Abstract
Ground wave propagation of low-frequency (LF) electromagnetic waves is well known for the canonical case of a flat, azimuthally homogeneous, soil. Moreover, it is well investigated for realistic propagation problems, some of which include Earth’s curvature, irregular and lossy terrain profiles, and mixed paths. In this paper, kinds of environment are considered in the far-field of the radiating antenna with an original methodology. It rests on the use of hybridization of finite-difference in time-domain (FDTD) with the direct numerical integration of Sommerfeld-type integrals which is also presented and validated. This hybridization uses domain decomposition and Huygens’ surfaces in a stratified dielectric medium in three-dimensional (3-D) space. The approach is validated with respect to a reference solution both in the canonical flat ground case and in a hilly one.
Highlights
U SUALLY the electromagnetic problem of low-frequency (LF) radiating antennas is decomposed into two parts: 1) the near-field radiation emitted by the antenna and 2) the propagation of this near-field in the far range for the ground wave [1]
An original hybrid approach using the finite-difference in time-domain (FDTD) method is proposed. It rests on the use of the direct numerical integration of Sommerfeld’s integrals, which is presented, and its hybridization with 3-D FDTD applied to the surroundings of the irregularity under consideration, yielding an approach free of the former numerical problems
First the hybridization technique is used with a homogeneous flat ground and compared with the analytical formulas given by Norton [2]
Summary
U SUALLY the electromagnetic problem of low-frequency (LF) radiating antennas is decomposed into two parts: 1) the near-field radiation emitted by the antenna and 2) the propagation of this near-field in the far range for the ground wave [1]. Perturbation methods using the compensation theorem treat typical forms of radial heterogeneity such as mixed paths and irregular ground [9], [10] These techniques do not take into account the 3D topography near the propagation path. An original hybrid approach using the FDTD method is proposed It rests on the use of the direct numerical integration of Sommerfeld’s integrals, which is presented, and its hybridization with 3-D FDTD applied to the surroundings of the irregularity under consideration, yielding an approach free of the former numerical problems. This hybridization technique aims at treating complex kinds of environment located in the far-field.
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