超高分辨率方位多通道星载SAR虚假目标抑制方法研究

High-resolution and wide-swath spaceborne synthetic aperture radar (SAR) has been the key support area of the national high-resolution earth observation system major project and many national defense projects. Future spaceborne SAR missions will further require very-high resolution and wide-swath imaging capabilities for different applications. Multichannel in azimuth spaceborne SAR has been developed into one of the most important technical means to achieve high-resolution and wide-swath imaging of the earth, which has been testified by many in-orbit satellites. However, as the spatial resolution improving to the sub-meter level, long synthetic aperture time and ultra-wide band signal bring new challenges to the ambiguities suppression of multichannel spaceborne SAR. In response to these problems, this project plans to verify the classical multichannel signal reconstruction algorithm under the curved-orbit situation in the first place. Developing new channel mismatch calibration methods under ultra-wide band and wide beam situation will then be focused on. Thirdly, the project would propose a new method to suppress the residual ambiguities based on range spectra segmentation. An efficient and complete processing scheme for very-high resolution multichannel spaceborne SAR would be established as one of the most crucial results of this program at last. The research output of this project can be utilized on the development of the high quality factor multichannel spaceborne SAR in China. Additionally, it can provide theoretical and technical support for future multichannel in azimuth spaceborne SAR system.

高分辨率宽幅星载合成孔径雷达(SAR)是国家高分对地观测重大科技专项和国防型号重点支持领域。未来新一代空间对地观测应用将进一步推动超高分辨率宽幅星载SAR成像需求。方位多通道体制是实现高分宽幅微波成像的主流技术手段之一，并率先得到在轨SAR卫星验证。但是随着空间分辨率进一步向亚米级提升，长合成孔径时间和超宽带信号特点使高精度虚假目标抑制面临新的挑战。本项目将围绕我国未来新体制、多模式高分宽幅SAR卫星发展趋势，深入研究弯曲轨道模型下传统多通道信号重建方法的可行性与精确性；突破面向超宽带、宽波束方位多通道星载SAR的通道失配补偿技术，发展基于频带分割的图像域残余强散射虚假目标检测与抑制方法，建立高效完善的超高分辨率宽幅方位多通道星载SAR信号处理方案。本项目成果可服务于我国在研多型高品质因数多通道星载SAR研制，并为我国未来新体制方位多通道星载SAR研发提供理论参考和技术支撑。

方位多通道是目前工程应用最为广泛的高分辨率宽幅星载SAR成像技术，目前国际上已有多颗工作于条带模式的多通道SAR卫星在轨运行。面向更高分辨率宽幅星载SAR成像需求，本项目重点围绕多通道滑动聚束这一先进SAR体制，从通道一致性校正和非均匀采样重建两方面出发解决影响SAR图像质量的虚假目标问题。. 在基金支持下，本项目主要开展了以下四个方面的研究工作：1)高阶斜距模型多通道SAR信号非均匀采样重建：采用更加精确的改进等效斜视斜距模型分析了多通道星载SAR系统传递函数，针对经典非均匀采样重建算法的有效性和精确性开展了分析论证工作；2)方位多通道滑动聚束SAR通道一致性校正与非均匀采样重建：针对滑动聚束与多通道技术结合引入的复杂多普勒频谱混叠，以及波束方位扫描产生的空变相位失配等问题，详细分析了多种天线设计方案下多通道滑动聚束SAR成像处理算法；3)面向低信噪比多通道SAR数据通道误差校正：采用总体最小二乘和改进的子空间投影法，实现鲁棒的通道一致性校正；4)方位多通道滑动聚束SAR星/机载SAR试验验证：利用在轨的高分三号SAR卫星超精细条带和滑动聚束模式结合开展系统参数设计和在轨试验，获取了方位双通道滑动聚束星载SAR数据，对研究的算法进行了试验验证。. 项目执行期间，我国陆续发射了多颗条带模式方位多通道SAR卫星，本项目研究成果一方面可服务于在轨星载多通道SAR遥感图像处理性能优化和提升，另一方面可为我国在研的方位扫描多通道星载SAR系统设计与算法研发提供支撑。