An Efficient SAR Ground Moving Target Refocusing Method Based on PPFFT and Coherently Integrated CPF

The problem of ground moving target imaging and detection is difficult due to the large range cell migration (RCM) and time-varying Doppler frequency migration (DFM) in synthetic aperture radar (SAR) system. To finely refocus a moving target, motion parameters need be accurately estimated for compensating the RCM and DFM. In this work, an efficient ground moving target refocusing method based on pseudopolar fast Fourier transform (PPFFT) and coherently integrated cubic phase function (CICPF) is proposed without a priori knowledge of the motion parameters. First, based on the known radar platform motion parameters, the range curvature correction is completed, and then the range walk is corrected using the efficient PPFFT via estimating the slope of the range walk. In doing so, the energy of the moving target has been focused into the same range cell. Second, time-varying DFM parameters are obtained utilizing the proposed CICPF, and thus the well-focused result of the moving target is obtained. Compared with the existing methods, the proposed method has the advantages in computational complexity due to avoiding the searching and interpolation operation, and anti-noise performances thanks to fully exploiting the two-dimensional (2-D) coherently accumulation characteristics and the energy of all the scatterers in moving target for estimating motion parameters. Finally, both the simulated and real SAR data processing results are presented to validate the proposed method.