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

v

Specially dedicated to

my friends, and family.

v

ACKNOWLEDGEMENT

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.

.

v

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.

v

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

Modified Prototype4.3.1 Three-branch Coupler Comparison 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

ix

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.

x

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

2.8 Slow wave structure (SWS) design (Sung et al., 2005) 16

2.9 (a) Compact branch line coupler using slow wave structure 18

(b) Conventional branch line coupler. (Sun et al., 2009)

2.10 SWS coupler and its performance 19

xi

2.11 Meandering line coupler and its performance 37

2.12 Lumped element version of branch line hybrid 45

2.13 First-order lumped element hybrid 46

2.14 Mixed element hybrid 46

3.1 Research methodology flow chart and main stages 49

3.2 The procedure of prototype design and simulation 50

3.3 The procedure of prototype fabrication 51

3.4 Keysight E5071C VNA for prototype measurement 52

3.5 The procedure of prototype measurement 53

3.6 The design parameters: Za = 37.4 Ω, Zb = 96.9 Ω, 55

Zc = 63.7 Ω, and θ = 90º

3.7 Design parameter of a modified three branch coupler 56where Za = 50Ω, θ= 90º

3.8 Wideband design parameters: Za= 54 Ω, Zb= 58.3 Ω, 57Zc= 143 Ω, θ = 90º

3.9 Design parameter of a modified three branch coupler type-1: 58Zc = 143 Ω, Za = 50Ω, θ = 90º

3.10 Design parameter of a modified three branch coupler type-2: 59Zc = 143 Ω, Za = 50Ω,θ = 90º

3.11 Design dimension for (a) Modified three-branch coupler. 60(b) Modified four-branch coupler

3.12 Conventional three branch coupler design 63

3.13 Conventional design and modified design for 63three branch coupler

3.14 Conventional four-branch coupler design 63

xii

3.15 Conventional design and modified design for 64four branch coupler

3.16 Modified four branch coupler and modified 64three branch coupler

4.1 S-parameter performance for conventional 68three-branch coupler

4.2 S-parameter performance for modified 69three-branch coupler

4.3 S-parameter performance for conventional 70four-branch coupler

4.4 S-parameter performance for modified 71four-branch coupler type-1

4.5 S-parameter performance for modified 72four-branch coupler type-2

4.6 Comparison for conventional and modified 73three-branch coupler

4.7 Phase different performance of conventional 74three-branch coupler

4.8 Phase different performance of modified 75three-branch coupler

4.9 Phase different performance of conventional 76four-branch coupler

4.10 Phase different performance of modified 77four-branch coupler type-1

4.11 Phase different performance of modified 78four-branch coupler type-2

4.12 Bandwidth performance of conventional 80three-branch coupler

xiii

4.13 Bandwidth performance of conventional 81four branch coupler

4.14 Bandwidth performance of modified 83three-branch coupler

4.15 Bandwidth performance of modified 85four-branch coupler type-1

4.16 Bandwidth performance of modified 86four-branch coupler type-2

4.17 Bandwidth performance comparison 88for additional substrate

xv

LIST OF ABBREVIATIONS

ATL – Artificial Transmission Line

AWR – Apply Wave Research

BCB – Benzo Cyclobutene

CCS CL – Complementary-Conducting Strip Coupling Line

ECPW – Elevated Coplanar Waveguides

LTCC – Low Temperature Co-fired Ceramics

ML – Meandering Lines

MMIC – Monolithic Microwave Integrated Circuit

MPC – Microstrip Printed Circuit

PCB – Printed Circuit Board

SWS – Slow Wave Structure

TFMS – Thin Film Microstrip Lines

TLs – Transmission Lines

UHF – Ultra High Frequency

VNA – Vector Network Analyzer

VHF – Very High Frequency

xvi

LIST OF SYMBOLS

D – Dimensions

|S11| – Return loss

|S21| – Insertion loss

|S31| – Coupling

|S41| – Isolation

|S21| – Insertion loss

S – Scattering parameters2 – Through factor

2 – Coupling factor

P1 – Input power

P2 – Through power

P3 – Coupled power

P4 – Isolated power

C – Coupling factor

dB – Decibel

– Phase different

n – Number of coupler’s main lines

ν – Phase velocity

L – Inductance per length

C – Capacitance per length

λ – Electrical wave length

Zo – Characteristic impedances

μ – Mikro

xvii

– Normalized frequency

Cs – Shunt Capacitor values

Cp – Coupling Capacitor values

εr – Dielectric constant

tan δ – Loss tangent

h – Substrate thickness

W – Strip width

θ – Phase in degree

fc – Center frequency

∆f – Operating bandwidth

xviii

CHAPTER 1

INTRODUCTION

1.1 Introduction

A hybrid junction is a four port network in which a signal on any one of the ports

divides between two out ports with the remaining port being isolated (Rizzi, 1988).

The first hybrid junction, known as Magic Tee Junction was developed by (Tyrell,

1947) as shown in Figure 1.1. The hybrid junction was modified by Mumford (1947),

and transformed it into slot directional coupler as shown in Figure 1.2. Finally, it was

improved again and turned into microstrip directional coupler by Lange (1969), as

shown in Figure 1.3.

Figure 1.1: The waveguide hybrid junction

2

(a) (b)

Figure 1.2: Diagram of two-element Directional Coupler

(a) Diagrammatic configuration (b) 3D configuration (Mumford et al., 1947)

Figure 1.3 Interdigitated 3-dB Coupler (Lange et al., 1969)

1.2 Background of the Problems

In the modern era, the slow wave structure (SWS) was applied by Sun et al.

(2005) to miniaturize conventional coupler. The performance of its S-parameters

remains almost the same value as conventional design. However, this approach does

not improve its bandwidth, where the operating bandwidth is remaining narrow.

3

Most research emphasis size miniaturization only in two branch coupler.

Sakagawi et al. (1997) proposed two branch line coupler miniaturization using eight

stubs. Eccleston et al. (2003) employing artificial transmission line (ATL) to

miniaturize the two-branch coupler. Here, miniaturization is conducted to three

branch line coupler and four-branch line coupler using slow wave structure (SWS)

and meandering lines technique (ML).

Some researcher did emphasize the miniaturization of three branch line coupler.

Chun et al. (2005) proposed three branch line coupler using lumped distributed

elements. But, its bandwidth is only 1.1 GHz using -13 dB as standard level. In 2012,

Nejad proposed a compact three branch line coupler which is 47 percent smaller than

conventional one. Even though the size is 47 percent compact, its bandwidth

performance is only 1 GHz at – 13 dB, which is consider as narrower band. Chun et

al. (2006) proposed a compact four branch line coupler modified by using lumped

distributed element. However, its bandwidth is only 1.4 GHz.

In this research, the main interest is to design and produce a prototype, which is

able to operate in wider operating frequency range (1 GHz - 5 GHz). The purpose is

to reduce the power loss, less than – 13 dB or lower during the prototype’s operation

within a wider operating frequency. Also, a more compact prototype is produced for

making it more portable in modern consumer market, by using the slow wave

structure (SWS) and meandering lines (ML). Its S-parameters performance such as

return loss |S11|, through |S21|, coupling |S31| and isolation |S41|, measured in dB

(Decibel), remains the same, or, even better than conventional design performance.

4

1.3 Problem Statement

Conventional branch line coupler has narrow band characteristics and requires

larger circuit area in its fabrication process, especially for the coupler which is

operating at lower frequency (< 2 GHz). The cascaded method is able to increase the

operating bandwidth. However, such method might increase the size of the coupler. It

is an undesired scenario in MMIC (Monolithic Microwave Integrated circuit)

production, which is requiring a more compact spacing in circuit fabrication.

Also, modern consumers are expecting electrical apparatus that is more

portable. Bigger prototype area can also increase its fabrication cost. Hence, the slow

wave structures (SWS) and meandering lines (ML) technique are implemented in

prototype design in order to solve the above problems. Slow wave structure (SWS)

would be able to shortening the coupler branch lines, whereas, and the folding

approach of meandering lines could reducing the area occupying by a narrow

microstrip lines.

1.4 Objectives of the study

The main objectives of the research are

(1) To develop compact directional couplers, which are modified from three branch

line coupler (180 º) and four branch line coupler (270 º).

(2) To design and fabricate a prototype, which is able to operate in wider operating

frequency range (1.5 GHz – 3.5 GHz) and lower frequency (1 GHz - 5 GHz).

(3) To miniaturize conventional coupler using slow wave structure (SWS) and

meandering techniques (ML) at its branch lines area.

(4) To study the S-parameters measured in dB (Decibel) of the prototype for ensuring

that the performances of prototypes are validate for wideband operation.

5

1.5 Scope of the project

In this study, the wideband compact branch line couplers were developed.

Three branches and four branches were applied on the quadrature branch line coupler

in order to achieve the wider operating bandwidth. A slow wave structure (SWS) and

meandering lines (ML) techniques are applied on the branch line parts of the

designed couplers in order to miniature the size of the couplers. Both techniques did

reduce the area occupied by the fabricated prototype.

The modified prototypes are designed using 2.4 GHz as the center frequency.

TX Line program calculator was used to roughly determine the dimensions of the

microstrip line of the coupler. A Microwave Office (AWR) simulator was used to

re-exam the performance of the couplers with first draft dimensions. From the

simulation results, a minor corrections of the dimensions for the couplers have been

made to achieve the desired performances with 1.4 GHz bandwidth (Operating

frequency: (1.6 GHz to 3 GHz), return loss, |S11| better than –13 dB and its size turns

50 % smaller than conventional branch line couplers. The performance is considered

acceptable within the wide operating frequency range (1.5GHz – 3.5 GHz).

The prototypes were fabricated and measured using Vector Network Analyzer

(VNA) within the range of 1 GHz to 5 GHz. The measured performance of the

prototype couplers were analysis and compared to the simulation results based on the

return loss, |S11|, insertion loss, |S21|, coupling, |S31|, isolation, |S41| and phase balance

(90º± 2º), respectively for determining its validity. From the results comparison, the

simulation and measured results show good agreement even though there is minor

deviation of 1 to 5 %.

6

1.6 Report Organization

This research thesis consists of five chapters overall. Chapter 1 as an

introduction, it describes the problem statement, objectives of research, and scope of

project. Some background of quadrature hybrid and branch line directional coupler

will be discussed.

Next, chapter 2 will describe some basic historical background of directional

coupler theory development that leads to development of miniaturize directional

coupler. Also, the characteristics of the coupler especially its parameters are

described in detail. Besides, various type branch line couplers and approaches of

miniaturization are discussing in detail within this chapter.

In chapter 3, it discusses the research process or methodology involved in

completing the research project. The design specifications of a conventional coupler

and modified coupler will be described in detail. It also includes the design

dimensions, process and material specifications used.

Chapter 4 will present a report about the results of the measurement, analysis

and discussion of research project. Also, the measurement and evaluation of variables

method is analyst and explained. Simulation and measurement results of

S-parameters, in graph, are also included. The measured results will be used to

compare with simulation results. The purpose is to double confirm of its validity.

Finally, chapter 5 summarized all about multi-branch branch line coupler

project, objectives achieved and the conclusion of the research project, suggestion of

future work and its future prospect.

REFERENCES

Alejandro Duenas Jimenez. (1997). Lumped- and Distributed-Element Equivalent

Circuits for Some Symmetrical Multiport Signal-Separation Structures. IEEE

Transactions on Microwave Theory and Techniques. 9th September. Mexico:

IEEE, 1537-1544.

Bader M. Alqahtani. (2009). New Compact Wide-Band Branch-Line Couplers. IEEE

Proceedings of the 39th European Microwave Conference. 29 Sep – 1 Oct. Rome,

Italy: IEEE, 1159-1162.

B. Mayer. (1990). New Broadband Branch line Coupler. Electronic Letters. 30th

August. Hamburg, West Germany. IEEE, 1477-1478.

B. Mayer, Reinhard Knochel. (1990). Branch line Couplers with Improved Design

Flexixibility and Broad Bandwidth. MTT-S Digest. February. Hamburg, West

Germany: IEEE, 391-394.

B.-F. Zong, G.-M. Wang,C.-X. Zhang, Y.-W. Wang. (2014). Miniaturised

Branch-line Coupler with ultra-wide high suppression stop band. Electronic

Letters. 11th September. Shanxi, China: IEEE, 1365-1367.

C.-W. Tang, M.-G. Chen, C.-H. Tsai. (2008). Miniaturization of Microstrip

Branch-Line Coupler with Dual Transmission Lines. IEEE Microwave and

Wireless Component Letters. March. Chiayi, Taiwan: IEEE, 185-187.

C.-W. Tang, C.-T. Tseng, K.-C. Hsu. (2014). Design of Wide Passband Microstrip

Branch-Line Couplers with Multiple Sections. IEEE Transactions on

Components Packaging and Manufactuirng Technology. 30th June. Chiayi

Taiwan: IEEE, 1222-1227.

C.-W. Tang, M.-G. Chen, Y.-S. Lin and J.-W. Wu. (2006). Broadband Microstrip

Branch-line Coupler with Defected Ground Structure. Electronic Letters. 7th

September. Chiayi, Taiwan: IEEE, Vol.42.

94

C.-W. Tang, M.-G. Chen, and C.-H. Tsai. (2008). Miniaturization of Microstrip

Branch-Line Couper with Dual Transmission Lines. Microwave and Wireless

Component Letters. Taipei, Taiwan: IEEE, Vol.18. No.18, 185-187.

David M. Pozar (2005). Microwave Engineering. (pp. 308-361). United States: John

Wiley and Sons, Inc.

D. Andrew (2006). Lumped Element Quadrature Hybrids (pp. 1-7). Canton Street,

Norwood: Artech House, Inc.

D.K. Paul, P. Gardner, B.Y Prasetyo. (1991). Broadband Branch line Coupler for

S-Band. Electronic Letters. 18th July. Manchester, United Kingdom: IEEE,

1318-1319.

F. Hassam, S. Boumaiza. (2008). Micro-strip Line Based Compact Wideband

Branch-Line Coupler Lumped Distributed Element Transformations. IEEE

Transactions on Microwave Theory and Techniques. 5-7th May. Niagara Falls,

Canada: IEEE, 001007-001010.

H.-R. Ahn (2006). Asymmetric Passive Components in Microwave Integrated

Circuits. (pp. 125-147). New Jersey: John Wiley and Sons Inc.

Harlan Howe. (1984). Microwave Integrated Circuits – A Historical Perspective.

IEEE Transactions on Microwave Theory and Techniques. 12th Dec. South

Avenue, Burlington: IEEE, 991-996.

Ilona Piekarz, Jakub Sorocki, Krzysztof Wincza, Slawomir Gruszcynski. (2012).

Meandered Coupled-Line Single-Section Diretional Coupler Designed in

Multilayer LTCC Technology. 20th Telecommunications forum TELFOR 2012.

20-22nd Nov. Serbia, Belgrade: IEEE, 983-986.

Iwata Sakagawi, Ryo Teraoka, Takatsugu Munehiro. (1997). A reduced Branch-Line

Coupler with Eight Stubs. Asia Pacific Microwave Conference. December.

Muroran-Shi, 050 Japan: IEEE, 1137-1140.

Joseph F. White (2004). High Frequency Techniques. An Introduction to RF and

Microwave Engineering. (pp.307-330). New Jersey: John Wiley and Sons Inc.

95

J.-G. Yang, Y.-S. Jeong, S.-K. Choi (2006). A New Compact 3-D Hybrid Coupler

using Multi-Layer Microstrip Lines at 15 GHz. European Microwave Conference.

15th September. Manchester, England: IEEE, 25-28.

J.-P. Wang, B.-Z. Wang, Y.-X. Guo. (2007). A Compact Slow-Wave Microstrip

Branch-Line Coupler with High Performance. Microwave and Wireless

Components Letters. July. Chengdu, China: IEEE, 501-503.

J. Reed and G, J. Wheeler. (1956). A method of Analysis of Symmetrical Four-Port

Networks. IRE Transactions on Microwave Theory and Techniques. February

2-3. Philadelphia, Pa: IEEE, 246-252.

J. -Y. Zou, C. -H. Wu, T. -G. Ma. (2011). Miniaturized branch-line coupler with

wide upper stopband using novel synthesized microstrip lines with series LC

tanks. Electromagnetic, Applications and Student Innovation. 8th August, 2011.

Taipei, Taiwan: IEEE, 234-238.

K. Hettak, M. G. Stubbs, K. Elgaid, G. Thayne (2005). A compact, high

performance, semi-lumped, low-pass filter fabricated with a standard air bridge

proces. European Microwave Conference. October. Paris, France: IEEE.

K. Hettak, G. A. Morin, M.G. Stubbs. (2014). A New Compact 3D SiGe 90º Hybrid

Coupler using the Meandering TFMS and Shielded Strip line at 20 GHz.

Preoceedings of the 39th European Microwave Conference. April. Ottawa,

Canada. IEEE, 1163-1166.

K.-Oh. Sun, S.-J. Ho, C.-C. Yen, Daniel van der Weide. (2005). A Compact

Branch-Line Coupler Using Discontinuous Microtrip Lines. IEEE Microwave

and Wireless Component Letters. August. Madison, USA: IEEE, 519-520.

Kimberly W. Eccleston, Sebastian H. M. Ong. (2003). Compact Planar

Microstripline Branch-Line and Rat-Race Couplers. IEEE Transactions on

Microwave Theory and Techniques. August. October. Singapore: IEEE,

2119-2124.

L. Volakis (2010). Small Antennas. Miniaturization Techniques and Applications (pp.

107-265). New York: McGrawHill.

96

Leung Chiu, Quan Xue. (2010). Investigation of a Wideband 90º Hybrid Coupler

with an Arbitrary Coupling level. IEEE Transactions on Microwave Theory and

Techniques. April. Kowloon, Hong Kong. IEEE, 1022-1029.

Leung Chiu. (2014). Wideband Microstrip 90º Hybrid Coupler Using High Pass

Network. International Journal of Microwave Science and technology. 7th April.

Hong Kong. Hindawi Publishing Corporation, 1-6.

Masahiro Muraguchi, Takeshi Yukitake. (1983). Optimum Design of 3-dB

Branch-Line Couplers Using Microstrip Lines. IEEE Transactions on Microwave

Theory and Techniques. August. Tokyo, Japan: IEEE, 674-678.

M. -J. Chiang, H. -S. Wu, C. -K. -C, Tzuang. (2008). A CMOS 3-dB directional

coupler using edge-coupled meandered synthetic transmission lines. Microwave

Symposium Digest. 15 June. Atlanta: IEEE, 771-774.

Peter A. Razzi (1988). Directional Couplers. Microwave Engineering, Passive

Circuits (pp. 367-393). New Jersey: Prentice Hall-Eaglewood Cliffs.

Phani Kumar, S. Karthikeyan. (2013). A novel design of rat race coupler using

defected microtsip structure and folding technique. Applied Electromagnetics

Conference. 18 Dec. Bhubaneswar: IEEE, 1-2.

R. K. Mongia (2007). RF and Microwave Coupled-line Circuits. (pp. 149-165).

Canton Street Norwood: Artech House, Inc.

Robert E. Collin (1992). Foundations for Microwave Engineering. (pp. 413-442).

United States: McGraw-Hill, Inc.

Reinhard Knochel. (1999). Broadband Flat Coupling Two-branch And Multi branch

Directional Couplers. IEEE MTT-S Digest. Oct. Kiel, Germany: IEEE,

1327-1330.

Robert M. Barrett. (1984). Microwave Printed Circuits – The early years. IEEE

Transaction on Microwave Theory and Techniques. 12th September. Bedford, MA:

IEEE, 983-990.

97

Seungku Lee, Yongshik Lee. (2012). Wideband Branch-Line Couplers with

Single-Section Quarter-Wave Transformers for Arbitrary Coupling Levels. IEEE

Microwave and Wireless Component Letters. 11th Jan. Ann Arbor, USA: IEEE,

19-21.

Siddig Gomha, El-Sayed M. El-Rabaie, Abdel Aziz T. Shalaby, Ahmed S. Elkorany.

(2014). Miniaturization of Branch-line Couplers using Open Stubs and Stepped

Impedance unit cells with Meandering Transmission Lines. Circuits and Systems:

An International Journal (CSIJ). July. Menouf, Egypt: IEEE, 13-26.

S.-C. Jung, Renato Negra, Fadhel. M. Ghannounchi. (2009). A Miniaturized

Double-Stage 3dB Broadband Branch-Line Hybrid Coupler Using Distributed

Capacitors. IEEE Transactions on Microwave Theory and Techniques. June.

Seoul, Korea: IEEE, 1323-1326.

Shinya Johnosono, Takao Fujiii, Isao Ohta. (2006). Design of Broadband CPW

Branch-Line 3-dB Couplers. Proceedings of the 36th European Microwave

Conference. September. Hyogo, Japan: IEEE, 36-39.

Peter A. Razzi (1988). Directional Couplers. Microwave Engineering, Passive

Circuits (pp. 367-393). New Jersey: Prentice Hall-Eaglewood Cliffs.

V. Iran-Nejad, A.A Lotfi-Neyestanak, A. Shahzadi. (2012). Compact Broadband

Quadrature Hybrid Coupler using Planar Artificial Transmission Line. Electronic

Letters. 6th December. Tehran, Iran: IEEE, Vol. 48 No. 25.

Wael M. Fathelbab. (2008). The Synthesis of a Class of Branch-Line Directional

Couplers. IEEE Transactions on Microwave Theory and Techniques. August.

South Dakota, USA. IEEE, 1985-1994.

W.-S. Chang, C.-Y. Chang. (2012). A High Slow-Wave Factor Microstrip Structure

with Simple Design Formulas and Its Application to Microwave Circuit Design.

IEEE Transactions on Microwave Theory and Techniques. 20th September.

Hsinchu, Taiwan. IEEE, 3376-3382.

Werner A. Arriola, J. -Y. Lee, I. -S. Kim. (2011). Wideband 3 dB Branch Line

Coupler Based on λ/4 Open Circuited Coupled Lines. IEEE Microwave and

Wireless Component Letters. 19th May. Gyeoggi-do, Korea. IEEE, 486-488.

98

W. W. Mumford. (1946). Directional Couplers. Proceding of the I.R.E. 6th May.

Holmdel, New Jersey: IEEE, 160-165.

Y.-C. Chiang, C.-Y. Chen. (2001). Design of a Wide-band Lumped-Element 3-dB

Quadrature Coupler. IEEE Transactions on Microwave Theory and Techniques.

March. Taiwan: IEEE, 476-479.

Y.-L. Then, K.-Y. You, Mohamad Ngasri Dimon, J.-C. Chong, T.-S. Tan. (2013).

Compact Microstrip S-Band 90º Hybrid Coupler. IEEE Symposium on Wireless

Technology and Application. 22-23rd September. Kuching: IEEE, 202-206.

Y.-H. Chun, J.-S. Hong. (2005). Design of a Compact Broadband Branch-Line

Hybrid. IEEE Transactions on Microwave Theory and Techniques. April.

Edinburg, United Kingdom: IEEE, 997-1000.

Y.-H. Chun, J.-S. Hong. (2006). Compact Wide-Band Branch-Line Hybrids. IEEE

Transactions on Microwave Theory and Techniques. February. Edinburg, United

Kingdom: IEEE, 704-709.