An irregular body scale inversion method based on distance expansion characteristics

Abstract

The application discloses an irregular body scale inversion method based on distance expansion characteristics, which comprises the following steps: step 1, coherent scattering radar sweep data preprocessing; step 2, establishment of a solving irregular body scale parameter inversion method; step 3, solving of a target function; and step 4, obtaining of an irregular body parameter. The method disclosed by the application is characterized in that: through preprocessing of multi-frequency coherent scattering radar echo data, distance expansion data are obtained, then a solving irregular body scale inversion target function is set according to a radar detection equation, and then a mode search method is used to calculate and solve the target function, so that the irregular body inversion parameter is obtained.

Description

Technical Field

[0001] This invention belongs to the field of ionospheric environment detection, and specifically relates to an irregular volume-scale inversion method based on distance extension characteristics in this field. Background Technology

[0002] The main method for detecting irregular bodies is VHF coherent scattering radar, which can detect irregular bodies in the radar's line of sight. For drifting irregular body clouds that cross the radar beam range, it can, to some extent, image the vertical profile of the irregular body cloud.

[0003] Conventional VHF coherent scattering radar detection methods assume that radar echoes are all strictly perpendicular to the geomagnetic field direction. However, relevant theoretical simulations show that VHF coherent scattering radar echoes are the sum of echoes strictly perpendicular to the geomagnetic field direction and echoes from irregular bodies at the same height. For example... Figure 1 As shown, in addition to the echo point S0 which is strictly perpendicular to the direction of the geomagnetic field and the echo S1 of the irregular body at the same height, the irregular body at a distance of dR can also generate an echo. At this time, the propagation distance increases to R+dR, which causes the echo power to broaden in the height or distance direction, forming a distance expansion phenomenon. Summary of the Invention

[0004] The technical problem to be solved by this invention is to overcome the shortcomings of existing coherent scattering radar in that it cannot detect the horizontal and vertical scales, thickness and height parameters of irregular bodies, and to provide a method for inverting the scale of irregular bodies based on range extension characteristics.

[0005] The present invention adopts the following technical solution:

[0006] An improved method for irregular volume scale inversion based on distance extension properties includes the following steps:

[0007] Step 1, Preprocessing of coherent scatter radar frequency sweep data:

[0008] Extracting data DM exhibiting range extension from coherent scattering radar echoes. i , as input to the objective function of the pattern search method;

[0009] Step 2, Set the objective function for the range extension characteristic mode search method—Based on radar detection data and radar cross-section equations, establish a method for solving the inversion of irregular volume scale parameters:

[0010] Using range extension data DM corresponding to each operating frequency of the radar i The objective function for inverting the parameters of the irregular volume is established, and the radar detection cross section is expressed as follows:

[0011]

[0012]

[0013] In the above formula, σ TL The cross-sections for detecting irregular bodies are represented by λ, which represents the wavelength of the radar detection signal. The mean square error of the electron density perturbation is represented by W, the width of the scatterer is A, and the half thickness of the scatterer is X. i Y i Z i Let ψ be the coordinates of the intersection point of the geomagnetic line and the Z-axis of the rectangular coordinate system, ψ be the angle between the intersection line of the geomagnetic line and the Z-axis of the index coordinate system, x(1) be the initial transverse dimension of the irregular body, x(2) be the initial longitudinal dimension of the irregular body, ΔV be the volume of the scattering body, and σ be the initial transverse dimension of the irregular body. WA The cross section for detecting the width and thickness of the irregular body is represented by T, the transverse dimension of the irregular body is represented by L, the thickness of the irregular body is represented by x(3), the initial width of the irregular body is represented by x(4), and the initial thickness of the irregular body is represented by x(4).

[0014] Let D1 be the distance expansion width containing unknowns in the horizontal and vertical directions of the irregular body, and D2 be the distance expansion width containing unknowns in the width and thickness of the irregular body. Establish two objective functions:

[0015]

[0016]

[0017] In the above formula, f TL Let f represent the horizontal and vertical objective functions of the irregular body, n represent the maximum value of the pattern search points, and f' ... WA Represent the objective function for the width and thickness of the irregular body;

[0018] Step 3, Solve the objective function—use the pattern search method to obtain the numerical solution corresponding to the parameters of the irregular volume:

[0019] The distance-extended characteristic pattern search method has two undetermined independent variables and degrees of freedom, denoted by e. i e j Let the detection step size be α, the starting point for both the lateral and longitudinal scale searches be 5m, and the starting point for the width and thickness searches of the irregular body be 3km. Define the position parameter x(i) of the irregular body. (j) For along e j The starting point of the direction, where j = 1, 2, 3, 4, x(i) (1) Let x(i) be the starting point along the direction e1. (n+1) For along e n The points obtained after direction detection, assuming the irregular volume parameters are from x(i) (1) First, probe along the positive x-axis, then:

[0020] x(i) (2) =x(i)(1) +αe1 (5)

[0021] The obtained parameter information x(i) (2) Substituting into the objective function of the distance extension characteristic pattern search method, if:

[0022] f TL (x(1) 2 ,x(2) 2 ) < f TL (x(1) 1 ,x(2) 1 ) or f WA (x(1) 2 ,x(2) 2 ) < f WA (x(1) 1 ,x(2) 1 ),

[0023] Then we take the new parameter x(i). (2) Replace x(i) (1) Otherwise, take the reverse probe of e1:

[0024] x(i) (2) =x(i) (1) -αe1 (6)

[0025] Repeat the above process again. If the objective function value comparison condition is met, then use the new parameter x(i). (2) Replace x(i) (1) Otherwise, use x(i). (1) As x(i) (2) After completing the search along the x-axis, from x(i)... (2) Begin probing along the Y-axis to obtain the parameter x(i) as described above. (3) ,

[0026] If f TL (x(1) 3 ,x(2) 3 ) < f TL (x(1) 1 ,x(2) 1 ) or f WA (x(1) 3 ,x(2) 3 ) < f WA (x(1) 1 ,x(2) 1 ), let R1=x(i) (3) R0 = x(i) (1) Therefore, the direction of decrease in the objective function of the distance expansion characteristic is determined to be R1→R0;

[0027] If the search along all degrees of freedom fails to meet the requirements, the initial step size reduction rate γ is adjusted, and the search is restarted from the starting point. When it is necessary to reduce the step size to start a new iteration, the initial step size becomes: α' = γα;

[0028] Pattern search point M K The formula for calculating the position is:

[0029] M K =R K +β(R K -R K-1 (7)

[0030] In the above formula, β is the acceleration factor, and R K R represents the search base point. K-1 Indicates the previous search base point;

[0031] Step 4, Obtain the parameters of the irregular body—Using the four solutions of the objective function, obtain the parameters corresponding to the irregular body:

[0032] The results x(1), x(2), x(3), and x(4) obtained by inversion using equations (3) and (4) correspond to the four parameters of the irregular body: horizontal scale, vertical scale, width, and thickness, respectively.

[0033] The beneficial effects of this invention are:

[0034] The method disclosed in this invention preprocesses multi-frequency coherent scattering radar echo data to obtain range-extended data. Then, based on the radar detection equation, it sets and solves an objective function for irregular volume scale inversion. Finally, it calculates and solves the objective function using a pattern search method to obtain the irregular volume inversion parameters. Since the irregular volume parameters are derived from the range-extended phenomenon, this method is innovative from the data source compared to similar detection methods. Furthermore, this method can be used in non-calibrated radar detection applications, which is of great significance for expanding the detection capabilities of coherent scattering radar and enriching the means of detecting irregular volumes. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of radar echoes;

[0036] Figure 2 This is a flowchart illustrating the method of the present invention;

[0037] Figure 3 This is a radar detection echo data diagram;

[0038] Figure 4 It shows the iterative process of the lateral scale parameter and the step size change graph of the distance extension feature pattern search;

[0039] Figure 5It shows the iterative process of the longitudinal scale parameter and the step size change graph for the distance extension feature pattern search;

[0040] Figure 6 It shows the thickness parameter iteration process and step size variation graph for distance extension characteristic mode search;

[0041] Figure 7 This is a graph showing the iteration process of the width parameter and the change in step size in the distance extension feature pattern search. Detailed Implementation

[0042] 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.

[0043] Example 1: Relevant theories show that inverting parameters of irregular bodies based on range extension characteristics is not limited by radar system parameters and is less restricted in its implementation. Furthermore, the range extension characteristics show a certain positive correlation with the radar operating frequency, which can provide some support for the analysis of irregular body parameters.

[0044] Therefore, this embodiment discloses an irregular volume-scale inversion method based on distance extension characteristics, such as... Figure 2 As shown, it includes the following steps:

[0045] Step 1, Preprocessing of coherent scatter radar frequency sweep data:

[0046] Extracting data DM exhibiting range extension from coherent scattering radar echoes. i , as input to the objective function of the pattern search method;

[0047] Since it is necessary to invert irregular volume parameters using coherent scattering radar detection data exhibiting range spreading, it is essential to select a dataset from the radar detection data that conforms to the range spreading characteristics as the input data for irregular volume parameter inversion. In this embodiment, the selected radar detection echo dataset possesses the following characteristics: Figure 3 The spindle-shaped feature shown.

[0048] The radar operating frequency is set to 30MHz–60MHz, with a scan step size of 1MHz. Range stretching data (DM) can be acquired centrally from each scan frequency dataset. i .

[0049] Step 2, set the objective function for the distance extension characteristic pattern search method:

[0050] Using range extension data DM corresponding to each operating frequency of the radar i The objective function for inverting the parameters of the irregular volume is established, and the radar detection cross section is expressed as follows:

[0051]

[0052]

[0053] In the above formula, σ TL The cross-sections for detecting irregular bodies are represented by λ, which represents the wavelength of the radar detection signal. The mean square error of the electron density perturbation is represented by W, the width of the scatterer is A, and the half thickness of the scatterer is X. i Y i Z i Let ψ be the coordinates of the intersection point of the geomagnetic line and the Z-axis of the rectangular coordinate system, ψ be the angle between the intersection line of the geomagnetic line and the Z-axis of the index coordinate system, x(1) be the initial transverse dimension of the irregular body, x(2) be the initial longitudinal dimension of the irregular body, ΔV be the volume of the scattering body, and σ be the initial transverse dimension of the irregular body. WA The cross section for detecting the width and thickness of the irregular body is represented by T, the transverse dimension of the irregular body is represented by L, the thickness of the irregular body is represented by x(3), the initial width of the irregular body is represented by x(4), and the initial thickness of the irregular body is represented by x(4).

[0054] Let D1 be the distance expansion width containing unknowns in the horizontal and vertical directions of the irregular body, and D2 be the distance expansion width containing unknowns in the width and thickness of the irregular body. Establish two objective functions:

[0055]

[0056]

[0057] In the above formula, f TL Let f represent the horizontal and vertical objective functions of the irregular body, n represent the maximum value of the pattern search points, and f' ... WA Represent the objective function for the width and thickness of the irregular body;

[0058] Step 3, Solve for the objective function:

[0059] The distance-extended characteristic pattern search method has two undetermined independent variables and degrees of freedom, denoted by e. i e j Let the detection step size be α, the starting point for both the lateral and longitudinal scale searches be 5m, and the starting point for the width and thickness searches of the irregular body be 3km. Define the position parameter x(i) of the irregular body. (j) For along e j The starting point of the direction, where j = 1, 2, 3, 4, x(i) (1) Let x(i) be the starting point along the direction e1. (n+1) For along e n The points obtained after direction detection, assuming the irregular volume parameters are from x(i) (1) First, probe along the positive x-axis, then:

[0060] x(i)( 2) =x(i) (1) +αe1 (5)

[0061] The obtained parameter information x(i) (2) Substituting into the objective function of the distance extension characteristic pattern search method, if:

[0062] f TL (x(1) 2 ,x(2) 2 ) < f TL (x(1) 1 ,x(2) 1 ) or f WA (x(1) 2 ,x(2) 2 ) < f WA (x(1) 1 ,x(2) 1 ),

[0063] Then we take the new parameter x(i). (2) Replace x(i) (1) Otherwise, take the reverse probe of e1:

[0064] x(i)( 2 )=x(i)( 1 )-αe1 (6)

[0065] Repeat the above process again. If the objective function value comparison condition is met, then use the new parameter x(i). (2) Replace x(i) (1) Otherwise, use x(i). (1) As x(i) (2) After completing the search along the x-axis, from x(i)... (2) Begin probing along the Y-axis to obtain the parameter x(i) as described above. (3) ,

[0066] If f TL (x(1) 3 ,x(2) 3 ) < f TL (x(1) 1 ,x(2) 1 ) or f WA (x(1) 3 ,x(2) 3 ) < f WA (x(1) 1 ,x(2) 1 ), let R1=x(i) (3) R0 = x(i) (1)Therefore, the direction of decrease in the objective function of the distance expansion characteristic is determined to be R1→R0;

[0067] If the search along all degrees of freedom fails to meet the requirements, the initial step size reduction rate γ is adjusted, and the search is restarted from the starting point. When it is necessary to reduce the step size to start a new iteration, the initial step size becomes: α' = γα;

[0068] Pattern search point M K The formula for calculating the position is:

[0069] M K =R K +β(R K -R K-1 (7)

[0070] In the above formula, β is the acceleration factor, and R K R represents the search base point. K-1 Indicates the previous search base point;

[0071] The initial search points for both the lateral and longitudinal dimensions are set at 5m. During the search, the radar transmit power is set to 20kW, antenna gain to 20dB, loss to 3dB, and electron density perturbation to 1.5%. The irregular body has a width of 10km, a thickness of 2km, a longitudinal dimension of 80m, a lateral dimension of 3m, and a scattering element size of 1×10⁻⁶. 9 m 3 The observation point coordinates are (-518, 0, 0). For the Gaussian density perturbation irregularity, the X-axis is selected from -10 km to 10 km, the Y-axis from -10 km to 10 km, and the Z-axis from 275 km to 285 km. The iteration process and step size changes of the horizontal and vertical scale parameters in the distance extension characteristic model search are as follows: Figure 4 , Figure 5 As shown, the iterative process and step size change of the thickness and width parameters in the distance extension characteristic pattern search are as follows: Figure 6 , Figure 7 As shown.

[0072] from Figures 4-7 It can be seen that the pattern search algorithm has good convergence and can accurately invert the parameters of irregular bodies.

[0073] Step 4, obtain the parameters of the irregular body:

[0074] The results x(1), x(2), x(3), and x(4) obtained by inversion using equations (3) and (4) correspond to the four parameters of the irregular body: horizontal scale, vertical scale, width, and thickness, respectively.

Claims

1. An irregular volume scale inversion method based on distance-extent characteristics, characterized by, The method comprises the following steps: Step 1, pre-processing of the coherent scattering radar sweep data: Extracting data DM with range expansion phenomenon from coherent scattering radar returns i as input to a pattern search method objective function; Step 2, setting a range expansion characteristic mode search method target function: The distance expansion data DM corresponding to each working frequency of the radar i The objective function for inverting the parameters of the irregular body is established, and the radar detection cross section is represented as In the above formula, σ TL represents the irregular body transverse and longitudinal detection cross section, λ represents the radar detection signal wavelength, represents the electron density perturbation mean square deviation, W is the scatterer width, A is the scatterer half thickness, X i , Y i , Z i is the intersection coordinate of the geomagnetic line and the Z axis of the rectangular coordinate system, ψ is the intersection line angle of the geomagnetic line and the Z axis of the index coordinate system, x(1) is the initial transverse dimension of the irregular body, x(2) is the initial longitudinal dimension of the irregular body, ΔV represents the scatterer volume, σ WA represents the irregular body width thickness detection cross section, T represents the irregular body transverse dimension, L represents the irregular body thickness, x(3) is the initial width of the irregular body, x(4) is the initial thickness of the irregular body; Let the range expansion width value containing unknowns of the irregular body horizontal and longitudinal be D1, and the range expansion width value containing unknowns of the irregular body width and thickness be D2, two target functions are established: In the above formula, f TL represents the irregular body transverse longitudinal target function, n represents the maximum value of the mode search point, f WA represents the irregular body width thickness target function; Step 3, solving the target function: The distance expansion characteristic mode search method has two undetermined independent variable degrees of freedom, which are represented by e i , e j , the detection step is α, the search starting point of the lateral and longitudinal dimensions is 5 m, the search starting point of the width and thickness of the irregular body is 3 km, and the irregular body position parameter x(i) (j) is defined as the starting point along the e j direction, where j=1, 2, 3, 4, x(i) (1) is the starting point along e1, x(i) (n+1) is the point obtained after detection along e n , and it is assumed that the parameters of the irregular body are from x(i) (1) First, detection is performed along the positive direction of the x axis, and then: x(i) (2) = x(i) (1) + ae1 (5) The obtained parameter information x(i) (2) Substitute the distance expansion characteristic mode search method objective function, if: f TL (x(1) 2 ,x(2) 2 ) < f TL (x(1) 1 ,x(2) 1 ) or f WA (x(1) 2 ,x(2) 2 ) < f WA (x(1) 1 ,x(2) 1 ), then take the new argument x(i) (2) instead of x(i) (1) else take the inverse probe of e1: x(i) (2) = x(i) (1) - ae1 (6) The above process is repeated again, and if the value comparison condition of the objective function is satisfied, the new parameter x(i) is used instead of x(i) (2) , otherwise x(i) (1) is still used as x(i) (1) , x(i) (2) , after the search along the x-axis direction is completed, the search along the Y-axis is performed from x(i) (2) , and the parameter x(i) (3) is obtained in the above manner, If f TL (x(1) 3 ,x(2) 3 )<f TL (x(1) 1 ,x(2) 1 ) or f WA (x(1) 3 ,x(2) 3 )<f WA (x(1) 1 ,x(2) 1 ), let R1=x(i) (3) R0 = x(i) (1) Therefore, the direction of decrease in the objective function of the distance expansion characteristic is determined to be R1→R0; If all the freedom degrees search cannot meet the requirements, the initial step reduction rate γ is adjusted, and the search is restarted from the starting point, when the step needs to be reduced to start a new iteration, the initial step becomes: α' = γα; Pattern search point M K The position calculation formula is: M K = R K + β(R K - R K-1 ) (7) In the above formula, β is an acceleration factor, R K denotes a search base point, R K-1 denotes the previous search base point; Step 4, obtaining the irregular body parameters: The results x(1), x(2), x(3), x(4) obtained by the inversion of formula (3), (4) correspond to the four parameters of the irregular body horizontal scale, longitudinal scale, width and thickness respectively.

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