Dual-polarized wideband 5G N77 band slotted MIMO antenna system for next-generation smartphones

In this work, a slotted wideband eight-element multiple-input multiple-output (MIMO) antenna system is presented, which covers the N77 (3.2-4.2 GHz) frequency band. The MIMO antennas are printed on a 0.8-mm-thick FR-4 substrate with dimensions of $150\times75$ mm2. The antennas are placed along the length and width of the printed circuit board (PCB). The arrangement of antenna elements offers pattern and polarization diversity, enhancing the smartphone's ability to receive signals from various directions. The wideband characteristics in the frequency range of 3.25-4.49 GHz are achieved by utilizing a T-slot and an inverted C-slotted stub together. The radiation and total efficiency are found to be >60% for all the MIMO elements. For enhanced isolation between antenna elements placed along the width of the PCB, a slot is introduced, which ensures an isolation of 14.5 dB. This helps achieve an envelope correlation coefficient (ECC) < 0.025, diversity gain (DG) >9.95 dB, and a maximum channel capacity (CC) of 40 bps/Hz. The performance of the MIMO antenna is also assessed in the presence of a human, and comparable results are observed. In addition, the examination of the specific absorption rate (SAR) confirms that it remains well within the safety margins when in proximity to humans.