Design of tri-band dual-polarized base station antenna for 2G/3G/4G/5G

To simplify the structure of a multi-frequency base station antenna, this paper presents a three-frequency dual-polarization base station antenna for the 2G/3G/4G/5G band. The antenna consists of two pairs of three-ring dipoles placed at ± 45° to produce a ± 45° dual-polarization characteristic. The three current paths, produced by outer, middle and inner rings, correspond to the three operating bands respectively. Balun feed of the loaded slot and stub optimizes the three-band impedance matching of the antenna. The measurement results show that the impedance bandwidths of the antenna in the three frequency bands reach 46.7% (1.69–2.72 GHz), 19.2% (3.3–4 GHz) and 8.7% (4.4–4.8 GHz). In the operating band, the gain of 3.6–4 GHz is maintained at 7 ± 2 dB, and the gain of the rest of the working band is maintained at 9 ± 0.5 dB as a whole. The cross-polarization ratio of the main axis of the antenna is greater than 26 dB. The antenna designed in this paper has the advantages of wide band, high gain and high polarization purity compared with the traditional multi-frequency base station antenna. These attributes make the proposed antenna a potential candidate for 5G commercial base stations.