Tunable Compact Metamaterial-Based Double-Negative/Near-Zero Index Resonator for 6G Terahertz Wireless Applications.

This paper introduces the tunability performance, concept, and analysis of a unique and miniaturized metamaterial (MTM) unit cell covering the upcoming 6G applications. The proposed metamaterial consists of two metallic star-shaped split-ring resonators (SRR). It has a line segment placed in the middle of the structure, which can feature tunable characteristics. The proposed design provides dual resonances of transmission coefficient S21 at 0.248 and 0.383 THz with a significant operating frequency span of 0.207-0.277 and 0.382-0.390 THz, respectively. Moreover, wide-range achievement, negative permittivity, double-negative (DNG) refractive index, and near-zero permeability characteristics have been exhibited in two (z and y) principal wave propagation axes. The resonance frequencies are selective and modified by adjusting the central slotted-strip line length. Furthermore, the metamaterial is constituted on a polyimide substrate while the overall dimensions are 160 × 160 μm 2 . A numerical simulation of the proposed design is executed in CST microwave studio and has been compared with advanced design software (ADS) to generate the proposed MTM's equivalent circuit, which exhibits a similar transmission coefficient (S21).