一种场效应管预失真电路对改善行波管非线性的作用

Improvement of TWT Nonlinearity with a Field Effect Transistor Predistortion Circuit

该文利用场效应管的非线性作用,替代通常预失真线性化电路中的衰减器和移相器,使这种预失真器在相位扩张量变化较小的同时,可以对增益扩张量进行调节控制,有效提升了预失真电路改善行波管非线性的作用。实际设计电路实验表明,在频率为8.38-8.58 GHz和额定输入功率范围内,设计了实际电路并完成相应的实验,获得了6 dB和45o的增益和相位扩张以及15.4 dB的载波与交叉调制分量比值的改善。

In this paper,a Field Effect Transistor（FET） operating in close to cut off frequency is used to replace the attenuator and the phase-shifter in most TWT predistortion circuit,which can realize good control for the amount of gain expansion with little phase expansion variation.The experiments with practically designed circuit show that,in the frequency range of 8.38~8.58 GHz,about 6 dB gain expansion and 45 degrees phase shift can be compensated for the TWTA saturation response in input power dynamic range,and the improvement of about 15.4 dB Carrier to Intermodulation（C/IM） at TWTA Output Power Back Off（OPBO） of only-3 dB can be reached with the linearizer.