A Fast BP Imaging Method For Highly Squint Spaceborne SAR Imaging Based On Non-Orthogonal Affine Coordinate System

Spaceborne SAR high squint and high resolution (HSHR) imaging is a key research topic at present, and there are many difficult problems to be solved. Firstly, the two-dimensional resolution is seriously coupled under high squint, and the traditional method cannot accurately characterize the two-dimensional resolution. Secondly, the imaging time of HSHR imaging is long and the orbit bending is serious, which leads to the complex space-varying characteristics of the signal and is difficult to deal with. In view of the above problems, this paper establishes a non-orthogonal affine coordinate system to ensure that the two-dimensional spectrum of the image is orthogonal and non-tilted. Aiming at the difficulty of imaging, a fast BP algorithm based on non-orthogonal affine coordinate system is proposed. A two-step wavenumber spectrum compression method is proposed to realize the Non-aliasing of sub-aperture BP image spectrum, which ensures that the sub-aperture image can be synthesized directly. Aiming at the problem of image geometric distortion in non-orthogonal affine coordinate system, a two-step geometric correction method is proposed. Finally, through simulation experiments, it is proved that the proposed algorithm is more suitable for HSHR imaging than the algorithm in Cartesian coordinate system.