Low-frequency wide-angle light 3D metamaterial wave-absorbing structure

Abstract

The invention discloses a low-frequency wide-angle light 3D (three-dimensional) metamaterial wave-absorbing structure. The wave-absorbing structure can realize a broadband wave-absorbing function with an average reflectivity of less than-10 dB in a frequency band of 0.5-2 GHz. The structural unit is composed of a planar resonant structure and a composite three-dimensional frame resonant structure, and the wave-absorbing structure is obtained by periodically arraying the unit structure. The wave-absorbing structure has the advantages of light weight, low-frequency broadband, excellent oblique incidence performance and the like, so that the wave-absorbing structure has a wide application prospect in the aspects of target stealth and electromagnetic protection.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of radar stealth and wave-absorbing materials, and particularly relates to a 3D composite wave-absorbing structure with low-frequency wide-angle wave-absorbing performance, which can be applied to radar detection, stealth technology, electromagnetic interference suppression and other military fields and electromagnetic protection fields. BACKGROUND

[0002] In the military field, with the rapid development of microwave radar technology, the working frequency band of radar is also continuously expanding. Since the low-frequency meter wave and decimeter wave have the advantages of long detection distance, large scanning area and short defense warning time, they play an increasingly important role in radar detection. However, the existing research work for the countermeasure of such detection mostly focuses on the design of wave-absorbing materials at a higher frequency band. Therefore, in recent years, in order to reduce the detection rate of long-wave radar on aircraft and improve the stealth capability of aircraft, the demand for wave-absorbing materials at the microwave low-frequency band, especially the P and L wave bands, becomes particularly urgent. In addition, the working frequency band of daily-used electronic products and communication equipment is mostly 0.5-3 GHz, which brings an increasingly serious electromagnetic interference problem. Research shows that the electromagnetic radiation in this frequency band can cause biological damage to the human body through thermal effects and cumulative effects, so the research on microwave low-frequency wave-absorbing materials is also extremely important in daily life.

[0003] The P wave band is close to the wavelength range of meter wave, and it is difficult to achieve wave-absorbing performance at a lower thickness by relying on traditional wave-absorbing materials. By using the characteristics of metamaterials that can achieve wave absorption at a thickness of several tenths of a wavelength, it is possible to design low-frequency wave-absorbing materials that meet the thickness requirements of actual installation. At present, the research on stealth technology of metamaterials at the P wave band is still basically at the initial stage, especially in the face of the challenge of current complex and variable anti-stealth means, so it is necessary to carry out research on high-performance and omnidirectional stealth technology for P and L wave radar waves, build an ultra-wideband intelligent stealth technology system, master the performance regulation of P wave and L wave wave-absorbing structures, break through the optimization design technology of polarization and wide-angle incidence stealth characteristics, and design multi-band, wide-angle, and lightweight wave-absorbing structures that take into account the P wave band and the L wave band, to provide theoretical and technical support for future high-performance stealth. SUMMARY

[0004] The purpose of the present application is to provide a low-frequency wide-angle 3D wave-absorbing structure design method. The wave-absorbing structure uses a multi-mode resonant planar structure to achieve low-frequency wideband wave absorption, and effectively improves the oblique incidence wave-absorbing performance through a composite three-dimensional frame resonant structure, and has the characteristics of low-frequency wideband wave absorption, good angle stability, and lightweight.

[0005] To achieve the above purpose, the present application provides the following technical scheme: A low-frequency wide-angle lightweight 3D metamaterial wave-absorbing structure, which is composed of a unit structure The unit structure is composed of a planar resonant structure, a middle three-dimensional frame structure and a bottom metal back plate; N is an integer greater than 20; The planar resonant structure is used for exciting multi-mode resonance to realize low-frequency broadband absorption; The middle three-dimensional frame structure is used for improving oblique incidence performance under horizontal polarization; The size of the unit structure and the resistance and inductance value of the loaded element are changed to adjust the wave-absorbing frequency band of the 3D metamaterial wave-absorbing structure.

[0006] Further, the planar resonant structure medium layer has a double-loop coupled metal resonant pattern printed on the front surface and working in a low-frequency band, and the double-loop coupled metal resonant pattern is connected by four patch inductors to form strong inductive and capacitive coupling between the double loops.

[0007] Further, the planar resonant structure has an outer loop metal strip pattern bent and covered on the back surface of the medium layer and connected with the metal strip pattern on the front surface of the planar resonant structure through a metal via hole, which effectively reduces the resonant frequency of the structure and reduces the unit period size of the structure, and improves the wave-absorbing performance under oblique incidence.

[0008] Further, four patch resistors are loaded at the bent corners of the metal line on the back surface of the planar resonant structure medium layer to realize loss absorption of resonant electromagnetic waves.

[0009] Further, a cross-shaped metal structure is added at the center position on the front surface of the planar resonant structure to increase the equivalent capacitance and inductance value of the structure, and realize low-frequency shift of the resonant frequency.

[0010] Further, the middle three-dimensional frame structure has a hole in the center to effectively reduce the overall weight of the structure. The middle three-dimensional frame structure has a metal bent line on the side surface and loads resistors and inductors at the center position, so that the vertical component of the incident wave electric field under horizontal polarization oblique incidence interacts with the resonant structure on the side surface of the middle three-dimensional frame structure and is loss absorbed, thereby effectively improving the oblique incidence performance under horizontal polarization.

[0011] Further, the planar resonant structure and the three-dimensional frame structure are separated by an air layer with a predetermined thickness.

[0012] Further, the side length of the planar resonant structure is p 1, the side length of the three-dimensional frame structure is p 2, and p 1> p 2. The 3D metamaterial wave-absorbing structure has good angle stability and can maintain an average reflectivity below -8 dB in the frequency band of 0.5-2 GHz under vertical polarization and horizontal polarization 60° oblique incidence.

[0013] Compared with the prior art, the present application has the following advantages: 1. In the low frequency broadband range of 0.5 GHz to 2 GHz, the 3D metamaterial wave-absorbing structure designed in the present application can realize the broadband wave-absorbing function with an average reflectivity less than -10 dB.

[0014] 2. The 3D metamaterial wave-absorbing structure designed in the present application has the characteristics of light weight and good angle stability, and thus has great application potential.

[0015] 3. The method for designing the metamaterial wave-absorbing structure with the planar resonant structure composite stereoscopic frame resonant structure provided by the present application provides a feasible scheme for improving the angle stability of the wave-absorbing structure. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 is a three-dimensional view of a periodic unit of the 3D metamaterial wave-absorbing structure; Figure 2 is a front view of a multi-mode resonant planar structure; Figure 3 is a back view of a multi-mode resonant planar structure; Figure 4 is a schematic diagram of the overall wave-absorbing structure of the periodic unit array; Figure 5 is a reflectivity curve of the 3D metamaterial wave-absorbing structure under normal incidence; Figure 6 is a reflectivity curve of the wave-absorbing structure when a transverse electric wave (TE wave) is obliquely incident at different incident angles; Figure 7 is a reflectivity curve of the wave-absorbing structure when a transverse magnetic wave (TM wave) is obliquely incident at different incident angles.

[0017] In the figure: 1, planar resonant structure; 2, patch inductance loaded on the front of the planar resonant structure; 3, cross-shaped metal patch; 4, inner circle resonant metal strip; 5, outer circle resonant metal strip; 6, metal through hole; 7, patch resistance loaded on the back of the planar resonant structure; 8, stereoscopic frame structure; 9, patch inductance loaded on the stereoscopic frame structure; 10, patch resistance loaded on the stereoscopic frame structure; 11, stereoscopic frame structure resonant metal strip; 12, metal back plate. DETAILED DESCRIPTION

[0018] The technical solutions of the present application will be described in detail below with reference to the accompanying drawings and specific examples.

[0019] The application is based on a multi-mode broadband wave-absorbing structure, and a three-dimensional frame resonant structure is combined to improve the oblique incidence performance, a low-frequency wide-angle light 3D metamaterial wave-absorbing structure is designed, and wideband wave absorption with an average reflectivity of less than -10 dB in the frequency range of 0.5-2 GHz is realized, and the angle stability is good, and the average reflectivity can be maintained below -8 dB in the working frequency range within the range of 60 degrees of incidence, and has good engineering application prospect.

[0020] Figure 4 The whole wave-absorbing structure is shown in the figure, which is obtained by Figure 1 20 array of the unit structure shown in the figure. The unit structure is composed of an upper plane resonant structure, a middle three-dimensional frame structure and a bottom metal back plate. The plane resonant structure is covered with metal resonant structures on both sides, and the width of the inner and outer metal rings on the front side is w 3 and w 4, connected by four patch inductors, marked as 2 in Figure 2 , with an inductance value of 87 nH. The outer metal ring is connected to the back of the dielectric layer through a metal via, and is arranged in a bending manner, thereby extending the length of the metal strip to the greatest extent in the limited size of the unit, realizing the miniaturization design of the structure resonating at a lower frequency, and the metal via is marked as 6 with a diameter size of d . It is found through simulation analysis that the surface current is concentrated at the corner position of the bent metal strip, so the patch resistance for loss excitation electromagnetic field is loaded at the four corner positions of the metal strip on the back of the dielectric, marked as 7 in Figure 3 , with a resistance value of 180 Ω. The cross-shaped metal structure in the center position of the front side of the dielectric layer has a width of w 2 and an arm length of a , which increases the equivalent capacitance and inductance value of the structure, and is beneficial to the shift of the resonant frequency of the structure to a low frequency. The dielectric layer material of the plane resonant structure is F4B, the dielectric constant is 4, the loss tangent is 0.001, and the thickness is h 1.

[0021] To optimize the oblique incidence performance, a three-dimensional frame structure is added between the plane resonant structure and the metal back plate. The dielectric layer material is the same as the plane structure, which is F4B, and the center of the structure is hollow, which effectively reduces the overall weight of the structure, the dielectric layer has a thickness of t , and the dielectric layer has a height of h 2. The side surface of the three-dimensional structure is covered with a metal bending line 11, marked as 11 in Figure 1 , and a 350 Ω resistance 9 and a 40 nH inductor 10 are loaded at the center position of the metal bending line, marked as 9 and 10 respectively. The plane resonant structure and the three-dimensional frame structure are separated by an air layer with a thickness of h 3, the side length of the plane resonant structure is p 1, and the side length of the three-dimensional frame structure isp 2.

[0022] By optimizing the design h 1、 h 2、 h 3、 w 1、 w 2、 w 3、 w 4、 l 1、 l 2、 l 3、 l 4、 p 1、 p 2、 t 、 d 、 m 、 n 、 s 、 a 、 b 、 q 、 g The values of 1, 2, 3 and 4 can achieve the wave-absorbing function of the wave-absorbing structure with reflectivity below -10 dB in a specific broadband frequency domain. In this example h 1=1mm、 h 2=23 mm、 h 3=6 mm、 w 1=2.5 mm、 w 2=3 mm、 w 3=1.2 mm、 w 4=1 mm、 l 1=16 mm、 l 2=8.5 mm、 l 3=9mm、 l 4=10 mm、 t =0.3 mm、 p 1=26.8 mm、 p 2=21 mm、 d =0.6 mm、 m =23.65 mm、 n =18mm、 s =2 mm、 a =14.8 mm、 b =1.8 mm、 q =14.21 mm、 g =1.8 mm, the total thickness of the overall wave-absorbing structure is 30 mm, and the size is 536 mm 536 mm, achieving the wave-absorbing function with average reflectivity less than -10 dB in a low-frequency broadband range from 0.5 GHz to 2 GHz, as shown in Figure 5 .

[0023] By the design method of combining the intermediate three-dimensional frame structure and minimizing the unit period, the oblique incidence performance of the overall wave-absorbing structure is effectively improved, especially the oblique incidence performance under horizontal polarization (TM polarization), and the average reflectivity can be kept below -12 dB in the range of 60° incidence angle, as shown in Figure 7 ; and under vertical polarization (TE polarization), the average reflectivity can be kept below -8 dB in the range of 60° incidence angle, as shown in Figure 6 .

[0024] The periodic unit structure of the application is composed of an upper plane resonant structure, an intermediate three-dimensional frame structure and a bottom metal back plate, Figure 1 which are marked as 1, 8 and 12 respectively. The plane resonant structure dielectric layer has a thickness of h 1, and the front and back surfaces are covered with metal structures and loaded with patch elements. The metal outer ring on the front surface is connected to the back surface of the dielectric layer through metal vias and is bent and distributed on the back surface, thereby increasing the current resonance path, reducing the resonance frequency, and realizing low-frequency resonance wave absorption. The three-dimensional frame structure can have an electric resonance with the vertical component of the electric field when oblique incidence occurs and be lost, thereby effectively optimizing the oblique incidence wave absorption performance under horizontal polarization. In addition, the reduction of the unit period size can make the phase difference between adjacent units of the wave-absorbing material as small as possible when oblique incidence occurs, reduce the difference in electromagnetic performance of the units when normal incidence occurs, meet the needs of the equivalent medium theory, thereby maintaining the wave-absorbing performance designed under normal incidence, and effectively improving the wave-absorbing performance under oblique incidence. Moreover, the structure is light and thin, with an equivalent medium thickness of 1.8 mm and a surface density of only 4.5 kg / m 2 . Then the unit structure is arranged in a periodic array to obtain a complete wave-absorbing structure, and by optimizing the setting of reasonable unit geometric parameters, low-frequency wide-angle wide-band wave-absorbing function can be realized.

[0025] The above description is only for the preferred embodiments of the application, and cannot limit the scope of the application. Any simple equivalent changes and modifications made according to the claims and the content of the application description shall still fall within the scope of the application.

Claims

1. A low-frequency wide-angle lightweight 3D metamaterial wave-absorbing structure, characterized in that: The 3D metamaterial wave-absorbing structure is obtained by arranging unit structures in N The unit structure is composed of an upper plane resonant structure, a middle three-dimensional frame structure and a bottom metal back plate; N is an integer greater than 20. The planar resonant structure is used for exciting multi-mode resonance, realizing low-frequency broadband absorption; The intermediate three-dimensional frame structure is used for improving oblique incidence performance under horizontal polarization; The size of the unit structure and the resistance and inductance value of the loaded element are changed to adjust the wave-absorbing frequency band of the 3D metamaterial wave-absorbing structure.

2. The 3D metamaterial wave-absorbing structure of claim 1, wherein: The planar resonant structure medium layer is printed with a double-loop coupled metal resonant pattern working in a low-frequency band on the front surface, and the double-loop coupled metal resonant pattern is connected by four patch inductors, so that the double loop forms strong inductive and capacitive coupling.

3. The 3D metamaterial wave absorbing structure of claim 2, wherein: The planar resonant structure covers the outer loop metal strip pattern on the back surface of the medium layer by bending, and connects the metal strip pattern on the front surface of the planar resonant structure through a metal via hole.

4. The 3D metamaterial wave absorbing structure of claim 3, wherein: Four patch resistors are loaded at the corners of the metal wire on the back surface of the planar resonant structure medium layer to realize loss absorption of resonant electromagnetic waves.

5. The 3D metamaterial wave absorbing structure of claim 1, wherein: A cross-shaped metal structure is added to the center of the front surface of the planar resonant structure to realize low-frequency shift of the resonant frequency.

6. The 3D metamaterial wave absorbing structure of claim 1, wherein: The intermediate three-dimensional frame structure is hollowed in the center, the side surface of the intermediate three-dimensional frame structure is covered with a metal bending line, and a resistance and an inductance are loaded at the center position, so that the vertical component of the incident wave electric field under horizontal polarization oblique incidence interacts with the resonant structure on the side surface of the intermediate three-dimensional frame structure and is loss absorbed.

7. The 3D metamaterial wave absorbing structure of claim 1, wherein: The planar resonant structure and the three-dimensional frame structure are separated by an air layer with a preset thickness.

8. The 3D metamaterial wave absorbing structure of claim 1, wherein: The side length of the planar resonant structure is p 1, the side length of the stereoscopic frame structure is p 2, and p 1> p 2.

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