Wireless power supply system

Abstract

Provided is a wireless power supply communication system capable of suppressing occurrence of a situation in which an electrical device cannot be supplied with sufficient power due to a null point being arranged by interference of electric waves, and capable of efficiently performing wireless power supply by electric waves radiated from a leaky coaxial cable. A wireless power supply system (1) supplies power to an electrical device (3) by electric waves radiated from a leaky coaxial cable (2). The wireless power supply system (1) is provided with an electric field intensity distribution variable unit (50) that makes the electric field intensity distribution of the electric waves radiated from the leaky coaxial cable (2) variable, and moves the position of a null point caused by interference of electric waves by changing the electric field intensity distribution using the electric field intensity distribution variable unit (50).

Description

Technical Field

[0001] This invention relates to a wireless power supply system for wirelessly supplying power to multiple electrical devices. Background Technology

[0002] Conventionally, a wireless power transmission device combining wireless power transmission and wireless communication functions has been known, as described in Patent Document 1. The wireless power transmission device described in Patent Document 1 includes a leaky coaxial cable held in a loop, an access point connected to one end of the leaky coaxial cable and connected to a higher-level line via a communication cable, and a terminating resistor connected to the other end of the leaky coaxial cable. Multiple slots for radiating radio waves for communication are formed on the outer conductor of the leaky coaxial cable. Furthermore, the outer conductor constitutes a power transmission coil for wireless power transmission to electrical devices such as mobile phones with receiving coils, and high-frequency power is supplied to this power transmission coil from the power transmission circuit. The receiving coil of the electrical device receives power for the operation of the electrical device from the power transmission coil through electromagnetic coupling. Specifically, as a method of wireless power transmission, methods such as electromagnetic induction utilizing electromagnetic induction and electromagnetic field resonance utilizing the resonance phenomenon of electromagnetic fields can be used.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2017-34935 Summary of the Invention

[0006] The problem that the invention aims to solve

[0007] In the wireless power transmission device described in Patent Document 1, when the power transmission coil (the outer conductor of the leaky coaxial cable) has only one turn, the electromagnetic coupling between the power transmission coil and the receiving coil is weak, making it impossible to efficiently supply power from the power transmission coil to the electrical equipment. In addition, if the power transmission coil is wound with multiple turns, the leaky coaxial cable becomes longer, increasing the size and cost of the device.

[0008] Therefore, the inventors considered radiating electromagnetic waves from a leaky coaxial cable to supply power to electrical equipment. However, when a zero point is generated due to interference of the electromagnetic waves radiated from the leaky coaxial cable, it is sometimes impossible to supply sufficient power to the electrical equipment located at that zero point. Here, a zero point refers to a location where electromagnetic waves radiated from multiple points along the length of the leaky coaxial cable interfere with each other and cancel each other out.

[0009] Therefore, the object of the present invention is to provide a wireless power supply communication system that can suppress the occurrence of situations where electrical equipment cannot be supplied with sufficient power due to the equipment being positioned at a zero point caused by interference of radio waves, and can efficiently provide wireless power through radio waves radiated from a leaky coaxial cable.

[0010] Methods for solving problems

[0011] To achieve the above objectives, the present invention provides a wireless power supply system that supplies power to electrical devices via radio waves emitted from a leaky coaxial cable. The wireless power supply system includes an electric field intensity distribution variable unit that allows the electric field intensity distribution of the radio waves emitted from the leaky coaxial cable to be variable. By using the electric field intensity distribution variable unit to change the electric field intensity distribution, the position of the zero point caused by the interference of the radio waves is moved.

[0012] Invention Effects

[0013] The wireless power supply system according to the present invention can suppress the occurrence of situations where insufficient power cannot be supplied to an electrical device due to the device being positioned at a zero point caused by interference of radio waves, and can efficiently provide wireless power through radio waves radiated from a leaky coaxial cable. Attached Figure Description

[0014] Figure 1 This is a structural diagram schematically illustrating an example of the structure of a wireless power supply system according to the first embodiment of the present invention.

[0015] Figure 2 In the diagram, (a) is a structural diagram showing a structural example of a leaky coaxial cable, and (b) is a cross-sectional view of the leaky coaxial cable at line AA in (a).

[0016] Figure 3 It is a schematic structural diagram representing an example of the structure of electrical equipment.

[0017] Figure 4 In the figure, (a) and (b) are curves showing the electric field intensity distribution when the resistance of the terminating resistance of the leaky coaxial cable is 50Ω and 0Ω, respectively.

[0018] Figure 5 In the diagram, (a) is a structural diagram schematically showing an example of the structure of the wireless power supply system according to the second embodiment of the present invention, and (b) and (c) are graphs showing an example of the change in the output voltage of the high-frequency power supply device when the frequency of the radio wave radiated from the leaky coaxial cable changes in the second embodiment.

[0019] Figure 6In the figure, (a) and (b) are curves showing the electric field intensity distribution when the frequencies of the electromagnetic waves emitted from the leaky coaxial cable are 916.7 MHz and 920.9 MHz.

[0020] Figure 7 This is a structural diagram schematically illustrating an example of the structure of a wireless power supply system according to a third embodiment of the present invention.

[0021] Figure 8 In the figure, (a)~(d) are curves showing the electric field intensity distribution of operation modes 1~4 when the resistance value of the first terminating resistor is set to 50Ω, the resistance value of the second terminating resistor R2 is set to 75Ω, the first frequency of the high-frequency power supply device is set to 916.7MHz, and the second frequency is set to 920.9MHz.

[0022] Figure 9 (a) to (d) are curves showing the electric field intensity distribution in operation modes 1 to 4 when the resistance value of the first terminating resistor is set to 50Ω, the resistance value of the second terminating resistor R2 is set to 0Ω, the first frequency of the high-frequency power supply device is set to 916.7MHz, and the second frequency is set to 920.9MHz.

[0023] Explanation of reference numerals in the attached figures

[0024] 1, 1A, 1B… Wireless power supply system, 2… Leaky coaxial cable, 3… Electrical equipment, 4, 4A… High frequency power supply device, 5, 5A… Attenuator, 40, 50… Variable electric field intensity distribution unit. Detailed Implementation

[0025] [First Implementation Method]

[0026] Figure 1 This is a structural diagram schematically illustrating an example of the structure of a wireless power supply system 1 according to the first embodiment of the present invention. Figure 1 In the attached diagram, the vertical direction corresponds to the vertical direction. The wireless power supply system 1 includes a leaky coaxial cable 2, a high-frequency power supply device 4 that supplies power to multiple electrical devices 3 via the leaky coaxial cable 2, and an attenuator 5 disposed at the end of the leaky coaxial cable 2, and supplies power to multiple electrical devices 3 by means of radio waves emitted from the leaky coaxial cable 2.

[0027] Leaky coaxial cable 2, also known as LCX (Leaky Coaxial Cable), is a coaxial cable designed to leak electromagnetic waves to the outside. The leaky coaxial cable 2 extends horizontally as a whole and is suspended at multiple points along its length by hangers 6. Between the hangers 6, the leaky coaxial cable 2 bends downwards due to its own weight. The length of the leaky coaxial cable 2 is, for example, 10 to 50 meters. The outer diameter of the leaky coaxial cable 2 is, for example, 5 mm or more and 80 mm or less.

[0028] Figure 2 (a) is a structural diagram representing a structural example of a leaky coaxial cable 2. Figure 2 (b) is Figure 2 (a) Cross-sectional view of the leaky coaxial cable 2 at line AA. The leaky coaxial cable 2 has an inner conductor 21, an insulator 22 covering the inner conductor 21, an outer conductor 23 consisting of a strip of metal foil wound into a spiral shape around the outer periphery of the insulator 22, and a sheath 24 covering the outer periphery of the insulator 22 and the outer conductor 23. The sheath 24 can be made of, for example, polyethylene, vinyl chloride, or a non-halogenated flame-retardant material.

[0029] The material for the inner conductor 21 is preferably copper, but it is not limited to copper; aluminum or copper-clad aluminum wire (CCA wire) can also be used. The material for the insulator 22 is, for example, polyethylene, polytetrafluoroethylene, vinyl chloride, or foams thereof. The outer conductor 23 is wound into a single helix around the outer periphery of the insulator 22 at a certain winding pitch P. Here, the winding pitch refers to the length by which the outer conductor 23 advances axially along the inner conductor 21 and the insulator 22 during one revolution around the outer periphery of the insulator 22. The material for the outer conductor 23 is preferably copper, but it is not limited to copper; aluminum or silver can also be used.

[0030] An adhesive is applied to the surface of the outer conductor 23 on the insulator 22 side, and the outer conductor 23 is attached to the outer peripheral surface 22a of the insulator 22 by means of the adhesive. However, it is also possible to fix the outer conductor 23 to the insulator 22 by pressing the outer conductor 23 to the outer peripheral surface 22a of the insulator 22 without using an adhesive and by means of a sheath 24.

[0031] The proportion of the area of ​​the outer peripheral surface 22a of the insulator 22 covered by the external conductor 23, i.e., the metal coverage, is 20% or more and less than 40%. Figure 2 In the example shown in (a), the width W of the spirally shaped outer conductor 23 along the axial direction of the inner conductor 21 and the insulator 22 is 35% of the winding pitch P ((W / P) × 100). That is, in Figure 2 In the leaky coaxial cable 2 shown in (a), the metal coverage is 35%. The winding pitch P is, for example, 100 mm or more and 300 mm or less.

[0032] The electromagnetic waves emitted from the leaky coaxial cable 2 for power supply are circularly polarized waves. Because circularly polarized waves travel while rotating in a spiral shape, their sensitivity is relatively stable relative to the setting angle of the receiving antenna, making it easy to install a receiving antenna for receiving electromagnetic waves for power supply in the electrical equipment 3 (described later). However, the leaky coaxial cable 2 can also be constructed by emitting linearly polarized waves from multiple locations.

[0033] Figure 3 This is a schematic structural diagram showing an example of the structure of electrical device 3. In this embodiment, electrical device 3 is configured as a sensor device for detecting physical quantities.

[0034] like Figure 3 As shown, the electrical device 3 includes a receiving antenna 31 that receives electromagnetic waves emitted from the leaky coaxial cable 2 for power supply, a rectifier circuit 32 that converts the AC power received by the receiving antenna 31 into DC power, a DC-DC converter 33, a detection unit 34 that detects the physical quantity of the object being detected, a microcomputer 35 that generates communication data packets based on the detection results of the detection unit 34, and a transmitting unit 36 ​​that transmits the communication data packets. The physical quantity detected by the detection unit 34 is not particularly limited, and may include, for example, temperature, humidity, magnetic field strength, light intensity, pressure, flow rate, acceleration, etc.

[0035] The detection unit 34, microcomputer 35, and transmission unit 36 ​​operate using power output from the DC-DC converter 33. The DC-DC converter 33 converts the DC power converted by the rectifier circuit 32 into a voltage suitable for the operation of the detection unit 34, microcomputer 35, and transmission unit 36. Alternatively, an energy storage element can be provided in the electrical device 3 to store the wirelessly powered power. In this case, for example, when the power stored in the energy storage element reaches a predetermined value or higher, power is supplied from the energy storage element to the detection unit 34, microcomputer 35, and transmission unit 36, and the detection result of the physical quantity is transmitted.

[0036] The transmitting unit 36 ​​can transmit the detection results of the physical quantity via a wired method based on a signal cable, for example, but it can also transmit the detection results of the physical quantity by transmitting a wireless signal to the leaky coaxial cable 2. In this case, the high-frequency power supply device 4 is connected to the leaky coaxial cable 2 via a common connector, and a communication device is connected to the common connector, wherein the communication device receives signals transmitted from the transmitting units 36 of each of the plurality of electrical devices 3. The transmitting unit 36 ​​has a transmitting antenna that transmits a wireless signal in a frequency band different from the radio waves used to supply power to the electrical devices 3, and modulates and transmits communication data packets. The communication device receives communication data packets via the leaky coaxial cable 2 and the common connector.

[0037] The high-frequency power supply device 4 applies a sinusoidal high-frequency voltage, for example, in the 920MHz band (915MHz~930MHz), between the inner conductor 21 and the outer conductor 23 of the leaky coaxial cable 2. Radio waves of the same frequency as the high-frequency voltage output from the high-frequency power supply device 4 are emitted from the leaky coaxial cable 2, and these emitted radio waves are energized by the receiving antenna 31 of the electrical equipment 3.

[0038] Attenuator 5 is located at the end (i.e., the termination section) of the leaky coaxial cable 2 on the side opposite to the high-frequency power supply device 4 along its length. In this embodiment, attenuator 5 is a variable attenuator capable of changing the resistance value of the termination resistance of the leaky coaxial cable 2 between R1 and R2. Figure 1 As shown in the amplification section, the attenuator 5 includes a first terminating resistor 51 with a resistance value of R1, a second terminating resistor 52 with a resistance value of R2, a switching switch 53, and a switching control unit 54 that controls the switching switch 53.

[0039] The switch 53 is capable of switching between a first connection state in which a first terminating resistor 51 is connected between the internal conductor 21 and the external conductor 23, and a second connection state in which a second terminating resistor 52 is connected between the internal conductor 21 and the external conductor 23. The switching control unit 54 controls the switch 53 at predetermined time intervals, switching between the first and second connection states. The switch 53 is, for example, a mechanical relay, but it can also be constructed from semiconductor switching elements such as transistors.

[0040] In the first connection state, the terminating resistor of the leaky coaxial cable 2 has a resistance value of R1, and in the second connection state, the terminating resistor of the leaky coaxial cable 2 has a resistance value of R2. The values ​​of R1 and R2 are not particularly limited; for example, R1 can be set to 50Ω and R2 to 75Ω. Alternatively, either R1 or R2 can be set to 0Ω, for example, R1 can be set to 50Ω and R2 to 0Ω. When R2 is set to 0Ω, in the second connection state, the inner conductor 21 and the outer conductor 23 are electrically short-circuited. Alternatively, either R1 or R2 can be made infinitely large; for example, when R2 is infinitely large, in the second connection state, the inner conductor 21 and the outer conductor 23 are open.

[0041] The electric field strength distribution around the leaky coaxial cable 2 changes according to the resistance value of the terminating resistor. In this embodiment, the first terminating resistor 51, the second terminating resistor 52, the switching switch 53, and the switching control unit 54 of the attenuator 5 function as an electric field strength distribution variable unit 50 that makes the electric field strength distribution of the electromagnetic waves emitted from the leaky coaxial cable 2 variable.

[0042] Figure 4 (a) is a graph showing the electric field intensity distribution when the frequency of the electromagnetic wave emitted from the leaky coaxial cable 2 is 916.7 MHz and the resistance of the terminal resistor of the leaky coaxial cable 2 is 50 Ω. Figure 4 (b) is a graph showing the electric field intensity distribution when the frequency of the electromagnetic wave emitted from the leaky coaxial cable 2 is 916.7 MHz and the resistance of the terminal resistor of the leaky coaxial cable 2 is 0 Ω. Figure 4The white line shown at the top of (a) and (b) indicates the leaky coaxial cable 2 that bends at bend point 20.

[0043] exist Figure 4 In (a) and (b), the distribution of electric field intensity is represented by the shade of the area where the electric field intensity is stronger. Figure 4 In (a) and (b), the island-shaped points represented by lighter colors where the electric field strength is weaker than the surrounding areas are null points caused by electromagnetic wave interference. If the position of the receiving antenna 31 of the electrical device 3 is always equivalent to a null point, the electrical device 3 cannot be adequately powered. However, in this embodiment, if... Figure 4 As shown in (a) and (b), due to the change in the resistance value of the terminating resistor, the electric field strength distribution around the leaky coaxial cable 2 will change, and the position of the zero point will move accordingly, thus enabling the electrical equipment 3 to be powered.

[0044] That is, for example, even if the position of the receiving antenna 31 of the electrical device 3 is zero when the switch 53 is in the first connection state, power can be supplied to the electrical device 3 as long as the position of the receiving antenna 31 is not zero when the switch 53 is in the second connection state. Furthermore, for example, even if the position of the receiving antenna 31 of the electrical device 3 is zero when the switch 53 is in the second connection state, power can be supplied to the electrical device 3 as long as the position of the receiving antenna 31 is not zero when the switch 53 is in the first connection state. Thus, the power required for the operation of the detection unit 34, the microcomputer 35, and the transmission unit 36 ​​of the electrical device 3 can be supplied.

[0045] Thus, according to this embodiment, it is possible to suppress the occurrence of situations where the electrical device 3 is positioned at a zero point caused by interference of radio waves, thereby preventing the supply of sufficient power to the electrical device 3. In addition, by using radio waves radiated from the leaky coaxial cable 2 to supply power to the electrical device 3, wireless power supply can be performed more efficiently compared to the case where, for example, the outer conductor of the leaky coaxial cable 2 is used as a power transmission coil as described in Patent Document 1 above.

[0046] [Second Implementation]

[0047] Next, a second embodiment of the present invention will be described. In the first embodiment, it was described that the electric field strength distribution could be varied by changing the resistance value of the terminal resistance of the leaky coaxial cable 2. However, in the second embodiment, the electric field strength distribution can be varied by changing the frequency of the electromagnetic waves emitted from the leaky coaxial cable 2.

[0048] Figure 5(a) is a structural diagram schematically showing an example of the structure of the wireless power supply system 1A according to the second embodiment of the present invention. The wireless power supply system 1A includes a leaky coaxial cable 2, a plurality of electrical devices 3, a high-frequency power supply device 4A, and an attenuator 5A disposed at the end of the leaky coaxial cable 2. The structure of the high-frequency power supply device 4A and the attenuator 5A is different from the structure of the high-frequency power supply device 4 and the attenuator 5 in the first embodiment.

[0049] The high-frequency power supply device 4A includes a first power supply unit 41, a second power supply unit 42, a switching switch 43, and a switching control unit 44 that controls the switching switch 43. The first power supply unit 41 outputs a high-frequency voltage of a first frequency F1. The second power supply unit 42 outputs a high-frequency voltage of a second frequency F2. The switching switch 43 is, for example, composed of a semiconductor switching element, and switches to output the high-frequency voltage of either the first power supply unit 41 or the second power supply unit 42 to the leaky coaxial cable 2. In a first connection state where the high-frequency voltage of the first power supply unit 41 is output to the leaky coaxial cable 2, a radio wave of the first frequency F1 is emitted from the leaky coaxial cable 2; in a second connection state where the high-frequency voltage of the second power supply unit 42 is output to the leaky coaxial cable 2, a radio wave of the second frequency F2 is emitted from the leaky coaxial cable 2.

[0050] When the switch 43 is in the first connection state, the multiple electrical devices 3 are powered by radio waves of frequency F1 emitted from the leaky coaxial cable 2, and when the switch 43 is in the second connection state, they are powered by radio waves of frequency F2 emitted from the leaky coaxial cable 2.

[0051] Attenuator 5A is similarly provided at the end of the leaky coaxial cable 2 as attenuator 5 in the first embodiment. The resistance value of the terminating resistor of attenuator 5A is fixed. The resistance value of this terminating resistor is, for example, 50Ω or 75Ω.

[0052] The electric field strength distribution around the leaky coaxial cable 2 varies according to the frequency of the electromagnetic waves emitted from the leaky coaxial cable 2. In this embodiment, the first power supply unit 41, the second power supply unit 42, the switching switch 43, and the switching control unit 44 of the high-frequency power supply device 4A function as an electric field strength distribution variable unit 40 that makes the electric field strength distribution of the electromagnetic waves emitted from the leaky coaxial cable 2 variable.

[0053] The variable electric field intensity distribution unit 40 changes the frequency of the electromagnetic waves emitted from the leaky coaxial cable 2 between the first frequency F1 and the second frequency F2. When switching from the first frequency F1 to the second frequency F2, it switches to the second frequency F2 at the time corresponding to the period of the first frequency F1. When switching from the second frequency F2 to the first frequency F1, it switches to the first frequency F1 at the time corresponding to the period of the second frequency F2.

[0054] Figure 5(b) is a graph illustrating an example of the change in the output voltage from the high-frequency power supply 4A when the frequency of the electromagnetic wave emitted from the leaky coaxial cable 2 switches from the first frequency F1 to the second frequency F2. Figure 5 (c) is a graph representing an example of the change in the output voltage from the high-frequency power supply 4A when the frequency of the electromagnetic wave emitted from the leaky coaxial cable 2 switches from the second frequency F2 to the first frequency F1. Figure 5 The horizontal axis of the graphs in (b) and (c) is the time axis. In this example, the case where the second frequency F2 is higher than the first frequency F1 is shown, but for clarity, the difference between the period of the first frequency F1 and the period of the second frequency F2 is exaggerated.

[0055] The switching control unit 44 switches the switching switch 43 when the output voltage of the high-frequency power supply 4A crosses zero. The length of the period P1 during which the high-frequency power supply 4A outputs an AC voltage of the first frequency F1 is an integer multiple of the period of the AC voltage of the first frequency F1 (e.g., 1 × 10⁻⁶). 3 (times). Furthermore, the length of period P2 during which the high-frequency power supply device 4A outputs an AC voltage of the second frequency F2 is an integer multiple of the period of the AC voltage of the second frequency F2 (e.g., 1 × 10⁻⁶). 3 (times). By switching in this way, the rectifier circuit 32 and DC-DC converter 33 in the electrical equipment 3 operate smoothly when the frequency of the electromagnetic waves radiated from the leaky coaxial cable 2 changes.

[0056] Figure 6 (a) is a graph showing the electric field distribution when the resistance of the leaky coaxial cable 2 is 50Ω and the frequency of the radio wave emitted from the leaky coaxial cable is 916.7MHz. Figure 6 (b) is a graph showing the electric field distribution when the terminating resistance of the leaky coaxial cable 2 is 50Ω and the frequency of the electromagnetic wave emitted from the leaky coaxial cable 2 is 920.9MHz. Figure 6 In (a) and (b), the referenced in the first embodiment is... Figure 4 Similarly, in (a) and (b), the distribution of electric field intensity is represented by the shade of the area where the electric field intensity is stronger.

[0057] like Figure 6 As shown in (a) and (b), due to the change in the frequency of the electromagnetic waves emitted from the leaky coaxial cable 2, the distribution of the electric field intensity around the leaky coaxial cable 2 changes, and consequently, the position of the zero point shifts. Thus, the same effect as in the first embodiment can be obtained.

[0058] [Third Implementation Method]

[0059] Next, a third embodiment of the present invention will be described. In the third embodiment, the electric field strength distribution is made variable by changing the resistance value of the terminal resistor of the leaky coaxial cable 2 and changing the frequency of the electromagnetic waves emitted from the leaky coaxial cable 2.

[0060] Figure 7 This is a structural diagram schematically illustrating a structural example of a wireless power supply system 1B according to a third embodiment of the present invention. The wireless power supply system 1B includes a leaky coaxial cable 2, multiple electrical devices 3, a high-frequency power supply device 4A identical to that in the second embodiment, and an attenuator 5 identical to that in the first embodiment.

[0061] In the third embodiment, the following modes are switched sequentially: operation mode 1, where the switching switch 43 of the high-frequency power supply device 4A is in the first connection state and the switching switch 53 of the attenuator 5 is in the first connection state; operation mode 2, where the switching switch 43 of the high-frequency power supply device 4A is in the second connection state and the switching switch 53 of the attenuator 5 is in the first connection state; operation mode 3, where the switching switch 43 of the high-frequency power supply device 4A is in the second connection state and the switching switch 53 of the attenuator 5 is in the second connection state; and operation mode 4, where the switching switch 43 of the high-frequency power supply device 4A is in the first connection state and the switching switch 53 of the attenuator 5 is in the second connection state. The electric field strength distribution around the leaky coaxial cable 2 changes sequentially with the switching of these operation modes 1 to 4. Figure 8 (a)~(d) and Figure 9 (a) to (d) represent examples of electric field intensity distribution in action modes 1 to 4.

[0062] Figure 8 (a) to (d) are curves showing the electric field intensity distribution of each of the operating modes 1 to 4 when the resistance value R1 of the first terminating resistor 51 of the attenuator 5 is set to 50Ω, the resistance value R2 of the second terminating resistor 52 is set to 75Ω, the first frequency F1 of the high-frequency power supply device 4A is set to 916.7MHz, and the second frequency F2 is set to 920.9MHz.

[0063] Figure 9 (a) to (d) are curves showing the electric field intensity distribution of each of the operating modes 1 to 4 when the resistance value R1 of the first terminating resistor 51 of the attenuator 5 is set to 50Ω, the resistance value R2 of the second terminating resistor 52 is set to 0Ω, the first frequency F1 of the high-frequency power supply device 4A is set to 916.7MHz, and the second frequency F2 is set to 920.9MHz.

[0064] As shown in these graphs, by combining changes in the resistance value of the termination resistor of the leaky coaxial cable 2 with changes in the frequency of the electromagnetic waves emitted from the leaky coaxial cable 2, the electric field strength distribution can be varied more significantly than in the first and second embodiments. This allows for more reliable suppression of situations where insufficient power cannot be supplied to the electrical equipment 3.

[0065] (Summary of Implementation Methods)

[0066] Next, the technical concept learned from the embodiments described above will be described by reference to the accompanying reference numerals and the like. However, the reference numerals in the following description do not limit the constituent elements in the claims to the components specifically shown in the embodiments.

[0067] [1] A wireless power supply system (1, 1A, 1B) supplies power to an electrical device (3) by means of radio waves emitted from a leaky coaxial cable (2). The wireless power supply system (1, 1A, 1B) includes an electric field strength distribution variable unit (40, 50) that makes the electric field strength distribution of the radio waves emitted from the leaky coaxial cable (2) variable. By using the electric field strength distribution variable unit (40, 50) to change the electric field strength distribution, the position of the zero point caused by the interference of the radio waves is moved.

[0068] [2] According to the wireless power supply system (1, 1A) described above [1], the electric field strength distribution variable unit (50) makes the electric field strength distribution variable by changing the resistance value of the terminal resistor of the leaky coaxial cable (2).

[0069] [3] According to the wireless power supply system (1, 1B) described above [1], the electric field strength distribution variable unit (40) makes the electric field strength distribution variable by changing the frequency of the radio waves emitted from the leaky coaxial cable (2).

[0070] [4] According to the wireless power supply system (1, 1B) described above [1], the electric field strength distribution variable unit (40) makes the electric field strength distribution variable by changing the resistance value of the terminal resistor of the leaky coaxial cable (2) and changing the frequency of the radio waves emitted from the leaky coaxial cable (2).

[0071] [5] According to the wireless power supply system (1, 1B) described in [3] or [4] above, the electric field intensity distribution variable unit (40) changes the frequency of the radio wave emitted from the leaky coaxial cable (2) between a first frequency (F1) and a second frequency (F2) different from the first frequency (F1). When switching from the first frequency (F1) to the second frequency (F2), it switches to the second frequency (F2) at a time corresponding to the period of the first frequency (F1). When switching from the second frequency (F2) to the first frequency (F1), it switches to the first frequency (F1) at a time corresponding to the period of the second frequency (F2).

[0072] The first to third embodiments of the present invention have been described above, but these embodiments do not limit the invention as claimed. Furthermore, it should be noted that the combinations of features described in the embodiments are not necessarily all necessary means to solve the problems of the invention.

[0073] Furthermore, the present invention can be implemented with appropriate modifications without departing from its spirit. For example, in the embodiment, the case where the electrical device 3 is a sensor device has been described, but the wireless power supply system can also be configured to wirelessly power electrical devices other than the sensor device. For example, RFID (Radio Frequency Identification) tags can be used as electrical devices other than the sensor device.

Claims

1. A wireless power supply system that supplies power to electrical devices via electromagnetic waves radiated from a leaky coaxial cable. The wireless power supply system includes an electric field strength distribution variable unit that allows the electric field strength distribution of the radio waves radiated from the leaky coaxial cable to be variable. By using the electric field strength distribution variable unit to change the electric field strength distribution, the position of the zero point caused by the interference of the radio waves is moved.

2. The wireless power supply system according to claim 1, wherein, The variable electric field strength distribution unit makes the electric field strength distribution variable by changing the resistance value of the terminal resistor of the leaky coaxial cable.

3. The wireless power supply system according to claim 1, wherein, The variable electric field strength distribution unit makes the electric field strength distribution variable by changing the frequency of the radio waves emitted from the leaky coaxial cable.

4. The wireless power supply system according to claim 1, wherein, The variable electric field strength distribution unit makes the electric field strength distribution variable by changing the resistance value of the terminal resistor of the leaky coaxial cable and changing the frequency of the radio waves emitted from the leaky coaxial cable.

5. The wireless power supply system according to claim 3 or 4, wherein, The variable electric field intensity distribution unit changes the frequency of the electromagnetic wave emitted from the leaky coaxial cable between a first frequency and a second frequency different from the first frequency. When switching from the first frequency to the second frequency, it switches to the second frequency at a time corresponding to the period of the first frequency. When switching from the second frequency to the first frequency, it switches to the first frequency at a time corresponding to the period of the second frequency.

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