Butler Matrix Based on Substrate Integrated Waveguide Without Crossover and Phase Shifter for Millimeter Waves...

Area of Science:

• Electrical Engineering
• Antenna Theory
• Microwave Engineering

Background:

• A novel low-loss 4x4 Butler Matrix for 26 GHz operation is presented.
• The design utilizes an inscribed structure, differing from traditional beamforming networks for 5G.
• It employs Substrate Integrated Waveguide (SIW) technology for a compact, wideband implementation.

Purpose of the Study:

• To design and demonstrate a compact, wideband 4x4 Butler Matrix for 5G millimeter-wave applications.
• To eliminate structural discontinuities, junction losses, and frequency-dependent phase errors inherent in conventional designs.
• To enable planar and monolithic integration for compact beamforming front ends.

Main Methods:

• The Butler matrix comprises four hybrid couplers without crossovers or phase shifters.
• Interdigital and non-metallic vias are incorporated into the coupler design to reduce size and increase bandwidth.
• Simulations were performed using CST software, and the design was implemented on a Rogers 8085 substrate, interfaced with SIW slot antennas.

Main Results:

• The matrix achieved an error magnitude loss of 1 dB and a phase error of 1.7°.
• A broad operational bandwidth of 3 GHz was obtained.
• Measured results demonstrated four phase-scanning states with return losses below -10 dB at 26 GHz.

Conclusions:

• The proposed Butler matrix provides a compact, efficient, and low-loss beamforming solution for 5G.
• It exhibits distinct scanning features without requiring crossovers or phase shifters.
• The design is well-suited for millimeter-wave beamforming front ends in 5G and future communication systems.