射频预失真是提高功率放大器线性度的一种有效手段,精确补偿放大器的非线性失真需保证幅度和相位补偿同时满足要求.针对Ka波段行波管放大器的线性化,提出一种新型射频预失真电路.该电路由前置、后置电平调节模块和基于矢量合成技术的非线性信号产生模块构成.改变两电平调节模块的增益,可实现补偿区间的调节;改变非线性信号产生模块中两支路的偏置电压,可实现预失真补偿量调节及幅度/相位的独立调节.将实际电路与配用Ka行波管联测,在输出功率回退6 dB时,行波管三阶互调系数提高约11.5 dBc.%The RF predistortion is an effective method to improve the linearity of High Power Amplifier (HPA).To obtain a better linearity of the HPA,accurate amplitude and phase compensation are required.A novel RF predistortion circuit is proposed for the linearization of a Ka-band Travelling Wave Tube Amplifier (TWTA),which consisted of a prepositive Variable Gain Amplifier (VGA),a post VGA and a nonlinear signal generating module based on vector synthesis technique.Changing the gain of the two VGAs can realize the adjustment of the compensation range.Reasonably changing the bias voltages of the two branches in nonlinear generating module can adjust the compensation amount and can also independently regulate the amplitude or phase characteristic.The Third Order Intermodulation (TOI) of a Ka-band TWTA is improved by 11.5 dB at 6dB output power back-off owing to the proposed RF predistortion linearizer.
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