Method for rapidly evaluating S parameter of multi-layer PCB port in multi-stage waveguide structure

Abstract

The invention discloses a method for rapidly evaluating an S parameter of a multi-layer PCB port in a multi-stage waveguide structure, and the method comprises the steps: decomposing a system into a plurality of mutually independent subsystems, representing a propagation channel of electromagnetic energy as a signal pipeline, and representing a reflection position of the energy as a reflection node, thereby building a signal energy flow diagram of the system. On the basis, scattering parameters of the subsystems are obtained through a numerical simulation method, and a corrected BLT equation capable of representing the electromagnetic field-circuit bidirectional coupling relation between the subsystems is deduced in combination with propagation equations of all signal pipelines and scattering equations of all reflection nodes of the system; and the S parameter of the multi-layer PCB port in the multi-stage waveguide structure can be obtained by solving the equation. The method has the advantages of being simple in algorithm, accurate in result, high in efficiency and the like, is suitable for a multi-stage waveguide structure of any geometrical shape, and can achieve rapid evaluation and analysis of the electromagnetic coupling effect in electronic equipment with a waveguide-shaped shielding structure in a complex electromagnetic environment.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of electromagnetic interference analysis, and particularly relates to a method for rapidly evaluating S parameters of a multi-layer PCB port in a multi-stage waveguide structure. BACKGROUND

[0002] In recent years, with the rapid development of modern information technology, electronic devices represented by computers and communication equipment have been widely used in military and civilian fields. As a core supporting component, printed circuit boards (PCB) bear key functions such as signal transmission and power distribution in the device. To meet the complex functional requirements, modern PCB design generally adopts high-density interconnection (HDI), multi-layer wiring and high-frequency high-speed signal processing technology. However, this high-integration trend also significantly increases the sensitivity and vulnerability of PCB to electromagnetic interference (EMI). External electromagnetic interference sources can enter the interior of the device through front or back door coupling paths, and generate coupled voltage and current on the multi-layer PCB, causing damage such as electrical breakdown and thermal breakdown of semiconductor devices and circuits, and then causing serious consequences such as data loss, system failure and abnormal function. Therefore, it is of great significance to quickly and accurately evaluate the coupling effect of the multi-layer PCB inside the device to improve its electromagnetic compatibility performance, and S parameters as a key indicator of electromagnetic coupling effect of multi-layer PCB can effectively describe the energy transfer relationship between external interference sources and internal circuits, and then provide a theoretical basis for electromagnetic interference strength evaluation and protection design of the device.

[0003] Y. Li et al. decomposed the coupling problem of transmission lines in a shielded cavity with an aperture under external electromagnetic field excitation using electromagnetic topology. First, the field distribution in the cavity with an aperture under external field excitation was solved by the Method of Moments (MoM) and Green's function, and then the load response of the transmission line in the cavity was solved using the obtained field distribution and Taylor form BLT (Baum-Liu-Tesche) equation. This method has important significance in the field of electromagnetic interference calculation, but this method relies on the solution of integral equations, and the consumption of computing resources is large, the efficiency is low, and since the combination of the moment method and multi-conductor transmission line theory is needed to handle the field-line coupling problem, the calculation process is complex and difficult to implement.

[0004] Gong YF proposed an analytical calculation theory model for calculating the near-field shielding effectiveness of double-layer metal cavity, equivalent near-field interference to electric dipole in outer cavity, and then based on Bethe small hole coupling theory, equivalent magnetic dipole moment and electric dipole moment at hole gap are obtained, and finally the electric field distribution in the inner cavity is solved by equivalent magnetic dipole field, electric dipole field and cavity Green function. Although this method has certain advantages in analytical solution, the derivation process is complex, and because the internal electronic devices of the equipment are usually complex, the structure parameters are difficult to accurately express by simple formula, thereby limiting its application range. SUMMARY

[0005] To solve the above technical problems, the present application provides a method for quickly evaluating the S parameters of multi-layer PCB ports in a multi-stage waveguide structure. The method first modifies the generalized BLT equation to output in the form of S parameters. Then, the target system is decomposed into multiple subsystems using the electromagnetic topology decomposition idea, and the scattering parameters of complex subsystems are calculated by numerical simulation. Finally, the modified BLT equation representing the electromagnetic coupling relationship between subsystems is derived, and the S parameters between any ports in the multi-stage waveguide are obtained by solving the equation, thereby realizing the fast evaluation of the electromagnetic coupling effect of the system. This method has the advantages of simple algorithm, efficient calculation and accurate results, and provides a theoretical basis for the electromagnetic coupling effect analysis and protection design of complex systems.

[0006] The technical solution of the present application is a method for quickly evaluating the S parameters of multi-layer PCB ports in a multi-stage waveguide structure, comprising the following specific steps:

[0007] Step S1, modify the generalized BLT equation to output in the form of S parameters;

[0008] Step S2, decompose the system into multiple independent and easily solvable subsystems using the electromagnetic topology decomposition idea, define the propagation channel of electromagnetic energy as a signal pipe, and define the position of energy reflection as a reflection node, thereby establishing the signal energy flow diagram of the system;

[0009] Step S3, combine electromagnetic field theory and numerical simulation software to obtain the propagation equation of each signal pipe, and integrate the propagation equations of all signal pipes to obtain the total propagation equation of the system;

[0010] Step S4, combine electromagnetic field theory and numerical simulation software to obtain the scattering equation of each reflection node, and integrate the scattering equations of all reflection nodes to obtain the total scattering equation of the system;

[0011] Step S5, construct the modified BLT equation of the system according to the total propagation equation of the system in step S3 and the total scattering equation of the system in step S4;

[0012] Step S6, by solving the modified BLT equation obtained in step S5, the S parameter between the excitation port Portl and the multi-layer PCB port PortA can be obtained.

[0013] Further, the modification method in step S1 is to introduce a reflection voltage source Modify the excitation term in the generalized BLT equation, BLT is the abbreviation of Baum-Liu-Tesche;

[0014] Step S11: The signal energy flow contains 2 signal channels: T1 and T2, 3 reflection nodes: J1, J2 and J3; The incident voltage equation is expressed as:

[0015]

[0016] Wherein, is the incident voltage vector containing all nodes of the system; P is the propagation matrix derived from the propagation relationship of all channels; is the reflection voltage vector containing all nodes of the system; is the external source V S The introduced incident voltage source vector is not 0 only at node J1 and node J2; Indicates the incident voltage propagated to node J j Through signal channel T i ; Indicates the reflection voltage away from node J j Through signal channel T i ; The external source V S acts on and Corresponding to and

[0017] Step S12: The reflection voltage source should be added to the incident voltage, and the reflection voltage equation is:

[0018]

[0019] Wherein, S is the scattering matrix derived from the scattering relationship of all nodes; is the external source V S The introduced reflection voltage source vector is not 0 only at the excitation port;

[0020] Step S13: Calculate the expression of incident voltage V inc Equation and reflection voltage V ref :

[0021]

[0022] The total voltage equation of the system can be expressed as:

[0023]

[0024] wherein U is a unit matrix.

[0025] Further, the subsystem in step S2 comprises a complex aperture subsystem and a multilayer PCB subsystem; the signal pipeline comprises (1) a propagation channel between the excitation port Port1 of the outer waveguide and the left port Port2 of the complex aperture subsystem; (2) a propagation channel between the right port Port3 of the complex aperture subsystem and the multilayer PCB load port PortA; the node comprises the excitation port Port1, the complex aperture subsystem and the multilayer PCB load port PortA.

[0026] Further, the total propagation equation of the system in step S3 is:

[0027]

[0028] wherein γ represents the propagation constant of the outer waveguide; d1 represents the propagation distance of the electromagnetic field in the outer waveguide, i.e. the length between the front panel of the outer waveguide and the front panel of the complex aperture subsystem; represents the reflection coefficient of Port4 in the PCB subsystem; represents the forward transmission coefficient under the excitation of Port4 in the PCB subsystem; represents the backward transmission coefficient under the excitation of PortA in the PCB subsystem; represents the reflection coefficient of PortA in the PCB subsystem;

[0029] When the signal pipeline is a propagation channel between the right port Port3 of the complex aperture subsystem and the multilayer PCB load port PortA, the scattering parameters of the multilayer PCB subsystem are calculated by numerical simulation software, so as to obtain the propagation equation of the signal pipeline.

[0030] Further, the total scattering equation of the system in step S4 is:

[0031]

[0032] wherein ρ1 represents the scattering parameter of the node J1; represents the reflection coefficient of Port2 in the complex aperture subsystem; represents the forward transmission coefficient under the excitation of Port2 in the complex aperture subsystem; represents the backward transmission coefficient under the excitation of Port3 in the complex aperture subsystem; represents the reflection coefficient of Port3 in the complex aperture subsystem;

[0033] When the reflection node is the excitation port Port1, it is assumed that the excitation port has no reflection, and thus ρ1=0;

[0034] When the reflection node is the complex aperture subsystem, the scattering parameters of the complex aperture subsystem are calculated by numerical simulation software, and the scattering equation at the reflection node is established.

[0035] When the reflection node is the multi-layer PCB port PortA, the scattering equation at the reflection node is established according to the numerical data calculated in step S3.

[0036] Further, the modified BLT equation of the system in step 5 is:

[0037]

[0038] wherein, V i,j represents the voltage at the upper node T i of the signal pipe T j .

[0039] Further, the calculation method in step S6 is to solve the modified BLT equation of the system to obtain the voltage vector V of each reflection node = [V 1,1 V 1,2 V 2,2 V 2,3 ] T ,

[0040] Solving the modified BLT equation, the voltage of the multi-layer PCB port PortA is:

[0041]

[0042] The voltage of the excitation port Port1 is:

[0043]

[0044] The normalized S parameter is S A1 =20log 10 (V 2,3 / V 1,1 );

[0045] wherein, A and B have no specific physical meaning, and are intermediate parameters introduced for convenience of calculation, and the specific expressions of A and B are respectively:

[0046]

[0047] The beneficial effects of the present application: the present application represents the propagation channel of electromagnetic wave in the multi-stage waveguide structure as a signal pipe, and represents the position of energy reflection as a reflection node, and constructs a signal energy flow diagram capable of reflecting the electromagnetic energy flow condition of the system. The generalized BLT equation is modified to output in the form of S parameters, and the scattering parameters of the complex subsystem obtained by numerical simulation are used to replace the corresponding values in the propagation matrix or scattering matrix, so that the modified BLT equation representing the electromagnetic coupling of the system is established. By solving the modified BLT equation, the S parameters at any port in the system can be obtained. The method has the advantages of simple algorithm, accurate results and high efficiency, and is suitable for multi-stage waveguide structures of any geometric shape, and can realize the rapid evaluation and analysis of the electromagnetic coupling effect in the electronic equipment with waveguide-shaped shielding structure in a complex electromagnetic environment. BRIEF DESCRIPTION OF DRAWINGS

[0048] Figure 1 is the scheme flowchart of the present application.

[0049] Figure 2 is the signal energy flow diagram used by a certain generalized BLT equation provided in the embodiment of the present application.

[0050] Figure 3 is a schematic diagram of a multi-stage waveguide structure provided in the embodiment of the present application.

[0051] Figure 4 is a detailed structure schematic diagram of a multi-layer PCB provided in the embodiment of the present application.

[0052] Figure 5 is a detailed structure and simulation port setting of a complex aperture subsystem after decomposition of the multi-stage waveguide structure provided in the embodiment of the present application.

[0053] Figure 6 is a detailed structure and simulation port setting of a PCB subsystem after decomposition of the multi-stage waveguide structure provided in the embodiment of the present application.

[0054] Figure 7 is a signal energy flow diagram reflecting the electromagnetic energy flow condition of the system, containing each signal pipe and reflection node, provided in the embodiment of the present application.

[0055] Figure 8 is a numerical simulation result of the scattering parameters of a complex aperture subsystem provided in the embodiment of the present application.

[0056] Figure 9 is a numerical simulation result of the scattering parameters of a multi-layer PCB subsystem provided in the embodiment of the present application.

[0057] Figure 10It is a comparison between the calculation method results of the present invention and the pure numerical simulation results provided in the embodiments of the present invention. DETAILED DESCRIPTION

[0058] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0059] like Figure 1 As shown in FIG, a flow chart of a method for rapidly evaluating the S parameters of a multi-layer PCB port in a multi-level waveguide structure of the present invention is shown, and the specific steps are as follows:

[0060] Step S1, modifying the generalized BLT equation so that it can be output in the form of S parameters;

[0061] like Figure 2 The following is a signal energy flow diagram used by a generalized BLT, which includes two signal pipelines ( Figure 2 T1 and T2) and 3 reflection nodes ( Figure 2 In the figure, Indicates that through the signal pipe T i Propagate to node J j The incident voltage; Indicates that through the signal pipe T i Away from node J j The reflected voltage; V S It represents the excitation voltage source of the external field coupled to the system, which propagates to nodes J1 and J2 through signal pipe T1.

[0062] To obtain Figure 2 In the external source V S To determine the voltage response of the excitation, the external source V S The role of adding and The effect of and The incident voltage equation can be expressed as:

[0063]

[0064] in, is the incident voltage vector including all nodes of the system; P is the propagation matrix, which is derived from the propagation relationship of all pipelines; is the reflected voltage vector including all nodes of the system; For external source V S The incident voltage source vector introduced is not zero only at nodes J1 and J2.

[0065] In order to make the generalized BLT equation output S parameters, the excitation term in the original equation needs to be modified, and the external source V S The role of adding Effect of reflected voltage source Indicates. For example, when calculating the scattering parameter S 31 When the node J1 is located at port 1 and the node J3 is located at port 3, the reflected voltage source should be Add to Then the reflected voltage equation can be expressed as:

[0066]

[0067] Where S is the scattering matrix, which is derived from the scattering relationship of all nodes; For external source V S The introduced reflected voltage source vector is not zero only at the excitation port (here, node J1).

[0068] Combining the above two equations, the incident voltage equation and the reflected voltage equation can be further calculated as follows:

[0069]

[0070] Therefore, the total voltage equation of the system can be expressed as:

[0071]

[0072] Among them, U is the unit matrix; when When , the above formula represents the generalized BLT equation; when When , the above formula represents the modified BLT equation.

[0073] Step S2: Using the concept of electromagnetic topological decomposition, the system is decomposed into multiple independent and easily solvable subsystems. The propagation channels of electromagnetic energy are defined as signal conduits, and the locations where energy is reflected are defined as reflection nodes, thereby establishing a signal energy flow diagram for the system.

[0074] like Figure 3 As shown, the multi-stage waveguide structure in this embodiment has an overall length of d1+d2+d3, a width of a, and a height of b. Its interior is separated into inner and outer waveguide layers by a metal partition. The metal partition has two rectangular holes of dimensions l×w, with a center-to-center distance of o. Assume that the system is filled with air, and that the outer shell, except for the excitation port Port1, is a perfect electric conductor (PEC).

[0075] In the multi-stage waveguide structure, the inner waveguide contains a multi-layer PCB structure to simulate the board-level integration environment in typical electronic devices. The multi-layer PCB adopts a typical S-G-P-S (signal-ground-power-signal) stack structure, with a total length of a1, a width of b1, and a height of h1+h2+h3. The detailed structure is shown in Figure 4 . Two representative signal traces are designed in the PCB: one is a top-layer through trace without via structure, and the other is a cross-layer trace connected by vias between the top and bottom layers. All trace materials are copper, and the relative dielectric constant of the internal dielectric layer material is ε r = 9.7.

[0076] In solving the S parameters of the multi-layer PCB port in the multi-stage waveguide structure, the overall system shown in Figure 3 is first decomposed into three independent subsystems: the outer waveguide, the complex aperture subsystem, and the multi-layer PCB subsystem. The outer waveguide has dimensions a x b x d1; the complex aperture subsystem has dimensions a x b x d2 and is internally a metal partition with rectangular holes; and the PCB subsystem is the inner waveguide containing a multi-layer PCB with dimensions a x b x d3. The detailed structures and port settings of the complex aperture subsystem and the multi-layer PCB subsystem are shown in Figure 5 and Figure 6 , respectively. Ports Port1, Port2, Port3, and Port4 represent waveguide port excitations, and ports PortA, PortB, PortC, and PortD represent lumped port excitations, which can be used for subsequent simulation and solution of scattering parameters.

[0077] For the multi-stage waveguide structure, the propagation channel of electromagnetic waves is represented by signal pipes, and the positions where electromagnetic waves reflect are represented by reflection nodes. The signal energy flow diagram reflecting the energy flow of the system is shown in Figure 7 . In actual analysis, the number of signal pipes between nodes depends on the types of propagation modes in the multi-stage waveguide structure. If multiple propagation modes are considered, the number of signal pipes between corresponding nodes should be increased to accurately represent the energy transmission characteristics of the system. It should be noted that only a single dominant mode propagation mode is used in this embodiment to construct the modified BLT equation.

[0078] Figure 7In the figure, node J1 represents the excitation port Port1 of the outer waveguide; node J2 represents the complex aperture subsystem; node J3 represents the port PortA of the multi-layer PCB in the inner waveguide; pipe T1 represents the propagation channel of the incident excitation electromagnetic wave between the excitation port Port1 of the outer waveguide and the left port Port2 of the complex aperture subsystem; pipe T2 represents the propagation channel of the electromagnetic wave between the right port Port3 of the complex aperture subsystem and the port PortA of the multi-layer PCB in the inner waveguide.

[0079] If the signals are represented by voltages, the incident and reflected voltages at each node can be defined as follows: the incident voltage at node J1 on pipe T1 is the reflected voltage is the incident voltage at node J2 on pipe T1 is the reflected voltage is the incident voltage at node J2 on pipe T2 is the reflected voltage is the incident voltage at node J3 on pipe T2 is the reflected voltage is

[0080] Step S3: Obtain the propagation equations of each signal pipe by combining electromagnetic field theory and numerical simulation software, and obtain the total propagation equation of the system by integrating the propagation equations of all signal pipes.

[0081] The total propagation equation of the system is:

[0082]

[0083] where γ represents the propagation constant of the outer waveguide; represents the scattering parameter of the PCB subsystem, which can be obtained by numerical simulation.

[0084] Step S4: Obtain the scattering equations of each reflection node by combining electromagnetic field theory and numerical simulation software, and obtain the total scattering equation of the system by integrating the scattering equations of all reflection nodes.

[0085] The total scattering equation of the system is:

[0086]

[0087] where ρ1 represents the scattering parameter of node J1, and ρ1 = 0 is assumed if there is no reflection at the excitation port; represents the scattering parameter of the complex aperture subsystem, which can be obtained by numerical simulation. It depends on the excitation mode applied to the waveguide system. When the excitation of the waveguide system is TE 10 mode, then

[0088] Step S5, constructing the modified BLT equation of the system according to the system total propagation equation of step S3 and the system total scattering equation of step S4;

[0089] The modified BLT equation of the system is obtained by synthesizing the system total propagation equation and the system total scattering equation as follows:

[0090]

[0091] Step S6, the S parameter between the excitation port Port1 and the multilayer PCB port PortA can be obtained by solving the modified BLT equation of step S5.

[0092] The voltage of the multilayer PCB port PortA can be obtained by solving the modified BLT equation as follows:

[0093]

[0094] The voltage of the excitation port Port1 is as follows:

[0095]

[0096] Wherein, A and B have no specific physical meaning, and are intermediate parameters introduced for convenience of calculation, and the specific expressions of A and B are as follows:

[0097]

[0098] Therefore, the S parameter between the excitation port Port1 and the multilayer PCB port PortA can be obtained from the calculation formula of the S parameter S A1 = 20log 10 (V 2,3 / V 1,1 ).

[0099] The method for quickly evaluating the S parameter of a multilayer PCB port in a multistage waveguide structure according to the present application is further described in the following specific embodiment. The dimensions of the multistage waveguide system are set as a = 60 mm, b = 38 mm, d1 = 70 mm, d2 = 10 mm, d3 = 110 mm, and two rectangular holes with a size of 50 mm x 5 mm are opened on the internal metal partition, the center distance of the two holes is o = 2 mm, the dimensions of the multilayer PCB are a1 = 50 mm, b1 = 20 mm, h1 = 0.76 mm, h2 = 1.52 mm, and h3 = 0.76 mm. The excitation mode of the system is waveguide port excitation, and the excitation mode is TE 10 mode.

[0100] First, the subsystem in the embodiment is numerically modeled and simulated by using the numerical simulation software CST to obtain the scattering parameters of the complex aperture subsystem in the frequency band of 0.5-4.5 GHz Scattering parameters of the curve and the multilayer PCB subsystem The frequency variation curves are shown in Figure 8 and Figure 9 respectively.

[0101] Subsequently, the subsystem scattering parameters obtained by numerical simulation are substituted into the modified BLT equation of the system, and the scattering parameters between the excitation port Port1 of the outer waveguide and the multilayer PCB load port PortA in the inner waveguide can be calculated. Figure 10 The scattering parameters S A1 obtained by the method proposed in the application and the pure CST numerical simulation are compared. A1 The abscissa Frequency is frequency, and the unit is GHz; the ordinate S-Parameter is S A1 Parameter, and the unit is dB. It can be seen that the calculation results of the application are in good agreement with the pure CST simulation results, can accurately reflect the resonance points of the system, and the method has high precision and reliability in calculating the S parameters of the multilayer PCB port. In addition, the method can modify the propagation constant γ in the total propagation matrix P of the system to consider various propagation modes inside the waveguide structure, and the process does not need to reestablish a complex simulation model or calculation process, is simple to operate, and has strong applicability.

[0102] Table 1 shows the grid number and calculation time required by the method of the application and pure CST simulation. The time used by the method of the application includes the time for solving the PCB subsystem scattering parameters by using CST and the time for solving the modified BLT equation by using MATLAB. The computer used for calculation and simulation is configured as Intel(R) Core(TM) i5-10210U CPU@1.60 GHz, with a memory of 12 GB, and runs under Window 11.

[0103] Table 1 shows the scattering parameter S A1 calculation efficiency comparison

[0104]

[0105] It can be seen from Table 1 that the time used by the method of the application is significantly shortened compared with the pure CST simulation, the overall calculation efficiency is improved by 11.9 times compared with the pure CST simulation, the grid number is greatly reduced, and the memory resources are less occupied. This shows that by decomposing the target system into multiple subsystems and incorporating the local scattering parameters into the modified BLT equation, the calculation efficiency and resource utilization can be effectively improved.

Claims

1. A method for rapidly evaluating the S-parameters of multi-layer PCB ports within a multi-level waveguide structure. The specific steps are as follows: Step S1, modifying the generalized BLT equation so that it can be output in the form of S parameters; Step S2: Using the concept of electromagnetic topological decomposition, the system is decomposed into multiple independent and easily solvable subsystems. The propagation channels of electromagnetic energy are defined as signal conduits, and the locations where energy is reflected are defined as reflection nodes, thereby establishing a signal energy flow diagram for the system. Step S3: Combining electromagnetic field theory and numerical simulation software, the propagation equation of each signal pipeline is obtained, and the propagation equation of all signal pipelines is integrated to obtain the overall propagation equation of the system; Step S4: combining electromagnetic field theory and numerical simulation software to obtain the scattering equation of each reflection node, and integrating the scattering equations of all reflection nodes to obtain the total scattering equation of the system; Step S5: constructing a modified BLT equation of the system based on the overall propagation equation of the system in step S3 and the overall scattering equation of the system in step S4, where BLT is the abbreviation of Baum-Liu-Tesche; Step S6: By solving the modified BLT equation obtained in step S5, the S parameters between the excitation port Port1 and the multilayer PCB port PortA can be obtained.

2. A method for rapidly evaluating S parameters of a multi-layer PCB port in a multi-stage waveguide structure according to claim 1, characterized in that: The correction method of step S1 is: introduce a reflected voltage source Modify the excitation term in the generalized BLT equation; Step S11: The signal energy flow includes two signal pipelines: T1 and T2, and three reflection nodes: J1, J2, and J3; the incident voltage equation is expressed as: in, is the incident voltage vector including all nodes of the system; P is the propagation matrix, which is derived from the propagation relationship of all pipelines; is the reflected voltage vector including all nodes of the system; For external source V S The incident voltage source vector introduced is not zero only at nodes J1 and J2; Indicates that through the signal pipe T i Propagate to node J j The incident voltage; Indicates that through the signal pipe T i Away from node J j The reflected voltage of the external source V S Effect and The corresponding expression is and Step S12: The reflected voltage source should be added to the incident voltage. The reflected voltage equation is: Where S is the scattering matrix, which is derived from the scattering relationship of all nodes; For external source V S The introduced reflected voltage source vector is not zero only at the excitation port; Step S13: Calculate the incident voltage V inc Equation and reflected voltage V ref The expressions are: Therefore, the total voltage equation of the system can be expressed as: Where U is the identity matrix.

3. The method for rapidly evaluating S parameters of a multi-layer PCB port in a multi-stage waveguide structure according to claim 1, wherein: The subsystems described in step S2 include: a complex aperture subsystem and a multi-layer PCB subsystem; the signal pipeline includes: (1) a propagation channel between the excitation port Port1 of the outer waveguide and the left port Port2 of the complex aperture subsystem of the incident excitation electromagnetic wave; (2) a propagation channel between the right port Port3 of the complex aperture subsystem and the load port PortA of the multi-layer PCB; the nodes include the excitation port Port1, the complex aperture subsystem, and the load port PortA of the multi-layer PCB.

4. The method for rapidly evaluating S parameters of a multi-layer PCB port in a multi-stage waveguide structure according to claim 1, wherein: The overall propagation equation of the system in step S3 is: Wherein, γ represents the propagation constant of the outer waveguide; d1 represents the propagation distance of the electromagnetic field in the outer waveguide, that is, the length from the front panel of the outer waveguide to the front panel of the complex aperture subsystem; Represents the reflection coefficient of Port4 in the PCB subsystem; It represents the forward transmission coefficient under the excitation of Port4 in the PCB subsystem; represents the reverse transmission coefficient under the excitation of PortA in the PCB subsystem; Represents the reflection coefficient of PortA in the PCB subsystem; When the signal conduit is the propagation channel between the right port Port3 of the complex aperture subsystem and the load port PortA of the multilayer PCB, the scattering parameters of the multilayer PCB subsystem are calculated using numerical simulation software, thereby obtaining the propagation equation of the signal conduit.

5. The method for rapidly evaluating S parameters of a multi-layer PCB port in a multi-level waveguide structure according to claim 1, wherein: The overall scattering equation of the system in step S4 is: Where ρ1 represents the scattering parameter of node J1; represents the reflection coefficient of Port2 in the complex hole-slit subsystem; represents the forward transmission coefficient under Port2 excitation in the complex pore-slit subsystem; represents the reverse transmission coefficient under Port3 excitation in the complex hole-slit subsystem; represents the reflection coefficient of Port3 in the complex hole-slit subsystem; When the reflection node is the excitation port Port1, assuming that the excitation port has no reflection, ρ1=0; When the reflection node is a complex hole-slot subsystem, the scattering parameters of the complex hole-slot subsystem are calculated by numerical simulation software, and the scattering equation at the reflection node is established; When the reflection node is the multi-layer PCB port PortA, a scattering equation at the reflection node is established based on the numerical data calculated in step S3.

6. The method for rapidly evaluating S parameters of a multi-layer PCB port in a multi-level waveguide structure according to claim 1, wherein: The modified BLT equation of the system in step 5 is: Among them, V i,j Represents the signal pipeline T i Upper node T j The voltage at .

7. The method for rapidly evaluating S parameters of a multi-layer PCB port in a multi-stage waveguide structure according to claim 1, wherein: The calculation method described in step S6 is: solve the modified BLT equation of the system to obtain the voltage vector V of each reflection node = [V 1,1 V 1,2 V 2,2 V 2,3 ] T , Solving the modified BLT equation, we obtain the voltage of the multilayer PCB port PortA as: The voltage of the excitation port Port1 is: Then the normalized S parameter is S A1 =20 log 10 (V 2,3 / V 1,1 ); Among them, A and B have no specific physical meaning. To facilitate the calculation, they are intermediate parameters introduced. The specific expressions of A and B are:

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