Ground Penetrating Radar
Electromagnetic simulations of Ground Penetrating Radar (GPR)  scenarios including realistic models of the antennas are not yet common. Accurate models of GPR antennas have been only occasionally developed during the past two decades -; rarely, they have been combined with realistic models of complex environments . In most cases, GPR electromagnetic simulations use hertzian dipoles or lines of current to represent the transmitting antennas; the physical structure of the receiving antennas is usually not included in the models and the electric field impinging on the receivers is calculated -. This simplified approach is customarily adopted because easier to implement and computationally cheaper; in fact, nowadays running realistic models of GPR scenarios is still a challenging task, notwithstanding computing power is increasing and becoming more accessible.
In this paper, we employed commercial software implementing the Finite-Integration technique (FIT)  (CST Microwave Studio) for modelling and simulating an antenna representative of a widely used high-frequency commercial device manufactured by Geophysical Survey Systems, Inc. (GSSI). All necessary information about the antenna was taken from Dr Craig Warren’s PhD Thesis , where the freeware tool GprMax3D  was used to develop a Finite-Difference Time-Domain (FDTD) model of the same antenna. It has to be noted that, in  and here, the numerical model does not exactly replicate the commercial antenna because the electromagnetic properties of some antenna materials are unknown, due to commercial sensitivity; the undisclosed values were estimated in  (the match between the real and synthetic crosstalk responses of the antenna in free-space was maximized, by using Taguchi's optimisation method). It is also worth mentioning that the FDTD model developed in  is currently included in the library of antennas of the open-source software gprMax [19, 20], therefore gprMax users can easily include this antenna into their simulations without having to build it step-by-step. The CST model that we developed was successfully validated via comparisons with synthetic and experimental data available in , in cooperation with colleagues from The University of Edinburgh (United Kingdom); such data were obtained with the antenna immersed in free space and in lossy dielectric environments, with and without a circular-section metallic target and some results of the performed comparisons were presented in a conference paper .
In Section 2 of the present paper, we describe in detail how we developed the CST Microwave Studio model of the antenna; this information was not included in . Then, in Section 3, we present new results that we obtained by simulating the antenna over a reinforced-concrete cell. Such cell is one of the reference scenarios included in the Open Database of Radargrams of COST Action TU1208  and hosts a series of five circular-section steel rods, having different diameters and/or embedded at different depths into the concrete . We compare results obtained by using the realistic CST antenna model, and results obtained by representing the transmitting antenna with a line of current and by neglecting the physical structure of the receiving antenna. The aim of this comparison is to confirm and further highlight the importance of including realistic models of the actual antennas in GPR simulations, whenever the objective of the simulations is to accurately replicate a real GPR response, or to exploit the simulation results into an inversion process. Moreover, the comparisons presented in this paper emphasize once more how strong are antenna effects, and therefore, how salient it is to develop methods for removing them as a pre-processing step of GPR data. The results of our simulations are attached to the paper as ‘Supplementary materials.’
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Read further papers published by the same Authors on Ground Penetrating Radar
- L. Pajewski, M. Vrtunski, Ž. Bugarinović, A. Ristić, M. Govedarica, A. van der Wielen, C. Grégoire, C. Van Geem, X. Dérobert, V. Borecky, S. Serkan Artagan, S. Fontul, V. Marecos, and S. Lambot, "GPR system performance compliance according to COST Action TU1208 guidelines," Ground Penetrating Radar, Volume 1, Issue 2, Article ID GPR-1-2-1, July 2018, pp. 2-36, doi.org/10.26376/GPR2018007.
- L. Pajewski, H. Tõnisson, K. Orviku, M. Govedarica, A. Ristić, V. Borecky, S. Serkan Artagan, S. Fontul, and K. Dimitriadis, "TU1208 GPR Roadshow: Educational and promotional activities carried out by Members of COST Action TU1208 to increase public awareness on the potential and capabilities of the GPR technique," Ground Penetrating Radar, Volume 2, Issue 1, Article ID GPR-2-1-4, pp. 67-109, March 2019, doi: 10.26376/GPR2019004.
For information concerning COST Action TU1208 and TU1208 GPR Association, please take contact with the Chair of the Action and President of the Association, Prof. Lara Pajewski. From 4 April 2013 to 3 October 2017, this website was supported by COST, European Cooperation in Science and Technology - COST is supported by the EU RTD Framework Programme Horizon2020. TU1208 Members are deeply grateful to COST for funding and supporting COST Action TU1208. As of 4 October 2017, this website is supported by TU1208 GPR Association, a non-profit association stemming from COST Action TU1208.