Design and preparation method of broadband strong-absorption microwave metamaterial based on impedance control

Abstract

The invention discloses a broadband strong-absorption microwave metamaterial design and preparation method based on impedance control, and belongs to the field of electromagnetic absorption metamaterials. The invention aims to solve the problem that a microwave absorption metamaterial is difficult to realize wide absorption bandwidth and strong absorption intensity at the same time. The method comprises the following steps of: 1, solving an impedance value range of a resistive film layer on the surface of the microwave absorption metamaterial; 2, further extracting the available value ranges of the equivalent resistance and the equivalent capacitance of the resistive film layer; 3, traversing value ranges of the equivalent resistance and the equivalent capacitance, and collecting phase information of electromagnetic waves reflected by the corresponding metamaterial; 4, calculating a reflected electromagnetic wave phase difference; 5, selecting two metamaterial units of which the difference between the average value of the absolute values of the phase differences and the pi is minimum in the target frequency band; and 6, forming a new metamaterial unit through chessboard type distribution and arrangement, and realizing the design of the broadband strong-absorption metamaterial through common regulation and control of amplitude and phase. The method has universality and can be used for efficiently designing other metamaterial microwave absorbers with target performance.

Description

Technical Field

[0001] The present invention belongs to the field of electromagnetic absorption metamaterials, and specifically relates to a design method of a broadband strong microwave absorption metamaterial based on impedance manipulation, and a preparation method of a broadband strong microwave absorption metamaterial based on impedance manipulation. Background Art

[0002] As human society enters the information age, electromagnetic waves, as the carrier of communication signals, play a key role in wireless communications. Simultaneously, the rapid development of electromagnetic technology has also promoted the widespread use of advanced electronic devices. However, while electromagnetic waves have effectively improved people's lives, they have also brought about a new type of environmental pollution. Furthermore, in the military field, radar detection technology based on electromagnetic waves poses a significant threat to targets such as aircraft and ships. Therefore, to meet these electromagnetic challenges, the development of efficient electromagnetic wave absorbing materials is urgent. Metamaterials are materials with periodic or non-periodic subwavelength artificial structures. Through structural design, they can achieve unique electromagnetic responses and are an effective means of achieving efficient electromagnetic absorption. Currently, metamaterial microwave absorbers face problems such as narrow absorption bandwidth and low absorption intensity, which greatly limit their practical application. Therefore, the development of microwave metamaterials with broadband and strong absorption is of great significance.

[0003] The Chinese patent publication number CN118099766A, "A Microwave Absorbing Metamaterial and Its Preparation Method," proposes a lightweight, corrosion-resistant microwave absorbing metamaterial by designing a protective layer, a dielectric layer, a resonant structure layer, and a reflective layer. However, its effective absorption bandwidth is only 2.2 GHz, and the narrow bandwidth limits its application in complex electromagnetic environments. The Chinese patent publication number CN119481724A, "Metamaterial Broadband Microwave Absorber," uses a semiconductor metamaterial periodic structure surface to broaden the absorption bandwidth. However, further improving the absorption intensity is crucial to more efficiently control electromagnetic pollution and achieve military stealth. In order to solve the problem that microwave absorbing metamaterials are difficult to achieve both wide absorption bandwidth and strong absorption intensity, the present invention provides a design and preparation method of broadband strong absorption microwave metamaterial based on impedance manipulation.

[0004] In order to solve the above technical problems, the present invention adopts the following technical solutions: The object of the present invention is to provide a method for designing a broadband strong microwave absorption metamaterial based on impedance manipulation, comprising the following steps: 1. Combining equivalent circuit theory and transmission line theory, and based on the effective absorption requirements for the amplitude and phase of the reflected electromagnetic wave, the impedance range of the surface resistance film layer of the microwave absorbing metamaterial is solved. The specific calculation method is as follows: According to transmission line theory, the reflection coefficient can be expressed as: (1) in ( ) is the electromagnetic wave reflection coefficient, Z in is the input impedance of the absorber, Z 0 is the free space wave impedance ( Z 0 = 377 Ω).

[0005] According to the equivalent circuit theory, the absorber can be regarded as a circuit, and Z in can be expressed as: (2) in Z FSS is the equivalent impedance of the resistive film layer, Z sub is the input impedance of the resistive film substrate.

[0006] According to equation (1), Z sub can be expressed as: (3) Among them sub It is the reflection coefficient of electromagnetic waves when the substrate is regarded as an absorber.

[0007] By combining equations (1-3), Z FSS can be expressed as: (4) Among them, e is a natural constant and j is an imaginary unit. α is the phase of the reflected electromagnetic wave. Further according to the definition of the effective absorption range, the range of the electromagnetic wave reflection coefficient Г can be expressed as: (5) Therefore, once the substrate of the resistive film layer is determined, the range of its equivalent impedance can be solved by substituting equation (5) into equation (4).

[0008] Second, further refine the acceptable range of equivalent resistance and equivalent capacitance of the resistive film layer to ensure that the metamaterial attenuates the amplitude of reflected electromagnetic waves.

[0009] 3. Traverse the value range of equivalent resistance and equivalent capacitance in step 2 to collect the phase information of the electromagnetic wave reflected by the corresponding metamaterial.

[0010] 4. Calculate the phase difference of the reflected electromagnetic waves between the metamaterial microwave absorbers obtained in step 3.

[0011] 5. Select two metamaterial units with the smallest difference between the average value of the absolute value of the phase difference and π in the target frequency band and name them as Unit 1 and Unit 2. R and equivalent capacitance C After that, its side length a and square resistance r You can refer to the following formula to obtain: (6) (7) in, R is the equivalent resistance value, C is the equivalent capacitance value, a is the side length of the resistor film, p For the cycle, ε 0 is the dielectric constant of vacuum.

[0012] 6. By arranging Unit 1 and Unit 2 in a checkerboard pattern, a new metamaterial unit is formed and named Unit 3. By jointly controlling the amplitude and phase, the design of a broadband strong absorption metamaterial is achieved.

[0013] The method for preparing the broadband strong absorption metamaterial comprises the following steps: 1. Weigh low-resistance conductive carbon paste and high-resistance conductive carbon paste in a beaker at a mass ratio of 2.21:1, and use mechanical stirring to mix the pastes evenly; 2. Customize a 250-mesh oil-based screen printing stencil with a circular printing shape of 6 cm in radius; 3. Customized oil-based 250 mesh, total size is 18 × 18 cm 2 A screen printing stencil having a shape required by a metamaterial microwave absorber is printed to subsequently prepare a resistive film layer in the metamaterial microwave absorber.

[0014] 4. Transfer the uniformly mixed slurry onto the corresponding screen, and further transfer the slurry onto a polyimide film with a thickness of 0.025 mm by screen printing; Fifth, the polyimide film printed with the conductive carbon paste was placed in a 120°C forced air drying oven and dried for 30 minutes, completing the preparation of the resistor film layer with a square resistance of 45 Ω / □ in the metamaterial microwave absorber. 6. Modify the mass ratio of the low-resistance conductive carbon paste to the high-resistance conductive carbon paste to 0.85:1 and 0.27:1, and repeat steps 1 to 5 to prepare resistor film layers with square resistances of 150 Ω / □ and 1920 Ω / □. (The circular resistor film layer prepared in step 2 is used as the sample for the four-probe square resistance test). 7. Polymethacrylimide foam with a thickness of 4 mm is used as the substrate of the resistive film layer in the metamaterial microwave absorber.

[0015] Compared with the prior art, the present invention has the following beneficial effects: The microwave absorbing metamaterial of the present invention can achieve strong microwave absorption in a wide frequency band. Its effective absorption range (reflection loss RL < -10 dB) is 6-18 GHz, the -20 dB range is 7.55-16.06 GHz, and the average reflection loss in the 6-18 GHz range is -26.43 dB. The broadband strong absorption metamaterial of the present invention is simple to prepare, low in cost, and can be produced on a large scale; The technical solution proposed in the present invention is universal and can be used to efficiently design other metamaterial microwave absorbers with target performance.

[0016] For a deeper understanding of the features and technical contents of the present invention, please refer to the detailed description and drawings attached hereto. It should be noted that the drawings are provided for illustrative purposes only and are not intended to limit the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 Schematic diagram of the broadband strong absorption metamaterial unit structure designed in Example 1; Figure 2 is the value range of the equivalent resistance and equivalent capacitance of the resistance film layer calculated in Example 1; Figure 3 The phase and phase difference of the two units with opposite phases selected in Example 1 obtained through simulation; Figure 4 The reflection loss simulation results of the metamaterial microwave absorber with Unit 1, Unit 2, and Unit 3 as periodic units in Example 1 are shown; Figure 5 The impedance characteristics of the resistive film layer in the metamaterial microwave absorber with Unit 3 as the periodic unit calculated in Example 1; Figure 6 The simulated radar cross sections of the metamaterial microwave absorber with Unit 3 as the periodic unit in Example 1 at 9.04 GHz and 13.22 GHz; Figure 7 Reflection loss test system: arch test system, and photos of metamaterial samples prepared in Examples 2, 3, and 4; Figure 8 Comparison of experimentally measured reflection loss of metamaterial samples with simulation results. DETAILED DESCRIPTION

[0018] The present invention will be described in detail below with reference to specific embodiments. These embodiments will help those skilled in the art further understand the present invention, but should not be construed as limiting the present invention. It should be noted that, without departing from the scope of the present invention, a number of variations and improvements may be made by those skilled in the art. These all fall within the scope of protection of the present invention.

[0019] The low-resistance conductive carbon paste and high-resistance conductive carbon paste used in the following examples were purchased from Shenzhen Sunflower Electronic Materials Co., Ltd., and their models are SW-S750 and SW-S760, respectively.

[0020] Example 1 1. As Figure 1 , it is proposed to design a metamaterial microwave absorber with 2 layers, and the selected period is p = 10 mm, the dielectric layer is thick h 1= h 2 = 4 mm two layers of air dielectric layer (relative dielectric constant and relative magnetic permeability are 1), the lower layer of resistive film layer is square resistance value r 1 = 150 Ω / □, side length is a 1 = 9 mm square; 2. According to the requirements of effective absorption on the amplitude and phase of the reflected electromagnetic wave, combined with the equivalent circuit theory and transmission line theory, the impedance value range of the resistive film layer with the structure described in step 1 as the substrate is obtained as follows: Figure 2 As shown in the gray shade in 3. Set the target absorption range to 6 GHz-18 GHz. Combined with the value range obtained in step 2, the equivalent resistance value range corresponding to the resistive film layer is: 150 Ω-2000 Ω, and the equivalent capacitance value range is: 0.02 pF-0.22 pF; Fourth, traverse the range of equivalent resistance and equivalent capacitance in step 3 with intervals of 50 Ω and 0.005 pF, and finally find the two metamaterial units with the largest phase difference, such as Figure 1 Shown: Unit 1 ( R = 150 Ω, C = 0.025pF) corresponds to a square resistance of r 2 = 45 Ω / □, the side length is a 2 = 5.5 mm square; Unit 2 ( R = 2000Ω, C = 0.022 pF) corresponds to a resistance film layer with a square resistance of r 2 = 1920 Ω / □, the side length is a 2 = 9.8 mm square; 5. Use the commercial electromagnetic simulation software CST Microwave Studio 2020 to simulate the two periodic units obtained in step 4. Figure 2 The impedance characteristics corresponding to Unit 1 and Unit 2 are inverted, which are consistent with the required equivalent resistance and equivalent capacitance impedance; six, Figure 3 The phase of the reflected electromagnetic waves of Unit 1 and Unit 2 obtained by simulation is given. The average difference between the phase difference and ±180° in the range of 6 GHz-18 GHz is 38.57°. 7. If Figure 1 As shown, Unit 1 and Unit 2 are arranged in a checkerboard pattern to form a new periodic unit Unit 3; eight, Figure 4 The reflection loss of a metamaterial microwave absorber with three units as the periodic unit is given by simulation. By jointly controlling the phase and amplitude, the absorption intensity of the metamaterial with Unit 3 as the periodic unit is significantly enhanced. Its effective absorption range is 6 GHz-18 GHz, the -20 dB range is 7.55 GHz-16.06 GHz, and the average reflection loss in the 6 GHz-18 GHz range is -26.43 dB. Nine, Figure 5 The impedance characteristics of the resistive film layer of the metamaterial with Unit 3 as the periodic unit were explored. The real and imaginary impedance parts of the metamaterial fit well with the value range. The change in surface impedance characteristics is the reason for the strong absorption of the metamaterial. ten, Figure 6 The radar cross sections (RCSs) of a metamaterial microwave absorber with Unit 3 as the periodic unit at absorption peaks of 9.04 GHz and 13.22 GHz are presented. Compared to an ideal conductor, the RCSs are reduced in all directions, demonstrating that the low reflection of electromagnetic waves by the metamaterial primarily comes from absorption rather than scattering. 11. To further verify the broadband strong absorption characteristics of metamaterials, such as Figure 7 As shown, a 18 × 18 cm 2 The reflectivity of the metamaterial samples was tested using an arch test system. Figure 8 As shown in Figure 3, the experimental results match the simulation results well, and the slight difference comes from the fluctuation of the square resistance of the resistor film during the experimental preparation process.

[0021] Example 2 1. Weigh 22.1 g of low-resistance conductive carbon paste and 10 g of high-resistance conductive carbon paste into a beaker and use mechanical stirring to mix the pastes evenly.

[0022] 2. Customize a 250-mesh oil-based screen printing stencil with a circular printing shape of 6 cm radius.

[0023] 3. Customized oil-based 250 mesh, total size is 18 × 18 cm 2 The printing shape is a screen printing stencil with a period of 10 mm and squares of 5.5 mm in length arranged in a checkerboard pattern.

[0024] 4. The uniformly mixed slurry was transferred to the corresponding screen, and the slurry was further transferred to a polyimide film with a thickness of 0.025 mm by screen printing.

[0025] 5. The polyimide film after printing the conductive carbon paste was placed in a forced air drying oven at 120°C and dried for 30 minutes to complete the preparation of the resistor film layer with a square resistance of 45 Ω / □ in the metamaterial microwave absorber.

[0026] Example 3 1. Weigh 19 g of low-resistance conductive carbon paste and 20 g of high-resistance conductive carbon paste into a beaker and use mechanical stirring to mix the pastes evenly.

[0027] 2. Customize a 250-mesh oil-based screen printing stencil with a circular printing shape of 6 cm radius.

[0028] 3. Customized oil-based 250 mesh, total size is 18 × 18 cm 2 The printing shape is a screen printing stencil with a period of 10 mm and a side length of 9 mm.

[0029] 4. The uniformly mixed slurry was transferred to the corresponding screen, and the slurry was further transferred to a polyimide film with a thickness of 0.025 mm by screen printing.

[0030] 5. The polyimide film after printing the conductive carbon paste was placed in a forced air drying oven at 120°C and dried for 30 minutes to complete the preparation of the resistor film layer with a square resistance of 150 Ω / □ in the metamaterial microwave absorber.

[0031] Example 4 1. Weigh 5.4 g of low-resistance conductive carbon paste and 20 g of high-resistance conductive carbon paste into a beaker and use mechanical stirring to mix the pastes evenly.

[0032] 2. Customize a 250-mesh oil-based screen printing stencil with a circular printing shape of 6 cm radius.

[0033] 3. Customized oil-based 250 mesh, total size is 18 × 18 cm 2The printing shape is a screen printing stencil with a period of 10 mm and squares with a side length of 9.8 mm arranged in a checkerboard pattern.

[0034] 4. The uniformly mixed slurry was transferred to the corresponding screen, and the slurry was further transferred to a polyimide film with a thickness of 0.025 mm by screen printing.

[0035] 5. The polyimide film after printing the conductive carbon paste was placed in a forced air drying oven at 120°C and dried for 30 minutes to complete the preparation of the resistor film layer with a square resistance of 2920 Ω / □ in the metamaterial microwave absorber.

[0036] The above describes in detail the specific embodiments of the present invention. It should be noted that the present invention is not limited to the specific embodiments described above. Without departing from the scope of protection defined by the claims, those skilled in the art can make various modifications or variations, and these modifications or variations are all technical solutions of the present invention.

Claims

1. A design method for broadband strong microwave absorption metamaterial based on impedance manipulation, characterized in that: The following steps are involved:

1. Combining equivalent circuit theory and transmission line theory, and based on the effective absorption requirements for the amplitude and phase of the reflected electromagnetic wave, the impedance range of the surface resistance film layer of the microwave absorbing metamaterial is solved; 2. Based on the impedance value range obtained in step 1, further refine the possible value ranges of the equivalent resistance and equivalent capacitance of the resistive film layer to ensure that the metamaterial attenuates the amplitude of the reflected electromagnetic wave; 3. Traverse the value range of equivalent resistance and equivalent capacitance in step 2 to collect phase information of electromagnetic waves reflected by the corresponding metamaterial; 4. Calculate the phase difference of the reflected electromagnetic waves between the metamaterial microwave absorbers obtained in step 3; 5. Select the two metamaterial units with the smallest difference between the average absolute value of the phase difference and π in the target frequency band and name them as Unit 1 and Unit 2 respectively; 6. By arranging Unit 1 and Unit 2 in a checkerboard pattern, a new metamaterial unit is formed and named Unit 3. By jointly controlling the amplitude and phase, the design of a broadband strong absorption metamaterial is achieved.

2. The method according to claim 1, characterized in that Equivalent impedance of the resistive film layer Z FSS (4) Z FSS is the equivalent impedance of the resistive film layer, Z sub is the input impedance of the resistive film substrate, ( ) is the electromagnetic wave reflection coefficient, Z in is the input impedance of the absorber, Z 0 is the free space wave impedance ( Z 0 = 377 Ω) The range of the electromagnetic wave reflection coefficient Г can be expressed as: (5)； Once the substrate of the resistive film layer is determined, the range of its equivalent impedance can be solved by substituting equation (5) into equation (4).

3. The method according to claim 1, characterized in that Step 5: Determine the equivalent resistance of the resistor film layer R and equivalent capacitance C After that, its side length a and square resistance r You can refer to the following formula to obtain: (6) (7)。 4. A method for preparing a broadband strong microwave absorption metamaterial based on impedance manipulation, characterized in that: The following steps are involved:

1. Mix the low-resistance conductive carbon paste and the high-resistance conductive carbon paste evenly with mechanical stirring; 2. Customized oil-based 250 mesh, total size is 18 × 18 cm 2 A screen printing stencil having a printing shape that is the shape required for the metamaterial microwave absorber; 3. The slurry obtained in step 1 is transferred onto the polyimide film through the screen plate in step 2 by screen printing and dried to obtain a resistor film layer.

5. The method according to claim 1, characterized in that: The mass ratio of low-resistance conductive carbon paste to high-resistance conductive carbon paste is (0.27~2.21):

1.

6. The method according to claim 1, characterized in that The circular resistor film layer prepared in step 2 is used for square resistance testing using the four-probe method.

7. The method according to claim 1, characterized in that: Step 5: The square resistance of the resistor film layer is 45 Ω / □-2920 Ω / □.

8. The method according to claim 1, characterized in that: The thickness of the polyimide film is 0.025 mm.

9. The method according to claim 1, characterized in that: The required shape of the metamaterial microwave absorber: The printed shape is a square with a period of 10 mm and a side length of 5.5 mm-9.8 mm.

10. The method according to claim 1, characterized in that: Dry at 120℃ for 30 min.

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