Highly angular stable broadband multilayer magnetic material wave absorbing structure

Abstract

The application relates to a broadband multilayer magnetic material wave-absorbing structure with high-angle stability. Most of the currently reported traditional wave-absorbing structures are based on resonant wave-absorbing structures, and a plurality of lumped elements are arranged in the unit. Although the traditional structure is easy to widen the wave-absorbing frequency band, it cannot efficiently absorb electromagnetic waves with different polarizations and large angles of incidence. In the application, magnetic wave-absorbing materials with different structure sizes are vertically arranged, and a dielectric layer is embedded between the materials for impedance matching, thereby realizing broadband high-angle stability of the wave-absorbing performance for different polarizations. The multilayer magnetic material wave-absorbing structure has clear principles, simple unit structure, is convenient to process, and has great potential engineering application value.

Description

Technical Field

[0001] This invention belongs to the field of microwave technology and relates to a high-angle stable broadband multilayer magnetic material microwave absorbing structure, which can be applied to various military fields such as wireless communication, radar technology, stealth technology, and electromagnetic interference suppression. Background Technology

[0002] In current military applications, absorbing materials or structures with broadband and high-angle stability characteristics have attracted much attention. Broadband absorption performance helps reduce electromagnetic reflection of communication systems across the entire communication frequency band, improving the stealth performance of weapon platforms over a wide frequency range; high-angle stability characteristics can improve the platform's wide-angle stealth characteristics under electromagnetic wave illumination at different angles, reducing the probability of it being detected by enemy detection radar and lowering the reaction sensitivity of enemy radar.

[0003] Traditional microwave absorbing structures typically achieve broadband absorption characteristics by matching lumped elements with multiple layers of dielectric material, a method that significantly increases the overall structure thickness. While high angular stability can be achieved by miniaturizing the unit structure to improve absorption of electromagnetic waves incident at large angles, this introduces impedance mismatch and increases design complexity. In conclusion, achieving broadband, high-angle-stability microwave absorption performance in traditional microwave absorbing structures has always been a challenging problem.

[0004] Magnetic materials are artificial materials that absorb electromagnetic waves in specific frequency bands. Absorption of specific frequencies, polarizations, and incident angles can be achieved by adjusting their composition and structure. Absorbers developed based on magnetic materials can increase the relative bandwidth of the absorption frequency band and enhance the absorption characteristics at higher angles with different polarizations. This significantly improves the stealth characteristics of the entire system, effectively enhancing the stealth performance of combat platforms and playing a crucial role in high-angle stealth capabilities.

[0005] Most of the reported microwave absorbing structures / materials only focus on the absorption bandwidth, making it difficult to absorb electromagnetic waves of different polarizations incident at large angles. Summary of the Invention

[0006] The purpose of this invention is to address the shortcomings of existing technologies by providing a high-angle-stable broadband multilayer magnetic material absorbing structure. This absorbing structure achieves high-angle-stable absorption performance for arbitrary polarized electromagnetic waves, covering both the S and C bands, by stacking two magnetic materials of different sizes and embedding a dielectric layer between them. This structure is extremely simple, easy to manufacture, has low design costs, a clear principle, and great application potential.

[0007] The high-angle-stable broadband multilayer magnetic material absorbing structure of the present invention is a three-layer vertically arranged structure, consisting of periodically distributed (seamlessly arranged in the x and y periodic directions) absorbing units. Each absorbing unit, from bottom to top, includes a first magnetic material absorbing body, a first dielectric layer, and a second magnetic material absorbing body. A first dielectric layer is left between the first and second magnetic material absorbing bodies.

[0008] The first magnetic material absorber includes a first magnetic unit and a metal surface. The metal surface is located on the lower surface of the first magnetic unit and has the same size as the first magnetic unit.

[0009] The second magnetic material absorber includes a second magnetic unit and a second dielectric layer, wherein the second magnetic unit is surrounded by the second dielectric layer, and the distance b3 between the second magnetic unit and the second dielectric layer satisfies 0.0052λ. a ~0.01λ a , λ a The wavelength corresponding to the starting frequency of the absorbing band of the absorbing structure;

[0010] The height h2 of the first dielectric layer satisfies 0.035λ. a ~0.045λ a , λ a This refers to the wavelength corresponding to the starting frequency of the absorbing band in the absorbing structure. The first dielectric layer serves to perform impedance matching, and simultaneously, coupling capacitance is generated between the second magnetic units in the periodic unit to achieve impedance matching.

[0011] Preferably, the medium used in the first dielectric layer and the second dielectric layer is air.

[0012] As a preferred embodiment, the first magnetic unit adopts a square structure with a seamless bottom attachment to the metal surface;

[0013] Preferably, the second magnetic unit has a square structure and is surrounded by a second dielectric layer.

[0014] Preferably, the first magnetic unit and the second magnetic unit are isolated by a first dielectric layer.

[0015] The second magnetic material absorber achieves impedance matching by matching the medium (preferably air) and the magnetic material, thus realizing high angular stability within the operating frequency band.

[0016] Preferably, the first magnetic material absorber, the first dielectric layer, and the second magnetic material absorber are all square, and their centers are located on the same straight line, which is parallel to the z-axis.

[0017] Preferably, the ratio of the second magnetic unit to the second dielectric layer is adjusted according to impedance matching.

[0018] Preferably, the first magnetic unit and the second magnetic unit are made of the same magnetic material, and the height h1 of the first magnetic unit is the same as the height h3 of the second magnetic unit, and the width ratio of the first magnetic unit and the second magnetic unit satisfies b1:b2 = 10:7.

[0019] Working principle: When electromagnetic waves within the operating frequency band are incident, the second magnetic unit absorbs the electromagnetic waves for the first time, followed by a second absorption through matching between the first dielectric layer and the first magnetic unit. Unabsorbed electromagnetic waves are reflected by the metal surface and then absorbed a third time by the first and second magnetic units, thus achieving a good absorption effect. Because the first magnetic material absorber has inherently high angular stability for TM-polarized electromagnetic waves, but poor high-angle stability for TE-polarized electromagnetic waves, impedance compensation is achieved through matching between the second magnetic material absorber and the first dielectric layer under obliquely incident TE-polarized electromagnetic waves. The larger the oblique incident angle, the greater the impedance compensation. This gives the absorbing structure not only broadband absorption performance but also the ability to absorb electromagnetic waves of different polarizations at large angles.

[0020] The high-angle-stable broadband multilayer magnetic material absorbing structure has the following advantages:

[0021] (1) High-angle stable broadband multilayer magnetic material absorbing structure: Based on magnetic materials, a absorbing structure unit with broadband high-angle stability was designed. By covering the first dielectric layer with the second magnetic unit, the impedance in the working frequency band is efficiently matched. Under the premise of hardly affecting the absorption capability of TM polarized electromagnetic waves, the absorption performance of TE polarized electromagnetic waves is greatly improved, and the stealth characteristics in a large spatial range are greatly improved.

[0022] (2) The high-angle stable broadband multilayer magnetic material wave absorption structure adopts a simple and novel unit structure, which efficiently controls the impedance between each material in the unit structure and the coupling capacitance between magnetic materials to compensate for the impedance characteristics at different incident angles, achieving a good impedance matching effect. The design principle is clear, the design structure is very simple, and the cost is low. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of a three-dimensional structural unit of the high-angle-stable broadband multilayer magnetic material wave-absorbing structure of the present invention;

[0024] Figure 2 This is a top view of the high-angle-stable broadband multilayer magnetic material wave-absorbing structure of the present invention;

[0025] Figure 3 This is a schematic diagram of the equivalent circuit of the high-angle stable broadband multilayer magnetic material wave-absorbing structure of the present invention;

[0026] Figure 4 , Figure 5 These are the h2 parameter scanning curves of the high-angle-stable broadband multilayer magnetic material absorbing structure of the present invention under TE and TM polarized electromagnetic wave irradiation at an incident angle of 60°.

[0027] Figure 6 , Figure 7 These are the b2 parameter scanning curves of the high-angle-stable broadband multilayer magnetic material absorbing structure of the present invention under TE and TM polarized electromagnetic wave irradiation at an incident angle of 60°.

[0028] Figure 8 This is a frequency response characteristic curve of the high-angle stable broadband multilayer magnetic material absorbing structure of the present invention under normal incident dual-polarized electromagnetic wave irradiation.

[0029] Figure 9 , Figure 10 These are frequency response characteristic curves of the high-angle stable broadband multilayer magnetic material absorbing structure of the present invention under TE and TM polarized electromagnetic wave irradiation at incident angles of 0°, 30°, and 60°, respectively.

[0030] Figure 11 , Figure 12 The graphs show the absorption rate of the high-angle-stable broadband multilayer magnetic material absorbing structure of the present invention under TE and TM polarized electromagnetic wave irradiation at incident angles of 0°, 60° and 70°, respectively.

[0031] The diagram is labeled as follows: Metal surface 1, First magnetic unit 2, First dielectric layer 3, Second magnetic unit 4, Second dielectric layer 5. Detailed Implementation

[0032] The present invention will be further analyzed below with reference to specific embodiments.

[0033] like Figure 1 As shown, the high-angle stable broadband multilayer magnetic material absorbing structure is a three-layer vertically arranged structure, including periodically distributed and seamlessly filled absorbing units. Each absorbing unit, from bottom to top, includes a first magnetic material absorbing body, a first dielectric layer 3, and a second magnetic material absorbing body. The first dielectric layer 3 uses air as the dielectric.

[0034] The first magnetic material absorber includes a metal surface 1 and a first magnetic unit 2; the second magnetic material absorber includes a second magnetic unit 4 and a second dielectric layer 5, wherein the medium used in the second dielectric layer 5 is air; the first magnetic material absorber and the second magnetic material absorber are connected by a first dielectric layer 3.

[0035] like Figure 2 As shown, the second magnetic unit 4 is proportionally smaller than the first magnetic unit 2, and is seamlessly covered by the second dielectric layer 5.

[0036] Above the first magnetic material absorber is a first dielectric layer structure, and above the first dielectric layer is a second magnetic material absorber.

[0037] The first magnetic material absorber, the first dielectric layer, and the second magnetic material absorber mentioned above are all square, and their centers are located on the same straight line, which is parallel to the z-axis.

[0038] like Figure 3 As shown, the high-angle stable broadband multilayer magnetic material absorbing structure of the present invention can be equivalent to a specific circuit model. The first magnetic unit 2 in the first magnetic material absorbing body can be equivalent to a structure with a characteristic impedance of Z. m1 Lossy transmission lines, where β m1 and t m1 The propagation constant and thickness of the first magnetic unit 2 are given, while the metal surface 1 is equivalent to the impedance Z. pec The shortest path; the first dielectric layer 3 can be equivalent to a characteristic impedance of Z. a1 A lossless transmission line, where β a1 and t a1 The propagation constant and thickness of the first dielectric layer 3 are given; the second magnetic unit 4 in the second magnetic material absorber can be equivalent to a unit with a characteristic impedance of Z. m2 Lossy transmission lines, where β m2 and t m2 The propagation constant and thickness of the second magnetic unit 4 are given, and the second dielectric layer 5 is equivalent to a characteristic impedance of Z. a2 Two lossless transmission lines, where β a2 and t a2 Given the propagation constant and thickness of the second dielectric layer 5, C m This is the coupling capacitance generated between the second magnetic units 4, which is the cascaded lossy transmission line equivalent to the second magnetic unit 4 and the two lossless transmission lines equivalent to the second dielectric layer 5.

[0039] Based on the equivalent circuit model, the ABCD transmission matrix of the first magnetic material absorber, the first dielectric layer 3, the second magnetic material absorber, and the absorber structure of the present invention can be obtained respectively:

[0040]

[0041] A m1 B m1 C m1 D m1 The transfer matrix describes the first magnetic material absorber, where Z m1 β m1 and t m1 Z represents the characteristic impedance, propagation constant, and thickness of the first magnetic unit 2. pecIt is a metal surface with zero impedance.

[0042]

[0043] A a1 B a1 C a1 D a1 The transmission matrix describes the first medium layer 3, where β a1 and t a1 Given the propagation constant and thickness of the first dielectric layer 3, and the characteristic impedance Z of the first dielectric layer 3 (preferably air). a1 It is 377Ω.

[0044]

[0045] A m2 B m2 C m2 D m2 The transfer matrix describes the second magnetic unit 4, where Z m2 β m2 and t m2 For the characteristic impedance, propagation constant and thickness of the second magnetic unit 4, the present invention preferably uses the same material for the first magnetic unit and the second magnetic unit, that is, the characteristic impedance, propagation constant and thickness of the two are the same.

[0046]

[0047] A a2 B a2 C a2 D a2 The transfer matrix describes the second medium layer 5, where β a2 and t a2 The propagation constant and thickness of the second dielectric layer 5, and the characteristic impedance Z of the second dielectric layer 5 (preferably air) a2 377Ω, C m This is the coupling capacitance generated between the second magnetic units 4. The coupling capacitance changes with the size of the second magnetic unit 4, thus playing a role in impedance matching.

[0048]

[0049] The ABCD transmission matrix describes the absorber structure of this invention. Formulas for the input impedance and reflection coefficient can be derived from this matrix.

[0050]

[0051] Under ideal conditions, Z0 is air with a impedance of 377Ω, and as the input impedance Z... inAfter matching, a reflection coefficient of -10dB was obtained, and the absorbing structure can achieve a significant wave absorption effect. At the same time, in order to obtain a better wave absorption effect and high angular stability, the thickness h2 of the first dielectric layer 3 and the width b2 of the second magnetic unit 4 were optimized.

[0052] like Figure 4 As shown, under TE polarization irradiation with electromagnetic waves incident at an angle of 60°, as the thickness h2 of the first dielectric layer 3 increases, the low-frequency portion of the absorption bandwidth shifts slightly to lower frequencies, while the high-frequency portion shifts significantly to lower frequencies. Simultaneously, the reflection coefficient decreases with increasing thickness, reaching below -15dB. Figure 5 As shown in the figure, under TM polarization irradiation with electromagnetic waves incident at an angle of 60°, as the thickness h2 of the first dielectric layer 3 increases, the low-frequency portion of the absorption bandwidth hardly changes, while the high-frequency portion maintains good absorption performance, and the reflection coefficient remains around -15dB. The two figures illustrate that the thickness h2 of the first dielectric layer 3 has no effect on the high-angle absorption bandwidth under TM polarization. In contrast, the thickness h2 of the first dielectric layer 3 has a significant impact on the high-angle absorption bandwidth under TE polarization. This is because the thickness h2 of the first dielectric layer 3 has a significant compensating effect on the impedance matching of the entire absorber structure under electromagnetic wave oblique incidence. In order to consider the low and high frequency cutoff frequencies of the absorption bandwidth, so that the low-frequency shift is not too large, and at the same time, more absorption bandwidth can be obtained at high frequencies, the thickness h2 of the first dielectric layer 3 is selected as 6mm.

[0053] like Figure 6 As shown, under TE polarization irradiation with electromagnetic waves incident at an angle of 60°, as the width b2 of the second magnetic unit 4 increases, the low-frequency portion of the absorption bandwidth shifts slightly to lower frequencies, while the high-frequency portion shifts significantly to lower frequencies. Simultaneously, the reflection coefficient decreases with increasing thickness, reaching below -17dB. Figure 7 As shown in the figure, under TM polarization irradiation with electromagnetic waves incident at an angle of 60°, as the width b2 of the second magnetic unit 4 increases, the low-frequency part of the absorption bandwidth hardly changes, while the high-frequency part still maintains good absorption effect, and the reflection coefficient remains at around -16dB. The two figures illustrate that the width b2 of the second magnetic unit 4 has no effect on the high-angle absorption bandwidth under TM polarization. In contrast, the width b2 of the second magnetic unit 4 has a greater impact on the high-angle absorption bandwidth under TE polarization. This is because the size of the width b2 of the second magnetic unit 4 has a significant compensating effect on the impedance matching of the entire absorber structure under electromagnetic wave oblique incidence. In order to consider the low and high frequency cutoff frequencies of the absorption bandwidth, so that the low-frequency offset should not be too large, and at the same time, more absorption bandwidth can be obtained at high frequencies, the width b2 of the second magnetic unit 4 is selected as 3.5mm.

[0054] In summary, to achieve high absorption performance at large angles of oblique incidence with different polarizations, the thickness h2 of the first dielectric layer 3 in the absorber structure of this invention is selected as 6 mm, and the width b2 of the second magnetic unit 4 is selected as 3.5 mm. The specific structural geometric parameters are as follows:

[0055] Where b1 represents the length and width of the entire unit structure in the x and y axes, and is also the length and width of the metal surface 1 and the first magnetic unit 2; b2 represents the length and width of the second magnetic unit 4; and b3 represents the width of the second dielectric layer 5 surrounding the second magnetic unit 4. h1 represents the thickness of the first magnetic unit 2; h3 represents the thickness of the second magnetic unit 4; and h2 represents the distance from the first magnetic unit 2 to the second magnetic unit 4, i.e., the thickness of the first dielectric layer 3.

[0056]

[0057] Figure 8 The graph shows the frequency response characteristics of the absorbing structure under normal incidence dual-polarized electromagnetic wave irradiation. It can be seen that, under normal incidence, the absorbing bandwidths of TE and TM polarizations in the –10dB range are 2.14–7.08 GHz and 2.13–7.15 GHz, respectively, with relative bandwidths of 107.2% and 108.2%. The absorbing structure of this invention still exhibits good reflection coefficients under normal incidence conditions. Figure 9 The frequency response characteristic curves of the absorbing structure under TE polarized electromagnetic wave irradiation at incident angles of 0°, 30°, and 60° are shown. It can be seen that the absorbing structure of the present invention still has a good absorbing effect under TE polarized 60° oblique incident, with a -10dB frequency band of 2.77–8.30GHz and a relative bandwidth of 100%. Figure 10 The graphs show the frequency response characteristics of the absorbing structure under TM polarized electromagnetic wave irradiation at incident angles of 0°, 30°, and 60°. It can be seen that the absorbing structure of the present invention has a better and better absorbing effect under TM polarized oblique incident light, and the absorbing effect is significant. Figure 11 The graphs show the absorption rate of the absorbing structure of the present invention under TE-polarized electromagnetic wave irradiation at incident angles of 0°, 60°, and 70°. It can be seen that the absorbing structure of the present invention can still achieve a 90% absorption effect under TE-polarized 60° oblique incident angle, and can still achieve a 80% absorption effect under 70° oblique incident angle. Figure 12 The graphs show the absorption rate of the absorbing structure of the present invention under TM polarized electromagnetic wave irradiation at incident angles of 0°, 60°, and 70°. It can be seen that the absorbing structure of the present invention can still achieve a 90% absorption effect under TM polarized 60° oblique incident, and still achieve a 80% absorption effect under 70° oblique incident, and even achieve a 90% absorption effect in the high frequency band. It can be seen that the absorbing structure of the present invention has a significant absorption effect under high-angle oblique incident with different polarizations.

[0058] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, without departing from the principle of the present invention, any changes or modifications, such as replacing the material type / properties of the first and second magnetic units and the first and second dielectric layers, or altering the structural form, size, etc., should also be considered within the scope of protection of the present invention.

Claims

1. A high-angle-stable broadband multilayer magnetic material absorbing structure, comprising a three-layer vertically arranged structure including periodically distributed absorbing units, characterized in that: Each absorbing unit, from bottom to top, includes a first magnetic material absorbing body, a first dielectric layer (3), and a second magnetic material absorbing body; The first magnetic material absorber includes a metal surface (1) and a first magnetic unit (2). The metal surface (1) is in close contact with the lower surface of the first magnetic unit (2), and its size is the same as that of the first magnetic unit (2). The second magnetic material absorber includes a second magnetic unit (4) and a second dielectric layer (5), wherein the second magnetic unit (4) is surrounded by the second dielectric layer (5); the spacing between the second magnetic unit (4) and the second dielectric layer (5) is... b 3 satisfies 0.0052 λ a ~ 0.01 λ a , λ a The wavelength corresponding to the starting frequency of the absorbing band of the absorbing structure; the height of the first dielectric layer (3) h 2 satisfies 0.035 λ a ~ 0.045 λ a , λ a The wavelength corresponding to the starting frequency of the absorbing band of the absorbing structure; When electromagnetic waves are incident within the operating frequency band, the second magnetic unit (4) absorbs the electromagnetic waves for the first time, and then the first dielectric layer (3) and the first magnetic unit (2) perform a second absorption. The unabsorbed electromagnetic waves are reflected by the metal surface (1) and then absorbed for the third time by the first magnetic unit (2) and the second magnetic unit (4). Through the matching of the second magnetic material absorber and the first dielectric layer (3), impedance compensation is performed on the unit under the TE polarized oblique incident electromagnetic wave irradiation.

2. The high-angle-stable broadband multilayer magnetic material absorbing structure according to claim 1, characterized in that... The height of the first magnetic unit (2) h 1 satisfies 0.02 λ a ~ 0.05 λ a ,width b 1 satisfies 0.035 λ a ~ 0.07 λ a , λ a The wavelength is the wavelength corresponding to the starting frequency of the absorbing band of the absorbing structure.

3. The high-angle-stable broadband multilayer magnetic material absorbing structure according to claim 1, characterized in that... The height of the second magnetic unit (4) h 3. Condition 0.02 is met. λ a ~ 0.05 λ a ,width b 2. Condition 0.025 is satisfied. λ a ~ 0.035 λ a , λ a The wavelength is the wavelength corresponding to the starting frequency of the absorbing band of the absorbing structure.

4. The high-angle-stable broadband multilayer magnetic material absorbing structure according to claim 1, characterized in that... The medium used in the first dielectric layer (3) and the second dielectric layer (5) is air.

5. The high-angle-stable broadband multilayer magnetic material absorbing structure according to claim 1, characterized in that... The centers of the first magnetic material absorber, the first dielectric layer (3), and the second magnetic material absorber are located on the same straight line.

6. The high-angle-stable broadband multilayer magnetic material absorbing structure according to claim 1, characterized in that... The ratio of the second magnetic unit (4) to the second dielectric layer (5) is adjusted according to impedance matching.

7. The high-angle-stable broadband multilayer magnetic material absorbing structure according to claim 1, characterized in that... The height of the first magnetic unit (2) h 1 and the height of the second magnetic unit (4) h 3. Consistent, the width of the first magnetic unit (2) b Width of 1 and the second magnetic unit (4) b The ratio of 2 satisfies 10:

7.

8. The high-angle-stable broadband multilayer magnetic material absorbing structure according to claim 1, characterized in that... The first magnetic unit (2) and the second magnetic unit (4) are made of the same magnetic material.

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