Low sidelobes are beneficial for many antenna applications. Reduction in sidelobe level for a single horn can be achieved by increasing the flare length and adjusting the the aperture dimensions accordingly, however, this leads to a larger structure. In arrays the sidelobe levels are normally reduced through specific excitation distributions.
The waveguide-fed horn array consists of three horns with a simple uniform feed. The reduction in sidelobes are achieved through a flatter phase distribution across the aperture due to the combined effect of three smaller apertures.
The bandwith of a conventional horn is limited by the waveguide’s bandwidth, but this horn array’s bandwidth may be limited even more by its pattern performance....Typical radiation pattern at the centre frequency; Typical normalized radiation patterns at the centre frequency.