Electromagnetic wave reflecting device
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- STAFF CO JP
- Filing Date
- 2025-01-24
- Publication Date
- 2026-08-05
Smart Images
Figure 2026126762000001_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to an electromagnetic wave reflection device that increases the range in which wireless communication is possible by reflecting high-frequency electromagnetic waves in an arbitrary direction.
Background Art
[0002] Currently, the fifth-generation, so-called 5G mobile communication standard has also been introduced in the commercial field. In this communication standard, high throughput, more channel capacity, and performance improvement with low latency are required.
[0003] As a method for realizing this, in fifth-generation communication, in addition to radio waves having a relatively high frequency called millimeter waves, even in the microwave band, a frequency higher than 3 to 5 GHz, which is higher than the conventional frequency, is newly used. In this case, problems may occur in the communicable area. When using a higher frequency band among such high frequencies, since the electromagnetic waves approach the properties of light, the electromagnetic waves have high directivity in their propagation. Therefore, the problem is an electromagnetic wave attenuation phenomenon called shadowing, and in this phenomenon, the communication performance may be significantly deteriorated. Shadowing occurs when the propagation of electromagnetic waves is blocked by a shielding object, resulting in a state equivalent to the phenomenon called a shadow in an optical phenomenon.
[0004] As a method for suppressing this shadowing phenomenon, there is a reflector for electromagnetic waves. A reflector is a method of bending the arrival direction of electromagnetic waves by reflection by a metal plate and allowing the electromagnetic waves to reach the shadow portion of the electromagnetic waves generated by shadowing (Non-Patent Document 1).
[0005] However, some means are needed to direct the reflected wave in any desired direction. A simple method would be to change the orientation of the reflector itself. However, directing the reflected wave in any direction requires space to allow the reflector to move, and a two-axis movement and fixing mechanism, such as a gimbal, to fix the reflector in a movable position. For reflectors that require a relatively large area of several tens of centimeters or more, it becomes difficult to place them in any desired location.
[0006] Therefore, a method has been proposed that uses diffraction grating technology, which is used in the field of optical technology, to control the propagation direction of reflected waves by the periodic spacing of the diffraction grating (Non-Patent Literature 2). According to this method, it is known that the reflection direction can be changed to a desired direction by arranging linear elements parallel to each other at equal intervals and on the same plane. [Prior art documents] [Non-patent literature]
[0007] [Non-Patent Document 1] Ministry of Internal Affairs and Communications Local 5G Introduction Guidebook (Technical Section) Final Version 1 [Non-Patent Document 2] Reflectarrays and metasurface reflectors as diffraction gratings Fu Liu, Do-Hoon Kwon,Sergei A. Tretyakov IEEEE 10 February 2023 P.21-32 [Overview of the project] [Problems that the invention aims to solve]
[0008] Linear elements are known to have lower reflection levels compared to plate-shaped elements. Therefore, a larger area is required to achieve performance equivalent to plate-shaped elements. Conversely, if the available mounting area is limited, a problem arises where the characteristics deteriorate compared to plate-shaped elements. Furthermore, requiring an even larger area leads to increased costs for the reflector.
[0009] The same applies to Non-Patent Document 2, which also indicates a need for further technologies to reduce the area required.
[0010] This invention has been made in view of the above, and its objective is to propose an electromagnetic wave reflecting device that can reflect electromagnetic waves in any direction and achieves higher reflection characteristics even under conditions of limited mounting volume. [Means for solving the problem]
[0011] To achieve the above objective, this invention arranges multiple linear elements appropriately.
[0012] Specifically, the first invention is constructed by arranging multiple linear elements of the same shape made of a metal material in parallel. The aforementioned linear elements are arranged in sets of two or more, with two or more sets of these elements placed parallel to each other at equal intervals. The linear elements are such that the central position of one set of linear elements, as viewed from the axial direction, is separated by at least one wavelength of the electromagnetic wave to be reflected from the central position of an adjacent set of linear elements, as viewed from the axial direction.
[0013] According to the above configuration, by forming a group of linear elements consisting of multiple linear elements as a set, the radius is equivalently increased, and the scattering cross-section can be increased compared to when there is only one linear element 1. Therefore, it is possible to increase the reflection level of the linear elements without using thick linear elements. Furthermore, by ensuring that the spacing between each set is one wavelength or more, the conditions for establishing a diffraction grating capable of propagating reflected waves in any direction can be met. In this way, by using linear elements as a diffraction grating and further increasing the reflection level by using multiple linear elements 1 as a set, the reflection level can be increased without increasing the overall area of the reflecting device.
[0014] In the second invention, in the first invention, The element interval between the linear elements in the same group is 1 / 6 of the group interval between the center positions of the linear elements in each group.
[0015] According to the above configuration, the reflection level can be effectively increased.
[0016] In the third invention, in the first invention, the electromagnetic wave to be reflected includes at least the electromagnetic wave of the first frequency and the electromagnetic wave of the second frequency, the second frequency is about 6 times the first frequency, the center position of the linear element in the axial direction in the one set of linear elements is separated by at least one wavelength of the electromagnetic wave of the first frequency from the center position in the axial direction in the other adjacent set of linear elements, the element interval between the linear elements in the same group is separated by at least one wavelength of the electromagnetic wave of the second frequency.
[0017] According to the above configuration, for example, when the Sub6 band (4.5 GHz) as the first frequency and the millimeter wave (28 GHz) as the second frequency, which are used in the 5G mobile communication standard, become the reflection targets, electromagnetic waves in any frequency band can be effectively reflected.
[0018] In the fourth invention, in the first invention, two selected longitudinal connection elements among the linear elements in the same group are connected by a plurality of widthwise connection elements extending in the width direction, the plurality of widthwise connection elements have the same length and are provided at equal intervals in the longitudinal direction of the longitudinal connection elements, the sum of the longitudinal interval and the length of the widthwise connection element is equal to the length of half a wavelength of the electromagnetic wave to be reflected.
[0019] According to the above configuration, the perimeter per unit composed of two widthwise connection elements and two longitudinal connection elements is equal to one wavelength of the electromagnetic wave to be reflected, and by resonance, a stronger reflection is generated.
[0020] In the fifth invention, in any one of the first to fourth inventions, the linear element has a continuous crank shape in which a portion normal to the plane in which the linear element is disposed is 1 / 6 wavelength and a horizontal portion is 1 / 3 wavelength with respect to the wavelength of the electromagnetic wave to be reflected.
[0021] According to the above configuration, the phases of the current distributions of the portions normal to the plane in which the linear element is disposed are aligned in the crank-shaped linear element, and as a result, reflected waves having horizontal and vertical polarizations in the direction along the plane in which the linear element is disposed are realized.
[0022] In the sixth invention, a plurality of linear elements made of a metal material are arranged in parallel, the linear element has a continuous crank shape in which a portion normal to the plane in which the linear element is disposed is 1 / 6 wavelength and a horizontal portion is 1 / 3 wavelength with respect to the wavelength of the electromagnetic wave to be reflected.
[0023] According to the above configuration, even without arranging a plurality of sets of the plurality of linear elements, by arranging a plurality of linear elements each having a crank shape at equal intervals, the phases of the current distributions of the portions normal to the plane in which the linear element is disposed are aligned in each linear element, and as a result, reflected waves in the direction along the plane in which the linear element is disposed are realized.
[0024] In the seventh invention, in any one of the first to sixth inventions, adjacent linear elements are connected to each other by a zigzag inclined member, so that the element interval between adjacent linear elements can be adjusted.
[0025] According to the above configuration, since the element interval between adjacent linear elements can be adjusted, the reflection direction can be adjusted by finely adjusting the element interval without rotating the reflection device, and even when the electromagnetic wave to be reflected is changed, the appropriate element interval can be quickly adjusted at the installation location.
Advantages of the Invention
[0026] As described above, according to the present invention, electromagnetic waves can be reflected in any direction, and higher performance can be achieved even under conditions of small mounting volume. [Brief explanation of the drawing]
[0027] [Figure 1] This is a perspective view showing an overview of a reflective device composed of five sets of linear elements according to Embodiment 1. [Figure 2] This is a plan view illustrating the principle of reflection using linear elements. [Figure 3] This is a plan view showing the configuration of four types of linear elements. [Figure 4] This graph shows the relationship between the number of linear elements and the reflection level. [Figure 5] This is a plan view showing how the confusion cross-section is measured. [Figure 6] This is a perspective view showing a reflective device having a group of three linear elements. [Figure 7] This graph compares experimental and calculated values of the confusion cross-section. [Figure 8] This is an enlarged plan view showing a set of three parallel linear elements according to Embodiments 2 and 3. [Figure 9] This graph shows the relationship between element spacing and reflection level. [Figure 10] This is a plan view showing an enlarged view of a group of five parallel linear elements according to Embodiment 2. [Figure 11] This graph shows the relationship between element spacing normalized by group spacing and reflection level. [Figure 12] This is a graph showing the relationship between the opening angle of a set of linear elements and the reflection level in an embodiment 3 of linear elements. [Figure 13] This graph shows the relationship between the opening angle and equivalent radius of linear elements in a set of linear elements. [Figure 14] This is a plan view showing a schematic of the reflecting device according to Embodiment 4. [Figure 15]This graph shows the relationship between the direction in which the linear elements are arranged, the inclination angle of the direction in which the linear elements are arranged in each group, and the reflection level. [Figure 16] This is a perspective view showing a reflective device according to Embodiment 5, in which a plurality of linear element groups are arranged at intervals. [Figure 17] This graph shows the relationship between the spacing between linear element groups and the maximum gain. [Figure 18] This is a perspective view showing the relationship between a linear element parallel to GND and the GND according to Embodiment 6. [Figure 19] This is a perspective view showing the relationship between GND and a linear element perpendicular to it according to Embodiment 6. [Figure 20] This is a perspective view showing the spacing and relationship between a group of linear elements parallel to GND according to Embodiment 6. [Figure 21] This graph shows the relationship between the spacing between linear elements parallel to GND and the reflection level, according to Embodiment 6. [Figure 22] This graph shows the relationship between the angle from the zenith and the reflection level when the spacing between the linear element group parallel to GND is changed, according to Embodiment 6. [Figure 23] This is a perspective view showing a reflective device according to Embodiment 7, in which bent linear elements are arranged in parallel. [Figure 24] This is a plan view showing a partially enlarged view of a reflective device according to Embodiment 7, in which bent linear elements are arranged in parallel. [Figure 25A] This is a perspective view showing the state of a reflective device with adjustable element spacing according to Embodiment 8, before expansion. [Figure 25B] This is a perspective view showing the expanded state of a reflective device with adjustable element spacing according to Embodiment 8. [Figure 26] This is a plan view illustrating the element spacing and group spacing according to Embodiment 9. [Figure 27] This is a graph showing the relationship between two different frequency electromagnetic waves and reflection levels according to Embodiment 9. [Figure 28] This is a perspective view showing a reflective device according to Embodiment 10, in which a ladder-shaped group of linear elements are arranged in parallel. [Figure 29] This is a perspective view showing a reflective device according to Embodiment 10, in which a ladder-shaped group of linear elements are arranged in parallel. [Figure 30] This is a graph comparing the circumference of a ladder-shaped cell and the reflection level for horizontal polarization and vertical polarization according to Embodiment 10. [Figure 31] This is a perspective view showing a reflective device according to Embodiment 11, which combines two ladder-shaped linear element groups. [Figure 32] This graph compares the reflection levels of a reflector device, according to Embodiment 11, which combines two ladder-shaped linear element groups, with a reflector device, which consists of one ladder-shaped linear element group. [Modes for carrying out the invention]
[0028] Embodiments of the present invention will be described below with reference to the drawings.
[0029] (Embodiment 1) -The principle of reflection using linear elements- First, the principle of reflection by the linear element 1 will be explained using diagrams. As shown in Figures 1 and 2, the linear element 1 generates diffraction. This diffraction phenomenon is the phenomenon in which reflected waves diffuse when electromagnetic waves strike an edge, the linear element 1, or a point element. The linear element 1 consists of a conductive linear element such as a copper wire or aluminum wire with a diameter of 0.1 mm to 1 mm and a length of about 0.5 m to 1 m.
[0030] As shown in Figure 2, when linear elements 1 are arranged periodically as a diffraction grating 7, a direction appears in which the phase of the reflected wave R coincides with the direction corresponding to the periodicity, and the reflected waves R reinforce each other in that direction. In other words, if multiple linear elements 1 are arranged, the reflected wave R will travel in the direction corresponding to the arrangement. The arrangement condition for the elements constituting the diffraction grating in this case is that, when there is an incident wave I from the normal direction to the plane P on which the linear elements 1 are arranged, if the wavelength is λ, the angle between the incident wave I and the reflected wave R is θ, and the spacing between elements is d, then d = λ / sinθ.
[0031] Reflection by linear elements 1 is at a lower level compared to reflection by plate elements. One reason for this is that a wave incident on a single linear element 1 becomes a diffracted wave from the linear element and is radiated uniformly around the linear element, whereas a wave incident on a single plate element is reflected in a direction that satisfies Snell's law with respect to the angle of incidence to the plate element's surface, thus exhibiting directionality. Therefore, when using linear elements 1, it is necessary to increase the reflection level by some means.
[0032] The theoretical validity of using multiple linear elements 1 to increase this reflection level is explained below. When electromagnetic waves are applied to an object, the scattering cross-section (RCS) is a value used to evaluate the reflection level from that object. This is a common value used to evaluate the reflection performance of a reflector. The scattering cross-section (RCS) of a linear element 1 can be expressed analytically when the cross-section is a round cylindrical shape. The formula for this analytical value is as follows, where a is the radius of the line, l is the length of the line, λ is the wavelength, θ is the angle with respect to the line, and N = 2 × π × l / λ × sinθ.
[0033] Scattering cross section = 2×π / λ×a×l 2 ×((sinN) / N) 2 ×cosθ…(1) As is clear from equation (1), the reflection level is proportional to the radius a of the line.
[0034] In this case, increasing the radius of the linear element 1 would increase the thickness of the reflector 2, leading to increased material costs and weight, which are undesirable for the reflector 2. Therefore, in this embodiment, a method of increasing the equivalent radius using multiple linear elements 1 is employed. Equivalent radius is a method of increasing the radius equivalently by combining multiple linear elements 1. The value of the equivalent radius increases or decreases depending on the radius a of the constituent linear elements 1 and the element spacing d, which is the distance between them, but basically the value increases compared to when there is only one linear element 1. This makes it possible to increase the reflection level of the linear element 1 without using a thick linear element 1.
[0035] In the reflector 2 of Embodiment 1, as shown in Figure 1, a method is used to increase the reflection level by configuring individual linear elements 1 in groups of multiple linear elements 3. Alternatively, the linear element groups 3 may be fixed at predetermined intervals using frame members such as Styrofoam (registered trademark) as shown in Figure 6, or the linear elements may be arranged and attached to a dielectric plate such as a flat Styrofoam, or fixed to a metal frame. The length of each linear element 1 is approximately 16 times the wavelength λ of the electromagnetic wave to be reflected (for example, a 5GHz electromagnetic wave), and the multiple linear elements 1 constituting a group are arranged to lie in a straight line within the range of λ / 6. The group spacing D, which is the distance between the center position of one group of linear elements 1 as viewed from the axial direction and the center position of another adjacent group of linear elements 1 as viewed from the axial direction, is arranged to be 1 wavelength (D=λ). The radius a of the linear element 1 is, for example, a=λ / 400.
[0036] As illustrated in Figure 3, the spacing D between each pair is 6 cm, which is one wavelength, for a 5 GHz electromagnetic wave. The element spacing d between linear elements is 1 cm (d=λ / 6) for two elements, 0.5 cm (d=λ / 12) for three elements, and 0.33 cm (d=λ / 18) for four elements.
[0037] Figure 4 shows the results of simulations conducted regarding the number of elements in each group and the corresponding reflection level (scattering cross-section RCS, unit dBsm: decibel square meter). From the graph in Figure 4, it can be seen that the reflection level increases as the number of elements constituting the linear element group 3 increases from 1 to 2 to 3. In this case, the spacing D between each group must be at least one wavelength apart (D≧λ). This is clear as a condition for constructing the diffraction grating 7. Thus, using linear elements 1 as a diffraction grating 7, and further increasing the reflection level by combining multiple linear elements 1 into a single group, was previously unknown. This shows that the reflection level can be increased without increasing the overall area. In this embodiment, the equivalent radius of the multiple linear elements 1 constituting a single group is λ / 20, which is about 20 times thicker than the individual linear elements 1. As a result, it is thought that the reflection level increased by about twofold.
[0038] To verify the validity of the calculation results, a prototype of the reflector 2 shown in Figures 5 and 6 was constructed, and the scattering cross-section (RCS) was measured in an anechoic chamber. The scattering cross-section (RCS) was measured by observing the reflected wave R at a position bent by 90° while rotating the reflector 2 in the anechoic chamber. The measured and simulation results are expressed in dB as RCS(σ / λ). 2 ) is described below. The operating frequency was set to 5 GHz. In the reflector used in this experimental evaluation, one set consisted of three linear elements 1 with an element spacing d = 1 cm and a length l = 1 m, and the set spacing D was set to 6 cm. As shown in Figure 6, as the reflector 2, the linear elements 1 were prepared by attaching the upper and lower parts to styrofoam 4 respectively.
[0039] As shown in Figure 7, when comparing the scattering cross-sectional area patterns in the Y-axis and Z-axis directions shown in Figure 5 with the experimental and calculated results, the peak positions and levels show relatively good agreement between the experimental and calculated results, confirming the validity of the calculation results.
[0040] (Embodiment 2) Figures 8 and 10 show Embodiment 2 of the present invention, which differs from Embodiment 1 mainly in the arrangement of the linear elements 1 in each set. In the following embodiments, the same reference numerals are used for parts that are the same as in Figures 1 to 7, and their detailed descriptions are omitted.
[0041] Specifically, the reflector 2 of Embodiment 2 shows the optimal value for the element spacing d of the multiple linear elements 1 that constitute each set in Embodiment 1. If the element spacing d of the linear elements 1 that constitute each set is narrowed, the receiving area of electromagnetic waves used for reflection will decrease. On the other hand, if the element spacing d of the linear elements 1 is widened, they will overlap with the linear elements 1 of the adjacent set, and the operation as a diffraction grating 7 will be suppressed. From the above, it is expected that there is an optimal element spacing d for the linear elements 1.
[0042] (1) Composition of 3 pieces / set As shown in Figure 8, when the set spacing D was changed to 1 wavelength (D=λ), 1.15 wavelengths (D=1.15λ), and 2 wavelengths (D=2λ), and the value of the element spacing d was changed, it was confirmed that the reflection level was maximized when the element spacing d was 1 / 6 of the set spacing D (d=D / 6), as shown in Figure 9. Here, the linear elements 1 consisted of copper wire and aluminum wire, with a diameter of 0.1 mm to 1 mm and a length of approximately 0.5 m to 1 m. The distances for placement were set as follows: set spacing D was 6 cm for 1 wavelength at 5 GHz, approximately 7 cm for 1.15 wavelengths, and 12 cm for 2 wavelengths, and the element spacing d was calculated as 6 cm for 1 wavelength at 5 GHz.
[0043] (2) Composition of 5 pieces / set When the element spacing d is varied with the set spacing D shown in Figure 10 as one wavelength, it was confirmed that the reflection level is maximized when the maximum inter-element distance dmax, as seen from the central element, is 1 / 6 of the set spacing D (dmax = λ / 6). It was also found that if the element spacing d is too narrow, it becomes no different from a single element, and if it is too wide, the element spacing d set as the diffraction grating 7 becomes narrower than the design value, resulting in a deterioration of the reflection level. For 5 elements / set, the element spacing d was set to 0.5 cm (5 mm) at 5 GHz, for example.
[0044] Figure 11 shows the results of changing the spacing D of each group composed of multiple linear elements 1, and then changing the element spacing d within each group. In the graph, the horizontal axis represents the element spacing d normalized by the group spacing D in each group, and the vertical axis represents the level of the reflected wave R (scattering cross-section RCS) at that time. As is clear from Figure 11, it was found that the reflection level increases when the element spacing d within a group is set to 1 / 6 of the group spacing D of each group (d = D / 6).
[0045] Thus, in this embodiment, it has become clear that optimal operation can be obtained by setting d = D / 6 in both the 3-piece / set and 5-piece / set configurations.
[0046] (Embodiment 3) Embodiment 3 shows the optimal position of the linear elements 1 constituting each set in Embodiments 1 and 2. For simplification, each set of linear elements 1 consists of three elements as shown in Figure 8, and each linear element 1 is positioned at the vertices of an isosceles triangle. At the same time, the configuration of each set was made to have the same shape. The angle α between the two equal-length sides was changed, and the reflection level at each angle α was checked. The results are shown in Figure 12. In the graph in Figure 12, the horizontal axis represents the angle α of the isosceles triangle composed of the linear elements 1 described above, and the vertical axis represents the reflection level (scattering cross-section RCS) at that time. As can be seen from Figure 12, there is no significant difference in the reflection level even when the angle α is changed, so it was found that when the linear elements 1 of each set are arranged to form a triangle, the shape of the triangle does not have much effect on the scattering cross-section RCS.
[0047] Next, we will explain the reason why the reflection level does not change even when the angle changes, using the equivalent radius. Figure 13 shows the equivalent radius in dB when the arrangement is changed. The arrangement is the same as in Figure 12, when the opening angle α is changed to 0°, 30°, and 45°, and when comparing these equivalent radii, it can be seen that they are almost the same value. In other words, even when the positional relationship of the reflective elements (linear elements 1) in the set is changed within these angular ranges, the equivalent radius hardly changes, and as a result, the reflection level of linear elements 1 does not change.
[0048] (Embodiment 4) Consider a case where a reflector 2 is installed in an L-shaped corridor to change the direction of electromagnetic waves to approximately a right angle. In such cases, it may be desirable to strongly emit the reflected wave R on only one side of the reflector 2. If the arrangement of each set of linear elements 1 is angled relative to the direction in which they are lined up, the reflection level in the direction where the inclined surface is the reflective surface 5 increases, and the reflection level in the opposite direction decreases. In other words, the reflection level on one side increases.
[0049] This embodiment describes a method for achieving bias in the direction of the reflected wave R. In embodiments 1 to 3, the reflection level was divided equally between the left and right sides, but in some cases, it may be necessary to reflect strongly to one side. This embodiment describes how to achieve this.
[0050] In this embodiment, using the configuration shown in Embodiment 3, first, the opening angle is set to 180° (α=0°), and three linear elements 1 are arranged at equal intervals within the same reflective surface 5, as shown in Figure 14. Then, the reflective surface 5 is tilted to one side. Figure 15 shows the relationship between the tilt angle β and the reflection level at this time. In the graph in the figure, the horizontal axis is the tilt angle β, and the vertical axis is the difference in the reflection levels (scattering cross-section RCS) of the two reflected waves R. As can be seen from Figure 15, by increasing the tilt angle β beyond 0, a difference in the reflection levels of the two reflected waves R is created, and by tilting it to around β=40°, the difference in reflection levels is maximized. From the above, it has been found that by changing the tilt angle β of the reflective surface 5, it is possible to generate a difference in reflection levels with the reflective device 2 of this embodiment.
[0051] (Embodiment 5) Regarding the method of constructing a diffraction grating using linear elements 1, in the above embodiments, a method was used in which multiple linear elements 1 were grouped together. Here, however, a method of combining multiple diffraction gratings, each consisting of one linear element, will be described, as shown in Figure 16. In this embodiment as well, the linear elements 1 are made of, for example, copper wire, aluminum wire, etc., with a diameter of 0.1 mm to 1 mm and a length of approximately 0.5 m to 1 m. The spacing D between each group is 6 cm, which is one wavelength for electromagnetic waves at 5 GHz, and the element spacing d between linear elements 1 is 1 cm (i.e., d = λ / 6).
[0052] Linear elements 1 located within the same plane are called a group of planar elements 6. In one group of planar elements 6, the linear elements 1 are arranged one by one. All of the multiple linear elements 1 constituting each group of planar elements 6 maintain the same element spacing d. The planes constituting these multiple groups of planar elements 6 are parallel and arranged at equal intervals X. Furthermore, the multiple linear elements 1 constituting each group of planar elements 6 are offset so that, when viewed from the direction in which the groups of planar elements 6 are arranged, they are centered between the linear elements 1 constituting adjacent groups of planar elements 6. With this configuration, an increase in the reflection level occurs when the spacing X of the planes constituting the groups of planar elements 6 is set to half a wavelength (X = λ / 2).
[0053] The graph in Figure 17 shows the reflection level (shown as the maximum gain) when there is only one planar element group 6, and the reflection level when three planar element groups 6 are used and the spacing L between them is varied. As is clear from Figure 17, the reflection level is maximized when the spacing X between the planar element groups 6 is half a wavelength (X = λ / 2), and a level improvement of more than 5 dB is achieved compared to when there is only one row of planar element groups 6. In other words, it was found that the reflection level increases by offsetting the reflector 2 by half a wavelength in both the width and depth directions.
[0054] (Embodiment 6) As shown in Figure 18, if there is a wall behind the reflector 2, its influence can be expected if the wall is made of metal or reinforced concrete. Hereafter, we will refer to the wall surface that causes these influences collectively as GND. If GND is on a plane parallel to the plane formed by the multiple linear elements 1 that make up the reflector 2, no reflected wave R will be emitted in the direction parallel to the plane of GND. The reason for this is that when the linear elements 1 are parallel to GND, the reflected wave R from the linear elements 1 is canceled out in the planar direction of GND by the image current of the linear elements 1 generated on GND. To prevent this, as shown in Figure 19, it is considered that the reflector 2 should have a component in the direction normal to GND so that it is not canceled out by the image current.
[0055] Therefore, as shown in Figure 20, the linear elements 1 were arranged in pairs, with the element spacing d (pair spacing D) set to one wavelength (d=D=λ), and the reflection characteristics were confirmed when they were placed close to GND. In this embodiment as well, the linear elements 1 consist of copper wire, aluminum wire, etc., with a diameter of 0.1 mm to 1 mm and a length of approximately 0.5 m to 1 m. The pair spacing D (element spacing d) for each is 6 cm, which is one wavelength for a 5 GHz electromagnetic wave, and the element spacing d between the linear elements 1 is 1 cm (i.e., d=λ / 6).
[0056] As shown in Figure 21, the optimal distance L from the wall (GND) was found to be λ / 3 (L=0.33 in Figure 21). In this case, for example, by placing a high dielectric material (e.g., glass epoxy, glass, plastic, etc.) between the linear element 1 and GND, the thickness can be reduced by the square root of the dielectric constant of the high dielectric material. On the other hand, as shown in Figure 22, which shows the distribution of the tilt angle γ from the angle of incidence (see Figure 20), it can be seen that the reflected wave is not radiated directly sideways (γ=90°), but that the tilt angle γ is sufficiently spread to about 80°.
[0057] Therefore, it was found that with the reflector 2 according to this embodiment, the reflection level is maximized when the linear elements 1 are arranged in pairs, the element spacing d (pair spacing D) is set to one wavelength (d=D=λ), and the distance L from the planar wall (GND) formed by the multiple linear elements 1 is set to λ / 3, and the tilt angle γ of the reflected wave can be widened to about 80°.
[0058] (Embodiment 7) As shown in Figure 23, the reflector 2 according to Embodiment 7 has linear elements 1 that are bent at intervals of one wavelength. These crank-shaped linear elements 1 enable radiation in the direction of GND. As shown in an enlarged view in Figure 24, the linear elements 1 are bent such that the portion 1a that is normal to the plane in which they are formed is λ / 6 and the portion 1b that is horizontal is λ / 3. In this way, the phase of the current distribution in the portion 1a that is normal is aligned, and as a result, the horizontal reflected wave R shown in Figure 23 is realized. In this embodiment as well, for example, the linear elements 1 are made of copper wire, aluminum wire, etc., with a diameter of 0.1 mm to 1 mm and a length of about 0.5 m to 1 m. The spacing D of each pair (i.e., the element spacing d) is 6 cm, which is one wavelength for electromagnetic waves at 5 GHz.
[0059] (Embodiment 8) In this embodiment, the element spacing d between each linear element 1 in the reflector 2 can be adjusted, as shown in Figure 25A when contracted and in Figure 25B when expanded. The vertically extending linear elements 1 are connected to each other by a pair of scissor-shaped inclined members 8, thereby allowing the element spacing d to be adjusted.
[0060] For example, the inclined member 8 is made of a rod-shaped dielectric material (such as ABS, polycarbonate, or glass epoxy), and both ends are rotatably supported by the linear element 1. In this embodiment, the reflection direction is adjustable, and the adjustment function makes it easy to set up the reflector 2 on-site for optimal results. Furthermore, adjustments can be easily made on-site even when the wavelength of the electromagnetic wave to be reflected changes.
[0061] (Embodiment 9) This embodiment is effective when the reflector 2 is to be able to handle not just one frequency but multiple frequencies. As shown in Figure 26, in this embodiment, if the wavelength λ of one frequency is assigned to the spacing D of the set of multiple linear elements, and the wavelength λ' of another frequency is assigned to the element spacing d, the effect will be observed at both frequencies λ and λ'.
[0062] In this embodiment as well, the linear element 1 is made of copper wire, aluminum wire, etc., with a diameter of 0.1 mm to 1 mm and a length of approximately 0.5 m to 1 m. When the frequency of the electromagnetic wave to be reflected is 5 GHz, the spacing D is D = λ = 6 cm, and the element spacing d is d = λ / 6 = 1 cm. When the frequency of the other electromagnetic wave to be reflected is 28 GHz, the element spacing d becomes d = λ' = 1 cm.
[0063] In this embodiment, by setting the pair spacing D=λ when the frequency of the electromagnetic wave to be reflected is 5GHz, and the element spacing d=λ' when the frequency of the electromagnetic wave to be reflected is 28GHz, as shown in Figure 27, in this embodiment, when a reflected wave R is generated in a direction perpendicular to the incident wave I at both frequencies of 5GHz and 28GHz, a higher reflection level is achieved compared to a comparative example of a single linear element 1 corresponding to only one frequency, 5GHz (shown at the bottom of the enlarged view in Figure 26).
[0064] When the first frequency and the second frequency are close together, for example, when the ratio is about 2, one frequency may be one wavelength while the other is half a wavelength, which can worsen the reflection level. As shown in Embodiment 1, the optimal setting is when the element spacing d of the linear elements 1 in a set is 1 / 6 of the set spacing D (d=D / 6). Therefore, as in this embodiment, when the first frequency and the second frequency are far apart by about 6 times (for example, 28GHz / 5GHz=5.6 times), it was found that a high reflection effect can be obtained for electromagnetic waves of either frequency.
[0065] In this embodiment, if θ1 is the angle between the incident direction and the first reflection direction of the electromagnetic wave of the first frequency (wavelength λ), and θ2 is the angle between the incident direction and the second reflection direction of the electromagnetic wave of the second frequency (wavelength λ'), then the pair spacing D = λ / sinθ1 and the element spacing d = λ' / sinθ2 may be used. This is based on the principle of reflection explained in Figure 2. From this, it can also be said that D ≥ λ and d ≥ λ'.
[0066] (Embodiment 10) There is a need to reflect both vertical and horizontal polarizations, and to achieve high reflection levels for both polarizations. However, normally, only polarizations parallel to the linear element 1 can be reflected. Simply combining vertical and horizontal linear elements 1 presents a problem: polarizations not parallel to the linear element 1 will not be reflected in the desired direction.
[0067] In this embodiment, as shown in Figure 28, two selected longitudinal connecting elements 1a from the same set of linear elements 1 are connected by a plurality of widthwise connecting elements 1b extending in the width direction, thereby enabling the reflection of vertical and horizontal polarization in the same direction.
[0068] As shown in Figure 29, a widthwise connecting element 1b is connected between a pair of longitudinal connecting elements 1a. By arranging the elements so that the sum of the length of the longitudinal connecting elements 1a and the spacing between the pair of longitudinal connecting elements 1a equals half the wavelength of the electromagnetic wave to be reflected, higher reflection can be expected. This is thought to be because, with this setup, the perimeter of the aperture per unit area composed of the two longitudinal connecting elements 1a and the widthwise connecting element 1b becomes one wavelength, leading to resonance and thus stronger reflection.
[0069] In this embodiment as well, the linear element 1 is made of copper wire, aluminum wire, etc., with a diameter of 0.1 mm to 1 mm and a length of approximately 0.5 m to 1 m. The spacing D of the group is set to 6 cm, which is the length of one wavelength, when the electromagnetic wave to be reflected is 5 GHz. In the reflector 2 of this embodiment, a resonance phenomenon not described in the above embodiments is utilized. As shown in Figure 30, it is known that resonance occurs when the length of the reflecting element is an integer multiple of half a wavelength of the electromagnetic wave to be reflected. In this embodiment, it is considered that the element length of the longitudinal connecting element 1a is optimal when it is an even multiple of half a wavelength. This is because, at odd multiples, the current on the widthwise connecting element 1b of the ladder-shaped element is reversed at each stage.
[0070] In this embodiment, two widthwise connecting elements 1b and two longitudinal connecting elements 1a sandwiched between them are integrated to form a loop antenna with a perimeter of one wavelength. If the polarization is in the same direction as the widthwise connecting elements 1b, a current distribution is generated such that the maximum current flows through the two widthwise connecting elements 1b, the adjacent widthwise connecting elements 1b become in phase, and the reflected waves R reinforce each other. The same applies to the longitudinal connecting elements 1a; a current distribution is generated such that the maximum current flows through the two longitudinal connecting elements 1a, and the radiation from these longitudinal connecting elements 1a reinforces each other. In this way, by generating a current distribution that reinforces the reflected waves R for both polarizations, optimal reflection characteristics are achieved.
[0071] (Embodiment 11) In this embodiment, as shown in Figure 31, two ladder-shaped linear elements, as shown in Embodiment 10, are combined. This further increases the reflection level. In this embodiment as well, the linear element 1 is made of copper wire, aluminum wire, etc., with a diameter of 0.1 mm to 1 mm and a length of approximately 0.5 m to 1 m. The spacing D of the combination is 6 cm, which is the length of one wavelength, when the target electromagnetic wave is 5 GHz. The length of the longitudinal connecting element 1a is 1.5 cm, which is λ / 4, when the frequency of the electromagnetic wave to be reflected is 5 GHz, and the element spacing d is also 1.5 cm, which is λ / 4.
[0072] As shown in Figure 32, it can be seen that the reflection level is even higher in this embodiment compared to embodiment 10.
[0073] The embodiments described above are essentially preferred examples and are not intended to limit the scope of the present invention, its applications, or uses. [Explanation of Symbols]
[0074] 1 Linear element 1a Longitudinal connecting element 1b Width-direction connecting element 2 Reflector 3 Linear element group 4 Styrofoam 5 Reflective surface 6 Planar element group 7 Diffraction gratings 8 Inclined member
Claims
1. It is constructed by arranging multiple linear elements of the same shape, made of metal material, in parallel. The aforementioned linear elements are arranged in sets of two or more, with two or more sets of these elements being arranged parallel to each other at equal intervals. The linear elements are such that the central position of one set of linear elements, as viewed from the axial direction, is separated by at least one wavelength of the electromagnetic wave to be reflected from the central position of an adjacent set of linear elements, as viewed from the axial direction. An electromagnetic wave reflecting device characterized by the following features.
2. The spacing between linear elements in the same set is 1 / 6 of the spacing between the centers of the linear elements in each set. The electromagnetic wave reflecting device according to feature 1.
3. The electromagnetic wave to be reflected includes at least an electromagnetic wave of a first frequency and an electromagnetic wave of a second frequency. The second frequency is approximately six times the first frequency. The linear elements are such that the central position of one set of linear elements, as viewed from the axial direction, is separated by at least one wavelength of the electromagnetic wave of the first frequency from the central position of an adjacent set of linear elements, as viewed from the axial direction. The spacing between linear elements in the same set is at least one wavelength apart from the electromagnetic wave of the second frequency. The electromagnetic wave reflecting device according to feature 1.
4. Two selected longitudinal connecting elements from the same set of linear elements are connected by multiple widthwise connecting elements extending in the width direction. Multiple widthwise connecting elements are of the same length and are provided at equal intervals in the longitudinal direction of the longitudinal connecting elements. The sum of the longitudinal spacing and the length of the widthwise connecting element is equal to the length of half a wavelength of the electromagnetic wave to be reflected. The electromagnetic wave reflecting device according to feature 1.
5. The linear element has a continuous crank shape such that, with respect to the wavelength of the electromagnetic wave to be reflected, the portion that is normal to the plane on which the linear element is arranged has a wavelength of 1 / 6 of the wavelength, and the portion that is horizontal has a wavelength of 1 / 3 of the wavelength. The electromagnetic wave reflecting device according to feature 1.
6. It is constructed by arranging multiple linear elements made of metal material in parallel. The linear element has a continuous crank shape such that, with respect to the wavelength of the electromagnetic wave to be reflected, the portion that is normal to the plane on which the linear element is arranged has a wavelength of 1 / 6 of the wavelength, and the portion that is horizontal has a wavelength of 1 / 3 of the wavelength. An electromagnetic wave reflecting device characterized by the following features.
7. The adjacent linear elements are connected to each other by a scissor-shaped inclined member, thereby allowing the spacing between adjacent linear elements to be adjusted. An electromagnetic wave reflecting device according to any one of claims 1 to 6.