Electromagnetic wave absorber

Abstract

The electromagnetic wave absorber (1) is an SIW resonator (20) having a surface conductor layer (21) in which a coupling slot (23) through which electromagnetic waves are introduced is formed, a back conductor layer (26) arranged opposite the surface conductor layer, and a through conductor (22) electrically connecting the surface conductor layer and the back conductor layer, and is provided with a plurality of resonator units (10) in which SIW resonators having mutually different resonant frequencies are arranged in multiple stages in the short direction of the coupling slot, and the plurality of resonator units are arranged in a plane such that the longitudinal directions of the coupling slots belonging to each resonator unit are oriented in two or more directions.

Description

[Technical field]

[0001] The present disclosure relates to an electromagnetic wave absorber. [Background technology]

[0002] With regard to the electromagnetic wave absorber according to the present disclosure, for example, Patent Document 1 discloses an invention (hereinafter also referred to as the "conventional invention") relating to a method for constructing a radio wave absorber. In the case where a radio wave absorber is formed by stacking high-permeability amorphous alloy ribbons in the direction in which the surface of a panel is extended, and the lamination lines are all arranged in the same direction to form a radio wave absorbing layer, the radio wave absorbing characteristics deteriorate when the polarization of the radio wave is not limited to only horizontal or vertical. In view of this, the conventional invention has been made with the objective of providing a method for constructing a radio wave absorber that can obtain good radio wave absorbing characteristics even when the polarization of the radio wave is not limited to only horizontal or vertical. To solve this problem, the conventional invention arranges panel-shaped radio wave absorbers having the above-mentioned configuration in a checkerboard pattern, with the lamination lines of the alloy ribbons of each radio wave absorber being oriented at right angles to each other, and sticks them to the exterior wall surface of a building or the like. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 5-335778 Summary of the Invention [Problem to be solved by the invention]

[0004] The conventional invention, by being provided with the above-mentioned configuration, realizes radio wave absorbing characteristics that are not dependent on the polarization direction of radio waves incident on the radio wave absorber. Also, in the conventional invention, the metallic magnetic material is made into the above-mentioned amorphous ribbon, thereby realizing radio wave absorbing characteristics in a frequency band of 100 MHz to 1 GHz. However, in the conventional invention, the frequency band depends on the properties of the metallic magnetic material, and it is difficult to flexibly set the frequency band of radio waves to be absorbed, for example, when it is desired to absorb radio waves in a specific frequency band within the above frequency band, or when it is desired to absorb radio waves in a specific frequency band other than the above frequency band.

[0005] The present disclosure has been made to solve the above-mentioned problems, and aims to obtain an electromagnetic wave absorber that is not dependent on the polarization direction of the incident electromagnetic wave and that allows the frequency band of the electromagnetic wave to be absorbed to be set more flexibly than before. [Means for solving the problem]

[0006] The electromagnetic wave absorber according to the present disclosure is an SIW resonator having a surface conductor layer in which a coupling slot through which an electromagnetic wave is introduced is formed, a back conductor layer disposed opposite to the surface conductor layer, and a through conductor electrically connecting the surface conductor layer and the back conductor layer, and includes a plurality of resonator units each formed by arranging SIW resonators having mutually different resonance frequencies in multiple stages in the short side direction of the coupling slot, and the plurality of resonator units are arranged in a plane such that the longitudinal directions of the coupling slots belonging to each resonator unit are oriented in two or more directions. The length of the coupling slot in the longitudinal direction is longer than 1 / 2 wavelength at the resonant frequency of the SIW resonator having the coupling slot. . Effect of the Invention

[0007] According to the present disclosure, it is possible to obtain an electromagnetic wave absorber that is not dependent on the polarization direction of the incident electromagnetic wave and that allows the frequency band of the electromagnetic wave to be absorbed to be set more flexibly than ever before. [Brief description of the drawings]

[0008] [Figure 1] 1 is a plan view showing a configuration example of an electromagnetic wave absorber according to a first embodiment. [Diagram 2] 2 is a diagram illustrating a configuration example of a resonator unit according to the first embodiment. FIG. [Diagram 3] FIG. 3A is a plan view of the SIW resonator according to the first embodiment, and FIG. 3B is a cross-sectional view taken along line AA in FIG. 3A. [Figure 4] FIG. 11 is a diagram showing an example of a case where the longitudinal direction of an open coupling slot is restricted in the first embodiment. [Diagram 5] 5A and 5B are diagrams showing the results of an experiment for measuring the electromagnetic wave absorption characteristics of the electromagnetic wave absorber according to the first embodiment. [Figure 6] 6A to 6C are diagrams showing the results of an experiment for measuring the electromagnetic wave absorption characteristics of the electromagnetic wave absorber according to the first embodiment. [Figure 7] FIG. 4 is a diagram showing the results of an experiment for measuring the absorption characteristics of an electromagnetic wave by the electromagnetic wave absorber according to the first embodiment. [Figure 8] FIG. 11 is a plan view showing a configuration example of an electromagnetic wave absorber according to a second embodiment. [Figure 9] FIG. 11 is a plan view showing a configuration example of an electromagnetic wave absorber according to a third embodiment. [Figure 10] FIG. 10A is a plan view of the SIW resonator according to the third embodiment, and FIG. 10B is a cross-sectional view of the SIW resonator according to the third embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. Embodiment 1

[0010] Fig. 1 is a plan view showing a configuration example of an electromagnetic wave absorber 1 according to embodiment 1. The electromagnetic wave absorber 1 is configured in a flat plate shape, for example, as shown in Fig. 1. Electromagnetic waves propagate through this electromagnetic wave absorber 1 in a direction from the front side to the back side of the paper surface of Fig. 1.

[0011] Specifically, the electromagnetic wave absorber 1 includes a plurality (100 in the example of FIG. 1) of sets of SIW resonators (hereinafter also referred to as "resonator units") 10 configured by stacking SIW resonators having mutually different resonance frequencies. The electromagnetic wave absorber 1 is configured by arranging these plurality of resonator units 10 in a planar manner on a base substrate. Hereinafter, first, the resonator unit 10 and the SIW resonators constituting the resonator unit 10 will be described.

[0012] <Resonator unit 10> A configuration example of the resonator unit 10 is shown in FIG. 2. The resonator unit 10 is configured by stacking SIW resonators having mutually different resonance frequencies. In FIG. 2, as an example, a configuration example of the resonator unit 10 in which SIW resonators having mutually different resonance frequencies are stacked in four stages is shown.

[0013] As shown in FIG. 2, the resonator unit 10 is configured by stacking four SIW resonators 20 having mutually different resonance frequencies in the short side direction (Y direction shown in FIG. 2) of a coupling slot 23 described later. At this time, the four coupling slots 23 belonging to the resonator unit 10 are all oriented in the same direction in the longitudinal direction (X direction shown in FIG. 2). Thereby, the resonator unit 10 has a predetermined resonance frequency band, and a broadband absorption effect obtained by adding the electromagnetic wave absorption characteristics of each of the four SIW resonators 20 can be realized.

[0014] <SIW resonator 20> Next, a configuration example of the SIW resonator 20 will be described with reference to FIG. 3. FIG. 3A is a plan view of the SIW resonator 20, and FIG. 3B is a cross-sectional view taken along line A-A in FIG. 3A. As shown in FIG. 3A, the SIW resonator 20 has a rectangular (rectangular) planar shape.

[0015] The SIW resonator 20 includes a multilayer dielectric substrate 27 and a through-hole row (through conductor) 22.

[0016] Multilayer dielectric substrate 27 has, for example, four dielectric layers sandwiched between two different layers of five conductor layers, and two adjacent dielectric layers included in these four dielectric layers are partially joined. Of the five conductor layers, a surface conductor layer is disposed on the main surface of multilayer dielectric substrate 27, and solid conductor pattern 26, which is a back conductor layer, is disposed on the back surface. Fig. 3A shows a plan view including surface conductor pattern 21, which is a surface conductor layer.

[0017] 3A, a surface conductor pattern 21 having a through hole row 22 and a coupling slot (coupling hole) 23 is disposed on the main surface of a multilayer dielectric substrate 27. The through hole row 22 is disposed in a rectangular (oblong) shape along the outer edge of the surface conductor layer disposed on the main surface of the multilayer dielectric substrate 27. The coupling slot 23 is disposed on a side closer to one of the longitudinal sides of the rectangularly disposed through hole row 22. In this case, the longitudinal direction of the coupling slot 23 and the longitudinal direction of the through hole row 22 are parallel, and the longitudinal direction of the coupling slot 23 and the transverse direction of the through hole row 22 are perpendicular to each other.

[0018] One coupling slot 23 is disposed in the surface conductor pattern 21 surrounded by the through-hole row 22. As a result, the main surface of the multilayer dielectric substrate 27 surrounded by the through-hole row 22 has a region where the surface conductor pattern 21, which is the surface conductor layer, is formed, and a dielectric exposure region where the dielectric layer is exposed by the coupling slot 23.

[0019] The row of penetrating through holes 22 is a penetrating conductor layer that electrically connects a surface conductor layer located on the main surface of the multilayer dielectric substrate 27 and a solid conductor pattern 26, which is a back conductor layer located on the surface opposite the main surface of the multilayer dielectric substrate 27.

[0020] 3B, the SIW resonator 20 has an electrically closed region inside the multilayer dielectric substrate 27 by the penetrating through-hole row 22, the surface conductor pattern 21, the inner layer conductor patterns 24 of the second to fourth layers, and the back surface solid conductor pattern 26. Here, the penetrating through-hole row 22 electrically connects the surface conductor layer and the back surface conductor layer, thereby forming an electrically closed region together with the surface conductor layer and the back surface conductor layer.

[0021] Moreover, two adjacent dielectric layers among the four dielectric layers 25 are each coupled at an inner layer coupling hole 28 located inside an electrically closed region. As a result, in the SIW resonator 20, as shown in Fig. 3B, the electromagnetic wave propagation path (indicated by dotted arrows in Fig. 3B) inside the multilayer dielectric substrate 27 from the coupling slot 23 to the rear conductor layer is configured to be folded three times. In this case, the thickness of the SIW resonator 20 (the length in the Z direction shown in Fig. 3B) is approximately 2.0 mm to 3.0 mm.

[0022] Moreover, a certain SIW resonator 20 is designed so that the distance L1 between both sides in the short-side direction is approximately 1 / 16 of the wavelength at frequency f1. Moreover, in this SIW resonator 20, the length of the coupling slot 23 in the long-side direction (symbol Ls in FIG. 3A) is formed to be longer than 1 / 2 the wavelength at frequency f1. Furthermore, in the SIW resonator 20, the length of the propagation path inside the multilayer dielectric substrate 27 (dotted arrow in FIG. 3B) is a length equivalent to 1 / 4 of the wavelength at frequency f1.

[0023] As a result, cavity resonance occurs in the SIW resonator 20 at frequency f1, and the electromagnetic wave of frequency f1 incident on the SIW resonator 20 is absorbed. That is, the SIW resonator 20 alone can achieve electromagnetic shielding characteristics having an extreme value at frequency f1. In particular, in the SIW resonator 20, the longitudinal length of the coupling slot 23 is formed to be longer than 1 / 2 the wavelength at frequency f1, so that the electromagnetic wave of frequency f1 can be efficiently absorbed.

[0024] In the resonator unit 10, the resonant frequencies of the four SIW resonators 20 are made different from each other, for example, at frequencies f1 to f4, so that the resonator unit 10, which is a multi-stage resonator having four SIW resonators, can realize wideband electromagnetic shielding characteristics having extreme values ​​at frequencies f1 to f4. In this case, in the resonator unit 10, the intervals L1 to L4 between both sides of each SIW resonator 20 in the short-side direction are designed to be approximately 1 / 16 wavelength at each of the resonant frequencies f1 to f4. In addition, in the resonator unit 10, it is also possible to adjust the electromagnetic shielding characteristics to be obtained by selecting the resonant frequency of each SIW resonator 20.

[0025] Although an example configuration of the resonator unit 10 in which the SIW resonators 20 are multi-staged into four stages has been described here, the number of stages of the SIW resonators 20 in the resonator unit 10 is not limited to this and may be two or more. Also, although a configuration in which the propagation path inside the multilayer dielectric substrate 27 from the coupling slots 23 to the rear conductor layer is folded three times has been described here, the number of times of folding is not limited to this and may be two or more.

[0026] In addition, if the number of folds in one SIW resonator 20 is large, the length of the SIW resonator 20 in the short side direction (Y direction shown in FIG. 3A) is short, so that the number of SIW resonators 20 that can be incorporated in one resonator unit 10 can be increased. On the other hand, if the number of folds in one SIW resonator 20 is large, the thickness of the SIW resonator 20 (length in the Z direction shown in FIG. 3B) is large. Thus, in the resonator unit 10, there is a trade-off between the number of SIW resonators 20 that can be incorporated, which varies depending on the number of folds of the propagation path in the SIW resonator 20, and the thickness of the SIW resonator 20 (resonator unit 10). Therefore, it is desirable to set the number of folds of the propagation path in one SIW resonator 20 to an appropriate number depending on the number of SIW resonators 20 incorporated in one resonator unit 10 and the thickness of the SIW resonator 20.

[0027] <Arrangement of the resonator unit 10> The electromagnetic wave absorber 1 is configured by packing a plurality of resonator units 10 (100 in FIG. 1) configured as described above into a plane on a base substrate.

[0028] In this case, all the resonator units 10 may have the same resonant frequency band (e.g., frequencies f1 to f4), or the resonant frequency band (e.g., frequencies f1 to f4) of a certain resonator unit 10 may at least partially overlap with the resonant frequency band (e.g., frequencies f2 to f5) of another resonator unit 10. In the former case, the electromagnetic wave absorber 1 can achieve particularly excellent absorption characteristics in a specific frequency band (e.g., frequencies f1 to f4). In the latter case, the electromagnetic wave absorber 1 can achieve excellent absorption characteristics in a wider frequency band than in the former case. The resonant frequency band of each resonator unit 10 may be appropriately determined according to the frequency band of the electromagnetic wave to be actually absorbed.

[0029] In the electromagnetic wave absorber 1, the planar shape of one resonator unit 10 is a square, as shown in Fig. 1. In the electromagnetic wave absorber 1, the longitudinal directions of the coupling slots 23 belonging to one resonator unit 10 are all oriented in the same direction, as described above. In Fig. 1, for the sake of simplicity, the longitudinal directions of the coupling slots 23 belonging to one resonator unit 10 are indicated by vertical and horizontal straight lines.

[0030] In addition, in the electromagnetic wave absorber 1, as shown in FIG. 1, the resonator units 10 are arranged such that the longitudinal direction of the coupling slots 23 belonging to a certain resonator unit 10 is staggered (orthogonal) with the longitudinal directions of the coupling slots 23 belonging to four resonator units 10 adjacent to the certain resonator unit 10.

[0031] In this case, in the electromagnetic wave absorber 1, the longitudinal directions of the coupling slots 23 belonging to 50 of the 100 resonator units 10 are oriented in the X direction shown in Fig. 1, and the longitudinal directions of the coupling slots 23 belonging to the 50 resonator units 10 are oriented in the Y direction shown in Fig. 1. That is, in the electromagnetic wave absorber 1, the longitudinal directions of the coupling slots 23 belonging to the 100 resonator units 10 are oriented in two directions (two types). In addition, in the electromagnetic wave absorber 1, the arrangement of the 100 resonator units 10 classified into two types according to the longitudinal directions of the coupling slots 23 is configured to be a mosaic-like periodic arrangement (two types are arranged alternately) as shown in Fig. 1.

[0032] In this embodiment, the resonator units 10 are arranged such that the longitudinal direction of the coupling slot 23 belonging to a certain resonator unit 10 and the longitudinal direction of the coupling slots 23 belonging to all (four) resonator units 10 adjacent to the certain resonator unit 10 are staggered (orthogonal). However, the electromagnetic wave absorber 1 is not limited to this, and the resonator units 10 may be arranged such that the longitudinal direction of the coupling slot 23 belonging to a certain resonator unit 10 and the longitudinal direction of the coupling slot 23 belonging to at least one of the resonator units 10 adjacent to the certain resonator unit 10 are different from each other. An example of this case will be described in the second embodiment.

[0033] <Effect of electromagnetic wave absorber 1> Next, a description will be given of the effects of the electromagnetic wave absorber 1. Below, the effects of the electromagnetic wave absorber 1 will be described based on the results of an experiment conducted by the inventors of the electromagnetic wave absorber 1 (hereinafter, simply referred to as the "inventors") to measure the electromagnetic wave absorption characteristics of the electromagnetic wave absorber 1.

[0034] First, the inventors configured a plurality of (here, 100) resonator units 10 by the above-mentioned method so as to have predetermined electromagnetic wave absorption characteristics in a specific frequency band centered around, for example, 2.52 GHz. Then, the inventors configured an electromagnetic wave absorber 1 by packing and arranging these 100 resonator units 10 in a planar manner as shown in FIG.

[0035] Then, as shown in Fig. 4, the inventors limited the longitudinal direction of the open coupling slots 23 of 50 resonator units 10, of the 100 resonator units 10, to the X direction shown in Fig. 4 by attaching copper foil tape to the coupling slots 23 belonging to the units and blocking the slots, as shown in Fig. 4. The inventors then measured the absorption rate of the electromagnetic wave by the electromagnetic wave absorber 1 while changing the polarization direction of the electromagnetic wave incident on the electromagnetic wave absorber 1 from 0 degrees to 90 degrees. Here, the X direction shown in Fig. 4 is set to 0 degrees, and the Y direction shown in Fig. 4 is set to 90 degrees.

[0036] The results are shown in Figures 5A and 5B. In Figure 5A, the horizontal axis represents the frequency (GHz) of the electromagnetic wave, and the vertical axis represents the absorption rate (%) of the electromagnetic wave. In Figure 5B, the horizontal axis represents the polarization direction (deg) of the electromagnetic wave, and the vertical axis represents the absorption rate (%) when the frequency of the electromagnetic wave is 2.52 GHz.

[0037] As shown in FIG. 5A and FIG. 5B, the absorption characteristics of the electromagnetic wave change almost linearly with respect to the polarization direction of the incident electromagnetic wave. In this example, when the polarization direction of the electromagnetic wave is 0 degrees, the absorption rate of the electromagnetic wave is minimum (almost 0), and when the polarization direction of the electromagnetic wave is 90 degrees, the absorption rate of the electromagnetic wave is maximum (about 80%). That is, in this example, the closer the angle between the polarization direction of the electromagnetic wave and the longitudinal direction of the coupling slot 23 opened in the electromagnetic wave absorber 1 is to 90 degrees, the higher the absorption rate of the electromagnetic wave becomes. On the other hand, in this example, as shown in FIG. 5A, a predetermined absorption rate is obtained in a specific frequency band centered on 2.52 GHz, but the absorption rate is maintained at a low value in other frequency bands. This indicates that the electromagnetic wave absorber 1 passes electromagnetic waves other than the specific frequency band without absorbing them.

[0038] Next, the inventors peeled off the above-mentioned silver foil tape to remove the restriction on the longitudinal direction of the coupling slots 23 open in the electromagnetic wave absorber 1. Then, the inventors measured the absorption rate of the electromagnetic wave by the electromagnetic wave absorber 1 while changing the polarization direction of the electromagnetic wave incident on the electromagnetic wave absorber 1 from 90 degrees to 0 degrees.

[0039] The results are shown in Fig. 6 and Fig. 7. Fig. 6A is a diagram showing the state of coupling between the electromagnetic wave and the resonator unit 10 when the polarization direction of the electromagnetic wave incident on the electromagnetic wave absorber 1 is 90 degrees (hereinafter also referred to as "condition 1"). Similarly, Fig. 6B is a diagram showing the state of coupling between the electromagnetic wave and the resonator unit 10 when the polarization direction of the electromagnetic wave incident on the electromagnetic wave absorber 1 is 45 degrees (hereinafter also referred to as "condition 2"), and Fig. 6C is a diagram showing the state of coupling between the electromagnetic wave and the resonator unit 10 when the polarization direction of the electromagnetic wave incident on the electromagnetic wave absorber 1 is 0 degrees (hereinafter also referred to as "condition 3"). In Figs. 6A to 6C, the polarization direction of the electromagnetic wave is indicated by a solid arrow. In Fig. 7, the horizontal axis indicates the frequency (GHz) of the electromagnetic wave, and the vertical axis indicates the absorption rate (%) of the electromagnetic wave.

[0040] 6A, under condition 1, of the 100 resonator units 10, 50 resonator units 10 having coupling slots 23 with a width direction of 0 degree are strongly coupled to the electromagnetic wave. That is, under condition 1, of the 100 resonator units 10, the resonator units 10 having coupling slots 23 with an angle of 90 degrees between the longitudinal direction of the coupling slots 23 and the polarization direction of the electromagnetic wave (90 degrees) are strongly coupled to the electromagnetic wave.

[0041] 6B, all of the 100 resonator units 10 are coupled to the electromagnetic wave with moderate strength under condition 2. That is, under condition 2, the angles between the longitudinal directions of the coupling slots 23 of the 100 resonator units 10 and the polarization direction of the electromagnetic wave (45 degrees) are all 45 degrees, and as a result, all of the 100 resonator units 10 are coupled to the electromagnetic wave with moderate strength.

[0042] 6C, under condition 3, 50 of the 100 resonator units 10 having coupling slots 23 with their longitudinal directions oriented at 90 degrees are strongly coupled to the electromagnetic wave. That is, under condition 3, of the 100 resonator units 10, the resonator units 10 having coupling slots 23 with an angle of 90 degrees between the longitudinal direction of the coupling slots 23 and the polarization direction of the electromagnetic wave (0 degrees) are strongly coupled to the electromagnetic wave.

[0043] Thus, in the electromagnetic wave absorber 1, even if the polarization direction of the incident electromagnetic wave changes from 90 degrees to 0 degrees, the angle between the longitudinal direction of the coupling slots 23 and the polarization direction of the electromagnetic wave is 45 degrees or more in at least 50 resonator units 10. In other words, in the electromagnetic wave absorber 1, even if the polarization direction of the incident electromagnetic wave changes from 90 degrees to 0 degrees, the angle between the longitudinal direction of the coupling slots 23 and the polarization direction of the electromagnetic wave does not become less than 45 degrees all at once. Therefore, as shown in FIG. 7, the electromagnetic wave absorber 1 can achieve a predetermined electromagnetic wave absorption characteristic in a specific frequency band centered on 2.52 GHz, regardless of the polarization direction of the incident electromagnetic wave.

[0044] Furthermore, in the electromagnetic wave absorber 1, the thickness of the SIW resonator 20 constituting the resonator unit 10 is very thin, about 2.0 mm to 3.0 mm, and as a result, the electromagnetic wave absorber 1 as a whole can have a similar thickness, making it possible to make it thinner. In this regard, for example, in the above-mentioned conventional invention, the thickness of the radio wave absorber is 10 mm, and the electromagnetic wave absorber 1 can be made thinner even compared to this radio wave absorber.

[0045] In the above description, an example has been described in which the electromagnetic wave absorber 1 realizes predetermined electromagnetic wave absorbing characteristics in a specific frequency band centered around 2.52 GHz. However, this is merely an example, and the electromagnetic wave absorber 1 may be intended for a frequency band other than the above.

[0046] In the above description, an example has been described in which the resonator unit 10 is configured by arranging the SIW resonators 20 having different resonant frequencies in multiple stages. However, the resonator unit 10 may be configured by arranging the SIW resonators 20 having the same resonant frequency in multiple stages, and in that case, it is sufficient that the resonant frequencies are different between the multiple resonator units 10. In other words, the electromagnetic wave absorber 1 may have a predetermined resonant frequency band as a whole of the multiple resonator units 10 by making the resonant frequencies different between the multiple resonator units 10, rather than providing each resonator unit 10 with a predetermined resonant frequency band.

[0047] In the above description, an example has been described in which 100 resonator units 10 classified into two types according to the longitudinal direction of the coupling slots 23 are arranged in a mosaic-like periodic array (two types are arranged alternately) as shown in Fig. 1. However, the electromagnetic wave absorber 1 is not limited to this, and for example, the area of ​​the electromagnetic wave absorber 1 shown in the plan view of Fig. 1 may be divided into four, with one type being arranged in the upper right and lower left areas and the other type being arranged in the upper left and lower right areas. In other words, the electromagnetic wave absorber 1 may be arranged in a plane such that the longitudinal directions of the coupling slots belonging to each resonator unit 10 are oriented in two or more directions (two types).

[0048] As described above, according to the first embodiment, the electromagnetic wave absorber 1 is an SIW resonator 20 having the surface conductor layer 21 in which the coupling slots 23 through which the electromagnetic waves are introduced are formed, the back conductor layer 26 disposed opposite to the surface conductor layer 21, and the through conductors 22 electrically connecting the surface conductor layer 21 and the back conductor layer 26, and includes a plurality of resonator units 10 each formed by arranging the SIW resonators 20 having mutually different resonance frequencies in multiple stages in the short direction of the coupling slots 23, and the plurality of resonator units 10 are arranged in a plane such that the longitudinal directions of the coupling slots 23 belonging to each resonator unit 10 are oriented in two or more directions. This makes it possible for the electromagnetic wave absorber 1 according to the first embodiment to set the frequency band of the electromagnetic wave to be absorbed more flexibly than ever before, regardless of the polarization direction of the incident electromagnetic wave.

[0049] In particular, in the electromagnetic wave absorber 1 according to the first embodiment, the frequency band does not depend on the properties of the metallic magnetic material as in the conventional invention, and therefore the frequency band of the electromagnetic wave to be absorbed can be set more flexibly than in the conventional invention. Also, in the electromagnetic wave absorber 1 according to the first embodiment, the thickness of the SIW resonator 20 constituting the resonator unit 10 is very thin, and therefore the electromagnetic wave absorber 1 as a whole can be made thin.

[0050] Furthermore, the longitudinal direction of the coupling slots 23 belonging to one resonator unit 10 is the same, and the multiple resonator units 10 are arranged such that the longitudinal direction of the coupling slots 23 belonging to a certain resonator unit 10 differs from the longitudinal direction of the coupling slots 23 belonging to a resonator unit 10 adjacent to the certain resonator unit 10. This allows the electromagnetic wave absorber 1 according to the first embodiment to achieve predetermined electromagnetic wave absorption characteristics regardless of the polarization direction of the incident electromagnetic wave.

[0051] Moreover, the length of the coupling slot 23 in the longitudinal direction is longer than a half wavelength at the resonant frequency of the SIW resonator 20 having the coupling slot 23. This allows the electromagnetic wave absorber 1 according to the first embodiment to efficiently absorb electromagnetic waves at the resonant frequency.

[0052] Moreover, the multiple resonator units 10 each have a square planar shape, and are arranged in a plane such that the longitudinal directions of the coupling slots 23 belonging to each resonator unit 10 are oriented in two directions. This allows the electromagnetic wave absorber 1 according to the first embodiment to achieve predetermined electromagnetic wave absorption characteristics regardless of the polarization direction of the incident electromagnetic wave, and also makes it easy to arrange the multiple resonator units 10.

[0053] Moreover, the multiple resonator units 10 are classified into at least two types according to the longitudinal direction of the coupling slots 23 belonging to each of the resonator units 10, and the classified at least two types of resonator units 10 are arranged in a mosaic-like periodic array. This allows the electromagnetic wave absorber 1 according to the first embodiment to achieve predetermined electromagnetic wave absorption characteristics regardless of the polarization direction of the incident electromagnetic wave.

[0054] In addition, the surface conductor layer 21 has N+1 (N≧2) conductor layers and N dielectric layers sandwiched between two different layers of the N+1 conductor layers, and is located on the main surface of the multilayer dielectric substrate 27 in which two adjacent dielectric layers included in the N dielectric layers are partially connected, the back conductor layer 26 is located on the surface opposite to the main surface of the multilayer dielectric substrate 27, the through conductor 22 electrically connects the surface conductor layer 21 and the back conductor layer 26 to form an electrically closed area together with the surface conductor layer 21 and the back conductor layer 26, the main surface of the multilayer dielectric substrate 27 surrounded by the through conductor 22 has a region in which the surface conductor layer 21 is formed and a dielectric exposed region in which the dielectric layer is exposed by a coupling slot 23 formed in the surface conductor layer 21, and the region in which two adjacent dielectric layers are partially connected is inside the electrically closed region. As a result, the electromagnetic wave absorber 1 of embodiment 1 can realize multi-layering of the SIW resonators 20 and miniaturization in the short direction, and can increase the number of SIW resonators 20 that can be incorporated into one resonator unit 10.

[0055] Moreover, each resonator unit 10 is formed by arranging the SIW resonators 20 having different resonant frequencies in multiple stages, so that each resonator unit 10 has a predetermined resonant frequency band, and the resonant frequency band of each resonator unit 10 is the same. This allows the electromagnetic wave absorber 1 according to the first embodiment to achieve particularly excellent absorption characteristics in a specific frequency band.

[0056] Moreover, each resonator unit 10 is formed by arranging the SIW resonators 20 having different resonant frequencies in multiple stages, so that each resonator unit 10 has a predetermined resonant frequency band, and the resonant frequency band of a certain resonator unit 10 among the resonator units 10 at least partially overlaps with the resonant frequency bands of the other resonator units 10. As a result, the electromagnetic wave absorber 1 according to the first embodiment can achieve excellent absorption characteristics in a wider frequency band than when the resonator units 10 have the same resonant frequency band.

[0057] According to the first embodiment, the electromagnetic wave absorber 1 is an SIW resonator 20 having a surface conductor layer 21 in which a coupling slot 23 for introducing an electromagnetic wave is formed, a back conductor layer 26 disposed opposite the surface conductor layer 21, and a through conductor 22 electrically connecting the surface conductor layer 21 and the back conductor layer 26, and includes a plurality of resonator units 10 each formed by arranging the SIW resonators 20 having the same resonance frequency in multiple stages in the short direction of the coupling slot 23, and the plurality of resonator units 10 have different resonance frequencies from each other, and are arranged in a plane such that the longitudinal directions of the coupling slots 23 belonging to each resonator unit 10 are oriented in two or more directions. This makes it possible for the electromagnetic wave absorber 1 according to the first embodiment to set the frequency band of the electromagnetic wave to be absorbed more flexibly than ever before, regardless of the polarization direction of the incident electromagnetic wave.

[0058] Embodiment 2 In the first embodiment, an example has been described in which the resonator units 10 are arranged such that the longitudinal direction of the coupling slot 23 belonging to a certain resonator unit 10 is different from the longitudinal direction of the coupling slots 23 belonging to all of the resonator units 10 adjacent to the certain resonator unit 10. In the second embodiment, a configuration will be described in which the resonator units 10 are arranged such that the longitudinal direction of the coupling slot 23 belonging to a certain resonator unit 10 is different from the longitudinal direction of the coupling slot 23 belonging to at least one of the resonator units 10 adjacent to the certain resonator unit 10.

[0059] 8 is a plan view showing a configuration example of an electromagnetic wave absorber 1b according to embodiment 2. The electromagnetic wave absorber 1b according to embodiment 2 differs from the electromagnetic wave absorber 1 according to embodiment 1 in that the planar shape of each of the multiple resonator units 10 is rectangular. Other configurations of the electromagnetic wave absorber 1b according to embodiment 2 are the same as those of the electromagnetic wave absorber 1 according to embodiment 1, so the same reference numerals are used and the description thereof will be omitted.

[0060] 8, the electromagnetic wave absorber 1b has a plurality of resonator units 10 each having a rectangular planar shape whose long side is twice as long as its short side. The configuration of the SIW resonator 20 used in the electromagnetic wave absorber 1b is similar to that of the SIW resonator 20 described in the first embodiment.

[0061] Furthermore, in the electromagnetic wave absorber 1b, the multiple resonator units 10 are arranged such that the longitudinal direction of the coupling slots 23 belonging to a certain resonator unit 10 is different from the longitudinal direction of the coupling slots 23 belonging to at least one of the resonator units 10 adjacent to the certain resonator unit 10. For example, in the example of Fig. 8, six other resonator units 10 are adjacent to one resonator unit 10, and the longitudinal directions of the coupling slots 23 belonging to four of these resonator units 10 are different (perpendicular) from the longitudinal direction of the coupling slots 23 belonging to the certain resonator unit 10.

[0062] Moreover, in the electromagnetic wave absorber 1b, the multiple resonator units 10 are arranged in a plane such that the longitudinal directions of the coupling slots 23 belonging to each resonator unit 10 are oriented in two directions (two types) as in the first embodiment. Moreover, in the electromagnetic wave absorber 1b, the resonator units 10 classified into two types according to the longitudinal directions of the coupling slots 23 are arranged in a mosaic-like periodic array (two types are arranged at a predetermined period) as shown in FIG.

[0063] <Effect of electromagnetic wave absorber 1b> The electromagnetic wave absorber 1b according to the second embodiment also basically achieves the same effect as the electromagnetic wave absorber 1 according to the first embodiment. That is, in the electromagnetic wave absorber 1b according to the second embodiment, as in the electromagnetic wave absorber 1 according to the first embodiment, even if the polarization direction of the incident electromagnetic wave changes from 90 degrees to 0 degrees, the angle between the longitudinal direction of the coupling slot 23 and the polarization direction of the electromagnetic wave is 45 degrees or more in at least half of the resonator units 10. In other words, in the electromagnetic wave absorber 1b, even if the polarization direction of the incident electromagnetic wave changes from 90 degrees to 0 degrees, the angle between the longitudinal direction of the coupling slot 23 and the polarization direction of the electromagnetic wave does not become less than 45 degrees all at once. Therefore, the electromagnetic wave absorber 1b can also achieve a predetermined electromagnetic wave absorption characteristic in a specific frequency band regardless of the polarization direction of the incident electromagnetic wave.

[0064] In the above description, the planar shape of each of the multiple resonator units 10 is a rectangle whose long side is twice as long as its short side. However, the electromagnetic wave absorber 1b is not limited to this, and each of the multiple resonator units 10 may have a planar shape of a rectangle whose long side is three times as long as its short side.

[0065] However, when the ratio between the long side length and the short side length is changed, the number of resonator units 10 that can be arranged on the base substrate changes, and the ratio between the resonator units 10 whose longitudinal directions of the coupling slots 23 are oriented in the X direction and the resonator units 10 whose longitudinal directions of the coupling slots 23 are oriented in the Y direction changes. Therefore, when configuring the electromagnetic wave absorber 1b, it is desirable to determine the ratio between the long side length and the short side length of the resonator units 10 while taking into consideration the required electromagnetic wave absorption characteristics. In addition, by determining the ratio between the long side length and the short side length in this way, the electromagnetic wave absorber 1b can flexibly customize the electromagnetic wave absorption characteristics obtained for the polarization direction of the electromagnetic wave.

[0066] As described above, according to the second embodiment, in the electromagnetic wave absorber 1b, the longitudinal directions of the coupling slots 23 belonging to one resonator unit 10 are the same, and the multiple resonator units 10 are arranged such that the longitudinal direction of the coupling slots 23 belonging to a certain resonator unit 10 is different from the longitudinal direction of the coupling slots 23 belonging to at least one of the resonator units 10 adjacent to the certain resonator unit 10. Thereby, similar to the first embodiment, the electromagnetic wave absorber 1b according to the second embodiment is not dependent on the polarization direction of the incident electromagnetic wave, and the frequency band of the electromagnetic wave to be absorbed can be set more flexibly than before.

[0067] Moreover, the multiple resonator units 10 each have a rectangular planar shape, and are arranged in a plane such that the longitudinal directions of the coupling slots 23 belonging to each resonator unit 10 are oriented in two directions. As a result, the electromagnetic wave absorber 1b according to the second embodiment can flexibly customize the electromagnetic wave absorption characteristics obtained for the polarization direction of the electromagnetic wave, in addition to the effect of the first embodiment.

[0068] Embodiment 3 In the third embodiment, as a variation of the planar shape of the resonator unit 10, an example will be described in which the planar shape of the resonator unit 10 is a rhombus with one of the interior angles being 60 degrees.

[0069] 9 is a plan view showing a configuration example of an electromagnetic wave absorber 1c according to embodiment 3. The electromagnetic wave absorber 1c according to embodiment 3 differs from the electromagnetic wave absorber 1 according to embodiment 1 in that the planar shape of each of the multiple resonator units 10 is a rhombus with one of the interior angles being 60 degrees, and that the planar shape of each SIW resonator 20 is a parallelogram. Since the other configurations of the electromagnetic wave absorber 1c according to embodiment 3 are the same as those of the electromagnetic wave absorber 1 according to embodiment 1, the same reference numerals are used and the description thereof will be omitted.

[0070] As shown in Fig. 9, the electromagnetic wave absorber 1c has a plurality of resonator units 10 each having a planar shape of a rhombus with one of the interior angles being 60 degrees. As shown in Fig. 10A, the SIW resonator 20 used in the electromagnetic wave absorber 1c has a planar shape of a parallelogram. Note that the components of the SIW resonator 20 and the cross-sectional view shown in Fig. 10B are similar to the configuration of the SIW resonator 20 described in the first embodiment.

[0071] Furthermore, in the electromagnetic wave absorber 1c, the multiple resonator units 10 are arranged such that the longitudinal direction of the coupling slots 23 belonging to a certain resonator unit 10 differs from the longitudinal direction of the coupling slots 23 belonging to a resonator unit 10 adjacent to the certain resonator unit 10. For example, in the example of Fig. 9, four other resonator units 10 are adjacent to one resonator unit 10, and the longitudinal directions of the coupling slots 23 belonging to all of these four resonator units 10 differ from the longitudinal direction of the coupling slots 23 belonging to the certain resonator unit 10.

[0072] Moreover, in the electromagnetic wave absorber 1c, the multiple resonator units 10 are arranged in a plane such that the longitudinal directions of the coupling slots 23 belonging to each resonator unit 10 are oriented in three directions (three types), unlike in the first embodiment. Moreover, in the electromagnetic wave absorber 1c, the resonator units 10 classified into three types according to the longitudinal directions of the coupling slots 23 are arranged in a mosaic-like periodic array (three types arranged at a predetermined period) as shown in Fig. 9.

[0073] <Effect of electromagnetic wave absorber 1c> The electromagnetic wave absorber 1c according to the third embodiment also basically achieves the same effect as the electromagnetic wave absorber 1 according to the first embodiment. That is, in the electromagnetic wave absorber 1c according to the third embodiment, as in the electromagnetic wave absorber 1 according to the first embodiment, even if the polarization direction of the incident electromagnetic wave changes from 90 degrees to 0 degrees, the angle between the longitudinal direction of the coupling slot 23 and the polarization direction of the electromagnetic wave is 45 degrees or more in at least one-third of the resonator units 10. In other words, in the electromagnetic wave absorber 1c, even if the polarization direction of the incident electromagnetic wave changes from 90 degrees to 0 degrees, the angle between the longitudinal direction of the coupling slot 23 and the polarization direction of the electromagnetic wave does not become less than 45 degrees all at once. Therefore, the electromagnetic wave absorber 1c can also achieve a predetermined electromagnetic wave absorption characteristic in a specific frequency band regardless of the polarization direction of the incident electromagnetic wave.

[0074] As described above, according to the third embodiment, the multiple resonator units 10 are arranged in a plane such that the planar shape of each resonator unit 10 is a rhombus with one of the interior angles being 60 degrees, and the longitudinal directions of the coupling slots 23 belonging to each resonator unit 10 are oriented in three directions. This allows the electromagnetic wave absorber 1c according to the third embodiment, like the first embodiment, to set the frequency band of the electromagnetic wave to be absorbed more flexibly than before, regardless of the polarization direction of the incident electromagnetic wave.

[0075] In addition, the present disclosure allows free combination of the respective embodiments, modification of any of the components of each embodiment, or omission of any of the components of each embodiment. [Industrial Applicability]

[0076] The present disclosure makes it possible to obtain an electromagnetic wave absorber that is not dependent on the polarization direction of the incident electromagnetic wave and that allows the frequency band of the electromagnetic wave to be absorbed to be set more flexibly than ever before, and is therefore suitable for use as an electromagnetic wave absorber. [Explanation of symbols]

[0077] 1, 1b, 1c electromagnetic wave absorber, 10 resonator unit, 20 SIW resonator, 21 surface conductor layer (surface conductor pattern), 22 penetrating conductor (row of penetrating through holes), 23 coupling slot, 24 inner layer conductor pattern, 25 dielectric layer, 26 back surface conductor layer (solid conductor pattern), 27 multilayer dielectric substrate, 28 inner layer coupling hole, L1 to L4 short side lengths of SIW resonators, Ls long side length of coupling slot.

Claims

1. An SIW resonator having a surface conductor layer in which a coupling slot through which an electromagnetic wave is introduced is formed, a back conductor layer disposed opposite to the surface conductor layer, and a through conductor electrically connecting the surface conductor layer and the back conductor layer, the SIW resonator including a plurality of resonator units each including SIW resonators having mutually different resonance frequencies arranged in multiple stages in a short side direction of the coupling slot, The plurality of resonator units include the coupling slots belonging to each resonator unit are arranged in a plane such that the longitudinal directions of the coupling slots are oriented in two or more directions; The length of the coupling slot in the longitudinal direction is longer than 1 / 2 wavelength at the resonant frequency of the SIW resonator having the coupling slot. Electromagnetic wave absorber characterized by:

2. The longitudinal directions of the coupling slots belonging to one resonator unit are the same, The plurality of resonator units include The longitudinal direction of the coupling slot belonging to a certain resonator unit is arranged so as to be different from the longitudinal direction of the coupling slot belonging to at least one of the resonator units adjacent to the certain resonator unit.

2. The electromagnetic wave absorber according to claim 1.

3. each of the plurality of resonator units has a square planar shape; The coupling slots belonging to each resonator unit are arranged on a plane such that the longitudinal directions of the coupling slots are oriented in two directions.

3. The electromagnetic wave absorber according to claim 1 or 2.

4. each of the plurality of resonator units has a rectangular planar shape; The coupling slots belonging to each resonator unit are arranged on a plane such that the longitudinal directions of the coupling slots are oriented in two directions.

3. The electromagnetic wave absorber according to claim 1 or 2.

5. each of the plurality of resonator units has a planar shape of a rhombus with one interior angle of 60 degrees; The coupling slots belonging to each resonator unit are arranged on a plane so that the longitudinal directions of the coupling slots are oriented in three directions.

3. The electromagnetic wave absorber according to claim 1 or 2.

6. The plurality of resonator units include The resonator units are classified into at least two types according to the longitudinal direction of the coupling slots belonging to each resonator unit, and the classified at least two types of resonator units are arranged in a mosaic-like periodic array.

2. The electromagnetic wave absorber according to claim 1.

7. The surface conductor layer is a multilayer dielectric substrate having N+1 (N≧2) conductor layers and N dielectric layers sandwiched between two different ones of the N+1 conductor layers, the N dielectric layers being located on a main surface of which two adjacent dielectric layers are partially joined to each other; the rear conductor layer is located on a surface opposite to the main surface of the multilayer dielectric substrate, the through conductor electrically connects the surface conductor layer and the back conductor layer to form an electrically closed region together with the surface conductor layer and the back conductor layer; The main surface of the multilayer dielectric substrate surrounded by the through conductor has a region in which the surface conductor layer is formed and a dielectric exposed region in which the dielectric layer is exposed by the coupling slot formed in the surface conductor layer, and the region in which the two adjacent dielectric layers are partially coupled is inside the electrically closed region.

3. The electromagnetic wave absorber according to claim 1 or 2.

8. Each of the resonator units comprises: By arranging SIW resonators having different resonant frequencies in multiple stages, each resonator unit has a predetermined resonant frequency band, The resonant frequency band of each resonator unit is the same resonant frequency band.

3. The electromagnetic wave absorber according to claim 1 or 2.

9. Each of the resonator units comprises: By arranging SIW resonators having different resonant frequencies in multiple stages, each resonator unit has a predetermined resonant frequency band, The resonant frequency band of one of the resonator units at least partially overlaps with the resonant frequency band of another of the resonator units.

3. The electromagnetic wave absorber according to claim 1 or 2.

10. a surface conductor layer having coupling slots formed therein through which electromagnetic waves are introduced; A back conductor layer disposed opposite the surface conductor layer; a through conductor electrically connecting the surface conductor layer and the back conductor layer, the SIW resonator including a plurality of resonator units each including a plurality of SIW resonators having the same resonant frequency arranged in a multi-stage manner in a short-side direction of the coupling slot; The plurality of resonator units include Each of the resonator units has a different resonant frequency, The coupling slots belonging to each resonator unit are arranged on a plane such that the longitudinal directions of the coupling slots are oriented in two or more directions. Electromagnetic wave absorber characterized by:

Images