CN113704685A - Deep sea blind deconvolution method based on vertical line array - Google Patents
Deep sea blind deconvolution method based on vertical line array Download PDFInfo
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Abstract
The invention relates to a blind deconvolution method based on a vertical line array, which is suitable for the estimation problem of channel impulse response between a deep-sea large-depth vertical line array and a broadband sound source near the sea surface, and belongs to the fields of ocean engineering, underwater acoustic engineering, array signal processing, sonar technology and the like. The method of the invention introduces the time delay difference information of direct waves and sea surface reflected waves in the conventional broadband wave beam output into the channel impulse response estimation, and utilizes the multi-path time delay difference information and the output phase of the wave beam former to construct a new phase compensation item. Under a typical deep sea environment, the method can correctly estimate the channel impulse response between the sound source and the receiving array, and the estimation effect is superior to that of the existing RBD method. The method is simple in calculation and small in calculation amount.
Description
Technical Field
The invention relates to a blind deconvolution method based on a vertical line array in a deep sea environment, which is suitable for the estimation problem of channel impulse response between a deep sea large-depth vertical line array and a broadband sound source near the sea surface, and belongs to the fields of ocean engineering, underwater sound engineering, array signal processing, sonar technology and the like.
Background
Accurately estimating the channel impulse response between the acoustic source and the receiving array is of great significance to underwater acoustic communications and underwater target localization. With array received signals, the blind deconvolution method can simultaneously estimate the channel impulse response and the sound source signal waveform, so it has been widely noticed by underwater acoustic workers. At present, the blind deconvolution method mainly includes a time-frequency analysis method, a least square method, a multi-convolution method, and a blind deconvolution method based on a ray theory.
Among the above blind deconvolution methods, the Ray-based blind deconvolution (RBD) method has the advantages of simple practical application, small calculation amount, and the like, and has been widely applied to the problems of channel equalization, shallow sea sound source localization, seabed parameter inversion, matrix calibration, and the like. The basic idea of the RBD method is as follows: firstly, separating a certain sound ray reaching a receiving array by using a conventional broadband beam former and outputting a beam, wherein the phase of the beam output comprises the phase of an unknown sound source and a time delay related to the selected sound ray; and then, the phase of the wave beam output is utilized to perform phase compensation on the received signals of each array element, so that the channel impulse response under the current transceiving configuration can be obtained.
However, in a deep sea environment, the conventional RBD method cannot be directly applied to a large-depth short-aperture vertical array. The reason for this is that: when the array is positioned near the sea bottom and the sound source is positioned near the sea surface, the amplitudes of the sound ray direct path and the sound ray reflection path (or the sea bottom reflection path and the sea surface-sea bottom reflection path) are approximately the same and the arrival pitch angle is very close, at the moment, for the short-aperture vertical line array, two paths with approximately equal amplitudes are contained in the output signal of the conventional broadband wave beam forming wave beam, and the aliasing of the two sound propagation paths limits the application of the conventional RBD method in the deep sea environment.
Disclosure of Invention
Technical problem to be solved
In order to solve the problem of performance degradation caused by insufficient array beam resolving power and multipath aliasing in the deep sea environment of the conventional RBD method, the invention provides a deep sea blind deconvolution method based on a vertical line array. The method constructs a phase compensation factor based on the time delay difference of direct and sea surface reflection paths and the output phase of a beam former, and performs phase compensation on a sound source receiving signal by using the constructed compensation factor so as to estimate channel impulse response.
Technical scheme
A deep sea blind deconvolution method based on a vertical line array is characterized by comprising the following steps:
step 1: a set of vertical line array is arranged on the deep sea bottom to receive broadband signals emitted by a sea sound source; the vertical line array consists of M array elements, the interval of the array elements is d, and the sampling frequency of the array is fsThe time domain signal received by the jth array element is xj(k) K is a sampling time point;
step 2: performing frequency domain broadband beam forming on the vertical line array receiving signals, wherein the specific process is as follows: firstly, fast Fourier transform is carried out on array element receiving signals to obtain frequency domain receiving signals, and the frequency domain receiving signals of the jth array element are recorded as Xj(f) (ii) a Next, in the designated frequency band [ B ]1,B2]Within Hz, the received signal on each frequency point is formed into wave beam, frequency point fnThe beamformer weighting at the pointing angle θ is
Wherein the superscript "T" represents transposition operation, c is a beam forming reference sound velocity, and i is an imaginary number unit; frequency point fnThe beamformer output at pointing angle θ is
Wherein the superscript "H" represents the conjugate transpose operation, "x" represents the vector multiplication, and N is 1,2, …, N is the number of beamforming frequency points;
in a specified frequency band [ B1,B2]Within Hz, the outputs of the beam formers of all frequency points are subjected to incoherent superposition to obtain a broadband beam forming azimuth spectrum
And step 3: note that the angle corresponding to the maximum value of the beam forming azimuth spectrum B (θ) is θmaxTake θmaxOutput component vector of beam former of all frequency points corresponding to direction
Y(θmax)＝[Y(θmax,f1),Y(θmax,f2),…Y(θmax,fN)]T (4)
And 4, step 4: for the output vector Y (theta) of the beam former in step 3max) Performing fast inverse Fourier transform to obtain time domain signal output by the beam former
y(k,θmax)＝2real{IFFT{Ya(θmax)}} (5)
Wherein real {. is } represents the operation of real part, IFFT {. is } represents the fast inverse Fourier transform, Ya(θmax) Representing the output vector of the frequency domain beam former after zero padding;
and 5: for y (k, theta)max) Carrying out autocorrelation to obtain autocorrelation function
Where L is the receiver turn-on duration, for R (σ, θ)max) Searching peak value to obtain time delay difference sigma between direct path and sea surface reflection pathD/SR
Wherein max {. means take the maximum value;
step 6: using thetamaxTime delay difference sigma of directional beamformer output and through-sea reflection pathD/SRConstructing a phase compensation factor, frequency fnHas a phase compensation factor of
Wherein arg (·) represents a phase taking operation;
and 7: performing phase compensation on the array element received signals by using the phase compensation factors in the step 6 to obtain an estimation result of channel impulse response; j-th array element frequency point fnThe frequency domain channel impulse response estimation result is
And 8: performing fast inverse Fourier transform on the frequency domain channel impulse response obtained in the step 7 to obtain a time domain channel impulse response result; forming the frequency domain impulse response results of all frequency points corresponding to the jth array element into a vector
Gj＝[Gj(f1),Gj(f2),…Gj(fN)]T (10)
For GjCarrying out zero filling operation, and setting components outside the processing frequency band to be zero; for frequency domain impulse response G after zero fillingajFast inverse Fourier transform is carried out to obtain the time domain channel impulse response at the jth array element
gj(k)＝2real{IFFT{Gaj}} (11)
And step 9: and 7, executing the step 7 and the step 8 for all array elements of the vertical line array to obtain an estimated value of channel impulse response between the vertical line array and the sound source.
The sound source is located 200m below the sea surface, and the bandwidth of a sound source signal is not less than 300 Hz.
The vertical linear array is located 500m above the sea floor and comprises 16 array elements.
The horizontal distance range between the sound source and the vertical linear array is 5-30 km.
Advantageous effects
Based on the sound propagation characteristics in the deep sea environment, the invention provides a blind deconvolution method based on a vertical line array. The method introduces the time delay difference information of direct waves and sea surface reflected waves in the conventional broadband wave beam output into channel impulse response estimation, and utilizes the multipath time delay difference information and the output phase of the wave beam former to construct a new phase compensation item. The method is suitable for the small-aperture vertical linear array, and is simple in calculation and small in calculation amount. The basic principle and the implementation scheme of the invention are verified by computer numerical simulation, and the result shows that under a typical deep sea environment, the method can correctly estimate the channel impulse response between a sound source and a receiving array, and the estimation effect is superior to that of the existing RBD method.
Compared with the existing RBD method, the blind deconvolution method provided by the invention has better performance in the deep sea environment, and has the advantages that: 1) the method provided by the invention can be applied to the vertical array with smaller aperture, and the hardware cost is low; 2) the method provided by the invention uses a conventional broadband beam forming method, and the calculated amount is small; 3) compared with the existing RBD method, the method provided by the invention can more accurately estimate the channel impulse response in the deep sea environment.
Drawings
The drawings are only for purposes of illustrating particular embodiments and are not to be construed as limiting the invention, wherein like reference numerals are used to designate like parts throughout.
FIG. 1 is a schematic diagram of a simulated scene sound velocity profile.
Fig. 2 is an ideal channel impulse response time domain result simulated using the Bellhop sound field model.
Fig. 3 is a normalized array received signal simulated using a Bellhop sound field model.
FIG. 4 is a signal processing flow chart of the deep sea blind deconvolution method based on the vertical line array.
Fig. 5 is a normalized frequency domain broadband beamforming azimuth spectrum.
Fig. 6 shows the time domain result of the channel impulse response estimated by the blind deconvolution method of the present invention.
Fig. 7 is a result of a channel impulse response time domain estimated using a prior art RBD method.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in further detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.
1. Deep sea waveguide environment, acoustic source and receiving vertical line array configuration.
In order to verify the effectiveness of the method, a computer is used for carrying out a simulation experiment. This example considers a typical deep sea environment with a sea depth of 3950m, a sea sound velocity profile as shown in FIG. 1, and a sea water density of 1.0g/cm3(ii) a The sound velocity of the seabed half space is 1600m/s, and the density is 1.5g/cm3The attenuation coefficient of the compression wave of the seabed sediment is 0.14 dB/lambda. The vertical line array used for reception consists of 16 array elements, the spacing of the array elements is 4m, and the depth of the center of the array is 3716 m. The depth of the sound source is 25m, and the horizontal distance from the sound source to the vertical linear array is 6.025 km. Consider a processing bandwidth of [100,1000]Hz, the ideal channel impulse response between the sound source and the vertical line array under this transmit-receive configuration, calculated using Bellhop, is shown in fig. 2.
2. Vertical line array receiving signal
This embodiment models the sound source signal as a piece of wideband white Gaussian noise with a length of 5s and a bandwidth of [100,1000%]Hz. The sound source signal is made of a section of 5s Gaussian random noise and passes through a passband [100,1000 ]]A bandpass filter in Hz. Simulating the received signals of each array element of a vertical linear array by using a Bellhop sound field model: assuming that the amplitude of the sound source signal is 1, each sensor starts to collect while the sound source signal is sent out, and the starting time of the receiver is TR20s, sampling frequency fs＝5kHz。
The simulation method of the received signal comprises the following steps: and calculating the arrival time and amplitude of the sound ray between the position of the sound source and the position of the receiving array element by using a Bellhop sound field model aiming at different array elements. These sound ray arrival structures are then used to construct channel impulse responses (as shown in figure 2), which will be described in more detail belowAnd performing time domain convolution on the sound source signal and the channel impulse response to obtain a receiving signal of the array element. And finally, adding noise in the simulated received signal according to the signal-to-noise ratio. Suppose that each array element is at TRThe received signal-to-noise ratios in the array are all SNR 0dB, and the above operations are sequentially performed on 16 array elements, so as to obtain the received signals of each array element, and the normalization result is shown in fig. 3.
3. Deep sea blind deconvolution method based on vertical line array
As shown in fig. 4, the deep sea blind deconvolution method based on the vertical line array according to the present invention is implemented as follows:
step 1: under the typical deep sea environment shown in fig. 1, a set of 16-array element vertical linear arrays is arranged near the sea bottom to receive broadband signals emitted by sound sources near the sea surface, the depth of the center of the array is 3716m, and the interval of the array elements is 4 m. The depth of the sound source is 25m, the horizontal distance between the sound source and the receiving array is 6.025km, and the sampling frequency of the array is 5 kHz. The jth sensor receives a signal xj(k) The length of which is 1X 105Where j is 1,2, …, 16. This step has been accomplished in this embodiment by simulation of the Bellhop sound field model.
Step 2: the method comprises the following specific processes of carrying out frequency domain conventional broadband beam forming on the vertical line array receiving signals: firstly, carrying out 1 × 10 array element signals5And performing Fast Fourier Transform (FFT) on the point to obtain a frequency domain receiving signal. Second, in the frequency band [100,1000]Within Hz, the received signal on each frequency point is processed by conventional wave beam forming, frequency point fnThe beamformer weighting at the pointing angle θ is
Where the beamforming reference sound speed c is taken as the sound speed value at the depth of the center of the array. Frequency point fnThe beamformer output at pointing angle θ is
Where N is 1,2, … N, where N is the number of beamforming frequency points. The frequency domain receiving signal of the jth array element is marked as Xj(f) The length of which is 1X 105The frequency domain spacing in the FFT results is 0.05 Hz. Xj(f) The 2000 th point corresponds to a signal component at 100Hz and the 20001 th point corresponds to a signal component at 1000Hz, so that the beamforming is performed N18002 times, f1＝100Hz,f2＝100.05Hz,…,f18002＝1000Hz。
At each frequency point, beam scanning is performed at 0.2 ° intervals, with 0 ° corresponding to the vertical (sea-surface) direction and 90 ° corresponding to the horizontal direction during scanning. The beam forming outputs of 18002 frequency points are added incoherently to obtain a broadband beam forming azimuth spectrum as shown in fig. 5
And step 3: the angle with the largest energy is found in the beamformed azimuth spectrum shown in fig. 5 and is θmax59.6. Forming output composition vector of wave beam with 18002 frequency points corresponding to direction of 59.6 degree
Y(θmax)＝[Y(θmax,f1),Y(θmax,f2),…Y(θmax,f18002)]T (15)
And 4, step 4: at Y (theta)max) Front complement 1999 zeros in Y (theta)max) 8 x 10 of anaplerosis4-1 zero to obtain Ya(θmax). For Ya(θmax) Fast inverse Fourier transform is carried out to obtain time domain signals output by the beam former
y(k,θmax)＝2real{IFFT{Ya(θmax)}} (16)
Wherein real {. is } represents the operation of real part, IFFT {. is } represents the inverse fast Fourier transform, Y in the above operationa(θmax) And y (k, θ)max) Are all 1X 105。
And 5: for y (k, theta)max) Performing autocorrelation to obtainCorrelation function
Wherein L is 1 × 105. For R (sigma, theta)max) Searching peak value to obtain time delay difference sigma between direct path and sea surface reflection pathD/SR
Where max {. cndot.) denotes taking the maximum value. In this embodiment, σD/SR＝0.0142s。
Step 6: using thetamaxTime delay difference estimation result sigma of directional beam former output and direct-sea surface reflection pathD/SRConstructing phase compensation factor, frequency point f of array element signalnHas a phase compensation factor of
Where arg (·) denotes a phase taking operation. For the present embodiment, f1＝100Hz,f2＝100.05Hz,…,f18002＝1000Hz。
And 7: and 6, performing phase compensation on the array element receiving signals by using the phase compensation factors in the step 6 to obtain an estimation result of the channel impulse response. The j-th array element frequency point is fnThe frequency domain channel impulse response estimation result is
For the present embodiment, f1＝100Hz,f2＝100.05Hz,…,f18002＝1000Hz，j＝1,2,…,16
And 8: and (4) performing fast inverse Fourier transform on the frequency domain channel impulse response obtained in the step (7) to obtain a time domain channel impulse response result. Forming the frequency domain impulse response results of all frequency points corresponding to the jth array element into a vector
Gj＝[Gj(f1),Gj(f2),…Gj(f18002)]T (21)
For GjZero filling operation is performed, 1999 zeros are filled in the front edge of the zero filling operation, and 8 multiplied by 10 are filled in the back edge of the zero filling operation41 zero gives Gaj. For frequency domain impulse response G after zero fillingajFast inverse Fourier transform is carried out to obtain the time domain channel impulse response corresponding to the jth array element
gj(k)＝2real{IFFT{Gaj}} (22)
And step 9: and (5) executing the step (7) and the step (8) for all array elements of the vertical array to obtain a time domain estimation result of the channel impulse response between the array and the sound source.
For this embodiment, the channel impulse response estimation result obtained by the method of the present invention is shown in fig. 6, and for comparison, fig. 7 shows the channel impulse response estimation result obtained by using the existing RBD method. Compared with the ideal impulse response shown in fig. 2, it can be found that, in the typical deep sea environment described in this embodiment, the existing RBD method cannot distinguish each arrival sound ray, but the method provided by the present invention successfully estimates 4 arrival paths, which has a better estimation effect.
While the invention has been described with reference to specific embodiments, the invention is not limited thereto, and various equivalent modifications or substitutions can be easily made by those skilled in the art within the technical scope of the present disclosure.
Claims (4)
1. A deep sea blind deconvolution method based on a vertical line array is characterized by comprising the following steps:
step 1: a set of vertical line array is arranged on the deep sea bottom to receive broadband signals emitted by a sea sound source; the vertical line array consists of M array elements, the interval of the array elements is d, and the sampling frequency of the array is fsOf 1 atThe time domain signals received by the j array elements are xj(k) K is a sampling time point;
step 2: performing frequency domain broadband beam forming on the vertical line array receiving signals, wherein the specific process is as follows: firstly, fast Fourier transform is carried out on array element receiving signals to obtain frequency domain receiving signals, and the frequency domain receiving signals of the jth array element are recorded as Xj(f) (ii) a Next, in the designated frequency band [ B ]1,B2]Within Hz, the received signal on each frequency point is formed into wave beam, frequency point fnThe beamformer weighting at the pointing angle θ is
Wherein the superscript "T" represents transposition operation, c is a beam forming reference sound velocity, and i is an imaginary number unit; frequency point fnThe beamformer output at pointing angle θ is
Wherein the superscript "H" represents the conjugate transpose operation, "x" represents the vector multiplication, and N is 1,2, …, N is the number of beamforming frequency points;
in a specified frequency band [ B1,B2]Within Hz, the outputs of the beam formers of all frequency points are subjected to incoherent superposition to obtain a broadband beam forming azimuth spectrum
And step 3: note that the angle corresponding to the maximum value of the beam forming azimuth spectrum B (θ) is θmaxTake θmaxOutput component vector of beam former of all frequency points corresponding to direction
Y(θmax)＝[Y(θmax,f1),Y(θmax,f2),…Y(θmax,fN)]T (4)
And 4, step 4: for the output vector Y (theta) of the beam former in step 3max) Performing fast inverse Fourier transform to obtain time domain signal output by the beam former
y(k,θmax)＝2real{IFFT{Ya(θmax)}} (5)
Wherein real {. is } represents the operation of real part, IFFT {. is } represents the fast inverse Fourier transform, Ya(θmax) Representing the output vector of the frequency domain beam former after zero padding;
and 5: for y (k, theta)max) Carrying out autocorrelation to obtain autocorrelation function
Where L is the receiver turn-on duration, for R (σ, θ)max) Searching peak value to obtain time delay difference sigma between direct path and sea surface reflection pathD/SR
Wherein max {. means take the maximum value;
step 6: using thetamaxTime delay difference sigma of directional beamformer output and through-sea reflection pathD/SRConstructing a phase compensation factor, frequency fnHas a phase compensation factor of
Wherein arg (·) represents a phase taking operation;
and 7: performing phase compensation on the array element received signals by using the phase compensation factors in the step 6 to obtain an estimation result of channel impulse response; j-th array element frequency point fnThe frequency domain channel impulse response estimation result is
And 8: performing fast inverse Fourier transform on the frequency domain channel impulse response obtained in the step 7 to obtain a time domain channel impulse response result; forming the frequency domain impulse response results of all frequency points corresponding to the jth array element into a vector
Gj＝[Gj(f1),Gj(f2),…Gj(fN)]T (10)
For GjCarrying out zero filling operation, and setting components outside the processing frequency band to be zero; for frequency domain impulse response G after zero fillingajFast inverse Fourier transform is carried out to obtain the time domain channel impulse response at the jth array element
gj(k)＝2real{IFFT{Gaj}} (11)
And step 9: and 7, executing the step 7 and the step 8 for all array elements of the vertical line array to obtain an estimated value of channel impulse response between the vertical line array and the sound source.
2. The blind deep-sea deconvolution method based on the vertical linear array as claimed in claim 1, wherein the acoustic source is located 200m below the sea surface, and the bandwidth of the acoustic source signal is not less than 300 Hz.
3. The method of claim 1, wherein the vertical linear array is located 500m above the sea floor and comprises 16 array elements.
4. The method of claim 1, wherein the horizontal distance between the sound source and the vertical linear array is in the range of 5-30 km.
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