A Dual-Band Filtering 4 × 4 Butler Matrix Based on SLR
Shi‐Shan Qi, Yue Guo, Jianpeng Wang, Xiang Wang, Wen Wu
Abstract
In this letter, a dual-band filtering 4×4 Butler matrix (DB-F-BM) based on a stub-loaded resonator (SLR) is proposed, operating at 12 and 17 GHz. The dual-band filtering (DB-F) 180° hybrid coupler can provide power allocation, phase shifting, and frequency selection at both frequencies. Each operating band reveals a second-order bandpass filtering response. This hybrid coupler is designed based on SLR and exploits different electromagnetic coupling to realize desired phase characteristics. A DB-F-BM was built, using DB-F 180° hybrid coupler, wideband 90° coupler, and phase shifter. The DB-F 180° hybrid coupler and DB-F-BM are fabricated and measured. The measured results are in good agreement with the theoretical ones. The lower and higher frequency bandwidth of DB-F-BM is approximately 8% and 3%, respectively. It also exhibits good out-of-band suppression. Furthermore, the DB-F-BM is applied to construct a 1 × 4 antenna array and verified the designed concepts and beamforming performance.