OFDM 系统功率放大器的自适应预失真线性化

对正交频分复用(OFDM)传输系统中大功率放大器的自适应预失真方法进行了研究。采用Wiener模型描述大功率放大器的输入输出关系, 该模型的结构是线性动态特性环节后级联一个无记忆的非线性静态单元,可以用一个复系数幂级数展开式来近似表示。为了补偿功率放大器的非线性失真, 用具有Hammer stein 结构的预失真器构成该功率放大器的逆系统, 并用递推最小二乘算法在线辨识预失真器的未知参数。该算法用于OFDM 系统时, 得到了一个快速的参数收敛特性。利用MATLAB 数值仿真考察了自适应预失真方法的有效性, 仿真结果表明,它可以有效实现从预失真器输入到功率放大器并实现输出的线性化

Linearization Technology of Adaptive Pre-Distortion for Power Amplifiers in OFDM Systems

In the orthogonal frequency division multiplexing(OFDM) transmission system,an adaptive pre-distortion method for high power amplifier(HPA) was studied.A Wiener model was adopted to describe the input-output relationship of HPA.In the model,a linear dynamic characteristic is followed by a memory-less nonlinear static element that can be approximated by using complex power series expression.In order to compensate the nonlinear distortion in the HPA,a pre-distorter(PD) that has a Hammerstein structure is constructed as an inverse system of the HPA.The unknown parameters of the PD were identified by RLS algorithm.The algorithm converges fast while it is applied to OFDM system.The effectiveness of the adaptive pre-distortion was observed in MATLAB simulation.The simulation results show that the adaptive pre-distortion can realize effectively the linearization from the input of PD to the HPA output.