Microwave/radar sensors and techniques are widely used for detecting underground or subsurface targets inarcheology, geophysics, and civil engineering. Among existing microwave/radar sensors and techniques, syntheticaperture radar (SAR) imaging enables researchers and engineers to conduct surface and subsurface detection ofmetallic objects with improved detectability. The noncontact, remote sensing feature of SAR imaging provides asafer approach in a dangerous mission, such as demining. The objective of this paper is to investigate the depth(d) effect of a metallic object buried in dry sand. A steel disk specimen of 15-cm diameter was buried insidea box (sandbox) filled up with dry sand at various depths (d = 10 cm, 18 cm, and 26 cm) and scanned by a10-GHz SAR system. Three ranges (R = 15 cm, 30 cm, and 60 cm) between the SAR antenna and the sandboxwere also considered in this research. It was found that the SAR amplitude and its distribution decrease withthe increase of buried depth and the increase of range. Distribution of SAR amplitudes representing the buriedmetal disk specimen also changed with the increase of buried depth. Empirical models were also proposed forrange and depth eects of subsurface metallic objects in SAR images.
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