Abstract
This study describes a high-gain, ultra-wideband quad-port THz MIMO antenna designed for 6G, TWPAN, and next-generation wireless communications. The design uses fractal radiating elements, graphene-based tunability, and a defective ground structure (DGS) to improve bandwidth, isolation, and impedance matching. The antenna's tiny polyimide substrate (130 × 130 μm²) enables an ultra-wide bandwidth of 62 THz, a peak gain of 15.24 dB, and port-to-port isolation of 43 dB, resulting in strong MIMO performance. Integrating metasurface structures and graphene tuning allows for dynamic frequency reconfiguration, making it suitable for a wide range of wireless applications. The performance study reveals good spatial diversity and low signal distortion, with an envelope correlation coefficient (ECC) of less than 0.05 and a Diversity Gain (DG) of nearly 10 dB. Additionally, the Total Active Reflection Coefficient (TARC) and Channel Capacity Loss (CCL) are kept to a minimum, maximising spectral efficiency. UV photolithography and electron beam evaporation (EBE) are employed to fabricate the antenna, yielding high precision and minimal losses. Compared to existing designs, it outperforms them in terms of gain, isolation, and multi-band operation. The suggested THz MIMO antenna's scalability, compact form factor, and customisable properties make it an attractive choice for future 6G wireless networks, sub-THz IoT systems, and ultra-fast personal area networks (PANs). Future research will focus on adaptive beamforming, real-world prototypes, and experimental validation to improve its application in next-generation THz communication systems.