High-Resolution SAR Imaging Characteristics for Multiple Scattering of Rotating Targets

The rotation of targets in high-resolution synthetic aperture radar (SAR) images results in complex and nonlinear micro-Doppler modulation of SAR returns, exhibiting distinct and diverse imaging characteristics under different conditions. This poses challenges to image interpretation, target detection and recognition. This article establishes signal models for single and multiple scattering of rotating targets in high-resolution spaceborne SAR and, in conjunction with the processing procedures of range Doppler algorithm (RDA), derives the azimuth bandwidth and the conditions for azimuth frequency aliasing caused by rotation. Quantitative analysis of the errors introduced by target rotation in various signal domains is performed, taking into account the stationary phase point offset, the rotation-induced range migration correction error, and the change of azimuth phase in detail. In addition, representative signatures of these influences in SAR images are simulated and interpreted and more accurate theoretical models of imaging results are derived. The processing and analysis of both simulation and real measured data validate the correctness of the theoretical derivation in this study and provide support for the interpretation and information extraction of high-resolution SAR rotating targets.