Near-range phase-based detection of small subsurface objects and characterization of local rough surfaces with bistatic wide-beamwidth antennas

A new multistatic phase-based GPR technique for precise characterization of rough surfaces in three-dimensional space and for ingenious detection of weak-contrast scattering objects buried beneath the air-ground interface is proposed. The technique has been tested by the data measured using wideband stepped-frequency GPR over the compound surface, which consists of flat surface, several small isolated areas of rough surfaces and areas with shallowly buried plastic objects as surrogate landmines. The maximum height of rough surfaces and the maximum depth of buried dielectric objects are made less than one practical range resolution cell. The buried objects have low dielectric contrast against their surrounding medium in the frequency range used in the measurements. The antennas adopted are broadband, have low gain and wide beamwidth. The results show good agreement with the actual distribution of the discrete scattering objects such as buried plastic M14 type mine (5 cm in diameter and 4.2 cm in height) and with the real shape of continuous scatterers (rough surfaces). Moreover a new spatial-based processing method is described for noise reduction and the measurement errors. The processed results show better accuracy and focusing patterns than those previously obtained. This technique neither requires a priori knowledge about the background medium nor needs any pure background measurement.