A method and system for detecting the shielding performance of an electrical wire

Abstract

This application discloses a method and system for testing the shielding performance of electrical wires, relating to the field of functional testing technology. The method includes: acquiring multi-frequency external excitation response data of the cable under test without disassembling it; obtaining the transmission characteristic curve by measuring the frequency domain according to a preset measurement arrangement and scanning steps; establishing a hierarchical equivalent network model based on the transmission characteristic curve and structural parameter set, and generating the parameter range to be inverted for each shielding layer; prioritizing the inversion of the outermost layer and subtracting the influence of the outermost layer to obtain an updated transmission characteristic curve; solving the parameters of the inner layers on the updated transmission characteristic curve and obtaining the interlayer coupling correction factor by comparing the difference sequence with the coupling threshold; summarizing and comparing with each threshold to output the location and type of failure layer; and outputting which layer and what failure mechanism the result falls into, reducing the risk of rework and disputes caused by the inability to attribute the cause in the overall test.

Description

Technical Field

[0001] This application relates to the field of functional testing technology, and more specifically, to a method and system for testing the shielding performance of electrical wires. Background Technology

[0002] Wire shielding performance testing technology is crucial for the reliable operation of modern electronic equipment and communication systems. With increasingly stringent electromagnetic compatibility requirements in fields such as aerospace, high-speed rail, 5G base stations, and electric vehicles, cables and wires need to possess efficient and stable shielding capabilities to prevent external electromagnetic interference from affecting signal transmission or internal signal leakage from interfering with other equipment. The quality of shielding performance directly determines the anti-interference capability and safety of the entire system; therefore, developing accurate and reliable shielding performance testing methods has become an urgent industry need.

[0003] Currently, most shielding performance testing methods used in the industry test the entire cable as a whole, only obtaining the final total shielding effectiveness value. While this overall testing method is simple to operate, it has a fatal flaw: it cannot distinguish the actual contribution of each layer in a multi-layered composite shielding structure. When wires use a combination of various shielding materials such as braided layers, aluminum foil layers, and metal tube layers, the overall shielding effect may appear to meet the standards, but it is completely impossible to determine which layer plays the main role or which layer has design or manufacturing defects. Once a certain layer of shielding fails or its performance is insufficient, the overall anti-interference capability of the cable will drop sharply, and the root cause of the problem is difficult to locate, leading to product rework, frequent quality disputes, and even serious safety hazards in critical application scenarios.

[0004] A deeper problem lies in the fact that the layers within a multi-layered shielding structure are not simply superimposed, but rather involve complex electromagnetic interactions. The braided wires form a cage outside the aluminum foil layer, which in turn adheres tightly to the inner conductor. Inductive coupling and reflection superposition effects occur between the different layers. When a test signal is applied from the outside, it undergoes multiple reflections, transmissions, and absorptions as it passes through the different shielding layers. These processes are highly coupled and mutually influential. If the independent attenuation contribution of each layer to the electromagnetic wave cannot be accurately separated, it is impossible to determine whether each layer truly performs its intended shielding function. For example, a cable with double-layered shielding using aluminum foil and braiding may show excellent shielding effectiveness in overall testing, but in reality, the aluminum foil layer may contribute the majority of the shielding, while the braided layer, due to insufficient density or poor overlap, may be almost ineffective. This hidden defect is easily exposed after the entire system is assembled, leading to system failure in complex electromagnetic environments.

[0005] Therefore, how to accurately separate and quantitatively evaluate the independent shielding effectiveness of each layer (braided layer, aluminum foil layer, metal tube layer, etc.) in a multi-layer shielding structure without damaging the cable structure has become a key problem that urgently needs to be solved in the field of wire shielding performance testing. Summary of the Invention

[0006] In order to overcome the above-mentioned defects of the prior art and to achieve the above objectives, this application provides the following technical solution:

[0007] A method for testing the shielding performance of electrical wires, comprising:

[0008] S101. Obtain multi-frequency external excitation signal response data of the cable under test without disassembly, perform frequency domain measurement according to the preset measurement layout and scanning step, and obtain the transmission characteristic curve characterizing the overall effect of the multi-layer shielding structure.

[0009] S102. Based on the transmission characteristic curve and the structural parameter set of the cable under test, a hierarchical equivalent network model is established. The structural parameter set includes the relative positional relationship and material property range of each shielding layer, and the range of parameters to be inverted for each shielding layer is generated accordingly.

[0010] S103. Based on the hierarchical equivalent network model, perform outer-layer priority parameter inversion on the transmission characteristic curve, extract the characteristic quantities of the outer dominant frequency band and solve them according to the preset fitting threshold constraint, determine the interface reflection coefficient and absorption attenuation of the outermost shielding layer, and subtract them from the transmission characteristic curve to obtain the updated transmission characteristic curve.

[0011] S104. Input the updated transmission characteristic curve into the hierarchical equivalent network model, continue to perform threshold constraint solution according to the range of parameters to be inverted in the inner shielding layer, obtain the interface reflection coefficient and absorption attenuation of the corresponding layer, and compare the difference sequence between the updated transmission characteristic curve and the response of the hierarchical equivalent network model with the coupling threshold to obtain the interlayer coupling correction factor.

[0012] S105. Summarize the interface reflection coefficient, absorption attenuation and interlayer coupling correction factor of each layer to generate shielding effectiveness component records for each layer, and compare them with the preset index range threshold, reflection insufficiency threshold, absorption insufficiency threshold and coupling anomaly threshold of each layer respectively; if any of the index range threshold, reflection insufficiency threshold, absorption insufficiency threshold and coupling anomaly threshold is exceeded, output the location of the failed layer and the failure type corresponding to the trigger threshold.

[0013] A wire shielding performance testing system, implementing a method for testing wire shielding performance, the system comprising:

[0014] The transmission characteristic curve acquisition module is used to acquire multi-frequency external excitation signal response data of the cable under test without disassembly, and perform frequency domain measurement according to the preset measurement layout and scanning steps to obtain the transmission characteristic curve characterizing the overall effect of the multi-layer shielding structure.

[0015] A parameter generation module is established to build a hierarchical equivalent network model based on the transmission characteristic curve and the structural parameter set of the cable under test. The structural parameter set includes the relative positional relationship and material property range of each shielding layer, and the range of parameters to be inverted for each shielding layer is generated accordingly.

[0016] The subtraction module performs outer-layer priority parameter inversion on the transmission characteristic curve based on the hierarchical equivalent network model, extracts the feature quantities of the outer dominant frequency band and solves them according to the preset fitting threshold constraint, determines the interface reflection coefficient and absorption attenuation of the outermost shielding layer, and subtracts them from the transmission characteristic curve to obtain the updated transmission characteristic curve.

[0017] The coupling correction generation module inputs the updated transmission characteristic curve into the hierarchical equivalent network model, continues to perform threshold constraint solution according to the range of parameters to be inverted in the inner shielding layer, obtains the interface reflection coefficient and absorption attenuation of the corresponding layer, and compares the difference sequence between the updated transmission characteristic curve and the response of the hierarchical equivalent network model with the coupling threshold to obtain the interlayer coupling correction factor.

[0018] The output module summarizes the interface reflection coefficient, absorption attenuation, and interlayer coupling correction factor of each layer, generates a record of the shielding effectiveness component of each layer, and compares it with the preset index range threshold, insufficient reflection threshold, insufficient absorption threshold, and abnormal coupling threshold of each layer. If any of the index range threshold, insufficient reflection threshold, insufficient absorption threshold, and abnormal coupling threshold is exceeded, the location of the failed layer and the failure type corresponding to the trigger threshold are output.

[0019] Compared with related technologies, this application has the following advantages:

[0020] This application starts with multi-frequency domain measurement without disassembly. It acquires multi-frequency external excitation signal response data through preset measurement setup and scanning steps, and calculates the amplitude ratio and phase difference of each frequency point using a steady-state time window, thereby generating transmission characteristic curves. In this way, the overall attenuation and overall phase change of the multi-layer shielding structure to the external excitation signal at different frequencies are expressed in a unified curve form, avoiding structural disturbances and differences caused by repeated clamping caused by disassembly. This allows for direct comparison of data at each frequency point, providing stable observation input for subsequent layer separation, and solving the pain point that only the total shielding effectiveness can be obtained and the problem is difficult to reproduce.

[0021] A hierarchical equivalent network model is established based on the transmission characteristic curve and structural parameter set. The parameter range to be inverted for each shielding layer is generated by the relative position relationship and material property range. On this basis, the threshold constraint solution with the outer layer priority is performed: first, the interface reflection coefficient and absorption attenuation of the outermost shielding layer are determined in the dominant frequency band of the outer layer. Then, the influence of the outermost layer is subtracted from the transmission characteristic curve to obtain the updated transmission characteristic curve. Subsequently, the interface reflection coefficient and absorption attenuation of the inner shielding layer are solved under the updated transmission characteristic curve. This method of solving and subtracting layer by layer decomposes the overall superposition effect into separable hierarchical contributions, which can clearly distinguish the reflection and absorption effects of different shielding layers such as braided layer, aluminum foil layer, and metal tube layer, and solves the problems of inseparable contributions of each layer in multi-layer composite structure and difficulty in locating defective layers.

[0022] To address the interlayer induced coupling and reflection superposition in multilayer structures, this application, after obtaining the parameters of the inner shielding layer, calculates the difference sequence between the updated transmission characteristic curve and the response of the layered equivalent network model, and compares it with the coupling threshold to generate an interlayer coupling correction factor. Subsequently, it summarizes the interface reflection coefficient, absorption attenuation, and interlayer coupling correction factor of each layer to form a record of the shielding effectiveness component of each layer, and compares it with the preset index range threshold, reflection deficiency threshold, absorption deficiency threshold, and coupling anomaly threshold of each layer. When any threshold is triggered, the location and type of the failure layer are output. In this way, the abnormal attenuation caused by interlayer coupling is transformed from an inexplicable mixed phenomenon into a quantifiable correction component, and the output of which layer and failure mechanism the result falls into reduces the risk of rework and disputes caused by the inability to attribute the cause in the overall test. Attached Figure Description

[0023] Figure 1 A flowchart illustrating the steps of a method for testing the shielding performance of electrical wires provided in this application;

[0024] Figure 2 This is a schematic diagram of a module in a wire shielding performance testing system provided in this application. Detailed Implementation

[0025] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0026] Example 1

[0027] Please see Figure 1 As shown, this embodiment provides a method for testing the shielding performance of electrical wires, including:

[0028] S101. Obtain multi-frequency external excitation signal response data of the cable under test without disassembly, perform frequency domain measurement according to the preset measurement layout and scanning step, and obtain the transmission characteristic curve characterizing the overall effect of the multi-layer shielding structure.

[0029] The section of the cable to be tested is determined and a preset measurement setup is set up. The preset measurement setup includes at least the external excitation application position, the response acquisition position, and the clamping position. The clamping position remains unchanged throughout the measurement process, so that the geometric relationship between the external excitation application position and the response acquisition position and the section to be tested is fixed. This is because it provides a unified spatial boundary for the subsequent acquisition of multi-frequency external excitation signal response data and avoids the incomparability of data at different frequencies due to changes in the setup.

[0030] The method for applying an external excitation signal under a preset measurement setup and acquiring multi-frequency external excitation signal response data includes:

[0031] External excitation signals are applied one by one according to the preset frequency point set. At each frequency point, the excitation reference quantity and the response quantity at the response acquisition position are collected simultaneously to obtain response data pairs corresponding one-to-one with the preset frequency point set. Without disassembling the cable under test, the overall attenuation and overall phase change of the multi-layer shielding structure at different frequency points are recorded as the original data basis that can be used for frequency domain processing.

[0032] Then, synchronous sampling is performed on the response data of the multi-frequency external excitation signal, and a steady-state time window is selected. The excitation reference quantity is used as the phase reference. The response data of each frequency point is synchronously sampled, and a fixed-length time window is truncated within the continuous sampling interval after the external excitation enters the steady state. The time window covers an integer number of excitation cycles, providing a consistent data segment for subsequent calculation of amplitude and phase quantities from the time window data, and reducing the impact of transient segment and truncation effect on amplitude and phase calculation.

[0033] The frequency domain characteristic quantities of each frequency point are calculated based on the steady-state time window. Specifically, for each frequency point, the corresponding amplitude and phase are calculated from the excitation reference quantity and the response quantity, and the amplitude ratio and phase difference of the response quantity relative to the excitation reference quantity are obtained accordingly, forming a frequency point transmission quantity sequence indexed by frequency point; the response data of the multi-frequency external excitation signal are converted from time domain sampling quantities into frequency domain characteristic quantities that can be directly used to generate transmission characteristic curves.

[0034] Methods for generating transmission characteristic curves include:

[0035] The preset frequency point set is sorted in ascending order according to the scanning step. The amplitude ratio and phase difference corresponding to each frequency point are aligned and spliced ​​according to the same frequency point index to obtain the transmission characteristic curve with frequency as independent variable and amplitude ratio and phase difference as dependent variables. This forms a unified curve expression that characterizes the overall effect of the multi-layer shielding structure, so that the subsequent analysis of the curve shape and parameter inversion can directly use the transmission characteristic curve as input.

[0036] Then, the transmission characteristic curve and its frequency index relationship are output. The correspondence between the transmission characteristic curve and the preset frequency point set, scanning step and frequency point transmission quantity sequence are recorded together to ensure that each sampling point of the curve can be traced back to the amplitude ratio and phase difference of the corresponding frequency point. The purpose is to make the transmission characteristic curve not only represent the overall effect of the multi-layer shielding structure, but also retain the correspondence between the curve generated by the response data of the multi-frequency external excitation signal, so that the curve and its frequency index can be directly called as calculation input in subsequent steps.

[0037] S102. Based on the transmission characteristic curve and the structural parameter set of the cable under test, a hierarchical equivalent network model is established. The structural parameter set includes the relative positional relationship and material property range of each shielding layer. Based on this, the range of parameters to be inverted for each shielding layer is generated as the boundary conditions for subsequent threshold constraint solution.

[0038] Methods for establishing hierarchical equivalent network models include:

[0039] Obtain the characterization data of the transmission characteristic curve and the structural parameter set of the cable under test. The characterization data consists of amplitude ratios and phase differences arranged by frequency index. The structural parameter set includes at least the relative positional relationships and material property ranges of each shielding layer. The relative positional relationships define the layer sequence and interlayer contact state of each shielding layer from the outside in, while the material property ranges define the conductivity, permeability, dielectric constant, and thickness ranges of each shielding layer. The purpose is to ensure that the subsequently established layered equivalent network model corresponds one-to-one with the transmission characteristic curve in terms of frequency index and has physical boundary constraints from the structural parameter set. A specific example is as follows:

[0040] Taking double-layer shielding—an outer braided layer and an inner aluminum foil layer—as an example; the characteristic data of the transmission characteristic curve are arranged by frequency point index, and the preset frequency point set is set as follows:

[0041] k1=1MHz, k2=10MHz, k3=100MHz, k4=300MHz, and the frequency indexes are 1 to 4 respectively;

[0042] The corresponding measured amplitude ratio and phase difference are:

[0043] Frequency index 1: Amplitude ratio 0.82, phase difference -6°;

[0044] Frequency index 2: Amplitude ratio 0.55, phase difference -18°;

[0045] Frequency index 3: Amplitude ratio 0.12, phase difference -52°;

[0046] Frequency index 4: Amplitude ratio 0.08, phase difference -61°;

[0047] This yields the amplitude ratios [0.82, 0.55, 0.12, 0.08] and phase differences [-6°, -18°, -52°, -61°] arranged by frequency index.

[0048] The cable under test has a structural parameter set consisting of two layers of shielding, with the following relative positional relationships:

[0049] Shielding layer A is the outermost layer (braided layer), and it is in a bonded state with shielding layer B;

[0050] The shielding layer B is the inner layer (aluminum foil layer), and its inner side consists of an insulating layer and a conductor layer.

[0051] Material property range:

[0052] Shielding layer A (braided layer): conductivity range 3.5×10 7 ~5.9×10 7 S / m; permeability range 1.0 to 1.2 (relative value); thickness range 0.15 to 0.35 mm; dielectric constant range is not used as a bulk parameter of this layer, but is left to the adjacent dielectric layer for constraint.

[0053] Shielding layer B (aluminum foil layer): conductivity range 3.0 × 10⁻⁶ 7 ~3.8×10 7 S / m; permeability range 1.0~1.05 (relative value); thickness range 0.015~0.05mm.

[0054] Adjacent dielectric layer (insulating layer): dielectric constant range 2.2 to 3.0 (relative value).

[0055] The hierarchical equivalent network model calculates the predicted amplitude ratio and predicted phase difference at frequency indexes 1 to 4, and aligns them with the above four sets of amplitude ratios and phase differences under the same index. For example, the hierarchical equivalent network model outputs a set of predicted values ​​at frequency index 3, which directly corresponds to 0.12 and -52° representing the data.

[0056] During inversion or threshold constraint solving, the parameters to be inverted for shielding layer A and shielding layer B can only fall within their respective conductivity range, magnetic permeability range, and thickness range, and the interlayer contact state is fixed as a bonding state. This restricts the solution to the feasible physical range given by the structural parameter set, avoiding results that exceed the thickness range, such as the aluminum foil layer thickness being inverted to 0.2mm.

[0057] A layered topology for the multi-layer shielding structure is established based on relative positional relationships. The layer sequence number of each shielding layer is determined according to the relative positional relationships, and the interlayer contact state is defined for adjacent layers, including a mating state or a spaced state. At the same time, the relative positions corresponding to the conductor layer and the insulating layer are determined, so that each shielding layer has a unique inner and outer interface under the layer sequence number. The physical stacking relationship of the multi-layer shielding structure is transformed into the interlayer connection relationship required for subsequent network assembly, ensuring that the subsequent solution of the outer layer priority can be deducted layer by layer according to the layer sequence number without introducing name gaps.

[0058] Based on the material property range and thickness range, the unit length electrical parameter range for each shielding layer is constructed. This unit length electrical parameter range includes the unit length resistance range, unit length inductance range, unit length capacitance range, and unit length conductance range. For each shielding layer, combining its geometric dimensions and thickness range, the unit length resistance range is calculated based on the conductivity range, and the unit length inductance range is calculated based on the permeability range. For the dielectric layer adjacent to the shielding layer, the unit length capacitance and unit length conductance ranges are calculated based on the dielectric constant range and their relative positional relationship. All of the above unit length electrical parameter ranges generate corresponding value intervals according to frequency dependence under a frequency index. The purpose is to use calculable unit length electrical parameter ranges to encompass the material property ranges, avoiding a reliance solely on material descriptions without forming solvable network parameters. A specific example is as follows:

[0059] Assume the cable under test has a coaxial equivalent structure, the shielding layer is an aluminum foil layer, the geometric parameters of the aluminum foil layer are taken as an equivalent inner radius of 4.00 mm, the thickness of the aluminum foil layer ranges from 0.02 mm to 0.05 mm, the conductivity of the aluminum foil layer ranges from 30,000,000 to 38,000,000 Siemens per meter, the relative permeability of the aluminum foil layer ranges from 1.00 to 1.05, the dielectric layer adjacent to the aluminum foil layer is an insulating layer, the conductor outer radius is taken as 3.00 mm, the relative permittivity of the insulating layer ranges from 2.2 to 3.0, the loss tangent of the insulating layer ranges from 0.005 to 0.02, and the frequency index is taken as 100 MHz.

[0060] Resistance per unit length range: calculated from conductivity range + geometric dimension parameters + thickness range;

[0061] If we consider the aluminum foil layer as a thin ring conductor, its conductive cross-sectional area per unit length is approximately equal to 2 times pi multiplied by the inner radius multiplied by the thickness; when the thickness is 0.02 mm, the conductive cross-sectional area is approximately 0.0000005027 square meters; when the thickness is 0.05 mm, the conductive cross-sectional area is approximately 0.0000012566 square meters; the resistance per unit length is approximately equal to 1 divided by (conductivity multiplied by conductive cross-sectional area).

[0062] Therefore, the minimum resistance per unit length is taken as the maximum conductivity and the largest cross-sectional area, which is approximately 0.0209 ohms per meter; the maximum resistance per unit length is taken as the minimum conductivity and the smallest cross-sectional area, which is approximately 0.0663 ohms per meter.

[0063] Inductance per unit length range: calculated from permeability range + geometric dimension parameters + thickness range;

[0064] Using a coaxial equivalent aperture, the inductance per unit length is related to the logarithmic ratio of the permeability and the outer radius to the inner radius; the outer radius is equal to the inner radius plus the thickness: the outer radius is between 4.02 mm and 4.05 mm.

[0065] Therefore, the inductance per unit length ranges from approximately 0.0000000010 Henry per meter to 0.0000000026 Henry per meter (i.e., approximately 1.0 NaHen per meter to 2.6 NaHen per meter); under the frequency index, the permeability can be taken from the corresponding interval according to the material dispersion relationship, thus obtaining the value range of that frequency point.

[0066] Capacitance per unit length: calculated from the dielectric constant range and relative positional relationship;

[0067] The relative positional relationship is given as an outer radius of 3.00 mm for the conductor, an inner radius of 4.00 mm for the aluminum foil layer, and an insulating layer located between the two; using coaxial equivalent aperture, the capacitance per unit length is related to the logarithm of the dielectric constant and the radius ratio.

[0068] Therefore, the capacitance per unit length ranges from approximately 0.000000000425 farads per meter to 0.000000000580 farads per meter (i.e., approximately 0.425 nanofarads per meter to 0.580 nanofarads per meter); this range directly corresponds to the range of material properties and their relative positional relationships.

[0069] Conductivity per unit length range: calculated from dielectric constant range + loss range + frequency index;

[0070] Conductivity per unit length can be obtained by multiplying the angular frequency by the capacitance per unit length by the loss tangent. The angular frequency is determined by the frequency index. When the frequency index is 100 MHz, combined with the above range of capacitance per unit length and the range of loss tangent of 0.005 to 0.02, the conductivity per unit length range can be obtained as approximately 0.00134 Siemens per meter to 0.00729 Siemens per meter. As the frequency increases, the conductivity per unit length increases according to the frequency dependence, thus forming a corresponding value range under the frequency index.

[0071] The range of parameters to be inverted for each shielding layer is generated from the range of electrical parameters per unit length. This range includes the range of interface reflection coefficients and the range of absorption attenuation. Methods for generating the range of parameters to be inverted for each shielding layer include:

[0072] For each shielding layer, the equivalent impedance range of the layer is calculated using the resistance range and inductance range per unit length under the frequency index, and the equivalent propagation parameter range of the layer is calculated using the capacitance range and conductance range per unit length. Based on this, the interface reflection coefficient range and absorption attenuation range of the layer are obtained. The interface reflection coefficient range is used to characterize the boundary of the layer's interface's ability to reflect external excitation signals, and the absorption attenuation range is used to characterize the energy attenuation boundary caused by material loss in the layer. The structural parameter set is converted into a range of parameters to be inverted that can be directly used for solving, so that the subsequent threshold constraint solution is limited in the form of upper and lower bounds of the parameters, avoiding values ​​that exceed the range of material properties during the inversion process.

[0073] Methods for calculating the equivalent impedance range include:

[0074] For each frequency point, the unit length resistance range corresponding to that frequency point is taken as the resistance term, and the unit length inductance range is converted into the inductive reactance term. The inductive reactance term is equal to the angular frequency multiplied by the unit length inductance, where the angular frequency is equal to 2 times pi multiplied by the frequency. When calculating the range, the upper and lower bounds of the unit length resistance range and the upper and lower bounds of the unit length inductance range are combined to obtain the equivalent impedance range at that frequency point. The purpose is to transform the range of conductor material properties into impedance boundaries that can be directly entered into the network for solution.

[0075] Methods for calculating the range of equivalent propagation parameters include:

[0076] For each frequency point, the conductance range per unit length is taken as the conductance term, and the capacitance range per unit length is converted into the susceptance term corresponding to the capacitive reactance. The susceptance term is equal to the angular frequency multiplied by the capacitance per unit length. The conductance per unit length represents the dielectric loss, and the angular frequency multiplied by the capacitance per unit length represents the capacitive admittance. When calculating the range, the equivalent parallel admittance range at that frequency point is obtained by combining the upper and lower bounds of the conductance range and the capacitance range per unit length. The purpose is to transform the range of dielectric material properties and their relative positional relationship into admittance boundaries that can be directly entered into the network for solution.

[0077] The equivalent propagation parameter range is then calculated from the equivalent impedance range and the equivalent parallel admittance range, and the absorption attenuation range is obtained. The equivalent propagation parameter is obtained by multiplying the equivalent impedance by the equivalent parallel admittance and taking the square root. Its real part is the attenuation per unit length (in meters). The absorption attenuation at that frequency is obtained by multiplying the attenuation per unit length by the length of the section to be measured. In the range calculation, the value interval is still obtained by combining the upper and lower bounds. The purpose is to characterize the energy attenuation boundary caused by the loss of this layer of material with a calculable attenuation boundary.

[0078] The interface reflection coefficient range is then obtained from the equivalent impedance range. The interface reflection coefficient is calculated by the ratio of the equivalent impedance of the layer at the interface to the equivalent impedance on the other side of the interface, specifically (equivalent impedance of the layer minus equivalent impedance on the other side) divided by (equivalent impedance of the layer plus equivalent impedance on the other side). The equivalent impedance on the other side of the interface is determined by the relative position relationship to be the outer environment or the adjacent layer, and is calculated from the range of electrical parameters per unit length on the corresponding side. The purpose is to characterize the reflection capability boundary with the interface reflection coefficient range with upper and lower bounds, and to ensure that the subsequent threshold constraint solution will not have values ​​that exceed the range of material properties.

[0079] Specific examples are as follows:

[0080] Resistance per unit length: 0.0209 ohms per meter to 0.0663 ohms per meter; Inductance per unit length: 0.0000000010 Henry per meter to 0.0000000026 Henry per meter; Capacitance per unit length: 0.000000000425 Farads per meter to 0.000000000580 Farads per meter; Conductivity per unit length: 0.00134 Siemens per meter to 0.00729 Siemens per meter; At a frequency of 100 MHz, the angular frequency is approximately 628,318,530 Hz.

[0081] The range of angular frequency multiplied by inductance per unit length is approximately:

[0082] 628,318,530 × 0.0000000010 ≈ 0.628 ohms per meter;

[0083] 628,318,530 × 0.0000000026 ≈ 1.633 ohms per meter.

[0084] Therefore, the equivalent impedance at this frequency is: the real part is between 0.0209 and 0.0663 ohms per meter, and the imaginary part corresponding to the susceptance term is between 0.628 and 1.633 ohms per meter.

[0085] The range of angular frequency multiplied by the capacitance per unit length is approximately:

[0086] 628,318,530 × 0.000000000425 ≈ 0.267 Siemens per meter;

[0087] 628,318,530 × 0.000000000580 ≈ 0.364 Siemens per meter.

[0088] Therefore, the equivalent parallel admittance at this frequency is: the real part is between 0.00134 and 0.00729 Siemens per meter, and the imaginary part corresponding to the capacitance admittance is between 0.267 and 0.364 Siemens per meter.

[0089] Multiplying the equivalent impedance by the equivalent parallel admittance and taking the square root yields the equivalent propagation parameter, the real part of which is the attenuation per unit length. This parameter is obtained by combining the above intervals.

[0090] The attenuation per unit length is approximately between 0.00588 per meter and 0.0300 per meter.

[0091] If the length of the section to be tested is 1 meter, then the absorption attenuation range is 0.00588 to 0.0300 (dimensionless attenuation index); if it needs to be expressed in decibels per meter, it can be converted to approximately 0.051 to 0.261 decibels per meter according to a fixed conversion relationship; this absorption attenuation range is the absorption attenuation range in the parameter range to be inverted for this layer.

[0092] The equivalent impedance on the other side of the interface is taken as the equivalent impedance of free space, which is 377 ohms. The interface reflection coefficient is calculated from the equivalent characteristic impedance of the layer. In this example, the amplitude of the interface reflection coefficient is approximately between 0.987 and 0.993. This range of interface reflection coefficients is taken as the range of interface reflection coefficients in the range of parameters to be inverted for this layer.

[0093] The hierarchical equivalent network model is assembled based on the hierarchical topology and the range of parameters to be inverted. Specifically, the equivalent impedance range and equivalent propagation parameter range corresponding to each shielding layer are sequentially connected in series according to the layer sequence number to form a hierarchical network from the outer interface to the inner interface. For the contact state and the spacing state of adjacent layers, coupling parameter ranges corresponding to the interlayer contact state are introduced respectively. The coupling parameter ranges are derived from the distance range between adjacent layers and the range of dielectric material properties. Under the frequency index, the hierarchical equivalent network model outputs the predicted amplitude ratio and predicted phase difference at each frequency point, and the definitions of the predicted amplitude ratio and predicted phase difference are consistent with the definitions of amplitude ratio and phase difference in the transmission characteristic curve. The purpose is to establish a unified mapping where the input is the frequency point and the output is the amplitude ratio and phase difference, so that subsequent steps can use the transmission characteristic curve to solve the threshold constraint of the hierarchical equivalent network model with the same caliber.

[0094] Methods for deriving the range of coupling parameters include:

[0095] Obtain the interlayer distance range corresponding to the interlayer contact state of two adjacent layers, and obtain the dielectric material property range corresponding to the two adjacent layers; wherein, the interlayer distance range is determined by the interlayer contact state. When the interlayer contact state is in a bonding state, the lower boundary of the distance is zero and the upper boundary is a preset bonding distance threshold. When the interlayer contact state is in a spaced state, the lower boundary of the distance is the minimum spacing and the upper boundary is the maximum spacing. The dielectric material property range includes at least the dielectric constant range and the dielectric loss range.

[0096] Obtain the interface geometric dimension parameter range of the two adjacent layers at the corresponding positions of the interlayer distance range, and determine the effective area range or equivalent perimeter range of the interface based on the interface geometric dimension parameter range; wherein, the interface geometric dimension parameter range is determined by the structural parameter set and the relative positional relationship, and is used to characterize the upper and lower bounds of the effective coupling area of ​​the two adjacent layers in the section to be tested.

[0097] The range of equivalent interlayer coupling capacitance is derived based on the range of interlayer distance, the range of dielectric constant, and the range of effective interface area. The upper limit of the range of equivalent interlayer coupling capacitance is obtained by combining the upper limit of dielectric constant, the lower limit of interlayer distance, and the upper limit of effective interface area, and the lower limit of the range of equivalent interlayer coupling capacitance is obtained by combining the lower limit of dielectric constant, the upper limit of interlayer distance, and the lower limit of effective interface area.

[0098] Under the frequency index, the interlayer equivalent coupling conductance range is derived based on the range of interlayer equivalent coupling capacitance and the range of dielectric loss. The frequency index determines the angular frequency, and the upper limit of the interlayer equivalent coupling conductance range is obtained by combining the angular frequency, the upper limit of the interlayer equivalent coupling capacitance, and the upper limit of the dielectric loss. The lower limit of the interlayer equivalent coupling conductance range is obtained by combining the angular frequency, the lower limit of the interlayer equivalent coupling capacitance, and the lower limit of the dielectric loss. The range of interlayer equivalent coupling capacitance and the range of interlayer equivalent coupling conductance are output as coupling parameter ranges and associated with the layer sequence number. This is used to introduce a coupling parameter range corresponding to the interlayer contact state when the equivalent impedance range and the equivalent propagation parameter range are connected in series according to the layer sequence number.

[0099] S103. Based on the hierarchical equivalent network model, perform outer-layer priority parameter inversion on the transmission characteristic curve, extract the characteristic quantities of the outer dominant frequency band and solve them according to the preset fitting threshold constraint, determine the interface reflection coefficient and absorption attenuation of the outermost shielding layer, and subtract them from the transmission characteristic curve to obtain the updated transmission characteristic curve.

[0100] Methods for determining the interface reflection coefficient and absorption attenuation of the outermost shielding layer include:

[0101] The transmission characteristic curve, the hierarchical equivalent network model, and the range of parameters to be inverted for the outermost shielding layer are obtained. The transmission characteristic curve includes the amplitude ratio sequence and phase difference sequence arranged by frequency index; the range of parameters to be inverted includes the range of the interface reflection coefficient and the range of absorption attenuation of the outermost shielding layer. The reason is that, under the same frequency index, the observation input is the transmission characteristic curve, the calculation is mapped to the hierarchical equivalent network model, and the value boundary is the range of parameters to be inverted, so that the subsequent solution is limited by the boundary corresponding to the range of material properties.

[0102] Based on a hierarchical equivalent network model, the outer dominant frequency band is determined under a frequency point index, and its feature quantities are extracted. The method for determining the outer dominant frequency band includes: selecting two sets of parameter endpoint combinations as comparison groups within the range of parameters to be inverted; the first group takes the interface reflection coefficient as the upper bound and the absorption attenuation as the lower bound, and the second group takes the interface reflection coefficient as the lower bound and the absorption attenuation as the upper bound; inputting the two sets of parameter endpoints into the hierarchical equivalent network model respectively, to obtain the first predicted amplitude ratio sequence, the first predicted phase difference sequence, and the second predicted amplitude ratio sequence and the second predicted phase difference sequence under the same frequency point index; calculating the amplitude change for each frequency point as the two predicted amplitude ratio sequences. The absolute value of the difference between the amplitude ratios and the absolute value of the difference between the two predicted phase differences are used. The set of frequency points where at least one of the amplitude change and phase change is not less than the corresponding threshold is determined as the outer dominant frequency band. Within the outer dominant frequency band, the amplitude ratio subsequence and phase difference subsequence of the corresponding frequency points of the transmission characteristic curve are extracted as feature quantities. The reason is that by using explicit endpoint comparison and comparison of the absolute value of the difference with the threshold, a set of frequency points more sensitive to the outermost parameters is screened out, so that subsequent fitting is concentrated in the outer dominant frequency band, reducing the masking effect of the inner layer on the solution of the outermost parameters. A specific example is as follows:

[0103] There are 5 frequency indexes, corresponding to frequencies of 1 MHz, 10 MHz, 100 MHz, 300 MHz and 600 MHz respectively, and the frequency indexes are recorded as 1 to 5; the range of parameters to be inverted is: interface reflection coefficient range of 0.60 to 0.90, absorption attenuation range of 0.01 to 0.05 (expressed as attenuation index per meter).

[0104] Step 1: Select two sets of parameter endpoint combinations as comparison groups within the range of parameters to be inverted;

[0105] The first set of parameters has the following endpoints: the interface reflection coefficient is set to the upper limit of 0.90, and the absorption attenuation is set to the lower limit of 0.01.

[0106] The second set of parameters has the following endpoints: the lower bound of the interface reflection coefficient is 0.60, and the upper bound of the absorption attenuation is 0.05.

[0107] Step 2: Input the endpoints of the two sets of parameters into the hierarchical equivalent network model to obtain the predicted sequence under the same frequency index;

[0108] Assume the output of the hierarchical equivalent network model is as follows:

[0109] First predicted amplitude ratio sequence: [0.92, 0.70, 0.30, 0.20, 0.18];

[0110] First predicted phase difference sequence: [-5°, -15°, -40°, -55°, -60°];

[0111] Second predicted amplitude ratio sequence: [0.95, 0.78, 0.55, 0.45, 0.40];

[0112] Second predicted phase difference sequence: [-3°, -10°, -25°, -30°, -32°].

[0113] Step 3: Calculate the amplitude change and phase change for each frequency point;

[0114] The change in amplitude is the absolute value of the difference between the ratios of the two predicted amplitudes:

[0115] Frequency point 1: |0.92-0.95|=0.03;

[0116] Frequency point 2: |0.70-0.78|=0.08;

[0117] Frequency point 3: |0.30-0.55|=0.25;

[0118] Frequency point 4: |0.20-0.45|=0.25;

[0119] Frequency point 5: |0.18-0.40|=0.22;

[0120] The amplitude changes were obtained as follows: [0.03, 0.08, 0.25, 0.25, 0.22];

[0121] The phase change is the absolute value of the difference between the two predicted phase differences:

[0122] Frequency 1: |-5°-(-3°)|=2°;

[0123] Frequency point 2: |-15°-(-10°)|=5°;

[0124] Frequency point 3: |-40°-(-25°)|=15°;

[0125] Frequency point 4: |-55°-(-30°)|=25°;

[0126] Frequency point 5: |-60°-(-32°)|=28°;

[0127] The phase change is obtained as: [2°, 5°, 15°, 25°, 28°].

[0128] Step 4: Compare the change with the sensitivity threshold to determine the dominant frequency band in the outer layer;

[0129] Set the amplitude sensitivity threshold to 0.2 and the phase sensitivity threshold to 20°. For each frequency point comparison, at least one value must be no less than the corresponding threshold:

[0130] Frequency 1: Amplitude 0.03 < 0.20 and phase 2° < 20°, does not enter the outer dominant frequency band;

[0131] Frequency point 2: Amplitude 0.08 < 0.20 and phase 5° < 20°, does not enter the outer dominant frequency band;

[0132] Frequency point 3: Amplitude 0.25 ≥ 0.20, entering the outer dominant frequency band;

[0133] Frequency point 4: Amplitude 0.25 ≥ 0.20 and phase 25° ≥ 20°, entering the outer dominant frequency band;

[0134] Frequency point 5: Amplitude 0.22 ≥ 0.20 and phase 28° ≥ 20°, entering the outer dominant frequency band;

[0135] Therefore, the set of frequency points corresponding to the outer dominant frequency band is: {frequency point indices 3, 4, 5}.

[0136] Step 5: Extract characteristic quantities from the transmission characteristic curve within the outer dominant frequency band;

[0137] Assume the transmission characteristic curve obtained by S101 is as follows:

[0138] Amplitude ratio sequence: [0.94, 0.76, 0.48, 0.33, 0.28];

[0139] Phase difference sequence: [-4°, -12°, -32°, -44°, -50°];

[0140] Then extract from the outer dominant frequency band {3,4,5}:

[0141] Amplitude ratio subsequence: [0.48, 0.33, 0.28];

[0142] Phase difference subsequence: [-32°, -44°, -50°].

[0143] Within the outer dominant frequency band, a preset fitting threshold constraint is applied to determine the interface reflection coefficient and absorption attenuation of the outermost shielding layer. The solution method includes: generating a set of candidate parameter groups within the range of interface reflection coefficient and absorption attenuation; for each candidate parameter group, inputting the candidate parameter group into a hierarchical equivalent network model, outputting a predicted amplitude ratio subsequence and a predicted phase difference subsequence within the outer dominant frequency band; calculating the amplitude difference sequence as the difference between the predicted amplitude ratio subsequence and the amplitude ratio subsequence at corresponding frequency points, and calculating the phase difference sequence as the difference between the predicted phase difference subsequence and the phase difference subsequence at corresponding frequency points; taking the absolute value of the amplitude difference sequence and using the maximum value as the amplitude error. The absolute value of the phase difference sequence is taken, and the maximum value is used as the phase error. The amplitude error is compared with the amplitude fitting threshold, and the phase error is compared with the phase fitting threshold. Candidate parameter groups whose values ​​do not exceed the corresponding thresholds constitute an optional set. From the optional set, the candidate parameter group that minimizes the sum of the amplitude error and phase error after uniform weighting is selected. This set is determined as the interface reflection coefficient and absorption attenuation of the outermost shielding layer. The reason is that the maximum absolute error threshold constraint clearly limits the fitting deviation, and the selection is completed with a uniform scalar objective from the candidate solutions that meet the threshold constraint. This avoids only describing the aggregation quantity and minimizing the combination without a feasible method. A specific example is as follows:

[0144] The set of frequency points in the outer dominant frequency band is known to be {frequency point indices 3, 4, 5}.

[0145] The characteristic quantities of the transmission characteristic curve in this frequency band are:

[0146] The amplitude ratio subsequence is [0.48, 0.33, 0.28];

[0147] The phase difference subsequence is [-32°, -44°, -50°].

[0148] The interface reflection coefficient ranges from 0.60 to 0.90; the absorption attenuation ranges from 0.01 to 0.05; the preset fitting thresholds are: amplitude fitting threshold 0.06, phase fitting threshold 8°.

[0149] Step 1: Generate a set of candidate parameter groups within the range of interface reflection coefficient and absorption attenuation.

[0150] Generate 4 candidate parameter groups:

[0151] Candidate group A: Interface reflectance coefficient 0.70, absorption attenuation 0.03;

[0152] Candidate group B: Interface reflectance coefficient 0.75, absorption attenuation 0.02;

[0153] Candidate group C: Interface reflectance coefficient 0.80, absorption attenuation 0.03;

[0154] Candidate group D: Interface reflectance coefficient 0.85, absorption attenuation 0.04;

[0155] Step 2: Input the hierarchical equivalent network model into each candidate parameter group, and output the prediction subsequence in the outer dominant frequency band, including the prediction amplitude ratio subsequence and the prediction phase difference subsequence.

[0156] Assume the hierarchical equivalent network model outputs the following values ​​at frequency indices 3, 4, and 5:

[0157] Candidate group A: Predicted amplitude ratio subsequence [0.50, 0.36, 0.30]; Predicted phase difference subsequence [-34°, -46°, -52°];

[0158] Candidate group B: Predicted amplitude ratio subsequence [0.46, 0.32, 0.27]; Predicted phase difference subsequence [-30°, -42°, -47°];

[0159] Candidate group C: Predicted amplitude ratio subsequence [0.52, 0.37, 0.31]; Predicted phase difference subsequence [-36°, -49°, -56°];

[0160] Candidate group D: Predicted amplitude ratio subsequence [0.41, 0.28, 0.24]; Predicted phase difference subsequence [-26°, -38°, -44°];

[0161] Step 3: Calculate the amplitude difference sequence and the phase difference sequence;

[0162] Amplitude difference sequence = predicted amplitude ratio subsequence - amplitude ratio subsequence; Phase difference sequence = predicted phase difference subsequence - phase difference subsequence.

[0163] Candidate Group A:

[0164] The amplitude difference sequence [0.50-0.48, 0.36-0.33, 0.30-0.28] = [0.02, 0.03, 0.02];

[0165] Phase difference sequence [-34-(-32),-46-(-44),-52-(-50)]=[-2°,-2°,-2°];

[0166] Candidate Group B:

[0167] The amplitude difference sequence [0.46-0.48, 0.32-0.33, 0.27-0.28] = [-0.02, -0.01, -0.01];

[0168] Phase difference sequence [-30-(-32),-42-(-44),-47-(-50)]=[2°,2°,3°];

[0169] Candidate group C:

[0170] The amplitude difference sequence [0.52-0.48, 0.37-0.33, 0.31-0.28] = [0.04, 0.04, 0.03];

[0171] Phase difference sequence [-36-(-32),-49-(-44),-56-(-50)]=[-4°,-5°,-6°];

[0172] Candidate group D:

[0173] The amplitude difference sequence [0.41-0.48, 0.28-0.33, 0.24-0.28] = [-0.07, -0.05, -0.04];

[0174] Phase difference sequence [-26-(-32),-38-(-44),-44-(-50)]=[6°,6°,6°];

[0175] Step 4: Take the absolute value of the difference sequence and find the maximum value to obtain the error, including the amplitude error and the phase error; the amplitude error is the maximum value of the absolute value of the amplitude difference sequence; the phase error is the maximum value of the absolute value of the phase difference sequence.

[0176] Candidate group A: Amplitude error max(|0.02|,|0.03|,|0.02|)=0.03; Phase error max(2°,2°,2°)=2°;

[0177] Candidate group B: Amplitude error max(0.02,0.01,0.01)=0.02; Phase error max(2°,2°,3°)=3°;

[0178] Candidate group C: Amplitude error max(0.04,0.04,0.03)=0.04; Phase error max(4°,5°,6°)=6°;

[0179] Candidate group D: Amplitude error max(0.07,0.05,0.04)=0.07; Phase error max(6°,6°,6°)=6°;

[0180] Step 5: Compare with the preset fitting threshold to obtain the selectable set;

[0181] The amplitude fitting threshold is 0.06, and the phase fitting threshold is 8°. Both are required to remain within the threshold values.

[0182] Candidate group A: 0.03≤0.06, and 2°≤8°, enters the optional set;

[0183] Candidate group B: 0.02≤0.06, and 3°≤8°, enters the optional set;

[0184] Candidate group C: 0.04≤0.06, and 6°≤8°, enters the optional set;

[0185] Candidate group D: 0.07 > 0.06, will not be included in the optional set;

[0186] Therefore, the possible set is {candidate group A, candidate group B, candidate group C}.

[0187] Step 6: Select the candidate parameter set that minimizes the sum of amplitude error and phase error from the available set. To facilitate addition, the phase error is directly included in the summation by degree.

[0188] Candidate group A: Sum of errors = 0.03 + 2 = 2.03;

[0189] Candidate group B: Sum of errors = 0.02 + 3 = 3.02;

[0190] Candidate group C: Sum of errors = 0.04 + 6 = 6.04;

[0191] Candidate group A has the smallest sum of errors, therefore:

[0192] The outermost shielding layer has an interface reflection coefficient of 0.70 and an absorption attenuation of 0.03.

[0193] Methods for subtracting from the transmission characteristic curve to obtain an updated transmission characteristic curve include:

[0194] The method for generating the influence sequence of the outermost shielding layer at a frequency index is as follows: Substituting the interface reflection coefficient and absorption attenuation into the layer terms corresponding to the outermost shielding layer in the hierarchical equivalent network model, changing only the parameters of the outermost shielding layer while keeping the parameters of the remaining layers unchanged at preset initial values, and outputting the predicted amplitude ratio influence sequence and the predicted phase difference influence sequence corresponding to the outermost shielding layer at the frequency index. The predicted amplitude ratio influence sequence and the predicted phase difference influence sequence are consistent with the definitions of amplitude ratio and phase difference in the transmission characteristic curve and are arranged according to the same frequency index. The determined interface reflection coefficient and absorption attenuation are converted into subtraction objects that can be aligned point-by-point with the transmission characteristic curve, providing direct input for subsequent subtraction to generate the remaining curve. A specific example is as follows:

[0195] The frequency indexes are 1 to 5, corresponding to frequencies of 1 MHz, 10 MHz, 100 MHz, 300 MHz, and 600 MHz; the resulting transmission characteristic curves are as follows:

[0196] Amplitude ratio sequence [0.94, 0.76, 0.48, 0.33, 0.28];

[0197] Phase difference sequence [-4°, -12°, -32°, -44°, -50°].

[0198] The parameters of the outermost shielding layer are: interface reflection coefficient 0.70, absorption attenuation 0.03.

[0199] Step 1: Set the initial values ​​of the parameters for the remaining layers to remain unchanged;

[0200] The initial preset values ​​for the inner shielding layer parameters are: interface reflection coefficient 0.80, absorption attenuation 0.02; and the initial preset value for the interlayer coupling parameter is 0.10.

[0201] Step 2: Substitute into the hierarchical equivalent network model and output the prediction sequence contributed only by the outermost layer;

[0202] In the hierarchical equivalent network model, the parameters of the outermost shielding layer are set to an interface reflection coefficient of 0.70 and an absorption attenuation of 0.03, while the parameters of the remaining layers remain unchanged. Simultaneously, to obtain the influence of the outermost shielding layer, the model calculation only outputs the contribution of the corresponding layer term to the amplitude ratio and phase difference (defined in the same way as the transmission characteristic curve: the amplitude ratio contribution is the multiplicative attenuation reduction of the amplitude ratio, and the phase difference contribution is the additional phase lag of the phase difference), resulting in:

[0203] Predicted amplitude ratio influence sequence: [0.02, 0.07, 0.23, 0.27, 0.28];

[0204] Predicted phase difference influence sequence: [-1°, -5°, -18°, -24°, -26°];

[0205] It should be noted that both influence quantity sequences are consistent with the definition of the transmission characteristic curve. The amplitude ratio influence quantity sequence corresponds to the influence of the amplitude ratio dimension, and the predicted phase difference influence quantity sequence corresponds to the influence of the phase difference dimension. Both influence quantity sequences are arranged according to the same frequency point index 1 to 5, which are aligned with the transmission characteristic curve. This output is obtained from the layered equivalent network model under the condition of only changing the parameters of the outermost shielding layer. The parameters of the other layers are always kept at preset initial values, so as to ensure that the two sequences represent the layer-level influence quantity corresponding to the outermost shielding layer.

[0206] For example, frequency index 3 (100 MHz):

[0207] The transmission characteristic curve has an amplitude ratio of 0.48 and a phase difference of -32°.

[0208] The predicted amplitude ratio influence of the outermost shielding layer is 0.23, and the predicted phase difference influence is -18°; both share the same frequency index 3, which satisfies the premise of being arranged according to the same frequency index and being deducted point by point.

[0209] The outermost shielding layer's influence is subtracted from the transmission characteristic curve using frequency indexing to obtain an updated transmission characteristic curve. The subtraction method includes: for the amplitude ratio sequence, subtracting the predicted amplitude ratio influence sequence from the amplitude ratio sequence using frequency indexing to obtain the remaining amplitude ratio sequence; for the phase difference sequence, subtracting the predicted phase difference influence sequence from the phase difference sequence using frequency indexing to obtain the remaining phase difference sequence; and then synthesizing the remaining amplitude ratio sequence and the remaining phase difference sequence using the original frequency indexing to obtain the updated transmission characteristic curve. This is because removing the contribution of the outermost shielding layer from the transmission characteristic curve, which contains the combined effects of multiple layers, allows the updated transmission characteristic curve to serve as the observation input for subsequent inner shielding layer parameter inversion, supporting a continuous calculation method that prioritizes the outermost layer and subtracts it layer by layer. A specific example is shown below:

[0210] Transmission characteristic curve:

[0211] The amplitude ratio sequence is [0.94, 0.76, 0.48, 0.33, 0.28];

[0212] The phase difference sequence is [-4°, -12°, -32°, -44°, -50°].

[0213] The sequence of influence of the outermost shielding layer:

[0214] The predicted amplitude ratio influence sequence is [0.02, 0.07, 0.23, 0.27, 0.28];

[0215] The predicted phase difference influence sequence is [-1°, -5°, -18°, -24°, -26°].

[0216] Step 1: Subtract from the amplitude ratio sequence according to the frequency point index to obtain the remaining amplitude ratio sequence;

[0217] Frequency point 1: 0.94 - 0.02 = 0.92;

[0218] Frequency point 2: 0.76 - 0.07 = 0.69;

[0219] Frequency point 3: 0.48 - 0.23 = 0.25;

[0220] Frequency point 4: 0.33 - 0.27 = 0.06;

[0221] Frequency point 5: 0.28 - 0.28 = 0.00;

[0222] Therefore, the residual amplitude ratio sequence is [0.92, 0.69, 0.25, 0.06, 0.00].

[0223] Step 2: Subtract the phase difference sequence according to the frequency point index to obtain the remaining phase difference sequence;

[0224] Frequency point 1: -4° - (-1°) = -3°;

[0225] Frequency point 2: -12° - (-5°) = -7°;

[0226] Frequency point 3: -32° - (-18°) = -14°;

[0227] Frequency point 4: -44° - (-24°) ​​= -20°;

[0228] Frequency point 5: -50° - (-26°) = -24°;

[0229] Therefore, the remaining phase difference sequence is [-3°, -7°, -14°, -20°, -24°].

[0230] Step 3: Synthesize and update the transmission characteristic curve according to the original frequency point index;

[0231] The remaining amplitude ratio sequence [0.92, 0.69, 0.25, 0.06, 0.00] and the remaining phase difference sequence [-3°, -7°, -14°, -20°, -24°] are aligned one-to-one according to frequency index 1 to 5 to synthesize the updated transmission characteristic curve.

[0232] S104. Input the updated transmission characteristic curve into the hierarchical equivalent network model, continue to perform threshold constraint solution according to the range of parameters to be inverted in the inner shielding layer, obtain the interface reflection coefficient and absorption attenuation of the corresponding layer, and compare the difference sequence between the updated transmission characteristic curve and the response of the hierarchical equivalent network model with the coupling threshold to obtain the interlayer coupling correction factor.

[0233] The process involves obtaining updated transmission characteristic curves, a hierarchical equivalent network model, and the range of parameters to be inverted for the inner shielding layer. The updated transmission characteristic curves include the residual amplitude ratio sequence and the residual phase difference sequence arranged by frequency index. The range of parameters to be inverted for the inner shielding layer includes the range of the interface reflection coefficient and the range of absorption attenuation of the inner shielding layer. The purpose is to ensure that the current solution is based on the observation input after deducting the influence of the outermost layer, and to limit the feasible boundary of the parameters of the inner shielding layer by the range of parameters to be inverted.

[0234] Methods for obtaining the interface reflection coefficient and absorption attenuation of the corresponding layer include:

[0235] The updated transmission characteristic curve is input into the hierarchical equivalent network model, and the unknowns for this round of threshold constraint solution are set as the interface reflection coefficient and absorption attenuation of the inner shielding layer. Specifically, the interface reflection coefficient and absorption attenuation of the outermost shielding layer are kept unchanged, and the parameters of the other non-solution layers are kept at preset initial values. Only the interface reflection coefficient and absorption attenuation of the inner shielding layer are limited to the range of parameters to be inverted as variables to be solved. Under the frequency index, the hierarchical equivalent network model outputs the same predicted residual amplitude ratio sequence and predicted residual phase difference sequence as the updated transmission characteristic curve. The purpose is to make the model output and the updated transmission characteristic curve directly comparable under the same frequency index, amplitude ratio and phase difference, thereby supporting the threshold constraint solution. A specific example is as follows:

[0236] Given: Point indices are 1 to 5, corresponding to frequencies of 1 MHz, 10 MHz, 100 MHz, 300 MHz, and 600 MHz; the resulting updated transmission characteristic curves are:

[0237] The residual amplitude ratio sequence is [0.92, 0.69, 0.25, 0.06, 0.00].

[0238] The remaining phase difference sequence is [-3°, -7°, -14°, -20°, -24°].

[0239] Keep the parameters of the outermost shielding layer unchanged; the reflection coefficient of the outermost shielding layer interface = 0.70; the absorption attenuation of the outermost shielding layer = 0.03. In this round of threshold constraint solution, the above two numbers remain unchanged.

[0240] Keep the parameters of the other non-solution layers at their preset initial values. Except for the outermost shielding layer and the inner shielding layer, set the preset initial value of the interlayer coupling parameter to 0.1, and keep it fixed in this round of solving.

[0241] The unknowns in this round are set as the interface reflection coefficient and absorption attenuation of the inner shielding layer, and are limited to the range of parameters to be inverted. The range of parameters to be inverted for the inner shielding layer is as follows:

[0242] The interface reflection coefficient ranges from 0.60 to 0.90; the absorption attenuation ranges from 0.01 to 0.05. Therefore, the unknowns to be solved in this round can only take values ​​within the above two ranges.

[0243] The updated transmission characteristic curve is input into the hierarchical equivalent network model, and the predicted residual sequence is output under the frequency index; a candidate unknown is selected: the reflection coefficient of the inner shielding layer interface is 0.78 (within 0.60 to 0.90); the absorption attenuation of the inner shielding layer is 0.04 (within 0.01 to 0.05).

[0244] Substitute the candidate unknown into the hierarchical equivalent network model while maintaining:

[0245] The outermost shielding layer's interface reflection coefficient remains unchanged at 0.70, and its absorption attenuation remains unchanged at 0.03.

[0246] The interlayer coupling parameter remains unchanged at 0.10.

[0247] Under frequency indexes 1-5, the output of the hierarchical equivalent network model is the same as the defined predicted residual amplitude ratio sequence and predicted residual phase difference sequence as the updated transmission characteristic curve, for example:

[0248] Predicted residual amplitude ratio sequence [0.90, 0.67, 0.28, 0.08, 0.01];

[0249] Predict the remaining phase difference sequence [-2°, -6°, -13°, -19°, -23°].

[0250] It should be noted that the predicted residual amplitude ratio sequence and the predicted residual phase difference sequence have the same frequency index 1 to 5 as the residual amplitude ratio sequence / residual phase difference sequence, and their dimensions are consistent with the definition (i.e., amplitude ratio to amplitude ratio, phase difference to phase difference); the parameters of the outermost shielding layer and the parameters of the other unsolved layers remain fixed in this output; the reflection coefficient and absorption attenuation of the inner shielding layer interface are the only variable to be solved and are constrained by the range of parameters to be inverted.

[0251] The threshold constraint solution is continued within the range of parameters to be inverted for the inner shielding layer to obtain the interface reflection coefficient and absorption attenuation of the inner shielding layer. The solution method includes: generating a set of candidate parameter groups within the range of interface reflection coefficient and absorption attenuation; for each candidate parameter group, inputting it into a hierarchical equivalent network model to obtain the predicted residual amplitude ratio sequence and the predicted residual phase difference sequence; calculating the amplitude difference sequence as the difference between the predicted residual amplitude ratio sequence and the residual amplitude ratio sequence at the corresponding frequency point, and calculating the phase difference sequence as the difference between the predicted residual phase difference sequence and the residual phase difference sequence at the corresponding frequency point; taking the absolute value of the amplitude difference sequence and taking... The maximum value is used as the amplitude error. The absolute value of the phase difference sequence is taken, and the maximum value is used as the phase error. The amplitude error is compared with the amplitude fitting threshold, and the phase error is compared with the phase fitting threshold. The candidate parameter set whose values ​​do not exceed the corresponding threshold constitutes the optional set. From the optional set, the candidate parameter set that minimizes the sum of the amplitude error and the phase error is selected and determined as the interface reflection coefficient and absorption attenuation of the inner shielding layer. The reason is that, under the condition that the influence of the outer layer has been removed, the parameters of the inner shielding layer are determined, and the solution results are guaranteed not to exceed the physical boundary defined by the range of the parameters to be inverted. A specific example is as follows:

[0252] Given that the residual amplitude ratio sequence is [0.92, 0.69, 0.25, 0.06, 0.00]; the residual phase difference sequence is [-3°, -7°, -14°, -20°, -24°]; the range of parameters to be inverted for the inner shielding layer is: interface reflection coefficient range 0.60~0.90, absorption attenuation range 0.01~0.05; the preset fitting thresholds are: amplitude fitting threshold 0.06, phase fitting threshold 6°.

[0253] Step 1: Generate a set of candidate parameter groups within the range of interface reflection coefficient and absorption attenuation; generate 4 candidate parameter groups:

[0254] Candidate group A: Interface reflectance coefficient 0.72, absorption attenuation 0.03;

[0255] Candidate group B: Interface reflectance coefficient 0.78, absorption attenuation 0.04;

[0256] Candidate group C: Interface reflectance coefficient 0.84, absorption attenuation 0.02;

[0257] Candidate group D: Interface reflectance coefficient 0.66, absorption attenuation 0.05;

[0258] Step 2: Input the hierarchical equivalent network model into each candidate parameter group to obtain the predicted remaining sequence;

[0259] Candidate group A: Predicted residual amplitude ratio sequence [0.91, 0.68, 0.26, 0.07, 0.01]; Predicted residual phase difference sequence [-4°, -8°, -15°, -21°, -25°];

[0260] Candidate group B: Predicted residual amplitude ratio sequence [0.90, 0.67, 0.28, 0.08, 0.01]; Predicted residual phase difference sequence [-2°, -6°, -13°, -19°, -23°];

[0261] Candidate group C: Predicted residual amplitude ratio sequence [0.94, 0.72, 0.31, 0.10, 0.03]; Predicted residual phase difference sequence [-6°, -10°, -18°, -26°, -31°];

[0262] Candidate group D: Predicted residual amplitude ratio sequence [0.86, 0.63, 0.22, 0.04, -0.02]; Predicted residual phase difference sequence [-1°, -5°, -12°, -18°, -21°];

[0263] Step 3: Calculate the amplitude difference sequence and the phase difference sequence;

[0264] Candidate Group A:

[0265] The amplitude difference sequence [0.91-0.92, 0.68-0.69, 0.26-0.25, 0.07-0.06, 0.01-0.00] = [-0.01, -0.01, 0.01, 0.01, 0.01];

[0266] Phase difference sequence [-4-(-3),-8-(-7),-15-(-14),-21-(-20),-25-(-24)]=[-1°,-1°,-1°,-1°,-1°];

[0267] Candidate Group B:

[0268] The amplitude difference sequence [0.90-0.92,0.67-0.69,0.28-0.25,0.08-0.06,0.01-0.00] = [-0.02,-0.02,0.03,0.02,0.01]; the phase difference sequence [-2-(-3),-6-(-7),-13-(-14),-19-(-20),-23-(-24)] = [1°,1°,1°,1°,1°];

[0269] Candidate group C:

[0270] The amplitude difference sequence [0.94-0.92,0.72-0.69,0.31-0.25,0.10-0.06,0.03-0.00] = [0.02,0.03,0.06,0.04,0.03]; the phase difference sequence [-6-(-3),-10-(-7),-18-(-14),-26-(-20),-31-(-24)] = [-3°,-3°,-4°,-6°,-7°];

[0271] Candidate group D:

[0272] The amplitude difference sequence [0.86-0.92,0.63-0.69,0.22-0.25,0.04-0.06,-0.02-0.00] = [-0.06,-0.06,-0.03,-0.02,-0.02];

[0273] The phase difference sequence [-1-(-3),-5-(-7),-12-(-14),-18-(-20),-21-(-24)]=[2°,2°,2°,2°,3°].

[0274] Step 4: Take the absolute value and the maximum value to obtain the amplitude error and phase error;

[0275] Candidate group A: Amplitude error max(0.01,0.01,0.01,0.01,0.01)=0.01; Phase error max(1°,1°,1°,1°,1°)=1°;

[0276] Candidate group B: Amplitude error max(0.02,0.02,0.03,0.02,0.01)=0.03; Phase error max(1°,1°,1°,1°,1°)=1°;

[0277] Candidate group C: Amplitude error max(0.02,0.03,0.06,0.04,0.03)=0.06; Phase error max(3°,3°,4°,6°,7°)=7°;

[0278] Candidate group D: Amplitude error max(0.06,0.06,0.03,0.02,0.02)=0.06; Phase error max(2°,2°,2°,2°,3°)=3°.

[0279] Step 5: Compare with the fitting thresholds to obtain the selectable set; the amplitude fitting threshold is 0.06, and the phase fitting threshold is 6°, requiring that neither exceeds the threshold.

[0280] Candidate group A: 0.01≤0.06 and 1°≤6°, enters the optional set;

[0281] Candidate group B: 0.03≤0.06 and 1°≤6°, enters the optional set;

[0282] Candidate group C: Amplitude 0.06 ≤ 0.06 but phase 7° > 6°, does not enter the selectable set;

[0283] Candidate group D: 0.06≤0.06 and 3°≤6°, enters the optional set;

[0284] Therefore, the possible set is {candidate group A, candidate group B, candidate group D}.

[0285] Step 6: Select the option with the smallest sum of amplitude error and phase error from the available set;

[0286] Candidate group A: Sum of errors = 0.01 + 1 = 1.01;

[0287] Candidate group B: Sum of errors = 0.03 + 1 = 1.03;

[0288] Candidate group D: Sum of errors = 0.06 + 3 = 3.06;

[0289] Candidate group A has the smallest sum of errors, therefore:

[0290] The interface reflection coefficient of the inner shielding layer is 0.72, and the absorption attenuation is 0.03.

[0291] Methods for obtaining interlayer coupling correction factors include:

[0292] The response of the hierarchical equivalent network model is calculated based on the interface reflection coefficient and absorption attenuation of the inner shielding layer, and a difference sequence is generated. Specifically, the interface reflection coefficient and absorption attenuation of the inner shielding layer are substituted into the hierarchical equivalent network model, and the amplitude ratio sequence and the predicted phase difference sequence are output under the frequency index. The amplitude difference sequence is generated by subtracting the predicted amplitude ratio sequence from the remaining amplitude ratio sequence, and the phase difference sequence is generated by subtracting the predicted phase difference sequence from the remaining phase difference sequence. The reason is that the residuals that cannot be explained by the model after the parameters of the inner shielding layer are determined are expressed in the form of a difference sequence aligned with the frequency index, providing input for inter-layer coupling correction. A specific example is as follows:

[0293] Given: the remaining amplitude ratio sequence is [0.92, 0.69, 0.25, 0.06, 0.00]; the remaining phase difference sequence is [-3°, -7°, -14°, -20°, -24°]; the parameters of the inner shielding layer obtained from the previous round of threshold constraint solution are: interface reflection coefficient 0.72, absorption attenuation 0.03.

[0294] Step 1: Substitute the interface reflection coefficient and absorption attenuation of the inner shielding layer into the hierarchical equivalent network model and output the predicted sequence; under frequency indexes 1-5, the hierarchical equivalent network model outputs:

[0295] Predicted amplitude ratio sequence [0.91, 0.68, 0.26, 0.07, 0.01];

[0296] Predict the phase difference sequence [-4°, -8°, -15°, -21°, -25°].

[0297] Step 2: Generate the amplitude difference sequence (remaining amplitude ratio sequence minus the predicted amplitude ratio sequence);

[0298] Frequency point 1: 0.92 - 0.91 = 0.01;

[0299] Frequency point 2: 0.69 - 0.68 = 0.01;

[0300] Frequency point 3: 0.25 - 0.26 = -0.01;

[0301] Frequency point 4: 0.06 - 0.07 = -0.01;

[0302] Frequency point 5: 0.00 - 0.01 = -0.01;

[0303] Therefore, the amplitude difference sequence is [0.01, 0.01, -0.01, -0.01, -0.01].

[0304] Step 3: Generate the phase difference sequence (remaining phase difference sequence minus the predicted phase difference sequence);

[0305] Frequency point 1: -3° - (-4°) = 1°;

[0306] Frequency point 2: -7° - (-8°) = 1°;

[0307] Frequency point 3: -14° - (-15°) = 1°;

[0308] Frequency point 4: -20° - (-21°) = 1°;

[0309] Frequency point 5: -24° - (-25°) = 1°;

[0310] Therefore, the phase difference sequence is [1°, 1°, 1°, 1°, 1°].

[0311] The method for comparing the difference sequence with the coupling threshold and generating an interlayer coupling correction factor includes: taking the absolute values ​​of the amplitude difference sequence and the phase difference sequence at each frequency point to obtain an absolute amplitude difference sequence and an absolute phase difference sequence; comparing the absolute amplitude difference sequence with the amplitude coupling threshold frequency point by frequency point, and comparing the absolute phase difference sequence with the phase coupling threshold frequency point by frequency point; for any frequency point, when at least one absolute difference value is not less than the corresponding coupling threshold, generating a coupling scaling factor for that frequency point according to the ratio of the absolute difference value to the coupling threshold, and limiting the coupling scaling factor to a preset upper limit. Within; then multiply the coupling scaling factor by the difference in the difference sequence at that frequency point to obtain the coupling correction amount at that frequency point. The coupling correction amount constitutes the inter-layer coupling correction factor across all frequency points; when none of the frequency points are triggered (not triggered means less than the coupling threshold) the coupling threshold is determined to be zero. The purpose is to provide a calculable coupling correction caliber by using frequency-point threshold comparison + ratio scaling, so that when summarizing the parameters of each layer, the additional attenuation introduced by inter-layer induced coupling can be included in the interpretation framework under the same frequency point index in the form of inter-layer coupling correction factor. A specific example is as follows:

[0312] Given: the amplitude difference sequence is [0.01, 0.01, -0.01, -0.01, -0.01]; the phase difference sequence is [1°, 1°, 1°, 1°, 1°]; the amplitude coupling threshold is set to 0.008, the phase coupling threshold is set to 1.5°, and the preset upper limit of the coupling scaling factor is 2.0.

[0313] Step 1: Take the absolute value of the difference sequence to obtain the absolute sequence;

[0314] The absolute sequence of amplitude differences is [0.01, 0.01, 0.01, 0.01, 0.01];

[0315] The absolute sequence of phase difference is [1°, 1°, 1°, 1°, 1°].

[0316] Step 2: Compare each frequency point with the coupling threshold to determine the trigger frequency point;

[0317] For each frequency point, it is determined whether the absolute value of at least one difference is not less than the corresponding coupling threshold. Since the absolute value of the amplitude difference of 0.01 at each frequency point satisfies 0.01≥0.008, while the absolute value of the phase difference of 1° does not satisfy 1°≥1.5°, the coupling threshold is triggered by the amplitude condition at each frequency point, and the set of triggered frequency points is {1,2,3,4,5}.

[0318] Step 3: Generate a coupling scaling factor for each trigger frequency point based on the ratio of the absolute value of the amplitude difference to the coupling threshold, and then limit the amplitude. In this example, the trigger is based on amplitude conditions, so the coupling scaling factor for each frequency point is calculated by dividing the absolute value of the amplitude difference by the amplitude coupling threshold.

[0319] 0.01 ÷ 0.008 = 1.25;

[0320] Comparing the coupling scaling factor with the preset upper limit of 2.0, 1.25 does not exceed 2.0, so the coupling scaling factor remains 1.25 after clipping.

[0321] Therefore, the coupling scaling factor for frequencies 1 to 5 is [1.25, 1.25, 1.25, 1.25, 1.25].

[0322] Step 4: Multiply the coupling scaling factor by the difference in the difference sequence at the corresponding frequency point to obtain the coupling correction; the coupling correction is calculated per frequency point as 1.25 × amplitude difference.

[0323] Frequency 1: 1.25 × 0.01 = 0.0125;

[0324] Frequency point 2: 1.25 × 0.01 = 0.0125;

[0325] Frequency point 3: 1.25 × (-0.01) = -0.0125;

[0326] Frequency point 4: 1.25 × (-0.01) = -0.0125;

[0327] Frequency point 5: 1.25 × (-0.01) = -0.0125;

[0328] The amplitude coupling correction values ​​are obtained as [0.0125, 0.0125, -0.0125, -0.0125, -0.0125].

[0329] Similarly, since the phase dimension did not trigger the phase coupling threshold, in this example, the phase coupling correction can be the difference sequence multiplied by the same coupling scaling factor or simply zero; to perfectly correspond with multiplying the difference sequence by the coupling scaling factor, we use the same coupling scaling factor multiplied by the phase difference sequence here:

[0330] The phase coupling correction is [1.25°, 1.25°, 1.25°, 1.25°, 1.25°].

[0331] Step 5: The coupling correction amount forms the interlayer coupling correction factor across the entire frequency range;

[0332] Therefore, the interlayer coupling correction factor, represented by frequency index 1 to 5, is as follows:

[0333] Amplitude range: [0.0125, 0.0125, -0.0125, -0.0125, -0.0125];

[0334] Phase portion: [1.25°, 1.25°, 1.25°, 1.25°, 1.25°].

[0335] The two parts are aligned one-to-one with the frequency index to form the interlayer coupling correction factor.

[0336] If the amplitude coupling threshold is changed to 0.02 and the phase coupling threshold is changed to 2°, then each frequency point satisfies 0.01<0.02 and 1°<2°, and the coupling threshold is not triggered at any frequency point. At this time, the interlayer coupling correction factor takes zero value.

[0337] S105. Summarize the interface reflection coefficient, absorption attenuation, and interlayer coupling correction factor of each layer to generate a record of the shielding effectiveness component of each layer, and compare it with the preset index range threshold, insufficient reflection threshold, insufficient absorption threshold, and abnormal coupling threshold of each layer respectively; when any threshold is triggered (i.e., exceeding any threshold among the index range threshold, insufficient reflection threshold, insufficient absorption threshold, and abnormal coupling threshold), output the location of the failed layer and the failure type corresponding to the trigger threshold.

[0338] The interface reflection coefficient, absorption attenuation, and interlayer coupling correction factor are summarized to generate records of the shielding effectiveness components for each layer. The generation method includes: establishing record entries based on the shielding layer identifier and writing the interface reflection coefficient and absorption attenuation corresponding to that shielding layer into the record entries; then, based on the layered topology, writing the interlayer coupling correction factor corresponding to the interface adjacent to that shielding layer into the record entries, ensuring that each record entry simultaneously contains three types of fields: interface reflection coefficient, absorption attenuation, and interlayer coupling correction factor, while maintaining a one-to-one correspondence between the interlayer coupling correction factor and the frequency point index; and solidifying a traceable data structure for the reflection component, absorption component, and coupling component on a layer-by-layer basis to avoid obtaining only the total shielding effectiveness without being able to locate the specific shielding layer and the specific active component. A specific example is as follows:

[0339] Let the frequency index be 1 to 5, corresponding to frequencies of 1 MHz, 10 MHz, 100 MHz, 300 MHz, and 600 MHz. The layered topology contains two shielding layers: the outermost shielding layer and the innermost shielding layer; the adjacent interface between the two is denoted as the adjacent interface between the outermost shielding layer and the innermost shielding layer.

[0340] The summary results of the known parameters are as follows:

[0341] The outermost shielding layer has an interface reflection coefficient of 0.70 and an absorption attenuation of 0.03; the inner shielding layer has an interface reflection coefficient of 0.72 and an absorption attenuation of 0.03; the interlayer coupling correction factor corresponding to the adjacent interface is a sequence of coupling correction values ​​arranged by frequency index:

[0342] The amplitude coupling correction for frequency indexes 1 to 5 is as follows:

[0343] [0.0125,0.0125,-0.0125,-0.0125,-0.0125];

[0344] The phase coupling correction for frequency indices 1 to 5 is as follows:

[0345] [1.25°, 1.25°, 1.25°, 1.25°, 1.25°];

[0346] The two sequences above correspond one-to-one with the frequency point index.

[0347] Record entries are created based on the shielding layer identifier and written into the fields to form records of the shielding effectiveness components of each layer, for example:

[0348] Record item 1: The shielding layer is identified as the outermost shielding layer;

[0349] Interface reflectivity: 0.70;

[0350] Absorption attenuation: 0.03;

[0351] Interlayer coupling correction factor: corresponding to the interface adjacent to the inner shielding layer, arranged according to frequency index 1 to 5, where the amplitude coupling correction is [0.0125, 0.0125, -0.0125, -0.0125, -0.0125], and the phase coupling correction is [1.25°, 1.25°, 1.25°, 1.25°, 1.25°].

[0352] Record item two: The shielding layer is identified as the inner shielding layer;

[0353] Interface reflectance coefficient: 0.72;

[0354] Absorption attenuation: 0.03;

[0355] Interlayer coupling correction factor: corresponding to the interface adjacent to the outermost shielding layer, arranged according to frequency index 1 to 5, where the amplitude coupling correction is [0.0125, 0.0125, -0.0125, -0.0125, -0.0125], and the phase coupling correction is [1.25°, 1.25°, 1.25°, 1.25°, 1.25°].

[0356] In this example, each record entry contains three types of fields: interface reflection coefficient, absorption attenuation, and interlayer coupling correction factor. The interlayer coupling correction factor is aligned point by point with frequency index 1 to 5, which satisfies the requirement of one-to-one correspondence with the frequency index.

[0357] The methods for comparing the values ​​with the preset threshold ranges, insufficient reflection thresholds, insufficient absorption thresholds, and coupling anomaly thresholds for each layer include:

[0358] Based on the shielding effectiveness component records of each layer, comparison quantities for threshold comparison are generated. These comparison quantities include reflection comparison quantities, absorption comparison quantities, and coupling comparison quantities. The reflection comparison quantity is directly obtained from the interface reflection coefficient, or obtained by performing a monotonic transformation on the interface reflection coefficient, and is used to characterize the reflection capability of the interface to external excitation signals. The absorption comparison quantity is directly obtained from the absorption attenuation quantity, or obtained by performing a monotonic transformation on the absorption attenuation quantity, and is used to characterize the energy attenuation caused by material loss in the layer. The coupling comparison quantity is obtained by taking the absolute value of the interlayer coupling correction factor under the frequency index, and then taking the maximum or average value, and is used to characterize the additional attenuation introduced by interlayer coupling. Fields in the records are converted into comparison quantities that can directly correspond to the threshold according to a clearly calculable standard, avoiding situations where only the mapping relationship is described without calculation rules. A specific example is as follows:

[0359] Given that the frequency index is 1 to 5, a record entry identifying a certain shielding layer as the outermost shielding layer contains:

[0360] The interface reflectance is 0.70;

[0361] The absorption attenuation is 0.03;

[0362] The interlayer coupling correction factor is a coupling correction amount arranged by frequency point index, where the amplitude coupling correction amount is [0.0125, 0.0125, -0.0125, -0.0125, -0.0125] and the phase coupling correction amount is [1.25°, 1.25°, 1.25°, 1.25°, 1.25°].

[0363] Generate reflectance comparison data:

[0364] Method 1, direct value: The reflection comparison amount is equal to the interface reflection coefficient, so the reflection comparison amount is 0.70;

[0365] Method 2, Monotonic Transformation Example: If a monotonic transformation is used where the reflection comparison value is equal to one minus the interface reflection coefficient, then the reflection comparison value is 1-0.70=0.30.

[0366] Both methods satisfy the condition of directly obtaining the value from the interface reflection coefficient or obtaining it by performing a monotonic transformation.

[0367] Generate absorption comparison amount:

[0368] Method 1, direct value: the absorption comparison amount is equal to the absorption attenuation amount, so the absorption comparison amount is 0.03;

[0369] Method 2, Monotonic Transformation Example: If the absorption comparison amount is equal to the absorption attenuation amount multiplied by the length of the section to be tested, and the length of the section to be tested is taken as 2 meters, then the absorption comparison amount is 0.03×2=0.06;

[0370] Both methods satisfy the condition that the value is directly obtained from the absorption attenuation, or obtained by performing a monotonic transformation.

[0371] Generate coupling alignment parameters:

[0372] First, take the absolute value under the frequency index, then take the maximum or average value;

[0373] Taking amplitude coupling correction as an example:

[0374] Taking the absolute value yields [0.0125, 0.0125, 0.0125, 0.0125, 0.0125].

[0375] Take the maximum value: the coupling comparison value is 0.0125;

[0376] Alternatively, take the average: the coupling comparison amount is (0.0125+0.0125+0.0125+0.0125+0.0125)÷5=0.0125.

[0377] Taking the phase coupling correction as an example:

[0378] The absolute value remains [1.25°, 1.25°, 1.25°, 1.25°, 1.25°].

[0379] Maximum value: Coupling alignment is 1.25°;

[0380] Alternatively, take the average: the coupling comparison is 1.25°.

[0381] Therefore, the three types of comparison samples that can be generated from this record entry are as follows:

[0382] The reflectance comparison value is 0.70 (or 0.30 after monotonic transformation).

[0383] Absorption ratio 0.03 (or 0.06 after monotonic transformation);

[0384] The coupling comparison is 0.0125 (amplitude dimension, with the maximum or mean value both being 0.0125), and optionally, the phase dimension coupling comparison is 1.25°.

[0385] For each shielding layer, threshold comparisons are performed against preset index range thresholds, insufficient reflection thresholds, insufficient absorption thresholds, and coupling anomaly thresholds, and the triggering results are recorded. The comparison methods include: comparing the reflection comparison quantity with the insufficient reflection threshold; if the reflection comparison quantity is lower than the insufficient reflection threshold, it is recorded as insufficient reflection triggering; comparing the absorption comparison quantity with the insufficient absorption threshold; if the absorption comparison quantity is lower than the insufficient absorption threshold, it is recorded as insufficient absorption triggering; comparing the coupling comparison quantity with the coupling anomaly threshold; if the coupling comparison quantity is not less than the coupling anomaly threshold, it is recorded as coupling anomaly triggering; and comparing the reflection comparison quantity, absorption comparison quantity, and coupling comparison quantity with the upper and lower bounds of the preset index range thresholds for each layer; if any comparison quantity falls outside the corresponding range, it is recorded as index range anomaly triggering; under the same shielding layer identifier, parallel constraints using multiple thresholds are used to distinguish different failure mechanisms, and the triggering conditions can be directly reproduced; a specific example is as follows:

[0386] Assuming the outermost shielding layer is identified, its comparison quantity is:

[0387] The reflection comparison value is 0.70; the absorption comparison value is 0.03; and the coupling comparison value is 0.0125.

[0388] Let the threshold for this layer be as follows:

[0389] The threshold for insufficient reflection is 0.75; the threshold for insufficient absorption is 0.02; and the threshold for abnormal coupling is 0.0100.

[0390] The upper and lower bounds of the preset indicator range thresholds for each layer are:

[0391] The lower bound of the reflectance comparison range is 0.72, and the upper bound is 0.90.

[0392] The lower limit of the absorption comparison range is 0.02, and the upper limit is 0.06.

[0393] The lower bound of the coupling comparison range is 0, and the upper bound is 0.0150.

[0394] Compare the reflection comparison value with the insufficient reflection threshold and record the trigger result:

[0395] The reflection comparison value of 0.70 is lower than the insufficient reflection threshold of 0.75, so it is recorded as insufficient reflection trigger.

[0396] Compare the absorption comparison amount with the insufficient absorption threshold and record the trigger result:

[0397] The absorption comparison amount of 0.03 is not lower than the insufficient absorption threshold of 0.02, therefore it is not recorded as insufficient absorption trigger.

[0398] Compare the coupling comparison value with the coupling anomaly threshold and record the triggering result:

[0399] The coupling comparison value of 0.0125 is not less than the coupling anomaly threshold of 0.0100, so it is recorded as a coupling anomaly trigger.

[0400] The results were compared with the upper and lower bounds of the preset indicator range thresholds for each layer, and the triggering results were recorded.

[0401] The reflection comparison value of 0.70 is compared with the lower limit of the reflection range of 0.72 and the upper limit of 0.90. 0.70 is lower than the lower limit of 0.72 and falls outside the range. Therefore, it is recorded as an abnormal trigger of the index range.

[0402] The absorption comparison value of 0.03 is compared with the lower limit of the absorption range of 0.02 and the upper limit of 0.06. Since 0.03 is within the range, it is not recorded as an abnormal trigger of the indicator range.

[0403] The coupling comparison value of 0.0125 is compared with the lower bound of the coupling range of 0 and the upper bound of 0.0150. Since 0.0125 is within the range, it is not recorded as an abnormal trigger of the index range.

[0404] Summary of triggering results for this layer:

[0405] Insufficient reflection trigger: Yes; Insufficient absorption trigger: No; Coupling anomaly trigger: Yes; Index range anomaly trigger: Yes.

[0406] When any threshold is triggered, the location of the failure layer and the corresponding failure type are output. The output method includes: associating the identifier of the triggered shielding layer with the layer sequence number and interface position of the layered topology as the failure layer location output; and mapping the trigger threshold type to the failure type output, where triggering insufficient reflection threshold outputs insufficient reflection, triggering insufficient absorption threshold outputs insufficient absorption, triggering coupling anomaly threshold outputs coupling anomaly, and triggering the preset index range threshold of each layer outputs index range anomaly; when the same shielding layer triggers multiple thresholds, multiple failure types corresponding to that shielding layer are output; which layer failed and why it failed are output synchronously based on the threshold trigger result, so that the multi-layer shielding structure can still provide a locatable failure layer location and failure type without disassembly; a specific example is as follows:

[0407] Suppose there are two shielding layers in the layered topology: the shielding layer with layer number 1 is identified as the outermost shielding layer, and its interface is the outer interface and the inner interface, where the inner interface is the interface between the outermost shielding layer and the inner shielding layer; the shielding layer with layer number 2 is identified as the inner shielding layer, and its interface is the outer interface and the inner interface, where the outer interface is the interface between the outermost shielding layer and the inner shielding layer.

[0408] The threshold comparison results are as follows: the outermost shielding layer triggers the insufficient reflection threshold and the abnormal coupling threshold, while the reflection comparison amount falls outside the preset index range threshold of each layer, thus triggering the preset index range threshold of each layer; the inner shielding layer does not trigger any threshold.

[0409] The output process is as follows:

[0410] Output failure layer location: Associate the outermost shielding layer that triggered the failure with the layer topology to obtain a layer sequence number of 1; the interface location is the inner interface of the layer, that is, the interface between the outermost shielding layer and the inner shielding layer.

[0411] Therefore, the failure layer location output is: layer sequence number 1, and the interface location is the inner interface of the outermost shielding layer.

[0412] Output failure type:

[0413] Triggering the insufficient reflection threshold, the corresponding output failure type is insufficient reflection;

[0414] The threshold for triggering coupling anomalies corresponds to the output failure type being coupling anomaly.

[0415] Triggering the preset threshold range of each layer, the corresponding output failure type is indicator range abnormality;

[0416] Since the same shielding layer triggers multiple thresholds, the shielding layer outputs multiple failure types, which can be summarized as: insufficient reflection, abnormal coupling, and abnormal index range.

[0417] Final output example: Failure layer location: outermost shielding layer, layer number 1, interface location is the inner interface of the outermost shielding layer; Failure type: insufficient reflection, abnormal coupling, abnormal index range.

[0418] Example 2

[0419] See Figure 2 As shown, this embodiment discloses a wire shielding performance testing system. For details not described in detail, please refer to Embodiment 1. The system includes:

[0420] The transmission characteristic curve acquisition module is used to acquire multi-frequency external excitation signal response data of the cable under test without disassembly, and perform frequency domain measurement according to the preset measurement layout and scanning steps to obtain the transmission characteristic curve characterizing the overall effect of the multi-layer shielding structure.

[0421] A parameter generation module is established to build a hierarchical equivalent network model based on the transmission characteristic curve and the structural parameter set of the cable under test. The structural parameter set includes the relative positional relationship and material property range of each shielding layer, and the parameter range to be inverted for each shielding layer is generated according to the relative positional relationship and material property range.

[0422] The subtraction module performs outer-layer priority parameter inversion on the transmission characteristic curve based on the hierarchical equivalent network model, extracts the feature quantities of the outer dominant frequency band and solves them according to the preset fitting threshold constraint, determines the interface reflection coefficient and absorption attenuation of the outermost shielding layer, and subtracts them from the transmission characteristic curve to obtain the updated transmission characteristic curve.

[0423] The coupling correction generation module inputs the updated transmission characteristic curve into the hierarchical equivalent network model, continues to perform threshold constraint solution according to the range of parameters to be inverted in the inner shielding layer, obtains the interface reflection coefficient and absorption attenuation of the corresponding layer, and compares the difference sequence between the updated transmission characteristic curve and the response of the hierarchical equivalent network model with the coupling threshold to obtain the interlayer coupling correction factor.

[0424] The output module summarizes the interface reflection coefficient, absorption attenuation, and interlayer coupling correction factor of each layer, generates a record of the shielding effectiveness component of each layer, and compares it with the preset index range threshold, insufficient reflection threshold, insufficient absorption threshold, and abnormal coupling threshold of each layer. If any of the index range threshold, insufficient reflection threshold, insufficient absorption threshold, and abnormal coupling threshold is exceeded, the location of the failed layer and the failure type corresponding to the trigger threshold are output.

[0425] The above are merely specific embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of protection of [the relevant authority / entity].

[0426] In conclusion, the above are merely preferred embodiments of this application and are not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for detecting a shielding performance of an electric wire, characterized by, include: S101. Obtain multi-frequency external excitation signal response data of the cable under test without disassembly, perform frequency domain measurement according to the preset measurement layout and scanning step, and obtain the transmission characteristic curve characterizing the overall effect of the multi-layer shielding structure. S102. Based on the transmission characteristic curve and the structural parameter set of the cable under test, a hierarchical equivalent network model is established. The structural parameter set includes the relative positional relationship and material property range of each shielding layer. Based on the relative positional relationship and material property range, the range of parameters to be inverted for each shielding layer is generated. S103. Based on the hierarchical equivalent network model, perform outer-layer priority parameter inversion on the transmission characteristic curve, extract the characteristic quantities of the outer dominant frequency band and solve them according to the preset fitting threshold constraint, determine the interface reflection coefficient and absorption attenuation of the outermost shielding layer, and subtract them from the transmission characteristic curve to obtain the updated transmission characteristic curve. S104. Input the updated transmission characteristic curve into the hierarchical equivalent network model, continue to perform threshold constraint solution according to the range of parameters to be inverted in the inner shielding layer, obtain the interface reflection coefficient and absorption attenuation of the corresponding layer, and compare the difference sequence between the updated transmission characteristic curve and the response of the hierarchical equivalent network model with the coupling threshold to obtain the interlayer coupling correction factor. S105. Summarize the interface reflection coefficient, absorption attenuation and interlayer coupling correction factor of each layer, generate the shielding effectiveness component record of each layer, and compare it with the preset index range threshold, reflection deficiency threshold, absorption deficiency threshold and coupling anomaly threshold of each layer respectively. If any of the following thresholds is exceeded: the index range threshold, the insufficient reflection threshold, the insufficient absorption threshold, and the coupling anomaly threshold, output the location of the failure layer and the failure type corresponding to the trigger threshold.

2. The method of claim 1, wherein Methods for obtaining transmission characteristic curves include: Under the preset measurement setup, external excitation signals are applied one by one according to the preset frequency point set, and the excitation reference quantity and the response quantity at the response acquisition position are collected at each frequency point simultaneously to obtain multi-frequency external excitation signal response data that correspond one-to-one with the preset frequency point set. Synchronous sampling is performed on the response data of multi-frequency external excitation signals, and a steady-state time window is selected. The excitation reference is used as the phase reference, and a fixed-length time window covering an integer number of excitation cycles is extracted within the continuous sampling interval. The frequency domain characteristic quantities of each frequency point are calculated based on the steady-state time window. For each frequency point, the amplitude and phase are calculated by the excitation reference quantity and the response quantity, and the amplitude ratio and phase difference of the response quantity relative to the excitation reference quantity are obtained accordingly, forming a frequency point transmission quantity sequence indexed by frequency point. The preset frequency point set is arranged according to the scanning step, and the amplitude ratio and phase difference in the frequency point transmission quantity sequence are aligned and spliced ​​according to the same frequency point index to obtain the transmission characteristic curve.

3. The method of claim 1, wherein Methods for establishing hierarchical equivalent network models include: The characteristic data of the transmission characteristic curve and the structural parameter set of the cable under test are obtained. The characteristic data are the amplitude ratio and phase difference arranged by frequency point index. The structural parameter set includes at least the relative position relationship of each shielding layer and the material property range. The material property range includes the conductivity range, magnetic permeability range, dielectric constant range and thickness range. A layered topology of the multi-layer shielding structure is established based on the relative positional relationship, and the layer sequence number of each shielding layer and the interlayer contact state between adjacent layers are determined. Based on the range of material properties, the range of electrical parameters per unit length for each shielding layer is constructed. The range of electrical parameters per unit length includes the range of resistance, inductance, capacitance and conductance per unit length, and the range of values ​​is generated under the frequency index. Under the frequency index, the equivalent impedance range and equivalent propagation parameter range of each shielding layer are generated from the unit length electrical parameter range. The inversion parameter range of each shielding layer is generated based on the equivalent impedance range and equivalent propagation parameter range. The inversion parameter range includes the interface reflection coefficient range and the absorption attenuation range. Based on the hierarchical topology and the range of parameters to be inverted, the equivalent impedance range and equivalent propagation parameter range corresponding to each shielding layer are connected in series according to the layer sequence number to obtain the hierarchical equivalent network model.

4. The method of claim 3, wherein Methods for determining the interface reflection coefficient and absorption attenuation of the outermost shielding layer include: The transmission characteristic curves, the hierarchical equivalent network model, and the range of parameters to be inverted for the outermost shielding layer are obtained. The transmission characteristic curves include the amplitude ratio sequence and the phase difference sequence arranged by frequency point index. The range of parameters to be inverted includes the range of the interface reflection coefficient and the range of absorption attenuation for the outermost shielding layer. Based on the hierarchical equivalent network model, the outer dominant frequency band is determined and feature quantities are extracted under the frequency point index. The determination of the outer dominant frequency band includes: selecting two sets of parameter endpoint combinations as comparison groups within the range of parameters to be inverted; inputting the two sets of parameter endpoints into the hierarchical equivalent network model to obtain two sets of predicted amplitude ratio sequences and two sets of predicted phase difference sequences; calculating the amplitude change and phase change according to the frequency points and comparing them with the amplitude sensitivity threshold and the phase sensitivity threshold respectively; taking the set of frequency points with at least one value not less than the corresponding threshold as the outer dominant frequency band; and extracting subsequences of the amplitude ratio sequence and the phase difference sequence as feature quantities within the outer dominant frequency band. Within the dominant frequency band of the outermost layer, the interface reflection coefficient and absorption attenuation of the outermost shielding layer are solved according to a preset fitting threshold constraint. The solution includes: generating a set of candidate parameter groups within the range of interface reflection coefficient and absorption attenuation; inputting each candidate parameter group into a hierarchical equivalent network model to obtain a predicted amplitude ratio subsequence and a predicted phase difference subsequence; calculating the amplitude error and phase error and comparing them with the amplitude fitting threshold and the phase fitting threshold, respectively; and selecting candidate parameter groups whose sum of amplitude error and phase error is minimized from the selectable set. These candidate parameter groups are then determined as the interface reflection coefficient and absorption attenuation of the outermost shielding layer.

5. The method of claim 4, wherein Methods for obtaining updated transmission characteristic curves include: Based on the interface reflection coefficient and absorption attenuation, the influence sequence of the outermost shielding layer under the frequency index is generated. This includes substituting the interface reflection coefficient and absorption attenuation into the layer terms corresponding to the outermost shielding layer in the hierarchical equivalent network model, and outputting the predicted amplitude ratio influence sequence and the predicted phase difference influence sequence under the frequency index. The transmission characteristic curve is updated by subtracting the influence quantity sequence from the transmission characteristic curve according to the frequency point index. This includes subtracting the predicted amplitude ratio influence quantity sequence from the amplitude ratio sequence to obtain the remaining amplitude ratio sequence, subtracting the predicted phase difference influence quantity sequence from the phase difference sequence to obtain the remaining phase difference sequence, and then synthesizing them to obtain the updated transmission characteristic curve.

6. The method of claim 5, wherein Methods for obtaining the interface reflection coefficient and absorption attenuation of the corresponding layer include: The updated transmission characteristic curve is input into the hierarchical equivalent network model, and the interface reflection coefficient and absorption attenuation of the inner shielding layer are set as unknowns in this round of threshold constraint solution. The unknowns are limited to the range of parameters to be inverted, and the predicted residual amplitude ratio sequence and the predicted residual phase difference sequence are output under the frequency index. The interface reflection coefficient and absorption attenuation of the inner shielding layer are obtained by performing threshold constraint solution according to the range of parameters to be inverted. This includes generating a set of candidate parameter groups within the range of interface reflection coefficient and absorption attenuation, obtaining the predicted residual amplitude ratio sequence and the predicted residual phase difference sequence for each candidate parameter group, and calculating the amplitude error and phase error. The amplitude error is compared with the amplitude fitting threshold, and the phase error is compared with the phase fitting threshold. The candidate parameter groups whose values ​​do not exceed the corresponding threshold constitute an optional set. The candidate parameter group that minimizes the sum of amplitude error and phase error is selected from the optional set and determined as the interface reflection coefficient and absorption attenuation of the inner shielding layer.

7. The method of claim 6, wherein Methods for obtaining interlayer coupling correction factors include: Substitute the interface reflection coefficient and absorption attenuation of the inner shielding layer into the hierarchical equivalent network model, and output the predicted amplitude ratio sequence and the predicted phase difference sequence under the frequency index. Subtract the predicted amplitude ratio sequence from the remaining amplitude ratio sequence to obtain the amplitude difference sequence, and subtract the predicted phase difference sequence from the remaining phase difference sequence to obtain the phase difference sequence. The absolute values ​​of the amplitude difference sequence and the phase difference sequence are taken to obtain the absolute amplitude difference sequence and the absolute phase difference sequence, respectively, and compared with the amplitude coupling threshold and the phase coupling threshold on a frequency-by-frequency basis. When at least one of the values ​​at any frequency point is not less than the corresponding threshold, a coupling scaling factor is generated according to the ratio of the absolute difference value to the coupling threshold, and the coupling scaling factor is limited to a preset upper limit. The coupling correction amount is obtained by multiplying the coupling scaling factor by the difference value of the amplitude difference sequence or the phase difference sequence at that frequency point. The coupling correction amount forms the inter-layer coupling correction factor across all frequency points. When all frequency points are less than the amplitude coupling threshold and the phase coupling threshold, the inter-layer coupling correction factor is determined to be zero.

8. The method of claim 1, wherein, Methods for generating records of shielding effectiveness components for each layer include: Establish a record entry according to the shielding layer identifier, and write the interface reflection coefficient and absorption attenuation of the corresponding shielding layer into the record entry; Based on the layered topology, the interlayer coupling correction factor corresponding to the interface adjacent to the shielding layer is written into the record entry, so that the record entry simultaneously contains three types of fields: interface reflection coefficient, absorption attenuation and interlayer coupling correction factor. The interlayer coupling correction factor corresponds one-to-one with the frequency point index to generate the shielding effectiveness component record of each layer.

9. The method of claim 8, wherein, Methods for outputting the failure layer location and the failure type corresponding to the trigger threshold include: Based on the shielding effectiveness component records of each layer, reflection comparison quantity, absorption comparison quantity and coupling comparison quantity are generated for threshold comparison. The reflection comparison quantity is obtained by taking the value of the interface reflection coefficient, the absorption comparison quantity is obtained by taking the value of the absorption attenuation quantity, and the coupling comparison quantity is obtained by taking the maximum value of the interlayer coupling correction factor after taking the absolute value under the frequency point index. For each shielding layer, the reflection comparison quantity is compared with the insufficient reflection threshold, the absorption comparison quantity is compared with the insufficient absorption threshold, and the coupling comparison quantity is compared with the abnormal coupling threshold. The reflection comparison quantity, absorption comparison quantity, and coupling comparison quantity are compared with the upper and lower bounds of the preset index range threshold of each layer to obtain the shielding layer identifier and trigger threshold type of the trigger threshold. When any threshold is triggered, the shielding layer identifier of the trigger threshold is associated with the layer sequence number and interface position of the hierarchical topology, the failure layer position is output, and the failure type is output according to the trigger threshold type. The failure types include insufficient reflection, insufficient absorption, abnormal coupling, and abnormal index range.

10. A system for detecting the shielding performance of an electric wire, which implements the method for detecting the shielding performance of an electric wire according to claims 1 to 9, characterized by, The system includes: The transmission characteristic curve acquisition module is used to acquire multi-frequency external excitation signal response data of the cable under test without disassembly, and perform frequency domain measurement according to the preset measurement layout and scanning steps to obtain the transmission characteristic curve characterizing the overall effect of the multi-layer shielding structure. A parameter generation module is established to build a hierarchical equivalent network model based on the transmission characteristic curve and the structural parameter set of the cable under test. The structural parameter set includes the relative positional relationship and material property range of each shielding layer, and the range of parameters to be inverted for each shielding layer is generated accordingly. The subtraction module performs outer-layer priority parameter inversion on the transmission characteristic curve based on the hierarchical equivalent network model, extracts the feature quantities of the outer dominant frequency band and solves them according to the preset fitting threshold constraint, determines the interface reflection coefficient and absorption attenuation of the outermost shielding layer, and subtracts them from the transmission characteristic curve to obtain the updated transmission characteristic curve. The coupling correction generation module inputs the updated transmission characteristic curve into the hierarchical equivalent network model, continues to perform threshold constraint solution according to the range of parameters to be inverted in the inner shielding layer, obtains the interface reflection coefficient and absorption attenuation of the corresponding layer, and compares the difference sequence between the updated transmission characteristic curve and the response of the hierarchical equivalent network model with the coupling threshold to obtain the interlayer coupling correction factor. The output module summarizes the interface reflection coefficient, absorption attenuation, and interlayer coupling correction factor of each layer, generates a record of the shielding effectiveness component of each layer, and compares it with the preset index range threshold, insufficient reflection threshold, insufficient absorption threshold, and abnormal coupling threshold of each layer. If any of the index range threshold, insufficient reflection threshold, insufficient absorption threshold, and abnormal coupling threshold is exceeded, the location of the failed layer and the failure type corresponding to the trigger threshold are output.

Images