Open-loop memory polynomial pre-distorter based on look-up table
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摘要: 提出了一种基于查表的开环记忆多项式模型(MPM,Memory Polynomial Model)预失真器.从MPM预失真器系数估计和执行信号预失真处理两方面加以考虑.首先,利用预失真器和高功率放大器(HPA,High Power Amplifier)传输特性的互补性,由采集到的HPA输入、输出基带数据进行单次最小二乘估计得到MPM预失真器的系数,避免了以往递归结构的收敛性和计算量大等问题.然后,利用MPM预失真器的特点,建立了基于输入信号强度索引的一维向量表,通过查表实现MPM预失真器的幂次累加项,极大地减少了实现预失真器所需的计算量及硬件开销.仿真显示,采用提出的预失真器可以有效补偿HPA对信号的记忆非线性失真,有效带宽内获得了近20 dB的功率改善,也显著改善了系统误码性能.Abstract: An open-loop memory polynomial pre-distorter based on look-up table was proposed. Both memory polynomial model(MPM) pre-distorter coefficient estimates and the implementation of signal pre-distortion processing were considered. First, with the complementarity on the transmission characteristics for pre-distorter and high power amplifier(HPA), the memory polynomial coefficient was extracted by using once least squares algorithm using sampling input and output signal of power amplifier. Therefore our scheme eliminates convergence issue and reduce calculated amount in iterative architecture which emerged in traditional pre-distorters. And then, by analyzing the feature of memory polynomial pre-distorter, one-dimensional vector table look-up was established, which based on look-up the index of amplitude of input signal. With power-accumulate operations in MPM pre-distorter was implemented through the look-up table, dramatically reduce the cost of computing and hardware for implementing pre-distorter. The simulation results show that, the proposed pre-distorter can effectively compensate memory nonlinearity distortion of system due to high-power amplifier, and the power spectrum characteristics improves approximately 20 dB in the valid bandwidth. Therefore, our scheme can dramatically improve the system bit error rate performance.
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