阅读说明：本技术 随机相位梯度多极化、极化无关广角rcs缩减超表面 (Random phase gradient multi-polarization independent wide-angle RCS (radar cross section) reduced super surface ) 是由 董果香 解川川 于 2021-08-16 设计创作，主要内容包括：本发明属于新型人工电磁材料和雷达隐身技术领域,公开了一种随机相位梯度多极化、极化无关广角RCS缩减超表面,随机相位梯度多极化、极化无关广角RCS缩减超表面由多种类型的非周期单元结构组成,包括金属图案层、介质基板和金属背板,上层金属图案层位于介质基板的上表面。多种类型的非周期单元由两个基本单元或一个基本单元组成；其他类型的单元最多由两个基本单元组成,形状为v或x结构,各个单元随机分布在所述超表面上。本发明超表面的单元没有特定的周期,通过改变单元上金属切割线的旋转角度以及采用多种类型单元来产生随机相位梯度,入射波被随机相位梯度打散至任意方向,实现了多极化、极化无关和广角RCS缩减特性。(The invention belongs to the technical field of novel artificial electromagnetic materials and radar stealth, and discloses a random phase gradient multi-polarization-independent wide-angle RCS reduced super-surface which is composed of various non-periodic unit structures and comprises a metal pattern layer, a dielectric substrate and a metal back plate, wherein the upper metal pattern layer is positioned on the upper surface of the dielectric substrate. The multiple types of non-periodic units are composed of two basic units or one basic unit; other types of cells consist of at most two elementary cells, shaped in a v or x structure, with the individual cells randomly distributed over the super-surface. The units on the super-surface have no specific period, the incident wave is scattered to any direction by the random phase gradient by changing the rotation angle of the metal cutting line on the units and adopting various types of units to generate the random phase gradient, and the multipolarization, polarization independence and wide-angle RCS reduction characteristics are realized.)

1. The random phase gradient multi-polarization-independent wide-angle RCS reduced super-surface is characterized by consisting of multiple types of non-periodic unit structures and comprising a metal pattern layer, a dielectric substrate and a metal back plate, wherein the upper metal pattern layer is located on the upper surface of the dielectric substrate.

2. The random phase gradient multipolar, polarization independent wide angle RCS reduced metasurface of claim 1, wherein the plurality of types of aperiodic elements consists of two elementary elements or one elementary element;

other types of elements consist of at most two elementary elements, shaped in a "v" or "x" structure, with the individual elements randomly distributed on the super-surface.

3. The random phase gradient multipolarization, polarization independent wide angle RCS reduced super-surface of claim 2, wherein the basic unit is a single metal cut line with random rotation angle, the thickness of the metal cut line is 35 μm, and the geometric parameters w-0.6 mm and l-5.6 mm.

4. The random phase gradient multipolar, polarization independent wide angle RCS reduced metasurface of claim 2, wherein distribution of the base units is a uniform distribution controlled by VBA language based programs and CST simulation software.

5. The random phase gradient multipolar, polarization independent wide angle RCS reduced super surface of claim 1, wherein the dielectric substrate is FR4, a relative dielectric constant and a loss tangent of 2.65 and 0.001, respectively, and a thickness h of 2.5 mm.

6. The random phase gradient multipolar, polarization independent wide angle RCS reduced metasurface of claim 1, wherein the plurality of types of non-periodic elements have no specific period, and wherein the random phase gradient is generated by changing the rotation angle of a metal cutting line on the elements and using the plurality of types of elements.

7. The random phase gradient multipolar, polarization independent wide angle RCS reduced metasurface of claim 6, wherein when provided with an appropriate phase gradient, the metasurface is capable of steering electromagnetic waves in any direction in space as follows:

where Ki is the wavevector of the incident wave, θ i is the incident angle formed by Ki and z-axis, Kr is the wavevector of the reflected wave, θ r is the projection of Kr on the ZOY plane and the reflection angle formed by Kr, φ r is the reflection angle formed by the projection of Kr on the ZOY plane and the z-axis,andare the x-polarization component and the y-polarization component of the phase gradient on the super-surface.

8. The random phase gradient multipolar, polarization independent wide angle RCS reduced metasurface of claim 6, wherein when there are a plurality of phase gradients and the phase gradients have the same scalar and direction, the reflected waves have the same direction.

9. The random phase gradient multipolar, polarization independent wide angle RCS reduced super-surface of claim 6, wherein when a super-surface has a plurality of random phase gradients, incident waves impinge on the super-surface, reflected waves are controlled by the random phase gradients, and the phase gradients formed on the super-surface have random scalar quantities and directions, resulting in the incident waves being reflected in different directions and thereby scattered; the phase gradient may be represented by:

wherein d phi represents the phase difference between adjacent units on the super surface, and dx and dy represent the distances between the adjacent units in the x direction and the y direction respectively; realizing random phase gradient on the super surface by making the phase difference d phi and the distances dx and dy random or increasing the diversity of the phase difference d phi, wherein the random phase gradient can scatter circularly polarized waves and linearly polarized waves, so that RCS (polarization independent resonance spectroscopy) is reduced;

when the incidence angle is increased, random phase gradients can be formed on the super-surface, so that RCS is reduced when the circularly polarized wave and the linearly polarized wave are obliquely incident.

10. The random phase gradient multi-polar, polarization independent wide angle RCS reduced super-surface of claim 6, wherein the reflection phase of the basic cell is insensitive to periodic variations for RHCP incident waves when the rotation angle is specified, the basic cell being a cell with a certain period.

Technical Field

The invention belongs to the technical field of novel artificial electromagnetic materials and radar stealth, and particularly relates to a random phase gradient multi-polarization independent wide-angle RCS (radar cross section) reduced super surface.

Background

At present, the stealth technology is mainly realized by reducing the Radar Cross Section (RCS) of a detected target, and the main methods for reducing the RCS include radar absorbing materials and scattered field redirection. The radar wave-absorbing material can absorb electromagnetic waves, reduce RCS of a covered object, and can adopt multiple layers of wave-absorbing materials to expand RCS and reduce bandwidth. The fringe field can be artificially controlled using fringe field reorientation techniques, commonly used for fringe field reorientation techniques, such that RCS is reduced to a desired extent.

Metamaterials, which are composed of sub-wavelength elements with exceptional electromagnetic properties, are widely used in the design of microwave devices and antennas, where one important application is RCS reduction. The additional wave vector generated by the phase gradient super-surface (PGM) proposed in 2012 can control the direction of the electromagnetic wave, resulting in abnormal reflection of the incident wave, confirming that PGM has the potential to reduce backscattering. Reduced RCS can also be achieved with checkerboard super surfaces, which typically consist of two types of AMC or one of different size AMC. All of these super-surface elements have a specific period, which means that only the phase of the super-surface elements can be designed. In addition, most super-surfaces only realize wide-angle RCS reduction under linear polarization waves, and do not realize real polarization independence.

Through the above analysis, the problems and defects of the prior art are as follows: in the prior art, most super surfaces only realize wide-angle RCS reduction under linear polarization waves, and do not realize real polarization independence.

The difficulty in solving the above problems and defects is: how to form random phase gradient on the super surface, so that the electromagnetic wave is incident on the super surface and scattered to other arbitrary directions, and RCS reduction under different polarization forms is realized.

The significance of solving the problems and the defects is as follows: the detection radar is non-directional, electromagnetic waves in different polarization forms can irradiate a target object, and a structure which can only realize good performance under specific conditions has certain limitation, so that the RCS reduction super-surface with multi-polarization and polarization-independent characteristics is necessary to be designed.

Disclosure of Invention

Aiming at the problems in the prior art, the invention provides a random phase gradient multi-polarization independent wide-angle RCS (radar cross section) reduced super surface.

The invention is realized in such a way that the random phase gradient multi-polarization and polarization-independent wide-angle RCS reduced super-surface is composed of various non-periodic unit structures and comprises a metal pattern layer, a dielectric substrate and a metal back plate, wherein the upper metal pattern layer is positioned on the upper surface of the dielectric substrate.

Further, the plurality of types of non-periodic units are composed of two basic units or one basic unit;

other types of elements consist of at most two elementary elements, shaped in a "v" or "x" structure, with the individual elements randomly distributed on the super-surface.

Further, the basic unit is a single metal cutting line with random rotation angle, the thickness of the metal cutting line is 35 μm, and the geometric parameters are w ═ 0.6mm and l ═ 5.6 mm.

Further, the distribution of the basic units is a uniform distribution controlled by programs based on the VBA language and the CST simulation software.

Furthermore, FR4 is adopted as the dielectric substrate, the relative dielectric constant and the loss tangent are respectively 2.65 and 0.001, and the thickness h is 2.5 mm.

Further, the plurality of types of non-periodic cells have no specific period, and random phase gradients are generated by changing the rotation angle of the metal cutting lines on the cells and adopting the plurality of types of cells.

Further, when providing a suitable phase gradient, the super-surface can manipulate electromagnetic waves in any direction in space as follows:

where Ki is the wavevector of the incident wave, θ i is the incident angle formed by Ki and z-axis, Kr is the wavevector of the reflected wave, θ r is the projection of Kr on the ZOY plane and the reflection angle formed by Kr, φ r is the reflection angle formed by the projection of Kr on the ZOY plane and the z-axis,andare the x-polarization component and the y-polarization component of the phase gradient on the super-surface.

Further, when there are many phase gradients and the phase gradients have the same scalar quantity and direction, the reflected waves have the same direction.

Further, when a super-surface has a plurality of random phase gradients, incident waves irradiate on the super-surface, reflected waves are controlled by the random phase gradients, and the phase gradients formed on the super-surface have random scalar quantities and directions, so that the incident waves are reflected in different directions and are scattered; the phase gradient may be represented by:

wherein d phi represents the phase difference between adjacent units on the super surface, and dx and dy represent the distances between the adjacent units in the x direction and the y direction respectively; realizing random phase gradient on the super surface by making the phase difference d phi and the distances dx and dy random or increasing the diversity of the phase difference d phi, wherein the random phase gradient can scatter circularly polarized waves and linearly polarized waves, so that RCS (polarization independent resonance spectroscopy) is reduced;

when the incidence angle is increased, random phase gradients can be formed on the super-surface, so that RCS is reduced when the circularly polarized wave and the linearly polarized wave are obliquely incident.

Further, when the rotation angle is specific, for an RHCP incident wave, the reflection phase of the basic unit is not sensitive to the period change, and the basic unit can be regarded as a unit with a certain period.

By combining all the technical schemes, the invention has the advantages and positive effects that: the units on the super-surface have no specific period, different reflection phases are realized by changing the rotation angle of the metal cutting lines on the units, so that phase gradients are generated, meanwhile, other types of units are adopted, phase differences and reflection differences can be generated compared with basic units, and the diversity of the phase differences is increased, so that random phase gradients can be generated on the super-surface, incident waves are scattered to any direction by the random phase gradients, and the characteristics of multi-polarization, polarization independence and wide-angle RCS reduction are realized. The invention can realize wide-angle RCS reduction on linear polarized waves and circular polarized waves, does not realize wide-angle RCS reduction only under the linear polarized waves, and is a real polarization-independent RCS reduction super surface. For right-hand circularly polarized (RHCP) waves and left-hand circularly polarized (LHCP) waves, RCS reduction amounts are more than 10dB in the ranges of 12.6GHz-17.0GHz and 18GHz-22GHz and the ranges of 12.4GHz-17.0GHz and 18.0GHz-21.8GHz respectively. For x-polarized waves and y-polarized waves, RCS reduction effects of more than 10dB are achieved in the ranges of 12.0GHz-17.0GHz and 13.0GHz-17.0GHz and 17.6GHz-21.8GHz respectively. When the incidence angle is increased, random phase gradients can be formed on the super-surface, and the RCS reduction effect can be achieved by oblique incidence of circularly polarized waves and linearly polarized waves.

The unit of the invention has no specific period, the rotation angle of the metal cutting line on the unit can be changed, and the unit structure comprises a plurality of types, thereby generating random phase gradient. Simulation results and experimental results show that the stealth technology is effectively realized by utilizing random phase gradients, and the invention has the characteristics of multi-polarization, polarization independence and wide-angle RCS reduction.

Drawings

FIG. 1 is a schematic diagram of an abnormal reflection of a super-surface according to an embodiment of the present invention.

Fig. 2 is a schematic diagram illustrating electromagnetic wave control by the phase gradient super surface according to the embodiment of the present invention.

FIG. 3 is a schematic diagram of a random phase gradient multi-polar, polarization independent wide-angle RCS reduced super-surface structure provided by an embodiment of the present invention;

in the figure: figure a, basic unit with rotation angle; and b, a super-surface structure.

Fig. 4 is a schematic diagram of reflection amplitude and reflection phase of a super-surface unit when RHCP waves are vertically incident under different sizes p according to an embodiment of the present invention.

FIG. 5 is a schematic diagram of reflection amplitude and reflection phase of a super-surface with different unit periods p and different rotation angles φ under normal incidence of RHCP waves, provided by an embodiment of the invention.

Fig. 6 is a schematic diagram of reflection amplitude and reflection phase of different units under normal incidence of RHCP waves according to an embodiment of the present invention.

FIG. 7 is a schematic representation of an RCS of a circularly polarized subsurface according to an embodiment of the present invention.

FIG. 8 is a schematic representation of RCS of a linearly polarized subsurface provided by an embodiment of the present invention.

FIG. 9 is a schematic representation of RCS of a circularly polarized wave provided by an embodiment of the present invention at different incident angles;

in the figure: graph a, RHCP wave; graph b, LHCP wave.

FIG. 10 is a schematic representation of RCS of linearly polarized waves provided by embodiments of the present invention at different incident angles;

in the figure: graph a, incident electric field at plane xoz; graph b, incident electric field in the yoz plane.

FIG. 11 is a three-dimensional dual-station RCS comparison plot of 14.2GHz at oblique incidence for PEC and super-surface of the same dimensions provided by an embodiment of the invention.

FIG. 12 is a schematic diagram of an RCS test platform provided by an embodiment of the present invention;

in the figure: FIG. a, super surface sample; FIG. b, experimental setup.

FIG. 13 is a comparative RCS diagram of simulation and testing provided by an embodiment of the present invention;

in the figure: graph a, x-polarized wave; graph b, y-polarized wave; graph c, RHCP wave; graph d, LHCP wave.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

In view of the problems of the prior art, the present invention provides a random phase gradient multi-polarization independent wide-angle RCS reduced super-surface, which is described in detail below with reference to the accompanying drawings.

Those skilled in the art can also implement other steps to provide a random phase gradient multi-polar, polarization independent wide angle RCS reduced super-surface, and the random phase gradient multi-polar, polarization independent wide angle RCS reduced super-surface provided by the present invention of fig. 3 is merely one specific example.

The random phase gradient multi-polarization independent wide-angle RCS reduced super-surface provided by the embodiment of the invention consists of various non-periodic unit structures, and comprises a metal pattern layer, a dielectric substrate and a metal back plate, wherein the upper metal pattern layer is positioned on the upper surface of the dielectric substrate. The invention can realize multi-polarization, polarization independence and wide-angle RCS reduced random phase gradient super surface.

As shown in fig. 3, in the random phase gradient super-surface provided by the embodiment of the present invention, all units have no specific period, and are composed of two basic units or one basic unit, the basic unit is a single metal cutting line with a random rotation angle, the thickness of the metal cutting line is 35 μm, the geometric parameters w is 0.6mm, l is 5.6mm, and the distribution of the basic units is a uniform distribution controlled by a program based on VBA language and CST simulation software; other types of elements consist of at most two elementary elements, shaped in a "v" or "x" configuration, and therefore can generate random phase gradients on the super-surface, on which the individual elements are randomly distributed. The dielectric substrate used was FR4, the relative dielectric constant and the loss tangent were 2.65 and 0.001, respectively, and the thickness h was 2.5 mm.

The units of the super-surface have no specific period, and random phase gradients can be generated by changing the rotation angle of the metal cutting lines on the units and adopting various types of units.

All cells have no specific period and are of various types. When an appropriate phase gradient is provided, the metasurface can steer electromagnetic waves in any direction in space as follows:

where Ki is the wavevector of the incident wave, θ i is the incident angle formed by Ki and z-axis, Kr is the wavevector of the reflected wave, θ r is the projection of Kr on the ZOY plane and the reflection angle formed by Kr, φ r is the reflection angle formed by the projection of Kr on the ZOY plane and the z-axis,andthe x-and y-polarization components of the phase gradient on the super-surface, as in fig. 1. When the super-surface has many phase gradients with the same scalar and direction, the reflected waves have the same direction. Assuming that a super-surface has many random phase gradients, as shown in fig. 2, when an incident wave is irradiated on the super-surface, a reflected wave is controlled by the random phase gradients, and the phase gradients formed on the super-surface have random scalar quantities and directions, so that the incident wave is reflected in different directions and is scattered. The phase gradient may be represented by:

where d φ represents the phase difference between adjacent elements of the super-surface, and dx, dy represent the distance between adjacent elements in the x, y directions, respectively. The above formula shows that random phase gradients can be realized on the super-surface by designing the phase difference d phi and the distances dx and dy to be random or increasing the diversity of the phase difference d phi, the random phase gradients can scatter circularly polarized waves and linearly polarized waves to reduce the RCS irrelevant to polarization, and when the incident angle is increased, random phase gradients can be formed on the super-surface to reduce the RCS when the circularly polarized waves and the linearly polarized waves are obliquely incident.

As shown in fig. 4, when the rotation angle is specific, for an RHCP incident wave, the reflection phase of the basic cell is not sensitive to the period change, and the basic cell can be regarded as a cell with a certain period.

As shown in fig. 5, the reflection phase difference is actually generated by rotating the basic cells having different periods to different rotation angles because the conventional P-B phase of the cell has a specific cell period.

As shown in fig. 6, this "v" or "x" shaped element can produce phase differences and reflection differences compared to the base element. Similar results can be obtained for the LHCP incident waves in FIGS. 4-6, but the LHCP waves and RHCP waves produce opposite phase gradients.

The technical solution of the present invention is further described below with reference to simulation experiments.

Aiming at the multipolarization and polarization-independent RCS reduction characteristics of the phase gradient super surface, an RCS graph of circularly polarized waves vertically incident to the super surface is simulated by means of electromagnetic simulation software. As can be seen from FIG. 7, the super-surface realizes RCS reduction in the range of 8GHz-28GHz, and RCS reduction amounts to more than 10dB in the ranges of 12.6GHz-17.0GHz and 18GHz-22GHz and 12.4GHz-17.0GHz and 18.0GHz-21.8GHz respectively for RHCP waves and LHCP waves. The RCS reduction band coincides with the phase difference band of FIG. 5, indicating that RCS reduction is due to the formation of random phase gradients on the metasurface, demonstrating the design idea of wave dispersion based on random phase gradients.

For linear polarization, one linear polarization can be decomposed into two circularly polarized waves with opposite rotation directions and the same size, so that the invention can also work under the linear polarization. RCS simulated by the super-surface and the PEC with the same size under the condition of normal incidence of linearly polarized waves is shown in FIG. 8, RCS reduction of the super-surface is realized in the range of 8GHz to 28GHz for the linearly polarized waves, and RCS reduction effects of more than 10dB are respectively realized in the ranges of 12.0GHz to 17.0GHz and 13.0GHz to 17.0GHz and 17.6GHz to 21.8GHz for the x-polarized waves and the y-polarized waves. Thus, the present invention achieves multi-polarization RCS reduction, including circularly polarized waves and linearly polarized waves, and RCS reduction is independent of polarization, since RCS reduction is based on random phase gradients formed on the metasurface.

Fig. 9 and 10 show the RCS reduction of the random phase gradient super-surface of the present invention under the oblique incidence of circularly polarized waves and linearly polarized waves, and the RCS reduction can be achieved for a wide incidence angle when the incidence angle is increased, because the present invention employs non-periodic elements, the phase difference of adjacent elements is random, and random phase gradients can be formed on the super-surface. To further verify that the present invention can be used for oblique incidence and can realize the dual-station RCS reduction characteristics, the far-field scattered field was simulated, and fig. 11 shows a three-dimensional dual-station RCS diagram of 14.2GHz at oblique incidence of the super-surface, and using a metal plate of the same size as a reference, the three-dimensional dual-station RCS diagram of the super-surface has no obvious main lobe when the incidence angle increases, which shows that the present invention can realize wide-angle RCS reduction at the incidence of circularly polarized waves and linearly polarized waves.

To further verify the ability of the super-surface of the present invention to achieve multi-polarization, polarization independent RCS reduction, a 108mm × 108mm sample was fabricated and its scattering intensity was measured, as shown in fig. 12, all parameters of the sample were the same as those of the simulation, the fabricated sample was placed vertically on a platform, the transceiver antenna was at the same height as the sample, and there was enough distance to irradiate the electromagnetic wave vertically onto the sample. Fig. 13 shows RCS test results of the sample under perpendicular incidence of x-polarized wave, y-polarized wave, RHCP wave, and LHCP wave, respectively, the test results are well matched with the simulation results, manufacturing errors may cause a slight difference between the test and simulation results, and the actually measured RCS reduction value indicates that the multi-polarization and polarization-independent RCS reduction of the super-surface is achieved.

The above description is only for the purpose of illustrating the present invention and the appended claims are not to be construed as limiting the scope of the invention, which is intended to cover all modifications, equivalents and improvements that are within the spirit and scope of the invention as defined by the appended claims.