A method for quickly calculating the shielding effectiveness of a triangular prism cavity with an opening

Abstract

A method for quickly calculating the shielding effectiveness of an open-hole triangular prism cavity, obtaining the shape data of the open-hole triangular prism cavity, obtaining the shape and size information of the cross-sectional triangle of the open-hole triangular prism cavity, and using the electromagnetic field numerical method to obtain the cross-sectional characteristic mode; performing circuit equivalence on the open-hole triangular prism cavity subjected to electromagnetic radiation, and calculating the frequency domain response of the open-hole triangular prism cavity in combination with the cross-sectional characteristic mode; obtaining the shielding effectiveness data of similar structures and the corresponding cavity structure and open-hole structure data, and using the SVR method to train a machine learning regression prediction model; determining the effect of the regression prediction model, and using the final obtained model to calculate the shielding effectiveness of the open-hole triangular prism cavity. The present invention can realize the calculation of the shielding effectiveness of a cavity with a complex triangular prism structure, and improve the calculation efficiency of the cavity shielding effectiveness.

Description

Technical Field

[0001] The invention belongs to the technical field of electromagnetic protection and shielding, and in particular relates to a method for quickly calculating the shielding effectiveness of an open-hole triangular prism cavity. Background Art

[0002] Electromagnetic shielding effectiveness is an important indicator in electromagnetic compatibility, and is widely used to determine the protection capabilities of electromagnetic protection measures for circuits or various components.

[0003] When calculating the shielding effectiveness of a general cavity, the most widely used method is the three-dimensional full-wave numerical simulation method, which has the advantage of high calculation accuracy, but the disadvantage is that it consumes more computer resources and requires a lot of calculation time. The BLT method was originally used to calculate transmission line signal transmission and coupling. After combining it with the circuit analysis method, it was extended to calculate the shielding effectiveness of the cavity. As an analytical method, it has the advantage of fast calculation speed, but the disadvantage is that it can only calculate the shielding effectiveness of rectangular or cylindrical cavities, which has limitations. Summary of the invention

[0004] In order to overcome the above-mentioned shortcomings of the prior art, the purpose of the present invention is to provide a method for quickly calculating the shielding effectiveness of an open triangular prism cavity, which can realize the calculation of the shielding effectiveness of a cavity with a complex triangular prism structure and improve the calculation efficiency of the cavity shielding effectiveness.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is:

[0006] A method for quickly calculating the shielding effectiveness of a perforated triangular prism cavity comprises the following steps:

[0007] Step (1), obtaining the shape data of the open-hole triangular prism cavity, including its longitudinal length d, the size of the opening, and the cavity wall thickness t; wherein d=2πR, R is the radius of the circle where the triangle of the cross section of the open-hole triangular prism cavity is located, and the opening is located on one end face of the triangular prism cavity;

[0008] Step (2), obtaining the shape and size information of the triangle of the cross section of the open triangular prism cavity, and obtaining the cross section characteristic mode using an electromagnetic field numerical method;

[0009] Step (3), performing circuit equivalence on the perforated triangular prism cavity subjected to electromagnetic radiation, and calculating the frequency domain response of the perforated triangular prism cavity in combination with the cross-sectional characteristic mode;

[0010] Step (4), obtaining shielding effectiveness data of similar structures and corresponding cavity structure and opening structure data, and using the SVR method to train a machine learning regression prediction model;

[0011] Step (5), determine the effect of the regression prediction model. If it meets the requirements, modify the result in step (3) to obtain the result; otherwise, adjust the training parameters of the SVR algorithm to obtain a new model until the result meets the requirements. Use the final model to calculate the shielding effectiveness of the open-hole triangular prism cavity.

[0012] Furthermore, in step (2), a numerical method of electromagnetic field is used to obtain a cross-sectional characteristic mode, by dividing or discretizing the perforated triangular prism cavity to obtain a cross-sectional characteristic mode, and then solving the electromagnetic field through a governing equation based on the cross-sectional characteristic mode and the law of electromagnetic wave propagation.

[0013] Furthermore, the open triangular prism cavity subjected to electromagnetic radiation is equivalent to a transmission line circuit, whose terminal is short-circuited and the propagation characteristic impedance is Z g0 , the propagation constant is k g0 , the equivalent impedance of the opening is Z ap , Z ap The calculation formula is as follows:

[0014]

[0015] Where k0 is the electromagnetic propagation constant of the free space outside the cavity, k0 = 2π / λ, λ is the wavelength of the free space, C ap is the opening location coefficient, w e is the equivalent width of the opening, When the opening structure is rectangular, l×w is its length and width; when the opening structure is circular, r a is the radius of the circular hole.

[0016] Furthermore, in step (3), the frequency domain response of the perforated triangular prism cavity is calculated as follows:

[0017] s31, establish the generalized BLT equation: V = (U + ρ) (Γ - ρ) -1 S

[0018] Where V represents the n-dimensional vector composed of the incident voltage and reflected voltage of each node, U is the n×n unit matrix, ρ is the scattering matrix composed of the scattering of each node, Γ is the pipeline propagation matrix, and S is the n-dimensional source vector; where pipelines are different electromagnetic wave propagation paths, nodes are the two ends of the pipeline, adjacent pipelines share a node, and the node numbers are arranged in the order of the signal transmission path, and n is equal to twice the number of pipelines; where:

[0019] s32, for the open triangular prism cavity:

[0020]

[0021] Where V 11Represents the voltage at node 1 of pipeline 1, V 12 Represents the voltage at node 2 of pipeline 1, V 22 Represents the voltage at node 2 of pipeline 2, V 23 Represents the voltage at node 3 of pipe 2, V 33 Represents the voltage at node 3 of pipeline 3, V 34 Represents the voltage at node 4 of pipe 3, expressed as V ij′ Refers to V 11 ~V 34 ,but i and j′ represent the pipeline number and node number respectively. represents the incident voltage signal at node j′ of pipeline i, represents the reflected voltage signal at node j′ of pipeline i;

[0022]

[0023] Γ1, Γ2, Γ3 are the scattering matrices of pipes T1, T2, and T3, d0 is the distance from the external observation point to the opening in the equivalent circuit, z p is the distance from the target point P to the other end face of the triangular prism cavity, and the target point P is a point located inside the triangular prism cavity; S1 and S2 represent the voltages transmitted by the voltage source to the left and right sides; d 01 is the voltage source V equivalent to the electromagnetic plane wave s Distance to external observation point, d 02 V s The distance to the opening; ρ1, ρ4 are the scattering values ​​of nodes j′1, j′4, ρ2, ρ3 are the scattering matrices of nodes j′2, j′3; Y0 and Y g0 are the admittances of free space and cavity waveguide respectively, and Z0 is the vacuum wave impedance;

[0024] s33, with V 33 This is the frequency domain response result of the open triangular prism cavity.

[0025] Furthermore, Z g0 Including the characteristic impedance of TE mode and the characteristic impedance of TM mode where λ is the wavelength, and Represents the characteristic frequency wavelengths of different TE modes and TM modes, with subscripts m,n∈{1,2,3...}.

[0026] Furthermore, the electric field at the target point P is The shielding effectiveness at the target point P is SE p =-20log10 (|E p / E0|);

[0027] in, is the electric field and of different TE modes at the target point P, C represents the normalization coefficient, which is used to correct the results after BLT settlement. represents the voltage response calculated from the equivalent circuit of the BLT equation in the TE mode, i.e. V 33 The value of is the field distribution of different TE modes; is the electric field and of different TM modes at the target point P, represents the voltage response calculated from the equivalent circuit of the BLT equation TM mode, i.e. V 33 The value of is the field distribution of different TM modes, m,n∈{1,2,3...}.

[0028] Furthermore, in step (4), the shielding effectiveness data with similar structure refers to the shielding effectiveness of the open triangular prism model used for machine learning, which is obtained through three-dimensional electromagnetic full-wave simulation; the input of the model is the size of the cavity opening and the size of the cavity cross-section, and the output is the shielding effectiveness corresponding to the input.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] 1. Compared with the full-wave numerical method, the present invention uses less computer resources and has a faster calculation speed and higher calculation efficiency.

[0031] 2. Compared with the BLT method, the present invention can calculate the shielding effectiveness of more complex cavity structures. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is an implementation flow chart of the present invention.

[0033] Figure 2 It is a schematic diagram of an open triangular prism cavity structure being irradiated.

[0034] Figure 3 It is the equivalent circuit of the open triangular prism cavity structure.

[0035] Figure 4 It is the signal flow diagram of electromagnetic waves in the triangular prism cavity structure.

[0036] Figure 5 It is a comparison of the structural shielding effectiveness in the open triangular prism cavity. DETAILED DESCRIPTION

[0037] The embodiments of the present invention are described in detail below with reference to the accompanying drawings and examples.

[0038] The existing technology mainly uses the three-dimensional full-wave numerical method to calculate the cavity shielding effectiveness. While the full-wave method has high precision, it also consumes too much computer resources and requires a lot of computing time. The traditional BLT (Baum–Liu–Tesche) method can only calculate rectangular cavities and cylindrical cavities, which has limitations. The essence of the BLT method for calculating shielding effectiveness is a calculation method based on the transmission line model. The present invention expands the scope of application of the BLT method, combines numerical methods and analytical methods, and improves the scope of application of the BLT method while improving the calculation efficiency.

[0039] like Figure 1 As shown, the present invention is a method for quickly calculating the shielding effectiveness of a perforated triangular prism cavity, comprising the following steps:

[0040] Step (1) is to obtain the shape data of the triangular prism cavity with an opening. In the present invention, the opening is located on an end face of the triangular prism cavity. It is easy to understand that the end face refers to the end faces of the two ends of the triangular prism cavity that are perpendicular to the axial direction. In the embodiment of the present invention, the opening is located on the left end face of the triangular prism cavity as an example for description.

[0041] The schematic diagram of the open triangular prism cavity being irradiated by electromagnetic waves is shown in the figure Figure 2 As shown in the figure, the z direction is the axial direction of the cavity. The shape data used in the present invention mainly include the longitudinal length d of the perforated triangular prism cavity, the size of the perforated cavity and the wall thickness t of the cavity. Where d = 2πR, R is the radius of the circle where the triangle of the cross section of the perforated triangular prism cavity is located. In the present invention, the perforation can have a variety of shapes. When the perforation structure is rectangular, its length and width are l×w. When the perforation is circular, r a is the radius of the circular hole.

[0042] Step (2), obtaining the shape and size information of the triangle in the cross section of the open triangular prism cavity, and using a numerical method to obtain the cross-sectional characteristic mode.

[0043] In this step, the electromagnetic field numerical method is used to obtain the cross-sectional characteristic mode. The method is: the object to be analyzed, that is, the perforated triangular prism cavity, is segmented or discretized to obtain the cross-sectional characteristic mode. and and Represents the field distribution of different TE and TM modes, with subscripts m, n∈{1,2,3...}; then, according to the cross-sectional characteristic mode and the electromagnetic wave propagation law, the electromagnetic field is solved by the governing equation. The solution process can be implemented by existing methods such as the finite element method and the moment method.

[0044] Step (3), performing circuit equivalence on the perforated triangular prism cavity subjected to electromagnetic radiation, and obtaining an equivalent circuit diagram as shown in Figure 3 As shown in Figure 1, the frequency domain response of the open triangular prism cavity can be calculated by combining the cross-sectional characteristic mode.

[0045] Specifically, the electromagnetic plane wave is equivalent to a voltage source V s , Z0 and k0 represent the electromagnetic propagation characteristic impedance and propagation constant of the free space outside the cavity respectively. The open triangular prism cavity of the present invention subjected to electromagnetic radiation is equivalent to a transmission line circuit, whose terminal is short-circuited and the propagation characteristic impedance (i.e., waveguide impedance) is Z g0 , the propagation constant is k g0 , the equivalent impedance of the opening is Z ap , d0 is the distance from the external observation point to the opening, V s The distance to the external observation point is d 01 , the distance to the opening is d 02 , P is the target point, located inside the open triangular prism cavity, z p is the distance from the target point P to the right bottom of the cavity, dz p is the distance from P to the opening surface.

[0046] Z ap The calculation formula is as follows:

[0047]

[0048] Where k0 is the electromagnetic propagation constant of the free space outside the cavity, k0 = 2π / λ, λ is the wavelength of the free space, C ap is the opening location coefficient, w e is the equivalent width of the opening,

[0049] Figure 4 The signal flow of electromagnetic waves in the open-hole triangular prism cavity structure is shown, corresponding to the equivalent circuit diagram. Figure 4 In the figure, j′1 is the external observation point position, j′2 represents the hole structure, j′2 is the internal observation point, i.e., the target point P, and j′4 represents the end of the cavity; the voltage source V s Corresponding to W s , T1, T2, T3 in the figure represent different electromagnetic propagation paths (pipelines). s It is generated at j′1 and transmitted to j′1, generating incident voltage signal and reflected voltage signal at the node and The voltage signal is transmitted to the j′2 node to generate an incident voltage signal and a reflected voltage signal. and The voltage signal transmitted to pipe 2 generates an incident voltage signal and a reflected voltage signal at node j′2. and The incident voltage signal and the reflected voltage signal are generated at the j′3 node and The voltage signal transmitted to pipe 3 generates an incident voltage signal and a reflected voltage signal at node j′3. and The incident voltage signal and the reflected voltage signal are generated at the j′4 node and

[0050] Therefore, the present invention calculates the frequency domain response of the perforated triangular prism cavity through the following process:

[0051] s31, establish the generalized BLT equation: V = (U + ρ) (Γ - ρ) -1 S

[0052] In the formula, V represents the n-dimensional vector composed of the incident voltage and reflected voltage of each node, U is the n×n unit matrix, ρ is the scattering matrix composed of the scattering of each node, Γ is the pipeline propagation matrix, and S is the n-dimensional source vector; where pipelines are different electromagnetic wave propagation paths, nodes are the two ends of the pipeline, adjacent pipelines share a node, and the node numbers are arranged in the order of the signal transmission path, and n is equal to twice the number of pipelines. s32, for the open triangular prism cavity:

[0053]

[0054] Where V 11 Represents the voltage at node 1 of pipeline 1, V 12 Represents the voltage at node 2 of pipeline 1, V 22 Represents the voltage at node 2 of pipeline 2, V 23 Represents the voltage at node 3 of pipe 2, V 33 Represents the voltage at node 3 of pipeline 3, V 34 Represents the voltage at node 4 of pipe 3, expressed as V ij′ Refers to V 11 ~V 34 ,but i and j′ represent the pipeline number and node number respectively. represents the incident voltage signal at node j′ of pipeline i, Represents the reflected voltage signal at node j′ of pipeline i.

[0055]

[0056] ρ1=0,ρ4=-1

[0057]

[0058] Γ1, Γ2, Γ3 are the scattering matrices of pipes T1, T2, and T3, d0 is the distance from the external observation point to the opening in the equivalent circuit, z p is the distance from the target point P to the other end face of the triangular prism cavity; S1 and S2 represent the voltages transmitted by the voltage source to the left and right sides; d 01 is the voltage source V equivalent to the electromagnetic plane wave s Distance to external observation point, d 02 V s The distance to the opening; ρ1, ρ4 are the scattering values ​​of nodes j′1, j′4, ρ2, ρ3 are the scattering matrices of nodes j′2, j′3; Y0 and Y g0 are the admittances of free space and cavity waveguide respectively, and Z0 is the vacuum wave impedance.

[0059] In a metal cavity, there is no TEM mode, and accordingly, the waveguide impedance Z g0 Including the characteristic impedance of TE mode and the characteristic impedance of TM mode The characteristic impedance of any TE and TM mode inside the metal cavity is: where λ is the wavelength, and Represents the characteristic frequency wavelengths of different TE modes and TM modes, with subscripts m,n∈{1,2,3...}.

[0060] s33, with V 33 This is the frequency domain response result of the open triangular prism cavity.

[0061] Step (4), obtaining shielding effectiveness data with similar structures and corresponding cavity structure and opening structure data, and using the SVR method to train a machine learning regression prediction model.

[0062] Machine learning methods have been widely used in the field of computational electromagnetics. SVR (Support Vector Regression) is an effective regression training method. In order to obtain realistic and predictable results, SVR can be used to train existing data, select appropriate kernel functions, error ranges and other parameters, and thus provide strong support for calculations.

[0063] In order to obtain data for machine learning, the shielding effectiveness of a triangular prism hole cavity structure similar to the solution target is obtained. The hole shape of these cavities can be any rectangular, and the cross section is similar to the cross section of the solution target, but the size is different. Therefore, the present invention uses shielding effectiveness data with similar structures, that is, the shielding effectiveness of the existing triangular prism model with holes for machine learning, which can be obtained through three-dimensional electromagnetic full-wave simulation. The input of the model is the size of the cavity opening and the size of the cavity cross section, and the output is the shielding effectiveness corresponding to the input.

[0064] Step (5) determines the effect of the regression prediction model. If it meets the requirements, the result in step (3) is corrected to obtain the result. Otherwise, the training parameters of the SVR algorithm are adjusted to obtain a new model until the result meets the requirements. The shielding effectiveness of the open-hole triangular prism cavity is calculated using the final model.

[0065] The principle is:

[0066] The numerical method is used to solve the distribution of the characteristic mode electric field of the cross-sectional triangle, that is, and

[0067]

[0068]

[0069] and represents the electric field and the electric field of different TE and TM modes at P, and represents the voltage response calculated from the equivalent circuit of the BLT equation in TE and TM modes, i.e. V 33 The value of .

[0070] Where C represents the normalization coefficient, which is used to correct the results after BLT settlement. C includes the contribution to the electric field in the cavity of different modes, and also considers the influence of the open hole structure on the electric field inside the cavity.

[0071] The present invention uses a machine learning method to predict the C value of a triangular prism hole cavity. Using multiple sets of numerical calculation results, the radius of the circle where the cavity cross section is located and the hole shape are selected as parameters for machine learning training. Finally, the electric field at the observation point P is obtained:

[0072]

[0073] The shielding effectiveness at the observation point P is obtained as:

[0074] SE p =-20log 10 (|E p / E0|), here, it is stipulated that E0=1.

[0075] Finally, the shielding effectiveness of the desired triangular prism cavity is obtained.

[0076] exist Figure 5 In the illustrated embodiment, the cross-section of the triangular prism structure is an equilateral triangle with a side length of 112.6 mm (not within the training data range). The geometric center of the right bottom surface of the triangular prism is used as the coordinate origin, the xoy plane coincides with the right bottom surface, the y axis passes through a vertex of the triangular prism, and the z axis passes through the cavity structure radially. In the case of an opening l=8 mm and w=8 mm at the geometric center of the left bottom surface, the longitudinal length of the cavity is 180 mm, and the shielding effectiveness at (0, 32.5, 80) is tested in mm. The direction of plane electromagnetic wave propagation is (0, 0, -1), and the direction of electric field polarization is (0, 1, 0). Obviously, the shielding effectiveness obtained by the method of the present invention is superior to the shielding effectiveness obtained by the three-dimensional numerical method.

Claims

1. A method for quickly calculating the shielding effectiveness of a perforated triangular prism cavity, characterized in that: The steps include: Step (1), obtaining the shape data of the open-hole triangular prism cavity, including its longitudinal length d, the size of the opening, and the cavity wall thickness t; wherein d=2πR, R is the radius of the circle where the triangle of the cross section of the open-hole triangular prism cavity is located, and the opening is located on one end face of the triangular prism cavity; Step (2), obtaining the shape and size information of the cross-section triangle of the open triangular prism cavity, and using the electromagnetic field numerical method to obtain the cross-section characteristic mode, the method is: The object to be analyzed, i.e., the triangular prism cavity with holes, is divided or discretized to obtain the cross-sectional characteristic model. and and Represents the field distribution of different TE and TM modes, with subscripts m, n∈{1,2,3...}; then, the electromagnetic field is solved by the governing equation according to the cross-sectional characteristic mode and the electromagnetic wave propagation law; Step (3), performing circuit equivalence on the perforated triangular prism cavity subjected to electromagnetic radiation, and calculating the frequency domain response of the perforated triangular prism cavity in combination with the cross-sectional characteristic mode; Step (4), obtaining shielding effectiveness data of similar structures and corresponding cavity structure and opening structure data, and using the SVR method to train a machine learning regression prediction model; Step (5), determine the effect of the regression prediction model. If it meets the requirements, modify the result in step (3) to obtain the result; otherwise, adjust the training parameters of the SVR algorithm to obtain a new model until the result meets the requirements. Use the final model to calculate the shielding effectiveness of the open-hole triangular prism cavity.

2. The method for rapidly calculating the shielding effectiveness of a perforated triangular prism cavity according to claim 1, characterized in that: The open triangular prism cavity subjected to electromagnetic radiation is equivalent to a transmission line circuit, whose terminal is short-circuited and the propagation characteristic impedance is Z g0 , the propagation constant is k g0 , the equivalent impedance of the opening is Z ap , Z ap The calculation formula is as follows: Where k0 is the electromagnetic propagation constant of the free space outside the cavity, k0 = 2π / λ, λ is the wavelength of the free space, C ap is the opening location coefficient, w e is the equivalent width of the opening, When the opening structure is rectangular, l×w is its length and width; when the opening structure is circular, r a is the radius of the circular hole.

3. The method for rapidly calculating the shielding effectiveness of a perforated triangular prism cavity according to claim 2, characterized in that: In the step (3), the frequency domain response of the perforated triangular prism cavity is calculated as follows: s31, establish the generalized BLT equation: V = (U + ρ) (Γ - ρ) -1 S Where V represents the n-dimensional vector composed of the incident voltage and reflected voltage of each node, U is the n×n unit matrix, ρ is the scattering matrix composed of the scattering of each node, Γ is the pipeline propagation matrix, and S is the n-dimensional source vector; where pipelines are different electromagnetic wave propagation paths, nodes are the two ends of the pipeline, adjacent pipelines share a node, and the node numbers are arranged in the order of the signal transmission path, and n is equal to twice the number of pipelines; where: s32, for the open triangular prism cavity: Where V 11 Represents the voltage at node 1 of pipeline 1, V 12 Represents the voltage at node 2 of pipeline 1, V 22 Represents the voltage at node 2 of pipeline 2, V 23 Represents the voltage at node 3 of pipeline 2, V 33 Represents the voltage at node 3 of pipeline 3, V 34 Represents the voltage at node 4 of pipe 3, expressed as V ij′ Refers to V 11 ~V 34 ,but i and j′ represent the pipeline number and node number respectively. represents the incident voltage signal at node j′ of pipeline i, represents the reflected voltage signal at node j′ of pipeline i; p1=0, p4=-1 Γ1, Γ2, Γ3 are the scattering matrices of pipes T1, T2, and T3, d0 is the distance from the external observation point to the opening in the equivalent circuit, z p is the distance from the target point P to the other end face of the triangular prism cavity, and the target point P is a point located inside the triangular prism cavity; S1 and S2 represent the voltages transmitted by the voltage source to the left and right sides; d 01 is the voltage source V equivalent to the electromagnetic plane wave s Distance to external observation point, d 02 V s The distance to the opening; ρ1, ρ4 are the scattering values ​​of nodes j′1, j′4, ρ2, ρ3 are the scattering matrices of nodes j′2, j′3; Y0 and Y g0 are the admittances of free space and cavity waveguide respectively, and Z0 is the vacuum wave impedance; s33, with V 33 This is the frequency domain response result of the open triangular prism cavity.

4. The method for rapidly calculating the shielding effectiveness of a perforated triangular prism cavity according to claim 3, characterized in that: Z g0 Including the characteristic impedance of TE mode and the characteristic impedance of TM mode where λ is the wavelength, and Represents the characteristic frequency wavelengths of different TE modes and TM modes, with subscripts m,n∈{1,2,3...}.

5. The method for rapidly calculating the shielding effectiveness of a perforated triangular prism cavity according to claim 3, characterized in that: The electric field at the target point P The shielding effectiveness at the target point P is SE p =-20log 10 (|E p / E0|); in, is the electric field and of different TE modes at the target point P, C represents the normalization coefficient, which is used to correct the results after BLT settlement. represents the voltage response calculated from the equivalent circuit of the BLT equation in the TE mode, i.e. V 33 The value of is the field distribution of different TE modes; is the electric field and of different TM modes at the target point P, represents the voltage response calculated from the equivalent circuit of the BLT equation TM mode, i.e. V 33 The value of is the field distribution of different TM modes, m,n∈{1,2,3...}.

6. The method for rapidly calculating the shielding effectiveness of a perforated triangular prism cavity according to claim 1, characterized in that: In the step (4), the shielding effectiveness data with similar structure refers to the shielding effectiveness of the open-hole triangular prism model used for machine learning, which is obtained through three-dimensional electromagnetic full-wave simulation; the input of the model is the size of the cavity opening and the size of the cavity cross-section, and the output is the shielding effectiveness corresponding to the input.

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