5G SAR-Reduction MIMO Antenna With High Isolation for Full Metal-Rimmed Tablet Device

This communication focuses on the specific absorption rate (SAR) reduction of multiple-input–multiple-output (MIMO) antenna with high isolation for fifth-generation (5G) full metal-rimmed tablet devices. This is the first study to undertake a longitudinal analysis between equalization mode and reduction of SAR. Therefore, the study makes a major contribution to the research on the reduction of SAR by demonstrating the cancellation of inverted phase currents generated by the equalization mode. In addition, the utilization of equalization mode and full metal-rim avoids a 44% decrease in efficiency caused by hand grip. Furthermore, the isolation capacitance is utilized to suppress the traveling wave on the ground plane. As a result, the isolation of the MIMO antenna is improved by 12.94 dB. An
$8\times 8$
MIMO tablet array antenna is manufactured to validate the simulation. The measured maximum normalized values of 0 mm body SAR averaged over any 1 g tissue is 0.4 W/kg, which is far below the standard of Institute of Electrical and Electronics Engineers (IEEE) and U.S. Federal Communications Commission (FCC). The measured −6 dB impedance bandwidth is 3.4–3.6 GHz and isolation is better than 20.11 dB. The measured efficiency is higher than 53% and envelop correlation coefficient (ECC) is less than 0.17.