目标粗糙对合成孔径激光雷达回波的退相干效应

Decoherence effect of target roughness in synthetic aperture ladar

本文研究了目标表面粗糙对回波信号探测的影响,通过蒙特卡罗方法建立一维和二维目标高斯随机粗糙面模型,并对目标回波信号的探测过程进行仿真,研究目标表面粗糙对中频信号的影响.还进行了粗糙面和光滑面两组光外差探测实验,验证目标粗糙对合成孔径激光雷达回波信号严重的"退相干"效应.同时,采用数字波前分析仪对探测器处本振光和信号光波前分别进行检测,检测结果与仿真一致,证明粗糙面回波相位畸变严重.文中研究结果对设计光源参数、接收系统参数以及评估系统作用距离奠定基础,为合成孔径激光雷达系统设计提供定量参考.

Optical heterodyne detection is one of the key techniques for developing synthetic aperture ladar. The decoherence effect caused by the roughness of the target surface is particularly important for the practical use of the synthetic aperture ladar. The effect of the target surface roughness on the echo signal detection is discussed in the paper. One-dimensional and two-dimensional Gaussian random rough surface model are created by the use of the Monte Carlo method. The detection process of the target echo signal is simulated to study the effect of the target surface roughness on the intermediate frequency signal. And two optical heterodyne detection experiments are conducted in which the targets each include a rough surface and a smooth surface to verify the serious decoherence effect of the target roughness on the synthetic aperture laser radar echo signal. Meanwhile, the wavefronts of both the local oscillator and the signal beam are monitored at the position of the detector with a digital wavefront analyzer. The measured phase distribution accords well with the simulation result. It is shown that the phase of the echo signal from a rough surface has a serious distortion. The results obtained could be useful for designing the parameters of the laser source and the receiver, as well as for estimating the detection range of the ladar system.