Transformer between a thin post-wall waveguide to a standard metal waveguide

The authors propose a transformer between a thin post-wall waveguide and a standard metal waveguide. The transformer is used to connect an RF circuit fed by a planar line with a waveguide planar antenna fed through an aperture. In the feed of a planar line, such as a triplate line, via an aperture, some posts are often placed around the line to prevent undesired leakage into the dielectric substrate. The post-wall waveguide consists of densely arrayed posts in the walls and the connection to a microstrip line with the same height is expected to be easy. However direct connection between a post-wall waveguide and a standard waveguide may be difficult because the post-wall waveguide is much thinner than the standard one. A piece of dielectric substrate with two gaps is inserted in a standard waveguide for matching to the post-wall. We analyze the transformer and manufacture a model for operation in the 22 GHz band. We also investigate the dimensions of the transformer for various heights of the postwall waveguide.