Pattern Reconfigurable Antenna.
PATTERN RECONFIGURABLE ANTENNA
ELISBETH A/P MURUGAS
This Report Is Submitted In Partial Fulfillment Of Requirement For The Bachelor Degree Of Electronic Engineering (Wireless Communication)
Faculty of Electronic and Computer Engineering Universiti Teknikal Malaysia Melaka
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BORANG PENGESAHAN STATUS LAPORAN PROJEK SARJANA MUDA II
Tajuk Projek : PATTERN RECONFIGURABLE ANTENNA
Sesi
Pengajian : 1 4 / 1 5
Saya ELISBETH A/P MURUGAS mengaku membenarkan Laporan Projek Sarjana Muda ini disimpan di Perpustakaan dengan syarat-syarat kegunaan seperti berikut:
1. Laporan adalah hakmilik Universiti Teknikal Malaysia Melaka.
2. Perpustakaan dibenarkan membuat salinan untuk tujuan pengajian sahaja.
3. Perpustakaan dibenarkan membuat salinan laporan ini sebagai bahan pertukaran antara institusi pengajian tinggi.
4. Sila tandakan ( √ ) :
SULIT*
*(Mengandungi maklumat yang berdarjah keselamatan atau kepentingan Malaysia seperti yang termaktub di dalam AKTA RAHSIA RASMI 1972)
TERHAD** **(Mengandungi maklumat terhad yang telah ditentukan oleh organisasi/badan di mana penyelidikan dijalankan)
TIDAK TERHAD
Disahkan oleh:
__________________________ ___________________________________ (ELISBETH A/P MURUGAS) (DR. MOHAMAD ZOINOL ABIDIN ABD AZIZ)
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“I hereby declare that this is the results of my own paper except for quotes as cited in the references.”
Signature :
Author : ELISBETH A/P MURUGAS Date : 30th JUNE 2015
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“I hereby declare that I have read this report and in my opinion this report is sufficient in terms of the scope and quality for the award of Bachelor Degree of Electronic and Computer Engineering (Wireless Communications) with Honors.”
Signature :
Supervisor’s Name : DR. MOHAMAD ZOINOL ABIDIN ABD AZIZ Date : 30th JUNE 2015
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This project and research work is dedicated to any beloved parents for their devoted caring throughout my life, my loving brother and sister, also my friends for their encouragement and love.
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ACKNOWLEGDEMENT
First and foremost, I want to thanks the god because without his grace I will not able to complete this Final Year Project (FYP) and report for the session 2015 as well as possible. Here, I would like to thank my University Teknikal Malaysia Melaka (UTeM) coordinator/supervisor Dr. Mohamad Zoinol Abidin Abd Aziz, who advice and guide me to complete the Final Year Project and report in time. During to complete this Final Year Project (FYP) and report, I face lots of problems and difficulties. However, I manage to crossed it all with patience and complete it properly. The journey in completing Final Year Project (FYP) and report really teach me in terms of leadership, proper time management, communication skill, technical knowledge, soft skill and so many more. The advice and encouragement from supervisor is really motivating me to do the best. In addition, my family members and friends also became a part of in completing the Final Year Project (FYP) and report, which help me in giving some rational idea and supports. Finally, I would like to thank those involved directly and indirectly in completing the Final Year Project (FYP) and report successfully. Thank very much to you all.
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ABSTRACT
The recent wireless communication systems tend to be high-capacious, multifunctional and cover more frequency bands. Therefore, the quantity of the antenna is becoming larger and larger. This will lead to large communication system equipment, increased costs, and electromagnetic compatibility problems. This thesis presents the design of a pattern reconfigurable antenna which can operable at 2.4GHz for wireless communication system using electrical switching technique with integration of RF PIN diodes. For this project, a rectangular microstrip patch antenna was first designed and fabricated as a reference. Then a microstrip patch antenna with a partial ground plane base equipped with two pin diode is designed to get pattern reconfigurability. Two PIN diode switches are mounted over the slots in the ground plane optimize to yield the maximum number of radiation pattern and to enhance the resonance frequency, return loss, gain and efficiencies. This antenna is an attractive candidate for WLAN applications. While standard antennas radiate the energy in a fixed direction, pattern reconfigurable antenna allows a single radiation structure to behave as several antennas with different radiation properties. Pattern reconfigurability enables wireless communication systems to avoid noisy environments, maneuver away from electronic jamming, and save energy by redirecting signals toward intended users only. Pattern configurable antennas are frequently used to increase channel capacity and broaden the coverage area of wireless system.
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ABSTRAK
Sistem komunikasi tanpa wayar hari cenderung untuk menjadi capacious tinggi, pelbagai fungsi dan merangkumi lebih banyak band frekuensi. Oleh itu, kuantiti antena menjadi lebih besar dan lebih besar. Ini akan membawa kepada peralatan sistem komunikasi yang besar, kos meningkat, dan masalah keserasian elektromagnet. Tesis ini akan membentangkan rekabentuk antena reconfigurable corak yang boleh beroperasi pada 2.4GHz sistem komunikasi tanpa wayar yang menggunakan teknik pensuisan elektrik dengan integrasi diodes RF PIN. Bagi projek ini, sebuah segi empat tepat microstrip patch antena pertama direka dan direka sebagai rujukan. Kemudian antena patch microstrip dengan kapal terbang sebahagian tanah asas dilengkapi dengan dua pin Diod direka untuk mendapatkan corak reconfigurability. Dua PIN Diod, suis dipasang ke slot dalam satah bawah mengoptimumkan hasil jumlah maksima corak sinaran dan meningkatkan kekerapan resonans, kehilangan kembali, keuntungan dan kecekapan. Antena ini adalah untuk calon yang menarik untuk aplikasi WLAN. Manakala standard antena memancar tenaga arah tetap, antena reconfigurable corak membolehkan sinaran satu struktur untuk berkelakuan sebagai beberapa antena dengan sifat-sifat sinaran yang berbeza. Corak reconfigurability membolehkan sistem komunikasi tanpa wayar untuk mengelakkan persekitaran bising, bergerak dari jamming elektronik dan menjimatkan tenaga dengan melencongkan isyarat ke arah pengguna sahaja. Corak dikonfigurasikan antena sering digunakan untuk meningkatkan kapasiti saluran dan meluaskan kawasan liputan sistem tanpa wayar.
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CONTENTS
CHAPTER TOPIC PAGES
PROJECT TITLE i
REPORT VERIFICATION STATUS FORM ii
DECLARATION iii
SUPERVISOR DECLARATION iv
DEDICATION v
ACKNOWLEDGEMENT vi
ABSTRACT vii
ABSTRAK viii
TABLE OF CONTENT ix
I INTRODUCTION
1.1 Introduction of the Project 1
1.2 Problem Statement 3
1.3 Objectives 5
1.4 Scope 5
II LITERATURE REVIEW
2.1 Introduction 6
2.2 Antenna 7
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2.3.1 Impedance 7
2.3.2 Return Loss 8
2.3.3 Bandwidth 8
2.3.4 Radiation Pattern 9
2.3.5 Gain 10
2.3.6 Polarization 10
2.4 Reconfigurable antennas 11
2.4.1 Frequency Reconfigurable antenna 12 2.4.2 Polarization Reconfigurable antenna 12 2.4.3 Pattern Reconfigurable Antenna 12 2.4.4 Compound/Multi Reconfigurable Antenna 13
2.5 Reconfiguration Techniques 13
2.5.1 Antenna Designs Based on the Integration of Radio Frequency Microelectromechanical Systems
(RF-MEMS) 15
2.5.1.1 Frequency Reconfigurable Antenna
with RF-MEMS 16
2.5.1.2 Pattern Reconfigurable Antenna with
RF-MEMS 17
2.5.1.3 Polarization Reconfigurable Antenna
with RF-MEMS 18
2.5.1.4 Biasing of RF-MEMS Switches 19 2.5.2 Antenna Designs Based on the Integration of
PIN Diodes 20
2.5.2.1 Frequency Reconfigurable Antenna with
Pin Diode 20
2.5.2.2 Polarization Reconfigurable Antenna
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2.5.2.3 Radiation Pattern Reconfigurable Antenna
with Pin Diode 24
2.5.2.4 Pattern and Polarization Reconfigurable
Antenna with PIN Diode 24
2.5.2.5 Biasing of PIN Diode Switches 25 2.5.3 Antenna Designs Based on the Integration of
Varactors 26
2.5.3.1 Frequency Reconfigurable Antenna with
Varactors 26
2.5.3.2 Biasing of the Varactor Switches 27 2.5.4 Antenna Designs Based on the Integration of
Photoconductive Switches 28
2.6 Application of Microstrip Antenna 30
2.7 Substrate Board Selection 30
2.8 Conclusions 32
III PROJECT METHODOLOGY
3.1 Introduction 34
3.2 Antenna Design 36
3.2.1 Design Specifications 37
3.2.2 Microstrip Patch Antenna (Design A) 37 3.2.3 Pattern Reconfigurable Antenna (Design B) 42
3.3 Simulation 43
3.4 Fabrication 44
3.5 Measurement 45
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IV RESULT AND DISCUSSION
4.1 Introduction 48
4.2 Microstrip Patch Antenna Design (Design A) 49 4.3 Microstrip Patch Pattern Reconfigurable Antenna
(Design B) 51
4.4 Comparison between Design A and Design B 57
4.5 Conclusion 59
V CONCLUSION AND RECOMMENDATION
5.1 Conclusion 60
5.2 Recommendation and Future Work 62
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LIST OF FIGURES
NO TOPIC PAGES
2.1 Various Techniques Adopted to Achieve 9
Reconfigurable Antennas
2.2 Schematic Layout of the RF MEMS Integrated Frequency
Reconfigurable Quasi-Yagi Folded Dipole Antenna 10 2.3 Reconfigurable Slot-Array Antenna with RF-MEMS 11
2.4 Slot with RF-MEMS Switch 14
2.5 Operation of the RSPMA 15
2.6 Fabricated FRSPMA 18
2.7 Prototype of Polarization Reconfigurable Antenna 19 2.8 Prototype of Multidirectional Pattern Reconfigurable Antenna 21 2.9 Schematic of the Reconfigurable Circular Patch Antenna For
Pattern and Polarization Antenna 22
2.10 Schematic of Dual-Band Bent Slot Antenna with Two Varactors 23 2.11 Topology of the Reconfigurable Dual-Band Slot Antenna Using
Varactors 24
2.12 Optically Shorted Stub-Loaded Frequency-Switching Patch
Antenna 25
2.13 Frequency Response for the Antenna 27
2.14 Radiation Pattern and 3dB Beamwidth 28
2.15 Commonly Types of Polarization 29
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3.2 Conventional Microstrip Patch Antenna 37
3.3 Dimension of Antenna Design 39
3.4 Geometrical Structure of Conventional Microstrip Patch
Antenna 41
3.5 Modified ground with PIN diode 43
3.6 Geometrical Structure of Pattern Reconfigurable Antenna 44 3.7 Fabricated Conventional Microstrip Patch Antenna And
Pattern Reconfigurable Antenna 45
3.8 Network Spectrum Analyzer 46
3.9 Anechoic Chamber 46
4.1 Simulated and Measured Return Loss Results for Design A 49 4.2(a) Simulated Radiation Pattern on Plane-E for Design A 50 4.2(b) Measured Radiation Pattern on Plane-H for Design A 50 4.3 Measured and Simulated Return loss results for Design B 51 4.4(a) Simulated and Measured Return loss for Design B on OFF_OFF
Mode 52
4.4(b) Simulated and Measured Return Loss for Design B on ON_OFF
Mode 52
4.4(c) Simulated and Measured Return Loss for Design B on OFF_ON
Mode 52
4.4(d) Simulated and Measured Return Loss for Design B on ON_ON
Mode 53
4.5(a) Simulated Radiation Pattern on Plane-E for Design B 54 4.5(b) Simulated Radiation Pattern on Plane-H for Design B 54 4.6(a) Comparison between Simulated and Measured Radiation Patterns
on Plane-E for Design A and Design B 58
4.6(b) Comparison between Simulated and Measured Radiation Patterns
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LIST OF TABLES
NO TOPIC PAGES
2.1 Different Type Of Switches Used In The Design Of Electrically
And Optically Reconfigurable Antennas 15
2.2 Applications of Microstrip Antennas 30
2.3 Common Substrate Materials for Microstrip Antenna 31 2.4 Electrical Properties for Electrically and Optically Switching 33
3.1 Design Specification for Dual Band Antenna 36
3.2 Dimension of Designed Antenna 40
4.1 Surface Current for Design A 51
4.2 Total Efficiency and Directivity for Design 53
4.3 Measured and Simulated Gain for Design B 53
4.4 Surface Current for Design B 56
4.5 Comparison between Resonance Frequency, Return Loss, Gain, Radiation Efficiency and Directivity for Design A and Design B 57
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CHAPTER 1
INTRODUCTION
1.1 Introduction to the Project
Electrical transmission of speech communication, music, pictures and other information by using the electrical signal. Speech and music sent directly from their sources to listeners across the close proximity through sound or acoustic waves. A photo of the same sent directly with optical or light waves over a short distance.
At longer distances, communication wire and radio communication used to send signals. It is a unusual circuit component, known as the ' antenna ' that has prepared radio communications may in practice. Creating an antenna burly enough electromagnetic field at huge distances and, mutual, it is extremely susceptible to external electromagnetic field intimidated it. However, coupling between the receiver and transmitter antenna is consequently miniature that the signals should be amplified in both the sending and receiving stations. It is impossible to try radio communications without an antenna.
Wireless communications system recently tends to be high, multi-functional and include more frequency band. Therefore, the quantity of the antenna gets larger and
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larger. This will lead to large equipment, communication systems, increasing cost and the problem of electromagnetic compatibility. Remodeling antenna, which offers a wide range of functions within the radiation pattern, frequency, or polarization, can realize the function of various dynamic antennas as it can adjust behavior to measure different situations and context operations. Therefore, it is effectively reducing adverse effects on the system of wireless communication brought about by the number of antennas.
Nowadays seen from most studies of the reconfigurable antenna by numerous institutions, reconfigurable antenna according to its function is divided into frequency reconfigurable antenna, polarization reconfigurable antenna, pattern reconfigurable antenna and hybrid reconfigurable antenna. The implementation methods contain using switches, changing material electromagnetic properties, loading variable reactance, using mechanical methods, using the parasitic units, using switchable feeding networks to improve their performances and so on [1].
The radiation pattern is one of the main characteristics of the antenna. Thus, the antenna pattern reconstruction cannot not be important instructions on remodeling antenna research. Antenna pattern reconstruction can be used to avoid noise sources, increase profit and safety systems, save energy with direct signals only in the desired direction. The pattern or the frequency of reconfigurability can be accomplished in several ways, such as moving to pass through the switch, using loading change to change current behavior at the antenna, or adding parasitic elements change to alter the elements of performance driven. Reconfigure patterns have been achieved mainly by using parasitic elements of variable length. Switching mechanism is used to change the existing password and giving patterns of behavior that reconstituted [2].
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1.2 Problem Statement
High capacity is very crucial in wireless as it is required for future application. It is because; the data transferred by users are becoming larger nowadays. For example, in the early years the data transferred consists of only text or voice only. As time goes by, the user is demanding higher channel capacity as they wish to send voice with picture or text with video or text, picture, and video at the same time. These data are required more capacity to be transferred. One of the main challenges in wireless communication is to gain high capacity in order to fulfill future application necessities. It is important in increasing the data transferred simultaneously. The enhancement insist for capacity in a wireless system has provoked large study intended at achieving advanced invention to the bandwidth provided.
Besides that, the current communication devices are portable and multiplications supported such as Bluetooth, Wi-Fi, GPS, and so much more. These applications are used different operating frequencies in order to avoid interferences between them. The conventional way to support this demand is by placing two or more antennas with different resonant frequency in that device. Obviously, this method is not effective because combining two or more antennas proving difficult because they will probably pair with each other causing degradation signals are received or sent. Placing two antennas in a device also bring in the space issue since it is usually designed to be a portable device and by placing multiple antennas in the device required more spaces. Moreover, this will lead to large communication system equipment, increased costs, and electromagnetic compatibility problems.
Some packages may use two or three antennas for diversity reception on small devices to increase the probability of receiving a usable signal, but usually only one of the antennas is used for transmission. The transmission from the portable device to a
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base station or other access point is the weakest part of the bidectional communication link because of the power, size, and cost restrictions imposed by portability. Moreover, the portable device is often used in unpredictable and /or harsh electromagnetic conditions, resulting in antenna performance that is certainly less than optimal. Reconfigurability antennas in such a situation can provide many advantages. For example, the capability to adjust the operating frequency antennas can be used to change the operating band, filter out annoying signals, or tune the antenna to take account of the novel surroundings. The radiation pattern of the antenna can be altered; it can be brought to the access point and employ fewer power for shipping, resulting in important savings in battery power.
Reconfigurable antennas, which offer diverse functions in radiation pattern, frequency, or polarization, can realize the function of the multiple antennas since it can dynamically adapt its behavior to different measurements situations and operational contexts. Therefore, it effectively reduces the adverse effects on the wireless communication system brought by the antenna number.
Reconfigurable antennas and devices represent a key technology for improving the performance of wireless communication systems. Accordingly, several design strategies for achieving reconfigurabilty in terms of one or more antenna parameters (i.e., operating frequency, polarization, etc.) Among these, antennas with a reconfigurable radiation pattern are of great interest due to their positive impact on network capacity and reliability by reducing interference problems and maximizing signal-to-noise ratio.
A remodeling pattern of electromagnetic radiation is radiator pattern changing with the switch. Typically, the frequency of such antenna operations is reserved unvarying. But in a few cases it is considered to contain dissimilar radiation patterns at
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dissimilar frequencies. Pattern reconfigurability allows wireless communication system in order to avoid a noisy environment, moving from electronic jamming, and save energy with the direct signal to the direction of the intended users. The antenna pattern is often used to raise the configured capacity channels and expanded the coverage of a wireless system.
1.3 Objective
The main purpose of this project is to design, simulate and fabricate pattern reconfigurable antenna for wireless communication system using electrical switching technique with integration of RF PIN diodes.
1.4 Project Scope
The project scope is focused on microstrip patch antenna designs which provide pattern reconfigurability. Slotted ground plane and switching techniques are added to control surface current in order to achieve pattern reconfigurabily .
1.5 Methodology
In order to achieve the objective, a number of activities have indentified, as outline below:
i. Investigate characteristics of microstrip patch antenna by means of simulation and numerical analysis.
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ii. Simulate the pattern reconfigurable antenna design model using antenna simulation software before the actual prototype built.
iii. Integrate RF Pin diode into the proposed antenna to evaluate the reconfigurable characteristics performance.
iv. Develop a new design prototype of pattern reconfigurable antenna. v. Antenna performance evaluation and optimization.
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LITERATURE REVIEW
2.1 Introduction
In recent years, wireless communication systems have shown tremendous growth. It will enable the accommodation of higher data rates owing to the advent of various services such as cellular, satellite communications and wireless local area networks. Since several applications operate either at different frequency bands or different radiation characteristics (such as pattern or polarization), the system requires multiple characteristic for several services. In addition, in urban areas, multipath fading phenomena may occur after multiple reflections or scatterings. As a large number of users are included within the limited frequency bandwidth, the probability of interference is increased. A reconfigurable antenna can solve these problems due to its diversity functions. In addition, it saves installation space and cost [3]. Reconfigurable antenna is able to change the antenna frequency, bandwidth, operational radiation pattern and polarization has become a very active field of research in the past decade. This is mainly due to their ability to provide dynamic reconciliation of changes in the channels of communication or system requirements [4].
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2.2 Antenna
The fields of wireless communication at present have given more emphasis to the field of antenna design In the early years when the available radio frequencies, an antenna with a design that is easy to use as a tool for transmitting electrical or radio waves in the air into all directions. This is an innovative way of communication to replace the wired technology wireless technology was first introduced by Galileo Marconi when he successfully start the first wireless telegraph in 1895. After that, the development of wireless technology make rapid. Antenna development plays an important role in wireless technology as the number of growing by leaps and bounds from the user in broadcasting, telecommunications, navigation, radar, sensor, and perhaps for the future cognitive radio wireless communications for example [5].
2.3 Basic Antenna Properties
The basic features that are used to explain the performance of the antenna including a fixed Voltage Impedance, Wave Ratio (VSWR), broadband, radiation pattern, 3 dB beam width, profitability and ultimately polarization.
2.3.1 Impedance
Antenna input impedance identically must match the characteristics of the transmission lines for maximum energy transfer archives between coaxial transmission line and antenna. If the antenna input impedance not equal to the characteristic impedance, transmission line will generate waves as shown at the antenna terminal and travel back towards energy sources. This reflects the energy cause a reduction in the
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efficiency of the system as a whole. The losses in efficiency will occur if the antenna is being used to send or receive energy.
2.3.2 Return Loss
In telecommunications, return loss refers to the ratio of power/power transmission delivered to the transmission lines. The value of the loss mitigation amplitude for the Return described in comparison to energy is reversed to send energy. Excellent antennas require a small value losses back less than point-10dB for best performance. Lost back to Pointe-10 dB is means that only 10% of the amounts of energy that can be seen while 90% of the amount of power delivered.
2.3.3 Bandwidth
Bandwidth is the frequency range antenna will be delivered efficiently where the antenna meets the criteria specified a set of performance specification. When the power antenna (3dB) ½, walk up and down this frequency has been reached and the antenna will no longer do. Antenna operates in a wide frequency range and still maintains satisfactory performance must have compensation circuit switched into the system to maintain the impedance matching. The relationship between the VSWR and bandwidth shown in Figure 2.13. Antenna bandwidth can be calculated as the equation 2.1. [6]
(2.1)
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base station or other access point is the weakest part of the bidectional communication link because of the power, size, and cost restrictions imposed by portability. Moreover, the portable device is often used in unpredictable and /or harsh electromagnetic conditions, resulting in antenna performance that is certainly less than optimal. Reconfigurability antennas in such a situation can provide many advantages. For example, the capability to adjust the operating frequency antennas can be used to change the operating band, filter out annoying signals, or tune the antenna to take account of the novel surroundings. The radiation pattern of the antenna can be altered; it can be brought to the access point and employ fewer power for shipping, resulting in important savings in battery power.
Reconfigurable antennas, which offer diverse functions in radiation pattern, frequency, or polarization, can realize the function of the multiple antennas since it can dynamically adapt its behavior to different measurements situations and operational contexts. Therefore, it effectively reduces the adverse effects on the wireless communication system brought by the antenna number.
Reconfigurable antennas and devices represent a key technology for improving the performance of wireless communication systems. Accordingly, several design strategies for achieving reconfigurabilty in terms of one or more antenna parameters (i.e., operating frequency, polarization, etc.) Among these, antennas with a reconfigurable radiation pattern are of great interest due to their positive impact on network capacity and reliability by reducing interference problems and maximizing signal-to-noise ratio.
A remodeling pattern of electromagnetic radiation is radiator pattern changing with the switch. Typically, the frequency of such antenna operations is reserved unvarying. But in a few cases it is considered to contain dissimilar radiation patterns at
(2)
dissimilar frequencies. Pattern reconfigurability allows wireless communication system in order to avoid a noisy environment, moving from electronic jamming, and save energy with the direct signal to the direction of the intended users. The antenna pattern is often used to raise the configured capacity channels and expanded the coverage of a wireless system.
1.3 Objective
The main purpose of this project is to design, simulate and fabricate pattern reconfigurable antenna for wireless communication system using electrical switching technique with integration of RF PIN diodes.
1.4 Project Scope
The project scope is focused on microstrip patch antenna designs which provide pattern reconfigurability. Slotted ground plane and switching techniques are added to control surface current in order to achieve pattern reconfigurabily .
1.5 Methodology
In order to achieve the objective, a number of activities have indentified, as outline below:
i. Investigate characteristics of microstrip patch antenna by means of simulation and numerical analysis.
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ii. Simulate the pattern reconfigurable antenna design model using antenna simulation software before the actual prototype built.
iii. Integrate RF Pin diode into the proposed antenna to evaluate the reconfigurable characteristics performance.
iv. Develop a new design prototype of pattern reconfigurable antenna. v. Antenna performance evaluation and optimization.
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LITERATURE REVIEW
2.1 Introduction
In recent years, wireless communication systems have shown tremendous growth. It will enable the accommodation of higher data rates owing to the advent of various services such as cellular, satellite communications and wireless local area networks. Since several applications operate either at different frequency bands or different radiation characteristics (such as pattern or polarization), the system requires multiple characteristic for several services. In addition, in urban areas, multipath fading phenomena may occur after multiple reflections or scatterings. As a large number of users are included within the limited frequency bandwidth, the probability of interference is increased. A reconfigurable antenna can solve these problems due to its diversity functions. In addition, it saves installation space and cost [3]. Reconfigurable antenna is able to change the antenna frequency, bandwidth, operational radiation pattern and polarization has become a very active field of research in the past decade. This is mainly due to their ability to provide dynamic reconciliation of changes in the channels of communication or system requirements [4].
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2.2 Antenna
The fields of wireless communication at present have given more emphasis to the field of antenna design In the early years when the available radio frequencies, an antenna with a design that is easy to use as a tool for transmitting electrical or radio waves in the air into all directions. This is an innovative way of communication to replace the wired technology wireless technology was first introduced by Galileo Marconi when he successfully start the first wireless telegraph in 1895. After that, the development of wireless technology make rapid. Antenna development plays an important role in wireless technology as the number of growing by leaps and bounds from the user in broadcasting, telecommunications, navigation, radar, sensor, and perhaps for the future cognitive radio wireless communications for example [5].
2.3 Basic Antenna Properties
The basic features that are used to explain the performance of the antenna including a fixed Voltage Impedance, Wave Ratio (VSWR), broadband, radiation pattern, 3 dB beam width, profitability and ultimately polarization.
2.3.1 Impedance
Antenna input impedance identically must match the characteristics of the transmission lines for maximum energy transfer archives between coaxial transmission line and antenna. If the antenna input impedance not equal to the characteristic impedance, transmission line will generate waves as shown at the antenna terminal and travel back towards energy sources. This reflects the energy cause a reduction in the
(6)
efficiency of the system as a whole. The losses in efficiency will occur if the antenna is being used to send or receive energy.
2.3.2 Return Loss
In telecommunications, return loss refers to the ratio of power/power transmission delivered to the transmission lines. The value of the loss mitigation amplitude for the Return described in comparison to energy is reversed to send energy. Excellent antennas require a small value losses back less than point-10dB for best performance. Lost back to Pointe-10 dB is means that only 10% of the amounts of energy that can be seen while 90% of the amount of power delivered.
2.3.3 Bandwidth
Bandwidth is the frequency range antenna will be delivered efficiently where the antenna meets the criteria specified a set of performance specification. When the power antenna (3dB) ½, walk up and down this frequency has been reached and the antenna will no longer do. Antenna operates in a wide frequency range and still maintains satisfactory performance must have compensation circuit switched into the system to maintain the impedance matching. The relationship between the VSWR and bandwidth shown in Figure 2.13. Antenna bandwidth can be calculated as the equation 2.1. [6]
(2.1) Where fu = upper frequency bandwidth