Ultra-wideband wave-absorbing material based on three-layer metasurface and application of ultra-wideband wave-absorbing material

Abstract

The invention belongs to the technical field of electromagnetic microwaves, and particularly discloses an ultra-wideband wave-absorbing material based on a three-layer metasurface and application of the ultra-wideband wave-absorbing material based on the three-layer metasurface. Each wave-absorbing resonance unit comprises a first resistor loading metasurface layer, a first resistor loading metasurface substrate, a first resistor element, a first resistor loading metasurface supporting dielectric layer, a second resistor loading metasurface substrate, a second resistor loading metasurface layer and a second resistor element which are sequentially arranged from top to bottom; the device comprises a first resistor loading metasurface substrate, a second resistor loading metasurface supporting dielectric layer, a third resistor loading metasurface layer, a third resistor loading metasurface substrate, a third resistor element, a third resistor loading metasurface supporting dielectric layer and a pure metal backboard. According to the ultra-wideband wave-absorbing material based on the three-layer metasurface and the application of the ultra-wideband wave-absorbing material, 90% of ultra-wideband wave absorption can be achieved under a small-size structure, and the ultra-wideband wave-absorbing material has extremely high strategic value in the fields of electromagnetic stealth and the like.

Description

Technical Field

[0001] The present invention relates to the field of electromagnetic microwave technology, and in particular to an ultra-wideband absorbing material based on a three-layer metasurface and its application. Background Art

[0002] The rapid development of wireless communication technology has facilitated people's production and life, but the increasingly serious electromagnetic pollution problem cannot be ignored. To ensure people's living safety and quality of life, there is an urgent need for electromagnetic shielding materials with light weight, small thickness, wide bandwidth, and high absorption intensity to avoid the harm caused by microwaves.

[0003] Metasurface electromagnetic absorbers have received much attention due to their excellent selective absorption function for electromagnetic waves in specific frequency bands. Technicians can freely design the absorber by adjusting the shape pattern, size parameters, dielectric type, and lumped element impedance value of the metasurface. If components with switching characteristics, such as high-speed MEMS switches, diodes, or triodes, are integrated, the working frequency band of the absorber can be adjusted in real time according to needs. Compared with traditional material absorbers, it has higher absorption flexibility and better absorption effect, so it has also become a research hotspot in the current stealth technology field.

[0004] In the prior art, the design of high-performance metasurface absorbers mainly uses a single-layer complex structure, multi-layer metasurface coupling, and a combination of both to achieve ultra-wideband absorption of electromagnetic waves. The former mainly realizes the broadening of the -10dB absorption bandwidth through multi-resonant frequency point design; the latter realizes -10dB ultra-wideband absorption through mutual coupling or cooperative enhancement of multi-layer metasurfaces. However, the design of ultra-wideband absorbing materials has always been the focus of research in this field. Summary of the Invention

[0005] The purpose of the present invention is to provide an ultra-wideband absorbing material based on a three-layer metasurface and its application, which uses single-layer miniaturization technology and multi-layer mutual coupling and cooperative enhancement to achieve ultra-wideband absorption of the absorbing material. It can achieve an absorption performance of 90% in the ultra-wideband range, and at the same time has polarization-insensitive characteristics, solves the problem of narrow bandwidth of traditional absorbing coatings, and does not have a transmission band in the ultra-wideband absorption frequency band. The overall structure is easy to integrate lossy electronic components such as resistors, and the manufacturing process is simple, making it have extremely high application value in the fields of electromagnetic stealth, signal shielding, and electromagnetic protection.

[0006] To achieve the above object, the present invention provides a ultra-wideband absorbing material based on a three-layer metasurface, including at least one periodic absorbing resonant unit arranged in a square pattern centered at the centroid. Each absorbing resonant unit includes a first resistively loaded metasurface layer, a first resistively loaded metasurface substrate, a first resistive element, a first resistively loaded metasurface support dielectric layer, a second resistively loaded metasurface substrate, a second resistively loaded metasurface layer, a second resistive element, a second resistively loaded metasurface support dielectric layer, a third resistively loaded metasurface layer, a third resistively loaded metasurface substrate, a third resistive element, a third resistively loaded metasurface support dielectric layer, and a pure metal backplane, which are arranged in sequence from top to bottom.

[0007] Preferably, the first resistively loaded metasurface layer is a square-like loop patch structure with the first resistive element loaded at the middle positions of the four sides. The square-like loop patch structure includes a plurality of alternately arranged large-width square patches and small-width square patches with unequal widths, and the first resistive element is loaded on the small-width square patches.

[0008] Preferably, the overall length of the square-like loop patch structure is 6.5 mm - 11.5 mm, and the width is 0.25 mm - 0.65 mm;

[0009] The length of the large-width square patch is 2 mm - 6.8 mm, and the width is 0.5 mm - 2 mm;

[0010] The length of the small-width square patch is 0.3 mm - 2 mm, and the width is 0.1 mm - 1 mm;

[0011] The gap for loading the first resistive element is 0.15 mm - 0.65 mm;

[0012] The resistance value of the first resistive element is 302 Ω - 500 Ω.

[0013] Preferably, the material of the first support dielectric layer is one of foam materials with a relative dielectric constant of 1.0 - 4.0 and a thickness of 2 mm - 7 mm or an air cavity;

[0014] The material of the second support dielectric layer is one of foam materials with a relative dielectric constant of 1.0 - 4.0 and a thickness of 3 mm - 8 mm or an air cavity;

[0015] The material of the third support dielectric layer is one of foam materials with a relative dielectric constant of 1.0 - 4.0 and a thickness of 8 mm - 12 mm or an air cavity;

[0016] The foam material is one of polymethacrylimide and polyimide;

[0017] The first resistor-loaded metasurface substrate, the second resistor-loaded metasurface substrate, and the third resistor-loaded metasurface substrate are all one of epoxy glass cloth laminates and polytetrafluoroethylene glass fiber cloth copper clad laminates, and their thickness is 0.1 mm - 0.6 mm.

[0018] Preferably, the second resistor-loaded metasurface layer includes a square-like ring zigzag discrete strip grating structure loaded with the second resistor element, an octagon ring structure loaded with the second resistor element, a square-like ring discrete strip grating structure loaded with the second resistor element, and a square ring structure loaded with the second resistor element, which are arranged in sequence from the inside to the outside.

[0019] Preferably, one second resistor element is loaded at each zigzag of the square-like ring zigzag discrete strip grating structure, and a total of twelve second resistor elements are loaded; the overall length of the square-like ring zigzag discrete strip grating structure is 8 mm - 12 mm, the patch width is 0.2 - 2 mm, and the zigzags extend alternately in the same direction by 0.2 mm - 0.8 mm;

[0020] One second resistor element is loaded at each of the eight corners of the octagon ring structure, and a total of eight second resistor elements are loaded; the outer ring radius of the octagon ring structure is 5.4 mm - 7.9 mm, the inner ring radius is 1 mm - 5.4 mm, and the patch width is 0.2 mm - 2 mm;

[0021] One second resistor element is loaded at the middle position of each strip grating of the square-like ring discrete strip grating structure, and a total of four second resistor elements are loaded; the overall length of the square-like ring discrete strip grating structure is 2.5 mm - 5.9 mm, and the patch width is 0.2 mm - 2 mm;

[0022] One second resistor element is loaded at the middle position of each side of the square ring structure, and a total of four second resistor elements are loaded; each side length of the square ring structure is 2.5 mm - 5.9 mm, and the patch width is 0.2 mm - 2 mm;

[0023] The gap for loading the second resistor element in the second resistor-loaded metasurface layer is 0.15 mm - 0.65 mm, and the resistance value of the second resistor is 302 Ω - 500 Ω.

[0024] Preferably, the third resistor-loaded metasurface layer includes a large square ring structure loaded with the third resistor element, an octagon ring structure loaded with the third resistor element, and a small square ring structure loaded with the third resistor element, which are arranged in sequence from the inside to the outside.

[0025] Preferably, one of the third resistance elements is loaded at the bending position of the large square ring structure, and a total of four third resistance elements are loaded; the side length of the large square ring structure is 3 mm - 6.5 mm, and the patch width is 0.2 mm - 1 mm;

[0026] One of the third resistance elements is loaded at the middle position of each side of the octagonal ring structure, and a total of eight third resistance elements are loaded; the outer ring width of the octagonal ring structure is 4.0 mm - 5.6 mm, the inner ring width is 2.5 mm - 4.0 mm, and the patch width is 0.2 mm - 1 mm;

[0027] One of the third resistance elements is loaded at the middle position of each side of the small square ring structure, and a total of four third resistance elements are loaded; the side length of the small square ring structure is 2.0 mm - 4.5 mm, and the patch width is 0.2 mm - 1 mm;

[0028] The gap for loading the third resistance element in the third resistance loaded metasurface layer is 0.5 mm, and the resistance value of the third resistance element is 100 Ω - 500 Ω.

[0029] Preferably, the first resistance loaded metasurface layer, the first resistance loaded metasurface substrate, the first resistance loaded metasurface support dielectric layer, the second resistance loaded metasurface layer, the second resistance loaded metasurface substrate, the second resistance loaded metasurface support dielectric layer, the third resistance loaded metasurface layer, the third resistance loaded metasurface substrate, the third resistance loaded metasurface support dielectric layer and the pure metal backplane are made into the absorbing resonant unit through a vacuum hot pressing process;

[0030] The first resistance element, the second resistance element and the third resistance element are all lumped resistance elements or equivalent resistances obtained by at least one of magnetron sputtering, screen printing and inkjet printing;

[0031] The materials of the first resistance loaded metasurface layer, the second resistance loaded metasurface layer and the third resistance loaded metasurface layer are all one of the transition metal element simple substances, and the first resistance loaded metasurface layer, the second resistance loaded metasurface layer and the third resistance loaded metasurface layer are respectively prepared on the first resistance loaded metasurface substrate, the second resistance loaded metasurface substrate and the third resistance loaded metasurface substrate by at least one of inkjet printing, electrochemical etching, mechanical engraving or magnetron sputtering.

[0032] The present invention also provides an application of a triple-layer metasurface-based ultra-wideband absorbing material in electromagnetic stealth, signal shielding and electromagnetic protection.

[0033] Therefore, by adopting the above-mentioned triple-layer metasurface-based ultra-wideband absorbing material and its application, the present invention has the following beneficial effects:

[0034] (1) The present invention achieves -10 dB wave absorption in the frequency band of 7 GHz - 12 GHz through the first layer structure; the second layer structure integrates a large-sized extremely low-frequency wave absorption structure on a high-frequency small-sized wave absorption structure by using miniaturization technology, enabling it to achieve -10 dB wave absorption in the frequency bands of 2.5 GHz - 4.6 GHz, 8 GHz - 13.2 GHz, and 14.89 GHz - 20 GHz, and broadening the high-frequency operating frequency band of the small size; the third layer structure achieves -10 dB wave absorption in the frequency band of 7.5 GHz - 16.68 GHz.

[0035] (2) The present invention uses a pure metal backplane to achieve multiple reflections of electromagnetic waves and utilizes the principle of 1 / 4 wavelength phase interference cancellation to achieve mutual coupling, broadening the operating frequency band; the three-layer structure realizes ultra-wideband wave absorption of 2 GHz - 18 GHz in a small-sized structure through inter-layer mutual coupling synergy enhancement. When electromagnetic waves are vertically incident, the frequency band with a reflectivity lower than -10 dB is 2.13 GHz - 18.19 GHz, and the relative bandwidth is 150.7%; the frequency band with an absorption rate greater than 90% is 2.13 GHz - 18.19 GHz; when the incident angle reaches 45°, the wave absorption rate can still remain greater than 85% within 2 GHz - 20 GHz; low-frequency wave absorption of 2 GHz - 4 GHz can be achieved in the small-sized structure corresponding to high-frequency wave absorption, and wave absorption performance of about 90% can be achieved within the ultra-wideband range. At the same time, it has the characteristic of polarization insensitivity, solves the problem of narrow bandwidth of traditional wave-absorbing coatings, and does not have a transmission wave band within the ultra-wideband wave absorption frequency band.

[0036] (3) The overall structure of the present invention is easy to integrate lossy electronic components such as resistors, and the manufacturing process is simple, enabling it to have extremely high application value in the fields of electromagnetic stealth, signal shielding, and electromagnetic protection.

[0037] The technical solution of the present invention will be further described in detail below through the accompanying drawings and embodiments. Description of the Drawings

[0038] Figure 1 is a schematic structural diagram of an embodiment of the present invention;

[0039] Figure 2 is a schematic cross-sectional diagram of an embodiment of the present invention;

[0040] Figure 3 is a schematic structural diagram of the first resistor-loaded metasurface layer of an embodiment of the present invention;

[0041] Figure 4 is a schematic structural diagram of the second resistor-loaded metasurface layer of an embodiment of the present invention;

[0042] Figure 5 is a schematic structural diagram of the third resistor-loaded metasurface layer of an embodiment of the present invention;

[0043] Figure 6 It is a graph showing the variation of the reflection coefficient of the first resistively loaded metasurface layer of the present invention with frequency at different incident angles;

[0044] Figure 7 It is a graph showing the variation of the absorption rate of the first resistively loaded metasurface layer of the present invention with frequency at different incident angles;

[0045] Figure 8 It is a graph showing the variation of the reflection coefficient of the second resistively loaded metasurface layer of the present invention with frequency at different incident angles;

[0046] Figure 9 It is a graph showing the variation of the absorption rate of the second resistively loaded metasurface layer of the present invention with frequency at different incident angles;

[0047] Figure 10 It is a graph showing the variation of the reflection coefficient of the third resistively loaded metasurface layer of the present invention with frequency at different incident angles;

[0048] Figure 11 It is a graph showing the variation of the absorption rate of the third resistively loaded metasurface layer of the present invention with frequency at different incident angles;

[0049] Figure 12 It is the variation of the reflection coefficient of the overall structure without a metal backplane with frequency at different incident angles in the embodiment of the present invention;

[0050] Figure 13 It is the variation of the absorption rate of the overall structure without a metal backplane with frequency at different incident angles in the embodiment of the present invention;

[0051] Figure 14 It is the variation of the reflection coefficient of the overall structure with frequency at different incident angles in the embodiment of the present invention;

[0052] Figure 15 It is the variation of the absorption rate of the overall structure with frequency at different incident angles in the embodiment of the present invention;

[0053] Figure 16 It is a graph showing the variation of the reflection coefficient of the TE wave corresponding to different incident angles with frequency in the embodiment of the present invention;

[0054] Figure 17 It is a graph showing the variation of the absorption rate of the TE wave corresponding to different incident angles with frequency in the embodiment of the present invention;

[0055] Figure 18 It is a graph showing the variation of the reflection coefficient of the TM wave corresponding to different incident angles with frequency in the embodiment of the present invention;

[0056] Figure 19 It is a graph showing the variation of the absorption rate of the TM wave corresponding to different incident angles with frequency in the embodiment of the present invention.

[0057] Reference numerals

[0058] 1. First resistor-loaded metasurface layer; 2. First resistor-loaded metasurface substrate; 3. First resistor element; 4. First resistor-loaded metasurface supporting dielectric layer; 5. Second resistor-loaded metasurface substrate; 6. Second resistor-loaded metasurface layer; 7. Second resistor element; 8. Second resistor-loaded metasurface supporting dielectric layer; 9. Third resistor-loaded metasurface layer; 10. Third resistor-loaded metasurface substrate; 11. Third resistor element; 12. Third resistor-loaded metasurface supporting dielectric layer; 13. Pure metal backplane. Detailed implementation manners

[0059] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0060] Unless otherwise defined, the technical terms or scientific terms used in the present invention shall have the ordinary meanings understood by those of ordinary skill in the field to which the present invention belongs.

[0061] Embodiment 1

[0062] As Figures 1 - 5 shown, a ultra-wideband microwave absorbing material based on a three-layer metasurface includes at least one periodic microwave absorbing resonant unit arranged in a square array centered at the centroid. Each microwave absorbing resonant unit includes, from top to bottom, a first resistor-loaded metasurface layer 1, a first resistor-loaded metasurface substrate 2, a first resistor element 3, a first resistor-loaded metasurface supporting dielectric layer 4, a second resistor-loaded metasurface substrate 5, a second resistor-loaded metasurface layer 6, a second resistor element 7, a second resistor-loaded metasurface supporting dielectric layer 8, a third resistor-loaded metasurface layer 9, a third resistor-loaded metasurface substrate 10, a third resistor element 11, a third resistor-loaded metasurface supporting dielectric layer 12, and a pure metal backplane 13.

[0063] The first resistor-loaded metasurface layer 1 is a square-ring patch structure with first resistor elements 3 loaded at the middle positions of the four sides. By setting the first resistor-loaded metasurface layer 1, it is mainly to achieve high-frequency impedance matching. Its electrical size corresponds to the wavelength near 8 GHz, realizing the absorption of electromagnetic waves in the frequency band of 7 GHz - 12 GHz.

[0064] The square-ring-like patch structure is composed of alternately arranged square patches with unequal widths to form a quadrilateral-like shape. Among them, the square patches with large widths are on both sides of the quadrilateral-like ring edge, and the square patches with small widths are between the two square patches with large widths and at the bends of the quadrilateral-like ring. Moreover, the structural dimension parameters of the small-width square patches at the bends and the small-width square patches between the two large-width square patches are the same. A first resistor element 3 is loaded between every two small-width square patches on each side of the quadrilateral-like shape; the overall length of each side of the quadrilateral-like shape is 6.5 mm - 11.5 mm, and the width of each side is 0.25 mm - 0.65 mm; the gap for loading the first resistor element 3 is 0.15 mm - 0.65 mm.

[0065] The resistance value of the first resistor element 3 is 300 Ω - 500 Ω.

[0066] The length of each large-width square patch of the quadrilateral-like shape is 2 mm - 6.8 mm, and the width is 0.5 mm - 2 mm; the length of each small-width square patch is 0.3 mm - 2 mm, and the width is 0.1 mm - 1 mm. The quadrilateral-like shape is prepared on the first resistor-loaded metasurface substrate 2 by at least one of the methods of inkjet printing, electrochemical etching, mechanical engraving, or magnetron sputtering. In this embodiment, the mechanical engraving process is used to engrave the metal square patches on the epoxy glass cloth laminate (FR4 board).

[0067] The second resistor-loaded metasurface layer 6 includes a square-ring-like meandering discrete strip grating structure loaded with a second resistor element 7, an octagonal-ring structure, a square-ring-like discrete strip grating structure, and a square-ring structure arranged in sequence from the inside to the outside; the frequencies corresponding to the wavelengths of the four discrete structures in the above structure are about 2 GHz. By meandering and winding, the electrical size of the strip grating with an overall length of the wavelength of 10 GHz is increased to the wavelength length corresponding to 2 GHz. However, in order to achieve stable oblique incident angles, the four discrete structures are arranged in a highly symmetric structure of a quadrilateral-like ring. At the same time, miniaturization technology is applied to reduce the large size corresponding to low-frequency wave absorption, which plays a certain positive role in improving the polarization-sensitive characteristics. Through the separate second resistor-loaded metasurface layer 6, mid- and high-frequency wave absorption in the range of 7.8 GHz - 18 GHz can be achieved. Through the interlayer mutual coupling of the complete structure, the low-frequency (2 GHz - 4 GHz) wave absorption effect of the second resistor-loaded metasurface layer 6 will be demonstrated.

[0068] The third resistor-loaded metasurface layer 9 includes a large square-ring structure, an octagonal-ring structure, and a small square-ring structure loaded with a third resistor element 11. Through the above structure, it has wave absorption functions in the ranges of 2 GHz - 14.67 GHz and 14.89 GHz - 20 GHz, strengthens the wave absorption effects in the ranges of 7.8 GHz - 18 GHz and 7 GHz - 12 GHz. At the same time, its bottom layer structure is loaded with a pure metal backplane 13, which can confine the electromagnetic waves in the absorber to generate interlayer mutual coupling and synergistic enhancement, strengthening the absorption depth and also expanding the working bandwidth.

[0069] The material of the first resistively loaded metasurface supporting dielectric layer 4 is a foam material or an air cavity with a relative dielectric constant close to that of air. Its relative dielectric constant is 1.0 - 4.0, and its thickness is 2 mm - 7 mm. The foam material is one of polymethacrylimide and polyimide. In this embodiment, the selected material is PMI (polymethacrylimide), whose relative dielectric constant is about 1.06, close to that of air, and can be regarded as a lossless dielectric support layer. The materials of the second resistively loaded metasurface supporting dielectric layer 8 and the third resistively loaded metasurface supporting dielectric layer 12 are the same as that of the first resistively loaded metasurface supporting dielectric layer 4. The difference is that the thickness of the second resistively loaded metasurface supporting dielectric layer 8 is 3 mm - 8 mm, and the thickness of the third resistively loaded metasurface supporting dielectric layer 12 is 8 mm - 12 mm.

[0070] The first resistively loaded metasurface substrate 2 is made of a material with a relative dielectric constant of 4.0 - 6.0 and a thickness of 0.1 mm - 1 mm, and is one of epoxy glass cloth laminate and polytetrafluoroethylene glass fiber cloth clad copper laminate. In this embodiment, the material selected for the first resistively loaded metasurface substrate 2 is epoxy glass cloth laminate (FR4 board), whose relative dielectric constant is 4.3 and the loss tangent value is 2.5×10 -3 , and the thickness is 0.1 mm - 1 mm. The materials of the second resistively loaded metasurface substrate 5 and the third resistively loaded metasurface substrate 10 are the same as that of the first resistively loaded metasurface substrate 2.

[0071] The pure metal backplane 13 during simulation is regarded as a perfect ideal electrical conductor, and in practice, a metal material with high electrical conductivity is selected. In this embodiment, pure copper (annealed copper) is selected, and its thickness is 0.023 mm.

[0072] The second resistively loaded metasurface layer 6 includes a square - like loop zigzag discrete strip - grid structure (the square - like loop zigzag discrete strip - grid structure is composed of four strip - grid - like structures that are zigzag - bent and arranged parallel to the edge of the second resistively loaded metasurface supporting dielectric layer 8), an octagonal loop structure, a square - like loop discrete strip - grid structure, and a square loop structure from inside to outside. A second resistor element 7 is loaded at each zigzag of each square - like loop zigzag discrete strip - grid structure, and a total of three second resistor elements 7 are loaded on each square - like loop zigzag discrete strip - grid structure. A second resistor element 7 is loaded at each of the eight corners of the octagonal loop structure, and a total of eight second resistor elements 7 are loaded. A second resistor element 7 is loaded at the middle position of each strip - grid of the square - like loop discrete strip - grid structure, and a total of four second resistor elements 7 are loaded. A second resistor element 7 is loaded at the middle position of each side of the square loop structure, and a total of four second resistor elements 7 are loaded.

[0073] The gap for loading the second resistor element 7 on the quasi-square loop zigzag discrete strip grating structure is 0.15 mm - 0.65 mm; the gap for loading the second resistor element 7 on the octagonal loop structure is 0.15 mm - 0.65 mm; the gap for loading the second resistor element 7 on the quasi-square loop discrete strip grating structure is 0.15 mm - 0.65 mm; the gap for loading the second resistor element 7 on the square loop structure is 0.15 mm - 0.65 mm. The resistance value of the second resistor element 7 is 300 Ω - 500 Ω.

[0074] The overall length of the quasi-square loop zigzag discrete strip grating structure is 8 mm - 12 mm, the patch width is 0.2 - 2 mm, the zigzag parts extend alternately in the same direction by 0.2 mm - 0.8 mm, and there are three extension positions on each zigzag discrete structure. The outer ring radius of the octagonal loop structure is 5.4 mm - 8 mm, the inner ring radius is 1 mm - 6 mm, and the patch width is 0.2 mm - 2 mm. The quasi-square loop discrete strip grating structure is composed of four rectangular strips, the overall length of each rectangular strip is 2.5 mm - 6 mm, and the patch width is 0.2 mm - 2 mm; each side length of the four-sided loop structure is 2.5 mm - 6 mm, and the patch width is 0.2 mm - 2 mm. The quasi-square loop zigzag discrete strip grating structure, the octagonal loop structure, the quasi-square loop discrete strip grating structure, and the four-sided loop structure are all prepared on the second resistor-loaded metasurface substrate 5 by at least one of spraying, electrochemical etching, mechanical engraving, or magnetron sputtering. In this embodiment, the mechanical engraving process is used to engrave the metal square patches on the FR4 board.

[0075] The third resistor-loaded metasurface layer 9 includes a large square loop structure, an octagonal loop structure, and a small square loop structure arranged in sequence from the inside to the outside. A third resistor element 11 is loaded at the bending part of the large square loop structure, and a total of four third resistor elements 11 are loaded. A third resistor element 11 is loaded at the middle position of each side of the octagonal loop structure, and a total of eight third resistor elements 11 are loaded. A third resistor element 11 is loaded at the middle position of each side of the small square loop structure, and a total of four third resistor elements 11 are loaded. A gap of 0.5 mm is reserved when each structure loads the third resistor element 11. The resistance value of the third resistor element 11 is 100 Ω - 500 Ω.

[0076] The side length of the large square ring structure is 3 mm - 6.5 mm, and the patch width is 0.2 mm - 1 mm. The outer ring width of the octagonal ring structure is 4.0 mm - 5.6 mm, the inner ring width is 2.5 mm - 4.0 mm, and the patch width is 0.2 mm - 1 mm. The patch side length of the small square ring structure is 2.0 mm - 4.5 mm, and the patch width is 0.2 mm - 1 mm. The large square ring structure, the octagonal ring structure, and the small square ring structure are all prepared on the third resistive loaded metasurface substrate 10 by at least one of the methods of inkjet printing, electrochemical etching, mechanical engraving, or magnetron sputtering. In this embodiment, a mechanical engraving process is used to engrave a metal square patch on an FR4 board.

[0077] The first resistive loaded metasurface layer 1, the second resistive loaded metasurface layer 6, and the third resistive loaded metasurface layer 9 (patch) are all one of the elemental substances of transition metals with conductive properties such as gold, silver, copper, aluminum, and iron. In this embodiment, the material of the metal patch is copper.

[0078] The first resistive element 3, the second resistive element 7, and the third resistive element 11 are all lumped resistive elements or equivalent resistances obtained by at least one of magnetron sputtering, screen printing, and inkjet printing. In this embodiment, a PCB soldering process is used to solder the lumped resistive element into the reserved gap.

[0079] The first resistive loaded metasurface layer 1, the first resistive loaded metasurface substrate 2, the first resistive element 3, the first resistive loaded metasurface supporting dielectric layer 4, the second resistive loaded metasurface substrate 5, the second resistive loaded metasurface layer 6, the second resistive element 7, the second resistive loaded metasurface dielectric supporting layer 8, the third resistive loaded metasurface layer 9, the third resistive loaded metasurface substrate 10, the third resistive element 11, the third resistive loaded metasurface supporting dielectric layer 12, and the pure metal backplane 13 are made into an electromagnetic wave absorbing unit through a vacuum hot pressing process.

[0080] Through the above structure, the following is achieved: the AC electric field component of a certain specific frequency of the incident electromagnetic wave generates an induced current in the first resistive loaded metasurface layer, the second resistive loaded metasurface layer, and the third resistive loaded metasurface layer. Due to the existence of the lumped resistance of the energy conversion device, the induced current is converted into ohmic heat loss, thereby achieving the absorption of electromagnetic waves. At the same time, the loading of the resistance can also achieve impedance matching between the structure and the free space impedance, enabling the incident electromagnetic wave to enter the absorber interior to the greatest extent. The first resistive loaded metasurface layer, the second resistive loaded metasurface layer, and the third resistive loaded metasurface layer enable the electromagnetic wave to achieve multiple ohmic loss resonances and absorptions within the layer through mutual coupling. The auxiliary pure metal backplane between the layers will achieve multiple reflections of the electromagnetic wave, and achieve ultra-wideband absorption through quarter-wavelength interference cancellation.

[0081] Experimental test

[0082] The simulation software is used to analyze the ultra-wideband absorbing material (triple-layer metasurface ultra-wideband absorber) prepared in the first embodiment to explain the working characteristics of the absorber.

[0083] It can be seen from Figure 6 that the -10 dB operating frequency band of the first-layer absorber structure is 7 GHz - 12 GHz. As the incident angle of the electromagnetic wave increases, the high-frequency operating frequency point gradually moves to a higher frequency, and the low-frequency point changes slightly. When the incident angle is greater than 30°, the reflection coefficient of the structure is greater than -10 dB. At this time, the tangential component of the electromagnetic wave energy along the surface of the structure is relatively large, resulting in a poor absorption effect of the structure. In addition, when the incident angle is greater than 30°, grating lobes appear after 15 GHz at high frequencies. The interlayer mutual coupling effect will optimize the grating lobe phenomenon and simultaneously broaden the absorption frequency band.

[0084] At the same time, it can be seen from Figure 7 that the 90% absorption frequency band corresponds to Figure 6 the -10 dB reflection coefficient frequency band in

[0085] It can be seen from Figure 8 that the -10 dB operating frequency band of the second-layer absorber structure is 2.5 GHz - 4.6 GHz, 8 GHz - 13.2 GHz, and 14.89 GHz - 20 GHz. The electrical size length corresponding to the absorption frequency point of 20 GHz in this structure is 15 mm. In order to avoid the appearance of grating lobes, the period of the absorption structure unit must be controlled within 7.5 mm. Therefore, a grating structure based on miniaturization technology is integrated on the second layer. The electrical size of this structure is 65.22 mm - 120 mm, and the absorption effect in the frequency band of 2.5 GHz - 4.6 GHz can be achieved, that is, the absorption effect of the extremely low-frequency large-size structure is realized on the high-frequency small-size absorber structure of the second layer. At the same time, the absorption of small-size high frequencies is integrated to broaden the working bandwidth, verifying the working principle of the present invention.

[0086] At the same time, it can be seen from Figure 9 that the 90% absorption frequency band corresponds to Figure 8 the -10 dB reflection coefficient frequency band in

[0087] It can be seen from Figure 10 that the -10 dB operating frequency band of the third-layer absorber structure is 7.5 GHz - 16.68 GHz. When the incident angle increases to 45°. For the absorption in the frequency bands of 7.5 GHz - 12 GHz of the first layer and 8 GHz - 13.2 GHz of the second layer, a certain degree of enhancement and broadening can be achieved.

[0088] It can be seen from Figure 11 that the 90% absorption frequency band corresponds to Figure 10 the -10 dB reflection coefficient frequency band in

[0089] It can be seen fromFigure 12 It can be seen that when the pure metal backplane 13 is not added to the overall absorber structure, the reflection coefficients in the frequency band of 2.13 GHz - 18.19 GHz are all around -7 dB, that is, the absorption rate is only about 80% when the pure metal backplane 13 is not added. This is mainly because the absorption effect of the absorber of the present invention is based on the multi-layer mutual coupling effect and the multiple interference cancellation absorption principle of the quarter-wavelength resonance loss principle. After removing the pure metal backplane 13, multiple reflections cannot be formed, resulting in a deterioration of the absorption effect, thus proving the working principle of the present invention.

[0090] At the same time, from Figure 13 it can be seen that the 80% absorption frequency band corresponds to Figure 12 the -7 dB reflection coefficient frequency band in

[0091] From Figure 14 it can be seen that after the three-layer absorber structures are coupled together, the -10 dB working frequency band is 2.13 GHz - 18.19 GHz, and the -9 dB working frequency band is 2 GHz - 18.5 GHz. The first-layer structure absorbs in the range of 7 GHz - 12 GHz, the second-layer miniaturized structure absorbs in the frequency bands of 2.5 GHz - 4.6 GHz, 8 GHz - 13.2 GHz and 14.89 GHz - 20 GHz, and the third-layer structure absorbs in the range of 7.5 GHz - 16.68 GHz. The mutual coupling effect of the three-layer absorber structures, assisted by the multiple reflections of the pure metal backplane 13, broadens the absorption frequency band, achieving 90% ultra-wideband absorption in the range of 2.13 GHz - 18.19 GHz and 87.4% ultra-wideband absorption in the range of 2 GHz - 18.5 GHz within a size of about 7.5 mm, thus verifying the working principle of the present invention.

[0092] At the same time, from Figure 15 it can be seen that the 90% absorption frequency band and the 87.4% absorption frequency band correspond to Figure 14 the -10 dB and -9 dB reflection coefficient frequency bands in

[0093] From Figure 16 it can be seen that under the perpendicular incidence of TE polarization, the maximum -10 dB corresponding working bandwidth is 2.13 GHz - 18.19 GHz. As the incident angle increases, the reflection coefficients in some frequency bands are higher than -10 dB but still lower than -9 dB. The high-frequency part of the -10 dB working frequency band starts to shift to higher frequencies as the incident angle increases, and the low-frequency part basically does not change with the change of the incident angle.

[0094] At the same time, from Figure 17 it can be seen that the 90% absorption frequency band and the 87.4% absorption frequency band correspond to Figure 16 the -10 dB and -9 dB reflection coefficient frequency bands in

[0095] From Figure 18It can be seen that the maximum operating bandwidth corresponding to -10 dB under TM polarization vertical incidence is 2.15 GHz - 18.11 GHz. As the incident angle increases, the reflection coefficients in some frequency bands are higher than -10 dB but still lower than -9 dB. The high-frequency band of the -10 dB operating frequency band begins to shift to higher frequencies as the incident angle increases, while the low-frequency band basically does not change with the change of the incident angle.

[0096] Meanwhile, it can be seen from Figure 19 that the 90% wave absorption frequency band and the 87.4% absorption frequency band correspond to the Figure 18 -10 dB and -9 dB reflection coefficient frequency bands in

[0097] Therefore, the present invention adopts the above-mentioned ultra-wideband wave-absorbing material based on a three-layer metasurface and its application. Through the synergistic enhancement effect of interlayer mutual coupling and miniaturization technology, the operating bandwidth of high-frequency wave absorption is broadened, enabling it to achieve ultra-wideband wave absorption of 2 GHz - 18 GHz under a small-size structure. This structure has extremely high strategic value in the fields of electromagnetic stealth, signal shielding, and electromagnetic protection.

[0098] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions of the present invention or make equivalent substitutions, and these modifications or equivalent substitutions cannot make the modified technical solutions deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. An ultra-wideband absorbing material based on a three-layer metasurface, characterized in that: It includes at least one periodic absorbing resonant unit arranged in a square centroid pattern. Each absorbing resonant unit includes a first resistively loaded metasurface layer, a first resistively loaded metasurface substrate, a first resistive element, a first resistively loaded metasurface support dielectric layer, a second resistively loaded metasurface substrate, a second resistively loaded metasurface layer, a second resistive element, a second resistively loaded metasurface support dielectric layer, a third resistively loaded metasurface layer, a third resistively loaded metasurface substrate, a third resistive element, a third resistively loaded metasurface support dielectric layer, and a pure metal backplane, which are arranged in sequence from top to bottom.

2. The ultra-wideband absorbing material based on a three-layer metasurface according to claim 1, characterized in that: The first resistively loaded metasurface layer is a square-ring-like patch structure with the first resistive element loaded at the middle positions of its four sides. The square-ring-like patch structure includes several alternately arranged large-width square patches and small-width square patches with unequal widths, and the first resistive element is loaded on the small-width square patches.

3. The ultra-wideband absorbing material based on a three-layer metasurface according to claim 2, characterized in that: The overall length of the square-ring-like patch structure is 6.5 mm - 11.5 mm, and the width is 0.25 mm - 0.65 mm; The length of the large-width square patch is 2 mm - 6.8 mm, and the width is 0.5 mm - 2 mm; The length of the small-width square patch is 0.3 mm - 2 mm, and the width is 0.1 mm - 1 mm; The gap for loading the first resistive element is 0.15 mm - 0.65 mm; The resistance value of the first resistive element is 302 Ω - 500 Ω.

4. The ultra-wideband absorbing material based on a three-layer metasurface according to claim 1, characterized in that: The material of the first support dielectric layer is one of foam materials or air cavities with a relative dielectric constant of 1.0 - 4.0 and a thickness of 2 mm - 7 mm; The material of the second support dielectric layer is one of foam materials or air cavities with a relative dielectric constant of 1.0 - 4.0 and a thickness of 3 mm - 8 mm; The material of the third support dielectric layer is one of foam materials or air cavities with a relative dielectric constant of 1.0 - 4.0 and a thickness of 8 mm - 12 mm; The foam material is one of polymethacrylimide and polyimide; The first resistively loaded metasurface substrate, the second resistively loaded metasurface substrate, and the third resistively loaded metasurface substrate are all one of epoxy glass cloth laminates and polytetrafluoroethylene glass fiber cloth copper clad laminates, and their thickness is 0.1 mm - 0.6 mm.

5. The ultra-wideband absorbing material based on a three-layer metasurface according to claim 1, wherein: The second resistively loaded metasurface layer includes a square-ring-like zigzag discrete strip grid structure for loading the second resistive element, an octagon-ring structure for loading the second resistive element, a square-ring-like discrete strip grid structure for loading the second resistive element, and a square-ring structure for loading the second resistive element, which are arranged in sequence from the inside to the outside.

6. The ultra-wideband absorbing material based on a three-layer metasurface according to claim 5, characterized in that: One second resistive element is loaded at each zigzag of the square-ring-like zigzag discrete strip grid structure, and a total of twelve second resistive elements are loaded; the overall length of the square-ring-like zigzag discrete strip grid structure is 8 mm - 12 mm, the patch width is 0.2 - 2 mm, and the zigzags alternately extend in the same direction by 0.2 mm - 0.8 mm; Each of the eight corners of the octagonal ring structure is loaded with one of the second resistor elements, and a total of eight second resistor elements are loaded; the outer radius of the octagonal ring structure is 5.4 mm - 7.9 mm, the inner radius is 1 mm - 5.4 mm, and the patch width is 0.2 mm - 2 mm; Each of the middle positions of the strip gratings of the quasi-square ring discrete strip grating structure is loaded with one of the second resistor elements, and a total of four second resistor elements are loaded; the overall length of the quasi-square ring discrete strip grating structure is 2.5 mm - 5.9 mm, and the patch width is 0.2 mm - 2 mm; Each of the middle positions of the sides of the square ring structure is loaded with one of the second resistor elements, and a total of four second resistor elements are loaded; each side length of the square ring structure is 2.5 mm - 5.9 mm, and the patch width is 0.2 mm - 2 mm; The gap of the second resistor loaded metasurface layer for loading the second resistor element is 0.15 mm - 0.65 mm, and the resistance value of the second resistor is 302 Ω - 500 Ω.

7. The ultra-wideband absorbing material based on a three-layer metasurface according to claim 1, characterized in that: The third resistor loaded metasurface layer includes a large square ring structure for loading the third resistor element, an octagonal ring structure for loading the third resistor element, and a small square ring structure for loading the third resistor element, which are arranged in sequence from the inside to the outside.

8. An ultra-wideband absorbing material based on a three-layer metasurface according to claim 7, characterized in that: One of the third resistor elements is loaded at the bend of the large square ring structure, and a total of four third resistor elements are loaded; the side length of the large square ring structure is 3 mm - 6.5 mm, and the patch width is 0.2 mm - 1 mm; One of the third resistor elements is loaded at the middle position of each side of the octagonal ring structure, and a total of eight third resistor elements are loaded; the outer width of the octagonal ring structure is 4.0 mm - 5.6 mm, the inner width is 2.5 mm - 4.0 mm, and the patch width is 0.2 mm - 1 mm; One of the third resistor elements is loaded at the middle position of each side of the small square ring structure, and a total of four third resistor elements are loaded; the side length of the small square ring structure is 2.0 mm - 4.5 mm, and the patch width is 0.2 mm - 1 mm; The gap of the third resistor loaded metasurface layer for loading the third resistor element is 0.5 mm, and the resistance value of the third resistor element is 100 Ω - 500 Ω.

9. The ultra-wideband absorbing material based on a three-layer metasurface according to claim 1, characterized in that: The first resistor loaded metasurface layer, the first resistor loaded metasurface substrate, the first resistor loaded metasurface support dielectric layer, the second resistor loaded metasurface layer, the second resistor loaded metasurface substrate, the second resistor loaded metasurface support dielectric layer, the third resistor loaded metasurface layer, the third resistor loaded metasurface substrate, the third resistor loaded metasurface support dielectric layer, and the pure metal backplane are made into the microwave absorption resonant unit through a vacuum hot pressing process; The first resistor element, the second resistor element, and the third resistor element are all lumped resistor elements or equivalent resistors obtained by at least one of magnetron sputtering, screen printing, and inkjet printing; The materials of the first resistive-loaded metasurface layer, the second resistive-loaded metasurface layer, and the third resistive-loaded metasurface layer are all one of the elemental transition metals. The first resistive-loaded metasurface layer, the second resistive-loaded metasurface layer, and the third resistive-loaded metasurface layer are respectively fabricated on the first resistive-loaded metasurface substrate, the second resistive-loaded metasurface substrate, and the third resistive-loaded metasurface substrate by at least one of the methods of spraying, electrochemical etching, mechanical engraving, or magnetron sputtering.

10. Application of the ultra-wideband absorbing material based on a three-layer metasurface according to any one of claims 1-9 in electromagnetic stealth, signal shielding, and electromagnetic protection.

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