Transmitting and absorbing integrated three-dimensional frequency selection wave absorber with optical transparency and adjustable wave transmitting window

Abstract

The invention discloses a transmission and absorption integrated three-dimensional frequency selection wave absorber with optical transparency and an adjustable wave transmission window, and belongs to the technical field of microwaves. The problems that an existing wave-transmitting and wave-absorbing integrated frequency selection structure cannot meet good permeability, a wide wave-absorbing band and optical transparency at the same time, a large number of lumped resistors need to be installed on a wave-absorbing layer to increase the wave-absorbing bandwidth, and the manufacturing difficulty and the total cost are increased are solved. The wave absorbing body is formed by periodically arranging wave absorbing body units; the wave absorber unit is composed of an FSS structure unit and a three-dimensional wave absorbing structure unit. The FSS unit structure comprises a first substrate and an ITO (Indium Tin Oxide) pattern layer in sequence from bottom to top; the three-dimensional wave-absorbing structure unit is vertically arranged on the upper surface of the FSS structure unit; the three-dimensional wave-absorbing structure unit is formed by two second substrates which are arranged in a crossed manner along two diagonals of the FSS structure unit, and metal strip-shaped groups are symmetrically arranged on the surfaces of the two sides of the second substrates. The invention is used for the transmission and absorption integrated three-dimensional frequency selection wave absorber with optical transparency and an adjustable wave transmission window.

Description

Technical Field

[0001] The invention belongs to the field of microwave technology. Background Art

[0002] Against the background of the rapid development of 5G communication technology, the transmission and shielding of electromagnetic waves has become an important research field. 5G communication requires a wider spectrum, higher capacity and lower latency, which makes the millimeter wave band widely used. However, with the establishment of a large number of 5G base stations, the problem of electromagnetic radiation has become increasingly prominent, which may not only cause information leakage, but also pose a threat to human health. Therefore, it is particularly important to develop a frequency selection structure that can transmit waves at low frequencies and absorb waves at high frequencies. Low-frequency wave transmission technology aims to meet the needs of 5G communications and ensure the effective transmission of low-frequency electromagnetic waves to maintain the transmission quality and stability of communication signals. High-frequency wave absorption technology aims to reduce electromagnetic pollution, protect human health and daily life, and achieve green electromagnetic shielding by absorbing high-frequency electromagnetic waves to reduce potential impacts on the environment and health.

[0003] As the top structure of the building, the ceiling uses this wave-transmitting and wave-absorbing integrated structure to effectively isolate external electromagnetic interference, protect the electronic equipment and systems inside the building from the influence of external electromagnetic waves, and also prevent the leakage of internal electromagnetic waves, which may cause information security problems. In addition, this structure needs to maintain a certain optical transparency so that natural light can enter the room through the ceiling, reduce dependence on artificial lighting, save energy, and also provide a good natural lighting environment for the room.

[0004] However, most of the current wave-transmitting and wave-absorbing integrated frequency-selective structures cannot simultaneously meet the characteristics of good transmittance and wide absorption band. Moreover, most of the current wave-transmitting and wave-absorbing integrated frequency-selective structures require a large number of lumped resistors to be installed on the absorbing layer to increase the absorption bandwidth, which increases the manufacturing difficulty and total cost. In addition, most of the current wave-transmitting and wave-absorbing integrated frequency-selective structures do not consider their optical transparency during design, which makes their optical transparency extremely poor, limiting their scope of application. Summary of the invention

[0005] The present invention aims to solve the problem that the existing integrated wave-transmitting and wave-absorbing frequency selective structure cannot simultaneously meet the requirements of good transmittance, wide wave-absorbing band and optical transparency, and a large number of lumped resistors need to be installed on the wave-absorbing layer to increase the wave-absorbing bandwidth, which increases the manufacturing difficulty and total cost. Thus, a three-dimensional frequency-selective wave-absorbing body with integrated wave-transmitting and wave-absorbing properties and optical transparency and an adjustable wave-transmitting window is proposed.

[0006] A three-dimensional frequency selective absorber with optical transparency and adjustable wave transmission window, which is composed of absorber units periodically arranged into N columns×M rows, wherein N≥5 and M≥5;

[0007] The absorber unit is composed of an FSS structural unit and a three-dimensional absorber structural unit;

[0008] The FSS structural unit is arranged horizontally, and the FSS structural unit is a first substrate and an ITO pattern layer from bottom to top; the ITO pattern layer is composed of a plurality of square ITO thin films periodically arranged into n columns×m rows, wherein n≥2 and m≥2; the first substrate is a transparent substrate;

[0009] The three-dimensional absorbing structure unit is vertically arranged on the upper surface of the FSS structure unit; the three-dimensional absorbing structure unit is formed by two second substrates arranged crosswise along the two diagonals of the FSS structure unit, and metal strip groups are symmetrically arranged on both side surfaces of the second substrates, and the metal strip group arranged on one side is composed of a first metal strip structure and a second metal strip structure that are symmetrical along the intersection line of the two second substrates; the first metal strip structure and the second metal strip structure are both composed of K metal strips.

[0010] The beneficial effects of the present invention are:

[0011] Compared with the prior art, the present invention has a wider absorption bandwidth and smaller insertion loss, so that the structure has good transmittance and absorption performance at the same time; the present invention adopts a transparent substrate, and the optical transmittance of the structure is good, so that the structure can be applied to occasions with certain requirements for optical transparency, such as the ceiling structure design of buildings; the present invention can achieve the regulation of the wave transmission band by simply adjusting the side length of the ITO film, so that the structure can be used in more scenarios, such as in the field of mobile communications, to improve the signal interference problem between different communication systems, and ensure the normal passage of signals within the working frequency band of communication equipment. The structure is small in size and simple in process, and in order to facilitate processing, the middle part of the metal strip array of the upper absorbing layer is removed, making the assembly process simpler and more flexible, and having good polarization stability.

[0012] The invention is used for a three-dimensional frequency selective wave absorbing body which has optical transparency and an adjustable wave transmission window and has a transparent and absorbing integrated body. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 This is a schematic structural diagram of a three-dimensional frequency selective absorber with optical transparency and an adjustable wave transmission window in accordance with the first embodiment;

[0014] Figure 2 This is a schematic structural diagram of an FSS structural unit in Example 1;

[0015] Figure 3 This is a schematic structural diagram of a three-dimensional wave absorbing structural unit in accordance with the first embodiment;

[0016] Figure 4 This is a comparison diagram of the FSS structural unit in Example 1 for adjusting the wave transmission band by changing the side length of the square ITO film on the substrate;

[0017] Figure 5 This is a simulation result diagram of the optically transparent and wave-transmitting window-adjustable three-dimensional frequency selective absorber (c=2 mm) of Example 1;

[0018] Figure 6 This is a simulation result diagram of the optically transparent and wave-transmitting window-adjustable three-dimensional frequency selective absorber (c=2 mm) under dual polarization conditions in Example 1;

[0019] Figure 7 This is a simulation result diagram of the optically transparent and wave-transmitting window-adjustable three-dimensional frequency selective absorber (c=1.8 mm) of Example 1;

[0020] Figure 8 This is a simulation result diagram of the optically transparent and wave-transmitting window-adjustable three-dimensional frequency selective absorber (c=2.2 mm) of Example 1;

[0021] Fig. 9 This is a simulation result diagram of the optically transparent and wave-transmitting window-adjustable three-dimensional frequency selective absorber (c=2.45 mm) of Example 1;

[0022] Fig.10 This is a schematic structural diagram of a three-dimensional wave absorbing structural unit in Example 2;

[0023] Fig.11 This is a schematic structural diagram of a three-dimensional wave absorbing structure unit in Example 3;

[0024] Fig.12 This is a schematic structural diagram of a three-dimensional wave absorbing structure unit in Example 4;

[0025] Fig.13 This is a schematic structural diagram of a three-dimensional wave absorbing structural unit in Example 5;

[0026] Fig.14 This is a schematic structural diagram of a three-dimensional frequency selective absorber with optical transparency and an adjustable wave transmission window according to Example 6;

[0027] Fig.15 This is a schematic structural diagram of a three-dimensional wave absorbing structural unit of Example 6;

[0028] Fig.16 This is a simulation result diagram of the optically transparent and wave-transmitting window-adjustable three-dimensional frequency selective absorber (c=2 mm) of Example 6;

[0029] Fig.17This is a simulation result diagram of the optically transparent and wave-transmitting window-adjustable three-dimensional frequency selective absorber (c=2 mm) under dual polarization conditions of Example 6;

[0030] Fig.18 A schematic diagram of the structure of a three-dimensional frequency selective absorber with optical transparency and adjustable wave transmission window for comparative experiment 1;

[0031] Fig.19 This is a simulation result diagram of the comparative experiment 1, which shows a three-dimensional frequency selective absorber with optical transparency and adjustable wave transmission window.

[0032] Fig. 20 This is a schematic diagram of the structure of the optically transparent three-dimensional absorber in comparative experiment 2;

[0033] Fig.21 This is a diagram showing the simulation results of the optically transparent three-dimensional absorber for comparison in Experiment 2. DETAILED DESCRIPTION

[0034] The technical solution of the present invention is not limited to the specific implementation modes listed below, but also includes any combination of the specific implementation modes.

[0035] Specific implementation method 1: This implementation method is a three-dimensional frequency selective absorber with optical transparency and adjustable wave transmission window, which is composed of absorber units periodically arranged into N columns × M rows, where N≥5 and M≥5;

[0036] The absorber unit is composed of an FSS structural unit and a three-dimensional absorber structural unit;

[0037] The FSS structural unit is arranged horizontally, and the FSS structural unit is a first substrate and an ITO pattern layer from bottom to top; the ITO pattern layer is composed of a plurality of square ITO thin films periodically arranged into n columns×m rows, wherein n≥2 and m≥2; the first substrate is a transparent substrate;

[0038] The three-dimensional absorbing structure unit is vertically arranged on the upper surface of the FSS structure unit; the three-dimensional absorbing structure unit is formed by two second substrates arranged crosswise along the two diagonals of the FSS structure unit, and metal strip groups are symmetrically arranged on both side surfaces of the second substrates, and the metal strip group arranged on one side is composed of a first metal strip structure and a second metal strip structure that are symmetrical along the intersection line of the two second substrates; the first metal strip structure and the second metal strip structure are both composed of K metal strips.

[0039] In this embodiment, the material of the metal strip group is a highly conductive metal, such as copper, aluminum, silver paste, silver nanowires, or a highly conductive semiconductor material ITO (indium tin oxide).

[0040] The three-dimensional absorbing structure described in this embodiment is arranged directly above the FSS structural unit, and there is no gap between the two.

[0041] This embodiment provides a three-dimensional frequency selective surface absorber (FSR) that is optically transparent and has wide-band transmission at low frequencies, ultra-wide-band absorption at high frequencies, and good optical transparency. It consists of a three-dimensional absorbing structure based on the SSPP structure design at the top and a two-dimensional frequency selective surface (FSS) with good optical transparency at the bottom. Symmetrical metal strip groups are printed on the front and back of the substrate of the three-dimensional absorbing structure at the top, replacing a large number of lumped resistors in the traditional absorbing layer, and the absorbing structure is twisted 45° as a whole to improve the absorbing performance of the absorbing layer, broaden the absorbing frequency band, and improve the absorbing performance of the overall structure; the bottom achieves low insertion loss within the working frequency band through the two-dimensional frequency selective surface structure with good optical transparency and the three-dimensional absorbing structure of the upper layer, and by changing the side length of the ITO film in the two-dimensional frequency selective surface structure, the wave transmission window can be regulated, so that the structure can be applied to more application scenarios.

[0042] The beneficial effects of this embodiment are:

[0043] Compared with the prior art, this embodiment has a wider absorption bandwidth and smaller insertion loss, so that the structure has both good transmittance and absorption performance; in this embodiment, a transparent substrate is used, and the optical transmittance of the structure is good, so that the structure can be applied to occasions with certain requirements for optical transparency, such as the design of the ceiling structure of a building; in this embodiment, the wave transmission band can be regulated by simply adjusting the side length of the ITO film, so that the structure can be applied to more scenarios, such as the field of mobile communications, to improve the signal interference problem between different communication systems, and to ensure the normal passage of signals within the working frequency band of the communication equipment. The structure is small in size and simple in process, and in order to facilitate processing, the middle part of the metal strip array of the upper absorbing layer is removed, making the assembly process simpler and more flexible, and having good polarization stability.

[0044] Specific implementation method 2: This implementation method is different from the specific implementation method 1 in that: the first substrate is in a square shape, with a thickness h1 of 0.1 mm to 0.5 mm, and a side length a of 10 mm to 20 mm; the first substrate is a PET substrate, a PEN substrate or a glass substrate; the second substrate is in a rectangular shape, with a thickness of 0.1 mm to 0.3 mm, and a width h2 of 8 mm to 12 mm; the second substrate is a FR-4 substrate, with a dielectric constant of 4.3 ± 0.05, and a loss tangent tanδ of 0.5 ± 0.001; the thickness of the metal strip group is 0.035 mm. Others are the same as the specific implementation method 1.

[0045] Specific implementation method three: This implementation method is different from specific implementation method one or two in that: the first metal strip structure and the second metal strip structure are spliced ​​to form a polygon or a circle. The rest is the same as specific implementation method one or two.

[0046] Specific embodiment 4: This embodiment differs from any one of specific embodiments 1 to 3 in that: the splicing edges of the first metal strip structure and the second metal strip structure are located on both sides of the intersection line of the two second substrates or at the edge of the second substrate;

[0047] When the splicing edges of the first metal strip structure and the second metal strip structure are located on both sides of the intersection line of the two second substrates, a gap b is provided between the splicing edges of the first metal strip structure and the second metal strip structure in the horizontal direction; when the splicing edges of the first metal strip structure and the second metal strip structure are located at the edge of the second substrate, the vertical distance between the splicing edges of the first metal strip structure and the second metal strip structure in the horizontal direction and the edge of the second substrate is b / 2;

[0048] When the first metal strip structure and the second metal strip structure are joined together to form a hexagon or rectangle, or when the first metal strip structure, the second metal strip structure and the gap b are joined together to form a circle, b=0.5mm-1.5mm; when the first metal strip structure and the second metal strip structure are joined together to form a triangle or a pentagon, b=0.3mm-0.5mm. Others are the same as the first to third embodiments.

[0049] In this specific embodiment, if the first metal strip structure and the second metal strip structure can be spliced ​​to form a hexagon, triangle, rectangle or pentagon after being attached, that is, when forming a hexagon, triangle, rectangle or pentagon, the gap between the two is not included.

[0050] In this specific implementation manner, the first metal strip structure, the second metal strip structure and the gap form a circle, that is, when forming a circle, the gap between the two is included.

[0051] Specific embodiment 5: This embodiment is different from specific embodiments 1 to 4 in that: when the first metal strip structure and the second metal strip structure are bonded and spliced ​​to form a hexagon, the length l0 of the longest metal strip in the first metal strip structure and the second metal strip structure is 2.25mm to 3.75mm, and the length of the metal strips on both sides of the longest metal strip decreases by 0.1mm to 0.3mm; K=17 to 25. Others are the same as specific embodiments 1 to 4.

[0052] Specific embodiment 6: This embodiment is different from specific embodiments 1 to 5 in that: when the first metal strip structure and the second metal strip structure are bonded and spliced ​​to form a triangle, the length l0 of the bottom metal strip of the first metal strip structure and the second metal strip structure is 2.35mm to 3.25mm, and the length of the metal strip above the bottom metal strip decreases gradually by 0.1mm to 0.2mm; K=18 to 26. Others are the same as specific embodiments 1 to 5.

[0053] Specific embodiment 7: This embodiment differs from specific embodiments 1 to 6 in that: when the first metal strip structure and the second metal strip structure are bonded and spliced ​​to form a rectangle, the length l0 of the metal strips of the first metal strip structure and the second metal strip structure is equal, and l0 is 2.25 mm to 3.75 mm; K is 17 to 25. The rest is the same as specific embodiments 1 to 6.

[0054] Specific embodiment 8: This embodiment is different from specific embodiments 1 to 7 in that: when the first metal strip structure and the second metal strip structure are bonded and spliced ​​to form a pentagon, the length l0 of the longest metal strip in the first metal strip structure and the second metal strip structure is 2.25mm to 3.75mm, the length of the metal strip above the longest metal strip decreases by 0.2mm to 0.4mm, and the length of the metal strip below the longest metal strip decreases by 0.1mm to 0.3mm; K=18 to 26. Others are the same as specific embodiments 1 to 7.

[0055] Specific embodiment 9: This embodiment differs from specific embodiments 1 to 8 in that: when the first metal strip structure, the second metal strip structure and the gap b are spliced ​​to form a circle, the circle radius r is 3.5 mm to 4.5 mm; K is 17 to 22. Others are the same as specific embodiments 1 to 8.

[0056] Specific embodiment 10: This embodiment differs from specific embodiments 1 to 9 in that: the surface resistance of the ITO graphic layer is 1Ω / sq to 10Ω / sq; the side length c of the square ITO film is 1mm to 2.45mm, and the spacing between adjacent square ITO films is (2.5-c)mm. Other features are the same as specific embodiments 1 to 9.

[0057] The following examples are used to verify the beneficial effects of the present invention:

[0058] Embodiment 1, combined with Figures 1 to 3 Specific instructions:

[0059] A three-dimensional frequency selective absorber with optical transparency and adjustable wave transmission window, which is composed of absorber units periodically arranged into N columns×M rows, wherein N=5 and M=5;

[0060] The absorber unit is composed of an FSS structural unit and a three-dimensional absorber structural unit;

[0061] Taking the XOY plane as the horizontal plane, the FSS structural unit is horizontally arranged, and the FSS structural unit is a first substrate and an ITO pattern layer from bottom to top; the ITO pattern layer is composed of a plurality of square ITO thin films periodically arranged into n columns×m rows, wherein n=4 and m=4; the first substrate is a transparent substrate;

[0062] The three-dimensional absorbing structure unit is vertically arranged on the upper surface of the FSS structure unit; the three-dimensional absorbing structure unit is formed by two second substrates arranged crosswise along the two diagonals of the FSS structure unit, and copper metal strip groups are symmetrically arranged on both side surfaces of the second substrates, and the copper metal strip group arranged on one side is composed of a first copper metal strip structure and a second copper metal strip structure that are symmetrical along the intersection line of the two second substrates; the first copper metal strip structure and the second copper metal strip structure are both composed of K metal strips, the spacing between adjacent metal strips is 0.2 mm, and the width of each metal strip is 0.2 mm.

[0063] The first substrate is square in shape, with a thickness h1 of 0.125 mm and a side length a of 10 mm; the first substrate is a PET (polyethylene terephthalate) substrate; the second substrate is rectangular in shape, with a thickness of 0.25 mm and a width h2 of 10 mm; the second substrate is a FR-4 substrate with a dielectric constant of 4.3 and a loss tangent tanδ of 0.5; the thickness of the copper metal strip group is 0.035 mm.

[0064] The first copper metal strip structure and the second copper metal strip structure are bonded and spliced ​​to form a hexagon, and the splicing edges of the first copper metal strip structure and the second copper metal strip structure are located on both sides of the intersection line of the two second substrates; a gap b is provided between the splicing edges of the first copper metal strip structure and the second copper metal strip structure in the horizontal direction; the longest metal strip length l0 in the first copper metal strip structure and the second copper metal strip structure is 3.25 mm, and the longest metal strip is located in the middle, and the lengths of the metal strips on both sides of the longest metal strip decrease by 0.2 mm; b is 1.5 mm; K=21;

[0065] The surface resistance of the ITO graphic layer is 5Ω / sq; the side length c of the square ITO film is 1.8mm, 2mm, 2.1mm, 2.2mm, 2.3mm, 2.4mm or 2.45mm, and the spacing between adjacent square ITO films is (2.5-c)mm.

[0066] In the following simulation results, S 11 is the reflection coefficient. The lower its value is, the smaller the reflection is during the transmission process. 21 is the transmission coefficient. The closer its value is to 0dB, the smaller the signal loss is during the transmission process.

[0067] Figure 4 This is a comparison diagram of the FSS structural unit in Example 1 to adjust the wave transmission band by changing the side length of the square ITO film on the substrate; when the side length of the square ITO film c = 1.8mm, the S of the FSS in the range of 0GHz to 23.2GHz 21 >-1dB, which means that the FSS has a wave transmission rate of more than 80% in this frequency band, that is, when the side length of the square ITO film is c=1.8mm, the wave transmission frequency band of FSS is 0GHz~23.2GHz; when the side length of the square ITO film is c=2mm, the wave transmission frequency band of FSS is 0GHz~16.59GHz; when the side length of the square ITO film is c=2.1mm, the wave transmission frequency band of FSS is 0GHz~13.7 ... When the film side length c = 2.2mm, the FSS wave transmission frequency band is 0GHz ~ 11.31GHz; when the square ITO film side length c = 2.3mm, the FSS wave transmission frequency band is 0GHz ~ 8.82GHz; when the square ITO film side length c = 2.4mm, the FSS wave transmission frequency band is 0GHz ~ 6.33GHz; when the square ITO film side length c = 2.45mm, the FSS wave transmission frequency band is 0GHz ~ 4.83GHz. It can be seen that when the square ITO film side length is changed, the FSS structure wave transmission frequency band also changes accordingly.

[0068] Figure 5 This is a simulation result diagram of the optically transparent and wave-transmitting window-adjustable three-dimensional frequency selective absorber (c=2 mm) of Example 1; Figure 6The simulation result diagram of the three-dimensional frequency selective absorber (c=2mm) with optical transparency and adjustable wave transmission window under dual polarization conditions in Example 1; the three-dimensional frequency selective absorber designed in the embodiment transmits waves in the range of 0GHz to 7.75GHz and absorbs waves in the range of 22.42GHz to 74.03GHz; the insertion loss of the normally incident TE and TM electromagnetic waves in the 0GHz to 7.75GHz band is less than 1dB, and the absorption rate in the 22.42GHz to 74.03GHz band is more than 80%, and the reflection coefficient in this band is less than -10dB. The structure designed in this embodiment is a symmetrical structure, so that the absorber is insensitive to the polarization direction of the incident electromagnetic wave.

[0069] Figure 7 The simulation result diagram of the first embodiment of the invention is a three-dimensional frequency selective absorber (c=1.8mm) with optical transparency and adjustable wave transmission window; the three-dimensional frequency selective absorber designed in the embodiment transmits waves in the range of 0GHz to 8.58GHz and absorbs waves in the range of 22.95GHz to 74.01GHz; the insertion loss of the normally incident TE and TM electromagnetic waves in the 0GHz to 8.58GHz band is less than 1dB, the absorption rate in the 22.95GHz to 74.01GHz band is more than 80%, and the reflection coefficient in this band is less than -10dB. The structure designed in this embodiment is a symmetrical structure, so that the absorber is insensitive to the polarization direction of the incident electromagnetic wave.

[0070] Figure 8 The simulation result diagram of the first embodiment of the invention is a three-dimensional frequency selective absorber (c=2.2mm) with optical transparency and adjustable wave transmission window; the three-dimensional frequency selective absorber designed in the embodiment transmits waves in the range of 0GHz to 6.01GHz and absorbs waves in the range of 21.72GHz to 73.61GHz; the insertion loss of the normally incident TE and TM electromagnetic waves in the 0GHz to 6.01GHz band is less than 1dB, the absorption rate in the 21.72GHz to 73.61GHz band is more than 80%, and the reflection coefficient in this band is less than -10dB. The structure designed in this embodiment is a symmetrical structure, so that the absorber is insensitive to the polarization direction of the incident electromagnetic wave.

[0071] Fig. 9The simulation result diagram of the first embodiment of the invention is a three-dimensional frequency selective absorber (c=2.45mm) with optical transparency and adjustable wave transmission window; the three-dimensional frequency selective absorber designed in the embodiment transmits waves in the range of 0GHz to 2.65GHz and absorbs waves in the range of 20.28GHz to 73.47GHz; the insertion loss of the normally incident TE and TM electromagnetic waves in the 0GHz to 2.65GHz band is less than 1dB, and the absorption rate in the 20.28GHz to 73.47GHz band is more than 80%, and the reflection coefficient in this band is less than -10dB. The structure designed in this embodiment is a symmetrical structure, so that the absorber is insensitive to the polarization direction of the incident electromagnetic wave.

[0072] Embodiment 2, combined with Fig.10 Specific description: The difference between this embodiment and the first embodiment is that the first copper metal strip structure and the second copper metal strip structure are joined and spliced ​​to form a triangle, the length l0 of the bottom metal strip of the first copper metal strip structure and the second copper metal strip structure is 2.35mm, and the length of the metal strip above the bottom metal strip decreases by 0.1mm; b=0.5mm; K=24. Others are the same as the first embodiment.

[0073] Embodiment 3, combined with Fig.11 Specific description: The difference between this embodiment and the first embodiment is that the first copper metal strip structure and the second copper metal strip structure are joined and spliced ​​to form a rectangle, the length of the metal strips of the first copper metal strip structure and the second copper metal strip structure are equal, l0 is 2.75mm; b=1.5mm; K=23. Others are the same as the first embodiment.

[0074] Embodiment 4, combined with Fig.12 Specific description: The difference between this embodiment and the first embodiment is that the first copper metal strip structure and the second copper metal strip structure are spliced ​​to form a pentagon, the longest metal strip length l0 of the first copper metal strip structure and the second copper metal strip structure is 3.75mm, there are 9 metal strip lengths above the longest metal strip and they decrease in length by 0.4mm, and there are 10 metal strip lengths below the longest metal strip and they decrease in length by 0.2mm; b=0.5mm; K=20. Others are the same as the first embodiment.

[0075] Embodiment 5, combined with Fig.13 Description: The difference between this embodiment and the first embodiment is that the first copper metal strip structure, the second copper metal strip structure and the gap b are spliced ​​to form a circle, and the radius r of the circle is 4.25 mm; b=1.5 mm; K=22; except for the top and bottom metal strips, the width of the remaining metal strips is 0.2 mm. The rest is the same as the first embodiment.

[0076] After the metal strip groups in the three-dimensional wave absorbing structure units are changed in the second to fifth embodiments, their performances are similar to the structure shown in the first embodiment.

[0077] Embodiment 6, combined Figures 14 to 15 Specific description: The difference between this embodiment and the first embodiment is that the splicing edge of the first copper metal strip structure and the second copper metal strip structure is located at the edge of the second substrate, and the vertical distance between the splicing edge of the first copper metal strip structure and the second copper metal strip structure and the edge of the second substrate in the horizontal direction is b / 2; the side length c of the square ITO film is 2 mm. Others are the same as the first embodiment.

[0078] Fig.16 This is a simulation result diagram of the optically transparent and wave-transmitting window-adjustable three-dimensional frequency selective absorber (c=2 mm) of Example 6; Fig.17 The simulation result diagram of the optically transparent and adjustable wave-transmitting window integrated three-dimensional frequency selective absorber (c=2mm) under dual polarization conditions in Example 6; the integrated three-dimensional frequency selective absorber designed in the embodiment transmits waves in the range of 0GHz to 7.39GHz and absorbs waves in the range of 20.85GHz to 73.57GHz; the insertion loss of the normally incident TE and TM electromagnetic waves in the 0GHz to 7.39GHz band is less than 1dB, and the absorption rate in the 20.85GHz to 73.57GHz band is more than 80%, and the reflection coefficient in this band is less than -10dB. The structure designed in this embodiment is a symmetrical structure, so that the absorber is insensitive to the polarization direction of the incident electromagnetic wave.

[0079] After the intersection line of the graphics described in this embodiment moves, the performance is similar to that before the movement.

[0080] Comparative experiment 1, combined with Fig.18 Specific description: The difference between this comparative experiment and the first embodiment is that the three-dimensional wave absorbing structure unit is formed by two second substrates arranged crosswise along the two symmetry axes of the FSS structure unit. The rest is the same as the first embodiment.

[0081] Fig.19The simulation result diagram of the three-dimensional frequency selective absorber with optical transparency and adjustable wave transmission window in the comparative experiment 1 is shown; it can be seen from the simulation result diagram that when the upper absorbing structure is arranged in a right cross relative to the FSS structure of the lower layer, it transmits waves in the range of 0GHz to 9.02GHz and absorbs waves in the range of 20.65GHz to 31.15GHz, 34.31GHz to 36.55GHz and 42.42GHz to 45.73GHz; compared with the first embodiment, the absorbing frequency band of the overall structure is greatly shortened. This shows that when the upper absorbing structure is twisted by 45°, the resonance effect is enhanced and the absorbing performance of the overall structure is improved.

[0082] Comparative experiment 2, combined with Fig. 20 Specific description: The difference between this comparative experiment and Example 1 is that the ITO pattern layer is fully covered by a square ITO film, c=10 mm. The rest is the same as Example 1.

[0083] Fig.21 This is the simulation result of the optically transparent three-dimensional absorber in comparison with Experiment 2; it can be seen from the simulation result that its absorption band is 19.31GHz~73.22GHz, and the entire structure has no wave-transmitting window. This shows that if there is no spacing between the small square ITO films on the bottom two-dimensional structure, the overall structure will not have a wave-transmitting window and the integrated absorption and transmission function cannot be achieved.

Claims

1. A three-dimensional frequency selective absorber with optical transparency and adjustable wave transmission window, characterized in that It is composed of absorber units periodically arranged into N columns×M rows, wherein N≥5 and M≥5; The absorber unit is composed of an FSS structural unit and a three-dimensional absorber structural unit; The FSS structural unit is arranged horizontally, and the FSS structural unit is a first substrate and an ITO pattern layer from bottom to top; the ITO pattern layer is composed of a plurality of square ITO thin films periodically arranged into n columns×m rows, wherein n≥2 and m≥2; the first substrate is a transparent substrate; The three-dimensional absorbing structure unit is vertically arranged on the upper surface of the FSS structure unit; the three-dimensional absorbing structure unit is formed by two second substrates arranged crosswise along the two diagonals of the FSS structure unit, and metal strip groups are symmetrically arranged on both side surfaces of the second substrates, and the metal strip group arranged on one side is composed of a first metal strip structure and a second metal strip structure that are symmetrical along the intersection line of the two second substrates; the first metal strip structure and the second metal strip structure are both composed of K metal strips.

2. The three-dimensional frequency selective absorber with optical transparency and adjustable wave transmission window according to claim 1, characterized in that The first substrate is in the shape of a square, with a thickness h1 of 0.1 mm to 0.5 mm and a side length a of 10 mm to 20 mm; the first substrate is a PET substrate, a PEN substrate or a glass substrate; the second substrate is in the shape of a rectangle, with a thickness of 0.1 mm to 0.3 mm and a width h2 of 8 mm to 12 mm; the second substrate is a FR-4 substrate, with a dielectric constant of 4.3±0.05 and a loss tangent tanδ of 0.5±0.001; the thickness of the metal strip group is 0.035 mm.

3. The three-dimensional frequency selective absorber with optical transparency and adjustable wave transmission window according to claim 1, characterized in that The first metal strip structure and the second metal strip structure are spliced ​​to form a polygon or a circle.

4. The three-dimensional frequency selective absorber with optical transparency and adjustable wave transmission window according to claim 3, characterized in that The splicing edges of the first metal strip structure and the second metal strip structure are located on both sides of the intersection line of the two second substrates or at the edge of the second substrate; When the splicing edges of the first metal strip structure and the second metal strip structure are located on both sides of the intersection line of the two second substrates, a gap b is provided between the splicing edges of the first metal strip structure and the second metal strip structure in the horizontal direction; when the splicing edges of the first metal strip structure and the second metal strip structure are located at the edge of the second substrate, the vertical distance between the splicing edges of the first metal strip structure and the second metal strip structure in the horizontal direction and the edge of the second substrate is b / 2; When the first metal strip structure and the second metal strip structure are bonded together to form a hexagon or a rectangle, or when the first metal strip structure, the second metal strip structure and the gap b are bonded together to form a circle, b=0.5mm~1.5mm; when the first metal strip structure and the second metal strip structure are bonded together to form a triangle or a pentagon, b=0.3mm~0.5mm.

5. The three-dimensional frequency selective absorber with optical transparency and adjustable wave transmission window according to claim 3, characterized in that When the first metal strip structure and the second metal strip structure are bonded and spliced ​​to form a hexagon, the longest metal strip length l0 in the first metal strip structure and the second metal strip structure is 2.25mm~3.75mm, and the length of the metal strips on both sides of the longest metal strip decreases gradually by 0.1mm~0.3mm; K=17~25.

6. The three-dimensional frequency selective absorber with optical transparency and adjustable wave transmission window according to claim 3, characterized in that When the first metal strip structure and the second metal strip structure are bonded and spliced ​​to form a triangle, the bottom metal strip length l0 of the first metal strip structure and the second metal strip structure is 2.35mm~3.25mm, and the length of the metal strip above the bottom metal strip decreases gradually by 0.1mm~0.2mm; K=18~26.

7. The three-dimensional frequency selective absorber with optical transparency and adjustable wave transmission window according to claim 3, characterized in that When the first metal strip structure and the second metal strip structure are bonded and spliced ​​to form a rectangle, the length l0 of the metal strips of the first metal strip structure and the second metal strip structure is equal, and l0 is 2.25mm-3.75mm; K=17-25.

8. The three-dimensional frequency selective absorber with optical transparency and adjustable wave transmission window according to claim 3, characterized in that When the first metal strip structure and the second metal strip structure are bonded and spliced ​​to form a pentagon, the length l0 of the longest metal strip in the first metal strip structure and the second metal strip structure is 2.25mm~3.75mm, the length of the metal strip above the longest metal strip decreases gradually by 0.2mm~0.4mm, and the length of the metal strip below the longest metal strip decreases gradually by 0.1mm~0.3mm; K=18~26.

9. The three-dimensional frequency selective absorber with optical transparency and adjustable wave transmission window according to claim 3, characterized in that When the first metal strip structure, the second metal strip structure and the gap b are spliced ​​to form a circle, the radius r of the circle is 3.5 mm to 4.5 mm; and K=17 to 22.

10. The three-dimensional frequency selective absorber with optical transparency and adjustable wave transmission window according to claim 1, characterized in that The surface resistance of the ITO graphic layer is 1Ω / sq~10Ω / sq; the side length c of the square ITO film is 1mm~2.45mm, and the distance between adjacent square ITO films is (2.5-c)mm.

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