Electromagnetic radiation from vertical dipole antennas near air–lossy soil interface—a finite-difference time-domain simulation

Abstract

Radiation from vertical dipole antennas, which are located over or under the surface of lossy earth, is analysed by the finite-difference time-domain (FDTD) method in cylindrical coordinates. A novel generalized perfectly matched layer (PML) has been developed and used for the truncation of the lossy soil. In order to decrease the memory requirements and for having an accurate modelling, an efficient ‘non-uniform’ mesh generation scheme is used. The excitation is considered in the form of sine carrier modulated by Gaussian pulse (SCMGP) and in each time step, computation is limited to that part of the mesh where the radiated pulse is passing (computational window). This could considerably reduce the required CPU time. In this manner, large-scale problems can be solved and the values of radiated field at far distances (up to 500λ₀ in this work) can be obtained directly by the FDTD method. The frequency-domain results are calculated from the obtained time-domain results by taking the Fourier transform. The spatial distributions of the amplitude and phase of radiated field are shown in illustrations for different types of soil and different positions of antenna. The influence of the lossy soil on dipole's admittance is also shown. Copyright © 2005 John Wiley & Sons, Ltd.