Analytical Modelling of Ultra-Wide Band Ground Penetrating Radar for Characterization of Subsurface Media

Ground penetrating radar (GPR) is becoming an attractive sensor for quantitative reconstruction of subsurface media. The accuracy and time-efficiency of GPR detection largely depends on the inverse modelling scheme used. In most of the cases, both accuracy and processing speed can't be achieved together because of the inherent limitation of modelling GPR signal propagation in complex media. Full wave models (FWMs) are most promising approaches to characterize multilayered media. However, they are computationally inefficient due to the requirement of significant integration time over singularity. In this work, an FWM is developed to model a monostatic GPR in far-field configuration. The subsurface media is assumed to be a multilayered one with each layer being homogeneous having a specific electromagnetic property. The synthetic data based on simulation and experimental study have demonstrated that the proposed FWM is accurate enough to describe the subsurface media electrically. Then three modified plane wave models (MPWMs) are derived based on the analytical solution of the FWM to achieve similar accuracy and better computational speed than the FWMs. MPWM-2 is the most accurate, and MPWM-3 is quite versatile to find response due to multilayered media. Rigorous analysis has been carried out to show the similarity between the proposed MPWMs and FWMs with high correlation across a broad frequency spectrum and large ranges of media parameters. The model inversion is achieved by novel layer stripping (LS) techniques followed by a gradient-based method. The proposed models are validated by correctly detecting a normal water layer and validating their accuracy with an existing FWM in the literature. The testing of layered media in laboratory environment demonstrates that the proposed MPWMs are as accurate as existing FWMs and computationally more efficient. The proposed integrated approach of GPR detection having superior speed, and similar accuracy as FWMs are valuable alternative for many real-time GPR applications