A method to quickly evaluate coupling parameters between PCBs

Abstract

The invention discloses a method for quickly evaluating coupling parameters between PCBs, by acquiring near-field magnetic field information of two PCBs that need to evaluate coupling parameters, establishing a magnetic dipole equivalent model of the two PCBs, confirming the relative position information of the two PCBs that need to evaluate coupling parameters, placing a radiation source PCB and a disturbed source PCB equivalent model, using an imaginary Huygens surface, surrounding the disturbed source PCB, removing the disturbed source PCB, dividing the imaginary Huygens surface, calculating the outer surface magnetic field of each face element, removing the radiation source PCB, placing the disturbed source PCB in the imaginary Huygens surface, dividing the imaginary Huygens surface, calculating the inner surface magnetic field of each face element, using the reciprocity principle, deriving the formula of the preceding term and the following term, and calculating the coupling parameters between the two PCBs. The method of the invention obtains the near-field magnetic field information of the two PCBs that need to evaluate coupling parameters, and can quickly evaluate the coupling parameters between the two PCBs, with the advantages of fast evaluation speed, not being restricted by test site and equipment conditions, and not requiring actual testing.

Description

Technical Field

[0001] The invention belongs to the field of electronic design, and in particular relates to a method for quickly evaluating coupling parameters between PCBs. Background Art

[0002] With the development of electronic technology, modern printed circuit boards are becoming more and more high-frequency, highly integrated and miniaturized. While the internal interference of the PCB system is serious, the external interference problem of the PCB is also becoming more and more serious. Since PCB is often a subsystem or an important component of a system, it plays the role of an interference source, emitting electromagnetic interference energy, and plays the role of a sensitive source, being interfered by surrounding equipment or systems. The coupling parameter is an important indicator for evaluating electromagnetic interference between PCBs.

[0003] In the later stages of PCB development, the evaluation of electromagnetic interference outside the PCB will be involved. The traditional method usually requires placing two working PCBs together and using a vector network analyzer for measurement. If the two existing PCBs are manufactured in different places, it is difficult to measure the coupling parameters between them.

[0004] The existing PCB near-field scanning technology is constantly developing, such as using a spectrum analyzer to scan the magnetic field amplitude three times for measurement, and using a vector grid analysis instrument for measurement, which makes it easy to obtain magnetic field data in the PCB near field.

[0005] Some patents have mentioned some methods for electromagnetic interference evaluation. For example, CN114065479A discloses a simulation method and computer equipment for electromagnetic interference evaluation based on the reciprocity principle. This method uses simulation methods, devices, chips, computer equipment, computer-readable storage media and computer program products to evaluate interference problems in advance in the early stages of terminal equipment development, determine whether the interference current exceeds a preset value, reduce the number of revisions of antenna product designs, shorten the development cycle, and reduce development costs. This method still has some shortcomings, such as being only applicable to electromagnetic interference evaluation of antennas and having a high reliance on simulation.

[0006] The existing method of obtaining coupling parameters between PCBs generally requires the experimental method to be carried out in a dark room, and requires two PCBs to be in the test environment at the same time, which is relatively complicated to implement. In addition, the calculation of coupling parameters can be obtained by full-wave simulation, but for the calculation of coupling parameters of two PCBs with complex structures, the early modeling and simulation calculations take a lot of time, and the calculation of some more complex PCBs is even impossible to complete. Summary of the invention

[0007] In order to solve the above technical problems, the present invention proposes a method for quickly evaluating the coupling parameters between PCBs. By acquiring the radiation near-field information of the PCB whose coupling parameters need to be measured and establishing a magnetic dipole equivalent model, the coupling parameters between two PCBs in the corresponding frequency band can be quickly evaluated based on the reciprocity principle.

[0008] The technical solution of the present invention is: a method for quickly evaluating coupling parameters between PCBs, and the specific steps are as follows:

[0009] Step S1, using full-wave simulation or near-field scanning to obtain near-field magnetic field information of two PCBs whose coupling parameters need to be evaluated;

[0010] Step S2, using a magnetic dipole equivalent modeling method to perform equivalent modeling on two PCBs;

[0011] Step S3, confirming the relative position information of the two PCBs whose coupling parameters need to be evaluated;

[0012] Step S4, establishing a mathematical model, placing equivalent models of the radiation source PCB and the victim PCB, using an imaginary Huygens plane to cover the victim PCB, removing the victim PCB, and calculating the tangential electromagnetic field of the equivalent model of the radiation source PCB on the outer surface of the Huygens plane;

[0013] The calculation method is: divide the Huygens surface into sufficiently small surface elements, calculate the tangential electromagnetic field on the outer surface of each surface element, and then obtain the tangential electromagnetic field on the outer surface of the Huygens.

[0014] Step S5, remove the equivalent model of the radiation source PCB, put the equivalent model of the victim PCB into the imaginary Huygens surface of step S4, and calculate the tangential electromagnetic field of the victim PCB on the inner surface of the Huygens surface;

[0015] The calculation method is: divide the Huygens surface into sufficiently small surface elements, calculate the tangential electromagnetic field on the inner surface of each surface element, and then obtain the tangential electromagnetic field of the Huygens inner surface.

[0016] Step S6: Calculate the coupling parameters between the two PCBs based on the tangential electromagnetic fields on the inner and outer surfaces of the hypothetical Huygens surfaces mentioned in Step S4 and Step S5 and using the reciprocity principle.

[0017] Furthermore, the near-field scanning method described in step S1 includes scanning using a spectrum analyzer, a vector network analyzer, an oscilloscope, and the like.

[0018] Furthermore, the near-field magnetic field information in step S1 includes magnetic field amplitude and phase information.

[0019] Furthermore, the magnetic dipole equivalent modeling method described in step S2 includes but is not limited to an artificial neural network algorithm, a least squares method, a regularization method, a genetic algorithm, and a particle swarm optimization algorithm.

[0020] Furthermore, the relative position described in step S3 includes size information and distance information of the two PCBs.

[0021] Furthermore, in step S6, the reciprocity principle is used, and the relationship between the tangential electromagnetic fields on the inner and outer surfaces of the Huygens plane in the preceding derivation problem and the following derivation problem is specifically:

[0022]

[0023] The superscript "fwd" indicates the forward problem, "rev" indicates the backward problem, J and M indicate the current source and magnetic current source, respectively. "a" indicates the excitation source port, and "c" indicates the imaginary Huygens surface. represents the tangential electric field on the inner surface of the hypothetical Huygens surface in the subsequent derivation, represents the current on the outer surface of the imaginary Huygens surface in the previous derivation, represents the tangential magnetic field on the inner surface of the hypothetical Huygens surface in the subsequent derivation, represents the current on the outer surface of the imaginary Huygens surface in the previous derivation, represents the electric field generated by the excitation source in the previous derivation, represents the current source of the excitation source in the subsequent derivation, represents the magnetic field generated by the excitation source in the previous derivation, represents the magnetic flux source of the excitation source in the subsequent derivation.

[0024] Furthermore, after using the basic relationship of the reciprocity principle and simplifying the formula, the electric field and magnetic field can be used to replace the current source and magnetic current source, and the coupling voltage can be obtained The calculation formula is:

[0025]

[0026] Among them, Z in , Z L They are the input impedance when excited by the disturbed source PCB (M-type microstrip line) and the load when excited by the radiating source PCB (early warning board), which are generally set to 50Ω. is the excitation voltage of the disturbed source PCB (M-type microstrip line), is the unit normal vector of each surface element after the Huygens box surface is divided, S cell is the area of ​​the surface element.

[0027] Furthermore, the coupling voltage is obtained Then, assume that the input voltage of the radiation source PCB (warning board) is U in , and then the basic coupling parameter calculation formula used is The coupling parameters can be calculated.

[0028] Beneficial effects of the present invention: The method of the present invention obtains the near-field magnetic field information of the two PCBs that need to evaluate the coupling parameters, establishes the magnetic dipole equivalent model of the two PCBs, confirms the relative position information of the two PCBs that need to evaluate the coupling parameters, puts in the equivalent model of the radiation source PCB and the disturbed source PCB, uses the imaginary Huygens surface to surround the disturbed source PCB, removes the disturbed source PCB, divides the imaginary Huygens surface, calculates the outer surface magnetic field of each face element, removes the radiation source PCB, puts the disturbed source PCB into the imaginary Huygens surface, divides the imaginary Huygens surface, calculates the inner surface magnetic field of each face element, uses the reciprocity principle, derives the formula of the antecedent and the posterior term, and calculates the coupling parameters between the two PCBs. The method of the present invention obtains the near-field magnetic field information of the two PCBs that need to evaluate the coupling parameters, and can quickly evaluate the coupling parameters between the two PCBs, and has the advantages of fast evaluation speed, no restrictions on test site and equipment conditions, and no need for actual testing. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a flow chart of a method for quickly evaluating coupling parameters between PCBs of the present invention.

[0030] Figure 2 It is an M-type microstrip line PCB simulation model in CST provided in an embodiment of the present invention.

[0031] Figure 3 It is a physical model of the early warning board PCB provided in the embodiment of the present invention.

[0032] Figure 4 It is an equivalent model of the M-type microstrip line PCB provided in the embodiment of the present invention.

[0033] Figure 5 It is an equivalent model of the early warning board PCB provided in the embodiment of the present invention.

[0034] Figure 6 It is a schematic diagram of the structure and relative positions of two PCBs for which coupling parameters need to be evaluated provided in an embodiment of the present invention.

[0035] Figure 7 This is the process of deriving the preceding term of the reciprocity principle provided in the embodiment of the present invention.

[0036] Figure 8 This is the process of deriving the latter term of the reciprocity principle provided in the embodiment of the present invention.

[0037] Fig. 9It is a schematic diagram comparing the calculation results of the method of the present invention provided in an embodiment of the present invention and the simulation results in the 1 GHz to 2 GHz frequency band.

[0038] Fig.10 It is a schematic diagram comparing the calculation results of the method of the present invention provided in an embodiment of the present invention and the simulation results in the 10 GHz to 12 GHz frequency band. DETAILED DESCRIPTION

[0039] The technical solution of the present invention is further described below in conjunction with the accompanying drawings.

[0040] like Figure 1 As shown, a flow chart of a method for quickly evaluating coupling parameters between PCBs of the present invention is shown, and the specific steps are as follows:

[0041] Step S1: using full-wave simulation or near-field scanning to obtain near-field magnetic field information of two PCBs whose coupling parameters need to be evaluated.

[0042] like Figure 2 As shown in the figure, the model of the M-type microstrip line established using the CST simulation method is used as the first PCB to directly extract its near-field magnetic field amplitude and phase information. Figure 3 The figure is a schematic diagram of a four-layer early warning board model. As the second PCB, it is scanned with a vector network analyzer and a magnetic field probe to obtain its near-field amplitude and phase information.

[0043] Step S2: Use the magnetic dipole equivalent modeling method to perform equivalent modeling on the two PCBs.

[0044] The M-type microstrip line is equivalently modeled using the least squares method and regularization method. The equivalent model is as follows: Figure 4 As shown in the figure, the warning board is modeled equivalently. The equivalent model is as follows Figure 5 shown.

[0045] Step S3: confirm the relative position information of the two PCBs whose coupling parameters need to be evaluated.

[0046] like Figure 6 As shown, in this embodiment, the two PCBs (M-type microstrip line and warning board) are symmetrical at the geometric center, and the edges are 10 mm apart.

[0047] Step S4, establish a mathematical model, put in the equivalent model of the radiation source PCB and the victim PCB, use the imaginary Huygens mask to cover the victim PCB (M-type microstrip line), remove the victim PCB (M-type microstrip line), perform the previous derivation, and calculate the tangential electromagnetic field of the equivalent model of the radiation source PCB (early warning board) on the outer surface of the Huygens plane.

[0048] Divide the Huygens surface into sufficiently small surface elements, calculate the tangential electromagnetic field on the outer surface of each surface element, and then obtain the tangential electromagnetic field on the outer surface of the Huygens surface. Figure 7 As shown, a hypothetical rectangular Huygens surface is used to completely shield the victim PCB (M-type microstrip line), and then the victim PCB (M-type microstrip line) is removed to excite the radiation source PCB (early warning board). The excitation electric field is recorded as The excitation magnetic field is denoted as An equivalent dipole model of the near-field radiation characteristics of the radiation source PCB (warning board) is established, and the radiation source PCB (warning board) is replaced by the equivalent dipole model. The Huygens surface is divided into sufficiently small surface elements, and the tangential electric field and tangential magnetic field on the outer surface of each surface element can be obtained by the equivalent dipole radiation electromagnetic field formula, which is recorded as

[0049] The mathematical model here can be implemented in environments such as MATLAB and C++.

[0050] Step S5, remove the radiation source PCB (early warning board), put the equivalent model of the victim PCB (M-type microstrip line) into the imaginary Huygens surface of step S4, perform the latter derivation, and calculate the tangential electromagnetic field of the victim PCB (M-type microstrip line) on the inner surface of the Huygens surface.

[0051] Divide the Huygens surface into sufficiently small surface elements, calculate the tangential electromagnetic field on the outer surface of each surface element, and then obtain the tangential electric field and tangential magnetic field on the inner surface of the Huygens surface. The process of the latter derivation is as follows Figure 8 As shown, remove the radiation source PCB (warning board), excite the disturbed source PCB (M-type microstrip line), and the excitation electric field is recorded as The excitation magnetic field is denoted as An equivalent dipole model of the near-field radiation characteristics of the victim PCB (M-type microstrip line) is established, and the victim PCB (M-type microstrip line) is replaced by the equivalent dipole model. On the same Huygens plane element as step S4, according to the equivalent dipole model of the victim PCB (M-type microstrip line), the surface tangential electric field in the Huygens plane can be obtained, which is recorded as The tangential magnetic field on the inner surface of the Huygens plane is obtained and recorded as

[0052] Step S6: Calculate the coupling parameters using the reciprocity principle.

[0053] The relationship between the tangential electromagnetic fields on the inner and outer surfaces of the Huygens plane in the former derivation problem in step S4 and the latter derivation problem in step S5 can be derived from the reciprocity theorem:

[0054]

[0055] The superscript "fwd" indicates the forward problem, "rev" indicates the backward problem, J and M indicate the current source and magnetic current source, respectively. "a" indicates the excitation source port, and "c" indicates the imaginary Huygens surface. represents the tangential electric field on the inner surface of the hypothetical Huygens surface in the subsequent derivation, represents the current on the outer surface of the imaginary Huygens surface in the previous derivation, represents the tangential magnetic field on the inner surface of the hypothetical Huygens surface in the subsequent derivation, represents the current on the outer surface of the imaginary Huygens surface in the previous derivation, represents the electric field generated by the excitation source in the previous derivation, represents the current source of the excitation source in the subsequent derivation, represents the magnetic field generated by the excitation source in the previous derivation, represents the magnetic flux source of the excitation source in the subsequent derivation.

[0056] The two terms on the left side of the equation for the tangential electromagnetic fields on the inner and outer surfaces of the Huygens plane can be expressed as:

[0057]

[0058]

[0059] In the formula, is the unit normal vector of each surface element after the Huygens box surface is divided, S cell is the area of ​​the surface element.

[0060] The two terms on the left side of the equation for the tangential electromagnetic fields on the inner and outer surfaces of the Huygens plane can be expressed by voltage U and current I on the right side:

[0061]

[0062]

[0063] Combining the above four formulas, the above relationship between the tangential electromagnetic fields on the inner and outer surfaces of the Huygens plane can finally be transformed into the following form:

[0064]

[0065] Using electric field and magnetic field to replace current source and magnetic current source, the coupling voltage can be obtained

[0066]

[0067] Among them, Z in , Z LThey are the input impedance when excited by the disturbed source PCB (M-type microstrip line) and the load when excited by the radiating source PCB (early warning board), which are generally set to 50Ω. is the excitation voltage of the disturbed source PCB (M-type microstrip line), which is 1V in this embodiment.

[0068] Assume that the input voltage of the radiation source PCB (warning board) is U in , and then the basic coupling parameter calculation formula The coupling parameters can be calculated.

[0069] This method is compared with the simulation results in CST software. Fig. 9 As shown in Figure 2, at 1 GHz to 2 GHz, the error between the analytical calculation method and the simulation calculation method does not exceed 2 dB; Fig.10 As shown, from 10GHz to 12GHz, the error between the analytical calculation method and the simulation calculation method does not exceed 3dB. The evaluation results of this invention well mark the two frequency points where the PCB coupling is serious, which fully demonstrates the feasibility of this method. In addition, on a computer with general configuration, the method of the present invention can complete the calculation and solution of the embodiment within ten minutes, while the CST simulation takes dozens of hours, which greatly shortens the evaluation time.

[0070] It can be seen from the above embodiments that, compared with the prior art, the method for quickly evaluating coupling parameters between PCBs of the present invention has the following advantages.

[0071] First, the method of the present invention has the advantage of not being limited by the test site and equipment conditions. The near-field magnetic field information can be obtained by using a device to scan the near-field of the PCB, can be obtained by full-wave simulation, and can be calculated by an analytical method. Only the near-field magnetic field information of the two PCBs needs to be known to evaluate the coupling parameters of the two PCBs using this method.

[0072] Second, the method of the present invention has the advantage of not requiring actual testing. Actual testing generally needs to be carried out in a darkroom, requires two manufactured PCBs to be in a test environment at the same time, and requires a large amount of professional testing equipment, which is very complicated to implement.

[0073] Third, the method of the present invention is fast and efficient. Compared with existing full-wave simulation software (such as CST, HFSS, etc.), for calculating the same frequency band for the same calculation object, the method of the present invention can complete the calculation and solution of the embodiment within ten minutes, while the full-wave simulation software requires dozens of hours, which greatly shortens the evaluation time.

[0074] Those skilled in the art will appreciate that the embodiments described herein are intended to help readers understand the principles of the present invention, and should be understood that the scope of protection of the present invention is not limited to such specific statements and embodiments. For those skilled in the art, the present invention may have various changes and variations. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of the claims of the present invention.

Claims

1. A method for quickly evaluating the coupling parameters between PCBs. The specific steps are as follows: Step S1, using full-wave simulation or near-field scanning to obtain near-field magnetic field information of two PCBs whose coupling parameters need to be evaluated; Step S2, using a magnetic dipole equivalent modeling method to perform equivalent modeling on two PCBs; Step S3, confirming the relative position information of the two PCBs whose coupling parameters need to be evaluated; Step S4, establishing a mathematical model, placing equivalent models of the radiation source PCB and the victim PCB, using an imaginary Huygens plane to cover the victim PCB, removing the victim PCB, and calculating the tangential electromagnetic field of the equivalent model of the radiation source PCB on the outer surface of the Huygens plane; Step S5, remove the radiation source PCB, put the equivalent model of the victim PCB into the imaginary Huygens surface of step S4, and calculate the tangential electromagnetic field of the victim PCB on the inner surface of the Huygens surface; Step S6, according to the tangential electromagnetic fields of the inner and outer surfaces of the imaginary Huygens surfaces mentioned in step S4 and step S5, using the reciprocity principle, calculating the coupling parameters between the two PCBs; The reciprocity principle described in step S6 is used. In the preceding derivation problem and the following derivation problem, the basic relationship of the reciprocity principle of the tangential electromagnetic field on the inner and outer surfaces of the Huygens plane is specifically: Where, the superscript "fwd" indicates the forward problem, "rev" indicates the backward problem, J and M indicate the current source and magnetic current source, respectively; "a" indicates the excitation source port, and "c" indicates the imaginary Huygens surface. represents the tangential electric field on the inner surface of the hypothetical Huygens surface in the subsequent derivation, represents the current on the outer surface of the imaginary Huygens surface in the previous derivation, represents the tangential magnetic field on the inner surface of the hypothetical Huygens surface in the subsequent derivation, represents the current on the outer surface of the imaginary Huygens surface in the previous derivation, represents the electric field generated by the excitation source in the previous derivation, represents the current source of the excitation source in the subsequent derivation, represents the magnetic field generated by the excitation source in the previous derivation, represents the magnetic current source of the excitation source in the subsequent derivation; After using the basic relationship of the reciprocity principle, the formula is simplified and the electric field and magnetic field are used to replace the current source and magnetic current source, then the coupling voltage The calculation formula is: Among them, Z in , Z L They are the input impedance when the disturbed PCB is excited and the load when the radiating PCB is excited. is the excitation voltage of the victim PCB, is the unit normal vector of each surface element after the Huygens box surface is divided, S cell is the area of ​​the surface element, represents the tangential magnetic field on the outer surface of the imaginary Huygens surface, represents the tangential electric field on the outer surface of the imaginary Huygens surface.

2. A method for rapidly evaluating coupling parameters between PCBs according to claim 1, It is characterized in that The near-field scanning method described in step S1 includes scanning using a spectrum analyzer, a vector network analyzer, or an oscilloscope.

3. A method for rapidly evaluating coupling parameters between PCBs according to claim 1, It is characterized in that The near-field magnetic field information in step S1 includes magnetic field amplitude and phase information.

4. A method for rapidly evaluating coupling parameters between PCBs according to claim 1, It is characterized in that The magnetic dipole equivalent modeling method described in step S2 is specifically an artificial neural network algorithm, a least squares method, a regularization method, a genetic algorithm, and a particle swarm optimization algorithm.

5. A method for rapidly evaluating coupling parameters between PCBs according to claim 1, It is characterized in that The relative position described in step S3 includes size information and distance information of the two PCBs.

6. A method for rapidly evaluating coupling parameters between PCBs according to claim 1, It is characterized in that The amplitude and phase information acquisition method of the near-field magnetic field of the PCB includes a vector grid analyzer electromagnetic field, a spectrum analyzer scanning amplitude near-field scanning method, or a CST, HFSS, FEKO electromagnetic simulation method.

7. A method for rapidly evaluating coupling parameters between PCBs according to claim 1, It is characterized in that The Huygens surface is specifically a surface of a cuboid, a surface of a sphere, or a surface of a tetrahedron, that is, a surface that can be easily divided into surface elements.

8. A method for rapidly evaluating coupling parameters between PCBs according to claim 1, It is characterized in that Get the coupling voltage Then, let the radiation source PCB input voltage be U in , then the basic coupling parameter calculation formula is The coupling parameters can be calculated.

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