星地激光链路中光束发散角与跟瞄误差的最佳比值

 实际星地光通信系统的发射光束为高斯型的情况下，跟瞄误差和大气闪烁是星地激光链路中的主要信道噪声源。在结合两者对系统性能影响的前提下，对星地激光通信链路进行了理论分析和模型建立。基于该模型对星地激光链路中光束发散角与跟瞄误差之比的优化选择问题进行了研究。结果表明：对于上行链路，在不同误码率需求下都存在一个光束发散角与跟瞄误差的最佳比值，使得上行链路余量最大；对于下行链路，在不同误码率要求下均存在一个光束发散角与跟瞄误差的最佳比值，使得下行发射光功率的需求最小。利用最优化方法和最小二乘法拟合，得到星地激光链路中光束发散角与跟瞄误差的最佳比值和系统误码率的经验公式。

Optimum ratio of beam divergence angle to pointing error for satellite-ground laser link

The transmitter beam is Gaussian for real satellite-ground laser communication system.The pointing jitter and atmospheric scintillation are the main noise sources for satellite-ground laser link.The channel model of satellite-ground laser communication link is presented in presence of the effects of atmospheric scintillation and pointing jitter on the quality of communication.The problem of the optimum ratio of beam divergence angle to pointing error is analyzed.The results indicate that there is an optimum ratio of beam divergence angle to pointing error that maximizes the link margin for different requirement of bit error rate for uplink,and there is an optimum ratio of beam divergence angle to pointing error that minimizes the required transmitter power to satisfy the bit error rate.By the optimization method and the least-squares fit,an experimental formula of the optimum ratio of beam divergence angle and pointing error and bit error rate is proposed for satellite-ground laser link.