Showing papers on "Metamaterial antenna published in 2014"

Metamaterial-Based Low-Profile Broadband Mushroom Antenna

Abstract: A metamaterial-based broadband low-profile mushroom antenna is presented. The proposed antenna is formed using an array of mushroom cells and a ground plane, and fed by a microstrip line through a slot cut onto the ground plane. With the feeding slot right underneath the center gap between the mushroom cells, the dual resonance modes are excited simultaneously for the radiation at boresight. A transmission-line model integrated with the dispersion relation of a composite right/left-handed mushroom structure is applied to analyze the modes. The proposed dielectric-filled (er=3.38) mushroom antenna with a low profile of 0.06λ0 ( λ0 is the operating wavelength in free space) and a ground plane of 1.10λ0×1.10λ0 attains 25% measured bandwidth with(|S11| <; - 10dB) 9.9-dBi average gain at 5-GHz band. Across the bandwidth, the antenna efficiency is greater than 76%, and cross-polarization levels are less than -20 dB.

Wireless Power Transfer Using Metamaterial Bonded Microstrip Antenna for Smart Grid WSN

Abstract: Wireless Power Transfer (WPT) system is a suitable alternative for power transmission where conventional wired power transfer faces geographical challenges. In a long range wireless power transmission system, power is transmitted through microwaves. A highly directive antenna is required for an effective transmission through this system. This paper talk about a circularly polarized microstrip rectangular patch antenna incorporated with a metamaterial slab. Use of microstrip antennas will considerably reduce the size of WPT system in comparison to other microwave antenna. In this paper the modeling and analysis of the wireless power transmission system is done on 2.45 GHz frequency and using GaAs Schottky barrier diode for the rectification of microwave power to DC power at the receiver end. Antenna assigned with metamaterial proposed in paper will enhance the amount of transferred power to wireless sensors network with less radiation loss.

Flat Luneburg Lens via Transformation Optics for Directive Antenna Applications

Abstract: The great flexibility offered by transformation optics for controlling electromagnetic radiation by virtually re-shaping the electromagnetic space has inspired a myriad of dream-tailored electromagnetic devices. Here we show a 3D-transformed microwave Luneburg lens antenna which demonstrates high directivity, low side-lobe level, broadband response and steerable capabilities. A conventional Luneburg lens is redesigned accounting for dielectric materials that implement a coordinate transformation, modifying the lens geometry to accommodate its size and shape for easy integration with planar microwave antenna applications. An all dielectric lens is manufactured following a thorough holistic analysis of ceramic materials with different volume fractions of bi-modal distributed titanate fillers. Fabrication and measurements of a 3-D flat Luneburg lens antenna validate the design and confirm a high-directivity performance. A directivity of 17.96 dBi, low side-lobe levels for both main planes ~ -26 dB, excellent directivity performance within the X-band and beam-steering up to 34 ° were achieved.

Scalable RF Energy Harvesting

Abstract: This paper discusses harvesting of low-power density incident plane waves for electronic devices in environments where it is difficult or impossible to change batteries and where the exact locations of the energy sources are not known. As the incident power densities vary over time and space, distributed arrays of antennas with optimized power-management circuits are introduced to increase harvested power and efficiency. Scaling in array size, power, dc load, frequency, and gain is discussed through three example arrays: a dual industrial-scientific-medical band Yagi-Uda array with a low-power startup circuit; a narrowband 1.96-GHz dual-polarized patch rectenna array with a reconfigurable dc output network designed for harvesting base-station power; and a broadband dual-polarized 2-18-GHz array with multi-tone performance. The efficiency of rectification and power management is investigated for incident power densities in the 1-100-μW/cm2 range.

Experimental investigation of compact metamaterial for high efficiency mid-range wireless power transfer applications

Abstract: We investigate a compact metamaterial for enhanced magnetic coupling in a resonator coupled wireless power transfer system operating at around 6.5 MHz. The metamaterial is constructed by realizing an array of three-turn spiral resonators on a thin slab. Although the metamaterial has its own loss, the experimental results show that the proposed metamaterial slab enhances the power transmission capability. The number of unit cells in the array is an important parameter, because exceeding a certain number of unit cells does not enhance the efficiency due to the loss of the slab. Furthermore, strong surface mode resonance is observed when two slabs are assembled with proper gap spacing between them. By using the optimization approach, we achieve a significant efficiency improvement at a mid-range distance. The measured efficiencies are 71.1% and 54.3% at a 0.6 and 1.0 m distance, respectively. At a 1.0 m distance, this efficiency performance corresponds to a 270% improvement compared to a case with no metamaterial slab. In addition, we experimentally confirm the threshold distances above which the metamaterial shows enhanced performance.

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

Abstract: 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.

Plasmonic planar antenna for wideband and efficient linear polarization conversion

Abstract: In this Letter, we demonstrate both theoretically and experimentally that plasmonic planar L-shaped antenna can nearly totally convert the linear polarization of light with a high efficiency in the infrared (3–5 μm). The nanoantenna geometry is engineered so that the polarization conversion occurred on a 1 μm-wide band ([3.25–4.25] μm) with a mean polarization conversion ratio of 95%. We show that this effect is due to two localized resonances in the L-shaped antenna, which wavelengths are tunable with the in-plane geometry of the nanoantenna. Eventually, the angular independence of the polarization conversion effect is evidenced.

Tunable terahertz left-handed metamaterial based on multi-layer graphene-dielectric composite

Abstract: A terahertz fishnet metamaterial, consisting of a gallium arsenide substrate sandwiched between multi-layer graphene-dielectric composites, is theoretically studied. Detailed analysis shows that this metamaterial has a left-handed transmission peak accompanied with an abnormal phase dispersion and a clear negative refractive index which originates from simultaneous magnetic and electric resonances. Our structure is unique because it has no metallic parts to achieve the left-handed properties. The most important utility of this metamaterial comes from the fact that its left-handed features can be dynamically controlled by applying external bias to shift the Fermi level in graphene.

Multi-Band Miniaturized Antenna Loaded by ZOR and CSRR Metamaterial Structures With Monopolar Radiation Pattern

Abstract: Miniaturized low-profile monopole antennas loaded by metamaterial (MTM) structures are presented. The antenna is loaded by zeroth-order resonator (ZOR) and complimentary split-ring resonator (CSSR) units, resonating over three frequency bands so that they can be tuned by changing the geometrical parameters of the MTM structures. Surface current distribution and equivalent circuit models are provided to describe the principle of operation. The experimental results are presented to validate the numerical results. Showing the monopole-shape radiation pattern characteristics at all resonant frequencies, the proposed MTM antennas are suitable for vehicular wireless applications.

60-GHz Thin Broadband High-Gain LTCC Metamaterial-Mushroom Antenna Array

Abstract: A low-profile broadband metamaterial-mushroom antenna array is proposed for high-gain 60-GHz band applications. The antenna array consists of a single-layer mushroom radiating structure and a simplified single-layer substrate integrated waveguide (SIW) feeding network. A new transmission-line based model is presented to estimate the resonant frequencies of the operating TM10 and antiphase TM20 modes. With the metamaterial-mushroom structure, the closely-placed antenna elements realize less mutual couplings, higher aperture illumination efficiency compared to conventional patch antennas. An 8 × 8 mushroom antenna array is designed and prototyped using low-temperature cofired ceramic (LTCC), the measurement shows the antenna array with the feeding transition proposed an impedance bandwidth of 56.3-65.7 GHz with a boresight gain greater than 21.2 dBi and up to 24.2 dBi at 62.3 GHz. The proposed antenna array features the merits of high gain, broadband, compact size, and low cross-polarization levels.

Beam Tilting Antenna Using Integrated Metamaterial Loading

Abstract: This communication presents a technique to re-direct the radiation beam from a planar antenna in a specific direction with the inclusion of metamaterial loading. The beam-tilting approach described here uses the phenomenon based on phase change resulting from an EM wave entering a medium of different refractive index. The metamaterial H-shaped unit-cell structure is configured to provide a high refractive index which was used to implement beam tilting in a bow-tie antenna. The fabricated unit-cell was first characterized by measuring its S-parameters. Hence, a two dimensional array was constructed using the proposed unit-cell to create a region of high refractive index which was implemented in the vicinity bow-tie structure to realize beam-tilting. The simulation and experimental results show that the main beam of the antenna in the E-plane is tilted by 17 degrees with respect to the end-fire direction at 7.3, 7.5, and 7.7 GHz. Results also show unlike conventional beam-tilting antennas, no gain drop is observed when the beam is tilted; in fact there is a gain enhancement of 2.73 dB compared to the original bow-tie antenna at 7.5 GHz. The reflection-coeflicient of the antenna remains <; - 10 dB in the frequency range of operation.

An Octave-Bandwidth Half Maxwell Fish-Eye Lens Antenna Using Three-Dimensional Gradient-Index Fractal Metamaterials

Abstract: The design and performance of a novel octave-bandwidth highly-directive half Maxwell fish-eye (HMFE) lens antenna are presented in superextended C band. The three-dimensional (3D) HMFE lens is implemented by gradient-refractive-index (GRIN) metamaterials and launched by an omnidirectional planar microstrip trapezoid printed monopole from the perspective of high integration, light weight and low profile. A new approach is proposed to design the GRIN metamaterial element in terms of a deep subwavelength feature by incorporating fractal geometry. Numerical and experimental results coincide well, showing that the lens enables a considerable gain enhancement of the monopole near 10 dB across a frequency range of 3 to 7.5 GHz while without significantly affecting the cross-polarization patterns and impedance matching. The near-field free-space measurement is also performed in an octave to afford a physical insight into the high gain, which is attributable to the accurate conversion of quasi-spherical waves to plane waves. Moreover, the truncation and homogenization effects of the lens on the antenna directivity are investigated to illustrate the fundamental mechanisms and afford the design guidelines.

A Dual Circularly Polarized Horn Antenna in Ku-Band Based on Chiral Metamaterial

Abstract: A dual circularly polarized horn antenna, which employs a chiral metamaterial composed of two-layered periodic metallic arc structure, is presented. The whole antenna composite has functions of polarization transformation and band-pass filter. The designed antenna produces left-handed circularly polarized wave in the band from 12.4 GHz to 12.5 GHz, and realizes right-handed circularly polarized wave in the range of 14.2 GHz-14.4 GHz. Due to low loss characteristic of the chiral metamaterial, the measured gains are only reduced by about 0.6 dB at the above two operation frequencies, compared with single horn antenna. The axial ratios are 1.05 dB at 12.45 GHz and 0.95 dB at14.35 GHz.

Circular polarization converters based on bi-layered asymmetrical split ring metamaterials

Abstract: In this paper, a kind of bi-layered asymmetrical split ring metamaterial was proposed as a circular polarization converter. Simulations and experiments at the microwave regime showed that the proposed structures can achieve the conversions from right-handed circularly polarized electromagnetic waves to left-handed ones and the reversed conversions in the opposite propagating direction. The linear to circular polarization transmission coefficients and the surface currents were investigated to understand the mechanism of the circular polarization conversions. Moreover, we optimized the proposed metamaterials by increasing the distance between the two metal layers. The proposed circular polarization converters have applications in microwave wave plates and metamaterial antennas.

Optically Controlled Frequency-Reconfigurable Microstrip Antenna With Low Photoconductivity

Abstract: In this letter, novel designs for optically switching the resonant frequency of a microstrip patch antenna via photoconductive switches are proposed, and design considerations for maximizing frequency switching ratio with finite photo-conductance are investigated. Furthermore, a configuration to switch the resonant frequency with low switch conductance is proposed for cheap and easy fabrication of a frequency-reconfigurable antenna that can be operated with low optical power. Experimental verification of the low-power configuration is presented.

Miniaturization of 3-D Anistropic Zero-Refractive-Index Metamaterials With Application to Directive Emissions

Abstract: Several strategies are explored for the first time toward the miniaturization of three-dimensional (3-D) anistropic zero-refractive-index metamaterials (AZIM). By incorporating the fractal, spiral, and meandered resonant metallic inclusions within a host dielectric medium, several AZIM elements are engineered in subwavelength at the plasma frequency. The influences of geometrical shape, arrangement, and dimensions of inclusions on electromagnetic features of the 3-D elements are also investigated to obtain the design guideline. In this frame, we have designed a set of AZIM elements with near-zero permittivity and near-zero permeability occurring at the same frequency. To demonstrate potential applications, a lens horn antenna by loading the 3-D AZIM lens has been designed, fabricated, and measured. Numerical and experimental results agree well and illustrate that the beamwidth of the E-plane pattern has reduced about 4.9 $^{\circ}$ while that of the H plane has reduced about 6.7 $^{\circ}$ . Moreover, the gain of the lens horn antenna has improved 1.6 dB relative to its conventional counterpart with identical aperture. The proposed avenue in 3-D AZIM design advances a step toward the compactness and homogenization.

Design and implementation of microstrip patch antenna array

Abstract: This paper refers to a detailed analysis on the design and implementation of 4×1 and 8×1 microstrip patch antenna (array) of given specifications using IE3D software and a dielectric material FR4 with dielectric substrate permittivity of 4.28, tangent loss of 0.002 and height of 1.6 mm. The microstrip patch antenna array is designed for WLAN applications, at an operating frequency of 2.4 GHz with microstrip line feed and power dividers.

Near-Zero-Index Metamaterial Lens Combined With AMC Metasurface for High-Directivity Low-Profile Antennas

Abstract: A high-gain reduced-profile antenna is designed by combining the effects of a near-zero-index volumetric metamaterial lens and an artificial magnetic conducting (AMC) ground plane. The AMC/metalens antenna design presented here has 20% reduced height over an equivalent metalens antenna with conventional metallic ground plane at the cost of reduced peak directivity and pattern bandwidth. Both the metamaterial unit cells and the mushroom-type AMC structure are designed independently and retuned in the presence of the other for optimal performance. The lens collimates the electromagnetic radiation of a dipole feed by refraction as well as via a Fabry-Perot cavity effect, with resulting gain and patterns that are better than either mechanism can achieve individually. Full wave simulations of the entire metamaterial and AMC structure with a feed dipole agree well with measurements of the fabricated design.

Metamaterial-based UWB antenna

Abstract: A metamaterial-based novel compact microstrip antenna is presented for ultra-wideband (UWB) applications. The antenna consists of two layers of metamaterials made by etching a π-shaped slot and crossed-shaped slots, on the radiating patch and the ground plane, respectively. The series capacitance and shunt inductance developed due to the patterned radiating patch and ground plane lead to the left-handed behaviour of the metamaterial. The proposed antenna has a compact size of 30.8 × 27.6 × 0.8 mm3 and is fed by a 50 Ω microstrip line. The impedance bandwidth (−10 dB) is from 3 GHz to more than 14 GHz with maximum radiation in the horizontal plane and tends towards a directional pattern as the frequency increases.

Dual-mode behavior of the complementary electric-LC resonators loaded on transmission line: Analysis and applications

Abstract: This article presents an analysis of metamaterial resonators coupled with microstrip transmission line. The behavior of complementary electric-LC resonators loaded on a microstrip line is analyzed using the equivalent circuit model. In this paper, it is shown that a special type of these resonators show a dual-mode behavior when excited through the electromagnetic field around the microstrip transmission lines. The bandstop and bandpass configurations of these dual mode resonators loaded with microstrip lines are introduced and analyzed. Their potential applications are highlighted through designing a displacement sensor and a dual-mode bandpass filter prototypes.

Discrete-dipole approximation model for control and optimization of a holographic metamaterial antenna.

Abstract: Since the discovery of materials with negative refractive index, widely known as metamaterials, it has been possible to develop new devices that utilize a metamaterial's ability to control the path of electromagnetic energy Of particular promise, and already under intensive development for commercial applications, are metamaterial antennas for satellite communications Using reconfigurable metamaterials in conjunction with the principles of holography, these new antennas can electronically steer the high gain antenna beam required for broadband communications while not having any moving parts, being thinner, lighter weight, and less expensive, and requiring less power to operate than conventional alternatives Yet, the promise of these devices will not be realized without efficient and effective control and optimization Toward this end, in this paper a discrete-dipole approximation (DDA) model of a waveguide-fed planar metamaterial antenna is derived The proposed model is demonstrated to accurately predict the radiation of a two-dimensional metamaterial at a much reduced computational cost to full-wave simulation and at much greater fidelity than simpler models typically used in the field The predictive capabilities of the derived DDA model opens possibilities for model-based control design for optimal beam steering

A Low-Profile High-Gain Substrate-Integrated Waveguide Slot Antenna Enabled by an Ultrathin Anisotropic Zero-Index Metamaterial Coating

Abstract: A low-profile high-gain unidirectional antenna is proposed and demonstrated using both metamaterial (MM) and substrate-integrated waveguide (SIW) technologies. First, the leaky modes supported by a grounded anisotropic slab are studied. These investigations reveal that a grounded slab consisting of an anisotropic zero/low index material can provide an extremely low value for the real part of the propagation constant of the leaky mode, thereby facilitating stable unidirectional broadside radiation over a wide frequency range. The truncation effect of the slab is then investigated through full-wave simulations, which is found to be beneficial for a practical implementation of dispersive metamaterials. Finally, to validate the proposed concept, a subwavelength end-loaded dipole array is designed to realize the required anisotropic zero-index property and is applied to a SIW fed longitudinal slot antenna for the 5.8 GHz wireless local area network (WLAN) band. Measurements of the fabricated antenna prototype are shown to be in strong agreement with simulation results, thus confirming the proposed antenna design. The resulting antenna is only 0.12 λ thick, all while accomplishing a broadside gain of more than 10 dBi and a front-to-back ratio larger than 26 dB, which is ~ 7 dB and ~ 10 dB higher than that of the SIW fed slot alone, respectively. The -10 dB impedance bandwidth is more than 9% both with and without the presence of the MM coating. The proposed technique offers a means for realizing low-cost and low-profile unidirectional antennas with moderate bandwidth.

Sidelobe Canceling for Optimization of Reconfigurable Holographic Metamaterial Antenna

Abstract: Accurate and efficient methods for beam-steering of holographic metamaterial antennas is of critical importance for enabling consumer usage of satellite data capacities. We develop an optimization algorithm capable of performing adaptive, real-time control of antenna patterns while operating in dynamic environments. Our method provides a first analysis of the antenna pattern optimization problem in the context of metamaterials and for the purpose of directing the central beam and significantly suppressing sidelobe levels. The efficacy of the algorithm is demonstrated both on a computational model of the antenna and experimentally. Due to their exceptional portability, low-power consumption and lack of moving parts, metamaterial antennas are an attractive and viable technology when combined with proven software engineering strategies to optimize performance.

A 2-D Multibeam Half Maxwell Fish-Eye Lens Antenna Using High Impedance Surfaces

Abstract: This letter describes the design and measurement of a planar multibeam half Maxwell fish-eye (HMFE) lens antenna with seven beams in azimuth based on variable high impedance surfaces (HISs). The desired refractive index profile is controlled by using slotted square mushroom metallic cells of different sizes on a grounded dielectric slab. The lens antenna, 6.2λ×3.1λ in lens plane and 0.65 λ total height, is fabricated and characterized in TM mode at 13 GHz for both single- and multiple-beam configurations. The optimized lens for single-beam operation achieves 14.1 dBi measured gain, 67 ° and 12 ° half-power beamwidth for E-plane and H-plane, respectively, and 55.3% impedance bandwidth for -10-dB return loss. This lens can be used to launch multiple beams by implementing an arc array of seven-element short monopoles at the periphery of the lens. The measured overall scan coverage is up to 45 ° with gain drop less than 2.4 dB. Its low profile, light weight (only 136 g), and ease of manufacturing makes it well suited for Local Multipoint Communication Systems (LMCS).

Ultra-fast selective sensing of ethanol and petrol using microwave-range metamaterial complementary split-ring resonators

Abstract: An extremely compact metamaterial microstrip sensor based on complementary split-ring-resonators (CSRRs) has been fabricated for chemical sensing. This device exhibits a resonance with high rejection at 4.5 GHz, which demonstrates concomitant variations when exposed to liquids of various permittivity values. The resonance frequency of CSRR is sensitive to the change in nearby dielectric material. The sensing of petrol shows a shift in frequency with a sharp dip in transmission, while, with ethanol, the frequency shift is accompanied with increase in the power of the signal. The ultra-fast reversibility and repeatability offers good headway towards hybrid fuel sensing applications.

Mechanical 144 GHz beam steering with all-metallic epsilon-near-zero lens antenna

Abstract: An all-metallic steerable beam antenna composed of an e-near-zero (ENZ) metamaterial lens is experimentally demonstrated at 144 GHz (λ0 = 2.083 mm). The ENZ lens is realized by an array of narrow hollow rectangular waveguides working just near and above the cut-off of the TE10 mode. The lens focal arc on the xz-plane is initially estimated analytically as well as numerically and compared with experimental results demonstrating good agreement. Next, a flange-ended WR-6.5 waveguide is placed along the lens focal arc to evaluate the ENZ-lens antenna steerability. A gain scan loss below 3 dB is achieved for angles up to ±15°.

Compact Fractal Left-Handed Structures for Improved Cross-Polarization Radiation Pattern

Abstract: A set of two-dimensional (2-D) left handed (LH) transmission line (TL) structures are proposed based on the single-layered and double-layered fractal-perturbed mushrooms. The effects of the Koch Island on the LH characteristics have been investigated physically by examining the dispersion diagram of the LH structure with and without fractal perturbations, showing that the parasitic transverse electric mode has been considerably suppressed without any deteriorative penalty on the dominant transverse magnetic mode. Therefore, the interaction of the degenerated parasitic mode with the operation modes has been considerably weakened. The concept has been employed to suppress the cross-polarization (XP) radiation of a microstrip antenna which incorporates a 2 × 2 array of the LH structure into a conventional microstrip patch. Numerical and experimental results indicate that the XP radiation (<; -30dB) has been notably reduced at three working frequencies (f-1 = 1.5, f0 = 2.96 and f+1 = 3.7 GHz) while the antenna performances such as gain, co-polarization radiation and impedance matching are without any deterioration.

Printed planar patch antennas based on metamaterial

Abstract: The article presents implementation of two antennas based on metamaterial (MTM) technology, standard printed planar patch manufacturing techniques and applying the proper capacitive and inductive c...

Optical antenna enhanced graphene photodetector

Abstract: We report on the integration of an individual, metal-based, plasmonic nano-antenna on a graphene photodetector. The device exhibits an electromagnetic resonance at a wavelength of 580 nm with well-defined polarization sensitivity. With no applied bias voltage, this antenna-coupled graphene photodetector features a responsivity of ∼17 nA/μW, which is four orders of magnitude higher than previously studied single antenna enhanced detectors. Finally, we measure a signal-to-noise ratio of ∼200 in a 1-Hz bandwidth, with an average photocurrent value of 1.2 nA.

Enhanced Modelling of Split-Ring Resonators Couplings in Printed Circuits

Abstract: An enhanced equivalent circuit approach for the magnetic/electric interaction of single split-ring resonators (SRRs) with printed lines is presented in this paper. A very simple and efficient lumped-element network is proposed to model the behavior of metamaterial-based printed lines over a wide frequency band. The same circuit topology can be used for the single- and two-mirrored SRRs loaded microstrip line. The corresponding circuit parameters are obtained from the multiconductor transmission line theory as well as from closed-form expressions that make use of just the resonance frequency and minimum of the reflection coefficient (which should be previously extracted from experiments or full-wave simulations). The comparison of our equivalent circuit results with measurements and full-wave simulations has shown a very good agreement in a considerably wider frequency band than other previously proposed simple equivalent circuits.