Metamaterial Cover Research Articles

Broadband omnidirectional patch antenna with horizontal gain enhanced by near‐zero‐index metamaterial cover

Enhancing the horizontal gain of the omnidirectional patch antenna is always a problem with great difficulty. Inspired by near-zero-index metamaterial (NZIM) cover that can improve the vertical gain of a directional patch antenna, the authors designed two kinds of NZIMs that are placed above the broadband omnidirectional antenna to enhance the horizontal gain. Simulated and measured results indicate that both covers can increase the values of horizontal gain >50% (1 dBi) at various frequencies in all directions, which provides a new approach to improve the horizontal gain of the broadband omnidirectional patch antenna.

High‐gain antipodal Vivaldi antenna with metamaterial covers

A metamaterial slab covered antipodal Vivaldi antenna (MSAVA) is proposed to improve the radiation properties of the antipodal Vivaldi antenna (AVA). The metamaterial covers (MCs) consist of two types of metal rectangular ring arrays that have a higher effective permittivity than the substrate. The MCs can achieve a guiding effect and direct electromagnetic waves radiated from the side of AVA to the end-fire direction. The original AVA and the proposed MSAVA are simulated, fabricated and measured. The results show that of the two antennas is less than −10 dB in the frequency band of 0.95–11 GHz. Due to the introduction of MCs, MSAVA obtains a much narrower H-plane's half-power beamwidth, and the E-plane's is narrowed as well. The radiation gain is also improved in the frequency band. Moreover, the maximum gain of the proposed MSAVA is 17.67 dBi. Compared with the original AVA, the maximum gain is enhanced by 6.86 dB for the proposed MSAVA. The presented MSAVA featuring broad bandwidth, high gain and narrow beam has a high potential in ground penetrating radar, microwave imaging application and other broadband wireless systems.

Design and Investigation of Circularly Polarized RMPA with Chiral Metamaterial Cover

In this paper, a simple method for designing a circular polarized antenna using chiral metamaterial is presented. The antenna proposed in this paper consists of conventional linear polarized Rectangular Microstrip Patch Antenna (RMPA) and cover of bilayer twisted cross wire Chiral Metamaterial (CM). The placement of CM cover over the linearly polarized RMPA changes its polarization from linear to circular and the antenna produces a left handed circularly polarized wave at resonant frequency of 6.24GHz with axial ratio of 0.46 dB. Investigation of performance parameter of proposed antenna and parameters of unit cell of CM is also presented in the paper. Index Terms: Chiral Metamaterial (CM), Left hand Circularly Polarized(LCP), Right hand Circular Polarized(RCP), Rectangular Microstrip Patch antenna(RMPA),linear polarization(LP), circular polarization(CP)

Nonresonant and resonant cloaking of an electrically large dielectric spherical object by a multilayer isotropic metamaterial cover.

Mie theory and genetic algorithms are used to determine the parameters and performance of cloaks made of homogeneous isotropic metamaterials that would hide a spherical dielectric object of size comparable to the incident radiation wavelength. A single-layer (SL) cover with negative permittivity and permeability can produce a much greater reduction in the extinction efficiency than one with the permittivity and permeability of positive or opposite signs. Minimization of the extinction efficiency in the former case leads to both nonresonant and resonant solutions. Adding a second layer to the cover can lead to a significant enhancement of the bandwidth, but only to a modest reduction in the extinction efficiency at the design wavelength. In the SL case, Debye's scattering series is used to show that the nonresonant and resonant minima of the extinction efficiency correspond to scattering phase shifts approximately equal to zero and -π, respectively, and to understand the simple approximate expressions for the cloak parameters of the nonresonant solutions. The series also explains the value of the outer radius of a multilayer cloak, provides a link to a previously studied isotropic approximation to a transformation optics cloak, and indicates that a cloak consisting of an odd number of alternate double-negative and double-positive layers will probably give the best possible performance.

Analyzing the performance of a microstrip patch antenna with metamaterial cover by varying the distance and dielectric constant in between

A metamaterial slab applied as cover in front of a patch antenna focuses the radiations from patch, reduces the beam-width, thus enhancing the Gain and Directivity. Usually the slab is placed at quarter wave distance from the patch; this paper focuses on investigating the effects of varying this distance. Also, if a dielectric is placed in between metamaterial cover and patch antenna, the effects of changing the value of dielectric constant are presented in this paper. The metamaterial under consideration is a modification of Pendry’s SRR structure, its unit cell is formed by connecting metallic traces of two-edge-coupled split ring resonators to form the infinity symbol on one side of the substrate and an array of conducting wires on the other. The unit cells were arranged to form an array and an investigation of S-parameters was done to check the negative index property. A conventional patch antenna generally shows 3 dB beam-width of ~80° and 5–6 dB gain, whereas the antenna presented in this paper with the metamaterial cover shows improved 3 dB beam-width of ~53° with gain more than 9 dB.

Directivity enhancement of miniaturized microstrip patch antenna using metamaterial cover

The variation in the spacing height of a metamaterial cover over the slotted patch antenna is reported to improve its directivity. HFSS software is used for simulations. An antenna is designed with a metamaterial cover to work in three bands within the frequency range of 1-4 GHz. A comparative result analysis of the effect of varying the spatial height of the metamaterial cover over patch antenna is shown theoretically. The proposed novel slotted patch antenna design has triband operation in the frequency range of 1-4 GHz with the miniaturized overall antenna size of the dimension 52.5 mm × 36.5 mm × 1.56 mm, that is equivalent to miniaturized design reported to our knowledge so far. For the very first time, the concept of Newton's divided difference method is applied for evaluating the performance parameters of the antenna. A global formula is developed to indicate the relationship of the directivity with the spatial height. The designed model has various applications in the field of satellite, aeronautical and optical communications mainly in the frequency range of L and S band.

Enhancement Various Parameters of Rectangular Microstrip Patch Antenna with Metamaterial

The antenna along with the proposed Meta material structure designed to Resonate at 8.0GHz frequency. But the proposed Meta material cover significantly reduces the return loss and increases the bandwidth, and gain of the antenna in comparison to rectangular micro strip patch antenna. The Metamaterial substrate has a potential to reduce the circuit size of the antenna as well as maintain the amplitude of the return loss at the specific resonant frequency. The most attractive feature of the substrate is the ability of enhancing the bandwidth of a patch antenna at 8.0GHz frequency. The system is firstly modelled by Computer Simulation Technology Software (CST-2010). With the help of CST-2010, The return loss, directivity, & radiation pattern of compact rectangular Patch Antenna operating at 8.0 GHz frequency and rectangular Patch Antenna along with designed Meta material shape have been evaluated in this work.

Controlling Scattering and Absorption With Metamaterial Covers

We discuss the use of metasurfaces and plasmonic metamaterials to minimize the scattering from receiving antennas and sensors, with the goal of maximizing their absorption efficiency. We first analytically study and highlight the potential of these approaches to realize optimized sensors with the desired level of efficiency, being able to minimize the electrical presence of a receiving antenna for a chosen level of overall absorption. Realistic cloak designs, investigated using full-wave simulations, verify the behavior analytically predicted by Mie theory. These optimized cloaks offer a practical way to flexibly tailor the scattering of receiving antennas, with great benefits in the design and optimization of near-field sensors, remote communication systems, spoof targets and improved antenna blockage resiliency. Optimized covers may also provide other interesting features for the same receiving antenna by just tuning its resistive load, such as optimal wireless power harvesting or high-to-low tunable absorption efficiency.

Design of a Single Negative Metamaterial based Microstrip Patch Antenna

paper describes the design and simulation of the new Ɛ negative metamaterial unit cell structure and then the unit cells are combined to form 3D array which use as metamaterial cover with a single microstrip patch antenna. The new Ɛ negative metamaterial is based on the ELC resonator structure, which is used for obtaining the negative value of permittivity and positive value of permeability. Simulation result shows that the gain of the antenna has been increased with metamaterial cover up to 1.46db .This has to proven that metamaterial as a cover enhance the directive properties of conventional microstrip patch antenna. Keywordsial (MTM), Epsilon negative (ENG) metamaterial, Microstrip Antenna (MSA), Electric-LC (ELC) Resonator, HFSS.

An experimental verification of metamaterial coupled enhanced transmission for antenna applications

Inspired by the work of Bethe on electromagnetic transmission through subwavelength hole, there has been immense interest on the extraordinary transmission through subwavelength slot/slit on metal plates. The invention of metamaterials has boosted the extra ordinary transmission through subwavelength slots. We examine computationally and experimentally the concept of metamaterial cover using an array of split ring resonators (SRRs), for enhancing the transmission in a stacked dipole antenna working in the S band. The front to back ratio is considerably improved by enhancing the magnetic resonant strength in close proximity of the slit of the upper parasitic dipole. The effect of stacking height of the SRR monolayer on the resonant characteristics of the split ring resonators and its effect on antenna radiation characteristics has been studied.

메타구조 기반의 고효율 공진형 무선전력전송 시스템

메타구조 기반의 고효율 공진형 무선전력전송 시스템

Scattering reduction at near-infrared frequencies using plasmonic nanostructures

Novel fabrication, detection and analysis approaches were employed to experimentally demonstrate scattering reduction by a plasmonic nanostructure operating at 1550 nm. The nanostructure consisted of a silicon nanorod surrounded by a plasmonic metamaterial cover comprised of eight gold nanowires and was fabricated by a combination of electron beam lithography, focused ion beam milling and dry and wet etching. The optical standing wave pattern of the device in the near-field was obtained using heterodyne near-field scanning optical microscopy. It was found that the spatial curvature of the interference fringes of the optical standing wave pattern was directly related to the scattering reduction of the device. The experiments were in excellent agreement with the theoretical predictions and suggested that the device reduced the scattering by 9.5 dB when compared to a bare silicon nanorod of diameter 240 nm and by 6 dB when compared to a bare silicon nanorod of diameter 160 nm.

Amelioration of rectangular microstrip patch antenna characterstics by incorporating it with double-Negative left-handed inspired metamaterial in L-band

With the numerous increases in the use of microwave frequencies in communication applications, certain antenna potential characteristics should be an integral part of the design process. For example, GPS, WLAN are all applications that share common potential characteristics requirement in their antenna. A “FRAMED SQUARE RINGS” double negative inspired metamaterial structure was introduced as a cover to the rectangular microstrip patch antenna at a height of 3.2 mm from the ground plane, operating at 1.95 GHz. The results showed that the proposed metamaterial cover, effectively improves the patch antenna’s gain and bandwidth. The complex permittivity and permeability of the proposed structure has been extracted by Nicolson-Ross-Weir (NRW) approach. The outcomes of this work open the possibility to use the proposed structure as a miniaturized and flexible antenna in L-Band for wireless communication applications.

TRANSMISSION PHASE CHARACTERIZATIONS OF METAMATERIAL COVERS FOR ANTENNA APPLICATION

Metamaterial covers exhibit inimitable electromagnetic properties which make them popular in antenna engineering. A traditional metamaterial cover has an identical transmission phase for a normally incident plane wave regardless of its polarization state. The purpose of this research is to show the possibility of using a polarization dependent metamaterial cover to change the polarization state of the incident plane wave. Novel polarization- dependent metamaterial (PDMTM) covers, whose transmission phases for two principal polarizations are difierent, are presented. A full-wave FDTD numerical technique developed by the authors is adopted for the simulations.

PATTERN OPTIMIZATION IN AN UWB SPIRAL ARRAY ANTENNA

We have proposed a new architecture for an array in which the elements are placed on a spiral curve in order to obtain an ultra wideband (UWB) radiation pattern. In addition, array factor and bandwidth of the proposed spiral array are calculated. Simulated results obtained by SuperNEC and CST software have shown good agreement with the analytic calculations. Although the proposed antenna array is wideband in nature, it lacks desirable e-ciency, due to poor front to back ratio (FBR) and sidelobe level (SLL). In this paper, we have chosen three difierent approaches in order to improve the e-ciency of proposed array. First, the efiect of length and thickness tapering of elements has been studied. Second, we have used Genetic Algorithm (GA) to optimized pattern shape. Finally, the in∞uence of metamaterial cover on array performance has been investigated. Although the flrst and second methods improve the radiation pattern, the array bandwidth is reduced. It is shown that the third method improves array directivity and FBR by 5{7dB and 15{17dB respectively within the frequency band of operation.

Plasmonic materials in transparency and cloaking problems: mechanism, robustness, and physical insights

The possibility of making a given object transparent to the impinging radiation, or cloaking it, by employing a suitable metamaterial or plasmonic cover has been recently studied theoretically, showing how this technique may overcome the limitations of other currently available techniques. Here we discuss the underlying mechanisms, physical insights and some computer simulations on the role of such homogeneous isotropic metamaterial covers near their plasma frequency in order to dramatically reduce the fields scattered by a given object. Not requiring any absorptive process, any anisotropy or inhomogeneity, and any interference cancellation, in this contribution we demonstrate, using full-wave numerical simulations, how a homogeneous isotropic plasmonic material shell may basically "re-route" the impinging field in such a way to make dielectric and even conducting or metallic objects of a certain size nearly transparent to an outside observer placed in its near as well as in its far field. In addition, it is discussed in detail how this technique, relying on a non-resonant phenomenon, is fairly robust to relatively high variations of the shape and of the geometrical and electromagnetic properties of the cloaked object.

Improved patch antenna performance by using a metamaterial cover

A new patch antenna system with a metamaterial cover is presented in this paper. The impedance, radiation pattern, and directivity of such an antenna are studied. A performance comparison between the conventional patch antenna and the new metamaterial patch antenna is given. The results show that the directivity of the metamaterial patch antenna is significantly improved. The effect of the metamaterial cover’s layer numbers on the radiation pattern of the patch antenna is also studied.

A new patch antenna with metamaterial cover

A metamaterial was introduced into the cover of a patch antenna and its band structure was analyzed. The metamaterial cover with correct selection of the working frequency increases by 9.14 dB the patch antenna’s directivity. The mechanism of metamaterial cover is completely different from that of a photonic bandgap cover. The mechanism of the metamaterial cover, the number of the cover’s layers, and the distance between the layers, were analyzed in detail. The results showed that the metamaterial cover, which works like a lens, could effectively improve the patch antenna’s directivity. The physical reasons for the improvement are also given.