A broadband angle-insensitive radome and its design method

Abstract

The present invention discloses an angle-insensitive broadband radome and its design method. The radome includes a high-reflectivity inner core, dielectric anti-reflection metasurfaces closely attached to the upper and lower surfaces of the inner core, and a narrow-beam linearly polarized feed source. The anti-reflection metasurface is composed of isotropic transmissive dielectric metasurface units with different parameters, and the arrangement mode of the metasurface units is determined according to the shape of the inner core of the radome and its positional relationship with the feed source. According to the relative permittivity of the inner core and the incident angle of the electromagnetic wave, gradient dielectric metasurfaces with different thicknesses and permittivities are loaded on the upper and lower surfaces of the inner core. The incident electromagnetic wave undergoes multiple interference cancellations in the anti-reflection metasurface, thereby reducing the reflection of the electromagnetic wave. The present invention realizes the improvement of the transmittance performance of the radome for any incident angle, verifies its broadband and angle-insensitive characteristics within the specified frequency band, and has high application value.

Description

Technical Field

[0001] The present invention belongs to the field of novel artificial electromagnetic materials, and particularly relates to an angle-insensitive broadband radome and a design method thereof. Background Art

[0002] The design of traditional radomes can be divided into two cases, namely single-layer radomes and sandwich-type sandwich radomes. Single-layer radomes have the characteristics of simple structure and low cost. However, in order to obtain the best transmission efficiency, the wall thickness needs to be an integer multiple of half-wavelength. And as the thickness increases, the bandwidth decreases and the angle stability deteriorates, which poses higher requirements for the geometric design of the radome. The sandwich radome is to load dielectric matching layers with equal thickness on both sides of the single-layer radome to improve the electromagnetic transmittance and bandwidth. This dielectric matching layer is only effective for a certain range of incident angles. As the incident angle increases, the effect of the matching layer gradually decreases and the reflected energy gradually increases. However, with the development of antenna technology, the performance of antennas is constantly improving and the functions are more abundant, which poses higher requirements for the performance of radomes. How to solve the angle sensitivity of radomes is an important problem faced by radome design.

[0003] Metasurface is a two-dimensional metamaterial composed of sub-wavelength planar structures arranged periodically according to certain rules. In recent years, it has received extensive attention due to its flexible regulation of the amplitude and phase of electromagnetic waves. Through reasonable design of the structure and size, the metasurface can achieve arbitrary equivalent permittivity within a certain range, which greatly increases the design freedom of the anti-reflection layer of the radome. Summary of the Invention

[0004] Object of the Invention: The object of the present invention is to provide a broadband angle-insensitive radome and a design method thereof. This method can increase the bandwidth and angle stability of the radome, is simple in design, low in processing cost, and light in weight.

[0005] Technical solution: To achieve the above-mentioned invention purpose, an angle-insensitive broadband radome of the present invention includes a broadband angle-insensitive anti-reflection metasurface, a high-reflectivity inner core, and a narrow-beam linearly polarized feed; wherein, broadband angle-insensitive anti-reflection metasurfaces are respectively arranged on the upper and lower surfaces of the high-reflectivity inner core, and the polarization direction of the narrow-beam linearly polarized feed is placed perpendicular to the electromagnetic wave incident plane of the broadband angle-insensitive anti-reflection metasurface, so that the radome receives a TE-polarized scanning beam; the angle-insensitive anti-reflection metasurface is composed of isotropic transmissive dielectric metasurface units with different equivalent dielectric constants and thicknesses. According to the oblique incidence quarter-wavelength matching formula derived in this article, the equivalent dielectric constants and thicknesses of the transmissive dielectric metasurface units at different positions are determined by the electromagnetic wave incident angle at that position. According to the relative dielectric constant of the high-reflectivity inner core and the electromagnetic wave incident angle, broadband angle-insensitive anti-reflection metasurfaces with different thicknesses and dielectric constants are loaded on the upper and lower surfaces of the high-reflectivity inner core, and the incident electromagnetic waves are interfered and canceled multiple times in this metasurface, thereby reducing the reflection of electromagnetic waves.

[0006] The transmissive dielectric metasurface unit is a sub-wavelength-sized through-hole dielectric structure, and the dielectric substrate used is a common microwave high-frequency dielectric substrate.

[0007] The high-reflectivity inner core is a ceramic plate with a uniform thickness, and the thickness of the ceramic plate is an integer multiple of half the wavelength of the ceramic medium to achieve the maximum electromagnetic wave transmittance.

[0008] The narrow-beam linearly polarized feed is a narrow-beam linearly polarized feed with a half-power beam width angle within 8°; when the polarization direction of the feed is perpendicular to the electromagnetic wave incident plane, the radome receives TE-polarized wave scanning. When the feed is rotated 90° along the main axis, the radome receives TM-polarized wave scanning.

[0009] The narrow-beam linearly polarized feed realizes dynamic beam scanning by mechanically rotating the feed, and the scanning angle is 0 - 60°.

[0010] The radome receives a TE-polarized scanning beam. Within the beam scanning range, the incident angle of the electromagnetic wave received by the radome varies within a certain interval; the required equivalent dielectric constant of the transmissive dielectric metasurface unit is between ε1 - ε2; 8 different equivalent dielectric constant values are selected at equal intervals and the sizes of the dielectric metasurface units are determined; through the reasonable arrangement of these 8 types of dielectric metasurface units, an anti-reflection metasurface with broadband and wide-angle characteristics can be realized.

[0011] The thickness of the broadband angle-insensitive anti-reflection metasurface continuously increases as the incident angle increases.

[0012] The broadband angle-insensitive antireflection metasurface is adjusted according to the shape of the radome and its positional relationship with the narrow-beam linear polarization feed source; when the radome is a flat structure, the vertical distance from the narrow-beam linear polarization feed source to the radome is d, and as the scanning angle increases, the equivalent permittivity of the broadband angle-insensitive antireflection metasurface decreases and the thickness increases; when the radome is a conical structure, the distance from the narrow-beam linear polarization feed source to the center position of the radome is D, and the broadband angle-insensitive antireflection metasurface is loaded in the semi-circular area with larger reflection; according to the incident angles at different positions of the radome, this semi-spherical area is divided into multiple rings such as the first ring, the second ring, the third ring, the fourth ring, and the fifth ring, and the equivalent nodal constants and thicknesses of the broadband angle-insensitive antireflection metasurfaces loaded at different rings are determined respectively.

[0013] The design method of the angle-insensitive broadband radome includes the following steps:

[0014] Step 1, determine the incident angles of electromagnetic waves at different positions according to the shape of the radome and its positional relationship with the narrow-beam linear polarization feed source;

[0015] Step 2, determine the permittivity range of the broadband angle-insensitive antireflection metasurface through the incident angle range and the equivalent permittivity of the high-reflectivity core material;

[0016] Step 3, design the isotropic transmissive dielectric antireflection metasurface unit; determine the substrate material, punching shape, and size parameters of the unit. The equivalent permittivity of the unit is equally spaced into 8 cases according to the required permittivity range and the degree of change;

[0017] Step 4, select and arrange the metasurface unit structure with corresponding through-hole sizes according to the established radome shape and narrow-beam linear polarization feed source;

[0018] Step 5, calculate the thickness of the metasurface unit at different positions according to the incident angle and the equivalent permittivity of the broadband angle-insensitive antireflection metasurface; the whole of the broadband angle-insensitive antireflection metasurface is loaded on both sides or one side of the high-reflectivity core inside the radome to obtain the overall structure of the radome;

[0019] Step 6, place the narrow-beam linear polarization feed source at a position d away from the radome, and realize dynamic beam scanning by mechanically rotating the feed source.

[0020] The specific steps for determining the parameters of the broadband angle-insensitive antireflection metasurface are as follows:

[0021] First, assume that the size of the flat radome is l x ×l ymm, the beam scanning is along the X direction. The narrow-beam linear polarization feed is located at a distance d below X = 0. The incident angle at position X is: θ = arctan(x / d);

[0022] For TE polarized waves, the electric field direction is perpendicular to the electromagnetic wave incident plane. The total reflection coefficient of the electromagnetic wave obliquely incident on the interface of three media with relative permittivities of ε1, ε2, and ε3 respectively is:

[0023]

[0024]

[0025]

[0026] Where R 12 is the total reflection coefficient, R 23 is the reflection coefficient at the interface between medium 2 and medium 3, K is an intermediate variable calculated to solve the thickness of the dielectric metasurface unit, θ in is the incident angle of the electromagnetic wave in region n, Z n is the wave impedance in region n, k n is the wave number in region n. Letting the total reflection coefficient be zero, the relationship between the permittivity and thickness of the metasurface unit with the incident angle can be obtained:

[0027]

[0028]

[0029] Where d is the thickness of the transmissive dielectric metasurface unit, ε2 is the equivalent permittivity of the metasurface unit, λ0 and λ g represent the free space wavelength and the medium wavelength respectively, and n is a positive integer;

[0030] For TM polarized waves, the relationship between the permittivity of the transmissive dielectric metasurface unit and the incident angle:

[0031]

[0032] Beneficial effects: Compared with the prior art, the present invention has the following advantages:

[0033] (1). Simple structure and low cost: The present invention has low requirements for precision. The anti-reflection metasurface can be realized by CNC technology, and the selection of the dielectric substrate can be flexibly selected according to the operating frequency band.

[0034] (2). Wide application range: The present invention is applicable to the design of radomes in any frequency band range of the microwave band and is suitable for radomes of most shapes.

[0035] (3). Wide operating frequency band: Compared with the traditional single-layer radome, the present invention greatly improves the bandwidth of the high electromagnetic wave transmittance band.

[0036] (4). Angle insensitivity: The broadband angle-insensitive radome of the present invention is particularly suitable for wide-angle scanning antennas and can achieve ultra-high electromagnetic wave transmittance within a wide angle range. Description of the Drawings

[0037] Figure 1 is a schematic structural diagram of a flat broadband angle-insensitive radome with double-sided loaded anti-reflection metasurface;

[0038] Figure 2 is a schematic diagram of the unit of the isotropic transmissive anti-reflection metasurface;

[0039] Figure 3 is a relationship curve between the side length L of the unit through hole and the equivalent dielectric constant;

[0040] Figure 4 is a schematic structural diagram of the anti-reflection metasurface of the flat radome;

[0041] Figure 5 is a relationship curve between the thickness of the anti-reflection metasurface of the flat radome at position X and the through hole size;

[0042] Figure 6(a) is a schematic structural diagram of a flat broadband angle-insensitive radome with single-sided loaded anti-reflection metasurface; Figure 6(b) is a schematic structural diagram of a conical broadband angle-insensitive radome with single-sided loaded anti-reflection metasurface;

[0043] Figure 7 is a radiation comparison diagram of the flat radome with double-sided loaded anti-reflection metasurface and the radome without loaded anti-reflection metasurface at TE polarized wave frequencies of 18, 20, and 22 GHz, and the scanning angles are 10, 20, 30, 40, 50, and 60° respectively; where a is the radiation comparison diagram at the operating frequency of 18 GHz, b is the radiation comparison diagram at the operating frequency of 20 GHz, and c is the radiation comparison diagram at the operating frequency of 22 GHz.

[0044] Figure 8 is a radiation comparison diagram of the flat radome with double-sided loaded anti-reflection metasurface and the radome without loaded anti-reflection metasurface at each scanning angle at the 20 GHz frequency point under TM polarized wave incidence;

[0045] Figure 9 is a radiation comparison diagram of the flat radome with single-sided loaded anti-reflection metasurface and the radome without loaded anti-reflection metasurface at each scanning angle at the 20 GHz frequency point under TE polarized wave incidence, where Figure 9 (a) The inner core thickness of the radome is 14 mm, Figure 9The thickness of the radome inner core in (b) is 15 mm, Figure 9 The thickness of the radome inner core in (c) is 16.77 mm.

[0046] Figure 10 It is a radiation comparison diagram of a conical radome with a single-layer loaded anti-reflection metasurface and a radome without a loaded anti-reflection metasurface at 20 GHz frequency point under TE-polarized wave incidence at scan angles of 0, 5, 15, 20, 25, and 30°.

[0047] In the figure: there are broadband angle-insensitive anti-reflection metasurface 1, high-reflectivity inner core 2, narrow-beam linearly polarized feed 3, conical structure 4, first ring 5, second ring 6, third ring 7, fourth ring 8, and fifth ring 9. Specific embodiments

[0048] The technical solution of the present invention will be further introduced below in combination with specific embodiments and the accompanying drawings. The following three embodiments are only the preferred embodiments of the present invention. It should be noted that: for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and equivalent replacements can be made, such as changing the shape and size of the isotropic transmissive anti-reflection metasurface, changing the applicable frequency band and shape of the radome, etc. It should be pointed out that all technical solutions obtained by improving and equivalently replacing the claims of the present invention fall within the protection scope of the present invention.

[0049] As Figure 1 shown in the first embodiment of the present invention, the figure is a scanning schematic diagram of a flat radome with a double-sided loaded anti-reflection metasurface and a mechanically rotating feed.

[0050] The angle-insensitive wide radome is composed of a high-reflectivity inner core 2 and anti-reflection metasurfaces 1 loaded on both sides. The metasurface units are reasonably arranged according to the established shape of the radome and the positional relationship with the feed 3 to improve the electromagnetic wave transmittance at any incident angle.

[0051] The anti-reflection metasurface unit is a sub-wavelength-sized perforated dielectric structure such as Figure 2As shown, the period p of the unit is 2.5 mm (one-sixth of the wavelength). The center is a square through-hole with different side lengths L. By changing the side length L of the through-hole, the equivalent dielectric constant of the unit can be continuously changed. The dielectric substrate used here is Rogers RT5880LZ with a relative dielectric constant of 2. The radomes of the present invention all operate in the K band. The high-reflectivity inner core is a ceramic flat plate with a uniform thickness and a relative dielectric constant of 3.2, and the thickness is 16.77 mm (about 4 times the half-wavelength). A high-gain antenna with a half-power beam width angle of 8° is placed below the flat radome at a distance d (80 mm) from the radome, and beam scanning is achieved by mechanically rotating the feed. The radome is designed flexibly, with a simple structure and low cost. Through simulation verification, it has a wide operating frequency band, a high electromagnetic wave transmittance, and good angle adaptability.

[0052] The design principle of the anti-reflection metasurface of the angle-insensitive wide radome is as follows. The oblique incidence of TE and TM polarized electromagnetic waves on three different dielectric interfaces is analyzed respectively. Taking the TE polarized wave as an example, the electric field direction is perpendicular to the incident plane. According to the different propagation directions of the electromagnetic waves, the electric and magnetic vectors in the three regions can be expressed in the following forms:

[0053]

[0054]

[0055]

[0056]

[0057]

[0058]

[0059]

[0060]

[0061]

[0062]

[0063] Where the superscripts ‘+’ and ‘−’ represent the forward and backward propagation of the electromagnetic waves respectively, and the subscript numbers represent the three different regions. Z n represents the wave impedance of the n region, and θ in represents the incident angle of the electromagnetic wave on the interface of the n region. According to the boundary conditions on the two dielectric interfaces:

[0064]

[0065] where the subscript t represents the tangential components of the electric and magnetic fields. Combining and simplifying Eqs. (1) and (2) can obtain the total reflection coefficient R of the oblique incidence of the three-layer medium 12 Expression:

[0066]

[0067] where R 23 is the expression of the reflection coefficient at the interface between regions 2 and 3. Observing Eq. (3), if the reflection coefficient of the three-layer medium is to be 0, the value of K must be real, and the thickness expression of the matching layer can be obtained as follows:

[0068]

[0069] where λ0 and λ g are the free-space wavelength and the medium wavelength in region 2, respectively. Combining Eqs. (3) and (4) to make R 12 = 0 can obtain the dielectric constant expression of the TE-polarized antireflection metasurface:

[0070]

[0071] According to Eqs. (4) and (5), the thickness and dielectric constant of the antireflection metasurface at any incident angle of the TE wave can be accurately predicted.

[0072] Similarly, the expression of the equivalent dielectric constant of the TM-polarized electromagnetic wave antireflection metasurface is:

[0073]

[0074] In the solutions of the quadratic equation of one variable in Eq. (6), the values less than 1 are excluded, and the dielectric constant value of the TM-polarized wave antireflection metasurface at any incident angle can be obtained.

[0075] The design steps of the flat broadband angle-insensitive radome loaded with the antireflection metasurface are described as follows:

[0076] 1. The area of the flat radome is 540×300 mm, and the inner core of the radome is a uniform-thickness ceramic plate with a relative dielectric constant of 3.2 and a thickness Hm of 16.77 mm. A high-gain linearly polarized antenna with a beam width of 8° is placed 80 mm below the flat plate, and dynamic beam scanning is achieved through mechanical rotation, and the scanning angle is between 0 - 60°. For the dielectric radome, the electromagnetic wave transmittance of the TE-polarized wave decreases with the increase of the incident angle, while the TM-polarized wave increases with the increase of the incident angle. Therefore, the present invention aims to improve the electromagnetic wave transmittance of the TE-polarized wave. After calculation, the equivalent dielectric constant of the antireflection metasurface should be between 1.1 - 1.9. Figure 3Shows the simulation results of the equivalent dielectric constant of the antireflection metasurface unit versus the via hole size L. For simplicity in design, the equivalent dielectric constant of the antireflection metasurface unit is divided into 8 cases at intervals of 0.1 between 1.15 - 1.85.

[0077] According to geometric analysis, the incident angle of the electromagnetic wave at the position X of the flat radome is, and according to equations (4) and (5), the thickness Hp and arrangement pattern of the antireflection metasurface unit are determined. The structure and details of the antireflection metasurface of the flat radome are shown as Figure 4 shown. Figure 5 Is the relationship curve between the unit thickness Hp and the via hole size L at the position X of the antireflection metasurface.

[0078] Example 1: Flat - type angle - insensitive wide - band radome with double - sided loaded antireflection metasurface

[0079] Full - wave simulation software CST is used for simulation verification. The radiation patterns at different scan angles of the flat - type wide - band angle - insensitive radome with double - sided loaded antireflection metasurface and the single - layer ceramic flat are compared at the frequency points of 18, 20, and 22 GHz, as Figure 7 shown. The ceramic flat is designed to be 16.77 mm thick, and the electromagnetic wave transmittance is optimal at 0 - degree incidence at 20 GHz. As the incident angle increases, the gain of the scanned beam decreases and the reflected beam increases. In the frequency band of 18 - A 22 GHz, the change in the electromagnetic wave transmittance of the single - layer ceramic flat radome within the scan range of 0 - 60 degrees is drastic, and the beam gain can drop by up to 3.2 dBi. The simulation results show that the antireflection metasurface is effective in the frequency band of 18 - 22 GHz, and the maximum decrease in the electromagnetic wave transmittance of the radome within the scan range of 0 - 60° is 0.7 dBi. After comparison, the wide - band angle - insensitive radome can effectively improve the electromagnetic wave transmittance within the scan range of 0 - 60° in the frequency band of 18 - 22 GHz compared with the traditional single - layer radome, and the maximum gain can be increased by 2.88 dBi. Figure 8 Is the radiation pattern at the 20 - GHz frequency point for TM - polarized waves, which verifies that the antireflection metasurface designed according to TE - polarized waves does not deteriorate the transmittance of TM - polarization.

[0080] Example 2: Angle - insensitive wide - band radome with single - sided loaded antireflection metasurface

[0081] Figure 6(a) is the schematic structure diagram of the wide - band angle - insensitive radome with single - sided loaded antireflection metasurface. Three cases where the thickness of the inner core 2 of the radome is 14, 15, and 16.77 mm are respectively simulated. The simulation frequency point is 20 GHz, and the scan angle is within 0 - 60°. Figure 9The results show that even when the radome with the anti - reflective metasurface 1 is unidirectionally loaded, its electromagnetic transmittance is still improved well at each scanning angle, and the gain is consistent within the angle range of 0 - 60°. The influence of the change in the inner core thickness on the gain has decreased significantly, greatly reducing the energy of the reflected wave. It can be concluded that the design method of the broadband angle - insensitive radome proposed in the present invention can not only broaden the frequency band, improve the electromagnetic wave transmittance and the angular stability of the radome, but also increase the robustness of the radome thickness, which means that the radome has greater design freedom.

[0082] Embodiment 3: Angle - insensitive broadband radome with a conical complex structure

[0083] A radome with a conical complex structure is proposed to verify the applicability of the present invention to complex radomes. The inside of the radome is loaded with a gradient anti - reflective metasurface as shown in Fig. 6(b). Through full - wave simulation by CST, the radiation comparison diagram within the scanning angle range of 0 - 60° at the 20 GHz frequency point is as Figure 10 shown. The results show that the electromagnetic wave transmittance of the radome is improved within the scanning angle range of 0 - 60°. Within the scanning angle range of 0 - 30°, the gain at the 10° scanning angle is the lowest, mainly because the electromagnetic wave front mutates when passing through the radome at the 10° scanning angle, resulting in waveform distortion, as shown by the solid line in the figure. The dotted line is the radiation curve of the radome loaded with the anti - reflective metasurface, and the waveform at the 10° scanning angle is significantly improved.

[0084] Based on the traditional quarter - wavelength matching theory and considering the influence of the incident angle, the present invention derives a calculation formula for the parameters of the new anti - reflective layer. This formula can predict the optimal dielectric constant and thickness of the matching layer according to different incident angles. The new artificial electromagnetic materials can achieve arbitrary equivalent dielectric constants, which enables the radome to be flexibly designed according to the incident angle of the received electromagnetic wave. The radome designed by the method of the present invention can achieve high electromagnetic wave transmittance at each scanning angle within a very wide frequency band. The dielectric materials used can be flexibly selected according to the frequency band and the application scenario. The structure is simple and the cost is low, and it can replace the traditional radome, having important application value in the fields of satellite communication, radar, etc.

Claims

1. An angle-insensitive broadband radome, characterized in that It includes an angle-insensitive anti-reflection metasurface (1) with a wideband, a high-reflectivity inner core (2), and a narrow-beam linearly polarized feed (3); wherein, angle-insensitive anti-reflection metasurfaces (1) with a wideband are respectively arranged on the upper and lower surfaces of the high-reflectivity inner core (2), and the polarization direction of the narrow-beam linearly polarized feed (3) is placed perpendicular to the electromagnetic wave incident plane of the angle-insensitive anti-reflection metasurface (1) with a wideband, so that the radome receives a TE-polarized scanning beam; the angle-insensitive anti-reflection metasurface (1) is composed of isotropic transmissive dielectric metasurface units with different equivalent dielectric constants and thicknesses. According to the oblique incidence quarter-wavelength matching formula, the equivalent dielectric constants and thicknesses of the transmissive dielectric metasurface units at different positions are determined by the electromagnetic wave incident angle at that position. According to the relative dielectric constant of the high-reflectivity inner core (2) and the electromagnetic wave incident angle, angle-insensitive anti-reflection metasurfaces with different thicknesses and dielectric constants are loaded on the upper and lower surfaces of the high-reflectivity inner core (2), and the incident electromagnetic waves interfere destructively multiple times in this metasurface, thereby reducing the reflection of electromagnetic waves. The specific steps for determining the parameters of the angle-insensitive anti-reflection metasurface (1) with a wideband are as follows: First, assume that the size of the planar radome is Lx×Lymm, the beam scans along the X direction, the narrow-beam linearly polarized feed (3) is located at a distance d below X = 0, and the incident angle at position X is: θ = arctan(X / d); for a TE-polarized wave, the electric field direction is perpendicular to the electromagnetic wave incident plane, and the total reflection coefficient of the electromagnetic wave obliquely incident on the interfaces of three dielectrics with relative dielectric constants of ε1, ε2, and ε3 respectively is: where R 12 is the total reflection coefficient, R 23 is the reflection coefficient at the interface between medium 2 and medium 3, K is an intermediate variable calculated to solve the thickness of the metasurface unit, θ in is the incident angle of the electromagnetic wave in region n, Z n is the wave impedance in region n, k n is the wave number in region n; setting the total reflection coefficient to zero, the relationship between the dielectric constant and thickness of the metasurface unit with respect to the incident angle is obtained as follows: where d is the thickness of the transmissive dielectric metasurface unit, ε2 is the equivalent permittivity of the metasurface unit, λ0 and λ g represent the free space wavelength and the dielectric wavelength respectively, and n is a positive integer.

2. The angle-insensitive broadband radome according to claim 1, wherein The transmissive dielectric metasurface unit is a sub-wavelength-sized via dielectric structure, and the dielectric substrate used is a microwave high-frequency dielectric substrate.

3. The angle-insensitive broadband radome according to claim 1, wherein The high-reflectivity inner core (2) is a ceramic plate with a uniform thickness, and the thickness of this ceramic plate is an integer multiple of half the wavelength of the electromagnetic wave in the ceramic medium to achieve the maximum electromagnetic wave transmittance.

4. The angle-insensitive broadband radome according to claim 1, characterized in that, The narrow-beam linearly polarized feed (3) is a narrow-beam linearly polarized feed with a half-power beam width angle within 8°; when the polarization direction of the feed is perpendicular to the electromagnetic wave incident plane, the radome receives a TE-polarized wave scan. Rotating the feed 90° along the main axis, the radome then receives a TM-polarized wave scan.

5. The angle-insensitive broadband radome according to claim 4, characterized in that The narrow-beam linearly polarized feed (3) realizes dynamic beam scanning by mechanically rotating the feed, and the scanning angle is 0 - 60°.

6. The angle-insensitive broadband radome according to claim 1, characterized in that The radome receives a TE-polarized scanning beam. Within the beam scanning range, the incident angle of the electromagnetic wave received by the radome varies within a certain interval; the required equivalent dielectric constant of the transmissive dielectric metasurface unit is between ε1 and ε2; 8 different equivalent dielectric constant values are selected at equal intervals and the sizes of the dielectric metasurface units are determined; the anti-reflection metasurface with wideband and wide-angle characteristics can be realized by arranging these 8 kinds of dielectric metasurface units.

7. The angle-insensitive broadband radome according to claim 1, wherein The thickness of the angle-insensitive anti-reflection metasurface (1) with a wideband continuously increases as the incident angle increases.

8. The angle-insensitive broadband radome according to claim 1, characterized in that, The broadband angle-insensitive anti-reflection metasurface (1) is adjusted according to the shape of the radome and its positional relationship with the narrow-beam linearly polarized feed (3); when the radome is of a flat-plate structure, the perpendicular distance from the narrow-beam linearly polarized feed (3) to the radome is d. As the scanning angle increases, the equivalent permittivity of the broadband angle-insensitive anti-reflection metasurface (1) decreases and its thickness increases.

9. A design method for an angle-insensitive broadband radome according to any one of claims 1-8, characterized in that, It includes the following steps: Step 1: Determine the incident angles of electromagnetic waves at different positions according to the shape of the radome and its positional relationship with the narrow-beam linearly polarized feed (3); Step 2: Determine the permittivity range of the broadband angle-insensitive anti-reflection metasurface (1) based on the incident angle range and the equivalent permittivity of the high-reflectivity core (2) material; Step 3: Design an isotropic transmissive dielectric anti-reflection metasurface unit; determine the substrate material, the punching shape, and the size parameters of the unit. The equivalent permittivity of the unit is equally spaced into 8 cases according to the required permittivity range and the degree of variation; Step 4: Select and arrange the metasurface unit structure with corresponding through-hole sizes according to the established radome shape and the narrow-beam linearly polarized feed (3); Step 5: Calculate the thickness of the metasurface unit at different positions according to the incident angle and the equivalent permittivity of the broadband angle-insensitive anti-reflection metasurface (1); the whole of the broadband angle-insensitive anti-reflection metasurface (1) is loaded on both sides of the high-reflectivity core (2) inside the radome to obtain the overall structure of the radome; Step 6: Place the narrow-beam linearly polarized feed (3) at a position d away from the radome, and achieve dynamic beam scanning by mechanically rotating the feed.

Images