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 optical communication system，a scheme of atmospheric turbulence compensation based on mode diversity combined with MRC ( Maximum Ratio Combining) algorithm is proposed． Different modes are used as independent channels for spatial diversity reception，and the maximum ratio combining algorithm is used to realize the diversity and union of multi-mode channels． In the aspect of MRC algorithm implementation，the phase and signal-to-noise ratio measurement in different branch weighting coefficients are transformed into the same frequency and phase adjustment in digital domain and the calculation of signal-to-noise ratio weight coefficients，which simplifies the hardware implementation difficulty． Applying VPItransmissionMaker simulation platform and combining with Matlab programming，a simulation system is built to verify the feasibility of this method． The simulation results show that this method can compensate the effect of atmospheric turbulence on the performance of air-optical communication system，and the compensation effect for strong turbulence is slightly better than that for weak turbulence． The more the number of mode diversity，the better the compensation effect．