Multi-degree-of-freedom beam control coding metasurface

Abstract

The invention provides a multi-degree-of-freedom beam control coding metasurface, and relates to the technical field of electromagnetic fields and electromagnetic waves. Comprising a metal floor, a dielectric substrate and a metal pattern layer, the dielectric substrate is arranged on the upper surface of the metal floor, the metal pattern layer is arranged on the upper surface of the dielectric substrate, and normal lines of the center of the metal floor, the center of the dielectric substrate and the center of the metal pattern layer coincide. The plurality of unit structures have different phase frequency sensitivities and anisotropy; the metal pattern layer comprises a first shape pattern layer or a second shape pattern layer, and the first shape pattern layer is any one of a circular-ring-shaped pattern layer, a first square-ring-shaped pattern layer, a circular pattern layer and a second square-ring-shaped pattern layer; and the second shape pattern layer is any one of a first square pattern layer, a second square pattern layer, a third square pattern layer and a fourth square pattern layer. Therefore, the angle range which can be covered by the reflection wave beam is relatively large, and polarization conversion can be realized.

Description

Technical Field

[0001] The present invention relates to the technical field of electromagnetic fields and electromagnetic waves, and particularly relates to a multi-degree-of-freedom beam control coded metasurface. Background Art

[0002] With the development of the research on coded metasurfaces, electromagnetic wave modulation has been promoted to a new level. Since the concept of coded metasurfaces was proposed in 2014, many functions can be realized by designing the structure and arrangement of coding units, such as anomalous reflection and refraction, radar cross-section reduction, beam deflection, polarization conversion, and holographic imaging, etc. The coding unit simplifies the design process of the metasurface. By coding the unit according to its electromagnetic characteristics in the spatial, temporal, and frequency domains, various functions can be achieved. Among various coding schemes, frequency-coded metasurfaces have attracted much attention due to their inherent ability to perform different functions at different frequencies. In order to enable the coded metasurface to control electromagnetic waves from the frequency domain, the concept of spatial-frequency gradient coded metasurfaces was proposed. By introducing a frequency phase gradient into the metasurface unit, a new degree of freedom was achieved. The phase response curves of the units of the space-frequency coded metasurface have different changing trends within the working frequency band, and the phase difference between the units will change approximately linearly with the change of the incident electromagnetic wave frequency, resulting in a large difference in the phase distribution pattern of the frequency-coded metasurface within the working frequency band. Therefore, the electromagnetic functions that the frequency-coded metasurface can achieve will also change with the change of frequency, so as to achieve the purpose of continuously and variably controlling electromagnetic waves.

[0003] Currently, the prior art discloses a spatial-frequency coded metasurface to manipulate the energy reflection of terahertz waves. The phase difference between adjacent units of the proposed spatial-frequency coded metasurface changes with the terahertz wave frequency. The prior art can control the energy radiation of terahertz waves by changing the working frequency without re-designing the structure of the coded metasurface. The presented spatial-frequency coded metasurface can manipulate the reflected terahertz wave to a set direction by changing the working frequency without changing the spatial coding mode. However, the spatial-frequency coded metasurface has a single performance, the angular range that the reflected beam can cover is small, and the metasurface unit is polarization-insensitive and cannot achieve polarization conversion. Summary of the Invention

[0004] The purpose of the embodiments of the present invention is to provide a multi-degree-of-freedom beam control coded metasurface to solve the problems that the angular range that the reflected beam can cover is small and polarization conversion cannot be achieved.

[0005] To solve the above technical problems, the embodiments of the present invention provide the following technical solutions:

[0006] The present invention provides a multi-degree-of-freedom beam control coding metasurface, comprising: a plurality of unit structures arranged periodically, and each of the plurality of unit structures includes a metal floor, a dielectric substrate, and a metal pattern layer. The dielectric substrate is disposed on the upper surface of the metal floor, and the metal pattern layer is disposed on the upper surface of the dielectric substrate. Moreover, the normal line passing through the geometric center of the metal floor, the normal line passing through the geometric center of the dielectric substrate, and the normal line passing through the geometric center of the metal pattern layer coincide with each other. The plurality of unit structures are unit structures with different phase sensitivities, different frequency sensitivities, and anisotropy.

[0007] The metal pattern layer includes a first shape pattern layer or a second shape pattern layer. The first shape pattern layer is any one of an annular pattern layer, a first square annular pattern layer, a circular pattern layer, and a second square annular pattern layer. The second shape pattern layer is any one of a first square pattern layer, a second square pattern layer, a third square pattern layer, and a fourth square pattern layer. The sizes of the first square annular pattern layer and the second square annular pattern layer are different, and the sizes of the first square pattern layer, the second square pattern layer, the third square pattern layer, and the fourth square pattern layer are all different.

[0008] In some embodiments, the plurality of unit structures are arranged in at least two periods along the positive x-axis direction.

[0009] In some embodiments, each period includes a plurality of first unit structures, a plurality of second unit structures, a plurality of third unit structures, and a plurality of fourth unit structures arranged in sequence along the positive x-axis direction. The plurality of first unit structures are unit structures including an annular pattern layer, the plurality of second unit structures are unit structures including a first square annular pattern layer, the plurality of third unit structures are unit structures including a circular pattern layer, and the plurality of fourth unit structures are unit structures including a second square annular pattern layer.

[0010] Alternatively, each period includes a plurality of fifth unit structures, a plurality of sixth unit structures, a plurality of seventh unit structures, and a plurality of eighth unit structures arranged in sequence along the positive x-axis direction. The plurality of fifth unit structures are unit structures including a first square pattern layer, the plurality of sixth unit structures are unit structures including a second square pattern layer, the plurality of seventh unit structures are unit structures including a third square pattern layer, and the plurality of eighth unit structures are unit structures including a fourth square pattern layer.

[0011] In some embodiments, the plurality of first unit structures, the plurality of second unit structures, the plurality of third unit structures, and the plurality of fourth unit structures are all arranged in at least one column; the plurality of fifth unit structures, the plurality of sixth unit structures, the plurality of seventh unit structures, and the plurality of eighth unit structures are all arranged in at least one column.

[0012] In some embodiments, the thickness of the dielectric substrate is 2 mm, the relative dielectric constant of the dielectric substrate is 2.65, and the tangent of the loss angle of the dielectric substrate is 0.003.

[0013] In some embodiments, in each unit structure, the length and width of the metal floor and the dielectric substrate are both 6 mm.

[0014] In some embodiments, the difference between the outer diameter and the inner diameter of the first square annular pattern layer is less than the difference between the outer diameter and the inner diameter of the second square annular pattern layer.

[0015] In some embodiments, the length of the inner diameter of the first square annular pattern layer is 2.5 mm, the length of the outer diameter of the first square annular pattern layer is 3.4 mm, the length of the inner diameter of the second square annular pattern layer is 2 mm, and the length of the outer diameter of the second square annular pattern layer is 5 mm.

[0016] In some embodiments, the inner radius of the circular annular pattern layer is 1.5 mm, the outer radius of the circular annular pattern layer is 3 mm, and the radius of the circular pattern layer is 2.25 mm.

[0017] In some embodiments, the length of the first square pattern layer is 3 mm, the width of the first square pattern layer is 6 mm, the length of the second square pattern layer is 4.8 mm, the width of the second square pattern layer is 3.6 mm, the length of the third square pattern layer is 5.2 mm, the width of the third square pattern layer is 4.3 mm, the length of the fourth square pattern layer is 6 mm, and the width of the fourth square pattern layer is 5 mm.

[0018] Compared with the prior art, a multi-degree-of-freedom beam control coding metasurface provided by the present invention includes a plurality of unit structures arranged periodically. The plurality of unit structures each include a metal floor, a dielectric substrate, and a metal pattern layer. The dielectric substrate is disposed on the upper surface of the metal floor, and the metal pattern layer is disposed on the upper surface of the dielectric substrate. Moreover, the normal line passing through the geometric center of the metal floor, the normal line passing through the geometric center of the dielectric substrate, and the normal line passing through the geometric center of the metal pattern layer coincide with each other. The plurality of unit structures are unit structures with different phase sensitivities, different frequency sensitivities, and anisotropy; the metal pattern layer includes a first shape pattern layer or a second shape pattern layer. The first shape pattern layer is any one of an annular pattern layer, a first square-annular pattern layer, a circular pattern layer, and a second square-annular pattern layer. The second shape pattern layer is any one of a first square pattern layer, a second square pattern layer, a third square pattern layer, and a fourth square pattern layer. The sizes of the first square-annular pattern layer and the second square-annular pattern layer are different, and the sizes of the first square pattern layer, the second square pattern layer, the third square pattern layer, and the fourth square pattern layer are all different. In this way, the plurality of unit structures including the annular pattern layer, the first square-annular pattern layer, the circular pattern layer, and the second square-annular pattern layer, or the plurality of unit structures with the second shape pattern layer being the first square pattern layer, the second square pattern layer, the third square pattern layer, and the fourth square pattern layer have different phase sensitivities and different frequency sensitivities, that is, the phase gradient of the plurality of unit structures changes continuously with the frequency, so that the reflected beam generates different reflection angles at different frequencies, making the angle range that the reflected beam can cover larger; and the plurality of unit structures have anisotropy, enabling the metasurface to have a polarization conversion function and realizing polarization conversion. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] By reading the following detailed description with reference to the accompanying drawings, the above and other objects, features, and advantages of the exemplary embodiments of the present invention will become readily understandable. In the drawings, several embodiments of the present invention are shown by way of illustration and not limitation, and the same or corresponding reference numerals represent the same or corresponding parts, wherein:

[0020] Figure 1 Schematically shows the structural diagram of the multi-degree-of-freedom beam control coding metasurface;

[0021] Figure 2 Schematically shows the schematic diagram of a plurality of unit structures;

[0022] Figure 3 Schematically shows the schematic diagram of the reflection amplitude and reflection phase of a coding metasurface;

[0023] Figure 4 Schematically shows the schematic diagram of the reflection amplitude and reflection phase of another coding metasurface;

[0024] Figure 5 Schematically shows a schematic diagram of the simulation results of a coded metasurface;

[0025] Figure 6 Schematically shows a schematic diagram of the simulation results of another coded metasurface;

[0026] Figure 7 Schematically shows a schematic diagram of the simulation results for verifying the coded metasurface.

[0027] Explanation of reference numerals:

[0028] 1. Metal floor; 2. Dielectric substrate; 3. Metal pattern layer; 31. First shape pattern layer; 311. Circular ring pattern layer; 312. First square ring pattern layer; 313. Circular pattern layer; 314. Second square ring pattern layer; 32. Second shape pattern layer; 321. First square pattern layer; 322. Second square pattern layer; 323. Third square pattern layer; 324. Fourth square pattern layer. Detailed implementation manners

[0029] The following further describes in detail the implementation manners of the present invention in conjunction with the drawings and embodiments. The detailed descriptions and drawings of the following embodiments are used to exemplarily illustrate the principles of the present invention, but cannot be used to limit the scope of the present invention. The present invention can be implemented in many different forms, is not limited to the specific embodiments disclosed in the text, but includes all technical solutions falling within the scope of the claims.

[0030] The following details a multi-degree-of-freedom beam control coded metasurface in an embodiment of the present invention.

[0031] See Figure 1 as shown Figure 1 Schematically shows the structural diagram of the multi-degree-of-freedom beam control coded metasurface, where Figure 1 (a) in it is the structural diagram of a coded metasurface, Figure 1 (b) in it is the structural diagram of another coded metasurface. An embodiment of the present invention proposes a multi-degree-of-freedom beam control coded metasurface, including: a plurality of unit structures arranged periodically. Each of the plurality of unit structures includes a metal floor 1, a dielectric substrate 2, and a metal pattern layer 3. The dielectric substrate 2 is disposed on the upper surface of the metal floor 1, and the metal pattern layer 3 is disposed on the upper surface of the dielectric substrate 2. Moreover, the normal line passing through the geometric center of the metal floor 1, the normal line passing through the geometric center of the dielectric substrate 2, and the normal line passing through the geometric center of the metal pattern layer 3 coincide with each other. The plurality of unit structures are unit structures with different phase sensitivities, different frequency sensitivities, and anisotropy;

[0032] The metal pattern layer 3 includes a first shape pattern layer 31 or a second shape pattern layer 32. The first shape pattern layer 31 is any one of an annular pattern layer 311, a first square annular pattern layer 312, a circular pattern layer 313, and a second square annular pattern layer 314. The second shape pattern layer 32 is any one of a first square pattern layer 321, a second square pattern layer 322, a third square pattern layer 323, and a fourth square pattern layer 324. The sizes of the first square annular pattern layer 312 and the second square annular pattern layer 314 are different, and the sizes of the first square pattern layer 321, the second square pattern layer 322, the third square pattern layer 323, and the fourth square pattern layer 324 are all different.

[0033] Specifically, multiple unit structures are arranged in a rectangular periodic pattern. The metal floor 1 and the dielectric substrate 2 completely overlap. Both the metal floor 1 and the dielectric substrate 2 are cuboids, and the shapes of the upper and lower surfaces of the metal floor 1 and the dielectric substrate 2 are both squares, and the side lengths of the upper and lower surfaces of the metal floor 1 and the dielectric substrate 2 are the same.

[0034] The multiple unit structures included in the multi-degree-of-freedom beam control coding metasurface can be of various types. They can be multiple unit structures including the annular pattern layer 311, multiple unit structures including the first square annular pattern layer 312, multiple unit structures including the circular pattern layer 313, and multiple unit structures including the second square annular pattern layer 314. The above-mentioned multiple unit structures can be referred to as one type of coding metasurface. Or, they can be multiple unit structures including the first square pattern layer 321, multiple unit structures including the second square pattern layer 322, multiple unit structures including the third square pattern layer 323, and multiple unit structures including the fourth square pattern layer 324. The above-mentioned multiple unit structures can be referred to as another type of coding metasurface.

[0035] In this embodiment, multiple unit structures are arranged in at least two periods along the positive half-axis direction of the x-axis.

[0036] In this embodiment, each period includes multiple first unit structures, multiple second unit structures, multiple third unit structures, and multiple fourth unit structures arranged in sequence along the positive half-axis direction of the x-axis. The multiple first unit structures are unit structures including the annular pattern layer 311, the multiple second unit structures are unit structures including the first square annular pattern layer 312, the multiple third unit structures are unit structures including the circular pattern layer 313, and the multiple fourth unit structures are unit structures including the second square annular pattern layer 314;

[0037] Alternatively, each period includes a plurality of fifth unit structures, a plurality of sixth unit structures, a plurality of seventh unit structures, and a plurality of eighth unit structures arranged in sequence along the positive half-axis direction of the x-axis. The plurality of fifth unit structures are unit structures including the first square pattern layer 321, the plurality of sixth unit structures are unit structures including the second square pattern layer 322, the plurality of seventh unit structures are unit structures including the third square pattern layer 323, and the plurality of eighth unit structures are unit structures including the fourth square pattern layer 324.

[0038] In this embodiment, the plurality of first unit structures, the plurality of second unit structures, the plurality of third unit structures, and the plurality of fourth unit structures are all arranged in at least one column; the plurality of fifth unit structures, the plurality of sixth unit structures, the plurality of seventh unit structures, and the plurality of eighth unit structures are all arranged in at least one column.

[0039] Specifically, the plurality of first unit structures, the plurality of second unit structures, the plurality of third unit structures, and the plurality of fourth unit structures arranged in sequence along the positive half-axis direction of the x-axis can be arranged in at least two periods. In each period, the plurality of first unit structures, the plurality of second unit structures, the plurality of third unit structures, and the plurality of fourth unit structures can be arranged in one column or multiple columns.

[0040] Alternatively, the plurality of fifth unit structures, the plurality of sixth unit structures, the plurality of seventh unit structures, and the plurality of eighth unit structures arranged in sequence along the positive half-axis direction of the x-axis can be arranged in at least two periods. In each period, the plurality of fifth unit structures, the plurality of sixth unit structures, the plurality of seventh unit structures, and the plurality of eighth unit structures can be arranged in one column or multiple columns.

[0041] Specifically, according to the generalized Snell's law, when a plane electromagnetic wave is incident on a multi-degree-of-freedom beam control coding metasurface with a certain gradient phase, the anomalous deflection angle of the beam, that is, the angle between the direction of the reflected wave and the normal, can be expressed as:

[0042]

[0043] where θ is the angle between the direction of the reflected wave and the normal, λ is the wavelength of the electromagnetic wave, is the phase of the medium surface, r is the distance, is the ratio of the change in the phase of the medium surface to the change in the distance.

[0044] When a spatial phase gradient and a frequency phase gradient are introduced, the relationship between the angle of the beam reflected by the space-frequency gradient metasurface and the space-frequency gradient of the metasurface can be derived as:

[0045]

[0046] where θ(f) is the functional relationship between the angle between the direction of the reflected wave and the normal and the electromagnetic wave frequency, f is the electromagnetic wave frequency, λ is the wavelength of the electromagnetic wave, is the ratio of the phase change amount to the distance change amount on the medium surface, c is the speed of light in vacuum, n is the number of unit structures in one period, a is the length of the multiple unit structures on the spatio-frequency multi-degree-of-freedom beam control coding metasurface, Ψ s is the phase gradient at the initial frequency, f0 is the starting frequency within the working range, Ψ f is the derivative of the phase gradient with respect to frequency.

[0047] By designing the metasurface units with specific initial phases and phase-frequency sensitivities, the energy of the reflected wave will gradually change in the designed direction. For the two coding metasurfaces, when changing the number of unit structures of the coding metasurface within one period (i.e., changing n in the expression of the functional relationship θ(f) between the angle between the direction of the reflected wave and the normal and the electromagnetic wave frequency), the beam deflection direction will also change. Thus, the flexible control of the beam direction is achieved. In addition, through two-dimensional spatial arrangement, the beam direction control can be extended from one-dimensional direction to two-dimensional direction.

[0048] The multiple unit structures are unit structures with different phase sensitivities, different frequency sensitivities and anisotropy. For the anisotropic unit structure, when its phase response to the x-polarized wave leads (or lags) the y-polarized wave by 90°, the 45° linearly polarized wave reflected by the unit structure will become a left (right) circularly polarized wave. Using the above multiple unit structures, when designing the coding metasurface, the coding pattern of the x polarization is the same as that of the y polarization. For the periodic coding metasurface, within one period, the 4 cell codings of the x-polarized wave are '00', '01', '10', '11' respectively, and the 4 cell codings of the y-polarized wave are '11', '00', '01', '10' respectively. Since the periodic spatial phase gradients of the x-polarized wave and the y-polarized wave are the same, after being reflected by the coding metasurface, the directions of the x-polarized wave and the y-polarized wave are the same, and the phase difference is 90°. Therefore, polarization conversion can be achieved while deflecting the beam direction.

[0049] According to the knowledge of traditional antenna arrays and the Pancharatnam-Berry (PB) phase principle, in order to generate a reflected beam in the desired direction, for the case of generating one beam after reflection, the phase distribution of the metasurface should meet the following requirements:

[0050]

[0051] where, is the required phase of the i-th cell, x i is the abscissa of the i-th cell, y iis the ordinate of the i-th cell, k0 is the free-space wave number, and θ0 is the angle between the z-axis and the reflected wave. is the angle between the x-axis and the reflected wave. According to the expression of the required phase of the i-th cell, the phase distribution of the metasurface can be deduced from the required beam direction.

[0052] For the case where two beams are generated after reflection, the phase distribution of the metasurface unit satisfies:

[0053]

[0054] Among them, is the phase required for the i-th cell to generate beam 1, x i is the abscissa of the i-th cell, y i is the ordinate of the i-th cell, k0 is the free-space wave number, θ1 is the angle between the z-axis and the first reflected wave, is the angle between the x-axis and the first reflected wave, is the phase required for the i-th cell to generate beam 2, θ2 is the angle between the z-axis and the second reflected wave, is the angle between the x-axis and the second reflected wave, φ i total (x i , y i ) is the phase required for the i-th cell to generate two beams, namely beam 1 and beam 2. The beam reflected by the coded metasurface, i.e., the reflected wave, will be divided into two beams according to the designed direction. Through the above expressions of the phase required for the i-th cell to generate two beams, namely beam 1 and beam 2, it can be analogized to the case of three or more beams.

[0055] By further introducing the Pancharatnam-Berry phase when arranging the units, arbitrary control of the number of reflected beams can be achieved.

[0056] In this embodiment, the thickness of the dielectric substrate 2 is 2 mm, the relative permittivity of the dielectric substrate 2 is 2.65, and the loss tangent of the dielectric substrate 2 is 0.003.

[0057] In this embodiment, the length and width of the metal floor 1 and the dielectric substrate 2 in each unit structure are both 6 mm.

[0058] In this embodiment, the difference between the outer diameter and the inner diameter of the first square annular pattern layer 312 is smaller than the difference between the outer diameter and the inner diameter of the second square annular pattern layer 314.

[0059] In this embodiment, the length of the inner diameter of the first square annular pattern layer 312 is 2.5 mm, the length of the outer diameter of the first square annular pattern layer 312 is 3.4 mm, the length of the inner diameter of the second square annular pattern layer 314 is 2 mm, and the length of the outer diameter of the second square annular pattern layer 314 is 5 mm.

[0060] In this embodiment, the inner radius of the circular annular pattern layer 311 is 1.5 mm, the outer radius of the circular annular pattern layer 311 is 3 mm, and the radius of the circular pattern layer 313 is 2.25 mm.

[0061] In this embodiment, the length of the first square pattern layer 321 is 3 mm, the width of the first square pattern layer 321 is 6 mm, the length of the second square pattern layer 322 is 4.8 mm, the width of the second square pattern layer 322 is 3.6 mm, the length of the third square pattern layer 323 is 5.2 mm, the width of the third square pattern layer 323 is 4.3 mm, the length of the fourth square pattern layer 324 is 6 mm, and the width of the fourth square pattern layer 324 is 5 mm.

[0062] Figure 2 The schematic diagrams of a plurality of unit structures are schematically shown. Refer to Figure 2 as shown Figure 2 In (a), there are a plurality of unit structures including the first shape pattern layer 31, that is, a plurality of unit structures of a coded metasurface. Among them, it includes a first unit structure, a second unit structure, a third unit structure, and a fourth unit structure. The first unit structure includes a metal floor 1, a dielectric substrate 2, and a circular annular pattern layer 311. The second unit structure includes a metal floor 1, a dielectric substrate 2, and a first square annular pattern layer 312. The third unit structure includes a metal floor 1, a dielectric substrate 2, and a circular pattern layer 313. The fourth unit structure includes a metal floor 1, a dielectric substrate 2, and a second square annular pattern layer 314. Among them, the material of the dielectric substrate 2 is F4B, the thickness h of all dielectric substrates 2 is 2 mm, and the relative dielectric constant ε of all dielectric substrates 2 rAll are 2.65, and the loss tangent δ of all dielectric substrates 2 is 0.003. The period of each first unit structure, each second unit structure, each third unit structure, and each fourth unit structure, that is, the length a and width of the metal floor 1 and the dielectric substrate 2 in each first unit structure, each second unit structure, each third unit structure, and each fourth unit structure are both 6 mm. The inner radius r1 of the circular pattern layer 311 in each first unit structure is 1.5 mm, and the outer radius r2 of the circular pattern layer 311 in each first unit structure is 3 mm. The inner diameter length w2 of the first square pattern layer 312 in each second unit structure is 2.5 mm, the outer diameter length w1 of the first square pattern layer 312 in each second unit structure is 3.4 mm, the radius r2 of the circular pattern layer 313 in each third unit structure is 2.25 mm, the inner diameter length w4 of the second square pattern layer 314 in each fourth unit structure is 2 mm, and the outer diameter length w3 of the second square pattern layer 314 in each fourth unit structure is 5 mm.

[0063] See Figure 2 as shown in Figure 2 In (b), there are multiple unit structures including the second shape pattern layer 32, that is, multiple unit structures of another coded metasurface. Among them, it includes a fifth unit structure, a sixth unit structure, a seventh unit structure, and an eighth unit structure. The fifth unit structure includes a metal floor 1, a dielectric substrate 2, and a first square pattern layer 321. The sixth unit structure includes a metal floor 1, a dielectric substrate 2, and a second square pattern layer 322. The seventh unit structure includes a metal floor 1, a dielectric substrate 2, and a third square pattern layer 323. The eighth unit structure includes a metal floor 1, a dielectric substrate 2, and a fourth square pattern layer 324. Among them, the material of the dielectric substrate 2 is F4B, the thickness h of all dielectric substrates 2 is 2 mm, and the relative dielectric constant ε r All are 2.65, and the loss tangent δ of all dielectric substrates 2 is 0.003. The period of each fifth unit structure, each sixth unit structure, each seventh unit structure, and each eighth unit structure, that is, the length a and width of the metal floor 1 and the dielectric substrate 2 in each fifth unit structure, each sixth unit structure, each seventh unit structure, and each eighth unit structure are both 6 mm. The length w6 of the first square pattern layer 321 in each fifth unit structure is 3 mm, the width w5 of the first square pattern layer 321 in each fifth unit structure is 6 mm, the length w8 of the second square pattern layer 322 in each sixth unit structure is 4.8 mm, the width w7 of the second square pattern layer 322 in each sixth unit structure is 3.6 mm, the length w 10= 5.2 mm, the width w9 of the third square pattern layer 323 in each seventh unit structure is 4.3 mm, and the length w of the fourth square pattern layer 324 in each eighth unit structure 11 = 6 mm, and the width w of the fourth square pattern layer 324 in each eighth unit structure 12 = 5 mm.

[0064] Figure 3 Schematically shows the reflection amplitude and reflection phase schematic diagrams of a coded metasurface. Refer to Figure 3 as shown. Figure 3 In (a) is the reflection amplitude diagram of a coded metasurface, Figure 3 In (b) is the reflection phase schematic diagram of a coded metasurface. The reflection amplitudes of the first unit structure, the second unit structure, the third unit structure, and the fourth unit structure in a coded metasurface remain stable within a wide frequency range, close to 0 dB, which means that the amplitudes of the reflected wave and the incident wave are basically the same. At the starting frequency, the phase gradient between adjacent unit structures is about π / 4. As the frequency increases, the phase gradient between adjacent unit structures also gradually increases. At 12 GHz, the phase gradient intervals of the first unit structure, the second unit structure, the third unit structure, and the fourth unit structure are about π / 4. In addition, at different frequencies, the phase differences between the four units are always approximately equal.

[0065] Figure 4 Schematically shows the reflection amplitude and reflection phase schematic diagrams of another coded metasurface. Refer to Figure 4 as shown. Figure 4 In (a) is the schematic diagram of the reflection amplitude of another coded metasurface for x-polarized waves, Figure 4 In (b) is the schematic diagram of the reflection amplitude of another coded metasurface for y-polarized waves, Figure 4 In (c) is the schematic diagram of the reflection phase of another coded metasurface for x-polarized waves, Figure 4 In (d) is the schematic diagram of the reflection phase of another coded metasurface for y-polarized waves. Whether the incident wave is x-polarized or y-polarized, the reflection amplitudes of the fifth unit structure, the sixth unit structure, the seventh unit structure, and the eighth unit structure are all close to 0 dB. At the starting frequency, the reflection phases of the x-polarized wave and the y-polarized wave are approximately equal. At the cut-off frequency, the reflection phase of the x-polarized wave lags behind the reflection phase of the y-polarized wave by 90°. In this way, left-handed circular polarization is obtained. When the unit rotates clockwise (or counterclockwise) by 90°, the responses to the x-polarized wave and the y-polarized wave will be interchanged. At this time, the reflection phase of the y-polarized wave will lag behind the reflection phase of the x-polarized wave by 90°, thus realizing right-handed circular polarization at the cut-off frequency.

[0066] Below, taking a coded metasurface, another coded metasurface, and coded metasurface C as examples, verify the performance of various coded metasurfaces.

[0067] Figure 5 Schematically shows a schematic diagram of the simulation results of a coded metasurface. See Figure 5 as shown. Figure 5 In (a) is a schematic diagram of the structure of a coded metasurface. Figure 5 In (b) is the normalized far-field pattern of a coded metasurface. Among them, the angle between the direction of the reflected wave and the normal, that is, the reflection angle θ, is from -90° to 90°. In a coded metasurface, multiple first unit structures, multiple second unit structures, multiple third unit structures, and multiple fourth unit structures are arranged in two periods. In each period, multiple first unit structures, multiple second unit structures, multiple third unit structures, and multiple fourth unit structures are all arranged in 3 columns, that is, repeated 3 times. At the starting frequency, the beam is reflected with a reflection angle θ of 0°. When the frequency gradually changes from the starting frequency to the cut-off frequency, the beam energy radiation of a coded metasurface is also constantly changing. The energy of the beam at the starting frequency will gradually decrease, while the energy of the beam at the cut-off frequency will gradually increase. When the frequency of the incident wave reaches the cut-off frequency, the beam at the starting frequency disappears, and almost all the energy of the electromagnetic wave is converted into the beam radiated along the direction of θ = 20°.

[0068] Figure 6 Schematically shows a schematic diagram of the simulation results of another coded metasurface. See Figure 6 as shown. Figure 6 In (a) is a schematic diagram of the structure of another coded metasurface. Figure 6 In (b) is the normalized far-field pattern of another coded metasurface. Figure 6 In (c) is the left-handed circularly polarized wave component of another coded metasurface at 12 GHz. Figure 6 In (d) is the right-handed circularly polarized wave component of another coded metasurface at 12 GHz. Figure 6 In (e) is the axial ratio of another coded metasurface at 12 GHz. Among them, Figure 6 in (c) and Figure 6 in (d), the blue to red represents the magnitude (i.e., the degree of concentration) of the energy in a certain direction. Figure 6In (e), the abscissa is the reflection angle and the ordinate is the axial ratio. In another coded metasurface, multiple fifth unit structures, multiple sixth unit structures, multiple seventh unit structures, and multiple eighth unit structures are arranged in two periods. In each period, the multiple fifth unit structures, multiple sixth unit structures, multiple seventh unit structures, and multiple eighth unit structures are all arranged in 4 columns, that is, repeated 4 times. At the starting frequency, since the reflection phases of the x-polarized wave and the y-polarized wave of 4 metasurface units are relatively close, the beam is vertically reflected by the coded metasurface, and the far-field pattern is a single beam emitted along the z-axis direction. When the frequency increases, the phase difference between the units of the other coded metasurface increases, and the beam begins to deflect. At the cut-off frequency, the beam energy completely reaches the direction of θ = 15°. As can be seen from Figure 6 (c)-(d) in, at the cut-off frequency, the main beam only has a left-handed circular polarization component, while the right-handed circular polarization component is almost zero. As can be seen from Figure 6 (e), the axial ratio of the main beam is less than 3 dB, which conforms to the circular polarization characteristic. The simulation results are in good agreement with the measured results.

[0069] Figure 7 Schematically shows a schematic diagram of the simulation results for verifying the coded metasurface. See Figure 7 as shown. Figure 7 (a) in is the coding pattern of the coded metasurface C. Figure 7 (b) in is the structure of the coded metasurface C. Figure 7 (c) in is the far-field pattern of the coded metasurface C at 8 GHz. Figure 7 (d) in is the far-field pattern of the coded metasurface C at 10 GHz. Figure 7 (e) in is the far-field pattern of the coded metasurface C at 12 GHz. Blue to red represents the magnitude of the energy (i.e., the degree of concentration) in a certain direction. In order to verify the possibility of combining the unit structure and the Pancharatnam-Berry phase, the coded metasurface C is designed. The function of the coded metasurface C is that as the frequency changes, the reflected single beam gradually becomes a double beam. The direction of the single beam is θ = 0°, and the directions of the double beams are θ = 20° and the phase of the dielectric surface According to the required beam direction, the unit structure distribution of the coded metasurface C can be calculated. As shown in Figure 7 (a), within one period, the 4 cell codings of the x-polarized wave are '00', '01', '10', '11' respectively, and the 4 cell codings of the y-polarized wave are '11', '00', '01', '10' respectively. The corresponding structure of the metasurface C is as shown in Figure 7As shown in Fig. (b), the structure of the metasurface C includes multiple fifth unit structures, multiple sixth unit structures, multiple seventh unit structures, and multiple eighth unit structures arranged periodically, which can be regarded as having three arrangement modes along the positive half-axis direction of the x-axis. In the first arrangement mode, multiple fifth unit structures, multiple sixth unit structures, multiple seventh unit structures, and multiple eighth unit structures are arranged in sequence along the negative half-axis direction of the y-axis. Multiple fifth unit structures, multiple sixth unit structures, multiple seventh unit structures, and multiple eighth unit structures are all arranged in 6 columns. In the second arrangement mode, multiple seventh unit structures, multiple eighth unit structures, multiple fifth unit structures, and multiple sixth unit structures are arranged in sequence along the negative half-axis direction of the y-axis. The third arrangement mode is exactly the same as the first arrangement mode. The parameters encoding the metasurface C are as Figure 7 shown in Figs. (c)-(d). At the starting frequency, the beam is vertically reflected by the encoded metasurface C. As the frequency gradually increases, the beam along the z-axis gradually becomes θ = 20°, resulting in two beams. The simulation results are consistent with the pre-designed directions.

[0070] Compared with the prior art, the structure of the multi-degree-of-freedom beam control encoded metasurface of the present invention is simple, easy to process, low in cost, and has more electromagnetic wave regulation functions and more flexible regulation methods. When arranging the unit structures, the Pancharatnam-Berry phase is further introduced to achieve flexible control of the number of reflected beams.

[0071] The multi-degree-of-freedom beam control coding metasurface according to an embodiment of the present invention includes: a plurality of unit structures arranged periodically. Each of the plurality of unit structures includes a metal floor 1, a dielectric substrate 2, and a metal pattern layer 3. The dielectric substrate 2 is disposed on the upper surface of the metal floor 1, and the metal pattern layer 3 is disposed on the upper surface of the dielectric substrate 2. Moreover, the normal line passing through the geometric center of the metal floor 1, the normal line passing through the geometric center of the dielectric substrate 2, and the normal line passing through the geometric center of the metal pattern layer 3 coincide with each other. The plurality of unit structures are unit structures with different phase sensitivities, different frequency sensitivities, and anisotropy. The metal pattern layer 3 includes a first shape pattern layer 31 or a second shape pattern layer 32. The first shape pattern layer 31 is any one of an annular pattern layer 311, a first square annular pattern layer 312, a circular pattern layer 313, and a second square annular pattern layer 314. The second shape pattern layer 32 is any one of a first square pattern layer 321, a second square pattern layer 322, a third square pattern layer 323, and a fourth square pattern layer 324. The sizes of the first square annular pattern layer 312 and the second square annular pattern layer 314 are different, and the sizes of the first square pattern layer 321, the second square pattern layer 322, the third square pattern layer 323, and the fourth square pattern layer 324 are all different. In this way, the plurality of unit structures including the annular pattern layer 311, the first square annular pattern layer 312, the circular pattern layer 313, and the second square annular pattern layer 314, or the plurality of unit structures including the second shape pattern layer 32 as the first square pattern layer 321, the second square pattern layer 322, the third square pattern layer 323, and the fourth square pattern layer 324 have different phase sensitivities and different frequency sensitivities, that is, the phase gradient of the plurality of unit structures changes continuously with the frequency, so that the reflected beam generates different reflection angles at different frequencies, making the angle range that the reflected beam can cover larger. Moreover, the plurality of unit structures have anisotropy, enabling the metasurface to have a polarization conversion function and realizing polarization conversion.

[0072] Although some specific embodiments of the present invention have been described in detail by way of examples, those skilled in the art should understand that the above examples are only for illustration and not for limiting the scope of the present invention. Those skilled in the art should understand that the above embodiments can be modified or partial technical features can be equivalently replaced without departing from the scope and spirit of the present invention. In particular, as long as there is no structural conflict, the various technical features mentioned in each embodiment can be combined in any way.

[0073] The above is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention can easily think of changes or substitutions, which should all be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims.

Claims

1. A multi-degree-of-freedom beam control coded metasurface, characterized in that, Comprising: A plurality of unit structures arranged periodically, each of the plurality of unit structures includes a metal floor, a dielectric substrate, and a metal pattern layer. The dielectric substrate is disposed on the upper surface of the metal floor, and the metal pattern layer is disposed on the upper surface of the dielectric substrate. Moreover, the normal line passing through the geometric center of the metal floor, the normal line passing through the geometric center of the dielectric substrate, and the normal line passing through the geometric center of the metal pattern layer coincide with each other. The plurality of unit structures are unit structures with different phase sensitivities, different frequency sensitivities, and anisotropy. The metal pattern layer includes a first shape pattern layer or a second shape pattern layer. The first shape pattern layer is any one of an annular pattern layer, a first square-annular pattern layer, a circular pattern layer, and a second square-annular pattern layer. The second shape pattern layer is any one of a first square pattern layer, a second square pattern layer, a third square pattern layer, and a fourth square pattern layer. The dimensions of the first square-annular pattern layer and the second square-annular pattern layer are different. The dimensions of the first square pattern layer, the second square pattern layer, the third square pattern layer, and the fourth square pattern layer are all different.

2. The multi-degree-of-freedom beam control coded metasurface according to claim 1, wherein The plurality of unit structures are arranged in at least two periods along the positive half-axis direction of the x-axis.

3. The multi-degree-of-freedom beam control coded metasurface according to claim 2, wherein Each period includes a plurality of first unit structures, a plurality of second unit structures, a plurality of third unit structures, and a plurality of fourth unit structures arranged in sequence along the positive half-axis direction of the x-axis. The plurality of first unit structures are unit structures including the annular pattern layer. The plurality of second unit structures are unit structures including the first square-annular pattern layer. The plurality of third unit structures are unit structures including the circular pattern layer. The plurality of fourth unit structures are unit structures including the second square-annular pattern layer. Alternatively, each period includes a plurality of fifth unit structures, a plurality of sixth unit structures, a plurality of seventh unit structures, and a plurality of eighth unit structures arranged in sequence along the positive half-axis direction of the x-axis. The plurality of fifth unit structures are unit structures including the first square pattern layer. The plurality of sixth unit structures are unit structures including the second square pattern layer. The plurality of seventh unit structures are unit structures including the third square pattern layer. The plurality of eighth unit structures are unit structures including the fourth square pattern layer.

4. The multi-degree-of-freedom beam control coded metasurface according to claim 3, wherein The plurality of first unit structures, the plurality of second unit structures, the plurality of third unit structures, and the plurality of fourth unit structures are all arranged in at least one column; the plurality of fifth unit structures, the plurality of sixth unit structures, the plurality of seventh unit structures, and the plurality of eighth unit structures are all arranged in at least one column.

5. The multi-degree-of-freedom beam control coded metasurface according to claim 1, wherein The thickness of the dielectric substrate is 2 mm, the relative dielectric constant of the dielectric substrate is 2.65, and the tangent of the loss angle of the dielectric substrate is 0.

003.

6. The multi-degree-of-freedom beam control coded metasurface according to claim 1, wherein The length and width of the metal floor and the dielectric substrate in each unit structure are both 6 mm.

7. The multi-degree-of-freedom beam control coded metasurface according to claim 1, wherein, The difference between the outer diameter and the inner diameter of the first square-annular pattern layer is less than the difference between the outer diameter and the inner diameter of the second square-annular pattern layer.

8. The multi-degree-of-freedom beam control coded metasurface according to claim 7, wherein The length of the inner diameter of the first square annular pattern layer is 2.5 mm, the length of the outer diameter of the first square annular pattern layer is 3.4 mm, the length of the inner diameter of the second square annular pattern layer is 2 mm, and the length of the outer diameter of the second square annular pattern layer is 5 mm.

9. The multi-degree-of-freedom beam control coded metasurface according to claim 1, wherein The inner radius of the circular annular pattern layer is 1.5 mm, the outer radius of the circular annular pattern layer is 3 mm, and the radius of the circular pattern layer is 2.25 mm.

10. The multi-degree-of-freedom beam control coded metasurface according to claim 1, wherein The length of the first square pattern layer is 3 mm, the width of the first square pattern layer is 6 mm, the length of the second square pattern layer is 4.8 mm, the width of the second square pattern layer is 3.6 mm, the length of the third square pattern layer is 5.2 mm, the width of the third square pattern layer is 4.3 mm, the length of the fourth square pattern layer is 6 mm, and the width of the fourth square pattern layer is 5 mm.

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