Broadband Radar Cross Section Reduction Metasurface with Reflection and Scattering Characteristics

Abstract

The present invention discloses a broadband radar cross section reduction metasurface with reflection and scattering characteristics, which includes a number of square structural units arranged in a set manner. Each square structural unit includes a bottom metal plate unit, an upper special-shaped metal strip unit, and a dielectric substrate unit disposed between the bottom metal plate unit and the upper special-shaped metal strip unit. The present invention can integrate two special functions within a relatively wide frequency band, namely the reflection and scattering of incident electromagnetic waves, so as to achieve the functions of specular reflection and RCS reduction.

Description

Technical Field

[0001] The present invention belongs to the field of microwave technology and relates to a broadband radar cross section reduction metasurface with reflection and scattering characteristics. Background Art

[0002] The rapid development of the modern electromagnetic environment has put increasingly stringent requirements on electronic systems. Therefore, various types of metasurfaces have received extensive attention due to their ability to manipulate the amplitude, phase, and polarization of incident electromagnetic waves. Metasurfaces are usually composed of a series of sub-wavelength units with different geometric parameters and are commonly used to achieve characteristics such as beamforming, gain enhancement, or reduction of radar cross section (RCS). Among them, RCS reduction is a basic requirement for most electronic systems.

[0003] In recent years, coded metasurfaces with diffuse reflection characteristics have been widely reported. This coded metasurface can effectively reduce the backscattering RCS because it can redistribute the energy of incident electromagnetic waves in different directions. Compared with traditional perfect metamaterial electromagnetic wave absorbers or circuit analog absorbers loaded with lossy elements, the coded metasurface has the advantages of low cost, simple processing, wide operating bandwidth, and small profile. Unfortunately, these metasurfaces with RCS reduction usually have only a single function or operate only in a single frequency band. There is little research on RCS reduction metasurfaces with multi-functional and multi-band characteristics. In addition, integrating multiple functions and multi-bands into one device highly meets the needs of modern technology and can better adapt to complex electromagnetic environments.

[0004] Therefore, how to design an RCS reduction metasurface with multi-functional integration and multi-band cooperation remains a challenge. Summary of the Invention

[0005] In view of this, the present invention provides a broadband RCS reduction metasurface with reflection and scattering characteristics, which can integrate two special functions, namely reflection and scattering of incident electromagnetic waves, within a relatively wide frequency band, so as to achieve the functions of specular reflection and RCS reduction.

[0006] The technical solution of the present invention is implemented as follows:

[0007] A broadband radar cross section reduction metasurface with reflection and scattering characteristics, comprising a plurality of square structural units arranged in a set manner. Each square structural unit includes a bottom metal plate unit, an upper special-shaped metal strip unit, and a dielectric substrate unit disposed between the bottom metal plate unit and the upper special-shaped metal strip unit.

[0008] Further, the upper-layer deformed metal strip unit includes a first deformed metal strip and a second deformed metal strip, and the first deformed metal strip and the second deformed metal strip are arranged along a diagonal line on the upper surface of the dielectric substrate unit.

[0009] Further, the second deformed metal strip is obtained by rotating the first deformed metal strip 180° around the center of the dielectric substrate unit, and the two do not contact each other.

[0010] Further, the first deformed metal strip is composed of 4 metal strips connected to each other, where two metal strips are respectively arranged along two adjacent sides of the dielectric substrate unit and have equal lengths; the other two metal strips are parallel to the diagonal line of the dielectric substrate unit, and the lengths of the two are unequal and there is a spacing.

[0011] Further, the upper-layer deformed metal strip unit and the bottom-layer metal plate unit are made of conductive metal materials.

[0012] Further, the dielectric substrate unit is a PCB board.

[0013] Beneficial effects:

[0014] 1. The broadband RCS reduction metasurface provided by the present invention introduces two specular reflection bands in the broadband RCS reduction frequency band, and better realizes multi-functional integration and multi-band cooperation, which is beneficial to the application of the metasurface in modern complex electronic systems.

[0015] 2. The metasurface provided by the present invention does not load lumped devices, such as lumped resistors, capacitors and other components. Therefore, it can be processed by a simple PCB processing technology, so it has low cost, high precision, and can work stably in high frequency bands (K, Ka and above frequency bands). Description of the drawings

[0016] Figure 1 (a) is a three-dimensional schematic diagram of the metasurface structure unit of the present invention.

[0017] Figure 1 (b) is a schematic diagram of the deformed metal strip of the metasurface structure of the present invention.

[0018] Figure 2 is the co-polarization reflection coefficient of the metasurface of the present invention under the incidence of plane electromagnetic waves.

[0019] Figure 3 (a) is the surface current distribution diagram of the metasurface of the present invention at the reflection point f1.

[0020] Figure 3 (b) is the surface current distribution diagram of the metasurface of the present invention at the reflection point f2.

[0021] Figure 4(a) is the trend graph of the reflection point f1 of the metasurface of the present invention varying with the length l1 of the metal strip 3.

[0022] Figure 4 (b) is the trend graph of the reflection point f2 of the metasurface of the present invention varying with the length l2 of the metal strip 4.

[0023] Figure 5 is the reflection coefficient of the broadband reflection structure realized by the metasurface of the present invention.

[0024] Figure 6 is the comparison of the RCS reduction performance realized by the metasurface of the present invention. Detailed implementation manners

[0025] The present invention will be described in detail below with reference to the accompanying drawings and by way of examples.

[0026] The present invention provides a broadband RCS reduction metasurface with reflection and scattering characteristics. Refer to Figure 1 (a), Figure 1 (a) is a schematic diagram of the shaped metal strips of the metasurface structure of the present invention. The metasurface structure unit consists of three parts, namely the metal plate at the bottom layer, the first and second shaped metal strips at the upper layer, and the dielectric substrate layer disposed therebetween. The overall thickness t of the unit structure is 2.3 mm, and the period p is 6.5 mm. Refer to Figure 1 (b), Figure 1 (b) is a schematic diagram of the shaped metal strips of the metasurface structure of the present invention. The first shaped metal strip and the second shaped metal strip are rotationally symmetric about the center of the square unit structure by 180°. Each of the shaped metal strips consists of 4 metal strips, namely metal strips 1-4. Among them, metal strip 1 and metal strip 2 are respectively parallel to two adjacent sides of the square unit structure and are connected at the vertex, and the lengths of metal strip 1 and 2 are equal, and their length l is 3.5 mm. Metal strip 3 and metal strip 4 are parallel to the diagonal of the square unit structure, and their lengths are different, being l1 = 3.3 mm and l2 = 2.7 mm respectively, and there is a certain distance d of 0.6 mm between them. Due to the different lengths of metal strip 3 and 4, this structure can introduce two specular reflection bands within the broadband RCS reduction frequency band.

[0027] Refer to Figure 2 , Figure 2 is the co-polarized reflection coefficient of the metasurface of the present invention under the incidence of plane electromagnetic waves. The metasurface of the present invention realizes good polarization conversion characteristics within the frequency band range of 12.54 GHz to 29.32 GHz, and introduces two reflection points f1 = 18.6 GHz and f2 = 21.5 GHz within the band, realizing multi-functional integration and multi-band cooperation characteristics. In order to reveal the formation principle of these two reflection points, Figure 3(a) and (b) show the structural surface current distribution diagrams at these two reflection points, where the darker the color, the stronger the surface current intensity. On paths A and B, the current intensity is minimum at both ends and reaches the maximum in the middle of the paths. Therefore, two half-wavelength resonances are formed on both of these paths, and their resonant frequencies can be calculated from the lengths of paths A and B, that is

[0028]

[0029]

[0030] where c is the speed of light, L pathA = l + l1 and L pathB = l + l2 are the lengths of paths A and B, and their lengths can be changed by controlling the lengths l1 and l2 of metal strips 3 and 4. ε r,eff is the effective dielectric constant of the dielectric substrate and can be expressed as

[0031]

[0032] where ε r is the dielectric constant of the dielectric substrate, t is the thickness of the dielectric substrate, and w is the width of the metal strip.

[0033] It can be seen from formulas (1) and (2) that the specular reflection points f1 and f2 will shift with the lengths l1 and l2 of metal strips 3 and 4, as Figure 4 (a) and (b) show. When the length l1 of metal strip 3 increases from 2 mm to 3.5 mm while the length l2 of metal strip 4 is fixed at 2.7 mm, the reflection point f1 shifts from 26.42 GHz to 17.65 GHz, while the reflection point f2 remains basically unchanged. Conversely, the reflection point f2 is negatively correlated with the length l2 of metal strip 4, while the reflection point f1 remains unchanged because the length l1 of metal strip 3 remains unchanged. Thus, when the lengths of metal strips 3 and 4 are close, that is, l1 = 3.4 mm and l2 = 3.2 mm, a broadband specular reflection band can be constructed, as Figure 5 shown. It can be seen that good cross-polarization reflection characteristics are achieved in two wide frequency bands from 12.05 GHz to 16.18 GHz and from 20.2 GHz to 28.85 GHz, while good specular reflection characteristics are achieved in the frequency band from 17.76 GHz to 19.44 GHz. Thus, by arranging the unit structures in a specific order, broadband RCS reduction on both sides and broadband specular reflection in the middle can be achieved, thereby integrating the reflection and scattering characteristics in one structure, as Figure 6 shown. Figure 6Comparing the metasurface of the present invention with a metal plate of the same area, a 10 dB RCS reduction is achieved in two frequency bands from 11.54 GHz to 16.02 GHz and from 19.38 GHz to 29.32 GHz (as shown by the gray area), while good specular reflection performance is maintained in the intermediate frequency bands of 17.36 GHz and 18.52 GHz.

[0034] Compared with the prior art, the significant advantages of the present invention are as follows: By means of a simple and lightweight two-dimensional topological structure, a multifunctional and multi-band RCS reduction metasurface with scattering and reflection characteristics is constructed, which can better adapt to modern electronic systems with high complexity and high integration. At the same time, the metasurface of the present invention has low processing difficulty, low cost, and thin thickness, and can work stably in high frequency bands, which is beneficial to be widely applied in communication and radar systems.

[0035] In summary, the above are only the preferred embodiments of the present invention and are not intended to limit the protection scope of 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 radar cross-section reduction metasurface with reflection and scattering characteristics, characterized in that, It includes a number of square structural units arranged in a set manner. Each square structural unit includes a bottom metal plate unit, an upper-layer special-shaped metal strip unit, and a dielectric substrate unit disposed between the bottom metal plate unit and the upper-layer special-shaped metal strip unit; The upper-layer special-shaped metal strip unit includes a first special-shaped metal strip and a second special-shaped metal strip. The first special-shaped metal strip and the second special-shaped metal strip are arranged along a diagonal line on the upper surface of the dielectric substrate unit; The second special-shaped metal strip is obtained by rotating the first special-shaped metal strip 180° around the center of the dielectric substrate unit, and the two do not contact each other; The first special-shaped metal strip is composed of 4 metal strips connected to each other. Two of the metal strips are respectively arranged along two adjacent sides of the dielectric substrate unit and have equal lengths; the other two metal strips are parallel to the diagonal line of the dielectric substrate unit, and the two have unequal lengths and there is a spacing between them.

2. The broadband radar cross-section reduction metasurface with reflection and scattering characteristics according to claim 1, characterized in that, The upper-layer special-shaped metal strip unit and the bottom metal plate unit are made of conductive metal materials.

3. The broadband radar cross-section reduction metasurface with reflection and scattering characteristics as claimed in claim 1, wherein The dielectric substrate unit is a PCB board.

Images