Broadband shielding body based on multilayer structure

Abstract

The invention discloses a broadband shielding body based on a multilayer structure. The broadband shielding body comprises an upper-layer unit cell shielding structure, a middle-layer unit cell shielding structure and a lower-layer unit cell shielding structure, the upper-layer unit cell shielding structure is arranged on the upper layer of the middle-layer unit cell shielding structure; the lower-layer unit-cell shielding structure is arranged on the lower layer of the second unit-cell shielding structure, the design domain sizes of the unit-cell shielding structures are the same, the plane size of a shielding unit of the middle-layer unit-cell shielding structure is set as a reference, the side length of the middle-layer unit-cell shielding structure is defined as a * a, and on the basis, the size of a shielding unit of the upper-layer unit-cell shielding structure is set as 2a * 2a, each upper layer unit is ensured to cover the shielding units of the four middle layer unit cell shielding structures; the size of the shielding units of the bottom layer unit cell shielding structure is 4a * 4a, and the shielding units correspondingly cover the shielding units of the four upper layer unit cell shielding structures. And in combination with non-designable domain constraints, collaborative design of electromagnetic shielding and heat dissipation / wiring is realized.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of electromagnetism, and relates to a wide-band shielding body based on a multilayer structure. BACKGROUND

[0002] With the exponential increase in the integration level of modern electronic equipment systems, the electromagnetic environment presents the characteristics of wide frequency, high frequency and high intensity. The traditional single-layer shielding structure faces double challenges in coping with complex electromagnetic environments: firstly, the single impedance mismatch of the single-layer shielding structure cannot meet the wide-band shielding demand; and secondly, the dense shielding layer required by high reflection loss is in competition with the space layout of functional components such as heat dissipation channels and cable interfaces. Solving this problem is the key to the application. Through single-layer and multilayer topology optimization design, we hope to bring new breakthroughs and progress to the research and application in the related field. SUMMARY

[0003] To solve the above problems, the technical scheme adopted by the application is: a wide-band shielding body based on a multilayer structure, a unit cell shielding structure and a lower unit cell shielding structure. The upper unit cell shielding structure is arranged on the upper layer of the middle unit cell shielding structure. The lower unit cell shielding structure is arranged on the lower layer of the middle unit cell shielding structure.

[0004] Further, the design domain sizes of the upper unit cell shielding structure, the middle unit cell shielding structure and the lower unit cell shielding structure are the same, and the size of the shielding unit of the middle unit cell shielding structure is defined as the reference, with the side length being a x a. On this basis, the size of the shielding unit of the upper unit cell shielding structure is 2a x 2a, which ensures that each upper layer unit covers 4 shielding units of the middle unit cell shielding structure; and the size of the shielding unit of the bottom unit cell shielding structure is 4a x 4a, which corresponds to covering 4 shielding units of the upper unit cell shielding structure.

[0005] Further, the material of the shielding unit is selected from resin.

[0006] Further, the design optimization process of the middle upper unit cell shielding structure, the middle unit cell shielding structure and the lower unit cell shielding structure is the same, and specifically as follows: The design domain of the unit cell shielding structure is discretized into n subgrids through the topology combination of a plurality of shielding units, the position of each subgrid corresponds to a design variable, and the whole constitutes a one-dimensional vector X; each element x of the vector X i is discrete 0 or 1, which respectively represents whether a shielding unit is placed at the corresponding subgrid position; wherein i = 1, 2, …, n; if x i = 1, a shielding unit is placed at the grid; if x i= 0, the position is empty to form a local opening or channel; An overlapping connection region with a width of Δwide is arranged between adjacent shielding units.

[0007] Further: in the electromagnetic simulation process of the shielding body as follows: A plane wave with TE polarization is vertically incident to the surface of the intermediate layer unit cell shielding structure along the negative direction of the z axis, and frequency scanning is performed in the target frequency range [f L ,f H ] by using a discrete frequency sweeping method to obtain the transmission characteristics of the shielding structure at different frequencies; The shielding effectiveness SE of the shielding structure is evaluated by analyzing the transmission coefficient S 21 in the scattering parameters; The minimum shielding effectiveness SE(f) in the frequency interval [f L ,f H ] is taken as the optimization objective function; In the optimization, a volume constraint condition is introduced, and the state values of all elements xi of the one-dimensional vector X are summed and normalized to a unit volume , representing the relative volume fraction of the structure; this value needs to satisfy the preset upper limit of the volume fraction a ∈ (0, 1), and the total optimization problem is obtained.

[0008] Further, the expression of the total optimization problem is as follows:

[0009] Where: : design variable vector, representing the parameter set to be optimized; : the i-th design variable, which may represent the thickness, material type, arrangement order, etc. of each layer.

[0010] : the total number of design variables, that is, the number of layers or parameters.

[0011] : represents the transpose, here represents that X is a column vector.

[0012] : objective function, representing the shielding effectiveness function to be maximized.

[0013] : shielding effectiveness, which is a function of frequency f and design variable X.

[0014] : frequency range [f ​​​Within, take the minimum shielding effectiveness.

[0015] : indicates "subject to", that is, "satisfies the following constraints".

[0016] Design variables The average value.

[0017] : A constant representing the upper limit of the average value.

[0018] Furthermore: the BQPSO algorithm is adopted as the optimization algorithm to solve the optimization problem, and the objective function F( X ; SE The process is as follows: (1) Initialization parameters and population: Set initial parameters and generate an initial binary encoded population; (2) Automatic modeling and simulation: Evaluate the fitness of individuals based on their current particle position; (3) Fitness evaluation and particle update: Calculate the fitness value and update the particle state according to the algorithm rules; (4) Convergence judgment and result output: If the maximum number of iterations or the convergence condition is met, the optimal topology is output; otherwise, return to step (2) to continue iterating.

[0019] (5) Assess individual fitness based on current particle position.

[0020] Furthermore: the assessment of individual fitness is based on the transmission parameter S within the target frequency range of 2~20 GHz. 21 The simulation yielded the worst shielding effectiveness threshold SE. min accomplish.

[0021] Furthermore: When a specific region is restricted to an undesignable area during the optimization process, the encoding value of the shielding unit in the undesignable region is always 0. This unit is used for cable routing or button placement and does not participate in the free evolution of topology optimization. Then, the overall optimization problem can be expressed as:

[0022] Design a variable vector, representing the set of parameters that need to be optimized.

[0023] : No. Each design variable may represent the thickness, material type, and arrangement order of each layer.

[0024] : Objective function, representing the shielding effectiveness to be maximized.

[0025] : Shielding effectiveness, is a function of frequency and design variables .

[0026] : In the frequency range , take the minimum value of shielding effectiveness.

[0027] : Represents "subject to", namely "meet the following constraints".

[0028] : This is a constraint condition, which forces the value of some design variables must be 0.

[0029] : The index of the design variable.

[0030] The application provides a wideband shielding body based on a multilayer structure, which faces double challenges in a complex electromagnetic environment, analyzes the shielding effectiveness of single-layer topology optimization under the premise of meeting the volume constraint, and constructs a multilayer structure that meets the wideband high-efficiency electromagnetic shielding; meanwhile, the non-designable domain constraint condition is introduced, the balance between electromagnetic protection and cable layout is realized, and an effective solution is provided for solving the key problems in the existing electromagnetic environment.

[0031] The application designs a multilayer topology optimization model and a BQPSO algorithm, breaks through the design bottleneck of wideband shielding, and realizes the collaborative design of electromagnetic shielding and heat dissipation / wiring by combining the non-designable domain constraint. Experimental and simulation verification of the excellent performance of the structure under wideband and multi-polarization conditions provides a reliable solution for electromagnetic compatibility design of high-integration electronic equipment. BRIEF DESCRIPTION OF DRAWINGS

[0032] In order to more clearly illustrate the technical solutions in the embodiments of the application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced. Obviously, the drawings in the following description are some embodiments of the application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0033] Figure 1 is a shielding unit and a unit cell structure grid diagram, wherein (a) is a shielding unit, (b) is a unit cell structure grid diagram; Figure 2 is a single-layer shielding structure topology optimization flowchart; Figure 3 is a single-layer shielding structure after topology optimization, wherein (a) is a top view, and (b) is a three-axis side view; Figure 4 is the shielding effectiveness simulation curve of the single-layer topology structure; Figure 5 is the top view of the supercell shielding unit composed of three unit cells, where (a) is the upper-layer unit cell shielding structure, (b) is the middle-layer unit cell shielding structure, and (c) is the bottom-layer unit cell shielding structure; Figure 6 is the top view of the supercell; Figure 7 is the optimization flowchart of the broadband shielding structure of the multi-layer topology structure; Figure 8 is the side view of the topology-optimized shielding structure and the simulation shielding effectiveness curve, where (a) is the multi-layer shielding supercell structure after topology optimization, and (b) is the simulation shielding effectiveness curve under the TE mode; Figure 9 is the supercell structure and its array, where (a) is the supercell structure, and (b) is the actual photo of the 14×7 supercell array; Figure 10 is the microwave dark box and experimental platform, where (a) is the schematic diagram of the microwave dark box, and (b) is the experimental operating table; Figure 11 is the experimental test shielding curve; Figure 12 is the electric field distribution of the shielding body at 5.5 GHz and 19.15 GHz, where (a) is 5.5 Hz, and (b) is 19.15 Hz; Figure 13 is the comparative structure and its shielding effectiveness curve, where (a) is the comparative structure diagram, and (b) is the shielding effectiveness curve; Figure 14 is the simulation and experimental shielding curve under the TM incident mode, where (a) is the simulation shielding effectiveness curve, and (b) is the experimental test shielding effectiveness curve; Figure 15 is the shielding structure containing non-designable domains, where (a) is the view of the non-designable domain, (b) is the test diagram, and (c) is the left view of the optimized shielding structure; Figure 16 is the shielding structure after topology optimization (containing non-designable domains), where (a) is the view of the non-designable domain, (b) is the test diagram, and (c) is the left view of the optimized shielding structure; Figure 17 is the shielding curve containing non-designable domains; Figure 18 is the aperture shielding structure and shielding effectiveness curve, where (a) is the top view, (b) is the shielding effectiveness curve, and (c) is the left view; Figure 19 is the comparison diagram of the heat dissipation effects of three cases, where (a) is the shielding body array, (b) is the conventional hollow array, and (c) is the ring-enclosed case. DETAILED DESCRIPTION

[0034] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict, and the present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0035] To make the purposes, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below in combination with the accompanying drawings of the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. The description of the at least one exemplary embodiment is actually only illustrative in nature and by no means as any limitation on the present application and its application or use. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the scope of protection of the present application.

[0036] A wideband shielding body based on a multi-layer structure, comprising an upper-layer unit cell shielding structure, a middle-layer unit cell shielding structure and a lower-layer unit cell shielding structure; The upper-layer unit cell shielding structure is arranged on the upper layer of the middle-layer unit cell shielding structure; The lower-layer unit cell shielding structure is arranged on the lower layer of the middle-layer unit cell shielding structure.

[0037] The design domain sizes of the upper-layer unit cell shielding structure, the middle-layer unit cell shielding structure and the lower-layer unit cell shielding structure are the same, and the size of the shielding unit of the middle-layer unit cell shielding structure is taken as a reference, with the side length being a x a. On this basis, the size of the shielding unit of the upper-layer unit cell shielding structure is 2a x 2a, and each upper-layer unit cell covers four shielding units of the middle-layer unit cell shielding structure. The size of the shielding unit of the lower-layer unit cell shielding structure is 4a x 4a, corresponding to covering four shielding units of the upper-layer unit cell shielding structure.

[0038] The material of the shielding unit is resin.

[0039] The design optimization processes of the middle-upper-layer unit cell shielding structure, the middle-layer unit cell shielding structure and the lower-layer unit cell shielding structure are the same, and are as follows: The unit cell shielding structure is discretized into n sub-grids by topological combination of a plurality of shielding units, the position of each sub-grid corresponds to a design variable, and the whole constitutes a one-dimensional vector X; each element x i is discrete 0 or 1, respectively representing whether a shielding unit is placed at the corresponding sub-grid position or not; wherein i = 1, 2, …, n; if x i = 1, a shielding unit is placed at the grid; if x i=0, then the position is empty, so as to form a local opening or channel; An overlapping connection area with a width of Δwide is set between adjacent shielding units.

[0040] The electromagnetic simulation of the intermediate layer unit cell shielding structure is as follows: A TE-polarized plane wave is incident perpendicularly along the negative z-axis onto the surface of the intermediate unit cell shielding structure, within the target frequency range [f L ,f H Within the range, a discrete frequency sweep method is used to perform frequency scanning in order to obtain the transmission characteristics of the shielding structure at different frequencies; By analyzing the transmission coefficient S in the scattering parameters 21 To evaluate the shielding effectiveness (SE) of the shielding structure; Take the maximum frequency range [f L ,f H The minimum shielding effectiveness SE(f) is the optimization objective function.

[0041] In the optimization, a volume constraint is introduced, and the state values ​​of all elements xi of the one-dimensional vector X are summed and normalized to a unit volume. , representing the relative volume fraction of the structure; this value must not exceed the preset upper limit of the volume fraction a∈(0,1) to obtain the overall optimization problem.

[0042] The overall optimization problem is expressed as follows:

[0043] Design a variable vector, representing the set of parameters that need to be optimized.

[0044] : No. Each design variable may represent the thickness, material type, and arrangement order of each layer.

[0045] The total number of design variables, which is the number of layers or parameters.

[0046] : indicates transpose, here it means It is a column vector.

[0047] : Objective function, representing the shielding effectiveness to be maximized.

[0048] Shielding effectiveness is frequency and design variables The function.

[0049] In the frequency range Within, take the minimum shielding effectiveness.

[0050] : indicates "subject to", that is, "satisfies the following constraints".

[0051] Design variables The average value.

[0052] : A constant representing the upper limit of the average value.

[0053] The BQPSO algorithm is used as the optimization algorithm to solve the optimization problem. MATLAB is used to control the optimization program and perform post-processing of simulation data to obtain the design objective F(…). X ; SE ).

[0054] The BQPSO algorithm is adopted as the optimization algorithm to solve the optimization problem, and the objective F( X ; SE The process is as follows: (1) Initialization parameters and population: Set initial parameters and generate an initial binary encoded population; (2) Automatic modeling and simulation: Evaluate the fitness of individuals based on their current particle position; (3) Fitness evaluation and particle update: Calculate the fitness value and update the particle state according to the algorithm rules; (4) Convergence judgment and result output: If the maximum number of iterations or the convergence condition is met, the optimal topology is output; otherwise, return to step (2) to continue iterating.

[0055] (5) Automatic modeling and simulation evaluates individual fitness based on the current particle position.

[0056] The assessment of individual fitness is based on the transmission parameter S within the target frequency range of 2–20 GHz. 21 The simulation yielded the worst shielding effectiveness threshold SE. min accomplish.

[0057] When a specific region is designated as an undesignable area during the optimization process, and the encoding value of the shielded unit in the undesignable region is always 0, used for cable routing or button placement, and does not participate in the free evolution of topology optimization, then the overall optimization problem can be expressed as:

[0058] Design a variable vector, representing the set of parameters that need to be optimized.

[0059] : No. Each design variable may represent the thickness, material type, and arrangement order of each layer.

[0060] : Objective function, representing the shielding effectiveness to be maximized.

[0061] Shielding effectiveness is frequency and design variables The function.

[0062] In the frequency range Within, take the minimum shielding effectiveness.

[0063] : indicates "subject to", that is, "satisfies the following constraints".

[0064] This is a constraint that requires certain design variables to have a value of 0.

[0065] : Index of the design variable.

[0066] Example 1: The topology optimization design process for a single-layer shielding structure is as follows: When simulating periodic electromagnetic structures, only one unit cell needs to be modeled and simulated to equivalently simulate the electromagnetic response of an infinite periodic array. Therefore, this section designs a single-layer shielding structure unit cell to simulate the shielding effectiveness of an infinitely large planar single-layer shielding structure. In the simulation settings, primary-secondary periodic boundary conditions are applied on the boundaries parallel to the yoz and xoz planes, and Floquet port excitation is introduced in the z-direction to accurately simulate the response characteristics of the periodic structure in the electromagnetic field.

[0067] A shielding unit cell is formed by the topological combination of several shielding units, and the shape of the shielding unit is as follows: Figure 1 As shown, (a) is a shielding unit, and (b) is a mesh diagram of a single-cell structure. The dimensions are set as length × width × height = l × l × h; during the electromagnetic simulation, the material of the shielding unit is resin, and a perfect electric conductor (PEC) boundary condition is applied to its outer surface to simulate the electromagnetic shielding effect of an ideal metal layer.

[0068] The design area of ​​the unit cell shielding structure is a×b. The design area is discretized into n sub-grids, and the position of each sub-grid corresponds to a design variable. Together, they form a one-dimensional vector X. Each element xi (i=1,2,…,n) in vector X is a discrete 0 or 1, which indicates whether a shielding unit is placed at the corresponding sub-grid position: if xi=1, a shielding unit is placed at that grid; if xi=0, the position is empty to form a local opening or channel.

[0069] Figure 2 This is a flowchart of the topology optimization process for a single-layer shielding structure; To ensure that the designed unit cell shielding structure maintains good electromagnetic performance while possessing the necessary structural rigidity, an overlapping connection region with a width of Δwide is introduced between adjacent shielding units. This approach not only helps enhance the overall mechanical stability of the structure but also meets the continuity requirements of the 3D printing manufacturing process, avoiding the appearance of suspended or fragile small structures.

[0070] In the electromagnetic simulation, a TE-polarized plane wave is incident perpendicularly along the negative z-axis onto the surface of a single-layer shielding structure. Within the target frequency range [fL, fH], a discrete frequency sweep is used to obtain the transmission characteristics of the shielding structure at different frequencies. In the simulation, the shielding effectiveness SE of the shielding structure is evaluated by analyzing the transmission coefficient S21 in the scattering parameters. To obtain the highest shielding effectiveness within the target frequency band, it is necessary to maximize the shielding effectiveness of the weakest shielding point throughout the entire band, taking the maximum frequency range [fL, fH]. L ,f H The minimum shielding effectiveness SE(f) is the optimization objective function.

[0071] Furthermore, in order to control material consumption and achieve lightweight structural design, volume constraints are introduced into the optimization process for one-dimensional vectors. X All elements x i Sum the state values ​​and normalize them to a unit volume , representing the relative volume fraction of the structure. This value must satisfy a preset upper limit for volume fraction a∈(0,1). The overall optimization condition is expressed as: (3.1) The BQPSO algorithm is used as the optimization algorithm to solve the optimization problem. The optimization program is controlled and simulation data is post-processed to obtain the design objective F(…). X ; SE The optimization process is as follows: Figure 2 As shown.

[0072] The BQPSO algorithm is used as the optimization algorithm to solve the optimization problem. MATLAB is used to control the optimization program and perform post-processing of simulation data to obtain the design objective F(…). X ; SE The process is as follows: (1) Initialize parameters and population: Set the initial parameters of the BQPSO algorithm and generate the initial binary encoded population; (2) Automatic modeling and simulation: MATLAB generates HFSS scripts based on the current particle position and calls HFSS to perform modeling and simulation solutions; (3) Fitness evaluation and particle update: MATLAB reads the HFSS simulation results, calculates the fitness value, and updates the particle state according to the algorithm rules; (4) Convergence judgment and result output: If the maximum number of iterations or the convergence condition is met, the optimal topology is output; otherwise, return to step (2) to continue iterating.

[0073] (5) Automatic modeling and simulation: MATLAB generates HFSS scripts based on the current particle position and calls HFSS to perform modeling and simulation solutions; The process of performing electromagnetic response calculations using HFSS scripts is as follows: A shielding structure model was established based on the coding sequence, and the transmission parameter S was measured within the target frequency range of 2~20GHz. 21 The simulation yielded the worst shielding effectiveness threshold SE. min .

[0074] Set the worst shielding effectiveness threshold S21 min For an individual, start with high frequencies, prioritizing the simulation of the 19GHz~20GHz frequency band; If the worst shielding effect in this frequency band is greater than S21 min Then continue simulating the 18GHz~18.95GHz frequency band; if the worst shielding effect in this frequency band is still greater than S21 min Then continue simulating the frequency band from 17GHz to 17.95GHz, and so on, until all sub-bands have been simulated; The worst shielding performance value of each sub-band is used as the fitness value of that band. Finally, the fitness values ​​of all sub-bands are summed up, and the worst shielding performance value is selected as the total fitness value of that individual and returned to the optimization algorithm. If the worst shielding effect in a certain frequency band is lower than S21 min If the design requirements are not met, the simulation is stopped immediately, and the worst shielding effect in that frequency band is returned to the optimization algorithm as the fitness value of that individual.

[0075] Based on the above theory, a single-layer metamaterial electromagnetic shielding structure was designed with a target frequency range of 2~20GHz. Considering the precision limitations in actual 3D printing manufacturing, the dimensions of the shielding unit were set to length × width × height = 1.475mm × 1.475mm × 1.2mm. The overall design area of ​​the single-cell shielding structure is 43.2mm × 23.8mm. The design area was discretized into 800 sub-grids to define the arrangement of the shielding units. A 0.3mm wide overlapping connection region was introduced between adjacent shielding units to enhance structural strength. The unit cell volume constraint was 65% of the full shielding unit volume. The topology-optimized single-layer shielding structure is shown below. Figure 3 As shown, (a) is a top view and (b) is a three-axis side view; Figure 4 The simulated shielding effectiveness curves of a single-layer topology in TE mode are presented. Within the frequency range of 2 GHz to 7 GHz, the electromagnetic shielding effectiveness (SE) of the single-layer shielding structure consistently remains above 10 dB, meaning it can effectively shield over 90% of incident electromagnetic wave energy, demonstrating its excellent shielding performance in this frequency band. However, as the frequency of the incident electromagnetic wave further increases, its wavelength gradually decreases and approaches the characteristic scale of the aperture in the shielding structure, causing the shielding effectiveness at some high-frequency points to drop below 8 dB. This shows that, under conditions of limited shielding material usage, a single-layer shielding structure cannot consistently provide highly efficient electromagnetic shielding capabilities over a wide frequency range.

[0076] The structural design process for multi-layer broadband shielding is as follows: With limited material availability, single-layer shielding unit structures struggle to achieve high-efficiency electromagnetic shielding performance over a wide frequency range. To achieve both wide-bandwidth and high-efficiency shielding, a multi-layer, multi-scale shielding unit structure model is proposed. This structure introduces grids in each layer to achieve multiple reflections, thereby improving shielding effectiveness and expanding the frequency response range of the shield.

[0077] Figure 5 This is a top view of a supercell shielding unit consisting of three unit cells, where (a) is the upper unit cell shielding structure, (b) is the middle unit cell shielding structure, and (c) is the bottom unit cell shielding structure. The shielding supercell structure is divided into three layers, each with the same design domain size, and the topology of the three unit cells is optimized. In order to form a multi-path, multi-scale electromagnetic wave reflection channel, the planar size of the shielding unit of the middle unit cell is set as the reference, and its side length is defined as a×a. Based on this, the size of the upper shielding unit is set to 2a×2a, ensuring that each upper unit covers 4 middle unit cells; similarly, the size of the bottom shielding unit is 4a×4a, corresponding to covering 4 upper unit cells. This hierarchical nested design helps to construct complex electromagnetic reflection paths.

[0078] Figure 6This is a top view of the supercell. As can be seen, this multi-layered structure forms a large number of irregular interfaces and reflection channels, providing diverse reflection paths for electromagnetic waves.

[0079] Topology optimization of multi-layered shielding structures, such as broadband shielding structure optimization process. Figure 7 As shown; Figure 8 Side view and simulated shielding performance curve of topology-optimized shielding structure, where (a) is the multi-layer shielding supercell structure after topology optimization, and (b) is the simulated shielding performance curve under TE mode; A three-dimensional metamaterial electromagnetic shielding structure was designed, and the topology optimization results are as follows: Figure 8 As shown in (a), the planar dimensions of the upper, middle, and lower three-layer unit cells of this structure are all 47.3 mm × 23.8 mm. Among them, the middle layer unit cell serves as the main design reference, and its design area is discretized into 40 × 20 shielding units. The planar dimensions of each shielding unit are 1.475 mm × 1.475 mm, and the height H1 is set to 1.2 mm.

[0080] To enhance shielding performance and construct multi-interface reflection channels, while avoiding the "checkerboard phenomenon" common in topology optimization, a 0.3mm overlap distance was introduced between shielding units. Based on this, the upper-layer unit size was set to twice that of the middle-layer units, i.e., 2.65mm × 2.65mm, to ensure that one upper-layer unit exactly covers four middle-layer units, with its height H2 set to 0.9mm. The lower-layer unit size was twice that of the upper-layer unit, i.e., 5mm × 5mm, thus achieving one lower-layer unit corresponding to four upper-layer units, with its height H3 set to 1.4mm, ensuring a good mapping relationship and nesting between the three layers.

[0081] Figure 8 (b) shows the shielding effectiveness curve simulated in TE mode. It can be seen that the shielding effectiveness is higher than 32.7dB in the range of 2GHz to 20GHz. That is, after passing through the shielding structure, the energy of the incident wave is attenuated to 0.0526% of the original.

[0082] Analyzing the quality properties of the optimized shielding structure, its surface area is 4396.54 mm², an increase of 160% compared to the undesigned surface area (23.8 × 47.3 × 2 + 47.3 × 3.5 × 2 + 23.8 × 3.5 × 2 = 2749.18 mm²), enabling sufficient reflection of electromagnetic waves and multiple reflections between interfaces. The volume of the optimized shielding structure model is only 2465.80 mm³, with a material usage ratio of 62.6%.

[0083] To verify the practicality of the designed shielding structure, a corresponding model was fabricated using 3D printing technology. Due to the size limitations of the experimental platform, the printed specimen consisted of a 14×7 supercell array, and its single cell and array structure are shown below. Figure 9 As shown, (a) is a supercell structure, and (b) is a physical image of a 14*7 supercell array. When testing shielding effectiveness inside a microwave anechoic chamber, to reduce reflection interference and improve measurement accuracy, the shielding structure is placed horizontally at the chamber window. The transmitting antenna is positioned vertically to illuminate the device surface, and the receiving antenna is positioned opposite the transmitting antenna and placed inside the chamber. Both the transmitting and receiving antennas are connected to a vector network analyzer (VNA) via coaxial cables to acquire transmitted signals. The microwave anechoic chamber and experimental platform are as follows: Figure 10 As shown, (a) is a schematic diagram of the microwave dark box, and (b) is the experimental operating table; Transmittance measured by VNA S 21 The test data was processed to obtain the shielding effectiveness. SE .

[0084] Since the horn antenna used in the experiment operates in the frequency range of 0.3 GHz to 18 GHz, the shielding effectiveness was verified only in the 2 GHz to 18 GHz band. The experimental shielding effectiveness curves are shown below. Figure 11 As shown, within the 2GHz~16GHz frequency band, the shielding effectiveness of the shielding structure is greater than 30dB, consistent with the simulation results, verifying the feasibility of the design method. However, within the 16GHz~18GHz frequency band, there are some differences between the simulation results and the actual test results. The main reasons are the limited manufacturing precision of the 3D printed parts, the incomplete fit between the shielding structure and the dark box window, and the fact that the horn antenna is located at the edge of the operating frequency, causing changes in its gain and standing wave characteristics.

[0085] Furthermore, the process of analyzing the shielding mechanism of the multi-layer shielding structure is as follows: To delve into the physical mechanisms behind broadband electromagnetic shielding performance, two representative peak shielding effectiveness frequencies of 5.50 GHz and 19.15 GHz were selected from the target frequency band. These two frequencies correspond to the typical frequencies at which the shielding structure experiences electromagnetic resonance. At these frequencies, the electric field distribution, magnetic field distribution, and volume power loss density distribution of the structure were analyzed through simulation, further revealing the specific roles and synergistic mechanisms of each layer in the shielding structure during the electromagnetic shielding process.

[0086] Figure 12 The electric field distributions of the shields are at 5.5 GHz and 19.15 GHz, where (a) is at 5.5 Hz and (b) is at 19.15 Hz. Figure 12 The electric field distribution of the shielding structure at two frequency points is shown. It can be observed that the electric field is mainly concentrated in the first layer of the shielding structure, while the electric field strength decreases significantly after the second layer, with almost no electric field penetrating the third layer. This indicates that the shielding structure can effectively suppress the propagation of the electric field at these frequency points, and its multi-layer design achieves a good shielding effect by blocking and attenuating the electric field layer by layer.

[0087] Furthermore, the analysis of the effectiveness and robustness of the shielding structure is as follows: To verify the shielding performance advantages of the proposed topology-optimized three-dimensional shielding structure under the same aperture volume conditions, this section designs a set of cylindrical hollow structures as a comparative model and compares them with the optimized structure. First, the volume characteristics of the topology-optimized three-dimensional shielding structure are analyzed. Its model volume is 2465.80 mm³, and the volume of the hollow area is 1474.29 mm³. To eliminate the interference of the difference in aperture volume on the shielding performance evaluation results and ensure that the comparison process accurately reflects the influence of the structural layout on the shielding effect, the hollow volume of the comparative model is set to be consistent with that of the optimized structure.

[0088] When constructing the comparison structure, a regular cylindrical hole with a side length of 4mm and a height of 3.5mm was selected as the basic unit. This size is equivalent to the maximum aperture in the topology optimization structure. The volume of each cylindrical hole is 4mm × 4mm × 3.5mm = 56mm³, and the number of holes that can be arranged accordingly is... 1474.29 / 56 =26. Finally, the comparison model consists of 26 randomly distributed cylindrical holes to ensure a consistent overall pore volume.

[0089] Under the same simulation conditions, electromagnetic simulation analysis was performed on the constructed comparative shielding structure. The frequency response curves of the comparative structure and its shielding effectiveness are shown below. Figure 13 As shown, (a) is a comparison structure diagram and (b) is a shielding effectiveness curve; The comparative structure exhibits significant resonance around 5.5 GHz, where the shielding effectiveness reaches its maximum. Subsequently, the shielding effectiveness gradually decreases with increasing frequency, dropping below 30 dB at 11.4 GHz, and reaching its worst value of only 7.45 dB at 16 GHz. The comparison reveals that the proposed topology optimization method, with consistent material usage and perforation volume, can maintain higher shielding effectiveness over a wider frequency band, significantly outperforming the traditional structure. This demonstrates the advantages and effectiveness of the proposed topology optimization design method in electromagnetic shielding structure design.

[0090] Given that the designed shielding structure is not geometrically symmetrical, in order to verify its adaptability to different electromagnetic wave polarization forms, the shielding effectiveness under TM polarized wave incident conditions was measured to verify the robustness of the shielding structure's polarization form.

[0091] Figure 14 These are the simulated and measured shielding curves under TM incident mode, where (a) is the simulated shielding effectiveness curve and (b) is the experimentally tested shielding effectiveness curve. When a TM-polarized incident wave strikes a unit cell structure perpendicularly, its shielding effectiveness curve is as follows: Figure 14 As shown in (a), it can be seen that although the shielding effectiveness of the shielding structure in the 2GHz~20GHz range is slightly lower than that in the TE mode, it is still greater than 30dB, showing good polarization insensitivity.

[0092] The shielding effectiveness curve in the microwave anechoic chamber test is as follows: Figure 14 As shown in (b), its shielding effectiveness curve in the range of 2GHz to 16GHz is basically consistent with the simulation results, indicating that the designed shielding structure has robustness to polarization mode; Furthermore, the design process for a multi-layered shielding structure containing undesignable domains is as follows: In practical engineering applications of shielding structures, efficient electromagnetic shielding typically relies on a dense, continuous conductive layer structure to effectively reflect and absorb electromagnetic waves. However, actual electronic devices often require reserved space within the shielding structure for the placement of necessary components such as cable interfaces and function buttons. These functional openings or non-conductive areas can disrupt the integrity of the shielding layer, creating potential electromagnetic leakage paths, especially noticeable in compact, small devices, leading to a significant decrease in electromagnetic shielding performance.

[0093] To accurately reflect the design constraints in actual engineering projects, this application introduces the concept of an undesignable region into the topology optimization model. An undesignable region is a fixed, reserved area for the arrangement of functional components (such as cables, buttons, etc.), and its geometric position and size are determined based on actual requirements. During topology optimization, this region is forcibly excluded from the evolution of shielding unit distribution; that is, the corresponding design variables remain fixed to avoid shielding unit coverage, thereby ensuring the feasibility of the functional layout. Figure 15 As shown, (a) is a view of the undesignable domain, (b) is a test diagram, and (c) is a left view of the optimized shielding structure. The designed undesignable domain is distributed in a stepped manner, which effectively avoids the possibility of electromagnetic waves penetrating the shielding structure in a straight path and plays a positive role in protecting the shielding performance in the high-frequency band.

[0094] Based on the topology optimization method described above, the design objective is to achieve the desired result at the lower frequency limit. f LUp to frequency limit f H Within the range, resulting in the worst shielding effectiveness SE ( f A larger value indicates improved worst-case shielding effectiveness across the entire frequency range. During optimization, specific regions are designated as undesignable domains. The encoding value of shielding units in these regions is always 0. These regions are used for cable routing or the placement of components such as buttons and do not participate in the free evolution of topology optimization. The optimization conditions are expressed as follows: (3.2) Figure 16 It is the topology-optimized shielding structure (including undesignable domains), where (a) is a view of the undesignable domains, (b) is a test diagram, and (c) is a left view of the optimized shielding structure; The shielding effectiveness curve of a topology-optimized shielding structure containing an undesignable domain, which is vertically irradiated by TE-polarized electromagnetic waves, is shown in the figure. Figure 17 As shown, the shielding effectiveness of this structure is consistently above 30dB in the 2GHz~11.6GHz range, demonstrating excellent electromagnetic shielding performance. In the high-frequency band of 11.6GHz~20GHz, although the shielding effectiveness decreases slightly, it still remains above 28dB overall, indicating that the structure has good electromagnetic shielding capability throughout the entire simulation frequency band and can effectively attenuate most of the incident electromagnetic energy.

[0095] Figure 18 The diagram shows the shielding structure with openings and the shielding effectiveness curve, where (a) is a top view, (b) is the shielding effectiveness curve, and (c) is a left view. A topology-optimized shielding structure without undesignable domains was selected, and apertures of the same size as those in the structure containing undesignable domains were created at corresponding locations. Simulations were then performed under the same operating conditions. The structure and shielding effect are as follows: Figure 3 As shown in Figure 22, the shielding effectiveness of this structure is consistently above 28 dB in the low-frequency range of 2 GHz to 12.5 GHz. However, in the high-frequency range, especially after 15 GHz, the electromagnetic wave wavelength gradually approaches or becomes smaller than the characteristic scale of the aperture, causing the electromagnetic wave to penetrate the aperture and propagate directly, resulting in a significant decrease in shielding effectiveness. Furthermore, at the frequency of 18.45 GHz, the shielding effectiveness drops to 18.60 dB, further verifying the adverse effect of the aperture effect on shielding performance under high-frequency conditions.

[0096] The above analysis demonstrates that by designing a shielding structure containing undesignable domains, the possibility of electromagnetic waves penetrating the shielding structure along a straight path is effectively avoided, thus playing a positive role in protecting the shielding performance in the high-frequency band.

[0097] Furthermore, the process of analyzing the heat dissipation performance of the shielding structure is as follows: Traditional electromagnetic shielding structures are typically closed designs. This enclosed, centralized structure can easily lead to internal heat buildup in practical applications. Electronic circuit modules continuously generate heat during operation. If heat dissipation is not timely, it will cause the equipment temperature to rise, thus affecting its stability and service life. Heat is transferred within the structure mainly through conduction, convection, and radiation. Currently, commonly used heat dissipation methods include natural cooling, forced air cooling, liquid cooling, and evaporative cooling. Among these, natural cooling has relatively low efficiency and is difficult to meet the heat dissipation requirements of high heat flux density devices; forced air cooling enhances convective heat transfer through external fans, effectively improving heat dissipation speed and is a common and mature engineering application; liquid cooling has high heat conduction efficiency, but the system structure is complex, the cost is high, and there are risks such as leakage; evaporative cooling may significantly increase the internal humidity of the equipment, inducing reliability problems such as corrosion of electronic components.

[0098] The three-dimensional electromagnetic shielding structure designed based on topology optimization methods possesses naturally porous topological characteristics, which facilitates air circulation and provides excellent ventilation and heat exchange potential. Therefore, forced air cooling will be employed to analyze the thermal performance and verify the heat dissipation effect of the designed shielding structure, further evaluating its feasibility and engineering application value in complex electromagnetic-thermal coupling environments.

[0099] The constructed simplified chassis structure mainly consists of four parts: a front panel, top and bottom covers, a rear shielding array structure, and a fan for forced air cooling. The chassis dimensions are 141.9mm × 119mm × 241.25mm. To verify the heat dissipation performance of the designed integrated shielding and heat dissipation structure in practical applications, the chassis perimeter was set as an adiabatic boundary condition, allowing heat to escape only through the porous structure within the shielding array. A heat source at 80℃ was placed at the center of the chassis to simulate the operating state of the internal high-heat-generating electronic modules. A shielding array structure was positioned on the side of the chassis directly opposite the heat source, and an air source was placed on the opposite side with an airflow velocity of 0.2m / s to simulate the heat dissipation process under forced air cooling conditions.

[0100] To verify the effectiveness of the designed shielding array in heat dissipation, it was compared and analyzed with a conventional perforated array structure and a fully enclosed structure with the same perforation volume. Thermal simulations were performed on the three structures under the same chassis size and heat source boundary conditions, and the resulting heat dissipation surface temperature distribution was analyzed. Figure 19 As shown, (a) is a shield array, (b) is a conventional perforated array, and (c) is a closed enclosure.

[0101] Simulation results show that the conventional perforated array structure exhibits the best heat dissipation performance, with its highest surface temperature reduced by 54.2℃ compared to the fully enclosed structure. The shielding array structure also demonstrates good heat dissipation; although its highest surface temperature is 2.06℃ higher than the conventional perforated structure, it is still significantly lower than the fully enclosed structure by 52.1℃. These results indicate that the proposed shielding array effectively achieves electromagnetic shielding while also possessing excellent heat dissipation capabilities, demonstrating superior overall performance in practical applications.

[0102] Based on topology optimization, a multifunctional electromagnetic shielding metamaterial structure was designed and verified. First, addressing the insufficient high-frequency performance of single-layer shielding structures, the Binary Quantum Particle Swarm Optimization (BQPSO) algorithm, combined with the HFSS simulation platform, was used to maximize the minimum shielding effectiveness (SE) in the 2-20 GHz range, achieving optimization within a 65% volume constraint. Simulations show that the SE drops below 8 dB in the high-frequency band >16 GHz, highlighting the need for multi-layer structures for broadband shielding. A three-layer nested supercell model was then proposed: the middle layer is the baseline unit (1.475 mm³), the upper layer unit (2.65 mm³) covers four middle layer units, and the bottom layer unit (5 mm³) covers four upper layer units. After optimization using an 18-subband subdivision strategy, the resulting structure achieves an SE >32.87 dB and an energy attenuation >99.947% across the entire 2-20 GHz band, with a measured SE >30 dB in the 2-16 GHz range. Mechanism analysis shows that the high-frequency 19.15GHz electric field mainly attenuates in the first layer, with the incident surface field strength at 1575V / m → exit surface ≈ 0. The low-frequency 5.5GHz magnetic field shielding dominates, with a field strength of 9.6A / m → 0. The interlayer interface has the highest power loss density, verifying the multiple reflection loss mechanism. Compared with a cylindrical hole structure with the same hollow volume, the optimized design improves the high-frequency SE from 18.6dB to over 28dB, while also exhibiting polarization insensitivity.

[0103] To address the specific cabling requirements of engineering projects, an innovative stepped undesignable domain constraint was introduced for re-optimization. Compared to direct via solutions, the designed structure exhibits significantly improved high-frequency shielding performance, with the SE at 18.45 GHz increasing from 18.6 dB to over 28 dB, effectively blocking linear electromagnetic wave leakage. Thermal simulations further demonstrate that under forced air cooling at 0.2 m / s, this porous topology reduces the maximum temperature by 52.1 °C compared to a fully enclosed chassis, approaching the heat dissipation effect of a dedicated perforated structure, thus confirming the synergistic optimization of electromagnetic shielding and thermal management. In summary, through multi-layer topology optimization design, a multi-functional integration of wide-band high shielding, optimized undesignable domains for cabling compatibility, and excellent heat dissipation was successfully achieved, providing an innovative solution for the protection of electronic equipment in complex electromagnetic environments.

[0104] In terms of performance, shielding performance has been significantly improved, with a minimum SE of 32.87dB and a transmission energy attenuation of 99.948% in the 2-20GHz range, and no attenuation in shielding effectiveness at the high-frequency band of 19.15GHz. Regarding weight reduction and material savings, the volume ratio is only 62.6%, saving 37.4% of raw materials compared to a solid structure and achieving greater weight reduction. In terms of synergistic optimization of heat dissipation and electromagnetic shielding, under 0.2m / s forced air cooling, the maximum temperature is reduced by 52.1℃ compared to a fully enclosed chassis. Thermal performance comparison: The heat dissipation effect is close to that of a hollow structure, balancing shielding and heat dissipation. The stepped perforated design, while reserving space for wiring, still maintains a 28dB SE at the 18GHz high-frequency band, a 50.5% improvement compared to a direct-perforation structure. Full-frequency protection: SE > 28dB in the 2-20GHz range, with no significant attenuation points. Integrated molding: 3D printing enables one-time processing, avoiding multi-process assembly. Design automation: The BQPSO algorithm improves optimization efficiency by 40%. Under TE / TM polarized wave incidence, the polarization robustness is >30dB for all SE values ​​and <3dB for performance fluctuation. The invention addresses three major shortcomings—high-frequency shielding failure heat dissipation and material redundancy—through multi-layer topology optimization and undesignable domain design.

[0105] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A broadband shielding body based on a multi-layer structure, characterized in that: It includes an upper unit cell shielding structure, a middle unit cell shielding structure, and a lower unit cell shielding structure; The upper-layer unit cell shielding structure is disposed on top of the middle-layer unit cell shielding structure; The lower-layer unit cell shielding structure is disposed below the middle-layer unit cell shielding structure.

2. A broadband shielding body based on a multi-layer structure according to claim 1, characterized in that: The upper, middle, and lower unit cell shielding structures have the same design domain size. The shielding unit planar size of the middle unit cell shielding structure is used as the reference, and its side length is defined as a×a. Based on this, the size of the shielding unit of the upper unit cell shielding structure is set to 2a×2a, ensuring that each upper unit covers 4 shielding units of the middle unit cell shielding structure. The size of the shielding unit of the lower unit cell shielding structure is 4a×4a, corresponding to covering 4 shielding units of the upper unit cell shielding structure.

3. A broadband shielding body based on a multi-layer structure according to claim 1, characterized in that: The shielding unit is made of resin.

4. A broadband shielding body based on a multi-layer structure according to claim 1, characterized in that: The design and optimization processes for the upper-middle layer unit cell shielding structure, the middle layer unit cell shielding structure, and the lower layer unit cell shielding structure are the same, as detailed below: By combining the topologies of several shielding units, the design domain of the unit cell shielding structure is discretized into n sub-grids. The position of each sub-grid corresponds to a design variable, and the whole structure forms a one-dimensional vector X. Each element x in vector X... i The values ​​are discrete 0 or 1, indicating whether a shielding element is placed at the corresponding subgrid position, respectively. Where i = 1, 2, ..., n; if x i =1, then place a shielding cell at that grid location; if x i =0, then the position is empty, so as to form a local opening or channel; An overlapping connection area with a width of Δwide is set between adjacent shielding units.

5. A broadband shielding body based on a multi-layer structure according to claim 1, characterized in that: The electromagnetic simulation process of the shielding body is as follows: A TE-polarized plane wave is incident perpendicularly along the negative z-axis onto the surface of the intermediate unit cell shielding structure, within the target frequency range [f L ,f H Within the range, a discrete frequency sweep method is used to perform frequency scanning in order to obtain the transmission characteristics of the shielding structure at different frequencies; By analyzing the transmission coefficient S in the scattering parameters 21 To evaluate the shielding effectiveness (SE) of the shielding structure; Take the maximum frequency range [f L ,f H The minimum shielding effectiveness SE(f) within the [inner space] is the optimization objective function; In the optimization, a volume constraint is introduced, and the state values ​​of all elements xi of the one-dimensional vector X are summed and normalized to a unit volume. , representing the relative volume fraction of the structure; This value must satisfy the condition that it does not exceed the preset upper limit of volume fraction a∈(0,1) to obtain the overall optimization problem.

6. A broadband shielding body based on a multi-layer structure according to claim 5, characterized in that: The overall optimization problem is expressed as follows: in: Design a variable vector, representing the set of parameters that need to be optimized; : No. Each design variable may represent the thickness, material type, and arrangement order of each layer; The total number of design variables, which is the number of layers or parameters; : indicates transpose, here it means It is a column vector; : Objective function, representing the shielding effectiveness to be maximized; Shielding effectiveness is frequency and design variables The function; In the frequency range Within, take the minimum shielding effectiveness. The average value of the design variables; : A constant representing the upper limit of the average value.

7. A broadband shielding body based on a multi-layer structure according to claim 1, characterized in that: The BQPSO algorithm is used as the optimization algorithm to solve the optimization problem, and the objective function F( X ; SE The process is as follows: (1) Initialization parameters and population: Set initial parameters and generate an initial binary encoded population; (2) Automatic modeling and simulation: Evaluate the fitness of individuals based on their current particle position; (3) Fitness evaluation and particle update: Calculate the fitness value and update the particle state according to the algorithm rules; (4) Convergence judgment and result output: If the maximum number of iterations or the convergence condition is met, the optimal topology is output; otherwise, return to step (2) to continue iterating. (5) Assess individual fitness based on current particle position.

8. A broadband shielding body based on a multi-layer structure according to claim 1, characterized in that: The assessment of individual fitness is based on transmission parameter S within the target frequency range of 2–20 GHz. 21 The simulation yielded the worst shielding effectiveness threshold SE. min accomplish.

9. A broadband shielding body based on a multi-layer structure according to claim 1, characterized in that: When a specific region is designated as an undesignable area during the optimization process, and the encoding value of the shielded unit in the undesignable region is always 0, used for cable routing or button placement, and does not participate in the free evolution of topology optimization, then the overall optimization problem can be expressed as: 。 in: Design a variable vector, representing the set of parameters that need to be optimized; : No. Each design variable may represent the thickness, material type, and arrangement order of each layer; : Objective function, representing the shielding effectiveness to be maximized; Shielding effectiveness is frequency and design variables The function; In the frequency range Within, take the minimum shielding effectiveness; Constraints; : Index of the design variable.

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