Single-layer electromagnetic wave absorbing material design method based on dielectric parameter matching

Abstract

The invention discloses a single-layer electromagnetic wave absorbing material design method based on dielectric parameter matching, and belongs to the field of electromagnetic wave absorbing materials. A dielectric loss type wave-absorbing material mainly comprises a conductive polymer, MXene, a carbon material and the like, and although the density is relatively small and the relative filling amount is low, impedance mismatch is easy to occur, so that the design difficulty of a coating wave-absorbing material is high. According to the specific requirements of the application target frequency band and the wave-absorbing performance, the wave-absorbing material with the optimal parameters is selected, and the design problem of the non-magnetic broadband wave-absorbing material is solved.

Description

Technical Field

[0001] The invention belongs to the field of electromagnetic wave absorbing materials, and in particular relates to a design method of a coating absorbing material, which can be used for the design and preparation of radar stealth materials. Background Art

[0002] With the rapid development of communication technology, multi-band radar detection technology has developed to a high level, and coating absorbing materials are facing severe challenges of multi-band detection technology. Therefore, it is crucial to develop lightweight, broadband, and efficient electromagnetic wave absorbing materials. Traditional absorbing materials are mainly divided into two categories according to their loss mechanism: magnetic loss absorbing materials and dielectric loss absorbing materials. Magnetic loss absorbing materials mainly include ferrites, magnetic metals, etc., which have defects such as high density, high addition amount and poor stability; dielectric loss absorbing materials mainly include conductive polymers, MXene and carbon materials, etc. Although they have low density and low relative filling amount, they are prone to impedance mismatch, which makes the design of coating absorbing materials difficult. Therefore, it is of great scientific significance and practical application value to propose a new general design method for non-magnetic coating absorbing materials. Summary of the invention

[0003] In view of the shortcomings of the existing design theories and methods of coating absorbing materials, a universal matching theory of dielectric parameters of non-magnetic absorbing materials and a design method for single-layer electromagnetic wave absorbing materials are proposed. According to the specific requirements of the application target frequency band and absorbing performance, the absorbing material with the best parameters is selected to solve the design problem of non-magnetic broadband absorbing materials.

[0004] Universal matching theory of dielectric parameters:

[0005] Single-layer absorbing coating materials are usually dominated by quarter-wavelength resonance, which means that increasing the absorption bandwidth requires resonant coupling of multiple frequencies. The quarter-wavelength resonance formula is as follows:

[0006]

[0007] Where: d is the material thickness, c is the speed of light in a vacuum, m is a natural number, and n is the refractive index.

[0008] According to the input impedance of the absorbing material and the resonant absorption theory, the theoretical relationship between the refractive index and the extinction factor is derived:

[0009]

[0010] in: Define t = k / n, where k is the extinction coefficient.

[0011] For non-magnetic materials Substituting into formula (2) we can get:

[0012]

[0013] When m=1, the quarter-wavelength resonance is satisfied, and the matching relationship between the dielectric constant and the loss tangent of the absorbing material is:

[0014]

[0015] When m=3, the quarter-wavelength resonance is satisfied, and the matching relationship between the dielectric constant and the loss tangent of the absorbing material is:

[0016]

[0017] When m>3, the quarter-wavelength resonance is satisfied, and the matching relationship between the dielectric constant and the loss tangent of the absorbing material is:

[0018]

[0019] According to the matching relationship equation (3) between the dielectric constant and loss tangent of the absorbing material, the dielectric Cole-Cole relationship of perfect absorption can be obtained as follows: Figure 1 shown.

[0020] ε<1.5 is generally not used as absorbing material, so there is a node division of ε>1.5.

[0021] Formulas (4a), (5a), and (6a) are general formulas for all absorbing materials with ε>1.5. Formulas (4b), (5b), and (6b) are simplified forms of (4a), (5a), and (6a), respectively. Because the ε of absorbing materials is usually greater than 4, the simplified formulas can be used in this case. For the few cases where ε<4, the more accurate formulas (4a), (5a), and (6a) are used.

[0022] m is the order of 1 / 4 wavelength resonance. No matter how much m is, it satisfies the macroscopic concept of 1 / 4 wavelength resonance. Formula (3) is the general formula when m is any natural number. It is a polynomial. As the value of m gradually increases, the last few terms of the polynomial can be omitted and simplified.

[0023] According to the matching relationship of the above dielectric parameters, the dielectric dispersion relationship that satisfies perfect absorption in different frequency bands at different thicknesses can be obtained, and the single-layer absorbing material required by the application target can be designed. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 Dielectric Cole-Cole diagram of a perfect electromagnetic wave absorbing material

[0025] Figure 2 Dielectric dispersion relation of perfect electromagnetic wave absorption material at 2-18GHz with 3mm thickness

[0026] Figure 3 2-18GHz perfect electromagnetic wave absorption material with 3mm thickness, wave absorption performance

[0027] Figure 4 Dielectric dispersion relation of perfect electromagnetic wave absorption material at 6-40GHz with a thickness of 1.5mm

[0028] Figure 5 1.5mm thickness 6-40GHz perfect electromagnetic wave absorption material absorption performance

[0029] Figure 6 Dielectric dispersion relation of perfect electromagnetic wave absorption material at 2-8THz with a thickness of 0.007mm

[0030] Figure 7 0.007mm thickness, 2-8THz perfect electromagnetic wave absorption material, wave absorption performance DETAILED DESCRIPTION Specific embodiment 1:

[0032] With the continuous advancement of information technology, the radar detection technology of major military powers in the world has gradually diversified, gradually changing from the traditional single detection method to multi-band detection, which greatly increases the probability of detection and destruction of facilities such as ground command posts and weapons and equipment such as aircraft and tanks on the battlefield, seriously threatening the survivability of facilities and weapons and equipment on the battlefield. Researching and designing absorbing materials for multi-band detection methods will help improve the survivability and offensive capabilities of my country's weapons and equipment on the battlefield, and is of great significance to my country's national defense and military security.

[0033] At present, the operating frequency range of most aviation or marine radars is 2-18 GHz, so the research on radar absorbing materials mostly focuses on this frequency range, requiring the material to have strong absorption characteristics for electromagnetic waves in this frequency band.

[0034] According to the dielectric parameter matching relationship proposed in the present invention, the dielectric dispersion relationship satisfied by the perfect absorbing material in the 2-18 GHz frequency band with a thickness of 3 mm is obtained, such as Figure 2 shown.

[0035] like Figure 3 As shown in the figure, the reflection loss of the perfect absorbing material in the 2-18GHz frequency band is less than -60dB at a thickness of 3mm, showing perfect absorbing performance. Figure 1 In the area enclosed by the blue curve shown, a reflection loss of less than -20dB can be achieved.

[0036] Implementation Step 1:

[0037] When m=1, combining the universal input impedance formula of the absorbing material with formulas (1)-(2), we can get the expression of the dielectric constant of the perfect absorbing material with respect to the thickness d and the loss tangent tanδ:

[0038]

[0039] When d = 3 mm, for each frequency point in the 2-18 GHz frequency band, formula (7) has only two unknown quantities: ε and tanδ.

[0040] Implementation Step 2:

[0041] According to the matching relationship between the dielectric constant and the loss tangent of the absorbing material proposed in this patent (m=1), it is combined with formula (7):

[0042]

[0043] At this point, we can solve the ε and tanδ corresponding to each frequency point in the 2-18 GHz frequency band, and then obtain the dielectric dispersion relationship satisfied by the perfect absorbing material with a thickness of 3 mm in the 2-18 GHz frequency band.

[0044] Implementation Step 3:

[0045] Substitute the dielectric constant, dielectric loss and material thickness d=3 mm obtained in the above steps into the general formula for calculating the reflection loss of the absorbing material to calculate the reflection loss of the perfect absorbing material in the 2-18 GHz frequency band. Specific embodiment 2:

[0047] With the continuous improvement of radar detection capabilities, the survival of weapons and equipment has been threatened more seriously, and higher requirements have been placed on the stealth performance of various weapon platforms and militarized equipment. For new absorbing materials, in addition to pushing the absorbing materials to the characteristics of "light, thin, wide, and strong", the development towards high frequency is also extremely important.

[0048] The higher the frequency of electromagnetic wave emission, the shorter the wavelength of the electromagnetic wave. High-frequency electromagnetic waves can improve the accuracy of radar ranging. Therefore, in the research and development of stealth materials, it is necessary to reduce electromagnetic wave reflection and widen the frequency band while continuously exploring high-frequency electromagnetic waves. Absorbing materials need to develop together with detection radars.

[0049] According to the matching relationship of the above dielectric parameters, the dielectric dispersion relationship satisfied by the perfect absorbing material in the 6-40GHz frequency band with a thickness of 1.5mm is obtained, such as Figure 4 shown.

[0050] like Figure 5As shown, the reflection loss of the perfect absorbing material in the 6-40GHz frequency band is less than -58dB at a thickness of 1.5mm, showing perfect absorbing performance.

[0051] Implementation Step 1:

[0052] When m=1, combining the universal input impedance formula of the absorbing material with formulas (1)-(2), we can get the expression of the dielectric constant of the perfect absorbing material with respect to the thickness d and the loss tangent tanδ:

[0053]

[0054] When d = 1.5 mm, for each frequency point in the 6-40 GHz frequency band, formula (7) has only two unknown quantities: ε and tanδ.

[0055] Implementation Step 2:

[0056] According to the matching relationship between the dielectric constant and the loss tangent of the absorbing material proposed in this patent (m=1), it is combined with formula (7):

[0057]

[0058] At this point, the ε and tanδ corresponding to each frequency point in the 6-40 GHz frequency band can be solved, and then the dielectric dispersion relationship satisfied by the perfect absorbing material with a thickness of 1.5 mm in the 6-40 GHz frequency band can be obtained.

[0059] Implementation Step 3:

[0060] Substitute the dielectric constant, dielectric loss and material thickness d=1.5 mm obtained in the above steps into the general formula for calculating the reflection loss of the absorbing material to calculate the reflection loss of the perfect absorbing material in the 6-40 GHz frequency band. Specific embodiment 3:

[0062] The rapid application of terahertz waves inevitably generates electromagnetic interference, which has an adverse effect on the normal operation of precision electronic instruments. Therefore, in order to effectively reduce the interference of terahertz signals, improve the transmission environment of terahertz signals, and ensure the normal operation of instruments, terahertz wave absorbing materials are urgently needed.

[0063] Terahertz absorbing materials are a type of absorbing materials with low reflection and high absorption rate in the terahertz frequency band. The existing selection and design of absorbing materials for stealth weapons will no longer be suitable for the absorption of terahertz electromagnetic waves to a large extent, and will be invisible under terahertz radar. In addition, since the magnetic loss parameters of most magnetic loss materials in the terahertz frequency band are very small, the research on terahertz absorbing materials focuses more on using electrical attenuation or dielectric attenuation materials to achieve the absorption loss of terahertz waves. Terahertz absorbing materials are developed for new high-precision terahertz detection systems and have important application prospects in national defense and military fields such as stealth weapon systems and civilian fields such as security detection. Especially in the space environment, the transmission of terahertz waves is almost lossless, and high-performance terahertz absorbing materials are of great significance to the stealth protection and information security protection of artificial satellites.

[0064] According to the matching relationship of the above dielectric parameters, the dielectric dispersion relationship satisfied by the perfect absorbing material in the 2-8THz frequency band with a thickness of 0.007mm is obtained, as follows: Figure 6 shown.

[0065] like Figure 7 As shown, at a thickness of 0.007 mm, the reflection loss of the perfect absorbing material in the 2-8 THz frequency band is less than -60 dB, showing perfect absorbing performance.

[0066] Implementation Step 1:

[0067] When m=1, combining the universal input impedance formula of the absorbing material with formulas (1)-(2), we can get the expression of the dielectric constant of the perfect absorbing material with respect to the thickness d and the loss tangent tanδ:

[0068]

[0069] When d = 0.007 mm, for each frequency point in the 2-8 THz frequency band, formula (7) has only two unknown quantities: ε and tanδ.

[0070] Implementation Step 2:

[0071] According to the matching relationship between the dielectric constant and the loss tangent of the absorbing material proposed in this patent (m=1), it is combined with formula (7):

[0072]

[0073] At this point, the ε and tanδ corresponding to each frequency point in the 2-8 THz frequency band can be solved, and then the dielectric dispersion relationship satisfied by the perfect absorbing material with a thickness of 0.007 mm in the 2-8 THz frequency band can be obtained.

[0074] Implementation Step 3:

[0075] Substitute the dielectric constant, dielectric loss and material thickness d=0.007 mm obtained in the above steps into the general formula for calculating the reflection loss of the absorbing material to calculate the reflection loss of the perfect absorbing material in the 2-8 THz frequency band.

Claims

1. A design method for a single-layer electromagnetic wave absorbing material based on dielectric parameter matching, characterized in that: The quarter-wavelength resonance formula is as follows: Where: d is the material thickness, c is the speed of light in a vacuum, m is a natural number, and n is the refractive index; According to the input impedance and resonant absorption theory of the absorbing material, the refractive index and extinction factor are derived to satisfy the following relationship: in: Define t = k / n, k is the extinction coefficient; For non-magnetic materials Substituting into formula (2) we get:

2. The method according to claim 1, characterized in that: For different values ​​of m, the matching relationship between the dielectric constant and the loss tangent of the absorbing material is derived from the following formula based on the formula in claim 1: When m=1, the quarter-wavelength resonance is satisfied, and the matching relationship between the dielectric constant and the loss tangent of the absorbing material is: When m=3, the quarter-wavelength resonance is satisfied, and the matching relationship between the dielectric constant and the loss tangent of the absorbing material is: When m>3, the quarter-wavelength resonance is satisfied, and the matching relationship between the dielectric constant and the loss tangent of the absorbing material is:

3. The method according to claim 2, characterized in that: Combining the universal input impedance formula of the absorbing material with formulas (1)-(2), we can obtain the expression of the dielectric constant of the perfect absorbing material with respect to the thickness d and the loss tangent tanδ: Based on the matching relationship between the dielectric constant and the loss tangent of the absorbing material when m=1, the ε and tanδ corresponding to each frequency point in the target frequency band are solved together with formula (7), and then the dielectric dispersion relationship satisfied by the perfect absorbing material at a specific thickness in the target frequency band is obtained.

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