v MINIATURIZED WIDEBAND HYBRID DIRECTIONAL COUPLER USING SLOW WAVE STRUCTURE SND MEANDERING LINES TECHNIQUE CHONG JAW CHUNG 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 AUGUST 2016
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MINIATURIZED WIDEBAND HYBRID DIRECTIONAL COUPLER USING
In the process of completing this research project, i would like to express my
warmest appreciation to my supervisor, Dr. You Kok Yeow, a professional member
of IEEE, for his professional advice and consultation in dealing with such
challenging research.
Also, I would like to thank Mr. Hou Kit, Yi Lung and Jia Yong who are PhD
students under supervising of Dr.You. they the person who give me special guidance
in numerical programming and circuit simulation using EM software. They provides
a lot of constructive personal tutoring in the technical aspect, especially in the
process of PCB fabrication and Data measurement.
Furthermore, I would like to thank Prof Dr. Ruzairi, who is the Head of
Department in RMC (Research Management Centre), for his kindness of approving
the great amount of research grant allocated by MOHE (Ministry of Higher
Education), Malaysia. The research grant is essential in purchasing of material or
apparatus for dealing with such challenging research.
Next, the librarians at Sultanah Zanariah Library (PSZ) also play a significant
role in helping me in completing this research project. They do provided some useful
advice in what kind of books should I borrow for references especially in engineering
field. The PSZ is also an informative place in looking for high impact factor journals,
which is essential in making reference for latest ideas in electrical engineering field.
Finally, I would like to express my greatest appreciation to all my friends and
colleagues who give me a lot of help in completing my thesis. Then, I would like to
say thank you to my family for their support and patient throughout the whole
research period which took about three years.
Thank you very much. I really appreciate it.
.
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ABSTRACT
Branch-line coupler is an important element in modern microwave circuit. Amore compact and wideband prototype is preferred, since; it lowers the productioncost and could operate well in wider bandwidth. However, most conventional branchline couplers consume bigger spacing and operate in narrow bandwidth. In thisresearch, a wideband three-branch line coupler and four-branch line coupler, whichare 20.6 % and 50.2 % respectively, compact than conventional couplers, had beenminiaturized using Slow Wave Structure (SWS) and Meandering Line (ML)techniques. The cascade method is implemented on conventional coupler forincreasing its bandwidth. The fabricated area of modified three-branch line and four-branch line coupler is (1729.9 mm2) and (1927.8 mm2), respectively. Both prototypeswere fabricated using etching technique. The performance results were obtainedusing Keysight E5071C VNA (Vector Network Analyzer). Calibration had beendone to VNA for all types of measurement. Its important parameters such as returnloss |S11|, through |S21|, coupling |S31| and isolation |S41| are studied for bothconventional and modified designs, within the frequency range of 1.0 GHz to 5.0GHz. The AWR Microwave Office Software is used for simulation, and designingthe prototypes using 2.4 GHz as centre frequency, where the operating bandwidthremains at 1.5 GHz to 3.5 GHz. The performance of both prototypes were validatedby comparing the simulation and measurement results, where, they show goodagreement in S-parameters performance similar to the conventional ones, or evenbetter. The modified three-branch line coupler experienced |S11| below -13 dB withoperating frequency band of 1.5 GHz, which is 0.1 GHz wider than conventionaldesign performance with 1.4 GHz frequency band, whereas, the modified four-branch line coupler experienced |S11| below -13 dB with operating frequency band of2.0 GHz, which is 0.6 GHz wider than conventional design performance with 1.4GHz frequency band. In conclusion, the modified prototypes are more compact,making it make portable and operates well within wider operating bandwidth.
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ABSTRAK
Cawangan talian pengganding adalah elemen penting dalam litar gelombangmikro moden. Satu prototaip lebih padat dan jalur lebar telah direkacipta kerana iamerendahkan kos pengeluaran dan boleh beroperasi dengan baik dalam jalur lebaryang lebih besar. Walau bagaimanapun, kebanyakan cawangan talian penggandingkonvensional mengambil jarak yang lebih besar dan beroperasi dalam jalur lebarsempit. Dalam kajian ini, tiga cawangan garis talian pengganding dan empatcawangan garis talian pengganding, yang 20.6% dan 50.2% masing-masing, padatdaripada pengganding konvensional, telah bersaiz kecil menggunakan StrukturGelombang Perlahan (SWS) dan teknik garis berliku-liku (ML). Kaedah latadilaksanakan pada pengganding konvensional untuk meningkatkan jalur lebar.Kawasan prototypaip yang diubahsuai garis tiga cawangan dan empat cawangangaris pengganding adalah (1729,9 mm2) dan (1927,8 mm2), masing-masing. Kedua-dua prototaip direka menggunakan teknik punaran. Keputusan pengukuran telahdiperolehi dengan menggunakan Keysight E5071C VNA (Vektor PenganalisisRangkaian). Penentukuran telah dilakukan untuk VNA untuk semua jenispengukuran. Parameter yang penting seperti kehilangan pulangan |S11| melalui |S21|,gandingan |S31| dan pengasingan |S41| dikaji untuk kedua-dua reka bentukkonvensional dan diubah suai, dalam julat frekuensi 1.0 GHz kepada 5.0 GHz.Perisian AWR Microwave Office digunakan untuk simulasi, dan mereka bentukprototaip menggunakan 2.4 GHz sebagai frekuensi pusat, di mana jalur lebar operasikekal pada 1.5 GHz kepada 3.5 GHz. Prestasi kedua-dua prototaip telah disahkandengan membandingkan keputusan simulasi dan keputusan pengukuran, di mana,kedua-dua keputusan menunjukkan perjanjian yang baik dalam keputusan S-parameter yang sama dengan prototaip konvensional, atau lebih baik. Protototaipyang diubah suai dengan tiga cawangan mengalami |S11| di bawah -13 dB denganoperasi jalur frekuensi 1.5 GHz, iaitu 0.1 GHz lebih luas daripada prestasi rekabentuk konvensional dengan 1.4 GHz jalur frekuensi, manakala, prototaip yangdiubah suai empat cawangan garis pengganding mengalami |S11| di bawah -13 dBdengan operasi jalur frekuensi 2.0 GHz, iaitu 0.6 GHz lebih luas daripada prestasireka bentuk konvensional dengan 1.4 GHz jalur frekuensi. Kesimpulannya, prototaipyang diubahsuai adalah lebih padat, menjadikannya membuat mudah alih danberoperasi dengan baik dalam lebar jalur operasi lebih luas.
TABLE OF CONTENTS
CHAPTER TITLE PAGE
DECLARATION
DEDICATION ii
ACKNOWLEDGEMENTS iii
ABSTRACT iv
ABSTRAK v
TABLE OF CONTENTS vi
LIST OF TABLES x
LIST OF FIGURES xi
LIST OF ABBREVIATIONS xv
LIST OF SYMBOLS xvi
1 INTRODUCTION
1.1 Introduction 1
1.2 Background of the Problems 2
1.3 Problem Statement 4
1.4 Objectives of the Study 4
1.5 Scope of the project 5
1.6 Report Organization 6
2 LITERATURE REVIEW
2.1 Introduction 7
2.2 Directional Coupler Theory 8
2.3 Conventional Quadrature Hybrids 10
2.4 Miniature Techniques for Microstrip Transmission Line 15
2.4.1 Slow Wave Structure (SWS) Techniques 15
2.4.2 Meandering Technique for Coupler Miniaturization 17
2.4.3 Review of Miniature Branch-Line Coupler 17
2.5 Lumped-Element Circuit Representation for Coupler 45
2.6 Summary 47
3 RESEARCH METHODOLOGY 49
3.1 Introduction 49
3.2 Methodology 49
3.2.1 Prototype Design and Simulation (Stage 1) 51
3.2.2 Prototype Fabrication (Stage2) 52
3.2.3 Prototype Measurement (Stage 3) 53
3.3 Prototype Design Specifications and Dimensions 55
3.4 Branch Line Design Theory 55
3.5 Three Branch-Line Coupler Design 56
3.5.1 Conventional Coupler 56
3.5.2 Modified Three-branch Coupler 57
3.6 Four Branch-Line Coupler 58
3.6.1 Conventional Wideband Coupler 58
3.6.2 Modified Wide-Band Coupler (Type-1) 59
3.6.3 Modified Wide-Band Coupler (Type-2) 60
3.6.4 Design Dimension of Modified Branch-Line Coupler 61
3.7 Comparison of Modified and Conventional Prototype Design 64
3.8 Summary 65
4 RESULT AND DISCUSSION 66
4.1 Introduction 67
4.2 Comparison of Measurement and Simulation 68
4.2.1 Conventional Three-branch Coupler 68
4.2.2 Modified Three-Branch Line Coupler 69
4.2.3 Conventional Four-branch Line Coupler 70
4.2.4 Modified Four-branch Line Coupler type-1 72
4.2.5 Modified Four-branch Coupler Type-2 734.3 Performance Comparison of Conventional and 74
4.4 Comparison of Phase Different and 75 ^-parameters Bandwidth4.4.1 Conventional Three-branch Coupler 75
Phase Different
4.4.2 Modified Three-branch Coupler 76
Phase Different
4.4.3 Conventional Four-branch Coupler 77
Phase Different
4.4.4 Modified Four-branch Coupler 78
Type-1 Phase Different
4.4.5 Modified Four-branch Coupler Type-2 79
Phase Different
4.5 Analysis of Bandwidth Performance 804.5.1 Conventional Three-branch Coupler 80
4.5.2 Conventional Four-branch Line Coupler 81
4.5.3 Modified Three-branch Coupler 83
4.5.4 Modified Four Branch Line Coupler Type-1 85
4.5.5 Modified Four Branch Line Coupler Type-2 86
4.5.6 Additional Layer and Bandwidth Performance 88
4.6 Summary 89
5 CONCLUSIONS AND RECOMMENDATION 90
5.1 Conclusions 90
5.2 Recommendations for Future Work 92
REFERENCES 93
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LIST OF TABLES
TABLE NO. TITLE PAGE
2.1 Miniaturised Branch line Coupler using 19slow wave structure.
2.2 Miniaturized branch line coupler using 37meandering line structures.
3.1 Dimension for modified three-branch directional 49coupler layout.
3.2 Dimension for modified three-branch directional 61coupler layout.
3.3 Dimension for modified four-branch directional 62coupler layout
3.4 Dimension for designed directional coupler 64
4.1 Performance comparison of three branch-line 83coupler.
4.2 Performance comparison of four branch-line 87couplers.
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LIST OF FIGURES
FIGURE NO. TITLE PAGE
1.1 The waveguide hybrid junction 1
1.2 Diagram of two-element Directional Coupler 2(a) Diagrammatic configuration (b) 3D configuration
1.3 Interdigitated 3-dB Coupler 2
2.1 Block diagram of a four-port network 8
2.2 A basic coupled transmission line 9
2.3 Quarter-wave branch line hybrid circuit 11
2.4 (a) Insertion loss at two output ports (Port-2 and Port-3) 11(b) Phase balance between two output ports(c) Return loss at input port (Port-1) and isolation port (Port-4)
2.5 Prototype proposed by Muraguchi 12fabricated on fine grained alumina
2.6 Multi-section branch line hybrid 13
2.7 Comparison of the regular structure length with 15slow wave structure (SWS) for the same electrical length