RF and Microwave Engineering: Fundamentals of Wireless Communications

8.1 Propagation Mechanisms

8.1.1 Reflection and Refraction

In free space plane waves and spherical waves may propagate. In Section 2.5.3 we looked at reflection and refraction of plane waves interacting with material interfaces. In the following we will summarize the basics and include further physical effects of wave propagation that are important when investigating path loss.

Figure 8.1a shows a plane wave (starting in medium 1) that impinges on a material interface under an angle of ϑ_f (oblique incidence). There are two physical effects to be observed:

Reflection: A plane wave that hits a material surface is partly reflected back into medium 1. The angle of reflection ϑ_r equals the angle of incidence ϑ_f.

Refraction: A plane wave that hits a material surface is partly transmitted through the material interface into medium 2. Due to different phase velocities in the different media, the plane wave changes its direction of travel. The angle of transmission ϑ_t may be smaller or greater than the angle of incidence ϑ_f (see Section 2.5.3).

Figure 8.1 Reflection and refraction of a plane wave that impinges on a plane interface of two media.

Figure 8.1b illustrates the situation by looking at a single, positive wavefront at a certain instant in time. The wavefront in medium 1 hits the dielectric material interface at an angle of ϑ_f = 45°. The relative permittivity of medium ...