A High-Performance Multi-Band Fractal MIMO Antenna Design for Terahertz Communication Systems in 6G and Beyond

Abstract

In this paper, a novel compact two-port multi-band terahertz (THz) Multiple-Input Multiple-Output (MIMO) antenna based on the dual-polarized slot technique is designed for 6G and beyond wireless communication systems. The proposed antenna is designed and simulated on a quartz substrate using a graphene-based radiating element and operates at seven distinct resonance frequencies, i.e., 5.804, 6.368, 6.932, 7.508, 8.08, 8.648, and 9.236 THz, having bandwidths of 0.45, 0.37, 0.36, 0.38, 0.44, 0.44, and 0.45 THz, respectively. In order to reduce mutual coupling, a diagonal element configuration is employed in the two-element MIMO antenna. An isolation greater than -47 dB is achieved in all bands, and a maximum isolation below 70 dB is obtained approximately at 6.6 THz and 9.45 THz. The antenna has a maximum gain of 15.21 dB, and it maintains a radiation efficiency of more than 92% at the important resonance frequencies. The diversity effect calculations showed an exceptionally low Envelope Correlation Coefficient (ECC = 1.37 × 10⁻⁵), a near-ideal value of Diversity Gain (DG = 9.9999 dB), and a Channel Capacity Loss (CCL) of less than 0.4 bps/Hz, which confirms very good channel independence. An RLC Equivalent Circuit Model (ECM) using Advanced Design System (ADS) has been developed and verified, showing a good agreement with the full-wave simulation in CST and accurately characterizing the impedance behavior of the antenna. The simulation findings demonstrate that the proposed antenna can provide wide multi-band frequency coverage, high gain, good isolation, and good diversity performance, which make it a strong contender for high-throughput THz MIMO applications in the future 6G wireless and sensing systems.