Design of Wideband Decoupling Antenna Array for 5G Smartphones at N77/N78/N79/WLAN 5 GHz Bands

We propose a broadband decoupled antenna pair for 5G mobile terminals. The broadband decoupled design of this antenna pair is based on the characteristic mode theory (CMA) and defective ground structure. First, CMA is applied to obtain the characteristic current distribution of the antenna, then the characteristic current sensitive regions are optimized to make the antenna introduce new modes and obtain a wide bandwidth. After that, an antenna pair is added with defective ground structure to obtain a wideband decoupled antenna pair that has small size and high isolation. Next, an eight-element MIMO antenna system is constructed with the obtained broadband decoupled antenna pair, and a composite decoupling technique consisting of defective ground structure (DGS) and decoupling strip is applied to the two antenna pairs on the same side of the bezel to improve the isolation. The simulation and prototype test results show that the eight-element MIMO antenna with -10 dB bandwidth of 3.28 similar to 5.85 GHz mainly covers the N77/N78/N79/WLAN 5 GHz band, and the antenna pair are only 1.6 mm apart with good isolation (-16.7 dB), the ECC is less than 0.01, and it has a good total efficiency at the main operating frequency. Finally, the effect of a user's hand on the antenna is briefly analyzed to verify the robustness of the proposed MIMO antenna system.