An electromagnetic super-transparent film for wireless signal enhancement

Abstract

The present invention discloses an electromagnetic super-transparent film for wireless signal enhancement, which belongs to the field of electromagnetic regulation technology. The electromagnetic super-transparent film of the present invention is composed of a large number of metal grid units with equal side lengths and a flexible transparent PET film substrate. The metal grid unit is a square metal structure with a plurality of adjustable metal sections in the middle. The changes in the side length of the structure and the length of the middle metal section can realize the transmission phase and amplitude modulation of the incident electromagnetic wave. The super-transparent film is respectively deployed on both sides of the transparent glass plate, and the whole formed by the super-transparent film and the glass can realize the macro-regulation of the incident electromagnetic wave to enhance the wireless signal coverage. The visible light transmittance of the super-transparent film exceeds 85%, can cover the beam adjustment range of more than 150°~150°, and the signal gain peak exceeds 30dB; by adjusting the structural parameters of the unit structure, signal enhancement of multiple communication frequency bands can be achieved.

Description

Technical Field

[0001] The present invention relates to the field of electromagnetic control technology, and more specifically to an electromagnetic super-transparent film for enhancing wireless signals. Background Art

[0002] With the rapid development of 5G communication technology, the diversification of business types and the continuous expansion of industry boundaries, users' demand for wireless networks is undergoing a significant shift from outdoor to indoor. According to industry forecasts, in the 5G era, the proportion of indoor consumer mobile communication services will increase significantly to more than 85%, which indicates that the importance of indoor wireless network coverage is becoming increasingly prominent.

[0003] However, the continuous evolution of wireless communication technology, especially the continuous increase in the operating frequency of electromagnetic waves, has brought unprecedented challenges to the coverage and penetration of electromagnetic signals. While pursuing higher performance, high-frequency communication technology must overcome the difficulty of electromagnetic signal propagation in complex environments, especially how to achieve millimeter-wave penetration through walls and efficient home access, which has become a key technical issue that needs to be solved urgently.

[0004] To solve the above problems, metamaterial planar transmission arrays with subwavelength periodic structures have emerged. This new material can redirect wireless signals to a specific direction by precisely controlling the transmission path of electromagnetic waves, thereby effectively improving the coverage of wireless networks and significantly increasing the strength of network signals. As an economical and practical solution, metamaterial planar transmission arrays have shown great application potential in the field of wireless communications, especially in millimeter-wave wall penetration, providing strong technical support.

[0005] When designing a planar transmission array, the following key requirements must be met: first, the phase coverage of the array unit should be as wide as possible to ensure all-round transmission of the signal; second, the transmission efficiency within the passband should be as high as possible to reduce signal loss; third, the passband bandwidth should be as wide as possible to accommodate signal transmission requirements of different frequencies; fourth, the preparation process should be as simple as possible to reduce production costs and improve production efficiency.

[0006] However, the existing transmissive metasurfaces with beam steering functions still have many structural deficiencies. In order to meet the requirements of 360-degree phase coverage, most transmissive metasurfaces adopt a multi-layer stacking design, and even have strict air cavities between layers. This design not only makes the overall structure less compact, but also places extremely high demands on manufacturing and assembly accuracy, increasing the difficulty of debugging. In addition, most transmissive metasurfaces use PCB boards as the base material, which are not light-transmissive and can hardly meet some application scenarios that require optical transparency or visual observation.

[0007] Although a few researchers have tried to use thin films and transparent media (such as glass) with high optical transparency as the core materials to design and develop some optically transparent antennas, these methods still face many challenges in practical applications. For example, the modification of existing glass is difficult and costly, and the designed antennas often have a certain thickness, making it difficult to achieve conformal deployment with actual scenarios. Therefore, developing a transmissive metasurface that has excellent beam steering performance, good light transmittance and compact structure has become a technical problem that needs to be solved urgently in the current wireless communication field. Summary of the invention

[0008] In view of this, the present invention provides an electromagnetic super-transparent film for wireless signal enhancement, which has excellent beam control performance, good light transmittance and compact structure.

[0009] In order to achieve the above object, the present invention adopts the following technical solution:

[0010] An electromagnetic super-transparent film for wireless signal enhancement, comprising:

[0011] A super surface unit, the super surface unit comprising: a flexible substrate layer, and a metal grid layer attached to the flexible substrate layer;

[0012] Preferably, it also includes a dielectric layer, and the metasurface unit is attached to the dielectric layer.

[0013] Preferably, the metal grid layer is a nano-copper metal grid pattern, and the structure of the nano-copper metal grid pattern is a square metal frame and double short stubs symmetrically arranged in the square metal frame.

[0014] Preferably, the design of the metasurface unit includes:

[0015] determining material properties of the dielectric layer;

[0016] Designing structural parameters of the metal grid layer according to the material properties of the dielectric layer, and determining the vibration starting point of the nano-copper metal grid pattern;

[0017] According to the center frequency of the frequency band where the target signal is located f Adjust the side length of the super surface unit w , further adjusting the structural parameters of the super surface unit so that the A metasurface array unit realizes a linear phase shift characteristic, and the structural parameters of the metasurface unit include line width and short line length;

[0018] For the incident angle ψ The incident wave is assumed to be in the direction of the desired beam. i , determine each unit structure of the metal mesh layer.

[0019] Preferably, the angle i Signal enhancement, i The phase distribution of the column unit must satisfy the following distribution:

[0020] ;

[0021] in, f represents the center frequency of the incident wave, c represents the propagation speed of electromagnetic waves, w represents the side length of each hypersurface unit, ψ Represents the angle of incidence of the incident wave.

[0022] Preferably, in order to simplify the overall design of the ultra-transparent film, the phase of each column of units is i i Quantized into 4 fixed unit structures, their transmission phases are: .

[0023] Preferably, i Column metasurface unit calculation phase i i , and then calculate the index of the required structural unit from the structural parameter library:

[0024] ;

[0025] At this time, select j The unit structure is used as the standard structure of this series of metasurfaces.

[0026] Preferably, the thickness of the metal mesh layer is between 0.2 and 1 μm between.

[0027] Preferably, the material of the flexible substrate layer is polyethylene terephthalate.

[0028] It can be known from the above technical solution that compared with the prior art, the present invention discloses an electromagnetic super-transparent film for wireless signal enhancement, which realizes a wide range of precise control of the electromagnetic wave phase by finely adjusting the size design of the pattern on the film. In experimental tests, in the operating frequency band of 5.2 to 5.8 GHz, the transmission efficiency of the super-transparent film is excellent, reaching more than 85%, and can effectively adjust the deflection angle of the transmitted wave within a wide range of -150° to 150°, while achieving a peak gain of more than 30 dB, and significantly improving the signal enhancement effect. The super-surface array composed of the nano-copper electromagnetic super-transparent film provided by the present invention not only has broadband response capability, but also has the dual advantages of high optical transparency and high transmittance, and can be flexibly deployed in various scenes that need to maintain optical transparency or require perspective observation, such as windows of buildings, windshields of vehicles, etc., thereby effectively improving the coverage and transmission quality of wireless signals without affecting the line of sight and aesthetics. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0030] Figure 1 A perspective view of the basic unit structure of the electromagnetic super-transparent film with nano-copper structure provided by the present invention;

[0031] Figure 2 A schematic diagram of an embodiment of an electromagnetic super-transparent film based on a transparent metal grid pattern provided by the present invention;

[0032] Figure 3 A schematic diagram of a unit metal fine line pattern of a transparent metal grid structure provided by the present invention;

[0033] Figure 4 A schematic diagram of the generation principle of the geometric phase provided by the present invention;

[0034] Figure 5 A flow chart of a preferred embodiment of the phase modulation method based on the electromagnetic super-transparent film provided by the present invention;

[0035] Figure 6 The invention provides a method for treating an electromagnetic super-transparent film The process in which each array unit modulates the phase of the incident electromagnetic wave;

[0036] Figure 7 This is a diagram of the simulated focusing results of the high-gain electromagnetic super-transparent film provided by the present invention. DETAILED DESCRIPTION

[0037] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0038] The present invention provides an electromagnetic super-transparent film for wireless signal enhancement. In the present invention, a metal grid pattern and a flexible substrate PET are sequentially arranged to form a nano-copper electromagnetic super-transparent film, wherein the nano-copper electromagnetic super-transparent film is deployed on a transparent glass plate carrying the super-transparent film in practical applications, and after forming a transmission array, the phase of the incident electromagnetic wave is modulated respectively, so that the expected phase distribution is obtained after beamforming, thereby improving the transmittance while realizing high-gain beam focusing control of the electromagnetic wave, thereby increasing the internal space coverage of the electromagnetic wave signal in depth and breadth.

[0039] The embodiment of the present invention discloses an electromagnetic super-transparent film for wireless signal enhancement, such as Figure 1 As shown, including:

[0040] The super surface unit includes a flexible substrate layer and a metal grid layer attached to the substrate layer. The flexible substrate layer and the metal grid layer are optically transparent and constitute a transparent nano copper electromagnetic super transparent film; the nano copper electromagnetic super transparent film is deployed on both sides of the transparent glass plate in practical applications.

[0041] When the incident electromagnetic wave is incident on the high-gain electromagnetic super-transparent film based on the nano-copper structure at a certain angle, the corresponding number of array units modulates the phase of the incident electromagnetic wave to obtain the expected phase distribution, thereby realizing the transmission of the electromagnetic wave, such as wide-band, high-transmittance, and high-transparency beamforming, for example, realizing high-gain beam focusing control of the incident electromagnetic wave, enhancing the penetration depth and breadth of the electromagnetic wave signal.

[0042] The metasurface array unit has high transmittance and transmission phase. The metal grid pattern is arranged on the transparent flexible substrate layer by any one of etching, photolithography, chemical plating and electroplating. The metal grid pattern layer and the flexible substrate layer are arranged in sequence to form a transmission array, and the incident electromagnetic wave is subjected to transmission phase modulation and beam control.

[0043] In the electromagnetic super-transparent film provided in the embodiment of the present invention, the beam controllability and visible light transparency of electromagnetic control are taken into account by using a thin film composed of a transparent flexible PET film substrate and a nano-copper metal grid pattern. That is, the present invention replaces the traditional thick and opaque transmission-type super surface with an ultra-thin transparent flexible substrate PET and a nano-copper metal grid structure to achieve the visual transparency of the electromagnetic super-transparent film, so that the electromagnetic super-transparent film can have conformal optical transparency, can be applied to scenes requiring optical transparency or transparent observation, and is suitable for glass walls inside and outside buildings in the city center, portholes of large vehicles, and other scenes that need to provide high-quality communication services for a large number of mobile terminal devices and have optical transparency requirements at the same time.

[0044] Figure 2 The electromagnetic super-transparent film based on the transparent metal grid pattern is One implementation manner of a transparent antenna array formed by arranging array units in a predetermined manner.

[0045] Specifically, after the phase distribution of the incident electromagnetic wave to be regulated after shaping (expected phase distribution) is known, according to all the pixel points in the expected phase distribution, The length of the double stubs of the metal pattern of each array unit is controlled accordingly so that the deployed Each array unit transmits the electromagnetic wave and obtains the expected phase distribution. Figure 6 Schematic diagram of the principle of geometric phase generation.

[0046] For example, when an electromagnetic wave is incident on a super-transparent film, its wavefront (i.e., an equiphase surface) passes through the The transparent antenna array consists of array units, where each array unit adjusts the local discrete phase at its location. After the artificial atoms are regulated, we get a The phase distribution composed of a local phase, and the super-transparent film prepared according to the new phase distribution is the electromagnetic super-transparent film based on the transparent metal grid pattern in the present invention.

[0047] In the present invention, an electromagnetic super-transparent film for high-gain beam focusing control of transmitted waves is designed by regulating and changing the pattern size, which can realize functions such as beam scanning, multi-beam, vortex field, etc. That is, a multifunctional high-gain electromagnetic super-transparent film that can be conformally deployed in buildings or vehicles and other scenes that require optical transparency or perspective observation is realized. The electromagnetic super-transparent film can be covered on traditional window glass. On the basis of high transmittance, high-gain beam focusing control is performed on the incident electromagnetic wave, which effectively enhances the penetration depth and breadth of the electromagnetic wave signal.

[0048] Specifically, the metal grid pattern layer is divided into a square closed area with double short stubs on the upper and lower sides and a middle area, and each metasurface array unit adjusts the phase by adjusting the size of the short stubs. Figure 3 As shown, the shape of the array unit metal fine line pattern is a square, the length and width of the array unit are both P, the transparent nano copper metal grid pattern layer is a square metal fine line pattern with double short stubs on the top and bottom, the square closed area 1.1 is the metal area, and the middle area 1.2 is the hollow area. The square metal fine line pattern structure with double short stubs on the top and bottom in the present invention can achieve an extremely low metal duty cycle and thus achieve high visible light transmittance; at the same time, it achieves a wide band and high transmittance amplitude response of electromagnetic waves.

[0049] Specifically, all the square metal fine line pattern layers with double short stubs on the top and bottom have the same specifications, that is, the thickness, shape and outer size of all the metal pattern layers are the same.

[0050] Furthermore, the metasurface array unit of the embodiment of the present invention includes four fixed unit structures, and the transmission phases of the four fixed unit structures are respectively: 0°, 90°, 180°, and 270°.

[0051] Furthermore, the thickness of the metal grid pattern layer is 0.2-1 μm The square resistance is less than or equal to 0.06Ω / sq, and the material is nano-scale copper. By controlling the thickness of the transparent metal grid structure to 0.2~1 μm Within the range of , it is possible to ensure the electrical connection stability and signal sensitivity between the unit patterns of the transparent metal grid structure while avoiding excessive thickness of the transparent metal grid structure, thereby facilitating the thinning and conformal design of the electromagnetic super-transparent film. Since the square resistance of the nano-copper metal grid structure used in the electromagnetic super-transparent film of the present invention is small, the transparent super-surface unit structure can have a small resistance value, which is beneficial to improving the conductive performance and signal sensitivity and is convenient to use.

[0052] In another embodiment, the material of the flexible substrate layer is polyethylene terephthalate.

[0053] In another embodiment, the thickness of the flexible substrate layer is 100 μm By controlling the thickness of the flexible transparent substrate to 100 μm The thickness of about 2000 nm can ensure that the flexible transparent substrate has sufficient structural strength to carry the transparent metal grid structure while avoiding the flexible transparent substrate from being too thick, which is conducive to the lightweight and conformal design of the electromagnetic super-transparent film.

[0054] On the other hand, an embodiment of the present invention further provides a method for preparing an electromagnetic super-transparent film for wireless signal enhancement, comprising:

[0055] Test the material properties of the target dielectric material, including thickness and dielectric constant;

[0056] Determine the metal structure layer according to the super surface design method;

[0057] Prepare the ultra-transparent film according to the parameters of the metal structure layer;

[0058] The ultra-transparent film is attached to the target medium layer to achieve signal enhancement in the specified angle domain. The design of the metasurface unit includes:

[0059] Determining material properties of the dielectric layer;

[0060] Designing structural parameters of the metal grid pattern layer according to the material properties of the dielectric layer, and determining the vibration starting point of the nano copper metal grid pattern;

[0061] According to the center frequency of the frequency band where the target signal is located f Adjust the side length of the hypersurface unit w , further adjusting the structural parameters of the metasurface unit so that the metasurface array unit realizes a linear phase shift characteristic, the structural parameters of the metasurface unit including line width and short line length;

[0062] For the incident angle ψ The incident wave is assumed to be in the direction of the desired beam. i , determine each unit structure of the metal mesh layer.

[0063] To achieve the angle i Signal enhancement, The phase distribution of the column unit must satisfy the following distribution:

[0064] ;

[0065] in, f represents the center frequency of the incident wave, c represents the propagation speed of electromagnetic waves, w Indicates the width of each unit, ψ represents the angle of the incident wave.

[0066] In order to simplify the overall design of the ultra-transparent film, the phase of each column unit is i i Quantized into 4 fixed unit structures, their transmission phases are: .

[0067] For i The phase of the metasurface unit is calculated i i , and then calculate the index of the required structural unit from the structural parameter library:

[0068] ;

[0069] At this time, select j The unit structure is used as the standard structure of this series of metasurfaces.

[0070] Further, such as Figure 4 As shown, the method for obtaining a transparent antenna array based on an electromagnetic super-transparent film comprises the following steps:

[0071] S100, The transparent antenna array is obtained by using the array units in a preset manner.

[0072] Specifically, in order to use the electromagnetic super-transparent film to realize the beam focusing control function of electromagnetic waves, first, The artificial atoms are connected in a preset manner to obtain a transparent antenna array, thereby utilizing the transparent antenna array to focus the electromagnetic wave beam.

[0073] Furthermore, S100, the step of obtaining the transparent antenna array according to the preset method by each array unit specifically includes: respectively determining the phase points in the expected phase distribution according to the phase points in the expected phase distribution. The double stub sizes of each array unit are adjusted to obtain a transparent antenna array.

[0074] Specifically, in order to realize the beam focusing control function of electromagnetic waves by using the electromagnetic super-transparent film, firstly, the desired phase distribution is known, that is, the expected phase distribution is known, and the phase points in the expected phase distribution are respectively controlled. The double stub size is adjusted for each array unit, that is, according to the degree of modulation required for each phase point and the functional relationship between the modulation degree and the adjustment size, the corresponding size of each array unit is adjusted accordingly, and finally a special glass array is obtained.

[0075] In order to realize the beam focusing function, according to the Huygens principle (Huygens principle means that every point (surface source) on the spherical wave surface is a sub-wave source of a secondary spherical wave, and the wave velocity and frequency of the sub-wave are equal to the wave velocity and frequency of the primary wave. After that, the envelope of the sub-wave surface at each moment is the wave surface of the total fluctuation at that moment. The lens focusing must satisfy the total phase accumulated by the spherical wave emitted by each sub-wave source on the wave front of the incident wave passing through the lens to the focus is equal), the phase distribution that needs to be modulated on the entire glass array plane must satisfy the following distribution, namely:

[0076] ;

[0077] in, f represents the center frequency of the incident wave, c represents the propagation speed of electromagnetic waves, w Indicates the width of each unit, ψ represents the angle of the incident wave.

[0078] Further, S200, the phase distribution electromagnetic super-transparent film modulates the phase of the incident electromagnetic wave to obtain a desired phase distribution.

[0079] like Figure 5 As shown, after the electromagnetic super-transparent film is prepared, the electromagnetic super-transparent film is used Each array unit modulates the phase of the incident electromagnetic wave respectively, and then beamforming obtains the expected phase distribution, thereby achieving the desired phase distribution by modulating the phase of the incident electromagnetic wave through the transparent antenna array.

[0080] For example, when a plane wave passes through The transparent antenna array consists of array units, where each array unit regulates the local phase (discretization) near its space. Then, after the transparent antenna array After adjusting the array units, we get a The new phase distribution (expected phase distribution) is composed of discrete local phases.

[0081] For further information, see Figure 7 , simulate the beam control of the high-gain electromagnetic super-transparent film (based on the phase modulation of the electromagnetic super-transparent film), and obtain the result diagram of the high-gain electromagnetic super-transparent film simulation beam, The electromagnetic super-transparent film example composed of array units achieves a 60° transmission wave deflection in the 5.2-5.8GHz operating frequency band at an incident angle of 30°, and the angle gain is not less than 25dB. The solid line represents the average gain, and the shaded area represents the standard deviation of the corresponding angle gain.

[0082] In summary, the present invention provides a high-gain electromagnetic super-transparent film based on a nano-copper structure and a manufacturing method, wherein the electromagnetic super-transparent film includes a transparent substrate and a transparent metal grid film; the transparent metal grid film is composed of a plurality of array units, including a transparent flexible substrate polyethylene terephthalate (PET) and a transparent metal grid pattern arranged on the PET, the grid pattern is arranged as a square pattern with two short stubs on the upper and lower sides respectively, and each array unit adjusts the phase by adjusting the size of the short stubs; the square resistance of the transparent metal grid pattern is less than or equal to 0.06Ω / sq, the transparent flexible substrate PET is arranged on the transparent substrate, and a transmission array is formed by sequentially arranging a first layer of transparent metal grid pattern, a second layer of transparent flexible substrate PET, and a third layer of transparent substrate, and phase modulation and beam control are performed on the incident electromagnetic wave to achieve electromagnetic signal spatial signal coverage enhancement and beamforming. The electromagnetic super-transparent film provided by the present invention realizes a wide range of phase regulation by changing the design of the pattern size, and in the 5.2-5.8GHz working frequency band, the transmission amplitude reaches more than -1db, and the 60° transmission wave deflection with an angle gain of 30dB is achieved, and the metal line width is only 20 μm , which makes the array have the advantages of wide bandwidth, good optical transparency, high transmittance and easy preparation. It can be deployed in scenes such as portholes of buildings or vehicles that require optical transparency or perspective observation.

[0083] In this specification, each embodiment is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments can be referred to each other. For the device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part.

[0084] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. An electromagnetic super-transparent film for wireless signal enhancement, characterized in that: include: A super surface unit, the super surface unit comprising: a flexible substrate layer, and a metal grid layer attached to the flexible substrate layer; a dielectric layer, the metasurface unit being attached to the dielectric layer; The metal grid layer is a nano copper metal grid pattern, and the structure of the nano copper metal grid pattern is a square metal frame and double short stubs symmetrically arranged in the square metal frame; the nano copper metal grid pattern is divided into a square closed area with double short stubs on the upper and lower parts and a middle area, and each metasurface array unit adjusts the phase by adjusting the size of the short stubs; The design of the metasurface unit includes: determining material properties of the dielectric layer; Designing structural parameters of the metal grid layer according to the material properties of the dielectric layer, and determining the vibration starting point of the nano-copper metal grid pattern; The side length w of the super surface unit is adjusted according to the center frequency point f of the frequency band where the target signal is located, and the structural parameters of the super surface unit are further adjusted so that the A metasurface unit realizes a linear phase shift characteristic, and the structural parameters of the metasurface unit include line width and short line length; For an incident wave with an incident angle of ψ, assuming that a desired beam direction is θ, each unit structure of the metal mesh layer is determined.

2. The electromagnetic super-transparent film for wireless signal enhancement according to claim 1, characterized in that: To achieve the angle θ Signal enhancement, i The phase distribution of the column unit must satisfy the following distribution: ； in, f represents the center frequency of the incident wave, c represents the propagation speed of electromagnetic waves, w represents the side length of each hypersurface unit, ψ Represents the angle of incidence of the incident wave.

3. The electromagnetic super-transparent film for wireless signal enhancement according to claim 1, characterized in that: In order to simplify the overall design of the ultra-transparent film, the phase of each column unit is θ i Quantized into 4 fixed unit structures, their transmission phases are: .

4. The electromagnetic super-transparent film for wireless signal enhancement according to claim 1, characterized in that: For i Column metasurface unit calculation phase θ i , and then calculate the index of the required structural unit from the structural parameter library: ； At this time, select j The unit structure is used as the standard structure of this series of metasurfaces.

5. The electromagnetic super-transparent film for wireless signal enhancement according to claim 1, characterized in that: The thickness of the metal mesh layer is 0.2~1 μm between.

6. The electromagnetic super-transparent film for wireless signal enhancement according to claim 1, characterized in that: The material of the flexible substrate layer is polyethylene terephthalate.

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