A modified spaceborne high-squint SAR imaging algorithm based on azimuth nonlinear chirp scaling

To process the spaceborne high-squint SAR data, the linear range cell migration correction (LRCMC) is conducted firstly. Although the target linear range cell migration (LRCM) is removed and the range-azimuth coupling of two-dimensional spectrum is reduced through LRCMC, it also causes the azimuth spatial variation of focusing parameters. The spatial variation of focusing parameters is caused by azimuth spatial variation of slant-range and equivalent velocity in spaceborne SAR system. However, the most existed imaging algorithms neglect the azimuth spatial-variant equivalent velocity, which will decrease the imaging quality. In this paper, the azimuth spatial variation of focusing parameters is analysed precisely. And a modified imaging algorithm based on azimuth nonlinear chirp scaling is proposed. Simulation of high-squint strip-map data verifies the accuracy of the proposed algorithm.