Broadband wide-angle electromagnetic wave absorption metasurface

Abstract

A broadband wide-angle electromagnetic wave absorption metasurface belongs to the field of radio frequency passive devices in the radio frequency technology, and is an electromagnetic wave absorption metasurface which is of a three-layer structure and sequentially comprises a top dielectric plate, a middle absorption metasurface layer and a lower dielectric plate from top to bottom. The absorption metasurface layer is formed by arranging and combining a plurality of metasurface units with the same structure; each metasurface unit is composed of a microstrip line, a chip resistor and a square chip with a metal branch knot. Due to the central symmetry characteristic of the absorber, the absorber has polarization insensitivity under normal incidence, namely, the absorber has the same absorption effect on x polarization and y polarization. The broadband large-angle electromagnetic wave absorption metasurface provided by the invention can realize broadband RCS reduction, is low in profile, easy to prepare and simple in design, and can effectively absorb incident waves at a large incident angle.

Description

Technical Field

[0001] The present invention belongs to the field of radio frequency control technology, and relates to a broadband and large-angle electromagnetic wave absorbing metasurface, specifically a radio frequency passive device in the field of radio frequency technology, and especially a technology and application for reducing a broadband and large-angle radar cross section (RCS). Background Art

[0002] With the advent of the 5G era, wireless communication technology has developed rapidly. Metasurface is a special artificial electromagnetic material with extraordinary electromagnetic properties that are difficult to exist in nature. As a two-dimensional form of metamaterial, in addition to the characteristics of low profile, easy preparation, and simple design, it shows more functions and greater flexibility in electromagnetic structure design. The radar cross section is reduced by loading the metasurface on the antenna. Secondly, the introduction of metasurface into the antenna also makes antenna design have more possibilities, such as lower profile, higher gain, more frequency bands, and smaller size. Although non-absorbent metasurfaces can achieve broadband RCS reduction, it is mainly for normal incidence. Once the angle of the incident wave exceeds 30°, its RCS reduction performance will deteriorate rapidly. Now the detection of radar targets is basically dual-station detection, so it is imperative to design an absorbent low RCS metasurface for large-angle incident waves.

[0003] In the present invention, impedance matching and wide-angle absorption are achieved by introducing a pure dielectric layer and a resistor in the design, and an equivalent circuit is established in the design to optimize the parameters so that the unit achieves the best performance. Through simulation verification, the broadband wide-angle absorption metasurface in this article has a reflection coefficient lower than -10dB in the frequency range of 5-19GHz when the incident wave angle is 0°. More importantly, when the incident wave angle of incidence is 60°, the reflection coefficient of the array in the working frequency band is still lower than -8dB. The overall thickness of the array is only 7mm, achieving a low profile. Due to the centrosymmetric characteristics of the absorber, it is polarization-insensitive under normal incidence, that is, it has the same absorption effect on x-polarization and y-polarization. Summary of the invention

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

[0005] In order to achieve the above object, the technical solution adopted by the present invention is:

[0006] A broadband large-angle electromagnetic wave absorption metasurface, wherein the broadband large-angle electromagnetic wave absorption metasurface is a three-layer structure, which is composed of a top dielectric plate, a middle absorption metasurface layer and a bottom dielectric plate from top to bottom. The absorption metasurface layer is composed of a plurality of metasurface units with the same structure arranged and combined. Each metasurface unit is composed of a microstrip line, a patch resistor, and a square patch with metal branches.

[0007] The front side of the lower dielectric plate is printed with metal to form a metasurface unit, and a plurality of chip resistors with the same resistance and structure are installed at specific positions on the front side; the back side of the lower dielectric plate is printed with a metal floor 17. The top dielectric plate and the lower dielectric plate have the same size.

[0008] The top dielectric plate is an upper square dielectric plate 3, which is a polytetrafluoroethylene (F4b) substrate with a dielectric constant of 2.65 and a thickness of 1 to 5 mm. The lower dielectric plate is a lower square dielectric plate 4, which is a F4b substrate with a dielectric constant of 2.65 and a thickness of 1 to 5 mm.

[0009] Furthermore, the resistance of the chip resistor is 150-300Ω.

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

[0011] Furthermore, 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. The top dielectric plate provides an appropriate reactive load effect, optimizes the impedance matching between the metasurface unit and the air, and significantly optimizes the wave absorbing effect of the metasurface unit.

[0012] Furthermore, the metasurface unit includes two microstrip lines, four square patches, and eight patch resistors. The microstrip lines include a first microstrip line 1 and a second microstrip line 2, 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 the square patches. The square patch includes a first square patch 5, a second square patch 6, a third square patch 7, and a fourth square patch 8. The four have the same size, and their edges close to the microstrip line are defined as inner edges. Then: the two outer edges of each square patch are parallel to the edges of the lower dielectric plate, the two inner edges are parallel to the microstrip line, and a metal branch is provided in the middle of each inner edge; the end of each metal branch does not contact the microstrip line, and a chip resistor is installed at the interval. There are eight chip resistors in total, namely the first chip resistor 9, the second chip resistor 10, the third chip resistor 11, the fourth chip resistor 12, the fifth chip resistor 13, the sixth chip resistor 14, the seventh chip resistor 15, and the eighth chip resistor 16; the microstrip line is connected to the square patch through the chip resistor.

[0013] Furthermore, 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 placed to form a cross structure. The first microstrip line 1 is located at the center of the horizontal part of the second microstrip line 2, forming a cross structure with the second microstrip line 2, and the entire absorption metasurface unit is symmetrical about the cross structure in the middle.

[0014] Furthermore, the four metal patches with metal branches of the same size are 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, and 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 sides with metal branches are both facing the center of the cross formed by the first microstrip line 1 and the second microstrip line 2. The metal branches of the metal patch are located at the center of the length of two adjacent sides of the adjacent square patches that are perpendicular to each other, and the metal branches are square with a side length of 0.1-1.0 mm.

[0015] Furthermore, the eight chip resistors are located between the metal branches of the four square patches and the cross-shaped structure formed by the two microstrip lines, and are used to connect the square metal patches and the cross-shaped structure formed by the microstrip lines to improve the performance of the absorption metasurface. Specifically: the cross-shaped structure formed by the first microstrip line 1 and the second microstrip line 2 is connected to the first square patch 5 through the first patch resistor 9 and the second patch resistor 10, respectively, and is connected to the second square patch 6 through the third patch resistor 11 and the fourth patch resistor 12, and is connected to the third square patch 7 through the fifth patch resistor 13 and the sixth patch resistor 14, and is connected to the fourth square patch 8 through the seventh patch resistor 15 and the eighth patch resistor 16. The formed 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] Furthermore, a plurality of absorbing metasurface units are used to form a metasurface array, and the gap between the metal layers of adjacent metasurface units ranges from 0.1 to 0.5 mm.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] (1) The broadband, large-angle electromagnetic wave absorption metasurface provided by the present invention can achieve broadband RCS reduction, low profile, easy preparation, and simple design. Specifically, chip resistors are installed on the metasurface layer. These resistors convert the incident electromagnetic wave energy into heat energy, thereby achieving broadband RCS reduction, low profile, and regular unit structure, so the preparation and design are simple and easy.

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

[0020] (3) The present invention verifies through simulation that when the incident wave angle of the broadband large-angle electromagnetic wave absorption metasurface unit is 0°, the reflection coefficient is lower than -10dB in the frequency range of 5-19GHz. When the incident wave angle is 60°, the reflection coefficient of the array in the working frequency band is still lower than -8dB. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic diagram of the planar structure of the broadband and large-angle electromagnetic wave absorption metasurface array proposed in the present invention.

[0022] Figure 2 It is a schematic diagram of the planar structure of the broadband and large-angle electromagnetic wave absorption metasurface unit proposed in the present invention.

[0023] Figure 3 It is a side view of the broadband, large-angle electromagnetic wave absorption metasurface unit proposed in the present invention.

[0024] Figure 4 is the reflection coefficient obtained by simulating the broadband and large-angle electromagnetic wave absorption metasurface unit structure proposed in the present invention, wherein the incident waves are x-polarized waves and y-polarized waves, and the incident angles are 0°, 45°, and 60°, respectively. Figure 4 (a) is the simulated reflection coefficient diagram of the absorbing metasurface unit when the y-polarized wave is incident; Figure 4 (b) in the figure is the simulated reflection coefficient diagram of the absorbing metasurface unit when x-polarized wave is incident.

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

[0026] The specific implementation scheme of the present invention is described in detail below in conjunction with the accompanying drawings and technical solutions of the specification.

[0027] refer to Figure 1 , Figure 2 and Figure 3 The broadband large-angle electromagnetic wave absorption metasurface of the present invention is a three-layer structure. The microstrip lines and square patches 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 floor 17 is printed on the lower surface of the lower square dielectric plate 4. The thickness of all metal microstrip lines, metal patches and metal floor 17 is 0.035mm. The material of the upper square dielectric plate 3 and the lower square dielectric plate 4 is F4b, which has a dielectric constant of 2.65 and a thickness of 3mm.

[0028] Furthermore, 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 square, with a side length of 0.5 mm and a thickness of 0.035 mm. The resistance of the patch resistor is 200 Ω. The side length and thickness of the upper and lower square dielectric plates are 8 mm and 3 mm respectively. The side length of the metal floor is 8 mm, and the thickness is 0.035 mm.

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

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

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

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

[0033] The above examples are only for illustrating the technical concept and features of the present invention, and are only used for a specific description of the present invention so that people familiar with the technology can understand the content of the present invention and implement it accordingly, and cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the content of the present invention should be included in the protection scope of the present invention.

Claims

1. A broadband, large-angle electromagnetic wave absorbing metasurface, characterized in that: The broadband, large-angle electromagnetic wave absorption metasurface is a three-layer structure, which consists of a top dielectric plate, a middle absorption metasurface layer and a lower dielectric plate from top to bottom; the absorption metasurface layer is composed of a plurality of metasurface units with the same structure arranged and combined; each metasurface unit is composed of a microstrip line, a patch resistor and a square patch with metal branches.

2. The broadband, large-angle electromagnetic wave absorbing metasurface according to claim 1, characterized in that: The top dielectric plate has the same size as the lower dielectric plate; The front side of the lower dielectric plate is printed with metal as the absorption super surface layer in the middle, and a plurality of chip resistors with the same resistance value and structure are installed at specific positions on the front side; the back side of the lower dielectric plate is printed with a metal floor (17).

3. 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.

4. The broadband and 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.

5. 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 is not in contact with the upper surface of the absorbing super surface.

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

7. The broadband and large-angle electromagnetic wave absorbing metasurface according to claim 1, characterized in that: The metasurface unit includes two microstrip lines, four square patches, and eight patch resistors; specifically: The microstrip line comprises a first microstrip line (1) and a second microstrip line (2), the two microstrip lines 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, and 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 is provided with a metal branch in the middle of the inner edge; each metal branch end does not contact the microstrip line, and a patch resistor is installed at the interval, that is, the microstrip line is connected to the square patch through the patch resistor.

8. The broadband, large-angle electromagnetic wave absorbing metasurface according to claim 7, characterized in that: The metal 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 toward the center of the cross formed by the first microstrip line (1) and the second microstrip line (2); the metal branches of the metal 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.

9. The broadband and large-angle electromagnetic wave absorbing metasurface according to claim 8, characterized in that: The edge of the square metal patch is 0.05-0.25 mm away from the edge of the lower square dielectric plate (4); and the side length of the metal branch is 0.1-1.0 mm.

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