Analysis of Electromagnetic Wave Propation in Forest Environment Along Multiple Paths

Abstract

The electromagnetic radiation of an electric dipole in a medium with four layers is examined using dyadic Green's functions in their vector wave eigenfunction expansion forms. In this four-layered model, two lossy dielectric layers are used to represent the canopy and trunks of vegetation that covers the ground plane. The dyadic Green's functions for a four-layered medium are first applied to derive the integral expression of the electric fields. Asymptotic evaluations of the integrals are then made using the steepest descent method, and the branch-cut integrations in complex planes; and correspondingly the direct wave, multi-reflected waves, and lateral waves along various interfaces have been obtained. The far-zone field for problems of this nature is, as found, primarily determined by the lateral wave. The transmission losses for tropical forest are calculated numerically for both vertical and horizontal dipoles, and a dipole with a 45° inclination. Also, a serious mistake made in the literature has been pointed out in this paper.