关键词: 水声通信, 盲均衡, 超指数, 判决反馈, 相位旋转, 数字锁相环

Abstract:

An improved super-exponential iteration decision feedback blind equalization algorithm with the second order digital phase-locked loop (NMSEI-DFE-2DPLL) is proposed in order to overcome the problem of the ill convergence performance of the super-exponential iteration decision feedback algorithm in the underwater acoustic communication system. Based on the analysis of the modified super-exponential iteration error function, a new fast convergence error function is presented which increases carrier recovery ability; a second order digital phase-locked loop is introduced in decision feedback equalization to track and compensate phase rotation, carrying out the transmitted sequence recovery. Computer simulations of the new algorithm about convergence and carrier recovery ability are carried out respectively under two underwater acoustic channels, using two modulation signals. Simulation results demonstrate that the mean square error and convergence rate of the proposed algorithm have been improved to a large extent compared with the SEI-DFE algorithm in mixed phase channel environment, and the phase rotation has been compensated and carrier recovery ability has been improved greatly in channel environment with phase rotation.

Key words: underwater acoustic communication, blind equalization, super-exponential, decision feedback, phase rotation, digital phase-locked loop