A full-space continuous tunable metasurface for b5g and 6g

Abstract

The present application relates to a kind of full space continuous adjustable metasurface for B5G and 6G, the metasurface includes multiple metasurface units, the metasurface unit includes: dielectric substrate, metal structure and adjustable material (for example: liquid crystal, graphene etc.); The metal structure generates the resonant response of target frequency band, the metal structure is arranged on the dielectric substrate, the adjustable material is combined with metal structure, form includes filled between two layers of metal structure, or with metal structure same layer, or with metal structure upper and lower layer connection.Compared with prior art, the present application is full space continuous adjustable in B5G and 6G high frequency band, realizes the accurate control of electromagnetic wave in full space range;Efficiency is high, reduces production cost, simple operation, high working frequency.The present application shows a kind of high-frequency full space continuous adjustable metasurface device, only with liquid crystal material as example.In addition, using graphene and other continuous adjustable tuning materials to control can also realize this function.

Description

TECHNICAL FIELD

[0001] The present application relates to a metasurface, and in particular to a full-space continuous adjustable metasurface for B5G and 6G. BACKGROUND

[0002] With the rapid development of global mobile communication technology, 5G technology has been commercialized and widely used in various industries. However, with the continuous advancement of social digitization and intelligentization, the existing 5G technology has certain limitations in coping with future demands. For example, with the increase in the number of intelligent devices and the popularity of data-intensive applications, global data traffic is growing explosively. The existing 5G technology is difficult to provide sufficient bandwidth and speed in the face of such huge data demand. In addition, the low-frequency and mid-frequency spectrum resources are already very crowded, and the existing spectrum resources are difficult to meet the growing demand for wireless communication. B5G (Beyond 5G) and 6G technology is the natural extension and development of 5G technology, aiming to solve the limitations of existing 5G technology and meet the complex and diverse application demands of the future. By developing B5G and 6G technology, it can also alleviate the shortage of spectrum resources and provide connectivity for more users and devices. B5G and 6G technology includes higher frequency millimeter wave and terahertz wave, which will provide higher data transmission rate to meet the future data demand. Therefore, it is necessary to study B5G and 6G technology, which will promote the further development of mobile communication technology.

[0003] Traditional optical components are based on the principles of light refraction, reflection, transmission, or diffraction, manipulating light waves by controlling the refractive index of the medium during propagation, such as lenses, waveplates, and optical modulators. Optical devices manufactured in this way are relatively bulky and no longer suitable for today's requirements for integration and miniaturization. However, planar two-dimensional metasurfaces with subwavelength thickness, through structural design, can manipulate electromagnetic waves and thus achieve various functions, leading to the rapid development of metasurfaces. Traditional metasurfaces have fixed topological geometries; once the physical structure of a metasurface is fabricated, it can only perform a specific function and cannot be changed in real time as needed. However, in some practical applications, metasurfaces often need to be able to switch between different functions in real time. To achieve tunable functionality, tunable materials or devices are integrated into a single metasurface device, allowing for flexible switching between different functions, effectively reducing the manufacturing cost of metasurfaces and broadening their application range. To date, active metasurfaces have been widely used in the microwave band for intrinsic diodes (PIN diodes) and varactor diodes. However, diodes cannot operate at high frequencies. Therefore, it is necessary to focus on other methods, such as microelectromechanical systems (MEMS) and tunable materials (liquid crystals, graphene, and vanadium dioxide), which possess the property of changing their physical properties in response to external stimuli (such as electric fields, temperature, and light). Among these tunable materials, most modulation methods are based on discontinuous tunability between two states. However, metasurfaces based on liquid crystals and graphene can be continuously tunable with voltage, allowing for flexible control of the amplitude and phase of electromagnetic waves, and have many applications in the high-frequency band.

[0004] Most existing tunable metasurfaces focus on half-space beam modulation, such as adjusting the direction of reflection or transmission, which hinders the application of metasurface devices. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a fully tunable metasurface for B5G and 6G, which realizes precise control of electromagnetic waves in the entire space range (from reflection to transmission); it is highly efficient, reduces production costs, is easy to operate, and has a high operating frequency.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] This invention achieves continuous electromagnetic wave control throughout space by adjusting the properties of tunable materials. For example, with tunable liquid crystals, the arrangement of liquid crystal molecules can be continuously changed by applying an external voltage, thereby altering the dielectric constant of the liquid crystal and enabling the control of incident electromagnetic waves. By designing a unit structure and continuously adjusting the liquid crystal material, a highly efficient beam deflection function is achieved in transmission mode, and an imaging function is achieved in reflection mode. This invention exhibits excellent all-space electromagnetic wave control performance and has potential applications in B5G and 6G communication, imaging, and sensing.

[0008] Most current modulation methods involve discontinuous tuning in two states. This invention uses continuously tunable materials and a designed metal structure to generate a resonant response in the target frequency band. Combined with the continuous tunability of the tunable material, it significantly suppresses radiation loss in transmission mode, achieving high transmittance. Furthermore, the steep phase dispersion generated by the frequency response due to the metal structure enables a large frequency shift, resulting in a phase difference with high transmittance. Simultaneously, due to the frequency shift, a large modulation depth can also be obtained in reflection mode. The continuous tunability of the tunable material enables free control of the electromagnetic wave beam throughout the entire space. High-efficiency beam deflection is achieved in transmission mode through the coding unit, and near-field imaging is realized in reflection mode.

[0009] This invention provides a fully spatially continuous tunable metasurface for B5G and 6G. The metasurface includes multiple metasurface units, each of which includes a dielectric substrate, a metal structure, and a tunable material (such as graphene, liquid crystal, etc.).

[0010] The metal structure generates a resonant response in the target frequency band. The metal structure is disposed on the dielectric substrate. The tunable material is bonded to the metal structure, either by filling between two metal layers, being in the same layer as the metal structure, or being connected to the upper and lower layers of the metal structure. The dielectric substrate provides a robust foundation to support the deposition and fabrication of other layers, and it exhibits low loss and high transmittance in the high-frequency band, ensuring that the overall performance of the device is not limited by the substrate material.

[0011] The metallic structure is the core component of a metasurface. By designing and arranging specific geometries, it is possible to modulate and manipulate terahertz waves. The metallic structure generates a resonant response in the target frequency band, and the asymmetric metallic structure designed in this invention excites a stronger resonant response. In conventional resonant structures, electromagnetic wave radiation loss is typically high, leading to reduced transmission efficiency. The metallic structure designed in this invention can reduce radiation loss and enhance interaction with electromagnetic waves, thereby achieving the desired phase shift and amplitude modulation.

[0012] Furthermore, the metasurface comprises periodically arranged metasurface units. In transmission mode, the generalized Snell's law of reflection is applied to the coded metasurface through a designed coding sequence. An angle-dependent coding sequence is assigned to the array to change the phase distribution of the array, so that electromagnetic waves are transmitted at the desired angle. In reflection mode, amplitude modulation is used to achieve near-field imaging through the designed coding sequence.

[0013] Furthermore, the metasurface unit is composed of a metal-insulator-metal resonator structure, and the size of the metasurface unit is p < λ / 2 (λ is the wavelength of the target frequency).

[0014] Furthermore, the thickness of the metal structure is 100nm to 300nm.

[0015] Furthermore, the metal structure is disposed on a dielectric substrate.

[0016] Furthermore, taking liquid crystal as an example, the adjustable material has a polyimide thickness of 0.1 μm and is spin-coated onto the metal structure.

[0017] Furthermore, taking liquid crystal as an example, the adjustable material is filled with 30-60 μm of liquid crystal between the two layers of polyimide.

[0018] Polyimide is commonly used as an alignment layer for liquid crystal molecules. During manufacturing, the polyimide layer is spin-coated onto a metal structure and then subjected to a tribological process to determine the initial orientation of the liquid crystal molecules. This polyimide layer ensures that the liquid crystal molecules are uniformly aligned on it and respond accurately to an applied electric field, thus enabling effective control of the liquid crystal layer.

[0019] The liquid crystal layer is a tunable core material. The arrangement of liquid crystal molecules can be changed by an external electric field, which in turn can change the dielectric constant of the liquid crystal. This liquid crystal layer can dynamically adjust the phase and amplitude of the incident terahertz wave.

[0020] Furthermore, tunable materials include liquid crystals, graphene, and vanadium dioxide. These materials can change their physical properties in response to external stimuli (such as electric fields, temperature, and light), thereby achieving dynamic tunability of metasurfaces. Most tunable materials can only achieve discontinuous tunability in two states. For example, vanadium dioxide is a material with phase transition properties, and its conductivity and optical properties can be controlled by temperature changes. Through temperature control, the phase transition of VO2 from an insulating state to a metallic state can be dynamically controlled, but VO2 only has two tunable states: an insulating state and a metallic state. However, in some specific applications, continuously tunable materials such as liquid crystals and graphene are needed to meet different functions, thus having many applications in the high-frequency band. Graphene, a two-dimensional material with a single layer of carbon atoms, has excellent conductivity and optical properties. By continuously controlling the external voltage, the carrier concentration of graphene can be adjusted, thereby continuously changing its conductivity and optical response. This invention uses liquid crystals as an example of tunable materials, but it can also be applied to other tunable materials and methods.

[0021] In a typical capacitor arrangement, liquid crystal cells are sandwiched between two metal layers without an applied bias voltage. The initial orientation of the liquid crystal molecules is controlled by coating a polyimide thin film layer (commonly called a pre-alignment film), ensuring that the liquid crystal molecules face the same direction, parallel to the pre-alignment film. As the voltage increases, the orientation of the liquid crystal continuously changes from its initial direction parallel to the metal plates to perpendicular to the metal plates. This change in liquid crystal molecule orientation ultimately results in a change in the relative permittivity. The relative permittivity tensor of the liquid crystal in the unbiased case is described as follows:

[0022]

[0023] Where ε ∥ It is the dielectric constant along the long axis of the liquid crystal, ε ⊥ It is the dielectric constant along the short axis of the liquid crystal;

[0024] When in a saturated biased state, the liquid crystal is oriented perpendicular to the metal layer, and the relative permittivity tensor of the liquid crystal is:

[0025]

[0026] Because the effective dielectric constant ε = ε z Therefore, when the bias voltage increases from 0V to the threshold voltage, it changes from ε ⊥ Increase to ε ∥ Liquid crystals change continuously with voltage, and their effective dielectric constant is ε. ⊥ to ε ∥The effective dielectric constant can be any value between ε and ε. This shows that the dielectric constant can be varied in different states of the liquid crystal as the bias voltage intensity changes. The change in the effective dielectric constant causes a frequency deviation in the electromagnetic response. Therefore, if the phase response of the element changes significantly with frequency, the frequency deviation will lead to a large phase shift. The effective dielectric constant of the liquid crystal used in this invention is: 2.55 ≤ ε ≤ 3.65.

[0027] Furthermore, in transmission mode, beam splitting is achieved by tuning the liquid crystal and changing the coding periodic sequence, thereby controlling the direction of the electromagnetic waves. Beam modulation in transmission mode:

[0028] The beam splitting angle of this invention is based on the generalized Snell's theorem:

[0029]

[0030] Where, θ t θ i The angle of refraction and the angle of incidence of electromagnetic waves, n i λ is the refractive index of the incident medium, and λ0 is the wavelength in vacuum. It is the phase gradient generated by the unit cell. From the generalized Snell's law, it can be seen that at the incident angle θ... i Given the situation, by changing the phase gradient Achieve deflection at any angle; because in this invention, the incident wave is incident perpendicularly from the air, i.e., the incident angle θ i =0, n i =1, and its angle of refraction can be derived from the generalized Snell's law of refraction:

[0031]

[0032] Furthermore, in reflection mode, an image with contrasting brightness is obtained in the near field through an amplitude modulation coding unit structure, i.e., near-field imaging in reflection mode:

[0033] The ability of a metasurface to modulate electromagnetic waves can be represented by the modulation depth MD, which is defined as:

[0034] MD = (Q1 - Q0) / (Q1 + Q0),

[0035] Q1 and Q0 are the highest and lowest reflectances at the operating frequency, respectively.

[0036] Compared with the prior art, the present invention has the following advantages:

[0037] (1) Wide range of applications: The metasurface structure designed in this invention generates a resonant response through a designed asymmetric metal structure and combines continuously tunable materials to achieve beam splitting in transmission mode and near-field imaging in reflection mode, realizing precise control of electromagnetic waves in the entire space range (from reflection to transmission).

[0038] (2) Reduced production costs: Full-space tunable metasurfaces, compared to half-space (reflective or transmissive) tunable metasurfaces, can achieve more efficient energy utilization and minimize energy loss. This is of great significance for improving system performance and energy saving.

[0039] (3) Simple operation: The integrated metasurface structure can change the resonant response of the unit structure by simply changing the voltage. After being combined with FPGA coding, the state of each unit structure can be easily controlled to achieve different adjustable functions.

[0040] (4) High operating frequency: The designed unit structure operates in the high frequency band, which has potential applications in B5G and 6G millimeter wave and terahertz communication, imaging, sensing and other fields. Attached Figure Description

[0041] Figure 1 This is a schematic diagram illustrating the working principle of the entire metasurface based on an embodiment of the present invention.

[0042] Figure 2 This is a schematic diagram of the structure of a liquid crystal metasurface microstructure unit based on an embodiment of the present invention; wherein, a is a schematic diagram of the three-dimensional structure of the microstructure unit, and b is a schematic diagram of the metal structure of the microstructure unit;

[0043] Figure 3 Based on the transmission mode of this invention, the simulated scattering amplitude and phase corresponding to microstructure units with effective dielectric constants of 2.55 and 3.65 of the liquid crystal are changed;

[0044] Figure 4 Based on the reflection mode of this invention, the simulated scattering amplitude and phase corresponding to microstructure units with effective dielectric constants of 2.7 and 3.65 of the liquid crystal are changed;

[0045] Figure 5 This is an example of simulation results based on the unit periodic array transmission mode of the present invention; where a is a specific coding periodic sequence diagram and b is a schematic diagram of the far field of beam splitting generated by coding.

[0046] Figure 6 This is a schematic diagram of near-field imaging in the coded sequence reflection mode based on an embodiment of the present invention;

[0047] Figure reference numerals: 1-quartz substrate; 2-metal structure; 3-polyimide; 4-liquid crystal. Detailed Implementation

[0048] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. Component models, material names, connection structures, control methods, algorithms, and other features not explicitly described in this technical solution are considered common technical features disclosed in the prior art.

[0049] Example 1

[0050] This embodiment provides a fully spatially continuous tunable metasurface for B5G and 6G, the metasurface comprising multiple metasurface units, such as... Figure 2 As shown in Figure a, the metasurface unit includes: a quartz substrate 1, a metal structure 2, a polyimide 3, and a liquid crystal 4;

[0051] The metal structure 2 includes an asymmetric split ring, the metal structure 2 is disposed on the quartz substrate 1, the polyimide 3 is disposed on the metal structure 2, and the liquid crystal 4 is filled between the two layers of polyimide 3.

[0052] The role of the quartz substrate 1 is to provide a robust foundation to support the deposition and fabrication of other layers, and it has low loss and high transmittance in the high-frequency band, ensuring that the overall performance of the device is not limited by the substrate material.

[0053] Metal structure 2 is the core component of the metasurface. By designing and arranging specific geometries, it enables the modulation and manipulation of terahertz waves. The asymmetric metal structure designed in this invention excites a resonant response. In conventional resonant structures, electromagnetic wave radiation loss is typically high, leading to reduced transmission efficiency. The metal structure designed in this invention reduces radiation loss and enhances the interaction with electromagnetic waves, thereby achieving the desired phase shift and amplitude modulation.

[0054] Polyimide 3 is commonly used as a liquid crystal molecule alignment layer. During manufacturing, the polyimide layer is spin-coated onto a metal structure and then subjected to a tribological process to determine the initial alignment of the liquid crystal molecules. This polyimide layer ensures that the liquid crystal molecules are uniformly aligned on it and respond accurately to an applied electric field, thereby achieving effective control over the liquid crystal layer.

[0055] The core material of the liquid crystal layer 4 is tunable. The arrangement of liquid crystal molecules can be changed by an external electric field, thereby continuously changing the dielectric constant of the liquid crystal. This liquid crystal layer can dynamically adjust the phase and amplitude of the incident terahertz wave.

[0056] In specific implementation methods, such as Figure 1As shown, the metasurface comprises periodic metasurface units. In transmission mode, the generalized Snell's law of reflection is applied to the coded metasurface through a designed coding sequence. An angle-dependent coding sequence is assigned to the array to change the phase distribution of the array, so that electromagnetic waves are transmitted at the desired angle. In reflection mode, amplitude modulation is used to achieve near-field imaging through the designed coding sequence.

[0057] In a specific embodiment, the metasurface unit is composed of a metal-insulator-metal resonator structure, and the size of the metasurface unit is p < λ / 2 (λ is the wavelength of the target frequency).

[0058] In a specific embodiment, the thickness of the metal structure 2 is 0.3 μm.

[0059] In specific implementation methods, such as Figure 2 As shown in b, to achieve a resonant response at THz, an asymmetric metal structure is used, where w = 10 μm, w1 = 30 μm, w2 = 50 μm, l1 = 15 μm, and l2 = 20 μm. The metal structure 2 is disposed on a 150 μm quartz substrate 1.

[0060] In a specific embodiment, the polyimide 3 has a thickness of 0.1 μm and is spin-coated onto the metal structure 2.

[0061] In a specific embodiment, a 60μm layer of liquid crystal 4 is filled between the two layers of polyimide 3.

[0062] In a specific embodiment, the present invention uses liquid crystal as a tunable material as an example.

[0063] In a typical capacitor arrangement, the liquid crystal cell is sandwiched between two metal layers without an applied bias voltage. The initial orientation of the liquid crystal molecules is controlled by coating a polyimide thin film layer (commonly called a pre-alignment film), ensuring that the liquid crystal molecules are aligned parallel to the pre-alignment film. As the voltage increases, the orientation of the liquid crystal continuously changes from its initial direction parallel to the metal plates to perpendicular to the metal plates. This change in liquid crystal molecule orientation ultimately results in a change in the relative permittivity. The relative permittivity tensor of liquid crystal 4 in the unbiased case is described as follows:

[0064]

[0065] Where ε ∥ ε is the dielectric constant along the long axis of the liquid crystal. ⊥ It is the dielectric constant along the short axis of the liquid crystal;

[0066] When under saturation bias, liquid crystal 4 is oriented perpendicular to the metal layer, and the relative permittivity tensor of liquid crystal 4 is:

[0067]

[0068] Because the effective dielectric constant ε = ε z Therefore, when the bias voltage increases from 0V to the threshold voltage, it changes from ε ⊥ Increase to ε ∥ The liquid crystal 4 changes continuously with voltage, and its effective dielectric constant is ε. ⊥ to ε ∥ The effective dielectric constant can be any value between ε and ε. This shows that the dielectric constant of the liquid crystal 4 can be varied in different states as the bias voltage intensity changes. The change in the effective dielectric constant causes a frequency deviation in the electromagnetic response. Therefore, if the phase response of the element changes significantly with frequency, the frequency deviation will lead to a large phase shift. The effective dielectric constant of the liquid crystal 4 used in this invention is: 2.55 ≤ ε ≤ 3.65.

[0069] In a specific implementation, beam modulation in transmission mode:

[0070] The beam splitting angle of this invention is based on the generalized Snell's theorem:

[0071]

[0072] Where, θ t θ i The angle of refraction and the angle of incidence of electromagnetic waves, n i λ is the refractive index of the incident medium, and λ0 is the wavelength in vacuum. It is the phase gradient generated by the unit cell. From the generalized Snell's law, it can be seen that at the incident angle θ... i Given the situation, by changing the phase gradient Achieve deflection at any angle; because in this invention, the incident wave is incident perpendicularly from the air, i.e., the incident angle θ i =0, n i =1, and its angle of refraction can be derived from the generalized Snell's law of refraction:

[0073]

[0074] In a specific embodiment, the metasurface operates at a frequency of 0.529 THz, such as... Figure 3 As shown, by changing the effective dielectric constant of liquid crystal 4 to 2.55 and 3.65, two unit cell structures with a transmittance of approximately 0.65 and a phase difference of 184° can be obtained. Using the concept of an encoded metasurface, the two unit cell structures of liquid crystal 4 with dielectric constants of 2.55 and 3.65 are defined as "0" and "1", respectively. Figure 5 As shown in Figure a, taking the encoded sequence 000111000111000111000111000111 as an example, it is applied to the entire metasurface to generate transmitted electromagnetic waves as shown in Figure a. Figure 5The beam splitting angle of approximately 36° shown in b is exactly in line with the theoretical value. By changing different coding cycle sequences, beam splitting at corresponding angles can be achieved, allowing for more flexible control of the electromagnetic wave direction.

[0075] Near-field imaging in reflection mode:

[0076] The ability of a metasurface to modulate electromagnetic waves can be represented by the modulation depth MD, which is defined as:

[0077] MD = (Q1 - Q0) / (Q1 + Q0),

[0078] Q1 and Q0 are the highest and lowest reflectivities at the operating frequency, respectively. For example... Figure 4 As shown, at 0.566 THz, the reflectance coefficients of liquid crystal 4 with dielectric constants of 3.65 and 2.7 are 0.963 and 0.194, respectively, with a phase difference of 0°. The modulation depth of the tunable liquid crystal metasurface of this invention is 66.5%. The two unit structures of liquid crystal 4 with dielectric constants of 2.7 and 3.65 are defined as "0" and "1", respectively. Due to the influence of the modulation depth, by arranging these two unit structures, images with contrasting brightness and darkness can be obtained in the incoming field. However, due to the coupling effect between the units, the image inevitably does not reach the ideal state. Figure 5 As shown, the units represented by the letters "S" and "U" are coded as "1" and are marked with white boxes, while other structural units are coded as "0". The image was captured in the near field, as shown below. Figure 6 As shown.

[0079] Components not described in detail in this embodiment are all existing components that can be purchased through public channels.

[0080] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A fully tunable metasurface for B5G and 6G, characterized in that, The metasurface comprises a plurality of periodically arranged metasurface units, each metasurface unit comprising: a dielectric substrate, a metallic structure, and a tunable material; The adjustable material can continuously adjust its dielectric constant or conductivity, achieving continuous adjustability throughout the entire space. The metasurface unit adopts a metal-insulator-metal resonator structure, and the metal structures are all asymmetric split rings disposed on the dielectric substrate. The tunable material is filled between the two metal structures or connected to the metal structures in the same layer / above and below the metal structures. By continuously adjusting the dielectric constant or conductivity of the tunable material, the metasurface unit can achieve continuous and gradual phase control in transmission mode and continuous and gradual amplitude control in reflection mode. In the transmission mode, beam splitting is achieved through phase gradient coding, and near-field imaging is achieved through amplitude coding in reflection mode. By using a designed coding sequence, the generalized Snell's law of reflection is applied to the coded metasurface in transmission mode, and angle-dependent coding sequences are assigned to the array to change the phase distribution of the array so that the electromagnetic wave is deflected at the desired angle; in reflection mode, amplitude modulation is used to achieve near-field imaging through the designed coding sequence.

2. The fully tunable metasurface for B5G and 6G according to claim 1, characterized in that, Continuous beamforming control is achieved through tunable materials; the tunable material is a liquid crystal material, where the liquid crystal molecule state changes continuously with voltage, and the effective dielectric constant can be selected. arrive Any value between these values, and the change in the effective dielectric constant, generates a frequency deviation in the electromagnetic response, thus achieving continuous beam control.

3. The fully tunable metasurface for B5G and 6G according to claim 1, characterized in that, In transmission mode, by tuning tunable materials, finding the corresponding coding units, and changing the coding period sequence, beam splitting is achieved, thus controlling the direction of electromagnetic waves; beam manipulation in transmission mode: Beam control of its beam splitting angle is based on the generalized Snell's theorem: ， in, , These are the angle of refraction and the angle of incidence of the electromagnetic wave, respectively. It is the refractive index of the incident medium. It is the wavelength in a vacuum. It is the phase gradient generated by the unit; according to the generalized Snell's law, at the incident angle Given the situation, by changing the phase gradient This allows for deflection at any angle; since the incident wave is perpendicular to the air, i.e., the angle of incidence is... , The angle of refraction is derived from the generalized Snell's law of refraction: 。 4. The fully tunable metasurface for B5G and 6G according to claim 1, characterized in that, In reflection mode, by tuning a tunable material and using amplitude modulation, the coding unit structure is found. By arranging the coding unit structure, an image with contrast between light and dark is obtained in the near field, i.e., near-field imaging in reflection mode: The ability of a metasurface to modulate electromagnetic waves is represented by the modulation depth MD, which is defined as: ， and These represent the highest and lowest reflectance at the operating frequency, respectively.

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