any wrong choice can end up my
afford in vain. As the saying state that “Think before you leap”, I have to put an extra care on
every steps that I moved.
Only with the foundation courses like Wireless Communication Systems (ENG315)
and Electronic Material (ENG323) taught in SIM University, there is a lot of knowledge and
skills require having a deeper understanding in miniature microstrip patch antenna theories,
and its mathematical relations. Therefore, the first step was to find the relevant papers and
books on this microstrip patch antenna.
Not to my surprise, there are a lot of researches done in this area, and this did not help
at all as I have somehow lost focus on what is desired, this is the typical information overload
during the literature survey. During the meet up with Dr Shen, he provides me with the
relevant comments and valuable inputs with regards to my progress. Without the help of my
dedicated tutor to guide me and to align the ideas, this project would not be completed.
When I started on this project, I have an initial idea on fabricating it and tested out in
the anechoic chamber. This can be given a reliable product. However, such facilities are
pretty expensive and difficult for a part-time student like me to make a time arrangement to
carry out. Therefore, I have decided to use the simulation software, which is specialized in
designing the antenna.
When I do the pre planning on the project, it seems to be going smoothly. Initial report
is seamlessly done. Timeline is drawn out according to my schedule. Planar antenna design is
chosen. However, when it come to part for the simulation and miniaturization, I start to
realize that substrate is playing an important role for the antenna. It can make a difference
putting the substrate in between ground and patch. Therefore, I have to modify my initial
design into microstrip type antenna, which is quite a well built up design. Substrate layer is
added between patch and ground layer.
This can be solved for one of the miniature
techniques.
On the other hand, simulation applications are quite hard to get within in my research.
Reliable and availability of software are main concerns for me. Some applications are
provided with evaluation version. It didn’t turn out to be reliable and easy to use. Results are
turn out to be limited to certain expectation.
ENG499 CAPSTONE PROJECT REPORT
52
The first application that I have tried out is Antenna Magus from CST MICROWAVE
STUDIO. This application is user friendly, but, since it provide evaluation version, I can only
able to use some of the designs. Simulation for the microstrip antenna is easily carried out,
because the antenna design are pre defined and user only need to put in the dimension of the
antenna patch and dielectric constant of the substrate. However, the simulation results are not
in detail. Graphs are pretty general. Moreover, pre defined design cannot be able to use for the
section 4, where I am going to deal with the changing of the design.
Next application that I have used is HFSS from ANSOFT. This application is like
professional software for designing the antenna design. It is quite powerful, user can draw his
own design and simulate. When I used this application, I found out that this software is too
powerful to be used on my notebook. It needs a high performance machine to handle the
simulation. For the first time, I have seen that my notebook have to keep on running for two
days in order to do the simulation, yet it didn’t complete. Therefore, I have to give up on this
application.
At the end, I found out the IE3D from ZELAND, which I have borrowed from one of
my close friend, is a good software for designing the antenna. Although it is not a user
friendly, it can be drawn my own design and do the simulation, which can give a satisfy result.
Day and night, trying and learning the tutorial on IE3D, finally, I have got my expected result
which has been stated in this report.
Putting so much effort on this report, it is not in vain at all. I have leant a lot. Such a
lesson cannot be able to find in the class room. We must go and try it, experience it. Learning
in the class room may not be giving me a same experience or lesson as I do the project. This
is a very good opportunity to use what we have leant in the class.
Work out such important thing with a full concentration would not be a problem, but it
doesn’t turn out in that way for me. I have to work full time in the morning and going for the
lesson in the evening. Life will not be easy if there is need of playing multiple roles. Job,
study and family are the only vocabulary to define my life for the past few years. Of course, I
am aware of that these are pains that I am giving or should I say investing. Nothing is free in
this world, “No Pain No Gain”, in order to achieve what I want. I have to cross this journey.
ENG499 CAPSTONE PROJECT REPORT
53
Acknowledgements
I would like to express my sincere gratitude and appreciation to my advisor Dr Shen Zhong
Xiang for his guidance and instruction during my years at SIM University made my graduate
career challenging, exciting and rewarding. I am indebted to them for their time, patience,
and support.
I would like to thank to Sean not only for his help and valuable suggestions for this
thesis, but also for his advice and taking the time to read my thesis.
I am especially indebted to my faithful colleague Lim Eng Ann, for her friendship,
support and encouragement. Without her help this work would have been a lot harder.
I would like to thank Hong Bo and Liu Pan for sharing with me his optimism and
intelligence. There are always willing to help anyone.
Acknowledgements are also due to Bao Chen, Chen Hua, Yen, Zhi Wei, for their
support and friendship.
I would like to thank my parents for their continued support and encouragement and
my family stood behind me for which I am thankful for them forever.
Finally, I would like to thank my wife Chen Qi for her patience, understanding and
unlimited encouragement.Without her support, I would not have made it.
ENG499 CAPSTONE PROJECT REPORT
54
References
[1]
C. A. Balanis, “Antenna Theory, Analysis and Design”, JOHN WILEY & SONS,
INC, New York 1997.
[2]
R. Garg, P. Bhartia, I. Bahl, A. Ittipiboon,“Microstrip Antenna Design Handbook”,
ARTECH HOUSE, Boston 2001.
[3]
S.Silver, “Microwave Antenna Theory and Design”, McGRAW-HILL BOOK
COMPANY, INC, New York 1949.
[4]
D.M.Pozar and D. H. Schaubert, Microstrip Antennas: The Analysis and Design of
Microstrip Antennas and Arrays, IEEE Press, 1995.
[5]
K. F. Lee, Ed., Advances in Microstrip and Printed Antennas, John Wiley, 1997.
[6]
F. E. Gardiol, “Broadband Patch Antennas,” Artech House.
[7]
D. R. Jackson and J. T. Williams, “A comparison of CAD models for radiation from
rectangular microstrip patches,” Intl. Journal of Microwave and Millimeter-Wave
Computer Aided Design, Vol. 1, No. 2, pp. 236-248, April 1991. 63
[8]
D. R. Jackson, S. A. Long, J. T. Williams, and V. B. Davis, “Computer aided design
of rectangular microstrip antennas”, Ch. 5 of Advances in Microstrip and Printed
Antennas, K. F. Lee, Editor, John Wiley, 1997.
[9]
J.-F. Zürcher and F. E. Gardiol, Broadband Patch Antennas, Artech House, 1995.
[10]
H. Pues and A Van de Capelle, “Accurate transmission-line model for the rectangular
microstrip antenna,” Proc. IEE, vol. 131, pt. H, no. 6, pp. 334-340, Dec. 1984.
[11]
D. M. Pozar, “Input impedance and mutual coupling of rectangular microstrip
antennas,” IEEE Trans. Antennas and Propagation, vol. AP-30, pp. 1191-1196, Nov.
1982.
[12]
C. J. Prior and P. S. Hall, “Microstrip disk antenna with short-circuited annular ring,”
Electronics Letters, Vol. 21, pp. 719-721, 1985.
[13]
Y.-X. Guo,C-L. Mak,K-M Luk, and K.-F. Lee, “Analysis and design of Lprobe
proximity fed patch antennas,” IEEE Trans. Antennas and Propagation, Vol. AP-49,
pp. 145-149, Feb. 2001.
[14]
K. Ghorbani and R. B. Waterhouse, “Ultrabroadband printed (UBP) antenna,”IEEE
Trans. Antennas and Propagation, vol. AP-50, pp. 1697-1705, Dec. 2002.
[15]
G. Kumar and K. C. Gupta, “Non-radiating edges and four edges gap coupled
multiple resonator broadband microstrip antennas,” IEEE Trans. Antennas and
Propagation, vol. AP-33, pp. 173-178, Feb. 1985.
[16]
D.M Pozar, “Microstrip Antennas”, IEEE Proceedings, vol. 80, pp. 79-91 Jan1992
ENG499 CAPSTONE PROJECT REPORT
55
[17]
Hazdra, P., Mazánek, M: The Miniature Fractal Patch Antenna, In: Radioelektronika
2005 - Conference Proceedings. Brno: VUT FEI, Ústav radioelektroniky, 2005, s.
207-210. ISBN 80-214-2904-6.
[18]
BAHL, I., GBARTIA, P., GARG, R., ITTIPIBOON, A. Microstrip Antenna Design
Handbook. Artech House, 2001.
[19]
JAMES J.R., and HALL P.S., “Handbook of Microstrip Antennas” Peter Peregrinus
Ltd. London, UK, 1989.
[20]
POZAR D.M., and SCHAUBERT D.H., “Microstrip Antennas, the Analysis and
Design of Microstrip Antennas and Arrays”, IEEE Press, New York,USA, 1995.
[21]
K.R.CARVER and J.W.MINK, “Microstrip Antenna Technology”, IEEE Trans.
Antenna Propag. Vol.AP-29, pp.2-24, Jan 1981.
[22]
I.J.BAHL and P.BHARTIA, “Microstrip Antennas”, Dedham, MA: Artech House,
1980.
[23]
J.R.JAMES, P.S.HALL and C.WOOD, “Microstrip Antenna Theory and Design”,
London, UK,: Peter Peregrinus, 1981.
[24]
M. Amman, Design of Microstrip Patch Antenna for the 2.4 Ghz Band, Applied
Microwave and Wireless, pp. 24-34, November /December 1997.
[25]
K. L. Wong, Design of Nonplanar Microstrip Antennas and Transmission Lines, John
Wiley & Sons, New York, 1999.
[26]
W. L. Stutzman. G. A. Thiele, Antenna Theory and Design, John Wiley & Sons, 2nd
Edition, New York, 1998.
[27]
M. Amman, “Design of Rectangular Microstrip Patch Antennas for the 2.4 GHz
Band”, Applied Microwave & Wireless, PP. 24-34, November /December 1997.
[28]
K. L. Wong, Compact and Broadband Microstrip Antennas, Wiley, New York, 2002.
[29]
G.S. Row, S. H. Yeh, and K. L. Wong, “ Compact Dual Polarized Microstrip
antennas”, Microwave & Optical Technology Letters, 27(4), pp. 284-287,November
2000.
[30]
M.O.Ozyalcm, Modeling and Simulation of Electromagnetic Problems via
Transmission Line Matrix Method, Ph.D. Dissertation, Istanbul Technical University,
Institute of Science, October 2002.
[31]
IE3D Software Release 11.0 (Zeland Software Inc., Fremont, California,USA).
[32]
W.L. Stutzman, G.A. Thiele, Antenna Theory and design, John Wiley & Sons, 2nd Ed.
New York, 1998.
[33]
A. Derneryd,“Linearly Polarized Microstrip Antennas”, IEEE Trans.Antennas and
Propagation, AP-24, pp. 846-851, 1976.
ENG499 CAPSTONE PROJECT REPORT
56