Reflection canceling plate

Abstract

The reflection canceling plate is formed by laminating a plurality of transmissive reflective layers (1)-(3), each of which reflects an incident wave of a different frequency and transmits an incident wave of a higher frequency than the frequency that it reflects.

Description

[Technical field]

[0001] The present disclosure relates to a reflection cancellation plate that reduces reflected waves due to incident waves incident on a target. [Background technology]

[0002] Reducing radio wave reflection and reducing radar cross section have been widely studied in order to make it harder for radar to detect it or to suppress unintended interference waves that cause communication failures in communications. Furthermore, although it is different from the reduction in radio wave reflection and the reduction in radar cross section, Patent Document 1 discloses an electromagnetic wave absorber that blocks the transmission and leakage of electromagnetic waves. The electromagnetic wave absorber disclosed in Patent Document 1 is a see-through electromagnetic wave absorber having two layers laminated on one side of a transparent substrate: a reflective layer made of a fine-wire mesh pattern that has the function of reflecting all electromagnetic waves that reach it, and a frequency-selective shielding layer that is placed on top of the reflective layer and attenuates electromagnetic waves of a specific frequency that is set to resonate due to a fine-wire pattern made of an FSS element. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2009-170887 A Summary of the Invention [Problem to be solved by the invention]

[0004] The electromagnetic wave absorber disclosed in Patent Document 1 is intended to control the frequency of absorption, and is difficult to apply to reducing or canceling reflected waves due to incident waves incident on a target. Moreover, since the electromagnetic wave absorber disclosed in Patent Document 1 is directly applied to electronic devices that generate electromagnetic waves, there are cases in which the original functions of the target electronic devices are impaired.

[0005] The present disclosure has been made in consideration of the above-mentioned points, and aims to provide a reflection cancellation plate that reduces reflected waves caused by incident waves incident on an object from which it is desired to cancel or reduce the reflected waves. [Means for solving the problem]

[0006] The reflection canceling plate according to the present disclosure has a plurality of transmissive and reflective layers. , when viewed from the surface side where the incident wave is incident, A plurality of transflective layers are laminated, each of which reflects an incident wave of a different frequency and transmits an incident wave of a higher frequency than the frequency that it reflects. Effect of the Invention

[0007] According to the present disclosure, it is possible to reduce reflected waves due to incident waves incident on a target. [Brief description of the drawings]

[0008] [Figure 1] 3A and 3B are diagrams illustrating an example of the configuration of a reflection canceling plate according to the first embodiment. [Diagram 2] 1 is a diagram for explaining the relationship between the frequency and reflection amplitude of the first transmissive reflective layer and the second transmissive reflective layer when the sizes of the first transmissive reflective layer and the second transmissive reflective layer are set in a reflection cancellation plate according to embodiment 1. [Diagram 3] 4 is a diagram showing the relationship between frequency and reflection amplitude during operation of the first to third transmission-reflection layers in the reflection cancellation plate according to the first embodiment. FIG. [Figure 4] 4 is a schematic diagram showing the relationship between frequency and reflection reduction in the reflection canceling plate according to the first embodiment. FIG. [Diagram 5] 4 is a diagram showing setting values ​​of a transflective layer in the reflection canceling plate according to the first embodiment. FIG. [Figure 6] 11 is a diagram showing an example of the configuration of a reflection canceling plate according to the second embodiment. FIG. [Figure 7] 13 is a diagram showing an example of the configuration of a reflection canceling plate according to the third embodiment. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Embodiment 1 The reflection canceling plate according to the first embodiment will be described with reference to FIGS. The reflection cancellation plate of embodiment 1 is a reflection cancellation plate for making a cancellation target (hereinafter referred to as target) 100, whose reflected waves are to be cancelled or reduced, less likely to be detected by a radar, or for suppressing unintended interference waves that cause communication failures in communications. The reflection canceling plate according to the first embodiment reduces radio wave reflection from the object 100 and reduces the radar cross-section (RCS).

[0010] As shown in Figure 1, the reflection cancellation plate of embodiment 1 comprises, in order from the surface side where the incident wave is incident, a first transmissive reflective layer 1, a second transmissive reflective layer 2, and a third transmissive reflective layer 3, each located on a different plane. The reflection cancellation plate of embodiment 1 has a layered structure in which a third transmissive reflective layer 3, a second transmissive reflective layer 2, and a first transmissive reflective layer 1 are layered in this order relative to a reflection position reference including the main scattering point of the object 100. The reflection canceling plate according to the first embodiment, which includes the first to third transmissive reflective layers 1 to 3, is placed on the target 100 or around the target 100. In FIG. 1, the object 100 is shown diagrammatically as an isotropic reflector (a sphere made of a perfect conductor).

[0011] The first to third transflective layers 1 to 3 each reflect an incident wave of a different frequency and transmit an incident wave of a higher frequency than the frequency that it reflects. Although the reflection canceling plate according to the first embodiment is a laminate of three transmissive reflective layers, that is, the first transmissive reflective layer 1 to the third transmissive reflective layer 3, it may be a laminate of two transmissive reflective layers. In short, it is sufficient that the laminate has at least two transflective layers that reflect incident waves of different frequencies and transmit incident waves of frequencies higher than the reflected frequencies.

[0012] Hereinafter, a reflection cancellation plate including a laminate of three layers from the first transmission reflection layer 1 to the third transmission reflection layer 3 will be described. The first transmission reflection layer 1 reflects an incident wave having a frequency of F1 or less and transmits an incident wave having a frequency higher than F1. The second transmission reflection layer 2 reflects an incident wave having a frequency higher than F1 and less than or equal to F2, and transmits an incident wave having a frequency higher than F2. The third transmission reflection layer 3 reflects an incident wave having a frequency higher than F2 and less than or equal to F3, and transmits an incident wave having a frequency higher than F3.

[0013] The frequencies of the first transmission reflection layer 1 to the third transmission reflection layer 3 are in the relationship of F1 < F2 < F3. That is, from the first transmission reflection layer 1 to the third transmission reflection layer 3, the frequencies for reflecting the incident wave increase in order from the first transmission reflection layer 1 to the second transmission reflection layer 2 and the third transmission reflection layer 3, which are located on the surface side where the incident wave is incident. In Embodiment 1, as an example, the frequency F1 is set to 4.7 GHz, the frequency F2 is set to 7 GHz, and the frequency F3 is set to 11 GHz.

[0014] The first transmission reflection layer 1 to the third transmission reflection layer 3 are each composed of a metal grid or a periodic structure. Since the metal grid and the periodic structure basically have the same function, hereinafter, the description will be centered on the metal grid. Each of the first transmission reflection layer 1 to the third transmission reflection layer 3 has a different grid period or period of the periodic structure.

[0015] Each of the first transmission reflection layer 1 to the third transmission reflection layer 3 has a square planar shape, and the central axes perpendicular to the plane passing through the center of the plane coincide. The second transmission reflection layer 2 is disposed in a positional relationship that completely covers the third transmission reflection layer 3, and the first transmission reflection layer 1 is disposed in a positional relationship that completely covers the second transmission reflection layer 2.

[0016] The planar area S1 of the first transmission reflection layer 1 is larger than the planar area S2 of the second transmission reflection layer 2. The plane area S 2 of the second transflective layer 2 is larger than the plane area S 3 of the third transflective layer 3 . The plane areas of the first transflective layer 1 to the third transflective layer 3 have a relationship of S1>S2>S3. That is, the plane areas of the first transmissive reflective layer 1 to the third transmissive reflective layer 3 decrease in the order of the first transmissive reflective layer 1 located on the surface side where the incident wave is incident, to the second transmissive reflective layer 2, and to the third transmissive reflective layer 3.

[0017] In the first transflective layer 1, an incident wave of frequency F1 is reflected by being configured with a grid period D1, or with a periodic structure, period D1 in the case of a periodic structure. In Fig. 1, the reflected wave from the first transflective layer 1 is shown as R1. 2, the size of the first transmissive reflective layer 1, that is, the length a1 of one side, is set so that the reflection amplitude by the first transmissive reflective layer 1 that reflects an incident wave of frequency F1 is the same as the amplitude of the reflected wave reflected by the object 100. In FIG. 1, the reflected wave from the object 100 is indicated as R.

[0018] In Figure 2, the horizontal axis indicates frequency and the vertical axis indicates reflection amplitude, with straight line S0 indicating the reflection amplitude of wave R reflected by object 100, curve A1 indicating the reflection amplitude of wave R1 reflected by first transmissive reflective layer 1, curve A2 indicating the reflection amplitude of wave R2 reflected by second transmissive reflective layer 2, dashed line B1 indicating the reflection amplitude of wave reflected by a metal plane plate with one side a1, and dashed line B2 indicating the reflection amplitude of wave reflected by a metal plane plate with one side a2. At frequency F1, if the reflection amplitude of the reflected wave R1 by the first transmissive reflective layer 1 is made the same as the reflection amplitude of the reflected wave R by the object 100, the size of the first transmissive reflective layer 1, i.e., the length a1 of one side, will be calculated using the following equation (1).

[0019] TIFF0007651082000001.tif22166

[0020] In the above equation (1), λ F1 is the wavelength of the incident wave of frequency F1 reflected by the first transflective layer 1, σ F1 is the radar cross section of the object 100 for an incident wave of frequency F1. In the first embodiment, as an example, when the frequency F1 is 4.7 GHz, the length a1 is 150 mm, the grid period D1 is 30 mm, and the number of grids is 5×5. The reflection amplitude versus frequency in the first transflective layer 1 at this time was calculated by numerical calculation and the result is shown as curve A1 in FIG.

[0021] In the second transflective layer 2, the grid period D2, or in the case of a periodic structure, the period D2, is used to reflect incident waves with a frequency equal to or lower than F2. In FIG. 1, the reflected wave from the second transflective layer 2 is shown as R2. The size of the second transmissive reflective layer 2, i.e., the length a2 of one side, is set so that the reflection amplitude by the second transmissive reflective layer 2 reflecting an incident wave of frequency F2 is identical to the amplitude of the reflected wave reflected by the object 100, as shown in Figure 2.

[0022] At frequency F2, if the reflection amplitude of the reflected wave R2 by the second transmissive reflective layer 2 is made the same as the reflection amplitude of the reflected wave R by the object 100, the size of the second transmissive reflective layer 2, i.e., the length a2 of one side, will be calculated using the following equation (2).

[0023] TIFF0007651082000002.tif20166

[0024] In the above equation (2), λ F2 is the wavelength of the incident wave of frequency F2 reflected by the second transflective layer 2, σ F2 is the radar cross section of the object 100 for an incident wave of frequency F2. In the first embodiment, as an example, when the frequency F2 is 7 GHz, the length a2 is 120 mm, the grid period D2 is 20 mm, and the number of grids is 6×6. The reflection amplitude versus frequency in the second transflective layer 2 at this time was calculated by numerical calculation and the result is shown as curve A2 in FIG.

[0025] In the third transflective layer 3, the grid period D3, or in the case of a periodic structure, the period D3 of the periodic structure is used to reflect incident waves with a frequency of F3 or less. In FIG. 1, the reflected wave from the third transflective layer 3 is shown as R3. The size of the third transmissive reflective layer 3, i.e., the length a3 of one side, is set so that the reflection amplitude by the third transmissive reflective layer 3 reflecting the incident wave of frequency F3 is identical to the amplitude of the reflected wave reflected by the object 100.

[0026] At frequency F3, if the reflection amplitude of the reflected wave R3 by the third transmissive reflective layer 3 is made the same as the reflection amplitude of the reflected wave by the object 100, the size of the third transmissive reflective layer 3, i.e., the length a3 of one side, will be calculated using the following equation (3).

[0027] TIFF0007651082000003.tif22166

[0028] In the above equation (3), λ F3 is the wavelength of the incident wave of frequency F3 reflected by the third transflective layer 3, σ F3 is the radar cross section of the object 100 for an incident wave of frequency F3. In the first embodiment, as an example, when the frequency F2 is 11 GHz, the length a3 is 91 mm, the grid period D3 is 13 mm, and the number of grids is 7×7. The reflection amplitude versus frequency in the third transflective layer 3 at this time was calculated by numerical calculation and the result is shown as curve A3 in FIG.

[0029] In addition, when a laminate of N transmissive reflective layers is used instead of a laminate of three layers, such as when a fourth transmissive reflective layer is placed under the third transmissive reflective layer 3, the size of the nth transmissive reflective layer, that is, the length of one side a n is the length calculated by the following formula (4).

[0030] TIFF0007651082000004.tif21166

[0031] In the above formula (4), n is an integer from 1 to N, N is an integer of 2 or more, and λ Fn is the wavelength of the incident wave reflected by the nth transmissive-reflective layer, σ Fn is the radar cross section of the object 100 for an incident wave of frequency Fn.

[0032] The length a1 of one side of the first transflective layer 1 is longer than the length a2 of one side of the second transflective layer 2, and the grid period D1 of the first transflective layer 1 is longer than the grid period D2 of the second transflective layer 2. The length a2 of one side of the second transflective layer 2 is longer than the length a3 of one side of the third transflective layer 3 , and the grid period D2 of the second transflective layer 2 is longer than the grid period D3 of the third transflective layer 3 .

[0033] The lengths of one side of the first to third transmissive reflective layers 1 to 3 satisfy the relationship a1>a2>a3, and the grid periods of the first to third transmissive reflective layers 1 to 3 satisfy the relationship D1>D2>D3. The first transmissive reflective layer 1 to the third transmissive reflective layer 3 are located on the surface side where the incident wave is incident, and the length of one side of each layer decreases in this order from the first transmissive reflective layer 1 to the second transmissive reflective layer 2 to the third transmissive reflective layer 3, and the grid period also decreases.

[0034] The position of the first transmissive reflective layer 1 with respect to the target 100 is spaced from the main scattering point of the target 100 by a distance d1 expressed by the following equation (5), that is, a distance d1 from the reflection phase reference including the main scattering point. d1=λ F1 / 4 (5)

[0035] The distance d1 shown in the above formula (5) is the wavelength λ of the incident wave at the frequency F1 reflected by the first transmissive reflective layer 1. F1 It is 1 / 4 wavelength. Therefore, the reflected wave R1 of frequency F1 reflected by the first transmissive reflective layer 1 and the reflected wave R of frequency F1 reflected by the target 100 have the same amplitude but are in opposite phase.

[0036] As a result, the reflected wave R1 of frequency F1 reflected by the first transmissive reflective layer 1 is superimposed on the reflected wave R of frequency F1 reflected by the object 100, canceling out the reflected wave R of frequency F1 reflected by the object 100. That is, due to the action of the first transflective layer 1, as shown in FIG. 4, the reflection of a superimposed wave S of the reflected wave R and the reflected wave R1 with respect to an incident wave of frequency F1 is reduced. Therefore, the reflected wave R of frequency F1 from the target 100 is reduced, and the radar cross section (RCS) for frequency F1 is reduced.

[0037] The second transmissive reflective layer 2 is positioned relative to the target 100 at a distance d2 from the main scattering point of the target 100 as shown in the following equation (6), that is, at a distance d2 from the reflection phase reference including the main scattering point. d2=λ F2 / 4 (6)

[0038] The distance d2 shown in the above formula (6) is the wavelength λ of the incident wave at the frequency F2 reflected by the second transmissive reflective layer 2. F2 It is 1 / 4 wavelength. Therefore, the reflected wave R2 of frequency F2 reflected by the second transmissive reflective layer 2 and the reflected wave R of frequency F2 reflected by the target 100 have the same amplitude but are in opposite phase.

[0039] As a result, the reflected wave R2 of frequency F2 reflected by the second transmissive reflective layer 2 is superimposed on the reflected wave R of frequency F2 reflected by the object 100, canceling out the reflected wave R of frequency F2 reflected by the object 100. That is, as shown in FIG. 4, the second transflective layer 2 acts to reduce reflection of a superimposed wave S of the reflected wave R and the reflected wave R2 with respect to an incident wave of frequency F2. Therefore, the reflected wave R of frequency F2 from the target 100 is reduced, and the radar cross section (RCS) for frequency F2 is reduced.

[0040] The third transmissive reflective layer 3 is positioned relative to the target 100 at a distance d3 from the main scattering point of the target 100 as shown in the following equation (7), that is, at a distance d3 from the reflection phase reference including the main scattering point. d3=λF3 / 4 (7)

[0041] The distance d3 shown in the above formula (7) is the wavelength λ of the incident wave at the frequency F3 reflected by the third transmissive reflective layer 3. F3 It is 1 / 4 wavelength. Therefore, the reflected wave R3 of frequency F3 reflected by the third transmissive reflective layer 3 has the same amplitude as the reflected wave R of frequency F3 reflected by the target 100 but is in the opposite phase.

[0042] As a result, the reflected wave R3 of frequency F3 reflected by the third transmissive reflective layer 3 is superimposed on the reflected wave R of frequency F3 reflected by the object 100, canceling out the reflected wave R of frequency F3 reflected by the object 100. Therefore, the reflected wave R of frequency F3 from the target 100 is reduced, and the radar cross section (RCS) for frequency F3 is reduced.

[0043] In addition, when a laminate of N transmissive reflective layers is used instead of a laminate of three layers, such as when a fourth transmissive reflective layer is placed under the third transmissive reflective layer 3, the position of the nth transmissive reflective layer relative to the target 100 is set to the position of the main scattering point of the target 100. (Scattered reference point) For the distance d given by the following equation (8), n , i.e., the distance d from the reflection phase reference containing the main scattering point n It is. d n = λ Fn / 4 (8)

[0044] The distance d shown in the above equation (8) n is the wavelength λ of the incident wave at frequency Fn reflected by the nth transmissive reflective layer Fn It is 1 / 4 wavelength. Therefore, the reflected wave of frequency Fn reflected by the nth transmissive reflective layer n has the same amplitude as the reflected wave R of frequency Fn reflected by the target 100 but has an opposite phase. Therefore, the reflected wave R of frequency Fn from the target 100 is reduced, and the radar cross section (RCS) for frequency Fn is reduced.

[0045] The distance d1 from the main scattering point of the object 100 at which the first transmissive reflective layer 1 is disposed is longer than the distance d2 from the main scattering point of the object 100 at which the second transmissive reflective layer 2 is disposed. The distance d2 from the main scattering point of the object 100 at which the second transmissive reflective layer 2 is disposed is longer than the distance d3 from the main scattering point of the object 100 at which the third transmissive reflective layer 3 is disposed. The distances from the main scattering point of the object 100 at which the first transflective layer 1 to the third transflective layer 3 are arranged satisfy the relationship d1>d2>d3.

[0046] In the reflection cancellation plate of embodiment 1, the first transmissive reflective layer 1 to the third transmissive reflective layer 3 have the same central axis perpendicular to the plane passing through the center of the plane, their distances from the main scattering point satisfy the relationship d1>d2>d3, and their side lengths satisfy the relationship a1>a2>a3, so that a three-layer laminate is formed in which the first transmissive reflective layer 1 located on the surface side where the incident wave is incident completely covers the second transmissive reflective layer 2 and the third transmissive reflective layer 3 located below, and the second transmissive reflective layer 2 completely covers the third transmissive reflective layer 3 located below.

[0047] Therefore, of the incident waves that are incident on the first transmissive reflective layer 1, incident waves with frequencies equal to or lower than frequency F1 are reflected by the first transmissive reflective layer 1, and incident waves with frequencies exceeding frequency F1 transmit through the first transmissive reflective layer 1 and reach the second transmissive reflective layer 2. Of the incident waves with frequencies exceeding frequency F1, those with frequencies equal to or lower than frequency F2 are reflected by the second transmissive reflective layer 2, and those with frequencies exceeding frequency F2 transmit through the second transmissive reflective layer 2 and reach the third transmissive reflective layer 3. Of the incident waves with frequencies exceeding frequency F2, incident waves with frequencies equal to or lower than frequency F3 are reflected by the third transmissive reflective layer 3, and incident waves with frequencies exceeding frequency F3 transmit through the third transmissive reflective layer 3 to the third transmissive reflective layer 3.

[0048] That is, the first transmissive reflective layer 1 reflects incident waves of frequencies equal to or lower than frequency F1, canceling out the reflected wave R of frequency F1 reflected by the object 100; the second transmissive reflective layer 2 reflects incident waves of frequencies greater than frequency F1 and equal to or lower than frequency F2, canceling out the reflected wave R of frequency F2 reflected by the object 100; and the third transmissive reflective layer 3 reflects incident waves of frequencies greater than frequency F2 and equal to or lower than frequency F3, canceling out the reflected wave R of frequency F3 reflected by the object 100.

[0049] In this way, the size of the transmissive reflective layers decreases from the surface side where the incident wave is incident, and they are stacked so that the lower transmissive reflective layers are hidden by the upper transmissive reflective layers, and the lower the transmissive reflective layer, the higher the frequency of the incident wave it reflects. By stacking multiple transmissive reflective layers so as to satisfy the above equations (4) and (8), the reflected wave of a frequency reflected at each transmissive reflective layer will have the same amplitude and opposite phase as the reflected wave of the corresponding frequency reflected by the target 100, so that the reflected wave of the corresponding frequency from the target 100 is cancelled out, the reflected wave from the target 100 is reduced to a wideband, and the radar cross section (RCS) of the target 100 is reduced to a wideband.

[0050] FIG. 5 shows an example of calculation of the grid period and the length of one piece with respect to the reflected frequency for each of the first to third transmissive reflective layers 1 to 3. By setting a reflected wave that reflects the incident wave and stacking multiple transmissive reflective layers that satisfy the above equations (4) and (8) for the frequency of the set reflected wave, the desired reflected wave from the target 100 can be canceled out.

[0051] In the reflection cancellation plate of embodiment 1, the first transmission reflective layer 1 to the third transmission reflective layer 3 each reflect incident waves of different frequencies and transmit incident waves of higher frequencies than the reflected frequencies, and are installed at a position that is 1 / 4 wavelength of the wavelength at the frequency of the reflected incident wave from the reflection phase reference.Therefore, the reflected waves R1 to R3 reflected from the first transmission reflective layer 1 to the third transmission reflective layer 3, respectively, are superimposed in opposite phase on the reflected wave R from the object at the reflecting frequency, so that the reflected wave R from the object 100 is reduced and the radar cross section (RCS) is reduced over a wide band.

[0052] The reflection cancellation plate of embodiment 1 acts to cancel out the reflected wave R from the object 100 by using the reflected waves R1 to R3 reflected from the first transparent reflective layer 1 to the third transparent reflective layer 3, respectively, so that the radar cross section (RCS) is reduced over a wide band without making any direct changes to the object 100.

[0053] Embodiment 2 The reflection canceling plate according to the second embodiment will be described with reference to FIG. In the reflection canceling plate according to the first embodiment, the transmissive reflective layers are stacked in order from the surface side to which the incident wave is incident, with the sizes of the transmissive reflective layers decreasing, so that the lower transmissive reflective layers are hidden by the upper transmissive reflective layers.

[0054] In contrast, the reflection cancellation plate of embodiment 2 differs from the reflection cancellation plate of embodiment 1 in that multiple transmissive reflective layers are stacked in sequence without overlapping when viewed from the surface side where the incident wave is incident, but in all other respects is the same as the reflection cancellation plate of embodiment 1. The reflection canceling plate according to the second embodiment is suitable for cases in which the frequencies of the waves reflected by the multiple transmission-reflection layers are close to each other and the spacing between the multiple transmission-reflection layers is narrow. The following description will focus on the differences from the reflection cancelling plate according to the first embodiment.

[0055] There are three methods for laminating a plurality of transmissive and reflective layers in order without overlapping each other. First, each of the plurality of transmission-reflection layers has a notch at one corner of a quadrilateral, and the lower transmission-reflection layer is configured to fit into the notch of the upper transmission-reflection layer when viewed from the surface side where the incident wave is incident, in order from the surface side where the incident wave is incident. Second, each of the plurality of transmission-reflection layers has a cut-out portion, and the lower transmission-reflection layer is configured to fit into the cut-out portion of the upper transmission-reflection layer when viewed from the surface side where the incident wave is incident, in order from the surface side where the incident wave is incident. Third, each of the plurality of transmission-reflection layers is arranged with a lateral shift so that the plurality of transmission-reflection layers do not overlap when viewed from the surface side where the incident wave is incident.

[0056] Hereinafter, the description will focus on the first configuration. As shown in FIG. 1, the reflection cancellation plate according to Embodiment 2 includes a first transmission-reflection layer 10, a second transmission-reflection layer 20, a third transmission-reflection layer 30, and a fourth transmission-reflection layer 40, which are located on different planes in order from the surface side where the incident wave is incident. The reflection cancellation plate according to Embodiment 2 has a laminated structure in which the fourth transmission-reflection layer 40, the third transmission-reflection layer 30, the second transmission-reflection layer 20, and the first transmission-reflection layer 10 are laminated in order with respect to a reflection position reference including the main scattering points of the target 100.

[0057] The first transmission-reflection layer 10 reflects an incident wave having a frequency of F10 or less and transmits an incident wave having a frequency higher than F10. The second transmission-reflection layer 20 reflects an incident wave having a frequency higher than F10 and F20 or less and transmits an incident wave having a frequency higher than F20. The third transmission-reflection layer 30 reflects an incident wave having a frequency higher than F20 and F30 or less and transmits an incident wave having a frequency higher than F30. The fourth transmission-reflection layer 40 reflects an incident wave having a frequency higher than F30 and F40 or less and transmits an incident wave having a frequency higher than F40. The frequencies of the first transmission-reflection layer 10 to the fourth transmission-reflection layer 40 satisfy the relationship of F1 < F2 < F3 < F4.

[0058] The first to fourth transflective layers 10 to 40 are composed of metal grids or periodic structures. Each of the first to fourth transflective layers 10 to 40 has a different grid period or period of the periodic structure.

[0059] Each of the first to fourth transmissive reflective layers 10 to 40 has a notch at one corner of a quadrangle, and in order from the surface side where the incident wave is incident, the lower transmissive reflective layer fits into the notch of the upper transmissive reflective layer when viewed from the surface side where the incident wave is incident. The cutout portions of each of the first to fourth transflective layers 10 to 40 are square. The fourth transflective layer 40 has a square planar shape with no cutout.

[0060] The view from the surface side where the incident wave is incident will be referred to as the surface view hereinafter. The second transmissive reflective layer 20 in a surface view is accommodated in the cutout portion of the first transmissive reflective layer 10, the third transmissive reflective layer 30 in a surface view is accommodated in the cutout portion of the second transmissive reflective layer 20, and the fourth transmissive reflective layer 40 in a surface view is accommodated in the cutout portion of the third transmissive reflective layer 30.

[0061] The laminate of the four transmissive reflective layers, the first transmissive reflective layer 10 to the fourth transmissive reflective layer 40, is arranged within a square whose one side is the longer side of the first transmissive reflective layer 10 when viewed from the front. When viewed from the surface side where the incident wave is incident, the lowest transmissive reflective layer, that is, the fourth transmissive reflective layer 40 in embodiment 2, has a square planar shape without a cutout, and the remaining transmissive reflective layers, that is, the first transmissive reflective layer 10 to the third transmissive reflective layer 30 in embodiment 2, have an L-shape with a cutout.

[0062] The first transflective layer 10 has a planar area S 10 and a periphery L 10 larger than the planar area S 20 and the periphery L 20 of the second transflective layer 20 . The second transflective layer 20 has a planar area S20 and a periphery L20 larger than the planar area S30 and the periphery L30 of the third transflective layer 30. The third transflective layer 30 has a planar area S30 and a periphery L30 larger than the planar area S40 and the periphery L40 of the fourth transflective layer 40.

[0063] The plane areas and peripheries of the first to fourth transmissive reflective layers 10 to 40 have the relationship S10>S20>S30>S40 and L10>L20>L30>L40. That is, the first transmissive reflective layer 10 to the fourth transmissive reflective layer 40 have decreasing plane areas and outer circumferences in the order of the first transmissive reflective layer 10 located on the surface side where the incident wave is incident, to the second transmissive reflective layer 20, the third transmissive reflective layer 30, and the fourth transmissive reflective layer 40.

[0064] In the first transflective layer 10, the grid period D 10 , and in the case of a periodic structure, the period of the periodic structure D 10 By configuring it as above, an incident wave of frequency F10 is reflected. In the second transflective layer 20, the grid period D 20 , and in the case of a periodic structure, the period of the periodic structure D 20 By configuring it as above, an incident wave of frequency F20 is reflected. In the third transflective layer 30, the grid period D 30 , and in the case of a periodic structure, the period of the periodic structure D 30 By configuring it as above, an incident wave of frequency F30 is reflected. In the fourth transflective layer 40, the grid period D 40 , and in the case of a periodic structure, the period of the periodic structure D 40 By configuring it as above, an incident wave of frequency F40 is reflected.

[0065] The period of the elements of the first transflective layer 10 to the fourth transflective layer 40 is D 10 >D 20 >D 30 >D 40 This is the relationship. That is, the element period of the first transmissive reflective layer 10 to the fourth transmissive reflective layer 40 decreases in the order of the first transmissive reflective layer 10 located on the surface side where the incident wave is incident, to the second transmissive reflective layer 20, the third transmissive reflective layer 30, and the fourth transmissive reflective layer 40.

[0066] The size of the first transflective layer 10, i.e., the length of one side a 10 is set so that the reflection amplitude by the first transmissive reflective layer 10 that reflects the incident wave of frequency F10 is the same as the amplitude of the reflected wave reflected by the object 100. The size of the second transflective layer 20, i.e., the length of one side a 20 is set so that the amplitude of the reflection by the second transmissive reflective layer 20 that reflects the incident wave of frequency F20 is the same as the amplitude of the reflected wave reflected by the object 100.

[0067] The size of the third transflective layer 30, i.e., the length of one side a 30 is set so that the reflection amplitude by the third transmissive reflective layer 30, which reflects the incident wave of frequency F30, is the same as the amplitude of the reflected wave reflected by the object 100. The size of the fourth transflective layer 40, that is, the length a of one side 40 is set so that the reflection amplitude by the fourth transmissive reflective layer 40 that reflects the incident wave of frequency F40 is the same as the amplitude of the reflected wave reflected by the object 100.

[0068] The length a of one side from the first transflective layer 10 to the third transflective layer 30 10 ~a 30 is the length calculated by the following equation (9).

[0069] TIFF0007651082000005.tif22166

[0070] In the above formula (9), n is an integer from 1 to N-1, N is an integer of 3 or more, and λ Fn is the wavelength of the incident wave reflected by the nth transmissive-reflective layer, σ Fn is the radar cross section of the object 100 for an incident wave of frequency Fn. In addition, the length a of one side of the bottommost transmissive reflective layer as viewed from the surface side where the incident wave is incident, that is, the fourth transmissive reflective layer 40 in the second embodiment, is 40 is the length calculated by the above formula (4).

[0071] First, the length a of one side of the bottommost transflective layer, that is, the fourth transflective layer 40 in the second embodiment, is 40 is determined by the above formula (4), and the length a of one side of the upper transmissive reflective layer, that is, the third transmissive reflective layer 30 in the second embodiment, is determined by the above formula (4). 30 , the length a of one side of the second transflective layer 20 20 , the length a of one side of the first transflective layer 10 10 is determined by the above equation (9).

[0072] The length of one side of the first transflective layer 10 to the fourth transflective layer 40 is a 10 >a 20 >a 30 >a 40 This is the relationship. The first to fourth transmissive reflective layers 10 to 40 have shorter sides and shorter grid periods in the order of the first transmissive reflective layer 10 located on the surface side where the incident wave is incident, the second transmissive reflective layer 20, the third transmissive reflective layer 30, and the fourth transmissive reflective layer 40.

[0073] The first transflective layer 10 to the fourth transflective layer 40 are disposed at positions relative to the target 100 such that the distance d 10 ~d 40 , i.e., the distance d from the reflection phase reference containing the main scattering point 10 ~d 40 It is. That is, the distance d between the first transflective layer 10 and the fourth transflective layer 40 is 10 ~d 10 is 1 / 4 wavelength of the incident wave at the frequency reflected by each of the transmissive reflective layers 10-40, and the reflected wave of the frequency reflected by each of the transmissive reflective layers 10-40 has the same amplitude but opposite phase as the reflected wave of the corresponding frequency reflected by the target 100.

[0074] As a result, even if the spacing between the layers of the first transmissive reflective layer 10 to the fourth transmissive reflective layer 40 is narrow, interference between the layers can be avoided and the reflected waves from the target 100 are reduced, thereby achieving broadband cancellation of reflections in a narrow space and reducing the radar cross section (RCS) of the target 100 over a wide band.

[0075] In the reflection canceling plate according to the second embodiment, the first to fourth transmission-reflection layers 10 to 40 each reflect an incident wave of a different frequency and transmit an incident wave of a higher frequency than the reflected frequency. When viewed from the surface side where the incident wave is incident, the bottommost transmission-reflection layer 40 has a planar shape without a notch, and the remaining transmission-reflection layers 10 to 30 other than the bottommost layer have an L-shape with a notch. When viewed from the surface, the lower transmission-reflection layer fits into the notch of the upper transmission-reflection layer, and the first to fourth transmission-reflection layers 10 to 30 are arranged in a plane shape without a notch. Since each of the four transmissive reflective layers 40 is positioned at a quarter wavelength of the wavelength at the frequency of the incident wave reflected from the reflection phase reference, even if the frequencies of the reflected waves by the first transmissive reflective layer 10 to the fourth transmissive reflective layer 40 are close and the interlayer spacing of the first transmissive reflective layer 10 to the fourth transmissive reflective layer 40 is narrow, interference between the incident wave and the reflected wave between the layers can be avoided, wideband cancellation of reflections in a narrow space is achieved, and the radar cross section (RCS) of the target 100 is reduced over a wide band.

[0076] The reflection cancellation plate of embodiment 2 acts to cancel out reflected waves from the object 100 by using reflected waves reflected from each of the first transmissive reflective layer 10 to the fourth transmissive reflective layer 40, thereby reducing the radar cross section (RCS) over a wide band without making any direct changes to the object 100.

[0077] When a cutout portion is provided in each of the plurality of transmissive reflective layers instead of a notch portion, the size of one side of each of the plurality of transmissive reflective layers and the installation positions thereof are determined as follows. That is, the outer shape of each of the multiple transflective layers is square, the central axes of each of the multiple transflective layers are coincident with each other and perpendicular to a plane passing through the center of the plane, and the remaining transflective layers other than the bottommost transflective layer have a cutout portion in the center.

[0078] First, the length a of one side of the bottommost transflective layer, that is, the fourth transflective layer 40 in the second embodiment, is 40 is determined by the above equation (4). Next, the length a of one side of the third transflective layer 30 located on the fourth transflective layer 40 is30 is determined by the above formula (4), and the center part is 40 This is the hollowed out part. Similarly, the length a of one side of the second transflective layer 20 20 and the length of one side of the cutout part a 30 , the length a of one side of the first transflective layer 10 10 and the length of one side of the cutout part a 20 is determined by the above formula (4). The locations of the multiple transmissive reflective layers are determined relative to the main scattering points of the object 100 using the above formula (8).

[0079] When there is no overlap, the size of one side of the multiple transmissive reflective layers and their installation positions are determined in the same manner as for the reflection canceling plate according to the first embodiment.

[0080] Embodiment 3 The reflection canceling plate according to the third embodiment will be described with reference to FIG. The reflection cancellation plate of embodiment 3 differs from the reflection cancellation plate of embodiment 1 in that it has a radio wave absorber 5 arranged parallel to the multiple transmission reflective layers 1 to 3, below the lowest transmission reflective layer seen from the surface side where the incident wave is incident (the third transmission reflective layer 3 in embodiment 1); otherwise, it is the same as the reflection cancellation plate of embodiment 1. In FIG. 7, the same reference numerals as those in FIG. 1 indicate the same or corresponding parts.

[0081] As shown in Figure 7, the reflection cancellation plate of embodiment 3 comprises, in order from the surface side where the incident wave is incident, a first transmissive reflective layer 1, a second transmissive reflective layer 2, and a third transmissive reflective layer 3, which are each located on different planes, and a radio wave absorber 5 arranged below the third transmissive reflective layer 3 and parallel to the third transmissive reflective layer 3. Since the laminate consisting of three layers, the first transmissive reflective layer 1 to the third transmissive reflective layer 3, is the same as the laminate consisting of three layers, the first transmissive reflective layer 1 to the third transmissive reflective layer 3, in the reflection cancellation plate of embodiment 1, a description thereof will be omitted.

[0082] The radio wave absorber 5 has a flat metal ground plate 5a and a radio wave absorbing layer 5b on the surface of the ground plate 5a onto which an incident wave is incident. The length of one side of the radio wave absorber 5, that is, the length of one side of the base plate 5a and the length of one side of the radio wave absorbing layer 5b, is the same as the length a1 of one side of the first transflective layer 1. In addition, it is sufficient that the length of one side of the radio wave absorbing layer 5b is at least the same as the length a1 of one side of the first transmitting reflective layer 1, and the length of one side of the base plate 5a may be longer than the length a1 of one side of the first transmitting reflective layer 1.

[0083] Next, the role of the radio wave absorber 5 will be described. The incident wave that has passed through the periphery of the first transmission-reflection layer 1 located on the outer periphery of the second transmission-reflection layer 2 is absorbed by the radio wave absorbing layer 5 b of the radio wave absorber 5 . The incident wave that has passed through the periphery of the second transmitting and reflecting layer 2 located on the outer periphery of the third transmitting and reflecting layer 3 is absorbed by the radio wave absorbing layer 5 b of the radio wave absorber 5 . The incident wave transmitted through the third transmitting-reflecting layer 3 is absorbed by the radio wave absorbing layer 5 b of the radio wave absorber 5 .

[0084] In this manner, the incident wave transmitted through the laminate of the three layers, the first transmissive reflective layer 1 to the third transmissive reflective layer 3, is absorbed by the radio wave absorbing layer 5b of the radio wave absorber 5. As a result, the radio wave absorber 5 blocks the incident waves that have passed through the three-layer laminate below the radio wave absorber 5, making it possible to avoid interference of unnecessary radio waves below the reflection canceling plate.

[0085] The reflection cancellation plate of embodiment 3 has the same effect as the reflection cancellation plate of embodiment 1, in particular, it acts to cancel out the reflected wave R from the target 100 by the reflected waves R1 to R3 reflected from the first transparent reflective layer 1 to the third transparent reflective layer 3, respectively, so that the radar cross section (RCS) is reduced over a wide band without making any direct changes to the target 100, and further, by providing the radio wave absorber 5, it is possible to avoid interference of unnecessary radio waves below the reflection cancellation plate.

[0086] In addition, in the reflection cancellation plate of embodiment 2, a radio wave absorber 5 may be provided below the lowest transmissive reflective layer seen from the surface side where the incident wave is incident, that is, the fourth transmissive reflective layer 40 in embodiment 2, and arranged parallel to the multiple transmissive reflective layers 10-40. In this case, the length of one side of the radio wave absorber 5 is equal to the length a of one side of the first transflective layer 10. 10 is the same as:

[0087] With this configuration, the incident wave transmitted through the first transmission-reflection layer 10 to the fourth transmission-reflection layer 40 is absorbed by the radio wave absorbing layer 5 b of the radio wave absorber 5 . As a result, the radio wave absorber 5 blocks the incident waves that have passed through the four-layer laminate below the radio wave absorber 5, making it possible to avoid interference of unnecessary radio waves below the reflection canceling plate.

[0088] Therefore, similar to the reflection cancellation plate of embodiment 2, the reflected waves reflected from each of the first transmissive reflective layer 10 to the fourth transmissive reflective layer 40 act to cancel out the reflected waves from the target 100, so that the radar cross section (RCS) is reduced over a wide band without making any direct changes to the target 100, and further, by providing the radio wave absorber 5, interference of unnecessary radio waves below the reflection cancellation plate can be avoided.

[0089] It should be noted that the embodiments may be freely combined, or any of the components in each embodiment may be modified, or any of the components in each embodiment may be omitted. [Industrial Applicability]

[0090] The reflection cancellation plate of the present disclosure is suitable as a reflection cancellation plate used to make an object whose reflected waves you want to cancel or reduce less likely to be detected by a radar, or to suppress unintended interference waves that cause communication failures in communications. [Explanation of symbols]

[0091] 1, 10 first transmissive reflective layer, 2, 20 second transmissive reflective layer, 3, 30 third transmissive reflective layer, 40 fourth transmissive reflective layer, 5 radio wave absorber, 5 base plate, 5b radio wave absorbing layer, 100 target.

Claims

1. A plurality of transmissive reflective layers are laminated in order without overlapping when viewed from the surface side where the incident wave is incident, A reflection-canceling plate in which each of the plurality of transmissive-reflective layers reflects an incident wave of a different frequency and transmits an incident wave of a higher frequency than the frequency that it reflects.

2. 2. The reflection canceling plate according to claim 1, wherein the plurality of transmissive reflective layers reflect incident waves at increasing frequencies in the order from the transmissive reflective layer located on the surface side to which the incident wave is incident.

3. 2. The reflection canceling plate according to claim 1, wherein the plurality of transmissive reflective layers have decreasing planar areas and peripheries in order from the transmissive reflective layer located on the surface side to which the incident wave is incident.

4. Each of the plurality of transflective layers is formed of either a metal grid or a periodic structure; 4. The reflection canceling plate according to claim 3, wherein the period of the elements constituting either the metal grid or the periodic structure decreases in order from the transmission-reflection layer located on the surface side to which the incident wave is incident.

5. The reflection cancellation plate according to any one of claims 1 to 4, wherein each of the plurality of transmissive reflective layers is positioned at a distance from a scattering reference point for which reflected waves are to be reduced, the distance being expressed by the following equation (8). D ｎ =λ Ｆｎ / 4 (8) In the above formula (8), n is an integer from 1 to N, N being an integer of 2 or more, and λFn is the wavelength of the incident wave reflected by the transflective layer.

6. each of the plurality of transmissive reflective layers, except for the lowermost transmissive reflective layer, has a notch at one corner of a quadrangle, and in order from the surface side on which an incident wave is incident, the lower transmissive reflective layer fits into the notch of the upper transmissive reflective layer as viewed from the surface side on which the incident wave is incident; The length of one side of each of the plurality of transmissive reflective layers is a length a represented by the following formula (4): ｎ 5. The reflection canceling plate according to claim 1, wherein In the above formula (4), n is an integer from 1 to N, N is an integer of 2 or more, and λ Ｆｎ is the wavelength of the incident wave reflected by the nth transmissive-reflective layer, σ Ｆｎ is the radar cross section of the target for which it is desired to reduce the reflected wave with respect to the incident wave of frequency Fn.

7. each of the plurality of transmissive reflective layers has a notch at one corner of a quadrangle, and in order from the surface side onto which an incident wave is incident, a lower transmissive reflective layer fits into the notch of an upper transmissive reflective layer as viewed from the surface side onto which the incident wave is incident; The length of one side of each of the plurality of transmissive reflective layers is a length a represented by the following formula (4): ｎ 6. The reflection cancelling plate according to claim 5, In the above formula (4), n is an integer from 1 to N, N is an integer of 2 or more, and λ Ｆｎ is the wavelength of the incident wave reflected by the nth transmissive-reflective layer, σ Ｆｎ is the radar cross section of the target for which it is desired to reduce the reflected wave with respect to the incident wave of frequency Fn.

8. each of the plurality of transmissive reflective layers has a cutout portion, and in order from the surface side onto which an incident wave is incident, a lower transmissive reflective layer is fitted into the cutout portion of an upper transmissive reflective layer as viewed from the surface side onto which the incident wave is incident; The length of one side of each of the plurality of transmissive reflective layers is a length a represented by the following formula (4): ｎ 5. The reflection canceling plate according to claim 1, wherein In the above formula (4), n is an integer from 1 to N, N is an integer of 2 or more, and λ Ｆｎ is the wavelength of the incident wave reflected by the nth transmissive-reflective layer, σ Ｆｎ is the radar cross section of the target for which it is desired to reduce the reflected wave with respect to the incident wave of frequency Fn.

9. each of the plurality of transmissive reflective layers has a cutout portion, and in order from the surface side onto which an incident wave is incident, a lower transmissive reflective layer is fitted into the cutout portion of an upper transmissive reflective layer as viewed from the surface side onto which the incident wave is incident; The length of one side of each of the plurality of transmissive reflective layers is a length a represented by the following formula (4): ｎ 6. The reflection cancelling plate according to claim 5, In the above formula (4), n is an integer from 1 to N, N is an integer of 2 or more, and λ Ｆｎ is the wavelength of the incident wave reflected by the nth transmissive-reflective layer, σ Ｆｎ is the radar cross section of the target for which it is desired to reduce the reflected wave with respect to the incident wave of frequency Fn.

10. A reflection cancellation plate as described in any one of claims 1 to 4, comprising a radio wave absorber arranged below the lowest transmissive reflective layer, as viewed from the surface side where the incident wave is incident, in parallel with the multiple transmissive reflective layers, and having a base plate and a radio wave absorbing layer on the surface of the base plate where the incident wave is incident.

11. 11. The reflection canceling plate according to claim 10, wherein the length of one side of the radio wave absorbing layer in the radio wave absorber is the same as the length of one side of the transmissive reflective layer located on the surface side to which the incident wave is incident.

12. 12. The reflection canceling plate according to claim 11, wherein the radio wave absorbing layer of the radio wave absorber is disposed as the lowest transmissive reflective layer as viewed from the surface side on which the incident wave is incident.

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