Chapter I - Microwave Transmission Lines

Abstract

This chapter focuses on microwave transmission lines. The purpose of uniform transmission lines is to transfer energy from a generator to a load. They can be of various types depending upon the application and the band of microwave or millimeter-wave frequency used. Transmission lines used at microwave frequencies support modes that can be broadly divided into two types—the transverse electromagnetic (TEM) and the nontransverse electromagnetic (non-TEM) modes of propagation. The chapter addresses two-wire balanced transmission lines, coaxial lines, waveguides, finlines, and dielectric waveguides. Coaxial lines find extensive use over the widest frequency spectrum, starting from ELF to the millimeter-wave band. The Q-factor of a coaxial line is an important parameter in realizing microwave filters using coaxial line resonators. Hollow metallic tubes, usually with rectangular or circular cross sections, are ideally suited for high-power and low-loss microwave applications. Such transmission lines are called waveguides. The finline can be considered a shielded slotline, with the finline being quasiplanar and suspended in the E-plane of a rectangular waveguide.