Citation

Nayyef Zubaidi, Nawres Abbas (2025) Bulter matrix based on substrate integrated waveguide without crossover and phase shifter for millimeter waves applications. PhD thesis, Multimedia University.

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Abstract

The swift rise in the need for wireless communication has led to the transition from 4G to 5G, necessitating enhancements in data speed, increased bandwidth, and more efficient spatial multiplexing. Considering these demands, this research outlines the design, simulation, fabrication, and testing of a compact and efficient 4 × 4 Butler matrix beamforming network that integrates a switched antenna array operating at 26 GHz, aimed at 5G base station applications. The study focuses on overcoming the limitations of conventional beamforming designs—such as high insertion loss, bulky crossovers, and restricted bandwidth—by utilizing Substrate Integrated Waveguide (SIW) technology and revised coupler designs. The goal is to create a small, low-loss beamforming network by eliminating standard crossovers and phase shifters, integrating instead modified SIW hybrid couplers that produce a 135° phase difference through strategic placement of vias. The adopted methodology combines analytical waveguide modeling, via-based phase manipulation, full-wave electromagnetic simulation using CST Microwave Studio, and experimental validation through fabrication on Rogers RT/Duroid 5880 substrate. A modified SIW hybrid coupler capable of generating a 135° phase difference via strategic metallic and non-metallic via placement was developed to eliminate conventional phase shifters and crossovers. The complete beamforming network was designed, optimized, fabricated, and characterized using vector network analysis and anechoic chamber measurements, including return loss, insertion loss, phase difference, gain, and radiation pattern evaluation. Simulation results reveal wide impedance bandwidths for both the SIW antenna (2 GHz spanning 25–27 GHz) and the hybrid coupler (7 GHz from 23–30 GHz), with return loss figures falling below –10 dB. The constructed coupler exhibited minimal phase error (133° ±2°), while the measured antenna gain reached 7.5 dB with efficiencies exceeding 95%. The complete 4 × 4 Butler matrix achieved a fractional bandwidth of 60%, ensured even power distribution across output ports, demonstrated low insertion loss (–1.4 to –2.2 dB), and exhibited excellent isolation. The output phase shifts of ±45.6° and ±133.6° facilitated efficient directional beam steering. Coupled with four SIW slot antennas, the network produced beams at ±14.43° and ±31.23°, showcasing effective beam-switching capabilities. The compact design (74 × 28 mm²) considerably reduces system size while maintaining outstanding performance in phase accuracy (1.8° average error) and insertion loss, The minor discrepancies observed between simulation and measurement results were attributed to connector mismatches and measurement losses. Overall, the performance reinforces the potential of this crossover-free SIW Butler matrix for 5G millimeter-wave applications.

Item Type:	Thesis (PhD)
Additional Information:	Call No.: TK5103.4835 .N39 2025
Uncontrolled Keywords:	Millimeter wave communication systems
Subjects:	T Technology > TK Electrical engineering. Electronics Nuclear engineering > TK5101-6720 Telecommunication. Including telegraphy, telephone, radio, radar, television
Divisions:	Faculty of Engineering and Technology (FET)
Depositing User:	Ms Nurul Iqtiani Ahmad
Date Deposited:	22 May 2026 08:37
Last Modified:	22 May 2026 08:37
URII:	http://shdl.mmu.edu.my/id/eprint/15907

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