Millimeter-Wave Broadband Multi-Beam End-Fire Dual Circularly Polarized Antenna Array

A millimeter-wave (mmWave) broadband multi-beam end-fire dual circularly polarized (CP) antenna array using dielectric loaded stepped slot elements is proposed. The proposed antenna element exhibits excellent performance, including broad bandwidth, wide beamwidth, and compact element size. The feeding network using substrate integrated waveguide (SIW) is designed for multi-beam array applications. A broadband 4 x 4 SIW Butler matrix, interconnections, and transitions are designed and applied in the array prototype. The fabricated array prototype achieves the impedance bandwidth of 29.3% and the 3-dB axial ratio bandwidth of 22.5%. The proposed multi-beam end-fire dual-CP antenna array would be an attractive candidate for 5G mmWave applications.