Antennas in a waveguide propagation environment

In this paper, we discuss antenna properties in a waveguide propagation environment. An example of this environment is heating, ventilation, and air conditioning (HVAC) ducts, which behave as multimode waveguides when used for indoor radio communications. An important antenna characteristic in waveguides is mode sensitivity gain, which is analogous to the antenna directive gain in free-space and is a function of antenna parameters. We demonstrate this with the example of a monopole probe antenna coupled into a multimode cylindrical waveguide.