An electrically controlled wave-absorbing composite material and a preparation method thereof

Abstract

The application discloses an electrically-controlled wave-absorbing composite material and a preparation method thereof, and belongs to the technical field of electromagnetic wave-absorbing materials. The electrically-controlled wave-absorbing composite material comprises, from top to bottom, a panel, an electrically-controlled metamaterial, a resistance film and a reflective back plate; a core layer is arranged between the panel, the electrically-controlled metamaterial, the resistance film and the reflective back plate; the resistance film comprises first structural units arranged periodically along x and y directions; the electrically-controlled metamaterial comprises second structural units containing PIN diodes arranged periodically along x and y directions; the PIN diodes are embedded into the structure and are integrally formed with the composite material. Therefore, the reliability of the electrically-controlled wave-absorbing material is improved.

Description

Technical Field

[0001] This invention belongs to the field of electromagnetic wave absorbing materials technology, specifically relating to an electrically controlled wave absorbing composite material and its preparation method. Background Technology

[0002] Electromagnetic wave absorption refers to the dissipation and absorption of energy from incident electromagnetic waves using high-loss materials or strong resonant structures. Generally speaking, electromagnetic wave absorption needs to meet two basic conditions: first, impedance matching must be used to maximize the penetration of the incident wave into the material; second, good attenuation characteristics must be used to dissipate the energy. Electromagnetic wave absorption technology improves radar performance and the stealth capabilities of weapons and equipment by coating with absorbing agents and using absorbing structures.

[0003] Metamaterial structures are artificial structures with precisely tunable electromagnetic properties, composed of periodic or aperiodic arrangements of subwavelength-scale unit structures, exhibiting electromagnetic characteristics opposite to those of conventional materials. Compared to traditional electromagnetic absorbing materials, metamaterial-based electromagnetic absorbing structures offer advantages such as low profile and superior structural performance, making them widely applicable in radar stealth. Since the performance of passive electromagnetic absorbing structures is fixed once fabricated, related research proposes loading materials with tunable conductivity into the absorbing structure to achieve dynamic control of reflectivity. Compared to other tunable absorbing materials, such as phase change materials, water-based or liquid metal-based tunable materials, and mechanically tunable materials, electrically controlled absorbing materials loaded with PIN diodes have the advantage of fast response speed and high engineering application value. However, in current research, active devices are exposed, leading to poor structural reliability and insufficient lifespan. Furthermore, related research lacks stealth performance outside the tunable frequency band. Summary of the Invention

[0004] To address the above problems, this invention provides an electrically controlled microwave absorbing composite material and its preparation method, in which a PIN diode is embedded inside the structure and integrally formed with the composite structure, thereby improving the reliability of the electrically controlled microwave absorbing material.

[0005] The first objective of this invention is to provide an electrically controlled microwave absorbing composite material, comprising, from top to bottom, a panel, an electrically controlled metamaterial, a resistive film, and a reflective backplate; a core layer is provided between the panel, the electrically controlled metamaterial, the resistive film, and the reflective backplate;

[0006] The resistive film includes first structural units arranged periodically along the x and y directions;

[0007] The electronically 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.

[0008] In a preferred embodiment of the present invention, the second structural unit containing PIN diodes includes a plurality of PIN diodes and a plurality of metallized zigzag lines welded together in sequence.

[0009] In a preferred embodiment of the present invention, the second structural unit containing PIN diodes is arranged in a grid-like periodic pattern, the metallized zigzag line serves as the negative electrode of the feed line, and the PIN diode serves as the positive electrode of the feed line.

[0010] In a preferred embodiment of the present invention, the sheet resistance of the resistive film is 65Ω / sq to 500Ω / sq; the first structural unit is a square ring structural unit.

[0011] In a preferred embodiment of the present invention, the core layer is a wave-transparent material.

[0012] In a preferred embodiment of the present invention, the core layer comprises:

[0013] The first core layer is disposed between the resistive film and the reflective backplate;

[0014] The second core layer is disposed between the electrically controlled metamaterial and the resistive film;

[0015] The third core layer is located between the electronically controlled metamaterial and the panel.

[0016] In a preferred embodiment of the present invention, the panel 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 to 1.5 mm.

[0017] In a preferred embodiment of the present invention, the reflective backplate is made of a conductive material.

[0018] A second objective of this invention is to provide a method for preparing the above-mentioned electrically controlled microwave absorbing composite material, comprising the following steps:

[0019] The panel, 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.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] In terms of structural performance, in the electrically controlled absorbing composite structure, the PIN diode is embedded inside the structure and integrally formed with it. Since the feed network containing the active devices is embedded entirely within the structure, it is protected, thereby improving the reliability of the electrically controlled absorbing material. In terms of electrical performance, the electrically controlled absorbing composite structure not only exhibits excellent dynamic reflectivity control performance within the band but also possesses wideband and strong absorption capabilities outside the band. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the electrically controlled absorbing composite structure provided in an embodiment of the present invention.

[0023] Figure 2 This is a schematic diagram of the resistive film in the electrically controlled microwave absorbing composite material provided in an embodiment of the present invention.

[0024] Figure 3 This is a schematic diagram of the electrically controlled metamaterial in the electrically controlled microwave absorbing composite structure provided in Embodiment 1 of the present invention.

[0025] Figure 4 The simulated reflectance spectrum of the electrically controlled absorbing composite structure is shown in Embodiment 1 of the present invention when the resistance value RP of the PIN diode changes and there is no resistive film.

[0026] Figure 5 The simulated reflectivity spectrum of the electrically controlled absorbing composite structure is given when the resistance value RP of the PIN diode varies in the range of 3Ω to 203Ω in Embodiment 1 of the present invention.

[0027] Figure 6 The simulated reflectivity spectrum of the electrically controlled absorbing composite structure is given when the resistance value RP of the PIN diode varies within the range of 253Ω to 1e+6Ω in Embodiment 1 of the present invention.

[0028] Figure 7 The simulated reflectivity spectrum of the electrically controlled absorbing composite structure is given when the PIN diode resistance RP is equal to 3Ω and the sheet resistance SR of the resistive film varies in the range of 85Ω / sq to 285Ω / sq in Embodiment 1 of the present invention.

[0029] Figure 8 This is the simulated reflectivity spectrum of the electrically controlled absorbing composite structure in Embodiment 1 of the present invention, when the PIN diode resistance RP is equal to 1e+6Ω and the sheet resistance SR of the resistive film varies in the range of 85Ω / sq to 285Ω / sq.

[0030] Figure 9 The reflectivity test spectrum of the electrically controlled absorbing composite structure under different bias voltages in Embodiment 1 of the present invention is shown.

[0031] Figure label:

[0032] 1-Resistive film, 2-Electrically controlled metamaterial, 3-Reflective backplate, 4-First core layer, 5-Second core layer, 6-Third core layer, 7-Panel, 11-First structural unit, 22-Second structural unit, h1-Thickness of the first core layer, h2-Thickness of the second core layer, h3-Thickness of the third 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-Stub length, g2-Stub spacing, g 22-PIN diode soldering area gap, l 22 - PIN diode soldering area length, d 22 -PIN diode soldering area width, w2-stub width. Detailed Implementation

[0033] 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.

[0034] As described in the background section, in current research, the active devices are exposed, often leading to poor reliability and insufficient lifespan of the composite structure. Furthermore, related research lacks stealth capabilities outside the tunable frequency band. To address these issues, this invention combines an electrically controlled metamaterial 2 and a resistive film 1, achieving integrated design, fabrication, and complementary advantages of both, thereby solving the aforementioned technical problems. The specific technical solution is as follows:

[0035] An electrically controlled microwave absorbing composite material comprises, from top to bottom, a panel 7, an electrically controlled metamaterial 2, a resistive film 1, and a reflective backplate 3; a core layer is provided between the panel 7, the electrically controlled metamaterial 2, the resistive film 1, and the reflective backplate 3;

[0036] The resistive film 1 includes first structural units 11 arranged periodically along the x and y directions;

[0037] It is understood that the present invention does not limit the type of the first structural unit 11; 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 size.

[0038] The electronically 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.

[0039] In the electrically controlled microwave absorbing composite material provided by the present invention, the panel 7 is set as the skin on the top of the structure to improve the mechanical strength of the electrically controlled microwave absorbing composite material. The electrically controlled metamaterial 2 dynamically adjusts the equivalent impedance at low frequency and transmits waves at high frequency. The resistive film 1 transmits waves at low frequency and loses electromagnetic waves at high frequency. The reflective backplate 3 is set at the bottom of the electrically controlled microwave absorbing composite material to provide an electrical boundary. The core layer is set as the core material in the middle of the structure to protect the active devices in the electrically controlled metamaterial 2 and the dielectric layer that serves as the electromagnetic structure.

[0040] In a preferred embodiment, the second structural unit 22 containing a PIN diode includes a PIN diode and a metallized zigzag line welded together in sequence;

[0041] The second structural unit 22 containing PIN diodes is arranged in a grid-like periodic pattern, with the metallized zigzag line serving as the negative electrode of the feed line and the PIN diode serving as the positive electrode of the feed line.

[0042] The electrically controlled metamaterial described in this invention is prepared using PCB technology. This invention does not impose any particular restrictions on the substrate in the electrically controlled metamaterial 2; any circuit board microwave board material well 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 0.08-0.3 mm.

[0043] It is understood that, in order to simplify the preparation process of the electrically controlled absorbing 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 electrically controlled absorbing composite material can be independently controlled under different polarizations. Specifically, the present invention proposes to achieve independent control of the reflectivity of the electrically controlled absorbing composite material under different polarizations by adjusting the external bias voltage.

[0044] In a preferred embodiment, the sheet resistance of the resistive film 1 is 65Ω / sq to 500Ω / sq; the first structural unit 11 is a square ring structural unit.

[0045] It is understandable that the resistive film 1 is prepared by screen printing process, and the substrate is a transparent film.

[0046] In a preferred embodiment, the core layer is a wave-transparent material, specifically, the core layer is a lightweight wave-transparent material such as foam or aramid honeycomb.

[0047] The core layer includes:

[0048] The first core layer 4 is disposed between the resistive film 1 and the reflective back plate 3; the thickness h1 of the first core layer 4 is 4.8±1.5mm;

[0049] The second core layer 5 is disposed between the electrically controlled metamaterial 2 and the resistive film 1; the thickness h2 of the second core layer 5 is 14.2±1.5mm;

[0050] The third core layer 6 is disposed between the electronically controlled metamaterial 2 and the panel 7, and the thickness h3 of the third core layer 6 is 3±1.5mm.

[0051] The present invention does not impose any particular restrictions on the thickness of the first core layer 4, the second core layer 5 and the third core layer 6, and the core material thickness will vary under different structural cycles.

[0052] It is understood that the present invention does not impose any particular limitations on the panel 7. Those skilled in the art can select and adjust the panel 7 according to the actual application, product quality and product performance. In a preferred embodiment, the panel 7 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 0.4 to 1 mm.

[0053] Specifically, the wave-transparent composite material is a wave-transparent fiber-reinforced resin-based composite material, wherein 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.

[0054] It is understood that the present invention does not impose any particular limitations on the reflective backplate 3. Those skilled in the art can select and adjust the reflective backplate 3 according to the actual application, product quality and product performance. In a preferred embodiment, the reflective backplate 3 is a conductive material with a thickness of 0.4 to 1 mm.

[0055] 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.

[0056] 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.

[0057] Unless otherwise specified, the methods described in the following embodiments are conventional methods; the reagents and materials mentioned are commercially available unless otherwise specified.

[0058] The technical solution of the present invention will be further described below with specific embodiments as examples.

[0059] Example 1

[0060] This embodiment provides an electrically controlled microwave absorbing composite material, specifically a foam-based sandwich composite material, such as... Figure 1 As shown, from top to bottom, it includes panel 7, third core layer 6, electro-controlled metamaterial 2, second core layer 5, resistive film 1, first core layer 4 and reflective backplate 3;

[0061] In this embodiment, the thickness h3 of the third core layer 6 is 3 mm, the thickness h2 of the second core layer 5 is 14.2 mm, and the thickness h1 of the first core layer 4 is 4.8 mm. The first core layer 4, the second core layer 5, and the third core layer 6 are foam core layers. The dielectric constant and loss angle of the first core layer 4, the second core layer 5, and the third core layer 6 range from 1.02 to 1.05 and from 0.002 to 0.008, respectively.

[0062] Panel 7 is a quartz fiber panel; the panel has a relative permittivity of 3.5, a dielectric loss angle of 0.006, and a thickness of 0.4 mm.

[0063] The reflective backplate 3 is a carbon fiber backplate with a relative permittivity of 0.006 and a thickness of 0.4 mm.

[0064] 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 17.8 mm, the outer side length l1 is 14.6 mm, and the inner side length g1 is 6.9 mm. That is, the spacing between adjacent first structural units 11 is p1-l1. 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 85 Ω / sq. The printing substrate of the resistive film is an FR-4 dielectric sheet with a thickness of 0.1 mm, a relative permittivity of 4.1, and a dielectric loss angle of 0.025°.

[0065] like Figure 3 As shown, in this embodiment, the electrically controlled metamaterial 2 includes a second structural unit 22. The second structural unit 22 includes two parts: a metallized zigzag line and a PIN diode.

[0066] The metallized zigzag line comprises multiple short segments, with a stub width w2 of 0.15 mm, a stub length l2 of 0.65 mm, and a stub spacing g2 of 0.15 mm. The length of the metallized zigzag line is l. t The calculation formula is as follows:

[0067] l t = (w2*2+g2*2)*n*2+w2.

[0068] Where n is the number of stubs in the zigzag line.

[0069] In this embodiment, the length of the metallized zigzag line unit is 4.65 mm. It should be noted that the metallized curve described in this invention is made of copper.

[0070] PIN diode soldering area length l 22 The width d of the PIN diode soldering area is 2.1mm. 22The gap g in the PIN diode soldering area is 0.5mm. 22 The area of ​​the PIN diode soldering region is much larger than the physical size of the PIN diode to reduce the impact of PIN diode displacement on adjustable performance. In this embodiment, the second structural unit 22 of the electronically controlled metamaterial 2 consists of three metallized zigzag lines and three PIN diodes, with a period p2 of 17.85 mm.

[0071] In this embodiment, the electrically controlled metamaterial 2 in the electrically controlled absorbing composite structure is a 17×17 unit array with a total size of 303.45mm×303.45mm. The feed method is as follows: Figure 2 As shown, at both ends of the electrically controlled metamaterial 2, the PIN diode and the metallized zigzag line serve as the positive and negative terminals of the feed line, respectively;

[0072] The electrically controlled metamaterial 2 was fabricated using PCB technology with FR-4 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 zigzag lines (feed lines) in the metal array were oriented in the same direction as the electric field polarization.

[0073] During preparation, the panel 7, the third core layer 6, the electronically controlled metamaterial 2, the second core layer 5, the resistive film 1, the first core layer 4 and the reflective backplate 3 are laid out in sequence, then bonded with adhesive, and processed using a hand lay-up molding process. After processing, it is cut to 330mm×330mm.

[0074] In this embodiment, a single PIN diode conducts at a voltage of 0.89V and a current of 4mA, while the electrically controlled absorbing composite structure conducts at a voltage of 44V and a current of 68mA. During the simulation, the resistance R of the PIN diode is measured in both conducting and non-conducting states. P These are equivalent to 1e+6Ω and 3Ω respectively; in diode adjustment mode, the resistance value of the PIN diode can be adjusted within the range of 3Ω to 1e+6Ω.

[0075] like Figure 4 As shown, when there is no resistive film layer 1 in the electrically controlled absorbing composite structure, when the equivalent resistance R of the PIN diode is... P From 3Ω to 1e+6Ω, within the 2-6GHz range, the simulated reflection first decreases and then increases; when R... P When the Ω is equal to 253Ω, the reflectivity reaches its minimum value, which is the optimal absorption performance.

[0076] like Figure 5 As shown, when the PIN diode is in the on-state, i.e., its equivalent resistance R PWhen the resistance is 3Ω, the electrically controlled metamaterial 2 in the electrically controlled absorbing composite structure is almost transparent to electromagnetic waves in the 2-6GHz range. However, due to the loss effect of the resistive film 1, its simulated reflectivity gradually decreases with increasing frequency spectrum. When the equivalent resistance R of the PIN diode... P As the impedance changes from 3Ω to 203Ω, the simulated reflectivity gradually decreases within the 2-6GHz range, indicating that the electrically controlled absorbing composite structure gradually transitions from a reflective state to an absorptive state. Simultaneously, due to the loss effect of resistive film 1, the simulated reflectivity of the electrically controlled absorbing composite structure is less than -10dB within the 6-18GHz range and less than -15dB within the 6-14GHz range.

[0077] like Figure 6 As shown, when the PIN diode is in the off state, i.e., its equivalent resistance R P When the resistance is 1e+6Ω, the electrically controlled metamaterial 2 in the electrically controlled absorbing composite structure almost reflects electromagnetic waves within the 2-6GHz range, and the simulated reflectivity of the electrically controlled absorbing composite structure is greater than -1dB. When the equivalent resistance R of the PIN diode... P As the resistance changes from 253Ω to 1e+6Ω, the simulated reflectivity gradually decreases within the 2-6GHz range, indicating that the electrically controlled absorbing composite structure gradually transitions from an absorption state to a reflection state. Simultaneously, due to the loss effect of resistive film 1, the simulated reflectivity of the electrically controlled absorbing composite structure is less than -10dB within the 6-18GHz range and less than -15dB within the 6-14GHz range.

[0078] like Figure 7 As shown, when the PIN diode is in the on-state, i.e., its equivalent resistance R P When the resistance is 3Ω, the electrically controlled metamaterial 2 in the electrically controlled absorbing composite structure is almost transparent to electromagnetic waves in the 2-6GHz range. However, due to the loss effect of the resistive film 1, its reflectivity gradually decreases with increasing frequency. When the sheet resistance SR of the resistive film 1 changes from 85Ω / sq to 285Ω / sq, the simulated reflectivity in the 8-18GHz range gradually decreases, but this change does not affect the reflectivity in the 2-6GHz range.

[0079] like Figure 8 As shown, when the PIN diode is in the off state, i.e., its equivalent resistance R P When the resistance is 1e+6Ω, the electrically controlled metamaterial 2 in the electrically controlled absorbing composite structure almost reflects electromagnetic waves within the 2-6GHz range, and the simulated reflectivity of the electrically controlled absorbing composite structure is greater than -1dB. When the sheet resistance SR of the resistive film 1 changes from 85Ω / sq to 285Ω / sq, the simulated reflectivity gradually decreases within the 8-18GHz range, and this change does not affect the reflectivity within the 2-6GHz range.

[0080] The electrically controlled absorbing composite structure was tested in a darkroom using the free-space method. Figure 9As shown, when the external bias voltage is adjusted from 0V to 43.8V, the tested reflectivity of the electrically controlled absorbing composite structure changes from -2dB to -20dB within the 2-6GHz range, with a tuning depth greater than 15dB. When the external bias voltage equals 28.8V, the reflectivity reaches its minimum value, i.e., optimal absorption performance. Within the 6-18GHz range, the tested reflectivity of the electrically controlled absorbing composite structure is below -8dB; within the 6-14GHz range, the tested reflectivity is below -15dB. The electrically controlled absorbing composite structure does not affect the absorption performance within the non-tunable 6-18GHz range during reflectivity tuning.

[0081] Example 2

[0082] This embodiment provides an electrically controlled microwave absorbing composite material, specifically a foam-based sandwich composite material, such as... Figure 1 As shown, from top to bottom, it includes panel 7, third core layer 6, electro-controlled metamaterial 2, second core layer 5, resistive film 1, first core layer 4 and reflective backplate 3;

[0083] In this embodiment, the thickness h3 of the third core layer 6 is 4.5 mm, the thickness h2 of the second core layer 5 is 12.7 mm, and the thickness h1 of the first core layer 4 is 3.3 mm. The first core layer 4, the second core layer 5, and the third core layer 6 are foam core layers. The dielectric constant and loss angle of the first core layer 4, the second core layer 5, and the third core layer 6 range from 1.02 to 1.05 and from 0.002 to 0.008, respectively.

[0084] Panel 7 is a quartz fiber panel; the panel has a relative permittivity of 3.5, a dielectric loss angle of 0.006, and a thickness of 1mm;

[0085] The reflective backplate 3 is a carbon fiber backplate with a relative permittivity of 0.006 and a thickness of 1 mm.

[0086] 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 17.8 mm, the outer side length l1 is 14.6 mm, and the inner side length g1 is 6.9 mm. That is, the spacing between adjacent first structural units 11 is p1-l1. In the preparation process, conductive paste is used to prepare the resistive film 1 by screen printing. In this embodiment, the sheet resistance of the resistive film layer is 55 Ω / sq. The printing substrate of the resistive film is an FR-4 dielectric sheet with a thickness of 0.1 mm, a relative permittivity of 4.1, and a dielectric loss angle of 0.025°.

[0087] Example 3

[0088] This embodiment provides an electrically controlled microwave absorbing composite material, specifically a foam-based sandwich composite material, such as... Figure 1As shown, from top to bottom, it includes panel 7, third core layer 6, electro-controlled metamaterial 2, second core layer 5, resistive film 1, first core layer 4 and reflective backplate 3;

[0089] In this embodiment, the thickness h3 of the third core layer 6 is 1.5 mm, the thickness h2 of the second core layer 5 is 15.7 mm, and the thickness h1 of the first core layer 4 is 6.3 mm. The first core layer 4, the second core layer 5, and the third core layer 6 are foam core layers. The dielectric constant and loss angle of the first core layer 4, the second core layer 5, and the third core layer 6 range from 1.02 to 1.05 and from 0.002 to 0.008, respectively.

[0090] Panel 7 is a quartz fiber panel; the panel has a relative permittivity of 3.5, a dielectric loss angle of 0.006, and a thickness of 0.8 mm.

[0091] The reflective backplate 3 is a carbon fiber backplate with a relative permittivity of 0.006 and a thickness of 0.8 mm.

[0092] In this embodiment, the resistive film 1 is a first structural unit 11 arranged in a circular periodic pattern. The first structural unit 11 has an outer diameter of 15 mm and an inner diameter of 7 mm. That is, the spacing between adjacent first structural units 11 is 3 mm. In the preparation process, conductive paste is used to prepare the resistive film 1 by screen printing. In this embodiment, the sheet resistance of the resistive film layer is 250 Ω / sq. The printing substrate of the resistive film is an FR-4 dielectric sheet with a thickness of 0.1 mm, a relative permittivity of 4.1, and a dielectric loss angle of 0.025°.

[0093] It should be noted that the material of the structure in this invention is merely one embodiment of the invention, and the specific choice should be determined according to the actual situation. This invention does not impose any limitations on this. It should also be noted that the above structural dimensions are only one embodiment, provided as an example. Specific dimensional variations should be determined according to the actual situation. This invention does not impose any limitations on this.

[0094] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention.

[0095] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. An electrically controlled microwave absorbing composite material, characterized in that, From top to bottom, it includes a panel (7), an electronically controlled metamaterial (2), a resistive film (1), and a reflective backplate (3); a core layer is provided between the panel (7), the electronically controlled metamaterial (2), the resistive film (1), and the reflective backplate (3); The resistive film (1) includes first structural units (11) arranged periodically along the x and y directions; the first structural unit (11) is a square ring structural unit; 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 second structural unit (22) containing PIN diodes includes a plurality of PIN diodes and a plurality of metallized zigzag lines welded in sequence; the second structural unit (22) containing PIN diodes is arranged in a grid-like periodic pattern, the metallized zigzag lines serve as the negative electrode of the feed line, and the PIN diodes serve as the positive electrode of the feed line.

2. The electrically controlled microwave absorbing composite material according to claim 1, characterized in that, The sheet resistance of the resistive film (1) is 65Ω / sq~500Ω / sq.

3. The electrically controlled microwave absorbing composite material according to claim 1, characterized in that, The core layer is a wave-transparent material.

4. The electrically controlled microwave absorbing composite material according to claim 1, characterized in that, The core layer includes: The first core layer (4) is disposed between the resistive film (1) and the reflective back plate (3); The second core layer (5) is disposed between the electrically controlled metamaterial (2) and the resistive film (1); The third core layer (6) is disposed between the electro-controlled metamaterial (2) and the panel (7).

5. The electrically controlled microwave absorbing composite material according to claim 1, characterized in that, The panel (7) 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 0.1~1.5mm.

6. The electrically controlled microwave absorbing composite material according to claim 1, characterized in that, The reflective backplate is made of conductive material.

7. A method for preparing the electrically controlled microwave absorbing composite material according to any one of claims 1-6, characterized in that, Includes the following steps: The panel (7), the electronically controlled metamaterial (2), the resistive film (1), the reflective backplate (3) and the core layer are laid out in sequence and then bonded, shaped and cut to obtain the final product.

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