星载高分辨频率步进SAR成像技术

星载合成孔径雷达(SAR)是一种2维高分辨率微波成像雷达。它通过发射大带宽信号实现距离向高分辨，通过合成孔径技术实现方位向高分辨。随着人们对分辨率需求的不断提升，星载SAR正朝着分米级分辨率发展。一方面，受限于现有器件水平，可以通过频率步进技术实现大带宽信号发射，需要研究高精度子带拼接技术、子带间幅相误差对成像的影响与补偿技术；另一方面，受限于有限的波束宽度，可以使系统工作在聚束模式或滑聚模式实现长合成孔径，此时需研究轨道弯曲、“Stop-go”假设误差、电离层与对流层传输误差等非理想因素对成像的影响与补偿技术。因此，该文详细介绍了频率步进信号时序设计与子带拼接，研究星载高分辨率频率步进SAR成像算法与非理想因素补偿方法，最后给出成像算法的仿真验证和性能分析。 

Spaceborne High-resolution Stepped-frequency SAR Imaging Technology

Spaceborne Synthetic Aperture Radar (SAR) is a type of microwave imaging radar with 2D high resolution. This technological device achieves range high resolution by transmitting wideband signals and azimuth high resolution through the synthetic aperture approach. With the increasing demand for high-resolution imaging, the resolution of spaceborne SAR has moved toward the decimeter level. On the one hand, limited by the present hardware technology, achieving wideband signal transmission through stepped-frequency technology is necessary. In this case, we need to study high-precision bandwidth synthesis technology. The influence of slant range error and amplitude and phase error between sub-bands should be considered. On the other hand, due to limited beamwidth, the system needs to work in sliding spot mode to achieve a long synthetic aperture. In this case, we need to study the problem of imaging parameter variance caused by curved orbit, “Stop–go” error, and the influence of ionospheric and tropospheric transmission errors on imaging. To solve these problems, this paper introduces the principle of stepped-frequency signal design and bandwidth synthesis technology in detail. A time-domain algorithm and non-ideal factor compensation method are proposed for spaceborne high-resolution stepped-frequency SAR imaging. Finally, simulation verification and performance analysis of the imaging algorithm are conducted.