Power transmission equipment, power supply system, and power supply method

Abstract

It supplies power to the power receiving device while suppressing interference with other wireless devices. [Solution] The power transmission device of this embodiment includes a receiving unit that receives signals from a power receiving device via a plurality of antennas, a control unit that detects a plurality of incoming directions of the signal by estimating the direction of arrival based on the received signal and selects one of the plurality of incoming directions, and a transmitting unit that performs transmission beamforming of a power signal having directionality in the selected one incoming direction.

Description

Technical Field

[0001] This embodiment relates to a power transmission device, a power supply system, and a power supply method.

Background Art

[0002] There is a microwave power supply system that performs remote power supply to a power receiving device using microwaves. As a method for enabling appropriate transmission of microwaves (control of beam directivity) even when the position of the power receiving device can change, a retro-directive method is known. In this method, a weak beacon signal transmitted from the power receiving device is received by a plurality of antennas of a power supply device (hereinafter referred to as a power transmission device), and power is supplied from the power transmission device to the power receiving device using the conjugate signals of the phases and amplitudes of the received signals of each antenna. By using this technique, it becomes possible to perform beamforming that can share the maximum power with the power receiving device.

[0003] However, when there is a signal path of a reflected wave in addition to the direct wave signal path between the power transmission device and the power receiving device, propagation path estimation is performed using propagation path information including a plurality of signal paths. Therefore, when performing beamforming, radiation of microwaves in a direction other than the direction (expected angle) looking from the power transmission device to the power receiving device also occurs. Therefore, when there is a wireless device using a nearby frequency band in a direction other than the expected angle, radio wave interference occurs with respect to the wireless device. Also, when the expected angle from the power transmission device to the power receiving device is parallel to or nearly parallel to the ground surface, a beam is generated in a direction parallel to or close to the ground surface, that is, a direction along the ground surface. Therefore, a problem may occur in that a high-power signal reaches a remote wireless device and radio wave interference occurs with the remote wireless device.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

[0005] This embodiment provides a power transmission device, a power supply system, and a power supply method that enable power supply to a power receiving device while suppressing radio interference to other wireless devices. [Means for solving the problem]

[0006] The power transmission device of this embodiment includes a receiving unit that receives signals from a power receiving device via a plurality of antennas, a control unit that detects a plurality of incoming directions of the signal by estimating the direction of arrival based on the received signal and selects one of the plurality of incoming directions, and a transmitting unit that performs transmission beamforming of a power signal having directionality in the selected one incoming direction. [Brief explanation of the drawing]

[0007] [Figure 1] A block diagram showing an example of a power supply system according to the first embodiment. [Figure 2] A diagram illustrating the operation of the control unit in the power transmission device of the first embodiment. [Figure 3] Diagram illustrating a comparative example of the first embodiment. [Figure 4] A block diagram showing an example of a power supply system according to the second embodiment. [Figure 5] A diagram illustrating the operation of the control unit in the power transmission device of the second embodiment. [Figure 6] Diagram illustrating a comparative example of the second embodiment. [Figure 7] A block diagram showing an example of a power supply system according to the third embodiment. [Figure 8] A flowchart illustrating an example of operation in the third embodiment. [Figure 9] A block diagram showing an example of a power supply system according to the fourth embodiment. [Figure 10] A diagram illustrating the operation of the control unit in the power transmission device of the fourth embodiment. [Figure 11] An explanatory diagram of a comparative example of the fourth embodiment. [Figure 12] A block diagram showing an example of a power supply system according to the fifth embodiment. [Figure 13] A block diagram showing an example of a power supply system according to the sixth embodiment. [Modes for carrying out the invention]

[0008] This embodiment will be described in detail below with reference to the drawings.

[0009] Figure 1 is a block diagram showing an example of a power supply system according to this embodiment. The power supply system in Figure 1 comprises a power transmission device (power supply device) 100 and a power receiving device 200. Wireless power transmission (wireless power supply) is performed from the power transmission device 100 to the power receiving device 200 using electromagnetic waves such as microwaves. In the example in Figure 1, the wireless power supply system comprises only one power receiving device 200, but it may comprise multiple power receiving devices 200.

[0010] The power receiving device 200 can be any device that receives power from the power transmitting device 100 and operates based on the supplied power. For example, the power receiving device 200 can be used in sensor devices attached to robot arms, mobile objects such as vehicles, cameras for fixed-point observation, sensors for monitoring factory processes, picking devices for goods in logistics centers, lock mechanism control devices for doors with automatic locks, smartphones, and the like.

[0011] [Power receiving device 200] The power receiving device 200 includes one or more power receiving antennas 201, an RF-DC converter 202 (rectifier or rectifier and battery charging circuit, etc.), a beacon signal generator 203 (power receiving side transmitter), a transmit / receive switch 204, a battery 205, a control unit 206, a communication unit 207, and a load device 208. The load device 200 may be provided outside the receiving device 200. The RF-DC converter 202, the beacon signal generator 203, the transmit / receive switch 204, the control unit 206, and the communication unit 207 are implemented by at least one of an analog circuit that performs analog signal processing and a digital circuit that performs digital signal processing. The digital circuit may be a CPU (Central Processing Unit), a DSP (Digital Signal Processor), a general-purpose processor, a microprocessor, an ASIC (Application Specific Integrated Circuit), an FPGA (Field Programmable Gate Array), or a combination thereof.

[0012] The transmit / receive switch 204 switches the connection destination of the antenna 201 between the RF-DC converter 202 and the beacon signal generator 203. When receiving, the antenna 201 is connected to the RF-DC converter 202, and when transmitting, it is connected to the beacon signal generator 203.

[0013] The beacon signal generator 203 generates a beacon signal 220 of a predetermined frequency using an oscillator. The beacon signal generator 203 transmits the beacon signal 220 to the power transmission device 100 via the antenna 201 in a state where the transmission / reception switch 204 is switched to the beacon signal generator 203 side. The beacon signal generator 203 functions as a transmission unit that transmits the beacon signal 220. The beacon signal 220 is a signal including a predetermined pattern and is used for estimating the propagation path between the power transmission device 100 and the power reception device 200 on the power transmission device 100 side. Compared with the power signal (power supply signal) transmitted from the power transmission device 100 for power supply, the beacon signal 220 may be a signal with weak power. The signal including the predetermined pattern may be an unmodulated signal or a signal not including data, for example, a sine wave signal. The transmission power of the beacon signal 220 is known to the power transmission device 100 and is, for example, predetermined. The frequency of the beacon signal 220 may be the same as or about the same as the frequency of the power signal transmitted from the power transmission device 100. "About the same" includes cases where there is an error of about 10%. In the present embodiment, transmission of the beacon signal 220 and reception of the power supply signal are switched by switching the antenna 201, but an antenna for transmitting the beacon signal 220 and an antenna for receiving the power supply signal may be prepared separately, and the beacon signal may be transmitted without switching the antenna.

[0014] The RF-DC converter 202 is a rectifier that converts AC power into DC power. The RF-DC converter 202 receives an AC power signal (power supply signal) 120 received by the antenna 201 from the power transmission device 100 in a state where the transmission / reception switch 204 is switched to the RF-DC converter 202 side. The RF-DC converter 202 converts the received AC power signal into DC and outputs DC power. The power supply signal 120 is a signal such as a microwave.

[0015] The storage battery 205 stores power based on the DC power output from the RF-DC converter 202. The stored power can be used as the operating power of each of the communication unit 207, the control unit 206, the load device 208, the RF-DC converter 202, the beacon signal generator 203, and the transmission / reception switch 204.

[0016] The communication unit 207 communicates information with the communication unit 110 of the power transmission device 100. For example, the communication unit 207 transmits information regarding the transmission power of the beacon signal (beacon power information) to the power transmission device 100 according to an instruction from the control unit 206. The transmission power is, for example, antenna power or equivalent isotropically radiated power (EIRP). Information such as the remaining battery level of the battery 205 may also be transmitted.

[0017] The wireless standard of the communication method used by the communication unit 207 may be arbitrary. For example, there are Bluetooth Low Energy (BLE), wireless LAN (Local Area Network), communication standards in the 920 MHz band, etc. The communication unit 207 includes a communication antenna separate from the antenna 201 and communicates using the communication antenna. However, a configuration in which the communication unit 207 communicates using the antenna 201 is not excluded.

[0018] The control unit 206 controls the entire power reception device 200 and controls, for example, at least one or all of the beacon signal generator 203, the RF-DC converter 202, the transmission / reception switch 204, and the communication unit 207. The control unit 206 may control to transmit a beacon signal to the power transmission device 100 in response to the reception of a beacon signal transmission request from the power transmission device 100 by the communication unit 207.

[0019] The beacon signal 220 includes a signal component of the direct wave 220A directly received from the power reception device 200 to the power transmission device 100 and a signal component of the reflected wave 220B reflected by the reflector 300 and received by the power transmission device 100. The path through which the direct wave 220A of the beacon signal is received is called the direct wave propagation path. The path through which the reflected wave 220B of the beacon signal is received is called the reflected wave propagation path. Thus, the beacon signal 220 is transmitted to the power transmission device 100 through a plurality of paths (arrival paths). However, the reflected wave propagation path is not limited to one, and two or more reflected wave propagation paths may exist.

[0020] [Power Transmission Device 100] The power transmission device 100 includes multiple antennas 102, a transmit / receive switch 103, a receiving unit 104, a transmitting unit 105 (power transmission side transmitting unit), a control unit 107, a weight setting unit 108, a high-frequency unit 109, and a communication unit 110. The transmit / receive switch 103, the receiving unit 104, the transmitting unit 105, the control unit 107, the weight setting unit 108, the high-frequency unit 109, and the communication unit 110 are implemented by at least one of an analog circuit that performs analog signal processing and a digital circuit that performs digital signal processing. The digital circuit may be a CPU, DSP, general-purpose processor, microprocessor, ASIC, FPGA, or a combination thereof.

[0021] The power transmission device 100 operates based on commercial power supplied from an external source or power supplied from an external energy storage device. However, the power transmission device 100 may also be equipped with an internal battery and operate based on the power stored in the battery.

[0022] The transmit / receive switch 103 switches the connection destination of the multiple antennas 102 between the receiving unit 104 and the transmitting unit 105. When receiving, the multiple antennas 102 are connected to the receiving unit 104, and when transmitting, they are connected to the transmitting unit 105.

[0023] The high-frequency unit 109 (signal generator) includes a local oscillator that generates a local signal, and uses the local oscillator to generate a high-frequency signal (power signal) for supplying power to the power receiving device 200. The local signal is, for example, a high-frequency analog signal. The high-frequency unit 109 sends the local signal generated by the local oscillator as a power signal (power supply signal) 120 to the transmission unit 105. The high-frequency unit 109 may also send a signal amplified by an amplifier as the power supply signal 120 to the transmission unit 105. The high-frequency unit 109 may frequency-convert the local signal before or after amplification, and may further bandwidth-control the frequency-converted signal using a filter.

[0024] The communication unit 110 communicates information with the communication unit 207 of the power receiving device 200. For example, the communication unit 110 receives information from the power receiving device 200 regarding the transmission power of the beacon signal. The communication unit 110 may also receive information from the power receiving device 200 regarding the optimal received power for wireless power supply. In this case, the control unit 107 may control the generation of the power supply signal 120 so that the power receiving device 200 receives power at the optimal received power. The communication unit 110 may also send a request to the power receiving device 200 to transmit a beacon signal. The wireless standard used by the communication unit 207 can be any standard.

[0025] The receiving unit 104 receives beacon signals from the power receiving device 200 via multiple antennas 102 and performs AD conversion of the received beacon signals using an ADC. The receiving unit 104 may perform amplification and bandwidth adjustment of the received signals before or after AD conversion.

[0026] The control unit 107 controls the entire power transmission device 100, and controls, for example, at least one or all of the following: the transmit / receive switch 103, the receiving unit 104, the transmitting unit 105, the weight setting unit 108, the high-frequency unit 109, and the communication unit 110.

[0027] The control unit 107 detects the phase and amplitude of the signal for each antenna 102, or detects the phase difference and amplitude difference from predetermined values ​​related to phase and amplitude, and performs propagation path estimation between each antenna 102 and the power receiving device 200, thereby acquiring propagation path information that shows the estimation result of the propagation path.

[0028] The control unit 107 estimates the direction of arrival of the beacon signal 220 for each antenna 102 based on the propagation path information. The direction of arrival estimation involves estimating the direction of arrival of the beacon signal 220, and the MUSIC method or any other arbitrary estimation method can be used.

[0029] The left panel of Figure 2 shows a graph illustrating the results of the direction of arrival estimation. The horizontal axis represents the angle of arrival, and the vertical axis represents the signal strength of the received signal (hereinafter also simply referred to as strength). In other words, it shows the distribution of signal strength for multiple angles included in the angle range to be estimated. Peaks A1 and A2 are shown in the directions of the angles of arrival θ1 and θ2. The direction of the angle of arrival with a peak corresponds to the direction of arrival. The angle of arrival θ1 corresponds to the direction in which the direct wave 220A of the beacon signal was directly received (direction of the direct wave propagation path). In other words, the angle of arrival θ1 corresponds to the angle direction from the power transmission device 100 looking towards the power receiving device 200. The angle of arrival θ2 corresponds to the direction in which the reflected wave 220B of the beacon signal was received (direction of the reflected wave propagation path). In other words, the angle of arrival θ2 corresponds to the angle direction from the power transmission device 100 looking towards the radio wave reflection position of the beacon signal on the reflector 300. Thus, the results of the direction of arrival estimation include peaks not only for the angle of arrival at which the direct wave is received via the direct wave propagation path, but also for the angle of arrival at which the reflected wave is received via the reflected wave propagation path.

[0030] Based on the arrival direction estimation results, the control unit 107 selects one arrival angle direction corresponding to the direction of arrival of the direct wave. It does not select an arrival angle direction corresponding to the direction of the reflected wave. More specifically, the control unit 107 determines that the arrival angle direction of the peak with the highest intensity in the arrival direction estimation results is the direction of arrival from which the direct wave was received, and selects that direction. The arrival angle directions of the second and subsequent peaks with high intensity are determined to be the directions of arrival from which the reflected wave was received, and are not selected. In the example in the left diagram of Figure 2, the direction of arrival angle θ1 is selected because the intensity at arrival angle θ1 is the highest, and the direction of arrival angle θ2, which has the second highest intensity, is not selected.

[0031] The center diagram in Figure 2 shows an example of the operation of the control unit 107 that selects the angle of arrival θ1. The control unit 107 sets a value of "1" for the angle of arrival θ1, which means that the beam will form a directivity.

[0032] The control unit 107 performs weight calculations to determine the weight for each antenna 102, so as to form directivity (maximum peak) in the direction of the arrival angle for which a value of "1" is set. For weight calculations, a general three-dimensional beamforming method with a peak in a specific direction (solid angle) can be used as an example. This determines the weight for transmit beamforming to form a beam that has directivity in the direction of arrival angle θ1 (has a maximum peak with radiated power above a threshold) and no directivity in the direction of arrival angle θ2. Alternatively, weights may be generated to form a null in the direction of θ2. The control unit 107 sends the weight determined for each antenna 102 to the weight setting unit 108. For example, a beam with directivity in the direction of θ1 has an intensity in the direction of θ1 that is 1.5 times or more than the intensity in other directions. For example, a beam with directivity in the direction of θ1 is fed mainly using the propagation path corresponding to θ1.

[0033] The weight setting unit 108 sets the weight for each antenna 102, received from the control unit 107, to the transmission unit 105. For each antenna 102, adjustment values ​​for phase and amplitude are set as the weight. However, a configuration that adjusts only one of the amplitude or phase is also possible.

[0034] The control unit 107 controls the high-frequency unit 109 to generate a high-frequency signal for power supply. The high-frequency unit 109 generates a high-frequency signal according to the instructions of the control unit 107 and supplies the generated high-frequency signal to the transmission unit 105. The power of the high-frequency signal (transmission power) may be predetermined. Alternatively, the control unit 107 may obtain information on the optimal received power from the power receiving device 200 via the communication unit 110 and cause the high-frequency unit 109 to generate a high-frequency signal with the transmission power corresponding to that information.

[0035] The transmitting unit 105 generates a signal to be transmitted for each antenna 102 by adjusting the phase and amplitude of the high-frequency signal supplied from the high-frequency unit 109 based on the weight of each antenna 102. The transmitting unit 105 then performs DA conversion on the generated signals using a DAC and an orthogonal frequency converter, respectively, and transmits them from the antennas 102. This enables transmission beamforming of a power signal (feed signal) that has directivity in the direction of the arrival angle of the direct wave but not in the direction of the arrival angle of the reflected wave. The transmitting unit 105 may also perform bandwidth adjustment and amplification on the DA-converted signal before transmitting the transmission signal. In this example, the phase and amplitude were adjusted in the digital domain before DA conversion, but the phase and amplitude may also be adjusted using an RF phase shifter and a variable gain amplifier or variable attenuator, or using an RF-DAC.

[0036] The right-hand figure in Figure 2 shows the radiation pattern of the beam transmitted from the transmitter 105. It has a peak P1 in the direction of arrival angle (radiation angle) θ1, and no peak in the direction of arrival angle (radiation angle) θ2. The radiation intensity at arrival angle θ1 is above the threshold, while the signal intensity at arrival angle θ2 and other angles is below the threshold. As a result, the beam has a single large peak in the direction of the receiving device 200.

[0037] Figure 3 shows an example of a beam radiation pattern when the value "1" is set for the arrival angles θ1 and θ2, respectively, to provide directivity in both the arrival angle (radiation angle) θ1 and θ2, as a comparative example. There are peaks P3 and P4 in both directions of the arrival angles (radiation angles) θ1 and θ2, and both have an intensity above the threshold. A beam is transmitted with directivity not only in the direction of the arrival angle θ1 of the direct wave but also in the direction of the arrival angle θ2 of the reflected wave. For this reason, if other wireless devices are present in the propagation path of the reflected wave, for example, radio interference with other wireless devices may occur. In contrast, in this embodiment, as shown in Figure 2, directivity is not formed in the direction of the arrival angle (radiation angle) θ2, so even if other wireless devices in the nearby frequency band are present in or near the propagation path of the reflected wave, for example, the effects of interference on other wireless devices can be avoided or suppressed.

[0038] As described above, according to this embodiment, the direction of arrival is estimated based on the beacon signal received from the power receiving device 200, and the direction in which the direct wave of the beacon signal was received (angle of arrival) is detected. Then, a beam that has directionality in the direction of the detected angle of arrival and does not have directionality in the directions of other angles of arrival is transmitted. This makes it possible to efficiently supply power while suppressing radio interference to other wireless devices.

[0039] (Second embodiment) Figure 4 is a block diagram showing an example of a power supply system according to this embodiment. Elements with the same names as in Figure 1 are denoted by the same reference numerals, and descriptions are omitted as appropriate, except for extended or modified processes. The following description will focus on the differences from the first embodiment.

[0040] The power transmission device 100 is installed on the ceiling 313 of the facility 311, which is built on the ground 310. The power receiving device 200 is installed on the floor 312 of the facility 311. Other wireless equipment 400 is installed on the ground 310 at a location far away from the facility. Note that the other wireless equipment 400 may be installed within facility 311 or in a facility separate from facility 311.

[0041] The power receiving device 200 transmits a beacon signal, similar to the first embodiment. The transmitted beacon signal is received by the power transmitting device 100 as a direct wave via the direct wave propagation path 230A, and also received by the power transmitting device 100 as a reflected wave reflected by the wall 314 inside the facility 311 via the reflected wave propagation path 230B.

[0042] The control unit 107 of the power transmission device 100 acquires propagation path information by estimating the propagation path based on the beacon signal received from the power receiving device 200, and further estimates the direction of arrival based on the propagation path information. Based on the results of the direction of arrival estimation, it detects all angles with peaks (arrival angles).

[0043] The left panel of Figure 5 is a graph showing the results of the arrival direction estimation. The horizontal axis represents the arrival angle, and the vertical axis represents the received signal intensity. Peaks A11 and A12 are present in the directions of arrival angles θ11 and θ12. Arrival angle θ11 corresponds to the direction in which the direct wave of the beacon signal was received, i.e., the direction of the direct wave propagation path 230A. Arrival angle θ12 corresponds to the direction in which the beacon signal was received after being reflected by wall 314, i.e., the direction of the reflected wave propagation path 230B.

[0044] The control unit 107 of the power transmission device 100 determines whether the direction of arrival of each detected peak is below a threshold with respect to the horizontal direction as viewed from the power transmission device 100. More specifically, it determines whether the angle is below a threshold with respect to the direction horizontal (parallel) to the ground or the installation surface of the power transmission device 100. The threshold is not limited to a specific value, but may be, for example, 5 degrees, 7 degrees, or 10 degrees. The threshold may also be determined in a direction where there is little or no possibility of a power receiving device 200 being present. The control unit 107 selects peaks (directions of arrival) greater than the threshold and does not select peaks (directions of arrival) below the threshold. Alternatively, it may select the direction of arrival that is furthest from the horizontal or parallel to the ground surface of the power transmission device 100, and not select any other directions of arrival. Or, it may select the direction of arrival with the greatest signal strength among the directions of arrival greater than the threshold, and not select any other directions of arrival.

[0045] In the example shown in the left diagram of Figure 5, the arrival angle θ12 is smaller than the threshold θr, and the arrival angle θ11 is larger than the threshold θr. Therefore, the control unit 107 selects the direction of the arrival angle θ11 and does not select the direction of the arrival angle θ12. The control unit 107 determines the direction of the arrival angle θ11 as the direction that forms the directivity of the transmitted beam.

[0046] The control unit 107 calculates a weight for each antenna 102 that is directional in the direction of the arrival angle θ11 and not directional in the direction of the arrival angle θ12. The weight setting unit 108 sets the calculated weight to the transmitting unit 105. Based on the set weight, the transmitting unit 105 transmits a beam that is directional in the direction of the arrival angle θ11 and not directional in other angles, including the arrival angle θ12. As a result, radiation of radio waves in a direction horizontal to or close to the plane of the ground 310 is suppressed, and thus radio interference to other wireless devices 400 located far outside the facility 311 can be suppressed.

[0047] The right-hand figure in Figure 5 shows the radiation pattern of the beam transmitted from the transmitting unit 105 of the power transmission device 100. It has a peak P11 in the direction of the angle of arrival (radiation angle) θ11, and no peak in the direction of the angle of arrival (radiation angle) θ12. The intensity of the radiated power in the direction of the angle of arrival (radiation angle) θ11 is above the threshold, and the intensity of the radiated power in the directions of other angles, including the angle of arrival (radiation angle) θ12, is below the threshold. As a result, a beam with a single large peak is transmitted to the power receiving device 200.

[0048] If a beam with a peak radiated power above a threshold is transmitted in the direction of the arrival angle θ12, the power signal component that is not reflected by the wall 314 may reach other wireless devices 400, potentially causing radio interference.

[0049] Figure 6 shows an example of transmitting a beam 121 (121A, 121B) that also has directivity in the direction of the arrival angle θ12, as a comparative example. Beam 121 includes a beam component 121A in the direction of the arrival angle θ11 and a beam component 121B in the direction of the arrival angle θ12. The component of the beam component 121B in the direction of the arrival angle θ12 that is not reflected by the wall 314 can reach other wireless devices 400. Since the power signal has significantly more power than a weak beacon signal, radio interference that is not a problem in the case of a weak beacon signal can occur. In this embodiment, as shown in the right figure of Figure 5, the directivity in the direction of the arrival angle θ12 is suppressed, so such interference can be avoided or reduced.

[0050] As described above, according to this embodiment, transmission beamforming is performed in which the radiated power from the power transmission device 100 in a direction horizontal to or close to horizontal (along the ground or installation surface) of the power transmission device 100 is suppressed. As a result, radiation to other wireless devices 400 located at a distance is suppressed, and radio interference can be avoided or reduced.

[0051] (Third embodiment) Figure 7 is a block diagram showing an example of a power supply system according to this embodiment. Elements with the same names as in Figure 4 are denoted by the same reference numerals, and descriptions are omitted as appropriate, except for extended or modified processes. The following description will focus on the differences from the second embodiment.

[0052] Unlike the block diagram in Figure 4, one or more wireless LAN (Local Area Network) devices 500 are installed within facility 311. No other wireless devices 400 are installed outside facility 311.

[0053] The wireless LAN device 500 is located on or near the reflected wave propagation path 230B of the beacon signal.

[0054] Similar to the second embodiment, the beacon signal transmitted from the power receiving device 200 is received by the power transmitting device 100 as a direct wave via the direct wave propagation path 230A, and also as a reflected wave reflected by the walls 314 within the facility via the reflected wave propagation path 230B.

[0055] The control unit 107 of the power transmission device 100 acquires propagation path information by estimating the propagation path based on the beacon signal received from the power receiving device 200, and further estimates the direction of arrival based on the propagation path information. The result of the direction of arrival estimation will be as shown in the left figure of Figure 5 described above, for example, similar to the second embodiment.

[0056] The control unit 107 of the power transmission device 100 detects the direction of all arrival angles with peaks (arrival directions) in the arrival direction estimation result. For each detected arrival direction, the control unit 107 calculates a weight to form a beam that is directional only to that arrival direction, that is, a weight that makes the reception sensitivity for that arrival direction higher than for other arrival directions. Using the calculated weight, the control unit 107 performs carrier sensing for frequencies used by the wireless LAN. Based on the carrier sensing result, it selects arrival directions where no carrier was detected (no wireless LAN usage was detected). The weight setting unit 108 sets the weight calculated for the selected arrival direction to the transmission unit 105. The transmission unit 105 transmits a power signal by beamforming based on the set weight. As a result, a beam that is directional in the direction of the selected arrival angle and not directional to other arrival directions is transmitted.

[0057] If there are multiple arrival directions in the carrier sensing results in which no carriers were detected, the arrival direction of the peak with the highest intensity among them may be selected, or the arrival direction having the angle furthest from the horizontal angle to the ground or the installation surface of the power transmission device 100 may be selected.

[0058] By performing beamforming with directionality in the direction of arrival where no carrier was detected in the carrier sense results, it is possible to reduce radio interference to wireless LAN equipment 500 located on or near the path of the beacon signal. Alternatively, the power transmission device 100 may perform carrier sense before transmission using a weight that has directionality only in the direction of arrival angle where no carrier was detected in the carrier sense results. This reduces the possibility of detection of radio wave usage by wireless LAN and also reduces the chance of power transmission loss, even when using a method in which the power transmission device 100 performs carrier sense before transmission and transmits power only if no carrier is detected.

[0059] Figure 8 is a flowchart illustrating an example of the operation of the power transmission device 100 in this embodiment. It assumes a case where, based on the estimation of the direction of arrival of the beacon signal, it is detected that there are multiple arriving waves (peaks) of the beacon signal. From the multiple arrival angles with peaks, the direction of a first arrival angle is selected, and weights are generated to form a beam that is directional only in the direction of the first arrival angle (i.e., has radiated power above a threshold), and carrier sensing is performed based on these weights (S01). If no carriers are detected as a result of carrier sensing (if frequency usage by other wireless systems such as Wi-Fi is not detected), power supply is started with weights for a beam directional in the direction of the first arrival angle (S03). If carriers are detected as a result of carrier sensing (if frequency usage by other wireless systems such as Wi-Fi is detected), the direction of a second arrival angle is selected. Then, weights are generated to form a beam that is directional only in the direction of the second arrival angle, and carrier sensing is performed based on these weights (S04). If no carrier is detected as a result of carrier sensing, power is started with a beam weight that has directionality in the direction of the second arrival angle (S06). If a carrier is detected as a result of carrier sensing, the process returns to step S01, which processes the direction of the first arrival angle again. If a third arrival angle exists, the same process may be performed for the direction of the third arrival angle. In this way, the selection of the arrival direction is repeated sequentially until an arrival angle in which no carrier is detected is found. Furthermore, if there are other receiving devices besides the receiving device 200 that the transmitting device 100 can transmit power to, the power transmission target may be switched from the receiving device 200 to another receiving device. According to the operation of this flowchart, in a situation in which multiple power transmission paths (propagation paths) exist, it is possible to select a power transmission path in order to avoid or reduce interference with other wireless devices.

[0060] (Fourth embodiment) Figure 9 is a block diagram showing an example of a power supply system according to this embodiment. Elements with the same names as in Figure 4 are denoted by the same reference numerals, and descriptions are omitted as appropriate, except for extended or modified processes. The following description will focus on the differences from the second embodiment.

[0061] The difference from the block diagram in Figure 4 is that the power receiving device 200 is supported by a support base 350 at a position higher than the floor 312 within the facility 311, rather than on the floor 312.

[0062] The beacon signal transmitted from the power receiving device 200 is received by the power transmitting device 100 as a direct wave via the direct wave propagation path 240A, and also received by the power transmitting device 100 as a reflected wave reflected off the floor 312 within the facility via the reflected wave propagation path 240B.

[0063] The control unit 107 of the power transmission device 100 acquires propagation path information by estimating the propagation path based on the beacon signal received from the power receiving device 200, and further uses the propagation path information to estimate the direction of arrival. Based on the results of the direction of arrival estimation, it detects the direction (direction of arrival) of all arrival angles that have a peak.

[0064] The left panel of Figure 10 is a graph showing the results of the arrival direction estimation. The horizontal axis represents the arrival angle, and the vertical axis represents the received signal intensity. Peaks A21 and A22 are present in the directions of arrival angles θ21 and θ22. Arrival angle θ21 corresponds to the direction in which the direct wave of the beacon signal was received (direction of direct wave propagation path 240A). Arrival angle θ22 corresponds to the direction in which the reflected wave of the beacon signal was received (direction of reflected wave propagation path 240B).

[0065] The control unit 107 of the power transmission device 100 determines whether the direction of the arrival angle (arrival direction) of each detected peak is less than or equal to a threshold value with respect to the angle in the direction horizontal to the ground or the installation surface of the power transmission device 100 as viewed from the power transmission device 100. The threshold value may be determined in the same manner as in the second embodiment. The control unit 107 selects the arrival direction of peaks greater than the threshold value and does not select the arrival direction of peaks less than or equal to the threshold value.

[0066] In the example shown in the left diagram of Figure 10, the direction of the arrival angle θ22 of the reflected wave is greater than the threshold θr, while the direction of the arrival angle θ21 of the direct wave is less than the threshold θr. Therefore, the control unit 107 selects the direction of the arrival angle θ22 of the reflected wave and does not select the direction of the arrival angle θ21 of the direct wave. The control unit 107 sets the direction of the arrival angle θ22 (the direction of the reflected wave propagation path 240B) as the direction of the directivity of the transmitted beam.

[0067] The control unit 107 calculates a weight for each antenna 102 for a beam that is directional in the direction of the arrival angle θ22 and does not have directionality in other directions, including the arrival angle θ21. The weight setting unit 108 sets the calculated weight to the transmitting unit 105. Based on the set weight, the transmitting unit 105 transmits the feed signal using a beam that is directional in the direction of the arrival angle θ22 and does not have directionality in other directions. Since the feed signal is transmitted along the reflected wave propagation path 240B, the feed efficiency to the power receiving device 200 is reduced, but the radiation of radio waves in directions along the ground is suppressed, thus suppressing radio wave interference to other wireless equipment 400 outside the facility 311.

[0068] The right-hand diagram of Figure 10 shows the radiation pattern of the beam transmitted from the transmitting unit 105 of the power transmission device 100. It has a peak P22 in the direction of the arrival angle (radiation angle) θ22, and no peak in the direction of the arrival angle (radiation angle) θ21. As a result, a beam with a single large peak is transmitted to the power receiving device 200, even though it passes through the reflected wave propagation path 240B. Directivity in the direction of the direct wave propagation path 240A is suppressed, making it possible to suppress the effects of interference on other wireless devices 400.

[0069] As a comparative example, consider the case where a beam is transmitted that has directionality not only in the direction of arrival angle θ22 but also in the direction of arrival angle θ21. In this case, the power signal component of the transmitted beam that is not reflected by the wall 314 may reach other wireless devices 400 and cause radio interference to those devices 400.

[0070] Figure 11 shows an example, as a comparative example, of transmitting a beam 131 (131A, 131B) that has directivity in the direction of arrival angle θ21 in addition to the direction of arrival angle θ22. Beam 131 includes a direct wave 131A with directivity in the direction of arrival angle θ21 and a reflected wave 131B with directivity in the direction of arrival angle θ22. The signal component of the direct wave 131A that is not reflected by the wall 314 also reaches other wireless devices 400. Since the power signal has significantly more power than the beacon signal, radio interference that is not a problem with weak beacon signals can occur. In this embodiment, as shown in Figure 10, directivity in the direction of arrival angle θ21 is not formed, so such radio interference can be avoided or reduced.

[0071] As described above, according to this embodiment, by transmitting a beam from the power transmission device 100 with suppressed directivity in the direction along the ground, radiation to other wireless devices 400 located at a distance is suppressed, and radio wave interference can be avoided or reduced. In other words, when the direction of the direct wave propagation path corresponds to the direction of the ground, a beam with directivity in the direction of the reflected wave propagation path is transmitted while suppressing directivity in this direction. As a result, although the power transmission efficiency may decrease, it becomes possible to avoid or reduce radio wave interference to other wireless devices.

[0072] (Fifth embodiment) Figure 12 is a block diagram illustrating an example of a power supply system according to this embodiment. Elements with the same names as those in Figure 1 are denoted by the same reference numerals, and explanations are omitted as appropriate, except for extended or modified processes. The following explanation will focus on the differences from the first embodiment. In this embodiment, it is assumed that the power receiving device 200 is located in the vicinity of the power transmitting device 100, and that the distances between each antenna 102 of the power transmitting device 100 and the power receiving device 200 are different. Figure 12 shows the direct wave propagation path 250 between each antenna 102 of the power transmitting device 100 and the antenna 201 of the power receiving device 200. In this example, it is assumed that there are four antennas 102, but the number of antennas 102 may be two, three, or five or more. In addition to the direct wave propagation path 250, a reflected wave propagation path may also exist, but it is not shown.

[0073] The control unit 107 of the power transmission device 100 estimates the propagation path and the angle of arrival based on the beacon signal received from the power receiving device 200, and calculates the angle of arrival corresponding to the direct wave propagation path. This allows it to calculate the azimuth θ and elevation angle φ relative to the power receiving device 200. It also calculates the distance r between the power transmission device 100 and the power receiving device 200 from the received strength of the beacon signal. This gives the position (coordinate values) of the power receiving device 200 relative to the power transmission device 100 as (r, θ, φ).

[0074] The control unit 107 of the power transmission device 100 calculates the distance between each antenna 102 and the power receiving device 200 based on the coordinate values ​​of each antenna 102 and the coordinate values ​​(r, θ, φ) of the power receiving device 200. More specifically, it calculates the distance between each antenna 102 and the antenna 201 of the power receiving device 200. Based on these distances, the control unit 107 determines the weight for each antenna 102 so that the phase of the signal transmitted from each antenna 102 of the power transmission device 100 matches when it is received by the antenna 201 of the power receiving device 200. Matching includes cases where there is an error of about 5% or 10%. In addition, as in the first embodiment, when the beacon signal is received via both the direct wave propagation path and the reflected wave propagation path, the weight for each antenna 102 is calculated so that a beam without directivity (peak) is formed in the direction of the reflected wave propagation path.

[0075] The weight setting unit 108 sets the weight calculated for each antenna 102 to the transmitting unit 105. Based on the weight set for each antenna 102, the transmitting unit 105 adjusts the phase and amplitude of the signal to be transmitted for each antenna 102 and transmits it. This transmits a feed signal beam that is directional in the direction of the power receiving device 200 and not directional in the direction of the reflected wave propagation path.

[0076] Thus, in this embodiment, by reflecting the difference in distance between each antenna 102 and the power receiving device 200 in the weight of each antenna 102, power can be transmitted to the power receiving device 200 more efficiently than the general three-dimensional beamforming method for the specific direction (solid angle) described above. General three-dimensional beamforming methods perform weight calculations assuming that the distance between each antenna 102 and the power receiving device 200 is the same, and are therefore effective for far-field feeding where the distance between each antenna and the power receiving device can be considered the same. However, when applied to the near-field, the difference in distance is not reflected, and the power transmission efficiency may decrease. Therefore, by reflecting the difference in distance between each antenna 102 and the power receiving device 200 in the weight calculation as in this embodiment, it becomes possible to transmit a large amount of power to the power receiving device 200.

[0077] (Sixth Embodiment) This embodiment is a configuration in which the power receiving device 200 is movable relative to the power transmitting device 100, that is, the power receiving device 200 is mounted on a mobile body, as in the first to fifth embodiments.

[0078] Figure 13 is a block diagram showing an example of a power supply system according to this embodiment. Elements with the same names as in Figure 1 are denoted by the same reference numerals, and descriptions are omitted as appropriate, except for extended or modified processes.

[0079] The power receiving device 200 is a mobile body that can move on the floor 312 within the facility in the direction indicated by the arrow in the figure. The mobile body is equipped with wheels 260 for movement. The power receiving device 200 may move along a fixed route at a fixed speed, for example. For example, the power receiving device 200 is a vehicle that repeatedly moves within a fixed range on rails.

[0080] The control unit 107 of the power transmission device 100 has a function to predict the position of the power receiving device 200 at any future time or timing. The prediction method may be machine learning (ML) such as generating a position prediction model, artificial intelligence (AI) such as a neural network, or statistical methods, or other methods may be used.

[0081] A camera may be mounted on the power transmission device 100, and the image data of the power receiving device 200 captured by the camera may be used for prediction. Information necessary for prediction may be obtained by communicating with the power receiving device 200. If a movement plan including the movement path and time of the moving object has been determined as information necessary for prediction, schedule information of the movement including said movement plan may be obtained. Alternatively, information such as the battery level value (battery level information) or the value of the power meter (meter information) of the moving object or the power receiving device 200 may be obtained. If the speed of the moving object changes according to the battery level, the speed of the moving object may be estimated from the battery level information or meter information, and the position of the moving object at a future time may be estimated from the estimated speed.

[0082] The control unit 107 of the power transmission device 100 considers the movement of the moving object during processing time such as direction of arrival estimation and weight calculation, predicts the position of the moving object at the time or timing of transmission of the power supply signal, and calculates a weight appropriate to that position. This makes it possible to continue efficient power supply even when the power receiving device 200 is moving, and also reduces the number of times direction of arrival estimation and weight calculation are performed. In this embodiment as well, it is possible to avoid or reduce radio wave interference to external wireless equipment, etc.

[0083] It should be noted that the present invention is not limited to the embodiments described above, and the components can be modified and implemented in practice without departing from the spirit of the invention. Furthermore, various inventions can be formed by appropriately combining the multiple components disclosed in the above embodiments. For example, some components may be deleted from all the components shown in the embodiments. Moreover, components from different embodiments may be appropriately combined.

[0084] This embodiment may also have the following configuration. [Item 1] A receiving unit that receives signals from a power receiving device via multiple antennas, A control unit that detects multiple directions of arrival of the signal by estimating the direction of arrival based on the received signal, and selects one of the multiple directions of arrival, A transmitting unit that performs transmission beamforming of a power signal having directionality in one selected direction of arrival, A suitable power transmission device. [Item 2] In the transmission beamforming described above, the signal intensity of the radiation for the selected one direction of arrival is greater than or equal to a threshold, and the signal intensity of the radiation for the other direction of arrival different from the selected one is less than the threshold. The power transmission equipment described in item 1. [Item 3] The control unit selects the direction of arrival with the highest received signal strength among the plurality of directions of arrival. Power transmission equipment as described in item 1 or 2. [Item 4] The control unit selects an incoming direction from among the plurality of incoming directions in which the angular difference with the direction parallel or horizontal to the installation surface of the power transmission device is greater than a threshold. Power transmission equipment as described in item 1 or 2. [Item 5] The control unit selects the direction of arrival from among the plurality of arrival directions that has the largest angular difference with the direction parallel or horizontal to the installation surface of the power transmission device. Power transmission equipment as described in item 1 or 2. [Item 6] The control unit sets the first weight of one of the multiple incoming directions to be higher than the second weight of the other incoming directions, performs carrier sensing of the frequency used for the transmit beamforming with the receiving sensitivity based on the first and second weights, and selects the incoming direction if no carrier is detected by the carrier sensing. A power transmission device as described in any one of items 1 to 5. [Item 7] The control unit sets a first weight for one of the multiple directions of arrival higher than the second weight for the other directions of arrival, and performs a first carrier sense for the frequency used for the transmit beamforming with the receiving sensitivity based on the first and second weights. If a carrier is detected, it sets a third weight for the other directions of arrival (excluding the one direction of arrival) higher than the fourth weight for the other directions of arrival, and performs a second carrier sense for the frequency used for the transmit beamforming with the receiving sensitivity based on the third and fourth weights. A power transmission device as described in any one of items 1 to 6. [Item 8] The control unit detects the position of the power receiving device based on the signal, calculates the distance between the multiple antennas and the power receiving device based on the positions of each of the multiple antennas and the position of the power receiving device, and determines the weights for the multiple antennas whose signals transmitted from the multiple antennas are in phase with the power receiving device based on the calculated distance. The transmitting unit performs the transmission beamforming of the power signal based on the weight. A power transmission device as described in any one of items 1 to 7. [Item 9] The control unit predicts the future time-based position of the power receiving device installed on the mobile body based on information obtained from the mobile body, and adjusts the selected one direction of arrival based on the predicted time-based position to perform transmission beamforming of the power signal. A power transmission device as described in any one of items 1 to 8. [Item 10] The information obtained from the moving object includes at least one of the following: image data obtained by imaging the moving object with a camera, meter information or battery level information of the moving object, and schedule information for the movement of the moving object. The power transmission equipment described in item 9. [Item 11] In the direction of arrival estimation, the control unit calculates the distribution of signal intensity for each angle based on the received signal, and detects the direction of the angle in which the signal intensity has a peak based on the distribution as the direction of arrival. A power transmission device as described in any one of items 1 through 10. [Item 12] The signal received by the receiving unit includes signals received from the power receiving device via multiple paths. A power transmission device as described in any one of items 1 through 11. [Item 13] The aforementioned signal is a beacon signal. A power transmission device as described in any one of items 1 through 12. [Item 14] The signal from the power receiving device is received via multiple antennas. By estimating the direction of arrival based on the received signal, multiple directions of arrival for the signal are detected. Select one of the aforementioned multiple directions of arrival, Transmit beamforming of a power signal having directionality in one of the selected directions of arrival is performed. Method of power transmission. [Item 15] Equipped with a power transmission device and a power receiving device, The power receiving device includes a power receiving side transmitting unit that transmits a signal to the power transmitting device, The aforementioned power transmission device is A receiving unit that receives the signal from the power receiving device via multiple antennas, A control unit detects multiple directions of arrival of the signal by estimating the direction of arrival based on the received signal, and selects one of the multiple directions of arrival. The system comprises a power transmission unit that performs transmission beamforming of a power signal having directionality in one of the selected incoming directions, The power receiving device is A receiving unit that receives the power signal from the power transmission device, A battery that stores power based on the aforementioned power signal, Power supply system. [Explanation of Symbols]

[0085] 100 Power transmission equipment 102 Antenna 103 Transmitter / Receiver Switch 104 Receiving Unit 105 Transmitter 107 Control Unit 108 Weight setting section 109 High-frequency section 110 Communications Department 120 Power signal (power supply signal) 120 Power supply signal 121 Beam 121A Beam Components 121B beam component 131 Beam 131A direct wave 131B Reflected wave 200 Power receiving equipment 201 Antenna 202 RF-DC Converter 203 Beacon signal generator 204 Transmitter / Receiver Switch 205 Battery 206 Control Unit 207 Communications Department 208 Load device 220 beacon signals 220A direct wave 220B reflected wave 230A Direct wave propagation path 230B Reflected wave propagation path 240A Direct wave propagation path 240B Reflected wave propagation path 250 Direct wave propagation paths 260 wheels 300 Reflective object 310 Earth 312 beds 313 Ceiling 314 Wall 350 Support stand 400 Wireless equipment 500 Wireless LAN equipment A1 Peak A11 Peak A21 Peak P1 Peak P3 Peak P11 Peak P22 Peak θ direction θ1 Arrival angle (radiation angle) θ1 Angle of arrival θ11 Arrival angle (radiation angle) θ11 Angle of arrival θ12 Arrival angle (radiation angle) θ12 Angle of arrival θ2 Arrival angle (radiation angle) θ2 Angle of arrival θ21 Angle of arrival θ22 Angle of arrival θr threshold φ elevation angle

Claims

1. A receiving unit that receives signals from a power receiving device via multiple antennas, A control unit detects multiple directions of arrival of the signal by estimating the direction of arrival based on the received signal, and selects one of the multiple directions of arrival. A transmitting unit that performs transmission beamforming of a power signal having directionality in one of the selected incoming directions, A suitable power transmission device.

2. In the transmission beamforming described above, the signal intensity of the radiation for the selected one direction of arrival is greater than or equal to a threshold, and the signal intensity of the radiation for the other direction of arrival different from the selected one is less than the threshold. The power transmission device according to claim 1.

3. The control unit selects the direction of arrival with the highest received signal strength among the plurality of directions of arrival. The power transmission device according to claim 1.

4. The control unit selects an incoming direction from among the plurality of incoming directions in which the angular difference with the direction parallel or horizontal to the installation surface of the power transmission device is greater than a threshold. The power transmission device according to claim 1.

5. The control unit selects the direction of arrival from among the plurality of arrival directions that has the largest angular difference with the direction parallel or horizontal to the installation surface of the power transmission device. The power transmission device according to claim 1.

6. The control unit sets the first weight of one of the plurality of arriving directions to be higher than the second weight of the other arriving directions, performs carrier sensing of the frequency used for the transmit beamforming with the receiving sensitivity based on the first and second weights, and selects the arriving direction if no carrier is detected by the carrier sensing. The power transmission device according to claim 1.

7. The control unit sets a first weight for one of the multiple directions of arrival higher than the second weight for the other directions of arrival, and performs a first carrier sense for the frequency used for the transmission beamforming with the receiving sensitivity based on the first and second weights. If a carrier is detected, it sets a third weight for the other directions of arrival (excluding the one direction of arrival) higher than the fourth weight for the other directions of arrival, and performs a second carrier sense for the frequency used for the transmission beamforming with the receiving sensitivity based on the third and fourth weights. The power transmission device according to claim 1.

8. The control unit detects the position of the power receiving device based on the signal, calculates the distance between the multiple antennas and the power receiving device based on the positions of each of the multiple antennas and the position of the power receiving device, and determines the weights for the multiple antennas whose signals transmitted from the multiple antennas are in phase with the power receiving device based on the calculated distance. The transmitting unit performs the transmission beamforming of the power signal based on the weight. The power transmission device according to claim 1.

9. The control unit predicts the future time-based position of the power receiving device installed on the mobile body based on information obtained from the mobile body, and adjusts the selected one direction of arrival based on the predicted time-based position to perform transmission beamforming of the power signal. The power transmission device according to claim 1.

10. The information obtained from the moving object includes at least one of the following: image data obtained by imaging the moving object with a camera, meter information or battery level information of the moving object, and schedule information for the movement of the moving object. The power transmission device according to claim 9.

11. In the direction of arrival estimation, the control unit calculates the distribution of signal intensity for each angle based on the received signal, and detects the direction of the angle in which the signal intensity has a peak based on the distribution as the direction of arrival. The power transmission device according to claim 1.

12. The signal received by the receiving unit includes signals received from the power receiving device via multiple paths. The power transmission device according to claim 1.

13. The aforementioned signal is a beacon signal. The power transmission device according to claim 1.

14. The signal from the power receiving device is received via multiple antennas. By estimating the direction of arrival based on the received signal, multiple directions of arrival for the signal are detected. Select one of the aforementioned multiple directions of arrival, Transmit beamforming of a power signal having directionality in one of the selected directions of arrival is performed. Power transmission method.

15. Equipped with a power transmission device and a power receiving device, The power receiving device includes a power receiving side transmitting unit that transmits a signal to the power transmitting device, The aforementioned power transmission device is A receiving unit that receives the signal from the power receiving device via multiple antennas, A control unit detects multiple directions of arrival of the signal by estimating the direction of arrival based on the received signal, and selects one of the multiple directions of arrival. The system comprises a power transmission unit that performs transmission beamforming of a power signal having directionality in one of the selected incoming directions, The power receiving device is A receiving unit that receives the power signal from the power transmission device, A battery that stores power based on the aforementioned power signal, Power supply system.

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