Transparent flexible polarization conversion metasurface for electromagnetic stealth
By designing a transparent and flexible polarization conversion metasurface and optimizing the coding matrix using genetic algorithms and simulated annealing algorithms, efficient RCS reduction in a wide frequency band was achieved, solving the problems of insufficient transparency and flexibility in existing technologies and maintaining good electromagnetic stealth performance.
Patent Information
- Application Number
- CN202423286219.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Priority Date
- 2024-10-23
- Filing Date
- 2024-12-31
- Publication Date
- 2026-01-16
- Estimated Expiration
- 2034-12-31
AI Technical Summary
Existing electromagnetic stealth metasurface materials have shortcomings in terms of transparency, flexibility and bandwidth, making it difficult to achieve effective radar cross section (RCS) reduction over a wide frequency band, especially when the radiation is bent or oblique.
A transparent and flexible polarization conversion metasurface composed of an ITO thin film layer and a PVC layer is designed. The encoding matrix is optimized by genetic algorithm and simulated annealing algorithm to achieve the arrangement of "0" and "1" super units with a phase difference of 180°, forming a 6×6 encoding matrix, which breaks through the bandwidth and transparency limitations of traditional metasurfaces.
Achieving RCS reduction of over -10dB in the 9–19 GHz frequency band, exhibiting excellent polarization insensitivity and broadband performance, and maintaining superior RCS reduction effect under bending or oblique incidence, breaking through the limitations of transparency and flexibility of traditional materials.
Smart Images
Figure CN223809249U_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The utility model belongs to the super surface technical field relates to a kind of transparent flexible polarization conversion super surface for electromagnetic invisibility. BACKGROUND
[0002] Electromagnetic metasurfaces are two-dimensional artificial materials that can change the transmission properties of electromagnetic waves, generally composed of subwavelength units. In recent years, metasurfaces have developed rapidly and become an important part of the electromagnetic field, widely used in polarization converters, broadband absorbers, electromagnetic cloaking, etc. For the field of electromagnetic cloaking, perfect metasurface absorber and diffuse reflection metasurface are two effective methods. The working principle of metasurface absorber is to convert the electromagnetic energy of incident waves into heat energy by introducing loss. In the paper“N.I. Landy, S. Sajuyigbe, J.J. Mock, D.R. Smith, and W.J. Padilla, “Perfect metamaterial absorber,” Phys. Rev. Lett. 100(20), 207402 (2008)”, Landy et al. first proposed a metasurface absorber, which can achieve nearly 100% absorption in a narrow band. Some researchers choose to load lumped elements or use multi-layer structures to improve the bandwidth of the working metasurface absorber. However, the processing difficulty and manufacturing cost may increase, and the conversion and accumulation of heat energy also increase the risk of exposure under infrared detection. Based on the research of diffuse reflection, the emergence of diffuse reflection metasurface provides another method, which pays more attention to phase control. In the paper“F. Capasso, N.F. Yu, and P. Genevet, “Light Propagation with Phase Discontinuities: Generalized Laws of Reflection and Refraction” Science, 334(6054), 333-337 (2011)”, Capasso et al. from Harvard University first proposed the“generalized Snell's law”based on phase gradient metasurface, and then designed a phase gradient metasurface based on V-shaped array structure to realize phase control of scattered electromagnetic waves. In the paper“T.J. Cui, M.Q. Qi, X. Wan, J. Zhao, and Q. Cheng, “Coding metamaterials, digital metamaterials and programmable metamaterials,” Light, Sci. Appl., 3(10), 218 (2014)”, Cui et al. proposed the coding theory of metasurface, which can scatter electromagnetic waves in all directions by controlling the phase of each unit and making it produce a stable phase difference.When the super unit is randomly arranged, the incident wave is reflected back to the free space randomly, so the scattering energy of each direction beam is small, and the effective reduction of the RCS can be realized, and the designed coding super surface has the characteristics of polarization insensitivity, and the RCS reduction of the incident electromagnetic wave in each polarization direction can be realized, and the phase of the structure unit is an important link in the RCS reduction, in order to realize different reflection phases, one selects the same structure unit with different sizes, which is difficult to break through the limitation of inherent bandwidth and makes the design complex, and some people introduce multi-resonant structures to improve the bandwidth, which makes the structure design more complex. Practical new type content
[0003] The utility model discloses a transparent flexible polarization conversion super surface for electromagnetic invisibility, which can realize RCS reduction of more than-10dB in the frequency band of 9-19GHz under perpendicular incidence, and still retains superior RCS reduction performance under bending or oblique incidence.
[0004] To achieve the above object, the transparent flexible polarization conversion super surface comprises an ITO film layer, a PVC layer and an ITO film layer from top to bottom, the thickness of the PVC layer is 2.73mm, the dielectric constant is 2.7, the loss tangent is 0.007, the surface resistance of the two ITO film layers is 5Ω / sq, and the thickness is 10um, wherein the ITO film layer at the bottom is used as a ground plate to make the transmission coefficient of the super surface 0, the upper ITO film layer has two rectangularly arranged rectangles, the length and width of the two rectangles are consistent, which are 6mm and 3mm respectively, the distance between the two rectangles is 1mm, the inner sides of the two rectangles are both concave semicircular ring structures, the inner ring radius of the semicircular ring is 2mm, the outer ring radius is 2.4mm, and the two rectangles are arranged on the ITO film layer by rotating 45 degrees around the horizontal direction.
[0005] The transparent flexible polarization conversion super surface can be used for preparing an electromagnetic super surface, rotating the transparent flexible polarization conversion super surface to obtain two basic coding units of "0" super unit and "1" super unit with a phase difference of 180°, the "0" super unit and the "1" super unit both comprise 4*4 transparent flexible polarization conversion super surfaces to form a local periodic environment, the electromagnetic super surface is a 6*6 super surface coding matrix arranged by the "0" super unit and the "1" super unit, and the arrangement order is obtained by optimizing the existing genetic algorithm and simulated annealing algorithm.
[0006] Compared with the prior art, the physical light transmittance of the transparent flexible polarization conversion metasurface is above 83.6%, the prepared electromagnetic metasurface realizes a wideband RCS reduction of more than 10 dB in a frequency band of 9-19 GHz, and the radar scattering cross section reduction effect has good effect advantages under different angles and different polarization states, and the specific advantages are as follows: first, the shortcomings of low transparency and poor flexibility of traditional metasurface materials are broken through, such as copper, FR4, F4B and the like, which do not have the characteristics of high transparency and high strength bending, and limit the application range of the metasurface; second, the low bandwidth problem of the traditional transparent flexible metasurface is broken through, and the relative bandwidth reaches 78%, which has advantages in transparent metasurfaces and flexible metasurfaces; third, the slow speed and poor effect of the traditional metasurface array optimization algorithm are broken through. BRIEF DESCRIPTION OF DRAWINGS
[0007] Figure 1 The structure diagram of the transparent flexible polarization conversion metasurface is described in the utility model.
[0008] Figure 2 The structure diagram of the "0" super unit (a) and the "1" super unit (b) is described in the utility model.
[0009] Figure 3 The simulation experiment result graph of the embodiment of the utility model is described, wherein (a) is a reflection coefficient graph of different polarization states when alpha is equal to 45 degrees, (b) is a PCR curve graph of the super unit "0" and "1" under x and y polarization incidence, and (c) is a reflection wave phase diagram under cross-polarization states of two super units when the rotation angle is 45 degrees and 135 degrees.
[0010] Figure 4 The process of optimizing the metasurface coding matrix by the genetic algorithm and the simulated annealing algorithm described in the embodiment of the utility model is described.
[0011] Figure 5 The genetic algorithm and the simulated annealing algorithm optimization result graph described in the embodiment of the utility model is described.
[0012] Figure 6 The three-dimensional scattering diagram of the ITO film patch MS and the PEC plate at 10 GHz, 14 GHz and 18 GHz is described in the embodiment of the utility model.
[0013] Figure 7 The single station RCS reduction curve graph of the coding metasurface when the X or Y polarized electromagnetic wave is vertically incident is described in the embodiment of the utility model.
[0014] Figure 8 The corresponding double station RCS reduction curve graph of the embodiment of the utility model under the incidence of electromagnetic waves at different angles under x polarization and y polarization is described.
[0015] Figure 9 This is a schematic diagram of conformal bending of the flexible coding element surface placed on a convex metal cylinder in an embodiment of the present invention.
[0016] Figure 10 This is a reduced RCS diagram of the metasurface described in the embodiment of this utility model under conformal conditions. Detailed Implementation
[0017] The present invention will be further described below with reference to the embodiments and accompanying drawings.
[0018] Example:
[0019] like Figure 1 As shown, the transparent flexible polarization conversion metasurface described in this embodiment consists of three layers from top to bottom: an ITO thin film layer, a PVC layer, and another ITO thin film layer. The PVC layer has a thickness h2 of 2.73 mm, a dielectric constant of 2.7, and a loss tangent of 0.007. The surface resistance of both ITO thin film layers is 5 Ω / sq, and their thicknesses h1 and h3 are 10 μm. The bottom ITO thin film layer serves as a ground plane, making the transmission coefficient of the metasurface zero. In the middle of the upper ITO thin film layer, two rectangles are arranged opposite each other. The length d and width l of the two rectangles are the same, which are 6 mm and 3 mm respectively. The distance m between the two rectangles is 1 mm. The inner sides of the two rectangles are concave semi-circular ring structures. The inner ring radius r of the semi-circular ring is 2 mm, and the outer ring radius is r + w = 2.4 mm. The two rectangles are arranged on the ITO thin film layer by rotating α = 45° around the horizontal direction.
[0020] In this embodiment, a transparent flexible polarization conversion metasurface is rotated to achieve a 180° phase difference, resulting in two basic coding units: "0" superunits and "1" superunits. Both "0" and "1" superunits contain 4×4 transparent flexible polarization conversion metasurfaces to form a local periodic environment. The electromagnetic metasurface is a 6×6 metasurface coding matrix composed of super "0" and "1" superunits. The arrangement order is optimized using a genetic algorithm and a simulated annealing algorithm, and the results are obtained through simulation experiments. This metasurface achieves an RCS reduction of more than -10dB in the 9–19 GHz frequency band under perpendicular incidence and retains excellent RCS reduction performance under bending or oblique incidence.
[0021] In this embodiment, the simulation experiment was conducted using the commercial simulation software CST Microwave Studio. Boundaries were used to simulate infinite periodic structures in the x and y directions, while an open (added space) boundary was used in the z direction. The results are as follows: Figure 3 As shown, the EM wave is incident along the -z axis with x-polarization and y-polarization. When α = 45°, the reflection coefficients of its different polarization states are as follows: Figure 3 As shown in (a). Figure 3(b) are the PCR curves of super unit "0" and "1" under x and y polarized incidence, which achieve a constant PCR value greater than 0.9 in the frequency band of 9.38-18.485GHz, and have good EM wave polarization conversion efficiency; when the unit rotation angle is 45° and 135°, the reflection wave phases of the two super units under cross-polarization state are shown in Figure 3 (c), and the phase difference always remains 180°, verifying the PB phase principle.
[0022] In order to ensure that the reflected waves are as uniformly distributed as possible in multiple directions in the upper half space, the metasurface coding matrix is updated by genetic algorithm and simulated annealing algorithm; the optimal fitness function value is calculated by the calculation module; and finally the optimal metasurface coding matrix is obtained by comparing the two optimization algorithms, and the initial solutions of the two algorithms are the same 6x6 matrix randomly generated, the process is shown in Figure 4 , the results are shown in Figure 5 , and the optimization process of the two algorithms is shown in Figure 5 (a), after the two algorithms converge, the output results are calculated by MATLAB in the theoretical 2D, 3D far-field scattering mode at 12.95GHz as shown in Figure 5 (b)-(e), by comparison, it can be seen that the scattering effect of the result optimized by genetic algorithm is better, and the RCS value is effectively reduced, and the optimal metasurface coding matrix is shown in Figure 5 (f); at the same time, when the x-polarized EM wave is incident on the coding metasurface, the full-wave simulation results of the 3D far-field scattering mode are shown in Figure 5 (h), the full-wave simulation results are consistent with the theoretical analysis, and both achieve good scattering of the coding metasurface to the spatial electromagnetic wave.
[0023] This embodiment also uses CST microwave studio to simulate and compare the effects of the ITO film patch metasurface and the existing metal patch, and the two metasurfaces have been simulated under the normal incidence of linearly polarized plane waves, Figure 6 , the three-dimensional scattering diagrams of ITO film patch MS and PEC plate at 10GHz, 14GHz and 18GHz are shown in Figure 7 , when the X or Y polarized electromagnetic wave is vertically incident, the coding metasurface can achieve more than 10dB of single station RCS reduction in the wide frequency band of 9-19GHz, and the maximum reduction reaches 24dB, the grid fragment is reduced, and the scattering field distribution is dispersed to different directions in the upper half space. As can be seen from the figure, the optimized coding metasurface reflects the scattering characteristics of diffuse reflection, and generates a very large number of beams in the upper half space, thereby effectively reducing the scattering field amplitude, including the backscattering RCS. These results also show that the proposed coding metasurface has polarization insensitivity in the planar case.
[0024] Since in actual situation, the incident electromagnetic wave of the metasurface is not all vertical incidence, Figure 8 The figure shows the bistatic RCS of the proposed MS under different angle of incidence electromagnetic wave in the case of x polarization and y polarization, it can be seen from the figure that the scattering pattern of the metal plate has a obvious main lobe in the specular reflection direction, while the main lobe of the scattering pattern of the MS appears when the incident angle is greater than 30°, which shows that the proposed metasurface still has the effect of regulating the amplitude of the scattering field when the electromagnetic wave deviates from the normal angle less than 30°.
[0025] The metasurface is widely used flexibly, and most of them are non-planar application environment, in order to analyze the RCS reduction performance of the conformal metasurface, the flexible coding metasurface is placed on the convex metal cylinder to conform to the bending, and the corresponding central angle is π / 2, π, 2π respectively, as shown in Figure 9 The full-wave simulation is carried out along the negative direction of the z axis under the normal x polarization monochromatic plane wave, and the curved PEC plate is simulated to obtain the simulation value as a reference, Figure 10 The figure shows that the metasurface is still effective in reducing RCS in the conformal case.
[0026] The algorithm process and English abbreviations not described in detail in the utility model are all adopted in the general technical solution or description in the field.
[0027] It should be noted that the purpose of the disclosed embodiments is to help further understand the utility model, but those skilled in the art understand that various substitutions and modifications are possible without departing from the spirit and scope of the utility model and the appended claims. Therefore, the utility model should not be limited to the disclosed content of the embodiments, and the scope of protection required by the utility model is the scope defined by the claims.
Claims
1. A transparent flexible polarization conversion metasurface for electromagnetic cloaking, characterized in that, The transparent flexible polarization conversion metasurface is composed of ITO film layer, PVC layer and ITO film layer from top to bottom, the thickness of the PVC layer is 2.73 mm, the dielectric constant is 2.7, the loss tangent is 0.007, the surface resistance of the two ITO film layers is 5 Ω / sq, and the thickness is 10 um, wherein the ITO film layer of the bottom layer is used as a ground plate, so that the transmission coefficient of the metasurface is 0, and the upper ITO film layer has two rectangularly arranged rectangles, the length and width of the two rectangles are consistent, which are 6 mm and 3 mm respectively, the distance between the two rectangles is 1 mm, and the inner sides of the two rectangles are both concave semicircular ring structures, the inner ring radius of the semicircular ring is 2 mm, the outer ring radius is 2.4 mm, and the two rectangles are arranged on the ITO film layer by rotating 45 degrees around the horizontal direction.