相干测风激光雷达望远镜孔径及截断因子的优化分析

Optimization analysis of telescope aperture and truncation factor of coherent LIDAR

基于相干多普勒测风激光雷达外差探测理论,给出自由空间和光纤耦合两种模式下外差效率的解析表达式,并通过参数替换使两者具有统一的形式;结合此表达式以及湍流环境下的信噪比公式,仿真给出了地基及星载相干测风激光雷达系统不同探测距离处的最优望远镜和截断因子。研究结果表明地基系统信噪比随着望远镜孔径变化比较陡峭,存在最优望远镜孔径和截断因子,如若取值不恰当,会造成系统信噪比巨大损失;而星载平台下回波信号的信噪比随着望远镜孔径先增加后保持平稳,望远镜孔径可以综合成本和信噪比进行合理取值,最优化的截断因子为80%。此研究对相干多普勒测风激光雷达探测理论的发展及系统器件的最优化配置提供了重要的理论依据。

Based on coherent Doppler LIDAR heterodyne detection theory, the heterodyne efficiency analytical expression under both free-space and fiber-coupled detect mode of the coaxial system were unified through the parameter substitution. Combined this formula with the signal-to-noise ratio under turbulent environment, the optimum values of the aperture and the truncation factor under different detection range were obtained for ground based and spaceborne system. The results show that the signal-to-noise ratio of the ground based LIDAR is relatively steep as the telescope aperture changes, the optimum truncation factor is 80% during the whole detect range, and if the aperture selected is not appropriate, it will cause losses of signal-to-noise huge in the system; For Spaceborne LIDAR the signal-to-noise ratio is first increased and then stable as the telescope aperture increased, the optimum telescope aperture can be balanced between the cost and signal-to-noise, and the optimum truncation factor is also 80%. The research has important theoretical significance and practical value both for the development of detection theory and optimal configuration of the coherent Doppler LIDAR.