基于阶梯阻抗变换器的宽带功率放大器设计

Design of broadband power amplifier based on step impedance converter

为满足汽车EMC测试系统对功率放大器带宽和效率的要求,采用阶梯阻抗变换器的宽带匹配方法扩展其带宽,设计了一款在一个倍频程内拥有良好效率和增益平坦度的宽带功率放大器。该放大器选用GaN HEMT晶体管进行搭建,采用负载牵引的方法对各频点基波最佳阻抗进行提取,选择阶梯阻抗变换器方法设计匹配网络,最终其仿真的性能达到汽车EMC测试系统对带宽和效率的要求。测试结果表明,该放大器在1~2 GHz频段内,饱和输出功率为40.2~41.5 dBm,功率附加效率为50%~65%,增益大于15 dB,增益平坦度小于±1.5 dB。该功率放大器的性能表现良好,其中效率和增益平坦度具有一定优势,可为后续汽车EMC测试的宽带功率放大器设计提供参考。

To satisfy the requirement of bandwidth and efficiency of power amplifier in automobile EMC test system,a broadband power amplifier was proposed with high efficiency and good gain flatness in an octave-band.Wide bandwidth was achieved through wideband matching method of step impedance converter.Optimal fundamental impedance was extracted through load traction method,and the matching network was designed with step impedance converter.With GaN HEMT transistors,this power amplifier is suitable for automobile EMC test system.Measurements reveals that the amplifier has saturation output power of 40.2-41.5 dBm from 1 GHz to 2 GHz,additional power efficiency of 50%-65%,gain of more than 15 dB,and gain flatness of less than±1.5 dB.The proposed power amplifier has good characteristics particular in efficiency and gain flatness,which can provide reference for the design of wideband power amplifier of automobile EMC test system in the future.