A low-SAR four-element antenna for ISM/NR78 band applications

This article introduces a novel four-port doughnut-shaped coplanar waveguide (CPW) multiple-input multiple-output (MIMO) antenna designed for dual-band operation. Operating within the 2.4-2.5 GHz and 4.4-5 GHz frequency ranges, the antenna boasts a remarkable 10 dB impedance bandwidth. Fabricated on a 55 mm x 55 mm x 1.6 mm FR4 substrate, this antenna achieves impressive isolation of over 20 dB among its elements through orthogonal placement, thereby enhancing key MIMO parameters such as envelope correlation coefficient (ECC), total active reflection coefficient (TARC), channel capacity loss (CCL), diversity gain (DG), and mutual coupling enhancement gain (MEG). Fabrication and measurement procedures validate the antenna's performance, demonstrating close alignment with simulation results. This validation confirms the antenna's suitability for deployment across various domains, including Industrial, Scientific, and Medical (ISM) bands and the n78 band for biomedical and 5 G applications. Additionally, specific absorption rate (SAR) calculations support the antenna's performance, ensuring compliance with regulatory standards for human exposure to electromagnetic fields.