A triband graphene-based linear array THz antenna for 6G IoT applications using Spotted Hyena Optimizer

This study introduces a novel tri-band terahertz (THz) antenna array designed with graphene on a flexible, low-profile polyimide base, integrated with a SiO₂ layer. The antenna element comprises a hexagonal patch integrated with a cross slot and a cross loop resonator, enabling three distinct resonances at 0.252 THz (sub-THz), 0.493 THz (transition range), and 0.696 THz (THz regime). These bands are realised through geometrical evolution and strong inter-resonator coupling. The structure is optimised using the Spotted Hyena Optimizer (SHO) to achieve fractional bandwidths of 10.7 %, 8.3 %, and 8.05 %, respectively. The design is further extended into a two-element differential-fed array with an element spacing of 0.034λ at 0.252 THz, which ensures excellent isolation above 50 dB across all frequency bands. The proposed array achieves gains of 7.22 dBi, 11.106 dBi, and 11.06 dBi at the three operating bands with corresponding efficiencies of 85 %, 87 %, and 86 %, confirming its high-performance radiation capability. The estimated Multiple Input Multiple Output (MIMO) performance shows an Envelope Correlation Coefficient (ECC) below 0.01, apparent Diversity Gain (DG) close to 10 dB, and a low Total Active Reflection Coefficient (TARC), confirming high diversity performance. The antenna’s compact geometry, superior electromagnetic isolation, and consistent far-field patterns position it as a suitable option for 6 G IoT systems and integrated THz networks.