New Architectures for RF Power Amplifier Linearization

Power amplifier linearization has become an important part of the transmitter system as 3G and developing 4G communication standards require higher linearity than ever before. The thesis proposes two power amplifier linearization solutions : two-point architecture and adaptive digital predistortion using a AE modulator for automatic inversion of power amplifier nonlinearity. Two-point architecture can be seen as a solution that extends the linearization bandwidth of the traditional feedback architecture while also offering decent digital predistortion linearization at much higher frequencies as well. It overcomes the bandwidth problem by combining Cartesian feedback and digital predistortion. As the Cartesian feedback loses its loop gain in high frequencies, the predistorted signal gradually takes over the linearization role. Effectively, this increases the operation bandwidth of the Cartesian feedback and allows wide-band transmission. For digital predistortion, the complexity involved in the implementation of adaptive algorithm and convergence issues in the look-up table training has limited its application in handset devices. Predistortion using a AE modulator presented in this work eliminates these problems as it is based on open-loop look-up table training and does not require adaptive algorithm. Thesis Supervisor: Joel L. Dawson Title: Assistant Professor Acknowledgments Reminiscing my student life during my master's work here at MIT, I am grateful for having been part of such a special community. I realize that I have developed tremendously, not just as a student, but also as a better person. First, I would like to thank my research advisor, Professor Joel L. Dawson, for enlightening me throughout my work. He has taught me how to think positively, love my work, collaborate with others, and of course, endure. My work wouldn't have been fruitful without his guidance and I am truly indebted to him. I have had countless memorable interactions with him: talking about the disappointment we each had for giving up our the childhood dream of becoming a jet pilot, engaging in intellectual debates, talking over the phone near 3A.M. to make paper corrections before submissions etc. I will cherish all these fond memories in the years to come. My academic and social experience wouldn't have been complete without the Dawson group members and class friends. Tania, thank you for playing along with all my pranks and jokes. Willie, thank you for always being the nice guy. Muyiwa, it was fun working late at night at lab with you. I especially would like to thank Sungwon. You were always there for me when situations seemed the darkest. You helped me throughout every stage from giving technical insights to helping with making measurements, and you have taught me how to think instead of laboring for hours. Mike, thank you for stopping by at my cubicle every once in a while to share conversations with me. I would also like to thank the Korean EECS student body for the monthly beer night and the fellowship. Finally, I want to share my excitement with my family. I would like to thank my sister Soojung for making the campus visit and checking up on me. My parents have always supported me with phone calls and even Korean foods! I couldn't have done this without you. Thank you and I love you all!