Compact 28-GHz two-dimensionally scanning multibeam array with sidelobe suppression

This work presents a compact 28-GHz two-dimensionally (2-D) scanning multibeam array antenna with sidelobe suppression in substrate integrated waveguide (SIW) technology. The proposed antenna is comprised of a 2 × 8 slot array and a beam-forming network (BFN), which is realized by combining two dual-layer 4 × 8 Butler matrixes (BMs) and four 90° couplers. The introduced 4 × 8 BM can help suppress the sidelobe level (SLL) in the E-plane so that the anti-interference capability in the E-plane can be improved. Taking the complicated structure of the classic 4 × 8 BM into account, some modifications of the BM are conducted to achieve better compactness.