Compact Quad‐Port Dual‐Polarized Wideband MIMO Antenna With Rotational‐Symmetry Decoupling Element for n77/n78 Band Diversity

ABSTRACT This article introduces a compact quad‐port wideband MIMO antenna intended for the globally popular 5G n77/78 NR bands. The proposed MIMO antenna is dedicated for densely packed 5G smart devices and beyond. A simple printed monopole antenna with a U‐shaped slot and a slit positioned at the second radiating edge is used as the antenna unit element (29.72 × 29.72 mm 2 ) for the 2 × 2 MIMO. The proposed antenna has an overall dimension of 67.21 × 67.21 mm 2 , fabricated using the commercial FR4 substrate of thickness 1.57 mm. The orthogonally fed radiators in MIMO demonstrate polarization‐diverse feature responding to dual linear polar component (dual LP) (horizontal and vertical). The spatial diversity nature of the proposed four‐port MIMO is met through the novel hash‐like shaped metamaterial‐inspired rotationally symmetric decoupling element (DE). The DE, through its meticulous design and positioning at the functional plane (co‐plane) of the MIMO radiator, helped maintain a minimal port isolation ( s ij , where i ≠ j ) of > 20 dB throughout the −10‐dB impedance bandwidth of 1.66 GHz (2.58–4.24 GHz), centering the popular 5G NR band of 3.5 GHz. The DE even aided improvement in reflection coefficient ( s ij , where i = j ) from −19.87 to −44.01 dB, along with improved maximum radiation gain of 4.28 dBi at 3.5 GHz, with negligible impact toward the antenna efficiency metrics. The associated MIMO metrices, such as envelope correlation coefficient (ECC) (< 0.0001) and diversity gain (DG) (> 9.99 dB), estimated from far field results also complied to the acceptable range. Above all, the measured outcomes of the proposed antenna comparably mimic the simulation results carried out using Computer Simulation Technology (CST). In addition, equivalent circuit model for the complete four‐port MIMO with the DE realized in Advanced Design System (ADS) is also reported in this article. Further, the proposed MIMO antenna is also verified for its viability to real‐world device integration and specific absorption rate (SAR) analysis in the CST simulator.