Method for calculating shielding effectiveness of multi-surface perforated cavity by considering leakage field

Abstract

The invention discloses a method for calculating the shielding effectiveness of a multi-surface perforated cavity considering a leakage field. The method comprises the following steps: decomposing any incident plane wave according to a rectangular coordinate system of the perforated cavity to obtain components in all directions; the electromagnetic field of any observation point in the cavity is the vector sum of a first electromagnetic field generated at the observation point when each component of an incident plane wave is incident from the front and passes through one hole of the hole cavity and a second electromagnetic field generated at the observation point when leakage fields of other holes are formed, the leakage fields of other open holes are approximately equivalent electric dipole moment fields and equivalent magnetic dipole moment fields at other open holes; according to the electromagnetic field measured by the observation point and the electromagnetic field of the same observation point when the cavity does not exist, the shielding effectiveness of the multi-surface perforated cavity is calculated; according to the method, the influence of the leakage field at the aperture on the shielding effectiveness calculation is considered, and the calculation reliability is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of shielding of multi-sided open-hole shielding cavities, and particularly relates to a method for calculating the shielding effectiveness of a multi-sided open-hole cavity considering the leakage field. Background Art

[0002] Shielding cavities are widely used in various electronic devices to suppress electromagnetic interference (EMI) and improve electromagnetic compatibility (EMC). In actual design, in order to meet the requirements of heat dissipation, signal transmission, and installation, openings are usually required on the shielding cavity. However, the openings will cause a reduction in shielding effectiveness and an increase in electromagnetic leakage. Therefore, accurately evaluating the shielding effectiveness has become an important link in electromagnetic compatibility design.

[0003] Currently, the calculation of the shielding effectiveness of open-hole shielding cavities is divided into two methods: numerical methods and analytical methods. Numerical methods such as the finite-difference time-domain method, transmission line matrix model, and method of moments, etc., have the advantage of high precision, but the calculation will consume a large amount of computing resources and take a long time. Analytical methods such as the equivalent circuit method, small-hole coupling theory, and eigenmode expansion method, etc., have the advantages of simple modeling and high calculation efficiency. For example, the shielding effectiveness calculation method in the literature "Fast Calculation Method for Shielding Effectiveness of Open-Hole Rectangular Cavities under Irradiation of Arbitrary Plane Waves, Hu Puyu, Transactions of China Electrotechnical Society, Vol. 33, No. 15, August 2018" uses the equivalent circuit method and is a front-side open-hole cavity model. Existing research on multi-sided open-hole cavities usually adopts the method of first decomposing the incident field vector onto each open-hole surface, calculating the electric field at the observation point respectively, and finally vector superposition. Although this method can obtain the general trend of the shielding effectiveness and relatively accurate resonance points, since the electromagnetic leakage characteristics of the multi-sided open-hole cavity are not considered when analyzing the problem and the influence of the leakage field on the cavity is ignored, there is a problem that some resonance points cannot be predicted.

[0004] In the related art, the calculation method of the internal field distribution of the open-hole cavity proposed in the patent application document with the publication number CN107255755A has great limitations, such as the model only calculates the field distribution on the central axis of the opening, and the plane wave is incident perpendicular to the surface of the small hole, etc. Summary of the Invention

[0005] The present invention aims to solve the problem that some resonance points cannot be predicted due to the lack of consideration of electromagnetic leakage when calculating the shielding effectiveness of a multi-sided open-hole cavity.

[0006] The present invention solves the above technical problems through the following technical means:

[0007] A method for calculating the shielding effectiveness of a multi-sided open-hole cavity considering the leakage field is proposed, and the method includes:

[0008] Decompose any incident plane wave into components in each direction according to the rectangular coordinate system of the open cavity;

[0009] The electromagnetic field at any observation point in the cavity is the vector sum of the first electromagnetic field generated at the observation point by the positive incidence of each component of the incident plane wave through one of the openings of the open cavity and the second electromagnetic field generated at the observation point by the leakage fields of the other openings. Among them, the leakage fields of the other openings are approximately the fields of the equivalent electric dipole moment and the equivalent magnetic dipole moment at the other openings;

[0010] Calculate the shielding effectiveness of the multi-sided open cavity according to the observed electromagnetic field and the electromagnetic field at the same observation point when the cavity does not exist.

[0011] Further, the decomposition of any incident plane wave into components in each direction according to the rectangular coordinate system of the open cavity is specifically as follows:

[0012] Select the lower left corner of one of the opening surfaces of the multi-sided open cavity as the coordinate origin to establish a space rectangular coordinate system, and establish a spherical coordinate system of the incident plane wave with this coordinate origin;

[0013] Decompose the electric field, magnetic field, and propagation vector of any incident plane wave into components in each direction according to the rectangular coordinate system of the open cavity.

[0014] Further, the method further includes:

[0015] According to Bethe small hole coupling theory, approximate the leakage field at the opening as the fields of the equivalent electric dipole moment and the equivalent magnetic dipole moment;

[0016] Among them, the equivalent electric dipole moment and the equivalent magnetic dipole moment are located at the center of the opening.

[0017] Further, the equivalent electric dipole moment p z and the equivalent magnetic dipole moment m x 、m y are expressed by the following formulas:

[0018] p z =2α e ε0E z

[0019] m x =-2α mx H x

[0020] m y =-2α my H y

[0021] In the formula, ε0 represents the vacuum permittivity, α e represents the electric susceptibility, α mx and αmy represents the magnetic susceptibility, E z is the component of the electric field of the incident plane wave in the z-axis direction of the rectangular coordinate system, H x and H y are respectively the components of the magnetic field of the incident plane wave in the x-axis and y-axis of the rectangular coordinate system.

[0022] Furthermore, when the opening is a circular hole with a radius of r, α e , α mx and α my are respectively:

[0023]

[0024]

[0025] Furthermore, when the opening is a rectangular hole, α e , α mx and α my are respectively:

[0026]

[0027] In the formula, l is the length of the rectangular hole, w is the width of the rectangular hole, and l > w.

[0028] Furthermore, the method further includes:

[0029] Using the Green's function to calculate respectively the electric field component generated by the equivalent electric dipole moment at any observation point in the cavity and the electric field component generated by the equivalent magnetic dipole moment at any observation point in the cavity;

[0030] Solving according to the orthogonal relationship between the electric field and the magnetic field to obtain the magnetic field component generated by the equivalent electric dipole moment at any observation point in the cavity and the magnetic field component generated by the equivalent magnetic dipole moment at any observation point in the cavity.

[0031] Furthermore, the using the Green's function to calculate respectively the electric field component generated by the equivalent electric dipole moment at any observation point in the cavity and the electric field component generated by the equivalent magnetic dipole moment at any observation point in the cavity includes:

[0032] The electric field components generated by the equivalent electric dipole moment p z at any observation point P(x p , y p , z p ) in the cavity are respectively expressed as:

[0033]

[0034] In the formula, k mn is the modal coefficient, Γ mn , Γ′mn and Γ″ mn are coefficients:

[0035]

[0036] In the formula, x a , y a are the central coordinates of the opening when the incident wave is normal, a, d, and b represent the length, width, and height of the multi-faceted opening cavity, j, ω, μ0, and k0 respectively represent the imaginary unit, the angular frequency of the incident plane wave, the vacuum permeability, and the wave number, m and n represent the mode indices, ε 0m , ε 0n represent the Neumann coefficients, x p , y p represent the coordinates of the observation point in the cavity;

[0037] The electric field components of the equivalent magnetic dipole moment m x at any observation point P(x p , y p , z p ) in the cavity are respectively expressed as:

[0038]

[0039] E mxx = 0

[0040] In the formula, the coefficients Γ mnx and Γ′ mnx are respectively:

[0041]

[0042] In the formula, m x represents the magnetic dipole moment in the x direction;

[0043] The electric field components of the equivalent magnetic dipole moment m y at any point P(x p , y p , z p ) in the cavity are respectively expressed as:

[0044]

[0045] E myy = 0

[0046]

[0047] In the formula, the mode coefficient k′ mn , the coefficient Γ mny and the coefficient Γ′ mny are respectively:

[0048]

[0049] In the formula, m y represents the magnetic dipole moment in the y direction.

[0050] Furthermore, the forward traveling wave of the leakage field is transmitted to the outside of the cavity, and the backward traveling wave of the leakage field is transmitted to the inside of the cavity.

[0051] Furthermore, the calculation formula for the electromagnetic field at any observation point in the cavity is:

[0052] E p = E incp + E leakp

[0053] E incp = E incxp + E incyp + E inczp

[0054] E leakp = E xleakp + E yleakp + E zleakp

[0055] In the formula, E xleakp , E yleakp and E zleakp respectively represent the electric fields of the backward traveling waves of the side leakage fields corresponding to E incx , E incy and E incz at the observation point, that is, calculate the x, y, and z directions of the electric fields of the incident wave passing through the aperture in the cavity and the electric fields of the leakage aperture in the cavity respectively. E incp represents the electric field of the incident plane wave at the observation point in the cavity, E leakp represents the electric field of the backward traveling wave of the leakage field at the observation point in the cavity, and E p represents the electromagnetic field at any observation point in the cavity.

[0056] The advantages of the present invention are as follows:

[0057] (1) For any observation point in the cavity irradiated by an arbitrary incident plane wave, the electromagnetic field of the present invention can be obtained by the vector sum of the electromagnetic fields of the forward incident components of the incident plane wave passing through the opening at the observation point and the electromagnetic fields of the other opening leakage fields at the observation point, and then the shielding effectiveness can be calculated. By considering the influence of the leakage field at the hole and slit on the calculation of the shielding effectiveness, the situation where some resonance points cannot be predicted is avoided, the reliability of the calculation is improved, the rapid and accurate calculation of the shielding effectiveness curve can be realized, and the design of the cavity structure can be assisted by the obtained shielding effectiveness curve at the initial stage of the design of the shielding cavity structure.

[0058] (2) The present invention uses equivalent electric and magnetic dipole moments to replace the electromagnetic field distribution at the openings, which can handle the cases of multiple openings and various opening shapes. For different opening conditions of different opening cavities, only the parameters need to be modified for calculation. Compared with the numerical calculation method in simulation software, the present invention can avoid the repeated modeling of openings and the complex mesh generation process, and has the advantages of flexibility and high efficiency.

[0059] Additional aspects and advantages of the present invention will be given in part in the following description, become apparent in part from the following description, or be learned through the practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] Figure 1 is a schematic flowchart of a method for calculating the shielding effectiveness of a multi-faceted opening cavity considering the leakage field proposed in an embodiment of the present invention;

[0061] Figure 2 is a schematic diagram of a multi-faceted opening cavity irradiated by an incident plane wave in an embodiment of the present invention;

[0062] Figure 3 is a schematic diagram of an incident plane wave in a spherical coordinate system in an embodiment of the present invention;

[0063] Figure 4 is a schematic diagram of a multi-faceted opening cavity irradiated by the decomposed incident plane wave in an embodiment of the present invention;

[0064] Figure 5 is a comparison chart of the shielding effectiveness calculated in an embodiment of the present invention and the shielding effectiveness curve obtained by simulation software. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0065] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Apparently, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the scope of protection of the present invention.

[0066] As Figure 1 shown, an embodiment of the present invention proposes a method for calculating the shielding effectiveness of a multi-faceted opening cavity considering the leakage field, and the method includes the following steps:

[0067] S10. Decompose an arbitrary incident plane wave into components in each direction according to the rectangular coordinate system of the opening cavity;

[0068] S20. The electromagnetic field at any observation point in the cavity is the vector sum of the first electromagnetic field generated at the observation point by the positive incidence of each component of the incident plane wave through one of the openings in the perforated cavity and the second electromagnetic field generated at the observation point by the leakage fields of the other openings. Among them, the leakage fields of the other openings are approximately the fields of the equivalent electric dipole moment and the equivalent magnetic dipole moment at the other openings.

[0069] S30. Calculate the electric field shielding effectiveness of the multi-sided perforated cavity according to the measured electromagnetic field and the electromagnetic field at the same observation point when the cavity does not exist.

[0070] In this embodiment, for any observation point in the cavity irradiated by an arbitrary incident plane wave, the electromagnetic field can be the vector sum of the electromagnetic field at the observation point due to the positive incidence of each component of the incident plane wave through the opening and the electromagnetic field at the observation point due to the leakage fields of the other openings. Then, the shielding effectiveness can be obtained. By considering the influence of the leakage fields at the apertures on the calculation of the shielding effectiveness, the situation where some resonance points cannot be predicted is avoided, the reliability of the calculation is improved, and thus the rapid and accurate calculation of the shielding effectiveness curve is realized.

[0071] As a further preferred technical solution, the step S10: decomposing an arbitrary incident plane wave into components in each direction according to the rectangular coordinate system of the perforated cavity specifically includes:

[0072] S11. Select the lower left corner of one of the opening surfaces of the multi-sided perforated cavity as the coordinate origin to establish a space rectangular coordinate system, and establish a spherical coordinate system of the incident plane wave with this coordinate origin.

[0073] Specifically, as Figure 2 shown, the dimensions of the multi-sided perforated cavity are: length a, width d, and height b; the same openings on two adjacent opening surfaces are located at the center of the surface, and the dimensions are recorded as: length l and width w; as Figure 3 shown, the parameters of the incident plane wave in the spherical coordinate system are: incident elevation angle θ, azimuth angle and polarization angle α.

[0074] S12. Decompose the electric field, magnetic field, and propagation vector of an arbitrary incident plane wave into components in each direction according to the rectangular coordinate system of the perforated cavity.

[0075] Specifically, the electric field components of the incident plane wave in each direction are:

[0076]

[0077] E y = E0cosαcosθ

[0078]

[0079] In the formula, E0 is the amplitude of the electric field strength of the incident plane wave.

[0080] The components of the propagation vector in each direction are as follows:

[0081]

[0082] k y = -k0sinθ

[0083]

[0084] where k0 = 2π / λ and λ is the wavelength.

[0085] The magnetic field components of the incident plane wave in each direction are as follows:

[0086]

[0087] where η represents the wave impedance, which is approximately equal to 377Ω in free space.

[0088] As a further preferred technical solution, the method further includes:

[0089] According to the Bethe small hole coupling theory, the leakage field at the opening is approximated as the field of an equivalent electric dipole moment and the field of an equivalent magnetic dipole moment;

[0090] where the equivalent electric dipole moment and the equivalent magnetic dipole moment are located at the center of the opening.

[0091] It should be noted that in this embodiment, according to the Bethe small hole coupling theory, the leakage field at the opening is approximated as the field of an equivalent electric dipole moment and the field of an equivalent magnetic dipole moment, which can simplify the solution of the small hole leakage field and make the electromagnetic leakage problem easier to analyze and calculate.

[0092] Specifically, in step S20, the Bethe small hole coupling theory is used to calculate the equivalent electric dipole moment p z and the equivalent magnetic dipole moment m x 、m y The formulas for are as follows:

[0093] p z = 2α e ε0E z

[0094] m x = -2α mx H x

[0095] m y = -2α my H y

[0096] where ε0 represents the vacuum permittivity, ε0 ≈ 8.85×10-12 F / m, α e represents the electric susceptibility, α mx and α my represents the magnetic susceptibility, E z is the component of the electric field of the incident plane wave in the z-axis direction of the rectangular coordinate system, H x and H y are respectively the components of the magnetic field of the incident plane wave in the x-axis and y-axis of the rectangular coordinate system.

[0097] It should be noted here that according to the Bethe small hole coupling theory, the aperture is equivalent to an electric dipole moment p along the z direction z and two magnetic dipole moments m along the x and y directions respectively x and m y , the three dipole moments are perpendicular to each other and are located at the center of the aperture. The electric dipole moment p z is perpendicular to the aperture plane, while the magnetic dipole moments m x and m y are parallel to the aperture plane.

[0098] Furthermore, when the aperture is a circular hole with a radius of r, α e , α mx and α my are respectively:

[0099]

[0100] Furthermore, when the aperture is a rectangular hole, α e , α mx and α my are respectively:

[0101]

[0102] In the formula, l is the length of the rectangular hole, w is the width of the rectangular hole, and l > w.

[0103] As a further preferred technical solution, the method further includes:

[0104] Using the Green's function to calculate respectively the electric field components generated by the equivalent electric dipole moment at any observation point in the cavity and the electric field components generated by the equivalent magnetic dipole moment at any observation point in the cavity;

[0105] Solving according to the orthogonality relationship between the electric field and the magnetic field to obtain the magnetic field components generated by the equivalent electric dipole moment at any observation point in the cavity and the magnetic field components generated by the equivalent magnetic dipole moment at any observation point in the cavity.

[0106] It should be noted that in this embodiment, using the Green's function can accurately and quickly calculate the electromagnetic field generated by the equivalent dipole moment.

[0107] Specifically, in the step S20, the fields of the equivalent electric dipole moment and the equivalent magnetic dipole moment at other opening positions can be calculated using the Green's function. The specific process is as follows:

[0108] Equivalent electric dipole moment p z At any observation point P(x p , y p , z p ) inside the cavity, the electric field components are respectively expressed as:

[0109]

[0110] In the formula, the modal coefficient k mn and the coefficients Γ mn , Γ' mn and Γ'' mn are respectively:

[0111]

[0112]

[0113] In the formula, x a , y a are the central coordinates of the opening during normal incidence. a, d, and b represent the length, width, and height of the multi-faceted opening cavity. j, ω, μ0, and k0 respectively represent the imaginary unit, the angular frequency of the incident plane wave, the vacuum magnetic permeability, and the wave number. m and n represent the mode indices. x p , y p represent the coordinates of the observation point inside the cavity; ε 0m , ε 0n represent the Neumann coefficients, and the formula is expressed as:

[0114]

[0115] Equivalent magnetic dipole moment m x At any observation point P(x p , y p , z p ) inside the cavity, the electric field components are respectively expressed as:

[0116]

[0117] E mxx = 0

[0118] In the formula, the coefficients Γ mnx and Γ' mnx are respectively:

[0119]

[0120] In the formula, m xRepresents the magnetic dipole moment in the x direction;

[0121] Equivalent magnetic dipole moment m y At any point P(x p ,y p ,z p ) in the cavity, the electric field components are respectively expressed as:

[0122]

[0123] E myy = 0

[0124]

[0125] Wherein, the modal coefficient k′ mn , coefficient Γ mny and coefficient Γ′ mny are respectively:

[0126]

[0127] Wherein, m y represents the magnetic dipole moment in the y direction.

[0128] Furthermore, for each magnetic field component, it can be obtained by solving according to the orthogonal relationship between the electric field and the magnetic field.

[0129] As a preferred technical solution, the forward traveling wave of the leakage field is transmitted to the outside of the cavity, and the backward traveling wave of the leakage field is transmitted to the inside of the cavity.

[0130] Furthermore, the electric field and magnetic field in the equivalent electric dipole moment and magnetic dipole moment at the opening of the other opening surfaces are the electric field and magnetic field at the side opening where the incident plane wave component passes through the opening.

[0131] Furthermore, in the step S20, the calculation process of the electromagnetic field at any observation point in the cavity is as follows:

[0132] The electric field of any incident plane wave can be expressed as:

[0133] E inc = E incx + E incy + E incz

[0134] Wherein, E incx , E incy and E incz are the electric field components of three plane waves perpendicular to the x, y, and z coordinate axes;

[0135] The electric field of the incident plane wave at the observation point in the cavity can be expressed as:

[0136] Eincp = E incxp + E incyp + E inczp

[0137] where E incxp , E incyp and E inczp are the electric fields of three plane-wave components passing through the front openings at the observation point inside the cavity;

[0138] The electric field of the backward traveling wave of the leakage field at the observation point inside the cavity can be expressed as:

[0139] E leakp = E xleakp + E yleakp + E zleakp

[0140] In the formula, E xleakp , E yleakp and E zleakp are respectively:

[0141] E xleakp = E x1 + E x2 + E x3 +... + E xm

[0142] E yleakp = E y1 + E y2 + E y3 +... + E yn

[0143] E zleakp = E z1 + E z2 + E z3 +... + E zk

[0144] where E xleakp , E yleakp and E zleakp represent the electric fields of the backward traveling waves of the side leakage fields corresponding to E incx , E incy and E incz at the observation point; E xm , E yn and E zk represent the electric fields of the backward traveling waves of the leakage fields of the respective side openings at the observation point;

[0145] The final electric field at the observation point inside the cavity is:

[0146] E p = E incp + E leakp .

[0147] Specifically, as Figure 4 shown, when the incident plane wave is normally incident perpendicular to the z-axis component in the rectangular coordinate system, the leakage field at the opening on the side can be represented by the fields generated by the equivalent electric dipole moment and magnetic dipole moment at the opening:

[0148] The electric field of the incident plane wave can be expressed as:

[0149] E inc = E incx + E incz

[0150] The electric field of the incident plane wave at the observation point in the cavity can be expressed as:

[0151] E incp = E incxp + E inczp

[0152] The electric field of the backward traveling wave of the leakage field at the observation point in the cavity can be expressed as:

[0153] E leakp = E xleakp + E zleakp

[0154] In the formula, E xleakp and E zleakp are respectively:

[0155] E xleakp = E x1

[0156] E zleakp = E z1 .

[0157] In this embodiment, when calculating the electric field at the observation point, the opening leakage problem of the multi-sided opening cavity is considered. By calculating the electric field of the backward traveling wave of the leakage field at the opening at the observation point, the resonance point of the cavity can be obtained more accurately, so that the shielding effectiveness curve can well match the numerical calculation results in the simulation software, greatly improving the calculation speed.

[0158] As a further preferred technical solution, the calculation formula for the shielding effectiveness SE of the multi-sided opening cavity is:

[0159] SE = -20log 10 |E p / E0|

[0160] where E0 represents the electric field of the incident plane wave at the observation point when the cavity does not exist.

[0161] Furthermore, in this embodiment, a simulation analysis is carried out on a method for calculating the shielding effectiveness of a multi-sided open cavity considering the leakage field. The simulation parameters are as follows: the length of the multi-sided open cavity is 300 mm, the width is 300 mm, and the height is 300 mm; the same openings on two adjacent open surfaces are located at the center of the surface, with a length of 30 mm and a width of 30 mm; the parameters of the incident plane wave in the spherical coordinate system are: the incident elevation angle is 0°, the azimuth angle is 45°, and the polarization angle is 0°; the amplitude of the electric field strength of the incident plane wave is 1 V / m. Figure 5 The TLM algorithm in Figure 5 is a numerical algorithm in the simulation software. By comparing it with the analytical algorithm of the present invention, it can be found that the two have a high degree of agreement and can obtain most of the resonant points of the cavity, corresponding to the minimum points in the shielding effectiveness curve, which reflects the reliability of the present invention.

[0162] It should be noted that the logic and / or steps represented in the flowchart or described in other ways herein, for example, can be considered as a definite sequence list of executable instructions for implementing logical functions, and can be specifically implemented in any computer-readable medium for use by an instruction execution system, apparatus, or device (such as a computer-based system, a system including a processor, or other systems that can fetch and execute instructions from the instruction execution system, apparatus, or device), or in combination with these instruction execution systems, apparatus, or devices. For the purposes of this specification, a "computer-readable medium" can be any device that can contain, store, communicate, propagate, or transport a program for use by or in connection with an instruction execution system, apparatus, or device. More specific examples (non-exhaustive list) of computer-readable media include the following: an electrical connection portion with one or more wirings (electronic device), a portable computer diskette (magnetic device), a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber device, and a portable compact disc read-only memory (CDROM). Additionally, the computer-readable medium can even be paper or other suitable media on which the program can be printed, because the program can be obtained electronically, for example, by optically scanning the paper or other media, followed by editing, interpretation, or other appropriate processing if necessary, and then stored in a computer memory.

[0163] It should be understood that the various parts of the present invention can be implemented by hardware, software, firmware, or a combination thereof. In the above embodiments, multiple steps or methods can be implemented by software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented by hardware, as in another embodiment, any one or a combination of the following techniques well known in the art can be used: discrete logic circuits having logic gate circuits for implementing logical functions on data signals, application specific integrated circuits having appropriate combinational logic gate circuits, programmable gate arrays (PGAs), field programmable gate arrays (FPGAs), and the like.

[0164] In the description of this specification, the description with reference to terms such as "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0165] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" can explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "a plurality" is at least two, such as two, three, etc., unless otherwise specifically defined.

[0166] Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those of ordinary skill in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention.

Claims

1. A calculation method for the shielding effectiveness of a multi-sided open cavity considering the leakage field, characterized in that Including: Decompose any incident plane wave according to the rectangular coordinate system of the multi-aperture cavity to obtain components in each direction; The electromagnetic field at any observation point in the cavity is the vector sum of the first electromagnetic field generated at the observation point by the positive incidence of each component of the incident plane wave through one of the apertures of the multi-aperture cavity and the second electromagnetic field generated at the observation point by the leakage fields of other apertures, where the leakage fields of other apertures are approximately the fields of the equivalent electric dipole moment and the equivalent magnetic dipole moment at other apertures; Calculate the shielding effectiveness of the multi-aperture cavity according to the measured electromagnetic field and the electromagnetic field at the same observation point when the cavity does not exist.

2. The method for calculating the shielding effectiveness of a multi-sided open-hole cavity considering the leakage field according to claim 1, wherein The step of decomposing any incident plane wave according to the rectangular coordinate system of the multi-aperture cavity to obtain components in each direction is specifically: Select the lower left corner of one of the aperture surfaces of the multi-aperture cavity as the coordinate origin to establish a spatial rectangular coordinate system, and establish a spherical coordinate system of the incident plane wave with this coordinate origin; Decompose the electric field, magnetic field and propagation vector of any incident plane wave according to the rectangular coordinate system of the multi-aperture cavity to obtain components in each direction.

3. The method for calculating the shielding effectiveness of a multi-sided open cavity considering the leakage field according to claim 2, wherein The method further includes: According to Bethe small hole coupling theory, approximate the leakage field at the aperture as the fields of the equivalent electric dipole moment and the equivalent magnetic dipole moment; Among them, the equivalent electric dipole moment and the equivalent magnetic dipole moment are located at the center of the aperture.

4. The method for calculating the shielding effectiveness of a multi-sided open cavity considering the leakage field according to claim 3, characterized in that, The equivalent electric dipole moment p z and the equivalent magnetic dipole moment m x 、m y are expressed by the formula as follows: p z = 2α e ε0E z m x = -2α mx H x m y = -2α my H y where ε0 represents the vacuum permittivity, and α e represents the electric susceptibility, and α mx and α my represent the magnetic susceptibility, E z is the component of the electric field of the incident plane wave in the z-axis direction of the rectangular coordinate system, and H x and H y are the components of the magnetic field of the incident plane wave in the x-axis and y-axis directions of the rectangular coordinate system, respectively.

5. The method for calculating the shielding effectiveness of a multi-sided open-hole cavity considering the leakage field according to claim 4, characterized in that, When the opening is a circular hole with a radius of r, α e , α mx and α my are respectively:

6. The method for calculating the shielding effectiveness of a multi-sided open cavity considering the leakage field according to claim 4, characterized in that When the opening is a rectangular hole, α e 、α mx and α my are respectively: In the formula, l is the length of the rectangular hole, w is the width of the rectangular hole, and l>w.

7. The method for calculating the shielding effectiveness of a multi-sided open cavity considering the leakage field as claimed in claim 1, wherein The method further includes: Use Green's function to calculate the electric field component generated by the equivalent electric dipole moment at any observation point in the cavity and the electric field component generated by the equivalent magnetic dipole moment at any observation point in the cavity respectively; Solve for the magnetic field component generated by the equivalent electric dipole moment at any observation point in the cavity and the magnetic field component generated by the equivalent magnetic dipole moment at any observation point in the cavity according to the orthogonality relationship between the electric field and the magnetic field.

8. The method for calculating the shielding effectiveness of a multi-sided open cavity considering the leakage field according to claim 7, wherein The step of using Green's function to calculate the electric field component generated by the equivalent electric dipole moment at any observation point in the cavity and the electric field component generated by the equivalent magnetic dipole moment at any observation point in the cavity respectively includes: Equivalent electric dipole moment p z At any observation point P(x p , y p , z p ) within the cavity, the electric field components generated are respectively expressed as: where the modal coefficient k mn and the coefficients Γ mn , Γ′ mn and Γ″ mn are respectively: where x a , y a are the center coordinates of the opening when the incident wave is normal, a, d, and b represent the length, width, and height of the multi-faceted opening cavity, j, ω, μ0, and k0 represent the imaginary unit, the angular frequency of the incident plane wave, the vacuum permeability, and the wave number, m and n represent the mode indices, ε 0m , ε 0n represent the Neumann coefficients, x p , y p represent the coordinates of the observation point inside the cavity; Equivalent magnetic dipole moment m x At any observation point P(x p , y p , z p ) within the cavity, the electric field components are respectively expressed as: E mxx ＝0 where the coefficient Γ mnx and Γ ′ mnx are respectively: where m x represents the magnetic dipole moment in the x direction; Equivalent magnetic dipole moment m y At any point P(x p , y p , z p ) in the cavity, the electric field components are respectively expressed as: E myy ＝0 where the modal coefficient k ′ mn , the coefficient Γ mny and the coefficient Γ ′ mny are respectively: where m y represents the magnetic dipole moment in the y direction.

9. The method for calculating the shielding effectiveness of a multi-sided open cavity considering the leakage field according to any one of claims 1 to 8, characterized in that The forward traveling wave of the leakage field is transmitted to the outside of the cavity, and the backward traveling wave of the leakage field is transmitted to the inside of the cavity.

10. The method for calculating the shielding effectiveness of a multi-sided open cavity considering the leakage field according to any one of claims 1 to 8, characterized in that, The calculation formula for the electromagnetic field at any observation point in the cavity is: E p = E incp + E leakp E incp = E incxp + E incyp + E inczp E leakp = E xleakp + E yleakp + E zleakp where, E xleakp , E yleakp and E zleakp respectively represent the electric fields at the observation point of the backward traveling waves of the side leakage fields corresponding to E incx , E incy and E incz . E incp represents the electric field of the incident plane wave at the observation point in the cavity, E leakp represents the electric field of the backward traveling wave of the leakage field at the observation point in the cavity, and E p represents the electromagnetic field at any observation point in the cavity.

Images