基于导航卫星辐射源的双基前视SAR成像方法研究

Bistatic Forward-Looking Synthetic Aperture Radar with GNSS illuminator (GNSS-BFSAR) is a novel radar technique in which the transmitters and receiver are placed on GNSS satellites and Unmanned Aerial Vehicles, respectively. GNSS-BFSAR is of great importance in the applications of remote sensing, such as aircraft autonomous navigation and autonomous landing. However, because of the velocity difference between the transmitter and receiver, the transmitter’s trajectory curvature and the receiver’s forward-looking mode, the echo has two-dimensional nonlinear spatial variation. Hence, the existed imaging methods cannot be applied in GNSS-BFSAR directly. Focusing on the fundamental problems in GNSS-BFSAR imaging, this project will study the imaging methods of GNSS-BFSAR. By building the resolution and echo model and introducing some theories and methods, such as Keystone-extended nonlinear chirp scaling, a breakthrough in the key technologies including azimuth parameter equalization will be achieved. All these work will lay theoretical and technical basis for promoting the development and application of GNSS-BFSAR. The research of this project is of great significance, since it can improve the fundamental research levels and the innovational abilities of our country in bistatic SAR imaging.

基于导航卫星辐射源的双基前视合成孔径雷达（Bistatic Forward-Looking SAR with GNSS illuminator,简写GNSS-BFSAR），是一种利用GNSS卫星作为发射站，接收站安装于无人机等低载荷飞行器上进行前视成像的新体制雷达，在飞行器自主导航、自主着陆等领域具有重要的应用价值。然而，由于GNSS-BFSAR收发站的运动速度差异、发射站轨道弯曲及接收站前视工作，其回波具有二维非线性空变特性，现有的成像方法不再适用。本项目将围绕GNSS-BFSAR成像的基础问题，开展空间结构建模、回波建模与特性分析、成像算法等研究工作，引入Keystone-方位扩展非线性CS等方法，突破方位信号空变多项式参数一致均衡等关键技术，并进行仿真验证。本项目的研究可以提高我国在双基SAR成像方面的基础研究水平和自主创新能力，具有重要的科学意义。

本项目围绕基于导航卫星辐射源的双基前视合成孔径雷达（Bistatic Forward-Looking SAR with GNSS illuminator,简写GNSS-BFSAR）成像难题，首先分析了GNSS-BFSAR系统的信号特性与成像可行性，建立了空间分辨率模型。提出了一种基于最小分辨单元面积的最优空间成像几何模型设计方法，解决多源条件下的辐射源选择问题；然后建立了GNSS-BFSAR 的回波模型，并分析其回波特性，包括距离徙动、多普勒、空变特性，为成像算法设计奠定了理论基础；最后，提出了一种基于Keystone 变换和方位扩展非线性CS 的成像算法，解决GNSS-BFSAR 回波数据大徙动、强耦合及二维非线性空变的问题，可使机载接收平台获得前视区域高分辨图像。..本项目的研究成果可使飞行器具备前视成像能力，在飞行器自主导航、自主着陆等领域具有重要的应用价值，有助于提高我国在双基SAR成像方面的基础研究水平和自主创新能力。