A method for setting dielectric constant of electromagnetic simulation model

Abstract

The present application discloses a method for setting the dielectric constant of an electromagnetic simulation model, which relates to the field of simulation technology. The method prepares two test transmission lines with different line lengths on a substrate using a target material, measures the transmission line S parameters of the two test transmission lines with different line lengths, and combines the mathematical derivation relationship to obtain a continuous curve relationship between the dielectric constant and the frequency of the target material, that is, the dielectric constant of the target material in the electromagnetic simulation model can be set at all operating frequencies according to the continuous curve relationship. The method can accurately set the dielectric constant of the target material at each frequency point, improve the accuracy of material parameter setting, and thus improve the accuracy of simulation results.

Description

Technical Field

[0001] The present application relates to the field of simulation technology, and in particular to a method for setting a dielectric constant of an electromagnetic simulation model. Background Art

[0002] HFSS (High Frequency Structure Simulator) is a commonly used 3D electromagnetic simulation software. Due to its powerful functions, convenient operation and accurate results, it is recognized by the industry as the industrial standard for 3D electromagnetic field design and analysis. As a high-frequency field solver, HFSS has strict requirements on the setting of material parameters. The accuracy of material parameter settings directly affects the accuracy of the final simulation results.

[0003] When setting material parameters, a very important setting is the dielectric constant (Dk) of the material. The dielectric constant reflects the relative ability of the dielectric to store electrostatic energy in an electric field and is an inherent electrical property of the material itself. The dielectric constant is closely related to impedance. If the dielectric constant is not set accurately, it will cause impedance mismatch of the transmission line and increase reflection, which will eventually cause incorrect simulation results.

[0004] In addition to being related to the material, the dielectric constant is actually a value that changes with frequency. The higher the frequency, the smaller the dielectric constant value. However, at present, the dielectric constant of the material at several typical frequency points is generally provided by the manufacturer. Therefore, when simulating a construction project in HFSS, generally only a dielectric constant at a typical frequency point (such as the common setting of 1GHz) is set. The dielectric constant is used to achieve simulation at full frequency during simulation. The dielectric constant set in this way is obviously not accurate enough. Or there are other practices that set the dielectric constant at multiple typical frequency points provided by the manufacturer, and fit the dielectric constants of these typical frequency points into a curve through the fitting algorithm embedded in HFSS, and set the dielectric constant at full frequency according to this curve. This approach has improved accuracy compared to setting a typical frequency point, but the number of typical frequency points provided by the manufacturer is very limited, generally only 5 or 6 typical frequency points, so the accuracy of the curve obtained by fitting is also low, so the accuracy of the set dielectric constant is also low. Therefore, it is difficult for the existing method to accurately set the dielectric constant of the material at full frequency, resulting in the difficulty in guaranteeing the accuracy of the simulation results. Summary of the invention

[0005] In view of the above problems and technical requirements, the applicant has proposed a method for setting the dielectric constant of an electromagnetic simulation model. The technical solution of this application is as follows:

[0006] A method for setting a dielectric constant of an electromagnetic simulation model, the method comprising:

[0007] Prepare and form two test transmission lines with different line lengths, wherein the two test transmission lines are formed on a substrate with the same substrate parameters, and the material type in the substrate parameters is the same as the target material for which the dielectric constant of the electromagnetic simulation model is to be set;

[0008] Determine the wavelength λ of the signal in the target material based on the transmission line S-parameters of the two test transmission lines at the full operating frequency;

[0009] Substitute the wavelength λ of the signal in the target material into the relationship between the dielectric constant and the frequency to obtain a continuous curve relationship between the dielectric constant and the frequency of the target material;

[0010] Set the dielectric constant at all operating frequencies for target materials in electromagnetic simulation models using a continuous curve relationship.

[0011] A further technical solution is to determine the wavelength λ of the signal in the target material based on the transmission line S parameters of the two test transmission lines at the full operating frequency, including:

[0012] Calculate the phase difference of the transmission line S-parameters of two test transmission lines

[0013] Using the phase difference between two test transmission lines The wavelength λ of the signal in the target material is calculated using the line length difference ΔL.

[0014] A further technical solution is to use the phase difference of two test transmission lines The wavelength λ of the signal in the target material is calculated by using the line length difference ΔL, including:

[0015] according to The formula is based on the phase difference The wavelength λ is calculated from the line length difference ΔL.

[0016] A further technical solution is to obtain a continuous curve relationship between the dielectric constant and frequency of the target material, comprising:

[0017] Substitute the wavelength λ of the signal in the target material into the relationship between dielectric constant and frequency The dielectric constant ε of the target material is obtained r A continuous curve with frequency f, where c is the speed of light.

[0018] A further technical solution is to set the dielectric constant of the target material in the electromagnetic simulation model at all operating frequencies according to a continuous curve relationship, including:

[0019] The power approximation fitting method is used to fit the continuous curve relationship between the dielectric constant and frequency of the target material, and the form is obtained: The dielectric constant frequency curve is used to set the dielectric constant of the target material in the electromagnetic simulation model at the full operating frequency in the HFSS software according to the dielectric constant frequency curve, where k1, k2, and k3 are coefficients.

[0020] A further technical solution is that the thickness parameter in the substrate parameter is the same as the target material of the electromagnetic simulation model whose dielectric constant is to be set, and the continuous curve relationship between the dielectric constant and frequency of the target material obtained corresponds to the thickness parameter.

[0021] A further technical solution is that, for target materials of the same material type, the method further comprises:

[0022] A test transmission line is prepared using substrates with at least two different thickness parameters and a continuous curve relationship between the dielectric constant and the frequency is obtained, a continuous curve relationship corresponding to at least two different thickness parameters of the target material is obtained, and the dielectric constant of the electromagnetic simulation model at the full operating frequency is set under different thickness parameters according to the corresponding continuous curve relationship.

[0023] A further technical solution is that the thickness parameter is pp thickness, or the thickness parameter includes pp thickness and core thickness.

[0024] Its further technical solution is that the method further comprises:

[0025] The vector network analyzer uses the same fixture connector to connect two test transmission lines to obtain the transmission line S parameters. The phase difference of the transmission line S parameters of the two test transmission lines is Independent of the error parameters of the fixture connector.

[0026] A further technical solution is that the line width and line spacing of the two test transmission lines are equal.

[0027] The beneficial technical effects of this application are:

[0028] The present application discloses a method for setting the dielectric constant of an electromagnetic simulation model. The method measures the transmission line S parameters of two test transmission lines with different line lengths. Combined with the mathematical derivation relationship, the continuous curve relationship between the dielectric constant of the target material and the frequency at the full operating frequency can be obtained, so that the dielectric constant of the target material at each frequency point can be accurately set, the accuracy of the material parameter setting can be improved, and thus the accuracy of the simulation results can be improved.

[0029] According to the usage requirements of HFSS, the power approximation fitting method is used to fit the continuous curve relationship between the dielectric constant and frequency of the target material to obtain the dielectric constant frequency curve that can be directly used by HFSS, so as to reduce the process of setting multiple frequency points of the dielectric constant during simulation and make the simulation work faster.

[0030] This method can be implemented using Matlab programming, making the results more accurate and faster. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 is a method flow chart of a dielectric constant setting method in an embodiment.

[0032] Figure 2 is a flow chart of a method for setting a dielectric constant in another embodiment.

[0033] Figure 3 It is an experimental data diagram of the original continuous curve relationship and the fitted dielectric constant frequency curve in an example. DETAILED DESCRIPTION

[0034] The specific implementation of the present application is further described below in conjunction with the accompanying drawings.

[0035] This application discloses a method for setting the dielectric constant of an electromagnetic simulation model. Please refer to Figure 1 The method comprises the following steps:

[0036] Step 110: Prepare two test transmission lines with different line lengths.

[0037] The two test transmission lines are formed on a substrate having the same substrate parameters, and the material type in the substrate parameters is the same as the target material for which the dielectric constant of the electromagnetic simulation model is to be set. In addition to the material type, the substrate parameters also include stacking structure and thickness parameters. The two test transmission lines can be formed on the same substrate, or on two different substrates having the same substrate parameters.

[0038] If the surface layer is routed, the thickness parameter is pp thickness. If the inner layer is routed, the thickness parameter includes pp thickness and core thickness.

[0039] The two test transmission lines are respectively recorded as a long transmission line and a short transmission line. It is assumed that the length of the long transmission line is L1 and the length of the short transmission line is L2. Since the two test transmission lines have different lengths, there is a length difference ΔL=L1-L2 between the two. After the test transmission lines are prepared, the length difference ΔL is a known parameter.

[0040] The other parameters of the two test transmission lines except the line length are the same, including the line width and line spacing of the two test transmission lines are equal.

[0041] Step 120, based on the transmission line S parameters of the two test transmission lines at the full operating frequency, determine the wavelength λ of the signal in the target material. This step specifically includes the following steps, please refer to Figure 2 :

[0042] (1) Measure the transmission line S parameters of the two test transmission lines. Use a vector network analyzer to connect the two test transmission lines using the same fixture connector at the full operating frequency to obtain the transmission line S parameters.

[0043] (2) Calculate the phase difference of the transmission line S parameters of the two test transmission lines Since the two test transmission lines have the same fixture connector during the test, when the phase difference is obtained by subtracting the phase of the S parameters of the two transmission lines, the influence of the fixture connector can be offset, making the phase difference of the transmission line S parameters of the two test transmission lines Independent of the error parameters of the fixture connector.

[0044] (3) Using the phase difference between two test transmission lines The wavelength λ of the signal in the target material is calculated using the line length difference ΔL.

[0045] Phase difference between two test transmission lines The relationship with time t is:

[0046]

[0047] in, is the circular frequency, T is the period, and f is the frequency.

[0048] For two test transmission lines with different line lengths, the relationship between the line length difference ΔL and time t is:

[0049]

[0050] Where v is the transmission rate of the signal in the target material, and the relationship between the transmission rate v and the period T is: Combining equations (1) and (2), we can obtain:

[0051]

[0052] According to formula (3), the phase difference The wavelength λ of the signal in the target material is calculated by the line length difference ΔL.

[0053] Step 130 , substituting the wavelength λ of the signal in the target material into the relationship between the dielectric constant and the frequency, to obtain a continuous curve relationship between the dielectric constant and the frequency of the target material.

[0054] The speed of establishing electromagnetic field has the following formula:

[0055]

[0056] c is the speed of light and c = 2.99 × 10 8 m / s, ε rIndicates the dielectric constant of the target material.

[0057] According to the wave transmission principle, the relationship between wavelength λ and wave speed v is:

[0058] v=λ×f (5)

[0059] Where f is the frequency. Combining equations (4) and (5), we can obtain the dielectric constant ε including the wavelength λ r The relationship with frequency f is:

[0060]

[0061] Substituting the wavelength λ of the signal in the target material into equation (6), the dielectric constant ε of the target material can be obtained. r Continuous curve relationship with frequency f.

[0062] Step 140: Set the dielectric constant of the target material in the electromagnetic simulation model at all operating frequencies according to the continuous curve relationship. Since the method of the present application obtains a continuous curve relationship, the dielectric constant at each frequency point can be determined according to the continuous curve relationship.

[0063] In one embodiment, the dielectric constant is not set directly according to the continuous curve relationship obtained in step 130, but a power approximation fitting method is further used to perform curve fitting on the continuous curve relationship between the dielectric constant and frequency of the target material to obtain a curve of the form: The dielectric constant frequency curve is obtained, where k1, k2, and k3 are coefficients. Then, according to the obtained dielectric constant frequency curve, the dielectric constant of the target material in the electromagnetic simulation model is set at the full working frequency in the HFSS software. The form of the dielectric constant frequency curve obtained by fitting is consistent with the formula form that can be used in HFSS, which is more convenient for HFSS to be used to set the dielectric constant.

[0064] Based on the above method, considering that the dielectric constant of the PCB is also affected by the thickness parameter of the substrate, and conventional HFSS can only select the dielectric constant under one thickness parameter for setting, it will also lead to the problem of inaccurate setting. Therefore, in the above method, when preparing the test transmission line, the thickness parameter in the substrate parameter of the substrate used is also the same as the target material of the electromagnetic simulation model whose dielectric constant is to be set, so that the continuous curve relationship between the dielectric constant and the frequency of the target material obtained corresponds to the thickness parameter.

[0065] In order to meet the simulation needs under different thickness parameters, for the target material of the same material type, test transmission lines are prepared using substrates with at least two different thickness parameters and a continuous curve relationship between the dielectric constant and the frequency is obtained, thereby obtaining a continuous curve relationship of the target material corresponding to at least two different thickness parameters, and according to the corresponding continuous curve relationship, the dielectric constant of the electromagnetic simulation model at the full operating frequency is set under different thickness parameters.

[0066] For example, for a substrate of material type TU883C, assuming that the inner layer routing and thickness parameters include pp thickness and core thickness. One thickness parameter is pp thickness of 5 miles and core thickness of 4 miles. Under this thickness parameter, the continuous curve relationship 1 is obtained according to the method provided in this application. Another thickness parameter is pp thickness of 6 miles and core thickness of 5 miles. Under this thickness parameter, the continuous curve relationship 2 is obtained according to the method provided in this application. Then in a simulation project, when the pp thickness of the electromagnetic simulation model is 5 miles and the core thickness is 4 miles, the dielectric constant can be set according to the continuous curve relationship 1. When the electromagnetic simulation model is adjusted to a pp thickness of 6 miles and a core thickness of 5 miles, the dielectric constant can be set according to the continuous curve relationship 2 instead, so as to adapt to different thickness parameters.

[0067] In an example, assuming that the material type of the target material for which the dielectric constant of the electromagnetic simulation model is to be set is TU883C, the pp thickness is 5 miles, and the core thickness is 4 miles, the relevant parameters of the two prepared test transmission lines are as follows:

[0068]

[0069] The two test transmission lines were connected by a vector network analyzer using the same fixture connector at the full operating frequency of 10MHz-50GHz to obtain the transmission line S parameters, and the continuous curve relationship between the dielectric constant and frequency of TU883C in the full operating frequency range of 10MHz-50GHz was obtained according to the method provided in this application. Then the form of fitting is obtained: The dielectric constant frequency curve is shown in the following figure. Figure 3 shown.

[0070] The dielectric constant frequency curve obtained by fitting is analyzed by four error indicators. The first indicator is the sum of squares due to error (SSE). This parameter is calculated by calculating the sum of squares of the errors between the dielectric constant frequency curve and the continuous curve at each frequency point. The value range is [0,1] and the smaller the better. The smaller the value, the closer the dielectric constant frequency curve is to the original continuous curve. The second indicator is the coefficient of determination (R-square), which characterizes the quality of a dielectric constant frequency curve through the change of data. The value range is [0,1] and the larger the better. The closer to 1, the better the dielectric constant frequency curve can explain the continuous curve relationship. The third parameter is the degree-of-freedom adjusted R-square (Adjusted R-square). The closer to 1, the better the dielectric constant frequency curve matches the original continuous curve relationship. The fourth parameter is the root mean squared error (RMSE), which is also called the fitting standard deviation of the regression system. It is similar to the SSE effect. The smaller it is, the more successful the dielectric constant frequency curve prediction is. In this example, the values ​​of various error indicators obtained based on the relationship between the dielectric constant frequency curve and the original continuous curve are shown in the following table:

[0071] Error indicators SSE R-square Adjusted R-square RMSE value 0.06728 0.9921 0.9921 0.003669

[0072] It can be seen that both SSE and RMSE are close to 0, indicating that the dielectric constant frequency curve is close enough to the original continuous curve at each frequency point. R-square and Adjusted R-square are close to 1, indicating that the dielectric constant frequency curve can well explain the original continuous curve relationship. Therefore, the fitted dielectric constant frequency curve can completely fit the original continuous curve relationship and smooth out the fluctuation points well. The dielectric constant frequency curve finally obtained in this example is expressed as ε r =109.8×f -0.3023 +3.465, so that the dielectric constant of each frequency point in the full operating frequency range can be accurately used for parameter setting to obtain accurate simulation results.

[0073] The above is only a preferred embodiment of the present application, and the present application is not limited to the above embodiments. It is understood that other improvements and changes directly derived or associated by those skilled in the art without departing from the spirit and concept of the present application should be considered to be included in the protection scope of the present application.

Claims

1. A method for setting the dielectric constant of an electromagnetic simulation model, characterized in that: The method comprises: Prepare two test transmission lines with different line lengths, where the two test transmission lines are formed on a substrate with the same substrate parameters, and the material type in the substrate parameters is the same as the target material for which the dielectric constant of the electromagnetic simulation model is to be set; Determine the wavelength of the signal in the target material based on the transmission line S parameters of the two test transmission lines at the full operating frequency ; The wavelength of the signal in the target material Substituting the dielectric constant into the relationship between the dielectric constant and the frequency, the continuous curve relationship between the dielectric constant and the frequency of the target material is obtained, including: substituting the wavelength of the signal in the target material into Substitute the relationship between dielectric constant and frequency into The dielectric constant of the target material is obtained With frequency The continuous curve relationship of is the speed of light; The dielectric constant of the target material in the electromagnetic simulation model at the full working frequency is set according to the continuous curve relationship, including: using a power approximation fitting method to perform curve fitting on the continuous curve relationship between the dielectric constant and frequency of the target material to obtain a form of The dielectric constant frequency curve is set according to which the dielectric constant frequency curve is used to set the dielectric constant at the full working frequency for the target material in the electromagnetic simulation model in the HFSS software, wherein is the coefficient.

2. The method according to claim 1, characterized in that The wavelength of the signal in the target material is determined based on the transmission line S parameters of the two test transmission lines at the full operating frequency. ,include: Calculate the phase difference of the transmission line S-parameters of two test transmission lines ; Using the phase difference between two test transmission lines And line length difference Calculate the wavelength of the signal in the target material .

3. The method according to claim 2, characterized in that The phase difference between the two test transmission lines is used And line length difference Calculate the wavelength of the signal in the target material ,include: according to The formula is based on the phase difference Difference in line length Calculate the wavelength .

4. The method according to claim 1, characterized in that: The thickness parameter in the substrate parameter is the same as the target material of the electromagnetic simulation model whose dielectric constant is to be set, and the obtained continuous curve relationship between the dielectric constant and the frequency of the target material corresponds to the thickness parameter.

5. The method according to claim 1, characterized in that For target materials of the same material type, the method further comprises: A test transmission line is prepared using substrates with at least two different thickness parameters and a continuous curve relationship between the dielectric constant and the frequency is obtained, a continuous curve relationship corresponding to at least two different thickness parameters of the target material is obtained, and the dielectric constant of the electromagnetic simulation model at the full operating frequency is set under different thickness parameters according to the corresponding continuous curve relationship.

6. The method according to claim 4 or 5, characterized in that: The thickness parameter is pp thickness, or the thickness parameter includes pp thickness and core thickness.

7. The method according to claim 2, characterized in that: The method further comprises: The vector network analyzer uses the same fixture connector to connect two test transmission lines to obtain the transmission line S parameters. The phase difference of the transmission line S parameters of the two test transmission lines is It is independent of the error parameters of the fixture connector.

8. The method according to claim 1, characterized in that The line width and line spacing of the two test transmission lines are equal.

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