Abstract
Many present spaceborne synthetic aperture radar (SAR) systems are constrained to only two channels for ground moving target indication (GMTI). Along-track interferometry (ATI) technique is currently exploited to detect slowly moving targets and measure their radial velocity and azimuth real position. In this paper, based on the joint probability density function (PDF) of interferogram's phase and amplitude and the two hypotheses and clutter plus signal, several constant false alarm rate (CFAR) detection criteria are analyzed for their capabilities and limitations under low signal-to-clutter ratio (SCR) and low clutter-to-noise ratio (CNR) conditions. The CFAR detectors include one-step CFAR detector with interferometric phase, two-step CFAR detectors, and two-dimensional (2D) CFAR detector. The likelihood ratio test (LRT) based on the Neyman-Pearson (NP) criterion is exploited as an upper bound for the performance of the other CFAR detectors. Performance analyses demonstrate the superiority of the 2D CFAR techniques to detect dim slowly moving targets for spaceborne system.
Highlights
Many present spaceborne synthetic aperture radar (SAR) systems, such as TerraSAR-X and RADARSAT-2, are constrained to two channels to detect slowly moving targets on the ground
Along-track interferometry (ATI) technique exploits the interferogram of the two channel SAR images to perform moving target detection, radial velocity measurement, and azimuth relocation
In this paper, based on the joint probability density function (PDF) of interferogram’s phase and amplitude and the two hypotheses “clutter” and “clutter plus signal”, several constant false alarm rate (CFAR) detection criteria are analyzed for their capabilities and limitations under low signal-to-clutter ratio (SCR) and low clutter-to-noise ratio (CNR) conditions
Summary
Many present spaceborne synthetic aperture radar (SAR) systems, such as TerraSAR-X and RADARSAT-2, are constrained to two channels to detect slowly moving targets on the ground. In this paper, based on the joint probability density function (PDF) of interferogram’s phase and amplitude and the two hypotheses “clutter” and “clutter plus signal”, several constant false alarm rate (CFAR) detection criteria are analyzed for their capabilities and limitations under low signal-to-clutter ratio (SCR) and low clutter-to-noise ratio (CNR) conditions. Some realistic assumptions are described as follows: (i) Gaussian distributed stationary clutter which is validated over homogeneous agricultural and natural areas [1]; (ii) moving target is modeled as point target of Swerling 0 case with a constant velocity; (iii) magnitude and phase errors caused by mismatched SAR processing or channel unbalance have been eliminated prior to the detection; (iv) the SAR resolution cell is larger than the target size that contains both clutter and moving target; (v) the definitions of SCR and CNR are proposed in [6], which are different from traditional definitions used in GMTI. Numerical integration can be used to calculate the theoretical PDF of phase or magnitude
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