Near-field transmission device

Abstract

This near-field transmission device performs transmission or reception in a near field and includes a primary radiator and a reflectarray that reflects radio waves radiated by the primary radiator. The reflectarray has a plurality of reflectarray elements. The reflectarray has an outer dimension of 10λ or more. When the wavelength of the radio waves radiated by the primary radiator is denoted by λ, the pitch of the plurality of reflectarray elements is 0.9λ or less.

Description

Near-field transmission device

[0001] The present disclosure relates to a near-field transmission device.

[0002] It has been proposed to use a large array antenna (ELAA: Extremely Large-Scale Antenna Array) as a reflectarray for high-speed communications in fifth-generation mobile communication systems (5G) or sixth-generation mobile communication systems (6G) (see, for example, Near-Field MIMO Communications for 6G: Fundamentals, Challenges, Potentials, and Future Directions, Mingyao Cui, Zidong Wu, Yu Lu, Xiuhong Wei, and Linglong Dai, pages 40 to 46, IEEE Communications Magazine, January 2023).

[0003] However, details of the specific configuration of conventional large-scale array antennas (reflectarrays) have not been disclosed. Also, in the near field, forming an electric field distribution on a beam enables high-quality communication with a high transmission rate and little leakage.

[0004] Therefore, an object of the present invention is to provide a near-field transmission device that enables high-quality communication in the near field.

[0005] A near-field transmission device according to an embodiment of the present disclosure is a near-field transmission device that transmits or receives in a near field, and includes a primary radiator and a reflectarray that reflects radio waves radiated by the primary radiator, the reflectarray having a plurality of reflectarray elements, the reflectarray having an outer dimension of 10λ or more, and where λ is the wavelength of the radio waves radiated by the primary radiator, the pitch of the plurality of reflectarray elements is 0.9λ or less.

[0006] A near-field transmission device capable of high-quality communication in the near field can be provided.

[0007] 1 is a diagram showing an example of the configuration of a near-field transmission system 200 using two near-field transmission devices 100 of an embodiment. FIG. 1 is a diagram showing an example of the configuration of a reflectarray 120 of the near-field transmission device 100 of an embodiment. FIG. 2 is a diagram showing an example of a simulation result of the electric field strength distribution of radio waves propagating between reflectarrays 120A and 120B of the near-field transmission system 200. FIG. 3 is a diagram showing an example of the specific configuration of a portion of one reflectarray element 122 of the reflectarray 120. FIG. 4 is a diagram showing an example of the configuration of a near-field transmission system 200 using two near-field transmission devices 100 of an embodiment. FIG. 5 is a diagram showing an example of the relationship between the length K1 and the amount of phase change in the reflectarray 120. FIG. 6 is a diagram showing an example of the relationship between the length K2 and the amount of phase change in the reflectarray 120. FIG. 7 is a diagram showing an example of the simulation result of the relationship between the ratio L / D of the distance L to the diameter D of the aperture surface and the S21 parameter. FIG. 8 is a diagram showing an example of the simulation result of the relationship between the pitch of the reflectarray element 122 and the transmission amount (%). 12A is a diagram showing an example of a simulation result of the electric field strength distribution of radio waves propagating in the near field between near-field transmission devices 100A and 100B. FIG. 12B is a diagram showing an example of a simulation result of the electric field strength distribution of radio waves propagating in the near field between near-field transmission devices 100A and 100B. FIG. 12C is a diagram showing an example of a simulation result of the electric field strength distribution of radio waves propagating in the near field between near-field transmission devices 100A and 100B. FIG. 12D is a diagram showing an example of a configuration of a reflectarray 120 having a plurality of reflectarray elements 122. FIG. 12E is a diagram showing an example of a simulation result using a Gaussian beam. FIG. 12F is a diagram showing an example of a simulation model of the reflectarray 120. FIG. 12F is a diagram showing an example of a simulation result regarding the relationship between lengths K1 and K2 and the amount of phase change. FIG. 12G is a diagram showing an example of a configuration of a near-field transmission system 200M1 according to a first modified example of the embodiment. FIG. 12G is a diagram showing the positional relationship between the reflectarray 120A and the primary radiator 110A of the near-field transmission system 200M1 extracted from FIG. 10A and 10B are diagrams illustrating an example of the configuration of a reflect array 120A of a near-field transmission system 200M1, and are diagrams illustrating an example of a simulation result.13A and 13B. FIG. 13B is a diagram showing an example of the configuration of a near-field transmission system 200M2 according to a second modified example of the embodiment. FIG. 13C is a diagram showing the positional relationship between the reflectarray 120A and the primary radiator 110A of the near-field transmission system 200M2 extracted from FIG. 12A. FIG. 13D is a diagram showing an example of the configuration of the reflectarray 120A of the near-field transmission system 200M2. FIG. 13E is a diagram showing an example of the configuration of the reflectarray 120A of the near-field transmission system 200M2. FIG. 13F is a diagram showing an example of the result of a simulation under ideal conditions obtained by applying the phase distribution of an electric field due to an infinitesimal dipole to the near-field transmission system 200M2. FIG. 13G is a diagram showing an example of the result of a simulation under ideal conditions obtained by applying the phase distribution of an electric field due to an infinitesimal dipole to the near-field transmission system 200M2. FIG. 13H is a diagram showing an example of the result of a simulation when a beam is radiated from the primary radiator 110A in the near-field transmission system 200M2. FIG. 13I is a diagram showing an example of the result of a simulation when a beam is radiated from the primary radiator 110A in the near-field transmission system 200M2. 12A and 12B are diagrams illustrating an example of the configuration of a reflectarray 120A of a near-field transmission system 200M3.

[0008] Hereinafter, an embodiment to which the near-field transmission device of the present disclosure is applied will be described. In the following, the same elements will be given the same reference numerals, and duplicated explanations may be omitted.

[0009] In the following description, the XYZ coordinate system is defined. The direction parallel to the X axis (X direction), the direction parallel to the Y axis (Y direction), and the direction parallel to the Z axis (Z direction) are perpendicular to one another. For ease of explanation, the -Z direction may be referred to as the lower side or bottom, and the +Z direction may be referred to as the upper side or top. Planar view refers to viewing from the XY plane. In the following description, the length, width, thickness, etc. of each part may be exaggerated to make the configuration easier to understand. Terms such as parallel, right angle, orthogonal, horizontal, vertical, and up and down may be misaligned to the extent that they do not impair the effects of the embodiments.

[0010] In the following description, "radio waves" refers to a type of electromagnetic wave, and generally, electromagnetic waves below 3 Hz are called radio waves. In the following, electromagnetic waves emitted from outdoor base stations or relay stations are called "radio waves," and electromagnetic waves in general are called "electromagnetic waves." In addition, in the following, when referring to "millimeter waves" or "millimeter wave band," this includes the quasi-millimeter wave band of 20 GHz to 30 GHz in addition to the frequency band of 30 GHz to 300 GHz.

[0011] The radio waves transmitted by the near-field transmission device of the embodiment are preferably radio waves in the millimeter wave band such as a fifth-generation mobile communication system (5G), a sixth-generation mobile communication system (6G), or a frequency band of 1 GHz to 300 GHz or higher, including Sub-6. Furthermore, the radio waves transmitted and received by the near-field transmission device of the embodiment may be LTE (Long Term Evolution), LTE-Advanced (LTE-A), or UMB (Ultra Mobile Broadband). Furthermore, the radio waves transmitted and received by the near-field transmission device of the embodiment may be IEEE 802.11 (Wi-Fi (registered trademark)), IEEE 802.16 (WiMAX (registered trademark)), IEEE 802.20, UWB (Ultra-Wideband), Bluetooth (registered trademark), LPWA (Low Power Wide Area), or the like. Furthermore, the near-field transmission device of the embodiment can also be used for wireless power transmission. The near-field transmission device of the embodiment is particularly effective when wireless communication is performed and the frequency of the transmitted radio waves is 100 GHz or higher, and when wireless power transmission is performed and the near-field transmission device is particularly effective when the frequency of the transmitted radio waves is 20 GHz or higher.

[0012] <Embodiment> FIG. 1 is a diagram illustrating an example of the configuration of a near-field transmission system 200 using two near-field transmission devices 100 according to an embodiment. The near-field transmission system 200 illustrated in FIG. 1 includes two near-field transmission devices 100A and 100B, but may include three or more near-field transmission devices 100. Furthermore, when the two near-field transmission devices 100A and 100B are not distinguished from each other, they will simply be referred to as the near-field transmission device 100. Hereinafter, the frequency of the radio waves transmitted by the near-field transmission device 100 will be referred to as the operating frequency of the near-field transmission device 100. The operating frequency of the near-field transmission device 100 is, for example, 20 GHz or higher. Because propagation loss in free space is inversely proportional to the square of the wavelength of the radio waves, the near-field transmission device 100 according to the embodiment is particularly effective in the band above 20 GHz, where propagation loss in free space is large.

[0013] <Configuration of Near-Field Transmission Device 100> The two near-field transmission devices 100A and 100B have the same configuration. The two near-field transmission devices 100A and 100B are arranged a predetermined distance L apart. The distance L is the distance between the reflective surfaces of the reflectarrays 120A and 120B of the near-field transmission devices 100A and 100B. The reflective surfaces of the reflectarrays 120A and 120B are planes that include surfaces of a plurality of reflectarray elements 122, which will be described later.

[0014] The diameter of the aperture of the near-field transmission devices 100A and 100B is D, and the wavelength in free space at the operating frequency of the near-field transmission devices 100A and 100B is λ. The aperture is an example of a radiation surface. The distance L is 2×D ２ / λ or less. ２ / λ is a distance that serves as a guide for the boundary between the near field and the far field from the reflecting surfaces of the reflectarrays 120A and 120B. The near-field transmission devices 100A and 100B are arranged so that the reflectarrays 120A and 120B are located within each other's near fields.

[0015] The near-field transmission device 100A has a primary radiator 110A and a reflectarray 120A. The near-field transmission device 100B has a primary radiator 110B and a reflectarray 120B. Since the near-field transmission devices 100A and 100B have the same configuration, the primary radiators 110A and 110B have the same configuration, and the reflectarrays 120A and 120B have the same configuration. For this reason, hereinafter, when there is no need to distinguish between the primary radiators 110A and 110B, they will simply be referred to as the primary radiator 110. When there is no need to particularly distinguish between the reflectarrays 120A and 120B, they will be referred to as the reflectarray 120.

[0016] Also, as an example, Figure 1 shows, with three arrows, how radio waves radiated from primary radiator 110 and reflected by reflect array 120A propagate to reflect array 120B via the near field, are reflected by reflect array 120B, and are received by primary radiator 110B.

[0017] <Primary radiator 110> The primary radiator 110 is provided on the reflecting surface side of the reflectarray 120, at a position offset from the central axis of the reflecting surface. The reflecting surface of the reflectarray 120 is a surface on which a plurality of reflectarray elements 122 are provided. The distance between the primary radiator 110 and the reflecting surface of the reflectarray 120 is shorter than the distance L, and is, for example, 1 / 50 to 1 / 3 of the distance L. Furthermore, it is preferable to install the primary radiator 110 at a position closest to the amplitude distribution of the desired aperture distribution.

[0018] The primary radiator 110 is configured, for example, by a horn antenna, a dipole antenna, etc. The primary radiator 110 is capable of radiating radio waves toward the reflecting surface of the reflect array 120 and receiving radio waves reflected by the reflecting surface of the reflect array 120.

[0019] The diameter of the aperture surface (radiation surface) of the primary radiator 110 may be 9λ or less, which is smaller than the outer dimension of the reflect array 120 (approximately 10λ or more).

[0020] The position of the primary radiator 110 relative to the reflectarray 120 is fixed by a fixing member (not shown). As an example, the primary radiator 110 may be fixed to the reflectarray 120. A stay or the like may be used as the fixing member, but any configuration may be used as long as it is fixable and does not adversely affect the propagation of radio waves between the primary radiator 110 and the reflecting surface of the reflectarray 120. Note that the primary radiator 110 may be rotatable in a circle around the reflectarray 120, and the beam direction may be changed by rotating it.

[0021] <Reflectarray 120> The reflectarray 120 includes a substrate 121, multiple reflectarray elements 122, and a ground layer 123. As an example, the reflectarray 120 is a passive reflector that reflects incident radio waves in a specific direction. The reflectarray 120 may be a reflector that is capable of non-specular reflection in a direction other than specular reflection. The reflectarray 120 is required to reflect radio waves incident from the primary radiator 110 in a desired direction and to reflect radio waves incident on the reflective surface toward the primary radiator 110. Regarding the reflectarray 120A, the reflectarray 120A is required to reflect radio waves incident from the primary radiator 110A toward the reflective surface of the reflectarray 120B and to reflect radio waves incident from the reflectarray 120B toward the primary radiator 110A by the reflective surface. The same applies to the reflectarray 120B.

[0022] The reflectarray 120 has an outer dimension of 10λ or more, and the pitch of the multiple reflectarray elements 122 is 0.9λ or less. λ is the wavelength in free space at the operating frequency of the near-field transmission device 100, and is the wavelength of the radio waves emitted or received by the primary radiator 110. The outer dimension of the reflectarray 120 is the maximum outer dimension of the reflectarray 120 in a planar view, and is the diameter of a circle circumscribing the multiple reflectarray elements 122. The diameter of the circle circumscribing the multiple reflectarray elements 122 corresponds to the diameter of the aperture surface of the near-field transmission device 100. The reason for setting the outer dimension of the reflectarray 120 to 10λ or more will be described later.

[0023] 2, the substrate 121 is circular as an example, but is not limited to a circle and may be elliptical, rectangular, etc. The substrate 121 may be made of any dielectric material that can support the reflect array element 122.

[0024] <Reflectarray element 122> The multiple reflectarray elements 122 are arranged in an array, for example, as shown in Fig. 2. The distances between the centers of adjacent reflectarray elements 122 in the X and Y directions are equal.

[0025] As an example, the reflect array element 122 is provided on the main surface on the +Z direction side of the substrate 121. However, the reflect array element 122 may be sandwiched between the substrate 121 and a substrate not shown and not exposed. Furthermore, if the substrate 121 has inner layers, the reflect array element 122 may be provided on one of the inner layers.

[0026] The reflect array element 122 is formed of a metal layer. The reflect array element 122 can be formed of a metal thin film such as copper, nickel, or gold. The reflect array element 122 can also be formed of a metal thin film such as zinc oxide (ZnO), tin oxide (SnO ２ The reflect array element 122 may be formed of a transparent conductive film such as tin-doped indium oxide (ITO) or indium oxide-tin oxide (IZO), a metal nitride such as titanium nitride (TiN) or chromium nitride (CrN), or a low-e film for low-e (low emissivity) glass. The reflect array element 122 may also be formed of a mesh-like metal thin film such as copper, nickel, or gold.

[0027] <Ground layer 123> The ground layer 123 is provided on one surface on the -Z direction side of the substrate 121. For this reason, the outer edge of the ground layer 123 is shown by a dashed line in Figure 2. The ground layer 123 overlaps with all of the multiple reflect array elements 122 in plan view. The outer edge of the ground layer 123 encompasses all of the multiple reflect array elements 122 in plan view. The ground layer 123 can be made from the same metal layer as the metal layer from which the reflect array elements 122 can be made. The ground layer 123 may also be made from a metal layer different from that from which the reflect array elements 122 are made.

[0028] <Near-field transmission> Fig. 3 is a diagram showing an example of a simulation result of the electric field intensity distribution of radio waves propagating between the reflectarrays 120A and 120B of the near-field transmission system 200. Fig. 3 shows only the reflectarrays 120A and 120B of the near-field transmission devices 100A and 100B, and omits the primary radiator 110.

[0029] The reflectarrays 120A and 120B shown in Fig. 3 are disk-shaped, for example, and the positions of the reflectarrays 120A and 120B are indicated by a coefficient ρ in units of wavelength λ. The wavelength λ in Fig. 3 is the wavelength of a 300 GHz radio wave in free space.

[0030] The reflectarrays 120A and 120B extend between +10ρ and -10ρ and have a diameter of 20ρ. Thus, the diameters of the reflectarrays 120A and 120B correspond to the diameters of the aperture surfaces of the near-field transmission devices 100A and 100B. As such, the aperture surfaces of the near-field transmission devices 100A and 100B shown in FIG. 3 have a diameter of 20λ, which is very large compared to the wavelength λ. Since the wavelength of a 300 GHz radio wave is approximately 1 mm, the diameter of the aperture surfaces of the near-field transmission devices 100A and 100B is approximately 20 mm.

[0031] Furthermore, the distance from the reflecting surfaces of the reflectarrays 120A and 120B at 300 GHz to the boundary between the near field and the far field is 800 mm. In Fig. 3, the distance between the reflectarrays 120A and 120B is set to 0.5 m, and the electric field strength distribution of the radio waves when transmitting radio waves in the 300 GHz band between the near-field transmission devices 100A and 100B is calculated.

[0032] 3, it was confirmed that a beam-shaped radio wave was transmitted between the reflectarrays 120A and 120B. The diameter of the beam was smaller than the diameter of the reflectarrays 120A and 120B, and the electric field strength was approximately 40 dBV / m at the center in the radial direction of the beam and approximately 25 dBV / m at the outer side in the radial direction of the beam.

[0033] In this way, it was confirmed that by setting the distance L so that the near-field transmission devices 100A and 100B are in a near-field, signals can be transmitted between the near-field transmission devices 100A and 100B using a beam of very strong electric field strength, with a high transmission rate and low leakage, and with high-quality communication.

[0034] 4A and 4B are diagrams showing an example of a specific configuration of one reflect array element 122 of the reflect array 120. The substrate 121 and reflect array element 122 shown in Figures 4A and 4B are a portion corresponding to one of the ten reflect array elements 122 shown in Figure 2.

[0035] The portion of the substrate 121 corresponding to one reflect array element 122 has, as an example, lengths of 0.8λ in the X and Y directions and a thickness of 0.1λ in the Z direction. Also, the thickness of the reflect array element 122 in the Z direction is, as an example, 18 μm. For example, when the operating frequency of the near-field transmission device 100 is 290 GHz, the wavelength λ is approximately 1.04 mm, so the lengths of the portion of the substrate 121 corresponding to one reflect array element 122 in the X and Y directions are approximately 0.8 mm and the thickness in the Z direction is 0.1 mm. In this case, the diameter of the circular substrate 121 shown in FIG. 2 is approximately 5 mm for the number of reflect array elements 122 shown in FIG. 2.

[0036] The reflect array element 122 is, for example, a patch-shaped element (patch element) having a square shape with four sides at 45-degree angles with respect to the X and Y directions in plan view. The length of one side of the reflect array element 122 is K1. The reflect array element 122 has a cross-shaped slot 122A. For example, the slot 122A is provided at a position that passes through the center of the reflect array element 122 in plan view.

[0037] The slot 122A is a cross-shaped slot that combines a slot parallel to the X direction and a slot parallel to the Y direction. The slot parallel to the X direction and the slot parallel to the Y direction intersect at the center of the reflect array element 122 in plan view. The slot 122A is a portion obtained by cutting out part of the metal layer of the reflect array element 122.

[0038] As an example, the slot 122A has lengths K2 in the X and Y directions and a width of 0.05 mm. As an example, the slot 122A has equal lengths K2 in the X and Y directions. By setting the length K1 of one side of the reflect array element 122 and the length K2 of the slot 122A in the X and Y directions to various lengths according to the operating frequency of the near-field transmission device 100, it is possible to adjust the amount by which the phase is changed (amount of phase change) when the reflect array element 122 reflects radio waves.

[0039] By individually setting the lengths K1 and K2 of the multiple reflect array elements 122 according to the operating frequency of the near-field transmission device 100, the direction in which the reflect array 120 reflects radio waves can be set.

[0040] 4A and 4B show a configuration in which the reflect array element 122 has four sides that form angles of 45 degrees with the X and Y directions, but the four sides of the reflect array element 122 may be parallel to the X and Y directions or may form angles other than 45 degrees. Furthermore, the two directions in which the cross-shaped slot 122A extends are not limited to the X and Y directions, and may form angles with respect to the X and Y directions.

[0041] <Relationship between lengths K1 and K2 and the amount of phase change in the reflectarray 120> Figures 5A and 5B are diagrams showing an example of the relationship between lengths K1 and K2 and the amount of phase change in the reflectarray 120. The characteristics shown in Figures 5A and 5B were obtained by calculation using an electromagnetic field simulator. Figure 5A shows an example of the relationship between the length K1 and the amount of phase change in the reflectarray 120, and Figure 5B shows an example of the relationship between length K2 and the amount of phase change in the reflectarray 120.

[0042] 5A, the horizontal axis represents the length K1 (mm) of one side of the reflectarray element 122, and the vertical axis represents the amount of phase change (degrees) calculated from the S11 parameter of the radio waves reflected by the reflectarray 120. In Fig. 5B, the horizontal axis represents the length K2 (mm) of the slot 122A in the X and Y directions, and the vertical axis represents the amount of phase change (degrees) calculated from the S11 parameter of the radio waves reflected by the reflectarray 120.

[0043] As shown in Figure 5A, when the length K1 was changed from 0.15 mm to 0.4 mm, it was confirmed that the phase change amount changed from 360 degrees to approximately 70 degrees. Also, as shown in Figure 5B, when the length K2 was changed from 0.05 mm to 0.5 mm, it was confirmed that the phase change amount changed from approximately 70 degrees to approximately 0 degree.

[0044] As shown in Figures 5A and 5B, it was confirmed that the amount of phase change can be adjusted by setting the lengths K1 and K2 of the reflect array element 122 to various lengths depending on the operating frequency of the near-field transmission device 100.

[0045] <Relationship between Distance L Between Near-Field Transmission Devices 100A and 100B and Diameter D of Aperture Surface> Fig. 6 is a diagram showing an example of simulation results of the relationship between the ratio L / D of the distance L to the diameter D of the aperture surface and the S21 parameter. In Fig. 6, the horizontal axis represents the ratio L / D, and the vertical axis represents the S21 parameter (transmission coefficient (dB)). The ratio L / D decreases as the diameter D of the aperture surface increases and the distance L decreases.

[0046] Simulations were performed with the diameter D set to 10λ, 50λ, 100λ, 200λ, 300λ, 500λ, and 1000λ. When the diameter D is fixed at each of 10λ, 50λ, 100λ, 200λ, 300λ, 500λ, and 1000λ, a smaller ratio L / D corresponds to a shorter distance L.

[0047] It was found that in each of the cases where the diameter D was 10λ, 50λ, 100λ, 200λ, 300λ, 500λ, and 1000λ, the smaller the ratio L / D, the larger the value of the S21 parameter.

[0048] If the diameter D is 50λ, the ratio L / D is 3×10 ２ It was found that by setting the value to about -20 dB or less, the value of the S21 parameter becomes -20 dB or more.

[0049] For example, when the S21 parameter is at a level of -3 dB and the ratio L / D is 100 λ, the distance L is 10 m. Also, when the S21 parameter is at a level of -10 dB and the ratio L / D is 250 λ, the distance L is 25 m. In this way, it was confirmed that signal transmission in the near field is possible with a sufficient distance L.

[0050] <Relationship Between Pitch of Reflect Array Element 122 and Transmission Amount (%)> Fig. 7 is a diagram showing an example of the simulation results of the relationship between the pitch of the reflect array element 122 and the transmission amount (%). In Fig. 7, the horizontal axis represents the distance L (m) between the near-field transmission devices 100A and 100B, and the vertical axis represents the transmission amount (%).

[0051] The pitch of the reflect array elements 122 is the distance in the X and Y directions between the centers of adjacent reflect array elements 122 shown in Fig. 2. Here, the pitches of the reflect array elements 122 in the X and Y directions are equal.

[0052] In the simulation, the operating frequency of the near-field transmission device 100 was set to 300 GHz, and the diameter D of the aperture surface of the near-field transmission devices 100A and 100B was set to 50 mm. The wavelength of a 300 GHz radio wave in free space was set to λ, and the pitch of the reflect array elements 122 was set to 0.7λ, 0.8λ, 0.9λ, and 1.0λ. For comparison, the transmission amount (%) was also calculated when a single large metal reflector was used instead of multiple reflect array elements 122.

[0053] In the case of the reflector, the transmission rate (%) was approximately 100% when the distance L was from approximately 0.01 m to approximately 0.7 m, and when the distance L was approximately 0.7 m or more, the transmission rate (%) gradually decreased, and when the distance L was approximately 1 m, the transmission rate (%) was approximately 95%.

[0054] Furthermore, when the pitch of the reflect array element 122 is 0.7λ, the transmission amount (%) increases from approximately 72% to approximately 95% as the distance L increases from approximately 0.01 m to approximately 0.9 m, and when the distance L becomes approximately 0.9 m or more, the transmission amount (%) decreases slightly, and when the distance L is approximately 1 m, the transmission amount (%) is approximately 93%.

[0055] When the pitch of the reflect array element 122 was 0.8λ, there was almost no difference from when it was 0.7λ. When the pitch of the reflect array element 122 was 0.9λ, the overall performance was about 3 dB lower than when it was 0.7λ and 0.8λ, but sufficiently good results were obtained.

[0056] Furthermore, when the pitch of the reflect array elements 122 was 1.0λ, the transmission rate (%) was approximately 7% to 8% for distances L from approximately 0.01 m to 1 m, which was a very low value. When the pitch was 1.0λ, it is thought that the extremely low transmission rate (%) was due to the radio waves reflected by adjacent reflect array elements 122 canceling each other out.

[0057] From the above, it has been found that in order to perform communication at a high transmission rate between the near-field transmission devices 100A and 100B, it is preferable that the pitch of the reflect array elements 122 be 0.9λ or less.

[0058] 8A to 8C are diagrams showing an example of the simulation results of the electric field strength distribution of radio waves propagating in the near field between the near-field transmission devices 100A and 100B. In the simulation, the operating frequency of the near-field transmission device 100 was set to 300 GHz, and the diameter D of the aperture planes of the near-field transmission devices 100A and 100B was set to 50 mm. At 300 GHz, the distance from the reflecting surfaces of the reflectarrays 120A and 120B, which serves as a guideline for the boundary between the near field and the far field, is 5000 mm. The distance between the near-field transmission devices 100A and 100B was set to 1 m.

[0059] 8A to 8C show the electric field strength distribution of radio waves in an area on one side of the central axis of the reflectarrays 120A and 120B. Figures 8A to 8C show simulation results when the pitch of the reflectarray elements 122 is set to 0.6λ, 0.8λ, and 1.0λ, respectively.

[0060] 8A to 8C, the horizontal axis represents the distance (m) from the central axis of the reflectarrays 120A and 120B. The vertical axis represents the distance (m) from the reflective surface of the reflectarray 120A. 0 m on the horizontal axis represents the position of the central axis of the reflectarrays 120A and 120B, and the diameter of the reflectarrays 120A and 120B is 0.02 m. 0 m on the vertical axis represents the position of the reflective surface of the reflectarray 120A. Also, dashed lines are shown connecting the 0.02 m positions of the reflectarrays 120A and 120B. The area to the left of the dashed lines is the area within the aperture planes of the reflectarrays 120A and 120B.

[0061] As shown in Figure 8A, when the pitch of the reflectarray elements 122 was set to 0.6λ, it was confirmed that the beam was narrowed within the aperture planes of the reflectarrays 120A and 120B. Because the beam was narrowed in this way, high-quality communication with a high transmission rate and little leakage was possible.

[0062] Furthermore, as shown in Figure 8B, when the pitch of the reflect array elements 122 was set to 0.8λ, it was slightly wider than when the pitch was 0.6λ, but it was confirmed that the beam was narrowed within the aperture planes of the reflect arrays 120A and 120B.

[0063] 8C, when the pitch of the reflect array elements 122 was set to 1.0λ, it was confirmed that almost no beams were obtained within the aperture planes of the reflect arrays 120A and 120B. This is thought to be because the pitch of the reflect array elements 122 was 1.0λ, causing radio waves reflected by adjacent reflect array elements 122 to cancel each other out.

[0064] <Simulation Results Using Gaussian Beam> Figure 9A is a diagram showing an example of the configuration of a reflectarray 120 having a plurality of reflectarray elements 122. The reflectarray 120 shown in Figure 9A has a configuration as an example in which a plurality of the reflectarray elements 122 shown in Figures 4A and 4B are arranged in an array. The reflectarray 120 shown in Figure 9A has a substrate 121, a plurality of reflectarray elements 122, and a ground layer 123, and the substrate 121 and the ground layer 123 are common to the plurality of reflectarray elements 122. Note that the substrate 121 is circular in a plan view, and the origin of the XYZ coordinate system is located at the center of the surface on the +Z direction side of the substrate 121.

[0065] The length K2 (see Figure 4A) of the slot 122A in the X and Y directions of the multiple reflect array elements 122 becomes shorter as they move radially outward from the center of the substrate 121, and the reflect array elements 122 close to the outer edge of the substrate 121 do not have the slot 122A, and the length K1 (see Figure 4A) of one side of the reflect array element 122 is shortened, thereby setting the amount of phase change in each reflect array element 122.

[0066] It has been confirmed that the amount of phase change can be adjusted by about 140 degrees by adjusting the length K1 of one side of the reflect array element 122 without providing the slot 122A, and that the amount of phase change can be further adjusted by about 220 degrees by providing the slot 122A and adjusting the length K2. In other words, it has been confirmed that the amount of phase change can be adjusted over a range of about 360 degrees by adjusting the length K1 of one side of the reflect array element 122 and the length K2 of the slot 122A.

[0067] FIG. 9B shows the results of a simulation of reflecting a beam emitted from a beam source using the reflectarray 120 shown in FIG. 9A. FIG. 9B is a diagram showing an example of the results of a simulation using a Gaussian beam. In FIG. 9B, the horizontal axis represents the distance (m) from the reflecting surface of the reflectarray 120. 0 m on the horizontal axis represents the position of the reflecting surface of the reflectarray 120. The vertical axis represents the distance (mm) from the central axis of the reflectarray 120 (the Z axis in FIG. 9A ). 0 m on the vertical axis represents the position of the central axis of the reflectarray 120.

[0068] The beam source was placed at a position 10.23 mm from the reflecting surface of the reflectarray 120, and a Gaussian beam was emitted in the −Z direction toward the reflectarray 120, and the beam intensity distribution was calculated when the beam was reflected in the +Z direction by the reflectarray 120. The range in which the beam intensity distribution was calculated was a range up to a position 50 mm from the reflecting surface of the reflectarray 120. The beam frequency was 300 GHz.

[0069] The reason for using a Gaussian beam is as follows: Because the near-field transmission device 100 includes the primary radiator 110, it is conceivable to set the beam of the primary radiator 110 by simulation. However, setting the beam of the primary radiator 110 by simulation requires an extremely large amount of calculation. For these reasons, a Gaussian beam, which can approximate the phase of a spherical wave, was used in the simulation.

[0070] In the simulation, the diameter of the reflect array 120 was set to 10.2 mm, the thickness of the substrate 121 to 0.127 mm, the relative dielectric constant of the substrate 121 to 2.97, and the dielectric loss tangent to 0.001. The thickness of the reflect array element 122 and the ground layer 123 was set to 18 μm, and the material was set to copper.

[0071] Furthermore, in order to bring the phase of the beam incident on each reflectarray element 122 closer to the phase when a spherical wave is used, the beam source was set as follows: Specifically, in order to achieve approximately the same phase as when a spherical wave source is located 10 mm in the Z direction from each reflectarray element 122, the position of the Gaussian beam source was set at a position 10.23 mm on the Z axis from the reflecting surface of the reflectarray 120. The beam source was set to emit a linearly polarized beam polarized in the X direction.

[0072] When the beam intensity distribution was calculated under these simulation conditions, it was confirmed that the beam was narrowed within the aperture plane of the reflectarray 120, as shown in Fig. 9B. Because the beam is narrowed in this way, high-quality communication with a high transmission rate and little leakage is possible.

[0073] The results of other simulations will be described below.

[0074] <Simulation model of reflectarray 120> Fig. 10 is a diagram showing an example of a simulation model of the reflectarray 120. Fig. 10 shows an example of an analysis space for one reflectarray element 122 of the entire reflectarray 120. In other words, the analysis space shown in Fig. 10 shows the periodic boundary condition of the reflectarray element 122. The substrate 121 shown in Fig. 10 is a portion of the entire substrate 121 that corresponds to one reflectarray element 122.

[0075] As an example, the portion of the substrate 121 corresponding to one reflect array element 122 has lengths of 0.5λ in the X and Y directions and a thickness of 0.127 mm in the Z direction. The analysis space used when simulating one reflect array element 122 has the same dimensions in the X and Y directions as the portion of the substrate 121 corresponding to one reflect array element 122, and is a space 0.5λ high from the reflecting surface of the reflect array 120. The surface on the +Z direction side of this analysis space is a Floquet port. In the simulation model, the reflect array element 122 and the ground layer 123 are assumed to be perfect conductors, and the relative permittivity of the substrate 121 is set to 2.97 and the dielectric loss tangent to 0.001. The reflecting surface of the reflect array 120 is a plane that includes the surfaces of the multiple reflect array elements 122.

[0076] <Relationship between Lengths K1 and K2 and Amount of Phase Change> Figures 11A and 11B are diagrams showing an example of simulation results regarding the relationship between the lengths K1 and K2 and the amount of phase change. The characteristics shown in Figures 11A and 11B were obtained by calculation using an electromagnetic field simulator. Figure 11A shows an example of the relationship between the length K1 and the amount of phase change in a reflectarray 120 in which no slots 122A are formed, and Figure 11B shows an example of the relationship between the length K2 of the slots 122A in the reflectarray 120 and the amount of phase change.

[0077] 11A, the horizontal axis represents the length K1 (mm) of one side of the reflectarray element 122 in which the slot 122A is not formed, and the vertical axis represents the amount of phase change (degrees) calculated from the S11 parameter of the radio waves reflected by the reflectarray 120 in which the slot 122A is not formed. In Fig. 11B, the horizontal axis represents the length K2 (mm) of the slot 122A in the X and Y directions, and the vertical axis represents the amount of phase change (degrees) calculated from the S11 parameter of the radio waves reflected by the reflectarray 120.

[0078] As shown in Fig. 11A, when the length K1 was changed from 0.05 mm to 0.35 mm, it was confirmed that the phase change amount changed from 360 degrees to approximately 150 degrees. Also, as shown in Fig. 11B, when the length K2 was changed from 0.05 mm to 0.43 mm, it was confirmed that the phase change amount changed from approximately 150 degrees to approximately 0 degree.

[0079] As shown in Figures 11A and 11B, in the simulation model shown in Figure 10, it was confirmed that the amount of phase change can be adjusted by setting the lengths K1 and K2 of the reflect array element 122 to various lengths depending on the operating frequency of the near-field transmission device 100.

[0080] Fig. 12A is a diagram showing an example of the configuration of a near-field transmission system 200M1 according to a first modified example of the embodiment. The near-field transmission system 200M1 includes two near-field transmission devices 100A and 100B, similar to the near-field transmission system 200 shown in Fig. 1. The near-field transmission system 200M1 differs from the near-field transmission system 200 shown in Fig. 1 in that the reflectarrays 120A and 120B are inclined with respect to the XY plane so as to face the primary radiators 110A and 110B, respectively.

[0081] The reflectarrays 120A and 120B are arranged so that the center of the reflective surface of the reflectarray 120A (the surface on the +Z direction side of the substrate 121 of the reflectarray 120A) and the center of the reflective surface of the reflectarray 120B (the surface on the -Z direction side of the substrate 121 of the reflectarray 120B) are located on the Z axis. The distance between the center of the reflective surface of the reflectarray 120A and the center of the reflective surface of the reflectarray 120B is 50 mm. In other words, the beam propagation distance between the reflectarrays 120A and 120B is 50 mm.

[0082] Figure 12B is a diagram illustrating the positional relationship between the reflect array 120A and the primary radiator 110A, extracted from Figure 12A. In Figure 12B, the reference numerals for the substrate 121, reflect array element 122, and slot 122A are omitted to show the angles and dimensions.

[0083] 12B, the reflect array 120A is tilted 16° clockwise with respect to the XY plane when viewed from the -X direction. That is, the reflect array 120A is tilted so that the reflect array elements 122 face diagonally downward. When tilted 16°, the length between both ends of the reflect array 120A in the Y direction is 10.2 mm.

[0084] 12B shows, in addition to the XYZ coordinates, an XY'Z' coordinate system with the center of the reflecting surface of the reflect array 120A as the origin. The Y' axis is tilted 16 degrees in a clockwise direction relative to the Y axis when viewed from the -X direction. Similarly, the Z' axis is tilted 16 degrees in a clockwise direction relative to the Z axis when viewed from the -X direction. The Z' axis is parallel to the normal to the substrate 121.

[0085] When viewed from the -X direction, the primary radiator 110A is disposed at a position where the radiation axis 111 of the beam of the primary radiator 110A is tilted by 32° in a clockwise direction relative to the Z axis. Therefore, the angle between the Z' axis and the radiation axis 111 of the beam of the primary radiator 110A is 16°. The distance between the primary radiator 110A and the origin of the XY'Z' coordinate system (the center of the reflecting surface of the reflect array 120A) is 10.23 mm. In addition, in FIG. 12B, the electric field direction of the Gaussian beam used in the simulation for the primary radiator 110A is indicated by an arrow 112. The electric field direction of the Gaussian beam indicated by the arrow 112 in FIG. 12B coincides with the electric field direction of the beam radiated from the primary radiator 110A shown in FIG. 12B.

[0086] Although the reflectarray 120A has been described here, the reflectarray 120B is also tilted in the same manner. The reflectarray 120B is tilted 16° counterclockwise with respect to the XY plane when viewed from the -X direction side. The size of the reflectarray 120B is the same as that of the reflectarray 120A.

[0087] Furthermore, the primary radiator 110B is disposed at an angle similar to that of the primary radiator 110A. When viewed from the −X direction side, the primary radiator 110B is disposed at a position where the radiation axis of the beam of the primary radiator 110B is tilted by 32° in a direction rotating counterclockwise with respect to the Z axis. Furthermore, the distance between the primary radiator 110B and the center of the surface on the −Z direction side of the substrate 121 of the reflect array 120B is 10.23 mm.

[0088] Fig. 12C is a diagram showing an example of the configuration of the reflect array 120A. Fig. 12C shows the configuration of the reflect array 120A when viewed from the Y'Z' plane. That is, Fig. 12C shows the configuration of the reflect array 120A when viewed from the normal direction of the substrate 121. The outer edge of the substrate 121 is a perfect circle, for example. Although omitted in Fig. 12C, a ground layer 123 is formed on one surface of the substrate 121 on the -Z' direction side.

[0089] The reflectarray 120A is configured to reflect the radio waves radiated from the primary radiator 110A in the +Z direction. Here, in Fig. 12A, the five vertical lines shown between the reflectarrays 120A and 120B indicate the positions of the wavefronts of the radio waves reflected by the reflectarray 120A on the YZ plane. The wavefronts indicated by four of the five lines except for the central one are curved with respect to the XY plane, but the wavefront of the central one of the five is parallel to the XY plane.

[0090] The reflectarray 120A is arranged at an angle so that the reflectarray elements 122 face diagonally downward. In this reflectarray 120A, in order to reflect the radio waves radiated from the primary radiator 110A in the +Z direction, all of the reflectarray elements 122 are arranged asymmetrically on the +Y' direction side and the -Y' direction side with respect to a line passing through the center of the substrate 121 in the XY' plane view and parallel to the X axis. More specifically, as shown in FIG. 12C , the centers of all of the reflectarray elements 122 in the XY' plane view are offset upward (toward the +Y' direction) with respect to the center of the substrate 121 in the XY' plane view. Note that the configuration of the reflectarray 120B when viewed from the reflectarray element 122 side is the same as the configuration of the reflectarray 120A shown in FIG. 12C .

[0091] <Simulation Results> Figures 13A and 13B are diagrams showing examples of simulation results. Figure 13A shows an example of the results of a simulation in which the reflectarray 120A shown in Figure 12C is used, the reflectarray 120A is arranged parallel to the XY plane, an electric field phase distribution is created by infinitesimal dipoles on the reflecting surface of the reflectarray 120A, and a beam emitted from the reflectarray 120A is reflected. The simulation result shown in Figure 13A represents an ideal result calculated on the assumption that a beam is emitted from the reflectarray 120A under ideal conditions.

[0092] In Fig. 13A, the horizontal axis represents the distance (m) in the Z direction from the center of the reflecting surface of the reflectarray 120A. That is, the horizontal axis represents the propagation distance of the beam reflected by the reflecting surface of the reflectarray 120A. 0 m on the horizontal axis represents the position of the reflecting surface of the reflectarray 120A. The vertical axis represents the distance (mm) in the X direction from the center of the reflecting surface of the reflectarray 120A. Fig. 13A shows the intensity distribution of the beam.

[0093] A phase distribution of an electric field was created by an infinitesimal dipole on the reflecting surface of the reflectarray 120A, and the intensity distribution of the beam was calculated when the beam was reflected in the +Z direction by the reflectarray 120A. The range in which the beam intensity distribution was calculated was a range up to a position 50 mm from the reflecting surface of the reflectarray 120. The beam frequency was 300 GHz.

[0094] In the simulation, the diameter of the reflect array 120 was set to 10.2 mm, the thickness of the substrate 121 to 0.127 mm, the relative dielectric constant of the substrate 121 to 2.97, and the dielectric loss tangent to 0.001. The thickness of the reflect array element 122 and the ground layer 123 was set to 18 μm, and the material was set to copper.

[0095] When the beam intensity distribution was calculated under these simulation conditions, it was confirmed that the beam was narrowed within the aperture plane of the reflectarray 120A, as shown in Fig. 13A. Because the beam is narrowed in this way, high-quality communication with a high transmission rate and little leakage is possible.

[0096] Fig. 13B is a diagram showing an example of a simulation result using a Gaussian beam with the reflectarray 120A shown in Fig. 12C in a state where the reflectarray 120A is arranged at an angle of 16° with respect to the XY plane as shown in Fig. 12B. A simulation was performed by placing a beam source of a Gaussian beam at the position of the primary radiator 110A arranged as shown in Fig. 12B. The electric field direction of the Gaussian beam is as shown by arrow 112 in Fig. 12B and is the same as the electric field direction of the beam radiated from the primary radiator 110A shown in Fig. 12B.

[0097] In Figure 13B, the horizontal axis represents the distance (m) in the Z direction from the center of the reflecting surface of the reflect array 120A. That is, the horizontal axis represents the propagation distance of the beam reflected by the reflecting surface of the reflect array 120A. 0 m on the horizontal axis represents the position of the center of the reflecting surface of the reflect array 120A. The vertical axis represents the distance (mm) in the X direction from the center of the reflecting surface of the reflect array 120A. Figure 13B, like Figure 13A, shows the intensity distribution of the beam.

[0098] 12B, a Gaussian beam was emitted from a beam source placed at the position of the primary radiator 110A, and the beam intensity distribution was calculated when the beam was reflected in the +Z direction by the reflectarray 120A. The range in which the beam intensity distribution was calculated was a range up to a position 50 mm from the reflecting surface of the reflectarray 120. The beam frequency was 300 GHz.

[0099] 13A , the diameter of the reflect array 120 was set to 10.2 mm, the thickness of the substrate 121 to 0.127 mm, the relative dielectric constant of the substrate 121 to 2.97, and the dielectric loss tangent to 0.001. The thickness of the reflect array element 122 and the ground layer 123 was set to 18 μm, and the material was set to copper.

[0100] When the beam intensity distribution was calculated under these simulation conditions, it was confirmed that the beam was narrowed within the aperture plane of the reflectarray 120A, as shown in Fig. 13B. Although the beam is slightly wider than the ideal beam shown in Fig. 13A, the narrowed beam enables high-quality communication with a high transmission rate and little leakage.

[0101] Figure 13C is a diagram showing the beam intensity distribution on the Z axis obtained from the simulation results of Figures 13A and 13B. In Figure 13C, the horizontal axis represents the propagation distance (mm) of the beam reflected by the reflecting surface of the reflectarray 120A. The vertical axis represents the beam intensity (dB). In Figure 13C, the beam intensity distribution in the simulation result of Figure 13A is shown by a dashed line, and the beam intensity distribution in the simulation result of Figure 13B is shown by a solid line.

[0102] As shown in Fig. 13C, the difference between the beam intensity on the Z axis in the simulation result of Fig. 13A and the beam intensity on the Z axis in the simulation result of Fig. 13B at a propagation distance of 500 mm was 0.33 dB. From this result, it was confirmed that the near-field transmission system 200M1 of the first modified example of the embodiment shown in Fig. 12A can realize a beam intensity distribution on the Z axis that is very close to the ideal result when a beam is radiated from the reflect array 120A under ideal conditions. In other words, it was confirmed that the near-field transmission system 200M1 of the first modified example of the embodiment shown in Fig. 12A can reflect the radio wave radiated from the primary radiator 110A in the +Z direction.

[0103] 14A is a diagram showing an example of the configuration of a near-field transmission system 200M2 according to a second modified example of the embodiment. The near-field transmission system 200M2 has a configuration in which the size of the two near-field transmission devices 100A and 100B of the near-field transmission system 200M1 according to the first modified example of the embodiment shown in FIG. 12A is increased, and the angle between the two near-field transmission devices 100A and 100B and the distance in the Z direction are changed. Here, the differences between the near-field transmission system 200M2 and the near-field transmission system 200M1 according to the first modified example of the embodiment will be described.

[0104] In the near-field transmission system 200M2, the distance between the center of the reflecting surface of the reflectarray 120A and the center of the surface on the −Z direction side of the substrate 121 of the reflectarray 120B is 200 mm. In other words, the beam propagation distance between the reflectarrays 120A and 120B is 200 mm.

[0105] Fig. 14B is a diagram extracted from Fig. 12A and showing the positional relationship between the reflectarray 120A and the primary radiator 110A. As shown in Fig. 14B, the reflectarray 120A is tilted 20° clockwise with respect to the XY plane when viewed from the -X direction side. When tilted 20°, the length between both ends of the reflectarray 120A in the Y direction is 20 mm.

[0106] The Y'-axis is tilted by 20 degrees in a clockwise direction relative to the Y-axis when viewed from the -X direction. Similarly, the Z'-axis is tilted by 20 degrees in a clockwise direction relative to the Z-axis when viewed from the -X direction. The Z'-axis is parallel to the normal to the substrate 121.

[0107] When viewed from the -X direction side, the primary radiator 110A is disposed at a position where the radiation axis 111 of the beam of the primary radiator 110A is tilted by 40° in a clockwise rotation direction with respect to the Z axis. Therefore, the angle formed by the Z' axis and the radiation axis 111 of the beam of the primary radiator 110A is 20°. Furthermore, the distance between the primary radiator 110A and the origin of the XY'Z' coordinate system (the center of the reflecting surface of the reflect array 120A) is 28 mm.

[0108] In the near-field transmission system 200M2, a diagonal horn is used as the primary radiator 110A, for example. The electric field direction of the beam indicated by arrow 112 in Fig. 14B indicates the electric field direction of the beam radiated from the diagonal horn.

[0109] Although the reflectarray 120A has been described here, the reflectarray 120B is also tilted in the same way. The reflectarray 120B is tilted 20° counterclockwise with respect to the XY plane when viewed from the -X direction side. The size of the reflectarray 120B is the same as that of the reflectarray 120A.

[0110] Furthermore, the primary radiator 110B is disposed at an angle similar to that of the primary radiator 110A. When viewed from the −X direction side, the primary radiator 110B is disposed at a position where the radiation axis of the beam of the primary radiator 110B is tilted by 40° in a direction rotating counterclockwise with respect to the Z axis. Furthermore, the distance between the primary radiator 110B and the center of the surface on the −Z direction side of the substrate 121 of the reflect array 120B is 28 mm.

[0111] 14C is a diagram showing an example of the configuration of the reflect array 120A of the near-field transmission system 200M2. The outer edge of the substrate 121 is, for example, an ellipse having a major axis extending in the Y′ direction.

[0112] In the near-field transmission system 200M2, similar to the near-field transmission system 200M1, the reflectarray 120A is configured to reflect the radio waves radiated from the primary radiator 110A in the +Z direction. Here, in Fig. 14A, the five vertical lines shown between the reflectarrays 120A and 120B indicate the position of the wavefront of the radio waves reflected by the reflectarray 120A on the YZ plane. The wavefronts indicated by four of the five lines except for the central one are curved with respect to the XY plane, but the wavefront of the central one of the five is parallel to the XY plane.

[0113] The reflectarray 120A is arranged at an angle so that the reflectarray elements 122 face diagonally downward. In this reflectarray 120A, in order to reflect the radio waves radiated from the primary radiator 110A in the +Z direction, all of the reflectarray elements 122 are arranged asymmetrically on the +Y' direction side and the -Y' direction side with respect to a line passing through the center of the substrate 121 in the XY' plane view and parallel to the X axis. More specifically, as shown in Figure 14C, the centers of all of the reflectarray elements 122 in the XY' plane view are offset upward (towards the +Y' direction) with respect to the center of the substrate 121 in the XY' plane view. Note that the configuration of the reflectarray 120B when viewed from the reflectarray element 122 side is the same as the configuration of the reflectarray 120A shown in Figure 14C.

[0114] 15A and 15B are diagrams showing an example of a simulation result under ideal conditions obtained by applying a phase distribution of an electric field due to an infinitesimal dipole to the near-field transmission system 200M2. Fig. 15A shows an example of an aperture distribution of beam intensity (beam amplitude (dB)) on the reflecting surface of the reflectarray 120A. Fig. 15B shows an example of an aperture distribution of beam phase (deg.) on the reflecting surface of the reflectarray 120A.

[0115] 15A shows an example of the beam intensity and aperture distribution on the reflecting surface of the reflect array 120A when the phase distribution of the electric field due to an infinitesimal dipole is applied to the near-field transmission system 200M2. In FIG. 15A and FIG. 15B, the horizontal axis indicates the position on the Y′ axis, and the vertical axis indicates the position on the X axis.

[0116] 15A and 15B, in a simulation under ideal conditions using an infinitesimal dipole, the aperture distribution of the beam intensity is highest at the center, is symmetrical in the X and Y' directions, and the beam intensity gradually decreases from the center to the outside. Furthermore, the aperture distribution of the beam phase periodically increases and decreases in the Y' direction and is uniform in the X direction.

[0117] Figures 15C and 15D are diagrams showing an example of the results of a simulation when a beam is radiated from the primary radiator 110A in the near-field transmission system 200M2. Figure 15C shows an example of the aperture distribution of beam intensity on the reflecting surface of the reflectarray 120A. Figure 15D shows an example of the aperture distribution of beam phase on the reflecting surface of the reflectarray 120A. The primary radiator 110A in the near-field transmission system 200M2 is a diagonal horn. In Figures 15C and 15D, the horizontal axis indicates position on the Y' axis, and the vertical axis indicates position on the X axis.

[0118] 15C , when a beam is radiated from the diagonal horn serving as the primary radiator 110A and reflected by the reflectarray 120A, the aperture distribution of the beam intensity on the reflecting surface of the reflectarray 120A is as follows: That is, although the distribution is coarser than the aperture distribution of the beam intensity shown in Fig. 15A , the beam intensity is highest at the center, is symmetrical in the X direction and the Y′ direction, and decreases gradually from the center to the outside, and a result showing a tendency similar to that of the ideal aperture distribution of the beam intensity shown in Fig. 15A was obtained.

[0119] Furthermore, the aperture distribution of the beam phase was coarser than the aperture distribution of the beam intensity shown in FIG. 15A, but it periodically increased and decreased in the Y′ direction and was uniform in the X direction, and the results showed a tendency similar to that of the ideal aperture distribution of the beam phase shown in FIG. 15B.

[0120] From the above, it was confirmed that the near-field transmission system 200M2 using a diagonal horn as the primary radiator 110A can obtain simulation results similar to those obtained under ideal conditions in which the phase distribution of the electric field due to an infinitesimal dipole is applied to the near-field transmission system 200M2. In other words, it was confirmed that the near-field transmission system 200M2 of the second modification of the embodiment shown in Fig. 14A can reflect the radio wave radiated from the primary radiator 110A in the +Z direction.

[0121] 16A is a diagram showing an example of the configuration of a near-field transmission system 200M3 according to a third modified example of the embodiment. The near-field transmission system 200M3 has a configuration in which the size of the two near-field transmission devices 100A and 100B of the near-field transmission system 200M2 according to the second modified example of the embodiment shown in FIG. 14A is increased, and the angle between the two near-field transmission devices 100A and 100B and the distance in the Z direction are changed. Here, differences between the near-field transmission system 200M3 and the near-field transmission systems 200M1 and 200M2 according to the first and second modified examples of the embodiment will be described.

[0122] In the near-field transmission system 200M3, the distance between the center of the reflecting surface of the reflectarray 120A and the center of the surface on the −Z direction side of the substrate 121 of the reflectarray 120B is 1000 mm. In other words, the beam propagation distance between the reflectarrays 120A and 120B is 1000 mm.

[0123] Fig. 16B is a diagram extracted from Fig. 12A and showing the positional relationship between the reflectarray 120A and the primary radiator 110A of the near-field transmission system 200M3. As shown in Fig. 16B, the reflectarray 120A is tilted 15° clockwise with respect to the XY plane when viewed from the -X direction side. When tilted 15°, the length between both ends of the reflectarray 120A in the Y direction is 45 mm.

[0124] The Y'-axis is tilted by 15 degrees in a clockwise direction relative to the Y-axis when viewed from the -X direction. Similarly, the Z'-axis is tilted by 15 degrees in a clockwise direction relative to the Z-axis when viewed from the -X direction. The Z'-axis is parallel to the normal to the substrate 121.

[0125] When viewed from the -X direction side, the primary radiator 110A is disposed at a position where the radiation axis 111 of the beam of the primary radiator 110A is tilted by 30° in a clockwise rotation direction with respect to the Z axis. Therefore, the angle formed by the Z' axis and the radiation axis 111 of the beam of the primary radiator 110A is 15°. Furthermore, the distance between the primary radiator 110A and the origin of the XY'Z' coordinate system (the center of the reflecting surface of the reflect array 120A) is 65 mm.

[0126] In the near-field transmission system 200M3, a diagonal horn is used as the primary radiator 110A, for example. The electric field direction of the beam indicated by arrow 112 in Fig. 16B indicates the electric field direction of the beam radiated from the diagonal horn.

[0127] Although the reflectarray 120A has been described here, the reflectarray 120B is also tilted in the same manner. The reflectarray 120B is tilted 15° counterclockwise with respect to the XY plane when viewed from the -X direction side. The size of the reflectarray 120B is the same as that of the reflectarray 120A.

[0128] Furthermore, the primary radiator 110B is disposed at an angle similar to that of the primary radiator 110A. When viewed from the −X direction side, the primary radiator 110B is disposed at a position where the radiation axis of the beam of the primary radiator 110B is tilted by 30° in a direction rotating counterclockwise with respect to the Z axis. Furthermore, the distance between the primary radiator 110B and the center of the surface on the −Z direction side of the substrate 121 of the reflect array 120B is 65 mm.

[0129] 16C is a diagram showing an example of the configuration of the reflect array 120A of the near-field transmission system 200M3. The outer edge of the substrate 121 is, for example, an ellipse having a major axis extending in the Y′ direction.

[0130] In the near-field transmission system 200M3, similar to the near-field transmission system 200M1, the reflectarray 120A is configured to reflect the radio waves radiated from the primary radiator 110A in the +Z direction. Here, in Fig. 16A, the five vertical lines shown between the reflectarrays 120A and 120B indicate the position of the wavefront of the radio waves reflected by the reflectarray 120A on the YZ plane. The wavefronts indicated by four of the five lines except for the central one are curved with respect to the XY plane, but the wavefront of the central one of the five is parallel to the XY plane.

[0131] The reflectarray 120A is arranged at an angle so that the reflectarray elements 122 face diagonally downward. In this reflectarray 120A, in order to reflect the radio waves radiated from the primary radiator 110A in the +Z direction, all of the reflectarray elements 122 are arranged asymmetrically on the +Y' direction side and the -Y' direction side with respect to a line passing through the center of the substrate 121 in the XY' plane view and parallel to the X axis. More specifically, as shown in FIG. 16C , the centers of all of the reflectarray elements 122 in the XY' plane view are offset upward (toward the +Y' direction) with respect to the center of the substrate 121 in the XY' plane view. Note that the configuration of the reflectarray 120B when viewed from the reflectarray element 122 side is the same as the configuration of the reflectarray 120A shown in FIG. 16C .

[0132] Such a near-field transmission system 200M3 can reflect the radio wave radiated from the primary radiator 110A in the +Z direction.

[0133] <Effects> The near-field transmission device 100 is a near-field transmission device 100 that transmits or receives in the near field, and includes a primary radiator 110 and a reflectarray 120 that reflects the radio waves radiated by the primary radiator 110, the reflectarray 120 having a plurality of reflectarray elements 122, the reflectarray 120 having an outer dimension of 10λ or more, and where λ is the wavelength of the radio waves radiated by the primary radiator 110, the pitch of the plurality of reflectarray elements 122 is 0.9λ or less. Therefore, high-quality communication with a high transmission rate and little leakage is possible through the near field.

[0134] Therefore, it is possible to provide a near-field transmission device 100 that is capable of high-quality communication in the near field.

[0135] Furthermore, the aperture surface (radiation surface) of the primary radiator 110 may be 9λ or less. High-quality communication with a higher transmission rate and less leakage is possible through the near field.

[0136] The frequency of the radio waves radiated by the primary radiator 110 may be 20 GHz or higher. High-quality communication with a high transmission rate and little leakage is possible through the near field in a high frequency band of 20 GHz or higher.

[0137] The reflectarray 120 has a substrate 121, a plurality of reflectarray elements 122 provided on a first surface of the substrate 121, and a ground layer 123 provided on a second surface of the substrate 121, and the plurality of reflectarray elements 122 may be patch elements. Using the reflectarray 120 in which the plurality of reflectarray elements 122 and the ground layer 123 are provided on the substrate 121, it is possible to provide a near-field transmission device 100 that is capable of high-quality communication in the near field.

[0138] The patch element may also have a configuration in which a cross-shaped slot 122 A is provided in a rectangular patch conductor. Using a plurality of reflect array elements 122 each provided with the cross-shaped slot 122 A, it is possible to provide a near-field transmission device 100 capable of high-quality communication in the near field.

[0139] While exemplary near-field transmission devices according to the present disclosure have been described above, the present disclosure is not limited to the specifically disclosed embodiments, and various modifications and variations are possible without departing from the scope of the claims.

[0140] The following supplementary notes are further disclosed with respect to the above embodiments. (Supplementary Note 1) A near-field transmission device that transmits or receives in a near field, comprising: a primary radiator; and a reflectarray that reflects radio waves radiated by the primary radiator, wherein the reflectarray has a plurality of reflectarray elements, the reflectarray has an outer dimension of 10λ or more, and where λ is the wavelength of the radio waves radiated by the primary radiator, a pitch of the plurality of reflectarray elements is 0.9λ or less. (Supplementary Note 2) The near-field transmission device according to Supplementary Note 1, wherein the radiation surface of the primary radiator is 9λ or less. (Supplementary Note 3) The near-field transmission device according to Supplementary Note 1 or 2, wherein the frequency of the radio waves radiated by the primary radiator is 20 GHz or more. (Supplementary Note 4) The near-field transmission device according to any one of Supplementary Notes 1 to 3, wherein the reflectarray has a base, the plurality of reflectarray elements provided on a first surface of the base, and a ground layer provided on a second surface of the base, and the plurality of reflectarray elements are patch elements. (Supplementary Note 5) The near-field transmission device according to Supplementary Note 4, wherein the patch element has a configuration in which a cross-shaped slot is provided in a rectangular patch conductor.

[0141] The disclosures of Japanese Patent Applications Nos. 2024-025136 and 2024-155109 are incorporated herein by reference in their entirety. All documents, patent applications, and technical standards mentioned herein are incorporated by reference into this specification to the same extent as if each individual document, patent application, and technical standard was specifically and individually indicated to be incorporated by reference.

[0142] 100, 100A, and 100B: Near-field transmission device 200, 200M1 to 200M3: Near-field transmission system 110A, 110B: Primary radiator 120, 120A, 120B: Reflect array 121: Substrate 122: Reflect array element 123: Ground layer

Claims

1. A near-field transmission device that transmits or receives in the near field, comprising: a primary radiator; and a reflectarray that reflects radio waves radiated by the primary radiator, wherein the reflectarray has a plurality of reflectarray elements, the reflectarray has an outer dimension of 10λ or more, and where λ is the wavelength of the radio waves radiated by the primary radiator, the pitch of the plurality of reflectarray elements is 0.9λ or less.

2. A near-field transmission device according to claim 1, wherein the radiation surface of said primary radiator is 9λ or less.

3. The near-field transmission device according to claim 1, wherein the frequency of the radio waves radiated by the primary radiator is 20 GHz or higher.

4. A near-field transmission device as described in claim 1, wherein the reflectarray has a base, the plurality of reflectarray elements provided on a first surface of the base, and a ground layer provided on a second surface of the base, and the plurality of reflectarray elements are patch elements.

5. A near-field transmission device according to claim 4, wherein the patch element has a configuration in which a cross-shaped slot is provided in a rectangular patch conductor.

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