An ultra-wideband absorbing material based on a three-layer metasurface and its application

Abstract

This invention belongs to the field of electromagnetic microwave technology, specifically disclosing an ultra-wideband absorbing material based on a three-layer metasurface and its applications. The material includes at least one periodic absorbing resonant unit arranged in a centroidal square pattern. Each absorbing resonant unit comprises, from top to bottom, a first resistive-loaded metasurface layer, a first resistive-loaded metasurface substrate, a first resistive element, a first resistive-loaded metasurface supporting dielectric layer, a second resistive-loaded metasurface substrate, a second resistive-loaded metasurface layer, a second resistive element, a second resistive-loaded metasurface supporting dielectric layer, a third resistive-loaded metasurface layer, a third resistive-loaded metasurface substrate, a third resistive element, a third resistive-loaded metasurface supporting dielectric layer, and a pure metal backplate. This invention, employing the aforementioned ultra-wideband absorbing material based on a three-layer metasurface and its applications, can achieve 90% ultra-wideband absorption in a small-size structure, possessing extremely high strategic value in fields such as electromagnetic stealth.

Description

Technical Field

[0001] This invention relates to the field of electromagnetic microwave technology, and in particular to an ultrawideband absorbing material based on a three-layer metasurface and its applications. Background Technology

[0002] The rapid development of wireless communication technology has facilitated people's production and life, but it has also brought about increasingly serious electromagnetic pollution problems. In order to ensure people's safety and quality of life, there is an urgent need for electromagnetic shielding materials that are lightweight, thin, have a wide bandwidth, and high absorption intensity to avoid the harm caused by microwaves.

[0003] Metasurface electromagnetic absorbers are highly favored due to their excellent selective absorption capabilities for specific frequency bands of electromagnetic waves. Technicians can freely design absorbers by adjusting the shape, pattern, size parameters, dielectric type, and impedance values ​​of lumped components on the metasurface. By integrating components with switching characteristics, such as high-speed MEMS switches, diodes, or transistors, the operating frequency band of the absorber can be controlled in real time as needed. Compared to traditional materials, this offers greater flexibility and better absorption performance, thus becoming a research hotspot in the field of stealth technology.

[0004] In existing technologies, the design of high-performance metasurface absorbers mainly utilizes single-layer complex structures, multi-layer metasurface coupling, and combinations of both to achieve ultra-wideband absorption of electromagnetic waves. The former primarily achieves the -10dB absorption bandwidth broadening through multi-resonant frequency design; the latter achieves -10dB ultra-wideband absorption through multi-layer metasurface mutual coupling or synergistic enhancement. However, the design of ultra-wideband absorbing materials remains a key focus of research in this field. Summary of the Invention

[0005] The purpose of this invention is to provide an ultra-wideband absorbing material based on a three-layer metasurface and its applications. By utilizing single-layer miniaturization technology and multi-layer mutual coupling synergistic enhancement, the absorbing material achieves ultra-wideband absorption, enabling 90% absorption performance in the ultra-wideband range. It also possesses polarization insensitivity, solving the problem of narrow bandwidth in traditional absorbing coatings. Furthermore, it does not have a wave-transmission band within 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 highly valuable for applications in electromagnetic stealth, signal shielding, and electromagnetic protection.

[0006] To achieve the above objectives, the present invention provides an ultra-wideband absorbing material based on a three-layer metasurface, comprising at least one periodic absorbing resonant unit arranged in a square pattern with the centroid as the center. Each absorbing resonant unit comprises, from top to bottom, a first resistive-loaded metasurface layer, a first resistive-loaded metasurface substrate, a first resistive element, a first resistive-loaded metasurface supporting dielectric layer, a second resistive-loaded metasurface substrate, a second resistive-loaded metasurface layer, a second resistive element, a second resistive-loaded metasurface supporting dielectric layer, a third resistive-loaded metasurface layer, a third resistive-loaded metasurface substrate, a third resistive element, a third resistive-loaded metasurface supporting dielectric layer, and a pure metal backplate.

[0007] Preferably, the first resistive loading metasurface layer is a square ring-like patch structure in which the first resistive element is loaded at the middle position of the four sides. The square ring-like patch structure includes several alternating large-width square patches and small-width square patches of different widths, and the first resistive element is loaded on the small-width square patch.

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

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

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

[0011] The gap used to load the first resistive element is 0.15mm-0.65mm;

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

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

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

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

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

[0017] The first resistive loading metasurface substrate, the second resistive loading metasurface substrate, and the third resistive loading metasurface substrate are all one of epoxy glass cloth laminate and polytetrafluoroethylene glass fiber cloth copper clad laminate, with a thickness of 0.1mm-0.6mm.

[0018] Preferably, the second resistive loading metasurface layer includes, from the inside out, a square ring-like zigzag discrete band gate structure for loading the second resistive element, an octagonal ring structure for loading the second resistive element, a square ring-like discrete band gate structure for loading the second resistive element, and a square ring structure for loading the second resistive element.

[0019] Preferably, a second resistive element is loaded at the bend of the quasi-square ring tortuous discrete strip gate structure, and a total of twelve second resistive elements are loaded; the overall length of the quasi-square ring tortuous discrete strip gate structure is 8mm-12mm, the patch width is 0.2-2mm, and the bends extend alternately in the same direction for 0.2mm-0.8mm;

[0020] The octagonal ring structure has a second resistor element loaded at each of its eight corners, for a total of eight second resistor elements; the outer ring radius of the octagonal ring structure is 5.4mm-7.9mm, the inner ring radius is 1mm-5.4mm, and the patch width is 0.2mm-2mm.

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

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

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

[0024] Preferably, the third resistive loading metasurface layer includes a large square ring structure for loading the third resistive element, an octagonal ring structure for loading the third resistive element, and a small square ring structure for loading the third resistive element, arranged sequentially from the inside out.

[0025] Preferably, a third resistor element 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 3mm-6.5mm, and the patch width is 0.2mm-1mm;

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

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

[0028] The gap in the third resistive loading metasurface layer used to load the third resistive element is 0.5 mm, and the resistance of the third resistive element is 100Ω-500Ω.

[0029] Preferably, the first resistive loading metasurface layer, the first resistive loading metasurface substrate, the first resistive loading metasurface support dielectric layer, the second resistive loading metasurface layer, the second resistive loading metasurface substrate, the second resistive loading metasurface support dielectric layer, the third resistive loading metasurface layer, the third resistive loading metasurface substrate, the third resistive loading metasurface support dielectric layer, and the pure metal backplate are manufactured by a vacuum hot pressing process to form the wave-absorbing resonant unit.

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

[0031] The first, second, and third resistance-loaded metasurface layers are all made of one of the transition metal elements. The first, second, and third resistance-loaded metasurface layers are prepared on the first, second, and third resistance-loaded metasurface substrates respectively by at least one of the following methods: inkjet printing, electrochemical etching, mechanical engraving, or magnetron sputtering.

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

[0033] Therefore, the present invention employs the above-mentioned ultra-wideband absorbing material based on a three-layer metasurface and its application, with the following beneficial effects:

[0034] (1) The present invention achieves -10dB absorption in the 7GHz-12GHz frequency band through the first layer structure; the second layer structure integrates an ultra-low frequency large-size absorption structure on the high-frequency small-size absorption structure using miniaturization technology, so that it can achieve -10dB absorption in the 2.5GHz-4.6GHz, 8GHz-13.2GHz and 14.89GHz-20GHz frequency bands, thus widening the high-frequency operating frequency band of the small size; the third layer structure achieves -10dB absorption in the 7.5GHz-16.68GHz frequency band.

[0035] (2) This invention utilizes a pure metal backplate to achieve multiple reflections of electromagnetic waves and uses the phase interference cancellation principle of 1 / 4 wavelength to achieve mutual coupling, thus broadening the working frequency band; the three-layer structure achieves ultra-wideband wave absorption of 2GHz-18GHz in a small-size structure through interlayer mutual coupling and synergistic enhancement. When electromagnetic waves are incident perpendicularly, the frequency band with a reflectivity of less than -10dB is 2.13GHz-18.19GHz, with a relative bandwidth of 150.7%, and the frequency band with an absorption rate of more than 90% is 2.13GHz-18.19GHz; when the incident angle reaches 45°, it can still maintain an absorption rate of more than 85% in the 2GHz-20GHz range; it can achieve low-frequency wave absorption of 2GHz-4GHz in a small-size structure corresponding to high-frequency wave absorption, and achieve a wave absorption performance of about 90% in the ultra-wideband range, while also having polarization insensitivity characteristics, solving the problem of narrow bandwidth of traditional wave-absorbing coatings and the problem of not having a wave-transmitting band in 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, which makes it highly valuable 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 with reference to the accompanying drawings and embodiments. Attached Figure Description

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

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

[0040] Figure 3 This is a schematic diagram of the structure of the first resistive-loaded metasurface layer according to an embodiment of the present invention;

[0041] Figure 4 This is a schematic diagram of the structure of the second resistive-loaded metasurface layer according to an embodiment of the present invention;

[0042] Figure 5 This is a schematic diagram of the structure of the third resistive-loaded metasurface layer according to an embodiment of the present invention;

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

[0044] Figure 7 This is a graph showing the variation of the absorptivity of the resistively loaded metasurface layer at different incident angles with frequency, according to an embodiment of the present invention.

[0045] Figure 8 This is a graph showing the variation of the reflection coefficient of the resistively loaded metasurface layer with frequency at different incident angles, according to a second embodiment of the present invention.

[0046] Figure 9 This is a graph showing the variation of the absorptivity of the resistively loaded metasurface layer with frequency at different incident angles, according to a second embodiment of the present invention.

[0047] Figure 10 This is a graph showing the variation of the reflection coefficient of the resistively loaded metasurface layer with frequency at different incident angles, according to the third embodiment of the present invention.

[0048] Figure 11 This is a graph showing the variation of the absorptivity of the resistively loaded metasurface layer with frequency at different incident angles in the third embodiment of the present invention.

[0049] Figure 12 This is an embodiment of the present invention showing the variation of the overall structure reflection coefficient with frequency under different incident angles without a metal backplate;

[0050] Figure 13 This is an embodiment of the present invention showing the variation of the overall structure absorptivity with frequency under different incident angles without a metal backplate.

[0051] Figure 14 This is an embodiment of the invention where the overall structural reflection coefficient varies with frequency under different incident angles;

[0052] Figure 15 The overall structural absorptivity varies with frequency under different incident angles in embodiments of the present invention;

[0053] Figure 16 This is a graph showing the variation of TE wave reflection coefficient with frequency for different incident angles according to embodiments of the present invention;

[0054] Figure 17 This is a graph showing the variation of TE wave absorption rate with frequency for different incident angles according to embodiments of the present invention;

[0055] Figure 18 This is a graph showing the variation of TM wave reflection coefficient with frequency for different incident angles according to embodiments of the present invention;

[0056] Figure 19 This is a graph showing the variation of TM wave absorptivity with frequency for different incident angles according to embodiments of the present invention.

[0057] Figure Labels

[0058] 1. First resistive loading metasurface layer; 2. First resistive loading metasurface substrate; 3. First resistive element; 4. First resistive loading metasurface supporting dielectric layer; 5. Second resistive loading metasurface substrate; 6. Second resistive loading metasurface layer; 7. Second resistive element; 8. Second resistive loading metasurface supporting dielectric layer; 9. Third resistive loading metasurface layer; 10. Third resistive loading metasurface substrate; 11. Third resistive element; 12. Third resistive loading metasurface supporting dielectric layer; 13. Pure metal backplate. Detailed Implementation

[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 or scientific terms used in this invention shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.

[0061] Example 1

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

[0063] The first resistive metasurface layer 1 is a square ring-like patch structure with a first resistive element 3 loaded at the center of each of the four sides. The main purpose of setting the first resistive metasurface layer 1 is to achieve high-frequency impedance matching. Its electrical size corresponds to the wavelength around 8 GHz, thereby absorbing electromagnetic waves in the 7 GHz-12 GHz frequency band.

[0064] The near-quadrilateral patch structure consists of alternating square patches of varying widths arranged to form a near-quadrilateral shape. Larger square patches are located on either side of the near-quadrilateral ring, while smaller square patches are located between the two larger square patches and at the bends in the near-quadrilateral ring. The smaller square patches at the bends and between the two larger square patches have the same structural dimensions. A first resistive element 3 is loaded between two smaller square patches on each side of the near-quadrilateral. The overall length of each side of the near-quadrilateral is 6.5mm-11.5mm, and the width of each side is 0.25mm-0.65mm. The gap for loading the first resistive element 3 is 0.15mm-0.65mm.

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

[0066] Each of the quadrilateral-like large-width square patches has a length of 2mm-6.8mm and a width of 0.5mm-2mm; each small-width square patch has a length of 0.3mm-2mm and a width of 0.1mm-1mm. The quadrilateral-like structures are fabricated on the first resistance-loaded metasurface substrate 2 using at least one of the following methods: inkjet printing, electrochemical etching, mechanical engraving, or magnetron sputtering. In this embodiment, mechanical engraving is used to engrave the metal square patches onto the epoxy glass cloth laminate (FR4 board).

[0067] The second resistive metasurface layer 6 comprises, from the inside out, a quasi-square ring discrete band gate structure, an octagonal ring structure, a quasi-square ring discrete band gate structure, and a square ring structure, all arranged sequentially from the inside out, with the second resistive element 7 in place. The four discrete structures correspond to wavelengths around 2 GHz. By bending and twisting, the overall length of the band gate, which is 10 GHz, is increased to the wavelength corresponding to 2 GHz. However, to achieve stable oblique incidence angles, the four discrete structures are arranged into a highly symmetrical quasi-square ring structure. Simultaneously, miniaturization techniques are applied to reduce the large size corresponding to low-frequency absorption, which plays a positive role in improving polarization sensitivity. The second resistive metasurface layer 6 alone can achieve mid-to-high frequency absorption in the 7.8 GHz-18 GHz range. The interlayer coupling of the complete structure allows the low-frequency (2 GHz-4 GHz) absorption effect of the second resistive metasurface layer 6 to be demonstrated.

[0068] The third resistive metasurface layer 9 includes a large square ring structure, an octagonal ring structure, and a small square ring structure with a third resistive element 11. These structures enable it to absorb electromagnetic waves in the 2GHz-14.67GHz and 14.89GHz-20GHz ranges, and enhance the absorption effect in the 7.8GHz-18GHz and 7GHz-12GHz ranges. Simultaneously, its underlying structure is loaded with a pure metal backplate 13, which can confine electromagnetic waves within the absorber, generating interlayer mutual coupling and synergistic enhancement, strengthening the absorption depth while also expanding the operating bandwidth.

[0069] The first resistive-loaded metasurface support dielectric layer 4 is made of a foam material or air cavity with a relative permittivity close to that of air, ranging from 1.0 to 4.0, and has a thickness of 2 mm to 7 mm. The foam material is either polymethacrylamide or polyimide. In this embodiment, PMI (polymethacrylamide) is used, with a relative permittivity of approximately 1.06, close to that of air, and can be considered a lossless dielectric support layer. The second resistive-loaded metasurface support dielectric layer 8 and the third resistive-loaded metasurface support dielectric layer 12 are made of the same material as the first resistive-loaded metasurface support dielectric layer 4. The difference is that the thickness of the second resistive-loaded metasurface support dielectric layer 8 is 3 mm to 8 mm, and the thickness of the third resistive-loaded metasurface support dielectric layer 12 is 8 mm to 12 mm.

[0070] The first resistive loading metasurface substrate 2 is made of a material with a relative permittivity of 4.0-6.0 and a thickness of 0.1mm-1mm, and is selected from either an epoxy glass cloth laminate or a polytetrafluoroethylene glass fiber cloth copper-clad laminate. In this embodiment, the first resistive loading metasurface substrate 2 is made of an epoxy glass cloth laminate (FR4 board) with a relative permittivity of 4.3 and a loss tangent of 2.5×10⁻⁶. -3 The thickness is 0.1mm-1mm. The materials of the second resistance-loaded metasurface substrate 5 and the third resistance-loaded metasurface substrate 10 are the same as those of the first resistance-loaded metasurface substrate 2.

[0071] In the simulation, the pure metal backplate 13 is considered to be a perfect ideal electrical conductor. In practice, a metal material with high electrical conductivity is selected. In this embodiment, pure copper (annealed copper) with a thickness of 0.023 mm is selected.

[0072] The second resistive-loaded metasurface layer 6 includes, from the inside out, a quasi-square-ring tortuous discrete strip gate structure (the quasi-square-ring tortuous discrete strip gate structure consists of four strip gate structures tortuously arranged parallel to the edge of the second resistive-loaded metasurface support dielectric layer 8), an octagonal ring structure, a quasi-square-ring discrete strip gate structure, and a square ring structure. Each quasi-square-ring tortuous discrete strip gate structure has a second resistive element 7 loaded at its tortuous point, for a total of three second resistive elements 7 loaded on each quasi-square-ring tortuous discrete strip gate structure. The octagonal ring structure has a second resistive element 7 loaded at each of its eight corners, for a total of eight second resistive elements 7 loaded. The quasi-square-ring discrete strip gate structure has a second resistive element 7 loaded at the middle position of each strip gate, for a total of four second resistive elements 7 loaded. The square ring structure has a second resistive element 7 loaded at the middle position of each edge, for a total of four second resistive elements 7 loaded.

[0073] The gap for loading the second resistive element 7 on the quasi-square ring discrete strip grid structure is 0.15mm-0.65mm; the gap for loading the second resistive element 7 on the octagonal ring structure is 0.15mm-0.65mm; the gap for loading the second resistive element 7 on the quasi-square ring discrete strip grid structure is 0.15mm-0.65mm; the gap for loading the second resistive element 7 on the square ring structure is 0.15mm-0.65mm. The resistance of the second resistive element 7 is 300Ω-500Ω.

[0074] The overall length of the quasi-square ring tortuous discrete band gate structure is 8mm-12mm, and the patch width is 0.2-2mm. The tortuous sections extend alternately in the same direction by 0.2mm-0.8mm, with three extension positions on each tortuous discrete structure. The outer ring radius of the octagonal ring structure is 5.4mm-8mm, the inner ring radius is 1mm-6mm, and the patch width is 0.2mm-2mm. The quasi-square ring discrete band gate structure consists of four rectangular strips, each with an overall length of 2.5mm-6mm and a patch width of 0.2mm-2mm; the quadrilateral ring structure has each side with a length of 2.5mm-6mm and a patch width of 0.2mm-2mm. The quasi-square ring tortuous discrete band gate structure, octagonal ring structure, quasi-square ring discrete band gate structure, and quadrilateral ring structure are all fabricated on the second resistance-loaded metasurface substrate 5 using at least one of the following methods: inkjet printing, electrochemical etching, mechanical engraving, or magnetron sputtering. In this embodiment, a mechanical engraving process is used to engrave square metal patches onto an FR4 board.

[0075] The third resistive loading metasurface layer 9 comprises a large square ring structure, an octagonal ring structure, and a small square ring structure arranged sequentially from the inside out. A third resistive element 11 is loaded at the bend of the large square ring structure, for a total of four third resistive elements 11. A third resistive element 11 is loaded at the middle of each side of the octagonal ring structure, for a total of eight third resistive elements 11. A third resistive element 11 is loaded at the middle of each side of the small square ring structure, for a total of four third resistive elements 11. A 0.5mm gap is reserved when loading the third resistive element 11 in each structure. The resistance value of the third resistive element 11 is 100Ω-500Ω.

[0076] The large square ring structure has a side length of 3mm-6.5mm and a patch width of 0.2mm-1mm. The octagonal ring structure has an outer ring width of 4.0mm-5.6mm, an inner ring width of 2.5mm-4.0mm, and a patch width of 0.2mm-1mm. The small square ring structure has a patch side length of 2.0mm-4.5mm and a patch width of 0.2mm-1mm. The large square ring structure, octagonal ring structure, and small square ring structure are all fabricated on the third resistive loading metasurface substrate 10 using at least one of the following methods: inkjet printing, electrochemical etching, mechanical engraving, or magnetron sputtering. In this embodiment, mechanical engraving is used to engrave the metal square patch onto the 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 transition metal elements 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, the lumped resistive elements are soldered into the reserved gaps using PCB soldering technology.

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

[0080] The above structure achieves the following: A specific frequency AC electric field component of the incident electromagnetic wave induces a current in the first, second, and third resistive metasurface layers. Due to the lumped resistance of the energy conversion device, the induced current is converted into ohmic heat loss, thus achieving electromagnetic wave absorption. Simultaneously, the resistance loading also achieves impedance matching between the structure and free space impedance, allowing the incident electromagnetic wave to penetrate the absorber to the maximum extent. The first, second, and third resistive metasurface layers are mutually coupled, enabling multiple ohmic loss resonance absorption of the electromagnetic wave within the layers. The interlayer auxiliary pure metal backplate achieves multiple reflections of the electromagnetic wave, resulting in ultra-wideband absorption through quarter-wavelength interference cancellation.

[0081] Test

[0082] The ultra-wideband absorbing material based on a three-layer metasurface (three-layer metasurface ultra-wideband absorber) prepared in this embodiment was analyzed using simulation software to explain the working characteristics of the absorber.

[0083] Depend on Figure 6 It is known that the -10dB operating frequency band of the first layer absorber structure is 7GHz-12GHz. As the incident angle of the electromagnetic wave increases, the high-frequency operating frequency gradually shifts to higher frequencies, while the low-frequency point changes slightly. When the incident angle is greater than 30°, the structure's reflection coefficient is greater than -10dB. At this point, the tangential component of the electromagnetic wave energy along the structure surface is larger, leading to a deterioration in the structure's absorption effect. Furthermore, when the incident angle is greater than 30°, grating lobes appear after 15GHz. The interlayer mutual coupling effect will optimize and eliminate the grating lobe phenomenon while simultaneously broadening the absorption frequency band.

[0084] At the same time Figure 7 It can be seen that 90% of the absorption frequency band is related to Figure 6 The -10dB reflection coefficient corresponds to the frequency band.

[0085] Depend on Figure 8 It is known that the -10dB operating frequency band of the second-layer absorber structure is 2.5GHz-4.6GHz, 8GHz-13.2GHz, and 14.89GHz-20GHz. The electrical dimension length corresponding to the 20GHz absorption frequency in this structure is 15mm. To avoid the grating lobes exhibiting a period of less than 7.5mm for the absorbing structure unit, a grating structure based on miniaturization technology is integrated into the second layer. This electrical dimension structure has a length of 65.22mm-120mm, achieving absorption in the 2.5GHz-4.6GHz frequency band. In other words, the absorption effect of a large-size structure at extremely low frequencies is achieved on the second-layer high-frequency small-size absorber structure. Simultaneously, the integration of small-size high-frequency absorption broadens the operating bandwidth, verifying the working principle of this invention.

[0086] At the same time Figure 9 It can be seen that 90% of the absorption frequency band is related to Figure 8 The -10dB reflection coefficient corresponds to the frequency band.

[0087] Depend on Figure 10 It can be seen that the -10dB operating frequency band of the third-layer absorber structure is 7.5GHz-16.68GHz. When the incident angle increases to 45°, the absorption of the first layer in the 7.5GHz-12GHz band and the second layer in the 8GHz-13.2GHz band can be enhanced and broadened to a certain extent.

[0088] Depend on Figure 11 It can be seen that 90% of the absorption frequency band is related to Figure 10 The -10dB reflection coefficient corresponds to the frequency band.

[0089] Depend on Figure 12 It can be seen that when the overall absorber structure does not include the pure metal backplate 13, the reflection coefficient in the 2.13GHz-18.19GHz frequency band is around -7dB, meaning that the absorption rate is only about 80% without the pure metal backplate 13. This is mainly because the absorption effect of the absorber of this invention is based on the principle of multiple interference phase cancellation absorption using multi-layer mutual coupling and quarter-wavelength resonant loss. Removing the pure metal backplate 13 prevents multiple reflections from being formed, thus leading to a deterioration in the absorption effect, thereby proving the working principle of this invention.

[0090] At the same time Figure 13 It can be seen that 80% of the absorption frequency band is related to Figure 12 The -7dB reflection coefficient corresponds to the frequency band.

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

[0092] At the same time Figure 15 It can be seen that the 90% absorption band and the 87.4% absorption band are related to... Figure 14 The -10dB and -9dB reflection coefficients correspond to the frequency bands.

[0093] Depend on Figure 16 It can be seen that under TE polarization and vertical incidence, the maximum operating bandwidth corresponding to -10dB is 2.13GHz-18.19GHz. As the incident angle increases, the reflection coefficient of some frequency bands is higher than -10dB but still lower than -9dB. The high-frequency band of the -10dB operating frequency band begins to shift to higher frequencies as the incident angle increases, while the low-frequency band remains basically unchanged with the change of the incident angle.

[0094] At the same time Figure 17 It can be seen that the 90% absorption band and the 87.4% absorption band are related to... Figure 16 The -10dB and -9dB reflection coefficients correspond to the frequency bands.

[0095] Depend on Figure 18It can be seen that the maximum operating bandwidth corresponding to -10dB under TM polarization and vertical incidence is 2.15GHz-18.11GHz. As the incident angle increases, the reflection coefficient of some frequency bands is higher than -10dB but still lower than -9dB. The high-frequency band of the -10dB 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] At the same time Figure 19 It can be seen that the 90% absorption band and the 87.4% absorption band are related to... Figure 18 The -10dB and -9dB reflection coefficients correspond to the frequency bands.

[0097] Therefore, this invention employs the aforementioned ultra-wideband absorbing material based on a three-layer metasurface and its applications. Through interlayer mutual coupling synergistic enhancement and miniaturization technology, the operating bandwidth of high-frequency absorption is broadened, enabling ultra-wideband absorption of 2GHz-18GHz in a small-size structure. This structure has extremely high strategic value in fields such as 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 not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A broadband microwave absorbing material based on a three-layer metasurface, characterized in that: It includes at least one periodic absorbing resonant unit arranged in a square with its centroid in the middle. Each absorbing resonant unit includes, from top to bottom, a first resistive loading metasurface layer, a first resistive loading metasurface substrate, a first resistive element, a first resistive loading metasurface supporting dielectric layer, a second resistive loading metasurface substrate, a second resistive loading metasurface layer, a second resistive element, a second resistive loading metasurface supporting dielectric layer, a third resistive loading metasurface layer, a third resistive loading metasurface substrate, a third resistive element, a third resistive loading metasurface supporting dielectric layer, and a pure metal backplate. The first resistive loading metasurface layer is a square ring-like patch structure in which the first resistive element is loaded at the middle position of the four sides. The square ring-like patch structure includes several alternating large-width square patches and small-width square patches of different widths. The first resistive element is loaded on the small-width square patch. The second resistive loading metasurface layer includes, from the outside to the inside, a square ring-like zigzag discrete band gate structure for loading the second resistive element, an octagonal ring structure for loading the second resistive element, a square ring-like discrete band gate structure for loading the second resistive element, and a square ring structure for loading the second resistive element; The third resistive loading metasurface layer includes, from the outside to the inside, a large square ring structure for loading the third resistive element, an octagonal ring structure for loading the third resistive element, and a small square ring structure for loading the third resistive element.

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

3. The ultrawideband absorbing material based on a three-layer metasurface according to claim 1, characterized in that: The first resistive loading metasurface support dielectric layer is made of either a foam material or an air cavity with a relative permittivity of 1.0-4.0 and a thickness of 2mm-7mm. The material of the second resistive loading metasurface support dielectric layer is either a foam material or an air cavity with a relative permittivity of 1.0-4.0 and a thickness of 3mm-8mm; The material of the third resistive loading metasurface support dielectric layer is either a foam material or an air cavity with a relative permittivity of 1.0-4.0 and a thickness of 8mm-12mm. The foam material is one of polymethacrylimide and polyimide; The first resistive loading metasurface substrate, the second resistive loading metasurface substrate, and the third resistive loading metasurface substrate are all one of epoxy glass cloth laminate and polytetrafluoroethylene glass fiber cloth copper clad laminate, with a thickness of 0.1mm-0.6mm.

4. The ultrawideband absorbing material based on a three-layer metasurface according to claim 1, characterized in that: The quasi-square ring tortuous discrete strip gate structure has a second resistor element loaded at each bend, and a total of twelve second resistor elements are loaded; the overall length of the quasi-square ring tortuous discrete strip gate structure is 8mm-12mm, the patch width is 0.2-2mm, and the bends extend alternately in the same direction for 0.2mm-0.8mm; The octagonal ring structure has a second resistor element loaded at each of its eight corners, for a total of eight second resistor elements; the outer ring radius of the octagonal ring structure is 5.4mm-7.9mm, the inner ring radius is 1mm-5.4mm, and the patch width is 0.2mm-2mm. The discrete band gate structure of the square ring has a second resistor element loaded at the middle position of each band gate, and a total of four second resistor elements are loaded; the overall length of the discrete band gate structure of the square ring is 2.5mm-5.9mm, and the patch width is 0.2mm-2mm; The square ring structure has a second resistor element loaded at the middle of each side, and a total of four second resistor elements are loaded; the length of each side of the square ring structure is 2.5mm-5.9mm, and the patch width is 0.2mm-2mm; The gap in the second resistor loading metasurface layer used to load the second resistor element is 0.15mm-0.65mm, and the resistance of the second resistor is 302Ω-500Ω.

5. The ultrawideband absorbing material based on a three-layer metasurface according to claim 1, characterized in that: A third resistor element 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 3mm-6.5mm, and the patch width is 0.2mm-1mm; The octagonal ring structure has a third resistor element loaded at the middle of each side, and a total of eight third resistor elements are loaded; the outer ring width of the octagonal ring structure is 4.0mm-5.6mm, the inner ring width is 2.5mm-4.0mm, and the patch width is 0.2mm-1mm; The small square ring structure has a third resistor element loaded at the middle of each side, and a total of four third resistor elements are loaded; the side length of the small square ring structure is 2.0mm-4.5mm, and the patch width is 0.2mm-1mm; The gap in the third resistive loading metasurface layer used to load the third resistive element is 0.5 mm, and the resistance of the third resistive element is 100Ω-500Ω.

6. The ultrawideband absorbing material based on a three-layer metasurface according to claim 1, characterized in that: The first resistive loading metasurface layer, the first resistive loading metasurface substrate, the first resistive loading metasurface support dielectric layer, the second resistive loading metasurface layer, the second resistive loading metasurface substrate, the second resistive loading metasurface support dielectric layer, the third resistive loading metasurface layer, the third resistive loading metasurface substrate, the third resistive loading metasurface support dielectric layer, and the pure metal backplate are manufactured by vacuum hot pressing process to form the wave absorbing resonant unit. The first, second, and third resistive elements are all lumped resistive elements or equivalent resistances obtained by at least one of magnetron sputtering, screen printing, and inkjet printing; The first, second, and third resistance-loaded metasurface layers are all made of one of the transition metal elements. The first, second, and third resistance-loaded metasurface layers are prepared on the first, second, and third resistance-loaded metasurface substrates respectively by at least one of the following methods: inkjet printing, electrochemical etching, mechanical engraving, or magnetron sputtering.

7. A method for applying the ultra-wideband absorbing material based on a three-layer metasurface as described in any one of claims 1-6 in electromagnetic stealth, signal shielding and electromagnetic protection.

Images