Numerical simulation method of electromagnetic energy absorption by human body in complex electromagnetic environment

Abstract

The present invention discloses a numerical simulation method for the absorption of electromagnetic energy by the human body in a complex electromagnetic environment, which mainly solves the problem that the existing methods are difficult to evaluate the absorption of electromagnetic energy by the human body in a complex electromagnetic environment. It includes: 1) establishing a geometric model of a complex electromagnetic environment and performing surface segmentation on it; 2) using the consistent diffraction theory to obtain the electric field strength at the location of the human body based on the information obtained by the surface segmentation; 3) establishing a high-precision human body geometric model and performing surface segmentation on it; 4) using a plane wave with the same electric field strength to irradiate the human body; 5) using a parallel multi-layer fast multipole algorithm to obtain the electric field distribution inside the human body model; 6) using the electric field distribution to calculate the specific absorption rate inside the model, and obtaining the SAR distribution of the entire human body model. The present invention can analyze the absorption of energy by people in a complex electromagnetic environment, quickly obtain accurate simulation data, and provide a reliable basis for the evaluation of the absorption of electromagnetic energy by people in a complex electromagnetic environment.

Description

Technical Field

[0001] The present invention belongs to the field of electrical technology, and further relates to computational electromagnetics, and specifically is a numerical simulation method for human body absorption of electromagnetic energy in a complex electromagnetic environment, which can be used to evaluate the electromagnetic energy absorption of a person in a complex electromagnetic environment. Background Art

[0002] Antennas are an essential component in the fields of radar and communications, and their main function is to transmit and receive electromagnetic waves. When the human body is near the antenna, part of the electromagnetic waves radiated by the antenna will be absorbed by human tissue, causing heating of human tissues and organs. If the temperature rise is too high, it may cause irreversible damage to the human body. Therefore, it is necessary to evaluate the electromagnetic energy absorbed by the human body. For ethical and evaluation accuracy considerations, it is obviously inappropriate to conduct experimental research on the absorption of electromagnetic energy by the human body. Therefore, numerical simulation technology is widely used in the evaluation of electromagnetic energy absorption by the human body. At present, numerical simulation technology is mainly used to evaluate the absorption of electromagnetic energy by the human body in the field of mobile communication technology. It is used to calculate the amount of energy absorbed by the human body from the electromagnetic waves radiated by the mobile phone antenna, so as to analyze the impact of mobile phone radiation on human health ([1] P.Bernardi, M.Cavagnaro, S.Pisa and E.Piuzzi, "Power absorption and temperature elevationsinduced in the human head by a dual-band monopole-helix antenna phone," IEEE Transactions on Microwave Theory and Techniques, vol.49, no.12, pp.2539-2546, Dec 2001. [2] Huang Zijian, Ni Jianping, Meng Cui, Xin Like, "FDTD simulation of human head absorbing radiation from mobile phones and wireless routers," Safety and Electromagnetic Compatibility, vol.01, pp.65-67, 2015.). Since mobile phones are very close to the human body when working, the influence of the human body's environment is usually ignored in numerical simulation. However, in the field of radar, radar antennas are usually installed on the outside of buildings, cars, ships, and airplanes, which are a certain distance away from the human body. At this time, when evaluating the human body's absorption of electromagnetic energy, the influence of the complex electromagnetic environment outside the human body must be considered. However, due to the large solution area and complex human body structure and materials when numerically simulating the integration of complex electromagnetic environment and human body, it is difficult to perform numerical simulation on this problem, and there are relatively few published studies in the literature. Summary of the invention

[0003] The purpose of the present invention is to address the deficiencies of the above-mentioned prior art, mainly to address the difficulty of numerical simulation of electromagnetic energy absorption by the human body in a complex electromagnetic environment, and to propose a hybrid method based on consistent diffraction theory and parallel multi-layer fast multipole algorithm. The consistent diffraction theory is used to simulate the complex electromagnetic environment to obtain the electric field strength at the location of the human body, and then the human body is irradiated with a plane wave with the same electric field strength, and the parallel multi-layer fast multipole algorithm is used to analyze the electric field distribution inside the human body, and then the specific absorption rate (SAR) inside the human body is calculated, thereby realizing the evaluation of electromagnetic energy absorption by people in a complex electromagnetic environment.

[0004] The idea of ​​the technical solution of the present invention is: considering that scenes such as buildings, cars, ships, and airplanes in complex electromagnetic environments have the characteristics of large calculation areas and relatively simple electromagnetic properties of the analysis object medium, while the electromagnetic properties of the medium of various organs of the human body are quite different, and usually need to meet higher calculation accuracy requirements; the present invention combines the consistent diffraction theory with the parallel multilayer fast multipole algorithm and applies it to the complex electromagnetic environment. First, the consistent diffraction theory is used to simulate the complex electromagnetic environment, and at the same time, the electric field distribution inside the human body is analyzed according to the parallel multilayer fast multipole algorithm, so as to analyze the specific situation of energy absorption by people in the electromagnetic environment, and realize the numerical simulation of electromagnetic energy absorption by the human body in the complex electromagnetic environment, which can provide a reliable basis for the evaluation of electromagnetic energy absorption by people in the complex electromagnetic environment.

[0005] The present invention achieves the above-mentioned purpose by the following specific steps:

[0006] (1) Establish a geometric model of complex electromagnetic environment;

[0007] (2) Use triangular units to perform surface segmentation on the complex electromagnetic environment geometric model to obtain the environment model grid discrete information file;

[0008] (3) Based on the discrete information of the environmental model grid, the consistent diffraction theory is used to perform electromagnetic simulation on the segmented model to obtain the electric field strength at the location of the human body in the complex electromagnetic environment;

[0009] (4) Establish a high-precision human body geometry model;

[0010] (5) Using triangular units to perform surface segmentation on the high-precision human body geometry model to obtain a human body model mesh discrete information file;

[0011] (6) irradiating the human body with a plane wave having the same electric field strength as that obtained in step (3);

[0012] (7) Based on the discrete information of the human body model grid, a parallel multi-layer fast multipole algorithm is used to perform electromagnetic simulation on a high-precision human body geometry model to obtain the electric field distribution inside the model;

[0013] (8) The electric field distribution inside the human body geometric model is used to calculate the specific absorption rate (SAR) inside the model, and the SAR distribution of the entire human body model is obtained, that is, the numerical simulation result of the human body's absorption of electromagnetic energy.

[0014] Compared with the prior art, the present invention has the following advantages:

[0015] First, since the present invention uses the consistent diffraction theory to simulate the complex electromagnetic environment, it can efficiently and accurately analyze the scene objects with relatively simple electromagnetic properties of the medium in the environment but large area, and the analysis process consumes little memory and has a fast calculation speed;

[0016] Second, because the present invention uses a parallel multi-layer fast multipole algorithm to analyze the electric field distribution inside the human body, it can accurately analyze complex objects with large differences in electromagnetic properties of various organ media in the human body's internal environment and small occupied areas, and can quickly and accurately solve the electromagnetic field distribution of complex media in small areas;

[0017] Third, the present invention combines the consistent diffraction theory and the parallel multi-layer fast multipole algorithm to comprehensively analyze the internal electric field distribution of the human body under plane wave irradiation, and collaboratively realizes the evaluation of electromagnetic energy absorption by people in complex electromagnetic environments. The obtained simulation data of electromagnetic energy absorption by the human body in a complex electromagnetic environment is accurate and reliable. This method has many advantages such as large analysis scenario, low memory consumption, high calculation accuracy and efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 Flow chart for realizing the method of the present invention;

[0019] Figure 2 A schematic diagram of a complex electromagnetic environment model established in the present invention;

[0020] Figure 3 A schematic diagram of electric field distribution in a sensitive area of ​​a complex electromagnetic environment in the present invention;

[0021] Figure 4 It is a schematic diagram of the high-precision human body geometric model in the present invention;

[0022] Figure 5 Schematic diagram of SAR distribution of the human body model in the present invention. DETAILED DESCRIPTION

[0023] The present invention is further described in detail below in conjunction with the accompanying drawings.

[0024] Reference Figure 1The implementation steps of the present invention are as follows:

[0025] The first step is to establish a geometric model of the complex electromagnetic environment.

[0026] The geometric model of the entire complex electromagnetic environment is established by using commercial software such as FEKO and CST. Figure 2 A complex electromagnetic environment consisting of multiple buildings, including ground and superstructures, is shown.

[0027] The second step is to perform surface segmentation on the geometric model of the complex electromagnetic environment.

[0028] In this embodiment, the complex electromagnetic environment geometric model is faceted by triangular units to obtain an environment model mesh discretization information file, which includes at least the following information: triangular unit number, vertex number and vertex coordinates of each triangular unit, and material properties corresponding to each triangular unit. In this embodiment, the complex electromagnetic environment geometric model is faceted by triangular units, specifically, triangular mesh units are selected in the commercial software FEKO to perform spatial discretization on the established complex electromagnetic environment geometric model, and the complex electromagnetic environment model is discretized into a finite number of triangular units. At this time, the complex electromagnetic environment model is divided into a finite number of triangular units, and each triangular unit has its own global number and vertex number as well as vertex coordinates and material properties. The global number information of these triangular units, the vertex number information of each triangular unit and the vertex coordinate information, and the material property information of each triangular unit are saved for use in the consistent diffraction theory electromagnetic simulation analysis.

[0029] The third step is to use the consistent diffraction theory to perform electromagnetic simulation on the segmented model based on the discrete information of the environmental model grid to obtain the electric field strength at the human body in a complex electromagnetic environment. Specifically, the electric field distribution value of the entire human body area at the human body in a complex electromagnetic environment is calculated, and the electric field strength vector of the point where the maximum electric field amplitude of the human body is located is recorded.

[0030] Electromagnetic simulation analysis methods can be divided into high-frequency methods and low-frequency methods. Among them, the commonly used high-frequency methods include geometric optics (GO), geometric diffraction theory (GTD), physical optics (PO), physical diffraction theory (PTD), uniform diffraction theory (UTD), bouncing ray method (SBR), etc., and the commonly used low-frequency methods include time domain finite difference method (FDTD), finite element method (FEM), moment method (MoM), etc. High-frequency methods have the advantages of fast calculation speed and small storage requirements, but are not suitable for analyzing complex structures and media. Low-frequency methods have high calculation accuracy and are suitable for analyzing complex structures and media, but they are slow in calculation speed and consume a lot of memory. Since complex electromagnetic environments have the characteristics of large calculation areas and relatively simple structure and medium properties, this example uses the uniform diffraction theory (UTD) to calculate the electric field strength E(r) at the location of the human body in a complex electromagnetic environment.

[0031] The fourth step is to establish a high-precision human body geometry model.

[0032] like Figure 4 As shown in the figure, the establishment of a high-precision human body geometry model is based on the data in the human anatomy database, which contains the main tissues and organs of various parts of the human body, such as the brain, lungs, heart, liver, kidneys, bones, muscles, skin, etc.; in order to facilitate the subsequent use of the multi-layer fast multipole algorithm for electromagnetic simulation, the model of each tissue and organ established here is a closed surface.

[0033] The fifth step is to perform surface segmentation on the high-precision human body geometry model.

[0034] The high-precision human body geometry model is face-divided by using triangular units to obtain a human body model mesh discretization information file, which at least includes the following information: triangular unit number, vertex number and vertex coordinates of each triangular unit, and material properties corresponding to each triangular unit. In this embodiment, the high-precision human body geometry model is face-divided by using triangular units, specifically, the established high-precision human body geometry model is spatially discretized by using triangular mesh units in the commercial software FEKO, and the high-precision human body geometry model is discretized into a finite number of triangular units. At this time, each tissue and organ of the high-precision human body geometry model is divided into a finite number of triangular units, and each triangular unit has its own global number and vertex number as well as vertex coordinates and material properties. The global number information of these triangular units, the vertex number information of each triangular unit and the vertex coordinate information, and the material property information of each triangular unit are saved for use in parallel multi-layer fast multipole algorithm analysis.

[0035] The sixth step is to use the parallel multi-layer fast multipole algorithm to perform electromagnetic simulation on the high-precision human body model after segmentation to obtain the electric field distribution E inside the human body geometric model. body (r).

[0036] The multi-layer fast multipole algorithm is an accelerated algorithm of the moment method. It has the advantages of high precision of the moment method and can greatly reduce the computational complexity of the moment method, improve computational efficiency, and reduce computational resource consumption. The present invention also combines the message passing interface (MPI) parallel technology to further accelerate the multi-layer fast multipole algorithm, thereby further improving the efficiency of electromagnetic simulation of high-precision human body models.

[0037] When using the parallel multi-layer fast multipole algorithm to perform electromagnetic simulation on a high-precision human body model, a plane wave source is needed to illuminate the high-precision human body model. The electric field intensity vector of the plane wave source is equal to the electric field intensity vector obtained in the third step. At the same time, the electromagnetic simulation is completed in combination with the discrete information of the human body model grid to obtain the electric field distribution E inside the human body geometric model. body (r).

[0038] Step 7: Use the electric field distribution E inside the human body geometry model body (r) Calculate the specific absorption rate (SAR) inside the high-precision human body model, obtain the SAR distribution of the entire human body model, and evaluate the electromagnetic energy absorbed by people in complex electromagnetic environments.

[0039] Using the electric field distribution E inside the human body geometric model body (r) Calculate the specific absorption rate SAR inside the high-precision human body model. The calculation formula is:

[0040]

[0041] Where σ is the conductivity of human tissue, in S / m, and ρ is the density of human tissue, in kg / m 3 , E body (r) represents the electric field at point r inside the human body model.

[0042] The effect of the present invention is further described below in conjunction with simulation experiments.

[0043] 1. Simulation conditions:

[0044] The simulation experiment of the present invention is carried out in a hardware environment with a CPU main frequency of 3.0 GHz, a memory of 1 TB, a graphics card GTX1660, and a hard disk of 4 TB, and a software environment of Windows 10 and FEKO.

[0045] 2. Simulation content:

[0046] Establish complex electromagnetic environment models, such as Figure 2 As shown, the entire area consists of 5 buildings, among which a parabolic antenna is installed on the top of the leftmost building, radiating electromagnetic waves outward;

[0047] Firstly, the method of the present invention is used to analyze the electric field distribution and Figure 3 The electric field distribution in the area in front of the middle building is shown in the figure;

[0048] Assume that the human body is located at the point with the maximum field strength in the sensitive area, and record the field strength value at this point;

[0049] Establish high-precision human body geometry model, such as Figure 4 As shown; based on the method of the present invention, a plane wave with the same electric field strength is used to irradiate the human body, and the method of the present invention is used to analyze the electric field distribution inside the human body geometric model.

[0050] 3. Simulation results:

[0051] The experiment obtains the SAR distribution of the entire human body model, that is, the simulation experiment results are as follows Figure 5 shown; according to Figure 5 It can be seen that in a complex electromagnetic environment, the numerical situation of electromagnetic energy absorption by various parts of the human body is clearly displayed, and based on this result, the situation of electromagnetic energy absorption by people in a complex electromagnetic environment can be further evaluated. It can be seen that the method of the present invention can complete the numerical simulation of electromagnetic energy absorption by people in a complex electromagnetic environment and obtain specific and intuitive simulation data.

[0052] The above simulation analysis proves the correctness and effectiveness of the method proposed in the present invention.

[0053] Parts of the present invention that are not described in detail belong to common knowledge among those skilled in the art.

[0054] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Obviously, for professionals in this field, after understanding the content and principles of the present invention, they may make various modifications and changes in form and details without departing from the principles and structures of the present invention. However, these modifications and changes based on the ideas of the present invention are still within the scope of protection of the claims of the present invention.

Claims

1. A numerical simulation method for the absorption of electromagnetic energy by the human body in a complex electromagnetic environment, characterized in that: The steps include: (1) Establish a geometric model of complex electromagnetic environment; (2) Use triangular units to perform surface segmentation on the complex electromagnetic environment geometric model to obtain the environment model grid discrete information file; (3) Based on the discrete information of the environmental model grid, the consistent diffraction theory is used to perform electromagnetic simulation on the segmented model to obtain the electric field strength at the location of the human body in the complex electromagnetic environment; Specifically, it calculates the electric field distribution value of the entire human body area at the location of the person in a complex electromagnetic environment, and records the electric field intensity vector at the point where the maximum electric field amplitude of the human body is located; (4) Establish a high-precision human body geometry model; (5) Using triangular units to perform surface segmentation on the high-precision human body geometry model to obtain a human body model mesh discrete information file; (6) irradiating the human body with a plane wave having the same electric field strength as that obtained in step (3); (7) Based on the discrete information of the human body model grid, a parallel multi-layer fast multipole algorithm is used to perform electromagnetic simulation on a high-precision human body geometry model to obtain the electric field distribution inside the model; (8) The electric field distribution inside the human body geometric model is used to calculate the specific absorption rate (SAR) inside the model, and the SAR distribution of the entire human body model is obtained, that is, the numerical simulation result of the human body's absorption of electromagnetic energy.

2. The method according to claim 1, characterized in that: The establishment of the complex electromagnetic environment geometric model described in step (1) is completed in a three-dimensional full-wave electromagnetic simulation software.

3. The method according to claim 1, characterized in that: The environment model mesh discrete information file and the human body model mesh discrete information in steps (2) and (5) include at least the following information: triangle unit number, vertex number and vertex coordinates of each triangle unit, and material properties corresponding to each triangle unit.

4. The method according to claim 1, characterized in that: The establishment of the high-precision human body geometric model in step (4) is based on data in the human anatomy database, which includes the main tissues and organs of various parts of the human body.

5. The method according to claim 4, characterized in that: The models of each tissue and organ in the main tissue and organs of each part of the human body are closed surfaces.

6. The method according to claim 1, characterized in that: The specific absorption rate SAR within the calculation model described in step (8) is calculated using the following formula: Where σ is the conductivity of human tissue, in S / m; ρ is the density of human tissue, in kg / m 3 ; E body (r) represents the electric field at point r inside the human body model.

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