Shielding cases and electronic equipment

Abstract

The present invention provides a shield case with a novel structure that can suppress spurious emissions originating from the shield case with a simpler structure than conventional shield cases, and electronic equipment using the same. [Solution] The shield case 10 includes a ridge line 10a and an inclined surface wall 10b connected to the ridge line, enclosing the shield area 10x from the ridge line and extending to the lower boundary of the shield area. The inclined surface wall 10b is composed of an inclined wall with a uniform slope. The electronic device 110 includes the shield case 10 and a high-frequency circuit 11 enclosed therein.

Description

[Technical Field]

[0001] The present invention relates to a shield case capable of suppressing spurious signals caused by resonance in the shield case, and an electronic device using the same. [Background Art]

[0002] Shield cases are widely used in electronic devices to reduce characteristic deterioration caused by unwanted electromagnetic waves. One type of unwanted electromagnetic wave is spurious signals generated due to resonance of the shield case. Examples of conventional techniques for suppressing this spurious signal include the following. Patent Document 1 describes a shield case configured of a rectangular parallelepiped shield box and a metal antenna member disposed inside the shield box with an optimized length, for suppressing radiation noise radiated from the entire shield box due to cavity resonance (see the abstract of Patent Document 1, etc.). Patent Document 2 describes a shield case in which, in order to suppress unwanted resonance caused by the shield case, all of the vertical, horizontal, depth, diagonal and arbitrary dimensions of the shield case are set to be shorter than half the wavelength of the maximum frequency among the used frequencies (see, for example, the abstract, paragraph 29, Figure 6, etc. of Patent Document 2).

[0003] Patent Document 3 describes a shield case in which, in order to suppress resonance within the shield case, the vertical, horizontal, and height dimensions of a cavity provided in the shield case are set such that a difference between a used frequency band and the resonance frequency of the cavity obtained by a predetermined formula is equal to or larger than a predetermined value (see, for example, the abstract, claim 3, etc. of Patent Document 3). [Prior Art Documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Unexamined Patent Application Publication No. 2004-214534 [Patent Document 2] Japanese Unexamined Patent Application Publication No. 2015-109551 [Patent Document 3] Japanese Patent Publication No. 2015-119295 [Overview of the project] [Problems that the invention aims to solve]

[0005] Conventional shielding cases are thought to be able to suppress spurious emissions caused by the resonance of the shielding case, but they require antenna components and detailed design of the length, width, and height dimensions of the shielding case. If it is possible to improve spurious emission suppression with a simpler configuration compared to these, it would be useful for the design of shielding cases. This application has been filed in view of these points, and therefore the object of this application is to provide a shield case having a novel structure that can suppress spurious emissions caused by the shield case with a simpler structure than conventional ones, and electronic equipment using the same. [Means for solving the problem]

[0006] To achieve this objective, the shield case of the first invention of this application is characterized by including a ridge line or top surface and an inclined surface-shaped wall connected to the ridge line or top surface and extending from the ridge line or top surface to surround the shield area and to the lower boundary of the shield area. In carrying out this invention, the inclined surface wall may be any of the following: an inclined wall with a uniform slope, an inclined wall with two or more varying slopes, a curved wall with a curved slope, or a wall that includes any of these types of walls. Furthermore, in carrying out this invention, the shield case may include a vertical wall connected to the aforementioned inclined surface wall.

[0007] Furthermore, the electronic device of the second invention of this application is characterized by including a shielding case according to the first invention and a high-frequency circuit enclosed within the shielding case. Here, high-frequency circuits refer to circuits that handle microwaves, millimeter waves, etc. However, they are not limited to these; any low-noise amplifiers, mixers, etc. that handle microwaves or millimeter waves are acceptable. Electronic equipment refers to various electronic devices that handle high frequencies and require shielding, such as signal generators (e.g., frequency synthesizers) and signal converters (e.g., frequency converters). [Effects of the Invention]

[0008] The shield case of this invention includes a predetermined inclined surface wall as a shield wall. As can be seen from the simulation results of the comparative examples and embodiments described later, compared to a shield case that is simply rectangular in shape, it has the effect of suppressing the generation of spurious emissions in the desired frequency band. Furthermore, even if the height dimension is the same as that of a conventional rectangular shield case, it has the effect of expanding the usable frequency band, i.e., the band unaffected by spurious emissions. Moreover, the above effects can be obtained with a simple configuration that includes an inclined surface and / or a curved surface wall within the shield wall. Therefore, it is possible to provide a shield case with a novel structure that can suppress spurious emissions caused by the shield case with a simpler structure than conventional ones, and electronic equipment using the same. [Brief explanation of the drawing]

[0009] [Figure 1] This is a diagram illustrating the shield case 10 of the first embodiment. [Figure 2] This is a diagram illustrating the shield case 20 of the second embodiment. [Figure 3] This is a diagram illustrating the shield case 30 of the third embodiment. [Figure 4] This is a diagram illustrating the shield case 40 of the fourth embodiment. [Figure 5] This is a diagram illustrating the shield case 50 of the fifth embodiment. [Figure 6] This is a diagram illustrating the shield case 60 of the sixth embodiment. [Figure 7] This is a diagram illustrating the comparative example shield case 200. [Figure 8] This figure illustrates the differences in spris suppression effects between the shield cases of the first, second, third, and fourth embodiments and the comparative example shield case.

[0010] The embodiments of each invention in this application will be described below with reference to the drawings. Note that the drawings used in this description are only schematic representations sufficient to understand the invention. Furthermore, in the drawings used in this description, similar components are indicated with the same number, and their descriptions may be omitted. Also, the shapes, dimensions, materials, etc., described below are merely preferred examples within the scope of this invention. Therefore, the present invention is not limited to the embodiments described below.

[0011] 1. Description of Embodiments 1-1. First Embodiment Figure 1 is a diagram illustrating the shield case 10 and electronic equipment 110 of the first embodiment. In particular, Figure (A) is a perspective view thereof, and Figure (B) is a side view seen from direction P in Figure (A). In Figure 1, 12 represents, for example, the housing or circuit board of the electronic equipment, and is any component used to fix the shield case 10. Also, 100 in Figure 1 represents any high-frequency circuit (which may include waveguides, etc.) enclosed within the shield case 10, and is a high-frequency circuit 100 including any microwave circuit 100a, etc. However, in the high-frequency circuit 100, input / output ports and other features are omitted from the illustration. In this case, the shield case 10 and the high-frequency circuit 100 constitute the electronic device 110 of the embodiment. The shield case 10 of the first embodiment includes a ridge line 10a, and an inclined surface-shaped wall connected to the ridge line 10a, surrounding a shield region 10x (the hatched region in FIG. 1(A)) from the ridge line 10a and extending to the lower boundary of the shield region 10x, which is an inclined wall 10b with uniform inclination in this case. More specifically, the inclined wall 10b extends from the ridge line 10a in two directions intersecting the ridge line 10a to the lower boundary of the shield region 10x. Accordingly, the inclined walls 10b constitute two opposing walls of the shield case 10. The other two side walls of the shield case 10 are vertical walls 10c in this case. Therefore, the shield case 10 of the first embodiment generally has a triangular tent shape. It should be noted that the other two side walls of the shield case 10 (here, the side walls on the vertical wall 10c side) may include the inclined surface-shaped wall referred to in the present invention.

[0012] The constituent material of the shield case 10 may be any conductive material, and metal is typically preferable. The shield case 10 may be manufactured by any suitable method, such as a press-molded product, a welded product of metal members, or a cut product in which the inner surface of a solid metal material forms the inclined wall referred to in the present invention. The shield case according to the present invention that is a cut product refers to a shield case in which the interior of a solid metal material has the wall structure according to the present invention. The length a of the ridge line 10a of the shield case 10 (which is also the depth dimension of the shield case 10 in this case), the height b of the shield case 10, the width L of the shield case 10, and the inclination angle θ of the inclined wall 10b can each be determined according to the area of the shield region 10x, the planar size of the included high-frequency circuit, the frequency handled by the high-frequency circuit, the height of the high-frequency circuit, and the like. Examples of these dimensions a, b, L and angle θ are shown in the section on electromagnetic field simulation described later.

[0013] 1-2. Second Embodiment FIG. 2 is a perspective view for explaining a shield case 20 of the second embodiment. The shield case 20 of the second embodiment comprises a top surface 20a (the hatched region in FIG. 2) and an inclined planar wall connected to the top surface 20a, surrounding the shield region 10x from the top surface 20a and extending to the lower boundary of the shield region 10x, which is an inclined wall 20b with uniform inclination in this case. More specifically, the top surface 20a in this case is a flat top surface having a rectangular shape in plan view, specifically an oblong shape. That is, it is a flat oblong surface having a long side dimension a and a short side dimension L1 (<L). Then, from the top surface 20a, the inclined walls 20b extend to the lower boundary of the shield region 10x in two directions intersecting the top surface 20a. Accordingly, the inclined walls 20b constitute two opposing walls of the shield case 20. The other two side walls of the shield case 20 are vertical walls 20c. Therefore, although the shield case 20 of the second embodiment has a flat top surface 20a, it generally has a triangular tent shape. It should be noted that the vertical wall 20c may optionally include the inclined planar wall according to the present invention. Furthermore, the top surface 20a is not limited to a flat surface, and may partially have a non-flat surface such as a curved surface.

[0014] 1-3. Third Embodiment FIG. 3 is a perspective view for explaining a shield case 30 of the third embodiment. The shield case 30 of the third embodiment comprises a ridge line 30a, an inclined planar wall connected to the ridge line 30a, surrounding the shield region 10x from the ridge line 30a and extending to the lower boundary of the shield region 10x, which is a curved wall 30b in this case, and an inclined planar wall formed by a vertical wall 30c (the hatched region in FIG. 3) connected to the curved wall 30b. The other two walls of the shield case 30 are vertical walls 30d. Accordingly, the shield case 30 of the third embodiment generally has a dome tent shape in which part of the side walls is formed as the vertical wall 30c. It should be noted that the vertical wall 30d may optionally include the inclined planar wall according to the present invention. The vertical height b1 of the curved wall 30b and the height b2 of the vertical wall 30c may be the same or different. The curvature r of the curved wall 30b can be determined according to design requirements. An example of these dimensions b1, b2, and r will be described in the section on electromagnetic field simulation later.

[0015] 1-4. Fourth Embodiment Figure 4 is a perspective view illustrating the shield case 40 of the fourth embodiment. The shield case 40 of the fourth embodiment includes a ridge line 40a and a curved wall 40b that is connected to the ridge line 40a and extends from the ridge line 40a to surround the shield area 10x and to the lower boundary of the shield area 10x. In other words, the shield case 40 of the fourth embodiment is equivalent to the shield case 30 of the third embodiment in that it does not have a vertical wall 30c.

[0016] 1-5. Fifth Embodiment Figure 5 is a perspective view illustrating the shield case 50 of the fifth embodiment. The shield case 50 of the fifth embodiment includes a ridge line 50a, an inclined surface wall connected to the ridge line 50a and extending from the ridge line 50a to surround the shield area 10x and to the lower boundary of the shield area 10x, in this case an inclined wall 50b, and a vertical wall 50c (the area with a diagonal pattern in Figure 5) connected to this inclined wall 50b. The other two walls of the shield case 50 are vertical walls 50d. Therefore, the shield case 50 of the fifth embodiment has a general shape resembling a house-shaped tent. Note that the vertical wall 50d may include the inclined surface wall as defined in this invention. The vertical height b1 of the inclined wall 50b and the height b2 of the overhanging wall 50c may be the same or different.

[0017] 1-6. Sixth Embodiment Figure 6 is a perspective view illustrating the shield case 60 of the sixth embodiment. The shield case 60 of the sixth embodiment includes a top surface 60a (the hatched area in FIG. 6), and an inclined wall connected to the top surface 60a, surrounding the shield region 10x from the top surface 60a and extending to the lower boundary of the shield region 10x, which is a curved wall 60b herein. More specifically, the top surface in this case is a flat top surface having a rectangular shape in plan view, specifically a rectangular shape. That is, it is a flat rectangular surface having a long side dimension a and a short side dimension L1 (<L). Curved walls 60b extend from the top surface 60a in two directions intersecting the top surface 20a to the lower boundary of the shield region 10x. Accordingly, two opposing walls of the shield case 60 are formed by the side walls 60b. The other two side walls of the shield case 60 are vertical walls 60c. Therefore, although the shield case 60 of the sixth embodiment has a flat top surface 60a, it generally has a dome tent shape. Note that the vertical wall 60c may include the inclined wall as referred to in the present invention. Further, the top surface 60a is not limited to a flat surface, and may partially have a non-flat surface, such as a curved surface.

[0018] 2. Simulation 2-1. Simulation Conditions Electromagnetic field simulation was performed on the shield cases of the first, second, third, and fourth embodiments among the above-described embodiments, and the shield case 200 of a comparative example described below with reference to FIG. 7, to confirm the spurious suppression effect of each shield case. The electromagnetic field simulation was performed using Ansys HFSS (registered trademark) electromagnetic field simulation software.

[0019] First, as the shield case of the comparative example, a rectangular parallelepiped shield case 200 having a width dimension L, a depth dimension a, and a height dimension b shown in the perspective view of FIG. 7 is used. Next, the width L of the comparative example shield case 200 was fixed at 2.4 mm and the depth at 4.4 mm, and the height b was varied to multiple levels between 0.21 mm and 2.4 mm. For these shield cases 200, the spurious emission frequencies for a 62.5 GHz signal were extracted by simulation. The reason for choosing 62.5 GHz is that it is near the center frequency of the frequency band used in automotive radar, etc. Therefore, the wavelength of the 62.5 GHz frequency used in the simulation is approximately 4.8 mm, and the half-wavelength is 2.4 mm. The 2.4 mm height level of the shield case in this simulation takes into account the half-wavelength of the simulation frequency of 64.5 GHz. However, the frequency used in the simulation is just an example, and other frequencies may be used.

[0020] Furthermore, in the shield case 10 of the first embodiment, the width dimension L in Figure 1 was changed to 2.4 mm, the depth dimension a to 4.4 mm, and the height dimension b to multiple levels between 0.6 mm and 2.4 mm, and the spurious emission frequencies for a 62.5 GHz signal were extracted by simulation for these shield cases 10.

[0021] Furthermore, for a shield case 20 of the second embodiment, in which the width dimension L in Figure 2 is 2.4 mm, the depth dimension is 4.4 mm, the height dimension b is 2.4 mm, and the short side dimension L1 of the top surface 20a is 1.2 mm, the spurious emission frequency for a signal with a frequency of 62.5 GHz was extracted by simulation.

[0022] Furthermore, for a shield case 30 of the third embodiment, in which the width dimension L in Figure 3 is 2.4 mm, the depth dimension a is 4.4 mm, the height dimension b is 2.4 mm, the curvature of the curved wall 30b is radius r of 1.2 mm, the height dimension b1 of the curved wall is 1.2 mm, and the height dimension b2 of the vertical wall 30c is 1.2 mm, the spurious emission frequency for a signal with a frequency of 62.5 GHz was extracted by simulation.

[0023] Furthermore, for the shield case 40 of the fourth embodiment, in which the width dimension L in Figure 4 is 2.4 mm, the depth dimension is 4.4 mm, the height dimension b is 2.4 mm, and the radius r of the curvature of the curved wall 40b is 2.4 mm, the spurious emission frequency for a signal with a frequency of 62.5 GHz was extracted by simulation.

[0024] 2-2. Simulation Results and Discussion Figure 8 shows the spurious emission status of the comparative example and each embodiment of the shield case based on the simulation described above, with the height dimension b on the horizontal axis and the spurious emission frequency on the vertical axis. In Figure 8, the multi-point plots marked with white circles (〇) represent the simulation results of the comparative example shield case, plot S1 marked with a diamond (◆) represents the simulation results of the shield case of the first embodiment, plot S2 represents the simulation results of the shield case of the second embodiment, plot S3 represents the simulation results of the shield case of the third embodiment, and plot S4 represents the simulation results of the shield case of the fourth embodiment. Figure 8 shows that, in the case of the comparative example shield case, within the 62.5 GHz frequency band, the spurious emission frequency shifts relatively significantly to the higher frequency side as the height increases, from approximately 0.21 mm to 1.4 mm. However, it then saturates around 65 GHz to 68 GHz. In other words, in the case of the comparative example shield case, no matter how much the height is increased beyond 1.4 mm, which corresponds to half a wavelength of the simulation frequency of 64.5 GHz, spurious emission occurs around the 62.5 MHz frequency band.

[0025] On the other hand, it can be seen that all of the shield cases in the embodiments produce higher spurious emission frequencies compared to the comparative examples. Specifically, when comparing the case where dimension b in Figure 8 is 2.4 mm, in the case of the shield case of the first embodiment (S1 in Figure 8), the spurious frequency is shifted to the higher frequency side by approximately 9.3 GHz compared to the comparative example; in the case of the shield case of the second embodiment (S2 in Figure 8), the spurious frequency is shifted to the higher frequency side by approximately 6.8 GHz compared to the comparative example; in the case of the shield case of the third embodiment (S3 in Figure 8), the spurious frequency is shifted to the higher frequency side by approximately 4.3 GHz compared to the comparative example; and in the case of the shield case of the fourth embodiment (S4 in Figure 8), the spurious frequency is shifted to the higher frequency side by approximately 2.3 GHz compared to the comparative example. Moreover, as can be seen by comparing plot S1 of the first embodiment in Figure 8 with the plot of the comparative example, even at each level where the height dimension b is smaller than 2.4 mm, the present invention can shift the spurious emission frequency to the higher frequency side compared to the comparative example. Therefore, it can be seen that the shield case of this invention can extend the bandwidth free from spurious emissions. From another perspective, it can also contribute to reducing the height of the shield case.

[0026] Furthermore, comparing the first to fourth embodiments, it can be seen that the structure composed of ridges and inclined walls, as in the first embodiment, is the most effective at shifting spurious signals to the high-frequency side. Subsequently, the second, third, and fourth embodiments show increasing effectiveness in shifting spurious signals to the high-frequency side. In the structures of the embodiments, structures with a top surface, curved walls, and vertical walls have a slightly smaller effect in shifting spurious signals to the high-frequency side, but they have the effect of widening the shielding space compared to the structure with only inclined surfaces (as in the first embodiment). In other words, the dimensional margin for the planar size and height of the high-frequency circuit enclosed within the shielding case can be increased. From the above description, the shield case of the present invention has the effect of suppressing the generation of spurious emissions in the desired frequency band simply by including simple inclined walls or curved walls, and furthermore, it has the effect of expanding the usable frequency band, i.e., the band unaffected by spurious emissions, when the height dimension is the same as that of a conventional rectangular parallelepiped shield case, and it also contributes to making the shield case lower in height. [Explanation of symbols]

[0027] 10: Shield case of the first embodiment 20: Shield case of the second embodiment 30: Shield case of the third embodiment 40: Shield case of the fourth embodiment 50: Shield case of the fifth embodiment 60: Shield case of the sixth embodiment 10a, 30a, 40a, 50a: Ridge 10b, 20b, 50b: Slanted wall 30b:40b:60b:Curved wall 10c, 20c, 30c, 30d, 40c, 50c, 50d, 60c: hanging wall 10x: Shield area 100: High-frequency circuits 110: Electronic device of an embodiment 200: Shield case of the comparative example

Claims

1. A shield case characterized by including a ridge line or top surface, and an inclined surface-shaped wall connected to the ridge line or top surface and extending from the ridge line or top surface to the lower boundary of the shield area, surrounding the shield area.

2. The shield case according to claim 1, characterized in that the aforementioned inclined surface wall is an inclined wall with a uniform slope or an inclined wall with two or more varying slopes.

3. The shield case according to claim 1, characterized in that the inclined surface wall is a curved wall whose inclination changes in a curved manner.

4. The shield case according to claim 1, characterized in that it includes the aforementioned inclined surface wall and a vertical wall connected to this wall.

5. The shield case according to claim 1, characterized in that the aforementioned inclined surface wall is an inclined wall with a uniform slope.

6. The shield case according to any one of claims 1 to 5, characterized in that the side walls of the shield case other than the side wall including the inclined surface wall are vertical walls.

7. An electronic device comprising a shielding case according to any one of claims 1 to 5 and a high-frequency circuit enclosed within the shielding case.

8. The electronic device according to claim 7, characterized in that the side walls of the shield case other than the side wall including the inclined surface wall are vertical walls.

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