基于射线追踪的分层粗糙面电磁散射研究
发布时间：2018-08-17 18:34
【摘要】：随机粗糙面的电磁散射在微波遥感,目标探测与识别领域具有显著的学术价值和广泛的应用前景,而自然界中的地海面往往是双层或多层的,因此研究分层粗糙面的电磁散射具有十分重要的应用价值。本文推导了基尔霍夫近似下的一维及二维单层粗糙面的电磁散射及透射,利用射线追踪方法,研究了一维及二维分层粗糙面的电磁散射,并利用一维分层粗糙面电磁散射理论研究了覆盖雪层土壤面以及溢油海面的电磁散射。论文介绍了粗糙面的几何建模,使用线性滤波法模拟了不同统计参量下的一维粗糙面及二维粗糙面;从简谐波满足的亥姆霍兹方程出发,结合边界条件,求解了粗糙面的平均散射强度及透射强度,同时引入基尔霍夫近似,推导了不同极化方式下的散射场及透射场的积分表达式。将生成的一维粗糙面离散为一系列的线段,在远场近似条件下求解了每条线段中点处的平均反射强度和平均透射强度,利用能量守恒定律验证了基尔霍夫方法的正确性,数值计算并分析了粗糙面的粗糙度以及介质的介电常数对双站散射系数和透射系数的影响。论文将射线追踪算法引入到一维分层粗糙面的电磁散射求解当中,数值计算了波在分层介质中传播的入射点、反射点和透射点的位矢及各点之间的相位差,数值计算并分析了平面波入射时一维分层粗糙面的电磁散射随中间层及底层介质的介电常数,中间层介质厚度,粗糙面的粗糙度等的变化。结合土壤和雪的等效介电常数及其随湿度和频率的变化,数值计算并分析了覆有雪层土壤面的电磁散射随雪层及土壤面的粗糙度,土壤湿度及雪层厚度等的变化;利用修正的PM谱模拟覆有油膜的海面轮廓,考虑油膜厚度及风速的变化,对比了不同极化方式下修正海谱与原始海谱的双站散射,证明了修正海谱的有效性。论文将锥形波引入到基尔霍夫近似下的二维粗糙面散射中,推导了锥形波入射下的二维单层粗糙面电磁散射及透射,将生成的二维粗糙面离散为三角面元,求得每个面元中点处的散射场及透射场,数值计算并分析了均方根高度、相关长度、介电常数等对散射系数及透射系数的影响。介绍了应用于二维分层粗糙面的射线追踪方法,给出了反射射线、透射射线方向的判定方法,并介绍了一种射线与三角面元的快速相交测试方法。基于分层粗糙面的几何特性,提出了粗网格细网格法和可行区域搜索算法对射线追踪进行加速,数值计算并分析二维分层粗糙面的电磁散射随中间层以及底层介质的介电常数,中间介质层厚度及粗糙面的粗糙度等的变化。
[Abstract]:Electromagnetic scattering from random rough surfaces is of great academic value and wide application prospect in microwave remote sensing, target detection and recognition. Therefore, the study of electromagnetic scattering from stratified rough surfaces has very important application value. In this paper, the electromagnetic scattering and transmission of one-dimensional and two-dimensional single-layer rough surfaces under Kirchhoff approximation are derived. The electromagnetic scattering of one-dimensional and two-dimensional stratified rough surfaces is studied by means of ray tracing method. Based on the theory of electromagnetic scattering from one-dimensional stratified rough surface, the electromagnetic scattering of snow cover soil and oil spill surface is studied. In this paper, the geometric modeling of rough surface is introduced, and the linear filtering method is used to simulate the one-dimensional rough surface and two-dimensional rough surface under different statistical parameters, starting from the Helmholtz equation satisfied by the simple harmonic, combining with the boundary conditions, The average scattering intensity and transmission intensity of rough surface are solved, and the integral expressions of scattering field and transmission field under different polarization modes are derived by introducing Kirchhoff approximation. The generated one-dimensional rough surface is discretized into a series of line segments, and the mean reflection and transmission intensity at the midpoint of each line segment is solved under the condition of far-field approximation. The validity of Kirchhoff's method is verified by energy conservation law. The effects of roughness of rough surface and dielectric constant on bistatic scattering coefficient and transmission coefficient are numerically calculated and analyzed. In this paper, the ray-tracing algorithm is introduced to solve the electromagnetic scattering of one-dimensional stratified rough surface. The incident point, the potential vector of reflection point and transmission point and the phase difference between each point are numerically calculated. The variation of electromagnetic scattering of one-dimensional stratified rough surface with the dielectric constant, the thickness of the interlayer medium and the roughness of the rough surface are numerically calculated and analyzed when the plane wave is incident. Combined with the equivalent dielectric constant of soil and snow and its variation with moisture and frequency, the variation of electromagnetic scattering from snow covered soil surface with roughness of snow layer and soil surface, soil moisture and snow layer thickness was numerically calculated and analyzed. The modified PM spectrum is used to simulate the sea surface profile with oil film, considering the variation of oil film thickness and wind speed, the bistatic scattering between the modified sea spectrum and the original sea spectrum under different polarization modes is compared, and the effectiveness of the modified sea spectrum is proved. In this paper, the conical wave is introduced into the two-dimensional rough surface scattering under Kirchhoff approximation, and the electromagnetic scattering and transmission of the two-dimensional single-layer rough surface under the incidence of the conical wave are derived. The generated two-dimensional rough surface is discretized into a triangular plane element. The scattering and transmission fields at the midpoint of each plane are obtained. The effects of root mean square height, correlation length and dielectric constant on the scattering and transmission coefficients are numerically calculated and analyzed. The ray tracing method applied to two-dimensional stratified rough surface is introduced. The method of determining the direction of reflected ray and transmission ray is given, and a fast method for measuring the intersection of ray and triangular plane is introduced. Based on the geometric characteristics of layered rough surfaces, a coarse grid fine mesh method and a feasible region search algorithm are proposed to accelerate the ray tracing. The dielectric constants of the two-dimensional layered rough surfaces with the dielectric constant of the intermediate layer and the underlying medium are numerically calculated and analyzed. The variation of the thickness of the intermediate layer and the roughness of the rough surface.
【学位授予单位】：西安电子科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TN011
本文编号：2188526
[Abstract]:Electromagnetic scattering from random rough surfaces is of great academic value and wide application prospect in microwave remote sensing, target detection and recognition. Therefore, the study of electromagnetic scattering from stratified rough surfaces has very important application value. In this paper, the electromagnetic scattering and transmission of one-dimensional and two-dimensional single-layer rough surfaces under Kirchhoff approximation are derived. The electromagnetic scattering of one-dimensional and two-dimensional stratified rough surfaces is studied by means of ray tracing method. Based on the theory of electromagnetic scattering from one-dimensional stratified rough surface, the electromagnetic scattering of snow cover soil and oil spill surface is studied. In this paper, the geometric modeling of rough surface is introduced, and the linear filtering method is used to simulate the one-dimensional rough surface and two-dimensional rough surface under different statistical parameters, starting from the Helmholtz equation satisfied by the simple harmonic, combining with the boundary conditions, The average scattering intensity and transmission intensity of rough surface are solved, and the integral expressions of scattering field and transmission field under different polarization modes are derived by introducing Kirchhoff approximation. The generated one-dimensional rough surface is discretized into a series of line segments, and the mean reflection and transmission intensity at the midpoint of each line segment is solved under the condition of far-field approximation. The validity of Kirchhoff's method is verified by energy conservation law. The effects of roughness of rough surface and dielectric constant on bistatic scattering coefficient and transmission coefficient are numerically calculated and analyzed. In this paper, the ray-tracing algorithm is introduced to solve the electromagnetic scattering of one-dimensional stratified rough surface. The incident point, the potential vector of reflection point and transmission point and the phase difference between each point are numerically calculated. The variation of electromagnetic scattering of one-dimensional stratified rough surface with the dielectric constant, the thickness of the interlayer medium and the roughness of the rough surface are numerically calculated and analyzed when the plane wave is incident. Combined with the equivalent dielectric constant of soil and snow and its variation with moisture and frequency, the variation of electromagnetic scattering from snow covered soil surface with roughness of snow layer and soil surface, soil moisture and snow layer thickness was numerically calculated and analyzed. The modified PM spectrum is used to simulate the sea surface profile with oil film, considering the variation of oil film thickness and wind speed, the bistatic scattering between the modified sea spectrum and the original sea spectrum under different polarization modes is compared, and the effectiveness of the modified sea spectrum is proved. In this paper, the conical wave is introduced into the two-dimensional rough surface scattering under Kirchhoff approximation, and the electromagnetic scattering and transmission of the two-dimensional single-layer rough surface under the incidence of the conical wave are derived. The generated two-dimensional rough surface is discretized into a triangular plane element. The scattering and transmission fields at the midpoint of each plane are obtained. The effects of root mean square height, correlation length and dielectric constant on the scattering and transmission coefficients are numerically calculated and analyzed. The ray tracing method applied to two-dimensional stratified rough surface is introduced. The method of determining the direction of reflected ray and transmission ray is given, and a fast method for measuring the intersection of ray and triangular plane is introduced. Based on the geometric characteristics of layered rough surfaces, a coarse grid fine mesh method and a feasible region search algorithm are proposed to accelerate the ray tracing. The dielectric constants of the two-dimensional layered rough surfaces with the dielectric constant of the intermediate layer and the underlying medium are numerically calculated and analyzed. The variation of the thickness of the intermediate layer and the roughness of the rough surface.
【学位授予单位】：西安电子科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TN011
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