Broadband electromagnetic radiation interference characteristic modeling method for shielding cable network

Abstract

The invention discloses a broadband electromagnetic radiation interference characteristic modeling method for a shielding cable network. The method comprises the following steps: 1) obtaining a scattering parameter matrix of a shielding connector and a transmission parameter matrix of a bent shielding cable; 2) constructing an equivalent N port model of the shielding connector by using the scattering parameter matrix, and deducing a transmission parameter matrix of the shielding connector; 3) establishing a multi-conductor transmission line equation reflecting the distribution of interference current on the shielding cable by using the shielding cable transfer impedance; 4) cascading the transmission parameter matrixes of all the bent shielding cables and the shielding connectors to obtain an overall transmission parameter matrix of the shielding cable network; and 5) solving the multi-conductor transmission line equation in combination with the boundary constraint condition to obtain the common-mode interference current of the shielding layer of the shielding cable, and calculating the electric field radiation of the shielding cable network through the dipole array theory. The method is suitable for uniform and non-uniform shielding cables and shielding cable networks of single-core and multi-core wire harness shielding wire types, and has good universality.

Description

Technical Field

[0001] The present invention relates to the field of electromagnetic compatibility technology, and in particular to a method for modeling broadband electromagnetic radiation interference characteristics of a shielded cable network. Background Art

[0002] With the widespread application of new high-frequency, high-power SiC power electronic devices and power converters with new topologies in electrical equipment and systems on platforms such as ships and aircraft, the overall performance of electrical equipment and systems, including efficiency, response speed, and power density, has been significantly improved. However, the increase in switching frequency, switching speed, and power capacity has also led to an increase in the amplitude of the electromagnetic interference energy generated by these electrical devices and an expansion of the spectrum to higher frequencies. This interference energy can radiate outward through the shielded cables connecting the devices, worsening the electromagnetic environment in the space where the electromechanical system is located, leading to serious electromagnetic compatibility (EMC) problems. Both theory and engineering practice have shown that the problem of radiated interference from the shielded power or radio frequency cables that interconnect and transmit between electronic and electrical equipment is one of the most common EMC problems in power electronics systems.

[0003] Radiated interference in complex electromechanical systems primarily originates from the electrical equipment within the system and the interconnecting cable networks. Shielded cables, due to their excellent electrical and electromagnetic shielding properties, are widely used as connecting components between various devices and modules in electrical systems. They not only transmit energy and information but also provide a path for energy leakage from interference sources. Because interconnecting shielded cables resemble wire antennas and have relatively large longitudinal and lateral dimensions, they are prone to radiating interference energy when subjected to broadband interference currents. This is the primary reason why most electrical and electronic equipment and systems fail to meet EMC emission testing standards. The power shielded cable networks in practical electromechanical systems are often very complex. First, shielded cables come in a variety of types, including shielded parallel cables, shielded twisted pairs, shielded ribbon cables, and combinations thereof. The cross-section structure of the cable harness is also very complex. Second, shielded cable networks utilize numerous connectors for electrical connections, which can alter the transmission characteristics of interference currents along the cables. Furthermore, due to space constraints on equipment platforms, shielded cable networks often adopt a curved layout with numerous branches, requiring installation across multiple compartments. Moreover, the electrical equipment connected by shielded cables is installed in various locations, which leads to complex routing of shielded cables and the transmission distance of some shielded cables is also quite long.

[0004] However, existing research still lacks effective methods for modeling the electromagnetic radiation characteristics of interconnected shielded cable networks. As the frequency of electronic devices in strong electromagnetic equipment continues to increase, the frequency band of the radiated interference generated by interconnected shielded cable networks is widening, and the electromagnetic energy is increasing. This requires considering the radiation characteristics of interconnected shielded cable networks when modeling the radiation characteristics of electromechanical systems. Therefore, in order to comprehensively model the radiation characteristics of electromechanical systems, in-depth research is needed to analyze and model the electromagnetic radiation characteristics of interconnected shielded cable networks.

[0005] Therefore, at the beginning of the design of electronic and electrical systems, it is necessary to propose an efficient and accurate radiation characteristic modeling method for complex shielded cable networks in electromechanical systems to evaluate the radiated electromagnetic interference (EMI) level of electrical shielded cable networks, thereby supporting the selection and wiring of shielded cables and improving the EMC performance of shielded cable networks.

[0006] In practical electromechanical systems, shielded cables between electrical devices often use curved routing and are connected to the electronic and electrical equipment via connectors, which can alter the current distribution on the shielded cables. Therefore, it is necessary to develop a radiation characteristic model for shielded cable networks that accounts for the curved layout of connectors and shielded cables. Furthermore, the complex relationship between the shielding energy of shielded cables and the internal and external coupling between the cores makes the modeling process even more difficult. Summary of the Invention

[0007] The present invention aims to provide a method for modeling the broadband electromagnetic radiation interference characteristics of a shielded cable network, comprising the following steps:

[0008] 1) Obtain the scattering parameter matrix of the shielded connector in the shielded cable network and the transmission parameter matrix of the curved shielded cable.

[0009] 2) The equivalent N-port model of the shielded connector is constructed using the scattering parameter matrix, and the transmission parameter matrix of the shielded connector is derived.

[0010] 3) The multi-conductor transmission line equation reflecting the distribution of interference current on the shielded cable is established using the transfer impedance of the shielded cable.

[0011] 4) The transmission parameter matrices of all curved shielded cables and shielded connectors are cascaded to obtain the transmission parameter matrix of the entire shielded cable network.

[0012] 5) The transmission parameter matrix of the entire shielded cable network is input into the multi-conductor transmission line equation, and the multi-conductor transmission line equation is solved in combination with the boundary constraints to obtain the common-mode interference current of the shielded cable shielding layer. The electric field radiation of the shielded cable network is calculated using the dipole array theory.

[0013] Furthermore, the equivalent N-port model includes a U-port and a V-port, wherein the signal transmission of the U-port and the V-port is as follows:

[0014]

[0015] Where S UU 、S UV 、S VU 、S VV are all elements of the scattering parameter matrix of the shielded connector. U 、b U They represent the incident wave and reflected wave of the U port of the equivalent N-port model, respectively. V 、b V They represent the incident wave and reflected wave of the V port of the equivalent N-port model respectively. UU 、B UV 、C VU 、D VV are all elements of the transmission parameter matrix of the shielded connector. U 、V V They are the voltage matrices of U port and V port respectively. U , I V They are the current matrices of U port and V port respectively.

[0016] Furthermore, the transmission parameter matrix of the shielded connector is as follows:

[0017]

[0018] Where, T C A is the transmission parameter matrix of the shielded connector. UU 、B UV 、C VU 、D VV They are all elements of the transmission parameter matrix of the shielded connector.

[0019] Among them, the transformation matrix J and the transformation matrix G are as follows:

[0020]

[0021] Where 1 is the identity matrix. U is the impedance matrix of the U port, Z V is the impedance matrix of the V port, The impedance matrix Z is U , Z V The conjugate of S UU 、S UV 、S VU 、S VV are all elements of the scattering parameter matrix of the shielded connector.

[0022] Among them, the impedance matrix g of the U port is U and the impedance matrix g of the V port V As shown below:

[0023]

[0024] Where i represents the port number, Z 0,i is the impedance of the ith port, is the impedance Z 0,i The conjugate of diag represents a diagonal matrix, g 0_i Indicates the set parameters.

[0025] Furthermore, the shielded cable transfer impedance is as follows:

[0026] Z T =Z R +jωL′ t +(1+j)ωL s (7)

[0027] Where Z T is the shielded cable transfer impedance, j is a complex number, and ω is the frequency.

[0028] Where, the impedance per unit length of the braided shield is Z R As shown below:

[0029]

[0030] Where R gs is the DC resistance per unit length of braid. R is the thickness of the equivalent metal filament. δ is the skin depth of the shield. N is the number of metal filaments in a single braid. is the braiding angle. C is the total number of braided strands. d is the diameter of a single metal filament. f is the frequency. μ is the magnetic permeability. Ω is the unit ohm. σ is the electrical conductivity.

[0031] Coupled inductor L' t As shown below:

[0032] L′ t =M′ L +L′ G (10)

[0033]

[0034] Where M′ L is the aperture inductance. L′ G is the braided inductor. F is the filling factor of the braided mesh parameter. D mis the average diameter of the braided layer. κ is the optical coverage. ξ is the ellipse eccentricity. F0 is the minimum κ filling factor of the braided mesh parameters. D is the outer diameter of the insulating medium. k1 is the mesh inductance. L′ a is the set parameter. H is the set parameter. μ0 is the vacuum permeability. E(ξ) is the elliptic integral of the first kind. K(ξ) is the elliptic integral of the second kind. α is the angle parameter.

[0035] Eddy current inductance L s As shown below:

[0036]

[0037] Where D L and D G is the imaginary diameter that simulates the corresponding skin effect. τ E is the set parameter. k2 is the set parameter.

[0038] Furthermore, the multi-conductor transmission line equation is as follows:

[0039]

[0040] Where z represents the position on the shielded cable.

[0041] Among them, the shielded harness voltage and shielded harness current As shown below:

[0042]

[0043] Where, is the induced current and induced voltage on the inner conductor core wire, It is the current and voltage of the outer conductor shielding layer.

[0044] Impedance matrix per unit length of shielded wiring harness and admittance As shown below:

[0045]

[0046] Where, is the impedance matrix of the conductor loop inside the core wire, is the impedance matrix of the outer conductor loop of the shielding layer, It is the coupling impedance matrix of the internal and external loops. represents the admittance matrix between the inner and outer conductors, Represents the admittance matrix between the shielding layer and the reference ground.

[0047] Furthermore, the impedance matrix of the conductor loop in the core wire is Impedance matrix of the outer conductor loop of the shield Coupling impedance matrix of internal and external loops Admittance matrix between inner and outer conductors Admittance matrix between the shielding layer and the reference ground As shown below:

[0048]

[0049]

[0050] Where n is the dimension of the impedance matrix of the conductor loop inside the core wire, j is a complex number, and ω is the frequency.

[0051] Let t = 1, 2, ..., n, where the self-inductance per unit length of the core wire is L tc,tc , shielding layer self-inductance per unit length L ts,ts , the mutual capacitance C between the inner conductor core and the outer conductor shield tc,ts , the capacitance C between the shield layer and the reference ground g,ts As shown below:

[0052]

[0053] Where z represents the unit length of the shielded cable. ts is the outer radius of the insulation layer. r tc is the inner conductor radius of the core wire. sh is the thickness of the shielding layer. h R (z) is the height of the shielded cable from the reference ground. sh is the outer radius of the shield. ε is the dielectric constant. ε0 is the dielectric constant of vacuum. r is the relative permittivity. μ0 is the magnetic permeability of vacuum.

[0054] The mutual inductance M between the shielding layer and the core conductor tc,ts The transfer impedance is used to characterize the interaction between the core wire and the shielding layer, as shown below:

[0055] Z T =jωM tc,ts (33)

[0056] Where Z T Transfer impedance for shielded cables.

[0057] Furthermore, in step 4), the steps of obtaining the transmission parameter matrix of the entire shielded cable network are as follows:

[0058] 4.1) Calculate the transmission matrix of the entire shielded cable as follows:

[0059]

[0060] Where o is the uniform shielded cable sub-segment index, m is the total number of uniform shielded cable sub-segments, and Δz is the number of wire elements in each shielded cable segment. It is the transmission matrix of the entire shielded cable. is the transmission parameter matrix of the oth uniformly shielded cable sub-segment. are all transmission parameter matrices elements. is the similarity diagonal matrix of the oth uniformly shielded cable subsegment, is the admittance matrix of the oth uniformly shielded cable sub-segment, is the propagation constant of the oth uniformly shielded cable subsection.

[0061] 4.2) The equivalent transmission parameter matrix of the parallel branch shielded cable is calculated as follows:

[0062]

[0063] Where, is the parallel branch transmission matrix. 1 is the identity matrix. is the equivalent input impedance of the branch line. They are the branch shield line input voltage and input current respectively. It is the terminal voltage of the branch shielded cable. It is the termination load of the branch shielded cable. and is the element of the transmission parameter matrix of the branch shielded cable.

[0064] 4.3) Cascade the transmission parameter matrix of the entire shielded cable network to obtain the transmission parameter matrix of the entire shielded cable network, as shown below:

[0065]

[0066] Where k is the node index, p is the total number of nodes, It is the transmission parameter matrix of the entire shielded cable network. is the transmission parameter matrix of the shielded connector, is the transmission parameter matrix of the shielded cable duct from the shielded connector to the kth node, is the equivalent transmission parameter matrix of all branches connected to node k. They are all elements of the transmission parameter matrix of the entire shielded cable network.

[0067] Furthermore, when the terminal is a voltage excitation source, the common-mode interference current of the shielded cable shield is as follows:

[0068]

[0069]

[0070] Where o is the uniform shielded cable sub-segment index, m is the total number of uniform shielded cable sub-segments, Δz o For each section of shielded cable, are the voltage and current of the oth uniform shielded cable sub-segment respectively. is the transmission parameter matrix of the oth uniform shielded cable sub-segment. l is the shielded cable network length, Respectively represent the voltage and current at the end of the shielded cable network. They are all elements of the transmission parameter matrix of the entire shielded cable network. are the equivalent load impedance matrices at the beginning and end of the terminal network respectively. are the equivalent voltage sources at the head end and the end end respectively. are the impedance matrix and admittance matrix of the oth uniform shielded cable sub-segment, is the characteristic impedance, is the characteristic admittance. is the admittance matrix per unit length of the shielded harness. is a similar diagonal matrix. is the propagation constant of the transmission line.

[0071] Furthermore, when the terminal is a current excitation source, the common-mode interference current of the shielded cable shield is as follows:

[0072]

[0073] Where o is the uniform shielded cable sub-segment index, m is the total number of uniform shielded cable sub-segments, Δz o For each section of shielded cable, are the voltage and current of the oth uniform shielded cable sub-segment respectively. is the transmission parameter matrix of the oth uniform shielded cable sub-segment. l is the shielded cable network length, Respectively represent the voltage and current at the end of the shielded cable network. They are all elements of the transmission parameter matrix of the entire shielded cable network. are the equivalent current sources at the beginning and end of the terminal network respectively, are the equivalent load admittance matrices at the head end and the end end of the terminal network respectively.

[0074] Furthermore, the electric field radiation of the shielded cable network is as follows:

[0075]

[0076] Where, is the electric field radiation of the shielded cable network, They are the total radiated electric field generated by the real current segment and the mirror current segment on the shielded cable network. They are the mirror electric field and the real electric field generated by the support end.

[0077] The technical effect of the present invention is unquestionable. The modeling and prediction method proposed in the present invention can be directly used for the radiation calculation of shielded cable networks that exist in large quantities in practice, which helps to better predict the broadband electromagnetic radiation characteristics of shielded cable networks in actual electromechanical systems; and provides an important basis for the EMC design and optimization of shielded cable networks in actual electromechanical systems.

[0078] The present invention proposes a modeling method for the wide-band electromagnetic radiation characteristics of shielded cables that integrates dipole array theory and transmission line theory. The method can effectively utilize the current data measured at the shielded cable terminal to establish a wide-band radiation interference characteristic model of the shielded cable, and can be combined with three-dimensional simulation software to quickly predict the radiation field distribution of the shielded cable within a large equipment platform.

[0079] The present invention utilizes transmission line equations and dipole array radiation theory to model the radiation interference characteristics of connectors in shielded cables and the internal core signal modeling of shielded cables, thereby realizing modeling and analysis of the radiation characteristics of shielded cable networks containing connectors in electronic and electrical systems. This method can accurately predict the wide-band radiation characteristics of shielded cable networks and physically reveal the external radiation mechanism of shielded cables and cable networks.

[0080] The present invention is based on S-parameters and multi-port circuit theory. It can establish an equivalent radiation model of a shielded connector based on multi-port ABCD parameters according to the S-parameters of the shielded connector. It has the outstanding advantage of ignoring the connector topology and internal specific structure, and can conveniently model and analyze the radiation characteristics of a shielded cable network composed of any form of connectors.

[0081] The modeling method of the radiation characteristics of the shielded cable network containing connectors based on the transmission line equation and the dipole array proposed in the present invention can be applied to uniform and non-uniform shielded cables and shielded cable networks with single-core and multi-core harness shielding lines, and has good versatility. BRIEF DESCRIPTION OF THE DRAWINGS

[0082] Figure 1 Flowchart for equivalent modeling of broadband radiated electromagnetic interference from shielded cables;

[0083] Figure 2 It is a schematic diagram of an N-port network;

[0084] Figure 3 Schematic diagram for the definition of shielded cable parameters;

[0085] Figure 4 This is a schematic diagram of a shielded cable;

[0086] Figure 5 Schematic diagram of a multi-conductor transmission line model for a shielded cable;

[0087] Figure 6 This is a schematic diagram of the structure of a shielded cable;

[0088] Figure 7 A schematic diagram of a complex interconnected shielded cable network;

[0089] Figure 8 This is a port network diagram of parallel branch shielded cables;

[0090] Figure 9 The diagram is a diagram of the Thevenin equivalent form of the terminal of the wiring harness network;

[0091] Figure 10 is a mirror image diagram of the current segment on the mirror plane;

[0092] Figure 11 This is a schematic diagram of the mirror principle;

[0093] Figure 12 This is a schematic diagram of the shielded cable test arrangement;

[0094] Figure 13 Schematic diagram of the common-mode current spectrum of the shielded cable at z = 0.61m;

[0095] Figure 14 Schematic diagram comparing the electric field calculation results and experimental data at (0m, 0.61m, 1.05m). DETAILED DESCRIPTION

[0096] The present invention will be further described below with reference to the following examples, but it should not be understood that the scope of the present invention is limited to the following examples. Without departing from the above technical ideas of the present invention, various substitutions and modifications can be made according to common technical knowledge and customary means in the art, and all should be included in the scope of protection of the present invention.

[0097] Example 1:

[0098] See also Figures 1 to 14 A method for modeling broadband electromagnetic radiation interference characteristics of a shielded cable network comprises the following steps:

[0099] 1) Obtain the scattering parameter matrix of the shielded connector in the shielded cable network and the transmission parameter matrix of the curved shielded cable.

[0100] The transmission parameter matrix of the curved shielded cable is calculated using the distributed parameters of the cable.

[0101] 2) The equivalent N-port model of the shielded connector is constructed using the scattering parameter matrix, and the transmission parameter matrix of the shielded connector is derived.

[0102] Transmission parameter matrix of the connector: The scattering parameters are obtained by direct measurement or simulation, and then the scattering parameters are converted into a transmission parameter matrix.

[0103] 3) The multi-conductor transmission line equation reflecting the distribution of interference current on the shielded cable is established using the transfer impedance of the shielded cable.

[0104] 4) The transmission parameter matrices of all curved shielded cables and shielded connectors are cascaded to obtain the transmission parameter matrix of the entire shielded cable network.

[0105] 5) The transmission parameter matrix of the entire shielded cable network is input into the multi-conductor transmission line equation, and the multi-conductor transmission line equation is solved in combination with the boundary constraints to obtain the common-mode interference current of the shielded cable shielding layer. The electric field radiation of the shielded cable network is calculated using the dipole array theory.

[0106] The boundary constraint condition is the cable port current.

[0107] Example 2:

[0108] A method for modeling broadband electromagnetic radiation interference characteristics of a shielded cable network. The main technical content is shown in Example 1. Furthermore, the equivalent N-port model includes a U port and a V port, wherein the signal transmission of the U port and the V port is as follows:

[0109]

[0110] Where S UU 、S UV 、S VU 、S VV are all elements of the scattering parameter matrix of the shielded connector. U 、b U They represent the incident wave and reflected wave of the U port of the equivalent N-port model, respectively. V 、b V They represent the incident wave and reflected wave of the V port of the equivalent N-port model respectively. UU 、B UV 、C VU 、D VV are all elements of the transmission parameter matrix of the shielded connector. U 、V V They are the voltage matrices of U port and V port respectively. U , I V They are the current matrices of U port and V port respectively.

[0111] Example 3:

[0112] A method for modeling broadband electromagnetic radiation interference characteristics of a shielded cable network. The main technical content is shown in any one of Examples 1 to 2. Furthermore, the transmission parameter matrix of the shielded connector is shown as follows:

[0113]

[0114] Where, T C A is the transmission parameter matrix of the shielded connector. UU 、B UV 、C VU 、D VV They are all elements of the transmission parameter matrix of the shielded connector.

[0115] Among them, the transformation matrix J and the transformation matrix G are as follows:

[0116]

[0117] Where 1 is the identity matrix. U is the impedance matrix of the U port, Z V is the impedance matrix of the V port, The impedance matrix Z is U , Z V The conjugate of S UU 、S UV 、S VU 、S VV are all elements of the scattering parameter matrix of the shielded connector.

[0118] Among them, the impedance matrix g of the U port is U and the impedance matrix g of the V port V As shown below:

[0119]

[0120] Where i represents the port number, Z 0,i is the impedance of the ith port, is the impedance Z 0,i The conjugate of diag represents a diagonal matrix, g 0_i Indicates the parameters for simplifying the formula settings.

[0121] Example 4:

[0122] A method for modeling broadband electromagnetic radiation interference characteristics of a shielded cable network, the main technical content of which is shown in any one of Examples 1 to 3. Furthermore, the shielded cable transfer impedance is as follows:

[0123] Z T =Z R +jωL′ t+(1+j)ωL s (7)

[0124] Where Z T is the shielded cable transfer impedance, j is a complex number, and ω is the frequency.

[0125] Where, the impedance per unit length of the braided shield is Z R As shown below:

[0126]

[0127] Where R gs is the DC resistance per unit length of braid. R is the thickness of the equivalent metal filament. δ is the skin depth of the shield. N is the number of metal filaments in a single braid. is the braiding angle. C is the total number of braided strands. d is the diameter of a single metal filament. f is the frequency. μ is the magnetic permeability. Ω is the unit ohm. σ is the electrical conductivity.

[0128] Coupled inductor L' t As shown below:

[0129] L′ t =M′ L +L′ G (10)

[0130]

[0131]

[0132] Where M′ L is the aperture inductance. L′ G is the braided inductor. F is the filling factor of the braided mesh parameter. D m is the average diameter of the braided layer. κ is the optical coverage. ξ is the ellipse eccentricity. F0 is the minimum κ filling factor of the braided mesh parameters. D is the outer diameter of the insulating medium. k1 is the mesh inductance. L′ a is the set parameter. H is the set parameter. μ0 is the vacuum permeability. E(ξ) is the elliptic integral of the first kind. K(ξ) is the elliptic integral of the second kind. α is the angle parameter.

[0133] Eddy current inductance L s As shown below:

[0134]

[0135] Where D L and D G is the imaginary diameter that simulates the corresponding skin effect. τ E is the set parameter. k2 is the set parameter.

[0136] Example 5:

[0137] A method for modeling broadband electromagnetic radiation interference characteristics of a shielded cable network, the main technical content of which is shown in any one of Examples 1 to 4. Furthermore, the multi-conductor transmission line equation is as follows:

[0138]

[0139] Where z represents the position on the shielded cable.

[0140] Among them, the shielded harness voltage and shielded harness current As shown below:

[0141]

[0142] Where, is the induced current and induced voltage on the inner conductor core wire, It is the current and voltage of the outer conductor shielding layer.

[0143] Impedance matrix per unit length of shielded wiring harness and admittance As shown below:

[0144]

[0145] Where, is the impedance matrix of the conductor loop inside the core wire, is the impedance matrix of the outer conductor loop of the shielding layer, It is the coupling impedance matrix of the internal and external loops. represents the admittance matrix between the inner and outer conductors, Represents the admittance matrix between the shielding layer and the reference ground.

[0146] Example 6:

[0147] A method for modeling the broadband electromagnetic radiation interference characteristics of a shielded cable network, the main technical content of which is shown in any one of embodiments 1 to 5. Further, the impedance matrix of the conductor loop in the core wire is Impedance matrix of the outer conductor loop of the shield Coupling impedance matrix of internal and external loops Admittance matrix between inner and outer conductors Admittance matrix between the shielding layer and the reference ground As shown below:

[0148]

[0149]

[0150] Where n is the dimension of the impedance matrix of the conductor loop inside the core wire, j is a complex number, and ω is the frequency.

[0151] Let t = 1, 2, ..., n, where the self-inductance per unit length of the core wire is L tc,tc , shielding layer self-inductance per unit length L ts,ts , the mutual capacitance C between the inner conductor core and the outer conductor shield tc,ts , the capacitance C between the shield layer and the reference ground g,ts As shown below:

[0152]

[0153] Where z represents the unit length of the shielded cable. ts is the outer radius of the insulation layer. r tc is the inner conductor radius of the core wire. sh is the thickness of the shielding layer. h R (z) is the height of the shielded cable from the reference ground. sh is the outer radius of the shield. ε is the dielectric constant. ε0 is the dielectric constant of vacuum. r is the relative permittivity. μ0 is the magnetic permeability of vacuum.

[0154] The mutual inductance M between the shielding layer and the core conductor tc,ts The transfer impedance is used to characterize the interaction between the core wire and the shielding layer, as shown below:

[0155] Z T =jωM tc,ts (33)

[0156] Where Z T Transfer impedance for shielded cables.

[0157] Example 7:

[0158] A method for modeling broadband electromagnetic radiation interference characteristics of a shielded cable network, the main technical content of which is shown in any one of Examples 1 to 6. Further, in step 4), the steps of obtaining the transmission parameter matrix of the entire shielded cable network are as follows:

[0159] 4.1) Calculate the transmission matrix of the entire shielded cable as follows:

[0160]

[0161] Where o is the uniform shielded cable sub-segment index, m is the total number of uniform shielded cable sub-segments, and Δz is the number of wire elements in each shielded cable segment. It is the transmission matrix of the entire shielded cable. is the transmission parameter matrix of the oth uniformly shielded cable sub-segment. are all transmission parameter matrices elements. is the similarity diagonal matrix of the oth uniformly shielded cable subsegment, is the admittance matrix of the oth uniformly shielded cable sub-segment, is the propagation constant of the oth uniformly shielded cable subsection.

[0162] 4.2) The equivalent transmission parameter matrix of the parallel branch shielded cable is calculated as follows:

[0163]

[0164] Where, is the parallel branch transmission matrix. 1 is the identity matrix. is the equivalent input impedance of the branch line. They are the branch shield line input voltage and input current respectively. It is the terminal voltage of the branch shielded cable. It is the termination load of the branch shielded cable. and is the element of the transmission parameter matrix of the branch shielded cable.

[0165] 4.3) Cascade the transmission parameter matrix of the entire shielded cable network to obtain the transmission parameter matrix of the entire shielded cable network, as shown below:

[0166]

[0167] Where k is the node index, p is the total number of nodes, It is the transmission parameter matrix of the entire shielded cable network. is the transmission parameter matrix of the shielded connector, is the transmission parameter matrix of the shielded cable duct from the shielded connector to the kth node, is the equivalent transmission parameter matrix of all branches connected to node k. They are all elements of the transmission parameter matrix of the entire shielded cable network.

[0168] Example 8:

[0169] A method for modeling the broadband electromagnetic radiation interference characteristics of a shielded cable network. The main technical content is shown in any one of Examples 1 to 7. Furthermore, when the terminal is a voltage excitation source, the common-mode interference current of the shielded cable shield is as follows:

[0170]

[0171] Where o is the uniform shielded cable sub-segment index, m is the total number of uniform shielded cable sub-segments, Δz o For each section of shielded cable, are the voltage and current of the oth uniform shielded cable sub-segment respectively. is the transmission parameter matrix of the oth uniform shielded cable sub-segment. l is the shielded cable network length, Respectively represent the voltage and current at the end of the shielded cable network. They are all elements of the transmission parameter matrix of the entire shielded cable network. are the equivalent load impedance matrices at the beginning and end of the terminal network respectively. are the equivalent voltage sources at the head end and the end end respectively. are the impedance matrix and admittance matrix of the oth uniform shielded cable sub-segment, is the characteristic impedance, is the characteristic admittance. is the admittance matrix per unit length of the shielded harness. Is a similar diagonal matrix, the product matrix The feature vectors of . is the propagation constant of the transmission line.

[0172] Example 9:

[0173] A method for modeling the broadband electromagnetic radiation interference characteristics of a shielded cable network. The main technical content is shown in any one of Examples 1 to 8. Furthermore, when the terminal is a current excitation source, the common-mode interference current of the shielded cable shield is as follows:

[0174]

[0175] Where o is the uniform shielded cable sub-segment index, m is the total number of uniform shielded cable sub-segments, Δz o For each section of shielded cable, are the voltage and current of the oth uniform shielded cable sub-segment respectively. is the transmission parameter matrix of the oth uniform shielded cable sub-segment. l is the shielded cable network length, Respectively represent the voltage and current at the end of the shielded cable network. They are all elements of the transmission parameter matrix of the entire shielded cable network. are the equivalent current sources at the beginning and end of the terminal network respectively, are the equivalent load admittance matrices at the head end and the end end of the terminal network respectively.

[0176] Example 10:

[0177] A method for modeling broadband electromagnetic radiation interference characteristics of a shielded cable network, the main technical content of which is shown in any one of Examples 1 to 9. Furthermore, the electric field radiation of the shielded cable network is as follows:

[0178]

[0179] Where, is the electric field radiation of the shielded cable network, They are the total radiated electric field generated by the real current segment and the mirror current segment on the shielded cable network. They are the mirror electric field and the real electric field generated by the support end.

[0180] Example 11:

[0181] See also Figures 1 to 14 , a modeling method for broadband electromagnetic radiation interference characteristics of shielded cable networks, mainly including the following contents:

[0182] The specific steps of shielded cable network broadband equivalent modeling are as follows, and the method flow chart is as follows: Figure 1 As shown:

[0183] 1) First, the equivalent N-port model of the shielded connector in the shielded cable is established using the scattering parameters of the connector, such as Figure 2 In order to accurately characterize the characteristics of the connector, its scattering parameters need to be obtained.

[0184]

[0185] Among them, S UU , S UV , S VU and S VV is the element of the scattering parameter matrix of the shielded connector port network; A UU , B UV , C VU and D VV is the element of the transfer matrix of the port network. V U and V V is the voltage matrix; I U and I V is the current matrix. The incident wave and reflected wave of the U port are expressed by a U and b U Indicates that here a U =diag(a1,…,a U ). The incident wave and reflected wave of the V port are expressed as a V and b V express.

[0186] Next, using multi-port network theory, the transmission parameter matrix of the connector is derived from the scattering parameters to facilitate subsequent network cascade analysis. According to equations (3) and (4), the transmission parameter matrix of the connector T C It can be obtained by converting the scattering parameters.

[0187]

[0188]

[0189] Where 1 is the identity matrix. U is the impedance matrix of the U port, Z V is the impedance matrix of the V port, Z U and Z V conjugation of g U and g V The calculation formulas are as follows (5) and (6).

[0190]

[0191] Where Z 0,i yes Figure 2 The corresponding port impedance shown is obtained by measurement or simulation. It's Z 0,i The conjugation of .

[0192] 2) Secondly, the transfer impedance is used to establish the coupling relationship between the inner conductor core and the outer conductor shield. On this basis, the multi-conductor transmission line (MTL) equation reflecting the coupling relationship between the core, shield and reference ground is established.

[0193] ① Shielded cable transfer impedance model:

[0194] For commonly used braided shielded cables, the transfer impedance is determined by the braiding parameters and physical parameters of the shielding layer. There are five basic braiding parameters, namely the total number of braided bundles (C), the number of metal filaments in a single braided bundle (N), the diameter of a single metal filament (d), and the shield braiding angle. The outer diameter (D) of the insulating medium, such as Figure 3 shown.

[0195] Based on these basic braiding parameters, secondary parameters such as the average diameter of the shielding layer and the filling factor can be calculated, as shown in formula (7).

[0196]

[0197] Among them, D m is the average diameter of the braided layer (unit: meter), F is the filling factor of the braided mesh parameter, F0 is the minimum filling factor of the braided mesh parameter, and is the optical coverage (unit: %).

[0198] The transfer impedance of a shielded cable based on the Kley model consists of three components, which can be expressed by equation (8).

[0199] Z T =Z R +jωL′ t +(1+j)ωL s (8)

[0200] Among them, Z R L' is the impedance of the braided shield per unit length. t is the coupled inductor, L s is the eddy current inductance.

[0201] Z R It is determined by the DC resistance of the braided layer per unit length and the skin effect, and can be calculated by formula (9).

[0202]

[0203] Among them, R gs is the DC resistance per unit length of braid. R is the thickness of the equivalent metal wire, approximately δ is the skin depth of the shielding layer, as shown in Equation (10).

[0204]

[0205] The coupled inductance is L' t It consists of two parts: the hole inductance M′, which represents the magnetic coupling effect of the woven hole L The braiding inductance L′ caused by the interlacing between the braided tapes G .

[0206] L′ t =M′ L +L′ G (11)

[0207] Aperture inductance M′ L It can be expressed by formula (12).

[0208]

[0209] Among them, L′ a It can be expressed by formula (13).

[0210]

[0211] Where ξ is the ellipse eccentricity, which can be calculated by Equation (14). E(ξ) and K(ξ) are the elliptic integrals of the first and second kinds, respectively, as expressed in Equation (15).

[0212]

[0213] Braided inductor L′ G It can be calculated according to formula (16):

[0214]

[0215] Eddy current inductance L s It consists of two parts and can be calculated by formula (17).

[0216]

[0217] Among them, D L and D G is the imaginary diameter that simulates the corresponding skin effect and is calculated by the following formula.

[0218]

[0219] ② Establish the MTL equation that reflects the distribution of interference current on the shielded cable.

[0220] At higher frequencies, transmission line effects are observed between the shield and the reference ground. Characteristic parameters are distributed resistance, inductance, capacitance, and conductance per unit length. Furthermore, the shield and inner conductor form a tightly coupled transmission line. Therefore, the transmission line model for shielded cables must account for the coupling between the inner and outer loops. Figure 4 The shielded cable can be regarded as a 2n+1 MTL system consisting of the inner conductor, shielding layer and ground. The equivalent circuit of the shielded transmission line is as follows: Figure 5 As shown, the shielding layers at both ends are connected to the reference ground.

[0221] In such an MTL system, since the electromagnetic field propagates in the transverse electromagnetic wave mode, the interaction between conductors can be expressed using the MTL equation, as shown in Equation (20).

[0222]

[0223] Where, Expressed as shielded harness voltage, It is expressed as the shielded wire harness current and is expressed by formula (21).

[0224]

[0225] in, is the induced current on the inner conductor core wire, is the current in the outer conductor shield.

[0226] Where, and are the unit length impedance matrix and admittance of the shielded harness, respectively, as shown in Equations (22) and (23).

[0227]

[0228] in, is the impedance of the conductor loop in the core wire, is the impedance of the outer conductor loop of the shield, It is the coupling impedance of the internal and external loops. represents the admittance between the inner and outer conductors, represents the admittance between the shield and the reference ground, and both are n×n matrices. It is worth noting that because the shield effectively eliminates the capacitive coupling between the inner conductor enclosed by the shield and the reference ground, the corresponding elements of the admittance matrix in the MTL equation for the shielded cable do not include the capacitance between the core wire and the reference ground.

[0229] Impedance matrix of the conductor inside the core wire It can be expressed by formula (24).

[0230]

[0231] Where, L 1c,1c 、L 2c,2c and L nc,nc It is the core wire self-inductance.

[0232] Impedance matrix of shielded wire conductors It can be expressed by formula (25).

[0233]

[0234] Where, L 1s,1s 、L 2s,2s and L ns,ns is the self-inductance of the shield.

[0235] Impedance matrix of shield and core wires It can be expressed by formula (26).

[0236]

[0237] Where M 1c,1s 、M 2c,2s and M nc,ns is the mutual inductance between the shield and the core conductor. The inductance effect is the current induced on the shield by the current in the inner conductor core. The interaction between the core and the shield can be characterized by transfer impedance, as shown in Equation (27).

[0238] Z T =jωM ic,is (27)

[0239] Admittance matrix between inner and outer conductors It can be expressed by formula (28).

[0240]

[0241] Where C 1c,1s 、C 2c,2s and C nc,ns It is the mutual capacitance between the inner core wire and the outer conductor shield.

[0242] Shielding admittance to ground It can be expressed by formula (29).

[0243]

[0244] Where C g,1s 、C g,2s and C g,ns is the capacitance between the shield layer and the reference conductor (ground).

[0245] Next, Figure 6 The shielded cable shown in the figure is used as an example to illustrate the calculation method of the distributed parameters of the shielded cable. Among them, the radius of the conductor inside the core wire is r ic ; r is is the outer radius of the insulation layer and also the inner radius of the shield conductor; r sh is the outer radius of the shield; t sh is the thickness of the shielding layer; h R It is the height of the shielded cable from the reference ground in meters.

[0246] If both ends of the shielded cable are ideally grounded, the current flows out from the core wire and returns from the shielding layer, so that the inner conductor core wire and the outer conductor shielding layer together form a current loop. This current loop will generate a magnetic field, which in turn leads to the generation of core wire self-inductance.

[0247] Therefore, the self-inductance per unit length of the core wire is calculated with the shielding layer as the reference surface, and the specific calculation is as shown in formula (30).

[0248]

[0249] The shielding layer and the reference ground form a loop, which can be regarded as a situation where the conductor is placed on the reference ground plane in a uniform dielectric space. The inductance of the shielding layer per unit length can be calculated by formula (31).

[0250]

[0251] The mutual capacitance between the inner conductor core and the outer conductor shield can be calculated by formula (32).

[0252]

[0253] The capacitance between the shielding layer and the reference ground can be calculated by formula (33).

[0254]

[0255] It should be noted that the height of a straight shielded cable from the ground is a constant, while the height of a curved shielded cable from the ground is h R As the line changes, the distributed inductance and capacitance parameters of the shielding layer also change accordingly.

[0256] 3) Subsequently, the transmission parameter matrices of all curved shielded cables and connectors are cascaded to obtain the overall transmission parameter matrix, and a cascade model of any interconnected shielded cables considering multiple factors can be established.

[0257] ① Transmission parameter matrix of transmission line

[0258] right Figure 7 For the cable network shown, without loss of generality, any shielded cable (including straight and irregularly curved) can be considered a non-uniform shielded cable. The four unit length parameters of a non-uniform shielded cable are unevenly distributed, so it can be divided into a cascade of several very short uniform line elements, which is approximately equivalent to a uniform transmission line. The transmission parameter matrix of the cascaded transmission line can be obtained by multiplying the transmission parameter matrices of each shielded cable segment. If a non-uniform shielded cable is decomposed into m segments, each with a line element Δz, the transmission matrix of the entire shielded cable can be calculated using Equation (34).

[0259]

[0260] Where, is the transmission parameter matrix of the oth uniformly shielded cable sub-segment and can be calculated as follows.

[0261]

[0262] Where, is the similarity diagonal matrix of the oth uniformly shielded cable subsegment, is the admittance matrix of the shielded cable segment, is the propagation constant of the oth uniformly shielded cable subsegment.

[0263] ②Equivalent transmission parameter matrix of parallel branch shielded cable

[0264] like Figure 7 As shown, the interconnected cable network consists of a main shielded cable and numerous branch shielded cables. Figure 7 The branch k shown can be equivalent to a multi-port model, as Figure 8As shown. First, the transmission parameter matrix of the branch shielded cable is calculated according to equations (34) to (36), which describes the relationship between the output voltage, current and input voltage, current of the shielded cable. Then, the parallel branch transmission matrix can be calculated by equation (37).

[0265]

[0266] Where 1 is the identity matrix; is the equivalent input impedance of the branch line. Equation (37) shows that the problem of finding the parallel branch transmission matrix can be transformed into solving the input impedance of the parallel branch. Based on the transmission parameter matrix of the branch cable, the equivalent input impedance of this branch line can be calculated, as shown in Equation (38).

[0267]

[0268] in, It is the ratio of the branch shield line input voltage to the input current. and They are the input voltage and input current of the branch shield line respectively; is the terminal voltage of the branch shielded cable; It is the termination load of the branch shielded cable. and is the element of the transmission parameter matrix of the branch shielded cable.

[0269] ③ Transmission parameter matrix of cascade network

[0270] The entire transmission matrix of the cascade network can be obtained by multiplying the T parameter matrices of each component of the cascade network. Figure 7 The T parameter matrix of the cable network shown can be expressed as Equation (39).

[0271]

[0272] in, is the transmission parameter matrix of the connector, is the transmission parameter matrix of the shielded cable of the kth pipeline, It is the equivalent transmission parameter matrix of all branches connected to node k. The intermediate multiplication part is the product of the transmission parameter matrix representing the port itself and the equivalent transmission parameter matrix of all branches connected to the node.

[0273] 4) Furthermore, the MTL equation of the shielded cable is solved in combination with the boundary constraints to obtain the common-mode current on the shielded cable. Then, the electric field radiation of the shielded cable network is calculated using the dipole array theory.

[0274] ① Calculate the common mode interference current of the shielded cable shield

[0275] When the terminal is excited by a voltage source and the network is linear, the voltage and current at the terminal port can be related by the Thevenin equivalent form, such as Figure 9 Terminal voltage and terminal current It can be expressed as formula (40).

[0276]

[0277] 其中， 和 分别为首端 z=0 和末端 z=l 处的等效电压源， 和 分 Especially the voltage and current at the end of the shielded cable network. and are the equivalent load impedance matrices at the beginning and end of the terminal network respectively.

[0278] The elements of the transmission parameter matrix can be calculated by equations (41) and (42).

[0279]

[0280] Where, is the characteristic impedance of the transmission line, is the characteristic admittance, which can be expressed by formula (43).

[0281]

[0282] When the terminal is excited by a current source and the network is linear, the voltage and current at the terminal port can be related by the Norton equivalent form, such as Figure 9 Terminal voltage and terminal current It can be expressed as formula (44).

[0283]

[0284] 其中， 和 分别为终端网络 z=0 和 z=l 处的等效电流源， 和 分别 It is the voltage and current at the end of the shielded cable network. and are the equivalent load admittance matrices at the head end and the end end of the terminal network respectively.

[0285] According to the multi-conductor transmission line theory, if the current and voltage at the end of each shielded cable path are obtained, the current at any point on the transmission line can be calculated. The voltage of the i-th segment on the transmission line is and current It can be calculated by formula (45).

[0286]

[0287] Where i is a positive integer in the range of 1 to m, and is the terminal voltage and current on this shielded cable path, is the transmission parameter matrix of the i-th shielded cable segment, is the transmission parameter matrix of the mth shielded cable segment, which can be calculated by equations (34) to (36).

[0288] ②Calculate the electric field radiation of the shielded cable network.

[0289] When a shielded cable is arbitrarily curved in space, the current in the cable does not propagate uniformly along its axis but rather in arbitrary directions in three-dimensional space. Therefore, it is necessary to decompose the arbitrarily oriented current into its x, y, and z components. Dipole array theory is then used to calculate the electric field radiated into space by each component current, and finally the electric field contributions of each segment are superimposed.

[0290] If the current at any point on the shielded cable is Then its components on the x, y and z axes are and The angles α between the cable and the x, y and z axes can be x ,α y and α z The calculation can be expressed by equations (46) and (47).

[0291]

[0292] After calculating the current distribution on the surface of the shielded cable network, each current-carrying section of the shielded cable is equivalent to an electric dipole, and the dipole array theory is applied to calculate its radiation field.

[0293] According to the dipole array theory, the radiation electric field values of all discrete current elements on the transmission line are superimposed in each coordinate direction to obtain the radiation electric field generated by the shielded cable. p ,y p ,z p )’s electromagnetic radiation can be expressed by equation (48).

[0294]

[0295] Among them, (x i ,y i ,z i ) is the position of the current-carrying section of the i-th shielded cable, r i is the distance between the current-carrying section of the i-th shielded cable and the electric field observation point; and are the x, y and z components of the current in the current-carrying section of the i-th shielded cable; Δx i , Δy i and Δz i is the length of the i-th current-carrying segment, and the product of the current of the dipole and its size is the electric dipole moment. and are the electric fields in the x, y, and z directions generated by the i-th current-carrying segment. ε is the external environment dielectric constant, ω is the current angular frequency, β is the free space wave number, and Nz is the number of current-carrying segments. zi and are the polar angle and azimuth angle of the i-th z-direction dipole current-carrying segment in the spherical coordinate system, which can be expressed by formula (49).

[0296]

[0297] θ yi and are the polar angle and azimuth angle of the i-th y-direction dipole current-carrying segment in the spherical coordinate system, respectively, which can be expressed by formula (50).

[0298]

[0299] θ xi and are the polar angle and azimuth angle of the i-th x-direction dipole current-carrying segment in the spherical coordinate system, which can be expressed by formula (51).

[0300]

[0301] It should be noted that when the ground is used as a reference conductor, the electromagnetic field will be reflected on the ground. Assuming that the ground is infinite in size, the mirror method can be introduced to deal with the reflection effect. It replaces the plane with the mirror image of the current-carrying conductor and calculates the superposition field generated by the actual conductor and its mirror image. The field in any direction above the mirror plane can be calculated, such as Figure 10 shown.

[0302] In addition, due to the complex current distribution inside the vertical terminal, it is difficult for the multi-conductor transmission line theory to determine the radiation contribution of the vertical structure. Assuming that the vertical structure at the load end is directly connected to the ground through a wire, or connected to the ground through the displacement current between them, these structures can be simplified to multiple vertical dipoles. Figure 11 As shown in Figure 1, the true current and mirror current along the shielded cable, as well as the vertical current from the source and load ends of the shielded cable to ground, constitute the common-mode (CM) signal transmission path. The current flowing from the excitation source and load ends of the cable bundle to ground is considered to be an additional vertical electric dipole. The current continuity principle can be used to approximately calculate the current in the vertical dipole and, therefore, its radiation.

[0303] The total radiated electric field generated by the shielded cable network can be expressed by equation (52).

[0304]

[0305] Where, and They are the total radiated electric field generated by the real current segment and the mirror current segment on the shielded cable network. and are the image and real electric fields generated at the support end, respectively. According to the same process as above, they can be calculated using dipole array theory.

[0306] Example 12:

[0307] A method for modeling the broadband electromagnetic radiation interference characteristics of a shielded cable network. The main technical content is shown in Example 11. Furthermore, in order to verify the effectiveness of the algorithm, a straight single-core shielded cable with a terminated connector is first selected as the research object, and its radiation characteristics are modeled using the method proposed in Example 11. The modeling method proposed in Example 11 is verified using the measured test data. The shielded cable model parameters are set to: h = 0.05m, L = 1.22m, Vs = 0.224V. The selected shielded cable type is RG58, and the shielding layers at both ends of the shielded cable are well grounded. The specific geometric electromagnetic parameters are as follows: Figure 12 shown.

[0308] Based on the modeling and analysis method proposed in Example 11, the common mode current at the midpoint of the shielded cable (z = 61 cm) was calculated, and the corresponding current spectrum was plotted ( Figure 13 ); At the same time, the radiated electric field 1m away from the shielded cable is calculated, and the electric field spectrum is drawn ( Figure 14 ).

[0309] Comparing the data in the figure, it can be seen that the method proposed in Example 11 is consistent with the experimental results. In the current spectrum and radiation frequency characteristic curve, the waveform and peak value of the calculated results are basically consistent with the measured results. Figure 13 The measured current spectrum in the figure shows significant attenuation above 450MHz. This is primarily due to signal reflections from the copper plates supporting the shielded cable and the high-frequency skin effect. The calculated electric field exhibits an error within 5dB at most frequencies, meeting EMC prediction accuracy requirements. Therefore, the radiation level of the shielded cable can be accurately calculated within the studied frequency band. The error may stem from the model's neglect of the inductance of the copper plates supporting the cables at both ends and from uncertainty in the antenna position during the measurement.

Claims

1. A method for modeling broadband electromagnetic radiation interference characteristics of a shielded cable network, characterized in that: The following steps are involved: 1) Obtain the scattering parameter matrix of the shielded connector in the shielded cable network and the transmission parameter matrix of the curved shielded cable. 2) Using the scattering parameter matrix, an equivalent N-port model of the shielded connector is constructed, and the transmission parameter matrix of the shielded connector is derived; 3) The multi-conductor transmission line equation reflecting the distribution of interference current on the shielded cable is established using the transfer impedance of the shielded cable. 4) Cascading the transmission parameter matrices of all curved shielded cables and shielded connectors to obtain the transmission parameter matrix of the entire shielded cable network; 5) The transmission parameter matrix of the entire shielded cable network is input into the multi-conductor transmission line equation, and the multi-conductor transmission line equation is solved in combination with the boundary constraints to obtain the common-mode interference current of the shielded cable shielding layer. The electric field radiation of the shielded cable network is calculated using the dipole array theory.

2. The method for modeling broadband electromagnetic radiation interference characteristics of a shielded cable network according to claim 1, characterized in that: The equivalent N-port model includes a U-port and a V-port, wherein the signal transmission of the U-port and the V-port is as follows: Where S UU 、S UV 、S VU 、S VV are all elements of the scattering parameter matrix of the shielded connector; a U 、b U They represent the incident wave and reflected wave of the U port of the equivalent N-port model, respectively. V 、b V They represent the incident wave and reflected wave of the V port of the equivalent N-port model respectively; A UU 、B UV 、C VU 、D VV are all elements of the transmission parameter matrix of the shielded connector; V U 、V V They are the voltage matrices of U port and V port respectively; I U , I V They are the current matrices of U port and V port respectively.

3. The method for modeling broadband electromagnetic radiation interference characteristics of a shielded cable network according to claim 1, characterized in that: The transmission parameter matrix of the shielded connector is shown below: Where, T C A is the transmission parameter matrix of the shielded connector; UU 、B UV 、C VU 、D VV are all elements of the transmission parameter matrix of the shielded connector; Among them, the transformation matrix J and the transformation matrix G are as follows: Where 1 is the identity matrix; Z U is the impedance matrix of the U port, Z V is the impedance matrix of the V port, The impedance matrix Z is U , Z V conjugation of S UU 、S UV 、S VU 、S VV are all elements of the scattering parameter matrix of the shielded connector; Among them, the impedance matrix gU of the U port and the impedance matrix g of the V port are V As shown below: Where i represents the port number, Z 0,i is the impedance of the ith port, is the impedance Z 0,i The conjugate of; diag represents the diagonal matrix, g 0_i Indicates the set parameters.

4. The method for modeling broadband electromagnetic radiation interference characteristics of a shielded cable network according to claim 1, characterized in that: The shielded cable transfer impedance is shown below: Z T =Z R +jωL′ t +(1+j)ωL s (7) Where Z T is the shielded cable transfer impedance, j represents a complex number; ω represents the frequency; Where, the impedance per unit length of the braided shield is Z R As shown below: Where R gs is the DC resistance per unit length of braid; d R is the thickness of the equivalent metal filament; δ is the skin depth of the shielding layer; N is the number of metal filaments in a single braided bundle; is the braiding angle; C is the total number of braided bundles; d is the diameter of a single metal filament; f is the frequency; μ is the magnetic permeability; Ω is the unit ohm; σ is the electrical conductivity; Coupled inductor L' t As shown below: L′ t =M′ L +L′ G (10) Where M′ L is the aperture inductance; L′ G is the braided inductor; F is the braided mesh parameter filling factor; D m is the average diameter of the braided layer; κ is the optical coverage; ξ is the ellipse eccentricity; F0 is the minimum κ filling factor of the braided mesh parameters; D is the outer diameter of the insulating medium; k1 is the mesh inductance; L′ a is the set parameter; τ H is the set parameter; μ0 is the vacuum permeability; E(ξ) is the first kind of elliptic integral; K(ξ) is the second kind of elliptic integral; α is the angle parameter; Eddy current inductance L s As shown below: Where D L and D G is the imaginary diameter simulating the corresponding skin effect; τ E is the set parameter; k2 is the set parameter.

5. The method for modeling broadband electromagnetic radiation interference characteristics of a shielded cable network according to claim 1, characterized in that: The multi-conductor transmission line equation is shown below: Where z represents the position on the shielded cable; Among them, the shielded harness voltage and shielded harness current As shown below: Where, is the induced current and induced voltage on the inner conductor core wire, is the current and voltage of the outer conductor shield; Impedance matrix per unit length of shielded wiring harness and admittance As shown below: Where, is the impedance matrix of the conductor loop inside the core wire, is the impedance matrix of the outer conductor loop of the shielding layer, is the coupling impedance matrix of the internal and external loops; represents the admittance matrix between the inner and outer conductors, Represents the admittance matrix between the shielding layer and the reference ground.

6. The method for modeling broadband electromagnetic radiation interference characteristics of a shielded cable network according to claim 5, characterized in that: The impedance matrix of the conductor loop in the core wire Impedance matrix of the outer conductor loop of the shield Coupling impedance matrix of internal and external loops Admittance matrix between inner and outer conductors Admittance matrix between the shielding layer and the reference ground As shown below: Where n is the dimension of the impedance matrix of the conductor loop in the core wire, j represents a complex number, and ω represents the frequency. Let t = 1, 2, ..., n, where the self-inductance per unit length of the core wire is L tc,tc , shielding layer self-inductance per unit length L ts,ts , the mutual capacitance C between the inner conductor core and the outer conductor shield tc,ts , the capacitance C between the shield layer and the reference ground g,ts As shown below: Where z represents the unit length of the shielded cable; r ts is the outer radius of the insulation layer; r tc is the inner conductor radius of the core wire; t sh is the thickness of the shielding layer; h R (z) is the height of the shielded cable from the reference ground; r sh is the outer radius of the shielding layer; ε is the dielectric constant; ε0 is the dielectric constant of vacuum; ε r is the relative dielectric constant; μ0 is the vacuum permeability; The mutual inductance M between the shielding layer and the core conductor tc,ts The transfer impedance is used to characterize the interaction between the core wire and the shielding layer, as shown below: WITH T =jωM tc,ts (33) Where Z T Transfer impedance for shielded cables.

7. The method for modeling broadband electromagnetic radiation interference characteristics of a shielded cable network according to claim 1, characterized in that: In step 4), the steps for obtaining the transmission parameter matrix of the entire shielded cable network are as follows: 4.1) Calculate the transmission matrix of the entire shielded cable as follows: Where o is the uniform shielded cable sub-segment index, m is the total number of uniform shielded cable sub-segments, and Δz is the number of wire elements in each shielded cable segment; It is the transmission matrix of the entire shielded cable; is the transmission parameter matrix of the oth uniformly shielded cable sub-segment; are all transmission parameter matrices Elements of is the similarity diagonal matrix of the oth uniformly shielded cable subsegment, is the admittance matrix of the oth uniformly shielded cable sub-segment, is the propagation constant of the oth uniformly shielded cable subsegment; 4.2) The equivalent transmission parameter matrix of the parallel branch shielded cable is calculated as follows: 式中， 为并联分支传输矩阵； 1 是单位矩阵； 是分支线路的等效输入阻抗； They are the input voltage and input current of the branch shield line respectively; is the terminal voltage of the branch shielded cable; It is the termination load of the branch shielded cable. and is the element of the transmission parameter matrix of the branch shielded cable; 4.3) Cascade the transmission parameter matrix of the entire shielded cable network to obtain the transmission parameter matrix of the entire shielded cable network, as shown below: Where k is the node index, p is the total number of nodes, is the transmission parameter matrix of the entire shielded cable network; is the transmission parameter matrix of the shielded connector, is the transmission parameter matrix of the shielded cable duct from the shielded connector to the kth node, is the equivalent transmission parameter matrix of all branches connected to node k; They are all elements of the transmission parameter matrix of the entire shielded cable network.

8. The method for modeling broadband electromagnetic radiation interference characteristics of a shielded cable network according to claim 1, characterized in that: When the terminal is a voltage excitation source, the common-mode interference current of the shielded cable shield is as follows: Where o is the uniform shielded cable sub-segment index, m is the total number of uniform shielded cable sub-segments, Δz o For each shielded line The cable element, are the voltage and current of the oth uniform shielded cable sub-segment respectively; is the transmission parameter matrix of the oth uniformly shielded cable sub-segment; l is the shielded cable network length, Respectively represent the voltage and current at the end of the shielded cable network; They are all elements of the transmission parameter matrix of the entire shielded cable network; are the equivalent load impedance matrices at the beginning and end of the terminal network respectively; are the equivalent voltage sources at the head end and the end end respectively; are the impedance matrix and admittance matrix of the oth uniform shielded cable sub-segment, is the characteristic impedance, is the characteristic admittance; is the admittance matrix per unit length of the shielded harness; is a similar diagonal matrix; is the propagation constant of the transmission line.

9. The method for modeling broadband electromagnetic radiation interference characteristics of a shielded cable network according to claim 1, characterized in that: When the terminal is the current excitation source, the common-mode interference current of the shielded cable shield is as follows: Where o is the uniform shielded cable sub-segment index, m is the total number of uniform shielded cable sub-segments, Δz o For each section of shielded cable, are the voltage and current of the oth uniform shielded cable sub-segment respectively; is the transmission parameter matrix of the oth uniformly shielded cable sub-segment; l is the shielded cable network length, Respectively represent the voltage and current at the end of the shielded cable network; They are all elements of the transmission parameter matrix of the entire shielded cable network; are the equivalent current sources at the beginning and end of the terminal network respectively, are the equivalent load admittance matrices at the head end and the end end of the terminal network respectively.

10. The method for modeling broadband electromagnetic radiation interference characteristics of a shielded cable network according to claim 1, characterized in that: The electric field radiation of the shielded cable network is shown below: Where, is the electric field radiation of the shielded cable network, They are the total radiated electric field generated by the real current segment and the mirror current segment on the shielded cable network. They are the mirror electric field and the real electric field generated by the support end.

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