Metamaterial Unit Cell Research Articles

Metamaterial Loaded Antenna with Improved Efficiency and Gain for Wideband Application

ABSTRACT A wideband antenna with excellent efficiency is the most important requirement in wireless communication. In this paper, a wideband and highly efficient planner metamaterial-based microstrip patch antenna is proposed and examined. The proposed patch antenna is designed whose size is 12 × 16 mm2 and has a metamaterial unit cell loading on the top patch and the bottom ground plane. The top unit cell, which consists of four triangular shapes capacitive coupled resonator (TSCCR) and the bottom unit cell, which is square-shaped with diagonal cross-slot (SSDCS) is loaded on patch and ground respectively. The proposed antenna gives impedance matching of −10 dB for frequency band 2.88–14 GHz. The antenna's highest gain of 7.2 dBi at 12.39 GHz, positive gain range of 1.5–7.8 dBi in its operating band, and average efficiency of 75% are attained. The wideband and high gain properties of the proposed antenna make it suitable for UWB (3.1–10.6 GHz), Wi-Max (3.5 and 5.8 GHz), 5G NR FR1 (3.3–5 GHz) and Wi-Fi 6E (5.59–7.12 GHz) application.

High temperature metamaterial terahertz quantum detector

We demonstrate a high-temperature performance quantum detector of Terahertz (THz) radiation based on three-dimensional metamaterial. The metamaterial unit cell consists of an inductor-capacitor (LC) resonator laterally coupled with antenna elements. The absorbing region, consisting of semiconductor quantum wells, is contained in the strongly ultra-subwavelength capacitors of the LC structure. The high radiation loss of the antenna allows strongly increased collection efficiency for the incident THz radiation, while the small effective volume of the LC resonator allows intense light-matter coupling with a reduced electrical area. As a result, our detectors operate at much higher temperatures than conventional quantum well detectors demonstrated so far.

Switchable multifunctional modulator realized by the stacked graphene-based hyperbolic metamaterial unit cells

A tunable multifunctional modulator of the stacked graphene-based hyperbolic metamaterial (HM) cells is proposed. The dielectric constant and group index of HM are theoretically investigated. The calculated results show that, for the cell structure, a transmission window in the reflection zone (TWRZ) can be obtained at the normal incidence, but all reflections are converted to the transmission when the incident angle is near 82°. Concurrently, a single frequency absorption in the transmission zone (SFATZ) is realized, which can be adjusted by the chemical potential of graphene. For the whole structure composed of cell structures with different chemical potentials, the ultra-wideband absorption and transmission window in the absorption zone (TWAZ) can be achieved, which can work in different frequency bands if the given structural parameters can be tailored. Those computed results can apply for switchable frequency-dependent and angle-dependent reflection-transmission modulations, single frequency and ultra-wideband absorbers, and a logic switch based on the TWAZ.

A Novel High-Isolation Resistor-Less Millimeter-Wave Power Divider Based on Metamaterial Structures for 5G Applications

In this article, a simple and effective method based on the metamaterial concept is proposed to achieve very high isolation between the output ports of a millimeter-wave power divider (MWPD). The proposed MWPD is designed for use in 5G applications (28–32 GHz). In order to increase the isolation, three metamaterial rows are used, each row containing eight proposed unit cells. These metamaterial unit cells are loaded between two dielectric layers. By using this method and without isolating resistors, isolation is improved by more than 36 dB, as compared with a prototype power divider in which no metamaterial element was used. The maximum measured isolation is 43 dB at 30 GHz. The final dimensions of the proposed MWPD are $8 \times 8\,\,\times0.582$ mm3 or $0.9\,\,\lambda _{\mathbf {g}} \times 0.9\,\,\lambda _{\mathbf {g}} \times 0.08\,\,\lambda _{\mathbf {g}}$ where $\lambda _{\mathbf {g}}$ is the guided wavelength at 30 GHz. The simplicity of design, its compactness, and most importantly, high isolation between output ports without any lumped resistor are the key advantages of the proposed MWPD.

Meta-neural-network for real-time and passive deep-learning-based object recognition

Analyzing scattered wave to recognize object is of fundamental significance in wave physics. Recently-emerged deep learning technique achieved great success in interpreting wave field such as in ultrasound non-destructive testing and disease diagnosis, but conventionally need time-consuming computer postprocessing or bulky-sized diffractive elements. Here we theoretically propose and experimentally demonstrate a purely-passive and small-footprint meta-neural-network for real-time recognizing complicated objects by analyzing acoustic scattering. We prove meta-neural-network mimics a standard neural network despite its compactness, thanks to unique capability of its metamaterial unit-cells (dubbed meta-neurons) to produce deep-subwavelength phase shift as training parameters. The resulting device exhibits the “intelligence” to perform desired tasks with potential to overcome the current limitations, showcased by two distinctive examples of handwritten digit recognition and discerning misaligned orbital-angular-momentum vortices. Our mechanism opens the route to new metamaterial-based deep-learning paradigms and enable conceptual devices automatically analyzing signals, with far-reaching implications for acoustics and related fields.

Metamaterial-Fractal-Defected Ground Structure Concepts Combining for Highly Miniaturized Triple-Band Antenna Design

Abstract In this paper, a novel method is proposed to increase the gain and radiation efficiency of a compact patch antenna. By employing a combination of three efficient techniques, we have developed a multi-resonance L-DGS antenna with a high gain of 5 dB and an efficiency of 99.6%. Furthermore, a novel compact Double Negative metamaterial unit cell and its equivalent circuit are investigated, to achieve high miniaturization of 30×30 mm2 and multi-band wireless applications (2.8 GHz, 4.1-4.45 GHz, 5.6 GHz). Koch snowflake fractal is introduced along radiation patch edges to improve the antenna matching. The antenna is designed using commercially available package CST software, printed on Rogers RT5880, and the probe feed mechanism is adopted for the antenna excitation. Then, to prove the validation of the antenna design, the equivalent circuit is presented and simulated using ADS of Agilent software. The compared simulation results given by CST, HFSS and ADS software have confirmed the antenna use for WIMAX, C-band and WLAN applications.

Flexural waves in graded metabeam lattice

Effect of the graded variation in terms of separation gap between the two successive resonators and their mass on the resultant band structure of the graded metabeam is investigated in this paper. The band-structure are explored by implementing the transfer matrix method in conjunction with Bloch-Floquet's theorem. The graded arrangement of oscillators modifies the relative position of the coupling coefficient in the transfer matrix, which plays a pivotal role in altering the band-gap formation. The flexural band-structure is highly sensitive to the natural frequency and the distance between two resonators. It is evidenced that around 20% shifting of attenuation band in lower frequency side and 2.5 times widening of overall attenuation band gap is achievable by proper graded arrangement of resonators in metamaterial unit cell. However, the level of attenuation deteriorates over the wider frequency range.

Highly filled resins for DLP-based printing of low density, high modulus materials

Digital Light Processing (DLP)-based 3D printing enables the fabrication of complex structures from a broad range of neat and filled resin formulations, yet mass sensitive applications in the automotive, aerospace, and electronics industries are hindered by the lack of low-density resins. This paper investigates the formulation of a resin suitable for DLP-based fabrication of low density, high modulus structures with fine resolution of negative and positive features. An acrylate-based resin is loaded with a high-volume fraction (50 vol%) of hollow glass microspheres achieving adequate cured depth to fabricate 25 µm layer thicknesses. The suspension stability over typical multi-hour DLP print durations is verified. The filled resin exhibited a viscosity less than 5 Pa-s, which is below the upper limit of viscosity to recoat the Polydimethylsiloxane (PDMS) window between layers. The printed material possesses a uniform density distribution of 0.81 g cm−3 investigated using thermogravimetric analysis (TGA) and micro-Computed Tomography (micro-CT) imaging. The minimum feature sizes for the formulation are demonstrated as 400 µm for internal cavities (negative features) and 250 µm for protruding features (positive features). An example of a structure with an intricate geometry is created by printing a repeating mechanical metamaterial unit cell.

An Ultrawideband and High-Gain Antenna Based on 3-D Impedance-Matching Metamaterial Lens

In this article, we present an ultrawideband and high-gain antenna based on a 3-D impedance-matching metamaterial (IMM) lens. First, we design a 3-D IMM lens which can convert spherical-like waves to plane ones and is nearly perfect impedance-matching with the free space. To realize the 3-D lens, we propose and design two kinds of ultrawideband sandwich-structured metamaterial unit cells that can cover the refraction index ranges from 1.25 to 1.4 and from 1.4 to 3.8, respectively. We also design a double-ridged pyramid horn antenna as an ultrawideband feed source. Measured results verify that the presented lens antenna can work in an ultrawide bandwidth from 5.2 to 15.13 GHz, and the relative bandwidth is 97.7%. Moreover, it achieves a high aperture efficiency of more than 66% from 5.2 to 14.3 GHz, with a relative bandwidth of 93.3%. A maximum aperture efficiency of 85.6% is obtained at 11.5 GHz. The proposed lens antenna has an average of 2 dB gain enhancement versus optimal horn with the same aperture area. And the length of the lens antenna reduces to 22% compared to a bare horn antenna with the same gain and aperture efficiency.

A Hybrid Approach on Metamaterial-Loaded Fractal Antenna Design

The paper provides the interoperable hybrid Grasshopper–Grey Wolf optimization (GHGWO) of the Square Split-Ring Resonator (SRR) metamaterial unit cell. This paper discusses the complex phase strategies of the electric and magnetic interplay of the charged microstrip line of the split ring resonator (SRR). Optimized unit of metamaterial cells for their bandwidth enhancement is packed into a new square fractal antenna. In the interim period of dual band efficiency, a new design is introduced for a microstrip line-feeding square fractal antenna with a faulty ground composition. In the second stage, a quasi-static SRR model is being used to streamline its structural parameters in an effort to reinforce the bandwidth so that optimized composition resonates at the required intensity area. In the GHGWO hybrid algorithm, SRR unit cell size limitations should be optimized and the convergence actions of the algorithm improved. Certain evolutions termed modified hybrid BF-PSO classical BFO, chaos PSO and IWO are being tested for efficiency of the Hybrid GHGWO algorithm. In the final stage, optimized SRR unit cells are stacked into a square fractal antenna that provides bandwidth output suited to wireless usages with upper and lower band. The prototype square fractal antenna without and with SRR unit cells is efficiently evaluated by trial results.

Strategic Damping Placement in Viscoelastic Bandgap Structures: Dissecting the Metadamping Phenomenon in Multiresonator Metamaterials

Abstract Energy dissipation in polymeric composite metamaterials requires special mathematical models owing to the viscoelastic nature of their constituents, namely, the polymeric matrix, bonding agent, and local resonators. Unlike traditional composites, viscoelastic metamaterials possess a unique ability to exhibit strong wave attenuation while retaining high stiffness as a result of the “metadamping” phenomenon attributed to local resonances. The objective of this work is to investigate viscoelastic metadamping in one-dimensional multibandgap metamaterials by combining the linear hereditary theory of viscoelasticity with the Floquet-Bloch theory of wave propagation in infinite elastic media. Important distinctions between metamaterial and phononic unit cell models are explained based on the free wave approach with wavenumber-eliminated damping-frequency band structures. The developed model enables viscoelastic metadamping to be investigated by varying two independent relaxation parameters describing the viscoelasticity level in the host structure and the integrated resonators. The dispersion mechanics within high damping regimes and the effects of boundary conditions on the damped response are detailed. The results reveal that in a multiresonator cell, strategic damping placement in the individual resonators plays a profound role in shaping intermediate dispersion branches and dictating the primary and secondary frequency regions of interest, within which attenuation is most required.

A miniaturized triple-band planar antenna combing single-cell metamaterial structure and defected ground plane for WLAN/WiMAX applications

In this paper, a novel miniaturized triple-band planar monopole antenna combing single-cell metamaterial structure and defected ground plane is proposed. The miniaturization and triple-band characteristic of the antenna are achieved by loading the designed multiresonant metamaterial unit cell. Furthermore, a compact annular defected ground structure is proposed and used to improve the bandwidth of the antenna effectively. The presented metamaterial inspired triple-band antenna has a compact size and a simple structure. To verify the performances of the antenna, a prototype is manufactured and measured. The experimental results indicate that the presented antenna has enough operating bandwidth of the 2.38–2.48, 3.37–3.79, and 4.36–6.06 GHz to cover all the desired WLAN and WiMAX operations. And the tested results also demonstrate that this antenna has good omnidirectional radiation patterns and reliable gains in three required bands. Thus, the presented antenna has broad prospects in many wireless communication applications.

A new double ш-shaped compact negative refractive index metamaterial for wideband applications

<p>This paper analyzed the new compact design and negative refractive index (NRI) metamaterial for wideband applications. The proposed metamaterial exhibits NRI and wideband characteristics of the x-axis wave propagation. It displayed the NRI property at the frequency of 1.54 GHz and wideband from 1.26 GHz to 7.08 GHz frequency (L, S, and C band). Moreover, the response of the 1×2 horizontal and 2×1 vertical array structure showed the wideband frequency in the 7.17 GHz to 13.62 GHz and 1.46 GHz to 9.53 GHz, respectively. Electromagnetic simulation software called CST has been used to design the metamaterial unit cell. The metamaterial has been displayed the multi-band characteristics such as L, S, C, X and K<sub>u</sub> bands with negative index material properties.</p>

Yüksek İzolasyonlu MIMO Anten Dizisi İçin FSS Duvar Tasarımı

In MIMO antennas, mutual coupling that adversely effects antenna performance is due to the surface currents. To date, many techniques have been proposed to suppress these surface currents such as Electromagnetic Band Gap (EBG) structures, metamaterial unit cell, band-stop filters and Frequency Selective Surfaces (FSS). FSSs, when properly designed, can act as a band-stop filter in a given frequency range and thus prevent the propagation of these surface waves in the microstrip patch arrays. In this study, a new FSS unit cell is designed to reduce the mutual coupling effect caused by surface currents between two identical 2x1 patch antenna arrays with a 3.49 GHz operating frequency. These designed FSS unit cells are placed between the patches with a 1x5 periodic sequence. According to the simulation results, mutual coupling effect decreased by 26.6 dB without any shift in the transmission band with only 0.48 dB change in S11. Finally, ECC curves are plotted separately for the antenna array with and without the FSS wall. It is observed that the ECC of the antenna array is dropped from 0.16 to 0.07 by applying the proposed isolation wall.

Gain‐enhancement technique for wearable patch antenna using grounded metamaterial

In this study, a metamaterial (MTM)-based high-gain compact-wearable antenna for 2.45 GHz industrial, scientific and medical radio band application has been proposed. To achieve the flexibility of the antenna, textile material felt fabric has been chosen as the substrate of the antenna as well as MTM. An omega (Ω) like structure has been taken as MTM unit cell design. High value of permeability is utilised for the gain enhancement of the antenna. In addition, very low specific absorption rate (SAR) is obtained using the MTM which makes the proposed antenna suitable for the biomedical application. The proposed antenna has achieved about 3 dB gain enhancement along with SAR value of 0.405 W/kg (1 g tissue). The design has been optimised and the prototype with the optimised parameter has been fabricated and tested over the semi-solid phantom and human body. Further, the proposed antenna over different type of textile material has also been validated.

Low-Profile Omnidirectional WIFI Antennas With Pattern Reconfigurability Inspired by Meta-Resonators

A family of low-profile, omnidirectional antennas inspired by metamaterial resonators (meta-resonators) for WIFI applications is proposed. Two novel meta-resonators with an inductive feeding are presented. They can be considered as an LC resonant tank. Arbitrary size miniaturization could be obtained. Three rotated metamaterial unit cells constitute a ring-shaped structure, which generates a horizontally polarized, omnidirectional radiation. A direct microstrip power divider is used to excite them in-phase, achieving a small and low-profile magnetic dipole-like antenna. Their working principles are illustrated in detail by equivalent circuit and current distribution. Two omnidirectional antennas based on different meta-resonators and one pattern-reconfigurable antenna are fabricated and measured, respectively. Their measured −10 dB frequency bandwidth, peak gain, and radiation efficiency are greater than 2.4–2.48 GHz, 1.17 dBi, and 80%, respectively. They demonstrate superior advantages in terms of a miniaturized/low-profile size, simple structure, good bandwidth, and omnidirectional radiation performance, which are well positioned for 2.40 GHz WIFI router or indoor communications.

A two element MIMO antenna for sub‐6 GHz and mmWave 5G systems using characteristics mode analysis

AbstractIn this article, a two‐element multiband multi‐input multi‐output (MIMO) antenna for 5G communication devices is presented. Characteristics mode analysis is used to develop the proposed antenna. The planar inverted‐F antenna (PIFA) structure is used as an antenna element operating at 3.5, 4.3, 28, and 35 GHz bands. The shape of the PIFA is L‐shaped patch with an L slot placed which is positioned above the ground plane at 4 mm height. The proposed antenna covers more than 400 MHz bandwidth at 3.5, 4.3 GHz bands, and wideband coverage of more than 12 GHz covering many millimeter Wave (mmWave) bands between 24 and 38 GHz. The use of complementary metamaterial unit cell resulted in a minimum of 21 dB isolation in 3.5 GHz band and a minimum of 24 dB in mmWave bands. The simulated and measured results are presented for the proposed MIMO antenna system, which is in good agreement with each other.

Simulation Study of Metamaterial Effect towards Ultra Wide Band Antenna

In this paper, the design of a metamaterial ultra-wideband (UWB) antenna with a goal towards application in microwave imaging systems for detecting unwanted cells in human tissue, such as in cases of breast cancer, heart failure and brain stroke detection is proposed. The metamaterial unit cell is constructed using circular split ring resonator (CSRR) technique and wire, to attain a design layout that simultaneously exhibits both a negative magnetic permeability and a negative electrical permittivity and attached as superstrate in front of the UWB antenna. This design results in an astonishing negative refractive index that enables amplification of the radiated power of this reported antenna, and therefore, high antenna performance. A Rogers (RT5880) substrate material is used to design and print this reported antenna, and has the following characteristics: thickness of 0.51 mm, relative permeability of one, relative permittivity of 2.70 and loss tangent of 0.02. The metamaterial antenna is design to be operated at frequency between 300MHz to 30GHz which is suitable for biomedical application such as Microwave Imaging. The overall metamaterial antenna size is 90 mm × 50 mm × 0.51 mm. The design and simulation has been carried out using Computer Simulation Technology Microwave Studio (CST MWS).

Simulated Triple Circular Split-Ring Resonator Metamaterial Unit Cell for THz application

Metamaterial used widely nowadays to overcome the limitation of the natural material in manipulating the electromagnetic wave and radiation. Split-Ring Resonator (SRR) have been used widely as a design to manipulate the electromagnetic waves but none of them used for higher frequency such as light frequency. Therefore, the objective of this paper is to design SRR unit cell that is capable to bend the light wave. The negative value of material properties obtained from the simulation of the metamaterial at three different part which are at phase=0, real value and imaginary value. CST Microwave Studio 2018 used as a simulation software. The results show all the negative value of material properties obtained at different frequency range. However, the negative value of material properties at phase=0 and imaginary part is obtained at same frequency range. While for real part, the negative value for all material properties occurred at different frequency range. This SRR design is suitable to manipulate the lights radiation waves.

Cross coupled interlinked split ring resonator based epsilon negative metamaterial with high effective medium ratio for multiband satellite and radar communications

In this paper, a cross coupled interlinked split ring resonator based (CCI-SRR) based metamaterial has been presented. Epsilon negative (ENG) with a highly effective medium ratio (EMR) is attained in this metamaterial. The metamaterial unit cell consists of one square shaped split ring resonator and two rectangular rings. The rectangular rings reside within the outer square split ring. Two internal rings are coupled together by using a cross-shaped metal segment. These inner rings are also interlinked to the outer ring by using metal strips. Coupling causes to increase the electrical length and modifies the inductance of the unit cell. Multiple resonances covering C, X and Ku-band are achieved due to the interconnection of rings. The symmetric nature of the CCI-SRR unit cell exhibits unique quality to minimize noise and harmonics effect. The unit cell is designed on FR4 substrate with a thickness of 1.6 mm. The overall dimension of the unit cell is 0.124λ × 0.124λ, where λ is the wavelength calculated at a lower resonance frequency of 4.15 GHz. Three resonances are obtained for |S21| at frequencies of 4.15 GHz, 10.38 GHz and 14.93 GHz performing numerical simulation in CST microwave studio. Permittivity, permeability, refractive index and impedance are explored by using the Newton-Ross-Weir (NRW) method. ENG performance is observed in frequencies ranging from 3.95 to 5.65 GHz, 9.57–11.46 GHz, 13.68–16 GHz. Near-zero refractive index is attained within the frequency ranges, 4.16–5.75 GHz, 10.16–11.58 GHz, 14.46–16 GHz. An LC equivalent circuit is designed, and component values are achieved by Advanced Design Software (ADS) justifying |S21| with CST result. The study of electromagnetic wave interaction between the unit cell and the double positive medium reveals that the unit cell exhibits evanescent wave properties. The compact nature of the unit cell is confirmed by calculating EMR with a value of 8.03. The electromagnetic coupling effect is examined for 2 × 2 array in various orientations. The |S21| performance of 2 × 2, 4 × 4 and 8 × 8 is matched with the unit cell. Due to symmetric patterns, near-zero refractive index, negative permittivity and high EMR, the proposed unit cell can be used to enhance the performance of microwave devices used for C, X and Ku-bands, especially Satellite and Radar communications.