Abstract
An inductively tuned modified split-ring resonator-based metamaterial (MTM) is presented in this article that provides multiple resonances covering S, C, X, and Ku-bands. The MTM is designed on an FR-4 substrate with a thickness of 1.5 mm and an electrical dimension of 0.063λ × 0.063λ where wavelength, λ is calculated at 2.38 GHz. The resonator part is a combination of three squared copper rings and one circular ring in which all the square rings are modified shaped, and the inner two rings are interconnected. The resonance frequency is tuned by adding inductive metal strips in parallel two vertical splits of the outer ring that causes a significant shift of resonances towards the lower frequencies and a highly effective medium ratio (EMR) of 15.75. Numerical simulation software CST microwave studio is used for the simulation and performance analysis of the proposed unit cell. The MTM unit cell exhibits six resonances of transmission coefficient (S21) at 2.38, 4.24, 5.98, 9.55, 12.1, and 14.34 GHz covering S, C, X, and Ku-bands with epsilon negative (ENG), near-zero permeability, and near-zero refractive index (NZI). The simulated result is validated by experiment with good agreement between them. The performance of the array of the unit cells is also investigated in both simulation and measurement. The equivalent circuit modeling has been accomplished using Advanced Design Software (ADS) that shows a similar S21 response compared to CST simulation. Noteworthy to mention that with the copper backplane, the same unit cell provides multiband absorption properties with four major absorption peaks of 99.6%, 95.7%, 99.9%, 92.7% with quality factors(Q-factor) of 28.4, 34.4, 23, and 32 at 3.98, 5.5, 11.73 and 13.47 GHz, respectively which can be applied for sensing and detecting purposes. The application of an array of the unit cells is investigated using it as a superstrate of an antenna that provides a 73% (average) increase of antenna gain. Due to its simple design, compact dimension with high EMR, ENG property with near-zero permeability, this multiband NZI metamaterial can be used for microwave applications, especially for multiband antenna gain enhancement.
Highlights
Metamaterial, as an artificial media, shows some exotic properties acquired from geometry rather than composition
A split-ring resonator (SRR) based material is introduced by Meng et al that is operable in THz frequency range and can be used to sensing dielectric
The unit cell is formed on a low-cost FR-4 substrate with a small electrical dimension of 0.063λ × 0.063λ, where λ is calculated at the lowest resonance frequencies of 2.38 GHz
Summary
Metamaterial, as an artificial media, shows some exotic properties acquired from geometry rather than composition. A metamaterial microwave absorber is presented in[17] that is constructed with asymmetric sectional resonators of different sizes This metamaterial absorber exhibits broadband near-unity absorption characteristics within 7–9 GHz. Cheng et al demonstrated an anisotropic metamaterial composed of a bi-layered disk-split-ring array and sandwiched sub-wavelength metal grating. A cross-coupled SRR based metamaterial has been reported in[30] that provides three resonances at covering C, X and Ku-bands with epsilon negative properties and suitable for the applications in satellite and radar communication devices. A tunable metamaterial is presented in[33] where the tunable unit is integrated in background metallic layer This MTM absorber shows modulated frequency depending upon the temperature, have the potentiality for temperature sensing and thermal emitters. The application of this MTM in the antenna is discussed, followed by the conclusion in the final section
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