JP2020047730A - Shield plate and electronic device - Google Patents

Abstract

To provide a shield plate having a through-hole shaped to radiate noise dispersed in vertical polarization and horizontal polarization as compared with a simple circular or square through-hole, and an electronic device using the shield plate.SOLUTION: A shield plate includes a through-hole 5 having a point symmetric shape and penetrating the shield plate, and a pair of embedding portions 62 that form a part of an edge that extends inward from both sides so as to narrow the interval between the embedding portions and define the through-hole 5, and the through-hole 5 emits noise approaching circular polarization as compared with an original opening 6 when the embedding portion 62 is cut off by extrapolating the edge of a portion excluding a part formed by the embedded portion 62 among the edges defining the through opening 5.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a shield plate and an electronic device.

  If the noise is radiated, it may adversely affect surrounding electronic devices, and it is necessary to take a noise countermeasure to suppress the noise to a radiation level below an allowable value. As one of the measures against the noise, an electronic circuit which may emit noise is covered with a metal shield case. Since metal shields radio waves, if the electronic circuit is completely covered with the shield case, noise radiated from the electronic circuit can be confined in the shield case.

    However, when an actual shield case must be provided with an opening (through opening) penetrating in and out for drawing out a cable connected to an electronic circuit in the shield case to the outside and a through opening for air circulation. There is a problem that these through openings serve as secondary antennas and noise is radiated outside the shield case.

  Here, Patent Document 1 proposes an antenna that can switch between circularly polarized wave and linearly polarized wave mutually.

  Patent Document 2 proposes that an antenna is mounted in a shield case containing a noise source, and that the antenna receives radiated noise, thereby suppressing noise radiation from a through-opening.

  Further, Patent Document 3 discloses that a double shield case is provided with a slit in the vertical direction and another slit in the horizontal direction to allow heat radiation and to have a polarization component in the vertical direction. It has been proposed to suppress both noise and noise having a horizontally polarized component.

  Further, Patent Literature 4 proposes, similarly to Patent Literature 3, that a shield case is provided with one slit in the vertical direction and another slit in the horizontal direction.

JP 07-154133 A JP-A-2004-214534 JP-A-09-046084 JP-A-2005-230951

  When the electronic circuit is covered with a shield case, radiation that leaks out of the shield case, such as reducing the noise emission level itself from the electronic circuit or devising the number of through openings and the positions of the through openings in the shield case It is fundamental to take measures to reduce the noise itself. However, in the EMI test which is an index of the level of the radiated noise, the radiated noise is divided into vertically polarized waves and horizontally polarized waves, and the respective electric field strengths are measured. For this reason, even if the radiation noise has the same level, noise dispersed in vertical polarization and horizontal polarization is more advantageous than noise in which one of vertical polarization and horizontal polarization is strong.

  The present invention provides a shield plate having a through-hole shaped to radiate noise dispersed in vertical polarization and horizontal polarization as compared to a simple circular or square through-hole, and an electronic device employing the shield plate. The purpose is to do.

Claim 1
A shield plate forming at least a part of a member that covers a built-in electronic circuit,
A through-opening having a point-symmetrical shape and penetrating on both sides,
A shield plate comprising: a pair of buried portions that extend inward from both sides to form a part of an edge that defines the through-opening so as to narrow a space between each other.

  According to a second aspect of the present invention, when the through-opening is cut off by extrapolating an edge of a portion excluding a part formed by the embedded portion among edges defining the through-opening, the embedded portion is cut off. 2. The shield plate according to claim 1, wherein the shield plate is a through-opening that emits a noise approaching a circular polarization as compared with the original opening.

According to a third aspect of the invention, when the major axis of the elliptical polarization of the noise approaching the circular polarization is A and the minor axis is B, the noise passes through the point-symmetric center point of the through-opening and is perpendicular to the through-opening. The noise radiated in the direction
Axial ratio = 10 · log (A / B)
Is a noise of 10 or less.

  The original opening when the embedded portion is cut off by extrapolating an edge of a portion excluding a part formed by the embedded portion among edges defining the through-opening is a square. A pair of triangular embeddings, each of which includes a rectangle and a rhombus, and wherein the embedding portion extends from each of a pair of corners of the original opening that face each other across a point symmetry center point. The shield plate according to any one of claims 1 to 3, wherein the shield plate is a part.

Claim 5 is that the opening angle φ of the common corner of the through opening and the original opening,
75 ° ≦ φ ≦ 100 °
The shield plate according to claim 4, wherein

Claim 6 is an angle θ between a side forming an edge of the through-opening and a side adjacent to the one side of the triangular embedding portion,
20 ° ≦ θ ≦ 70 °
The shield plate according to claim 4 or 5, wherein

8. The method according to claim 7, wherein a length of a first side extending in the first direction of the rectangle forming the original opening is a, and a second side of the rectangle extending in a second direction intersecting the first direction. When the length of each of the remaining two sides of the triangular shape excluding the edge formed by the triangular embedding portion of the through opening is L,
0.25 ≦ L / a, L / b ≦ 0.55
The shield plate according to any one of claims 4 to 6, wherein:

  9. The original opening when the embedding portion is cut off by extrapolating an edge of a portion excluding a part formed by the embedding portion of the edge defining the through opening, , A pair of square-shaped embeddings including a rectangle and a rhombus, wherein the embedding portion extends from each of a pair of corners of the original opening facing each other across a point-symmetric center point. The shield plate according to any one of claims 1 to 3, wherein the shield plate is a part.

The length of a first side extending in the first direction of the square forming the original opening is a, and the second side of the square extending in the second direction intersecting the first direction is defined in claim 9. Where b is the length of the edge of the through-opening and x and y are the lengths of the portions formed by the buried portions, which extend in the first direction and the second direction, respectively.
0.23 ≦ a / x, b / y <0.5
The shield plate according to claim 8, wherein

According to a tenth aspect of the present invention, the lengths of the portions formed by the buried portions of the edge of the through-opening extending in a first direction and a second direction intersecting the first direction are defined as x and y, respectively. When
0.41 ≦ x / y ≦ 2.44
The shield plate according to claim 8, wherein:

The length of a first side extending in a first direction of a square forming the original opening is a, and a second side of the square extending in a second direction intersecting the first direction is provided. Where b is the length of
0.75 ≦ b / a ≦ 1.33
The shield plate according to any one of claims 4 to 10, wherein

The length of the first side extending in the first direction of the square forming the original opening is a, and the second side of the square extending in the second direction intersecting with the first direction is provided. Where b is the length of
a, b ≦ 5m
The shield plate according to any one of claims 4 to 11, wherein

  The original opening when the embedding portion is cut off by extrapolating the edge of a portion excluding a part formed by the embedding portion among the edges defining the through opening, , Including an ellipse and an ellipse, a point-symmetrical round shape, wherein the embedding part has a side of an arc formed by an edge part buried by the embedding part among the edges of the original opening. The shield plate according to any one of claims 1 to 3, wherein the shield plate is an embedded portion protruding inward.

Claim 14 is that the length of the quadrangular embedding portion in the protruding direction from the original opening is a, and the protruding direction and the dimension of the diameter of the original opening in the width direction intersecting with the protruding direction are respectively When s and t,
0.08 ≦ a / s, a / t ≦ 0.43
The shield plate according to claim 13, wherein:

Claim 15 is that the length of the rectangular embedding portion in the width direction intersecting with the protruding direction from the original opening is b, and the diameter of the original opening in the protruding direction and the width direction is When s and t,
0.2 ≦ b / s, b / t ≦ 0.75
The shield plate according to claim 13 or 14, wherein:

  The original opening when the embedded portion is cut off by extrapolating an edge of a portion excluding a part formed by the embedded portion among edges defining the through opening, , Including an ellipse and an ellipse, a point-symmetrical round shape, wherein the embedding portion has a triangular shape whose one side is an arc formed by an edge portion buried by the embedding portion among the edges of the original opening. The shield plate according to any one of claims 1 to 3, wherein the shield plate is an embedded portion protruding inward.

17. The method according to claim 17, wherein two sides of the triangular embedding portion forming an edge of the through-opening are x and y, respectively, and a diameter of the original opening in a direction in which the embedding portion protrudes. Where s is the dimension of
0.23 ≦ x / s, y / s <0.5
The shield plate according to claim 16, wherein:

According to claim 18, when the lengths of two sides forming the edge of the through-opening of the triangular embedding portion are x and y, respectively.
0.8 ≦ x / y ≦ 1.2
The shield plate according to claim 16 or 17, wherein

Claim 19 is a projection direction of the embedding portion from the original opening and the dimension of the diameter of the original opening in the width direction intersecting the projecting direction is s, t, respectively,
0.66 ≦ s / t, t / s ≦ 1.5
The shield plate according to any one of claims 13 to 18, wherein:

Claim 20 is that, when the diameter of the round original opening in the protruding direction of the embedded portion is s, and the diameter of the original opening in the direction intersecting with the protruding direction is t,
s, t ≦ 5m
The shield plate according to any one of claims 13 to 19, wherein:

  An electronic device comprising: the shield plate according to any one of claims 1 to 20; and an electronic circuit.

  According to the shield plates of the first and second aspects and the electronic device of the twenty-first aspect, noise dispersed in vertical polarization and horizontal polarization is radiated compared to a simple circular or square through-opening. .

  According to the shield plate of the third aspect, compared to the case where the axial ratio exceeds 10, noise dispersed in the vertical polarization and the horizontal polarization is radiated.

  According to the shield plate of the fourth aspect, noise dispersed in vertical polarization and horizontal polarization is radiated as compared with the case where the square original opening is a through opening.

  According to the shield plate of the fifth aspect, compared to the through-opening of φ <75 ° or 100 ° <φ, noise dispersed in vertical polarization and horizontal polarization is radiated.

  According to the shield plate of the sixth aspect, compared to the through-opening of θ <20 ° or 70 ° <θ, noise dispersed in vertical polarization and horizontal polarization is radiated.

  According to the shield plate of the seventh aspect, compared to the through-opening of L / a, L / b <0.25 or 0.55 <L / a, L / b, the shield plate is dispersed into vertically polarized waves and horizontally polarized waves. Noise is radiated.

  According to the shield plate of the eighth aspect, noise dispersed in vertical polarization and horizontal polarization is radiated as compared with the case where the square original opening is a through opening.

  According to the shield plate of the ninth aspect, compared to the through-opening of a / x, b / y <0.23, noise dispersed in the vertical polarization and the horizontal polarization is radiated.

  According to the shield plate of the tenth aspect, compared to the through-hole of x / y <0.41 or 2.44 <x / y, noise dispersed in the vertical polarization and the horizontal polarization is radiated.

  According to the shield plate of the eleventh aspect, compared to the through-opening of b / a <0.75 or 1.33 <b / a, noise dispersed in vertical polarization and horizontal polarization is radiated.

  According to the shield plate of the twelfth aspect, noise having a frequency of 30 MHz or more, which is a test standard value of the EMI test, is dispersed into the vertical polarization and the horizontal polarization.

  According to the shield plate of the thirteenth aspect, noise dispersed in vertically polarized waves and horizontally polarized waves is radiated as compared with the case where the round original opening is a through-opening.

According to the shield plate of claim 14,
a / s, a / t <0.08 or 0.43 <a / s, a / t
In comparison with the through aperture, noise dispersed in vertical polarization and horizontal polarization is radiated.

According to the shield plate of claim 15,
b / s, b / t <0.2 or 0.75 <b / s, b / t
In comparison with the through aperture, noise dispersed in vertical polarization and horizontal polarization is radiated.

  According to the shield plate of the sixteenth aspect, compared to the case where the round original opening is a through-hole, noise dispersed in vertical polarization and horizontal polarization is radiated.

  According to the shield plate of the seventeenth aspect, compared to the through aperture of x / s, y / s <0.23, noise dispersed in the vertical polarization and the horizontal polarization is radiated.

  According to the shield plate of the eighteenth aspect, compared to the through-opening of x / y <0.8 or 1.2 <x / y, noise dispersed in vertical polarization and horizontal polarization is radiated.

    According to the shield plate of the nineteenth aspect, as compared with the through opening of s / t <0.66, t / s <0.66, 1.5 <s / t, or 1.5 <t / s, the vertical deviation is larger. Noise dispersed in waves and horizontal polarization is emitted.

  According to the shield plate of the twentieth aspect, noise having a frequency of 30 MHz or more, which is a test standard value of the EMI test, is dispersed into the vertical polarization and the horizontal polarization.

FIG. 1 is a conceptual diagram of an electronic device as one embodiment of the present invention. It is a principle explanatory view regarding the shape of the through-opening provided in the shield plate. It is the figure which showed the concept (A) of the circularly polarized wave and the simulation result (B) of the axial ratio. FIG. 3 is a diagram showing a first basic form of a through opening. FIG. 7 is a diagram showing a through-opening (A) when a dimension L of an embedded portion is changed in the first basic form and a simulation result thereof. It is the figure which showed the penetration opening (A) when the longitudinal dimension was extended in the 1st basic form, and the simulation result. FIG. 9 is a diagram showing a through-opening (A) when the internal angle φ is changed so that the original opening becomes a rhombus in the first basic form, and a simulation result thereof. FIG. 6 is a diagram showing a through-opening (A) when the lateral dimension j of the embedded portion is changed in the first basic form and a simulation result thereof. It is a figure showing the 2nd basic form of a penetration opening. FIG. 10 is a diagram showing the through-opening (A) when the dimensions x and y of the embedded portion are changed while maintaining x = y in the second basic form, and a simulation result thereof. FIG. 8 is a diagram showing a through-opening (A) when the vertical dimension y of the embedded section is changed while the horizontal dimension x of the embedded section is fixed in the second basic form, and a simulation result thereof. It is a figure showing the 3rd basic form of a penetration opening. It is the figure which showed the penetration opening (A) when the protrusion dimension a of the embedded part was changed in the 3rd basic form, and the simulation result. It is the figure which showed the penetration opening (A) when the width dimension b of an embedding part was changed in the 3rd basic form, and the simulation result. In the third basic form, the through-opening (A) when the diameter b in the direction orthogonal to the original opening is changed while the diameter a in the protruding direction of the embedded portion of the original opening is kept constant, and the simulation results are shown. FIG. In the third basic form, the through-opening (A) when the diameter a of the original opening in the protruding direction of the buried portion is changed while the diameter b in the direction perpendicular to the original opening is kept constant, and the simulation results are shown. FIG. It is the figure which showed the penetration opening (A) when the dimension x, y of an embedding part was changed, keeping x = y in the 4th basic form, and its simulation result. It is the figure which showed the penetration opening (A) when the dimension x, y of an embedding part was changed, keeping x = y in the 4th basic form, and its simulation result. It is the figure which showed the penetration opening (A) when both dimensions x and y of the embedding part were changed in the 4th basic form, and the simulation result.

  Hereinafter, embodiments of the present invention will be described.

  FIG. 1 is a conceptual diagram of an electronic device as one embodiment of the present invention.

  In the electronic device 1 shown in FIG. 1, a circuit board 2 on which an electronic circuit (not shown) is mounted is built in a shield case 3. The shield case 3 has a through opening 5 for wiring or air circulation. When the circuit board 2 is operated, the through-opening 5 may serve as a secondary antenna and radiate noise outside the shield case 3. The allowable level of noise radiated to the outside is defined by the EMI (Electromagnetic Interference) standard.

  FIG. 2 is a diagram illustrating the principle of the shape of the through-opening provided in the shield case.

  FIG. 2A shows an example of the shape of the through-opening. Here, terms used in the following are explained. The through-opening 5 is an opening actually opened in the shield case 3. The through-opening 5 shown in FIG. 2 (A) is hatched so as to extend inward from each of a pair of corners 61 facing each other across the center point O of the square original opening 6 shown by the broken line. It has a rotationally symmetric shape that fills a pair of triangular regions. Here, a region (the triangular region in the example shown here) buried as compared with the original opening 6 is referred to as a buried portion 62. The original opening 6 was cut off by embedding the edge of a portion excluding a part formed by the embedding portion 62 among the edges defining the through opening 5 and cutting off the embedding portion 62, and was the embedding portion 62. An opening having a shape obtained by taking a region as a part of the opening.

  When a radio wave is radiated from the through-opening 5, an electric field is generated only in one direction if the original opening 6 is square. On the other hand, when the buried portion 62 is formed, the excitation mode changes, and electric fields in two directions (the # 1 direction and the # 2 direction) orthogonal to each other are excited by the through-opening 5. At this time, since the electric field path length excited in the # 1 direction is shorter than the electric field path length in the # 2 direction, as shown in FIG. 1B, the resonance frequency f1 in the # 1 direction is changed to the resonance frequency in the # 2 direction. It becomes higher than the frequency f2. Further, since the resonance frequencies f1 and f2 in the # 1 direction and the # 2 direction are different, a phase difference occurs at a frequency f0 between the two resonance frequencies as shown in FIG.

  Thus, by making the electric field path length different between the direction of # 1 and the direction of # 2, noise that is dispersed into vertical polarization and horizontal polarization and approaches circular polarization is radiated. As described above, in the EMI test, which is an index of the degree of the intensity of the radiation noise, the electric field intensity of the radiation noise is measured by dividing the electric field intensity of the radiation noise into vertical polarization and horizontal polarization. For this reason, even if the radiation noise has the same level, it is more advantageous to disperse the vertically polarized wave and the horizontally polarized wave and approach the circularly polarized wave.

  FIG. 3 is a diagram showing a concept (A) of the circularly polarized wave and a simulation result (B) of the axial ratio thereof.

The term “inert-polarization” refers to a polarization in which one of vertical polarization and horizontal polarization is stronger than the other, and as shown in FIG. The major axis of this coast polarization is A, and the minor axis is B. The axial ratio is
Axial ratio (dB) = 10 · log (A / B) ·· (1)
Is defined by Axial ratio = 0 is perfect circular polarization, axial ratio = 10, minor axis B is 1/10 the length of major axis A, axial ratio = 20, minor axis B is 1/100 of major axis A The length, axis ratio = 30 indicates that the short axis B is 1/1000 the length of the long axis A, and the axis ratio = 40 indicates that the short axis B is 1/10000 the length of the long axis A. ing. In other words, it means that the larger the value of the axial ratio is, the more the deviation from the circular polarization and the closer to the linear polarization. Here, for the sake of simulation, the upper limit is set to the axial ratio = 40. In the following, a condition that the axial ratio is 10 or less is used as a reference for circularly polarized waves.

  FIG. 3B shows the through-opening 5 having the shape shown in FIG. 2, where the vertical and horizontal dimensions a and b of the original opening 6 are a = b = 75 mm, the embedding section 62 is an isosceles triangle, and the embedding section 62 Is a simulation result when the vertical and horizontal length L is 30 mm and the frequency is 2 GHz. In FIG. 3B, the vertical axis represents the axial ratio represented by the above equation (1), and the horizontal axis represents the radiation angle. The radiation angle 0 ° is the direction of the perpendicular to the through-opening 5 passing through the center point O of the through-opening 5 shown in FIG. The radiation angles other than the radiation angle of 0 ° are angles formed by a direction passing through the center point O and inclined in the direction of the arrow X and a direction of the radiation angle of 0 °.

  FIG. 3B shows two graphs a and b. Graph a represents a simulation result when the square original opening 6 itself shown by the broken line in FIG. 2 is a through opening. This graph a is a horizontal line passing through the axis ratio 40, which is the limit value of the simulation. In other words, when the square original aperture 6 itself is a through aperture, it is linearly polarized regardless of the radiation angle. Graph b represents a simulation result for the through-opening 5 having the shape shown in FIG. The axial ratio is 10 or less in a range where the radiation angle is wider than -60 ° to 60 °. That is, the formation of the buried portion 62 shown in FIG. 2 significantly reduces the axial ratio and approaches the circularly polarized wave.

  In addition, here, the simulation result in the case where the original aperture is a square is shown. However, it is confirmed that, even when the original aperture is a circular shape, which will be described later, it becomes closer to the circularly polarized wave by forming the embedded portion. .

  FIG. 4 is a diagram showing a first basic form of the through-opening.

  The through-opening 5A shown in FIG. 4 has a square shape as the original opening, and a pair of corners extending from each of a pair of corners of the original opening facing each other with the center point O interposed therebetween, like the through-opening 5 shown in FIG. Is a through-opening having a triangular embedded portion.

In the case of the through-opening 5A whose basic shape is shown in FIG.
The vertical and horizontal dimensions a and b are
a, b ≦ 5m (2)
When the vertical and horizontal dimensions of the embedded part are L,
0.25 ≦ L / a, L / b ≦ 0.55 (3)
Aspect ratio b / a is
0.75 ≦ b / a ≦ 1.33 (4)
The angle φ of the corner is
75 ° ≦ φ ≦ 100 ° ・ ・ (5)
The angle θ of the embedded part is
20 ° ≦ θ ≦ 70 ° (6)
It is preferable to satisfy the following.

  Hereinafter, each of the expressions (2) to (6) will be described.

When the wavelength and frequency of the radiation noise are λ and f, respectively, and the speed of light is c (3 × 10E8 m / s),
λ = c / f (7)
Holds. Here, when the sides a and b of the original aperture have a half wavelength λ / 2 of noise, the radiation is the largest. The EMI test standard value is that the half-wavelength λ / 2 when the frequency f is 30 MHz or more and f = 30 MHz is
λ / 2 = 5m (8)
It is. That is, when adjusted to the EMI test, the above equation (2) is satisfied.

Next, expressions (3) to (6) will be described. In describing these expressions,
a, b = 75 mm, φ = 90 °, θ = 45 °, L = 30 mm,
Is referred to as a “reference value” of the first basic form, and a simulation result of radiation noise at a frequency of 2 GHz corresponding to a, b = 75 mm in the “reference value” will be described.

  FIG. 5 is a diagram showing the through-opening (A) when the dimension L of the embedded portion is changed in the first basic form, and a simulation result thereof. Other dimensions and angles other than the dimension L of the embedded portion remain as the above “reference value”.

When the dimension L of the buried portion is changed, the electric field path length of # 1 shown in FIG. 5A changes, and thus the axial ratio changes. Therefore, when the axial ratio is simulated by changing the dimension L, as shown in FIG. 5B, the axial ratio is within the range of the above equation (3), that is,
0.25 ≦ L / a, L / b ≦ 0.55 (3)
Within this range, the axial ratio ≦ 10 is realized. As described above, if the axial ratio is ≦ 10, it is determined that the circularly polarized wave is close to the degree advantageous for the EMI test.

  FIG. 6 is a diagram showing the through-opening (A) when the longitudinal dimension is extended in the first basic form and a simulation result thereof. The other dimensions and angles except the vertical dimension b remain the above-mentioned “reference values”.

  When the vertical dimension b is changed, the axial ratio increases because the electric field paths of # 1 and # 2 are not orthogonal. As can be seen from FIG. 6B, if b / a ≦ 1.3, the axial ratio ≦ 10 or less is maintained.

Here, the simulation result when the horizontal dimension a is fixed and the vertical dimension b is extended is shown. On the contrary, the same applies when the vertical dimension b is fixed and the horizontal dimension a is extended. I can say that. That is, the above equation (4), that is,
0.75 ≦ b / a ≦ 1.33 (4)
Within this range, the axial ratio ≦ 10 is realized.

  This means that the opening may be a rectangular original opening as long as it is within the range of the above equation (4).

  FIG. 7 is a diagram showing a through-opening (A) when the internal angle φ is changed so that the original opening becomes a rhombus in the first basic form, and a simulation result thereof. The other dimensions and angles except for the inner angle φ remain the above “reference values”.

When the inner angle φ is changed, the axial ratio changes because the electric field path lengths of # 1 and # 2 change. Equation (5) above, ie,
75 ° ≦ φ ≦ 100 ° ・ ・ (5)
Within this range, the axial ratio ≦ 10 is maintained.

  This means that the original opening may be a rhombus as long as it is within the range of the above equation (5).

  FIG. 8 is a diagram showing the through-opening (A) when the lateral dimension j of the buried portion is changed in the first basic form, and a simulation result thereof. The angle θ of the embedding portion also changes with the change of the lateral dimension j of the embedding portion, but the other dimensions and angles remain the above “reference values”.

When the lateral dimension j of the embedded portion is changed, the axial ratio changes because the electric field path lengths of # 1 and # 2 change. Equation (6) above, ie,
20 ° ≦ θ ≦ 70 ° (6)
Within this range, the axial ratio ≦ 10 is maintained.

  FIG. 9 is a diagram showing a second basic form of the through-opening.

  The through-opening 5B shown in FIG. 9 has a square shape as the original opening like the through-opening 5A shown in FIG. 4, but the shape of the embedded portion is different. That is, the through-opening 5B shown in FIG. 9 is a through-opening having a pair of square-shaped embedded portions extending from each of a pair of corners of the original opening opposed to each other with the center point O interposed therebetween.

The vertical and horizontal dimensions a and b are
a, b ≦ 5m (9)
The ratio b / a of the vertical and horizontal dimensions a and b is
0.75 ≦ b / a ≦ 1.33 (10)
When the horizontal and vertical dimensions of the embedded part are x and y, respectively,
0.23 ≦ x / a, y / b <0.5 (11)
The aspect ratio x / y of the embedding part is
0.41 ≦ x / y ≦ 2.44 (12)
It is preferable to satisfy the following.

  Equations (9) and (10) above are the same as equations (2) and (4) in the first basic form (see FIG. 4), respectively, and redundant description will be omitted.

Hereinafter, equations (11) and (12) will be described. In describing these equations,
a, b = 75 mm, φ = 90 °, θ = 90 °, x = y = 30 mm,
Is referred to as a “reference value” of the second basic form, and a description will be given of a simulation result of radiation noise at a frequency of 2 GHz corresponding to a, b = 75 mm in the “reference value”.

  FIG. 10 is a diagram showing the through-opening (A) when the dimensions x and y of the buried portion are changed while maintaining x = y in the second basic form, and a simulation result thereof. The dimensions and angles other than the dimensions x and y of the buried portion remain the above-mentioned “reference values”.

When the dimensions x and y of the buried portion are changed while maintaining x = y, the electric field path length of # 1 shown in FIG. 10A changes, and the axial ratio changes. Therefore, when the axial ratio is simulated by changing the dimensions x and y, as shown in FIG. 10B, 0.23 ≦ x / a. On the other hand, when 0.5 ≦ x / a, the two embedded portions are short-circuited and connected, so it is necessary to set x / a <0.5. Therefore, within the range of the above equation (11), that is,
0.23 ≦ x / a, y / b <0.5 (11)
Within this range, the axial ratio ≦ 10 is realized. As described above, if the axial ratio is ≦ 10, it is determined that the circularly polarized wave is close to the degree advantageous for the EMI test.

  FIG. 11 is a diagram showing a through-opening (A) when the vertical dimension y of the embedded section is changed while the horizontal dimension x of the embedded section is fixed in the second basic form, and a simulation result thereof. Other dimensions and angles other than the vertical dimension y of the embedding portion remain the above-mentioned “reference values”.

When the vertical dimension y of the buried portion is changed, the electric field path length of # 1 shown in FIG. 11A is changed and the electric field paths of # 1 and # 2 are not orthogonal, so that the axial ratio is increased. Therefore, when the axial ratio is simulated by changing the vertical dimension y, as shown in FIG. 11B, the axial ratio is within the range of the above equation (12), that is,
0.41 ≦ x / y ≦ 2.44 (12)
Within this range, the axial ratio ≦ 10 is realized.

  FIG. 12 is a diagram showing a third basic form of the through-opening.

  The through-opening 5C shown in FIG. 12 has a circular shape as an original opening, and extends inward from each of two arc portions facing each other across a center point O, which is a part of the edge of the original opening. It is a through-opening having a pair of embedding portions that partially fills the original opening in a square shape when defined as one side.

In the case of the through-opening 5C whose basic form is shown in FIG.
The diameter s of the original opening in the protruding direction of the embedding portion and the diameter t in the direction orthogonal thereto are:
s, t ≦ 5m (13)
When the protrusion size of the embedded portion is a,
0.08 ≦ a / s, a / t ≦ 0.43 (14)
When the width of the embedded part is b,
0.2 ≦ b / s, b / t ≦ 0.75 (15)
The ratio s / t of the long axis and short axis of the original aperture is
0.66 ≦ s / t, t / s ≦ 1.5 (16)
It is preferable to satisfy the following.

  Hereinafter, each of the expressions (13) to (16) will be described.

Equation (13) is the same as equation (2) in the first basic form and equation (9) in the second basic form. That is, when the wavelength and frequency of the radiation noise are λ and f, respectively, and the speed of light is c (3 × 10E8 m / s),
λ = c / f (17)
Holds. Here, when the diameter s, t of the original aperture is half the wavelength λ / 2 of the noise, the radiation is the largest. The EMI test standard value is that the half-wavelength λ / 2 when the frequency f is 30 MHz or more and f = 30 MHz is
λ / 2 = 5m (18)
It is. That is, when adjusted to the EMI test, the above equation (13) is satisfied.

Hereinafter, expressions (14) to (16) will be described. In describing these expressions,
s, t = 150 mm, a = 55 mm, b = 80 mm,
Is referred to as a “reference value” of the third basic form, and a description will be given of a simulation result of radiation noise at a frequency of 1 GHz corresponding to s, t = 150 mm in the “reference value”.

  FIG. 13 is a diagram showing the through-opening (A) when the protrusion dimension a of the embedded portion is changed in the third basic form, and a simulation result thereof. The other dimensions other than the protrusion dimension a of the buried portion remain as the “reference value” described above.

When the protrusion dimension a of the embedded portion is changed, the electric field path length of # 1 shown in FIG. 13A changes, and therefore, the axial ratio changes. Therefore, when the axial ratio is simulated by changing the dimension a, as shown in FIG. 13B, the ratio is within the range of the above equation (14), that is,
0.08 ≦ a / s, a / t ≦ 0.43 (14)
Within this range, the axial ratio ≦ 10 is realized. As described above, if the axial ratio is ≦ 10, it is determined that the circularly polarized wave is close to the degree advantageous for the EMI test.

  FIG. 14 is a diagram showing the through-opening (A) when the width dimension b of the buried portion is changed in the third basic form and a simulation result thereof. Other dimensions other than the width dimension b of the buried portion remain as the “reference value” described above.

Even if the width dimension b of the buried portion is changed, the electric field path lengths of # 1 and # 2 shown in FIG. 14A do not change, and the electric field paths are kept orthogonal. Is changed to simulate the axial ratio, the axial ratio changes as shown in FIG. Within the range of the above equation (15), that is,
0.2 ≦ b / s, b / t ≦ 0.75 (15)
Within the range, the axial ratio ≦ 10 is maintained.

  FIG. 15 shows the through-opening (A) when the diameter t in the direction orthogonal to the original opening is changed while the diameter s of the original opening in the protruding direction of the embedded portion is kept constant in the third basic form, and It is a figure showing a simulation result. Other dimensions other than the diameter t remain as the “reference value” described above.

When the diameter t is changed, the electric field path length # 2 shown in FIG. 15A changes, so that the axial ratio changes. As a result of simulating the axial ratio by changing the dimension t, as shown in FIG.
0.66 ≦ s / t ≦ 1.5 (19)
Within the range, the axial ratio ≦ 10 is maintained.

  FIG. 16 shows a through-opening (A) when the diameter s of the original opening in the protruding direction of the embedded portion is changed while the diameter t of the original opening in the width direction of the embedded portion is kept constant. It is a figure showing the simulation result. The other dimensions other than the diameter s remain the “reference value” described above.

When the diameter s is changed, the electric field path length of # 1 shown in FIG. 16A changes, so that the axial ratio changes. As a result of simulating the axial ratio by changing the dimension s, as shown in FIG.
0.66 ≦ t / s ≦ 1.5 (20)
Within the range, the axial ratio ≦ 10 is maintained.

Therefore, by combining the above equations (19) and (20), the above equation (16), that is,
0.66 ≦ s / t, t / s ≦ 1.5 (16)
Holds.

  In other words, this means that the opening may be an elliptical or oval original opening as long as it is within the range of the above expression (16).

  FIG. 17 is a diagram showing a fourth basic form of the through-opening.

  The through-opening 5D shown in FIG. 17 has a circular shape as an original opening, and extends inward from each of two arc portions facing each other across a center point O, which is a part of the edge of the original opening. It is a through-opening having a pair of buried portions that partially fill the original opening in a triangular shape when one side is set.

In the case of the through-opening 5D whose basic shape is shown in FIG.
a, b ≦ 5m (21)
The ratio s / t, t / s of the long axis and the short axis of the original aperture is
0.66 ≦ s / t, t / s ≦ 1.5 (22)
When the horizontal dimension of the embedded part is x and the vertical dimension is y,
0.23 ≦ x / s, y / s <0.5 (23)
The aspect ratio y / x of the embedding part is
0.8 ≦ x / y ≦ 1.2 (24)
It is preferable to satisfy the following.

  The above equations (21) and (22) are the same as equations (13) and (16) in the third basic form (see FIG. 12), respectively, and redundant description will be omitted.

Hereinafter, equations (23) and (24) will be described. In describing these equations,
Original opening diameter s, t = 150 mm, apex angle of triangular embedding part θ = 90 °
Is referred to as a “reference value” of the fourth basic form, and a description will be given of a simulation result of radiation noise at a frequency of 1 GHz corresponding to s, t = 150 mm in the “reference value”. In each of the two simulations described below, since the dimensions x and y of the embedded portion are changed, there is no “reference value” for the dimensions x and y of the embedded portion.

  FIG. 17 is a diagram showing the through-opening (A) when the dimensions x, y of the buried portion are changed while maintaining x = y in the fourth basic form, and a simulation result thereof. The dimensions and angles other than the dimensions x and y of the buried portion remain the above-mentioned “reference values”.

When the dimensions x and y of the buried portion are changed while maintaining x = y, the electric field path length of # 1 shown in FIG. 18A changes, and the axial ratio changes. Therefore, when the axial ratio is simulated by changing the dimensions x and y, as shown in FIG. 18B, the ratio is within the range of the above equation (23), that is,
0.23 ≦ x / s, y / s <0.5 (23)
Within the range, the axial ratio ≦ 10 is maintained. As described above, if the axial ratio is ≦ 10, it is determined that the circularly polarized wave is close to the degree advantageous for the EMI test.

  FIG. 19 is a diagram showing the through-opening (A) when both the dimensions x and y of the buried portion are changed in the fourth basic form, and a simulation result thereof. The dimensions and angles other than the dimensions x and y of the buried portion remain the above-mentioned “reference values”.

Here, both x and y values were changed while maintaining x + y = 104.56 mm. When the dimensions x and y of the buried portion are changed, the electric field paths # 1 and # 2 shown in FIG. 19A are not orthogonal, and the electric field path length of # 1 changes, so that the axial ratio increases. . Therefore, when the axial ratio is simulated by changing the dimensions x and y, as shown in FIG. 19B, the ratio x / y of the vertical and horizontal dimensions of the embedding part is within the range of the above equation (24). That is,
0.8 ≦ x / y ≦ 1.2 (24)
Within this range, the axial ratio ≦ 10 is maintained.

  As described above, in any of the through-openings of the first basic type to the fourth basic type, within the above-described respective numerical ranges, the polarization approaches the circularly polarized wave, and the EMI is smaller than the case where the respective numerical ranges are not satisfied. A through opening of a shape advantageous for meeting the standard is realized.

  Here, the through-opening provided in the shield case 3 has been described with the shield case 3 shown in FIG. 1 in mind, but the object of the present invention does not need to be configured as a shield case. For example, a shield plate that covers an electronic circuit in cooperation with a metal housing or in cooperation with another part of the shield case may be used.

1 electronic equipment 2 d
3 Shield Case 5, 5A, 5B, 5C, 5D Through-Opening 6 Original Opening 61 Corner of Original Opening 62 Embedded Part

Claims (21)

A shield plate forming at least a part of a member that covers a built-in electronic circuit,
A through-opening having a point-symmetrical shape and penetrating on both sides,
A pair of buried portions that extend inward from both sides to form a part of an edge defining the through-opening so as to reduce a distance between the two.   Compared with the original opening when the through-opening is extrapolated by cutting off the embedded portion by extrapolating the edge of a portion excluding a part formed by the embedded portion of the edge defining the through-opened portion, The shield plate according to claim 1, wherein the shield plate is a through-opening that emits noise approaching circular polarization. When the major axis as the elliptical polarization is A and the minor axis is B, the noise approaching the circular polarization is radiated in a direction perpendicular to the through opening through the point symmetry center point of the through opening. The noise
Axial ratio = 10 · log (A / B)
3. The shield plate according to claim 2, wherein the noise is 10 or less.   The original opening when extrapolating the edge of the part excluding the part formed by the embedded part of the edge defining the through-opening and cutting off the embedded part is square, rectangular and rhombic. Wherein the embedding portion is a pair of triangular embedding portions extending from each of a pair of corner portions facing each other across the point-symmetric center point of the original opening. The shield plate according to any one of claims 1 to 3, wherein: The opening angle φ of a common corner of the through opening and the original opening is
75 ° ≦ φ ≦ 100 °
The shield plate according to claim 4, wherein An angle θ between one side forming the edge of the through-opening and one side adjacent to the one side of the triangular embedding portion,
20 ° ≦ θ ≦ 70 °
The shield plate according to claim 4, wherein: The length of a first side extending in a first direction of a square forming the original opening is a, and the length of a second side of the square extending in a second direction intersecting with the first direction is b. When the length of each of the remaining two sides of the triangular shape is L, excluding the edge formed by the triangular embedded portion of the through opening,
0.25 ≦ L / a, L / b ≦ 0.55
The shield plate according to any one of claims 4 to 6, wherein:   The original opening when extrapolating the edge of the part excluding the part formed by the embedded part of the edge defining the through-opening and cutting off the embedded part is square, rectangular and rhombic. Wherein the embedding portion is a pair of quadrangular embedding portions extending from each of a pair of corner portions facing each other across the point-symmetric center point of the original opening. The shield plate according to any one of claims 1 to 3, wherein: The length of a first side extending in a first direction of a square forming the original opening is a, and the length of a second side of the square extending in a second direction intersecting with the first direction is b. , When the lengths of the portions of the edge of the through opening extending in the first direction and the second direction and formed by the embedded portion are x and y, respectively.
0.23 ≦ a / x, b / y <0.5
The shield plate according to claim 8, wherein Assuming that the lengths of the portions of the edge of the through-opening formed by the buried portion, extending in a first direction and a second direction intersecting the first direction, are x and y, respectively.
0.41 ≦ x / y ≦ 2.44
The shield plate according to claim 8, wherein: The length of a first side extending in a first direction of a square forming the original opening is a, and the length of a second side of the square extending in a second direction intersecting with the first direction is b. And when
0.75 ≦ b / a ≦ 1.33
The shield plate according to any one of claims 4 to 10, wherein The length of a first side extending in a first direction of a square forming the original opening is a, and the length of a second side of the square extending in a second direction intersecting with the first direction is b. And when
a, b ≦ 5m
The shield plate according to claim 4, wherein:   The original opening when the embedded portion is cut off by extrapolating the edge of a portion excluding a part formed by the embedded portion among the edges defining the through-opening is a circle, an ellipse, and an oval. Wherein the embedding portion protrudes inward into a quadrangular shape having an arc formed by an edge portion of the edge of the original opening, the edge portion being buried by the embedding portion. The shield plate according to any one of claims 1 to 3, wherein the shield plate is a buried portion. The length of the rectangular embedding portion in the protruding direction from the original opening is a, and the protruding direction and the dimension of the diameter of the original opening in the width direction intersecting the protruding direction are s and t, respectively. When
0.08 ≦ a / s, a / t ≦ 0.43
The shield plate according to claim 13, wherein: The length in the width direction of the rectangular embedding portion intersecting with the protruding direction from the original opening is b, and the diameters of the original opening in the protruding direction and the width direction are s and t, respectively. When
0.2 ≦ b / s, b / t ≦ 0.75
The shield plate according to claim 13, wherein:   The original opening when the embedded portion is cut off by extrapolating the edge of a portion excluding a part formed by the embedded portion among the edges defining the through-opening is a circle, an ellipse, and an oval. Wherein the embedding portion protrudes inward in a triangular shape having an arc formed by an edge portion of the edge of the original opening, the edge portion being buried by the embedding portion. The shield plate according to any one of claims 1 to 3, wherein the shield plate is a buried portion. The lengths of two sides forming the edge of the through-opening of the triangular embedding portion are x and y, respectively, and the diameter of the original opening in the direction in which the embedding portion protrudes is s. When
0.23 ≦ x / s, y / s <0.5
The shield plate according to claim 16, wherein: When the lengths of two sides of the triangular embedding portion forming the edge of the through-opening are x and y, respectively,
0.8 ≦ x / y ≦ 1.2
The shield plate according to claim 16, wherein: When the dimensions of the diameter of the original opening in the width direction intersecting with the projection direction and the projection direction from the original opening of the embedding portion are s and t, respectively.
0.66 ≦ s / t, t / s ≦ 1.5
The shield plate according to any one of claims 13 to 18, wherein: When the diameter of the round original opening in the protruding direction of the embedded portion is s, and the diameter of the original opening in the direction intersecting with the protruding direction is t,
s, t ≦ 5m
20. The shield plate according to claim 13, wherein:   An electronic device comprising the shield plate according to any one of claims 1 to 20, and an electronic circuit.

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