Phased-array antenna co-location electromagnetic interference coupling prediction method

Abstract

The invention discloses a phased-array antenna co-location electromagnetic interference coupling prediction method. The method comprises the following steps: 1) performing radiation characteristic analysis in an array element of a phased-array antenna; 2) analyzing an electromagnetic interference field under the influence of a complex platform structure by using a bounce ray method according to a radiation characteristic analysis result in the phased-array antenna array element array; and 3) obtaining a total electric field vector of the transmitting antenna array element of the phased-array antenna at the receiving antenna according to the electromagnetic interference coupling field of each target observation angle from the transmitting antenna array element of the phased-array antenna to the receiving antenna. According to the invention, the improved bounce ray method is adopted to improve the calculation efficiency of the ray tube tracking process of the electrically large complex target.

Description

Technical Field

[0001] The invention relates to electromagnetic compatibility simulation design technology, and in particular to a method for predicting co-site electromagnetic interference coupling of phased array antennas. Background Art

[0002] Phased array antennas can achieve fast and flexible scanning of antenna beams by controlling the excitation amplitude and phase of each element of the phased array antenna, and can form multiple independent antenna beams to perform different functions, so that phased array antennas have the advantages of multiple functions, being able to deal with multiple targets at the same time, and having strong anti-interference capabilities; and phased array antennas adopt the form of planar array antennas, which are easy to be integrated conformally into the installation platform, and are increasingly widely used in platforms such as ships and aircraft. However, these platforms inevitably cause relatively serious electromagnetic interference problems, especially electromagnetic interference problems caused by high-power phased array antennas, because they integrate a large number of frequency-using equipment antennas in a limited space. Therefore, in the overall design of the platform, it is necessary to accurately predict the electromagnetic interference coupling of the phased array antenna to support the optimization layout of the phased array antenna and the electromagnetic interference control design. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide a method for predicting co-site electromagnetic interference coupling of phased array antennas in view of the defects in the prior art.

[0004] The technical solution adopted by the present invention to solve the technical problem is: a method for predicting co-site electromagnetic interference coupling of phased array antennas, comprising the following steps:

[0005] 1) Analyze the radiation characteristics of phased array antenna elements;

[0006] 2) Based on the analysis results of radiation characteristics in the phased array antenna elements, the bouncing ray method is used to analyze the electromagnetic interference field under the influence of the complex structure of the platform;

[0007] 2.1) Call the CAD mesh model loading of the initialization module to extract the point list and point connection list of the CAD mesh model from the platform surface element file;

[0008] 2.2) Call the ray initialization in the initialization module and use the CAD grid to initialize the ray tracing tree structure (such as BSP tree, KD tree, etc.) to accelerate the ray tracing process; radiate rays around the emission point TX to form a list of incident angles Among them, i, j are traversed from 1 to n, n is determined by the ray density and the wave number on the calculation frequency, I represents the incident and collected emission ray data intersecting with the CAD grid (see ray emission process), we call the emission ray intersecting with the CAD grid as a valid ray, and the emission ray not intersecting with the CAD grid as an invalid ray; each ray is emitted from the ray tube; the observation target angle is initialized to form a target angle list Where i and j traverse from 1 to m S , j traverses from 1 to n S , S represents the target observation angle, m S With n S Determined by the user, defines the density of the far-field viewing angle grid:

[0009] 2.3) Call the transmitting antenna initialization process to calculate the direction of each effective transmitting ray The vertical polarization component E of the initial electric field on ⊥ and the horizontal polarization component E ∥ , and the initial electric field complex vector is obtained

[0010]

[0011] 2.4) Call the ray tracing module to trace the ray path

[0012] Valid rays are found by intersecting with the tree structure and leaves in sequence, and the grid numbers intersected by each valid ray are obtained. The mapping relationship between valid rays and grid numbers is established using the hash table mapRayCell, that is, mapRayCell(iray) obtains the grid number (the grid number corresponding to the shortest path) where the iray ray first intersects. If a valid ray iray has no intersection with any CAD grid, mapRayCell(iray) is -1.

[0013] 2.5) Call the ray tracing module to trace the ray path, looping the starting point coordinates start, intersection point coordinates end, and path length trip of the ray reflected at most maxbnc times; use a list to record the starting point coordinates start of the i-th reflection i , intersection point coordinates end i And the path length trip i ; Call ray visualization to display the path of the ray through multiple reflections through the interface;

[0014] 2.6) Calculate the amplitude and phase of each ray at each intersection point; obtain the reflected field intensity at the reflection point after the last reflection of each ray That is, after the Nth reflection, the ray will escape the scatterer and enter the free space, where N≤maxbnc;

[0015] Ray amplitude tracing: including the first reflection calculation and the i-th reflection calculation;

[0016] Among them, the formula for the incident wave before the first reflection is:

[0017]

[0018] in, is the initial electric field complex vector in step 3; is the incident electric field at the first reflection point; t0 is the distance from the transmitting antenna to the first reflection point;

[0019] The horizontal polarization wave TM and vertical polarization wave TE of the i-th incident wave are decomposed as follows:

[0020]

[0021]

[0022] in, is the normal vector of the surface element at the i-th reflection; is the incident wave direction vector; is the angle of incidence; is the unit length vector of the horizontal polarization wave direction of the incident wave, is the unit length vector of the vertical polarization wave direction of the incident wave:

[0023] Applying the geometric optics formula to the i-th reflection of the horizontally polarized wave and the vertically polarized wave, the field iteration formula is:

[0024]

[0025]

[0026]

[0027] in, is the reflection angle; t i is the distance from the i-th reflection point to the i+1-th reflection point; k is the free space wave number;

[0028] 2.7) Collect the field strength contributions of all rays at each target observation angle, and perform complex vector summation to obtain the far field amplitude at each target observation angle;

[0029] Next, calculate the observation angle of a target obtained by all rays in step 2 Far-field radiation electric field strength in the direction

[0030] 2.7.1) Obtain the electric field at the last reflection point (x, y, z) of each ray from step 2.6)

[0031] 2.7.2) Obtain the initial tube sizes du and dv from step 2.2);

[0032] du=dv=Δλ, where λ is the wavelength of the ray;

[0033] 2.7.3) Obtain the total optical path tall of the i-th effective ray from step 2.5);

[0034]

[0035] 2.7.4) Solve the far-field scattering characteristics of the X-ray tube after reflection on the target surface, and get Far-field radiation electric field strength E in the direction S :

[0036]

[0037] Where r is the distance from the target surface to the observation point; k is the free space wave number;

[0038]

[0039]

[0040] I=S(u,v) / S(0,0)

[0041]

[0042] S(0,0)=(du*tall)*(dv*tall)

[0043]

[0044] Among them, θ i and is the angular coordinate corresponding to the reflection direction of the last reflection point of the i-th effective ray; s x and y are the x and y coordinate values ​​of the viewing direction vector;

[0045] 3) According to the electromagnetic interference coupling field tracking solution, the electromagnetic interference coupling field from the transmitting antenna element of the phased array antenna to each target observation angle of the receiving antenna under the influence of the platform structure can be obtained, and then vector synthesis is performed to obtain the total electric field vector of the transmitting antenna element of the phased array antenna at the receiving antenna.

[0046] The beneficial effects produced by the present invention are:

[0047] The traditional bouncing ray method divides the virtual aperture surface based on a fixed resolution size. In order to ensure the calculation accuracy, for electrically large and complex targets, the number of ray tubes is very large, and the entire ray tube tracking process will be extremely time-consuming, and the RCS of ultra-large electrical size targets cannot be calculated normally. The present invention adopts an improved bouncing ray method to improve the calculation efficiency of the ray tube tracking process of electrically large and complex targets.

[0048] The present invention adopts the finite element analysis method to analyze the radiation characteristics of the phased array antenna element array. Combined with the bouncing ray method, it can accurately predict the near-field electromagnetic interference coupling of the phased array antenna in the platform, and provide quantitative support for the overall electromagnetic compatibility optimization design of the platform. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] The present invention will be further described below with reference to the accompanying drawings and embodiments, in which:

[0050] Figure 1 is a method flow chart of an embodiment of the present invention;

[0051] Figure 2 is a schematic diagram of a virtual surface boundary of an antenna according to an embodiment of the present invention;

[0052] Figure 3 is an equivalent principle schematic diagram of an embodiment of the present invention;

[0053] Figure 4 is a schematic diagram of a far-field extrapolated from a data storage boundary according to an embodiment of the present invention;

[0054] Figure 5 is a ray diagram of an embodiment of the present invention;

[0055] Figure 6 is a schematic diagram of the i-th reflection tracking according to an embodiment of the present invention;

[0056] Figure 7 It is a schematic diagram of reflection of a horizontally polarized wave TM and a vertically polarized wave TE of an incident wave according to an embodiment of the present invention. DETAILED DESCRIPTION

[0057] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0058] like Figure 1 As shown, a method for predicting electromagnetic interference coupling of phased array antenna co-site includes the following steps:

[0059] 1) Analyze the radiation characteristics of phased array antenna elements;

[0060] The radiation characteristics analysis of the phased array antenna array elements can be performed by using the multi-layer fast multipole method (MLFMA) and the finite element analysis method. In this embodiment, a finite element analysis method is provided;

[0061] Finite element radiation analysis;

[0062] 1.1) Define boundary conditions;

[0063] Consider a simple antenna structure. The antenna consists of a density J imp The electric field radiated by the antenna structure is affected by the current source excitation. The antenna may contain or be embedded in an anisotropic medium, which is represented by the dielectric constant tensor and the magnetic permeability tensor The main purpose of antenna analysis is to predict the performance indicators of the antenna, including the prediction of input impedance and radiation pattern.

[0064] Since the radiated electromagnetic field can propagate to infinity, this problem involves an infinite solution area. The premise of using the finite element method to solve the problem is that the infinite space must be truncated within a finite space. Therefore, this goal can be achieved by introducing a virtual surface containing the antenna and represented by Γ0, as follows: Figure 2 shown.

[0065] In order to define the electromagnetic problem with the boundary Γ0, it is necessary to specify the boundary conditions satisfied on Γ0. This boundary condition should make Γ0 transparent enough for the radiation field. The ideal boundary condition is to make Γ0 completely transparent so that no deformation or reflection occurs when the radiation field passes through. Although it is impossible to achieve completely ideal boundary conditions in practice, approximate boundary conditions can be used:

[0066]

[0067] in, Represents the unit normal vector of the Γ0 surface, and its direction points to the external space. Here, it is assumed that Γ0 is in the air. The above conditions are also called first-order absorbing boundary conditions. In order to ensure the accuracy of the absorbing boundary conditions, Γ0 is generally placed at a distance of about half a wavelength from the antenna (theoretically, the farther the distance, the better).

[0068] 1.2) Expression of functional variation

[0069] The finite element solution process is introduced as follows. The vector wave equation for the electric field E is as follows:

[0070]

[0071] in, represent the relative magnetic permeability and relative permittivity respectively; as well as They represent the free space wave number and intrinsic impedance respectively; Ω represents the volume contained by Γ0;

[0072] In order to solve the boundary value problem defined by equations (1) and (2), we first find the functional variation expression of the electric field according to the variational principle:

[0073]

[0074] Using the following vector Green's theorem:

[0075]

[0076] Can be changed to:

[0077]

[0078] In the above formula, Γ0∪Γ PEC represents the outer surface of volume Ω. Since there is no electric field inside an ideal conductor, the outer surface of Ω is the sum of the outer surface of Γ0 and any conductor inside Γ0. Using the first-order absorbing boundary condition in equation (1), we can finally obtain the functional satisfied by the electric field inside Ω:

[0079]

[0080] In this way, the original boundary value problem is equivalent to the following variational problem:

[0081]

[0082] Establishing a correct and accurate antenna feed model can not only provide the excitation required by the antenna, but also is the basis for calculating the antenna input impedance or other parameters. Although antennas can be fed in a variety of ways in actual engineering, in order to ensure the accuracy of the solution during numerical simulation, wave port excitation is usually used as the antenna feed. This model requires truncating the feeding waveguide to generate a waveguide port, at which appropriate boundary conditions are applied. The ideal boundary conditions can both emit electromagnetic waves into the waveguide and absorb waves reflected back from the antenna without spurious reflections.

[0083] When waveguide port feeding is used, at the waveguide port Γ f The total field can be expressed as the superposition of the incident wave and the reflected wave:

[0084]

[0085] Where E0 is the amplitude of the incident wave, β is the propagation constant, R represents the reflection coefficient, and e TEMis the mode function of the TEM wave, and z represents the propagation direction vector perpendicular to the waveguide port and pointing to the incident wave.

[0086] Performing vector operations on both ends of the above equation yields:

[0087]

[0088] in, represents the unit normal vector pointing to the outside of the waveguide port, that is, is the direction; the mode function e of the main mode in the coaxial waveguide TEM for:

[0089]

[0090] Further calculations:

[0091]

[0092] By e TEM From the form of TEM There is only a tangential component, so:

[0093]

[0094] Write the above equation in the form of the third kind of boundary condition:

[0095]

[0096] Where γ=jβ,U inc =-2jβE inc .

[0097] 1.3) Analysis of near-field and far-field changes of electromagnetic radiation

[0098] To calculate the post-processing parameters of the radiation electrical characteristics, it is first necessary to analyze the near-field and far-field changes of the electromagnetic radiation.

[0099] To obtain the scattering or radiation field in the far region, the equivalent principle must be applied to make a closed surface in the calculation area, and then the equivalent electromagnetic current on this surface is obtained by extrapolation. Combined with the requirements of near-far field extrapolation, the equivalent principle is briefly described as follows: Introduce a virtual interface A around the scatterer, such as Figure 3 As shown in the left figure. Assume that the outside of surface A is vacuum. If the field E at interface A is maintained s , H s The tangential component of remains unchanged, and the field in the A plane is set to zero, such as Figure 3 As shown in the figure on the right. According to the uniqueness theorem, Figure 3 Two cases of field E outside surface A s , H s have the same distribution.

[0100] According to the boundary conditions, such as Figure 3 In the case shown, there is an equivalent surface current at A and surface magnetic current J m , which are equal to:

[0101]

[0102] In the formula is the unit external normal of surface A. Therefore, through surface A The equivalent surface current can be determined Surface magnetic flux This prepares for the electromagnetic field solution in the far field.

[0103] For the time-harmonic field case, Maxwell's equations for the presence of electric and magnetic currents in a homogeneous medium are:

[0104]

[0105] The radiation field of the electric and magnetic currents is

[0106]

[0107] in

[0108]

[0109] In the expression, A and F are vector potential functions; is the free space Green's function.

[0110] The Green's function of free space in three dimensions is:

[0111]

[0112] in are the position vectors of the observation point and the source point respectively, such as Figure 4 shown.

[0113] Take the far area near in is the unit vector in the r direction, then

[0114]

[0115] That is, the spherical wave factor can be separated from the far field.

[0116]

[0117] are the current moment and magnetic moment respectively, where is the scattered wave vector.

[0118]

[0119] Written in spherical coordinate component form, we have

[0120]

[0121] as well as

[0122]

[0123] Thus we get

[0124]

[0125] It can be expressed in terms of current moment and magnetic moment

[0126]

[0127] In the formula Assume the direction of the observation point is φ,θ, then

[0128]

[0129] Then f, f m The rectangular coordinate components of can be expressed as

[0130]

[0131] Among them, ξ=x, y, z represents the three components of the rectangular coordinate system.

[0132] Using the transformation relationship between rectangular coordinates and spherical coordinates, we have

[0133]

[0134] Then the calculation formula for the three-dimensional far-zone electric field is as follows:

[0135]

[0136] 1.4) The post-processing parameters of the electromagnetic radiation electrical characteristics solved by finite element method mainly include the antenna's directivity pattern, gain, input impedance, return loss, polarization ratio, and axial ratio.

[0137] 1.4.1) Directional pattern

[0138] The antenna pattern is a graph that characterizes the relationship between the antenna's radiation characteristics (field intensity amplitude, phase, polarization) and the spatial angle. It is used to characterize the antenna's ability to radiate electromagnetic waves in a certain direction. For a receiving antenna, it indicates the antenna's ability to receive radio waves from different directions. The antenna's directional characteristic curve is usually represented by a pattern. The pattern can be used to illustrate the antenna's ability to transmit or receive electromagnetic waves in all directions in space.

[0139] The complete radiation pattern is a three-dimensional spatial diagram. It is drawn by rotating the antenna azimuth or elevation angle on a spherical surface with a sufficiently large radius r, with the antenna phase center as the sphere center (coordinate origin), and measuring its radiation characteristics point by point. Although the three-dimensional spatial radiation pattern can be conveniently measured using existing software, in actual engineering applications, it is generally sufficient to measure the horizontal plane H and vertical plane E radiation patterns.

[0140] 1.4.2) Gain

[0141] Gain is an extremely important parameter of the antenna. It can be used to measure the concentration of the antenna's radiated energy. Antenna gain can be divided into directional gain and power gain. When the radiated power is the same, the antenna is Radiation intensity in a direction The ratio of the radiation intensity to the ideal point source is defined as the directional gain of the antenna.

[0142]

[0143] When the input power is the same, the ratio of the antenna's radiation intensity p(θ,φ) in the (θ,φ) direction to the radiation intensity of an ideal point source is defined as the antenna's power gain G(θ,φ):

[0144]

[0145] Where p(θ,φ) is the radiation intensity of the antenna in the (θ,φ) direction; P t is the antenna radiation power; P0 is the antenna input power.

[0146] From the above two formulas, we can get

[0147] G(θ,φ)=η D (θ,φ);

[0148] In the formula, η antenna efficiency = antenna radiated power / antenna input power. From this, we can see that the antenna gain is equal to the antenna efficiency multiplied by the directional gain.

[0149] 1.4.3) Input impedance

[0150] The ratio of the signal voltage induced at both ends of the feed point, that is, the signal current, is called the input impedance of the antenna. The input impedance has a resistance component and a reactance component. The reactance component of the input impedance will reduce the effective signal power entering the feeder from the antenna. Therefore, the reactance component must be made as zero as possible so that the input impedance of the antenna is pure resistance.

[0151] The concept of impedance is particularly useful for medium and low frequency antennas, because in medium and low frequency antennas, it is easy to determine a pair of input points, the impedance is single-valued and easy to measure. Although the concept of impedance is still valid at higher frequencies, it is more difficult to directly determine and measure the impedance value. For example, at microwave frequencies, most antennas are connected to waveguides, and the waveguide impedance has multiple values. Therefore, it is almost impossible to directly measure the impedance value of the antenna. Instead, the input impedance of the antenna is calculated by measuring the standing wave coefficient or reflection loss.

[0152] When the antenna and feeder do not match, that is, when the antenna impedance is not equal to the characteristic impedance of the feeder, the antenna cannot absorb all the high-frequency energy transmitted on the feeder, but can only absorb part of the energy.

[0153] Part of the energy of the incident wave is reflected back to form a reflected wave, and the incident wave and the reflected wave are combined to form a standing wave. The ratio of the standing wave amplitude voltage to the node voltage is called the voltage standing wave ratio (VSWR):

[0154]

[0155] According to the definition of voltage standing wave ratio, it can be known that the value range of S is 1≤S≤∞. It can usually be divided into three categories according to the size of S: S<3 is a small standing wave ratio; 3≤S≤10 is a medium standing wave ratio; S>10 is a large standing wave ratio.

[0156] The ratio of the amplitude of the reflected wave to the incident wave is called the reflection coefficient:

[0157]

[0158] The range of the reflection coefficient modulus is 0≤Γ≤1, which is a dimension less than 1. When the transmission line is terminated with a characteristic impedance, all the energy is transmitted to the load, no energy is reflected, and ρ = 0. When the transmission line is terminated with an open circuit or a short circuit, all the energy is reflected, that is, ρ = 1.

[0159] Return loss (RL) is defined as the ratio of incident power to reflected power at a point on a transmission line. It is a scalar reflection coefficient expressed in decibels, that is, the loss from incident wave to reflected wave, so it is called return loss. It is related to the reflection coefficient as follows:

[0160] RL = -20lg|Γ|;

[0161] The range of return loss is: 0 to ∞; 0dB means full reflection (open circuit / short circuit); ∞ means no reflection and full absorption. Therefore, it is very convenient and intuitive to use return loss as a measurement value.

[0162] 1.4.4) Polarization

[0163] If the direction of the electric field of an electromagnetic wave rotates during propagation, that is, the end trajectory of the field vector is a circle, and the amplitude and size of the electric field remain unchanged during the rotation, we call it a circularly polarized wave. Circular polarization can be divided into right-hand circular polarization and left-hand circular polarization. Waves that rotate clockwise in the direction of propagation are called right-hand circularly polarized waves, and waves that rotate counterclockwise are called left-hand circularly polarized waves. If the end trajectory of the field vector is an ellipse, it is called an elliptically polarized wave. Both circularly polarized waves and elliptically polarized waves can be synthesized by two mutually orthogonal linearly polarized waves. When the amplitudes of the two orthogonal linearly polarized waves are equal and the phase difference is 90°, a circularly polarized wave is synthesized; when the amplitudes are unequal or the phase difference is not 90°, an elliptically polarized wave is synthesized.

[0164] Circular polarization and linear polarization are both special cases of elliptical polarization. There are three parameters that describe elliptically polarized waves: the axis ratio refers to the ratio of the major axis to the minor axis of the polarization ellipse; the inclination refers to the angle between the major axis of the polarization ellipse and the horizontal coordinate; and the rotation direction refers to left-hand or right-hand.

[0165] When the polarization direction of the receiving antenna is inconsistent with the polarization direction of the incident wave, polarization loss occurs due to polarization mismatch. Definition of polarization efficiency: the ratio of the power actually received by the antenna to the power received in the same direction, with the same intensity and polarization matching.

[0166] 1.4.5) Axis ratio

[0167] Axis ratio definition: ellipticity ratio, the ratio of the major axis to the minor axis of a polarized plane wave. The voltage axis ratio of an antenna is expressed by the formula:

[0168]

[0169] The axial ratio expressed in decibels is:

[0170] AR = 20lg|r|;

[0171] As we all know, circular polarization and linear polarization are two special cases of elliptical polarization, that is, when r = ±1, it is circular polarization; when r = ∞, it is linear polarization; when 1<|r|<∞, it is elliptical polarization.

[0172] 2) Use the bouncing ray method to analyze the electromagnetic interference field under the influence of the platform's complex structure;

[0173] Use the bouncing ray method to analyze the electromagnetic interference field under the influence of the platform's complex structure, and obtain path tracking and field value tracking;

[0174] 2.1) Load the CAD mesh model, extract the point list and point connection list of the CAD mesh model from the platform surface element file in nastran format, and perform mesh division of the scatterer;

[0175] 2.2) Ray initialization, and use the CAD grid to initialize the ray tracing tree structure (such as BSP tree, KD tree and other structures) to accelerate the ray tracing process;

[0176] Emit rays around the emission point TX to form a list of incident angles Where i and j are traversed from 1 to n, n is determined by the ray density and the wave number on the calculation frequency, I represents the incident and collected emission ray data that intersects with the CAD grid (see ray emission process), we call the emission ray that intersects with the CAD grid a valid ray, and the emission ray that does not intersect with the CAD grid is called an invalid ray, such as Figure 5 ; Each ray is emitted from the ray tube; the observation target angle is initialized to form a target angle list Where i and j traverse from 1 to m S , j traverses from 1 to n S , S represents the target observation angle, m S With n S Determined by the user, defines the density of the far-field viewing angle grid:

[0177] 2.3) Call the transmitting antenna initialization process to calculate the direction of each effective transmitting ray The vertical polarization component E of the initial electric field on ⊥ and the horizontal polarization component E ∥ , and the initial electric field complex vector is obtained

[0178]

[0179] 2.4) Ray path tracing;

[0180] According to the ray tracing tree structure, the valid rays are found by intersecting with the tree structure and leaves in turn, and the grid numbers intersected by each valid ray are obtained. The hash table mapRayCell is used to establish the mapping relationship between the valid rays and the grid numbers, that is, mapRayCell(iray) obtains the grid number (the grid number corresponding to the shortest path) where the iray ray first intersects. If a valid ray iray has no intersection with all the grids of the CAD, mapRayCell(iray) is -1.

[0181] 2.5) The coordinates of the starting point start, the intersection point end, and the path length trip of the ray that has been reflected for a maximum of maxbnc times; maxbnc is the maximum number of reflections allowed during the ray tracing process; Figure 6 ;

[0182] Use a list to record the starting point coordinates of the i-th reflection start i , intersection point coordinates endi And the path length trip i ; Call ray visualization to display the path of the ray through multiple reflections through the interface;

[0183] 2.6) Calculate the amplitude and phase of each ray at each intersection point; obtain the reflected field intensity at the reflection point after the last reflection of each ray That is, after the Nth reflection, the ray will escape the scatterer and enter the free space, where N≤maxbnc;

[0184] Ray amplitude tracing: including the first reflection calculation and the i-th reflection calculation;

[0185] Among them, the formula for the incident wave before the first reflection is:

[0186]

[0187] in, is the initial electric field complex vector in step 3; is the incident electric field at the first reflection point; t0 is the distance from the transmitting antenna to the first reflection point;

[0188] like Figure 7 , the horizontal polarization wave TM and vertical polarization wave TE of the i-th incident wave are decomposed as follows:

[0189]

[0190]

[0191] in, is the normal vector of the surface element at the i-th reflection; is the incident wave direction vector; is the angle of incidence; is the unit length vector of the horizontal polarization wave direction of the incident wave, is the unit length vector of the vertical polarization wave direction of the incident wave:

[0192] Applying the geometric optics formula to the i-th reflection of the horizontally polarized wave and the vertically polarized wave, the field iteration formula is:

[0193]

[0194]

[0195]

[0196] in, is the reflection angle; t i is the distance from the i-th reflection point to the i+1-th reflection point; k is the free space wave number;

[0197] 2.7) Determine the reflection path and facet, collect the field strength contribution of all rays at each target observation angle, and perform complex vector summation to obtain the far field amplitude at each target observation angle;

[0198] Next, calculate the observation angle of a target obtained by all rays in step 2 Far-field radiation electric field strength in the direction;

[0199] 2.7.1) Obtain the electric field at the last reflection point (x, y, z) of each ray from step 2.6)

[0200] 2.7.2) Obtain the initial tube sizes du and dv from step 2.2);

[0201] du=dv=Δλ, where λ is the wavelength of the ray;

[0202] 2.7.3) Obtain the total optical path tall of the i-th effective ray from step 2.5);

[0203]

[0204] 2.7.4) Solve the far-field scattering characteristics of the X-ray tube after reflection on the target surface, and get Far-field radiation electric field strength E in the direction S :

[0205]

[0206] Where r is the distance from the target surface to the observation point; k is the free space wave number;

[0207]

[0208] I=S(u,v) / S(0,0)

[0209]

[0210] S(0,0)=(du*tall)*(dv*tall)

[0211]

[0212] Among them, θ i and is the angular coordinate corresponding to the reflection direction of the last reflection point of the i-th effective ray; s x and yare the x and y coordinate values ​​of the observation direction vector; S(u,v) represents the intensity of the ray tube at the coordinate (u,v), and S(0,0) represents the intensity of the ray tube at the initial emission point;

[0213] 3) According to the electromagnetic interference coupling field tracking solution, the electromagnetic interference coupling field from the transmitting antenna element of the phased array antenna to each target observation angle of the receiving antenna under the influence of the platform structure can be obtained, and then vector synthesis is performed to obtain the total electric field vector of the transmitting antenna element of the phased array antenna at the receiving antenna.

[0214] It should be understood that those skilled in the art can make improvements or changes based on the above description, and all these improvements and changes should fall within the scope of protection of the appended claims of the present invention.

Claims

1. A method for predicting electromagnetic interference coupling of phased array antenna co-site, characterized in that: The following steps are involved: 1) Analyze the radiation characteristics of phased array antenna elements; 2) Based on the analysis results of radiation characteristics in the phased array antenna elements, the bouncing ray method is used to analyze the electromagnetic interference field under the influence of the complex structure of the platform; 3) According to the electromagnetic interference coupling field from the transmitting antenna element of the phased array antenna to each target observation angle of the receiving antenna, the total electric field vector of the transmitting antenna element of the phased array antenna at the receiving antenna is obtained.

2. The method for predicting co-site electromagnetic interference coupling of phased array antennas according to claim 1, characterized in that: In step 2), the bouncing ray method is used to analyze the electromagnetic interference field under the influence of the complex structure of the platform, including path tracing and field value tracing, as follows: 2.1) Load the CAD mesh model, extract the point list and point connection list of the CAD mesh model from the platform surface element file, and perform mesh division of the scatterer; 2.2) Ray initialization, and use the CAD grid to initialize the ray tracing tree structure to accelerate the ray tracing process; Emit rays around the emission point TX to form a list of incident angles Where i and j are traversed from 1 to n, n is determined by the wave number of the ray density and the calculation frequency, I represents the incident and collected emission ray data intersecting with the CAD grid; the emission ray intersecting with the CAD grid is called a valid ray, and the emission ray not intersecting with the CAD grid is called an invalid ray, and each ray is emitted from the ray tube; the observation target angle is initialized to form a target angle list Where i and j traverse from 1 to m S , j traverses from 1 to n S , the superscript S represents the target observation angle, m S With n S The density of the far-field observation angle grid is defined as a constant set by: 2.3) Call the transmitting antenna initialization process to calculate the direction of each effective transmitting ray The vertical polarization component E of the initial electric field on ⊥ and the horizontal polarization component E ∥ , and the initial electric field complex vector is obtained 2.4) Ray path tracing; According to the ray tracing tree structure, the valid rays are found by intersecting with the tree structure and leaves in turn, and the grid number intersected by each valid ray is obtained. The mapping relationship between the valid ray and the grid number is established using the hash table mapRayCell, that is, mapRayCell(iray) obtains the grid number that the irayth ray intersects for the first time. 2.5) The coordinates of the starting point start, the intersection point end, and the path length trip of the ray that has been reflected for a maximum of maxbnc times; maxbnc is the maximum number of reflections allowed during the ray tracing process; Use a list to record the starting point coordinates of the i-th reflection start i , intersection point coordinates end i And the path length trip i ; 2.6) Calculate the amplitude and phase of each ray at each intersection point; obtain the reflected field intensity at the reflection point after the last reflection of each ray That is, after the Nth reflection, the ray will escape the scatterer and enter the free space, where N≤maxbnc; Ray amplitude tracing: including the first reflection calculation and the i-th reflection calculation; Among them, the formula for the incident wave before the first reflection is: in, is the initial electric field complex vector of step 2.3); is the incident electric field at the first reflection point; t0 is the distance from the transmitting antenna to the first reflection point; The horizontal polarization wave TM and vertical polarization wave TE of the i-th incident wave are decomposed as follows: in, is the normal vector of the surface element at the i-th reflection; is the incident wave direction vector; is the angle of incidence; is the unit length vector of the horizontal polarization wave direction of the incident wave, is the unit length vector of the vertical polarization wave direction of the incident wave: The field iteration formula is obtained by using the geometric optics formula for the i-th reflection of the horizontally polarized wave and the vertically polarized wave: in, is the reflection angle; t i is the distance from the i-th reflection point to the i+1-th reflection point; k is the free space wave number; 2.7) Determine the reflection path and facet, collect the field strength contribution of all rays at each target observation angle, and perform complex vector summation to obtain the far-field amplitude at each target observation angle.

3. The method for predicting co-site electromagnetic interference coupling of phased array antennas according to claim 2, characterized in that: In step 2.7), calculate the angle of observation of all rays at the target The far-field radiation electric field strength in the direction is as follows: 2.7.1) Obtain the electric field at the last reflection point (x, y, z) of each ray from step 2.6) 2.7.2) Obtain the initial tube sizes du and dv from step 2.2); du=dv=Δλ, where λ is the wavelength of the ray; 2.7.3) Obtain the total optical path tall of the i-th effective ray from step 2.5); tall=∑trip i 2.7.4) Solve the far-field scattering characteristics of the X-ray tube after reflection on the target surface, and get Far-field radiation electric field strength E in the direction S : Where r is the distance from the target surface to the observation point; k is the free space wave number; I=S(u,v) / S(0,0) S(0,0)=(du*tall)*(dv*tall) Among them, θ i and is the angular coordinate corresponding to the reflection direction of the last reflection point of the i-th effective ray; s x and y are the x and y coordinate values ​​of the observation direction vector; S(u,v) represents the intensity of the ray tube at the coordinate (u,v), and S(0,0) represents the intensity of the ray tube at the initial emission point.

4. The method for predicting co-site electromagnetic interference coupling of phased array antennas according to claim 1, characterized in that: In the step 1), the radiation characteristics analysis of the phased array antenna elements is performed using a finite element analysis method.

5. The method for predicting co-site electromagnetic interference coupling of phased array antennas according to claim 4, characterized in that: In the step 1), the radiation characteristics analysis of the phased array antenna element array is performed using a finite element analysis method, including the following steps: 1.1) Define boundary conditions; Use approximate boundary conditions: in, Represents the unit normal vector of the Γ0 surface, pointing to the external space; 1.2) Obtain the expression for functional variation Where, γ=jβ,U inc =-2jβE inc ; 1.3) Analysis of near-field and far-field changes of electromagnetic radiation Equivalent analysis: According to the boundary conditions, there is an equivalent surface current at point A and surface magnetic current J m : In the formula, is the unit external normal of surface A, passing through surface A The equivalent surface current J and surface magnetic current can be determined For the time-harmonic field case, Maxwell's equations for the presence of electric and magnetic currents in a homogeneous medium are: The radiation field of the electric and magnetic currents is in Where A and F are vector potential functions; is the free space Green’s function; The Green's function of free space in three dimensions is: in, are the position vectors of the observation point and the source point respectively; Take the far area near in is the unit vector in the r direction, then That is, the spherical wave factor can be separated from the far field, and are the current moment and magnetic moment respectively, in is the scattered wave vector, Written in spherical coordinate component form, we have as well as Thus we get Expressed in terms of current moment and magnetic moment In the formula Assume the direction of the observation point is φ,θ, then Then f, f m The rectangular coordinate components of can be expressed as Among them, ξ=x, y, z represent the three components of the rectangular coordinate system; Using the transformation relationship between rectangular coordinates and spherical coordinates, we have Then the calculation formula for the three-dimensional far-zone electric field is as follows: 1.4) Obtain post-processing parameters of electromagnetic radiation electrical characteristics solved by finite element method, including antenna radiation pattern, gain, input impedance, return loss, polarization ratio, and axial ratio.

6. The method for predicting co-site electromagnetic interference coupling of phased array antennas according to claim 1, characterized in that: In the step 3), the electromagnetic interference coupling field is tracked and solved to obtain the electromagnetic interference coupling field at each target observation angle from the transmitting antenna element of the phased array antenna to the receiving antenna under the influence of the platform structure, and then vector synthesis is performed to obtain the total electric field vector of the transmitting antenna element of the phased array antenna at the receiving antenna.

7. An electronic device, characterized in that: include: one or more processors; as well as a storage device for storing one or more programs, When the one or more programs are executed by the one or more processors, the one or more processors are caused to execute the method according to any one of claims 1 to 6.

8. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the method according to any one of claims 1 to 6 is implemented.

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