基于GaN HEMT的高效率Doherty功率放大器设计

Design of High Efficiency Doherty Power Amplifier Based on GaN HEMT

通过分析传统Doherty功放的负载调制网络存在的带宽限制和晶体管输出电容对于效率的影响问题。利用改善阻抗变换比和补偿载波功放晶体管的输出电容的方法提出一种新型负载调制网络,使用GaN HEMT晶体管并基于此网络设计完成了一款高效率的Doherty功率放大器。该Doherty功率放大器采用不等分结构设计。此外,采用阶跃式阻抗匹配方法设计主辅功放的输入输出匹配网络来拓展Doherty功放的工作带宽。测试结果显示,在2.8~3.2 GHz频段内,饱和输出功率达到45 dBm,饱和漏极效率65%~73.18%。功率回退6 dB时,漏极效率在45%~50%之间,功率回退9 dB时,漏极效率在38.94%~44.68%之间。

This paper analyzes the bandwidth limitations of the traditional Doherty power amplifier’s load modulation network and the effect of transistor output capacitance on drain efficiency.A novel load modulation network is proposed by improving the impedance conversion ratio and compensating the output capacitance of the transistor.Based on this network,a high efficiency Doherty power amplifier is designed and fabricated.The Doherty power amplifier is designed in an unequal power structure.In addition,the step-impedance matching method is used to design the input and output matching network of the main and auxiliary amplifiers to expand the working bandwidth of the Doherty amplifier.The test results show that the saturated output power reaches 45 dBm and the saturated drain efficiency is 65%-73.18%in the 2.8-3.2 GHz band.When the power is backed off by 6 dB,the drain efficiency is between 45%-50%,and when the power is backed off by 9 dB,the drain efficiency is between 38.94%-44.68%.