Combined rectangular cavity broadband wave-absorbing structure loaded with gradient metal band array

Abstract

The invention discloses a combined rectangular cavity broadband wave-absorbing structure loaded with a gradient metal band array, the wave-absorbing structure is formed by sequentially arranging a plurality of wave-absorbing units, and each wave-absorbing unit comprises four rectangular cavities with different sizes, the gradient metal band array and an NDDP3 wave-absorbing material; the four rectangular cavities with different sizes are sequentially arranged according to the sizes; the NDDP3 wave-absorbing material is impregnated on the surfaces of the four rectangular cavities; and the gradient metal strip arrays are respectively loaded on four side surfaces of the three rectangular cavities with smaller sizes. The absorption bandwidth of the wave absorber can be widened by combining the rectangular cavities of different sizes, meanwhile, the problem that the wave absorbing performance of the combined rectangular cavity in a low-frequency band is poor can be solved by loading the gradient metal band array, and the wave absorber has good wave absorbing performance in the frequency band of 2-40 GHz; and meanwhile, under the condition of large-angle oblique incidence, the microwave absorbing material still has a relatively wide microwave absorbing bandwidth.

Description

Technical Field

[0001] The invention belongs to the technical field of electromagnetic wave absorption, and in particular relates to a combined rectangular cavity broadband wave absorption structure loaded with a gradient metal strip array. Background Art

[0002] Structural absorbing materials are multifunctional composite materials that can be used as structural parts to carry loads and have good electromagnetic wave absorption or penetration capabilities. This material combines the advantages of composite materials, such as light weight and high strength, and has shown broad application prospects in the fields of modern electronic countermeasures and military stealth.

[0003] However, structural absorbing materials often have a narrow absorption band and only have efficient electromagnetic wave absorption capabilities within a specific frequency range, but poor absorption effects in other frequency bands, and rarely consider the absorbing performance of electromagnetic waves under large-angle oblique incidence. In order to solve the above problems, the present invention proposes a combined rectangular cavity broadband absorbing structure loaded with a gradient metal strip array. Summary of the invention

[0004] The present invention aims to solve the deficiencies of the prior art and provides the following solutions:

[0005] A combined rectangular cavity broadband absorbing structure loaded with a gradient metal strip array, the absorbing structure is composed of a plurality of absorbing units arranged in sequence, the absorbing units comprising: 4 rectangular cavities of different sizes, a gradient metal strip array and NDDP3 absorbing material;

[0006] The four rectangular cavities of different sizes are arranged in order according to their sizes;

[0007] The NDDP3 absorbing material is impregnated on the surfaces of the four rectangular cavities;

[0008] The gradient metal strip arrays are respectively loaded on the four sides of the three rectangular cavities with smaller sizes.

[0009] Preferably, the rectangular cavity is made of a photocurable resin.

[0010] Preferably, the four rectangular cavities of different sizes include: a first rectangular cavity, a second rectangular cavity, a third rectangular cavity and a fourth rectangular cavity;

[0011] The first rectangular cavity has a height of h1, a width of a1, and a length of b1;

[0012] The second rectangular cavity has a height of h2, a width of a2, and a length of b2;

[0013] The third rectangular cavity has a height of h3, a width of a3, and a length of b3;

[0014] The fourth rectangular cavity has a height of h4, a width of a4, and a length of b4;

[0015] Among them, h1>h2>h3>h4, a1>a2>a3>a4, b1>b2>b3>b4.

[0016] Preferably, the thickness of the NDDP3 absorbing material is t=1 mm.

[0017] Preferably, the gradient metal strip array is loaded on four sides of the second rectangular cavity, the third rectangular cavity and the fourth rectangular cavity respectively.

[0018] Preferably, the gradient metal strip array is composed of a number of metal strips of different lengths;

[0019] The widths of the plurality of metal strips are the same, and the spacing distances between the plurality of metal strips are the same;

[0020] The metal strips on each rectangular cavity are arranged in sequence from short to long in a gradual length variation.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] The present invention combines rectangular cavities of different sizes and loads a gradient metal array, so that the structure has good wave absorption performance in the 2-40GHz frequency band. In the case of oblique incidence of electromagnetic waves, since the structure is a three-dimensional superstructure, when the electromagnetic waves are incident on the side of the combined rectangular cavity, scattering will occur, so that the structure still has a wide wave absorption bandwidth under a larger incident angle. The present invention is made by photocuring 3D printing, and compared with traditional absorbing materials, the production is relatively simple. At the same time, due to the high hardness of the photocuring resin, the mechanical strength of the structure is relatively high. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solution of the present invention, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0024] Figure 1 Schematic diagram of the wave absorbing structure of an embodiment of the present invention;

[0025] Figure 2 is a schematic diagram of an absorbing unit according to an embodiment of the present invention;

[0026] Figure 3 A side view of an absorbing unit according to an embodiment of the present invention;

[0027] Figure 4 A top view of an absorbing unit according to an embodiment of the present invention;

[0028] Figure 5 A dimension diagram of a gradient metal strip array according to an embodiment of the present invention;

[0029] Figure 6 1 is a comparison diagram of the reflectivity under a vertical incident angle of a combined rectangular cavity broadband absorbing structure loaded with a gradient metal strip array and not loaded with a gradient metal strip array according to an embodiment of the present invention, wherein a is a comparison diagram of the reflectivity under TE polarization, and b is a comparison diagram of the reflectivity under TM polarization;

[0030] Figure 7 A schematic diagram of an electric field in an electromagnetic wave incident on a gradient metal strip array and an equivalent circuit diagram of the gradient metal strip array according to an embodiment of the present invention;

[0031] Figure 8 Schematic diagram of a destructive interference model according to an embodiment of the present invention;

[0032] Fig. 9 Graphs showing changes in reflectivity with frequency at different incident angles for a combined rectangular cavity broadband absorbing structure loaded with a gradient metal strip array according to an embodiment of the present invention, wherein a is a graph showing changes in reflectivity with frequency under TE polarization, and b is a graph showing changes in reflectivity with frequency under TM polarization. DETAILED DESCRIPTION

[0033] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0034] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0035] Embodiment 1

[0036] In this embodiment, a combined rectangular cavity broadband absorbing structure loaded with a gradient metal strip array is provided. The absorbing structure is composed of a plurality of absorbing units arranged in sequence. The absorbing units include: 4 rectangular cavities of different sizes, a gradient metal strip array, and NDDP3 absorbing material. The 4 rectangular cavities of different sizes are arranged in sequence according to their sizes; the NDDP3 absorbing material is impregnated on the surfaces of the 4 rectangular cavities; the gradient metal strip array is loaded on the 4 sides of the 3 smaller rectangular cavities respectively. The material of the rectangular cavity is a light-curing resin. The thickness of the NDDP3 absorbing material is t=1 mm.

[0037] The four rectangular cavities of different sizes include: a first rectangular cavity, a second rectangular cavity, a third rectangular cavity and a fourth rectangular cavity; the first rectangular cavity has a height of h1, a width of a1 and a length of b1; the second rectangular cavity has a height of h2, a width of a2 and a length of b2; the third rectangular cavity has a height of h3, a width of a3 and a length of b3; the fourth rectangular cavity has a height of h4, a width of a4 and a length of b4. Among them, h1>h2>h3>h4, a1>a2>a3>a4, b1>b2>b3>b4.

[0038] The gradient metal strip array is loaded on the four sides of the second rectangular cavity, the third rectangular cavity and the fourth rectangular cavity respectively. The gradient metal strip array is composed of a number of metal strips of different lengths; the widths of the metal strips are the same, and the spacing distances between the metal strips are the same; the metal strips on each rectangular cavity are arranged in order from short to long according to the gradient length.

[0039] Embodiment 2

[0040] In this embodiment, if Figure 2 As shown, a combined rectangular cavity broadband absorbing structure loaded with a gradient metal strip array is formed by 9 absorbing units arranged in sequence.

[0041] Absorbing unit such as Figure 2 As shown, it includes: 4 rectangular cavities of different sizes, a gradient metal strip array and NDDP3 absorbing material. The 4 rectangular cavities of different sizes are arranged in order according to their sizes; the NDDP3 absorbing material is impregnated on the surface of the 4 rectangular cavities; the gradient metal strip array is loaded on the 4 sides of the 3 smaller rectangular cavities respectively. The material of the rectangular cavity is a photocurable resin, which is made by a photocurable printer. The thickness of the NDDP3 absorbing material is t = 1mm.

[0042] like Figure 2 , Figure 3 , Figure 4 As shown, the four rectangular cavities of different sizes include: a first rectangular cavity, a second rectangular cavity, a third rectangular cavity and a fourth rectangular cavity; the height of the first rectangular cavity is h1=10mm, the width is a1=12mm, and the length is b1=12mm; the height of the second rectangular cavity is h2=8mm, the width is a2=8mm, and the length is b2=10mm; the height of the third rectangular cavity is h3=6mm, the width is a3=6mm, and the length is b3=8mm; the height of the fourth rectangular cavity is h4=4mm, the width is a4=4mm, and the length is b4=6mm.

[0043] like Figure 5As shown, the gradient metal strip array is loaded on the four sides of the second rectangular cavity, the third rectangular cavity and the fourth rectangular cavity respectively. The gradient metal strip array is composed of a number of metal strips of different lengths; the widths of the metal strips are the same, all w = 0.3mm, and the spacing distances between the metal strips are the same, all s = 0.5mm; the metal strips on each rectangular cavity are arranged in order from short to long according to the gradient length, respectively L1 = 10mm, L2 = 9mm, L3 = 8mm, L4 = 7mm, L5 = 6mm, L6 = 5mm, L7 = 4mm, L8 = 3mm, L9 = 2mm, L10 = 1mm, L11 = 8mm, L12 = 7mm, L13 = 6mm, L14 = 5mm, L15 = 4mm, L16 = 3mm, L17 = 2mm, L18 = 6mm, L19 = 5mm, L20 = 4mm, L21 = 3mm, L22 = 2mm.

[0044] Embodiment 3

[0045] In this embodiment, the comparison of TE polarization and TM polarization reflectivity under the vertical incident angle of the combined rectangular cavity broadband absorbing structure loaded with the gradient metal strip array and without the gradient metal strip array is shown in FIG. Figure 6 (a) Figure 6 As shown in (b), it can be seen that in the 6-40 GHz frequency band, whether the gradient metal strip array is loaded or not, the wave absorption performance of the combined rectangular cavity is not much different. This is because when the electromagnetic wave is vertically incident on the gradient metal strip array, the electric field is incident parallel to the long side of the metal strip, such as Figure 7 As shown, when the direction of the electric field component of the incident electromagnetic wave is parallel to the metal strip grid, the electrons on the strip grid will accelerate due to the action of the electric field force. When the direction of the electric field changes, the speed of the electrons is the largest. Because in this case, the metal strip grid has a relatively reduced restriction on the distance that the electrons can move in space. When a low-frequency electromagnetic wave is incident, the electrons can accelerate along the same direction for a long period of time, and thus will obtain relatively large kinetic energy. In other words, the lower the frequency of the incident electromagnetic wave, the more electromagnetic energy the electrons can consume, and the weaker the transmission capacity of the incident electromagnetic wave. When a high-frequency electromagnetic wave is incident, the direction of the electric field component of the incident electromagnetic wave changes relatively quickly, the time for the electrons to accelerate is shorter, the kinetic energy obtained is smaller, and the electromagnetic energy consumed by the electrons is relatively less, so the incident electromagnetic wave will have a higher transmission capacity. Therefore, when the electric field direction of the incident electromagnetic wave is parallel to the metal strip grid structure, the filtering characteristic of the metal strip grid structure is high-pass, and the metal strip array structure at this time is inductive. As shown in Figure 7It is shown that the metal array in this case is equivalently modeled. In this equivalent circuit, the current of high-frequency signals can pass from the incident end to the exit end, and the current of low-frequency signals will flow into the ground through the inductor, which is equivalent to a high-pass filter. Therefore, for high-frequency incident electromagnetic waves, the gradient metal array has less energy loss. When the high-frequency electromagnetic wave is incident on the surface of the metal strip, it will propagate through the metal strip to the inside of the combined rectangular cavity. The electromagnetic wave mainly loses energy through the combined rectangular cavity. Therefore, whether the gradient metal strip array is loaded in the 6-40GHz frequency band, the wave absorption performance of the combined rectangular cavity is not much different.

[0046] In the 2-6GHz frequency band, Figure 6 As shown in the figure, the absorption performance of the loaded gradient metal tape array is significantly improved compared with the unloaded gradient metal tape array. The reason is that when the low-frequency electromagnetic wave is incident on the surface of the metal tape, the electrons in the metal tape will move at high speed under the action of the electric field to consume the electromagnetic wave energy. The reason why metal tapes of different lengths are combined to form a metal tape array is that for metal tapes of different lengths, the corresponding frequencies of the absorption peaks of electromagnetic waves are different, and the shorter the length of the metal tape, the higher the frequency corresponding to the absorption peak. Therefore, when multiple metal tapes of different lengths are combined, the absorption peaks of different resonant frequencies will gather to form a broadband, thereby achieving broadband absorption of electromagnetic waves.

[0047] According to the above analysis, electromagnetic waves in the 6-40GHz frequency band are mainly absorbed by the combined rectangular cavity structure. Figure 6 As shown in the figure, the structure still has good wave absorption performance in the 6-40GHz frequency band. The combined rectangular cavity absorbs waves in the 6-40GHz frequency band mainly in the following three ways:

[0048] The first is that after the electromagnetic wave is incident on the rectangular cavity and passes through the absorbing material NDDP3 impregnated on the surface of the rectangular cavity, the electromagnetic wave is dissipated in the form of electromagnetic loss. NDDP3 is a magnetic loss material that can effectively absorb electromagnetic waves. When the electromagnetic wave is incident on the inside of NDDP3, the magnetic induction effect will generate an induced current inside the NDDP3, which will lead to the generation of eddy currents. When the eddy currents flow inside the material, they will convert the energy of the incident electromagnetic wave into heat energy and consume it. This type of loss is called eddy current loss. In addition, the movement and rotation of the magnetic domain wall inside NDDP3 cannot keep up with the changes in the external magnetic field, causing the change in magnetic induction intensity to lag behind the change in the external magnetic field. This hysteresis phenomenon will cause part of the energy of the incident electromagnetic wave to be lost in the form of heat energy, which is called hysteresis loss.

[0049] In addition to the above two losses, when the electromagnetic field is incident on the inside of NDDP3, the relaxation process during the magnetization process will also cause losses. These relaxation processes include the accelerated movement of the domain wall, the consumption of elastic energy, and the magnetic aftereffect.

[0050] The second part is the interference loss between the reflected wave incident on the surface of the structure and the wave incident on the inside of the structure and propagating to the surface of the structure after being reflected by the metal backing plate at the bottom of the structure. Figure 8 The figure shows the destructive interference model, which can explain the interference loss mechanism of the combined rectangular cavity. When an electromagnetic wave propagates in the air to the surface of the absorber, part of the energy will be reflected at the front interface (denoted as R1), and the remaining energy will penetrate the front interface into the lossy medium and continue to propagate. After propagating to the metal backing plate, it will be reflected and finally return to the air through the front interface (denoted as R2). The two reflected waves will meet at the front interface. At this time, the phase difference between R1 and R2 depends on the optical path difference of the two waves, that is, twice the thickness of the absorber material:

[0051]

[0052] Among them, d represents the thickness of the absorber, λ represents the wavelength of the electromagnetic wave, f represents the frequency of the electromagnetic wave, c represents the speed of light, μ represents the magnetic permeability of the absorber, and ε represents the dielectric constant of the absorber. If the phase difference between the two reflected waves is exactly equal to an odd number of 180 degrees (i.e. ), the two waves interfere with each other and the total reflected wave intensity reaches the weakest, that is, a strong reflection loss peak appears.

[0053] The third part is that the electromagnetic wave is incident on the side of the rectangular cavity and is reflected multiple times, and is eventually reduced in the form of scattering loss. Since the combined rectangular cavity is a 3D superstructure absorber, it has structural inhomogeneity. This feature enables the combined rectangular cavity to effectively interact with electromagnetic waves, causing electromagnetic waves to scatter during propagation. This scattering causes the energy of the electromagnetic wave to be dispersed inside the medium, increasing the chance of interaction between the electromagnetic wave and the material, thereby losing the electromagnetic wave energy.

[0054] The embodiment of the present invention proposes a combined rectangular cavity broadband absorbing structure loaded with a gradient metal strip array, which still has a wide absorbing bandwidth under large angle oblique incidence. This is similar to the scattering loss mechanism of the combined rectangular cavity in the 6-40GHz frequency band mentioned above. Under oblique incidence of electromagnetic waves, scattering occurs when the electromagnetic waves enter the side of the combined rectangular cavity, so that the structure still has a wide absorbing bandwidth under large incident angles. Fig. 9 The figure shows the variation of TE polarization and TM polarization reflectivity with frequency at different incident angles of the combined rectangular cavity broadband absorbing structure loaded with a gradient metal strip array in an embodiment of the present invention. It can be seen from the figure that it still has good absorbing performance at an incident angle of 50°.

[0055] In addition, an embodiment of the present invention proposes a combined rectangular cavity broadband absorbing structure loaded with a gradient metal strip array. Since the combined rectangular cavity is made by photocuring 3D printing, it is simpler to make compared with traditional absorbing materials. At the same time, due to the high hardness of the photocuring resin, the mechanical strength of the structure is high.

[0056] The embodiments described above are only descriptions of the preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A combined rectangular cavity broadband absorbing structure loaded with a gradient metal strip array, characterized in that: The absorbing structure is composed of a plurality of absorbing units arranged in sequence, wherein the absorbing units include: 4 rectangular cavities of different sizes, a gradient metal strip array and NDDP3 absorbing material; The four rectangular cavities of different sizes are arranged in order according to their sizes; The NDDP3 absorbing material is impregnated on the surfaces of the four rectangular cavities; The gradient metal strip arrays are respectively loaded on the four sides of the three rectangular cavities with smaller sizes.

2. According to claim 1, a combined rectangular cavity broadband absorbing structure loaded with a gradient metal strip array is characterized in that: The rectangular cavity is made of a light-curing resin.

3. According to claim 1, a combined rectangular cavity broadband absorbing structure loaded with a gradient metal strip array is characterized in that: The four rectangular cavities of different sizes include: a first rectangular cavity, a second rectangular cavity, a third rectangular cavity and a fourth rectangular cavity; The first rectangular cavity has a height of h1, a width of a1, and a length of b1; The second rectangular cavity has a height of h2, a width of a2, and a length of b2; The third rectangular cavity has a height of h3, a width of a3, and a length of b3; The fourth rectangular cavity has a height of h4, a width of a4, and a length of b4; Among them, h1>h2>h3>h4, a1>a2>a3>a4, b1>b2>b3>b4.

4. According to claim 1, a combined rectangular cavity broadband absorbing structure loaded with a gradient metal strip array is characterized in that: The thickness of the NDDP3 absorbing material is t=1 mm.

5. According to claim 3, a combined rectangular cavity broadband absorbing structure loaded with a gradient metal strip array is characterized in that: The gradient metal strip array is loaded on four sides of the second rectangular cavity, the third rectangular cavity and the fourth rectangular cavity respectively.

6. According to claim 1, a combined rectangular cavity broadband absorbing structure loaded with a gradient metal strip array is characterized in that: The gradient metal strip array is composed of a number of metal strips of different lengths; The widths of the plurality of metal strips are the same, and the spacings between the plurality of metal strips are the same; The metal strips on each rectangular cavity are arranged in sequence from short to long in a gradual length variation.

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