Broadband wide-angle polarization insensitive metamaterial wave absorber

Abstract

The invention discloses a broadband wide-angle polarization insensitive metamaterial wave absorber, which comprises three layers of structures, namely a microstructure unit layer, an FR-4 substrate layer and a metal bottom plate layer which are sequentially superposed from top to bottom, the whole microstructure unit layer is in axial symmetry and comprises four layers of structures, the four layers of structures sequentially comprise a rectangular metal resonance piece, four fan-shaped metal resonance pieces, a first opening metal resonance ring and a second opening metal resonance ring from inside to outside, the first opening metal resonance ring and the second opening metal resonance ring are concentric opening circular rings, and the circle centers of the first opening metal resonance ring and the second opening metal resonance ring are the centers of the rectangular metal resonance pieces. The circle centers of the four fan-shaped metal resonance sheets are located at the four corners of the rectangular metal resonance sheet respectively, the arc angles of the four fan-shaped metal resonance sheets are 90 degrees, and the edges of the four fan-shaped metal resonance sheets are located on the extension lines of the edges of the rectangular metal resonance sheet respectively. The first opening metal resonance ring and the second opening metal resonance ring are respectively provided with two openings along the transverse axis and the longitudinal axis, and the width of the openings is equal to the side length of the rectangular metal resonance piece. The wave-absorbing material has wider wave-absorbing bandwidth and better absorbing performance.

Description

Technical Field

[0001] The present invention belongs to the technical field of electromagnetic metamaterial absorbers, and in particular relates to a broadband, wide-angle, polarization-insensitive metamaterial absorber. Background Art

[0002] An absorber is a device or material that absorbs electromagnetic wave energy, converting it into heat or other forms of energy, thereby reducing its reflection and transmission. In recent years, metamaterials, artificial electromagnetic materials with physical properties not found in conventional materials, have garnered widespread attention.

[0003] Metamaterials are artificially designed, three-dimensional composite structural systems whose electromagnetic response characteristics differ significantly from those of natural materials. The basic unit size of these materials is significantly smaller than the operating wavelength, and they are finely arranged in periodic or aperiodic arrays to form artificial microstructure systems with subwavelength characteristics. By performing parametric design and electromagnetic optimization on the unit structure, electromagnetic parameters such as the material's equivalent dielectric constant and magnetic permeability can be flexibly set, breaking through the natural limitations of traditional materials in their electromagnetic properties and bringing unprecedented freedom to electromagnetic wave control. This unique electromagnetic control capability has given it groundbreaking application prospects in cutting-edge technologies such as super-resolution imaging, electromagnetic stealth, and energy absorption.

[0004] Metamaterial absorber (MMA), as an electromagnetic device that efficiently converts incident electromagnetic wave energy into forms such as heat, has important application value in the fields of radar stealth and electromagnetic interference suppression. However, existing absorbers have the problem of narrow bandwidth, which makes it difficult to meet the needs of broadband absorption in complex electromagnetic environments. In order to solve the bandwidth limitation, multi-frequency resonant structure design or multi-layer metal stacking method is often used to widen the absorption frequency band by superimposing the frequency responses of different resonant units. However, this type of solution will lead to a significant increase in the thickness of the absorber. Although the interlayer coupling effect can expand the bandwidth, it is contrary to the lightweight requirements of modern electronic equipment and stealth equipment, which seriously restricts the engineering application of metamaterial absorbers in aerospace, mobile terminals and other fields. At the same time, the stability of the absorber is also crucial. Stability includes the stability of the angle of the incident electromagnetic wave and the stability of polarization. The higher the stability, the higher the reliability in practical applications.

[0005] At present, how to achieve a lightweight and thin design of the device while ensuring efficient absorption performance, and at the same time ensure that the device has broadband, wide-angle and polarization-insensitive characteristics, has become a key technical bottleneck that needs to be overcome in this field. Summary of the Invention

[0006] In response to the shortcomings of the existing technology, the present invention provides a broadband, wide-angle, polarization-insensitive metamaterial absorber, which solves the problem of narrow absorption band and inability to balance the absorption band and thin structure proposed in the above background, and does not have the characteristics of wide angle and polarization insensitivity.

[0007] The metamaterial absorber includes a three-layer structure, namely a microstructure unit layer, an FR-4 substrate layer, and a metal base plate layer stacked in sequence from top to bottom. The microstructure unit layer is axisymmetric as a whole and includes a four-layer structure, which includes, from the inside to the outside, a rectangular metal resonant plate, four fan-shaped metal resonant plates, a first open metal resonant ring, and a second open metal resonant ring. The first open metal resonant ring and the second open metal resonant ring are concentric open circular rings, and the center of the circle is the center of the rectangular metal resonant plate.

[0008] Furthermore, the arc angles of the four sector-shaped metal resonant plates are 90°, the centers of the four sector-shaped metal resonant plates are respectively located at the four corners of the rectangular metal resonant plate, and the sides of the four sector-shaped metal resonant plates are respectively located on the extension lines of the sides of the rectangular metal resonant plate.

[0009] Furthermore, the side length of the rectangular metal resonant plate is 1 mm, and the radius of the arcs of the four sector-shaped metal resonant plates from the center of the rectangular metal resonant plate is 2 mm.

[0010] Furthermore, the first open metal resonant ring and the second open metal resonant ring are respectively provided with two openings along the horizontal axis and the vertical axis, and the width of the opening is equal to the side length of the rectangular metal resonant plate.

[0011] Furthermore, the openings of the second open metal resonant ring are connected via resistors, the four fan-shaped metal resonant plates are respectively connected to the first open metal resonant ring via resistors, and the first open metal resonant ring and the second open metal resonant ring are connected via resistors.

[0012] Furthermore, the resistance value of each resistor is 200Ω.

[0013] Furthermore, the radius of the second open metal resonant ring is 5 mm, the width is 0.5 mm, and the thickness is 0.035 mm.

[0014] Furthermore, the radius of the first open metal resonant ring is 3.3 mm, the width is 0.5 mm, and the thickness is 0.035 mm.

[0015] Furthermore, the FR-4 substrate layer is made of FR-4 material and is in the shape of a square with a side length of 13 mm and a thickness of 2.9 mm.

[0016] Furthermore, the metal bottom plate layer is made of metal copper and is in the shape of a square with a side length of 13 mm and a thickness of 0.035 mm.

[0017] Beneficial effects of the present invention:

[0018] The metamaterial absorber designed in the present invention can achieve an absorption rate of more than 90% for electromagnetic waves in the frequency range of 8GHz-16GHz, and a maximum of 99.39%. The absorption bandwidth can reach 8GHz, which is an absorption bandwidth that traditional metamaterial absorbers do not have.

[0019] The present invention has the advantages of small size and easy production, and its overall size is 13mm×13mm×2.97mm.

[0020] In the simulation of TE and TM modes, the present invention changes the incident angle of the wave and the rotation angle of the structure, and still maintains good absorption performance in the frequency range of 8GHz-16GHz. This significant polarization insensitivity and angle stability give the absorber great advantages in practical applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Schematic diagram of the overall structure of an embodiment of the present invention;

[0022] Figure 2 A top view of an embodiment of the present invention;

[0023] Figure 3 A side view of an embodiment of the present invention;

[0024] Figure 4 is a graph showing the absorption rate of an embodiment of the present invention during simulation;

[0025] Figure 5 This is a graph showing the absorption rate at oblique incidence in the TE mode during simulation according to an embodiment of the present invention;

[0026] Figure 6 This is a graph showing the absorption rate at oblique incidence in the TM mode during simulation according to an embodiment of the present invention;

[0027] Figure 7 1 is a graph showing the absorption rate at different rotation angles in the TE mode during simulation according to an embodiment of the present invention;

[0028] Figure 8 is a graph showing the absorption rate at different rotation angles in the TM mode during simulation according to an embodiment of the present invention;

[0029] In the accompanying drawings: 1 is a microstructure unit layer, 2 is an FR-4 substrate layer, 3 is a metal base plate layer, 4 is a rectangular metal resonant plate, 5 is a fan-shaped metal resonant plate, 6 is a first open metal resonant ring, 7 is a second open metal resonant ring, R represents resistance, a represents the side length of the rectangular metal resonant plate, r1 represents the radius of the arc of the fan-shaped metal resonant plate from the center of the rectangular metal resonant plate, r2 represents the radius of the inner arc of the first open metal resonant ring to the center of the rectangular metal resonant plate, r3 represents the radius of the outer arc of the first open metal resonant ring to the center of the rectangular metal resonant plate, r4 represents the radius of the inner arc of the second open metal resonant ring to the center of the rectangular metal resonant plate, r5 represents the radius of the outer arc of the second open metal resonant ring to the center of the rectangular metal resonant plate, h represents the thickness of the metamaterial absorber, and L represents the width of the metamaterial absorber. DETAILED DESCRIPTION

[0030] In the specification and claims of this application and the accompanying drawings, the terms "first," "second," and the like are used to distinguish similar objects, and are not necessarily used to describe a specific order or precedence. The terms "upper," "lower," "inner," "outer," and "outermost" are used to describe relative positional relationships, and are not necessarily used to describe specific positional relationships. It should be understood that the terms used in this manner are interchangeable where appropriate, and are merely used to describe the distinctions used when describing objects with the same attributes in the embodiments of this application.

[0031] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0032] The embodiment of the present invention proposes a broadband, wide-angle, polarization-insensitive metamaterial absorber, referring to Figure 1-3 As shown, the metamaterial absorber includes a three-layer structure, namely, a microstructure unit layer 1, an FR-4 substrate layer 2, and a metal base plate layer 3 stacked in sequence from top to bottom; the microstructure unit layer is axisymmetric as a whole, and includes a four-layer structure, which includes, from the inside to the outside, a rectangular metal resonant plate 4, four fan-shaped metal resonant plates 5, a first open metal resonant ring 6, and a second open metal resonant ring 7. The first open metal resonant ring and the second open metal resonant ring are concentric open circular rings, and the center of the circle is the center of the rectangular metal resonant plate.

[0033] In the illustrated embodiment, reference is made to Figure 2As shown, the arc angles of the four sector-shaped metal resonant plates are 90°. The centers of the four sector-shaped metal resonant plates are located at the four corners of the rectangular metal resonant plate, and the sides of the four sector-shaped metal resonant plates are located on the extension lines of the sides of the rectangular metal resonant plate. The centers of the arcs of the four sector-shaped metal resonant plates are the center of the rectangular metal resonant plate.

[0034] In the illustrated embodiment, reference is made to Figure 2 As shown, the side length of the rectangular metal resonant plate is 1 mm, that is, a=1 mm, and the radius of the arc of the four sector-shaped metal resonant plates from the center of the rectangular metal resonant plate is 2 mm, that is, r1=1 mm.

[0035] In the illustrated embodiment, reference is made to Figure 2 As shown, the first open metal resonant ring and the second open metal resonant ring are respectively provided with two openings along the horizontal axis and the vertical axis, that is, the openings are respectively provided at positions intersecting with the first open metal resonant ring and the second open metal resonant ring along the horizontal axis and the vertical axis, and the width of the opening is equal to the side length of the rectangular metal resonant plate, that is, a = 1 mm.

[0036] In the illustrated embodiment, reference is made to Figure 2 As shown, each opening of the second open metal resonant ring is connected by a resistor, that is, the four openings of the outermost open metal resonant ring are connected by resistors. The four fan-shaped metal resonant plates are connected to the first open metal resonant ring via resistors at corresponding positions, that is, each fan-shaped metal resonant plate is provided with a resistor on the diagonal extension line of the rectangular metal resonant plate, and is connected to the first open metal resonant ring (i.e., the open metal resonant ring located in the inner layer) through the resistor. The first open metal resonant ring and the second open metal resonant ring (i.e., the outermost open metal resonant ring) are connected at corresponding positions via four resistors, where the corresponding positions specifically refer to the diagonal extension lines of the rectangular metal resonant plates within the plane.

[0037] In the illustrated embodiment, reference is made to Figure 2 As shown, the resistance value of the resistor R is 200Ω, that is, R=200Ω.

[0038] In the illustrated embodiment, reference is made to Figure 2 As shown, the radius of the second open metal resonant ring (ie, the open metal resonant ring located in the inner layer) is 5 mm, the width is 0.5 mm, and the thickness is 0.035 mm.

[0039] In the illustrated embodiment, reference is made to Figure 2 As shown, the radius of the first open metal resonant ring (ie, the outermost open metal resonant ring) is 3.3 mm, the width is 0.5 mm, and the thickness is 0.035 mm.

[0040] In the illustrated embodiment, reference is made to Figure 2 、 3 As shown, the FR-4 substrate layer is made of FR-4 material and is in a square shape with a side length of 13 mm and a thickness of 2.9 mm. It should be noted that FR-4 is a reinforced epoxy resin laminate material with a dielectric constant of 4.3. FR-4 material has a consistent dielectric constant across the entire RF spectrum.

[0041] In the illustrated embodiment, reference is made to Figure 2 、 3 As shown, the metal bottom plate layer is made of metal copper and is in the shape of a square with a side length of 13 mm and a thickness of 0.035 mm.

[0042] The metamaterial absorber designed in this invention has a microstructure unit layer (i.e., a metasurface) consisting of two concentric metal resonant rings and a sector-shaped metal resonant plate. The metal resonant rings facilitate the circulation of incident surface currents generated by electromagnetic waves, inducing resonance and subsequently enhancing absorption. Narrow gaps form between adjacent sector-shaped metal resonant plates. Under the influence of an electromagnetic field, this structure accumulates opposite charges between the sectors, producing a capacitive effect. While resistance increases ohmic losses, the current and field strength within the structure are greatly enhanced during resonance, and resistance directly converts the huge resonant current into heat. Therefore, the metamaterial absorber designed in this invention has enhanced wave absorption capabilities.

[0043] The metamaterial absorber designed in the present invention has a symmetrical microstructure unit layer (i.e., metasurface) that is symmetrical about the X-axis and the Y-axis, respectively. This allows TE polarization and TM polarization to have the same absorption rate, indicating that the structure is polarization-insensitive.

[0044] Broadband absorption is caused by the destructive interference between two parallel reflecting surfaces caused by the Fabry-Perot effect, which causes multiple reflections in the cavity, resulting in absorption.

[0045] When the metamaterial absorber designed by the present invention is in operation, when the incident electromagnetic wave reaches the top layer of the metamaterial absorber, part of the energy is reflected back into the air, and the other part of the energy is transmitted into the dielectric layer. The transmitted wave propagates in the dielectric layer to the bottom metal plate, causing total reflection. The totally reflected wave propagates upward through the dielectric layer again and reaches the top layer. When it reaches the top layer, part of it will be transmitted back into the air again, and the other part will be reflected back into the cavity for a new round of reflection cycle. When the phase of the reflected wave at the top layer differs by (2k+1)π from the phase of the transmitted wave after one round trip through the cavity, the two beams undergo destructive interference. As a result, the intensity of the superimposed reflected wave becomes extremely small, the interference causes minimal reflection, and the lost energy is converted into heat.

[0046] Simulation verification:

[0047] Simulation software: CST Studio Suite, referred to as CST software.

[0048] During simulation verification of the present invention, two modes were observed: the TE (Transverse Electric) mode and the TM (Transverse Magnetic) mode. In the TE mode, the electric field vector is perpendicular to the wave propagation direction, and the magnetic field vector is parallel to it. In the TM mode, the magnetic field vector is perpendicular to the wave propagation direction, and the electric field vector is parallel to it.

[0049] Figure 4 FIG. 4 is a graph showing the absorption rate of an embodiment of the present invention during simulation. Figure 4 , the abscissa Frequency represents the frequency, the ordinate Absorption represents the absorption rate, TE Polarization represents the TE polarization, and TM Polarization represents the TM polarization.

[0050] like Figure 4 As shown in Figure 1, in the TE mode, when the electromagnetic wave is incident in a fixed direction, the magnetic field component is located in the XY plane, while the electric field component is perpendicular to the propagation direction, forming a perpendicular relationship between the electric and magnetic fields. In the TM mode, when the electromagnetic wave is incident in a fixed direction, the electric field component is located in the XY plane, while the magnetic field component is perpendicular to the propagation direction, forming a perpendicular relationship between the magnetic and electric fields. The absorption rate of the metamaterial absorber is determined based on the transmission coefficient and reflection coefficient of the S parameter, which is specifically expressed as:

[0051] A(ω)=1-|S 11 (ω)| 2 -|S 21 (ω)| 2

[0052] Where A(ω) represents the absorption rate of the metamaterial absorber, S 11 (ω) represents the reflection coefficient of the metamaterial absorber, S 21 (ω) represents the transmission coefficient of the metamaterial absorber.

[0053] Simulation results show that the metamaterial absorber designed in this invention achieves an absorption rate exceeding 90% for electromagnetic waves in the 8GHz-16GHz frequency range, with a maximum of 99.39%. The metamaterial absorber exhibits four-fold symmetry, with equal absorption in the TE and TM modes, demonstrating its polarization-insensitive nature.

[0054] Figure 5 This is a graph showing the absorption rate at oblique incidence in TE mode during simulation according to an embodiment of the present invention. Figure 5In the figure, the horizontal axis Frequency represents the frequency, the vertical axis Absorption represents the absorption rate, and θ represents the incident angle.

[0055] like Figure 5 As shown, the metamaterial absorber designed in the present invention studies the absorption rate of the incident angle θ=0° to 45° on an absorber with a resistance value of 200Ω in TE mode.

[0056] Simulation results show that at an incident angle of θ = 40°, the metamaterial absorber designed in this invention maintains a relatively stable absorption rate. For electromagnetic waves in the frequency range of 8 GHz to 16 GHz, its absorption rate can reach over 80%. However, as the incident angle increases, the absorption rate tends to decrease.

[0057] Figure 6 FIG. 4 is a graph showing the absorption rate of an embodiment of the present invention under oblique incidence in TM mode during simulation. Figure 6 In the figure, the horizontal axis Frequency represents the frequency, the vertical axis Absorption represents the absorption rate, and θ represents the incident angle.

[0058] like Figure 6 As shown in the figure, the absorptivity of the metamaterial absorber designed in this invention was studied in TM mode at incident angles θ = 0° to 45° on an absorber with a resistance of 200Ω. For the TM mode, the results show that the absorptivity significantly decreases with increasing incident angle compared to the TE mode. At an incident angle θ = 45°, the absorptivity drops to 0.6 at 11 GHz. However, it remains above 80% for the remaining frequency range.

[0059] Figure 7 FIG. 4 is a graph showing the absorption rate at different rotation angles in the TE mode during simulation according to an embodiment of the present invention.

[0060] Figure 8 FIG. 4 is a graph showing the absorption rate at different rotation angles in the TM mode during simulation according to an embodiment of the present invention.

[0061] Figure 7 、 Figure 8 In the figure, the horizontal axis Frequency represents the frequency, the vertical axis Absorption represents the absorption rate, and φ represents the rotation angle.

[0062] like Figure 7-Figure 8As shown in the figure, the effect of the metamaterial absorber's rotation angle on the absorption bandwidth is studied when electromagnetic waves are incident in a fixed direction under different polarization modes. The resistance value is maintained at 200Ω, and the results are analyzed for different rotation angles φ = 0° to 90°. For the TE mode, when the electromagnetic wave is incident in a fixed direction, the magnetic field component lies in the XY plane, while the electric field component is perpendicular to the propagation direction, forming a perpendicular relationship between the electric and magnetic fields. Within the range of φ = 0° to 90°, the absorption rate remains unchanged and is consistent with the simulation results for the TM mode, indicating that the structure is not only insensitive to both TE and TM modes, but also has strong angular stability.

[0063] In summary, the broadband, wide-angle, polarization-insensitive metamaterial absorber proposed in this invention, compared to the multi-resonant structures or multi-layer metal stacking strategies of the prior art, only has four metal conductive structures and several resistors. The structural design of these four metal conductive structures enables the metamaterial absorber unit to achieve broadband absorption (absorbing electromagnetic waves in the frequency range of 8GHz-16GHz), wide-angle stability, polarization insensitivity, high absorption efficiency (absorption rate exceeding 90% between 8GHz and 16GHz), and a thin structure (thickness is lower than that of multi-resonant structures or structures using multi-layer metal stacking strategies). This balances performance and practicality, promoting metamaterial absorbers towards more efficient and convenient applications. Furthermore, the preparation method is simple and easy to implement.

[0064] Those skilled in the art will understand that all or part of the steps in the various methods of the above embodiments can be completed by instructing the relevant hardware through a program, and the program can be stored in a computer-readable storage medium, which may include: ROM, RAM, disk or CD, etc.

[0065] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A broadband, wide-angle, polarization-insensitive metamaterial absorber, characterized in that: The metamaterial absorber comprises a three-layer structure, comprising a microstructure unit layer (1), an FR-4 substrate layer (2) and a metal base plate layer (3) stacked in sequence from top to bottom; the microstructure unit layer is axisymmetric as a whole and comprises a four-layer structure, comprising, from the inside to the outside, a rectangular metal resonant plate (4), four fan-shaped metal resonant plates (5), a first open metal resonant ring (6) and a second open metal resonant ring (7); the first open metal resonant ring and the second open metal resonant ring are concentric open circular rings, the center of which is the center of the rectangular metal resonant plate.

2. The broadband, wide-angle, polarization-insensitive metamaterial absorber according to claim 1, characterized in that: The arc angles of the four sector-shaped metal resonant plates are 90°, the centers of the four sector-shaped metal resonant plates are respectively located at the four corners of the rectangular metal resonant plate, and the sides of the four sector-shaped metal resonant plates are respectively located on the extension lines of the sides of the rectangular metal resonant plate.

3. The broadband, wide-angle, polarization-insensitive metamaterial absorber according to claim 1, characterized in that: The side length of the rectangular metal resonant plate is 1 mm, and the radius of the arc of the four sector-shaped metal resonant plates from the center of the rectangular metal resonant plate is 2 mm.

4. The broadband, wide-angle, polarization-insensitive metamaterial absorber according to claim 1 or 3, characterized in that: The first open metal resonant ring and the second open metal resonant ring are each provided with two openings along the horizontal axis and the vertical axis, respectively. The width of the opening is equal to the side length of the rectangular metal resonant plate.

5. The broadband, wide-angle, polarization-insensitive metamaterial absorber according to claim 1, characterized in that: The openings of the second open metal resonant ring are connected via resistors, the four sector-shaped metal resonant plates are connected to the first open metal resonant ring via resistors, and the first open metal resonant ring and the second open metal resonant ring are connected via resistors.

6. The broadband, wide-angle, polarization-insensitive metamaterial absorber according to claim 5, characterized in that: The resistance value of the resistors is 200Ω.

7. The broadband, wide-angle, polarization-insensitive metamaterial absorber according to claim 1, characterized in that: The second open metal resonant ring has a radius of 5 mm, a width of 0.5 mm, and a thickness of 0.035 mm.

8. The broadband, wide-angle, polarization-insensitive metamaterial absorber according to claim 1, characterized in that: The first open metal resonant ring has a radius of 3.3 mm, a width of 0.5 mm, and a thickness of 0.035 mm.

9. The broadband, wide-angle, polarization-insensitive metamaterial absorber according to claim 1, characterized in that: The FR-4 substrate layer is made of FR-4 material and is in a square shape with a side length of 13 mm and a thickness of 2.9 mm.

10. The broadband, wide-angle, polarization-insensitive metamaterial absorber according to claim 1, characterized in that: The metal bottom plate layer is made of copper and is in the shape of a square with a side length of 13 mm and a thickness of 0.035 mm.

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