28 GHz Multi-Beam Antenna Array based on Wideband High-dimension 16x16 Butler Matrix

A 28 GHz multi-beam array system employing a wideband high-dimension 16x16 Butler matrix as the Beamforming Network (BFN) is presented for wireless communication with high data rate. The complexity of high-dimension 16x16 Butler matrix is significantly reduced by utilizing a simple three-layer Microstripline (ML) structure to ease the design and fabrication. The proposed multi-beam array system based on wideband components can operate in a frequency range of 25 GHz to 30 GHz with the insertion loss of 4.8 dB at 28 GHz. 16 orthogonal beams with enhanced directional characteristics, i.e. 16 dBi main beam gain and 7° Half Power Beam Width (HPBW) covering a spatial angle range of ±68° are experimentally achieved. In addition, the measured radiation patterns at the different feeding frequencies (27 GHz, 28 GHz and 29 GHz) are compared to evaluate the true-time-delay effect in Butler matrix.