Abstract
Directly measuring the radiation characteristics of Ground Penetrating Radar (GPR) antennas in environments typically encountered in GPR surveys, presents many practical difficulties. However it is very important to understand how energy is being transmitted and received by the antenna, especially for areas of research such as antenna design, signal processing, and inversion methodologies. To overcome the difficulties of experimental measurements, we used an advanced modelling toolset to simulate detailed three-dimensional Finite-Difference Time-Domain (FDTD) models of GPR antennas in realistic environments. 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 volumetric fraction of water. The radiated energy from the antenna was studied in lossless homogeneous dielectrics as well as, for the first time, in lossy heterogeneous environments. Significant variations in the magnitude and pattern shape were observed between the lossless homogeneous and lossy heterogeneous environments. Also, despite clear differences in time domain responses from simulations that included only an infinitesimal dipole source model and those that used the full antenna model, there were strong similarities in the radiated energy distributions.
Highlights
The diversity of Ground Penetrating Radar (GPR) usage means there are a variety of different GPR systems and antennas
This paper presents an investigation of the radiation characteristics of a high-frequency GPR antenna in lossless homogeneous and, for the first time, in lossy heterogeneous environments using detailed Finite-Difference Time-Domain (FDTD) models
All of the simulations conducted for this research used gprMax which is an electromagnetic wave simulator based on the Finite-Difference Time-Domain (FDTD) method. gprMax was originally developed in 1996 [11] and over the past 20 years has been one of the most widely used simulation tools in the GPR community
Summary
The diversity of Ground Penetrating Radar (GPR) usage means there are a variety of different GPR systems and antennas. Measuring antenna radiation patterns in lossy heterogeneous environments that are realistic for GPR presents many practical difficulties. This has prompted researchers to develop numerical simulations of GPR antenna radiation patterns. The energy distribution of a shielded dipole antenna over various lossless half-spaces was studied by [10], and [7] used an FDTD antenna model to compare simulated and measured data. This paper presents an investigation of the radiation characteristics of a high-frequency GPR antenna in lossless homogeneous and, for the first time, in lossy heterogeneous environments using detailed FDTD models. Giannopoulos / Signal Processing 132 (2017) 221–226 toolset allowed a detailed model of a GPR antenna to be used in heterogeneous environments that simulate realistic soils. Principal electric and magnetic field patterns are analysed at a range of observation distances from the antenna using a total energy metric
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