Approximation-Free Elimination Method of First-Order Doppler Spatial Variance for Lateral Maneuvering SAR

For traditional frequency-domain synthetic aperture radar (SAR) algorithms, such as nonlinear chirp scaling (NCS), spatially variant Doppler phase that can be eliminated is limited by the number of undetermined coefficients. To solve this problem, an approximation-free elimination method for first-order spatial variance is proposed in this paper. In azimuth processing, the first partial derivative with respect to Doppler spatial variance is derived. Subsequently, resampling mapping relationship for slow time is constructed, which is capable of eliminating all first-order spatial variance of Doppler parameters at once. The proposed method does not employ any zero-padding, and the elimination effect of spatial variance is not limited by the number of undetermined coefficients. When lateral maneuverability of SAR sensor is high enough, the proposed method significantly outperforms traditional NCS method. Effectiveness of the proposed method is verified by simulation results.