EMC simulation method based on finite element-boundary element hybrid algorithm

Abstract

The invention provides an EMC (Electro Magnetic Compatibility) simulation method based on a finite element-boundary element hybrid algorithm, which comprises the following steps of: carrying out joint simulation on a finite element algorithm and a boundary element algorithm, carrying out full-wave simulation in an area near single equipment by adopting the finite element algorithm, and calculating electromagnetic interaction between the equipment through the boundary element method. As the boundary element method only needs to consider surface grids of the area nearby single equipment, the total grid number is greatly reduced, and the technical scheme has remarkable advantages when being used for a finite element-boundary element coupling algorithm for electromagnetic compatibility system-level radiation interference simulation.

Description

Technical Field

[0001] The present invention relates to the technical field of electromagnetic compatibility simulation design of electronic equipment, and is specifically applied to electromagnetic interference simulation between system-level devices, and specifically relates to an EMC simulation method based on a finite element-boundary element hybrid algorithm. Background Art

[0002] Electromagnetic field simulation algorithms can be divided into quasi-static algorithms, full-wave algorithms for solving wave equations, and high-frequency approximate algorithms based on the calculation scale. When the solution area is much smaller than the wavelength, the wave characteristics of the electromagnetic field are ignored, and the quasi-static algorithm should be used; when the solution area size is comparable to the wavelength, a strict full-wave algorithm is used; when the solution area size is much larger than the wavelength, due to the limitation of the computer's computing power, approximate high-frequency electromagnetic algorithms such as geometric optics and diffraction theory are used.

[0003] The current mainstream electromagnetic simulation full-wave algorithms include boundary element method (moment method), finite element method, finite difference method and other methods. Based on these algorithms, a series of commercial software have been developed, such as COMSOL, HFSS, FEKO and FDTD. COMSOL is a multi-physics field simulation commercial software, which contains a variety of simulation algorithms such as finite element method, finite volume method, boundary element method, and has developed different physical field calculation modules for different physical problems. HFSS is an electromagnetic simulation software developed by Ansys, mainly based on finite element algorithm. FEKO is an electromagnetic simulation commercial software developed based on the moment method, mainly for radio frequency electromagnetic simulation, such as the electromagnetic emission performance simulation of antennas. FDTD is a commercial software developed based on the finite difference method, with high computational efficiency, but the grid processing capability for complex and fine models is still insufficient. Summary of the invention

[0004] The technical problem to be solved by the technical solution of the present invention is: since system-level electromagnetic compatibility simulation usually takes into account the electromagnetic coupling problem between multiple devices, there is a certain distance between devices. When the distance is much larger than the wavelength, the finite element algorithm cannot simulate the large-scale space electromagnetic radiation problem. The full-wave algorithm needs to ensure that the spatial grid size is less than 1 / 6 of the wavelength to ensure the convergence of the algorithm. Therefore, when the calculation area size is much larger than the wavelength, the number of grids increases sharply, exceeding the computing power of the computer. If a high-frequency approximation algorithm is used, the approximate processing will cause the algorithm to be unable to calculate the electromagnetic field resonance effect inside the chassis device, and the calculation results cannot meet the accuracy requirements.

[0005] In order to solve the above technical problems, the technical solution of the present invention provides an EMC simulation method based on a finite element-boundary element hybrid algorithm, which is used to simulate a simulation area consisting of two chassis and an air domain surrounding the chassis, comprising the following steps:

[0006] Move the boundary of the air domain surrounding the chassis one wavelength away from the chassis;

[0007] Preset the x distance and y distance in the x-axis and y-axis directions of the two chassis;

[0008] Tetrahedral meshing was used for both chassis, and the air domain was divided into a cuboid containing six rectangular faces and quadrilateral meshing was used;

[0009] The six surfaces of the air domain of each chassis are used as the source surfaces of electromagnetic emission, and the finite element electromagnetic full-wave algorithm is used for calculation;

[0010] The electromagnetic field physical quantities of different air domain boundaries of the two chassis are coupled and solved using the electromagnetic field full-wave boundary element algorithm, and the results calculated using the finite element electromagnetic full-wave algorithm are combined for joint simulation to reduce the total number of grids.

[0011] Preferably, the air domain is divided into quadrilateral grids on the basis of ensuring that the grid size meets the 1 / 6 wavelength convergence condition.

[0012] Preferably, the electromagnetic field physical quantities corresponding to the grid cells of the source surface are used as unknown quantities to be solved in the boundary element method.

[0013] Preferably, the EMC simulation method comprises: obtaining a set of equations by discrete body units in the air domain according to the differential form of the wave equation, obtaining another set of equations by discrete surface units at the air domain boundary according to the boundary element method, and coupling the two sets of equations through electric field continuity boundary conditions.

[0014] The technical solution of the present invention proposes an EMC simulation method based on a finite element-boundary element hybrid algorithm, which jointly simulates the finite element algorithm and the boundary element algorithm, uses the finite element algorithm to perform full-wave simulation in the vicinity of a single device, and calculates the electromagnetic interaction between devices using the boundary element method. Since the boundary element method only needs to consider the surface mesh of the area near a single device, the total number of meshes is greatly reduced. The technical solution of the present invention has significant advantages in the finite element-boundary element coupling algorithm used for electromagnetic compatibility system-level radiation interference simulation. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is the layout diagram of the chassis equipment;

[0016] Figure 2 This is the hole and seam structure diagram of the chassis;

[0017] Figure 3 It is the chassis mesh and air domain mesh diagram;

[0018] Figure 4 is the spatial electric field distribution;

[0019] Figure 5 is the electric field distribution in the space near device 1;

[0020] Figure 6 is the electric field distribution of device 2;

[0021] Figure 7 is the electric field distribution of device 1. DETAILED DESCRIPTION

[0022] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall within the scope limited by the appended claims of the application equally.

[0023] like Figure 1 As shown in FIG. 1 , the embodiment of the present invention proposes an EMC simulation method based on a finite element-boundary element hybrid algorithm. The simulation area includes two chassis and an air domain surrounding the chassis. The boundary of the air domain surrounding the chassis is one wavelength away from the chassis. The distance between the two chassis devices in the x-axis direction is 3m, and the distance in the y-axis direction is 2m. The chassis devices surrounded by the air domain are divided into tetrahedral meshes. The mesh is as follows: Figure 2 , Figure 3 As shown, Figure 2 (a) and (b) are views of the chassis hole structure from different angles. Figure 3 (a) and (b) are different angle views of the chassis mesh and the air domain mesh. The air domain is a cuboid with six rectangular faces. On the basis of ensuring that the mesh size meets the 1 / 6 wavelength convergence condition, a structured quadrilateral mesh is used to effectively reduce the number of surface units.

[0024] The principle of the simulation algorithm is as follows: the finite element electromagnetic full-wave algorithm is used to calculate the air domain surrounding the chassis. The six surfaces of each air domain are used as the source surfaces of electromagnetic emission, and the electromagnetic field physical quantities corresponding to the grid units of these source surfaces become the unknown quantities to be solved in the boundary element method. The full-wave boundary element algorithm of the electromagnetic field couples and solves the electromagnetic field physical quantities at the boundaries of different air domains. The discrete body units in the air domain obtain a set of equations based on the differential form of the wave equation, and the discrete surface units at the boundaries of the air domain obtain another set of equations based on the boundary element method. The two sets of equations are coupled through the electric field continuity boundary condition, thereby constructing a fully coupled solution method.

[0025] The chassis model was simulated by the finite element-boundary element hybrid algorithm to obtain the corresponding data results. An equivalent current source was set in device 2, and the electromagnetic field distribution in the entire space was obtained by simulation, such as Figure 4 shown.

[0026] Figure 4The result is the result of the splicing of the finite element area and the boundary element calculation area. The values ​​within the white frame are the finite element calculation values, and the values ​​outside the frame are the boundary element calculation values. The two parts of the results are completely connected. Figure 4 It can be seen that device 2 generates strong radiation on the front and rear panels, and the radiated electromagnetic field generated by the fan vents on the rear panel acts on device 1 through long-distance transmission, and the front panel of device 1 produces obvious reflection and generates electromagnetic resonance inside the chassis. The electric field distribution in the space near device 1 is as follows: Figure 5 shown.

[0027] This method can also be used to obtain the detailed electromagnetic field distribution inside the device. The electric field distribution results of device 2 are as follows: Figure 6 shown.

[0028] from Figure 6 It can be seen that the chassis has obvious electromagnetic oscillation phenomenon and generates standing waves at a frequency of 2GHz, which enhances the radiation effect. Figure 7 The electric field distribution result inside the chassis device 1 is given. It can be seen from the figure that when the electromagnetic wave irradiates the front panel of the chassis, the electromagnetic wave leaked from the front panel oscillates inside the chassis, and an electric field enhancement effect occurs at the ventilation holes of the rear panel of the chassis.

[0029] By adopting the above technical solution, the problem of system-level electromagnetic coupling simulation in electromagnetic compatibility is solved. Ordinary electromagnetic full-wave finite element algorithms require a lot of computing resources and a lot of time to simulate such problems, and when the distance between devices is large, the computing memory cannot meet the requirements. A single boundary element algorithm is more difficult to calculate complex models inside the chassis. The holes and internal complex devices of the chassis need to be divided into a large number of grids. Since the solution matrix constructed by the boundary element method is a dense matrix, its efficiency is not as good as the finite element method. By combining the finite element method with the boundary element method, the advantages of the finite element in solving fine structures and the advantages of the boundary element in dealing with long-distance transmission problems are brought into play. The requirements for computer memory resources are reduced, and the time for simulation calculations is reduced. The efficiency of electromagnetic compatibility simulation is improved, bringing economic benefits to enterprises.

Claims

1. An EMC simulation method based on a finite element-boundary element hybrid algorithm, characterized in that: The method is used to simulate a simulation area consisting of two chassis and an air domain surrounding the chassis, including the following steps: Move the boundary of the air domain surrounding the chassis one wavelength away from the chassis; Preset the x distance and y distance in the x-axis and y-axis directions of the two chassis; Tetrahedral meshing was used for both chassis, and the air domain was divided into a cuboid containing six rectangular faces and quadrilateral meshing was used; The six surfaces of the air domain of each chassis are used as the source surfaces of electromagnetic emission, and the finite element electromagnetic full-wave algorithm is used for calculation; The electromagnetic field physical quantities of different air domain boundaries of the two chassis are coupled and solved using the electromagnetic field full-wave boundary element algorithm, and the results calculated using the finite element electromagnetic full-wave algorithm are combined for joint simulation to reduce the total number of grids.

2. The EMC simulation method based on the finite element-boundary element hybrid algorithm as claimed in claim 1, characterized in that: On the basis of ensuring that the grid size meets the 1 / 6 wavelength convergence condition, the air domain is divided into quadrilateral grids.

3. The EMC simulation method based on the finite element-boundary element hybrid algorithm as claimed in claim 1, characterized in that: The electromagnetic field physical quantities corresponding to the grid units of the source surface are used as unknown quantities to be solved in the boundary element method.

4. The EMC simulation method based on the finite element-boundary element hybrid algorithm as claimed in claim 1, characterized in that: The EMC simulation method comprises: obtaining a set of equations by using discrete body units in the air domain according to the differential form of wave equations, obtaining another set of equations by using the boundary element method for discrete surface units at the air domain boundary, and coupling the two sets of equations through electric field continuity boundary conditions.

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