Clutter Suppression for Wideband Radar STAP

Abstract

Space-time adaptive processing (STAP) has been known as a leading technique for airborne/spaceborne radar to detect ground slow-moving targets such as vehicles or tanks. Traditional STAP theory is based on the assumption of narrowband or "zero-bandwidth", where the decorrelation within the space-time snapshot is ignored. However, with radar bandwidths increasing, this assumption becomes invalid, due to the deteriorated decorrelation of the received signals within the space-time snapshot. The decorrelation directly causes the dispersion of the received signals in both spatial and temporal domains, leading to the spreading of the clutter spectrum in the twodimensional (2D) frequency (Doppler-spatial frequency) domain. With the spreading of the clutter spectrum, the clutter suppression notch in the traditional STAP methods is widened, resulting in a relative poor ability to detect slowmoving targets. In this paper, we focus on the clutter suppression for wideband radar STAP. A general signal model of the ground clutter is first established for the wideband array radar. Using this outcome, we analyze the influence of bandwidth on the 2D spectrum of the ground clutter and quantitatively describe the 2D spreading of the ground clutter on the Doppler-spatial frequency plane. Finally, a 2D keystone transform algorithm, referred to as space-time keystone transform (ST-KT), is proposed to eliminate the spreading of the ground clutter in the 2D frequency domain caused by increasing bandwidths. Simulation results demonstrate that the ST-KT improves the performance of wideband STAP (W-STAP) methods in terms of the output signal-to-clutter plus noise ratio (SCNR) of moving targets.