A three-dimensional angle-insensitive polarization conversion metasurface

Abstract

The application discloses a three-dimensional angle-insensitive polarization conversion metasurface, which comprises a dielectric substrate, a metal patch, a lumped resistor, a trapezoidal metal patch in the vertical direction, an air layer, a rectangular metal patch in the vertical direction and a metal ground plate. The application adopts a three-dimensional structure, introduces the trapezoidal metal patch and the rectangular metal patch in the vertical direction, and can receive incident electromagnetic waves in a larger pitch angle range, so that the PCM structure is not sensitive to the incident angle. The lumped resistor is loaded on the PCM unit structure, that is, the resistance loss is added, so that the incident electromagnetic wave energy is absorbed, the radar cross section (RCS) reduction of the absorption and abnormal reflection double mechanism is realized, and the RCS reduction capability of the PCM structure is enhanced. The application has the characteristics of simple structure and practicality, realizes that the PCM unit structure is not sensitive to the incident angle, and after the PCM unit is arrayed, the RCS reduction can reach more than 10 dB in the range of 0°-45° of the incident angle.

Description

Technical Field

[0001] This invention belongs to the field of metasurface design technology, and in particular to a three-dimensional angle-insensitive polarization conversion metasurface. Background Technology

[0002] Metamaterials are composed of a series of ordered subwavelength units in three-dimensional structures. They typically have a certain volume and thickness, resulting in high losses and narrow operating bandwidths, which is also unfavorable for fabrication and integration. To overcome these inherent limitations, researchers have extended the concept of electromagnetic metamaterials to two-dimensional cases, arranging subwavelength units on a surface to form electromagnetic metasurfaces. To date, angularly stable metasurfaces have attracted significant attention in recent years due to their superior stability and performance in engineering applications. However, considering that electromagnetic waves are not always incident perpendicularly to a surface in practical applications, oblique incidence is more common. Therefore, designing and fabricating metasurfaces insensitive to the incident angle has become a pressing goal for researchers.

[0003] In recent years, many methods for achieving metasurface angular stability have been proposed in various literatures. In reference 1 (Guo Y, Xu J, Lan C, et al. Broadband and high-efficiency linear polarization converter based on reflective metasurface[J]. Engineered Science, 2021, 14(2):39-45.), the metasurface unit consists of a metal ground plane, an F4B dielectric substrate, and a rectangular metal structure with two identical T-slots. The bandwidth of this linear polarization converter can be adjusted by the length of the metal patch and the width of the T-slots. Under both vertical and horizontal polarization, the structure exhibits relatively stable frequency response when the incident angle is less than 36°. Reference 2 (Zhao Y, Qi B, Niu T, et al. Ultra-wideband and wide-angle polarization rotator based on double W-shaped metasurface[J]. AIPA Advances, 2019, 9(8).) designed a metasurface consisting of a double W-shaped top metal patch, a bottom metal ground plane, and an F4B dielectric substrate sandwiched between them. The top metal pattern consists of two W-shaped structures arranged diagonally. This polarization conversion metasurface can efficiently convert linearly polarized incident waves into cross-polarized reflected waves over a wide frequency band and maintain PCR stability when the incident angle is less than 30°. Although the above studies can achieve polarization conversion under vertical and horizontal polarization conditions, the incident electromagnetic waves cannot be received vertically at large elevation angles, thus failing to maintain stability when electromagnetic waves are incident at large elevation angles. Furthermore, the above studies mainly rely on anomalous reflection of the incident wave to achieve RCS reduction, without absorbing the incident wave energy, which will affect the RCS reduction effect in practical scenarios. Summary of the Invention

[0004] The purpose of this invention is to address the problems existing in the prior art by providing a three-dimensional angle-insensitive polarization conversion metasurface.

[0005] The technical solution to achieve the purpose of this invention is as follows: a three-dimensional angle-insensitive polarization conversion metasurface, employing a three-dimensional structure, including a rectangular dielectric substrate and a rectangular metal ground plane arranged sequentially from top to bottom along the vertical direction, with an air layer between them; along the vertical direction, a trapezoidal metal patch is provided at each of the four sides of the lower surface of the rectangular dielectric substrate, and a rectangular metal patch is provided at each of the four sides of the upper surface of the rectangular metal ground plane; a metal patch is provided at each of the four corners of the lower surface of the rectangular dielectric substrate; the metal patch has an L-shaped structure, and the two arms of the "L" shape are parallel to the adjacent sides of the rectangular metal ground plane, with a chamfer on the outer side of the corner of the L-shaped structure, and a lumped resistor is loaded at the connection point of the two arms.

[0006] Furthermore, along the vertical direction, the lower side of the trapezoidal metal patch is shorter than the upper side.

[0007] Furthermore, the trapezoidal metal patch has an upper side length Lsupper = 5.3 mm, a lower side length Lbottom = 0.9 mm, and a height h1 = 1.7 mm.

[0008] Furthermore, the two arms of the metal patch have the same length, L3 = 3.61 mm, but different widths, Ws1 = 0.485 mm and Ws2 = 0.5 mm, respectively.

[0009] Furthermore, the rectangular metal patch and the trapezoidal metal patch have the same thickness.

[0010] Furthermore, the thickness of the rectangular metal patch is 0.1 mm.

[0011] Furthermore, the rectangular metal patch has a length L2 = 5.7 mm and a height W2 = 1.8 mm.

[0012] Furthermore, the rectangular dielectric substrate has a length Lsub = 7.2 mm, a width Wsub = 7.2 mm, a thickness of 0.5 mm, is made of F4B material, has a relative permittivity of 2.65, and a loss tangent of 0.001.

[0013] Furthermore, the thickness of the air layer is 5.7 mm.

[0014] Furthermore, the lumped resistance is 30 ohms.

[0015] Compared with the prior art, the significant advantages of this invention are:

[0016] (1) The three-dimensional polarization conversion metasurface proposed in this invention has the characteristic of being insensitive to the incident angle by providing trapezoidal and rectangular metal patches in the vertical direction.

[0017] (2) The present invention loads a lumped resistance in the structure, that is, adds resistance loss, so that the energy of the incident electromagnetic wave is absorbed, realizing the RCS reduction of the dual mechanism of absorption and abnormal reflection, thus giving it a good RCS reduction feature. That is, the RCS reduction of the structure can reach more than 10dB in the range of incident angle of 0°-45°.

[0018] (3) The present invention has the characteristics of simple structure and small size, and is more suitable for practical applications.

[0019] The present invention will now be described in further detail with reference to the accompanying drawings. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the layout of a three-dimensional angle-insensitive polarization conversion metasurface in one embodiment.

[0021] Figure 2 This is a side view of a polarization conversion metasurface in one embodiment.

[0022] Figure 3 This is a schematic diagram of a metal patch with a lumped resistance loaded onto a polarization conversion metasurface in one embodiment.

[0023] Figure 4 This is a diagram of the copolarization reflection coefficients of a polarization-converting metasurface in one embodiment.

[0024] Figure 5 This is a diagram of the cross-polarization reflection coefficients of a polarization-converting metasurface in one embodiment.

[0025] Figure 6 This is an array diagram of a polarization conversion metasurface in one embodiment.

[0026] Figure 7 This is a schematic diagram of the reduction of the single-station RCS of an array of polarization-converting metasurfaces when electromagnetic waves are incident perpendicularly, as shown in one embodiment.

[0027] Figure 8 This is a schematic diagram of bistatic RCS reduction when an array of electromagnetic waves is obliquely incident on a polarization-converting metasurface in one embodiment. Detailed Implementation

[0028] It is readily understood that, based on the technical solution of this invention, various embodiments of the invention can be conceived by those skilled in the art without altering the essential spirit of the invention. Therefore, the following detailed embodiments and accompanying drawings are merely illustrative examples of the technical solution of this invention and should not be considered as the entirety of the invention or as limitations or restrictions on the technical solution of this invention. Rather, these embodiments are provided to enable those skilled in the art to gain a more thorough understanding of the invention. Preferred embodiments of the invention are described below in conjunction with the accompanying drawings, which form part of this application and, together with the embodiments of the invention, serve to illustrate the innovative concept of the invention.

[0029] In one embodiment, the present invention employs a three-dimensional structure, in which trapezoidal and rectangular metal patches positioned in the vertical direction receive incident electromagnetic waves at large pitch angles. A three-dimensional angle-insensitive polarization-conversion metasurface (PCM) unit is proposed, combined with… Figure 1 The device includes a rectangular dielectric substrate 1 and a rectangular metal floor 6 arranged vertically from top to bottom, with an air layer 7 between them. Vertically, a trapezoidal metal patch 4 is provided on the lower surface of the rectangular dielectric substrate 1 near each of its four sides, and a rectangular metal patch 5 is provided on the upper surface of the rectangular metal floor 6 near each of its four sides. A metal patch 2 is provided at each of the four corners of the lower surface of the rectangular dielectric substrate 1. The metal patch 2 has an L-shaped structure, with the two arms of the "L" shape parallel to the adjacent sides of the rectangular metal floor 6. A chamfer is provided at the outer corner of the L-shaped structure, and a lumped resistor 3 is applied at the connection point of the two arms.

[0030] Here, the PCM unit adopts a three-dimensional structure, with trapezoidal metal patches 4 and rectangular metal patches 5 in the vertical direction. They can receive incident electromagnetic waves in a large range of pitch angles, so that the PCM unit structure is insensitive to the incident angle. After the PCM unit is arrayed, the RCS reduction can reach more than 10dB in the range of incident angles of 0°-45°.

[0031] Here, a lumped resistor 3 is loaded on each of the PCM units, that is, resistance loss is added, so that the energy of the incident electromagnetic wave is absorbed, realizing the RCS reduction through the dual mechanism of absorption and abnormal reflection, thereby enhancing the RCS reduction capability of the PCM structure. That is, the RCS reduction of the structure can reach more than 10dB in the range of incident angle of 0°-45°.

[0032] Combination Figure 2 Preferably, along the vertical direction, the lower side of the trapezoidal metal patch 4 is shorter than the upper side.

[0033] Preferably, the trapezoidal metal patch 4 has an upper side length Lsupper = 5.3 mm, a lower side length Lbottom = 0.9 mm, and a height h1 = 1.7 mm.

[0034] Preferably, the rectangular metal patch 5 and the trapezoidal metal patch 4 have the same thickness.

[0035] Preferably, the thickness of the rectangular metal patch 5 is 0.1 mm.

[0036] Preferably, the rectangular metal patch 5 has a length Lrec = 5.7 mm and a height Wrec = 1.8 mm.

[0037] Preferably, the rectangular dielectric substrate 1 has a length Lsub = 7.2 mm, a width Wsub = 7.2 mm, a thickness of 0.5 mm, is made of F4B material, has a relative permittivity of 2.65, and a loss tangent of 0.001.

[0038] Preferably, the thickness of the air layer 7 is 5.7 mm.

[0039] Preferably, the lumped resistance 3 is 30 ohms.

[0040] Preferably, combined with Figure 3 The two arms of the metal patch 2 have the same length, L3 = 3.61 mm, but different widths, Ws1 = 0.485 mm and Ws2 = 0.5 mm respectively.

[0041] As a specific example, the present invention will be further verified and illustrated.

[0042] The PCM unit structure was simulated and analyzed in the electromagnetic simulation software CST. Periodic boundary conditions were set in the x and y directions: unit cell; along the +z direction: electric (Et=0) (perfect electric boundary); along the -z direction: open (add space); and in the z direction: Floquet port mode. The Floquet port mode extends a single PCM unit infinitely along the x and y directions to form an infinitely large periodic structure array. The simulation results are as follows: Figure 4 , Figure 5 As shown, Figure 4 The diagram shows the common polarization reflection coefficient of the reflected wave. Figure 5The diagram shows the cross-polarization reflection coefficients of the reflected wave. It can be seen that when the incident angle is within the range of 0°-45°, the cross-polarization reflection coefficients rxy and ryx in the 7GHz-20GHz band are close to 0dB. This indicates that as the incident angle changes from 0° to 45°, when an x ​​(y-polarized) electromagnetic wave is incident on the surface of this PCM structure, its reflected wave is y (x-polarized), thus achieving linear polarization wave conversion. That is, this PCM unit can achieve linear polarization of over 10dB, with a conversion bandwidth of 7GHz-20GHz, covering the X-band (8GHz-12GHz) and the Ku-band (12GHz-18GHz).

[0043] Combination Figure 6 The aforementioned PCM units are arranged in a checkerboard pattern along the x and y directions to form a 16×16 array. The principle behind the checkerboard structure's RCS reduction is the destructive interference between the reflected waves from the two different artificial magnetic conductor (AMC) structures constituting the checkerboard structure. However, using a polarization-conversion metasurface structure, it is only necessary to rotate the same PCM structure 90° around its center to obtain two mirror-image PCM units, which can always maintain a 180° phase difference. Figure 6 As shown, the PCM elements and their mirror elements are arranged in a checkerboard structure. Assuming the incident wave is an x-polarized electromagnetic wave, it is reflected after passing through the PCM surface and transformed into a y-polarized reflected wave orthogonal to the incident wave. Destructive interference occurs between the reflected waves generated by the PCM elements and their mirror elements, thus weakening the reflected wave energy. Therefore, RCS reduction can be achieved by arranging the PCM elements and their mirror elements in a checkerboard pattern.

[0044] Will Figure 6 The array structure shown was simulated and analyzed in the electromagnetic simulation software CST, and the simulation results are as follows. Figure 7 and Figure 8 As shown. Figure 7 The simulation results show the reduction effect of the single-station RCS when electromagnetic waves are incident perpendicularly on the array structure. Figure 8 The figure shows the bistatic RCS reduction effect obtained from simulation when electromagnetic waves are incident at an oblique angle. As can be seen from the figure, the RCS reduction can reach more than 10dB in both the X-band and Ku-band when the incident angle of electromagnetic waves is from 0° to 45°.

[0045] In summary, this invention has the advantages of simple structure and practical applicability. It realizes that the PCM unit structure is insensitive to the incident angle, and the RCS reduction can reach more than 10dB in the incident angle range of 0°-45° after the PCM unit array is assembled.

[0046] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

[0047] It should be understood that, in order to simplify the present invention and help those skilled in the art understand its various aspects, in the above description of exemplary embodiments of the present invention, various features of the present invention are sometimes described in a single embodiment or with reference to a single figure. However, the present invention should not be construed as including all features in the exemplary embodiments as essential technical features of the claims of this patent.

[0048] It should be understood that the modules, units, components, etc., included in the device of one embodiment of the present invention can be adaptively changed to be placed in a device different from that embodiment. Different modules, units, or components included in the device of the embodiment can be combined into a single module, unit, or component, or they can be divided into multiple sub-modules, sub-units, or sub-components.

Claims

1. A three-dimensional angle-insensitive polarization conversion metasurface, characterized in that, The structure employs a three-dimensional design, comprising a rectangular dielectric substrate (1) and a rectangular metal floor (6) arranged vertically from top to bottom, with an air layer (7) between them. Vertically, a trapezoidal metal patch (4) is provided on the lower surface of the rectangular dielectric substrate (1) near both the first and second sides, and a rectangular metal patch (5) is provided on the upper surface of the rectangular metal floor (6) near the positions corresponding to the first and second sides. A metal patch (2) is provided at one corner of the lower surface of the rectangular dielectric substrate (1) adjacent to the trapezoidal metal patch (4). The metal patch (2) has an L-shaped structure, with the two arms of the "L" shape parallel to the adjacent sides of the rectangular metal floor (6). A chamfer is provided at the outer side of the corner of the L-shaped structure, and a lumped resistor (3) is applied at the connection point of the two arms. In the vertical direction, the lower side of the trapezoidal metal patch (4) is shorter than the upper side.

2. The three-dimensional angle-insensitive polarization conversion metasurface according to claim 1, characterized in that, The trapezoidal metal patch (4) has an upper side length Lsupper = 5.3 mm, a lower side length Lbottom = 0.9 mm, and a height h1 = 1.7 mm.

3. The three-dimensional angle-insensitive polarization conversion metasurface according to claim 1, characterized in that, The two arms of the metal patch (2) have the same length, L3 = 3.61 mm, but different widths, Ws1 = 0.485 mm and Ws2 = 0.5 mm respectively.

4. The three-dimensional angle-insensitive polarization conversion metasurface according to claim 1, characterized in that, The rectangular metal patch (5) has the same thickness as the trapezoidal metal patch (4).

5. The three-dimensional angle-insensitive polarization conversion metasurface according to claim 4, characterized in that, The thickness of the rectangular metal patch (5) is 0.1 mm.

6. The three-dimensional angle-insensitive polarization conversion metasurface according to claim 1, characterized in that, The rectangular metal patch (5) has a length Lrec = 5.7 mm and a height Wrec = 1.8 mm.

7. The three-dimensional angle-insensitive polarization conversion metasurface according to claim 1, characterized in that, The rectangular dielectric substrate (1) has a length Lsub = 7.2 mm, a width Wsub = 7.2 mm, a thickness of 0.5 mm, is made of F4B, has a relative permittivity of 2.65, and a loss tangent of 0.

001.

8. The three-dimensional angle-insensitive polarization conversion metasurface according to claim 1, characterized in that, The thickness of the air layer (7) is 5.7 mm.

9. The three-dimensional angle-insensitive polarization conversion metasurface according to claim 1, characterized in that, The lumped resistance (3) is 30 ohms.

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