微波高频段复杂海环境雷达杂波仿真与多普勒谱分析

This project will be focused on the research of the electromagnetic scattering from sea surface and the composite scattering from an electrically large moving ship-like targets at sea surface. The main purposes are to build an efficient simulator for the radar clutter from complex sea scene at high microwave frequencies, and to analyze the characteristics of the mean levels and Doppler spectra of the simulated radar echo, which might be useful and could provide physical explanations for the understanding of real experiment data. The main works of this project are in order as follows: First, based on the treatment of the facet-based scattering model, a model for fast evaluation on the complex reflection fuction of two-dimensional sea surface will be developed. The nonlinear relationship between the long and short components of sea waves will also be under consideration, in order to facilitate the facet model to the application to the simulation on sea clutter at higher microwave frequencies. Second, the capability and performance of the multi-path model, iterative physical optical method, and ray-tracing theory on coupling scattering calculations will be under careful examination, so as to find an efficient model for the analysis on the scattering contributions of coulping interaction between ship and sea surface. Third, with the long term goal of fast prediction on the electromagnetic composite scattering from the moving ship-like target at time-evolving sea surfaces, the research group will firstly examine the characteristics of the sea-keeping motions of typical ship models, then combine the aforementioned two models (facet-based sea scattering model and ship-sea coulping scattering model) to develop an efficient simulator of the radar return signals from the "fully dynamic" ship-sea scene at high microwave frequencies.

本项目将在系统研究海面电磁散射及其与电大尺寸船类目标复合散射问题的基础上，建立微波高频段动态海面散射模型和动态海面及其上方运动目标复合散射模型，从而实现微波高频段复杂海环境下雷达回波的快速仿真模拟。从理论角度进一步分析雷达回波幅度均值的分布规律及多普勒谱特性，为外场实测数据的理解提供参考依据和物理解释。本项目将从以下几个方面开展特色研究工作：其一，在小面元模型物理描述的基础上，拟建立二维海面复反射函数快速预估模型，同时考虑海浪大小两种尺度波成分之间的非线性作用，建立引入非线性效应影响的面元散射模型，以适应微波高频段海杂波模拟的需求；其二，考察多路径模型、迭代物理光学法以及射线追踪理论等三种高频方案的预估能力及精度，建立典型目标与海面之间耦合散射的有效分析模型；其三，拟采用六自由度船舶随浪运动模型研究典型船模的随浪运动特征，在此基础上建立"全动态"船海复合环境下雷达回波快速预估模型。

本项目针对微波高频段复杂海环境下雷达回波的快速仿真与规律分析等问题，重点研究了基于粗糙面统一散射理论的线性和非线性海面面元散射模型，分析了单纯海背景下海杂波的多普勒谱分布规律以及Kelvin尾迹散射特性。完成了粗糙海面介质样本制作及其散射特性测量实验，验证了面元散射模型的有效性。在目标与环境的耦合散射计算方面，本项目提出了一种基于海面面元散射模型的射线追踪一体化快速仿真模型，采用“半确定性”思路将海洋表面精细结构对雷达传感器的贡献以统计方式计入，大大提高了计算效率，并以此为基础分析了船海复合场景的机载成像雷达原始回波成像特性。考虑到动态海面水动力作用对船只姿态的影响，本项目基于高效率的二维切片理论，建立了任意船型的六自由度随浪运动模型。并完成了典型船体（s60系列船模）的六自由度随浪运动规律预估和分析。在此基础上结合已经完成的海面散射模型、六自由度随浪运动模型、耦合散射分析模型等，建立了接近真实海场景描述的三维“全动态”复杂海场景下雷达杂波模型，充分讨论了海上船类目标摇荡及平行运动对复合场景雷达回波幅度时变特性及多普勒谱特性的影响。. 本项目系统研究了微波高频段复杂海洋环境下的电磁散射计算问题，给出了高效的便于工程应用的海杂波模型、复合散射模型以及动态散射模型等，开发了复杂海环境雷达杂波可视化仿真和分析平台，有效支撑了雷达信号的模拟和回波计算，为超电大尺寸目标及其环境的电磁散射特性预估、海面目标雷达成像及识别、复杂海战场电磁态势模拟及对抗等相关应用领域提供技术基础和理论指导。