地海交界分区域复合粗糙面建模及电磁散射特性研究

研究了地海交界分区域复合粗糙面的建模方法及其电磁散射特性。采用蒙特卡罗方法建立地海交界分区域复合粗糙面模型,采用高斯谱模拟实际地面,采用变浅系数与北海联合海浪计划(joint north sea wave project, JONSWAP)谱结合而成的有限水深海谱模拟实际近海海面,基于分区域复合粗糙面建模理论,运用多种加权反正切函数处理实现了线型、月牙型、峡谷型自然环境。考虑了各介质区域内部的面元耦合以及区域之间和交界处面元的耦合作用,对地海交界分区域复合粗糙面的散射问题,提出了一种基于分区域面元的迭代物理光学法,采用快速远场近似（fast far field approximation, FaFFA）与局部耦合技术加速其迭代过程。对比了陆地粗糙面、海面和地海交界分区域复合粗糙面的电磁散射特性,计算了分区域复合粗糙面的散射系数,并讨论了极化方式、入射角、边界形状、陆地粗糙面的均方根高度、相关长度和近海海面的风速对地海交界分区域复合粗糙面电磁散射特性的影响。基于迭代物理光学法所获取的分区域复合粗糙面总散射场,采用正侧视条带式成像模式,选用距离多普勒算法对不同特点的地海分区域复合粗糙面进行合〖JP2〗成孔径雷达(synthetic aperture radar, SAR)成像,并讨论了陆地粗糙面与海面各自的相对介电常数对SAR成像的影响。该研究包括了地海交界环境的建模、电磁散射特性的求解及其SAR成像,由仿真结果得到了地海交界分区域复合粗糙面的SAR像特点,对反演地海交界环境的电磁特性以及遥感、探测具有借鉴意义。

Study on modeling and electromagnetic scattering characteristics of composite rough surface of ground and ocean in adjacent region

The modeling and electromagnetic scattering characteristics of composite rough surface of ground and ocean in adjacent region are studied. The Monte Carlo method is applied to construct composite rough surface of ground and ocean in adjacent region, Gauss spectral function is used to simulate actual ground surface, and joint north sea wave project （JONSWAP） spectral function which is combined with shallow coefficient is used to simulate actual near sea surface. Based on the theory of composite rough surface modeling, different weighted inverse tangent functions are presented to realize diverse actual environments, such as adjacent region with linear boundary, crescent boundary, and valley boundary. The couplings of facets in respective region and facets of region near borderline are considered, and an iterative physical optics (IPO) based on facets of composite rough surface of ground and sea in adjacent region is presented. The fast far field approximation (FaFFA) and partial coupling technology are applied to accelerate the process of IPO. The curves of bistatic scattering coefficient (BSC) of ground rough surface, sea surface and composite rough surface are compared. Electromagnetic scattering characteristics of composite rough surface are analyzed. The influences of polarization, incident angle, shape of borderline, root mean square (RMS) and correlation length of ground rough surface, wind velocity of sea surface on BSC are discussed. Based on the electromagnetic scattering field of composite rough surface which is calculated by IPO, the synthetic aperture radar (SAR) images of composite rough surfaces with special boundaries are obtained by the Rang-Doppler method with the stripmap mode. The influences of relative dielectric constants of ground rough surface and sea surface on SAR imaging are discussed. This research includes construction of an adjacent environment model, calculation of the electromagnetic scattering field, and application of SAR imaging technology. The simulation results show the characteristics of the SAR image of the composite rough surface, which can be a reference for detection, remote sensing and inversion of the electromagnetic characteristics of the environment of ground and sea in adjacent region.