Zero-power absorption type adjustable metasurface composite material and preparation method thereof

Abstract

The invention belongs to the technical field of electromagnetic wave-absorbing materials, and particularly relates to a zero-power absorption type adjustable metasurface composite material and a preparation method thereof. Comprising a panel, a square-ring-shaped metal layer, a cross-shaped metal layer, an electric control metamaterial, a resistive film and a reflecting back plate from top to bottom in sequence, a core layer is arranged among the square metal layer, the cross curve metal layer, the electric control metamaterial, the resistive film and the reflecting back plate; the electric control metamaterial comprises second structure units which are periodically arranged along x and y directions and contain PIN diodes, and the PIN diodes are embedded into the structure; the cross curve metal layer and the square metal layer respectively comprise a third structure unit and a fourth structure unit which are periodically arranged along the x direction and the y direction. Through a cascade structure formed by the electric control metamaterial, the cross-shaped metal layer and the square ring-shaped metal layer, when the PIN diode is switched off, the wave absorbing state is presented, when the PIN diode is switched on, the reflecting state is presented, and electromagnetic waves are absorbed under the condition that bias voltage is not applied.

Description

Technical Field

[0001] This invention belongs to the field of electromagnetic wave absorbing materials technology, specifically relating to a zero-power absorption type tunable metasurface composite material and its preparation method. Background Technology

[0002] Electromagnetic wave absorption technology refers to the physical process of effectively dissipating or converting the energy of incident electromagnetic waves into other forms of energy (such as heat) through high-loss materials or resonant structures. The core objective of this technology is to maximize energy absorption and minimize electromagnetic wave reflection and transmission, making it a key means of achieving radar stealth and electromagnetic compatibility. Its efficient implementation relies on two fundamental physical conditions: 1. Impedance matching condition: To reduce electromagnetic wave reflection at material interfaces, the complex permittivity and permeability of the material must be adjusted to match its wave impedance as closely as possible to the free-space wave impedance, thereby maximizing the coupling of the incident wave into the material's interior. 2. Strong attenuation condition: Electromagnetic waves entering the material's interior must be rapidly attenuated through an efficient loss mechanism. This mainly relies on the material's electrical losses (such as conductivity loss and dielectric relaxation) and magnetic losses (such as natural resonance and domain wall resonance), or on structural resonances (such as metamaterial unit resonance) to achieve energy localization and dissipation in specific frequency bands.

[0003] Metamaterial absorbing structures are artificial composite structures composed of subwavelength-scale units arranged periodically or aperiodically. Their electromagnetic parameters can be precisely controlled through structural design, and they can exhibit anomalous electromagnetic properties such as negative refractive index. Compared with traditional absorbing materials that rely on intrinsic loss, metamaterial absorbing structures have significant advantages such as low profile and flexible design of absorption performance, showing important application potential in the field of radar stealth. However, once the traditional passive metamaterial absorbing structure is fabricated, its operating frequency band and absorption performance are fixed, making it difficult to adapt to complex and variable electromagnetic environments and mission requirements. To address this, researchers have proposed integrating tunable elements into metamaterial units to achieve dynamic control of absorption performance. Among various tunable technologies (such as those based on phase change materials, water-based fluids, liquid metals, or mechanical deformation), the electronically controlled tuning method using PIN diodes is considered to have high engineering application value due to its advantages such as fast switching speed, high control precision, and ease of integration. However, this type of structure still faces two key challenges: First, in most designs, active devices such as PIN diodes are directly exposed to the external environment or bare on the substrate surface, leading to decreased reliability and shorter lifespan under mechanical vibration, temperature changes, or humid conditions. Second, the absorbing state of existing tunable absorbing metamaterials usually needs to be realized in an active state (requiring an external bias voltage). Summary of the Invention

[0004] The purpose of this invention is to provide a zero-power absorption type adjustable metasurface composite material and its preparation method. By embedding a PIN diode inside the structure, the reliability of the absorbing material is improved. Through the cascaded structure composed of an electrically controlled metamaterial, a cross-shaped metal layer and a square ring metal layer, the material exhibits a wave-absorbing state when the PIN diode is turned off and a reflection state when the PIN diode is turned on. This allows for the absorption of electromagnetic waves without applying a bias voltage, i.e., zero-power wave absorption. With an applied bias voltage, the reflectivity can be adjusted, and the reflectivity changes with the voltage.

[0005] To achieve the above objectives, the specific technical solution provided by the present invention is as follows: The first objective of this invention is to provide a zero-power absorption type adjustable metasurface composite material, which, from top to bottom, comprises a panel, a square annular metal layer, a cross-shaped metal layer, an electrically controlled metamaterial, a resistive film, and a reflective backplate; a core layer is provided between the square metal layer, the cross-shaped metal layer, the electrically controlled metamaterial, the resistive film, and the reflective backplate; The electro-controlled metamaterial includes a second structural unit containing PIN diodes arranged periodically along the x and y directions, with the PIN diodes embedded inside the structure and integrally formed with the composite material; The cross-shaped metal layer includes third structural units arranged periodically along the x and y directions; the third structural unit is a cross-shaped structural unit. The square metal layer includes a fourth structural unit arranged periodically along the x and y directions; the fourth structural unit is a square ring structural unit. The cascaded structure, consisting of an electronically controlled metamaterial, a cross-shaped metal layer, and a square ring-shaped metal layer, exhibits a wave-absorbing state when the PIN diode is turned off and a reflection state when the PIN diode is turned on.

[0006] Furthermore, the second structural unit containing PIN diodes includes multiple PIN diodes and multiple metallized rectangles sequentially soldered together; the second structural unit containing PIN diodes is arranged in a grid-like periodic pattern, with the metallized rectangles serving as the negative electrode of the feed line and the PIN diodes serving as the positive electrode of the feed line.

[0007] Furthermore, the resistive film includes first structural units arranged periodically along the x and y directions.

[0008] Furthermore, the sheet resistance of the resistive film is 65Ω / sq to 500Ω / sq, and the first structural unit is a square ring structure unit.

[0009] Furthermore, the core layer is made of a wave-transparent material.

[0010] Furthermore, the core layer includes: The first core layer is located between the resistive film and the reflective backplate; The second core layer is located between the electrically controlled metamaterial and the resistive film; The third core layer is located between the cross-shaped metal layer and the electrically controlled metamaterial; The fourth core layer is located between the square annular metal layer and the cross-shaped metal layer.

[0011] Furthermore, the panel is made of a wave-transparent composite material with a relative permittivity of 2.7 to 5.6, a dielectric loss angle of 0.15 to 0.025, and a thickness of 0.1 mm to 1.5 mm.

[0012] Furthermore, the reflective backplate is made of conductive material.

[0013] The first objective of this invention is to provide a method for preparing the above-mentioned zero-power absorption tunable metasurface composite material, comprising the following steps: The panel, square ring metal layer, cross-shaped metal layer, electronically controlled metamaterial, resistive film, reflective backplate and core layer are laid out in sequence, and then bonded, shaped and cut to obtain the final product.

[0014] Compared with the prior art, the beneficial effects of the present invention are as follows: The zero-power absorption tunable metasurface composite material provided by this invention embeds a PIN diode inside the structure, integrally forming the composite structure. Since the feed network containing the active device is integrally embedded inside the structure, it is protected, thereby improving the reliability of the electrically controlled absorbing material. Through the cascaded structure composed of the electrically controlled metamaterial, the cross-shaped metal layer, and the square annular metal layer, when the PIN diode is off, the entire structure of the three layers exhibits a transparent state; when the PIN diode is on, the entire structure of the three layers exhibits a reflective state. Placing the cascaded structure of the electrically controlled metamaterial, the cross-shaped metal layer, and the square annular metal layer above the resistive film, when the PIN diode is off, the entire structure of the four layers exhibits an absorbing state; when the PIN diode is on, the entire structure of the four layers exhibits a reflective state. By effectively combining the transparent metamaterial and the resistive film, zero-power absorption of the tunable metamaterial is achieved. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of a zero-power absorption type tunable metasurface composite structure provided in an embodiment of the present invention.

[0016] Figure 2 This is a schematic diagram of the resistive film in the zero-power absorption tunable metasurface composite material provided in an embodiment of the present invention.

[0017] Figure 3 This is a schematic diagram of the electrically controlled metamaterial in the zero-power absorption tunable metasurface composite structure provided in the embodiments of the present invention.

[0018] Figure 4This is a schematic diagram of the cross-shaped metal layer in the zero-power absorption tunable metasurface composite structure provided in this embodiment of the invention.

[0019] Figure 5 This is a schematic diagram of the annular metal layer in the zero-power absorption tunable metasurface composite structure provided in this embodiment of the invention.

[0020] Figure 6 The above is a simulated spectrum of the reflectivity of the zero-power absorption type tunable metasurface composite structure when the resistance value RP of the PIN diode varies in the range of 3Ω to 1e+6Ω in an embodiment of the present invention.

[0021] Figure 7 The simulated reflectance spectrum of the zero-power absorption type tunable metasurface composite structure is shown in the embodiment of the present invention when the PIN diode resistance RP is equal to 3Ω and the sheet resistance SR of the resistive film varies in the range of 215Ω / sq to 415Ω / sq.

[0022] Figure 8 The simulated reflectance spectrum of the zero-power absorption type tunable metasurface composite structure is shown in the embodiment of the present invention when the PIN diode resistance value RP is equal to 1e+6Ω and the sheet resistance SR of the resistive film varies in the range of 215Ω / sq to 415Ω / sq.

[0023] Figure 9 The image shows the reflectivity test spectrum of the zero-power absorption tunable metasurface composite structure under different bias voltages in this embodiment of the invention.

[0024] Figure label: 1-Resistive film, 2-Electrically controlled metamaterial, 3-Cross-shaped metal layer, 4-Square annular metal layer, 5-Reflective backplate, 6-First core layer, 7-Second core layer, 8-Third core layer, 9-Fourth core layer, 10-Panel, 11-First structural unit, 22-Second structural unit, 33-Third structural unit, 44-Fourth structural unit, h1-Thickness of the first core layer, h2-Thickness of the second core layer, h3-Thickness of the third core layer, h4-Thickness of the fourth core layer, p1-Period of the first structural unit, l1-Outer side length, g1-Inner side length, p2-Period of the second structural unit, l2-Length of the rectangular metal, w2-Width of the rectangular metal, g2-Gap between the PIN diode soldering areas, p3-Period of the third structural unit, l3-Length of the cross-shaped metal, w3-Width of the cross-shaped metal, p4-Period of the fourth structural unit, l4-Outer side length, g4-Inner side length. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without inventive effort are within the scope of protection of this invention.

[0026] As described in the background section, in current research, most designs expose active devices such as PIN diodes directly to the external environment or the substrate surface, leading to decreased reliability and shorter lifespan under mechanical vibration, temperature changes, or humid conditions. Furthermore, the absorption state of existing tunable absorbing metamaterials typically requires an active state to be achieved. To address these issues, this invention combines a square annular metal layer 4, a cross-shaped metal layer 3, an electrically controlled metamaterial 2, and a resistive film 1, achieving integrated design, fabrication, and complementary advantages of these four components, thereby solving the aforementioned technical problems. The specific technical solution is as follows:

[0027] On one hand, a zero-power absorption type adjustable metasurface composite material includes, from top to bottom, a panel 10, a square annular metal layer (capacitive) 4, a cross-shaped metal layer (inductive) 3, an electrically controlled metamaterial 2, a resistive film 1, and a reflective backplate 5; a core layer is provided between the square metal layer 4, the cross-shaped metal layer 3, the electrically controlled metamaterial 2, the resistive film 1, and the reflective backplate 5.

[0028] The electronically controlled metamaterial 2 includes second structural units 22 containing PIN diodes arranged periodically along the x and y directions, with the PIN diodes embedded inside the structure and integrally formed with the composite material.

[0029] The cross-shaped metal layer 3 includes third structural units 33 arranged periodically along the x and y directions; the third structural unit 33 is a cross-shaped structural unit.

[0030] The square metal layer 4 includes a fourth structural unit 44 arranged periodically along the x and y directions; the fourth structural unit 44 is a square ring structural unit.

[0031] The cascaded structure consisting of the electronically controlled metamaterial 2, the cross-shaped metal layer 3, and the square ring metal layer 4 exhibits a wave-absorbing state when the PIN diode is turned off and a reflection state when the PIN diode is turned on.

[0032] In this invention, the zero-power absorption tunable metasurface composite material is provided to achieve electromagnetic wave absorption without applying a bias voltage, i.e., zero-power wave absorption. After applying a bias voltage, the reflectivity can be adjusted, and the reflectivity changes with the voltage. In this structure, panel 10 is positioned at the top as a skin to enhance the mechanical strength of the zero-power absorbing and reflective adjustable composite material. The cascaded structure composed of the electronically controlled metamaterial 2, the cross-shaped metal layer 3, and the square annular metal layer 4 exhibits a wave-transmitting state when the PIN diode is off and a reflective state when the PIN diode is on. Placing this cascaded structure above the resistive film 1 ensures that the four layers absorb waves when the PIN diode is off and reflect waves when the PIN diode is on. By effectively combining the wave-transmitting metamaterial and the resistive film, zero-power absorption of the adjustable metamaterial is achieved. The reflective backplate 5 is positioned at the bottom of the zero-power absorbing and reflective adjustable composite material to provide an electrical boundary. The core layer is positioned in the middle of the structure as the core material to protect the active devices in the electronically controlled metamaterial 2 and the dielectric layer serving as the electromagnetic structure.

[0033] In this invention, when the PIN diode is off, its equivalent resistance approaches infinity, and the PIN diode only provides capacitance Cp. At this time, the capacitance Cp of the PIN diode, together with the capacitance C provided by the square annular metal layer 4, the inductance L provided by the cross-shaped metal layer 3, and the additional inductance introduced by each dielectric layer (such as foam or air gap), constitute an LC parallel resonant circuit. The LC parallel resonance exhibits very high impedance near its resonant frequency. According to transmission line theory, when an electromagnetic wave is incident on such a high-impedance surface, most of the energy will pass through without being reflected, thus achieving an overall transparent state. When the PIN diode is on, its equivalent resistance approaches zero, which is equivalent to the PIN diode's Cp being short-circuited, effectively "connecting" the gaps between the strips. This makes the orthogonal metal strips on the upper and lower surfaces of the square annular metal layer 4 electrically approximately connected into a continuous metal surface. This causes the square annular metal layer 4 to behave like an electrical boundary or electromagnetic shielding layer. When the incident electromagnetic wave encounters this continuous metal surface, it follows the "skin effect," current flows on the surface, and the electromagnetic wave is strongly reflected back. This achieves an overall reflective appearance.

[0034] In a preferred embodiment, the second structural unit 22 containing PIN diodes includes a plurality of PIN diodes and a plurality of metallized rectangles sequentially soldered together; the second structural unit 22 containing PIN diodes is arranged in a grid-like periodic pattern, with the metallized rectangles serving as the negative electrode of the feed line and the PIN diodes serving as the positive electrode of the feed line.

[0035] In this invention, the electrically controlled metamaterial 2 is prepared by PCB process. This invention does not impose any particular restrictions on the substrate in the electrically controlled metamaterial 2. Any circuit board microwave board material known to those skilled in the art can be used as the substrate. Those skilled in the art can select and adjust the substrate according to the actual application, product quality and product performance. Preferably, the thickness is 0.08mm to 0.3mm.

[0036] It is understandable that, in order to simplify the preparation process of the zero-power absorption tunable metasurface composite structure, the electrically controlled metamaterial 2 adopts a series feed method to etch metal patterns on the front and back sides of the substrate respectively. The reflectivity of the zero-power absorption tunable metasurface composite material can be independently controlled under different polarizations. Specifically, the present invention proposes to achieve independent control of the reflectivity of the zero-power absorption tunable metasurface composite material under different polarizations by adjusting the external bias voltage.

[0037] In a preferred embodiment, the resistive film 1 includes first structural units 11 arranged periodically along the x and y directions.

[0038] In this invention, the type of the first structural unit 11 is not limited; for example, square, circular, and annular shapes are all applicable. The spacing between the first structural units 11 can be freely adjusted according to their period. As a preferred embodiment of this invention, the sheet resistance of the resistive film 1 is 65Ω / sq to 500Ω / sq, and the first structural unit 11 is a square annular structural unit. The resistive film 1 is prepared by screen printing, and the substrate is a transparent film.

[0039] In a preferred embodiment, the core layer is a wave-transparent material. In this invention, the core layer can be a lightweight wave-transparent material such as foam or aramid honeycomb.

[0040] In a preferred embodiment, the core layer includes: The first core layer 6 is disposed between the resistive film 1 and the reflective backplate 5.

[0041] The second core layer 7 is located between the electrically controlled metamaterial 2 and the resistive film 1.

[0042] The third core layer 8 is located between the cross-shaped metal layer 3 and the electrically controlled metamaterial 2.

[0043] The fourth core layer 9 is located between the square annular metal layer 4 and the cross-shaped metal layer 3.

[0044] In this invention, there are no particular restrictions on the thickness of the first core layer 6, the second core layer 7, the third core layer 8 and the fourth core layer 9, and the core material thickness will vary under different structural cycles.

[0045] In a preferred embodiment, the panel 10 is a wave-transparent composite material with a relative permittivity of 2.7 to 5.6, a dielectric loss angle of 0.15 to 0.025, and a thickness of 0.1 mm to 1.5 mm.

[0046] In this invention, there are no particular limitations on the panel 10. Those skilled in the art can select and adjust the panel 10 according to actual application conditions, product quality, and product performance. As a preferred embodiment of this invention, the panel 10 is a wave-transparent composite material with a relative permittivity of 2.7–5.6, a dielectric loss angle of 0.15–0.025, and a thickness of 0.4 mm–1 mm. The wave-transparent composite material is a wave-transparent fiber-reinforced resin-based composite material, and the wave-transparent fibers are glass fibers, quartz fibers, etc. The dielectric constant and loss angle of the quartz fiber-reinforced epoxy resin-based composite material are 3.5 and 0.006, respectively; the dielectric constant and loss angle of the glass fiber-reinforced epoxy resin-based composite material are 4.1 and 0.02, respectively.

[0047] In a preferred embodiment, the reflective backplate 5 is made of a conductive material.

[0048] In this invention, there are no particular limitations on the reflective backplate 5. Those skilled in the art can select and adjust the reflective backplate 5 according to the actual application, product quality and product performance. As a preferred embodiment of this invention, the thickness of the reflective backplate 5 is 0.4 mm to 1 mm.

[0049] In order to provide a clearer understanding of the technical features, objectives and beneficial effects of the present invention, the technical solution of the present invention will now be described in detail below, but it should not be construed as limiting the scope of implementation of the present invention.

[0050] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0051] Unless otherwise specified, the methods described in the following embodiments are conventional methods; the reagents and materials mentioned are commercially available unless otherwise specified.

[0052] The following specific examples will provide further explanation.

[0053] Example 1 A zero-power-absorbing tunable metasurface composite material, specifically a foam-based sandwich composite material, such as... Figure 1As shown, from top to bottom, it includes a panel 10, a square ring metal layer 4, a fourth core layer 9, a cross-shaped metal layer 3, a third core layer 8, an electronically controlled metamaterial 2, a second core layer 7, a resistive film 1, a first core layer 6, and a reflective backplate 5.

[0054] Among them, the thickness h4 of the fourth core layer 9 is 4.2 mm, the thickness h3 of the third core layer 8 is 4.2 mm, the thickness h2 of the second core layer 7 is 15 mm, the thickness h1 of the first core layer 6 is 16 mm, the first core layer 6, the second core layer 7, the third core layer 8 and the fourth core layer 9 are foam core layers, and the dielectric constant and loss angle of the first core layer 6, the second core layer 7, the third core layer 8 and the fourth core layer 9 range from 1.02 to 1.05 and 0.002 to 0.008, respectively.

[0055] Panel 10 is a quartz fiber panel; the relative permittivity of the panel is 3.5, the dielectric loss angle is 0.006, and the thickness is 0.42mm; The reflective backplate 5 is a carbon fiber backplate with a relative permittivity of 0.006 and a thickness of 0.4 mm.

[0056] like Figure 2 As shown, in this embodiment, the resistive film 1 is a first structural unit 11 arranged in a square ring periodic pattern. The period p1 of the first structural unit 11 is 22.44 mm, the outer side length l1 is 19.21 mm, and the inner side length g1 is 7.42 mm. That is, the spacing between adjacent first structural units 11 is p1l1. In the preparation process, conductive paste is used to prepare the resistive film by screen printing. The sheet resistance of the resistive film is within the range of 65 Ω / sq to 500 Ω / sq. In this embodiment, the sheet resistance of the resistive film layer is 215 Ω / sq. The printing substrate of the resistive film is an FR4 dielectric sheet with a thickness of 0.1 mm, a relative permittivity of 4.1, and a dielectric loss angle of 0.025°.

[0057] like Figure 3 As shown, in this embodiment, the electrically controlled metamaterial 2 includes a second structural unit 22. The second structural unit 22 comprises two parts: a metallized rectangle and a PIN diode. The period p2 of the second structural unit 22 is 22.44 mm. The length l2 of the metallized rectangle is 5.38 mm, and the width w2 of the metallized rectangle is 5.05 mm. It should be noted that the metallized rectangle in this invention is made of copper. The PIN diode is soldered to the center of the gap in the metallized rectangle, and the gap g2 is 0.56 mm.

[0058] In this embodiment, the electrically controlled metamaterial 2 in the zero-power absorption tunable metasurface composite structure is a 27×27 unit array with a total size of 302.87mm×302.87mm. The feed method is as follows: Figure 3 As shown, at both ends of the electrically controlled metamaterial 2, the PIN diode and the metallized rectangle serve as the positive and negative terminals of the feed line, respectively.

[0059] The electrically controlled metamaterial 2 was fabricated using PCB technology with FR4 copper-clad laminate as the material. The copper thickness was 0.017 mm, the dielectric thickness was 0.1 mm, the relative permittivity was 4.1, and the dielectric loss angle was 0.025°. To obtain polarization-independent characteristics, the electrically controlled metamaterial 2 was etched on both the front and back sides of the copper-clad laminate. The rectangular (feed lines) in the metal array were oriented in the same direction as the electric field polarization.

[0060] like Figure 4 As shown, in this embodiment, the cross-shaped metal layer is a third structural unit 33 arranged in a cross-shaped periodic pattern. The period p3 of the third structural unit 33 is 22.44 mm, the side length l3 is 11.22 mm, and the line width w3 is 1.02 mm. It is fabricated using PCB technology, using FR4 copper-clad laminate with a copper thickness of 0.017 mm, a dielectric thickness of 0.1 mm, a relative permittivity of 4.1, and a dielectric loss angle of 0.025°.

[0061] like Figure 5 As shown, in this embodiment, the square annular metal layer is a fourth structural unit 44 arranged in a square annular period. The period p4 of the fourth structural unit 44 is 22.44 mm, the outer side length l4 is 10.02 mm, and the inner side length g4 is 4.54 mm. That is, the spacing between adjacent fourth structural units 44 is (p42l4) / 2. It is fabricated using PCB technology, using FR4 copper-clad laminate with a copper thickness of 0.017 mm, a dielectric thickness of 0.1 mm, a relative permittivity of 4.1, and a dielectric loss angle of 0.025°.

[0062] During preparation, the panel 10, the square ring metal layer 4, the fourth core layer 9, the cross-shaped metal layer 3, the third core layer 8, the electronically controlled metamaterial 2, the second core layer 7, the resistive film 1, the first core layer 6 and the reflective backplate 5 are laid out in sequence, then bonded with adhesive, and processed by hand lay-up molding process. After processing, it is cut to 325mm×325mm.

[0063] Figure 6 This is a simulated spectrum of the reflectivity of the zero-power absorption tunable metasurface composite structure when the resistance RP of the PIN diode varies within the range of 3Ω to 1e+6Ω in an embodiment of the present invention. Figure 6As shown, when the PIN diode is off, i.e., its equivalent resistance RP = 1e+6Ω, the structure composed of the electrically controlled metamaterial 2, the cross-shaped metal layer 3, and the square annular metal layer 4 in the zero-power absorption tunable metasurface composite structure is almost transparent to electromagnetic waves in the 2GHz to 4GHz range. However, due to the loss effect of the resistive film 1, the sheet resistance is 215Ω / sq, and the reflectivity is less than -10dB in the 2.5-3.5GHz range, with the lowest reflectivity approaching -30dB. When the PIN diode is off, i.e., its equivalent resistance RP = 3Ω, the structure composed of the electrically controlled metamaterial 2, the cross-shaped metal layer 3, and the square annular metal layer 4 in the zero-power absorption tunable metasurface composite structure almost reflects electromagnetic waves in the 2GHz to 4GHz range, and the reflectivity is greater than -1dB in the 2GHz to 4GHz range. As the equivalent resistance RP of the PIN diode changes from 3Ω to 1e+6Ω, the simulated reflectivity gradually decreases.

[0064] Figure 7 This is a simulated spectrum of the reflectivity of the zero-power absorption tunable metasurface composite structure when the PIN diode resistance RP is equal to 3Ω and the sheet resistance SR of the resistive film varies within the range of 215Ω / sq to 415Ω / sq in an embodiment of the present invention. Figure 7 As shown, when the PIN diode is in the conducting state, that is, when its equivalent resistance RP = 3Ω, the structure composed of the electrically controlled metamaterial 2, the cross-shaped metal layer 3 and the square ring metal layer 4 in the zero-power absorption type adjustable metasurface composite structure almost reflects electromagnetic waves in the range of 2GHz to 4GHz. When the sheet resistance SR of the resistive film 1 changes from 215Ω / sq to 415Ω / sq, the reflectivity hardly changes and is greater than -1dB.

[0065] Figure 8 This is a simulated reflectivity spectrum of the zero-power absorption tunable metasurface composite structure when the PIN diode resistance RP is equal to 1e+6Ω and the sheet resistance SR of the resistive film varies within the range of 215Ω / sq to 415Ω / sq in an embodiment of the present invention. Figure 8 As shown, when the PIN diode is in the off state, i.e., when its equivalent resistance RP = 1e + 6Ω, the structure composed of the electrically controlled metamaterial 2, the cross-shaped metal layer 3 and the square ring metal layer 4 in the zero-power absorption type adjustable metasurface composite structure is almost transparent to electromagnetic waves in the range of 2GHz to 4GHz. When the sheet resistance SR of the resistive film 1 changes from 215Ω / sq to 415Ω / sq, the reflectivity gradually increases.

[0066] The zero-power absorption tunable metasurface composite structure was tested using the free-space method. Figure 9 This is a spectrum of reflectivity test results for a zero-power absorption tunable metasurface composite structure under different bias voltages in an embodiment of the present invention. Figure 9As shown, when the external bias voltage is adjusted from 0V to 48V, the test reflectivity of the zero-power absorption and adjustable reflection composite structure changes from 20dB to -3dB within the 2GHz to 6GHz range, with an adjustment depth greater than 15dB. When the external bias voltage is equal to 0V, the reflectivity reaches its minimum value, i.e., zero-power absorption. As the external bias voltage increases, the reflectivity gradually increases, reaching its maximum value when the external bias voltage is equal to 48V. It can be seen that there is a significant discontinuity in reflectivity at 2.6GHz. This is because the 2GHz to 4GHz test here uses two pairs of horn antennas for frequency band testing (2GHz to 2.6GHz and 2.6GHz to 4GHz respectively). Therefore, there is a discontinuity in reflectivity at 2.6GHz, which is unavoidable in frequency band testing. This is hereby explained.

[0067] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, it is intended to include any modifications and variations that fall within the scope of the claims and their equivalents.

Claims

1. A zero-power absorption tunable metasurface composite material, characterized in that, From top to bottom, it includes a panel (10), a square annular metal layer (4), a cross-shaped metal layer (3), an electrically controlled metamaterial (2), a resistive film (1), and a reflective backplate (5); a core layer is provided between the square metal layer (4), the cross-shaped metal layer (3), the electrically controlled metamaterial (2), the resistive film (1), and the reflective backplate (5); The electrically controlled metamaterial (2) includes a second structural unit (22) containing PIN diodes arranged periodically along the x and y directions, with the PIN diodes embedded inside the structure and integrally formed with the composite material; The cross-shaped metal layer (3) includes a third structural unit (33) arranged periodically along the x and y directions; the third structural unit (33) is a cross-shaped structural unit; The square metal layer (4) includes a fourth structural unit (44) arranged periodically along the x and y directions; the fourth structural unit (44) is a square ring structure unit; Among them, the cascaded structure composed of the electronically controlled metamaterial (2), the cross-shaped metal layer (3) and the square ring metal layer (4) exhibits a wave-absorbing state when the PIN diode is turned off and a reflection state when the PIN diode is turned on.

2. The zero-power absorption tunable metasurface composite material according to claim 1, characterized in that, The second structural unit (22) containing PIN diodes includes multiple PIN diodes and multiple metallized rectangles that are sequentially soldered together; the second structural unit (22) containing PIN diodes is arranged in a grid-like periodic pattern, with the metallized rectangles serving as the negative electrode of the feed line and the PIN diodes serving as the positive electrode of the feed line.

3. The zero-power absorption tunable metasurface composite material according to claim 1, characterized in that, The resistive film (1) includes first structural units (11) arranged periodically along the x and y directions.

4. The zero-power absorption tunable metasurface composite material according to claim 1, characterized in that, The sheet resistance of the resistive film (1) is 65Ω / sq to 500Ω / sq, and the first structural unit (11) is a square ring structure unit.

5. The zero-power absorption tunable metasurface composite material according to claim 1, characterized in that, The core layer is made of a wave-transparent material.

6. The zero-power absorption tunable metasurface composite material according to claim 1, characterized in that the core layer include: The first core layer (6) is disposed between the resistive film (1) and the reflective back plate (5); The second core layer (7) is disposed between the electrically controlled metamaterial (2) and the resistive film (1); The third core layer (8) is located between the cross-shaped metal layer (3) and the electrically controlled metamaterial (2); The fourth core layer (9) is located between the square annular metal layer (4) and the cross-shaped metal layer (3).

7. The zero-power absorption tunable metasurface composite material according to claim 1, characterized in that, The panel (10) is a wave-transparent composite material with a relative permittivity of 2.7 to 5.6, a dielectric loss angle of 0.15 to 0.025, and a thickness of 0.1 mm to 1.5 mm.

8. The zero-power absorption tunable metasurface composite material according to claim 1, characterized in that, The reflective backplate (5) is made of conductive material.

9. A method for preparing a zero-power absorption tunable metasurface composite material according to any one of claims 1 to 8, characterized in that, Includes the following steps: The panel (10), the square ring metal layer (4), the cross-shaped metal layer (3), the electronically controlled metamaterial (2), the resistive film (1), the reflective back plate (5) and the core layer are laid out in sequence and then bonded, shaped and cut to obtain the final product.

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