A multi-mode fusion high-frequency-ratio dual-frequency metamaterial absorber

Abstract

This invention proposes a multi-mode fusion, high-ratio, independent dual-band metamaterial absorber, which consists of K×K periodically arranged resonant units. Each resonant unit includes a top frustum-shaped integrated absorption structure and a bottom Helmholtz resonant cavity absorption structure. The frustum-shaped integrated absorption structure comprises a square first dielectric substrate, a square second dielectric substrate, and metal patches printed on their surfaces. The bottom Helmholtz resonant cavity includes two rectangular slots intersecting in a cross shape on the upper surface of a square cubic metal structure, and a triangular prism cavity with an isosceles triangular cross-section located inside the cubic metal structure, penetrating its front, back, left, and right sides. The rectangular slots and the triangular prism cavity are filled with dielectric material. This invention achieves dual-band absorption by combining the Helmholtz resonant mode and the frustum-shaped integrated absorption mode, and improves the absorption ratio of the dual-band absorption. It can be used in the field of decoupling high-ratio dual-band antenna arrays.

Description

Technical Field

[0001] This invention belongs to the field of artificial electromagnetic absorbing materials technology, and relates to a high frequency ratio dual-frequency metamaterial absorber. Specifically, it uses a multi-mode fusion method to combine the Helmholtz resonant cavity absorbing mode with the truncated pyramidal absorbing and penetrating integrated mode to achieve high frequency ratio dual-frequency absorbing. It can be applied to electromagnetic compatibility design in the field of communication and stealth in electronic countermeasures. Background Technology

[0002] Electromagnetic wave absorbers are functional structures that can effectively absorb incident electromagnetic waves, significantly reducing transmitted and reflected waves. Electromagnetic metamaterial absorbers, as an important branch of electromagnetic wave absorbers, have been extensively studied, offering advantages such as lightweight, flexibility, and high absorption rate compared to traditional absorbing materials. Artificial electromagnetic metamaterials refer to man-made materials composed of periodically or aperiodically arranged subwavelength unit structures, possessing properties not found in naturally occurring materials. Their greatest advantage lies in the ability to customize the unit structure or arrangement to achieve desired medium properties. The absorption of electromagnetic waves by metamaterial absorbers primarily relies on impedance matching and electromagnetic loss; adjusting the structure of the metamaterial absorber can alter its absorption frequency.

[0003] With the development of 5G communication technology, the development of dual-band antennas that can simultaneously meet the requirements of Sub-6GHz (450MHz-6GHz) and millimeter-wave bands (24.25GHz-52.6GHz) is gradually trending towards a high frequency ratio (high-frequency center frequency / low-frequency center frequency) design. Consequently, the demand for dual-band absorbers with a high frequency ratio (high-frequency absorbing band center frequency / low-frequency absorbing frequency center frequency) will also increase. However, the most common method for designing dual-band metamaterial absorbers is to combine two substructures of different sizes but similar structures or resonant modes, using a smaller unit to achieve high-frequency absorption and a larger unit to achieve low-frequency absorption. Increasing the absorption frequency ratio is usually achieved by adjusting the size of the resonant unit to increase the high-frequency absorption frequency or decrease the low-frequency absorption frequency. This method is limited by the overall size of the metamaterial unit and cannot achieve a high frequency ratio dual-band absorption; its frequency ratio (high-frequency absorbing frequency / low-frequency absorbing frequency) is usually within 3. On the other hand, both absorption modes of this method are usually FP resonant modes. When the frequency ratio is increased, the frequency doubling characteristic of the low-frequency absorption frequency will cause an additional absorption frequency between the two frequencies, making it impossible to achieve accurate dual-frequency absorption.

[0004] For example, patent application CN 114204280A, entitled "A Microwave Dual-Band Metamaterial Absorber," discloses a microwave dual-band metamaterial absorber. The unit structure employed in this invention includes an electromagnetic resonant layer, a dielectric layer, and a metal grounding layer; the electromagnetic resonant layer is located above the dielectric layer, which is located above the metal grounding layer. The electromagnetic resonant layer consists of a closed loop, a cross, and symmetrical rectangular strips. It achieves polarization-insensitive absorption with an absorption rate exceeding 99% at both 3.77 GHz and 9.75 GHz, with a frequency ratio less than 3. However, on the one hand, increasing the frequency ratio can only be achieved by changing the size of the resonant unit, which is limited by the overall unit size; on the other hand, the FP resonance mechanism it relies on means that when increasing the high-frequency absorption frequency or decreasing the low-frequency absorption frequency, the harmonics of the low-frequency absorption frequency will cause additional absorption frequencies to appear between the two target absorption frequencies, preventing the frequency ratio from increasing to above 3.

[0005] Application publication number CN114142246, entitled "A Broadband Large-Angle Metamaterial Absorber Based on Gradient Impedance and Its Fabrication Method," discloses a broadband large-angle metamaterial absorber and its fabrication method. The absorber includes: an absorbing unit support platform, a substrate, and a resistive mode absorbing structure. The resistive mode absorbing structure includes at least one strip-shaped resistive mode, and the spacing between two adjacent strip-shaped resistive modes is determined by the inclination angle of the sidewall of the absorbing unit support platform and the length scaling factor of the strip-shaped resistive mode, where the length scaling factor is the ratio of the lengths of two adjacent strip-shaped resistive modes. This achieves broadband large-angle metamaterial absorption; however, because it realizes a "reflective absorber," it exhibits total reflection characteristics at low frequencies, making it unsuitable for designing stacked high-frequency-ratio dual-frequency metamaterial absorbers. Summary of the Invention

[0006] The purpose of this invention is to overcome the defects of the prior art and propose a multi-mode fusion high frequency ratio dual-frequency metamaterial absorber. By combining the Helmholtz resonator absorption mode with the truncated pyramidal absorption-transmission integrated mode, the technical problem of limited frequency ratio in the prior art is solved.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] A multi-mode fusion high-frequency-ratio dual-frequency metamaterial absorber includes K×K periodically arranged resonant units, where K≥2; each resonant unit includes M×M truncated pyramidal penetration-absorbing integrated structures 1 and low-frequency absorbing structures 2 stacked below them, where M≥2; each truncated pyramidal penetration-absorbing integrated structure 1 includes a square first dielectric substrate 11 and a quadrangular truncated unit 12 located at the center of its upper surface, the quadrangular truncated unit 12 being a truncated structure formed by stacking N square second dielectric substrates 121 with side lengths decreasing linearly from bottom to top, the upper surface of the second dielectric substrate 121 being printed with... The structure includes a metal patch 122. The low-frequency absorbing structure 2 is a cubic metal structure 21 with a square plate surface and a Helmholtz resonant cavity. The Helmholtz resonant cavity includes two rectangular slits intersecting in a cross shape on the upper surface of the cubic metal structure 21, and two triangular prism cavities with cross-sections of isosceles triangles that run through the front, back, left, and right sides of the cubic metal structure 21. The two rectangular slits are located directly above the two triangular prism cavities and connected to their vertices. The rectangular slits and triangular prism cavities are filled with a dielectric material. The cubic metal structure 21, filled with the two rectangular slits and the two triangular prism cavities, constitutes the Helmholtz resonant cavity.

[0009] The resonant frequency f of the Helmholtz resonant cavity is determined by the dimensions of the rectangular slit and the triangular prism cavity:

[0010]

[0011] Where c is the speed of light in a vacuum, w1 and h1 are the width and height of the rectangular slit, respectively, w2 and h2 are the width and height of the bottom surface of the triangular prism cavity, respectively, and ε r The relative permittivity of the dielectric material selected for the rectangular slit and the triangular prism cavity. The resonant frequency of the Helmholtz resonator is determined by the structural dimensions of the rectangular slit and the triangular prism cavity, as well as the permittivity of the filling material.

[0012] In the aforementioned multi-mode fusion high-frequency-ratio dual-frequency metamaterial absorber, the cubic metal structure 21 has two rectangular slits on its upper surface, which are respectively located on the line connecting the midpoints of two sets of opposite sides on the upper surface of the cubic metal structure 21.

[0013] In the aforementioned multi-mode fusion high-frequency-ratio dual-frequency metamaterial absorber, the cubic metal structure 21 has two triangular prism cavities whose edges are parallel to the lines connecting the midpoints of the front and rear sides and the left and right sides of the cubic metal structure 21, respectively, and whose bottom surface is parallel to the upper and lower surfaces of the cubic metal structure 21.

[0014] The aforementioned multimode fusion high frequency ratio dual-frequency metamaterial absorber has two rectangular slits and two triangular prism cavities filled with the same lossy dielectric material.

[0015] In the aforementioned multimode fusion high frequency ratio dual-frequency metamaterial absorber, the central normal of the frustum unit 12 coincides with the central normal of the first dielectric substrate 11.

[0016] Compared with the prior art, the present invention has the following advantages:

[0017] (1) Due to its frustum-shaped integrated absorber-transmitter unit, the present invention has broadband absorption characteristics at high frequencies when it has a bottom metal reflector plate, and transmittance characteristics at low frequencies when it removes the bottom metal reflector plate; its low-frequency Helmholtz resonant cavity absorbing unit exhibits absorption characteristics at low frequencies and total reflection characteristics at other frequencies; after the two units are stacked and distributed to form the final structure, when low-frequency electromagnetic waves are incident, the upper frustum-shaped integrated absorber-transmitter unit has no effect on the electromagnetic waves, and the bottom Helmholtz resonant cavity absorbing unit absorbs the electromagnetic waves; when high-frequency electromagnetic waves are incident, the Helmholtz resonant cavity can be equivalent to a metal reflector layer, and the upper frustum-shaped integrated absorber-transmitter unit absorbs the electromagnetic waves; since the absorption frequency of the Helmholtz resonant cavity is not limited by its overall structural size, by replacing one of the modes in the dual-frequency absorption with the Helmholtz resonant cavity, the low-frequency absorption frequency in the dual-frequency absorption is reduced, thereby achieving a high frequency ratio (frequency ratio greater than 7) dual-frequency absorption.

[0018] (2) The present invention uses a Helmholtz resonant cavity for low-frequency design in dual-frequency absorption. The Helmholtz resonant cavity absorber has single-frequency absorption characteristics. When designing a large frequency ratio, the low-frequency absorption frequency does not have the harmonic absorption characteristics, while the harmonic characteristics of the high-frequency broadband absorption are at a higher frequency. Therefore, the overall structure achieves a large frequency ratio dual-frequency absorption without additional absorption frequency points between the two frequencies, thus achieving a more accurate large frequency ratio dual-frequency absorption. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the resonant unit structure according to an embodiment of the present invention.

[0020] Figure 2 This is a schematic diagram of the frustum-shaped integrated absorbent and breathable unit structure in an embodiment of the present invention.

[0021] Figure 3 This is a schematic diagram of the low-frequency Helmholtz resonant absorbing unit structure in an embodiment of the present invention.

[0022] Figure 4 This is a left-side view schematic diagram of the low-frequency Helmholtz resonant absorbing unit structure in an embodiment of the present invention.

[0023] Figure 5 This is a comparison chart of the calculation results of the Helmholtz resonant cavity resonant frequency formula of this invention and the software simulation results.

[0024] Figure 6 These are the low-frequency absorption results and high-frequency total internal reflection results of the Helmholtz resonant cavity in the embodiments of the present invention.

[0025] Figure 7 The results show the high-frequency absorption and low-frequency transmission results of the truncated pyramid-shaped integrated absorption and transmission structure in this embodiment of the invention.

[0026] Figure 8 This is an absorption curve diagram of an embodiment of the present invention under the condition of perpendicular electromagnetic wave incidence.

[0027] Figure 9 This is an absorption curve diagram of an embodiment of the present invention when electromagnetic waves are incident at an oblique angle of 10 degrees.

[0028] Figure 10 This is an absorption curve diagram of an embodiment of the present invention when electromagnetic waves are incident at an oblique angle of 20 degrees.

[0029] Figure 11 This is an absorption curve diagram of an embodiment of the present invention when electromagnetic waves are incident at an oblique angle of 30 degrees. Detailed Implementation

[0030] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0031] Reference Figure 1 The resonant unit of the present invention includes M×M truncated pyramidal absorbing and penetrating integrated structures 1 and low-frequency absorbing structures 2 stacked below them. In this embodiment, M=4, and the bottom surface of the resonant unit is parallel to the xoy plane.

[0032] Reference Figure 2The single frustum-shaped integrated absorption structure 1 of the present invention includes a square first dielectric substrate 11 and a quadrangular frustum unit 12 located at the center of its upper surface. The quadrangular frustum unit 12 is a frustum structure formed by stacking N square second dielectric substrates 121 with side lengths decreasing linearly from bottom to top. In this embodiment, N=16. A metal patch 122 is printed on the upper surface of the second dielectric substrate 121. The central normal of the quadrangular frustum unit 12 coincides with the central normal of the first dielectric substrate 11. Each layer of second square dielectric substrate 121 and its printed metal patch 122 constitutes a sub-absorbing structure to absorb a specific frequency of high-frequency electromagnetic waves. Since the side lengths of the 16 second square dielectric substrates 121 decrease sequentially from bottom to top, the absorption frequency corresponding to each layer of second square dielectric substrate 121 and its printed metal patch 122 increases sequentially from bottom to top. The 16 high-frequency absorption points corresponding to the 16 square second dielectric substrates are combined to achieve the final high-frequency broadband absorption effect. The square first dielectric substrate 11 has a side length of 5mm and a thickness of 0.3mm. The N square second dielectric substrates have an equal thickness of 0.1mm, with the bottom square second dielectric substrate having a side length of 4mm, and the side lengths of the remaining square second dielectric substrates decreasing by 0.12mm from bottom to top, based on the side length of the bottom square second dielectric substrate. The square first dielectric substrate 11 and the square second dielectric substrate 121 are made of FR4 dielectric material, with a dielectric constant of 4.3 and a loss tangent of 0.25. The metal patch 122 printed on the upper surface of the square second dielectric substrate 121 is made of copper, with a thickness of 0.035mm and a conductivity of 5.96e7 S / m.

[0033] Reference Figure 3 The single low-frequency absorbing structure 2 of the present invention employs a cubic metal structure 21 with a square plate surface and a Helmholtz resonant cavity. The Helmholtz resonant cavity includes two rectangular slots intersecting in a cross shape on the upper surface of the cubic metal structure 21, and two triangular prism cavities with cross-sections of isosceles triangles that penetrate the front, rear, left, and right sides of the cubic metal structure 21. The two rectangular slots are located directly above the two triangular prism cavities and connected to their vertices. The rectangular slots and triangular prism cavities are filled with a dielectric material. The two rectangular slots on the upper surface of the cubic metal structure 21 are located on the lines connecting the midpoints of two sets of opposite sides of the upper surface of the cubic metal structure 21. The edges of the two triangular prism cavities inside the cubic metal structure 21 are parallel to the lines connecting the midpoints of the front, rear, left, and right sides of the cubic metal structure 21, and their bottom surfaces are parallel to the upper and lower surfaces of the cubic metal structure 21.

[0034] Reference Figure 4The cubic metal structure 21 has a side length of 20mm on both the top and bottom surfaces and an overall height of 3.5mm. The rectangular slit has a length of 20mm, a width w1 of 0.2mm, and a height h1 of 1mm. The triangular prism cavity has a bottom side length w2 of 7mm and a height h2 of 2mm. The rectangular slit and the triangular prism cavity are filled with the same dielectric material FR4. The Helmholtz resonance principle is similar to the series LC resonance principle. The rectangular slit in the Helmholtz resonant cavity structure can be considered equivalent to a capacitor, and the triangular prism cavity can be considered equivalent to an inductor. The equivalent capacitance of the rectangular slit is:

[0035]

[0036] Where ε₀ is the vacuum permittivity, ε r Let w1 be the relative permittivity, w1 be the width of the rectangular slot, and h1 be the height of the rectangular slot. The equivalent inductance of its triangular prism cavity can be determined by the following formula:

[0037]

[0038] Where μ0 is the vacuum permeability, w2 is the width of the base of the triangular prism cavity, h2 is the height of the triangular prism cavity, and w3 is the side length of the lower surface of the cubic metal structure 21. The resonant frequency f of the Helmholtz resonator can then be approximately determined by the following formula:

[0039]

[0040] Where c is the speed of light in a vacuum, the resonant frequency of the Helmholtz resonant cavity can be uniquely determined by the structural dimensions of the rectangular slit and the triangular prism cavity and the medium material it is filled with, as shown by the resonant frequency calculation formula.

[0041] When an electromagnetic wave with the same resonant frequency as the Helmholtz resonant cavity is incident on the upper surface of the cubic metal structure 21, the electromagnetic wave passes through the rectangular slit into the triangular prism cavity and is lost due to the lossy medium filling it. When electromagnetic waves of other frequencies are incident on the upper surface of the cubic metal structure 21, they are all reflected and are not absorbed.

[0042] The absorption characteristics of the entire high-ratio dual-frequency metamaterial absorber are jointly determined by the frustum-shaped integrated absorption structure and the low-frequency Helmholtz resonant cavity absorption structure. When high-frequency electromagnetic waves are incident, the low-frequency Helmholtz resonant absorption structure performs total reflection, acting like a metal reflector, ensuring that the frustum-shaped integrated absorption structure absorbs them. When low-frequency electromagnetic waves are incident, the frustum-shaped integrated absorption structure has no effect on them, meaning the electromagnetic waves are directly incident on the Helmholtz resonant cavity and absorbed. By designing the Helmholtz resonant cavity to operate at a lower frequency, a high-ratio absorption effect is achieved, and the single-frequency absorption characteristics of the Helmholtz resonant cavity ensure that no additional absorption frequency points appear between the two frequency points.

[0043] The technical effects of this invention will be explained below with reference to simulation experiments:

[0044] 1. Experimental conditions and contents:

[0045] Experimental conditions

[0046] Simulation 1 simulates the resonant frequency of the Helmholtz resonant cavity absorbing structure in this invention. Except for the dielectric cavity width w2, all other parameters are designed according to the above structural relationships. The base width w2 of the triangular prism cavity inside the cubic metal structure 21 is varied from 5-12 mm. The incident direction of the electromagnetic wave is perpendicular. The resonant frequency of this Helmholtz resonant cavity is obtained using CST software simulation. Simultaneously, the theoretical resonant frequency is calculated using the Helmholtz resonant cavity resonant frequency calculation formula. The simulation results are as follows: Figure 5 As shown.

[0047] Simulation 2: The Helmholtz resonant cavity absorbing structure of this invention is simulated. The frequency range is set to 1-5 GHz, and the incident direction of the electromagnetic wave is perpendicular. The absorption performance of the Helmholtz resonant cavity absorbing structure of this invention is simulated using CST software. The simulation results are as follows: Figure 6 As shown in (a), with a frequency range of 5-30 GHz, the reflection performance of the Helmholtz resonant cavity absorbing structure in this invention was simulated using CST software. The simulation results are as follows. Figure 6 As shown in (b).

[0048] Simulation 3: The high-frequency broadband absorbing structure of this invention is simulated. The frequency range is set to 1-15 GHz, and the incident direction of the electromagnetic wave is perpendicular. The wave transmission performance of the high-frequency broadband absorbing structure of this invention is simulated using CST software. The simulation results are as follows: Figure 7 As shown in (a), the absorption performance of the high-frequency broadband absorbing structure in this invention was simulated using CST software with a frequency range of 1-30 GHz. The simulation results are as follows. Figure 7 As shown in (b).

[0049] Simulation 4 simulates the absorption performance of the present invention. The frequency range is set to 1-30 GHz. X-polarized electromagnetic waves and Y-polarized electromagnetic waves are incident perpendicularly. The absorption characteristics of the present invention are simulated using CST, and the results are as follows: Figure 8 As shown.

[0050] Simulation 5 simulates the absorption performance of the present invention. The frequency range is set to 1-30 GHz, and the x-polarized electromagnetic waves are incident at oblique angles of 10°, 20°, and 30°. The absorption characteristics of the present invention are simulated using CST, and the results are as follows: Figure 9-11 As shown.

[0051] 2. Analysis of experimental results:

[0052] Reference Figure 5 The horizontal axis represents the width of the base of the triangular prism cavity inside the cubic metal structure 21, and the vertical axis represents the resonant frequency of the Helmholtz resonator. Under the condition of perpendicular incident x-polarized waves, as the width of the base of the triangular prism cavity w2 increases from 5mm to 12mm, the theoretical value curve of the Helmholtz resonator frequency calculated using the Helmholtz resonator frequency calculation formula almost matches the Helmholtz resonator frequency curve obtained from CST software simulation.

[0053] Reference Figure 6 , Figure 6 (a) shows that when the electromagnetic wave is incident perpendicularly, as the frequency of the incident electromagnetic wave changes from 1 GHz to 5 GHz, the Helmholtz resonator achieves 100% absorption at 3.1 GHz. Figure 6 (b) shows that when the frequency of the incident electromagnetic wave changes from 5 GHz to 30 GHz, the Helmholtz resonator achieves total reflection when the electromagnetic wave is incident perpendicularly.

[0054] Reference Figure 7 , Figure 7 (a) shows that when the incident electromagnetic wave frequency changes from 1 GHz to 15 GHz under the condition of perpendicular electromagnetic wave incidence, the truncated pyramid-shaped integrated absorption and transmission structure achieves high wave transmission effect at low frequency. Figure 7 (b) When the frequency of the incident electromagnetic wave changes from 15 GHz to 30 GHz under the condition of perpendicular electromagnetic wave incidence, the truncated pyramid-shaped integrated absorption structure achieves a broadband wave absorption effect in the range of 18.36 GHz to 29.8 GHz.

[0055] Reference Figure 8 When x-polarized and y-polarized waves are incident perpendicularly, and the incident electromagnetic wave frequency varies from 1 GHz to 30 GHz, the absorber exhibits an absorption rate exceeding 99% at 3 GHz and exceeding 90% in the 18.4-29.8 GHz range, with a relative bandwidth of 47%. The ratio of the high-frequency absorption center frequency to the low-frequency absorption center frequency is greater than 8, indicating that this invention achieves a high frequency ratio absorption effect at low frequency (3 GHz) and high frequency (18.4-29.8 GHz) under x-polarized and y-polarized wave perpendicular incidence, with the frequency ratio exceeding 8.

[0056] Reference Figure 9-11When the incident electromagnetic wave frequency changes from 1 GHz to 30 GHz, with x-polarized waves incident at oblique angles of 10 degrees, 20 degrees, and 30 degrees respectively, at an incident angle of 10 degrees, the absorber exhibits an absorption rate higher than 99% at 3 GHz and an absorption rate higher than 90% in the 18.4-29.6 GHz range, with a relative bandwidth of 46.7%, and a ratio of high-frequency absorption center frequency to low-frequency absorption center frequency greater than 8. At an incident angle of 20 degrees, the absorber exhibits an absorption rate higher than 97% at 3 GHz and an absorption rate higher than 90% in the 18.4-28.3 GHz range, with a relative bandwidth of 42.7%, and a ratio of high-frequency absorption center frequency to low-frequency absorption center frequency greater than 7. When the incident angle is 30 degrees, the absorber has an absorption rate of over 97% at 3 GHz and an absorption rate of over 90% in the range of 18.4-26 GHz. The relative bandwidth is 34.2%, and the ratio of the high-frequency absorption center frequency to the low-frequency absorption center frequency is greater than 7.

[0057] The above description is only a preferred embodiment of the present invention and does not constitute a limitation on the present invention. For those skilled in the art, various modifications and improvements can be made without departing from the innovative concept of the present invention, but these changes all fall within the protection scope of the present invention.

Claims

1. A multi-mode fusion high-frequency-ratio dual-frequency metamaterial absorber, comprising periodically arranged... One resonant unit Its characteristics are: The resonant unit includes A frustum-shaped integrated absorber structure (1) and a low-frequency absorbing structure (2) stacked below it. The frustum-shaped absorbent integrated structure (1) includes a square first dielectric substrate (11) and a quadrangular frustum unit (12) located at the center of its upper surface. The quadrangular frustum unit (12) adopts a shape whose side length decreases linearly from bottom to top. A frustum structure formed by stacking square second dielectric substrates (121), The upper surface of the second dielectric substrate (121) is printed with a metal patch (122); the low-frequency absorbing structure (2) adopts a cubic metal structure (21) with a square plate surface and a Helmholtz resonant cavity. The Helmholtz resonant cavity includes two rectangular slits arranged on the upper surface of the cubic metal structure (21) and intersecting in a cross shape, and two triangular prism cavities with cross-sections of isosceles triangles that penetrate the front and rear sides and left and right sides of the cubic metal structure (21) inside. The two rectangular slits are located directly above the two triangular prism cavities and connected to the vertices of the triangular prism cavities. The rectangular slits and triangular prism cavities are filled with dielectric material. The frustum-shaped integrated absorption and transmission structure (1) is used to achieve low-frequency transmission characteristics and high-frequency broadband absorption characteristics under the reflection of the low-frequency absorption structure (2); the low-frequency absorption structure (2) is used to achieve low-frequency absorption and high-frequency reflection characteristics. The resonant frequency of the Helmholtz resonant cavity The dimensions of the rectangular slit and the triangular prism cavity are determined accordingly: ； in The speed of light in a vacuum. and These represent the width and height of the rectangular slit, respectively. and These are the width and height of the bottom surface of the triangular prism cavity, respectively. The relative permittivity of the dielectric material selected for the rectangular slit and the triangular prism cavity.

2. The multi-mode fusion high-frequency-ratio dual-frequency metamaterial absorber according to claim 1, characterized in that, The cube metal structure (21) has two rectangular gaps on its upper surface, which are respectively located on the line connecting the midpoints of two sets of opposite sides on the upper surface of the cube metal structure (21).

3. The multi-mode fusion high-frequency-ratio dual-frequency metamaterial absorber according to claim 1, characterized in that, The cube metal structure (21) has two triangular prism cavities inside which the edges are parallel to the lines connecting the midpoints of the front and rear sides and the left and right sides of the cube metal structure (21), and its bottom surface is parallel to the upper and lower surfaces of the cube metal structure (21).

4. The multi-mode fusion high-frequency-ratio dual-frequency metamaterial absorber according to claim 1, characterized in that, The two rectangular slits and the two triangular prism cavities are filled with the same lossy medium material.

5. The multi-mode fusion high-frequency-ratio dual-frequency metamaterial absorber according to claim 1, characterized in that, The central normal of the truncated quadrangular unit (12) coincides with the central normal of the first dielectric substrate (11).

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