A Planar Series-Feed Antenna Array With an Extremely Low Sidelobe Level

This letter proposes a novel design of a planar series-feed antenna array with an extremely low sidelobe level. The feeding network of the antenna array is designed based on a planar construction of a novel quadrature hybrid coupler. This quad-hybrid coupler can split its input power unequally into three different outputs. Detailed mathematical modeling and design procedures for such a quad-hybrid coupler are presented. This methodology allows the feeding network to provide a sufficient tapered weight distribution serially in both dimensions of the planar array simultaneously. This array is constructed and achieves a sidelobe level as low as −32 dB, which makes the proposed design an excellent candidate for applications that require antennas with low sidelobe levels, such as radar systems and space satellites.