High Efficiency, High Research And Design Of Linear Base Station Amplifier

The design of power amplifiers for wireless systems has become a challenging task due to increasingly stringent requirements placed upon transmitters using spectrum efficient modulation techniques. The Doherty power amplifier (DPA) is an important candidate for this type of application due to its feature of high efficiency over an extended power range. However, DPA in practice have often failed to exhibit the superb efficiency predicted by theory and their linearity is not always adequate to meet strict specifications of systems with high Peak-to-Average Ratio (PAR) signals. The objective of this dissertation is to provide a path for DPA that lead to a simultaneous high efficiency and high linearity performance.First, analyze the nonlinear characters and the memory effects of RF Power amplifier. Based on detailed understanding of DPA theory and careful investigation of behavior of DPA, a series of guidelines for designing a DPA was created. A DPA based on LDMOS devices was accordingly designed in simulation and then fabricated.Following, the ways of improving the memory effects is introduced. In order to optimize the performance, envelope tracking technique, asymmetrical Doherty, N-way Doherty, inverted Doherty and sweet spot character are researched.Because the high power amplifier of the base station is commonnly operated with digital predistortion (DPD), we introduce the principle and structure of DPD and research the operation of them. Finally we debug the DPA, explain matters need attention and get the result of the measurement.