KR102575570B1 - Electromagnetic metamaterial absorber including via holes - Google Patents

Abstract

The present invention relates to an electromagnetic wave metamaterial absorber including a plurality of via holes. According to the present invention, a metal reflective layer is coupled to the lower surface of the dielectric, a conductive metapattern made of a conductive material is formed on the upper surface, and a plurality of via holes connecting some points of the conductive metapattern and the surface of the metal reflective layer are formed. Provided is an electromagnetic wave metamaterial absorber having a structure formed by penetrating the dielectric.
The electromagnetic wave metamaterial absorber including a plurality of via holes according to the present invention has an advantage of maintaining excellent absorption performance under a wide-angle incident condition as well as a broadband.

Description

Electromagnetic metamaterial absorber including via holes}

The present invention relates to an electromagnetic wave metamaterial absorber including a plurality of via holes, and more particularly, to an electromagnetic wave metamaterial absorber including a plurality of via holes inside a substrate.

Electromagnetic absorber can be widely applied as a material for preventing electromagnetic wave interference generated from wireless communication terminals and radars, and as a defense stealth technology that can reduce the radar reflection area of weapon systems such as fighter jets and ships.

So far, electromagnetic wave absorbers have been successfully developed using magnetic loss of ferrite composites or conductivity loss of carbon composites. However, the composite material-based electromagnetic wave absorber has a disadvantage in that it is relatively bulky and has a high specific gravity.

An electromagnetic metamaterial absorber, which has recently been attracting attention, combines a conductive pattern, a relatively thin dielectric, and a metal reflective layer so that it not only matches the impedance with air, but also uses the high conductivity loss generated in the pattern to improve electromagnetic wave reflectivity. It is a next-generation electromagnetic wave absorber that can dramatically lower the

The electromagnetic wave metamaterial absorber has the advantage of realizing a wide absorption bandwidth performance based on the optimization of the conductivity pattern. However, as the incident angle increases, the absorption performance rapidly decreases.

The background technology of the present invention is disclosed in Korean Patent Publication No. 10-1567260 (announced on November 9, 2015).

An object of the present invention is to provide an electromagnetic wave metamaterial absorber including a plurality of via holes maintaining absorption performance even under wide-angle incident conditions.

In the present invention, a metal reflective layer is coupled to the lower surface of the dielectric and a conductive metapattern made of a conductive material is formed on the upper surface, and a plurality of via holes connecting some points of the conductive metapattern and the surface of the metal reflective layer are formed. Provided is an electromagnetic wave metamaterial absorber having a structure formed by penetrating a dielectric.

In addition, the dielectric may be formed of a material including at least one of acrylic, Teflon, FR4, PET, styrofoam, foam composite, and glass epoxy.

In addition, the conductive material may be formed of a material including at least one of carbon, copper (Cu), silver (Ag), gold (Au), graphene, and indium tin oxide (ITO).

In addition, the via hole may have a structure in which an inner wall is coated or filled with copper, silver, gold, iron, or carbon material.

In addition, the conductive meta-pattern may be formed by combining and arranging a plurality of first parallelogram pixels filled with the conductive material and a plurality of second parallelogram pixels in an empty state.

In addition, the plurality of via holes may connect a plurality of pixels selected from among the plurality of first parallelogram pixels and the metal reflective layer.

In addition, the conductive meta-pattern is based on a hexagonal unit structure in which three parallelogram pixels are in contact and may be formed by arranging at least one type of parallelogram among the first and second parallelograms in each hexagonal unit structure. .

In addition, the outer shape of the meta-material absorber may be a hexagonal shape, a square shape, or a rectangular shape.

In addition, the outer shape of the metamaterial absorber is hexagonal, and when the conductive metapattern is divided into three areas with a central angle of 120 ° based on the center of the metamaterial absorber, the pattern shape and via hole position in each of the three areas may have a symmetric structure with each other.

In addition, two of the plurality of via holes may form a pair and exist as a pair in each of the three regions.

In addition, the conductive metapattern is formed on the first to third regions of the three regions, respectively, and is composed of a combination of the first and second parallelogram pixels, but the top of a pair of via holes formed on the corresponding region may include first to third pattern parts electrically connecting the first to third pattern parts, and may have a structure in which each of the first to third pattern parts is separated from each other by the second parallelogram pixels in the empty state above the dielectric. .

In addition, the via hole may have a cylindrical columnar shape or a polygonal columnar shape.

In addition, the conductive pattern may be formed as a pattern shown in the drawing below, which is configured by combining the parallelogram pixels filled with the conductive material and the parallelogram pixels in the empty state.

The electromagnetic wave metamaterial absorber including a plurality of via holes according to the present invention has an advantage of maintaining excellent absorption performance under a wide-angle incident condition as well as a broadband.

In addition, based on its excellent absorption performance under wide-angle incident conditions, the metamaterial antenna of the present invention can be applied to solve the electromagnetic wave interference problem of a multi-antenna system and minimize the radar reflection area of weapon systems such as fighter jets and ships.

1 is a perspective view of an electromagnetic wave metamaterial absorber including a plurality of via holes according to an embodiment of the present invention.
FIG. 2 is a diagram illustrating an implementation method of the conductive metapattern shown in FIG. 1 .
FIG. 3 is a diagram explaining in detail the structure of the conductive metapattern and the via hole of FIG. 1 .
FIG. 4 is a view showing a conductive metapattern coupled to an upper surface of the dielectric of FIG. 1 .
5 is a schematic diagram of a current induced when a TE polarized wave in which a time-varying electric field is formed in a direction perpendicular to an xoz plane and a time-varying magnetic field is formed in a direction perpendicular to a plane including two metal via holes is induced at an oblique incidence.
6 is a schematic diagram of a current induced when a TM polarized wave in which a time-varying magnetic field is formed in a direction perpendicular to the xoz plane and a time-varying electric field is formed in a direction parallel to two metal via holes is obliquely incident.
7 shows simulation results of the reflectivity of the metamaterial absorber at normal incidence and 60° oblique incidence of TE and TM polarized waves.
8 is a simulation result of absorption of a metamaterial absorber when TE and TM polarized waves are incident at an angle of 0° to 60°.
9 shows current distribution simulation results on a conductive metapattern at 9.6 and 11.8 GHz, respectively, when TE and TM polarized waves are incident at a 60° angle.

Then, with reference to the accompanying drawings, an embodiment of the present invention will be described in detail so that those skilled in the art can easily practice it. However, the present invention may be implemented in many different forms and is not limited to the embodiments described herein. And in order to clearly explain the present invention in the drawings, parts irrelevant to the description are omitted, and similar reference numerals are attached to similar parts throughout the specification.

Throughout the 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 element in between. . In addition, when a certain component is said to "include", this means that it may further include other components without excluding other components unless otherwise stated.

1 is a perspective view of an electromagnetic wave metamaterial absorber including a plurality of via holes according to an embodiment of the present invention.

As shown in FIG. 1, the electromagnetic wave metamaterial absorber 100 including a plurality of via holes according to an embodiment of the present invention includes a dielectric material 110, a metal reflective layer 120, a conductive meta pattern 130, and a plurality of via holes ( 140).

Here, the dielectric may be formed of a material including at least one of acrylic, Teflon, FR4, PET, styrofoam, foam composite, and glass epoxy.

The metal reflection layer 120 is a metal reflection plate coupled to the lower surface of the dielectric 110 and may be formed of various known metal materials. Total reflection occurs through the metal reflection layer 120 .

The conductive metapattern 130 is formed on the upper surface of the dielectric 110 and absorbs electromagnetic waves incident from the outside. According to an embodiment of the present invention, the conductive material (eg, carbon ink) has a set height (thickness: 20 μm) may have various pattern shapes depending on the combination of the filled area and the blank area that is not.

That is, the conductive metapattern 130 can be designed and manufactured in various combinations and various types of patterns according to design conditions, parameters, product specifications, and the like.

In this case, the conductive material may be formed of a material including at least one of carbon, copper (Cu), silver (Ag), gold (Au), graphene, and indium tin oxide (ITO). The embodiments of the present invention mainly illustrate carbon ink.

The plurality of via holes 140 are formed through the dielectric 110 and connect between some points of the conductive metapattern 130 and the surface of the metal reflective layer 120 . Here, the inner wall of the via hole 140 may be coated with copper, silver, gold, iron, or carbon, or filled with copper, silver, gold, iron, or carbon material. Here, the via hole 140 may have a cylindrical columnar or polygonal columnar shape (eg, quadrangular, hexagonal, etc.).

As described above, the upper surface of the dielectric 110 has a mixture of areas filled with a conductive material and areas that are not, which is because in an embodiment of the present invention, a conductive metapattern is formed by a combination of two different types of pixels. according to it

FIG. 2 is a diagram illustrating a method of implementing the conductive meta-pattern shown in FIG. 1 , and FIG. 3 is a diagram explaining the conductive meta-pattern and via hole structure of FIG. 1 in detail.

First, (a) of FIG. 2 shows the concept of designing a pattern through a combination of a parallelogram pixel filled with a conductive material and a parallelogram pixel in an empty state, and (b) shows an actual pattern realized thereby.

The conductive metapattern 130 has a parallelogram-shaped pixel as a basic unit, and specifically, a plurality of parallelogram pixels (first parallelogram pixels; shadow pixels) filled with a conductive material and a plurality of parallelogram pixels in an empty state ( The second parallelogram pixels (blank white pixels) are arranged in combination with each other.

Here, referring to FIG. 3 , the conductive metapattern 130 is based on a hexagonal unit structure in which three parallelogram pixels are in contact with each other, and several of these unit structures meet to form a conductive metapattern. In addition, it can be seen that at least one type of parallelogram pixels of the first and second parallelogram pixels are arranged and formed in each hexagonal unit structure.

For example, the hexagonal unit structure may include a first form (a) composed of only three first parallelogram pixels filled with a conductive material, a second form (b) composed only of three blank second parallelogram pixels, and a first parallelogram pixel structure. It can be divided into a third form (c) composed of a combination of two quadrilateral pixels and one second parallelogram pixel, and a fourth form (d) composed of a combination of one first parallelogram pixel and two second parallelogram pixels.

Accordingly, it can be seen that the above-described hexagonal unit structures of various shapes coexist in the conductive pattern visible in the unit cell.

In addition, as shown in FIGS. 1 and 3 , in the embodiment of the present invention, the plurality of via holes 140 include a plurality of pixels selected from among a plurality of first parallelogram pixels (shaded pixels) constituting the conductive metapattern 130 and a metal reflective layer (120) Connect the liver.

As such, the present invention optimally places parallelogram pixels filled with a conductive material on top of the dielectric 110 to which the metal reflective layer 120 is coupled to the lower surface, and some pixels and the metal reflective layer 120 form a plurality of via holes 140. By connecting to, it is possible to design a metamaterial absorber capable of efficiently absorbing electromagnetic waves incident at a wide angle.

The metamaterial absorber 100 may correspond to one unit cell constituting the absorber, and the designed absorption performance may be implemented by periodically repeating and arranging the unit cells. In the case of an embodiment of the present invention, a hexagonal unit cell structure is illustrated as shown in FIG. 1 . In addition, when a plurality of unit cells having such a hexagonal edge are arranged in a grid, it can be freely implemented to have an arbitrary area required for an absorber.

Of course, the unit cell shape of the metamaterial absorber may be configured not only in a hexagonal shape, but also in a square shape, a rectangular shape, and the like. An exemplary embodiment of the present invention is one having a hexagonal outer shape as shown in FIG. 1 as a representative example.

In an embodiment of the present invention, a unit pixel has a parallelogram shape, and patterns of various shapes may be formed by optimally arranging two types of pixels on top of the dielectric 110 . In addition, it can be implemented in the form of a pattern having symmetry for each of a plurality of regions divided at equal angles based on the center point of the unit cell.

Referring to FIG. 3, the outer shape of the metamaterial absorber is hexagonal. In this case, when the conductive metapattern is divided into three areas with a central angle of 120 ° based on the center of the metamaterial absorber, the pattern shape and It can be seen that the via hole locations have a symmetrical structure between regions.

Specifically, as shown in FIGS. 1 to 3 , two via holes 140 form a pair and exist as a pair in each of the three regions. Referring to FIG. 3 , the conductive metapattern 130 may include first to third pattern portions 130-1, 130-2, and 130-3 respectively formed on first to third regions divided at an angle of 120 degrees. there is.

Here, the first to third pattern portions 130-1, 130-2, and 130-3 are composed of a combination of first and second parallelogram pixels, respectively, and each pattern portion 130-1, 130-2, and 130-3 is itself It is configured to electrically connect upper ends of the pair of via holes H1, H2, and H3 formed on the corresponding region.

At this time, empty second parallelogram pixels are arranged between each of the first to third pattern portions 130-1, 130-2, and 130-3, and a dielectric top surface is formed between each pattern portion 130-1, 130-2, and 130-3. As a standard, they have a structure that is electrically separated from each other. That is, adjacent pattern units (between 130-1 and 130-2, between 130-2 and 130-3, and between 130-3 and 130-1) are configured to be electrically separated from each other.

For example, when viewed from the top, the first pattern unit 130-1 electrically connects upper ends of the pair of via holes H1, and the second pattern unit 130-1 and the second pattern unit ( 130-2) are separated from each other. Hereinafter, the electromagnetic characteristics of the conductive metapattern designed in this way will be described.

FIG. 4 is a view showing a conductive metapattern coupled to an upper surface of the dielectric of FIG. 1 .

As shown in FIG. 4, the conductive metapattern is designed in a symmetrical shape even in the diagonal direction of the metamaterial unit cell. In addition, a plurality of via holes included in the dielectric are connected to the conductive metapattern. The diameter of the via hole exemplifies 0.2 mm.

In the case of the present invention, by using the conductive pattern and the via hole designed on the dielectric substrate, the electromagnetic wave absorption rate can be increased even for the incident electromagnetic wave at a high angle (eg, 60°) that is incident in an oblique direction rather than perpendicular to the surface.

When an electromagnetic wave is incident on the surface in a vertical or oblique direction, a time-varying electric field (Electric, E field) is applied in a direction parallel to the plane including the conductive metapattern of FIG. While forming, a strong induced current is generated in the conductive metapattern of FIG. 4, so that high absorption can be realized through Ohmic loss.

The conductive meta-pattern of FIG. 4 is implemented with carbon, a conductive material with high loss, and the series resonator composed of the self-inductance of the meta-pattern and the capacitance due to the space between the patterns has a low Q factor, resulting in broadband absorption performance. is implemented

In the case of the present invention, both TE and TM polarized waves exhibit broadband absorption performance when they are incident vertically or obliquely. However, as constructive interference between the incident time-varying electric field and the reflected wave reflected from the metal reflective layer 120 is weakened at the time of oblique incidence, the absorptivity may decrease. FIG. 5 shows a case where TE polarized waves are obliquely incident on a conductive metasurface, and FIG. 6 shows a case where TM polarized waves are obliquely incident on a conductive metasurface.

First, FIG. 5 is a schematic diagram of a current induced upon oblique incidence of a TE polarized wave in which a time-varying electric field is formed in a direction perpendicular to an xoz plane and a time-varying magnetic field is formed in a direction perpendicular to a plane including two metal via holes.

5 shows an induced current that can be additionally induced when a time-varying magnetic field (Magnetic, H field) is formed in a direction perpendicular to a plane including a pair of via holes, the upper part of which is connected to a conductive metasurface and the lower part to which a metal reflective layer is connected. A schematic diagram of the distribution is shown.

Since the structure coupled to the top of the metal reflection layer and the current distribution formed according to the mirror image symmetry theory based on the metal reflection layer form a closed curve, current is additionally induced as shown in FIG. 5 by magnetic induction by the time-varying incident magnetic field. It can be. At this time, the induced current is determined by Lenz's law applying the right-hand rule to the time-varying induced magnetic field when the time-varying induced magnetic field is defined in the opposite direction to the time-varying incident magnetic field.

In more detail, when the TE (Transverse electric) polarized wave is obliquely incident as shown in FIG. ) and vertically penetrates a plane including a pair of via holes arranged side by side. That is, when the TE polarized wave is obliquely incident, a magnetic field is formed in a direction perpendicular to the via hole. Therefore, an additional induced current may be generated by magnetic induction according to the principle described above, and the additional induced current may cause additional loss in the conductive metapattern connected to the top of the via hole. Here, loss means absorption of electromagnetic waves. The TE polarization described above refers to electromagnetic waves in which the electric field is fixed in a direction perpendicular to the xoz plane, which is the plane of incidence.

6 is a schematic diagram of a current induced when a TM polarized wave in which a time-varying magnetic field is formed in a direction perpendicular to the xoz plane and a time-varying electric field is formed in a direction parallel to two metal via holes is obliquely incident.

6 shows a current distribution that can be additionally induced when a time-varying electric field is incident in a direction parallel to a metal via hole. When a time-varying electric field is formed in a direction parallel to (horizontal to) the metal via hole, an induced electromotive force is generated along the metal surface, thereby generating an induced current. That is, when the TM polarized wave is obliquely incident, an electric field is formed in a horizontal direction with the via hole.

In more detail, when the transverse magnetic (TM) polarization in FIG. 6 is obliquely incident, the electric field can decompose components in the x-axis and z-axis directions, and since the electric field in the z-axis direction is parallel to the via hole, additional A current can be induced. At this time, the induced current flows into the conductive metapattern connected to the top of the via hole, and may cause additional loss. The TM polarization described above refers to an electromagnetic wave in which the magnetic field is fixed in a direction perpendicular to the xoz plane, which is the incident plane.

7 shows simulation results of the reflectivity of the metamaterial absorber at normal incidence and 60° oblique incidence of TE and TM polarized waves.

From FIG. 7, reflectivity of less than -10 dB was confirmed in the frequency range of 8.8 to 11.6 GHz for both normal incidence and 60° oblique incidence under two polarization conditions. Here, the reflectivity of less than -10dB means that the incident electromagnetic wave is reflected by 10% or less, which means that the absorption rate is high. From FIG. 7, it can be seen that the metamaterial absorber 100 proposed in the present invention has excellent electromagnetic wave absorption performance under wide-angle incidence in the range of 0 ° to 60 ° and broadband frequency in the range of 8.8 to 11.6 GHz.

8 shows absorption simulation results of a metamaterial absorber when incident at an angle of 0° to 60° of TE and TM polarization. From this FIG. 8, it was confirmed that the absorption of 90% or more was confirmed in the frequency range of 8.8 to 11.6 GHz when incident at an angle of 0 ° to 60 ° under the two polarization conditions. From the -10 dB reflectance bandwidth, which is in good agreement with the 90% absorption bandwidth, it can be confirmed that the reduction of the reflected wave is due to the electromagnetic wave absorption effect of the metamaterial absorber. High absorption means that the incident electromagnetic wave is not reflected and most of it is lost (dissipated).

9 shows current distribution simulation results on a conductive metapattern at 9.6 and 11.8 GHz, respectively, when TE and TM polarized waves are incident at a 60° angle. 9 shows current density simulation results on the conductive metapattern at frequencies 9.6 and 11.8 GHz, respectively, where the reflectivity at 60° incidence of TE and TM polarized waves was confirmed to be minimal.

From FIG. 9 , strong current density can be confirmed at the location where the via hole and the conductive metapattern are connected (ie, the via hole point) in both cases when the TE and TM polarized waves are obliquely incident. That is, it can be seen that the embodiment of the present invention shows high radio wave absorption performance not only at normal incidence but also at oblique incidence by adding a plurality of via holes to the conductive metapattern, and shows excellent absorption effects for both TE and TM polarized waves.

As such, the metamaterial absorber including a plurality of via holes proposed in the present invention has an advantage of maintaining excellent absorption performance even under a wide-angle incident condition. In addition, when TE polarized waves are obliquely incident between a pair of via holes, the upper part of which is connected to the conductive metasurface and the lower part is connected to the metal reflective layer, additional current is generated by magnetic induction. An additional current is induced, resulting in increased loss in the upper conductive meta-pattern, which means that it absorbs electromagnetic waves well.

In addition, the proposed metamaterial absorber based on its excellent absorption performance under wide-angle incident conditions can be applied to solving the problem of electromagnetic interference in multi-antenna systems and minimizing the radar reflection area of weapon systems such as fighter jets and ships.

Although the present invention has been described with reference to the embodiments shown in the drawings, this is merely exemplary, and those skilled in the art will understand that various modifications and equivalent other embodiments are possible therefrom. Therefore, the true technical scope of protection of the present invention should be determined by the technical spirit of the appended claims.

100: electromagnetic wave metamaterial absorber
110: dielectric 120: metal reflective layer
130: conductive metapattern 140: via hole

Claims (13)

A metal reflective layer is coupled to the lower surface of the dielectric, and a conductive metapattern made of a conductive material is formed on the upper surface, and a plurality of via holes connecting some points of the conductive metapattern and the surface of the metal reflective layer penetrate the dielectric. has a structure formed,
The conductive metapattern is formed by combining and arranging a plurality of first parallelogram pixels filled with the conductive material and a plurality of second parallelogram pixels in a blank state,
The outer shape is hexagonal, and when the conductive metapattern is divided into three regions with a central angle of 120 ° based on the center, the pattern shape and via hole position in each of the three regions have a symmetrical structure. Electromagnetic wave metamaterial absorber. The method of claim 1,
The dielectric,
An electromagnetic wave metamaterial absorber made of a material including at least one of acrylic, teflon, FR4, PET, styrofoam, foam composite, and glass epoxy. The method of claim 1,
The conductive material,
An electromagnetic wave metamaterial absorber formed of a material containing at least one of carbon, copper (Cu), silver (Ag), gold (Au), graphene, and indium tin oxide (ITO). The method of claim 1,
The via hole,
An electromagnetic wave metamaterial absorber having a structure in which the inner wall is coated or filled with copper, silver, gold, iron or carbon material. delete The method of claim 1,
The plurality of via holes,
An electromagnetic wave metamaterial absorber connecting a plurality of pixels selected from among the plurality of first parallelogram pixels and the metal reflective layer. The method of claim 1,
The conductive metapattern,
An electromagnetic wave metamaterial absorber based on a hexagonal unit structure in which three parallelogram pixels are in contact and formed by arranging at least one type of parallelogram among the first and second parallelograms in each hexagonal unit structure. The method of claim 1,
The outer shape of the metamaterial absorber is a hexagonal shape, a square shape, or a rectangular electromagnetic wave metamaterial absorber. delete The method of claim 1,
The plurality of via holes,
An electromagnetic wave metamaterial absorber in which two form a pair and exist as a pair in each of the three regions. The method of claim 1,
The conductive metapattern,
First to third regions are respectively formed on the first to third regions among the three regions, and are composed of a combination of the first and second parallelogram pixels and electrically connect upper ends of a pair of via holes formed on the corresponding regions. Including a third pattern portion,
An electromagnetic wave metamaterial absorber having a structure in which each of the first to third pattern portions on the dielectric is separated from each other by the second parallelogram pixels in a blank state. The method of claim 1,
The via hole,
An electromagnetic wave metamaterial absorber having a cylindrical column or polygonal column shape. The method of claim 1,
The conductive metapattern,
An electromagnetic wave metamaterial absorber formed in a pattern shown in the drawing below, in which the parallelogram pixels filled with the conductive material and the parallelogram pixels in the empty state are combined with each other.