针对传统Doherty放大器在提高效率后会恶化线性指标的关键问题进行了分析与讨论.提出了一种基于二次谐波注入((SHD的Doherty结构.采用GaN功率管CGH21240的仿真模型,设计了一款Doherty功率放大器.仿真结果显示,该放大器的效率在输出大于50 dBm后可以达到47%以上,比平衡式放大器改善约15%;三阶交调在输出为53 dBm时仍低于-30 dBc;在输出为50 dBm时,比未采用二次谐波注入改善约10 dBc.该放大器结构简单,且实现了效率和线性的同时改善.%The key problem that the traditional Doherty power amplifier's linearity index may turn to worse after efficiency improvement is analysed and discussed.A novel Doherty structure based on second harmonic injection (SHI) is presented.A Doherty power amplifier is designed based on ADS simulation model of GaN power device CGH21240.The efficiency of the amplifier is higher than 47％ when the output power is more than 50 dBm.That is, the efficiency is increased by about 15％in comparison with the balance AB amplifier.The third order IMD is lower than -30 dBc when the output power is 53 dBm,and is increased by about 10dBc in comparison with the amplifier which has no SHI when the output power is 50dBm.The structure of this amplifier is simple.Both efficiency and linearity of the amplifier are improved at the same time.
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