Doherty Power Amplifier In Mobile Communication

In order to enhance the efficiency effectively, the third generation communication system, such as WCDMA, TD-SCDMA, CDMA2000 and LTE(long term-evolution), employ the moderating method, including QAM, QPSK DPSK and so on. These methods change the amplitude and phase, so the signal will be no-constant envelope. WCDMA employs non-constant envelope modulation techniques with a high peak to average ratio. The power back-off technique is an effective method to enhance the linearity. However, unfortunately, with the power backed off region from saturation, the PAE (Power Additional Efficiency) will drop immediately. At the same time, as the PA is the high-power dissipation component, a design of a high efficiency power amplifier is necessary, to overcome the battery lifetime limitation and PA's MTBF (Mean Time between Failures). The Doherty Amplifier technique can be good for resolving these problems.The thesis includes six chapters. The first chapter is exordium. In the second chapter, the character of non-linear PA and the technology indexes will be introduced. In the third chapter, some techniques to improve the efficiency of PA will be mentioned, including the analysis of Doherty PA. In the fourth chapter, Electronical Memory Effect is introduced. In the fifth chapter, which focus on the comparison of a single-ended class AB, a balance and a Doherty power Amplifier, is simulated and designed according to the theoretical analysis. In the last chapter the figures of main circuits and test results are shown, and compares the test results of three kinds of structure introduced above.