Antenna array electromagnetic shielding rapid evaluation method for integrated joined wing platform

Abstract

The invention provides an antenna array electromagnetic shielding rapid assessment method for an integrated joined wing platform, and the method comprises the steps: firstly, neglecting the thickness of a patch antenna for a to-be-assessed integrated joined wing aircraft model with an antenna layout scheme, and dividing the surface of an aircraft into triangular grid units; secondly, a field source is set on the ground, and a receiving end is set on the joined-wing aircraft; generating rays carrying a set electric field according to the direction from the field source to the receiving end; whether the rays intersect with the triangular grid units or not is judged, and if yes, the rays are emitted to the bright area; performing electric field intensity tracking on rays emitted to the bright area, and calculating field intensity distribution of each patch antenna by adopting an improved bounce ray method; and finally, based on the field intensity distribution and the field source electric field intensity of each patch antenna, calculating the electromagnetic shielding rate of each patch antenna and the total electromagnetic shielding rate of the integrated joined wing aircraft. According to the method, the electromagnetic shielding rate of the integrated joined wing aircraft can be rapidly solved.

Description

Technical Field

[0001] The present invention relates to the field of electromagnetic analysis of aircraft, and in particular to a rapid evaluation method for electromagnetic shielding of an antenna array for an integrated linked wing platform. Background Art

[0002] In the design of traditional ultra-long-endurance unmanned aerial platforms, the design focuses mainly on how to increase the flight time and improve the performance and field of view of the antenna, so as to obtain all-round and long-term data acquisition capabilities. At present, conventional layout and flying wing layout aircraft are difficult to meet both requirements at the same time; the unmanned aerial platform with an integrated linked wing configuration can solve the above problems. Its good aerodynamic characteristics ensure the flight time requirements. In addition, the swept front wing and the swept rear wing in the linked wing configuration can be used for antenna installation, which can provide omnidirectional field of view detection capabilities and have advantages that traditional aircraft cannot match.

[0003] From the perspective of antennas, a single antenna can be designed very ideally, but after integrating the integrated linked wing configuration platform, the large flat plate components connecting the end plates, front wings, and rear wings in the linked wing configuration will also bring a large shielding effect to the patch antenna. Therefore, how to efficiently and accurately evaluate the shielding effect of shielding components on patch antennas is very critical for the optimal antenna array design of the integrated linked wing platform.

[0004] At present, there are two types of analysis methods for antenna electromagnetic simulation. One type is based on solving Maxwell's equations, including finite element method, moment method, etc. This type of method has good calculation accuracy, but has the problems of low efficiency and long analysis time. In the design process of aircraft considering antenna array layout, it is necessary to calculate the electromagnetic shielding rate of a large number of layout schemes. The use of this type of method will lead to low design efficiency; the other type is based on high-frequency approximation methods, such as the bouncing ray method (SBR), physical optics method (PO), etc. This type of method calculates electromagnetic characteristics by simulating the reflection, refraction and scattering of rays, and has higher calculation efficiency than the first type of method. However, the applicant's research found that , when this type of method is used to calculate the electromagnetic obscuration rate of the antenna array of an integrated coupled wing configuration aircraft, there are the following problems: 1) When dealing with the edge diffraction of rays, the traditional method needs to solve a set of vector equations in combination with boundary conditions to obtain the diffraction angle and the direction of the diffraction ray. The calculation is relatively complicated. When the number of rays is large, the calculation efficiency is affected; 2) The calculation of the electromagnetic obscuration rate of the antenna array of an integrated coupled wing configuration aircraft mainly relies on electric field information, while the traditional method is mainly used for the calculation of the radar reflection cross-sectional area of ​​the aircraft. During the calculation process, it is necessary to repeatedly calculate the electric field and magnetic field, which is not suitable for the rapid calculation of the electromagnetic obscuration rate of the antenna array of an integrated coupled wing configuration aircraft. Summary of the invention

[0005] To solve the above problems, the present invention proposes a rapid assessment method for electromagnetic shielding of antenna arrays for integrated linked-wing platforms. The method is improved on the basis of the bouncing ray method. On the one hand, the diffraction coefficient is directly defined for rapid solution of the diffraction angle; on the other hand, the third-order diffraction tensor coefficient in the traditional bouncing ray method is reduced in dimension to avoid magnetic field calculation, and the electric field of the diffraction ray can be quickly solved. The method of the present invention can quickly calculate the electromagnetic shielding rate of the antenna array of the integrated linked-wing configuration aircraft, and is suitable for rapid evaluation of targets during the antenna array layout design process of the integrated linked-wing configuration aircraft.

[0006] The technical solution of the present invention specifically comprises the following steps:

[0007] Step 1: In the finite element software, for the integrated connected-wing aircraft model with antenna array layout to be evaluated, the thickness of the patch antenna is ignored, the aircraft surface is divided into the patch antenna area and other areas, triangular mesh units are generated by area, the leading and trailing edges of the wing are meshed, and the vertex coordinates of the mesh units are stored;

[0008] Step 2: Import the integrated coupled wing aircraft model in step 1 into the electromagnetic analysis software. In the electromagnetic analysis software, set the field source on the ground and set the receiving end on the integrated coupled wing aircraft model; generate a plane wave as an incident wave in the direction from the field source to the receiving end; the incident wave is composed of a number of rays carrying a set electric field, and the number of rays is equal to the number of grid units in step 1; perform a judgment on the intersection of the ray and the grid unit, and if the ray intersects with the grid unit, it is determined that the ray is directed to the bright area;

[0009] Step 3: Tracing the field intensity of the rays directed to the bright area, and using the improved bouncing ray method to calculate the field intensity distribution of each patch antenna on the integrated joint-wing aircraft;

[0010] Step 4: Based on the field intensity distribution of each patch antenna and the electric field strength of the field source, the electromagnetic shielding rate of each patch antenna on the integrated linked-wing aircraft and the total electromagnetic shielding rate of the integrated linked-wing aircraft are calculated.

[0011] Furthermore, in step 1, the size of the grid unit is selected according to the working wavelength of the patch antenna, which is one tenth of the working wavelength of the patch antenna.

[0012] Furthermore, in step 2, the process of determining whether the ray is directed toward the bright area is as follows: for each ray, traverse each grid unit on the surface of the integrated coupled wing aircraft model:

[0013] For each grid cell, first perform a single occlusion check:

[0014] Obtain the ray direction vector based on the source position and the integrated wing aircraft model position , get the normal vector of the mesh cell according to the vertex coordinates of the mesh cell ;

[0015] like , it is determined to be non-intersecting, the grid unit is marked as a dark area, and the ray is directed to the dark area; if , it is determined to be an intersection, the grid unit is marked as a bright area, and the ray is directed toward the bright area;

[0016] Then consider the mutual occlusion between grid cells and make multiple occlusion judgments:

[0017] For a grid cell marked as a bright area, draw a line segment from its center point to the field source, and determine whether this line segment intersects with other grid cells. If the line segment intersects with other grid cells, the grid cell is blocked by other grid cells, and the grid cell is re-marked as a dark area;

[0018] Finally, all the rays directed toward the bright area are obtained.

[0019] Furthermore, step 3 specifically includes the following sub-steps:

[0020] Step 31: For the rays directed toward the bright area, assuming that the rays propagate in a straight line in a uniform medium, the electric field strength at the intersection point where the rays propagate in a straight line is calculated using the following formula: :

[0021]

[0022] in, is the grid cell differential at the source, Differentiate the grid cell at the intersection point; the complex expression Used to describe the propagation characteristics of plane electromagnetic waves in space. is an imaginary unit, is the wave number, is the distance from the intersection point to the field source, is the wavelength of the ray; is the electric field strength of the source;

[0023] Step 32: Determine the intersection type between the ray and the integrated linked-wing aircraft model, where the intersection type includes intersection within a plane and intersection at an edge; if the ray intersects with the grid unit within a plane, use the geometric optics method to simulate the ray reflection and calculate the ray direction vector after reflection. and the electric field strength of the reflected rays ; If the intersection is at the edge, the improved consistent diffraction theory is used to simulate the ray diffraction and calculate the ray direction vector after diffraction And the electric field strength of the rays after diffraction ;

[0024] Step 33: trace each ray after reflection and diffraction, and determine whether the ray intersects with the grid unit. If the ray intersects with the grid unit, the ray is directed to the bright area.

[0025] Step 34: Repeat steps 31 to 33 until the electric field carried by the traced ray is less than a set value or is directed toward a dark area;

[0026] Step 35: For each patch antenna in the patch antenna area of ​​the integrated linked-wing aircraft model, the field strength distribution of the patch antenna is obtained by the following process:

[0027] For each grid cell corresponding to the patch antenna, the sum of the electric fields carried by the rays directly, reflected, and diffracted on each grid cell is calculated to obtain the total electric field of each grid cell on the patch antenna:

[0028]

[0029] The patch antenna The total electric field of the grid units is calculated to obtain the field strength distribution of the patch antenna; each patch antenna is traversed to obtain the field strength distribution of each patch antenna area on the integrated linked wing aircraft under the antenna array layout.

[0030] Furthermore, the method for determining the intersection type in step 32 is that if the angle between the normal of a bright area grid unit and the normal of an adjacent grid unit is less than 10 degrees, the intersection type is determined to be an intersection within the plane; if the normal angle is greater than or equal to 10 degrees, the intersection type is determined to be an intersection at the edge, and the bright area grid unit is an edge grid unit.

[0031] Furthermore, in step 32, when the intersection type is intersection at the edge, the improved consistent diffraction theory is used to simulate the ray diffraction, and the ray direction vector after diffraction is calculated. And the electric field strength of the rays after diffraction The specific process is:

[0032] First, solve the ray direction vector after diffraction :

[0033] Get the vertex coordinates of the edge grid unit and its adjacent grid units, and get the normal vector of the edge grid unit according to the vertex coordinates of the edge grid unit ; Obtain the edge vector based on the common edges of the edge grid cell and its adjacent grid cells ;

[0034] Assume the incident direction vector of the ray is , the incident direction vector and the normal vector The angle between ; The incident direction vector of the ray With edge vector The angle between ; Treat the diffraction phenomenon as the incident ray around the edge vector Deflect an angle , let the direction vector of the ray after diffraction be , the direction vector of the ray after diffraction With normal vector The angle between the two is the diffraction angle ;

[0035] According to the incident direction vector of the ray and the normal vector Calculate the angle of incidence :

[0036]

[0037] According to the formula

[0038]

[0039] Calculate the deflection angle ,in is the diffraction coefficient;

[0040] Assumptions , is the normal vector The three-axis components of the edge vector are calculated by the following expression Rotation The transformation matrix :

[0041]

[0042] Will Decomposed into parallel Vector and perpendicular to Vector , the specific expression is:

[0043]

[0044]

[0045] Then the direction vector of the ray after diffraction is for:

[0046]

[0047] Then solve the electric field intensity of the ray after diffraction :

[0048] According to the incident direction vector of the ray and the edge vector calculate :

[0049]

[0050] According to the diffraction direction vector of the ray and the normal vector Calculate the diffraction angle :

[0051]

[0052] The electric field intensity of the ray after diffraction is calculated by the following formula :

[0053]

[0054] In the formula, is the electric field strength at the point where the ray propagates in a straight line. At this time, the intersection point is the diffraction point. is the diffraction coefficient tensor, is the defocus distance, is the distance from the observation point to the diffraction point;

[0055] The diffraction coefficient tensor is calculated by :

[0056]

[0057] D s = - e -jπ / 4 2π 2πbsin β 0 [ F( b The( i s - I will i ) ) cos (( i s - I will i ) / 2) - F( bLa( i s + I will i ) ) cos (( i s + I will i ) / 2) ]

[0058] D h = - e -jπ / 4 2π 2πbsin β 0 [ F bLa i s - I will i cos i s - I will i 2 + F( bLa( i s + I will i ) ) cos (( i s + I will i ) / 2) ]

[0059] The function in the above expression , , and intermediate variables The explanation is as follows:

[0060] when : F x =[ πx -2x e j π 4 -2 x 2 e -j π 4 ] e j( π 4 +x)

[0061] when :

[0062]

[0063]

[0064] .

[0065] Furthermore, step 4 is specifically as follows:

[0066] First, each patch antenna is regarded as a region. According to the field strength distribution of the patch antenna obtained in step 3, weighted average is performed according to the size of the grid unit area to obtain the average electric field of the patch antenna. , the specific calculation formula is:

[0067]

[0068] in, Indicates the number of The total electric field of each grid cell is Indicates the number of The area of ​​a grid cell, represents the sum of the areas of all grid cells of the patch antenna; and They are all obtained by calculating the vertex coordinates of the grid cells;

[0069] Then calculate the electromagnetic shielding rate of the patch antenna according to the following formula: :

[0070]

[0071] in, Represents the electric field strength of the field source; traverse each patch antenna to obtain the electromagnetic shielding rate of all patch antennas;

[0072] Considering all patch antennas as one area, the above calculation process is repeated to obtain the total electromagnetic shielding rate of the integrated linked-wing aircraft.

[0073] Beneficial effects:

[0074] The present invention provides a rapid assessment method for electromagnetic shielding of an antenna array for an integrated linked wing platform. The method is improved on the basis of a bouncing ray method. On the one hand, the diffraction coefficient is directly defined for rapid solution of the diffraction angle; on the other hand, the third-order diffraction tensor coefficient in the traditional bouncing ray method is dimensionally reduced to avoid magnetic field calculation, and the electric field of the diffraction ray can be rapidly solved. The method of the present invention can rapidly calculate the electromagnetic shielding rate of the antenna array of an integrated linked wing configuration aircraft, and is suitable for rapid assessment of targets during the antenna array layout design process of the integrated linked wing configuration aircraft. BRIEF DESCRIPTION OF THE DRAWINGS

[0075] Figure 1 It is a flowchart of the implementation of the scheme of rapid assessment of electromagnetic shielding of antenna array in an embodiment of the present invention;

[0076] Figure 2 The initial configuration of the connecting wing of the embodiment of the present invention;

[0077] Figure 3 A simplified electromagnetic analysis three-dimensional model of a coupling wing with an antenna according to an embodiment of the present invention;

[0078] Figure 4 A schematic diagram of a grid for analyzing the electromagnetic shielding rate according to an embodiment of the present invention;

[0079] Among them: 1-first patch antenna; 2-second patch antenna; 3-third patch antenna; 4-fourth patch antenna; 5-fuselage; 6-connecting end plate; 7-front wing; 8-rear wing. DETAILED DESCRIPTION

[0080] In order to make the technical problems, technical solutions and beneficial effects solved by the present invention clearer and more understandable, and to enable those skilled in the art to better understand the solutions of the present invention, the present invention is further described and fully described in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0081] The embodiment of the present invention takes a double-beam type linked wing ultra-long flight time unmanned platform with an antenna array layout as an example. The initial configuration of the linked wing aircraft is as follows: Figure 2 As shown in FIG. 1 , the electromagnetic shielding rapid assessment method for the antenna array of the integrated wing platform proposed in the present invention is used to perform electromagnetic shielding analysis on the integrated wing platform and calculate the electromagnetic shielding rate under the layout. In order to simplify the calculation, the half-module of the integrated wing configuration is taken for calculation, as shown in FIG. Figure 3 As shown, the model consists of a fuselage, connecting end panels, front wings and rear wings, and the antenna array layout is as follows: 4 patch antennas are arranged at equal intervals on the side of the fuselage.

[0082] The implementation flow chart of the solution of the embodiment of the present invention is as follows Figure 1 As shown, the specific steps include:

[0083] Step 1: In the finite element software, for the integrated connected-wing aircraft model with antenna array layout to be evaluated, ignore the thickness of the patch antenna, divide the aircraft surface into the patch antenna area and other areas, generate triangular mesh units by area, and then encrypt the mesh of the leading and trailing edges of the wing to better fit the shape, and store the vertex coordinates of the mesh units.

[0084] In this embodiment, the size of the patch antenna on the side of the fuselage is , the operating frequency is , the corresponding wavelength is The size of the triangular grid unit is selected according to the wavelength of the incident wave. Specifically, the grid unit size is one tenth of the wavelength, that is, 0.05m. Due to the large curvature of the leading and trailing edges of the wing, the grid is appropriately encrypted to better fit the shape. A total of 7134 grid units are divided. Figure 4 shown.

[0085] Step 2: Import the integrated coupled wing aircraft model in step 1 into the electromagnetic analysis software. In the electromagnetic analysis software, set the field source on the ground and set the receiving end on the integrated coupled wing aircraft model; generate a plane wave as an incident wave in the direction from the field source to the receiving end; the incident wave is composed of a number of rays carrying a set electric field, and the number of rays is equal to the number of grid units in step 1; perform a judgment on the intersection of the ray and the grid unit, and if the ray intersects with the grid unit, it is determined that the ray is directed to the bright area;

[0086] The process of judging whether the ray is directed to the bright area is as follows: for each ray, traverse each grid unit on the surface of the integrated joint-wing aircraft model;

[0087] For each grid cell, first perform a single occlusion check:

[0088] Obtain the ray direction vector based on the source position and the integrated wing aircraft model position , get the normal vector of the mesh cell according to the vertex coordinates of the mesh cell ;

[0089] In this embodiment, the coordinate axis system is established As follows: The coordinate axis system takes the center of mass of the integrated joint wing aircraft model as the origin , The axis coincides with the aircraft body axis and points to the tail of the aircraft; The axis is on the longitudinal symmetry plane of the aircraft, vertical Axially; Axis perpendicular to axis, axis, forming a right-hand coordinate system; the height of the integrated joint-wing aircraft model is set to 1000m, and the field source is 2000m to the left of the aircraft model, then the receiving end coordinate , field source coordinates , the ray direction vector After normalization, , set the initial electric field strength of the ray (field source electric field strength) to .

[0090] like , it is determined to be non-intersecting, the grid unit is marked as a dark area, and the ray is directed to the dark area; if , it is determined to be an intersection, the grid unit is marked as a bright area, and the ray is directed toward the bright area;

[0091] Then consider the mutual occlusion between grid cells and make multiple occlusion judgments:

[0092] For a grid cell marked as a bright area, draw a line segment from the center point to the field source, and determine whether this line segment intersects with other grid cells. If the line segment intersects with other grid cells, the grid cell is blocked by other grid cells, and the grid cell is re-marked as a dark area;

[0093] Finally, all the rays directed toward the bright area are obtained.

[0094] The following is a specific description of a triangular mesh unit T3 on the lower surface of the front wing. The coordinates of its three vertices are

[0095]

[0096] Assume the unnormalized mesh element normal vectors ;

[0097] First, perform single occlusion judgment:

[0098] Find the vectors on both sides:

[0099]

[0100]

[0101] Using vector cross product, , we can get:

[0102]

[0103]

[0104]

[0105] Finally Normalize and get the expression of the normal vector:

[0106]

[0107] Then there is

[0108]

[0109] This means that the angle between the ray direction vector and the grid element normal vector is greater than , which means that the ray propagates in the direction of the triangular mesh unit T3 on the surface of the aircraft model, so it is determined to be an intersection, and the triangular mesh unit T3 is marked as a bright area.

[0110] Then consider the mutual occlusion between triangular mesh units to perform multiple occlusion judgments:

[0111] For the grid cell T3 marked as the bright area, make a line segment passing through its center point to the field source, and determine whether this line segment intersects with other grid cells. If the line segment intersects with other grid cells, the grid cell T3 is blocked by other grid cells, and the grid cell T3 is re-marked as the dark area; if the line segment does not intersect with other grid cells, the grid cell T3 is still a bright area.

[0112] Step 3: Tracing the field intensity of the rays directed to the bright area, and using the improved bouncing ray method to calculate the field intensity distribution of each patch antenna on the integrated linked-wing aircraft; specifically, the following sub-steps are included:

[0113] Step 31: For the rays directed toward the bright area, assuming that the rays propagate in a straight line in a uniform medium, the electric field strength at the intersection point where the rays propagate in a straight line is calculated using the following formula: :

[0114]

[0115] in, is the grid cell differential at the source, Differentiate the grid cell at the intersection point; the complex expression Used to describe the propagation characteristics of plane electromagnetic waves in space. is an imaginary unit, is the wave number, is the distance from the intersection point to the field source, is the wavelength of the ray;

[0116] Step 32: Determine the intersection type between the ray and the integrated linked-wing aircraft model, where the intersection type includes intersection within a plane and intersection at an edge; if the ray intersects with the grid unit within a plane, use the geometric optics method to simulate the ray reflection and calculate the ray direction vector after reflection. and the electric field strength of the reflected rays ; If the intersection is at the edge, the improved consistent diffraction theory is used to simulate the ray diffraction and calculate the ray direction vector after diffraction And the electric field strength of the rays after diffraction ;

[0117] In this embodiment, the method for determining the intersection type is that if the angle between the normal of a bright area grid unit and the normal of an adjacent grid unit is less than 10 degrees, it is determined that the intersection is in the plane; if the angle between the normals is greater than or equal to 10 degrees, it is determined that the intersection is at the edge, and the bright area grid unit is an edge grid unit.

[0118] ① When the intersection is in the plane, the geometric optics method (GO) is used to simulate the reflection of the ray and calculate the direction vector of the ray after reflection. and the electric field strength of the reflected rays The specific process is:

[0119] First solve the direction vector of the ray after reflection :

[0120] Get the normal vector of the mesh cell according to the vertex coordinates of the mesh cell ;

[0121] Assume the incident direction vector of the ray is , the incident direction vector of the ray and the normal vector of the grid cell The angle between ; Let the direction vector of the reflected ray be , the direction vector of the ray after reflection and the normal vector of the grid cell The angle of reflection is ; According to the law of reflection, the angle of incidence Equal to the reflection angle ; In the incident direction vector and the normal vector In the plane composed of Decomposed into normal vector Parallel vectors Sum and normal vector Vertical Vector ;

[0122] in That is exist The projection vector on

[0123] ;

[0124]

[0125] because ,so and About Normal Vectors Symmetrical, that is

[0126]

[0127] get The expression is

[0128]

[0129] Then the electric field intensity of the reflected ray is solved by the following formula :

[0130]

[0131] in, is the electric field strength at the intersection point where the ray straight line propagates from step 31. At this time, the intersection point is the reflection point. represents the reflection coefficient, is the grid cell differential at the incident point, is the differential of the grid cell after reflection, is the distance from the observation point to the incident point after reflection.

[0132] The following is still a specific explanation using a grid unit T3 on the lower surface of the front wing as an example. First, the normal angles between the grid unit and its adjacent grid units are calculated, which are 0.7 degrees, 1.1 degrees, and 0.6 degrees, respectively, all less than 10 degrees, that is, they are judged to intersect within the plane; when the intersection is within the plane, the geometric optics method (GO) is used to simulate the reflection of the ray, and the direction vector of the ray after reflection and the electric field intensity of the ray after reflection are calculated. ;

[0133] First solve the direction vector of the ray after reflection :

[0134]

[0135] Then the electric field intensity of the reflected ray is solved by the following formula :

[0136]

[0137] in, is the electric field strength at the intersection point where the ray propagates in a straight line obtained in step 31:

[0138]

[0139] So, get

[0140] ;

[0141] ② When the intersection is at the edge, the improved consistent diffraction theory is used to simulate the diffraction of the ray and calculate the direction vector of the ray after diffraction. And the electric field strength of the rays after diffraction The specific process is:

[0142] First, solve the ray direction vector after diffraction :

[0143] Get the vertex coordinates of the edge grid unit and its adjacent grid units, and get the normal vector of the edge grid unit according to the vertex coordinates of the edge grid unit ; Obtain the edge vector based on the common edges of the edge grid cell and its adjacent grid cells ;

[0144] The main shielding parts of the integrated wing aircraft are the connecting end plates and the front and rear wings. The diffraction problem is simplified to the flat plate diffraction problem. The incident direction vector of the ray is , the normal vector of the plate is taken as , the edge vector of the plate is taken as , the incident direction vector of the ray and the normal vector The angle between ; The incident direction vector of the ray and the edge vector The angle between ; Treat the diffraction phenomenon as the incident ray around the edge vector Deflect an angle , let the direction vector of the ray after diffraction be , the direction vector of the ray after diffraction and the normal vector The angle between the two is the diffraction angle ;

[0145] According to the incident direction vector of the ray and the normal vector Calculate the angle of incidence :

[0146]

[0147] Defining the diffraction coefficient , calculate the deflection angle :

[0148]

[0149] Assumptions , is the normal vector The three-axis components of the edge vector are calculated by the following expression Rotation The transformation matrix :

[0150]

[0151] Will Decomposed into parallel Vector and perpendicular to Vector , the specific expression is:

[0152]

[0153]

[0154] Then the direction vector of the ray after diffraction is for:

[0155]

[0156] Then solve the electric field intensity of the ray after diffraction :

[0157] According to the incident direction vector of the ray and the edge vector calculate :

[0158]

[0159] According to the diffraction direction vector of the ray and the normal vector Calculate the diffraction angle :

[0160]

[0161] According to the Keller cone, the electric field intensity of the ray after diffraction is calculated by the following formula: :

[0162]

[0163] In the formula, is the electric field strength at the point where the ray propagates in a straight line. At this time, the intersection point is the diffraction point. is the diffraction coefficient tensor, is the defocus distance, is the distance from the observation point to the diffraction point; As mentioned above, the main shielding components of the integrated joint-wing aircraft are the connecting end plates and the front and rear wings, simplifying the diffraction problem to a flat plate diffraction problem. For the flat plate diffraction problem, we have , ;

[0164] The diffraction coefficient tensor in the conventional bouncing ray method To reduce the dimension, we do not consider the spatial dimension characteristics of the electromagnetic field, but only consider the electric field solution, and calculate the diffraction coefficient tensor by the following formula: :

[0165]

[0166] D s = - e -jπ / 4 2π 2πbsin β 0 [ F( b The( i s - I will i ) ) cos (( i s - I will i ) / 2) - F( bLa( i s + I will i ) ) cos (( i s + I will i ) / 2) ]

[0167] D h = - e -jπ / 4 2π 2πbsin β 0 [ F bLa i s - I will i cos i s - I will i 2 + F( bLa( i s + I will i ) ) cos (( i s + I will i ) / 2) ]

[0168] The functions and intermediate variables in the above expressions are explained as follows:

[0169]

[0170] when : F x =[ πx -2x e j π 4 -2 x 2 e -j π 4 ] e j( π 4 +x)

[0171] when :

[0172]

[0173]

[0174]

[0175] Let's take a triangular mesh unit T4 located in the bright area and at the edge of the connecting end plate as an example to illustrate. First, solve the ray direction vector after diffraction. :

[0176] The incident direction vector of the ray coming from the field source is known , the normal vector of the plate is obtained according to the vertex coordinates of the triangular mesh unit T4: , the edge vector is , according to the incident direction vector of the ray and the normal vector of the plate Calculate the angle of incidence :

[0177]

[0178] Defining the diffraction coefficient , calculate the deflection angle :

[0179]

[0180] according to and Calculate the edge vector Rotation The transformation matrix :

[0181]

[0182] Will Decomposed into parallel Vector and perpendicular to Vector , the specific expression is:

[0183]

[0184]

[0185] Then the direction vector of the ray after diffraction is for:

[0186]

[0187] Then solve the electric field intensity of the ray after diffraction :

[0188] The electric field strength at the diffraction point obtained in step 31 is :

[0189]

[0190] According to the incident direction vector of the ray and the edge vector of the plate calculate :

[0191]

[0192] According to the diffraction direction of the ray and the normal vector of the plate Calculate the diffraction angle :

[0193]

[0194] according to , , The diffraction coefficient tensor is calculated by :

[0195]

[0196]

[0197]

[0198]

[0199]

[0200] According to the Keller cone, the electric field intensity of the ray after diffraction is calculated by the following formula: :

[0201]

[0202] is the distance from the observation point to the diffraction point, , then

[0203]

[0204] Step 33: trace each ray after reflection and diffraction, and determine whether the ray intersects with the grid unit. If the ray intersects with the grid unit, the ray is directed to the bright area.

[0205] Step 34: Repeat steps 31 to 33 until the electric field carried by the traced ray is less than the set value Or shoot towards the dark area;

[0206] In this embodiment, the setting value , that is, when the electric field intensity of the reflected or diffracted ray is less than When , it is considered that the ray is emitted into the dark area and no longer contributes to the superposition of the electric field strength of the patch antenna.

[0207] Step 35: For each patch antenna in the patch antenna area of ​​the integrated linked-wing aircraft model, the field strength distribution of the patch antenna is obtained by the following process:

[0208] For each grid cell corresponding to the patch antenna, the sum of the electric fields carried by the rays directly, reflected, and diffracted on each grid cell is calculated to obtain the total electric field of each grid cell on the patch antenna:

[0209]

[0210] The patch antenna The total electric field of the grid cells is obtained to obtain the field strength distribution of the patch antenna;

[0211] Each patch antenna is traversed to obtain the field strength distribution of each patch antenna on the integrated joint-wing aircraft.

[0212] Step 4: Based on the field intensity distribution of each patch antenna and the electric field strength of the field source, the electromagnetic shielding rate of each patch antenna on the integrated joint-wing aircraft and the total electromagnetic shielding rate of the integrated joint-wing aircraft are calculated, specifically:

[0213] First, each patch antenna is regarded as a region. According to the field strength distribution of the patch antenna obtained in step 3, weighted average is performed according to the size of the grid unit area to obtain the average electric field of the patch antenna. , the specific calculation formula is:

[0214]

[0215] in, Indicates that the area The total electric field of each grid cell is Indicates that the area The area of ​​a grid cell, Represents the sum of the areas of all grid cells in the region; and Obtained through calculation of vertex coordinates of mesh cells;

[0216] Then calculate the electromagnetic shielding rate of the patch antenna according to the following formula: :

[0217]

[0218] in, Indicates the electric field strength of the field source;

[0219] By traversing each patch antenna, the electromagnetic shielding rate of all patch antennas is obtained; the electromagnetic shielding rate The larger the value, the greater the impact of obstacles. If there is no obstacle, ;

[0220] Considering all patch antennas as one area, the above calculation process is repeated to obtain the total electromagnetic shielding rate of the integrated linked-wing aircraft.

[0221] Taking the first patch antenna as an example, the total electric field of each grid unit of the first patch antenna is obtained by step 3: , and weighted average is performed according to the size of the grid unit area, and the average electric field of the entire first patch antenna is obtained as follows:

[0222]

[0223] The electromagnetic shielding rate (in decibels) is

[0224]

[0225] In order to illustrate the beneficial effects of the method of the present invention, the traditional bouncing ray method and HFSS commercial software are used to calculate the present embodiment based on the finite element method as a comparison. The following table lists the calculation results of the electromagnetic shielding rate of four patch antennas using the fast calculation method of the present invention, the traditional bouncing ray method and the HFSS commercial software. The error is the relative error calculated by the method of the present invention using the HFSS commercial software as the standard value:

[0226] Table 1 Comparison of calculation results

[0227]

[0228] From the data in the above table, it can be seen that the error range of the fast calculation method of the present invention is within 4~11% compared with the HFSS commercial software, which is equivalent to the result of the bouncing ray method and meets the error requirements in engineering design; in addition, in terms of calculation efficiency, the method of the present invention is about 5 times higher than the HFSS commercial software, about 20% faster than the traditional bouncing ray method, and can achieve rapid electromagnetic shielding rate calculation under the premise of ensuring accuracy. In summary, the electromagnetic shielding rapid evaluation method for antenna arrays for integrated linked wing platforms proposed in the present invention can provide a reliable target evaluation basis for the rapid design of antenna array layouts for integrated linked wing aircraft.

[0229] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention without departing from the principles and intent of the present invention.

Claims

1. A rapid assessment method for electromagnetic shielding of antenna arrays for integrated linked wing platforms, characterized by: The steps include: Step 1: In the finite element software, for the integrated connected-wing aircraft model with antenna array layout to be evaluated, the thickness of the patch antenna is ignored, the aircraft surface is divided into the patch antenna area and other areas, triangular mesh units are generated by area, the leading and trailing edges of the wing are meshed, and the vertex coordinates of the mesh units are stored; Step 2: Import the integrated coupled wing aircraft model in step 1 into the electromagnetic analysis software. In the electromagnetic analysis software, set the field source on the ground and set the receiving end on the integrated coupled wing aircraft model; generate a plane wave as an incident wave in the direction from the field source to the receiving end; the incident wave is composed of a number of rays carrying a set electric field, and the number of rays is equal to the number of grid units in step 1; perform a judgment on the intersection of the ray and the grid unit, and if the ray intersects with the grid unit, it is determined that the ray is directed to the bright area; Step 3: Tracing the field intensity of the rays directed to the bright area, and using the improved bouncing ray method to calculate the field intensity distribution of each patch antenna on the integrated joint-wing aircraft; Step 4: Based on the field intensity distribution of each patch antenna and the electric field strength of the field source, the electromagnetic shielding rate of each patch antenna on the integrated linked-wing aircraft and the total electromagnetic shielding rate of the integrated linked-wing aircraft are calculated.

2. The method for rapid assessment of electromagnetic shielding of antenna array for integrated linked wing platform according to claim 1 is characterized by: In step 1, the grid unit size is selected according to the working wavelength of the patch antenna, which is one tenth of the working wavelength of the patch antenna.

3. The method for rapid assessment of electromagnetic shielding of antenna array for integrated linked wing platform according to claim 1 is characterized by: In step 2, the process of determining whether the ray is directed to the bright area is as follows: for each ray, traverse each grid unit on the surface of the integrated joint-wing aircraft model: For each grid cell, first perform a single occlusion check: Obtain the ray direction vector based on the source position and the integrated wing aircraft model position , get the normal vector of the mesh cell according to the vertex coordinates of the mesh cell ; like , it is determined to be non-intersecting, the grid unit is marked as a dark area, and the ray is directed to the dark area; if , it is determined to be an intersection, the grid unit is marked as a bright area, and the ray is directed toward the bright area; Then consider the mutual occlusion between grid cells and make multiple occlusion judgments: For a grid cell marked as a bright area, draw a line segment from its center point to the field source, and determine whether this line segment intersects with other grid cells. If the line segment intersects with other grid cells, the grid cell is blocked by other grid cells, and the grid cell is re-marked as a dark area. Finally, all the rays directed toward the bright area are obtained.

4. The method for rapid assessment of electromagnetic shielding of antenna array for integrated linked wing platform according to claim 1 is characterized by: Step 3 specifically includes the following sub-steps: Step 31: For the rays directed toward the bright area, assuming that the rays propagate in a straight line in a uniform medium, the electric field strength at the intersection point where the rays propagate in a straight line is calculated using the following formula: : in, is the grid cell differential at the source, Differentiate the grid cell at the intersection point; the complex expression Used to describe the propagation characteristics of plane electromagnetic waves in space. is an imaginary unit, is the wave number, is the distance from the intersection point to the field source, is the wavelength of the ray; is the electric field strength of the source; Step 32: Determine the intersection type between the ray and the integrated linked-wing aircraft model, where the intersection type includes intersection within a plane and intersection at an edge; if the ray intersects with the grid unit within a plane, use the geometric optics method to simulate the ray reflection and calculate the ray direction vector after reflection. and the electric field strength of the reflected rays ; If the intersection is at the edge, the improved consistent diffraction theory is used to simulate the ray diffraction and calculate the ray direction vector after diffraction And the electric field strength of the rays after diffraction ; Step 33: trace each ray after reflection and diffraction, and determine whether the ray intersects with the grid unit. If the ray intersects with the grid unit, the ray is directed to the bright area. Step 34: Repeat steps 31 to 33 until the electric field carried by the traced ray is less than a set value or is directed toward a dark area; Step 35: For each patch antenna in the patch antenna area of ​​the integrated linked-wing aircraft model, the field strength distribution of the patch antenna is obtained by the following process: For each grid cell corresponding to the patch antenna, the sum of the electric fields carried by the rays directly, reflected, and diffracted on each grid cell is calculated to obtain the total electric field of each grid cell on the patch antenna: The patch antenna The total electric field of the grid units is calculated to obtain the field strength distribution of the patch antenna; each patch antenna is traversed to obtain the field strength distribution of each patch antenna area on the integrated linked wing aircraft under the antenna layout.

5. The method for rapid assessment of electromagnetic shielding of antenna array for integrated linked wing platform according to claim 4 is characterized in that: The method for determining the intersection type in step 32 is: if the angle between the normal of a bright area grid unit and the normal of an adjacent grid unit is less than 10 degrees, the intersection type is determined to be an intersection within the plane; if the normal angle is greater than or equal to 10 degrees, the intersection type is determined to be an intersection at the edge, and the bright area grid unit is an edge grid unit.

6. The method for rapid assessment of electromagnetic shielding of antenna array for integrated linked wing platform according to claim 5 is characterized by: When the intersection type is intersection at the edge, the improved consistent diffraction theory is used to simulate the ray diffraction and calculate the ray direction vector after diffraction. And the electric field strength of the rays after diffraction The specific process is: First, solve the ray direction vector after diffraction : Get the vertex coordinates of the edge grid unit and its adjacent grid units, and get the normal vector of the edge grid unit according to the vertex coordinates of the edge grid unit ; Obtain the edge vector based on the common edges of the edge grid cell and its adjacent grid cells ; Assume the incident direction vector of the ray is , the incident direction vector With normal vector The angle between ; The incident direction vector of the ray With edge vector The angle between ; Treat the diffraction phenomenon as the incident ray around the edge vector Deflect an angle , let the direction vector of the ray after diffraction be , the direction vector of the ray after diffraction With normal vector The angle between the two is the diffraction angle ; According to the incident direction vector of the ray and the normal vector Calculating the angle of incidence : According to the formula Calculate the deflection angle ,in is the diffraction coefficient; Assumptions , is the normal vector The three-axis components of the edge vector are calculated by the following expression Rotation The transformation matrix : Will Decomposed into parallel Vector and perpendicular to Vector : Then the direction vector of the ray after diffraction is for: Then solve the electric field intensity of the ray after diffraction : According to the incident direction vector of the ray and the edge vector calculate : According to the diffraction direction vector of the ray and the normal vector Calculate the diffraction angle : The electric field intensity of the ray after diffraction is calculated by the following formula : In the formula, is the electric field strength at the point where the ray propagates in a straight line. At this time, the intersection point is the diffraction point. is the diffraction coefficient tensor, is the defocus distance, is the distance from the observation point to the diffraction point; The diffraction coefficient tensor is calculated by : The function in the above expression , , and intermediate variables The explanation is as follows: when : when : 。 7. The method for rapid assessment of electromagnetic shielding of antenna array for integrated linked wing platform according to claim 1 is characterized by: Step 4 is as follows: First, each patch antenna is regarded as a region. According to the field strength distribution of the patch antenna obtained in step 3, weighted average is performed according to the size of the grid unit area to obtain the average electric field of the patch antenna. , the specific calculation formula is: in, Indicates the number of The total electric field of each grid cell is Indicates the number of The area of ​​a grid cell, represents the sum of the areas of all grid cells of the patch antenna; and They are all obtained by calculating the vertex coordinates of the grid cells; Then calculate the electromagnetic shielding rate of the patch antenna according to the following formula: : in, Represents the electric field strength of the field source; traverse each patch antenna to obtain the electromagnetic shielding rate of all patch antennas; Considering all patch antennas as one area, the above calculation process is repeated to obtain the total electromagnetic shielding rate of the integrated linked-wing aircraft.

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