Design of 4×4 Multi-layer Butler-like Matrix with Flexible Phase Differences and Filtering Integration for 5G Applications

A universal topology for the filtering integrated Butler-like matrix (BLM) with flexible beam steering has been proposed based on the N/2 × N Butler matrix (BM). This structure is constructed on three-layer circuits, with compact size and no crossover owing to the path distribution. Besides, the filtering function has been integrated into the BLM by utilizing the multi-stage coupled lines. For validation, a 4×4 BLM operating at 4.9 GHz was designed and fabricated. Measured results reveal that the 4×4 BLM exhibits a working bandwidth of 18.4% and filtering integrated functions, with a compact size of 1.2×2.3 λg2. The measured scatting parameters and phase characteristics show great agreement with the simulated ones.