A broadband large-angle electromagnetic wave absorbing metasurface

Abstract

The application relates to a broadband large-angle electromagnetic wave absorption metasurface, which belongs to the field of radio frequency passive devices in radio frequency technology and is an electromagnetic wave absorption metasurface.The absorption metasurface is a three-layer structure, and the top layer is a dielectric plate, the middle layer is an absorption metasurface layer, and the bottom layer is a dielectric plate; the absorption metasurface layer is composed of a plurality of metasurface units arranged in combination; each metasurface unit is composed of a microstrip line, a patch resistor and a square patch with a metal branch; due to the central symmetry of the absorber, the absorber has polarization insensitivity under normal incidence, that is, the absorber has the same absorption effect on x polarization and y polarization; the broadband large-angle electromagnetic wave absorption metasurface can realize wideband RCS reduction, low profile, easy preparation, simple design and effective absorption of incident waves with a large incidence angle.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of radio frequency regulation, and relates to a broadband large-angle electromagnetic wave absorption metasurface, in particular to a radio frequency passive device in the technical field of radio frequency, and particularly relates to a technology and application for reducing a radar cross section (RCS) in a wide frequency range and a large angle range. BACKGROUND

[0002] With the advent of the 5G era, wireless communication technology has developed rapidly. The metasurface is a kind of special electromagnetic material artificially composed, which has super electromagnetic properties that cannot exist in nature. As a two-dimensional form of metamaterial, it has more functions and greater flexibility in electromagnetic structure design, in addition to the characteristics of low profile, easy preparation and simple design. The metasurface is loaded on the antenna to realize the reduction of the radar cross section. Secondly, the introduction of the metasurface into the antenna also makes the antenna design have more possibilities, such as lower profile, higher gain, more frequency bands and smaller size. Although the non-absorbing metasurface can achieve wideband RCS reduction, it is mainly for normal incidence. When the angle of the incident wave exceeds 30°, the RCS reduction performance will deteriorate rapidly. Now the detection of radar targets is basically double-station detection, so it is imperative to design an absorbable low RCS metasurface for large-angle incident waves.

[0003] In the application, by introducing pure dielectric layers and resistors in the design, impedance matching and large-angle absorption are realized, and an equivalent circuit is established in the design to optimize the parameters and make the unit achieve the best performance. Through simulation verification, the broadband large-angle absorption metasurface in this paper has a frequency range of 5-19GHz when the angle of the incident wave is 0°, and the reflection coefficient is less than-10dB. More importantly, when the incident wave is incident at an angle of 60°, the reflection coefficient of the array is still less than-8dB within the working frequency band. The overall thickness of the array is only 7mm, realizing low profile. Due to the central symmetry of the absorber, it has polarization insensitivity under normal incidence, that is, it has the same absorption effect for x polarization and y polarization. SUMMARY

[0004] In view of the problems in the prior art, the application provides a broadband large-angle electromagnetic wave absorption metasurface. The broadband large-angle electromagnetic wave absorption metasurface proposed in the application is a new type of radio frequency passive device, which can effectively absorb incident electromagnetic waves in a wide frequency range and a large angle range, thereby significantly reducing the RCS of the target.

[0005] In order to achieve the above purpose, the technical scheme adopted by the application is as follows:

[0006] The application discloses a broadband large-angle electromagnetic wave absorbing metasurface, which is a three-layer structure from top to bottom, namely a top dielectric plate, a middle absorbing metasurface layer and a lower dielectric plate.

[0007] The front surface of the lower dielectric plate is printed with metal to form a metasurface unit, and a plurality of patch resistors with the same structure are arranged at specific positions on the front surface; and the back surface of the lower dielectric plate is printed with a metal floor 17.

[0008] The top dielectric plate is a top square dielectric plate 3, which is a polytetrafluoroethylene (F4b) substrate with a dielectric constant of 2.65 and a thickness of 1-5 mm.

[0009] Further, the resistance of the patch resistor is 150-300 ohms.

[0010] Further, the metal floor (17) is printed on the lower surface of the lower square dielectric plate (4) and has a thickness of 0.018-0.05 mm.

[0011] Further, the lower surface of the top dielectric plate is located at a distance of 0.1-2 mm from the upper surface of the lower dielectric plate, and the lower surface of the top dielectric plate is not in contact with the upper surface of the absorbing metasurface. The top dielectric plate provides a proper reactive loading effect, optimizes the impedance matching between the metasurface unit and air, and makes the wave absorbing effect of the metasurface unit obviously optimized.

[0012] Further, the super surface unit comprises two microstrip lines, four square patches, and eight patch resistors. The microstrip lines comprise a first microstrip line 1 and a second microstrip line 2, which are of the same size and arranged in a cross shape, with the center points of the microstrip lines coinciding with the center point of the lower dielectric plate. The cross-shaped microstrip lines divide the lower dielectric plate into four areas for placing the square patches. The square patches comprise a first square patch 5, a second square patch 6, a third square patch 7, and a fourth square patch 8, which are of the same size. If the edge of each square patch close to the microstrip line is defined as an inner edge, then: two outer edges of each square patch are parallel to the edges of the lower dielectric plate, two inner edges are parallel to the microstrip lines, and a metal stub is arranged at the middle of each inner edge. The end of each metal stub is not in contact with the microstrip line, and a patch resistor is arranged at the interval, so that there are eight patch resistors, namely a first patch resistor 9, a second patch resistor 10, a third patch resistor 11, a fourth patch resistor 12, a fifth patch resistor 13, a sixth patch resistor 14, a seventh patch resistor 15, and an eighth patch resistor 16. The microstrip lines are connected to the square patches through the patch resistors.

[0013] Further, the first microstrip line 1 and the second microstrip line 2 are perpendicular to each other, and the center position of the lower square dielectric plate 4 is arranged to form a cross-shaped structure. The first microstrip line 1 is located at the center of the horizontal part of the second microstrip line 2, and forms a cross-shaped structure with the second microstrip line 2. The entire absorption super surface unit is symmetric about the cross-shaped structure in the middle.

[0014] Further, the four square metal patches with metal stubs are printed on the four corners of the upper surface of the lower square dielectric plate 4, forming a center-symmetric structure about the cross-shaped center formed by the first microstrip line 1 and the second microstrip line 2. The edge of the square metal patch is 0.05-0.25 mm away from the edge of the lower square dielectric plate 4. The two edges with metal stubs are both directed towards the cross-shaped center formed by the first microstrip line 1 and the second microstrip line 2. The metal stub of the metal patch is located at the length center of the adjacent two edges of the adjacent square patches, which are perpendicular to each other. The metal stub is square-shaped, with a side length of 0.1-1.0 mm.

[0015] Further, the eight patch resistors are located between the cross-shaped structure formed by the two microstrip lines and the four square metal patches, and are used for connecting the cross-shaped structure formed by the microstrip lines and the square metal patches, so that the performance of the absorption metasurface is improved. Specifically, the cross-shaped structure formed by the first microstrip line 1 and the second microstrip line 2 is connected with the first square patch 5 through the first patch resistor 9 and the second patch resistor 10, connected with the second square patch 6 through the third patch resistor 11 and the fourth patch resistor 12, connected with the third square patch 7 through the fifth patch resistor 13 and the sixth patch resistor 14, and connected with the fourth square patch 8 through the seventh patch resistor 15 and the eighth patch resistor 16. The metal structure is printed on the upper surface of the lower square dielectric plate 4, and the metal ground 17 is printed on the lower surface of the lower square dielectric plate 4.

[0016] Further, a plurality of absorption metasurface units are used to form a metasurface array, and the gap between the metal layers of adjacent metasurface units ranges from 0.1 mm to 0.5 mm.

[0017] Compared with the prior art, the beneficial effects of the present application are:

[0018] (1) The wideband large-angle electromagnetic wave absorption metasurface provided by the present application can realize wideband RCS reduction, low profile, easy preparation and simple design. Specifically, patch resistors are installed on the metasurface layer, which convert the incident electromagnetic wave energy into heat energy, thereby realizing wideband RCS reduction, low profile, and simple and easy-to-design unit structure.

[0019] (2) The present application can effectively absorb incident waves with large incident angles. Specifically, this is achieved by adding a top dielectric plate. The top layer is a pure dielectric layer without metallization, which helps to improve the impedance matching of large-angle incident waves and optimize the absorption performance.

[0020] (3) According to simulation verification, when the wideband large-angle electromagnetic wave absorption metasurface unit is used, the frequency range of the reflection coefficient less than -10 dB is 5-19 GHz when the incident wave angle is 0°. When the incident wave incident angle is 60°, the reflection coefficient of the array in the working frequency band is still less than -8 dB. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 is a plan view of the wideband large-angle electromagnetic wave absorption metasurface array provided by the present application.

[0022] Figure 2 is a plan view of the wideband large-angle electromagnetic wave absorption metasurface unit provided by the present application.

[0023] Figure 3 is a side view of the wideband large-angle electromagnetic wave absorption metasurface unit provided by the present application.

[0024] Figure 4 is the reflection coefficient of the broadband large-angle electromagnetic wave absorption metasurface unit structure obtained by simulation. Among them, the incident wave is x-polarized wave and y-polarized wave, and the incident angle is 0°, 45° and 60°, respectively. Figure 4 (a) in is the simulation reflection coefficient diagram of the absorption metasurface unit when the y-polarized wave is incident; Figure 4 (b) in is the simulation reflection coefficient diagram of the absorption metasurface unit when the x-polarized wave is incident.

[0025] In the figure: 1 first microstrip line; 2 second microstrip line; 3 upper square dielectric plate; 4 lower square dielectric plate; 5 first square patch; 6 second square patch; 7 third square patch; 8 fourth square patch; 9 first patch resistor; 10 second patch resistor; 11 third patch resistor; 12 fourth patch resistor; 13 fifth patch resistor; 14 sixth patch resistor; 15 seventh patch resistor; 16 eighth patch resistor; 17 metal ground plate. DETAILED DESCRIPTION

[0026] The specific embodiments of the present application will be described in detail below in combination with the drawings and technical solutions of the present application.

[0027] Reference Figure 1 , Figure 2 and Figure 3 , the broadband large-angle electromagnetic wave absorption metasurface described in the present application is a three-layer structure, the microstrip line and the square patch are printed on the upper surface of the lower square dielectric plate 4, the patch resistors are installed on the upper surface of the lower square dielectric plate 4, and the metal ground plate 17 is printed on the lower surface of the lower square dielectric plate 4. The thicknesses of all the metal microstrip lines, metal patches and metal ground plate 17 are 0.035 mm. The materials of the upper square dielectric plate 3 and the lower square dielectric plate 4 are selected from F4b, the dielectric constant of which is 2.65, and the thickness is 3 mm.

[0028] Further, the length of the first microstrip line 1 and the second microstrip line 2 is 7.6 mm, and the width is 0.6 mm. The side length of the square patch is 2.5 mm, and the thickness is 0.035 mm. The edge of the square metal patch is 0.2 mm away from the edge of the lower square dielectric plate 4. The metal branch is a square with a side length of 0.5 mm and a thickness of 0.035 mm. The resistance of the patch resistor is 200Ω. The side length and thickness of the upper square dielectric plate and the lower square dielectric plate are 8 mm and 3 mm, respectively. The side length of the metal ground plate is 8 mm, and the thickness is 0.035 mm.

[0029] Further, 23*23 absorption metasurface units are used to form a metasurface array, and the physical size of the array is 184 mm*184 mm.

[0030] Figure 4 is a reflection coefficient curve diagram obtained by simulation of the broadband large-angle electromagnetic wave absorption metasurface unit. In Figure 4 In the simulation results of the unit of (a), when the incident angle of the y-polarized wave is 0°, the frequency range of the reflection coefficient below -10 dB is 5-19 GHz. Since the absorption metasurface unit is polarization-insensitive, Figure 4 (b) shows that the same frequency range exists for the x-polarized wave with an incident angle of 0°.

[0031] Figure 4 (a) shows that when the angle of the incident wave is 45°, the frequency range of the reflection coefficient of the y-polarized unit simulation below -10 dB is 5.25-18.66 GHz; Figure 4 (b) shows that the frequency range of the reflection coefficient of the x-polarized unit simulation below -10 dB is 6-16.63 GHz.

[0032] Figure 4 (a) shows that when the angle of the incident wave is 60°, the frequency range of the reflection coefficient of the y-polarized unit simulation below -8 dB is 5.43-18.44 GHz; Figure 4 (b) shows that the frequency range of the reflection coefficient of the x-polarized unit simulation below -8 dB is 6.6-15.7 GHz.

[0033] The above examples are only for illustrating the technical concept and characteristics of the present application, only for specifically describing the present application, so that those skilled in the art can understand the content of the present application and implement it, and cannot limit the protection scope of the present application. Any equivalent changes or modifications made according to the content of the present application should be covered within the protection scope of the present application.

Claims

1. A broadband, large-angle electromagnetic wave absorbing metasurface, characterized in that: The broadband, wide-angle electromagnetic wave absorption metasurface has a three-layer structure, consisting of a top dielectric plate, a middle absorption metasurface layer, and a bottom dielectric plate. The absorption metasurface layer is composed of a plurality of metasurface units with the same structure. Each metasurface unit is composed of a microstrip line, a chip resistor, and a square patch with metal branches. The top dielectric plate and the lower dielectric plate have the same size; The front side of the lower dielectric plate is printed with metal as the central absorption super surface layer, and the back side of the lower dielectric plate is printed with a metal floor (17); The metasurface unit includes two microstrip lines, four square patches, and eight chip resistors; specifically: The microstrip line comprises a first microstrip line (1) and a second microstrip line (2), both of which are of the same size and arranged in a cross shape. The center point of the microstrip line coincides with the center point of the lower dielectric plate. The cross-shaped microstrip line divides the lower dielectric plate into four areas for placing square patches. The entire absorption metasurface unit is symmetrical about the cross-shaped structure in the middle. The four square patches have the same size, and each square patch has a metal branch in the middle of its inner edge; the end of each metal branch does not contact the microstrip line, and a chip resistor is installed at the interval, that is, the microstrip line is connected to the square patch through the chip resistor; The square patch is printed on the four corners of the upper surface of the lower square dielectric plate (4), forming a central symmetrical structure about the center of the cross formed by the first microstrip line (1) and the second microstrip line (2); the two sides with metal branches are both oriented towards the center of the cross formed by the first microstrip line (1) and the second microstrip line (2); the metal branches of the square patch are located at the center of the length of two adjacent sides of adjacent square patches that are perpendicular to each other, and the metal branches are square.

2. The broadband, large-angle electromagnetic wave absorbing metasurface according to claim 1, characterized in that: The top dielectric plate is an upper square dielectric plate (3) made of a polytetrafluoroethylene-based dielectric plate; the lower dielectric plate is a lower square dielectric plate (4) made of a polytetrafluoroethylene-based dielectric plate.

3. The broadband, large-angle electromagnetic wave absorbing metasurface according to claim 1, characterized in that: In the absorption super surface layer, the gap between adjacent super surface unit metal layers ranges from 0.1 to 0.5 mm.

4. The broadband, large-angle electromagnetic wave absorbing metasurface according to claim 1, characterized in that: The lower surface of the top dielectric plate is located 0.1 to 2 mm away from the upper surface of the lower dielectric plate, and the lower surface of the top dielectric plate does not contact the upper surface of the absorbing metasurface.

5. The broadband, large-angle electromagnetic wave absorbing metasurface according to claim 1, characterized in that: The resistance of the chip resistor is 150~300Ω.

6. The broadband, large-angle electromagnetic wave absorbing metasurface according to claim 1, characterized in that: The distance between the edge of the square patch and the edge of the lower square dielectric plate (4) is 0.05-0.25 mm; and the side length of the metal branch is 0.1-1.0 mm.

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