ITO flexible coding metasurface based on topological optimization design and preparation method

Abstract

The invention belongs to the technical field of metasurfaces, and relates to an ITO flexible coding metasurface based on topological optimization design and a preparation method, the ITO flexible coding metasurface is a metasurface array shaped like a Chinese character'gu 'formed by a plurality of coding units, each coding unit is composed of four layers of structures, wherein an n-type semiconductor material ITO is used as a top pattern and a bottom grounding structure of the metasurface, a PET layer and a PVC layer are sequentially arranged in the middle from top to bottom, the ITO flexible coding metasurface has the polarization conversion rate close to 1 in a broadband, RCS reduction of 10 dB or above can be achieved, and the good far-field scattering effect is achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of supersurfaces and relates to an ITO flexible coding supersurface based on topological optimization design and a preparation method thereof. Background Art

[0002] In recent years, codeable metasurfaces have gained tremendous momentum and become one of the most promising fields in electromagnetics. Stealth technology has always been an important field of metasurface applications. The reduction of radar cross section (RCS) is one of the main challenges in many defense applications of sensing systems and communications. Metasurfaces are composed of basic units with constant phase difference at a certain frequency point or a wide frequency band. These basic units can scatter electromagnetic waves irregularly in all directions, thereby weakening the echo signal and achieving RCS reduction. The desired phase difference, the so-called Pancharatnam-Berry (PB) phase, is obtained by simply rotating the anisotropic structure instead of using several different isotropic elements or changing specific size parameters. The metal pattern of the digital coding unit rotates θ, resulting in an abrupt geometric phase of ±2θ in the reflected phase. In addition, the existing research on coding element surfaces is often limited to rigid materials, and flexibility is not mentioned in most research results. However, flexible coding element surfaces are required in many microwave and terahertz potential applications in the fields of antennas, radars, aircraft, etc. In addition, rendering flexibility to metasurfaces can make it possible to wrap light-colored and transparent metasurfaces around objects or attach flexible devices to all surfaces. Lan et al. (C. Lan, D. Zhu, J. Gao, B. Li, and Z. Gao, "Flexible and tunableterahertz all-dielectric metasurface composed of ceramic spheres embed-ded ina ferroelectric / elastomer composite," Opt. Exp., vol. 26, no. 9, pp. 11633–11638, Apr. 2018.) designed a tunable and flexible all-dielectric terahertz metasurface; Burrow et al. (JA Burrow, R. Yahiaoui, A. Sarangan, I. Agha, J. Mathews, and T. A. Earles, "Polarization-dependent electromagnetic responses of ultrathin and highly flexible asymmetric terahertz An ultrathin, highly flexible, polarization-dependent asymmetric terahertz metasurface is proposed in the paper, “metasurfaces,” Opt. Exp., vol. 25, no. 26, pp. 32540–32549, Dec. 2017. Therefore, flexible, large-area, and non-planar metasurfaces open up new areas for the application of electromagnetic functional elements.However, there is still a lack of microwave-band broadband coding unit surfaces based on flexible materials. By utilizing the freedom and flexibility of unit surface design, the concept of frequency-selective flexible coding element surfaces is proposed. Summary of the invention

[0003] The purpose of the present invention is to overcome the shortcomings of the prior art and to provide an ITO flexible coding metasurface based on topological optimization design and a preparation method thereof.

[0004] To achieve the above-mentioned purpose, the ITO flexible coding metasurface described in the present invention is composed of a "porridge"-shaped metasurface array composed of multiple coding units, and each coding unit is composed of a four-layer structure, in which the n-type semiconductor material ITO (tin-doped indium oxide) is used as the top layer pattern of the metasurface and the bottom layer grounding structure, and the middle layer is PET layer and PVC layer from top to bottom.

[0005] The process of preparing the ITO flexible coding super surface of the present invention is as follows:

[0006] (1) Design the top ITO pattern using HFSS software using topology optimization combined with genetic algorithm and co-simulation;

[0007] (2) Use Matlab to write relevant genetic algorithms to obtain the optimal arrangement.

[0008] As a further technical solution of the present invention, the specific process of designing the top ITO pattern is:

[0009] (11) Determine two coding units "0" and "1" with different phases. The phase difference between the units "0" and "1" is maintained at ±180° in the entire frequency range, where different rotation angles θ are used to represent coding units with different phases, where θ is the angle between the x-axis of HFSS and the two symmetrical "bows"; specifically, units "0" and "1" with different phase distributions are obtained according to the PB phase. The "0" coding unit on the surface of a 1-bit coding element has a phase gradient along the x or y direction. The "0" coding unit is rotated by θ=90° to obtain the "1" coding unit. The phase difference between the two coding units is 180°;

[0010] (12) A 2×2 “0” and “1” coding unit atomic array is used to form a “0” and “1” super unit, which is the designed top ITO pattern.

[0011] Compared with the prior art, the ITO flexible coding metasurface prepared by the present invention has a polarization conversion rate close to 1 in a wide frequency band, can achieve an RCS reduction of more than 10 dB, and has a good far-field scattering effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1This is a structural diagram of the "0" encoding unit (a) and the "1" encoding unit (b) described in the present invention.

[0013] Figure 2 This is a reflection performance curve diagram of the two encoding units described in the present invention when the phase difference is 180°.

[0014] Figure 3 This is a diagram of the "0", "1" super unit structure composed of a 2×2 "0", "1" atomic array in the present invention.

[0015] Figure 4 This is the optimal arrangement of the ITO flexible coding supersurface described in the present invention.

[0016] Figure 5 PCR curves of coding units “0” and “1” under x and y polarization vertical incidence of the present invention.

[0017] Figure 6 This is the RCS reduction curve of the ITO flexible coding supersurface prepared by the present invention.

[0018] Figure 7 The simulation results of the far-field scattering theory of the optimal arrangement obtained by the embodiment of the present invention are as follows Figure 7 .

[0019] Figure 8 Bistatic RCS diagram of the ITO flexible coding metasurface prepared according to an embodiment of the present invention under in-plane far-field scattering and vertical polarization.

[0020] Fig. 9 This is a bistatic RCS diagram of the ITO flexible coding metasurface bent 90° prepared in an embodiment of the present invention.

[0021] Fig.10 This is a bistatic RCS diagram of the ITO flexible coding metasurface bent 180° prepared in an embodiment of the present invention. DETAILED DESCRIPTION

[0022] The present invention will be further described below by way of embodiments in conjunction with the accompanying drawings.

[0023] Example:

[0024] The ITO flexible coding metasurface described in this embodiment is composed of a "porridge"-shaped metasurface array composed of multiple coding units, and each coding unit is composed of a four-layer structure, in which the n-type semiconductor material ITO (tin-doped indium oxide) is used as the top layer pattern of the metasurface and the bottom layer grounding structure, and the middle layer is PET layer and PVC layer from top to bottom.

[0025] The process of preparing the ITO flexible coding metasurface in this embodiment is as follows: the top ITO pattern is designed by combining topology optimization with genetic algorithm and joint simulation; different rotation angles θ (θ is the angle between the x-axis of HFSS and the two symmetrical "bows") represent two different phase coding units "0" and "1", and the phase difference between units "0" and "1" is maintained at ±180° in the entire frequency range; according to the PB phase, units "0" and "1" with different phase distributions are obtained, and the "0" coding unit of the 1-bit coding element surface has a phase gradient along the x or y direction. The "1" coding unit can be obtained by rotating the "0" coding unit by θ=90°, as shown in FIG. Figure 1 As shown; the phase difference between the two encoding units is 180°, as shown Figure 2 As shown; to ensure excellent reflection performance, a 2×2 "0", "1" atomic array is used to form a "0", "1" super unit, such as Figure 3 As shown; then use matlab to write the relevant genetic algorithm to get the optimal arrangement, as shown Figure 4 shown.

[0026] In this embodiment, numerical simulation is performed on the prepared ITO flexible coding metasurface. Figure 5 As shown in the figure, in the frequency range of 13.93-20.96 GHz, the PCR exceeds 90%, and in the ranges of 15.38-16.24 GHz and 20.24-20.41 GHz, it reaches more than 99%, which indicates that the proposed coding unit has a polarization conversion rate close to 1 in a wide frequency band. In addition, numerical simulations show that the prepared ITO flexible coding metasurface can achieve an RCS reduction of more than 10 dB, as shown in the figure. Figure 6 shown.

[0027] This embodiment simulates the far-field scattering theory of the optimal arrangement obtained by writing a genetic algorithm program in MATLAB, and the results are as follows: Figure 7 As shown in Figure 2, in order to further verify the far-field scattering performance in both planar and conformal states, the optimal arrangement model is established in CST for simulation. Taking the 16 GHz frequency point as an example, the far-field scattering of the plane and the dual-station RCS under vertical polarization are shown in Figure 2. Figure 8 , bending 90° and bending 180° are as follows Fig. 9 ,and Fig.10 As shown, the simulation results show that the designed ITO flexible coding metasurface has good far-field scattering effect.

[0028] The software and algorithms used in this article are all existing technologies in this field.

[0029] The above content is a further detailed description of the present invention in combination with specific implementation methods. It cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, some simple deductions or substitutions can be made without departing from the concept of the present invention, which should be regarded as belonging to the scope of protection determined by the claims submitted for the present invention.

Claims

1. An ITO flexible coding metasurface based on topological optimization design, characterized in that The ITO flexible coding metasurface is composed of a "porridge"-shaped metasurface array composed of multiple coding units, and each coding unit is composed of a four-layer structure, in which the n-type semiconductor material ITO is used as the top layer pattern of the metasurface and the bottom layer grounding structure, and the middle layer is PET layer and PVC layer from top to bottom.

2. A method for preparing the ITO flexible coding supersurface according to claim 1, characterized in that: The specific preparation process is as follows: The process of preparing ITO flexible coding super surface is as follows: (1) Design the top ITO pattern using HFSS software using topology optimization combined with genetic algorithm and co-simulation; (2) Use Matlab to write relevant genetic algorithms to obtain the optimal arrangement.

3. According to claim 2, the method for preparing the ITO flexible coding super surface is characterized in that: The specific process of designing the top ITO pattern is as follows: (11) Determine two coding units "0" and "1" with different phases. The phase difference between units "0" and "1" is maintained at ±180° in the entire frequency range, where different rotation angles θ are used to represent coding units with different phases, where θ is the angle between the x-axis of HFSS and the two symmetrical "bows". Specifically, units "0" and "1" with different phase distributions are obtained according to the PB phase. The "0" coding unit on the surface of a 1-bit coding element has a phase gradient along the x or y direction. The "0" coding unit is rotated by θ = 90° to obtain the "1" coding unit. The phase difference between the two coding units is 180°. (12) A 2×2 "0" and "1" coding unit atomic array is used to form a "0" and "1" super unit, which is the designed top ITO pattern.

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