Reconfigurable transparent absorber based on slit enhancement

Abstract

The application relates to a reconfigurable transparent wave absorber based on slit enhancement, and relates to the technical field of transparent wave absorbers.The application solves the problem that the existing wave absorber cannot realize the absorption of low-frequency 5G communication electromagnetic waves, realizes the design of a low-frequency wave absorber, solves the problem that the existing wave absorber cannot adjust the absorption intensity according to signal requirements, and causes excessive absorption to affect normal signal communication.The wave absorber is arranged by periodic units composed of three layers of transparent conductive films and two air layers;the upper layer and the middle layer of transparent conductive films are both engraved with a plurality of annular patterns, and a slit is arranged between adjacent annular patterns;the annular pattern area has conductivity, and the remaining area is a bare non-conductive base;the lower layer of transparent conductive film is not patterned.The application realizes the absorption of low-frequency 5G communication electromagnetic waves, can adjust the absorption intensity according to signal requirements, does not affect normal signal communication, keeps transparent, and does not affect the building appearance.The application is suitable for scenes with microwave absorption requirements.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of transparent wave absorber, and particularly relates to a reconfigurable transparent wave absorber based on slit enhancement. BACKGROUND

[0002] Nowadays, microwave communication technology has entered the 5G era, which promotes the rapid development of people's production and life. However, with the wide application of microwave communication technology, people begin to realize the potential threat of microwave radio frequency to health. In 2011, microwave radio frequency signals were classified as 2B carcinogens by the International Agency for Research on Cancer under the World Health Organization, and long-term exposure to high-intensity radio frequency signals may slightly increase the risk of tumor, so the energy control of electromagnetic waves in people's living and working environment is becoming increasingly important. Many researchers have developed wave absorbers in various frequency bands. Due to the existence of Rozanov limit, the development of low-frequency wave absorbers is particularly difficult. However, the 5G communication frequency band includes sub-6GHz to several tens of GHz, and the 5G communication microwave frequency used by people in daily life is concentrated in the sub-6GHz low-frequency band. Low-frequency electromagnetic waves have a long propagation distance and good penetration for buildings. In order to efficiently absorb low-frequency microwave signals, the present application proposes a reconfigurable transparent wave absorber based on slit enhancement, which has the characteristics of expanding the working frequency band of the wave absorber to sub-6GHz by introducing slits on the conventional frequency selective surface pattern, and adjusting the absorption intensity through thickness reconfiguration to face different signal requirements, making up for the shortcomings of other wave absorbers affecting communication while maintaining transparency and not affecting the beauty of the building. SUMMARY

[0003] The present application solves the problem that the existing wave absorber cannot realize the absorption of low-frequency 5G communication electromagnetic waves, and realizes the design of a low-frequency wave absorber.

[0004] At the same time, the present application also solves the problem that the existing wave absorber cannot adjust the absorption intensity according to the signal requirements, resulting in excessive absorption affecting normal signal communication.

[0005] To achieve the above purpose, the present application provides the following technical scheme:

[0006] The present application provides a reconfigurable transparent wave absorber based on slit enhancement, which is arranged by periodic units composed of three layers of transparent conductive film and two air layers.

[0007] Further, there is a preferred embodiment, the upper layer and the middle layer of the three layers of transparent conductive film are engraved with a plurality of annular patterns, and a slit is provided between adjacent annular patterns, the annular pattern area has conductivity, and the remaining area is bare non-conductive substrate; the lower layer of transparent conductive film has no pattern.

[0008] Further, there is a preferred embodiment that the annular pattern is a regular polygon ring.

[0009] Further, there is a preferred embodiment that the periodic unit length a of the regular polygon ring is 2-20 mm, and the inner contour side length b is 0.5-15 mm.

[0010] Further, there is a preferred embodiment that when the annular pattern is an equilateral triangle ring, the annular pattern is arranged in a staggered manner by regular triangles and inverted triangles.

[0011] Further, there is a preferred embodiment that the width of the gap between adjacent annular patterns is 0.03-0.1 mm.

[0012] Further, there is a preferred embodiment that by adjusting the thickness of the two air layers h1 and h2, the wave absorber can quantitatively absorb or reflect incident electromagnetic waves.

[0013] Further, there is a preferred embodiment that 0

[0014] Further, there is a preferred embodiment that the surface resistance of the upper transparent conductive film is 150-300 Ω / sq, the surface resistance of the middle transparent conductive film is 50-200 Ω / sq, and the surface resistance of the lower transparent conductive film is 3-10 Ω / sq. up mid down

[0015] The beneficial effects of the present application are:

[0016] 1. The present application proposes a reconfigurable transparent wave absorber based on slit enhancement. By designing slits with appropriate width on the conventional frequency selective surface, the absorption frequency range is covered to sub-6GHz, realizing the absorption of low-frequency 5G communication electromagnetic waves. The absorption intensity can also be adjusted according to signal requirements, avoiding long-term high-intensity radio frequency exposure of the crowd while not affecting normal signal communication and maintaining transparency without affecting the beauty of the building.

[0017] Further, the present application can also realize the switching of microwave absorption and reflection of the wave absorber by continuously adjusting the thickness of the two interlayer air, realizing the quantitative absorption or reflection of the main frequency band electromagnetic waves of 5G communication.

[0018] ​​​Further, compared with the prior art, the application provides a design strategy for extending the working frequency band of a wave absorber to a low frequency, changes the field distribution on the film by introducing a slit to make a wider frequency band of electromagnetic waves resonate, thereby enhancing the absorption effect of low frequency electromagnetic waves while maintaining the original frequency band absorption efficiency, and the application does not depend on complex external stimulation, but adjusts the thickness of the structure to quickly and flexibly regulate the microwave absorption characteristics.

[0019] 2、The application designs a slit on a simple and common polygon ring pattern frequency selective surface, so that more than 90% absorption of wide frequency bands of 4.0-22.3GHz (relative bandwidth 139%), 3.3-21.8GHz (relative bandwidth 147%), and 3.7-22.6GHz (relative bandwidth 144%) is achieved for normally incident TE and TM polarized electromagnetic waves respectively while maintaining a simple pattern; in addition, the application can realize controllable dynamic absorption or reflection of the wave absorber to incident electromagnetic waves by continuously adjusting the air thickness between the layers, which is more rapid and stable than the existing reconfigurable mode relying on folding and phase change.

[0020] The application is suitable for scenarios with microwave absorption needs. BRIEF DESCRIPTION OF DRAWINGS

[0021] In order to more clearly illustrate the specific embodiments of the application or the technical solutions in the prior art, the following will briefly introduce the drawings needed to be used in the specific embodiments or the prior art description. Obviously, the drawings in the following description are some embodiments of the application, and other drawings can be obtained by those skilled in the art without creative labor.

[0022] Figure 1 is a schematic diagram of the geometric size of the square ring wave absorber described in the application;

[0023] Figure 2 is a schematic diagram of the absorption state of the square ring wave absorber described in the application;

[0024] Figure 3 is a schematic diagram of the reflection state of the square ring wave absorber described in the application;

[0025] Figure 4 is a comparison chart of the absorption rate spectrum of the absorption state, reflection state of the square ring wave absorber described in the application and the absorption state of the ordinary square ring wave absorber without a slit;

[0026] Figure 5 is an absorption rate spectrum chart of the square ring wave absorber described in the application for oblique incidence TE wave;

[0027] Figure 6 is the absorption rate spectrum diagram of the square ring wave absorber of the present application to oblique incidence TM wave;

[0028] Figure 7 is the geometric size schematic diagram of the equilateral triangle ring wave absorber of the present application;

[0029] Figure 8 is the absorption state schematic diagram of the equilateral triangle ring wave absorber of the present application;

[0030] Figure 9 is the reflection state schematic diagram of the equilateral triangle ring wave absorber of the present application;

[0031] Figure 10 is the absorption rate spectrum comparison diagram of the absorption state, the reflection state and the ordinary equilateral triangle ring wave absorber without slits of the equilateral triangle ring wave absorber of the present application;

[0032] Figure 11 is the absorption rate spectrum diagram of the equilateral triangle ring wave absorber of the present application to oblique incidence TE wave;

[0033] Figure 12 is the absorption rate spectrum diagram of the equilateral triangle ring wave absorber of the present application to oblique incidence TM wave;

[0034] Figure 13 is the geometric size schematic diagram of the regular octagonal ring wave absorber of the present application;

[0035] Figure 14 is the absorption state schematic diagram of the regular octagonal ring wave absorber of the present application;

[0036] Figure 15 is the reflection state schematic diagram of the regular octagonal ring wave absorber of the present application;

[0037] Figure 16 is the absorption rate spectrum comparison diagram of the absorption state, the reflection state and the ordinary regular octagonal ring wave absorber without slits of the regular octagonal ring wave absorber of the present application;

[0038] Figure 17 is the absorption rate spectrum diagram of the regular octagonal ring wave absorber of the present application to oblique incidence TE wave;

[0039] Figure 18 is the absorption rate spectrum diagram of the regular octagonal ring wave absorber of the present application to oblique incidence TM wave. DETAILED DESCRIPTION

[0040] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings and examples. The following examples will help those skilled in the art to further understand the present invention, but do not limit the present invention in any way. It should be noted that those skilled in the art can make several changes and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention.

[0041] Implementation Method 1: This implementation method addresses the problem that existing absorbers cannot effectively absorb low-frequency 5G communication electromagnetic waves, and that existing absorbers cannot adjust the absorption intensity according to signal requirements, leading to excessive absorption that affects normal signal communication and complex control methods. Therefore, a reconfigurable transparent absorber based on slit enhancement is proposed. The absorber is composed of periodic units arranged from three layers of transparent conductive films and two air layers.

[0042] Implementation Method 2: This implementation method is an example of a reconfigurable transparent absorber based on slit enhancement as described in Implementation Method 1 above.

[0043] The upper and middle transparent conductive films of the three layers are each engraved with multiple annular patterns, and slits are provided between adjacent annular patterns. The annular pattern areas are conductive, while the remaining areas are exposed non-conductive substrates. The lower transparent conductive film has no patterns. By introducing slits, the absorption effect of low-frequency electromagnetic waves (sub-6GHz) is enhanced while maintaining the original frequency band absorption efficiency. Furthermore, the microwave absorption and reflection of the absorber can be switched by continuously adjusting the air thickness between the two layers, achieving quantitative absorption or reflection of electromagnetic waves in the main frequency bands of 5G communication.

[0044] In practical applications, all three transparent conductive films in this embodiment use PET (polyethylene terephthalate) as a substrate. The upper and middle transparent conductive films have multiple annular patterns etched on their PET substrates, with slits of a specific width designed between adjacent annular patterns. The annular pattern areas are conductive, while the remaining areas are exposed non-conductive substrates, thus widening the absorption frequency band. The principle is to change the field distribution on the film through the slits to generate a resonant mode for a wider range of electromagnetic waves, enabling the absorption frequency band to cover sub-6GHz and absorbing low-frequency 5G communication electromagnetic waves. The lower transparent conductive film does not require pattern design. In the reflective state, the lower transparent conductive film reflects electromagnetic waves, and in the absorption state, it forms a resonant cavity with the upper and middle transparent conductive films to absorb electromagnetic waves.

[0045] Further, preferably, the surface resistance ρ of the upper transparent conductive film up The surface resistivity ρ of the middle transparent conductive film is 150–300 Ω / sq. mid The surface resistivity ρ of the lower transparent conductive film is 50–200 Ω / sq.down 3-10 Ω / sq.

[0046] Further, preferably, the transparent conductive film is implemented by any one of an indium tin oxide film (ITO), a metal film layer, MXene, or graphene. For example, when the indium tin oxide film (ITO) is selected, the transparent conductive film is implemented by the substrate + the indium tin oxide film.

[0047] Further, preferably, the embodiment also designs the width range of the slits between adjacent ring patterns. For a regular pattern, a too wide slit will not produce low-frequency absorption characteristics, and the working frequency band cannot cover the 5G communication wave band; and a too narrow slit is not easy to manufacture, and the cost and performance instability will increase. Therefore, the embodiment designs the width w of the slit between adjacent ring patterns to be 0.03 mm-0.1 mm.

[0048] Further, preferably, the embodiment can also realize the quantitative absorption or reflection of the incident electromagnetic wave by the wave absorber by continuously adjusting the air thickness between the two layers. Its working principle is to realize the dynamic absorption (or reflection) performance of a specific wave band by changing the interlayer resonance frequency, which simplifies the regulation process and also improves the response speed. In the working frequency range, the proportion of the electromagnetic wave energy absorbed (or reflected) by the wave absorber at the center frequency to the total incident electromagnetic wave energy is greater than 50% or -3 dB, and the wave absorber is considered to be in the absorption state (or reflection state). The corresponding absorption (or reflection) critical air layer thickness is h1=1 mm, h2=2 mm, and 0

[0049] Embodiment three, the embodiment is a specific description of the ring pattern in the reconfigurable transparent wave absorber based on slit enhancement as described in the above embodiment;

[0050] The ring pattern can be designed as a regular polygon ring.

[0051] The period unit length a of the regular polygon ring is 2 mm-20 mm; and the inner contour side length b is 0.5 mm-15 mm.

[0052] Embodiment four, see Figures 1 to 6 The embodiment is described, and the embodiment is an example of the ring pattern described in the above embodiment three;

[0053] Preferably, the regular polygon ring can be designed as an equilateral triangle ring, a square ring, or a regular octagon ring.

[0054] When the ring pattern is designed as a square ring in the embodiment, as shown in Figure 1As shown, the slit width ranges from 0.03mm to 0.1mm, and the slit width w of the square ring pattern is designed to be 0.1mm. The period unit length a of the square ring is designed to be 4mm. The inner contour side length b of the regular polygon ring is designed to be 2mm. The above geometric dimensions are the optimal dimensions of the square ring pattern for absorbing electromagnetic waves in the main frequency band of 5G communication, and similar dimensions have similar absorption effects.

[0055] In actual application, the controllable quantitative absorption or reflection of the incident electromagnetic wave by the wave absorber can be realized by continuously adjusting the air thickness between the layers (i.e. h1 and h2). In this embodiment, an air layer with a thickness of h1 = 5mm is arranged between the lower transparent conductive film and the middle transparent film, and an air layer with a thickness of h2 = 5mm is arranged between the middle transparent conductive film and the upper transparent conductive film, so that a square ring wave absorber in an absorption state is formed as shown in the figure. Figure 2 As shown in the figure, different air layer thicknesses between the layers can absorb electromagnetic waves in different wave bands to different extents, and the size of h1 = 5mm and h2 = 5mm can absorb more than 90% of the electromagnetic waves in the main frequency band of 5G communication. By adjusting the air thickness between the layers again, a square ring wave absorber in a reflection state can be formed as shown in the figure. Figure 3 As shown in the figure, different air layer thicknesses between the layers can absorb electromagnetic waves in different wave bands to different extents, and the size of h1 = 5mm and h2 = 5mm can absorb more than 90% of the electromagnetic waves in the main frequency band of 5G communication. By adjusting the air thickness between the layers again, a square ring wave absorber in a reflection state can be formed as shown in the figure.

[0056] Figure 4 The absorption rate spectrum comparison chart of the square ring wave absorber in the absorption state, the reflection state and the ordinary square ring wave absorber without slits in the absorption state can be seen from the figure. The reconfigurable transparent wave absorber can realize dynamic absorption (or reflection) of 10%-90% in the range of 3.3-21.8GHz, and compared with the transparent wave absorber composed of the ordinary frequency selective surface without slits, the range of 5G communication frequency band below 8GHz is widened.

[0057] Figure 5 The absorption rate spectrum chart of the square ring wave absorber to the oblique incidence TE wave, Figure 6 The absorption rate spectrum chart of the square ring wave absorber to the oblique incidence TM wave; from Figure 5 and Figure 6 It can be seen from the figures that the designed square ring transparent wave absorber has an absorption rate of more than 90% for the TE and TM electromagnetic waves in the range of 3.3-21.8GHz; for the TE and TM polarized electromagnetic waves with an incident angle range of 0-60°, the above wave band can maintain stable absorption rate; by adjusting the air layer thickness h1 and h2 in different scenes, the continuous regulation of the absorption rate (or the reflectivity) of the C, X, Ku full wave band TE and TM polarized electromagnetic waves from <10% to >90% (or from >90% to <10%) can be realized.

[0058] Embodiment five, see Figures 7 to 12 This embodiment illustrates the ring pattern described in Embodiment Three.

[0059] Preferably, the regular polygon ring can be designed as an equilateral triangle ring, a square ring or a regular octagon ring.

[0060] The present embodiment designs the ring pattern as an equilateral triangle ring, as shown in Figure 7 The ring pattern is arranged in a staggered manner in the form of regular triangles and inverted triangles, and the slit width ranges from 0.03 mm to 0.1 mm. The equilateral triangle ring pattern slit width w is designed to be 0.03 mm. The period unit length a of the equilateral triangle ring is designed to be 4 mm. The inner contour side length b of the equilateral triangle ring is designed to be 2.27 mm. The above geometric dimensions are the optimal dimensions for the equilateral triangle ring pattern to absorb electromagnetic waves in the main frequency band of 5G communication, and similar dimensions have similar absorption effects.

[0061] In actual application, the controllable dynamic absorption or reflection of the incident electromagnetic wave by the wave absorber can be realized by continuously adjusting the air thickness between the layers (i.e. h1 and h2). In the present embodiment, an air layer with a thickness of h1 = 5 mm is arranged between the lower transparent conductive film and the middle transparent film, and an air layer with a thickness of h2 = 5 mm is arranged between the middle transparent conductive film and the upper transparent conductive film, so as to form an equilateral triangle ring wave absorber in the absorption state, as shown in Figure 8 Different interlayer air layer thicknesses can absorb electromagnetic waves in different wave bands to different extents, and the dimensions of h1 = 5 mm and h2 = 5 mm can absorb more than 90% of the electromagnetic waves in the main frequency band of 5G communication. By adjusting the air thickness between the layers again, an equilateral triangle ring wave absorber in the reflection state can be formed, as shown in Figure 9

[0062] Figure 10 The absorption rate spectrum comparison chart of the equilateral triangle ring wave absorber in the absorption state, the reflection state and the ordinary equilateral triangle ring wave absorber without slits in the absorption state shows that the reconfigurable transparent wave absorber can realize dynamic absorption (or reflection) of 10%-90% in the range of 4.0-22.3 GHz, and compared with the transparent wave absorber composed of the ordinary frequency selective surface without slits, the range of 5G communication frequency band below 6 GHz is widened.

[0063] Figure 11 The absorption rate spectrum chart of the equilateral triangle ring wave absorber for oblique incidence TE wave; Figure 12 The absorption rate spectrum chart of the equilateral triangle ring wave absorber for oblique incidence TM wave; from Figure 11 and Figure 12 ​As can be seen from the figure, the designed equilateral triangle ring transparent wave absorber has an absorption rate of more than 90% for normally incident TE and TM electromagnetic waves in the 4.0-22.3 GHz band; for TE and TM polarized electromagnetic waves with an incident angle range of 0-60°, the absorption rate can be kept stable in the above-mentioned band; by adjusting the air layer thickness h1 and h2 in different scenarios, the continuous regulation of the absorption rate of C, X and Ku full-band normally incident TE and TM polarized electromagnetic waves from <10% to >90% (or the reflection rate from >90% to <10%) can be realized.

[0064] Embodiment six, see Figures 13 to 18 This embodiment illustrates the above-mentioned ring pattern of embodiment three;

[0065] Preferably, the regular polygon ring can be designed as an equilateral triangle ring, a square ring or a regular octagon ring.

[0066] This embodiment designs the ring pattern as a regular octagon ring, as Figure 13 As shown in the figure, the slit width ranges from 0.03 mm to 0.1 mm, and the slit width w of the regular octagon ring pattern is designed as 0.046 mm. The regular octagon ring period unit length a is designed as 4 mm, and the regular octagon ring inner contour side length b is designed as 0.82 mm. At the same time, the shape is adapted to the pattern, and the above-mentioned geometric dimensions are the optimal dimensions of the regular octagon ring pattern for absorbing electromagnetic waves in the main frequency band of 5G communication, and similar dimensions have similar absorption effects.

[0067] In actual application, the controllable dynamic absorption or reflection of the wave absorber to incident electromagnetic waves can be realized by continuously adjusting the air thickness between the layers (i.e. h1 and h2). In this embodiment, an air layer with a thickness of h1=5 mm is arranged between the lower transparent conductive film and the middle transparent film, and an air layer with a thickness of h2=5 mm is arranged between the middle transparent conductive film and the upper transparent conductive film, so as to form a regular octagon ring wave absorber in the absorption state, as Figure 14 As shown in the figure, different air layer thicknesses between the layers can absorb electromagnetic waves in different bands to different degrees, and the size of h1=5 mm and h2=5 mm can absorb more than 90% of the electromagnetic waves in the main frequency band of 5G communication. By adjusting the air thickness between the layers again, a regular octagon ring wave absorber in the reflection state can be formed, as Figure 15 As shown in the figure.

[0068] Figure 16 The absorption rate spectrum comparison chart of the regular octagon wave absorber in the absorption state, the reflection state and the ordinary regular octagon ring wave absorber without slits in the absorption state can be seen from the figure, and the reconfigurable transparent wave absorber can realize dynamic absorption (or reflection) of 10%-90% in the range of 3.7-22.6 GHz, and compared with the transparent wave absorber composed of the ordinary frequency selective surface without slits, the range of 5G communication frequency band of <6 GHz is widened.

[0069] Figure 17 the absorption rate spectrum diagram of the positive octagonal ring wave absorber to oblique incidence TE wave, Figure 18 the absorption rate spectrum diagram of the positive octagonal ring wave absorber to oblique incidence TM wave, from Figure 17 and Figure 18 It can be seen from the above that the designed positive octagonal ring transparent wave absorber has more than 90% absorption rate to TE and TM electromagnetic waves with normal incidence in the 3.7-22.6GHz wave band; the stable absorption rate can be maintained in the above wave band for TE and TM polarized electromagnetic waves with an incident angle range of 0-60°; the continuous regulation from <10% to >90% absorption rate (or from >90% to <10% reflectivity) can be realized for C, X and Ku full wave band TE and TM polarized electromagnetic waves with normal incidence by adjusting the air layer thickness h1 and h2 in different scenes.

[0070] The above only describes the embodiments of the present application and does not limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the scope of claims of the present application.

Claims

1. A reconfigurable transparent metamaterial absorber based on slit enhancement, characterized in that, The wave absorber is arranged by periodic units composed of three layers of transparent conductive films and two air layers; The upper layer and the middle layer of the three layers of transparent conductive films are both engraved with a plurality of annular patterns, and a slit is arranged between adjacent annular patterns, the annular pattern area has conductivity, and the remaining area is a bare non-conductive substrate; The lower layer of the transparent conductive film is free of patterns; By adjusting the thickness of the two air layers h1 and h2, the wave absorber can realize quantitative absorption or reflection of incident electromagnetic waves.

2. The reconfigurable transparent metamaterial absorber based on slit enhancement of claim 1, wherein, The annular pattern is a regular polygon ring.

3. The reconfigurable transparent metamaterial absorber based on slit enhancement of claim 2, wherein, The periodic unit length a of the regular polygon ring is 2 mm to 20 mm; and the inner contour side length b of the regular polygon ring is 0.5 mm to 15 mm.

4. The reconfigurable transparent metamaterial absorber based on slit enhancement of claim 2, wherein, When the annular pattern is an equilateral triangle ring, the annular pattern is arranged in a staggered manner according to the regular triangle and the inverted triangle.

5. The reconfigurable transparent wave-absorber based on slot enhancement according to any one of claims 1-4, characterized in that, The width of the slit between adjacent annular patterns ranges from 0.03 mm to 0.1 mm.

6. The reconfigurable transparent metamaterial absorber based on slit enhancement of claim 1, wherein, 0 < h1 < h2 < 10 mm.

7. The reconfigurable transparent metamaterial absorber based on slit enhancement of claim 1, wherein, The surface resistance of the upper transparent conductive film ρ up is 150 - 300 Ω / sq, the surface resistance of the middle transparent conductive film ρ mid is 50 - 200 Ω / sq, and the surface resistance of the lower transparent conductive film ρ down is 3 - 10 Ω / sq.

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