Electric-field integral equation model for transient GPR antennas

Abstract

In this paper we present the electric field integral equation (EFIE) method for the analysis of transient metallic antennas above a lossy half-space. This formulation is suitable for the analysis of a wide class of metallic GPR antennas that does not contain any dielectric material. Ground influence is properly taken into account by the Green's function for layered media. The EFIE is solved numerically by the method of moments using the well-known Rao-Wilton-Glisson basis function. For GPR antennas, the free-space Green's function is replaced by the dyadic Green's function for layered media. The time-domain solution for transient antennas is obtained using Fourier transform method and a time-window technique. By using time window to remove reflections from antenna open ends, the solution for transient antennas is obtained. To speed up computations, several approaches are used, which include the exploitation of antenna symmetry, a special treatment for integration over singularity, and an interpolation method to expedite the evaluation of Sommerfeld integrals. We have found that those approaches allow rapid and accurate computations for obtaining the time-domain solution. Good agreement between the computation and measurement of the input impedance of a wire dipole and a wire bow-tie antenna is obtained.