Quad-Port MIMO Antenna Design with Low SAR for 3.5 GHz 5G and 5.8 GHz ISM Bands

A 4-port MIMO antenna with a low specific absorption rate (SAR) is presented in this paper for $3.5 \mathrm{GHz} 5 \mathrm{G}$, and 5.8 GHz ISM (Industrial, Scientific, and Medical) band applications. The antenna is developed on a $0.252 \mathrm{~mm}$ thick Rogers 5880 substrate with a compact size of $36.2 \mathrm{~mm} \times 36.2$ mm. The designed antenna offers a bandwidth of more than 100 $\mathrm{MHz}(3.47-3.58 \mathrm{GHz}$), and $350 \mathrm{MHz}(5.64-6.01 \mathrm{GHz})$ at 3.5 GHz and 5.8GHz bands, respectively. The antenna also provides a good radiation efficiency higher than $90 \%$ within the functioning frequency bands with a peak gain of 2.01 dBi and 1.71 dBi at 3.5GHz and 5.8GHz, respectively. To check the radiation effect of the antenna in terms of SAR on the human tissue, a 3-layer biological tissue model is created. And, the SAR value of the designed antenna is calculated. With $125 \mathrm{~mW}$ of supply power, the proposed antenna shows a SAR value of 1.92 $\mathrm{W} / \mathrm{Kg}$ and $0.465 \mathrm{~W} / \mathrm{kg}$ averaging on $10 \mathrm{~g}$ of tissue, while the antenna is positioned $10 \mathrm{~mm}$ away from the 3-layer human tissue model. The suggested antenna is a good fit for dual-band MIMO systems operating at sub-6 GHz based on its overall performance metrics.