Radio Propagation and Adaptive Antennas for Wireless Communication Networks, 2nd Edition

CHAPTER FOURElectromagnetic Aspects of Wave Propagation over Terrain

When both antennas are far from the ground surface, a free-space propagation concept is usually used, which is based on the scalar or vector wave equation description, valid for infinite source-free homogeneous media. In Section 4.1, based on Green's theorem and the Huygens's principle, we introduce the Fresnel zone presentation that will be used for the description of terrain and other obstruction effects, such as reflection and diffraction on radio channels. In Section 4.2, we present the main formulas for path loss prediction for a free-space communication link. Next, in Section 4.3, the reflection phenomena due to a flat terrain are described [1–4]. Here, on the basis of Huygens's principle, Fresnel zone concepts, and stationary phase methods, we give main formulas for the resultant reflection coefficients. Section 4.4 deals with the electromagnetic (EM) aspects of radiowave propagation above a rough terrain. Here, the three methods of mathematical derivation of the field strength are presented to obtain the effects of radiowave scattering from ground surfaces with various roughness (large, median, and small) with respect to the wavelength. In Section 4.5, the effect of the ground curvature is considered by using Fock's theory of diffraction. Section 4.6 describes diffraction phenomena caused by a single obstruction placed at the flat ground surface.

4.1.  Wave Propagation in Free Space

According to References ...