Target Scattering Angle Estimation Method Based on Electromagnetic Vortex Mode Information Entropy

Abstract

This invention discloses a target scattering angle estimation method based on electromagnetic vortex mode information entropy: Step 1, obtain the complex form of the target vortex scattering field; Step 2, extract the modal spectral purity of mode l of the target vortex scattering field according to the complex form of the target vortex scattering field; Step 3, obtain the target vortex scattering mode information entropy according to the calculation formula of the modal spectral purity of vortex mode l in a given annular region; Step 4, estimate the target scattering angle based on the target vortex scattering mode information entropy. This invention utilizes the new dimensional characteristics of vortices and the concept of information entropy to introduce a new characteristic quantity of target scattering echo. This characteristic quantity characterizes the law of modal spectrum distribution and can, to a certain extent, compensate for the defect of traditional signals being easily affected by the intensity of complex electromagnetic environmental noise. On this basis, a target scattering angle estimation model based on modal information entropy is constructed, combined with a neural network model, to achieve high-precision estimation of the target scattering angle, which has high practical value.

Description

Technical Field

[0001] This invention belongs to the field of target detection technology for new radar systems, specifically relating to a target scattering angle estimation method based on electromagnetic vortex mode information entropy, which can be applied to target scattering angle estimation and other spatial characteristic value estimation fields. Background Technology

[0002] With the rapid development of electronic warfare, military, civil aviation, and other radar users have placed higher demands on radar, such as the ability to quickly, efficiently, and accurately estimate and track space targets, achieving real-time performance. Target angle estimation plays a crucial role in space target tracking and identification. Traditional radars, which rely on the amplitude and phase of space target echo signals, are highly susceptible to the influence of complex electromagnetic noise, causing the echo signals to be submerged in noise and making it difficult to achieve high-precision and effective estimation.

[0003] Vortex electromagnetic waves, carrying orbital angular momentum information, possess a higher degree of freedom in information modulation compared to traditional electromagnetic waves, making them highly promising for applications in radar target detection and imaging. As a cutting-edge technology, numerous researchers have explored the orbital angular momentum characteristics of vortex electromagnetic wave radar: in radar imaging, it can achieve super-resolution imaging and high-precision imaging of high-speed targets; in wireless communication, it can significantly increase communication capacity and frequency efficiency; and in target detection, it can sense richer rotating Doppler information about targets. A deeper understanding of the characteristics of this new type of vortex electromagnetic wave radar can promote the development and application of imaging, sensing, and communication technologies.

[0004] To address the challenge of estimating target scattering angles using vortex radar technology, this patent introduces the concept of information entropy to describe the complex spatial distribution of target vortex scattering mode spectra. Informatics defines information entropy as the probability of a specific piece of information occurring. From an information propagation perspective, information entropy represents the value of information, referring to its uncertainty. High-information-content information corresponds to low entropy, while low-information-content information corresponds to high entropy. This patent innovatively equates different modal purity to the probability of that mode's occurrence. Therefore, a large vortex mode information entropy value indicates a significantly scattered spatial distribution of modal spectrum information, containing a large amount of modal type information; a small vortex mode information entropy value indicates a more concentrated spatial distribution of modal spectrum information, with more clearly defined specific modal values. In this case, the angle between the incident angle and the scattering angle is generally very small.

[0005] Traditional radar detection relies on the plane wave approximation, where the received echoes are scatterings of the plane waves by the target. In contrast, vortex electromagnetic waves possess a helical phase wavefront, and the continuous variation of this wavefront allows vortex electromagnetic waves to distinguish targets in the azimuth direction. Combining this with the concept of vortex mode entropy introduces new characteristic values ​​for vortex radar imaging and detection applications.

[0006] In summary, it is necessary to study target scattering angle estimation technology based on electromagnetic vortex mode information entropy to further improve the performance of vortex radar systems. Summary of the Invention

[0007] The technical problem solved by this invention is to overcome the shortcomings of traditional signals being easily affected by the intensity of complex electromagnetic environmental noise. It creatively proposes a target scattering angle estimation technique based on electromagnetic vortex mode information entropy. This feature represents the law of mode spectrum distribution. Combined with a deep neural network model, it can achieve high-precision estimation of the target scattering angle.

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] A target scattering angle estimation method based on electromagnetic vortex mode information entropy specifically includes the following steps:

[0010] Step 1: Obtain the complex form of the target vortex scattering field;

[0011] Step 2: Based on the complex form of the target vortex scattering field obtained in Step 1, extract the modal spectral purity of mode l of the target vortex scattering field;

[0012] Step 3: Based on the modal spectrum purity calculation formula of the given annular region vortex mode l obtained in Step 2, obtain the target vortex scattering mode information entropy.

[0013] Step 4: Estimate the target scattering angle based on the target vortex scattering mode information entropy obtained in Step 3.

[0014] Further, the specific operation of step 1: Assuming the wavelength of the vortex electromagnetic wave is λ, set the sampling step size λ2, and the number of sampling points in the X direction is N. X The number of sampling points in the Y direction is N. Y , constitute N X ×N Y The target vortex scattering field spatial acquisition array is defined with the lower left corner of the acquisition array as the origin (0,0). Assume that any sampling point on the spatial acquisition array is located at (X... m ,Y n The spatial amplitude of vortex scattering at point A is... m,n The phase is φ m,n , where X m =1,2,...N X Y n =1,2,...N Y Then the complex form of the target vortex scattering field at that location can be expressed as:

[0015]

[0016] Where j is a complex number.

[0017] Further, the specific operation of step 2 is as follows: Based on the distribution of the target vortex scattering spatial amplitude collected in step 1, determine the sampling point number (X) of the location of the minimum amplitude in the central region of the target vortex scattering field. min ,Y min Find the sampling point number (X) at the location of the maximum amplitude in the X direction. min +d,Y min ), where d is the number of sampling points between the maximum and minimum values ​​of the vortex amplitude at the main ring position in the X direction, and the numerical E of the target vortex scattering field on the ring with radius d is extracted. s (X Get ,Y Get The formula for calculating the modal spectrum purity of vortex mode l in the annular region is:

[0018]

[0019] In the formula, C l It is the modal spectral purity of mode l of the target vortex scattering field. It is the angle sampling interval of the ring. It is the angle value from the horizontal direction to any sampling point on the ring, (X) Get ,Y Get ) represents the coordinates of any point on the annulus, and the round(·) function rounds the value in parentheses to the nearest integer.

[0020] Further, the specific operation of step 3 is as follows: using the modal spectrum purity calculation formula obtained in step 2, calculate the vortex mode range [-L] OAM ,L OAM ] Total 2L OAM The purity values ​​of the +1 group of modal spectra are calculated, and the sum of the purity values ​​of all groups of modal spectra within the vortex mode range is calculated. The purity values ​​of the modal spectra are then normalized using the sum of the purity values ​​to obtain the equivalent occurrence probability of each modal component within the modal range, as shown in the following formula:

[0021] C lp =C l / sum[C l ], lp=l∈[-L OAM ,L OAM ]

[0022] In the formula, lp represents the normalized mode corresponding to mode l;

[0023] The entropy of the target vortex scattering mode information in the sampling annular region is:

[0024]

[0025] Furthermore, the specific operation of step 4: using the process of calculating the vortex scattering mode information entropy in steps 1 to 3, it is possible to calculate any incident angle θ. i , incident azimuth angle ψ i Scattering angle θ s Scattering azimuth angle ψ s Based on the modal information entropy, construct a target vortex scattering modal information entropy database D. OAM ,Right now:

[0026] D OAM =[θ i ,ψ i ,θ s ,ψ s H OAM ]

[0027] In the formula, the minimum values ​​of the incident angle, incident azimuth angle, scattering angle, and scattering azimuth angle are respectively θ imin ψ imin θ smin ψ smin The maximum values ​​are θ imax ψ imax θ smax ψ smax ,Right now:

[0028] θ i ∈[θ imin ,θ imax ],ψ i ∈[ψ imin ,ψ imax ],θ s ∈[θ smin ,θ smax ],ψ s ∈[ψ smin ,ψ smax ]

[0029] Using the MATLAB deep neural network module, [θ] in the database i ,ψ i ,θ s ,ψ s [θ] is used as input. s As output, the ratio of the training set, validation set, and test set, as well as the number of hidden neural network layers, are set according to the instructions of the deep neural network module. Training is then performed to obtain a trained deep neural network. The input to be predicted [θ] is then fed into the trained deep neural network. i ,ψ i ,ψ s H OAM The parameter set and the result of the operation are the target scattering angle estimates.

[0030] The advantages of this invention compared to the prior art are as follows:

[0031] This invention addresses the problem of target scattering angle estimation in vortex radar by creatively proposing a target scattering angle estimation method based on electromagnetic vortex mode information entropy. Compared with traditional radar target angle estimation methods, this method utilizes new dimensional features of vortices and the concept of information entropy to introduce a new characteristic quantity of the target scattered echo. This characteristic quantity characterizes the distribution law of the mode spectrum and can, to some extent, compensate for the deficiency of traditional signals being easily affected by complex electromagnetic environmental noise intensity. Based on this, a target scattering angle estimation model based on mode information entropy is constructed and combined with a neural network model to achieve high-precision estimation of the target scattering angle, which has high practical value. Attached Figure Description

[0032] Figure 1 This is a block diagram of a target scattering angle estimation technique based on electromagnetic vortex mode information entropy;

[0033] Figure 2 The amplitude and phase spatial distributions of the scattered field of the mode 1 vortex electromagnetic wave by the flat plate target are shown, where (a) is the amplitude spatial distribution and (b) is the phase spatial distribution.

[0034] Figure 3 The distribution of the mode spectrum of mode scattering of mode 1 vortex electromagnetic waves by a flat plate target;

[0035] Figure 4 The curves show the variation of information entropy of electromagnetic vortex modes with incident and scattering angles.

[0036] Figure 5 The results are the target scattering angle estimation results based on modal information entropy, where (a) is the fitted distribution of the prediction results and (b) is the error histogram. Detailed Implementation

[0037] The present invention will now be described in further detail with reference to the accompanying drawings.

[0038] The application scenarios of this invention are as follows:

[0039] This invention addresses the problem of target scattering angle estimation in vortex radar by proposing a target scattering angle estimation technique based on electromagnetic vortex mode information entropy. By utilizing new dimensional feature parameters of the vortex mode spectrum, it achieves high-precision target vortex scattering angle estimation, providing theoretical and technical reserves for vortex radar detection technology.

[0040] Step 1: Obtain the complex form of the target vortex scattering field.

[0041] Specifically, assuming the wavelength of the vortex electromagnetic wave is λ, the sampling step size is set to λ2, and the number of sampling points in the X direction is N. X The number of sampling points in the Y direction is N. Y , constitute NX ×N Y The target vortex scattering field spatial acquisition array is defined with the lower left corner of the acquisition array as the origin (0,0). Assume that any sampling point on the spatial acquisition array is located at (X... m ,Y n The spatial amplitude of vortex scattering at point A is... m,n The phase is φ m,n , where X m =1,2,...N X Y n =1,2,...N Y Then the complex form of the target vortex scattering field at that location can be expressed as:

[0042]

[0043] Where j is a complex number.

[0044] Step 2: Based on the complex form of the target vortex scattering field obtained in Step 1, extract the modal spectral purity of mode l of the target vortex scattering field.

[0045] Specifically, based on the distribution of the target vortex scattering spatial amplitude collected in step 1, the sampling point number (X) at the location of the minimum amplitude in the central region of the target vortex scattering field is determined. min ,Y min Find the sampling point number (X) at the location of the maximum amplitude in the X direction. min +d,Y min ), where d is the number of sampling points between the maximum and minimum values ​​of the vortex amplitude at the main ring position in the X direction, and the numerical E of the target vortex scattering field on the ring with radius d is extracted. s (X Get ,Y Get The formula for calculating the modal spectrum purity of vortex mode l in the annular region is:

[0046]

[0047] In the formula, C l It is the modal spectral purity of mode l of the target vortex scattering field. It is the angle sampling interval of the ring. It is the angle value from the horizontal direction to any sampling point on the ring, (X) Get ,Y Get ) represents the coordinates of any point on the annulus, and the round(·) function rounds the value in parentheses to the nearest integer.

[0048] Step 3: Based on the modal spectrum purity calculation formula of the given annular region vortex mode l obtained in Step 2, obtain the target vortex scattering mode information entropy.

[0049] Specifically, the modal spectrum purity calculation formula obtained in step 2 is used to calculate the vortex mode range [-L] OAM ,L OAM ] Total 2L OAM The purity values ​​of the +1 group of modal spectra are calculated, and the sum of the purity values ​​of all groups of modal spectra within the vortex mode range is calculated. The purity values ​​of the modal spectra are then normalized using the sum of the purity values ​​to obtain the equivalent occurrence probability of each modal component within the modal range, as shown in the following formula:

[0050] C lp =C l / sum[C l ], lp=l∈[-L OAM ,L OAM (5)

[0051] In the formula, lp represents the normalized mode corresponding to mode l.

[0052] The entropy of the target vortex scattering mode information in the sampling annular region is:

[0053]

[0054] Step 4: Estimate the target scattering angle based on the target vortex scattering mode information entropy obtained in Step 3.

[0055] The process of calculating the information entropy of vortex scattering modes using steps 1 to 3 can be used to calculate any incident angle θ. i , incident azimuth angle ψ i Scattering angle θ s Scattering azimuth angle ψ s Based on the modal information entropy, construct a target vortex scattering modal information entropy database D. OAM ,Right now:

[0056] D OAM =[θ i ,ψ i ,θ s ,ψ s H OAM (7)

[0057] In the formula, the minimum values ​​of the incident angle, incident azimuth angle, scattering angle, and scattering azimuth angle are respectively θ imin ψ imin θ smin ψ smin The maximum values ​​are θ imax ψ imax θ smax ψ smax ,Right now:

[0058] θ i ∈[θimin ,θ imax ],ψ i ∈[ψ imin ,ψ imax ],θ s ∈[θ smin ,θ smax ],ψ s ∈[ψ smin ,ψ smax (8)

[0059] Using MATLAB's deep neural network module (Neural Net fitting), the database [θ i ,ψ i ,ψ s H OAM As inputs, [θ] s As outputs (Targets), the proportions of the deep neural network training set, validation set, and test set, as well as the number of hidden neural network layers, are set according to the instructions of the deep neural network module. Training is then performed to obtain a trained, predictable scattering angle θ. s A deep neural network; input the [θ] to be predicted into the trained deep neural network. i ,ψ i ,ψ s H OAM The parameter set and the result of the operation are the estimated values ​​of the target scattering angle.

[0060] The effects of the present invention will be further illustrated below using simulation data.

[0061] First, the process of calculating the information entropy of electromagnetic vortex modes in this invention is verified through simulation. With a vortex electromagnetic wave frequency of 16 GHz, an incident angle of 0 degrees, an incident azimuth angle and a scattering azimuth angle of 0 degrees, and a scattering angle of 2 degrees, a high-frequency algorithm is used to simulate the spatial distribution of the scattered field of a flat target irradiated by a vortex electromagnetic wave of mode 1. For example... Figure 2 (a) shows the spatial distribution of the target vortex scattering amplitude. Figure 2 (b) shows the spatial distribution of the target vortex scattering phase, with the horizontal and vertical axes representing the size of the simulated sampling area. In Figure 2(a), the minimum amplitude is at the center position, and the minimum distance from the maximum amplitude in the X direction is 0.84λ (with a sampling point interval of 13). Based on the relationship between the sampling interval and the number of samples, the scattering mode spectrum distribution of the annular region with a radius of 0.84λ (with a sampling point interval of 13) is calculated as follows. Figure 3 As shown. Based on this, the simulation included incident angles ranging from 0 to 66 degrees, scattering angles ranging from 0 to 80 degrees, with an angle interval of 2 degrees, and both the incident and scattering azimuth angles being 0 degrees. A vortex mode information entropy database was constructed, containing a total of 1394 data sets. Curves of some of the data are shown below. Figure 4As shown, the modal information entropy changes significantly under different scattering and incident angles, especially on the sampling surface parallel to the top of the flat target, where the change with the incident angle is particularly pronounced. Using the MATLAB deep neural network module (NeuralNet fitting), 70% of the data was used as the training set, 15% as the validation set, and 15% as the test set, according to the module's instructions. The number of hidden neural network layers was set to 32. Figure 5 The results of scattering angle estimation using the modal information entropy database are presented. The R-squared determination coefficient reaches 0.9603, the error is less than 2 degrees, and the linear correlation and accuracy are very high, which can realize the estimation of the target scattering angle.

[0062] Simulation analysis conclusions: For the new dimension characteristics of the new vortex radar modes, combining the feature information extracted by the target vortex scattering mode information entropy of this invention and adopting a deep neural network model can provide a new approach for estimating the target vortex scattering angle.

Claims

1. A method for estimating the target scattering angle based on electromagnetic vortex mode information entropy, characterized in that, Specifically, the steps include the following: Step 1: Obtain the complex form of the target vortex scattering field; Step 2: Extract the target vortex scattering mode based on the complex form of the target vortex scattering field obtained in Step 1. Modal spectral purity; Specific steps: Based on the distribution of the target vortex scattering spatial amplitude collected in step 1, determine the sampling point number of the location of the minimum amplitude in the central region of the target vortex scattering field. Find the sampling point number at the location of the maximum amplitude in the X direction. ,in, The number of sampling points at the position of the main ring of the vortex amplitude in the X direction is used to extract the maximum and minimum values. Numerical value of the vortex scattering field of the target on a circular ring with radius . The vortex mode in the annular region The formula for calculating the modal spectrum purity is: In the formula, It is the target vortex scattering field mode Modal spectral purity, It is the angle sampling interval of the ring. It is the angle value from the horizontal direction to any sampling point on the ring. It represents the coordinates of any point on the annulus. The function represents rounding the value in parentheses to an integer value; Step 3, based on the given annular region vortex mode obtained in Step 2 The modal spectrum purity calculation formula is used to obtain the target vortex scattering modal information entropy; Specific steps: Use the modal spectrum purity calculation formula obtained in step 2 to calculate the vortex mode range. Total The purity values ​​of the modal spectra of all groups are calculated, and the sum of the purity values ​​of the modal spectra of all groups within the vortex mode range is calculated. The purity values ​​of the modal spectra are then normalized using the sum of the purity values ​​to obtain the equivalent occurrence probability of each modal component within the modal range. The formula is as follows: In the formula, Indicates the corresponding mode Normalized modes; The entropy of the target vortex scattering mode information in the sampling annular region is: ； Step 4: Estimate the target scattering angle based on the target vortex scattering mode information entropy obtained in Step 3.

2. The target scattering angle estimation method based on electromagnetic vortex mode information entropy as described in claim 1, characterized in that, Step 1: Specific steps: Assume the wavelength of the vortex electromagnetic wave is... Set sampling step size The number of sampling points in the X direction is The number of sampling points in the Y direction is ,constitute The target vortex scattering field spatial acquisition array is defined with the lower left corner of the acquisition array as the origin. Assuming the location of any sampling point on the spatial acquisition array... The spatial amplitude of vortex scattering at that location is Phase is ,in , Then the complex form of the target vortex scattering field at that location can be expressed as: Where j is a complex number.

3. The target scattering angle estimation method based on electromagnetic vortex mode information entropy as described in claim 1, characterized in that, Step 4: The process of calculating the entropy of the vortex scattering mode is followed by steps 1 to 3, which can be used to calculate the entropy of any incident angle. azimuth of incidence Scattering angle Scattering azimuth angle Based on the modal information entropy, construct a target vortex scattering modal information entropy database. ,Right now: In the formula, the minimum values ​​of the incident angle, incident azimuth angle, scattering angle, and scattering azimuth angle are respectively... , , , The maximum values ​​are respectively , , , ,Right now: Using MATLAB's deep neural network module, the database As input, As output, the ratio of the training set, validation set, and test set, as well as the number of hidden neural network layers, are set according to the instructions of the deep neural network module. Training is then performed to obtain a trained deep neural network. The input to be predicted is then fed into the trained deep neural network. The parameter set and the result of the operation are the target scattering angle estimates.

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