Four-square phased array for multi-beam applications using novel matrix feed

Modern communications systems use multi-beam antennas for the sectorization of 360deg azimuthal coverage or diversity and MIMO concepts. One suitable antenna realization is based on the phased array principle, where four elements placed at the edges of a square are required in order to form four overlapping beams in azimuth. In its basic form, excitation phases of 0deg, 90deg and 180deg are required for beam forming. The paper presents a novel multi-beam matrix network created by four 90deg-hybrid couplers which realizes the required excitation for four beams spaced by 90deg in the azimuth plane. A proof-of-concept antenna was designed which employs miniature surface- mount couplers in a microstrip feed network and uses vertical monopole radiators.