| Power amplifiers, as one of the most important components in modern wireless communication systems, are subject to more and more widespread concern. The third generation (3G), such as WCDMA, and the upcoming fourth generation (4G) communication standards both make use of the linear modulation schemes to improve the spectrum utilization efficiency. These modulation schemes pose stringent demands to the linearity of the power amplifiers. 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. Consequently, the traditional class-A or class-AB amplifiers are less attractive since their efficiency are seriously degraded when operating them below the peak power. As one of the largest energy-consuming components, the efficiency level of the power amplifier directly determines the operation cost and the reliability of the system. Thus, there is increased interest in high-efficiency power amplifier techniques. Various power amplifier architectures with improved efficiency have been proposed over time. Doherty power amplifier technology, which is simple in structure and easy to implementation and has low cost, has become the most widely used efficiency-enhancement technique.The main purpose of this paper is to research the advantages and disadvantages of the three-way Doherty power amplifier (compared with the two-way Doherty power amplifier). We made use of the load-pull technique, in combination with the simulation software and the model of the power amplifiers, to study the matching circuits designing and simulations of the Main, Peak1 and Peak2 power amplifiers, as well as the simulation of the three-way Doherty amplifier in detail. Besides, we put forward some improved methods to optimize the design. Finally, we implemented a corresponding practical circuit for debugging and testing and made some comparisons with the two-way Doherty power amplifier.The paper is divided into seven chapters. In Chapter 1, we made a brief introduction. In Chapter 2, we introduced the parameters and the basic operation classifications of the power amplifier. In Chapter 3, the matching circuit of the power amplifier was introduced. In Chapter 4, we analyzed the operation principle and deduced some formulations of the three-way Doherty power amplifier. In Chapter 5, we described the design and simulation steps of the three-way Doherty power amplifier and put forward some methods to improve the design. In Chapter 6, we listed the test results of the three-way Doherty power amplifier and made some comparisons. In Chapter 7, we made a summary of the paper. |
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