Signal transmitter / receiver, moving means, traffic route, and communication facility

Abstract

To provide a signal transmitter / receiver capable of achieving both target detection performance and reduction of erroneous detection.SOLUTION: A signal transceiver comprising: a control circuit; an antenna body including an antenna element group that is an assembly of a plurality of antenna elements; and an electromagnetic wave absorber, wherein the electromagnetic wave absorber and the antenna body have all of the following features 1 to 3. Feature 1: An angle φ formed between the electromagnetic wave absorber and the antenna body surface is π / 4 or more and 3 π / 4 or less. Feature 2: An electromagnetic wave absorber is installed toward an electromagnetic wave transmission direction of the antenna body surface. Feature 3: The following expressions 1 and 2 are satisfied, where A (k) is a return loss at a peak top when an electromagnetic wave is incident on the electromagnetic wave absorber from the antenna body at an incident angle k, and θ is an angle formed by a traveling direction of the electromagnetic wave transmitted by the antenna body and a direction of a main side lobe. A (π / 2 - θ)> A (2 π / 3 - θ) Expression 1 A (π / 2 - θ)> A (π / 3 - θ) Expression 2 SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a signal transmitter / receiver, a means of transportation, a traffic route, and a communication facility that has excellent target detection performance and is less affected by noise. [Background technology]

[0002] In recent years, in the fields of sensing and communications, there has been progress in the development of technologies that use electromagnetic waves in the millimeter wave band with frequencies of 20 to 100 GHz. For example, in the field of automotive sensing, the use of millimeter wave electromagnetic waves is being considered for rear and side radar (frequency 24 GHz), forward radar (frequency 77 to 79 GHz), and in-vehicle radar (frequency 60 GHz), and its use is expected to lead to advances in autonomous driving technology.

[0003] In addition, millimeter wave communications (5G, 6G), which is becoming increasingly widespread worldwide, enables faster, larger capacity communications, multiple simultaneous connections, and lower latency than communications using conventional frequency bands. However, because the electromagnetic waves used are high frequency, they tend to travel in a direction that is strong and they are easily affected by obstacles.

[0004] Furthermore, when using millimeter-wave electromagnetic waves for sensing purposes, noise caused by side lobes becomes a problem. When the side lobes are reflected by surrounding objects and the sensor detects the reflected waves, the radar erroneously recognizes that an object is present in a location where there is no object to be detected. One technique that has been disclosed to reduce false detections caused by noise is to install an electromagnetic wave absorber inside the radar housing (Patent Document 1). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2022-55763 [Patent Document 2] International Publication No. 2021 / 100566 [Non-patent literature]

[0006] [Non-Patent Document 1] J.McNaband A.Sandborg:TheEDAX EDITOR, Vol.14, No.1, p.37(1984) Summary of the Invention [Problem to be solved by the invention]

[0007] However, as described in Patent Document 1, the method of installing an electromagnetic wave absorber inside the radar housing has the problem that the electromagnetic wave absorber blocks the main lobe or does not sufficiently absorb the side lobes. Therefore, the method described in Patent Document 1 makes it difficult to maintain target detection performance while reducing false detections. Therefore, an object of the present invention is to provide a signal transceiver that reduces the blockage of the main lobe and absorbs the side lobes, thereby maintaining target detection performance and reducing false detections due to noise. [Means for solving the problem]

[0008] The present invention aims to solve the above-mentioned problems and comprises the following configuration: A signal transceiver including a control circuit, an antenna having an antenna element group that is an assembly of a plurality of antenna elements, and an electromagnetic wave absorber, wherein the electromagnetic wave absorber and the antenna have all of the following features 1 to 3. Feature 1: The angle φ formed between the electromagnetic wave absorber and the antenna surface is equal to or greater than π / 4 and equal to or less than 3π / 4. Feature 2: An electromagnetic wave absorber is installed on the surface of the antenna facing the direction in which the electromagnetic waves are emitted. Feature 3: When an electromagnetic wave is incident from the antenna onto the electromagnetic wave absorber at an incident angle k, the return loss at the peak top is defined as A(k), and the angle formed between the propagation direction of the electromagnetic wave emitted by the antenna and the direction of the main side lobe is defined as θ, the following formulas 1 and 2 are satisfied. Note that in the present invention, angles are expressed in radians. Equation 1: A(π / 2-θ)>A(2π / 3-θ) Equation 2: A(π / 2-θ)>A(π / 3-θ).

[0009] The signal transmitter / receiver of the present invention may also be configured as follows, and may be used to form a means of transportation, a traffic route, and a communication facility. (1) A signal transceiver comprising a control circuit, an antenna body having an antenna element group which is an aggregate of a plurality of antenna elements, and an electromagnetic wave absorber, wherein the electromagnetic wave absorber and the antenna body have all of the following characteristics 1 to 3. Feature 1: The angle φ formed between the electromagnetic wave absorber and the antenna surface is equal to or greater than π / 4 and equal to or less than 3π / 4. Feature 2: An electromagnetic wave absorber is installed on the surface of the antenna facing the direction in which the electromagnetic waves are emitted. Feature 3: When an electromagnetic wave is incident from the antenna onto the electromagnetic wave absorber at an incident angle k, the reflection loss at the peak top is defined as A(k), and the angle formed between the traveling direction of the electromagnetic wave emitted by the antenna and the direction of the main side lobe is defined as θ, the following formulas 1 and 2 are satisfied. Equation 1: A(π / 2-θ)>A(2π / 3-θ) Equation 2: A(π / 2-θ)>A(π / 3-θ) (2) A signal transceiver according to (1), wherein at least one of the antennas satisfies the following formula 3, where C is the center point of the antenna element group, P1 is the point on the electromagnetic wave absorber closest to C, L1 is the distance between C and P1, P2 is the point on the electromagnetic wave absorber that exists in the direction of propagation of the electromagnetic wave and is farthest from P1 on a plane that includes C and P1 and is perpendicular to the antenna surface, and L2 is the distance between P1 and P2. Formula 3: tan(θ) / 20≦L1 / L2≦tan(θ) / 2 (3) A signal transceiver according to (1) or (2), wherein the antenna element group includes at least one transmitting antenna element group and one receiving antenna element group, and the following formula 4 is satisfied when the inter-element distance in the transmitting antenna element group is d and the peak top wavelength of the electromagnetic wave emitted by the transmitting antenna element group is λ. Equation 4: sinθ=(λ / d)-1 (4) The signal transceiver according to any one of (1) to (3), wherein the electromagnetic wave absorber is disposed in the arrangement direction of the group of antenna elements. (5) The signal transceiver according to (3) or (4), wherein the electromagnetic wave absorber is installed between the group of transmitting antenna elements and the group of receiving antenna elements. (6) The signal transceiver according to any one of (1) to (5), wherein the electromagnetic wave absorbers are provided on at least two of the four sides of the antenna. (7) A signal transceiver according to any one of (3) to (6), wherein the angle between the polarization direction of the electromagnetic waves emitted by the transmitting antenna element group and the orientation direction of the electromagnetic wave absorber is greater than or equal to 0 and less than or equal to π / 6. (8) The signal transceiver according to any one of (1) to (7), wherein the electromagnetic wave absorber has a return loss peak in a frequency band of 20 to 100 GHz, the return loss A(k) at the peak top of which is 15 dB or more. (9) A signal transceiver according to any one of (1) to (8), wherein the electromagnetic wave absorber includes an alternating laminate unit in which two types of layers (layer A and layer B) with different conductivity are alternately laminated in 5 to 1001 layers. (10) The signal transceiver according to any one of (1) to (9), wherein the electromagnetic wave absorber is located in a control circuit portion. (11) The signal transceiver according to any one of (1) to (10), wherein the electromagnetic wave absorber includes a surface having an arithmetic mean height Sa of 1 nm or more and 500 nm or less. (12) A means of transportation comprising the signal transceiver according to any one of (1) to (11). (13) A traffic route equipped with a signal transmitter / receiver according to any one of (1) to (11). (14) A communication facility equipped with a signal transmitter / receiver according to any one of (1) to (11). [Effects of the Invention]

[0010] According to the present invention, it is possible to provide a signal transmitter / receiver that maintains target detection performance while reducing false detection due to noise by reducing main lobe obstruction and absorbing side lobes. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a schematic diagram of a signal transceiver according to an embodiment of the present invention, viewed from the direction of propagation of electromagnetic waves. [Figure 2] 1 is a schematic diagram showing the electromagnetic wave transmission direction when a signal transceiver according to an embodiment of the present invention is viewed from a direction perpendicular to the antenna body. [Figure 3] 1 is a schematic diagram of a signal transceiver according to one embodiment of the present invention (an embodiment having an electromagnetic wave absorber attached to a control circuit portion) viewed from the direction of propagation of electromagnetic waves. [Figure 4] 1 is a schematic diagram showing points C, P1, and P2 when a signal transceiver according to an embodiment of the present invention is viewed from the electromagnetic wave transmission direction. [Figure 5] 1 is a schematic diagram showing points C, P1, and P2 when a signal transceiver according to an embodiment of the present invention is viewed from a direction perpendicular to the antenna. DETAILED DESCRIPTION OF THE INVENTION

[0012] The signal transceiver of the present invention comprises a control circuit, an antenna having an antenna element group that is an aggregation of a plurality of antenna elements, and an electromagnetic wave absorber, wherein the electromagnetic wave absorber and the antenna have all of the following features 1 to 3. The signal transceiver of the present invention will be described in detail below. Feature 1: The angle φ formed between the electromagnetic wave absorber and the antenna surface is equal to or greater than π / 4 and equal to or less than 3π / 4. Feature 2: An electromagnetic wave absorber is installed on the surface of the antenna facing the direction in which the electromagnetic waves are emitted. Feature 3: When an electromagnetic wave is incident from the antenna onto the electromagnetic wave absorber at an incident angle k, the reflection loss at the peak top is defined as A(k), and the angle formed between the traveling direction of the electromagnetic wave emitted by the antenna and the direction of the main side lobe is defined as θ, the following formulas 1 and 2 are satisfied. Equation 1: A(π / 2-θ)>A(2π / 3-θ) Equation 2: A(π / 2-θ)>A(π / 3-θ).

[0013] In the present invention, a signal transmitter / receiver refers to all devices that transmit and receive electromagnetic waves, and all devices that transmit electromagnetic waves.

[0014] The signal transmitter / receiver of the present invention includes a control circuit, an antenna having an antenna element group that is a collection of multiple antenna elements, and an electromagnetic wave absorber. The antenna plays a role in transmitting and / or receiving electromagnetic waves that become signals in the signal transmitter / receiver, and this function is realized by the antenna elements that make up the antenna and the antenna element group that is a collection of such antenna elements. The antenna element group may be divided into a receiving element group and a transmitting element group. In such cases, each antenna element group may be referred to as a receiving antenna element group and a transmitting antenna element group. Here, the receiving antenna element group is responsible for receiving signals (electromagnetic waves), and the transmitting antenna element group is responsible for transmitting signals. The control circuit is responsible for sending signals to the antenna, receiving and processing electromagnetic waves received by the antenna (e.g., detection processing and frequency analysis processing), and communicating with external devices. The electromagnetic wave absorber also plays a role in absorbing unnecessary electromagnetic waves, thereby reducing malfunctions such as false detection.

[0015] The configuration of a signal transceiver of the present invention will be described below with reference to the drawings. Fig. 1 is a schematic diagram of a signal transceiver according to an embodiment of the present invention, viewed from the direction of propagation of electromagnetic waves. The signal transceiver A of the embodiment shown in Fig. 1 includes a control circuit 2 and an antenna 3 on a substrate 1. The antenna 3 has a group of receiving antenna elements 4 and a group of transmitting antenna elements 5. The electromagnetic wave absorbers include an electromagnetic wave absorber 6 attached to the outside of the antenna, an electromagnetic wave absorber 7 attached along the antenna element arrangement direction, and an electromagnetic wave absorber 8 attached between the group of receiving antenna elements and the group of transmitting antenna elements. Note that the electromagnetic wave absorber 7 has a hole in the antenna element portion.

[0016] It is important that the signal transmitter / receiver of the present invention has an electromagnetic wave absorber installed facing the electromagnetic wave transmission direction on the antenna surface. Here, the "electromagnetic wave transmission direction on the antenna surface" refers to the three-dimensional range in which, when the direction in which the antenna is installed on the board is defined as the O direction along a line perpendicular to the antenna, the angle formed with the O direction is between 0 and π / 2 for at least one antenna element. "An electromagnetic wave absorber installed facing the electromagnetic wave transmission direction on the antenna surface" refers to a state in which the electromagnetic wave absorber is positioned so that it partially overlaps with the electromagnetic wave transmission direction on the antenna surface and is irradiated with electromagnetic waves from the antenna. A schematic diagram of this "electromagnetic wave transmission direction on the antenna surface" is shown in Figure 2. In Figure 2, reference numeral 9 denotes the O direction, and reference numeral 10 denotes the electromagnetic wave transmission direction. This configuration can reduce false detections caused by side lobes.

[0017] When the signal transmitter / receiver of the present invention has a group of transmitting antenna elements and a group of receiving antenna elements as in the embodiment of Fig. 1, it is preferable that an electromagnetic wave absorber be installed between the group of transmitting antenna elements and the group of receiving antenna elements. This configuration can reduce false detections caused by noise such as interference of side lobes of the group of transmitting antenna elements with the group of receiving antenna elements, or interference of unwanted electromagnetic waves generated by reflections or external sources with the group of receiving antenna elements.

[0018] In the signal transceiver of the present invention, it is preferable that electromagnetic wave absorbers are installed on at least two of the four sides of the antenna. "An electromagnetic wave absorber is installed on one of the four sides of the antenna" refers to a state in which, when the entire antenna is surrounded by a rectangular parallelepiped with the smallest volume and an attempt is made to view the antenna from a line drawn outward from the center of each face except for the face that includes the electromagnetic wave transmission direction of the antenna face and the opposite face, the antenna is invisible in one direction due to the electromagnetic wave absorber. "Electromagnetic wave absorbers are installed on two of the four sides of the antenna" means that, when an attempt is made to view the antenna under the above conditions, there are two directions in which the antenna is invisible due to the electromagnetic wave absorber, and the same interpretation can be applied hereinafter even if the number of directions changes.

[0019] By configuring the signal transceiver of the present invention in this manner, noise caused by interference of the antenna elements with unwanted electromagnetic waves from multipath or external sources can be reduced, and the occurrence of false detections due to this can be suppressed. From the above viewpoint, it is more preferable that electromagnetic wave absorbers are provided on at least three of the four sides of the antenna, and even more preferable that electromagnetic wave absorbers are provided on all four sides of the antenna.

[0020] In the signal transceiver of the present invention, it is preferable that the electromagnetic wave absorber be arranged in the arrangement direction of the antenna element group. Here, "the electromagnetic wave absorber is arranged in the arrangement direction of the antenna element group" means that the electromagnetic wave absorber is arranged so as to cover at least a portion of the antenna body other than the antenna element group. For example, in the embodiment shown in FIG. 1, this refers to a state in which the electromagnetic wave absorber is arranged so as to cover the surface of the substrate on which the antenna element group is attached. Typically, the antenna element group is arranged on the substrate as shown in FIG. 1, but by arranging the electromagnetic wave absorber in the arrangement direction of the antenna element group, it is possible to reduce interference with other antenna element groups due to noise caused by electromagnetic waves reflected by the substrate and the resulting false detection.

[0021] In the signal transceiver of the present invention, it is preferable that the electromagnetic wave absorber is located in the control circuit section. Here, "the electromagnetic wave absorber is located in the control circuit section" means that the electromagnetic wave absorber is arranged so as to cover at least a part of the control circuit section. For example, in the embodiment shown in FIG. 3, this refers to a state in which the electromagnetic wave absorber is installed so as to cover the surface of the control circuit section present on the substrate (in FIG. 3, reference numeral 11 indicates the electromagnetic wave absorber located in the control circuit section). By adopting such an embodiment, noise caused by electromagnetic waves reflected by the control circuit section can be absorbed, thereby reducing false detection.

[0022] The electromagnetic wave absorber is preferably installed in at least one location on two sides (preferably all four sides) of the antenna, between the transmitting antenna element group and the receiving antenna element group, in the arrangement direction of the antenna element group, and in the control circuit portion, and more preferably in two or more locations.Since the side lobes of the electromagnetic waves emitted by the control circuit are transmitted in multiple directions, installing electromagnetic wave absorbers that absorb the side lobes in multiple locations can improve the effect of reducing false detection.

[0023] In the signal transceiver of the present invention, it is important that the angle φ between the electromagnetic wave absorber and the antenna surface be between π / 4 and 3π / 4, in order to reduce false detections caused by side lobes. Here, the antenna surface refers to the surface on which the antenna is located (in the embodiment of FIG. 1, this corresponds to the surface of the substrate). In an embodiment in which multiple electromagnetic wave absorbers are installed, the phrase "the angle φ between the electromagnetic wave absorber and the antenna surface is between π / 4 and 3π / 4" means that at least one electromagnetic wave absorber satisfies this requirement. From this perspective, it is more preferable that at least two electromagnetic wave absorbers satisfy this requirement. With this configuration, the electromagnetic wave absorber absorbs the side lobes without interfering with the main lobe transmitted from the control circuit, thereby reducing false detections and noise while maintaining object detection strength. From this perspective, the angle φ between the electromagnetic wave absorber and the antenna surface is preferably between π / 3 and 2π / 3, more preferably greater than 5π / 12 and less than 7π / 12.

[0024] If the electromagnetic wave absorber has a curved surface, the angle φ between the electromagnetic wave absorber and the antenna surface is the angle between the plane that is in contact with the center of gravity of the electromagnetic wave absorber and the antenna surface. The same applies when the antenna surface is curved.

[0025] Furthermore, as mentioned above, in the signal transmitter / receiver of the present invention, it is important to install an electromagnetic wave absorber in the direction of electromagnetic wave transmission, but an electromagnetic wave absorber may also be installed behind the control circuit (in other words, on the opposite side of the control circuit from the direction of electromagnetic wave transmission).

[0026] In the signal transceiver of the present invention, it is preferable that at least one of the antennas satisfies the following formula 3, where the center point of the antenna element group is point C, the point on the electromagnetic wave absorber closest to point C is point P1, the distance between point C and point P1 is L1, the point on the electromagnetic wave absorber that exists in the direction of propagation of the electromagnetic wave and is farthest from point P1 on a plane that includes points C and P1 and is perpendicular to the surface of the antenna is point P2, and the distance between points P1 and P2 is L2. Equation 3: tan(θ) / 20≦L1 / L2≦tan(θ) / 2.

[0027] Here, "at least one of the antennas satisfies the following formula 3" means that the signal transmitter / receiver has a combination of an antenna and an electromagnetic wave absorber that satisfies formula 3. In other words, if the signal transmitter / receiver has multiple antennas and / or multiple electromagnetic wave absorbers, it is sufficient that at least one combination satisfies formula 3.

[0028] Each point will be explained below with reference to the drawings. Fig. 4 is a schematic diagram showing points C, P1, and P2 when viewed from the electromagnetic wave transmission direction of a signal transceiver according to an embodiment of the present invention, and Fig. 5 is a schematic diagram showing points C, P1, and P2 when viewed from a direction perpendicular to the antenna body of a signal transceiver according to an embodiment of the present invention. Point C 13 is the center of gravity of a rectangle drawn to include all of the receiving antenna element group 4 and minimize its area when the receiving antenna element group 4 is observed from a direction perpendicular to the board (substrate 1 in the embodiment of Figs. 4 and 5) on which the antenna element group (receiving antenna element group 4 in Figs. 4 and 5) is attached (the rectangle is shown by a dashed line in Fig. 4). Once point C 13 is determined as described above, the point on the electromagnetic wave absorber (electromagnetic wave absorber 6 attached to the radar side on all four sides of the antenna in Figures 4 and 5) closest to point C 13 is determined as point P1 12 (not shown in Figure 4 because it is hidden by point P2 14), and the point furthest from point P1 12 on a plane that includes point C 13 and point P1 12 and is perpendicular to the antenna surface is determined as point P2 14. Note that the antenna surface refers to the surface on which the antenna (antenna element group) is located (the surface of substrate 1 in the embodiment of Figures 4 and 5).

[0029] By installing the antenna element group and electromagnetic wave absorber so as to satisfy Equation 3, the signal transmitter / receiver can cut the side lobes with the electromagnetic wave absorber without obstructing the main lobe. Note that while Figures 4 and 5 assume that the installation angle of the electromagnetic wave absorber is π / 2, if the installation angle is not π / 2, from the above perspective, it is preferable that L1 / L2 satisfy cos(θ-φ) / 20cos(θ)≦L1 / L2≦cos(θ-φ) / 2cos(θ).

[0030] In the signal transceiver of the present invention, the antenna element group includes at least one transmitting antenna element group and one receiving antenna element group, and preferably satisfies the following formula 4, where d is the inter-element distance in the transmitting antenna element group and λ is the peak-top wavelength of the electromagnetic waves emitted by the transmitting antenna element group. By satisfying the following formula 4, it is possible to determine the direction of the side lobes emitted from the antenna and install an electromagnetic wave absorber in an effective position, thereby effectively reducing noise caused by the side lobes. Note that the inter-element distance d in the transmitting antenna element group refers to the shortest distance between two adjacent antenna elements. Furthermore, when the transmitting antenna element group includes three or more antenna elements and the distance between adjacent antenna elements is not constant, d is the shortest distance among the shortest distances between the antenna elements. Equation 4: sinθ=(λ / d)−1.

[0031] To set θ within the range that satisfies the above formula 4, it is preferable to adjust the angle of the antenna element or the aspect ratio of the antenna element. Adjusting the angle of the antenna element means adjusting the angle between one antenna element and another antenna element in the antenna element group in the in-plane direction of the board. Another preferable method is to make the signals input to each antenna element in the same phase.

[0032] In the signal transmitter / receiver of the present invention, since the side lobes increase in angle of incidence with respect to the electromagnetic wave absorber surface, it is important to use an electromagnetic wave absorber that exhibits a high absorption amount in the direction in which the side lobes are incident. Therefore, when the return loss at the peak top when an electromagnetic wave is incident from an antenna onto the electromagnetic wave absorber at an incident angle k is A(k), and the angle between the propagation direction of the electromagnetic wave emitted by the antenna and the direction of the main side lobe is θ, the following formulas 1 and 2 are satisfied. Note that when 2π / 3-θ and π / 3-θ exceed π / 2 or are less than 0, A(2π / 3-θ) and A(π / 3-θ) are set to A(17π / 36) and A(0), respectively, so long as formulas 1 and 2 are satisfied. When 2π / 3-θ exceeds π / 2, A(2π / 3-θ) is set to A(17π / 36) instead of A(π / 2). This is because when the incident angle of the electromagnetic wave incident on the electromagnetic wave absorber exceeds 17π / 36, it becomes difficult to measure the amount of electromagnetic wave absorption using the measurement method described in (1) Return Loss in the Examples. Equation 1: A(π / 2-θ)>A(2π / 3-θ) Equation 2: A(π / 2-θ)>A(π / 3-θ).

[0033] Here, "the direction of propagation of the electromagnetic wave emitted by the antenna" refers to the direction of propagation of the strongest electromagnetic wave (main lobe) emitted by the antenna. Furthermore, "main side lobe" refers to the electromagnetic wave emitted by the antenna that has the second strongest intensity after the main lobe, and "direction of the main side lobe" refers to the direction of propagation of the main side lobe. Note that the main lobe and side lobe are not emitted in a straight line but radially, so their propagation direction is defined as the direction of strongest intensity. Satisfying both Equations 1 and 2 simultaneously means that the reflection attenuation effect of the electromagnetic wave absorber is greater when the incident angle k is π / 2-θ than when the incident angle k is 2π / 3-θ or π / 3-θ.

[0034] It is preferable that the electromagnetic wave absorber satisfies formulas 1 and 2 in one of four locations: two directions (preferably four directions) of the antenna, between the transmitting and receiving antenna elements, the array direction of the antenna elements, and the control circuit. This configuration enhances absorption of side lobes with large angles of incidence on the electromagnetic wave absorber surface, thereby reducing near-field false detection and long-field noise floor. Here, near-field false detection occurs when side lobes are reflected by surrounding objects and received by the receiving antenna elements, resulting in the false detection of an object in a location where there is no object. For example, electromagnetic waves reflected by an object and returned to the millimeter-wave radar are reflected by the millimeter-wave radar's circuit board or control circuit, and then reflected back to the millimeter-wave radar, resulting in second and third harmonics, etc., which can also cause near-field false detection. The long-field noise floor is an unwanted electrical signal generated by electromagnetic wave interference.

[0035] In order to make the electromagnetic wave absorber have a high absorption amount from a specific direction, it is preferable that the peak top of the return loss of the electromagnetic wave absorber is present in the frequency band of the electromagnetic wave to be absorbed. As a method for changing the position of the peak top, for example, a method can be mentioned in which the electromagnetic wave absorber includes an alternating laminate unit in which two types of layers (A layer and B layer) with different conductivity are alternately laminated in 5 to 1001 layers (details will be described later), and then the lamination ratio, thickness, dielectric constant, etc. of each layer constituting the alternating laminate unit of the electromagnetic wave absorber is changed.

[0036] One method for increasing the electromagnetic wave absorption capacity of an electromagnetic wave absorber by adjusting the lamination ratio is to adjust the screw rotation speed (rpm) of a twin-screw extruder to change the extrusion rate of the thermoplastic resin or thermoplastic resin composition used to form each layer, thereby adjusting the lamination ratio. Methods for increasing the electromagnetic wave absorption capacity of an electromagnetic wave absorber by adjusting the dielectric constant of each layer include, for example, adjusting the content of conductive material in each layer or using a conductive material with a high aspect ratio, taking into account that the apparent dielectric constant and magnetic permeability change depending on the angle of incidence when electromagnetic waves are incident from an oblique direction relative to the electromagnetic wave absorber surface. Another method for increasing the electromagnetic wave absorption capacity of an electromagnetic wave absorber by adjusting the thickness involves, for example, calculating the propagation distance within the electromagnetic wave absorber from the frequency of the incident electromagnetic wave and then using an electromagnetic wave absorber with an optimal thickness calculated from that distance and the angle of incidence when the wave is incident from a specific direction. Specifically, if absorption is high at normal incidence and decreases at an angle, increasing the thickness of each layer can increase the electromagnetic wave absorption capacity from a specific direction.

[0037] In the signal transceiver of the present invention, the electromagnetic wave absorber preferably includes an alternating laminate unit in which two types of layers (A layers and B layers) with different conductivities are alternately laminated in 5 to 1001 layers. "A layers and B layers are alternately laminated" refers to an embodiment in which A layers and B layers are alternately positioned in the thickness direction. For example, in a configuration in which A layers are included as at least one of the outermost layers, this refers to a state in which A layers and B layers with different conductivities are laminated according to a regular arrangement of A(BA)n or A(BA)nB (n is an integer of 2 or more representing a repeating unit). A method for alternately laminating A layers and B layers with different conductivities will be described later. Hereinafter, an alternating laminate unit in which A layers and B layers are alternately laminated may be simply referred to as an "alternating laminate unit." When the signal transceiver of the present invention includes multiple electromagnetic wave absorbers, it is sufficient that at least one of them includes the alternating laminate unit. However, it is preferable that many of the electromagnetic wave absorbers include the alternating laminate unit, and most preferably, all of the electromagnetic wave absorbers include the alternating laminate unit.

[0038] The materials constituting the A layer and the B layer are not particularly limited, and may be transparent / opaque, flexible / rigid, flat / non-flat, or organic (polymer) or inorganic (metal) materials. However, from the viewpoint of processability, it is preferable that the A layer and the B layer be primarily composed of an organic polymer material that exhibits flexibility. Here, the term "primary component" refers to a component that is contained in an amount of more than 50% by mass but not more than 100% by mass when the entire layer is taken as 100% by mass, and the same applies hereinafter to "primary component." In addition, a functional layer such as a hard coat using a thermosetting resin or a photocurable resin can be provided on the surface of the alternating laminate unit.

[0039] The A layer and the B layer in the alternating laminate unit preferably have different electrical conductivities. The difference in electrical conductivities between the A layer and the B layer means that the A layer and the B layer have different surface resistivities, which are indicators of electrical conductivity and insulating properties in the layer direction (plane direction of the sheet) of each layer. More specifically, when the higher surface resistivity of the A layer and the B layer is α [Ω / sq] and the lower surface resistivity is β [Ω / sq], α / β is 1.1 or more. From the viewpoint of enhancing the electromagnetic wave absorption effect due to polarization at the layer interface, α / β is preferably 1.0 × 10 2 More preferably, 1.0 × 10 5 or more, more preferably 1.0 × 10 9 The upper limit of α / β is 1.0×10 20 In addition, the surface resistivity is 1.0 × 10 5 The presence of a layer with a surface resistivity of Ω / sq or more on the outermost surface improves electromagnetic wave absorption. Therefore, the layer with the lower conductivity between A and B has a surface resistivity of 1.0×10 5 Ω / sq or more, and the highly conductive layer has a surface resistivity of 1.0×10 5 It is more preferable that the outermost layer is a layer having low conductivity, with α / β being 1.1 or more or in the above-mentioned preferred range while showing a conductivity of less than Ω / sq.

[0040] The method for making the A and B layers different in conductivity is not particularly limited. For example, the A and B layers may be made of materials with different dielectric constants as their main components, or the types and amounts of conductive and magnetic materials contained in each layer may be different. A combination of these methods is also possible. In particular, to adjust the frequency of the return loss peak to the desired frequency band, a configuration that allows for fine adjustment of the conductivity of the A and B layers is preferred. For example, a configuration in which the A and B layers have different dielectric constants and contain conductive or magnetic materials to change the difference in surface resistance is preferred. The dielectric constant referred to here is a dimensionless quantity that represents the magnitude of the dielectric constant when the dielectric constant (electric constant) in a vacuum is used as the reference. Hereinafter, the dielectric constant will be referred to as the dielectric constant (a detailed measurement method will be described later).

[0041] As the organic polymer material exhibiting flexibility in the A layer and B layer, from the viewpoint of processability and film-forming properties, an elastomer resin such as rubber or a thermoplastic resin is preferable, and a thermoplastic resin is more preferable.Examples of thermoplastic resins include polyolefin resins such as polyethylene, polypropylene, poly(1-butene), poly(4-methylpentene), polyisobutylene, polyisoprene, polybutadiene, polyvinylcyclohexane, polystyrene, poly(α-methylstyrene), poly(p-methylstyrene), polynorbornene, and polycyclopentene; polyamide resins such as nylon 6, nylon 11, nylon 12, and nylon 66; vinyl monomer copolymer resins such as ethylene / propylene copolymer, ethylene / vinylcyclohexane copolymer, ethylene / vinylcyclohexene copolymer, ethylene / alkyl acrylate copolymer, ethylene / acrylic methacrylate copolymer, ethylene / norbornene copolymer, ethylene / vinyl acetate copolymer, propylene / butadiene copolymer, isobutylene / isoprene copolymer, and vinyl chloride / vinyl acetate copolymer; and acrylic resins such as polyacrylate, polymethacrylate, polymethyl methacrylate, polyacrylamide, and polyacrylonitrile. Polyester resins typified by polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate, polyethylene-2,6-naphthalate, etc.; polyether resins typified by polyethylene oxide, polypropylene oxide, polyacrylene glycol, cellulose ester resins typified by diacetyl cellulose, triacetyl cellulose, propionyl cellulose, butyryl cellulose, acetylpropionyl cellulose, nitrocellulose; biodegradable polymers typified by polylactic acid, polybutyl succinate, etc.; and other polymers such as polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol, polyvinyl butyral, polyacetal, polyglycolic acid, polycarbonate, polyketone, polyether sulfone, polyether ether ketone, modified polyphenylene ether, polyphenylene sulfide, polyetherimide, polyimide, polysiloxane, tetrafluoroethylene resin, trifluoroethylene resin, trifluorochloroethylene resin, tetrafluoroethylene-hexafluoropropylene copolymer, polyvinylidene fluoride, etc.These thermoplastic resins may be used alone in each layer, or as a polymer blend or polymer alloy of two or more types. Blends and alloys can impart heat resistance, viscosity characteristics, and adhesion at the interlayer interface that cannot be obtained from a single type of thermoplastic resin. Furthermore, these thermoplastic resins may be copolymerized as needed.

[0042] In the signal transmitter / receiver of the present invention, when the electromagnetic wave absorber includes an alternating laminate unit in which layers A and B with different electrical conductivities are alternately laminated, dielectric polarization is induced within the laminated sheet at the interface between the two layers from a macroscopic perspective, thereby achieving the effect of further enhancing electromagnetic wave absorption. Furthermore, by increasing the difference in dielectric constant between layers A and B in the alternating laminate unit, it is possible to strengthen the dielectric polarization and further enhance electromagnetic wave absorption. One method for increasing the difference in dielectric constant is to use thermoplastic resins with different dielectric constants for each layer.

[0043] The thermoplastic resin for the low-dielectric-constant layer is preferably one with a dielectric constant of 3.0 or less, from the viewpoint of increasing the difference in dielectric constant with the highly conductive layer and strengthening dielectric polarization. Considering versatility, it is preferable to select from polyolefin resins, polyester resins, acrylic resins, vinyl monomer copolymer resins, etc. The thermoplastic resin for the high-dielectric-constant layer is preferably nylon resin (dielectric constant: 3.5 to 5.0), cellulose resin (dielectric constant: 6.7 to 8.0), fluororesin (dielectric constant: 4.0 to 8.0), etc. Here, polyolefin resin refers to a thermoplastic resin with more than 50 mol% of olefin units when the total structural units constituting the resin are taken as 100 mol%, and the same can be applied to other thermoplastic resins.

[0044] Examples of methods for alternately laminating elastomer resins such as rubber or resin compositions containing them as main components include a method in which resin compositions A and B having different compositions are roll-pressed to produce sheets, and the different sheets are alternately stacked and thermocompressed to obtain an alternately laminated unit.

[0045] On the other hand, methods for layering thermoplastic resins or compositions containing them as main components (sometimes referred to as master pellets) include, for example, using separate extruders to feed master pellets prepared by distributing / dispersing and mixing thermoplastic resins and appropriate additives through different channels, followed by layering using known lamination devices such as multi-manifold feed blocks or static mixers. In particular, as described below, the layer thickness of the layered unit of the present invention is preferably small and uniform, so it is preferable to increase the layering accuracy. Therefore, from the perspective of achieving high-precision layering, it is preferable to form the layered unit using a feed block with fine slits. When forming the layered unit using a slit-type feed block, the thickness and thickness distribution of each layer can be adjusted by adjusting the length and width of the slits to achieve a pressure balance. The slit length refers to the length of the comb teeth that form the channels for alternately flowing the thermoplastic resins that make up layer A and layer B within the slit plate that makes up the slit-type feed block.

[0046] The number of layers in the alternating laminate unit is preferably 5 to 1001. When the number of layers in the alternating laminate unit is 5 or more, any of the above-mentioned regular arrangements will contain two or more layers with relatively high conductivity. This configuration allows dielectric polarization to occur at the interface between layers with different conductivity, facilitating current flow within the sheet and resulting in losses due to the resistance of the conductive material. Furthermore, when at least one of the A and B layers contains a conductive material in this configuration, the conductive material is more likely to be aligned parallel to the electromagnetic wave absorber surface, improving the conductivity and dielectric constant of the alternating laminate unit. Therefore, when the number of layers in the alternating laminate unit is 5 or more, high electromagnetic wave absorption can be achieved while reducing the amount of conductive material added and the sheet thickness compared to conventional single-film products, and this effect is particularly pronounced when a layer containing a conductive material is present.

[0047] From the viewpoint of improving the performance of the electromagnetic wave absorber, the number of layers of the alternating laminated unit is preferably 9 or more, more preferably 31 or more. As the number of layers of the alternating laminated unit increases, the number of layers that cause dielectric polarization increases, thereby improving the performance of the electromagnetic wave absorber. Furthermore, when the alternating laminated unit of the electromagnetic wave absorber is formed of layers of the same thickness and at least one layer contains a conductive material, increasing the number of layers increases the packing density of the conductive material in the layer, thereby narrowing the distance between the conductive materials and increasing the electron transfer efficiency between the conductive materials. Therefore, the performance of the electromagnetic wave absorber, i.e., the return loss, increases as the number of layers of the alternating laminated unit increases.

[0048] As such, the greater the number of layers in the alternating laminated unit, the greater the dielectric polarization effect. Therefore, there is no particular upper limit to the number of layers in the alternating laminated unit. However, when using a feed block with fine slits, increasing the number of layers increases the size of the equipment, resulting in increased manufacturing costs. Furthermore, depending on the dispersion, shape, and size of the filler, if the number of layers increases and the thickness of each layer becomes thinner, using a thixotropic material may cause the layer thickness to become more irregular, impairing the inherent high shielding and steep electromagnetic wave absorption properties. For these reasons, the practical upper limit for the number of layers in the alternating laminated unit that constitutes the electromagnetic wave absorber is 1001 layers.

[0049] A functional layer such as a reflective layer that reflects another electromagnetic wave or an absorbing layer that absorbs electromagnetic waves may be provided on the alternately laminated unit of the electromagnetic wave absorber. The electromagnetic wave absorber may have one or more alternately laminated units, and in the latter case, alternately laminated units having peak tops in different frequency bands may be superimposed on each other to form a material that simultaneously absorbs desired multiple frequency bands.

[0050] In the signal transceiver of the present invention, it is preferable that the electromagnetic wave absorber has a return loss peak in the frequency band of 20 to 100 GHz, where the return loss A(k) at the peak top is 15 dB or more. Note that hereinafter, the return loss A(k) at the peak top may be simply referred to as A(k). A method for evaluating A(k) is described in detail in Patent Document 2, and the measurement conditions in the present invention will be described later. A(k) can be calculated using Equation 5, which is a relational expression using the ratio (T [%]) of the intensity of the returned electromagnetic wave to the intensity of the incident electromagnetic wave. Equation 5: A(k)=-20log(T / 100).

[0051] Examples of methods for making the A(k) of the electromagnetic wave absorber 15 dB or more include a method of including a reflective layer in at least one of the alternating laminate units, a method of making the lamination ratio (A / B) of the A layer to the B layer less than 1, a method of making the concentration of the conductive material 3 mass % or more, a method of using an inorganic carbon material as the conductive material, etc. Here, the reflective layer has a frequency range in which the return loss of the electromagnetic wave is 1 dB or less in the frequency band of 20 GHz to 100 GHz, and / or a surface resistivity of 1.0 × 10 5 It refers to a layer with a resistivity of Ω / sq or less. These methods may be used in combination as appropriate.

[0052] Suitable reflective layers include metal foils such as aluminum, copper, iron, gold, silver, platinum, nickel, zinc, and lead; alloy foils such as stainless steel and brass; and non-metallic conductive films such as carbon films and PEDOT / PSS (a dispersion of polyethylenedioxythiophene and polystyrene sulfonic acid). Reflective layers using these materials can be formed by bonding via an adhesive layer or by thermocompression bonding. It is also preferable to form the reflective layer by sputtering or vapor deposition of metals such as aluminum, copper, iron, gold, silver, platinum, nickel, zinc, and lead. When forming the reflective layer by vapor deposition, vapor deposition of two or more metal species facilitates thinning, improving conductivity, and weather resistance. For non-metallic conductive films, it is preferable to use flexible materials such as PEDOT / PSS. Increasing the thickness of such a reflective layer can also increase A(k). The thickness of the reflective layer is preferably 10 nm to 10 μm, and particularly preferably 100 nm to 1 μm. By setting the thickness of the reflective layer within this range, it is possible to achieve both good electromagnetic wave shielding properties and thin film thickness.

[0053] It is also preferable to provide the electromagnetic wave absorber with a reflective layer, which is a layer in which a conductive material is added at a high concentration to a resin. Such a reflective layer may also be included in an alternating laminate unit. When forming such a reflective layer, the thinning of each layer can improve the electron transfer efficiency between the conductive materials, but this must also be achieved while adjusting the frequency of the reflection attenuation peak. A preferred method for forming such a reflective layer is to apply a paste containing metal nanoparticles, which are particularly highly conductive and easily moldable materials. By using such a method, the metal nanoparticles form a network structure, which is expected to maintain high conductivity even after molding.

[0054] Conductive materials include non-metallic conductive materials such as carbon fiber, carbon nanotubes, carbon black, graphite, and graphene, as well as compounds containing metallic particles such as aluminum, copper, iron, gold, silver, platinum, nickel, zinc, and lead. Among these, non-metallic conductive materials are preferred in terms of their affinity with the matrix resin. Low affinity between the matrix resin and the conductive material can lead to reduced conductivity due to voids between the resin and the conductive material or aggregation of the conductive material. Furthermore, from the viewpoint of conductivity, cylindrical or fibrous conductive materials such as carbon fiber and carbon nanotubes are more preferred among non-metallic conductive materials. The use of a magnetic conductive material in combination with the conductive material is also preferred in terms of enhancing electromagnetic wave absorption. Examples of matrix resins for compounds include rubber, thermoplastic resins, and thermosetting resins. Thermoplastic resins are preferred in terms of moldability.

[0055] When a reflective layer is a layer in which a conductive material is added at a high concentration to a resin, it is preferable to make the thickness thicker than a reflective layer made of metal foil, vapor deposition, or non-metallic conductive film, from the viewpoint of reducing variations in electromagnetic wave shielding properties. More specifically, the thickness of such a reflective layer is preferably more than 1 μm and not more than 200 μm, and more preferably 10 μm or more and not more than 100 μm. By making the thickness of the reflective layer more than 1 μm, it is possible to reduce the loss of electromagnetic waves due to uneven distribution of the conductive material.

[0056] In the signal transceiver of the present invention, the alternating laminate unit preferably contains a conductive material. By including a conductive material in the alternating laminate unit, the return loss can be increased. Only one type of conductive material may be included, or multiple types of conductive materials may be used in combination. Considering that the primary particle size is small and suitable for melt extrusion, it is preferable that at least one of the conductive materials contains a non-metallic material, and it is more preferable that the conductive material is exclusively non-metallic. When a laminated sheet is produced using an extruder using only inorganic metal materials, the inorganic metal, which is the conductive material, may rub against the wall surface of the device, which is usually made of metal, resulting in the conductive material being crushed or the device being damaged. However, this embodiment can alleviate the above problems.

[0057] Furthermore, when considering the use of the signal transmitter / receiver in close proximity to a living body as a component of a sensor such as a vital sensor, and future disposal, there are concerns about metal allergies and increased environmental impact during manufacturing and disposal, but this embodiment can alleviate these concerns. Whether or not a conductive material is an inorganic metal-based material can be determined, for example, by using energy dispersive X-ray spectroscopy (SEM-EDX). The peak positions specific to each metal in this method are shown in publicly known literature (e.g., J. McNab and A. Sandborg: The EDAX EDITOR, Vol. 14, No. 1, p. 37).

[0058] Non-metallic conductive materials are broadly divided into conductive polymers and inorganic carbons. Examples of conductive polymer materials include polyacetylene, polyphenylene, polyaniline, polypyrrole, polyisothianaphthene, and polythiophene, and these can be used alone or in combination. Although conductive polymers can provide electromagnetic wave absorption, it is more preferable to use inorganic carbon-based conductive materials, as described below, for the signal transmitter / receiver of the present invention in order to further improve the performance of the electromagnetic wave absorber.

[0059] Examples of inorganic carbon-based conductive materials that can be used alone or in combination include carbon black (spherical carbon) such as acetylene black, channel black, lamp black, thermal black, ketjen black, and furnace black; carbon nanotubes, which are cylindrical carbons such as single-walled nanotubes, multi-walled nanotubes, and cup-stacked nanotubes; flat carbons such as graphite and graphene; and other spherical graphite, cylindrical graphite, carbon microcoils, fullerenes, and carbon fibers (long fibers and short fibers).

[0060] In particular, from the viewpoint of improving the electromagnetic wave absorption performance due to charge transfer by improving the conductivity, it is preferable that the conductive material includes at least one of carbon black, carbon nanotubes, and carbon fibers. Furthermore, in order to utilize the effect of particle alignment in the plane direction due to the laminated structure and improve the conductivity of the layer containing the conductive material, it is more preferable to use carbon black, which easily develops a primary structure (linear structure). Furthermore, in order to form a stronger conductive path in the in-plane direction of the layer, it is even more preferable to use carbon nanotubes or flat carbon, which have a uniform structure and a high aspect ratio, in addition to carbon black, which easily develops a primary structure in any direction. By combining an inorganic carbon material, which easily develops a primary structure, with an inorganic carbon material, which has a uniform structure and a high aspect ratio, the frequency band absorbed by the alternating laminated unit can be easily adjusted by adjusting the ratio of the two conductive materials.

[0061] Carbon black suitable for use in the layer-by-layer laminate unit for electromagnetic wave absorption in the signal transmitter / receiver of the present invention includes, for example, carbon black having a dibutyl phthalate (DBP) oil absorption of 150 mL / 100 g or more. DBP oil absorption is an index showing the degree of development of the primary structure of carbon black. Carbon black with a high DBP oil absorption value indicates that particles are more likely to be connected in a linear chain, which tends to result in the formation of many voids within the primary structure. Therefore, when such carbon black is used, a conductive path can be formed with a smaller amount, imparting conductivity to the layer-by-layer laminate unit. From the above perspective, the DBP oil absorption of the carbon black is more preferably 200 mL / 100 g or more, and even more preferably 350 mL / 100 g or more.

[0062] When the primary structure of carbon black develops and a conductive path is formed, when an electric field is generated by electromagnetic radiation, charge accumulates at the interface between the dielectric substrate and the conductive material, converting the electromagnetic energy into thermal energy and demonstrating high electromagnetic wave absorption. While there is no upper limit for the DBP oil absorption of carbon black, taking into account the possibility of destruction of the primary structure when dispersed in the polymeric material that makes up the alternating laminate unit, the upper limit is set at 800 mL / 100 g. DBP oil absorption can be measured in accordance with ASTM D 2414 (2019).

[0063] Examples of carbon black having a DBP oil absorption within the above range include acetylene black (e.g., Li-100 manufactured by Denka Co., Ltd., CRM5715-a manufactured by Kanto Chemical Co., Ltd.), furnace black (e.g., MA100R manufactured by Mitsubishi Chemical Corporation, Asahi F-200GS manufactured by Asahi Carbon Co., Ltd., 5550 manufactured by Tokai Carbon Co., Ltd.), and ketjen black (e.g., EC300J manufactured by Lion Specialty Chemicals).

[0064] Examples of inorganic carbon-based materials with a uniform structure and a high aspect ratio that can be used in combination with the carbon black described above, which develops a primary structure, include cylindrical materials such as carbon nanotubes and flat materials such as graphite, graphene, etc. The use of such inorganic carbon-based materials in combination can improve the performance of the electromagnetic wave absorber. The mechanism behind this is explained below.

[0065] First, by using such inorganic carbon-based materials, conductive materials with high aspect ratios are dispersed in the thickness direction, improving the performance of the electromagnetic wave absorber (Maxwell-Wagner effect). Furthermore, when such inorganic carbon-based materials are used in combination, microscopic dielectric polarization is formed at the interface between the dielectric resin substrate (e.g., thermoplastic resin substrates such as polyolefin resins, polyester resins, acrylic resins, and vinyl monomer copolymer resins, which are listed above as examples of resins with low dielectric constants) and the conductive material. Furthermore, the cylindrical and flat materials are aligned parallel to the thickness direction of the alternating laminate unit, and these polarizations are parallel and face each other like parallel plate capacitors. Therefore, when an electromagnetic wave is irradiated onto the electromagnetic wave absorber and an electric field is applied, charge is easily accumulated at the interface between the dielectric substrate and the conductive material, increasing the conductivity within the alternating laminate unit. Due to this effect, when electromagnetic waves are incident, they are resisted by the conductive material, and the electromagnetic wave energy is easily converted into thermal energy. These mechanisms also improve the performance of the electromagnetic wave absorber.

[0066] From the above mechanism, it is preferable that the dielectric polarization formed at the interface between the A layer and the B layer in the alternately laminated unit, as well as at the interface between the polymer substrate and the conductive material within the layer, is aligned in the plane direction of each layer of the alternately laminated unit. Usually, the more the conductive material has a structure that makes it easier to align in the planar direction (layer direction), the more easily this state is formed during a stretching process or the like. From this perspective, it is preferable to use a cylindrical material that is a conductive material with a high aspect ratio in combination, and from the above-mentioned perspectives, carbon black, carbon nanotubes, and carbon fibers are particularly suitable conductive materials.

[0067] The amount of conductive material added to the highly conductive layer is preferably 2% by mass or more but less than 50% by mass, more preferably 2% by mass or more but less than 30% by mass, and even more preferably 2% by mass or more but less than 10% by mass, assuming that the total components of the highly conductive layer are 100% by mass. If the amount of conductive material added to the highly conductive layer is less than 50% by mass, the layer can become brittle, which can reduce the deterioration of formability. Furthermore, if the amount of conductive material added to the highly conductive layer is 2% by mass or more, electromagnetic waves can be sufficiently absorbed without poor impedance matching, thereby reducing the deterioration of directivity.

[0068] The electromagnetic wave absorber constituting the signal transceiver of the present invention may exhibit anisotropy in the dielectric constant and return loss depending on the orientation of the conductive material. In the signal transceiver of the present invention, the angle between the polarization direction of the electromagnetic waves transmitted from the transmitting antenna element group and the orientation direction of the electromagnetic wave absorber is preferably 0 to π / 6, more preferably 0 to π / 8. This configuration allows the electromagnetic wave absorber to exhibit high return loss and further reduce noise. As a result, the signal transceiver is less prone to malfunction. From the above perspective, the angle between the orientation direction and the polarization direction of the transmitted electromagnetic waves is more preferably 0 to π / 12, even more preferably 0 to π / 36. Note that when multiple electromagnetic wave absorbers are present, the requirement is satisfied if there is at least one electromagnetic wave absorber whose magnitude of the angle is 0 to π / 6. However, from the above perspective, it is preferable that the magnitude of the angle be 0 to π / 6 for all of the electromagnetic wave absorbers.

[0069] Methods for imparting anisotropy to an electromagnetic wave absorber (methods for making the magnitude of the angle between 0 and π / 6) include using a conductive material with a high aspect ratio for the electromagnetic wave absorber, or strongly orienting the electromagnetic wave absorber in a specific direction by stretching, etc. These methods may be used in combination as appropriate.

[0070] In the signal transceiver of the present invention, the electromagnetic wave absorber preferably includes a surface having an arithmetic mean height Sa of 1 nm to 500 nm, more preferably 1 nm to 300 nm, and even more preferably 1 nm to 100 nm (hereinafter, the arithmetic mean height Sa may be simply referred to as Sa). This configuration suppresses electromagnetic wave scattering on the surface of the electromagnetic wave absorber, thereby preventing false detection due to scattered electromagnetic waves. Examples of methods for suppressing the Sa value include a method for obtaining a laminate (alternate laminate unit) by alternately stacking a total of five or more sheets formed to a desired thickness by batch press rolling or melt extrusion, as described below, and pressing or laminating them; and a method for producing an alternating laminate unit when a flexible thermoplastic resin is used, in which the thermoplastic resins or thermoplastic resin compositions constituting layers A and B are alternately laminated in a multi-layer lamination device and then formed into a sheet by a calendaring cast method.

[0071] Furthermore, when forming a sheet-like product using a method other than calendering casting, the Sa of the surface of the alternating laminate unit can also be reduced by adjusting the melt viscosity ratio of the A layer to the B layer extruded from the die (melt viscosity of the A layer / melt viscosity of the B layer). The Sa of the alternating laminate unit can be reduced by adjusting the melt viscosity ratio to 0.5 or more and 1.2 or less. The ratio is preferably 0.6 or more and 1.1 or less, and even more preferably 0.7 or more and 1.0 or less. Methods for adjusting the melt viscosity ratio of the A layer to the B layer include changing the extrusion temperature, adjusting the molecular weight and intrinsic viscosity (IV) of the resins used for the A layer and the B layer, and adjusting the shear rate at which the resin is extruded from the die. To change the shear rate, the screw rotation speed (rpm) of the twin-screw extruder can be adjusted to change the amount of thermoplastic resin or thermoplastic resin composition extruded to form each layer, or by changing the die width, lip width, etc.

[0072] When a cooling roll is used to cool and solidify a melt-extruded sheet material, the surface in contact with the cooling roll is usually the non-vapor-deposited surface, and it is preferable that this surface has an arithmetic mean height Sa of 1 nm or more and 500 nm or less.

[0073] Sa can be measured using a known surface roughness meter (for example, "VertScan" (registered trademark) 2.0 R5300GL-Lite-AC manufactured by Ryoka Systems Co., Ltd.), and the measurement method using the above-mentioned device will be described in detail later.

[0074] Preferred embodiments of the signal transceiver of the present invention include means of transportation such as vehicles, aircraft, and ships, communication facilities such as telegraphs and telephones, and traffic routes such as crosswalks, intersections, railway lines, roads, sea routes, and air routes. That is, all of the means of transportation, traffic routes, and communication facilities of the present invention are equipped with the signal transceiver of the present invention. When the signal transceiver of the present invention is applied to means of transportation, traffic routes, and communication facilities, it is preferable to install it in a location with ample space, since the installation of an electromagnetic wave absorber will increase the volume.

[0075] Next, preferred methods for manufacturing the signal transceiver of the present invention will be described below using several examples, but the signal transceiver of the present invention should not be construed as being limited to such examples.

[0076] First, we will explain an example in which rubber, thermoplastic elastomer, or the like is used as the base polymer for the electromagnetic wave absorber. First, a predetermined amount of conductive material is blended with the base polymer and kneaded using a known device such as a kneader, Banbury mixer, mill mixer, roll mill, jet mill, or ball mill to obtain a conductive material-containing base polymer mixture. The base polymer alone and the obtained conductive material-containing base polymer are then rolled using a batch press or melt extruded to form sheets of desired thickness, obtaining sheets corresponding to Layer A and Layer B. These are then alternately stacked in a total of five or more layers and pressed or laminated to obtain a laminate (alternate laminate unit). The temperature during this process varies depending on the type of base polymer used, but is preferably 150°C to 400°C, more preferably 250°C to 380°C. If the layer obtained from the base polymer alone is Layer A and the layer obtained from the conductive material-containing base polymer is Layer B, Layer A is preferably the outermost layer.

[0077] Next, we will explain an example of a method for manufacturing an alternating laminate unit when a flexible thermoplastic resin is used as the base polymer. First, the thermoplastic resin prepared in pellet form and a predetermined amount of conductive material are mixed in a twin-screw extruder and extruded into a gut shape. This is then cooled in a water tank and cut with a chip cutter to produce master pellets containing the conductive material. In this process, the conductive material may be dry-blended with the thermoplastic resin and then metered and fed from a hopper, or it may be side-fed into the molten resin using a side feeder from any position in the extruder. The feeding method is not limited to the above method and can be selected appropriately depending on the specific gravity and shape of the conductive material used.

[0078] The thermoplastic resins or thermoplastic resin compositions constituting Layer A and Layer B differ in composition. These thermoplastic resins or thermoplastic resin compositions are dried in hot air or under vacuum, then fed into separate extruders, where they are heated and melted to a temperature above the melting point of the thermoplastic resin. The extrusion rate is then equalized using a gear pump or similar device, and the thermoplastic resin or thermoplastic resin composition is discharged. Any foreign matter or modified resin is removed using a filter or similar device. For example, if Layer A is a layer made from a simple thermoplastic resin and Layer B is made from a resin composition containing a conductive material, Layer A is preferably the outermost layer.

[0079] Next, these thermoplastic resins or thermoplastic resin compositions are layered alternately in a multilayer lamination device, molded into the desired shape using a die, and extruded into a sheet. The sheet-like material extruded from the die is extruded onto a cooling body such as a casting drum and cooled to solidify, resulting in a cast sheet. Methods for cooling and solidifying the sheet include a method in which air is blown from a slit-shaped, spot-shaped, or planar device to bring the material into close contact with a cooling body such as a casting drum; a calendering casting method in which the material is rapidly cooled and solidified by using a nip roll; a method in which a liquid is applied to a casting drum and the extruded sheet is then brought into close contact with a cooling body such as a casting drum to enhance flatness; and an SI casting method using electrostatic application. The SI casting method cannot be applied when a layer containing a conductive material is placed on the outermost layer, but the SI casting method using electrostatic application can be used when a layer not containing a conductive material is placed on the outermost surface.

[0080] To suppress surface roughness, a calendering casting method using rolls with small surface roughness is preferred. In the calendering casting method, the sheet material extruded from the die is passed between two rolls installed below the die to cool it under pressure. The linear pressure applied to the sheet material is preferably 50 N / cm or more. By using these conditions, a smoother cast sheet can be obtained.

[0081] Multi-layer lamination devices such as multi-manifold dies, feed blocks, and static mixers can be used. However, to efficiently obtain the layer-by-layer laminated unit of the present invention, it is particularly preferable to use a feed block with fine slits. The use of such a feed block prevents the device from becoming excessively large, thereby reducing the amount of foreign matter generated due to thermal degradation and enabling high-precision lamination even when the number of layers is extremely large. Furthermore, the lamination accuracy in the width direction is significantly improved compared to conventional technologies. Furthermore, such a feed block has the advantages of easily achieving any layer thickness by adjusting the shape (length and width) of the slits, and of easily orienting the conductive material in the plane direction of the laminated sheet due to the effect of resin flow during the lamination process. As in the example shown here, when a conductive material is added to one of the layers, the flow of resin through the slits facilitates the dispersion and alignment of the conductive material within the layer, which may help improve the dielectric constant.

[0082] When using a slit-type feedblock to fabricate an alternating laminate unit, the thickness and distribution of each layer can be adjusted by adjusting the length and width of the slit to achieve a proper pressure balance. The slit length refers to the length of the comb-like portion that forms the flow path for alternately flowing layers A and B through the slit plate. Another suitable method for increasing the number of layers is to form a laminate in the feedblock, then stack the layers in a static mixer to double the number of layers.

[0083] The resulting cast sheet can be biaxially stretched in the longitudinal and transverse directions as needed. When biaxial stretching is performed, the stretching may be performed sequentially or simultaneously. Furthermore, if necessary, the sheet may be further stretched again in the longitudinal and / or transverse directions.

[0084] First, we will explain sequential biaxial stretching, in which the sheet is first stretched in the longitudinal direction and then in the width direction. Here, stretching in the longitudinal direction refers to uniaxial stretching to impart longitudinal molecular orientation to the sheet, and is usually performed by varying the peripheral speed of rolls. This stretching can be performed in a single stage using a pair of rolls, or in multiple stages using multiple pairs of rolls. The stretching ratio varies depending on the type of thermoplastic resin, but is usually preferably 1.1 to 7.0 times, more preferably 1.5 to 4.0 times. Furthermore, the stretching temperature is preferably set within the range from the glass transition temperature of the thermoplastic resin constituting the sheet to the glass transition temperature + 100°C. (If the thermoplastic resin that is the main component of Layer A and the thermoplastic resin that is the main component of Layer B have different glass transition temperatures, the glass transition temperature referred to here refers to that of the resin with the higher glass transition temperature. Hereinafter, this applies to temperature conditions in film formation, and also applies when the temperature is the melting point.) The uniaxially stretched laminate film obtained in this manner can be subjected to surface treatment such as corona treatment, flame treatment, or plasma treatment, as necessary, and then a primer layer can be formed to improve adhesion to the film to be laminated on top. In the in-line coating process, the primer layer may be applied to one side, or to both sides simultaneously or one side at a time.

[0085] Width-direction stretching refers to stretching to impart width-direction orientation to a sheet (uniaxially stretched film). This is typically performed using a tenter, with both width-direction ends of the uniaxially stretched film being held with clips while being conveyed. The width-direction stretching ratio varies depending on the type of thermoplastic resin, but is typically preferably 1.1 to 7.0 times, with 1.5 to 5.0 times being particularly preferred. The stretching temperature is preferably between the glass transition temperature of the thermoplastic resin constituting the uniaxially stretched film and the glass transition temperature + 120°C. The biaxially stretched film is then heat-treated in the tenter from the stretching temperature to the melting point, uniformly cooled slowly, and then cooled to room temperature and wound up. If necessary, relaxation treatments, such as a relaxation treatment, may be performed in the longitudinal and / or width directions during the heat-treatment and slow cooling process to impart a low orientation angle and thermal dimensional stability to the film.

[0086] Next, simultaneous biaxial stretching will be described. In the case of simultaneous biaxial stretching, the obtained cast sheet may be subjected to a surface treatment such as corona treatment, flame treatment, or plasma treatment as necessary, and then provided with properties such as easy slippage, easy adhesion, and antistatic properties by in-line coating. In the in-line coating process, the coating layer may be applied to one side of the sheet, or to both sides simultaneously or one side at a time.

[0087] The cast sheet is then introduced into a simultaneous biaxial tenter, where it is conveyed while both widthwise ends of the sheet are held with clips and simultaneously and / or stepwise stretched in the longitudinal and width directions. Simultaneous biaxial stretching machines (tenters) include pantograph, screw, drive motor, and linear motor types. Drive motor or linear motor types are preferred, as they allow for variable stretching ratios and relaxation treatment at any desired location. The stretching ratio varies depending on the type of thermoplastic resin constituting Layer A and Layer B. Generally, an area ratio of 2.0 to 50 times is preferred, with 4.0 to 20 times being more preferred. The stretching speeds may be the same or different in the longitudinal and width directions. The stretching temperature is preferably between the glass transition temperature of the thermoplastic resin constituting the laminate unit and glass transition temperature + 120°C.

[0088] The simultaneously biaxially stretched film is preferably subsequently heat-treated in a tenter at a temperature equal to or higher than the stretching temperature but lower than the melting point to impart flatness and dimensional stability. During this heat treatment, it is preferable to instantly relax the film in the longitudinal direction immediately before and / or immediately after entering the heat treatment zone to suppress the distribution of the main orientation axis in the width direction. After heat treatment in this manner, the film is uniformly and slowly cooled, cooled to room temperature, and wound up. If necessary, relaxation treatment may also be performed in the longitudinal and / or width directions during the slow cooling from the heat treatment. The film may also be instantly relaxed in the longitudinal direction immediately before and / or immediately after entering the heat treatment zone.

[0089] The biaxially stretched film (alternate laminate unit) thus obtained can itself be used as an electromagnetic wave absorber. Furthermore, a highly conductive reflective layer can be laminated on the outermost surface of the alternating laminate unit for purposes such as electromagnetic wave reflection. In this case, a coating layer containing a material exhibiting suitable conductivity can be applied, or different resin layers / mesh layers can be laminated via an adhesive sheet or the like. Furthermore, resin / metal layers can be appropriately laminated according to the required function using sheet metal coating techniques such as physical vapor deposition, sputtering (e.g., planar or rotary magnetron sputtering), evaporation (e.g., electron beam evaporation), chemical vapor deposition, metalorganic chemical vapor deposition, plasma-enhanced / assisted / activated chemical vapor deposition, and ion sputtering.

[0090] 1 x 10 for physical vapor deposition -2 A reflective layer can be formed by heating a conductive metal filament, chip, or pellet such as aluminum above its boiling point in an evaporation chamber whose pressure is reduced to below 100 Pa, and then adsorbing and solidifying the evaporated metal on the surface of the alternating laminate unit.

[0091] The control circuit in the signal transceiver of the present invention can be fabricated by mounting a digital signal processing IC chip and external connector for communicating with the outside, an overall control microcomputer, a power supply, a transmitting / receiving circuit, a millimeter-wave modulation module, an antenna connector, and other components on a circuit board depending on the application. The antenna can be fabricated by attaching multiple antenna elements, such as chip antennas, pattern antennas, and array antennas, to a substrate. From the perspective of improving directivity, it is preferable to use an array antenna, particularly a phased array antenna, which allows for phase adjustment. The antenna substrate and the circuit board may be the same, but it is preferable to provide an electromagnetic wave absorber or metal plate between the antenna substrate and the circuit board to block noise from the control circuit. The antenna element can be fabricated from a conductive material, for example, by etching using a resist layer.

[0092] Methods for mounting the control circuit and antenna on the substrate include using a pressure sensitive adhesive or adhesive, screwing, using a male-female fitting connector, etc. As the pressure sensitive adhesive or adhesive, epoxy adhesives and urethane adhesives that are highly weather resistant and vibration resistant are preferably used.

[0093] Methods for installing an electromagnetic wave absorber in a signal transmitter / receiver include methods using pressure-sensitive adhesives or adhesives, methods using a male-female mating connector, and integral molding by vacuum / pressure molding. For example, a far-infrared heater is used to heat the surface of the alternating laminate unit until the surface temperature is at least 30°C higher than the softening point of the thermoplastic resin with the highest softening point temperature used in the alternating laminate unit. Then, a mold heated to approximately that softening point is pressed against the alternating laminate unit, the pressure is reduced between the mold and the alternating laminate unit, and pressure is applied to the surface of the alternating laminate unit opposite the mold. The electromagnetic wave absorber can also be provided with holes or steps for connection to a substrate or holes for external connectors. It can also be molded by overlaying a sheet body on the alternating laminate unit to enhance strength and weather resistance. Examples of sheets for enhancing strength include filler-reinforced thermoplastic resins and thermoplastic prepregs, and these can be used in appropriate combinations. [Example]

[0094] The present invention will be described below with reference to examples, but the present invention is not limited to these examples. Methods for measuring various properties and methods for evaluating effects in the present invention are as follows.

[0095] (1) Return loss (1-1) Frequency band between 20 GHz and 40 GHz A 300mm square electromagnetic wave absorber was irradiated with electromagnetic waves at angles of incidence k of π / 3-7π / 36, π / 2-7π / 36, and 2π / 3-7π / 36 using a Keycom lens antenna type oblique incidence electromagnetic wave absorber return loss measurement system LAF-26.5B, in accordance with JIS R 1679 (2007). The return loss was measured for each angle of incidence in the frequency bands of 18 to 26.5 GHz (WR-42) and 26.5 to 40 GHz (WR-28). The angle between the incident electromagnetic wave and the orientation of the electromagnetic wave absorber was set as shown in Table 1. For the value at 26.5 GHz, where the measurement range overlaps, the measurement value measured in the range of 26.5 to 40 GHz was used.

[0096] (1-2) Frequency band between 40 GHz and 100 GHz A 150mm square electromagnetic wave absorber was irradiated with electromagnetic waves at angles of incidence k of π / 3-7π / 36, π / 2-7π / 36, and 2π / 3-7π / 36 using a Keycom lens antenna type electromagnetic wave absorber return loss measurement system (LAF-26.5B) in accordance with JIS R 1679 (2007). The return loss was measured for each angle of incidence in the frequency bands of 33-50 GHz (WR-22), 50-75 GHz (WR-15), and 75-110 GHz (WR-10). The angle between the incident electromagnetic wave and the orientation of the electromagnetic wave absorber was set as shown in Table 1. For the 50 GHz and 75 GHz ranges, where the measurement ranges overlap, the values ​​measured in the 50-75 GHz and 75-110 GHz ranges were used. Although this measurement method also measures values ​​from 33 to 40 GHz, the return loss in the frequency band of 33 GHz or more and less than 40 GHz was measured using the measurement data in (1-1).

[0097] (2) Layer structure of the alternating laminate unit and thickness of the aluminum vapor deposition layer The layer structure of the alternating laminate unit of the electromagnetic wave absorber was identified and the thickness of the aluminum vapor-deposited layer was measured by microscopic observation, differential interference contrast observation, or transmission electron microscope (TEM) observation of cross-sectional samples obtained by cutting the electromagnetic wave absorber perpendicular to the surface. Depending on the thickness of each layer constituting the alternating laminate unit, the cross-section of the sample was observed and photographed using a digital microscope VHX5000 (Keyence Corporation) when the thickness of each layer of the alternating laminate unit was 10 μm or more. The layer structure of the alternating laminate unit was identified and the thickness of the aluminum vapor-deposited layer was measured (measurements were performed using the accompanying software (VHX5000_900F)). When the thickness of each layer of the alternating laminate unit was 1 μm or more but less than 10 μm, the cross-section of the sample was observed and photographed using a differential interference contrast microscope DMLBHC (Leica Corporation). The layer structure of the alternating laminate unit was identified and the thickness of the aluminum vapor-deposited layer was measured (measurements were performed using particle size analysis software Macview). When the thickness of each layer of the alternating laminate unit was less than 1 μm, a transmission electron microscope H-7100FA (Hitachi, Ltd.) was used to observe the cross section of the sample and take cross-sectional photographs to identify the layer structure of the alternating laminate unit and measure the thickness of the aluminum vapor deposition layer. When observing the cross section, staining techniques using RuO4 or OsO4 were used to obtain high contrast as necessary.

[0098] (3) Dielectric constant An Agilent Technologies Vector Network Analyzer (E8361A) was used. The permittivity was measured in the frequency range of 26.5 to 40 GHz using a rectangular waveguide with an internal shape of 3.56 mm x 7.11 mm. Measurement samples were obtained by punching an electromagnetic wave absorber into the same shape as the internal shape of the rectangular waveguide (the short side direction was the measurement direction). The electromagnetic wave absorber was punched out by changing the angle from the short side direction of the first punched sample by increments of π / 36. This process was repeated until the angle change reached 35π / 36. Each obtained sample was inserted vertically into the rectangular waveguide, and the permittivity was measured. The direction with the highest permittivity was defined as the orientation direction. 200 measurements were performed, and the permittivity was analyzed using the analysis software N1500A-001 provided with the instrument. The average permittivity of all samples was taken as the permittivity of the electromagnetic wave absorber.

[0099] (4) Target strength evaluation The signal transmitter / receiver was installed with the antenna facing vertically, and the signal transmitter / receiver and the target, a 0.5mm thick, 12cm x 12cm metal plate (SUS304), were placed 1m apart in a straight line. The antenna surface of the signal transmitter / receiver was installed parallel to the metal plate. Evaluation was performed using the Peakval value of the signal obtained using the test software (TitanDemoKitApp) included with the Estacaya millimeter-wave radar used in the signal transmitter / receiver. The settings in the test software were as follows: Config:2T14RE_2R5D_Short_fft CFAR Range Threshold: 15 CFAR Noise win:8 Guard Len:4 Peak Grouping: Yes.

[0100] Among the signals obtained, the response present at a position 1 m from where the target was installed is the target response. The target response strength (dB) detected by the signal transmitter / receiver with the electromagnetic wave absorber removed was used as the blank, and the amount of reduction in the target response strength when the electromagnetic wave absorber was installed was measured and evaluated using the following indexes. Evaluations were made using the electromagnetic wave absorber before and after the reliability test in (8). A: The amount of reduction was less than 1.0%. ○: The amount of decrease was 1.0% or more and less than 3.0%. △: The amount of decrease was 3.0% or more and less than 5.0%. ×: The amount of reduction was 5.0% or more.

[0101] (5) Noise reduction effect The signal transmitter / receiver was installed with the antenna facing vertically, and the signal transmitter / receiver and the target, a 0.5mm thick, 12cm x 12cm metal plate (SUS304), were placed 1m apart in a straight line. The antenna surface of the signal transmitter / receiver was installed parallel to the metal plate. Evaluation was performed using the Peakval value of the signal obtained using the test software (TitanDemoKitApp) included with the Estacaya millimeter-wave radar used in the signal transmitter / receiver. The settings in the test software were as follows: Config:2T14RE_2R5D_Short_fft CFAR Range Threshold: 15 CFAR Noise win:8 Guard Len:4 Peak Grouping: Yes.

[0102] Among the signals obtained, responses at positions where there are no objects such as a target or surrounding walls are responses due to false detection. Using this false detection strength as a blank, the amount of reduction in false detection strength when the electromagnetic wave absorber was installed was measured and evaluated using the following index. Many false detection peaks were detected in the signal transmitter / receiver, and the noise reduction effect was evaluated by the amount of reduction in the strongest peak among them. The evaluation was carried out using the electromagnetic wave absorber before and after the reliability test in (8). ◎: The reduction amount was 7.0% or more. ○: The amount of reduction was 4.0% or more and less than 7.0%. △: The amount of decrease was 1.0% or more and less than 4.0%. ×: The amount of reduction was less than 1.0%.

[0103] (6) DBP fuel amount The electromagnetic wave absorber was dissolved in orthochlorophenol, which can dissolve resin components, and the extracted and separated conductive material was measured using a Brabender Absorbtometer C type in accordance with ASTM D2414 (2019). For the measurement, the conductive material placed in the mixer was rotated at a speed of 125 min -1 While kneading, DBP was added dropwise at a rate of 4 mL / min, and the DBP oil absorption was analyzed based on the obtained viscosity curve.

[0104] (7) Arithmetic mean height Sa The measurement was performed using Ryoka Systems' "VertScan" (registered trademark) 2.0 R5300GL-Lite-AC. The accompanying analysis software (measurement software: VS-Measure Version 5.5.1, analysis software: VS-Viewer Version 5.5.1) was used to measure and calculate Sa on both sides of the alternating laminate unit before deposition. Prior to measurement, the sample was cut to 3 cm x 4 cm, and its four edges were fixed to the sample stage with double-sided tape to prevent wrinkles. After measurement, 100 10 x 10 fields of view were combined with a 10% overlap in stitching mode, and full interpolation, median 3 x 3, and quartic surface correction were performed to calculate Sa. Three measurements were performed, and the average value was used as the measured value. The measurement conditions were as follows: <Measurement conditions> Camera: CCD camera SONY HR-57 1 / 2 inch Objective lens: 10x Intermediate lens: 0.5x Wavelength filter: 530nm white Measurement mode: Wave Measurement area: 5109.181μm x 5109.181μm.

[0105] (8) Reliability test (humid heat resistance) A moist heat resistance test was conducted using a Lightspec thermostat (humidity) chamber LHU-114 manufactured by Espec Corporation. The electromagnetic wave absorber was subjected to a test for 1000 hours under conditions of 85°C and 85% RH, and the return loss was measured in the same manner as in (1). The reliability was evaluated based on the change in return loss before and after the test, in accordance with the following index. The change in return loss was calculated from the return loss value when k = π / 2-θ, and the reliability was evaluated based on the amount of change, in accordance with the following criteria. ⊚: The reduction was 0.0 dB or more and less than 1.0 dB. ○: The reduction was 1.0 dB or more and less than 4.0 dB. △: The reduction was 4.0 dB or more and less than 7.0 dB. ×: The reduction was 7.0 dB or more.

[0106] Example 1 (electromagnetic wave absorber) Conductive master pellets were prepared by side-feeding 95 parts by weight of isophthalic acid copolymerized PET resin (10 mol% isophthalic acid copolymerization (PET / I)) with an intrinsic viscosity (IV) of 0.7 with 5 parts by weight of carbon black (DBP feed rate: 500 ml / 100 g) through a twin-screw extruder. The isophthalic acid copolymerized PET resin was used as the thermoplastic resin for Layer A, and the conductive master pellets were used as the resin composition for Layer B. The isophthalic acid copolymerized PET resin and the conductive master pellets were separately fed into separate twin-screw extruders, melted at 270 °C, and kneaded. The screw rotation speed (rpm) of the twin-screw extruder was set to 0.7 per kg / h output. The extruded molten resin and the molten resin mixture were then merged in a multi-manifold feed block with 101 slits at a layer stacking ratio of 1.0 (Layer A / Layer B). 101 layers were laminated alternately in the thickness direction, with Layer A serving as the outermost layer on both sides. Next, the film was cast from the T-die onto a cooling roll at 80°C, and the thickness was adjusted so that the peak top of the return loss appeared at 79 GHz, producing a layer-by-layer unit with a thickness of 500 μm. The layer-by-layer unit was placed in a bell jar-type deposition machine and 1.0 × 10 -2 Aluminum was vapor-deposited under conditions of 0.1 Pa to form an aluminum layer with a thickness of 200 nm on the alternately laminated unit. Note that aluminum was vapor-deposited on the side of the alternately laminated unit with a larger Sa (i.e., the Sa of the non-vapor-deposited side is the value of the alternately laminated unit). The evaluation results of the obtained electromagnetic wave absorber are shown in Table 1.

[0107] (signal transmitter / receiver) An Estacaya millimeter-wave radar (T18PE_01120112_2R5D_76G) was used for the antenna and control circuit. A signal transceiver was fabricated by installing electromagnetic wave absorbers between the antenna element groups, on all four sides of the antenna, in the antenna element array direction, and in the control circuit. The evaluation results are shown in Table 1. For the antenna four-sided installation, electromagnetic wave absorbers were installed on two sides of the antenna as shown in Figure 1. The electromagnetic wave absorbers installed between the antenna element groups and on all four sides of the antenna were set to meet the conditions below. Note that L1 / L2 was set to 0.3, and the angle between the radar polarization direction and the electromagnetic wave absorber polarization direction was set to 0° for all absorbers.

[0108] <Condition> The electromagnetic wave absorber and the antenna have all of the following characteristics 1 to 3. Feature 1: The angle φ formed between the electromagnetic wave absorber and the antenna surface is equal to or greater than π / 4 and equal to or less than 3π / 4. Feature 2: An electromagnetic wave absorber is installed on the surface of the antenna facing the direction in which the electromagnetic waves are emitted. Feature 3: When an electromagnetic wave is incident from the antenna onto the electromagnetic wave absorber at an incident angle k, the reflection loss at the peak top is defined as A(k), and the angle formed between the traveling direction of the electromagnetic wave emitted by the antenna and the direction of the main side lobe is defined as θ, the following formulas 1 and 2 are satisfied. Equation 1: A(π / 2-θ)>A(2π / 3-θ) Equation 2: A(π / 2-θ)>A(π / 3-θ) Feature 4: When the center point of the antenna element group is point C, the point on the electromagnetic wave absorber closest to point C is point P1, the distance between point C and point P1 is L1, the point on the electromagnetic wave absorber that exists in the direction of propagation of the electromagnetic wave and is farthest from point P1 on a plane that includes points C and P1 and is perpendicular to the antenna surface is point P2, at least one of the antenna element groups satisfies the following formula 3. Equation 3: tan(θ) / 20≦L1 / L2≦tan(θ) / 2.

[0109] Example 2 A signal transceiver was produced in the same manner as in Example 1, except that the alternate laminate was produced by the calendaring cast method. In the calendaring cast, pressure cooling was performed using two rolls, the linear pressure was 100 N / cm, and the roll temperature was 80°C. The evaluation results of the electromagnetic wave absorber and the signal transceiver are shown in Table 1.

[0110] (Examples 3 to 9, Comparative Examples 2 to 3) A signal transmitter / receiver was produced in the same manner as in Example 1, except that the arrangement of the electromagnetic wave absorber was changed as shown in Table 1. Table 1 shows the evaluation results of the electromagnetic wave absorber and the signal transmitter / receiver.

[0111] Example 10 A signal transceiver was produced in the same manner as in Example 1, except that the electromagnetic wave absorber was produced by increasing or decreasing the discharge amount to change the lamination ratio as shown in Table 1. The evaluation results of the electromagnetic wave absorber and the signal transceiver are shown in Table 1.

[0112] Example 11 5 parts by mass of carbon black (DBP oil amount 500 ml / 100 g) was side-fed to 95 parts by mass of polycarbonate resin with an intrinsic viscosity IV of 0.6, and conductive master pellets were produced through kneading in a twin-screw extruder. The above polycarbonate resin was used as the thermoplastic resin for Layer A, and the above conductive master pellets were used as the resin composition for Layer B. A signal transmitter / receiver was produced in the same manner as in Example 10, except that the resins used were changed as described above. The evaluation results of the electromagnetic wave absorber and the signal transmitter / receiver are shown in Table 1.

[0113] Example 12 A signal transmitter / receiver was produced in the same manner as in Example 1, except that a millimeter-wave radar (T18PE_01030103_2R5D) manufactured by Estacaya was used as the antenna and control circuit, and θ was set as shown in Table 1. The evaluation results of the electromagnetic wave absorber and the signal transmitter / receiver are shown in Table 1.

[0114] Example 13 Except for changing the number of layers by using a multi-manifold type feed block having three slits, a signal transceiver was produced in the same manner as in Example 1. The evaluation results of the electromagnetic wave absorber and the signal transceiver are shown in Table 1.

[0115] (Comparative Example 1) By adjusting the thickness of the electromagnetic wave absorber, an electromagnetic wave absorber exhibiting high return loss at normal incidence was manufactured and used in a signal transceiver. Here, the thickness was adjusted from the electromagnetic wave absorber thickness D (500 μm) of Example 1 to D / cos(φ-θ) (532 μm). The thickness was adjusted by adjusting the rotation speed of the cooling roll, increasing or decreasing the discharge amount of the resin or resin composition, and adjusting the draw ratio.

[0116] [Table 1] In the table, the diagonal lines in Comparative Example 3 indicate that measurement was not performed due to the absence of an electromagnetic wave absorber, and that no electromagnetic wave absorber capable of satisfying the conditions of claim 2 was present. The surface roughness Sa was measured in the state of the alternating laminated unit, and the surface with the larger value (the surface not in contact with the cooling roll) was subjected to vapor deposition treatment (when the values ​​were equal, vapor deposition treatment was performed on any surface). The circles and crosses next to the electromagnetic wave absorber installation locations in the table indicate the presence or absence of an absorber in each location. When electromagnetic wave absorbers are installed on at least one of the four sides of the antenna and between the antenna element groups, this means that "electromagnetic wave absorbers are installed facing the electromagnetic wave transmission direction on the antenna surface." When the antenna is installed on all four sides, φ was set to the same value on all four sides. When k is set to π / 3-θ, π / 2-θ, or 2π / 3-θ, if the peak-top return loss is 15 dB or more, it was deemed that "the electromagnetic wave absorber has a return loss peak with a peak-top return loss A(k) of 15 dB or more within the 20 to 100 GHz frequency band." [Industrial Applicability]

[0117] The present invention provides a signal transceiver that can maintain target detection performance while reducing false detections due to noise by reducing main lobe interference and absorbing side lobes. Because of the above-mentioned excellent characteristics, the signal transceiver of the present invention can be suitably used in transportation means, traffic routes, communication facilities, etc. [Explanation of symbols]

[0118] A: Signal transmitter / receiver 1 board 2. Control circuit 3 Antenna body 4 Receiving antenna elements 5 Transmitting antenna elements 6 Electromagnetic wave absorbers attached to the radar side on all four sides of the antenna 7 Electromagnetic wave absorber attached along the antenna element arrangement direction 8 Electromagnetic wave absorber attached between the receiving antenna element group and the transmitting antenna element group 9 O direction 10 Electromagnetic wave emission direction 11 Electromagnetic wave absorber located in the control circuit section 12 P1 point 13 Point C 14 P2 points

Claims

1. A signal transceiver comprising a control circuit, an antenna body having an antenna element group which is an aggregation of a plurality of antenna elements, and an electromagnetic wave absorber, wherein the electromagnetic wave absorber and the antenna body have all of the following characteristics 1 to 3. Feature 1: The angle φ formed between the electromagnetic wave absorber and the antenna surface is equal to or greater than π / 4 and equal to or less than 3π / 4. Feature 2: An electromagnetic wave absorber is provided on the surface of the antenna facing the direction of electromagnetic wave emission. Feature 3: When an electromagnetic wave is incident from the antenna onto the electromagnetic wave absorber at an incident angle k, the reflection loss at the peak top is A(k), and the angle formed by the traveling direction of the electromagnetic wave transmitted by the antenna and the direction of the main side lobe is θ, the following formulas 1 and 2 are satisfied. Formula 1: A(π / 2-θ)>A(2π / 3-θ) Formula 2: A(π / 2-θ)>A(π / 3-θ)

2. 2. The signal transceiver according to claim 1, wherein at least one of the antenna element groups satisfies the following formula 3, where C is the center point of the antenna element group, P1 is the point on the electromagnetic wave absorber that is closest to C, L1 is the distance between C and P1, P2 is the point on the electromagnetic wave absorber that exists in the direction of propagation of the electromagnetic wave and is farthest from P1 on a plane that includes C and P1 and is perpendicular to the antenna surface, and L2 is the distance between P1 and P2. Formula 3: tan(θ) / 20≦L1 / L2≦tan(θ) / 2

3. 3. A signal transceiver as described in claim 1 or 2, wherein the antenna element group includes at least one transmitting antenna element group and one receiving antenna element group, and the following formula 4 is satisfied when the inter-element distance in the transmitting antenna element group is d and the peak top wavelength of the electromagnetic waves emitted by the transmitting antenna element group is λ. Formula 4: sinθ=(λ / d)-1

4. 3. The signal transceiver according to claim 1, wherein the electromagnetic wave absorber is disposed in the direction of arrangement of the antenna elements.

5. 4. The signal transceiver according to claim 3, wherein the electromagnetic wave absorber is disposed between the group of transmitting antenna elements and the group of receiving antenna elements.

6. 3. The signal transceiver according to claim 1, wherein the electromagnetic wave absorbers are provided on at least two of the four sides of the antenna.

7. 4. The signal transmitter / receiver according to claim 3, wherein an angle formed between the polarization direction of the electromagnetic waves transmitted by said transmitting antenna element group and the orientation direction of said electromagnetic wave absorber is between 0 and π / 6.

8. 3. The signal transceiver according to claim 1, wherein the electromagnetic wave absorber has a return loss peak in a frequency band of 20 to 100 GHz, the return loss A(k) at the peak top of which is 15 dB or more.

9. 3. The signal transceiver according to claim 1, wherein the electromagnetic wave absorber includes an alternating laminate unit in which two types of layers (layers A and B) having different electrical conductivities are alternately laminated in 5 to 1001 layers.

10. 3. The signal transceiver according to claim 1, wherein the electromagnetic wave absorber is located in a control circuit portion.

11. 3. The signal transceiver according to claim 1, wherein the electromagnetic wave absorber includes a surface having an arithmetic mean height Sa of 1 nm or more and 500 nm or less.

12. A means of transport comprising the signal transceiver according to claim 1 or 2.

13. A traffic route comprising a signal transceiver according to claim 1 or 2.

14. A communication facility comprising a signal transceiver according to claim 1 or 2.

Images