KR101435892B1 - elasitc electronic hybrid smart meta material and cloaking method using thereof - Google Patents

elasitc electronic hybrid smart meta material and cloaking method using thereof Download PDF

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KR101435892B1
KR101435892B1 KR1020130140786A KR20130140786A KR101435892B1 KR 101435892 B1 KR101435892 B1 KR 101435892B1 KR 1020130140786 A KR1020130140786 A KR 1020130140786A KR 20130140786 A KR20130140786 A KR 20130140786A KR 101435892 B1 KR101435892 B1 KR 101435892B1
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김경식
신동혁
알 스미스 데이비드
에이 우르주모브 야로슬라프
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연세대학교 산학협력단
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    • GPHYSICS
    • G01MEASURING; TESTING
    • G01SRADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/02Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00
    • G01S7/38Jamming means, e.g. producing false echoes
    • HELECTRICITY
    • H01BASIC ELECTRIC ELEMENTS
    • H01PWAVEGUIDES; RESONATORS, LINES, OR OTHER DEVICES OF THE WAVEGUIDE TYPE
    • H01P1/00Auxiliary devices
    • H01P1/08Dielectric windows
    • HELECTRICITY
    • H01BASIC ELECTRIC ELEMENTS
    • H01PWAVEGUIDES; RESONATORS, LINES, OR OTHER DEVICES OF THE WAVEGUIDE TYPE
    • H01P7/00Resonators of the waveguide type
    • H01P7/10Dielectric resonators

Abstract

According to an aspect of the present invention, provided is an elastic electronic hybrid smart meta material which includes a positive value of the Poisson′s ratio of a first structure and a second structure in the form of coupling the first structure and the second structure formed with air or free space between the array of dielectrics, wherein the dielectrics which can be elastically deformed are periodically arranged.

Description

TECHNICAL FIELD The present invention relates to an elastic electromagnetic hybrid meta material and a cloaking method using the same,

The present invention relates to a metamaterial, and more particularly, to an elastic electromagnetic hybrid smart meta material and a cloning method using the same.

Based on Maxwell 's equations being invariant at the time of coordinate transformation, transflective optics and optical conformal mapping have presented a new way to manipulate the progression of electromagnetic fields and waves. As a well-known application in this emerging design approach, transparent cloaks make objects of various shapes invisible. This is possible by applying coordinate transformation from the virtual space to the physical space so that the volume of the object to be hidden is zero.

In the case of an omnidirectional transparent cloak, the coordinates of the object to be hidden are compressed at one point, making it invisible in any direction. However, the properties of the material required by the conversion are dielectric constant and permeability values that are close to zero or too large values that are hard to exist in the physical medium. Since these extreme physical properties of metamaterials are difficult to fabricate, there are only a few cases of omni-directional transparent cloaks that have been experimentally implemented.

On the other hand, in the case of a carpet-type transparent cloak, it starts with the concept of compressing the object to be hidden with a plate of a very small thickness. Dimensions reduced by reduced dimensional transformations allow the transparent cloak to have only an appropriate range of permittivity, permeability, and refractive index. These devices have the advantage of reducing the range of required properties and are exhibited in a wide range of operating bandwidths.

Obtaining magnetic permeability without significant dispersion is very difficult. Certain coordinate transformations combined with the isometric limit approach (ignoring the impedance slope) eliminate the out-of-plane magnetic response, eliminating any self-reactivity. Using this, a two-dimensional (2D) A suitable device has been proposed. These approaches do not apply to vertical electrical-wave (TE) devices because they are devices by conversion optics that respond to in-plane magnetic reactions, which generally can not be eliminated at the Iconer limit. Fortunately, special transformations known as QCMs can minimize or eliminate in-plane magnetic permeability deviations from one. This is possible by minimizing the degree of anisotropy of the metric tensor of the transformation.

The carpet-type transparent cloak can be made entirely of dielectric materials as long as it can find the quadrature-angle transformation for a given boundary shape with a TE polarization conversion optic. The metamaterial of the artificial structure was used to preferentially satisfy the gradient distribution of the complex permittivity and permeability required in the transparent cloak and other conversion optical media, since the material properties that make up the considerable control can be widened even further.

The spatial distribution of the variables constituted in the previously proposed transparency strategy is derived from the assumption that the inner and outer boundaries of the transparent cloak are fixed because the shape to hide is determined. If there is a deviation in the shape of the hidden object, redesign of the metamaterial to be implemented along with the overall redesign of the transparent cloak is required. In addition, degradation of the translucent transparent cloak is generally caused by deformation of the outer boundary exposed to the surrounding medium such as air. In the case of the conventional metamaterial transparent cloak, a substantially unavoidable mechanical load, such as aerodynamic pressure at the outer boundary, could cause deformation beyond the resistance of the unit cell.

Figure 1 shows the basic concept of cloaking. 1 (a), when the reflective surface is flat, the same object as the incident object is reflected. However, if the reflective surface is deformed such as convex as shown in FIG. 1 (b), an object reflected by the incident surface is reflected on a convex reflective surface . However, when a cloaking device (a triangular device) is added as shown in Fig. 1 (c), the same object as the incident object appears to be reflected although the reflecting surface is actually convex.

2 shows a cloaking method using a conventional meta-material. When the cloaking device is installed on the basis of the basic concept shown in FIG. 1, conventionally, the silicon posts are arranged in a manner of arranging one by one as shown in FIG. That is, the cloaking can be realized by arranging the silicon posts around the convex degree of the reflection surface one by one at the correct position. Since the conventional transparent meta-material transparent cape has to be arranged one by one in accordance with the interface, it is difficult to mass-produce the transparent cape, and a problem that the function can not be performed even with minute deformation has occurred.

Accordingly, in the embodiment of the present invention, a new meta material capable of performing cloaking by the occurrence of deformation is newly defined as a 'smart meta material', and this is to be realized.

Korean Patent Publication No. 10-2013-0047860

Gabrielli, L. H., Cardenas, J., Poitras, C. B. & Lipson, M. Silicon nanostructure cloak operating at optical frequencies. Nature Photonics 3, 461-463 (2009)

Embodiments of the present invention provide an elastic electro-magnetic hybrid smart meta material that is automatically fitted to an object by elastic deformation, rather than being wrapped in a structure fixed to an object in a conventional manner, thereby changing an electromagnetic field to make an object invisible .

In addition, we want to make large area by uniform arrangement and same meta material elements.

According to an aspect of the present invention, there is provided a structure in which a dielectric material capable of elastic deformation is arranged, air or a free space is formed between the arrangements of the dielectrics, and the Poisson's ratio of the structure has a negative value, Or greater than the dielectric constant of the free space.

According to another aspect of the present invention, there is provided a structure in which a dielectric material capable of being elastically deformed is arranged, air or a free space is formed between the arrangements of the dielectric material, and the Poisson's ratio of the structure has a negative value, Or greater than the dielectric constant of the free space.

In addition, the dielectric may be a structure having a periodic arrangement of a dielectric material having elasticity and a unit volume consisting of ambient air or a free space.

Further, the dielectric may be a silicone rubber tube.

In addition, the dielectric may be characterized by changing the Jacobian of the individual unit volume by elastic deformation to change the effective dielectric constant of the dielectric.

The dielectric constant of the dielectric constituting the unit volume may be 2 or more.

In addition, the size of the unit volume of the dielectric may be less than 25% of the wavelength of the electromagnetic wave to be operated.

In addition, the silicone rubber tube may have a rectangular periodic arrangement with a period of 10 mm.

The second structure may have a triangular shape, and the base of the triangle may be coupled to the first structure, and the length of the base of the triangle of the second structure may be equal to the base length of the deformed shape.

According to another aspect of the present invention, there is provided a method of fabricating a plasma display panel in which a dielectric structure capable of being elastically deformed is periodically arranged, and a first structure and a second structure, in which air or a free space is formed between the arrangements of the dielectric, Wherein the first structure and the second structure have a positive value, wherein the second structure and one of the structures are contacted and compressed with the object to be cloaked, and the spatial density distribution of the dielectric And a cloaking method using an elastic electro-magnetic hybrid smart meta material that changes the effective refractive index so as to follow the quadratic mapping, thereby cloaking the object.

In addition, the dielectric may be a structure having a periodic arrangement of a dielectric material having elasticity and a unit volume consisting of ambient air or a free space.

Further, the dielectric may be a silicone rubber tube.

In addition, the dielectric may be characterized by changing the Jacobian of the individual unit volume by elastic deformation to change the effective dielectric constant of the dielectric.

The dielectric constant of the dielectric constituting the unit volume may be 2 or more.

In addition, the size of the unit volume of the dielectric may be less than 25% of the wavelength of the electromagnetic wave to be operated.

In addition, the period of the unit volume may be a square or a hexagonal array that is within 25% of the wavelength of the operating electromagnetic wave.

The second structure may have a triangular shape, and the base of the triangle may be coupled to the first structure, and the length of the base of the triangle of the second structure may be equal to the base length of the deformed shape.

Further, in the case where the object to be cloaked is derived, the height of the triangle and the shape of the curved surface of the second structure may be adjusted according to the degree of protrusion.

Embodiments of the present invention can provide an elastic electromagnetic hybrid smart meta material which is automatically fitted to an object by an elastic deformation, not a conventional shape fixed to an object, and which changes an electromagnetic field to make an object invisible And it is possible to cloak an object or a radio wave by using it.

Also, it is possible to fabricate large area by uniform arrangement and same meta material elements.

Figure 1 shows the basic concept of cloaking.
2 shows a cloaking method using a conventional meta-material.
3 is a conceptual diagram illustrating transparency according to elastic deformation of a transparent cloak boundary according to an embodiment of the present invention.
FIG. 4 shows a theoretical implementation of an elastic electromagnetic hybrid smart meta material according to an embodiment of the present invention.
FIG. 5 shows an experimental sample of a non-electrostatic electromagnetic hybrid smart meta material according to an embodiment of the present invention.
FIG. 6 is an electric field cross-sectional view of an experimental sample of a non-electrostatic electromagnetic hybrid hybrid smart meta material according to an embodiment of the present invention at 10 GHz.
FIG. 7 is a graph showing an experiment result of a non-electrostatic hybrid electromagnetic smart meta material test sample at 10 GHz according to a buffer size according to an embodiment of the present invention.
FIG. 8 illustrates an electric field measured according to frequency and incidence when a bump height is 6 mm using an experimental sample of a non-electrostatic hybrid electromagnetic smart meta material according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, configurations and operations according to embodiments of the present invention will be described in detail with reference to the accompanying drawings.

In smart conversion optics, the boundary strain deforms the unit cells, leading to a new distribution of electromagnetic properties to which the coordinate transformation is applied. It is generally very difficult to easily understand this phenomenon through solutions of complex equations of stress and deformation distributions in the mechanically equilibrium state of the structure under load. Although the shape of a deformation is determined by unique boundary conditions, it is not simple to obtain the deformation distributions required over the entire range of the device, since generally the corresponding problems must be solved inversely. When the shape of the deformation due to the given boundary strain is completed, the elasticity-related properties of the entire device are matched to one distribution. As a consequence of the difficulty in constructing a gradual distribution of elasticity-related properties, the distribution of the mechanical properties resulting therefrom does not solve the problem of smart-conversion optics: in general, since such a distribution is dependent on boundary strain, It works by.

The embodiment of the present invention proposes a smart meta-material capable of creating a step-wise exponential distribution suitable for a conversion optical apparatus even when arbitrary boundary deformation is given. 3 is a conceptual diagram illustrating transparency according to elastic deformation of a transparent cloak boundary according to an embodiment of the present invention.

Referring to FIG. 3, ab is a conceptual diagram of a smart meta-material transparent cloak that operates in response to elastic deformation of a cloak boundary. The arrows show the behavior of the light rays that are incident on the cloak and then propagate as reflected on the planar reflector. cd represents the coordinate transformation of the elastic deformation before (X1, X2) and after (x1, x2). The frame is an incompressible dielectric material and the void space is air. The deformation compresses the volume of the unit cell from A to A 'and produces twist angles α and β. For example, the larger the pitch PR , the less the anisotropy of the unit cell deformation. Is the square (dotted line) so that the one half of the y-axis size to the above direction, and then compressed into a deformed shape (solid line) and Jacco Albion (J) PR (e) 0.3 , (f) -0.99, (g) -10 , Respectively.

Hereditary The meta-  Used Standard angle  conversion.

To illustrate the working principle of the transparent metamaterial transparent cape, we reviewed the general conversion optics theory for the TE polarization device confined to the in - plane wave. Magnetic permeability Any 2D coordinate transformation associated with the anisotropic transformation of the in-plane tensor is given by the following equation (1).

Figure 112013105263072-pat00001
(1)

From here

Figure 112013105263072-pat00002
Is the Jacobian matrix in this transformation, and | G | Is the determinant of this matrix and [mu] is the permeability tensor of the virtual frame. In the case of a transparent cloak, relative permeability (μ) and permittivity (ε) in virtual space are both 1, μ = ε = 1.

The electromagnetic properties of the transparent cloak mimic the free space. The magnetic permeability by the conversion optics of this transparent cloak is simply

Figure 112013105263072-pat00003
Respectively.

The only case where an unmatched transform makes μ 'anisotropic is the isotropic transform. The conformal transformation is named to match the conditions that preserve the angle. The isometric transformation preserves the sum of the two angles? And? Of the micro-quadrangle (grid element) in FIGS. 3c and 3d. This equilibrium requirement is related to the isotropic stretching of the grid elements, as any transformation can be seen as a combination of locally rotating and simultaneously stretching in two orthogonal directions. Thus, the isochronous transformation has a Jacobian matrix with two local eigenvalues that are equal to each other,

Figure 112013105263072-pat00004
. In this way, the general coordinate transformation can be limited to a part based on conformal mapping, which can be applied to a T-polarizer device which does not require a magnetic permeability.

On the other hand, the conversion rule for the dielectric constant is very simple as shown in equation (2). :

Figure 112013105263072-pat00005
... (2)

Conversion rule Equation (2) is maintained in any general coordinate transformation, and this transformation does not have to be conformal or semi-conformal. However, if this transformation is not an isotropic transformation, the magnetic permeability is transformed into an insignificant type by Eq. (1), resulting in anisotropy. In order to eliminate the execution constraints that are caused by the use of non-uniform permeability, we want to use isochronous or near-conformal (quadrature) transforms rather than general coordinate transformations.

Example  One - Ozeich  smart Metamaterial

We have found a kind of electromagnetic metamaterial with a Ti polarization problem whose dielectric constant change is defined by the conversion optical rule of Eq. (2) as a function of elastic deformation. The strain gradient tensor (F ij ) in the elastic deformation that is transformed from (X 1 , X 2 ) to (X ' 1 , x' 2 )

Figure 112013105263072-pat00006
And the tensile strain tensor Jacobian
Figure 112013105263072-pat00007
Is a value of volume change due to elastic deformation
Figure 112013105263072-pat00008
. Smart transparency requires both sufficient permittivity change (Δε) and near-equiva- lence that μ is consistent with a single cloak transformation. The change in permittivity required for a two-dimensional electromagnetic metamaterial consists of an initial volume fraction fd and fa (= 1-fd) of dielectric material (εd) and air or free space (εa≈1)
Figure 112013105263072-pat00009
Figure 112013105263072-pat00010
As shown in Fig.

Next, consider what happens after this elastic permutation that the effective permittivity does not hold the volume of the meta material element. This conversion requires the use of compressible materials whose Poisson's ratio ( PR ) is much smaller than 0.5.

If the dielectric material portion is incompressible,

Figure 112013105263072-pat00011
And the effective permittivity of the two-dimensional crystal structure are
Figure 112013105263072-pat00012
Figure 112013105263072-pat00013
. Where A 'is the area of the deformed microelements in the initial area A. The ratio after and after the deformation of effective permittivity
Figure 112013105263072-pat00014
. Elasticity and electromagnetic metamaterials enable smart transparency to change the permittivity distribution appropriately when the cloak boundary changes.

The dielectric constant of the elastic matrix is

Figure 112013105263072-pat00015
, The effective permittivity ratio is approximately
Figure 112013105263072-pat00016
. The effective permittivity is proportional to the reciprocal of the area strain factor (A '/ A). This equation exactly matches the conversion optics of equation (2), regardless of the type of conversion used.

To ensure 'smart' behavior, which is a problem associated with elastic statics, it should be confirmed that the mechanical equilibrium of the modified metamaterial grid represents a desirable QCM. As described above, this behavior requires maintaining the single permeability of Equation (1). It can be seen that the elastic deformation of a homogeneous medium with a very large negative PR value produces a deformed grid that exactly matches the conformal transformation conditions. A substance with a negative PR value is known as an oesitic. In order to explain this, squares (dotted lines) having different PR values of 0.3, -0.99, and -10 are compressed in half in the y direction as shown in e and g of Fig. The elastic modulus (solid line) and the Jacobian value (J) were calculated as the solid mechanics module of commercial finite element software. As the PR becomes smaller, the modified grid resembles a conformal transformation, and at a sufficiently small negative PR value such as -10, it becomes a high-precision quadrature transformation.

Thus, it is possible to have rules of transformation of dielectric constants consistent with transformed optics, such as transformed optics, which are similar to quasi-angular transformations, which are important factors that make smart transparency possible in a single elastic electromagnetic metamaterial.

In order to prove the concept of transparency of smart metamaterials, we carried out the electromagnetic electromagnetic finite element computation in which the monochromatic Gaussian beam in the microwave X band (10 GHz) region is incident at 45 degrees. In this work, the reflective surface of a hidden object with smart transparentization behavior

Figure 112013105263072-pat00017
Figure 112013105263072-pat00018
And h is different for each experiment.

Figure 4

Figure 112013105263072-pat00019
Wave propagation passing through the material of the planar reflector and computer simulations reflected on the flat reflector. This result can be seen as a definite case without the height of the hidden object. Then we were each shown in FIG. 4 bd was executed while gradually lowering the solid mechanics simulation, increase the height, h of the object to 10 mm in several different PR 0.3, -0.99, -10. To determine conformity requirements,
Figure 112013105263072-pat00020
Dimensional micro-quadrilateral material element having a size of about 2 mm is considered to take the form of a parallelogram by elastic deformation. 4E, the angular changes between the two line segments AC and AB in the rectangle with the dotted line after the transformation are as shown in the following equation (3).

Figure 112013105263072-pat00021
... (3)

In the case of an exact conformal mapping, this value should be zero in Figure 4 f-h.

If you use a common material with a PR of 0.3, the mating condition is not exactly conformal and the bump will not be completely hidden. Figures 4b, f show that a strongly scattered secondary beam produces a power gap from the primary scattered light resulting from the protruding reflector. PR = -0.99, the angle variation alpha + beta is significantly lowered; However, the reflected light beam still has a significant power gap (Figure 4c, g). When the deformed material is an opaque material containing a negative PR having a large absolute value of -10, it can be seen that the angle α + β is close to 0 and almost conformal mapping is achieved (FIG. 4h). As a result of the fact that the transformed permittivity distribution map and the permittivity map described by the carpet transparent cloop design are nearly identical, the power gap (indicating the presence of bumps on the reflector) is no longer visible (FIG. 4D) It was restored as if it were completely reflected on the plane while propagating the genus.

Any piece of a compartmentalized piece of an ozetic material with PR << 1 is produced by a definite conformal transformation. Therefore, oesthetic materials provide a smart way to keep the angle-preserved coordinate transformations required for quasi-conformal optics. The theoretical results are shown in FIGS. 3 and 4 and clearly show that as the absolute value of the negative PR increases, the elastic deformation gradually approaches a definite conformation. Oesthetic materials with a negative PR value of between -1 and 0 have been known for a long time because they can be applied to media with all volume and ply density elastic moduli. The regime with PR <-1 requires a negative elastic modulus of elasticity

Figure 4 shows a theoretical implementation of a transparent meta-material transparent cape as (a) a calculated electric field pattern of a Gaussian beam fired to a flat reflective surface at 45 [deg.] From the left. (bd) at Auger ticks calculated electric field pattern of the transparent mantle (red dotted line box) of the bottom to a smart metamaterial transparent mantle (b) PR = 0.3, (c) PR = -0.99, or (d) PR = -10. (e) Schematic view of elastic deformation of microelements. (f) bd in the red dotted line box, (f) PR = 0.3, (g) PR = -0.99, (h) PR = -1. (i) An unmodified state of a non-oethetic smart transparent cape in a red dotted polygon. A piece of triangle 125 mm long and 65 mm long is attached to the bottom of the rectangle. (j) Biodetric smart metamaterial The calculated electric field pattern when the boundary of transparent cloak in transparent cloak is deformed to h = 8 mm, (k) h = 10 mm, (l) h = 15 mm . (m) The calculated Jacobian value of the unit cells in the area of the red dotted line in i after the elastic deformation

Figure 112013105263072-pat00022
. (n) h = 8 mm, (o) h = 10 mm, and (p) h = 15 mm, respectively.

Example  2 - Biotec  smart Metamaterial

In fact, the high negative PR Value with a large amount of dielectric constant

Figure 112013105263072-pat00023
Lt; / RTI &gt; can not be easily realized. Since the ε d of the test sample is not large enough compared to ε a , additional structures (triangular pieces) are attached at the bottom to have very small Jacobians for smart transparency. For example, close to our experimental conditions
Figure 112013105263072-pat00024
The conversion rule of effective permittivity in the condition of
Figure 112013105263072-pat00025
. For proper operation of this carpet transparent cloak, the maximum permittivity change is highest
Figure 112013105263072-pat00026
Figure 112013105263072-pat00027
(After elastic deformation), which is
Figure 112013105263072-pat00028
. To obtain the required range of effective permittivities required, an additional triangular piece of 125 mm horizontal and 65 mm vertical was placed at the bottom of the sample, giving a strain Jacobian value as small as 0.19

In an experimental implementation of smart transparency, we placed our elastic metamaterial structure on the bump, creating an elastic deformation of the curved surface at h = 8 mm and h = 10 mm, respectively, at its boundary. In both case simulations, the bumps covered by the other transparent cloak boundaries produce one beam that is reflected by a perfectly flat surface, which implies the invisibility of the bump below the metamaterial structure. When further transforming the smart transparent cloak of the bump with h = 15 mm, a strongly scattered bifurcated ray of light is produced, which means the deformation limit of the metamaterial as a carpet transparent cloak. In the case of h = 8 mm, 10 mm and 15 mm, the effective permittivity distribution in the dotted line of the rectangle after deformation is shown in Fig. 4 np, respectively. These results demonstrate that the smart transparent cloak gives the observer the impression that the bottom physical bump is a flat surface in various heights and shapes. Since the bump is covered with a reflector that blocks the electromagnetic field inside, the volume inside the bump is used as a hidden space

Example  3 - Smart Metamaterial

Because it is difficult to realize an ohmic material with a very high dielectric constant and a negative PR, we have conducted more realistic experiments with low dielectric constant materials. In the experiment, an elastic crystalline structure consisting of a silicone rubber (ε d) and empty air (ε a) was used,

Figure 112013105263072-pat00029
And the initial volume fraction (fd) of our sample is fd = 0.15. This structure is made of a rectangular periodic array with a 10 mm period of a silicone rubber tube with a 10 mm extensible outer diameter. The empty air space has two areas: an inner diameter of 9 mm and a gap area between the inside of the tube and the unit rubber tube. The smart carpet transparent cloak consists of two triangular areas (denoted C1 and C2) with a uniform tube arrangement serving as a uniform medium with an effective dielectric constant of 1.28. The lower triangular area (labeled C1) is elastically compressed to a curved surface with a maximum height h to create a spatial density distribution of the silicone rubber in the void space. The spatial distribution of the silicone rubber causes a change in the effective refractive index across the surface to the surface. Because we have successfully achieved smart transparent devices from a constant elastic crystal structure, these self-tunable transparent cloams enable easy fabrication in large areas and potential application areas. By changing the Jacobian ( J ), we can reach the required effective permittivity range of 1.28 to 2.88.

The size of the unit cell, 10 mm, is much smaller than the wavelength of the microwave at 10 GHz. Thus, this periodic structure generally operates in the lowest sound field of dispersion, which is regarded as an effective medium or 'metamaterial' in terms of electromagnetic properties. We first pushed the transparent cloak of the installed smart metamaterial in a uniform medium into the triangular bump of a nearly complete electrical conductor and pressed it in the opposite direction. As described above, deformation in a certain range always results in some effective permittivity contour mimicking the quadratic coordinate transformation: thanks to the appropriately selected elastic properties of the elastic tube array. As in the previous reference plane transparent cloak experiments, the purpose of this device is to make the reflected light rays indistinguishable from the regular reflection on a flat unmodified conductor surface (the "ground").

FIG. 5 shows an experimental sample of a transparent cloak of nonoetic smart meta material. A photograph of the sample used in the experiment has an additional triangular piece measuring 125 mm (width) and 65 mm (length). As shown in the photographs (a) and (b) before the deformation of the sample, the figure inserted in a is an elastic crystal structure and the figure inserted in b is an effective permittivity curve for Jacobian values. To prevent refraction of air and sample boundary, the upper part of the transparent cloak was made a right triangle.

smart Metamaterial  Confirmation of transparency effect

To confirm the expected behavior of smart transparency, the cloak was experimented by mapping a TF field distribution within a planar waveguide by launching an 8-14 GHz microwave at an incident angle of 0 ° -90 ° to the reflective surface. Self-Adjustable Carpet To observe the smart ability of the transparent cloak, we installed a transparent metamaterial transparent cloak by pushing it with a metal bump and pressed it in the opposite direction. Followed were carried out in accordance with the change to h = 11 mm in the h = 0 mm to the measurement of the cross-sectional view of a 45 ° angle of incidence of 10 GHz, as the electric field is also drawn to 6 ah. At a bump of h = 2 mm or less, the additional piece creates a significantly higher refractive index as a convex lens in the central region, which causes the reflected light to be concentrated. The scattered light sections in the wide bump range from h = 4 mm to h = 8 mm show a single ray without a power gap, ie the performance of the cloak is not significantly affected by the shape of the cloak boundary in a certain range. In bumps with h = 9 mm or more, the effective permittivity change due to deformation is not sufficient to make the carpet transparent, resulting in a bifurcated beam with strong scattered power gaps that hits the performance of the cloak and impairs carpet transparency. The upward deformation limit of the self-tuning smart transparent cloak is ultimately limited by the dielectric constant size of the dielectric material. As shown in FIG. 6i, the deformation of the transparent cloak-free surface ( h = 6 mm) produces a bifurcated beam with strongly scattered power gaps. The reflected scattered waves interfere with the incident waves, and the fringe pattern as shown in the electric field cross-section of FIG. 6 makes it difficult to evaluate the performance of the transparency apparatus. In order to eliminate the interference effect between the incident and scattering waves, we obtained the ray cross-section of the reflected output region as shown in Figure 7 and averaged the cross-section of the wave length distance.

Figure 6 shows an electric field cross-section of a bump covered with smart transparent clay and an inner cover bump measured experimentally at 10 GHz. (A) plane ( h = 0 mm) and (b) h = 2 mm, (c) 4 mm, (d) 6 mm, (e) 8 mm, (f) 9 mm, (g) 10 mm, and (h) 11 mm bumps, respectively. (i) A beam was incident on a h = 6 mm bump without a smart transparent cape. The triangular dotted line in red indicates the size of the sample.

7 is an average ray cross-section of the reflected scattered waves on the output surface. In order to eliminate the interference effect, the average cross-section of the output area was shown. The bump size of the transparent metamaterial transparent cloak was h = 0 mm, 2 mm, 4 mm, 6 mm, 8 mm, 9 mm, 10 mm and 11 mm . Without a clear cloak, a second ray of strongly scattered light emerges.

To ensure that the transparency effect is maintained in the broadband (instant lane width less than 10%), the device tests for microwave radiation between 8 GHz and 14 GHz at an angle of incidence of 45 ° on the reflective surface and mapping the Ti field distribution in the planar waveguide Respectively. A smart metamaterial transparent cloak pressed with a metal bump with a height h = 6 mm, the electric field cross-section at a 45-degree incident angle was measured at frequencies of 8 GHz, 11 GHz, 12 GHz and 14 GHz, respectively, as shown in FIGS. The dispersion curve of the silicon rubber mass shows that the dielectric constant of the silicone rubber does not change sensitively over the wide frequency range. Obviously, in this 8-12 GHz range, the transparent cloak works fairly well in the experimental setup, especially at 11 GHz to 12 GHz experimental frequencies. It is complicated to observe the transparency of the Gaussian beam at the specimen setup and the diffraction limit of the Gaussian beam width. At the other extreme (14 GHz), metamaterial unit cells are not small enough to be exactly uniform in wavelength. This explains the poor performance seen in Figure 8d.

An ideal carpet (plane) transparent cloak cancels the reflection spectrum of an object that receives the light of a plane wave at an arbitrary incident angle and leaves only the specular reflection reflected on the plane. In order to study the dependence of the incident angle on the experimental sample (the device installed on the same parallel plate waveguide), a microwave ray of 10 GHz T-polarized light was launched on the reflecting surface at an incident angle of 0 ° to 90 ° to 45 °. At 10 GHz with a transparent metamaterial transparent cape pressed with a metal object of height h = 6 mm, the electric field cross-section was measured as shown in Figure 8f-h at incident angles 0 °, 60 ° and 90 ° for the selected vertical. These results show that this device works as a transparent carpet cloak for multiple angles of incidence.

Figure 8 is an electric field cross section of a transparent meta-material transparent cape measured experimentally. (B) 11 GHz, (c) 12 GHz, (d) 14 GHz, electric fields measured experimentally at frequencies and incident angles at b = h = 6 mm (e) a dispersion curve of a silicone rubber, which is an experimentally measured electric field cross section at various incident angles (f) 0 °, (g) 60 °, and (h) 90 °.

Experimental results show an experimental proof of the self-regulating 'smart' transparent cloak device at microwave frequencies (made of an elastic meta-crystal of a single dielectric with uniform initial electromagnetic and mechanical properties). The implemented smart transparent cloak has almost lossless broadband (10-12 GHz) characteristics, can be extended to cover a wider range of objects, and can be easily fabricated at low cost. Its 'smart' electromagnetic configuration tensors are derived from the combination of electromagnetic and elastic properties. Such a hybrid elastic-electromagnetic metamaterial approach will have a variety of applications based on quadrature-angle conversion optics.

Claims (18)

  1. Wherein air or a free space is formed between the arrangements of the dielectrics and the Poisson's ratio of the structure has a negative value and the permittivity of the dielectric is larger than the permittivity of the air or the free space Wherein the hybrid electromagnetic meta-material is a hybrid electromagnetic meta-material.
  2. Wherein a dielectric structure capable of being elastically deformable is periodically arranged and a first structure and a second structure having air or free space formed between the arrangements of the dielectrics are in the form of a combination of the first structure and the second structure, Wherein the hybrid electromagnetic smart meta-material is an elastic electromagnetic hybrid smart meta material.
  3. 3. The method of claim 2,
    Wherein the dielectric is a structure consisting of a dielectric material having elasticity and a periodic arrangement of unit volume consisting of ambient air or free space.
  4. The method of claim 3,
    Wherein the dielectric material is a silicon rubber tube.
  5. The method of claim 3,
    Wherein the dielectric material is elastically deformed to change an individual unit volume of Jacobians to change an effective dielectric constant of the dielectric material.
  6. 6. The method of claim 5,
    Wherein the dielectric constant of the dielectric constituting the unit volume is 2 or more.
  7. 6. The method of claim 5,
    Wherein the size of the unit volume of the dielectric is within 25% of the wavelength of the operating electromagnetic wave.
  8. 5. The method of claim 4,
    Wherein the silicone rubber tube has a rectangular periodic arrangement with a period of 10 mm.
  9. 3. The method of claim 2,
    Wherein the second structure is in the form of a triangle, and the base of the triangle is coupled to the first structure, and the length of the base of the triangle of the second structure is the same as the base length of the shape to be deformed.
  10. Wherein a dielectric constant of the first structure and the second structure is periodically arranged such that the dielectric structure is elastically deformable and air or a free space is formed between the dielectric arrangements, The cloaking method using the elastic electromagnetic hybrid smart meta material is characterized in that a part of the second structure and one structure are contacted with and compressed by the object to be cloched to change the spatial density distribution of the dielectric and the effective refractive index And cloaking the target object by changing the shape of the target object so as to follow each pattern.
  11. 11. The method of claim 10,
    Wherein the dielectric is a structure consisting of a dielectric material having elasticity and a periodic arrangement of unit volume consisting of ambient air or free space.
  12. 12. The method of claim 11,
    Wherein the dielectric material is a silicon rubber tube.
  13. 12. The cloaking method according to claim 11, wherein the dielectric is elastically deformed to change the Jacobian of an individual unit volume to change an effective permittivity of the dielectric.
  14. 14. The cloaking method using the elastic electromagnetic hybrid smart meta material according to claim 13, wherein the permittivity of the dielectric constituting the unit volume is 2 or more.
  15. 14. The cloaking method according to claim 13, wherein the size of the unit volume of the dielectric is within 25% of a wavelength of an electromagnetic wave to be operated.
  16. 14. The method of claim 13, wherein the period of the unit volume comprises a square or hexagonal arrangement that is within 25% of a wavelength of an operating electromagnetic wave.
  17. 11. The method of claim 10, wherein the second structure is in the form of a triangle, wherein the base of the triangle is coupled to the first structure, and the length of the base of the triangle of the second structure is the same as the base length of the deformed shape A cloaking method using an electromagnetic hybrid smart meta material.
  18. 18. The cloaking method using the elastic electromagnetic hybrid smart meta-material according to claim 17, wherein the height of the triangle and the curved shape of the second structure are adjusted according to the degree of protrusion when the object to be cloaked is derived.
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KR20180054105A (en) * 2016-11-15 2018-05-24 한국과학기술원 Metamaterial having a high refractive index, and method for preparing the same

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US20110268910A1 (en) 2010-04-30 2011-11-03 Bratkovski Alexandre M Flexible metamaterial structure based on graphene structures

Patent Citations (1)

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Publication number Priority date Publication date Assignee Title
US20110268910A1 (en) 2010-04-30 2011-11-03 Bratkovski Alexandre M Flexible metamaterial structure based on graphene structures

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR20180054105A (en) * 2016-11-15 2018-05-24 한국과학기술원 Metamaterial having a high refractive index, and method for preparing the same
KR101894909B1 (en) 2016-11-15 2018-09-04 한국과학기술원 Metamaterial having a high refractive index, and method for preparing the same

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