Airborne radar clutter compensation method based on partition

Abstract

The invention discloses a partition-based airborne radar clutter compensation method, and belongs to the technical field of radars. The method comprises the following steps: firstly, constructing a pulse distance two-dimensional matrix of M pulses and N distance sampling units, and then correcting a Doppler center to a central position of zero Doppler in a Doppler channel number through Doppler center estimation, compensation and Fourier transform; straight clutter areas are separated through estimation of Doppler center bandwidth; a bent clutter area is straightened through a method of compensating the residual Doppler of the bent clutter; and finally, the two regions are recombined to obtain a clutter compensation result, so that the complexity of subsequent clutter suppression and target detection is reduced.

Description

Technical Field

[0001] The invention relates to the field of radar technology, and in particular to a partition-based airborne radar clutter compensation method. Background Art

[0002] For airborne radars that monitor moving targets in the air, 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 makes the clutter non-uniform when the Doppler channel is processed in the space-time adaptive manner in the distance dimension, resulting in performance degradation.

[0003] The core of the influence of the Doppler change of the main clutter with distance on the space-time processing is that the change of Doppler makes the distribution of clutter not have continuous distribution characteristics in both the distance dimension and the Doppler dimension, which makes the signal processing method using adjacent units for environmental perception estimation unable to obtain sufficient samples. In order to solve the phenomenon of clutter bending, a large number of researchers at home and abroad have conducted in-depth research. One idea is to reduce the dimension and rank of space-time processing, thereby reducing the demand for the number of samples for space-time processing and reducing the influence of the main clutter Doppler with distance; another is to compensate for the clutter, compensating the changing Doppler to the same Doppler, thereby reducing the non-uniformity of the clutter in the distance dimension; a method based on waveform design is also proposed, all of which require specific application conditions; another method is to partition according to the distribution of clutter, and different partitions use different processing methods, such as: space-time processing is used for areas with stable Doppler; special processing methods such as dimensionality reduction and rank reduction are used for areas with Doppler changes.

[0004] The above methods have achieved certain processing effects, but due to the influence of system parameters, computational complexity, system design complexity and other factors, they are subject to certain limitations in engineering applications. Considering the computational complexity and engineering feasibility, the clutter compensation method has good engineering feasibility and has been well applied in low-repetition-rate radar systems. However, in airborne radar systems for detecting moving targets in the air, medium-repetition-rate working configurations are generally used. At this time, short-range clutter and long-range fuzzy clutter are simultaneously located in the same distance unit, resulting in an increase in the Doppler component of the distance sampling unit. Direct Doppler compensation of short-range clutter will cause bending of far-range clutter.

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

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

[0007] The present invention solves the above technical problems through the following technical solutions, and the present invention comprises the following steps:

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

[0009] S2: Calculate the Doppler center frequency of the main clutter based on the carrier inertial navigation information and correct it to obtain the range Doppler dimension matrix

[0010] S3: Calculate the number of Doppler units in the direct clutter area and obtain the direct clutter area matrix that does not change with the distance sampling unit.

[0011] S4: 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: Bend clutter area matrix Doppler compensation is performed to obtain

[0013] S6: Combine the straight clutter area matrix and the curved clutter area matrix after Doppler compensation The synthesis is performed to realize clutter compensation based on partition processing.

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

[0015] S11: Model the echo signal of the mth pulse and the nth range sampling unit as follows:

[0016]

[0017] Where f0 is the radar operating center frequency, T r is the pulse repetition period, is the distance fuzzy cycle, c is the electromagnetic wave propagation speed, p is the number of fuzzy cycles, P is the maximum number of fuzzy cycles, a(·) represents the scattering intensity, R np (mT r ) represents the distance of the target at the mth pulse in the nth distance sampling unit and pth fuzzy period, f d (r) represents the Doppler frequency at distance r;

[0018] S12: The echoes of M pulses and N range sampling units are constructed in the form of a matrix, that is, a complex echo data matrix model X is obtained:

[0019] X=S+Γ=[X1,X2,...,X n ,...,XN ]

[0020] Among them, S is the echo signal, Γ is M×N Gaussian white noise, X n =[x 1n ,x 2n ,...,x Mn ] T , n=1,2,...,N is the column vector of the matrix model X.

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

[0022] S21: Calculate the Doppler center frequency F of the long-range main clutter based on the carrier inertial navigation information dc :

[0023]

[0024] Among them, v p is the speed of the carrier, 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: Move the main clutter to the zero Doppler channel and convert it to the Doppler dimension matrix through pulse dimension FFT processing That is, we get the distance Doppler matrix

[0027]

[0028] in, is the Doppler compensation vector, fftshift represents the cyclic shift of the sequence by half the length of the FFT point number M;

[0029] Furthermore, in step S22, the specific processing process 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, is the matrix X rd The element in the mth row and nth column of ;

[0036] S223: Obtain the Doppler channel with the maximum energy based on the Doppler dimension energy distribution

[0037] S224: Then get the corrected Doppler center frequency

[0038]

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

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

[0041] S31: Calculate the number of Doppler cells in the straight clutter area:

[0042]

[0043] in, represents rounding up, D represents the aperture length of the antenna, v p represents the speed of the carrier, β is the beam pointing cone angle, and α is the angle between the beam and the speed;

[0044] S32: Construct the direct clutter region matrix:

[0045]

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

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

[0048] S51: Calculate the Doppler value of each range sampling unit:

[0049]

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

[0051] S52: Doppler Transform to pulse dimension matrix Y through IFFT W :

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

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

[0054] S53: Perform Doppler bending compensation on each range sampling unit to obtain a matrix

[0055]

[0056] in,

[0057] S54: Transform the compensated bending clutter region matrix into the Doppler dimension to obtain a matrix

[0058]

[0059] in,

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

[0061]

[0062] Compared with the prior art, the present invention has the following advantages: the partition-based airborne radar clutter compensation method first constructs a pulse distance two-dimensional matrix of M pulses and N distance sampling units, then corrects the Doppler center to a central position where zero Doppler is located in the number of Doppler channels through Doppler center estimation, compensation and Fourier transform; separates the straight clutter region through Doppler center bandwidth estimation; straightens the curved clutter region through a method of compensating the residual Doppler of the curved clutter; and finally recombines the two regions to obtain a clutter compensation result, thereby reducing the complexity of subsequent clutter suppression and target detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0063] Figure 1 is a flow chart of an airborne radar clutter compensation method based on partition processing in an embodiment of the present invention;

[0064] Figure 2is a schematic diagram of the geometric coordinate system of each angle in the embodiment of the present invention, wherein 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 is the range Doppler matrix of step (2) in the embodiment of the present invention Schematic diagram;

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

[0067] Figure 5 is the matrix after clutter compensation in step (6) of the embodiment of the present invention Schematic diagram. DETAILED DESCRIPTION

[0068] The following is a detailed description of an embodiment of the present invention. This embodiment is implemented on the premise of the technical solution of the present invention, and a detailed implementation method and a specific operation process are given, but the protection scope of the present invention is not limited to the following embodiment.

[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 range sampling units;

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

[0072] Step (1a): Model the echo signal of the mth pulse and the nth range sampling unit as:

[0073]

[0074] Where f0 is the radar operating center frequency, T r is the pulse repetition period, is the distance fuzzy cycle, c is the electromagnetic wave propagation speed, p is the number of fuzzy cycles, P is the maximum number of fuzzy cycles, a(·) represents the scattering intensity, R np (mT r ) represents the distance of the target at the mth pulse in the nth distance sampling unit and pth fuzzy period, f d (r) represents the Doppler frequency at distance r;

[0075] Step (1b): construct the echoes of M pulses and N range sampling units into a matrix form, that is, obtain the complex echo data matrix model X:

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

[0077] Among them, S is the echo signal, Γ is M×N Gaussian white noise, X n =[x 1n ,x 2n ,...,x Mn ] T , n=1,2,...,N is the column vector of the matrix model X.

[0078] Step (2): Calculate the Doppler center of the main clutter based on the carrier inertial navigation information and correct it to obtain the range Doppler dimension matrix

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

[0080] Step (2a): Calculate the Doppler center frequency F of the long-range main clutter based on the carrier inertial navigation information dc :

[0081]

[0082] Among them, v p is the speed of the carrier, λ is the wavelength, and α is the angle between the beam and the speed. Figure 2 ;

[0083] Step (2b): Get 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 of each distance sampling unit:

[0086]

[0087] in,

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

[0089]

[0090] Where m = 1, 2, ..., M, is the matrix X rd The element in the mth row and nth column of ;

[0091] Step (2bc): Obtain the Doppler channel with the maximum energy according to the Doppler dimension energy distribution

[0092] Step (2bd): Then obtain the corrected Doppler center frequency

[0093]

[0094] Where q = int(F dc T r ) is the number of ambiguity cycles calculated based on the Doppler center frequency estimated from the airborne inertial navigation information; Step (2c): Move the main clutter to the zero Doppler channel and convert it to the Doppler dimension matrix through pulse dimension FFT processing That is, we get the distance Doppler matrix

[0095]

[0096] in, is the Doppler compensation vector, fftshift represents the cyclic shift of the sequence by half the length of the FFT point number M;

[0097] Step (3): Obtain a direct clutter region matrix that does not change with the distance sampling unit

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

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

[0100]

[0101] in, represents rounding up, D represents the aperture length of the antenna, v p represents the speed of the carrier, β is the beam pointing cone angle, and α is the angle between the beam and the speed, see Figure 2 ;

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

[0103]

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

[0105] Step (4): The corresponding elements of the straight clutter area in the matrix are set to zero to obtain the curved clutter area matrix

[0106] Step (5): Matrix of curved clutter regions Doppler compensation is performed to obtain

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

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

[0109]

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

[0111] Step (5b): The Doppler Transform to pulse dimension matrix Y through IFFT W :

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

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

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

[0115]

[0116] in,

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

[0118]

[0119] in,

[0120] Step (6): The straight clutter area matrix and the curved clutter area matrix after Doppler compensation are integrated to realize clutter compensation based on partition processing:

[0121]

[0122] In summary, the partition-based airborne radar clutter compensation method of the above embodiment first constructs a pulse distance two-dimensional matrix of M pulses and N distance sampling units, and then corrects the Doppler center to zero Doppler located at the center of the Doppler channel number through Doppler center estimation, compensation and Fourier transform; separates the straight clutter area by estimating the Doppler center bandwidth; straightens the curved clutter area by compensating the residual Doppler of the curved clutter; and finally recombines the two areas to obtain a clutter compensation result, thereby reducing the complexity of subsequent clutter suppression and target detection.

[0123] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A partition-based airborne radar clutter compensation method, characterized in that: The following steps are involved: S1: Construct an M×N dimensional complex echo data matrix model X of M pulses and N range sampling units; S2: Calculate the Doppler center frequency of the main clutter based on the carrier inertial navigation information and correct it to obtain the range Doppler dimension matrix S3: Calculate the number of Doppler units in the direct clutter area and obtain the direct clutter area matrix that does not change with the distance sampling unit. S4: The distance Doppler matrix The corresponding elements of the straight clutter region are set to zero to obtain the curved clutter region matrix S5: Bend clutter area matrix Doppler compensation is performed to obtain S6: Combine the straight clutter area matrix and the curved clutter area matrix after Doppler compensation The synthesis is performed to realize clutter compensation based on partition processing.

2. The method for airborne radar clutter compensation based on partition according to claim 1, characterized in that: In step S1, the specific processing process is as follows: S11: Model the echo signal of the mth pulse and the nth range sampling unit as follows: Where f0 is the radar operating center frequency, T r is the pulse repetition period, is the distance fuzzy cycle, c is the electromagnetic wave propagation speed, p is the number of fuzzy cycles, P is the maximum number of fuzzy cycles, a(·) represents the scattering intensity, R np (mT r ) represents the distance of the target at the mth pulse in the nth distance sampling unit and pth fuzzy period, f d (r) represents the Doppler frequency at distance r; S12: The echoes of M pulses and N range sampling units are constructed in the form of a matrix, that is, a complex echo data matrix model X is obtained: X=S+Γ=[X1,X2,…,X n ,…,X N ] Among them, S is the echo signal, Γ is M×N Gaussian white noise, X n =[x 1n ,x 2n ,...,x Mn ] T , n=1,2,...,N is the column vector of the matrix model X.

3. The method for airborne radar clutter compensation based on partition according to claim 2, characterized in that: In step S2, the specific processing process is as follows: S21: Calculate the Doppler center frequency F of the long-range main clutter based on the carrier inertial navigation information dc : Among them, v p is the speed of the carrier, 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: Move the main clutter to the zero Doppler channel and convert it to the Doppler dimension matrix through pulse dimension FFT processing That is, we get the distance Doppler matrix in, is the Doppler compensation vector, and fftshift represents a cyclic shift of the sequence by half the length of the FFT point number M.

4. The method for airborne radar clutter compensation based on partition according to claim 3, characterized in that: In step S22, the specific processing process 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, is the matrix X rd The element in the mth row and nth column of ; S223: Obtain the Doppler channel with the maximum energy based on the Doppler dimension energy distribution S224: Then get the corrected Doppler center frequency Where q = int(F dc T r ) is the number of ambiguity cycles calculated based on the Doppler center frequency estimated from the airborne inertial navigation information.

5. The method for airborne radar clutter compensation based on partition according to claim 4, characterized in that: In step S3, the specific processing process is as follows: S31: Calculate the number of Doppler cells in the straight clutter area: in, represents rounding up, D represents the aperture length of the antenna, v p represents the speed of the carrier, β is the beam pointing cone angle, and α is the angle between the beam and the speed; S32: Construct the direct clutter region matrix: Where ca = M / 2, Representation Matrix The row vector consisting of the m-th row elements of .

6. The method for airborne radar clutter compensation based on partition according to claim 5, characterized in that: In step S5, the specific processing process is as follows: S51: Calculate the Doppler value of each range sampling unit: in, is the azimuth angle, ψ is the angle between the antenna axis and the velocity, β is the beam pointing cone angle, θ(n) is the ground grazing angle corresponding to the nth range sampling unit, f s is the sampling frequency, H is the height of the carrier aircraft; S52: Doppler Transform to pulse-dimensional matrix Y through IFFT W : in, For the matrix A vector consisting of the elements in the nth column of ; S53: Perform Doppler bending compensation on each range sampling unit to obtain a matrix in, S54: Transform the compensated bending clutter region matrix into the Doppler dimension to obtain a matrix in, 7. The method for airborne radar clutter compensation based on partition according to claim 6, characterized in that: In step S6, the clutter compensation method based on partition processing is as follows:

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