High-power double-screen symmetric structure invisible antenna housing based on frequency selective surface

Abstract

The invention discloses a high-power double-screen symmetric structure stealth antenna housing based on a frequency selective surface, and aims to solve the problem that a high-power microwave antenna array housing cannot have an electromagnetic transmission characteristic and a stealth function at the same time. The double-screen FSS is in a flat plate shape and is formed by periodically and uniformly arranging N double-screen FSS units; the double-screen FSS unit is a regular hexagonal prism and is formed by coaxially connecting a first screen FSS unit, a connecting medium layer and a second screen FSS unit from input to output, and the first screen FSS unit and the second screen FSS unit are symmetrically distributed about the connecting medium layer; the first screen FSS unit is composed of a first dielectric layer, a first metal dielectric nested layer and a second dielectric layer. The first metal dielectric nested layer is formed by embedding a regular hexagon metal ring in a filling medium. The connecting dielectric layer is a regular hexagon dielectric substrate. The antenna can be transparent in a working frequency band and cut off outside the working frequency band, can realize electromagnetic stealth in a specific frequency range, and is high in power capacity, wide in pass band and good in polarization performance.

Description

Technical Field

[0001] The present invention belongs to the technical field of microwave frequency band electromagnetic wave control, and in particular relates to a frequency selective surface double-screen symmetrical structure stealth antenna cover applied to the high-power microwave field. Background Art

[0002] High-power microwave (HPM) generally refers to strong electromagnetic radiation with a frequency of 300MHz to 300GHz, a peak power greater than 100MW or an average power greater than 1MW. As the terminal of the entire high-power microwave system, the high-power microwave antenna array radiates the energy generated by the microwave source into the free space in a specific form. Its performance directly determines whether the energy generated by the microwave source can be effectively radiated outward and accurately act on the target. With the development of high-power microwave applications towards practicality, high-power microwave antennas currently cannot have both electromagnetic transmission characteristics and electromagnetic stealth functions. Although individual technologies such as electromagnetic stealth and high-power microwave antennas have been widely studied, there is still a lack of in-depth research on antennas with electromagnetic stealth functions in the field of high-power microwaves.

[0003] In current stealth technology, in order to achieve the stealth effect of the target and reduce the detectability of the target, the research mainly focuses on how to reduce the radar cross section (RCS) of the target. Traditional stealth methods include appearance design, coating with absorbing materials, and plasma stealth. However, the antenna is an electromagnetic field radiator. If the traditional stealth method is used to coat the absorbing material or change its shape, it will seriously affect the radiation performance of the antenna. Therefore, under the condition of maintaining the basic working performance of the antenna unchanged, the mainstream method to effectively reduce the radar cross section of the antenna is to use a radome to physically protect the antenna and electromagnetically stealth it.

[0004] Frequency Selective Surface (FSS) can selectively control the transmission, reflection and absorption of electromagnetic waves, thereby achieving the regulation of electromagnetic waves within a specific frequency range, which not only exhibits certain filtering characteristics, but also can reduce RCS, which has greatly promoted the development of stealth technology to a certain extent. Combining the frequency selective surface with the traditional all-dielectric radome can produce an FSS stealth radome that is transparent in the passband and reflective outside the passband, which can effectively reduce the RCS of the target. For every 12dB reduction in RCS, the detectability of the target is reduced by 50%, thereby improving the electromagnetic stealth performance of the target.

[0005] However, the application of FSS in the field of high-power microwaves to achieve stealth will cause the following problems: First, the FSS structure will expand and deform due to thermal effects under the strong electromagnetic radiation of high-power microwaves, which will affect the filtering characteristics and the stability of the incident wave; second, the FSS structure is prone to field enhancement when it resonates. If the power capacity of the FSS structure cannot reach the GW level, the antenna cover will be broken down by the high-power microwave and fail; finally, the FSS structure used in the field of high-power microwaves needs to take into account higher power capacity and electromagnetic field strength, and factors such as the high temperature resistance and dielectric properties of the material need to be considered, which increases the design complexity, processing difficulty and manufacturing cost. At present, there is no public literature involving the application of dual-screen frequency selective surface units to the field of high-power microwaves as a technical solution for achieving electromagnetic stealth. Combined with the current development trend of the widespread application of high-power microwave antenna arrays, it is increasingly urgent to develop a dual-screen antenna cover that can be used in the field of high-power microwaves and has both electromagnetic stealth performance and good transmission characteristics. Summary of the invention

[0006] The technical problem to be solved by the present invention is to provide a high-power double-screen symmetrical structure stealth antenna cover based on frequency selective surface, which has both electromagnetic stealth performance and good electromagnetic transmission characteristics, and the power capacity can reach GW level. It has good polarization stability and can selectively transmit or reflect electromagnetic waves within a specific frequency range. It does not affect the normal radiation of the high-power microwave antenna array within the working frequency band, and can reduce the radar scattering cross section RCS of the high-power microwave antenna array within the specific frequency range. Compared with the single-screen FSS unit, it has a wider working bandwidth and a stronger RCS reduction capability, which solves the problem that the current high-power microwave antenna array cover cannot have both electromagnetic transmission characteristics and electromagnetic stealth functions, and the ordinary FSS structure is easily penetrated by strong electromagnetic radiation, and meets the requirements for the development of high-power microwave antenna arrays.

[0007] The technical solution adopted by the present invention to solve its technical problem is:

[0008] The high-power dual-screen symmetrical structure stealth antenna cover based on the frequency selective surface provided by the present invention is in the shape of a flat plate, and its length is L a , width is L b , thickness is t, and it is composed of N double-screen FSS units with the same structure arranged periodically and evenly, and the periodic spacing between the geometric centers of adjacent double-screen FSS units is p.

[0009] The high-power dual-screen symmetrical structure stealth radome based on frequency selective surface is defined such that the end close to the high-power microwave antenna array is the output end, and the end away from the high-power microwave antenna array is the input end. Each dual-screen FSS unit is composed of a first-screen FSS unit, a connecting dielectric layer, and a second-screen FSS unit. The first-screen FSS unit and the second-screen FSS unit are symmetrically distributed about the connecting dielectric layer. The first-screen FSS unit, the connecting dielectric layer, and the second-screen FSS unit are coaxially connected in order from input to output.

[0010] The first screen FSS unit is composed of a first dielectric layer, a first metal dielectric nested layer, and a second dielectric layer. The first dielectric layer, the first metal dielectric nested layer, and the second dielectric layer are coaxially connected in order from input to output. The surface of the first dielectric layer near the output end is completely in contact with the surface of the first metal dielectric nested layer near the input end. The surface of the first metal dielectric nested layer near the output end is completely in contact with the surface of the second dielectric layer near the input end. The first dielectric layer and the second dielectric layer are symmetrically loaded on both sides of the first metal dielectric nested layer. The first metal dielectric nested layer is composed of a first regular hexagonal metal ring and a layer of filling medium, and the first regular hexagonal metal ring is embedded in the filling medium. The second screen FSS unit has the same structure as the first screen FSS unit, and is composed of a third dielectric layer, a second metal dielectric nested layer, and a fourth dielectric layer. The second metal dielectric nested layer is composed of a second regular hexagonal metal ring and a layer of filling medium, and the second regular hexagonal metal ring is embedded in the filling medium. The material properties and size of the third dielectric layer and the fourth dielectric layer are completely the same as those of the first dielectric layer, the second metal dielectric nested layer is completely the same as the first metal dielectric nested layer, and the second regular hexagonal metal ring is completely the same as the first regular hexagonal metal ring.

[0011] A xy two-dimensional coordinate system is established with the surface of the second screen FSS unit close to the output end as the reference plane, the lower left vertex O of the rectangular surface of the second screen FSS unit close to the output end is set as the coordinate origin, and the output end-input end is set as the positive direction of the z-axis, thereby forming an xyz three-dimensional coordinate system, and the subsequent description will be based on this coordinate system.

[0012] The high-power dual-screen symmetrical structure stealth radome based on frequency selective surface is composed of N dual-screen FSS units in the shape of regular hexagonal prisms arranged periodically and evenly. Each dual-screen FSS unit is a regular hexagonal prism with a side length of l. The height of the regular hexagonal prism is equal to the thickness t of the radome. The geometric center period spacing of adjacent dual-screen FSS units is p. Define the dual-screen FSS unit adjacent to the coordinate origin O to be in the first row and first column. Then the geometric center of all dual-screen FSS units can be expressed by the coordinates (x, y) in the xy plane, and there is y=(3n-1)·l / 2, x is the horizontal coordinate of the coordinate (x, y) corresponding to the geometric center of the dual-screen FSS unit at different positions, y is the vertical coordinate (x, y), m represents the number of columns of the dual-screen FSS unit in the antenna cover, n represents the number of rows of the dual-screen FSS unit in the antenna cover, and m and n are integers.

[0013] The first dielectric layer is made of polyetheretherketone (PEEK) material and is a regular hexagonal dielectric substrate with a side length of l and a thickness of t1. Its dielectric constant ε r1 =3.2; the second dielectric layer is also made of polyetheretherketone material and is a regular hexagonal dielectric substrate with a side length of l and a thickness of t3. Its material properties and size are exactly the same as those of the first dielectric layer, that is, t1 = t3. The material properties and size of the third and fourth dielectric layers are exactly the same as those of the first dielectric layer.

[0014] The first metal medium nesting layer is composed of a first regular hexagonal metal ring and a layer of filling medium, and the first regular hexagonal metal ring is embedded in the filling medium. The first regular hexagonal metal ring is made of aluminum, and its inner ring side length is a, the outer ring side length is b, the metal ring width is w, the metal ring thickness is h, and the side wall edges of the metal ring parallel to the z-axis are chamfered, and the chamfer radius is r1; the metal edges on the two surfaces of the first regular hexagonal metal ring parallel to the xy plane close to the input end and the output end are also chamfered, and the chamfer radius of the inner ring edge on both surfaces is r2, and the chamfer radius of the outer ring edge is r3; the filling medium is made of high molecular polyethylene material, and the dielectric constant ε r2 =2.3, the filling medium is also a regular hexagonal prism with a side length equal to l, the thickness of the filling medium is equal to the thickness t2 of the metal medium nesting layer, and is equal to the thickness of the metal ring, that is, t2 = h. The second metal medium nesting layer is exactly the same as the first metal medium nesting layer, and the second regular hexagonal metal ring is exactly the same as the first regular hexagonal metal ring.

[0015] The connecting dielectric layer is made of polymethacrylimide (PMI) foam material, which is a regular hexagonal dielectric substrate with a side length of l and a thickness of t4. Its dielectric constant ε r3 =1.05.

[0016] When electromagnetic waves with passband frequencies are incident on the surface of the radome near the input end at the elevation angle θ, since the period p of the periodic arrangement of the double-screen FSS units is related to the wavelength of the incident electromagnetic waves, when the electromagnetic waves interact with the frequency selective surface, only the electromagnetic waves within the working frequency band can cause resonance in the double-screen FSS units when incident, enabling the electromagnetic waves to pass through, while the electromagnetic waves outside the working frequency band will be reflected or absorbed, thus achieving the filtering effect on electromagnetic waves of specific frequencies. At the same time, the periodic structure of the frequency selective surface will cause the incident electromagnetic waves to diffract on the surface, and electromagnetic waves of different wavelengths will interfere with each other in different ways, thus producing the effects of beam offset or beam divergence. By designing the periodic structure and geometric shape corresponding to the working frequency band, the control of different frequency components can be achieved to reach the filtering effect.

[0017] For the convenience of description, the conditions satisfied by the structural parameters of the above design are uniformly introduced here:

[0018] 1. Loading the first dielectric layer and the second dielectric layer on both sides of the first metal-dielectric nested layer will reduce the resonance frequency of the double-screen FSS unit. The working frequency corresponding to the double-screen FSS unit is f 0 is the frequency of the incident wave in free space, f 0 = c / λ 0 , where c is the speed of light in vacuum, λ 0 is the wavelength of the incident wave in free space, ε r1 is the relative dielectric constant of the polyetheretherketone (PEEK) material, ε r1 = 3.2.

[0019] 2. The thickness h of the first regular hexagonal metal ring in the double-screen FSS unit needs to satisfy 0mm < h < 20mm. The larger the thickness h, the better the filtering characteristics of the double-screen FSS unit, but if the thickness of the first regular hexagonal metal ring is too large, it will affect the incident angle stability of the double-screen FSS unit and the overall volume and weight of the radome; the ring width w of the first regular hexagonal metal ring needs to satisfy 0mm < w < 10mm, otherwise, if the ring width of the first regular hexagonal metal ring is too small, the structural strength of the radome will be insufficient, and if the ring width is too large, the transmission loss will be too high; the inner ring side length a and the outer ring side length b of the first regular hexagonal metal ring satisfy 0 < a < b.

[0020] 3. In the present invention, the double-screen FSS units are periodically arranged uniformly at equal intervals, and the center connection lines of three adjacent double-screen FSS units form an equilateral triangle. To avoid the generation of grating lobes, it should be ensured that the distance p between adjacent double-screen FSS units is less than λ / 2, where λ is the working wavelength of the incident wave in the medium, Therefore and it satisfies θ is the maximum elevation angle of the incident electromagnetic wave, θ ∈ [0°, 45°], so the side length l of the regular hexagon of the double-screen FSS unit needs to satisfy

[0021] 4. The length L of the radome a and the width L b are consistent with the dimensions of the rectangular array of high-power microwave antennas. The thickness t of the radome is the sum of the thicknesses of the first-screen FSS unit, the connecting dielectric layer, and the second-screen FSS unit. The thickness of the first-screen FSS unit is the sum of the thickness t1 of the first dielectric layer, the thickness t2 of the first metal-dielectric nested layer, and the thickness t3 of the second dielectric layer. The thickness of the second-screen FSS unit is the same as that of the first-screen FSS unit, that is, t = 2(t1 + t2 + t3) + t4. Loading the first dielectric layer and the second dielectric layer helps to improve the polarization stability of the double-screen FSS unit, but the thicknesses t1 of the first dielectric layer and t3 of the second dielectric layer should not be too large, otherwise it will cause a relatively high overall profile of the radome. Therefore, 0 mm < t1 = t3 < 5 mm, 0 mm < t2 = h < 20 mm, 0 mm < t4 < 30 mm.

[0022] 5. The larger the fillet radius r1 of the side wall edge of the first regular hexagon metal ring parallel to the z-axis in the double-screen FSS unit, the higher the power capacity of the radome. However, if r1 is too large, the first regular hexagon metal ring will tend to be circular, deviating from the original design intention of the regular hexagon metal ring. Therefore, 0 mm < r1 < 12 mm. When chamfering the metal edges on the two surfaces parallel to the xoy plane near the input end and the output end, the sum of the chamfer radii r2 of the inner ring edges and r3 of the outer ring edges needs to be less than the ring width w, that is, r2 + r3 < w, otherwise the chamfering operation cannot be completed.

[0023] 6. The coordinates (x, y) of the geometric center of the double-screen FSS unit in the x-y plane are y = (3n - 1)·l / 2, where x is the abscissa of the coordinates (x, y) corresponding to the geometric center of the double-screen FSS unit at different positions, y is the ordinate of (x, y), m represents the column number of the double-screen FSS unit in the radome, n represents the row number of the double-screen FSS unit in the radome, m and n are positive integers. Under the array surface with length L a and width L b , m and n need to satisfy That is

[0024] 7. The radome is composed of N double-screen FSS units with the same structure arranged periodically and uniformly. N is the maximum number of double-screen FSS units with side length l that can be accommodated under the array surface with length L a and width L b . If m is an even number, then If m is an odd number, then

[0025] Through the electromagnetic simulation software CST Studio Suite (2022 and above), when 0<a<b is satisfied, ε r1 =3.2, ε r2 =2.3,ε r3 =1.05,0mm <h<20mm, θ∈[0°,45°], t=2(t1+t2+t3)+t4,0mm <t1=t3<5mm,0mm<t2=h<20mm,0mm<t4<30mm,0mm<r1<12mm,r2+r3<w,0mm<w<10mm, y=(3n-1)·l / 2, m and n are non-negative integers, and If m is an even number, then If m is an odd number, then L a , L b Under the condition that the size of the high-power microwave antenna array is consistent, the dual-screen FSS unit resonance is set at the operating frequency of the high-power microwave antenna array, the reflection coefficient S11<-20dB at the operating frequency, the insertion loss is less than 0.5dB, and the power capacity reaches the GW level as the optimization goal. The parameters are optimized through the scanning parameter function of the electromagnetic simulation software to obtain the optimal and accurate values ​​of parameters a, b, h, l, p, r1, r2, r3, t, t1, t2, t3, t4, w, and N.

[0026] The working process of the present invention is:

[0027] When electromagnetic waves within the working frequency band of the high-power microwave antenna array are incident on the surface of the antenna cover near the input end at a pitch angle θ, each double-screen FSS unit in the antenna cover resonates, so that the incident waves of vertical polarization and horizontal polarization can generate transmission coefficient waveforms with stable center frequency and bandwidth in the corresponding incident surface as the incident angle increases, and the incident waves are transmitted from the surface near the output end and transmitted to the high-power microwave antenna array; when electromagnetic waves outside the working frequency band of the high-power microwave antenna array are incident on the surface of the antenna cover near the input end, the double-screen FSS unit can reflect or scatter the incident electromagnetic waves to other directions, and electromagnetic waves outside the working frequency band cannot be normally transmitted to the high-power microwave antenna array. Therefore, the high-power microwave antenna array can normally transmit and receive electromagnetic waves within the working frequency band, and the electromagnetic waves are cut off outside the working frequency band, thereby realizing a stable filtering function.

[0028] At the same time, the periodically arranged dual-screen FSS units can interact with the wavelength of the incident electromagnetic wave. When the wavelength of the incident wave matches the periodic spacing of the dual-screen FSS unit, the metal conductor or dielectric structure in the dual-screen FSS unit will exhibit resonance, causing an enhancement effect of the local electromagnetic field, and the dual-screen FSS unit will selectively transmit or reflect the electromagnetic wave of this wavelength; while for electromagnetic waves of other wavelengths, the dual-screen FSS unit will exhibit a higher reflectivity or absorption rate, reducing the reflected echo in other frequency bands, thereby achieving the effect of reducing the RCS of the high-power microwave antenna array within a specific frequency range, reducing the possibility of being detected by radar, thereby realizing the function of electromagnetic stealth.

[0029] Compared with the prior art, the present invention can achieve the following technical effects:

[0030] 1. The present invention adopts a dual-screen FSS unit as the basic unit of the radome. Due to the filtering characteristics of the frequency selective surface itself, when electromagnetic waves propagate in the FSS radome, only waves in a specific frequency band can be transmitted, while waves in other frequency bands will be efficiently reflected or absorbed, so that the radome can achieve a selective transmission effect of transmitting waves within the working frequency band and cutting off waves outside the working frequency band. Compared with the single-screen FSS unit, it has a steeper frequency selectivity curve.

[0031] 2. The present invention can reduce the radar cross section of a high-power microwave antenna array within a specific frequency range without affecting the transmission performance within the passband of the high-power microwave antenna array, thereby reducing the possibility of being detected by radar and achieving the function of electromagnetic stealth within a specific frequency range.

[0032] 3. The dual-screen FSS unit in the present invention is a bandpass unit. The dual-screen FSS unit is arranged uniformly, equidistantly and periodically to avoid the generation of grating lobes. At the same time, the dual-screen FSS unit has high transmittance at the operating frequency of the high-power microwave antenna array and high reflectivity at other frequencies. Compared with the single-screen FSS unit, it can better filter out stop-band electromagnetic waves.

[0033] 4. The present invention rounds off all edges of the regular hexagonal metal ring in the double-screen FSS unit to avoid excessive concentration of the electric field at the sharp points of the metal, thereby effectively improving the overall power capacity of the present invention and can be applied to high-power microwave radiation antennas.

[0034] 5. The present invention has the characteristics of wide passband, good polarization performance and large power capacity, which meets the requirements that high-power microwave antenna arrays can effectively transmit electromagnetic waves.

[0035] 6. The present invention is highly flexible and can adjust the size of the antenna cover accordingly according to the size of the high-power microwave antenna array. It can still maintain a stable electromagnetic stealth function and good filtering characteristics within a certain size range, which meets the requirements for the development of high-power microwave antenna arrays. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 It is a schematic diagram of the overall structure of the high-power dual-screen symmetrical structure stealth radome based on the frequency selective surface of the present invention. Figure 1 (a) is the overall isometric view of the radome. Figure 1 (b) Yes Figure 1 (a) A magnified partial view.

[0037] Figure 2 It is a schematic diagram of the layered structure of a high-power dual-screen symmetrical structure stealth radome based on a frequency selective surface.

[0038] Figure 3 This is a schematic diagram of the layout of dual-screen FSS units.

[0039] Figure 4 It is a schematic diagram of the layered structure of the dual-screen FSS unit.

[0040] Figure 5 yes Figure 4 Isometric view of the regular hexagonal metal ring in the dual-screen FSS unit.

[0041] Figure 6 This is the S parameter simulation result curve of the dual-screen FSS unit. Figure 6 (a) is the reflection coefficient curve of the dual-screen FSS unit when the TE wave and TM wave are incident at θ = 0° respectively. Figure 6 (b) is the transmission coefficient curve of the double-screen FSS unit when the TE wave and TM wave are incident at θ = 0° respectively.

[0042] Figure 7 The electric field distribution diagram of the double-screen FSS unit array in an infinite plane when the TE wave and TM wave are incident at θ = 0°, Figure 7 (a) is the electric field distribution diagram of the double-screen FSS unit array when the TE wave is incident at θ = 0°. Figure 7 (b) is the electric field distribution diagram of the double-screen FSS unit array when the TM wave is incident at θ=0°.

[0043] Figure 8 It is a curve chart of simulation results of the RCS reduction effect of the high-power microwave antenna array based on the frequency selective surface of the high-power double-screen symmetrical structure stealth antenna cover and the all-dielectric antenna cover. DETAILED DESCRIPTION

[0044] The specific implementation of the present invention is further described below in conjunction with the drawings and examples.

[0045] Figure 1 It is a schematic diagram of the overall structure of the high-power dual-screen symmetrical structure stealth radome based on the frequency selective surface of the present invention. Figure 1 (a) is the overall isometric view of the high-power dual-screen symmetrical structure stealth radome based on the frequency selective surface. Figure 1 (b) Yes Figure 1 (a) A local enlarged view of point I. Figure 1 As shown, the high-power dual-screen symmetrical structure stealth antenna cover based on the frequency selective surface provided by the present invention is in the shape of a flat plate, and its length is L a , width is L b , with the same aperture as the high-power microwave antenna rectangular array, thickness t, and composed of N double-screen FSS units with the same structure arranged periodically and evenly, and the periodic spacing between the geometric centers of adjacent double-screen FSS units is p. N is a positive integer.

[0046] Figure 2 This is a schematic diagram of the layered structure of a high-power dual-screen symmetrical stealth radome based on a frequency selective surface. Figure 2 As shown, the end of the antenna cover close to the high-power microwave antenna array is defined as the output end, and the end away from the high-power microwave antenna array is defined as the input end. Each double-screen FSS unit is composed of a first-screen FSS unit 1, a connecting dielectric layer 2, and a second-screen FSS unit 3. The first-screen FSS unit 1 and the second-screen FSS unit 3 are symmetrically distributed about the connecting dielectric layer 2. The first-screen FSS unit 1, the connecting dielectric layer 2, and the second-screen FSS unit 3 are coaxially connected in the order from input to output. The first-screen FSS unit 1 and the second-screen FSS unit 3 have exactly the same structure. An xy two-dimensional coordinate system is established with the surface of the second-screen FSS unit 3 close to the output end as the reference plane, and the lower left vertex O of the rectangular surface of the second-screen FSS unit 3 close to the output end is set as the coordinate origin, and the output end-input end is set as the positive direction of the z-axis, thereby forming an xyz three-dimensional coordinate system.

[0047] like Figure 2 As shown, when the electromagnetic wave of the passband frequency (i.e., the incident wave) is incident on the surface of the radome near the input end at a pitch angle θ, each dual-screen FSS unit of the radome resonates, so that the incident waves of vertical polarization and horizontal polarization can generate transmission coefficient waveforms with stable center frequency and bandwidth in the corresponding incident plane as the pitch angle θ increases, and are transmitted from the surface of the radome near the output end, thereby realizing a stable filtering function.

[0048] Figure 3 This is a schematic diagram of the arrangement of dual-screen FSS units. Figure 3As shown in the figure, the high-power dual-screen symmetrical structure stealth radome based on frequency selective surface is composed of N dual-screen FSS units arranged periodically and evenly. Each dual-screen FSS unit is a regular hexagonal prism with a side length of l. The height of the regular hexagonal prism is equal to the thickness t of the radome. The geometric center period spacing of adjacent dual-screen FSS units is p. Define the dual-screen FSS unit adjacent to the coordinate origin O to be in the first row and first column. Then the geometric center of all dual-screen FSS units can be expressed by the coordinates (x, y) in the xy plane, and there is y=(3n-1)·l / 2, x is the horizontal coordinate of the coordinate (x, y) corresponding to the geometric center of the dual-screen FSS unit at different positions, y is the vertical coordinate (x, y), m represents the number of columns of the dual-screen FSS unit in the antenna cover, n represents the number of rows of the dual-screen FSS unit in the antenna cover, and m and n are integers.

[0049] Figure 4 Figure 1 is a schematic diagram of the hierarchical structure of a dual-screen FSS unit. Figure 4 As shown, the double-screen FSS unit is composed of a first screen FSS unit 1, a connecting dielectric layer 2 and a second screen FSS unit 3. The first screen FSS unit 1 and the second screen FSS unit 3 are symmetrically distributed about the connecting dielectric layer 2. The first screen FSS unit 1 is composed of a first dielectric layer 11, a first metal dielectric nesting layer 13 and a second dielectric layer 14. The first dielectric layer 11 is a regular hexagonal dielectric substrate made of polyetheretherketone (PEEK) material with a side length of l and a thickness of t1. Its dielectric constant ε r1 =3.2; the second dielectric layer 14 is also a regular hexagonal dielectric substrate made of polyetheretherketone (PEEK) material with a side length of l and a thickness of t3. Its material properties and size are exactly the same as those of the first dielectric layer 11, that is, t1=t3, and the first dielectric layer 11 and the second dielectric layer 14 are symmetrically loaded on both sides of the first metal dielectric nested layer 13. The first metal dielectric nested layer 13 is composed of a first regular hexagonal metal ring 12 and a layer of filling medium, and the first regular hexagonal metal ring 12 is embedded in the filling medium. The second screen FSS unit 3 is exactly the same in size and material as the first screen FSS unit 1, and is composed of a third dielectric layer 31, a second metal dielectric nested layer 33 and a fourth dielectric layer 34. The second metal dielectric nested layer 33 is composed of a second regular hexagonal metal ring 32 and a layer of filling medium, and the second regular hexagonal metal ring 32 is embedded in the filling medium. The material properties and size of the third dielectric layer 31 and the fourth dielectric layer 34 are exactly the same as those of the first dielectric layer 11, and the second metal dielectric nested layer 33 is exactly the same as the first metal dielectric nested layer 13. The connecting dielectric layer 2 is a regular hexagonal dielectric substrate made of polymethacrylimide (PMI) foam material with a side length of l and a thickness of t4. Its dielectric constant ε r3 =1.05.

[0050] Figure 5 This is an isometric view of the hexagonal metal ring in the dual-screen FSS unit. Figure 5 As shown, the first regular hexagonal metal ring 12 is made of aluminum, and its inner ring side length is a, the outer ring side length is b, the ring width is w, and the thickness is h; the side wall edges of the first regular hexagonal metal ring 12 parallel to the z-axis are chamfered, and the chamfer radius is r1; the metal edges on the two surfaces of the first regular hexagonal metal ring 12 parallel to the xy plane close to the input end and the output end are also chamfered, and the chamfer radius of the inner ring edges on the two surfaces is r2, and the chamfer radius of the outer ring edges is r3; the filling medium is made of high molecular polyethylene material, and the dielectric constant ε r2 =2.3, the filling medium is also a regular hexagonal prism with a side length equal to l, the thickness of the filling medium is equal to the thickness of the first metal medium nested layer 13, both are t2, and are equal to the thickness of the first regular hexagonal metal ring 12, that is, t2=h, so that the regular hexagonal metal ring 12 is completely wrapped in the filling medium.

[0051] Example 1

[0052] The following is an example 1 of a high-power dual-screen symmetrical structure stealth antenna cover based on a frequency selective surface for 4.3 GHz (corresponding to a microwave wavelength of 69.72 mm):

[0053] At this operating frequency, the length L of the high-power dual-screen symmetrical structure stealth radome based on the frequency selective surface is a =624mm, width is L b =334mm, thickness t=39mm, number of dual-screen FSS units N=208, side length of each dual-screen FSS unit l=26.53mm, thickness of regular hexagonal prism equals thickness of radome t=39mm, geometric center period spacing of adjacent dual-screen FSS units The thickness of the first dielectric layer 11 is t1 = 3 mm, the thickness of the first metal dielectric nested layer 13 is t2 = 9 mm, and the thickness of the second dielectric layer 14 is t3 = 3 mm. The first regular hexagonal metal ring 12 is made of aluminum, with an inner ring side length a=16.6mm, an outer ring side length b=20.76mm, a ring width w=3.6mm, and a thickness h=9.0mm. The side wall edges of the first regular hexagonal metal ring 12 parallel to the z-axis are chamfered, and the chamfer radius is r1=6.0mm; the metal edges on the two surfaces of the first regular hexagonal metal ring 12 parallel to the xy plane close to the input end and the output end are also chamfered, and the chamfer radius of the inner ring edge on the two surfaces is r2=1.5mm, and the chamfer radius of the outer ring edge is r3=2.0mm; the first dielectric layer 11 and the second dielectric layer 14 are made of polyetheretherketone (PEEK) material to form a regular hexagonal dielectric substrate with a side length l=26.53mm and a thickness t1=3.0mm, and its dielectric constant εr1 =3.2; the filling medium is made of high molecular polyethylene material, the dielectric constant ε r2 =2.3, the filling medium is also a regular hexagonal prism with a side length of l = 26.53 mm, and the thickness of the filling medium is t2 = h = 9.0 mm; the connecting medium layer 2 is made of polymethacrylimide (PMI) foam material to form a regular hexagonal dielectric substrate with a side length of l = 26.53 mm and a thickness of t4 = 9.0 mm, and its dielectric constant ε r3 =1.05.

[0054] Example 1 The S parameter simulation results of the dual-screen FSS unit in the high-power dual-screen symmetrical structure stealth antenna cover based on the frequency selective surface with a center frequency of 4.3 GHz are as follows Figure 6 As shown, Figure 6 (a) is the reflection coefficient curve of the dual-screen FSS unit when the TE wave and TM wave are incident at θ = 0° respectively. Figure 6 (a) The horizontal axis is frequency (Frequency), and the vertical axis is the reflection coefficient (Reflection Coefficient) S11 of the dual-screen FSS unit; Figure 6 (b) is the transmission coefficient curve of the double-screen FSS unit when the TE wave and TM wave are incident at θ = 0° respectively. Figure 6 (b) The horizontal axis is frequency, and the vertical axis is the transmission coefficient S21 of the dual-screen FSS unit. Figure 6 It can be seen that because the dual-screen FSS unit is a regular hexagon with extremely high geometric symmetry, the S parameter curves of the TE wave and the TM wave almost completely overlap, and the bandwidth of S11<-10dB is 1.02GHz, indicating that the dual-screen FSS unit has a wide operating bandwidth and excellent polarization stability.

[0055] Figure 7 The electric field distribution diagram of the dual-screen FSS unit in an infinite plane is simulated when the TE wave and TM wave are incident at θ = 0°. Figure 7 (a) is the electric field distribution diagram of the double-screen FSS unit array when the TE wave is incident at θ = 0°. Figure 7 (b) is the electric field distribution diagram of the double-screen FSS unit array when the TM wave is incident at θ = 0°. Figure 7It can be seen that the electric field distribution inside the first regular hexagonal metal ring 12 is relatively uniform. When the TE wave is incident at θ = 0°, the maximum electric field strength after the double-screen FSS unit array is 2218.39V / m; when the TM wave is incident at θ = 0°, the maximum electric field strength is 2410.56V / m. When the injection power is 0.5W, according to the dielectric window surface breakdown threshold of 60kV / cm, when the double-screen FSS unit array works at 4.3GHz, the power capacity when the TE wave is incident is 2GW / m 2 , the power capacity when TM wave is incident is 1.69GW / m 2 , all reaching the GW level, meeting the power capacity requirements of high-power microwave strong electromagnetic radiation.

[0056] Another length L is constructed using polyetheretherketone (PEEK) material. a =624mm, width is L b =334mm, and a full dielectric radome with a thickness of t=39mm. The full dielectric radome and Example 1 are respectively combined with the same high-power microwave antenna array for simulation, and the simulation result curve of the RCS reduction effect of the full dielectric radome and Example 1 on the high-power microwave antenna array is obtained, as shown in FIG. Figure 8 As shown. Figure 8 It can be seen that compared with the all-dielectric antenna cover, the high-power dual-screen symmetrical structure stealth antenna cover based on the frequency selective surface in Example 1 of the present invention has a significant reduction in RCS in the frequency band range of 8GHz-10GHz, with an average RCS reduction of 10.4dB in the 8GHz-10GHz range, and a maximum RCS reduction of 35.5dB at 9.5GHz. This shows that the dual-screen FSS unit structure design of Example 1 is better, and the overall performance of Example 1 is better. It can effectively selectively reflect electromagnetic waves, play a role in reducing the RCS of a single station in a specific frequency range, reduce the detectability of the high-power microwave antenna array, and have a certain electromagnetic stealth effect.

[0057] The present invention has both electromagnetic stealth performance and good electromagnetic transmission characteristics, the power capacity can reach the GW level, it has good polarization stability, and can selectively transmit or reflect electromagnetic waves within a specific frequency range, which neither affects the normal radiation of the high-power microwave antenna array within the working frequency band, nor can it reduce the radar scattering cross section of the high-power microwave antenna array within the specific frequency range. Compared with the single-screen FSS unit, it has a wider working bandwidth and a stronger RCS reduction capability, and can solve the problem that the current high-power microwave antenna array cannot have both electromagnetic transmission characteristics and electromagnetic stealth functions, and the ordinary FSS structure is easily penetrated by strong electromagnetic radiation. The present invention has strong flexibility and can adjust the size of the antenna cover according to the high-power microwave antenna arrays with different array sizes, which meets the requirements for the development of high-power microwave antenna arrays.

[0058] The above implementation modes are only used to illustrate the present invention, but not to limit the present invention. Ordinary technicians in the relevant technical field can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, all equivalent technical solutions also fall within the protection scope of the present invention.

Claims

1. A high-power dual-screen symmetrical structure stealth antenna cover based on frequency selective surface, characterized in that The high-power dual-screen symmetrical structure stealth radome based on frequency selective surface is flat and its length is L. a , width is L b , with a thickness of t, and is composed of N double-screen FSS units of the same structure arranged periodically and evenly at equal intervals, where N is the maximum number of double-screen FSS units accommodated under the array surface of the radome, and N is a positive integer; The end of the antenna cover close to the high-power microwave antenna array is defined as the output end, and the end away from the high-power microwave antenna array is defined as the input end; each double-screen FSS unit is composed of a first-screen FSS unit (1), a connecting medium layer (2) and a second-screen FSS unit (3); the first-screen FSS unit (1) and the second-screen FSS unit (3) are symmetrically distributed about the connecting medium layer (2); the first-screen FSS unit (1), the connecting medium layer (2) and the second-screen FSS unit (3) are coaxially connected in order from input to output; the first-screen FSS unit (1) and the second-screen FSS unit (3) have the same structure; an xy two-dimensional coordinate system is established with the surface of the second-screen FSS unit (3) close to the output end as a reference plane, the lower left vertex O of the rectangular surface of the second-screen FSS unit (3) close to the output end is set as the coordinate origin, and the output end-input end is set as the positive direction of the z-axis, thereby forming an xyz three-dimensional coordinate system; When the electromagnetic wave of the passband frequency, i.e., the incident wave, is incident on the surface of the radome near the input end at a pitch angle θ, each double-screen FSS unit of the radome will resonate, so that the incident waves of vertical polarization and horizontal polarization will generate transmission coefficient waveforms with stable center frequency and bandwidth in the corresponding incident plane as the pitch angle θ increases, and will be transmitted from the surface of the radome near the output end, thus achieving filtering; The dual-screen FSS unit is a regular hexagonal prism with a side length of l. The height of the regular hexagonal prism is equal to the thickness t of the radome. The periodic spacing between the geometric centers of adjacent dual-screen FSS units is p. The dual-screen FSS unit adjacent to the coordinate origin O is defined as being in the first row and first column. The geometric centers of all dual-screen FSS units are represented by coordinates (x, y) in the xy plane. y=(3n-1)·l / 2, x is the abscissa of the coordinates (x, y) corresponding to the geometric center of the dual-screen FSS unit at different positions, y is the ordinate of (x, y), m represents the number of columns where the dual-screen FSS unit is located in the radome, n represents the number of rows where the dual-screen FSS unit is located in the radome, and m and n are integers; The double-screen FSS unit is composed of a first-screen FSS unit (1), a connecting dielectric layer (2) and a second-screen FSS unit (3), wherein the first-screen FSS unit (1) and the second-screen FSS unit (3) are symmetrically distributed with respect to the connecting dielectric layer (2); the first-screen FSS unit (1) is composed of a first dielectric layer (11), a first metal dielectric nested layer (13) and a second dielectric layer (14), wherein the first dielectric layer (11) is a regular hexagonal dielectric substrate made of polyetheretherketone material with a side length of l and a thickness of t1; The second dielectric layer (14) is also a regular hexagonal dielectric substrate made of polyetheretherketone material with a side length of l and a thickness of t3. The material properties and size of the second dielectric layer (14) are the same as those of the first dielectric layer (11), that is, t1=t3, and the first dielectric layer (11) and the second dielectric layer (14) are symmetrically loaded on both sides of the first metal dielectric nested layer (13); the first metal dielectric nested layer (13) is composed of a first regular hexagonal metal ring (12) and a layer of filling dielectric, and the first regular hexagonal metal ring (12) is embedded in the filling dielectric; the second screen FSS unit (3) has the same size and material as the first screen FSS unit (1), and is composed of a third dielectric layer (31), a second metal dielectric nested layer (33) and a fourth dielectric layer (34); the second metal dielectric nested layer (33) is composed of a second regular hexagonal metal ring (32) and a layer of filling dielectric, and the second regular hexagonal metal ring (32) is embedded in the filling dielectric; The material properties and dimensions of the third dielectric layer (31) and the fourth dielectric layer (34) are the same as those of the first dielectric layer (11); the second metal dielectric nested layer (33) is the same as the first metal dielectric nested layer (13); the connecting dielectric layer (2) is a regular hexagonal dielectric substrate made of polymethacrylimide foam material with a side length of l and a thickness of t4; The first regular hexagonal metal ring (12) is made of aluminum, and has an inner ring side length of a, an outer ring side length of b, a ring width of w, and a thickness of h. The side wall edges of the first regular hexagonal metal ring (12) parallel to the z-axis are chamfered, and the chamfer radius is r1. The metal edges on the two surfaces of the first regular hexagonal metal ring (12) parallel to the xy plane close to the input end and close to the output end are also chamfered, and the chamfer radius of the inner ring edges on both surfaces is r2, and the chamfer radius of the outer ring edges is r3. The filling medium is made of high molecular polyethylene material, and the filling medium is also in the form of a regular hexagonal prism with a side length equal to l. The thickness of the filling medium is equal to the thickness of the first metal medium nesting layer (13), which is t2, and is equal to the thickness of the first regular hexagonal metal ring (12), that is, t2=h, so that the regular hexagonal metal ring 12 is completely wrapped in the filling medium.

2. The high-power dual-screen symmetrical structure stealth antenna cover based on frequency selective surface as claimed in claim 1, characterized in that The relative dielectric constant ε of the polyetheretherketone material used in the first dielectric layer (11) and the second dielectric layer (14) is r1 =3.2, the dielectric constant ε of the polymethacrylimide foam material used in the connecting medium layer (2) r3 =1.05, the dielectric constant ε of the filling medium is a high molecular polyethylene material r2 =2.3; the operating frequency corresponding to the dual-screen FSS unit f0 is the frequency of the incident wave in free space, f0 = c / λ0, where c is the speed of light in a vacuum, and λ0 is the wavelength of the incident wave in free space.

3. The high-power dual-screen symmetrical structure stealth antenna cover based on frequency selective surface as claimed in claim 1, characterized in that In the double - screen FSS unit, the thickness h of the first regular - hexagon metal ring (12) satisfies 0mm < h < 20mm; the ring width w of the first regular - hexagon metal ring (12) satisfies 0mm < w < 10mm; the inner - ring side length a and the outer - ring side length b of the first regular - hexagon metal ring (12) satisfy 0 < a < b; the fillet radius r1 of the side - wall edge parallel to the z - axis of the first regular - hexagon metal ring (12) satisfies 0mm < r1 < 12mm, and the sum of the chamfer radius r2 of the inner - ring edge and the chamfer radius r3 of the outer - ring edge satisfies r2 + r3 < w.

4. The high-power dual-screen symmetrical structure stealth antenna cover based on frequency selective surface as claimed in claim 1, characterized in that The geometric center period spacing of adjacent double-screen FSS units And meet is the working wavelength of the incident wave in the medium, θ is the maximum elevation angle of electromagnetic wave incidence, θ∈[0°,45°], and the side length l of the regular hexagon of the double-screen FSS unit satisfies λ0 is the wavelength of the incident wave in free space, ε r1 is the relative dielectric constant of polyetheretherketone material.

5. The high-power dual-screen symmetrical structure stealth antenna cover based on frequency selective surface as claimed in claim 1, characterized in that The length L of the radome a and width L b In keeping with the size of the rectangular array of high-power microwave antennas, the thickness t of the antenna cover is the sum of the thicknesses of the first screen FSS unit (1), the connecting dielectric layer (2) and the second screen FSS unit (3). The thickness of the first screen FSS unit (1) is the sum of the thickness t1 of the first dielectric layer (11), the thickness t2 of the first metal dielectric nested layer (13) and the thickness t3 of the second dielectric layer (14). The thickness of the second screen FSS unit (3) is the same as the thickness of the first screen FSS unit (1), that is, t=2(t1+t2+t3)+t4; 0mm <t1=t3<5mm,0mm<t2=h<20mm,0mm<t4<30mm。 6. The high-power dual-screen symmetrical structure stealth antenna cover based on frequency selective surface as claimed in claim 1, characterized in that The horizontal coordinate (x, y) of the geometric center of the dual-screen FSS unit in the xy plane The ordinate y of (x, y) is (3n-1)·l / 2, m represents the number of columns where the dual-screen FSS unit is located in the radome, n represents the number of rows where the dual-screen FSS unit is located in the radome, m and n are positive integers, and the length is L a , width is L b Under the front, m, must satisfy Right now 7. The high-power dual-screen symmetrical structure stealth antenna cover based on frequency selective surface as claimed in claim 1, characterized in that The N satisfies that if m is an even number, then If m is an odd number, then 8. The high-power dual-screen symmetrical structure stealth antenna cover based on frequency selective surface as claimed in claim 1, characterized in that Through electromagnetic simulation software, in the <a<b, ε r1 =3.2, ε r2 =2.3,ε r3 =1.05,0mm <h<20mm, θ∈[0°,45°], t=2(t1+t2+t3)+t4,0mm <t1=t3<5mm,0mm<t2=h<20mm,0mm<t4<30mm,0mm<r1<12mm,r2+r3<w,0mm<w<10mm, y=(3n-1)·l / 2, m and n are non-negative integers, and If m is an even number, then If m is an odd number, then L a , L b Under the condition that the size of the high-power microwave antenna array is consistent, the double-screen FSS unit resonance is set at the operating frequency of the high-power microwave antenna array, the reflection coefficient S11<-20dB at the operating frequency, the insertion loss is less than 0.5dB, and the power capacity reaches the GW level as the optimization goal. The scanning parameter function of the electromagnetic simulation software is used to optimize each parameter to obtain the optimal and precise values ​​of parameters a, b, h, l, p, r1, r2, r3, t, t1, t2, t3, t4, w, and N.

9. The high-power dual-screen symmetrical structure stealth antenna cover based on frequency selective surface as claimed in claim 8, characterized in that The electromagnetic simulation software is CST Studio Suite 2022 and above.

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