Improved coaxial line excitation source simulation method based on magnetic flow ring

Abstract

The application relates to an improved coaxial line excitation source simulation method based on a magnetic current loop. First, the electromagnetic boundary conditions of a conductor structure to be simulated are established, and then a coaxial line excitation source model is constructed. The annular aperture at the opening of the coaxial line is equivalent to a magnetic current loop, and equivalent magnetic current density and a corresponding excitation field distribution are generated according to the radial electric field distribution of the TEM main mode of the coaxial line. Then, the excitation field distribution is projected onto the triangular meshes and RWG basis functions of the inner conductor or the feed connection area to form a right end excitation vector of the moment method equation. Finally, the electromagnetic field integral equation is solved to obtain the equivalent current on the conductor surface, the port admittance parameter and the scattering parameter. The application can more accurately represent the aperture field distribution, the probe effect and the high-frequency phase change of the coaxial feed without manually establishing a complete coaxial line entity, can reduce the influence of unstable excitation end voltage on the simulation result, and can improve the consistency and modeling efficiency of the electromagnetic compatibility simulation of radio frequency devices, antennas and chips.

Description

Technical Field

[0001] This invention relates to the field of electromagnetic simulation technology, and in particular to an improved coaxial excitation source simulation method based on a magnetic flux loop, applicable to electromagnetic simulation software and systems that use the Method of Moments (MoM) to solve equations.

[0002] This invention can be used for electromagnetic simulation scenarios involving radio frequency devices, microwave circuits, patch antennas, package interconnects, chip electromagnetic compatibility analysis, and other scenarios requiring coaxial feeding or quasi-coaxial feeding equivalent modeling. Background Technology

[0003] In the design of radio frequency devices and antennas, electromagnetic simulation is an important tool for predicting performance and shortening the R&D cycle. The commonly used Method of Moments (MoM) requires, after discretizing the integral equation, to correctly fill in the excitation terms on the right side of the matrix equation. The accuracy of this filling directly determines whether the simulation results can match actual measurements. Therefore, the modeling method of the excitation source becomes a key factor affecting computational accuracy.

[0004] In RF circuit simulation, virtual probe structures are commonly used as voltage source excitation methods. Specifically, the reference plane of the power supply negative terminal is applied to a metal plate serving as the ground reference plane, and the power supply positive terminal is the excitation point on the antenna, thus forming a virtual vertical feed line from the ground to the antenna. By introducing basis functions at the pin locations, the diffusion of current flowing on the vertical pins onto the antenna is simulated. However, this simplified voltage source excitation method has shortcomings in practical applications: firstly, it ignores the physical effects of a real coaxial probe, causing the simulation results to deviate from reality; secondly, this method is susceptible to voltage fluctuations in practical applications, especially when the distance between the excitation positive and negative terminals is large, leading to voltage instability and consequently decreased simulation accuracy.

[0005] On the other hand, if a complete solid coaxial cable is manually created in the simulation model, it is necessary to construct the outer conductor, inner conductor, filling medium, transition connection surface, and port cross-section of the coaxial cable, and then perform detailed meshing on it. This not only increases the modeling complexity and the number of meshes, but may also significantly increase the solution scale, which is not conducive to rapid simulation in engineering software.

[0006] Therefore, there is an urgent need for a coaxial line excitation source simulation method that can balance physical accuracy and modeling efficiency. This method should be able to reflect the field distribution of the coaxial line master mode TEM wave at the opening, and also embed the method of moments excitation vector filling process in a simple equivalent manner, thereby improving the accuracy and engineering applicability of RF device, antenna and chip interconnect structure simulation. Summary of the Invention

[0007] The purpose of this invention is to address the shortcomings of existing technologies by providing an improved coaxial line excitation source simulation method based on a magnetic flux ring.

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] In a first aspect, the present invention provides an improved coaxial line excitation source simulation method based on a magnetic flux ring, comprising the following steps:

[0010] An electromagnetic simulation model of the object to be simulated is established, which includes conductor structure, material electromagnetic parameters, port connection relationships, and simulation boundary conditions. In the electromagnetic simulation model, the inner conductor connection object, outer conductor connection object, inner diameter, and outer diameter parameters of the coaxial line excitation source are determined.

[0011] A coaxial line excitation source model is constructed, which simulates the TEM wave field distribution of the coaxial line principal mode through a magnetic flux loop equivalent method;

[0012] The coaxial line excitation source model is modeled by discretizing the inner conductor surface with a triangular element mesh and filling the excitation matrix with the voltage distribution obtained based on the magnetic flux loop equivalent.

[0013] The discretized equivalent current is expanded using RWG basis functions to obtain the electric field integral equation that needs to be solved, and then the equivalent current on the conductor surface is obtained.

[0014] Under a preset port voltage condition, the port current and admittance parameters are extracted based on the equivalent current on the conductor surface, and the admittance parameters are converted into scattering parameters to complete the electromagnetic simulation under the coaxial line excitation source.

[0015] Preferably, the input parameters of the coaxial line excitation source model include the layer where the inner conductor is connected, the layer where the outer conductor is connected, and the inner and outer diameters of the coaxial line.

[0016] Preferably, the specific process of the magnetic flux ring equivalent is as follows:

[0017] Determine the connection end face and port normal of the coaxial line based on the inner conductor connection object and the outer conductor connection object;

[0018] The annular region between the inner and outer conductor boundaries at the opening of the coaxial line is regarded as an annular aperture closed by an ideal conductor. According to the equivalence principle, an equivalent magnetic flux density is established on this annular aperture as an excitation source.

[0019] Preferably, the tangential electric field of the TEM mode on the annular aperture is determined based on the port excitation voltage, the radial coordinate of the aperture, the inner radius of the coaxial line, and the outer radius of the coaxial line, and the tangential electric field is non-uniformly distributed along the radial coordinate.

[0020] Preferably, the specific process of filling the excitation vector includes:

[0021] Traverse the RWG basis functions of the surface of the structure to be simulated, and determine the supporting triangle pair of each RWG basis function and its geometric relationship with the coaxial inner conductor, the inner conductor connection pad or the feed transition region;

[0022] For the RWG basis function located within the influence region of the feed connection, calculate the area integral of its test function with the equivalent incident field;

[0023] The area integral is used as an element of the excitation vector on the right-hand side of the corresponding method of moments equation;

[0024] For RWG basis functions that are not within the influence region of the feed connection, corresponding excitation values ​​or zero excitation values ​​are assigned according to their interaction with the equivalent incident field.

[0025] As a preferred method, in the solution process of the method of moments, the RWG basis function is used to expand the equivalent current on the conductor surface to be solved, and the Galerkin method is used to discretize the electric field integral equation and the magnetic field integral equation respectively to construct the corresponding impedance matrix and excitation vector, and then solve the matrix equation to obtain the equivalent current on the conductor surface.

[0026] As a preferred embodiment, the integral equation is constructed in the following manner:

[0027] Based on the equivalence principle and the boundary conditions of the electromagnetic field, an integral equation is established based on the boundary conditions of the electric and magnetic fields, which includes physical quantities such as the incident electromagnetic field, the electromagnetic field generated by the equivalent source on the object surface, the unit normal vector out of the closed plane, and the current on the object surface.

[0028] Since the medium space is a uniform unbounded space, we further introduce wave impedance, wave number, angular frequency, standard Green's function, distance and position vector between the source point and the field point, imaginary unit, gradient operator, divergence operator, infinitesimal vector element of the source region, and unknowns to be solved, which constitute the linear operators L and K.

[0029] Substituting the L operator and the K operator into the integral equation, we obtain the final forms of the electric field integral equation and the magnetic field integral equation.

[0030] As a preferred option, the unknown current function on the surface of the object is expanded within the defined region specified by the L operator using RWG basis functions, and the unknown current on the surface of the target object is expressed as a linear combination of RWG basis functions, thus obtaining the current expansion formula.

[0031] Then, the electric field integral equation is solved, and the current expansion is substituted into the electric field integral equation to obtain the discrete form of the electric field integral equation. The Galerkin method is used to test the equation with the RWG basis function as the test function, and the discrete linear equation system is obtained.

[0032] The system of equations is rewritten in matrix form, where the impedance matrix is ​​a square matrix whose elements are integrals of the RWG basis functions; the current vector is an unknown current coefficient vector; and the voltage vector is determined by the excitation source.

[0033] For the magnetic field integral equation, the RWG basis function is also used as the expansion function, and the Galerkin method is used for verification to obtain the corresponding matrix equation;

[0034] Under constant voltage conditions, the admittance parameters are extracted from the solved current vector and converted into scattering parameters to complete the simulation.

[0035] Secondly, the present invention provides an improved coaxial line excitation source simulation system based on a magnetic flux ring for implementing the above method, comprising the following modules:

[0036] The model building module is used to model the object to be simulated in a set electromagnetic parameter space and establish electromagnetic field boundary conditions based on the ideal conductor assumption.

[0037] The coaxial line excitation source modeling module constructs a coaxial line excitation source model based on the magnetic flux ring equivalent principle.

[0038] The simulation solution module is used to perform triangular element meshing on the inner conductor surface of the coaxial line excitation source model, discretize the equivalent current using RWG basis functions, construct and solve the electromagnetic field integral equation, calculate the admittance parameter based on the current vector obtained from the solution, and convert it to obtain the S-scattering parameter.

[0039] Thirdly, the present invention provides a computer-readable storage medium having a computer program stored thereon, which, when executed in a computer, causes the computer to perform the method described thereon.

[0040] The beneficial effects of this invention are:

[0041] Compared to traditional virtual probe voltage excitation methods, the method of this invention can better simulate the process of phase change with space when voltage is transmitted in a metal feeder. Compared with single-point or local virtual probe voltage sources, it can more realistically characterize the coaxial feed boundary.

[0042] This invention can be used in conjunction with the electric field integral equation, magnetic field integral equation, or mixed field integral equation in the method of moments. It can also be extended to the extraction process of multi-port admittance matrix and scattering parameter matrix, and has strong software integration and engineering applicability.

[0043] Furthermore, compared to other commercial software that requires manual modeling of coaxial cable models, this method only requires setting the layer where the inner conductor is connected, the layer where the outer conductor is connected, and the size of the inner and outer diameters in the software. It can then automatically generate an equivalent coaxial cable excitation source within the simulation software, significantly improving efficiency. Attached Figure Description

[0044] Figure 1 This is a schematic diagram showing the connection relationship between the coaxial excitation source and the metal layer of the present invention.

[0045] Figure 2 This is a three-dimensional model diagram of the slot-coupled feed patch array model provided in the embodiment of the present invention; wherein, the brown T-shaped metal line at the top is the feed structure, the blue rectangular metal surface in the middle is the finite grounding plane with a slot, the red periodic metal patch at the bottom is the array structure, and the yellow vertical metal on the left is the coaxial line excitation source connection structure.

[0046] Figure 3 This is a schematic diagram of the layer information for a slit-coupled fed patch array model.

[0047] Figure 4 This is a schematic diagram of the mesh generation for a slit-coupled feed patch array model.

[0048] Figure 5 This is a comparison chart of the calculation results of the present invention, the calculation results of the virtual port, and the calculation results of manually establishing a coaxial port. Detailed Implementation

[0049] The present invention will be further described below with reference to the accompanying drawings.

[0050] An improved coaxial line excitation source simulation method based on a magnetic flux loop includes the following steps:

[0051] Step (1), with electromagnetic parameters as In the medium space, the object is considered to be in the incident field. An ideal conductor under illumination; due to the ideal properties of the conductor, its internal electric field and magnetic field Both are zero; in the outer region of the conductor, the electric field and magnetic field are respectively zero. , ; Let be the dielectric constant of the medium space. Let be the permeability of the medium space;

[0052] Step (2): Construct a coaxial excitation source model using a magnetic flux ring equivalent. Connect the inner conductor to the bottom of the antenna and the outer conductor to the ground. Consider only TEM wave transmission and set the parameters for the inner conductor layer, outer conductor layer, inner diameter, and outer diameter. Figure 2As shown, the brown T-shaped metal line at the top is the power supply structure, the blue rectangular metal surface in the middle is a finite grounding plane with slits, the red periodic metal patch at the bottom is the array structure, and the yellow vertical metal on the left is the conductor connection structure of the coaxial excitation source. Figure 3 This represents the layered information structure of the model.

[0053] Step (2) is as follows:

[0054] To preserve the structural characteristics and feeding electromagnetic properties of a real coaxial physical probe in electromagnetic simulation and reduce simulation errors introduced by neglecting the probe effect in traditional virtual probe excitation, this invention proposes an improved coaxial line excitation source simulation method based on magnetic flux loop equivalence. The Magnetic Frill excitation method commonly used in antenna simulation is applied to chip simulation, with the excitation model being a coaxial line, referred to as the coaxial line excitation source. Because coaxial line excitation in chip simulation can convert the effect of a magnetic flux loop into the effect of an electric field, equivalent to the entire metal transmission line, the electric field distribution from the reference ground to the antenna is a steadily decreasing value, which can better simulate voltage transmission fluctuations.

[0055] The coaxial line excitation source is formed by the equivalent magnetic flux loop. The formation principle of the magnetic flux loop model can be intuitively understood through the coaxial line-fed monopole model. The monopole antenna can be viewed as a structure where the inner conductor of the coaxial line is directly connected to the bottom of the antenna, while the outer conductor is connected to the ground or other type of ground plane. The coaxial line excitation source model simulates the field distribution of the coaxial line's dominant mode using a magnetic flux loop. Here, we only consider TEM (Transverse Electric and Magnetic) wave transmission, with a dielectric filling the space between the inner and outer conductors, and the coaxial line along... Axis placement;

[0056] According to the equivalence principle, when the gap at the opening of a coaxial line is closed by a metal conductor, the metal conductor forms a continuous conductive surface. Since the metal conductor is an ideal conductor, electric field lines terminate on this surface and cannot radiate outwards through the gap. Therefore, the electric field strength on the gap surface is zero, and there is no equivalent surface current. However, magnetic field lines are different. Magnetic field lines can pass through the gap, so a magnetic field exists on the gap surface. Therefore, an equivalent magnetic flux ring model is used to represent the excitation source in the annular aperture of the coaxial line.

[0057] The annular aperture is located on the coaxial opening section. This represents the radial distance from the field point to the central axis of the coaxial line, satisfying... , and These represent the inner conductor radius and the outer conductor inner radius of the coaxial line, respectively.

[0058] On the annular aperture, the tangential electric field, transmitted along the coaxial line in TEM mode, is represented as follows:

[0059] Formula (1)

[0060] In the formula, This indicates the radial distance from the center axis of the coaxial line on the annular aperture. TEM mode electric field at the location, This represents the port voltage provided by the excitation source. This represents the radial unit vector pointing from the inner conductor to the outer conductor. This is the normalization factor for the radial electric field along the coaxial line. This is the voltage distribution factor when the source impedance and load impedance are matched, and this expression applies to... The annular medium region.

[0061] The equivalent magnetic flux density over the annular aperture is expressed as:

[0062] Formula (2)

[0063] In the formula, This represents the surface magnetic flux density at the annular aperture, obtained by equivalent magnetic flux rings. Represents the unit vector along the coaxial line. Represents a circumferential unit vector. This represents the port voltage provided by the excitation source. This is the normalization factor for the radial electric field along the coaxial line.

[0064] The field distribution generated on the surface of the conductor metal within the coaxial line, according to the magnetic flux density formula, is as follows:

[0065]

[0066] Formula (3)

[0067] In the formula, This represents the axial electric field component generated by the equivalent magnetic flux ring on the coaxial surface. This represents the axial equivalent length of the coaxial line excitation source. and These represent the axial coordinates and circumferential angular coordinates of the field point, respectively. Indicates the medium wavenumber. This represents the distance from the field point to the radius of the inner conductor. It is the imaginary unit.

[0068] The field generated on the surface of the coaxial line can be approximated as: In a coordinate system, the above equation can be transformed into:

[0069] Formula (4)

[0070] In the formula, This represents the distance from the field point to the boundary of the inner conductor of the coaxial line. .

[0071] Based on the equivalent magnetic flux density, the axial equivalent incident electric field generated by the coaxial excitation source on the metal surface can be obtained. This electric field is used to characterize the field difference distribution formed by the boundaries of the inner and outer conductors of the coaxial line, and participates in the assembly of the right-hand excitation vector as the incident excitation field in the electric field integral equation of the method of moments.

[0072] When using a coaxial cable as the excitation source as the port, the feed model is much more complex than the virtual feed model, requiring consideration of the selection of inner and outer diameters and the filling of the internal dielectric. All RWG (Rao-Wilton-Glisson) basis functions formed after network partitioning on the coaxial cable core will have voltage values; none will be zero. Furthermore, the ratio of the inner to outer diameter also affects the coaxial cable's transmission performance and impedance matching characteristics. Therefore, multiple factors need to be comprehensively considered when designing coaxial cables.

[0073] Step (3): Model the coaxial line excitation source model. The inner conductor surface structure is discretized using triangular elements (e.g., Figure 4 (As shown); the voltage distribution on the surface of the inner conductor is obtained by equivalent magnetic flux loop, and the excitation matrix is ​​filled. The equivalent current on the surface after mesh discretization is discretized using RWG basis functions, and Galerkin matching is used to obtain the matrix equation to be solved and solve the electromagnetic field inside the conductor.

[0074] Step (4): Excitation vector based on the moment method of filling the equivalent field of the magnetic flux loop.

[0075] In traditional virtual probe voltage sources, the excitation is often concentrated on a small number of basis functions or local geometric objects, which can easily cause discontinuities in the electric field distribution near the port. This invention uses an equivalent field of a magnetic flux loop to fill the right-hand side of the method of moments, so that the excitation term can reflect the non-uniform field distribution of the coaxial annular aperture.

[0076] Based on the aforementioned field distribution of the coaxial TEM mode and the equivalent relationship of the magnetic flux ring, the radial electric field at the annular aperture can be used to determine the relationship. Constructing equivalent magnetic flux density Furthermore, the equivalent incident electric field generated by this equivalent magnetic flux ring at the metal surface or Gaussian integration point is calculated, denoted as .therefore, The port excitation field generated by the equivalent coaxial line excitation source of the magnetic flux ring is used to participate in the assembly of the right-hand side of the electric field integral equation.

[0077] In one embodiment, the equivalent incident electric field can be taken as its electric field component along the coaxial axis, i.e.:

[0078] Formula (5)

[0079] in,

[0080] Formula (6)

[0081] In the formula, Indicates the equivalent field of the magnetic flux loop at the field point The axial electric field component generated at that location.

[0082] For the m-th RWG basis function If its supporting triangle is located within the influence region of the feed connection, then the excitation vector The m-th element can be determined by the following integral:

[0083] Formula (7)

[0084] In the formula, represents the supporting triangle pair of the m-th RWG basis function. This represents the equivalent incident electric field obtained from the magnetic flux ring and acting on the supporting region.

[0085] In practical implementation, formula (7) can be calculated using Gaussian integration or other numerical integration methods. For triangular elements close to the coaxial line opening, higher-order integration points or local refinement integration strategies can be used to enhance the numerical stability of the excitation distribution near the port. After discretization using Gaussian integration, formula (7) can be expressed as:

[0086] Formula (8)

[0087] When a certain RWG basis function does not belong to the influence region of the feed connection and the contribution of the magnetohydrodynamic loop equivalent field to its support region is negligible, the corresponding excitation vector element can be set to zero. For other ports or excitation forms that do not use coaxial line excitation sources, their excitation vector elements are not filled according to the magnetohydrodynamic loop equivalent field in this step, but are calculated according to the general form of the right-hand side of the electric field integral equation of the method of moments in subsequent steps.

[0088] Through the above processing, the port excitation using a coaxial excitation source is no longer limited to a single local voltage value, but is distributed across a set of RWG basis functions related to the physical field of the coaxial feed, thereby reducing the virtual probe model's dependence on the port grid and probe position. For other non-coaxial port excitations, the method of moments excitation vector under the corresponding port type is still used. Assembly is performed to ensure that different port excitation methods are handled uniformly within the same method of moments solution framework.

[0089] In steps (5) and (3), the impedance matrix is ​​constructed using the method of moments. and activation vector Solve the matrix equation The details are as follows:

[0090] Based on the equivalence principle and the boundary conditions of the electromagnetic field, we can obtain the integral equations established by the electric and magnetic field boundary conditions:

[0091] Formula (9-a)

[0092] Formula (9-b)

[0093] in , For the incident electromagnetic field, , Let S be the electromagnetic field generated by the equivalent source on the surface S of the object. It is the outward normal unit vector of the closed surface. The current on the surface of the object;

[0094] Since the equivalent problem space is a uniform unbounded space, we can obtain:

[0095] Formula (10-a)

[0096] Formula (10-b)

[0097] Formula (11)

[0098] Formula (12)

[0099] In the formula The wave impedance in the medium space, The wavenumber in the medium space, Angular frequency; Let Green's function be the standard Green's function in the medium space. The distance from the source point to the field point. , These represent the position vectors of the field point and the source point, respectively. represents an imaginary number; Represents the gradient operator. Denotes the divergence operator, Represents the surface vector infinitesimal element of the source region; This represents the unknown quantity (vector) to be solved.

[0100] Both the L operator and the K operator are linear operators. Substituting the L operator and the K operator into equation (9), we can obtain the final forms of the electric field integral equation and the magnetic field integral equation:

[0101] Formula (13-a)

[0102] Formula (13-b)

[0103] The unknown current function J on the surface of an object needs to be expanded according to a set of basis functions within the defined region specified by the L operator. This set of basis functions adopts the RWG basis functions, which can simulate the distribution of electric and magnetic currents on the surface of any object.

[0104] RWG basis functions are defined as follows:

[0105] Formula (14)

[0106] The two adjacent triangles involved in defining the RWG basis functions are defined as follows: and , Let be the common side of two triangles, and their areas are respectively and , This refers to the triangle vertex Points pointing inside the triangle The vector, and This refers to the triangle vertex Points pointing inside the triangle ;

[0107] The unknown current on the surface of the target object can be represented using RWG basis functions:

[0108] Formula (15)

[0109] in It is the unknown current expansion coefficient, representing the unknown quantity, and N represents the number of unknown quantities equal to the number of common sides of the triangle; Indicates the first in the field region One RWG basis function;

[0110] Among them, the method of moments solution for the electric field integral equation (13-a):

[0111] Substituting equation (15) into equation (13-a) yields the discrete electric field integral equation:

[0112] Formula (16)

[0113] in Indicates the first in the source region One RWG basis function;

[0114] Using the Galerkin method, with the RWG basis function as the test function, a weighted test is performed on the equation shown in formula (16), and the following results are obtained:

[0115] Formula (17)

[0116] in Let m be the m-th RWG basis function in the field region. Since it is always tangential to the surface of the object, it can be rewritten as follows:

[0117] Formula (18)

[0118] This avoids calculating the external normal vector of the object's surface; formula (18) can be written in matrix form:

[0119] Formula (19)

[0120] in Defined as a The matrix represents the impedance matrix in the method of moments; simultaneously, the column vectors... yes The column vector represents the current vector in the method of moments. yes The voltage vector in the method of moments;

[0121] matrix The OK Column elements ,matrix The row element They are respectively:

[0122] Formula (20)

[0123] Formula (21)

[0124] in, It is the nth basis function The triangle pair it belongs to (source triangle pair). It is the m-th basis function The triangle pair in which it is located (field triangle pair); Represents the surface vector element of the field region;

[0125] Among them, the method of moments solution for the magnetic field integral equation (13-b) is as follows:

[0126] Using RWG basis functions as expansion functions and Galilean's method for verification, we have:

[0127] Formula (22)

[0128] Rewritten in matrix form as formula (19), where, and The matrix elements are represented as follows:

[0129] Formula (23)

[0130] Formula (24)

[0131] in, It is the nth basis function The triangle pair it belongs to (source triangle pair). It is the m-th basis function The triangle pair (field triangle pair) it belongs to. This indicates the distance between the field point and the source point.

[0132] After solving formula (19), the equivalent current I on the conductor surface can be obtained. Under constant voltage conditions, the current I is characterized by the admittance parameter Y. By converting the admittance parameter Y, the S scattering parameter can be obtained.

[0133] Figure 5 This is a comparison chart of the S-parameter calculation results of the present invention, the results of the virtual port calculation, and the results of the manually constructed coaxial port calculation. It can be seen that the accuracy is very high. As shown in the figure, within the frequency range of 5GHz to 10GHz, the overall trend of the three methods is consistent, with a significant resonance valley value appearing around 7.8GHz. The calculation curve of the present invention basically overlaps with the result of the manually constructed coaxial port method, maintaining good consistency in the resonant frequency position, resonance depth, and high-frequency band variation trend. This indicates that the magnetohydrodynamic loop equivalent coaxial line excitation source constructed by the present invention can accurately characterize the feeding characteristics of the physical coaxial port. In contrast, the traditional virtual port method shows some deviation from the results of the manual coaxial port near the resonance valley value, indicating that its equivalence capability for the coaxial probe structure and feeding field distribution is relatively insufficient. Therefore, the present invention can obtain simulation results close to those of a physical coaxial port model without manually constructing a complete physical coaxial port, while maintaining high modeling efficiency.

[0134] The embodiments of the present invention have been described in detail above with reference to the examples, but the present invention is not limited to the described embodiments. For those skilled in the art, various changes, modifications, substitutions, and variations can be made to these embodiments, including components, without departing from the principles and spirit of the present invention, and these variations still fall within the protection scope of the present invention.

Claims

1. An improved coaxial line excitation source simulation method based on a magnetic flux loop, characterized in that, Includes the following steps: An electromagnetic simulation model of the object to be simulated is established, which includes conductor structure, material electromagnetic parameters, port connection relationships, and simulation boundary conditions. In the electromagnetic simulation model, the inner conductor connection object, outer conductor connection object, inner diameter, and outer diameter parameters of the coaxial line excitation source are determined. A coaxial line excitation source model is constructed, which simulates the TEM wave field distribution of the coaxial line principal mode through a magnetic flux loop equivalent method; The coaxial line excitation source model is modeled by discretizing the inner conductor surface with a triangular element mesh and filling the excitation vector with the voltage distribution obtained based on the magnetic flux loop equivalent. The specific process of filling the excitation vector includes: traversing the RWG basis functions on the surface of the structure to be simulated, determining the supporting triangle pair of each RWG basis function and its geometric relationship with the inner conductor of the coaxial line, the inner conductor connection pad, or the feed transition region; for RWG basis functions located within the feed connection influence region, calculating the area integral of its test function with the equivalent incident field; using the area integral as an element of the excitation vector on the right-hand side of the corresponding moment method equation; and assigning corresponding excitation values ​​or zero excitation values ​​to RWG basis functions that do not belong to the feed connection influence region according to their interaction with the equivalent incident field. The discretized equivalent current is expanded using RWG basis functions to obtain the electric field integral equation that needs to be solved, and then the equivalent current on the conductor surface is obtained. Under a preset port voltage condition, the port current and admittance parameters are extracted based on the equivalent current on the conductor surface, and the admittance parameters are converted into scattering parameters to complete the electromagnetic simulation under the coaxial line excitation source.

2. The improved coaxial line excitation source simulation method based on magnetic flux rings according to claim 1, characterized in that, The input parameters of the coaxial line excitation source model include the layer where the inner conductor is connected, the layer where the outer conductor is connected, and the inner and outer diameters of the coaxial line.

3. The improved coaxial line excitation source simulation method based on magnetic flux rings according to claim 1, characterized in that, The specific process of the equivalent magnetic flux ring is as follows: Determine the connection end face and port normal of the coaxial line based on the inner conductor connection object and the outer conductor connection object; The annular region between the inner and outer conductor boundaries at the opening of the coaxial line is regarded as an annular aperture closed by an ideal conductor. According to the equivalence principle, an equivalent magnetic flux density is established on this annular aperture as an excitation source.

4. The improved coaxial line excitation source simulation method based on magnetic flux rings according to claim 3, characterized in that, The tangential electric field of the TEM mode on the annular aperture is determined based on the port excitation voltage, the radial coordinate of the aperture, the inner radius of the coaxial line, and the outer radius of the coaxial line, and the tangential electric field is non-uniformly distributed along the radial coordinate.

5. The improved coaxial line excitation source simulation method based on magnetic flux rings according to claim 1, characterized in that, In the method of moments, the RWG basis functions are used to expand the equivalent current on the conductor surface to be solved, and the Galerkin method is used to discretize the electric field integral equation and the magnetic field integral equation respectively to construct the corresponding impedance matrix and excitation vector, and then solve the matrix equation to obtain the equivalent current on the conductor surface.

6. The improved coaxial line excitation source simulation method based on magnetic flux rings according to claim 5, characterized in that, The integral equation is constructed as follows: Based on the equivalence principle and the boundary conditions of the electromagnetic field, an integral equation is established based on the boundary conditions of the electric and magnetic fields, which includes physical quantities such as the incident electromagnetic field, the electromagnetic field generated by the equivalent source on the object surface, the unit normal vector out of the closed plane, and the current on the object surface. Since the medium space is a uniform unbounded space, we further introduce wave impedance, wave number, angular frequency, standard Green's function, distance and position vector between the source point and the field point, imaginary unit, gradient operator, divergence operator, infinitesimal vector element of the source region, and unknowns to be solved, which constitute the linear operators L and K. Substituting the L operator and the K operator into the integral equation, we obtain the final forms of the electric field integral equation and the magnetic field integral equation.

7. The improved coaxial line excitation source simulation method based on magnetic flux rings according to claim 6, characterized in that, The unknown current function on the surface of the object is expanded within the defined region specified by the L operator using RWG basis functions. The unknown current on the surface of the target object is expressed as a linear combination of RWG basis functions, and the current expansion is obtained. Then, the electric field integral equation is solved, and the current expansion is substituted into the electric field integral equation to obtain the discrete form of the electric field integral equation. The Galerkin method is used to test the equation with RWG basis functions as test functions, resulting in a discrete system of linear equations. The system of equations is rewritten in matrix form, where the impedance matrix is ​​a square matrix whose elements are integrals of the RWG basis functions; the current vector is an unknown current coefficient vector; and the voltage vector is determined by the excitation source. For the magnetic field integral equation, the RWG basis function is also used as the expansion function, and the Galerkin method is used for verification to obtain the corresponding matrix equation; Under constant voltage conditions, the admittance parameters are extracted from the solved current vector and converted into scattering parameters to complete the simulation.

8. A simulation system for an improved coaxial line excitation source based on a magnetic flux ring, implementing the method as described in any one of claims 1-7, comprising the following modules: The model building module is used to model the object to be simulated in a set electromagnetic parameter space and establish electromagnetic field boundary conditions based on the ideal conductor assumption. The coaxial line excitation source modeling module constructs a coaxial line excitation source model based on the magnetic flux ring equivalent principle. The simulation solution module is used to perform triangular element meshing on the inner conductor surface of the coaxial line excitation source model, discretize the equivalent current using RWG basis functions, construct and solve the electromagnetic field integral equation, calculate the admittance parameter based on the current vector obtained from the solution, and convert it to obtain the S-scattering parameter.

9. A computer-readable storage medium, characterized in that, It stores a computer program that, when executed in a computer, causes the computer to perform the method as described in any one of claims 1-7.

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