Automatic measurement method for array gain of acoustic array

Abstract

The invention provides a method for automatically measuring the gain of an acoustic array, and particularly relates to the technical field of sonar acoustic array performance testing. The method comprises the following steps of: 1, reading a receiving signal of an acoustic array, and performing pulse interception processing on array element time domain data to obtain starting and ending moments of a pulse signal; 2, intercepting a target signal and a noise signal according to the starting moment and the ending moment; step 3, performing narrowband filtering on the target signal and the noise signal according to a set frequency to filter out-of-band noise; 4, setting variable decimal time delay filter parameters; 5, time delay filtering is carried out on the filtered target signal and noise signal, and filter parameters are set according to the target orientation; 6, solving a correlation coefficient of the signal and the noise; and step 7, generating and outputting the gain of the acoustic array. According to the test method, the array gain of the sonar is calculated by measuring the correlation coefficient of the signal and the correlation coefficient of the noise. The measurement process of the array gain is simplified to the greatest extent, and the measurement efficiency is improved.

Description

Technical Field

[0001] The invention relates to the technical field of sound-based array gain measurement, and mainly relates to an automatic measurement method for sound-based array gain. Background Art

[0002] In the engineering design of sonar systems, in order to ensure the amplitude and phase consistency and detection performance of the acoustic array, it is usually necessary to measure the array gain of the acoustic array. The array gain of the acoustic array is one of the important contents of underwater acoustic measurement and testing, and it is also an important indicator for measuring sonar detection performance. The array gain refers to the ratio between the output signal-to-noise ratio and the input signal-to-noise ratio. The higher the array gain, the stronger the spatial noise suppression capability of the acoustic array. Conversely, the worse the spatial noise suppression capability of the acoustic array.

[0003] The specific steps of measuring the array gain of a traditional acoustic array are as follows: Step 1: Measure the noise power and target signal power, and calculate the input signal-to-noise ratio; Step 2: Perform single-beam listening processing on the time domain signal of the acoustic array to obtain the output time domain data; Step 3: Calculate the signal power and noise power of the output time domain data. The traditional array gain underwater acoustic measurement method has some defects: First, the calculation of the input signal-to-noise ratio requires manual reading, which is prone to human reading errors, especially the actual noise background and numerous interference targets will cause fluctuations in the measurement results; second, the operation is complicated, the test results are inaccurate, and automatic measurement cannot be achieved by relying on algorithms. Therefore, it is necessary to propose a new measurement method to measure the array gain of an acoustic array, and the test method should be robust and reliable. Summary of the invention

[0004] The purpose of the present invention is to overcome the shortcomings of the prior art and provide an automatic measurement method for acoustic base array gain.

[0005] The object of the present invention is achieved by the following technical solution. The present invention proposes an automatic measurement method of acoustic base array gain, comprising the following steps:

[0006] Step 1: Read the received signal of the acoustic array, and perform pulse capture processing on the array element time domain data to obtain the start and end time of the pulse signal;

[0007] Step 2: Intercept the target signal and the noise signal according to the start and end times;

[0008] Step 3: Perform narrow-band filtering on the target signal and noise signal according to the set frequency to filter out the out-of-band noise;

[0009] Step 4: Set the variable fractional delay filter parameters;

[0010] Step 5: Perform time delay filtering on the filtered target signal and noise signal, and the filter parameters are set according to the target direction.

[0011] Step 6: Solve the correlation coefficient between signal and noise;

[0012] Step 7: Generation and output of sound-based array gain.

[0013] The beneficial effects of the present invention are as follows: a brand-new strategy is adopted to solve the shortcomings of the prior art that the measurement accuracy of the effective value of the signal and noise and the signal-to-noise ratio is not accurate enough, or there are too many measurement steps in the measurement process. The present invention is an automatic measurement method, which can automatically output the acoustic base array gain by inputting signal data, target signal parameters and other data, and utilizes the correlation coefficient of the signal and the correlation coefficient of the noise, that is, utilizes the correlation of the signal to solve the array gain, thereby avoiding the estimation of the input signal-to-noise ratio, avoiding human reading errors, simplifying the operation steps, and improving the measurement efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art or ordinary technicians, other drawings can be obtained based on these drawings without paying creative work.

[0015] Figure 1 A flow chart of a method for automatically measuring the gain of a base array according to the present invention;

[0016] Figure 2 It is a schematic diagram of the time domain signal waveform;

[0017] Figure 3 Schematic diagram of the intercepted pulse target signal and noise signal;

[0018] Figure 4 Schematic diagram of pulse target signal and noise signal after filtering;

[0019] Figure 5 Schematic diagram of the amplitude-frequency characteristic curve of the variable fractional delay filter;

[0020] Figure 6 It is a schematic diagram of the phase-frequency characteristic curve of the variable fractional delay filter;

[0021] Figure 7 It is a schematic diagram of the pulse target signal and the noise signal after time delay filtering;

[0022] Figure 8 Schematic diagram of the pulse target signal of array element No. 1 and the pulse target signal of array element No. 5 after delay filtering. DETAILED DESCRIPTION

[0023] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work belong to the protection scope of the present invention.

[0024] Embodiments of the present invention will now be described with reference to the accompanying drawings. Figure 1 As shown, the method of the embodiment of the present invention includes the following steps:

[0025] Step 1: Read the received signal of the acoustic array and perform pulse capture processing on the array element time domain data to obtain the start and end time of the pulse signal. The specific steps are:

[0026] Step 1.1: Read the received signal of the acoustic array and obtain the time domain signal x m (n), 1≤m≤M, 1≤n≤N1, where M is the total number of array elements of the acoustic array, and N1 is the length of the time domain data sequence;

[0027] Step 1.2: Use the setting signal s(n), 1≤n≤N2 to calculate the time domain signal x m (n) Conduct relevant tests;

[0028]

[0029] Step 1.3: Find the maximum value of the cross-correlation function [Amp, Imax] = max(R sx (k)), Amp is the maximum value of the cross-correlation function, and Imax is the time corresponding to the maximum value.

[0030] Step 1.4: Get the starting N of the target pulse signal b and the end time N e ;

[0031] N b =Imax-N1+1

[0032] N e =Imax

[0033] Step 2: Intercept the target signal and noise signal according to the start and end time. The specific steps are:

[0034] Step 2.1: The target signal is

[0035]

[0036] Step 2.2: The noise signal is

[0037]

[0038] Step 3: Perform narrow-band filtering on the target signal and noise signal according to the set frequency to filter out the out-of-band noise. The specific steps are:

[0039] Step 3.1: For the time domain data xs m (n) and xn m (n) Perform narrowband filtering to remove out-of-band noise to obtain narrowband signals and narrowband noise signals:

[0040] xs1 m (n) = filter(H1,xs m (n))

[0041] xn1 m (n) = filter(H1,xn m (n))

[0042] Among them, H1 is a narrowband filter with a set frequency;

[0043] Step 4: Set the variable fractional delay filter parameters. The specific steps are:

[0044] Step 4.1: The objective function of fitting the frequency characteristics of the digital delay filter is

[0045] minimax W(ω)|H(ω,p)-H d (ω,p)|

[0046] Where H(ω,p) is the ideal infinite length h m The Fourier transform of (p), H d (ω,p) is the target frequency characteristic, and W(ω) is the frequency weighting function. The structure of the fitting filter is

[0047]

[0048] Where Nf is the number of taps of the filter, h m (p) is the filter coefficient of delay p, then the delay filter is:

[0049]

[0050] Among them, P is the order of fitting, a mn is the filter coefficient.

[0051] Step 5: Perform time delay filtering on the filtered target signal and noise signal, and the filter parameters are set according to the target direction.

[0052] The specific steps are:

[0053] Step 5.1: Assuming the target direction is θ, the delay of the mth array element compared to the first array element is

[0054]

[0055] Step 5.2: Set the filter parameters of the variable fractional delay filter and set τ m Substitute the filter parameters obtained by the time delay filter to perform time delay filtering on the signal and noise of the mth array element. The output result can be expressed as:

[0056] yx m (t) = filter(H d (ω,τ m ),xs1 m (n))

[0057] yn m (t) = filter(H d (ω,τ m ),xn1 m (n))

[0058] Step 6: Solve the correlation coefficient between signal and noise. The specific steps are:

[0059] Step 6.1: Solve the signal correlation coefficient between any two array elements

[0060]

[0061] The “horizontal line” represents the time average, and the denominator represents the normalization factor, ρs mn represents the signal correlation coefficient between the mth array element and the nth array element.

[0062] Step 6.2: Solve for the noise correlation coefficient between any two array elements

[0063]

[0064] Among them, ρn mn represents the noise correlation coefficient between the mth array element and the nth array element.

[0065] Step 7: Generation and output of sound-based array gain.

[0066] Step 7.1: Calculate the array gain of the sonar receiving array using the signal and noise between each array element:

[0067]

[0068] Example:

[0069] Figure 1 The invention relates to an automatic measurement method of the gain of a base array; Figure 2 is the input time domain signal waveform; by performing correlation detection on the time domain signal, the pulse target signal and the noise target signal are obtained at the start and end time of the target, such as Figure 3 As shown; the pulse target signal and the noise signal are subjected to narrowband filtering to obtain the filtered pulse target signal and the noise signal, as shown Figure 4 As shown; Figure 5 is the amplitude-frequency characteristic curve of the variable fractional delay filter; Figure 6 is the phase-frequency characteristic curve of the variable fractional delay filter; Figure 7 are the target pulse signal and the noise signal after being filtered by the variable fractional delay filter; Figure 8 are the target pulse signals of array element No. 1 and array element No. 5 after filtering by the variable fractional delay filter; Table 1 is the correlation coefficient of the target pulse signals between the array elements, and Table 2 is the correlation coefficient of the noise signals between the array elements. According to the calculation method of array gain, the array gain estimated by the new method is 5.4dB, and the theoretical array gain is 7dB. Since the actual noise is non-Gaussian white noise, there is a certain correlation, which will cause an array gain loss of about 2dB. The above results verify the feasibility of the new method.

[0070] Table 1

[0071] Array 1 Array 2 Array 3 Array 4 Array 5 Array 1 1.0000 0.9999 0.9999 0.9999 0.9999 Array 2 0.9999 1.0000 0.9999 0.9999 1.0000 Array 3 1.0000 0.9999 1.0000 1.0000 1.0000 Array 4 1.0000 0.9999 1.0000 1.0000 0.9999 Array 5 1.0000 0.9999 1.0000 0.9999 1.0000

[0072] Table 2

[0073] Array 1 Array 2 Array 3 Array 4 Array 5 Array 1 1.00 -0.11 0.18 0.43 0.01 Array 2 -0.11 1.00 -0.10 0.02 0.04 Array 3 0.18 -0.10 1.00 0.31 0.31 Array 4 0.43 0.02 0.31 1.00 -0.01 Array 5 0.01 0.04 0.31 -0.01 1.00

[0074] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention shall be based on the protection scope of the claims.

Claims

1. An automatic measurement method for acoustic base array gain, characterized in that: The following steps are involved: Step 1: Read the received signal of the acoustic array, perform pulse capture processing on the array element time domain data to obtain the start and end time of the pulse signal; Step 2: Intercept the target signal and the noise signal according to the start and end times; Step 3: Perform narrow-band filtering on the target signal and noise signal according to the set frequency to filter out the out-of-band noise; Step 4: Set the variable fractional delay filter parameters; Step 5: Delay filtering is performed on the filtered target signal and noise signal, and the filter parameters are set according to the target direction; Step 6: Solve the correlation coefficient between signal and noise; Step 7: Generation and output of sound-based array gain.

2. The automatic measurement method of acoustic base array gain according to claim 1, characterized in that: The specific steps of step 1 are: Step 1.1: Read the received signal of the acoustic array and obtain the time domain signal x m (n), 1≤m≤M, 1≤n≤N1, where M is the total number of array elements of the acoustic array, and N1 is the length of the time domain data sequence; Step 1.2: Use the setting signal s(n), 1≤n≤N2 and the time domain signal x m (n) Conduct relevant tests; Step 1.3: Find the maximum value of the cross-correlation function [Amp, Imax] = max(R sx (k)), Amp is the maximum value of the cross-correlation function, and Imax is the time corresponding to the maximum value; Step 1.4: Get the starting N of the target pulse signal b and the end time N e ; 3. The automatic measurement method of acoustic base array gain according to claim 2, characterized in that: The specific steps of step 2 are: Step 2.1: The target signal is Step 2.2: The noise signal is 4. The automatic measurement method of acoustic base array gain according to claim 3, characterized in that: The specific steps of step 3 are: Step 3.1: For the time domain data xs m (n) and xn m (n) Perform narrowband filtering to remove out-of-band noise to obtain narrowband signals and narrowband noise signals: xs1 m (n)=filter(H1,xs m (n)) xn1 m (n)=filter(H1,xn m (n)) Among them, H1 is a narrowband filter with a set frequency.

5. The automatic measurement method of acoustic base array gain according to claim 4, characterized in that: The specific steps of step 4 are: Step 4.1: The objective function of fitting the frequency characteristics of the digital delay filter is minimax W(ω)|H(ω,p)-H d (ω,p)| Where H(ω,p) is the ideal infinite length h m The Fourier transform of (p), H d (ω,p) is the target frequency characteristic, W(ω) is the frequency weighting function, and the structure of the fitting filter is Where Nf is the number of taps of the filter, h m (p) is the filter coefficient of delay p, then the delay filter is: Among them, P is the order of fitting, a mn is the filter coefficient.

6. The automatic measurement method of acoustic base array gain according to claim 5, characterized in that: The specific steps of step 5 are: Step 5.1: Assuming the target direction is θ, the delay of the mth array element compared to the first array element is Step 5.2: Set the filter parameters of the variable fractional delay filter and set τ m Substitute the filter parameters obtained by the time delay filter to perform time delay filtering on the signal and noise of the mth array element. The output result is expressed as:

7. The automatic measurement method of acoustic base array gain according to claim 6, characterized in that: The specific steps of step 6 are: Step 6.1: Solve the signal correlation coefficient between any two array elements The "horizontal line" represents the time average, and the denominator represents the normalization factor, ρs mn represents the signal correlation coefficient between the mth array element and the nth array element; Step 6.2: Solve for the noise correlation coefficient between any two array elements Among them, ρn mn represents the noise correlation coefficient between the mth array element and the nth array element.

8. The automatic measurement method of acoustic base array gain according to claim 7, characterized in that: The specific steps of step 7 are: Step 7.1: Calculate the array gain of the sonar receiving array using the signal and noise between each array element:

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