Metasurface inspired wideband high isolation THz MIMO antenna for nano communication including 6G applications and liquid sensors

In this paper, a circular-shaped microstrip feed wideband THz antenna with a small dimension of 480 × 480 $\times$ $150\mu m$³ is presented on a gold-plated diffused quartz substrate with a relative permittivity of 3.50. It has an impedance operational bandwidth of 0.51-1.46 THz (80.76%) with a peak gain of 10.16 dBi. Throughout the desired bandwidth, radiation efficiency is more than 70%. This single-element antenna is transformed into a two-element MIMO antenna using a butterfly-shaped decoupling structure that included an electromagnetic coupling structure and a metasurface absorber to increase isolation and diversity characteristics along with impedance bandwidth 0.4-2.0 THz. Return loss, gain, radiation efficiency, co-cross E and H-polarization, electric field, magnetic field, current density, SAR, and diversity parameters such as Envelope Correlation Coefficient (ECC), Directive Gain (DG), Total Active Reflection Coefficient (TARC), and Channel Capacity Loss (CCL) are all within acceptable limits for Nano wireless applications. The proposed wideband THz MIMO antenna can also be used as a sensor to measure the proportion of crystallized sugar (C₁₂H₂₂O₁₁) and salt (NaCl) in water. The fields in which this antenna has applications include 6G, imaging, 3D printing, THz-wave radar, healthcare, liquid sensors with excellent sensitivity, and astronomy radiometric.