基于步长优化的改进功放非线性失真补偿算法  

Improved Compensation Alogrithm based on Optimal Step for Nonlinear Amplifier

作　　者：于坚[1] 黄天赠[1] 黄标[1] 张子平[2] YU Jian HUANG Tian-zeng HUANG Biao ZHANG Zi-ping(PLA Unit 73683, Fuzhou Fujian 350003, China College of Communication Engineering, PLA University of Science and Technology, Nanjing Jiangsu 210007, China)

机构地区：[1]中国人民解放军73683部队 [2]解放军理工大学通信工程学院

出　　处：《通信技术》2017年第4期636-640,共5页Communications Technology

摘　　要：随着无线通信的迅猛发展,频谱资源紧张和功放功率效率低等问题亟待解决。虽然采用高阶调制方式可以缓解资源紧张问题,但信号通过功放时会产生非线性失真,严重影响通信质量。由于数字信号处理(DSP)技术的高速发展,基带自适应数字预失真补偿技术成为了实现功放线性化最有效的方式之一。于是,提出了一种基于步长优化的改进LMS自适应功放预失真算法,其利用预失真前后星座图的EVM改善值作为优化目标函数,通过目标函数的最大化来确定LMS算法的最佳步长因子。以64QAM信号作为测试信号,建立功放无记忆非线性模型,并基于三阶无记忆多项式预失真模型和间接学习结构获取预失真器补偿参数。仿真结果表明,经过预失真补偿的星座图和功率谱带外再生得到了较好矫正,幅度和相位失真得到极大改善,系统线性化性能非常理想。With the rapid development of wireless communication techniques, the main limitations of wireless communications lie in spectrum resource constraints and nonlinearity of HAP （high amplifier power）. Albeit＇s exploration on high-order modulation improves the spectrum efficiency significantly, and however, the nonlinear distortion seriously degrades the performance,especially when nonlinearity-sensitive high-order non-constant envelop modulation signal passes through the saturate regime of HPA. For its good performance in linearization, adaptive baseband digital pre-distortion is widely developed and applied. And in particular, the optimization of the parameters for adaptive pre-distortion algorithm has a positive impact on linearization. In this paper, an improved algorithm is proposed to determine the optimum step by taking maximum error vector magnitude EVM improvement as the objective function. And thus the nonlinearity of power amplifier is compensated with indirect learning architecture and optimum step adaptive algorithm. Simulation results indicate that the constellations are well compensated and out-band power spectrum regenerations significantly suppressed, thus yieldin~ a fairly ideal system performance linearization.

关 键 词：功放非线性 记忆效应 预失真 间接学习结构 误差矢量幅度 

分 类 号：TN929.5[电子电信—通信与信息系统]