Analysis and Design of Efficiency-Enhancement Microwave Power Amplifiers Using the Doherty ...

249 Pages·2013·12.76 MB·English

Analysis and Design of Efficiency-Enhancement
Microwave Power Amplifiers Using the Doherty
Technique
Vorgelegt von
M.Sc. Khaled Bathich
aus Aleppo/Syrien
von der Fakult¨at IV - Elektrotechnik und Informatik
der Technischen Universit¨at Berlin
zur Erlangung des akademischen Grades
Doktor der Ingenieurwissenschaften
- Dr.-Ing. -
genehmigte Dissertation
Promotionsausschuss:
Vorsitzender: Prof. Dr.-Ing. Reinhold Orglmeister
Gutachter: Prof. Dr.-Ing. Georg B¨ock
Gutachter: Prof. Dr. sc. techn. Renato Negra
Tag der wissenschaftlichen Aussprache: 12. Juli, 2013
Berlin, 2013
D83

To my father Abdul Razak, my mother Madiha, my wife Muna and lovely son
Waleed, for their love, devotion and prayers.
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Acknowledgements
All praise to our Creator, who gave us the tools to develop and ease our life. I wish
to express my sincere gratitude to my Doktorvater Prof. Dr.-Ing. Georg B¨ock who
gave me the opportunity to conduct this research work at the Microwave Engineering
Lab of Berlin Institute of Technology. His continuous supervision and support during
this period was crucial to complete this work.
I would also like to thank Prof. Dr. sc. techn. Renato Negra who accepted to be a
second examiner for this Ph.D. thesis as well as Prof. Dr.-Ing. Reinhold Orglmeister
being the chairman of the dissertation committee.
I am very grateful to all members and students at the Microwave Engineering Lab
for the fruitful discussions and the convenient team work environment which helped
me alot during my research work.
Khaled Bathich
Berlin, December 2012
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Contents
Dedication iii
Acknowledgements v
List of Figures xi
List of Tables xxi
List of Symbols xxii
List of Abbreviations and Acrynoms xxv
Abstract xxviii
Zusammenfassung xxx
Chapter 1 1
1 Introduction 1
Chapter 2 5
2 Power Amplifiers and Efficiency Enhancement 5
2.1 Active Devices for Power Amplifiers . . . . . . . . . . . . . . . . . . . 6
2.1.1 AlGaN/GaN HEMT . . . . . . . . . . . . . . . . . . . . . . . 6
2.2 Amplifier Classes of Operation . . . . . . . . . . . . . . . . . . . . . . 8
vii
2.2.1 Conventional Amplifiers . . . . . . . . . . . . . . . . . . . . . 9
2.2.2 Current-Mode and Switch-Mode Amplifiers . . . . . . . . . . . 12
2.3 Efficiency Enhancement in Power Amplifiers . . . . . . . . . . . . . . 16
2.3.1 Efficiency Enhancement by Load Modulation . . . . . . . . . . 17
2.3.2 The Doherty Amplifier . . . . . . . . . . . . . . . . . . . . . . 20
2.4 Linearity in Power Amplifiers . . . . . . . . . . . . . . . . . . . . . . 28
2.4.1 Nonlinearity Characterization . . . . . . . . . . . . . . . . . . 29
2.4.2 Linearity of the Doherty Amplifier . . . . . . . . . . . . . . . 31
2.4.3 Linearization Techniques . . . . . . . . . . . . . . . . . . . . . 33
Chapter 3 36
3 Design of Narrowband Uneven Doherty Amplifiers 36
3.1 The Uneven Doherty Amplifier . . . . . . . . . . . . . . . . . . . . . 36
3.2 Uneven 8 W Si LDMOS Doherty Amplifier Design . . . . . . . . . . . 39
3.2.1 Main Amplifier Design . . . . . . . . . . . . . . . . . . . . . . 40
3.2.2 Peaking Amplifier Design . . . . . . . . . . . . . . . . . . . . 41
3.2.3 Output Combining Network Design . . . . . . . . . . . . . . . 43
3.2.4 Uneven Power Divider . . . . . . . . . . . . . . . . . . . . . . 44
3.2.5 Amplifier Assembly and Experimental Characterization . . . . 45
3.3 Uneven 85W GaN HEMT Doherty Amplifier Design . . . . . . . . . 51
Chapter 4 58
4 Frequency Response Analysis and Bandwidth Extension of the Do-
herty Amplifier 58
4.1 Bandwidth Limiting Factors in the Doherty Amplifier . . . . . . . . . 59
4.2 Frequency Response Analysis of the Output Combining Network . . . 63
4.2.1 Analysis up to the 6 dB Back-Off Point . . . . . . . . . . . . . 64
4.2.2 Analysis for the Upper 6dB Regime . . . . . . . . . . . . . . . 67
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4.3 Bandwidth Extension of the Output Combining Network . . . . . . . 75
Chapter 5 81
5 Design of Dual-Band and Wideband GaN Doherty Amplifiers 81
5.1 The Unsymmetrical Doherty Amplifier . . . . . . . . . . . . . . . . . 82
5.2 Design of 16W Dual-Band Unsymmetrical Doherty Amplifier . . . . . 83
5.2.1 Output Combining Network . . . . . . . . . . . . . . . . . . . 84
5.2.2 Main Amplifier Design . . . . . . . . . . . . . . . . . . . . . . 85
5.2.3 Peaking Amplifier Design . . . . . . . . . . . . . . . . . . . . 88
5.2.4 Input Power Divider and Offset Lines . . . . . . . . . . . . . . 88
5.2.5 Final Schematic and Experimental Characterization . . . . . . 89
5.3 Design of 20W Wideband Uneven Doherty Amplifier . . . . . . . . . 94
5.3.1 Main Amplifier Design . . . . . . . . . . . . . . . . . . . . . . 94
5.3.2 Peaking Amplifier Design . . . . . . . . . . . . . . . . . . . . 96
5.3.3 Power Combiner and Divider Networks . . . . . . . . . . . . . 97
5.3.4 Experimental Characterization . . . . . . . . . . . . . . . . . . 100
5.4 Design of 20W Wideband Unsymmetrical Doherty Amplifier . . . . . 105
5.4.1 Main Amplifier Design . . . . . . . . . . . . . . . . . . . . . . 106
5.4.2 Peaking Amplifier Design . . . . . . . . . . . . . . . . . . . . 107
5.4.3 Experimental Characterization . . . . . . . . . . . . . . . . . . 108
5.5 Design of 20W Bandwidth Extended Unsymmetrical Doherty Amplifier113
5.5.1 Main Amplifier Design . . . . . . . . . . . . . . . . . . . . . . 116
5.5.2 Peaking Amplifier Design . . . . . . . . . . . . . . . . . . . . 117
5.5.3 Output Combining Network and Power Divider Designs . . . . 118
5.5.4 Assembly and Optimization of the Wideband Doherty PA . . 120
5.5.5 Experimental Characterization . . . . . . . . . . . . . . . . . . 122
5.6 Design of 80W Wideband Harmonically-Tuned Unsymmetrical Do-
herty Amplifier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 128
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5.6.1 Main Amplifier Design . . . . . . . . . . . . . . . . . . . . . . 130
5.6.2 Peaking Amplifier Design . . . . . . . . . . . . . . . . . . . . 136
5.6.3 Assembly and Simulation of the Wideband Doherty Amplifier 137
5.6.4 Experimental Characterization . . . . . . . . . . . . . . . . . . 140
5.7 Design of 200W Wideband Harmonically-Tuned Doherty Amplifier . 148
5.7.1 Main Amplifier Design . . . . . . . . . . . . . . . . . . . . . . 148
5.7.2 Peaking Amplifier Design . . . . . . . . . . . . . . . . . . . . 149
5.7.3 Assembly and Simulation of the 200W Doherty PA . . . . . . 150
5.7.4 Experimental Characterization . . . . . . . . . . . . . . . . . . 151
5.8 Design of 80W Wideband Asymmetrical Doherty Amplifier . . . . . . 157
5.8.1 FrequencyResponseAnalysisoftheAsymmetricalDohertyAm-
plifier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 159
5.8.2 PA Design and Experimental Characterization . . . . . . . . . 164
Chapter 6 169
6 Conclusions and Further Work 169
Appendices 172
A ADS Circuit Schematics of the Narrowband Doherty Amplifiers 172
B ADS Circuit Schematic of the Dual-Band GaN Doherty Amplifier 180
C ADS Circuit Schematics of the 20W Wideband Doherty Amplifiers184
D ADSCircuit Schematics of the80Wand200WWidebandHarmonically-
Tuned GaN Doherty Amplifiers 194
List of Publications 202
Bibliography 205
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