Low-profile corrugated feeder horn antenna (Bulls Eye)

Image of the Low-profile corrugated feeder horn antenna (Bulls Eye).

This interesting reflector feed antenna originated from optical studies which showed that sub-wavelength apertures in corrugated metallic films enhance transmission. By scaling the same concept to microwave frequencies, a very-low profile feeder antenna with approximately 20 dBi gain can be realized.

This very low-profile horn antenna consists of a waveguide terminated by a sub-wavelength aperture or slot in the centre of a conducting plate with concentric periodic corrugations. By correctly designing the corrugations, the radiation pattern of the slot can be dramatically adjusted, resulting in a highly directed beam as shown in the following radiation pattern images:

Typical 3D radiation pattern.
Typical 2D radiation pattern.