适用于QAM信号的方形判决超指数迭代盲均衡算法

Square contour decision-based super-exponential iteration blind equalization for QAM signals

针对超指数迭代判决反馈(Super-Exponential Iteration Decision Feedback Equalization,SEI-DFE)盲均衡算法在水声通信系统中表现出的收敛性差的问题,提出了一种基于正方形判决的修正超指数迭代判决反馈盲均衡算法。该算法在修正超指数算法的基础上,引入判决正方形机制分别对输出信号的同相分量和正交分量进行均衡,以进一步提高相位补偿能力;在判决反馈均衡器中引入二阶数字锁相环,实现对相位旋转的跟踪和补偿。消声水池实验采用16QAM调制信号,从滤波器阶数、步长以及Q矩阵大小三个方面对算法的影响来验证算法的误码率性能,结果表明,新算法的误码率相比修正超指数迭代判决反馈(Modified Super-Exponential Iteration Decision Feedback Equalization,MSEI-DFE)算法改善了两个量级,实现了对相位旋转的有效补偿,大大改善了载波恢复性能。

A modified super-exponential iteration decision feedback blind equalization algorithm based on square con- tour decision （SDMSEI-DFE-2DPLL） is proposed, in order to solve the problem about the ill convergence performance of super-exponential iteration decision feedback algorithna in underwater acoustic communication system. Firstly, based on modified super-exponential iteration algorithm, equalization of the in-phase and quadrature components of output signals are implemented by square contour decision to improve phase compensation ability. At the same time, a second order digital phase-locked loop is introduced in order to track and compensate phase rotation. Experiments are carried out by using 16QAM modulation signals in anechoic tank to verify the performance of algorithms in terms of bit error rate （BER） by comparing the influences caused by filter weight vector length, step size and Q matrix size. The results show that the BER of the proposed algorithm is better than that of the MSEI-DFE algorithm by two magnitudes, and the phase rotation can be compensated and the carrier recovery ability is improved very weU.