30 April 2018 Backscattering stripmapped synthetic aperture air acoustic array experiments for imaging a ground canonical target through a hexagonal rod array of clutter
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Abstract
There is interest in imaging ground target threats that are hidden in vegetation, straw grass, and foliage. In some instances, radar signals cannot penetrate through the “clutter.” Long wavelength sound waves might be capable of penetrating through the clutter so that the target can be acoustically detected and imaged. We study sound scattering by a canonical target “model disk” (aluminum, 4 inches diameter x 0.75 inch thick) in the presence of clutter. The clutter is modeled by a vertical hexagonal array of slender stainless steel rods that have an overall diameter D = 8 cm. The individual rods (diameter d = 0.089 cm, length L = 91 cm) are aligned and supported by two perforated thin (thickness = 1.8 mm) circular aluminum plates of diameter = 10 cm. Results for received backscattered tone burst echoes (at a frequency of 25.8 kHz) show that it is possible to detect the details of the target disk in the presence of a twodimensional circularly shaped cluster of rigid cylinders in air (representing clutter). The disk and “model” clutter targets were then taken out of the laboratory environment to an outdoor test site where the High Bandwidth Acoustic Detection System (HBADS) [developed by the US Army’s Night Vision and Electronic Sensors Directorate] performed an acoustic imaging experiment on the target-clutter and mechanical rigging apparatus. Using a linear frequency modulated LFM chirp pulse signal (2-15 kHz) driving a single speaker, echoes are detected by a 16 element microphone array while the HBADS vehicle is traveling ~ 1 m/s along a road. The strip-mapped synthetic aperture acoustic array SAA can image certain features of the apparatus.
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Steven S. Bishop, Steven S. Bishop, Timothy R. Moore, Timothy R. Moore, Peter Gugino, Peter Gugino, Brett Smith, Brett Smith, Kathryn P. Kirkwood, Kathryn P. Kirkwood, Joshua R. Gong, Joshua R. Gong, Michael Kickbush, Michael Kickbush, Murray S. Korman, Murray S. Korman, } "Backscattering stripmapped synthetic aperture air acoustic array experiments for imaging a ground canonical target through a hexagonal rod array of clutter", Proc. SPIE 10628, Detection and Sensing of Mines, Explosive Objects, and Obscured Targets XXIII, 106281I (30 April 2018); doi: 10.1117/12.2307676; https://doi.org/10.1117/12.2307676
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