Butler Matrix Based on Dual-Mode Transmission Lines for Millimeter Wave Dual-Polarized Applications

This paper proposes a dual-mode Butler matrix based on the air suspended line (ASL) for millimeter-wave (mm-wave) dual-polarized antenna arrays. The ASL, which can simultaneously support TEM-mode and TE
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-mode, is used to design 90° hybrid coupler, 0 dB crossover, phase shift, and construct the dual-mode Butler matrix with high integration and low loss. A 4×4 dual-mode Butler matrix which is operating in mm-wave band is designed. Simulation results show that the reflection coefficients of this design are better than -15 dB in the range of 26.5 to 29.5 GHz, and have stable amplitude and phase response. The proposed butler matrix has wide application potential in 5G mm-wave dual-polarized multi-beam antenna arrays.