基于ADS平台不对称Doherty功率放大器的仿真设计

为在高线性的前提下提高WCDMA基站系统中功率放大器的效率,仿真设计了一款工作于2.14 GHz频段不对称功率驱动的Doherty功率放大器。基于ADS平台,采用MRF6S21140H LDMOS晶体管,通过优化载波放大器和峰值放大器的栅极偏置电压改善三阶互调失真(IMD3),同时通过调节输入功率分配比例改善由于峰值放大器对载波放大器牵引不足导致的失配问题,从而改善不对称Doherty功率放大器的输出性能。仿真结果表明,当载波放大器的栅极偏置电压为2.84 V,峰值放大器的栅极偏置电压为0.85 V并且输入功率比例为1:2.3,输出功率为44 dBm时其功率附加效率(PAE)为24.21%,IMD3为-44.46 dBc,和传统AB类平衡功率放大器相比PAE提高了8.58%,IMD3改善了6.98 dBc。

Design and simulation of asymmetric Doherty power amplifier based on ADS

A uneven power drive asymmetric Doherty power amplifier was designad,to improve efficiency and linearity at 2.14GHz WCDMA base-station system.This design used ADS simulation platform and MRF6S21140H LDMOS transistor.By optimizing gate bias voltage at carrier and peaking amplifier,the third-order intermodulation distortion was advanced.Meanwhile,it adjusted input power distributions to improved mismatch problem and advanced performance.This problem is caused by insufficient carrier amplifier’s impedance which pulled with peaking amplifier.The test result shows that,power-added efficiency is 24.21%,and the third-order intermodulation distortion is-44.46dBc,when the output power is 44dBm,the peaking amplifier gate bias voltage at 0.85V,carrier amplifier gate bias voltage at 2.84V,and using 1:2.3 uneven power drive to asymmetric Doherty power amplifier.The result verifies the asymmetric Doherty power amplifier perform with 8.58% higher power-added efficiency and 6.98dBc better third-order intermodulation distortion than the traditional balanced class-AB amplifier.