Radar strong scattering source elimination method for dihedral structure and dihedral structure

Abstract

The present application relates to a kind of radar strong scattering source elimination method and dihedral angle structure for dihedral angle structure, belong to electromagnetic wave radar stealth field, solve the problem that existing coating wave-absorbing material and structure shaping cannot eliminate dihedral angle structure angle point strong scattering source.The method comprises: design broadband coding metasurface is laid on the angle surface of two-angle surface structure;MxN array is formed by first coding unit and second coding unit according to the best coding mode, for making electromagnetic wave evenly reflect to each direction in space;Each coding unit includes three layers;Each layer is formed by substrate and PI film covered on substrate, PI film has specific size metal square ring pattern, the reflection phase difference of two coding units is stable as 180 ° in broadband range;Design cylindrical metal, located in two angle surface middle, axis is parallel to the edge of two-angle surface structure, for making incident electromagnetic wave evenly scattered to the metasurface of angle surface. Strong scattering point of dihedral angle structure angle point is eliminated.

Description

Technical Field

[0001] This invention belongs to the field of electromagnetic wave radar stealth technology, specifically relating to a method for eliminating strong radar scattering sources for dihedral structures. Background Technology

[0002] The principle of radar stealth is to achieve stealth by reducing the radar cross section (RCS) of a target. Currently, passive stealth solutions can be divided into two categories: one is to coat the target with stealth coatings to absorb incident electromagnetic waves to the greatest extent, reducing the detection range of the equipment and making the target "invisible" to the detection equipment; the other is to give the target a low-scattering overall structure, thereby changing the echo characteristics of the incident electromagnetic waves by changing the target structure, thus achieving stealth and reducing the detection range.

[0003] However, for targets with dihedrals, trihedrals (12,13), or similar special structures, the strong scattering sources at the corners make them difficult to "hide" due to the multiple internal reflections and range compression characteristics of the structure. If the first type of solution is adopted, that is, coating the dihedrals with absorbing materials to attenuate the incident wave multiple times within the dihedral, although this method can weaken the reflected wave to a certain extent, the RCS value in the corner domain of right and acute dihedrals is still very high. Therefore, the second type of shaping solution is still mostly used for the treatment of dihedrals, such as constructing right dihedrals into obtuse or acute dihedrals. However, its effect is similar to that of the first type of solution, which can only weaken the intensity of focal scattering to a certain extent, but cannot completely eliminate it.

[0004] In summary, neither of the above two methods can eliminate the strong scattering sources at the corners of a target with a dihedral structure. Therefore, it is necessary to find other feasible ways to achieve the "stealth" of the target. Summary of the Invention

[0005] Based on the above analysis, the present invention aims to provide a method for eliminating strong radar scattering sources for dihedral structures, in order to solve the problem that existing methods of coating absorbing materials and structural shaping cannot eliminate strong scattering sources at the corners of dihedral structures.

[0006] On one hand, embodiments of the present invention provide a method for eliminating strong radar scattering sources for dihedral structures, including:

[0007] A broadband coded metasurface is designed and laid on the corner facets of a diagonal structure. The broadband coded metasurface is an M×N array formed by first and second coded units according to an optimal coding scheme, used to uniformly reflect electromagnetic waves to all directions in space. Each coded unit comprises three layers; each layer is formed by a substrate and a PI film covering the substrate, the PI film having a metal square ring pattern of a specific size; wherein, the outer side length of each metal square ring in the first coded unit is L... 11 ,L 12 ,L 13 The ring widths are w 11 ,w 12 ,w 13 The outer side length of each layer of metal square ring in the second coding unit is L. 21 ,L 22 ,L 23 The ring widths are w 21 ,w 22 ,w 23 The reflection phase difference between the two coding units is stable at 180° over a wide frequency range;

[0008] A columnar metal is designed, located between two corner faces covered by a broadband coded metasurface. The axis of the columnar metal is parallel to the edge of the two-face structure, so as to uniformly scatter incident electromagnetic waves onto the metasurface of the corner faces.

[0009] Specifically, the side lengths of the metal square rings of the first and second coding units are designed as follows:

[0010] Step S1: Construct K coding unit models with different sizes of metal square rings in the simulation software; wherein, any coding unit L k The side lengths of the three-layered metal square rings (k = 1, 2, ..., K) are L... k1 ,L k2 ,L k3 The ring widths are w k1 ,w k2 ,w k3 ;

[0011] Step S2: Obtain the reflection phase-frequency curve of each coding unit, and the phase difference-frequency curve between any two coding units;

[0012] Step S3: Based on the phase difference-frequency curve, select two coding units with a phase difference of 180° at all frequencies, and use them as the first coding unit and the second coding unit, respectively.

[0013] Specifically, the optimal encoding method for the encoding unit in the broadband coded metasurface is obtained according to the following process:

[0014] Step SS1: Use the simulated annealing algorithm to obtain the optimal coding scheme for each frequency point within the wide bandwidth. The maximum value of the directional function of the optimal coding scheme for frequency point i satisfies:

[0015]

[0016] in, Let represent the maximum value of the directional function of frequency point i under the j-th coding method, and h be the number of frequency points;

[0017] Step SS2: Based on the optimal coding scheme for each frequency point, the optimal coding scheme for the broadband coded metasurface is obtained using the simulated annealing algorithm; the pattern function of the optimal coding scheme satisfies:

[0018]

[0019] in, This represents the directionality function of the j-th coding scheme generated at frequency point i. It is the directional function of the optimal coding scheme for frequency point i.

[0020] Specifically, the step of using simulated annealing to obtain the optimal coding scheme for each frequency point within a wide bandwidth includes:

[0021] Step SS101: For any frequency point within the wide bandwidth, randomly generate an initial coding scheme W0, and calculate the directional function f under this coding scheme. 0 The maximum value of the function is max(f) 0 );

[0022] Step SS102: Design a perturbation to generate coding scheme W1, and calculate the directional function f under this coding scheme. 1 The maximum value of the function is max(f) 1 );

[0023] Step SS103: Calculate the directional function f 1 and f 0 The difference between the maximum values ​​Δ = max(f) 1 )-max(f 0 If Δ≤0, then accept the new encoding method, making W0=W1,f 0 =f 1 Otherwise, accept the new encoding method according to the Metropolis guidelines;

[0024] Step SS104: Determine if the number of iterations has been reached; if yes, proceed to step SS105; if no, proceed to step SS102.

[0025] Step SS105: Determine if the termination condition is met; if yes, end the operation and output the new encoding method as the optimal encoding method for this frequency point; if no, slowly reduce the temperature, reset the number of iterations, and then proceed to step SS102.

[0026] Step SS106: Change the frequency point and repeat the above steps until the optimal encoding method for each frequency point in the wideband range is obtained.

[0027] Specifically, the optimal coding method based on each frequency point, using simulated annealing algorithm to obtain the optimal coding method for the wideband coded metasurface, includes:

[0028] Step SS201: Randomly generate coding scheme R0, and calculate the directional function f0 of the coding scheme at each frequency point. i (i = 1, 2, ..., h), where h is the number of frequency points;

[0029] Step SS202: Design a perturbation to generate coding scheme R1, and calculate the directional function under this coding scheme.

[0030] Step SS203, Calculation If Δ R If ≤0, accept the new encoding method, making R0 = R1. Otherwise, accept the new encoding method according to the Metropolis guidelines;

[0031] Step SS204: Determine if the number of iterations has been reached; if yes, proceed to step SS205; if no, proceed to step SS202.

[0032] Step SS205: Determine if the termination condition is met; if yes, end the operation and output the new encoding method as the best encoding method for the broadband encoded metasurface; if no, slowly reduce the temperature, reset the number of iterations, and then proceed to step SS202.

[0033] Specifically, the initial temperature of the simulated annealing algorithm is set to 1000°C, the annealing coefficient is 0.01, and the number of iterations for each temperature is 1000; the termination condition is: the temperature drops to the minimum.

[0034] Specifically, the broadband coded metasurface comprises 24×24 coding units; the side lengths of each layer of the first coding unit's metal square rings are: L 11 =3mm,L 12 =9mm,L 13 = 3.5mm; The side lengths of each layer of metal square rings in the second coding unit are: L 21 =3mm,L 22 =5.5mm,L 23 =3mm; the ring width is 1mm.

[0035] Furthermore, the columnar metal is a cylindrical metal with a length equal to the edge length of the dihedral structure; the radius r of the cylindrical metal satisfies:

[0036]

[0037] Where l represents the distance between the centers of the dihedral faces, and λ represents the wavelength corresponding to the center frequency of the incident electromagnetic wave; the cylindrical metal is supported by metal pillars in the middle of the two faces, the axis is perpendicularly equidistant from the center of the two faces, and the perpendicular distance from the edge of the dihedral face does not exceed the difference between the height of the dihedral structure and the radius of the cylinder.

[0038] Specifically, the substrate is a dielectric foam with a dielectric constant of 1.09 and a loss of 0.001 at 10 GHz.

[0039] On the other hand, embodiments of the present invention provide a dihedral structure, comprising: a dihedral structure, a broadband coded metasurface laid on the two corner faces, and a columnar metal fixed in the middle of the two corner faces by metal pillars; wherein,

[0040] The broadband coded metasurface is an M×N array formed by the first and second coded units according to an optimal coding scheme, used to uniformly reflect electromagnetic waves to all directions in space; each coded unit includes three layers; each layer is formed by a substrate and a PI film covering the substrate, the PI film having a metal square ring pattern of a specific size; wherein, the outer side length of each metal square ring in the first coded unit is L. 11 ,L 12 ,L 13 The ring widths are w 11 ,w 12 ,w 13 The outer side length of each layer of metal square ring in the second coding unit is L. 21 ,L 22 ,L 23 The ring widths are w 21 ,w 22 ,w 23 The reflection phase difference between the two coding units is stable at 180° over a wide frequency range;

[0041] The axis of the columnar metal is parallel to the edge of the diagonal structure and is at the same vertical distance from the center of the two diagonal faces; it is used to uniformly scatter incident electromagnetic waves onto the metasurface of the diagonal faces.

[0042] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0043] 1. First, a designed broadband coded metasurface is laid on the corner surface to uniformly disperse the reflected electromagnetic waves in all directions of space;

[0044] 2. Further, columnar metal is fixed between the dihedral corners, utilizing its natural dispersing effect on electromagnetic waves to further disperse the reflected electromagnetic waves; ultimately, the distance of the dihedral structure is decompressed, achieving the effect of eliminating strong scattering points.

[0045] In this invention, the above-described technical solutions can be combined with each other to achieve more preferred combinations. Other features and advantages of this invention will be set forth in the following description, and some advantages may become apparent from the description or be learned by practicing the invention. The objects and other advantages of this invention can be realized and obtained from what is particularly pointed out in the description and drawings. Attached Figure Description

[0046] The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts.

[0047] Figure 1 This is a schematic diagram of the propagation of electromagnetic waves in a right-angled dihedral structure.

[0048] Figure 2 This is a flowchart of the method for eliminating strong scattering sources at the corners of dihedrals as described in this invention;

[0049] Figure 3 (a) is a schematic diagram of a broadband coded metasurface; Figure 3 (b) is a schematic diagram of a cylindrical metal object;

[0050] Figure 4 A front view of the structure of each coding unit;

[0051] Figure 5 (a) is a top view of the structure of any layer of the coding unit; Figure 5 (b) is a three-dimensional structural diagram of any layer of the coding unit;

[0052] Figure 6 The diagram shows the phase-frequency curves of the first and second coding units, as well as the phase difference-frequency curves of the two coding units.

[0053] Figure 7 This is a broadband coded metasurface for the optimal coding method described in this invention;

[0054] Figure 8 (a) is a physical image of the dihedral structure; (b) is a spatial distribution diagram of the reflected electromagnetic wave field strength at various locations within the structure.

[0055] Figure 9(a) is a physical diagram of a dihedral structure using the method for eliminating strong scattering sources at the corners of the dihedral corners described in this invention; (b) is a spatial distribution diagram of the reflected electromagnetic wave field strength at various locations on the structure.

[0056] Figure 10 A flowchart for obtaining the optimal coding scheme for any frequency point using the simulated annealing algorithm;

[0057] Figure 11 A flowchart illustrating how to obtain the optimal encoding method for a wide bandwidth using the simulated annealing algorithm;

[0058] Figure 12 (a) is a schematic diagram of a regular triangular prism metal and its placement. Figure 12 (b) is a schematic diagram of a regular pentagonal metal prism and its placement.

[0059] Figure label:

[0060] 1-Dihedral corner face; 2-Dihedral edge; 3-Broadband coding metasurface; 4-Cylindrical metal; 5-First coding unit; 6-Second coding unit; 7-Substrate; 8-PI film; 9-Metal square ring. Detailed Implementation

[0061] Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which form part of this application and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not intended to limit the scope of the present invention.

[0062] The theoretical explanation for the strong scattering source at the corner of a dihedral structure is as follows:

[0063] by Figure 1 Taking a right-angled dihedral structure as an example, according to the geometric optics method, the straight line passing through the origin and parallel to the radar incident wave is set as... The axis is equivalent to the xOy coordinate system in the diagram rotating counterclockwise. The radar illumination coordinate system is obtained after rotation.

[0064] When a radar wave is incident at an angle θ, assuming the coordinates of P1 are (x, 0), according to the principle of specular reflection, the radar wave will propagate to P2 (0, y) and be reflected back to the radar at an angle θ. This can be determined by calculating the coordinates of P1 and P2 in the radar illumination coordinate system. Below The coordinates are used to determine the distance the echo has traveled. Because the same... Points with coordinates can be considered as a single point in the radar's range direction. P1 and P2 are in the radar illumination coordinate system. Below The coordinates are as follows:

[0065]

[0066]

[0067] The distance the electromagnetic wave travels from P1 to P2 can be calculated as follows:

[0068]

[0069] Therefore, for a monostatic radar, the phase difference generated from transmission to reception of the echo is:

[0070]

[0071] As can be seen from the phase difference expression, the range information obtained by the radar is compressed at the corner point (0,0). From the perspective of the entire dihedral structure, a very strong echo signal is generated at the corner point.

[0072] Therefore, in order to make a target with a dihedral structure "invisible", it is essential to eliminate strong scattering sources at the dihedral corners.

[0073] A specific embodiment of the present invention discloses a method for eliminating strong radar scattering sources for dihedral structures, such as... Figure 9 As shown in (a), it includes:

[0074] design Figure 3 The broadband coded metasurface 3 shown in (a) is laid on the corner face 1 of the diagonal structure; the broadband coded metasurface 3 is an M×N array formed by the first coding unit 5 and the second coding unit 6 according to the optimal coding method, used to uniformly reflect electromagnetic waves to all directions in space; the structure of each coding unit is as follows Figure 4 As shown, it includes three layers; each layer is as follows: Figure 5 As shown in (a) and (b), both are formed by a substrate 7 and a PI film 8 covering the substrate, wherein the PI film has a metal square ring pattern 9 of a specific size; wherein the outer side length of each layer of metal square rings in the first encoding unit is L. 11 ,L 12 ,L 13 The ring widths are w 11 ,w 12 ,w 13 The outer side length of each layer of metal square ring in the second coding unit is L. 21 ,L 22 ,L 23 The ring widths are w 21 ,w 22 ,w 23 The reflection phase difference between the two coding units is stable at 180° over a wide frequency range; the two coding units have different sizes.

[0075] Designing columnar metal, for example, could be... Figure 3 The cylindrical metal shown in (b) is used to uniformly scatter incident electromagnetic waves onto the supersurface of the corner face.

[0076] Specifically, the cylindrical metal surface is smooth, and its length is the same as the edge length of the dihedral structure; the radius r of the cylindrical metal satisfies:

[0077]

[0078] Where l represents the distance between the centers of the dihedral facets, and λ represents the wavelength corresponding to the center frequency of the incident electromagnetic wave; a retractable metal support is used to support the cylindrical metal in the middle of the two facets covered by a broadband coded metasurface. The axis of the cylinder is parallel to the edge of the dihedral structure and is at the same vertical distance from the center of the two facets. The vertical distance between the axis of the cylindrical metal and the edge of the dihedral structure should not exceed the difference between the height of the dihedral structure and the radius of the cylinder. Preferably, the cylinder and the support are made of the same material, such as conductive metals like aluminum, copper, or silver.

[0079] In simple terms, designing the coding method for a broadband coded metasurface includes: 1) determining the size of the metal square rings of the first and second coding units; 2) using optimization algorithms to determine the optimal arrangement of the coding units.

[0080] Specifically, the dimensions (including outer side length and ring width) of the metal square rings of the first encoding unit 5 and the second encoding unit 6 are designed as follows:

[0081] Step S1: Construct K coding unit models with different sizes of metal square rings in the simulation software; wherein, any coding unit L k The outer side lengths of the three-layered metal square rings (k = 1, 2, ..., K) are respectively L k1 ,L k2 ,L k3 The ring widths are w k1 ,w k2 ,w k3 ;

[0082] Step S2: Obtain the reflection phase-frequency curve of each coding unit, and the phase difference-frequency curve between any two coding units;

[0083] Step S3: Based on the phase difference-frequency curve, select two coding units with a phase difference of 180° at all frequencies, and use them as the first coding unit and the second coding unit, respectively.

[0084] like Figure 6As shown, the reflection phase-frequency curves of the first coding unit and the second coding unit, as well as the phase difference-frequency curves of the two coding units, are shown. It can be seen from the phase difference curves that the reflection phase difference between the first coding unit and the second coding unit remains at 180° in the wide frequency range of 12GHz-18GHz.

[0085] Those skilled in the art will understand that a certain error range is permissible in actual calculations, and the aforementioned phase difference is considered to meet the 180° requirement as long as it is within the permissible error range.

[0086] Specifically, the optimal encoding method for the encoding unit in the broadband coded metasurface is obtained according to the following process:

[0087] Step SS1: Use the simulated annealing algorithm to obtain the optimal coding scheme for each frequency point within the wide bandwidth. The maximum value of the directional function of the optimal coding scheme for frequency point i satisfies:

[0088]

[0089] in, Let represent the maximum value of the directional function of frequency point i under the j-th coding method, and h be the number of frequency points;

[0090] Step SS2: Based on the optimal coding scheme for each frequency point, the optimal coding scheme for the broadband coded metasurface is obtained using the simulated annealing algorithm; the pattern function of the optimal coding scheme satisfies:

[0091]

[0092] in, This represents the directionality function of the j-th coding scheme generated at frequency point i. It is the directional function of the optimal coding scheme for frequency point i.

[0093] Specifically, the simulated annealing algorithm is used to obtain the optimal coding scheme for each frequency point within a wide bandwidth, such as... Figure 10 As shown, it includes:

[0094] Step SS101: For any frequency point within the wide bandwidth, randomly generate an initial coding scheme W0, and calculate the directional function f under this coding scheme. 0 The maximum value of the function is max(f) 0 );

[0095] Step SS102: Design a perturbation to generate coding scheme W1, and calculate the directional function f under this coding scheme. 1 The maximum value of the function is max(f) 1 );

[0096] Step SS103: Calculate the directional function f 1 and f 0 The difference between the maximum values ​​Δ = max(f) 1 )-max(f 0 If Δ≤0, then accept the new encoding method, making W0=W1,f 0 =f 1 Otherwise, accept the new encoding method according to the Metropolis guidelines;

[0097] Step SS104: Determine if the number of iterations has been reached; if yes, proceed to step SS105; if no, proceed to step SS102.

[0098] Step SS105: Determine if the termination condition is met; if yes, end the operation and output the new encoding method as the optimal encoding method for this frequency point; if no, slowly reduce the temperature, reset the number of iterations, and then proceed to step SS102.

[0099] Step SS106: Change the frequency point and repeat the above steps until the optimal encoding method for each frequency point in the wideband range is obtained.

[0100] The initial temperature of the simulated annealing algorithm is set to 1000°C, the annealing coefficient is 0.01, and the number of iterations for each temperature is 1000. The termination condition is that the temperature drops to the minimum.

[0101] Specifically, the optimal coding method based on each frequency point utilizes the simulated annealing algorithm to obtain the optimal coding method for the wideband coded metasurface, such as... Figure 11 As shown, it includes:

[0102] Step SS201: Randomly generate coding scheme R0, and calculate the directional function f0 of the coding scheme at each frequency point. i (i = 1, 2, ..., h), where h is the number of frequency points;

[0103] Step SS202: Design a perturbation to generate coding scheme R1, and calculate the directional function under this coding scheme.

[0104] Step SS203, Calculation If Δ R If ≤0, accept the new encoding method, making R0 = R1. Otherwise, accept the new encoding method according to the Metropolis guidelines;

[0105] Step SS204: Determine if the number of iterations has been reached; if yes, proceed to step SS205; if no, proceed to step SS202.

[0106] Step SS205: Determine if the termination condition is met; if yes, end the operation and output the new encoding method as the best encoding method for the broadband encoded metasurface; if no, slowly reduce the temperature, reset the number of iterations, and then proceed to step SS202.

[0107] in, or Both are called fitness functions The initial temperature of the simulated annealing algorithm is set to 1000°C, the annealing coefficient is 0.01, and the number of iterations for each temperature is 1000. The termination condition is: the temperature drops to the minimum.

[0108] Preferably, since the optimal coding method for any frequency point is fixed, i.e., in the fitness function... It is fixed and theoretically can be chosen arbitrarily, but in practice, 0 is taken as a reference value. Therefore, the fitness function used for optimization can be simplified to... or The calculation formula is:

[0109]

[0110] Where m and n represent the number of rows and columns of the metasurface array, respectively, and F begin F represents the initial frequency. end Represents the cutoff frequency; This represents the phase response of each metasurface element; k represents the wave vector, and d represents the edge length of the element. This represents the initial directional function.

[0111] like Figure 7 As shown, this is the optimal coding scheme for the broadband coded metasurface obtained using the above optimization algorithm, where the light-colored area and the black area are the first and second coding units, respectively.

[0112] For example, the overall size of the encoding unit of the present invention is 12.5mm × 12.5mm × 6mm; the encoding unit includes three layers, each with a height of 2mm; the substrate of each layer is made of dielectric foam with a dielectric constant of 1.09 and a loss of 0.001 at 10GHz; a PI film laid on top of each layer of foam has a metal square ring pattern printed with silver paste, the size of the square ring is obtained by the above-mentioned calculation process of the encoding unit size, preferably, the outer side lengths of the metal square rings in the three-layer structure of the first encoding unit are L 11 =3mm,L 12 =9mm,L 13 = 3.5mm, the side lengths of each layer of metal square rings in the second coding unit are: L 21 =3mm,L 22 =5.5mm,L 23 =3mm, and the ring width is 1mm.

[0113] Metasurfaces composed of two sub-units, such as Figure 7 As shown. The metasurface has dimensions of 300mm × 300mm and includes 24 × 24 coding units. The first coding unit is called the "0" unit, and the second coding unit is called the "1" unit.

[0114] During implementation, targeting Figure 8 The dihedral structure shown in (a) has a corner face size of 300mm × 300mm and an included angle of 90°. Figure 7 The broadband coded metasurface shown is laid on a dihedral structure and mounted with columnar metal to form... Figure 9 The structure shown in (a) has a cylindrical metal diameter of 40 mm and a height of 280 mm between the dihedral angles.

[0115] Using monostation antennas respectively Figure 8 The structure shown in (a) and Figure 9 The antenna scans and receives echo signals above the structure shown in (a). The vertical distance between the antenna and the dihedral corner is 1m, the scanning distance is 800mm, the scanning accuracy is 6mm, the scanning frequency range is 15GHz-17GHz, and the number of scanning points is 101. The SAR radar imaging results are calculated using a back projection algorithm. Figure 8 (b) is Figure 8 The distribution of electromagnetic wave field intensity reflected by the structure in (a) in space shows that the corner points are strong scattering points. Figure 9 (b) is Figure 9 The distribution of the electromagnetic wave field strength reflected by the structure in (a) shows that the reflected electromagnetic waves are uniformly distributed throughout the space.

[0116] As can be seen from the above comparison results, by using the method described in this invention, the strong scattering sources at the corners of the dihedral structure are successfully dispersed to various parts of space, that is, the strong scattering points at the corners are completely eliminated.

[0117] Furthermore, the cylindrical metal in this method embodiment can be replaced with... Figure 12 The regular triangular prism metal shown in (a), or Figure 12 The regular pentagonal prism metal shown in (b) has a base side length of 40mm for the regular triangular prism metal and a base side length of 30mm for the regular pentagonal prism metal; the lengths of both prism metals are the same as the lengths of their two corner faces; the fixing and placement methods are as follows: Figure 12As shown in (a) and (b), similar to the fixing method of the cylindrical metal, metal supports are used for support. One end of the metal support is connected to the center of one side of the cylindrical metal, and the other end is connected to the midpoint of the dihedral angle structure edge. The axis of the cylindrical metal is parallel to the dihedral angle edge. Simulation results show that both the "wideband coded metasurface + regular triangular prism metal" and "wideband coded metasurface + regular pentagonal prism metal" schemes can eliminate the strong scattering source at the corner of the dihedral angle structure, achieving the same effect as the above embodiments.

[0118] In summary, existing coating and shaping methods are insufficient to eliminate strong scattering sources at the corners of dihedral structures. By employing the "wideband coded metasurface + cylindrical metal" method described in this invention, strong scattering sources at the corners of dihedral structures can be eliminated. The wideband coded metasurface, laid on the corner surface of the dihedral structure, allows electromagnetic waves to be reflected uniformly in all directions of space. Furthermore, by utilizing the natural dispersing effect of the cylinder, the incident electromagnetic waves are uniformly scattered onto the metasurface, and the reflected electromagnetic waves in space are further dispersed.

[0119] Another specific embodiment of the present invention discloses a dihedral structure, such as... Figure 8 As shown in (a), it includes: a dihedral structure, a broadband coded metasurface laid on the two corner faces, and a cylindrical metal fixed in the middle of the two corner faces by metal pillars; wherein, the broadband coded metasurface is an M×N array formed by the first and second coded units according to the optimal coding method, used to uniformly reflect electromagnetic waves to all directions in space; each coded unit includes three layers; each layer is formed by a substrate and a PI film covering the substrate, the PI film having a metal square ring pattern of a specific size; wherein, the outer side length of each metal square ring in the first coded unit is L 11 ,L 12 ,L 13 The ring widths are w 11 ,w 12 ,w 13 The outer side length of each layer of metal square ring in the second coding unit is L. 21 ,L 22 ,L 23 The ring widths are w 21 ,w 22 ,w 23 The reflection phase difference between the two coding units is stable at 180° over a wide frequency range; the axis of the columnar metal is parallel to the edge of the diagonal structure and the vertical distance from the center of the two diagonal faces is the same; it is used to uniformly scatter the incident electromagnetic waves onto the metasurface of the diagonal faces.

[0120] Specifically, the size design of the first and second coding units, as well as the optimal coding method for the broadband coding metasurface, all adopt the method described in the first embodiment.

[0121] Similar to the beneficial effects of the method described in the first embodiment, the dihedral structure based on a broadband coded metasurface described in the second embodiment, by adopting a "metasurface + cylindrical metal" approach, completely eliminates strong scattering sources at the corners compared to existing dihedral structures, allowing reflected electromagnetic waves to be evenly dispersed throughout space, thereby enabling targets with dihedral structures to achieve a better "stealth" effect.

[0122] Those skilled in the art will understand that all or part of the processes of the methods described in the above embodiments can be implemented by a computer program instructing related hardware, and the program can be stored in a computer-readable storage medium. The computer-readable storage medium may be a disk, optical disk, read-only memory, or random access memory, etc.

[0123] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for eliminating strong radar scattering sources for dihedral structures, characterized in that, include: A broadband coding metasurface (3) is designed and laid on the two corner faces (1) of the diagonal structure; the broadband coding metasurface is formed by the first coding unit (5) and the second coding unit (6) according to the optimal coding method. An array is used to uniformly reflect electromagnetic waves to all directions in space; each encoding unit includes three layers; each layer includes a substrate (7) and a PI film (8) covering the substrate, the PI film having a metal square ring pattern (9); wherein, the outer side lengths of the metal square rings in each layer of the first encoding unit are respectively The ring widths are respectively The outer side lengths of each layer of metal square rings in the second coding unit are respectively The ring widths are respectively The reflection phase difference between the two coding units is stable over a wide frequency range. ; The outer side length and ring width of each metal square ring in the first and second coding units are designed according to the following method: Step S1, construct K coding unit models with different metal square ring sizes; wherein, any coding unit The side lengths of the metal square rings are respectively The ring widths are respectively ; Step S2: Obtain the reflection phase-frequency curve of each coding unit to obtain the phase difference-frequency curve between any two coding units; Step S3: Based on the phase difference-frequency curve, select the frequency at which the phase difference is zero. The dimensions corresponding to the two coding units are respectively used as the dimensions of the first coding unit and the second coding unit; The optimal encoding method for the encoding unit in the broadband encoded metasurface is obtained according to the following process: Step SS1, using the simulated annealing algorithm, obtain the optimal encoding method for each frequency point within the broadband range. The frequency point The maximum value of the directionality function of the optimal encoding method satisfies: in, , indicating frequency point In the The maximum value of the directional function under this encoding method For the number of frequency points; Step SS2: Based on the optimal coding method for each frequency point, use the simulated annealing algorithm to obtain the optimal coding method for the broadband coded metasurface; the pattern function of the optimal coding method satisfies: in, , indicating frequency point The next generated The directional function of the encoding method Frequency The directionality function of the optimal encoding method; A columnar metal is designed, located between two corner faces covered by a broadband coded metasurface. The axis of the columnar metal is parallel to the edge of the two-face structure, so as to uniformly scatter incident electromagnetic waves onto the metasurface of the corner faces.

2. The method for eliminating strong radar scattering sources for dihedral structures according to claim 1, characterized in that, The method of using simulated annealing to obtain the optimal coding scheme for each frequency point within a wide bandwidth includes: Step SS101: For any frequency point within a wide bandwidth, randomly generate an initial encoding scheme. Calculate the encoding method Directional function below The maximum value of the function is ; Step SS102: Generating encoding method based on perturbation Calculate the encoding method Directional function below The maximum value of the function is ; Step SS103: Calculate the directional function and Difference of maximum value ;like Then accept the new encoding method, so that Otherwise, accept the new encoding method according to the Metropolis guidelines; Step SS104: Determine if the number of iterations has been reached; if yes, proceed to step SS105; if no, proceed to step SS102. Step SS105: Determine if the termination condition is met; if yes, end the operation and output the new encoding method as the optimal encoding method for this frequency point; if no, slowly reduce the temperature, reset the number of iterations, and then proceed to step SS102. Step SS106: Change the frequency point and repeat the above steps until the optimal encoding method for each frequency point in the wideband range is obtained.

3. The method for eliminating strong radar scattering sources for dihedral structures according to claim 2, characterized in that, The optimal coding method based on each frequency point utilizes the simulated annealing algorithm to obtain the optimal coding method for the broadband coded metasurface, including: Step SS201: Randomly generate encoding method Calculate the coding method for each frequency point. Directional function , Number of frequency points; Step SS202: Generating encoding method based on perturbation Calculate the directional function under this encoding method. ; Step SS203, Calculation ;like Accept new encoding methods, make Otherwise, accept the new encoding method according to the Metropolis guidelines; Step SS204: Determine if the number of iterations has been reached; if yes, proceed to step SS205; if no, proceed to step SS202. Step SS205: Determine if the termination condition is met; if yes, end the operation and output the new encoding method as the best encoding method for the broadband encoded metasurface; if no, slowly reduce the temperature, reset the number of iterations, and then proceed to step SS202.

4. The method for eliminating strong radar scattering sources for dihedral structures according to claim 3, characterized in that, The initial temperature of the simulated annealing algorithm is set to Annealing coefficient is The number of iterations for each temperature is The termination condition is: the temperature drops to its lowest level.

5. The method for eliminating strong radar scattering sources for dihedral structures according to claim 4, characterized in that, The broadband coded metasurface includes One coding unit; the side lengths of each layer of metal square rings in the first coding unit are as follows: The side lengths of each layer of metal square rings in the second coding unit are as follows: The ring width is 1. .

6. The method for eliminating strong radar scattering sources for dihedral structures according to claim 1, characterized in that, The columnar metal is a cylindrical metal, and the length of the cylindrical metal is the same as the edge length of the dihedral structure; the radius of the cylindrical metal... satisfy: in, This indicates the distance between the centers of the dihedral faces. It represents the wavelength corresponding to the center frequency of the incident electromagnetic wave; the cylindrical metal is supported by metal pillars in the middle of the two corner faces, the axis is equidistant from the center of the two corner faces, and the perpendicular distance from the edge of the two corner faces does not exceed the difference between the height of the dihedral structure and the radius of the cylinder.

7. The method for eliminating strong radar scattering sources for dihedral structures according to any one of claims 1-6, characterized in that, The substrate is a dielectric foam with a dielectric constant of 1.09 and a loss of 0.001 at 10 GHz.

8. A dihedral structure for performing the method according to any one of claims 1 to 7, characterized in that, include: The structure comprises a dihedral angle, a broadband coded metasurface laid on the two corner faces, and a columnar metal column fixed in the middle of the two corner faces using metal supports; among which, The broadband coded metasurface is formed by the first and second coding units according to the optimal coding method. An array is used to uniformly reflect electromagnetic waves in all directions of space; each encoding unit comprises three layers; each layer is formed by a substrate and a PI film covering the substrate, the PI film having a metal square ring pattern of a specific size; wherein, the outer side length of each metal square ring in the first encoding unit is respectively... The ring widths are respectively The outer side lengths of each layer of metal square rings in the second coding unit are respectively The ring widths are respectively The reflection phase difference between the two coding units is stable over a wide frequency range. ; The axis of the columnar metal is parallel to the edge of the diagonal structure and is at the same vertical distance from the center of the two diagonal faces; it is used to uniformly scatter incident electromagnetic waves onto the metasurface of the diagonal faces.

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