Passive multi-beam narrow-band detection method under influence of near-field suppression type strong interference

Abstract

The invention relates to the technical field of sonar signal processing, in particular to a passive multi-beam narrow-band detection method under the influence of near-field suppression type strong interference, which quickly realizes the estimation of strong interference distance and direction through multi-scale focusing distance scanning and relying on conventional beam forming with low computational complexity, thereby realizing the correction of a near-field model; according to the passive sonar narrow-band target detection method, strong interference can be effectively suppressed by combining a tolerance interference suppression method and utilizing a corrected focusing steering vector, the influence of near-field strong interference can be well suppressed, and the passive sonar narrow-band target detection efficiency in a near-field strong interference environment can be effectively improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of sonar signal processing, and particularly relates to a passive multi-beam narrowband detection method under the influence of near-field suppressing strong interference. BACKGROUND

[0002] Under the actual underwater acoustic countermeasure interference environment, the detection performance of sonar equipment is sharply reduced, so the target detection technology under the underwater acoustic countermeasure interference gradually becomes one of the focuses in the detection field. The narrowband line spectrum detection is the core feature of the current quiet submarine detection, and the target feature under the current strong interference environment is seriously affected by the interference leakage. The interference suppression method is the main means to solve this problem. However, when the strong interference is located in the near field, the propagation model is mismatched, and the existing interference suppression method loses its spatial filtering performance when the model is mismatched, and the strong interference leakage is still very serious. SUMMARY

[0003] In view of the defects in the prior art, the purpose of the present application is to provide a passive multi-beam narrowband detection method under the influence of near-field suppressing strong interference.

[0004] To achieve the above purpose, the present application provides the following technical scheme: a passive multi-beam narrowband detection method under the influence of near-field suppressing strong interference, the steps of which are as follows:

[0005] (1) First, set the focusing distance scanning interval;

[0006] (2) Calculate the steering vector of different focusing distances, and weight the sonar array data to obtain the multi-focusing distance conventional spatial spectrum estimation result;

[0007] (3) The focusing distance and the direction corresponding to the maximum output energy of the near-field interference are searched to obtain the direction and distance estimation of the near-field interference;

[0008] (4) Then, calculate the interference steering power spectrum density matrix;

[0009] (5) Obtain the tolerant estimation result through feature space processing;

[0010] (6) Use it to construct the interference suppression distance, and perform spatial filtering processing on the sonar array data to obtain the sonar array data after near-field interference suppression;

[0011] (7) Finally, scan the steering vector of the specified focusing distance to obtain the multi-beam time domain data;

[0012] (8) After long-time coherence processing, the multi-beam narrowband detection result is obtained through time-frequency transformation.

[0013] In some embodiments, according to step (1), the specific manner is as follows:

[0014] The focusing distance scanning gear is set, and the focusing distance is set for near-field suppression type strong interference (unit: meter), and the gear can be adjusted according to requirements and computing resources; according to the focusing distance gear, the focusing steering vector under the spherical wave model is calculated

[0015]

[0016] In the formula, is the scanning azimuth, is the focusing scanning position x-axis and y-axis coordinates, is the sonar array coordinate x-axis and y-axis coordinates, is the processing frequency, is the lower limit of the processing frequency, is the upper limit of the processing frequency, represents an imaginary number, is the sound velocity, is the sound path difference, is the focusing steering vector, is the number of sonar array elements.

[0017] In some embodiments, according to step (2), the specific manner is as follows:

[0018] The frequency domain data of each sonar array element is phase compensated by using the focusing steering vector, and square weighted processing is performed to obtain the spatial spectrum estimation result under each focusing distance

[0019]

[0020] In the formula, is the complex matrix conjugate transpose, and the spatial spectrum results of each frequency point are uniformly weighted and summed to obtain the wideband detection result under each focusing distance,

[0021] .

[0022] In some embodiments, according to step (3), the specific manner is as follows:

[0023] The near-field strong interference suspected azimuth near each focusing distance is searched to obtain the near-field interference distance and azimuth estimation value corresponding to the maximum interference output power

[0024]

[0025] In the formula, is the suspected near-field interference azimuth, which is obtained by calculation of a traditional plane wave processing model,​​​ The distance and bearing estimates of the near-field interference are obtained quickly.

[0026] In some embodiments, according to step (4), the specific way is:

[0027] The interference focusing steering vector is calculated based on the distance and bearing estimates of the near-field interference ,

[0028] ;

[0029] wherein, are the x-axis and y-axis coordinates of the near-field interference, is the sound path difference of the near-field suppressing interference to each array element;

[0030] The interference steering power spectral density matrix is calculated based on the interference focusing steering vector and the array frequency domain data

[0031]

[0032] is a diagonal matrix composed of the focusing steering vector corresponding to the frequency point, the direction, called focusing matrix, defined as:

[0033] .

[0034] In some embodiments, according to step (5), the specific way is:

[0035] The singular value decomposition is performed on the steering power spectral density matrix, and the maximum eigenvalue corresponding to the eigenvalue space is taken to construct the interference steering power spectral density matrix with fast convergence

[0036]

[0037]

[0038] wherein is the singular value decomposition function, and are the eigenvalue and eigenvector matrices respectively, and are the maximum eigenvalue and the eigenvector corresponding to the maximum eigenvalue respectively;

[0039] The interference optimal steering vector is estimated by using the projection method

[0040] ​​

[0041] where is a unit vector, .

[0042] In some embodiments, according to step (6), the specific way is:

[0043] Constructing interference suppression matrix by using the modified interference steering vector , filtering the element domain frequency domain data to obtain sonar array data after near-field interference suppression ,

[0044]

[0045]

[0046] where is a unit diagonal matrix, .

[0047] In some embodiments, according to step (7), the specific way is:

[0048] Beamforming by using the sonar array data after near-field interference suppression to restore time domain signals and perform long-time coherent accumulation

[0049]

[0050]

[0051]

[0052] where, is the multi-beam frequency domain data of the beamforming output, is the steering vector of the specified scanning distance, , is the specified scanning distance, is the Fourier transform point number, is the inverse Fourier transform function, is the restored time domain signal, is the multi-beam time domain data of the long-time coherent accumulation, is the long-time coherent processing time length.

[0053] In some embodiments, according to step (8), the specific way is:

[0054] Performing time-frequency transformation on the long-time coherent accumulation multi-beam data to obtain multi-beam narrowband detection results

[0055]

[0056] wherein is the long-time coherent accumulation corresponding frequency.

[0057] Compared with the prior art, the present application has the beneficial effects that: on the basis of studying the influence mode of near-field suppression jamming on detection, a multi-beam narrowband detection technology under the influence of near-field suppression strong jamming is proposed, through multi-scale focusing distance scanning, relying on the conventional beam forming with low calculation complexity, the estimation of strong jamming distance and azimuth is quickly realized, so that the correction of the near-field model is realized; combined with the tolerant interference suppression method, the corrected focusing steering vector can be used to realize the effective suppression of strong jamming. The method is verified by sea test data.

[0058] The details of one or more embodiments of the present application are presented in the following drawings and description, so that other features, objects and advantages of the present application are more apparent, and the present application is more fully described and understood through the embodiments of the present application. BRIEF DESCRIPTION OF DRAWINGS

[0059] Figure 1 is the flow chart of the method of the present application;

[0060] Figure 2 is the traditional wideband detection result of the 1m interval towed line array sea test data;

[0061] Figure 3 is the wideband detection result under different focusing distances;

[0062] Figure 4 is the narrowband detection result before and after near-field jamming suppression under the traditional plane wave model;

[0063] Figure 5 is the narrowband detection result before and after near-field jamming suppression after matching the focusing distance. DETAILED DESCRIPTION

[0064] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0065] Please refer to Figure 1The application provides a technical scheme: a passive multi-beam narrowband detection method under near-field suppression type strong interference, first, a focusing distance scanning interval is set, a steering vector at different focusing distances is calculated, sonar array data is weighted and processed, and a multi-focusing distance conventional spatial spectrum estimation result is obtained, since the energy of the near-field suppression type strong interference is strong, the focusing distance and the azimuth corresponding to the moment when the output energy of the near-field interference is maximum are searched, and the azimuth and distance estimation of the near-field interference is obtained; then, an interference steering power spectrum density matrix is calculated, a tolerant estimation result is obtained through feature space processing, and the interference suppression distance is constructed by using the tolerant estimation result, spatial domain filtering processing is performed on the sonar array data, and sonar array data after near-field interference suppression is obtained; finally, the steering vector at a specified focusing distance is scanned and processed, multi-beam time domain data is obtained, after long-time coherence processing, time-frequency transformation is performed, and multi-beam narrowband detection results are obtained. Through the sea test data verification, the achievement can well suppress the influence of the near-field strong interference, and can effectively improve the narrowband target detection efficiency of the passive sonar in the near-field strong interference environment.

[0066] Based on the above scheme, the specific implementation scheme is:

[0067] (1) setting a focusing distance scanning gear, for near-field suppression type strong interference, the focusing distance can be set as ( unit: meter), the gear can be adjusted according to requirements and calculation resources; according to the focusing distance gear, the focusing steering vector under the spherical wave model is calculated

[0068]

[0069] In the formula, is a scanning azimuth, is a focusing scanning position x-axis and y-axis coordinate, is a sonar array coordinate x-axis and y-axis coordinate, is a processing frequency, is a lower limit of the processing frequency, is an upper limit of the processing frequency, indicates an imaginary number, is a sound velocity, is a sound path difference, is a focusing steering vector, is a number of sonar array elements;

[0070] (2) the focusing steering vector is used for phase compensation on sonar each array element frequency domain data , and square weighting processing is performed, so that the spatial spectrum estimation result at each focusing distance is obtained

[0071]

[0072] in, To obtain the broadband detection results at each focusing distance, the spatial spectrum results at each frequency point are uniformly weighted and summed using the conjugate transpose of the complex matrix.

[0073]

[0074] (3) For each focusing distance By searching near the suspected azimuth of strong near-field interference, the estimated near-field interference range and azimuth corresponding to the maximum interference output power are obtained.

[0075]

[0076] in, The suspected near-field interference location can be calculated using a traditional plane wave processing model. This is the range and azimuth estimate of the near-field interference obtained through a fast search.

[0077] (4) Calculate the interference focusing steering vector based on the range and azimuth estimates of near-field interference. ,

[0078]

[0079] in, The x and y coordinates are for near-field interference. The acoustic path difference reaching each array element is used to suppress near-field interference.

[0080] (5) Based on interference focusing guidance vector With array element frequency domain data Calculate the interference-guided power spectral density matrix

[0081]

[0082] in For corresponding Frequency point, The focusing guide vector corresponding to the direction The resulting diagonal matrix is ​​called the focusing matrix, and is defined as follows:

[0083] ;

[0084] (6) Perform singular value decomposition on the steering power spectral density matrix, process the eigenspace, and construct a fast-converging interference steering power spectral density matrix by taking the eigenspace corresponding to the largest eigenvalue.

[0085]

[0086]

[0087] where is a singular value decomposition function, and are eigenvalue and eigenvector matrices, respectively, and are the largest eigenvalue and the eigenvector corresponding to the largest eigenvalue, respectively;

[0088] (7) The optimal interference steering vector is corrected by using the projection method

[0089]

[0090] where is a unit vector, ;

[0091] (8) The interference suppression matrix is constructed by using the corrected interference steering vector , and the sonar array data after near-field interference suppression is obtained by filtering the element domain frequency domain data ,

[0092]

[0093]

[0094] where is a unit diagonal matrix, ;

[0095] (9) The sonar array data after near-field interference suppression is used to perform beamforming, restore the time domain signal, and perform long-time coherent accumulation

[0096]

[0097]

[0098]

[0099] where, is the multi-beam frequency domain data output by beamforming, is the steering vector of a specified scanning distance, , is the specified scanning distance, is the Fourier transform point number, is the inverse Fourier transform function, is the restored time domain signal, is the multi-beam time domain data of long-time coherent accumulation, is the long-time coherent processing time length;

[0100] (10) Time-frequency transformation is performed on long-time coherent cumulative multibeam data to obtain multibeam narrowband detection results.

[0101]

[0102] in The frequency corresponding to long-time coherent accumulation

[0103] The technical solution of this application is used to verify the data from sea trials:

[0104] Appendix Figure 2 The traditional broadband detection results for the towed linear array sea trial data with a 1m spacing, with a processing frequency band of 250-400Hz, show that strong near-field interference moves rapidly, shifting from 83° to around 150° in 6 minutes. The target signal in this trial was located around 130°, creating a large-scale interference blind zone, which severely restricted the detection of weak signals in the vicinity.

[0105] Appendix Figure 3 Broadband detection results at different focusing distances, Figure 3 (a) shows the broadband detection results at different focusing distances; Figure 3 (b) shows the broadband detection amplitude results under different focusing distances; the focusing distance settings are set to [1000:100:8000]m. It can be seen that the output energy and azimuth of the interference change with the focusing distance. The distance estimation and azimuth estimation results of the near-field interference are obtained by searching.

[0106] Appendix Figure 4 These are the narrowband detection results before and after near-field interference suppression under the traditional plane wave model. Figure 4 (a) shows the detection results before interference suppression; Figure 4 (a) shows the detection results after interference suppression. It can be seen from the figure that the strong interference energy is severely dispersed, completely masking the target line spectrum [270Hz, 370Hz] near 130°. Due to model mismatch, the interference suppression effect is not obvious.

[0107] Appendix Figure 5 To focus on the narrowband detection results before and after near-field interference suppression following distance matching, Figure 5 (a) shows the detection results before interference suppression; Figure 5 (b) shows the detection results after interference suppression. It can be seen from the figure that the strong interference energy is concentrated, and the interference suppression has a significant effect on the strong interference. The target line spectrum [270Hz, 370Hz] near 130° can be detected.

[0108] The above embodiments only express several implementation ways of the present application, and the description is specific and detailed, but it should not be understood as a limitation to the patent scope of the application. It should be pointed out that for ordinary skilled in the art, several modifications and improvements can be made without departing from the concept of the present application, which are all within the protection scope of the present application. Therefore, the protection scope of the patent of the present application should be subject to the appended claims.

[0109] Although embodiments of the present application have been shown and described, it is to be understood that various modifications, substitutions, replacements and changes can be made to these embodiments without departing from the principles and spirit of the present application, and the scope of the present application is defined by the appended claims and their equivalents.

Claims

1. A passive multi-beam narrowband detection method under the influence of near-field suppression strong interference, characterized in that: The steps are: (1) Firstly, set the focusing distance scanning interval; (2) Calculate the steering vector of different focusing distances, weight the sonar array data, and obtain the multi-focusing distance conventional spatial spectrum estimation result; (3) Through searching the focusing distance and azimuth corresponding to the moment when the near-field interference output energy is maximum, the azimuth and distance estimation of the near-field interference are obtained; (4) Then, calculate the interference steering power spectrum density matrix; (5) Obtain the tolerant estimation result through feature space processing; (6) Use it to construct the interference suppression distance, perform spatial filtering processing on the sonar array data, and obtain the sonar array data after near-field interference suppression; (7) Finally, scan the steering vector by specifying the focusing distance, and obtain the multi-beam time domain data; (8) After long-time coherence processing, perform time-frequency transformation to obtain the multi-beam narrowband detection result.

2. The passive multi-beam narrowband detection method under the influence of near-field suppression type strong interference according to claim 1, characterized in that: According to step (1), the specific mode is: Set the focus distance scanning gear, for near-field suppression type strong interference, set the focus distance ( As a unit of meters, the gear can be adjusted according to demand and computing resources; according to the focus distance gear, calculate the focus steering vector under the spherical wave model , wherein is the scan azimuth, is the focus scan position x and y axis coordinates, is the sonar array coordinate x and y axis coordinates, is the processing frequency, is the processing frequency lower limit, is the processing frequency upper limit, denotes the imaginary number, is the sound speed, is the sound path difference, is the focus steering vector, is the number of sonar array elements.

3. The passive multi-beam narrowband detection method under the influence of near-field suppression type strong interference according to claim 2, characterized in that: According to step (2), the specific mode is: Using focused steering vector on sonar array element frequency domain data Phase compensation is performed, and square weighting processing is performed to obtain spatial spectrum estimation results at each focusing distance wherein, The wideband detection results at each focusing distance are obtained by uniformly weighting and summing the spatial spectrum results of each frequency point. 。 4. The passive multi-beam narrowband detection method under the influence of near-field suppression type strong interference according to claim 3, characterized in that: According to step (3), the specific mode is: For each focusing distance Search around the suspected azimuth of the near-field strong jamming, get the near-field jamming distance and azimuth estimation value corresponding to the maximum jamming output power wherein, is the suspected near-field interference azimuth, calculated from the conventional plane wave processing model, is the distance and azimuth estimate of the near-field interference obtained from the fast search.

5. The passive multi-beam narrowband detection method under the influence of near-field suppression type strong interference according to claim 4, characterized in that: According to step (4), the specific mode is: Distance and bearing estimation based on near field interference for interference focusing steering vector computation , ； wherein, x and y coordinates of the near-field interference, is the sound path difference of the near-field interference to each array element; Interference focusing steering vector And array element frequency domain data , compute interference steering power spectral density matrix corresponding to frequency points, a focusing direction corresponding to a focusing direction vector a diagonal matrix, called focusing matrix, defined as: 。 6. The passive multi-beam narrowband detection method under the influence of strong interference according to claim 5, characterized in that: According to step (5), the specific mode is: Perform singular value decomposition on the steering power spectrum density matrix, process the feature space, and take the feature space corresponding to the maximum eigenvalue to construct the fast-converging interference steering power spectrum density matrix wherein is a singular value decomposition function, and are eigenvalue and eigenvector matrices, respectively, and are the largest eigenvalue and the eigenvector corresponding to the largest eigenvalue, respectively. Estimate the best steering vector of the interference by using the projection method wherein is a unit vector, .

7. The method of claim 6, wherein the method is a passive multi-beam narrowband detection method under the influence of strong interference in near field. According to step (6), the specific mode is: Utilizing a modified interference steering vector , constructing an interference suppression matrix, filtering the element domain frequency domain data to obtain sonar array data after near-field interference suppression , wherein is a unit diagonal matrix, .

8. The passive multi-beam narrowband detection method under the influence of near-field suppression type strong interference according to claim 7, characterized in that: According to step (7), the specific mode is: Perform beamforming on the sonar array data after near-field interference suppression, restore the time domain signal, and perform long-time coherence accumulation wherein, is the multi-beam frequency domain data for the beamformed output, is the steering vector for a specified scan distance, , is the specified scan distance, is the number of Fourier transform points, is the inverse Fourier transform function, is the recovered time domain signal, is the multi-beam time domain data for long-time coherent accumulation, is the long-time coherent processing duration.

9. The passive multi-beam narrowband detection method under the influence of strong near-field interference according to claim 8, characterized in that: According to step (8), the specific mode is: Long time coherent accumulation multi-beam data Performing time-frequency transform to obtain multi-beam narrowband detection result wherein is the frequency corresponding to the long-time coherence accumulation.

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