Effect of antenna-medium coupling in the analysis of ground-penetrating radar data

Physically-based ground-penetrating radar (GPR) data processing is essential for quantitative characterization of soils and materials. A novel near-field GPR antenna model coupled with layered media Green's functions was used to investigate the effect of antenna-medium coupling in the analysis of GPR data. The radar antennas are modelled using an equivalent set of infinitesimal electric dipoles and characteristic, frequency-dependent, global reflection and transmission coefficients. These coefficients determine through plane wave decomposition, wave propagation between the radar reference plane, point sources and field points. We calibrated an actual commercial 400 MHz time-domain antenna, from which synthetic GPR data sets were generated. We observed that, depending on the model configuration, antenna effects may affect the topography of the objective function in full-waveform inverse problems. In addition, antenna-medium coupling has a significant impact on the medium surface reflection, whether in terms of amplitude or propagation time (which usually defines the so-called time zero). We also showed that an effective source cannot be used for simulating near-field radar data as the antenna-medium coupling strongly depends on medium properties. In this respect, numerical experiments demonstrated promising perspectives for simultaneous estimates of medium permittivity and conductivity from antenna-medium coupling