A clutter compensation method for airborne radar based on partitioning

Abstract

This invention discloses a clutter compensation method for airborne radar based on partitioning, belonging to the field of radar technology. The invention first constructs a two-dimensional pulse-range matrix with M pulses and N range sampling units. Then, it corrects the Doppler center to zero Doppler at the center of the Doppler channel number through Doppler center estimation, compensation, and Fourier transform. The straight clutter region is separated by estimating the Doppler center bandwidth. The curved clutter region is straightened by compensating for the residual Doppler of the curved clutter. Finally, the two regions are recombined to obtain the clutter compensation result, reducing the complexity of subsequent clutter suppression and target detection.

Description

Technical Field

[0001] This invention relates to the field of radar technology, and specifically to a clutter compensation method for airborne radar based on partitioning. Background Technology

[0002] When the installation angle of the antenna is not parallel to the flight direction, the clutter bending phenomenon of the short-range main clutter Doppler changes rapidly with distance. This makes the clutter non-uniform when performing range-dimensional space-time adaptive processing of the Doppler channel, resulting in a performance degradation.

[0003] The core issue regarding the impact of distance-dependent Doppler variations in the main clutter on spatiotemporal processing lies in the fact that these variations cause the clutter distribution to lack continuity in both the range and Doppler dimensions. This results in insufficient sample sizes for signal processing methods that utilize neighboring cells for environmental perception estimation. To address the clutter curvature phenomenon, numerous researchers both domestically and internationally have conducted in-depth studies. One approach involves dimensionality reduction and rank reduction in spatiotemporal processing to decrease the required sample size and mitigate the impact of distance-dependent Doppler variations in the main clutter. Another approach is to compensate for the clutter by bringing the varying Doppler values ​​to a uniform level, thereby reducing the non-uniformity of the clutter in the range dimension. Waveform-based design methods have also been proposed, but all require specific application conditions. A further approach involves partitioning the clutter distribution into different regions, employing different processing methods for each region. For example, spatiotemporal processing is used for Doppler-stable regions, while dimensionality reduction and rank reduction are used for regions with varying Doppler values.

[0004] The above methods have all achieved certain processing results, but their application in engineering is limited by factors such as system parameters, computational load, and system design complexity. Considering computational load and engineering feasibility, clutter compensation methods have better engineering feasibility and have been well applied in low-repetition-rate radar systems. However, airborne radar systems for detecting moving targets in the air generally use a medium repetition-rate operating configuration. In this case, short-range clutter and long-range range-ambiguous clutter are located in the same range cell, resulting in an increase in the Doppler component of the range sampling cell. Directly performing Doppler compensation on short-range clutter will cause curvature of the far-range clutter.

[0005] The above problems urgently need to be solved. To address this, a partition-based airborne radar clutter compensation method is proposed. Summary of the Invention

[0006] The technical problem to be solved by this invention is: how to achieve clutter compensation of medium repetition frequency radar with low computational load, thereby reducing the complexity of subsequent space-time processing, and provides a clutter compensation method for airborne radar based on partitioning.

[0007] The present invention solves the above-mentioned technical problems through the following technical solution, and the present invention includes the following steps:

[0008] S1: Construct an M×N dimensional complex echo data matrix model X with M pulses and N distance sampling units;

[0009] S2: Calculate the Doppler center frequency of the main clutter based on the aircraft's inertial navigation information and correct it, thereby obtaining the range-Doppler matrix.

[0010] S3: Calculate the Doppler element number in the straight clutter region to obtain the straight clutter region matrix that does not change with the distance sampling element.

[0011] S4: Transform the distance Doppler matrix The corresponding elements of the straight clutter region are set to zero to obtain the curved clutter region matrix.

[0012] S5: Matrix for curved clutter region Doppler compensation was performed to obtain

[0013] S6: Combine the straight clutter region matrix and the Doppler-compensated curved clutter region matrix. By integrating the data, clutter compensation based on partitioned processing can be achieved.

[0014] Furthermore, in step S1, the specific processing procedure is as follows:

[0015] S11: Model the echo signal of the m-th pulse and the n-th distance sampling unit as:

[0016]

[0017] Where f0 is the radar's operating center frequency, T r The pulse repetition period, The distance ambiguity period is denoted by c, the electromagnetic wave propagation speed is denoted by p, the number of ambiguity periods is denoted by P, the maximum number of ambiguity periods is denoted by a(·), and the scattering intensity is denoted by R. np (mT r f represents the distance of the target at the nth distance sampling unit and the pth ambiguity period at the mth pulse. d (r) represents the Doppler frequency at a distance r;

[0018] S12: Construct the echoes from M pulses and N distance sampling units into a matrix form, thus obtaining the complex echo data matrix model X:

[0019] X = S + Γ = [X1, X2, ..., X n ,...,XN ]

[0020] Where S is the echo signal, Γ is M×N dimensional Gaussian white noise, X n =[x 1n ,x 2n ,...,x Mn ] T , where n = 1, 2, ..., N are the column vectors of the matrix model X.

[0021] Furthermore, in step S2, the specific processing procedure is as follows:

[0022] S21: Calculate the Doppler center frequency F of the remote main clutter based on the aircraft's inertial navigation information. dc :

[0023]

[0024] Among them, v p λ is the speed of the carrier aircraft, λ is the wavelength, and α is the angle between the beam and the speed.

[0025] S22: Doppler center frequency corrected based on clutter distribution

[0026] S23: Shift the main clutter to the zero-Doppler channel and convert it to a Doppler-dimensional matrix through pulse-dimensional FFT processing. That is, the distance Doppler matrix is ​​obtained.

[0027]

[0028] in, The FFT vector is the Doppler compensation vector, and fftshift represents a cyclic shift of half the length of the FFT point M of the sequence.

[0029] Furthermore, in step S22, the specific processing procedure is as follows:

[0030] S221: Perform FFT processing on each column of the echo distance to obtain the Doppler echo of each distance sampling unit:

[0031]

[0032] in,

[0033] S222: Obtain the Doppler energy distribution of clutter:

[0034]

[0035] Where m = 1, 2, ..., M, Let X be a matrix rd The element in the m-th row and n-th column;

[0036] S223: The Doppler channel with the highest energy is obtained based on the Doppler energy distribution.

[0037] S224: This leads to the corrected Doppler center frequency.

[0038]

[0039] Where q = int(F dc T r The number of fuzzy cycles is calculated from the Doppler center frequency estimated based on airborne inertial navigation information.

[0040] Furthermore, in step S3, the specific processing procedure is as follows:

[0041] S31: Calculate the number of Doppler elements in the straight clutter region:

[0042]

[0043] in, This indicates rounding up, where D represents the aperture length of the antenna, and v p The speed of the carrier aircraft is represented by β, the beam pointing cone angle is represented by α, and the angle between the beam and the speed is represented by α.

[0044] S32: Constructing the straight clutter region matrix:

[0045]

[0046] Where ca = M / 2, Representation matrix The row vector consisting of the elements of the m-th row.

[0047] Furthermore, in step S5, the specific processing procedure is as follows:

[0048] S51: Calculate the Doppler value for each distance sampling unit:

[0049]

[0050] in, Let θ be the azimuth angle, ψ be the angle between the antenna axis and the velocity, β be the beam pointing cone angle, and θ(n) be the ground rubbing angle corresponding to the nth range sampling unit. f s Where H is the sampling frequency and H is the altitude of the carrier aircraft;

[0051] S52: Dopplerweis Transformed into a pulse-dimensional matrix Y by IFFT W :

[0052] Y W =[Y1,Y2,...,Y n ,...,Y N ]

[0053] in, For matrix A vector composed of the elements in the nth column;

[0054] S53: Perform Doppler bending compensation on each distance sampling unit to obtain the matrix.

[0055]

[0056] in,

[0057] S54: Transform the compensated curved clutter region matrix to Doppler to obtain the matrix.

[0058]

[0059] in,

[0060] Furthermore, in step S6, the clutter compensation method based on partitioning is as follows:

[0061]

[0062] Compared with the prior art, the present invention has the following advantages: This partition-based airborne radar clutter compensation method first constructs a pulse-range two-dimensional matrix with M pulses and N range sampling units, then corrects the Doppler center to zero Doppler at the center of the Doppler channel number through Doppler center estimation, compensation, and Fourier transform; the straight clutter region is separated by estimating the Doppler center bandwidth; the curved clutter region is straightened by compensating the residual Doppler of the curved clutter; finally, the two regions are recombined to obtain the clutter compensation result, reducing the complexity of subsequent clutter suppression and target detection. Attached Figure Description

[0063] Figure 1 This is a flowchart illustrating the airborne radar clutter compensation method based on partitioning in an embodiment of the present invention.

[0064] Figure 2This is a schematic diagram of the geometric coordinate system for each angle in the embodiment of the present invention, where Rs is the distance between the radar and the target, and Rg is the position of the radar ground projection point and the target.

[0065] Figure 3 It is the distance Doppler matrix of step (2) in the embodiment of the present invention. Schematic diagram;

[0066] Figure 4 This is the curved clutter region matrix in step (4) of the embodiment of the present invention. Schematic diagram;

[0067] Figure 5 This is the clutter-compensated matrix in step (6) of this embodiment of the invention. Schematic diagram. Detailed Implementation

[0068] The embodiments of the present invention are described in detail below. These embodiments are implemented based on the technical solution of the present invention, and provide detailed implementation methods and specific operation processes. However, the scope of protection of the present invention is not limited to the following embodiments.

[0069] like Figure 1 As shown, this embodiment provides a technical solution: a partition-based airborne radar clutter compensation method, comprising the following steps:

[0070] Step (1): Construct an M×N dimensional complex echo data matrix model X with M pulses and N distance sampling units;

[0071] In this embodiment, step (1) includes the following sub-steps:

[0072] Step (1a): Model the echo signal of the m-th pulse and the n-th distance sampling unit as follows:

[0073]

[0074] Where f0 is the radar's operating center frequency, T r The pulse repetition period, The distance ambiguity period is denoted by c, the electromagnetic wave propagation speed is denoted by p, the number of ambiguity periods is denoted by P, the maximum number of ambiguity periods is denoted by a(·), and the scattering intensity is denoted by R. np (mT r f represents the distance of the target at the nth distance sampling unit and the pth ambiguity period at the mth pulse. d (r) represents the Doppler frequency at a distance r;

[0075] Step (1b): Construct the echoes from M pulses and N range sampling units into a matrix, thus obtaining the complex echo data matrix model X:

[0076] X = S + Γ = [X1, X2, ..., X n ,...,X N ]

[0077] Where S is the echo signal, Γ is M×N dimensional Gaussian white noise, X n =[x 1n ,x 2n ,...,x Mn ] T , where n = 1, 2, ..., N are the column vectors of the matrix model X.

[0078] Step (2): Calculate the Doppler center of the main clutter based on the aircraft's inertial navigation information and correct it to obtain the range-Doppler matrix.

[0079] In this embodiment, step (2) specifically includes the following sub-steps:

[0080] Step (2a): Calculate the Doppler center frequency F of the remote main clutter based on the aircraft's inertial navigation information. dc :

[0081]

[0082] Among them, v p Let λ be the speed of the carrier aircraft, λ be the wavelength, and α be the angle between the beam and the speed. See [reference needed]. Figure 2 ;

[0083] Step (2b): Obtain the corrected Doppler center frequency based on the clutter distribution.

[0084] In this embodiment, step (2b) specifically includes the following sub-steps:

[0085] Step (2ba): Perform FFT processing on each column of the echo distance to obtain the Doppler echo for each distance sampling unit:

[0086]

[0087] in,

[0088] Step (2bb): Obtain the Doppler energy distribution of the clutter:

[0089]

[0090] Where m = 1, 2, ..., M, Let X be a matrix rd The element in the m-th row and n-th column;

[0091] Step (2bc): Obtain the Doppler channel with the highest energy based on the Doppler energy distribution.

[0092] Step (2bd): The corrected Doppler center frequency is then obtained.

[0093]

[0094] Where q = int(F dc T r The number of ambiguity cycles is calculated based on the Doppler center frequency estimated from the airborne inertial navigation information; Step (2c): The main clutter is shifted to the zero Doppler channel and converted to a Doppler matrix through pulse-dimensional FFT processing. That is, the distance Doppler matrix is ​​obtained.

[0095]

[0096] in, The FFT vector is the Doppler compensation vector, and fftshift represents a cyclic shift of half the length of the FFT point M of the sequence.

[0097] Step (3): Obtain the straight clutter region matrix that does not change with distance sampling units.

[0098] In this embodiment, step (3) specifically includes the following sub-steps:

[0099] Step (3a): Calculate the number of Doppler elements in the straight hybrid region:

[0100]

[0101] in, This indicates rounding up, where D represents the aperture length of the antenna, and v p This indicates the speed of the carrier aircraft, β is the beam pointing cone angle, and α is the angle between the beam and the speed. See [reference needed]. Figure 2 ;

[0102] Step (3b): Construct the straight clutter region matrix:

[0103]

[0104] Where ca = M / 2, Representation matrix The row vector consisting of the elements of the m-th row.

[0105] Step (4): By setting the corresponding elements of the straight clutter region in the matrix to zero, the curved clutter region matrix is ​​obtained.

[0106] Step (5): Calculate the curved clutter region matrix. Doppler compensation was performed to obtain

[0107] In this embodiment, step (5) specifically includes the following sub-steps:

[0108] Step (5a): Calculate the Doppler value for each distance sampling unit:

[0109]

[0110] in, Let θ be the azimuth angle, ψ be the angle between the antenna axis and the velocity, β be the beam pointing cone angle, and θ(n) be the ground rubbing angle corresponding to the nth range sampling unit. f s Where H is the sampling frequency and H is the altitude of the carrier aircraft.

[0111] Step (5b): Doppler's Transformed into a pulse-dimensional matrix Y by IFFT W :

[0112] Y W =[Y1,Y2,...,Y n ,...,Y N ]

[0113] in, For matrix A vector composed of the elements in the nth column;

[0114] Step (5c): Perform Doppler bending compensation on each distance sampling unit to obtain the matrix.

[0115]

[0116] in,

[0117] Step (5d): Transform the compensated curved clutter region matrix to Doppler to obtain the matrix.

[0118]

[0119] in,

[0120] Step (6): Combine the straight clutter region matrix and the Doppler-compensated curved clutter region matrix to achieve clutter compensation based on partitioning:

[0121]

[0122] In summary, the partition-based airborne radar clutter compensation method described in the above embodiments first constructs a pulse-range two-dimensional matrix with M pulses and N range sampling units. Then, it corrects the Doppler center to zero Doppler at the center of the Doppler channel number through Doppler center estimation, compensation, and Fourier transform. The straight clutter region is separated by estimating the Doppler center bandwidth. The curved clutter region is straightened by compensating for the residual Doppler of the curved clutter. Finally, the two regions are recombined to obtain the clutter compensation result, reducing the complexity of subsequent clutter suppression and target detection.

[0123] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A partition-based airborne radar clutter compensation method, characterized in that, Includes the following steps: S1: Construct an M×N dimensional complex echo data matrix model X with M pulses and N distance sampling units; S2: Calculate the Doppler center frequency of the main clutter based on the aircraft's inertial navigation information and correct it, thereby obtaining the range-Doppler matrix. S3: Calculate the Doppler element number in the straight clutter region to obtain the straight clutter region matrix that does not change with the distance sampling element. S4: Transform the distance Doppler matrix The corresponding elements of the straight clutter region are set to zero to obtain the curved clutter region matrix. S5: Matrix for curved clutter region Doppler compensation was performed to obtain S6: Combine the straight clutter region matrix and the Doppler-compensated curved clutter region matrix. By integrating the data, clutter compensation based on partitioned processing can be achieved.

2. The airborne radar clutter compensation method based on partitioning according to claim 1, characterized in that, In step S1, the specific processing procedure is as follows: S11: Model the echo signal of the m-th pulse and the n-th distance sampling unit as: Where f0 is the radar's operating center frequency, T r The pulse repetition period, The distance ambiguity period is denoted by c, the electromagnetic wave propagation speed is denoted by p, the number of ambiguity periods is denoted by P, the maximum number of ambiguity periods is denoted by a(·), and the scattering intensity is denoted by R. np (mT r f represents the distance of the target at the nth distance sampling unit and the pth ambiguity period at the mth pulse. d (r) represents the Doppler frequency at a distance r; S12: Construct the echoes from M pulses and N distance sampling units into a matrix form, thus obtaining the complex echo data matrix model X: X=S+Γ=[X1,X2,…,X n ,…,X N ] Where S is the echo signal, Γ is M×N dimensional Gaussian white noise, X n =[x 1n ,x 2n ,...,x Mn ] T , where n = 1, 2, ..., N are the column vectors of the matrix model X.

3. The airborne radar clutter compensation method based on partitioning according to claim 2, characterized in that, In step S2, the specific processing procedure is as follows: S21: Calculate the Doppler center frequency F of the remote main clutter based on the aircraft's inertial navigation information. dc : Among them, v p λ is the speed of the carrier aircraft, λ is the wavelength, and α is the angle between the beam and the speed. S22: Doppler center frequency corrected based on clutter distribution S23: Shift the main clutter to the zero-Doppler channel and convert it to a Doppler-dimensional matrix through pulse-dimensional FFT processing. That is, the distance Doppler matrix is ​​obtained. in, The FFT vector is the Doppler compensation vector, and fftshift represents a cyclic shift of half the length of the FFT point M of the sequence.

4. The airborne radar clutter compensation method based on partitioning according to claim 3, characterized in that, In step S22, the specific processing procedure is as follows: S221: Perform FFT processing on each column of the echo distance to obtain the Doppler echo of each distance sampling unit: in, S222: Obtain the Doppler energy distribution of clutter: Where m = 1, 2, ..., M, Let X be a matrix rd The element in the m-th row and n-th column; S223: The Doppler channel with the highest energy is obtained based on the Doppler energy distribution. S224: This leads to the corrected Doppler center frequency. Where q = int(F dc T r The number of fuzzy cycles is calculated from the Doppler center frequency estimated based on airborne inertial navigation information.

5. The airborne radar clutter compensation method based on partitioning according to claim 4, characterized in that, In step S3, the specific processing procedure is as follows: S31: Calculate the number of Doppler elements in the straight clutter region: in, This indicates rounding up, where D represents the aperture length of the antenna, and v p The speed of the carrier aircraft is represented by β, the beam pointing cone angle is represented by α, and the angle between the beam and the speed is represented by α. S32: Constructing the straight clutter region matrix: Where ca = M / 2, Representation matrix The row vector consisting of the elements of the m-th row.

6. The airborne radar clutter compensation method based on partitioning according to claim 5, characterized in that, In step S5, the specific processing procedure is as follows: S51: Calculate the Doppler value for each distance sampling unit: Where ψ is the angle between the antenna axis and the velocity, β is the beam pointing cone angle, and θ(n) is the ground rubbing angle corresponding to the nth range sampling unit. f s Where H is the sampling frequency and H is the altitude of the carrier aircraft; S52: Dopplerweis Transformed into a pulse-dimensional matrix Y by IFFT W : Y W =[Y1,Y2,...,Y n ,...,Y N ] in, For matrix A vector composed of the elements in the nth column; S53: Perform Doppler bending compensation on each distance sampling unit to obtain the matrix. in, S54: Transform the compensated curved clutter region matrix to Doppler to obtain the matrix. in, 7. The airborne radar clutter compensation method based on partitioning according to claim 6, characterized in that, In step S6, the clutter compensation method based on partitioning is as follows:

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