一种基于开路短截线相位补偿的模拟预失真电路

传统的单路并联式模拟预失真电路,其可调性不高,对功率放大器的三阶交调改善量也非常有限。为了解决上述问题,提出了一种能用开路短截线进行适当相位补偿的S 波段模拟预失真电路。该模拟预失真电路使用肖特基二极管产生三阶交调信号,通过改变开路短截线的长度,来调整基波信号与三阶交调信号的相位差,使它的特性跟功率放大器的特性相反,从而抵消功放的三阶交调信号。实验结果表明,在3.5 GHz 的AB 类功放的1 dB压缩点处,加模拟预失真电路后,三阶交调量改善了约34 dB。

Analog Pre-distortion Circuit Using the Phase Compensation of the Open Stub

The traditional single parallel analog pre-distortion circuit has low adjustability and it is limited to improve the third-order intermodulation (IMD3) of the power amplifier. In order to solve the above problems, this paper presents an S-band analog predistortion circuit,which can effectively compensate the phase distortion using the open stub. The analog predistortion circuit can adjust the phase difference between the fundamental signal and the IMD3 signal generated by the Schottky diode. Consequently, the characteristics of the analog predistortion circuit are opposite to that of the power amplifier, thus the IMD3 signal of the power amplifier can be reduced. Experimental results show that using the analog predistortion circuit, the IMD3 has been reduced over 34 dB at the 1dB of the 3.5 GHz class AB power amplifier.