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STUDY OF CIRCULARLY POLARIZED PATCH ANTENNA FOR
WIRELESS LOCAL AREA NETWORK
ACCESS POINT APPLICATION
YII MING LEONG
A project report submitted in partial fulfillment of the
requirements for the award of the degree of
Master of Engineering
(Electrical – Electronics and Telecommunications)
Faculty of Electrical Engineering
Universiti Teknologi Malaysia
NOVEMBER 2007
PSZ 19:16 (Pind. 1/07)
UNIVERSITI TEKNOLOGI MALAYSIA
DECLARATION OF THESIS / UNDERGRADUATE PROJECT PAPER AND COPYRIGHT
Author’s full name : Yii Ming Leong
Date of birth : 6th November 1977
Title : Study Of Circularly Polarized Patch
Antenna For Wireless Local Area
Network Access Point Application
Academic Session : 2007/2008
I declare that this project report is classified as :
CONFIDENTIAL (Contains confidential information under the Official Secret
Act 1972)*
RESTRICTED (Contains restricted information as specified by the
organization where research was done)*
OPEN ACCESS I agree that my project report to be published as online open
access (full text)
I acknowledged that Universiti Teknologi Malaysia reserves the right as follows:
1. The project report is the property of Universiti Teknologi Malaysia.
2. The Library of Universiti Teknologi Malaysia has the right to make copies for the purpose
of research only.
3. The Library has the right to make copies of the project report for academic exchange.
Certified by :
SIGNATURE SIGNATURE OF SUPERVISOR
771106-13-5065
Prof. Dr. Tharek bin Abdul Rahman
(NEW IC NO. /PASSPORT NO.) NAME OF SUPERVISOR
Date : Date :
NOTES : * If the project report is CONFIDENTAL or RESTRICTED, please attach with the letter from
the organization with period and reasons for confidentiality or restriction
√
“I hereby declare that I have read this project report
and in my opinion this project report is sufficient
in terms of scope and quality for the award of the degree of
Master of Engineering (Electrical – Electronics and Telecommunications)”
Signature :
Name of Supervisor : Prof. Dr. Tharek bin Abdul Rahman
Date :
STUDY OF CIRCULARLY POLARIZED PATCH ANTENNA FOR
WIRELESS LOCAL AREA NETWORK
ACCESS POINT APPLICATION
YII MING LEONG
A project report submitted in partial fulfillment of the
requirements for the award of the degree of
Master of Engineering
(Electrical – Electronics and Telecommunications)
Faculty of Electrical Engineering
Universiti Teknologi Malaysia
NOVEMBER 2007
ii
I declare that this project report entitled
“Study of Circularly Polarized Patch Antenna for Wireless Local Area Network
Access Point Application”
is the result of my own research except as cited in the references. The project report
has not been accepted for any degree and is not concurrently submitted in
candidature of any other degree.
Signature :
Name : Yii Ming Leong
Date :
iii
My Beloved Family
and
Jacinta Yeo
iv
ACKNOWLEDGEMENTS
All glory and honor to my Lord and Saviour Jesus Christ!
This project was initiated by Professor Dr. Tharek Abdul Rahman, the
Director of Wireless Communication Centre (WCC). I sincerely appreciate his
supervision and guidance throughout the project. His simple and strait forward
comments gave me clear sign posts to aim for results.
I would like to thank also to the team of WCC staff who gave me their best
support. They are Puan Azliza, En. Mohamed, En. Khomeini, and En Ghani,
To my ex-lecturer En. Thelaha who gave me unreservedly his competent
technical knowledge. The research officers En. Nazri, En. Osman, En. Huda and my
friends who motivated me with their competitive spirit.
I owe much to my parents, my family members, and Jacinta for their
emotional, financial, prayers, and loving support.
.
v
ABSTRACT
Circular Polarized (CP) antennas are attractive for wireless communication
applications because no strict orientation between the access point and the mobile
unit are required. The purpose of this project is to make a comparative study
between a CP patch antenna and a standard monopole antenna for Wireless Local
Area Network Access Point (WLAN AP) applications at 2.4 ~ 2.485GHz frequency
band. Circularly polarized operation is achieved by truncating two opposite corners
of a square patch and airgap with a long probe feed is used as bandwidth
enhancement technique. The best 3dB axial ratio bandwidth and 10dB impedance
bandwidth reached 8.55% and 8.9% respectively, for gain of 6dBi with airgap
thickness of 5mm. Details of the antenna design, the process involved, and the
simulation and experimental results are presented.
vi
ABSTRAK
Antena kutup berpusing (CP) amat menarik untuk applikasi perhubungan
tanpa wayar kerana ia tidak memerlukan orientasi antena yang tepat di antara tempat
masuk (AP) dan unit mobil. Tujuan projek ini adalah untuk membuat kajian
perbandingan di antara antena monopol standard dengan antena CP untuk kegunaan
applikasi tempat memasuki rangkaian setempat tanpa wayar (WLAN AP) pada jalur
frekuensi 2.4 ~ 2.485GHz. Operasi kutup berpusing telah dicapai dengan memotong
dua pepenjuru bertentangan pada satu tampal segi-empat sama dan gap udara dengan
suapan prob yang panjang digunakan sebagai teknik memperbesarkan julat jalur.
Julat jalur terbaik yang dicapai untuk 3dB Axial Ratio(AR) dan 10dB impedance
adalah 8.55% dan 8.9% masing-masing untuk 6dBi tambahan pada ketebalan gap
udara 5mm. Rekaan antena, proses berkenalan serta keputusan-keputusan simulasi
dan ujikasi yang terperinci telah dibuat.
vii
TABLE OF CONTENTS
CHAPTER TITLE PAGE
DECLARATION ii
DEDICATION iii
ACKNOWLEDGEMENTS iv
ABSTRACT v
ABSTRAK vi
TABLE OF CONTENTS vii
LIST OF TABLES xi
LIST OF FIGURES xii
LIST OF APPENDICES xv
1 INTRODUCTION 1
1.1 Overview 1
1.2 Objective 2
1.3 Scope of Study 2
1.4 Problem statement 2
2 LITERATURE REVIEW 4
2.1 Important Features of Microstrip Patch Antennas 5
2.1.1 Patch Shapes 5
2.1.2 Substrates 6
2.1.3 Feeding Structures 6
2.2 Transmission-line model 7
2.3 Circular polarization 11
viii
2.4 Polarization measurements 13
2.4.1 Polarization Loss Factor 13
2.5 Recent works of Circularly Polarized Antennas 14
2.5.1 Effects Of Circular And Linear Polarized Antennas
On Wideband Propagation Parameters In Indoor
Radio Channel 14
2.5.2 Study Of Broadband Cp Patch Antenna With Its
Ground
Plane Having An Elevated Portion. 14
2.5.3 Low-Cost Broadband Circularly Polarized Patch
Antenna 15
2.5.4 A Broadband Planar Patch Antenna Feb By A Short
Probe Feed. 16
3 DESIGN OF A CICURLARY POLARIZED ANTENNA 18
3.1 Introduction 18
3.2 Design methodology 19
3.3 Selection of antenna structure 20
3.4 Design specifications 20
3.5 Theoretical Calculations 21
3.6 Modeling and simulation 23
3.6.1 Design Entry 23
3.6.2 Optimizations 24
3.7 Fabrication Process Flowchart 25
3.8 Comparison of result 26
3.8.1 Return Loss (S11) 26
3.8.2 Impedance Bandwidth 27
3.8.3 Radiation Pattern 28
3.8.4 Axial Ratio (AR) Bandwidth 30
3.8.5 Gain 31
3.9 Conclusion 32
4 MEASUREMENTS RESULT AND ANALYSIS 33
ix
4.1 Introduction 33
4.2 Parametric Studies 33
4.2.1 The Effect of Different Sizes of Ground Plane on
Return Loss 35
4.2.2 The Effect of Different Patch Length on Return Loss 36
4.2.3 The Effect of Different Truncated Sizes on Return
Loss 37
4.2.4 The Effect of Different Feed Location on Return
Loss 38
4.2.5 The Effect of Different Airgap Thickness on
Return Loss 39
4.2.6 The Effect of Different Dielectric Constant on
Return Loss 40
4.2.7 Summary of Parametric Study 41
4.3 The effect of Plastic enclosure 42
4.3.1 Return Loss 42
4.3.2 Radiation Pattern 43
4.4 System level measurement 44
4.4.1 Experiment Purpose 44
4.4.2 Experiment Setup and Procedures 44
4.4.3 Experiment Result 46
4.5 Consistence Measurement 48
4.5.1 Return Loss (S11) 48
4.5.2 Radiation Pattern 49
4.6 Second prototype 50
4.6.1 Return Loss (S11) 51
4.6.2 Radiation Pattern 52
4.6.3 Axial Ratio 53
4.6.4 System Level Measurement 54
4.7 Comparison for two Prototypes 55
4.7.1 Return Loss (S11) 55
4.7.2 Radiation Pattern 56
4.7.3 Axial Ratio Bandwidth 57
x
4.7.4 Gain 58
4.7.5 Prototype Costing 59
4.8 Conclusion 59
4.8.1 Lesson learned 59
4.8.2 Project Constraints 61
5 CONCLUSION AND FUTURE WORKS 62
5.1 Final product specifications 62
5.2 Future work 63
5.2.1 Miniaturization of the Patch Dimension 63
5.2.2 Parasitic Element As Way To Improve Gain 63
5.2.3 CP Patch Antenna Array 63
REFERENCES 64
Appendices A-B 66 - 71
xi
LIST OF TABLES
TABLE NO. TITLE PAGE
3.1 Design Specifications 20
3.2 Theoretical Calculations 22
3.3 Return Loss Comparison 27
3.4 Radiation Pattern Comparison 29
3.5 Axial Ratio Comparison 31
3.6 Transfer Gain Measurement 32
4.1 Summary of Parametric Studies 41
4.2 Effect of Plastic Enclosure on Return Loss 42
4.3 Effect of Plastic Enclosure on Radiation Pattern 43
4.4 Winbox Experiment Results for 1st Prototype 47
4.5 Return Loss Comparison of Two Identical Antennas 49
4.6 Radiation Pattern Comparison of Two Identical Antennas 50
4.7 Second Prototype Return Loss 51
4.8 Second Prototype Radiation Pattern 52
4.9 Second Prototype Axial Ratio 53
4.10 Experiment Result for 2nd Prototype 54
4.11 Return Loss Comparison 56
4.12 E-Co Radiation Pattern Beamwidth 57
4.13 Axial Ratio Comparison 57
4.14 Gain Comparison 58
4.15 Prototypes Costing 59
5.1 Final Prototype Specifications 62
xii
LIST OF FIGURES
FIGURE NO. TITLE PAGE
2.1 Basic Structure of a Microstrip Patch Antenna 5
2.2 Shapes of radiators 5
2.3 Types of feeding structure used in microstrip patch antennas 6
2.4 Microstrip antenna 8
2.5 Microstrip line and its electric field lines, and effective
dielectric constant geometry 9
2.6 Physical and effective length of rectangular microstrip patch 9
2.7 Suggested arrangements for CP operation 12
2.8 Polarization unit vectors of incident wave and antenna 13
2.9 (a) Geometry of the proposed broadband circularly polarized
patch antenna having an elevated ground plane portion;
(b) cross-sectional view in the x-z plane. 15
2.10 Geometry of the proposed broadband circularly polarized patch
antenna. 16
2.11 Geometry of the proposed broadband probe-feed patch antenna 17
3.1 Design Methodology Flowchart 19
3.2 Mathcad calculation 21
3.3 Designed EM structure 23
3.4 Design results 25
3.5 PCB Fabrication Flowchart 25
3.6 Return Loss Measurement Experiment Setup 26
3.7 Return Loss Comparison 27
3.8 Anechoic Chamber 28
3.9 Radiation Pattern Comparison 29
xiii
3.10 Axial Ratio Comparison 30
3.11 Transfer Gain Measurement 31
4.1 Areas of Parametric Studies 34
4.2 Simulation and Measurement Settings for Different Ground
Plane Sizes 35
4.3 Effect of Differing Ground Plane Size 35
4.4 Simulation and Measurement Settings for Different Ground
Plane Sizes 36
4.5 Effect of Differing Patch Length Size 37
4.6 Simulation and Measurement Settings for Different Truncated
Sizes 37
4.7 Effect of Differing Truncated Size 37
4.8 Simulation and Measurement Settings for Different Feed
Location 38
4.9 Effect of Differing Feed Location 38
4.10 Simulation and Measurement Settings for Different Airgap
Thicknesses 39
4.11 Effect of Differing Airgap Thickness 39
4.12 Simulation and Measurement Settings for Different Dielectric
Constants 40
4.13 Effect of Differing Dielectric Constant 40
4.14 Effect of Plastic Enclosure on S11 42
4.15 Effect of Plastic Enclosure on Radiation Pattern 43
4.16 System Performance Experiment Setup 44
4.17 Client Antenna Orientations 45
4.18 Sample Bridge Performance Reading from Winbox 46
4.19 Return Loss Comparison of Two Identical Antennas 48
4.20 Radiation Pattern Comparison of Two Identical Antennas 49
4.21 Second Prototype 50
4.22 Second Prototype Return Loss 51
4.23 Second Prototype Radiation Pattern 52
4.24 Second Prototype Axial Ratio 53
4.25 Return Loss Comparison 55
xiv
4.26 E-Co Radiation Pattern Comparison 56
4.27 Axial Ratio Comparison 57
4.28 Gain Comparison 60
4.29 Modified Design Methodology 60
5.1 Prototype with Inside Enclosure 62
xv
LIST OF APPENDICES
APPENDIX TITLE PAGE
A Parametric Study 68
B Radiation Pattern 71
64
REFERENCES
[1] Rackley,S., “Wireless Networking Technology:From Principles to Successful
Implementation” Elsevier, pg 1, Oxford, 2007.
[2] T.S. Rappaport & D.A. Hawbaker, “Effects of circular and linear polarized
antennas on wideband propagation parameters in indoor radio channels”
IEEE journal pp. 1287 - 1291 vol.2 GLOCOM 2-5 Dec 1991.
[3] Balanis, C.A., “ANTENNA THEORY ANALYSIS AND DESIGN,” John
Wiley, 3rd Ed. pp 75, 811-872, New Jersey, 2005.
[4] Chen, Z. N. & Chia M. Y. W., “Broadband Planar Antennas: Design and
Applications”, John Wiley, West Sussex, 2006
[5] Yu-Bo Tzeng, Che-Wei Su, and Ching-Her Lee, “STUDY OF
BROADBAND CP PATCH ANTENNA WITH ITS GROUND PLANE
HAVING AN ELEVATED PORTION,” APMC 2005 Proc., Vol. 4, Dec.
2005
[6] F.S. Chang, K.L. Wong, and T.W. Chiou, “Low-Cost Broadband Circularly
Polarized Patch Antenna,” in IEEE Trans. Antennas and Propagat.,Vol. 51,
pp. 3007-3009,Oct 2003.
[7] P.L. Teng, C. L. Tang, & K.L. Wong, “A Broadband Planar Patch Antenna
Feb by A Short Probe Feed,” APMC 2001,vol. 3,pp. 1243-1246, 2001.
65
[8] Barclay, L.W., “Propagation of Radiowaves”, IEE, 2nd Ed., pp 38-44, London,
2003.
[9] Garg, R., “Microstrip Antenna Design Handbook”, Artech House, pg 357,
London,2001.
[10] Sung, M.K., Ji, M.S., Hyuck, J.K., Woon, G.Y., “Design and Implementation
of Dual-Band Square Patch Antenna for Wireless LAN of 2.4GHz and
5.7GHz” APMC 2005 Proc., vol. 5, 2005.
[11] Z.N. Chen, “Impedance characteristics of a probe-fed L-shaped plate
antenna,” Radio Science, vol. 36, no.6, pp. 1377-1384, 2001.
[12] Pozar, D.M., “Microwave Engineering,” John Wiley & Sons, 2nd Ed., Canada,
July 1997.
[13] Wong, M.L, Wong, H., Luk, K.-M, “Small circularly polarized patch
antenna,” IEE, vol. 41, no. 16, pp. 7-8, April 2005.
[14] Row, J.S., “Design of square-ring microstrip antenna for circular
polarization,” IEE, vol.40, no.2, pp. 93-95, Jan 2004
[15] Tanaka,T., Takahashi, M., Ito, K., “Study on the Radiation Characteristics of
a Miniaturized Circularly Polarized Circular Sector Patch Antenna” IEEE, pp
1561-1564, 2006.
71
2. 2nd Prototype
angle e-co e-cross
0 -52.82 -53.94
4 -52.82 -54.06
8 -53.26 -53.92
12 -53.32 -54.14
16 -53.52 -53.94
20 -53.97 -54.58
24 -54.53 -54.67
28 -55.003 -55.52
32 -55.44 -55.97
36 -55.92 -56.92
40 -56.94 -57.62
44 -57.97 -57.89
48 -59.09 -58.76
52 -59.84 -59.66
56 -60.34 -60.15
60 -60.17 -60.57
64 -60.88 -61.94
68 -62.13 -62.5
72 -62.39 -63.82
76 -64.12 -64.87
80 -64.84 -64.87
84 -66.44 -65.61
88 -67.89 -66.7
92 -67.16 -66.49
96 -67.43 -67.3
100 -66.83 -67.68
104 -66.76 -67.44
108 -66.89 -66.66
112 -67.18 -67.85
116 -66.88 -67.21
120 -67.16 -67.64
124 -67.9 -68.39
128 -67.75 -68.15
132 -66.92 -67.61
136 -65.88 -68.56
140 -65.48 -66.64
144 -64.19 -66.29
148 -64.3 -66.57
152 -65.07 -66.44
156 -65.63 -65.45
160 -65.86 -66.41
164 -66.79 -66.59
168 -66.94 -66.79
172 -66.55 -67.8
176 -67.15 -67.05
180 -67.13 -67.19
184 -67.21 -67.54
188 -66.61 -66.95
192 -65.71 -68.52
196 -65.99 -67.18
200 -64.85 -68.2
204 -66.33 -67.81
208 -66.22 -67.76
212 -66.79 -67.32
216 -66.8 -66.69
220 -66.99 -66.24
224 -68.14 -67.73
228 -67.84 -68.4
232 -67.46 -68.15
236 -65.72 -67.09
240 -65.5 -67.09
244 -64.66 -65.78
248 -64.78 -65.66
252 -64.1 -64.32
256 -64.09 -64.33
260 -64.38 -63.65
264 -64.18 -63.8
268 -64.88 -63.82
272 -64.69 -62.93
276 -63.75 -63.07
280 -63.51 -62.53
284 -63.41 -61.98
288 -62.04 -61.26
292 -61.71 -60.3
296 -60.51 -59.66
300 -60.17 -58.99
304 -59.46 -58.85
308 -58.86 -58.85
312 -58.2 -58.56
316 -57.23 -57.43
320 -56.5 -56.54
324 -55.92 -56.05
328 -55.25 -55.76
332 -54.83 -55.09
336 -54.31 -55.06
340 -53.9 -54.07
344 -53.69 -54.39
348 -53.4 -54.16
352 -53.15 -54.14
356 -53.08 -53.97
360 -52.88 -53.73
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