氮化鎵材料在功率元件的應用上相較於矽材料有相當大的優勢，因為有寬能隙、高臨界電場以及高熱導係數，使其能承受高電壓，此外，因氮化鎵屬於HEMT，故有高電子飽和速度的特性，使其在高頻領域有良好表現。半導體第一代材料是矽(Si)，帶隙寬約為1.17eV；第二代材料是砷化鎵(GaAs)，帶隙寬約為1.42eV，是現今絕大部分通信設備的材料；第三代材料是指帶隙寬在2.3eV及以上的半導體材料，氮化鎵的帶隙寬約為3.5eV，因此成為功率或射頻元件的新材料。近幾年來，由於通訊頻段上升到毫米波，如何製作高頻功率放大器被廣泛的研究，其中氮化鎵被認為是最有潛力的選項，因為第三代半導體主要應用於5G、電動車、雷達及高功率應用(如快速充電)，功率放大器必須提供更高的輸出功率，同時必須盡可能的提高效率，避免廢熱造成能源的浪費和影響電路與系統之運轉。本論文將探討使用氮化鎵製程之Doherty、Class-F^(-1)以及Class-F射頻功率放大器。首先，在第一章介紹論文之研究動機、氮化鎵元件之特性及論文架構；第二章節，討論功率放大器之基本概念以及重要設計考量；第三章至第五章分別討論三個功率放大器電路之設計流程以及細節，包含整體電路架構、電晶體大小、被動元件的設計以及模擬和量測結果。第一個電路為9-dB回退之Doherty 10 GHz功率放大器，採用不相等汲級偏壓方法，此方法經過數學推導及Matlab驗證，推廣傳統6-dB回退之Doherty功率放大器之模型，此設計經修正後，功率附加效率可在9-dB回退區間內超過40%；第二個電路為5.8 GHz之Class-F^(-1)功率放大器;第三個電路為6 GHz Class-F功率放大器，後兩者功率附加效率皆高於45%。

Gallium Nitride HEMT is exceptional in high-frequency and high-power applications compared with silicon due to wide bandgap, high critical electric field, high electron mobility, and high thermal conductivity. The first-generation semiconductor material is Si (1.17eV bandgap), and the second-generation material is GaAs (1.42eV bandgap), applied in most modern communication equipment. The third-generation material includes GaN (3.5eV bandgap) and those with a higher than 2.3eV bandgap. Recently, millimeter wave is considered as a new domain in the next generation of wireless mobile communication, and GaN is the most promising candidate since the main applications in third-generation semiconductor include 5G communications, electric vehicle, radar, and high power oriented such as fast charging. To be noticed, good power amplifiers must not only deliver high output power, but also have high efficiency to avoid seriously heating issue in circuits and systems. This thesis presents the research on RF power amplifiers based on the topologies of Doherty, Class-F^(-1), and Class-F using 0.25-μm GaN on SiC technology from WIN Semiconductors. The first chapter includes motivation, characteristic of GaN materials, and thesis organization. Chapter II presents basic design concepts of power amplifiers. From chapter III to chapter V, three PAs are presented in details, including topology, transistor size, passive components, and simulation and measurement results. The first circuit is a 9-dB back-off 10 GHz Doherty PA, which employs novel uneven drain bias technique that generalizes traditionally 6-dB back-off Doherty PA design, and is verified by analytical derivation and Matlab. The revised design achieved PAE above 40% within 9-dB back-off region. The subsequent designs are 5.8 GHz Class-F^(-1) PA and 6 GHz Class-F PA both with PAE over 45%.

摘要 i
ABSTRACT ii
TABLE OF CONTENTS iii
LIST OF FIGURES vi
LIST OF TABLES ix
Chapter 1 Introduction 1
1.1 Motivation 1
1.2 Characteristic of GaN Materials 2
1.3 Thesis Organization 3
Chapter 2 Basic Concepts of Power Amplifier 4
2.1 Introduction 4
2.2 Critical Specifications 5
2.2.1 Output Power 5
A. Saturation Power 5
B. 1dB Compression Point 5
2.2.2 Efficiency 6
A. Drain Efficiency 6
B. Power-Added Efficiency 7
2.2.3 Linearity 7
A. Intermodulation, IMD 8
B. Third-Order Intercept Point, 〖IP〗_3 or TOI 9
2.2.4 Stability 10
2.3 Load-line & Optimized Output Matching 10
2.4 Classification of Power Amplifiers 12
2.5 Summary 14
Chapter 3 Design of A Generalized Backoff Doherty Power Amplifier 15
3.1 Introduction 15
3.2 Generalization of Doherty Power Amplifier 16
3.2.1 Mathematical Generalization 16
3.2.2 Verification by Matlab 20
3.3 9-dB Back-off Doherty Power Amplifier 22
3.3.1 Circuit Topology 22
3.3.2 Transistor Size Selection & Uneven Drain Bias 23
3.3.3 Power Divider 26
3.4 Simulation and Measurement 27
3.4.1 Circuit Layout 27
3.4.2 Small-Signal Performance 27
3.4.3 Large-Signal Performance 28
3.5 Revised Design of the 9-dB Back-off Doherty Power Amplifier 31
3.6 An Alternative Way of Doherty PA Generalization 34
3.7 Summary 36
Chapter 4 Design of Sub-6 GHz Class-F^(-1) Power Amplifier 37
4.1 Introduction 37
4.2 Design Concept 38
4.2.1 Circuit Topology 38
4.2.2 Transistor Size Selection 39
4.2.3 Harmonic Termination Network 40
4.3 Simulation and Measurement 41
4.3.1 Circuit Layout 41
4.3.2 Small-Signal Performance 42
4.3.3 Large-Signal Performance 42
4.4 Summary 45
Chapter 5 Design of Sub-6 GHz Class-F Power Amplifier 46
5.1 Introduction 46
5.2 Circuit Topology 47
5.2.1 Transistor Size Selection 48
5.2.2 Harmonic Termination Network 49
5.3 Simulation and Measurement 51
5.3.1 Circuit Layout 51
5.3.2 Small-Signal Performance 51
5.3.3 Large-Signal Performance 52
5.4 Summary 55
Chapter 6 Conclusion and Future Work 56
References 57

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