An Approach for Refocusing of Ground Moving Target Without Target Motion Parameter Estimation

Abstract

In synthetic aperture radar (SAR), long integration time may induce range migration and Doppler frequency migration of a received signal, which may degrade the SAR imaging performance of ground moving targets. Most of the conventional algorithms deal with the problems of range migration and Doppler frequency migration based on parameter searching. However, the exhaustive searching of target motion parameters may result in heavy computational burden. To avoid this problem, this paper proposes a new imaging method for ground moving targets without target motion parameter estimation. First, Keystone transform is applied to correct the range walk. Second, range curvature is compensated by the matched filtering function. Third, Doppler frequency migration is compensated via multiplying the data in range-and azimuth-time domains by its reversed conjugate data according to the equal interval sampling of the azimuth slow time, which avoids the searching procedure for target motion parameter estimation. Finally, the signal energy will be well accumulated in the range-Doppler domain, and thus, the moving targets can be efficiently recognized in the focused image. The major advantage of the proposed method is that it can obtain well-focused images of all targets in one processing step without target motion parameter estimation; thus, it is computationally efficient. Both simulated and real data processing results are used to validate the effectiveness of the proposed method.Index Terms-Doppler frequency migration, equal interval sampling, ground moving target indication (GMTI), Keystone transform, synthetic aperture radar (SAR).

Coherent Integration Algorithm for a Maneuvering Target Based on Frequency Spectrum Segment Processing

“…where * denotes the complex conjugation operation, t a is a lag variable and q denotes a constant time-delay. Unlike the PSIAF of LVD [15,Eq. (2)], the time variable t n , lag variable t a and the number of subband signal m coupled with each other in the exponential terms of (14).…”

“…(2)], the time variable t n , lag variable t a and the number of subband signal m coupled with each other in the exponential terms of (14). To remove the coupling of the first exponential term, the scaling operation is performed on t n for each t a and m. The scaling transform is defined as follows Substituting (15) into (14) yields…”

“…On the other hand, let N v2 be the searching number of the velocity ambiguity factor for KT-TRT. According to [15], the computational complexity of KT-TRT is about O 2N r N v2 N 2 . For SGRFT, let N v3 and N a3 denote the searching numbers of the velocity and the acceleration, respectively.…”

“…It is widely employed to correct the RM in synthetic aperture radar (SAR) imaging and long-time coherent integration [8][9][10][11][12][13][14]. Recently, a method based on keystone transform and time reversing transform (KT-TRT) was proposed for SAR imaging of ground moving targets, which is computationally efficient at the cost of serious performance loss in low SNR scenarios [15].…”

Moving Target Indication for Dual-Channel Circular SAR/GMTI Systems

“…Synthetic aperture radar (SAR) combined with ground moving target indication (GMTI) [1] technology has been extensively studied in remote sensing. The circular SAR (CSAR), which employs the long-time and multi-angle observation of a scene, has the potential for moving target detection (MTD) [2].…”