Polarization-rotating metasurface and its application in antenna rcs reduction

Abstract

The application relates to a polarized rotating super surface and application thereof in antenna RCS reduction, comprising a super surface structure, a dielectric substrate and a metal floor, the super surface structure is arranged in a chessboard mode by four super surface modules, each super surface module is composed of 5*5 super surface units arranged periodically, each super surface unit is composed of L-shaped metal patches distributed in a diagonal mode, the L-shaped metal patch structure uses a folding technology to achieve the effect of size reduction, is beneficial to the miniaturization of the super surface unit, the L-shaped metal patch can hinder reflected current due to the structural characteristics, and the polarized rotating effect of 90 degrees is realized, the application realizes significant scattering suppression effect on the basis of not reducing the antenna radiation performance, can be widely applied to RCS reduction of an antenna, has the characteristics of simple structure, miniaturization, low profile, low cost and the like, and has wide application prospects in long-distance communication systems such as wireless communication, radar, remote sensing systems and satellite communication.

Description

Technical Field

[0001] This invention relates to a polarized rotating metasurface and its application in antenna RCS reduction, belonging to the field of wireless communication electronics technology. Background Technology

[0002] With the development of electronic technology, the scattering characteristics of devices have become increasingly important. Antennas play a vital role in fields such as radar, communication, and navigation. Therefore, the key to reducing the radar cross section (RCS) of an antenna is to reduce backscattering while maintaining radiation, which is currently a hot topic in antenna research.

[0003] As a special type of scatterer, antenna scattering consists of two parts: one is the structural mode term scattering field, which is independent of the antenna load and is caused by the secondary radiation of the induced current generated by electromagnetic waves illuminating the antenna; this part is mainly related to the antenna's shape. The other part is the antenna mode term scattering field, which varies with the antenna load; this part is caused by the re-radiation of power reflected due to a mismatch between the antenna's back-end load and the antenna itself, and is related to the antenna's radiation performance. Low-scattering antenna design usually requires a trade-off between the antenna's radiation and scattering characteristics to ensure that antenna performance is not severely affected while achieving a certain level of scattering suppression.

[0004] In recent decades, numerous methods have been developed to reduce the RCS of antennas, primarily through the integration of radar absorbing materials and metasurface materials with the antenna. Metasurface materials achieve effective modulation of amplitude, phase, and polarization by artificially designing the topological or ordered structure of unit cells. Metasurfaces typically possess low-profile structures and various exotic electromagnetic properties, opening new doors for the design of novel antenna technologies. For example, the use of metasurface materials can significantly overcome the inherent narrow operating bandwidth of microstrip antennas. Besides improving antenna radiation performance, another promising application of metasurface technology is controlling antenna scattering performance. The application of metasurface technology in reducing the RCS of microstrip antennas can be summarized into three categories. The first category utilizes the spatial filtering capability or absorption properties of metasurfaces. For instance, by employing two frequency selective surface units (FSS) etched on both sides of the antenna substrate, the different compensation phases of the two FSSs with different positive reflection phase gradient bands and reflection amplitudes can redirect the reflected wave, achieving phase cancellation between the retransmitted wave and the reflected wave, thus reducing the RCS. The second category utilizes the phase modulation function of metasurfaces. High RCS of antennas can be suppressed by redirecting the scattered energy of metasurfaces using passive cancellation methods or wave propagation transformation methods. The third approach utilizes special methods based on metasurfaces. For example, combining metasurfaces with antennas in terms of both structure and electrical performance. Anisotropic metasurfaces are proposed to replace traditional patches, serving directly as the radiating structure of the antenna without increasing its size. Through proper connection of metasurface elements, this antenna exhibits the same radiation performance as a traditional microstrip antenna, but with a lower in-band RCS under any polarization incident radiation.

[0005] Using metasurfaces to reduce the RCS of antennas typically has advantages such as simple structure, large reduction bandwidth, and low profile. However, it often requires a metasurface structure that is much larger than the antenna area, which is not conducive to antenna miniaturization. Summary of the Invention

[0006] To overcome the shortcomings of existing research, this invention provides a polarization rotating metasurface and its application in antenna RCS reduction. It adopts a folded structure, folding the long metal arm of the traditional L-shaped metal patch outward or inward multiple times, and then performing corner cutting. Under the premise of minimizing the impact on the frequency band, the size of the metasurface polarization rotating unit is reduced, resulting in a significant reduction in the overall size of the metasurface.

[0007] A polarization-rotating metasurface includes an antenna array and a metasurface plate distributed from top to bottom; the metasurface plate is composed of a metasurface structure, a dielectric substrate and a metal ground plane, realizing the integration of the array antenna and the polarization-conversion metasurface.

[0008] The antenna array consists of four antenna elements, each consisting of an upper dielectric substrate and a pair of coaxially connected metal ground planes. The upper dielectric substrate has a printed feed structure and a pair of strip patches, which are coaxially connected to the metal ground planes. The antenna elements are arranged either in a sequential rotational distribution along the center or in parallel distribution along the coordinate axes, using either sequential rotational feeding or parallel feeding to form rotating and parallel antenna arrays, respectively. The rotating antenna array exhibits circular polarization characteristics.

[0009] The metasurface structure consists of 2×2 checkerboard-arranged metasurface modules, each of which comprises 5×5 metasurface units. The metasurface modules are distributed clockwise around the center. By utilizing the phase inversion properties between adjacent metasurface modules, scattered energy can be directed to non-threatening angular regions, achieving effective RCS reduction.

[0010] The power supply structure is coaxially powered at the reserved coaxial line pad.

[0011] Furthermore, the basic unit of the metasurface includes a set of L-shaped patches symmetrically distributed along the diagonal. These L-shaped patches are created by repeatedly folding the longer antenna arms of traditional L-shaped patches outwards or inwards, followed by chamfering. This reduces the size of the metasurface polarization rotation unit while minimizing impact on the frequency band. Simultaneously, it generates more resonances, expanding the operating bandwidth of the metasurface and improving the polarization conversion efficiency (PCR).

[0012] Furthermore, the strip patch of the antenna element is folded outward or inward multiple times and then chamfered, which greatly reduces the size of the antenna element. This reduces the impact of the antenna element on the overall RCS reduction, thereby reducing the number of polarization rotating metasurface units required and further reducing the overall size.

[0013] Furthermore, by employing 2×2 antenna elements with the same length, width, and number of folds, each antenna structure can generate induced current and operate in the same frequency band under normal coaxial feeding, thus achieving effective radiation of the array antenna.

[0014] Furthermore, the antenna elements of the rotating antenna array are positioned 90° apart from each other, and are fed in a sequential rotational manner. The phase of each feeding point is 90° apart, resulting in two polarizations of the same size but opposite directions, thus achieving circular polarization characteristics.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0016] This invention proposes a polarization-rotating metasurface and its application in antenna RCS reduction. First, a novel polarization-conversion metasurface unit is designed, employing a folded structure to achieve miniaturization of the metasurface unit, achieving a polarization conversion efficiency (PCR) greater than 90% over a wide frequency range of 6.44-18.8 GHz.

[0017] This invention arranges the aforementioned metasurface units in a checkerboard pattern and loads them into an antenna array, achieving an RCS reduction of over 5dB in a wide frequency band of 6.4-20.81GHz, completely covering the antenna's operating frequency band. Furthermore, due to the coupling effect between the PCM and the antenna, the antenna gain is increased by an average of 3.1dB within the operating frequency band, achieving a significant scattering suppression effect without reducing the antenna's radiation performance, and this effect covers the antenna's operating frequency band.

[0018] This invention features a simple structure with only two dielectric layers and a cross-sectional height of just 5mm, representing a significant reduction in overall size compared to previous research. It can be fabricated using printed circuit technology, resulting in low cost, easy assembly, and convenient use. This makes it better suited for long-distance communication systems such as wireless communication, radar, and remote sensing systems. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a three-dimensional structural diagram of the metasurface structure in an embodiment of the present invention;

[0021] Figure 2 This is a three-dimensional structural diagram of the rotating antenna array in an embodiment of the present invention;

[0022] Figure 3 This is a three-dimensional structural diagram of the parallel antenna array in an embodiment of the present invention;

[0023] Figure 4 This is a three-dimensional structural side view of the rotating antenna array in an embodiment of the present invention;

[0024] Figure 5 This is a schematic diagram of the planar structure of the metasurface structure in an embodiment of the present invention;

[0025] Figure 6 This is a schematic diagram of the antenna element structure of the rotating antenna array in an embodiment of the present invention;

[0026] Figure 7 This is a schematic diagram of the antenna array structure in an embodiment of the present invention;

[0027] Figure 8 The curve showing the change in polarization conversion efficiency (PCR) of the metasurface unit as a function of frequency in an embodiment of the present invention;

[0028] Figure 9 This is a comparison chart of the S-parameters of the antenna array with the metasurface structure of this embodiment (design antenna) and the antenna array without the metasurface structure of this embodiment (reference antenna);

[0029] Figure 10 It is a comparison diagram of the radiation patterns of the reference antenna array and the designed antenna array;

[0030] Figure 11 It is the axial ratio diagram for designing an antenna array;

[0031] Figure 12 This is a comparison diagram of the x-polarized incident wave incidence in the radar cross section (RCS) of the reference antenna and the design antenna;

[0032] Figure 13 This refers to the incident wave incidence situation with y-polarized radar cross section (RCS) of the reference antenna and the design antenna.

[0033] In the figure: 1. Metasurface structure; 2. Dielectric substrate; 3. Metal ground plane; 4. Rotating antenna array; 5. Parallel antenna array; 6. Strip patch; 7. Upper dielectric substrate; 8. Coaxial line; 9. Feed structure; 11. Metasurface unit; 111. L-shaped metal patch. Detailed Implementation

[0034] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0035] This invention proposes a polarization-rotating metasurface and its application in antenna RCS reduction. A novel polarization-conversion metasurface unit is designed, employing a folded structure to achieve miniaturization of the metasurface unit, achieving a polarization conversion efficiency (PCR) greater than 90% over a wide frequency range of 6.44-18.8 GHz. Arranging the aforementioned metasurface unit in a checkerboard pattern and loading it into a rotating antenna array achieves an RCS reduction of over 5 dB over a wide frequency band of 6.4-20.81 GHz, completely covering the antenna's operating frequency band. Furthermore, due to the coupling effect between the PCM and the antenna, the antenna gain is increased by an average of 3.1 dB within the operating frequency band, achieving significant scattering suppression without compromising antenna radiation performance, and this effect covers the antenna's operating frequency band. This invention has a simple structure, consisting of only two dielectric layers with a cross-sectional height of only 5 mm, representing a significant reduction in overall size compared to previous research. It can be fabricated using printed circuit technology, resulting in low cost, easy assembly, and convenient use, making it better suited for long-distance communication systems such as wireless communication, radar, and remote sensing systems.

[0036] The invention will now be further described with reference to the accompanying drawings.

[0037] Reference Figure 1 A polarized rotating metasurface plate is disclosed, comprising a metasurface structure 1 composed of metasurface modules and a metal ground plane 3 beneath a dielectric substrate 2. The metasurface structure 1 consists of 2×2 checkerboard-arranged metasurface modules; each metasurface module consists of 5×5 metasurface basic units 11. Adjacent metasurface modules are distributed in a clockwise rotation around the center, forming a 60mm×60mm×5mm whole.

[0038] Reference Figure 2 A rotating antenna array is added to the metasurface plate. Through holes are punched in the dielectric layer, and eight coaxial cables can pass through the through holes to fix it. The dipole patch antenna above is fed by a central rotation. The antenna elements are distributed around the center to form a rotating antenna array.

[0039] Reference Figure 3 A parallel antenna array is added to the metasurface plate. Through holes are punched in the dielectric layer, and eight coaxial cables can pass through the through holes to fix it. The dipole patch antenna above is fed in parallel, and the antenna elements are distributed in parallel along the coordinate axis.

[0040] Reference Figure 4 The thicknesses of the dielectric substrate 2 and the upper dielectric substrate 7 are H = 4 mm and H1 = 1 mm, respectively, and they can be considered to be tightly attached together.

[0041] Reference Figure 5The basic unit 11 includes a set of folded L-shaped metal patches 111 symmetrically distributed along the diagonal. In this embodiment, the periodic spacing A of the basic unit is 6 mm, the distance from the edge of the folded L-shaped metal patch 111 to the edge of the dielectric substrate is 0.2 mm, the arm length L1 is 4 mm, the arm width W1 = 1.1 mm, and the middle of the two arms is a folded thin arm. The thin arm is folded multiple times towards the center in a relatively outward direction. The width of the thin arm is the same as the width of the fold, which is W3 = 0.13 mm. The ends of the two arms are chamfered, and the width W2 left after chamfering is 0.4 * W1 = 0.44 mm.

[0042] refer to Figure 6 This demonstrates the design process of the polarization rotating unit. Figure 8 PCR performance was calculated for each step. First, Model 1 used an L-shaped band with a length of 0.25λ; second, the same band was added to expand the PCR bandwidth; then, the patch was folded inward to form Model 3, enabling it to resonate at a higher frequency; finally, the number of folds in the patch was increased to further optimize the PCR performance of Model 4. Figure 8 The PCR changes of the four models are shown in the figure, and model 4 is selected as the model to be used.

[0043] refer to Figure 7 The rotating antenna array 4 consists of 2×2 antenna elements, each consisting of a pair of folded strip patches and a feed structure 9. Adjacent dipole antenna elements are rotated around the center. The width of the strip patch is the same as the width of the upper dielectric substrate, W = 1.5 mm, and the length of the strip patch L2 is 5.3 mm. The middle part of the strip patch is replaced by a folded thin strip with the same width as the fold, W4 = 0.2 mm. The ends of the strip patch are chamfered, with a width of W5 = 0.9 mm after chamfering. The diameter of the coaxial line is D = 1.19 mm.

[0044] This embodiment describes a polarization rotating metasurface and its application in antenna RCS reduction. It features a broadband metasurface unit with high polarization conversion efficiency, which is arranged in a checkerboard array to form a PCM and loaded into an antenna array. The coupling effect between the PCM and the antenna is used to improve the antenna's radiation gain. At the same time, by introducing a phase difference of 180±37° between the metasurface modules, the PCM can achieve interference cancellation of the reflected waves, redirecting the scattered beam to a non-threatening angular direction, thus achieving an effective broadband RCS reduction effect.

[0045] The technical effects of the present invention will be further explained below with reference to simulation experiments:

[0046] 1. Simulation software: HFSS_15.0 full-wave simulation software.

[0047] 2. Simulation content and results:

[0048] Simulation 1 simulates the polarization conversion efficiency (PCR) of the polarization conversion metasurface (PCM) in this embodiment. The results are as follows: Figure 7 As shown. From Figure 8 As can be seen, Model 4 performs significantly better than the other three models. The polarization conversion metasurface in this embodiment has a polarization conversion efficiency (PCR) greater than 90% in a wide frequency range of 6.44 GHz to 18.8 GHz, indicating that the PCM described in this embodiment has a high-efficiency polarization conversion capability in a wide frequency range. Its wide bandwidth and high efficiency characteristics are obtained by using a multi-resonant structure to combine multiple effective frequency bands.

[0049] Simulation 2 simulates the S-parameters and gain of the rotating antenna array (design antenna) with and without the metasurface in this embodiment. The results are as follows: Figure 9 , Figure 10 As shown, Figure 11 This is the axial aspect ratio diagram of the rotating antenna array. Among them, Figure 9 It is an S-parameter simulation graph; Figure 10 This is a simulation diagram of radiation gain.

[0050] from Figure 9 As can be seen, both the designed antenna and the reference antenna in this embodiment have a wide impedance bandwidth (S-parameter < -10dB) within the operating frequency band. The reference antenna has an impedance bandwidth of 6.85-7.02GHz, while the designed antenna has a bandwidth of 6.80-7.13GHz, indicating a slight increase in the bandwidth of the designed antenna. Figure 10 As can be seen, the radiation gain of the antenna designed in this embodiment is approximately 7.5 dB higher than that of the reference antenna at the operating frequency of 7 GHz, representing an increase of approximately 0.31 dB in the maximum gain. This is attributed to the increased radiation gain of the reference antenna due to the coupling effect between the PCM and the antenna when the PCM is loaded onto it. Figure 7 The results show that adding a metasurface does not reduce the antenna's radiation characteristics; from Figure 11 As can be seen, the AR value in this example is less than 3dB in the 6-9GHz range, which means that the antenna has circular polarization characteristics in this frequency band, covering the antenna's operating frequency band.

[0051] Simulation 3 simulates the RCS of the rotating antenna array (design antenna) with a metasurface and the antenna without a metasurface (reference antenna) in this embodiment. The x-polarized incident wave illumination is recorded, and the RCS reduction is calculated. The results are as follows: Figure 12 and Figure 13 As shown.

[0052] from Figure 12 and Figure 13As can be seen, the antenna designed in this embodiment has a significant RCS reduction effect under both polarizations of incident wave illumination. It has an RCS reduction effect of more than 5dB in the 6.4-20.8GHz frequency band, covering the antenna's operating frequency band. This is due to the checkerboard arrangement of the PCM. By introducing a phase difference of 180±37° between adjacent elements, the interference cancellation of the reflected wave can be achieved, and the scattered beam can be redirected to the non-incident wave direction, thus achieving an effective broadband RCS reduction effect.

[0053] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the present invention is not limited to the described embodiments. For those skilled in the art, various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and these variations still fall within the protection scope of the present invention.

Claims

1. A polarized rotating metasurface, characterized in that: It includes an antenna array and a metasurface plate distributed from top to bottom; the metasurface plate consists of a metasurface structure, a dielectric substrate, and a metal ground plane distributed from top to bottom. The metasurface structure includes four metasurface modules arranged in a checkerboard pattern, which reduce the RCS by canceling out the polarization of the reflected waves in pairs. The metasurface modules are periodically arranged with metasurface units, and the metasurface units have foldable L-shaped metal patches distributed diagonally. The antenna array consists of four antenna elements. Each antenna element includes an upper dielectric substrate and a pair of coaxial lines connecting to a metal ground plane. The upper dielectric substrate has a feed structure and a pair of strip patches printed on its upper surface. The coaxial lines connect the strip patches to the metal ground plane. The feed structure is coaxially fed at a reserved coaxial line pad. The L-shaped metal patch is folded with a chamfered top, and the length and width of each fold are the same; the strip patch is folded in the middle with a chamfered top, and the length and width of each fold are the same; both the strip patch and the L-shaped metal patch are folded 8 times, but the fold widths are different.

2. The polarized rotating metasurface according to claim 1, characterized in that: The antenna elements are either rotated sequentially around the center or distributed parallel to the coordinate axes, and are divided into rotating antenna arrays and parallel antenna arrays.

3. The polarized rotating metasurface according to claim 1, characterized in that: The metasurface structure consists of 2×2 checkerboard-arranged metasurface modules; each metasurface module consists of 5×5 basic metasurface units.

4. The polarized rotating metasurface according to claim 1, characterized in that: The polarization conversion metasurface exhibits a polarization conversion efficiency (PCR) greater than 90% over a wide frequency range of 6.44–18.8 GHz, and the miniaturized low-RCS circularly polarized array antenna based on the checkerboard metasurface structure achieves an RCS reduction of more than 5 dB over a wide frequency band of 6.4–20.8 GHz.

5. An application of a polarized rotating metasurface according to any one of claims 1-4 in antenna RCS reduction.

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