Estimation of Soil Permittivity in Presence of Antenna-Soil Interactions

This work deals with a technique for estimating the soil permittivity starting from Ground-Penetrating-Radar (GPR) measurements collected under a reflection mode single view (one transmitting antenna) multistatic (plurality of receivers) configuration. The technique consists of two steps: i) first the soil Fresnel reflection coefficient is estimated; ii) then the soil electromagnetic parameters are inferred from the retrieved reflection coefficient. In real scenarios, the transmitting antenna couples with the soil as it is in close proximity of the air-soil interface so that mutual interactions arise. Accordingly, the transmitting antenna plane-wave spectrum depends on the electromagnetic properties of the medium under investigation. This strongly complicates the problem as the first step becomes a non-linear inverse problem. To overcome such a drawback, a pre-processing stage consisting of a suitable time gating procedure is here introduced. This allows to restore linearity of the Fresnel coefficient estimation. Moreover, it is also able to mitigate negative effect due to not matched transmitting antenna. Numerical examples are presented to assess the feasibility of the proposed technique.