| Summary: | In a 5G base station, a Butler Matrix (BM) feed circuit is requested to achieve multibeam patterns while maintaining a compact structure. However, the conventional design and size raise issues in installation and efficiency, especially at the lower 5G band, the 3.5GHz. To cater to many antenna elements, the BM size is increased, and the losses are severe, affecting the phase sensitivity. To address these issues, a stacked 4x4 BM with a dual-layer thin substrate is connected through non-uniform vias that act as a fine-tuning mechanism, where the desired phase difference is obtained by adjusting the circular slot diameter of the via. The BM features a low-profile structure with a 1.03 Ȝ [1.1 Ȝ GLPHQVLRQ, a significant reduction from the conventional 4x4 BM. The designed BM measured results show transmission amplitude of -7dB, and an acceptable range of output phase difference at the operating band. © 2024 IEEE.
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