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CHAPTER14: WAVEGUIDE AND ANTENNA FUNDAMENTALSAs

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Tham khảo tài liệu 'chapter14: waveguide and antenna fundamentalsas', tài liệu phổ thông, vật lý phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | CHAPTER 14 WAVEGUIDE AND ANTENNA FUNDAMENTALS As a conclusion to our study of electromagnetics we investigate the basic principles of two important classes of devices waveguides and antennas. In broad definitions a waveguide is a structure through which electromagnetic waves can be transmitted from point to point and within which the fields are confined to a certain extent. An antenna is any device that radiates electromagnetic fields into space where the fields originate from a source that feeds the antenna through a transmission line or waveguide. The antenna thus serves as an interface between the confining line and space when used as a transmitter or between space and the line when used as a receiver. In our study of waveguides we will first take a broad -view OÍ waveguide devices to obtain a physical understanding of how they work and the conditions under which they are used. We will next explore the simple parallel-plate waveguide and study the concept of waveguide modes and the condi I ions under which these will occur. We will study the electric and magnetic field configurations of the guided modes using simple plane wave models and through use of the wave equation. We will then study more complicated structures including the rectangular waveguide and the dielectric slab guide. Our study of antennas will include the derivation of the radiated fields I rom an elemental dipole beginning with the retarded vector potentials that we studied in Chap. 10. We will address issues that include the efficiency of power radiation from an antenna and the parameters that govern this. 484 I e-Text Main Menu Textbook Table of Contents WAVEGUIDE AND ANTENNA FUNDAMENTALS 485 14.1 BASIC WAVEGUIDE OPERATION Waveguides assume many different forms that depend on the purpose of the guide and on the frequency of the waves to he transmitted. The simplest form in terms of analysis is the parallel-plate guide shown in Fig. 14.1. Other forms are the hollow-pipe guides including the .