FREQUENCY RECONFIGURABLE LOG-PERIODIC
ANTENNA DESIGN
MUHAMMAD FAIZAL BIN ISMAIL
UNIVERSITI TEKNOLOGI MALAYSIA
FREQUENCY RECONFIGURABLE LOG-PERIODIC ANTENNA DESIGN
MUHAMMAD FAIZAL BIN ISMAIL
A thesis submitted in fulfilment of the
requirements for the award of the degree of
Master of Engineering (Electrical)
Faculty of Electrical Engineering
Universiti Teknologi Malaysia
NOVEMBER 2011
iii
Specially dedicated to my beloved mom and dad,
Hjh Arapah bte Osman and Hj Ismail bin Baba,
my siblings and family, for their encouragement and support;
as well as my lovely fiancé, Noraini Khalil and all my friends who always inspired
and motivated me along my excellent journey of education
iv
ACKNOWLEDGEMENT
In the name of Allah, Most Gracious, Most Merciful. Praise be to Allah, the
Cherisher and Sustainer of the Worlds. With His permission I have completed my
Master Degree of Electrical Engineering and hopefully this thesis will benefit the
development of the Ummah all over the world.
Special thanks as well to my project supervisor, Associate Professor Dr.
Mohamad Kamal A. Rahim, for his guidance, motivations, support and constructive
comments in accomplishing this project.
My family deserves special mention for their constant support and for their
role of being the driving force towards the success of my project. My friends
deserve recognition for lending a helping hand when I need them. I would also like
to thank the wonderful members of P18; Mr. Huda A. Majid, Mr. Mohd Nazri A.
Karim, Mr. Osman Ayop, Mr. Farid Zubir, Mr. Amiruddeen Wahid, Mrs. Maisarah
Abu, Mrs. Kamilia, Mrs. Mai Abdul Rahman and Mr. Mohsen Khalily, who have
been extremely kind and helpful throughout my stay. “We don’t remember days, but
we remember moments” and I had a great time and moments with all these guys
during my study in UTM.
My sincere appreciation also goes to everyone whom I may not have
mentioned above; who have helped directly or indirectly in the completion of my
project. A million thanks for all.
v
ABSTRACT
The concept of reconfigurable antenna is widely used as additional features of
reconfigurable ability for future wireless communication system. There are various
configurations of reconfigurable antenna such as monopole, dipole and log-periodic
wideband antenna. The integrations of reconfigurable antennas with radio frequency
(RF) switches are needed to perform the switchable ability. In this research, a log-
periodic antenna (LPA) has been designed to perform a wideband frequency
operation by connecting thirteen square-patch antennas using inset feed line
technique. Then, the reconfigurable log-periodic antenna (RLPA) is designed by
connecting positive-intrinsic-negative (PIN) diodes at every transmission lines with a
quarter-wave length radial stub biasing. The representation of real PIN diodes and
the locations of biasing circuits in simulation are also included. Three different sub-
band frequencies with a bandwidth of 20% (3 - 4, 3.7 - 5, and 4.8 - 6 GHz for each
band) are configured from the total of 73% bandwidth (3 to 6 GHz) of the wideband
operations by switching ON and OFF of the PIN diode. Other sub-bands or narrow
band can also be configured by selecting other group of patches. Validation for the
LPA and RLPA is achieved by comparing the simulated and measured radiation
patterns. The measured half-power beamwidth (HPBW) for LPA are 62°, 58° and
72° at frequency 3.4 GHz, 4.0 GHz and 5.8 GHz, respectively, while 73°, 67° and
72° for RLPA at the same frequency band. The simulated gain for LPA and RLPA
are around 4.9 dB and 5.0 dB respectively, while the measured gain is around 5.5 dBi
for LPA and 5.7 dBi for RLPA within a frequency range of 3 – 6 GHz. All the
structures have been fabricated and the measurement results show accuracies of
97.5% for return loss, 80.2% for gain and 98.4% for HPBW with the simulation
results.
vi
ABSTRAK
Konsep antena boleh-ubah telah digunakan secara meluas sebagai
penambahan ciri dalam keupayaan boleh-ubah untuk sistem perhubungan tanpa
wayar di masa hadapan. Terdapat pelbagai konfigurasi antena boleh-ubah
menggunakan antena jenis jalur lebar seperti antena satu-polar, dwipolar dan log-
periodik. Penyepaduan antena dan suis RF diperlukan untuk melaksanakan
keupayaan boleh-ubah. Dalam penyelidikan ini sebuah antena log-periodik telah
direkabentuk untuk operasi jalur lebar dengan menyambung sebanyak tiga belas
antena tampalan segi empat dengan menggunakan teknik kemasukan jalur suapan.
Kemudian, Antena Boleh-Ubah Log-Periodik direkabentuk dengan meletakan diod
PIN pada setiap jalur penghantaran antena bersama dengan pincangan suku
gelombang puntung berjejari. Perwakilan diod PIN yang sebenar dan lokasi litar
pincangan dalam proses simulasi juga disertakan dalam projek ini. Tiga sub jalur
frekuensi yang berlainan dengan lebar jalur sebanyak 20% (3-4, 3.7-5 dan 4.8-6 GHz
bagi setiap jalur) telah dikonfigurasikan dari operasi jalur lebar yang mempunyai 73
% (3 hingga 6 GHz) lebar jalur dengan menukar diod PIN kepada keadaan ON dan
OFF. Sub jalur atau jalur sempit yang lain juga boleh diubah dengan memilih
kumpulan antena tampalan yang lain. Pengesahan untuk LPA dan RLPA tercapai
dengan membandingkan corak sinaran dari hasil simulasi dan pengukuran. Separuh-
Kuasa Lebaralur (HPBW) bagi LPA adalah 62°, 58° dan 72° pada frekuensi 3.4
GHz, 4.0 GHz dan 5.8 GHz manakala sebanyak 73°, 67° and 72° bagi RLPA pada
julat frekuensi yang sama. Gandaan simulasi untuk LPA dan RLPA adalah masing-
masing sekitar 4.9 dB dan 5.0 dB, manakala bagi gandaan pengukuran adalah sekitar
5.5 dBi bagi LPA dan 5.7 dBi bagi RLPA pada julat frekuensi 3-6 GHz. Kesemua
struktur telah difabrikasi dan keputusan pengujian mempunyai ketepatan 97.5% bagi
kehilangan balikan, 80.2% bagi gandaan dan 98.4% bagi HPBW berbanding
keputusan simulasi.
vii
TABLE OF CONTENT
CHAPTER TITLE PAGE
DECLARATION ii
DEDICATION iii
ACKNOWLEGMENT iv
ABSTRACT v
ABSTRAK vi
TABLE OF CONTENTS vii
LIST OF TABLES xi
LIST OF FIGURES xiii
LIST OF SYMBOLS xviii
LIST OF ABBREVIATIONS xix
1 INTRODUCTION 1
1.1 Introductions 1
1.2 Project Background 2
1.3 Problem Statement 3
1.4 Objective 4
1.5 Scope and Limitation of the Project 4
1.6 Organization of the Thesis 5
2 LITERATURE REVIEW 7
2.1 Introductions 7
2.2 Antenna Properties 8
2.2.1 Return Loss 8
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2.2.2 Bandwidth 9
2.2.3 Radiation Pattern 10
2.2.4 Half-Power Beamwidth 11
2.2.6 Gain 11
2.3 Wideband Antenna 12
2.3.1 Log-Periodic Antenna 13
2.4 Reconfigurable Antenna 14
2.5 RF Switching 17
2.5.1 PIN Diode Switch 18
2.5.2 PIN Diode Equivalent Circuit Modeling 19
2.5.2 Biasing Circuit 20
2.6 Previous Related Research 23
2.6.1 The Log-Periodic Antenna Development 23
2.6.2 Reconfigurable Using Log-Periodic Antenna 27
2.6.3 Others Reconfigurable Antenna 30
2.7 Summary 37
3 LOG-PERIODIC ANTENNA DESIGN 38
3.1 Introductions 38
3.2 Project Methodology and Flow Chart of Log
Periodic Antenna
41
3.3 Single Patch Antenna Design 43
3.4 The Design of Log-Periodic Wideband Antenna 48
3.5 Parametric Study of Log-Periodic Antenna 51
3.5.1 Simulation on Distance of Adjacent Patch 51
3.5.2 Simulation on Different Length of Inset Feed
Line
53
3.5.3 Simulation on Different Scaling Factor 54
3.5.4 Parametric Studies Conclusion 55
3.6 Summary 56
ix
4 RECONFIGURABLE LOG-PERIODIC ANTENNA
DESIGN
57
4.1 Introductions 57
4.2 Project Methodology and Flow Chart 58
4.3 Analysis of PIN Diode Representation 60
4.3.1 PIN Diode Representation using Lumped
Element
61
4.3.2 PIN Diode Representation using PEC Pad 63
4.4 Analysis of Biasing Circuit Location 65
4.4.1 Biasing circuit at the transmission line of
patch
66
4.4.2 Biasing circuit at the middle of length patches 67
4.4.3 Biasing circuit at the back of antenna 69
4.4.4 Parametric Studies Conclusion 70
4.5 Reconfigurable Log-Periodic Antenna (RLPA)
Design
71
4.6 Fabrication Process 78
4.7 Measurement Process 80
4.7.1 Input Return Loss Measurement Setup 80
4.7.2 Radiation Pattern Measurement Setup 81
4.8 Summary 82
5 RESULT ANALYSIS AND DISCUSSION 83
5.1 Introductions 83
5.2 Analysis Result and Discussion of Log-Periodic
Antenna
84
5.2.1 Input Return Loss 84
5.2.2 Current Distribution 86
5.2.3 Realized Gain and Power Received 87
5.2.4 Radiation Pattern and Half-Power
Beam- width
89
5.3 Analysis Result of Frequency Reconfigurable Log-
Periodic Antenna and Discussion
93
x
5.3.1 Return Loss (S11) 94
5.3.2 Current Distribution 96
5.3.3 Simulated Realized Gain and Power
Received Measurement
97
5.3.4 Radiation Pattern and Half-Power
Beam-width
100
5.4 Overall Discussion 104
5.5 Summary 105
6 CONCLUSION 106
6.1 Overall Conclusion 106
6.2 Key Contribution 108
6.3 Future Research 108
REFERENCES 109
Appendices A - C 116-135
xi
LIST OF TABLES
TABLE NO. TITLE PAGE
2.1 Parameters value of equivalent circuits for PIN
Diodes
20
2.2 Lumped element’s representation in low and high
frequency
21
2.3 The switches' states of U-Koch reconfigurable
microstrip antenna
32
2.4 Previous researches on reconfigurable antenna 35
3.1 Design description of log-periodic antenna 48
3.2 LPA dimension for each patch. 50
3.3 Result of varying the adjacent patch 52
3.4 Result of varying the length of inset feed line 54
3.5 Summaries result of varying the scaling factor. 55
4.1 The value of lumped elements as a PIN diode 62
4.2 Reconfigurable log-periodic antenna properties 77
4.3 The dimensions for each patches of RLPA. 72
4.4 Switches’ states for each case 75
4.5 Performances of antenna using different PIN
diode representation
77
4.6 Antenna Fabrication Process 78
5.1 Comparison return loss between simulation and
measurement for LPA
86
5.2 Simulated realized gain and efficiency of the LPA 88
5.3 Half-power beam-width for Log-Periodic Antenna 93
xii
5.4 Comparison of return loss between simulation
and measurement of RLPA
96
5.5 Half-power beam-width for Reconfigurable Log-
Periodic Antenna
104
5.6 Comparison of overall performances in term of
frequency, bandwidth, gain and HPBW between
LPA and RLPA
105
xiii
LIST OF FIGURES
FIGURE NO. TITLE PAGE
2.1 Coordinate system for radiation pattern measurement 10
2.2 Two-dimensional of power pattern 11
2.3 Reconfigurable Antenna Block Diagram 15
2.4 Cross section diagram of PIN diode 18
2.5 (a) Equivalent circuit for forward biased
(b) Equivalent circuit for reverse biased
19
2.6 Equivalent circuit for a PIN diode 20
2.7 Schematic design of Series SPST Switch 22
2.8 Bias network configuration using radial line stub 23
2.9 Log-Periodic Slot Antenna Array structure 24
2.10 VSWR of Log-Periodic Slot Antenna Array. (Line-
measured, dotted line - computed)
24
2.11 Log-periodic Dipole Fractal Koch Antenna design 25
2.12 Return loss of Log-periodic Dipole Fractal Koch
Antenna
25
2.13 The structure of Log-Periodic Terahertz Antenna 26
2.14 The simulated return loss of Log-Periodic Terahertz
Antenna
26
2.15 Proposed prototype antenna 27
2.16 Measured (a) S-parameter in dB of wideband log
periodic antenna and (b) Efficiency of reconfigurable
antenna
27
2.17 The structure of reconfigurable LPDA (a) the 28
xiv
schematic design and (b) fabricated proposed antenna
2.18 a) Simulated and b) measured return loss response of
the reconfigurable LPDA
28
2.19 Schematic design of reconfigurable log-periodic
dipole antenna with harmonic traps
29
2.20 Measured return loss of reconfigurable log-periodic
dipole antenna
30
2.21 The dimension of annular slot antenna design. The
feeding line with the matching stubs is on the bottom
and the annular slot antenna is on the top side of the
substrate
31
2.22 Simulated and measurement result of reconfigurable
annular slot antenna at three different frequency
31
2.23 Radiation pattern of the reconfigurable annular slot
antenna (a) Simulation (b) Measurement
32
2.24 The structure of U-Koch reconfigurable microstrip
antenna
33
2.25 The measured return loss of U-Koch reconfigurable
microstrip antenna
33
2.26 Geometry of the reconfigurable Vivaldi antenna: (a)
top view, (b) side view, and (c) bottom view.
34
2.27 Measured return loss of reconfigurable Vivaldi
antenna for wideband and sub-band operation
34
3.1 Flow chart of overall process including log-periodic
antenna and reconfigurable antenna
40
3.2 Flow chart of research methodology for LPA 42
3.3 Simulated design of square patch antennas 44
3.4 Return loss of single patch antenna 46
3.5 3-D view radiation pattern of single patch antenna at
3.0 GHz
46
3.6 (a) Polar plot of radiation pattern at 3.0 GHz in E-
plane and (b) Polar plot of radiation pattern at 3.0
GHz in H-plane for single patch antenna with theta
47
xv
and phi setup in simulation.
3.7 Layout of Log-Periodic Antenna 49
3.8 Dimension of Log-Periodic Antenna 50
3.9 Result of varying distance of adjacent patch (Sa) 52
3.10 Result of varying the length of inset feed line (lf) 53
3.11 Result of varying scaling factor (τ) 55
4.1 RLPA design flow chart 59
4.2 (a) PIN diode representation using lumped element in
single patch antenna. (b) Lumped element data in
CST.
61
4.3 Lumped element circuit that use in CST software (a)
RLC-Serial (b) RLC-Parallel.
62
4.4 Return loss of antenna (lumped element as a PIN
diode)
63
4.5 PIN Diode representation using PEC pad in (a) ON
state (b) OFF state.
63
4.6 Return loss of antenna. (PEC stripe as a PIN diode) 64
4.7 The structure of Antenna A1 66
4.8 Current distribution of Antenna A1 66
4.9 Return loss of Antenna A1 67
4.10 The structure of Antenna A2 67
4.11 Current distribution of Antenna A2 68
4.12 Return loss of Antenna A2 68
4.13 The structure of Antenna A3 (a) front view (b) back
view
69
4.14 Current distribution of Antenna 3 (a) front view (b)
back view
70
4.15 Return loss of Antenna 3 70
4.16 The geometrical structure of reconfigurable log-
periodic antenna
74
4.17 Design description of reconfigurable log-periodic
antenna
74
4.18 Reconfigurable log-periodic antenna design. (a) PEC 76
xvi
stripe as a PIN diode (b) Lumped element circuit as a
PIN diode
4.19 Comparison of PIN diode representation for RLPA in
wideband operation
76
4.20 Return loss measurement setup. (a) Network analyzer
(b) Calibration kit
81
4.21 Power received and radiation pattern measurement
set-up.
81
4.22 Anechoic chamber 82
5.1 Photo of fabricated LPA 84
5.2 Simulated and measured return loss for LPA 85
5.3 Simulated current distribution for LPA at: (a) 3 GHz
(b) 4 GHz (c) 5 GHz (d) 6 GHz.
87
5.4 Measured received of the LPA and the horn antenna 89
5.5 Simulated radiation pattern of LPA at 3.4 GHz (a) 3-
D view. (b) 2-D view in E-plane. (c) 2-D view in H-
plane
90
5.6 Measured radiation pattern of LPA at 3.4 GHz (a) E-
plane. (b) H-plane
90
5.7 Simulated radiation pattern of LPA at 4.0 GHz (a) 3-
D view. (b) 2-D view in E-plane. (c) 2-D view in H-
plane
91
5.8 Measured radiation pattern of LPA at 4.0 GHz (a) E-
plane. (b) H-plane
91
5.9 Simulated radiation pattern of LPA at 5.8 GHz (a) 3-
D view. (b) 2-D view in E-plane. (c) 2-D view in H-
plane
92
5.10 Measured radiation pattern of LPA at 5.8 GHz (a) E-
plane. (b) H-plane
92
5.11 Photo of Reconfigurable Log-Periodic Antenna 93
5.12 Simulation and measurement return loss of the
antenna when all switches are in ON state.
94
5.13 Return loss of simulated reconfigurable log-periodic 95
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antenna for different band
5.14 Return loss of measured reconfigurable log-periodic
antenna for different band
95
5.15 Simulated current distribution for reconfigurable log-
periodic antenna at: (a) 3 GHz (b) 4 GHz (c) 5 GHz
(d) 6 GHz.
97
5.16 (a) Simulated realized gain, directivity and efficiency
of RLPA.
(b) Simulated realized gain of RLPA in different
sub-bands.
98
5.17 Power received for different types of antenna at
measurement set-up
99
5.18 Power received of reconfigurable log-periodic
antenna (a) E-Plane (b) H-Plane
99
5.19 Simulated radiation pattern of RLPA at 3.4 GHz (a)
3-D view. (b) 2-D view in E-plane. (c) 2-D view in H-
plane
101
5.20 Measured radiation pattern of RLPA at 3.4 GHz (a)
E-plane. (b) H-plane
101
5.21 Simulated radiation pattern of RLPA at 4.0 GHz (a)
3-D view. (b) 2-D view in E-plane. (c) 2-D view in H-
plane
102
5.22 Measured radiation pattern of RLPA at 4.0 GHz (a)
E-plane. (b) H-plane
102
5.23 Simulated radiation pattern of RLPA at 5.8 GHz (a)
3-D view. (b) 2-D view in E-plane. (c) 2-D view in H-
plane
103
5.24 Measured radiation pattern of RLPA at 5.8 GHz (a)
E-plane. (b) H-plane
103
xviii
LIST OF SYMBOLS
fl - Low frequency
fh - High frequency
τ - Scaling factor
E - Electric field.
H - Magnetic field.
h - Substrate thickness.
t - Copper thickness
wp - Width of patch
εr - Relative permittivity of material.
tan δ - Tangential loss of material.
dB - Decibel
lf - Length of inset fed
ltx - Length of transmission line
mm - millimeter
R - Resistor
L - Inductor
C - Capacitor
xix
LIST OF ABBREVIATIONS
LPA - Log-Periodic Antenna
RLPA - Reconfigurable Log-Periodic Antenna
WLAN - Wireless Local Area Network
WiMAX - Worldwide Interoperability for Microwave Access
UWB - Ultra Wide Band
CR - Cognitive Radio
VSWR - Voltage Standing Wave Ratio
RL - Return Loss
BW - Bandwidth
BW% - Bandwidth Percentage
HPBW - Half Power Bandwidth
FR-4 - Fire Retardant Type 4
mm - Millimeter
GHz - Gigahertz
THz - Terahertz
SMA - Sub-Miniature version A
UV - Ultra Violet
CST - Computer Simulation Technology
xx
LIST OF APPANDICES
APPENDIX TITLE PAGE
A List of publications 116
B Datasheet of PIN Diode Infineon BAR 64 117
C Datasheet of wideband horn antenna 134
CHAPTER 1
INTRODUCTION
1.1 Introductions
This thesis proposes the design and development of wideband antenna using
log-periodic technique. The integration of the antenna with PIN diode switches and
lumped elements forms the reconfigurable antenna that enables the antenna to select
several sub-bands from a wideband frequency. This work involves the design,
fabrication and measurement process of the antenna that has wideband frequency
operation with frequency reconfigurability for future wireless communication system
such as cognitive radio, radar system and wireless communication network.
This thesis describes the antenna’s development including the literature
review on the reconfigurable antenna, the simulation design until the fabrication and
measurement process. In this first chapter, the brief background of the project is
discussed, providing problem statements, objectives, methodology, and scope of
work in conducting the research including the project’s possible outcome and
contributions and also the thesis organization.
2
1.2 Project Background
The field of wireless communication nowadays has put more emphasis on the
field of antenna design. In the early years when radio frequency was discovered, an
antenna with a simple design was used as a device to transmit electrical energy or
radio wave through the air in all directions. This innovative way of communication
to replace wired technology to wireless technology was first introduced by Galileo
Marconi when he successfully initiated the first wireless telegraph transmission in
1895 [1]. After that, the development of wireless technology makes leaps and
bounds.
Antenna development play a key role in wireless technology since the rapidly
increasing number of users in broadcasting, telecommunications, navigation, radar,
sensors, military and perhaps for future wireless communication e.g. the cognitive
radio [2]. The increasing number of users may lead to congestion of existing
spectrum such as Wireless Local Area network (WLAN), Wireless Personal Area
Network (WPAN), mobile communication and radio spectrum. Therefore, the
development of a reconfigurable antenna is very interesting in the improvement of
modern wireless communication system because they enable users to provide a
single antenna to be used in many systems.
The advantage of the reconfigurable antenna is they can alter or change the
antenna parameters based on their field of operation. The development of a
reconfigurable antenna is usually related to the microstrip antenna and their
integration with switching circuit. Its advantages include a low fabrication cost, light
weight, low profile, conforming, and compatible with integrated circuits devices [3,
4]. Besides, it can be designed at a specific resonant mode to radiate the required
frequency bands for the applications of wireless communication systems. However,
the new era of wireless communication requires antenna to operate in a wideband
range, possesses good radiation and has switchable ability [5, 6].
3
1.3 Problem Statement
As modern wireless communication systems have developed rapidly in recent
years, an antenna as a front component is required to have a wide band, good
radiation performances and sometimes switchable ability. To obtain the switchable
ability of the antenna, the concept of a reconfigurable antenna was proposed to easily
select the frequency from wideband to narrowband. The reconfigurable
characteristics of antennas are very valuable for many modern wireless
communication and radar system applications, such as object detection, secure
communications, multi-frequency communications, vehicle speed tests and so on.
Besides, the reconfigurable antenna can also operate within multiple systems by just
using a single antenna. For example, a single antenna can be used for both WLAN
2.4 GHz and 5.8 GHz by reconfiguring their dual-band operation.
The RF switch is important parts in development of reconfigurable antenna as
selection devices to makes tunable ability. The modeling of the RF switch in
simulation tools with an antenna also important that can give better results when
comparing with the fabricated antenna. From the previous research on reconfigurable
antenna [7-11], the implementation of real RF switches into the proposed antenna are
limited and not included with the simulation of an antenna. Some researchers have
used an ideal case to simulate the reconfigurable antenna. This project has propose
the development of reconfigurable antenna with integration of real RF switch and its
modeling in simulation to give better results when comparing with fabricated
antenna.
The development of wideband antenna usually uses a monopole structure [7]
because of various advantages: it is low profile, thin and small, has the ability to
produce very wide frequencies and possesses an omni-directional pattern. However,
by using a monopole structure, there has a difficulty on selection of location to
configure from wideband to narrow bands. Therefore, the log-periodic concept is
used to perform a wideband operation since it has directional radiation pattern; it also
easily selects a narrow band frequency since the log-periodic antenna allows a single
patch to radiate at single frequency. The integration of log-periodic antenna with RF
switching circuit can make the reconfigurable antenna even better.
4
1.4 Objective
The main objectives of this project are as follows:
i. Design, simulate and fabricate frequency reconfigurable antenna from
wideband range to narrow band range with integration of real PIN diodes
and biasing circuits.
ii. Design, simulate and fabricate a wideband antenna using log-periodic
technique.
iii. To characterize the antenna parameters in term of input return loss,
radiation pattern, half power beam width and gain for both simulation and
measurement.
1.5 Scope and Limitation of the Project
The main scopes of this research are:
i. Literature review and previous research study on log-periodic antenna and
reconfigurable antenna.
ii. Design, simulate and analyze the log-periodic wideband antenna and
reconfigurable log-periodic antenna using CST Microwave Studio
Software.
iii. Fabricate and measure the log-periodic antenna and reconfigurable log-
periodic antenna. The fabrication part includes soldering the PIN diode
and lumped elements.
iv. Analyze and compare the results between simulation and measurement.
v. Journal and thesis documentation.
5
The limitations of this research are:
i. The range of frequency is limit to 6GHz due to available low cost RF PIN
diode from the manufacturers.
ii. There are multiple parameters can be tuned for reconfigurable antenna.
However, this research only focuses on frequency reconfigurable from
wideband, to narrowband.
iii. The measurements of the antenna are based on available facilities in this
university. The anechoic chamber for radiation pattern measurement can
only measure from 0° to 180° rotation. Hence, only front lobes of
radiation patterns are compared with the simulation.
iv. The switching mechanism of this antenna is using manually by DIP
switch to control the PIN diode.
1.6 Organization of the Thesis
This thesis is divided into six chapters that describe all the work done for this
project. The first chapter consists of the introduction, project background, problem
statement, objectives, scope of study and project contribution. Chapter 2 is literature
review that explains literature about the log-periodic antenna and the reconfigurable
antenna. The basics of the antenna properties such as radiation pattern, bandwidth,
gain and HPBW are presented. The log-periodic concept is introduced and explained
to get a wideband operation before integrated with the lumped elements and PIN
diodes. Besides, the circuit representation of PIN diode and its biasing circuit have
also been explained for reconfigurable purposes. Some overview of previous studies
is also presented.
The design process of Log-Periodic Wideband Antenna is presented in
Chapter 3. The initial result of single patch antenna and the designing process of the
log-periodic wideband antenna are also presented. In order to get an optimum result
in term of return loss and bandwidth, a parametric study by varying the adjacent
distance between the patches, the length of inset feed line and the scaling factor value
6
are presented. While Chapter 3 discusses the passive antenna, the active antenna that
integrated with lumped element is discussed in Chapter 4. In this chapter, the
research flow, design methodology and simulation setup of Reconfigurable Log-
Periodic Antenna is briefly described. The PIN diode representation and biasing
circuit location in RLPA are also presented. This chapter also presents the fabrication
and measurement process of the antenna.
The simulated and measured results of the Log-periodic Wideband Antenna
and Reconfigurable Log-Periodic Antenna are presented in Chapter 5. The simulated
result such as return loss, current distribution, realized gain and radiation pattern is
clearly presented. Then, the measurement process is done to validate the simulated
results and both results have been compared to each other in terms of return loss,
received power and radiation pattern. A discussion of the results is presented clearly.
Lastly, the conclusion of the project is presented in Chapter 6. This chapter concludes
the findings of the project, some key contribution and provides recommendations for
future work.
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