Compact Substrate-Integrated 4 × 8 Butler Matrix With Sidelobe Suppression for Millimeter-Wave Multibeam Application

This letter presents a compact dual-layer 4 × 8 Butler matrix (BM) with sidelobe level (SLL) suppression in substrate-integrated waveguide (SIW) technology. Addressing the excessive crossovers in the classic 4 × 8 BM, a novel dual-layer configuration is proposed here. Such a configuration can help reduce the required crossovers from original five sets to merely one set. Therefore, the 4 × 8 BM can be significantly simplified to achieve better compactness. Based on this configuration, a SIW dual-layer 4 × 8 BM is designed with a dimension of 6.1 λ × 4.1 λ. To evaluate its SLL suppression effect, a multibeam array fed by the proposed BM is designed, simulated, and measured.