A polarization and scattering pattern jointly modulated spatiotemporal coding electromagnetic metasurface

Abstract

The application relates to a kind of polarization and scattering pattern joint regulation space-time coding electromagnetic super surface, by anisotropic basic unit in two-dimensional plane periodic extension, aim at dynamically generating arbitrary polarization multi-beam. By respectively loading a pair of switch diode along the horizontal direction and vertical direction of super surface unit, the super surface can be independently supported dynamic 1 bit phase control under a pair of orthogonal polarization electromagnetic wave incidence. By independently loading two groups of voltage control signals periodically changed with time for each unit, not only can the super surface realize arbitrary equivalent reflection coefficient, thereby simulating the anisotropic parameters required to generate target scattering pattern, but also can redistribute spectrum energy, thereby extending the working frequency from fundamental wave to harmonic. The application can generate multiple polarized, deflection angle can be arbitrarily dynamically regulated beams under the polarization incident wave, while having the advantages of high integration and complete theoretical basis, and has important application prospect in the field of secure communication, stereoscopic imaging and the like.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of artificial electromagnetic materials, and particularly relates to a spatiotemporal coding electromagnetic metasurface with polarization and scattering pattern joint regulation. BACKGROUND

[0002] A metasurface is a kind of planar artificial electromagnetic material, which is usually composed of a large number of basic units. By introducing discontinuous field distribution at the interface, the metasurface can realize electromagnetic functions such as negative refraction and perfect imaging, which are difficult to be realized by natural materials. In order to make the same metasurface have electromagnetic functions suitable for different application scenarios, researchers have proposed a design method of embedding reconfigurable devices such as switch diodes and variable capacitance tubes in the structure. By adjusting the working state of the reconfigurable device, the metasurface can exhibit different electromagnetic characteristics.

[0003] At present, most of the reconfigurable metasurfaces with polarization regulation capability are limited to the mutual conversion between linear polarization and circular polarization, and cannot fully utilize all polarization resources. At the same time, most of the reconfigurable metasurfaces with scattering pattern regulation capability are limited to generating multiple beams with the same polarization, and cannot provide additional information, thereby limiting the information capacity of the metasurface.

[0004] Therefore, in order to improve the information capacity of the metasurface and utilize all polarization resources, it is urgent to explore a reconfigurable metasurface solution that can realize polarization and scattering pattern regulation, and simultaneously has multiple functions of dynamically adjusting the number, deflection angle and polarization component of electromagnetic beams. SUMMARY

[0005] The purpose of the application is to provide a spatiotemporal coding electromagnetic metasurface with polarization and scattering pattern joint regulation, which aims to dynamically generate arbitrary polarization multi-beams with adjustable deflection angle and number.

[0006] Technical scheme: In order to achieve the above-mentioned purpose of the application, the application proposes the following technical scheme:

[0007] The application discloses a time-space coding electromagnetic super surface with polarization and scattering pattern jointly regulated, which is periodically extended in an xy two-dimensional plane by basic units, and the basic unit structure comprises a first metal patch layer, a first dielectric layer, a second metal patch layer, a second dielectric layer and a third metal patch layer from top to bottom; the first metal patch layer is composed of a square metal patch in the middle and four T-shaped metal patches around the square metal patch, four switch diodes are loaded between the square metal patch and the four T-shaped metal patches respectively; the second metal patch layer is connected with the square metal patch in the first metal patch layer through a metal via; the third metal patch layer is connected with the T-shaped metal patch in the first metal patch layer through a metal via, the second and third metal patch layers are connected with a negative electrode and a positive electrode of an external circuit system respectively, and an inductor is connected to a metal wire connected with an output port of the external circuit system in the third metal patch layer.

[0008] Preferably, the first metal patch layer is center-symmetric, which can improve the isolation between horizontal and vertical polarization electromagnetic responses, and the metal via connecting the first and second metal patch layers is located at the center of the unit.

[0009] Preferably, the second metal patch layer is composed of a square metal patch with four circular regions removed, the center of the removed circular region is consistent with the center of the metal via connecting the first and third metal patch layers, and the radius of the circular region is slightly larger than the radius of the metal via, so as to isolate the second metal patch layer from the first and third metal patch layers.

[0010] Preferably, the square metal patch constituting the second metal patch layer is consistent in size with the unit size along the x and y axes, which can be used to block electromagnetic wave transmission and realize high-efficiency reflection.

[0011] Preferably, the third metal patch layer is composed of four square metal patches and four metal wires, wherein two metal wires connected with the inductor provide independent bias circuits for the switch diodes loaded in the horizontal and vertical directions of each unit, and the other two metal wires are connected with two square metal patches in the same direction respectively; the introduction of the inductor isolates the connected metal wires from the resonant structure, so that the related metal narrow-band wires hardly affect the electromagnetic response of the unit.

[0012] Preferably, the two metal wires connecting the square metal patches in the same direction in the third metal patch layer are in a cross structure, one of the metal wires is cut off at the center and connected with a 0-ohm resistor, which helps to maintain the independent regulation of the diodes loaded in the orthogonal directions while improving the center symmetry of the unit structure.

[0013] Preferably, the pair of switch diodes loaded along the x-axis and the y-axis in the first metal patch layer are oppositely loaded relative to the center of the unit, so that the working states of the two switch diodes loaded in the same direction are consistent.

[0014] Preferably, the second metal patch layer is connected to the negative pole of the external circuit system, and the two metal lines connected to the inductance in the third metal patch layer are respectively connected to the two output ports of the external circuit system, and the bias voltage is provided as the positive pole.

[0015] Under the incidence of horizontally and vertically polarized electromagnetic waves, by simultaneously turning on or turning off the switch diodes loaded in the corresponding direction, the basic unit can present two electromagnetic responses with a phase difference of about 180° in the design frequency band, thereby forming a dynamic regulation of the dual-polarized 1-bit reflection phase. The electromagnetic responses of orthogonal polarization not only support independent regulation, but also can basically remain consistent.

[0016] By independently loading a voltage that changes periodically with time for each pair of switch diodes in each unit, the time dimension can be additionally introduced for regulation, so as to arbitrarily and independently regulate the dual-polarized equivalent reflection coefficients of the metasurface at the harmonic frequency point, and finally simulate the anisotropic parameters required for generating a target scattering pattern.

[0017] Advantages: The present application combines switch diodes to form a polarization and scattering pattern jointly regulated spatiotemporal coding electromagnetic metasurface. By using a field-programmable gate array (FPGA) to independently load a voltage control signal that changes periodically with time for each unit, polarization arbitrary regulation and scattering pattern dynamic adjustment can be realized at the harmonic frequency point. Compared with the prior art, the present application has the following advantages:

[0018] 1. The polarization and scattering pattern jointly regulated spatiotemporal coding electromagnetic metasurface proposed in the present application supports independent and dynamic phase regulation of a pair of orthogonal polarization channels, which not only realizes low cross-polarization reflection and provides two independent information channels, but also has the advantage of high polarization isolation.

[0019] 2. The polarization and scattering pattern jointly regulated spatiotemporal coding electromagnetic metasurface proposed in the present application can extend discrete electromagnetic responses to arbitrary combinations of equivalent reflection amplitude and phase by additionally introducing time dimension regulation, thereby effectively solving the problem of limited dynamic polarization regulation capability.

[0020] 3. The present application introduces patch inductance in the third metal patch layer, which can effectively eliminate the influence of the two metal narrowband lines in the third metal patch layer on the reflection coefficient of the metasurface, thereby realizing independent control of each unit and finally expanding the ability of the metasurface to dynamically regulate the scattering pattern.

[0021] 4、The application has the advantages of simple structure, low preparation cost, low profile, etc., can be moved from the microwave band to other target frequency bands through equal scaling and other means, has good frequency band flexibility, and is expected to be applied in the fields of low-scattering antenna arrays, imaging, wireless communication, etc. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 is a schematic diagram of a metasurface according to an embodiment of the application.

[0023] Figure 2 is a schematic diagram of a basic unit according to an embodiment of the application, showing the front view (a) and the back view (b).

[0024] Figure 3 is a schematic diagram of a basic unit according to an embodiment of the application, showing the co-polarized reflection amplitude and phase diagrams under (a) x-polarized and (b) y-polarized electromagnetic wave incidence.

[0025] Figure 4 is a schematic diagram of a processed sample according to an embodiment of the application, showing the front view (a) and the back view (b).

[0026] Figure 5 is a schematic diagram of a time-varying periodic coding pattern loaded into diodes in (a) the x direction and (b) the y direction according to an embodiment of the application.

[0027] Figure 6 is a test result diagram of an embodiment of the application under the coding shown in Figure 5 .

[0028] Figure 7 is a schematic diagram of a time-varying periodic coding pattern loaded into diodes in (a) the x direction and (b) the y direction according to an embodiment of the application.

[0029] Figure 8 is a test result diagram of an embodiment of the application under the coding shown in Figure 7 . DETAILED DESCRIPTION

[0030] The application will be further described below in conjunction with the drawings and specific embodiments. It should be understood that the application can be implemented in various forms, and some exemplary and non-limiting embodiments shown in the drawings and described below are not intended to limit the application to the specific embodiments described.

[0031] As Figure 1As shown, the spatial and temporal encoding electromagnetic metasurface provided by the embodiment of the present application is periodically extended in the xy two-dimensional plane by basic units. Under the incidence of electromagnetic waves with 45-degree linear polarization and a frequency of fc, by independently loading each unit of the metasurface with a control voltage with a frequency of f0 and periodically changing with time, arbitrary polarized beams such as circularly polarized, linearly polarized and elliptically polarized beams can be generated at the +1 order harmonic (fc+f0), and the deflection angle of each beam can be dynamically controlled.

[0032] Specifically, the structure of the basic unit of the metasurface is as shown in Figure 2 As shown from top to bottom, it is a first metal patch layer, a first dielectric layer, a second metal patch layer, a second dielectric layer and a third metal patch layer. The first metal patch layer is composed of a square metal patch and four "T" type metal patches, and four switch diodes are respectively loaded between the square metal patch and the four "T" type metal patches; the second and third metal patch layers are respectively connected with the negative and positive electrodes of the external circuit system to provide a bias voltage. In this embodiment, the second metal patch layer is composed of a square metal patch with four circular regions removed, which is connected with the square metal patch in the first metal patch layer through a metal via; the third metal patch layer is composed of four square metal patches and four metal narrow band lines, the four square metal patches are respectively connected with the "T" type metal patches in the first metal patch layer through a metal via, and two square metal patches are connected with two metal narrow band lines through an inductor, the metal narrow band line at the center of the unit and extending along the x direction is truncated and connected through a 0 ohm resistor.

[0033] In this embodiment, the dielectric layer adopts F4B material with a dielectric constant of 2.2 and a loss tangent of 0.001, and the metal patch is a copper sheet. The thickness of the first dielectric layer is 3 mm, and the thickness of the second dielectric layer is 0.5 mm. The period of the basic unit is 24 mm, the side length of the square metal patch in the first metal patch layer is 9 mm, the length of the patch close to the outer side of the unit in the "T" type metal patch is 15 mm, and the length of the smaller rectangular metal patch in the "T" type metal patch is 4.4 mm and the width is 2.9 mm.

[0034] During electromagnetic full-wave simulation, the unit cell is taken as the boundary of the x and y axes. Mark the diode as code 1 when it is turned on, and mark it as code 0 when it is turned off, then the unit contains four working states of "0 / 0", "0 / 1", "1 / 0" and "1 / 1", and the two-bit binary code represents the working state of the diode loaded along the x and y axes, respectively. Under the incidence of x polarized electromagnetic waves, the co-polarized reflection coefficients of the four working states are as shown in Figure 3are shown in (a). In the range of 4.8-5.1 GHz, switching the working state of the diode loaded along the x direction can constitute 1-bit phase control, while switching the working state of the diode loaded along the y direction has little effect on the co-polarization reflection coefficient of the x polarization. Under the incidence of y polarized electromagnetic waves, the co-polarization reflection coefficients of the four working states are shown in (b). In the range of 4.8-5.1 GHz, switching the working state of the diode loaded along the y direction can constitute 1-bit phase control, while switching the working state of the diode loaded along the x direction has little effect on the co-polarization reflection coefficient of the y polarization; and the co-polarization reflection coefficients of the two orthogonal polarizations are basically identical. Therefore, the two orthogonal polarizations not only support independent control, but also have basically identical electromagnetic responses under the same external voltage control. Figure 3

[0035] In this embodiment, 8x8 units are taken as examples for sample processing and experimental illustration. The sample is shown in (a). When the diodes loaded along the x direction and the y direction in each unit are loaded with codes that periodically change with time as shown in (b) and (c) respectively, the test directional diagram is shown in (d), i.e., the metasurface can generate an elliptical polarized wave beam and a linear polarized wave beam in the xoz plane respectively. Figure 4 Figure 5 Figure 6 Figure 7 Figure 8

[0036] The technical features of the above-described embodiments can be combined in any manner. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described, but as long as the combinations of the technical features do not contradict, they should be considered as within the scope of the present disclosure.

[0037] The above-described embodiments are only preferred embodiments of the present disclosure. The same structure can be obtained by scaling the size of the unit by the same proportion, flexibly designing the working frequency band of the reconfigurable metasurface unit jointly controlled by the polarization and scattering directional diagram, or even directly extending to the millimeter wave band, infrared, terahertz, and visible light band. Obviously, for those skilled in the art, after understanding the content and principles of the present disclosure, various modifications and changes in form and details can be made without departing from the principles and structures of the present disclosure. Any simple equivalent changes and modifications made according to the claims and the disclosure of the present disclosure should still fall within the scope of the present disclosure.​​​​​​

Claims

1. A spatiotemporally encoded electromagnetic metasurface with joint polarization and scattering pattern modulation, characterized in that, It is formed by periodically extending basic units in a two-dimensional plane; the basic unit structure, from top to bottom, consists of a first metal patch layer, a first dielectric layer, a second metal patch layer, a second dielectric layer, and a third metal patch layer; the first metal patch layer consists of a central square metal patch and four surrounding "T"-shaped metal patches with protruding ends close to the square metal patch, with four switching diodes respectively loaded between the square metal patch and the four "T"-shaped metal patches; the second metal patch layer is connected to the square metal patch in the first metal patch layer through metal vias; the third metal patch layer is connected to the "T"-shaped metal patches in the first metal patch layer through metal vias; the second and third metal patch layers are respectively connected to the negative and positive terminals of the external circuit system; an inductor is connected to the metal line in the third metal patch layer that connects to the output port of the external circuit system; By independently applying a periodically varying voltage to the two pairs of switching diodes in each unit, additional time-dimensional control can be introduced, thereby arbitrarily and independently controlling the dual-polarization equivalent reflection coefficient of the metasurface at harmonic frequencies; it also has multiple functions for dynamically adjusting the number of electromagnetic beams, deflection angle, and polarization components; where the diode is marked as code 1 when it is on and code 0 when it is off, the unit contains four operating states: "0 / 0", "0 / 1", "1 / 0", and "1 / 1", where two binary codes represent the operating states of the diodes applied along the x-axis and y-axis, respectively.

2. The spatiotemporally encoded electromagnetic metasurface with joint polarization and scattering pattern modulation according to claim 1, characterized in that, The first metal patch layer is centrally symmetrical, and the metal vias connecting the first and second metal patch layers are located at the center of the unit.

3. The spatiotemporally encoded electromagnetic metasurface with joint polarization and scattering pattern modulation according to claim 1, characterized in that, The second metal patch layer is composed of square metal patches with four circular areas removed. The center of the removed circular areas is consistent with the center of the metal vias connecting the first and third metal patch layers, and the radius of the circular areas is larger than the radius of the metal vias, thereby isolating the second metal patch layer from the first and third metal patch layers.

4. The spatiotemporally encoded electromagnetic metasurface with joint polarization and scattering pattern modulation according to claim 3, characterized in that, The square metal patches that make up the second metal patch layer have the same size as the basic unit.

5. The spatiotemporally encoded electromagnetic metasurface with joint polarization and scattering pattern modulation according to claim 1, characterized in that, The third metal patch layer consists of four square metal patches and four metal wires. The two metal wires connected to the inductor provide independent bias circuits for the switching diodes loaded in the horizontal and vertical directions of each unit, respectively. The other two metal wires are connected to two square metal patches in the same direction.

6. The spatiotemporally encoded electromagnetic metasurface with joint polarization and scattering pattern modulation according to claim 5, characterized in that, In the third metal patch layer, the two metal lines connecting the square metal patches in the same direction form a cross structure, with one of the metal lines cut off at the center and connected using a 0-ohm resistor.

7. The spatiotemporally encoded electromagnetic metasurface with joint polarization and scattering pattern modulation according to claim 1, characterized in that, In the first metal patch layer, a pair of switching diodes loaded in the horizontal and vertical directions are both loaded in opposite directions relative to the cell center, so that the two switching diodes loaded in the same direction maintain the same operating state.

8. The spatiotemporally encoded electromagnetic metasurface with joint polarization and scattering pattern modulation according to claim 1, characterized in that, The second metal patch layer is connected to the negative terminal of the external circuit system, and the two metal lines in the third metal patch layer that are connected to the inductor are connected to the two output ports of the external circuit system respectively, serving as the positive terminal to provide bias voltage.

9. The spatiotemporally encoded electromagnetic metasurface with joint polarization and scattering pattern modulation according to claim 1, characterized in that, Under the incidence of horizontally and / or vertically polarized electromagnetic waves, by simultaneously turning on or off switching diodes loaded in the corresponding directions, the basic unit can exhibit two electromagnetic responses with a phase difference of 180° within the design frequency band, thereby constituting dynamic control of the dual-polarized 1-bit reflected phase.

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