A Low‐Cost 4x4 Butler Matrix‐Fed Patch Antenna Array for Millimeter Wave Applications
Chang‐Keng Lin, Ding‐Bing Lin, Mon‐Li ChangABSTRACT
A low‐cost, low‐profile, high‐performance antenna array based on a 4×4 series‐fed patch with elliptical slots is presented in this article for fifth‐generation millimeter‐wave communications (5G mmWave). The antenna array can be manufactured easily on a two‐layer printed circuit board because of its simple design and lack of complex structures. It is designed for the Ka‐band (n257 band) with an impedance bandwidth of 3.1 GHz, covering the range from 26.1 GHz to 29.2 GHz. There is a fractional bandwidth of about 11.2%, several times greater than the fractional bandwidth of a series‐fed antenna. Within the impedance bandwidth, the radiation gain exceeds 11 dBi, with a maximum gain of 18.25 dBi. The radiation efficiency reaches an impressive 94% and the aperture efficiency reaches 44.6%. The isolation between the four excitation ports is less than −30 dB. Additionally, the 70% impedance bandwidth features right‐hand elliptical polarization with a 3:1 axial ratio. It also has an excellent beam steering range (theta angle: ). The following section will provide a detailed description of the antenna array and an analysis of the resonance frequencies. Further, the array antenna is combined with the Butler matrix network to form a beamforming function. Finally, the measured results agree well with the simulation results. This low‐cost, low‐profile, high‐performance antenna array will promote the popularization of 5G mmWave communications, which will be widely used worldwide.