A broadband sandwiched antenna radome based on dual-band metasurface

Abstract

The application discloses a kind of wideband sandwich radome based on double-band super surface, it includes sequentially arranged first impedance matching layer, radome frequency selective surface layer, second impedance matching layer, the radome frequency selective surface layer includes several periodic frequency selective surface units, radome frequency selective surface layer is formed by multilayer metal structure and dielectric substrate A space filter, so that corresponding wideband sandwich radome has wave band selectivity;When electromagnetic wave irradiates to the surface of wideband sandwich radome based on double-band super surface, two transmission poles are generated in low frequency band to form second-order band-pass filter response, and three transmission poles are generated in high frequency band to form third-order band-pass filter response.The advantages are: the wideband sandwich radome has the excellent characteristics of double-band wideband wave transmission, large-angle stability, out-of-band steep cutoff, adjustable frequency ratio of wave transmission band center frequency, polarization insensitivity and the like by the above structure, and the overall structure is simple and easy to process.

Description

Technical Field

[0001] This invention relates to the field of radomes, and more specifically to a broadband sandwich radome based on a dual-band metasurface. Background Technology

[0002] Radomes are typically located at the front of an aircraft. They must protect the internal radar system from harsh external environments such as rain, fog, frost, sandstorms, intense sunlight, or extreme temperatures, while also ensuring normal communication of the antennas within the radome during flight. Therefore, radomes need to possess load-bearing, protective, and communication capabilities. As the requirements for aircraft anti-jamming and anti-stealth capabilities continue to increase, single-homing guidance methods are no longer sufficient for operational missions. Dual-band composite homing guidance methods have broad application prospects and development potential. On the other hand, the requirements for precision guidance are constantly increasing the operating bandwidth of radar antennas, which necessitates that radomes also possess broadband wave transmission performance. However, traditional half-wavewall radomes lack broadband wave transmission characteristics, while thin-wall radomes offer wider bandwidth but have limited load-bearing capacity. Therefore, it is necessary to develop a new radome that can meet current requirements. Summary of the Invention

[0003] Based on the aforementioned technical problems, the purpose of this invention is to overcome the shortcomings and defects in the prior art. Specifically, this invention provides a broadband sandwich radome based on a dual-band metasurface. This radome combines a first impedance matching layer, a frequency selective surface layer, and a second impedance matching layer. The frequency selective surface layer forms a spatial filter through a multi-layer metal structure and a dielectric substrate, enabling the corresponding broadband sandwich radome to have selective transmission bands. At the same time, it also has excellent characteristics such as dual-band broadband transmission, large-angle stability, steep out-of-band cutoff, adjustable transmission band center frequency ratio, and polarization insensitivity. The overall structure is simple and easy to manufacture.

[0004] To achieve the above objectives, the present invention is implemented through the following technical solution:

[0005] A broadband sandwich radome based on a dual-band metasurface includes a first impedance matching layer, a frequency selective surface layer, and a second impedance matching layer arranged sequentially. The frequency selective surface layer comprises a plurality of periodically arranged frequency selective surface elements, and each frequency selective surface element comprises a first metal structure, a first dielectric substrate, a second metal structure, a second dielectric substrate, and a third metal structure arranged sequentially.

[0006] The first metal structure includes a first inner metal square ring and a first outer metal square ring surrounding the first inner metal square ring; the second metal structure includes a Jerusalem cross structure and a second outer metal square ring surrounding the Jerusalem cross structure; the third metal structure includes a third inner metal square ring and a third outer metal square ring surrounding the third inner metal square ring.

[0007] When electromagnetic waves irradiate the surface of a broadband sandwich radome based on a dual-band metasurface, two transmission poles are generated in the low-frequency band to form a second-order bandpass filter response, and three transmission poles are generated in the high-frequency band to form a third-order bandpass filter response.

[0008] Optionally, the first metal structure and the third metal structure can be equivalent to an "LC" series circuit with a second inductor L connected in parallel. b The first metal structure's "LC" series circuit includes a first capacitor C connected in series. a and the first inductor L a The first metal structure and the third metal structure are completely identical; the second metal structure can be equivalent to an "LC" series circuit connected in parallel with another "LC" parallel circuit, and the "LC" series circuit of the second metal structure includes a third capacitor C. c and the fourth inductor L d Its "LC" parallel circuit includes a second capacitor C connected in parallel. b and the third inductor L c ;

[0009] The first dielectric substrate and the second dielectric substrate can be equivalent to transmission lines;

[0010] The equivalent circuit of the frequency selective surface layer of the radome can generate two transmission poles in the low-frequency band, forming a transmission passband with a second-order bandpass filter response; and can generate three transmission poles in the high-frequency band, forming a transmission passband with a third-order bandpass filter response, thereby expanding the bandwidth of the radome's transmission frequency band.

[0011] Optionally, based on the equivalent circuit of the frequency-selective surface layer of the radome, the center frequency f1 of its first transmission passband depends on the second inductor L. b Third inductor L c Second capacitor C b and the third capacitor C c The value; the center frequency f2 of the second transmission passband depends on the first inductor L. a Second inductor L b Fourth inductor L d First capacitor C a Second capacitor C b and the third capacitor C cThe value; by adjusting the geometric dimensions of the topologies of the first metal structure, the second metal structure, and the third metal structure, the frequency ratio of the center frequencies of the two transmission passbands can be adjusted.

[0012] Optionally, the first capacitor C a The capacitance range is 10 to 11 fF, and the first inductor L a The inductance range is 3.0–5.0 nH, and the second inductor L b The inductance range is 23.0–26.0 nH;

[0013] And / or, the third capacitor C c The capacitance range is 40–60 fF, and the fourth inductor L d The inductance range is 2–3 nH, and the third inductor L c The capacitance range is 4–6 nH, and the second capacitor C b The capacitance range is 100–150 fF;

[0014] And / or, the first dielectric substrate and the second dielectric substrate can be equivalent to having a characteristic impedance of Transmission lines;

[0015] And / or, the frequency ratio R of the two transmission passband center frequencies ranges from 2 to 5.

[0016] Optionally, the first impedance matching layer includes a first high-strength high-dielectric-constant dielectric substrate and a first low-strength low-dielectric-constant dielectric substrate, wherein the first low-strength low-dielectric-constant dielectric substrate is located between the first high-strength high-dielectric-constant dielectric substrate and the radome frequency selection surface layer.

[0017] The second impedance matching layer includes a second high-strength high-dielectric-constant dielectric substrate and a second low-strength low-dielectric-constant dielectric substrate, the second low-strength low-dielectric-constant dielectric substrate being located between the second high-strength high-dielectric-constant dielectric substrate and the radome frequency selective surface layer.

[0018] Optionally, by optimizing the dielectric constant and thickness of the first high-strength high-dielectric-constant dielectric substrate, the first low-strength low-dielectric-constant dielectric substrate, the second high-strength high-dielectric-constant dielectric substrate, and the second low-strength low-dielectric-constant dielectric substrate, the broadband sandwich radome can be matched with the air impedance under large-angle electromagnetic wave incidence. The above parameters can be optimized according to formulas (1) and (2).

[0019]

[0020]

[0021] The first impedance matching layer and the second impedance matching layer have the same composition, ε oyt ε1 is the equivalent dielectric constant of the first impedance matching layer and the second impedance matching layer; ε2 is the dielectric constant of the first low-strength low-dielectric-constant dielectric substrate and the second low-strength low-dielectric-constant dielectric substrate; ε3 is the dielectric constant of the first high-strength high-dielectric-constant dielectric substrate and the second high-strength high-dielectric-constant dielectric substrate; d2 is the thickness of the first low-strength low-dielectric-constant dielectric substrate and the second low-strength low-dielectric-constant dielectric substrate; d3 is the thickness of the first high-strength high-dielectric-constant dielectric substrate and the second high-strength high-dielectric-constant dielectric substrate; θ max λ0 is the maximum incident angle of the electromagnetic wave, which ranges from 45° to 75°, and λ0 is the wavelength of the transmission frequency in free space.

[0022] Optionally, the dielectric constant ε3 of the first high-strength high-dielectric-constant dielectric substrate and / or the second high-strength high-dielectric-constant dielectric substrate ranges from 2 to 3, and the thickness d3 of the first high-strength high-dielectric-constant dielectric substrate and / or the second high-strength high-dielectric-constant dielectric substrate ranges from 0.5 to 1.5 mm.

[0023] And / or, the dielectric constant ε2 of the first low-strength low-dielectric-constant dielectric substrate and / or the second low-strength low-dielectric-constant dielectric substrate ranges from 1 to 1.5, and the thickness d2 of the first low-strength low-dielectric-constant dielectric substrate and / or the second low-strength low-dielectric-constant dielectric substrate ranges from 1.4 to 3.4 mm.

[0024] Optionally, the side length L1 of the first inner metal square ring is in the range of 2.5 to 3.0 mm, and its width W1 is in the range of 0.3 to 0.55 mm; the side length L2 of the first outer metal square ring is in the range of 4.0 to 4.18 mm, and its width W2 is in the range of 0.05 to 0.15 mm, and the distance S between the first outer metal square ring and the outer edge of the unit period of the first dielectric substrate is greater than or equal to 0.01 mm;

[0025] And / or, the side length of the third inner metal square ring is in the range of 2.5 to 3.0 mm, and its width is in the range of 0.3 to 0.55 mm; the side length of the third outer metal square ring is in the range of 4.0 to 4.18 mm, and its width is in the range of 0.05 to 0.15 mm, and the distance between the third outer metal square ring and the outer edge of the unit period of the second dielectric substrate is greater than or equal to 0.01 mm;

[0026] And / or, the side length L3 of the second outer metal square ring is the same as the side length P of the unit period of the first dielectric substrate, and its width W3 ranges from 0.42 to 0.62 mm; the long side length L4 of the Jerusalem cross structure ranges from 2.12 to 2.32 mm, its long side width W4 ranges from 0.1 to 0.3 mm, its short side length L5 ranges from 0.42 to 0.62 mm, and its short side width W5 ranges from 0.2 to 0.4 mm;

[0027] And / or, the center of the first inner metal square ring coincides with the center of the first outer metal square ring; the Jerusalem cross structure is placed in the middle of the second outer metal square ring and their centers coincide; the center of the third inner metal square ring coincides with the center of the third outer metal square ring.

[0028] Optionally, the thickness d1 of the first dielectric substrate ranges from 1.5 to 1.7 mm, the dielectric constant ε1 of the first dielectric substrate ranges from 3.0 to 3.2, the loss tangent of the first dielectric substrate is less than or equal to 0.008, and the side length P of the cell period of the first dielectric substrate ranges from 4.2 to 4.4 mm.

[0029] And / or, at least one of the following: the material used to prepare the second dielectric substrate, its thickness range, dielectric constant range, loss tangent range, and cell period side length range is the same as that of the first dielectric substrate.

[0030] Optionally, each of the first metal structure, the second metal structure, and the third metal structure of the broadband sandwich radome is symmetrical about the x-axis and the y-axis, so that the broadband sandwich radome has polarization insensitive characteristics.

[0031] Between the two transmission passbands of the broadband sandwich radome, the transmission coefficient of electromagnetic waves is much less than -10dB, and the broadband sandwich radome exhibits total internal reflection characteristics.

[0032] The transmission coefficients of electromagnetic waves in the transition bands of the upper and lower sidebands of the two transmission passbands of the broadband sandwich radome can rapidly drop to below -10dB, and the broadband sandwich radome has a steep cutoff characteristic outside the passband.

[0033] Compared with the prior art, the present invention has the following advantages:

[0034] In a broadband sandwich radome based on a dual-band metasurface of the present invention, the radome combines a first impedance matching layer, a frequency selective surface layer, and a second impedance matching layer. The frequency selective surface layer forms a spatial filter through a multi-layer metal structure and a dielectric substrate, so that the corresponding broadband sandwich radome has selective transmission band. At the same time, it also has excellent characteristics such as dual-band broadband transmission, large-angle stability, steep out-of-band cutoff, adjustable transmission band center frequency ratio, and polarization insensitivity. The overall structure is simple and easy to process.

[0035] Furthermore, the broadband sandwich radome of the present invention has two independent resonant points in the first transmission passband, forming a bandpass filter response with second-order resonant characteristics; and has three independent resonant points in the second transmission passband, forming a bandpass filter response with third-order resonant characteristics.

[0036] Furthermore, the broadband sandwich radome of the present invention exhibits an electromagnetic wave transmission coefficient much less than -10dB between the two transmission passbands, and the radome displays total internal reflection characteristics. In the transition band between the upper and lower sidebands of the two transmission passbands, the transmission coefficient can rapidly decrease to below -10dB, and the radome possesses a steep cutoff characteristic outside the passband.

[0037] Furthermore, the broadband sandwich radome of the present invention can achieve adjustable frequency ratio of the two transmission passband center frequencies by adjusting the geometric dimensions of the topology. Attached Figure Description

[0038] Figure 1 This is a schematic diagram of the overall three-dimensional structure of a broadband sandwich radome based on a dual-band metasurface according to the present invention.

[0039] Figure 2 This is a schematic diagram of the first metal structure of the frequency selection surface layer of the radome of the present invention;

[0040] Figure 3 This is a schematic diagram of the second metal structure of the frequency selection surface layer of the radome of the present invention;

[0041] Figure 4 This is a schematic diagram of the equivalent circuit structure of the frequency selection surface layer of the radome of the present invention;

[0042] Figure 5 The S11 simulation results are for the broadband sandwich radome based on a dual-band metasurface of the present invention.

[0043] Figure 6 The equivalent circuit of the frequency selective surface layer of the radome of the present invention is in L d C a The center frequency of the second transmission band changes under different values;

[0044] Figure 7The simulation results of TE polarization S21 of the broadband sandwich radome based on dual-band metasurface of the present invention under different electromagnetic wave incident angles are shown.

[0045] Figure 8 The simulation results of the TM polarization S21 of the broadband sandwich radome based on dual-band metasurface of the present invention under different electromagnetic wave incident angles are shown. Detailed Implementation

[0046] The present invention will be further described below with reference to the accompanying drawings and embodiments: This embodiment is implemented under the premise of the technical solution of the present invention, and provides detailed implementation methods and specific operation processes, but the protection scope of the present invention is not limited to the following embodiments.

[0047] like Figure 1 As shown, this invention provides a broadband sandwich radome based on a dual-band metasurface. The broadband sandwich radome includes a first impedance matching layer I, a radome frequency selective surface layer II, and a second impedance matching layer III arranged sequentially. The radome frequency selective surface layer II includes several periodically arranged frequency selective surface units with the same structure. The frequency selective surface units have a "sandwich" structure, which includes a first metal structure 3, a first dielectric substrate 4 (i.e., the upper dielectric substrate), a second metal structure 5, a second dielectric substrate 6 (i.e., the lower dielectric substrate), and a third metal structure 7 arranged sequentially.

[0048] In this embodiment, the first impedance matching layer I and the second impedance matching layer III are respectively disposed on both sides of the frequency selective surface layer II of the radome, to achieve impedance matching between the broadband sandwich radome based on the dual-band metasurface and the air impedance under large-angle electromagnetic wave illumination. The first dielectric substrate 4 and the second dielectric substrate 6 provide support. The first metal structure 3 is located between the first impedance matching layer I and the first dielectric substrate 4, and the third metal structure 7 is located between the second dielectric substrate 6 and the second impedance matching layer III. That is, the first metal structure 3 is the top metal structure, the second metal structure 5 is the middle metal structure, and the third metal structure 7 is the bottom metal structure. The frequency selective surface layer II of the radome is composed of several frequency selective surface units with identical structures arranged periodically along the x and y directions. That is, each of the first metal structure 3, the second metal structure 5, and the third metal structure 7 of the frequency selective surface layer II of the radome is symmetrical about the x-axis and the y-axis, so that the broadband sandwich radome has polarization insensitivity characteristics.

[0049] Among them, such as Figure 2 As shown, the first metal structure 3 includes a first inner metal square ring 3-1 and a first outer metal square ring 3-2 surrounding the first inner metal square ring 3-1; as Figure 3As shown, the second metal structure 5 includes a Jerusalem cross structure 5-1 and a second outer metal square ring 5-2 surrounding the Jerusalem cross structure 5-1; the third metal structure 7 includes a third inner metal square ring and a third outer metal square ring surrounding the third inner metal square ring. When electromagnetic waves irradiate the surface of the broadband sandwich radome based on a dual-band metasurface, two transmission poles are generated in the low-frequency band to form a second-order bandpass filter response, and three transmission poles are generated in the high-frequency band to form a third-order bandpass filter response. In this embodiment, the first transmission frequency band of the broadband sandwich radome is the C-band, and the second transmission frequency band is between the Ku and K bands.

[0050] like Figure 1 , Figure 4 and Figure 5 As shown, in this embodiment, the first metal structure 3 and the third metal structure 7 can be equivalent to an "LC" series circuit with a second inductor L connected in parallel. b The "LC" series circuit of the first metal structure 3 includes a first capacitor C connected in series. a and the first inductor L a The first metal structure 3 and the third metal structure 7 are completely identical; the second metal structure 5 can be equivalent to an "LC" series circuit connected in parallel with another "LC" parallel circuit, and the "LC" series circuit of the second metal structure 5 includes a third capacitor C. c and the fourth inductor L d Its "LC" parallel circuit includes a second capacitor C connected in parallel. b and the third inductor L c The first dielectric substrate 4 and the second dielectric substrate 6 can be equivalent to transmission lines. The equivalent circuit of the frequency selective surface layer II of the radome can generate two transmission poles in the low-frequency band, forming a transmission passband with a second-order bandpass filter response; and can generate three transmission poles in the high-frequency band, forming a transmission passband with a third-order bandpass filter response, so as to effectively extend the bandwidth of the radome's transmission frequency band.

[0051] like Figure 1 , Figure 4 and Figure 6 As shown, based on the equivalent circuit of the frequency-selective surface layer II of the radome, the center frequency f1 of its first transmission passband depends on the second inductor L. b Third inductor L c Second capacitor C b and the third capacitor C c The value; the center frequency f2 of the second transmission passband depends on the first inductor L. a Second inductor L b Fourth inductor L d First capacitor C a Second capacitor Cb and the third capacitor C c The value of R. By adjusting the geometric dimensions of the topological structures of the first metal structure 3, the second metal structure 5, and the third metal structure 7, the frequency ratio of the center frequencies of the two transmission passbands can be adjusted. That is, by changing the dimensions of the first outer metal square ring 3-2 of the first metal structure 3 and the Jerusalem cross structure 5-1 of the second metal structure 5, the frequency ratio R (R = f2 / f1) of the center frequencies of the two transmission passbands can be changed. Optionally, the value of R is between 2 and 5. In this embodiment, R is 3.7. In this embodiment, the first metal structure 3 and the third metal structure 7 are identical in size, shape, and material to facilitate the adjustment of the entire radome.

[0052] Optionally, the first capacitor C a The capacitance range is 10 to 11 fF, and the first inductor L a The inductance range is 3.0–5.0 nH, and the second inductor L b The inductance range is 23.0–26.0 nH; and / or, the third capacitor C c The capacitance range is 40–60 fF, and the fourth inductor L d The inductance range is 2–3 nH, and the third inductor L c The capacitance range is 4–6 nH, and the second capacitor C b The capacitance range is 100–150 fF; and / or, the first dielectric substrate 4 and the second dielectric substrate 6 can be equivalent to having a characteristic impedance of The transmission line; and / or, the frequency ratio R of the two transmission passband center frequencies ranges from 2 to 5. It is understood that the aforementioned first capacitor C... a First inductor L a The value range of etc. is not limited to the above. In practical applications, it can also be other ranges of values, as long as the corresponding function can be achieved. This invention does not impose any restrictions on this. In this embodiment, the first capacitor C a The first inductor L is 10.6fF. a The second inductor is 4.0nH. b It is 24.5nH. The fourth inductor L d The second capacitor C is 2.7nH. b The third inductor L is 48.5fF. c The third capacitor C is 5.3nH. c It is 137.1fF.

[0053] like Figure 1As shown, in this embodiment, the first impedance matching layer I includes a first high-strength, high-dielectric-constant dielectric substrate 1 and a first low-strength, low-dielectric-constant dielectric substrate 2, with the first low-strength, low-dielectric-constant dielectric substrate 2 located between the first high-strength, high-dielectric-constant dielectric substrate 1 and the radome frequency selective surface layer II. The second impedance matching layer III includes a second high-strength, high-dielectric-constant dielectric substrate 9 and a second low-strength, low-dielectric-constant dielectric substrate 8, with the second low-strength, low-dielectric-constant dielectric substrate 8 located between the second high-strength, high-dielectric-constant dielectric substrate 9 and the radome frequency selective surface layer II.

[0054] By optimizing the dielectric constants (ε2, ε3) and thicknesses (d2, d3) of the first high-strength high-dielectric-constant dielectric substrate 1, the first low-strength low-dielectric-constant dielectric substrate 2, the second high-strength high-dielectric-constant dielectric substrate 9, and the second low-strength low-dielectric-constant dielectric substrate 8, the broadband sandwich radome can be matched with the air impedance under large-angle electromagnetic wave incidence. Furthermore, the above parameters can be optimized according to formulas (1) and (2).

[0055]

[0056]

[0057] The first impedance matching layer I and the second impedance matching layer III have the same composition, ε out ε1 is the equivalent dielectric constant of the first impedance matching layer I and the second impedance matching layer III; ε2 is the dielectric constant of the first low-strength low-dielectric-constant dielectric substrate 2 and the second low-strength low-dielectric-constant dielectric substrate 8; ε3 is the dielectric constant of the first high-strength high-dielectric-constant dielectric substrate 1 and the second high-strength high-dielectric-constant dielectric substrate 9; d2 is the thickness of the first low-strength low-dielectric-constant dielectric substrate 2 and the second low-strength low-dielectric-constant dielectric substrate 8; d3 is the thickness of the first high-strength high-dielectric-constant dielectric substrate 1 and the second high-strength high-dielectric-constant dielectric substrate 9; θ max θ is the maximum incident angle of the electromagnetic wave, ranging from 45° to 75°, and λ0 is the wavelength of the transmission frequency in free space. In this embodiment, θ max At a 60° angle, this broadband sandwich radome can still maintain extremely high transmittance even when incident at a large angle of 60°.

[0058] Optionally, the dielectric constant ε3 of the first high-strength high-dielectric-constant dielectric substrate 1 and / or the second high-strength high-dielectric-constant dielectric substrate 9 ranges from 2 to 3, and the thickness d3 of the first high-strength high-dielectric-constant dielectric substrate 1 and / or the second high-strength high-dielectric-constant dielectric substrate 9 ranges from 0.5 to 1.5 mm; and / or, the dielectric constant ε2 of the first low-strength low-dielectric-constant dielectric substrate 2 and / or the second low-strength low-dielectric-constant dielectric substrate 8 ranges from 1 to 1.5, and the thickness d2 of the first low-strength low-dielectric-constant dielectric substrate 2 and / or the second low-strength low-dielectric-constant dielectric substrate 8 ranges from 1.4 to 3.4 mm. In this embodiment, the dielectric constant ε3 of the first high-strength high-dielectric-constant dielectric substrate 1 and the second high-strength high-dielectric-constant dielectric substrate 9 is 2.5, and its thickness d3 is 1.0 mm, which can serve as a load-bearing function; the dielectric constant ε2 of the first low-strength low-dielectric-constant dielectric substrate 2 and the second low-strength low-dielectric-constant dielectric substrate 8 is 1.0, and its thickness d2 is 2.4 mm, which can serve as a heat insulation function.

[0059] Optionally, the side length L1 of the first inner metal square ring 3-1 ranges from 2.5 to 3.0 mm, and its width W1 ranges from 0.3 to 0.55 mm; the side length L2 of the first outer metal square ring 3-2 ranges from 4.0 to 4.18 mm, and its width W2 ranges from 0.05 to 0.15 mm, and the distance S between the first outer metal square ring 3-2 and the outer edge of the unit period of the first dielectric substrate 4 is greater than or equal to 0.01 mm. And / or, the side length of the third inner metal square ring ranges from 2.5 to 3.0 mm, and its width ranges from 0.3 to 0.55 mm; the side length of the third outer metal square ring ranges from 4.0 to 4.18 mm, and its width ranges from 0.05 to 0.15 mm, and the distance between the third outer metal square ring and the outer edge of the unit period of the second dielectric substrate 6 is greater than or equal to 0.01 mm. And / or, the side length L3 of the second outer metal square ring 5-2 is the same as the side length P of the unit period of the first dielectric substrate 4, and its width W3 ranges from 0.42 to 0.62 mm; the long side length L4 of the Jerusalem cross structure 5-1 ranges from 2.12 to 2.32 mm, its long side width W4 ranges from 0.1 to 0.3 mm, its short side length L5 ranges from 0.42 to 0.62 mm, and its short side width W5 ranges from 0.2 to 0.4 mm. And / or, the center of the first inner metal square ring 3-1 coincides with the center of the first outer metal square ring 3-2; the Jerusalem cross structure 5-1 is placed in the middle of the second outer metal square ring 5-2 and their centers coincide; the center of the third inner metal square ring coincides with the center of the third outer metal square ring.

[0060] like Figure 2As shown, in this embodiment, the side length L1 of the first inner metal square ring 3-1 is 2.75 mm, and its width W1 is 0.425 mm; the side length L2 of the first outer metal square ring 3-2 is 4.17 mm, and its width W2 is 0.085 mm. The distance S between the first outer metal square ring 3-2 and the outer edge of the unit period of the first dielectric substrate 4 is 0.015 mm, and the centers of the two metal square rings coincide. Further, as... Figure 3 As shown, the Jerusalem cross structure 5-1 is positioned in the middle of the second outer metal square ring 5-2, with their centers coinciding. The width W3 of the second outer metal square ring 5-2 is 0.52 mm. The length L4 of the long side of the Jerusalem cross structure 5-1 is 2.22 mm, the width W4 is 0.2 mm, and the length L5 of the short side is 0.52 mm, the width W5 is 0.3 mm. In this embodiment, all metal structures used in the broadband sandwich radome are made of copper foil with a thickness of 0.017 mm.

[0061] Optionally, the thickness d1 of the first dielectric substrate 4 ranges from 1.5 to 1.7 mm, the dielectric constant ε1 ranges from 3.0 to 3.2, the loss tangent of the first dielectric substrate 4 is less than or equal to 0.008, and the unit period side length P of the first dielectric substrate 4 ranges from 4.2 to 4.4 mm. In this embodiment, the thickness d1 of the first dielectric substrate 4 is 1.6 mm, its dielectric constant ε1 is 3.1, its loss tangent is 0.005, and the unit period side length P of the first dielectric substrate 4 is 4.2 mm. Optionally, at least one of the following—the material used to fabricate the second dielectric substrate 6, its thickness range, dielectric constant range, loss tangent range, and unit period side length range—is the same as that of the first dielectric substrate 4. In this embodiment, the first dielectric substrate 4 and the second dielectric substrate 6 are completely identical. It is understood that in practical applications, the parameters can be adjusted according to application requirements, such as optimizing the combination of dielectric constant and thickness to achieve the desired filtering effect in the required frequency band.

[0062] Simulation tests were conducted on a broadband sandwich radome based on a dual-band metasurface. Simulation results show that within the frequency ranges f1±0.315GHz and f2±2.29GHz%, the broadband sandwich radome designed in this invention exhibits a transmission loss of less than 1dB, with relative transmission bandwidths reaching 12.94% and 25.43%, respectively, and a center frequency ratio of 3.7 between the two transmission bands. Between the low-frequency and high-frequency transmission bands, the broadband sandwich radome exhibits total internal reflection characteristics and a steep out-of-band cutoff. Due to its symmetrical structure, the metasurface radome is polarization-insensitive and has a simple and easy-to-manufacture structure. Therefore, the broadband sandwich radome based on a dual-band metasurface designed in this invention has broad application prospects in satellite communication systems, electromagnetic countermeasures, and military stealth.

[0063] like Figure 7 and Figure 8 As shown, in this embodiment, the transmission coefficient of electromagnetic waves between the two transmission passbands of the broadband sandwich radome is much less than -10dB, and the broadband sandwich radome exhibits total internal reflection characteristics. Furthermore, the transmission coefficient of electromagnetic waves in the transition bands of the upper and lower sidebands of the two transmission passbands can rapidly decrease to below -10dB, and the broadband sandwich radome has a steep cutoff characteristic outside the passband.

[0064] In summary, the broadband sandwich radome based on a dual-band metasurface of the present invention combines a first impedance matching layer I, a frequency selective surface layer II, and a second impedance matching layer III. The frequency selective surface layer II forms a spatial filter through a multilayer metal structure and a dielectric substrate, enabling the corresponding broadband sandwich radome to have selective transmission bands. At the same time, it also has excellent characteristics such as dual-band broadband transmission, large-angle stability, steep out-of-band cutoff, adjustable transmission band center frequency ratio, and polarization insensitivity. The overall structure is simple and easy to manufacture.

[0065] It should be noted that the technical solution of the present invention is not limited to the specific examples mentioned above. For example, the present invention is a C-band and Ku-K band radome that is transparent to waves. Changing the structural geometry (not limited to square) can make it applicable to other microwave bands. All technical modifications made according to the technical solution of the present invention fall within the protection scope of the present invention.

[0066] 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 broadband sandwich radome based on a dual-band metasurface, characterized in that, The device comprises a first impedance matching layer, a radome frequency selective surface layer, and a second impedance matching layer arranged sequentially. The radome frequency selective surface layer includes a plurality of periodically arranged frequency selective surface units. Each frequency selective surface unit includes a first metal structure, a first dielectric substrate, a second metal structure, a second dielectric substrate, and a third metal structure arranged sequentially. The first metal structure includes a first inner metal square ring and a first outer metal square ring surrounding the first inner metal square ring; the second metal structure includes a Jerusalem cross structure and a second outer metal square ring surrounding the Jerusalem cross structure; the third metal structure includes a third inner metal square ring and a third outer metal square ring surrounding the third inner metal square ring. When electromagnetic waves irradiate the surface of a broadband sandwich radome based on a dual-band metasurface, two transmission poles are generated in the low-frequency band to form a second-order bandpass filter response, and three transmission poles are generated in the high-frequency band to form a third-order bandpass filter response.

2. The broadband sandwich radome based on a dual-band metasurface as described in claim 1, characterized in that, The first metal structure and the third metal structure can be equivalent to an "LC" series circuit with a second inductor L connected in parallel. b The "LC" series circuit of the first metal structure includes a first capacitor C connected in series. a and the first inductor L a The first metal structure and the third metal structure are completely identical; the second metal structure can be equivalent to an "LC" series circuit connected in parallel with another "LC" parallel circuit, and the "LC" series circuit of the second metal structure includes a third capacitor C. c and the fourth inductor L d Its "LC" parallel circuit includes a second capacitor C connected in parallel. b and the third inductor L c ; The first dielectric substrate and the second dielectric substrate can be equivalent to transmission lines; The equivalent circuit of the frequency selective surface layer of the radome can generate two transmission poles in the low-frequency band, forming a transmission passband with a second-order bandpass filter response; and can generate three transmission poles in the high-frequency band, forming a transmission passband with a third-order bandpass filter response, thereby expanding the bandwidth of the radome's transmission frequency band.

3. The broadband sandwich radome based on a dual-band metasurface as described in claim 2, characterized in that, Based on the equivalent circuit of the frequency-selective surface layer of the radome, the center frequency f1 of its first transmission passband depends on the second inductor L. b Third inductor L c Second capacitor C b and the third capacitor C c The value; the center frequency f2 of the second transmission passband depends on the first inductor L. a Second inductor L b Fourth inductor L d First capacitor C a Second capacitor C b and the third capacitor C c The value; by adjusting the geometric dimensions of the topologies of the first metal structure, the second metal structure, and the third metal structure, the frequency ratio of the center frequencies of the two transmission passbands can be adjusted.

4. The broadband sandwich radome based on a dual-band metasurface as described in claim 2, characterized in that, The first capacitor C a The capacitance range is 10 to 11 fF, and the first inductor L a The inductance range is 3.0–5.0 nH, and the second inductor L b The inductance range is 23.0–26.0 nH; And / or, the third capacitor C c The capacitance range is 40–60 fF, and the fourth inductor L d The inductance range is 2–3 nH, and the third inductor L c The capacitance range is 4–6 nH, and the second capacitor C b The capacitance range is 100–150 fF; And / or, the first dielectric substrate and the second dielectric substrate can be equivalent to having a characteristic impedance of Transmission lines; And / or, the frequency ratio R of the two transmission passband center frequencies ranges from 2 to 5.

5. The broadband sandwich radome based on a dual-band metasurface as described in claim 1, characterized in that, The first impedance matching layer includes a first high-strength high-dielectric-constant dielectric substrate and a first low-strength low-dielectric-constant dielectric substrate, wherein the first low-strength low-dielectric-constant dielectric substrate is located between the first high-strength high-dielectric-constant dielectric substrate and the radome frequency selective surface layer. The second impedance matching layer includes a second high-strength high-dielectric-constant dielectric substrate and a second low-strength low-dielectric-constant dielectric substrate, the second low-strength low-dielectric-constant dielectric substrate being located between the second high-strength high-dielectric-constant dielectric substrate and the radome frequency selective surface layer.

6. The broadband sandwich radome based on a dual-band metasurface as described in claim 5, characterized in that, By optimizing the dielectric constants and thicknesses of the first high-strength, high-dielectric-constant dielectric substrate, the first low-strength, low-dielectric-constant dielectric substrate, the second high-strength, high-dielectric-constant dielectric substrate, and the second low-strength, low-dielectric-constant dielectric substrate, the broadband sandwich radome can be matched with the air impedance under large-angle electromagnetic wave incidence. Furthermore, the parameters can be optimized according to formulas (1) and (2). The first impedance matching layer and the second impedance matching layer have the same composition, ε out ε1 is the equivalent dielectric constant of the first impedance matching layer and the second impedance matching layer; ε2 is the dielectric constant of the first low-strength low-dielectric-constant dielectric substrate and the second low-strength low-dielectric-constant dielectric substrate; ε3 is the dielectric constant of the first high-strength high-dielectric-constant dielectric substrate and the second high-strength high-dielectric-constant dielectric substrate; d2 is the thickness of the first low-strength low-dielectric-constant dielectric substrate and the second low-strength low-dielectric-constant dielectric substrate; d3 is the thickness of the first high-strength high-dielectric-constant dielectric substrate and the second high-strength high-dielectric-constant dielectric substrate; θ max λ0 is the maximum incident angle of the electromagnetic wave, which ranges from 45° to 75°, and λ0 is the wavelength of the transmission frequency in free space.

7. The broadband sandwich radome based on a dual-band metasurface as described in claim 5, characterized in that, The dielectric constant ε3 of the first high-strength high-dielectric-constant dielectric substrate and / or the second high-strength high-dielectric-constant dielectric substrate ranges from 2 to 3, and the thickness d3 of the first high-strength high-dielectric-constant dielectric substrate and / or the second high-strength high-dielectric-constant dielectric substrate ranges from 0.5 to 1.5 mm. And / or, the dielectric constant ε2 of the first low-strength low-dielectric-constant dielectric substrate and / or the second low-strength low-dielectric-constant dielectric substrate ranges from 1 to 1.5, and the thickness d2 of the first low-strength low-dielectric-constant dielectric substrate and / or the second low-strength low-dielectric-constant dielectric substrate ranges from 1.4 to 3.4 mm.

8. The broadband sandwich radome based on a dual-band metasurface as described in claim 1, characterized in that, The side length L1 of the first inner metal square ring is in the range of 2.5 to 3.0 mm, and its width W1 is in the range of 0.3 to 0.55 mm; the side length L2 of the first outer metal square ring is in the range of 4.0 to 4.18 mm, and its width W2 is in the range of 0.05 to 0.15 mm, and the distance S between the first outer metal square ring and the outer edge of the unit period of the first dielectric substrate is greater than or equal to 0.01 mm. And / or, the side length of the third inner metal square ring is in the range of 2.5 to 3.0 mm, and its width is in the range of 0.3 to 0.55 mm; the side length of the third outer metal square ring is in the range of 4.0 to 4.18 mm, and its width is in the range of 0.05 to 0.15 mm, and the distance between the third outer metal square ring and the outer edge of the unit period of the second dielectric substrate is greater than or equal to 0.01 mm; And / or, the side length L3 of the second outer metal square ring is the same as the side length P of the unit period of the first dielectric substrate, and its width W3 ranges from 0.42 to 0.62 mm; the long side length L4 of the Jerusalem cross structure ranges from 2.12 to 2.32 mm, its long side width W4 ranges from 0.1 to 0.3 mm, its short side length L5 ranges from 0.42 to 0.62 mm, and its short side width W5 ranges from 0.2 to 0.4 mm; And / or, the center of the first inner metal square ring coincides with the center of the first outer metal square ring; the Jerusalem cross structure is placed in the middle of the second outer metal square ring and their centers coincide; the center of the third inner metal square ring coincides with the center of the third outer metal square ring.

9. The broadband sandwich radome based on a dual-band metasurface as described in claim 1, characterized in that, The thickness d1 of the first dielectric substrate ranges from 1.5 to 1.7 mm, the dielectric constant ε1 of the first dielectric substrate ranges from 3.0 to 3.2, the loss tangent of the first dielectric substrate is less than or equal to 0.008, and the side length P of the cell period of the first dielectric substrate ranges from 4.2 to 4.4 mm. And / or, at least one of the following: the material used to prepare the second dielectric substrate, its thickness range, dielectric constant range, loss tangent range, and cell period side length range is the same as that of the first dielectric substrate.

10. The broadband sandwich radome based on a dual-band metasurface as described in claim 1, characterized in that, Each of the first, second, and third metal structures of the broadband sandwich radome is symmetrical about the x-axis and y-axis, so that the broadband sandwich radome has polarization insensitive characteristics. Between the two transmission passbands of the broadband sandwich radome, the transmission coefficient of electromagnetic waves is much less than -10dB, and the broadband sandwich radome exhibits total internal reflection characteristics. The transmission coefficients of electromagnetic waves in the transition bands of the upper and lower sidebands of the two transmission passbands of the broadband sandwich radome can rapidly drop to below -10dB, and the broadband sandwich radome has a steep cutoff characteristic outside the passband.

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