Electromagnetic super-transmissive and transparent film oriented to wireless signal enhancement

Abstract

Disclosed in the present invention is an electromagnetic super-transmissive and transparent film oriented to wireless signal enhancement, belonging to the technical field of electromagnetic regulation. The electromagnetic super-transmissive and transparent film of the present invention consists of a large number of metal grid units having equal side length and a flexible transparent PET film substrate. Each metal grid unit is a square metal structure having a plurality of adjustable metal stubs in the middle, and changes in the side length of the structure and the length of the metal stubs in the middle can realize the modulations of the transmission phase and amplitude of incident electromagnetic waves. The super-transmissive and transparent films are respectively deployed on two sides of a transparent glass plate, and the entirety consisting of the super-transmissive and transparent films and the glass can realize macroscopic regulation and control of incident electromagnetic waves, so as to enhance wireless signal coverage. The visible light transmittance of the super-transmissive and transparent film exceeds 85%, which can cover a beam adjustment range from -150° to 150°or above, and the peak value of signal gain exceeds 30 dB; adjusting structural parameters of the unit structures can achieve signal enhancement in a plurality of communication frequency bands.

Description

An electromagnetic superpermeable membrane for enhancing wireless signals Technical Field

[0001] This invention relates to the field of electromagnetic control technology, and more specifically to an electromagnetic supertransparent membrane for enhancing wireless signals. Background Technology

[0002] With the rapid development of 5G communication technology, the diversification of service types, and the continuous expansion of industry boundaries, user demand for wireless networks is undergoing a significant shift from outdoor to indoor focus. Industry forecasts predict that in the 5G era, the proportion of indoor consumer mobile communication services will increase substantially to over 85%, highlighting the growing importance of indoor wireless network coverage.

[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 problem of electromagnetic signal propagation in complex environments, especially how to achieve millimeter wave penetration through walls and efficient entry into homes, which has become a key technical problem that urgently needs to be solved.

[0004] To address the aforementioned issues, metamaterial planar transmission arrays with subwavelength periodic structures have emerged. This novel material, by precisely controlling the transmission path of electromagnetic waves, redirects wireless signals in specific directions, effectively improving the coverage of wireless networks and significantly enhancing signal strength. As an economical and practical solution, metamaterial planar transmission arrays have demonstrated enormous application potential in the field of wireless communication, particularly in millimeter-wave through-wall transmission, 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 elements should be as wide as possible to ensure omnidirectional signal transmission; 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 adapt to the signal transmission requirements of different frequencies; and fourth, the fabrication process should be as simple as possible to reduce production costs and improve production efficiency.

[0006] However, existing transmissive metasurfaces with beamforming capabilities still have many structural shortcomings. To meet the requirement of 360-degree phase coverage, most transmissive metasurfaces employ a multi-layer stacked design, with even strictly controlled air cavities between layers. This design not only makes the overall structure less compact but also places extremely high demands on manufacturing and assembly precision, increasing the difficulty of debugging. Furthermore, most transmissive metasurfaces use PCB boards as the substrate material, which lacks light transmittance, making it difficult to meet the needs of some applications requiring optical transparency or visual observation.

[0007] Although a few researchers have attempted to design and develop optically transparent antennas using thin films and transparent media (such as glass) with high optical transparency as the core material, these methods still face many challenges in practical applications. For example, modifying existing glass is difficult and costly, and the designed antennas often have a certain thickness, making it difficult to achieve conformal deployment in actual scenarios. Therefore, developing a transmissive metasurface that possesses both excellent beam control performance and good light transmittance and a compact structure has become a pressing technical challenge in the field of wireless communication. Summary of the Invention

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

[0009] To achieve the above objectives, the present invention adopts the following technical solution:

[0010] An electromagnetic supertransparent membrane for enhancing wireless signals, comprising:

[0011] N×M metasurface units, each metasurface unit comprising: a flexible substrate layer and a metal mesh layer attached to the flexible substrate layer;

[0012] The metal mesh layer is a nano-copper metal mesh pattern. The structure of the nano-copper metal mesh pattern is a square metal frame and double short lines symmetrically arranged within the square metal frame. The nano-copper metal mesh pattern is divided into a square closed area with double short lines at the top and bottom and a middle area. Each metasurface array unit adjusts the phase by adjusting the size of the short lines.

[0013] The design of the metasurface unit includes:

[0014] Determine the material properties of the dielectric layer;

[0015] The structural parameters of the metal mesh layer are designed based on the material properties of the dielectric layer, and the starting point of the nano-copper metal mesh pattern is determined.

[0016] The side length w of the metasurface unit is adjusted according to the center frequency f of the frequency band where the target signal is located, and the structural parameters of the metasurface unit are further adjusted so that the N×M metasurface units achieve linear phase shift characteristics. The structural parameters of the metasurface unit include linewidth and short line length.

[0017] For an incident wave with an incident angle of ψ, assuming the desired beam direction is θ, determine the structure of each unit cell in the metal mesh layer.

[0018] Preferably, it also includes a dielectric layer, on which the metasurface unit is attached.

[0019] Preferably, to achieve signal enhancement at angle θ, the phase distribution of the i-th column cells must satisfy the following distribution:

[0020] Where f represents the center frequency of the incident wave, c represents the propagation speed of the electromagnetic wave, w represents the side length of each metasurface unit, and ψ represents the incident angle of the incident wave.

[0021] Preferably, to simplify the overall design of the ultra-transparent membrane, the phase θ of each column of units is... i The structure is quantized into four fixed unit cells, with the following transmission phases:

[0022] Preferably, the phase θ is calculated for the i-th column of metasurface units. i Then, the indices of the required structural elements are calculated from the structural parameter library:

[0023] At this point, the j-th unit structure is selected as the standard structure for this column of metasurfaces.

[0024] Preferably, the thickness of the metal mesh layer is between 0.2 and 1 μm.

[0025] Preferably, the flexible substrate layer is made of polyethylene terephthalate.

[0026] As can be seen from the above technical solution, compared with the prior art, this invention discloses an electromagnetic supertransparent film for wireless signal enhancement. Through precise control of the pattern size design on the film, a wide range of accurate control over the phase of electromagnetic waves is achieved. In experimental tests, within the 5.2 to 5.8 GHz operating frequency band, the supertransparent film exhibits excellent transmission efficiency, exceeding 85%, effectively adjusting the deflection angle of the transmitted wave within a wide range of -150° to 150°, while achieving a peak gain exceeding 30 dB, resulting in a significant improvement in signal enhancement. The metasurface array composed of the nano-copper electromagnetic supertransparent film provided by this invention not only possesses broadband response capabilities but also boasts the dual advantages of high optical transparency and high transmittance. It can be flexibly deployed in various scenarios requiring optical transparency or see-through observation, such as building windows and vehicle windshields, thereby effectively improving wireless signal coverage and transmission quality without affecting visibility or aesthetics. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0028] Figure 1 is a perspective view of the basic unit structure of the electromagnetic superpermeable membrane with nano-copper structure provided by the present invention.

[0029] Figure 2 is a schematic diagram of one embodiment of the electromagnetic super-transparent film based on a transparent metal mesh pattern provided by the present invention;

[0030] Figure 3 is a schematic diagram of the unit metal wire pattern of the transparent metal mesh structure provided by the present invention;

[0031] Figure 4 is a schematic diagram of the geometric phase generation principle provided by the present invention;

[0032] Figure 5 is a flowchart of a preferred embodiment of the phase modulation method based on an electromagnetic supertransparent membrane provided by the present invention;

[0033] Figure 6 illustrates the process by which the N×M array units in the electromagnetic supertransparent membrane modulate the phase of the incident electromagnetic wave, as provided by the present invention.

[0034] Figure 7 shows the simulation focusing results of the high-gain electromagnetic ultra-transparent membrane provided by the present invention. Detailed Implementation

[0035] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0036] This invention provides an electromagnetic supertransparent film for enhancing wireless signals. The invention constructs a nano-copper electromagnetic supertransparent film by sequentially arranging a metal mesh pattern and a flexible PET substrate. In practical applications, the nano-copper electromagnetic supertransparent film is deployed on a transparent glass plate supporting the supertransparent film, forming a transmission array. This modulates the phase of the incident electromagnetic waves, achieving the desired phase distribution after beamforming. This improves light transmittance while simultaneously enabling high-gain beam focusing and control of the electromagnetic waves, thereby increasing the internal spatial coverage of the electromagnetic signal in both depth and breadth.

[0037] This invention discloses an electromagnetic supertransparent film for enhancing wireless signals, as shown in Figure 1, comprising:

[0038] The system comprises N×M metasurface units, each including a flexible substrate layer and a metal mesh layer attached to the substrate layer. The flexible substrate layer and the metal mesh layer are optically transparent, forming a transparent nano-copper electromagnetic supertransparent film. In practical applications, this nano-copper electromagnetic supertransparent film is deployed on both sides of a transparent glass plate.

[0039] When an incident electromagnetic wave is incident on a high-gain electromagnetic supertransparent membrane based on a nano-copper structure at a certain angle, the corresponding number of array units modulate the phase of the incident electromagnetic wave to obtain the desired phase distribution, thereby realizing the transmission of electromagnetic waves. For example, it can achieve wide-bandwidth, high-transmittance, and high-transparency beamforming, such as realizing high-gain beam focusing and control of incident electromagnetic waves, enhancing the penetration depth and breadth of electromagnetic wave signals.

[0040] Among them, the metasurface array unit has high transmittance and transmission phase. The metal mesh pattern is set on the transparent flexible substrate layer by any of the following methods: etching, photolithography, chemical plating, and electroplating. By sequentially setting the metal mesh pattern layer and the flexible substrate layer to form a transmission array, the transmission phase of the incident electromagnetic wave is modulated and the beam is controlled.

[0041] In the electromagnetic super-transparent film provided in this embodiment of the invention, the electromagnetic beam controllability and visible light transparency are achieved by using a transparent flexible PET film substrate and a nano-copper metal mesh pattern. That is, the invention achieves visual transparency of the electromagnetic super-transparent film by replacing the traditional thick and opaque transmissive metasurface with an ultra-thin transparent flexible PET substrate and a nano-copper metal mesh structure. This enables the electromagnetic super-transparent film to have conformal optical transparency, which can be applied to scenarios that require optical transparency or translucent observation. It is suitable for glass walls inside and outside buildings in city centers, portholes of large vehicles, and other scenarios that need to provide high-quality communication services for a large number of mobile terminal devices while also requiring optical transparency.

[0042] Figure 2 shows one embodiment of a transparent antenna array formed by arranging N×M array elements of an electromagnetic supertransparent film based on a transparent metal mesh pattern in a predetermined manner.

[0043] Specifically, after the phase distribution (expected phase distribution) of the incident electromagnetic wave after shaping is known, the length of the double stubs of the metal pattern of the N×M array units is controlled accordingly based on all pixels in the expected phase distribution, so that the deployed N×M array units can transmit electromagnetic waves and obtain the expected phase distribution. Figure 6 is a schematic diagram of the principle of geometric phase generation.

[0044] For example, when an electromagnetic wave is incident on an ultra-transparent membrane, its wavefront (i.e., an equiphase surface) passes through a transparent antenna array composed of N×M array elements. Each array element modulates the locally discretized phase at its location. After being modulated by N×M artificial atoms on the transparent antenna array, a phase distribution composed of N×M local phases is obtained. The ultra-transparent membrane prepared according to the new phase distribution is the electromagnetic ultra-transparent membrane based on a transparent metal mesh pattern in this invention.

[0045] This invention designs an electromagnetic supertransparent film that enables high-gain beam focusing of transmitted waves by adjusting the pattern size, achieving functions such as beam scanning, multi-beam control, and vortex fields. In other words, it realizes a multifunctional high-gain electromagnetic supertransparent film that can be conformally deployed in buildings, vehicles, and other scenarios requiring optical transparency or see-through observation. This electromagnetic supertransparent film can be applied to traditional window glass, achieving high light transmittance while effectively enhancing the depth and breadth of electromagnetic wave signal penetration through high-gain beam focusing.

[0046] Specifically, the metal mesh pattern layer is divided into a square closed region with double stubs at the top and bottom, and a middle region. The phase of each metasurface array unit is adjusted by adjusting the size of the stubs. As shown in Figure 3, the shape of the metal wire pattern of the array unit is square, and the length and width of the array unit are both P. The transparent nano-copper metal mesh pattern layer is a square metal wire pattern with double stubs at the top and bottom. The square closed region 1.1 is the metal region, and the middle region 1.2 is the hollow region. The square metal wire pattern structure with double stubs at the top and bottom in this invention can achieve an extremely low metal duty cycle, thereby achieving high visible light transmittance; at the same time, it achieves a wide bandwidth and high transmission amplitude response for electromagnetic waves.

[0047] Specifically, all square metal line pattern layers with double short stubs on the top and bottom have the same specifications, meaning that all metal pattern layers have the same thickness, shape, and outer dimensions.

[0048] Furthermore, the metasurface array unit of this embodiment includes four fixed unit structures, and the transmission phases of the four fixed unit structures are 0°, 90°, 180°, and 270°, respectively.

[0049] Furthermore, the thickness of the metal mesh pattern layer is 0.2-1 μm, the sheet resistance is less than or equal to 0.06 Ω / sq, and the material is nanoscale copper. By controlling the thickness of the transparent metal mesh structure within the range of 0.2-1 μm, the electrical connection stability and signal sensitivity between the unit patterns of the transparent metal mesh structure can be ensured while avoiding excessive thickness of the transparent metal mesh structure. This facilitates the thinning and conformal design of the electromagnetic ultra-transparent film. Because the nanoscale copper metal mesh structure used in the electromagnetic ultra-transparent film of this invention has a low sheet resistance, the transparent metasurface unit structure can have a low resistance value, which is beneficial for improving conductivity and signal sensitivity, and is convenient to use.

[0050] In another embodiment, the flexible substrate layer is made of polyethylene terephthalate.

[0051] In another embodiment, the thickness of the flexible substrate layer is 100 μm. By controlling the thickness of the flexible transparent substrate to around 100 μm, it is possible to ensure that the flexible transparent substrate has sufficient structural strength to support the transparent metal mesh structure, while avoiding excessive thickness of the flexible transparent substrate. This facilitates the realization of a thinner and more conformal design for the electromagnetic ultra-transparent film.

[0052] On the other hand, embodiments of the present invention also provide a method for preparing an electromagnetic supertransparent membrane for enhancing wireless signals, including:

[0053] The material properties of the target dielectric material are tested, including thickness and dielectric constant.

[0054] The metal structure layers are determined based on metasurface design methods;

[0055] Ultrapermeable membranes were prepared based on the parameters of the metal structural layers;

[0056] Attaching an ultratransparent film to a target dielectric layer achieves signal enhancement in a specified angular domain. The design of the metasurface unit includes:

[0057] Determine the material properties of the dielectric layer;

[0058] The structural parameters of the metal mesh pattern layer are designed based on the material properties of the dielectric layer, and the starting point of the nano-copper metal mesh pattern is determined.

[0059] Adjust the side length w of the metasurface unit according to the center frequency f of the target signal frequency band, and further adjust the structural parameters of the metasurface unit to enable the metasurface array unit to achieve linear phase shift characteristics. The structural parameters of the metasurface unit include linewidth and short line length.

[0060] For an incident wave with an incident angle of ψ, assuming the desired beam direction is θ, determine the structure of each unit cell in the metal mesh layer.

[0061] To achieve signal enhancement at angle θ, the phase distribution of the i-th column cells must satisfy the following distribution:

[0062] Where f represents the center frequency of the incident wave, c represents the propagation speed of the electromagnetic wave, w represents the width of each unit, and ψ represents the angle of the incident wave.

[0063] To simplify the overall design of the ultra-transparent membrane, the phase θ of each column of cells is... i The structure is quantized into four fixed unit cells, with the following transmission phases:

[0064] Calculate the phase θ of the i-th metasurface element. i Then, the indices of the required structural elements are calculated from the structural parameter library:

[0065] At this point, the j-th unit structure is selected as the standard structure for this column of metasurfaces.

[0066] Furthermore, as shown in Figure 4, the method for obtaining a transparent antenna array based on an electromagnetic supertransparent film includes the following steps:

[0067] S100 and N×M array elements are used to obtain a transparent antenna array according to a preset method.

[0068] Specifically, in order to achieve beam focusing and control of electromagnetic waves using an electromagnetic supertransparent membrane, firstly, N×M artificial atoms are arranged in a preset manner to obtain a transparent antenna array, thereby using the transparent antenna array to focus electromagnetic waves.

[0069] Furthermore, the steps of obtaining a transparent antenna array by means of array elements in S100 according to a preset method specifically include: adjusting the double stub size of N×M array elements according to the phase points in the expected phase distribution to obtain a transparent antenna array.

[0070] Specifically, in order to achieve beam focusing and control of electromagnetic waves using an electromagnetic supertransparent film, firstly, the desired phase distribution is known, i.e., the expected phase distribution is known. Based on the phase points in the expected phase distribution, the double stub size of N×M array units is adjusted. That is, based on the degree of modulation required for each phase point and the functional relationship between the modulation degree and the adjustment size, the size of each array unit is adjusted accordingly, and finally a specially made glass array is obtained.

[0071] To achieve beam focusing, according to Huygens' principle (which states that every point (surface source) on a spherical wavefront is a secondary spherical wavelet source, and the wave velocity and frequency of the secondary wavelet are equal to the wave velocity and frequency of the primary wave; thereafter, the envelope of the wavelet wavefront at each moment is the total wavefront of that moment; lens focusing requires that the total phase accumulated by the spherical waves emitted by each secondary wavelet source on the incident wavefront passing through the lens to the focal point be equal), the phase distribution to be modulated across the entire glass array plane must satisfy the following distribution:

[0072] Where f represents the center frequency of the incident wave, c represents the propagation speed of the electromagnetic wave, w represents the width of each unit, and ψ represents the angle of the incident wave.

[0073] Furthermore, the S200 phase-distribution electromagnetic supertransparent film modulates the phase of the incident electromagnetic wave to obtain the desired phase distribution.

[0074] As shown in Figure 5, after the electromagnetic supertransparent film is prepared, the phase of the incident electromagnetic wave is modulated by the N×M array units in the electromagnetic supertransparent film. Then, beamforming is performed to obtain the expected phase distribution, thereby realizing the modulation of the phase of the incident electromagnetic wave through the transparent antenna array to obtain the expected phase distribution.

[0075] For example, when a plane wave passes through a transparent antenna array consisting of N×M array elements, where each array element modulates the local phase (discretization) of its spatial vicinity, then after being modulated by the N×M array elements on the transparent antenna array, a new phase distribution (the expected phase distribution) consisting of N×M discrete local phases is obtained.

[0076] Furthermore, referring to Figure 7, a simulated beamforming of a high-gain electromagnetic supertransparent membrane (based on phase modulation of the electromagnetic supertransparent membrane) was performed, yielding the simulated beamforming results. An example of an electromagnetic supertransparent membrane composed of N×M array units achieved a 60° deflection of transmitted waves within the 5.2-5.8 GHz operating frequency band at an incident angle of 30°, with an angular gain of no less than 25 dB. The solid line represents the average gain, and the shaded area represents the standard deviation of the corresponding angular gain.

[0077] In summary, this invention provides a high-gain electromagnetic supertransparent film based on a nano-copper structure and its manufacturing method. The electromagnetic supertransparent film includes a transparent substrate and a transparent metal mesh film. The transparent metal mesh film is composed of multiple array units, including a transparent flexible substrate polyethylene terephthalate (PET) and a transparent metal mesh pattern disposed on the PET. The mesh pattern is a square pattern with two short stubs at the top and bottom. The phase of each array unit is adjusted by adjusting the size of the short stubs. The sheet resistance of the transparent metal mesh pattern is less than or equal to 0.06 Ω / sq. The transparent flexible substrate PET is disposed on the transparent substrate. By sequentially arranging the first layer of transparent metal mesh pattern, the second layer of transparent flexible substrate PET, and the third layer of transparent substrate to form a transmission array, the incident electromagnetic wave is phase-modulated and beam-controlled to achieve spatial signal coverage enhancement and beamforming of electromagnetic signals. The electromagnetic supertransparent film provided by this invention achieves a wide range of phase control through design variations in pattern size. Within the 5.2-5.8GHz operating frequency band, the transmission amplitude reaches above -1dB, achieving a 60° transmission wave deflection with an angle gain of 30dB. The metal linewidth is only 20μm, giving the array advantages such as wide bandwidth, good optical transparency, high transmittance, and ease of fabrication. It can be deployed in scenarios requiring optical transparency or perspective observation, such as portholes in buildings or vehicles.

[0078] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to the method section.

[0079] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those 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 invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. An electromagnetic superlens oriented to wireless signal enhancement, characterized in that, include: N×M metasurface units, each metasurface unit comprising: a flexible substrate layer and a metal mesh layer attached to the flexible substrate layer; A dielectric layer, on which the metasurface units are attached; The metal mesh layer is a nano-copper metal mesh pattern. The structure of the nano-copper metal mesh pattern is a square metal frame and double short lines symmetrically arranged within the square metal frame. The nano-copper metal mesh pattern is divided into a square closed area with double short lines at the top and bottom and a middle area. Each metasurface array unit adjusts the phase by adjusting the size of the short lines. The design of the metasurface unit includes: Determine the material properties of the dielectric layer; The structural parameters of the metal mesh layer are designed based on the material properties of the dielectric layer, and the starting point of the nano-copper metal mesh pattern is determined. The side length w of the metasurface unit is adjusted according to the center frequency f of the frequency band where the target signal is located, and the structural parameters of the metasurface unit are further adjusted so that the N×M metasurface units achieve linear phase shift characteristics. The structural parameters of the metasurface unit include linewidth and short line length. For an incident wave with an incident angle of ψ, assuming the desired beam direction is θ, determine the structure of each unit cell in the metal mesh layer.

2. The electromagnetic superlens according to claim 1, wherein, To achieve the signal enhancement of angle θ, the phase distribution of the i-th column unit should satisfy the following distribution: Where f represents the center frequency of the incident wave, c represents the propagation speed of the electromagnetic wave, w represents the side length of each metasurface unit, and ψ represents the incident angle of the incident wave.

3. The electromagnetic superlens according to claim 1, wherein, To simplify the overall design of the superlattice, the phase θ of each column of cells is quantized to 4 fixed cell structures, whose transmission phases are respectively: i quantized to 4 fixed cell structures, whose transmission phases are respectively:

4. The electromagnetic superlens according to claim 1, wherein, Calculate the phase θ for the i-th column of metasurface units i Then calculate the index of the required structure unit from the structure parameter library: At this point, the j-th unit structure is selected as the standard structure for this column of metasurfaces.

5. The electromagnetic superlens according to claim 1, wherein, The thickness of the metal mesh layer is between 0.2 and 1 μm.

6. The electromagnetic superlens according to claim 1, wherein, The flexible substrate layer is made of polyethylene terephthalate.

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