In Chapter 4, we explained the two conductor structures, usually referred to as transmission lines, which can support a transverse electromagnetic (TEM) mode of propagation. The electric and magnetic fields of TEM waves have only transverse components; that is, in the direction of propagation, Ez = Hz = 0. Coaxial cables, parallel plates, and two-wire lines are examples of practical transmission lines. This chapter investigates a special form of transmission line known as a waveguide. In general, the term waveguide is applied to structures consisting of a single conductor. Unlike the two-conductor structures, the single-conductor structures cannot support a TEM mode. A waveguide is just a hollow metallic tube that ...