• The article presents a PIFA MIMO antenna for 5G and WLAN bands. • The proposed antenna is optimized by characteristic mode theory (CMT). • The proposed antenna is analyzed for SAR and MIMO diversity parameters. This article presents a compact, wideband, four-port, multiple-input-multiple-output (MIMO) planar inverted-F antenna (PIFA) for the sub-6 GHz 5G and WLAN bands. The dimensions and strategic placements of the shorting pin, feed plate, and radiator are determined using characteristic mode theory (CMT), as it is a rapid development tool. The current distribution on the antenna structure is solved using an integral solver to investigate and enhance the specific mode of interest. The process is repeated by modifying the antenna structure and applying the solver till the desired modes are generated. Through CMT, two complementary structures are evolved and incorporated into the MIMO antenna for efficient performance. Furthermore, the antennas ground plane is tuned with eight slots, which enhanced the bandwidth, isolation, and directivity (at θ = ± 52 ∘ ). Again, these slot positions have been strategically chosen to keep the ground free for other RF circuitry. The four radiating elements are arranged to exploit the benefits of spatial and pattern diversity, achieving isolation better than 20 dB across the 3.2-5.46 GHz operating band (52.19% fractional bandwidth). The antenna achieves a gain of 5.5–7 dBi with an average total efficiency of 84%. MIMO performance metrics, including envelope correlation coefficient (ECC), diversity gain (DG), and channel capacity loss (CCL), confirm reliable operation. Specific absorption rate (SAR) values are well within international limits (0.558 W/kg at 1 g and 1.24 W/kg at 10 g). Moreover, stable performance is achieved even when operated with a mobile casing. The antenna also demonstrated a data rate of over 25 Gbps for a 15 dB SNR. It shows reliable connectivity delivering >10 Gbps of data over more than 80 m. Thus, the proposed antenna is a strong candidate for next-generation portable wireless devices due to its compactness, simple geometry, and robust performance.
Shariff et al. (Sun,) studied this question.