基于星载高速调制器的预失真算法研究

在卫星高速数传系统中，为满足高速率通信业务的需求，新型数字调制体制（如OFDM，M-QAM等）被越来越多地采用，但由此带来的功率放大器的非线性效应也日益严重，对解调器性能造成很大影响.传统的数字预失算法因其收敛速度慢和计算复杂度大的特点不适用于资源严格受限的星载高速数传系统.本文中提出了一种基于QR分解的递归最小二乘算法（QRD-RLS），对该算法进行了理论分析和性能仿真.相比传统的预失真算法，该算法具有稳态误差小、收敛速度快和计算复杂度低的优势.并基于该算法设计了带有预失真器的高速调制器结构，对16QAM信号的实测效果显示，基于QRD-RLS的预失真方案对失真信号补偿效果显著，误差向量幅度（EVM）从7.4%降低到2.5%，带外干扰抑制提升10 dB. 

Study on Predistortion Algorithm of Spaceborne High Rate Modulator

In order to meet the demand of high rate communication services in the spaceborne high rate data transmission system,the new digital modulation systems (such as OFDM, M-QAM, etc.) are increasingly used, but the resulting nonlinear effect of the power amplifier is also becoming more serious, which has a great impact on the performance of the demodulator. The traditional digital predistortion algorithm is not suitable for the spaceborne high rate data transmission system with strict resource limitation due to its slow convergence speed and higher computational complexity. In this study, a recursive least squares algorithm based on QR decomposition (QRD-RLS) was proposed. The theoretical analysis and performance simulation of the algorithm were carried out. Compared with the traditional predistortion algorithm, the algorithm has the advantages of small steady-state error, fast convergence speed and low computational complexity. Based on the algorithm, a high rate modulator structure with predistorter was designed. The test results of 16QAM signal show that the predistortion scheme based on QRD-RLS can provide a significant compensation effect on the distortion signal, and the error vector magnitude (EVM) can be reduced from 7.4% to 2.5%, the out of band interference suppression can be increased by 10 dB.