Design, fabrication, and characterization of epsilon negative and near-zero index metasurface

This paper delves into the intricacies of designing, fabricating, and characterizing a metasurface exhibiting epsilon-negative (ENG) and near-zero index (NZI) properties. Specifically, it focuses on an eye-shaped coupled circular split ring resonator (CC-SRR) metasurface, crafted from copper on an epoxy resin fiber (FR-4) dielectric substrate material. The design is further optimized to induce resonance frequencies at approximately 7.5, 8.8, and 13.4 GHz within the C, X, and Ku bands, respectively. Utilizing the COMSOL Multiphysics and CST Microwave Studio simulation tools, the structural design is developed to ascertain its electromagnetic properties across the 1–15 GHz frequency spectrum. Experimental measurements of the transmission characteristics of the fabricated metasurface align closely with the simulated results. The electromagnetic field distributions of the proposed metasurface structure are scrutinized, revealing tunable characteristics contingent upon variations in the thickness (({t}_s)) of the dielectric substrate material and the copper resonator thickness (({t}_m)). Additionally, a theoretical model employing an equivalent circuit, featuring various inductor (L) and capacitor (C) components, is presented to compare against simulated results for the targeted resonance frequencies.