Wideband signals without pre-distortion will be distorted by memory with nonlinear effect when going through the high power amplifier. For compensating these distortions, we propose an adaptive pre-distorter method which is based on orthogonal polynomials. Based on the orthogonal criterion, a derivation method is put forward to get a series of orthogonal polynomials, and it is used to get the polynomials under circular symmetric complex Gaussian distribution. Indirect learning architecture and recursive least square algorithm are used for estimating the parameters of this orthogonal polynomials-based pre-distorter, and the iterative formula of the recursive least square is presented as well. In end of the paper we introduce two kinds of power amplifier models used in the simulation. The performances of the proposed pre-distorter is simulated in an OFDM system, results show that the proposed pre-distorter can effectively compensate the distortions produced by high power amplifier.%宽带信号未经补偿而通过高功率放大器,会产生有记忆的非线性失真.为了补偿这些失真,介绍了一种基于正交多项式的自适应预失真方法.基于正交化准则,提出正交多项式组的推导方法,并使用该方法得到循环对称复高斯分布下的正交多项式组.采用间接学习结构和递归最小二乘方法对这种基于正交多项式的预失真器系数进行求解,并给出递归最小二乘的迭代公式.最后介绍仿真所采用的两种功放模型,并使用所述的预失真方法对基于OFDM(Orthogonal Frequency Division Multiplexing)系统的预失真性能做了仿真.结果表明,该预失真方法能有效地补偿高功率放大器失真.
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