Space-time domain joint sparse driven adaptive line enhancement method

Abstract

The application discloses a kind of space-time domain joint's sparse drive adaptive line spectrum enhancement method, including the uniform linear array of hydrophone receives the far-field plane wave signal of signal source;The far-field plane wave signal received by entire uniform linear array is input into space-time domain joint filter;The far-field plane wave signal received by next array element is input into space-time domain joint filter as reference signal, until processing all the far-field plane wave signal received by array element, to obtain the output signal corresponding to each array element respectively;The output spectrum corresponding to each output signal is obtained respectively;Square superposition is carried out to multiple output spectrums and is averaged, to obtain output result;Output result is converted from frequency domain to time domain, obtain the input signal of norm-based sparse drive adaptive line spectrum enhancer;Input signal is input into norm-based sparse drive adaptive line spectrum enhancer and carries out weight updating;According to the length of input signal, iterative adaptive weight is continued, and corresponding output signal is obtained.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of ship radiated noise line spectrum enhancement, and particularly relates to a space-time domain joint sparse driving adaptive line spectrum enhancement method. BACKGROUND

[0002] Ship radiated noise contains line spectrum, etc., and the line spectrum has good stability and strength. In order to effectively extract the line spectrum component from the ship radiated noise, a series of measures need to be taken. The most effective one is to perform adaptive enhancement on the line spectrum.

[0003] The space-time joint filter proposed in the paper "Underwater unknown line spectrum target detection method in space-time domain" (published in Electronics and Information Journal, 2019, 41(07): 1682-1689) can match line spectrum signals of multiple directions and multiple frequencies, but does not consider the steady-state error problem of adaptive filtering.

[0004] The paper "Underwater target spectrum entropy detection of sparse driving adaptive line spectrum enhancement" (published in Acta Acustica Sinica, 2021, 46(06): 1059-1069) considers the frequency domain sparsity of the line spectrum, and proposes a sparse driving ALE algorithm based on norm. By comparing the performance differences of ALEs driven by and , it is proved that the adaptive line spectrum enhancer driven by norm has better weight frequency domain sparsity and stronger performance, but its performance is still susceptible to steady-state adaptive weight noise, and under low input signal-to-noise ratio conditions, performance degradation occurs. SUMMARY

[0005] The present application aims to at least solve one of the problems in the prior art.

[0006] The present application aims to at least solve one of the problems in the prior art.

[0007] According to the embodiments of the present application, a space-time domain joint sparse driving adaptive line spectrum enhancement method is provided, comprising the following steps:

[0008] Step 1, receiving a far-field plane wave signal of a signal source by a uniform linear array of a hydrophone, and the far-field plane wave signal received by the entire uniform linear array is , which can be expressed by a formula as

[0009]

[0010] wherein, is an integer greater than or equal to 1, representing the number of array elements in the uniform linear array; is an integer greater than or equal to 0, represents the far-field plane wave signal received by the th array element at the th time instant;

[0011] Step 2, inputting the far-field plane wave signal received by the entire uniform linear array as the first input signal into the joint space-time domain filter;

[0012] Step 3, inputting the far-field plane wave signal received by the th array element as the reference signal into the joint space-time domain filter, and the corresponding output signal is expressed by the formula:

[0013]

[0014] wherein, is an integer greater than or equal to 1, representing the number of array elements in the uniform linear array; is an integer greater than or equal to 1, representing the length of the delay line in the joint space-time domain filter; represents the time delay length of the joint space-time domain filter; represents the far-field plane wave signal received by the th array element at the th time instant the adaptive weight coefficient of the length delay line at the th length; represents the signal time-delayed by units for the th array element; The initial value of is the all-zero vector, and the corresponding update expression is:

[0015]

[0016] wherein, is an integer greater than or equal to 1, representing the number of array elements in the uniform linear array; is an integer greater than or equal to 1, representing the length of the delay line in the joint space-time domain filter; is the adaptive step size; represents the signal time-delayed by units for the th array element; represents the Adaptive error at time step ; Indicates the first Time of the first Individual Length delay line at the 1st Adaptive weighting coefficients at the length;

[0017] Step 4: Repeat step 3, using the far-field plane wave signal received by the next array element as a reference signal input to the spatiotemporal joint filter, until all far-field plane wave signals received by all array elements in the uniform linear array have been processed, to obtain the far-field plane wave signal received by each array element. Each corresponding output signal ;

[0018] Step 5: Acquire each output signal separately. The corresponding output spectrum ;

[0019] Step 6: Perform tests on multiple output spectra. Perform the summation of squares and take the average to obtain the output result. , Expressed as a formula:

[0020]

[0021] In the formula, An integer greater than or equal to 1 represents the number of array elements in the uniform linear array; Represents discrete frequency points, with values ​​ranging from 0 to... between, Indicates the sampling frequency;

[0022] Step 7: Output the results From frequency domain to time domain, obtain based on Sparse-driven adaptive line spectrum enhancer based on norm ( -ALE) second input signal ;

[0023] Step 8: Transfer the second input signal Input based on Sparse-driven adaptive line spectrum enhancer based on norm ( -ALE) is used to update the weights, and the weight update formula is:

[0024]

[0025] In the formula, Indicates adaptive step size; This represents the balance parameter used to adjust the weights of sparse terms; Representing vectors of Norm; This represents the element-wise multiplication of vectors. Represents discrete frequency points, with values ​​ranging from 0 to... between, Represents the sampling frequency; This represents the adaptive error of the previous iteration cycle; The frequency domain representation of the adaptive weight vector before iterative update; This is the frequency domain representation of the adaptive weight vector after iterative updates; Input time-domain signal vector After time delay Signal of one unit Frequency domain representation;

[0026] Step 9, based on Sparse-driven adaptive line spectrum enhancer based on norm ( The weight update formula for -ALE is based on the second input signal. Length of continuous iterative adaptive weights To obtain the output signal of the spatiotemporally joint sparse-driven adaptive line spectrum enhancer. .

[0027] In the above method, in step 5, the output spectrum is... Expressed as a formula:

[0028]

[0029] In the formula, This indicates that after step 4, the... The output signal of each array element; It represents discrete sampling time points, determined by the sampling length and sampling frequency; Represents discrete frequency points, with values ​​ranging from 0 to... between, Indicates the sampling frequency; This represents the Fourier transform.

[0030] In the above method, the result is output in step 7. The formula for converting from the frequency domain to the time domain is:

[0031]

[0032] In the formula, Indicates the inverse Fourier transform; Represents discrete frequency points, with values ​​ranging from 0 to... between, Represents the sampling frequency; Represents frequency point Spectral values ​​on; Representing discrete points in time, Indicates the first The processing result at any given moment, i.e., based on The second input signal of the norm-driven sparse adaptive line spectrum enhancer.

[0033] According to the technical solution provided in this application, at least the following beneficial effects are achieved: The output signal corresponding to each array element is obtained by using the far-field plane wave signal received by the corresponding array element as a reference signal and the far-field plane wave signal received by the entire uniform linear array as the first input signal to a joint space-time filter; then, the corresponding output spectrum is obtained based on the output signal of each array element, and the multiple output spectra are squared and averaged to obtain the output result; finally, the output result is converted from the frequency domain to the time domain to obtain a result based on… The second input signal of the sparse-driven adaptive line spectrum enhancer based on the norm; finally, this second input signal is input to a line spectrum enhancer based on... A sparse-driven adaptive line spectrum enhancer based on the norm updates its weights to obtain the output signal of a spatiotemporally joint sparse-driven adaptive line spectrum enhancer. This application, based on spatiotemporally joint information processing, can adaptively enhance line spectrum signals in both the spatial and temporal domains, with lower signal-to-noise ratio requirements. Utilizing the sparsity of the frequency domain for line spectrum enhancement, this application solves the problems of conventional adaptive line spectrum enhancers being susceptible to steady-state adaptive weight noise and performance degradation under low input signal-to-noise ratio conditions, effectively improving line spectrum enhancement performance.

[0034] Other features and advantages of this application will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the application. The objectives and other advantages of this application may be realized and obtained by means of the structures particularly pointed out in the description, claims and drawings. Attached Figure Description

[0035] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0036] Figure 1 A flowchart illustrating the method provided in this application embodiment;

[0037] Figure 2 This is a schematic diagram of the structure of the joint space-time filter provided in the embodiments of this application;

[0038] Figure 3 A schematic diagram of the structure of a spatiotemporally joint sparse-driven adaptive line spectrum enhancer provided in an embodiment of this application;

[0039] Figure 4 The spectrum of a far-field plane wave signal received by a single array element in an embodiment of this application;

[0040] Figure 5 The spectral output processed by the average power spectrum method provided in the embodiments of this application;

[0041] Figure 6 The spectral output of the joint spatiotemporal power spectrum estimation method provided in the embodiments of this application;

[0042] Figure 7 The spectral output of the line spectrum enhancement method provided in the embodiments of this application. Detailed Implementation

[0043] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0044] It should be noted that although functional modules are divided in the device schematic diagram and a logical order is shown in the flowchart, in some cases, the steps shown or described may be performed in a different order than the module division in the device or the order in the flowchart. The terms "first," "second," etc., in the specification, claims, and the aforementioned drawings are used to distinguish similar objects and not to describe a specific order or sequence.

[0045] To make the objectives, technical solutions, and advantages of this application clearer, the embodiments of this application will be described in further detail below with reference to the accompanying drawings.

[0046] This application addresses the issues of existing sparse-driven adaptive line spectrum enhancers being susceptible to steady-state adaptive weight noise and experiencing performance degradation under low input signal-to-noise ratio conditions. By combining spatiotemporal joint filtering techniques with frequency-domain sparse-driven adaptive line spectrum enhancement techniques, a spatiotemporal joint sparse-driven adaptive line spectrum enhancement method is proposed.

[0047] like Figure 1 As shown, embodiments of this application provide a spatiotemporally joint sparse-driven adaptive line spectrum enhancement method, which includes the following steps:

[0048] Step 1: Use a uniform linear array of hydrophones to receive the far-field plane wave signal from the source. The far-field plane wave signal received by the entire uniform linear array is... , Expressed as a formula:

[0049]

[0050] In the formula, An integer greater than or equal to 1, representing the number of elements in a uniform linear array; For integers greater than or equal to 0, Indicates the first The array element in the first The far-field plane wave signal received at any given time.

[0051] Step 2: Receive the far-field plane wave signal from the entire uniform linear array. It serves as the first input signal to the space-time joint filter.

[0052] In this step, the structure of the joint space-time filter is as follows: Figure 2 As shown, its essence is an improved structure of a multi-input adaptive filter. The reference signal is the far-field plane wave signal received by the corresponding array element, and the first input signal is the far-field plane wave signal received by all array elements. The far-field plane wave signals received by all array elements are first subjected to an additional delay in the spatiotemporal joint filter. The difference between the signal and the corresponding reference signal after processing by the Tapped Delay Line (TDL) is used as the error signal for the LMS adaptive algorithm to perform adaptive weight iterative updates.

[0053] Step 3, place the first Far-field plane wave signal received by each array element As a reference signal input to the space-time joint filter, its corresponding output signal Expressed as a formula:

[0054]

[0055] In the formula, An integer greater than or equal to 1 represents the number of array elements in the uniform linear array; An integer greater than or equal to 1, representing the length of the tapped delay line (TDL) in the space-time joint filter; Indicates the time delay of the combined space-time filter; Indicates the first Time of the first Individual Length delay line at the 1st Adaptive weighting coefficients at the length; Indicates the first Each array element experiences time delay. Signal of one unit; The initial value is a vector of all zeros, and its corresponding update expression is:

[0056]

[0057] In the formula, An integer greater than or equal to 1, representing the number of elements in a uniform linear array; is an integer greater than or equal to 1, representing the length of the delay line in the space-time joint filter; For adaptive step size; Indicates the first Each array element experiences time delay. Signal of one unit; Indicates the first Adaptive error at time step ; Indicates the first Time of the first Individual Length delay line at the 1st Adaptive weighting coefficients at the length.

[0058] Step 4: Repeat step 3, using the far-field plane wave signal received by the next array element as a reference signal input to the space-time joint filter, until all far-field plane wave signals received by all array elements in the uniform linear array have been processed, in order to obtain the far-field plane wave signal received by each array element. Each corresponding output signal .

[0059] In this step, when the far-field plane wave signal received by the first array element is acquired... Corresponding output signal At that time, the far-field plane wave signal received by the first array element needs to be... As a reference signal input to the spatiotemporal joint filter, the far-field plane wave signals received by all array elements are subject to additional delay. The signal obtained by subtracting the delay line signal and the superimposed signal from the reference signal is used as the error signal of the first array element. This error signal is then fed into the LMS adaptive algorithm to iteratively update the adaptive weights of the delay line. The output signal is obtained in each iteration. The amplitude corresponding to a point in time; when the iteration ends, the output signal is obtained. By analyzing the amplitudes at all time points, the output signal corresponding to the first array element can be obtained. .

[0060] When the far-field plane wave signal received by the second array element is acquired Corresponding output signal At that time, the far-field plane wave signal received by the second array element needs to be... As a reference signal input to the spatiotemporal joint filter, the far-field plane wave signals received by all array elements are subject to additional delay. The signal obtained by subtracting the delay line signal and the superimposed signal from the reference signal is used as the error signal of the second array element. This error signal is then fed into the LMS adaptive algorithm to iteratively update the adaptive weights of the delay line. The output signal is obtained in each iteration. The amplitude corresponding to a point in time; when the iteration ends, the output signal is obtained. By analyzing the amplitudes at all time points, the output signal corresponding to the second array element can be obtained. .

[0061] When acquiring the output signal corresponding to the far-field plane wave signal received by the other array elements, the process is similar to that described above and will not be repeated here.

[0062] Step 5: Acquire each output signal separately. The corresponding output spectrum .

[0063] In this step, the output spectrum is... Expressed as a formula:

[0064]

[0065] In the formula, This represents the result after step 4. The output signal of each array element; It represents discrete sampling time points, determined by the sampling length and sampling frequency; Represents discrete frequency points, with values ​​ranging from 0 to... between, Represents the sampling frequency; This represents the Fourier transform.

[0066] Step 6: Perform tests on multiple output spectra. Perform the summation of squares and take the average to obtain the output result. , Expressed as a formula:

[0067]

[0068] In the formula, An integer greater than or equal to 1, representing the number of elements in a uniform linear array; Represents discrete frequency points, with values ​​ranging from 0 to... between, Represents the sampling frequency;

[0069] Step 7: Output the results From frequency domain to time domain, obtain based on The second input signal of the norm-driven sparse adaptive line spectrum enhancer .

[0070] In this step, the output result is... The formula for converting from the frequency domain to the time domain is:

[0071]

[0072] In the formula, Indicates the inverse Fourier transform; Represents discrete frequency points, with values ​​ranging from 0 to... between, Represents the sampling frequency; Represents frequency point Spectral values ​​on; Representing discrete points in time, Indicates the first The processing result at any given moment, i.e., based on The second input signal of the norm-driven sparse adaptive line spectrum enhancer.

[0073] Step 8: Transfer the second input signal Input based on Sparse-driven adaptive line spectrum enhancer based on norm ( -ALE) is used to update the weights, and the weight update formula is:

[0074]

[0075] In the formula, Indicates adaptive step size; This represents the balance parameter used to adjust the weights of sparse terms; Representing vectors of Norm; This represents the element-wise multiplication of vectors. Represents discrete frequency points, with values ​​ranging from 0 to... between, Represents the sampling frequency; This represents the adaptive error of the previous iteration cycle; The frequency domain representation of the adaptive weight vector before iterative update; This is the frequency domain representation of the adaptive weight vector after iterative updates; Input time-domain signal vector After time delay Signal of one unit The frequency domain representation of .

[0076] Step 9, based on The weight update formula for the norm-driven sparse adaptive line spectrum enhancer is based on the second input signal. Length of continuous iterative adaptive weights To obtain the output signal of the spatiotemporally joint sparse-driven adaptive line spectrum enhancer. .

[0077] In this application, the structure of the spatiotemporally joint sparse-driven adaptive line spectrum enhancer is as follows: Figure 3 As shown, the spatiotemporally joint sparse-driven adaptive line spectrum enhancer combines the spatiotemporally joint filter with a sparse-driven line spectrum enhancer based on... The norm-based sparse-driven adaptive line spectrum enhancer combines the squared superposition and average of the output spectra of each element of the spatiotemporal joint filter to obtain the corresponding output result. Then output the result After conversion from the frequency domain to the time domain, the input is based on The norm-driven sparse adaptive line spectrum enhancer is used to obtain the final output signal.

[0078] The following section will compare and verify the sparse-driven adaptive line spectrum enhancement method based on spatiotemporal domain joint proposed in this application from the perspective of computer simulation.

[0079] The specific parameters of the simulation environment are as follows:

[0080] Number of signal sources: 4;

[0081] Signal source frequencies: (50Hz, 80Hz, 140Hz, 180Hz);

[0082] Signal source nature: Single-frequency signal;

[0083] Sampling frequency: 2000Hz;

[0084] Snap count: 3000;

[0085] Signal-to-noise ratio: -25dB;

[0086] Adaptive step size: ;

[0087] The filter length of the joint space-time filter is 128.

[0088] Delay points of the joint space-time filter: 10;

[0089] Sparse weight coefficients of the sparse-driven adaptive line spectrum enhancer: ;

[0090] Tap length of sparse-driven adaptive line spectrum enhancer: 2000;

[0091] The demodulation delay of the sparse-driven adaptive line spectrum enhancer is 100.

[0092] Array type: 8-element horizontal hydrophone array;

[0093] Element spacing: half the incident wavelength of the signal;

[0094] like Figure 4 As shown, four lines in the spectrum of the far-field plane wave signal received by a single array element are obscured by noise and are difficult to observe. Based on the average power spectrum method, by directly superimposing and averaging the power spectra of the far-field plane wave signal received by the array element, the following can be obtained: Figure 5 The normalized frequency output is shown. (Through...) Figure 4 and Figure 5 It is evident that, compared to the power spectrum of a single array element, the average power spectrum method significantly reduces the output error of the line spectrum and increases the amplitude of the line spectrum, but the background noise suppression is not thorough enough.

[0095] The far-field plane wave signals received by each array element are processed using a joint spatiotemporal power spectrum estimation method, and the output results are as follows: Figure 6 As shown. (Through) Figure 5 and Figure 6 It is evident that, compared to the average power spectrum method, the power spectrum estimation method based on the joint space-time domain has higher spectral peaks and lower background noise; this indicates that the power spectrum estimation method based on the joint space-time domain can more effectively utilize two-dimensional space-time information.

[0096] The power spectrum estimation method based on the joint space-time domain is used as a reference. The preprocessing module of the norm-based sparse-driven adaptive line spectrum enhancer processes the line spectrum input after it has been processed by the joint spatiotemporal power spectrum estimation method. Norm-driven sparse adaptive line spectrum enhancer processing can yield results such as Figure 7 The output results are shown below. Figure 7 As can be seen, the spectral peaks of the line spectrum are more obvious, and the background noise is also more significantly suppressed; this shows that the sparse-driven adaptive line spectrum enhancement method with spatiotemporal joint proposed in this application can significantly improve the enhancement performance of the line spectrum.

[0097] This application is based on a sparse-driven adaptive line spectrum enhancer, which is suitable for underwater acoustic environments with low signal-to-noise ratios.

[0098] The above is a detailed description of the preferred embodiments of this application. However, this application is not limited to the above embodiments. Those skilled in the art can make various equivalent modifications or substitutions without departing from the spirit of this application. All such equivalent modifications or substitutions are included within the scope defined by the claims of this application.

Claims

1. A spatiotemporally joint sparse-driven adaptive line spectrum enhancement method, characterized in that, Includes the following steps: Step 1: Utilize a uniform linear array of hydrophones to receive the far-field plane wave signal from the signal source. The far-field plane wave signal received by the entire uniform linear array is... , Expressed as a formula: In the formula, An integer greater than or equal to 1 represents the number of array elements in the uniform linear array; For integers greater than or equal to 0, Indicates the first The array element in the first The far-field plane wave signal received at any given time; Step 2: Receive the far-field plane wave signal from the entire uniform linear array. As the first input signal, input to the space-time joint filter; Step 3, place the first Far-field plane wave signal received by each array element As a reference signal input to the space-time joint filter, its corresponding output signal Expressed as a formula: In the formula, An integer greater than or equal to 1 represents the number of array elements in the uniform linear array; is an integer greater than or equal to 1, representing the length of the delay line in the space-time joint filter; Indicates the time delay of the combined space-time filter; Indicates the first Time of the first Individual Length delay line at the Adaptive weighting coefficients at the length; Indicates the first Each array element undergoes time delay. Signal of one unit; The initial value is a vector of all zeros, and its corresponding update expression is: In the formula, An integer greater than or equal to 1 represents the number of array elements in the uniform linear array; is an integer greater than or equal to 1, representing the length of the delay line in the space-time joint filter; For adaptive step size; Indicates the first Each array element undergoes time delay. Signal of one unit; Indicates the first Adaptive error at time step ; Indicates the first Time of the first Individual Length delay line at the Adaptive weighting coefficients at the length; Step 4: Repeat step 3, using the far-field plane wave signal received by the next array element as a reference signal input to the spatiotemporal joint filter, until all far-field plane wave signals received by all array elements in the uniform linear array have been processed, to obtain the far-field plane wave signal received by each array element. Each corresponding output signal ; Step 5: Acquire each output signal separately. The corresponding output spectrum ; Step 6: Perform tests on multiple output spectra. Perform the summation of squares and take the average to obtain the output result. , Expressed as a formula: In the formula, An integer greater than or equal to 1 represents the number of array elements in the uniform linear array; Represents discrete frequency points, with values ​​ranging from 0 to... between, Indicates the sampling frequency; Step 7: Output the results From frequency domain to time domain, obtain based on The second input signal of the norm-driven sparse adaptive line spectrum enhancer ; Step 8: Transfer the second input signal Input based on The norm-driven sparse adaptive line spectrum enhancer performs weight updates, and the weight update formula is as follows: In the formula, Indicates adaptive step size; This represents the balance parameter used to adjust the weights of sparse terms; Representing vectors of Norm; This represents the element-wise multiplication of vectors. Represents discrete frequency points, with values ​​ranging from 0 to... between, Represents the sampling frequency; This represents the adaptive error of the previous iteration cycle; The frequency domain representation of the adaptive weight vector before iterative update; This is the frequency domain representation of the adaptive weight vector after iterative updates; Input time-domain signal vector After time delay Signal of one unit Frequency domain representation; Step 9, based on The weight update formula for the norm-driven sparse adaptive line spectrum enhancer is based on the second input signal. Length of continuous iterative adaptive weights To obtain the output signal of the spatiotemporally joint sparse-driven adaptive line spectrum enhancer. .

2. The spatiotemporally joint sparse-driven adaptive line spectrum enhancement method according to claim 1, characterized in that, In step 5, the output spectrum is... Expressed as a formula: In the formula, This indicates that after step 4, the... The output signal of each array element; It represents discrete sampling time points, determined by the sampling length and sampling frequency; Represents discrete frequency points, with values ​​ranging from 0 to... between, Indicates the sampling frequency; This represents the Fourier transform.

3. The spatiotemporally joint sparse-driven adaptive line spectrum enhancement method according to claim 1, characterized in that, In step 7, the results are output. The formula for converting from the frequency domain to the time domain is: In the formula, Indicates the inverse Fourier transform; Represents discrete frequency points, with values ​​ranging from 0 to... between, Represents the sampling frequency; Represents frequency point Spectral values ​​on; Representing discrete points in time, Indicates the first The processing result at any given moment, i.e., based on The second input signal of the norm-driven sparse adaptive line spectrum enhancer.

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