The Key Technology Of High Linearity And High Efficiency Power Amplifier

Efficiency and linearity are crucial characters in microwave power amplifiers.However,they are trade-off to each other.To this point,The most accepted method to raise them both is to enhance the efficiency of PA as high as possible while ignoring the linearity of itself first,and then add an additional pre-distortion circuit to enhance its output linearity.Typical analog pre-distortion technology is usually achieved in form of microwave hybrid integrated circuit(HMIC).For its shortcomings,this technology can not behave Satisfactorily in some special applications.Microwave monolithic integrated circuit(MMIC)is attractive for its advantatges in size,weight and cost.It is able to take the place of HMIC for pre-distortion circuit designing.This article centres on how to transplant analog pre-distortion technology from HMIC to MMIC.The main contents of this article are as follows.Based on 0.15?m GaAs pHEMT process,we discuss and summary a method to design a novel pHEMT balanced predistortor,which provides 6~8dB gain expanding and 30~40 degree phase suppress when working on 30GHz,and its VSWR is satisfactory in 29~31 GHz.Based on the same process,a linearizer driver module is designed in a 3.5×2.18mm~2 chip,The unit circuits include:the predistortor we have designed,two driver amplifiers and a pHEMT voltage-controlled attenuation.The gain of one driver amplifier is 17dB,the other is 26 dB.The power scale of attenuation that can be tuned is-25dB~-14d B.to the whole module,the least insertion loss is 4.5dB.Gain-controlled scale is 10dB.It provides 4~7 dB gain expanding and 40~50 degree phase suppress when working on 29.5~30.5GHz.