Subaperture Approach Based on Azimuth-Dependent Range Cell Migration Correction and Azimuth Focusing Parameter Equalization for Maneuvering High-Squint-Mode SAR

The challenge in the imaging of high-squint-mode synthetic aperture radar (SAR) mounted on maneuvering platforms is the azimuth dependence of both the range migration and the azimuth focusing parameters (the azimuth frequency-modulation rate and higher order coefficients), which are caused by range walk correction and acceleration. In order to accommodate the dependence, a modified subaperture imaging algorithm is proposed. Based on the fact that the azimuth times corresponding to the same Doppler frequency are different for targets in the same range gate, after making blocks in the azimuth frequency domain, the azimuth-dependent range cell migration correction is performed in the azimuth time domain for each block. Considering that the regions of support in the azimuth frequency domain are different for targets in the same range gate, the equalization of the azimuth focusing parameters is achieved by a new azimuth nonlinear chirp scaling method in the azimuth frequency domain. In order to verify the effectiveness of the proposed algorithm, the simulation of a point target array is presented. Furthermore, the real SAR data with a squint angle of 70° are processed, and high-quality images with a resolution of 1 m are provided.