COMPARATIVE STUDY OF RADIAL LINE SLOT ARRAY ANTENNA WITH

DIFFERENT DIELECTRIC SUBSTRATES

WAN ASILAH BINTI WAN MUHAMAD

UNIVERSITI TEKNOLOGI MALAYSIA

COMPARATIVE STUDY OF RADIAL LINE SLOT ARRAY ANTENNA WITH

DIFFERENT DIELECTRIC SUBSTRATES

WAN ASILAH BINTI WAN MUHAMAD

A thesis submitted in fulfilment of the

requirements for the award of the degree of

Master of Engineering (Electrical)

Faculty of Electrical Engineering

Universiti Technologi Malaysia

NOVEMBER 2013

iii

Specially dedicated to my beloved husband, parents, brothers and sisters

iv

ACKNOWLEDGEMENT

In the name of Allah, the Most Gracious, the Most Merciful. All praise to

Allah for the blessing that lead to my successfulness in completing my research.

First and foremost, I would like to express my utmost gratitude to my MsC

supervisor, Prof. Dr. Tharek Abd Rahman for his valuable encouragement, freedom

and trust that enabled this research to run smoothly. I would like to convey a million

thanks to all members of the Wireless Communication Centre (WCC), UTM and

Advanced Communication Engineering Center (ACE), UniMAP for the help,

guidance and friendship.

A million thanks to my beloved husband, Dr. Mohd Faizal Jamlos, my

parents and my parents in law, all my family members for the endless support and

encouragement. Their prays, patience, endless encouragement, inspiration and

motivation understanding have driven me to this extends.

v

ABSTRAK

Radial Line Slot Array Antena (RLSA) adalah salah satu alat komunikasi

yang telah lama di gunakan di sebabkan oleh profil yang rendah, gandaan yang

tinggi, dan tahan lasak untuk kegunaan dalam perhubungan titik ke titik. Daripada

RLSA antena yang telah sedia ada, penyelidik mereka bentuk saiz antena dalam

jejari yang besar secara tidak langsung membuatkan antena mereka menjadi berat.

Oleh itu, tumpuan thesis ini adalah untuk meningkatkan prestasi antena dalam saiz

yang lebih kecil atau padat dan pada masa yang sama mengekalkan operasi frekuensi

pada 5.8 GHz. Dengan mengurangkan saiz antena, pertindihan slot akan berlaku dan

seterusnya mengurangkan gain. Oleh yang sedemikian, teknik tambahan dengan

substrat yang lain adalah salah satu cara untuk mengatasi masalah ini. Oleh itu,

kajian ini membentangkan reka bentuk antena dengan tiga struktur yang berbeza: slot

labah-labah-Radial Line Array Slot (SRLSA) antena yang berbeza iaitu lapisan

tunggal SRLSA, satu jurang udara dan Compact Sandwich Polypropylene antena

(CSPA). Pembinaan reka bentuk bermula dengan satu lapisan SRLSA antena dengan

dimensi (100x100) mm. Bilangan slot dan sudut slot dari sinaran elemen secara

ketara mempengaruhi prestasi keseluruhan SRLSA antena. Gandaan maksimum yang

diperoleh daripada lapisan tunggal SRLSA antena hanya 3.42 dBi dan di anggap

lemah untuk aplikasi titik ke titik. Oleh itu, struktur udara jurang disiasat. Bilangan

yang sama untuk slot dan sudut digunakan. Selepas simulasi, gandaan 7.68 dBi

dicapai. Peningkatan ini adalah disebabkan oleh perubahan ketelusan, ɛ antena. Nilai

yang lebih rendah daripada 'ɛ' meningkatkan bidang pinggiran di pinggir dan secara

tidak langsung memancarkan kuasa. Kajian lanjut telah dilakukan ke atas

polypropylene (PP) substrat walaupun nilai gandaan antena jurang udara adalah lebih

baik daripada lapisan tunggal SRLSA. Penggunaan PP dalam RLSA antenna telah

berjaya meningkatkan keuntungan sehingga 10.52 dBi dalam julat frekuensi 5.49

GHz kepada 5.89 GHz. Hal ini kerana, substrat PP yang di gunakan sebagai pengisi

dielektrik menambah baikkan nilai dielektrik dalam CSPA antena sekali gus menjana

gandaan yang optimum. Dengan segala kemampuan yang disebut, antena CSPA ini

adalah sangat berpotensi untuk digunakan dalam aplikasi perhubungan titik ke titik.

vi

ABSTRACT

Radial Line Slot Array Antenna (RLSA) is the legendary types of

communication device due to its low profile, high gain, and durable antenna for point

to point. From the existing RLSA antenna, most researcher designed their antenna

with a huge size indirectly make antenna become weight. Hence, this dissertation

focus on enhancement performance of antenna in compact size and at the same time

retain a frequency operation which is at 5.8 GHz. By reducing the size of antenna,

the overlapping of slots will be occurred and subsequently decrease the gain. Thus,

the attachment technique with another substrate is one of the options to overcome

this problem. Hence, the research presents the antenna designed with three different

structures: Spider-Radial Line Slot Array (SRLSA) antennas which are Single Layer

of RLSA, an Air-Gap RLSA and Compact Sandwich Polypropylene Antenna

(CSPA). The design construction is started with a single layer of SRLSA antenna

with a dimension of (100x100) mm. The number of slots and degree angles of

radiating element are significantly affected the overall performance of SRLSA

antenna. Parameter sweeps study on the number of slots and degree angles are

executed to obtain an optimum gain of SRLSA antenna. The maximum gain obtained

of single layer SRLSA antenna is only 3.42 dBi which is consider average for point

to point application. Thus, air-gap structure is investigated. The similar number of

slots and degree angles is used. After simulation, the gain of 7.68 dBi is achieved.

This improvement gain is due to the changes of permittivity, ɛ. The lower value of ɛ

increased the fringing field at the patch periphery and thus radiated power. Further

research has been done on polypropylene (PP) substrate even though the gain of air

gap antenna is better than single layer of SRLSA. The deployment of PP has

successfully boost the gain up to 10.52 dB within the frequency range of 5.49 GHz to

5.89 GHz. It is found that the incorporation of PP filler improved the dielectric

constant and inclined the dielectric loss of the CSPA antenna thus generating an

optimum gain. With all capabilities mentioned, this CSPA antenna is highly potential

to be deployed for point to point application.

vii

TABLE OF CONTENTS

CHAPTER TITTLE PAGE

DECLARATION

DEDICATION

ACKNOWLEDGEMENT

ABSTRAK

ABSTRACT

TABLE OF CONTENTS

LIST OF TABLES

LIST OF FIGURES

LIST OF ABBREVIATIONS

LIST OF SYMBOLS

ii

iii

iv

v

vi

vii

xi

xii

xvi

xvii

1 INTRODUCTION 1

1.0 Introduction 1

1.1 Problem Statement 2

1.2 Objectives 2

1.3 Scope of works 3

1.4 Contributions 3

1.5 Thesis outline 4

2 LITERATURE REVIEW 5

2.0 Reviews of Microstrip Antenna 5

2.1 Radial Line Slot Antenna (RLSA) 7

2.1.1 Double Layer RLSA Antenna 8

viii

2.1.2 Liner Polarization RLSA Antenna 9

2.1.3 Small RLSA antenna 11

2.1.4 Multi-Layer of RLSA antenna by FR-4

Substrate

11

2.3 Dielectric Substrate 15

2.3.1 Flame Retardant Substrate (FR-4) 15

2.4 Air Gap Structure 16

2.4.1 Wide Band of Air Gap RLSA Antenna 17

2.5 Polypropylene 18

2.5.1 Polypropylene (PP) of Monopole Antenna

18

2.6 Summary 20

3 METHODOLOGY ON DESIGNING A RADIAL

LINE SLOT ARRAY ANTENNA (RLSA)

21

3.1 Introduction 21

3.2 Flowchart of overall project 22

3.2.1 Methodology of overall project 23

3.3 Design Specification 26

3.4 Development of Single Layer of Spider Radial

Line Slot Array (SRLSA) Antenna.

27

3.4.1 Calculation of Slots and Lambda 27

3.4.2 Design and Optimization of SRLSA

antenna

28

3.4.3 Fabrication of Single layer of SRLSA

antenna

30

3.5 Design Structure of Air Gap SRLSA antenna 32

3.5.1 Fabrication of air-gap SRLSA antenna 33

3.6 Design structure of Compact Sandwich 34

ix

Polypropylene Antenna (CSPA)

3.7 Summary 36

4 A DESIGN OF SRLSA ANTENNA, AIR GAP

STRUCTURE AND COMPACT SANDWICH

POLYPROPLYENE ANTENNA (CSPA)

37

4.1 Introduction 37

4.2 Single Layer of Compact Spider-RLSA

(SRLSA) antenna

38

4.2.1 Measurement Results of Single Layer

of Compact Spider-RLSA (SRLSA) antenna

41

4.2.2 Summary of Single Layer SRLSA

antenna

42

4.3 Air Gap SRLSA Antenna 42

4.3.1 Simulation of Air Gap SRLSA Antenna 43

4.3.2 Measurement Results of air-gap SRLSA

antenna

45

4.4 Comparison between Single Layer of SRLSA

Antenna and Air-Gap SRLSA Antenna

46

4.5 Simulation Results of CSPA antenna 46

4.5.1 Number of Spider-Slots Technique 46

4.5.2 Degree Angles Technique 49

4.5.3 Measurement results of CSPA 52

4.6 Comparison between CSPA, Air-Gap SRLSA

Antenna and Single Layer of SRLSA

Antenna

53

4.7 Summary 55

x

5 CONCLUSION AND FUTURE WORK 56

5.1 Conclusion 56

5.2 Future Work 57

REFERENCES 59

Appendices A-C 65-67

xi

LIST OF TABLES

TABLE NO. TITLE PAGE

2.1 Some applications of microstrip antennas 6

3.1 Result of return loss and gain for single layer of SRLSA

antenna at differ degree angles

29

3.2 Antenna parameters design 31

4.1 Result of reflection coefficient and gain for single layer of

SRLSA antenna at differ degree angles.

40

4.2 The various of total slots number towards CSPA

performance

49

4.3 The effects of various degree slots towards on SRLSA

performance

50

4.4 Measurement result of return loss, gain and HPBW 55

xii

LIST OF FIGURES

FIGURE NO. TITLE PAGE

2.1 Microstrip antenna current and charge distribution 6

2.2 The orientation of RLSA lot (a) circular slot formed by

a multiplicity of short linear slots and (b) Annular slot

aperture and space geometry

7

2.3 A double layer RLSA antenna structure (a) Radiating

element with side view (b) Current flow

9

2.4 Slot arrangement for the linear polarized RLSA 10

2.5 Extra reflection-cancelling slots are arranged in the unit

radiator geometry

10

2.6 CP RLSA antenna proposed by Zagriatski and

Bialkowski.

11

2.7 Prototype of RLSA using three layers FR-4 substrate 12

2.8 Three-layers structure within the radial cavity of RLSA

antenna

12

2.9 Simulation results of LP-BSRLSA antenna 13

2.10 Simulated vertical plane of LP-BSRLSA and

Simulated horizontal plane of LP-BSRLSA

13

2.11 The structure of the 900 mm RLSA antenna 14

2.12 Graph of directivity gain of 900 mm RLSA antenna 14

2.13 Total loss FR4 substrate over frequency in GHz 15

2.14 Basic of air gap structure (a) top substrate (b) lower

substrate

16

2.15 An air-gap structure of LP-BSRLSA 17

2.16 Simulated reflection coefficient of RLSA 17

xiii

2.17 Simulated Radiation pattern for Air Gap RLSA (a) in

polar and (b) in3D

18

2.18 The structure of PP as a based - CPW-fed monopole

antenna and result of S11 at frequency 2.4 GHz and 5.8

GHz [49].

19

2.19 Radiation Pattern of PP-CPW monopole antenna at 5.8

GHz

19

3.1 Flowchart of the project 22

3.2 Typical Radiation Pattern of a Microwave Antenna 24

3.3 Setting dialogue box of CST (a) FR-4 (b) Copper (c)

Vacuum

29

3.4 Overall structure of compact spider RLSA antenna (a)

back view (b) front view

30

3.5 Printed film 31

3.6 Prototype of single layer of SRLSA antenna. (a) front

view (b) back view (c) side view

32

3.7 Structure of air gap antenna (a) radiating element (b)

ground layer and (c) coaxial feeding of air gap structure.

33

3.8 Prototype of Air-Gap SRLSA 33

3.9 Polypropylene Composite 34

3.10 Complete structure of CSPA antenna. (a) Fabricated (b)

Simulated

35

3.11 The proposed CSPA radiating surface 35

4.1 The deviation of degree angle single layer of SRLSA (a)

1° degree angle of spider slots (b) 5° degree angle of

spider slots (c) 8° degree angle of spider slots

38

4.2 Parameter sweeps on return loss of 1° degree, 5° degree

and 8° degree angles of single layer of SRLSA antenna

39

4.3 3D radiation pattern for single layer SRLSA antenna. (a)

1° degree. (b) 5° degree. (c) 8° degree angles for slot

39

xiv

plotted and (d) Comparison on polar radiation pattern

for 1° degree, 5° degree and 8° degree angles

4.4 Measurement results of Single Layer SRLSA antenna.

(a) Reflection Coefficient (b) Radiation pattern.

41

4.5 Coaxial feeding of Air-Gap Spider-RLSA antenna 42

4.6 The electrical flow inside the Air-Gap Spider-RLSA

antenna

42

4.7 Reflection Coefficient of air-gap SRLSA antenna. 44

4.8 Radiation pattern of single layer of SRLSA antenna (a)

3-D (b) Polar

45

4.9 Comparison on return loss results between measurement

and simulation for air-gap SRLSA antenna.

45

4.10 Comparison on radiation pattern results between

measurement and simulation for air-gap SRLSA

antenna.

46

4.11 Reflection Coefficient of 8, 10 and 12 slots CSPA per

ring

48

4.12 Simulation results of radiation pattern of 8, 10 and 12

slots CSPA per ring

49

4.13 Reflection Coefficient simulation results of 5, 8, 15, 18

and 20 degree angles of CSPA.

51

4.14 Simulation results of radiation pattern of 5, 8, 15, 18, 20

degree spider-slots angles of CSPA.

51

4.15 Comparison between simulation and measurement

results of return loss.

51

4.16 Comparison between simulation and measurement

results of radiation pattern.

52

4.17 Reflection Coefficient results for Single Layer of

SRLSA, Air Gap SRLSA antenna and CSPA (a)

simulation and (b) measurement

53

xv

4.18 Polar radiation pattern of Single Layer of SRLSA

antenna, Common Air gap antenna and CSPA (a)

simulation and (b) measurement

54

xvi

LIST OF ABBREVIATIONS

RLSA - Radial Line Slot Array Antenna

P2P - Point to point

CSPA - Compact Sandwich Polypropylene Antenna

CST - Computer Simulation Technology

WCC - Wireless Communication Centre

SRLSA - Spider-Radial Line Slot Array

TEM - Transverse Electromagnetic Wave

VSWR - Voltage Standing Wave Ratio

LP-BSRLSA - Linear Polarized Beam Squinted RLSA

PP - Polypropylene

CPW - Coplanar Waveguide

RFID - Radio Frequency Identification

CP - Co-Polarization

XP - Cross Polarization

HPBW - Half Power Beamwidth

IEEE - Institute of Electrical and Electronic Engineers

PCB - Printed Circuit Board

NiZn - Ferrite Tiles

xvii

LIST OF SYMBOLS

dBi - Decibels isotropic

% - Percentage

λ - Semi-lambda

dB - Decibel

θ - Theta

φ - Phase

r - Constant radius

φi - Inner termination angles

φo - Outer termination angles

fo - Frequency of operation

εr - Dielectric constant

Ω - Ohm

Г - Reflection coefficient

c - Speed of light

λg - Wavelength in cavity

λ0 - Wavelength in air

mm - Milimeter

m - Meter

˚ - Degree Angle

3D - Three Dimension

S11 - Return Loss

η - Antenna Efficiency

tan δ - Lost Tangent

G - Gain

D -- Directivity

QT - Total quality

xviii

QD - Dielectric Loss

QRad - Radiation loss

d - Air gap distance

- Radiating power

- Input power

Rr - Radiation resistance

RL - Dielectric resistance

Qs - Surface waves loss

Qc - Ohmic loss

≈ - Approach

xix

LIST OF APPENDICES

APPENDIX TITLE PAGE

A Anechoic Chamber measurement Setup. 65

B Gain measurement test system. 66

C1 3D Radiation Patterns of Single Layer of

SRSLA antenna. (a) front view and (b) up

view.

66

C2 3D Radiation Patterns of air gap antenna. (a)

front view and (b) up view.

67

C3 3D Radiation Patterns of CSPA. (a) front view

and (b) up view.

67

CHAPTER 1

INTRODUCTION

1.0 Introduction

Presently, the radial line slot array (RLSA) antenna has achieved a large

attention among researchers and industry players. This is due to the capability of low

profile, attractive, high gain and durable antenna for point to point, point to

multipoint and satellite broadcasting applications. Low cost feature of RLSA has

inspired some researchers to investigate more design for lower frequency

applications such as researcher Imran Ibrahim et al [1] . Based on the IEEE 802.1ln

standard, the operating frequency of wireless bridging is in range of 5.725-5.875

GHz.

For a number of years, a standard parabolic dish antenna was implanted for

point to point communications systems. However, such antenna has some

disadvantages of aperture blockage. For this concern, the RLSA antenna might be

favorable.

A unique type of slot's orientation and variable in degree angle will be

focused on this dissertation. It is believed that both technique can give a solid result

in order to achieve a high gain antenna's performance. The combination of

polypropylene material with FR-4 is a novelty in this research. The proposed antenna

2

will be compared with the common type of antenna such as one layer RLSA antenna

and air-gap antenna.

1.1 Problem statement

Point to point (P2P) communication has tremendous growth nowadays.

Various types of appropriate antennas, including parabolic reflectors, microstrip

arrays and radial line slot arrays (RLSA) have been proposed. Parabolic reflectors are

the most widely used. Unfortunately, this type of antenna have disadvantage of

aperture blockage in a primary fed design.

Instead of patch array, a radial line slot array (RLSA) antenna might be

another option. An RLSA antenna has as much as 50% higher gain than the patch

array antenna [2]. Nonetheless, the size of that RLSA is as big as 200 mm from

Imran Ibrahim et al [1]. Such big diameter needs to be optimized. Reducing its

dimension will lead towards efficiency degradation. Subsequently the same reduction

goes to the gain parameter. Moreover, overlapping slot is likely going to happen by

minimizing the dimension of the RLSA antenna. Additional reflection-cancelling slot

and attachment of another substrate is considered as one of the option to solve the

problems.

1.2 Objectives

The objectives of this dissertation are as follows:

1. To enhance gain of RLSA antenna by integrating additional

polypropylene substrate.

2. To compare three prototypes of spider-RLSA antenna; single layer of

RLSA, Air-Gap RLSA and Compact Sandwich Polypropylene Antenna

3

(CSPA) in terms of radiation pattern, return loss and half-power

beamwidth.

1.3 Scope of works

This research focuses on enhancement performance of antenna in compact

size and at the same time retain a frequency operation which is at 5.8 GHz. The

proposed antenna is designed using Computer Simulation Technology (CST)

software and fabricated in etching room at Wireless Communication Centre (WCC),

UTM. The fabricated prototypes are tested and measured in the anechoic chamber

and their results are compared with the simulated results. The measured return losses

and radiation patterns are compared with simulations.

1.4 Contributions

1. Introducing a novel spider-Radial Line Slot Array (SRLSA) of common air-

gap antenna with a small size but good in performanced.

2. Finding of polymer material (polyproplyene) with permittivity of 2.33 as a

potential replacement for an air-gap layer.

3. The compact polyproplyene spider-RLSA antenna is capable to produce a

broadside return loss, single sided broadside radiation pattern and enhanced

the antenna performanced.

4

1.5 Thesis outline

This thesis is organized into five chapters. Chapter 1 consists of the

introduction, problem statements, objectives, scopes of works, contributions and

thesis outlined. In Chapter 2, literature review of several different antenna geometries

which form the basis for the radial line slot array (RLSA) antenna designs and theory

of antenna issues are included. Moreover, it also provides history and analysis of

RLSA antenna likes designs antenna, polarization antenna, and radiation pattern

antenna. Other than that, theory of basic antenna such as gain, radiation pattern,

return loss, bandwidth and beamwidth is also explained.

In Chapter 3 contains of three different types of antennas; single layer of

spider-Radial Line Slot Array (SRLSA) antenna, air-gap antenna SRLSA and

Compact Sandwich Polypropylene antenna (CSPA). It provides an expanded and

detailed analysis of dissimilar antenna concept for those antennas. This part also

presents the technique in designing of proposed antenna which are number of slots

and slot's degree angle.

Meanwhile, a results of specific investigations using simulations and

experimental methods would be described in details in Chapter 4. The investigation

of these SRLSA types of antenna is carried out by Computer Simulation Technology

(CST) software with an analysis of the measured fabrication antennas. Assessment of

those antennas which are single layer of SRLSA antenna, common air gap antenna

and CSPA antenna also written in this chapter. Lastly, the conclusion will be

obtained in Chapter 5.

REFERENCES

1. Imran Mohd Ibrahim et.al "Pembangunan Antena Lubang Alur untuk Aplikasi

Capaian Wayerles Berjalur Lebar Tetap pada Frekuensi 5725-5875MHz",

April 2005.

2. M. F.Jamlos, O. A. Aziz, T. A. Rahman and M. R. Kamarudin “A

Reconfigurable Radial Line Slot Array (RLSA) Antenna For Beam Shape And

Broad Side Application” J. of Electromagn. Waves and Appl., Vol. 24, 1171–

1182, 2010.

3. Bahl and Bhartia: "Microstrip Antenna Design Handbook" (Artech House

Antennas and Propagation Library), (November 2000)

4. M. T. Islam, M. N. Shakib and N. Misran, "Design Analysis Of High Gain

Wideband L-Probe Fed Microstrip Patch Antenna" Progress In

Electromagnetics Research, PIER 95, 397-407, 2009.

5. David.M Pozar, “Analysis of an infinite phased Array of Aperture Coupled

Microstrippatches", IEEE transactions on antennas and propagation, vol. 37,

no. 4, April 1989.

6. Theodore S. Rappaport, “Wireless Communications: Principles and

Practice”, Prentice Hall, December 2001.

7. G. K. Theofilogiannakos, T. V. Yioultsis, and T. D. Xenos, "Experimental

Validation of A Hybrid Wide-Angle Parabolic Equation - Integral Equation

Technique for Modeling Wave Propagation in Indoor Wireless

Communications," Progress In Electromagnetics Research, PIER 82, 333-

350, 2008.

8. Davis, P.W. and Bialkowski, M.E. (1997), " Experimental investigations into

a linearly polarized radial slot antenna for DBS TV in Australia” IEEE

Transactions on Antennas and Propagation, Vol. 45. No. 7. 1123-1129

9. Akiyama, A.,Yamamoto, T., Hirokawa, J., Ando,M., Takeda, E., Arai, A.,

“High gain radial line slot antennas for millimeter wave applications” , IEEE

Proc. Microw. Antennas Propagation. Vol.147, no. 2, pp. 134-138, April

2000.

10. Kelly, K. "Recent Annular Slot Array Experiments", IRE International

Convention Record.Vol. 5. Mar 1957. pp. 144 – 152.

11. Takashi, M., Takada, J. Ando, M., Goto, N. "Characteristics of Small

Aperture, Single Layered, Radial Line Slot Antennas", IEE Proc. Pt. H. Feb

1992. Vol 139(1). pp. 79-83.

12. Ando, M.; Sakurai, K.; Goto, N. "Characteristics of A Radial Line Slot

Antenna for 12 GHz Band Satellite TV Reception", IEEE Transactions on

Antennas and Propagation [legacy, pre - 1988]. Vol. 34. Issue: 10. Oct 1986.

pp. 1269 – 1272.

13. Akiyama, A., Yamamoto, T., Ando, M., Goto, N. "Efficiency of Very Small

Concentric Array Radial Line Slot antenna", Proc. ISAP. Mac 1996. Chiba,

Japan. pp. 501-504.

14. Goto, N. and Yamamoto, M. "Circularly Polarized Radial Line Slot

Antennas", IECE Japan Technical Report. Aug 1980. AP80-57.

15. Sasazawa, H., Oshima, Y., Sakurai, K., Ando, M., Goto, N. "Slot Coupling in

a Radial Line Slot antenna for 12GHz Band Satellite TV reception", IEEE

Trans. on Antennas and Propagations. Sept. 1988. Vol AP-36. pp. 1221-1226.

16. Sierra-Castaner, M.; Sierra-Perez, M.; Vera-Isasa, M.; Fernandez-Jambrina,

J.L. "Low-Cost Monopulse Radial Line Slot Antenna", IEEE Trans. Antenna

and Propagation. Vol.51. Issue: 2. Feb. 2003. pp. 256 – 263.

17. Ando, M., Numata, T., Takada, J., Goto, N. "A Linearly Polarized Radial

Line Slot Antenna", IEEE Trans. on Antenna and Propagation. Dec 1988. Vol

36(12). pp. 1675-1680.

18. Takada, J. Ando, M., Goto, N. "A Reflection Cancelling Slot Set in a Linearly

Polarized Radial Line Slot Antennas", IEEE Trans. Antenna Propagation.

April 1992. Vol. 40(4). pp. 433-438.

19. Zagriatski, S.; Bialkowski, M.E. "Circularly Polarised Radial Line Slot Array

Antenna for Wireless LAN Access Point", 15th Int. Conf. on Microwaves,

Radar and Wireless Communications, 2004. MIKON-2004. Vol. 2. 17-19

May 2004. pp.649 – 652.

20. Tharek, A. R, Farah Ayu, I. K, "Theoretical Investigations of Linearly

Polarized Radial Line Slot Array (RLSA) Antenna for Wireless LAN Indoor

Application at 5.5 GHz", IEEE MELECON 2002, May 2002.

21. Lim, T.S.; Tharek, A.R.; Wan Khairuddin, W.A.; Hasnain, "A Prototypes

Development for Reflection Canceling Slot Design of Radial Line Slot Array

(RLSA) Antenna for Direct Broadcast Satellite Reception", Asia-Pacific

Conference on Applied Electromagnetics, 2003. APACE 2003. 12-14 Aug.

2003. pp. 34 – 37.

22. http://www.ee.surrey.ac.uk/Personal/D.Jeffries/antenna.htm (current August)

23. Allan W.Scott, “Understanding Mircowave,” John Wiley & Sons, Inc, 1993.

24. SkyCross, “Antenna Terminology” http://www.skycross.com (current August

2003)

25. Moteco Group Website, “Antenna Basics” http://www.moteco.com (current

July 2003)

26. Wikipedia the free encyclopedia, “Return Loss”

http://en.wikipedia.org/wiki/Return_loss

27. Jamlos, M. F., Rahman, T. A, Kamaruddin, M. R., "The Effects of Air Stacked

on Reconfigurable Quadratic Aperture-coupled Slots Antenna for WiMAX

Application"

28. http://www.rfcafe.com/references/electrical/dielectric-constants-strengths.htm

29. M. F. Jamlos, T. A. Rahman, and M. R. Kamarudin, “A Novel Adaptive Wi-Fi

System With Rfid Technology”, Progress In Electromagnetics Research, Vol.

108, 417-432, 2010.

30. M. F. Jamlos, T. A. Rahman, and M. R. Kamarudin, “Adaptive Beam Steering

Of Rlsa Antennawith Rfid Technology”, Progress In Electromagnetics

Research, Vol. 108, 65-80, 2010.

31. M. F. Jamlos, O. A. Aziz, T. A. Rahman and M. R. Kamarudin “A beam

steering radial line slot array (rlsa) antenna with reconfigurable operating

frequency”, J. of Electromagn. Waves and Appl., Vol. 24, 1079–1088, 2010

32. M.F.Jamlos, M.Jusoh, M.F. Malek, M.A.Jamlos, Z.A.Ahmad, A.H. Ismail,

M.R.Kamarudin and M.H.Muslim, “A unique Reconfigurable Slot Array

Antenna for WiMAX Application” IEEE-APS Topical Conference on

Antennas and Propagation in Wireless Communications, 2011.

33. Quadratic Slots Antenna for WiMAX and 4G Applications", Microwave and

Optical Technology Letters (MOTL)", Volume: 54, Issue: 9, Page (s): 2139-

2144, 2012.

34. Yusuf, Y. Xun Gong, “A Low-Cost Patch Antenna Phased Array With

Analog Beam Steering Using Mutual Coupling and Reactive Loading”, IEEE

Antennas and Wireless Propagation Letters, Vol.7, pg 81-84, 2008.

35. https://sites.google.com/site/ppsolutions2/Home/polypropylene

information/test-page 2/polypropylene-structure, "Polypropylene Structure"

36. Neeraj Rao and Dinesh Kumar V," Gain and Bandwidth Enhancement of a

Microstrip Antenna UsingPartial Substrate Removal in Multiple-layer

Dielectri Substrate", Progress In Electromagnetics Research Symposium

Proceedings, Suzhou, China, Sept. 12-16, 2011.

37. Allan W.Scott, “Understanding Mircowave,” John Wiley & Sons, Inc, 1993

38. Wireless ictp handbook, “Antenna Basic”

http://wireless.ictp.it/handbook/C4.pdf

39. M. T. Ali, M. R. Kamarudin, and T. A. Rahman, “Design of Reconfigurable

Multiple Elements Microstrip Rectangular Linear Array Antenna”, Progress

In Electromagnetics Research C,Vol.21–35, 2009.

40. J. S. Roy and M. Thomas, “Design of A Circularly Polarized Microstrip

Antenna for WLAN”, Progress In Electromagnetics Research M, Vol. 3, 79–

90, 2008.

41. H. Fayad and P. Record, "Mutual coupling between a pair of identical beam

steering dielectric resonator antennas," Progress In Electromagnetics

Research B, Vol. 14, 23-44, 2009.

42. N. Yousefzadeh, C. Ghobadi, and M. Kamyab, "Consideration of mutual

coupling in a microstrip patch array using fractal elements," Progress In

Electromagnetics Research, Vol. 66, 41-49, 2006.

43. J.I.Herranz-Herruzo, A.Valero-Nogueira, M.Ferrando-Bataller, "Optimization

technique for linearly polarized radial-line slot-array antennas using the

multiple sweep method of moments," IEEE Trans. Antennas Propagat., vol.

52, no. 4, pp. 1015-1023, April 2004.

44. Takada, J. Ando, M., Goto, N. "A Beam Tilted Linearly Polarized Radial

Line Slot Antenna",. Electron. Comm. Japan. 1989. Part 1. Vol. 72(11). pp.

27-33.

45. Md. Rafi Ui Islam, Tharek Abd. Rahman, "Novel and Simple Design of Multi

Layer Radial Line Slot Array (RLSA) Antenna using FR-4 Substrate", 2008

Asia-Pacific Symposium on Electromagnetic Compatibility & 19th

International Zurich Symposium on Electromagnetic Compatibility, 19-22

May 2008, Singapore.

46. Tharek Abdul Rahman, Imran Mohd Ibrahim, Pak Siau Wei, Johari Ahmad,

Ab Ghani Che Wahab, " A Study on Effectiveness of FR4 as a Dielectric

Material for Radial Line Slot Array Antenna for Wireless Backhaul

Application ", Asia-Pacific Conference on Communications (APCC), Sutera

Harbour Resort, Kota Kinabalu, Sabah, Malaysia, October 2011.

47. I.M. Ibrahim, T.A.Rahman, M.I.Sabran, "Wide Band Open Ended Air Gap

RLSA Antenna at 5.8GHz Frequency Band", IEEE, 2012.

48. Tung Xuan Nguyen, Rushanthi .S. Jayawardene, Yasutomo Takano, Kimio

Sakurai, Takuichi Hirano, Jiro Hirokawa, Makoto Ando, Osamu Amano,

Shuichi Koreeda, Takaomi Matsuzaki, "An Equivalent Two-Layer Model for

a Fast Design of a High Gain Multi-Layer Radial Line Slot Antenna using

MoM", Proceedings of APMC 2012, Kaohsiung, Taiwan, Dec. 4-7, 2012.

49. M.E. de Cos and F. Las-Heras, "Polypropylene-Based Dual-Band CPW-Fed

Monopole Antenna", IEEE Antennas and Propagation Magazine, Vol. 55,

No.3, June 2013.