Migration through range cells compensation and ISAR imaging for maneuvering target

Maneuvering target will generate nonlinear migration through range cells (MTRC) and high-order phase term, which make inverse synthetic aperture radar image obtained by range-Doppler algorithm severely defocused in azimuth domain. A rotational motion estimation method is proposed to eliminate the high-order phase term and nonlinear MTRC, which greatly improves the computational efficiency. Frequency axis reversal transform is applied to directly compensate the range migration and Radon-nonuniform fractional Fourier transform is proposed to estimate the rough motion parameter. Then, the search algorithm-based minimizing entropy is used to obtained fine estimation. Based on the two steps, the parameter can be estimated quickly and accurately. Then, resampling and Keystone transform are used to eliminate the high-order phase term and nonlinear MTRC. Finally, focused image can be obtained by performing Fourier transform along the slow-time dimension. Experimental results based on simulated and real data show the effectiveness and computational efficiency of the proposed algorithm. (C) 2021 Society of Photo-Optical Instrumentation Engineers (SPIE)