Beamforming Network Design Utilizing Node Microstrip Architectures for Dual-Polarized Endfire Millimeter-Wave Antenna Arrays

A node microstrip architecture is proposed for designing a compact Butler matrix (BM) that is integrated with a dual-polarized endfire antenna array. The node microstrip architecture can be used to form a variety of compact 2 × 2 port networks including, but not limited to, couplers and crossovers. By concatenating the 2 × 2 port networks together, a compact BM with any number of ports can be formed. Using the proposed method, a compact 4 × 4 port BM operating in the millimeter wave (mmWave) band is designed and integrated with a dual-polarized endfire antenna array. The size of the compact BM is $2.1\lambda \times 2\lambda $ and the size of the whole dual-polarized endfire antenna array with BM is $2.6\lambda \times 4.8\lambda $ , which is smaller than traditional structures. The measured radiation pattern of the dual-polarized antenna array can achieve beam scanning up to ±38° in the azimuth plane. The two beams in the dual-polarized endfire antenna array can also be independently steered. The optimized compact BM is potentially suitable for use in fifth-generation (5G) wireless communication handsets.