Buried target signature extraction from ground-penetrating radar signal: measurements and simulations

Ground-penetrating radar (GPR) proves to be a very valuable tool in the field of humanitarian demining, especially for the detection of plastic land-mines. Recently, a monostatic stepped-frequency continuous-wave (SFCW) GPR, together with a conceptual model of the radar-antenna-soil system, has been developed for the characterization of the electromagnetic parameters of soil, i.e. dielectric permittivity (epsilon), magnetic permeability (mu) and electric conductivity (sigma). This approach is extended here to the extraction of the GPR signal and to modelling the signatures of buried targets. The equivalence principle is used to decompose the GPR signal into its soil and target-in-soil components, as well as to model the radar-soil-target system. It permits the soil contribution to be subtracted from the total GPR signal to provide the signature of the buried target. This signature is compared to simulations. For a proof of the concept, the GPR return signal from a buried metal sphere has been simulated using the Method of Moments and it shows good agreement with its measured counterpart. We also have extracted clean frequency- and time-domain signatures of a PMN-2 plastic mine embedded in a multilayered medium, subject to various water contents. The method is also applied to a B-scan above a buried conducting cylinder. Finally, a study of the main sources of errors in the extraction of the signature of a buried target shows that mistakes in antenna height measurement lead to errors more important than those due to misestimating the relative dielectric permittivity of the soil.