Mutual Coupling Reduction in Multiple-Input Multiple-Output Antenna Based on Metamaterial at Low THz Frequency Band

In this study, spiral resonator and complementary spiral resonator metamaterials have been applied to increase isolation in a dual-element MIMO antenna operated in the low terahertz frequency range 0.55 THz to 0.63 THz. Mutual coupling is reduced in the entire working bandwidth of the antenna, relatively wide bandwidth of 13.5%, and is at its maximum value, equal to 23 dB, at the antenna resonance frequency of 0.58 THz. In addition, the values of envelope correlation coefficient, diversity gain, back-lobe radiation and realized gain over frequency are enhanced with metamaterial loading. Effectiveness of the metamaterial loading on mutual coupling reduction is confirmed through investigating surface current on the antenna structure. Compared to other methods of mutual coupling reduction which mentioned in the text of this study, the proposed method has a relative advantage in terms of wide bandwidth, simplicity of design and increase high isolation in the terahertz frequency band. Applications of this structure include beyond 5G technologies, medical imaging, high-bandwidth and high capacity in short-range communications at low THz frequency band.