JP5000672B2 - Electromagnetic field analysis method, electromagnetic field analysis apparatus, and computer program - Google Patents

Description

  The present invention relates to an electromagnetic field analysis method, an electromagnetic field analysis device, and a computer program, and is particularly suitable for use in analyzing electromagnetic waves in a minute analysis target region such as a joint portion of a metal plate.

  In an electronic device, a component such as a CPU that generates electromagnetic waves is incorporated. Therefore, it is required to prevent electromagnetic waves generated inside the electronic device from leaking outside. Therefore, in order to design a housing that does not leak electromagnetic waves generated inside the electronic device to the outside, it is necessary to analyze an electromagnetic field (electromagnetic wave) generated in the electronic device.

Patent Document 1 describes that an electromagnetic field is analyzed by a time domain difference method (FDTD (Finite Difference Time Domain) method, hereinafter referred to as FDTD method).
As described in Patent Document 1, in the FDTD method, when the electric field E is calculated at time (n−1) Δt, the magnetic field H is calculated at time (n−1 / 2) Δt. Here, Δt is a time step width (step time). Subsequently, the electric field E is calculated at time (n) Δt, and the magnetic field H is calculated at time (n + 1/2) Δt. Such an FDTD method is a technique often used when an analysis target region is small (for example, for an analysis target region on the order of several μm to several tens of μm on a side).

No. 2003-223426

  However, if the operating frequency f of the CPU of the electronic device is 1 [GHz], an electromagnetic wave having a wavelength λ of 300 [mm] is generated inside the electronic device. When such an electromagnetic wave having a long wavelength (high frequency) is input to a region on the order of several μm to several tens of μm and an electromagnetic field in the region is analyzed by the FDTD method, the time step width must be extremely shortened. I must. Therefore, the existing computer cannot analyze the electromagnetic field in a realistic calculation time.

  In addition to the FDTD method, in the conventional electromagnetic field analysis, when an electromagnetic field having a long wavelength is input, it is necessary to set a large analysis target region. For example, when an electromagnetic wave having a wavelength of 300 [mm] is input, it is necessary to set an analysis target region having a side of about 3 [m]. Therefore, when such an electromagnetic wave having a long wavelength (high frequency) is input to a region on the order of several μm to several tens of μm on one side, the analysis target region becomes too large when attempting to analyze the electromagnetic field in the region. . Therefore, the existing computer cannot analyze the electromagnetic field in a realistic calculation time.

  For example, when trying to analyze an electromagnetic field of a joint portion of a metal plate in a housing of an electronic device, it is necessary to analyze an electromagnetic field in a region on the order of several μm to several tens of μm on one side. Therefore, for the reasons described above, the conventional technique cannot analyze the electromagnetic field of the joint portion of the metal plate in the casing of such an electronic device.

The present invention has been made in view of such problems, and an object thereof is to make it possible to analyze an electromagnetic field in a region extremely smaller than the wavelength of an electromagnetic wave more easily than in the past. In particular, when a high frequency electromagnetic wave of MHz (= 10 ⁶ [Hz]) or more is input to an area having a side of 100 [μm] or less, the electromagnetic field in the area can be analyzed more easily than in the past. The purpose is to do.

In the electromagnetic field analysis method of the present invention, an electromagnetic wave having a frequency of 10 ⁶ [Hz] or more is included in an analysis target region including a conductor therein and having a side length of 1/100 of the wavelength of the input electromagnetic wave. An electromagnetic field analysis method for analyzing an electromagnetic field in the analysis target region when input, wherein the information on the position, shape, size, and physical property value of a substance included in the analysis target region is input by an input unit. As the boundary conditions of the analysis target region set based on the input step and the information input in the first input step, the electric field and magnetic field conditions that allow the analysis target region to be considered to repeatedly exist spatially are When the electromagnetic wave is input to the analysis target region set based on the second input step input by the input means and the information input by the first input step The electromagnetic field in the region to be analyzed is defined as jω (j is an imaginary unit, ω) that represents time differentiation in Maxwell's equation with the electric field and magnetic field conditions input in the second input step as boundary conditions. Is analyzed by electromagnetic field analysis means using the jω method for obtaining a quasi-stationary solution by replacing each frequency [rad / sec]) of the electromagnetic wave, and the finite element method, finite difference method, space element method or boundary element method. An electromagnetic field analysis step.
The electromagnetic field analysis apparatus of the present invention contains an electromagnetic wave having a frequency of 10 ⁶ [Hz] or more in an analysis target region that includes a conductor and whose side length is 1/100 of the wavelength of the input electromagnetic wave. An electromagnetic field analysis device that analyzes an electromagnetic field in the analysis target region when input, and a first input unit that inputs information on a position, a shape, a size, and a physical property value of a substance included in the analysis target region; As a boundary condition of the analysis target region set based on the information input by the first input means, a first condition for inputting an electric field and a magnetic field that allow the analysis target region to be considered to exist spatially repeatedly is input. 2, the electromagnetic field in the analysis target region when the electromagnetic wave is input to the analysis target region set based on the information input by the first input unit, Using the electric field and magnetic field conditions input by the input means as boundary conditions, ω / ∂t representing time differentiation in Maxwell's equation is jω (j is an imaginary unit, ω is each frequency of the electromagnetic wave [rad / sec]) And an electromagnetic field analysis means for analyzing using a finite element method, a finite difference method, a spatial element method, or a boundary element method.
The computer program of the present invention causes a computer to execute each step of the electromagnetic field analysis method.

  According to the present invention, the electric field and magnetic field conditions that allow the region to be analyzed to be spatially repeatedly present are used as boundary conditions for the region to be analyzed, and the electromagnetic field in the region to be analyzed is represented by the jω method, the finite element method, Analysis was performed using a difference method, a spatial difference method, or a boundary element method. Therefore, the analysis target area can be made smaller than before, and the calculation time can be reduced as compared with the case of performing transient analysis such as FDTD. Therefore, even when the analysis target region is extremely small compared to the wavelength of the input electromagnetic wave, the electromagnetic field in the analysis target region can be analyzed more easily than in the past.

It is a figure which shows embodiment of this invention and shows an example of the housing | casing for electronic devices. It is a figure which shows embodiment of this invention and shows an example of a functional structure of an electromagnetic field analyzer. It is a figure which shows embodiment of this invention and shows an example of the analysis object area | region of the junction part of the metal plate for electromagnetic wave shielding. FIG. 6 is a diagram illustrating an example of the relationship between the thickness d of plate-like iron included in an analysis target region and the penetration depth δ of eddy current flowing in the plate-like iron according to the embodiment of the present invention. It is a figure which shows embodiment of this invention and shows an example of the boundary conditions of an analysis object area | region. It is a figure which shows embodiment of this invention and shows the 1st-3rd specific example of an analysis object area | region. FIG. 7 shows the embodiment of the present invention and is a diagram showing the relationship between power attenuation rate and frequency in the three analysis target regions shown in FIG. 6.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
In the present embodiment, as will be described later, the analysis target region when an electromagnetic wave having a frequency of 10 ⁶ [Hz] or more is input to a cubic or rectangular parallelepiped analysis target region having a side of 100 [μm] or less. The electromagnetic field at is analyzed. First of all, the reason why such an analysis is necessary will be described.
FIG. 1 is a diagram illustrating an example of an electronic device casing. Specifically, FIG. 1A is a diagram illustrating an example of a vertical cross section of an electronic device casing. Moreover, FIG.1 (b) is a figure which shows notionally the mode of the junction part of the metal plate for electromagnetic wave shielding in the housing | casing for conventional electronic devices. Moreover, FIG.1 (c) is a figure which shows an example of the mode of the junction part of the metal plate for electromagnetic wave shielding in the housing | casing for electronic devices of this embodiment.

As shown in FIG. 1A, the electronic device casing 10 is formed by processing an electromagnetic wave shielding metal plate 11 so as to cover the periphery of an electromagnetic wave generation source 12 such as a CPU in the inside. .
Moreover, as shown in FIG.1 (b), the conventional metal plate 11 for electromagnetic wave shielding is the surface by which the steel plate 14 by which the plating process of zinc (Zn) etc. was performed on the surface, and the plating process of the steel plate 14 was performed. The resin 15 of the upper and lower electromagnetic wave shielding metal plates 11 is opposed to each other at the joint portion 13 of the electromagnetic shielding metal plate 11.

  If the inner wall surface of the electronic device casing 10 is entirely covered with a metal plate, the electromagnetic waves generated from the electromagnetic wave generation source 12 inside the electronic device casing 10 leak to the outside of the electronic device casing 10. There is nothing. However, as shown in FIG. 1 (a), the electronic device casing 10 is formed by processing the electromagnetic shielding metal plate 11. Therefore, the electronic shielding housing 10 includes the electromagnetic shielding metal plate 11. A joint portion 13 (portion surrounded by a broken line in FIG. 1A) is generated. And as shown in FIG.1 (b), the insulating resin 15 exists in the junction part 13 of the metal plate 11 for electromagnetic wave shielding. As a result of intensive studies, the inventors of the present application have caused the electromagnetic wave generated from the electromagnetic wave generation source 12 inside the electronic device casing 10 to be generated by the presence of the insulating resin 15 in the joint portion 13. The phenomenon of leaking to the outside of 10 was elucidated. This phenomenon will be described below.

  First, it is assumed that the total thickness of the upper resin 15 and the lower resin 15 of the joint portion 13 of the electromagnetic shielding metal plate 11 is 2 [μm], for example. Further, it is assumed that the operating frequency of the CPU, which is an example of the electromagnetic wave generation source 12, is 1 [GHz]. In this case, the wavelength of the electromagnetic wave generated from the electromagnetic wave generation source 12 is 300 [mm], which is sufficiently longer than the thickness of the resin 15. For this reason, it is considered that the electromagnetic waves do not leak directly to the outside through the joint portion 13.

  However, as shown in FIG. 1B, eddy current 16 flows on the surface of the steel plate 14 due to the electromagnetic wave generated from the electromagnetic wave generation source 12. 15, eddy current does not flow between the joining portions 13 of the steel plate 14, current flows in parallel to the joining portion 13 of the steel plate 14, and eddy current flows outside the housing 10 for the electronic device. . The eddy current flowing outside the electronic device casing 10 generates an alternating magnetic field 17 having the same frequency as the electromagnetic wave generation source 12 according to Ampere's law outside the electronic device casing 10. When the alternating magnetic field 17 is generated outside the electronic device casing 10, an alternating magnetic flux density is generated outside the electronic device casing 10, and the electric field is generated in the electronic device casing 10 according to Lenz's law. It will occur outside. In this way, when the conventional electromagnetic shielding metal plate 11 is used, the electromagnetic wave generated from the electromagnetic wave generation source 12 is indirectly leaked to the outside of the electronic device casing 10.

As a result of intensive studies based on the knowledge found for the first time in this way, the inventors of the present application have determined that the electromagnetic shielding metal plates 11 facing each other in the joint portion 13 of the electromagnetic shielding metal plate 11 have certain conditions. It was found that the generation of the eddy current 16 as described above can be suppressed by electrically connecting to each other.
Specifically, as shown in FIG. 1C, the electromagnetic shielding metal plate 11 has a steel plate 18 having a surface plated with zinc (Zn) or the like, and a surface on which the steel plate 18 is plated. In addition to the insulating resin 19 formed in the above, the resin 19 includes conductors 20a to 20l that are at least partially included. A part of the conductors 20 a to 20 l protrudes above the surface of the resin 19. The conductor 20 has various shapes such as a granular shape and a prismatic shape, and further has various sizes such as a thickness larger than the thickness of the resin 19 and a shape other than the thickness.

And as shown in FIG.1 (c), the conductor 20 above the junction part 13 of the metal plate 11 for electromagnetic wave shielding and the conductor 20 below are physically contacted, and the junction part 13 The electromagnetic shielding metal plates 11 facing each other are electrically connected.
As described above, in the joint portion 13 of the electromagnetic wave shielding metal plate 11, it is necessary to electrically connect the electromagnetic shielding metal plates 11 opposed to each other via the electric conductor 20. It is necessary to verify how it should be included in the resin 19. For this purpose, it is necessary to analyze the electromagnetic field at the joint portion 13 of the electromagnetic shielding metal plate 11.
Therefore, “10 ⁶ [Hz]” corresponding to the operating frequency of the CPU corresponds to the “cubic or rectangular parallelepiped analysis target region whose side is 100 [μm] or less” corresponding to the joint portion 13 of the electromagnetic shielding metal plate 11. When an electromagnetic wave having the above frequency "is input, it is necessary to analyze the electromagnetic field in the analysis target region. Hereinafter, an example of a technique for performing such an analysis will be described.

FIG. 2 is a diagram illustrating an example of a functional configuration of the electromagnetic field analysis apparatus. The electromagnetic field analysis apparatus 100 shown in FIG. 2 can be realized by a computer system having a CPU, ROM, RAM, HDD, user interface, and the like, for example.
The electromagnetic field analysis apparatus 100 includes an analysis model input unit 101, a joining condition input unit 102, a boundary condition input unit 103, an electromagnetic field input unit 104, an electromagnetic field analysis unit 105, a power attenuation factor calculation unit 106, and a power attenuation factor. And a display unit 107.

(Analysis target area input unit 101)
The analysis target area input unit 101 inputs information on the analysis target area of the electromagnetic field based on a user interface operation or the like by the user. The analysis target area input unit 101 is realized, for example, by the CPU recognizing the content of the user interface operation.
FIG. 3 is a diagram illustrating an example of an analysis target region of the joint portion 13 of the electromagnetic shielding metal plate 11. Specifically, FIG. 3A is an overhead view of the analysis target region, and FIG. 3B is a cross-sectional view of AA ′ in FIG.

  In the analysis target region 21 shown in FIG. 3, two plate-like irons (Fe) 22 a and 22 b and a prismatic shape arranged so as to be electrically connected to the two plate-like irons 22 a and 22 b. The resin 26 that is an insulator disposed in a region where the iron 26 and the prismatic iron 26 between the two plate-like irons 22a and 22b do not exist and the two steel plates 18 face each other. Air regions 27a and 27b located on both side surfaces are included.

Here, the plate-like irons 22a and 22b correspond to the steel plate 18 shown in FIG. 1, the resin 23 corresponds to the resin 19 shown in FIG. 1, and the prismatic iron 26 is the conductor 20 shown in FIG. Corresponding to
The analysis target region 21 has a length in the x direction shown in FIG. 3 of 40 [μm], a length in the y direction of 6 [μm], and a length in the z direction of 50 [μm]. is there. The length (thickness) in the Y-axis direction of the resin 23 and the prismatic iron 26 included in the analysis target region 21 is 2 [μm]. The length (thickness) in the Y-axis direction of the plate-like irons 22a and 22b included in the analysis target region 21 is also 2 [μm].

FIG. 4 shows the thickness d [m] of the plate-like irons 22a and 22b included in the analysis target region 21 and the penetration depth δ [m] of the eddy currents 41a and 41b flowing in the plate-like irons 22a and 22b. It is a figure which shows an example of a relationship. FIG. 4 is a diagram corresponding to FIG.
As shown in FIG. 4, in this embodiment, the length (thickness) d in the Y-axis direction of the plate-like irons 22a and 22b is larger than the penetration depth δ [m] expressed by the following equation (1). (D> δ) so that the plate-like irons 22 a and 22 b are included in the analysis target region 21.

In equation (1), δ is the penetration depth [m] of the eddy currents 41a and 41b, ω is the angular frequency [rad / sec] of the electromagnetic wave (electric field) input to the analysis target region 21, and σ is the plate The conductivity [S / m] and μ of the plate-like irons 22a and 22b are the magnetic permeability [H / m] of the plate-like irons 22a and 22b.
Under the above conditions, the analysis target area input unit 101 inputs information on the analysis target area 21 based on the contents of the user interface operation by the user. More specifically, the analysis target region input unit 101 inputs, for example, the positions, shapes, sizes, and physical property values of the plate-like irons 22a and 22b, the resin 23, and the prismatic iron 26. The analysis target area input unit 101 inputs the positions, shapes, sizes, and physical property values of the air areas 27a and 27b. Examples of physical property values include electrical conductivity σ [S / m], relative magnetic permeability, and relative dielectric constant. The physical property values of the plate-like irons 22a and 22b, the resin 23, and the prismatic iron 26 are, for example, as shown in Table 1 below.

The analysis target area input unit 101 sets the analysis target area 21 based on the information input as described above.
In the present embodiment, the length (thickness) d in the Y-axis direction of the plate-like irons 22a and 22b is determined based on the depth of penetration δ [m] from the information on the analysis target region 21 input by the user interface operation by the user. ], The analysis target area input unit 101 prompts the user to re-input the information of the analysis target area 21.
In the present embodiment, the tip surface of the air region 27 a is the electric field setting surface 24 in the analysis target region 21. As described later, this field setting surface 24 enter the electric field E _y in the y direction, and to obtain the power in the field setting plane 24 as the input power W _in. Further, the front end surface of the air region 27 b is used as the field emission surface 25. As will be described later, the power at the field emission surface 25 is obtained as the output power _Wout .

(Boundary condition input unit 102)
The boundary condition input unit 102 inputs information on boundary conditions of the analysis target region 21 set by the analysis target region input unit 101 based on a user interface operation by the user. The boundary condition input unit 102 is realized by, for example, the CPU recognizing the content of the user interface operation.
FIG. 5 is a diagram illustrating an example of the boundary condition of the analysis target region 21. In the present embodiment, the boundary condition input unit 102 inputs, as boundary conditions, conditions of an electric field E [V / m] and a magnetic field H [A / m] that make it possible to consider that the analysis target region 21 exists spatially repeatedly. (The electric field E and the magnetic field H are vectors having a component in the x direction, a component in the y direction, and a component in the z direction).

More specifically, the boundary condition input unit 102 sets E _x = as a boundary condition (Electrical Field Wall boundary condition) of a plane (Z-X plane) having the x direction and the z direction in the analysis target region 21 as plane directions. Enter 0, E _y = Y ₁ , E _z = 0. Here, E _x , E _y , and E _z are values of the x component, the y component, and the z component of the electric field E, and Y ₁ is an arbitrary real number.
Further, the boundary condition input unit 102 uses H _x = H ₁ , H ₁ as a boundary condition (Magnetic Field Wall boundary condition) of a plane (YZ plane) having the y direction and the z direction as plane directions in the analysis target region 21. Enter _y = 0 and _Hz = 0. Here, H _x , H _y and H _z are values of the x component, y component and z component of the magnetic field H, and X ₁ is an arbitrary real number.
Further, the boundary condition input unit 102 has E _z = 0 and H _z = 0 as a boundary condition (transparent boundary condition) of a plane (XY plane) having the x direction and the y direction as plane directions in the analysis target region 21. Enter.
By setting the boundary conditions as described above, it is possible to perform an electromagnetic field analysis assuming that the analysis target region 21 is periodically and repeatedly present in the x direction and the y direction. Therefore, even when an electromagnetic wave having a frequency of 10 ⁶ [Hz] or more is handled, the analysis target region 21 can be a region having a side of 100 [μm] or less.

(Electromagnetic field input unit 103)
The electromagnetic field input unit 103 inputs electromagnetic field information to be input to the analysis target region 21 based on a user interface operation by the user. The analysis target area input unit 101 is realized, for example, by the CPU recognizing the content of the user interface operation.
As described above, in the present embodiment, the electric field E _y in the y direction is input to the electric field setting surface 24. Therefore, the electromagnetic field input unit 103 inputs the value of the electric field E _y (value of the real part). As described above, in this embodiment, an electromagnetic wave having a frequency of 10 ⁶ [Hz] or more is input. Therefore, the electromagnetic field input unit 103 inputs a frequency value of 10 ⁶ [Hz] or more.

As shown in FIGS. 3A and 5, the length in the y direction of the electric field setting surface 24 to which the electric field E _y is input is 6 [μm], and the length in the x direction is 40 [μm]. . On the other hand, if an electromagnetic wave having a frequency of 1 [GHz] is input, the wavelength is 300 [mm]. That is, the size (length of one side) of the electric field setting surface 24 is sufficiently smaller than the wavelength of the electromagnetic wave. Therefore, the electromagnetic field analysis can be performed assuming that the uniform electric field E _y is input to the electric field setting surface 24 (that is, the change in the value of the electric field E _y can be ignored when performing the electromagnetic field analysis).
The electromagnetic field input unit 103 sets an electromagnetic wave to be input to the electric field setting surface 24 in the analysis target region 21 based on the information input as described above. The electromagnetic field input unit 103 also inputs analysis time information and displacement current information in addition to the information described above.

(Electromagnetic field analysis unit 104)
The electromagnetic field analysis unit 104 applies an electromagnetic wave (electric field E _y or magnetic field H _x , generally an electric field set by the electromagnetic field input unit 103 to the electric field setting surface 24 of the analysis target region 21 set by the analysis target region input unit 101. Therefore, the electromagnetic field in the analysis target region 21 when the electric field is input is analyzed using the boundary condition input by the boundary condition input unit 102. The electromagnetic field analysis unit 104 is realized by the CPU executing a program stored in the ROM or HDD.
In the present embodiment, the jω method for obtaining a quasi-stationary solution by replacing ∂ / ∂t representing time differentiation in Maxwell's equation with jω (j is an imaginary unit, ω is each frequency of the electromagnetic wave [rad / sec]) is used. Use. As a result, the variables for calculating the real part and the imaginary part are doubled, the memory is increased, and the calculation time is increased accordingly. However, not only can the steady field of the electromagnetic wave at the given boundary condition be calculated, Unlike the transient analysis that must be calculated every time, the steady state can be calculated by a single calculation, and the calculation time can be greatly reduced. Although there is a transient analysis method in which ∂ / ∂t is time-difference (the FDTD method is a transient analysis), in this model, it takes time to move electromagnetic waves, and therefore it takes too much time for analysis, so transient analysis cannot be used.
As for the space division method, the electromagnetic field in the analysis target region 21 is analyzed using a finite element method (FEM). Various known methods can be used as these methods (jω method, finite element method). Here, an example of electromagnetic field analysis when the side element finite element method and the jω method are used will be briefly described.

  First, as basic equations used in the electromagnetic field analysis, the following equations (2) to (6) or equivalent equations obtained by converting these with other variables are used.

In these formulas, a letter or symbol preceded by an arrow (→) represents a vector having components in three directions of space (x direction, y direction, z direction) (the same applies hereinafter, but in the text of the description) (The arrow at the beginning is omitted.) A is a vector potential [V · s / m], φ is a scalar potential [V], ∂D / ∂t is a displacement current vector [A / m ² ], and J _e is an eddy current density vector [A / m ^2]. ], [Sigma] is conductivity [S / m], and [mu] is permeability [H / m].

  A finite element method is used to solve these partial differential equations. In the finite element method, the analysis target region 21 is spatially divided into a number of relatively simple sub-regions called “elements”, and an unknown function to be obtained is approximated by a relatively simple function on each element. Is the method. Specifically, on each element, the potential to be obtained is expanded by an approximate function, and the potential is obtained by using the variational principle so that the energy in the analysis target region 21 is minimized.

An approximation method using a function that imposes an unknown variable on the side of each element as an approximation function of the above-described unknown function is called side element approximation.
Here, since the side element approximation function belongs to a function space in which the gauge transformation satisfied by the electromagnetic field is established, it is possible to adopt a gauge in which the scalar potential φ in the equation (4) is 0 (zero). Therefore, in the following description, φ = 0.

  Discretization of the fundamental equation of the electromagnetic field is performed using the Galerkin method, which is a method equivalent to the variational principle, using the edge element approximate function. The vector potential A in the element is approximated by the following equation (7).

In equation (7), N _q is a side element approximation function (vector function), and A _q is an unknown variable. In addition, the subscript q and the subscript k appearing below each represent a side number, and m represents the total number of sides in each element.

First, the Galerkin method is applied to equation (2). That is, the equation (2) is multiplied by the vector N _k , volume integration within the element is performed, and this is added up for all elements, and rearranged using Gauss's theorem and vector formula. Then, the following equation (8) is obtained.

Then, by substituting Eq. (7) into Eq. (8) and applying the jω method to the time derivative term, as shown in Eq. (9) below, A _q is an unknown variable and simultaneous terms with integral terms as coefficients. A linear equation is obtained.

  By applying the discretized equation as described above to the analysis target region 21, the electromagnetic field generated there can be analyzed. That is, as an initial analysis condition, equation (9) is calculated based on input data such as the shape data, physical property value data, time data, boundary condition data, and displacement current (= （D / ∂t). To do. At this time, the integration of equation (9) is calculated by numerical integration, for example.

When this integration is performed to create a simultaneous linear equation for each element, and these are added for all the elements, the entire simultaneous linear equation to be solved is obtained. This equation is solved by using, for example, the Gaussian elimination method, which is one of the direct methods, or the incomplete Cholesky conjugate gradient method, which is one of the iterative methods, and the desired vector potential is calculated. From the calculated vector potential, the electric field E = (E _x , E _y , E _z ) and the magnetic field H = (H _x , H _y , H _z ) generated in the analysis target region 21 are calculated in the form of complex numbers. .

  Here, the case where the side element finite element method using the side element approximation is used has been described as an example, but the nodal element finite element method may be used. Instead of the finite element method, a boundary element method (BEM), a finite difference method (FDM), or a spatial difference method can be used. Since it is realizable, those detailed description is abbreviate | omitted.

(Power decay rate calculation unit 105)
The power attenuation rate calculation unit 105 uses the “electric field E and magnetic field H generated in the analysis target region 21” calculated by the electromagnetic field analysis unit 104, and the electric power P _in [W] in the electric field setting surface 24 and the electric field emission surface 25. The power P _out [W] is calculated, and the power attenuation rate a [dB] in the analysis target region 21 is calculated using the ratio of the powers P _in and P _out . The power decay rate calculation unit 105 is realized by the CPU executing a program stored in the ROM or HDD.

Specifically power attenuation factor calculating section 105, the following (10) power attenuation factor and the power P _in in a field setting surface 24, to calculate the power P _out of the field emission face 25 by the following expression (11) by equation a is calculated.

(Power decay rate display unit 106)
The power attenuation rate display unit 106 displays on the LCD (liquid crystal display) the power attenuation rate a calculated by the power attenuation rate calculation unit 105 and information on the analysis target area 21 that is the calculation target of the power attenuation rate a. To do. The power decay rate calculation unit 105 is realized by the CPU executing a program stored in the ROM or HDD to generate display data, and outputting the generated display data to an LCD (liquid crystal display). .
In this way, the user can easily grasp the position, size, number, etc. of the prismatic iron 26 that increases the absolute value of the power attenuation rate a, and the leakage of the electromagnetic field is reduced. Such a case of the electronic device can be easily designed.

(Analysis result)
Next, the analysis result of the electromagnetic field in the analysis target region 21 is shown. FIG. 6 is a diagram illustrating first to third specific examples of the analysis target region 21. FIG. 6 is a view of the analysis target region 21 viewed from the B direction (directly above) in FIG.

  The analysis target region 21 a shown in FIG. 6A is one in which one prismatic iron having a top surface and a bottom surface of 4 [μm] × 4 [μm] is arranged at the center of the resin 23. In addition, the analysis target region 21b shown in FIG. 6B is obtained by uniformly arranging four prismatic irons having an upper surface and a bottom surface of 2 [μm] × 2 [μm] at intervals of 18 [μm]. It is. In addition, the analysis target region 21c shown in FIG. 6C is obtained by uniformly arranging 16 prismatic irons having a top surface and a bottom surface of 1 [μm] × 1 [μm] at intervals of 9 [μm]. It is. The analysis target areas 21a to 21c shown in FIGS. 6A to 6C and the analysis target area 21 shown in FIG. 3 differ only in the number, size, and position of prismatic iron. Yes, the rest is the same.

Then, the analysis target area 21a~21c field setting surface 24 of the illustrated in FIG. 6 (a) ~ FIG 6 (c), the input power P _in is 1.0 [W], the frequency is 1 [MHz], 3 [MHz ] As described above, the electric power _Pout at the electric field emission surface 25 when an electromagnetic wave of 10 [MHz], 30 [MHz], 100 [MHz], and 300 [MHz] is input is obtained. The relationship between the power attenuation rate a and the frequency was obtained.

FIG. 7 is a diagram illustrating a relationship between the power attenuation rate a and the frequency in the three analysis target regions 21a to 21c illustrated in FIG.
In FIG. 7, graphs 401 to 403 are graphs obtained from the electromagnetic field analysis of the analysis target regions 21 a to 21 c illustrated in FIGS. 6A to 6C, respectively. As shown in FIG. 7, the absolute value of the power attenuation rate a in the analysis model 21c is the largest (see graph 403). Therefore, if the conductor 20 is arranged like the analysis target region 21c, it is possible to effectively prevent electromagnetic waves generated inside the electronic device casing 10 from leaking to the outside of the electronic device casing 10. I understand that I can do it.
Here, as shown in FIG. 6, the total area of the top and bottom surfaces of the prismatic iron is the same in the three analysis models. Therefore, it can be seen from the results of FIGS. 6 and 7 that it is desirable to dispose the prismatic iron as dispersed as possible in the entire joint portion 13. In addition, when the total area of the top and bottom surfaces is the same, it is desirable to reduce the area of the top and bottom surfaces of the prismatic iron as much as possible and to increase the number of prismatic irons to be arranged as much as possible. I understand that.
As described above, the phenomenon that electromagnetic waves leak to the outside of the electronic device casing 10 through eddy current is first elucidated by the above-described electromagnetic field analysis, so that rather than the contact areas of the upper surface and the bottom surface of the joint portion 13. It has been found that the number of conductive contact points that contact each other in the joint portion 13 is important. That is, it has been found for the first time that the contact portions of the upper surface and the bottom surface of the joint portion 13 are evaluated by the number of contact points by performing the electromagnetic field analysis by the method described in the present embodiment.

As described above, in this embodiment, the frequency is 10 ⁶ [on the electric field setting surface 24 of the analysis target region 21 whose side is 100 [μm] or less, which is a region corresponding to the joint portion 13 of the electromagnetic shielding metal plate 11. The electromagnetic field in the analysis target region 21 when an electromagnetic wave of [Hz] or higher is input is analyzed using the finite element method and the jω method. As described above, since the quasi-stationary solution is obtained by the jω method instead of the transient analysis such as the FDTD method, it is not necessary to set the time step size, and the calculation time can be greatly reduced as compared with the conventional method. it can.
Further, when analyzing the electromagnetic field in this way, the conditions of the electric field E [V / m] and the magnetic field H [A / m] for allowing the analysis target region 21 to be considered to repeatedly exist spatially are set as the analysis target region. Input as 21 boundary conditions. Therefore, the analysis target region 21 can be made significantly smaller than before, and electromagnetic field analysis can be performed even in a minute space.
Therefore, it is possible to analyze an electromagnetic field, which could not be analyzed temporally and spatially with the prior art, in a realistic calculation time.

Further, the length (thickness) d [m] in the Y-axis direction of the plate-like irons 22a and 22b is set in the analysis target region 21 so that the penetration depth δ [m] of the eddy currents 41a and 41b is larger. The plate-like irons 22a and 22b are included. Therefore, the electromagnetic field analysis can be reliably performed in consideration of the eddy currents 41a and 41b that affect the electromagnetic field leaking to the outside of the field emission surface 25 (outside of the electromagnetic shielding metal plate 11).
Further, since the length of one side of the electric field setting surface 24 can be made sufficiently smaller than the wavelength of the electromagnetic wave input to the electric field setting surface 24, a uniform electric field E _y is input to the electric field setting surface 24. Electromagnetic field analysis can be performed as

In the present embodiment, the case where the plate-like iron 22, the resin 23, the prismatic iron 26, and the air region 27 are included in the analysis target region 21 is described as an example, but the conductor is included. In this case, the configuration of the analysis target area 21 can be appropriately set according to the configuration of the analysis target. For example, other metal plates can be used instead of iron. Moreover, you may use the thing of the structure coat | covered or plated with the metal different from the base metal plate instead of the irons 22 and 26. As the metal different from the base metal plate or steel plate to be coated or plated, an organic or inorganic material having conductivity can be used. Further, the air region 27 may not be included in the analysis target region 21. Further, air may be used instead of the resin 23.
Further, in the present embodiment, the case where the length of one side of the analysis target region is 100 [μm] or less has been described as an example. However, the length of one side of the analysis target region is not necessarily 100 [μm] or less as long as it is 1/100 or less of the wavelength of the electromagnetic wave input to the analysis target region.

The embodiment of the present invention described above can be realized by a computer executing a program. Further, a means for supplying the program to the computer, for example, a computer-readable recording medium such as a CD-ROM recording such a program, or a transmission medium for transmitting such a program may be applied as an embodiment of the present invention. it can. A program product such as a computer-readable recording medium in which the program is recorded can also be applied as an embodiment of the present invention. The above programs, computer-readable recording media, transmission media, and program products are included in the scope of the present invention.
In addition, the embodiments of the present invention are merely examples of implementation in carrying out the present invention, and the technical scope of the present invention should not be construed as being limited thereto. . That is, the present invention can be implemented in various forms without departing from the technical idea or the main features thereof.

DESCRIPTION OF SYMBOLS 11 Electromagnetic wave shielding metal plate 12 Electromagnetic wave generation source 13 Joint part 18 Steel plate 19 Resin 20 Conductor 21 Analysis object region 22 Plate-like iron 23 Resin 24 Electric field setting surface 25 Electric field emission surface 26 Rectangular columnar iron 27 Air region 100 Electromagnetic field analysis Device 101 Analysis target region input unit 102 Boundary condition input unit 103 Electromagnetic field input unit 104 Electromagnetic field analysis unit 105 Power attenuation factor calculation unit 106 Power attenuation factor display unit

Claims (7)

The analysis target region when an electromagnetic wave having a frequency of 10 ⁶ [Hz] or more is input to the analysis target region including a conductor inside and having a side length of 1/100 of the wavelength of the input electromagnetic wave. An electromagnetic field analysis method for analyzing an electromagnetic field in
A first input step of inputting information on a position, shape, size, and physical property value of a substance included in the analysis target region by an input unit;
As the boundary condition of the analysis target region set based on the information input in the first input step, the electric field and magnetic field conditions that allow the analysis target region to be considered to exist spatially repeatedly are input by the input unit. A second input step,
The electromagnetic field in the analysis target area when the electromagnetic wave is input to the analysis target area set based on the information input in the first input step is the electric field and magnetic field input in the second input step. Ω / ∂t representing the time differentiation in Maxwell's equation is replaced with jω (j is an imaginary unit, ω is each frequency of the electromagnetic wave [rad / sec]) to obtain a quasi-stationary solution. And an electromagnetic field analysis step of analyzing by an electromagnetic field analysis means using a finite element method, a finite difference method, a spatial element method, or a boundary element method. The analysis target region includes two metal plates, a conductor disposed between the two metal plates so as to be electrically connected to the two metal plates, and the two metal plates, Including an insulator disposed in a region where no conductor exists,
The first input step inputs information on a position, shape, size, and physical property value of a metal plate, an insulator, and a conductor included in the analysis target region. Electromagnetic field analysis method. In the first input step, the thickness of the metal plate included in the analysis target region is set to be larger than an eddy current penetration depth δ [m] expressed by the following equation (A). The electromagnetic field analysis method according to claim 2, wherein information on the position, shape, and size of the metal plate is input.
δ = [2 / (ωμσ)] ^1/2 (A)
Here, ω is the angular frequency [rad / sec] of the electromagnetic wave, σ is the conductivity [S / m] of the metal plate, and μ is the magnetic permeability [H / m] of the metal plate. Based on the electromagnetic field analyzed by the electromagnetic field analysis step, a power attenuation rate deriving step for deriving a power attenuation rate in the analysis target region by a power attenuation rate deriving unit;
A display step of displaying information on the power attenuation rate derived by the power attenuation rate deriving step on a display device by a display means;
The electromagnetic field analysis step analyzes an electromagnetic field in the analysis target region when an electromagnetic field is input to an input surface that is one side of the two metal plates in a side direction among the surfaces defining the analysis target region. ,
In the power attenuation rate deriving step, the power in the input surface and the power in the output surface that is the surface facing the input surface among the surfaces defining the analysis target region are analyzed by the electromagnetic field analysis step. The electromagnetic field analysis method according to claim 2, wherein the electromagnetic field analysis method is derived based on an electromagnetic field, and a power attenuation rate in the analysis target region is derived using a ratio of the derived power. The electromagnetic field is input to one surface in the lateral direction of the two metal plates among the surfaces defining the analysis target region,
In the second input step, the direction in which the electromagnetic wave is input is the z direction, and the thickness direction of the two metal plates is orthogonal to the y direction, the z direction, and the y direction among the regions that divide the analysis target region. When the direction to perform is the x direction, the electric field value in the i direction is E _i , and the magnetic field values in the i direction are H _i , X ₁ , Y ₁ are arbitrary real numbers
Of the surfaces defining the analysis target region, E _x = 0, E _y = Y ₁ , E _z = 0 are input as boundary conditions of surfaces having the x direction and the z direction as surface directions,
H _x = X ₁ , H _y = 0, H _z = 0 are input as boundary conditions of a plane having the y direction and the z direction as plane directions among the planes defining the analysis target region,
5. The system according to claim 2, wherein E _z = 0 and H _z = 0 are input as boundary conditions of a plane having the x direction and the y direction as plane directions among the planes defining the analysis target region. The electromagnetic field analysis method according to any one of claims. The analysis target region when an electromagnetic wave having a frequency of 10 ⁶ [Hz] or more is input to the analysis target region including a conductor inside and having a side length of 1/100 of the wavelength of the input electromagnetic wave. An electromagnetic field analyzer for analyzing electromagnetic fields in
First input means for inputting information on the position, shape, size, and physical property value of a substance included in the analysis target region;
As a boundary condition of the analysis target region set based on the information input by the first input means, a second condition for inputting an electric field and a magnetic field condition for allowing the analysis target region to be considered to exist spatially repeatedly is input. Input means,
The electromagnetic field in the analysis target area when the electromagnetic wave is input to the analysis target area set based on the information input by the first input means is the electric field and magnetic field input by the second input means. Ω / ∂t representing the time differentiation in Maxwell's equation is replaced with jω (j is an imaginary unit, ω is each frequency of the electromagnetic wave [rad / sec]) to obtain a quasi-stationary solution. And an electromagnetic field analysis means for analyzing using a finite element method, a finite difference method, a spatial element method, or a boundary element method.   A computer program for causing a computer to execute each step of the electromagnetic field analysis method according to any one of claims 1 to 5.

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