Split-Ring Enclosed K-shaped Rotational Symmetric Metamaterial Absorber for Multiband Wireless Applications

This article describes a metamaterial absorber (MMA) with an enclosed K-shaped structure based on a rotationally symmetric Square Split Ring Resonator (SSRR). The MMA's unit cell was developed using FR-4, an easily accessible, reasonably priced substrate material with a dielectric constant 4.3. In this work, three resonances covering the 6 GHz band (5.925 to 6.725 GHz), the 8 GHz band (7.725-8.275 GHz), and the 15 GHz band (14.4-15.35 GHz) are shown. These resonances have adjustable multifunctional properties, Single Negative (SNG), Epsilon Negative (ENG), and near zero index characteristics. Additionally, at these frequencies, its refractive index is almost zero, and its electric length is 0.2λ×0.2λ×0.2λ×.032λ, where λ is the wavelength determined at the lowest resonance frequency (6 GHz). The planned unit cell's increased effective medium ratio (EMR) demonstrates the MMA's compactness. Due to its tiny size, robust EMR, negative permittivity, permeability, and almost zero refractive index, this MTM is perfect for WiFi 6E, Civil, and multiband wireless applications, especially for outstanding gain with enhanced directivity.