Wireless power supply device

Abstract

To provide a wireless power feeding device capable of transmitting microwaves appropriately to a flying body in flight having a mission apparatus.SOLUTION: A wireless power feeding device 1 wirelessly feeding power to a flying body 2 in flight includes: a transmission antenna 11 that is a planar array antenna having a plurality of antenna elements arranged in a planar state; and a power transmission part 12 that transmits microwaves from each of the plurality of antenna elements of the transmission antenna 11. The power transmission part 12 transmits the microwaves so that strength of power transmitted from the transmission antenna 11 becomes minimum in a center of a power reception antenna 21 surface of the flying body 2. Thus, an efficient wireless power feeding can be realized even if a mission apparatus 25 is arranged in the center of the power reception antenna 21 surface, and even if a hole opens in the center of the power reception antenna 21 surface.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a wireless power supply device that wirelessly supplies power to an aircraft in flight, and to an aircraft that is wirelessly powered by a wireless power supply device. [Background technology]

[0002] Conventionally, power supply to an aircraft such as a drone has been performed after the aircraft has landed on the ground (see, for example, Patent Documents 1 and 2). If the aircraft had to land on the ground every time power was supplied, the amount of time it could fly continuously would be shortened. This poses a problem in that the mission being carried out by the aircraft during flight would be interrupted.

[0003] It is also possible to supply power to an aircraft in flight from the ground via a wired cable, but in this case, the flight altitude and flight range would be limited, which would reduce the freedom of flight.

[0004] To solve the above problem, it is conceivable to transmit power to an aircraft by microwave from a wireless power supply device on the ground to the aircraft during flight, which has the advantage of being able to supply power to the aircraft during flight without interrupting the flight. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2020-202734 [Patent Document 2] Japanese Patent Publication No. 2020-125021 Summary of the Invention [Problem to be solved by the invention]

[0006] An airborne vehicle has a specific mission, such as photographing the ground or relaying radio waves. This mission is performed using mission equipment, such as a camera or a repeater, which is located at the bottom of the vehicle. Meanwhile, a receiving antenna that receives microwaves transmitted from a wireless power supply device on the ground is also located at the bottom of the vehicle. Therefore, if the mission equipment is located at a part of the receiving antenna, the microwaves may be partially blocked by the mission equipment, potentially reducing the amount of power received by the receiving antenna. Furthermore, if the mission equipment is a repeater, microwaves used for power transmission may be irradiated onto the repeater, causing the repeater to malfunction. Furthermore, microwaves may be irradiated onto the mission equipment, potentially causing the mission equipment to malfunction.

[0007] The present invention has been made to solve the above-mentioned problems, and aims to provide a wireless power supply device that can appropriately transmit microwaves for wireless power supply to an aircraft having mission equipment in flight, and an aircraft that can appropriately receive microwaves for wireless power supply transmitted from the wireless power supply device in flight. [Means for solving the problem]

[0008] In order to achieve the above-mentioned object, a wireless power supply device according to one aspect of the present invention is a wireless power supply device that wirelessly supplies power to an aircraft in flight, and is equipped with a transmitting antenna that is a planar array antenna having multiple antenna elements arranged in a plane, and a transmitting unit that transmits microwaves from each of the multiple antenna elements of the transmitting antenna, and the transmitting unit transmits microwaves so that the intensity of the power transmitted from the transmitting antenna is minimum at the center of the aircraft's receiving antenna surface. This configuration allows for appropriate wireless power supply using areas other than the center of the receiving antenna surface, so that efficient wireless power supply can be achieved even when, for example, the mission equipment is located at the center of the receiving antenna surface or when a hole is opened in the center of the receiving antenna surface.

[0009] In addition, in the wireless power supply device according to one aspect of the present invention, the power transmitting unit may transmit microwaves so as to form a beam in which the intensity of the power transmitted from the power transmitting antenna is minimized on a central axis in the power transmission direction. This configuration enables wireless power transmission using a beam with an air-core region at its center. Therefore, even if the vertical distance between the aircraft and the power transmitting antenna changes during wireless power transmission, the center of the receiving antenna surface will be located in the air-core region of the beam, and the power intensity at the center of the receiving antenna surface will remain at a minimum.

[0010] In the wireless power supply device according to one aspect of the present invention, the beam waist of the beam may be located at the plane of the power receiving antenna. With this configuration, more efficient wireless power feeding can be achieved, and for example, the size of the power receiving antenna can be made smaller.

[0011] In addition, a wireless power supply device according to one aspect of the present invention may further include an altitude acquisition unit that acquires the altitude of the flying object, a design unit that uses the altitude to design a beam whose beam waist is located at the position of the receiving antenna surface, and a control unit that controls the power transmission unit so that power transmission is performed according to the beam designed by the design unit. With this configuration, even if the vertical distance between the power transmitting antenna and the power receiving antenna changes, optimal power transmission can be achieved in response to the change.

[0012] Furthermore, an aircraft according to one aspect of the present invention is an aircraft that flies in the air, and is equipped with a receiving antenna that is positioned below the aircraft and receives microwaves transmitted from a transmitting antenna, flight means that is powered by the power of the microwaves received by the receiving antenna, and mission equipment for performing a predetermined mission, and a hole is provided in the center of the surface of the receiving antenna to allow the mission equipment to perform its mission. This configuration allows the mission equipment to perform a predetermined mission through the hole in the center of the receiving antenna surface. Also, for example, by transmitting microwaves from the transmitting antenna so that the power intensity is minimized at the center of the receiving antenna surface, efficient power reception can be achieved. [Effects of the Invention]

[0013] According to one aspect of the present invention, a wireless power supply device can appropriately supply power wirelessly using an area other than the center of the receiving antenna face of an aircraft during flight. Also, according to one aspect of the present invention, a hole provided in the center of the receiving antenna face enables a mission device to perform a predetermined mission during flight. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 1 is a schematic diagram illustrating an example of wireless power supply from a power transmitting antenna of a wireless power supply device to a power receiving antenna of an aircraft according to an embodiment of the present invention. [Figure 2] FIG. 2 is a block diagram showing the configuration of a wireless power supply device and an aircraft according to the embodiment. [Figure 3] FIG. 2 is a circuit diagram showing an example of the configuration of a power transmission unit of the wireless power supply device according to the embodiment. [Figure 4] FIG. 10 is a diagram showing an example of a beam having an air-core region in the embodiment; [Figure 5A] FIG. 10 is a diagram showing the relationship between the distance between antennas and the diameter of the power transmitting antenna in the embodiment; [Figure 5B]FIG. 10 is a diagram showing the relationship between the distance from the center and the relative power density in the embodiment; [Figure 6A] FIG. 4 is a diagram showing an example of the amplitude of each antenna element of the power transmitting antenna according to the embodiment; [Figure 6B] FIG. 4 is a diagram showing an example of the phase of each antenna element of the power transmitting antenna according to the embodiment; [Figure 6C] FIG. 10 is a diagram showing an example of power density in a cross section including the central axis of a microwave beam in the embodiment; [Figure 7] FIG. 10 is a diagram showing another example of a beam in the embodiment; [Figure 8A] FIG. 10 is a diagram showing an example of power and phase in the diameter direction of the power transmitting antenna surface in the embodiment; [Figure 8B] FIG. 10 is a diagram showing an example of power density in a cross section including the central axis of a microwave beam in the embodiment; [Figure 8C] FIG. 10 is a diagram showing an example of power density on the plane of the power receiving antenna according to the embodiment; [Figure 9] FIG. 10 is a block diagram showing another example of the configuration of the wireless power supply device according to the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0015] Hereinafter, a wireless power supply device and an aircraft according to the present invention will be described using embodiments. In the following embodiments, components with the same reference numerals are the same or equivalent, and repeated description may be omitted. The wireless power supply device according to this embodiment wirelessly supplies power so that the intensity of the power transmitted from the power transmitting antenna is minimized at the center of the plane of the power receiving antenna of the aircraft flying in the air.

[0016] FIG. 1 is a schematic diagram illustrating an example of wireless power supply from a wireless power supply device 1 according to the present embodiment to an aircraft 2 in flight, and FIG. 2 is a block diagram illustrating a configuration of a wireless power supply system 100. FIG. 3 is a circuit diagram illustrating an example of a configuration of a power transmission unit 12 capable of changing the amplitude and phase for each antenna element 11a. As illustrated in FIG. 2, the wireless power supply system 100 includes a wireless power supply device 1 and an aircraft 2. The wireless power supply device 1 wirelessly supplies power to the aircraft 2 in flight and is typically located on the ground. The wireless power supply device 1 may be mounted on a mobile object such as a power supply vehicle 4 as illustrated in FIG. 1, or may be fixed on the ground. From the viewpoint of wirelessly supplying power to the aircraft 2 moving in the air, it is preferable that the wireless power supply device 1 be mounted on a mobile object that can move on the ground. As illustrated in FIG. 2, the wireless power supply device 1 includes a power transmission antenna 11, a power transmission unit 12, and a control unit 13.

[0017] The power transmitting antenna 11 is a planar array antenna having multiple antenna elements 11a arranged in a plane. Each antenna element 11a is not particularly limited as long as it can form a planar array antenna. For example, it may be a linear antenna such as a dipole antenna, a slot antenna, or a microstrip antenna, which has low gain and a wide beam width. The multiple antenna elements 11a may be arranged at equal intervals in a plane. The spacing between the antenna elements 11a is not particularly limited, but may be shorter than the wavelength λ of the transmitted microwave, such as 0.7λ. Furthermore, as shown in FIG. 1 , the power transmitting antenna 11 may have a disk shape in a planar view. The polarization of this planar array antenna and the beam formed thereby may be, for example, linear polarization or circular polarization. Considering that the aircraft 2 rotates around the axis of the beam, circular polarization is preferable.

[0018] The power transmitting unit 12 transmits microwaves from each of the multiple antenna elements 11a of the power transmitting antenna 11. The frequency of the microwaves is not particularly limited, and may be, for example, a frequency within a range of 300 MHz to 300 GHz. The power transmitting unit 12 may transmit the microwaves so that the intensity of the power transmitted from the power transmitting antenna 11 is minimized at the center of the plane of the power receiving antenna 21 of the aircraft 2. For example, the power transmitting unit 12 may transmit the microwaves so that a beam is formed in which the intensity of the power transmitted from the power transmitting antenna 11 is minimized at the central axis of the power transmission direction. The beam waist of the beam may be located at the plane of the power receiving antenna 21. Note that the method for achieving such power transmission is not critical. For example, such power transmission may be performed by controlling the power transmitting unit 12 with the control unit 13, or may be performed without such control. In this embodiment, the former case will be mainly described, and the latter case will be described later. The power transmitting unit 12 may have a mechanism for changing the amplitude and phase for each antenna element 11a, for example. 3, the power transmitting unit 12 includes an oscillator 12a that generates microwaves of a predetermined frequency, multiple phase shifters 12b that change the phase of the signal, and multiple amplifiers 12c that amplify the signal. The signals oscillated by the oscillator 12a are phase-shifted by the multiple phase shifters 12b, amplified by the multiple amplifiers 12c, and then radiated from the antenna element 11a. The degree of phase shift by each phase shifter 12b and the degree of amplitude change by each amplifier 12c are controlled by the control unit 13, as described below, so that the microwaves transmitted from the power transmitting antenna 11 form a desired beam.

[0019] The power transmitting unit 12 may have a configuration other than that shown in FIG. 3. For example, the power transmitting unit 12 may transmit microwaves from each of the multiple antenna elements 11a by digital beamforming. In this case, the power transmitting unit 12 may generate a digital signal of a desired phase in the baseband for each of the multiple antenna elements 11a, perform digital-to-analog conversion on the generated digital signal, frequency convert (modulate) it to a transmission frequency, and amplify it to a desired amplitude. The signal that has undergone these processes may then be emitted from each antenna element 11a.

[0020] The control unit 13 controls the power transmitting unit 12 so that the intensity of the power transmitted from the power transmitting antenna 11 is minimum at the center of the surface of the power receiving antenna 21 of the aircraft 2. The term "minimum power intensity at the center of the surface of the power receiving antenna 21" may mean that, in a region including the center of the surface of the power receiving antenna 21, the power intensity in the central portion is lower than the power intensity in the peripheral portion surrounding the center. Conventionally, when wireless power is transmitted, the power intensity at the center of the surface of the power receiving antenna 21 generally peaks. However, in this embodiment, the peak region may be a ring-shaped region surrounding the center of the surface of the power receiving antenna 21. The center of the surface of the power receiving antenna 21 may be the center of the surface of the power receiving antenna 21. Note that controlling the power transmitting unit 12 may mean controlling the amplitude and phase of the signal output from the power transmitting unit 12 to each antenna element 11a. For example, the control unit 13 may control the power transmitting unit 12 so that a beam is formed in which the intensity of the power transmitted from the power transmitting antenna 11 is minimum on the central axis in the power transmission direction. The power transmission direction may be, for example, a direction perpendicular to the plane of the power transmitting antenna 11. The central axis of the power transmission direction may be a central axis extending in the power transmission direction of the microwave beam. The beam with the minimum power intensity on the central axis of the power transmission direction is not particularly limited, but may be a Laguerre-Gaussian beam, for example. In this embodiment, a case where power transmission is performed using a Laguerre-Gaussian beam will be mainly described. Specific amplitude and phase control will be described later.

[0021] The aircraft 2 is preferably capable of stopping in the air, i.e., hovering, and may be, for example, a rotorcraft, an airship, or any other aircraft capable of hovering. From the viewpoint of being capable of hovering and moving to any location, the aircraft is preferably a rotorcraft. The rotorcraft may be, for example, a helicopter, or a multicopter having three or more rotors. The multicopter may be a so-called drone. The multicopter may be, for example, a quad rotor with four rotors, or may have any other number of rotors. In this embodiment, the case where the aircraft 2 is a drone will be mainly described. As shown in FIG. 2, the aircraft 2 includes a power receiving antenna 21, a battery 22, a power receiving unit 23, flight means 24, and mission equipment 25.

[0022] The power receiving antenna 21 is an antenna that receives microwaves transmitted from the power transmitting antenna 11. The power receiving antenna 21 is disposed below the aircraft 2. As shown in FIG. 1 , a hole 21a may be provided at the center of the surface of the power receiving antenna 21 through which the mission equipment 25 performs its mission. The power receiving antenna 21 is a planar antenna, and its shape is not particularly limited. For example, it may be disk-shaped in plan view, or a disk-shaped with a hole 21a in its center, i.e., an annular disk-shaped. In this embodiment, a case where the power receiving antenna 21 is annular disk-shaped will be mainly described. The shape of the hole 21a is not particularly limited. For example, it may be circular. Like the power transmitting antenna 11, the power receiving antenna 21 may also be a planar array antenna having multiple antenna elements arranged in a plane. It is preferable that the power receiving antenna 21 be disposed so that its plane is horizontal during stationary flight. The power receiving antenna 21 may be, for example, a rectenna.

[0023] The battery 22 stores power wirelessly supplied from the wireless power supply device 1. The battery 22 is preferably a rechargeable secondary battery.

[0024] Power receiving unit 23 charges battery 22 with the power received by power receiving antenna 21. Note that, for example, if power receiving antenna 21 is a rectenna, power receiving unit 23 may charge battery 22 with the rectified DC power as is, or if power receiving antenna 21 is not a rectenna, power receiving unit 23 may rectify the received AC power and charge battery 22 with the rectified DC power.

[0025] Flight means 24 is a means for flying aircraft 2, and may have, for example, rotors and drive means for driving the rotors. The drive means may be, for example, a motor. Flight means 24 may have two or more pairs of rotors and drive means. Flight means 24 is powered by microwave power received by power receiving antenna 21. This power may be power charged in battery 22 after receiving the power. "Flight means 24 being powered by power from battery 22" may also mean that the drive means of flight means 24 is powered by power from battery 22.

[0026] The mission device 25 is a device for performing a predetermined mission. This mission device 25 may also be powered by power received from the wireless power supply device 1, i.e., power from the battery 22. The predetermined mission may be, for example, photography or radio wave relay. If the mission is photography, the mission device 25 may be, for example, a camera. If the mission is relaying, the mission device 25 may be, for example, a repeater. When the aircraft 2 is flying, the mission device 25 may be located above or below the surface of the power receiving antenna 21. In the former case, the mission device 25 may perform photography or radio wave relay through, for example, the hole 21a of the power receiving antenna 21. In the latter case, the mission device 25 may be supported by, for example, a support member 25a, as shown in FIG. 1, and the support member 25a may be fixed to the main body of the aircraft 2 through the hole 21a of the power receiving antenna 21.

[0027] When power is being wirelessly supplied from the wireless power supply device 1, the flying object 2 may, for example, be stationary when the wireless power supply device 1 is stopped, or may fly so as to maintain a constant positional relationship relative to the power transmitting antenna 11 when the wireless power supply device 1 is moving. The flying object 2 may, for example, fly autonomously or in response to an operator's operation. Furthermore, the wireless power supply device 1 and the flying object 2 may each include a communication unit for wireless communication therebetween.

[0028] Next, the Laguerre-Gaussian beam will be explained. The electric field distribution of the Laguerre-Gaussian beam is expressed by the following equation.

number

[0029] r, φ, and z are the distance from the reference axis, the azimuth angle around the reference axis, and the distance in the reference axis direction in a cylindrical coordinate system. As shown in FIG. 4, when the disk-shaped transmitting antenna 11 and the power receiving antenna 21 are arranged in parallel and the centers of the transmitting antenna 11 and the power receiving antenna 21 coincide in a planar view, the reference axis is a line connecting the centers of the transmitting antenna 11 and the power receiving antenna 21. z is 0 at the position of the power receiving antenna 21, and the direction toward the transmitting antenna 11, i.e., downward in FIG. 4, is taken as positive. In the electric field distribution of this Laguerre-Gaussian beam, the position of z=0, i.e., the position of the power receiving antenna 21, is the position of the beam waist. E0 is a proportional coefficient of a positive real number. p and m are mode indices. Note that p is an integer equal to or greater than 0, and m is an arbitrary integer. w(z) is the beam radius in a situation where there is no air-core region on the reference axis, which is the center, and is expressed by the following equation. Furthermore, L p is a Laguerre polynomial, k is the wave number of the transmitted microwave, R(z) is the radius of curvature of the wavefront that constitutes the beam, and is given by the following equation: Also, Ψ(z) is the Gouy phase, and is given by the following equation: j is the imaginary unit.

[0030] The beam radius w(z) is given by the following equation: where w0 = w(0) and z c =(πw0 2 ) / λ, where λ is the wavelength of the microwave.

number

[0031] The radius of curvature R(z) of the wavefront is given by the following equation:

number

[0032] The Gouy phase Ψ(z) is given by the following equation:

number

[0033] The beam dispersion σ is expressed by the following equation. This dispersion σ indicates the spread of the beam in a plane direction perpendicular to the central axis of the beam, and may be considered as the radius of a beam with an air-core region at the central axis. The cross-sectional shape of the beam in a direction perpendicular to the reference axis is a single ring when p=0, and is N+1 concentric rings when p=N (N≧1). In this embodiment, the cross-sectional shape of the beam only needs to be ring-shaped, so we will mainly consider the case of p=0.

number

[0034] This beam has an infinite radial extent, i.e., away from the reference axis, like a Gaussian distribution, but it is cut off by the edge of the disk-shaped antenna. Edge taper T e Let z be the value that indicates the degree of attenuation of the peak intensity, including up to the end of the antenna. Then, the variance σ(z) at the position z and the radius r of the antenna placed at the position z are A The relationship between the radius r of the power receiving antenna 21 and the power receiving angle r is as follows: A(0)=r0. For example, T e = 20 dB, the antenna will include a range of intensity up to 1 / 100 of the peak intensity.

number

[0035] Therefore, the radius r0 of the receiving antenna 21 and the angle T e By determining this, the variance σ(0) at the receiving antenna 21 can be calculated, and the calculated variance σ(0) can be used to calculate the beam radius w0=w(0) at the receiving antenna 21. As a result, the electric field distribution of the Laguerre-Gaussian beam is determined.

[0036] Next, when the distance z1 from the power transmitting antenna 11 to the power receiving antenna 21 is determined, w(z1) can be calculated, and σ(z1) can be calculated using the calculated w(z1) = w1. In addition, the radius r of the power transmitting antenna 11 can be calculated using the calculated σ(z1). A (z1)=r1 can be calculated.

[0037] As shown in FIG. 5A, the diameter of the power transmitting antenna 11 is 2r AThe relationship between (z1) and the distance z1 between the antennas varies depending on the value of the mode index m. From FIG. 5A, it can be seen that, assuming the distance between the antennas remains constant, the larger the absolute value of the mode index m, the larger the diameter of the transmitting antenna 11. Furthermore, the relationship between the distance from the center of the beam on the plane of the receiving antenna 21 and the relative power density, with the peak set to 0, is shown in FIG. 5B. From FIG. 5B, it can be seen that the power intensity is minimum near the central axis of the beam. Furthermore, from FIG. 5B, it can be seen that the larger the absolute value of the mode index m, the larger the air-core region at the center of the beam. Therefore, it is preferable to set the mode index m to the largest value within the allowable range of the size of the transmitting antenna 11. For example, if the distance between the antennas is z1=40 (m) and the allowable diameter of the transmitting antenna 11 is up to 4.5 (m), it is preferable to set m=3. This is because, when m=3, the diameter of the transmitting antenna 11 is 4.2 (m), which is less than 4.5 (m). Also, even if the diameter of the power transmitting antenna 11 is predetermined, A It is preferable to select a mode index m such that (z1) is equal to or smaller than the diameter of the transmitting antenna 11. The air-core region is a region near the central axis that is attenuated by a predetermined amount or more relative to the peak power density of the beam. In FIG. 5B, for a beam with m=3, the central region that is attenuated by 20 dB or more relative to the peak is indicated by a double-headed arrow as the air-core region. For a beam with m=3, the diameter of the air-core region is approximately 14 cm. Therefore, for example, the diameter of the hole 21a provided in the center of the power receiving antenna 21 may be set to approximately 14 cm.

[0038] Once the mode index m and the distance z1 between the antennas are determined, the electric field distribution at the power transmitting antenna 11 can be calculated by substituting them into the equation for the electric field distribution of the Laguerre-Gaussian beam. The proportionality coefficient E0 included in the calculated electric field distribution can be determined by calculating the total power of the electromagnetic waves to be transmitted and determining the total power so that it becomes the target power. For example, if r0=0.5 (m), r1=2.1 (m), and T e= 20 (dB), microwave frequency f0 = 24 (GHz), p = 0, m = 3, z1 = 40 (m), and proportionality coefficient E0 is determined so that the total transmitted power is 1 kW. The amplitude and phase at the power transmitting antenna 11 are shown in Figures 6A and 6B, and the power density in the plane including the reference axis is shown in Figure 6C. Figure 6C shows that the power intensity is minimum near the central axis of the beam. Note that, from the equation for the electric field distribution of a Laguerre-Gaussian beam, when m ≥ 1, one revolution around the reference axis, i.e., a change in φ by 2π, results in m phase changes of 2π. This can be confirmed by Figure 6B. Therefore, a Laguerre-Gaussian beam for m ≥ 1 can be said to be a beam whose phase changes in the azimuth direction around the central axis of the power transmission direction, i.e., the reference axis. 6A to 6C are shown in an XYZ orthogonal coordinate system in which the reference axis of the cylindrical coordinate system is the Z-axis direction and the XY plane where Z=0 is the plane direction of the power transmitting antenna 11.

[0039] The control unit 13 may control the power transmitting unit 12 so that the amplitude and phase of each antenna element 11a of the power transmitting antenna 11 become the amplitude and phase calculated using the electric field distribution of a Laguerre-Gaussian beam. Specifically, the position (r, φ) of each antenna element 11a of the power transmitting antenna 11 is substituted into the equation for the electric field distribution of a Laguerre-Gaussian beam, and the amplitude and phase in the equation are determined, thereby determining the amplitude and phase for each position of the multiple antenna elements 11a constituting the power transmitting antenna 11. The control unit 13 may then control the power transmitting unit 12 so that the amplitude and phase of each antenna element 11a become the determined amplitude and phase. More specifically, if the amplitude and phase of each antenna element 11a calculated using the equation for the electric field distribution of a Laguerre-Gaussian beam are stored in a recording medium, the control unit 13 may read the amplitude and phase from the recording medium and control the power transmitting unit 12. In addition, when the power transmission unit 12 is the circuit shown in Figure 3, the control unit 13 may control the phase shifter 12b and amplifier 12c corresponding to each antenna element 11a so that a signal of a specified phase and amplitude is radiated from the antenna element 11a.

[0040] In this embodiment, a Laguerre-Gaussian beam is mainly used as a beam whose power intensity is minimum on the central axis, i.e., the reference axis in the cylindrical coordinate system, but this is not essential. For example, a beam whose power intensity is minimum on the central axis can be formed by superposing spherical waves. Wireless power feeding may be performed using the beam whose power intensity is minimum on the central axis formed in this way.

[0041] Furthermore, in this embodiment, the case where a beam is formed in which the beam waist is located at the position of the power receiving antenna 21 has been mainly described, but this is not necessarily the case. A beam may be formed in which the position of the power receiving antenna 21 is shifted from the beam waist. Note that the beam waist is the point where the beam is most narrowed, so by setting the position of the power receiving antenna 21 as the beam waist, it is possible to achieve the most efficient wireless power transfer when the diameter of the power receiving antenna 21 is fixed. Furthermore, when the diameter of the power receiving antenna 21 is not fixed, it is also possible to minimize the diameter of the power receiving antenna 21 by setting the position of the power receiving antenna 21 as the beam waist.

[0042] Although the present embodiment has been described primarily with reference to a case where wireless power is supplied using a beam whose power intensity is minimum at the central axis, this is not essential. Other wireless power supply methods may be used as long as the power intensity transmitted from the power transmitting antenna 11 is minimum at least at the center of the surface of the power receiving antenna 21. For example, by setting the difference between the phase in a disk-shaped central region extending from the center of the power transmitting antenna 11 to a radius R1 and the phase in a ring-shaped annular region extending from the radius R1 to the radius R2 to be π, and by setting the power transmitted from the central region to be equal to the power transmitted from the annular region, the power intensity can be set to zero at a predetermined focal position. The focal position exists on the reference axis of the cylindrical coordinate system described above. Therefore, by designing this doughnut beam so that its focal position is at the center of the surface of the power receiving antenna 21, and by controlling the power transmitting unit 12 so that the designed doughnut beam is formed, the power intensity transmitted from the power transmitting antenna 11 can be set to minimum at the center of the surface of the power receiving antenna 21. In this donut beam, there is no hollow core region at the central axis of the beam. For more information on donut beams, please refer to the following website: site<URL:https: / / optipedia.info / app / lsm / doughnut_beam / >

[0043] Furthermore, two Gaussian beams may be superimposed so that the intensity of the power transmitted from the power transmitting antenna 11 is minimized at least at the center of the plane of the power receiving antenna 21. In this case, the cross-sectional amplitude of the Gaussian beam, whose beam waist is at the height of the plane of the power receiving antenna 21 of the aircraft 2, is realized by the multiple antenna elements 11a of the planar array antenna, which is the power transmitting antenna 11, to form a conical beam in which energy is concentrated on the plane of the power receiving antenna 21. Furthermore, by using different beam waist radii w 10 , w 20 (w 10 <w 20 ) are superimposed in opposite phases to cancel out the intensities in the central region of the beam waist, and a beam of radius w is formed on the surface of the receiving antenna 21 as shown in Figure 7. 10 It is possible to form an attenuation region of a size of . Note that the cylindrical coordinate system used in Figure 7 is the same as that used in Figure 4.

[0044] In this case, the radius of each Gaussian beam on the plane of the power transmitting antenna 11 is given by the following equation using the propagation distance z1: where n (=1, 2) is an index for identifying the Gaussian beam, and λ is the wavelength of the microwave.

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[0045] The beam waist is small 10 In this mode, the beam divergence angle is large, and the beam radius increases with increasing z. Therefore, the antenna radius at the beam waist, i.e., the radius r0 of the receiving antenna 21, is 20 is the edge taper T of the Gaussian beam e2 The radius r1 of the power transmitting antenna 11 is determined by the beam radius w 11 and its edge taper T e1That is, the following equation is obtained: In other words, the required diameter of the power transmitting antenna 11 is determined mainly by the size of the attenuation region to be formed.

number

[0046] Next, in a numerical simulation of beam formation, the electromagnetic field of a beam in which two Gaussian beams are superimposed was calculated using a program that calculates the beam electromagnetic field from an array antenna. Here, the microwave frequency was 24 GHz, the transmission power was 1 kW, the radius of the transmitting antenna 11 was 2.1 (m), the radius of the receiving antenna 21 was 1.0 (m), and the height from the transmitting antenna 11 to the receiving antenna 21 was 40 (m). The edge taper of the Gaussian beam was T e1 =T e2 = 20 dB. At this time, the beam waist radius w 10 , w 20 can be calculated as 0.12 (m) and 0.33 (m) using the above formula. In this simulation, the beam electromagnetic field was formed by arranging small dipole antennas corresponding to antenna element 11a in a square shape at intervals of 0.7 wavelengths.

[0047] The input power and phase distribution of the transmitting antenna 11 obtained as described above is shown in FIG. 8A. Note that FIG. 8A shows the relative power density and phase in the diameter direction passing through the center of the surface of the transmitting antenna 11. From FIG. 8A, it can be seen that the distribution is close to that of a normal Gaussian beam near the center, but the amplitude becomes constant near a radius of 0.8 m. Furthermore, the beam profile radiated from the transmitting antenna 11, which is a planar array antenna, with such amplitude and phase is shown in FIG. 8B. Note that in FIGS. 8A to 8C, the same XYZ Cartesian coordinate system as in FIGS. 6A to 6C is set. From FIG. 8B, it can be seen that an attenuation region exists on the beam central axis at an altitude of 40 m, as designed. FIG. 8C shows the cross-sectional intensity of the beam at an altitude of 40 m, i.e., on the surface of the receiving antenna 21. From FIG. 8C, it can be seen that the diameter of the attenuation region is approximately 15 cm. Therefore, it can be seen that by overlapping two Gaussian beams so that they cancel each other out at the center of the surface of the power receiving antenna 21, the intensity of the power transmitted from the power transmitting antenna 11 can be minimized at the center of the surface of the power receiving antenna 21. It goes without saying that the intensity of the power can be minimized at the center of the surface of the power receiving antenna 21 by a method other than using a doughnut beam or overlapping two Gaussian beams.

[0048] Next, the operation of the wireless power feeding system 100 according to this embodiment will be described using a specific example. When the charge level of the battery 22 of the flying object 2 falls below a threshold, the flying object 2 transmits a signal to the wireless power feeder 1 indicating that wireless power feeding will be performed. In response, the wireless power feeder 1 may, for example, transmit its current location to the flying object 2. Alternatively, if the current location of the flying object 2 is included in the transmission from the flying object 2, the power supply vehicle 4 carrying the wireless power feeder 1 may move to the current location of the flying object 2. When at least one of the power supply vehicle 4 and the flying object 2 moves and the flying object 2 is positioned above the power transmitting antenna 11 of the wireless power feeder 1, the flying object 2 flies, following the movement of the power supply vehicle 4, so that the distance between the power transmitting antenna 11 and the power receiving antenna 21 becomes a predetermined distance. Then, the control unit 13 of the wireless power feeder 1 controls the power transmitting unit 12 to transmit microwaves in a predetermined beam. In this manner, power can be transmitted from the power transmitting antenna 11 to the power receiving antenna 21. The received power is charged into the battery 22 by the power receiving unit 23, and when the charge reaches a target level, wireless power feeding is terminated. Note that the microwave beam used for power transmission is designed to have the minimum power intensity at the center of the face of the power receiving antenna 21, so that the mission device 25 located at the center is not affected. Furthermore, even if a hole 21a is provided at the center of the face of the power receiving antenna 21 to enable the mission device 25 to perform a predetermined mission, the hole 21a can prevent a decrease in power receiving efficiency. Furthermore, the mission device 25 can continue its mission even while wireless power feeding is being performed.

[0049] As described above, the wireless power feeder 1 according to this embodiment wirelessly feeds power so that the power intensity is minimized at the center of the surface of the power receiving antenna 21. This reduces the effects of radio wave interference on the mission device 25, even if the mission device 25 is located at the center of the surface of the power receiving antenna 21 or if a hole 21a through which the mission device 25 performs its mission is provided at the center of the surface of the power receiving antenna 21. This also enables efficient wireless power feed. Furthermore, microwave irradiation of the mission device 25 can be avoided, thereby reducing the possibility of malfunction of the mission device 25. Furthermore, if the microwave beam used in wireless power feed is a beam with minimum power intensity along the central axis in the power transmission direction, even if the vertical position of the aircraft 2 shifts due to wind or other factors during wireless power feed, the state in which the power intensity is minimum at the center of the surface of the power receiving antenna 21 is maintained, preventing problems such as radio wave interference. Furthermore, by aligning the beam waist of the microwave beam used in wireless power feed at the surface of the power receiving antenna 21, efficient wireless power feed can be achieved. Furthermore, according to the flying object 2 of this embodiment, a hole 21a is provided in the center of the surface of the power receiving antenna 21, so that the mission equipment 25 can perform a predetermined mission during flight through the hole 21a.

[0050] In this embodiment, the case where wireless power is supplied using a pre-designed beam has been mainly described, but this is not necessarily the case. The wireless power supply device 1 may design a beam in real time according to the altitude of the flying object 2, and supply wireless power using the beam according to the altitude of the flying object 2. In this case, as shown in Fig. 9, the wireless power supply device 1 may further include an altitude acquisition unit 14 and a design unit 15.

[0051] The altitude acquisition unit 14 acquires the altitude of the air vehicle 2. For example, the altitude acquisition unit 14 may measure the altitude of the air vehicle 2, or may receive the altitude of the air vehicle 2 from the air vehicle 2 or another device. When measuring the altitude of the air vehicle 2, the altitude acquisition unit 14 may measure the altitude of the air vehicle 2 using, for example, a distance measurement sensor. The distance measurement sensor may be, for example, a sensor that measures distance using laser light, infrared light, ultrasound, microwaves, or the like, or a sensor that measures distance using a stereo camera. Note that this altitude may be any altitude as long as it can determine the distance from the power transmitting antenna 11 to the power receiving antenna 21, i.e., the vertical distance between the two antennas. The altitude acquired by the altitude acquisition unit 14 may be, for example, the altitude from the ground to the power receiving antenna 21 of the air vehicle 2, or the altitude from the power transmitting antenna 11 to the power receiving antenna 21. In the former case, for example, the height from the ground to the power transmitting antenna 11 may be used to calculate the distance between the two antennas from the altitude.

[0052] The design unit 15 uses the altitude of the aircraft 2 acquired by the altitude acquisition unit 14 to design a beam whose beam waist is located at the plane of the power receiving antenna 21. First, the design unit 15 may acquire the distance from the power transmitting antenna 11 to the power receiving antenna 21, for example, using the acquired altitude. When wireless power transfer is performed using a Laguerre-Gaussian beam, the radii of the power transmitting antenna 11 and the power receiving antenna 21 are already determined. Therefore, the design unit 15 may determine a value of the mode index m that is equal to or less than the diameter of the power transmitting antenna 11 using the graph of FIG. 5A. Then, the design unit 15 may use the electric field distribution of the Laguerre-Gaussian beam into which the determined m and other parameters are substituted to calculate the amplitude and phase for each position of the antenna element 11a of the power transmitting antenna 11 and pass the calculated value to the control unit 13. In this way, the design by the design unit 15 may calculate the amplitude and phase for each antenna element 11a. The control unit 13 may control the power transmitting unit 12 so that power is transferred according to the beam designed by the design unit 15. The processing of the control unit 13 is the same as that described above, and a detailed description thereof will be omitted. In this way, by designing a beam in real time according to the altitude of the flying object 2, even if the altitude of the flying object 2 changes, efficient wireless power feeding that adapts to the change can be realized. Note that, for example, when the altitude acquired by the altitude acquisition unit 14 changes beyond a predetermined threshold, the design unit 15 may design a new beam according to the changed altitude.

[0053] Here, the case where efficient wireless power feeding adapted to the altitude of the flying object 2 has been described. However, efficient wireless power feeding adapted to the horizontal position of the flying object 2 may also be performed. In this case, the wireless power feeding device 1 may, for example, acquire the relative positional relationship of the flying object 2 with respect to the power transmitting antenna 11, design a beam with minimum power intensity at the center of the face of the power receiving antenna 21 in that positional relationship, and control the power transmitting unit 12 so that power is transmitted according to the designed beam. In this case, even if the center of the face of the power receiving antenna 21 is not located vertically above the center of the face of the power transmitting antenna 11, wireless power feeding using a beam with minimum power intensity at the center of the face of the power receiving antenna 21 can be achieved. Because the power transmitting antenna 11 is a planar array antenna, such wireless power feeding is also possible.

[0054] Furthermore, in the present embodiment, the case where the control unit 13 controls the power transmitting unit 12 has been mainly described. However, as described above, power transmission by the power transmitting unit 12 may be performed without control by the control unit 13. In this case, the wireless power supply device 1 may not include the control unit 13. When the wireless power supply device 1 does not include the control unit 13, the power transmitting unit 12 may transmit microwaves so that the output of each antenna element 11a of the power transmitting antenna 11 has a predetermined amplitude and phase. For example, the degree of phase shift by the multiple phase shifters 12b and the degree of amplification by the multiple amplifiers 12c included in the power transmitting unit 12 may be fixed. In this case, the phase shifters 12b and the amplifiers 12c may not be able to change the degree of phase shift or amplification, for example.

[0055] Although the present embodiment has been described mainly with reference to the case where the wireless power supply device 1 is located on the ground, the wireless power supply device 1 may be mounted on an aircraft. Then, power may be supplied wirelessly from the power transmitting aircraft to the power receiving aircraft 2.

[0056] Although the present embodiment has been described mainly with reference to a case where the hole 21a is provided at the center of the surface of the power receiving antenna 21 of the aircraft 2, this is not necessarily the case. The surface of the power receiving antenna 21 does not necessarily have to have the hole 21a. In this case, for example, the mission device 25 may be fixed to the center of the surface of the power receiving antenna 21 by, for example, gluing or screwing. In this case, microwaves cannot be received in the area of ​​the surface of the power receiving antenna 21 where the mission device 25 is fixed. However, as described above, by wirelessly feeding power so that the power intensity is minimized at the center of the surface of the power receiving antenna 21, it is possible to achieve power reception that is not affected by the mission device 25 or that reduces the effect of the mission device 25. Furthermore, in this case, for example, an antenna element does not need to be arranged in the area of ​​the surface of the power receiving antenna 21 that corresponds to the air-core region of the microwave beam.

[0057] In the above embodiments, each component may be configured by dedicated hardware, or a component that can be realized by software may be realized by executing a program. For example, each component may be realized by a program execution unit such as a CPU reading and executing a software program recorded on a recording medium such as a hard disk or semiconductor memory. During execution, the program execution unit may execute the program while accessing a memory unit or recording medium.

[0058] Furthermore, the above-described embodiments are merely examples for specifically implementing the present invention, and are not intended to limit the technical scope of the present invention. The technical scope of the present invention is defined by the claims, not by the description of the embodiments, and is intended to include modifications within the literal scope of the claims and within the scope of equivalent meanings. [Explanation of symbols]

[0059] 1. Wireless power supply device 2. Aircraft 11 Power transmission antenna 12 Power Transmission Unit 13 Control Unit 14 Altitude acquisition section 15 Design Department 21 Receiving antenna 22 Battery 23 Power receiving unit 24 Flight means 25 Mission Equipment

Claims

1. A wireless power supply device that wirelessly supplies power to an aircraft in flight, a power transmitting antenna that is a planar array antenna having a plurality of antenna elements arranged in a plane; a power transmitting unit that transmits microwaves from each of the plurality of antenna elements of the power transmitting antenna, The wireless power supply device in which the power transmission unit transmits microwaves by superimposing two fundamental mode Gaussian beams in opposite phases so that the intensity of the power transmitted from the power transmitting antenna is minimized at the center of the plane of the power receiving antenna of the aircraft.

2. The wireless power supply device according to claim 1 , wherein a beam waist of a beam obtained by superposing the Gaussian beams of the two fundamental modes in opposite phases is located at a position of the plane of the power receiving antenna.

3. an altitude acquisition unit that acquires the altitude of the aircraft; a design unit that uses the altitude to design a beam whose beam waist is located at the position of the power receiving antenna plane; The wireless power supply device according to claim 2 , further comprising: a control unit that controls the power transmission unit so that power transmission is performed according to the beam designed by the design unit.

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