STUDY OF CIRCULARLY POLARIZED PATCH ANTENNA FOR WIRELESS LOCAL AREA NETWORK ACCESS POINT APPLICATION

Transcription

1 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

2 UNIVERSITI TEKNOLOGI MALAYSIA PSZ 19:16 (Pind. 1/07) DECLARATION OF THESIS / UNDERGRADUATE PROJECT PAPER AND COPYRIGHT Author s full name : Yii Ming Leong Date of birth : 6 th 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 RESTRICTED OPEN ACCESS (Contains confidential information under the Official Secret Act 1972)* (Contains restricted information as specified by the organization where research was done)* 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 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

3 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 :

4 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

5 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 :

6 iii My Beloved Family and Jacinta Yeo

7 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..

8 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.

9 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.

10 vii TABLE OF CONTENTS CHAPTER TITLE PAGE DECLARATION DEDICATION ACKNOWLEDGEMENTS ABSTRACT ABSTRAK TABLE OF CONTENTS LIST OF TABLES LIST OF FIGURES LIST OF APPENDICES ii iii iv v vi vii xi xii xv 1 INTRODUCTION Overview Objective Scope of Study Problem statement 2 2 LITERATURE REVIEW Important Features of Microstrip Patch Antennas Patch Shapes Substrates Feeding Structures Transmission-line model Circular polarization 11

11 viii 2.4 Polarization measurements Polarization Loss Factor Recent works of Circularly Polarized Antennas Effects Of Circular And Linear Polarized Antennas On Wideband Propagation Parameters In Indoor Radio Channel Study Of Broadband Cp Patch Antenna With Its Ground Plane Having An Elevated Portion Low-Cost Broadband Circularly Polarized Patch Antenna A Broadband Planar Patch Antenna Feb By A Short Probe Feed DESIGN OF A CICURLARY POLARIZED ANTENNA Introduction Design methodology Selection of antenna structure Design specifications Theoretical Calculations Modeling and simulation Design Entry Optimizations Fabrication Process Flowchart Comparison of result Return Loss (S11) Impedance Bandwidth Radiation Pattern Axial Ratio (AR) Bandwidth Gain Conclusion 32 4 MEASUREMENTS RESULT AND ANALYSIS 33

12 ix 4.1 Introduction Parametric Studies The Effect of Different Sizes of Ground Plane on Return Loss The Effect of Different Patch Length on Return Loss The Effect of Different Truncated Sizes on Return Loss The Effect of Different Feed Location on Return Loss The Effect of Different Airgap Thickness on Return Loss The Effect of Different Dielectric Constant on Return Loss Summary of Parametric Study The effect of Plastic enclosure Return Loss Radiation Pattern System level measurement Experiment Purpose Experiment Setup and Procedures Experiment Result Consistence Measurement Return Loss (S11) Radiation Pattern Second prototype Return Loss (S11) Radiation Pattern Axial Ratio System Level Measurement Comparison for two Prototypes Return Loss (S11) Radiation Pattern Axial Ratio Bandwidth 57

13 x Gain Prototype Costing Conclusion Lesson learned Project Constraints 61 5 CONCLUSION AND FUTURE WORKS Final product specifications Future work Miniaturization of the Patch Dimension Parasitic Element As Way To Improve Gain CP Patch Antenna Array 63 REFERENCES 64 Appendices A-B 66-71

14 xi LIST OF TABLES TABLE NO. TITLE PAGE 3.1 Design Specifications Theoretical Calculations Return Loss Comparison Radiation Pattern Comparison Axial Ratio Comparison Transfer Gain Measurement Summary of Parametric Studies Effect of Plastic Enclosure on Return Loss Effect of Plastic Enclosure on Radiation Pattern Winbox Experiment Results for 1 st Prototype Return Loss Comparison of Two Identical Antennas Radiation Pattern Comparison of Two Identical Antennas Second Prototype Return Loss Second Prototype Radiation Pattern Second Prototype Axial Ratio Experiment Result for 2 nd Prototype Return Loss Comparison E-Co Radiation Pattern Beamwidth Axial Ratio Comparison Gain Comparison Prototypes Costing Final Prototype Specifications 62

15 xii LIST OF FIGURES FIGURE NO. TITLE PAGE 2.1 Basic Structure of a Microstrip Patch Antenna Shapes of radiators Types of feeding structure used in microstrip patch antennas Microstrip antenna Microstrip line and its electric field lines, and effective dielectric constant geometry Physical and effective length of rectangular microstrip patch Suggested arrangements for CP operation Polarization unit vectors of incident wave and antenna (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 Geometry of the proposed broadband circularly polarized patch antenna Geometry of the proposed broadband probe-feed patch antenna Design Methodology Flowchart Mathcad calculation Designed EM structure Design results PCB Fabrication Flowchart Return Loss Measurement Experiment Setup Return Loss Comparison Anechoic Chamber Radiation Pattern Comparison 29

16 xiii 3.10 Axial Ratio Comparison Transfer Gain Measurement Areas of Parametric Studies Simulation and Measurement Settings for Different Ground Plane Sizes Effect of Differing Ground Plane Size Simulation and Measurement Settings for Different Ground Plane Sizes Effect of Differing Patch Length Size Simulation and Measurement Settings for Different Truncated Sizes Effect of Differing Truncated Size Simulation and Measurement Settings for Different Feed Location Effect of Differing Feed Location Simulation and Measurement Settings for Different Airgap Thicknesses Effect of Differing Airgap Thickness Simulation and Measurement Settings for Different Dielectric Constants Effect of Differing Dielectric Constant Effect of Plastic Enclosure on S Effect of Plastic Enclosure on Radiation Pattern System Performance Experiment Setup Client Antenna Orientations Sample Bridge Performance Reading from Winbox Return Loss Comparison of Two Identical Antennas Radiation Pattern Comparison of Two Identical Antennas Second Prototype Second Prototype Return Loss Second Prototype Radiation Pattern Second Prototype Axial Ratio Return Loss Comparison 55

17 xiv 4.26 E-Co Radiation Pattern Comparison Axial Ratio Comparison Gain Comparison Modified Design Methodology Prototype with Inside Enclosure 62

18 xv LIST OF APPENDICES APPENDIX TITLE PAGE A Parametric Study 68 B Radiation Pattern 71

19 64 REFERENCES [1] Rackley,S., Wireless Networking Technology:From Principles to Successful Implementation Elsevier, pg 1, Oxford, [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 vol.2 GLOCOM 2-5 Dec [3] Balanis, C.A., ANTENNA THEORY ANALYSIS AND DESIGN, John Wiley, 3 rd Ed. pp 75, , New Jersey, [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 [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 ,Oct [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 , 2001.

20 65 [8] Barclay, L.W., Propagation of Radiowaves, IEE, 2 nd Ed., pp 38-44, London, [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, [11] Z.N. Chen, Impedance characteristics of a probe-fed L-shaped plate antenna, Radio Science, vol. 36, no.6, pp , [12] Pozar, D.M., Microwave Engineering, John Wiley & Sons, 2 nd Ed., Canada, July [13] Wong, M.L, Wong, H., Luk, K.-M, Small circularly polarized patch antenna, IEE, vol. 41, no. 16, pp. 7-8, April [14] Row, J.S., Design of square-ring microstrip antenna for circular polarization, IEE, vol.40, no.2, pp , 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 , 2006.

21 71 angle e-co e-cross nd Prototype