Conformal protective cover based on gradient metasurface

Abstract

The application provides a conformal protective cover based on a gradient metasurface, which comprises a protective layer, a first phase gradient metasurface layer, a first dielectric layer, a second phase gradient metasurface layer and a second dielectric layer; the first phase gradient metasurface layer is sandwiched between the protective layer and the first dielectric layer; the second phase gradient metasurface layer is sandwiched between the first dielectric layer and the second dielectric layer. The profile of the protective cover is a hexagon, wherein the first layer of phase gradient metasurface is conformal to the circular arc-shaped protective layer, and the second layer of phase gradient metasurface is arranged between the circular arc-shaped first dielectric layer and the second dielectric layer. The phase gradient metasurface is composed of a plurality of phase gradient metasurface units arranged periodically, and each phase gradient metasurface unit comprises a square patch and a Jerusalem cross structure. The application is transparent to electromagnetic waves in a communication frequency band, and is stealthy outside the communication frequency band, and has the advantages of being insensitive to electromagnetic wave polarization, simple overall structure, light weight and easy processing.

Description

Technical Field

[0001] This invention belongs to the field of electromagnetic field and microwave technology, specifically relating to a conformal protective cover based on a gradient metasurface. Background Technology

[0002] The protective shield is a crucial component that protects microwave devices such as antennas and transceiver units (TR components) within the shield from interference from harsh external environments such as high temperatures, humidity, rain, snow, and hail. It must also ensure normal radar communication functionality. For stealth aircraft, the metal antennas inside the shield can generate strong specular reflections, resulting in a larger radar cross section (RCS) within certain viewing angles. This makes the aircraft easier to detect by radar, increasing the risk of it being shot down. Applying radar-absorbing coatings or materials to the shield surface is one way to reduce the RCS, but this method also absorbs electromagnetic waves emitted by the antenna within the communication frequency band, reducing the transmittance within that band.

[0003] Furthermore, to achieve stealth in the low-frequency band, more coatings or thicker absorbing materials are required, increasing the size and weight of the protective cover. Using a frequency selective surface (FSS) cover is another effective way to achieve stealth. Within the communication frequency band, the FSS cover has good wave transmission performance; outside the communication frequency band, the FSS cover is equivalent to an all-metal cover. Electromagnetic waves irradiating the cover are scattered in all directions by its streamlined surface, thereby reducing the RCS of the cover.

[0004] The existing protective cover technology has the following defects: (1) It is only applicable to the stealth design of non-curved structure antenna covers spliced ​​with flat structure, and the stealth bandwidth is relatively narrow; (2) It does not have the steep cutoff characteristic outside the communication band; (3) It adopts an all-metal structure, does not have heat insulation and moisture protection functions, and is relatively heavy. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings and defects of the existing technology and provide a conformal protective cover based on gradient metasurface, which can effectively reduce the RCS of the antenna protective cover. At the same time, the conformal protective cover based on gradient metasurface of this invention is transparent within the communication frequency band and stealthy outside the communication frequency band, and has no impact on the performance of the antenna inside the protective cover. It has the advantages of being insensitive to electromagnetic wave polarization, having a simple overall structure, being lightweight, and being easy to process.

[0006] To achieve the above objectives, the present invention provides a conformal protective cover based on a gradient metasurface, comprising: a protective layer, a first phase gradient metasurface layer, a first dielectric layer, a second phase gradient metasurface layer, and a second dielectric layer; the first phase gradient metasurface layer is sandwiched between the protective layer and the first dielectric layer; and the second phase gradient metasurface layer is sandwiched between the first dielectric layer and the second dielectric layer.

[0007] Preferably, the protective layer, the first phase gradient metasurface layer, the first dielectric layer, the second phase gradient metasurface layer, and the second dielectric layer are all hexagonal in shape, with each hexagon having an interior angle of 120°, and the phase gradient metasurface layer is integrally molded with the protective layer or the dielectric layer to form the conformal protective cover based on the gradient metasurface.

[0008] Preferably, the protective layer, the first dielectric layer, and the second dielectric layer are prepared by molding at least one layer of quartz fiber reinforced cyanate ester-based composite material; the first phase gradient metasurface layer is composed of a polyimide film and a periodically arranged phase gradient metasurface unit etched on the polyimide film.

[0009] Preferably, the protective layer and the first dielectric layer are curved arc-shaped; the second dielectric layer includes a first support portion and a second support portion, wherein the first support portion is hexagonal in shape and curved arc-shaped, and the thickness of the first support portion gradually decreases from the middle to both ends along the axial direction; the second support portion is a rectangular cavity, which is used to house the transmitting or receiving antenna array of the protective cover.

[0010] Preferably, the protective layer is made of a single layer of quartz fiber reinforced cyanate ester-based composite material with a thickness of 0.1 mm and an arc radius of 800 mm; the first dielectric layer is made of multiple layers of quartz fiber reinforced cyanate ester-based composite material with a thickness of 1.5 mm and an arc radius of 799.9 mm; the length, width, and height of the rectangular cavity are 120 mm, 100 mm, and 30 mm, respectively, and the thickness of each side of the rectangular cavity is 3 mm.

[0011] Preferably, the protective layer, the first dielectric layer, and the second dielectric layer, made of quartz fiber reinforced cyanate ester-based composite material, have a dielectric constant of 3.3 and a loss tangent of 0.005; the polyimide film has a thickness of 0.1 mm, a dielectric constant of 3.3, and a loss tangent of 0.008; the phase gradient metasurface unit is a subwavelength metal unit, which consists of a square patch and a Jerusalem cross structure, and the centers of the square patch and the Jerusalem cross structure coincide.

[0012] Preferably, the first phase gradient metasurface layer is fixed between the protective layer and the first dielectric layer by molding, and conforms to the arc-shaped protective layer and the first dielectric layer; the second phase gradient metasurface layer is fixed between the first dielectric layer and the second dielectric layer by molding, and conforms to the arc-shaped first dielectric layer and the second dielectric layer; the second phase gradient metasurface layer has the same gradient metasurface unit structure as the first phase gradient metasurface layer, and the two gradient metasurface unit structures coincide at the center position in the thickness direction, so that the phase gradient metasurface units on the first phase gradient metasurface layer correspond one-to-one with the phase gradient metasurface units on the second phase gradient metasurface layer.

[0013] Conductive adhesive is sprayed onto each of the six contour edges of the conformal protective cover with a hexagonal profile to ensure the electrical continuity of the conformal protective cover.

[0014] Preferably, the phase gradient metasurface element calculates the element compensation phase according to formula (1-1), and the element phases with compensation phase Δψ exceeding 360° are taken modulo 360°:

[0015]

[0016] Where m and n are the sequence numbers of the metasurface unit, m is the x-axis sequence number, n is the y-axis sequence number, p is the metasurface unit period, L is the geometric distance between the antenna phase center and the metasurface center, and λ is the free space wavelength corresponding to the operating center frequency.

[0017] Preferably, the compensation phase calculated by the metasurface unit according to formula (1-1) is quantized according to the following rules: the compensation phase Δψ between α° and (α+30)° is processed as α°, where the value of α includes 0, 30, 60, 90, 120, 150, 180, 210, 240, 270, 300, and 330. The compensation phase of Δψ between α° and (α+30)° is calculated in sequence to obtain the final compensation phase distribution.

[0018] Preferably, the gradient metasurface conformal protective cover has good reflection characteristics for both TE-polarized and TM-polarized electromagnetic waves outside the communication frequency band, and good transmission characteristics for both TE-polarized and TM-polarized electromagnetic waves within the communication frequency band; wherein the frequency band outside the communication frequency band is the L-Ku band, and the frequency band within the communication frequency band is the K band.

[0019] In summary, compared with the prior art, the conformal protective cover based on gradient metasurface provided by the present invention has the following beneficial effects:

[0020] 1. The phase gradient design method can be applied to the stealth design of protective shields with arbitrary radii of curvature, achieving conformal stealth;

[0021] 2. Achieving ultra-wideband stealth in the L-Ku band and high transmittance in the K band using a two-layer phase gradient metasurface structure;

[0022] 3. The protective cover adopts a hexagonal outline, which has lower gap scattering characteristics compared with rectangular, circular or other geometric shapes, and can effectively reduce the RCS of the protective cover.

[0023] 4. The protective cover is made of cyanate resin, which can withstand high temperatures of 200℃;

[0024] 5. The protective cover is coated with conductive adhesive to ensure the electrical continuity of the cover. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the overall three-dimensional structure of the conformal protective cover based on gradient metasurface of the present invention;

[0026] Figure 2 This is a top view of the conformal protective shield based on gradient metasurfaces of the present invention;

[0027] Figure 3 This is a side view of the conformal protective shield based on gradient metasurfaces of the present invention;

[0028] Figure 4 This is a schematic diagram of the gradient metasurface layer of the conformal protective shield based on gradient metasurface of the present invention;

[0029] Figure 5 This is a schematic diagram of the phase distribution of the gradient metasurface layer of the conformal protective cover based on gradient metasurface of the present invention after quantization;

[0030] Figure 6 This is a partial schematic diagram of the gradient metasurface distribution in the conformal protective shield based on gradient metasurfaces of the present invention;

[0031] Figure 7 This is a schematic diagram of the gradient metasurface unit of the conformal protective cover based on gradient metasurfaces of the present invention;

[0032] Figure 8 The transmittance simulation results are for the gradient metasurface unit of the conformal protective cover based on gradient metasurface of the present invention.

[0033] Figure 9 Simulation results of voltage standing wave ratio before and after loading the conformal protective cover based on gradient metasurface of the present invention onto the waveguide slot array antenna;

[0034] Figure 10 Simulation results of the radiation patterns before and after loading the conformal protective cover based on the gradient metasurface of the present invention onto the waveguide slot array antenna;

[0035] Figure 11 The results are the single-station RCS simulation results of the conformal protective shield based on gradient metasurface under plane wave illumination according to the present invention. Detailed Implementation

[0036] The following will be combined with the appendix in the embodiments of the present invention. Figure 1 ~Attached Figure 11 The technical solutions, structural features, objectives and effects achieved in the embodiments of the present invention will be described in detail.

[0037] It should be noted that the accompanying drawings are in a very simplified form and use non-precise proportions. They are only used to facilitate and clarify the purpose of illustrating the embodiments of the present invention, and are not intended to limit the implementation conditions of the present invention. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in the proportional relationship, or adjustments to the size should still fall within the scope of the technical content disclosed in the present invention, provided that they do not affect the effects and objectives that the present invention can produce.

[0038] It should be noted that, in this invention, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only the expressly listed elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus.

[0039] This embodiment provides a conformal protective shield based on a gradient metasurface, such as... Figure 1 As shown, the conformal protective cover based on gradient metasurfaces has a communication frequency band of K-band and includes: a protective layer 1, a first phase gradient metasurface layer 2, a first dielectric layer 3, a second phase gradient metasurface layer 4, and a second dielectric layer 5; wherein the first phase gradient metasurface layer 2 is sandwiched between the protective layer 1 and the first dielectric layer 3; the second phase gradient metasurface layer 4 is sandwiched between the first dielectric layer 3 and the second dielectric layer 5, and the phase gradient metasurface layer is integrally molded with the protective layer or the dielectric layer respectively.

[0040] Specifically, in this embodiment, as Figure 2 As shown, Figure 2 This is a top view of a conformal protective shield based on a gradient metasurface, the dimensions of which are 200 × 140 mm. 2(Length × Width), the shape outline is hexagonal, and the six interior angles are all 120°. The outline shapes of the protective layer 1, the first phase gradient metasurface layer 2, the first dielectric layer 3, the second phase gradient metasurface layer 4 and the second dielectric layer 5 that form the conformal protective cover based on gradient metasurface are all hexagonal.

[0041] Furthermore, in this embodiment, the protective layer 1, the first dielectric layer 3, and the second dielectric layer 5 constituting the conformal protective shield based on the gradient metasurface are all prepared by molding from at least one layer of quartz fiber reinforced cyanate ester-based composite material with a thickness of 0.1 mm. Further, as... Figure 1 As shown, the protective layer 1 is bent into a curved arc shape and is made of a single layer of quartz fiber reinforced cyanate ester-based composite material, with a thickness H1 of 0.1 mm and an arc radius of 800 mm; the first dielectric layer 3 is bent into a curved arc shape and is made of multiple layers of quartz fiber reinforced cyanate ester-based composite material, with a thickness H2 of 1.5 mm and an arc radius of 799.9 mm; as Figure 3 As shown, the second dielectric layer 5 includes a first support portion 51 and a second support portion 52. The first support portion 51 is hexagonal in shape, and its upper surface is curved into an arc shape with a radius of 798.4 mm. It is symmetrical along the axial direction. The thickness of the first support portion 51 gradually decreases from a thickness H3 = 3.5 mm in the middle to a thickness of 1.5 mm at both ends. That is, the cross-sectional shape of the first support portion 51 is thick in the middle and thin at both ends. The lower surface of the first support portion 51 is flat. The second support portion 52 is a rectangular cavity with a length, width, and height of 120 mm, 100 mm, and 30 mm, respectively. The thickness H4 of each side of the rectangular cavity is 3 mm (e.g., ...). Figure 3 As shown in the diagram, the upper surface of the second support portion 52 is connected to the lower surface of the first support portion 51. This rectangular cavity is used to house the transmitting or receiving antenna array of the protective cover. In this embodiment, the antenna placed inside the rectangular cavity is a waveguide slot antenna array.

[0042] Among them, such as Figure 1 As shown, in this embodiment, the dielectric constant of the protective layer 1, the first dielectric layer 3, and the second dielectric layer 5, which are made of quartz fiber reinforced cyanate ester-based composite material, is 3.3, and the loss tangent (i.e., the ratio of the active power P to the reactive power Q of the capacitor) is 0.005.

[0043] Among them, such as Figure 1 , Figure 4 and Figure 7As shown, the first phase gradient metasurface layer 2 in this embodiment is composed of a polyimide film 21 and periodically arranged phase gradient metasurface units 22 etched on the polyimide film; wherein the polyimide film 21 has a thickness of 0.1 mm, a dielectric constant of 3.3, and a loss tangent of 0.008. The phase gradient metasurface unit 22 is a subwavelength metal unit, which is composed of a square patch 221 and a Jerusalem cross structure 222 stacked together, with their centers coinciding. In this embodiment, the subwavelength metal material etched on the polyimide film is copper foil, and the copper foil has a thickness of 0.017 mm.

[0044] Furthermore, such as Figure 1 As shown, in this embodiment, the first phase gradient metasurface layer 2 is fixed between the protective layer 1 and the first dielectric layer 3 by molding, and conforms to the arc-shaped protective layer 1 and the first dielectric layer 3. That is, the upper surface of the first phase gradient metasurface layer 2 is in contact with the lower surface of the protective layer 1, and the lower surface of the first phase gradient metasurface layer 2 is in contact with the upper surface of the first dielectric layer 3. Similarly, the second phase gradient metasurface layer 4 is fixed between the first dielectric layer 3 and the second dielectric layer 5 by molding, and conforms to the arc-shaped first dielectric layer 3 and the second dielectric layer 5. That is, the upper surface of the second phase gradient metasurface layer 4 is in contact with the lower surface of the first dielectric layer 3, and the lower surface of the second phase gradient metasurface layer 4 is in contact with the upper surface of the first support portion 51 in the second dielectric layer 5. The second phase gradient metasurface layer 4 has the same gradient metasurface unit structure as the first phase gradient metasurface layer 2 (i.e., the second phase gradient metasurface layer 4 is also composed of a polyimide film and a periodically arranged phase gradient metasurface unit etched on the polyimide film), and the two gradient metasurface unit structures are in the thickness direction (i.e., Figure 1 The center positions of the phase gradient metasurface units 22 on the first phase gradient metasurface layer 2 and the phase gradient metasurface units on the second phase gradient metasurface layer 4 are aligned to ensure that their positions correspond one-to-one.

[0045] Specifically, such as Figure 1 , Figure 2 , Figure 5 , Figure 6 and Figure 7 As shown, the phase gradient metasurface unit described in this embodiment calculates the unit compensation phase according to formula (1-1):

[0046]

[0047] Where m and n are the sequence numbers of the metasurface unit, m is the x-axis sequence number, n is the y-axis sequence number, p is the metasurface unit period, L is the geometric distance between the antenna phase center and the metasurface center, the antenna phase center refers to the position of the equivalent point source of the antenna electromagnetic radiation transmitted by the antenna array in the rectangular cavity (i.e., the second support part 52) ​​(for example, if the antenna radiates a spherical equiphase surface, then the center of the sphere is its phase center); λ is the free space wavelength corresponding to the operating center frequency.

[0048] After calculating the compensation phase for each element, the compensation phase is quantized. Δψ values ​​between 0° and 30° are treated as 0°, Δψ values ​​between 30° and 60° are treated as 30°, and so on, with Δψ values ​​between 330° and 360° treated as 330°. Based on the thickness of the second dielectric layer 5 at the location of the metasurface element, the gradient metasurface element size is obtained through electromagnetic software simulation optimization. This allows the spherical wave radiated by the antenna within the rectangular cavity to be converted into a plane wave.

[0049] Specifically, such as Figure 5 , Figure 6 and Figure 7 As shown, the parameters for calculating the compensated phase of the computational unit in this embodiment are as follows: metasurface unit period p = 4 mm, geometric distance L between the antenna phase center and the metasurface center = 20 mm, free space wavelength λ corresponding to the operating center frequency = 12 mm, H1 = 0.1 mm, geometric dimensions of the Jerusalem cross structure L1 = 1.5 mm, W1 = 0.2 mm, W2 = 0.1 mm, H2 = 1.5 mm. The compensated phase Δψ(m,n) of the metasurface unit varies within the range of 0° to 360°, and the quantized gradient metasurface distribution is as follows. Figure 5 As shown.

[0050] In this embodiment, the geometric dimensions of the Jerusalem cross structure remain unchanged, and the dimensions of the square patch 221 are optimized based on the thickness variation of the first support portion 51 in the second dielectric layer 5. The thickness variation is determined by the thickness H3 of the second dielectric layer corresponding to each metasurface unit number arranged according to the y-axis sequence number. Figure 3 The z-axis direction is increased by 0.2 mm, and the optimized patch size L2 of the square patch 221 is shown in Table 1:

[0051] Table 1. Optimized L2 dimensions of gradient metasurface elements

[0052] Metasurface element numbering (m,n) (1,1) (1,2) (1,2) (1,3) (1,4) (1,5) (1,6) (1,7) (1,8) (1,9) (1,10) The corresponding compensation phase Δψ 210 240 270 330 30 120 210 300 30 150 240 <![CDATA[Thickness H3 (mm) of the second dielectric layer]]> 3.5 3.5 3.3 3.3 3.1 3.1 2.9 2.7 2.7 2.5 2.5 <![CDATA[Chip size L2 (mm)]]> 3.72 3.5 3.4 3.28 2.86 2.54 1.94 2.2 2.75 2.47 2.2

[0053] Preferred, such as Figure 1 As shown in the figure, conductive adhesive is sprayed onto the six contour edges of the hexagonal conformal protective cover based on gradient metasurface in this embodiment to ensure the electrical continuity characteristics of the conformal protective cover based on gradient metasurface.

[0054] It should be noted that, as Figure 1 As shown, the conformal protective cover based on gradient metasurface described in this embodiment has good reflection characteristics for both TE-polarized and TM-polarized electromagnetic waves outside the communication frequency band, and good transmission characteristics for both TE-polarized and TM-polarized electromagnetic waves within the communication frequency band.

[0055] Specifically, such as Figure 8 As shown, the phase gradient metasurface layer described in this embodiment has a transmittance of less than 10% in the frequency range of 1 to 18 GHz and a transmittance of greater than 80% in the frequency range of 24 to 26.7 GHz; indicating that it has good reflection characteristics for both TE-polarized and TM-polarized electromagnetic waves outside the communication band and good transmission characteristics for both TE-polarized and TM-polarized electromagnetic waves within the communication band.

[0056] like Figure 9 As shown, when the waveguide slot antenna array is loaded with the conformal protective cover based on the gradient metasurface described in this embodiment, the voltage standing wave ratio is less than 2 in the frequency range of 24 to 25.3 GHz, indicating that the conformal protective cover based on the gradient metasurface has good high transmission characteristics in the K-band (18 to 27 GHz).

[0057] like Figure 10 As shown, when the waveguide slot antenna array is loaded with the conformal protective cover based on the gradient metasurface described in this embodiment, the antenna gain drops by no more than 0.5dB at 25GHz, which also indicates that the conformal protective cover based on the gradient metasurface has high transmission characteristics in the K-band (18-27GHz).

[0058] like Figure 11 As shown, in the frequency range of 1–18 GHz under online polarized plane wave illumination, the monostatic RCS (where the monostatic RCS refers to the scattering capability exhibited by the scattering object when the incident wave emission and the reflected wave reception are completed by the radar station at the same location) of the conformal protective cover based on the gradient metasurface described in this embodiment is reduced by 4.5–9.2 dB compared to the monostatic RCS without the protective cover. This indicates that the conformal protective cover based on the gradient metasurface has lower gap scattering characteristics and can effectively reduce the RCS of the protective cover.

[0059] It should be noted that the conformal protective cover based on gradient metasurface provided in this embodiment is stealthy in the L-Ku band and transparent in the K band. By changing the size, the conformal protective cover based on gradient metasurface provided in this embodiment can be applied to other microwave bands, which will not be elaborated here.

[0060] In summary, compared with the prior art, the conformal protective cover based on gradient metasurface provided by the present invention has the characteristics of not affecting the antenna orientation and standing wave characteristics, while achieving stealth outside the communication band and wave transmission within the communication band, and has broad application prospects.

[0061] Although the present invention has been described in detail through the preferred embodiments above, it should be understood that the above description should not be considered as a limitation of the present invention. Various modifications and substitutions to the present invention will be apparent to those skilled in the art after reading the above description. Therefore, the scope of protection of the present invention should be defined by the appended claims.

Claims

1. A conformal protective shield based on a gradient metasurface, characterized in that, include: The protective layer (1), the first phase gradient metasurface layer (2), the first dielectric layer (3), the second phase gradient metasurface layer (4), and the second dielectric layer (5) are sandwiched between the protective layer (1) and the first dielectric layer (3); the second phase gradient metasurface layer (4) is sandwiched between the first dielectric layer (3) and the second dielectric layer (5). The protective layer (1), the first phase gradient metasurface layer (2), the first dielectric layer (3), the second phase gradient metasurface layer (4), and the second dielectric layer (5) are all hexagonal in shape, with each hexagon having an interior angle of 120°. The phase gradient metasurface layer is integrally molded with the protective layer or the dielectric layer to form the conformal protective cover based on the gradient metasurface. The protective layer (1), the first dielectric layer (3), and the second dielectric layer (5) are prepared by molding at least one layer of quartz fiber reinforced cyanate ester-based composite material; the first phase gradient metasurface layer (2) is composed of a polyimide film (21) and a periodically arranged phase gradient metasurface unit (22) etched on the polyimide film; The protective layer (1) and the first dielectric layer (3) are curved arc-shaped; the second dielectric layer (5) includes a first support part (51) and a second support part (52), wherein the first support part (51) is hexagonal in shape and curved arc-shaped, and the thickness of the first support part (51) gradually decreases from the middle to both ends along the axial direction; the second support part (52) is a rectangular cavity, which is used to place the transmitting or receiving antenna array of the protective cover; The protective layer (1) is made of a single layer of quartz fiber reinforced cyanate ester composite material with a thickness of 0.1 mm and an arc radius of 800 mm; the first dielectric layer (3) is made of multiple layers of quartz fiber reinforced cyanate ester composite material with a thickness of 1.5 mm and an arc radius of 799.9 mm; the length, width and height of the rectangular cavity are 120 mm, 100 mm and 30 mm respectively, and the thickness of each side of the rectangular cavity is 3 mm; The protective layer (1), the first dielectric layer (3), and the second dielectric layer (5) made of quartz fiber reinforced cyanate ester-based composite material have a dielectric constant of 3.3 and a loss tangent of 0.005; the polyimide film (21) has a thickness of 0.1 mm, a dielectric constant of 3.3, and a loss tangent of 0.008; the phase gradient metasurface unit (22) is a subwavelength metal unit, which is composed of a square patch (221) and a Jerusalem cross structure (222), and the centers of the square patch (221) and the Jerusalem cross structure (222) coincide. The first phase gradient metasurface layer (2) is fixed between the protective layer (1) and the first dielectric layer (3) by molding, and conforms to the arc-shaped protective layer (1) and the first dielectric layer (3); The second phase gradient metasurface layer (4) is fixed between the first dielectric layer (3) and the second dielectric layer (5) by molding, and is conformal with the arc-shaped first dielectric layer (3) and the second dielectric layer (5); The second phase gradient metasurface layer (4) has the same gradient metasurface unit structure as the first phase gradient metasurface layer (2), and the two gradient metasurface unit structures coincide at the center position in the thickness direction, so that the phase gradient metasurface unit (22) on the first phase gradient metasurface layer (2) and the phase gradient metasurface unit on the second phase gradient metasurface layer (4) correspond one-to-one. Conductive adhesive is sprayed onto each of the six contour edges of the conformal protective cover with a hexagonal profile to ensure the electrical continuity of the conformal protective cover.

2. The conformal protective cover based on gradient metasurfaces as described in claim 1, characterized in that, The phase gradient metasurface element calculates the element compensation phase according to formula (1-1): （1-1） Where m and n are the sequence numbers of the metasurface unit, m is the x-axis sequence number, n is the y-axis sequence number, p is the metasurface unit period, L is the geometric distance between the antenna phase center and the metasurface center, and λ is the free space wavelength corresponding to the operating center frequency.

3. The conformal protective cover based on gradient metasurfaces as described in claim 2, characterized in that, The compensation phase calculated by the metasurface unit according to formula (1-1) is quantized according to the following rules: The compensation phase... For values ​​between α° and (α+30)°, treat them as α°, where α can take values ​​of 0, 30, 60, 90, 120, 150, 180, 210, 240, 270, 300, and 330, and calculate accordingly. The final compensated phase distribution is obtained within the compensated phase range of α° to (α+30)°.

4. The conformal protective cover based on gradient metasurfaces as described in claim 1, characterized in that, The gradient metasurface conformal protective cover has good reflection characteristics for both TE-polarized and TM-polarized electromagnetic waves outside the communication frequency band, and good transmission characteristics for both TE-polarized and TM-polarized electromagnetic waves within the communication frequency band; wherein the frequency band outside the communication frequency band is the L~Ku band, and the frequency band within the communication frequency band is the K band.

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