Planar 2-D Scanning SIW Multibeam Array With Low Sidelobe Level for Millimeter-Wave Applications.

A two-dimensionally (2-D) scanning multibeam array with planar structure and low sidelobe level (SLL) is realized in this paper. It is for the first time that the SLL of 2-D scanning multibeam array is properly addressed. To suppress the SLL, a $4 \times 16$ beam-forming network (BFN) is proposed in this paper. Different from the existing schemes, such BFN can provide tapered illuminations in two orthogonal directions and thus can be applied to realize low-SLL 2-D scanning beams. The proposed $4 \times 16$ BFN is formed by interconnecting two sets of sub-BFNs, each of which is stacked by several $2 \times 4$ Butler matrices (BMs). Like other 2-D scanning schemes, the preliminary $4 \times 16$ BFN is of 3-D topology so that it is challenging to be integrated into planar substrate integrated waveguide (SIW) structure. Facing this problem, some modifications of the proposed topology are conducted. Operation principle, simulation, and experiment of a planar, low-SLL 2-D scanning multibeam array operating at 28 GHz are illustrated, which can help to demonstrate its feasibility for millimeter-wave applications. [ABSTRACT FROM AUTHOR]