| With the rapidly development of the new generation of mobile communication systems, many new modulation techniques such as QAM, QPSK and OFDM, are envelope varied. These modulated signals with a high peak-to-average power ratio (PAR) demand that the transmitter keep high linearity at larger dynamic range. In order to meet the linearity requirements of the system, power amplifiers need to function most of their time much lower levels than the peak powers they are designed for, which is called power back-off.As one of the largest energy-consuming components, the efficiency level of the power amplifier directly determines the operation cost of the system. Thus, there is increased interest in high-efficiency power amplifier techniques. Doherty power amplifier technology, which is simple in structure and has low cost, has become the most widely used efficiency-enhancement technique. The conventional two-way Doherty PA gradually can’t meet the requirements of the modulated signals with high PAR for its low back off range. For the improvement of the high efficiency at a larger back-off range and reduce the overall power consumption of new generation mobile communication system, the dissertation focuses on the design of the novel three-way Doherty structure.The dissertation first introduces the technical indicators of power amplifier, and then analyze the efficiency and design principles of the conventional two-way Doherty PA, conventional three-way Doherty PA and the novel three way Doherty PA in theory. Then, by applying the microwave EDA software and the power tube model to design different kinds of structure, the dissertation finally choose the novel three-way Doherty PA. Design the Lim-Eom three way splitter and realize the actual circuit of the novel three way Doherty PA. The PA work at the frequency band of TD-LTE (2570MHz-2620MHz) is achieved by adopting three identical power tubes with peak output power of75W. Finally, the layout of the circuit system is achieved, including the driver PA, the single PA, the three-way power divider and the final stage PA.The final test result of driver PA, the single PA, and the Lim-Eom power divider is excellent. The test and results analyze of the novel three-way Doherty power amplifier is finally achieved as below:the maximum output power is53.4dBm, the power added efficiency(PAE) is above45%and the IMD3is below-25dBc at the9.5dB power back-off point. The test results and the simulation results are basically consistent the performance meet the design requirements... |
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