Wide-frequency-band wave-absorbing cavity structure and wave-absorbing method under large-angle electromagnetic wave incidence

Abstract

The invention relates to a wide-frequency-band wave-absorbing cavity structure under large-angle electromagnetic wave incidence, which comprises a wave-absorbing screen and a wave-absorbing cavity cylinder defined by one wave-absorbing screen or at least two wave-absorbing screens which are connected with each other, the two ends of the wave-absorbing cavity cylinder are open, the opening at one end is used as an electromagnetic wave incidence opening, and the opening at the other end is provided with a bottom surface absorbing screen; the wave-absorbing screen comprises a metal backboard, an intermediate dielectric layer and a resistive resonance layer. The resistive resonance layer comprises a plurality of resistive resonance rings arranged on the middle dielectric layer in a matrix mode, and each resistive resonance ring comprises a plurality of lumped resistors used for losing electromagnetic waves and widening the wave absorbing bandwidth and a metal wire used for connecting the lumped resistors in series. By optimizing the wave-absorbing structure and material, the wave-absorbing efficiency of the wave-absorbing cavity structure is still kept at 90% or above under the oblique incidence condition, and the wave-absorbing cavity structure can be applied to the fields of radar stealth, electronic countermeasure and the like and is arranged in a cavity with a certain shape to achieve efficient absorption of wide-frequency-band and wide-angle electromagnetic waves.

Description

Technical Field

[0001] The present invention relates to the technical field of electromagnetic metamaterial wave absorption, and particularly to an absorbing structure and method composed of absorbing metamaterials. Background Art

[0002] Electromagnetic metamaterials are a class of artificial composite materials with special electromagnetic properties. They are formed by arranging unit structures at the sub-wavelength scale in a specific manner and can achieve extraordinary physical properties that are not possessed by materials in nature.

[0003] The Salisbury absorption screen is an electromagnetic metamaterial based on the principle of electromagnetic resonance for absorbing electromagnetic waves. The classic Salisbury absorption screen consists of three layers: a resistive film, a dielectric, and a perfect conductor. It can achieve perfect wave absorption at the resonant frequency. Replacing the surface metal resonant unit with a resistive resonant unit can also achieve broadband wave absorption and can effectively control the propagation mode, polarization, and wavefront of electromagnetic waves. At the same time, compared with traditional wave-absorbing materials such as carbonyl iron powder and carbon fiber tubes, the Salisbury screen has the advantages of light weight, thin thickness, simple structure, high wave absorption rate, and low cost, so it is widely used in the design applications of wave absorbers, electromagnetic shielding, polarization converters, etc.

[0004] However, at present, most Salisbury absorption screens have a narrow effective absorption bandwidth, and have a high wave absorption rate for vertically incident electromagnetic waves (incident angle 0°). When the incident wave deviates from the normal direction (such as when the incident angle is greater than 15°), due to impedance mismatch, the wave absorption rate usually drops significantly, making it difficult to meet the actual application requirements of wide-angle wave absorption. Summary of the Invention

[0005] The purpose of the present invention is to avoid the deficiencies of the prior art and provide a broadband wave-absorbing cavity structure and wave-absorbing method with broadband wave absorption, light weight, and capable of regulating the radar cross section (RCS) in a broadband waveband and achieving effective wave absorption under large-angle electromagnetic wave incidence.

[0006] To achieve the above purpose, the technical solution adopted by the present invention is: a broadband wave-absorbing cavity structure under large-angle electromagnetic wave incidence, including an absorbing screen, which is formed by connecting one absorbing screen or at least two absorbing screens to enclose an absorbing cavity cylinder with both ends open. One end opening serves as the incident opening for electromagnetic waves, and the other end opening is provided with a bottom absorbing screen; The absorbing screen includes a metal backplane for totally reflecting and outputting the remaining electromagnetic waves, an intermediate dielectric layer for absorbing part of the incident electromagnetic waves, and a resistive resonant layer for making the incident electromagnetic waves resonate; when the absorbing screen encloses the absorbing cavity cylinder, the metal backplane is arranged on one side surface of the intermediate dielectric layer as the outer surface layer of the absorbing cavity cylinder, and the resistive resonant layer is arranged on the other side surface of the intermediate dielectric layer as the inner surface layer of the absorbing cavity cylinder; And the bottom absorption screen has the same structure as the absorption screen that forms the absorbing cavity column The resistive resonance layer includes a plurality of resistive resonance rings arranged in a matrix on the intermediate dielectric layer. The resistive resonance rings include a plurality of lumped resistors for loss of electromagnetic waves and broadening of the absorption bandwidth, and metal wires for connecting the plurality of lumped resistors in series.

[0007] Further, a rectangular or square resistive resonance ring with a side length a of 4.5 - 6 mm is formed by connecting a plurality of lumped resistors in series with the metal wire And at least one lumped resistor is provided on each side of the rectangular or square shape of the resistive resonance ring.

[0008] Further, the metal backplane is a copper - clad film with a thickness of 0.01 - 0.05 mm, and the copper - clad film is printed on the surface of the intermediate dielectric plate.

[0009] Further, the intermediate dielectric layer is a glass fiber layer with a thickness D of 2 - 5 mm.

[0010] Further, the resistance value of the lumped resistor is 25 - 200 Ω.

[0011] Further, the metal wire is a copper wire, the width w of the metal wire is 0.15 - 0.25 mm, the thickness is 0.02 - 0.05 mm, and the metal wire is printed on the surface of the intermediate dielectric layer.

[0012] Further, the two connection ends of the metal wire and the lumped resistor are thickened for easy soldering of the lumped resistor.

[0013] Further, the longitudinal and lateral distances between the plurality of resistive resonance rings are both 9 - 12 mm, so that the plurality of resistive resonance rings are uniformly arranged circumferentially and axially on the inner surface layer of the absorbing cavity column.

[0014] Further, the plurality of resistive resonance rings are arranged in a 10×10 array on the surface of the intermediate dielectric layer.

[0015] The present invention also provides an absorption method for a wide - band absorption cavity structure under large - angle electromagnetic wave incidence as described above When the electromagnetic wave enters the inner cavity of the absorbing cavity column in the axial direction of the absorbing cavity column and perpendicular to the bottom absorption screen, the electromagnetic wave is resonantly absorbed and lost by the resistive resonance rings on the bottom absorption screen, that is, the electromagnetic wave in the 5 - 13 GHz frequency band is absorbed. When the electromagnetic wave obliquely enters the cavity interior at an angle greater than 0° and less than 90° with respect to the axis of the absorbing cavity cylinder (1), due to impedance mismatch, it cannot be completely absorbed. However, the scattered electromagnetic wave will be absorbed again by the resistive resonant rings on the inner surface of the absorbing cavity cylinder, that is, the absorption of electromagnetic waves in the 5 - 13 GHz frequency band with different path lengths is realized.

[0016] The beneficial effects of the present invention are as follows: A cavity structure with a specific shape is formed by enclosing a Salisbury absorption screen with lumped resistors added, and an absorbing cavity structure with high insensitivity to the incident wave angle is obtained.

[0017] The cavity structure proposed by the present invention can be applied to cavity structures with various shapes such as wings and ships. It has a small density, light weight, and low cost. The cavity structure is used to reflect and absorb the incident electromagnetic wave multiple times, reducing the electromagnetic wave scattering of components.

[0018] In the embodiment of the present invention, a cuboid cavity structure is adopted. The resonant unit array with lumped resistors is arranged on the resistive resonant layer on the surface forming the absorption screen. The absorbing cavity structure formed by enclosing multiple absorption screens realizes a performance with an absorption rate greater than 90% in the 5 - 13 GHz frequency band under the condition of perpendicular incidence of electromagnetic waves. At the same time, by optimizing the cavity geometry and material matching, the absorption efficiency still remains above 90% under the condition of oblique incidence (greater than 0° and less than 90°). The present invention can be applied to fields such as radar stealth and electronic countermeasures. It is set inside a cavity with a certain shape to realize the efficient absorption of electromagnetic waves in a wide frequency band and wide angle. Description of the Drawings

[0019] Figure 1 It is a schematic diagram of the structure of the absorbing cavity cylinder of the present invention; Figure 2 It is a schematic diagram of the side sectional structure of the absorption screen of the present invention; Figure 3 It is a schematic diagram of the structure of the resistive resonant rings arranged in a periodic array of the present invention; In the figure, 1. Absorbing cavity cylinder; 2. Bottom absorption screen; 3. Metal backplane; 4. Intermediate dielectric layer; 5. Resistive resonant layer; 51. Resistive resonant ring; 511. Metal wire; 512. Lumped resistor; Figure 4 It is a schematic diagram of the side sectional structure of the inner cavity of the absorbing cavity cylinder when the electromagnetic wave enters the absorbing cavity cylinder in the axial direction of the absorbing cavity cylinder and is perpendicular to the bottom absorption screen; Figure 5 It is a schematic diagram of the side sectional structure of the inner cavity of the absorbing cavity cylinder when the electromagnetic wave obliquely enters the cavity interior at an angle greater than 0° and less than or equal to 45° with respect to the axis of the absorbing cavity cylinder; Figure 6 It is the curve graph of the wave absorption rate of the wave absorption cavity structure of a specific example of the present invention for electromagnetic waves with different incident angles; Figure 7 It is the comparison graph of the wave absorption rate curves between the wave absorption cavity structure of a specific example of the present invention and the wave absorption plane of the same material when the incident wave is at 30°. Specific embodiments

[0020] The principles and features of the present invention will be described below with reference to the accompanying drawings. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0021] To achieve the above object, the present invention provides the following specific embodiments: Example 1: As Figure 1 、 Figure 2 shown, a wide-band wave absorption cavity structure under the incidence of large-angle electromagnetic waves includes a wave absorption screen. An absorption cavity column 1 with two open ends is formed by connecting one wave absorption screen or at least two wave absorption screens. One open end serves as the electromagnetic wave incident opening, and the other open end is provided with a bottom surface absorption screen 2; As Figure 2 shown, the wave absorption screen includes a metal backplane 3 for totally reflecting and outputting the remaining electromagnetic waves, an intermediate dielectric layer 4 for absorbing part of the incident electromagnetic waves, and a resistive resonance layer 5 for making the incident electromagnetic waves resonate; when the wave absorption screen encloses the absorption cavity column 1, the metal backplane 3 is arranged on one side surface of the intermediate dielectric layer 4 as the outer surface layer of the absorption cavity column 1, and the resistive resonance layer 5 is arranged on the other side surface of the intermediate dielectric layer 4 as the inner surface layer of the absorption cavity column 1; and the bottom surface absorption screen 2 has the same structure as the wave absorption screen forming the absorption cavity column 1; Among them, the metal backplane 3 is a copper-clad film with a thickness t of 0.01 - 0.05 mm, and the copper-clad film is printed on the surface of the intermediate dielectric plate 4; the intermediate dielectric layer 4 is a glass fiber layer with a thickness D of 2 - 5 mm; As Figure 3 shown, the resistive resonance layer 5 includes a plurality of resistive resonance rings 51 arranged in a matrix on the intermediate dielectric layer 4. The resistive resonance rings 51 include a plurality of lumped resistors 512 for losing electromagnetic waves and broadening the wave absorption bandwidth and metal wires 511 for connecting in series the plurality of lumped resistors 512, Among them, the resistance value of the lumped resistor 512 is 25 - 200 Ω; the metal wire 511 is a copper wire, the width w of the metal wire 511 is 0.15 - 0.25 mm, the thickness t is 0.02 - 0.05 mm, and the metal wire 511 is printed on the surface of the intermediate dielectric layer 4.

[0022] The longitudinal and transverse distances between the plurality of resistive resonance rings 51 are both 9 - 12 mm, so that the plurality of resistive resonance rings 51 are uniformly arranged in the circumferential and axial directions on the inner surface layer of the absorption cavity column 1.

[0023] Embodiment 2: The same as Embodiment 1, except that: A plurality of lumped resistors 512 are connected in series by a metal wire 511 to form a rectangular or square resistive resonant loop 51 with a side length a of 4.5 - 6 mm, and at least one lumped resistor 512 is provided on each side of the rectangular or square of the resistive resonant loop 51.

[0024] A plurality of resistive resonant loops 51 are arranged in a 10×10 array on the surface of the middle dielectric layer 4.

[0025] Embodiment 3: The same as Embodiment 1, except that: The two connection ends of the metal wire 511 and the lumped resistor 512 are thickened to facilitate the soldering of the lumped resistor.

[0026] Embodiment 4: As Figure 4 shown, the present invention also provides an absorbing method for a wide - band absorbing cavity structure under large - angle electromagnetic wave incidence as provided in Embodiments 1, 2, and 3, As Figure 4 shown, when the electromagnetic wave enters the inner cavity of the absorbing cavity cylinder 1 along the axial direction of the absorbing cavity cylinder 1 and perpendicular to the bottom absorbing screen 2, the electromagnetic wave is absorbed by the resonant loss of the resistive resonant loop 51 on the bottom absorbing screen 2, that is, the electromagnetic wave absorption in the 5 - 13 GHz frequency band is realized; Embodiment 5: The same as Embodiment 4, except that when the electromagnetic wave obliquely enters the cavity interior at an axial angle greater than 0° and less than 90° with respect to the axis of the absorbing cavity cylinder (1), due to impedance mismatch, it cannot be completely absorbed, but the scattered electromagnetic wave will be absorbed again by the resonant loss of the resistive resonant loop 51 on the inner surface of the absorbing cavity cylinder 1, that is, the electromagnetic wave absorption in the 5 - 13 GHz frequency band with different path lengths is realized.

[0027] Embodiment 6, as Figure 5 shown, the same as Embodiment 5, except that in Figure 5 when the electromagnetic wave obliquely enters the cavity interior at an axial angle greater than 0° and less than or equal to 45° with respect to the axis of the absorbing cavity cylinder 1, due to impedance mismatch, it cannot be completely absorbed, but the scattered electromagnetic wave will be absorbed again by the resonant loss of the resistive resonant loop 51 on the inner surface of the absorbing cavity cylinder 1, that is, the electromagnetic wave absorption in the 5 - 13 GHz frequency band with different path lengths is realized.

[0028] As Figures 1-6 shown, in order to further illustrate the technical solutions and technical effects provided by the present invention, the following specific examples are provided: Specific Embodiment 1: As Figure 3As shown, the resistive resonant ring 51 is composed of a metal wire 511 and a lumped resistor 512. The metal wire 511 is a copper wire with side length a = 5.1 mm, width w = 0.15 mm, and is thickened at the connection with the lumped resistor 512. The lumped resistor 512 is welded between the copper wires; the lumped resistor is in 0402 package with a resistance value of 150 Ω. The period length p of the resistive resonant unit is 9 mm.

[0029] As Figure 1 , 2 shown, the absorbing cavity cylinder 1 with a rectangular cavity structure is adopted in the embodiment of the present invention. The outermost layer is a copper-clad film with a thickness of 0.035 mm as the metal backplane 3. The intermediate dielectric layer 4 is a fiberglass layer, model FR4, with a thickness D = 3.2 mm. Five surfaces inside the absorbing cavity cylinder 1 are respectively composed of 10×10 resistive resonators 51. The height of the entire absorbing cavity cylinder 1 is H = 113.2 mm, and the length and width are L = 116.4 mm.

[0030] The specific example of the present invention absorbs a large amount of incident electromagnetic waves through the following mechanism: As Figure 4 shown, when the electromagnetic wave is vertically incident on the surface of the bottom absorbing screen 2, the electromagnetic wave is resonantly absorbed by the resistive resonant ring 51 on the surface of the bottom absorbing screen 2, broadening the absorbing working frequency band; As Figure 5 shown, when the electromagnetic wave is obliquely incident into the inner cavity of the absorbing cavity cylinder 1, due to impedance mismatch, it cannot be completely absorbed, but the scattered electromagnetic wave will be incident on other inner surfaces again inside the cavity of the absorbing cavity cylinder 1 for re-absorption, realizing multi-path absorption of the electromagnetic wave, thereby broadening the absorbing angle.

[0031] As Figure 6 shown, in the embodiment of the present invention, when the electromagnetic wave is vertically incident, the absorption rate reaches more than 90% in the frequency band of 5 - 13 GHz. As the incident angle increases, the absorption rate changes little and remains stable at more than 90%, and even the absorption rate is higher at low frequencies, indicating good angle stability of the absorbing cavity.

[0032] As Figure 7 shown, compared with the metamaterial absorber with a resistive resonant surface arranged in a plane periodic manner, the embodiment of the present invention has obvious improvement in the absorption of 30° obliquely incident electromagnetic waves.

[0033] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A broadband wave-absorbing cavity structure under the incidence of large-angle electromagnetic waves, characterized in that It includes an electromagnetic wave absorbing screen. One electromagnetic wave absorbing screen or at least two electromagnetic wave absorbing screens are interconnected to form a columnar electromagnetic wave absorbing cavity (1) with openings at both ends. One end opening serves as the incident opening for electromagnetic waves, and the other end opening is provided with a bottom absorbing screen (2). The electromagnetic wave absorbing screen includes a metal backplane (3) for totally reflecting and outputting the remaining electromagnetic waves, an intermediate dielectric layer (4) for absorbing part of the incident electromagnetic waves, and a resistive resonance layer (5) for resonating the incident electromagnetic waves. When the electromagnetic wave absorbing screen forms the columnar electromagnetic wave absorbing cavity (1), the metal backplane (3) is arranged on one side surface of the intermediate dielectric layer (4) as the outer surface layer of the columnar electromagnetic wave absorbing cavity (1), and the resistive resonance layer (5) is arranged on the other side surface of the intermediate dielectric layer (4) as the inner surface layer of the columnar electromagnetic wave absorbing cavity (1). And the bottom absorbing screen (2) has the same structure as the electromagnetic wave absorbing screen forming the columnar electromagnetic wave absorbing cavity (1). The resistive resonance layer (5) includes a plurality of resistive resonance rings (51) arranged in a matrix on the intermediate dielectric layer (4). The resistive resonance ring (51) includes a plurality of lumped resistors (512) for loss of electromagnetic waves and broadening of the electromagnetic wave absorption bandwidth, and a metal wire (511) for connecting a plurality of lumped resistors (512) in series.

2. The broadband wave-absorbing cavity structure under large-angle electromagnetic wave incidence according to claim 1, characterized in that A rectangular or square resistive resonance ring (51) with a side length a of 4.5 - 6 mm is formed by connecting a plurality of lumped resistors (512) in series with the metal wire (511). And at least one lumped resistor (512) is provided on each side of the rectangle or square of the resistive resonance ring (51).

3. The broadband wave-absorbing cavity structure under the incidence of large-angle electromagnetic waves according to claim 1, characterized in that, The metal backplane (3) is a copper-clad film with a thickness of 0.01 - 0.05 mm, and the copper-clad film is printed on the surface of the intermediate dielectric plate (4).

4. The broadband wave-absorbing cavity structure under the incidence of large-angle electromagnetic waves according to claim 1, characterized in that, The intermediate dielectric layer (4) is a glass fiber layer with a thickness D of 2 - 5 mm.

5. The broadband wave-absorbing cavity structure under large-angle electromagnetic wave incidence according to claim 1, characterized in that, The resistance value of the lumped resistor (512) is 25 - 200 Ω.

6. The broadband wave-absorbing cavity structure under large-angle electromagnetic wave incidence according to claim 1, characterized in that The metal wire (511) is a copper wire. The width w of the metal wire (511) is 0.15 - 0.25 mm, and the thickness is 0.02 - 0.05 mm. And the metal wire (511) is printed on the surface of the intermediate dielectric layer (4).

7. The broadband wave-absorbing cavity structure under large-angle electromagnetic wave incidence according to claim 1, characterized in that The two connection ends of the metal wire (511) and the lumped resistor (512) are thickened to facilitate the welding of the lumped resistor.

8. The broadband wave-absorbing cavity structure under large-angle electromagnetic wave incidence according to any one of claims 1-7, characterized in that, The longitudinal and lateral distances between the plurality of resistive resonance rings (51) are both 9 - 12 mm, so that the plurality of resistive resonance rings (51) are uniformly arranged in the circumferential and axial directions of the inner surface layer of the columnar electromagnetic wave absorbing cavity (1).

9. The broadband wave-absorbing cavity structure under the incidence of large-angle electromagnetic waves according to claim 8, characterized in that, The plurality of resistive resonance rings (51) are arranged in a 10×10 array on the surface of the intermediate dielectric layer (4).

10. An electromagnetic wave absorption method for a wide-band electromagnetic wave absorption cavity structure under large-angle electromagnetic wave incidence as described in claims 1 - 9, characterized in that When the electromagnetic wave enters the inner cavity of the columnar electromagnetic wave absorbing cavity (1) in the axial direction of the columnar electromagnetic wave absorbing cavity (1) and perpendicular to the bottom absorbing screen (2), the electromagnetic wave is resonantly absorbed by the resistive resonance rings (51) on the bottom absorbing screen (2), that is, the electromagnetic wave absorption in the frequency band of 5 - 13 GHz is realized. When electromagnetic waves are obliquely incident into the cavity interior at an axial angle greater than 0° and less than 90° with respect to the axis of the absorbing cavity cylinder (1), they cannot be completely absorbed due to impedance mismatch. However, the scattered electromagnetic waves will be absorbed again by the resistive resonant rings (51) on the inner surface of the absorbing cavity cylinder (1), that is, the absorption of electromagnetic waves in the 5 - 13 GHz frequency band with different path lengths is achieved.

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