Extended Nonlinear Chirp Scaling Algorithm for High-Resolution Spaceborne SAR Data Processing

High-resolution spaceborne synthetic aperture radar (SAR) imaging faces significant challenges due to approximation errors in traditional signal models and algorithms. This paper proposes an extended nonlinear chirp scaling (ENCS) algorithm to address these limitations. The ENCS algorithm incorporates high-order phase filtering to compensate for cubic and quartic coupling terms and employs fourth-order nonlinear chirp scaling for differential range cell migration correction (RCMC), effectively mitigating range-variant effects caused by cubic coupling terms and velocity variations. Additionally, the algorithm integrates a two-step orbit compensation (OCO) to correct slant range deviations induced by orbital curvature, a compensation method for the fast-time and slow-time effects caused by the stop-and-go approximation (SAG), and a deramp operation to resolve Doppler spectrum aliasing in high-resolution scenarios. Simulation results demonstrate that the proposed ENCS algorithm achieves superior focusing performance compared to conventional methods. The algorithm's computational efficiency, requiring only fast Fourier transforms (FFT) and phase multiplications, further validates its practicality for high-resolution SAR data processing.