Broadband absorbing structure and fabrication method based on multilayer resistive film

Abstract

This invention relates to a broadband absorbing structure based on multilayer resistive films and its fabrication method. The structure includes a bottom metal layer, on which spacer support layers and resistive film layers are sequentially and crosswise stacked. The uppermost resistive film layer comprises a cross-shaped structure and a hollow square ring structure in the center, while the remaining resistive film layers are square sheet structures. The thickness of the spacer support layers is 5-9 mm, and the sheet resistance of the resistive film layers is 162-343 Ohm / sq. This absorbing structure exhibits excellent low-frequency absorption performance, with a reflection loss of less than -15 dB in the 1.5 GHz to 2.4 GHz range, and maintaining a reflection loss of less than -12.5 dB in the 1.4 GHz to 18.6 GHz range.

Description

Technical Field

[0001] This invention belongs to the field of functional materials technology, specifically relating to a broadband absorbing structure based on a multilayer resistive film and its preparation method. Background Technology

[0002] As radar detection technology continues to advance and the ability to reduce radar cross section (RCS) through shape design reaches its limits, radar absorbing materials offer a parallel approach to detection mitigation. These materials absorb the electromagnetic energy emitted by enemy radar, thereby reducing the probability of detection. Traditional absorbing materials offer advantages such as simple processing and convenient construction, but also have disadvantages such as high thickness, heavy weight, and narrow absorption bandwidth.

[0003] CN114597672A discloses a multilayer resistive FSS broadband absorbing structure, which utilizes the synergistic effect of multiple resistive films to broaden the absorption bandwidth and enhance low-frequency absorption performance with a low thickness. However, its multilayer absorbing structure only covers the S-band in low-frequency absorption performance, with a significant decrease in L-band absorption performance. Furthermore, the curved line structure resistive film used in its multilayer absorbing structure has a minimum linewidth and spacing of 0.4 mm and achieves full area coverage, resulting in a high manufacturing error rate for the resistive film. Summary of the Invention

[0004] This invention provides a broadband absorbing structure based on multilayer resistive films and its preparation method. By setting up multilayer resistive films and combining different structures in the same layer of resistive films, the absorption bandwidth can be broadened and the low-frequency absorption performance can be enhanced.

[0005] The technical solution of the present invention is a broadband absorbing structure based on multilayer resistive films, comprising a bottom metal layer, on which spacer support layers and resistive film layers are sequentially and crosswise stacked, the resistive film layers being at least 4 layers, the uppermost resistive film layer comprising a cross-shaped structure and a square ring structure with a hollow center, and the remaining resistive film layers being square sheet structures; the thickness of the spacer support layer is 5-9 mm, and the sheet resistance of the resistive film layers is 162-343 Ohm / sq.

[0006] Furthermore, the cross-shaped structure is formed by four T-shaped units arranged clockwise, with the bottom of the T-shaped units connected together, and the included angle between two adjacent T-shaped units is 90°; the total length of the cross-shaped structure is 9.4 mm, the short side length of the T-shaped unit is 3.3 mm, and the width of both the short and long sides is 0.87 mm.

[0007] Furthermore, the outer side length of the square ring structure is 9.5 mm, and the width of the ring wall is 1.4 mm.

[0008] Furthermore, the resistive film layer is made of one or more of the following composite materials: graphene, carbon nanotubes, polymer conductive materials, graphite, and carbon black.

[0009] Furthermore, a total of 4 resistive film layers are disposed on the metal layer. The other resistive film layers between the metal layer and the top resistive film layer are rectangular structures. Each rectangular structure consists of two square structures with a side length of 7.4 to 9.8 mm. A gap is left between the two square structures with a gap width of 0.2 to 2.6 mm.

[0010] Furthermore, the sheet resistance of the four resistive film layers is Rs1, Rs2, Rs3, and Rs4, where Rs3 > Rs4 > Rs2 > Rs1.

[0011] Furthermore, the spacer support layer is made of PVC foam, PMI foam or honeycomb material, and the relative permittivity ε satisfies: 1.0≤ε≤1.5.

[0012] The present invention also relates to a method for preparing the aforementioned structure, comprising the following steps:

[0013] 1) Using screen printing, resistive film paste is printed on polyimide film according to the shape and size requirements of different resistive film layers, and each resistive film layer is bonded to the spacer support layer to form a unit with multiple sets of spacer support layers and resistive film layers.

[0014] 2) Place each unit on the metal layer in the design order and glue them together with foam to obtain a broadband absorbing structure based on multilayer resistive film.

[0015] The beneficial effects of this invention are as follows:

[0016] (1) The absorbing structure provided by the present invention introduces two structures in the repeating unit structure of the uppermost resistive film. The cross-shaped structure enhances the absorbing performance, while the square ring structure broadens the absorption bandwidth. The combination of the two structures can produce a synergistic effect, enhancing the absorbing performance and broadening the absorption bandwidth.

[0017] (2) The absorbing structure of the present invention is provided with multiple resistive films, and the shapes and sizes of the resistive films are different. The first resistive film mainly improves the absorption performance of the C and Ku bands, the second resistive film mainly improves the absorption performance of the C, X and Ku bands, the third layer mainly improves the absorption performance of the L, S and C bands, and the fourth layer mainly improves the absorption performance of the C and Ku bands. Through the synergistic effect of the four resistive films, the absorbing structure has excellent absorption performance in the L to Ku bands.

[0018] (3) The absorbing structure provided by this invention has excellent low-frequency absorption performance. Within the range of 1.5 GHz to 2.4 GHz, the reflection loss is less than -15 dB, and within the range of 1.4 GHz to 18.6 GHz, the reflection loss remains less than -12.5 dB. The absorbing structure provided by this invention, through the synergistic effect of four layers of resistive film, broadens the absorption frequency band to the L, S, and C bands.

[0019] (4) The minimum line spacing of each layer of resistive film in the absorbing structure provided by the present invention is 0.4 mm and is only between the cross and the square ring. It does not exist in a large area in the repeating unit, thus avoiding the manufacturing error rate of resistive film caused by the small line width and line spacing. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the absorbing structure in Embodiment 1 of the present invention.

[0021] Figure 2 This is a side view of the absorbing structure in Example 1.

[0022] Figure 3 This is a schematic diagram of the structure of the uppermost resistive film in Example 1.

[0023] Figure 4 This is a schematic diagram of the intermediate resistive film layer structure in Example 1.

[0024] Figure 5 The reflection curve of the absorbing structure under vertical incidence in Example 1 is shown.

[0025] Figure 6 The reflection curve of the absorbing structure under vertical incidence is shown in Example 2.

[0026] Figure 7 The reflection curve of the absorbing structure under vertical incidence in Example 3 is shown.

[0027] Figure 8 The reflection curve of the absorbing structure under vertical incidence is shown in Example 4.

[0028] Figure 9 The reflection curve of the absorbing structure under vertical incidence in Example 5 is shown. Detailed Implementation

[0029] The embodiments of the present invention will be described in detail below with reference to examples. However, those skilled in the art will understand that the following examples are only for illustrating the present invention and should not be regarded as limiting the scope of the present invention.

[0030] Example 1:

[0031] Example 1-1

[0032] like Figure 1As shown, the present invention provides a broadband absorbing structure based on multilayer resistive films, including a bottom metal layer made of aluminum alloy 7075 with a thickness of 1.0 mm, on which four spacer support layers and four resistive film layers are sequentially and crosswise stacked, from top to bottom as follows: first resistive film, first resistive film spacer support layer, second resistive film, second resistive film spacer support layer, third resistive film, third resistive film spacer support layer, fourth resistive film, and fourth resistive film spacer support layer.

[0033] like Figure 2 As shown, the thicknesses of the first, second, third, and fourth resistive film spacer support layers are H1 = 5.70 mm, H2 = 6.30 mm, H3 = 8.00 mm, and H4 = 6.00 mm, respectively. The resistive film spacer support material can be PVC foam, PMI foam, or honeycomb material, and its relative permittivity ε satisfies the condition: 1.0 ≤ ε ≤ 1.5; in this embodiment, PMI foam is specifically used.

[0034] The first resistive film consists of a cross-shaped structure and a hollow square ring structure in the center, as shown in the figure. Figure 3 As shown, the dimensions are listed in Table 1 below.

[0035] Table 1

[0036] Size symbol Dimensions / mm L_1 8.00 L_2 3.30 L_3 9.50 W1 0.87 W2 1.40

[0037] The repeating unit structures of the second, third, and fourth resistive films are all square sheet structures, such as... Figure 4 As shown in Table 2, the dimensions enhance the low-frequency absorption performance through the synergistic effect of multilayer resistive films in frequency division.

[0038] Table 2

[0039]

[0040]

[0041] The sheet resistance Rs of each resistive film layer is shown in Table 3.

[0042] Table 3

[0043] name Square resistance / (Ohm / sq) First resistive film 162.00 Second resistive film 208.00 Third resistive film 343.00 Fourth resistive film 242.00

[0044] The resistive film described above can be made of one or more composites of graphene, carbon nanotubes, conductive polymer materials, graphite, and carbon black. In this embodiment, carbon black is used.

[0045] The preparation method of the above structure is as follows:

[0046] 1) Using screen printing, resistive film paste is printed on different spacer support layers according to the shape and size requirements of different resistive film layers, forming multiple units combining spacer support layers and resistive film layers;

[0047] 2) Place each unit on the metal layer in the design order and glue them together with foam to obtain a broadband absorbing structure based on multilayer resistive film.

[0048] The broadband absorbing structure based on multilayer resistive films provided in this embodiment exhibits the following reflection curves under TE and TM polarization in the 0.5GHz–20GHz frequency band under vertical incidence: Figure 5 As shown in the figure, with -10dB as the standard, the effective absorption bandwidth of this absorbing structure is 1.3GHz to 19.2GHz. In the low frequency range of 1.5GHz to 2.4GHz, the reflection loss is less than -15dB, and in the range of 1.4GHz to 18.6GHz, the reflection loss can be kept less than -12.5dB.

[0049] Examples 1-2:

[0050] The broadband absorbing structure based on multilayer resistive film in this embodiment is the same as that in Embodiment 1-1, except that the first layer of resistive film is composed of two symmetrically arranged cross-shaped structures, and its shape and size are the same as those in Embodiment 1-1.

[0051] Examples 1-3:

[0052] The broadband absorbing structure based on multilayer resistive film in this embodiment is the same as that in Embodiment 1-1, except that the first layer of resistive film is composed of two symmetrically arranged square ring structures, and its shape and size are the same as those in Embodiment 1-1.

[0053] Examples 1-4:

[0054] The broadband absorbing structure based on multilayer resistive film in this embodiment is the same as that in Embodiment 1-1, except that the first resistive film is composed of two symmetrically arranged square structures with a side length of 9.5 mm and a gap of 1.0 mm between the two square structures.

[0055] Examples 1-5:

[0056] The broadband absorbing structure based on multilayer resistive film in this embodiment is the same as in Embodiment 1-1, except that the dimensions of the third resistive film layer and the fourth resistive film layer are swapped.

[0057] The reflectivity of the broadband absorbing structures based on multilayer resistive films involved in the above embodiments was tested, with reference standard GJB 2038A. The reflection curves of the structures in Examples 1-1 to 1-5 under vertical incidence are shown below. Figures 5-9 .

[0058] In Example 1-1, under vertical incidence, the reflection curves of TE and TM polarizations in the 0.5GHz to 20GHz frequency band are as follows: Figure 5 As shown. By Figure 5 It can be seen that, with -10dB as the standard, the effective absorption bandwidth of this absorbing structure is 1.3GHz to 19.2GHz. In the low frequency range of 1.5GHz to 2.4GHz, the reflection loss is less than -15dB, and in the range of 1.4GHz to 18.6GHz, the reflection loss can be kept less than -12.5dB.

[0059] In Examples 1-2, under vertical incidence, the reflection curves of TE and TM polarizations in the 0.5GHz to 20GHz frequency band are as follows: Figure 6 As shown. By Figure 6 It can be seen that, with -10dB as the standard, the effective absorption bandwidth of this absorbing structure is 1.4GHz to 18.7GHz. In the low frequency range of 1.7GHz to 2.5GHz, the reflection loss is less than -15dB, and in the range of 1.5GHz to 18.0GHz, the reflection loss can be kept less than -12.5dB.

[0060] Examples 1-3, under vertical incidence, show the reflection curves of TE and TM polarizations in the 0.5GHz to 20GHz frequency band as follows: Figure 7 As shown. By Figure 7 It can be seen that, with -10dB as the standard, the effective absorption bandwidth of this absorbing structure is 1.2GHz to 19.6GHz. In the low frequency range of 1.3GHz to 2.1GHz, the reflection loss is less than -15dB, and in the range of 1.3GHz to 19.4GHz, the reflection loss can be kept less than -11.0dB.

[0061] Examples 1-4, under vertical incidence, show the reflection curves of TE and TM polarizations in the 0.5GHz to 20GHz frequency band as follows: Figure 8 As shown. By Figure 8 It can be seen that, based on -10dB as the standard, the effective absorption bandwidth of this absorbing structure is 1.1GHz to 2.0GHz.

[0062] Examples 1-5, under vertical incidence, show the reflection curves of TE and TM polarizations in the 0.5GHz to 20GHz frequency band as follows: Figure 9 As shown. By Figure 9 It can be seen that, based on -10dB as the standard, the effective absorption bandwidth of this absorbing structure is 1.4GHz~2.6GHz and 4.3GHz~17.5GHz.

Claims

1. A broadband absorbing structure based on a multilayer resistive film, characterized in that, The device includes a bottom metal layer, on which spacer support layers and resistive film layers are stacked in a crisscross pattern. There are four resistive film layers. The top resistive film layer contains a cross-shaped structure and a square ring structure with a hollow center. The cross-shaped structure and the square ring structure are arranged side by side. The other three resistive film layers between the metal layer and the top resistive film layer are rectangular structures. Each rectangular structure consists of two square structures. One square structure is located directly below the cross-shaped structure, and the other square structure is located directly below the square ring structure. The side length of the square structure is 7.4~9.8mm. There is a gap between the two square structures with a gap width of 0.2~2.6mm. The sheet resistance of the four resistive film layers is Rs1, Rs2, Rs3, and Rs4, where Rs3 > Rs4 > Rs2 > Rs1. The first resistive film enhances the absorption performance in the C and Ku bands, the second resistive film enhances the absorption performance in the C, X, and Ku bands, the third layer enhances the absorption performance in the L, S, and C bands, and the fourth layer enhances the absorption performance in the C and Ku bands. Through the synergistic effect of the four resistive film layers, the absorbing structure has absorption performance in the L to Ku bands. The thickness of the spacer support layer is 5~9mm, and the sheet resistance of the resistive film layers is 162~343 Ohm / sq.

2. The structure according to claim 1, characterized in that: The cross-shaped structure is formed by four T-shaped units arranged clockwise, with the bottom of the T-shaped units connected and the included angle between two adjacent T-shaped units being 90°; the total length of the cross-shaped structure is 9.4 mm, the short side length of the T-shaped unit is 3.3 mm, and the width of both the short and long sides is 0.87 mm.

3. The structure according to claim 1, characterized in that: The outer side length of the square ring structure is 9.5 mm, and the width of the ring wall is 1.4 mm.

4. The structure according to claim 1, characterized in that: The resistive film layer is made of one or more of the following composite materials: graphene, carbon nanotubes, polymer conductive materials, graphite, and carbon black.

5. The structure according to claim 1, characterized in that: The spacer support layer is made of PVC foam, PMI foam or honeycomb material, and the relative permittivity ε satisfies: 1.0≤ε≤1.

5.

6. A method for preparing the structure according to any one of claims 1 to 5, characterized in that, The steps are as follows: 1) Using screen printing, resistive film paste is printed on polyimide film according to the shape and size requirements of different resistive film layers, and each resistive film layer is bonded to the spacer support layer to form a unit with multiple sets of spacer support layers and resistive film layers. 2) Place each unit on the metal layer in the design order and glue them together with foam to obtain a broadband absorbing structure based on multilayer resistive film.

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