1887
Volume 2 Number 1
  • ISSN: 1569-4445
  • E-ISSN: 1873-0604

Abstract

ABSTRACT

The generation and recording of electromagnetic waves by ground‐penetrating radar (GPR) systems are complex phenomena. To investigate the characteristics of typical surface GPR antennae operating in realistic environments, we have developed an antenna simulation tool based on a finite‐difference time‐domain (FDTD) approximation of Maxwell’s equations in 3D Cartesian coordinates. The accuracy of the algorithm is validated with respect to laboratory measurements for comparable antenna systems. Numerically efficient and accurate modelling of small antenna structures and high permittivity materials is achieved through a grid‐refinement procedure. We simulate the radiation characteristics of a wide range of common surface GPR antenna types ranging from thin‐wire antennae to bow‐tie antennae with arbitrary flare angles based on the assumption of perfect electrical conductivity (PEC) of the metal parts. Due to the modular structure of the algorithm, additional planar antenna designs can readily be added. Shielding is achieved by placing a metal box immediately above the antenna. To enhance the damping effects, this metal box can be filled with a dielectric absorber and/or connected to the antenna panels through discrete resistors. Finally, we also consider the effects of continuous resistive loading of the antenna panels using a sub‐cell algorithm. We find that GPR antennae with Wu–King‐type resistivity profiles radiate compact, broadband pulses and, as opposed to PEC antennae, are largely insensitive to their operating environment. Unfortunately, these favourable radiation characteristics are accompanied by a dramatic loss in radiation efficiency compared to the corresponding PEC antennae.

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2003-12-01
2020-04-03
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References

  1. AnnanA.P., WallerW.M., StrangwayD.W., RossiterJ.R., RedmanJ.D. and WattsR.D.1975. The electromagnetic response of a low‐loss, 2‐layer, dielectric earth for horizontal dipole excitation.Geophysics40, 285–298.
    [Google Scholar]
  2. ArconeS.A.1995. Numerical studies of the radiation patterns of resistively loaded dipoles. Journal of Applied Geophysics33, 39–52.
    [Google Scholar]
  3. BahrK.1997. Electrical anisotropy and conductivity distribution functions of fractal random networks and of the crust: the scale effect of conductivity. Geophysical Journal International130, 649–660.
    [Google Scholar]
  4. BergmannT., RobertssonJ.O.A. and HolligerK.1996. Numerical properties of staggered finite‐difference solutions of Maxwell’s equations for ground‐penetrating radar modelling. Geophysical Research Letters23, 45–18.
    [Google Scholar]
  5. BourgeoisJ.M. and SmithG.S.1996. A fully three‐dimensional simulation of ground‐penetrating radar: FDTD theory compared with experiment. IEEE Transactions on Geoscience and Remote Sensing34, 36–44.
    [Google Scholar]
  6. BrownG.H. and WoodwardO.M.1952. Experimentally determined radiation characteristics of conical and triangular antennas. RCA Reviews13, 425–452.
    [Google Scholar]
  7. ChevalierM.W., LuebbersR.J. and CableV.P.1997. FDTD local grid with material traverse. IEEE Transactions on Antennas and Propagation45, 411–121.
    [Google Scholar]
  8. FangJ. and WuZ.1996. Generalized perfectly matched layer for the absorption of propagating and evanescent waves in lossless and lossy media. IEEE Transactions on Microwave Theory and Techniques44, 2216–2222.
    [Google Scholar]
  9. HardyH.H. and BeierR.A.1994. Fractals in Reservoir Engineering. World Scientific.
    [Google Scholar]
  10. HolligerK. and BergmannT.1998. Accurate and efficient modeling of ground‐penetrating radar antenna radiation. Geophysical Research Letters25, 3883–3886.
    [Google Scholar]
  11. HolligerK. and GoffJ.A.2003. A generic model for the 1/f‐nature of seismic velocity fluctuations. In: Heterogeneity in the Crust and Upper Mantle – Nature, Scaling, Seismic Properties (eds J.A.Goff and K.Holliger ), pp. 131–154. Kluwer Academic/Plenum Publishers.
    [Google Scholar]
  12. KunzK.S. and LuebbersR.J.1993. The Finite Difference Time Domain Method for Electromagnetics. CRC Press.
    [Google Scholar]
  13. LampeB. and HolligerK.2003. Effects of fractal fluctuations in topographic relief, permittivity, and conductivity on ground‐penetrating radar antenna radiation. Geophysics, in press.
    [Google Scholar]
  14. LampeB., HolligerK. and GreenA.G.2003. A finite‐difference time‐domain simulation tool for ground‐penetrating radar antennas. Geophysics68, 971–988.
    [Google Scholar]
  15. LeatC.J.1999. Modelling and design of GPR antennas. PhD thesis, University of Queensland.
    [Google Scholar]
  16. LeatC.J., SchuleyN.V. and StickleyG.F.1998. Triangular‐patch models of bowtie antennas: validation against Brown and Woodward. IEEE Proceedings – Microwaves, Antennas and Propagation145, 465–470.
    [Google Scholar]
  17. LevanderA.R.1988. Fourth‐order finite‐difference P‐SV seismograms. Geophysics53, 1425–1436.
    [Google Scholar]
  18. MaloneyJ., ShlagerK.L. and SmithG.1994. A simple FDTD model for transient excitation of antennas by transmission lines. IEEE Transactions on Antennas and Propagation42, 289–292.
    [Google Scholar]
  19. MaloneyJ. and SmithG.1992. The efficient modeling of thin material sheets in the finite‐difference time‐domain (FDTD) method. IEEE Transactions on Antennas and Propagation40, 323–330.
    [Google Scholar]
  20. RobertsR.L. and DanielsJ.J.1997. Modeling near‐field GPR in three dimensions using the FDTD method. Geophysics65, 1114–1126.
    [Google Scholar]
  21. ShlagerK.L., SmithG.S. and MaloneyJ.G.1994. Optimization of bow‐tie antennas for pulse radiation. IEEE Transactions on Antennas and Propagation42, 975–982.
    [Google Scholar]
  22. SmithG.S.1984. Directive properties of antennas for transmission into a material half‐space. IEEE Transactions on Antennas and Propagation32, 232–246.
    [Google Scholar]
  23. TafloveA. and HagnessS.C.2000. Computational Electrodynamics: The Finite‐Difference Time‐Domain Method. 2nd edition, Artech House.
    [Google Scholar]
  24. TafloveA., UmshankarK.R., BekerB., HarfoushF. and YeeK.S.1988. Detailed FDTD analysis of electromagnetic fields penetrating narrow slots and lapped joints in conducting screens. IEEE Transactions on Antennas and Propagation36, 247–257.
    [Google Scholar]
  25. TurcotteD.L.1997. Fractals and Chaos in Geology and Geophysics. Cambridge University Press.
    [Google Scholar]
  26. WensinkW.A., GreeuwG., HofmanJ. and van DeenJ.K.1990. Measured underwater near‐field E‐patterns of a pulsed, horizontal dipole antenna in air. Comparison with theory of the continuous wave, infinitesimal dipole. Geophysical Prospecting38, 805–830.
    [Google Scholar]
  27. WuT. and KingR.1965. The cylindrical antenna with nonreflective resistive loading. IEEE Transactions on Antennas and Propagation13, 369–373.
    [Google Scholar]
  28. YeeK.S.1966. Numerical solution of initial boundary value problems involving Maxwell’s equations in isotropic media. IEEE Transactions on Antennas and Propagation14, 302–307.
    [Google Scholar]
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