Mu-negative Research Articles

Ultra-thin wide-band split-ring resonator-based compact mu-negative metamaterial for terahertz applications

This paper focuses on designing and investigating a new type of metamaterial called an ultra-thin wide-band mu-negative (MNG) metamaterial. The targeted frequency range is 0.1–10 THz. At the resonance frequency of 6.37 THz, the permeability (μ) of the structure is negative, allowing it to function as an MNG metamaterial. Computer Simulation Technology (CST) and High-Frequency Structure Simulator (HFSS) 3D software simulations, examining the scattering and medium parameters of the MNG metamaterial. The findings demonstrate that the proposed MNG metamaterial exhibits resonance peaks in the mu-negative region at 6.37 THz and wide frequency bands of 8.79 THz at −10 dB in the CST simulator. The structure is adaptable based on design parameters. This MNG metamaterial is unique due to its ultra-thin, a form mu-negative wide bandwidth of 3.20 THz, and suitable resonance frequencies. The simulation results from Ansys HFSS software almost align with CST results. The structure, resonating in the THz region with wide bandwidth, shows potential applications in spectroscopy and biomedical engineering. The study encountered difficulties in achieving precise fabrication at the nanoscale and ensuring the reproducibility of metamaterial properties across various samples. Despite these challenges, the proposed metamaterial shows significant advancements in terahertz technology.

Permeability negative split square resonator for solid materials dielectric constant and aqueous solution pH sensing applications

Metamaterials (MTMs) offer unique electromagnetic properties with wide-ranging applications in microwave sensing. This work introduces a unique approach for non-invasive pH level measurement in aqueous solutions and dielectric properties sensing in solid materials. Mu Negative (MNG) Metamaterial with transmission line and rejection band shifting techniques are utilized for this sensing. The MTM unit cell comprises coupled split square resonators arranged in a 4 × 4 unit cell array with a transmission line underneath. The compact unit cell and array sizes are 0.3 λ × 0.3 λ × 0.06 λ and 1.6 λ × 1.6 λ × 0.06 λ, respectively. The sensor demonstrates impressive performance, with a narrow half-power bandwidth (HPBW) of 0.09 GHz and a high Q-factor of 135.22 for dielectric constant sensing of the solid material. It also achieves an HPBW of 0.38 GHz and a Q-factor of 37.3 for pH sensing. The proposed pH sensor achieves a high sensitivity of 6.15 (MHz/pH). Additionally, the MTM sensor boasts a substantial Figure of Merit (FoM) of 8.311 for solid materials and 16.2 for pH measurements. These promising results are validated through measurements, highlighting the potential of MTM sensors to revolutionize microwave sensing across various applications.

Propagation behavior in rectangular metallic waveguide periodically loaded with single negative metamaterial slabs

This paper focused on propagation characteristics of a single mode supporting waveguide enclosed by metallic sidewalls periodically loaded with lossless single negative (SNG) metamaterial slabs along axial direction. The gap between two successive SNG slabs is filled with a double positive (DPS) material. For the analysis, the periodic structure is assumed having symmetric unit cell (UC) and simplified as a two-port network which is one-half of the symmetric UC. Scattering parameters (S-parameters) are defined by even/odd mode analysis of the symmetric UC, and then the total S-parameters are calculated by solving the cascade connection of N unit cells. Eigenvalue equations are also obtained to explicit the solutions of band edge and pass/stopband diagrams in the microwave regime. Since a SNG can be either epsilon-negative (ENG) or mu-negative (MNG), S-parameters and dispersion behavior are illustrated with numerical examples and discussed for each periodic structure constructed with ENG or MNG slabs.

Near zero index Metamaterial-based SIW antenna for 6G Sub-Terahertz applications

This paper introduces a novel high-gain circularly polarized (CP) antenna that utilizes a NRZI (Near Zero Refractive Index) and MNG (Mu Negative) metamaterialslab. The antenna employs a substrate integrated waveguide (SIW) technique and loaded with compact square split ring resonator (SSRR) combined with a hexagonal-shaped structure by a 0.2 mm width slab as a unit cell to achieve high gain and circular polarization. The metamaterial characteristics were examined through material wave propagation in two main directions at the y and x-axis. For wave propagation at the y-axis, the MTM structure demonstrates mu-near-zero (MNZ) with more than 88 GHz bandwidth, NZRI, and Epsilon-Near-Zero (ENZ) properties. However, for x-axis wave propagation, it indicates a wide negative range of single mu metamaterial from 176 to 220 GHz, NZRI, and ENZ properties. By using six unit cells, the antenna acts as an aperture-efficient focusing metasurface lens and polarization converter for a primary source antenna. The NRZI-MNG enhances the gain of the suggested antenna by 6–7 dB, and converts the linearly polarized wave emitted by the patch antenna into circularly polarized waves. The designed antenna has an impedance bandwidth from 176.5 to 285 GHz, with a 3 dB axial ratio achieved from 177 to 204 GHz. The peak gain of the antenna is 11.3 dBi at 223 GHz, and a gain of around 10 dBi is achieved over the entire CP bandwidth with a good cross-polarization level. In addition, the transmittance of the suggested metamaterial antenna is between 80% and 90% in the operating band. These excellent performances make this antenna very promising for sub-THz 6G applications.

Scattering of Laguerre–Gaussian Beam by a Topological Insulator Cylinder Coated with Metamaterials

A theoretical investigation is presented to study the orbital angular momentum (OAM) beam scattering from a topological insulator (TI) cylinder coated with metamaterials. To calculate the electromagnetic (EM) response of the scattered field, the field equations are modified using Laguerre–Gaussian (LG) potential and plane wave scattering. The response of the metamaterial coated geometry has been reported for Double positive (DPS), Double negative (DNG), Epsilon negative (ENG), and Mu negative (MNG) coating layers, respectively. The normalized bistatic echo widths for the TI cylinder also change by changing the topological charge ( $$l$$ ), the radius of the metamaterial coated layer $$(b)$$ , source frequency $$(f)$$ , and beam waist radius $$({w}_{0})$$ . Our result for $${LG}_{00}$$ beam exactly tones with plane wave scattering as a reference. Numerical results in the form of bistatic echo widths have been calculated. Besides, the prementioned parameters, the influence of OAM mode index on the bistatic echo width is also analyzed. It can be seen that OAM mode number plays major role in controlling the scattering amplitude and intensity.

Investigation of a quad-band microstrip antenna using a DNG-MTM radiation patch

A compact quad-band microstrip antenna based on double-negative metamaterial (DNG-MTM) is proposed in this letter. To realize miniaturization and multi-band characteristics, a novel coplanar tri-band DNG-MTM unit, consisted of an epsilon negative (ENG) MTM and a mu negative (MNG) MTM, is firstly designed and employed as the antenna radiator. The antenna’s electrical dimension is 0.23λ0 × 0.37λ0, where λ0 is the free space wavelength at 3.5 GHz. The peak gain is 5.3, 6.3, 5.8, and 3.4 dBi and the radiation efficiency reaches 96%, 82%, 91% and 86% for 2.84–3.55 (22.2%), 6.6–7.18 (8.4%), 7.44–9.08 (19.9%), and 11.1–14.74 (28.2%) GHz, respectively. These four bands have effectively covered 5G (3.5-GHz), C-band, X-band, and Ku-band for satellite systems. The size of the proposed antenna has been reduced by about 55% in comparison to the traditional method.

극초음속 플라즈마 환경에서의 통신두절 극복을 위한 메타물질 구현

Communication blackout of hypersonic flights refers to an interruption in communication when a flight enters an extreme environment of atmospheric gas ionization. Specifically, as the ionized gas and electron density goes over the plasma density, the gas medium becomes conductive, where the conductivity can be translated into a permittivity with a negative real number. The resulting class of material can be characterized as an ENG (Epsilon-Negative) material, which induces a significant decaying constant and absorbs or reflects most of the electromagnetic waves, even within an ultrathin layer. In this study, we propose MNG (Mu-Negative) metamaterials that achieve complete transmission through the layering of the MNG material after the plasmonic layer. Moreover, we calculated the transmittance and reflectance of multilayers as a function of incident angle and frequency to prove that transmittance can be improved by x4 larger with the MNG material in aerospace conditions. This study is the result of theoretical analysis proving the usefulness of MNG metamaterials and can be regarded as a fundamental study that can be applied in the development of MNG metamaterials or real-life applications.

Double-E-Triple-H-Shaped NRI-Metamaterial for Dual-Band Microwave Sensing Applications

This paper presents a new Double-E-Triple-H-Shaped NRI (negative refractive index) metamaterial (MM) for dual-band microwave sensing applications. Here, a horizontal H-shaped metal structure is enclosed by two face-to-face E-shaped metal structures. This double-E-H-shaped design is also encased by two vertical H-shaped structures along with some copper links. Thus, the Double-E-Triple-H-Shaped configuration is developed. Two popular substrate materials of Rogers RO 3010 and FR-4 were adopted for analyzing the characteristics of the unit cell. The proposed structure exhibits transmission resonance inside the S-band with NRI and ENG (Epsilon Negative) metamaterial properties, and inside the C-band with ENG and MNG (Mu Negative) metamaterial properties. A good effective medium ratio (EMR) of 8.06 indicates the compactness and effectiveness of the proposed design. Further analysis has been done by changing the thickness of the substrate material as well and a significant change in the effective medium ratio is found. The validity of the proposed structure is confirmed by an equivalent circuit model. The simulated result agrees well with the calculated result. For exploring microwave sensing applications of the proposed unit cell, permittivity and pressure sensitivity performance were investigated in different simulation arrangements. The compact size, effective parameters, high sensitivity and a good EMR represent the proposed metamaterial as a promising solution for S-band and C-band microwave sensing applications.

Multichannel tunable polarizing filter properties of one-dimensional ternary photonic crystal containing single-negative materials

Angle and polarization-dependent tunable transmission properties of a one-dimensional (1D) ternary photonic crystal (TPC) whose period consists of three alternate layers of two different kinds of single-negative [Epsilon-negative (ENG) and mu-negative (MNG)] media are theoretically investigated by using the transfer matrix method (TMM). It has been shown that the proposed polarizing filter is capable of transmitting multiple polarized transmission peaks (called as channels) by adjusting the incident angle from 21° to 89° as per need. The resonant frequencies of these respective transmission channels are completely different for the case of TE and TM polarizations. The proposed structure contains only twelve SNG material layers corresponding to the period number N = 4. This structure filters 18 separate transmission channels for TE and TM waves each at incident angle $$ \theta_{0} = 21^{\circ} $$ . The number of polarization dependent channels can be further increased to 35 and 37 for TE and TM polarizations, respectively, when the period number of 1D TPC increases from 4 to 8 at $$ \theta_{0} = 89^{\circ} $$ . This eight-period 1D TPC structure requires only 24 SNG material layers. The effect of lossy SNG materials on the performance of the filter is also investigated. This study may find its application in the field of optical communication for accommodating a large number of optical channels in the same bandwidth. Such types of filters may have their applications in integrated optics for dense wavelength division multiplexing systems and ultrafast light information processing.

Design of wideband AMC integrated monopole antenna with enhanced radiation performances for off‐body systems

AbstractA low‐profile, wideband, high gain artificial magnetic conductor (AMC) integrated monopole antenna is proposed in the letter. The bowl‐shaped stair styled monopole with defected round type partial ground is integrated with the AMC containing 2 × 2 unit‐cells to broaden the impedance bandwidth by 92.7%/66.2%/53.9% at the three resonating notches at 6/8.4/10.3 GHz respectively. The AMC has covered ±90° reflection phase bandwidth from 6.20 to 7.44 GHz (18.56%). The planar AMC proffers mu‐negative (MNG) properties and polarization independent behavior. Introduction of AMC beneath the monopole achieves wideband from 5.39 to 10.95 GHz. The AMC integrated monopole provides peak gain up to 10.6 dB which is 66.8% better than that of the only monopole. The integrated antenna offers low‐profile features with unidirectional radiation behavior, up to 18.6 dB front to back ratio (FBR) and >90% efficiency. The proposed design reduces 1‐g averaged Specific Absorption Rate (SAR) at 1 mm distance up to 96.6% at the respective bands.

A Metamaterial-Inspired Approach to Mitigating Radio Frequency Blackout When a Plasma Forms Around a Reentry Vehicle

Radio frequency (RF) blackout and attenuation have been observed during atmospheric reentry since the advent of space exploration. The effects range from severe attenuation to complete loss of communications and can last from 90 s to 10 min depending on the vehicle’s trajectory. This paper examines a way of using a metasurface to improve the performance of communications during reentry. The technique is viable at low plasma densities and matches a split-ring resonator (SRR)-based mu-negative (MNG) sheet to the epsilon-negative (ENG) plasma region. Considering the MNG metasurface as a window to the exterior of a reentry vehicle, its matched design yields high transmission of an electromagnetic plane wave through the resulting MNG-ENG metastructure into the region beyond it. A varactor-based SRR design facilitates tuning the MNG layer to ENG layers with different plasma densities. Both simple and Huygens dipole antennas beneath a matched metastructure are then employed to demonstrate the consequent realization of significant signal transmission through it into free space beyond the exterior ENG plasma layer.

Scattered field from a single/double negative grounded slab with rough interface

In this paper, we assume a dispersive grounded slab with rough interface to study the scattering properties using the perturbation theory (PT). The Lorentz-Drude model is used to find out the positive/negative permittivity and permeability of the slab. For different operating frequencies, the dispersive slab behaves as epsilon negative (ENG), double negative (DNG), mu negative (MNG) and double positive (DPS) material. Using the PT, the unknown scattering and transmission coefficients are evaluated. It is observed that the period of the surface affects the scattering from DNG slab more than that from DPS slab. For small period, the scattered field from the ENG slab is very small while it is large for MNG slab. Moreover, as the thickness of the slab is changed, the scattering behavior of ENG slab shows an increasing trend opposite to that of the MNG slab. The roughness of the Gaussian surface has dominant effect on the scattering compared with the material properties of the slab.

Mu-Negative Metamaterials Seen as Band-Limited Non-Foster Impedances in Inductive Power Transmission Systems

In the last decade, various works have demonstrated that a class of artificial material called metamaterials (MTM) can synthesize mu-negative (MNG) media capable of evanescent-wave focusing which largely enhances the magnetic coupling between coils, which is the basic mechanism of Inductive Power Transmission (IPT) systems. In the present work, MTM-enhanced coupling in IPT systems is examined through analytical and numerical results, which are validated by experimental data. Adopting a transmission-line (TL) based approach to describe the general MTM-enhanced IPT system, it is evidenced that MNG MTMs can be interpreted as a negative impedance from a circuital point of view.

One-way absorption properties in asymmetric single-negative-based Cantor photonic crystals

In this work we theoretically study the one-way optical properties in asymmetric triadic-Cantor-set (TCS) photonic crystals (PCs), air/TCSN/G/TCSM/air, where TCSN is the stage N TCS composed of a lossy epsilon-negative (ENG) material and a lossy mu-negative (MNG) material. In addition, the defect layer G is a dielectric. Our results show that the absorption spectra are different in forward and backward propagation. Specially, it is first discovered that the one-way properties will disappear if the layer thicknesses are large. Besides, the layer thickness limit is smaller when the TCS stage is larger. Additionally, comparing with previous studies, we find that the type of interaction between the defect and non-defect modes is decided by the layer materials of the PC structure.

Use of Kobayashi potential method and Lorentz–Drude model to study scattering from a PEC strip buried below a lossy dispersive NID dielectric-magnetic slab

Kobayashi potential method is applied to investigate the scattering behavior of a perfect electric conducting (PEC) strip buried below a lossy dispersive non-integer dimensional (NID) dielectric-magnetic slab. Dispersion characteristics are introduced through the Lorentz–Drude model. Due to dispersive nature of the medium occupying the slab, it operates as epsilon negative (ENG), double negative (DNG), mu negative (MNG), or double positive (DPS) material depending upon the operating frequency. Scattered fields have been obtained when the slab behaves as ENG/MNG/DNG or DPS. Efforts have also been made to highlight the impact of NID parameter and dispersion characteristics of the material of the slab. It has been observed that increase/decrease in the thickness of the slab decreases/increases the scattered field from the strip below the slab. Moreover, it also decreases as size of the obstacle increases. It has been noted that the effect of real part of constitutive parameters on scattering pattern is opposite to that of imaginary part of constitutive parameters for ENG, MNG and DPS slab while for DNG slab the trend remains same.

Design and performance analysis of a conformal CPW fed wideband antenna with Mu-Negative metamaterial for wearable applications

AbstractIn this paper, a flexible CPW fed ultrawide band (UWB) antenna with mu-negative (MNG) metamaterial is designed, fabricated, and tested for wearable applications. Initially, a UWB antenna of size 50 mm × 43 mm is fabricated on two different substrates, viz. flexible FR4 and semi-flexible Rogers RT/duroid 5880. A metamaterial structure fabricated on flexible FR4 shows a magnetic resonance from 7.2 GHz to 9.2 GHz with maximum stop band attenuation (−49 dB) and high MNG value (−2121.6) at 7.87 GHz. Then a (3 × 3) array of designed MNG metasurface is used as ground plane with flexible UWB antenna, which improves its overall gain and radiation pattern. The performance of the flexible antenna with/without metamaterial at various distances from flat and cylindrical three-layered human phantom of skin, fat, and muscle is studied. Further, the bending characteristics at different angles and performance over thin metallic sheet is also evaluated. Additionally, the peak specific absorption rate value averaged over 1 g of tissue at three chosen frequencies from UWB range (3, 5, 10 GHz) with/without metamaterial using 0.3 and 0.1 W of input power is also analyzed. The simulated and measured results are in good agreement which confirms that the designed antenna is a good candidate for wearable applications.

Impact of NID dielectric–magnetic medium on reflection and transmission characteristics of a Lorentz–Drude slab

Impact of non-integer dimensional (NID) dielectric–magnetic medium on the behavior of power transmitted and reflected from a planar NID Lorentz–Drude slab is analyzed for uniform electromagnetic plane wave excitation. The dispersive slab is terminated by NID dielectric–magnetic medium and dispersion in the slab has been indulge through the Lorentz–Drude model. It is assumed that medium inside the Lorentz–Drude slab and medium backing the slab are NID in direction perpendicular to surface of the slab but their dimensions are described by different NID parameters. According to the characteristics of the model, while the operating frequency increases the NID Lorentz–Drude slab operates as epsilon negative (ENG), double negative (DNG), mu negative (MNG), double positive (DPS) metamaterial respectively. Effect of NID parameter of the terminating medium, dielectric magnetic properties of the terminating medium and impact of their combination on the powers is noted one by one. It is noticed that parameters describing the NID dielectric–magnetic medium significantly change the behavior of powers. These parameters can be effectively used to control the power according to the requirements.

Compact zeroth-order resonator (ZOR) antennas

In this paper, we introduce and review the zeroth-order resonator (ZOR) antennas with outstanding characteristics including various applications that have been researched so far. Since the zeroth-order resonance frequency is independent of a physical length of antenna, the ZOR antenna can theoretically be designed quite small and have a possibility to apply to considerably lots of applications. First, we have presented the ZOR antennas implemented by double-negative (DNG), epsilon-negative (ENG), and mu-negative (MNG) transmission lines. Then, the research related on extremely small, wide beamwidth, wideband, and circularly polarized (CP) ZOR antennas have been continuously carried out. Based on a series of these studies, the ZOR antennas were utilized for various applications such as a wireless power transfer (WPT), a compact controlled reception pattern antenna (CRPA), a penta-band mobile antenna, and a wide steering array antenna.

Miniaturization of Planar Yagi Antennas Using Mu-Negative Metamaterial-Loaded Reflector

A technique to reduce the size and enhance the operating bandwidth (BW) of planar Yagi antennas, while maintaining their unidirectional radiation characteristics, is proposed in this paper. In this technique, the reflector element is loaded with mu-negative (MNG) metamaterial unit cells to excite a mu-zero resonance (MZR), which is independent of the size of the antenna. Thus, the antenna can operate at lower frequencies without the need to increase its physical size. To implement the proposed idea, the reflector, which acts as the host transmission line, is positioned at a close distance to the driven element, which is typically a dipole antenna. To validate the proposed technique, two design concepts based on coplanar and broadside-coupled strip configurations are presented, and a wideband Yagi antenna is presented. The antenna achieves a wide operating BW of 70% (0.72–1.48 GHz) with a peak front-to-back ratio (FBR) of 14 dB and peak gain of 4.1 dBi with a compact size of $0.24\lambda \times 0.24\lambda $ , where $\lambda $ is the wavelength at the lowest operating frequency. The proposed antenna achieves a 45% wider operating BW compared to similar structures, while being miniaturized by more than 60% compared to available structures that have over 50% fractional BWs.

Gain Enhancement of Wideband Metamaterial-Loaded Loop Antenna With Tightly Coupled Arc-Shaped Directors

A wideband and unidirectional loop antenna with enhanced and stable gain is presented. To reduce the size of the antenna, the loop is loaded with three mu-negative (MNG) metamaterial unit-cells. The proposed unit-cells consist of a series-gap capacitor and a shunt meandered floating inductor. The series capacitive loading is used to excite the zeroth order resonance (ZOR) of the MNG unit-cell, whereas the floating inductor is used to improve impedance matching. To enhance the front-to-back-ratio (FBR) of the antenna and widen its operating bandwidth, the loop is loaded with a tuning slot in the vicinity of the loaded unit-cells. To overcome the low gain of the antenna at frequencies above the ZOR and thus obtain a stable gain, two tightly coupled dumbbell and arc-shaped directors are proposed. The shape and operation of these directors are inspired by the cylindrical capacitor, which achieves higher coupling compared to a planar capacitor with the same area. The antenna achieves a compact size of $0.25\lambda _{0} \times 0.29\lambda _{0}$ with a wide fractional bandwidth of 34% at 0.76–1.07 GHz, and peak measured gain and FBR values of 4.5 dBi and 16 dB, respectively.