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

Dong Li,Qinghua Liu,Haining Ma,Jia Su,Hongqing Liu,Chengxiang Zhang

doi:10.1109/access.2019.2930560

Abstract

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.

Highlights

Synthetic aperture radar (SAR) has been widely adopted in many fields of civil and military applications because it has the capacity to obtain high-resolution images regardless the weather condition, day and night [1]–[3]
range cell migration (RCM) CORRECTION BASED ON pseudopolar fast Fourier transform (PPFFT) In practice, since the motion of the moving targets is noncooperative, the target signal is usually buried in strong and complex airborne clutter, and high resolution imaging requires a long coherent integration time leading to large range curvature
Range walk correction results obtained by Keystone transform (KT), Radon transform (RT), and gradient feature method (GFM) are respectively depicted in Fig 7(c), Fig 7(d), and Fig 7(e)

Summary

Introduction

Synthetic aperture radar (SAR) has been widely adopted in many fields of civil and military applications because it has the capacity to obtain high-resolution images regardless the weather condition, day and night [1]–[3]. It is wellknown that longer synthetic aperture time produces high resolution images of ground moving targets, which is beneficial. It is important to accurately compensate RCM and DFM for obtaining the wellfocused moving target SAR image. The main components of RCM consist of range walk (i.e., linear RCM) and range curvature (i.e., quadratic RCM), and higher order components are assumed.

Methods

Results

Conclusion