A Full-Aperture Imaging Algorithm for High Resolution Spaceborne SAR Based on NCS

High-resolution spaceborne Synthetic Aperture Radar (SAR) imaging is constrained by curved orbits, Earth’s rotation, and the curvature of the Earth, leading to significant 2-D spatial variations, particularly in the azimuth dimension. Current approaches to high-resolution spaceborne SAR imaging primarily involve resampling, interpolation, and sub-aperture techniques. However, these methods tend to be computationally intensive and less efficient. Nonlinear Chirp Scaling (NCS) is a relatively effective method for addressing azimuth spatial variations, which could enable full-aperture processing without interpolation. This paper first introduces a two-step distance domain molecular band method that effectively removes range frequency spatial variations. Subsequently, a method combining time-frequency transformation/inverse transformation with NCS is proposed, which effectively eliminates 2-D spatial variations, particularly in the azimuth dimension. Finally, simulation experiments are conducted to validate the availability of this algorithm.