Full-waveform modeling of ground-coupled GPR antennas for wave propagation in multilayered media: The problem solved?

We propose a full-waveform approach for modeling time and frequency domain, off-ground and on-ground radars for wave propagation in multilayered media. The radar antennas are modeled using an equivalent set of infinitesimal electric dipoles placed over the antenna aperture. The linear relations between the fields in the transmission line, the sources, and the backscattered fields over the antenna aperture are expressed in terms of frequency dependent, global reflection and transmission coefficients, which are characteristic to the antenna. The interactions between the antenna and the layered medium are thereby accounted for. Far-field and near-field measurements are used to determine these antenna coefficients. The fields over the antenna aperture are calculated using three-dimensional Green´s functions. We validated the approach using measurements with a 900 MHz centre frequency transmitting and receiving antenna situated at different heights above a copper plane. For heights larger than the antenna, a single point source and receiver was sufficient for accurately modeling the radar data. For smaller distances, using six sources and receivers provided remarkably good results. Although some simplifications were made in this paper, the proposed method shows great promise for characterizing multilayered media using full-waveform inversion, with very limited computation time compared to numerical methods.