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A new algorithm is presented to indicate ground moving targets in synthetic aperture radar (SAR) images. Two symmetric SAR images, one is referred to as a positive Doppler view and the other as a negative Doppler view, are generated by refocusing the positive Doppler plane and the negative Doppler plane, respectively. In the two Doppler views, the backgrounds have the same intensity except that their azimuth resolution becomes half of that of the original image, but the moving targets appear at different positions and have different intensities due to their different Doppler contents arising from nonzero Doppler centroid caused by across-track motion. Therefore, moving targets can be indicated by the patch-by-patch intensity comparison of the two Doppler views. The results of the simulated and real data confirm that this algorithm is effective and efficient.Index Terms-Ground moving target indication (GMTI), symmetric Doppler views, synthetic aperture radar (SAR). . Her current research interests include error correction techniques, communication signal processing, and resource allocation in cognitive sensor networks.

Abstract-In the ground moving target indication with synthetic aperture radar (SAR) community, algorithms used to estimate the velocity of a detected moving target are important because they are relative to the topics about refocusing and azimuth displacement correction. The velocity is regarded as a vector with two components, one in azimuth and one in range direction, and new algorithms aiming at estimating the two components are proposed and verified. The range velocity estimator transforms a detected patch containing a moving target to range Doppler domain by using the 1-D fast Fourier Transform in each range bin to achieve its range Doppler locus. The slope of the range Doppler locus is computed by using the Radon Transform on the range Doppler plane and the range velocity component is worked out according to radar system parameters and the slope value. Two estimators are proposed to compute the azimuth velocity component. One is based on symmetric defocusing in Doppler domain, the other is based on phase gradient in wave-number domain. Experiments confirm the effectiveness of the estimators by using simulated and field data.