基于点目标大气闪烁的目标回波分布研究

Investigation on the distribution of target echo based on point target atmospheric scintillation

激光在大气传输过程中受到大气湍流的随机扰动,使激光产生光强闪烁效应,影响激光成像雷达目标探测。为探究大气湍流对目标回波功率分布的影响,文中采用数值模拟手段对5 m×5 m灰色瓷砖进行湍流情况下激光成像雷达目标回波功率分布研究。基于FFT谱反演大气湍流相位屏构造方法、激光雷达方程及点目标闪烁孔径平滑理论的分析,对目标进行不同湍流强度下128×128像素在探测器之前的激光成像雷达目标回波分布仿真模拟;在目标距离为2 000 m情况下,大气折射率结构常数为2×10-16 m^(-2)/3~2×10-13 m^(-2)/3时,相对无湍流回波功率的归一化均方差为0.72~0.93,并获得实际大气折射率结构常数为3.32×10-16 m^(-2)/3,在实际条件下,目标在距离为500~2 000 m时,相对无湍流回波功率的归一化均方差为0.19~0.81。仿真实验结果表明,在强大气湍流及激光远距离传输条件下,考虑大气湍流影响的激光回波相对无湍流情况下的激光回波功率分布波动较大,湍流对激光成像雷达目标探测的影响不可忽略。

In the process of propagation in the atmosphere, the laser is randomly disturbed by atmospheric turbulence, which leads to the laser intensity scintillation effect, and influences imaging lidar＇s target detection. In order to explore the influence of atmospheric turbulence on the power distribution of target echo, in this paper, a numerical simulation method was used to investigate the target-echo power distribution caught by imaging lidar of 5 m×5 m gray ceramic tile in the situation of turbulence. Based on the FFT spectral inversion method which can construct atmospheric turbulence phase screens, lidar equation and the analyzing of the aperture smoothing theory on scintillation effect, the target echo, which is in front of the detector, caught by 128×128-pixel imaging lidar with different turbulence intensity was simulated; at the distance of 2000m, and the atmospheric refractive index structure constant is 2×10-16m-2/3- 2×10-13 m-2/3, the target echo-power normalized mean square deviation relative to which considered the situation of no turbulence was 0.72-0.93, and the actual atmospheric refractive index structure constant which is 3.32×10-16m-2/3 was obtained, under actual conditions, at the distance of 500-2 000m, the target echo-power normalized mean square deviation relative to which considered the situation of no turbulence was 0.19-0.81, Simulation experimental results show that, under the strong atmospheric turbulence and long-distance transmission conditions, considering the influence of atmospheric turbulence on the laser echo, the laser echo power distribution fluctuates larger relative to which not considering the influence of turbulence, so the influence of turbulence on imaging lidar target detection can＇t be ignored.