Search Results (32)

We propose a single-phase chiral elastic metamaterial capable of simultaneously exhibiting negative effective mass density and negative bulk modulus in the ultrasonic frequency range. The unit cell consists of a regular hexagonal frame connected to a central circular mass through six obliquely oriented, slender aluminum beams. The design avoids the manufacturing complexity of multi-phase systems by relying solely on geometric topology and chirality to induce dipolar and rotational resonances. Dispersion analysis and effective parameter retrieval confirm a double-negative frequency region from 30.9 kHz to 34 kHz. Finite element simulations further demonstrate negative refraction behavior when the metamaterial is immersed in water and subjected to 32 kHz and 32.7 kHz incident plane wave. Equifrequency curves (EFCs) analysis shows excellent agreement with simulated refraction angles, validating the material’s double-negative performance. This study provides a robust, manufacturable platform for elastic wave manipulation using a single-phase metallic metamaterial design. Full article

In natural materials, thermal expansion is typically positive, and negative thermal expansion is rarely observed. The tunable thermal expansion properties of mechanical metamaterials offer a promising solution to challenges caused by rapid temperature fluctuations. Therefore, this study proposes a dual-material double-trapezoidal hexagonal mechanical metamaterial (DTH), and derives the thermoelastic equations that build the relationship between temperature, external force, and displacement. Through theoretical analysis and numerical simulation, the intrinsic mechanism between the CTE and geometric parameters of DTH is revealed. Through the synergistic effect of dual materials and structural design, this metamaterial not only achieves thermal expansion regulation but also enhanced lightweight performance. The results show that by controlling the geometric parameters of DTH, the adjustment of effective CTE and elastic modulus can be realized, and the metamaterial composed of positive CTE materials can achieve a range of thermal expansion behaviors, including near-zero CTE and negative CTE. The tunable thermal expansion range extends from +39.92 ppm/°C to −3640.6191 ppm/°C. The metamaterials proposed in this study are not only superior to traditional materials in terms of thermal expansion performance but also have the characteristics of light weight and simple structure. This multifunctional material achieves higher performance and adaptability in applications. Full article

This article presents a symmetrical reduced-size eight-element MIMO antenna array with high electromagnetic isolation among radiators. The array utilizes easy-to-build techniques to cover the n77 and n78 new radio (NR) bands. It is based on an octagonal double-negative metamaterial split-ring resonator (SRR), which enables a size reduction of over 50% for the radiators compared to a conventional disc monopole antenna by increasing the slow-wave factor. Additionally, due to the extreme proximity between the radiating elements in the array, the modal significance (MS) method was employed to identify which propagation modes had the most impact on the electromagnetic coupling among elements. This approach aimed to mitigate their effect by using an electromagnetic barrier, thereby enhancing electromagnetic isolation. The electromagnetic barriers, implemented with strip lines, achieved isolation values exceeding 20 dB for adjacent elements (<0.023 λ) and approaching 40 dB for opposite ones (<0.23 λ) after analyzing the surface current distribution by the MS method. The elements are arranged in axial symmetry, forming an octagon with each antenna port located on a side. The array occupies an area of 0.32 λ² at 3.5 GHz, significantly smaller than previously published works. It exhibits excellent performance for MIMO applications, demonstrating an envelope correlation coefficient (ECC) below 0.0001, a total active reflection coefficient (TARC) lower than −10 dB for various incoming signals with random phases, and a diversity gain (DG) close to 20 dB. Full article

Using a theory of homogenization that consists in the discretization of the inclusion of a binary phononic crystal in small volumes, in which the material parameters can be expanded in Fourier series, we have determined the dependence of the effective elastic parameters as a function of the frequency. In particular, the frequency dependence of all the elements that constitute the effective tensors of stiffness (moduli of elasticity) and density was analyzed for a 1D phononic crystal conformed of materials whose main characteristic is the high contrast between their elastic properties. In this dynamic case of homogenization, it was found that the effective parameters can reproduce the exact dispersion relations for the acoustic modes that propagate along the periodicity direction of the crystal. Particularly, in the second pass band (high-frequency branch) corresponding to the transverse vibrational modes, the homogenized elastic phononic crystal exhibits a metamaterial behavior because the effective C₄₄-component (shear modulus) and dynamic mass density were found to be both negative. It is noteworthy that the study derived from this homogenization technique can lead to design of double negative metamaterial systems for potential applications. Full article

This article presents the design and analysis of a low profile double-negative (DNG) metamaterial unit structure for 5G mmWave (millimeter wave) applications. The structure, comprised of double-slotted rectangular ring patches, experiences the peak current value near the magnetic resonance, causing the metamaterial to resonate at 28 GHz where it exhibits negative effective permittivity and permeability. The 3.05 mm × 2.85 mm compact structure is designed over a substrate Rogers RT/Duroid 5880 to attain better effective medium ratio (EMR) in the 5G frequency range (27.1–29.2 GHz). A rigorous parametric study is conducted to obtain the proposed design. Full-wave electromagnetic simulation software tools CST and HFSS are used to generate the scattering parameters for the analysis. The Nicolson–Ross–Wier method is used to observe the negative effective permittivity and permeability. In addition, different output quantities, e.g., surface current and electric and magnetic field distribution, are investigated. The structure is further tested with 1 × 2, 2 × 2, and 4 × 4 arrays, where the results show adequate agreement to be considered for 5G mmWave applications. Full article

The interaction between an electromagnetic plane wave and a metallic wedge coated with a uniform layer made of a double-negative metamaterial is studied by means of the uniform asymptotic physical optics method in the high-frequency range, e.g., at microwave and optical frequencies. The apex angle of the structure is arbitrarily chosen, and the wave is at a skew incidence with respect to the external edge, which is formed by the metamaterial layers covering the wedge faces. The proposed method is built on the scattering integral involving electric and magnetic surface currents as physical optics equivalent sources, and it takes advantage of analytic evaluations. The last step uses a uniform asymptotic procedure to obtain a closed form expression of the diffracted field to be added to the geometrical optics one for computing the total field at the observation point in the neighboring free space. The study also includes a numerical validation of the method. Full article

The strong localization of the electric and magnetic fields in metamaterial-based structures has attracted a new era of radiation fields in the microwave range. In this research work, we represent a double split ring enclosed nested meander-line-shaped metamaterial resonator with a high effective medium ratio layered on a dielectric substrate to enhance the sensitivity for the material characterization. Tailoring a metallic design and periodical arrangement of the split ring resonator in a subwavelength range introduced field enhancement and strong localization of the electromagnetic field. The design methodology is carried out through the optimization technique with different geometric configurations to increase the compactness of the design. The CST microwave studio is utilized for the extraction of the scattering computational value within the defined boundary condition. The effective parameters from the reflection and transmission coefficient are taken into account to observe the radiation characteristics for the interaction with the applied electromagnetic spectrum. The proposed metamaterial-based sensor exhibits high sensitivity for different dielectric materials with low permittivity values. The numerical data of the frequency deviation for the different dielectric constants have shown good agreement using the linear regression analysis where the sensitivity is R² = 0.9894 and the figure of merit is R² = 0.9978. Full article

A symmetric engineered high polarization-insensitive double negative (DNG) metamaterial (MM) reflector with frequency tunable features for fifth-generation (5G) antenna gain and directivity enhancement is proposed in this paper. Four identical unique quartiles connected by a metal strip are introduced in this symmetric resonator that substantially tunes the resonance frequency. The proposed design is distinguished by its unique symmetric architecture, high polarization insensitivity, DNG, and frequency tunable features while retaining a high effective medium ratio (EMR). Moreover, the suggested patch offers excellent reflectance in the antenna system for enhancing the antenna gain and directivity. The MM is designed on a Rogers RO3010 low loss substrate, covering the 5G sub-6GHz band with near-zero permeability and refractive index. The performance of the proposed MM is investigated using Computer Simulation Technology (CST), Advanced Design Software (ADS), and measurements. Furthermore, polarization insensitivity is investigated up to 180° angles of incidence, confirming the identical response. The 4 × 4 array of the MM has been utilized on the backside of the 5G antenna as a reflector, generating additional resonances that enhance the antenna gain and directivity by 1.5 and 1.84 dBi, respectively. Thus, the proposed prototype outperforms recent relevant studies, demonstrating its suitability for enhancing antenna gain and directivity in the 5G network. Full article

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 μm². 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). Full article

This research paper proposes an analytical approach for evaluating electromagnetic scattering from a planar complex object made of a perfect electric conductor, which hosts a double negative metamaterial half-layer on the lit face. The method is based on the physical optics approximation of equivalent sources and works in the framework of the uniform geometrical theory of diffracion, so that the scattered field in the surrounding free space is obtained by adding the reflected contribution and the diffracted one, which is originated by the surface break. The effectiveness of the proposed approach is tested and proved by using a full-wave numerical tool to generate reference values. Full article

Aiming at the unsatisfactory sound transmission loss (STL) of thin-plate structures in the low-mid frequency range, this paper proposes an acoustic insulation metamaterial with distributed piezoelectric resonators. A complete acoustic prediction model is established based on the effective medium method and classical plate theory, and the correctness is verified by the STL simulation results of the corresponding acoustic-structure fully coupled finite-element model. Moreover, the intrinsic relationship between the dual equivalent negative properties and STLs is investigated to reveal the insulation mechanisms of this metamaterial. Then, the influence of the geometric and material parameters on the double equivalent negative characteristics is studied to explore the broadband STL for distributed multi-modal resonant energy-dissipation modes in the frequency band of interest. The results show that the two acoustic insulation crests correspond to the dual equivalent negative performances, and the sound insulation in the low-mid frequency range is improved by more than 5 dB compared with that of the substrate, even up to 44.49 dB. Full article

The development and improvement of the dual-band 802.11ac standard Wi-Fi and wide bandwidth satellite communication devices are currently research subjects that have garnered significant interest. In this paper, double C-shaped two split-ring resonator (SRR) bounded unit cells were developed, which are applicable for S, C, and X band applications, including dual-band Wi-Fi communication devices and satellite communication applications for its effective medium ratio (EMR) of 15.6, which results in a 2.4 GHz resonance frequency and wide bandwidth (S21 < −10 dB) of 1650 MHz at an 11.5 GHz resonance frequency. A copper resonator and the popular substrate material Rogers RT 5880 (thickness of 1.575 mm) were adopted for analyzing the characteristics of this unit cell. The $8\times 8 {\mathrm{mm}}^2$ structure was designed and simulated using a commercially available electromagnetic simulator CST (Computer Simulation Technology) Studio Suite 2019, which was utilized at four resonance frequencies: 2.4 GHz, 5.6 GHz, 8.93 GHz, and 11.5 GHz. The electric field, magnetic field, and surface current distribution were examined by modifying the metamaterial unit cell design structure, showing effective results. To confirm the CST simulation results, the newly designed double C-shaped double-negative metamaterial (DNG) was also simulated with the Ansys High-Frequency Structure Simulator (HFSS) and compared with the extracted results. The suggested metamaterial is advised for usage in Wi-Fi and satellite communication applications for superior long-distance communication performance and efficiency with the compactness of the structure. Full article

This study presents a double-inverse-epsilon-shaped, triple-band epsilon-negative (ENG) metamaterial with two split ring resonators (SRRs). The proposed unit cell comprises a single slit two SRRs with two inverse-epsilon-shaped metal bits. Rogers RT6002, of dimension 10 × 10 × 1.524 mm³, is used as a substrate. An electromagnetic simulator CST microwave studio is used to investigate the effective medium parameters of the material. The proposed metamaterial shows three resonance peaks that are demarcated at the frequencies 2.38 GHz, 4.55 GHz and 9.42 GHz consecutively. The negative permittivity of the metamaterial is observed at the frequency ranges of 2.39–2.62 GHz, 4.55–4.80 GHz and 9.42–10.25 GHz. The goodness of the material was presented by the effective medium ratio (EMR) of the unit cell at 12.61. In addition, the simulated results are authenticated by using different electromagnetic simulators such as HFSS and ADS for the equivalent circuit model, which exhibits insignificant disparity. The anticipated scheme was finalised through some parametric analyses, together with configuration optimisation, different unit cell dimensions, several substrate materials, and altered electromagnetic (EM) field transmissions. The proposed triple band (S-, C- and X-bands) with negative permittivity (ε) metamaterial is practically used for numerous wireless uses, for instance, far distance radar communication, satellite communication bands and microwave communication. Full article

In this article, a compact dual band metamaterial inspired circular microstrip patch antenna for WLAN applications is presented. The antenna consists of a circular patch loaded with a complementary double negative metamaterial structure which produces a percentage miniaturisation of 60.7%. The circular microstrip patch antenna used for developing the proposed antenna has a resonant frequency of 6.2 GHz with an impedance bandwidth of 3.5% before the metamaterial structure is applied upon it. The loading of the proposed metamaterial structure inspires the antenna to lower its resonant frequency with enhanced bandwidth and generate one additional resonance. The designed antenna can be tuned throughout the C-band by simply altering the size of the metamaterial structure loaded upon it. However, the prototype of the antenna is designed for the most commonly used wireless communication bands at 2.4 GHz and 5.2 GHz. The 10 dB impedance bandwidth of 1.63% at 2.4 GHz and 13.15% at 5.2 GHz are achieved by this design. The electrical parameters of the proposed antenna are ka = 0.72 and Q_Chu = 4.07 rendering it electrically small. This electrical compactness and bandwidth enhancement are caused by the loading of metamaterial structure. The proposed antenna is fabricated on low cost FR4 substrate and has an overall compact electrical size of 0.164 λ₀ × 0.164 λ₀ × 0.013 λ₀ and physical dimensions 20 × 20 × 1.6 mm³, with peak gain 3.8 dBi and 2.9 dBi at 2.4 GHz and 5.2 GHz respectively. Full article

This paper presents a metamaterial sensor using a double slit complementary square ring resonator (DS-CSRR) that has been utilized for the measurement of dielectric materials, especially coal powder. The design is optimized for best performance of deep notch depth in transmission coefficient (Magnitude of S${}_{21}$). Sensitivity analysis of transmission coefficient with respect to structure dimensions has been carried out. Metamaterial properties of double negative permitivity and permeability were extracted from the S–parameters of this sensor. The optimized structure is fabricated using low cost FR-4 PCB board. Measured result shows resonance frequency of 4.75 GHz with a deep notch up to −41 dB. Simulated and measured results show good agreement in desired frequency band. For material characterization, first, two known materials are characterized using this metamaterial sensor. Their respective resonances and dielectric constants are known, so the transcendental equation of the sensor is formulated. Afterwards, the proposed sensor is used for dielectric measurement of two types of coal powder, i.e., Anthracite and Bituminous. The measured value of dielectric constant of Anthracite coal is 3.5 and of Bituminous coal is 2.52. This is a simple and effective nondestructive measurement technique for material testing applications. Full article