基于模式分集的大气湍流补偿技术研究

针对空间光通信系统中大气湍流对系统性能影响较大的问题，提出了基于模式分集结合最大比合并( MRC: Maximum Ratio Combining) 算法的大气湍流补偿方案，采用不同模式作为独立信道进行空间分集接收，利用最大比合并算法实现多模式信道的分集合并。其中在最大比合并算法实现方面，把不同支路的信噪比测量问题转化为数字域的信噪比权重系数计算问题，简化了硬件实现难度。应用VPItransmissionMaker 仿真平台并结合Matlab 编程，搭建仿真系统，验证了该方法的有效性。仿真结果表明，该方法能很好地补偿大气湍流对空间光通信系统性能的影响，而且对强湍流的补偿效果略好于弱湍流，模式分集数量越多，补偿效果越好。

Simulation of Atmospheric Turbulence Compensation System Based on Mode Division Multiplexing

Aiming at the great influence of atmospheric turbulence on the performance of space opticalcommunication system，a scheme of atmospheric turbulence compensation based on mode diversity combined withMRC ( Maximum Ratio Combining) algorithm is proposed． Different modes are used as independent channels forspatial diversity reception，and the maximum ratio combining algorithm is used to realize the diversity and unionof multi-mode channels． In the aspect of MRC algorithm implementation，the phase and signal-to-noise ratiomeasurement in different branch weighting coefficients are transformed into the same frequency and phaseadjustment in digital domain and the calculation of signal-to-noise ratio weight coefficients，which simplifies thehardware implementation difficulty． Applying VPItransmissionMaker simulation platform and combining withMatlab programming，a simulation system is built to verify the feasibility of this method． The simulation resultsshow that this method can compensate the effect of atmospheric turbulence on the performance of air-opticalcommunication system，and the compensation effect for strong turbulence is slightly better than that for weakturbulence． The more the number of mode diversity，the better the compensation effect．