Deep sea active target ranging method based on Doppler frequency shift correction

Abstract

The invention belongs to the technical field of signal processing, and particularly relates to a deep sea active target ranging method based on Doppler frequency shift correction, which comprises the following steps of: obtaining a target signal arrival angle and a relationship between the arrival angle and a target distance corresponding to the arrival angle through a time-frequency history graph, and estimating and obtaining an actual target arrival angle based on a Doppler frequency shift correction method; according to the distance measurement method, side lobe interference can be reduced, and the algorithm stability and the data accuracy are improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of signal processing, and in particular relates to a deep-sea active target ranging method based on Doppler frequency shift correction. Background Art

[0002] Deep-sea target ranging has always been a hot research topic. There are three main traditional active target ranging methods: one is matching field positioning, which constructs an acoustic field calculation model by inputting ocean environmental parameters to obtain a copy field, and matches the copy field sound pressure with the measurement field sound pressure to estimate the target's position information. However, this method requires accurate ocean environmental parameters and has poor tolerance. Especially in deep-sea active detection, it is necessary to simulate the channel function twice, which increases the cumulative error; the second is multi-path delay ranging, which uses the two main propagation models of acoustic signals in the deep sea: direct sound propagation and seabed reflected sound propagation, calculates the time delay between array elements, and combines the geometric structure of the acoustic signal propagation path to estimate the distance between array elements. The target distance is estimated by using this method. The calculation amount of ranging is small, but the sound propagation mode needs to be determined before ranging, and the accuracy of the distance estimation value is low; the third is the matching target arrival angle ranging method. It only needs to calculate the sound field model once to construct the relationship between the target distance and the simulated target arrival angle, and then calculate the actual signal arrival angle by receiving the array signal. By matching the actual signal arrival angle with the simulated signal arrival angle, the target distance can be quickly estimated. However, in deep-sea active ranging, the Doppler frequency shift will be generated due to the target movement. The traditional matching target arrival angle ranging method will produce side lobes when estimating the target arrival angle, making it difficult to accurately estimate the distance. Summary of the Invention

[0003] In order to solve the problem of deep-sea active target ranging, the present invention provides a deep-sea active target ranging method based on Doppler frequency shift correction.

[0004] The specific technical solutions of the present invention are as follows:

[0005] A deep-sea active target ranging method based on Doppler shift correction, the method comprising the following steps:

[0006] S1. Build an acoustic field model based on the BELLHOP ray model and calculate the target signal arrival angle and the target distance corresponding to the arrival angle.

[0007] S2. After receiving the target signal data through the receiving array deployed on the deep seabed, conventional beamforming is performed on the received data of each snapshot to form a time-frequency history diagram to search for moving targets;

[0008] S3. After a moving target is detected, the data of the target's appearance period is intercepted, the beamforming result of the data at the frequency after Doppler shift is calculated, and the arrival angle of the target signal is estimated;

[0009] S4. Calculate the target distance corresponding to the target signal arrival angle estimated in step S3 based on the relationship between the target signal arrival angle calculated in step S1 and the target distance corresponding to the arrival angle to obtain a target distance estimation result.

[0010] Furthermore, in step S1, the sound field model is used to calculate the strongest incoming wave direction at different receiving distances to form an arrival angle-target distance relationship.

[0011] Furthermore, in step S2, the receiving array is a bottom-mounted vertical linear array for receiving sound pressure data, the actively transmitted sound source signal is a narrowband signal, the horizontal axis of the time-frequency history diagram is the time after the signal is transmitted, and the vertical axis is the frequency difference centered on the frequency of the transmitted signal.

[0012] Furthermore, in step S2, when conventional beamforming is performed on the data of each snapshot, the frequency search center is the frequency of the transmitted signal. When the transmitting sound source is stationary, the relationship between the receiving frequency and the transmitting frequency due to Doppler shift is:

[0013]

[0014] Where f′ is the received signal frequency, f is the frequency of the transmitted signal, c is the speed of sound in seawater, and v0 is the speed of the target. The Doppler frequency shift is: This ensures that the frequency search range is larger than the Doppler frequency shift Δf.

[0015] In general, the above technical solutions conceived by the present invention can achieve the following beneficial effects compared with the prior art:

[0016] The present invention obtains the relationship between the target signal arrival angle and the target distance corresponding to the arrival angle through a time-frequency history diagram, and estimates the actual target arrival angle based on a Doppler shift correction method, and derives the corresponding distance position from this angle. This ranging method can reduce sidelobe interference and improve algorithm stability and data accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 Flow chart of the distance measurement method of the present invention;

[0018] Figure 2 This is a time-frequency history diagram of the appearance of a moving target during the sea trial of the present invention (the long bright spot in the figure is the target);

[0019] Figure 3 Figure 2 shows the angle of arrival estimation results obtained by the conventional ranging method and the ranging method based on Doppler shift correction (the blue solid line in the figure represents the angle of arrival estimation result obtained by the ranging method based on Doppler shift correction, and the red dotted line represents the angle of arrival estimation result obtained by the conventional ranging method);

[0020] Figure 4 Figure 2 is a graph showing the relationship between the arrival angle and target distance obtained using the ranging method based on Doppler shift correction (the circles in the figure indicate the distance position corresponding to the estimated angle). DETAILED DESCRIPTION

[0021] The following is a clear and complete description of the technical solutions in the embodiments of the present application in conjunction with the accompanying drawings. Obviously, the embodiments described are only part of the embodiments of the present application, not all of them. Based on the embodiments, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0022] Combined with attachment Figure 1 As shown, a deep-sea active target ranging method based on Doppler shift correction includes the following steps:

[0023] S1. Build an acoustic field model based on the BELLHOP ray model and calculate the target signal arrival angle and the target distance corresponding to the arrival angle.

[0024] S2. After receiving the target signal data through the receiving array deployed on the deep seabed, with the active sound source transmitting signal as the target, conventional beamforming is performed on the received data of each snapshot to form a time-frequency history diagram to search for the moving target;

[0025] S3. After a moving target is detected, the data of the target's appearance period is intercepted, the beamforming result of the data at the frequency after Doppler shift is calculated, and the arrival angle of the target signal is estimated;

[0026] S4. Calculate the target distance corresponding to the target signal arrival angle estimated in step S3 based on the relationship between the target signal arrival angle calculated in step S1 and the target distance corresponding to the arrival angle to obtain a target distance estimation result.

[0027] Specifically, in step S1, the sound field model is used to calculate the strongest incoming wave direction at different receiving distances to form an arrival angle-target distance relationship.

[0028] Specifically, in step S2, the receiving array is a bottom vertical linear array for receiving sound pressure data. The actively transmitted sound source signal is a narrowband signal. The horizontal axis of the time-frequency history graph is the time after the signal is transmitted, and the vertical axis is the frequency difference centered on the frequency of the transmitted signal, as shown in the attached figure. Figure 2 As shown in the figure, the target (marked with a red circle) appears 11s to 14s after the signal is transmitted, and the Doppler shift caused by the target motion is 25Hz.

[0029] Specifically, in step S2, when conventional beamforming is performed on the data of each snapshot, the frequency search center is the frequency of the transmitted signal. When the transmitting sound source is stationary, the relationship between the receiving frequency and the transmitting frequency due to the Doppler shift is:

[0030]

[0031] Where f′ is the received signal frequency, f is the frequency of the transmitted signal, c is the speed of sound in seawater, and v0 is the speed of the target. The Doppler frequency shift is: This ensures that the frequency search range is larger than the Doppler frequency shift Δf.

[0032] As attached Figure 3 As shown in the figure, the blue solid line represents the angle of arrival estimation result obtained using the Doppler shift correction method, and the red dashed line represents the angle of arrival estimation result obtained using the conventional method. The figure shows that the conventional method estimates the angles of arrival to be -4° and 20°, where -4° is due to sidelobe interference. The angle of arrival estimated using the Doppler shift correction method is 21°. This shows that using the Doppler shift correction method for angle of arrival estimation can reduce sidelobe interference and improve algorithm stability.

[0033] As attached Figure 4 The figure shows the relationship between the angle of arrival and target range obtained using the Doppler shift-corrected ranging method. The circles in the figure indicate the distances corresponding to the estimated angles. For example, when the angle of arrival estimated using the Doppler shift-corrected method is 21°, the corresponding distance is 8 km.

[0034] The above is only a preferred embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any modification and replacement based on the technical solution and inventive concept provided by the present invention should be included in the protection scope of the present invention.

Claims

1. A deep-sea active target ranging method based on Doppler shift correction, characterized in that: The method comprises the following steps: S1. Build an acoustic field model based on the BELLHOP ray model and calculate the target signal arrival angle and the target distance corresponding to the arrival angle. S2. After receiving the target signal data through the receiving array deployed on the deep seabed, conventional beamforming is performed on the received data of each snapshot to form a time-frequency history diagram to search for moving targets; S3. After a moving target is detected, the data of the target's appearance period is intercepted, the beamforming result of the data at the frequency after Doppler shift is calculated, and the arrival angle of the target signal is estimated; S4. Calculate the target distance corresponding to the target signal arrival angle estimated in step S3 based on the relationship between the target signal arrival angle calculated in step S1 and the target distance corresponding to the arrival angle to obtain a target distance estimation result.

2. The deep-sea active target ranging method based on Doppler shift correction according to claim 1, characterized in that: In step S1, the sound field model is used to calculate the strongest incoming wave direction at different receiving distances to form an arrival angle-target distance relationship.

3. The deep-sea active target ranging method based on Doppler shift correction according to claim 1, characterized in that: In step S2, the receiving array is a bottom-mounted vertical linear array for receiving sound pressure data. The actively transmitted sound source signal is a narrowband signal. The horizontal axis of the time-frequency history graph is the time after the signal is transmitted, and the vertical axis is the frequency difference centered on the frequency of the transmitted signal.

4. The deep-sea active target ranging method based on Doppler shift correction according to claim 3, characterized in that: In step S2, when conventional beamforming is performed on the data of each snapshot, the frequency search center is the frequency of the transmitted signal. When the transmitting sound source is stationary, the relationship between the receiving frequency and the transmitting frequency due to Doppler shift is: Where f′ is the received signal frequency, f is the frequency of the transmitted signal, c is the speed of sound in seawater, and v0 is the speed of the target. The Doppler frequency shift is: This ensures that the frequency search range is larger than the Doppler frequency shift Δf.

Images