KR102532609B1 - Electromagnetic wave absorber with metasurface - Google Patents

Abstract

The present disclosure relates to an electromagnetic wave absorber including a metasurface having electromagnetic wave absorbing performance with an extended effective incident angle range.

Description

Electromagnetic wave absorber including a metasurface {ELECTROMAGNETIC WAVE ABSORBER WITH METASURFACE}

The present disclosure relates to an electromagnetic wave absorber including a metasurface having electromagnetic wave absorbing performance with an extended effective incident angle range.

Reflection by an object is determined by the impedance of the object and the impedance of the surrounding material (usually air). The smaller the difference between the impedance of an object and its surroundings, the lower the reflectance.

Metamaterial refers to a material whose optical properties are artificially adjusted by properly designing a structure having a size of less than half a wavelength of a target wavelength band and periodically arranging it in space. It is possible to adjust the impedance by applying the concept of the metamaterial, and it is possible to design a metamaterial absorber having low reflectance and high absorption at the same time through impedance matching in a desired wavelength band. A method for achieving impedance matching in a specific wavelength band is to design a structure mainly including a resonant element. The impedance of the dielectric substrate only changes according to the wavelength, and it is possible to obtain impedance matching of the entire structure through a rapid impedance change in a target band by a resonant element. However, the electromagnetic wave absorber developed so far has a problem in that the effective incident angle range for exhibiting absorption performance is narrow, and thus the electromagnetic wave absorption is not properly performed at the part where the two surfaces meet perpendicularly, resulting in retroreflection.

[Prior art literature]

(Patent Document 1) KR 10-1957798 B

In order to solve the above problems, the present invention provides an electromagnetic wave absorber including a metasurface designed to have a feature in which the effective incident angle range is extended and the retroreflectivity of electromagnetic waves is reduced.

However, the problem to be solved by the present application is not limited to the above-mentioned problem, and other problems not mentioned will be clearly understood by those skilled in the art from the description below.

A first aspect of the present application is a metal reflector; a first dielectric layer formed on the metal reflection plate; and an absorber module including a conductive pattern structure formed on the first dielectric layer, wherein retroreflectivity of electromagnetic waves incident from the outside is reduced.

A second aspect of the present application provides a design method for absorbing electromagnetic waves, which includes arranging the electromagnetic wave absorber according to the first aspect on a surface of an object.

The electromagnetic wave absorber according to embodiments of the present disclosure can maintain excellent electromagnetic wave absorption performance even when the incident angle changes by realizing a high absorption rate of 15 dB or more within a target bandwidth based on normal incidence. In addition, by including a protective layer with high mechanical strength and excellent insulation properties, it protects the conductive patterned structure and can be applied as a high-tech stealth material to weapon systems operated in extreme environments such as tanks, fighters, and ships in the future.

The electromagnetic wave absorber according to the embodiments of the present invention, when used in a single plane, has a slope in the X-band (8.2 to 12.4 GHz) band for incident electromagnetic waves, -9 dB or less in the case of TM polarization, TE polarization In the case of -5 dB or less reflectance can be shown. When the electromagnetic wave absorber is applied to both sides of a vertical junction where two surfaces meet vertically, a reflectance effect of -15 dB or less in the X-band band, that is, a retroreflection reduction effect, can be obtained regardless of the polarization direction, so that the target frequency band For the X-band (8.2 to 12.4 GHz), radio wave absorption can be 70% or more in a single plane and 96% or more in a vertical junction.

1 is a diagram illustrating a cross-sectional view of an electromagnetic wave absorber and a shape of a conductive pattern structure according to an exemplary embodiment of the present disclosure.
2 is a graph showing simulation results of reflectivity in an X band (8 to 12 GHz), which is a target band of an electromagnetic wave absorber, according to an embodiment of the present disclosure.
3 is a graph showing simulation results of reflectivity of an electromagnetic wave absorber for vertical (transverse electric, TE) and horizontal (transverse magnetic, TM) polarized waves at a 45 degree oblique incidence, according to an embodiment of the present disclosure.
4 is a graph showing radar cross-sectional area (RCS) measurement results before (red line) and after (blue line) an electromagnetic wave absorber is placed on a metal corner structure disposed at 90 degrees in an embodiment of the present disclosure. .
5 is a graph showing the degree of radar cross-sectional area (RCS) change after the electromagnetic wave absorber is placed on a metal corner structure compared to before it is disposed in an embodiment of the present application.
6 is a schematic diagram showing an electromagnetic wave absorber disposed at a junction of two surfaces disposed at 90 degrees according to one embodiment of the present application.
7 is a schematic diagram showing an electromagnetic wave absorber disposed at a junction of three surfaces arranged at 90 degrees, respectively, according to one embodiment of the present application.
8A is a schematic diagram illustrating a shape of an electromagnetic wave absorber using a conductive pattern structure including a quadrangular doubling pattern according to an exemplary embodiment of the present disclosure.
8B shows the reflectance in a planar structure (Flat TE, Flat TM) and a vertical junction structure (Corner TE, Corner TM) of an electromagnetic wave absorber using a conductive pattern structure including a square doubling pattern in one embodiment of the present application. This is a verified graph.

Throughout this specification, when a part is said to be "connected" to another part, this includes not only the case of being "directly connected" but also the case of being "electrically connected" with another device in between. do.

Throughout the present specification, when a member is said to be located “on” another member, this includes not only a case where a member is in contact with another member, but also a case where another member exists between the two members.

Throughout the present specification, when a certain component is said to "include", it means that it may further include other components without excluding other components unless otherwise stated.

As used herein, the terms "about," "substantially," and the like are used at or approximating that number when manufacturing and material tolerances inherent in the stated meaning are given, and are intended to assist in the understanding of this disclosure. Accurate or absolute figures are used to prevent undue exploitation by unscrupulous infringers of the stated disclosure.

The term "step of" or "step of" as used throughout this specification does not mean "step for".

Throughout this specification, the term "combination(s) of these" included in the expression of the Markush form means one or more mixtures or combinations selected from the group consisting of the components described in the expression of the Markush form, It means including one or more selected from the group consisting of the above components.

Throughout this specification, reference to "A and/or B" means "A or B, or A and B".

Hereinafter, embodiments and embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. However, the present application is not limited to these embodiments and examples and drawings.

A first aspect of the present application is a metal reflector; a first dielectric layer formed on the metal reflection plate; and an absorber module including a conductive pattern structure formed on the first dielectric layer, wherein retroreflectivity of electromagnetic waves incident from the outside is reduced.

In one embodiment of the present application, the conductive pattern structure may be a metasurface and include a bitmap pattern or a doubling pattern. When the shape of the conductive pattern structure is a bitmap pattern, design freedom may be provided, and the structure of the doubling pattern may be simple to provide ease in a manufacturing process.

In one embodiment of the present application, the bitmap pattern includes the following bitmap structure,

; (하얀색: 전도성 패턴 구조체; 보라색: 제 1 유전체층),

; (white: conductive pattern structure; purple: first dielectric layer),

The doubling pattern may include the following doubling structure.

; (검정색: 전도성 패턴 구조체, 파란색: 제 1 유전체층).

; (Black: conductive pattern structure, blue: first dielectric layer).

Referring to FIG. 1, the absorber module of the present application includes a metal reflector, a first dielectric layer, and a conductive pattern structure in order from the bottom, and optionally a second dielectric layer, a third dielectric layer, or both of them on the conductive pattern structure. All may be formed as a protective layer. The conductive pattern structure may be a bitmap pattern, and the pattern may be designed such that the conductive pattern structure serves as a metasurface and exhibits high absorption and low reflectance for electromagnetic waves within a desired range.

The electromagnetic wave absorber of the present application realizes a high absorption rate of 15 dB or more within a target bandwidth based on normal incidence, and thus can maintain excellent electromagnetic wave absorption performance even when the incident angle of external electromagnetic waves changes. In particular, while the target frequency band, X-band (8.2 GHz to 12.4 GHz), shows a wide range of absorption performance of 70% or more on average, in the case of the prior art (prior art), absorption of 50% or more in the range of about 1 GHz around 10.5 GHz From the fact that only performance is shown, it can be seen that the performance of the electromagnetic wave absorber of the present application is more excellent.

In one embodiment of the present application, the first dielectric layer may include one or more selected from acrylic resin, PET, PP, PE, PMMA, polyurethane, silicone rubber, and styrofoam.

In one embodiment of the present application, the conductive pattern structure may include one or more selected from carbon ink, copper (Cu), silver (Ag), graphene, and indium tin oxide (ITO).

In one embodiment of the present application, the metal reflector may include one or more selected from aluminum, gold, silver and copper.

In one embodiment of the present application, a second dielectric layer, a third dielectric layer, or both may be further included on the conductive pattern structure. Specifically, the second dielectric layer implements heat insulation performance, and the third dielectric layer may impart mechanical strength, but is not limited thereto. More specifically, the second dielectric layer includes one or more selected from air, styrofoam, acrylic resin, PET, PP, PE, PMMA, polyurethane, silicone rubber, and airgel, and the third dielectric layer includes tempered glass, FR- 4 may include one or more selected from epoxy glass fiber laminate and epoxy glass. The second dielectric layer and the third dielectric layer may serve as a protective layer having high mechanical strength and excellent thermal insulation properties, and through them, the conductive pattern structure is protected, and weapons operated in extreme environments such as tanks, fighters, and traps. It could also be applied to advanced stealth materials in systems.

In one embodiment of the present application, the electromagnetic wave absorber may include a plurality of absorber modules, and the plurality of absorber modules may be disposed perpendicular to each other. The electromagnetic wave absorber can ensure impedance matching and reflectance reduction in the target band, X-band. In particular, when applied to a corner vertical joint structure, the structure is optimized for oblique incidence of electromagnetic waves, so that for the entire X-band band - It has the effect of showing a reflectance of less than 10 dB, that is, an absorption rate of 90% or more. Specifically, there is a very high possibility of retroreflection, in which incident electromagnetic waves can be reflected and returned to the same direction, at the vertical junction where planes meet perpendicularly, and in this case, the probability of being detected by radar in the microwave band this greatly increases In order to prevent this and reduce the detection probability, general absorbers can be used in the prior art, but they are most often designed to correspond to normal incidence and are not suitable structures for reducing retroreflection. The present invention provides an electromagnetic wave absorber in which an absorption rate of electromagnetic waves in a microwave band having an inclination angle is optimized to reduce retroreflection.

In one embodiment of the present application, when the absorber module is applied to a single plane, -9 dB or less for TM polarization and -5 dB for TE polarization for electromagnetic waves incident with an inclination in the X-band band The following reflectances can be seen. In addition, when the absorber module is applied to both sides of a vertical junction where two surfaces meet vertically, a reflectance effect of -15 dB or less in the X-band band, that is, a retroreflection reduction effect, can be exhibited regardless of the polarization direction.

Referring to FIGS. 2 and 3 , it can be confirmed the reflectivity simulation results when the absorber module of the present application is applied to a single plane. It was confirmed that an absorption rate of 15 dB or more was implemented in the X-band (8 GHz to 12 GHz), which is a target band, for electromagnetic waves normally incident on the absorber module. In addition, as a result of confirming the simulation results of reflectivity of the electromagnetic wave absorber for vertical (Transverse electric, TE) and horizontal (Transverse magnetic, TM) polarized waves at 45 degree oblique incidence in the electromagnetic wave absorber, the entire X-band (8 GHz to 12 GHz) It was confirmed that absorption rates of 13 dB or more for TE polarization and 8 dB or more for TM polarization were realized.

Referring to FIGS. 4 and 5 , it can be confirmed the reflectivity simulation result when the absorber module of the present invention is applied to a metal corner structure arranged so that two surfaces form 90 degrees. As shown in FIG. 4, the results were measured based on horizontal polarization, and the radar cross-section area was effectively reduced after application of the absorber through comparison of the two graphs before (red line) and after (blue line) the absorber module was applied. was able to confirm that In addition, as shown in FIG. 5, it was confirmed that the cross-sectional area of the radar was reduced by 10 dB or more in the entire X-band (8 GHz to 12 GHz), and it was confirmed that the electromagnetic wave absorber could significantly lower the reflectance in the vertical junction structure.

As shown in FIGS. 6 and 7 , a schematic view of a case where the absorber module is applied to a metal corner structure arranged so that two or three sides form 90 degrees can be confirmed ( FIGS. 6 and 7 , respectively). Specifically, the metal reflector 102, the first dielectric layer 103, and the conductive pattern structure 104 are sequentially stacked at the vertical junction 101 of the two surfaces, and absorber modules may be disposed on each surface. In addition, in the three-sided vertical joint 201, an absorber module in which the metal reflector 202, the first dielectric layer 203, and the conductive pattern structure 204 are sequentially stacked may be disposed on each surface.

In one embodiment of the present application, the electromagnetic wave absorber excluding the metal reflector may have a thickness of 1 mm to 12.5 mm. The following examples can be derived in a state in which the thickness of the electromagnetic wave absorber (excluding the metal reflector) of the present application is fixed, and the thickness of the electromagnetic wave absorber excluding the metal reflector of the present application is 1 mm to 12.5 mm, 2 mm to 12.5 mm, 4 mm to 12.5 mm, 1 mm to 10 mm, 2 mm to 10 mm, 4 mm to 10 mm, 1 mm to 8 mm, 2 mm to 8 mm, or 4 mm to 8 mm. In addition, the thickness of the metal reflection plate may be 10 μm to 100 μm, and the thickness of the conductive pattern structure may be 10 μm to 300 μm. The conductive pattern structure may exist on the surface of the first dielectric layer, but may exist in a form buried in the first dielectric layer.

In one embodiment of the present application, the conductive pattern structure includes a square doubling pattern, the width of the inner ring surrounded by the inner ring is 1 mm to 3 mm, the width of the inner ring is 1 mm to 3 mm, The shortest distance between the inner ring and the outer ring may be 1 mm to 3 mm, and the interval between each square doubling structure may be 1 mm to 3 mm.

A specific example of application of the doubling pattern can be confirmed through FIGS. 8A and 8B. While the thickness of the absorber module was fixed at 4 mm, the shape of the doubling ring, which is a conductive pattern, was searched for and optimized, and a structure exhibiting optimal performance was selected from among various trial examples. A total of five variables were used for optimization: the width of the inner ring surrounded by the inner ring (d _in ), the width of the inner ring (W _in ), the shortest distance between the inner and outer rings (L _out ), and the width of the outer ring. (W _out ), and the interval (P _margin ) between periodically arranged doublings. During optimization, it was set to search within a specific range for the corresponding variables, and the range is shown in Table 1 below.

variable minimum max value d _in 1 mm 3 mm W _in 1 mm 3 mm L _out 1 mm 3 mm W _out 1 mm 3 mm P _margin 1 mm 3 mm

The optimization was performed by applying the Particle Swarm Optimization (PSO) algorithm. As shown in Table 1, a pre-set number (n) of particles search for the 5-dimensional optimization parameter space having a limited range, and electromagnetic simulation is performed for the absorber structure corresponding to the parameter value assigned to each particle. did By comparing the Figure of Merit (FOM) of each particle, the position of the particle in the parameter space was changed, and the electromagnetic simulation was repeated to find the optimal solution. At this time, the target band for each FOM is determined by the total sum of the reflectance values for 45-degree oblique incidence in the 8.2 to 12.4 GHz band, and the points where the reflectance exceeds 10% are summed by giving a 40-fold penalty. Optimization was carried out in the direction of minimizing the FoM. Through the above, optimization was performed for the case of sheet resistance of 40 Ω/□, and the results are shown in Table 2 below.

variable optimization value d _in 1 mm W _in 1 mm L _out 1.35 mm W _out 1.33 mm P _margin 1.49 mm

The reflectivity confirmed using the period of the optimized conductive pattern structure (FIG. 8a) and the width and width of each ring is shown in FIG. 8b. In the graph of FIG. 8B, the reflectance of the X-band of the embodiment can be confirmed. When disposed in a flat structure (Flat TE, Flat TM), for electromagnetic waves incident at an angle of 45 degrees, in the case of TE polarization, -5 dB or less , it was confirmed that the reflectivity of -9 dB or less was secured in the case of TM polarization. In particular, in the case of vertical junction structures (Corner TE, Corner TM), it was confirmed that the reflectance was less than -15 dB, that is, the absorption was greater than 90% regardless of the polarization direction.

A second aspect of the present application provides a design method for absorbing electromagnetic waves, which includes arranging the electromagnetic wave absorber according to the first aspect on a surface of an object.

In one embodiment of the present application, the electromagnetic wave absorber may include a plurality of absorber modules, and the plurality of absorber modules may include disposing the plurality of absorber modules at a portion where surfaces of the target object vertically meet.

Detailed descriptions of portions overlapping with the first aspect of the present application have been omitted, but the description of the first aspect of the present application can be equally applied even if the description is omitted in the second aspect of the present application.

In one embodiment of the present application, the target object may be a fighter jet, a trap, or an unmanned aerial vehicle, and a part where two surfaces of their body meet vertically (non-limiting example, a part where a body and a tail meet, a part where a horizontal and vertical tail meet) A microwave stealth function may be implemented by disposing the electromagnetic wave absorber on a part, etc.).

The above description of the present application is for illustrative purposes, and those skilled in the art will understand that it can be easily modified into other specific forms without changing the technical spirit or essential features of the present application. Therefore, the embodiments described above should be understood as illustrative in all respects and not limiting. For example, each component described as a single type may be implemented in a distributed manner, and similarly, components described as distributed may be implemented in a combined form.

The scope of the present application is indicated by the following claims rather than the detailed description above, and all changes or modifications derived from the meaning and scope of the claims and equivalent concepts thereof should be construed as being included in the scope of the present application.

Claims (14)

metal reflector; a first dielectric layer formed on the metal reflection plate; and a conductive pattern structure formed on the first dielectric layer.
As an electromagnetic wave absorber comprising a,
It has the characteristic of reducing the retroreflectance of electromagnetic waves incident from the outside,
The electromagnetic wave absorber includes a plurality of absorber modules,
Wherein the plurality of absorber modules are disposed perpendicular to each other,
electromagnetic wave absorber.
According to claim 1,
The conductive pattern structure is a metasurface and includes a bitmap pattern or a doubling pattern, the electromagnetic wave absorber.
According to claim 2,
The bitmap pattern includes the following bitmap structure,

; (white: conductive pattern structure; purple: first dielectric layer),
The doubling pattern includes the following doubling structure, the electromagnetic wave absorber:

; (Black: conductive pattern structure, blue: first dielectric layer).
According to claim 1,
Wherein the first dielectric layer comprises at least one selected from acrylic resin, PET, PP, PE, PMMA, polyurethane, silicone rubber and styrofoam, the electromagnetic wave absorber.
According to claim 1,
The conductive pattern structure includes at least one selected from carbon ink, copper (Cu), silver (Ag), graphene, and indium tin oxide (ITO).
According to claim 1,
Wherein the metal reflector includes at least one selected from aluminum, gold, silver and copper.
According to claim 1,
An electromagnetic wave absorber further comprising a second dielectric layer, a third dielectric layer, or both on the conductive pattern structure.
According to claim 7,
The second dielectric layer implements thermal insulation performance,
The third dielectric layer imparts mechanical strength, the electromagnetic wave absorber.
According to claim 7,
The second dielectric layer includes at least one selected from air, styrofoam, acrylic resin, PET, PP, PE, PMMA, polyurethane, silicone rubber, and airgel,
Wherein the third dielectric layer comprises at least one selected from tempered glass, FR-4 epoxy glass fiber laminate, and epoxy glass, the electromagnetic wave absorber.
delete According to claim 1,
The total thickness of the electromagnetic wave absorber excluding the metal reflector is 1 mm to 12.5 mm, Electromagnetic wave absorber.
According to claim 2,
The conductive pattern structure includes a square doubling pattern,
The inner width surrounded by the inner ring is 1 mm to 3 mm,
The width of the inner ring is 1 mm to 3 mm,
The shortest distance between the inner ring and the outer ring is 1 mm to 3 mm,
The interval between each square doubling structure is 1 mm to 3 mm, the electromagnetic wave absorber.
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