Comparison between different rectangular horn elements for array antenna applications

The coupling and directivity characteristics of an array with rectangular open-ended waveguide elements are considered. In particular waveguides with soft and hard boundaries are analyzed and discussed with respect to array applications. A soft waveguide or horn (e.g. corrugated horn) is characterized by zero intensity of the aperture field at the wall, while a hard waveguide or horn is characterized by a uniform aperture field distribution. The latter has higher directivity than the former, at the expense of higher sidelobes. Applications of hard and soft horn elements are discussed.<>