Shallow sea underwater acoustic target sounding method based on time delay cross-spectrum integral matching

Abstract

The invention provides a shallow sea underwater acoustic target passive sounding method based on time delay cross spectrum integral matching, which comprises the following steps: carrying out time delay on a broadband acoustic signal received by a single hydrophone to construct a broadband acoustic signal received by a virtual array element, and carrying out accumulation processing on an actual array element and a virtual array element broadband cross spectrum in a time dimension. A shallow sea sound field feature-time delay cross-spectrum integral sensitive to the target depth is extracted, finally, the target depth is estimated by matching the time delay cross-spectrum integral of actually measured data with the copy field cross-spectrum integral under the assumed target depth and array element spacing, and the feasibility of the method is verified based on simulation data. The method solves the problem of target depth estimation under silent field vertical dimension information sampling, and has remarkable military and economic benefits.

Description

Technical Field

[0001] The invention belongs to the field of hydroacoustic engineering, relates to theories of hydroacoustic propagation, hydroacoustic signal processing, and more particularly to a shallow water hydroacoustic target depth measurement method based on time-delay cross-spectrum integral matching. Background Art

[0002] As an important basis for submarine identification and precision strike, the acquisition of underwater acoustic target depth information is a key research content of anti-submarine detection.

[0003] In the early stage, domestic and foreign research mainly focused on the acquisition of sound source depth information based on buoy nodes. Bucker first proposed matched field processing to use the measured acoustic information to estimate the distance and depth of the sound source. However, matched field processing is very sensitive to changes in environmental parameters and requires a larger base array aperture. Since the modal functions of each order of the simple normal wave change with depth, and the vertical array is used for the aperture in the vertical direction, sampling in the depth direction can be achieved. In view of this, some scholars have proposed matched modal processing (MMP) based on the vertical array for target depth estimation. This type of method first uses the sound field simulation program to calculate the modal function corresponding to the depth of each array element according to the environmental parameters and construct a modal decomposition matrix. Then, the modal filtering is performed using the signal received by the vertical array and the modal decomposition matrix to calculate the modal intensity of each order excited by the sound source, and the target depth is discriminated by the distribution of the modal intensity. It is worth noting that in the case of a finite base array aperture and a finite array element, the modal decomposition matrix is ​​not orthogonal and complete.

[0004] Domestic research on target depth estimation started relatively late, and most of them are still in the stage of concept and principle verification. Typical research works are as follows: Yu Yun, Hui Junying and others used the phase angle relationship between the complex sound intensity reactive component and the interactive negative sound intensity of the sound pressure and vertical velocity simple normal waves of dual receiving sensors to distinguish underwater targets on the water surface, which improved the working frequency. However, the method is limited by the depth of the two receiving sensors and requires that the simple normal waves that can be propagated in the waveguide are of the second order. Fang Shiliang and others studied the single hydrophone distance and depth estimation method based on dispersion characteristics combined with time-frequency analysis. They used a multi-mode joint matching method and a time-frequency filtering method of binary mask filtering to extract the required mode. By calculating the error between the actual extracted mode energy and the predicted mode energy, a cost function was established, and the depth of the sound source was determined by mode energy matching. The effectiveness of the method was verified by simulation in the shallow sea environment of the Pekeris waveguide model. Zhang Lu et al. used a vector vertical array to judge the positive and negative signs of the active components of the sound pressure and vibration velocity cross-spectral functions, and verified the method using numerical simulation and lake tests.

[0005] It can be seen that a lot of research has been done at home and abroad on using the vertical aperture of the vertical array of the buoy to obtain target depth information. However, for towed linear array sonar, since there is no vertical aperture, it is impossible to obtain the vertical dimension information of the sound field for obtaining the target depth-dependent features. Therefore, there is no shallow water target depth estimation method suitable for towed linear arrays. Summary of the invention

[0006] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a shallow water acoustic target depth measurement method based on time-delay cross-spectrum integral matching.

[0007] The objective of the present invention is achieved through the following technical solutions: A shallow sea acoustic target sounding method based on time-delay cross-spectrum integral matching, which delays the broadband acoustic signal received by a single hydrophone to construct a broadband acoustic signal received by a virtual array element, and extracts the shallow sea acoustic field feature sensitive to the target depth - the time-delay cross-spectrum integral through the accumulation processing of the broadband cross-spectrum of the actual array element and the virtual array element in the time dimension, and finally estimates the target depth by matching the time-delay cross-spectrum integral of the measured data with the copy field cross-spectrum integral processing under the assumption of target depth and array element spacing.

[0008] Furthermore, the method comprises the following steps:

[0009] (1) Extracting the time-delay cross-spectral integral characteristics of the single hydrophone received data

[0010] ① Assume that the short-time Fourier transform of the signal received by a single hydrophone is p(t,f), which is the data of the actual array element, where t represents time and f represents frequency;

[0011] ② The data after a certain time interval △T is used as the received data p(t+△T,f) of the virtual array element;

[0012] ③Construct the cross-spectrum between the actual array element and the virtual array element,

[0013] p(t,f)p * (t+△T,f)e -i2πf△T (1)

[0014] In the formula, i is the imaginary unit, e -i2πf△T Phase correction for time variation;

[0015] ④Integrate the cross-spectrum in the time dimension to obtain the time-delay cross-spectrum integral characteristics of the time data

[0016] B data (f) = ∫p(t,f)p * (t+△T,f)e -i2πf△T dt (2)

[0017] (2) Constructing the time-delay cross-spectral integral of the copy field

[0018] ① The shallow sea acoustic environment information is related to the sea depth H and the sound velocity profile c(z). The hydrophone receiving depth z r As input, the copy sound field is generated using the normal wave sound field calculation program, where the copy field of array element 1 is represented by p rpl (f,r+R0,z), the copy field of element 2 is represented by p rpl (f,r+R0+△R,z), R0 is the initial distance, △R is the interval between element 1 and element 2, r is the distance integral length, and z represents the depth;

[0019] ② The cross-spectral integral of the copy field is expressed as the integral of the cross-spectrum of the copy field of element 1 and the copy field of element 2,

[0020]

[0021] Where L represents the integration length;

[0022] (3) Estimating target depth by matching the time-delay cross-spectral integral

[0023] The ambiguity surface of the time-delay cross-spectrum integral matching process is expressed as follows:

[0024]

[0025] where f l Indicates the lower frequency limit, f h It represents the lower limit of frequency. The z value corresponding to the peak value of the two-dimensional ambiguity surface M(△R,z) is the depth of the target.

[0026] The beneficial effects of the present invention are as follows: the present invention delays the broadband acoustic signal received by a single hydrophone to construct a broadband acoustic signal received by a virtual array element, and extracts the shallow sea acoustic field feature sensitive to the target depth - the time-delayed cross-spectrum integral by accumulating the broadband cross-spectrum of the actual array element and the virtual array element in the time dimension, and finally estimates the target depth by matching the time-delayed cross-spectrum integral of the measured data with the copy field cross-spectrum integral processing under the assumption of target depth and array element spacing, and verifies the feasibility of the method based on simulation data. The present invention solves the problem of target depth estimation without vertical dimension information sampling of the sound field, and has significant military and economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] 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.

[0028] Figure 1 The present invention is a schematic diagram of the processing flow of a shallow water acoustic target sounding method based on time-delay cross-spectrum integral matching.

[0029] Figure 2 Schematic diagram of the sound velocity profile input for the simulation study.

[0030] Figure 3 This is a schematic diagram of the variation of the simulated delay cross-spectrum integral amplitude with frequency when the target depth is 5m and 50m.

[0031] Figure 4 The ambiguity surface of the matching time delay cross-spectrum integration processing when the real target depth is 5m and 50m. DETAILED DESCRIPTION

[0032] 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.

[0033] like Figure 1 As shown, the present invention proposes a shallow water acoustic target depth measurement method based on time-delay cross-spectrum integral matching, and the method comprises the following steps:

[0034] (1) Extracting the time-delay cross-spectral integral characteristics of the single hydrophone received data

[0035] ① Assume that the short-time Fourier transform of the signal received by a single hydrophone is p(t,f), which is the data of the actual array element, where t represents time and f represents frequency;

[0036] ② The data after a certain time interval △T is used as the received data p(t+△T,f) of the virtual array element;

[0037] ③Construct the cross-spectrum between the actual array element and the virtual array element, and consider the phase correction due to time change -i2πf△T ,have

[0038] p(t,f)p * (t+△T,f)e -i2πf△T (1)

[0039] Where i is the imaginary unit.

[0040] ④Integrate the cross-spectrum in the time dimension to obtain the time-delay cross-spectrum integral characteristics of the time data

[0041] B data (f) = ∫p(t,f)p *(t+△T,f)e -i2πf△T dt (2)

[0042] (2) Constructing the time-delay cross-spectral integral of the copy field

[0043] Since the real radial motion speed of the target is unknown, that is, the distance difference between the target and the receiving platform within the △T time is unknown, when constructing the copy field data, it is necessary to add a one-dimensional search, the search of the distance change △R, on the premise of the depth dimension search.

[0044] ① Based on the shallow sea acoustic environment information such as sea depth H and sound velocity profile c(z), the hydrophone receives the depth z r As input, the simple normal wave sound field calculation program KRAKEN is used to generate the copy sound field, where the copy field of array element 1 is represented by p rpl (f,r+R0,z), the copy field of element 2 is represented by p rpl (f,r+R0+△R,z), R0 is the initial distance, △R is the interval between element 1 and element 2, r is the distance integral length, and z represents the depth.

[0045] ② The cross-spectral integral of the copy field can be expressed as the integral of the cross-spectrum of the copy field of element 1 and the copy field of element 2,

[0046]

[0047] Where L represents the integration length. Generally, when it is greater than 3 km, the cross-spectrum integral tends to a stable value.

[0048] (3) Estimating target depth by matching the time-delay cross-spectral integral

[0049] The ambiguity surface of the time-delay cross-spectrum integral matching process is expressed as follows:

[0050]

[0051] where f l Indicates the lower frequency limit, f h Indicates the lower frequency limit. The z value corresponding to the peak of the two-dimensional ambiguity surface M(△R,z) is the depth of the target.

[0052] Figure 2 The sound velocity profile input for the simulation study is given, typical Pekeris waveguide, sea depth 200m, moderate hydrological environment, 0.05s -1 Negative gradient of the speed of sound.

[0053] Figure 3 (a) shows the variation of the simulated delay cross-spectrum integral amplitude with frequency when the target depth is 5m. Figure 3(b) shows the variation of the amplitude of the simulated delay cross-spectrum integral with frequency when the target depth is 50m. First, based on Kraken, broadband data with a frequency band of 20-200Hz are generated for target depths of 5m and 50m, respectively. The initial distance is 6km, the horizontal distance between the real array element and the virtual array element is 700m, and the integration distance is 3000m, and the data cross-spectrum integral is generated. It can be seen that there is a significant difference in the broadband cross-spectrum integral corresponding to the two target depths. The cross-spectrum integral of the 5m shallow target has a small amplitude at low frequencies. It can be seen that the delay cross-spectrum integral is a pair of acoustic field features that are sensitive to the target depth.

[0054] Figure 4 (a) shows the ambiguity surface of the matched time delay cross-spectrum integral processing when the real target depth is 5m. Figure 4 (b) The ambiguity surface of the matching time delay cross-spectrum integral processing when the real target depth is 50m is given. The target depth search interval is set to 1-100m for the copy field construction, the horizontal distance search interval between the real array element and the virtual array element is set to 0-2000m, and the integration distance is 5000m. The copy field cross-spectrum integral is constructed accordingly, and the matching processing ambiguity surface is calculated. The peaks of the ambiguity surface point to the depths of 5m and 50m respectively, which verifies the feasibility of the proposed method for target depth estimation.

[0055] 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. A shallow water acoustic target sounding method based on time-delay cross-spectral integral matching, characterized in that: The broadband acoustic signal received by a single hydrophone is delayed to construct a broadband acoustic signal received by a virtual array element. The shallow sea acoustic field feature sensitive to the target depth - the time-delay cross-spectrum integral - is extracted by accumulating the broadband cross-spectrum of the actual array element and the virtual array element in the time dimension. Finally, the target depth is estimated by matching the time-delay cross-spectrum integral of the measured data with the copy field cross-spectrum integral processing under the assumption of target depth and array element spacing.

2. The shallow water acoustic target sounding method based on time-delay cross-spectrum integral matching according to claim 1 is characterized in that: The method comprises the following steps: (1) Extracting the time-delay cross-spectral integral characteristics of the single hydrophone received data ① Assume that the short-time Fourier transform of the signal received by a single hydrophone is p(t,f), which is the data of the actual array element, where t represents time and f represents frequency; ② The data after a certain time interval △T is used as the received data p(t+△T,f) of the virtual array element; ③Construct the cross-spectrum between the actual array element and the virtual array element, p(t,f)p * (t+△T,f)e -i2πf△T (1) In the formula, i is the imaginary unit, e -i2πf△T Phase correction for time variation; ④Integrate the cross-spectrum in the time dimension to obtain the time-delay cross-spectrum integral characteristics of the time data B data (f)=∫p(t,f)p * (t+△T,f)e -i2πf△T dt (2) (2) Constructing the time-delay cross-spectral integral of the copy field ① The shallow sea acoustic environment information is related to the sea depth H and the sound velocity profile c(z). The hydrophone receiving depth z r As input, the copy sound field is generated using the normal wave sound field calculation program, where the copy field of array element 1 is represented by p rpl (f,r+R0,z), the copy field of element 2 is represented by p rpl (f,r+R0+△R,z), R0 is the initial distance, △R is the interval between element 1 and element 2, r is the distance integral length, and z represents the depth; ② The cross-spectral integral of the copy field is expressed as the integral of the cross-spectrum of the copy field of element 1 and the copy field of element 2, Where L represents the integration length; (3) Estimating target depth by matching the time-delay cross-spectral integral The ambiguity surface of the time-delay cross-spectrum integral matching process is expressed as follows: where f l Indicates the lower frequency limit, f h It represents the lower limit of frequency. The z value corresponding to the peak value of the two-dimensional ambiguity surface M(△R,z) is the depth of the target.

Images