SAR/ISAR REAL-TIME IMAGE PROCESSING FOR AIR ASW PLATFORMS

Three signal processing approaches are proposed here to better exploit the SAR/ISAR signal differences between sea surface noise clutter/speckle and periscope/other small manmade target signatures that have been used in previous algorithms. A special high-resolution, two-dimensional (2-D) spectral analysisapproach for creating the SAR/ISAR image, rather than using the traditional 2-D fast Fourier Transform (FFT), is demonstrated to significantly reduce clutter while sharpening the resolution of target signatures. After the radar image is formed, two other signal processing techniques can be used to enhance detection of small targets in the presence of image clutter. Polycorrelation techniques (specifically, the biocoherence) are shown to yield uniquely distinctive signatures between target-in-clutter regions and clutter-only regions of SAR imagery. Time-versus-frequency representation (TFR) signal processing techniques can better exploit the Doppler signature difference between targets and clutter, as demonstrated with helicopter radar data in this proposal.