Matching scene clutter characteristic fine processing method based on space-based double-station detection

Abstract

The invention discloses a matching scene clutter characteristic fine processing method based on space-based double-station detection, and the method comprises the steps: obtaining the spatial frequency and Doppler frequency of each sampling point on a to-be-compensated double-station distance ring of a current wave position, and evaluating the space-time distribution difference of the current wave position; judging whether the current wave position space-time distribution difference meets a preset requirement or not; if the preset requirement is met, clutter echo data are obtained, a compensation matrix of each bistatic distance ring is constructed, the clutter echo data are compensated distance by distance, and compensated clutter echo data are obtained; if the preset requirement is not met, clutter echo data are obtained, a space-time interpolation method is adopted, a compensation matrix of each bistatic distance ring is constructed, the clutter echo data are compensated distance by distance, and the compensated clutter echo data are obtained; and according to the compensated clutter echo data, calculating a clutter covariance matrix of the to-be-compensated bistatic distance ring of the current wave position. According to the invention, partition fine processing can be realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of signal processing, and particularly relates to a method for refined processing of clutter characteristics of a matching scene based on space-based bistatic detection. Background Technique

[0002] When the velocities of the transmitting and receiving platforms of a bistatic radar relative to the ground are both large, the Doppler frequency of the clutter is no longer determined only by the receiving platform, but is jointly modulated by the transmitting and receiving platforms. However, the spatial frequency is still determined only by the spatial cone angle of the receiving array surface. This difference causes the equal-Doppler lines and the equal-receiving spatial cone angle lines not to coincide. In a bistatic configuration and observation area with strong range dependence of clutter, the independent and identically distributed (IID) characteristics of samples are destroyed. If the sample data of adjacent range rings around the bistatic range ring to be detected are directly used to estimate the clutter covariance matrix, inaccurate estimation will occur, resulting in wide and shallow filtering notches, thus significantly reducing the performance of space-time adaptive processing (STAP).

[0003] Existing commonly used range-dependent clutter spectrum compensation methods include Doppler Warping (DW) method, Angle-Doppler Compensation (ADC) method, Adaptive Angle-Doppler Compensation (A2DC) method, and Space-Time Interpolation (STINT) method, etc. The DW method translates the space-time spectrum center of each range ring along the Doppler direction to the Doppler center of the bistatic range ring to be detected. Since only the Doppler frequency center of each range ring is compensated, when the spatial frequency centers of different range rings differ greatly, the method faces failure. The ADC method and the A2DC method compensate the spatial frequency center along the spatial frequency direction on the basis of compensating the Doppler frequency center of each range ring. However, when the clutter space-time distributions of different range rings differ greatly, the curved clutter spectra of the sidelobes cannot be effectively compensated. The STINT method uses the mapping relationship between the space-time spectra of each bistatic range ring and the range ring to be detected for compensation. In theory, it can achieve complete compensation of the clutter spectrum, but it has a high computational complexity and high requirements for parameter accuracy. When the space-time distributions of the bistatic range rings differ slightly, there is an over-interpolation problem.

[0004] In summary, on the one hand, the prior art is significantly affected by the bistatic configuration and the observation area. There are large differences in clutter distribution and processing at different wave positions. Performing the same processing on different wave positions will not only increase the difficulty but may even make it impossible to detect effective targets. On the other hand, the prior art has a serious problem of bistatic clutter distance dependence when performing multi-sample clutter suppression. In addition, the existing method for dividing scattering units of clutter signals in space-based bistatic systems uses a uniform division method, ignoring the influence of resolution space variability. In areas where the Doppler resolution deteriorates severely, different receiving space cone angles may correspond to the same Doppler resolution unit. If the resolution is not considered, it will affect the accuracy of analyzing the clutter characteristics of spaceborne bistatic radars. Therefore, it is urgent to improve the above-mentioned defects existing in the prior art. Summary of the Invention

[0005] To solve the above problems existing in the prior art, the present invention provides a method for fine processing of clutter characteristics in a matching scenario based on space-based bistatic detection. The technical problems to be solved by the present invention are achieved through the following technical solutions:

[0006] In the first aspect, the present invention provides a method for fine processing of clutter characteristics in a matching scenario based on space-based bistatic detection, including:

[0007] Obtain the spatial frequency and Doppler frequency of each sampling point on the bistatic distance ring to be compensated at the current wave position, and evaluate the spatio-temporal distribution difference at the current wave position;

[0008] Determine whether the spatio-temporal distribution difference at the current wave position meets the preset requirements;

[0009] If the preset requirements are met, obtain the clutter echo data, calculate the interference phase between the clutter echo data in the range-Doppler domain after pulse compression of each spatial channel and the reference spatial channel; perform a discrete Fourier transform on the complex exponential of the interference phase along the range direction, estimate the interference phase slope according to the transform result, and calculate the interference phase compensation function; construct a compensation matrix for each bistatic distance ring according to the interference phase compensation function, and compensate the clutter echo data distance by distance to obtain the compensated clutter echo data;

[0010] If the preset requirements are not met, obtain the clutter echo data, use the spatio-temporal interpolation method to construct a compensation matrix for each bistatic distance ring, and compensate the clutter echo data distance by distance to obtain the compensated clutter echo data;

[0011] Calculate the clutter covariance matrix of the bistatic distance ring to be compensated at the current wave position according to the compensated clutter echo data.

[0012] Advantages of the present invention:

[0013] A refined processing method for clutter characteristics of a matching scenario based on space-based bistatic detection provided by the present invention uses prior information to calculate the spatial frequency differences corresponding to the same Doppler frequency on the minimum bistatic distance ring and the reference bistatic distance ring, and between the reference bistatic distance ring and the maximum bistatic distance ring to evaluate the magnitude of the spatio-temporal distribution difference of the current wave position, and then performs zoning processing to improve the clutter suppression efficiency. For wave positions with small spatio-temporal distribution differences, calculate the interference phase between the clutter data in the range-Doppler domain after pulse compression of the reference spatial channel and other spatial channels, perform discrete Fourier transform along the range direction, estimate the interference phase slope, calculate the compensation functions for different channels and ranges, construct a spatio-temporal compensation matrix, and compensate the clutter echo data distance by distance; for wave positions with large spatio-temporal distribution differences, use the spatio-temporal interpolation method to construct a compensation matrix, compensate the clutter echo data distance by distance, and finally calculate the clutter covariance matrix of the distance ring to be detected to achieve refined zoning processing.

[0014] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Description of the Drawings

[0015] Figure 1 is a flowchart of a refined processing method for clutter characteristics of a matching scenario based on space-based bistatic detection provided by an embodiment of the present invention;

[0016] Figure 2 is another flowchart of a refined processing method for clutter characteristics of a matching scenario based on space-based bistatic detection provided by an embodiment of the present invention;

[0017] Figure 3 is a schematic diagram of the relative relationship and observation area of any orbital plane configuration provided by an embodiment of the present invention;

[0018] Figure 4 is a schematic diagram of the distribution curve of the spatio-temporal spectrum of different bistatic distance rings when the spatio-temporal difference of the wave position is small under any orbital plane configuration provided by an embodiment of the present invention;

[0019] Figures 5(a) to 5(d) is a schematic diagram of the spatio-temporal spectrum when the spatio-temporal difference of the wave position is small under any orbital plane configuration provided by an embodiment of the present invention;

[0020] Figures 6(a) to 6(d) is a schematic diagram of the output SCNR loss curve when the spatio-temporal difference of the wave position is small under any orbital plane configuration provided by an embodiment of the present invention;

[0021] Figure 7 is a schematic diagram of the distribution curve of the spatio-temporal spectrum of different bistatic distance rings when the spatio-temporal difference of the wave position is large under any orbital plane configuration provided by an embodiment of the present invention;

[0022] Figures 8(a) to 8(d)It is a schematic diagram of the spatio-temporal spectrum when the spatio-temporal difference of wave positions is large under any orbital plane configuration provided by the embodiments of the present invention;

[0023] Figures 9(a) to 9(d) It is a schematic diagram of the output SCNR loss curve when the spatio-temporal difference of wave positions is large under any orbital plane configuration provided by the embodiments of the present invention. Detailed implementation manners

[0024] The present invention will be further described in detail below in conjunction with specific embodiments, but the implementation manners of the present invention are not limited thereto.

[0025] In view of the defects existing in the prior art, the present invention proposes a refined processing method for clutter characteristics of a matching scenario based on spaceborne bistatic detection. Aiming at the spatio-temporal distribution differences in different scenarios of the spaceborne bistatic system, it alleviates the problems of operation redundancy and over-interpolation existing in the use of spatio-temporal interpolation methods when the spatio-temporal distribution differences in the bistatic range ring are small, reduces the influence of clutter range dependence, effectively increases the number of IID samples, and further realizes a better clutter suppression effect.

[0026] Please refer to Figure 1 and Figure 2 , Figure 1 It is a flowchart of a refined processing method for clutter characteristics of a matching scenario based on spaceborne bistatic detection provided by the embodiments of the present invention, Figure 2 It is another flowchart of a refined processing method for clutter characteristics of a matching scenario based on spaceborne bistatic detection provided by the embodiments of the present invention. A refined processing method for clutter characteristics of a matching scenario based on spaceborne bistatic detection provided by the present invention includes:

[0027] S101. Obtain the spatial frequency and Doppler frequency of each sampling point on the bistatic range ring to be compensated for the current wave position, and evaluate the spatio-temporal distribution difference of the current wave position.

[0028] Specifically, in this embodiment, it includes:

[0029] According to prior information, obtain the Doppler frequencies on the minimum bistatic range ring, reference bistatic range ring, and maximum bistatic range ring, and draw the distribution curve (Direction-Doppler Curve, DD-Curve) of the spatio-temporal spectrum of the current wave position;

[0030] Within the common Doppler frequency range (f dmin , f dmax ) of the minimum bistatic range ring, reference bistatic range ring, and maximum bistatic range ring, equally spaced take the Doppler frequencies f d,1 , f d,2 ... f d,M of M sampling points;

[0031] Based on M sampling points, calculate the spatial frequency difference Δcosψ′ corresponding to the same Doppler frequency on the reference bistatic range ring and the minimum bistatic range ring. R , which is expressed as:

[0032] Δcosψ′ R = [Δcosψ′ R (f d,1 ),... Δcosψ′ R (f d,m ),... Δcosψ′ R (f d,M )];

[0033] Δcosψ′ R,m = |cosψ R,ref (f d,m ) - cosψ R,min (f d,m )|;

[0034] Among them, Δcosψ′ R,m represents the spatial frequency difference corresponding to the Doppler frequency f d,m on the reference bistatic range ring and the minimum bistatic range ring, cosψ R,ref (f d,m ) represents the spatial frequency corresponding to the Doppler frequency f d,m on the reference bistatic range ring, and cosψ R,min (f d,m ) represents the spatial frequency corresponding to the Doppler frequency f d,m on the minimum bistatic range ring;

[0035] Based on M sampling points, calculate the spatial frequency difference Δcosψ″ corresponding to the same Doppler frequency on the reference bistatic range ring and the maximum bistatic range ring. R , which is expressed as:

[0036] Δcosψ″ R = [Δcosψ″ R (f d,1 ),... Δcosψ″ R (f d,m ),... Δcosψ″ R (f d,M )];

[0037] Δcosψ′ R,m = |cosψ R,ref (f d,m ) - cosψ R,max (f d,m )|;

[0038] Among them, Δcosψ′ R,mDenote the Doppler frequency \(f\) on the reference bistatic range ring and the maximum bistatic range ring d,m The corresponding spatial frequency difference, \(\cos\psi\) R,ref (\(f\) d,m ) denotes the Doppler frequency \(f\) on the reference bistatic range ring d,m The corresponding spatial frequency, \(\cos\psi\) R,min (\(f\) d,m ) denotes the Doppler frequency \(f\) on the maximum bistatic range ring d,m The corresponding spatial frequency;

[0039] Calculate the variance \(\sigma_{\Delta\cos\psi'}\) of the spatial frequency difference \(\Delta\cos\psi'\) corresponding to the same Doppler frequency on the reference bistatic range ring and the minimum bistatic range ring R of 2 ', expressed as:

[0040]

[0041] Calculate the variance \(\sigma_{\Delta\cos\psi''}\) of the spatial frequency difference \(\Delta\cos\psi''\) corresponding to the same Doppler frequency on the reference bistatic range ring and the maximum bistatic range ring R of 2″ , expressed as:

[0042]

[0043] Take the variance \(\sigma_{\Delta\cos\psi'}\) 2 and the variance \(\sigma_{\Delta\cos\psi''}\) 2 as the space-time distribution difference of the current wave position.

[0044] Optionally, in this embodiment, the spatial frequencies and normalized Doppler frequencies of the minimum, reference, and maximum bistatic range rings obtained a priori can also be used to draw their DD-Curve, calculate the spatial frequency difference \(\Delta\cos\psi\) R corresponding to the same Doppler frequency, and use the fluctuation of \(\Delta\cos\psi\) R to evaluate the size of the space-time distribution difference of the current wave position. The size of the space-time distribution difference of the current wave position can be directly evaluated by using the difference between the spatial frequencies and the normalized Doppler frequency centers in the echo data of different range rings in the echo data.

[0045] S102. Determine whether the space-time distribution difference of the current wave position meets the preset requirements.

[0046] Specifically, in this embodiment, determine whether the variance \(\sigma_{\Delta\cos\psi'}\) 2′ and the variance \(\sigma_{\Delta\cos\psi''}\) 2″ are both less than the reference value If both are less than, it meets the preset requirements, that is, the clutter space-time distribution difference of this wave position is small; otherwise, it does not meet the preset requirements, that is, the clutter space-time distribution difference of this wave position is large.

[0047] S103. If the preset requirements are met, obtain the clutter echo data, calculate the interference phase between the clutter echo data in the range-Doppler domain after pulse compression of each spatial channel and the reference spatial channel; perform a discrete Fourier transform on the complex exponent of the interference phase along the range direction, estimate the interference phase slope according to the transform result, and calculate the interference phase compensation function; construct the compensation matrix for each bistatic range ring according to the interference phase compensation function, and compensate the clutter echo data distance by distance to obtain the compensated clutter echo data.

[0048] Specifically, in this embodiment, the interference phase between the clutter echo data in the range-Doppler domain after pulse compression of each spatial channel and the reference spatial channel is expressed as:

[0049] U = {U2, U3, …, U N};

[0050] where U n represents the interference phase matrix of the nth spatial channel (n > 1) relative to the reference spatial channel, with dimensions of L num ×K. Optionally, the reference spatial channel is the first spatial channel, expressed as:

[0051]

[0052] where x n (l, k) represents the clutter echo data of the nth spatial channel, the lth bistatic range ring, and the kth Doppler channel, [·] * represents taking the conjugate of a complex number, and angle(·) represents taking the phase angle of a complex number. N represents the total number of spatial channels.

[0053] In this embodiment, perform a discrete Fourier transform (DFT) on the complex exponent of the interference phase along the range direction:

[0054]

[0055] where f n,k (j) is the result after the discrete Fourier transform. L represents the number of bistatic range rings to be compensated. f n,k represents the range-direction interference phase frequency of the nth spatial channel and the kth Doppler channel, and exp(ju n (l, k)) represents the complex exponent of the interference phase.

[0056] In this embodiment, according to the transform result, estimate the interference phase slope and calculate the interference phase compensation function, including:

[0057] Estimate the interference phase slope f n,k,ML , expressed as:

[0058]

[0059] According to the interference phase slope, obtain the interference phase compensation function Δf of the clutter echo data for the nth spatial channel, the lth bistatic range bin, and the kth Doppler channel, expressed as: n (l,k),

[0060] Δf n (l,k) = exp(j2πf n,k,ML (l ref -l));

[0061] where l ref represents the subscript of the reference bistatic range bin.

[0062] In this embodiment, according to the interference phase compensation function, construct the compensation matrix for each bistatic range bin, and compensate the clutter echo data distance by distance to obtain the compensated clutter echo data, including:

[0063] According to the interference phase compensation function, construct the spatial domain compensation matrix T for the lth bistatic range bin and the kth Doppler channel, expressed as: l,k ,

[0064]

[0065] According to the spatial domain compensation matrix T for the lth bistatic range bin and the kth Doppler channel l,k , construct the spatio-temporal compensation matrix T l , expressed as:

[0066]

[0067] x l ′ = T l x l ;

[0068] where T l represents the compensation matrix for the lth bistatic range bin, x l represents the clutter echo data, and x′ represents the compensated clutter echo data, and their dimensions are all NK×1.

[0069] S104. If the preset requirements are not met, obtain the clutter echo data, use the spatio-temporal interpolation method, construct the compensation matrix for each bistatic range bin, and compensate the clutter echo data distance by distance to obtain the compensated clutter echo data.

[0070] Specifically, in this embodiment, it includes:

[0071] Obtain the spatial frequency α and the normalized Doppler frequency of the N sampling points on the lth bistatic range bin, respectively expressed as:

[0072]

[0073] Among them, represents the spatial frequency of the i-th sampling point on the l-th bistatic range ring, represents the normalized Doppler frequency of the i-th sampling point on the l-th bistatic range ring;

[0074] Among them, N α spatial frequencies of sampling points and the normalized Doppler frequencies are respectively expressed as:

[0075]

[0076] Obtain the spatio-temporal steering matrix S of the reference bistatic range ring l and the spatio-temporal steering matrix S of the l-th bistatic range ring ref , which are respectively expressed as:

[0077]

[0078] According to the spatio-temporal steering matrix S of the reference bistatic range ring l and the spatio-temporal steering matrix S of the l-th bistatic range ring ref , describe the optimization problem; by solving the optimization problem, obtain the compensation matrix T of the l-th bistatic range ring l , which is expressed as:

[0079]

[0080] Among them, ||·|| F represents the Frobenius norm of the matrix, represents the conjugate transpose of the compensation matrix T l , I NK represents the NK-dimensional identity matrix, and the optimization problem is expressed as:

[0081]

[0082] Among them, and are both non-negative. Minimizing is equivalent to maximizing represents the conjugate transpose of the spatio-temporal steering matrix S ref , represents the conjugate transpose of the spatio-temporal steering matrix S l . Perform singular value decomposition on , which is expressed as:

[0083]

[0084] Among them, UZV H represents the result of singular value decomposition, U represents a unitary matrix, and its column vectors are the eigenvectors of the matrix ; Z represents a diagonal matrix, and the elements on its diagonal are the singular values of the matrix ; V represents a unitary matrix, and its column vectors are the eigenvectors of the matrix .

[0085] There is an inequality, expressed as:

[0086]

[0087] Among them, is a unitary matrix, and its diagonal elements are all less than or equal to 1; when , obtains the maximum value, and the compensation matrix T l of the l-th bistatic range ring is expressed as:

[0088] T l =UV H .

[0089] S105. Calculate the clutter covariance matrix of the bistatic range ring to be compensated at the current waveform position according to the compensated clutter echo data.

[0090] Specifically, in this embodiment, the clutter covariance matrix of the bistatic range ring to be compensated at the current waveform position is expressed as:

[0091]

[0092] Among them, x l represents the clutter echo data, x' represents the compensated clutter echo data, and T l represents the compensation matrix of the l-th bistatic range ring.

[0093] Optionally, in this embodiment, full-dimensional Doppler processing is used in space-time adaptive processing. Post-Doppler processing can be selected. After localizing the Doppler channels to the Doppler channel where the target is located and its adjacent m-1 channels, unified equalization main direction compensation is utilized.

[0094] In summary, the present invention adopts a refined processing method that matches the clutter characteristics in a space-based bistatic detection system. Aiming at the spatio-temporal distribution differences of the space-based bistatic system in different scenarios, it alleviates the problems of operation redundancy and over-interpolation existing when using the space-time interpolation method when the spatio-temporal distribution difference of the bistatic range ring is small, reduces the influence of clutter range dependence, effectively increases the number of IID samples, and thus achieves a better clutter suppression effect.

[0095] The present invention utilizes prior information to calculate the spatial frequency differences corresponding to the same Doppler frequency on the minimum bistatic distance ring and the reference bistatic distance ring, and between the reference bistatic distance ring and the maximum bistatic distance ring to evaluate the difference in the spatio-temporal distribution of the current wave position. Then, partition processing is performed to improve the clutter suppression efficiency. For wave positions with small spatio-temporal distribution differences, taking the first spatial channel as a reference, the interference phase between the clutter data in the range-Doppler domain after pulse compression of this spatial channel and other spatial channels is calculated, and discrete Fourier transform is performed along the range direction to estimate the interference phase slope, calculate the compensation functions for different channels and ranges, construct a spatio-temporal compensation matrix, and compensate the clutter echo data distance by distance; for wave positions with large spatio-temporal distribution differences, a compensation matrix is constructed using the spatio-temporal interpolation method, and the clutter echo data is compensated distance by distance. Finally, the clutter covariance matrix of the distance ring to be detected is calculated to achieve refined partition processing.

[0096] In an optional embodiment of the present invention, the effect of the refined processing method for clutter characteristics in a matching scenario based on spaceborne bistatic detection provided in the above embodiment is verified through simulation experiments. Specifically:

[0097] I. Simulation conditions

[0098] The simulation experiment includes an observation scenario for the performance of the method in the configuration of an arbitrary orbital plane of a spaceborne bistatic radar. The detailed parameters are shown in Table 1.

[0099] Table 1 Simulation parameters for the configuration of an arbitrary orbital plane of a spaceborne bistatic radar

[0100]

[0101]

[0102] II. Simulation content and result analysis

[0103] Simulation content:

[0104] In this embodiment, the above refined processing method for clutter characteristics in a matching scenario based on the spaceborne bistatic detection system is used to perform simulation of range-dependent clutter spectrum compensation for an arbitrary orbital plane configuration of a spaceborne bistatic radar.

[0105] Result analysis I:

[0106] Please refer to Figure 3 ~Fig. 6, Figure 3 which is a schematic diagram of the relative relationship of an arbitrary orbital plane configuration and the observation area provided by the embodiment of the present invention, Figure 4 and is a schematic diagram of the distribution curve of the spatio-temporal spectrum of different bistatic distance rings when the spatio-temporal difference of the wave position is small in the arbitrary orbital plane configuration provided by the embodiment of the present invention. Figures 5(a) to 5(d)It is a schematic diagram of the spatio-temporal spectrum when the spatio-temporal difference of wave positions is small under any orbital plane configuration provided by the embodiments of the present invention. 5(a) Before compensation, 5(b) OPT, 5(c) STINT, 5(d) Guided equalization method. Figures 6(a) to 6(d) It is a schematic diagram of the output SCNR loss curve when the spatio-temporal difference of wave positions is small under any orbital plane configuration provided by the embodiments of the present invention. 6(a) Before compensation, 6(b) OPT, 6(c) STINT, 6(d) Guided equalization method.

[0107] Figure 3 The minimum, beam center, and maximum bistatic distance rings are plotted in it, which are represented by red, blue, and green lines respectively in the figure, and their sum of bistatic distances is 4000 km, 4400 km, and 4800 km respectively.

[0108] Figure 4 The DDCurve characteristics of the bistatic distance rings corresponding to the minimum, maximum, and beam center positions in the observation area are analyzed. Among them, the minimum bistatic distance is 4000 km, the maximum bistatic distance is 4400 km, and the bistatic distance at the beam center is 4800 km.

[0109] In Fig. 5, under any orbital plane configuration, the distance dependence of clutter is extremely significant, resulting in a large increase in the spatio-temporal spectrum broadening range. The problem of clutter ridge broadening is prominent before compensation. The clutter ridge is sharp in the OPT case. In the STINT method, the compensation result is relatively ideal, but this method involves matrix decomposition, has a high computational complexity, and depends on the accuracy of prior information. The guided equalization unified compensation method proposed in this paper can still achieve a spatio-temporal spectrum compensation effect close to the theoretical value even under strong distance dependence conditions when the spatio-temporal difference of wave positions is small, showing strong adaptability and stability.

[0110] In Fig. 6, the SCNR loss performance is relatively poor before compensation. The guided equalization unified compensation method proposed in this paper shows excellent performance and can effectively meet the clutter suppression requirements in complex scenarios.

[0111] Result analysis two:

[0112] Please refer to Figure 7 ~Fig. 9, Figure 7 It is a schematic diagram of the distribution curve of the spatio-temporal spectrum of different bistatic distance rings when the spatio-temporal difference of wave positions is large under any orbital plane configuration provided by the embodiments of the present invention. Figures 8(a) to 8(d) It is a schematic diagram of the spatio-temporal spectrum when the spatio-temporal difference of wave positions is large under any orbital plane configuration provided by the embodiments of the present invention. 8(a) Before compensation, 8(b) OPT, 8(c) STINT, 8(d) Guided equalization method. Figures 9(a) to 9(d)It is a schematic diagram of the output SCNR loss curve when the space-time difference of wave positions is large under any orbital plane configuration, 9(a) before compensation, 9(b) OPT, 9(c) STINT, 9(d) guiding equalization method.

[0113] Figure 7 The DDCurve characteristics of the bistatic range rings corresponding to the minimum, maximum, and beam center positions in the observation area are analyzed. Among them, the minimum bistatic range is 4000 km, the maximum bistatic range is 4400 km, and the bistatic range at the beam center is 4800 km. The results show that the DDCurves of different range rings show significant differences, and the clutter characteristics change violently with the range.

[0114] Figure 8 Under any orbital plane configuration, the range dependence of clutter is extremely significant, resulting in a large increase in the space-time spectrum broadening range. The problem of clutter ridge broadening is prominent before compensation. The clutter ridge is sharp in the OPT case. The unified compensation method of guiding equalization proposed in this paper has a poor space-time spectrum compensation effect under the condition of large space-time distribution differences. Under the STINT method, a space-time spectrum compensation effect close to the theoretical value can be achieved.

[0115] Figure 9 The SCNR loss performance is relatively poor before compensation. The STINT method shows excellent performance and can effectively meet the clutter suppression requirements in complex scenarios.

[0116] It can be seen from the simulation experiment results that when the space-time distribution difference of the current wave position is small, the unified compensation method of guiding equalization proposed in the present invention is used to compensate through clutter echo data, which does not depend on the accuracy of prior information and has better stability and engineering applicability. When the space-time distribution difference of the current wave position is large, the space-time interpolation method can achieve a space-time spectrum compensation effect closer to the theoretical value compared with the guiding equalization method. Therefore, zoning processing according to the space-time distribution difference of wave positions has better practicability.

[0117] It should be noted that in this text, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprising", "including" or any other variant are intended to cover non-exclusive inclusion, so that an article or device comprising a series of elements not only includes those elements, but also includes other elements not expressly listed. Without further limitation, an element defined by the statement "comprising an..." does not exclude the presence of additional identical elements in the article or device comprising the element. Words such as "connected" or "coupled" are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. The orientation or positional relationship indicated by "above", "below", "left", "right", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as a limitation on the present invention.

[0118] In the description of this specification, the description with reference to terms such as "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine the different embodiments or examples described in this specification.

[0119] The above content is a further detailed description of the present invention in combination with specific preferred embodiments, and it cannot be determined that the specific implementation of the present invention is only limited to these descriptions. For those of ordinary skill in the technical field to which the present invention pertains, without departing from the concept of the present invention, several simple deductions or substitutions can be made, and all should be regarded as belonging to the protection scope of the present invention.

Claims

1. A refined processing method for clutter characteristics of a matching scenario based on space-based bistatic detection, characterized in that Including: Obtain the spatial frequency and Doppler frequency of each sampling point on the bistatic range ring to be compensated for the current beam position, and evaluate the spatio-temporal distribution difference of the current beam position; Judge whether the spatio-temporal distribution difference of the current beam position meets the preset requirements; If the preset requirements are met, obtain the clutter echo data, calculate the interference phase between the clutter echo data in the range-Doppler domain after pulse compression of each spatial channel and the reference spatial channel; perform a discrete Fourier transform on the complex exponential of the interference phase along the range direction, estimate the interference phase slope according to the transform result, and calculate the interference phase compensation function; construct a compensation matrix for each bistatic range ring according to the interference phase compensation function, and compensate the clutter echo data distance by distance to obtain the compensated clutter echo data; If the preset requirements are not met, obtain the clutter echo data, use the spatio-temporal interpolation method to construct a compensation matrix for each bistatic range ring, and compensate the clutter echo data distance by distance to obtain the compensated clutter echo data; Calculate the clutter covariance matrix of the bistatic range ring to be compensated for the current beam position according to the compensated clutter echo data.

2. The refined processing method for clutter characteristics of a matching scenario based on space-based bistatic detection according to claim 1, wherein The obtaining the spatial frequency and Doppler frequency of each sampling point on the bistatic range ring to be compensated for the current beam position, and evaluating the spatio-temporal distribution difference of the current beam position includes: Obtain the Doppler frequencies on the minimum bistatic range ring, the reference bistatic range ring and the maximum bistatic range ring, and draw the distribution curve of the spatio-temporal spectrum of the current beam position; The common Doppler frequency range (f dmin , f dmax ) on the minimum bistatic distance ring, the reference bistatic distance ring, and the maximum bistatic distance ring, take M sampling points of Doppler frequency f d,1 , f d,2 … f d,M at equal intervals; Based on M sampling points, calculate the spatial frequency difference Δcosψ′ corresponding to the same Doppler frequency on the reference bistatic range ring and the minimum bistatic range ring, which is expressed as: R , which is expressed as: Δcosψ′ R =[Δcosψ′ R (f d,1 ),...Δcosψ′ R (f d,m ),...Δcosψ′ R (f d,M )]; Δcosψ′ R,m = |cosψ R,ref (f d,m ) - cosψ R,min (f d,m )|; where, Δcosψ′ R,m represents the spatial frequency difference corresponding to the Doppler frequency f d,m on the reference bistatic range ring and the minimum bistatic range ring, and cosψ R,ref (f d,m ) represents the spatial frequency corresponding to the Doppler frequency f d,m on the reference bistatic range ring, and cosψ R,min (f d,m ) represents the spatial frequency corresponding to the Doppler frequency f d,m on the minimum bistatic range ring; Based on M sampling points, calculate the spatial frequency difference Δcosψ″ corresponding to the same Doppler frequency on the reference bistatic range ring and the maximum bistatic range ring, expressed as: R , expressed as: Δcosψ″ R = [Δcosψ″ R (f d,1 ),...Δcosψ″ R (f d,m ),...Δcosψ″ R (f d,M )]; Δcosψ′ R,m = |cosψ R,ref (f d,m ) - cosψ R,max (f d,m )|; where, Δcosψ′ R,m represents the spatial frequency difference corresponding to the Doppler frequency f d,m on the reference bistatic range ring and the maximum bistatic range ring, and cosψ R,ref (f d,m ) represents the spatial frequency corresponding to the Doppler frequency f d,m on the reference bistatic range ring, and cosψ R,min (f d,m ) represents the spatial frequency corresponding to the Doppler frequency f d,m on the maximum bistatic range ring; Calculate the spatial frequency difference Δcosψ′ corresponding to the same Doppler frequency on the calculated reference bistatic range ring and the minimum bistatic range ring R of the variance σ 2 ′, expressed as: Calculate the spatial frequency difference Δcosψ″ corresponding to the same Doppler frequency on the computational reference bistatic range ring and the maximum bistatic range ring R of the variance σ 2″ , expressed as: Take the variance σ 2′ and the variance σ 2″ as the difference in the spatio-temporal distribution of the current wave position.

3. The refined processing method for clutter characteristics of a matching scenario based on space-based bistatic detection according to claim 2, wherein The judging whether the spatio-temporal distribution difference of the current beam position meets the preset requirements includes: Judge the variance σ 2′ and the variance σ 2″ whether they are both less than the reference value If both are less than, the preset requirements are met; otherwise, the preset requirements are not met.

4. The refined processing method for clutter characteristics of a matching scenario based on space-based bistatic detection according to claim 1, characterized in that The interference phase between the clutter echo data in the range-Doppler domain after pulse compression of each spatial channel and the reference spatial channel is expressed as: U = {U2, U3, …, U N}; Among them, U n represents the interference phase matrix of the nth spatial channel relative to the reference spatial channel, with dimensions of L num ×K, expressed as: where x n (l,k) represents the clutter echo data of the nth spatial channel, the lth bistatic range bin, and the kth Doppler channel, [·] * denotes taking the conjugate of a complex number, angle(·) denotes taking the phase angle of a complex number, and N denotes the total number of spatial channels.

5. The refined processing method for clutter characteristics of a matching scenario based on space-based bistatic detection according to claim 1, characterized in that Perform a discrete Fourier transform on the complex exponential of the interference phase along the range direction: Among them, f n,k (j) is the result after discrete Fourier transform. L represents the number of bistatic range rings to be compensated. f n,k represents the range - direction interference phase frequency of the nth spatial channel and the kth Doppler channel. exp(ju n (l,k)) represents the complex exponential of the interference phase.

6. The refined processing method for clutter characteristics of a matching scenario based on space-based bistatic detection according to claim 1, characterized in that According to the transform result, estimating the interference phase slope and calculating the interference phase compensation function includes: Estimate the interference phase slope f n,k,ML , expressed as: Obtain the interference phase compensation function Δf(l,k) of the clutter echo data of the nth spatial channel, the lth bistatic range bin, and the kth Doppler channel according to the interference phase slope, which is expressed as: n (l,k) Δf n (l,k) = exp(j2πf n,k,ML (l ref -l)); where l ref represents the subscript of the reference bistatic range ring.

7. The refined processing method for clutter characteristics of a matching scenario based on space-based bistatic detection according to claim 1, wherein Constructing a compensation matrix for each bistatic range ring according to the interference phase compensation function, and compensating the clutter echo data distance by distance to obtain the compensated clutter echo data includes: Construct the spatial compensation matrix \(T\) for the \(l\)-th bistatic range ring and the \(k\)-th Doppler channel according to the interference phase compensation function l,k , which is expressed as: According to the spatial domain compensation matrix T of the l-th bistatic range ring and the k-th Doppler channel l,k , construct the space-time compensation matrix T l , which is expressed as: x l ′ = T l x l ; Among them, T l represents the compensation matrix of the l-th double-base distance ring, and x l represents the clutter echo data, and x' represents the compensated clutter echo data, both with dimensions of NK×1.

8. The refined processing method for clutter characteristics of a matching scenario based on space-based bistatic detection according to claim 1, wherein Using the spatio-temporal interpolation method to construct a compensation matrix for each bistatic range ring, and compensating the clutter echo data distance by distance to obtain the compensated clutter echo data includes: Obtain the spatial frequency and the normalized Doppler frequency of N α sampling points on the l-th bistatic range ring which are respectively expressed as: ​ Among them, represents the spatial frequency of the i-th sampling point on the l-th bistatic range ring, represents the normalized Doppler frequency of the i-th sampling point on the l-th bistatic range ring; Among them, N α spatial frequencies of sampling points and normalized Doppler frequencies are respectively expressed as: Obtain the spatio-temporal steering matrix \(S\) of the reference bistatic range ring l and the spatio-temporal steering matrix \(S\) of the \(l\)-th bistatic range ring ref , which are respectively expressed as: According to the spatio-temporal steering matrix S of the reference bistatic range ring l and the spatio-temporal steering matrix S of the l-th bistatic range ring ref , describe the optimization problem; by solving the optimization problem, obtain the compensation matrix T of the l-th bistatic range ring l , which is expressed as: where, ||·|| F denotes the Frobenius norm of a matrix, denotes the compensation matrix T l of the conjugate transpose, I NK denotes the NK-dimensional identity matrix, and the optimization problem is expressed as: wherein, and are both non - negative, minimizing is equivalent to maximizing denotes the conjugate transpose of the space - time steering matrix S ref and denotes the conjugate transpose of the space - time steering matrix S l Performing singular value decomposition on results in: Among them, UZV H represents the result of singular value decomposition, where U represents a unitary matrix, and its column vectors are the eigenvectors of the matrix , Z represents a diagonal matrix, and the elements on its diagonal are the singular values of the matrix , and V represents a unitary matrix, and its column vectors are the eigenvectors of the matrix ; There is an inequality, expressed as: Among them, is a unitary matrix, and its diagonal elements are all less than or equal to 1; when holds, reaches the maximum value, and the compensation matrix T l of the l-th double-base distance ring has the following expression: T l = UV H .

9. The refined processing method for clutter characteristics of a matching scenario based on space-based bistatic detection according to claim 1, wherein The clutter covariance matrix of the bistatic range cell to be compensated for the current wave position is expressed as: where x l represents clutter echo data, x' represents the compensated clutter echo data, and T l represents the compensation matrix for the l-th bistatic range bin.

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