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.

In this article, a symmetric split ring resonator (SRR) based metamaterial (MTM) is presented that exhibits three resonances of transmission coefficient (S₂₁) covering S, C, and X-bands with epsilon negative (ENG) and near zero index properties. The proposed MTM is designed on an FR4 substrate with the copper resonator at one side formed with two square rings and one circular split ring. The two square rings are coupled together around the split gap of the outer ring, whereas two split semicircles are also coupled together near the split gaps. Thus, gap coupled symmetric SRR is formed, which helps to obtain resonances at 2.78 GHz, 7.7 GHz and 10.16 GHz with desired properties of the MTM unit cell. The MTM unit cell's symmetric nature helps reduce the mutual coupling effect among the array elements. Thus, different array of unit cells provides a similar response to the unit cell compared with numerical simulation performed in CST microwave studio and validated by measurement. The equivalent circuit is modelled for the proposed MTM unit cell in Advanced Design System (ADS) software, and circuit validation is accomplished by comparing S₂₁ obtained in ADS with the same of CST. The effective medium ratio (EMR) of 10.7 indicates the compactness of the proposed MTM. A test antenna is designed to observe the effect of the MTM over it. Numerical analysis shows that the proposed MTM have an impact on the antenna when it is used as the superstrate and helps to increase the gain of the antenna by 95% with increased directivity. Thus, compact size, high EMR, negative permittivity, near zero permeability and refractive index makes this MTM suitable for S, C and X band applications, especially for antenna gain with directivity enhancement.

In this paper, a meander-lines-based epsilon negative (ENG) metamaterial (MTM) with a high effective medium ratio (EMR) and near-zero refractive index (NZI) is designed and investigated for multiband microwave applications. The metamaterial unit cell is a modification of the conventional square split-ring resonator in which the meander line concept is utilized. The meander line helps to increase the electrical length of the rings and provides strong multiple resonances within a small dimension. The unit cell of proposed MTM is initiated on a low-cost FR4 substrate of 1.5 mm thick and electrical dimension of 0.06λ × 0.06λ, where wavelength, λ is calculated at the lowest resonance frequency (2.48 GHz). The MTM provides four major resonances of transmission coefficient (S₂₁) at 2.48, 4.28, 9.36, and 13.7 GHz covering S, C, X, and Ku bands. It shows negative permittivity, near-zero permeability, and near-zero refractive index in the vicinity of these resonances. The equivalent circuit is designed and modeled in Advanced Design System (ADS) software. The simulated S₂₁ of the MTM unit cell is compared with the measured one and both show close similarity. The array performance of the MTM is also evaluated by using 2 × 2, 4 × 4, and 8 × 8 arrays that show close resemblance with the unit cell. The MTM offers a high effective medium ratio (EMR) of 15.1, indicating the design's compactness. The frequency hopping characteristics of the proposed MTM is investigated by open and short-circuited the three outer rings split gaps by using three switches. Eight different combinations of the switching states provide eight different sets of multiband resonances within 2–18 GHz; those give the flexibility of using the proposed MTM operating in various frequency bands. For its small dimension, NZI, high EMR, and frequency hopping characteristics through switching, this metamaterial can be utilized for multiband microwave applications, especially to enhance the gain of multiband antennas.

In this paper, a tuned metamaterial (MTM) consisting of a symmetric split ring resonator is presented that exhibits epsilon negative (ENG), near zero permeability and refractive index properties for multiband microwave applications. The proposed metamaterial is constituted on a Rogers (RT-5880) substrate with 1.57 mm thickness and the electrical dimension of 0.14λ × 0.14λ, where wavelength, λ is calculated at 4.2 GHz. The symmetric resonating patch is subdivided into four equal and similar quartiles with two interconnecting split rings in each quartile. The quartiles are connected at the center of the substrate with a square metal strip with which four tuning metal strips are attached. These tuning metal strips are acted as spacers between four quartiles of the resonator patch. Numerical simulation of the proposed design is executed in CST microwave studio. The proposed MTM provides four resonances of transmission coefficient (S₂₁) at 4.20 GHz, 10.14 GHz, 13.15 GHz, and 17.1 GHz covering C, X and Ku bands with negative permittivity, near zero permeability and refractive index. The calculated effective medium ratio (EMR) is 7.14 at 4.2 GHz indicates its compactness. The resonance frequencies are selective in nature which can be easily tuned by varying the length of the tuning metal stubs. The equivalent circuit of the proposed MTM is modelled in Advanced Design Software (ADS) that exhibits a similar S₂₁compared with CST simulation. Surface current, electric and magnetic fields are analyzed to explain the frequency tuning property and other performances of the MTM. Compact size, ENG with near zero permeability and refractive index along with frequency selectivity through tuning provides flexibility for frequency selective applications of this MTM in wireless communications.

This study has investigated the impact of inverse G-like shape resonators that exhibited epsilon negative (ENG) and near-zero refractive index (NZI) properties for multi-band wireless communications applications. The electrical measurement of structure is 0.118λ × 0.118λ × 0.021 λ, which is calculated at 3.94 GHz. FR-4 is used as a substrate layer, and the resonator is designed on it. This structure is manifested in the ENG and NZI characteristics within the frequency range of 3.8–4.17, 7.68–8.54, 10.67–11.36 GHz, and 4.07–4.15 and 8.29–8.37 GHz, respectively. This study also manifests the polarization insensitivity nature of 0°–90°, and the incident angle is investigated up to 60° for both TE and TM modes. The proposed structure achieves triple resonance at 3.94 GHz, 8.08 GHz, and 11.17 GHz, respectively, included in the S, C, and X frequency bands. The CST Microwave Studio 2019 software is conducted to design, develop, perform analysis, investigate electromagnetic properties, and extract effective medium parameters. The Advanced Design Software (ADS) is used to model the equivalent circuit of the unit cell. The simulated, measured, and ADS results verified the scattering parameter performance. The EMR value of the structure is 8.47, indicating the structure's compactness. The compact design with simplicity, ENG, and NZI properties make the proposed structure significant for microwave application, mainly to enhance the antenna bandwidth and gain filter design. ENG and NZI properties the operation frequency stability and efficiency for low earth orbit nanosatellite communications.