Negative Permeability Metamaterials Research Articles

A metamaterial‐incorporated wireless power transmission system for efficiency enhancement

SummaryIn this paper, an efficient wireless power transmission (WPT) system that incorporates a new negative permeability metamaterial is presented. The operating principle of the metamaterial with negative permeability is first analyzed. To improve transmission efficiency of the WPT system at the operating frequency of 13.56 MHz, a new metamaterial with three open rings is designed. By respectively placing a single metamaterial slab and double metamaterial slabs at different positions between transmitting coil and receiving coil, the performance of the proposed WPT system is evaluated by simulation work. The corresponding magnetic field distribution is also analyzed. Besides, comparison is made with the conventional WPT system without metamaterial. It is found that transmission efficiency of the proposed WPT system is obviously improved when incorporating the metamaterial since the designed metamaterial effectively focuses magnetic field towards the receiving coil. Comparing with the conventional system, the results also show that the proposed WPT system is more robust to lateral and angular misalignment of the receiving coil. With the designed metamaterial, it is found that the proposed system with double metamaterial slabs performs better than that with a single metamaterial slab.

Applications of negative permeability metamaterials for electromagnetic resonance type wireless power transfer systems

With the development of electric drive systems such as unmanned aerial vehicles and electric vehicles, the charging problem of power supply devices has become increasingly prominent. However, the traditional charging method requires physical circuits, which makes it impossible to achieve freedom of the position in actual use. The wireless power transmission technology, which mainly relies on electromagnetic wave to complete energy transmission, is expected to get rid of the restriction of physical space location and solve the problem of charging location, which has great potential in medical treatment, rescue, detection and other fields. However, the low transmission efficiency and short transmission distance caused by electromagnetic field leakage are the two main problems faced by radio energy transmission systems. In general, with the increase of transmission distance, the transmission efficiency will drop sharply. Fortunately, inserting a negative permeability metamaterial with extraordinary electromagnetic characteristics into the transmitting and receiving coils will greatly alleviate this attenuation trend and can also shield electromagnetic radiation to a certain extent. In this paper, some experiments of negative permeability metamaterials used in electromagnetic resonance type wireless power transfer systems are summarized for reference.

A Dual-Band Negative Permeability and Near-Zero Permeability Metamaterials for Wireless Power Transfer System

A contactless energy charging platform is an emerging technology that can improve the conveniences of electronic charging devices. This article presents a novel asymmetric wireless power transfer (WPT) system by integrating with two kinds of dual-band metamaterials, which is suitable for recharging the portable electronic devices. The design key of the metamaterial is to achieve the dual-band negative permeability (DB-MNG) and near-zero permeability (DB-MNZ) for enhancing efficiency and reducing leakage magnetic field of the WPT system, simultaneously. Especially, the corresponding simulation and experimentation are carried out to verify the validity of the DB-MNG metamaterial for increasing the efficiency at 13.56 and 27.12 MHz. Moreover, considering the charging environment of portable devices, various misalignments between the device and DB-MNG metamaterial are discussed to maintain continuous power availability. Meanwhile, the dual-band shielding performance of DB-MNZ metamaterial is proved at 13.56 and 27.12 MHz. As a result, the DB-MNZ metamaterial shield performs better than ferrite sheet and its performance is similar to that of aluminum sheet.

Tunneling modes induced by interface states in 1D photonic crystals with single negative materials

We investigate the electromagnetic wave propagating in one dimensional photonic crystals with alternating layers of negative permittivity materials and negative permeability metamaterials. The band structure and transmission spectra are obtained. In the negative effective permittivity and negative effective permeability regime, we find new interface modes propagating along the interfaces between the two different media with even and odd parities, respectively. For the oblique incident case, the new propagation modes result in the emergence of a transmission band within the zero-ϕeff gap of these photonic crystals. By adjusting the plasma density or the thickness of the plasma layer, the zero-ϕeff gap as well as the transmission band of the interface modes can be tuned, which can facilitate the design of tunable filters at the microwave frequency range.

Comprehensive Analysis of Side-Placed Metamaterials in Wireless Power Transfer System

In this article, we propose the side-placed negative-permeability metamaterial (NPM) and zero-permeability metamaterial (ZPM) in the wireless power transfer (WPT) system to simultaneously enhance the level of efficiency and meet the electromagnetic field (EMF) safety regulations. A theoretical analysis, simulation, and experiment are conducted to verify the feasibility of the proposed system model. Based on the principle of magneto-inductive waves (MIWs) and the shielding theory, the transmission characteristics of the WPT system without and with two NPM slabs, two ZPM slabs, and the combination of NPM and ZPM slabs are analyzed. The results demonstrate that the ZPM slabs and the combination of NPM and ZPM slabs have a high efficiency improvement when the transfer distance is located under 40 cm and exceeds 40 cm, respectively. Both methods can control the EMF leakage. Moreover, the side-placed metamaterial exhibits tolerance to the misalignment of the coil. Finally, comparative studies on the ZPM slab and aluminum are carried out. The experimental and simulation results show that the ZPM slab performs better than aluminum.

Investigation of Negative and Near-Zero Permeability Metamaterials for Increased Efficiency and Reduced Electromagnetic Field Leakage in a Wireless Power Transfer System

In order to meet both safety and efficiency requirements of wireless power transfer (WPT) systems, reducing electromagnetic field (EMF) leakage and improving efficiency are critical factors in the implementation of systems. Recently, metamaterials have exhibited the ability to control the electromagnetic wave propagation. In this paper, the WPT system integrating with near-field mu-near-zero (NF-MNZ) and mu-negative permeability (MNG) metamaterials is proposed to control EMF leakage below a certain level and improve transfer efficiency. The NF-MNZ and the MNG metamaterials are placed on both sides and in the middle of the WPT system, respectively. In addition, the property of the NF-MNZ metamaterial slab and its working principle on the WPT system are analyzed. The shielding performance of the NF-MNZ metamaterial are evaluated via numerical simulation and experimental investigation. Finally, the efficiency and the magnetic field strength of the WPT system with two different types of metamaterials have been investigated by the experimental measurements. At the transfer distance of 40 cm, the experimental results show that the efficiency of the WPT system is increased by 12.06% and the magnetic field strength is reduced by 62.09%.

Study of efficiency improvement for wireless power transfer based on negative permeability metamaterials

In order to enhance the transmission efficiency of wireless power transfer (WPT), a negative permeability metamaterials (NPM) with a structure of honeycomb composed by units of hexagon-shaped spirals copper is proposed in this paper. The unit parameters of the NPM are optimized, to make sure the negative permeability at 6.78 MHz. The S -parameters of the designed NPM are measured by a network analyzer and the permeability is extracted. It shows that the honeycomb NPM have a negative permeability at 6.2–6.7 MHz. A two-coil WPT is setup and the transmission efficiency of WPT embedded with NPM at the different position and with different structure are investigated. The measured results show that the 2-slab honeycomb NPM have a good performance compared with the 1-slab NPM, and the efficiency can be increased up to 12.5% at a distance of 30 cm.

Structural Evolution Design and Optimization for the Metamaterials with Broadband Frequency-Independent Negative Permeability

Broadband frequency-independent operations are strongly desired in metamaterial applications. In this work, we unveil the roles of each element acting in the metamaterial unit with a structural evolution design methodology. Starting with “split ring resonator” (SRR) prototype structures, we focus on the variations of elements on the magnetic response and successfully realize the structures of “clock-like” and “wire pairs” with double and broadband frequency-independent negative permeability (0.725 to 0.9 THz, μ = − 0.75). Our results suggested that multi-resonance modes induced by elements integration could extend working bands. By well parameters tuning, the phase mismatch during multi-modes interactions could be utilized to modify the working bands with frequency-independent features as well. Our investigations are beneficial to the design of functional negative permeability metamaterials with broadband operations.

Investigation of negative permeability metamaterials for wireless power transfer

In order to enhance the transmission efficiency of wireless power transfer (WPT), a negative permeability metamaterials (NPM) with a structure of honeycomb composed by units of hexagon-shaped spirals copper is proposed in this paper. The unit parameters of the NPM are optimized, to make sure the negative permeability at the special frequency. The S-parameters of the designed NPM are measured by a network analyzer and the permeability is extracted, it shows the honeycomb NPM has a negative permeability at 6.43 MHz. A two-coil WPT is setup and the transmission efficiency of WPT embedded with NPM at the different position and with different structure are investigated. The measured results show that the 2-slab honeycomb NPM have a good perform compared with the 1-slab NPM, and the efficiency can be increased up to 51%. The results show that honeycomb NPM embedded in the WPT help to improve the transmission efficiency remarkable.

Impedance matching control method for an underwater magnetic resonance-based wireless power transfer system with metamaterials

In this paper, a new method of improving the efficiency of the underwater magnetic resonance-based wireless power transfer (MRWPT) system is proposed. A kind of the negative permeability (MNG) metamaterials with low megahertz frequency is designed, which can be adjusted to work well in the system. The S-parameters, resonant frequency, and permeability of metamaterials are worked out for analysis. A new impedance matching control method was also proposed for reducing the reflection loss in a way to help the sea water MRWPT system to achieve the maximum efficiency. This method is also able to reduce the unnecessary power loss caused by power fluctuation. The measured results show that the performance of the proposed metamaterials and the proposed control method are perfect in improving its efficiency in sea water.

Negative-permittivity plasma generation in negative-permeability space with high-energy metamaterials

Plasma generation by electromagnetic waves in negative-permeability space is analyzed using experimental results and theoretical models. Installation of negative-permeability metamaterials triggers drastic changes to the propagation of electromagnetic waves. Unlike usual cases in which permeability is +1, negative permeability induces evanescent modes in a space without plasma. However, if permittivity becomes negative due to high-electron-density or overdense plasma, electromagnetic waves can propagate because negative-refractive-index states emerge. In this study, reviewing our previous experimental data, we study the underlying physical processes in plasma generation in terms of wave propagation and parameters of wave media. We confirm nonlinear (transition) processes in the phase of density evolution up to the negative permittivity state and negative-refractive-index states in the quasi-steady phase. We also note that such energetic metamaterials are built up when we use plasma, unlike conventional metamaterials composed of solid-state materials.

Experiments on multiple-receiver magnetic resonance-based wireless power transfer in low megahertz with metamaterials

In this paper, an efficient magnetic resonance-based wireless power transfer (MRWPT) system with metamaterials is proposed. The negative permeability (MNG) metamaterials for this system with low-megahertz frequency is designed, which can be adjusted to work well at a variable receiving angle ranging from 0° to 45° along z-direction. The S-parameters, resonant frequency and permeability of metamaterials are computed for analysis. The transmission efficiency of the multiple-receiver MRWPT system in free space is compared to that in the presence of metamaterials placed in front of transmission and receive coils. The measured results show that the performance of the proposed metamaterials is perfect in improving the efficiency with incident electromagnetic waves from various directions.

Improving Power Transfer Efficiency of a Short-Range Telemetry System Using Compact Metamaterials

Wireless power transfer using resonant inductive coupling has been employed in a number of applications, including wireless charging of electronic devices and powering of implanted biomedical devices. In these applications, power is transferred over short distances, which are much smaller (~ λ/100) than the wavelength of operation. In such systems, the power transfer efficiency of the link is inversely related to the range of operation. The power transfer efficiency is principally a function of the Q's of the individual coils and the coupling between them. In this paper, we demonstrate improvements in power transfer efficiencies using negative permeability metamaterials by increasing the mutual coupling between coils. A metamaterial slab is designed for operation at 27 MHz and is compact in size. The power transfer efficiency of the telemetry system in free space is compared to that in the presence of the metamaterial placed near one of the coils. The efficiency of the system increased in the presence of the metamaterial even as the free-space separation was held constant. This shows that compact negative permeability metamaterials can be used to increase power transfer efficiency of short-range telemetry systems used in various applications.

Tunable negative permeability in a quantum plasmonic metamaterial

We consider the integration of quantum emitters into a negative permeability metamaterial design in order to introduce tunability as well as nonlinear behavior. The unit cell of our metamaterial is a ring of metamolecules, each consisting of a metal nanoparticle and a two-level semiconductor quantum dot (QD). Without the QDs, the ring of the unit cell is known to act as an artificial optical magnetic resonator. By adding the QDs we show that a Fano interference profile is introduced into the magnetic field scattered from the ring. This induced interference is shown to cause an appreciable effect in the collective magnetic resonance of the unit cell. We find that the interference provides a means to tune the response of the negative permeability metamaterial. The exploitation of the QD's inherent nonlinearity is proposed to modulate the metamaterial's magnetic response with a separate control field.

Multiband meandered miniaturized patch antenna loaded with split ring resonator and thin wire arrays

ABSTRACTArtificial materials have attracted considerable attention as potential solutions to meet the demands of modern microwave technology for simultaneously achieving component minimization and higher performance in wireless communications, mobile communications, and satellite communication applications. So in this letter, we have investigated a multiband meandered miniaturized patch antenna with the use of split ring resonator (SRR) and thin wire arrays. SRR are promising building blocks for negative permeability metamaterials and thin wire arrays for negative permittivity. By combining SRR arrays and wire arrays together, we observed a transmission band where both permittivity and permeability are simultaneously negative. Simulated results for the S11 and electric field of an antenna are presented. The result shows multibands centered at 1.89, 2.04, 2.13, and 2.31 GHz. Design results are obtained by a high frequency structure simulator which is used for simulating microwave passive components. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:306–310, 2014

A High Gain Omnidirectional Antenna Using Negative Permeability Metamaterial

A high gain omnidirectional antenna with low profile is proposed and is investigated numerically and experimentally. Based on the conventional center-fed circular epsilon-negative (ENG) zeroth-order resonator (ZOR) antenna, dendritic structure negative permeability metamaterial (NPM) is used as the substrate to enhance the gain of the omnidirectional antenna. The experimental results show that the gain of a center-fed circular ENG ZOR antenna with NPM substrate is enhanced about 2.2 dB, and the efficiency is enhanced about 38%, in the whole broad operating bandwidth as compared to that of the antenna without NPM substrate, which can be used to improve the reliability of wireless communications.

Enhancement of the Gain for Microstrip Antennas Using Negative Permeability Metamaterial on Low Temperature Co-Fired Ceramic (LTCC) Substrate

A novel method for enhancement of the gain for microstrip antennas is demonstrated. Compact nested tridimensional split-ring resonators (SRRs) are embedded in low temperature co-fired ceramic (LTCC) substrate integrated with a single patch antenna. The maximum dimension of the SRRs structure is only <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$0.13\lambda_{\rm g}$</tex> </formula> . The SRRs generate an effective magnetic response and give rise to negative effective permeability, which can be designed as a metamaterial insulator to reflect surface waves. A high-gain microstrip antenna is designed for WLAN, operating at 5.2 GHz, surrounded with proposed SRRs in the E-plane. The performance of the antenna shows that the side and backward radiation decreased and the forward radiation increased. Compared to the conventional microstrip antenna, the gain of proposed microstrip antenna is enhanced by 1.5 dB, and the 3-dB beamwidth of the E-plane can be reduced by 14 <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$^{\circ}$</tex></formula> .

EXPERIMENTAL STUDY OF EFFICIENT WIRELESS POWER TRANSFER SYSTEM INTEGRATING WITH HIGHLY SUB-WAVELENGTH METAMATERIALS

In this paper, an e-cient wireless power transfer (WPT) system integrating with highly sub-wavelength metamaterials is proposed. The negative refractive index (NRI) and negative permeability (MNG) metamaterials for operation at radio frequencies are designed and applied to WPT system for improvement of power transfer e-ciency. A dual-layer design which consists of a planar spiral on one side and a meander line touching with narrow metallic strips on the other side produces the properties of efiective negative permittivity and permeability simultaneously, i.e., negative refractive index. In addition, the structure of double spirals produces a negative permeability. The cell size of the NRI and MNG metamaterials is about 253 times smaller than the operation wavelength. By integrating one, two, three or four metamaterial slabs between the two coupling copper rings, the transfer e-ciency is improved signiflcantly. The measured results show that the contribution of high transfer e-ciency is due to the property of negative permeability which can make the WPT system work in the mechanism of magnetic resonance.

Magnetic levitation of metamaterial bodies enhanced with magnetostatic surface resonances

We propose that macroscopic objects built from negative-permeability metamaterials may experience resonantly enhanced magnetic force in low-frequency magnetic fields. Resonant enhancement of the time-averaged force originates from magnetostatic surface resonances (MSRs), which are analogous to the electrostatic resonances of negative-permittivity particles, well known as surface plasmon resonances in optics. We generalize the classical problem of the MSR of a homogeneous object to include anisotropic metamaterials and consider the most extreme case of anisotropy, where the permeability is negative in one direction but positive in the others. It is shown that deeply subwavelength objects made of such indefinite (hyperbolic) media exhibit a pronounced magnetic dipole resonance that couples strongly to uniform or weakly inhomogeneous magnetic field and provides strong enhancement of the magnetic force, enabling applications such as enhanced magnetic levitation.

Isotropic negative permeability metamaterials and left-handed metamaterials based on miniature structure

We propose an isotropic structure based on double split-ring resonator. We investigate experimentally and numerically the electromagnetic resonant properties of the proposed structure. The result shows that when the electromagnetic wave transmits in the directions parallel and perpendicular to the plane of the split ring resonator, respectively, the resonant bands having the negative permeability both arise at the same frequencies. However, when the electromagnetic wave transmits with oblique angle, the resonant characteristic is still unchanged. That is to say, resonant characteristic of the proposed structure is independent of incidence angle. This result indicates that the proposed structure is an isotropic medium. Combining the proposed double split-ring resonator structure with the wires, the left-handed metamaterial with negative refractive index can be obtained. In addition, the proposed structure has the merit of the miniaturization due to adding the metallic via-hole, which can increase the electric length of the structure. As a result, the resonant frequency of the structure shifts toward lower frequency greatly without increasing the dimension of the structure, and then the structure is still compact in the low frequency case. The introduction of the metallic via-hole can reduce the dimension of the structure by 50%. Therefore, the proposed structure will be a good candidate in the microwave applications such as antennas, filter, among others.