Passive weak signal enhancement detection method for deep sea near-seabed direct sound area

Abstract

The invention relates to a deep-sea near-seabed direct sound area passive weak signal enhancement detection method, which comprises the following steps of: giving deep-sea environment input, sea depth H and seawater sound velocity c; the N-element vertical receiving array is arranged near the seabed, the depths of the array elements are respectively z1, z2,..., zN, and the distance between the array elements is d; and under the condition of assuming that the target distance is r, calculating the sound signal arrival angle # imgabs0 # when the direct wave reaches the N-element vertical receiving array. The deep sea direct sound area weak signal enhancement method realizes enhancement of deep sea direct sound area weak signals, improves the weak signal detection capability, and has remarkable scientific significance and application prospect.

Description

Technical field:

[0001] The invention belongs to the technical field of underwater acoustic engineering, and in particular relates to a method for enhancing detection of passive weak signals in a deep-sea near-bottom direct sound zone. Background technology:

[0002] With the rapid increase in the demand for deep-sea operations, the detection of underwater moving targets in the deep-sea direct sound zone within medium and long distances has become a top priority in current research on hydroacoustic technology.

[0003] The deep-sea near-bottom direct sound zone detection has attracted widespread attention since the establishment of the Deep-ocean Assessment and Reporting of Tsunamis (DART) system in the United States. Around 2000, the Defense Advanced Research Projects Agency (DARPA) of the United States Department of Defense launched the Distributed Agile Submarine Hunting (DASH) system, recognizing the low propagation loss and low noise level of reliable sound paths from the DART system. Deep-sea sonar nodes are placed at extremely deep locations in the high seas to achieve submarine detection in a large range of sea areas in the vertical direction. Based on the advantages of the wide detection range and low noise level of deep-sea sonar nodes, the DASH system allows multiple nodes to work together to achieve a larger range of underwater target detection and tracking.

[0004] The deep sea near-bottom direct sound zone has the characteristics of long sound propagation distance, small propagation loss, stable transmission channel, and low low-frequency environmental noise level. It is convenient to use the sonar platform near the deep seabed to realize effective and blind-spot-free monitoring of medium and short-range targets near the sea surface. In recent years, the passive detection of targets in the deep sea near-bottom direct sound zone has attracted much attention and research from scholars at home and abroad.

[0005] At present, the research on passive detection of targets in the direct sound zone near the deep seabed mostly uses vertical receiving arrays to detect the direct sound signals arriving from the target to the receiving array in the forward direction. However, in reality, in addition to the direct sound signal energy arriving in the forward direction, there is also the seabed reflected sound signal energy arriving in the reverse direction from the vertical receiving array. In other words, the existing processing methods lack the utilization of the seabed reflected sound energy, and the detection capability is limited. Summary of the invention:

[0006] The technical problem to be solved by the present invention is to provide a method for enhancing the detection of passive weak signals in the direct sound zone near the deep seabed. The method takes into account the high similarity between the direct wave and the seabed reflection wave, makes full use of the seabed reflection wave information in the received signal, realizes the enhancement of the weak signals in the direct sound zone of the deep sea, and improves the detection capability of the weak signals. The method has significant scientific significance and application prospects.

[0007] The technical solution of the present invention is to provide a method for enhancing detection of passive weak signals in a deep sea near-bottom direct sound zone, comprising the following steps:

[0008] (1) Given a deep-sea environment input, the sea depth is H, the seawater sound speed is c; N vertical receiving arrays are arranged near the seabed, and the array element depths are z1, z2, …, z N , the array element spacing is d;

[0009] (2) Assuming the target distance is r, calculate the arrival angle of the acoustic signal when the direct wave reaches the N-element vertical receiving array

[0010]

[0011] (3) Assuming the target distance is r, calculate the arrival angle of the acoustic signal of the seabed reflection wave reaching the N-element vertical receiving array

[0012]

[0013] (4) Constructing a steering vector w1 for extracting direct wave single beam data based on the vertical receiving array,

[0014]

[0015] (5) Constructing a steering vector w2 for extracting single-beam data of seafloor reflection waves based on a vertical receiving array,

[0016]

[0017] (6) Perform beam forming for the direct wave and the sea surface reflected wave respectively, and obtain the direct sound single beam output P1(ω,r) and the seabed reflected sound single beam output P2(ω,r).

[0018] P1(ω,r)=w1′(ω,r)p r (ω) (5)

[0019] P2(ω,r)=w′2(ω,r)p r (ω) (6)

[0020] Where p r (ω)=[p1(ω),p2(ω),…,pN (ω)] T The spectrum of the signal received by the vertical receiving array;

[0021] (7) Perform inverse Fourier transform on the direct sound single beam output spectrum P1(ω,r) and the seabed reflected sound single beam output spectrum P2(ω,r) to obtain the direct sound single beam output time domain signal P1(t,r) and the seabed reflected sound single beam output time domain signal P2(t,r),

[0022] P1(t,r)=F -1 {P1(ω,r)} (7)

[0023] P2(t,r)=F -1 {P2(ω,r)} (8)

[0024] Where F -1 {} is the inverse Fourier transform operator;

[0025] (8) Calculate the cross-correlation function between the direct sound single beam output time domain signal P1(t, r) and the seabed reflected sound single beam output time domain signal P2(t, r), and take the maximum value of the cross-correlation function as the beam output value B(r) under the condition of assuming the target distance r.

[0026]

[0027] In the formula represents the cross-correlation operator, and max{} represents the maximum value of the function;

[0028] (9) The distance corresponding to the maximum value of B(r) is the target distance corresponding to the detection.

[0029] The present invention proposes a method for enhanced detection of passive weak signals in a direct sound zone near the seabed in the deep sea. The method provides the implementation steps of range domain beamforming. On the basis of calculating the arrival angles of direct wave and seabed reflection wave acoustic signals, a distance-related steering vector for direct wave extraction and seabed reflection wave extraction is constructed, and then single-beam data of the direct wave and the sea surface reflection wave are extracted. Finally, the maximum value of the cross-correlation of the single beam of the direct wave and the sea surface reflection wave is taken as the output of the range domain beamforming. The target is detected by detecting the peak value of the range domain beam output, and numerical simulation is used to verify the improvement of the detection capability of the method for weak signals.

[0030] Compared with the prior art, the present invention has the following advantages:

[0031] This method takes into account the high similarity between direct waves and seabed reflected waves, makes full use of the seabed reflected wave information in the received signal, realizes the enhancement of weak signals in the deep-sea direct sound zone, and improves the detection capability of weak signals. It has significant scientific significance and application prospects. Description of the drawings:

[0032] Figure 1 A processing flow chart of a passive weak signal enhancement detection method in the deep sea near seabed direct sound zone is given.

[0033] Figure 2 A schematic diagram of enhanced detection in the deep sea near-bottom direct sound zone is given.

[0034] Figure 3 A comparison of the processing capabilities of the conventional beamforming method and the enhanced detection method is given when the target is 5 kilometers away. Specific implementation method:

[0035] The present invention will be further described below with reference to the accompanying drawings:

[0036] A method for enhancing detection of passive weak signals in the deep sea near the seabed direct sound zone, such as Figure 1 As shown, the following steps are included:

[0037] (1) Given a deep-sea environment input, the sea depth is H, the seawater sound speed is c; N vertical receiving arrays are arranged near the seabed, and the array element depths are z1, z2, …, z N , the array element spacing is d;

[0038] (2) Assuming the target distance is r, calculate the arrival angle of the acoustic signal when the direct wave reaches the N-element vertical receiving array

[0039]

[0040] (3) Assuming the target distance is r, calculate the arrival angle of the acoustic signal of the seabed reflection wave reaching the N-element vertical receiving array

[0041]

[0042] (4) Constructing a steering vector w1 for extracting direct wave single beam data based on the vertical receiving array,

[0043]

[0044] (5) Constructing a steering vector w2 for extracting single-beam data of seafloor reflection waves based on a vertical receiving array,

[0045]

[0046] (6) Perform beam forming for the direct wave and the sea surface reflected wave respectively, and obtain the direct sound single beam output P1(ω,r) and the seabed reflected sound single beam output P2(ω,r).

[0047] P1(ω,r)=w1′(ω,r)p r (ω) (5)

[0048] P2(ω,r)=w′2(ω,r)p r (ω) (6)

[0049] Where p r (ω)=[p1(ω),p2(ω),…,p N (ω)] T is the spectrum of the signal received by the vertical receiving array.

[0050] (7) Perform inverse Fourier transform on the direct sound single beam output spectrum P1(ω,r) and the seabed reflected sound single beam output spectrum P2(ω,r) to obtain the direct sound single beam output time domain signal P1(t,r) and the seabed reflected sound single beam output time domain signal P2(t,r),

[0051] P1(t,r)=F -1 {P1(ω,r)} (7)

[0052] P2(t,r)=F -1 {P2(ω,r)} (8)

[0053] Where F -1 {} is the inverse Fourier transform operator.

[0054] (8) Calculate the cross-correlation function between the direct sound single beam output time domain signal P1(t, r) and the seabed reflected sound single beam output time domain signal P2(t, r), and take the maximum value of the cross-correlation function as the beam output value B(r) under the condition of assuming the target distance r.

[0055]

[0056] In the formula represents the cross-correlation operator, and max{} represents the maximum value of the function.

[0057] (9) The distance corresponding to the maximum value of B(r) is the target distance corresponding to the detection.

[0058] like Figure 2 As shown, this embodiment provides a schematic diagram of enhanced detection of direct sound areas near the deep sea bottom, where the sea depth is H; the receiving array is marked as a vertical receiving array, and the first array element is deployed at a depth of z1; the horizontal distance between the target and the vertical receiving array is r; in addition, the direct sound path and the sound signal arrival angle are marked in the figure Seabed reflected sound path and sound signal arrival angle

[0059] During the simulation, Figure 3 As shown in the figure, the processing capability comparison between the conventional beamforming method and the enhanced detection method is given when the target distance is 5 kilometers. Figure 3 (a) is the processing result of the conventional beamforming method, and (b) is the processing result of the enhanced detection method. The simulation parameters are as follows: sea depth 4300m, sound speed 1528m / s, 32-element vertical receiving array is placed near the seabed, the last array element is 4290m deep, the array element spacing is 7.5m, the target distance is 5km from the vertical receiving array, the depth is 100m, the processing frequency band is 100Hz~200Hz, and the array element domain signal-to-noise ratio is -10dB; By comparing the two figures, it can be seen that the output signal-to-noise ratio of the traditional conventional beamforming method is about 3dB, and the output signal-to-noise ratio of the enhanced detection new method is about 5dB, and the processing capacity is improved by about 2dB, that is, the signal is enhanced by about 2dB.

[0060] The present invention provides the implementation steps of distance domain beamforming. On the basis of calculating the arrival angle of the direct wave and the seabed reflection wave acoustic signal, the distance-related steering vector for direct wave extraction and seabed reflection wave extraction is constructed, and then the single beam data of the direct wave and the sea surface reflection wave are extracted. Finally, the maximum value of the cross-correlation of the single beam of the direct wave and the sea surface reflection wave is taken as the output of the distance domain beamforming, and the target is detected by detecting the peak value of the distance domain beam output. The method is verified by numerical simulation to improve the detection capability of weak signals. The method realizes the enhancement of weak signals in the deep-sea direct sound zone and improves the detection capability of weak signals, which has significant scientific significance and application prospects.

[0061] The above is only an explanation of the preferred embodiments of the present invention, which should not be construed as a limitation on the claims. Any equivalent process changes made using the present invention specification are included in the patent protection scope of the present invention.

Claims

1. A method for enhancing detection of passive weak signals in the direct sound zone near the deep sea bottom, characterized in that: The following steps are included: (1) Given a deep-sea environment input, the sea depth is H, the seawater sound speed is c; N vertical receiving arrays are arranged near the seabed, and the array element depths are z1, z2, …, z N , the array element spacing is d; (2) Assuming the target distance is r, calculate the arrival angle of the acoustic signal when the direct wave reaches the N-element vertical receiving array (3) Assuming the target distance is r, calculate the arrival angle of the acoustic signal of the seabed reflection wave reaching the N-element vertical receiving array (4) Constructing a steering vector w1 for extracting direct wave single beam data based on the vertical receiving array, (5) Constructing a steering vector w2 for extracting single-beam data of seafloor reflection waves based on a vertical receiving array, (6) Perform beam forming for the direct wave and the sea surface reflected wave respectively, and obtain the direct sound single beam output P1(ω,r) and the seabed reflected sound single beam output P2(ω,r). P1(ω,r)=w′1(ω,r)p r (oh) (5) P2(ω,r)=w′2(ω,r)p r (ω) (6) Where p r (ω)=[p1(ω),p2(ω),…,p N (ω)] T The spectrum of the signal received by the vertical receiving array; (7) Perform inverse Fourier transform on the direct sound single beam output spectrum P1(ω,r) and the seabed reflected sound single beam output spectrum P2(ω,r) to obtain the direct sound single beam output time domain signal P1(t,r) and the seabed reflected sound single beam output time domain signal P2(t,r), P1(t,r)=F -1 {P1(ω,r)} (7) P2(t,r)=F -1 {P2(ω,r)} (8) Where F -1 {} is the inverse Fourier transform operator; (8) Calculate the cross-correlation function between the direct sound single beam output time domain signal P1(t, r) and the seabed reflected sound single beam output time domain signal P2(t, r), and take the maximum value of the cross-correlation function as the beam output value B(r) under the condition of assuming the target distance r. In the formula represents the cross-correlation operator, and max{} represents the maximum value of the function; (9) The distance corresponding to the maximum value of B(r) is the target distance corresponding to the detection.

Images