A wideband wide-angle wave absorber based on three-dimensional frequency selective surface

Abstract

The application provides a kind of wideband wide-angle wave absorber based on three-dimensional frequency selective surface, comprising a plurality of three-dimensional frequency selective surface units with same structure and continuous arrangement, each three-dimensional frequency selective surface unit is a hollow cuboid, and each three-dimensional frequency selective surface unit comprises horizontal structure, vertical structure and metal bottom plate arranged in sequence from top to bottom; the wave absorber provided by the application can significantly improve the angle stability of the wave absorber by combining the horizontal structure with the vertical structure, and for 0-60° oblique incidence of TE and TM waves, more than 90% absorption can be achieved within 2.1 times the frequency bandwidth; meanwhile, the wave absorber in the application has the advantages of low profile, small thickness and period size, is easy to integrate with other devices, and is high in convenience; in addition, a center-symmetric pattern design is used in each layer structure of the frequency selective surface unit in the application, which reduces the polarization direction sensitivity of the wave absorber to incident electromagnetic waves.

Description

Technical Field

[0001] This invention relates to the field of microwave technology, and more specifically, to a broadband wide-angle absorber based on a three-dimensional frequency-selective surface. Background Technology

[0002] An electromagnetic absorber is a device that absorbs electromagnetic waves within a specific frequency band. It is widely used in stealth technology, microwave anechoic chambers, and improving system electromagnetic compatibility. Whether it is electromagnetic stealth, microwave anechoic chambers, or many other applications, the absorber needs to have broadband, low-profile absorption characteristics, and it also needs to have broadband absorption characteristics at wide incident angles.

[0003] The Salisbury absorber is an early, classic two-dimensional planar absorber, consisting of resistive plates placed at intervals in front of a metal backplate. This type of absorber has a narrow operating bandwidth, failing to meet broadband stealth requirements. Later, researchers designed the Jauman absorber using a multi-layer stacking approach, utilizing different layers resonating at different frequencies to extend the absorption bandwidth; however, this resulted in a significant thickness. To achieve better performance in terms of bandwidth and thickness, researchers replaced the resistive plates in the Salisbury absorber with frequency-selective surfaces, obtaining a two-dimensional conventional frequency-selective surface absorber, achieving a larger bandwidth at the same thickness. Subsequently, researchers further achieved a smaller thickness-bandwidth ratio through multi-layer frequency-selective surface structure designs.

[0004] However, due to the interaction between layers, there is a limit to improving the thickness-bandwidth ratio, known as the Rozanov limit. Traditional two-dimensional multilayer frequency-selective surface absorbers (FSBs) have achieved thickness-bandwidth ratios very close to the Rozanov limit. However, traditional two-dimensional absorbers often suffer from bandwidth contraction under oblique incidence, resulting in insufficient angular absorption performance and making it difficult to achieve stealth and electromagnetic interference elimination over a wide angular range. Early three-dimensional absorbers, such as honeycomb, wedge, and cone absorbers, possessed broadband and wide-angle absorption performance, making them well-suited for applications such as microwave anechoic chambers. However, their large size, weight, and poor mechanical stability made them unsuitable for stealth applications in aircraft, antennas, and other equipment. In recent years, researchers have discovered that three-dimensional frequency-selective surface structures can better respond to obliquely incident electromagnetic waves and have proposed many broadband and wide-angle three-dimensional absorbers, but each has its own set of problems. For example, an existing absorber that includes a traditional horizontal frequency-selective surface structure and a vertical "I-ring" structure achieves 50° angular stability for obliquely incident TE and TM waves, but only has a relative bandwidth of 48.6%. Another absorber with a "mushroom-shaped" structure has a relative bandwidth of 103% and good absorption for obliquely incident TM waves from 0 to 82°, but its angular stability for obliquely incident TE waves is only 45°. Furthermore, although introducing a wide-angle matching layer into a traditional frequency-selective surface absorber can achieve a relative bandwidth of 110.5% for TE and TM waves from 0 to 45°, the angular stability of this absorber is still poor.

[0005] Existing technology discloses an ultra-miniaturized 2.5D broadband absorber, comprising several continuously and periodically arranged metamaterial units. Each metamaterial unit includes a top resonant layer, a first dielectric layer, a second dielectric layer, and a metal substrate layer stacked sequentially from top to bottom. The top resonant layer includes a first metal patch unit, a thin-film resistor, and four second metal patch units. Four third metal patch units are disposed at the bottom of the first dielectric layer. Each third metal patch unit is connected to a corresponding second metal patch unit through a metallized via. The existing solution has an angular stability of less than 45°, which is poor and cannot simultaneously achieve bandwidth and oblique incidence angle stability. Summary of the Invention

[0006] To overcome the shortcomings of the prior art in balancing bandwidth and oblique incidence angle stability, this invention provides a broadband wide-angle absorber based on a three-dimensional frequency selective surface. This absorber has a wide bandwidth while significantly improving the angle stability of the absorber. In addition, the absorber has a low profile and is insensitive to the polarization direction of the incident electromagnetic wave.

[0007] To solve the above-mentioned technical problems, the technical solution of the present invention is as follows:

[0008] A three-dimensional frequency selective surface unit includes: a horizontal structure, a vertical structure, and a metal base plate arranged sequentially from top to bottom;

[0009] The horizontal structure includes a square horizontal substrate, a square ring-shaped surface mount unit and a cross-shaped surface mount unit printed on the square horizontal substrate, four identical first surface mount resistors and four identical second surface mount resistors.

[0010] The square ring patch unit is a square ring structure with the same recess at each of its four corners pointing towards the center of a square horizontal dielectric substrate.

[0011] The square ring patch unit includes four identical first folded metal strip patches, which are centrally symmetrical about the center of the square horizontal dielectric substrate; each pair of adjacent first folded metal strip patches are connected by a first patch resistor.

[0012] The cross-shaped patch unit is disposed within the square ring patch unit. The cross-shaped patch unit includes four T-shaped patches and one cross patch. The center of the cross patch is located at the center of the square horizontal dielectric plate. The four T-shaped patches are centrally symmetrical about the center of the square horizontal dielectric plate.

[0013] Each of the T-shaped patches includes a rectangular patch and a rectangular metal strip patch, one end of which is connected to the rectangular patch and the other end is connected to one end of the cross patch through a second patch resistor;

[0014] The vertical structure includes four rectangular vertical dielectric plates and four TM wave intensity response units. The four rectangular vertical dielectric plates, the square horizontal dielectric plate, and the metal base plate constitute a cuboid structure.

[0015] A TM wave intensity response unit is printed on the inner surface of each of the rectangular vertical dielectric plates. All TM wave intensity response units have the same shape, and the orthographic projections of the TM wave intensity response units on opposite rectangular vertical dielectric plates coincide.

[0016] Each of the TM wave intensity response units includes: a second folded metal strip patch, a third folded metal strip patch, and a third patch resistor;

[0017] The third surface mount resistor is located at the center of the rectangular vertical dielectric substrate. One end of the third surface mount resistor is connected to the second folded metal strip surface mount, and the other end is connected to the third folded metal strip surface mount.

[0018] Preferably, the ends of the second and third folded metal strip patches connected to the third patch resistor are both located on the same vertical line within a preset length range;

[0019] The ends of the second and third folded metal strip patches connected to the third patch resistor are bent in opposite directions outside the preset length range.

[0020] Preferably, the total thickness h of the three-dimensional frequency selective surface unit is 0.118λ. L The side length p of the square horizontal medium plate is 0.152λ. L The thickness of the square horizontal dielectric plate and all rectangular vertical dielectric plates is 0.005λ. L , where λ L Select the wavelength corresponding to the lowest operating frequency of the surface unit for the three-dimensional frequency.

[0021] Preferably, in the horizontal structure, the distance L1 between two opposite sides of the quasi-square ring patch unit is 0.117λ. L The outer side length L3 of the square ring patch unit is 0.103λ. L The folding depth d of the first folded metal strip patch is 0.056λ. L The width W1 of the square ring patch unit is 0.004λ. L .

[0022] Preferably, in the horizontal structure, the maximum arm length L2 of the cross-shaped patch unit is 0.080λ. L The length L4 of the rectangular patch is 0.013λ. L The width W3 of the rectangular patch is 0.010λ. L The width W2 of the rectangular metal strip patch is 0.004λ. L .

[0023] Preferably, in the vertical structure, the width W4 of the TM wave intensity response unit is 0.003λ. L ;

[0024] The distance h1 between the top of the TM wave intensity response unit and the bottom of the square horizontal dielectric plate is 0.010λ. L The distance h2 between the bottom of the TM wave intensity response unit and the top of the metal base plate is 0.005λ. L .

[0025] Preferably, the resistance value of each first surface mount resistor is in the range of 171 to 189 Ω, the resistance value of each second surface mount resistor is in the range of 114 to 126 Ω, and the resistance value of each third surface mount resistor is in the range of 300 to 700 Ω.

[0026] The square horizontal dielectric plate and all rectangular vertical dielectric plates are made of non-magnetic materials with a dielectric constant ranging from 3.8 to 5 and a loss angle ranging from 0.01 to 0.03.

[0027] The materials of the quasi-square loop patch unit, cross-shaped patch unit, second folded metal strip patch, and third folded metal strip patch are all conductive metals.

[0028] Preferably, the first folded metal strip patch forms a "zigzag" shape after being bent multiple times in sequence;

[0029] Both the second folded metal strip patch and the third folded metal strip patch are bent k times, where k is a non-negative integer.

[0030] The present invention also provides a broadband wide-angle absorber based on a three-dimensional frequency selective surface, which applies the above three-dimensional frequency selective surface unit and includes a plurality of three-dimensional frequency selective surface units that are identical in structure and arranged continuously;

[0031] The arrangement manner of the three-dimensional frequency selective surface units is specifically a matrix arrangement of m×n, where m and n are the number of rows and columns of the matrix arrangement respectively.

[0032] Preferably, all the outermost rectangular vertical dielectric plates in the absorber are cancelled.

[0033] Compared with the prior art, the beneficial effects of the technical solution of the present invention are:

[0034] The present invention provides a broadband wide-angle absorber based on a three-dimensional frequency selective surface, which includes a plurality of frequency selective surface units that are identical in structure and arranged continuously. Each frequency selective surface unit is of a cuboid structure and includes: a horizontal structure, a vertical structure, and a metal bottom plate arranged in sequence from top to bottom; the horizontal structure includes a square horizontal dielectric plate, a quasi-square loop patch unit and a cross-shaped patch unit printed on the square horizontal dielectric plate, 4 completely identical first patch resistors, and 4 completely identical second patch resistors; the quasi-square loop patch unit is a quasi-square loop structure with the same recesses opened at the four corners towards the center point of the square horizontal dielectric plate; the quasi-square loop patch unit includes 4 completely identical first folded metal strip patches, and the 4 first folded metal strip patches are centrosymmetrically distributed about the center of the square horizontal dielectric plate; each two adjacent first folded metal strip patches are connected by a first patch resistor; the cross-shaped patch unit is arranged within the quasi-square loop patch unit, and the cross-shaped patch unit includes 4 T-shaped patches and 1 cross patch, the center of the cross patch is located at the center of the square horizontal dielectric plate, and the 4 T-shaped patches are centrosymmetrically distributed about the center of the square horizontal dielectric plate; each T-shaped patch includes a rectangular patch and a rectangular metal strip patch, one end of the rectangular metal strip patch is connected to the rectangular patch, and the other end is connected to one end of the cross patch through 1 second patch resistor;

[0035] The vertical structure includes four rectangular vertical dielectric plates, which, together with a square horizontal dielectric plate and a metal base plate, form a cuboid structure. A TM wave intensity response unit is printed on the inner surface of each rectangular vertical dielectric plate. All TM wave intensity response units have the same shape, and the orthographic projections of the TM wave intensity response units on opposite rectangular vertical dielectric plates coincide. Each TM wave intensity response unit includes a second folded metal strip patch, a third folded metal strip patch, and a third surface-mount resistor. The third surface-mount resistor is located at the center of the rectangular vertical dielectric plate, with one end connected to the second folded metal strip patch and the other end connected to the third folded metal strip patch.

[0036] The absorber provided by this invention, through the combination of horizontal and vertical structures, can significantly improve the angular stability of the absorber. For TE and TM waves incident at an angle of 0–60°, it can achieve more than 90% absorption within a 2.1 octave bandwidth. At the same time, the absorber of this invention has the advantage of low profile, small thickness and period size, which facilitates integration with other devices and is highly convenient. In addition, each layer of the frequency selective surface unit in this invention adopts a centrally symmetrical pattern design, which reduces the absorber's sensitivity to the polarization direction of the incident electromagnetic wave. Attached Figure Description

[0037] Figure 1 The diagram shows the structure and equivalent circuit model of the conventional single-layer frequency selective surface absorber provided in Example 1.

[0038] Figure 2 The diagram shows the structure and equivalent circuit model of the three-dimensional frequency selective surface absorber provided in Example 1.

[0039] Figure 3 In the equivalent models of the conventional frequency selective surface absorber and the three-dimensional frequency selective surface absorber provided in Example 1, Y sub2 Comparison of the imaginary part of the signal with the incident angle under TE or TM waves.

[0040] Figure 4 This is a three-dimensional structural schematic diagram of the three-dimensional frequency selective surface unit provided in Example 2.

[0041] Figure 5 This is a schematic diagram of the horizontal structure 1 provided in Example 2.

[0042] Figure 6 This is a schematic diagram of the vertical structure 2 provided in Embodiment 2.

[0043] Figure 7 and Figure 8 These are schematic diagrams of two other shapes of the square ring patch unit 12 and the cross-shaped patch unit 13 provided in Embodiment 2.

[0044] Figures 9-12 These are schematic diagrams of four other shapes of the TM wave intensity response unit 22 provided in Example 2.

[0045] Figures 13-14 These are schematic diagrams of the horizontal structure 1 and vertical structure 2 of the three-dimensional frequency selective surface unit implemented by printing resistive films in Example 2.

[0046] Figure 15 This is a three-dimensional structural schematic diagram of the broadband wide-angle absorber (3×3) based on a three-dimensional frequency selective surface provided in Example 3.

[0047] Figure 16 The simulation curve of the reflection coefficient of the absorber provided in Example 3 as the incident angle of TE wave increases from 0° to 60°.

[0048] Figure 17 The simulation curve of the reflection coefficient of the absorber provided in Example 3 as the incident angle increases from 0° to 60° under oblique incidence of TM waves. Detailed Implementation

[0049] The accompanying drawings are for illustrative purposes only and should not be construed as limiting the scope of this patent.

[0050] To better illustrate this embodiment, some parts in the accompanying drawings may be omitted, enlarged, or reduced, and do not represent the actual product dimensions;

[0051] It will be understood by those skilled in the art that certain well-known structures and their descriptions may be omitted in the accompanying drawings.

[0052] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0053] Example 1

[0054] This embodiment provides a three-dimensional frequency selective surface unit, including: a horizontal structure 1, a vertical structure 2, and a metal base plate 3 arranged sequentially from top to bottom;

[0055] The horizontal structure 1 includes a square horizontal substrate 11, a square ring-shaped patch unit 12 and a cross-shaped patch unit 13 printed on the square horizontal substrate 11, four identical first patch resistors 14 and four identical second patch resistors 15.

[0056] The square ring patch unit 12 is a square ring structure with the same recess at each of its four corners facing the center point of the square horizontal dielectric plate 11.

[0057] The square ring patch unit 12 includes four identical first folded metal strip patches 121, which are centrally symmetrical about the center of the square horizontal dielectric substrate 11; each pair of adjacent first folded metal strip patches 121 are connected by a first patch resistor 14.

[0058] The cross-shaped patch unit 13 is disposed within the square ring patch unit 12. The cross-shaped patch unit 13 includes four T-shaped patches 131 and one cross patch 132. The center of the cross patch 132 is located at the center of the square horizontal dielectric plate 11. The four T-shaped patches 131 are centrally symmetrical about the center of the square horizontal dielectric plate 11.

[0059] Each of the T-shaped patches 131 includes a rectangular patch 1311 and a rectangular metal strip patch 1312. One end of the rectangular metal strip patch 1312 is connected to the rectangular patch 1311, and the other end is connected to one end of the cross patch 132 through a second patch resistor 15.

[0060] The vertical structure 2 includes four rectangular vertical dielectric plates 21 and four TM wave intensity response units 22. The four rectangular vertical dielectric plates 21, the square horizontal dielectric plate 11 and the metal base plate 3 form a cuboid structure.

[0061] A TM wave intensity response unit 22 is printed on the inner surface of each rectangular vertical dielectric plate 21. All TM wave intensity response units 22 have the same shape, and the orthographic projections of the TM wave intensity response units 22 on opposite rectangular vertical dielectric plates 21 coincide.

[0062] Each of the TM wave intensity response units 22 includes: a second folded metal strip patch 221, a third folded metal strip patch 222, and a third patch resistor 223;

[0063] The third surface mount resistor 223 is located at the center of the rectangular vertical dielectric plate 21. One end of the third surface mount resistor 223 is connected to the second folded metal strip patch 221, and the other end is connected to the third folded metal strip patch 222.

[0064] In the specific implementation process, the traditional single-layer frequency selective surface absorber was first analyzed. A traditional single-layer frequency selective surface absorber has the following characteristics: Figure 1 The structure shown in (a) includes a substrate dielectric plate, a frequency selective surface structure printed on the substrate dielectric plate, and a metal base plate, with an air cavity separating the substrate dielectric plate and the metal base plate; when an electromagnetic wave is obliquely incident on the absorber surface at an angle θ0, it is refracted in the substrate dielectric plate, and the angle becomes θ. t θ0 and θ t It has the following relationship:

[0065]

[0066] Where, ε r is the relative permittivity of the substrate dielectric. Figure 1 (b) is the equivalent circuit model of a traditional single-layer frequency-selective surface absorber, where Y0 and Y1 are the waveguide admittances of air and the substrate dielectric, respectively. FSS The equivalent admittance of the surface structure is selected for the horizontal frequency. The height of the air cavity and the thickness of the substrate dielectric are t and L, respectively, which are equivalent to transmission lines of equal length.

[0067] Under obliquely incident electromagnetic waves, the waveguide admittance and longitudinal propagation constant vary with the incident angle θ0, as given by the following formulas:

[0068]

[0069] For TE waves:

[0070] For TM waves:

[0071] Wherein, β0 and β t These are the longitudinal propagation constants in air and the substrate dielectric, respectively, Y 0,TE / TM Y 0,TE / TM Let Y be the waveguide admittance of air and the substrate dielectric plate under TE / TM wave incidence, respectively. In the expected design, the absorber thickness is much smaller than the wavelength λ, i.e., t+L<<λ, thus the absorber input admittance Y is obtained. A A simple expression for this can be used to calculate the reflection coefficient Γ under TE / TM wave incidence. TE / TM As shown below:

[0072] For TE waves:

[0073]

[0074] For TM waves:

[0075]

[0076] Based on the above formula, we first analyze the conditions under which the absorber can achieve good impedance matching over a wide incident angle range: On the one hand, Y A The real part of Y needs to approximate the wave impedance of air at the corresponding incident angle, therefore Y needs to be... FSS The real part decreases with the incident angle under TE wave and increases with the incident angle under TM wave; on the other hand, Y is required. A The imaginary part of the admittance approaches zero over a wide range of incident angles. Since the imaginary part of the admittance decreases with increasing incident angle, for a normally incident wave, Y needs to be...A The imaginary part of the is slightly greater than 0 in the absorption frequency band, which can be easily achieved by adjusting the thickness of the absorber.

[0077] Furthermore, we obtained Figure 3 Y shown sub2,TE / Y0 and Y sub2,TM The two normalized curves / Y0 show that, without considering the change of the equivalent admittance of the frequency-selective surface with the incident angle, the imaginary part of the admittance decreases with increasing incident angle under both TE and TM waves. Furthermore, the imaginary part of the absorber's equivalent admittance changes more drastically with the incident angle under obliquely incident TM waves than under obliquely incident TE waves, thus the absorber is more prone to impedance mismatch under obliquely incident TM waves.

[0078] Based on the above analysis, it is relatively easy for a traditional frequency-selective surface absorber to achieve wide-angle TE wave absorption over a wide bandwidth, but it is difficult to achieve wide-angle TM wave absorption.

[0079] Furthermore, a design strategy for three-dimensional frequency-selective surface absorbers is proposed:

[0080] Considering that the longitudinal electric field of TM waves increases with the incident angle, and that a vertical frequency-selective surface structure (referred to as the vertical structure) can be excited by the longitudinal electric field, a three-dimensional frequency-selective surface absorber is constructed by combining a traditional frequency-selective surface absorber (which only has a horizontal structure) with a vertical structure; for example... Figure 2 As shown in (a), a three-dimensional frequency selective surface absorber is constructed by introducing a vertical frequency selective surface structure on the basis of a traditional frequency selective surface absorber. Here, the superposition structure of air and vertical frequency selective surface is qualitatively regarded as a lossy medium with a complex permittivity of ε. L =ε' L -jε” L When an electromagnetic wave strikes the surface of the absorber at an incident angle θ0, the angle of refraction in the lossy dielectric layer is θ. L It should be noted that in practice, ε L It varies with frequency and incident angle; for the sake of simplifying the analysis, we assume ε L It is a constant; in Figure 2 In the equivalent model of (b), the lossy dielectric layer is equivalent to a lossy transmission line with waveguide admittance Y2. To analyze the impedance matching of the absorber under TM waves after introducing a vertical frequency selective surface, the condition t+L<<λ is also considered. Under obliquely incident TM waves, the input admittance of the three-dimensional frequency selective surface absorber can be calculated by the following formula:

[0081]

[0082]

[0083] From the above formula, we can obtain Im[Y'] sub2,TM / Y0] in different ε L The two normalized curves below, as follows Figure 3 As shown; it can be seen that when a traditional frequency-selective surface absorber is combined with a vertical structure to form a three-dimensional frequency-selective surface absorber, under TM waves, on the one hand, the imaginary part of the absorber's input admittance changes significantly less with angle compared to the traditional frequency-selective surface absorber, and when ε' L The effect is more significant when the value is increased; on the other hand, as can be seen from the formula, Y increases after adding a vertical structure. sub2 The real part is greater than 0, so under TM wave, the real part of the absorber's input admittance increases, the impedance matching is better, which is beneficial to improving the TM wave absorption performance;

[0084] The working principle of the absorber in this embodiment is as follows:

[0085] When electromagnetic waves are incident on the surface of the absorber from above, the frequency-selective surface unit resonates at a specific frequency, confining the electromagnetic wave energy within the absorber and dissipating the electromagnetic energy through dielectric loss and resistive loss.

[0086] The absorption performance of horizontal structure 1 mainly comes from the excitation of the horizontal electric field. Therefore, it has good absorption for normally incident waves and obliquely incident TE waves because TE waves have a constant horizontal electric field amplitude. However, for obliquely incident TM waves, the horizontal electric field amplitude decreases as the incident angle increases, so its absorption performance is poor at large incident angles.

[0087] The vertical structure 2 is less affected by the horizontal electric field, and only generates a weak resonance at a higher frequency, which can slightly improve the bandwidth. In this embodiment, the vertical structure 2 has a strong response to the vertical electric field, and the vertical electric field component of the TM wave increases with the increase of the incident angle. Therefore, the vertical structure has a strong response to the obliquely incident TM wave, which can compensate for the response of the horizontal structure and improve the absorption of the TM wave.

[0088] Finally, by combining the horizontal structure 1 and the vertical structure 2 and integrating them together on the metal base plate 3, both bandwidth and oblique incidence angle stability can be taken into account, thus achieving broadband and wide-angle wave absorption.

[0089] The three-dimensional frequency selective surface unit provided in this embodiment can significantly improve the angular stability of the absorber by combining horizontal and vertical structures. At the same time, the three-dimensional frequency selective surface unit in this embodiment has the advantage of low profile, small thickness and period size, which makes it easy to integrate with other devices and is highly convenient. In addition, each layer of the frequency selective surface unit in this embodiment adopts a centrally symmetrical pattern design, which reduces the absorber's sensitivity to the polarization direction of the incident electromagnetic wave.

[0090] Example 2

[0091] like Figure 4 As shown, this embodiment provides a three-dimensional frequency selective surface unit, including: a horizontal structure 1, a vertical structure 2, and a metal base plate 3 arranged sequentially from top to bottom;

[0092] like Figure 5 As shown, the horizontal structure 1 includes a square horizontal substrate 11, a square ring-shaped patch unit 12 and a cross-shaped patch unit 13 printed on the square horizontal substrate 11, four identical first patch resistors 14 and four identical second patch resistors 15.

[0093] The square ring patch unit 12 is a square ring structure with the same recess at each of its four corners facing the center point of the square horizontal dielectric plate 11.

[0094] The square ring patch unit 12 includes four identical first folded metal strip patches 121, which are centrally symmetrical about the center of the square horizontal dielectric substrate 11; each pair of adjacent first folded metal strip patches 121 are connected by a first patch resistor 14.

[0095] The cross-shaped patch unit 13 is disposed within the square ring patch unit 12. The cross-shaped patch unit 13 includes four T-shaped patches 131 and one cross patch 132. The center of the cross patch 132 is located at the center of the square horizontal dielectric plate 11. The four T-shaped patches 131 are centrally symmetrical about the center of the square horizontal dielectric plate 11.

[0096] Each of the T-shaped patches 131 includes a rectangular patch 1311 and a rectangular metal strip patch 1312. One end of the rectangular metal strip patch 1312 is connected to the rectangular patch 1311, and the other end is connected to one end of the cross patch 132 through a second patch resistor 15.

[0097] like Figure 6 As shown, the vertical structure 2 includes four rectangular vertical dielectric plates 21 and four TM wave intensity response units 22. The four rectangular vertical dielectric plates 21, the square horizontal dielectric plate 11 and the metal base plate 3 form a cuboid structure.

[0098] A TM wave intensity response unit 22 is printed on the inner surface of each rectangular vertical dielectric plate 21. All TM wave intensity response units 22 have the same shape, and the orthographic projections of the TM wave intensity response units 22 on opposite rectangular vertical dielectric plates 21 coincide.

[0099] Each of the TM wave intensity response units 22 includes: a second folded metal strip patch 221, a third folded metal strip patch 222, and a third patch resistor 223;

[0100] The third surface mount resistor 223 is disposed at the center of the rectangular vertical dielectric plate 21. One end of the third surface mount resistor 223 is connected to the second folded metal strip patch 221, and the other end is connected to the third folded metal strip patch 222.

[0101] The ends of the second folded metal strip patch 221 and the third folded metal strip patch 222 connected to the third patch resistor 223 are both located on the same vertical line within a preset length range;

[0102] The ends of the second folded metal strip patch 221 and the third folded metal strip patch 222 connected to the third patch resistor 223 are bent in opposite directions outside the preset length range;

[0103] The total thickness h of the three-dimensional frequency-selective surface unit is 0.118λ. L The side length p of the square horizontal medium plate 11 is 0.152λ. L The thickness of the square horizontal medium plate 11 and all the rectangular vertical medium plates 21 is 0.005λ. L , where λ L Select the wavelength corresponding to the lowest operating frequency of the surface unit for the three-dimensional frequency;

[0104] In the horizontal structure 1, the distance L1 between two opposite sides of the quasi-square ring patch unit 12 is 0.117λ. L The outer side length L3 of the square ring patch unit 12 is 0.103λ. L The folding depth d of the first folded metal strip patch 121 is 0.056λ. L The width W1 of the square ring patch unit 1212 is 0.004λ. L ;

[0105] In the horizontal structure 1, the maximum arm length L2 of the cross-shaped patch unit 13 is 0.080λ. L The length L4 of the rectangular patch 1311 is 0.013λ. L The width W3 of the rectangular patch 1311 is 0.010λ. L The width W2 of the rectangular metal strip patch 1312 is 0.004λ. L ;

[0106] In the vertical structure 2, the width W4 of the TM wave intensity response unit 22 is 0.003λ. L ;

[0107] The distance h1 between the top of the TM wave intensity response unit 22 and the bottom of the square horizontal dielectric plate 11 is 0.010λ. L, the distance h2 between the bottom of the TM wave strong response unit 22 and the top of the metal bottom plate 3 is 0.005λ L ;

[0108] The resistance value range of each of the first patch resistors 14 is 171 - 189Ω, the resistance value of each of the second patch resistors 15 is 114 - 126Ω, and the resistance value of each of the third patch resistors 223 is 300 - 700Ω;

[0109] The square horizontal dielectric plate 11 and all the rectangular vertical dielectric plates 21 are made of non-magnetic materials, with a dielectric constant range of 3.8 - 5 and a loss angle range of 0.01 - 0.03;

[0110] The materials of the quasi-square ring patch unit 12, the cross-shaped patch unit 13, the second folded metal strip patch 221, and the third folded metal strip patch 222 are all conductive metals;

[0111] The first folded metal strip patch 121 is bent multiple times in sequence to form a "zigzag" shape;

[0112] The second folded metal strip patch 221 and the third folded metal strip patch 222 are both bent k times, where k is a non-negative integer.

[0113] In the specific implementation process, in this embodiment, the thickness h of the frequency selective surface unit is 12.4mm, and the period size, that is, the side length p of the square horizontal dielectric plate 11 is 16mm; the thicknesses of the square horizontal dielectric plate 11 and all the rectangular vertical dielectric plates 21 are both 0.5mm;

[0114] In the horizontal structure 1, the distance L1 between two opposite sides of the quasi-square ring patch unit 12 is 12.3mm, the outer side length L3 of the quasi-square ring patch unit 12 is 10.8mm, the folding depth d of the first folded metal strip patch 121 is 5.9mm, and the width W1 of the quasi-square ring patch unit 12 is 1mm;

[0115] In the horizontal structure 1, the maximum arm length L2 of the cross-shaped patch unit 13 is 8.4mm, the length L4 of the rectangular patch 1311 is 1.38mm, the width W3 of the rectangular patch 1311 is 1mm, and the width W2 of the rectangular metal strip patch 1312 is 0.4mm;

[0116] In the vertical structure 2, the width W4 of the TM wave strong response unit 22 is 0.3mm;

[0117] Starting from one end of the third patch resistor 223, the second folded metal strip patch 221 is bent 3 times at 90° in sequence, and the lengths of the folded parts of the second folded metal strip patch 221 are respectively L a= 5 mm, L b = 3 mm and L c = 5 mm;

[0118] Starting from one end of the third chip resistor 223, the third folded metal strip patch 222 is bent 3 times at 90° in sequence, and the lengths of the folded parts of the third folded metal strip patch 222 are L a = 5 mm, L b = 3 mm and L d = 7 mm;

[0119] The distance h1 between the top of the TM wave strong response unit 22 and the bottom of the square horizontal dielectric plate 11 is 1 mm, and the distance h2 between the bottom of the TM wave strong response unit 22 and the top of the metal bottom plate 3 is 0.5 mm;

[0120] The resistance value of each of the first chip resistors urchased from the second chip resistor urchased from the third chip resistor urchased from the third chip resistor urchased from the third chip resistor urchased from the third chip resistor urchased from the third chip resistor urchased from the third chip resistor urchased from the third chip resistor urchased from the third chip resistor urchased from the third chip resistor urchased from the third chip resistor urchased from the third chip resistor urchased from the third chip resistor urchased from the third chip resistor urchased from the third chip resistor urchased from the third chip resistor urchased from the third chip resistor urchased from the third chip resistor urchased from the third chip resistor urchased from the third chip resistor urchased from the third chip resistor urchased from the third chip resistor urchased from the third chip resistor urchased from the third chip resistor urchased from the third chip resistor urchased from the third chip resistor urchased from the third chip resistor urchased from the third chip resistor urchased from the third chip resistor urchased from the third chip resistor urchased from the third chip resistor urchased from the third chip resistor urchased from the third chip resistor urchased from the third chip resistor urchased from the third chip resistor urchased from the third chip resistor urchased from the third chip resistor urchased from the third chip resistor urchased from the third chip resistor urchased from the third chip resistor urchased from the third chip resistor urchased from the third chip resistor urchased from the third chip resistor urchased from the third chip resistor urchased from the third chip resistor urchased from the third chip resistor urchased from the third chip resistor urchased from the third chip resistor urchased from the third chip resistor urchased from the third chip resistor urchased from the third chip resistor urchased from the third chip resistor urchased from the third chip resistor urchased from the third chip resistor urchased from the third chip resistor urchased from the third chip resistor urchased from the third chip resistor urchased from the third chip resistor urchased from the third chip resistor urchased from the third chip resistor urchased from the third chip resistor urchased from the third chip resistor urchased from the third chip resistor urchased from the third chip resistor urchased from the third chip resistor urchased from the third chip resistor urchased from the third chip resistor urchased from the third chip resistor urchased from the third chip resistor urchased from the third chip resistor urchased from the third chip resistor urchased from the third chip resistor urchased from the third chip resistor urchased from the third chip resistor urchased from the third chip resistor urchased from the third chip resistor urchased from the third chip resistor urchased from the third chip resistor urchased from the third chip resistor urchased from the third chip resistor urchased from the third chip resistor urchased from the third chip resistor urchased from the third chip resistor urchased from the third chip resistor urchased from the third chip resistor urchased from the third chip resistor urchased from the third chip resistor urchased from the third chip resistor urchased from the third chip resistor urchased from the third chip resistor urchased from the third chip resistor urchased from the third chip resistor urchased from the third chip resistor urchased from the third chip resistor urchased from the third chip resistor urchased from the third chip resistor urchased from the third chip resistor urchased from the third chip resistor is 500 Ω;

[0121] The materials of the square horizontal dielectric plate 11 and all the rectangular vertical dielectric plates 21 are FR4, the dielectric constants are all 4.4, and the loss tangent tanδ = 0.02;

[0122] The materials of the quasi-square ring patch unit 12, the cross-shaped patch unit 13, the second folded metal strip patch 221, and the third folded metal strip patch 222 are all copper, and the conductivities are all 5.8×10 9 S / m;

[0123] In this embodiment, the first folded metal strip patch 121 is bent 4 times at angles of 45°, 90°, 90°, and 45° in sequence, and the shape is "Z" - shaped. The second folded metal strip patch 221 and the third folded metal strip patch 222 are bent 3 times at 90° in sequence, and the shapes are both "door" - shaped;

[0124] In addition, the quasi - square ring patch unit 12, the cross - shaped patch unit 13, the second folded metal strip patch 221, and the third folded metal strip patch 222 can also be other shapes;

[0125] As Figure 7 and Figure 8 shown, the quasi - square ring patch unit 12 only needs to satisfy that there are depressions from the four corners towards the center. The depressions can be changed by bending the first folded metal strip patch 121 at multiple different angles or by arc - shaped bending. After changing the shape, very close performance can be achieved by adjusting its parameters;

[0126] In Figure 7 and Figure 8In the cross-shaped patch unit 13, the rectangular patch 1311 can also be replaced with other different shapes such as circles and hexagons. By adjusting its parameters, very similar performance can be achieved.

[0127] like Figures 9-12 The diagram shows the shapes of four interchangeable TM wave intensity response units 22. The second folded metal strip patch 221 and the third folded metal strip patch 222 can be left unbent, as shown... Figure 9 As shown, it can also be bent any number of times and at any angle to one or both sides, such as... Figure 10 and Figure 11 It can also be bent into an arc shape, such as Figure 12 It is only necessary to satisfy that the bending directions of the second folded metal strip patch 221 and the third folded metal strip patch 222 are opposite and approximately centrally symmetrical, and that the ends of the second folded metal strip patch 221 and the third folded metal strip patch 222 connected to the third patch resistor 223 are on the same vertical line. Different folding methods of the TM wave intensity response unit 22 will result in slight differences in bandwidth, but will not affect the angle stability.

[0128] In addition to the above description, the three-dimensional frequency selective surface unit can also be implemented by printing a resistive film on the square horizontal dielectric plate 11 and the rectangular vertical dielectric plate 21, that is: replacing the original metal patch units and patch resistors with a resistive film with a certain sheet resistance, while keeping the original shape of the resistive film pattern.

[0129] like Figure 13 As shown, the original square ring patch unit 12 and first patch resistor 14, the cross-shaped patch unit 13 and second patch resistor 15 are respectively replaced with square ring resistive film and cross-shaped resistive film; as Figure 14 As shown, the original TM wave intensity response unit 22 is replaced with a folded strip resistive film;

[0130] The three-dimensional frequency selective surface unit provided in this embodiment can significantly improve the angular stability of the absorber by combining horizontal and vertical structures. At the same time, the three-dimensional frequency selective surface unit in this embodiment has the advantage of low profile, small thickness and period size, which makes it easy to integrate with other devices and is highly convenient. In addition, each layer of the frequency selective surface unit in this embodiment adopts a centrally symmetrical pattern design, which reduces the absorber's sensitivity to the polarization direction of the incident electromagnetic wave.

[0131] Example 3

[0132] like Figure 15 As shown, this embodiment provides a broadband wide-angle absorber based on a three-dimensional frequency selective surface, using the three-dimensional frequency selective surface unit in embodiment 2, which includes several three-dimensional frequency selective surface units with the same structure and arranged continuously.

[0133] The arrangement of the three-dimensional frequency selective surface units is specifically a 3×3 matrix arrangement, while all the outermost rectangular vertical dielectric plates 21 in the absorber are removed.

[0134] In the specific implementation process, this embodiment verifies and illustrates the performance of the absorber through simulation experiments:

[0135] The specific simulation conditions are as follows: The reflection coefficient of the broadband wide-angle absorber based on the three-dimensional frequency selective surface in this embodiment is simulated using the high-frequency electromagnetic simulation software HFSS; the simulation model is the three-dimensional frequency selective surface element, using master-slave boundary conditions and Floquet port excitation;

[0136] Because of the addition of the metal base plate 3, electromagnetic waves cannot be transmitted from the back of the absorber. Therefore, electromagnetic wave energy only exists in reflection and absorption. When the reflection coefficient is less than -10dB, the corresponding absorption rate is greater than 90%.

[0137] Simulation content and results: Simulations were performed in TE mode and TM mode respectively, and the reflection coefficient curves of the absorber were obtained as the incident angle increased from 0° to 60°. Figure 16 and Figure 17 The following are simulation curves of the reflection coefficient of the absorber provided in the embodiments of the present invention when the incident angle increases from 0° to 60° in TE mode and TM mode, respectively.

[0138] Simulation results show that when the incident angle θ ranges from 0 to 60°, the absorber exhibits a reflectivity of less than -10 dB in the 3.14–6.62 GHz frequency band for both TE and TM wave incidence. This indicates that the absorber possesses excellent bandwidth and angular stability, meeting the requirements of applications such as broadband and large-angle stealth technology. Furthermore, the absorber's thickness is only 0.118λ. L The periodic size is only 0.152λ. L Therefore, it has a low profile and is easy to integrate with other devices;

[0139] In this embodiment, when manufacturing the absorber, all the outermost rectangular vertical dielectric plates 21 in the absorber are omitted to facilitate the assembly of the horizontal structure 1 and the vertical structure 2 together. (Refer to...) Figure 7 In this embodiment, the frequency selective surface unit of the absorber is arranged in a 3×3 continuous matrix; and when the number of arrays is relatively large (such as 20×20), reducing the outermost ring of rectangular vertical dielectric plates 21 has little impact on the absorber performance; it should be noted that the actual processing method is not limited to the method described in this embodiment. As long as the three-dimensional frequency selective surface unit of the present invention is used as the periodic unit of the absorber, the processed products will meet the design requirements.

[0140] The absorber provided in this embodiment, by combining horizontal and vertical structures, can significantly improve the angular stability of the absorber. For TE and TM waves incident at an angle of 0–60°, it can achieve more than 90% absorption within a 2.1 octave bandwidth. At the same time, the absorber in this embodiment has the advantage of low profile, small thickness and period size, which facilitates integration with other devices and is highly convenient. In addition, each layer of the frequency selective surface unit in this embodiment adopts a centrally symmetrical pattern design, which reduces the absorber's sensitivity to the polarization direction of the incident electromagnetic wave.

[0141] The same or similar labels correspond to the same or similar parts;

[0142] The terms used to describe positional relationships in the accompanying drawings are for illustrative purposes only and should not be construed as limiting this patent.

[0143] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A three-dimensional frequency-selective surface unit, characterized in that, include: The horizontal structure (1), vertical structure (2), and metal base plate (3) are arranged sequentially from top to bottom. The horizontal structure (1) includes a square horizontal substrate (11), a square ring patch unit (12) and a cross-shaped patch unit (13) printed on the square horizontal substrate (11), four identical first patch resistors (14) and four identical second patch resistors (15). The square ring patch unit (12) is a square ring structure with the same recess at the four corners facing the center point of the square horizontal dielectric plate (11); The square ring patch unit (12) includes four identical first folded metal strip patches (121), which are centrally symmetrical about the center of the square horizontal dielectric plate (11); each pair of adjacent first folded metal strip patches (121) are connected by a first patch resistor (14). The cross-shaped patch unit (13) is disposed within the square ring patch unit (12). The cross-shaped patch unit (13) includes four T-shaped patches (131) and one cross-shaped patch (132). The center of the cross-shaped patch (132) is located at the center of the square horizontal substrate (11). The four T-shaped patches (131) are centrally symmetrical about the center of the square horizontal substrate (11). Each of the T-shaped patches (131) includes a rectangular patch (1311) and a rectangular metal strip patch (1312). One end of the rectangular metal strip patch (1312) is connected to the rectangular patch (1311), and the other end is connected to one end of the cross patch (132) through a second patch resistor (15). The vertical structure (2) includes four rectangular vertical dielectric plates (21) and four TM wave intensity response units (22). The four rectangular vertical dielectric plates (21), the square horizontal dielectric plate (11) and the metal base plate (3) constitute a cuboid structure. The TM wave intensity response unit (22) is printed on the inner surface of the rectangular vertical dielectric plate (21). All TM wave intensity response units (22) have the same shape, and the orthographic projections of the TM wave intensity response units (22) on the opposite rectangular vertical dielectric plates (21) coincide. Each of the TM wave intensity response units (22) includes: a second folded metal strip patch (221), a third folded metal strip patch (222), and a third patch resistor (223). The third chip resistor (223) is located at the center of the rectangular vertical dielectric plate (21). One end of the third chip resistor (223) is connected to the second folded metal strip patch (221), and the other end is connected to the third folded metal strip patch (222). One end of each of the second folded metal strip patches (221) and the third folded metal strip patches (222) connected to the third chip resistor (223) is on the same vertical line within a preset length range; one end of each of the second folded metal strip patches (221) and the third folded metal strip patches (222) connected to the third chip resistor (223) is bent in opposite directions outside the preset length range. The total thickness h of the three-dimensional frequency-selective surface unit is 0.118λ. L The side length p of the square horizontal medium plate (11) is 0.152λ. L The thickness of the square horizontal medium plate (11) and all the rectangular vertical medium plates (21) is 0.005λ. L , where λ L Select the wavelength corresponding to the lowest operating frequency of the surface unit for the three-dimensional frequency; In the vertical structure (2), the width W4 of the TM wave intensity response unit (22) is 0.003λ. L ; The distance h1 between the top of the TM wave intensity response unit (22) and the bottom of the square horizontal dielectric plate (11) is 0.010λ. L The distance h2 between the bottom of the TM wave intensity response unit (22) and the top of the metal base plate (3) is 0.005λ. L ; The resistance value range of each of the first chip resistors (14) is 171~189Ω, the resistance value of each of the second chip resistors (15) is 114~126Ω, and the resistance value of each of the third chip resistors (223) is 300~700Ω. The square horizontal dielectric plate (11) and all the rectangular vertical dielectric plates (21) are made of non-magnetic materials, with a dielectric constant range of 3.8~5 and a loss angle range of 0.01~0.

03. The materials of the quasi-square loop patch unit (12), the cross-shaped patch unit (13), the second folded metal strip patch (221), and the third folded metal strip patch (222) are all conductive metals.

2. The three-dimensional frequency selective surface unit according to claim 1, characterized in that, In the horizontal structure (1), the distance L1 between two opposite sides of the square ring patch unit (12) is 0.117λ. L The outer side length L3 of the square ring patch unit (12) is 0.103λ. L The folding depth d of the first folded metal strip patch (121) is 0.056λ. L The width W1 of the square ring patch unit (12) is 0.004λ. L .

3. A three-dimensional frequency selective surface unit according to claim 2, characterized in that, In the horizontal structure (1), the maximum arm length L2 of the cross-shaped patch unit (13) is 0.080λ. L The length L4 of the rectangular patch (1311) is 0.013λ. L The width W3 of the rectangular patch (1311) is 0.010λ. L The width W2 of the rectangular metal strip patch (1312) is 0.004λ. L .

4. A three-dimensional frequency selective surface unit according to claim 3, characterized in that, The first folded metal strip patch (121) is bent in a "zigzag" shape after being bent multiple times in sequence. Each of the second folded metal strip patches (221) and the third folded metal strip patches (222) is bent k times, where k is a non-negative integer.

5. A broadband wide-angle absorber based on a three-dimensional frequency selective surface, using the three-dimensional frequency selective surface unit as described in any one of claims 1 to 4, characterized in that, It includes a number of three-dimensional frequency selective surface units with the same structure and arranged continuously. The arrangement mode of the three-dimensional frequency selective surface units is specifically a matrix arrangement of m×n, where m and n are the number of rows and columns of the matrix arrangement respectively.

6. A broadband wide-angle absorber based on a three-dimensional frequency-selective surface according to claim 5, characterized in that, Cancel the setting of all the outermost rectangular vertical dielectric plates (21) in the absorber.

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