The waveguide is based on these two models:
A waveguide is a pipe in which an electromagnetic wave can propagate as either transverse electric or transverse magnetic waves. The dimensions of the waveguide determine the longest wavelength, and hence lowest frequency, that will propagate. The dominant mode of propagation in a waveguide called the transverse electric (TE) mode is the mode for which there is one half-wavelength in the long dimension and zero half-wavelength in the short dimension. The electric field must be orthogonal to the conductor in order to exist at the surface of that conductor, and the magnetic field must not be orthogonal to the surface of the waveguide.
Transmission lines are conduits for radio frequency (RF) signals and are equivalent to complex RLC circuits. It functions in a manner similar to delay lines. Three basic forms of transmission line are parallel line, coaxial cable, and stripline. The characteristic impedance of a transmission line is the impedance set by the stray inductance, and capacitance of the line. When a transmission line is terminated in resistive impedance equal to its characteristic impedance, the line is said to be matched, and no signal is reflected. A transmission line exhibits a looking-in impedance that is a function of its length, characteristic impedance, and load impedance. The reflection phenomenon can be used to evaluate the line in a measurement method called “time-domain reflectometry.” The interference between reflected and incident waves produces standing waves on the line. The standing-wave ratio (SWR) is a measure of the standing waves, and hence the degree of mismatch on the line. SWR can be expressed either as a ratio or in decibel form. Standing waves on a transmission line give rise to mismatch losses, which can vary from negligible to severe depending on the situation, especially the natural line losses of the transmission line.
The source of the information above is from a microwave course that I took when I was an engineering student.
Thanks for your time!
