ELECTROMAGNETIC WAVE ABSORBER

Provided is an electromagnetic wave absorber capable of further expanding applicable objects while reducing a size of a unit structure, and at the same time, improving the degree of freedom in arrangement. An electromagnetic wave absorber 201 includes a substrate 202, a first wiring pattern 203 mounted on one surface of the substrate, and a second wiring pattern 204 mounted on the other surface opposite to the one surface, the first wiring pattern 203 includes a line portion 211 extending in parallel to a direction in which an external electric field is generated, a capacitor portion 212 in which a potential difference is generated by the external electric field, and a first connecting portion 213 and a second connecting portion 214 which connect each of ends of the line portion with the capacitor portion, and the second wiring pattern 204 includes a wire portion 221 which extends in the same direction as the line portion and is arranged at a position opposite to the line portion, and extension portions 222 and 223 that are branched to be bent from ends of the wire portion.

TECHNICAL FIELD

The present technology relates to an electromagnetic wave absorber, and more particularly, to an electromagnetic wave absorber that absorbs an electromagnetic wave using wiring patterns arranged on both surfaces of a substrate.

BACKGROUND ART

In recent years, many electronic devices that emit electromagnetic waves, such as wireless communication devices, medical devices, and home appliances, have been used in various fields. There is a possibility that unnecessary electromagnetic waves emitted by an electronic device causes malfunction in the electronic device, surrounding devices, or the like, or impairs the health of a human body. In order to suppress such an influence, electromagnetic wave absorbers and electromagnetic wave shields that absorb or shield unnecessary electromagnetic waves have been proposed.

For example, Patent Document 1 proposes an electromagnetic wave absorber having a metamaterial structure provided with at least a pair of split ring conductors, opposite to each other with a predetermined gap interposed therebetween, the pair of split ring conductors being electrically connected by a via conductor.

Furthermore, Patent Document 2 proposes an electromagnetic wave shielding material for shielding an electromagnetic wave having a specific frequency, the electromagnetic wave shielding material including a substrate and a plurality of resonance loops arranged on the substrate, the plurality of resonance loops being arranged to be magnetically coupled to each other, and each of the resonance loops being configured to form an LC parallel resonance circuit and resonate at the specific frequency.

Moreover, Non-Patent Document 1 proposes an absorber having a metamaterial structure that almost completely absorbs an electromagnetic wave of a specific linearly polarized wave component incident from one surface without using a lossy material such as ferrite. The absorber of Non-Patent Document 1 does not include a solid GND surface, and thus, can transmit frequencies other than a specific absorption frequency.

CITATION LIST

Patent Document

SUMMARY OF THE INVENTION

Problems to be Solved by the Invention

In the technologies of Patent Document 1 and Patent Document 2, however, a solution for expansion of applicable objects with a size reduction of a unit structure is not proposed, and there is a demand for further development of an electromagnetic wave absorber simultaneously satisfying the both.

Furthermore, the technology of Non-Patent Document 1 can be configured inexpensively only with a substrate on which a metal wiring pattern is drawn, but a periodic structure is required, and thus, it is difficult to obtain a sufficient effect without a certain number of cells. Here, a long side of a size of a unit structure body (unit cell) described in Non-Patent Document 1 is as large as about λ/2, there is a problem that applicable objects are limited when its practical use is considered. For example, assuming that a minimum of 3×3 cells are required to obtain sufficient absorption characteristics, mounting is possible only for an object having a large plane of approximately 1.4λ×0.5λ or more.

Therefore, a main object of the present technology is to provide an electromagnetic wave absorber capable of further expanding applicable objects while reducing a size of a unit structure, and at the same time, improving the degree of freedom in arrangement.

Solutions to Problems

An electromagnetic wave absorber according to the present technology includes: a substrate; a first wiring pattern mounted on one surface of the substrate; and a second wiring pattern mounted on the other surface opposite to the one surface, the first wiring pattern includes a line portion extending in parallel to a direction in which an external electric field is generated, a capacitor portion in which a potential difference is generated by the external electric field, and a first connecting portion and a second connecting portion which connect each of ends of the line portion with the capacitor portion, and the second wiring pattern includes a wire portion which extends in the same direction as the line portion and is arranged at a position opposite to the line portion, and an extension portion that is branched to be bent from an end of the wire portion. Here, the extension portion refers to a wiring portion that has a plurality of bent portions, and thus, has a total length longer than that of a line segment connecting both ends of the extension portion at the shortest distance.

Effects of the Invention

According to the present technology, it is possible to provide the electromagnetic wave absorber capable of further expanding applicable objects while reducing the size of the unit structure, and at the same time, improving the degree of freedom in arrangement. Note that the above-described effect is not necessarily limited, and any effect illustrated in the present specification or other effects that can be grasped from the present specification may be exhibited in addition to the above-described effect or instead of the above-described effect.

MODE FOR CARRYING OUT THE INVENTION

Hereinafter, preferred embodiments for carrying out the present technology will be described with reference to the drawings. The embodiments to be described hereinafter illustrate examples of representative embodiments of the present technology, and can be combined with any embodiment. Furthermore, the scope of the present technology is not narrowly construed by these. Note that a description will be given in the following order.1. First Embodiment(1) Configuration Example of Conventional Electromagnetic Wave Absorber(2) Configuration Example of Electromagnetic Wave Absorber201(3) Operation Example of Electromagnetic Wave Absorber201(4) Configuration Example of Electromagnetic Wave Absorbing Unit200(5) Example (Simulation)2. Second Embodiment3. Other Applicable Uses

1. First Embodiment

(1) Configuration Example of Conventional Electromagnetic Wave Absorber

First, a configuration example of a conventional electromagnetic wave absorber will be described with reference toFIG.1.FIG.1is a schematic view illustrating a configuration example of an electromagnetic wave absorber according to the related art.FIG.1Ais a perspective view illustrating a configuration example of an electromagnetic wave absorbing unit (electromagnetic wave absorbing sheet) according to the related art.FIG.1Bis an enlarged perspective view illustrating a configuration example of the electromagnetic wave absorber which is a unit structure body (unit cell) of the electromagnetic wave absorbing unit illustrated inFIG.1A.

As illustrated inFIG.1A, an electromagnetic wave absorbing unit100according to the related art has, for example, a metamaterial structure in which unit structure bodies each having a size sufficiently smaller than a wavelength of an electromagnetic wave and having a resonator therein are arrayed in a dielectric. Note that, as an example, an interval between the unit structure bodies (resonators) of the metamaterial is set to about 1/10 or less, or about ⅕ or less of the wavelength of the electromagnetic wave to be used.

With such a configuration, a dielectric constant ε and/or a magnetic permeability μ of the metamaterial can be artificially controlled, and a refractive index n (=±[ε·μ]1/2) of the metamaterial can be artificially controlled. In particular, in the metamaterial, the refractive index can be set to a negative value with respect to an electromagnetic wave having a desired wavelength by appropriately adjusting, for example, a shape, a dimension, and the like of the unit structure body to simultaneously achieve a negative dielectric constant and a negative magnetic permeability.

Meanwhile, a resonance (operation) frequency ω of the metamaterial is determined by an inductance L and a capacitance C in a case where the metamaterial is described as a circuit according to the LC circuit theory, and the resonance frequency becomes lower as the inductance L and the capacitance C increase. That is, if a high-density structure with the large inductance L and the large capacitance C is provided, even metamaterial having a small size can function for a wave having a long wavelength (=a low frequency).

As illustrated inFIG.1B, an electromagnetic wave absorber101, which is the unit structure body of the electromagnetic wave absorbing unit100, is formed in a similar configuration as a unit cell described in Non-Patent Document 1, for example. The electromagnetic wave absorber101includes: a substrate102having a rectangular planar shape; a first wiring pattern103mounted on an upper surface of the substrate102on which an electromagnetic wave is incident; and a second wiring pattern104mounted on a lower surface opposite to the upper surface of the substrate102. The first wiring pattern103and the second wiring pattern104are formed using metal wirings as an example.

The first wiring pattern103includes: a line portion111extending in parallel to a direction in which an external electric field is generated; a pair of capacitor portions112in which a potential difference is generated by the external electric field; and a connecting portion113that connects both ends of the line portion111with each of the capacitor portions112.

The line portion111is arranged at a center position of the substrate102in a width direction so as to extend in a direction parallel to an extending direction of the substrate102. The pair of capacitor portions112is arranged symmetrically on both sides of the substrate102in the width direction from the line portion111. The line portion111, the capacitor portion112, and the connecting portion113constitute one closed circuit on each of both sides of the line portion111.

The second wiring pattern104has a wire portion121which extends in the same direction as the line portion111of the first wiring pattern103and is arranged at a position opposite to line portion111. The wire portion121is arranged at a center position of the substrate102in the width direction so as to extend in the direction parallel to the extending direction of the substrate102, which is similar to the line portion111.

As illustrated inFIG.1B, a case is considered in which an external electric field E exists in a direction parallel to the line portion111above the outside of the electromagnetic wave absorber101, an external magnetic field H orthogonal to the external electric field E exists in a width direction of the line portion111, and an electromagnetic wave k is incident on an upper surface of the electromagnetic wave absorber101.

In a case where the electromagnetic wave k is incident on the upper surface of the electromagnetic wave absorber101, first, a current flowing in the extending direction (arrow direction inFIG.1B) of the line portion111of the first wiring pattern103is induced by the external electric field E. Next, an LC resonant current ILCinduced by the external electric field E flows through each of the closed circuits formed on the both sides of the line portion111. Then, ring currents IHthat generate magnetic fields coupled with the external magnetic field H flow through the line portion111and the wire portion121in directions opposite to each other. Therefore, the electromagnetic wave absorber101can absorb the electromagnetic wave k incident on the upper surface and suppress an electromagnetic wave to be transmitted.

Here, as an example, the electromagnetic wave absorber101having a structure similar to that of the unit cell described in Non-Patent Document 1 has a unit cell size of long side 12.0 mm×short side 4.2 mm×thickness 0.65 mm. When a wavelength λ of the electromagnetic wave k is used, the unit cell size can be expressed as long side 0.466λ×short side 0.163λ×thickness 0.0252λ. Therefore, a unit cell size of about λ/2 is required in a long side direction, which corresponds to a size of about 60 mm in the 2.4 GHz band, about 30 mm in the 5 GHz band, and about 5 mm in the 28 GHz band.

Since the metamaterial requires a periodic structure, it is difficult to obtain a sufficient effect of an electromagnetic wave absorption characteristic without a certain number of unit cells. Then, for example, assuming that of 3×3 cells or more of the electromagnetic wave absorbers101are required in order to form the electromagnetic wave absorbing unit100having the metamaterial structure using the electromagnetic wave absorbers101, the electromagnetic wave absorbers101can be applied only to an object having a large mounting surface of 1.4λ×0.5λ or more.

Therefore, an example of a configuration of an electromagnetic wave absorber capable of further expanding applicable objects while reducing a size of the electromagnetic wave absorber, which is a unit structure body of the metamaterial, and at the same time, improving the degree of freedom in arrangement will be described in the present embodiment.

(2) Configuration Example of Electromagnetic Wave Absorber201

A configuration example of an electromagnetic wave absorber201according to a first embodiment of the present technology will be described with reference toFIGS.2and3.FIG.2is a perspective view illustrating a configuration example of the electromagnetic wave absorber201according to the present embodiment.FIG.3Ais a plan view illustrating one surface of a substrate on which a first wiring pattern of the electromagnetic wave absorber201is mounted.FIG.3Bis a plan view illustrating the other surface of the substrate on which a second wiring pattern of the electromagnetic wave absorber201is mounted. The electromagnetic wave absorber201is a unit structure body of a metamaterial, and can control a pulse of an electromagnetic wave, a sound wave, or the like.

As illustrated inFIG.2, the electromagnetic wave absorber201includes, as an example, a substrate202having a rectangular planar shape, a first wiring pattern203mounted on an upper surface which is one surface of the substrate102on which an electromagnetic wave is incident, and a second wiring pattern204mounted on a lower surface which is the other surface opposite to the one surface of the substrate102. The first wiring pattern203and/or the second wiring pattern204are formed in a metamaterial structure, as an example.

As an example, the substrate202is a multilayer substrate having the upper surface and the lower surface, and can be manufactured by a general manufacturing method such as bonding dielectric substrates to each other with an adhesive. An aspect ratio (long side/short side) of the substrate202according to the present embodiment is 1.5 or more. Therefore, the electromagnetic wave absorber201having a smaller area can be achieved.

Here, in a case where the substrate202is such thick that it is difficult to ignore a phase difference of an external electromagnetic field between the surface of the first wiring pattern203and the surface of the second wiring pattern204, coupling with an external magnetic field is weakened, which leads to a decrease in an absorption rate. From this viewpoint, it is preferable not to thicken the substrate202above a certain extent. Therefore, as an example, the thickness of the substrate202is formed to be thinner than ⅕ of an effective wavelength. Therefore, it is possible to maintain a high absorption rate.

As illustrated inFIGS.2and3A, the first wiring pattern203includes: a line portion211extending in parallel to a direction in which an external electric field is generated; a pair of capacitor portions212in which a potential difference is generated by the external electric field; and a first connecting portion213and a second connecting portion214that connect both ends of the line portion211with each of the capacitor portions212.

A first meandering portion215meandering to extend a wiring length is formed between the capacitor portion212and the first connecting portion213. Similarly, a second meandering portion216meandering to extend a wiring length is formed between the capacitor portion212and the second connecting portion214. Here, the meandering portion refers to a wiring portion that has a plurality of zigzag bent portions, and thus, has a total length longer than that of a line segment connecting both ends of the meandering portion at the shortest distance. Note that shapes of the first meandering portion215and the second meandering portion216are not limited to shapes of the present embodiment, and may be any shape that extends a wiring length.

The line portion211is arranged at a center position of the substrate202in a width direction so as to extend in a direction parallel to an extending direction of the substrate202. The pair of capacitor portions212is arranged symmetrically on both sides of the substrate202in the width direction from the line portion211. The line portion211, the capacitor portion212, the first connecting portion213, the first meandering portion215, the second connecting portion214, and the second meandering portion216constitute one closed circuit C1on each of both sides of the line portion211. It is preferable to set a high density such that a total wiring length of the first meandering portion215and the second meandering portion216in the closed circuit C1is twice or more a length of the line portion211in the extending direction. Furthermore, a width of the line portion211is preferably wider than widths of the other wiring parts of the first wiring pattern203.

As illustrated inFIGS.2and3B, the second wiring pattern204includes a wire portion221that extends in the same direction as the line portion211of the first wiring pattern203and is arranged at a position opposite to the line portion211.

The wire portion221is arranged at a center position of the substrate202in the width direction so as to extend in the direction parallel to the extending direction of the substrate202, which is similar to the line portion211. The second wiring pattern204includes a first extension portion222and a second extension portion223which are branched to be bent symmetrically from both ends of the wire portion221in the width direction. The first extension portion222and the second extension portion223are arranged at effective positions on a lower surface of the electromagnetic wave absorber201.

The wire portion221, the first extension portion222, and the second extension portion223constitute one open circuit on each of both sides of the wire portion221. Furthermore, a width of the wire portion221is preferably wider than widths of the other wiring parts of the second wiring pattern204. Note that shapes of the first extension portion222and the second extension portion223are not limited to shapes of the present embodiment, and may be any shape that extends a wiring length.

Each distal end of the first extension portion222extends toward one end of the substrate202in the extending direction. Each distal end of the second extension portion223extends toward the other end of the substrate202in the extending direction. The first extension portion222and the second extension portion223are formed in a high-density structure, and are arranged at positions not to overlap with the capacitor portion212, the first connecting portion213, and the second connecting portion214. Here, the high density means that the total wiring length of the extension portions is equal to or longer than the length of the wire portion, for example, twice or more. Therefore, unnecessary resonance between the upper and lower surfaces of the substrate202is prevented, and electromagnetic coupling that is difficult to control is reduced, and thus, a desired characteristic is easily achieved.

As described above, the first wiring pattern203is formed to be symmetric with respect to a central axis in the width direction and/or a central axis in the extending direction of line portion211. Furthermore, the second wiring pattern204is formed to be symmetric with respect to a central axis in the width direction and/or a central axis in the extending direction of the wire portion221. Note that a thickness of the second wiring pattern204is preferably larger than a thickness of the first wiring pattern203. As the thickness increases, a resistance of such a part decreases, and thus, a current can easily flow by the second wiring pattern204. Therefore, the electromagnetic wave absorber201is easily coupled to the external magnetic field since the current easily flows through the wire portion221, and as a result, the absorption rate can be increased.

(3) Operation Example of Electromagnetic Wave Absorber201

Next, an operation example of the electromagnetic wave absorber201according to the present embodiment will be described with reference toFIGS.2and3. Similarly toFIG.1B, a case is considered in which an external electric field E exists in a direction parallel to the line portion211above the outside of an upper surface of the electromagnetic wave absorber201, an external magnetic field H orthogonal to the external electric field E exists in a width direction of the line portion211, and an electromagnetic wave k is incident on an upper surface of the electromagnetic wave absorber201.

In a case where the electromagnetic wave k is incident on the upper surface of the electromagnetic wave absorber201, first, a current flowing in the extending direction of the line portion211of the first wiring pattern203is induced by the external electric field E. Next, an LC resonant current ILc induced by the external electric field E flows through each of the closed circuits C1formed on the both sides of the line portion211.

In this manner, each of the closed circuits C1operates as an LC resonance circuit by making the potential difference in each of the capacitor portions212by the electromagnetic wave k incident on the upper surface of the electromagnetic wave absorber201. When a capacitance of each of the capacitor portions212is C, and a total inductance of the respective closed circuits C1is L, a resonance frequency f at this time is expressed by the following Formula (1).

The electromagnetic wave absorber201can increase the inductance L of the closed circuit C1by forming the first meandering portion215and the second meandering portion216in each of the closed circuits C1of the first wiring pattern203, and thus, a lower resonance frequency f can be achieved as compared with the related art. Therefore, when compared at the same resonance frequency f, the electromagnetic wave absorber201can be formed to be smaller than that in the related art.

Moreover, ring currents IHthat generate magnetic fields coupled with the external magnetic field H flow through the line portion211and the wire portion221of the second wiring pattern204in directions opposite to each other in the extending direction. In this manner, in the electromagnetic wave absorber201, the current flows through the wire portion221in the opposite direction to the line portion211, and the magnetic field in a direction parallel to a width direction of the electromagnetic wave absorber201formed by the ring current IHis coupled with the external magnetic field H, thereby generating an effect of absorbing the incident electromagnetic wave k.

At this time, in order to facilitate the coupling with the external magnetic field H, an electrical length of the open circuit including the wire portion221needs to be sufficiently long. Since the electromagnetic wave absorber201has the first extension portion222and the second extension portion223branched to be bent from both the ends of the wire portion221on both the sides in the width direction, the coupling with the external magnetic field H can be facilitated similarly to or more than the related art even if the size of the electromagnetic wave absorber201in the extending direction is reduced.

Therefore, the electromagnetic wave absorber201can be formed to have a size smaller than λ/2 in the extending direction, the size being about λ/2 in the related art, for example. That is, in a case of being manufactured to have the same size as that of the related art, the electromagnetic wave absorber201can be operated at a lower frequency than that of the related art.

With the electromagnetic wave absorber201according to the present embodiment, each of two wiring surfaces is formed in the high-density structure having the meandering portion and the extension portion, the unit cell size can be greatly reduced as compared with the related art while maintaining electromagnetic wave absorption performance. Therefore, according to the electromagnetic wave absorber201, applicable objects can be expanded as compared with the related art while reducing the size of the unit structure, and at the same time, the degree of freedom in arrangement can be improved. Note that the electromagnetic wave absorber201can reflect an electromagnetic wave as well as absorb an electromagnetic wave.

(4) Configuration Example of Electromagnetic Wave Absorbing Unit200

Next, a configuration example of an electromagnetic wave absorbing unit (electromagnetic wave absorbing sheet)200according to the present embodiment will be described with reference toFIG.4.FIG.4Ais a schematic view illustrating a configuration example of the electromagnetic wave absorbing unit100according to the related art.FIG.4Bis a schematic view illustrating a configuration example of the electromagnetic wave absorbing unit200according to the present embodiment.

As illustrated inFIG.4A, the electromagnetic wave absorbing unit100according to the related art is formed, for example, in a periodic structure in which the electromagnetic wave absorbers101are periodically arrayed. Furthermore, a cell region S1indicates a region having a size of 3×3 cells of the electromagnetic wave absorbers101in the electromagnetic wave absorbing unit100. An area of the electromagnetic wave absorber101having a size similar to that of the unit cell described in Non-Patent Document 1 is long side 0.466λ×short side 0.163λ (with thickness 0.0252λ) as described above.

As illustrated inFIG.4B, the electromagnetic wave absorbing unit200according to the present embodiment is formed, for example, in a periodic structure in which the electromagnetic wave absorbers201are periodically arrayed. Furthermore, a cell region S2indicates a region having a size of 3×3 cells of the electromagnetic wave absorbers201in the electromagnetic wave absorbing unit200. An area of the electromagnetic wave absorber101having an effect similar to that of the electromagnetic wave absorber101according to the related art can be set to long side 0.177λ×short side 0.0887λ (with thickness 0.0355λ) by having the above-described configuration.

In this manner, the electromagnetic wave absorbing unit200has an area ratio of about 21% (volume ratio of about 29%) as compared with the electromagnetic wave absorbing unit100according to the related art, and can be greatly reduced in size. Therefore, the electromagnetic wave absorbing unit200can further expand applicable objects, and at the same time, can improve the degree of freedom in arrangement.

Next, an example (simulation) of an electromagnetic wave absorption rate of an electromagnetic wave absorbing unit300using the electromagnetic wave absorber201according to the present embodiment will be described.FIG.5Ais a schematic view illustrating a structure in which periodic boundary conditions are set on both side surfaces of the electromagnetic wave absorber201in the width direction.FIG.5Bis a schematic view illustrating a structure in which periodic boundary conditions are set on both end surfaces of the electromagnetic wave absorber201in the extending direction.

First, a technique of the present example (simulation) will be described. Three-dimensional electromagnetic field analysis by a finite element method (FEM) is used as an analysis technique of the present embodiment. Furthermore, a high frequency structure simulator (HFSS) is used as software of the present example.

The electromagnetic wave absorbing unit300having the electromagnetic wave absorber201as a unit structure body is used for modeling of the present example. The electromagnetic wave absorber201of the present example has a size of long side 8 mm×short side 4 mm×thickness 1.6 mm, and a dielectric constant εr=3.66. In the present example, the electromagnetic wave absorber201is operated at a frequency of 6.65 GHz. Note that an aspect ratio (long side/short side) of the substrate202according to the present example is set to 2. Here, in the present example, effective wavelength=wavelength λ/(3.66)1/2≈23.6 mm. Therefore, an effective wavelength ratio of the thickness is approximately 1/15, and an effective wavelength ratio of the short side is approximately 1/6.

As illustrated inFIG.5A, the electromagnetic wave absorbing unit300includes the electromagnetic wave absorber201and periodic boundary condition surfaces301set on both the side surfaces of the electromagnetic wave absorber201in the width direction. Here, the periodic boundary condition is a condition that electromagnetic fields of opposite surfaces are the same, and this enables a simulation of an infinite periodic structure. Furthermore, as illustrated inFIG.5B, the electromagnetic wave absorbing unit300may include periodic boundary condition surfaces302set on both the end surfaces of the electromagnetic wave absorber201in the extending direction.

Moreover, air regions (or vacuum regions) R1and R2are formed above and below the electromagnetic wave absorber201of the electromagnetic wave absorbing unit300. Each of the air regions R1and R2only needs to be formed at a height of λ/4 or more in the vertical direction.

Next, with reference toFIG.6, setting of a surface called a port as an inlet or an outlet of power to a system of the electromagnetic wave absorbing unit300will be described.FIG.6Ais a schematic view illustrating a structure in which a power port is set above the electromagnetic wave absorber201.FIG.6Bis a schematic view illustrating a structure in which a power port is set below the electromagnetic wave absorber201. In the present example, a technique called “Floquet Port” used in combination with the periodic boundary conditions301and302illustrated inFIG.5is used for the electromagnetic wave absorbing unit300having the periodic structure such as a metamaterial.

As illustrated inFIG.6A, the electromagnetic wave absorbing unit300includes a power port surface303above the electromagnetic wave absorber201. Furthermore, as illustrated inFIG.6B, the electromagnetic wave absorbing unit300includes a power port surface304below the electromagnetic wave absorber201. The power port surfaces303and304are the inlet and outlet of power to the system of the electromagnetic wave absorbing unit300.

Since a value obtained from an analysis result according to the present example is an S parameter that is electrical power balance between the power port surface303and the power port surface304, characteristics including air characteristics of the upper surface and the lower surface of the substrate202of the electromagnetic wave absorber201appear. However, a value to be desirably obtained is a characteristic of only the substrate202.

Therefore, a transfer coefficient of air is subtracted from the value obtained from the analysis result to extract the characteristic of only the substrate202. From the S parameter of only the substrate202thus obtained, an absorption rate (Abs) of an electromagnetic wave with respect to an incident wave from the power port surface303is calculated by the following Formula (2).

Here, in Formula (2), a transfer coefficient of the upper surface of the substrate202is set to S11, and a transfer coefficient of the lower surface is set to S21.

Next, an electromagnetic wave absorption rate of the electromagnetic wave absorber201in the electromagnetic wave absorbing unit300according to the present example will be described with reference toFIG.7.FIG.7is a graph illustrating a relationship between a frequency at which the electromagnetic wave absorber201is operated and an electromagnetic wave absorption rate. The horizontal axis inFIG.7indicates the frequency at which the electromagnetic wave absorber201is operated. The vertical axis inFIG.7indicates the electromagnetic wave absorption rate of the electromagnetic wave absorber201.

A curve L1and a curve L2illustrated inFIG.7represent absorption rates with respect to the incident wave from the power port surface303due to a difference in “polarized wave” of the electromagnetic wave absorbed by the electromagnetic wave absorber201. Similarly to the electromagnetic wave illustrated inFIG.1A, the curve L1represents the absorption rate for a polarized wave in which a long side direction of the electromagnetic wave absorber201coincides with a vector of the electric field E. A curve L2represents an absorption rate for a polarized wave in which directions of vectors of the electric field E and the magnetic field H are reversed from those of the electromagnetic wave illustrated inFIG.1A.

As illustrated inFIG.7, in the case of the curve L1, the frequency has a peak in the vicinity of 6.65 GHz, and the electromagnetic wave absorption rate is 95% or more (0.9534). On the other hand, in the case of the curve L2, the frequency has a peak in the vicinity of 9.95 GHz, and the electromagnetic wave absorption rate is 8% or less (less than 0.08).

According to the present example, it has been found that the electromagnetic wave absorbing unit300formed in the periodic structure of the electromagnetic wave absorbers201can absorb the polarized wave of the electromagnetic wave in which the vector of the electric field E coincides with the long side direction of the electromagnetic wave absorber201with extremely high accuracy.

2. Second Embodiment

Next, a configuration example of an electromagnetic wave absorber401according to a second embodiment of the present technology will be described with reference toFIG.8.FIG.8Ais a plan view illustrating one surface of a substrate on which a first wiring pattern of the electromagnetic wave absorber401is mounted.FIG.8Bis a plan view illustrating the other surface of the substrate on which a second wiring pattern of the electromagnetic wave absorber401is mounted.

The electromagnetic wave absorber401is different from the electromagnetic wave absorber201according to the first embodiment in that the first wiring pattern and the second wiring pattern are asymmetrically formed on the respective surfaces. The other configurations of the electromagnetic wave absorber401are similar to the configurations of the electromagnetic wave absorber201.

As illustrated inFIGS.8A and8B, the electromagnetic wave absorber401includes, as an example, a substrate402having a rectangular planar shape, a first wiring pattern403mounted on an upper surface which is one surface of the substrate402on which an electromagnetic wave is incident, and a second wiring pattern404mounted on a lower surface which is the other surface opposite to the one surface of the substrate402. The first wiring pattern403and/or the second wiring pattern404are formed in a metamaterial structure, as an example.

As illustrated inFIG.8A, the first wiring pattern403includes: a line portion411extending in parallel to a direction in which an external electric field is generated; a capacitor portion412in which a potential difference is generated by the external electric field; and a first connecting portion413and a second connecting portion414that connect both ends of the line portion411with the capacitor portion412. A meandering portion415meandering to extend a wiring length is formed between the capacitor portion412and the first connecting portion413.

As an example, the line portion411is arranged to extend in a direction parallel to an extending direction of the substrate402on the right side in a width direction of the substrate402with respect to the paper surface ofFIG.8A. The capacitor portion412is arranged on the left side in the width direction of the substrate402with respect to the paper surface ofFIG.8A.

In the first wiring pattern403, the line portion411, capacitor portion412, the first connecting portion413, the second connecting portion414, and the meandering portion415constitute one closed circuit C2. A total wiring length of the meandering portion415in the closed circuit C2is formed to be twice or more a length of the line portion411in an extending direction. Furthermore, a width of the line portion411is formed to be wider than widths of the other wiring parts of the first wiring pattern403.

As illustrated inFIG.8B, the second wiring pattern404includes a wire portion421that extends in the same direction as the line portion411of the first wiring pattern403and is arranged at a position opposite to the line portion411.

The wire portion421is arranged to extend in the direction parallel to the extending direction of the substrate402on the right side of the substrate402in the width direction, which is similar to the line portion411. The second wiring pattern404includes a first extension portion422and a second extension portion423which are branched to be bent from both ends of the wire portion421. The first extension portion422has a meandering portion having a zigzag shape. Note that the second extension portion423may be formed in a shape including a meandering portion.

In the second wiring pattern404, the wire portion421, the first extension portion422, and the second extension portion423constitute one open circuit. Furthermore, a width of the wire portion421is formed to be wider than widths of the other wiring parts of the second wiring pattern404.

A distal end of the first extension portion422extends toward one end of the substrate402in the extending direction. A distal end of the second extension portion423extends toward the other end of the substrate402in the extending direction. It is preferable that the first extension portion422and the second extension portion423be formed in a high-density structure, and be arranged at positions not to overlap with the capacitor portion412, the first connecting portion413, and the second connecting portion414.

Note that a thickness of the second wiring pattern404is formed to be thicker than a thickness of the first wiring pattern403. As the thickness increases, a resistance of such a part decreases, and thus, a current can easily flow.

With the electromagnetic wave absorber401according to the present embodiment, a unit cell size can be greatly reduced as compared with the related art while maintaining electromagnetic wave absorption performance, which is similar to the electromagnetic wave absorber201according to the first embodiment. Therefore, according to the electromagnetic wave absorber401, applicable objects can be expanded as compared with the related art while reducing a size of a unit structure, and at the same time, the degree of freedom in arrangement can be improved.

3. Other Applicable Uses

Next, applicable uses of a metamaterial having the electromagnetic wave absorbers according to the above-described embodiments of the present technology will be described.

Conventionally, it has been proposed to use a metamaterial having characteristics of a negative refractive index and the like for reflection, shielding, absorption, phase modulation, and the like of various waves including radio waves, light waves, and sound waves. Here, the metamaterial refers to an artificial structure body that generates a function that is hardly exhibited with a substance existing in nature. The metamaterial is produced to exhibit an unnatural property, for example, by arraying unit microstructure bodies such as metal, a dielectric, a magnetic body, a semiconductor, and a superconductor at sufficiently short intervals with respect to a wavelength. The metamaterial thus produced can control pulses of electromagnetic waves or the like by controlling a dielectric constant and a magnetic permeability.

Therefore, the metamaterial having the electromagnetic wave absorbers according to the above-described embodiments can be applied to uses including a pulse control device that performs transmission and reception or light reception and emission, a small antenna, a low-height antenna, a frequency selection filter, an artificial magnetic conductor, an electro-band gap member, an anti-noise member, an isolator, a radio wave lens, and a radar member, an optical lens, an optical film, an optical element for terahertz, a radio wave and optical camouflage/non-visualization member, a heat dissipation member, a heat shielding member, a heat storage member, modulation and demodulation of electromagnetic waves, wavelength conversion, a non-linear device, a speaker, and the like in addition to sensors such as an ETC and a radar.

Note that the present technology can have the following configurations.

An electromagnetic wave absorber including: a substrate; a first wiring pattern mounted on one surface of the substrate; and a second wiring pattern mounted on another surface opposite to the one surface,in which the first wiring pattern includes a line portion extending in parallel to a direction in which an external electric field is generated, a capacitor portion in which a potential difference is generated by the external electric field, and a first connecting portion and a second connecting portion which connect each of ends of the line portion with the capacitor portion, andthe second wiring pattern includes a wire portion which extends in the same direction as the line portion and is arranged at a position opposite to the line portion, and an extension portion that is branched to be bent from an end of the wire portion.

The electromagnetic wave absorber according (1), in which the first connecting portion and/or the second connecting portion includes a meandering portion formed in a zigzag manner.

The electromagnetic wave absorber according (2), in which a total wiring length of the meandering portion is twice or more a length of the line portion.

The electromagnetic wave absorber according to any one of (1) to (3), in which the extension portion is formed in a high-density structure.

The electromagnetic wave absorber according to any one of (1) to (4), in which the extension portion is arranged at a position not to overlap with the capacitor portion, the first connecting portion, and the second connecting portion.

The electromagnetic wave absorber according to any one of (1) to (5), in which a width of the line portion and/or the wire portion is wider than widths of other wiring parts of each of the wiring patterns.

The electromagnetic wave absorber according to any one of (1) to (6), in which the first wiring pattern is formed symmetrically with respect to a central axis in a width direction or a central axis in an extending direction of the line portion.

The electromagnetic wave absorber according to any one of (1) to (7), in which the second wiring pattern is formed symmetrically with respect to a central axis in a width direction or a central axis in an extending direction of the wire portion.

The electromagnetic wave absorber according to any one of (1) to (8), in which a thickness of the second wiring pattern is thicker than a thickness of the first wiring pattern.

The electromagnetic wave absorber according to any one of (1) to (9), in which the first wiring pattern and/or the second wiring pattern is formed using a metamaterial.

The electromagnetic wave absorber according to any one of (1) to (10), in which the substrate has an aspect ratio (long side/short side) of 1.5 or more.

The electromagnetic wave absorber according to any one of (1) to (11), in which a thickness of the substrate is thinner than ⅕ of an effective wavelength.

REFERENCE SIGNS LIST