Open-ended waveguide antenna excitation with microstrip patch elements

In this paper, a new method is presented to excite an open-ended circular waveguide feed. A circular microstrip patch element is embedded near the bottom end of the waveguide, which excites the dominant TE₁₁ mode at the aperture of the antenna. The technique is simple and capable of generating a relatively pure mode over a respectable frequency band. The technique eliminates the need of using a waveguide transition for the feeding network. In terms of volume, the proposed technique leads to a less bulky structure as opposed to the conventional probe excitation method in waveguides, which laterally occupies more space since it is perpendicular to the waveguide wall.