3D Target Localization Based on FrFT from Spaceborne Curve SAR

Synthetic aperture radar (SAR) three-dimensional (3D) imaging technology can reconstruct the complete structure of observed targets and has been a hot topic. Compared with tomographic SAR, array interferometric SAR, and circular SAR, curve SAR can use less data to achieve 3D positioning of targets. Most existing algorithms for estimating Doppler frequency modulation (FM) rate are based on sub aperture partitioning, resulting in low computational efficiency. To address this, this article establishes a target height estimation model, which reflects the relationship between the height and the residual Doppler FM rate for spaceborne curve SAR. Then, a fast SAR 3D localization processing flow based on fractional Fourier transform (FrFT) is proposed. Experimental verification demonstrates that this method can estimate the Doppler FM of the target column by column, and the 3D position error for non-overlapping targets is controlled within 1 m. For overlapping points with an intensity ratio greater than 1.5, the root mean square error (RMSE) of the estimation results is around 5 m. If the separation between overlapping points is greater than 35 m, the RMSE decreases to approximately 2 m.