Frequency Selective Absorber

Abstract

This application belongs to the field of microwave absorber technology, and particularly relates to a frequency-selective microwave absorber. The frequency-selective absorber includes a support layer having a first surface and a second surface disposed opposite to each other; a first dielectric layer bonded to the first surface; a second dielectric layer bonded to the second surface; a loss layer bonded to the side of the first dielectric layer away from the first surface to absorb electromagnetic waves of a preset frequency band; and a transmission layer bonded to the side of the second dielectric layer away from the second surface, allowing electromagnetic waves of the preset frequency band to pass through. The support layer, the first dielectric layer, the second dielectric layer, the loss layer, and the transmission layer are all transparent structures. This application can solve the technical problem in the prior art where frequency-selective absorbers lack optical transparency.

Description

Technical Field

[0001] This application belongs to the field of absorber technology, and particularly relates to a frequency selective absorber. Background Technology

[0002] Metamaterial perfect absorbers that simultaneously possess both transmission passband and absorption band are called frequency selective absorbers. Their basic implementation method is to combine circuit-simulated absorbers with frequency selective surfaces to achieve absorption and transmission functions in different frequency bands.

[0003] Traditional metamaterial absorbers and frequency-selective surfaces employ metallic electric resonant structures, and most of these substrates do not possess optical transparency. This limits their application in optically transparent viewing windows and transparent devices. Furthermore, achieving optically transparent frequency-selective absorbers remains a challenge, as it requires simultaneously ensuring low-loss transmission at the passband frequency and a wide absorption band at the absorption frequency. Summary of the Invention

[0004] The purpose of this application is to provide a frequency selective absorber to solve the technical problem that existing frequency selective absorbers do not have optical transparency.

[0005] To achieve the above objectives, the technical solution adopted in this application is: to provide a frequency-selective absorber, comprising:

[0006] A support layer having a first surface and a second surface disposed opposite to each other;

[0007] A first dielectric layer is bonded to the first surface;

[0008] A second dielectric layer is bonded to the second surface;

[0009] A lossy layer is bonded to the side of the first dielectric layer away from the first surface and is used to absorb electromagnetic waves of a preset frequency band.

[0010] A transmission layer, which is bonded to the side of the second dielectric layer away from the second surface, and is used to allow electromagnetic waves of a preset frequency band to pass through;

[0011] The support layer, the first dielectric layer, the second dielectric layer, the loss layer, and the transmission layer are all transparent structures.

[0012] The beneficial effects of the frequency-selective absorber provided in this application are as follows: Compared with the prior art, this application places the loss layer and the transmission layer on opposite sides. When an electromagnetic wave passes through the frequency-selective absorber, the loss layer absorbs electromagnetic waves within a preset frequency band, and the transmission layer inputs electromagnetic waves within the preset frequency band. While satisfying the above functions, this technical solution, by making the support layer, first dielectric layer, second dielectric layer, loss layer, and transmission layer all transparent, makes the frequency-selective absorber provided in this application entirely transparent. This allows for wide application in optically transparent observation windows and transparent devices. Furthermore, the support layer structure effectively increases the overall mechanical strength of the frequency-selective absorber, which is superior to the prior art.

[0013] Optionally, the loss layer includes a first absorption unit and a second absorption unit; the first absorption unit and the second absorption unit are intersecting, and the center of the first absorption unit coincides with the center of the second absorption unit. In this application, the loss layer can be equivalent to a series resonant circuit. Using this structure, electromagnetic waves in the absorption frequency band can resonate with the loss layer, converting the energy of the incident electromagnetic wave into internal energy for dissipation. No resonance occurs in the non-absorption frequency band, allowing electromagnetic waves of a preset frequency band to pass through the loss layer structure with low loss. Furthermore, since the center of the first absorption unit coincides with the center of the second absorption unit, it possesses polarization insensitivity, ensuring the absorption effect of the loss layer on electromagnetic waves from multiple directions.

[0014] Optionally, the first absorption unit includes a first arm and a second arm, the second arm being connected to both ends of the first arm, and the first arm being connected to the center of the second arm; the second absorption unit includes a third arm and a fourth arm, the fourth arm being connected to both ends of the third arm, and the third arm being connected to the center of the fourth arm; the center of the first arm coincides with the center of the third arm. Thus, the first arm, second arm, third arm, and fourth arm in this application form a Jerusalem-like cross-shaped structure, which significantly enhances the absorption capability of the loss layer for electromagnetic waves in different absorption frequency bands and in different directions. Furthermore, since the surface area of ​​the loss layer using the above structure is relatively small compared to the first dielectric layer, the loss layer structure provided in this application can also effectively ensure low-loss transmission of electromagnetic waves in non-absorption frequency bands.

[0015] Optionally, the loss layer further includes a first patch; the first patch is attached to the overlapping position of the first arm and the third arm, and the width of the first patch is greater than the width of the first arm and the width of the third arm. This application utilizes the first patch to effectively widen the width at the center of the first and third arms, reducing the insertion loss of electromagnetic waves in the non-absorption frequency band through the loss layer, and ensuring that electromagnetic waves in the non-absorption frequency band can pass through the loss layer with lower loss.

[0016] Optionally, the loss layer further includes a second patch; the second patch is attached to the first arm and the third arm, and is spaced apart from the first patch; the width of the second patch is greater than the width of the first arm and the width of the third arm. Thus, this application utilizes the second patch to widen the width of other positions on the first and second arms. On the one hand, the second patch can reduce the insertion loss of electromagnetic waves passing through the loss layer in the non-absorption frequency band; on the other hand, the first patch can cooperate with the second patch to form multiple resonant modes, enabling the loss layer in this embodiment to provide a more diverse electromagnetic wave selective transmission effect.

[0017] Optionally, the transmission layer includes at least a first ring, a second ring, and a third ring nested from the inside out; the first ring has a first transmission gap, the second ring and the first ring have a second transmission gap, and the third ring and the second ring have a third transmission gap. Thus, the transmission layer of this application forms a three-gap nested structure, which can be equivalent to a parallel RLC resonant circuit. When the incident electromagnetic wave frequency is within the passband, the transmission layer structure resonates, allowing the electromagnetic wave to pass through the structure with low loss. When the incident electromagnetic wave is not within the passband, the transmission layer structure is equivalent to a metal ground plane, completely reflecting the incident electromagnetic wave, and together with the loss layer on the opposite side, it completes the wave absorption function.

[0018] Optionally, the transmission layer further includes a fourth ring body surrounding the third ring body. The fourth ring body includes a plurality of spaced-apart third patches evenly distributed on the ring body. In this application, the transmission layer forms a gridded structure outside the third ring body. The gridded fourth ring body can, on the one hand, be equivalent to a metal ground plane, completely reflecting electromagnetic waves outside the passband, thus completing the absorption function together with the loss layer. On the other hand, the gridded structure can further improve the overall optical transparency of this frequency-selective absorber.

[0019] Optionally, the first ring, the second ring, the third ring, and the fourth ring are all centrosymmetric structures with identical shapes. The passband layer structure in this application is set to be centrosymmetric, possessing polarization insensitivity characteristics. The incident angle within the absorption band can reach 50°, and the passband frequency can maintain stable incident performance within 30°, which is superior to existing technologies.

[0020] Optionally, both the loss layer and the transmission layer are metallic material layers. In this application, the loss layer and the transmission layer are essentially transparent metallic material layers, which not only ensures the overall optical transparency of the frequency-selective absorber, but also utilizes the excellent absorption and reflection effects of metallic materials on electromagnetic waves to fabricate a frequency-selective absorber with selective absorption of electromagnetic waves in a preset frequency band.

[0021] Optionally, the frequency-selective absorber further includes a first adhesive layer and a second adhesive layer; both the first adhesive layer and the second adhesive layer are transparent structures, the first dielectric layer is bonded to the support layer through the first adhesive layer, and the second dielectric layer is bonded to the support layer through the second adhesive layer. Thus, the overall optical transparency of the frequency-selective absorber provided in this application is further improved, and the overall light transmittance is not less than 70%, making it suitable for a wide range of applications. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 A schematic diagram of the overall structure of the frequency selective absorber provided in the embodiments of this application. Figure 1 ;

[0024] Figure 2 A schematic diagram of the overall structure of the frequency selective absorber provided in the embodiments of this application. Figure 1 ;

[0025] Figure 3 A top view of the overall structure of the frequency selective absorber provided in the embodiments of this application;

[0026] Figure 4 A bottom view of the overall structure of the frequency selective absorber provided in the embodiments of this application;

[0027] Figure 5 This is a schematic diagram of the loss layer structure dimensions of a frequency-selective absorber provided in an embodiment of this application;

[0028] Figure 6 This is a schematic diagram of the transmission layer structure dimensions of the frequency-selective absorber provided in an embodiment of this application;

[0029] Figure 7 The S11 reflection coefficient and S21 transmission coefficient of the frequency selective absorber provided in the embodiments of this application under TE and TM wave incident conditions;

[0030] Figure 8 The absorption rate of the frequency selective absorber provided in this application embodiment at different incident angles for TE and TM waves;

[0031] Figure 9 The S21 transmission coefficient of the frequency selective absorber provided in the embodiments of this application under different incident angles of TE wave and TM wave.

[0032] The following are the labeling elements in the figure:

[0033] 100, Loss layer; 101, First arm; 102, Second arm; 103, Third arm; 104, Fourth arm; 105, First patch; 106, Second patch; 200, First dielectric layer; 300, Support layer; 400, Second dielectric layer; 500, Transmission layer; 501, First ring; 502, Second ring; 503, Third ring; 504, Fourth ring; 541, Third patch. Detailed Implementation

[0034] To make the technical problems, technical solutions, and beneficial effects to be solved by this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and are not intended to limit the scope of this application.

[0035] It should be noted that when a component is referred to as being "fixed to" or "set on" another component, it can be directly on or indirectly on that other component. When a component is referred to as being "connected to" another component, it can be directly connected to or indirectly connected to that other component.

[0036] It should be understood that the terms "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0037] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0038] Please refer to the following as well: Figure 1 and Figure 2 The frequency-selective absorber provided in the embodiments of this application will now be described. The frequency-selective absorber includes a support layer 300, a first dielectric layer 200, a second dielectric layer 400, a loss layer 100, and a transmission layer 500. Wherein:

[0039] The support layer 300 is the main support body of the frequency selective absorber provided in this embodiment, and it has a first surface and a second surface disposed opposite to each other. The function of the support layer 300 is to provide a bonding position for the first dielectric layer 200 and the second dielectric layer 400; that is, the first dielectric layer 200 can be bonded to the first surface of the support layer 300, and the second dielectric layer 400 can be bonded to the second surface of the support layer 300. It is understood that the shapes of the first and second surfaces in this embodiment are not limited, and can be selected from common shapes in the art such as circles, squares, rectangles, or other polygons, or can be designed into other special shapes according to actual needs. For ease of explanation, this embodiment and other embodiments described below use square surfaces as an example for illustration.

[0040] In this embodiment, the first dielectric layer 200 is bonded to the first surface of the support layer 300, serving as a bonding substrate for the loss layer 100. The second dielectric layer 400 is bonded to the second surface of the support layer 300, serving as a bonding substrate for the transmission layer 500. It can be understood that the shapes of the first dielectric layer 200 and the second dielectric layer 400 can be designed according to the structure of the loss layer 100 and the transmission layer 500. That is, the first dielectric layer 200 and the second dielectric layer 400 can be simply configured for bonding the loss layer 100 and the transmission layer 500; or, the first dielectric layer 200 and the second dielectric layer 400 can also be adapted to the first and second surfaces, that is, the overall shape of the first dielectric layer 200 adapts to the shape of the first surface, and the overall shape of the second dielectric layer 400 adapts to the shape of the second surface. For ease of explanation, this embodiment uses the example of the first dielectric layer 200 and the second dielectric layer 400 being adapted to square first and second surfaces.

[0041] In this embodiment, the loss layer 100 is bonded to the side of the first dielectric layer 200 away from the first surface, and its function is to absorb electromagnetic waves of a preset frequency band. The transmission layer 500 is bonded to the side of the second dielectric layer 400 away from the second surface and is configured to allow electromagnetic waves of the preset frequency band to pass through. Based on the configuration of the loss layer 100 and transmission layer 500 in this embodiment, it can be seen that the loss layer 100 and transmission layer 500 are located on opposite sides. During the propagation of an electromagnetic wave from the side of the loss layer 100 to the side of the transmission layer 500, the loss layer 100 can absorb electromagnetic waves of the preset frequency band. The remaining electromagnetic waves not absorbed by the loss layer 100 can reach the transmission layer 500 through the first dielectric layer 200, the support layer 300, and the second dielectric layer 400. Since the transmission layer 500 only allows electromagnetic waves of the preset frequency band to pass through, through the selective action of the transmission layer 500, electromagnetic waves of the desired frequency band can be obtained on the side of the transmission layer 500 away from the loss layer 100.

[0042] In addition to absorbing and transmitting electromagnetic waves in the target frequency band, the frequency selective absorber provided in this embodiment has its support layer 300, first dielectric layer 200, second dielectric layer 400, loss layer 100, and transmission layer 500 all configured as transparent structural layers. Through this structure, the frequency selective absorber provided in this embodiment can be widely used in optically transparent observation windows and transparent devices, and has a wider range of application scenarios compared to the prior art.

[0043] In this embodiment, the support layer 300 provides mechanical support for the overall frequency-selective absorber. Its material can be PMMA (polymethyl methacrylate), a commonly used material in the art, which offers advantages such as high transparency, low cost, and ease of machining. In existing technologies, frequency-selective absorbers typically use air between the absorbing and transmitting structures. This application effectively increases the mechanical strength of the overall frequency-selective absorber by setting the support layer 300 between the loss layer 100 and the transmission layer 500. The first dielectric layer 200 and the second dielectric layer 400 can be made of PET (polyethylene terephthalate), a commonly used material in the art, which has good mechanical properties and high transparency, making it an excellent carrier for the loss layer 100 and the transmission layer 500. The structures of the loss layer 100 and the transmission layer 500 can be flexibly configured according to actual needs, and will not be elaborated upon in this embodiment.

[0044] In another embodiment of this application, please refer to Figure 1 , Figure 2 and Figure 3The loss layer 100 includes a first absorption unit and a second absorption unit, wherein the first and second absorption units are intersecting, and the center of the first absorption unit coincides with the center of the second absorption unit. According to this structure, the loss layer 100 described in this embodiment can be equivalent to a series resonant circuit. Using this structure, the loss layer 100 can resonate with electromagnetic waves in the absorption frequency band, converting the energy of the incident electromagnetic wave into internal energy for dissipation. No resonance occurs in the non-absorption frequency band, allowing electromagnetic waves of a preset frequency band to pass through the loss layer 100 structure with low loss. Furthermore, since the center of the first absorption unit coincides with the center of the second absorption unit, it possesses polarization insensitivity, ensuring the electromagnetic wave absorption effect of the loss layer 100 for electromagnetic waves from multiple directions.

[0045] It is understood that the intersection angle between the first absorption unit and the second unit in this embodiment can be flexibly set according to actual production needs. Since the first absorption unit and the second absorption unit intersect in a cross shape, they can act on electromagnetic waves in a wider range of frequencies. Therefore, in this embodiment, the first absorption unit and the second absorption unit are further set to intersect in a cross shape, that is, the first absorption unit is set perpendicular to the second absorption unit, which has a better electromagnetic wave absorption effect.

[0046] Based on the above-described embodiment where the loss layer 100 includes a first absorption unit and a second absorption unit, please refer to some embodiments. Figure 1 , Figure 2 and Figure 3 The first absorption unit includes a first arm 101 extending along a first direction and a second arm 102 extending along a second direction. The first arm 101 is connected to a second arm 102 at its starting and ending points along its extension direction, and the first arm 101 is connected to the geometric center of the second arm 102. The second absorption unit includes a third arm 103 extending along the second direction and a fourth arm 104 extending along the first direction. The third arm 103 is connected to a fourth arm 104 at its starting and ending points along its extension direction, and the third arm 103 is connected to the geometric center of the fourth arm 104. In this embodiment, the geometric centers of the first arm 101 and the third arm 103 coincide, and the first direction is perpendicular to the second direction. Based on the above description of the loss layer 100 structure, it can be understood that the structure of the loss layer 100 in this embodiment is actually a Jerusalem cross-like structure, that is, a Jerusalem cross without the four Greek crosses.

[0047] The Jerusalem cross shape of the loss layer 100 provided in this embodiment can be equivalent to an RLC series resonant circuit. It resonates within the absorption frequency band, converting the energy of the incident electromagnetic wave into internal energy for dissipation. It does not resonate within the non-absorption frequency band, allowing electromagnetic waves of a preset frequency band to pass through the loss layer 100 structure. It is understood that the size of the loss layer 100 described in this embodiment is not limited. In the actual production process of this frequency-selective absorber, the size of the loss layer 100 can be adjusted to easily obtain the electromagnetic wave absorption effect within the preset frequency band. Furthermore, since the cross-shaped loss layer 100 has a smaller surface area than the first dielectric layer 200, the loss layer 100 structure provided in this embodiment can also effectively ensure low-loss passage of electromagnetic waves in the non-absorption frequency band. Moreover, since the loss layer 100 is designed as a Jerusalem cross-like structure, the loss layer 100 structure provided in this embodiment is also a centrally symmetrical structure, exhibiting polarization insensitivity.

[0048] Based on the attenuation layer 100 being configured as the aforementioned Jerusalem cross, in another embodiment of this application, please refer to... Figure 1 , Figure 2 and Figure 3 The loss layer 100 also includes a first patch 105, which is attached to the overlapping position of the first arm 101 and the third arm 103. The width of the first patch 105 is greater than the width of both the first arm 101 and the third arm 103. For example, the first patch 105 can be a square patch and includes two sides opposite to each other along a first direction and two sides opposite to each other along a second direction.

[0049] Based on the structural configuration of the first patch 105 described above, it can be seen that the first patch 105 in this embodiment corresponds to the cross-shaped orientation of the loss layer 100. Its function is to effectively widen the width at the center of the first arm 101 and the third arm 103, thereby reducing the electromagnetic wave insertion loss in the non-absorption frequency band and ensuring that electromagnetic waves in the non-absorption frequency band can pass through the loss layer 100 with lower loss. The specific size of the first patch 105 in this embodiment is not limited. In the actual production process of this frequency-selective absorber, the insertion loss of the electromagnetic wave can be adjusted by adjusting the size of the first patch 105. It is worth noting that the first patch 105 can be combined with the aforementioned Jerusalem-like cross-shaped structure as a separate structural component, or it can be integrally formed with the cross-shaped structure. For example, the first patch 105 can be prepared simultaneously during the preparation of the loss layer 100 using magnetron sputtering. Different preparation processes achieve the same technical effect, which will not be elaborated further here.

[0050] Based on the embodiment where the loss layer 100 is configured to have the first patch 105 described above, in another embodiment of this application, please refer to... Figure 1 , Figure 2 and Figure 3 The loss layer 100 also includes a second patch 106, which is attached to the first arm 101 and the third arm 103 and spaced apart from the first patch 105. The width of the second patch 106 is greater than the width of the first arm 101 and the width of the third arm 103. For example, please refer to [reference needed]. Figure 3 The second patch 106 can be disposed at one-quarter position along the respective extension direction of the first arm 101 and the third arm 103, and at three-quarter position along the respective extension direction of the first arm 101 and the third arm 103. In this embodiment, the second patch 106 can be configured as a rectangular patch, which includes two sides arranged opposite to each other along the first direction and two sides arranged opposite to each other along the second direction. The working principle of the second patch is the same as that of the first patch, and will not be described again. The significance of setting the second patch 106 in this embodiment is that, on the one hand, the second patch 106 can reduce the insertion loss of electromagnetic waves passing through the loss layer 100 in the non-absorption frequency band; on the other hand, the first patch 105 can cooperate with the second patch 106 to form multiple resonance modes, so that the loss layer 100 in this embodiment can provide a more diversified electromagnetic wave selective transmission effect.

[0051] For example, in another embodiment of this application, please refer to Figure 5 The loss layer 100 structure of the frequency selective absorber is configured to include the Jerusalem cross-like structure in the aforementioned embodiment, as well as the first patch 105 and the second patch 106. The preferred specific design dimensions of the loss layer 100 are as follows:

[0052] The length L1 of both the first arm 101 and the third arm 103 is 5.8 mm; the width L3 of both the first arm 101 and the third arm 103 is 0.2 mm.

[0053] The length L2 of the second arm 102 and the fourth arm 104 is 0.6 mm; the width L4 of the second arm 102 and the fourth arm 104 is 0.2 mm.

[0054] The side length a of the first patch 105 is 0.4mm, the length b of the second patch 106 is 0.4mm, and the width of the second patch 106 is less than 0.4mm.

[0055] In addition to the structural dimensions of the loss layer 100 mentioned above, the dimensional adaptation settings of other structures of the frequency selective absorber in this embodiment are as follows:

[0056] The loss layer 100 is bonded to the first dielectric layer 200 by magnetron sputtering, and the thickness of the loss layer 100 is 0.2 μm.

[0057] The first dielectric layer 200, the support layer 300, and the second dielectric layer 400 are all square structures, and the thickness of the first dielectric layer 200 and the second dielectric layer 400 is set to 0.125 mm; the thickness of the support layer 300 is set to 3 mm.

[0058] Based on the overall size and structure of the frequency-selective absorber provided in this embodiment, please refer to... Figure 7 and Figure 8 The frequency-selective absorber provided in this application generates two resonant modes at 9 GHz and 16 GHz, and its absorption rate of normally incident electromagnetic waves in the 7.6-18.3 GHz frequency band is greater than 90%. The absorption bandwidth is 10.7 GHz, with a relative bandwidth exceeding 80%, fully covering the X-Ku band. Currently existing frequency-selective absorbers mostly operate with bandwidths lower than the X-band; in contrast, this invention extends the absorption band to the Ku-band, which is superior to existing technologies.

[0059] In another embodiment of this application, please refer to Figure 1 , Figure 2 and Figure 4 The transmission layer 500 includes at least a first ring 501, a second ring 502, and a third ring 503 nested from the inside out. A first transmission gap is formed inside the first ring 501, a second transmission gap is formed between the second ring 502 and the first ring 501, and a third transmission gap is formed between the third ring 503 and the second ring 502.

[0060] Based on the aforementioned passband layer structure, the passband layer provided in this embodiment can essentially be equivalent to a parallel RLC resonant circuit. When the frequency of the incident electromagnetic wave is within the passband, the transmission layer 500 structure resonates, allowing the electromagnetic wave to pass through the structure with low loss. When the incident electromagnetic wave is not within the passband, the transmission layer 500 structure is equivalent to a metal ground plane, completely reflecting the incident electromagnetic wave, and together with the loss layer 100 on the opposite side, it completes the wave absorption function. In the actual production process of the frequency selective absorber, by adjusting the size of the first ring 501, the second ring 502, and the third ring 503, it is possible to ensure that after a specific frequency electromagnetic wave is incident, it does not resonate with the first transmission gap, the second transmission gap, and the third transmission gap, and thus completely passes through the transmission layer 500; while other frequency incident electromagnetic waves exhibit different degrees of reflection, thereby achieving the technical objective of the transmission layer 500 in this embodiment to transmit electromagnetic waves of a preset frequency band, effectively improving the transmittance of the transmission layer 500 for specific frequency electromagnetic waves.

[0061] In another embodiment of this application, please refer to Figure 1 , Figure 2 and Figure 4 The transmission layer 500 also includes a fourth ring 504, which surrounds the third ring 503. In this embodiment, the fourth ring 504 includes a plurality of third patches 541 arranged at uniform intervals along its circumferential direction. The third patches 541 are evenly distributed on the ring of the fourth ring. The specific shape of the third patches 541 is not limited and can adopt circular, square, rectangular or polygonal structures commonly used in the art. For ease of explanation, this embodiment uses a square patch as an example for the third patch 541.

[0062] By adopting the above technical solution, the transmission layer of this application forms a gridded structure outside the third ring 503. The gridded fourth ring 504 can be equivalent to a metal ground plane, completely reflecting electromagnetic waves outside the passband, and together with the loss layer 100, it completes the wave absorption function. On the other hand, the gridded structure can further improve the overall optical transparency of this frequency-selective absorber.

[0063] Based on the above-described embodiments with a first ring body 501, a second ring body 502, a third ring body 503, and a fourth ring body 504, in one embodiment of this application, please refer to... Figure 1 , Figure 2 and Figure 4 The first ring 501, the second ring 502, the third ring 503, and the fourth ring 504 are all centrally symmetrical structures with the same annular shape. For example, the first ring 501, the second ring 502, the third ring 503, and the fourth ring 504 can all be configured as square rings. Furthermore, the first ring 501, the second ring 502, and the third ring 503 each include two sides arranged opposite each other along a first direction and two sides arranged opposite each other along a second direction. The frequency-selective absorber provided in this embodiment, due to the centrally symmetrical design of the passband layer, possesses polarization-insensitive characteristics, allowing the incident angle within the absorption frequency band to reach 50°, and ensuring stable incident performance within a 30° passband frequency range.

[0064] In another embodiment of this application, please refer to Figure 5 and Figure 6 In conjunction with the aforementioned specific design dimensions of the loss layer 100 and the adaptation dimensions of other structures, this embodiment provides a specific structural dimension design for a transmission layer 500, including a first ring 501, a second ring 502, a third ring 503, and a fourth ring 504. The preferred specific design dimensions of the transmission layer 500 are as follows:

[0065] The outer wall side length L5 of the second ring 502 is 1mm, and the inner wall side length L6 of the second ring 502 is 0.8mm.

[0066] The outer wall side length L7 of the third ring body 503 is 3.2mm, and the inner wall side length L8 of the third ring body 503 is 2mm.

[0067] The side length c of the third patch 541 is 0.3mm, and the spacing d between the third patches 541 is 0.1mm.

[0068] Based on the overall size and structure of the frequency-selective absorber provided in this embodiment, please refer to... Figure 7 and Figure 8 and Figure 9 In this embodiment, the center frequency of the transmission layer is 28 GHz. This center frequency is the spectrum used by many Ka-band high-throughput satellites and is also one of the key frequency bands for 5G millimeter-wave communication, with broad application prospects. In addition, the minimum passband loss of the transmission layer 500 in this application is 1 dB, the -3 dB transmittance frequency band is 25-30 GHz, and the passband frequency of the frequency-selective absorber can be extended to the Ka-band, which is superior to the existing technology.

[0069] It is understood that the frequency-selective absorber provided in this application operates in the X, Ku, and K bands, and its structural dimensions can be scaled up or down proportionally to operate at other frequencies. In actual production, it can be flexibly designed according to the needs of the working scenario. By adopting the structure of the frequency-selective absorber provided in this embodiment, selective transmission of electromagnetic waves can be achieved in other operating frequency bands, and it has the technical effect of optical transparency. Therefore, it should also be regarded as a modified implementation of this embodiment and is within the protection scope of this application, and will not be described in detail here.

[0070] Please refer to another embodiment of this application. Figure 1 and Figure 2 Furthermore, the loss layer 100 and the transmission layer 500 are configured as metal material layers. Since metals are the best materials for absorbing and reflecting electromagnetic waves, they are the preferred materials for fabricating the loss layer 100 and the transmission layer 500. Therefore, the loss layer 100 and the transmission layer 500 of the frequency selective absorber provided in this embodiment are essentially transparent metal material layers. The fact that the loss layer 100 and the transmission layer 500 are made of transparent metal material layers can achieve both the technical effect of electromagnetic wave frequency selection and the technical effect of overall optical transparency of the frequency selective absorber.

[0071] It is understood that some commonly used transparent metallic materials in the art can be used to prepare the loss layer 100 and transmission layer 500 described in this embodiment. In another embodiment of this application, the loss layer 100 and transmission layer 500 are further defined as indium tin oxide (ITO) material layers. ITO is currently the main transparent metallic material in the art, possessing both excellent properties of light transmittance and conductivity, which can further improve the electromagnetic wave selective absorption effect and optical transparency effect of the frequency-selective absorber in this embodiment. During the fabrication of the frequency-selective absorber, ITO material can be bonded to the first dielectric layer 200 or the second dielectric layer 400 by magnetron sputtering to form the loss layer 100 or transmission layer 500. The magnetron sputtering process described in this embodiment is a conventional fabrication process for preparing the loss layer 100 or transmission layer 500, and will not be described in detail here.

[0072] In another embodiment of this application, please refer to Figure 1 and Figure 2 The frequency-selective absorber also includes a first adhesive layer and a second adhesive layer. Both the first and second adhesive layers are transparent. The first dielectric layer 200 is bonded to the support layer 300 via the first adhesive layer, and the second dielectric layer 400 is bonded to the support layer 300 via the second adhesive layer. It can be understood that in this embodiment, both the first and second adhesive layers can be selected from optically transparent adhesive materials commonly used in the art. By bonding the first and second dielectric plates to the support layer 300 using optically transparent adhesive, and then bonding them with a transparent metal material, the optical transparency of the overall structure of the frequency-selective absorber provided in this application is achieved, with an overall light transmittance of not less than 70%, making it suitable for a wide range of applications.

[0073] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A frequency-selective absorber, characterized in that, include: A support layer having a first surface and a second surface disposed opposite to each other; A first dielectric layer is bonded to the first surface; A second dielectric layer is bonded to the second surface; A loss layer is bonded to the side of the first dielectric layer away from the first surface and is used to absorb electromagnetic waves of a preset frequency band. A transmission layer, bonded to the side of the second dielectric layer away from the second surface, is used to allow electromagnetic waves of a preset frequency band to pass through; The support layer, the first dielectric layer, the second dielectric layer, the loss layer, and the transmission layer are all transparent structures; The loss layer includes a first absorption unit and a second absorption unit; The first absorption unit and the second absorption unit are arranged intersectingly, and the center of the first absorption unit coincides with the center of the second absorption unit; The first absorption unit includes a first arm extending in a first direction and a second arm extending in a second direction, the second arm being connected to both ends of the first arm, and the first arm being connected to the center of the second arm. The second absorption unit includes a third arm extending along a second direction and a fourth arm extending along a first direction, wherein the fourth arm is connected to both ends of the third arm and the third arm is connected to the center of the fourth arm. The center of the first arm coincides with the center of the third arm, and the first direction is perpendicular to the second direction; wherein, the structure of the loss layer is a Jerusalem cross-like structure; the Jerusalem cross-like structure refers to the Jerusalem cross after removing the four Greek crosses; The transport layer includes at least a first ring body, a second ring body, and a third ring body nested from the inside out; The first ring body has a first transmission gap inside, the second ring body and the first ring body have a second transmission gap, and the third ring body and the second ring body have a third transmission gap; The transmission layer further includes a fourth ring body, which surrounds the third ring body. The fourth ring body includes a plurality of spaced third patches, which are evenly arranged on the ring body of the fourth ring body. The first ring body, the second ring body, the third ring body, and the fourth ring body are all configured as square rings; The specific design dimensions of the transport layer are as follows: The outer wall of the second ring has a side length of 1 mm, and the inner wall of the second ring has a side length of 0.8 mm. The outer wall of the third ring has a side length of 3.2 mm, and the inner wall of the third ring has a side length of 2 mm. The third patch has a side length of 0.3 mm, and the spacing between the third patches is 0.1 mm.

2. The frequency-selective absorber as described in claim 1, characterized in that: The loss layer also includes a first patch; The first patch is attached to the position where the first support arm and the third support arm overlap, and the width of the first patch is greater than the width of the first support arm and the width of the third support arm.

3. The frequency-selective absorber as described in claim 2, characterized in that: The loss layer also includes a second patch; The second patch is attached to the first arm and the third arm, and is spaced apart from the first patch; The width of the second patch is greater than the width of the first arm and the width of the third arm.

4. The frequency-selective absorber as described in claim 1, characterized in that: The first ring, the second ring, the third ring, and the fourth ring are all centrally symmetrical structures and have the same shape.

5. The frequency-selective absorber as described in any one of claims 1-4, characterized in that: Both the loss layer and the transmission layer are metallic material layers.

6. The frequency-selective absorber as described in any one of claims 1-4, characterized in that: The frequency selective absorber also includes a first adhesive layer and a second adhesive layer; Both the first adhesive layer and the second adhesive layer are transparent structures. The first medium layer is bonded to the support layer through the first adhesive layer, and the second medium layer is bonded to the support layer through the second adhesive layer.

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