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CHAPTER12: PLANE WAVES AT BOUNDARIES AND IN DISPERSIVE MEDIAIn

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Tham khảo tài liệu 'chapter12: plane waves at boundaries and in dispersive mediain', khoa học tự nhiên, vật lý phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | CHAPTER 12 PLANE WAVES AT BOUNDARIES AND IN DISPERSIVE MEDIA In Chapter 11 we considered basic electromagnetic wave principles. We learned how to mathematically represent waves as functions of frequency medium properties and electric field orientation. We also learned how to calculate the wave velocity attenuation and power. In this chapter wc consider wave reflection ami transmission at planar boundaries between media having different properties. Our study will allow any orientation between the wave and boundary and will also include the important cases of multiple boundaries. We will also study the practical case of waves that carry power over a finite band of frequencies as would occur for example in a modulated carrier. We will consider such waves in dispersive media in which some parameter that affects propagation permittivity for example varies with frequency. The effect of a dispersive medium on a signal is of great importance since the signal envelope will change its shape as it propagates. This can occur to an extent that at the receiving end detection and faithful representation of the original signal become problematic. Dispersion thus becomes an important limiting factor in allowable propagation distances in a similar way that we found to be true for attenuation. 387 I e-Text Main Menu Textbook Table of Contents 388 ENGINEERING ELECTROMAGNETICS 12.1 REFLECTION OF UNIFORM PLANE WAVES AT NORMAL INCIDENCE In this section we will consider the phenomenon of reflection which occurs when a uniform plane wave is incident on the boundary between rcịịK is composed of two different materials. The treatment is specialized to the case of normal incidence in which the wave propagation direction is perpendicular to the boundary. In later sections we remove this restriction. We shall establish expressions for the wave that is reflected from the interface and i or that which is transmitted from one region into the other. These results will be directly applicable to .