A dual-polarized ultra-wideband three-dimensional wave-absorbing structure metamaterial

Abstract

The present application relates to the field of metamaterials, in particular to a dual-polarized ultra-wideband three-dimensional wave-absorbing structure metamaterial, which comprises a four-prism support body, a full-coverage resistive film arranged on the sidewall of the four-prism support body to form a wave-absorbing structure, and a matrix of the wave-absorbing structures to obtain the metamaterial, so that the electromagnetic wave absorption rate is greater than 90% in the frequency band of 2.1GHz-18GHz, and the relative bandwidth is close to 160%, thereby achieving the ultra-wideband wave-absorbing performance.Further, the anisotropy is introduced by the asymmetric three-dimensional wave-absorbing structure, and the deterioration of TE polarization at a large angle under the isotropy is improved, so that the TE and TM polarizations are both highly absorbed within the wide-angle oblique incidence range of 0° to 65°. The present application provides a new idea for the design of dual-polarized ultra-wideband wide-angle wave-absorbing bodies, and can be quickly prepared by combining the current 3D printing technology, without any magnetic material or composite material, and has great application potential.

Description

Technical Field

[0001] This invention relates to the field of metamaterials, specifically to a dual-polarized ultrawideband three-dimensional absorbing metamaterial. Background Technology

[0002] Stealth technology, also known as low-observable technology, is one of the most core and critical technologies developed in the 21st century. Depending on the detection method, stealth technology includes radar stealth, infrared stealth, acoustic stealth, and visible light stealth, but radar stealth remains the most important, accounting for approximately 60%. Radar stealth technology mainly includes shape design and the application of radar stealth materials. When the shape is fixed, the application of radar stealth materials becomes the primary means.

[0003] Radar stealth materials mainly include radar-absorbing coatings and radar-absorbing structures. Radar-absorbing coatings were used earlier, involving mixing absorbers and binders and coating them onto the target surface. They are low-cost, but have limitations under the requirements of being thin, lightweight, wide, and strong. Radar-absorbing structures combine load-bearing and radar-absorbing functions, making them the primary means of stealth materials. Compared to radar stealth coatings, radar-absorbing structures have significant advantages in absorption bandwidth and absorption efficiency. Furthermore, radar-absorbing structures offer more complex surface designs and more flexible interface matching capabilities, attracting widespread attention in the industry.

[0004] Currently, the development trend of radar absorbing structures mainly focuses on broadband, wide-angle, and polarization-insensitive characteristics. Based on the transmission characteristics and impedance relationship of obliquely incident electromagnetic waves, achieving dual-polarization ultra-wideband wide-angle absorption requires specific transverse electromagnetic parameters (ε) in the material. t μ t ) and normal electromagnetic parameter (ε n μ n Satisfy: ε t +μ t =(ε n +μ n ) / ε n μ n Therefore, the material possesses anisotropic properties. Research on narrow-bandwidth angular polarization-insensitive absorbing structures mainly focuses on high-impedance surface structures. Research on ultra-widebandwidth angular polarization-insensitive absorbing structures currently focuses on multilayer and composite mechanisms. However, research directions such as multilayer and composite mechanisms face challenges such as complex absorbing structure design methods and difficulties in material selection (e.g., excessive thickness in three-dimensional structures). Summary of the Invention

[0005] To address the aforementioned problems and shortcomings, and to overcome the issues of complex design methods and difficult material selection in existing absorbing structures, this invention provides a dual-polarized ultrawideband three-dimensional absorbing metamaterial. This three-dimensional absorbing structure can cover the S, C, X, and Ku wavebands. Furthermore, by selecting an asymmetric three-dimensional absorbing structure as the basic unit, it enables efficient absorption of both TE and TM polarizations under oblique incidence conditions from 0° to 65°, thereby achieving dual-polarized ultrawideband bandwidth.

[0006] The technical solution of the present invention is as follows:

[0007] A dual-polarized ultrawideband three-dimensional absorbing metamaterial is constructed from basic units with period P arranged in a matrix. Each basic unit is a three-dimensional absorbing structure, comprising a bottom reflective layer, an intermediate support, and a sidewall resistive film.

[0008] The bottom reflective layer is a square metal base plate with a side length of P located at the bottom of the basic unit, and has an electrical conductivity of 2 to 9 × 10⁻⁶. 7 s / m, thickness 10-70μm; with the bottom reflective layer as the reference, adjacent basic units are arranged in a matrix manner in a corresponding manner;

[0009] The intermediate support is a truncated pyramid with rectangular upper and lower faces. The center points of the upper and lower faces overlap in the height direction and are centrally located on the bottom reflective layer. The edges of the upper and lower faces are parallel to the edges of the bottom reflective layer, respectively. The four sidewalls of the truncated pyramid are isosceles trapezoids, mainly serving to support the resistive film. The intermediate support is made of a material with a dielectric constant of 1 to 1.5, and its height h is (20 to 30) ± 10% mm. The angle θ between the sidewalls of the truncated pyramid and the lower base is an acute angle.

[0010] The sidewall resistive film is fully covered and affixed to the four sides of the quadrangular frustum (intermediate support).

[0011] Furthermore, the basic unit is a symmetrical three-dimensional absorbing structure (such as...). Figure 1 As shown in -a), the upper and lower faces of the truncated pyramid are both squares: the lower face (the face in contact with the bottom reflective layer) is a square with side length b, and the upper face is a square with side length a, where b > a. Four resistive films are appropriately placed on the four side walls of the truncated pyramid, as shown in the unfolded diagram. Figure 1 As shown in -b. The vertex of the square platform is taken as the origin of the coordinate system, and the two sides corresponding to the vertex are taken as the x-axis and y-axis respectively. 2b>p>b, and the resistance of the four resistive films is R, with R ranging from (60 Ohm / sq to 400 Ohm / sq) ±10%.

[0012]

[0013] Furthermore, the basic unit is an asymmetric three-dimensional absorbing structure (such as...). Figure 6 As shown in -a), at least one face of the upper and lower faces of the frustum is a rectangle:

[0014] The lower rectangular platform is defined by taking one vertex as the origin, with the two sides corresponding to that vertex as the x-axis and y-axis, respectively. The side lengths of the lower platform along the x and y directions are b, respectively. x and b y The corresponding side lengths of the upper platform are a. x and a y The angle between the sidewall of the frustum and the bottom surface along the x-direction is θ. x The angle between the sidewall of the quadrangular frustum and the bottom surface along the y-direction is θ. y b x >a x b y >a y Its unfolded diagram is as follows Figure 6 -b is shown. 2b x >p>b x 2b y >p>b y The resistance values ​​of the resistive film along the x and y directions of the asymmetric three-dimensional absorbing structure are R0 and R0, respectively. x and R y , where R x The value range is (300 Ohm / sq~600 Ohm / sq)±10%, R y The value range is (1000 Ohm / sq~1400 Ohm / sq)±10%.

[0015]

[0016]

[0017] Furthermore, both the upper and lower faces of the quadrangular truncated pyramid are rectangular, which improves the overall performance of the dual-polarized ultrawideband three-dimensional absorbing metamaterial.

[0018] This invention introduces a truncated quadrangular support structure, with a fully covered resistive film on its sidewalls forming an absorbing structure. The absorbing structure is arranged in a matrix to obtain a metamaterial, achieving an electromagnetic wave absorption rate greater than 90% and a relative bandwidth approaching 160% in the 2.1GHz-18GHz frequency band, exhibiting ultra-wideband absorption performance. Furthermore, anisotropy is introduced through an asymmetric three-dimensional absorbing structure, improving the degradation of TE polarization at large angles under isotropic conditions. This results in efficient absorption of both TE and TM polarizations within a wide angle of incidence from 0° to 65°.

[0019] In summary, this invention provides a new approach for the design of dual-polarized ultrawideband bandwidth absorbers. The proposed basic unit structure can be rapidly fabricated using current 3D printing technology, without requiring any magnetic or composite materials. It aligns with the application context where absorption performance deteriorates under a certain polarization when incident at large angles, and thus has significant potential. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of a symmetrical three-dimensional absorbing structure and its unfolding along the XOY plane.

[0021] Figure 2 Absorption curves of a symmetrical three-dimensional absorbing structure under TE and TM polarization.

[0022] Figure 3 The reflection loss curves of electromagnetic waves incident at oblique angles from 0° to 70° under TE and TM polarization for a symmetrical three-dimensional absorbing structure.

[0023] Figure 4 The normalized real and imaginary impedance curves under TE polarization for a symmetrical three-dimensional absorbing structure.

[0024] Figure 5 The normalized real and imaginary impedance curves under TM polarization for a symmetrical three-dimensional absorbing structure.

[0025] Figure 6 This is a schematic diagram of an asymmetric absorbing structure and its unfolding along the XOY plane.

[0026] Figure 7 Absorption curves of the asymmetric three-dimensional absorbing structure under TE and TM polarization.

[0027] Figure 8 The reflection loss curves of electromagnetic waves incident at oblique angles from 0° to 70° under TE and TM polarization of the asymmetric three-dimensional absorbing structure.

[0028] Figure 9 The normalized real and imaginary impedance curves are given for an asymmetric three-dimensional absorbing structure under TE polarization.

[0029] Figure 10 The normalized real and imaginary impedance curves are given for the asymmetric three-dimensional absorbing structure under TM polarization.

[0030] Figure 11 This is a schematic diagram illustrating the application of two three-dimensional absorbing structures in the embodiments.

[0031] Figure 12 This is a schematic diagram illustrating the structure of the two basic units of the present invention. Detailed Implementation

[0032] The technical solution of the present invention will be described in detail below with reference to the accompanying drawings and embodiments. In practical use, the relationship between the minimum operating frequency and wavelength must be met, and the device must be manufactured according to the calculated minimum size. Figure 11 Examples of implementation structures for the two basic units are provided in this embodiment. Figure 12 This is a schematic diagram illustrating the structure of the two basic units of the present invention.

[0033] Example 1

[0034] This embodiment uses a symmetrical three-dimensional absorbing structure as the basic unit, such as Figure 1 As shown, this includes a bottom metal layer with an electrical conductivity of 8 × 10⁻⁶. 7 For a metal substrate with s / m, the period along both the x and y directions is p, i.e., p x =p y =p=8.5mm, thickness is 35μm, on which a truncated pyramidal central support and an ultra-thin sidewall resistive film are sequentially arranged. The top side length of the truncated pyramid is a=4.74mm, the bottom side length is b=8.5mm, the support is made of foam material with a dielectric constant of 1.006, and its height is h=20mm. Four trapezoidal resistive films with a resistance value R=100Ohm / sq are tightly attached to the sidewall of the foam support. The resistive film material can be one or a composite of carbon black and graphite; in this embodiment, it is specifically carbon black.

[0035] Electromagnetic wave oblique incidence analysis was performed on the structure of this embodiment in CST. The absorption curves of the symmetrical three-dimensional quadrangular frustum-based absorbing structure provided in this embodiment under TE and TM polarization in the 2GHz-18GHz frequency band under perpendicular electromagnetic wave incidence are shown below. Figure 2 As shown in the figure, with 90% as the standard, the effective bandwidth of this absorbing structure is 2.1GHz-18GHz, and the relative bandwidth is close to 160%. Its oblique incidence performance is analyzed... Figure 3 It can be seen that under TE polarization, the absorption is good in the range of 0° to 30°, but as the angle increases, the reflection loss of electromagnetic waves deteriorates severely (>-10dB) after the incident angle of 30°, and the absorption deteriorates severely. On the other hand, under TM polarization, the absorption performance is maintained in the range of 0° to 65°, and the reflection loss is always below -10dB.

[0036] Example 2

[0037] The difference between this embodiment and Embodiment 1 is that the central support of the foam frustum is an asymmetrical structure, with bottom side lengths b along the x and y directions respectively. x =6mm and b y = 7.5mm, with top edge lengths a along the x and y directions respectively. x =4mm and a y=5mm. The interval periods of the quadrangular frustums of adjacent basic elements are different along the x and y directions, respectively p x =6.2mm and p y = 7.7mm. The resistance values ​​of the resistive film along the x-direction and y-direction sidewalls are R and R, respectively. x =1000 Ohm / sq and R y = 400 Ohm / sq. All other parameters and materials are the same as in Example 1.

[0038] The absorptivity of the structure in Example 2 under vertical incidence is as follows: Figure 7 As shown, within the 2GHz-18GHz frequency band, the effective bandwidth under TE polarization and TM polarization is slightly narrower, with relative bandwidths of 144.5% and 149.5%, respectively. Example 2, based on Example 1, introduces anisotropy asymmetrically, significantly improving the impedance matching under TE polarization without affecting the impedance matching of TM polarization. This results in the real part of the normalized impedance of TE polarization being near 1, and the imaginary part being near 0 (e.g., ...). Figure 4-5 , Figure 9-10 (As shown); thus, based on the structure of Example 1, the structure of Example 2 can achieve efficient absorption of both TE and TM polarizations in the electromagnetic wave oblique incidence range of 0° to 65°, thus possessing a dual-polarization ultra-wide bandwidth absorption effect, such as Figure 8 As shown.

[0039] As can be seen from the above embodiments, the dual-polarized ultrawideband three-dimensional absorbing metamaterial provided by this invention: 1) Based on the structural characteristics of the three-dimensional structure itself and the phenomenon of multiple standing wave modes when electromagnetic waves are incident, a symmetrical three-dimensional absorbing structure is established, which can achieve dual-polarized ultrawideband absorption in the 2GHz-18GHz frequency band; 2) When electromagnetic waves are obliquely incident, TE polarization deteriorates severely after 30°, while TM polarization is stably absorbed in the range of 0° to 65°; 3) Through asymmetric design, anisotropy is introduced to solve the impedance matching deterioration problem under TE polarization, enabling the structure to achieve dual-polarized ultrawideband wide-angle absorption. This invention provides a new design concept for achieving dual-polarized wide-angle absorption in three-dimensional structures. It is highly operable, easy to design and verify, and has the potential to be used in situations where electromagnetic waves are incident at large angles, making it worthy of promotion. Furthermore, since the basic unit structure of this invention uses only three materials, it can be combined with existing 3D printing technology during processing, greatly reducing processing difficulty and cost. Its superior characteristics of integrating ultrawideband and wide-angle absorption are beneficial for the use of this absorber in some large-angle incident environments.

Claims

1. A dual-polarized ultrawideband three-dimensional absorbing metamaterial, characterized in that: It is composed of basic units with a period of P arranged in a matrix. The basic unit is a three-dimensional wave-absorbing structure, including a bottom reflective layer, a middle support body and a side wall resistive film. The bottom reflective layer is a square metal base plate with side length P located at the bottom of the basic unit, and has an electrical conductivity of (2~9)×10⁻⁶. 7 s / m, thickness 10-70μm; with the bottom reflective layer as the reference, adjacent basic units are arranged in a matrix manner in a corresponding manner; The intermediate support is a quadrangular frustum with rectangular upper and lower surfaces. The center points of the upper and lower surfaces overlap in the height direction and are centrally located on the bottom reflective layer. The edges of the upper and lower surfaces are parallel to the edges of the bottom reflective layer, and the four side walls of the quadrangular frustum are isosceles trapezoids. The intermediate support is made of a material with a dielectric constant of 1 to 1.5, and the height h is (20 to 30) ± 10% mm. The angle θ between the side wall of the quadrangular frustum and the bottom surface is an acute angle. The sidewall resistive film is fully covered and attached to the four sides of the middle support.

2. The dual-polarized ultrawideband three-dimensional absorbing metamaterial as described in claim 1, characterized in that: The basic unit is a symmetrical three-dimensional absorbing structure, that is, the upper and lower faces of the quadrangular frustum are both squares: the lower face is a square with a side length of b, the upper face is a square with a side length of a, b>a, and the height is h; 2b>p>b, and the resistance of the four resistive films is R, with R taking the value of (60Ohm / sq~400Ohm / sq)±10%.

3. The dual-polarized ultrawideband three-dimensional absorbing metamaterial as described in claim 1, characterized in that: The basic unit is an asymmetric three-dimensional absorbing structure, that is, at least one face of the upper and lower faces of the truncated pyramid is rectangular: Let one vertex of the rectangular lower platform be the origin of the coordinate system, and the two sides corresponding to the vertex be the x-axis and y-axis, respectively. The side lengths of the lower platform along the x-direction and y-direction are b and b, respectively. x and b y The corresponding side lengths of the upper platform are a. x and a y The angle between the sidewall of the frustum and the bottom surface along the x-direction is θ. x The angle between the side wall of the quadrangular frustum and the bottom surface along the y-direction is θ. y b x >a x b y >a y ;2b x >p>b x 2b y >p>b y The resistance values ​​of the sidewall resistive films of the asymmetric three-dimensional absorbing structure along the x and y directions are R0 and R0, respectively. x and R y , where R x The value range is (300 Ohm / sq~600 Ohm / sq)±10%, R y The value range is (1000 Ohm / sq~1400 Ohm / sq)±10%; 4. The dual-polarized ultrawideband three-dimensional absorbing metamaterial as described in claim 3, characterized in that: The upper and lower faces of the truncated pyramid are both rectangular.

5. The dual-polarized ultrawideband three-dimensional absorbing metamaterial as described in claim 1, characterized in that: The resistive film material is one or a composite of carbon black and graphite.

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