Impact of the antenna offset and the number of frequencies on layered media reconstruction using full-wave inversion in near-field conditions

Pipes and water leaks can potentially be detected using ground-penetrating radar (GPR). Recently, a new generalized model was developed to quantify the medium electrical properties by full-wave inverse modelling. It takes advantage of a closed form solution of Maxwell's equations for describing the coupled antenna-medium system. In this study, we used that model to evaluate the inverse problem for different radar configurations and various multilayered medium layouts. Numerical experiments were performed by generating and inverting synthetic Green's functions in order to show the influence of the antenna offset on the response surface topography of the objective functions. The impact of a reduced number of frequencies on these objective functions was also investigated for a monostatic configuration before combining this approach with a multioffset configuration. The results showed an improvement in the response surface topography when the number of antennas was increased. However, the importance of this enhancement varied according to the number of frequencies taken into account. It also pointed out the possibility of reducing the number of frequencies used for the inversion while preserving the information content. This work highlights the great potential of the model to improve the medium parameter retrieval while reducing the computation time.