Rapid and high-precision estimation method for target distance and orientation in deep-sea shadow area

Abstract

The invention relates to a deep-sea shadow area target distance and orientation rapid high-precision estimation method, which comprises the following steps: firstly, dividing a large-aperture horizontal array into two sub-arrays with a certain horizontal interval, and respectively carrying out target orientation estimation on array receiving signals of the two sub-arrays; secondly, estimating a target sound ray propagation distance based on target orientation estimation results of the two sub-arrays and a geometrical relationship with the target, and converting the sound ray propagation distance into a horizontal distance between the target and the receiving array through a virtual source model; and finally correcting the direction finding error of the horizontal array system by using the obtained horizontal distance and combining geometric knowledge. Compared with a traditional two-station direction-finding cross positioning method, the method provided by the invention is higher in positioning precision. The basic principle and the implementation scheme of the method provided by the invention are verified by computer numerical simulation, and the result shows that under a typical deep sea environment, the method provided by the invention can effectively estimate the distance and the orientation of the near sea surface target.

Description

Technical Field

[0001] The present invention belongs to the fields of ocean engineering, underwater acoustic engineering, array signal processing and sonar technology, and relates to a method for fast and high-precision estimation of the distance and azimuth of targets in deep-sea shadow areas, which is applicable to the problem of azimuth estimation of near-sea surface targets by a deep-sea large-aperture towed array. Background Art

[0002] Sonar is the primary means of sensing underwater targets. Passive sonar utilizes target radiated noise signals for passive detection, positioning, tracking, and identification. Its high concealment makes it a crucial tool for detecting underwater targets. Towed linear array sonar is a typical passive detection method. It operates away from the carrier, significantly reducing the impact of towed platform noise. Furthermore, its aperture is not limited by the vessel. Compared to broadside array sonar, towed arrays can improve the received signal-to-noise ratio by increasing the number of hydrophones and reduce the sonar operating frequency band by increasing the spacing between array elements.

[0003] Due to the axial symmetry of the horizontal array, it is impossible to distinguish the horizontal azimuth angle and vertical pitch angle of the signal when estimating the target direction. Therefore, the conventional target direction estimation result is the result of the combined effect of the signal azimuth angle in the horizontal plane and the arrival pitch angle in the vertical plane, and the three satisfy certain constraints. For large-aperture horizontal arrays, they are divided into two sub-arrays with a certain interval, and the target distance estimation can be achieved by using the angle difference between the target and each sub-array. However, due to the large direction-finding error in the target azimuth result of the horizontal array, in this case, the traditional two-station direction-finding cross-positioning method also has a large error, which limits the application of this method in actual engineering. Based on the sound propagation characteristics and geometric knowledge of the acoustic shadow zone, the present invention proposes a fast and high-precision estimation method for the shadow zone target distance and azimuth based on the horizontal array, and improves the positioning accuracy by improving the traditional two-station direction-finding cross-positioning method. This method has strong real-time performance, fast calculation speed, and is easy to implement in engineering. Summary of the Invention

[0004] Technical problems to be solved

[0005] In order to avoid the shortcomings of the existing technology, the present invention proposes a method for fast and high-precision estimation of the distance and azimuth of a target in a deep-sea shadow area, thereby improving the estimation accuracy of the azimuth of the target in the shadow area.

[0006] The traditional two-station cross-positioning method suffers from unsatisfactory positioning results when applied in shadow environments due to large direction-finding errors. This method first divides a large-aperture horizontal array into two sub-arrays with a certain horizontal spacing, and estimates the target direction of the array-received acoustic signals of the two sub-arrays. Secondly, based on the target direction estimation results of the two sub-arrays and their geometric relationship with the target, the target sound line propagation distance is estimated, and the sound line propagation distance is converted into the horizontal distance between the target and the receiving array using a virtual source model. Finally, the obtained horizontal distance is used to correct the horizontal array system direction-finding error. Compared with the traditional two-station direction-finding cross-positioning method, the method proposed in this invention has higher positioning accuracy.

[0007] Technical Solution

[0008] A method for quickly and accurately estimating the distance and orientation of a target in a deep-sea shadow area is characterized by the following steps:

[0009] Step 1: Divide the N-element horizontal line array into subarrays, where the element spacing is d. When dividing the subarrays, the first N1 elements at the head are used as the first subarray 1, and the last N2 elements are used as the second subarray 2. θ1 and θ2 are the azimuth angles of the target relative to subarray 1 and subarray 2 in the horizontal plane.

[0010] Step 2: Target azimuth estimation is performed on the array received acoustic signals of the two sub-arrays respectively. First, the beam output power spectrum P(θ) of the two sub-arrays is calculated, and the azimuth estimation angles corresponding to the peak values ​​of the beam output power spectrum P(θ) of the target relative to sub-array 1 and sub-array 2 are obtained respectively. and

[0011]

[0012] Step 3: Based on the triangular relationship between the two sub-arrays and the target's mirror image on the seabed interface, the propagation path length of the sound line emitted from the target after being reflected from the seabed and propagated to sub-array 1 and sub-array 2 is obtained. and They are:

[0013]

[0014] Where L is the interval between the two sub-arrays, which is defined as the horizontal distance between the centers of the two sub-arrays;

[0015] Step 4: Based on the virtual source model, the distance of the sound ray propagation path in the shadow area is converted into the horizontal distance between the target and each sub-array;

[0016] The length of the sound propagation path and Substitute into the following formulas respectively:

[0017]

[0018] The obtained horizontal distances R1 and R2 of the target relative to the two sub-arrays;

[0019] Where: H represents the sea depth;

[0020] Step 5: Calculate the target's position coordinates in the horizontal plane (x s ,y s )for:

[0021]

[0022] Where: (x1, y1) is the position coordinate of the center of the first sub-array, (x2, y2) is the position coordinate of the center of the second sub-array; a and b are intermediate variables;

[0023] Step 6: Based on the target position coordinates obtained in step 5, the estimated results of the target's orientation relative to each sub-array are:

[0024]

[0025] The horizontal line array adopts a large-aperture uniform horizontal line array.

[0026] The azimuth angle does not consider the starboard and port ambiguity, and defines the starboard direction as 0 to 180° and the port direction as 0 to -180°.

[0027] The target direction estimation method of the two sub-array array receiving acoustic signals is as follows:

[0028] Calculate beam output power spectrum

[0029] Where θ is the beam pointing angle, which is θ1 or θ2; P(θ) is the output power of the beamformer, L is the number of frequency points, and w(f l ,θ) is the frequency point f l The beam weight vector corresponding to the angle θ, the superscript H represents the conjugate transpose; R(f l ) is the frequency f l The covariance matrix of the received acoustic signal at .

[0030] The frequency f l The beam weight vector w(f l ,θ) is calculated as follows:

[0031]

[0032] Where, k = 2πf / c, f is the frequency f l The corresponding frequency value, c is the reference sound speed, and the superscript (·) T Indicates transpose.

[0033] The frequency fl The covariance matrix R(f l ) is calculated as follows:

[0034] R(f l )=E[x H (f l )x(f l )]

[0035] Among them, x(f l ) is the array receiving signal at frequency f l , the spectrum vector at , E[.] means to find the expectation.

[0036] The intermediate variables a and b are:

[0037]

[0038] The target depth range is 0 to 500m, and the signal is single frequency or broadband.

[0039] The receiving array is located near the sea surface. For a typical deep-sea Munk environment, the receiving distance range is 6 to 40 km and the receiving depth range is 0 to 500 m.

[0040] An application of the method for fast and high-precision estimation of target distance and azimuth in deep-sea shadow areas is characterized by being applicable to conventional beamforming methods and uniform linear arrays, as well as other azimuth estimation methods and non-uniform linear arrays.

[0041] Beneficial effects

[0042] The present invention proposes a method for fast and high-precision estimation of the distance and azimuth of targets in deep-sea shadow zones. The method directly provides a closed-form solution to the distance and azimuth of targets in the shadow zone. The calculation formula is simple and the physical meaning of the parameters is clear. The proposed method does not rely on complex ocean environment parameters and does not require sound field modeling, which greatly saves calculation complexity and is easy to quickly implement in engineering applications.

[0043] The proposed method fully considers and utilizes the acoustic field characteristics of the deep-sea shadow zone. First, the method divides a large-aperture horizontal array into two subarrays with a certain horizontal spacing. The target azimuth is estimated for the array received signals of the two subarrays. Second, the target sound ray propagation distance is estimated based on the target azimuth estimation results of the two subarrays and their geometric relationship with the target. This sound ray propagation distance is converted into the horizontal distance between the target and the receiving array using a virtual source model. Finally, the obtained horizontal distance is combined with geometric knowledge to correct the horizontal array system direction-finding error. Compared with the traditional two-station direction-finding cross-location method, the proposed method has higher positioning accuracy. The basic principles and implementation scheme of the proposed method have been verified by computer numerical simulation. The results show that in typical deep-sea environments, the proposed method can effectively estimate the distance and azimuth of near-surface targets. In the typical implementation case presented, the proposed method (compared to the traditional method) can reduce the distance estimation error from 46.32% to 6.82% and the azimuth estimation error from 71.67% to 4.97%. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 It is a schematic diagram of the sound speed profile of the simulation scenario.

[0045] Figure 2 This is a schematic diagram of the cross positioning of two sub-arrays.

[0046] (a) 3D schematic diagram;

[0047] (b) Top view of the scene.

[0048] Figure 3 It is the characteristic sound ray propagation trajectory of the deep sea shadow area obtained using the ray model. Figure 4 It is the output result of the two sub-array beams.

[0049] Figure 5 It is the result of cross positioning of the two sub-arrays in the horizontal plane.

[0050] Figure 6 These are the distance estimation results at different target distances (relative to subarray 1, target azimuth 30°, depth 200m, receiving depth 200m).

[0051] (a) Comparison between estimated distance and actual distance;

[0052] (b) Distance estimation error.

[0053] Figure 7 These are the azimuth estimation results at different target distances (relative to subarray 1, target azimuth 30°, depth 200m, receiving depth 200m).

[0054] (a) Comparison between estimated and actual position;

[0055] (b) Azimuth estimation error. DETAILED DESCRIPTION

[0056] The present invention will now be further described with reference to the embodiments and accompanying drawings:

[0057] The traditional two-station cross-positioning method suffers from unsatisfactory positioning results when applied in shadow environments due to large direction-finding errors. This method first divides a large-aperture horizontal array into two sub-arrays with a certain horizontal spacing, and estimates the target direction of the array-received acoustic signals of the two sub-arrays. Secondly, based on the target direction estimation results of the two sub-arrays and their geometric relationship with the target, the target sound line propagation distance is estimated, and the sound line propagation distance is converted into the horizontal distance between the target and the receiving array using a virtual source model. Finally, the obtained horizontal distance is used to correct the horizontal array system direction-finding error. Compared with the traditional two-station direction-finding cross-positioning method, the method proposed in this invention has higher positioning accuracy.

[0058] The technical solution adopted by the present invention to solve its technical problem is: the receiving array is located near the sea surface. For a typical deep-sea Munk environment, the receiving distance range is 6 to 40 km, and the receiving depth range is 0 to 500 m.

[0059] The target depth range is 0 to 500m and can be either single frequency or broadband.

[0060] A method for quickly and accurately estimating the range and orientation of a target in a deep-sea shadow area is characterized by comprising the following steps:

[0061] Step 1: For an N-element large-aperture uniform horizontal linear array with element spacing d, first divide the array into subarrays. Take the first N1 elements at the front as subarray 1, and the last N2 elements as subarray 2. Define θ1 and θ2 as the target's azimuth angles relative to subarray 1 and subarray 2 in the horizontal plane. Ignoring port and starboard ambiguity, define the starboard direction as 0 to 180°, and the port direction as 0 to -180°.

[0062] Step 2: Calculate the target azimuth for the array received acoustic signals of the two sub-arrays respectively, and obtain the target azimuth estimation angles relative to sub-array 1 and sub-array 2 respectively. and Among them, the target direction estimation method is as follows:

[0063]

[0064] Where θ is the beam pointing angle, P(θ) represents the output power of the beamformer, L is the number of frequency points, and w(f l ,θ) is the frequency point f l The beam weight vector corresponding to the angle θ, the superscript H represents the conjugate transpose, taking sub-array 1 as an example, w(f l,θ) can be expressed as,

[0065]

[0066] Where, k = 2πf / c, f is the frequency f l The corresponding frequency value, c is the reference sound speed, and the superscript (·) T Indicates transposition. R(f l ) is the frequency f l The covariance matrix of the received sound signal at can be calculated by the following formula:

[0067] R(f l )=E[x H (f l )x(f l )] (3)

[0068] Among them, x(f l ) is the array receiving signal at frequency f l , the spectrum vector at , E[.] means to find the expectation.

[0069] The azimuth corresponding to the peak of the beam output power spectrum P(θ) is the target azimuth estimation angle:

[0070]

[0071] Step 3: Based on the triangular relationship between the two sub-arrays and the target's mirror image on the seabed interface, the propagation path length of the sound line emitted from the target after being reflected from the seabed and propagated to sub-array 1 and sub-array 2 can be estimated. and They are:

[0072]

[0073] Where L is the interval between the two sub-arrays, which is defined as the horizontal distance between the centers of the two sub-arrays.

[0074] Step 4: Based on the virtual source model, convert the distance of the sound line propagation path in the shadow area into the horizontal distance between the target and each sub-array. For near-sea targets and receiving horizontal arrays, the influence of their depth can be ignored and the sound line propagation path length is converted to and Substituting the following equations respectively, the calculated results are the horizontal distances R1 and R2 of the target relative to the two sub-arrays obtained by the method proposed in this invention:

[0075]

[0076] Here, H represents the ocean depth.

[0077] Step 5: Assume that the position coordinates of the centers of the two sub-arrays are (x1, y1) and (x2, y2) respectively. Then, according to the geometric relationship between the target and the two sub-arrays, the position coordinates of the target in the horizontal plane (x s ,y s )for:

[0078]

[0079] Among them, define the intermediate variables:

[0080]

[0081] Step 6: Based on the target position coordinates obtained in step 5, the estimated results of the target's position relative to each sub-array are:

[0082]

[0083] The specific embodiments are:

[0084] 1. Deep sea environment configuration

[0085] In order to verify the effectiveness of the method of the present invention, a computer simulation experiment was conducted. This embodiment considers a typical deep sea environment, Munk sound velocity profile, and a sea depth of 5000m. Figure 1 As shown. The sea surface sound speed is 1548.5m / s, the sound channel axis depth is 1100m, the sound channel axis sound speed is 1500m / s, the critical depth is 4050m, and the seabed sound speed is 1567m / s. The seabed is modeled as a uniform infinite half space, the seabed sound speed is 1600m / s, and the density is 1.6g / cm 3 , attenuation coefficient 0.2dB / λ.

[0086] 2. A method for estimating the distance and orientation of targets in deep-sea shadow areas

[0087] The specific implementation process of the method for estimating the distance and orientation of a target in a deep-sea shadow area proposed in the present invention is as follows:

[0088] Step 1: The number of large aperture horizontal array elements is 225, the element spacing is d = 4m, and the receiving depth is z r = 200m. Take the first and last 100 array elements as subarray 1 and subarray 2 respectively. The horizontal distance between the centers of the two subarrays is the subarray spacing L = 500m. Assume that the target radiates a broadband signal with a frequency of 100-200Hz and a depth of z s =200m.

[0089] With the first element of the horizontal array as the coordinate origin and the array axis as the X axis, establish the XOY and XOY' coordinate systems respectively, as shown in the attached figure. Figure 2As shown, point O represents the position coordinates of sub-array 1 (x1, y1) is (0, 0), point A represents the position coordinates of sub-array 2 (x2, y2) is (L, 0), and point B is the target with coordinates (x s ,y s ), point C is the mirror image of the target with respect to the seabed interface; θ1 and θ2 are the azimuths of the target relative to subarray 1 and subarray 2 in the horizontal plane, that is, the XOY plane; R1 and R2 are the horizontal distances between the target and subarray 1 and subarray 2 respectively; and are the solid angles of the target relative to subarray 1 and subarray 2 in the XOY' plane, that is, the target azimuth estimation angles of the two subarrays, and are the straight-line distances between the mirror target and subarray 1 and subarray 2, respectively, that is, the path lengths that the sound line emitted by the target from point B travels through after being refracted by the water body and reflected by the seabed and sea surface to reach the receiving point.

[0090] Without considering the starboard and port ambiguity, the starboard side is defined as the direction of 0 to 180 degrees, and the port side is defined as the direction of 0 to -180 degrees. Assume that at time t, the horizontal distances between the target and sub-array 1 and sub-array 2 are R1 = 10 km and R2 = 10.44 km respectively, and the true azimuth angles relative to sub-array 1 and sub-array 2 are θ1 = 30 degrees and θ2 = 28.63 degrees respectively. At this time, the target's true position coordinates (x s ,y s ) is (-8.66, 5) km and is located on the starboard side of the array, obtaining the array receiving signals of the two sub-arrays. Using the Bellhop ray model simulation, the propagation trajectories of the four primary seabed reflection characteristic sound lines received by the first array element of the sub-array under this transceiver configuration are obtained, as shown in the attached figure. Figure 3 As shown in the figure, the acoustic field in the acoustic shadow zone is mainly contributed by the primary seabed reflection wave. The secondary and higher seabed reflection waves have a large energy attenuation due to the large number of interface reflections, so their impact on the acoustic field is negligible. In this case, the sound line can be approximated as a straight line after being reflected by the sea surface and seabed.

[0091] Step 2: Target azimuth estimation is performed on the array received acoustic signals of the two sub-arrays respectively, and the target azimuth estimation angles relative to sub-array 1 and sub-array 2 are obtained respectively. and Among them, the target direction estimation method is as follows:

[0092]

[0093] Where θ is the beam pointing angle, P(θ) represents the output power of the beamformer, L is the number of frequency points, and w(f l ,θ) is the frequency point f l The beam weight vector corresponding to the angle θ, the superscript H represents the conjugate transpose, taking sub-array 1 as an example, the weight vector w(f l,θ) can be expressed as,

[0094]

[0095] Where, k = 2πf / c, f is the frequency f l The corresponding frequency value, c is the reference sound speed, and the superscript (·) T Indicates transpose.

[0096] R(f l ) is the frequency f l The covariance matrix of the received sound signal at can be calculated by the following formula:

[0097] R(f l )=E[x H (f l )x(f l )] (12)

[0098] Among them, x(f l ) is the array receiving signal at frequency f l , the spectrum vector at , E[.] means to find the expectation.

[0099] The azimuth corresponding to the peak value of the beam output power spectrum P(θ) is the target azimuth estimation angle.

[0100]

[0101] The two sub-array beam output results calculated by the above method are shown in the attached figure. Figure 4 As shown, the peak azimuths of the beam output are and At this time, the true direction of the target is considered to be in the direction of 51.5° for sub-array 1 and in the direction of 50° for sub-array 2.

[0102] Step 3: Based on the triangular relationship between the two sub-arrays and the target's mirror image on the seabed interface, the path length of the sound line emitted from the target after being reflected from the seabed and propagated to each sub-array can be estimated, that is, the length of the line segments OC and AC and They are,

[0103]

[0104] Where L is the distance between two sub-arrays, in this implementation case L = 500m. The target azimuth estimated angle obtained by each sub-array is and Substituting the sub-array spacing L into formula (12) yields

[0105] Step 4: Based on the virtual source model, convert the distance of the sound line propagation path in the shadow area into the horizontal distance between the target and each sub-array. For near-sea targets and receiving horizontal arrays, the influence of their depth can be ignored and the sound line propagation path length is converted to and Substitute the following equations respectively and the calculated results are the horizontal distances R1 and R2 of the target relative to the two sub-arrays obtained by the method proposed in this invention.

[0106]

[0107] Where H is the sea depth. and Substituting into equation (13), we can obtain the estimated horizontal distances of the target relative to sub-array 1 and sub-array 2 as R1 = 10.68 km and R2 = 11.11 km, respectively.

[0108] Step 5: Assume that the position coordinates of the centers of the two sub-arrays are (x1, y1) and (x2, y2) respectively. Then, according to the geometric relationship between the target and the two sub-arrays, the position coordinates of the target in the horizontal plane (x s ,y s )for,

[0109]

[0110] Among them, define the intermediate variables,

[0111]

[0112] In this implementation case, the target is located on the starboard side of the horizontal array. Therefore, the parameters (x1, y1) and (x2, y2) and the horizontal distances R1 and R2 of the target relative to the two sub-arrays obtained in step 4 are substituted into equations (14) and (15) to obtain x s =-9.11km, y s =5.58km. That is, the target coordinates estimated by the present invention are (-9.11, 5.58)km, and the positioning results are shown in the attached Figure 5 shown.

[0113] Step 6: Based on the target position coordinates obtained in step 5, the estimated results of the target's position relative to each sub-array are:

[0114]

[0115] By calculating the above formula, we can get the horizontal azimuth angles of the target relative to each sub-array, which are θ1=31.49° and θ2=30.14° respectively. The azimuth estimation errors are 4.97% and 5.28% respectively. The conventional beamforming estimation results before correction are and The errors are 71.67% and 74.66% respectively. It can be seen that the present invention effectively improves the target direction estimation accuracy.

[0116] When the traditional two-station cross-positioning method is used to estimate the target distance, it is assumed that there is no error in the target orientation estimation result, and the distance estimation results are The distance estimation errors relative to each sub-array are 46.32% and 43.24% respectively. However, the distance estimation results are corrected to R1=10.68km and R2=11.11km based on the acoustic propagation characteristics of the shadow area, and the distance estimation errors are reduced to 6.82% and 6.47%.

[0117] Figure 6 The distance estimation results and errors (relative to subarray 1) of the cross-location method proposed in the present invention at different target distances are shown when the target azimuth is 30°, the target depth is 200m, and the receiving depth is 200m. Figure 7 The figures show the azimuth estimation results and errors at different target distances, compared with the positioning results of traditional methods. The average distance estimation error of the proposed method at different target distances is 6.05%, and the average azimuth estimation error is 3.14%. As can be seen from the figures, the distance and azimuth estimation accuracy of the proposed method is significantly improved compared to traditional methods, especially at close distances in shadow areas, which also verifies the effectiveness of the proposed method.

Claims

1. A method for fast and high-precision estimation of target distance and orientation in deep sea shadow area, characterized in that Here are the steps: Step 1: Divide the N-element horizontal line array into subarrays, where the element spacing is d. When dividing the subarrays, the first N1 elements at the head are used as the first subarray 1, and the last N2 elements are used as the second subarray 2. θ1 and θ2 are the azimuth angles of the target relative to subarray 1 and subarray 2 in the horizontal plane. Step 2: Target azimuth estimation is performed on the array received acoustic signals of the two sub-arrays respectively. First, the beam output power spectrum P(θ) of the two sub-arrays is calculated, and the azimuth estimation angles corresponding to the peak values ​​of the beam output power spectrum P(θ) of the target relative to sub-array 1 and sub-array 2 are obtained respectively. and Step 3: Based on the triangular relationship between the two sub-arrays and the target's mirror image on the seabed interface, the propagation path length of the sound line emitted from the target after being reflected from the seabed and propagated to sub-array 1 and sub-array 2 is obtained. and They are: Where L is the interval between the two sub-arrays, which is defined as the horizontal distance between the centers of the two sub-arrays; Step 4: Based on the virtual source model, the distance of the sound ray propagation path in the shadow area is converted into the horizontal distance between the target and each sub-array; The length of the sound propagation path and Substitute into the following formulas respectively: The obtained horizontal distances R1 and R2 of the target relative to the two sub-arrays; Where: H represents the sea depth; Step 5: Calculate the target's position coordinates in the horizontal plane (x s ,y s )for: Where: (x1, y1) is the position coordinate of the center of the first sub-array, (x2, y2) is the position coordinate of the center of the second sub-array; a and b are intermediate variables; Step 6: Based on the target position coordinates obtained in step 5, the estimated results of the target's orientation relative to each sub-array are:

2. The method for fast and high-precision estimation of distance and azimuth of a target in a deep-sea shadow area according to claim 1, characterized in that: The horizontal line array adopts a large-aperture uniform horizontal line array.

3. The method for fast and high-precision estimation of distance and azimuth of a target in a deep-sea shadow area according to claim 1, characterized in that: The azimuth angle does not consider the starboard and port ambiguity, and defines the starboard direction as 0 to 180° and the port direction as 0 to -180°.

4. The method for fast and high-precision estimation of distance and azimuth of a target in a deep-sea shadow area according to claim 1, characterized in that: The target direction estimation method of the two sub-array array receiving acoustic signals is as follows: Calculate beam output power spectrum Where θ is the beam pointing angle, which is θ1 or θ2; P(θ) is the output power of the beamformer, L is the number of frequency points, and w(f l ,θ) is the frequency point f l The beam weight vector corresponding to the angle θ, the superscript H represents the conjugate transpose; R(f l ) is the frequency f l The covariance matrix of the received acoustic signal at .

5. The method for fast and high-precision estimation of distance and azimuth of a target in a deep-sea shadow area according to claim 1, characterized in that: The frequency f l The beam weight vector w(f l ,θ) is calculated as follows: Where, k = 2πf / c, f is the frequency f l The corresponding frequency value, c is the reference sound speed, and the superscript (·) T Indicates transpose.

6. The method for fast and high-precision estimation of distance and azimuth of a target in a deep-sea shadow area according to claim 1, characterized in that: The frequency f l The covariance matrix R(f l ) is calculated as follows: R(f l )=E[x H (f l )x(f l )] Among them, x(f l ) is the array receiving signal at frequency f l , the spectrum vector at , E[.] means to find the expectation.

7. The method for fast and high-precision estimation of distance and azimuth of a target in a deep-sea shadow zone according to claim 1, characterized in that: The intermediate variables a and b are:

8. The method for fast and high-precision estimation of distance and azimuth of a target in a deep-sea shadow area according to claim 1, characterized in that: The target depth range is 0 to 500m, and the signal is single frequency or broadband.

9. The method for fast and high-precision estimation of distance and azimuth of a target in a deep-sea shadow area according to claim 1, characterized in that: The receiving array is located near the sea surface. For a typical deep-sea Munk environment, the receiving distance range is 6 to 40 km and the receiving depth range is 0 to 500 m.

10. An application of the method for fast and high-precision estimation of distance and azimuth of a deep-sea shadow target according to any one of claims 1 to 9, characterized in that: It is applicable to conventional beamforming methods and uniform linear arrays, as well as other azimuth estimation methods and non-uniform linear arrays.

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