“…A horn antenna with high aperture efficiency and low crosspolarization has interest for several applications. For instance, it may be used in arrays in order to decrease the spacing between the elements and at the same time keep the desired gain, as described in [1] and also mentioned in [2], or in cluster-fed reflector antennas, as in [3][4][5][6]. In the latter case, the high aperture efficiency makes it possible to place these elements close to each other without jeopardizing the requirements on beam isolation and smooth beam coverage.…”