Epsilon-negative Metamaterials Research Articles

Development of an innovative patch antenna design and implementation using ENG materials for health care systems and 5G networks

The object of this study is a new design of an overhead microstrip antenna, including Epsilon Negative (ENG) metamaterials and L-shaped parasitic overlays aimed at achieving dual-band operation and improving the performance of modern wireless communication systems. The research is aimed at solving the problem of limited bandwidth and dual-band functionality in conventional antenna designs. This study solves the problem of limited bandwidth and dual-band functionality in conventional microstrip patch antenna designs, which are crucial for modern wireless communication systems. The inclusion of L-shaped parasitic overlays effectively expands the bandwidth in each frequency range. The results indicate significant improvements: at the upper resonant frequency, a 10 dB return loss bandwidth of 27.84 % (2.88–3.81 GHz) and a 3 dB axial ratio bandwidth of 5.05 % (2.90–3.05 GHz) are achieved, while at the lower resonant frequency, a return loss bandwidth is 10 dB, which is 6.11 % (2.22–2.36 GHz). These improvements indicate a significant increase in antenna performance compared to conventional designs, which is confirmed by comparing the simulation results with the measurement results. Distinctive features contributing to these results include the use of ENG metamaterials, which improve electromagnetic properties and signal propagation; vertical transitions, which provide efficient dual-band operation; and L-shaped parasitic overlays, which significantly expand bandwidth. These characteristics combine to eliminate the limitations of traditional designs, which makes the proposed antenna suitable for use in a wide frequency range in modern wireless communication systems.

Controlling Thermal Radiation in Photonic Quasicrystals Containing Epsilon-Negative Metamaterials

The transfer matrix approach is used to study the optical characteristics of thermal radiation in a one-dimensional photonic crystal (1DPC) with metamaterial. In this method, every layer within the multilayer structure is associated with its specific transfer matrix. Subsequently, it links the incident beam to the next layer from the previous layer. The proposed structure is composed of three types of materials, namely InSb, ZrO2, and Teflon, and one type of epsilon-negative (ENG) metamaterial and is organized in accordance with the laws of sequencing. The semiconductor InSb has the capability to adjust bandgaps by utilizing its thermally responsive permittivity, allowing for tunability with temperature changes, while the metamaterial modifies the bandgaps according to its negative permittivity. Using quasi-periodic shows that, in contrast to employing absolute periodic arrangements, it produces more diverse results in modifying the structure’s band-gaps. Using a new sequence arrangement mixed-quasi-periodic (MQP) structure, which is a combination of two quasi periodic structures, provides more freedom of action for modifying the properties of the medium than periodic arrangements do. The ability to control thermal radiation is crucial in a range of optical applications since it is frequently unpolarized and incoherent in both space and time. These configurations allow for the suppression and emission of thermal radiation in a certain frequency range due to their fundamental nature as photonic band-gaps (PBGs). So, we are able to control the thermal radiation by changing the structure arrangement. Here, the We use an indirect method based on the second Kirchoff law for thermal radiation to investigate the emittance of black bodies based on a well-known transfer matrix technique. We can measure the transmission and reflection coefficients with associated transmittance and reflectance, T and R, respectively. Here, the effects of several parameters, including the input beam’s angle, polarization, and period on tailoring the thermal radiation spectrum of the proposed structure, are studied. The results show that in some frequency bands, thermal radiation exceeded the black body limit. There were also good results in terms of complete stop bands for both TE and TM polarization at different incident angles and frequencies. This study produces encouraging results for the creation of Terahertz (THz) filters and selective thermal emitters. The tunability of our media is a crucial factor that influences the efficiency and function of our desired photonic outcome. Therefore, exploiting MQP sequences or arrangements is a promising strategy, as it allows us to rearrange our media more flexibly than quasi-periodic sequences and thus achieve our optimal result.

Targeted dielectric coating of silver nanoparticles with silica to manipulate optical properties for metasurface applications

An epsilon-negative metamaterial (ENM) containing core@shell nanoparticles (NPs) was designed, where silver (Ag) NPs served as core and silica (SiO2) was used as spacer shell. AgNPs were synthesized in large scale, using microwave-assisted polyol method, in three average particle sizes, as 30, 54, and 61 nm, with a narrow particle size distribution. Optical absorption of Ag NPs was investigated using UV–Vis spectroscopy. Their optical behavior was also theoretically predicted for different thicknesses of the SiO2 shell immersed in media of different refractive indices using the Clausius - Mossotti equation. Based on the results, optimal outputs were obtained with a SiO2 shell of 10 nm in thickness encompassing 54 nm Ag NPs based on the analytical model and numerical simulations here developed for core-shell structures. Then 10 nm SiO2 shell was grown on 54 nm Ag NPs by sol-gel synthesis. The NPs were then characterized by UV–Vis, TEM, SEM, EDX, DLS, and zeta potential analyses. The synthesized core-shell NPs can be used to establish epsilon-negative properties in polymer layers within visible range of wavelengths.

Modified Hexagonal Split Ring Resonator Based on an Epsilon-Negative Metamaterial for Triple-Band Satellite Communication.

A triple-band epsilon-negative (ENG) metamaterial based on a split ring resonator (SSR) with a modified hexagonal-shaped metal strip proposed in this study is a new combination of a single slit square resonator and a modified hexagonal-shaped metal strip. The desired unit cell FR-4 (lossy) that was selected as the substrate was 1.6 mm thick. Following the assessment of the unit cell, a high-frequency electromagnetic simulator like the computer simulation technology (CST) microwave studio was applied to assess the S-parameters. The proposed design exhibited resonance at 2.89, 9.42, and 15.16 GHz. The unit cell also demonstrated negative permittivity in the frequency ranges 2.912–3.728 GHz, 9.552–10.144 GHz, and 15.216–17.328 GHz, along with a negative refractive index. An effective medium ratio (EMR) of 11.53 is an indicator of the goodness of the metamaterial unit cell. It is deliberate at the lowermost resonance frequency of 2.89 GHz. Moreover, the simulated results that were validated using HFSS and equivalent circuit model indicated slight variations. The proposed design was finalised based on several parametric studies, including design optimisation, different unit cell sizes, various substrate materials, and different electromagnetic (EM) field propagations. The proposed triple band (S, X, and Ku bands) negative permittivity metamaterial unit cell can be utilised for various wireless applications, such as microwave communication, satellite communication, and long-distance radio communication.

A mutual coupled spider net-shaped triple split ring resonator based epsilon-negative metamaterials with high effective medium ratio for quad-band microwave applications

This paper discusses a spider net-shaped triple split ring resonator (SNTSRR) based epsilon-negative metamaterial with a high effective medium ratio. The proposed SNTSRR unit cell structure is a modification of the general split ring resonator and consists of three octagonal-shaped split ring resonators (SRR). Two metal strips attach the split ring resonators to increase the electrical length of the proposed SNTSRR unit cell. The optimized size of the proposed SNTSRR unit cell, using Rogers RO4350B substrate material, is 10 × 10 × 1.524 mm3. The frequency ranges of the transmission of microwave applications are: 2.83–2.89 GHz for S-band, 4.24–4.31 GHz and 6.74–7.06 GHz for C-band, 9.17–9.26 GHz and 10.98–11.16 GHz for X-band, and 12.62–13.00 GHz for Ku-band. The unit cell achieves six resonant frequencies of 2.86 GHz, 4.28 GHz, 6.94 GHz, 9.22 GHz, 11.10 GHz, and 12.89 GHz for S-, C-, X-, and Ku-bands, respectively. A comprehensive investigation of effective medium parameters, scattering parameters, mutual coupling effect, and the unit cell properties with electromagnetic propagation were accomplished in this paper. The proposed SNTSRR unit cell revelations epsilon negative (ENG) properties in the frequency ranges of 2.87–3.05 GHz, 4.27–4.45 GHz, 6.94–7.39 GHz, 9.24–9.34 GHz, 11.12–11.26 GHz, and 12.90–13.24 GHz. For experimental validation, we fabricated the proposed SNTSRR unit cell along with its array construction. After that, we measured the scattering parameters, which showed better agreement between the simulated and the measured outcomes. Furthermore, the coupling effects between the 1 × 2 and the 2 × 2 array structures with different distances were analyzed, and they showed better performance with low impact. Additionally, the calculated effective medium ratio (EMR) is 10.48, which infers compactness and efficacy of the unit cell. It should be noted that the compact size, effective medium parameters, S-parameters, and high EMR make the proposed SNTSRR metamaterial appropriate for quad-band microwave applications. Finally, the proposed SNTSRR unit cell has been employed as an application in 3D cross-fed wideband antenna to enhance the bandwidth and gain of the antenna, which is appropriate for microwave head imaging applications.

A Subwavelength Microstrip Resonator Based on Metamaterials

A metamaterial-based subwavelength microstrip resonator with high quality factor and simple fabrication process was proposed. For the experimental result, a quality factor of about 70 was achieved when the length of the resonator was about one third of the wavelength. Firstly, the mu-negative metamaterial (MNM) and the epsilon-negative metamaterial (ENM) were implemented by loading only chip capacitors or only chip inductors onto the microstrip. The implementation process is simpler in comparison to the traditional implementation method of the MNM and the ENM based on the microstrip. Then, the transmission characteristics of the heterostructure constructed of the MNM and the ENM fabricated through the simple method were investigated and the results showed that a subwavelength microstrip resonator could be built by the MNM–ENM heterostructure. Moreover, the quality-factor enhancement of the subwavelength microstrip resonator based on the MNM–ENM heterostructure was also explored. The results showed that the quality factor could be notably boosted and increased by about 15 times for the experimental result of the sample owing to more intensive confinement of the electromagnetic field when the electromagnetically induced transparency-like metamaterial was introduced at the interface of the MNM–ENM heterostructure.

A new method of fabricating single negative metamaterials based on coplanar waveguide

A new simple method to fabricate single negative metamaterials (SNM) based on the coplanar waveguide (CPW) was studied. It was found that the epsilon-negative metamaterial (ENM) could be realized (under the frequency f0 = 3.67 GHz for our experiment) when the sole shunt chip inductors were loaded onto the CPW, and the mu-negative metamaterial (MNM) could be achieved (under the frequency f0 = 3.23 GHz for our experiment) when loading the sole series chip capacitors onto the CPW. In addition, in order to further confirm the single negative property of the two kinds of SNM fabricated by the new method and meanwhile explore their applications, heterostructures and photonic crystals constructed by the new ENM and MNM were fabricated and their transmission properties investigated. The results showed that the tunneling phenomenon really emerged for the heterostructure fabricated with the new ENM and MNM and the tunneling frequency was also independent of the heterostructure length, making the heterostructure applicable in the subwavelength resonator. Moreover, for the photonic crystals constructed by the new ENM and MNM, the closing and opening of the zero effective phase gap was observed, and so this article provides a simple structure to achieve photonic crystals composed of SNM based on transmission lines.

Inductive Meandered Metal Line Metamaterial for Rectangular Waveguide Linings

Metal-based epsilon negative metamaterials (MTMs) have been investigated for use as a waveguide liner to allow for an electromagnetic passband below the cutoff frequency of the empty waveguide. In this paper, we investigate both the theory and a practical implementation of an MTM lined waveguide. Specifically, we have investigated the use of inductive meander lines as the elements of a vacuum-electronics-compatible MTM structure to line one side of a rectangular waveguide. The MTM implementation creates an effective medium with a Drude–Lorentz dispersion response. The transmission of the waveguide and dispersion were both simulated and measured experimentally and demonstrate good agreement.

Metamaterial-Enhanced Resistive Wall Amplifiers: Theory and Particle-in-Cell Simulations

The resistive wall amplifier (RWA), a vacuum electron device, has been theoretically predicted to provide extremely high gain. However, the properties of practical, naturally available bulk materials for the resistive wall support structure significantly reduce achievable gain. This paper investigates the capabilities of a metamaterial-enhanced RWA (ME-RWA). We predict that using epsilon-negative metamaterials can yield high gains that closely approach the idealized performance limit. ME-RWAs may exhibit bandwidths and gains much higher than many commercially available vacuum electron devices.

Multi-channeled filtering properties of the sandwich structures composed of epsilon-negative metamaterials

Multi-channeled filtering properties are found in the sandwich structure composed of two ε-negative layers with dielectric permittivity described by Drude model separated by another normal material layer. Epsilon-negative metamaterials are successfully realized by using composite right/left-handed transmission line, based on which the Fabry–Perot (FP) cavity was also constituted. The single resonant mode is split into some discrete resonant peaks, leading to the multi-channeled filtering phenomenon through the several coupled FP cavity resonators. In comparison with the conventional multichanneled filters, the proposed structure is more compact and tunable. The microwave experiment results are found in agreement with simulation results.

Trapping of electromagnetic wave in single-negative metamaterial waveguides

We study the trapping properties of transverse magnetic (TM) waves in single-negative metamaterial waveguides including epsilon-negative (ENG) metamaterial and mu-negative (MNG) metamaterial. The relationship between effective refractive index and reduced core width is analyzed when the permittivities of ENG and MNG metamaterials are different, and the inflection on this curve can be regarded as the trapping point. Simulation results show that the properties in an ENG–MNG–ENG metamaterial waveguide are contrary to that in a MNG–ENG–MNG metamaterial waveguide. The sensitivity of trapping point to the change of permittivity makes the single-negative metamaterial waveguides to be an effective method to detect the permittivity variation and can be used as a new kind of waveguide sensor.

Highly localized mode in a pair structure made of epsilon-negative and mu-negative metamaterials

In this paper, the tunneling phenomenon occurring in a pair structure made of epsilon-negative (ENG) and mu-negative (MNG) metamaterials is experimentally studied. The ENG and MNG metamaterials are fabricated using coplanar waveguide loading with lumped-element series capacitors and shunt inductors. The properties of the tunneling mode are investigated by means of the transfer-matrix method, based on the experiment parameters of effective permittivity and permeability. The results show that the tunneling frequency is independent of the pair length and the electric field is highly localized at the interface of the ENG-MNG pair. These features illustrate that the pair behaves as a cavity with strongly enhanced electric field and with dimensions beyond the half-wavelength limit.