Mu-near-zero Research Articles

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.

A Compact Mu-Near-Zero Metamaterial Integrated Wideband High-Gain MIMO Antenna for 5G New Radio Applications.

This article demonstrates a compact wideband four-port multiple-input-multiple-output (MIMO) antenna system integrated with a wideband metamaterial (MM) to reach high gain for sub-6 GHz new radio (NR) 5G communication. The four antennas of the proposed MIMO system are orthogonally positioned to the adjacent antennas with a short interelement edge-to-edge distance (0.19λmin at 3.25 GHz), confirming compact size and wideband characteristics 55.2% (3.25-5.6 GHz). Each MIMO system component consists of a fractal slotted unique patch with a transmission feed line and a metal post-encased defected ground structure (DGS). The designed MIMO system is realized on a low-cost FR-4 printed material with a miniature size of 0.65λmin × 0.65λmin × 0.02λmin. A 6 × 6 array of double U-shaped resonator-based unique mu-near-zero (MNZ) wideband metamaterial reflector (MMR) is employed below the MIMO antenna with a 0.14λmin air gap, improving the gain by 2.8 dBi and manipulating the MIMO beam direction by 60°. The designed petite MIMO system with a MM reflector proposes a high peak gain of 7.1 dBi in comparison to recent relevant antennas with high isolation of 35 dB in the n77/n78/n79 bands. In addition, the proposed wideband MMR improves the MIMO diversity and radiation characteristics with an average total efficiency of 68% over the desired bands. The stated MIMO antenna system has an outstanding envelope correlation coefficient (ECC) of <0.045, a greater diversity gain (DG) of near 10 dB (>9.96 dB), a low channel capacity loss (CCL) of <0.35 b/s/Hz and excellent multiplexing efficiency (ME) of higher than -1.4 dB. The proposed MIMO concept is confirmed by fabricating and testing the developed MIMO structure. In contrast to the recent relevant works, the proposed antenna is compact in size, while maintaining high gain and wideband characteristics, with strong MIMO performance. Thus, the proposed concept could be a potential approach to the 5G MIMO antenna system.

Meta-Antennas: From Academic Research to Industrial Applications of Mobile Terminals [Industry Activities

Meta-antennas, including mu-near-zero (MNZ) and epsilon-near-zero (ENZ) antennas, have been intensively studied in academia, but very few of them have been applied to industrial products. This article first introduces my career path from academia to industry and then presents some application cases of meta-antennas in mobile terminals, including smartphones, tablets, and routers. I hope that this article can build a bridge between academia and industry and guide the study direction for academic researchers.

Momentum considerations inside near-zero index materials

Near-zero index (NZI) materials, i.e., materials having a phase refractive index close to zero, are known to enhance or inhibit light-matter interactions. Most theoretical derivations of fundamental radiative processes rely on energetic considerations and detailed balance equations, but not on momentum considerations. Because momentum exchange should also be incorporated into theoretical models, we investigate momentum inside the three categories of NZI materials, i.e., inside epsilon-and-mu-near-zero (EMNZ), epsilon-near-zero (ENZ) and mu-near-zero (MNZ) materials. In the context of Abraham–Minkowski debate in dispersive materials, we show that Minkowski-canonical momentum of light is zero inside all categories of NZI materials while Abraham-kinetic momentum of light is zero in ENZ and MNZ materials but nonzero inside EMNZ materials. We theoretically demonstrate that momentum recoil, transfer momentum from the field to the atom and Doppler shift are inhibited in NZI materials. Fundamental radiative processes inhibition is also explained due to those momentum considerations inside three-dimensional NZI materials. Absence of diffraction pattern in slits experiments is seen as a consequence of zero Minkowski momentum. Lastly, consequence on Heisenberg inequality, microscopy applications and on the canonical momentum as generator of translations are discussed. Those findings are appealing for a better understanding of fundamental light-matter interactions at the nanoscale as well as for lasing applications.

Overview of Metamaterials-Integrated Antennas for Beam Manipulation Applications: The Two Decades of Progress

Metamaterials (MMs) are synthetic composite structures with superior properties not found in naturally occurring materials. MMs have gained massive attention over the last two decades because of their extraordinary properties, such as negative permittivity and permeability. These materials enable many applications in communication subsystems, especially in the field of antenna design, to enhance gain, bandwidth, and efficiency, reduce the size, and deflect the radiation pattern. The demand for beam-deflection antennas is significant in modern wireless communication research studies due to their importance in enhancing service quality, system security, avoiding interference, and economizing power. The MM structures are usually included in the vicinity of the radiating element or incorporated in the antenna substrate for controlling the radiation pattern. This review study provides an introduction to MMs, focusing on their electromagnetic properties, classification, and design approaches. Furthermore, a detailed study of using the MMs to manipulate the radiation is carried out, where different properties such as the positive/negative refractive index, epsilon-near-zero (ENZ), and mu near-zero (MNZ) are employed to achieve a beam-deflection antenna. Reconfigurable MMs are also loaded to the antenna to achieve multi-directional beam deflection with negligible effect on the antenna&#x2019;s physical size. Moreover, the gradient-index (GRIN) based on MMs is used to obtain high deflection angles with minor effects on other antenna properties.

Overview of Planar Antenna Loading Metamaterials for Gain Performance Enhancement: The Two Decades of Progress

Metamaterials (MTMs) are artificially engineered materials with unique electromagnetic properties not occurring in natural materials. MTMs have gained considerable attention owing to their exotic electromagnetic characteristics such as negative permittivity and permeability, thereby a negative refraction index. These extraordinary properties enable many practical applications such as super-lenses, and cloaking technology, and are used to design different electromagnetic devices like filters, polarization converters, sensors, and absorbers. Advances in MTMs have made new application fields to emerge in communication subsystems, especially in the field of antennas. MTMs are usually arranged in front or above the radiating element, or incorporated in the same substrate to improve the performance of planar antennas, in terms of improving directivity, gain, bandwidth, and efficiency, reducing the size and mutual coupling, and deflecting the radiation characteristics. High gain antennas are demanded in modern wireless communication systems. Their importance is in improving the signal strength by reducing the interference and alleviating the free space path loss. This review paper provides a brief introduction to MTMs, with the focus on their operating principles. Furthermore, a detailed study of antenna gain enhancement based on the various properties of MTMs is carried out. MTMs with low values of constitutive parameters; zero-index material (ZIM), low-index material (LIM), epsilon-near-zero (ENZ), and mu-near-zero (MNZ) are discussed in detail in the context of their capability to enhance the gain of a broad class of planar antennas. The low impedance property and lensing property, which is achieved by three different characteristics: high refractive index (HRI), gradient refractive index (GRIN), and negative refractive index (NRI) materials, are loaded to planar antennas for gain enhancement. The scope of this review has been limited to antennas that were experimentally validated in the respective source papers.

Computational Investigation of Multiband EMNZ Metamaterial Absorber for Terahertz Applications

This study presents an Epsilon Mu near-zero (EMNZ) nanostructured metamaterial absorber (NMMA) for visible regime applications. The resonator and dielectric layers are made of tungsten (W) and quartz (fused), where the working band is expanded by changing the resonator layer's design. Due to perfect impedance matching with plasmonic resonance characteristics, the proposed NMMA structure is achieved an excellent absorption of 99.99% at 571 THz, 99.50% at 488.26 THz, and 99.32% at 598 THz frequencies. The absorption mechanism is demonstrated by the theory of impedance, electric field, and power loss density distributions, respectively. The geometric parameters are explored and analyzed to show the structure's performance, and a near-field pattern is used to explain the absorption mechanism at the resonance frequency point. The numerical analysis method describes that the proposed structure exhibited more than 80% absorbability between 550 and 900 THz. The Computer Simulation Technology (CST Microwave Studio 2019) software is used to design the proposed structure. Furthermore, CST-HFSS interference is validated by the simulation data with the help of the finite element method (FEM). The proposed NMMA structure is also exhibits glucose concentration sensing capability as applications. So the proposed broadband absorber may have a potential application in THz sensing, imaging (MRI, thermal, color), solar energy harvesting, light modulators, and optoelectronic devices.

Design of highly directive slot antenna using metamaterial structure under optimal condition

In this article, a highly directive slot antenna design using a parallel incident magnetic metamaterial (MTM) structure has been presented. A split ring resonator (SRR) structure having mu near-zero and epsilon very large with low impedance behavior is employed to enhance the directivity of the antenna. In the proposed optimized design, four-MTM slabs with an array of 2 × 2 SRR unit cell have been placed perpendicularly over the slot antenna to enhance the directivity. The thickness of utilized MTM slab in the vertical direction is under the optimal condition, which is highly desired to obtain better improvement in directivity. In spite of directivity enhancement of about 6 dB, antenna miniaturization of 11.4% is also obtained due to the loading effect of the MTM slab. The proposed directivity enhancement approach of the slot antenna is established by simulation and verified by measurements. It is perceived from both measured and simulated results that over the whole working band, a significant directivity enhancement is sustained along with reduced backward radiation compared to the unloaded slot.

Goos–Hanchen-effect for near-zero-index metamaterials excited by fractional dual fields

The purpose of this paper is to examine the Goos–Hanchen-effect (GH-effect) for near-zero-index metamaterials taking fractional dual fields as the source of excitation. Fractional dual fields are intermediate states between the s-polarized and p-polarized fields. The behavior of reflection coefficient, corresponding phase, and GH-effect, for epsilon-near-zero (ENZ)/mu-near-zero (MNZ) metamaterial is analyzed. Both lossless and lossy ENZ/MNZ metamaterial are treated in this regard. Impact of variation of fractional parameter on the behavior of reported quantities is noted in detail.

Parabolic Split Ring Resonator (PSRR) based MNZ metamaterial with angular rotation for WiFi/WiMax/Wireless/ISM band applications

The engineering in artificial inclusions of metamaterials has immense potential to explore in the field of electromagnetic wave manipulation that created enormous opportunities in the design of millimetre or sub-millimetres structures. In this research paper, Parabolic Split Ring Resonator (PSRR) based MNZ (Mu-Near-Zero) metamaterial with a wider refractive index is introduced for WiFi/WiMax/Wireless/ISM band applications and printing on Rogers RT-5880 lossy substrate with a copper-based metallic structure at 5.8 GHz within the microwave frequency region. The resonant frequency, negative permittivity, near-zero permeability, and negative refractive index are between 5.5-6.3 GHz. This proposed metamaterial structure is analysed with array structures, different substrate material, different orientations, and split gaps.

Equivalent circuit method for Mu‐Negative‐Magnetic and Mu‐Near‐Zero metamaterials in wireless power transfer system

The application of the metamaterial (MM) in wireless power transfer (WPT) system has received a great deal of attention in improving the transfer efficiency and reducing the leakage of electromagnetic field (EMF) in recent years. However, most of the analytical methods for MM-inspired WPT system are based on microwave technologies, such as negative refraction effect, magnetic dipole coupling model and magneto-inductive wave theory. In this study, the equivalent circuit model of the MM in the WPT system is analysed in detail. Two different types of MMs, Mu-Negative-Magnetic (MNM) and Mu-Near-Zero (MNZ), are constructed to verify this method. In particular, a tuning strategy by changing the distances between the drive (load) loop and internal coils is established to improve the power transfer efficiency for the WPT system with the MNM-MM. In addition, the MNZ-MM is described to cancel EMF leakage in the WPT systems by this method. Moreover, a series of practical experiments are carried out to prove the numerical analysis, which are well consistent with the theoretical solution employed by the Advanced Design System software. Finally, the combination of two types of MMs applied in the WPT system is also discussed.

Novel MNZ-type microwave sensor for testing magnetodielectric materials

A novel microwave sensor with the mu-near-zero (MNZ) property is proposed for testing magnetodielectric material at 4.5 GHz. The sensor has a double-layer design consisting of a microstrip line and a metal strip with vias on layers 1 and 2, respectively. The proposed sensor can detect a unit change in relative permittivity and relative permeability with a difference in the operating frequency of 45 MHz and 78 MHz, respectively. The MNZ sensor is fabricated and assembled on two layers of Taconic RF-35 substrate, with thicknesses of 0.51 mm and 1.52 mm, respectively, for the measurement of the sample under test using a vector network analyzer. The dielectric and magnetic properties of two standard dielectric materials (Taconic CER-10 and Rogers TMM13i) and of yttrium–gadolinium iron garnet are measured at microwave frequencies. The results are found to be in good agreement with the values available in the literature, which shows the applicability of the prototype for sensing of magnetodielectric materials.

A Dual-Polarized Magnetoelectric Dipole Array Based on Printed Ridge Gap Waveguide With Dual-Polarized Split-Ring Resonator Lens

In this article, a 1x4 dual-polarized magnetoelectric (ME) dipole antenna array is proposed. The antenna is excited by a dual-polarized fork-shaped microstrip line based on printed ridge gap waveguide technology. To achieve additional gain, a dual-polarized split-ring resonator (SRR) is designed, which has a mu-near zero (MNZ) feature. This scatterer works as a meta-lens to convert the radiated spherical wave to a plane wave for both polarizations. Integrating four layers of the proposed inclusions on top of the ME dipole antenna results in an increase in the antenna gain by a maximum of 3 dB. The proposed 1 x 4 antenna array was fabricated and tested, and the measured reflection coefficient at Port 1 is less than -10 dB over the frequency band of 28-35 GHz, while the measured realized gain varies from 14.3 to 15.4 dBi, and the measured radiation efficiency varies from 78% to 88%. The measured reflection coefficient at Port 2 for the orthogonal polarization is less than -8 dB over the frequency band of 28-35 GHz, with a measured gain of 14.8-16 dBi, and the measured radiation efficiency varies from 81% to 90%.

Hexagonal Shaped Near Zero Index (NZI) Metamaterial Based MIMO Antenna for Millimeter-Wave Application

A single-layered multiple-input multiple-output (MIMO) antenna working at 28 GHz loaded with a compact planar-patterned metamaterial (MTM) structures is presented in this paper for millimeter-wave application. A combination of a split square and hexagonal shaped unit cell is designed and investigated with a wide range of effective near-zero index (NZI) of permeability and permittivity, along with a refractive index (NZRI) property. The metamaterial characteristics were examined through the material wave propagation in two main directions at y and x-axis. For wave propagation at the y-axis, it demonstrates mu-near-zero (MNZ) with more than 6 GHz bandwidth, near-zero refractive index (NZRI), and epsilon-near-zero (ENZ) properties. However, it indicates a wide negative range of single mu metamaterial (MNG) from 27.6 to 28.9 GHz frequency span at x-axis wave propagation. A single antenna with $3\times 3$ metamaterial unit cells is proposed to operate at a frequency band (24 – 30) GHz. Furthermore, MIMO antenna with only 4 mm space between antenna elements provides high isolation of more than 24 dB. The measured results show that the MIMO antenna is satisfied with 6 GHz bandwidth, and maximum peak gain of 12.4 dBi. In addition to that, the proposed MIMO antenna loaded with MTM has also shown good performances with high diversity gain (DG > 9.99), envelope correlation coefficient (ECC) lower than 0.0013, channel capacity loss (CCL) $\times23$ mm.

Dual-band negative-permittivity metamaterial using crossed loop resonator

This paper presents a novel dual-band negative-permittivity metamaterial (MTM). The MTM is based on a crossed loop resonator (CLR) which exhibits negative-permittivity property at 4.85–5.58 GHz and 9.34–15.48 GHz frequency bands under the normal incidence of EM wave. The MTM shows epsilon-very-large (EVL) and mu-near-zero (MNZ) properties near the resonance frequencies (4.85 GHz and 9.34 GHz). Thus, low-impedance characteristics are obtained around the resonance frequencies of the CLR. The CLR MTM is insensitive to the polarization and incident angle of the imposed EM wave (for incident angle < 20°). This MTM, which is polarization and incident angle independent, can be used for gain enhancement of magnetic dipole antennas, design of filters and ultrathin microwave absorbers.

Design of a PIN Diode-Based Reconfigurable Metasurface Antenna for Beam Switching Applications

In this paper, we propose a reconfigurable metasurface antenna for beam switching applications. The reconfigurable metasurface is formed by uniformly distributed double-split square rings loaded with positive-intrinsic-negative (PIN) diodes for dual operations of a wave reflector and a wave director. Specifically, when the PIN diodes are forward biased, an epsilon-negative (ENG) metasurface is realized which reflects all incident waves with appropriate polarization; when the diodes are reverse biased, at the same operating frequency, a mu-near-zero (MNZ) metasurface is acquired which directs wave propagation. For excitation, a dipole radiator loaded with the same type of PIN diode is designed. Simulation and measurement results show good agreement and verify the beam switching functionality of the proposed metasurface antenna.

High-Efficient Circularly Polarized Magnetoelectric Dipole Antenna for 5G Applications Using Dual-Polarized Split-Ring Resonator Lens

A circularly polarized magnetoelectric dipole antenna with high efficiency based on printed ridge gap waveguide is presented. The antenna gain is improved by using a wideband lens in front of the antennas. The lens consists of three layers dual-polarized mu-near zero (MNZ) inclusions. Each layer consists of a $3\times4$ MNZ unit cell. The measured results indicate that the magnitude of $S_{11}$ is below −10 dB in the frequency range of 29.5–37 GHz. The resulting 3-dB axial ratio is over a frequency range of 32.5–35 GHz. The measured realized gain of the antenna is more than 10 dBi over a frequency band of 31–35 GHz achieving a radiation efficiency of 94% at 34 GHz.

Dispersivity of Balanced Near-Zero Permittivity and Permeability (EMNZ) Medium

$\epsilon $ -near-zero (ENZ), $\mu $ -near-zero (MNZ), and $\epsilon $ -and- $\mu $ -near-zero (EMNZ) materials all exhibit the property of $n=\sqrt {\epsilon _{r}\mu _{r}}\approx 0$ . The wave impedance $Z=({\mu /{\epsilon }})^{1/2}$ , though, is different for the different materials. For the EMNZ, the impedance can remain finite, in contrast to the ENZ and MNZ materials. Therefore, the electric and magnetic fields within the EMNZ can remain coupled, unlike the ENZ and MNZ. This paper presents an analysis of dispersivity in an EMNZ layer under the condition of balance $\mu _{r}=\epsilon _{r}$ . One possible application for this condition is seen in the analysis of transmission and reflection from an EMNZ–free space interface, which reveals that a perfect match condition is possible for normal incidence, while for any other incidence angle, this interface is a perfect reflector.

µ-near-zero supercoupling

Theoretical predictions and experimental results demonstrate that mu-near zero metamaterials allow enhanced transmission (supercoupling) between two waveguides coupled by a channel with a disproportionately wide cross section. This effect is related but distinctly different from (and cannot be reduced to) a previously reported supercoupling effect using epsilon-near-zero metamaterials.

Roles of epsilon-near-zero (ENZ) and mu-near-zero (MNZ) materials in optical metatronic circuit networks.

The concept of metamaterial-inspired nanocircuits, dubbed metatronics, was introduced in [Science 317, 1698 (2007); Phys. Rev. Lett. 95, 095504 (2005)]. It was suggested how optical lumped elements (nanoelements) can be made using subwavelength plasmonic or non-plasmonic particles. As a result, the optical metatronic equivalents of a number of electronic circuits, such as frequency mixers and filters, were suggested. In this work we further expand the concept of electronic lumped element networks into optical metatronic circuits and suggest a conceptual model applicable to various metatronic passive networks. In particular, we differentiate between the series and parallel networks using epsilon-near-zero (ENZ) and mu-near-zero (MNZ) materials. We employ layered structures with subwavelength thicknesses for the nanoelements as the building blocks of collections of metatronic networks. Furthermore, we explore how by choosing the non-zero constitutive parameters of the materials with specific dispersions, either Drude or Lorentzian dispersion with suitable parameters, capacitive and inductive responses can be achieved in both series and parallel networks. Next, we proceed with the one-to-one analogy between electronic circuits and optical metatronic filter layered networks and justify our analogies by comparing the frequency response of the two paradigms. Finally, we examine the material dispersion of near-zero relative permittivity as well as other physically important material considerations such as losses.