横向沙丘表面电磁散射的时域有限差分法研究

空对地海目标的监测、识别是用电磁波与处于地海环境中的目标相互作用的散射和辐射来获取信息、制导和目标截获的，为了满足地海环境中目标的监测、识别的需要，首先要研究地海环境的电磁散射特性；应用指数型分布粗糙面模拟横向沙丘表面的高度起伏情况，采用蒙特卡罗方法模拟横向沙丘迎风坡、背风坡表面以及沙丘之间的平坦沙漠表面，使用Herkelrath提出的土壤湿度与介电常数的通用式计算沙土的介电常数，运用FDTD计算方法研究了横向沙丘的电磁散射特性，得到了散射系数的角分布曲线；数值计算了沙丘坡顶高度，沙丘迎风坡与背风坡坡底到坡顶的水平距离，沙丘坡顶间间距，入射角度以及沙土湿度对散射系数的影响；计算结果表明，沙丘坡顶高度、沙丘迎风坡坡底到坡顶的水平距离、沙丘坡顶间间距、入射角度和沙土湿度对散射系数的影响较大，而沙丘背风坡坡底到坡顶的水平距离对散射系数的影响较为复杂。

Study on Electromagnetic Scattering from the Surface of Transverse Dunes Using Finite Difference Time Domain Method

Electromagnetic scattering and propagation in natural environment plays important role for defense hitechnology, such as radar surveillance, missile guidance, and target tracking etc. In order to meet the needs of monitoring and identification of targets in the ground-sea environment, first, we must study the electromagnetic scattering characteristics of the earth and sea environment; use the exponential distribution rough surface to simulate the height fluctuations of the transverse dune surface, and use the Monte Carlo method to simulate the windward slope, leeward slope of the transverse dune and the flat desert surface between the dunes. The general formula of soil moisture and dielectric constant proposed by Herkelrath is used to calculate the dielectric constant of sand. The FDTD calculation method is used to study the electromagnetic scattering characteristics of the transverse dune, and the angular distribution curve of the scattering coefficient is obtained. The influence of the height of the top of the sand dune, the horizontal distance between the windward slope and the leeward slope bottom to the top of the sand dune, the distance between the top of the sand dune, the angle of incidence and the sand moisture on the scattering coefficient are numerically calculated. The calculation results show that the height of the top of the sand dune, the horizontal distance between the windward slope bottom and the top of the sand dune, the distance between the top of the sand dune, the incident angle and the sand soil humidity have great influence on the scattering coefficient. The horizontal distance from the bottom to the top of the leeward slope has a complex effect on the scattering coefficient.