Theory of Waveguides and Transmission Lines

Edward F. Kuester

• Publisher: CRC Press
• Year: 2020
• ISBN:
  9781498730945
• Edition: 1
• Topic: Technology & Engineering
• Subtopic: Electrical Engineering & Telecommunications
• Index: Technology & Engineering

This book covers the principles of operation of electromagnetic waveguides and transmission lines. The approach is divided between mathematical descriptions of basic behaviors and treatment of specific types of waveguide structures. Classical (distributed-network) transmission lines, their basic properties, their connection to lumped-element networks, and the distortion of pulses are discussed followed by a full field analysis of waveguide modes. Modes of specific kinds of waveguides - traditional hollow metallic waveguides, dielectric (including optical) waveguides, etc. are discussed. Problems of excitation and scattering of waveguide modes are addressed, followed by discussion of real systems and performance.

1Modes of a Classical Transmission Line

1.1Introduction

In the broadest sense, all of electrical engineering deals with some sort of guided-wave system. Maxwell’s equations and Poynting’s theorem indicate to us that, even in an elementary low-frequency circuit, energy is stored and power is transferred, not by wires or circuit elements, but by the electromagnetic fields surrounding them. The configurations themselves serve merely to “arrange” or “guide” the fields in an advantageous manner. As operating frequency increases, this physical picture remains the same, but the quasi-static approximation of circuit theory which was useful at lower frequencies breaks down. Moreover, the electrical parameters of materials generally change at higher frequencies (conductors become more lossy, atomic and molecular vibrations begin to influence the dielectric properties, and so on). Circuits designed on quasi-static principles no longer operate efficiently, and new structures, along with new methods to analyze them, must be found.

In this same broad context, of course, antennas could also be thought of as guided-wave structures, especially so if designed with a highly directional pattern. The advantage of an antenna in a communication system is that no structure need be erected over a long distance. However, even in the best antenna systems it is difficult to achieve a really good degree of “guidance”, and tens or hundreds of dB of signal may be lost as a result. This is in part because no actual antenna guides a signal in a single direction exclusively, a...