The Research On Class J Power Amplifier Applied For Multimode Mobile Base Station

Current wireless communication systems’ urgent needs drives broadband with high efficiency power amplifiers(PA) a hot topic. Class-J is a new PA design concept proposed in 2006, which changes a single PA operating mode into continuous operating mode to achieve a good bandwidth characteristics. Class-J PA solves the contradiction between bandwidth and efficiency for the harmonic control class PA in a good way, but there is still room for Class-J to improve its efficiency. In addition, traditional matching network design methodoloty for Class-J PA is complicated and not suitable for engineering applications. For this situation, this paper conduct a study on the design methodology of Class-J PA.The design for this paper don’t adopt the tranditional method which consider the linear capatitancor situation only, but conduct a research on the characteristics of the nonlinear capacitor, namely through the research of the fundamental and second harmonic impedance changing law affected by the nonlinear capacitor, proposing a new methodology to realize the fundamental matching and second harmonic controlling together. In this way, the output mathing network design procedure and the performance of the Class-J PA is simplified and improved.The specific content of the work are as follows:1. The basic theory of Class-J PA is summarized systematicly.The drain voltage and current waveforms is presented and analysed to explain the Class-J’s harmonic controlling principle. In addition, the Class J continuous mode concept is and the design space is illustrated to explained the reason why Class J has good bandwidth characteristics;2. The nonlinear characteristics of the transistor output capacitance is studied, focusing on the effects by the nonlinear output capacitance of the fundamental and second harmonic impedance of the Class J PA, and the law of changing for the fundamental and second harmonic impedance of Class J PA is presented, which is employed in the improved design;3. A new matching network topology is presented. This matching network can synthesize the equivalent parasitic transistor model, to realize the fundamental matching and second harmonic controlling together. The simulation results show that the matching network can well achieve the Class-J PA impedanceenvironment;4. The design and implementation validate the feasibility of a new integrated design method proposed in this paper. Test results show that Class-J PA design based on the improved method achieve obvious good performance.This paper describes the principle and design method J class amplifier, providing reference for scholars.