A New Multiple Slot Antenna System for Sub 6 GHz Smartphones

This work presents a sub-6 GHz multiple-input multiple-output (MIMO) antenna array with sufficient characteristics for mobile phone applications. At the four corners of the mobile phone mainboard, there are eight compact hook-shaped slot antennas mounted. The mainboard size of the smartphone is chosen such that it fits inside 5-inch phones or larger, the size of the antenna board is 150 mm x 70 mm. The proposed antenna design is built on an FR-4 substrate material with a thickness of 0.8 mm. For maximum area utilization purposes, the proposed antenna elements occupy a small area with respect to the whole board area. The presented MIMO smartphone antenna covers an 800 MHz bandwidth from 3.2 GHz to 4 GHz. The MIMO performance, critical characteristics of the introduced monopole antenna array design, and the impact of the user’s hand on the radiation pattern are studied. The reflection coefficient (S
nn
) of the designed MIMO monopole array is below -10 dB. The reported radiation efficiency characteristic is higher than 85%, and a total efficiencies level is more than 60% as well. The values of the envelope correlation coefficient (ECC) are quite low. The obtained results make the presented MIMO antenna a very good candidate for 5G sub-6 GHz applications.