High-bandwidth metamaterial wave absorber based on K wave band

Abstract

The invention belongs to the technical field of electromagnetic metamaterial wave absorbers, and particularly relates to a K-band-based high-bandwidth metamaterial wave absorber which is of a three-layer structure and is formed by stacking a metal resonance layer, a dielectric layer and a metal bottom plate from top to bottom. The metal resonance layer is composed of an open rectangular resonance ring, two circular metal resonance rings and two rectangular metal patches and is arranged above the dielectric layer, the middle dielectric layer is FR-4, and the bottom layer is a fully-covered metal copper bottom plate. According to the invention, within a K wave band (18GHz-26GHz) and between 20.76 GHz and 24.20 GHz, the wave absorbing bandwidth for electromagnetic waves is 3.44 GHz, within the wave absorbing range, the absorption rate is higher than 90%, and the highest absorption rate is 98.16%. A traditional metamaterial wave absorber design method is adopted, the structure is simple, the wave absorbing bandwidth is large, the problems of electromagnetic interference and radar stealth can be effectively solved, and great application value is achieved in practical application.

Description

Technical Field

[0001] The present invention relates to a high-bandwidth metamaterial absorber based on K band, and specifically belongs to the technical field of electromagnetic metamaterial absorbers. Background Art

[0002] As modern electronic systems are developing towards high integration, miniaturization and intelligence, electromagnetic radiation suppression is becoming more and more important, and it is more urgent to study new electromagnetic energy control technologies to suppress electromagnetic radiation. Metamaterial refers to a type of artificial composite structure with extraordinary physical properties that natural materials do not have. Compared with natural materials, metamaterials have more physical properties that natural materials do not have, such as negative refraction effect, inverse Doppler effect, inverse Cherenkov effect and other physical properties. Since metamaterials can obtain excellent performance through structural design, the electromagnetic properties exhibited by metamaterials are not limited to the basic particles that constitute them. When the wavelength of the working environment of the metamaterial is much larger than the size of the unit cell in its periodic structure, the unit cell can be regarded as the basic component particle of the metamaterial, and the entire metamaterial can be regarded as a uniform medium. In recent years, the application of metamaterials, such as invisibility cloaks and perfect lenses, has emerged in the fields of optics, communications, and national defense. At present, most of the traditional metamaterial absorbers only stay at frequency point absorption, and the remaining part is narrow-band absorption. However, how traditional metamaterial absorbers can absorb high-bandwidth continuous frequencies of electromagnetic waves remains a major problem currently faced. Summary of the invention

[0003] 1. Technical issues to be resolved

[0004] In view of the shortcomings of the prior art, the present invention provides a high-bandwidth metamaterial absorber based on the K-band, which solves the problem of narrow absorption band proposed in the above background technology, inability to ensure high-bandwidth electromagnetic wave absorption under simple structure conditions, and only able to absorb at certain frequency points.

[0005] (II) Technical solution

[0006] In order to achieve the above-mentioned purpose, the present invention specifically adopts the following technical solutions:

[0007] A high-bandwidth metamaterial absorber based on the K band has a three-layer structure, which is composed of a metal resonance layer, a dielectric layer, and a metal bottom plate stacked in sequence from top to bottom; the metal resonance layer is composed of a rectangular open metal resonance ring and two circular metal resonance rings, which are connected by two rectangular metal patches in the middle of the two circular resonance rings; the metal resonance layer uses metal copper as the resonance material, the dielectric layer is FR-4, and the metal bottom plate is fully covered on the bottom layer with metal copper as the material.

[0008] Furthermore, the surface metal resonance layer is made of metal copper with a thickness of h3=0.035mm, the size of the open resonant square ring is L1=7.75mm, the opening size is d=0.5mm, the radius of the open resonant circular ring is R1=2.9mm, the width of the circular ring is 0.4mm, the radius of the resonant circular ring is R3=1.4mm, the width of the circular ring is 0.5mm, and the length of the rectangular metal patch is b=1.061mm.

[0009] Furthermore, the dielectric layer is made of FR-4 material, has a dielectric constant of 4.3, a square structure, a size of P=9 mm, and a thickness of h=1.575 mm.

[0010] Furthermore, the dielectric layer of the absorber is composed of a FR-4 dielectric plate with a thickness of h2=1.575 mm and a dielectric constant of 4.3.

[0011] Furthermore, the metal bottom plate is a metal copper full-covering structure with a thickness of h3=0.035mm, a square structure in shape, and a size of P=9mm.

[0012] Furthermore, the K-band based high-bandwidth metamaterial absorber can achieve high-bandwidth absorption of electromagnetic waves in a continuous frequency band.

[0013] Furthermore, the K-band based high bandwidth metamaterial absorber is equivalently fitted as an RLC circuit.

[0014] Furthermore, the K-band based high bandwidth metamaterial absorber is measured in reality, and its S parameters are compared with the S parameters obtained by simulation.

[0015] (III) Beneficial effects

[0016] Compared with the prior art, the present invention provides a high-bandwidth metamaterial absorber based on the K-band, which has the following beneficial effects:

[0017] The present invention can absorb more than 90% of electromagnetic waves within the range of 20.76 GHz-24.20 GHz, and has an absorption bandwidth that all currently proposed K-band traditional metamaterial absorbers do not have.

[0018] The invention has the advantages of small size, easy manufacture and low cost, and its overall size is 9mm×9mm×1.645mm.

[0019] The absorber of the present invention has different absorption ranges at different polarization angles, wherein the absorption range at a polarization angle of 15° is 20.77GHz-22.90GHz (2.13GHz), at 45° is 21.08GHz-22.48GHz (1.4GHz), at 30° and 60° is the same, 21GHz-22.58GHz (1.58GHz), and at a polarization angle of 0°, i.e., the electromagnetic wave is incident vertically, the absorption bandwidth is up to 3.44GHz. It can meet the absorption of electromagnetic waves with different bandwidth requirements.

[0020] The present invention maintains more than 80% absorption of multiple frequency points or continuous frequency bands when the electromagnetic wave is incident obliquely at 0-60 degrees, and still maintains good absorption performance under oblique incidence. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic diagram of the overall structure of the present invention;

[0022] Figure 2 A top view of the present invention;

[0023] Figure 3 are the effective electromagnetic parameters of the real and imaginary parts of the present invention;

[0024] Figure 4 The electric field, magnetic field and surface current distribution diagram of the present invention;

[0025] Figure 5 It is a curve diagram of polarization angle and wave absorption rate under oblique incidence of the present invention;

[0026] Figure 6 A comparison diagram of the S parameters of the equivalent circuit of the present invention and the simulated S parameters;

[0027] Figure 7 This is a comparison diagram of the S parameters measured by the actual object and the simulated S parameters of the present invention. DETAILED DESCRIPTION

[0028] 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.

[0029] Example

[0030] like Figure 1 and Figure 2 As shown, an embodiment of the present invention proposes a high-bandwidth metamaterial absorber based on the K band, the thickness of the substrate FR-4 of the structure is 1.575 mm, and the dielectric constant is is 4.3. The absorber metal bottom plate has the same size as the dielectric layer, both of which are P=9mm; the thickness of the metal bottom plate is h1=0.035mm. The surface metal resonance layer is made of metal copper with a thickness of h3=0.035mm. The size of the open resonant square ring is L1=7.75mm, the opening size is d=0.5mm, the radius of the open resonant ring is R1=2.9mm, and the radius of the resonant ring is R3=1.4mm.

[0031] like Figure 3 As shown, in some embodiments, a systematic simulation is performed on the dielectric constant, magnetic permeability, refractive index and normalized impedance of the metamaterial absorber. The electromagnetic characteristics of the structure are analyzed by the reflection coefficient S11 and the transmission coefficient S21 using CST software, and then the effective parameters of the structure, the dielectric constant, magnetic permeability, refractive index and normalized impedance are calculated using the robust retrieval method. The equations for the reflection coefficient S11 and the transmission coefficient S21 are, , .in, , , the calculation formula of normalized impedance is, , the refractive index calculation formula is, Here, ()' is used to represent the real part, ()'' is used to represent the imaginary part, m is the integer of the real part of the refractive index, k0 is the spatial frequency of the incident electromagnetic wave in free space, that is, the wave number, which is the reciprocal of the wavelength λ, and d is the thickness of the substrate, so the refractive index can also be expressed as, The calculation formula of dielectric constant and magnetic permeability is expressed as, and .

[0032] like Figure 4 As shown, in some instances, at 21.12 GHZ, the electric field strength and magnetic field strength on the resonant ring and between the open resonant ring gap show higher values, and the structure has a stronger electromagnetic response at this frequency. At the same time, the surface current density is high, showing an obvious current distribution, which is consistent with the distribution of the electric field strength. The distribution of surface current further confirms the effective electromagnetic absorption capacity of the structure at this frequency. At 22.60 GHZ, the electric field strength shows that strong electromagnetic coupling occurs at the opening of the open resonant square ring, and the current distribution also reflects this characteristic. For 23.86 GHZ, the electric field strength is similar to that of 22.60 GHZ, but the magnetization intensity is stronger, which also confirms that there is strong electromagnetic coupling at this point and has a strong absorption capacity for electromagnetic waves. From Figure 4It can be observed that the electric field strength is consistent with the current distribution, while the magnetic field and the electric field are perpendicular to each other. Therefore, the magnetic field strength and the electric field strength will show different trends, which can also confirm the strong electromagnetic coupling characteristics of the three absorption peaks. In the TE mode and TM mode, there is almost no difference in the electric field strength, magnetic field strength and current distribution, which also verifies that when the electromagnetic wave is incident perpendicular to the plane, the absorbing structure is insensitive to the two modes.

[0033] like Figure 5 As shown in FIG. 1 , in some embodiments, the absorption rate of the metamaterial absorber under different polarizations and incident angles. In the TE mode, when the electromagnetic wave is incident in a fixed direction, the magnetic field component is located in the xy plane, while the electric field component is perpendicular to the propagation direction, forming a perpendicular relationship between the electric field and the magnetic field. When the structure is rotated 90°, the absorption range shows a 45° symmetry. This asymmetric structure enhances the flexibility of the metamaterial in practical applications. Figure 5 As shown in (a), under different polarization angles, the absorption ranges of 15° and 75° are both 20.77GHz-22.90GHz (2.13GHz), 45° is 21.08GHz-22.48GHz (1.4GHz), 30° and 60° are both 21GHz-22.58GHz (1.58GHz), while the absorption ranges of 0° and 90° are the same, with the highest absorption bandwidth of 3.44GHz. Due to the symmetry of the structure about 45°, the absorption bandwidth of the metamaterial changes with the change of polarization angle.

[0034] In TE mode, CST software was used to simulate and analyze the electromagnetic wave incident angle from 0° to 75°. The simulation results are as follows: Figure 5(b) As shown. According to the theory of multiple interference reflection, the surface metal patch behaves as a reflective structure, while the substrate behaves as a transmissive structure. When the electromagnetic wave passes through the substrate structure to the underlying metal base plate, reflection occurs, and this process promotes the absorption of the electromagnetic wave. Due to the asymmetry of the absorbing structure, transmission and reflection are not completely symmetrical. According to the transmission line theory, the directional impedance changes with the angle of the incident electromagnetic wave, resulting in significant differences in the electromagnetic wave absorption efficiency. When the electromagnetic wave is incident on the medium, a plane is formed, and different incident angles will cause changes in the equivalent impedance according to the Doppler effect. This unique characteristic opens up more possibilities for the practical application of metamaterials. Due to this difference, the absorption characteristics of electromagnetic waves change from continuous frequency absorption to multi-frequency absorption peaks in the K band. Specifically, at an incident angle of 15°, three absorption peaks were observed, located at 21.17 GHz, 23.16 GHz, and 24.20 GHz, respectively. At 30°, six absorption peaks were observed in the K band, which were 18.50 GHz, 19.97 GHz, 20.91 GHz, 22.11 GHz, 23.88 GHz and 24.78 GHz. At 45°, there were four absorption peaks, which were 18.14 GHz, 19.69 GHz, 22.19 GHz and 24.60 GHz. At 60°, there were three absorption peaks, which were 18.01 GHz, 19.41 GHz and 24.54 GHz. At 75°, one absorption peak was observed, which was 19.21 GHz.

[0035] For the TM mode, when the electromagnetic wave is incident in a fixed direction, the electric field component is located in the xy plane, while the magnetic field component is perpendicular to the propagation direction, forming a perpendicular relationship between the magnetic field and the electric field. In different polarization modes, the rotation angle of the material has a significant effect on the absorption bandwidth. In the range of 0° to 90°, the absorption bandwidths of 0° and 90° overlap and are consistent with the simulation results of the TE mode, indicating that at these two angles, the structure is insensitive to both TE and TM modes. Figure 5 As shown in (c), only a low-bandwidth absorption peak is observed at 15°, while the electromagnetic wave absorption efficiency at other angles is generally less than 80%. In the TM mode, the transmission and reflection of electromagnetic waves can be equivalent to impedance form through transmission line theory. Due to the change of the incident angle, the impedance of the asymmetric structure changes accordingly, and there are significant differences between the TE and TM modes in different directional components, which is the reason for the different oblique incidence absorption curves of the two.

[0036] like Figure 5As shown in (d), in the TM mode, there is a specific frequency absorption phenomenon at a specific angle. For example, at 15°, two absorption peaks are observed, located at 24.20 GHz and 24.89 GHz respectively; at 30°, there is an absorption peak at 24.22 GHz; at 45°, the absorption peak is located at 24.32 GHz; at 60°, the absorption peak is located at 23.95 GHz; and at 75°, three absorption peaks are observed, located at 23.28 GHz, 23.56 GHz and 25.06 GHz respectively.

[0037] like Figure 6 As shown, in some embodiments, the structure of the metamaterial absorber can be fitted by inductance and capacitance. The metal patch can be equivalent to an inductor in the circuit, and the gap between the metal patches can be equivalent to a capacitor. In the ADS software, the unit structure of the metamaterial can be fitted by connecting the inductor and the capacitor in series or in parallel. The equivalent circuit of the metamaterial is fitted by the R-L-C structure, and the values ​​of R, L, and C are tuned to simulate the S parameters in the ADS software. Its essence is an LC oscillation circuit, and the feasibility can be verified by comparing the fitting equivalent circuit with the simulation.

[0038] like Figure 7 As shown, in some embodiments, in order to verify the absorption characteristics of the metamaterial absorber in the K band of this article, the absorbing structure is measured in kind and compared with the simulation results. First, a single broadband horn antenna is placed in a darkroom, and the back all-metal backboard of the metamaterial absorber is tested as an ideal reflection structure. Then the front structure is tested. The absorbing structure is tested in the form of a broadband horn antenna in a self-transmitting and self-receiving manner. At the same time, a vector network tester is connected to observe its S parameters. Afterwards, two broadband horn antennas are used for testing, and the S parameters and wave absorption characteristics are compared and verified by comparing the test results of the previous single horn antenna. One of the two horn antennas is a transmitting antenna, and the other is a receiving antenna and is connected to a vector network analyzer. Before testing the structure, the previous operation is repeated, and the all-metal back is first used as an ideal reflection structure, and then the front structure is tested to achieve the best effect. After comparing the two tests, in the physical test, when the antenna transmits and receives electromagnetic waves, the beam will have a certain path loss and the position requirements of the metamaterial absorbing structure are also very strict in each set of measurements. Even in the presence of errors, the S parameter results of the absorber under normal incidence are basically consistent with the S parameters simulated in the CST software, and the deviation is within the normal range.

[0039] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, 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 high-bandwidth metamaterial absorber based on K-band, characterized by: The metamaterial absorber has a three-layer structure, which is composed of a metal resonance layer, a dielectric layer and a metal bottom plate stacked in sequence from top to bottom; the metal resonance layer is composed of an outer open resonance square ring, an open resonance circular ring and a resonance circular ring nested together, and the open resonance circular rings are connected to the resonance circular rings by two metal strips inclined at 45°; its overall structure is 45° symmetrical.

2. The K-band high-bandwidth metamaterial absorber according to claim 1, characterized in that: The outermost open resonant square ring has four openings located at the center of the four sides respectively, the opening size is d=0.5mm, the resonant ring size is 7.75mm, and the width is 1.24mm.

3. The K-band high-bandwidth metamaterial absorber according to claim 1, characterized in that: The radius of the open resonant ring in the middle is R1=2.9mm, the width of the ring is 0.4mm, and its opening direction intersects the two metal patches at 90 degrees. The radius of the resonant ring is R3=1.4mm, the width of the ring is 0.5mm, and the length of the rectangular metal patch is b=1.061mm and the width is 0.58mm.

4. The K-band high-bandwidth metamaterial absorber according to claim 1, characterized in that: The dielectric layer is made of FR-4 material and has a square structure. Its size is P=9 mm and its thickness is h=1.575 mm.

5. The K-band high-bandwidth metamaterial absorber according to claim 1, characterized in that: The metal bottom plate is a metal copper full-cover structure with a thickness of h3=0.035mm, a square structure and a size of P=9mm.

6. The K-band high-bandwidth metamaterial absorber according to claim 1, characterized in that: The K-band based high-bandwidth metamaterial absorber can achieve high-bandwidth absorption of electromagnetic waves in a continuous frequency band.

7. The K-band high-bandwidth metamaterial absorber according to claim 1, characterized in that: The K-band based high bandwidth metamaterial absorber is equivalently fitted to an RLC circuit.

8. The K-band high-bandwidth metamaterial absorber according to claim 1, characterized in that: The K-band based high bandwidth metamaterial absorber is measured in reality, and its S parameters are compared with the S parameters obtained by simulation.

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