Rectenna device and system

Abstract

To provide a rectenna device that allows for easy impedance matching between an antenna and a rectifier circuit.SOLUTION: A rectenna device 100 includes an antenna unit 10 that has a loop antenna 11 consisting of a long side and a short side, and receives microwaves, a rectifier circuit 51 that converts high-frequency signals from the antenna unit 10 into DC power, a harmonic reflection circuit 53 that returns harmonics generated from the rectifier circuit 51 to the rectifier circuit 51, and a matching circuit 52 that performs impedance matching between the antenna unit 10 and the rectifier circuit 51 and is electrically connected to the antenna unit 10 via a feeding point 12 located on the long side.SELECTED DRAWING: Figure 8

Description

[Technical Field]

[0001] The present disclosure relates to a rectenna device using a loop antenna. [Background technology]

[0002] Rectenna devices that integrate a power receiving antenna and a rectifier circuit have been known for some time. For example, Non-Patent Document 1 discloses a rectenna device that has an antenna portion and a rectifier. The rectifier of the rectenna device in Non-Patent Document 1 includes, in addition to a matching circuit, a harmonic reflection circuit that reflects harmonics generated from the diode and returns them to the diode.

[0003] Furthermore, Non-Patent Document 2 shows an example of a rectenna device using a high-impedance folded dipole antenna. In Non-Patent Document 2, a low-pass filter is used to match the bridge diode to the antenna impedance, so that it is open at high frequencies.

[0004] Patent Document 1 also discloses a configuration in which a folded dipole antenna is formed on one side of a substrate, and a line that operates as an open stub is placed on the other side of the substrate at a position opposite the folded dipole antenna, thereby functioning as a DC cut. Patent Document 1 also discloses a configuration in which an inductor and a capacitive stub are inserted in the feed line to function as a reflection circuit for the third harmonic. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2021-118536 [Non-patent literature]

[0006] [Non-Patent Document 1] High Efficient Bridge Rectifiers in 100 MHz and 2.4 GHz bands, Motoki ITO, Kenji ITOH, et al., 2014 IEEE wireless Power Transfer Conference, p64‐67 [Non-patent document 2] Study on a 2.4GHz band high efficiency rectenna using direct matching, Atsuya Hirono, Kenji Ito et al., IEICE Technical Report, vol.119, no. 135, WPT2019-22, pp.1-6 Summary of the Invention [Problem to be solved by the invention]

[0007] In the above-described configuration, the rectifier circuit, the matching circuit that performs impedance matching between the antenna and the rectifier circuit, and the harmonic reflection circuit influence each other, making it difficult to optimize the circuits. In particular, it is not clear how to adjust the relationship between the antenna and the matching circuit, and a configuration that makes it easy to optimize the impedance matching between the antenna and the rectifier circuit has been desired.

[0008] In order to solve the above problem, an object of the present disclosure is to provide a rectenna device that can easily perform impedance matching between an antenna and a rectifier circuit. [Means for solving the problem]

[0009] In order to achieve the above object, the rectenna device of the present disclosure employs a technique in which the antenna section and the matching section are connected via a feed point located on the long side of the loop antenna.

[0010] Specifically, the rectenna device of the present disclosure includes: an antenna unit having a loop antenna with long and short sides for receiving microwaves; a rectifier unit that converts a high-frequency signal from the antenna unit into DC power; a harmonic reflection unit that returns the harmonics generated from the rectification unit to the rectification unit; a matching unit that performs impedance matching between the antenna unit and the rectifier unit and is electrically connected to the antenna unit via a feeding point located on the long side; Equipped with.

[0011] This allows the impedance to be easily adjusted according to the position of the feed point on the long side, and allows for easy direct matching to the conjugate impedance of the circuit according to the matching section.

[0012] Further, the loop antenna has a long side having a length of 1 / 2 to 2 / 3 wavelength at the center frequency, and a short side having a length of 1 / 6 to 1 / 4 wavelength at the center frequency, The feed point may be located near the center of the long side.

[0013] This makes it possible to provide an antenna with a wide usable frequency band. Also, by feeding power from near the center of the long side, it becomes possible to feed power with high impedance.

[0014] The matching section, the harmonic reflection section, the connection section, and the rectification section may be configured with balanced lines.

[0015] By configuring the transmission line in this way, it is possible to reduce the influence of the substrate that constitutes the line and to create a low-loss circuit, compared to a microstrip line that requires a ground plane.

[0016] The rectifier unit is a balanced rectifier circuit in which diodes with reversed polarity are arranged in parallel, The harmonic reflection section may be a series resonance type harmonic reflection circuit that resonates at a frequency three times the frequency of the fundamental wave and has an impedance of zero.

[0017] This allows for efficient power conversion while suppressing triple harmonic waves.

[0018] The present invention may also include a substrate on which the loop antenna is arranged on one side and the matching section, the harmonic reflection section, the rectification section, the connection section, and an open-end pattern connected between the matching section and the antenna section, extending parallel to the loop antenna, and having a length of 1 / 4 wavelength at the center frequency are arranged on the other side.

[0019] This allows the antenna section and the circuit section, which are located on opposite sides of the rectenna substrate, to be electrically connected without using a via hole or the like for the fundamental wave.

[0020] The antenna may also include a metallic reflector that faces the other surface of the substrate and is positioned ¼ wavelength away from the other surface of the substrate at the center frequency.

[0021] This increases the antenna gain in the front direction of the antenna unit, enabling more efficient power transmission.

[0022] The reflector may also be a metal foil, a conductive metal film, or a metal plate formed on the side opposite the antenna of a spacer that is disposed between the substrate and the reflector and has a thickness of 1 / 4 wavelength at the center frequency.

[0023] This simplifies the overall structure of the rectenna device and reduces its weight, making it easier to handle, and also improving the productivity of the rectenna device.

[0024] The present disclosure also provides: A plurality of the above-mentioned rectenna devices are provided, the plurality of rectenna devices are arranged so that the spacing between the loop antennas is equal to or less than 1 / 2 wavelength at the center frequency; DC outputs from the rectification units of the plurality of rectenna devices are connected in parallel or in series. Provide a system.

[0025] This makes it possible to prevent the area required for placing the rectenna device 100 from increasing, while configuring the DC output power supply circuit to switch between series and parallel connections depending on the situation, thereby increasing the received power and voltage in the same area.

[0026] The present disclosure also provides: A plurality of the above rectenna devices, two transmitting antennas whose polarization planes are orthogonal to each other and which transmit at any time interval; a part of the plurality of rectenna devices is arranged so that its polarization matches with that of one of the two transmitting antennas, and another part of the plurality of rectenna devices is arranged so that its polarization matches with that of the other of the two transmitting antennas; Provide a system.

[0027] This allows for low power consumption as a system that does not transmit unnecessary power.

[0028] The above disclosures can be combined as much as possible. [Effects of the Invention]

[0029] According to the rectenna device of the present disclosure, impedance matching between the antenna and the rectifier circuit can be easily performed. [Brief explanation of the drawings]

[0030] [Figure 1] FIG. 1 is a diagram illustrating an overview of a rectenna device. [Figure 2] These are plan and perspective views of each side of the rectenna substrate, where (A) is a plan view seen from the loop antenna side, (B) is a plan view seen from the feed pattern side, and (C) is a perspective view with the patterns on both sides superimposed. [Figure 3] FIG. 2 is a circuit diagram illustrating a rectifier circuit. [Figure 4] FIG. 2 is a block diagram illustrating the configuration of a circuit unit. [Figure 5]1A and 1B are diagrams illustrating the lines that make up the circuit section, where (A) shows the cross section and electric field distribution of a microstrip line, which is an unbalanced line, and (B) shows the cross section and electric field distribution of a differential line, which is an example of a balanced line that makes up the rectenna of the present invention. [Figure 6] 1A and 1B are diagrams illustrating examples of patterns of the circuit parts of a harmonic reflection circuit and a matching circuit, and various equivalent circuits; (A) shows examples of patterns of the harmonic reflection circuit and the matching circuit part; (B) shows (A) as a distributed parameter equivalent circuit; and (C) shows (A) as a lumped parameter equivalent circuit. [Figure 7] 10 is a graph illustrating frequency characteristics of impedance of a harmonic reflection circuit. [Figure 8] FIG. 2 is a diagram illustrating the position of a feeding point in a loop antenna. [Figure 9] 1A and 1B are diagrams illustrating the gain of the loop antenna section when there is no reflector, where (A) is a diagram showing the antenna characteristics in three dimensions, and (B) is a diagram showing the antenna characteristics as a central axis cross section. [Figure 10] 10 is a diagram illustrating that the open-end pattern is formed in parallel with the ring antenna pattern. FIG. [Figure 11] These figures show the relationship between the rectenna substrate and the reflector, where (A) shows that a plate-shaped reflector is placed opposite the rectenna substrate, and (B) shows the structure in which a metal foil or the like is attached to the surface of the spacer facing the rectenna substrate. [Figure 12] 1A and 1B are diagrams illustrating the antenna gain achieved by providing a reflector, where (A) is a diagram showing the antenna characteristics in three dimensions, and (B) is a diagram showing the antenna characteristics as a central axis cross section. [Figure 13] This is a diagram explaining how multiple rectenna substrates are arranged and DC outputs are connected in parallel or in series. [Figure 14] FIG. 10 is a diagram illustrating the independent supply of power to a rectenna device whose polarization matches that of a transmitting antenna. DETAILED DESCRIPTION OF THE INVENTION

[0031] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. Note that the present disclosure is not limited to the embodiments shown below. These implementation examples are merely illustrative, and the present disclosure can be implemented in various forms with various modifications and improvements based on the knowledge of those skilled in the art. Note that components with the same reference numerals in this specification and drawings indicate the same components.

[0032] (First embodiment) [Rectenna Device Overview] A rectenna device 100 according to a first embodiment of the present disclosure will be described with reference to Figures 1 to 9. The rectenna device 100 is a power-receiving rectenna (rectenna: antenna + rectifier) ​​that receives radio waves from an external transmitting antenna, converts the radio waves into DC power, and supplies it to external equipment. Figure 1 is a diagram illustrating an overview of the rectenna device 100. The rectenna device 100 mainly comprises an antenna section 10 formed on a rectenna substrate 20, a reflector 30, and a spacer 40.

[0033] Rectenna substrate 20 is a thin printed circuit board or film substrate formed in a substantially square shape. For example, rectenna substrate 20 may be made of a resin film such as PET (Poly Ethylene Terephthalate).

[0034] The antenna unit 10 is configured to receive radio waves from an external transmitting antenna. Specifically, the antenna unit 10 is configured to be able to receive microwaves of frequencies of 2.4 GHz / 5.7 GHz or higher. However, the scope of the present disclosure is not limited thereto, and for example, the antenna unit 10 may be configured to be able to receive microwaves of other frequencies, such as 920 MHz.

[0035] The antenna unit 10 also includes a loop antenna (ring antenna) 11. The loop antenna 11 is formed as a pattern extending in a predetermined direction at approximately the center of the surface of the rectenna substrate 20. For example, the loop antenna 11 may be formed as a copper pattern or a pattern printed with conductive ink or the like.

[0036] The reflector 30 is a plate-like member disposed opposite the rectenna substrate 20 via the spacer 40. For example, the reflector 30 is a metal plate. Alternatively, the reflector 30 is attached to the surface of the spacer 40 facing the rectenna substrate 20 and is formed by applying metal foil or conductive ink, or by vapor deposition or other methods, or is a conductive metal film formed by other methods. The spacer 40 is made of a foam material such as expanded polystyrene or expanded polypropylene. The reflector 30 and the spacer 40 will be described in detail in the second embodiment.

[0037] Next, the positional relationship of each component in various plan views of the rectenna substrate 20 will be described with reference to Figure 2. Figure 2 shows plan views and perspective views of each surface of the rectenna substrate 20. Figure 2(A) is a plan view of the rectenna substrate 20 seen from the loop antenna side, Figure 2(B) is a plan view of the rectenna substrate 20 seen from the feed pattern side, and Figure 2(C) is a perspective view in which the patterns on both surfaces of the rectenna substrate 20 are superimposed.

[0038] As described above, as shown in Figure 2(A), the antenna section 10 extends in the vertical direction of the figure at approximately the center of the front surface of the rectenna substrate 20. As shown in Figure 2(B), the circuit section 50 and associated components are provided in approximately the center of the back surface of the rectenna substrate 20, extending in the vertical direction of the figure. A rectifier circuit 51 and other electronic components are mounted on the circuit section 50. As shown in Figure 2(C), the antenna section 10 and the circuit section 50 are provided on the front and back surfaces of the rectenna substrate 20 so as to be approximately opposite each other.

[0039] [Electrical configuration] Next, the electrical configuration of the circuit unit 50 will be described with reference to FIGS. 3 to 7. First, the rectifier circuit 51, which is one of the components of the circuit unit 50, will be described with reference to FIG. 3. The rectifier circuit 51 functions as a "rectifier unit." In this embodiment, the rectifier circuit 51 is configured on an IC (Integrated Circuit) chip. A high-frequency signal from the antenna unit 10 is input from the left side of the diagram (RF (Radio Frequency) input). Power converted to direct current by the rectifier circuit 51 is output from the right side of the diagram (DC (Direct Current) output). In the following description, the frequency of the fundamental wave from the antenna unit 10 is represented as f0, and the frequency of the n-th harmonic (harmonic) generated from the rectifier circuit 51 is represented as nf0. As shown in the diagram, the rectifier circuit 51 includes a bridge diode 51A, a pair of DC-blocking capacitors 51B for blocking direct current, and a smoothing capacitor 51C.

[0040] The bridge diode 51A is provided to rectify a high-frequency signal from the antenna unit 10 into direct current. The rectifier circuit 51 using the bridge diode 51A is a balanced rectifier circuit in which diodes with reversed polarity are arranged in parallel. The scope of the present disclosure is not limited to rectification using the bridge diode 51A. In other words, instead of the bridge diode 51A, any balanced rectifier circuit that can be regarded as diodes with reversed polarity arranged in parallel in terms of high frequency may be used. For example, instead of the bridge diode 51A, a voltage doubler diode rectifier circuit may be used.

[0041] A pair of DC blocking capacitors 51B are inserted in series with the input terminals of the bridge diode 51A. This prevents the current rectified by the bridge diode 51A from being transmitted to the antenna side, increasing the flexibility of the input circuit configuration, optimizing the matching between the antenna unit 10 and the rectifier circuit 51 and enabling efficient conversion to DC power. A smoothing capacitor 51C is connected between the output terminals of the bridge diode 51A. This prevents high-frequency signals from leaking to the DC output side, removes ripples, etc., and maintains a constant output voltage.

[0042] In this embodiment, the rectifier circuit, consisting of the bridge diode 51A, DC-blocking capacitor 51B, and smoothing capacitor 51C, is formed on an IC chip with a size sufficiently smaller than the wavelength used. This allows for a well-balanced circuit configuration with few parasitic components (resistance, inductance, capacitance, etc.). Even-order harmonic (nf0) components (double, quadruple, etc.) are canceled by the reversed bridge diode 51A, so only odd-order components are generated. Therefore, when providing a circuit to reflect harmonics to improve power supply efficiency, it is sufficient to provide a circuit that reflects odd-order harmonics.

[0043] FIG. 4 is a block diagram illustrating the configuration of the circuit unit 50. A high-frequency signal from the antenna unit 10 is input from the left side of the diagram (RF (Radio Frequency) input). Power converted to direct current by the circuit unit 50 is output from the right side of the diagram (DC (Direct Current) output). The circuit unit 50 includes a matching circuit 52, a harmonic reflection circuit 53, a pair of phase adjustment lines 54, a rectifier circuit 51, and an external smoothing capacitor 55, and these components are arranged in this order from the input side to the output side. The matching circuit 52 and the antenna unit 10 are connected by a power feed line.

[0044] Here, referring to FIG. 5, the transmission lines constituting the circuit unit 50 will be described. FIG. 5(A) shows a microstrip line, which is an example of an unbalanced line, as a comparative example, and FIG. 5(B) shows a differential line, along with its electric field distribution, as an example of a balanced line constituting the circuit unit 50 according to this embodiment. In this embodiment, the circuit unit 50 (antenna unit 10, matching circuit 52, harmonic reflection circuit 53, and phase adjustment line 54) is configured with balanced lines without a ground plane (FIG. 5(B)). Specifically, the matching circuit 52, harmonic reflection circuit 53, phase adjustment line 54, and rectifier circuit 51 are configured with balanced lines. This transmission line configuration reduces the influence of the substrate constituting the line, resulting in a low-loss circuit, compared to a microstrip line (see FIG. 5(A)) that requires a ground plane. Alternatively, a film structure can be used in which a conductive pattern is formed on a flexible substrate or a PET (Poly Ethylene Terephthalate) film. Furthermore, when connecting circuit unit 50 to a loop antenna or the like, a balun, which is required when using an unbalanced line such as a coaxial line, is not required, which simplifies the circuit and is therefore suitable for broadening the bandwidth and reducing loss. This also improves the productivity of rectenna device 100.

[0045] Specifically, the circuit section 50 is represented by a pattern example as shown in FIG. 6(A), and when shown as an equivalent circuit, it is represented by a distributed parameter equivalent circuit in FIG. 6(B) and a lumped parameter equivalent circuit in FIG. 6(C).

[0046] Returning to Fig. 4, the matching circuit 52 is configured to correct the impedance matching between the antenna unit 10 and the harmonic reflection circuit 53 and the rectifier circuit 51 for the fundamental wave (f0) component from the antenna unit 10, and to make adjustments so that power is sent efficiently to the rectifier circuit 51. The matching circuit 52 functions as a "matching unit."

[0047] The harmonic reflection circuit 53 is configured to pass the fundamental wave (f0) but reflect the third harmonic wave (3f0), which has a large conversion energy and leaks to the antenna among the harmonic components generated in the rectifier circuit 51, and return it to the rectifier circuit 51. The harmonic reflection circuit 53 functions as a "harmonic reflector." Specifically, as shown in the impedance (Z) frequency characteristic graph in FIG. 7, the harmonic reflection circuit 53 is configured so that the impedance (Z) becomes nearly 0 Ω (short) at the resonant frequency of the third harmonic wave (3f0), resulting in total reflection (a series-resonant third harmonic reflection circuit), but the fundamental wave (f0) can pass with almost no loss. Therefore, by placing a line approximately 1 / 4 wavelength long for the third harmonic wave as a phase adjustment line (54) between the diode (rectifier circuit 51) and the third harmonic wave, the diode end (ZD) has infinite impedance (open) without interfering with the input of the fundamental wave to the diode, allowing it to be efficiently converted into power within the diode. However, the scope of the present disclosure is not limited to using a series resonant third harmonic wave reflection circuit as a harmonic reflection circuit, and other circuits that reflect third harmonic waves can also be used.

[0048] 7, the impedance of the double wave (2f0) is greater than 0Ω, but as described above, this is canceled out by the reverse bridge diode 51A, so the harmonics that are actually generated are only odd-order components. Also, since filtering by the harmonic reflection circuit 53 as described above has almost no effect on the fundamental wave (f0), optimization is possible independently of the matching circuit 52 for the fundamental wave.

[0049] In the example of Fig. 4, the pair of phase adjustment lines 54 are provided between the harmonic reflection circuit 53 and the rectifier circuit 51. The pair of phase adjustment lines 54 are configured to adjust the phase of the signal depending on the length of the transmission line. The phase adjustment lines 54 function as "connection parts."

[0050] The external smoothing capacitor 55 has a larger capacity than the smoothing capacitor 51C included in the rectifier circuit 51. By providing the external smoothing capacitor 55, the output voltage can be more suitably kept constant.

[0051] [Antenna configuration] Next, the configuration of the antenna unit 10 will be described in detail with reference to Fig. 8. The loop antenna 11 of the antenna unit 10 has a pair of long sides extending in the vertical direction of the figure and a pair of short sides extending in the horizontal direction of the figure.

[0052] The pair of long sides of loop antenna 11 have a length of 1 / 2 to 2 / 3 wavelength at the center frequency, and the pair of short sides have a length of 1 / 6 to 1 / 4 wavelength at the center frequency. Feed points 12 are provided at approximately symmetrical positions near the centers of the pair of long sides in the up-down direction. Feed points 12 are connected to circuit section 50 by lines (see FIG. 6).

[0053] As shown in the figure, circuit section 50 is positioned on the front and back of rectenna substrate 20 so that it can be connected to feed point 12 with the shortest line length. In this embodiment, the antenna impedance can be adjusted by adjusting the position of symmetrical feed point 12, which is slightly offset from near the center of the pair of long sides in the vertical direction, and the position of circuit section 50 is also determined according to the position of the feed point.

[0054] As described above, the rectenna device 100 an antenna unit 10 having a loop antenna 11 with long and short sides for receiving microwaves; a rectifier circuit 51 that converts a high-frequency signal from the antenna unit 10 into DC power; a harmonic reflection circuit 53 that returns harmonics generated from the rectifier circuit 51 to the rectifier circuit 51; a matching circuit 52 that performs impedance matching between the antenna unit 10 and the rectifier circuit 51 and is electrically connected to the antenna unit 10 via a feeding point 12 located on the long side; Equipped with.

[0055] The loop antenna 11 configured as described above can be considered a type of antenna consisting of two symmetrically connected loop antennas with a wavelength of λ, and has a wide usable frequency band. Furthermore, the impedance can be easily adjusted depending on the position of the feed point 12 on the pair of long sides. For example, in this embodiment, feeding power to the circuit unit 50 from near the center of the pair of long sides enables high-impedance power supply. This method, combined with the matching circuit 52, allows for easy direct matching to the conjugate impedance of the circuit unit 50. In other words, this embodiment provides a rectenna structure that facilitates both reflection of harmonics and optimization of matching between the rectifier circuit and the antenna, enabling highly efficient operation, particularly in high-frequency configurations.

[0056] Furthermore, the polarization plane of the antenna unit 10 becomes linearly polarized in the direction shown in Fig. 8, resulting in a high orthogonal polarization rate. Fig. 9(A) is a diagram showing the directivity of the antenna unit 10 in three dimensions. Fig. 9(B) is a diagram showing the antenna gain of the fundamental wave (f0) and the antenna gain of the third harmonic wave (3f0). As shown in Fig. 9(B), characteristics that are nearly uniform and omnidirectional are obtained except for null points in a plane perpendicular to the front direction of the antenna.

[0057] 9(B), the antenna gain of the third harmonic wave (3f0) is kept extremely low due to the effect of harmonic reflection circuit 53, and it can be seen that the third harmonic wave is efficiently reflected toward rectifier circuit 51. In this way, this embodiment can provide a highly efficient rectenna structure that can efficiently convert the third harmonic wave into electric power.

[0058] In this embodiment, the rectenna device 100 is configured symmetrically from front to back without using a ground, so radio waves from either the front or rear of the rectenna device 100 can be converted into DC power.

[0059] Next, the structure of feed point 12 of antenna section 10 will be described with reference to Fig. 10. Fig. 10 is a diagram illustrating that circuit section 50, feed point 12, and open-end pattern 56 are formed on the back surface of rectenna substrate 20.

[0060] In this embodiment, an open-end pattern 56 having a length of approximately 1 / 4 wavelength is formed on the back surface of the rectenna substrate 20 parallel to the ring antenna pattern. One end of the open-end pattern 56 is open, and the other end forms the feed point 12 to the circuit section 50. At the open end of the open-end pattern 56, the voltage is always maximum at high frequencies and the current is zero, creating a boundary condition. At a position approximately 1 / 4 wavelength away from the open end, the impedance between the open end and the ring pattern on the surface is zero, which is equivalent to being connected to the ring pattern on the surface at the frequency of the fundamental wave f0. Therefore, the high frequency received by the ring antenna is transmitted to the circuit section 50 on the back surface of the rectenna substrate 20 without the need for a through-hole or the like.

[0061] In this way, the rectenna device 100 The rectenna substrate 20 has a loop antenna 11 arranged on one side, and a matching circuit 52, a harmonic reflection circuit 53, a rectifier circuit 51, a phase adjustment line 54, and an open-end pattern 56 connected between the matching circuit 52 and the antenna section 10, extending parallel to the loop antenna 11, and having a length of 1 / 4 wavelength at the center frequency arranged on the other side.

[0062] In this embodiment, the provision of an open-end pattern 56 having a length of approximately ¼ wavelength allows the antenna section 10 and circuit section 50, located on opposite sides of the rectenna substrate 20, to be electrically connected without using via holes or other devices for the fundamental wave (f0). This allows the DC output line 57 to be easily routed from the circuit section 50, located near the center of the loop antenna 11, beyond the antenna ring (below the figure) without using through-holes or other devices. Furthermore, the loop antenna 11 of this invention is formed with short and long sides that are symmetrical vertically and horizontally, and the impedance at the center of the short side of the loop antenna 11 for the fundamental wave (f0) is 0Ω. Therefore, even if a metal pattern such as a bias line passes through the back surface of the rectenna substrate 20 near the center of the short side of the loop antenna 11, the antenna characteristics are not affected. Therefore, even when the DC outputs of multiple rectenna devices 100 are connected in series or in parallel, they can be connected simply by forming a pattern without using through-holes. When circuits are formed on a film substrate using conductive ink or other devices, roll-to-roll mass production using offset printing is possible.

[0063] (Second embodiment) A rectenna device 100 according to a second embodiment of the present disclosure will be described with reference to Figures 11 and 12. Figure 11 is a diagram illustrating that the rectenna substrate 20 faces the reflector 30 via a spacer 40. Note that the rectenna substrate 20 and the reflector 30 are not connected.

[0064] As shown in FIG. 11A, the reflector 30 is disposed parallel to the rectenna substrate 20 and approximately a quarter wavelength away from it. As described above, the reflector 30 is, for example, a metal plate. The area of ​​the reflector 30 is larger than that of the antenna unit 10. This allows the reflector 30 to function as a reflector, and the antenna gain behind the antenna unit 10 is reflected forward. As shown in FIG. 12, this increases the antenna gain in the front direction of the antenna unit 10, enabling more efficient power transmission. FIG. 12 is a diagram illustrating the antenna gain achieved by providing the reflector 30. FIG. 12A is a three-dimensional diagram illustrating the directivity of the antenna unit 10. FIG. 12B is a diagram illustrating the antenna gain of the fundamental wave (f0) and the antenna gain of the third harmonic wave (3f0). It can be seen that the antenna gain of the third harmonic wave (3f0) is kept very low due to the effect of the harmonic reflection circuit 53, and the third harmonic wave is efficiently reflected toward the rectifier circuit 51. Comparing FIG. 12(B) with FIG. 9(B), it can be seen that the antenna gain in the front direction of the antenna unit 10 is improved.

[0065] In particular, in the present disclosure, radio waves from the front direction of the antenna unit 10 can be efficiently converted into DC power, thereby improving the power conversion efficiency.

[0066] Returning to FIG. 11, FIG. 11(B) shows a structure for arranging the reflector 30, in which the reflector 30 is attached to the back surface of a spacer 40 made of foamed polystyrene, foamed polypropylene, or the like, with a thickness of approximately ¼ wavelength, and the rectenna substrate 20 is attached to the front surface. When the reflector 30 is attached to the back surface of the spacer 40 in this manner, the reflector 30 may be a metal foil or a metal film formed by applying conductive paint or by metal vapor deposition. This structure simplifies and reduces the overall structure of the rectenna device 100, making it easier to handle. This also improves the productivity of the rectenna device 100.

[0067] In this way, the rectenna device 100 A metallic reflector 30 is provided which faces the other surface of the rectenna substrate 20 and is positioned 1 / 4 wavelength away from the other surface of the substrate at the center frequency.

[0068] In addition, in the rectenna device 100, The reflector 30 is a metal foil, a conductive metal film, or a metal plate formed on the side opposite the antenna of a spacer that is disposed between the rectenna substrate 20 and the reflector 30 and has a thickness of 1 / 4 wavelength at the center frequency.

[0069] (Third embodiment) As a third embodiment of the present disclosure, a configuration in which multiple rectenna substrates 20 are arranged will be described with reference to FIG. 13. FIG. 13(A) shows a case in which DC outputs are connected in series, and FIG. 13(B) shows a case in which DC outputs are connected in parallel. Conventionally, when multiple rectenna devices are arranged, if there is gain in a direction 90 degrees from the front of the antenna, mutual interference occurs, destroying the antenna directivity. Therefore, to prevent any effect on the antenna directivity, it was necessary to separate the antennas by approximately one wavelength.

[0070] In contrast, as described above, the rectenna device 100 of the present disclosure has low gain at 90 degrees from the front, and the effect on directivity is small even when the antennas are spaced closer to 1 / 2 wavelength or less. Therefore, multiple rectenna devices 100 can be arranged with antenna spacing closer to 1 / 2 wavelength or less. This makes it possible to increase the received power and voltage in the same area while suppressing an increase in the area required to arrange the rectenna devices 100, by configuring the DC output power supply circuits with series connections, parallel connections, or other combinations depending on the situation.

[0071] It should be noted that the scope of the present disclosure is not limited to antenna spacing approaching 1 / 2 wavelength or less. For example, the antenna spacing may be one wavelength or less.

[0072] As noted above, the present disclosure provides: A plurality of rectenna devices 100 are provided, A plurality of rectenna devices are arranged so that the interval between the loop antennas is equal to or less than 1 / 2 wavelength at the center frequency. The DC outputs from the rectifier circuits 51 of the plurality of rectenna devices 100 are connected in parallel or in series. Provide a system.

[0073] (Fourth embodiment) As a fourth embodiment of the present disclosure, an independent supply of power to a rectenna device 100 whose polarization matches that of a transmitting antenna 200 will be described with reference to Fig. 14. Fig. 14 is a diagram illustrating an independent supply of power to a rectenna device 100 whose polarization matches that of a transmitting antenna 200.

[0074] As shown in Fig. 14, in this embodiment, two transmitting antennas 200A and 200B with mutually orthogonal polarizations are prepared as transmitting antennas. Transmission is performed from the two transmitting antennas 200 at any timing. Then, the rectenna substrates 20 corresponding to the antenna units 10A and 10B are arranged on each device to be wirelessly powered by the rectenna device 100 so that each of the antenna units 10A and 10B corresponds one-to-one to the polarization of one of the transmitting antennas. In the figure, there is one-to-one correspondence between the transmitting antenna 200A and the antenna unit 10B, and one-to-one correspondence between the transmitting antenna 200B and the antenna unit 10A.

[0075] The rectenna device 100 according to the present disclosure has a high orthogonal polarization ratio, so that a rectenna device 100 that matches the polarization direction of the transmitting antenna 200 can receive power with high efficiency, but a rectenna device 100 that is orthogonal to the polarization direction cannot receive power. By utilizing this characteristic and as described above, a system that selectively transmits power can be constructed by matching the transmitting antenna 200 and the rectenna device 100 one-to-one.

[0076] For example, if there are two types of sensors or rectenna devices within the radio wave area and the operating intervals for each are different, power can be supplied independently by arranging the two types of rectenna devices so that they are oriented perpendicular to each other. This allows for low power consumption as a system that does not transmit unnecessary power.

[0077] The scope of the present disclosure is not limited to a one-to-one correspondence between the transmitting antenna 200 and the rectenna device 100, but rather more rectenna devices 100 may be provided and a one-to-many correspondence between the transmitting antenna 200 and the rectenna device 100 may be achieved.

[0078] As noted above, the present disclosure provides: a plurality of rectenna devices 100; Two transmitting antennas 200 whose polarization planes are orthogonal to each other and which transmit at any time interval; Some of the multiple rectenna devices 100 are arranged so that their polarization matches with that of one of the two transmitting antennas 200, and other parts of the multiple rectenna devices 100 are arranged so that their polarization matches with that of the other of the two transmitting antennas 200. Provide a system. [Industrial Applicability]

[0079] The rectenna device disclosed herein is suitable for applications where it is necessary to efficiently supply power via radio waves, and can be used in situations where it is difficult to supply power via a wired connection within a room or device, or for applications where it is necessary to supply power to multiple sensors simultaneously when needed without the need for wiring or other construction work. [Explanation of symbols]

[0080] 10: Antenna section 11: Loop antenna 12: Power supply point 20, 20A, 20B: Rectenna board 30:Reflector 40: Spacer 50:Circuit section 51: Rectifier circuit 51A: Bridge diode 51B: DC cut capacitor 51C: Smoothing capacitor 52: Matching circuit 53: Harmonic reflection circuit 54: Phase adjustment line 55: External smoothing capacitor 56:1 / 4 wavelength open pattern 57: DC output line 100: Rectenna device 200A, 200B: Transmitting antenna

Claims

1. an antenna unit having a loop antenna with long and short sides for receiving microwaves; a rectifier unit that converts a high-frequency signal from the antenna unit into DC power; a harmonic reflection unit that returns the harmonics generated from the rectification unit to the rectification unit; a matching section that performs impedance matching between the antenna section and the rectifier section and is electrically connected to the antenna section via a feeding point located on the long side; Equipped with Rectenna device.

2. the loop antenna has a long side having a length of 1 / 2 to 2 / 3 wavelength at the center frequency and a short side having a length of 1 / 6 to 1 / 4 wavelength at the center frequency; The feed point is located near the center of the long side. The rectenna device of claim 1 .

3. the matching section, the harmonic reflection section, the connection section, and the rectification section are configured with balanced lines; The rectenna device of claim 1 .

4. the rectifier unit is a balanced rectifier circuit in which diodes with reversed polarity are arranged in parallel, the harmonic reflection unit is a series resonance type harmonic reflection circuit that resonates at a frequency three times the frequency of the fundamental wave and has an impedance of zero; The rectenna device of claim 1 .

5. a substrate on one side of which the loop antenna is disposed, and on the other side of which the matching section, the harmonic reflecting section, the rectifying section, the connecting section, and an open-end pattern connected between the matching section and the antenna section, extending parallel to the loop antenna, and having a length of ¼ wavelength at a center frequency, are disposed; The rectenna device of claim 1 .

6. a metal reflector located opposite the other surface of the substrate and spaced a quarter wavelength from the other surface of the substrate at a center frequency; The rectenna device according to claim 5 .

7. the reflector is a metal foil, a conductive metal film, or a metal plate formed on a surface of a spacer, which is disposed between the substrate and the reflector and has a thickness of a quarter wavelength at the center frequency, opposite to the antenna; The rectenna device according to claim 6 .

8. A plurality of rectenna devices according to any one of claims 1 to 7 are provided, the plurality of rectenna devices are arranged so that the spacing between the loop antennas is equal to or less than 1 / 2 wavelength at the center frequency; DC outputs from the rectification units of the plurality of rectenna devices are connected in parallel or in series. system.

9. a plurality of rectenna devices according to any one of claims 1 to 7; two transmitting antennas whose polarization planes are orthogonal to each other and which transmit at any time interval; a part of the plurality of rectenna devices is arranged so that its polarization matches with that of one of the two transmitting antennas, and another part of the plurality of rectenna devices is arranged so that its polarization matches with that of the other of the two transmitting antennas; system.

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