| In order to improve the spectrum utilization, the amplitude modulation and phase modulation are applied in modern wireless communication systems. These modulation methods contain more information in the unit bandwidth than traditional ones, but they will result in large high peak to average power ratio (PAPR) due to their non-constant envelope which is very sensitive to nonlinear distortions. The power amplifiers typically operated in backoff status relative to peak power, which implies a low efficiency. Power amplifier's efficiency and linearity become research hotspot.An in-depth research on several key techniques for improving efficiency and linearity of the transmitter is done in this dissertation. Simulation results validate the effectiveness of the new design method. And the new algorithms are also introduced.The contributions of this paper are presented as follows:1. The background and significance of linearity transmitter techniques are introduced in this dissertation. Through analyzing the research status about LINC at home and abroad, the emphasis of this dissertation is proposed.2. This dissertation describes the fundamental theory of LINC, and analyzes several key technologies and key signal characteristics. At the same time, the factors of affecting the transmitter linearity and efficiency are summarized.3. A power Combiner's mathematical model is proposed and analyzed in this dissertation. The computer simulation results based on Agilent's Advanced Design System (ADS) demonstrate the performance of the proposed model. At last, two new design methods are proposed: one is optimizing the circuit parameters; the other is using a new algorithm named double threshold signal components separate (DTSCS).4. The imbalance between two branches is described by transform matrix. The method is used to analyze the imbalance in LINC. The complex imbalance mode can be divided into several simple ones, which bring different distortions and are corrected by corresponding correction approaches. |
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