Realistic modelling of surface ground‐penetrating radar antenna systems: where do we stand?

Abstract

ABSTRACTThe generation and recording of electromagnetic waves by ground‐penetrating radar (GPR) systems are complex phenomena. To investigate the characteristics of typical surface GPR antennae operating in realistic environments, we have developed an antenna simulation tool based on a finite‐difference time‐domain (FDTD) approximation of Maxwell’s equations in 3D Cartesian coordinates. The accuracy of the algorithm is validated with respect to laboratory measurements for comparable antenna systems. Numerically efficient and accurate modelling of small antenna structures and high permittivity materials is achieved through a grid‐refinement procedure. We simulate the radiation characteristics of a wide range of common surface GPR antenna types ranging from thin‐wire antennae to bow‐tie antennae with arbitrary flare angles based on the assumption of perfect electrical conductivity (PEC) of the metal parts. Due to the modular structure of the algorithm, additional planar antenna designs can readily be added. Shielding is achieved by placing a metal box immediately above the antenna. To enhance the damping effects, this metal box can be filled with a dielectric absorber and/or connected to the antenna panels through discrete resistors. Finally, we also consider the effects of continuous resistive loading of the antenna panels using a sub‐cell algorithm. We find that GPR antennae with Wu–King‐type resistivity profiles radiate compact, broadband pulses and, as opposed to PEC antennae, are largely insensitive to their operating environment. Unfortunately, these favourable radiation characteristics are accompanied by a dramatic loss in radiation efficiency compared to the corresponding PEC antennae.