Influence of lossless and lossy, heterogeneous environments on Ground Penetrating Radar antenna behaviour

Directly measuring the radiation characteristics of Ground Penetrating Radar (GPR) antennas in complex environments, typically encountered in GPR surveys, presents many practical difficulties. However it is crucial to be able to understand how energy is being transmitted and received by the antenna. This in turn is important for areas of research such as GPR antenna design, GPR system design, and data processing and inversion algorithms. To overcome these practical challenges an advanced modelling toolset has been developed. It enables detailed 3D Finite-Difference Time-Domain (FDTD) models of GPR antennas to be used in realistic environments that include models of heterogeneous soils. A semi-empirical soil model was utilised, which relates the relative permittivity of the soil to the bulk density, sand particle density, sand fraction, clay fraction and water volumetric fraction. In this initial investigation clear differences in the directivity (power and pattern shape) of the antenna have been observed between a lossless dielectric environment and a more realistic environment featuring a heterogeneous soil model. These findings are part of an on-going parametric study incorporating a range of different soils, soil property distributions, and the inclusion of rough surface modelling.