Wireless power supply system

Abstract

The present invention provides a wireless power transfer communication system that can efficiently transfer power wirelessly using radio waves radiated from a leaky coaxial cable, while suppressing situations where electrical devices cannot be supplied with sufficient power due to being placed in null points caused by radio wave interference. [Solution] The wireless power supply system 1 supplies power to an electrical device 3 using radio waves radiated from a leaky coaxial cable 2. The wireless power supply system 1 is equipped with an electric field strength distribution variable means 50 that varies the electric field strength distribution of the radio waves radiated from the leaky coaxial cable 2. By changing the electric field strength distribution using the electric field strength distribution variable means 50, the position of the null point generated by radio wave interference moves.

Description

Technical Field

[0001] The present invention relates to a wireless power supply system for wirelessly supplying power to a plurality of electrical devices.

Background Art

[0002] Conventionally, as a wireless power transmission device having both a wireless power transmission function and a wireless communication function, the one described in Patent Document 1 is known. The wireless power transmission device described in Patent Document 1 includes a leaky coaxial cable held in a loop shape, an access point connected to one end of the leaky coaxial cable and connected to an upper line via a communication cable, and a termination resistor connected to the other end of the leaky coaxial cable. A plurality of slots for radiating radio waves for communication are formed in the outer conductor of the leaky coaxial cable. Further, the outer conductor constitutes a power transmission coil that performs wireless power transmission to an electrical device such as a mobile phone having a power receiving coil, and high-frequency power is supplied from a power transmission circuit to this power transmission coil. The power receiving coil of the electrical device receives power for operating the electrical device from the power transmission coil by electromagnetic coupling. Specifically, as a method of wireless power transmission, it is said that an electromagnetic induction method using electromagnetic induction or an electromagnetic field resonance method using a resonance phenomenon of an electromagnetic field can be used.

Prior Art Documents

Patent Documents

[0003] [[ID=二十一]] [[ID=二十二]]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the wireless power transmission device described in Patent Document 1, if the power transmission coil (outer conductor of the leaky coaxial cable) has only one turn, the electromagnetic coupling between the power transmission coil and the power receiving coil is weak, making it impossible to efficiently supply power from the power transmission coil to the electrical device. Furthermore, if the power transmission coil has multiple turns, the leaky coaxial cable becomes longer, increasing the size and cost of the device.

[0005] Therefore, the inventors considered radiating radio waves from a leaky coaxial cable and using these radio waves to supply power to an electrical device. However, when null points occurred due to interference of radio waves radiated from the leaky coaxial cable, it was sometimes not possible to supply sufficient power to the electrical device located at that null point. Here, a null point refers to a point in the leaky coaxial cable where radio waves radiated from multiple points along its longitudinal direction interfere with and cancel each other out.

[0006] Therefore, the present invention aims to provide a wireless power supply communication system that can efficiently provide wireless power using radio waves radiated from a leaky coaxial cable, while suppressing the occurrence of situations where sufficient power cannot be supplied to an electrical device due to the placement of the electrical device at a null point caused by radio wave interference. [Means for solving the problem]

[0007] To achieve the above objective, the present invention provides a wireless power supply system that supplies power to an electrical device using radio waves radiated from a leaky coaxial cable, comprising a variable electric field strength distribution means for varying the electric field strength distribution of the radio waves radiated from the leaky coaxial cable, wherein by changing the electric field strength distribution using the variable electric field strength distribution means, the position of the null point generated by interference of the radio waves moves. [Effects of the Invention]

[0008] According to the wireless power supply system of the present invention, it is possible to efficiently perform wireless power supply using radio waves radiated from a leaky coaxial cable while suppressing the occurrence of situations in which sufficient power cannot be supplied to an electrical device due to the placement of the electrical device in a null point caused by radio wave interference. [Brief explanation of the drawing]

[0009] [Figure 1] This is a schematic diagram showing an example of the configuration of a wireless power supply system according to the first embodiment of the present invention. [Figure 2] (a) is a diagram showing an example of the configuration of a leaky coaxial cable. (b) is a cross-sectional view of the leaky coaxial cable in line AA of (a). [Figure 3] This is a schematic diagram showing an example of the configuration of an electrical device. [Figure 4] (a) and (b) are graphs showing the electric field strength distribution when the termination resistance of the leaky coaxial cable is 50Ω and 0Ω, respectively. [Figure 5] (a) is a schematic diagram showing an example of the configuration of a wireless power supply system according to a second embodiment of the present invention. (b) and (c) are graphs showing an example of the state of change in the output voltage from the high-frequency power supply when the frequency of the radio waves radiated from the leaky coaxial cable is switched in the second embodiment. [Figure 6] (a) and (b) are graphs showing the electric field strength distribution when the frequencies of the radio waves radiated from the leaky coaxial cable are 916.7 MHz and 920.9 MHz, respectively. [Figure 7] This is a schematic diagram showing an example of the configuration of a wireless power supply system according to a third embodiment of the present invention. [Figure 8] Figures (a) to (d) are graphs showing the electric field strength distribution for operating modes 1 to 4, where the resistance value of the first termination resistor is 50Ω, the resistance value of the second termination resistor R2 is 75Ω, and the first frequency of the high-frequency power supply is 916.7MHz and the second frequency is 920.9MHz. [Figure 9](a) to (d) are graphs showing the electric field strength distribution for operating modes 1 to 4 when the resistance value of the first termination resistor is 50Ω, the resistance value of the second termination resistor R2 is 0Ω, and the first frequency of the high-frequency power supply is 916.7MHz and the second frequency is 920.9MHz. [Modes for carrying out the invention]

[0010] [First Embodiment] Figure 1 is a schematic diagram showing an example of the configuration of a wireless power supply system 1 according to a first embodiment of the present invention. In Figure 1, the top and bottom directions correspond to the vertical direction. The wireless power supply system 1 comprises a leaky coaxial cable 2, a high-frequency power supply device 4 that supplies power to a plurality of electrical devices 3 via the leaky coaxial cable 2, and an attenuator 5 provided at the end of the leaky coaxial cable 2, and supplies power to the plurality of electrical devices 3 by radio waves radiated from the leaky coaxial cable 2.

[0011] Leaky coaxial cable 2, also known as LCX (Leaky Coaxial Cable), is a coaxial cable configured to allow electromagnetic waves to leak out. The leaky coaxial cable 2 is suspended by suspension devices 6 at multiple points along its longitudinal direction, so that it extends horizontally as a whole. Between the suspension devices 6, the leaky coaxial cable 2 is curved downward due to its own weight. The length of the leaky coaxial cable 2 is, for example, 10 to 50 m. The outer diameter of the leaky coaxial cable 2 is, for example, between 5 mm and 80 mm.

[0012] Figure 2(a) is a diagram showing an example of the configuration of a leaky coaxial cable 2. Figure 2(b) is a cross-sectional view of the leaky coaxial cable 2 in line AA of Figure 2(a). The leaky coaxial cable 2 has an inner conductor 21, an insulator 22 covering the inner conductor 21, an outer conductor 23 made of a strip of metal foil spirally wound around the outer circumference of the insulator 22, and a sheath 24 covering the outer circumference of the insulator 22 and the outer conductor 23. For example, polyethylene, polyvinyl chloride, or a non-halogen flame retardant can be used as the material for the sheath 24.

[0013] As the material of the inner conductor 21, for example, copper can be preferably used, but it is not limited thereto, and aluminum or copper-clad aluminum wire (CCA wire) may also be used. As the material of the insulator 22, for example, polyethylene, polytetrafluoroethylene, vinyl chloride, or foams thereof can be used. The outer conductor 23 is wound around the outer periphery of the insulator 22 in a single-layer spiral shape with a certain winding pitch P. Here, the winding pitch refers to the length that the outer conductor 23 advances in the axial direction of the inner conductor 21 and the insulator 22 while the outer conductor 23 makes one turn around the outer periphery of the insulator 22. As the material of the outer conductor 23, for example, copper can be preferably used, but it is not limited thereto, and aluminum or silver may also be used.

[0014] An adhesive is applied to the surface of the outer conductor 23 on the side of the insulator 22, and the outer conductor 23 is attached to the outer peripheral surface 22a of the insulator 22 by the adhesive. However, the outer conductor 23 may be fixed to the insulator 22 by pressing the outer conductor 23 against the outer peripheral surface 22a of the insulator 22 with a sheath 24 without using an adhesive.

[0015] The metal cover rate, which is the ratio of the area covered by the outer conductor 23 on the outer peripheral surface 22a of the insulator 22, is 20% or more and 40% or less. In the example shown in Fig. 2(a), the ratio ((W / P)×100) of the width W of the spiral outer conductor 23 in the axial direction of the inner conductor 21 and the insulator 22 to the winding pitch P is 35%. That is, in the leaky coaxial cable 2 shown in Fig. 2(a), the metal cover rate is 35%. The winding pitch P is, for example, 100 mm or more and 300 mm or less.

[0016] The radio wave for power supply radiated from the leaky coaxial cable 2 is a circularly polarized wave. Since the circularly polarized wave advances while the radio wave rotates spirally, the sensitivity is relatively stable with respect to the installation angle of the power receiving antenna, and it is easy to install the power receiving antenna (described later) that receives the radio wave for power supply in the electric device 3. However, the leaky coaxial cable 2 may be configured such that linearly polarized waves are radiated from a plurality of locations of the leaky coaxial cable 2.

[0017] FIG. 3 is a schematic configuration diagram showing a configuration example of the electric device 3. In the present embodiment, the electric device 3 is configured as a sensor device that detects a physical quantity.

[0018] As shown in FIG. 3, the electric device 3 includes a power receiving antenna 31 that receives radio waves for power supply radiated from the leaky coaxial cable 2, a rectifier circuit 32 that converts the AC power received by the power receiving antenna 31 into DC power, a DC-DC converter 33, a detection unit 34 that detects the physical quantity to be detected, a microcomputer (microcontroller) 35 that generates a communication packet based on the detection result of the detection unit 34, and a transmission unit 36 that transmits the communication packet. The physical quantity detected by the detection unit 34 is not particularly limited, and examples thereof include temperature, humidity, magnetic field strength, light intensity, pressure, flow rate, acceleration, and the like.

[0019] The detection unit 34, the microcomputer 35, and the transmission unit 36 operate by the power output from the DC-DC converter 33. The DC-DC converter 33 converts the voltage of the DC power converted by the rectifier circuit 32 into a voltage suitable for the operations of the detection unit 34, the microcomputer 35, and the transmission unit 36. Also, a power storage element for storing the wirelessly supplied power may be provided in the electric device 3. In this case, for example, when the power stored in the power storage element reaches a predetermined value or more, power is supplied from the power storage element to the detection unit 34, the microcomputer 35, and the transmission unit 36, and the detection result of the physical quantity is transmitted.

[0020] The transmission unit 36 may transmit the detection result of the physical quantity by a wired method using, for example, a signal cable, or may transmit the detection result 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 coupler, and a communication device that receives the signals transmitted from the respective transmission units 36 of the plurality of electric devices 3 is connected to this coupler. The transmission unit 36 has a transmission antenna that transmits a wireless signal in a frequency band different from the frequency of the radio wave for power supply to the electric device 3, and transmits the communication packet by frequency modulation. The communication device receives this communication packet via the leaky coaxial cable 2 and the coupler.

[0021] ' The high-frequency power supply unit 4 applies a sinusoidal high-frequency voltage, for example, in the 920MHz band (915MHz to 930MHz), between the inner conductor 21 and the outer conductor 23 of the leaky coaxial cable 2. The leaky coaxial cable 2 emits radio waves of the same frequency as the high-frequency voltage output from the high-frequency power supply unit 4, and these emitted radio waves are received by the receiving antenna 31 of the electrical device 3.

[0022] The attenuator 5 is provided at the terminal end of the leaky coaxial cable 2, which is the end opposite to the high-frequency power supply unit 4 in the longitudinal direction of the cable. The attenuator 5 in this embodiment is a variable attenuator that can change the resistance value of the termination resistor of the leaky coaxial cable 2 between R1 and R2. As shown in the blown-out portion of Figure 1, the attenuator 5 consists of a first termination resistor 51 with resistance value R1, a second termination resistor 52 with resistance value R2, a changeover switch 53, and a changeover control unit 54 that controls the changeover switch 53.

[0023] The changeover switch 53 can switch between a first connection state in which a first termination resistor 51 is connected between the internal conductor 21 and the external conductor 23, and a second connection state in which a second termination resistor 52 is connected between the internal conductor 21 and the external conductor 23. The switching control unit 54 controls the changeover switch 53, for example, at predetermined time intervals, to switch between the first connection state and the second connection state. The changeover switch 53 is, for example, a mechanical relay, but it may also be configured using a semiconductor switching element such as a transistor.

[0024] In the first connection state, the resistance value of the termination resistor of the leaky coaxial cable 2 is R1, and in the second connection state, the resistance value of the termination resistor of the leaky coaxial cable 2 is R2. The values ​​of R1 and R2 are not particularly limited, but for example, R1 can be 50Ω and R2 can be 75Ω. Alternatively, either R1 or R2 can be set to 0Ω, for example, R1 can be 50Ω and R2 can be set 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 set to infinity, for example, when R2 is infinite, the inner conductor 21 and the outer conductor 23 are open-circuited in the second connection state.

[0025] The electric field strength distribution around the leaky coaxial cable 2 changes as the resistance value of the termination resistor changes. In this embodiment, the first termination resistor 51, the second termination resistor 52, the changeover switch 53, and the changeover control unit 54 of the attenuator 5 function as an electric field strength distribution variable means 50 that varies the electric field strength distribution of the radio waves radiated from the leaky coaxial cable 2.

[0026] Figure 4(a) is a graph showing the electric field strength distribution when the frequency of the radio waves radiated from the leaky coaxial cable 2 is 916.7 MHz and the resistance value of the termination resistor of the leaky coaxial cable 2 is 50 Ω. Figure 4(b) is a graph showing the electric field strength distribution when the frequency of the radio waves radiated from the leaky coaxial cable 2 is 916.7 MHz and the resistance value of the termination resistor of the leaky coaxial cable 2 is 0 Ω. The white line shown at the top of Figures 4(a) and (b) represents the leaky coaxial cable 2 bent at the bending point 20.

[0027] Figures 4(a) and 4(b) show the electric field strength distribution using shades of gray, with darker colors indicating stronger electric fields. In Figures 4(a) and 4(b), the island-like points shown in lighter colors, where the electric field strength is weaker than the surrounding areas, are null points generated by radio wave interference. If the receiving antenna 31 of the electrical device 3 is always positioned at a null point, it becomes impossible to adequately supply power to the electrical device 3. However, in this embodiment, as shown in Figures 4(a) and 4(b), the electric field strength distribution around the leaky coaxial cable 2 changes as the resistance value of the termination resistor changes, and the position of the null point shifts accordingly, making it possible to supply power to the electrical device 3.

[0028] In other words, even if the position of the receiving antenna 31 of the electrical device 3 is a null point when the changeover 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 a null point when the changeover switch 53 is in the second connection state. Also, even if the position of the receiving antenna 31 of the electrical device 3 is a null point when the changeover 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 a null point when the changeover switch 53 is in the first connection state. This makes it possible to supply the power necessary for the operation of the detection unit 34, microcontroller 35, and transmission unit 36 ​​of the electrical device 3.

[0029] Thus, according to this embodiment, by positioning the electrical device 3 at a null point caused by radio wave interference, the occurrence of a situation where sufficient power cannot be supplied to the electrical device 3 is suppressed. Furthermore, by supplying power to the electrical device 3 with radio waves radiated from the leaky coaxial cable 2, wireless power transmission can be performed more efficiently compared to the case where the outer conductor of the leaky coaxial cable 2 is used as a single-turn power transmission coil, as described in Patent Document 1 above.

[0030] [Second Embodiment] Next, a second embodiment of the present invention will be described. In the first embodiment, the case in which the electric field strength distribution is varied by changing the resistance value of the termination resistor of the leaky coaxial cable 2 was described, but in the second embodiment, the electric field strength distribution is varied by changing the frequency of the radio waves radiated from the leaky coaxial cable 2.

[0031] Figure 5(a) is a schematic diagram showing an example of the configuration of a wireless power supply system 1A according to a second embodiment of the present invention. The wireless power supply system 1A comprises a leaky coaxial cable 2, a plurality of electrical devices 3, a high-frequency power supply unit 4A, and an attenuator 5A provided at the end of the leaky coaxial cable 2. The configuration of the high-frequency power supply unit 4A and the attenuator 5A differs from the configuration of the high-frequency power supply unit 4 and the attenuator 5 of the first embodiment.

[0032] The high-frequency power supply unit 4A includes a first power supply unit 41 and a second power supply unit 42, a changeover switch 43, and a changeover control unit 44 that controls the changeover 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 changeover switch 43 is made of, for example, a semiconductor switching element and switches which high-frequency voltage of the first power supply unit 41 or the second power supply unit 42 is output to the leaky coaxial cable 2. In the first connection state, when the high-frequency voltage of the first power supply unit 41 is output to the leaky coaxial cable 2, radio waves of the first frequency F1 are radiated from the leaky coaxial cable 2, and in the second connection state, when the high-frequency voltage of the second power supply unit 42 is output to the leaky coaxial cable 2, radio waves of the second frequency F2 are radiated from the leaky coaxial cable 2.

[0033] Multiple electrical devices 3 are powered by radio waves of frequency F1 radiated from the leaky coaxial cable 2 when the changeover switch 43 is in the first connection state, and by radio waves of frequency F2 radiated from the leaky coaxial cable 2 when the changeover switch 43 is in the second connection state.

[0034] Attenuator 5A is provided at the end of the leaky coaxial cable 2, similar to attenuator 5 in the first embodiment. Attenuator 5A has a fixed resistance value for its termination resistor. This resistance value is, for example, 50Ω or 75Ω.

[0035] The electric field strength distribution around the leaky coaxial cable 2 changes as the frequency of the radio waves radiated from the leaky coaxial cable 2 changes. In this embodiment, the first power supply unit 41, the second power supply unit 42, the changeover switch 43, and the changeover control unit 44 of the high-frequency power supply device 4A function as an electric field strength distribution variable means 40 that varies the electric field strength distribution of the radio waves radiated from the leaky coaxial cable 2.

[0036] The electric field strength distribution variable means 40 changes the frequency of the radio waves radiated from the leaky coaxial cable 2 between a first frequency F1 and a second frequency F2. When switching from the first frequency F1 to the second frequency F2, it switches to the second frequency F2 at a timing 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 timing corresponding to the period of the second frequency F2.

[0037] Figure 5(b) is a graph showing an example of the change in output voltage from the high-frequency power supply 4A when the frequency of the radio waves radiated from the leaky coaxial cable 2 is switched from a first frequency F1 to a second frequency F2, and Figure 5(c) is a graph showing an example of the change in output voltage from the high-frequency power supply 4A when the frequency of the radio waves radiated from the leaky coaxial cable 2 is switched from a second frequency F2 to a first frequency F1. The horizontal axis of the graphs in Figures 5(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 the sake of clarity, the difference between the period of the first frequency F1 and the period of the second frequency F2 is exaggerated.

[0038] The switching control unit 44 switches the changeover switch 43 when the output voltage of the high-frequency power supply unit 4A crosses zero. The length of the period P1 during which the high-frequency power supply unit 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 (for example, 1 × 10⁻¹⁰). 3 (times). Also, the length of the period P2 during which the high-frequency power supply 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 (for example, 1 × 10⁻¹⁰). 3 This is double the frequency. By switching in this manner, the rectifier circuit 32 and the DC-DC converter 33 in the electrical device 3 operate smoothly when the frequency of the radio waves radiated from the leaky coaxial cable 2 changes.

[0039] Figure 6(a) is a graph showing the electric field strength distribution when the termination resistance of the leaky coaxial cable 2 is 50Ω and the frequency of the radio waves radiated from the leaky coaxial cable is 916.7MHz. Figure 6(b) is a graph showing the electric field strength distribution when the termination resistance of the leaky coaxial cable 2 is 50Ω and the frequency of the radio waves radiated from the leaky coaxial cable 2 is 920.9MHz. In Figures 6(a) and (b), similar to Figures 4(a) and (b) referenced in the first embodiment, the electric field strength distribution is shown using shades of gray, with darker colors indicating stronger electric field strengths.

[0040] As shown in Figures 6(a) and 6(b), the frequency of the radio waves radiated from the leaky coaxial cable 2 changes, which alters the electric field strength distribution around the leaky coaxial cable 2, and consequently, the position of the null point shifts. This provides the same effect as in the first embodiment.

[0041] [Third Embodiment] 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 termination resistor of the leaky coaxial cable 2 and by changing the frequency of the radio waves radiated from the leaky coaxial cable 2.

[0042] Figure 7 is a schematic diagram showing an example of the configuration of a wireless power supply system 1B according to a third embodiment of the present invention. The wireless power supply system 1B comprises a leaky coaxial cable 2, a plurality of electrical devices 3, a high-frequency power supply device 4A similar to that of the second embodiment, and an attenuator 5 similar to that of the first embodiment.

[0043] In the third embodiment, the following modes are sequentially switched: Operation Mode 1, where the changeover switch 43 of the high-frequency power supply 4A is in the first connection state and the changeover switch 53 of the attenuator 5 is in the first connection state; Operation Mode 2, where the changeover switch 43 of the high-frequency power supply 4A is in the second connection state and the changeover switch 53 of the attenuator 5 is in the first connection state; Operation Mode 3, where the changeover switch 43 of the high-frequency power supply 4A is in the second connection state and the changeover switch 53 of the attenuator 5 is in the second connection state; and Operation Mode 4, where the changeover switch 43 of the high-frequency power supply 4A is in the first connection state and the changeover 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 between these operation modes 1 to 4. Examples of electric field strength distributions in operation modes 1 to 4 are shown in Figures 8(a) to 9(d) and Figures 9(a) to 9(d).

[0044] Figures 8(a) to 8(d) are graphs showing the electric field strength distribution for each of the operating modes 1 to 4, when the resistance value R1 of the first termination resistor 51 of the attenuator 5 is 50Ω, the resistance value R2 of the second termination resistor 52 is 75Ω, and the first frequency F1 of the high-frequency power supply unit 4A is 916.7MHz and the second frequency F2 is 920.9MHz.

[0045] Figures 9(a) to (d) are graphs showing the electric field strength distribution for each of the operating modes 1 to 4, when the resistance value R1 of the first termination resistor 51 of the attenuator 5 is 50Ω, the resistance value R2 of the second termination resistor 52 is 0Ω, and the first frequency F1 of the high-frequency power supply unit 4A is 916.7MHz and the second frequency F2 is 920.9MHz.

[0046] As shown in these graphs, by combining the change in the resistance value of the termination resistor of the leaky coaxial cable 2 with the change in the frequency of the radio waves radiated from the leaky coaxial cable 2, the electric field strength distribution can be changed more significantly than in the first and second embodiments. This makes it possible to more reliably suppress the occurrence of situations where sufficient power cannot be supplied to the electrical device 3.

[0047] (Summary of the embodiments) Next, the technical concept understood from the embodiments described above will be described using the reference numerals and other symbols from the embodiments. However, the reference numerals in the following description are not limited to the components in the claims that are specifically shown in the embodiments.

[0048] [1] A wireless power supply system (1,1A,1B) that supplies power to an electrical device (3) by radio waves radiated from a leaky coaxial cable (2), comprising a variable electric field strength distribution means (40,50) for varying the electric field strength distribution of the radio waves radiated from the leaky coaxial cable (2), wherein the position of the null point generated by interference of the radio waves moves by changing the electric field strength distribution using the variable electric field strength distribution means (40,50).

[0049] [2] The wireless power supply system (1,1A) described in [1] above, wherein the electric field strength distribution variable means (50) makes the electric field strength distribution variable by changing the resistance value of the termination resistor of the leaky coaxial cable (2).

[0050] [3] The electric field strength distribution variable means (40) is configured to vary the electric field strength distribution by changing the frequency of the radio waves radiated from the leaky coaxial cable (2), as described in [1] above (1,1B).

[0051] [4] The wireless power supply system (1,1B) described in [1] above, wherein the electric field strength distribution variable means (40) varies the electric field strength distribution by changing the resistance value of the termination resistor of the leaky coaxial cable (2) and changing the frequency of the radio waves radiated from the leaky coaxial cable (2).

[0052] [5] The electric field strength distribution variable means (40) changes the frequency of the radio waves radiated from the leaky coaxial cable (2) between a first frequency (F1) and a second frequency (F2) different from the first frequency (F1), and when switching from the first frequency (F1) to the second frequency (F2), switches to the second frequency (F2) at a timing corresponding to the period of the first frequency (F1), and when switching from the second frequency (F2) to the first frequency (F1), switches to the first frequency (F1) at a timing corresponding to the period of the second frequency (F2), the wireless power supply system (1,1B) as described in [3] or [4] above.

[0053] Although the first and subsequent embodiments of the present invention have been described above, these embodiments do not limit the invention as defined in the claims. Furthermore, it should be noted that not all combinations of features described in the embodiments are necessarily essential for solving the problem of the invention.

[0054] Furthermore, the present invention can be implemented with appropriate modifications without departing from its spirit. For example, although the embodiment described the case where the electrical device 3 is a sensor device, the wireless power supply system may be configured to wirelessly supply power to electrical devices other than sensor devices. Examples of electrical devices other than sensor devices include RFID (Radio Frequency Identification) tags. [Explanation of Symbols]

[0055] 1, 1A, 1B... Wireless power supply system 2... Leaky coaxial cable 3…Electrical devices 4,4A…High-frequency power supply devices 5, 5A... Attenuator 40, 50... Variable electric field strength distribution means

Claims

1. A wireless power supply system that supplies power to electrical devices using radio waves radiated from a leaky coaxial cable, The system includes an electric field strength distribution variable means for varying the electric field strength distribution of the radio waves radiated from the leaky coaxial cable, By changing the electric field strength distribution using the electric field strength distribution variable means, the position of the null point generated by the interference of the radio waves moves. Wireless power supply system.

2. The electric field strength distribution variable means varies the electric field strength distribution by changing the resistance value of the termination resistance of the leaky coaxial cable. The wireless power supply system according to claim 1.

3. The electric field strength distribution variable means varies the electric field strength distribution by changing the frequency of the radio waves radiated from the leaky coaxial cable. The wireless power supply system according to claim 1.

4. The electric field strength distribution variable means varies the electric field strength distribution by changing the resistance value of the termination resistor of the leaky coaxial cable and by changing the frequency of the radio waves radiated from the leaky coaxial cable. The wireless power supply system according to claim 1.

5. The electric field strength distribution variable means changes the frequency of the radio waves radiated from the leaky coaxial cable between a first frequency and a second frequency different from the first frequency, switches to the second frequency at a timing corresponding to the period of the first frequency when switching from the first frequency, and switches to the first frequency at a timing corresponding to the period of the second frequency when switching from the second frequency to the first frequency. The wireless power supply system according to claim 3 or 4.

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