A method for intercepting an effective imaging scene of a large-angle strabismus SAR imaging by radar technology index

Abstract

The application relates to a method for intercepting an effective imaging scene of large-oblique SAR imaging by radar technical indexes, and belongs to the technical field of large-oblique SAR imaging. According to technical index requirements of a radar signal processor, such as a signal bandwidth, a sampling rate, a pulse accumulation time and the like, which are set by a project, the following specific requirements are calculated: an imaging scene center distance, an imaging width and a resolution in a distance direction and an azimuth direction of an imaging scene in a ground plane, and the like; according to a conversion relationship of oblique plane ground plane coordinate axes, the following are calculated: a distance dimension point number and an azimuth direction pulse pressure accumulation point number of a two-dimensional imaging scene in an oblique plane, so that effective data in data recording is retained, redundant data is removed, time consumption of real-time processing of an imaging algorithm is shortened, and design requirements are met.

Description

Technical Field

[0001] This invention belongs to the field of large-angle SAR imaging technology, specifically relating to a method for extracting effective imaging scenes for large-angle SAR imaging using radar technical indicators. Background Technology

[0002] Synthetic Aperture Radar (SAR), as an active imaging system for long-range telemetry, has advantages such as all-weather imaging, resistance to weather interference such as clouds, fog and smoke, and high-resolution detection imaging at long distances. When applied to precision-guided weapons, SAR imaging technology can display images during navigation and continuously correct deviations generated by the missile during flight, thereby ensuring the missile's strike accuracy. It is often used in the terminal guidance phase of missile flight.

[0003] Slant range models are fundamental to imaging algorithms. Traditional SAR imaging algorithms assume the radar platform flies at a constant velocity in a straight line, resulting in a hyperbolic slant range model. However, in SAR curvilinear trajectory imaging of missile-borne mobile platforms, both the constant velocity straight-line flight trajectory and the hyperbolic slant range model no longer hold true. Therefore, establishing an accurate, simplified curvilinear trajectory slant range model that can be integrated with high-precision imaging algorithms, based on the motion characteristics of missile-borne platforms, is the primary challenge in SAR imaging algorithm research.

[0004] The transmit signal bandwidth determines the range resolution within the oblique plane, while the pulse accumulation time determines the lateral range resolution within the oblique plane. The two-dimensional resolution within the oblique plane is easily obtained through imaging parameters. However, in general, two-dimensional resolution parameters are not proposed based on the imaging coordinate system but rather on the geodetic coordinate system. Therefore, it is necessary to establish a correspondence between the resolution of the ground plane and the oblique plane, realizing the conversion from ground plane resolution parameters to oblique plane resolution parameters, and thus constraining the design of SAR imaging parameters. Summary of the Invention

[0005] The technical problem to be solved by this invention is:

[0006] To overcome the shortcomings of existing technologies, this invention provides a method for extracting the effective imaging scene in large-angle SAR imaging based on radar technical specifications. Redundant data in the data acquisition process is removed by calculating imaging parameters according to specific requirements, thus shortening the real-time processing time of the imaging algorithm and meeting design requirements.

[0007] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0008] A method for extracting effective imaging scenes from large-slant-view SAR imaging using radar technical specifications, characterized by comprising:

[0009] The imaging swath width and resolution in the distance direction of the imaging scene and the ground plane imaging scene are calculated based on the technical specifications of the radar signal processor.

[0010] Based on the center distance of the imaging scene and the SAR parameters, a geometric model of the SAR imaging scene at azimuth zero time is established to obtain the distance from the radar platform to any point in the imaging scene.

[0011] Based on the geometric model of the SAR imaging scene at azimuth zero time, the imaging scene coordinate system and the geodetic coordinate system where the radar platform is located at azimuth zero time are constructed respectively, namely the coordinate system where the oblique plane is located and the coordinate system where the ground plane is located. According to the transformation relationship between the coordinate axes of the oblique plane and the ground plane, the relationship between the coordinate values ​​of the coordinate system where the oblique plane is located and the coordinate values ​​of the coordinate system where the ground plane is located is obtained, and the distance from the radar platform to any point in the imaging scene is transformed into an expression of the coordinate values ​​of the coordinate system where the ground plane is located.

[0012] The distance from the radar platform to any point in the imaging scene is calculated based on the imaging swath width and resolution of the range dimension of the ground plane imaging scene, and the number of range units in the range direction is estimated; based on the number of range units in the range direction, valid data is retained and redundant data is removed from the data acquisition.

[0013] A further technical solution of the present invention: the technical specifications of the radar signal processor include signal bandwidth, sampling rate, and pulse accumulation time.

[0014] A further technical solution of the present invention: the distance R from the radar platform to any point in the imaging scene is:

[0015]

[0016] Where H represents the platform's flight altitude, OP represents the ground projection of the center distance of the imaging scene, (x n ,y n Let be the coordinates of any point in the inclined plane at the center of the imaging scene.

[0017] A further technical solution of the present invention: the distance from the radar platform to any point in the imaging scene is expressed as coordinates in the coordinate system of the ground plane as follows:

[0018] R 2 =H 2 +(OP+x'sinγ+y'cosγ) 2 +(-x'cosγ+y'sinγ) 2

[0019] =H 2 +OP 2 +(x'sinγ+y'cosγ) 2+2*OP*(x'sinγ+y'cosγ)+(-x'cosγ+y'sinγ) 2

[0020] =H 2 +OP 2 +x '2 sin 2 γ+y '2 cos 2 γ+2*x'sinγ*y'cosγ+2*OP*(x'sinγ+y'cosγ)+......+x '2 cos 2 γ+y '2 sin 2 γ-2*x'cosγ*y'sinγ

[0021] =H 2 +OP 2 +x '2 +y '2 +2*OP*(x'sinγ+y'cosγ)

[0022] Where (x',y') is (x n ,y n The index value of the coordinate system corresponding to the ground plane, where γ represents the azimuth angle.

[0023] A further technical solution of the present invention: The distance from the radar platform to any point in the imaging scene is calculated based on the imaging swath width and resolution of the ground-plane imaging scene in the range dimension, and the number of range units is then deduced. Specifically:

[0024] The maximum and minimum values ​​of x' are determined based on the ratio of the imaging swath width to the resolution of the distance dimension of the ground plane imaging scene;

[0025] The maximum and minimum values ​​of y' are determined based on the imaging swath width of the distance dimension of the ground plane imaging scene;

[0026] Find the maximum and minimum values ​​of distance R based on the maximum and minimum values ​​of x' and y';

[0027] The number of distance units is determined by subtracting the maximum and minimum values ​​of R.

[0028] A further technical solution of the present invention: determining the number of distance-to-distance units by subtracting the maximum and minimum values ​​of R includes:

[0029] When ΔR≤2048, the number of distance dimension points required for the data acquisition plane is Nrn=2048;

[0030] When 2048 < ΔR ≤ 4096, the number of distance dimension points required for the data acquisition plane is Nrn = 4096;

[0031] And so on, satisfying the condition that the number of distance-to-distance units is 2. n .

[0032] A further technical solution of the present invention: when the number of distance unit points to be intercepted is greater than the actual number of admission points, zeros are added after the admission data.

[0033] A computer system is characterized by comprising: one or more processors, and a computer-readable storage medium for storing one or more programs, wherein when the one or more programs are executed by the one or more processors, the one or more processors cause the one or more processors to implement the method described above.

[0034] A computer-readable storage medium is characterized by storing computer-executable instructions, which, when executed, are used to implement the above-described method.

[0035] The beneficial effects of this invention are as follows:

[0036] This invention provides a method for extracting effective imaging scenes in large-angle SAR imaging based on radar technical specifications. According to the technical requirements of the radar signal processor, such as signal bandwidth, sampling rate, and pulse accumulation time, the method calculates specific requirements such as the center distance of the imaging scene, the range and azimuth imaging swath widths and resolutions within the ground plane. Then, based on the coordinate transformation relationship between the oblique plane and the ground plane, the method calculates the number of range points and the number of azimuth pulse compression accumulation points in the two-dimensional imaging scene within the oblique plane. This retains effective data and removes redundant data during data acquisition, shortening the real-time processing time of the imaging algorithm and meeting design requirements. Attached Figure Description

[0037] The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts.

[0038] Figure 1 Schematic diagram of SAR imaging geometric model.

[0039] Figure 2 Schematic diagram of the conversion of sloping ground plane index.

[0040] Figure 3 Schematic diagram of the transformation relationship between the inclined plane coordinate system.

[0041] Figure 4 The curve showing the correspondence between the distance R between the radar platform and any point Q in the imaging scene and the coordinate axes of the ground plane.

[0042] Figure 5The curve showing the correspondence between the distance R between the radar platform and any point Q in the imaging scene and the coordinate axes of the ground plane.

[0043] Figure 6 Schematic diagram of SAR range data acquisition. Detailed Implementation

[0044] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0045] This invention provides a method for extracting effective imaging scenes from large-angle SAR imaging based on radar technical indicators. It involves establishing coordinate axes between the ground plane and the oblique plane, the conversion relationship between the ground plane and the oblique plane indicators, and the derivation of related formulas. The algorithm is used to calculate the specific imaging scene center distance, imaging scene swath width, and resolution based on different radar technical indicators such as signal bandwidth, sampling rate, and pulse accumulation time. This allows for the deduction of the number of SAR imaging distance dimensions required for the data acquisition plane, retaining effective data while removing redundant data, and optimizing the real-time processing time of the imaging algorithm.

[0046] Reference Figure 1 , Figure 2 , Figure 3 , Figure 4 , Figure 5 The specific implementation steps of this invention are as follows:

[0047] Step 1. Establish the geometric model of the SAR imaging scene at time zero, as follows: Figure 1 As shown.

[0048] The radar platform is flying in a dive at a speed of v, with a pitch angle of α (the angle between the flight direction and true north). At azimuth zero, point A represents the spatial position of the radar platform, point O represents the ground projection point of the platform, H represents the platform's flight altitude, point P represents the intersection of the beam centerline and the ground plane, and R... s Let OP represent the effective distance of the radar reaching the center point of the scene (center-to-center distance of the imaging scene), γ represent the ground projection of the effective distance, β represent the azimuth angle (the angle between the projection of the beam center onto the ground plane and true north), and β represent the ground rubbing angle (the angle between the beam center and the ground plane). A scene coordinate system is established with the OP direction as the x-axis. For any point Q in the scene, a set of orthogonal variables (x...) can be used. n ,y n The unique representation is that the distance from the radar platform to point Q is R, and the spatial oblique angle is θ (the angle between the perpendicular flight direction and the line connecting the radar platform and any point in the scene).

[0049]

[0050] Step 2. Construct the imaging scene coordinate system (the coordinate system where the oblique plane is located) and the geodetic coordinate system (the coordinate system where the ground plane is located) where the radar platform is located at azimuth zero time, respectively, as follows: Figure 2 The yellow and green ellipses are shown in the middle. Figure 3 The coordinate relationship of the sloping ground plane completes the imaging of the sloping plane scene (x n ,y n The conversion of indices between the ground plane scene (x', y') and the ground plane scene (x', y').

[0051] x n =x'sinγ+y'cosγ

[0052] y n = -x'cosγ + y'sinγ

[0053] R 2 =H 2 +(OP+x'sinγ+y'cosγ) 2 +(-x'cosγ+y'sinγ) 2

[0054] =H 2 +OP 2 +(x'sinγ+y'cosγ) 2 +2*OP*(x'sinγ+y'cosγ)+(-x'cosγ+y'sinγ) 2

[0055] =H 2 +OP 2 +x '2 sin 2 γ+y '2 cos 2 γ+2*x'sinγ*y'cosγ+2*OP*(x'sinγ+y'cosγ)+......+x '2 cos 2 γ+y '2 sin 2 γ-2*x'cosγ*y'sinγ

[0056] =H 2 +OP 2 +x' 2 +y' 2 +2*OP*(x'sinγ+y'cosγ)

[0057] Step 3. R can be used 2Consider it as a bivariate function of (x', y'), denoted as f(x', y'). Find the first-order partial derivatives of f(x', y') with respect to x' and y', respectively, and denot them as fi. x (x',y') and f y (x',y'), let f x (x',y') and f y Given that (x', y') are both 0, find the coordinates of the stationary point of the bivariate function f(x', y') as (x', y'). n ,y' n According to the sufficient condition for the extrema of a multivariable function, find the second-order partial derivatives and mixed partial derivatives of f(x',y') with respect to x' and y', respectively, and denote them as A, B, and C. Since A > 0, AC - B 2 >0, indicating that when x' = x' n y'=y' n The value of the bivariate function f(x',y') is obtained by finding f(x'). n ,y' n ) represents the minimum value of the bivariate function.

[0058]

[0059]

[0060] A = f xx (x',y')=2,B=f xy (x',y')=0,C=f yy (x',y')=2

[0061] Step 4.R 2 The relationship between (i.e., the bivariate function f(x',y')) and x' is as follows: Figure 4 As shown, W is the ratio of the swath width to the resolution of the distance-dimensional imaging scene in the ground plane. When y' takes a fixed value y0', the coordinates of the minimum value of f(x',y') are (x'). n ,y'0) can be divided into the following four cases:

[0062] Situation ①: hour,

[0063] Situation 2: hour,

[0064] Situation ③: hour,

[0065] Situation 4: hour,

[0066] Similarly, R 2The relationship between (i.e., the bivariate function f(x',y')) and y' is as follows: Figure 5 As shown, W represents the swath width of the distance-dimensional imaging scene in the ground plane. When x' takes a fixed value x0', the coordinates of the minimum value of f(x',y') are (x'0,y'). n There are four possible scenarios:

[0067] Situation 5: hour,

[0068] Situation 6: hour,

[0069] Situation ⑦: hour,

[0070] Situation ⑧: hour,

[0071] Substitute cases ①②③④ and cases ⑤⑥⑦⑧ into the solution R. 2 This allows us to obtain the minimum slope moment of 16 different data acquisition planes. maximum of the slope moment By combining the results and taking the square root of the difference, we can obtain ΔR = R. max -R min ΔR represents the number of range units required to meet the imaging scene's swath width and resolution specifications. To facilitate FFT and IFFT operations in real-time SAR imaging algorithms, when ΔR ≤ 2048, the required range dimension points Nrn for the data acquisition plane are 2048; when 2048 < ΔR ≤ 4096, the required range dimension points Nrn for the data acquisition plane are 4096, and so on. Note that if the required number of range units to be extracted is greater than the actual number of points to be acquired, zeros can be added after the acquired data.

[0072] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the scope of the technology disclosed in the present invention, and such modifications or substitutions should all be covered within the scope of protection of the present invention.

Claims

1. A method for extracting the effective imaging scene of large-slant-view SAR imaging based on radar technical specifications, characterized in that, include: The imaging swath width and resolution in the distance direction of the imaging scene and the imaging scene in the ground plane are calculated based on the technical specifications of the radar signal processor. The technical specifications of the radar signal processor include signal bandwidth, sampling rate, and pulse accumulation time; Based on the center distance of the imaging scene and the SAR parameters, a geometric model of the SAR imaging scene at azimuth zero time is established to obtain the distance from the radar platform to any point in the imaging scene. Based on the geometric model of the SAR imaging scene at azimuth zero time, the imaging scene coordinate system and the geodetic coordinate system where the radar platform is located at azimuth zero time are constructed respectively, namely the coordinate system where the oblique plane is located and the coordinate system where the ground plane is located. According to the transformation relationship between the coordinate axes of the oblique plane and the ground plane, the relationship between the coordinate values ​​of the coordinate system where the oblique plane is located and the coordinate values ​​of the coordinate system where the ground plane is located is obtained, and the distance from the radar platform to any point in the imaging scene is transformed into an expression of the coordinate values ​​of the coordinate system where the ground plane is located. The distance from the radar platform to any point in the imaging scene is calculated based on the imaging swath width and resolution of the range dimension of the ground plane imaging scene, and the number of range units in the range direction is estimated; based on the number of range units in the range direction, valid data is retained and redundant data is removed from the data acquisition. The distance from the radar platform to any point in the imaging scene is calculated based on the imaging swath width and resolution of the ground plane imaging scene in the range dimension, and the number of range units in the range dimension is estimated. Specifically: Determined based on the ratio of imaging swath width to resolution in the distance dimension of the ground plane imaging scene. The maximum and minimum values; The imaging swath width is determined based on the distance dimension of the ground plane imaging scene. The maximum and minimum values; according to , Find the distance between the maximum and minimum values. The maximum and minimum values; right The number of distance units is determined by subtracting the maximum and minimum values. include: When ΔR≤2048, the number of distance dimension points required for the data acquisition plane. ; When 2048 < ΔR ≤ 4096, the number of distance dimension points required for the data acquisition plane. ; And so on, satisfying the condition that the number of distance-to-distance units is 2. n .

2. The method for extracting the effective imaging scene of large-angle SAR imaging based on radar technical indicators according to claim 1, characterized in that, The distance from the radar platform to any point in the imaging scene for: in, H Indicates the platform's flight altitude. OP Ground projection representing the center distance of the imaging scene. Let be the coordinates of any point in the center of the imaging scene within this inclined plane.

3. The method for extracting the effective imaging scene of large-slant-view SAR imaging based on radar technical indicators according to claim 2, characterized in that, The distance from the radar platform to any point in the imaging scene, converted into coordinate values ​​in the coordinate system of the ground plane, is expressed as follows: in, for The index value corresponding to the coordinate system of the ground plane. Indicates the azimuth angle.

4. The method for extracting the effective imaging scene of large-slant-view SAR imaging based on radar technical indicators according to claim 3, characterized in that, When the number of distance unit points to be intercepted is greater than the actual number of admitted points, zeros are added after the admitted data.

5. A computer system, characterized in that... include: One or more processors, a computer-readable storage medium for storing one or more programs, wherein, when the one or more programs are executed by the one or more processors, the one or more processors cause the one or more processors to perform the method of any one of claims 1-4.

6. A computer-readable storage medium, characterized in that... The device stores computer-executable instructions, which, when executed, are used to implement the method described in any one of claims 1-4.

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