Noise reduction structure

Abstract

To provide a noise reduction structure that contributes to reducing the effects of noise by disposing a noise-shielding metal plate with a shape that provides high noise-shielding effect between a noise source and a receiving antenna.SOLUTION: A noise reduction structure includes a noise-shielding metal plate shaped to form a region where a current generated by a noise source is reduced, and the noise-shielding metal plate is installed between a receiving antenna of the wireless device and a noise source such that the receiving antenna corresponds to a position within a region where the current generated by the noise source is reduced.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a noise reduction structure.

Background Art

[0002] Regarding shield substrates, the following documents can be cited.

[0003] Patent Document 1 relates to a shield substrate for a connector having a high electromagnetic shielding effect.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The following analysis is provided by the inventor of the present invention.

[0006] In wireless devices, the reception sensitivity decreases due to noise generated by the device itself or by surrounding devices. In wireless devices, the decrease in reception sensitivity due to noise is an issue that needs to be improved. If the noise is generated by the device itself, as a noise countermeasure, means such as covering the IC or the like that is the noise source with a metal wall to shield the noise source are common and highly effective. On the other hand, when the noise is generated by surrounding devices, it is often impossible to take measures against the devices that are the noise sources that generate the noise, and there are few effective countermeasures. In addition, since wireless devices are equipped with antennas, covering the antenna also impairs the original communication performance, which is also one of the reasons that makes it difficult to take countermeasures. Currently, there is no clear guideline regarding the shielding method.

[0007] In a situation where the noise source cannot be shielded, for example, when the noise source and the receiver are separate devices, a metal plate is placed between the noise source and the receiving antenna, and means for shielding the noise is used. In such a case, the metal plate needs to be large enough to obtain a shielding effect. However, the size of the metal plate that can achieve the shielding effect is determined by the frequency, and generally, a metal plate with a size of at least half a wavelength can obtain a reflection effect. Therefore, the lower the frequency of the noise, the longer the wavelength, and the larger the metal plate needs to be. However, in a small device, a metal plate of sufficient size cannot be installed, resulting in a problem of reduced shielding effect.

[0008] An object of the present invention is to provide a noise reduction structure that contributes to reducing the influence of noise by arranging a noise shielding metal plate (hereinafter also referred to as a "metal plate") having a shape with a high noise shielding effect between a noise source and a receiving antenna.

Means for Solving the Problems

[0009] According to a first aspect of the present invention, the noise shielding metal plate has a shape that forms a region where the current generated by the noise source decreases, A noise reduction structure can be provided in which the noise shielding metal plate is installed between the receiving antenna and the noise source so that the receiving antenna of the wireless device corresponds to a position within the region where the current generated by the noise source decreases.

Effects of the Invention

[0010] According to the present invention, a noise reduction structure can be provided that contributes to reducing the influence of noise by installing a metal plate having a shape with a high noise shielding effect between a noise source and a receiving antenna.

Brief Description of the Drawings

[0011]

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[0012] In the present disclosure, the drawings may be associated with one or more embodiments. Further, each of the embodiments described below can be combined with other embodiments as appropriate, and the present invention is not limited by each embodiment.

[0013] First, an overview of one embodiment will be described with reference to the drawings. Note that the reference numerals of the drawings appended to this overview are for convenience of each element as an example for assisting understanding, and are not intended to limit the present invention to the illustrated aspects. Also, the connection lines between the blocks of the drawings and the like referred to in the following description include both bidirectional and unidirectional ones. The one-way arrow schematically shows the flow of the main signal (data), and does not exclude bidirectionality.

[0014] FIG. 6 is a block diagram showing an example of the configuration of the noise reduction structure according to the present disclosure.

[0015] Referring to FIG. 1, a noise shielding metal plate 100, a noise source 200, a wireless device 300, and a receiving antenna 400 are shown.

[0016] The noise reduction structure 10 has a shape in which the noise shielding metal plate 100 forms a region where the current generated by the noise source 200 decreases. Due to the shape of the noise shielding metal plate 100, a region where the current generated by the noise source 200 decreases is formed, thereby increasing the noise shielding effect.

[0017] The noise reduction structure 10 has the noise shielding metal plate 100 installed between the receiving antenna 400 and the noise source 200 such that the receiving antenna 400 of the wireless device 300 corresponds to a position within the region where the current generated by the noise source 200 decreases.

[0018] Note that the noise shielding metal plate 100 may be installed inside the wireless device 300. When the noise shielding metal plate 100 is installed inside the wireless device 300, it is possible to reduce noise and provide a wireless device with good reception performance.

[0019] Therefore, according to one embodiment, it is possible to provide a noise reduction structure that contributes to reducing the influence of noise by installing a metal plate having a high noise shielding effect between the noise source and the receiving antenna.

[0020] [First Embodiment] Next, the first embodiment will be described in detail with reference to the drawings. Note that the first to fourth embodiments described below are embodiments regarding the shape of a noise shielding metal plate (also referred to as a "metal plate") 100 installed between the noise source 200 and the receiving antenna 400 of the noise reduction structure 10 described in the above one embodiment. Therefore, the metal plates described in each embodiment are installed between the noise source 200 and the receiving antenna 400 of the noise reduction structure 10 described in the above one embodiment and constitute the noise reduction structure 10.

[0021] In the first embodiment, the noise source 200 and the receiving antenna 400 shown in FIG. 1 are each represented by a dipole antenna. As an example of the frequency, 850 MHz used in the communication system of 4G-LTE (Fourth Generation - Long Term Evolution) will be described. Therefore, in a general dipole antenna, the size is λ / 2 = approximately 180 mm (where λ represents the wavelength).

[0022] FIG. 2 is a block diagram showing the configuration of a dipole antenna. FIG. 2(a) shows an 850 MHz dipole antenna 500 including a signal input 550. In the first to fourth embodiments described below, a dipole antenna with a miniaturized shape using inductors 410 and 420 as the receiving antenna 400 shown in FIG. 2(b) will be described.

[0023] FIG. 3 is a diagram showing an example of the noise source 200 and the receiving antenna 400. FIG. 4 is a diagram showing an example of a configuration in which a metal plate 101 is disposed between the noise source 200 and the receiving antenna 400.

[0024] Referring to FIG. 3, when the noise source 200 and the receiving antenna 400 are arranged in parallel, the amount of noise received by the receiving antenna 400 is the largest. In such a situation, assume a situation where a metal plate 101 is installed between the noise source 200 and the receiving antenna 400 as shown in FIG. 4. The distances between the noise source 200 and the metal plate 101, and between the receiving antenna 400 and the metal plate 101 are each 40 mm, but in the present invention, the above-mentioned distances do not have a particularly important meaning.

[0025] FIG. 5 is a diagram showing an example of a configuration in which a metal plate is installed between a noise source and a receiving antenna as viewed from the receiving antenna side, and an example of the passing characteristics in each case. That is, FIG. 5 is a view of FIG. 4 as viewed from the receiving antenna 400 side, and the noise source 200 and the receiving antenna 400 assuming a miniaturized dipole antenna are arranged at the center of the metal plate 101 and horizontally, respectively, and the passing characteristics (hereinafter expressed as S21) when the size of the metal plate 101 is changed are shown correspondingly.

[0026] Since S21 corresponds to the amount of radio waves radiated from the noise source 200 received by the receiving antenna 400, it serves as an index indicating the influence of noise. S21 has a maximum value of 0 (zero) and is represented by a negative numerical value. The larger the numerical value (closer to 0), the greater the influence of noise, and the smaller the numerical value, the smaller the influence of noise. In the present disclosure, S21 is a numerical value calculated by an electromagnetic field simulator.

[0027] In the simulation by the electromagnetic field simulator, the material of the metal plate 101 was iron, but there is no significant difference even when other metals such as copper, aluminum, and stainless steel are used. Therefore, the metal plate 101 may be manufactured using any of these materials, or a combination of multiple metals. In the present embodiment and the following other embodiments, the metal plate may be manufactured using any of the above materials.

[0028] From the table in FIG. 5, even when the distance between the noise source 200 and the dipole antenna indicating the receiving antenna 400 and the width of the metal plate 101 in the vertical direction (i.e., vertical: 240 mm, 180 mm, 120 mm), which is the distance to the side parallel to the receiving antenna 400, are changed, S21 does not change significantly. It can be seen that when the width of the metal plate 101 in the direction perpendicular to the receiving antenna 400 (i.e., horizontal: 240 mm, 180 mm, 120 mm), which is the side in the horizontal direction, is changed, S21 changes significantly. Also, it is well-known technology that the above-mentioned horizontal width makes it easier for radio waves to pass through when it is shorter than half a wavelength (λ / 2) with respect to the desired frequency, and more difficult for radio waves to pass through when it is longer than half a wavelength.

[0029] FIG. 6 is a diagram showing an example of a metal plate of a noise reduction structure of the prior art. As an example of the prior art, a metal plate 101 shown in FIG. 6 having a width of 140 mm and a shape shorter than half a wavelength was used as a comparison target. In the first embodiment, since the frequency was 850 MHz, the half wavelength was approximately 180 mm.

[0030] FIG. 7 is a diagram showing an example (trapezoid) of a metal plate of a noise reduction structure according to the present disclosure. Referring to FIG. 7 showing the first shape of the metal plate according to the present disclosure with respect to an example of the metal plate 101 of the noise reduction structure of the prior art in FIG. 6, the width at the position overlapping the receiving antenna 400, that is, at a position 40 mm from the top of the metal plate 102 of the first shape (half of the height 80 mm) is set to 140 mm as in the width of the metal plate 101 shown in FIG. 6, and a trapezoid with the left and right sides inclined at 45° is formed. S21 is improved by 8 dB to -25 dB in the shape of FIG. 7 compared to -17 dB in the shape of FIG. 6.

[0031] FIG. 8 is a diagram showing an example (including an extended portion obtained by extending the long side of the trapezoid) of a metal plate of a noise reduction structure according to the present disclosure. Referring to FIG. 8, the long side portions of the two parallel sides of the trapezoidal metal plate 102 in FIG. 7 are extended in a direction away from the receiving antenna 400. FIG. 8 shows an example in the case of a metal plate 103 extended by 40 mm, and the shape of this metal plate 103 shows the second shape of the metal plate according to the present disclosure. In the shape of the metal plate 103 shown in FIG. 8, S21 is further improved to -29 dB.

[0032] FIG. 9 is a diagram showing an example of the noise improvement effect of a metal plate with a noise reduction structure according to the present disclosure (including an extended portion obtained by extending the long side of a trapezoid). When including the extended portion obtained by extending the long side portion of the trapezoid described above, as shown in FIG. 9, the noise improvement effect is high when the length h2 of the extended portion is around 20 to 40 mm, but the noise improvement effect decreases to -21 dB (the vertical width h1 of the trapezoid portion = 80 mm) when it is around 140 mm. When the length h2 of the extended portion with a high noise improvement effect is 20 to 40 mm, in terms of the wavelength λ, it corresponds to 0.06λ or more and 0.11λ or less (f = 850 MHz), and when h2 with a decreased noise improvement effect is 140 mm, it corresponds to 0.4λ (f = 850 MHz). Note that even if the vertical width of the trapezoid portion indicated by h1 in FIG. 9 is changed, this tendency does not change.

[0033] FIG. 10 is a diagram showing an example of a metal plate with a noise reduction structure according to the present disclosure (including an extended portion obtained by extending the long side of a trapezoid). The metal plate 104 shown in FIG. 10 shows the shape in which the noise improvement effect is most decreased in FIG. 9 (however, h1 = 80 mm).

[0034] FIG. 11 is a diagram showing an example of a metal plate with a noise reduction structure according to the present disclosure (including a notch in the extended portion obtained by extending the long side of a trapezoid). When the noise improvement effect decreases as in the metal plate 104 shown in FIG. 10, by providing a predetermined notch in the extended portion of the long side of the trapezoid, like the shape of the metal plate 110 shown in FIG. 11, S21 is improved. In the dimensions of the metal plate 110 shown in FIG. 11, S21 was improved to -32 dB. In FIG. 11, the vertical position of the notch in the extended portion of the long side of the trapezoid was set to a position 40 mm below from the lower part of the trapezoid shape. This is to make the shape above the notch the same as the shape of the metal plate 103 shown in FIG. 8. Even when the dimension corresponding to h2 is set to 20 mm as in the metal plate 103 shown in FIG. 9, a noise improvement effect can be expected.

[0035] FIG. 12 is a diagram showing an example of the noise improvement effect of a metal plate with a noise reduction structure according to the present disclosure (including a notch in an extended portion of the long side of a trapezoid). It is a diagram summarizing the change in S21 when the dimensions of the notch portion included in the extended portion of the metal plate 110 shown in FIG. 11 described above are changed. It is shown that the noise improvement effect is high when the dimension W2 between the left and right notches is 100 mm or less. In terms of the wavelength λ, it is about 0.3λ or less (f = 850 MHz). The vertical dimension W1 of the notch portion has little change in S21 even when the dimension is changed. The shape of the metal plate 110 is the third shape of the metal plate according to the present disclosure.

[0036] FIG. 13 is a diagram showing an example of a list of metal plates with a noise reduction structure according to the present disclosure. Referring to FIG. 13, the shapes are shown summarized in a list. (2), (3), and (5) correspond to the first, second, and third shapes according to the present disclosure, and it can be seen that the noise improvement effect of S21 is high.

[0037] On the other hand, FIG. 14 shows the characteristics when the metal plate is extended in the shape corresponding to (7) and (8) in FIG. 13. FIG. 14 is a diagram showing an example of the noise improvement effect of a metal plate with a noise reduction structure according to the present disclosure (including an extended portion obtained by extending a quadrilateral). When the metal plate 120 has a rectangular shape, even if the portion corresponding to h2 is extended, there is no significant change in the characteristics regarding the noise improvement effect.

[0038] Similarly, FIG. 15 shows a case where the notch dimensions are changed in the shape corresponding to (9) in FIG. 13. FIG. 15 is a diagram showing an example of the noise improvement effect of a metal plate with a noise reduction structure according to the present disclosure (including a notch in an extended portion obtained by extending a quadrilateral). In the metal plate 130 having an extended rectangular shape, even if the notch dimensions are changed, there is no significant change in the characteristics regarding the noise improvement effect.

[0039] Next, the operation of the first embodiment will be described with reference to FIGS. 16 to 21.

[0040] FIG. 16 is a diagram showing an example of the current distribution on the metal plate 101 of the prior art noise reduction structure shown in FIG. 6. FIG. 16 shows the current distribution as seen from the front (the receiving antenna 400 side) of the metal plate 101. The noise radiated from a noise source 200 (not shown) placed deep in the back of the metal plate 101 becomes a noise current on the back of the metal plate 101, and wraps around from the left and right ends of the metal plate 101 and is transmitted to the front. Since the dipole antenna used as the noise source 200 is horizontally arranged on the back, the noise current also flows horizontally, that is, in the left-right direction. The magnetic field and the electric field generated by this noise current radiate in the horizontal direction, so it can be said that the horizontally arranged receiving antenna 400 is in a state most susceptible to noise.

[0041] On the other hand, FIG. 17 is a diagram showing an example of the current distribution on the metal plate (trapezoidal) of the noise reduction structure according to the present disclosure shown in FIG. 7. That is, FIG. 17 shows an example of the current distribution on the metal plate 102, which is one shape of the metal plate of the noise reduction structure of the present invention, as seen from the front (the receiving antenna 400 side). In FIG. 17, an area 102A where no current flows is generated at the upper part of the metal plate 102 with respect to the receiving antenna 400. This is the reason why S21 is improved.

[0042] Next, the reason for the generation of the area 102A where no current flows will be described with reference to FIG. 18.

[0043] FIG. 18 is a diagram showing an example of the current flowing on the metal plate 102 (trapezoidal) of the noise reduction structure according to the present disclosure shown in FIG. 7. In FIG. 18, the current flowing on the metal plate 102 is illustrated by arrows. FIG. 18(a) shows a perspective view of the back side of the metal plate 102 (that is, a view seen from the front, but the current flowing on the back is shown), and FIG. 18(b) shows the front side of the metal plate 102. Also, the shading attached to the arrows indicates the strength of the current, and it is assumed that "the darker the color, the stronger the current".

[0044] When a horizontal current as shown in Fig. 18(a) is generated due to the noise radiated from the noise source 200, the current is folded back at the left and right ends inclined at 45°, and is transmitted to the front side of the metal plate 102 as shown in Fig. 18(b). Since the left and right ends are inclined at 45°, the current transmitted to the front side at that time changes the direction of the current to the vertical direction as shown in Fig. 18(b). Further, this current is stronger near the center on the back side of the metal plate 102 of the noise source 200 (not shown). For this reason, as shown in Fig. 18(b), the vertical current on the front side of the metal plate 102 is stronger at the upper part of the metal plate 102 and weaker at the lower part. Therefore, at the upper part of the metal plate 102, since the directions of the left and right currents are different, they cancel each other out, and an area 102A (hatched part) where no current flows between the currents is generated. On the other hand, at the lower part of the metal plate 102, since the current is weak, the canceling effect is small.

[0045] Fig. 19 is a diagram showing an example of the current distribution on the metal plate (extending the long side of the trapezoid) of the noise reduction structure according to the present disclosure shown in Fig. 8. In Fig. 17 described above, since the area where no current flows was slightly shifted upward with respect to the receiving antenna 400, the noise improvement effect of S21 was small. On the other hand, in the shape of the metal plate 103 in which the lower part of the trapezoid is extended by 40 mm as shown in Fig. 8, as shown in Fig. 19, the receiving antenna 400 and the area 103A where no current flows coincide, and the noise improvement effect of S21 is enhanced.

[0046] Fig. 20 is a diagram showing an example of the current distribution on the metal plate (extending the long side of the trapezoid) of the noise reduction structure according to the present disclosure shown in Fig. 10. In the shape of the metal plate 104 in which the lower part of the trapezoid is further extended to 140 mm as described in Fig. 10, as shown in Fig. 20, the area 104A where no current flows moves too far downward, and the current near the receiving antenna 400 increases. For this reason, S21 deteriorates.

[0047] FIG. 21 is a diagram showing an example of the current distribution on the metal plate (extending the long side of the trapezoid) of the noise reduction structure according to the present disclosure shown in FIG. 11. When S21 deteriorates as in the metal plate 104 described in FIG. 20, if a notch is made in the 140 mm extended portion at the lower part of the trapezoid, like the shape of the metal plate 110 shown in FIG. 11, as shown in FIG. 21, the current distribution near the receiving antenna 400 becomes equivalent to the current distribution in the case of the metal plate 103 shown in FIG. 19. As a result, S21 is improved by reducing the current in the current-free area 110A near the receiving antenna 400.

[0048] According to the first embodiment, it is possible to provide a noise reduction structure that contributes to reducing the influence of noise by installing a metal plate having a shape with a high noise shielding effect between the noise source and the receiving antenna.

[0049] [Second Embodiment] Next, the second embodiment will be described in detail with reference to the drawings.

[0050] FIG. 22 is a diagram showing an example of a metal plate (circular) of the noise reduction structure according to the present disclosure and an example of its noise improvement effect. Referring to FIG. 22, the noise source 200 and the receiving antenna 400 are arranged 40 mm below the upper end of the metal plate 150 shown in FIG. 22(a) under the same conditions as in the case of the first embodiment described above. When S21 is calculated with the diameter of the metal plate 150 being R, characteristics as shown in the graph of FIG. 22(b) are obtained. From this graph, it can be seen that S21 tends to deteriorate when the diameter is 220 mm to 280 mm. Note that FIG. 22(c) shows the values shown in the graph of FIG. 22(b) in a table.

[0051] FIG. 23 is a diagram showing an example of a metal plate (circular and notched) of the noise reduction structure according to the present disclosure and an example of its noise improvement effect. (a) of FIG. 23 shows a metal plate 160 with the upper end of the notch arranged at a position 80 mm below the receiving antenna 400, similar to the first embodiment. (b) of FIG. 23 is a graph plotted for each value of W1 with W1, W2, and R (the vertical width of the notch, the dimension between notches, and the diameter, respectively) as parameters. (c) of FIG. 23 shows the values indicated by the graph of (b) of FIG. 23 in a table. From this result, it can be seen that the deterioration of S21 at diameters of 220 to 280 mm existing in the metal plate 150 of FIG. 22 is improved by adding notches regardless of the values of W1 and W2. The present shape of the metal plate 160 is the fourth shape of the metal plate according to the present disclosure. Note that the dimension between notches is preferably 0.3 wavelength (λ) or less.

[0052] Next, the reason for the improvement by adding notches will be described with reference to the current distribution. FIG. 24 is a diagram showing an example of the current distribution on a metal plate (circular) 150 of the noise reduction structure according to the present disclosure shown in FIG. 22. The diameter of the metal plate 150 is set to 260 mm, which is the deterioration point. Referring to FIG. 24, it can be seen that a strong current is flowing near the receiving antenna 400.

[0053] FIG. 25 is a diagram showing an example of the current distribution on a metal plate (circular and notched) 160 of the noise reduction structure according to the present disclosure shown in FIG. 23. That is, FIG. 25 is a diagram showing the current distribution on the metal plate 160 obtained by adding notches to the metal plate 150. The diameter R = 260 mm, W1 = 60 mm, and W2 = 100 mm are set. It can be seen that an area 160A where no current flows is generated near the receiving antenna 400.

[0054] As described above, according to the present second embodiment, it is possible to provide a noise reduction structure that contributes to reducing the influence of noise by installing a metal plate having a shape with a high noise shielding effect between the noise source and the receiving antenna.

[0055] [Third Embodiment] Next, the third embodiment will be described in detail with reference to the drawings.

[0056] FIG. 26 is a diagram showing an example of a metal plate (donut shape) of a noise reduction structure according to the present disclosure and an example of its noise improvement effect. Further, FIG. 27 is a diagram showing the reason for a portion where the noise improvement effect cannot be obtained in an example of a metal plate (donut shape) of the noise reduction structure shown in FIG. 26. In FIG. 26(a), a donut-shaped metal plate 170 having a hole in the center of a circle is shown. FIG. 26(b) shows S21 of a shape without a hole (i.e., the metal plate (circular) 150 shown in FIG. 22), and FIG. 26(c) shows S21 with respect to the hole diameter. Further, FIG. 26(d) is a table showing the values of the graph of FIG. 26(c). Referring to FIGS. 26(b) and 26(c), it can be seen that S21 tends to deteriorate when the hole diameter is 100 mm or more with respect to the shape without a hole. In addition, the portions filled with gray in the table of FIG. 26(d) are portions that are excluded from evaluation because, as shown in FIG. 27(a), the hole overlaps the noise source 200 and the receiving antenna 400 and no shielding effect can be obtained. The reason for opening a hole in the center is to assume actual use such as passing a power cord or a fixing structure.

[0057] FIG. 28 is a diagram showing an example of a metal plate with a noise reduction structure according to the present disclosure (doughnut shape and notch (lower position)) and an example of its noise improvement effect. Further, FIG. 29 is a diagram showing the reason for the portion where the noise improvement effect cannot be obtained in an example of the metal plate with the noise reduction structure shown in FIG. 28 (doughnut shape and notch (lower position)). (a) of FIG. 28 is a metal plate 180 having a shape in which the notch adopted in the first embodiment is added to the doughnut-shaped metal plate 170 shown in FIG. 26. (b) of FIG. 28 is a diagram plotting the values shown in the table of (c) of FIG. 28, and the table of (c) of FIG. 28 shows S21 when the diameter R is changed with respect to the hole diameter and W1 and W2. Looking at the graph of (b) of FIG. 28, it can be seen that in the case of the doughnut-shaped metal plate 180, even if a notch is added, a large noise improvement effect cannot be obtained. Incidentally, the hatched portion in the table of (c) of FIG. 28 is a portion excluded from evaluation because, as shown in (a) of FIG. 29, the hole and the notch overlap and the shape of the metal plate 180 cannot be maintained.

[0058] FIG. 30 is a diagram showing an example of a metal plate with a noise reduction structure according to the present disclosure (doughnut shape and notch (left and right positions of the hole)) and an example of its noise improvement effect. In the case of the doughnut-shaped metal plate 170 as shown in (a) of FIG. 26, as shown in (a) of FIG. 30, the center position of the notch is aligned with the same height as the center of the hole so that notches come to the left and right of the hole. (b) of FIG. 30 is a diagram plotting the values shown in the table of (c) of FIG. 30, and the table of (c) of FIG. 30 shows S21 when the diameter R is changed with respect to the hole diameter and W1. By using a metal plate 190 having such a shape, a large noise improvement effect can be obtained particularly at diameters of 220 to 280 mm. This shape is the fifth shape of the metal plate according to the present disclosure.

[0059] FIG. 31 is a diagram showing an example of a metal plate with a noise reduction structure according to the present disclosure (changing the distance from the hole with a donut shape and notches (left and right positions of the hole)) and an example of its noise improvement effect. As shown in FIG. 31(a), the distance between the hole and the notch is defined as D such that notches come on the left and right of the hole. FIG. 31(b) is a diagram plotting the values shown in the table of FIG. 31(c), and the table of FIG. 31(c) shows S21 when the diameter R is changed with respect to the distance D between the hole and the notch. As shown in FIG. 31(b), in this shape, it can be seen that the closer the distance D between the hole and the notch is, the higher the noise improvement effect is.

[0060] Next, the reason why the noise improvement effect is high will be described with reference to the current distributions shown in FIGS. 32 and 33. FIG. 32 is a diagram showing an example of the current distribution on a metal plate 170 which is an example of the donut shape shown in FIG. 26. Further, FIG. 33 is a diagram showing an example of the current distribution on a metal plate 190 which is an example of the donut shape including notches (left and right positions of the hole) shown in FIG. 30. With respect to the current distribution in the current non-flow area 170A near the receiving antenna 400 on the donut-shaped metal plate 170 described in FIG. 32, in the metal plate 190 with the shape having notches added to the left and right in FIG. 33, it can be seen that the current decreases in the current non-flow area 190A near the receiving antenna 400.

[0061] According to the third embodiment, it is possible to provide a noise reduction structure that contributes to reducing the influence of noise by installing a metal plate with a shape having a high noise shielding effect between the noise source and the receiving antenna.

[0062] [Fourth Embodiment] Next, the fourth embodiment will be described in detail with reference to the drawings.

[0063] FIG. 34 is a diagram showing an example of the noise improvement effect when changing the shape of the donut-shaped hole and the shape of the notch (left and right positions of the hole) in the metal plate 190 which is an example of the noise reduction structure according to the present disclosure shown in FIG. 30. In the third embodiment, the value of S21 when the shape of the donut-shaped hole is circular and the left and right notch shapes are angular is shown. On the other hand, in FIG. 34, S21 is shown when the shape of the hole is circular, rhombic, or angular, and the shape of the left and right notches is circular, rhombic, or angular. The case where the hole is circular and the left and right notches are angular, which is the shape shown in the fourth embodiment, has the highest noise improvement effect of S21.

[0064] According to the fourth embodiment, it is possible to provide a noise reduction structure that contributes to reducing the influence of noise by installing a metal plate having a shape with a high noise shielding effect between the noise source and the receiving antenna.

[0065] Note that each of the noise shielding metal plates (metal plates) 100, 101, 102, 103, 104, 110, 120, 130, 150, 160, 170, 180, 190 described in one embodiment and the first to fourth embodiments, and each of the noise shielding metal plates (metal plates) described in FIG. 34 may be installed in the wireless device 300 shown in FIG. 1. When each of the noise shielding metal plates 100, 101, 102, 103, 104, 110, 120, 130, 150, 160, 170, 180, 190 and each of the noise shielding metal plates (metal plates) described in FIG. 34 are installed in the wireless device 300, it is possible to reduce noise and provide a wireless device 300 with good reception performance.

[0066] The reason is that according to the present invention, even when the noise shielding metal plate becomes less than half a wavelength (λ) in a small wireless device and a sufficient shielding effect cannot be obtained, the noise reduction effect can be enhanced by changing the shape of the noise shielding metal plate.

[0067] As described above, each embodiment of the present invention has been explained. However, the present invention is not limited to the above-described embodiments, and further modifications, substitutions, and adjustments can be made without departing from the basic technical idea of the present invention. For example, the network configuration shown in each drawing, the configuration of each element, and the expression form of the message are examples for helping the understanding of the present invention, and are not limited to the configurations shown in these drawings. Also, "A and / or B" is used to mean at least either A or B.

[0068] Finally, the preferred forms of the present invention will be summarized. [First Form] The noise shielding metal plate of the noise reduction structure may have a shape that forms a region where the current generated by the noise source decreases. In the noise reduction structure, the noise shielding metal plate may be installed between the receiving antenna and the noise source so that the receiving antenna of the wireless device corresponds to a position within the region where the current generated by the noise source decreases. [Second Form] In the noise reduction structure according to the first form, it is preferable that the shape includes the other two sides inclined at 45° with respect to the two parallel sides of the trapezoid. [Third Form] In the noise reduction structure according to the first form, the shape includes the other two sides inclined at 45° with respect to the two parallel sides of the trapezoid, and includes an extended portion obtained by extending the long side of the two parallel sides of the trapezoid in an extending direction orthogonal to the short side of the two parallel sides of the trapezoid, and it is preferable that the extended length of the extended portion is 0.06 wavelength (λ) or more and 0.11 wavelength (λ) or less of the wavelength (λ) of the signal of the noise source to be shielded. [Fourth Form] In the noise reduction structure according to the first form, the shape includes the other two sides inclined at 45° with respect to the two parallel sides of the trapezoid, and includes an extended portion obtained by extending the long side of the two parallel sides of the trapezoid in an extending direction orthogonal to the short side of the two parallel sides of the trapezoid, It is preferable that notches are provided on both of two sides parallel to the extension direction in the extension part. [Fifth Embodiment] In the noise reduction structure according to the fourth embodiment, the extended length of the extension part is 0.4 wavelengths (λ) of the wavelength (λ) of the signal of the noise source to be shielded, the notch is provided starting from a position that is 0.06 wavelengths (λ) or more and 0.11 wavelengths (λ) or less away from the long side position of the trapezoid, it is preferable that the dimension between the notches provided on both of the two sides parallel to the extension direction is 0.3 wavelengths (λ) or less. [Sixth Embodiment] In the noise reduction structure according to the first embodiment, it is preferable that the shape is circular and includes notches provided at the edge ends facing the line symmetry of the circle. [Seventh Embodiment] In the noise reduction structure according to the sixth embodiment, the notch is located on a straight line passing through the edge end and the center of the circle, and is equidistant from the position of the noise source closer to the edge end than the center by the distance between the edge end and the noise source, and is further separated from the center direction of the circle by the same distance, and is provided starting from a position that is 0.06 wavelengths (λ) or more and 0.11 wavelengths (λ) or less away from the center direction, it is preferable that the dimension between the notches is 0.3 wavelengths (λ) or less. [Eighth Embodiment] In the noise reduction structure according to the first embodiment, the shape is a donut shape, and includes notches provided at the second outermost edge end and the third outermost edge end of the donut shape that are point-symmetric with respect to the center of the donut shape on a straight line in a direction orthogonal to the straight line passing through the first outermost edge end of the donut shape, the noise source, and the center of the donut shape, it is preferable that the hole of the donut shape is circular. [Ninth Embodiment] In the noise reduction structure according to the first embodiment, it is preferable that the noise shielding metal plate is installed inside the wireless device. [Tenth Embodiment] In the noise reduction structure according to the first embodiment, it is preferable that the material of the noise shielding metal plate is iron, copper, aluminum, stainless steel, or a combination thereof.

[0069] Note that the disclosures of the above patent documents are incorporated herein by reference. Within the scope of the entire disclosure of the present invention (including the claims), further modifications and adjustments of the embodiments or examples can be made based on the basic technical idea. Also, within the scope of the disclosure of the present invention, various combinations or selections of various disclosure elements (including each element of each claim, each element of each embodiment or example, each element of each drawing, etc.) are possible. That is, the present invention naturally includes all the disclosures including the claims, and various deformations and modifications that a person skilled in the art could make according to the technical idea. In particular, regarding the numerical ranges described in this document, any numerical value or small range included within the range should be construed as specifically described even without separate description. Furthermore, each disclosure item of the above-cited documents is, if necessary, considered to be included in the disclosure of the present application as part of the disclosure of the present invention, and can be used in combination with the description items of this document, either in part or in whole, in accordance with the spirit of the present invention.

Explanation of Reference Numerals

[0070] 10 Noise reduction structure 100, 101, 102, 103, 104, 110, 120, 130, 150, 160, 170, 180, 190 Noise shielding metal plate (metal plate) 102A, 103A, 104A, 110A, 160A, 170A, 180A Area where no current flows 200 Noise source 300 Wireless device 400 Receiving antenna

Claims

1. The noise shielding metal plate has a shape that forms a region where the current generated by the noise source decreases, A noise reduction structure in which a noise shielding metal plate is installed between the receiving antenna and the noise source so that the receiving antenna of the wireless device corresponds to a position within the region where the current generated by the noise source decreases.

2. The noise reduction structure according to claim 1, wherein the shape includes two other sides inclined at 45° with respect to two parallel sides of a trapezoid.

3. The shape includes two other sides inclined at 45° with respect to two parallel sides of a trapezoid, and The long side of the two parallel sides of the trapezoid includes an extended portion extended in an extending direction orthogonal to the short side of the two parallel sides of the trapezoid, The noise reduction structure according to claim 1, wherein the extended length of the extended portion is 0.06 wavelength (λ) or more and 0.11 wavelength (λ) or less of the wavelength (λ) of the signal of the noise source to be shielded.

4. The shape includes two other sides inclined at 45° with respect to two parallel sides of a trapezoid, and The long side of the two parallel sides of the trapezoid includes an extended portion extended in an extending direction orthogonal to the short side of the two parallel sides of the trapezoid, The noise reduction structure according to claim 1, wherein notches are provided on both of two sides parallel to the extending direction in the extended portion.

5. The extended length of the extended portion is 0.4 wavelength (λ) of the wavelength (λ) of the signal of the noise source to be shielded, The notch is provided starting from a position 0.06 wavelength (λ) or more and 0.11 wavelength (λ) or less away from the long side position of the trapezoid, The noise reduction structure according to claim 4, wherein the dimension between the notches provided on both of the two sides parallel to the extending direction is 0.3 wavelength (λ) or less.

6. The noise reduction structure according to claim 1, wherein the shape is circular and includes notches provided at the opposite edges of the circular line symmetry.

7. The notch is located on a straight line passing through the edge and the center of the circle, and is separated from the position of the noise source closer to the edge than the center by an equal distance in the direction of the center of the circle, and further, in the same direction as the center direction, starting from a position 0.06 wavelength (λ) or more and 0.11 wavelength (λ) or less away, The noise reduction structure according to claim 6, wherein the dimension between the notches is 0.3 wavelength (λ) or less.

8. The shape is a donut shape, Including notches provided at the second outermost edge and the third outermost edge of the donut shape that are symmetric with respect to a point across the center of the donut shape on a straight line orthogonal to the straight line passing through the outermost edge of the first donut shape, the noise source, and the center of the donut shape. The noise reduction structure according to claim 1, wherein the hole of the donut shape is circular.

9. The noise reduction structure according to claim 1, wherein the noise shielding metal plate is installed inside the wireless device.

10. The noise reduction structure according to claim 1, wherein the material of the noise shielding metal plate is iron, copper, aluminum, stainless steel, or a combination thereof.

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