無論在微波系統或毫米波系統中，微帶線耦合器在電路系統的設計過程中都扮演著舉足輕重的角色。在實際應用上該元件具有分配功率及控制訊號相位的功能，使其應用層面非常廣泛，從功率放大器、偵測器、調制器、混頻器、相移器、天線陣列到微波儀器系統都可以看見它的蹤影。為了因應日益蓬勃發展的通訊產業及雷達系統，考量到使用頻段及系統整體面積，因此在耦合路徑的設計上必須更加寬頻及減少整體電路的面積。
本篇論文藉由嚴謹的理論推導及反覆的實驗驗證，實現兼具寬頻及微型化的15及20 dB之90度耦合線耦合器。在實驗上分別在Advanced Design System (ADS) 及High Frequency Simulation Software (HFSS) 建立相同的實驗模組，針對兩組資料進行模擬及實驗論證，並配合不同的微帶線斜切方式探討其實驗結果及各項操縱變因所帶來的影響。在設計架構上，採用3節平行的耦合微帶線設計此耦合器架構，使其頻率範圍2.3-6 GHz時，具有 ± 1 dB以內之耦合係數變化量，大於18 dB的折返損耗與隔離度，以及90°±5°的耦合係數相位範圍。 此實驗也有一系列的貢獻，舉例來說 曲面的形式來形成饋入線 開路株的實線來保持電容的平衡 作為旁帶耦合線與中間部分的交會處。最後利用基板厚度0.8 mm、介電常數4.4介質損耗係數是0.02且金屬厚度0.01 mm的FR4基板完成此一耦合器架構，並將實驗結果與模擬結果進行比對，驗證此實驗之精準性。

The coupled-line coupler is one of the most important components in microwave and millimeter-wave systems. Such devices are used for distributing power, tapping signals and for measurements purposes in power amplifiers, detectors, modulators, mixers, phase shifters, antenna arrays and microwave instruments. Due to the increasing development and deployment of communications and radar applications, it is necessary in particular the reduction in size with a wideband coupling. In the present thesis, the design, fabrication and measurement of miniaturized wideband 15 and 20 dB 90-degree coupled-line couplers are exposed. The realization of this component involves the use of different microstrip mitering techniques and computer aided design (CAD) tools such as Advanced Design System (ADS) and High Frequency Simulation Software (HFSS) for modeling, optimization and tuning. Based on this structure, a three-section coupled-line coupler having a frequency range from 2.3 to 6 GHz, a coupling of 15 or 20 ± 1 dB, a return loss and an isolation of more than 18 dB, and a coupling phase of 90º ±5º is presented. There is also a series of contributions for such work which are discussed in detail such as the use of a tapered line to form a feedline, the implementation of open stubs to keep a capacitive balance and also the junctions to connect the lateral coupled lines to the middle section. Finally, the coupler has been realized on a 0.8 mm thick FR4 substrate with a dielectric constant of 4.4, loss tangent of 0.02 and a metal thickness of 0.01 mm. After testing fabricated design, measurement results present a high agreement with the simulations results, thus verifying the design accuracy.

Contents Pages
Thesis Validation Letter in Chinese...........................................................................................i
Thesis Validation Letter in English...........................................................................................ii
Declaration................................................................................................................................iii
Acknowledgements..................................................................................................................iv
Dedication…………………………………………………………………………………….v
Abstract (Chinese)....................................................................................................................vi
Abstract (English)....................................................................................................................vii
Table of Contents...................................................................................................................viii
List of Figures...........................................................................................................................x
List of Tables...........................................................................................................................xii
List of Symbols.......................................................................................................................xiii

CHAPTER 1 Introduction
1. Background…………………………………………………………………………...1
2. Motive............................................................................................................................2
3. Thesis Structure..............................................................................................................3

CHAPTER 2 Transmission lines
1. Introduction..………………………………………………….……………………...4
2. Definition of a Transmission Line.................................................................................4
3. Types of Planar Transmission Lines….........................................................................6
4. Microstrip Line..............................................................................................................8






CHAPTER 3 Coupled Lines and Couplers

3.1 Coupled Microstrip Lines....................................................................................10
3.2 Principle of Operation……………………………………………………….….12
3.3 Multisection Coupled-Line Couplers…………………………………………...18
3.4 Discontinuities of Multisection Couplers…………...…………………………..20
3.4.1 Microstrip Bends……………………………………………...……………..21
3.4.2 Steps in Width…………………………………………………………….....21
3.5 Coupled-Line Coupler Mathematical Design.……………………………………21
3.5.1 Designing of 50Ω Ports for SMA Connectors……………………………....25
3.5.2 Designing of Feedlines……………………………………………………....30
3.5.3 Designing of Junctions……………………………………………………....36
3.5.4 Coupler Parts Assembling...………………………………………………....37
3.5.5 Final Layout and Results of Coupler………………………….………….....39
3.6 Compared Designs………………………………………………………………..44
3.6.1 Compared Design no.1………………..…………………………………......45
3.6.2 Compared Design no.2……………………..……………………………......49
3.7 15 Degrees Coupled Line Coupler……………………………………………..52

CHAPTER 4 Conclusion
4.1 Summary ...............................................................................................................57
5.3 Conclusion and Scope for Future Work.................................................................58
5.3 Contribution of Thesis…………………………………………………………....59

References ...........................................................................................................................60
Appendix A .........................................................................................................................67
Appendix B .........................................................................................................................68

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