Target bounce ray projection three-dimensional scattering center modeling method and near-field echo simulation method

Abstract

A method for modeling a three-dimensional scattering center using target bounce ray projection and simulating near-field echoes involves inputting a target CAD model and, in combination with near-field detector parameters, using multi-bounce ray tracing technology to obtain ray trajectories and exit aperture fields. The imaging space is divided according to resolution requirements, and the ray exit points are projected into three-dimensional space. All rays are superimposed to obtain the target's three-dimensional scattering center. A dynamic area search is performed on the target's three-dimensional scattering center model, combining the near-field detector's motion trajectory relative to the target and the antenna pattern, to obtain the scattering center in the area illuminated by the antenna's main beam. Near-field dynamic echoes are generated based on the near-field reconstruction formula for the point scattering center. This method avoids time-consuming integral operations, reducing the computational effort by orders of magnitude and making it suitable for calculating massive amounts of near-field scattering characteristic data from targets in short-range detection.

Description

Technical Field

[0001] The present invention relates to the field of electromagnetic scattering echo simulation, and in particular to a three-dimensional scattering center modeling method based on a bouncing ray method and a near-field echo fast simulation technology based on the method. Background Art

[0002] The near-field scattering echo characteristics of a target are crucial for proximity detection and form the basis of short-range radar detection. However, unlike the target's far-field scattering characteristics, the near-field scattering echo characteristics of a target are influenced by numerous factors, including the antenna pattern, spherical wave, distance, attitude angle, local illumination range, and polarization, resulting in a large state space. Describing the target's near-field scattering characteristics requires traversing this state space to obtain a massive amount of near-field echo simulation data. Currently, near-field electromagnetic scattering echo simulation methods based on discrete target grid models and high-frequency approximation algorithms are commonly used, but obtaining these massive near-field scattering echoes is computationally intensive. Summary of the Invention

[0003] The purpose of the present invention is to provide a target bouncing ray projection three-dimensional scattering center modeling method and a near-field echo simulation method, which reduces the amount of calculation by orders of magnitude, avoids complex integral operations, and is suitable for calculating massive target near-field scattering characteristic data in short-range detection.

[0004] To achieve the above object, the present invention provides a method for modeling a three-dimensional scattering center of a target bouncing ray projection, comprising the following steps:

[0005] Input the target CAD model, combine it with the near-field detector parameters, and use the multi-bounce ray tracing technology to obtain the ray trajectory and exit aperture field;

[0006] The imaging space is divided according to the resolution requirements, the ray exit point is projected into the three-dimensional space, and all rays are superimposed to obtain the target three-dimensional scattering center.

[0007] The target CAD model is a triangular mesh model.

[0008] The incident ray density is less than one tenth of the wavelength.

[0009] Assume that the imaging space consists of a range window R, a pitch window Θ, and an azimuth window φ. The three-dimensional imaging window is evenly divided into L×M×N pixel units, where (R, Θ, φ) is at least 1.5 times the maximum size of the target in that direction, and the value of (L, M, N) satisfies the Nyquist sampling theorem.

[0010] The three-dimensional space contains:

[0011] The first dimension, distance The scattering center occurs at This is the total distance traveled by the i-th ray minus riA At half of the incident direction projection, the range resolution is calculated as:

[0012]

[0013] Where c is the speed of light in vacuum, B is the bandwidth, and the range sampling interval Δr = R / L is less than one-third to one-fifth of the resolution, that is, Thus, L was determined;

[0014] The second dimension, pitch The scattering center occurs at At r iA exist The projection position in the direction and the pitch resolution calculation formula are:

[0015]

[0016] Among them, Δθ is the angular sampling width in this direction; similarly And thus determine M = Θ / Δxθ;

[0017] The third dimension, the perpendicular direction of the second distance, also known as the azimuth Perpendicular to plane, the maximum value occurs at At r iA exist The projection position in the direction and the azimuth resolution calculation formula are:

[0018]

[0019] in, is the angle sampling width in this direction, corresponding to the pitch direction, and the same is true And thus determine

[0020] The ray exit point is projected into three-dimensional space, and the contributions of all rays are superimposed to obtain the target three-dimensional scattering center model.

[0021] The present invention also provides a near-field echo simulation method, comprising the following steps:

[0022] Combined with the motion trajectory of the near-field detector relative to the target and the antenna pattern, a dynamic area search is performed on the target three-dimensional scattering center model obtained by the target bounce ray projection three-dimensional scattering center modeling method to obtain the scattering center of the antenna main beam illumination area;

[0023] The near-field dynamic echo is generated based on the near-field reconstruction formula of the point scattering center.

[0024] The near-field dynamic echo is determined by the superposition of the contributions of the scattering centers within the irradiated area to the total field. The near-field reconstruction formula of the point scattering center is as follows:

[0025]

[0026] The scattering centers that are illuminated are superimposed to obtain the scattering field under local illumination:

[0027]

[0028] Among them, subscript n l =1,…,N l Refers to the sequence of scattering centers within the antenna illumination range, represents the total scattered field of the target under local illumination, represents the contribution of the nlth scattering center on the target to the total field, is the wave vector of the incident electromagnetic wave, which includes frequency, pitch angle, and azimuth angle. It is a collection of other parameters, including the distance between the target and the radar antenna and other mathematical parameters.

[0029] The present invention establishes a three-dimensional scattering center model of the target based on the bouncing ray method. Compared with the traditional method of extracting scattering centers based on synthetic aperture imaging, the computational complexity is reduced by orders of magnitude, and it is suitable for the establishment of global scattering centers. Based on the above three-dimensional scattering center model, the present invention proposes a target near-field dynamic echo generation method, which changes the traditional algorithm of tracking the target geometric model itself and instead tracks the target three-dimensional scattering center model, avoiding complex integral operations. The target near-field scattering dynamic echo can be obtained through simple superposition operations, which is suitable for the calculation of massive target near-field scattering characteristic data in short-range detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a flow chart of a target bouncing ray projection three-dimensional scattering center modeling method and a near-field echo simulation method provided by the present invention.

[0031] Figure 2 is a schematic diagram of the imaging space.

[0032] Figure 3 It is a schematic diagram of the dynamic area search of the target three-dimensional scattering center model. DETAILED DESCRIPTION

[0033] The following is based on Figures 1 to 3 , specifically describe the preferred embodiments of the present invention.

[0034] The present invention provides a method for modeling a three-dimensional scattering center of a target bouncing ray projection, comprising the following steps:

[0035] Step S1: Input the target CAD model, which is generally a triangular mesh model. Combined with the near-field detector center frequency, relative incident angle and other parameters, use the multi-bounce ray tracing technology to obtain the ray trajectory and exit aperture field;

[0036] Step S2: Divide the imaging space according to the resolution requirement, project the ray exit point into the three-dimensional space, and obtain the target three-dimensional scattering center after superposition of all rays.

[0037] The present invention also provides a near-field echo simulation method, comprising the following steps:

[0038] Step S1: Combine the motion trajectory of the detector relative to the target and the antenna pattern to perform a dynamic area search on the target's three-dimensional scattering center model to obtain the scattering center of the antenna main beam illumination area;

[0039] Step S2: Generate dynamic near-field echo based on the near-field reconstruction formula of the point scattering center.

[0040] In one embodiment of the present invention, the target three-dimensional scattering center modeling and dynamic echo simulation process is as follows: Figure 1 As shown, it specifically includes the following steps:

[0041] Step 1. Input the target CAD model, which is generally a triangular mesh model. Input the near-field detector center frequency, relative incident angle and other parameters. Use the multi-bounce ray tracing technique to obtain the ray trajectory and exit aperture field. The incident ray density should be less than one-tenth of the wavelength. In the software implementation, the ray tracing process is determined by the computer graphics algorithm and will not be detailed here.

[0042] Step 2: Divide the imaging space according to the resolution requirements. Assuming that the imaging space consists of a range window R, a pitch window Θ, and an azimuth window φ, the three-dimensional imaging window is evenly divided into L×M×N pixel units. Here, (R, Θ, φ) is determined by the geometric size of the target and is generally at least 1.5 times the maximum size of the target in that direction. The value of (L, M, N) must satisfy the Nyquist sampling theorem.

[0043] Combine Figure 2 The schematic diagram of the imaging space shown divides the space into three dimensions:

[0044] The first dimension, distance The scattering center occurs at This is the total distance traveled by the i-th ray minus r iA At half of the incident direction projection, the range resolution is calculated as:

[0045]

[0046] Where c is the speed of light in vacuum, B is the bandwidth, and the range sampling interval Δr = R / L should be less than one-third to one-fifth of the resolution, that is, Thus, L was determined;

[0047] The second dimension, the vertical direction of the first distance, also known as the pitch direction The scattering center occurs at At r iA exist The projection position in the direction and the pitch resolution calculation formula are:

[0048]

[0049] Among them, Δθ is the angular sampling width in this direction; similarly And thus determine M = Θ / Δxθ;

[0050] The third dimension, the perpendicular direction of the second distance, also known as the azimuth Perpendicular to plane, the maximum value occurs at At r iA exist The projection position in the direction and the azimuth resolution calculation formula are:

[0051]

[0052] in, is the angle sampling width in this direction, corresponding to the pitch direction, and the same is true And thus determine

[0053] Project the ray exit point into three-dimensional space, and superimpose the contributions of all rays to obtain the target three-dimensional scattering center model;

[0054] Step 3: In short-range detection, the main beam of the antenna only illuminates a local area of ​​the target. Combined with the motion trajectory of the detector relative to the target and the antenna pattern, the antenna illumination range is searched point by point on the target's three-dimensional scattering center model on the motion trajectory, such as Figure 3 As shown, the scattering center set within the antenna main beam illumination area is obtained, as Figure 3 The part shown in the middle circle, this part of the scattering center contributes to the scattered echo at this position, and the other scattering centers not within the irradiation range do not contribute to the local irradiation echo here and will not be counted in the scattered echo at this position;

[0055] Step 4: Due to the independence of the scattering centers, the near-field dynamic echo is determined by the superposition of the contributions of the scattering centers to the total field within the irradiated area. The near-field reconstruction formula of the point scattering center is as follows:

[0056]

[0057] The scattering centers that are illuminated are superimposed to obtain the scattering field under local illumination:

[0058]

[0059] Among them, subscript n l =1,…,N l Refers to the sequence of scattering centers within the antenna illumination range, represents the total scattered field of the target under local illumination, represents the contribution of the nlth scattering center on the target to the total field, is the wave vector of the incident electromagnetic wave, which includes frequency, pitch angle, and azimuth angle. It is a collection of other parameters, including the distance between the target and the radar antenna and other mathematical parameters.

[0060] This paper proposes a ray-projected three-dimensional scattering center modeling and dynamic near-field echo generation technology based on the scattering center model. This method has the advantage of using only a single ray tracing operation to obtain the target's three-dimensional scattering center at the corresponding attitude angle, reducing the computational complexity by an order of magnitude compared to traditional scattering center extraction methods based on synthetic aperture imaging. The proposed method for dynamically generating target near-field echoes based on the three-dimensional scattering center model searches for point scattering centers within the antenna main beam illumination area and superimposes their contributions to the near field to obtain near-field dynamic echoes. This method significantly reduces computational complexity and memory usage compared to traditional direct integration calculations of the target mesh model. The method described in this paper is suitable for applications requiring the generation of massive amounts of near-field echo data.

[0061] It should be noted that, in the embodiments of the present invention, the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the embodiments, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore should not be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only and should not be understood as indicating or implying relative importance.

[0062] In the present invention, unless otherwise expressly specified or limited, the terms "mounted," "connected," "connect," "fixed," etc. should be understood broadly. For example, they may refer to fixed connection, detachable connection, or integration; mechanical connection or electrical connection; direct connection or indirect connection through an intermediate medium; internal communication between two components or interaction between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0063] Although the present invention has been described in detail through the above preferred embodiments, it should be understood that the above description is not intended to limit the present invention. After reading the above description, various modifications and substitutions of the present invention will become apparent to those skilled in the art. Therefore, the scope of protection of the present invention should be defined by the appended claims.

Claims

1. A target bounce ray projection three-dimensional scattering center modeling method, characterized in that: The following steps are involved: Input the target CAD model, combine it with the near-field detector parameters, and use the multi-bounce ray tracing technology to obtain the ray trajectory and exit aperture field; Divide the imaging space according to the resolution requirements, project the ray exit point into the three-dimensional space, and superimpose all rays to obtain the target three-dimensional scattering center; The three-dimensional space includes: The first dimension, distance The scattering center occurs at This is the total distance traveled by the i-th ray minus r iA At half of the incident direction projection, the range resolution is calculated as: Where c is the speed of light in vacuum, B is the bandwidth, and the range sampling interval Δr = R / L is less than one-third to one-fifth of the resolution, that is, Δr ≤ (◇r) / (3-5), thus determining L; The second dimension, pitch The scattering center occurs at At r iA exist The projection position in the direction and the pitch resolution calculation formula are: Wherein, Δθ is the angular sampling width in the direction; similarly, ΔxB≤(◇xθ) / (3-5) and thus M=Θ / Δxθ is determined; The third dimension, the perpendicular direction of the second distance, also known as the azimuth Perpendicular to plane, the maximum value occurs at At r iA exist The projection position in the direction and the azimuth resolution calculation formula are: in, is the angle sampling width in this direction, corresponding to the pitch direction, and the same is true And thus determine The ray exit point is projected into three-dimensional space, and the contributions of all rays are superimposed to obtain the target three-dimensional scattering center model.

2. The target bounce ray projection three-dimensional scattering center modeling method according to claim 1, characterized in that: The target CAD model is a triangular mesh model.

3. The target bounce ray projection three-dimensional scattering center modeling method according to claim 1, characterized in that: The incident ray density is less than one tenth of the wavelength.

4. The target bounce ray projection three-dimensional scattering center modeling method according to claim 1, characterized in that: Assume that the imaging space consists of a range window R, a pitch window Θ, and an azimuth window φ. The three-dimensional imaging window is evenly divided into L×M×N pixel units, where (R, Θ, φ) is at least 1.5 times the maximum size of the target in that direction, and the value of (L, M, N) satisfies the Nyquist sampling theorem.

5. A near-field echo simulation method, characterized in that: The following steps are involved: In combination with the motion trajectory of the near-field detector relative to the target and the antenna pattern, a dynamic area search is performed on the target three-dimensional scattering center model obtained by the target three-dimensional scattering center modeling method according to any one of claims 1 to 4 to obtain the scattering center of the antenna main beam illumination area; The near-field dynamic echo is generated based on the near-field reconstruction formula of the point scattering center.

6. The near-field echo simulation method according to claim 5, wherein: The near-field dynamic echo is determined by the superposition of the contributions of the scattering centers within the irradiated area to the total field. The near-field reconstruction formula of the point scattering center is as follows: The scattering centers that are illuminated are superimposed to obtain the scattering field under local illumination: Among them, subscript n l =1,…,N l Refers to the sequence of scattering centers within the antenna illumination range, represents the total scattered field of the target under local illumination, represents the contribution of the nlth scattering center on the target to the total field, is the wave vector of the incident electromagnetic wave, which includes frequency, pitch angle, and azimuth angle. It is a collection of other parameters, including the distance between the target and the radar antenna and other mathematical parameters.

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