This patent application claims the benefit and priority of Chinese Patent Application No. 202210426030.3, filed with the China National Intellectual Property Administration on Apr. 22, 2022, the disclosure of which is incorporated by reference herein in its entirety as part of the present application.
The present disclosure belongs to the field of underwater target detection, and in particular, to a method for detecting a moving target based on spatial slices of transformed spatio-temporal frequency space, an electronic device, and a readable storage medium.
In the underwater acoustic environment with a low signal-to-noise ratio (SNR), the traditional signal detection methods seriously restrict the detection performance of the underwater sonar array. In recent years, the method for improving the SNR of a target signal using multi-frame data accumulation has become a research hotspot. A large amount of design analysis and computer simulation has demonstrated the advantages of the tracking algorithm before detection, but only a limited number of finished systems have been applied in practical work. One of the main reasons is that with the increase of integration time (frame number), the change of signal parameters caused by target movement cannot be ignored. Therefore, when the target movement parameters are unknown, it is impossible to accurately integrate the signal for a long time.
In the field of underwater acoustics, the research work based on long time integration to improve the SNR focuses on the discussion of parameters of the target in the frequency domain or the space domain. Most of them only consider the frequency change of the moving target alone or only analyze the target movement based on bearings-only. It is not until recent years that the processing and analysis method of spatio-temporal frequency combination is discussed. However, most of the solutions only consider the analysis of the moving parameters of the target in a high SNR environment, because the search problem of multidimensional movement parameters needs to be solved for the moving target in a low SNR environment. So far, there is still a lack of a simple, fast and effective method for multi-frame accumulation of moving targets with a low SNR.
The present disclosure provides a method for detecting a moving target based on spatial slices of transformed spatio-temporal frequency space, so as to solve passive detection of uniformly moving targets in a low SNR environment, especially for targets with fast azimuth change.
The present disclosure provides an electronic device, configured to run steps of a method in a computer readable storage medium.
The present disclosure provides a computer readable storage medium, configured to store steps of the method for detecting a moving target based on spatial slices of transformed spatio-temporal frequency space.
The present disclosure is implemented through the following technical solutions.
The present disclosure provides a method for detecting a moving target based on spatial slices of transformed spatio-temporal frequency space, including the following steps:
In the method for detecting a moving target based on spatial slices of transformed spatio-temporal frequency space, step 1 is specifically as follows:
sm(τp,n)=s((τp−1)Tb+n) (1),
where
τp=1,2, . . . , P, n=1,2, . . . , T0fs, and m=1,2, . . . , M, and
In the method for detecting a moving target based on spatial slices of transformed spatio-temporal frequency space, step 2 is specifically as follows:
where
In the method for detecting a moving target based on spatial slices of transformed spatio-temporal frequency space, step 3 is specifically as follows:
In the method for detecting a moving target based on spatial slices of transformed spatio-temporal frequency space, step 3 is specifically as follows:
where
in the new 3D space.
In the method for detecting a moving target based on spatial slices of transformed spatio-temporal frequency space, step 5 is specifically as follows: searching a transmitting signal frequency f0 and a velocity v, and determining a slice in the 3D space A:
according to the parameters.
The present disclosure provides a computer readable storage medium, storing a computer program. When executed by a processor, the computer program implements steps of the above-described method.
The present disclosure provides an electronic device, including a processor, a communication interface, a memory, and a communication bus. The processor, the communication interface, and the memory communicate with each other through the communication bus.
The memory is configured to store a computer program.
The processor is configured to implement steps of the above-described method when executing the program stored in the memory.
The present disclosure has the following beneficial effects:
The present disclosure improves the detection performance of the underwater sonar array.
The method of the present disclosure is simple, fast, and effective.
The present disclosure increases the processing time of the moving target signal.
Compared with a low frequency array (LOFAR) diagram and an azimuth history diagram, the present disclosure can display the change of frequency and azimuth with time more excellently.
The present disclosure is conducive to the detection of targets whose azimuth varies greatly with time.
The algorithm of the present disclosure has low computation.
The technical solutions of the embodiments of the present disclosure are clearly and completely described below with reference to the accompanying drawings. Apparently, the described embodiments are only illustrative ones, and are not all possible ones of the present disclosure. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present disclosure without creative efforts shall fall within the protection scope of the present disclosure.
The present disclosure provides a method for detecting a moving target based on spatial slices of transformed spatio-temporal frequency space, including the following steps.
Step 1: A target radiated acoustic signal s(t) received by an M-element horizontal line array in an underwater acoustic environment with a low SNR is segmented.
Step 2: N-point DFT is performed on the received signal on each array element in each period of time τp in step 1, where N=T0·fs.
For the azimuth α(τp), each period of time τp has an azimuth α(τp), and step S3 compensates this azimuth for each segment of signal. However, during compensation, the azimuth is unknown, so it is compensated once in sequence from 0 to 180 degrees. In the formula, α is a variable, and α(τp) is a constant.
Step 3: Frequency domain beamforming is performed on an array signal after each section of DFT in step 2, and stacking is performed after a phase difference between arrays brought by an azimuth α(τp) of each primitive element is compensated.
Step 4: Coordinate transformation is performed on a frequency-azimuth-time (f-α-t) 3D matrix space obtained in step 3.
Step 5: A slice is taken from the frequency-azimuth-time (f-cos θ-t) 3D space subjected to the coordinate transformation obtained in step 4.
Step 6: Segmented Radon transform is performed on the spatial slice obtained in step 5 to detect the target.
In the method for detecting a moving target based on spatial slices of transformed spatio-temporal frequency space, step 1 is specifically as follows:
(τp,n)=s((τp−1)Tb+n) (1),
where
τp=1,2, . . . , P, n=1,2, . . . , T0fs, and m=1,2, . . . , M, and
P represents a number of segments into which data is divided, τp represents a p-th segment of signal, T0 represents a length of each segment of signal, in unit of second, Tb represents a segmentation stride, in unit of second, fs is a sampling rate of the signal, τp represents a slow time, n represents a fast time, and m is an array element number.
In the method for detecting a moving target based on spatial slices of transformed spatio-temporal frequency space, step 2 is specifically as follows:
Within T0 seconds, a frequency ωp and azimuth α(τp) of the received signal are approximately unchanged, and ωp=ω0+{right arrow over (k)}·{right arrow over (v)} is a frequency received by the array at a time τp after the Doppler effect caused by target movement, where {right arrow over (v)} is a target velocity vector, and {right arrow over (k)} is a wave number vector; and {right arrow over (r)}0 is a distance vector between the target and a central receiving array element at an initial time, d is an array element spacing, and both ω0 and f0 are frequencies of the target transmitting a single-frequency signal.
In the method for detecting a moving target based on spatial slices of transformed spatio-temporal frequency space, step 3 is specifically as follows:
In the method for detecting a moving target based on spatial slices of transformed spatio-temporal frequency space, step 3 is specifically as follows.
According to a mathematical expression of space transformation:
The signal is represented as a curve on a plane
in the new 3D space.
In the method for detecting a moving target based on spatial slices of transformed spatio-temporal frequency space, step 5 is specifically as follows: searching a transmitting signal frequency f0 and a velocity v, and determining a slice in the 3D space A:
according to the parameters.
The present disclosure provides a computer readable storage medium, storing a computer program. When executed by a processor, the computer program implements steps of the method described above.
The present disclosure provides an electronic device, including a processor, a communication interface, a memory, and a communication bus. The processor, the communication interface, and the memory communicate with each other through the communication bus.
The memory is configured to store a computer program.
The processor is configured to implement steps of the method described above when executing the program stored in the memory.
cos θ(t)=−sin(α(t)+γ0).
Assuming that the acoustic field is an infinite free plane and the receiving array is located in the far field of the signal source, the received signal can be approximately considered as a plane wave. Within a period of time, due to the Doppler effect brought by the target movement, the signal received by the array element at the origin of coordinates is:
then the signal received by any array element can be written as:
According to the moving target model in
S(f,α,t)=∫−∞+∞∫−∞+∞s(t′,x)γ*(t′−t)e−i2π(ft′+x cos α)dtdx.
By substituting Formula (3), the formula is simplified into:
By sliding the window function and performing the 2D Fourier transform, the function expression of the received signal in the 3D space represented by the three axes of frequency-azimuth-time (f-α-t) is obtained. As shown in
According to the above derivation, the frequency of the received signal at any time is:
Since f0, v, and c are all constants, the relationship between f(t) and cos θ(t) is linear. Therefore, according to the mathematical expression of space transformation:
the angle γ0 is searched, and coordinate transformation as shown in Formula (6) is performed on the (f-α-t) 3D space according to the parameter to obtain a new 3D space (f-cos θ-t). The position of the signal in (f-cos θ-t) is shown in
in the new 3D space, whose equation is:
A transmitting signal frequency f0 and a velocity v are searched, and a slice in the 3D space A:
can be determined according to the parameters, that is, the plane represented by the blue block diagram in
As shown in
Number | Date | Country | Kind |
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202210426030.3 | Apr 2022 | CN | national |
Number | Name | Date | Kind |
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7173562 | Garren | Feb 2007 | B2 |
11520043 | Kruse | Dec 2022 | B2 |
11737726 | Kruse | Aug 2023 | B2 |
Number | Date | Country | |
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20230341547 A1 | Oct 2023 | US |