Multi-beam lofar processing method and device based on spectral line extraction and storage medium

Abstract

The application discloses a spectrum line extraction-based multi-beam LOFAR processing method and device and a storage medium. The method comprises the following steps: performing spectrum line extraction on an equalized narrowband instantaneous diagram; obtaining a reconstructed narrowband instantaneous diagram through spectrum line extraction data; and merging adjacent n beams in the reconstructed narrowband instantaneous diagram in a preset manner to form a plurality of merged beams. The spectrum line extraction-based multi-beam LOFAR processing method and device and the storage medium provided by the application enhance the line spectrum and suppress the noise through background equalization and spectrum line extraction, and the line spectrum is clearer. Merging adjacent beams reduces the overall display quantity, and the line spectrum signal across multiple beams can be further energy-enhanced after being merged. When there is a certain overlap between the merged beams, the total beam quantity is reduced, and the problem that the line spectrum signal across the merged beams cannot be energy-enhanced when the merged beams are not overlapped can be solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of sonar detection line spectrum detection, and particularly relates to a multi-beam LOFAR processing method and device based on spectrum line extraction and a storage medium. BACKGROUND

[0002] Low Frequency Analysis And Recording (LOFAR) is a classical line spectrum detection method, which is obtained by performing short-time Fourier transform (STFT) on a received signal. In sonar signal processing, the LOFAR plot is a two-dimensional image of "frequency x time", and the brightness represents the amplitude. Since the frequency of the same narrowband signal will not change much at adjacent time, the bright spots corresponding to the same narrowband signal at multiple time form a clear bright line (i.e. spectrum line). The LOFAR processing utilizes the time accumulation of low frequency line spectrum to detect the line spectrum, i.e. the continuous line spectrum spectrum line is found from the LOFAR plot by the visual accumulation effect of the human eye.

[0003] In a sonar device, in order to effectively detect all narrowband targets in the observable range, a multi-beam display is used for the narrowband LOFAR plot. That is, a plurality of beams are divided according to the cosine value in the observable range, and the LOFAR plots of "frequency x time" of these beams are displayed simultaneously to form a multi-beam LOFAR plot of "azimuth x frequency x time". Due to the limitation of the pixels of the plot, the number of beams divided by the multi-beam LOFAR cannot be as large as the narrowband instantaneous plot of "frequency x azimuth". It is necessary to first reduce the number of beams by 1 / n proportion using the narrowband instantaneous plot, and then perform data time accumulation processing to obtain the multi-beam LOFAR plot. The conventional method of reducing the number of beams generally adopts extraction and large selection processing, which can cause a serious decline in target resolution and a phenomenon that the broadband noise covers the line spectrum. SUMMARY

[0004] The main purpose of the present application is to provide a multi-beam LOFAR processing method and device based on spectrum line extraction and a storage medium, which aims to solve the problems of insufficient target resolution and broadband noise covering the line spectrum in the sonar detection line spectrum detection.

[0005] In order to achieve the above purpose, the present application provides a multi-beam LOFAR processing method based on spectrum line extraction, comprising:

[0006] Step 1: obtaining narrowband instantaneous plot data;

[0007] Step 2: performing background equalization on the narrowband instantaneous plot data to obtain equalized narrowband instantaneous plot data;

[0008] Step 3: performing spectrum line extraction on the equalized narrowband instantaneous plot;

[0009] Step 4: Calculate the reconstructed narrowband instantaneous diagram by data extracted by spectral line;

[0010] Step 5: Merge adjacent n beams in the reconstructed narrowband instantaneous diagram in a preset manner to form a plurality of merged beams, wherein 2≤n≤5, and at most one repeated beam is included in adjacent two merged beams.

[0011] Further, in the step 5, the merging manner of adjacent n beams in the reconstructed narrowband instantaneous diagram is:

[0012]

[0013]

[0014]

[0015] BeamNum2 is the total number of merged beams, and 2≤n≤5.

[0016] Further, the step 3 comprises:

[0017] Step 3.1: Extract a peak point;

[0018] Step 3.2: Perform signal-to-noise ratio threshold screening on the peak point, and if it passes, determine it as a real peak point.

[0019] Further, in the step 3.2, the signal-to-noise ratio threshold screening method is:

[0020] Determine whether (Y1(i,j)-E(i,j)) / E(i,j) is greater than T0, wherein Y1(i,j) is the peak point, E(i,j) is the background estimation value of the peak point, and T0 is the signal-to-noise ratio threshold.

[0021] Further, the step 3.2 further comprises a step 3.3:

[0022] The step 3.3 comprises: if it does not pass, verify whether Max(Y1(i-W,j),Y1(i+W,j)) is less than Y1(i,j), and if so, determine it as a real peak point, wherein Max() is a maximum value operation from a matrix range, and W is a selected frequency band width.

[0023] Further, the step 3.3 further comprises a step 3.4:

[0024] The step 3.4 comprises: performing spectral peak width threshold screening on the real peak point.

[0025] Further, the step 3.3 further comprises:

[0026] The spectral lines that pass the extraction process are enhanced in energy amplitude, and the spectral lines that do not pass the extraction process are eliminated.

[0027] Further, the step 2 comprises:

[0028] The narrowband instantaneous diagram data is background equalized by the sorting truncation method to obtain equalized narrowband instantaneous diagram data.

[0029] The application further provides a device for performing the multi-beam LOFAR processing method based on spectral line extraction, comprising:

[0030] The first acquisition unit is configured to acquire narrowband instantaneous diagram data.

[0031] The first calculation unit is configured to background equalize the narrowband instantaneous diagram data to obtain equalized narrowband instantaneous diagram data.

[0032] The first extraction unit is configured to perform spectral line extraction on the equalized narrowband instantaneous diagram.

[0033] The second calculation unit is configured to calculate reconstructed narrowband instantaneous diagram data based on the spectral line extraction data.

[0034] The third calculation unit is configured to merge adjacent n beams in the reconstructed narrowband instantaneous diagram in a preset manner to form a plurality of merged beams, wherein 2<=n<=5, and at most one repeated beam is included in adjacent two of the merged beams.

[0035] The application further provides a computer readable storage medium having a computer program stored thereon, wherein the computer program is executed by a processor to implement the steps of the multi-beam LOFAR processing method based on spectral line extraction.

[0036] The multi-beam LOFAR processing method, device and storage medium based on spectral line extraction provided by the application enhance the line spectrum and suppress the noise through background equalization and spectral line extraction, so that the line spectrum is clearer; the adjacent beams are merged to reduce the overall display quantity, and the line spectrum signal across multiple beams can be further enhanced in energy after being merged; when there is a certain overlap between the merged beams, the total beam quantity is reduced, and the problem that the line spectrum signal across the merged beams cannot be enhanced in energy when there is no overlap between the merged beams is solved. BRIEF DESCRIPTION OF DRAWINGS

[0037] Figure 1 is a schematic diagram of the multi-beam LOFAR processing method based on spectral line extraction according to an embodiment of the application;

[0038] Figure 2 is a schematic diagram of the device for performing the multi-beam LOFAR processing method based on spectral line extraction according to an embodiment of the application.

[0039] The objectives, functional characteristics and advantages of the present application will be further illustrated in conjunction with the embodiments with reference to the accompanying drawings. DETAILED DESCRIPTION

[0040] It should be understood that the specific embodiments described herein merely exemplify the application and do not impose any limitation on the application.

[0041] It should be understood by those skilled in the art that the singular forms "a", "an", "said" and "the" used herein include plural references unless specifically stated otherwise. It should be further understood that the use of the term "comprise" in the specification of the present application means that the features, integers, steps, operations, elements, units, modules and / or components described in the specification exist, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, units, modules, components and / or combinations thereof. It should be understood that when we say that an element is "connected" or "coupled" to another element, it can be directly connected or coupled to the other element, or there can be intermediate elements. In addition, "connected" or "coupled" used herein can include wireless connection or wireless coupling. The term "and / or" used herein includes all or any combination of the associated listed items and all combinations thereof.

[0042] It should be understood by those skilled in the art that unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as that understood by a person of ordinary skill in the art to which the present application belongs. It should also be understood that terms such as those defined in a general dictionary should be understood to have meanings consistent with those in the context of the prior art, and should not be interpreted in an idealized or overly formal sense unless specifically defined as such.

[0043] Reference Figure 1 In an embodiment of the present application, a multi-beam LOFAR processing method based on spectral line extraction includes:

[0044] Step 1: Obtain narrowband instantaneous diagram data;

[0045] Step 2: Perform background equalization on the narrowband instantaneous diagram data to obtain equalized narrowband instantaneous diagram data;

[0046] Step 3: Perform spectral line extraction on the equalized narrowband instantaneous diagram;

[0047] Step 4: Calculate and obtain reconstructed narrowband instantaneous diagram from the spectral line extraction data;

[0048] Step 5: Merge adjacent n beams in the reconstructed narrowband instantaneous diagram in a predetermined manner to form a plurality of merged beams, wherein 2≤n≤5, and at most one repeated beam is included in adjacent two of the merged beams.

[0049] In the prior art, the LOFAR diagram is obtained by performing a short-time Fourier transform on the received signal. In sonar signal processing, the LOFAR diagram is a two-dimensional image of "frequency x time". In a sonar device, in order to effectively detect narrow-band targets in all directions within an observable range, a narrow-band LOFAR picture adopts multi-beam display. That is, a plurality of beams are divided according to the cosine value of the observable range, and the "frequency x time" LOFAR diagrams of the beams are displayed simultaneously to form a multi-beam LOFAR diagram of direction x frequency x time. Due to the limitation of picture pixels, it is necessary to reduce the number of beams by 1 / n times by using a narrow-band instantaneous diagram, and then perform data time accumulation processing to obtain a multi-beam LOFAR diagram. The conventional method of reducing the number of beams generally adopts extraction and large selection processing, which can cause a serious decline in target resolution and a phenomenon that broadband noise covers a line spectrum.

[0050] In the above step 1, narrow-band instantaneous diagram data is obtained for subsequent processing.

[0051] In the above step 2, the narrow-band instantaneous diagram data is preprocessed. Background equalization can improve the image quality of the direction history display, enhance the detection capability or improve the resolution, and filter random fluctuations. The target trajectory in the frequency resolution unit becomes clearer.

[0052] In the above steps 3 and 4, the spectrum lines in the equalized narrow-band instantaneous diagram are extracted and processed to obtain a reconstructed narrow-band instantaneous diagram. In this process, it can be necessary to strengthen the key signals and suppress the interference signals. Since the spectrum line extraction process is completed through step 3, various desirable operations can be performed to reconstruct the narrow-band instantaneous diagram, such as completely retaining the spectrum lines that are focused on, and suppressing or directly removing the spectrum lines that are determined to be noise in a corresponding proportion, so as to calculate and obtain the reconstructed narrow-band instantaneous diagram.

[0053] In the above step 5, a plurality of adjacent beams are merged to reduce the overall display quantity. The plurality of beams are summed to perform the merging, and the line spectrum signals across the plurality of beams can be further strengthened after being merged. Meanwhile, there is a certain overlap between the merged beams. Therefore, under the premise of reducing the total number of beams, the problem that the line spectrum signal amplitude across the merged beams cannot be strengthened in energy can be solved when the merged beams are not overlapped. In the following embodiments, the beam merging method will be specifically described.

[0054] In summary, the line spectrum is enhanced and the noise is suppressed by background equalization and line extraction, and the line spectrum is clearer. The number of total beams is reduced by merging adjacent beams, and the energy of the line spectrum signal across multiple beams is further enhanced after merging. When there is a certain overlap between the merged beams, the total number of beams is reduced, and the problem of the line spectrum signal across the merged beams not being able to obtain energy enhancement when there is no overlap between the merged beams is solved.

[0055] In one embodiment, the manner of merging adjacent n waves in the reconstructed narrowband instantaneous diagram in step 5 is as follows:

[0056]

[0057]

[0058]

[0059] BeamNum2 is the total number of merged beams, and 2≤n≤5.

[0060] Using n beam summation can cause the amplitude of some line spectrum signals across the merged area to be unable to obtain energy enhancement. In this embodiment, n+1 beam summation (with overlap) is used. In this embodiment, the calculation formula of BeamNum2 can be as follows: floor() is a down rounding operation. The first and last beams are processed separately, that is, when k=0 and k=BeamNum2-1, the processing of formula 2.1 and formula 2.3 is performed, respectively, and when 0

[0061] In one embodiment, step 3 includes:

[0062] Step 3.1: Extracting a peak point;

[0063] Step 3.2: The peak point is subjected to a signal-to-noise ratio threshold screening, and if it passes, it is determined to be a real peak point.

[0064] In this embodiment, the manner of extracting a peak point in step 3.1 is to determine whether the energy amplitude is greater than the amplitude of the left and right frequency points. The equalized narrowband instantaneous diagram is Y1, so if Y1(i,j) > Y1(i-1,j) and Y1(i,j) > Y1(i+1,j), then Y1(i,j) is a peak point. The peak point is subjected to a signal-to-noise ratio threshold screening, and if it passes, it is determined to be a real peak point.

[0065] In one embodiment, in the step 3.2, the signal-to-noise ratio threshold screening method is:

[0066] determining whether (Y1(i,j)-E(i,j)) / E(i,j) is greater than T0, wherein Y1(i,j) is a peak point, E(i,j) is a background estimation value of the peak point, and T0 is a signal-to-noise ratio threshold.

[0067] In the embodiment, a simple peak point confirmation manner is provided, and the value of the signal-to-noise ratio detection threshold T0 is directly related to the spectral line extraction capability.

[0068] In one embodiment, the step 3.2 is followed by step 3.3:

[0069] The step 3.3 includes: if not passed, verifying whether Max(Y1(i-W,j),Y1(i+W,j)) is less than Y1(i,j), and if so, determining that the peak point is a true peak point, wherein Max() is a maximum value operation in a matrix range, and W is a selected frequency band width.

[0070] In order to extract points on a weak spectral line, the signal-to-noise ratio detection threshold T0 must be reduced, but reducing the threshold will also cause noise to pass the threshold, and the processing effect will decrease, so the strongest energy in the frequency band range is added on the basis of the traditional threshold. T0 is not reduced to be too low, and the peak points that do not pass the signal-to-noise ratio threshold screening are subjected to the strongest energy in the frequency band range, and if the condition is met, it is considered that the peak point is a spectral line. If Y1(i,j) is a peak point, the strongest energy in the frequency band range screening condition is as follows:

[0071] Y1(i,j)>Max(Y1(i-W,j),Y1(i+W,j))

[0072] Max() is a maximum value operation in a matrix range. W is a selected frequency band width, which can be set to 1 / 50 of the total number of frequency points to meet the effect of screening weak spectral lines. In addition to the spectral peak width threshold screening and the signal-to-noise ratio threshold screening, the strongest energy in the frequency band range screening can meet the requirements of not losing weak spectral lines with low signal-to-noise ratio and at the same time extracting as little noise as possible.

[0073] In one embodiment, the step 3.3 is followed by step 3.4:

[0074] The step 3.4 includes: performing spectral peak width threshold screening on the true peak point.

[0075] In the embodiment, the spectral peak width threshold screening condition is R(i,j)-L(i,j)>T1, E(i,j) is the background estimation value of the peak point, R(i,j) is the left boundary frequency point sequence number of the peak, L(i,j) is the right boundary frequency point sequence number of the peak, and T1 is the peak width threshold. Then, the true peak point detected is verified through a peak width threshold. It is particularly pointed out that after the screening ability of the signal-to-noise ratio threshold is relaxed, the strongest energy in the frequency range is screened, and at this time, the spectral peak width threshold screening condition can be set to be more stringent, so that the spectral line is clearer.

[0076] In one embodiment, the step 3.3 further comprises:

[0077] The spectral line that passes the extraction process is subjected to energy amplitude enhancement, and the spectral line that does not pass the extraction process is removed.

[0078] In the embodiment, the spectral line that does not pass the above extraction process can be directly removed because the difference between the peak point and the background estimation value is verified relative to the size relationship of the signal-to-noise ratio threshold, and whether the related peak point is the strongest energy in the frequency range is verified. Therefore, the clarity of the spectral line is improved.

[0079] In one embodiment, the step 2 comprises:

[0080] The background of the narrowband instantaneous graph data is balanced by the sorting and truncation method, and balanced narrowband instantaneous graph data is obtained.

[0081] In the embodiment, the sorting and truncation method (OTA) is used for background balancing. The continuous spectral background is estimated by the method, the input is the narrowband instantaneous graph data, the background is normalized, and the balanced narrowband instantaneous graph is output. The image quality of the bearing history display is improved, the detection ability is enhanced or the resolution is improved, the random fluctuations are filtered, and the target trajectory of the frequency resolution unit becomes clearer.

[0082] Reference Figure 2 The application further provides a device for performing the multi-beam LOFAR processing method based on spectral line extraction, comprising:

[0083] A first acquisition unit 100 is configured to acquire narrowband instantaneous graph data.

[0084] A first calculation unit 200 is configured to balance the background of the narrowband instantaneous graph data, and obtain balanced narrowband instantaneous graph data.

[0085] A first extraction unit 300 is configured to perform spectral line extraction on the balanced narrowband instantaneous graph.

[0086] A second calculation unit 400 is configured to calculate and obtain a reconstructed narrowband instantaneous graph through the spectral line extraction data.

[0087] The third computing unit 500 is configured to combine adjacent n beams in the reconstructed narrowband instantaneous diagram in a preset manner to form a plurality of combined beams, wherein 2≤n≤5, and at most one repeated beam is included in two adjacent combined beams.

[0088] The application further provides a computer readable storage medium, which stores a computer program. The computer program is executed by a processor to implement the steps of the above-mentioned multi-beam LOFAR processing method based on spectral line extraction.

[0089] Those skilled in the art can understand that all or part of the processes in the above-mentioned embodiment methods can be completed by a computer program instructing related hardware. The computer program can be stored in a non-volatile computer readable storage medium, and when executed, can include the processes of the above-mentioned embodiment methods. Any reference to memory, storage, database or other medium provided by the present application and used in the embodiments can include non-volatile and / or volatile memory. Non-volatile memory can include read-only memory (ROM), programmable ROM (PROM), electrically programmable ROM (EPROM), electrically erasable programmable ROM (EEPROM) or flash memory. Volatile memory can include random access memory (RAM) or external cache memory. As an illustration but not limitation, RAM is available in various forms, such as static RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), double data rate SDRAM (SSRSDRAM), enhanced SDRAM (ESDRAM), synchronous link (Synchlink) DRAM (SLDRAM), memory bus (Rambus) direct RAM (RDRAM), direct memory bus dynamic RAM (DRDRAM) and memory bus dynamic RAM (RDRAM) and the like.

[0090] In summary, the multi-beam LOFAR processing method based on spectral line extraction, the device and the storage medium provided by the present application can enhance the line spectrum, suppress the noise and make the line spectrum clearer through background equalization and spectral line extraction. Combining adjacent beams reduces the overall display quantity, and the line spectrum signal across multiple beams can be further energy enhanced after being combined. When there is a certain overlap between the combined beams, the total beam quantity is reduced, and the problem that the line spectrum signal across the combined beams cannot be energy enhanced when there is no overlap between the combined beams can be solved.

[0091] The above merely describes preferred embodiments of the present application, and is not intended to limit the patent scope of the present application, and any equivalent structure or equivalent process conversion made by using the content of the present application specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. A method of multi-beam LOFAR processing based on spectral line extraction, characterized in that, The method comprises the following steps: Step 1: obtaining narrowband instantaneous diagram data; Step 2: background equalization on the narrowband instantaneous diagram data to obtain equalized narrowband instantaneous diagram data; Step 3: spectral line extraction on the equalized narrowband instantaneous diagram; Step 4: obtaining a reconstructed narrowband instantaneous diagram through the data of the spectral line extraction; Step 5: merging adjacent n-beams in the reconstructed narrowband instantaneous diagram in a preset manner to form a plurality of merged beams, wherein 2≤n≤5, and at most one repeated beam is included in adjacent two of the merged beams.

2. The spectral line extraction based multi-beam LOFAR processing method according to claim 1, characterized in that, In the step 5, the merging manner of the adjacent n-beams in the reconstructed narrowband instantaneous diagram is as follows: ； wherein BeamNum2 is the total number of the merged beams, and 2≤n≤5.

3. The spectral line extraction based multi-beam LOFAR processing method of claim 1, wherein, The step 3 comprises the following steps: Step 3.1: extracting a peak point; Step 3.2: performing signal-to-noise ratio threshold screening on the peak point, and if the screening is passed, the peak point is determined as a real peak point.

4. The spectral line extraction based multi-beam LOFAR processing method according to claim 3, characterized in that, In the step 3.2, the signal-to-noise ratio threshold screening method is as follows: determining whether (Y1(i,j)-E(i,j)) / E(i,j) is greater than T0, wherein Y1(i,j) is the peak point, E(i,j) is a background estimation value of the peak point, and T0 is a signal-to-noise ratio threshold.

5. The spectral line extraction based multi-beam LOFAR processing method according to claim 3, characterized in that, The step 3.2 further comprises the following step 3.3: The step 3.3 comprises: if the screening is not passed, verifying whether Max(Y1(i-W,j),Y1(i+W,j)) is less than Y1(i,j), and if yes, the peak point is determined as a real peak point, wherein Max() is a maximum value operation in a matrix range, Y1(i,j) is the peak point, and W is a selected frequency band width.

6. The spectral line extraction based multi-beam LOFAR processing method according to claim 5, characterized in that, The step 3.3 further comprises the following step 3.4: The step 3.4 comprises: performing spectral peak width threshold screening on the real peak point.

7. The spectral line extraction based multi-beam LOFAR processing method according to claim 5, characterized in that, The step 3.3 further comprises the following step: performing energy amplitude enhancement on the spectral line passing the extraction process, and eliminating the spectral line not passing the extraction process.

8. The spectral line extraction based multi-beam LOFAR processing method of claim 1, wherein, The step 2 comprises: performing background equalization on the narrowband instantaneous diagram data by a sorting truncation method to obtain the equalized narrowband instantaneous diagram data.

9. An apparatus for performing a spectral line extraction based multi-beam LOFAR processing method, characterized in that, The method comprises the following steps: a first obtaining unit (100) configured to obtain narrowband instantaneous diagram data; a first calculating unit (200) configured to perform background equalization on the narrowband instantaneous diagram data to obtain equalized narrowband instantaneous diagram data; a first extracting unit (300) configured to perform spectral line extraction on the equalized narrowband instantaneous diagram; a second calculating unit (400) configured to obtain a reconstructed narrowband instantaneous diagram through the data of the spectral line extraction; a third calculating unit (500) configured to merge adjacent n-beams in the reconstructed narrowband instantaneous diagram in a preset manner to form a plurality of merged beams, wherein 2≤n≤5, and at most one repeated beam is included in adjacent two of the merged beams.

10. A computer readable storage medium having stored thereon a computer program, characterized in that, The computer program is executed by a processor to implement the steps of the multi-beam LOFAR processing method based on spectral line extraction in any one of claims 1 to 8.

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