High-frequency band-pass radar and infrared dual-stealth optical transparent metamaterial

Abstract

The invention provides a high-frequency band-pass radar and infrared dual-stealth optical transparent metamaterial, and aims to overcome the defect that an existing stealth material cannot have optical transparency, infrared low emission, microwave broadband absorption and high-frequency band-pass at the same time. The antenna is formed by periodically arranging a plurality of structural units, and each structural unit sequentially comprises a low infrared emission layer, a first transparent dielectric substrate, a radar wave absorbing layer, a second transparent dielectric substrate and a frequency selection wave-transparent layer from top to bottom; the low infrared emission layer and the radar wave absorbing layer are respectively composed of a square patch array made of a transparent conductive material and a low duty ratio circular ring; the frequency selection wave-transparent layer is composed of a square ring aperture type metal mesh. Optical transparency, infrared stealth and radar stealth are integrated, meanwhile, the band-pass performance is achieved in the high-frequency guidance wave band, and the high application prospect is achieved in the field of actual engineering.

Description

Technical Field

[0001] The invention relates to the technical field of multi-spectrum stealth materials, in particular to a high-frequency bandpass radar and infrared dual stealth optical transparent metamaterial. Background Art

[0002] With the improvement of stealth and anti-stealth technology, multi-spectrum composite detection technology has also developed rapidly. Stealth technology with a single frequency band can no longer meet the needs of modern and future military applications. Radar detection and infrared detection are currently the most important detection methods in the military and civilian fields. Designing a radar infrared compatible stealth structure has become a current research hotspot. Radar stealth requires high absorption and low reflectivity in the radar band, while infrared stealth requires high reflectivity and low absorption (low emissivity) in the infrared atmospheric window. Therefore, the requirements for the electromagnetic properties of materials for radar stealth and infrared stealth are mutually restricted, and it is difficult for traditional materials to have the characteristics of high radar absorption and low infrared emission at the same time.

[0003] In addition, with the upgrading of confrontation means in future battlefields, multi-mode, multi-band precision detection instruments have put forward more and higher requirements on the comprehensive performance of stealth materials. In addition to meeting the requirements of radar infrared compatibility stealth, stealth materials should also have excellent optical transmittance in the visible light band to meet the requirements of optical imaging and detection, and should have a microwave transmission window in the high-frequency guidance band to freely send and receive electromagnetic waves to achieve the purpose of signal communication.

[0004] Metamaterials proposed in recent years provide new ideas for the design of stealth materials that integrate optical transparency, low infrared emission, broadband microwave absorption, and high-frequency bandpass. Metamaterials are composite materials composed of periodic arrangement of subwavelength microstructure units. By artificially designing their structural units, electromagnetic parameters such as the material's equivalent dielectric constant, magnetic permeability, and wave impedance can be controlled to achieve exotic physical properties that natural materials do not have. Since metamaterials have the ability to flexibly regulate electromagnetic waves, they have shown great application value in electromagnetic stealth.

[0005] Patent CN112928492B discloses a tunable optically transparent broadband metamaterial absorber based on a water layer, which uses a cross and concentric rings made of transparent conductive materials as a resonant structure, and a transparent medium and a water layer as a dielectric substrate, and simultaneously achieves optical transparency and broadband absorption of electromagnetic waves in the radar band. However, the metamaterial absorber lacks a low infrared emissive layer and the bottom layer is a metal backplane, which cannot achieve infrared stealth and high-frequency bandpass functions, which limits its application in multi-spectrum compatible stealth and signal communications. Patent CN115173075A discloses an optically transparent multi-spectral stealth integrated metamaterial, which integrates radar stealth and infrared stealth functions into the same transparent patterned impedance film, but its infrared emissivity is relatively high (0.534) and cannot meet the needs of practical applications. Patent CN112622391B discloses an optically transparent ultra-wideband radar and infrared dual stealth structure, which achieves both optical transparency and infrared radar compatible stealth. However, the multi-layer structure stacking results in its visible light transmittance of only about 50%, and the bottom layer is a metal backplane, which cannot realize the high-frequency bandpass transmission window, limiting its further application in high-frequency guidance.

[0006] Therefore, developing a functional integrated stealth metamaterial that combines optical transparency, low infrared emission, microwave broadband absorption and high-frequency bandpass remains a difficult problem that needs to be solved urgently. Summary of the invention

[0007] In view of the above-mentioned deficiencies in the prior art, the object of the present invention is to realize a stealth metamaterial that integrates multiple functions such as optical transparency, low infrared emission, microwave broadband absorption and high-frequency bandpass.

[0008] The technical solution of the present invention is as follows:

[0009] A high-frequency bandpass radar and infrared dual stealth optical transparent metamaterial, characterized in that it comprises a plurality of periodically arranged structural units, wherein the structural units sequentially comprise, from top to bottom, a low infrared emission layer of a transparent conductive material, a first transparent dielectric substrate, a radar absorbing layer of a transparent conductive material, a second transparent dielectric substrate and a frequency selective wave-transmitting layer;

[0010] The low infrared emission layer is composed of 9×9 square patches of transparent conductive material arranged in an array;

[0011] The radar absorbing layer is composed of a low duty cycle circular ring of transparent conductive material;

[0012] The frequency selective wave-transmitting layer is composed of a square ring aperture type metal grid;

[0013] The first transparent medium substrate and the second transparent medium substrate are medium materials with high light transmittance;

[0014] The low infrared emission layer and the radar absorbing layer are film layer structures, respectively attached to the upper and lower surfaces of the first transparent medium substrate;

[0015] The frequency selective wave-transmitting layer is a metal grid structure and is attached to the lower surface of the second transparent medium substrate;

[0016] The first transparent medium substrate and the second transparent medium substrate are bonded together by optically transparent adhesive or heat pressing.

[0017] The transparent conductive material is an indium tin oxide (ITO) film, a graphene film, a metal transparent conductive film or a metal grid.

[0018] The low infrared emission layer and the radar absorbing layer are formed on the surface of the first transparent medium substrate by using the coating technology, and then processed by laser etching and stripping technology.

[0019] The material of the frequency selective wave-transmitting layer is composed of one of gold, silver, copper and aluminum or a combination of multiple thereof.

[0020] The metal grid is in the shape of a square, a ring or a hexagon.

[0021] The frequency selective wave transmission layer square ring aperture type metal grid is formed on the lower surface of the second transparent medium substrate by using coating technology, and then is directly etched on the lower surface of the second transparent medium substrate by using femtosecond laser direct writing technology or excimer laser processing technology.

[0022] The material of the first transparent medium substrate and the second transparent medium substrate is composed of one or more combinations of quartz glass, soda-lime glass, polymethyl methacrylate (PMMA) or polyvinyl chloride (PVC).

[0023] Preferably, the thickness of the first transparent medium substrate is 1 to 3 mm, and the thickness of the second transparent medium substrate is 1 to 3 mm.

[0024] Preferably, the side length of the square patch of the low infrared emission layer transparent conductive material is 0.4-0.45 mm, and the interval between adjacent patches is 0.5 mm.

[0025] Preferably, the low duty cycle circular rings made of the transparent conductive material of the radar absorbing layer have an inner diameter of 3-4 mm, a line width of 0.1-0.2 mm, and a center spacing of adjacent circular rings of 4.5 mm.

[0026] Preferably, the sheet resistance of the transparent conductive material of the low infrared emission layer is 6-8Ω / sq, and the sheet resistance of the transparent conductive material of the radar absorbing layer is 6-30Ω / sq.

[0027] Preferably, the frequency selective wave-transmitting layer is a square ring aperture type metal grid, the side length of the square ring aperture is 2 to 4 mm, and the line width is 0.5 to 1 mm; the grid period is 100 to 200 μm, the line width is 5 to 15 μm, and the metal thickness is 200 to 500 nm.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] (1) The present invention provides a high-frequency bandpass radar and infrared dual stealth optical transparent metamaterial, which has an average transmittance of 61.5% in the visible light and near-infrared bands of 400-1500nm and has good visible light-near-infrared transparency properties;

[0030] (2) The present invention provides a high-frequency bandpass radar and infrared dual stealth optical transparent metamaterial, which achieves an emissivity as low as 0.33 in the infrared band of 8-14 μm by reasonably designing the duty cycle of the square patch of transparent conductive material in the low infrared emission layer, thereby achieving infrared stealth;

[0031] (3) The present invention provides a high-frequency bandpass radar and infrared dual stealth optical transparent metamaterial, in which the resonant unit in the radar absorbing layer has a narrow line width and a large ring spacing, and can achieve microwave absorption with an absorption rate of more than 90% in the wide frequency range of 7.5-16.2 GHz. Its relative bandwidth is 73.4%, thereby achieving radar stealth;

[0032] (4) The present invention provides a high-frequency bandpass radar and infrared dual stealth optically transparent metamaterial, which replaces the bottom metal reflective layer of the traditional absorber with an optically transparent square ring aperture metal grid frequency selective wave transmission layer, and has an electromagnetic shielding effect in its non-responsive band and a bandpass function in its electromagnetic response band. Therefore, it can achieve broadband absorption in the radar band and achieve good bandpass performance in the high-frequency guidance band.

[0033] (5) The present invention provides a high-frequency bandpass radar and infrared dual stealth optically transparent metamaterial, which adopts metamaterial technology to better solve the contradictory problems of optical transparency, infrared stealth, radar stealth, and high-frequency bandpass from the perspective of structural design, filling the current technical gap and having high application value in the fields of radar infrared compatible stealth radome and multi-mode composite guidance window. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a three-dimensional schematic diagram of a single structural unit of a high-frequency bandpass radar and infrared dual stealth optical transparent metamaterial of the present invention;

[0035] Figure 2 is a side view of a single structural unit in the present invention;

[0036] Figure 3is a schematic diagram of a low infrared emission layer of a single structural unit in the present invention;

[0037] Figure 4 It is a schematic diagram of a radar absorbing layer of a single structural unit in the present invention;

[0038] Figure 5 It is a schematic diagram of a frequency selective wave-transmitting layer of a single structural unit in the present invention;

[0039] Figure 6 is a schematic diagram of a metal grid in the present invention;

[0040] Figure 7 It is the simulation result of the low-frequency absorption rate of a high-frequency bandpass radar and infrared dual stealth optical transparent metamaterial under normal incidence of electromagnetic waves in the present invention;

[0041] Figure 8 It is the simulation result of high-frequency electromagnetic transmittance of a high-frequency bandpass radar and infrared dual stealth optical transparent metamaterial of the present invention when the electromagnetic wave is normally incident;

[0042] Fig. 9 It is the transmittance test result of a high-frequency bandpass radar and infrared dual stealth optical transparent metamaterial in the visible light and near-infrared bands of the present invention.

[0043] Explanation of the reference numerals: 1 - low infrared emission layer; 2 - first transparent dielectric substrate; 3 - radar absorbing layer; 4 - second transparent dielectric substrate; 5 - frequency selective wave-transmitting layer. DETAILED DESCRIPTION

[0044] The present invention will be further described below in conjunction with the accompanying drawings and specific implementation methods.

[0045] Example:

[0046] A high-frequency bandpass radar and infrared dual stealth optical transparent metamaterial includes a plurality of periodically arranged structural units. A single structural unit such as Figure 1 , Figure 2 As shown, from top to bottom, it includes a low infrared emission layer 1, a first transparent dielectric substrate 2, a radar absorbing layer 3, a second transparent dielectric substrate 4 and a frequency selective wave transmission layer 5. The thicknesses of the first transparent dielectric substrate 2 and the second transparent dielectric substrate 4 are h1 and h2 respectively, and the material used is highly transparent quartz glass, and its dielectric constant is 3.8 (1-j0.0004).

[0047] Figure 3This is a schematic diagram of the low infrared emission layer 1 of an embodiment of the present invention. The material used is indium tin oxide (ITO), and its square resistance is R1. Square indium tin oxide (ITO) patches are arranged on the upper surface of the first transparent medium substrate 2 in a 9×9 matrix array. The patch size is w1 and the period is P2. The conductive indium tin oxide (ITO) film deposited on the upper surface of the first transparent medium substrate 2 is etched by laser lift-off technology.

[0048] Figure 4 This is a schematic diagram of a radar absorbing layer 3 of an embodiment of the present invention. The material used is indium tin oxide (ITO), whose square resistance is R2, and the structural unit is a circular ring pattern with a low duty cycle. The inner diameter of the circular ring is D1, the line width is w2, and the period of the structural unit is P1. The conductive indium tin oxide (ITO) film deposited on the lower surface of the first transparent medium substrate 2 is etched and prepared by laser lift-off technology.

[0049] Figure 5 This is a schematic diagram of a frequency selective wave-transmitting layer 5 according to an embodiment of the present invention, which is composed of a square ring aperture type grid, wherein the side length of the square ring aperture is a1 and the line width is a2. The square ring aperture type grid is composed of a metal grid.

[0050] like Figure 6 As shown, the grid period is P3, the line width is w3, the metal material is gold which is not easy to oxidize, and the conductivity is 4.1×10 7 S / m, with a thickness of t1, is deeply etched into the lower surface of the second transparent medium substrate 4 using femtosecond laser direct writing processing technology, so that it has excellent film firmness, salt spray corrosion resistance, durability and other harsh environment adaptability in practical applications.

[0051] According to an embodiment of the present invention, the low infrared emissive layer 1 is used to shield infrared rays and transmit microwaves. The square indium tin oxide (ITO) patch occupies a large space on the top surface, thereby reducing the infrared emissivity of the surface as a whole, thereby realizing the infrared stealth function, and having almost no effect on the incident microwaves, so that the incident microwaves can be almost completely transmitted. The function of the radar absorbing layer 3 is mainly to achieve impedance matching with free space by electromagnetic resonance with the incident electromagnetic wave in the low-frequency radar band, thereby achieving broadband absorption of electromagnetic waves, and then achieving a reduction in the radar scattering cross section, and finally achieving the radar stealth function. The function of the frequency selective wave-transmitting layer 5 is mainly to have an electromagnetic shielding effect in the low-frequency non-responsive band, and to have a bandpass window in the high-frequency electromagnetic response band, so as to realize signal communication within a preset frequency range. By reasonably designing the period of the low infrared emission layer 1, the number and side length of the square patches, the period of the radar absorption layer 3, the diameter and line width of the circular ring, the period of the frequency selective wave-transmitting layer 5, the side length and line width of the square ring aperture, the period and line width of the metal grid, the conductivity and thickness of the metal material used, the material type and thickness of the transparent medium substrate, etc., optical transparency, infrared stealth in the infrared atmospheric window of 8-14μm, radar stealth in the radar band of 1-18GHz and bandpass performance in the high-frequency guidance band can be achieved simultaneously.

[0052] After optimization, the various parameters in the embodiment of the present invention are specifically set as follows:

[0053] P1=4.5mm, h1=1.5mm, h2=1.5mm, P2=0.5mm, w1=0.42mm, D1=3.8mm, w2=0.15mm,

[0054] a1=2.7mm, a2=0.6mm, P3=150μm, w3=10μm, t1=350nm, R1=6Ω / sq, R2=6Ω / sq.

[0055] Figure 7 This is the simulation result of the low-frequency absorption rate of a high-frequency bandpass radar and infrared dual stealth optically transparent metamaterial when the electromagnetic wave is vertically incident. It can be seen from the figure that it can achieve broadband microwave absorption in the 7.5-16.2GHz frequency band, with an absorption rate of more than 90% and a relative bandwidth of 73.4%, and has good radar stealth performance. Figure 8 This is the simulation result of the high-frequency transmittance of a high-frequency bandpass radar and infrared dual stealth optically transparent metamaterial in this embodiment when the electromagnetic wave is vertically incident. It can be seen from the figure that the electromagnetic transmittance of the metamaterial at 27.9 GHz is more than 80%, which can meet the needs of signal communication in a specific frequency band.

[0056] Since the low infrared emissive layer 1 uses indium tin oxide (ITO) with a square resistance of 6Ω / sq, which has low infrared emissivity and high duty cycle, the overall infrared emissivity can be reduced to achieve infrared stealth, and the infrared stealth performance can be improved by further increasing the duty cycle of indium tin oxide (ITO). Specifically, the formula u=u m f m +u d (1-f m ) to calculate the emissivity, where u is the emissivity of the structure as a whole, u m and u d are the emissivity of indium tin oxide (ITO) and dielectric substrate, respectively, and f m is the duty cycle of indium tin oxide (ITO), where the emissivity of indium tin oxide (ITO) with a square resistance of 6Ω / sq is 0.1, and the emissivity of the quartz glass dielectric substrate is 0.9. It is calculated that the infrared emissivity of the entire structure is 0.33.

[0057] In addition, since the prepared material is optically transparent, the metamaterial can maintain a high optical transmittance to meet the needs of optical imaging and detection. In order to accurately characterize its optical transparency properties, the transmittance of the overall structure was measured using a spectrophotometer, such as Fig. 9 As shown, the average transmittance of the metamaterial in the visible light and near-infrared band of 400-1500nm is 61.5%, which has good visible light-near-infrared transparency. In addition, the optical transmittance of the overall structure can be further improved by replacing the materials of the low infrared emission layer 1 and the radar absorbing layer 3 with metal grids.

[0058] The embodiments of the present invention solve the contradictory problems of optical transparency, infrared stealth, radar stealth, and high-frequency bandpass from the perspective of metamaterial structure design, and have high application prospects.

[0059] The above specific implementations explain the main features, basic principles and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. The above embodiments and descriptions are only for explaining the principles of the present invention. By proportionally enlarging or reducing the size of the present invention, or using different materials and dielectric substrates, as well as grids of different shapes to form a frequency selective wave-transmitting layer, broadband absorption and bandpass functions of electromagnetic waves in different bands can be achieved. Without departing from the design concept and scope of the present invention, the present invention may have various changes and improvements. For example, technicians may modify the above various parameters to make it work in different bands, or modify related parameters to make its structure and performance different from the present embodiment. These changes and improvements all fall within the scope of the present invention to be protected. The scope of protection claimed by the present invention is defined by the claims and their equivalents.

Claims

1. A high-frequency bandpass radar and infrared dual stealth optically transparent metamaterial, characterized in that: The invention comprises a plurality of periodically arranged structural units, wherein the structural units comprise, from top to bottom, a low infrared emission layer (1), a first transparent dielectric substrate (2), a radar absorbing layer (3), a second transparent dielectric substrate (4) and a frequency selective wave transmission layer (5); The low infrared emission layer (1) is composed of 9×9 square patches made of transparent conductive material arranged in an array; The radar absorbing layer (3) is composed of a low duty cycle circular ring made of a transparent conductive material; The frequency selective wave-transmitting layer (5) is composed of a metal grid; The first transparent medium substrate (2) and the second transparent medium substrate (4) are light-transmitting medium materials; The low infrared emission layer (1) and the radar absorbing layer (3) are film layer structures, and are respectively attached to the upper and lower surfaces of the first transparent medium substrate (2); The frequency selective wave-transmitting layer (5) is a metal grid structure and is attached to the lower surface of the second transparent medium substrate (4); The first transparent medium substrate (2) and the second transparent medium substrate (4) are bonded together by an optically transparent adhesive or by heat pressing.

2. The high-frequency bandpass radar and infrared dual stealth optically transparent metamaterial according to claim 1, characterized in that: The transparent conductive material is an indium tin oxide (ITO) film, a graphene film, a metal transparent conductive film or a metal grid.

3. The high-frequency bandpass radar and infrared dual stealth optically transparent metamaterial according to any one of claims 1-2, characterized in that: The low infrared emission layer (1) and the radar absorbing layer (3) are formed on the surface of the first transparent medium substrate (2) by using a coating technology, and then processed by laser etching and stripping technology.

4. The high-frequency bandpass radar and infrared dual stealth optically transparent metamaterial according to claim 1, characterized in that: The material of the frequency selective wave-transmitting layer (5) is composed of one of gold, silver, copper and aluminum or a combination of multiple thereof.

5. The high-frequency bandpass radar and infrared dual stealth optically transparent metamaterial according to claim 1, characterized in that: The metal grid is in the shape of a square, a ring or a hexagon.

6. The high-frequency bandpass radar and infrared dual stealth optically transparent metamaterial according to claim 1, characterized in that: The square ring aperture type metal grid of the frequency selective wave transmission layer (5) is formed on the lower surface of the second transparent medium substrate (4) by using a coating technology, and then directly etched on the lower surface of the second transparent medium substrate (4) by using a femtosecond laser direct writing processing technology or an excimer laser processing technology.

7. The high-frequency bandpass radar and infrared dual stealth optically transparent metamaterial according to claim 1, characterized in that: The material of the first transparent medium substrate (2) and the second transparent medium substrate (4) is composed of a combination of one or more of quartz glass, soda-lime glass, polymethyl methacrylate (PMMA) or polyvinyl chloride (PVC).

8. The high-frequency bandpass radar and infrared dual stealth optically transparent metamaterial according to claim 1, characterized in that: The thickness of the first transparent medium substrate (2) is 1 to 3 mm, and the thickness of the second transparent medium substrate (4) is 1 to 3 mm.

9. The high-frequency bandpass radar and infrared dual stealth optically transparent metamaterial according to claim 1, characterized in that: The side length of the square patch of transparent conductive material of the low infrared emission layer (1) is 0.4-0.45 mm, and the interval between adjacent patches is 0.5 mm.

10. The high-frequency bandpass radar and infrared dual stealth optically transparent metamaterial according to claim 1, characterized in that: The radar absorbing layer (3) is a low duty cycle circular ring made of transparent conductive material, with an inner diameter of 3-4 mm, a line width of 0.1-0.2 mm, and a center spacing of 4.5 mm between adjacent circular rings.

11. The high-frequency bandpass radar and infrared dual stealth optically transparent metamaterial according to claim 1, characterized in that: The sheet resistance of the transparent conductive material of the low infrared emission layer (1) is 6 to 8 Ω / sq, and the sheet resistance of the transparent conductive material of the radar absorbing layer (3) is 6 to 30 Ω / sq.

12. The high-frequency bandpass radar and infrared dual stealth optically transparent metamaterial according to claim 1, characterized in that: The frequency selective wave-transmitting layer (5) is a square ring aperture type metal grid, the side length of the square ring aperture is 2 to 4 mm, and the line width is 0.5 to 1 mm; the metal grid period is 100 to 200 μm, the line width is 5 to 15 μm, and the metal grid thickness is 200 to 500 nm.

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