Large-angle incidence insensitive ultra-wideband transparent wave absorber based on slit enhancement

Abstract

The invention relates to a transparent wave absorber, in particular to a wide-angle incidence insensitive ultra-wideband transparent wave absorber based on slit enhancement. The invention aims to solve the problems that an existing wave absorber is insensitive to large-angle oblique incidence of a radio frequency electromagnetic field, and inherent contradiction exists between low-thickness design and low-frequency absorption performance of the wave absorber. The transparent wave absorber is composed of N * M wave absorber units in an array. Each wave absorber unit is composed of a horizontal transparent conductive film and two vertical transparent conductive films. And the transparent conductive film is etched on the surface of the vertical transparent conductive film to form one or more strip slit non-conductive areas. The invention is used for the wide-angle incidence insensitive ultra-wideband transparent wave absorber based on slit enhancement.

Description

Technical Field

[0001] The invention relates to a transparent wave absorbing body. Background Art

[0002] In recent years, microwave communication technology has promoted the rapid development of human society in all aspects, and people are enjoying the convenience and speed brought by real-time communication. However, the radio frequency electromagnetic field used in microwave communication carries information as well as energy, posing a potential threat to people's life and health. In the era when technologies such as mobile phones and wireless networks were not popular, this potential danger did not attract people's attention, but nowadays, the widely used microwave communication technology has made people's living environment permeated with radio frequency electromagnetic fields that oscillate with time and space. Therefore, in recent years, researchers have developed many types of absorbers with different working frequency bands to absorb excess electromagnetic waves. Most absorbers usually use the absorption rate of normal incident electromagnetic waves and working bandwidth as the criteria for judging the quality of their absorbing performance when designing. In order to pursue a wider working frequency band, the existing absorbers will greatly weaken their absorption performance when facing oblique incident electromagnetic waves due to impedance mismatch and other reasons. However, in practical applications, electromagnetic waves in the air are often incident in a specific direction, which puts higher requirements on the performance of absorbers in absorbing oblique incident electromagnetic waves. On the other hand, due to the existence of the Rozanov limit of the absorber, the lower the frequency of the electromagnetic wave, the greater the theoretical minimum thickness of the absorber with a 90% absorption rate. For a broadband absorber of a certain thickness, its thickness is closer to the Rozanov limit, and it is more difficult to achieve a good absorption effect for low-frequency electromagnetic waves. Therefore, there is always an inherent contradiction between the low-thickness design of the absorber and the low-frequency absorption performance. Summary of the invention

[0003] The present invention aims to solve the problems that the existing absorbers are insensitive to large-angle oblique incidence of radio frequency electromagnetic fields, and there is an inherent contradiction between the low-thickness design of the absorbers and the low-frequency absorption performance, and further proposes a large-angle incidence-insensitive ultra-wideband transparent absorber based on slit enhancement.

[0004] A wide-angle incident insensitive ultra-wideband transparent absorber based on slit enhancement, which is composed of N×M absorber units arranged periodically, wherein N≥4 columns and M≥4 rows;

[0005] The absorber unit is composed of a horizontal transparent conductive film and two vertical transparent conductive films;

[0006] The two vertical transparent conductive films are connected along one side edge in the vertical direction, and the bottom is vertically arranged at the two side edges of the upper surface of the horizontal transparent conductive film, and the angle between the two vertical transparent conductive films is 90°;

[0007] Part of the conductive layer is etched off the surface of the vertical transparent conductive film to form one or more long slit non-conductive areas;

[0008] Suppose the side length of the horizontal transparent conductive film is a; suppose the side length of the vertical transparent conductive film along the horizontal direction is b, b=a.

[0009] The beneficial effects of the present invention are:

[0010] The present invention proposes a low-thickness absorber, in which low-frequency electromagnetic waves near 4 GHz can enter the absorber structure and be absorbed by loss, thus solving the inherent contradiction between the low-thickness design of the absorber and the low-frequency absorption performance.

[0011] The present invention proposes a wide-angle incidence insensitive ultra-wideband transparent absorber based on slit enhancement. By introducing slits on a transparent conductive film, ultra-wideband absorption of normally incident electromagnetic waves is achieved, and the broadband absorption stability of the absorber to obliquely incident electromagnetic waves is enhanced. At the same time, transparency is maintained to cooperate with architectural design without affecting the aesthetics. It can also be used in scenes that require optical transparency, such as portholes, windshields, etc.

[0012] The transparent absorber designed by the present invention has an absorption rate of more than 90% for normally incident TE and TM polarized electromagnetic waves in the frequency band of 4.0GHz to 30.6GHz, covering some of the main frequency bands and extended frequency bands of 5G microwave communications. The designed transparent absorber can maintain an absorption rate of more than 75% for obliquely incident TE polarized electromagnetic waves within a range of 60° in the frequency band of 4.0GHz to 30.0GHz; and can maintain an absorption rate of more than 85% for obliquely incident TM polarized electromagnetic waves within a range of 75° in the frequency band of 4.0GHz to 30.0GHz.

[0013] The invention is used for a wide-angle incident insensitive ultra-wideband transparent wave absorber based on slit enhancement. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a schematic structural diagram of the absorber unit of the present invention;

[0015] Figure 2 It is a schematic diagram of the structure of the wide-angle-incidence-insensitive ultra-wideband transparent absorber based on slit enhancement of the present invention;

[0016] Figure 3 This is a comparison diagram of the absorption curves of the TE and TM polarized electromagnetic waves of the transparent absorber without slit enhancement at normal incidence based on the large-angle incidence insensitive ultra-wideband transparent absorber of Example 1 and the comparative experiment 1;

[0017] Figure 4 The first embodiment shows the absorption characteristics of obliquely incident TE polarized electromagnetic waves by a wide-angle incident insensitive ultra-wideband transparent absorber based on slit enhancement;

[0018] Figure 5This is the absorption characteristics of obliquely incident TM polarized electromagnetic waves by a wide-angle incident insensitive ultra-wideband transparent absorber based on slit enhancement in Example 1;

[0019] Figure 6 The absorption curves of the wide-angle-incidence ultra-wideband transparent absorber insensitive to slit enhancement in Examples 1 to 3 and the comparative experiment 1 of the transparent absorber without slit enhancement for TE polarized electromagnetic waves with oblique incidence of 30° are compared. DETAILED DESCRIPTION

[0020] The technical solution of the present invention is not limited to the specific implementation modes listed below, but also includes any combination of the specific implementation modes.

[0021] Specific implementation method 1, combined with Figure 1 and Figure 2 Specific description: This embodiment is a wide-angle incident insensitive ultra-wideband transparent absorber based on slit enhancement, which is composed of N×M absorber units arranged periodically, where N≥4 columns and M≥4 rows;

[0022] The absorber unit is composed of a horizontal transparent conductive film and two vertical transparent conductive films;

[0023] The two vertical transparent conductive films are connected along one side edge in the vertical direction, and the bottom is vertically arranged at the two side edges of the upper surface of the horizontal transparent conductive film, and the angle between the two vertical transparent conductive films is 90°;

[0024] Part of the conductive layer is etched off the surface of the vertical transparent conductive film to form one or more long slit non-conductive areas;

[0025] Suppose the side length of the horizontal transparent conductive film is a; suppose the side length of the vertical transparent conductive film along the horizontal direction is b, b=a.

[0026] The beneficial effects of this embodiment are:

[0027] This embodiment proposes a low-thickness absorber, and low-frequency electromagnetic waves near 4 GHz can enter the absorber structure and be absorbed by loss, thereby solving the inherent contradiction between the low-thickness design of the absorber and the low-frequency absorption performance.

[0028] This embodiment proposes a wide-angle incidence insensitive ultra-wideband transparent absorber based on slit enhancement. By introducing slits on the transparent conductive film, ultra-wideband absorption of normally incident electromagnetic waves is achieved, and the broadband absorption stability of the absorber to obliquely incident electromagnetic waves is enhanced. At the same time, transparency is maintained to cooperate with the architectural design without affecting the aesthetics. It can also be used in scenes that require optical transparency, such as portholes, windshields, etc.

[0029] The transparent absorber designed in this embodiment has an absorption rate of more than 90% for normally incident TE and TM polarized electromagnetic waves in the 4.0GHz to 30.6GHz frequency band, covering some of the main frequency bands and extended frequency bands of 5G microwave communications. The designed transparent absorber can maintain an absorption rate of more than 75% for obliquely incident TE polarized electromagnetic waves within a range of 60° in the 4.0GHz to 30.0GHz frequency band; and can maintain an absorption rate of more than 85% for obliquely incident TM polarized electromagnetic waves within a range of 75° in the 4.0GHz to 30.0GHz frequency band.

[0030] Specific implementation example 2: This implementation example is different from the specific implementation example 1 in that the one horizontal transparent conductive film and the two vertical transparent conductive films are both ITO films with PET as the substrate. The rest is the same as the specific implementation example 1.

[0031] Specific implementation method 3: This implementation method is different from specific implementation method 1 or 2 in that the thickness of the PET substrate is 0.125 mm to 0.2 mm. The rest is the same as specific implementation method 1 or 2.

[0032] Specific embodiment 4: This embodiment is different from specific embodiments 1 to 3 in that the shape of the horizontal transparent conductive film is a square. The rest is the same as specific embodiments 1 to 3.

[0033] Specific implementation example 5: This implementation example is different from specific implementation examples 1 to 4 in that the vertical transparent conductive film is in a square or rectangular shape. The rest is the same as specific implementation examples 1 to 4.

[0034] Specific implementation method 6: This implementation method is different from specific implementation methods 1 to 5 in that: a=4 mm to 20 mm. The rest is the same as specific implementation methods 1 to 5.

[0035] Specific embodiment 7: This embodiment is different from specific embodiments 1 to 6 in that: the side length of the vertical transparent conductive film along the vertical direction is h, h=3mm-15mm. The rest is the same as specific embodiments 1 to 6.

[0036] Specific embodiment 8: This embodiment differs from specific embodiments 1 to 7 in that: the width of the long slit non-conductive region is w, w=0.01mm-0.10mm; the height of the long slit non-conductive region is l, l=h. The rest is the same as specific embodiments 1 to 7.

[0037] Specific embodiment 9: This embodiment is different from specific embodiments 1 to 8 in that the surface resistance of the horizontal transparent conductive film is set to ρ1, ρ1 = 3Ω / sq to 10Ω / sq. Other aspects are the same as specific embodiments 1 to 8.

[0038] Specific embodiment 10: This embodiment differs from specific embodiments 1 to 9 in that the surface resistance of the vertical transparent conductive film is set to ρ2, ρ2 = 150Ω / sq to 300Ω / sq. Other aspects are the same as specific embodiments 1 to 9.

[0039] The following examples are used to verify the beneficial effects of the present invention:

[0040] Embodiment 1:

[0041] A wide-angle incident insensitive ultra-wideband transparent absorber based on slit enhancement, which is composed of N×M absorber units arranged periodically, wherein N=10 columns and M=10 rows;

[0042] The absorber unit is composed of a horizontal transparent conductive film and two vertical transparent conductive films;

[0043] The two vertical transparent conductive films are connected along one side edge in the vertical direction, and the bottom is vertically arranged at the two side edges of the upper surface of the horizontal transparent conductive film, and the angle between the two vertical transparent conductive films is 90°;

[0044] The conductive layer is etched away on both sides of the vertical transparent conductive film surface to form a long slit non-conductive area;

[0045] Assume that the side length of the horizontal transparent conductive film is a, a = 8.4 mm;

[0046] Assume that the side length of the vertical transparent conductive film along the horizontal direction is b, b = a; Assume that the side length of the vertical transparent conductive film along the vertical direction is h, h = 9 mm

[0047] The one horizontal transparent conductive film and the two vertical transparent conductive films are all ITO films with PET as the substrate.

[0048] The thickness of the PET substrate is 0.125 mm.

[0049] The shape of the horizontal transparent conductive film is a square.

[0050] The vertical transparent conductive film is in the shape of a rectangle.

[0051] The width of the long slit non-conductive region is assumed to be w, w=0.0625 mm; the height of the long slit non-conductive region is assumed to be l, l=h.

[0052] Assume that the surface resistance of the horizontal transparent conductive film is ρ1, ρ1=5Ω / sq.

[0053] Assume that the surface resistance of the vertical transparent conductive film is ρ2, ρ2=200Ω / sq.

[0054] Embodiment 1 The wide-angle-incidence-insensitive ultra-wideband transparent absorber based on slit enhancement is an enhanced transparent absorber with double longitudinal slits arranged on the unit.

[0055] Embodiment 2: This embodiment is different from Embodiment 1 in that: the conductive layer is etched off at both sides of the vertical transparent conductive film in the vertical direction to form a first long slit non-conductive region, and the conductive layer is etched off at the center of the vertical transparent conductive film in the vertical direction to form a second long slit non-conductive region, so as to obtain an enhanced transparent absorber with three longitudinal slits on the unit; the width of the first long slit non-conductive region is w=0.0625mm, the width of the second long slit non-conductive region is 2w=0.125mm, and the heights of the first and second long slit non-conductive regions are both h. The rest is the same as Embodiment 1.

[0056] Embodiment 3: This embodiment is different from Embodiment 1 in that the conductive layer of the vertical transparent conductive film is etched away at the center in the horizontal direction to form a long slit non-conductive area with a length a and a width 2w (0.125 mm), thereby obtaining an enhanced transparent absorber with a single transverse slit on the unit. The rest is the same as Embodiment 1.

[0057] Comparative Experiment 1: This comparative experiment is different from Example 1 in that the vertical transparent conductive film is not etched to obtain a slit-free enhanced transparent absorber. The rest is the same as Example 1.

[0058] Figure 3 This is a comparison diagram of the absorption curves of the TE and TM polarized electromagnetic waves of the embodiment 1 based on the slit enhancement and the comparative experiment 1 of the transparent absorber without slit enhancement for the normally incident TE and TM polarized electromagnetic waves; it can be seen from the figure that the absorber without slit only produces an absorption effect of more than 90% for the normally incident TE and TM polarized electromagnetic waves in the frequency band of 12GHz to 25.4GHz (relative bandwidth 72%); the transparent absorber with slits arranged on the vertical transparent conductive film can produce an absorption effect of more than 90% for the normally incident TE and TM polarized electromagnetic waves in the frequency band of 4GHz to 30.6GHz (relative bandwidth 154%), and has a larger absorption bandwidth, especially reflected in the enhanced absorption capacity of electromagnetic waves in the low frequency band of 4GHz to 12GHz.

[0059] Figure 4 This is Example 1, which shows the absorption characteristics of obliquely incident TE polarized electromagnetic waves by a wide-angle incident insensitive ultra-wideband transparent absorber based on slit enhancement; as can be seen from the figure, the absorber can maintain an absorption rate of more than 75% for obliquely incident TE polarized electromagnetic waves within a range of 60° in the frequency band of 4.0 GHz to 30.0 GHz, and the absorption characteristics of TE polarized electromagnetic waves with wide-angle incidence can maintain good angular stability.

[0060] Figure 5This is Example 1, based on slit-enhanced large-angle incidence insensitive ultra-wideband transparent absorber, the absorption characteristics of obliquely incident TM polarized electromagnetic waves; as can be seen from the figure, the absorber can maintain an absorption rate of more than 85% for obliquely incident TM polarized electromagnetic waves within a range of 75° in the frequency band of 4.0GHz to 30.0GHz, and the absorption characteristics of large-angle incident TM polarized electromagnetic waves can maintain good angular stability.

[0061] Figure 6 The absorption curves of the wide-angle incident insensitive ultra-wideband transparent absorber based on slit enhancement in Examples 1 to 3 and the comparative experiment 1 of the transparent absorber without slit enhancement for 30° oblique incident TE polarized electromagnetic waves are compared; it can be seen from the figure that the absorber without slit only produces an absorption rate of more than 85% for 30° oblique incident TE polarized electromagnetic waves in the frequency band of 12.1GHz to 22.3GHz; the slit-enhanced transparent absorber in Examples 1 to 3 produces an absorption rate of more than 85% in the frequency bands of 4GHz to 22.5GHz, 4.4GHz to 22.8GHz, and 4.1GHz to 22.5GHz, respectively. Under the same incident angle, setting a horizontal or vertical slit on the vertical transparent conductive film will enhance the oblique incident absorption of the absorber without slits, especially in the low frequency band of 4GHz to 12GHz.

Claims

1. A wide-angle incident insensitive ultra-wideband transparent absorber based on slit enhancement, characterized in that It is composed of N×M absorber units arranged periodically, wherein N≥4 columns and M≥4 rows; The absorber unit is composed of a horizontal transparent conductive film and two vertical transparent conductive films; The two vertical transparent conductive films are connected along one side edge in the vertical direction, and the bottom is vertically arranged at the two side edges of the upper surface of the horizontal transparent conductive film, and the angle between the two vertical transparent conductive films is 90°; Part of the conductive layer is etched off the surface of the vertical transparent conductive film to form one or more long slit non-conductive areas; Suppose the side length of the horizontal transparent conductive film is a; suppose the side length of the vertical transparent conductive film along the horizontal direction is b, b=a.

2. The wide-angle-insensitive ultra-wideband transparent absorber based on slit enhancement according to claim 1, characterized in that The one horizontal transparent conductive film and the two vertical transparent conductive films are all ITO films with PET as the substrate.

3. The wide-angle-insensitive ultra-wideband transparent absorber based on slit enhancement according to claim 2, characterized in that The thickness of the PET substrate is 0.125 mm to 0.2 mm.

4. The wide-angle-insensitive ultra-wideband transparent absorber based on slit enhancement according to claim 1, characterized in that The shape of the horizontal transparent conductive film is a square.

5. The wide-angle-insensitive ultra-wideband transparent absorber based on slit enhancement according to claim 1, characterized in that The shape of the vertical transparent conductive film is square or rectangular.

6. The wide-angle-insensitive ultra-wideband transparent absorber based on slit enhancement according to claim 1, characterized in that a=4mm~20mm.

7. The wide-angle-insensitive ultra-wideband transparent absorber based on slit enhancement according to claim 1, characterized in that Assume that the side length of the vertical transparent conductive film along the vertical direction is h, where h=3 mm to 15 mm.

8. The wide-angle-insensitive ultra-wideband transparent absorber based on slit enhancement according to claim 1, characterized in that The width of the long slit non-conductive region is assumed to be w, where w=0.01 mm to 0.10 mm; the height of the long slit non-conductive region is assumed to be l, where l=h.

9. The wide-angle-insensitive ultra-wideband transparent absorber based on slit enhancement according to claim 1, characterized in that Assume that the surface resistance of the horizontal transparent conductive film is ρ1, ρ1=3Ω / sq~10Ω / sq.

10. The wide-angle incident insensitive ultra-wideband transparent absorber based on slit enhancement according to claim 1, characterized in that The surface resistance of the vertical transparent conductive film is ρ2, ρ2=150Ω / sq~300Ω / sq.

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