Broadband RCS reduced polarization conversion metasurface antenna and design method thereof

Abstract

The invention relates to the technical field of electromagnetic metamaterial polarization conversion and RCS reduction, in particular to a broadband RCS reduction polarization conversion metasurface antenna and a design method thereof.The antenna comprises two layers of polarization conversion metasurfaces, the back face of the lower polarization conversion metasurface is fully covered with a metal layer, and eight linearly-arranged feed grooves are formed in the metal layer; the polarization conversion metasurface is formed by periodically arranging n * n metasurface conversion units, each metasurface conversion unit is of a five-layer structure which comprises a first conversion layer, a first dielectric layer, a second conversion layer, a second dielectric layer and a reflecting layer from top to bottom, the first conversion layer is of a circular chamfer structure, and the second conversion layer is of a circular chamfer structure. The second conversion layer is in the shape of a circular split ring, and the corner cutting direction of the first conversion layer is consistent with the opening direction of the second conversion layer. The metasurface is formed by the metasurface conversion units which are arranged in a chessboard shape, and a remarkable RCS reduction effect can be achieved within a broadband range.

Description

Technical Field

[0001] The present invention relates to the technical field of electromagnetic metamaterial polarization conversion and RCS reduction, and in particular to a broadband RCS reduction polarization conversion metasurface antenna and a design method thereof. Background Art

[0002] Radar cross section (RCS) reduction of antenna systems is very important in communication and sensing systems for many defense applications. The RCS of antenna systems can be reduced by electromagnetic bandgap (EBG) radio absorbers, metamaterial absorbers, and microstrip resonators, but usually at the expense of the radiation performance of the antenna. It has been documented that phase cancellation between artificial magnetic conductors (AMCs) and holographic metasurfaces is used to achieve broadband RCS reduction of antennas, respectively. It has been documented that periodic resistor elements are used to improve the RCS characteristics of antennas, and metal parasitic elements are used to enhance the radiation performance of antennas. It has been reported that frequency selective surfaces (FSS) and EBG are used to reduce the in-band and out-of-band radar characteristics of antennas, where the antenna gain is enhanced by using mushroom-based EBG. Therefore, the key to RCS reduction of antennas is to achieve RCS reduction over a larger frequency range while ensuring that the antenna impedance and radiation performance meet the application requirements. In recent years, the development hotspot of metamaterials has been applied to the field of electromagnetic stealth of antennas, reducing scattering while ensuring various characteristics of the antenna.

[0003] The concept of phase cancellation has been studied for RCS reduction. The reflection phase difference between artificial magnetic conductors and perfect electric conductor units is about 180°, so the two can be combined into a checkerboard structure to achieve RCS reduction. Through the application of metasurfaces, destructive interference is established at the operating frequency, so that the incident electromagnetic wave is mainly scattered in multiple directions, thereby reducing the reflection in the direction of the incident electromagnetic wave to achieve the purpose of reducing RCS. In addition, there are literature reports on planar multilayer structures based on metal patches, which achieve RCS reduction through destructive interference formed between different layers. The results show that in currents with passband characteristics, the main way to reduce current reflection is to use components that can absorb current, such as resistors. In addition, the RCS reduction achieved by the phase cancellation principle does not involve the application of resistor components, so it has little effect on the radiation efficiency within the antenna operating frequency band.

[0004] However, the use of phase cancellation methods can effectively achieve in-band and out-of-band RCS reduction for a single antenna, but there are still problems when applied to in-band RCS reduction of linearly polarized antenna arrays. A grid contains 4×4 or more units, each of which covers an antenna unit as part of the radiator. Since the four adjacent grids form a minimum structure that can achieve reflection phase cancellation, the four adjacent grids can be reconstructed into the entire antenna unit. However, in the latest reported results, the size of the four adjacent grids is often significantly larger than the radiation wavelength of the antenna, or even larger than twice the wavelength. An array composed of such antennas will inevitably lead to multiple beams. Miniaturization of polarization conversion metasurfaces (PCMs) can reduce the grid size and achieve more compact, low-RCS linearly polarized antenna elements.

[0005] Therefore, the present invention develops a new type of polarization conversion metasurface and designs and implements a metasurface antenna to achieve efficient antenna operation in a wider frequency range and achieve wide-band RCS reduction, which is of great significance for improving the electromagnetic stealth and adaptability of communication and radar systems. Summary of the invention

[0006] The present invention aims to address the problems of traditional PCM-based RCS reduction, such as narrow operating frequency band, low polarization conversion rate, complex structure and difficulty in mass production. A broadband RCS reduction polarization conversion metasurface antenna and a design method thereof are proposed. The metasurface conversion units are designed to efficiently realize polarization conversion, and the metasurface formed by these units arranged in a checkerboard pattern can achieve significant RCS reduction effect within a wide frequency band.

[0007] To achieve the above purpose, the technical solution adopted is:

[0008] The present invention provides a broadband RCS reduction polarization conversion metasurface antenna, comprising two layers of polarization conversion metasurfaces, the back side of the polarization conversion metasurface located at the bottom is fully covered with a metal layer, 8 linearly arranged feeding slots are provided on the metal layer, and a one-to-eight feeder structure is provided on the back side of the metal layer in one-to-one correspondence with the feeding slots;

[0009] The polarization conversion metasurface is composed of n*n metasurface conversion units arranged periodically. The metasurface conversion unit is a five-layer structure as a whole. The center of the five-layer structure is located on the same vertical line. From top to bottom, they are the first conversion layer, the first dielectric layer, the second conversion layer, the second dielectric layer and the reflection layer. The shape of the first conversion layer is a circular cut-angle structure, and the shape of the second conversion layer is a circular open ring. The cutting direction of the first conversion layer is consistent with the opening direction of the second conversion layer; the reflection layer fully covers the back side of the second dielectric layer.

[0010] According to the broadband RCS reduction polarization conversion metasurface antenna of the present invention, further, the first dielectric layer and the second dielectric layer are made of 8mm*8mm*3.5mm F4B plates, the dielectric constants of the two dielectric layers are 2.2, and the loss tangent is 0.0025.

[0011] According to the broadband RCS reduction polarization conversion metasurface antenna of the present invention, further, the materials and thicknesses of the first conversion layer, the second conversion layer and the reflection layer are the same, and the materials are selected from copper, gold, silver or aluminum.

[0012] According to the broadband RCS reduction polarization conversion metasurface antenna of the present invention, further, the first conversion layer, the second conversion layer and the reflection layer adopt a conductivity of 5.8×10 7 S / m of metallic copper foil.

[0013] According to the broadband RCS reduced polarization conversion metasurface antenna of the present invention, further, the side length of the metasurface conversion unit is 8 mm; the diameter of the first conversion layer circle is 4.3 mm, and the cut corner part is a right angle with a length of 1.8 mm; the outer diameter of the second conversion layer circle is 7.4 mm, the width is 0.8 mm, and the opening width is 3 mm of the open ring; the thickness of the first dielectric layer and the second dielectric layer is 3.5 mm, and the thickness of the first conversion layer, the second conversion layer and the reflective layer is 0.035 mm.

[0014] According to the broadband RCS reduction polarization conversion metasurface antenna of the present invention, further, the polarization conversion metasurface is composed of four regions consisting of n*n metasurface conversion units, each region is composed of n / 2*n / 2 metasurface conversion units arranged periodically, and a checkerboard arrangement is obtained.

[0015] According to the broadband RCS-reduced polarization-conversion metasurface antenna of the present invention, further, a basic PCM unit is formed by 4*4 metasurface conversion units with the same opening direction, and then the openings of the basic PCM unit are rotated 90° in sequence to form a one-to-two small unit, and finally the one-to-two small unit array forms a one-to-four polarization-conversion metasurface.

[0016] According to the broadband RCS reduction polarization conversion metasurface antenna of the present invention, further, when the incident electromagnetic wave passes through the polarization conversion metasurface, a 180° phase difference is generated.

[0017] Furthermore, the present invention also provides a design method for the broadband RCS reduction polarization conversion metasurface antenna based on the above-mentioned method, comprising:

[0018] Select feed line structure feeding, polarization conversion metasurface structure and chessboard layout according to the design requirements of the antenna;

[0019] Design the material, size and shape of the smallest unit of the antenna - the metasurface conversion unit;

[0020] The metasurface conversion units are arranged in a chessboard pattern to form a polarization conversion metasurface;

[0021] Design an upper and lower polarization conversion metasurface. The back of the lower polarization conversion metasurface is fully covered with a metal layer. The metal layer is provided with 8 linearly arranged feeding slots. A one-to-eight feeder structure is set on the back of the metal layer to correspond to the feeding slots one by one.

[0022] Use electromagnetic simulation software to simulate the antenna design and optimize the antenna structure based on the simulation results;

[0023] According to the optimized design, a sample of the antenna is manufactured.

[0024] The beneficial effects achieved by adopting the above technical solution are:

[0025] 1. The polarization conversion metasurface provided by the present invention is cleverly arranged in a chessboard-like structure, and utilizes the conversion between the incident wave and the reflected wave in a wide frequency band, so that the phase difference is 180° in the wide frequency band, thereby achieving an excellent RCS reduction effect. Since the present invention adopts two kinds of graphic designs of the metasurface conversion layer, the graphics of different structures produce different resonant frequencies. By controlling the distance and size between each other, four resonance points connected end to end are generated, and a stable RCS reduction of more than 5dB is achieved in the frequency band of 6GHz to 17GHz, and the relative bandwidth of this frequency band reaches 110%. In addition, at three specific frequency points of 6GHz, 8GHz and 10GHz, the polarization conversion rate is close to 100%. Since the present invention adopts a two-layer conversion layer design, it has a conversion effect on both horizontally polarized waves and vertically polarized waves.

[0026] 2. The dielectric material F4B and metal copper used in the antenna of the present invention have the advantages of being easy to obtain and process, and can achieve simple integration, significantly reducing the complexity and cost of the preparation process. Compared with traditional materials, the present invention effectively solves the problems of material design, complex process and high cost, and has high practicality and economy.

[0027] 3. The chessboard-like structure formed by the metasurface conversion unit of the present invention can achieve a 180° phase flip. The metasurface structure constructed using this feature can achieve the reduction of electromagnetic wave backscattering. In the X-band of 8GHz to 12GHz, it can stably achieve a continuous RCS reduction effect of more than 12dB, reducing the radar detection probability of the target. The polarization conversion metasurface of the present invention uses four areas to form a chessboard-like design, so that the peaks and troughs of the electromagnetic waves are superimposed on each other after being reflected by the metasurface to achieve mutual cancellation between the electromagnetic wave backscattering. The present invention overcomes the shortcomings of traditional absorbing materials such as heat release, narrow frequency band, complex process and expensive materials, and provides a solution with superior performance and economic efficiency.

[0028] 4. The antenna of the present invention has a wide range of application potentials and can be widely used in the fields of radar stealth of important targets. Specifically, the antenna designed by the present invention has significant advantages in RCS reduction and bandwidth increase, can improve the stealth effect of the target, effectively reduce the complexity and cost of manufacturing, and has excellent application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings of the embodiments of the present invention, wherein the drawings are only used to illustrate some embodiments of the present invention, but not to limit all embodiments of the present invention thereto.

[0030] Figure 1 is a schematic structural diagram of a metasurface conversion unit according to an embodiment of the present invention;

[0031] Figure 2 is a schematic structural diagram of a polarization conversion metasurface according to an embodiment of the present invention;

[0032] Figure 3 Schematic diagram of the design size structure of the metasurface conversion unit according to an embodiment of the present invention;

[0033] Figure 4 It is a three-dimensional and physical picture of the broadband RCS reduction polarization conversion metasurface antenna according to an embodiment of the present invention;

[0034] Figure 5 is a graph of the co-polarization coefficient and the cross-polarization coefficient of the metasurface conversion unit according to an embodiment of the present invention;

[0035] Figure 6 is a graph showing the polarization conversion rate of a metasurface conversion unit according to an embodiment of the present invention;

[0036] Figure 7 are two groups of basic PCM unit reflection phase curves of an embodiment of the present invention;

[0037] Figure 8It is a comparison curve of the RCS values ​​of the small unit (including 8*8 metasurface conversion units) of the embodiment of the present invention and the PEC metal plate of the same size;

[0038] Fig. 9 is a graph showing RCS reduction performance of a small unit (including 8*8 metasurface conversion units) according to an embodiment of the present invention;

[0039] Fig.10 It is a three-dimensional far-field radiation diagram of electromagnetic waves of a small unit (including 8*8 metasurface conversion units) of an embodiment of the present invention and a PEC metal plate of the same size;

[0040] Fig.11 is the measured radiation pattern of the H plane of the designed antenna according to the embodiment of the present invention;

[0041] Fig.12 VSWR and Gain curves of the designed antenna and the reference antenna according to the embodiment of the present invention. DETAILED DESCRIPTION

[0042] The following will be combined with the drawings of specific embodiments of the present invention to clearly and completely describe the exemplary scheme of the embodiment of the present invention. Unless otherwise defined, the technical terms or scientific terms used in the present invention should be the common meanings understood by people with ordinary skills in the field.

[0043] This embodiment discloses a broadband RCS reduction polarization conversion metasurface antenna, such as Figure 4 As shown, it includes two layers of polarization conversion metasurfaces, and the back of the polarization conversion metasurface located below is fully covered with a metal layer. There are 8 linearly arranged feeding slots on the metal layer, and a one-to-eight feeder structure is set on the back of the metal layer to correspond to the feeding slots. It can not only convert the phase of the reflected electromagnetic wave at 6-17GHz to achieve effective RCS reduction of the structure, but also achieve good antenna performance. The antenna sample size is 256mm*256mm*7.5mm. According to actual needs, the thickness can be kept unchanged, and the number of repetition periods of the metasurface conversion unit can be increased to achieve RCS reduction on the surface of a larger object.

[0044] The polarization conversion metasurface with phase cancellation proposed in this scheme can achieve RCS reduction of the antenna; the metasurface covers an ultra-wide frequency range from C-band to X-band, and achieves efficient polarization conversion within this frequency band, while having the advantages of simple structure, light weight and easy mass production. Figure 2As shown in FIG. 1 , the polarization conversion metasurface is composed of 32*32 metasurface conversion units arranged periodically. The polarization conversion metasurface is composed of 32*32 metasurface conversion units forming four regions, each region is composed of 16*16 metasurface conversion units arranged periodically, and a chessboard arrangement is obtained. The metasurface conversion unit is a five-layer structure as a whole, and the center of the five-layer structure is located on the same vertical line, as shown in FIG. Figure 1 As shown, from top to bottom, they are the first conversion layer, the first dielectric layer, the second conversion layer, the second dielectric layer and the reflective layer. The first conversion layer is in the shape of a circular cut-angle structure, the second conversion layer is in the shape of a circular open ring, the cut-angle direction of the first conversion layer is consistent with the opening direction of the second conversion layer, and the reflective layer fully covers the back of the second dielectric layer.

[0045] The first dielectric layer and the second dielectric layer are made of 8mm*8mm*3.5mm F4B sheet material, two dielectric layers: εr = 2.2, loss tangent tanδ = 0.0025, where εr is the dielectric constant and loss tangent tanδ is the loss tangent. The dielectric layer preferably uses F4B material with low dielectric constant, low loss and good stability to ensure that the performance is not affected within the C-band wide frequency range.

[0046] The materials and thickness of the first conversion layer, the second conversion layer and the reflective layer are the same. The materials can be copper, gold, silver or aluminum. For the convenience of production, the conductivity is preferably 5.8×10 7 S / m of metallic copper foil.

[0047] like Figure 3 As shown, since the resonant frequency of the conversion layer is related to its geometric size and dielectric constant, in order to produce a specific resonant frequency, a conversion layer and a dielectric substrate of fixed size and thickness are used to ensure the polarization conversion effect. The side length of the metasurface conversion unit is p = 8mm, the diameter of the first conversion layer circle is l3 = 4.3mm, and the cut corner part is a right angle with a length of l4 = 1.8mm. The outer diameter of the second conversion layer circle is l1 = 7.4mm, the width is w = 0.8mm, and the opening width is a = 3mm. The cutting direction of the first conversion layer is consistent with the opening direction of the second conversion layer. The thickness of the first dielectric layer and the second dielectric layer is t1 = t2 = 3.5mm, and the copper foil thickness of the first conversion layer, the second conversion layer and the reflective layer is 0.035mm.

[0048] When processing the metasurface conversion unit, the first conversion layer is first printed on the first dielectric layer, the second conversion layer is printed on the second dielectric layer, and then the first conversion layer, the second conversion layer and the reflective layer are fastened into a whole by nylon screws.

[0049] The metasurface conversion unit has a regular structure and is easy to process and produce. It can convert the polarization of the incident electromagnetic wave with almost no change in the electric field strength, and can meet a polarization conversion rate of more than 90% within a wide bandwidth.

[0050] The basic PCM unit is composed of 4*4 metasurface conversion units with the same opening direction, and then the openings of the basic PCM unit are rotated 90° in sequence to form a small unit divided into two (including 8*8 metasurface conversion units), such as Figure 7 As shown in (a), the one-to-two small unit array is finally formed into a one-to-four polarization conversion metasurface (including 32*32 metasurface conversion units). Figure 7 (b) When the incident electromagnetic wave passes through PCM1 and PCM2, a 180° phase difference will be generated and the two will cancel each other out, causing the main lobe of the electromagnetic wave to disappear and distributing side lobes in different directions, thereby weakening the scattered energy and reducing the radar cross section. The principle of phase cancellation achieved by PCM3 and PCM4 is as described above.

[0051] like Figure 5 As shown, taking the horizontally polarized incident wave as an example, the reflection coefficient curve of the metasurface conversion unit includes the co-polarization conversion coefficient r xx and the cross-polarization conversion coefficient r yx , where r xx Four resonance points are generated at 4.844 GHz, 5.852 GHz, 8.066 GHz and 9.884 GHz. The four resonances are interconnected, so that the co-polarization conversion coefficient is less than -15 dB in the range of 4-11 GHz, and the cross-polarization conversion coefficient is close to 0 dB in this range, that is, most of the energy is converted in the conversion band. For the reflective polarization conversion metasurface, the linear polarization conversion rate is

[0052] like Figure 6 As shown, the polarization conversion rate of the metasurface conversion unit exceeds 90% in the 4-11 GHz frequency band, covering the C and X bands, and realizing broadband polarization conversion.

[0053] like Figure 8 As shown, the RCS value of the small unit proposed in this scheme (including 8*8 metasurface conversion units) is compared with that of the PEC metal plate with the same size and the same incident angle. It can be seen that the designed small unit has a good RCS reduction capability in the frequency range of 6-17GHz.

[0054] like Fig. 9As shown in the figure, except for the 12.5-15.2GHz band where the RCS reduction is slightly less than 7dB and the minimum reduction is 5.3dB, the RCS reduction values ​​of other frequency bands are all greater than 7dB. In the 8-12GHz X-band, the average reduction is 12dB. The small unit of this scheme (including 8*8 metasurface conversion units) achieves good RCS reduction performance and has broad application prospects in the field of electromagnetic stealth technology.

[0055] like Fig.10 As shown, in order to more intuitively demonstrate the effect of the present invention, Figures (a)-(d) respectively show the three-dimensional scattering field comparison of the reference copper metal plate of the same size and square chessboard structure at frequencies of 5GHz, 6GHz, 8GHz and 10GHz. When the electromagnetic wave is incident vertically, the RCS of the small unit of this scheme is significantly reduced compared with the all-metal structure, forming four reflection side lobes, and the reflected electromagnetic wave is in a diffuse reflection state. It can be seen that the small unit structure of this scheme can effectively reduce the RCS near the vertical direction by reducing the energy of the reflected main lobe and redirecting it to other non-vertical directions. Specifically, the small unit increases the energy of the side lobe and weakens the energy of the main lobe, thereby significantly improving the scattering effect and optimizing the reflection characteristics of the electromagnetic wave. This design has good directional control capabilities, can effectively reduce the detectability of the target, and has wide application potential.

[0056] like Fig.11 As shown, the measured radiation patterns of the H-plane of the designed antenna at 6.5 GHz, 7 GHz and 7.5 GHz are given. By observing the patterns, it can be concluded that the antenna of this scheme has good radiation characteristics.

[0057] like Fig.12 As shown in the figure, the simulated and measured voltage standing wave ratio (VSWR) and gain curves of the polarization conversion metasurface design antenna are given. By observing the curves, it can be concluded that within the 5.8-8GHz C band, the fluctuation range of the VSWR curve is small, and the measured gain is approximately 1dBi higher than the simulated gain, and the simulation and measured results are consistent. The antenna of this solution achieves good performance stability.

[0058] In summary, the polarization conversion metasurface of this embodiment achieves the functions of simultaneously satisfying antenna radiation gain enhancement and wide-band RCS reduction, and this structure has good application prospects in the field of low detection of stealth equipment.

[0059] This embodiment also discloses a design method for a broadband RCS reduction polarization conversion metasurface antenna, comprising the following steps:

[0060] Step S1: Analyze the requirements of the target application in detail, including frequency range, radiation characteristics, gain requirements, bandwidth, polarization characteristics, low RCS requirements, etc. Combined with the actual application scenario, clarify the performance objectives and constraints of the design.

[0061] Step S2: select feed line structure feeding, polarization conversion metasurface structure and chessboard layout according to the requirements of antenna design, and determine its basic configuration.

[0062] Step S3, design the material, size, and shape of the smallest unit of the antenna, the metasurface conversion unit, as described above; the designed metasurface conversion unit ensures that the antenna can maintain good polarization conversion performance, thereby improving the radiation gain and directivity of the antenna.

[0063] Step S4: The metasurface conversion units are arranged in a chessboard pattern to form a polarization conversion metasurface.

[0064] Step S5, designing an upper and lower polarization conversion metasurface, wherein the back side of the lower polarization conversion metasurface is completely covered with a metal layer, 8 linearly arranged feeding slots are provided on the metal layer, and a one-to-eight feeder structure is arranged on the back side of the metal layer in one-to-one correspondence with the feeding slots.

[0065] Step S6: Use electromagnetic simulation software (HFSS, CST) to simulate the antenna design and analyze its performance indicators (such as radiation gain, directivity, bandwidth, RCS value, etc.); optimize and adjust the antenna structure according to the simulation results to meet the design goals.

[0066] Step S7: According to the optimized design, a sample of the antenna is manufactured. During the antenna sample manufacturing process, it is ensured that the antenna sample is manufactured strictly in accordance with the designed dimensions and the selected material parameters.

[0067] Step S8: In a microwave darkroom, test the actual performance of the antenna, including S 11 , voltage standing wave ratio (VSWR), gain, directivity pattern, etc., to ensure consistency with the simulation results.

[0068] Step S9: After completing the optimization and testing work, confirm the feasibility and stability of the final design to ensure that the antenna can work stably in the target application environment and meet all design requirements.

[0069] Unless otherwise specifically stated, the components, steps, numerical expressions and values ​​set forth in these embodiments do not limit the scope of the present invention.

[0070] In this specification, each embodiment is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments can be referred to each other. For the system disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part.

[0071] The units and method steps of each example described in conjunction with the embodiments disclosed herein can be implemented by electronic hardware, computer software, or a combination of the two. In order to clearly illustrate the interchangeability of hardware and software, the composition and steps of each example have been generally described in the above description according to function. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. A person of ordinary skill in the art may use different methods to implement the described functions for each specific application, but such implementation is not considered to be beyond the scope of the present invention.

[0072] Those skilled in the art will appreciate that all or part of the steps in the above method can be completed by instructing related hardware through a program, and the program can be stored in a computer-readable storage medium, such as a read-only memory, a disk or an optical disk. Optionally, all or part of the steps in the above embodiment can also be implemented using one or more integrated circuits, and accordingly, each module / unit in the above embodiment can be implemented in the form of hardware or in the form of software function modules. The present invention is not limited to any specific form of combination of hardware and software.

[0073] Finally, it should be noted that the above-described embodiments are only specific implementations of the present invention, which are used to illustrate the technical solutions of the present invention, rather than to limit them. The protection scope of the present invention is not limited thereto. Although the present invention is described in detail with reference to the above-described embodiments, ordinary technicians in the field should understand that any technician familiar with the technical field can still modify the technical solutions recorded in the above-described embodiments within the technical scope disclosed by the present invention, or replace some of the technical features therein by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims

1. A broadband RCS reduction polarization conversion metasurface antenna, characterized in that: It comprises two layers of polarization conversion metasurfaces, the back side of the polarization conversion metasurface located at the bottom is fully covered with a metal layer, eight linearly arranged feeding slots are provided on the metal layer, and a one-to-eight feeder structure is provided on the back side of the metal layer corresponding to the feeding slots one by one; The polarization conversion metasurface is composed of n*n metasurface conversion units arranged periodically. The metasurface conversion unit is a five-layer structure as a whole. The center of the five-layer structure is located on the same vertical line. From top to bottom, they are the first conversion layer, the first dielectric layer, the second conversion layer, the second dielectric layer and the reflection layer. The shape of the first conversion layer is a circular cut-angle structure, and the shape of the second conversion layer is a circular open ring. The cutting direction of the first conversion layer is consistent with the opening direction of the second conversion layer; the reflection layer fully covers the back side of the second dielectric layer.

2. The broadband RCS reduction polarization conversion metasurface antenna according to claim 1, characterized in that: The first dielectric layer and the second dielectric layer are made of 8mm*8mm*3.5mm F4B plate, the dielectric constant of the two dielectric layers is 2.2, and the loss tangent is 0.0025.

3. The broadband RCS reduction polarization conversion metasurface antenna according to claim 1, characterized in that: The materials and thicknesses of the first conversion layer, the second conversion layer and the reflective layer are the same, and the materials are selected from copper, gold, silver or aluminum.

4. The broadband RCS reduction polarization conversion metasurface antenna according to claim 3, characterized in that: The first conversion layer, the second conversion layer and the reflective layer have a conductivity of 5.8×10 7 S / m of metallic copper foil.

5. The broadband RCS reduction polarization conversion metasurface antenna according to claim 1, characterized in that: The side length of the metasurface conversion unit is 8mm; the circular diameter of the first conversion layer is 4.3mm, and the cut corner part is a right angle with a length of 1.8mm; the circular outer diameter of the second conversion layer is 7.4mm, the width is 0.8mm, and the opening width is an open ring of 3mm; the thickness of the first dielectric layer and the second dielectric layer is 3.5mm, and the thickness of the first conversion layer, the second conversion layer and the reflective layer is 0.035mm.

6. The broadband RCS reduction polarization conversion metasurface antenna according to claim 1, characterized in that: The polarization conversion metasurface is composed of four regions consisting of n*n metasurface conversion units, and each region is composed of n / 2*n / 2 metasurface conversion units arranged periodically, resulting in a checkerboard arrangement.

7. The broadband RCS reduction polarization conversion metasurface antenna according to claim 6, characterized in that: The basic PCM unit is composed of 4*4 metasurface conversion units with the same opening direction. The openings of the basic PCM unit are then rotated 90° in sequence to form a one-in-two small unit. Finally, the one-in-two small unit array forms a one-in-four polarization conversion metasurface.

8. The broadband RCS reduction polarization conversion metasurface antenna according to claim 1, characterized in that: When the incident electromagnetic wave passes through the polarization conversion metasurface, a 180° phase difference is generated.

9. A design method for a broadband RCS reduction polarization conversion metasurface antenna based on any one of claims 1 to 8, characterized in that: Include: Select feed line structure feeding, polarization conversion metasurface structure and chessboard layout according to the design requirements of the antenna; Design the material, size and shape of the smallest unit of the antenna - the metasurface conversion unit; The metasurface conversion units are arranged in a chessboard pattern to form a polarization conversion metasurface; Design an upper and lower polarization conversion metasurface. The back of the lower polarization conversion metasurface is fully covered with a metal layer. The metal layer is provided with 8 linearly arranged feeding slots. A one-to-eight feeder structure is set on the back of the metal layer to correspond to the feeding slots one by one. Use electromagnetic simulation software to simulate the antenna design and optimize the antenna structure based on the simulation results; According to the optimized design, a sample of the antenna is manufactured.

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