Radio wave reflection device and radio wave reflection system including same

Abstract

This radio wave reflection device comprises a plurality of radio wave reflective plates, each having a reflective surface for reflecting radio waves. The plurality of radio wave reflective plates are arranged adjacent to each other. The reflective surface of one radio wave reflective plate forms an angle θ with respect to the reflective surface of an adjacent radio wave reflective plate. The angle θ is greater than 0° and less than 90°. The plurality of radio wave reflective plates may be arranged so that the reflective surfaces follow a parabolic shape.

Description

Radio wave reflecting device and radio wave reflecting system including the same

[0001] The present invention relates to a radio wave reflecting device that reflects radio waves transmitted from a wave source, and a radio wave reflecting system including the same.

[0002] The fifth generation communication standard known as 5G is being introduced in the field of communications. 5G uses millimeter wave frequencies between 26 GHz and 29 GHz. 5G communications enable transmission over a wide bandwidth, achieving extremely high throughput.

[0003] Because millimeter wave frequency radio waves have a high tendency to travel in a straight line, radio waves emitted from base stations have difficulty reaching areas such as the back of a building. For this reason, radio wave reflectors, such as those described in Patent Document 1, are installed in areas where radio waves have difficulty reaching in order to change the direction of radio wave transmission.

[0004] Special table 2019-530387 publication

[0005] In order for a radio wave reflector to reflect radio waves uniformly, it is necessary for the radio wave to be incident without any directionality. For this reason, the radio wave reflector must be placed far enough away from the wave source. The higher the frequency of the radio wave and the larger the area of ​​the radio wave reflector, the longer the distance from the wave source. If the distance from the wave source is too long, there is a risk that the test equipment will not fit into the laboratory. There is also a risk that the actual equipment will not be able to be installed in the desired location.

[0006] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a radio wave reflecting device and a radio wave reflecting system including the same, which can reduce the distance from the wave source to the installation location.

[0007] A radio wave reflection device according to one embodiment of the present invention comprises a plurality of radio wave reflection plates each having a reflective surface that reflects radio waves, the plurality of radio wave reflection plates being arranged adjacent to each other, and the reflective surface of one of the radio wave reflection plates being arranged at an angle θ with respect to the reflective surface of an adjacent radio wave reflection plate, the angle θ being greater than 0° and less than 90°.

[0008] FIG. 1 is a schematic diagram of a radio wave reflecting device according to one embodiment of the present invention when viewed from the front. FIG. 2 is a schematic cross-sectional view of the radio wave reflecting device shown in FIG. 1 taken along line II-II. FIG. 3 is a plan view of a radio wave reflector (liquid crystal reflector) according to one embodiment of the present invention. FIG. 4 is a cross-sectional view of the liquid crystal reflector taken along line A-B shown in FIG. 3. FIG. 5 is a plan view of a unit cell constituting the liquid crystal reflector. FIG. 6 is a cross-sectional view of the unit cell taken along line C-D shown in FIG. 5. FIG. 6 is a schematic diagram showing that the propagation direction of scattered waves is changed by a liquid crystal reflector. FIG. 7 is a schematic diagram of a radio wave reflecting system according to one embodiment of the present invention. FIG. 7 is a schematic diagram of a radio wave reflecting system according to one embodiment of the present invention.

[0009] Hereinafter, embodiments of the present invention will be described with reference to the drawings. To clarify the description, the drawings may show the width, thickness, shape, etc. of each part more schematically than the actual embodiment, but these are merely examples and are not intended to limit the interpretation of the present invention. In this specification and each drawing, elements similar to those previously described with reference to the previous drawings are designated by the same reference numerals, and detailed descriptions may be omitted as appropriate.

[0010] <Radio wave reflecting device> Fig. 1 is a schematic diagram of a radio wave reflecting device 10 according to one embodiment of the present invention, as seen from the front. As shown in Fig. 1, the radio wave reflecting device 10 includes a plurality of radio wave reflecting plates 100, which are arranged adjacent to each other. The radio wave reflecting device 10 can include a control device that can adjust the reflection angle of the radio waves incident on each of the plurality of radio wave reflecting plates 100.

[0011] The radio wave reflecting device 10 has a total of nine radio wave reflecting plates 100 arranged symmetrically in the vertical and horizontal directions, three in the vertical and horizontal directions. The direction and number of the arranged radio wave reflecting plates 100 are not limited to this, and examples include two in the vertical direction and one in the horizontal direction for a total of two, two in the vertical direction and two in the horizontal direction for a total of four, or five in the vertical direction and five in the horizontal direction for a total of 25. The vertical and horizontal directions are used for the purpose of explanation and specifically refer to the directions shown in FIG. 1.

[0012] The radio wave reflecting device 10 has an array of radio wave reflecting plates 100 each having a square plate shape when viewed from the front. The shape of the radio wave reflecting plate 100 is not limited to this, and examples include a rectangular plate shape when viewed from the front and a circular plate shape when viewed from the front. In the case of a radio wave reflecting plate 100 having a square plate shape when viewed from the front, the size is set to, for example, 50 mm to 1000 mm on a side and 1 mm to 10 mm in thickness.

[0013] The radio wave reflecting device 10 has liquid crystal reflectors arranged as the radio wave reflector 100. The radio wave reflector 100 is not limited to this, and examples thereof include a metal plate, a metasurface reflector, and a liquid crystal reflector. Among these, a liquid crystal reflector is preferred from the viewpoint of arbitrarily controlling the reflection angle of the radio waves. The specific configuration of the liquid crystal reflector will be described later.

[0014] Fig. 2 is a schematic cross-sectional view taken along line II-II in Fig. 1. In the radio wave reflecting device 10, the radio wave reflecting plates 100 are arranged symmetrically in the vertical and horizontal directions, so the schematic cross-sectional view taken along line II'-II' in Fig. 1 is similar. As shown in Fig. 2, in a cross-sectional view, an angle θ is formed between the reflecting surface 100r of one radio wave reflecting plate 100 and the reflecting surface 100r of an adjacent radio wave reflecting plate 100. The angle θ is set to be greater than 0° and less than 90°.

[0015] The angle θ is fixed in the radio wave reflecting device 10. The radio wave reflecting device 10 may further include angle adjustment means between adjacent radio wave reflecting plates 100 so that the angle θ can be finely adjusted.

[0016] In the radio wave reflecting device 10, the radio wave reflectors 100 are arranged so that the centers of the reflecting surfaces 100r are along a spherical surface whose radius is the distance from the surface of the antenna 20 that emits radio waves to the reflecting surface 100r. The arrangement of the radio wave reflectors 100 is not limited to this, and examples include an arrangement in which the reflecting surface 100r is along a concave curved surface facing the antenna 20, or an arrangement in which the reflecting surface 100r is along a parabolic shape. Among these, an arrangement in which the reflecting surface 100r is along a parabolic shape is preferable from the viewpoint of converging the reflection direction of radio waves to one point.

[0017] <Liquid Crystal Reflector> Fig. 3 is a plan view of a liquid crystal reflector that is a radio wave reflector 100. Fig. 4 is a cross-sectional view corresponding to the line A-B shown in Fig. 3. In the following description, both Fig. 3 and Fig. 4 will be referred to as appropriate.

[0018] The liquid crystal reflector 100 includes at least one common electrode 102, at least one bias electrode 104, and a liquid crystal layer 106 disposed between these electrodes. As shown in FIG. 3 , the common electrodes 102 are arranged in the X-axis direction and the Y-axis direction, and the bias electrodes 104 are arranged in a matrix in the X-axis direction and the Y-axis direction so as to correspond to the common electrodes 102. Therefore, the liquid crystal reflector 100 has a structure in which a plurality of common electrodes 102 and a plurality of bias electrodes 104 are arranged to form a matrix. The X-axis direction and the Y-axis direction are used for the purpose of explanation and specifically refer to the directions shown in FIG. 3 . The X-axis direction and the Y-axis direction can also be interpreted as one direction and a direction intersecting one direction.

[0019] Adjacent common electrodes 102 are connected to each other by common wiring 108. Adjacent common electrodes 102 do not necessarily have to be connected to each other by common wiring 108; they may be connected only along the X-axis direction or only along the Y-axis direction. In contrast, adjacent bias electrodes 104 are arranged with a gap between them, so that they are physically separated. The common electrodes 102 are provided on the first substrate 132, and the bias electrodes 104 are provided on the second substrate 134. The liquid crystal reflector 100 is a device that scatters radio waves incident on the incident surface in a predetermined direction, with the first substrate 132 disposed on the incident surface side and the second substrate 134 disposed behind the incident surface. That is, the common electrode 102 is disposed on the incident surface, and the bias electrode 104 is disposed behind the common electrode 102 with the liquid crystal layer 106 sandwiched therebetween.

[0020] The liquid crystal reflector 100 has a structure in which the common electrode 102, the liquid crystal layer 106, and the bias electrode 104 are arranged so as to overlap in a planar view. The liquid crystal reflector 100 is arranged so that the surface of the first substrate 132 on which the common electrode 102 is provided faces the surface of the second substrate 134 on which the bias electrode 104 is provided, with the liquid crystal layer 106 disposed therebetween. The liquid crystal reflector 100 has a basic unit which is a stacked structure of a set of the common electrode 102, the liquid crystal layer 106, and the bias electrode 104 (which may also include the first substrate 132 and the second substrate 134). Hereinafter, this basic unit will be referred to as a unit cell 1000.

[0021] The second substrate 134 is provided with selection signal lines 110 extending in the X direction, bias signal lines 112 extending in the Y direction, and switching elements 116. The switching elements 116 are provided in one-to-one correspondence with the bias electrodes 104. The switching operations (on / off states) of the switching elements 116 are controlled by selection signals from the selection signal lines 110, and bias signals (bias voltages) are input from the bias signal lines 112. The bias signals are input individually to the bias electrodes 104 by the switching elements 116. That is, the bias signals are input individually to the bias electrodes 104 arranged in a matrix by the switching elements 116.

[0022] A first alignment film 114A is provided on the first substrate 132, and a second alignment film 114B is provided on the second substrate 134. The first alignment film 114A is provided to cover the common electrode 102, and the second alignment film 114B is provided to cover the bias electrode 104. The first alignment film 114A and the second alignment film 114B are provided to control the alignment state of the liquid crystal layer 106. The liquid crystal layer 106 includes elongated rod-shaped liquid crystal molecules. The initial alignment state of the liquid crystal molecules (the alignment state when no electric field is applied) is controlled by the first alignment film 114A and the second alignment film 114B.

[0023] The first alignment film 114A and the second alignment film 114B may be made of any material as long as they have the function of aligning the liquid crystal molecules, and may be made of either an organic or inorganic material, such as polyimide. The alignment direction may be horizontal, vertical, or tilted, but this embodiment shows the case where the film is a horizontal alignment film.

[0024] The orientation state of the liquid crystal molecules in the liquid crystal layer 106 is controlled by the bias electrode 104. Because the bias voltage applied to the bias electrode 104 can be controlled for each unit cell 1000, the orientation state of the liquid crystal molecules in the liquid crystal layer 106 can also be controlled for each unit cell 1000. The dielectric constant of the liquid crystal layer 106 changes depending on the orientation state of the liquid crystal molecules. The phase of the scattered waves from the liquid crystal reflector 100 changes depending on the dielectric constant of the liquid crystal layer 106. Therefore, by changing the dielectric constant of the liquid crystal layer 106 for each unit cell 1000, a phase difference is generated within the plane of the liquid crystal reflector 100, making it possible to control the propagation direction of the scattered waves.

[0025] The liquid crystal reflector 100 scatters incident waves on the surface on which the common electrodes 102 are arranged, and therefore the common electrodes 102 are also called scatterers. The unit cell 1000 can also be regarded as a patch antenna in which a patch electrode (common electrode 102) is provided on the top surface of the dielectric (liquid crystal layer 106) and a reflecting electrode (bias electrode 104) is provided on the back surface.

[0026] 3 and 4, the second substrate 134 may be provided with a drive circuit that outputs a selection signal to the selection signal line 110 and a drive circuit that outputs a bias signal to the bias signal line 112. Also, input terminals for inputting signals and drive power for driving these drive circuits may be provided.

[0027] 5 and 6 show details of a unit cell 1000 that constitutes the liquid crystal reflector 100. Fig. 5 shows a plan view of the unit cell 1000, and Fig. 6 is a cross-sectional view taken along line C-D in Fig. 5. As shown in Fig. 5 and 6, the unit cell 1000 is arranged so that the common electrode 102, the liquid crystal layer 106, and the bias electrode 104 overlap in plan view.

[0028] The common electrode 102 used in this embodiment has a shape that is symmetrical with respect to the vertically polarized and horizontally polarized waves of the incident radio waves. Fig. 5 shows an example in which the common electrode 102 is square. The size (vertical and horizontal dimensions) of the common electrode 102 is set appropriately depending on the frequency of the target radio waves. Note that the shape of the common electrode 102 is not limited to a square, and may be rectangular or have another geometric shape.

[0029] The common electrode 102 is connected to a common wiring 108. The common wiring 108 has a predetermined length and width. One end of the common wiring 108 is connected to the center point of one side of the common electrode 102. In other words, the common wiring 108 is connected so that the center point of one side of the common electrode 102 is included in the width portion of the common wiring 108. There is no limitation on the connection structure between the common wiring 108 and the common electrode 102. For example, the common wiring 108 and the common electrode 102 may be formed from the same conductive layer. The common wiring 108 is connected to a power supply circuit (not shown). Alternatively, the common wiring 108 may be grounded or connected to a grounded wiring. As shown in FIG. 3 , the common wiring 108 connects adjacent common electrodes 102. By connecting the common electrodes 102 to each other via the common wiring 108, the common electrodes 102 arranged in a matrix have an equipotential.

[0030] The bias electrode 104 is formed with a large area so as to function as a reflector. As shown in Fig. 5, in the unit cell 1000, the bias electrode 104 has a larger area than the common electrode 102. The bias electrode 104 and the common electrode 102 are provided so as to overlap each other, with the common electrode 102 being disposed in an area inside the bias electrode 104.

[0031] The bias electrode 104 is connected to the bias signal line 112 via the switching element 116. FIGS. 5 and 6 show an example in which the switching element 116 is formed of a transistor. The transistor has a structure in which a semiconductor layer 120, a gate insulating layer 122, and a gate electrode 124 are stacked. An interlayer insulating layer 126 is provided on the gate electrode 124, and the bias signal line 112 is provided on top of that. The switching element 116 and the bias signal line 112 are buried with a planarizing layer 128. The bias electrode 104 is provided on the planarizing layer 128. The bias electrode 104 is connected to the input / output terminal (drain) of the switching element (transistor) 116 via a contact hole. The gate electrode 124 of the switching element (transistor) 116 is connected to the selection signal line 110, and the input / output terminal (source) not connected to the bias electrode 104 is connected to the bias signal line 112.

[0032] The orientation state of the liquid crystal molecules in the liquid crystal layer 106 is controlled by the bias electrodes 104. That is, the orientation state of the liquid crystal molecules in the liquid crystal layer 106 is controlled by a bias signal applied to the bias electrodes 104. The bias signal is a DC voltage signal or a polarity-reversed DC voltage signal in which a positive DC voltage and a negative DC voltage are alternately reversed.

[0033] The liquid crystal layer 106 is made of a liquid crystal material having dielectric anisotropy. For example, the liquid crystal material forming the liquid crystal layer 106 may be any material that exhibits liquid crystallinity and has dielectric anisotropy, and nematic liquid crystal is particularly preferred. The effect of this embodiment is the same whether the dielectric anisotropy of the liquid crystal material is positive or negative. Hereinafter, this embodiment will be described using a liquid crystal layer 106 having positive dielectric anisotropy.

[0034] The dielectric constant of the liquid crystal layer 106 changes depending on the orientation of the liquid crystal molecules. The orientation of the liquid crystal molecules is controlled by the bias electrode 104. When an incident wave is scattered by the unit cell 1000, the phase of the scattered wave changes depending on the dielectric constant of the liquid crystal layer.

[0035] The liquid crystal reflector 100 is applicable to the following frequency bands: the very high frequency (VHF) band, the ultra-high frequency (UHF) band, the super high frequency (SHF) band, the submillimeter wave (THF) band, the extra high frequency (EHF) band, and the terahertz wave band. The orientation of the liquid crystal molecules in the liquid crystal layer 106 changes depending on the bias voltage applied to the bias electrode 104, but does not change substantially with the frequency of the radio waves incident on the common electrode 102. Due to these characteristics of the liquid crystal molecules, the dielectric constant of the liquid crystal layer 106 can be changed by the bias electrode 104, and the common electrode 102 can scatter the radio waves, thereby controlling the phase of the scattered radio waves.

[0036] The first substrate 132 and the second substrate 134 sandwich the liquid crystal layer 106 and are provided for forming wiring and the like. They are formed of flat materials such as glass, resin, and metal plates. Transparency is not an issue. The layers provided on the first substrate 132 and the second substrate 134 are formed using the following materials. The semiconductor layer 120 is provided for forming the switching elements 116 and is formed of a silicon semiconductor such as amorphous silicon or polycrystalline silicon, or an oxide semiconductor including a metal oxide such as indium oxide, zinc oxide, or gallium oxide. The gate insulating layer 122 and the interlayer insulating layer 126 are provided to insulate the respective wiring layers and may be made of any insulating material, such as a silicon oxide film, a silicon nitride film, or a laminate structure thereof. The selection signal line 110 and the gate electrode 124 are provided to transmit electrical signals and are preferably made of a conductive material, such as a metal film. For example, they may be made of molybdenum (Mo), tungsten (W), or an alloy thereof. The bias signal line 112 is installed to transmit electrical signals and is preferably made of a conductive material, such as a metal film. For example, it is composed of a titanium (Ti) / aluminum (Al) / titanium (Ti) layer structure or a molybdenum (Mo) / aluminum (Al) / molybdenum (Mo) layer structure. The planarization layer 128 is formed to smooth out irregularities formed by switching elements and other components. Any material with flatness and insulating properties may be used, such as an organic material, such as an acrylic resin, an epoxy resin, or a polyimide material. The common electrode 102, bias electrode 104, and common wiring 108 function to conduct signals for driving the liquid crystal and to scatter input radio waves. All of these may be conductive, such as a metal film. Materials with low conductivity are particularly desirable, such as aluminum, copper, gold, or alloys thereof. Furthermore, to reduce resistance, it is desirable to make the film thicker than the bias signal line and selection signal line.

[0037] Although not shown in FIG. 6 , the first substrate 132 and the second substrate 134 are disposed with a gap therebetween and are bonded together with a sealant. The sealant need only function to bond the first substrate 132 and the second substrate 134 together, and is formed of an organic material such as an acrylic resin or an epoxy resin. The liquid crystal layer 106 is sealed within the area surrounded by the first substrate 132, the second substrate 134, and the sealant. The gap between the first substrate 132 and the second substrate 134 is approximately 20 μm to 100 μm, and is, for example, 40 μm. Although not shown, a spacer may be provided between the first substrate 132 and the second substrate 134 to maintain a constant gap.

[0038] 5, common electrodes 102 arranged in a matrix are connected to one another by common wiring 108, and bias electrodes 104 are connected to bias signal lines 112 via switching elements 116, making it possible to control the potential individually, thereby changing the dielectric constant of the liquid crystal layer 106 for each unit cell 1000. This makes it possible to control the phase of the scattered wave for each unit cell 1000.

[0039] 7 schematically illustrates how the propagation direction of a reflected wave is changed by the first unit cell 1000-1 and the second unit cell 1000-2. A bias signal V1 is applied to the bias electrode 104A of the first unit cell 1000-1 from a bias signal line 112A, and a bias signal V2 is applied to the bias electrode 104B of the second unit cell 1000-2 from a bias signal line 112B. The bias signals V1 and V2 have different voltage levels (V1≠V2). The common electrodes 102 of the first unit cell 1000-1 and the second unit cell 1000-2 are at the same potential, for example, set to a common potential.

[0040] 7 shows a schematic diagram illustrating that when radio waves are incident on the first unit cell 1000-1 and the second unit cell 1000-2 with the same phase, different bias signals (V1≠V2) are applied to the first unit cell 1000-1 and the second unit cell 1000-2, resulting in a larger phase change in the scattered wave by the second unit cell 1000-2 than by the first unit cell 1000-1. As a result, the phases of the scattered waves R1 scattered by the first unit cell 1000-1 and R2 scattered by the second unit cell 1000-2 are different (in FIG. 8, the phase of the scattered wave R2 leads the phase of the scattered wave R1), and the apparent propagation direction of the scattered waves changes obliquely.

[0041] As shown in FIG. 7 , the liquid crystal reflector 100 can cause the phase of the scattered wave relative to the incident wave to differ between the first unit cell 1000-1 and the second unit cell 1000-2. While FIG. 7 shows two unit cells schematically, in reality, by individually controlling the unit cells 1000 arranged in a matrix, the propagation direction of the scattered wave can be controlled to any direction without changing the direction of the liquid crystal reflector 100. Multiple common electrodes 102 arranged on the reflective surface of the liquid crystal reflector 100 are maintained at a constant potential (e.g., ground potential). Bias electrodes 104A and 104B and bias signal lines 112A and 112B that apply a bias voltage to the liquid crystal layer 106 are arranged on the back surface of the common electrodes 102. This prevents the front side of the liquid crystal reflector 100 from being affected by the electric field generated by the bias signal lines 112A and 112B.

[0042] <Radio wave reflection system> Fig. 8 is a schematic diagram of a radio wave reflection system 1 according to one embodiment of the present invention. As shown in Fig. 8, the radio wave reflection system 1 includes an antenna 20 that emits radio waves and a radio wave reflection device 10. The antenna 20 is installed in, for example, a base station and serves as a wave source for the transmitted radio waves.

[0043] In the radio wave reflecting system 1, when the diameter of the antenna 20 is d, the wavelength of the radio wave is λ, the diameter of the radio wave reflector 100 is D, and the distance from the antenna 20 to the radio wave reflector 100 is R, the radio wave reflector 100 is disposed so as to satisfy the following formula (1). In formula (1), the diameter d, wavelength λ, diameter D, and distance R can be expressed in units of millimeters, for example. R≧2(D+d) ２ / λ (1)

[0044] By satisfying formula (1), the radio wave reflector 100 is in the far field from the antenna 20, and non-directional radio waves are incident on it. As shown in formula (1), the shorter the wavelength λ (the higher the frequency) and the longer the diameter D of the radio wave reflector 100 (the larger the area), the longer the distance R required from the antenna 20 to the radio wave reflector 100.

[0045] In the radio wave reflecting system 1, the reflecting surface 100r of one radio wave reflector 100 forms an angle θ with the reflecting surface 100r of an adjacent radio wave reflector 100. If the angle θ is not formed (if the angle θ is 0°), the diameter of the radio wave reflector 100 must be 3D, and equation (1) must be satisfied. However, by forming the angle θ, the diameter of the radio wave reflector 100 only needs to be D, which is 1 / 3 of the diameter of the radio wave reflector 100, so that equation (1) is satisfied. Therefore, the distance R from the antenna 20 to the radio wave reflector 100 can be reduced.

[0046] In the radio wave reflecting system 1, an angle θ is formed between the reflecting surface 100r of the radio wave reflector 100 and an adjacent radio wave reflector 100. As shown in FIG. 9 , if the reflection angle of a radio wave at the reflecting surface 100r of a certain radio wave reflector 100 is δ, the reflection direction of the radio waves can be aligned overall by reflecting the radio waves so that the reflection angle of the radio waves at the reflecting surface 100r of an adjacent radio wave reflector 100 is δ±θ. If the radio wave reflector 100 is a liquid crystal reflector, the bias signal applied to the unit cell 1000 of the liquid crystal reflector is adjusted so that the reflection angle of the radio waves at the reflecting surface 100r of the certain liquid crystal reflector is δ. Then, the bias signal applied to the unit cell 1000 of the liquid crystal reflector of the adjacent liquid crystal reflector is adjusted so that the reflection angle of the radio waves at the reflecting surface 100r is δ±θ. In this way, by using a liquid crystal reflector as the radio wave reflector 100, it becomes easier to control the reflection direction of each radio wave reflector 100 that makes up the radio wave reflection system 1, and the overall radio wave reflection direction can be made uniform.

[0047] Other effects and advantages brought about by the aspects described in this embodiment that are clear from the description in this specification or that can be appropriately thought of by a person skilled in the art are naturally understood to be brought about by the present invention.

[0048] 1 Radio wave reflection system 10 Radio wave reflection device 20 Antenna 100 Radio wave reflector (liquid crystal reflector) 100r Reflection surface

Claims

1. A radio wave reflecting device comprising a plurality of radio wave reflectors having reflective surfaces that reflect radio waves, the plurality of radio wave reflectors being arranged adjacent to each other, and the reflective surfaces of the adjacent radio wave reflectors form an angle θ with respect to the reflective surface of one of the radio wave reflectors, the angle θ being greater than 0° and less than 90°.

2. The radio wave reflecting device according to claim 1, wherein the plurality of radio wave reflecting plates are arranged so that the reflecting surfaces are aligned along a parabolic shape.

3. A radio wave reflecting device as described in claim 1, which reflects radio waves such that, when the reflection angle of the radio waves on the reflecting surface of the radio wave reflector is δ, the reflection angle of the radio waves on the reflecting surface of the adjacent radio wave reflector is the reflection angle δ ± the angle θ.

4. The radio wave reflecting device according to claim 3, wherein the plurality of radio wave reflecting plates are liquid crystal reflecting plates.

5. A radio wave reflecting system including an antenna that emits radio waves and the radio wave reflecting device according to claim 1, wherein the relationship between the diameter d of the antenna, the wavelength λ of the radio waves, the diameter D of the radio wave reflecting plate, and the distance R from the antenna to the radio wave reflecting plate satisfies the following formula (1): R≧2(D+d). ２ / λ (1)

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