A Perfect Scattering Reduction Metamaterial Based on Artificial Surface Plasmons

Abstract

The present invention proposes a perfect scattering reduction coding metamaterial based on artificial surface plasmons. The metamaterial includes a first metal layer, an SSPPs layer, and a second metal layer from top to bottom. The SSPPs layer adopts a gradient metal strip structure, and periodically, mirror-symmetric, and parallel-arranged gradient metal strips are vertically attached to the central axis. By adjusting the number and size of the metal strips, the dispersion characteristics and loss characteristics of the structure can be controlled, ultimately affecting the amplitude and phase of the reflected wave. This adjustment method can keep the phase of the reflected wave unchanged within a relatively wide band. The present invention constructs two types of units, 0 and 1. The reflection amplitude of the 0 unit remains near 0° within a wide band; the reflection amplitude of the 1 unit is constantly 180°. By arranging them in a certain proportion, the scheme for perfect backward scattering can be obtained, and a scattering reduction of -30 dB can be achieved. This scheme makes full use of the three-dimensional space and has the characteristics of simple structure, easy processing, and light weight.

Description

Technical Field

[0001] The present invention relates to the field of electromagnetic stealth technology, and particularly to a broadband absorber of spoof surface plasmon polaritons (SSPPs) and a coding metamaterial. Background Art

[0002] In the field of national defense and military, electromagnetic stealth technology can avoid the tracking and detection of enemy radars, making weaponry disappear from the view of enemy radar detectors, thereby enhancing the battlefield survival ability of weaponry; in daily life, electromagnetic stealth technology can be used to reduce the electromagnetic leakage phenomenon of various electronic devices and mitigate the negative impacts of electromagnetic waves on the human body and the environment. Therefore, electromagnetic stealth technology has wide applications in both military and civilian fields, and its primary feature is to reduce the radar cross section (RCS, scattering) of the target.

[0003] SSPPs have a dispersion curve similar to that of surface plasmon polaritons, and can excite a surface wave on the surface of a metal structure. Its group velocity is less than the speed of light in vacuum, becoming the excitation of a slow wave mode. People can regulate the dispersion characteristics and loss characteristics of SSPPs by adjusting the parameters of the artificial structure, thereby exciting slow waves in a specified frequency band, and then realizing the absorption of electromagnetic waves by introducing a lossy medium.

[0004] A coding metamaterial is composed of two units, 0 and 1. The design of its 0 and 1 units, the arrangement of the units, and the proportion of the units can all be flexibly designed, with a very high degree of design freedom and wide applications in various fields.

[0005] Currently, there are studies on electromagnetic wave absorption based on SSPPs. For example, the literature (Pang Y Q, Wang J F, Qu S B, et al. Spatial k-dispersion engineering of spoof surface plasmon polaritons for customized absorption [J]. Scientific Reports, 2016, 6: 29429.) proposed a broadband electromagnetic wave absorber with customizable absorption, but there is still room for improvement in the absorption performance of this absorber.

[0006] Currently, there are also studies on improving the wave absorption performance of SSPPs absorbers. For example, the literature (Shen Y, Zhang J Q, Qu S B, et al. Merging absorption bands of plasmonic structures via dispersion engineering[J]. Appl. Phys. Lett, 2018, 112: 254103.) proposed a method to expand the wave absorption bandwidth of SSPPs absorbers. However, achieving perfect scattering reduction is meaningful in some fields, and there has been no work on achieving perfect scattering reduction based on SSPPs. Summary of the Invention

[0007] Aiming at the deficiencies in the prior art, the present invention provides a perfect scattering reduction coding metamaterial based on SSPPs. By controlling the dispersion and loss of SSPPs, it can achieve -10 dB absorption within a wideband, while keeping the reflection phase near 0°, and construct a 0 unit. Then, arrange the 0 unit with a small number of 1 units (perfect reflection, reflection phase always 180°) to construct a coding metamaterial to achieve perfect scattering reduction. This metamaterial also has the characteristics of thin thickness, light weight, and simple structure.

[0008] To achieve the above technical objectives, the technical solution adopted by the present invention is as follows:

[0009] A perfect scattering reduction metamaterial based on surface plasmon polaritons (SPPs) includes, from top to bottom, a first metal layer, a surface plasmon polaritons (SSPPs) layer, and a second metal layer. The second metal layer is the bottom layer, and the SSPPs layer is arranged in a grid pattern on the second metal layer. A part of the SSPPs layer is provided with the first metal layer as the top layer. The first metal layer is used to achieve total reflection of electromagnetic waves, ensuring that the reflection phase is always 180°. The SSPPs layer is used to strongly absorb electromagnetic waves in a certain frequency band and keep the phase of its reflected wave near 0° within a wideband. The second metal layer is used to provide a reflecting surface to make the transmission zero.

[0010] A further optimized solution of the present invention is:

[0011] The above-mentioned metamaterial is composed of several basic units of 0 and 1. Among them, both the 0 and 1 basic units have an SSPPs layer and a second metal layer. The difference is that only the 1 unit has a first metal layer.

[0012] The above-mentioned SSPPs layer includes a plurality of horizontally and vertically absorbing bodies with the same structure. These absorbing bodies are connected end to end to form a grid. Each absorbing body includes a dielectric layer and a silver paste pattern attached thereto. The silver paste pattern includes a central axis and periodically, mirror-symmetrically, and parallelly arranged tapered silver paste strips vertically attached thereto. The lengths of the tapered silver paste strips increase successively from top to bottom.

[0013] The above-mentioned first metal layer and second metal layer are arranged in parallel, and the SSPPs layer is arranged perpendicular to the first metal layer and the second metal layer.

[0014] The thickness of the above-mentioned SSPPs layer is 8 mm.

[0015] Denote the bottommost side of the tapered silver paste strip as the first strip. Then, the lengths of the tapered silver paste strips are arranged according to the following functional relationship:

[0016]

[0017] In the formula, L w is the length of the w-th strip, L 1 is the length of the bottom strip, and g is the gradient coefficient.

[0018] The periodic dimensions of both the 0 and 1 basic unit structures are 20 mm; for the 1 unit, the cross-sectional size of the metal thin film patch serving as the first metal layer is 20 mm × 20 mm.

[0019] The above-mentioned second metal layer uses a conductive material that totally reflects electromagnetic waves.

[0020] The arrangement of the 0 and 1 basic units is randomly arranged, and the quantity ratio of the 0 basic unit to the 1 basic unit is 1:4.

[0021] The present invention has the following advantages:

[0022] In the perfect scattering reduction coding metamaterial based on SSPPs of the present invention, the 0 unit has a certain absorption effect on electromagnetic waves. The phase difference between the small amount of electromagnetic waves reflected on the 0 unit and the electromagnetic waves reflected on the 1 unit is about 180°. Therefore, these electromagnetic waves will be scattered in other directions, so perfect scattering reduction can be achieved. This material also has the characteristics of thin thickness, light weight, and simple structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 is the overall schematic diagram of the present invention;

[0024] Figure 2 is the three-dimensional diagram of the unit structure of the present invention. The left figure is the 0 unit, and the right figure is the 1 unit;

[0025] Figure 3 is the plan view of the SSPPs layer of the present invention;

[0026] Figure 4 This is the reflection coefficient curve graph of the metamaterial in the embodiment of the present invention; wherein (a) is the reflection phase of the 0 and 1 units, and (b) is the comparison between the scattering reduction curve of the random arrangement of the two in a ratio of 1:4 and the scattering reduction curve of the 0 unit.

[0027] The reference signs in the drawings are: the first metal layer 1, the SSPPs layer 2, and the second metal layer 3. Specific embodiments

[0028] The present invention will be further clarified below in conjunction with the drawings and specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. After reading the present invention, various equivalent modifications of the present invention by those skilled in the art fall within the scope defined by the appended claims of this application.

[0029] An embodiment of the present invention discloses a perfect scattering reduction coding metamaterial based on spoof surface plasmonic polariton (SSPPs). The three-dimensional structures of its 0 and 1 units are as Figure 2 shown. Whether it is the 0 unit or the 1 unit, the height is h and the period is p. Taking the 1 unit as an example and looking from top to bottom, the first layer is the first metal layer 1, which is used to achieve total reflection of electromagnetic waves, so the reflection amplitude is 0 dB and the reflection phase is 180°; the second layer is the SSPPs layer 2, which uses its dispersion effect to achieve slow wave transmission in a certain frequency band, and then introduces a lossy dielectric with a thickness of d to achieve absorption of electromagnetic waves, so that the reflection amplitude of the 0 unit is less than -10 dB in the broadband and the reflection phase is about 0° in the absorption band; the third layer is the second metal layer 3, which is the metal bottom plate and provides a reflection surface to make the transmission zero. Among them, the first metal layer is connected to the second metal layer through the SSPPs layer. In this example, the material structure parameters are as follows: h = 8 mm, p = 20 mm, d = 0.762 mm.

[0030] As Figure 1 shown, the coding metamaterial includes orthogonally arranged 0 units and 1 units to achieve insensitivity to the polarization state of electromagnetic waves. The two are randomly arranged in a plane of 300×300 mm and maintain a ratio of 0 and 1 units of 4:1.

[0031] The planar structure of the SSPPs layer is as Figure 3 shown. In this example, the number of silver paste strip structures in one SSPPs layer is 20, and the line width of a single strip is w. The lengths of the tapered strips increase sequentially from top to bottom. Denote the bottom edge as the first strip, then the lengths of each strip should adopt the functional relationship to achieve the arrangement, where L w is the length of the w-th strip, and L 1is the length of the bottom strip, and g is the gradient coefficient. In this example, the material structure parameters are as follows: w 0 = 0.4 mm, w = 0.2 mm, L 1 = 18.5 mm, L 20 = 9.33 mm, g = 27.

[0032] The CST STUDIO SUITE software is used to perform theoretical calculations on the model, as shown in Figure 4 (a), which shows the reflection phases of Unit 0 and Unit 1 under normal incidence. The specially designed SSPPs layer can keep the reflection phase of Unit 0 near 0° (within ±37°) in the range of 3.66 - 9.85 GHz. Here, due to the reflection of the first metal layer, the reflection phase of Unit 1 is constantly 180°.

[0033] The simulation results show that the material of Unit 0 can achieve a scattering reduction of -10 dB (i.e., the absorption rate is greater than 90%) in the frequency band of 4.72 - 8.91 GHz, and the reflection phase in this frequency band is near 0°. If Unit 0 and Unit 1 are randomly arranged in a ratio of 4:1, since the reflection phase difference between the two units is near 180°, the electromagnetic waves that are not absorbed but reflected on Unit 0 will cancel out the scattered electromagnetic waves that are completely reflected on Unit 1, further reducing the scattering of the coded metamaterial in this frequency band. The scattering reduction of the overall structure is also shown in Figure 4 (b), which verifies the feasibility of this scheme.

[0034] FR-4 board with a relative dielectric constant of 4.3 and a loss tangent angle of 0.025 is used as the high-loss dielectric. Silver paste with a sheet resistance of 1 Ohm / sq is printed on the dielectric board through screen printing technology. The first metal layer can use thin metal sheets such as aluminum foil and tin foil, and the metal bottom plate can use metals such as copper, iron, and aluminum.

[0035] The above is only the preferred implementation mode of the present invention. The protection scope of the present invention is not limited to the above embodiments. All technical solutions within the idea of the present invention belong to the protection scope of the present invention. It should be pointed out that for those of ordinary skill in the art, several improvements and refinements made without departing from the principle of the present invention should be regarded as within the protection scope of the present invention.

Claims

1. A perfect scattering reduction metamaterial based on artificial surface plasmons, Characterized in that: It successively includes a first metal layer (1), an artificial surface plasmon SSPPs layer (2), and a second metal layer (3) from top to bottom; the second metal layer (3) is the bottom layer, the SSPPs layer (2) is arranged in a grid pattern on the second metal layer (3), and a part of the SSPPs layer (2) is provided with the first metal layer (1) as the top layer. The first metal layer (1) is used to achieve total reflection of electromagnetic waves, ensuring that the reflection phase is constantly 180°; the SSPPs layer (2) is used to strongly absorb electromagnetic waves in a certain frequency band and keep the phase of its reflected wave near 0° within a broadband; the second metal layer (3) is used to provide a reflecting surface to make the transmission zero; The metamaterial is composed of several basic units of 0 and 1. Among them, both the basic units of 0 and 1 have the SSPPs layer (2) and the second metal layer (3). The difference is that only the basic unit of 1 has the first metal layer (1); The second metal layer (3) uses a conductive material that totally reflects electromagnetic waves; The arrangement of the basic units of 0 and 1 is randomly arranged, and the quantity ratio of the basic unit of 0 to the basic unit of 1 is 1:

4.

2. A perfect scattering reduction metamaterial based on artificial surface plasmons according to claim 1, Characterized in that: The SSPPs layer (2) includes a plurality of laterally absorbing bodies and longitudinally absorbing bodies with the same structure. These absorbing bodies are connected end to end to form a grid. Each absorbing body includes a dielectric layer and a silver paste pattern attached thereto. The silver paste pattern includes a central axis and periodically, mirror-symmetrically, and parallelly arranged gradient silver paste strips vertically attached thereto. The lengths of the gradient silver paste strips increase successively from top to bottom.

3. A perfect scattering reduction metamaterial based on artificial surface plasmons according to claim 1, Characterized in that: The first metal layer (1) and the second metal layer (3) are arranged in parallel, and the SSPPs layer (2) is arranged perpendicular to the first metal layer (1) and the second metal layer (3).

4. A perfect scattering reduction metamaterial based on artificial surface plasmons according to claim 3, Characterized in that: The thickness of the SSPPs layer (2) is 8 mm.

5. A perfect scattering reduction metamaterial based on artificial surface plasmons according to claim 3, Characterized in that: Denote the bottommost side of the gradient silver paste strip as the first strip. Then, the lengths of the gradient silver paste strips are arranged according to the following functional relationship: where L w is the length of the w-th thin strip, and L 1 is the length of the bottom thin strip, and g is the gradient coefficient.

6. A perfect scattering reduction metamaterial based on artificial surface plasmons according to claim 5, Characterized in that: The periodic dimensions of the basic unit structures of 0 and 1 are both 20 mm; for the basic unit of 1, the cross-sectional size of the metal thin film patch serving as the first metal layer (1) is 20 mm × 20 mm.

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