Aperiodic 3D Folded Metamaterial and Defected Ground Structures to Enhance Isolation of Miniaturized MIMO Antenna

This paper proposes a novel miniaturized 3D folded metamaterial structure, combined with a segmented and defected ground optimization method, to design a compact, low-profile Multiple-Input Multiple-Output (MIMO) antenna with low coupling and high isolation. The 3D folded metamaterial utilizes the upper and lower metal layers of the dielectric substrate, folding the traditional metamaterial in half to achieve miniaturization. Additionally, the MIMO antenna system incorporates a defected ground structure to reduce electromagnetic wave reflection and scattering, leveraging the three-dimensional ground defect space to integrate the 3D folded metamaterial. The physical dimensions of the aperiodic 3D folded metamaterial are determined through a segmented optimization method. By utilizing the filtering characteristics of the metamaterial, a dual-band, dual-element MIMO antenna system is realized with high integration, high isolation, low coupling, and low return loss. Simulation results indicate that the antenna model demonstrates strong performance in the commonly used frequency band of 5.43 – 5.52 GHz, with an antenna spacing of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathbf{0.1}\ \lambda$</tex>, characterized by low return loss and high isolation. The effectiveness of the proposed design is validated through fabrication and testing.