含破碎波电大海面与目标高分辨复合散射建模及回波特征分析

In order to meet the demand of target detection, tracking and recognition for radar, this project aims to establish a composite scattering model from target and time-varying electrically large sea surface with breaking waves. First of all, the geometrical model of target is need to be accurately built. The scattering from target is calculated by using SBR and PTD method. Secondly, the sea surface is physically modeled and divided into breaking area and non-breaking areas according to the slope criterion. The scattering from non-breaking area is simulated by capillary wave modification which is based on two scale method. The scattering from breaking waves is solved by ray tracing method, which can capture the multiple interactions between the concave and convex parts of breaking wave. Then the couplings between the sea and target are captured by the idea of four-path model. The four-path model is modified by the slope modulation from complex sea. Based on the scattering model，this project also attempt to collect the scattering field. By calculating the decorrelation time, the distribution of echo amplitude and the Doppler spectra of time series under different sea states, incident angles, and radar resolution sizes, this project will analyze the characteristics of time series, especially the characteristics of “sea spikes”. This project attempt to provide theoretical foundations for real target detection and recognition in strong sea clutter background.

本项目以雷达在复杂海况下目标的探测、跟踪、识别的迫切需求为牵引，建立包含多个破碎波的电大尺寸海面时变几何模型，并对实际海上复杂目标进行精确几何建模；采用弹跳射线方法（SBR）并结合物理绕射理论（PTD）对目标的电磁散射进行求解；利用斜率判据判断仿真的海面上破碎波存在的位置，由此可将海面划分为破碎区域和非破碎区域，破碎区域局部采用射线追踪方法，非破碎区域海面采用基于双尺度方法的毛细波修正面元散射模型计算其散射场。海面与目标的耦合散射采用海上面元斜率调制的多路径思想求解。本项将先从含多个破碎波海面与目标复合散射特性着手，待夯实基础后，再过度到时变含破碎波复杂海面与目标复合散射回波时间序列研究，通过时间相关性分析，杂波幅度分布，多普勒谱等分析不同海情、不同雷达照射角度和分辨率时“海尖峰”干扰下复合散射回波特性的变化。为强杂波背景下，海上目标的探测，识别提供一定理论依据。

本项目以雷达在复杂海况下目标的探测、跟踪、识别的迫切需求为牵引，针对高海情高分辨情况下，海上微弱目标检测难的问题，以海洋流体力学为基础，根据N-S方程，建立含波浪破碎现象的时变海面与目标复合散射模型；采用基于双尺度的半确定面元法，SBR+PTD方法等计算了卷浪，含卷浪海面，含卷浪海面与目标电磁散射；并借助NVIDIA Optix 光线追踪引擎实现了射线追踪的算法加速，并额外实现了复杂结构材料目标的电磁散射特性建模；最后实现了含卷浪海面与目标复合散射回波时间序列的仿真，分析了含杂波海面回波特性，幅度分布，时频特性，多普勒谱等特征，给出了不同海情和雷达参数下回波特性的变化规律。本项目将为高海情高分辨下目标检测，杂波抑制，微弱目标检测和识别提供理论基础和技术支撑。