Creating finite-difference time-domain models of commercial ground-penetrating radar antennas using Taguchi’s optimization method

Abstract

Very few researchers have developed numerical models of Ground-Penetrating Radar (GPR) that include realistic descriptions of both the antennas and the subsurface. This is essential to be able to accurately predict responses from near-surface, near-field targets. This paper presents detailed three-dimensional (3D) Finite-Difference Time-Domain (FDTD) models of two commercial GPR antennas-a Geophysical Survey Systems, Inc. (GSSI) 1.5 GHz antenna and a MALÅ Geoscience 1.2 GHz antenna-developed using simple analyses of the geometries and the main components of the antennas. Values for unknown parameters in the antenna models (due to commercial sensitivity) were estimated by using Taguchi's optimisation method, resulting in a good match between the real and modelled crosstalk responses in free-space. Validation using a series of oil-in-water emulsions to simulate the electrical properties of real materials demonstrated that it was essential to accurately model the permittivity and dispersive conductivity. When accurate descriptions of the emulsions were combined with the antenna models the simulated responses showed very good agreement with real data. This provides confidence for use of the antenna models in more advanced studies.

An evaluation of Finite-Difference and Finite-Integration Time-Domain modelling tools for Ground Penetrating Radar antennas

“…The antenna models include all of the main features and geometry of the real antennas. Details of the development of antenna models and initial validation can be found in [13]. Fig.…”

“…The permittivity and conductivity of the emulsions were set by controlling ratios of the constituent chemicals [13]. A further advantage of using liquids was the ease with which targets could be positioned.…”

“…There has been very limited published work of GPR simulations with models of commercial antennas [11], [12], [13]. In fact, many simulations have used a theoretical infinitesimal dipole source to represent a real GPR antenna where only far-field behaviour or traveltime information was of interest, or where computational resources were limited.…”

Validated ground penetrating radar simulation model for estimating rebar location in infrastructure monitoring

“…Research into related work revealed the most common method for concrete analogs for use with GPR testing are oil-water based emulsions [9] [10] [11]. A different approach was chosen by instead developing and utilizing a sand based mixture.…”

“…To adjust the permittivity value of the material, using the approach similar utilized by [9] and [11], water was added until the desired permittivity value was obtained. To adjust conductivity values, salt (sodium chloride) could be added to raise the conductivity to suit.…”