Typical ground-pentrating radar (GPR) transmitters and receivers consist of dipole-type antennas. These antennas have pronounced directive properties and exhibit strong coupling to interfaces across which there are changes in electric material properties. Whereas coupling of antennas to smooth interfaces has been the subject of intense research for several decades, the behaviour of antennas in the vicinity of realistic small-scale heterogeneities is largely unexplored. To address this issue, we simulate the responses of a typical surface GPR antenna to a suite of scale-invariant earth models of increasing complexity. Finite-difference time-domain (FDTD) simulations demonstrate that roughness of the air-soil interface has a pronounced effect on radiation patterns. By comparison, small-scale fluctuations of permittivity only cause relatively minor local distortions of the radiation patterns.
The generation and recording of electromagnetic waves by typical ground-penetrating radar (GPR) sounding systems is complex and the effects of the antennas on the recorded data are not well understood. To address this problem, we present a versatile and efficient GPR system simulation tool. This algorithm is based on a finite-difference time-domain (FDTD) approximation of Maxwell's equations and allows us to model realistically the radiation characteristics of a wide variety of typical surface GPR antenna systems. The accuracy of the algorithm is benchmarked and validated with respect to extensive laboratory measurements for comparable antenna systems. Given the flexibility of this GPR modeling software, we anticipate that it will be useful not only for the design and interpretation of GPR surveys, but also for the design of novel GPR sounding systems.
KEYWORDS: Antennas, General packet radio service, Electromagnetism, Ground penetrating radar, 3D modeling, Maxwell's equations, Near field, Metals, Modeling, Magnetism
The interaction of high-frequency electromagnetic wave-fields with a typical ground-penetrating radar (GPR) antenna is complex and its effects on the recorded data are not well understood. Further distortions of the radiation pattern and pulse shape must be expected to arise in the presence of a shielding of the antenna. To address these issues, we present a three-dimensional finite-difference approximation of Maxwell's equations that allows to model realistically the near-field radiation characteristic of a typical GPR system.
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