Showing papers on "Metamaterial antenna published in 2011"
TL;DR: It is demonstrated that a broadband, extremely high index of refraction can be realized from large-area, free-standing, flexible terahertz metamaterials composed of strongly coupled unit cells.
Abstract: Controlling the electromagnetic properties of materials, going beyond the limit that is attainable with naturally existing substances, has become a reality with the advent of metamaterials. The range of various structured artificial 'atoms' has promised a vast variety of otherwise unexpected physical phenomena, among which the experimental realization of a negative refractive index has been one of the main foci thus far. Expanding the refractive index into a high positive regime will complete the spectrum of achievable refractive index and provide more design flexibility for transformation optics. Naturally existing transparent materials possess small positive indices of refraction, except for a few semiconductors and insulators, such as lead sulphide or strontium titanate, that exhibit a rather high peak refractive index at mid- and far-infrared frequencies. Previous approaches using metamaterials were not successful in realizing broadband high refractive indices. A broadband high-refractive-index metamaterial structure was theoretically investigated only recently, but the proposed structure does not lend itself to easy implementation. Here we demonstrate that a broadband, extremely high index of refraction can be realized from large-area, free-standing, flexible terahertz metamaterials composed of strongly coupled unit cells. By drastically increasing the effective permittivity through strong capacitive coupling and decreasing the diamagnetic response with a thin metallic structure in the unit cell, a peak refractive index of 38.6 along with a low-frequency quasi-static value of over 20 were experimentally realized for a single-layer terahertz metamaterial, while maintaining low losses. As a natural extension of these single-layer metamaterials, we fabricated quasi-three-dimensional high-refractive-index metamaterials, and obtained a maximum bulk refractive index of 33.2 along with a value of around 8 at the quasi-static limit.
572 citations
TL;DR: In this article, the authors proposed a CRLH leaky-wave antenna for antenna applications, which is realized by etching interdigital slots on the waveguide surface and the ground.
Abstract: Composite right/left-handed (CRLH) substrate integrated waveguide (SIW) and half mode substrate integrated waveguide (HMSIW) leaky-wave structures for antenna applications are proposed and investigated. Their propagation properties and radiation characteristics are studied extensively. Their backfire-to-endfire beam-steering capabilities through frequency scanning are demonstrated and discussed. These metamaterial radiating structures are realized by etching interdigital slots on the waveguide surface and the ground. The slot behaves as a series capacitor as well as a radiator leading to a CRLH leaky-wave application. Four antennas are fabricated, measured, and analyzed, including two balanced CRLH SIW designs characterized by single-side or double-side radiation, and two unbalanced HMSIW designs characterized by different boundary conditions. Antenna parameters such as return loss, radiation patterns, gain, and efficiency are all provided. Measured results are consistent with the simulation. All these proposed antennas possess the advantages of low profile, low cost, and low weight, while they are also showing their own unique features, like high directivity, quasi-omnidirectional radiation, miniaturized size, continuous beam-steering capabilities covering both the backward and forward quadrants, etc., providing much design flexibility for the real applications.
304 citations
TL;DR: In this paper, the use of metamaterials was proposed to enhance the evanescent wave coupling and improve the transfer efficiency of a wireless power transfer system based on coupled resonators.
Abstract: In this letter, we propose the use of metamaterials to enhance the evanescent wave coupling and improve the transfer efficiency of a wireless power transfer system based on coupled resonators. A magnetic metamaterial is designed and built for a wireless power transfer system. We show with measurement results that the power transfer efficiency of the system can be improved significantly by the metamaterial. We also show that the fabricated system can be used to transfer power wirelessly to a 40 W light bulb.
289 citations
01 Oct 2011
TL;DR: Recent developments with this NFRP electrically small paradigm will be reviewed, including considerations of increased bandwidths, as well as multiband and multifunctional extensions.
Abstract: A variety of antennas have been engineered with metamaterials (MTMs) and metamaterial-inspired constructs to improve their performance characteristics. Examples include electrically small, near-field resonant parasitic (NFRP) antennas that require no matching network and have high radiation efficiencies. Experimental verification of their predicted behaviors has been obtained. Recent developments with this NFRP electrically small paradigm will be reviewed. They include considerations of increased bandwidths, as well as multiband and multifunctional extensions.
271 citations
TL;DR: In this article, a compact coplanar waveguide (CPW)-fed zeroth-order resonant (ZOR) antennas are designed on a CPW single layer where vias are not required.
Abstract: This paper presents the design and analysis of compact coplanar waveguide (CPW)-fed zeroth-order resonant (ZOR) antennas. They are designed on a CPW single layer where vias are not required. The ZOR phenomenon is employed to reduce the antenna size. The novel composite right/left-handed (CRLH) unit cell on a vialess single layer simplifies the fabrication process. In addition, the CPW geometry provides high design freedom, so that bandwidth-extended ZOR antennas can be designed. The antenna's bandwidth is characterized by the circuit parameters. Based on the proposed bandwidth extension technique, symmetric, asymmetric, and chip-loaded antennas are designed. The ZOR characteristic and bandwidth extension are verified by a commercial EM simulator. Their performances are compared with those of previously reported metamaterial resonant antennas. They provide further size reduction, higher efficiency, easier manufacturing, and extended bandwidth.
181 citations
TL;DR: In this article, a three-dimensional broadband, low-loss, dual-polarization, and high-directivity lens antenna using gradient index (GRIN) metamaterials, which is composed of multi-layer microstrip square-ring arrays.
Abstract: We present the theoretical modeling and prototype demonstration of a three-dimensional broadband, low-loss, dual-polarization, and high-directivity lens antenna using gradient index (GRIN) metamaterials, which is composed of multi-layer microstrip square-ring arrays. The elements of metamaterials, closed square-ring units of variable sizes, are distributed on the planar substrate to satisfy the radial gradient index function and the axial impedance matching layer configuration of the lens. The gradient-index metamaterials are designed to transform the spherical wave-front into the planar wave-front and to minimize the reflection loss. A prototype lens antenna, which consists of a metal conical horn and the gradient-index lens, are simulated, constructed, and measured. The resemblance of simulation and measurement results shows that the prototype lens antenna maintains low return loss and high directivity on the whole X-band (from 8 GHz to 12 GHz). Compared to the traditional horn antenna, the metamaterial...
174 citations
TL;DR: In this paper, an equivalent transmission line (TL) model using linearized series and shunt immittances to approximate the periodic (Bloch) antenna structure, asymptotic TL formulas for the characteristic propagation constant, impedance, energy, power and quality factor are derived for two fundamentally different near and off-broadside radiation regimes.
Abstract: It is shown, using three specific examples-a series fed patch (SFP) array, a phase reversal (PR) array and a composite right/left-handed (CRLH) antenna-that one-dimensional periodic leaky-wave antennas scanning through broadside build a class of leaky-wave antennas sharing qualitatively similar and quantitatively distinct dispersion and radiation characteristics. Based on an equivalent transmission line (TL) model using linearized series and shunt immittances to approximate the periodic (Bloch) antenna structure, asymptotic TL formulas for the characteristic propagation constant, impedance, energy, power and quality factor are derived for two fundamentally different near- and off-broadside radiation regimes. Based on these formulas, it is established that the total powers in the series and shunt elements are always equal at broadside, which constitutes one of the central results of this contribution. This equal power splitting implies a severe degradation of broadside radiation when only one of the two elements series or shunt efficiently contributes to radiation and the other is mainly dissipative. A condition for optimum broadside radiation is subsequently established and shown to be identical to the Heaviside condition for distortionless propagation in TL theory. Closed-form expressions are derived for the constitutive (LCRG) parameters of the TL model for the specific SFP, PR and CRLH antenna circuit models, and quantitative information on the validity range of the TL model is subsequently provided. Finally, full-wave simulation and measurement LCRG parameter extraction methods are proposed and validated.
142 citations
TL;DR: In this article, several metamaterial-inspired, electrically small, near-field resonant parasitic antennas are presented and compared with electric and magnetic couplings to the parasitic antennas.
Abstract: Several metamaterial-inspired, electrically small, near-field resonant parasitic antennas are presented. Both electric and magnetic couplings to the parasitic are compared and contrasted. The electric-coupled versions are shown to be more efficient and to have more bandwidth. The evolution of circular polarized designs from their linear counterparts by introducing multiple parasitics having different resonant frequencies is demonstrated. Single L1 and dual band L1/L2 GPS systems are emphasized for practical illustrations of the resulting performance characteristics. Preliminary experimental results for a dual band, circularly polarized GPS L1/L2 antenna are provided and underscore several practical aspects of these designs.
123 citations
TL;DR: In this article, the nature of typical homogenization artifacts, relating them to an inherent form of magnetoelectric coupling associated with the finite phase velocity along metamaterial arrays, is explained.
Abstract: Metamaterial homogenization is often based on implicit assumptions inspired by naturalmaterial models. However, retrieved permittivity and permeability frequently retain nonphysical values, especially near the metamaterial resonances where most interesting features are expected. We explain here the nature of typical homogenization artifacts, relating them to an inherent form of magnetoelectric coupling associated with the finite phase velocity along metamaterial arrays. Our findings allow restoring the proper definition and physical meaning of local constitutive parameters for metamaterials.
122 citations
TL;DR: This work designs metamaterials that considerably improve conventional horn antennas over greater than an octave bandwidth with negligible loss and advance the state of the art in the process.
Abstract: Metamaterials provide an unprecedented ability to manipulate electromagnetic waves and are an enabling technology for new devices ranging from flat lenses that focus light beyond the diffraction limit to coatings capable of cloaking an object. Nevertheless, narrow bandwidths and high intrinsic losses arising from the resonant properties of metamaterials have raised doubts about their usefulness. New design approaches seek to turn the perceived disadvantages of dispersion into assets that enhance a device's performance. Here we employ dispersion engineering of metamaterial properties to enable specific device performance over usable bandwidths. In particular, we design metamaterials that considerably improve conventional horn antennas over greater than an octave bandwidth with negligible loss and advance the state of the art in the process. Fabrication and measurement of a metahorn confirm its broadband, low-loss performance. This example illustrates the power of clever implementation combined with dispersion engineering to bring metamaterials into their full potential for revolutionizing practical devices.
112 citations
TL;DR: In this paper, an experimental demonstration of the overcoming of basic dispersion energy constraints in metamaterials with the help of active non-Foster negative capacitors is reported.
Abstract: Experimental demonstration of the overcoming of basic dispersion-energy constraints in metamaterials with the help of active non-Foster negative capacitors is reported. The experimental metamaterial operates in RF regime, and it is based on air transmission line loaded with negative capacitors. Measurement results clearly show almost dispersionless Epsilon-Near-Zero behavior, accompanied with superluminal both phase and group velocities, over a bandwidth of more than four octaves (2 MHz-40 MHz). The principle of periodic loading of transmission line with negative capacitors may find applications in ultra-broadband active metamaterials for antennas and cloaking technology.
TL;DR: In this article, a broad-bandwidth metamaterial-inspired electric and magnetic antennas are characterized numerically by augmenting their narrow bandwidth counterparts with internal non-Foster elements.
Abstract: Realistic designs of broad-bandwidth metamaterial-inspired electric and magnetic antennas are characterized numerically By augmenting their narrow bandwidth counterparts with internal non-Foster elements, active metamaterial unit cells are introduced as near-field resonant parasitic (NFRP) elements The driven and NFRP elements in each presented case are designed to achieve nearly complete matching of the entire system to a 50- Ω source without any matching network and to yield high radiation efficiencies over their FBW10 dB bandwidths that are more than 75 times their original values
TL;DR: A metamaterial design composed of square plasmonic loops loaded by Kerr nonlinearities that combines enhanced nonlinear response with strong artificial magnetism, ensuring a negative refractive index with bistable and self-tunable response is introduced.
Abstract: We introduce a metamaterial design composed of square plasmonic loops loaded by Kerr nonlinearities that combines enhanced nonlinear response with strong artificial magnetism, ensuring a negative refractive index with bistable and self-tunable response. We verify with full-wave simulations that positive-to-negative switching of refractive index may be obtained with moderate loss. The design of a finite-size metamaterial prism is also presented, supporting at the same frequency, and for the same light intensity, positive or inverted Snell refraction as a function of its previous excitation history.
12 May 2011
TL;DR: The paper begins by introducing the equivalence between in-plane anisotropy and coupled TRLs to realize degenerate band edge (DBE) and magnetic photonic crystal (MPC) modes, followed by the design of miniature antenna elements via dispersion engineering, demonstrating their performance on small finite substrates.
Abstract: Historically, antennas and microwave devices relied on isotropic media. This provided for limited degrees of freedom (one for dielectric and another for magnetic) in the design process. In contrast, anisotropic media introduce several more degrees of freedom (at least three more for dielectrics and three additional ones for magnetic) opening a new direction in designing radio-frequency (RF) communication devices and wireless systems. A focus of the paper is the introduction of anisotropic media parameters emulated using simple printed, but highly coupled, transmission lines (TRLs). The paper begins by introducing the equivalence between in-plane anisotropy and coupled TRLs to realize degenerate band edge (DBE) and magnetic photonic crystal (MPC) modes. This is followed by the design of miniature antenna elements via dispersion engineering, demonstrating their performance on small finite substrates. The second part of the paper is focused on concatenating DBE and MPC antenna elements to realize smaller size wideband arrays. Such arrays exploit the current sheet antenna (CSA) concept to achieve the coveted goal of small wideband metamaterial arrays. For example, by constructing an array of antenna elements ~ λ/10tλ/10 in size, highly conformal (very thin) apertures delivering 5 : 1 bandwidth are demonstrated while avoiding grating lobes. In contrast to transitional approaches, the proposed method exploits (rather than suppressing) the metallic ground plane inductance. Instead, the capacitance of the tightly coupled antenna elements is used to cancel the inductance over wide bandwidths. By further employing small size array elements, large bandwidths can be achieved using a smaller footprint.
TL;DR: It is shown that the fabricated metamaterial exhibits a dispersive effective permeability, i.e. artificial magnetism, which might serve as a starting point for achieving bulk meetamaterials by using bottom-up approaches.
Abstract: We investigate the optical properties of a true three-dimensional metamaterial that was fabricated using a self-assembly bottom-up technology. The metamaterial consists of closely packed spherical clusters being formed by a large number of non-touching gold nanoparticles. After presenting experimental results, we apply a generalized Mie theory to analyze its spectral response revealing that it is dominated by a magnetic dipole contribution. By using an effective medium theory we show that the fabricated metamaterial exhibits a dispersive effective permeability, i.e. artificial magnetism. Although this metamaterial is not yet left-handed it might serve as a starting point for achieving bulk metamaterials by using bottom-up approaches.
TL;DR: In this paper, an electrically small rectenna was designed and tested at the global positioning system (GPS) L1 frequency (1.5754 GHz), and the simulated and measured rectifying efficiencies were respectively, 75.7% and 79.6% when the input power to the rectifying circuit was 0.0 dBm (1 mW).
Abstract: An electrically small rectenna was designed and tested at the global positioning system (GPS) L1 frequency (1.5754 GHz). The metamaterial-inspired near-field resonant parasitic antenna size (ka ∼ 0.467) and its direct match to the input impedance of the rectifying circuit decreased the whole size of the rectenna (ka ∼ 0.611). The simulated and measured rectifying efficiencies were, respectively, 75.7% and 79.6% when the input power to the rectifying circuit was 0.0 dBm (1 mW). The highest rectifying efficiency, 84.7%, was achieved at the GPS L1 frequency for a 3.0 dBm input power. The simulated and measured results are in good agreement.
TL;DR: This work demonstrated that negative index material can be obtained with a net gain when an external source is incorporated and maintained the left handedness of the transmission line metamaterial.
Abstract: We studied the active metamaterial transmission line at microwave frequency. The active composite right-handed or left-handed transmission line was designed to incorporate a germanium tunnel diode with a negative differential resistance property as the gain device at the unit cell level. Measurements of the fabricated planar transmission line structures with one-, two-, and three-unit cells showed that the addition of the dc pumped tunnel diodes not only provided gain but also maintained the left handedness of the transmission line metamaterial. Simulation results agree well with experimental observation. This work demonstrated that negative index material can be obtained with a net gain when an external source is incorporated.
TL;DR: In this article, a flexible anisotropic metamaterial (MM) coating was proposed to enhance the impedance bandwidth of a quarter-wave monopole to over an octave, which greatly enhances the effective permittivity for the tensor component oriented along the direction of the monopole.
Abstract: A new type of compact flexible anisotropic metamaterial (MM) coating is proposed, which greatly enhances the impedance bandwidth of a quarter-wave monopole to over an octave. The MM coating has a high effective permittivity for the tensor component oriented along the direction of the monopole. By properly choosing the radius and tensor parameter of the MM coating, another resonance at a higher frequency can be efficiently excited without affecting the fundamental mode of the monopole. Additionally, the similar current distributions on the monopole at both resonances make stable radiation patterns possible over the entire band. To experimentally verify the concept, an S-band MM coated monopole was designed, fabricated, and characterized, exhibiting a 2.14:1 bandwidth (2.15-4.6 GHz) with a VSWR of less than 2:1. The demonstrated MM coating has a radius of only λ/24 and extremely light weight, which renders it attractive for use in applications such as broadband arrays and portable wireless devices.
TL;DR: In this article, a new concept for modulating guided and lossless transmission of electromagnetic energy in the gigahertz and tera-hertz frequency range is proposed, where metamaterials and surface electromagnetic waves join force in an experimentally demonstrated new concept.
Abstract: Metamaterials and surface electromagnetic waves join force in an experimentally demonstrated new concept for modulating guided and lossless transmission of electromagnetic energy in the gigahertz and terahertz frequency range important to modern telecommunication.
TL;DR: In this article, a nonlinear metamaterial coating is introduced, and it is demonstrated its performance as a thin, broadband, absorbing surface for high-power pulsed RF currents, but becomes strongly absorbing under high power RF illumination, which may reduce the performance of other antenna systems or disturb other aspects of the electromagnetic design.
Abstract: High-power radio frequency transmitters can cause interference or damage to sensitive receivers and other electronic equipment. These signals may be coupled into circuitry through currents in the surfaces of metal enclosures, and even a small gap in conductive shielding can represent a vulnerable point of entry. This problem can be mitigated by using a lossy coating or a reactive surface to suppress surface currents. However, this may reduce the performance of other antenna systems or disturb other aspects of the electromagnetic design. Nonlinear metamaterials provide an attractive alternative. By including nonlinear behavior into a periodic structure through embedded electronic circuits, it is possible to construct a coating that provides minimal disturbance to low-power surface currents, but becomes strongly absorbing under high-power RF illumination. In this letter, a nonlinear metamaterial coating is introduced, and we demonstrate its performance as a thin, broadband, absorbing surface for high-power pulsed RF currents.
TL;DR: In this paper, a magneto-dielectric substrate was proposed to reduce the antenna dimensions by increasing the constitutive parameters of the substrate, and the proposed structure is thin enough to be embedded in a single dielectric material.
Abstract: Miniaturization of a rectangular microstrip antenna using a magneto-dielectric substrate is discussed theoretically and experimentally. A compact magneto-dielectric substrate is designed using a metamaterial structure that can reduce the antenna dimensions by increasing the constitutive parameters of the substrate. Furthermore, the proposed structure is thin enough to be embedded in a single dielectric substrate. The area of the microstrip antenna with the proposed magneto-dielectric substrate at 2.4 GHz is reduced up to about 65% compared to a conventional dielectric microstrip antenna. The bandwidth of the miniaturized antenna is almost unchanged due to the increase of the magnetic permeability at the designed 2.4-GHz frequency. Finally, a fabricated version of the miniaturized antenna is tested and measured. The results of the measurement and simulation are in good agreement.
TL;DR: In this paper, the authors apply composite right-left-hand CRLH-based RF design to print penta-band handset antennas directly on the printed circuit board (PCS), and balanced-antennas for Wi-Fi access points.
Abstract: Recent growth in the use of wireless wide-area networks (WWAN), the adoption of broadband wireless local-area networks (WLAN), and consumer demand for seamless global access has pushed the wireless industry to support most broadband wireless standards. These are supported in different geographical areas by supporting multi-band and multimode operation in cellular handsets, access points, laptops, and client cards. This has created a great challenge for engineers. It has pushed RF and antenna design beyond the capabilities of current technologies, opening the door for creative solutions that are 1) multi-band, 2) low profile, 3) small, 4) better performing (including MIMO), 5) accelerate time to market, 6) low cost, and 7) easy to integrate in the devices listed above. Conventional state-of-the-art antenna technologies satisfy a subset of these seven criteria; however, they hardly satisfy all of them. In this paper, we apply composite right-left-hand “CRLH-based” RF design to print penta-band handset antennas directly on the printed circuit board (PCS), and balanced-antennas for Wi-Fi access points. Full active and passive performance is presented, while describing key benefits of metamaterial antennas. We also analyze in detail how these antennas operate, while focusing on the main left-handed (LH) mode that enables antenna size reduction, and the ability to print them directly on the printed circuit board.
Patent•
17 Aug 2011
TL;DR: A radio frequency identifier (RFID) tag can comprise an RFID chip, an antenna, and a feed line electrically coupling the RFID chips to the antenna as mentioned in this paper.
Abstract: A radio frequency identifier (RFID) tag can comprise an RFID chip, an antenna, and a feed line electrically coupling the RFID chip to the antenna. An encoded information reading (EIR) terminal can comprise a microprocessor, a memory communicatively coupled to the microprocessor, a communication interface, and an EIR device provided by a bar code reading device, an RFID reading device, or a card reading device. The RFID reading device can further comprise an antenna and a feed line. The antenna for the RFID tag or for the RFID reading device can be provided by a patch cell, a patch cell array comprising two or more patch cells, or by a patch cell stack comprising two or more patch cells. An equivalent circuit for the patch can comprise at least two inductances and a shunt capacitance. An equivalent circuit for the patch cell array can comprise two or more inductance groups connected via a series capacitance and two or more shunt capacitances. An equivalent circuit for the patch cell stack can comprises two or more capacitances connected via a series inductance and two or more shunt inductances. The antenna can have a composite right- and left-handed (CRLH) structure.
TL;DR: In this paper, a broadband and ultra-low-loss electric metamaterial EM isolation slab is proposed to improve the performance of a microstrip array by periodically grounded edge-coupled split-ring resonators (PGE-SRRs).
Abstract: A novel broadband and ultra-low-loss electric metamaterial EM isolation slab is proposed to improve the performance of a microstrip array. The metamaterial slab is formed by periodically grounded edge-coupled split-ring resonators (PGE-SRRs). Outstanding improvements - including over -50 dB peak isolation, 15% fractional bandwidth (-10 dB isolation) and almost lossless operation - are obtained. The metamaterial slab is inserted halfway between the adjacent E-coupled elements in the microstrip array to suppress mutual coupling. A strong mutual-coupling suppression of -16.8 dB was exhibited experimentally in a two-element microstrip array with an element spacing of three-quarters of the operating wavelength. Theoretical and numerical studies were done to improve the performance of microstrip phased arrays using the proposed metamaterial slab. The analysis indicated that the scan blindness in an infinite phased array is well eliminated, the wide-angle impedance matching is remarkably improved, and the scanning range is extended from [-13°, 13°] to [-28°, 28°]. A 7×3 microstrip array was simulated to study the influence of the metamaterial slab on the array's performance. The results indicated that the metamaterial slab can also enhance the radiation characteristics, extend the scanning range and suppressing grating lobes in microstrip phased arrays.
TL;DR: In this paper, the authors demonstrate a nonlinear metamaterial that can be switched between low and high transmission by controlling the power level of the incident beam, and show that with moderate RF power of about 22 dBm it is possible to quench the superconducting state as a result of extremely strong current densities at the corners of the split-ring resonators.
Abstract: We demonstrate a nonlinear metamaterial that can be switched between low and high transmission by controlling the power level of the incident beam. The origin of this nonlinear response is the superconducting Nb thin film employed in the metamaterial structure. We show that with moderate RF power of about 22 dBm it is possible to quench the superconducting state as a result of extremely strong current densities at the corners of the metamaterial's split-ring resonators. We measure a transmission contrast of 10 dB and a change in group delay of 70 ns between the low and high power states.
Patent•
30 Nov 2011
TL;DR: In this article, a wave-absorbing metamaterial is proposed, where a plurality of periodically arranged artificial metal microstructures are attached on at least one of the two opposite lateral surfaces.
Abstract: The present invention relates to a wave-absorbing metamaterial, comprising a substrate which is provided with two opposite lateral surfaces, wherein a plurality of periodically arranged artificial metal microstructures are attached on at least one of the two opposite lateral surfaces; when an electromagnetic wave having an incident direction vertical to the two opposite lateral surfaces of the substrate is transmitted to the wave-absorbing metamaterial, a relative permittivity of the metamaterial is substantially equal to a relative magnetic conductivity of the metamaterial. A wave-absorbing principle different from that of a conventional wave-absorbing material is employed on the wave-absorbing metamaterial; an ideal wave-absorbing effect is achieved by periodically arranging various artificial metal microstructures on the substrate and adjusting the artificial metal microstructures; and the wave-absorbing metamaterial has the advantages of minor weight, small thickness and simply adjustable electromagnetic parameters.
TL;DR: In this paper, a metamaterial spiral antenna is proposed to radiate a dual circularly polarized (CP) wave and a right-handed CP wave in a specific direction (single CP radiation).
Abstract: Conventional spiral antennas radiate either a left-handed circularly polarized (CP) wave or a right-handed CP wave in a specific direction (single CP radiation). This letter presents a novel spiral antenna, designated as the metamaterial spiral, which radiates a dual CP wave. First, the principle for left-handed CP radiation and right-handed CP radiation is explained using “current bands.” Second, based on this principle, a prediction for dual CP radiation is made for a spiral structure. Third, for confirming this prediction, spiral arms are constructed using numerous straight filaments, each having a left-handed property with an inherent right-handed property. Numerical simulation confirms the predicted dual CP radiation. The gain and radiation pattern are discussed.
Proceedings Article•
11 Apr 2011Abstract: In this paper, wireless power transfer based on resonant coupling with metamaterials is studied. We show with numerical studies that the coupling between transmitter and receiver can be enhanced, and the power transfer efficiency can be improved by metamaterials. A prototype wireless power transfer system and a metamaterial is designed and built. Experiment results prove the efficiency improvement with the fabricated metamaterial. The system with metamaterial is capable of transferring power wirelessly at roughly double the efficiency of the same system without a metamaterial.
TL;DR: In this paper, the authors analyzed the strain-dependent effective medium properties for a metamaterial electric-LC (ELC) resonator, commonly used in metammaterial designs to provide a tailored electric response to electromagnetic waves.
Abstract: In this paper, we analytically describe the strain-dependent effective medium properties for a metamaterial electric-LC (ELC) resonator, commonly used in metamaterial designs to provide a tailored electric response to electromagnetic waves. Combining an equivalent circuit model of the ELC resonator with existing analytic expressions for the capacitive and inductive regions comprising the structure, we obtain strain-dependent permittivity and permeability curves for the metamaterial. The derived expressions account for the effects of spatial dispersion and losses.
TL;DR: In this article, a single-feed dual-band dual-mode and dual-polarized microstrip antenna based on metamaterial structure is proposed, where the composite right/left-handed transmission line (CRLH TL) theory is used to design this antenna.
Abstract: A novel single-feed dual-band dual-mode and dual-polarized microstrip antenna based on metamaterial structure is proposed. The composite right/left-handed transmission line (CRLH TL) theory is used to design this antenna. Dual-mode can be obtained by exciting the antenna with a monopolar radiation in the n = 0 mode and a patch-like radiation pattern in the n = +1 mode, respectively. As the geometry of the radiating patch does not affect the infinite wavelength mode, circular polarization (CP) is obtained for the n = +1 mode by truncating the square radiating patch with the n = 0 mode, linear polarization (LP) staying unchangeable. Results of a fabricated one illustrate that this antenna is valuable in practical application for its low-profile, easy fabrication, radiation pattern selectivity and polarized diversity.