A method for locating and identifying electromagnetic interference sources in a shielded box

Abstract

The application relates to a method for locating and identifying an electromagnetic interference source in a shielding box, which comprises the following steps: acquiring tangential magnetic field information of a sampling plane outside the shielding box, constructing an equivalent source model based on the tangential magnetic field information, acquiring dipole moment information of an initial equivalent electric dipole, and realizing first source reconstruction; acquiring a contribution degree evaluation index of each electric dipole based on the dipole moment information of the initial equivalent electric dipole, removing electric dipoles with low contribution degrees based on the contribution degree evaluation index, updating the equivalent source model, acquiring dipole moment information of an updated equivalent dipole, and realizing second source reconstruction; and realizing location and identification of the electromagnetic interference source in the shielding box based on the dipole moment information of the updated equivalent dipole. Compared with the prior art, the application has the advantages of improving equivalent source accuracy, being capable of accurately locating and identifying the electromagnetic interference source in the shielding box, and the like.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of electronic technology, and in particular to a method for positioning and identifying electromagnetic interference sources in a shielding box. BACKGROUND

[0002] The miniaturization, integration and high speed of modern electronic devices have brought great challenges to electromagnetic compatibility design. Various electronic components assembled in the same electromagnetic environment can generate electromagnetic radiation, leading to serious electromagnetic interference and signal / power integrity problems. Although interference signals can be isolated by shielding devices such as shielding boxes, electromagnetic radiation can still leak from the ventilation slots and joints of the shielding boxes. Therefore, positioning and identifying electromagnetic interference sources inside the shielding box are of great significance for electromagnetic compatibility diagnosis.

[0003] Near-field scanning is an effective technology for identifying electromagnetic interference sources. According to the near-field data, the source reconstruction method can be implemented to replace the real radiation source with an equivalent source (equivalent current, magnetic current or dipole), and then realize the positioning and identification of the electromagnetic interference source. However, for the electromagnetic interference source inside the shielding box, the traditional source reconstruction method is difficult to accurately reconstruct its equivalent source, so it cannot effectively identify the interference source. Jun-Jian Ju et al. used a differential evolution algorithm to locate an ideal dipole radiation source inside a shielding box (Asia-Pacific International Symposium on Electromagnetic Compatibility (APEMC), 2022, pp. 813-815), but this method cannot effectively locate real electromagnetic interference sources (such as transmission lines).

[0004] Chinese patent application No. CN202110969969.X discloses a method and device for quickly detecting parasitic electromagnetic radiation of an electronic system in a shielding box, the method comprising the following steps: sampling to obtain tangential electric field data on the ventilation hole of the shielding box; establishing a shielding box model filled with ideal electric conductors, placing magnetic Hertz dipoles on the sampling points, and simulating to extract the corresponding numerical Green's function; based on the numerical Green's function and the tangential electric field data, obtaining the magnetic field on the first radius spherical surface surrounding the shielding box; based on the magnetic field on the first radius spherical surface, using near-far field transformation to obtain the electric field of the test point, the second radius of the spherical surface on which the test point is located is greater than the first radius; based on the electric field of the test point, judging the parasitic radiation of the electronic system in the shielding box. However, this application solves the problem that when the equipment in the shielding box changes, a complete full-wave numerical solution process needs to be implemented again, which will bring huge computational consumption. This application does not solve the problem that the existing positioning and identification method of electromagnetic interference sources cannot accurately position and identify real electromagnetic interference sources (such as transmission lines).

[0005] It can be seen that due to the limitations of the traditional method, it is difficult to realize the accurate positioning and identification of the electromagnetic interference source in the shielding box. SUMMARY

[0006] The purpose of the present application is to overcome the defects of the prior art and provide a positioning and identification method for electromagnetic interference sources in a shielding box. The method realizes effective characterization of electromagnetic interference sources in the shielding box through two source reconstructions, improves the accuracy of the equivalent source, and can accurately position and identify the transmission line. The method solves or partially solves the problem that the existing positioning and identification method for electromagnetic interference sources cannot accurately position and identify real electromagnetic interference sources such as transmission lines.

[0007] The purpose of the present application can be achieved by the following technical solutions:

[0008] The present application provides a positioning and identification method for electromagnetic interference sources in a shielding box, comprising the following steps:

[0009] Obtain tangential magnetic field information of a sampling plane outside the shielding box, construct an equivalent source model based on the tangential magnetic field information, obtain dipole moment information of an initial equivalent electric dipole, and realize the first source reconstruction;

[0010] Based on the dipole moment information of the initial equivalent electric dipole, obtain a contribution degree evaluation index of each electric dipole, remove electric dipoles with low contribution degree based on the contribution degree evaluation index, update the equivalent source model, obtain updated dipole moment information of the equivalent dipole, and realize the second source reconstruction;

[0011] Based on the updated dipole moment information of the equivalent dipole, realize the positioning and identification of the electromagnetic interference source in the shielding box.

[0012] As a preferred technical solution, the tangential magnetic field information is obtained by near-field scanning.

[0013] As a preferred technical solution, the dipole moment information acquisition includes the following steps:

[0014] Based on the equivalent source model, a matrix equation is established based on a numerical Green function, and the dipole moment information is obtained based on the matrix equation.

[0015] As a preferred technical solution, the matrix equation is solved by Tikhonov regularization to obtain the dipole moment information.

[0016] As a preferred technical solution, the tangential magnetic field generated by a unit dipole on the sampling plane is extracted by full-wave simulation to obtain the numerical Green function.

[0017] As a preferred technical solution, the equivalent source model includes a shielding box and an array of horizontal electric dipoles uniformly distributed on a source plane.

[0018] As a preferred technical solution, the updated equivalent dipole includes an electric dipole and a magnetic dipole.

[0019] As a preferred technical solution, the removing of the electric dipole with low contribution degree based on the contribution degree evaluation index is specifically:

[0020] If the ratio of the contribution degree index corresponding to the electric dipole to all the highest contribution degree indexes is lower than a preset threshold value, the electric dipole is removed.

[0021] As a preferred technical solution, the contribution degree evaluation index is obtained by using the following formula:

[0022]

[0023] In the formula, η n is the contribution degree evaluation index, P n is the nth element of the dipole matrix P, e k,n is the kth eigenvector of P k is the nth element of e m is a numerical Green function matrix.

[0024] As a preferred technical solution, the initial equivalent electric dipole includes an x-direction electric dipole and a y-direction electric dipole arranged in pairs.

[0025] Compared with the prior art, the present application has the following advantages:

[0026] (1) The effective characterization of the electromagnetic interference source in the shielding box is realized through two source reconstruction steps, the accuracy of the equivalent source is improved, and the electromagnetic interference source in the shielding box can be accurately positioned and identified, which is of great significance for electromagnetic compatibility and electromagnetic interference diagnosis.

[0027] (2) Based on the updated equivalent dipole obtained by the present application, the electromagnetic radiation generated by each of the multiple electromagnetic interference sources in the shielding box can be further calculated, and the electromagnetic compatibility design efficiency can be effectively improved. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 It is a flow chart of the positioning and identification method of the electromagnetic interference source in the shielding box in Example 1.

[0029] Figure 2 It is a schematic diagram of an electronic device in a shielding box and a near-field sampling plane.

[0030] Figure 3 It is a schematic diagram of an initial equivalent electric dipole model of an electronic device in a shielding box.

[0031] ​Figure 4 schematic diagram of the equivalent electric dipole model process;

[0032] Figure 5 schematic diagram of the updated equivalent dipole model;

[0033] Figure 6 schematic diagram of the electromagnetic interference source in embodiment 1;

[0034] Figure 7 schematic diagram of the shielding box in embodiment 1,

[0035] Figure 8 schematic diagram of the equivalent dipole P Figure 6 and Figure 7 of the electromagnetic interference source in the shielding box in embodiment 1 using the method of the present application; x schematic diagram of the amplitude of the equivalent dipole P

[0036] Figure 9 schematic diagram of the amplitude of the equivalent dipole P Figure 6 and Figure 7 of the electromagnetic interference source in the shielding box in embodiment 1 using the method of the present application; y

[0037] Figure 10 comparison of the calculation and simulation results of the radiation far field generated by the electromagnetic interference source in the shielding box in Figure 6 and Figure 7 at 3 meters, wherein (10a) is the amplitude of E θ in the xoz plane, (10b) is the amplitude of E θ in the yoz plane, (10c) is the amplitude of H in the xoz plane, and (10d) is the amplitude of H in the yoz plane,

[0038] wherein 1 is the near-field scanning plane, 2 is the shielding box, 3 is the electromagnetic interference source, 4 is the source plane, 5 is the initial equivalent electric dipole, 6 is the remaining electric dipole, 7 is the removed electric dipole, 8 is the updated equivalent dipole, 9 is the interference source 1, and 10 is the interference source 2. DETAILED DESCRIPTION

[0039] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor should fall within the scope of protection of the present application.

[0040] ​In the present application, the terms "first", "second" are only for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined with "first", "second" can explicitly or implicitly include one or more of the features. In the description of the present application, the meaning of "multiple" is two or more, unless otherwise explicitly and specifically limited.

[0041] Embodiment 1

[0042] As Figure 1 described, the present embodiment provides a method for locating and identifying electromagnetic interference sources in a shielded box, comprising the following steps:

[0043] Step S1, near-field scanning is performed on the sampling plane to obtain tangential magnetic field data.

[0044] Step S2, an initial equivalent model is established, which is composed of an array of electric dipoles uniformly placed in the shielded box.

[0045] Step S3, numerical Green's function is extracted through full-wave simulation to construct a matrix equation.

[0046] Step S4, the dipole moment of the initial equivalent electric dipole is solved.

[0047] Step S5, the contribution of the equivalent electric dipole is evaluated, and the electric dipoles with small contribution are removed.

[0048] Step S6, magnetic dipoles are added, numerical Green's function is extracted, and a matrix equation is constructed.

[0049] Step S7, the dipole moment of the updated equivalent dipole is solved, and the electromagnetic interference source in the shielded box is located and identified.

[0050] The core idea of the method is to construct an equivalent source model composed of a shielded box and equivalent dipoles, to simplify the initial equivalent electric dipoles, and to solve the updated equivalent dipoles through two source reconstruction processes. The specific implementation steps of the method are divided into two steps: first, an initial equivalent electric dipole model is established, and the dipole moment of the initial equivalent electric dipole is obtained through the source reconstruction method based on numerical Green's function. Second, the contribution of the initial equivalent electric dipole is evaluated, the electric dipoles with small contribution are removed, and magnetic dipoles are added at the remaining electric dipoles as supplements, and the dipole moment of the updated equivalent dipole is obtained through the second source reconstruction.

[0051] The first step is implemented as follows:

[0052] First, magnetic near-field scanning is performed on the sampling plane above the shielded box, as shown in Figure 2 The tangential magnetic field information obtained by sampling is used to construct matrices H x and H y, respectively, represent the magnetic field components in x and y directions, and the dimension of the matrix is M x 1, M is the number of sampling points.

[0053] Next, an initial equivalent source model as shown in Figure 3 is established, which contains a shielding box and an array of horizontal electric dipoles uniformly distributed on the source plane. Two electric dipoles P x and P y are placed at each source point, which respectively represent the x and y polarized electric dipole components. The number of electric dipoles is N. The tangential magnetic field generated by each unit dipole on the sampling plane is extracted using full-wave simulation software FEKO, and the numerical Green's function matrix and are constructed, where and respectively represent the x and y magnetic field components generated by the x direction unit electric dipole; and respectively represent the x and y magnetic field components generated by the y direction unit electric dipole. After obtaining the numerical Green's function, the following matrix equation is constructed:

[0054]

[0055] In order to ensure the stability of the equation solution, it should be ensured that M ≥ N. The above matrix equation can be represented in the following simplified form:

[0056]

[0057] where G m is the numerical Green's function matrix with a dimension of 2M x N; P is the initial electric dipole matrix with a dimension of N x 1; and H is the sampling tangential magnetic field matrix with a dimension of 2M x 1. The matrix equation is solved using the Tikhonov regularization method to obtain the dipole moment of the initial equivalent electric dipole. According to the initial equivalent electric dipole, it is difficult to directly realize the positioning and identification of the electromagnetic interference source. It is necessary to update the equivalent source through the following steps.

[0058] The second step is specifically implemented as follows:

[0059] First, the contribution of each electric dipole to the initial equivalent source is evaluated using the eigenvectors e k (1 ≤ k ≤ N) of :

[0060]

[0061] where P n (1 ≤ n ≤ N) is the nth element of the dipole matrix P, and e k,n is the nth element of the kth eigenvector e k . Then, η n is normalized to its maximum value ηmax , and remove the electric dipoles whose contribution is less than the threshold η

[0062]

[0063] like Figure 4 As shown in Figure 2, the remaining electric dipole can reflect the location of the electromagnetic interference source to a certain extent. According to the equivalent principle, a horizontal magnetic dipole M is added at the location of the remaining electric dipole. x and M y As a supplement, to improve the accuracy and stability of the equivalent source, such as Figure 5 The full-wave simulation software FEKO is used to extract the tangential magnetic field generated by each unit magnetic dipole on the sampling plane and construct the numerical Green's function matrix. and Then construct the matrix equation

[0064]

[0065] in

[0066]

[0067]

[0068]

[0069]

[0070]

[0071] in, and represent the x and y magnetic field components generated by the unit magnetic dipole in the x direction; and They represent the x and y magnetic field components generated by the unit magnetic dipole in the y direction; N r and N a Denote the number of residual electric dipoles and added magnetic dipoles respectively. The matrix equation is solved using the Tychonov regularization method to obtain the updated dipole moment of the equivalent dipole.

[0072] Because each updated equivalent dipole contains information such as position, amplitude, and type, a visualization signal can be generated based on this information. The current distribution of the interference source can be determined on a visualization terminal, allowing the precise location and identification of the electromagnetic interference source within the shielding box. Furthermore, the updated equivalent dipole model can be imported into the full-wave simulation software FEKO, where full-wave simulation can be used to obtain the electromagnetic radiation generated by the electromagnetic interference source.

[0073] The solution of the above matrix equation is realized by MATLAB programming algorithm, and the calculation result is verified by FEKO software.

[0074] In order to verify the accuracy of the present application, the method of the present application is used to reconstruct the equivalent sources of the structures in Figure 6 and Figure 7 . Figure 6 and Figure 7 are a transmission line and a shielded box respectively, Figure 6 is a circuit board printed with a U-shaped transmission line (interference source 1) and an L-shaped transmission line (interference source 2), Figure 7 is a shielded box used for experimental verification, Figure 6 The circuit board in Figure 7 is placed inside the shielded box, and the shielded box has two ventilation slots. The specific dimensions are: a1 = 120, b1 = 80, a2 = 150, b2 = 100, w1 = 4, d1 = 40, d2 = 50, d3 = 40, d4 = 60, h = 30, l = 100, w = 15, d = 25 (unit: millimeter). The dielectric constant of the substrate is 4.8, and the thickness is 3 millimeters. The working frequency of the electronic device is 1 GHz. The near-field scanning plane is 10 millimeters away from the shielded box, with a size of 150 x 200 millimeters, and a total of 1271 sampling points. The number of initial equivalent electric dipoles is N = 1200, the threshold is set to η = -4 dB, and the updated equivalent sources include 70 electric dipoles and 140 magnetic dipoles. The amplitudes of the reconstructed equivalent electric dipoles P x and P y are shown in Figure 8 and Figure 9 respectively. In the figure, the positions of the interference sources (i.e. the transmission lines) are marked by dashed lines. It can be seen that the updated equivalent dipoles are distributed near the interference sources, and the types of electric dipoles correspond to the direction of the transmission line current, so the real electromagnetic interference sources can be accurately located and identified according to the updated equivalent dipoles. Based on the equivalent dipoles corresponding to each interference source, the radiation emission at 3 meters generated by each interference source is calculated by full-wave simulation, as shown in Figure 10 . It can be seen that the calculation result and the simulation result are very consistent, proving the accuracy of the algorithm of the present application.

[0075] Example 2

[0076] The present embodiment provides an electronic device, comprising: one or more processors and a memory, the memory having one or more programs stored therein, the one or more programs comprising instructions for performing the method of locating and identifying electromagnetic interference sources in the shielded box as described in embodiment 1.

[0077] Example 3

[0078] The embodiment provides a computer readable storage medium, comprising one or more programs for execution by one or more processors of an electronic device, the one or more programs comprising instructions for performing the method for locating and identifying an electromagnetic interference source in a shielded box as described in embodiment 1.

[0079] The above merely provides a specific implementation of the present application, but the protection scope of the present application is not limited thereto, and any person skilled in the art can easily think of various equivalent modifications or replacements within the technical range disclosed by the present application, and these modifications or replacements shall be encompassed within the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims.

Claims

1. A method for locating and identifying electromagnetic interference sources in a shielding box, characterized in that: The steps include: Obtaining tangential magnetic field information of a sampling plane outside the shielding box, constructing an equivalent source model based on the tangential magnetic field information, obtaining dipole moment information of an initial equivalent electric dipole, and realizing a first source reconstruction; Obtaining a contribution evaluation index of each electric dipole based on the dipole moment information of the initial equivalent electric dipole, removing electric dipoles with low contribution based on the contribution evaluation index, updating the equivalent source model, adding a horizontal magnetic dipole at the position of the remaining electric dipole, obtaining the dipole moment information of the updated equivalent dipole, and realizing a second source reconstruction; Based on the updated dipole moment information of the equivalent dipole, the electromagnetic interference source in the shielding box is located and identified.

2. The method for locating and identifying an electromagnetic interference source in a shielding box according to claim 1, wherein: The tangential magnetic field information is acquired through near-field scanning.

3. The method for locating and identifying an electromagnetic interference source in a shielding box according to claim 1, wherein: The acquisition of the dipole moment information comprises the following steps: For the equivalent source model, a matrix equation is established based on the numerical Green's function, and the dipole moment information is obtained based on the matrix equation, wherein the matrix equation is: Where, is the numerical Green's function matrix; is the initial electric dipole matrix; is the sampled tangential magnetic field matrix.

4. The method for locating and identifying an electromagnetic interference source in a shielding box according to claim 3, wherein: The matrix equation is solved by Tikhonov regularization to obtain the dipole moment information.

5. The method for locating and identifying an electromagnetic interference source in a shielding box according to claim 3, wherein: The tangential magnetic field generated by the unit dipole on the sampling plane is extracted through full-wave simulation to obtain the numerical Green's function.

6. The method for locating and identifying an electromagnetic interference source in a shielding box according to claim 3, wherein: The contribution evaluation index is obtained using the following formula: Where, is the contribution evaluation index, is the dipole matrix No. n elements, yes No. k Eigenvectors No. n elements, is the numerical Green's function matrix, N is the number of electric dipoles.

7. The method for locating and identifying an electromagnetic interference source in a shielding box according to claim 1, wherein: The equivalent source model includes a shielding box and a horizontal electric dipole array uniformly distributed on a source plane.

8. The method for locating and identifying an electromagnetic interference source in a shielding box according to claim 1, wherein: The specific method of removing electric dipoles with low contribution based on the contribution evaluation index is as follows: If the ratio of the contribution index corresponding to the electric dipole to all the highest contribution indexes is lower than a preset threshold, the electric dipole is removed.

9. The method for locating and identifying an electromagnetic interference source in a shielding box according to claim 1, wherein: The initial equivalent electric dipoles include pairs of x Directional electric dipole and y Directional electric dipole.

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