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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 (Snn) 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.