为提高频谱利用效率，未来通信系统将采用具有更高瞬时带宽和峰均比值的复杂调制信号，并且需要覆盖多个工作频段。Doherty功率放大器因具有回退效率高、结构简单等优势，已经成为目前功放研究领域的一大热点。但是，受负载调制网络、阻抗匹配电路和晶体管数目等的限制，常规的Doherty结构只能窄带工作且高效率回退范围较小，难以满足未来需求。因此，本项目将开展对提升Doherty功放带宽和回退范围的研究。通过全面分析常规负载调制网络的阻抗频率特性，掌握其带宽限制机理。在此基础上，探讨各种新型宽带负载调制网络设计方案。同时，研究基于谐波负载牵引技术构建融合多功能宽带匹配电路的设计方案。最后，探索研究同时提升工作带宽和回退范围的多目标协同设计技术，完善具有超高回退范围的宽带多路Doherty功放设计理论。本项目的实施将解决目前Doherty功放的一些主要技术难题，具有重要的科学和应用价值。

To improve spectrum efficiency, future communication system will adopt complex modulated signals with higher transient signal bandwidth and higher peak-to-average power ratio (PAPR), and cover multiple operating bands in the meantime. Doherty power amplifier (PA) has become one of hot research topics nowadays due to its advantages of large back-off range and simple structure. However, limited by the load modulation network (LMN), impedance matching network and transistor number, conventional Doherty power amplifier has small bandwidth and high-efficiency back-off range. Therefore, it is hard to meet the requirements of future system. This project will investigate how to expand bandwidth and enhance high-efficiency back-off range for the Doherty PA. We will give a comprehensive analysis of the impedance-frequency response characteristics of the conventional LMN, and study its bandwidth limiting mechanism. On the basis of these efforts, new wideband LMN solutions will be studied. In addition, this project will develop a syncretic multi-functional wideband matching network based on harmonic load-pull techniques. Finally, a synergistic design methodology to deal with bandwidth extension and back-off range improvement simultaneously will be explored in order to meet the practical demand of efficiently amplifying signal with ultra-high PAPR. By developing complete design theory for wideband Doherty PA with large back-off range, this work will help to solve some critical technical challenges faced by the Doherty PA and is therefore believed to have great scientific worthiness and application prospect.