Simulations and Effects of Natural Environments on Low Frequency Antennas With Three-Dimensional FDTD Method

Abstract

Abstract-Three-dimensional Finite-Difference in Time-Domain method is applied to simulate Low Frequency antennas in the presence of natural environments. All antennas are made up of wires set down on a square shaped ground plane and their dimensions depend on the wavelength of the source. Both monopole and inverted L antennas are considered in this paper. The antenna systems are computed in the presence of two examples of natural elements: a large forest and then on the top of a hill. The main aim of this paper is to show the effects of these environments on the properties of the antennas and on the efficiency of the ground wave excitation. The outcome of these investigations shows a power ratio enhancement of several decibels when the two kinds of antenna described in this paper are located on the top of a hill. On the other hand, the effects of a large forest depend on the geometry of the antenna. It doesn't affect the radiation of a quarter-wave monopole antenna, on the contrary losses disrupt radiation when an inverted L antenna is built in the middle of a large forest.

Long-Range Three-Dimensional Ground Wave Propagation Modeling Over Flat, Irregular Terrain

“…In [14] and [15], bi-dimensional FDTD is applied to obtain the electric field both in the near and the far-field over an irregular terrain, with the constraint of a radial cylindrical geometry. FDTD in three dimensions has been applied to study the near-field radiation of wire antennas in a complex environment [16]. However, FDTD is not applicable in three dimensions at large distance because of the huge amount of computational resources which are required and also because of the numerical problems arising at very long distances (numerical dispersion, precision, boundary conditions, etc.…”