A Miniaturized Metamaterial-Based Dual-Band 4×4 Butler Matrix With Enhanced Frequency Ratio for Sub-6 GHz 5G Applications

• Main Authors: ABDULKADIR BELLO SHALLAH, ABDULKADIR BELLO SHALLAH, FARID ZUBIR, FARID ZUBIR, MOHAMAD KAMAL A. RAHIM, MOHAMAD KAMAL A. RAHIM, NOORLINDAWATY MD. JIZAT, NOORLINDAWATY MD. JIZAT, ABDUL BASIT, ABDUL BASIT, MAHER ASSAAD, MAHER ASSAAD, HUDA A. MAJID, HUDA A. MAJID
• Format: Article
• Language: English
• Published: Ieee Acces 2024
• Subjects: TK5101-6720 Telecommunication. Including telegraphy, telephone, radio, radar, television
• Online Access: http://eprints.uthm.edu.my/11059/1/J17535_3c24e4f901ae05410d662a6a942e9eb2.pdf; http://eprints.uthm.edu.my/11059/; https://doi.org/10.1109/ACCESS.2024.3371027

This paper introduces an innovative 4 × 4 dual-band Butler matrix (BM) characterized by compactness and an enhanced frequency ratio (K). The design employs meandered lines and an interdigital capacitor (IDC) unit-cell-based composite right/left-handed transmission-line (CRLH-TL) metamaterial (MTM) structure. The BM integrates compact dual-band 3 dB branch-line couplers (BLC), a 0 dB crossover, and dual-band ±45◦ phase shifters on a single Rogers RT5880 substrate having relative permittivity εr of 2.2 and thickness h of 0.787 mm. Simulations and measurement results demonstrate reflection and isolation coefficients exceeding −20 dB at all ports, with obtained insertion loss of −6±3 dB over the 0.7 GHz and 3.5 GHz frequency bands. The achieved output phase differences of ±45◦ , ±135◦ , ±135◦ , and ±45◦ at the designed frequencies indicate a maximum average phase tolerance of ±4.5◦ concerning the ideal values. Importantly, the BM’s overall dimensions are 143 mm × 186 mm, resulting in an impressive 78% size reduction compared to traditional T-shaped BM designs. The proposed configuration is designed and simulated using CST Microwave Studio, with the agreement between simulated and measured parameters highlighting design reliability and effectiveness. Additionally, a performance evaluation comparing the proposed BM with existing circuits reveals its suitability for sub-6 GHz 5G dual-band antenna array beamforming networks (BFN) due to its compact size and improved band ratio.