A slit-enhanced, large-angle incident-insensitive, ultrawideband transparent absorber

Abstract

This invention relates to a transparent absorber that is insensitive to large-angle incident light based on slit reinforcement. The invention addresses the inherent contradiction between existing absorbers' insensitivity to large-angle oblique incidence of radio frequency electromagnetic fields and the inherent limitations of their low-thickness design and low-frequency absorption performance. The transparent absorber consists of an array of N×M absorber units; each absorber unit comprises a horizontally transparent conductive film and two vertically transparent conductive films; the surface of the vertically transparent conductive films is etched away to form one or more elongated, non-conductive slit regions. This invention is used for a large-angle incident light-insensitive, ultra-wideband transparent absorber based on slit reinforcement.

Description

Technical Field

[0001] This invention relates to a transparent microwave absorber. Background Technology

[0002] In recent years, microwave communication technology has driven the rapid development of human society in various aspects, and people are enjoying the convenience and speed brought by real-time communication. However, the radio frequency electromagnetic fields used in microwave communication carry energy along with information, posing a potential threat to human health and life. In the era before the widespread use of mobile phones and wireless networks, this potential danger did not attract people's attention, but today's widely used microwave communication technology has permeated people's living environment with radio frequency electromagnetic fields that oscillate with space and time. Therefore, in recent years, researchers have developed many types of absorbers with different operating frequency bands to absorb excess electromagnetic waves. Most absorbers are designed using the absorption rate of normally incident electromagnetic waves and the operating bandwidth as the criteria for judging their absorption performance. In order to pursue a wider operating frequency band, existing absorbers have significantly reduced absorption performance when facing obliquely 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 places higher demands on the absorption performance of absorbers for obliquely incident electromagnetic waves. On the other hand, due to the Rozanov limit of absorbers, the theoretical minimum thickness of an absorber with 90% absorption rate increases as the frequency of electromagnetic waves decreases. For broadband absorbers of a certain thickness, the thickness is closer to the Rozanov limit, making it more difficult to achieve good absorption of low-frequency electromagnetic waves. Therefore, there is always an inherent contradiction between the design of low-thickness absorbers and their low-frequency absorption performance. Summary of the Invention

[0003] This invention aims to address the problem that existing absorbers are insensitive to large-angle oblique incidence of radio frequency electromagnetic fields, and that there is an inherent contradiction between the low-thickness design and low-frequency absorption performance of absorbers. Therefore, it proposes an ultrawideband transparent absorber that is insensitive to large-angle incidence based on slit enhancement.

[0004] A slit-enhanced, large-angle incident-insensitive, ultrawideband transparent absorber is composed of N×M periodically arranged absorber units, where N≥4 columns and M≥4 rows.

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

[0006] Two vertical transparent conductive films are connected along one side of the vertical direction, and the bottom is set vertically on both sides of the upper surface of the horizontal transparent conductive film, and the included angle between the two vertical transparent conductive films is 90°.

[0007] The vertical transparent conductive film surface is etched to remove part of the conductive layer to form one or more long, narrow, non-conductive regions.

[0008] Let the side length of the horizontal transparent conductive film be a; let the side length of the vertical transparent conductive film along the horizontal direction be b, where b = a.

[0009] The beneficial effects of this invention are:

[0010] This invention proposes a low-thickness absorber that allows low-frequency electromagnetic waves near 4GHz to enter the absorber structure and be absorbed by loss, thus solving the inherent contradiction between the low-thickness design and the low-frequency absorption performance of the absorber.

[0011] This invention proposes a large-angle incident insensitive ultrawideband transparent absorber based on slit enhancement. By introducing slits into a transparent conductive film, ultrawideband absorption of normally incident electromagnetic waves is achieved, and the broadband absorption stability of the absorber for obliquely incident electromagnetic waves is enhanced. At the same time, the transparency is maintained to match the architectural design and does not affect the aesthetics. It can also be used in scenarios that require optical transparency, such as portholes and windshields.

[0012] The transparent absorber designed in this invention exhibits an absorption rate exceeding 90% for normally incident TE and TM polarized electromagnetic waves in the 4.0 GHz to 30.6 GHz frequency band, covering some of the main and extended frequency bands of 5G microwave communication. The designed transparent absorber maintains an absorption rate of over 75% for obliquely incident TE polarized electromagnetic waves within a 60° range in the 4.0 GHz to 30.0 GHz frequency band; and maintains an absorption rate of over 85% for obliquely incident TM polarized electromagnetic waves within a 75° range in the same frequency band.

[0013] This invention relates to a wide-angle incident insensitive ultrawide transparent absorber based on slit enhancement. Attached Figure Description

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

[0015] Figure 2 This is a schematic diagram of the structure of the large-angle incident insensitive ultrawide transparent absorber based on slit enhancement according to the present invention;

[0016] Figure 3 Example 1: A comparison of the absorption curves of normally incident TE and TM polarized electromagnetic waves by a slit-enhanced, large-angle incident insensitive ultrawideband transparent absorber and a slit-unenhanced transparent absorber.

[0017] Figure 4 Example 1 illustrates the absorption characteristics of obliquely incident TE-polarized electromagnetic waves by a slit-enhanced, large-angle incident insensitive, ultrawide-bandgap transparent absorber.

[0018] Figure 5Example 1 illustrates the absorption characteristics of obliquely incident TM polarized electromagnetic waves by a slit-enhanced, large-angle incident insensitive ultrawideband transparent absorber.

[0019] Figure 6 Examples 1 to 3 show the absorption curves of TE-polarized electromagnetic waves incident at 30° oblique incidence using slit-enhanced large-angle incident ultrawide transparent absorbers and a comparative experiment 1 using a transparent absorber without slit enhancement. Detailed Implementation

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

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

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

[0023] Two vertical transparent conductive films are connected along one side of the vertical direction, and the bottom is set vertically on both sides of the upper surface of the horizontal transparent conductive film, and the included angle between the two vertical transparent conductive films is 90°.

[0024] The vertical transparent conductive film surface is etched to remove part of the conductive layer to form one or more long, narrow, non-conductive regions.

[0025] Let the side length of the horizontal transparent conductive film be a; let the side length of the vertical transparent conductive film along the horizontal direction be b, where b = a.

[0026] The beneficial effects of this embodiment are:

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

[0028] This embodiment proposes a large-angle incident insensitive ultrawideband transparent absorber based on slit enhancement. By introducing slits into a transparent conductive film, ultrawideband absorption of normally incident electromagnetic waves is achieved, and the broadband absorption stability of the absorber for obliquely incident electromagnetic waves is enhanced. At the same time, the transparency is maintained to match the architectural design and does not affect the aesthetics. It can also be used in scenarios that require optical transparency, such as portholes and windshields.

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

[0030] Specific Implementation Method Two: This implementation method differs from Specific Implementation Method One in that both the horizontal transparent conductive film and the two vertical transparent conductive films are ITO films with PET as the substrate. Everything else is the same as in Specific Implementation Method One.

[0031] Specific Implementation Method Three: This implementation method differs from Specific Implementation Method One or Two in that the thickness of the PET substrate is 0.125mm to 0.2mm. Everything else is the same as in Specific Implementation Method One or Two.

[0032] Specific Implementation Method Four: This implementation method differs from Specific Implementation Methods One to Three in that the shape of the horizontal transparent conductive film is square. Otherwise, it is the same as Specific Implementation Methods One to Three.

[0033] Specific Implementation Method Five: This implementation method differs from Specific Implementation Methods One to Four in that the vertically transparent conductive film is square or rectangular in shape. Otherwise, it is the same as Specific Implementation Methods One to Four.

[0034] Specific Implementation Method Six: This implementation method differs from Specific Implementation Methods One to Five in that a = 4mm to 20mm. Everything else is the same as Specific Implementation Methods One to Five.

[0035] Specific Implementation Method Seven: This implementation method differs from Specific Implementation Methods One through Six in that: the vertical side length of the transparent conductive film is set to h, where h = 3mm to 15mm. Everything else is the same as Specific Implementation Methods One through Six.

[0036] Specific Implementation Method Eight: This implementation method differs from Specific Implementation Methods One to Seven in that: the width of the non-conductive region of the elongated slit is set to w, where w = 0.01 mm to 0.10 mm; and the height of the non-conductive region of the elongated slit is set to l, where l = h. Everything else is the same as in Specific Implementation Methods One to Seven.

[0037] Specific Implementation Method Nine: This implementation method differs from Specific Implementation Methods One to Eight in that the surface resistance of the horizontal transparent conductive film is set to ρ1, where ρ1 = 3Ω / sq to 10Ω / sq. Everything else is the same as in Specific Implementation Methods One to Eight.

[0038] Specific Implementation Method Ten: This implementation method differs from Specific Implementation Methods One through Nine in that the sheet resistance of the vertical transparent conductive film is set to ρ2, where ρ2 = 150Ω / sq to 300Ω / sq. Everything else is the same as in Specific Implementation Methods One through Nine.

[0039] The beneficial effects of the present invention are verified using the following embodiments:

[0040] Example 1:

[0041] A slit-enhanced, large-angle incident-insensitive, ultrawideband transparent absorber is composed of N×M periodically arranged absorber units, where N = 10 columns and M = 10 rows.

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

[0043] Two vertical transparent conductive films are connected along one side of the vertical direction, and the bottom is set vertically on both sides of the upper surface of the horizontal transparent conductive film, and the included angle between the two vertical transparent conductive films is 90°.

[0044] The conductive layer on both sides of the vertically transparent conductive film surface is etched away to form long, narrow, non-conductive slits.

[0045] Let the side length of the horizontal transparent conductive film be a, where a = 8.4 mm;

[0046] Let the horizontal side length of the vertically perpendicular transparent conductive film be b, where b = a; let the vertical side length of the vertically perpendicular transparent conductive film be h, where h = 9 mm.

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

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

[0049] The horizontal transparent conductive film is square in shape.

[0050] The vertically transparent conductive film is rectangular in shape.

[0051] Let w be the width of the non-conductive region of the long narrow slit, where w = 0.0625 mm; and let l be the height of the non-conductive region of the long narrow slit, where l = h.

[0052] Let the sheet resistance of the horizontal transparent conductive film be ρ1, where ρ1 = 5Ω / sq.

[0053] Let the sheet resistance of the vertical transparent conductive film be ρ2, where ρ2 = 200 Ω / sq.

[0054] Example 1: The large-angle incident insensitive ultrawideband transparent absorber based on slit enhancement is a reinforced transparent absorber with double longitudinal slits on the unit.

[0055] Example 2: This example differs from Example 1 in that: the conductive layer of the vertically transparent conductive film is etched away from both sides along the vertical direction to form a first elongated slit non-conductive region; the conductive layer of the vertically transparent conductive film is etched away from the center along the vertical direction to form a second elongated slit non-conductive region, resulting in an enhanced transparent absorber with three longitudinal slits on the unit; the width of the first elongated slit non-conductive region is w = 0.0625 mm, the width of the second elongated slit non-conductive region is 2w = 0.125 mm, and the height of both the first and second elongated slit non-conductive regions is h. Everything else is the same as in Example 1.

[0056] Example 3: This example differs from Example 1 in that the conductive layer of the vertical transparent conductive film is etched away at its center along the horizontal direction to form a long, narrow, non-conductive region with a length of 'a' and a width of 2w (0.125 mm), resulting in an enhanced transparent absorber with a single horizontal slit on the unit. Everything else is the same as in Example 1.

[0057] Comparative Experiment 1: This comparative experiment differs from Example 1 in that no vertical transparent conductive film was etched, resulting in a slit-free enhanced transparent absorber. Everything else is the same as in Example 1.

[0058] Figure 3 The figures show a comparison of the absorption curves of normally incident TE and TM polarized electromagnetic waves for Example 1, which is based on a slit-enhanced, large-angle incident insensitive ultrawideband transparent absorber, and a comparative experiment, which is based on a slit-less enhanced transparent absorber. As can be seen from the figures, the slit-less absorber only achieves a greater than 90% absorption effect for normally incident TE and TM polarized electromagnetic waves within the 12GHz–25.4GHz frequency band (72% relative bandwidth). The transparent absorber with a slit on a vertically transparent conductive film can achieve a greater than 90% absorption effect for normally incident TE and TM polarized electromagnetic waves within the 4GHz–30.6GHz frequency band (154% relative bandwidth), exhibiting a larger absorption bandwidth, particularly enhanced absorption capability for low-frequency electromagnetic waves in the 4GHz–12GHz range.

[0059] Figure 4 Example 1 shows the absorption characteristics of obliquely incident TE-polarized electromagnetic waves by a slit-enhanced, large-angle incident insensitive ultrawideband transparent absorber. As shown in the figure, the absorber can maintain an absorption rate of over 75% for obliquely incident TE-polarized electromagnetic waves within a 60° range in the 4.0GHz to 30.0GHz frequency band, and its absorption characteristics for large-angle incident TE-polarized electromagnetic waves can maintain good angular stability.

[0060] Figure 5Example 1 shows the absorption characteristics of obliquely incident TM-polarized electromagnetic waves by a slit-enhanced, large-angle incident insensitive ultrawideband transparent absorber. As shown in the figure, the absorber can maintain an absorption rate of over 85% for obliquely incident TM-polarized electromagnetic waves within a 75° range in the 4.0 GHz to 30.0 GHz frequency band, and its absorption characteristics for large-angle incident TM-polarized electromagnetic waves can maintain good angular stability.

[0061] Figure 6 This paper compares the absorption curves of slit-enhanced, large-angle incident insensitive ultrawideband transparent absorbers (Examples 1-3) and a slit-free enhanced transparent absorber for 30° oblique incident TE-polarized electromagnetic waves. As shown in the figure, the slit-free absorber only exhibits an absorption rate greater than 85% for 30° oblique incident TE-polarized electromagnetic waves in the 12.1GHz–22.3GHz frequency band. The slit-enhanced transparent absorbers in Examples 1-3 exhibit absorption rates greater than 85% in the 4GHz–22.5GHz, 4.4GHz–22.8GHz, and 4.1GHz–22.5GHz frequency bands, respectively. Under the same incident angle, placing transverse or longitudinal slits on the vertical transparent conductive film enhances the oblique incident absorption of the slit-free absorber, especially in the low-frequency band of 4GHz–12GHz.

Claims

1. A slit-enhanced, large-angle incident-insensitive, ultrawideband transparent absorber, characterized in that... It consists of N×M periodically arranged absorber units, where N≥4 columns and M≥4 rows; The absorber unit consists of a horizontal transparent conductive film and two vertical transparent conductive films; Two vertical transparent conductive films are connected along one side of the vertical direction, and the bottom is set vertically on both sides of the upper surface of the horizontal transparent conductive film, and the included angle between the two vertical transparent conductive films is 90°. The vertical transparent conductive film surface is etched to remove part of the conductive layer to form one or more long, narrow, non-conductive regions. Let the side length of the horizontal transparent conductive film be a; let the side length of the vertical transparent conductive film along the horizontal direction be b, where b = a.

2. The ultrawideband transparent absorber with large-angle incident insensitivity based on slit enhancement according to claim 1, characterized in that... The horizontal transparent conductive film and the two vertical transparent conductive films are both ITO films with PET as the substrate.

3. The ultrawideband transparent absorber with large-angle incident insensitivity based on slit enhancement according to claim 2, characterized in that... The thickness of the PET substrate is 0.125mm to 0.2mm.

4. The ultrawideband transparent absorber with large-angle incident insensitivity based on slit enhancement according to claim 1, characterized in that... The horizontal transparent conductive film is square in shape.

5. The ultrawideband transparent absorber with large-angle incident insensitivity based on slit enhancement according to claim 1, characterized in that... The vertically transparent conductive film is square or rectangular in shape.

6. The ultrawideband transparent absorber with large-angle incident insensitivity based on slit enhancement according to claim 1, characterized in that... a = 4mm ~ 20mm.

7. The ultrawideband transparent absorber with large-angle incident insensitivity based on slit enhancement according to claim 1, characterized in that... Let the length of the vertical transparent conductive film along the vertical direction be h, where h = 3mm to 15mm.

8. The ultrawideband transparent absorber with large-angle incident insensitivity based on slit enhancement according to claim 1, characterized in that... Let w be the width of the non-conductive region of the long narrow slit, where w = 0.01 mm to 0.10 mm; and let l be the height of the non-conductive region of the long narrow slit, where l = h.

9. The ultrawideband transparent absorber with large-angle incident insensitivity based on slit enhancement according to claim 1, characterized in that... Let the sheet resistance of the horizontal transparent conductive film be ρ1, where ρ1 = 3Ω / sq ~ 10Ω / sq.

10. A large-angle incident insensitive ultrawideband transparent absorber based on slit enhancement according to claim 1, characterized in that it is provided with The sheet resistance of the vertical transparent conductive film is ρ2, where ρ2 = 150Ω / sq to 300Ω / sq.

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