A method and system for distinguishing surface and underwater targets based on horizontal array active sonar

Abstract

The present invention relates to the fields of underwater acoustic physics and target depth resolution, and discloses a method and system for distinguishing surface and underwater targets based on a horizontal array active sonar, the method comprising: calculating the broadband sound field ratio phase spectrum of multiple horizontal array elements in the actual measurement field; using a sound field simulation program to calculate a broadband sound field ratio phase spectrum data set at different sound source depths and different receiving distances in a copy field; matching and correlating the two to construct a depth-distance ambiguity function; based on the constructed depth-distance ambiguity function, calculating the distinguishability of surface and underwater sound sources, and determining whether the target sound source in the actual measurement field is a surface sound source or an underwater sound source based on the size relationship between the distinguishability of surface and underwater sound sources and a distinguishability threshold. The solution of the embodiment of the present invention utilizes the phase information of the sound field ratio that implies the target depth information, and uses the copy field data set to construct the ambiguity function, so it can accurately distinguish whether the target sound source is from the water surface or from underwater.

Description

Technical Field

[0001] The invention relates to the fields of underwater acoustic physics and target depth resolution, and in particular to a method and system for resolving surface and underwater targets based on a horizontal array active sonar. Background Art

[0002] Depth discrimination and depth estimation of sound sources in shallow water waveguide environments are one of the core issues in the field of hydroacoustics, and have important guiding significance for discerning target types and their threat levels. As classic methods for estimating target depth, matched field processing (MFP) and matched mode processing (MMP) have attracted extensive attention and in-depth research in the field of hydroacoustics.

[0003] However, the distance-depth ambiguity map of the traditional matching field bathymetry method has sharp highlights, and the depth estimation result is heavily dependent on the accuracy of environmental information. However, the marine environment is highly spatiotemporal and temporal. When there is a mismatch between the environmental model and the actual situation, the positioning performance of the matching field method is significantly reduced. Therefore, a more robust matching algorithm with higher environmental tolerance is needed. Secondly, the traditional matching field depth estimation method mainly relies on vertical arrays, but vertical arrays face problems in engineering practice, such as difficulty in maintaining vertical posture and aperture length being limited by sea depth. Summary of the invention

[0004] The purpose of the present invention is to overcome the defects of the prior art, and proposes a method for distinguishing surface and underwater targets based on a horizontal array active sonar. The present invention also discloses a system for distinguishing surface and underwater targets based on a horizontal array active sonar.

[0005] On the one hand, the present invention provides a method for distinguishing surface and underwater targets based on a horizontal array active sonar, comprising:

[0006] Calculate the broadband sound field ratio of multiple horizontal array elements in the actual measurement field, and take the phase to obtain the broadband sound field ratio phase spectrum of the actual measurement field, wherein the broadband sound field ratio is defined based on the simple normal wave theory;

[0007] The broadband sound field ratio at different sound source depths and different receiving distances in the copy field is calculated using a sound field simulation program, and the phase is taken to obtain a broadband sound field ratio phase spectrum data set of the simulated copy field;

[0008] The broadband sound field ratio phase spectrum of the actual measurement field is matched with the broadband sound field ratio phase spectrum data set of the simulated copy field to construct a depth-distance ambiguity function;

[0009] Based on the constructed depth-distance ambiguity function, the distinguishability of surface and underwater sound sources is calculated, where the distinguishability of surface and underwater sound sources is the difference between the ambiguity peak of the depth matching below the shallow sea thermocline and the ambiguity peak above the shallow sea thermocline;

[0010] Based on the relationship between the distinguishability of surface and underwater sound sources and the distinguishability threshold, it is determined whether the target sound source in the actual measurement field is a surface sound source or an underwater sound source.

[0011] In an improved method for distinguishing surface and underwater targets based on horizontal array active sonar, the calculation of the broadband sound field ratio of multiple horizontal array elements in the actual measurement field includes:

[0012] When the number of array elements is 2, the broadband sound field ratio of the two array elements is directly used;

[0013] When the number of array elements is more than 2, two representative array elements are selected from multiple array elements, and the broadband sound field ratios of the two representative array elements are used, or two array elements are selected in sequence according to a certain rule to obtain the sound field ratios and then the average broadband sound field ratio is obtained by averaging them.

[0014] In an improved method for distinguishing underwater targets on the surface based on a horizontal array active sonar, the method of obtaining an average broadband sound field ratio by taking two array elements in sequence according to a certain rule and then averaging the obtained sound field ratio includes: obtaining an average broadband sound field ratio η(z s ,ω) and then take the average to get the average broadband sound field ratio

[0015] The first rule: One adjacent array element:

[0016] The second rule: a group of adjacent array elements:

[0017] The third rule: j array elements apart:

[0018] Among them, G is the number of array elements, z s is the depth of the target sound source in the actual measurement field, and ω is the frequency of the target sound source.

[0019] In an improved method for distinguishing surface and underwater targets based on horizontal array active sonar, the broadband sound field ratio of any two array elements is obtained by the following method:

[0020] intercepting the echo signal in the dual-element receiving element domain data;

[0021] Perform Fourier transform on the intercepted echo signal to obtain dual-channel frequency domain data P1(z s ,ω)、P2(z s ,ω);

[0022] Calculating Broadband Sound Field Ratio

[0023] In an improved method for distinguishing underwater targets on the surface based on a horizontal array active sonar, the method of using a sound field simulation program to calculate the broadband sound field ratio at different sound source depths and different receiving distances in the copy field includes:

[0024] Determine an estimate of the target sound source direction and an estimate of the echo arrival time;

[0025] Determine horizontal array element parameters and known environmental parameters, wherein: horizontal array element parameters include: frequency range, hydrophone receiving depth, search depth and part or all of the search interval; known environmental parameters include: sound velocity profile, seabed sediment layer and basement layer thickness, sound velocity and attenuation part or all of the above;

[0026] Input the above two estimated values ​​and the above two types of parameters into the sound field calculation program to obtain the frequency domain simulated sound field;

[0027] Calculate the broadband sound field ratio of the simulation data at different sound source depths and different receiving distances.

[0028] In an improved method for distinguishing underwater targets on the surface based on a horizontal array active sonar, matching and correlating the broadband sound field ratio phase spectrum of the actual measurement field with the broadband sound field ratio phase spectrum data set of the simulated copy field to construct a depth-range ambiguity function includes:

[0029] The broadband acoustic field ratio phase spectrum of the actual measurement field Broadband acoustic field ratio phase spectrum dataset with simulated copy field Perform cross-correlation operations to construct the depth-range ambiguity function A(z);

[0030]

[0031] Among them, z is the depth of each sound source in the simulated copy field, and ω is the target sound source frequency.

[0032] In an improved method for distinguishing surface and underwater targets based on a horizontal array active sonar, the method of determining whether a target sound source in an actual measurement field is a surface sound source or an underwater sound source based on the magnitude relationship between the distinguishability of surface and underwater sound sources and a distinguishability threshold comprises:

[0033] If D>0 and |D|>D1, the received signal is determined to be an underwater sound source; if D<0 and |D|>D2, the received signal is determined to be a surface sound source;

[0034] Where D is the distinguishability of surface and underwater sound sources, D1 is the preset first distinguishability threshold, D2 is the preset second distinguishability threshold, z up is the upper boundary depth of the shallow sea thermocline, z down is the depth of the lower boundary of the shallow sea thermocline, z H is the sea water depth, and D1 and D2 are determined according to the target sound source type and shallow sea thermocline environmental parameters.

[0035] In an improved method for distinguishing underwater targets on the surface based on a horizontal array active sonar, after matching and correlating the broadband sound field ratio phase spectrum of the actual measurement field with the broadband sound field ratio phase spectrum data set of the simulated copy field to construct a depth-range ambiguity function, the method further includes:

[0036] According to the energy concentration distribution of the ambiguity surface, it is judged whether the target sound source in the actual measurement field is a surface sound source or an underwater sound source.

[0037] On the other hand, the present invention also proposes a system based on the above-mentioned surface and underwater target discrimination method, comprising:

[0038] The measurement field phase data determination module is used to calculate the broadband sound field ratio of multiple horizontal array elements in the actual measurement field, and obtain the phase to obtain the broadband sound field ratio phase spectrum of the actual measurement field, wherein the broadband sound field ratio is defined based on the simple normal wave theory;

[0039] A copy field phase data determination module is used to calculate the broadband sound field ratio at different sound source depths and different receiving distances in the copy field using a sound field simulation program, and obtain the phase to obtain a broadband sound field ratio phase spectrum data set of the simulated copy field;

[0040] An ambiguity function construction module is used to perform matching correlation operations on the broadband sound field ratio phase spectrum of the actual measurement field and the broadband sound field ratio phase spectrum data set of the simulated copy field to construct a depth-distance ambiguity function;

[0041] A calculation module, used for calculating the distinguishability of surface and underwater sound sources based on the constructed depth-distance ambiguity function, wherein the distinguishability of surface and underwater sound sources is the difference between the ambiguity peak value of the depth matching below the shallow sea thermocline and the ambiguity peak value above the shallow sea thermocline; and

[0042] The judgment module is used to determine whether the target sound source in the actual measurement field is a surface sound source or an underwater sound source based on the magnitude relationship between the distinguishability of the surface and underwater sound sources and the distinguishability threshold.

[0043] Compared with the prior art, the advantages of the present invention are:

[0044] (1) Compared with the existing active broadband matching field processing method, the matching feature of the embodiment of the present invention does not require the scattering function of the target to be known and is tolerant to complex target scattering.

[0045] (2) Compared with the sharp ambiguity bright spots in the traditional matching field depth sounding method, the ambiguity surface bright spots in the resolution results of the method of the embodiment of the present invention are large in area and have high tolerance to distance mismatch and environmental parameter mismatch.

[0046] (3) The method of the embodiment of the present invention can be applied to a horizontal array with two array elements or a horizontal array with multiple array elements. The horizontal array is easy to tow or can be stably deployed on the seabed for operation, and is more practical in engineering.

[0047] (4) The method of the embodiment of the present invention is suitable for distinguishing surface and underwater targets in a complex shallow sea negative thermocline environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 This is a flow chart of a method for distinguishing surface and underwater targets based on a horizontal array active sonar according to an embodiment of the present invention;

[0049] Figure 2 A geometric relationship diagram of the horizontal dual array elements and the sound source position according to an embodiment of the present invention;

[0050] Figure 3 A schematic diagram of shallow sea thermocline waveguide environmental parameters and sound source hydrophone deployment according to an embodiment of the present invention;

[0051] Figure 4 The result of resolving the sound source depth by the target resolution method of the embodiment of the present invention without environment mismatch;

[0052] Figure 5 The sound source depth resolution result and distinguishability diagram of the target resolution method of the embodiment of the present invention under different sound velocity gradient mismatch conditions;

[0053] Figure 6 The sound source depth resolution results and distinguishability diagram of the target resolution method of the embodiment of the present invention under different sea depth mismatch conditions;

[0054] Figure 7 The sound source depth resolution results and distinguishability diagram of the target resolution method of an embodiment of the present invention under different sound velocity mismatch conditions of sediment layers. DETAILED DESCRIPTION

[0055] In order to clearly describe the technical solution of the present invention, the most critical matching feature used in the embodiment of the present invention: the broadband sound field ratio of two array elements and its characteristics under certain conditions are first derived and explained, and then the technical solution of the present invention is explained through specific embodiments.

[0056] Broadband sound field ratio of two array elements Broadband sound field ratio:

[0057] According to the simple normal wave theory of horizontally invariant layered waveguide, for a depth of zs A unit intensity point sound source at a receiving distance r and receiving depth z r The acoustic field excited at can be expressed as the superposition of several simple normal waves:

[0058]

[0059] Among them, k rm and are the horizontal wave number and eigenfunction of the mth order simple normal wave respectively, M is the total order of simple normal waves in the waveguide at the current frequency, ρ is the density of seawater medium, and ω is the frequency of the sound source.

[0060] Assume that there is a single point sound source, and two array elements at close distance and the same depth receive the radiation / scattering signal S(ω) of the sound source. The receiving depth of both array elements is z r , the distances from the point sound source are r1 and r2 respectively, and the sound fields at the two array elements can be expressed as:

[0061]

[0062] Among them, m and n are the orders of the simple normal wave.

[0063] Since the sound source radiation / scattering signal S(ω) received by the hydrophone is consistent, the two received signals can be used to eliminate the influence of the target radiation / scattering characteristics. The sound field ratio η of the two is expressed as:

[0064]

[0065] Let r2=r1+△r, the above formula can be rewritten as:

[0066]

[0067] in,

[0068] Given the distances r1 and r2, the depth information of the target is reflected in the simple normal wave eigenfunction excited by the sound source at different depths. The difference is implicit in η(r1,r2; z s ,z r ,ω) with the oscillation and fluctuation distribution of frequency. In the case of r2-r1=△r<<r1, the influence of the change of frequency within a certain bandwidth on the amplitude change of the sound field ratio η is mainly achieved by affecting the phase of the sound field ratio η. Therefore, the depth information of the target is mainly implicit in η(r1,r2; z s ,z r ,ω) is distributed in the oscillation fluctuation of the phase with frequency. Under the condition of satisfying △r<<r1, the horizontal dual-element broadband sound field ratio η can be approximately expressed as:

[0069]

[0070] The technical solution of the present invention is described in detail below with reference to the accompanying drawings and embodiments.

[0071] Example 1

[0072] The present invention provides a method for distinguishing surface and underwater targets based on horizontal array active sonar. Figure 1 As shown, the following steps are included:

[0073] Step 1: Calculate the broadband sound field ratio of multiple horizontal array elements in the actual measurement field, and take the phase to obtain the broadband sound field ratio phase spectrum of the actual measurement field, where the broadband sound field ratio is defined based on the simple normal wave theory;

[0074] Assuming that the number of array elements is G, when G is 2, the broadband sound field ratio of the dual array elements can be directly obtained; when G is greater than 2, two representative array elements can be randomly selected from the G array elements, and the broadband sound field ratio of the two representative array elements can be used. Alternatively, the sound field ratio of the dual array elements can be obtained according to a certain rule and then averaged to obtain the average broadband sound field ratio.

[0075] The above-mentioned rule can be any one of the following three rules, of course, it is not limited to these three rules:

[0076] The first rule: One adjacent array element:

[0077] The second rule: a group of adjacent elements:

[0078] The third rule: j array elements apart: 2≤j≤G.

[0079] Specifically, the broadband sound field ratio η(z s ,ω):

[0080] Step 1-1: intercepting the echo signal in the dual-element receiving element domain data;

[0081] Step 1-2: Perform Fourier transform on the intercepted echo signal to obtain dual-channel frequency domain data P1(z s ,ω)、P2(z s ,ω);

[0082] Step 1-3: Calculate the broadband sound field ratio

[0083] Then take the phase to get the sound field ratio phase spectrum as η P =Angle(η).

[0084] Step 2: Use the sound field simulation program to calculate the broadband sound field ratio at different sound source depths and different receiving distances in the copy field, and take the phase to obtain a broadband sound field ratio phase spectrum data set of the simulated copy field;

[0085] Specifically, the broadband sound field ratio can be obtained by following steps 2-1 to 2-3:

[0086] Step 2-1: Determine an estimate of the target sound source direction and an estimate of the echo arrival time.

[0087] The geometric relationship diagram of the dual-element horizontal hydrophone and the sound source position is shown in the attached figure. Figure 2 As shown:

[0088] It is known that the spacing between array elements is △d. When the array is not aimed at the sound source in the end-fire direction, first use the estimated direction of the sound source Calculate the radial array element spacing as:

[0089]

[0090] Then according to the estimated echo arrival time and the reference sound speed c, the distance between the array and the sound source is calculated as:

[0091]

[0092] Step 2-2: Determine the horizontal array element parameters and known environmental parameters, wherein the horizontal array element parameters include: part or all of the frequency range, hydrophone receiving depth, search depth and search interval; the known environmental parameters include: part or all of the sound velocity profile, seabed sediment layer and basement layer thickness, sound velocity, attenuation and other parameters;

[0093] Step 2-3: Input the above two estimated values ​​and the above two types of parameters into the sound field calculation program to obtain the frequency domain simulated sound field;

[0094] Here, the hydrophone receiving distance Distance search interval Other simulation parameters including: frequency range, hydrophone receiving depth, search depth and search interval, sound velocity profile, seabed sediment layer, basement layer and other known environmental parameters are input into the acoustic field calculation program Krakenc to obtain the frequency domain simulated acoustic field. The acoustic field ratio of the simulation data at different depths and distances is calculated.

[0095] Step 2-3: Calculate the broadband sound field ratio of the simulation data at different sound source depths and different receiving distances.

[0096] After the broadband sound field ratio of the simulation data is obtained, its phase can be taken to obtain the phase spectrum data set of the broadband sound field ratio of the copy field.

[0097] When calculating the broadband sound field ratio of the copy field, you can refer to the formula in step 1. Specifically, you need to replace the z in step 1 that represents the real sound source depth in the measurement field with s becomes the parameter z to represent different assumed depths in the copy field.

[0098] Step 3: Perform matching correlation operations on the broadband sound field ratio phase spectrum of the actual measurement field and the broadband sound field ratio phase spectrum data set of the simulated copy field to construct a depth-distance ambiguity function;

[0099] Specifically, the acoustic field ratio phase spectrum of the measured data can be Phase spectrum of the ratio of the acoustic field to the copy field Perform relevant operations and construct the depth-distance ambiguity function A(z) as follows:

[0100]

[0101] This step 3 is matching related processing.

[0102] When the environmental parameters of the simulated sound field are consistent with those calculated from the measured data, the maximum value of the depth-distance ambiguity function is obtained, and the corresponding depth is the depth of the target.

[0103] However, usually, the environmental parameters of the simulated sound field are inconsistent with the environmental parameters calculated from the measured data, that is, there is an environmental mismatch phenomenon. The following step 4 is to determine whether the target sound source is a surface sound source or an underwater sound source.

[0104] Step 4: Based on the constructed depth-distance ambiguity function, the distinguishability of the surface and underwater sound sources is calculated, where the distinguishability of the surface and underwater sound sources is the difference between the ambiguity peak of the depth matching below the shallow sea thermocline and the ambiguity peak above the shallow sea thermocline;

[0105] Step 5: Based on the relationship between the distinguishability of the surface and underwater sound sources and the distinguishability threshold, determine whether the target sound source in the actual measurement field is a surface sound source or an underwater sound source.

[0106] Specifically, it can be determined whether the target sound source in the actual measurement field is a water surface sound source or an underwater sound source by the following method:

[0107] Calculate the distinguishability D of the surface and underwater sound sources. If D>0 and |D|>D1, the target sound source in the actual measurement field is determined to be an underwater sound source; if D<0 and |D|>D2, the target sound source in the actual measurement field is determined to be a surface sound source, where:

[0108]

[0109] D1 is the preset first distinguishability threshold, D2 is the preset second distinguishability threshold, z up is the upper boundary depth of the shallow sea thermocline, z down is the depth of the lower boundary of the shallow sea thermocline, z H is the sea water depth, and D1 and D2 are determined according to the target sound source type and shallow sea thermocline environmental parameters.

[0110] The embodiment of the present invention is to statistically analyze the influence of different hydrological conditions and environmental mismatches on the algorithm performance, and obtain the end depth of the upper isothermal layer, i.e., the shallow sea thermocline, according to the sound velocity profile. up , the lower boundary depth of the sea thermocline is z down , the seawater depth is z H The difference between the ambiguity peak value of the depth match below the thermocline and the ambiguity peak value of the depth match above the thermocline is defined as the distinguishability of the surface and underwater sound sources.

[0111] Optionally, after step 4, it is also possible to determine whether the target sound source in the actual measurement field is a water surface sound source or an underwater sound source according to the energy concentration distribution of the ambiguity surface.

[0112] In the scheme of the embodiment of the present invention, the horizontal dual-element broadband sound field ratio η containing the sound source depth information is defined as a new matching feature based on the simple normal wave theory; first, the simulation data sets of the phase spectrum of the sound field ratio η of the measurement field and the phase spectrum of the sound field ratio of different depths of the copy field are calculated respectively; then the two are matched and related operations are performed to construct the depth-distance ambiguity function; finally, when the environmental parameters of the simulation sound field are consistent with the environmental parameters of the measurement data, the depth corresponding to the maximum value of the ambiguity function is the depth of the target, and when the environmental parameters are inconsistent, the difference between the ambiguity peak value of the depth matching below the jump layer and the ambiguity peak value above the jump layer is defined as the distinguishability of the underwater sound source on the water surface, and the distinguishability thresholds D1 and D2 are given: if D>0 and |D|>D1, it is determined to be an underwater sound source; if D<0 and |D|>D2, it is determined to be a surface sound source. Since the phase information of the sound field ratio containing the target depth information is used and the ambiguity function is constructed using the simulation field data set, it is possible to accurately distinguish whether the target sound source is from the water surface or from underwater.

[0113] Figure 3 The schematic diagram of the shallow sea thermocline waveguide environmental parameters and the sound source hydrophone deployment in the feasibility simulation verification of the present invention is as follows: the water layer depth is 70m, the sound velocity of the upper isothermal layer is 1510m / s, the sound velocity of the lower isothermal layer is 1480m / s, and the density is 1g / cm 3 ; Sediment thickness 10m, sound velocity 1550m / s, density 1.5g / cm 3 , absorption coefficient is 0.2dB / λ; sound velocity of substrate layer is 1650m / s, density is 1.65g / cm 3, the absorption coefficient is 0.2dB / λ. Assuming that the target sound sources (considered as point sound sources) are all located in the end-fire direction of the dual-element horizontal linear array, and the distance from the center of the horizontal dual-element receiving array is r=15km, the depth of the near-surface sound source 1 is zs1=10m, the depth of the underwater sound source 2 is zs2=50m, and the depth of the horizontal receiving array is zr=50m, the measurement field data is generated by simulation. Under the same environmental parameters, the matching positioning search area is 14~16km in the horizontal direction, the horizontal search step is 10m, and the vertical direction is 2~70m, with a vertical search step of 2m. The sound field is divided into 201×35 grids in the horizontal and vertical directions, and the copy field data of different sound source depths and different receiving distances are generated by simulation.

[0114] Figure 4 The depth estimation results of the present invention for a 10m sound source and a 50m sound source under the condition of no environmental mismatch include ambiguity maps (a) and (c) and ambiguity curves (b) and (d), and the black frame indicates the position where the peak value of the correlation coefficient appears. The results show that when there is no environmental mismatch, the energy distribution of the upper and lower parts of the ambiguity map is obviously different, the peak value of the ambiguity curve is unique and the position is accurate, and the depth of the sound source can be accurately estimated. In addition, the bright spot area of ​​the ambiguity map is large, and the algorithm has good tolerance to the mismatch of the sound source distance, and the depth of the sound source can be correctly distinguished without the accurate known distance.

[0115] Figure 5 The 10m and 50m sound source depth resolution results and distinguishability diagrams of different sound velocity gradient mismatch conditions of the present invention. Figure 3 As shown, the real upper isothermal layer sound speed is set to 1510 m / s, the measurement field data is generated, and the upper isothermal layer sound speed of the copy field is changed to 1480 m / s with an interval of 10 m / s to 1530 m / s. In the simulation environment of the embodiment of the present invention, the distinguishability threshold D1=D2=0.2 is selected. Figure 5 In the simulation result diagram, the black box indicates the corresponding depth and the sound velocity of the upper isothermal layer where the maximum correlation coefficient appears. It can be seen that the algorithm is sensitive to the change of the sound velocity gradient. When the sound velocity gradient of the copy field is smaller than that of the measurement field, the distinguishability is significantly reduced, the distinguishability of the underwater sound source is less than the threshold, and the target cannot be correctly distinguished. When the sound velocity gradient of the copy field is greater than that of the measurement field, the resolution result is basically not affected by the sound velocity gradient mismatch, and the upper and lower distribution of energy in the ambiguity surface is obvious, which can achieve accurate resolution of surface and underwater targets.

[0116] Figure 6 The 10m and 50m sound source depth resolution results and distinguishability diagrams of different sea depth mismatch conditions of the present invention are shown in the figure. The real sea depth is set to 70m, the measurement field data is generated, and the copy field sea depth is changed to 60m with intervals of 10m to 120m. Figure 6 It can be seen from the simulation results that the algorithm has a high tolerance to changes in sea depth, and the impact of sea depth mismatch on the method can be ignored.

[0117] Figure 7 The 10m and 50m sound source depth resolution results and distinguishability diagrams of different sediment layer sound velocity mismatch conditions of the present invention. Set the real sediment layer sound velocity to 1550m / s, generate measurement field data, and change the copy field sediment layer sound velocity to 1500m / s with an interval of 10m / s to 1700m / s. Figure 7 The simulation result shows that the algorithm has a certain tolerance to the change of sound velocity in the sediment layer. The sound velocity error of the sediment layer can achieve correct distinction between the water surface and underwater within ±50m / s. From the distinguishability diagram, the influence of the sound velocity mismatch of the sediment layer on the distinction of the water surface sound source is slightly greater than that of the underwater sound source.

[0118] Example 2

[0119] Embodiment 2 of the present invention provides a system for distinguishing surface and underwater targets based on the above-mentioned horizontal array active sonar, comprising:

[0120] The measurement field phase data determination module is used to calculate the broadband sound field ratio of multiple horizontal array elements in the actual measurement field, and obtain the phase to obtain the broadband sound field ratio phase spectrum of the actual measurement field, wherein the broadband sound field ratio is defined based on the simple normal wave theory;

[0121] A copy field phase data determination module is used to calculate the broadband sound field ratio at different sound source depths and different receiving distances in the copy field using a sound field simulation program, and obtain the phase to obtain a broadband sound field ratio phase spectrum data set of the simulated copy field;

[0122] An ambiguity construction module is used to perform matching correlation operations on the broadband sound field ratio phase spectrum of the actual measurement field and the broadband sound field ratio phase spectrum data set of the simulated copy field to construct a depth-distance ambiguity function;

[0123] A calculation module, used for calculating the distinguishability of surface and underwater sound sources based on the constructed depth-distance ambiguity function, wherein the distinguishability of surface and underwater sound sources is the difference between the ambiguity peak value of the depth matching below the shallow sea thermocline and the ambiguity peak value above the shallow sea thermocline; and

[0124] The judgment module is used to determine whether the target sound source in the actual measurement field is a surface sound source or an underwater sound source based on the magnitude relationship between the distinguishability of the surface and underwater sound sources and the distinguishability threshold.

[0125] In the scheme of the embodiment of the present invention, in order to solve the problem of difficulty in distinguishing underwater / surface targets under the condition of unknown scattering characteristics of target sound sources in shallow sea environments, a target discrimination method using the difference in the sound field of simple normal waves excited by sound sources below / above the jump layer is proposed. This method is based on the generalized field matching concept. By matching the sound field ratio between two array elements of the horizontal array, the influence of the scattering characteristics of the target source is eliminated to distinguish underwater / surface targets. Numerical simulation results show that compared with the traditional matching field bathymetry method, this method has a larger bright spot area on the ambiguity surface and has a higher tolerance to distance mismatch and environment mismatch.

[0126] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention is described in detail with reference to the embodiments, it should be understood by those skilled in the art that any modification or equivalent replacement of the technical solutions of the present invention does not depart from the spirit and scope of the technical solutions of the present invention and should be included in the scope of the claims of the present invention.

Claims

1. A method for distinguishing surface and underwater targets based on a horizontal array active sonar, comprising: Calculate the broadband sound field ratio of multiple horizontal array elements in the actual measurement field, and take the phase to obtain the broadband sound field ratio phase spectrum of the actual measurement field, wherein the broadband sound field ratio is defined based on the simple normal wave theory; The broadband sound field ratio at different sound source depths and different receiving distances in the copy field is calculated using a sound field simulation program, and the phase is taken to obtain a broadband sound field ratio phase spectrum data set of the simulated copy field; The broadband sound field ratio phase spectrum of the actual measurement field is matched with the broadband sound field ratio phase spectrum data set of the simulated copy field to construct a depth-distance ambiguity function; Based on the constructed depth-distance ambiguity function, the distinguishability of surface and underwater sound sources is calculated, where the distinguishability of surface and underwater sound sources is the difference between the ambiguity peak of the depth matching below the shallow sea thermocline and the ambiguity peak above the shallow sea thermocline; Based on the relationship between the distinguishability of surface and underwater sound sources and the distinguishability threshold, it is determined whether the target sound source in the actual measurement field is a surface sound source or an underwater sound source.

2. The method for distinguishing surface and underwater targets based on horizontal array active sonar according to claim 1, characterized in that: The calculating of the broadband sound field ratio of multiple horizontal array elements in the actual measurement field comprises: When the number of array elements is 2, the broadband sound field ratio of the two array elements is directly used; When the number of array elements is more than 2, two representative array elements are selected from multiple array elements, and the broadband sound field ratios of the two representative array elements are used, or two array elements are selected in sequence according to a certain rule to obtain the sound field ratios and then the average broadband sound field ratio is obtained by averaging them.

3. The method for distinguishing surface and underwater targets based on horizontal array active sonar according to claim 2, characterized in that: The method of taking two array elements in sequence according to a certain rule to obtain the sound field ratio and then taking the average to obtain the average broadband sound field ratio includes: taking two array elements according to any one of the following three rules to obtain the sound field ratio η(z s ,ω) and then take the average to get the average broadband sound field ratio The first rule: One adjacent array element: The second rule: a group of adjacent array elements: The third rule: j array elements apart: Among them, G is the number of array elements, z s is the depth of the target sound source in the actual measurement field, and ω is the frequency of the target sound source.

4. The method for distinguishing surface and underwater targets based on horizontal array active sonar as claimed in claim 3, characterized in that: The broadband sound field ratio of any two array elements is obtained by the following method: intercepting the echo signal in the dual-element receiving element domain data; Perform Fourier transform on the intercepted echo signal to obtain dual-channel frequency domain data P1(z s ,ω)、P2(z s ,ω); Calculating Broadband Sound Field Ratio 5. The method for distinguishing surface and underwater targets based on horizontal array active sonar according to claim 1, characterized in that: The method of using a sound field simulation program to calculate the broadband sound field ratio at different sound source depths and different receiving distances in the copy field includes: Determine an estimate of the target sound source direction and an estimate of the echo arrival time; Determine horizontal array element parameters and known environmental parameters, wherein: horizontal array element parameters include: frequency range, hydrophone receiving depth, search depth and part or all of the search interval; known environmental parameters include: sound velocity profile, seabed sediment layer and basement layer thickness, sound velocity and attenuation part or all of the above; Input the above two estimated values ​​and the above two types of parameters into the sound field calculation program to obtain the frequency domain simulated sound field; Calculate the broadband sound field ratio of the simulation data at different sound source depths and different receiving distances.

6. The method for distinguishing surface and underwater targets based on horizontal array active sonar according to claim 1, characterized in that: The matching correlation operation is performed on the broadband sound field ratio phase spectrum of the actual measurement field and the broadband sound field ratio phase spectrum data set of the simulated copy field to construct a depth-distance ambiguity function, including: The broadband acoustic field ratio phase spectrum of the actual measurement field Broadband acoustic field ratio phase spectrum dataset with simulated copy field Perform cross-correlation operations to construct the depth-range ambiguity function A(z); Among them, z is the depth of each sound source in the simulated copy field, and ω is the target sound source frequency.

7. The method for distinguishing surface and underwater targets based on horizontal array active sonar according to claim 1, characterized in that: The determining, based on the magnitude relationship between the distinguishability of the surface and underwater sound sources and the distinguishability threshold, whether the target sound source in the actual measurement field is a surface sound source or an underwater sound source comprises: If D>0 and |D|>D1, the received signal is determined to be an underwater sound source; if D<0 and |D|>D2, the received signal is determined to be a surface sound source; Where D is the distinguishability of surface and underwater sound sources, D1 is the preset first distinguishability threshold, D2 is the preset second distinguishability threshold, z up is the upper boundary depth of the shallow sea thermocline, z down is the depth of the lower boundary of the shallow sea thermocline, z H is the sea water depth, and D1 and D2 are determined according to the target sound source type and shallow sea thermocline environmental parameters.

8. The method for distinguishing surface and underwater targets based on horizontal array active sonar according to any one of claims 1 to 7, characterized in that: After performing matching correlation operations on the broadband sound field ratio phase spectrum of the actual measurement field and the broadband sound field ratio phase spectrum data set of the simulated copy field to construct the depth-distance ambiguity function, the method further includes: According to the energy concentration distribution of the ambiguity surface, it is judged whether the target sound source in the actual measurement field is a surface sound source or an underwater sound source.

9. A system for distinguishing surface and underwater targets based on the horizontal array active sonar of claim 1, characterized in that: include: The measurement field phase data determination module is used to calculate the broadband sound field ratio of multiple horizontal array elements in the actual measurement field, and obtain the phase to obtain the broadband sound field ratio phase spectrum of the actual measurement field, wherein the broadband sound field ratio is defined based on the simple normal wave theory; A copy field phase data determination module is used to calculate the broadband sound field ratio at different sound source depths and different receiving distances in the copy field using a sound field simulation program, and obtain the phase to obtain a broadband sound field ratio phase spectrum data set of the simulated copy field; An ambiguity function construction module is used to perform matching correlation operations on the broadband sound field ratio phase spectrum of the actual measurement field and the broadband sound field ratio phase spectrum data set of the simulated copy field to construct a depth-distance ambiguity function; A calculation module, used for calculating the distinguishability of surface and underwater sound sources based on the constructed depth-distance ambiguity function, wherein the distinguishability of surface and underwater sound sources is the difference between the ambiguity peak value of the depth matching below the shallow sea thermocline and the ambiguity peak value above the shallow sea thermocline; and The judgment module is used to determine whether the target sound source in the actual measurement field is a surface sound source or an underwater sound source based on the magnitude relationship between the distinguishability of the surface and underwater sound sources and the distinguishability threshold.

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