Radio wave absorbers and antennas

Abstract

To provide an electromagnetic wave absorber and an antenna that suppress incident radio waves from becoming reflected waves with a simple configuration.SOLUTION: An electromagnetic wave absorber includes a conductor layer 10 including a plurality of metal patches 11 arranged at predetermined intervals, a dielectric layer 12 laminated under the conductor layer 10, and a slot layer 13 having a plurality of slots 15 and laminated under the dielectric layer 12, and a metal patch 11 and a slot 15 overlapping through the dielectric layer 12 are formed to have similar matching frequencies.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This disclosure relates to a radio wave absorber constructed by laminating a conductor layer, a dielectric layer, and a slot layer, and to an antenna constructed by providing a waveguide in the radio wave absorber. [Background technology]

[0002] When using microwaves for wireless power transmission (WPT), it is required that the system does not affect the human body or other wireless systems. One technique for performing WPT (Wireless Transmitting Technology) while avoiding obstacles such as the human body involves emitting a microwave beam. This technique uses a pilot signal transmitted from the power receiving system to estimate the direction of the beam's arrival and transmits power along a path free from obstacles such as the human body. One technique to suppress re-emission on the receiving end of microwaves is to reduce the radar cross-section (RCS).

[0003] For example, there is an antenna device having a planar antenna and a reflective structure (EBG structure) to reduce the above-mentioned RCS (Patent Document 1). In this device, the patch reflective surface provided on the reflective structure is arranged to face the boresight direction (maximum gain direction) of the planar antenna, and the reflected waves of the planar antenna and the reflected waves of the reflective structure cancel each other out, thereby reducing the RCS. Furthermore, there is an antenna device configured such that a step based on a predetermined wavelength is provided between the antenna aperture surface of the array antenna and the frame portion located around the antenna aperture surface, so that the reflected waves generated at the antenna aperture surface and the reflected waves generated at the frame portion are superimposed and these reflected waves cancel each other out (Patent Document 2).

[0004] Furthermore, there is an antenna device in which an antenna element receives radar waves, a circulator adjusts the amplitude and phase of the received signal to generate a re-radiated wave, and this re-radiated wave is radiated to the outside (Patent Document 3). This device calculates the amplitude gain and phase shift so that the complex electric field value of the reflected wave of the entire antenna device matches the complex electric field value of a desired target reflected wave. For example, by setting the complex electric field value of the target reflected wave to zero, the RCS of the entire antenna device can be reduced.

[0005] Furthermore, there is an antenna device that includes multiple patch antennas, a dielectric substrate, and a ground conductor stacked on top of each other, and a plate with cutouts in which the patch antennas are placed (Patent Document 4). The above-mentioned plate has a first surface that is in contact with the antenna substrate equipped with the patch antennas, and a second surface that is back-to-back with respect to the first surface, and is formed such that the second surface is inclined with respect to the first surface. This device, by attaching a plate to the antenna substrate, reduces the amount of radio waves reflected in the same direction when radio waves are incident perpendicularly to the antenna substrate, thereby reducing the RCS (Radio Cross Section) in front of the device. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2010-252172 [Patent Document 2] Japanese Patent Publication No. 2014-195232 [Patent Document 3] Japanese Patent Publication No. 2015-68688 [Patent Document 4] Japanese Patent Publication No. 2020-161867 [Overview of the project] [Problems that the invention aims to solve]

[0007] In the aforementioned beam emission technology, the energy of the beam wave is stronger than that of ordinary radio waves, making it difficult to prevent re-emission in the receiving system or to effectively suppress strong reflected waves. The technology disclosed in Patent Document 1 involves arranging a planar antenna and a reflective structure side by side on a plane, resulting in an installation area (installation area) that is more than twice the installation area of ​​the antenna alone. The technology disclosed in Patent Document 2 requires a step corresponding to the wavelength, which increases the thickness of the radio wave absorber or antenna. For example, to accommodate a frequency of 6 GHz, a step of 12.5 mm is required, resulting in a considerably large overall thickness for the radio wave absorber or antenna. This makes it difficult to actually manufacture and use such a device.

[0008] The technology disclosed in Patent Document 3 requires the prior preparation of data such as reference adjustment amounts corresponding to the entire antenna device and structures surrounding the antenna device, and also requires the provision of a device for storing this data and a device for performing calculations using this data. In other words, it is not possible to incorporate the characteristic of suppressing reflected waves as a passive characteristic in radio wave absorbers or antenna devices, and the manufacturing and operating costs become high, making it difficult to actually manufacture and use such devices. The technology disclosed in Patent Document 4 suppresses reflected waves from the front of the plate by tilting the plate, making it difficult to suppress the intensity of reflected waves in locations (spaces) other than the front of the plate. Furthermore, it is difficult to reliably suppress reflected waves for radio waves incident at an oblique angle on the plate (antenna substrate).

[0009] Furthermore, the technologies disclosed in the above-mentioned Patent Documents 1 to 4 are, for example, technologies that suppress (adjust) radio wave reflection so that radar antennas mounted on aircraft or ships are not detected by other radars. Therefore, they do not take into consideration the need to avoid adverse effects on the human body or other persons in a populated environment. Thus, the technology used in conventional antennas (devices for incident radio waves) and the like requires a complex configuration or the like in order to suppress the incident radio waves from becoming reflected waves, and it has been difficult to configure simply.

[0010] This disclosure has been made to solve the above problems, and provides a radio wave absorber and an antenna that suppress the incident radio waves from becoming reflected waves with a simple configuration.

Means for Solving the Problems

[0011] The radio wave absorber according to this disclosure includes a conductor layer provided with a plurality of patch conductors at a predetermined arrangement interval, a dielectric layer laminated on the lower side of the conductor layer, and a slot layer provided with a plurality of slots and laminated on the lower side of the dielectric layer, and the patch conductors and the slots overlapping through the dielectric layer are formed so as to have similar resonance frequencies.

[0012] Further, the patch conductor is formed in a circular shape, and the slot is formed in a rectangular shape or a ring shape.

[0013] Further, the patch conductor is formed in a rectangular shape, and the slot is formed in a rectangular shape. [[ID=二十一]]

[0014] [[ID=二十二]] Further, the plurality of patch conductors are composed of a first patch conductor formed in a circular shape and a second patch conductor formed in a rectangular shape, and among the plurality of slots, the first slot overlapping the first patch conductor is formed in a rectangular shape or a ring shape, and among the plurality of slots, the second slot overlapping the second patch conductor is formed in a rectangular shape.

[0015] Further, a plurality of the conductor layer and the dielectric layer are laminated on a single slot layer.

[0016] The antenna according to this disclosure comprises a conductor layer having a plurality of patch conductors arranged at predetermined intervals, a first dielectric layer laminated below the conductor layer, a slot layer having a plurality of slots and laminated below the first dielectric layer, and a waveguide disposed below the slot layer, wherein the patch conductors and slots overlapping via the first dielectric layer are formed to have similar matching frequencies.

[0017] Furthermore, the patch conductor is formed in a circular shape, and the slot is formed in a rectangular or ring shape.

[0018] Furthermore, the patch conductor is formed in a rectangular shape, and the slot is formed in a rectangular shape.

[0019] Furthermore, the plurality of patch conductors consist of a first patch conductor formed in a circular shape and a second patch conductor formed in a rectangular shape, and of the plurality of slots, the first slot that overlaps with the first patch conductor is formed in a rectangular or ring shape, and of the plurality of slots, the second slot that overlaps with the second patch conductor is formed in a rectangular shape.

[0020] Furthermore, the present invention is characterized by stacking multiple conductor layers and the first dielectric layers on a single slot layer.

[0021] Furthermore, the invention is characterized in that a second dielectric layer having a lower relative permittivity than the first dielectric layer is provided between the slot layer and the waveguide, and the waveguide is a microstrip line or a post-wall waveguide.

[0022] Furthermore, the waveguide is characterized by being a waveguide.

[0023] Furthermore, the present invention is characterized by stacking multiple conductor layers and the first dielectric layers on a single slot layer. [Effects of the Invention]

[0024] According to this disclosure, the slots in the slot layer provided beneath the conductor layer are configured to resonate with the radio waves incident on the conductor layer, thereby suppressing the conversion of the radio waves incident on the conductor layer into reflected waves with a simple configuration. [Brief explanation of the drawing]

[0025] [Figure 1] This is an explanatory diagram showing the configuration of a radio wave absorber according to Embodiment 1 of the present disclosure. [Figure 2] This is an explanatory diagram showing a portion of the radio wave absorber in Figure 1. [Figure 3] Figure 2 is an explanatory diagram showing the configuration of the area where the metal patch is provided. [Figure 4] This is an explanatory diagram showing an example configuration of a printed slot antenna. [Figure 5] This is an explanatory diagram showing the configuration of a radio wave absorber according to Embodiment 2 of the present disclosure. [Figure 6] This is an explanatory diagram showing the configuration of a radio wave absorber according to Embodiment 3 of the present disclosure. [Figure 7] This is an explanatory diagram showing the configuration of a radio wave absorber according to Embodiment 4 of the present disclosure. [Figure 8] This is an explanatory diagram showing the configuration of the antenna according to Embodiment 5 of the present disclosure. [Figure 9] This is an explanatory diagram showing the configuration of the antenna according to Embodiment 6 of the present disclosure. [Figure 10] This is an explanatory diagram showing the configuration of a waveguide provided in an antenna according to Embodiment 7 of the present disclosure. [Figure 11] This is an explanatory diagram showing the schematic configuration of a measurement system for measuring reflected waves emitted from a radio wave absorber. [Figure 12] This is an explanatory diagram showing the reflected wave measured by the measurement system in Figure 11. [Figure 13] This is an explanatory diagram showing the schematic configuration of a measurement system for measuring the receiving characteristics of an antenna. [Figure 14] This is an explanatory diagram showing the receiving characteristics of the antenna measured by the measurement system in Figure 13. [Figure 15]This is an explanatory diagram showing the dimensions of each part of the radio wave absorber and the antenna used in the measurement. [Modes for carrying out the invention]

[0026] One embodiment of this invention will be described below. (Embodiment 1) Figure 1 is an explanatory diagram showing the configuration of the radio wave absorber 1 according to Embodiment 1 of the present disclosure. In this figure, the upper side shows the configuration of the radio wave absorber 1 as viewed from above, and the lower side shows the configuration of the radio wave absorber 1 as viewed from the thickness portion (laminated portion). The radio wave absorber 1 is composed of a conductor layer 10 having a plurality of metal patches 11 (patch conductors), a dielectric layer 12 stacked below the conductor layer 10, and a slot layer 13 stacked below the dielectric layer 12 and having a plurality of slots 15. In other words, the dielectric layer 12 is the substrate for the radio wave absorber 1, with multiple metal patches 11 arranged on the surface of this substrate and slots 15 arranged on the back surface of the substrate.

[0027] Figure 2 is an explanatory diagram showing a portion of the radio wave absorber 1 in Figure 1. This diagram shows the configuration of the portion of the radio wave absorber 1 in which one metal patch 11 is provided. Here, in the radio wave absorber 1, the width and depth of the portion (the substrate portion) on which one metal patch 11 is provided are denoted as W, and the thickness as h. That is, multiple metal patches 11 are arranged according to the arrangement period W (with an arrangement interval W) to form a conductive layer 10.

[0028] The metal patch 11 of the conductive layer 10 is formed in a circular shape with a diameter d using, for example, copper foil. The dielectric layer 12, which is laminated on the underside of the conductive layer 10, is formed using, for example, a dielectric material 12a, which is a glass epoxy material. The slot layer 13, which is laminated on the lower side of the dielectric layer 12, is formed by creating slots 15 in a metal foil 14, such as a copper foil.

[0029] Figure 3 is an explanatory diagram showing the configuration of the portion where the metal patch 11 in Figure 2 is provided. In this figure, the upper part shows the configuration (surface) of the portion where one metal patch 11 is provided, viewed from above, and the lower part shows the configuration (layered structure) of the thickness portion where the metal patch 11 is provided. Hereinafter, in the radio wave absorber 1, the portion where a single metal patch 11 is provided will be referred to as a patch cell.

[0030] Slot 15 is a rectangular hole provided in the metal foil 14, with a length in the longitudinal direction (slot length) of S l The length in the shorter direction (slot width) is S w It has a certain size and is positioned to overlap with one metal patch 11 stacked above it (when viewing the radio wave absorber 1 or the conductor layer 10 from above). Furthermore, slot 15 is located a predetermined distance (slot shift length S) from the circular center 0 of the metal patch 11. sf It is positioned in a spaced (shifted) position. Furthermore, a patch cell having the metal patch 11, slot 15, etc., has a port 100, which is a space into which radio waves are incident.

[0031] The size and other properties of the metal patch 11, slot 15, etc., are set according to the design formulas described below, so that they absorb a predetermined radio wave (so that they resonate at an arbitrary frequency). First, we will explain the method for calculating the size of the metal patch 11. The circular metal patch 11 can be designed in the same way as a circular microstrip antenna. In a patch cell having the metal patch 11, the thickness of the dielectric layer 12 or dielectric 12a is h, and the relative permittivity of the dielectric layer 12 or dielectric 12a is ε r Therefore, the relationship between the size of the metal patch 11 and the frequency of the radio waves it absorbs (matching frequency or resonant frequency) can be expressed by the following equations (1) and (2).

[0032]

number

[0033]

Number

[0034] Here, in formula (1) and formula (2), f is the resonance frequency, c is the speed of light, ε r is the relative permittivity of the dielectric 12a as described above, r is the radius of the metal patch 11, r eff is the effective radius of the metal patch 11. In other words, f is the frequency of the radio wave to be absorbed, and r is d / 2. For the substrate to be used (corresponding to the dielectric layer 12), specifically, after determining a dielectric substrate having an appropriate relative permittivity ε r and determining the frequency f of the radio wave to be absorbed, using each value of the relative permittivity ε r and the frequency f, the diameter (r or d) of the metal patch 11 is calculated from formula (1) and formula (2). In this way, the size of the metal patch 11 that absorbs radio waves of an arbitrary frequency (resonates at an arbitrary frequency) is obtained.

[0035] Next, a method for calculating the size of the slot 15 using the design formula of the printed slot antenna will be described. The slot width S of the slot 15 w is set within the range of S w = 0.01λ to 0.1λ. The above λ is the free space wavelength of an arbitrary resonance frequency (resonance frequency) set for the slot 15.

[0036] The slot length S of the slot 15 l is obtained as follows. FIG. 4 is an explanatory diagram showing a configuration example of a printed slot antenna. The printed slot antenna illustrated in FIG. 4 has a slot of length L s , width W s that is disposed on the back surface of a dielectric substrate (relative permittivity ε r , thickness h) and has a width W fIt is configured to be fed by electromagnetic coupling to a microstrip line. This printed slot antenna is equivalent to a printed dipole antenna. A dipole antenna with a resonant length L0 when placed in free space, with relative permittivity ε r The resonant length L when placed on the substrate s Using the formula to determine the slot length S of slot 15 that resonates at an arbitrary frequency, l The slot length S can be calculated. l The formula for finding is expressed as follows: (3)

[0037]

number

[0038] L0 in equation (3) is calculated by the following equation (4).

[0039]

number

[0040] Note that λ in equation (4) is the free-space wavelength of the matching frequency mentioned above. ε in equation (3) re This can be expressed as shown in equation (5) below.

[0041]

number

[0042] However, in each of the above equations, λ <hである。 ε re This is the effective relative permittivity, which represents the wavelength shortening effect of the dielectric substrate (dielectric layer 12). Note that equation (5) is an approximate formula for calculating the arithmetic mean of the effective relative permittivity. From the above equations, a high relative permittivity ε rIt can be seen that using dielectric material 12a improves the wavelength shortening effect, making it possible to miniaturize the metal patches 11 and reduce the arrangement period (arrangement interval) W of each metal patch 11, thereby enabling miniaturization of the radio wave absorber 1.

[0043] Using equations (1) to (5) above, the diameter (size) of the metal patch 11 that resonates at the desired frequency, the size of the slot 15, etc., are calculated to construct a radio wave absorber 1 that absorbs radio waves of the above arbitrary frequency. Furthermore, an electromagnetic field analysis is performed on the radio wave absorber 1 constructed based on the above calculated values, and the size, shape, arrangement, etc. of each part are optimized to construct the radio wave absorber 1 so that the desired radio wave absorption characteristics can be obtained.

[0044] When a rectangular slot 15 is placed on top of a circular metal patch 11, the way the slot 15 is positioned relative to the metal patch 11 greatly affects the reflected wave suppression characteristics (frequency characteristics) and the radio wave transmission characteristics. When performing optimization as described above, it is preferable to stack the radio wave absorber 1 or the conductor layer 10 so that, when viewed from above, the outer edge of the circular metal patch 11 and the slot 15 overlap, in order to obtain the desired frequency characteristics and to ensure good transmission characteristics.

[0045] The metal patches 11 and slots 15 described here can be configured using design formulas to determine their size and other properties. However, when using metal patches or slots of shapes for which such design formulas are not known, electromagnetic field analysis is performed to determine (optimize) their appropriate size and other properties, thereby constructing the radio wave absorber.

[0046] By calculating the sizes of the matching frequency (resonance frequency) of the metal patch 11 and the matching frequency (resonance frequency) of the slot 15 that overlaps the metal patch 11 via the dielectric layer 12 using the above design formula, and by performing electromagnetic field analysis as described above and optimizing these sizes, the radio wave absorber 1 is constructed. For example, when radio waves passing through port 100 in Figure 2 are incident on the metal patch 11, the radio waves at the frequency at which the metal patch 11 resonates are absorbed by the dielectric layer 12. The radio waves absorbed by the dielectric layer 12 are converted into thermal energy, and any energy that does not change into thermal energy is attracted to the slots 15 (slot layer 13) which have matching frequencies similar to those of the metal patch 11. In other words, the radio wave absorber 1 can suppress the emission of reflected radio waves (energy) that have been incident on the metal patch 11 to the outside of the radio wave absorber 1.

[0047] The radio wave absorber 1 comprises multiple metal patches 11 and slots 15. Therefore, it is also possible to configure the radio wave absorber 1 to have multiple metal patches 11 with different matching frequencies, and to arrange slots 15 having the same matching frequency as each metal patch 11 in pairs with each metal patch 11 (layered arrangement via a dielectric layer 12) in order to absorb radio waves in a predetermined frequency range (having multiple frequency characteristics).

[0048] (Embodiment 2) Figure 5 is an explanatory diagram showing the configuration of the radio wave absorber 1a according to Embodiment 2 of this disclosure. In this figure, the upper side shows the configuration of the radio wave absorber 1a as viewed from above, and the lower side shows the configuration of the radio wave absorber 1a as viewed from the thickness portion (laminated portion). The radio wave absorber 1a includes a conductor layer 10a configured in the same manner as the conductor layer 10 of the aforementioned radio wave absorber 1. In other words, the conductor layer 10a is provided with a circular metal patch 11a similar to the metal patch 11 provided on the conductor layer 10. Furthermore, the radio wave absorber 1a is equipped with a dielectric layer 12 similar to that of the radio wave absorber 1, and the dielectric layer 12 is laminated on the underside of the conductor layer 10a.

[0049] The radio wave absorber 1a has a slot layer 13a stacked on the underside of the dielectric layer 12. The slot layer 13a is formed from a metal foil 14, similar to the slot layer 13 described above, and has multiple ring-shaped (annular) slots 15a provided in the metal foil 14. The slots 15a are arranged so that one slot 15a is stacked on top of one metal patch 11a (overlapping via the dielectric layer 12), and are formed to have a size that has the same matching frequency (resonant frequency) as the metal patch 11a. The size of the ring-shaped slot 15a with a desired matching frequency is determined by a known design formula. Similarly, the size of the circular metal patch 11a with an arbitrary matching frequency is determined by the same design formula as described above for the metal patch 11.

[0050] Furthermore, electromagnetic field analysis is performed on the radio wave absorber 1a constructed based on the values ​​calculated using the above design formula, and the size, shape, arrangement, etc. of each part are optimized to construct the radio wave absorber 1a so that the desired radio wave absorption characteristics can be obtained. The radio wave absorber 1a configured in this way, like the radio wave absorber 1 described above, can suppress the emission of reflected radio waves from the radio wave absorber 1a when radio waves incident on the metal patch 11a.

[0051] The radio wave absorber 1a, like the radio wave absorber 1 described above, can be configured to have multiple metal patches 11a with different matching frequencies, and also to have slots 15a having the same matching frequency as each metal patch 11a paired with each metal patch 11a, thereby absorbing radio waves in a predetermined frequency range (having multiple frequency characteristics).

[0052] (Embodiment 3) Figure 6 is an explanatory diagram showing the configuration of the radio wave absorber 1b according to Embodiment 3 of the present disclosure. In this figure, the upper side shows the configuration of the radio wave absorber 1b as viewed from above, and the lower side shows the configuration of the radio wave absorber 1b as viewed from the thickness portion (laminated portion). The radio wave absorber 1b comprises a conductive layer 10b having a rectangular metal patch 11b, which will be described later. Furthermore, the radio wave absorber 1b is equipped with a dielectric layer 12 similar to that of the aforementioned radio wave absorber 1, and the dielectric layer 12 is laminated on the underside of the conductor layer 10b. Furthermore, the radio wave absorber 1b includes, for example, a slot layer 13b configured in the same way as the slot layer 13 of the aforementioned radio wave absorber 1. That is, the slot layer 13b is provided with rectangular slots 15b in the metal foil 14, similar to the slots 15 described above.

[0053] The size of each part of the rectangular metal patch 11b is determined using the design formula described below, so that it has an arbitrary matching frequency. Here, let W be the width and L be the length of the metal patch 11b. Also, let ε be the relative permittivity of the dielectric 12a stacked on the metal patch 11b. r The thickness of the dielectric 12a or dielectric layer 12 is h, the speed of light is c, and the matching frequency of the metal patch 11b is f. r Let's assume that. In this case, the width W of the metal patch 11b is given by equation (6), and the length L is given by equation (7). Furthermore, ΔL included in equation (7) is given by equation (8).

[0054]

number

[0055] The x1, x3, x4, x5, and x2 in the expression for x3 in equation (7) above can be expressed as follows:

[0056]

number

[0057] Substituting x1, x3, x4, and x5 into equation (7), we find that for the metal patch 11b with matching frequency fr, W = L. That is, the length of one side of the metal patch 11b having the desired matching frequency (resonance frequency) can be determined by equation (6). The size of the metal patch 11b having the desired matching frequency fr is determined as described above.

[0058] The slot 15b in the radio wave absorber 1b is formed in a rectangular shape as described above. The size of slot 15b is determined using the same design formula as when determining the size of slot 15 in the radio wave absorber 1, so that it has the same matching frequency fr as the metal patch 11b that overlaps it via the dielectric layer 12.

[0059] Furthermore, an electromagnetic field analysis is performed on the radio wave absorber 1b constructed based on the values ​​calculated using the above design formula, and the size, shape, arrangement, etc. of each part are optimized to construct the radio wave absorber 1b so that the desired radio wave absorption characteristics can be obtained. The radio wave absorber 1b configured in this manner, like the aforementioned radio wave absorber 1, can suppress the emission of reflected radio waves from the radio wave absorber 1b after they have been incident on the metal patch 11b.

[0060] The radio wave absorber 1b, like the radio wave absorber 1 described above, may be configured to have multiple metal patches 11b with different matching frequencies, and also to have slots 15b having the same matching frequency as each metal patch 11b, paired with each metal patch 11b, thereby absorbing radio waves in a predetermined frequency range (having multiple frequency characteristics).

[0061] The aforementioned radio wave absorbers 1, 1a, and 1b all have metal patches 11 of the same shape on a single conductor layer 10, but it is also possible to provide metal patches of different shapes (multiple shapes) on a single conductor layer. Furthermore, it is possible to construct the system by stacking slots of different shapes (multiple shapes) for each metal patch (stacking metal patches and slots in a one-to-one ratio). Even when providing metal patches and slots of multiple shapes in this way, the size and other characteristics of each are determined so that the matching frequencies of the stacked metal patches and slots are similar.

[0062] Specifically, circular metal patches 11, 11a and rectangular metal patch 11b are provided on the same conductive layer, with slot 15 or slot 15a positioned to overlap with the circular metal patches 11, 11a, and slot 15b positioned to overlap with the rectangular metal patch 11b. In this case, slots 15, 15a, and 15b are provided, for example, on the same slot layer.

[0063] (Embodiment 4) Figure 7 is an explanatory diagram showing the configuration of the radio wave absorber 1c according to Embodiment 4 of this disclosure. This figure shows the configuration when viewing the thickness portion (laminated portion) of the radio wave absorber 1c. The aforementioned radio wave absorbers 1, 1a, and 1b each comprise a single conductor layer 10 and a single dielectric layer 12, while radio wave absorber 1c is constructed by laminating multiple conductor layers 10c and dielectric layers 12.

[0064] The radio wave absorber 1c, for example, has a first conductor layer 10c arranged as the uppermost layer, and a first dielectric layer 12 stacked below the first conductor layer 10c. Furthermore, a second conductive layer 10c is stacked below the first dielectric layer 12, and a second dielectric layer 12 is stacked below the second conductive layer 10c. In this manner, the conductive layer 10c and the dielectric layer 12 are stacked alternately, with the nth dielectric layer 12 stacked below the nth conductive layer 10c, and the slot layer 13c stacked below the nth dielectric layer 12.

[0065] The metal patches 11c provided on the first to nth conductor layers 10c are formed in the same manner as, for example, the aforementioned metal patch 11, metal patch 11a, and metal patch 11b, and each metal patch 11c is arranged so as not to overlap in the stacking direction (when the radio wave absorber 1 is viewed from above). That is, the metal patches 11c of each conductor layer 10c are arranged to stack in a one-to-one ratio with the slots (not shown) provided in the bottommost slot layer 13c, without being obstructed by the metal patches 11c of the conductor layer 10c below.

[0066] Each slot provided in the slot layer 13c has a shape similar to, for example, any of the aforementioned slots 15, 15a, or 15b, and is formed to have a size that has a matching frequency similar to that of the stacked (overlapping) metal patches 11c.

[0067] The metal patches 11c provided in the first to nth conductor layers 10c may be configured to have the same matching frequency, but it is also possible to provide metal patches 11c of different sizes, etc., for each conductor layer 10c, so that each conductor layer 10c has a different matching frequency. In other words, the radio wave absorber 1c may be configured to absorb radio waves in a desired frequency range by setting different matching frequencies for each of the multiple conductor layers 10c.

[0068] Furthermore, the radio wave absorber 1c, like the radio wave absorbers 1, 1a, and 1b described above, is equipped with metal patches of multiple shapes (such as a circular metal patch 11 and a rectangular metal patch 11b) in a single conductor layer, and it is also possible to configure the slot layer 13c to be equipped with slots of multiple shapes (such as a rectangular slot 15 and a ring-shaped slot 15a) corresponding to these metal patches.

[0069] The radio wave absorber 1c can also be configured as an antenna by providing a radio wave waveguide on the underside of the slot layer 13c. Furthermore, the aforementioned radio wave absorbers 1, 1a, and 1b can also be configured as antennas by providing a waveguide on the underside of the lowest layer, such as the slot layer 13.

[0070] Next, we will describe the antenna of this disclosure. Here, we will explain using an antenna in which a waveguide is provided in the radio wave absorber 1 as an example.

[0071] (Embodiment 5) Figure 8 is an explanatory diagram showing the configuration of antenna 2 according to Embodiment 5 of this disclosure. This figure shows a part of antenna 2 configured by providing a waveguide 16 to the radio wave absorber 1 described in Embodiment 1, for example. More specifically, this figure shows a stacked configuration of a unit portion of antenna 2 in which one metal patch 11 (and one slot 15, not shown) is provided.

[0072] The unit portion of antenna 2 in Figure 8 is a unit portion (patch cell) of the radio wave absorber 1 shown in Figure 2, with a waveguide 16 provided. A dielectric layer 22 is stacked below the slot layer 13, and a microstrip line 17 is stacked below the dielectric layer 22, for example. In other words, a metallic microstrip line 17, which is the waveguide 16, is formed on the lower surface (bottom end surface) of the dielectric layer 22 in the figure.

[0073] In other words, the microstrip line 17 is formed on the lower end surface of the dielectric layer 22 and is arranged so as not to come into contact with (is insulated from) the slot layer 13 formed by the metal foil 14. Furthermore, the conductor layer 10, dielectric layer 12, and slot layer 13 constituting the antenna 2 are formed from the same materials as those used for the aforementioned radio wave absorber 1. In addition, the metal patch 11 of the conductor layer 10 and the slots 15 of the slot layer 13 have the same size and shape as those used for the radio wave absorber 1.

[0074] The microstrip line 17 is positioned so as to overlap with the metal patch 11 and slot 15 when viewed from above as a unit portion of the antenna 2, and is configured to conduct radio waves in the direction indicated by the arrow 101 shown in Figure 8. The radio waves conducted by the microstrip line 17 (waveguide 16) are those that pass through port 100 in Figure 2, enter the metal patch 11, and propagate to the slot layer 13 (attracted by the resonance of slot 15).

[0075] The microstrip line 17 is installed, for example, at the bottom layer of antenna 2, after calculating its width, length, arrangement, etc., using known slot antenna design formulas and microstrip line design formulas, so as to match the resonant frequency of the slots 15 stacked on the microstrip line 17. In other words, the microstrip line 17 is arranged such that its relationship (arrangement, etc.) with the slots 15 stacked on top of it is determined by the above design formula, and the direction of radio wave transmission by the microstrip line 17 (arrow 101) is perpendicular to the longitudinal direction of the slots 15. Furthermore, the microstrip line 17 is formed to have a matching frequency similar to that of the stacked slots 15 and metal patches 11.

[0076] The dielectric layer 22 has a wavelength shortening effect. Therefore, when the microstrip line 17 stacked on the dielectric layer 22 is formed to resonate at a predetermined frequency as described above and conduct radio waves, it is necessary to form the line thinly, for example, to correspond to the wavelength shortening effect of the dielectric layer 22. Since thinning the microstrip line 17 requires advanced processing technology, the antenna 2 is constructed, for example, by thinning the microstrip line 17 to an appropriate degree and reducing the wavelength shortening effect of the dielectric layer 22. Specifically, the dielectric layer 22 is formed using a dielectric material with a lower relative permittivity than the dielectric layer 12 (dielectric 12a), so that the microstrip line 17 does not become excessively thin.

[0077] Antenna 2 uses a dielectric material with a high relative permittivity (dielectric 12a) to form the dielectric layer 12 in order to miniaturize the metal patch 11 (conductor layer 10), slot 15 (slot layer 13), and dielectric layer 12 (to make Antenna 2 thinner) at a predetermined frequency (matching frequency). Furthermore, Antenna 2 uses a dielectric layer 22 made of a low dielectric loss tangent material to conduct radio waves that have passed through the slot layer 13 (slot 15 has resonated) to the microstrip line 17 with low loss.

[0078] As described above, antenna 2 is made smaller (thinner) by having two dielectric layers 12 and 22 with different relative permittivity, while also improving radio wave absorption (suppression of reflected waves) characteristics and antenna characteristics.

[0079] (Embodiment 6) Figure 9 is an explanatory diagram showing the configuration of antenna 2a according to Embodiment 6 of this disclosure. This figure shows a part of antenna 2a configured by providing a waveguide 16 to the radio wave absorber 1 described in Embodiment 1. More specifically, this figure shows the stacked configuration of a unit portion of antenna 2a in which one metal patch 11 (and one slot 15, not shown) is provided.

[0080] The unit portion of antenna 2a in Figure 9 is a unit portion (patch cell) of the radio wave absorber 1 shown in Figure 2, equipped with a waveguide 16, and includes a waveguide 18 as the waveguide 16 located below the slot layer 13. Furthermore, the conductor layer 10, dielectric layer 12, and slot layer 13 constituting antenna 2a are formed from the same materials as those used in the aforementioned radio wave absorber 1, and the metal patches 11 of the conductor layer 10, the slots 15 of the slot layer 13, etc., have the same size and shape as those used in the radio wave absorber 1.

[0081] Waveguide 18 is installed, for example, at the bottom of antenna 2a, after calculating its width, length, arrangement, etc., using known design formulas, and optimizing its shape and size, etc., through electromagnetic field analysis, so that it has a matching frequency similar to that of the metal patches 11 and slots 15 stacked on the waveguide 18. In other words, the waveguide 18 is positioned such that its relationship (arrangement, etc.) with the stacked slots 15 is determined by a known design formula, and the direction of radio wave transmission by the waveguide 18 (arrow 101) is perpendicular to the longitudinal direction of the slots 15.

[0082] Furthermore, the waveguide 18 is positioned below the slot layer 13 (in the vicinity of the slot layer 13) so as not to conduct electricity with the slot layer 13, that is, so as not to come into direct contact with the slot layer 13, for example, by providing an appropriate space to give it dielectric properties. For example, the aforementioned dielectric layer 22 may be provided between the slot layer 13 and the waveguide 18 to constitute the antenna 2a.

[0083] The radio waves conducted by the waveguide 18 are those that pass through the port 100 in Figure 2, enter the metal patch 11, and propagate through the dielectric layer 12 to the slot layer 13 (transmitted through the slot layer 13 due to the resonance of the slot 15). In other words, the waveguide 18 is incident on radio waves in which the slot 15 has resonated.

[0084] Antenna 2a, by incorporating a dielectric layer 12 with a high relative permittivity, enables miniaturization of the metal patch 11 and slot 15 at a predetermined frequency (matching frequency). Furthermore, by providing a waveguide 18 below (near) the slot layer 13 as described above, antenna 2a enables low-loss conduction of radio waves that have passed through the slot layer 13 to the waveguide 18, thereby improving radio wave absorption (suppression of reflected waves) characteristics and antenna characteristics.

[0085] (Embodiment 7) Figure 10 is an explanatory diagram showing the configuration of a waveguide 16 provided in an antenna according to Embodiment 7 of the present disclosure. The waveguide 16 in Figure 10 is provided with a post-wall waveguide 19 composed of multiple metal posts 20, instead of the microstrip line 17 in Figure 8. The post-wall waveguide 19 is constructed by arranging a plurality of metal posts 20, formed in a cylindrical or columnar shape using a conductor such as metal, in two rows inside the dielectric layer 22 or on the lower end surface of the dielectric layer 22. The conductor layer 10, dielectric layer 12, slot layer 13, etc., which are stacked on the post-wall waveguide 19 and are not shown in the figure, are the same as those shown in Figure 8.

[0086] The post-wall waveguide 19 is configured to match the matching frequency of the slots 15 stacked on the post-wall waveguide 19 (as well as the matching frequency of the metal patch 11). The size and arrangement of each metal post 20 are calculated using known design formulas, and their shape and size are optimized through electromagnetic field analysis, so that they can be installed, for example, at the bottom layer of the antenna 2. The spacing between each metal post 20 is determined in accordance with the wavelength of the radio waves to be conducted, when the values ​​are calculated using the design formulas as described above, or when they are optimized as described above. When the post-wall waveguide 19 is provided on the antenna 2, the post-wall waveguide 19 is stacked on the slot layer 13 via the dielectric layer 22 such that each metal post 20 overlaps (stacks) with the slot 15. In other words, the slot layer 13 and the post-wall waveguide 19 (metal posts 20) are insulated from each other.

[0087] The radio waves that enter the metal patch 11 (conductor layer 10) and propagate through the dielectric layer 12 to the slot layer 13 (by resonating in the slot 15 and passing through the slot layer 13) are conducted through the two rows of metal posts 20 in the direction of the extension of the rows, that is, in the direction indicated by arrow 101.

[0088] The antenna 2, equipped with a post-wall waveguide 19, forms a dielectric layer 12 using a dielectric material (dielectric 12a) with a high relative permittivity, similar to that described in Embodiment 5. Furthermore, a dielectric layer 22 is formed using a low dielectric loss tangent material. In the antenna 2 equipped with a post-wall waveguide 19, as described above, by providing two dielectric layers 12 and 22 with different relative permittivity, it is possible to miniaturize (thinnen) the antenna while also improving its radio wave absorption (suppression of reflected waves) characteristics and antenna characteristics.

[0089] As described above, each radio wave absorber in this disclosure can function as an antenna by having a waveguide on the lower side of the slot layer. Furthermore, each radio wave absorber and each antenna in this disclosure can have any frequency characteristics (one or more frequency characteristics). Furthermore, each of the radio wave absorbers and antennas in this disclosure can be made thinner, and for example, the overall thickness of the laminated configuration can be made to 2 mm or less.

[0090] (Measurement of reflected waves emitted from radio wave absorber 1) Next, the method for measuring reflected waves emitted from the radio wave absorber 1 of Embodiment 1, as well as the measurement results, will be described. Figure 11 is an explanatory diagram showing the schematic configuration of a measurement system for measuring reflected waves emitted from the radio wave absorber 1. The measurement system shown in Figure 11 includes a turntable 30 on which the radio wave absorber 1 is placed, a transmitting antenna 31 that transmits radio waves toward the radio wave absorber 1 placed on the turntable 30, and a receiving antenna 32 that receives reflected waves radiated from the radio wave absorber 1 placed on the turntable 30.

[0091] The turntable 30 is configured to change the orientation of the radio wave absorber 1 by rotating the turntable 30, thereby adjusting the incidence angle of the radio waves incident on the radio wave absorber 1 from the transmitting antenna 31.

[0092] Furthermore, this measurement system includes a measuring instrument 33 that controls the strength and frequency of the radio waves transmitted from the transmitting antenna 31. The measuring instrument 33 also has the function of analyzing the frequency and intensity of the reflected wave received by the receiving antenna 32, and is, for example, a network analyzer.

[0093] In the measurement system shown in Figure 11, the radio wave absorber 1 is positioned such that the orientation of the uppermost conductor layer 10, i.e., the surface with the metal patch 11, changes with the rotation of the turntable 30. Furthermore, this measurement system is configured such that, as the orientation of the radio wave absorber 1 changes, radio waves from the transmitting antenna 31 are incident at an incident angle of 0 to 60 degrees with respect to the normal to the surface of the radio wave absorber 1. In addition, when measuring reflected waves, this measurement system is configured so that the receiving antenna 32 can be moved to a position where reflected waves with a reflection angle equal to the above-mentioned incident angle can be measured.

[0094] In this measurement system, the distance between the transmitting antenna 31 and the radio wave absorber 1 placed on the turntable 30, and the distance between the receiving antenna 32 and the radio wave absorber 1 placed on the turntable 30 are both 1 [m].

[0095] Figure 15 is an explanatory diagram showing the dimensions of each part of the radio wave absorber 1 used in the measurement system of Figure 11, and the dimensions of each part of the antenna 2 used in the measurement system of Figure 13, which will be described later. The radio wave absorber 1 used in the measurement system shown in Figure 11 was formed to the dimensions shown in Figure 15, for example, by setting the resonant frequency to 5.7 [GHz] and calculating the size of each part.

[0096] Figure 12 is an explanatory diagram showing the reflected wave measured by the measurement system in Figure 11. In Figure 12, the horizontal axis represents the frequency of the reflected wave (frequency of the radio waves transmitted from the transmitting antenna 31), and the vertical axis represents the measured amount of reflection (intensity of the reflected wave). The measurement of reflected waves using the measurement system shown in Figure 11 involves measuring the reflected wave from the radio wave absorber 1 installed in the measurement system, and also measuring the reflected wave from a total reflection structure (not shown) installed in place of the radio wave absorber 1 in the same measurement system, and then calculating the difference between these reflected waves. Here, a metal plate is used as the total reflection structure. The amount of reflection shown on the vertical axis of Figure 12 is the difference between the intensity of the reflected wave from the radio wave absorber 1 and the intensity of the reflected wave from the metal plate.

[0097] The reflectance shown in Figure 12 is the value obtained using a radio wave absorber 1 with a surface size of 200 × 200 [mm] and a metal plate. In detail, radio waves of each frequency are transmitted from the transmitting antenna 31 to the radio wave absorber 1, and the radio waves reflected by the radio wave absorber 1 (reflected waves) are received by the receiving antenna 32 to measure the radio wave strength. Furthermore, even when the metal plate is installed in the measurement system (turntable 30) instead of the radio wave absorber 1, the measurement is performed with a distance of 1 m between the metal plate and the transmitting antenna 31 and the receiving antenna 32, similar to the measurement with the radio wave absorber 1.

[0098] Furthermore, only when the incidence angle of the radio waves transmitted from the transmitting antenna 31 to the radio wave absorber 1 is 0 degrees, the transmitting antenna 31 is used to receive the reflected waves from the radio wave absorber 1 or the metal plate, and the amount of reflection obtained from the measured radio wave intensity at this time is shown in the graph of Figure 12.

[0099] From the measurement results shown in Figure 12, it was confirmed that the radio wave absorber 1 exhibits reduced reflection at the matching frequency (or a frequency near that frequency) set for the metal patch 11 and slot 15, and that its reflection characteristics become -20 dB or less at the matching frequency, i.e., near the design frequency of the metal patch 11 and slot 15.

[0100] Next, the method for measuring the reflected waves radiated from antenna 2 and the measurement results will be explained. Here, we will illustrate the measurement using antenna 2 equipped with the microstrip line 17 of Embodiment 5. Figure 13 is an explanatory diagram showing the schematic configuration of the measurement system for measuring the receiving characteristics of antenna 2. The measurement system shown in Figure 13 includes a turntable 40 on which antenna 2 is placed, and a transmitting antenna 41 that transmits radio waves toward antenna 2 placed on the turntable 40. The turntable 40 is configured to change the orientation of the antenna 2 by rotating the turntable 40, thereby adjusting the incidence angle of the radio waves incident on the antenna 2 from the transmitting antenna 41.

[0101] Furthermore, this measurement system includes a measuring instrument 42 that controls the strength and frequency of the radio waves transmitted from the transmitting antenna 41. The measuring instrument 42 also has the function of analyzing the frequency and intensity (attenuation) of the radio waves received by the antenna 2, and is, for example, a network analyzer.

[0102] In the measurement system shown in Figure 13, the antenna 2 is positioned such that the orientation of the uppermost conductor layer 10, i.e., the surface with the metal patch 11, changes with the rotation of the turntable 40. Furthermore, this measurement system is configured such that, as the orientation of antenna 2 changes, radio waves from the transmitting antenna 41 are incident on antenna 2 within an incident angle range of 0 to 60 degrees, similar to the measurement system in Figure 11. Furthermore, in this measurement system, the distance between the transmitting antenna 41 and the antenna 2 mounted on the turntable 40 is 1 [m].

[0103] The antenna 2 used in the measurement system in Figure 13 has a microstrip line 17 (the microstrip line shown in Figure 15) as described above, and is formed to the size shown in Figure 15. That is, this antenna 2 has a conductor layer 10, a dielectric layer 12, and a slot layer 13 similar to the radio wave absorber 1 used in the measurement system in Figure 11, and further comprises a dielectric layer 22 and a microstrip line 17.

[0104] Figure 14 is an explanatory diagram showing the receiving characteristics of antenna 2 as measured by the measurement system in Figure 13. In Figure 14, the horizontal axis represents the receiving frequency (frequency of the radio waves transmitted from transmitting antenna 41), and the vertical axis represents the gain of antenna 2, which will be described later. The measurement of the receiving characteristics (antenna gain) using the measurement system shown in Figure 13 is performed as follows: The difference between the intensity of the radio waves received by antenna 2 installed in the measurement system shown in Figure 13 and the intensity of the radio waves transmitted from the transmitting antenna 41, i.e., the attenuation, is determined. Alternatively, for example, an arbitrary reference antenna (not shown) can be installed in place of antenna 2 in the measurement system, and the attenuation is determined in the same way as with antenna 2. After this, the gain of antenna 2 is determined by comparing the attenuation of antenna 2 with the attenuation of the reference antenna.

[0105] From the measurement results using the measurement system shown in Figure 13, it was confirmed that antenna 2 has a gain of approximately 3 dBi. Note that the measurement results exemplified in Figure 14 were calculated using Frith's transfer formula in the far-field approximation, without using the attenuation of the reference antenna. [Explanation of symbols]

[0106] 1,1a,1b,1c Radio wave absorber 2.2a antenna 10, 10a, 10b, 10c Conductor layer 11, 11a, 11b, 11c Metal patches 12,22 Dielectric layer 12a Dielectric 13,13a,13b,13c Slot Layer 14 Metal foil 15, 15a, 15b slots 16 Waveguides 17 Microstrip Tracks 18 Waveguide 19 Post-wall waveguide 20 Metal Post 30, 40 Turntables 31,41 Transmitting antenna 32 Receiving antenna 33,42 Measuring instruments 100 ports

Claims

1. A conductor layer comprising multiple patch conductors arranged at predetermined intervals, A dielectric layer is laminated below the conductor layer, A slot layer having multiple slots, which is stacked on the lower side of the dielectric layer, It has, The patch conductors and slots that overlap across the dielectric layer are formed to have similar matching frequencies. A radio wave absorber characterized by the following features.

2. The aforementioned patch conductor is formed in a circular shape, The slot is formed in a rectangular or ring shape. The radio wave absorber according to feature 1.

3. The patch conductor is formed in a rectangular shape, The aforementioned slot is formed in a rectangular shape. The radio wave absorber according to feature 1.

4. The plurality of patch conductors consist of a first patch conductor formed in a circular shape and a second patch conductor formed in a rectangular shape. Of the plurality of slots, the first slot that overlaps with the first patch conductor is formed in a rectangular or ring shape. Of the plurality of slots, the second slot that overlaps with the second patch conductor is formed in a rectangular shape. The radio wave absorber according to feature 1.

5. Multiple conductor layers and dielectric layers are stacked on a single slot layer. A radio wave absorber according to any one of claims 1 to 4.

6. A conductor layer comprising multiple patch conductors arranged at predetermined intervals, A first dielectric layer is laminated below the conductor layer, A slot layer having multiple slots, which is stacked below the first dielectric layer, A waveguide is disposed below the slot layer via a second dielectric layer, It has, The patch conductors and slots overlapping via the first dielectric layer have similar matching frequencies, and the waveguide is formed to match the slots. Furthermore, the aforementioned second dielectric layer is formed using a low dielectric loss tangent material. An antenna characterized by the following features.

7. The aforementioned patch conductor is formed in a circular shape, The slot is formed in a rectangular or ring shape. The antenna according to feature 6.

8. The patch conductor is formed in a rectangular shape, The aforementioned slot is formed in a rectangular shape. The antenna according to feature 6.

9. The plurality of patch conductors consist of a first patch conductor formed in a circular shape and a second patch conductor formed in a rectangular shape. Of the plurality of slots, the first slot that overlaps with the first patch conductor is formed in a rectangular or ring shape. Of the plurality of slots, the second slot that overlaps with the second patch conductor is formed in a rectangular shape. The antenna according to feature 6.

10. Multiple conductor layers and the first dielectric layer are stacked on a single slot layer. The antenna according to any one of claims 6 to 9, characterized in that it is an antenna.

11. The second dielectric layer has a lower relative permittivity than the first dielectric layer. The waveguide is, It is a microstrip line or post-wall waveguide. The antenna according to any one of claims 6 to 10, characterized by...

12. The waveguide is a waveguide. The antenna according to any one of claims 6 to 10, characterized by...

13. Multiple conductor layers and the first dielectric layer are stacked on a single slot layer. The antenna according to any one of claims 6 to 12.

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