Design of an Overmoded-Waveguide Directional Antenna for Use in In-Building Ventilation Duct Wireless Networks

We present an adaptation of a Yagi-Uda antenna design for use inside the overmoded waveguide environment of building ventilation ducts. We obtain experimentally the element size and spacing of a reflector and driven element that can be used for IEEE 802.11b/g/n signals in a cylindrical duct to provide 3.1 dB of gain and a front-to-back ratio of 9.1 dB compared to a simple monopole antenna. We also discuss the usefulness of such an antenna in a duct network used to distribute wireless signals in a building.