Active target echo data generation method considering random disturbance fluctuation of ocean channel

Abstract

The invention relates to an active target echo data generation method considering ocean channel random disturbance fluctuation, and the method comprises the following steps: in ray acoustics, sound wave propagation paths are called intrinsic sound rays, and have a series of sound field information of different amplitudes, phases, glancing angles, propagation time and the like; amplitude of sound rays reflects attenuation of sound waves when the sound waves propagate along the path, so that scattering intensity and the amplitude of the sound rays are combined to obtain active target echoes, and an impulse response function of an underwater acoustic coherent multipath channel is obtained according to a ray model theory. According to the method, the random disturbance of the ocean channel is simulated by adding the random time delay on each path, and the generation of the active target echo data under the condition of the random disturbance of the ocean channel is realized.

Description

Technical field:

[0001] The invention belongs to the technical field of underwater acoustic detection and identification, and in particular relates to a method for generating active target echo data taking into account random disturbance fluctuations of an ocean channel. Background technology:

[0002] Active target echo signals are the main source of target feature information for active sonar. Establishing an accurate mathematical model of active target echoes is helpful for the analysis and research of active sonar target detection, tracking and identification methods. In addition, it is also of great significance for the theoretical research related to active target echoes. The working mode of active sonar can be described as follows: the sonar transmitting system (sound source) transmits a sound signal with specific information into the seawater, which is called a transmitting signal. When the transmitting signal propagates in the underwater sound channel (seawater), it encounters obstacles such as submarines, mines, torpedoes, etc., which are usually called sonar targets. Since the sound waves are reflected and scattered on the target, an echo signal about the target will be formed. The echo signal continues to propagate in the underwater sound channel. Among them, the echo signal in a specific direction propagates to the receiving hydrophone (array), and the hydrophone (array) receives the signal. The receiving hydrophone (array) converts the sound signal into a corresponding electrical signal, and then the processor processes it to obtain the distance, direction, motion parameters and other information of the target. This is the complete information flow of active sonar.

[0003] The active co-located / separately located target echo contains the two-way ocean channel acoustic field information and complex target scattering characteristics. In addition, due to the influence of the time-varying, space-varying, and frequency-varying characteristics of the underwater acoustic channel, multipath effects, and ocean background interference, the active target echo will inevitably be distorted when it is propagated to the detection array through the coupling of the underwater acoustic channel, which makes modeling difficult in theory. Summary of the invention:

[0004] The technical problem to be solved by the present invention is to provide a method for generating active target echo data taking into account the random disturbance fluctuations of the ocean channel. The method simulates the random disturbance of the ocean channel by adding a random time delay on each path, thereby realizing the generation of active target echo data under the random disturbance conditions of the ocean channel.

[0005] The technical solution of the present invention is to provide a method for generating active target echo data taking into account the random disturbance fluctuations of the ocean channel, comprising the following steps:

[0006] S1: In ray acoustics, the sound wave propagation path is called the eigenvalue sound ray. They have different amplitudes, phases, grazing angles, propagation time and other sound field information. The amplitude of the sound ray reflects the attenuation of the sound wave when it propagates along this path. Therefore, the scattering intensity is combined with the sound ray amplitude to obtain the active target echo. According to the ray model theory, the impulse response function of the underwater acoustic coherent multipath channel can be expressed as:

[0007]

[0008] Wherein, t is the time of sound ray propagation; M is the number of intrinsic sound rays, where the intrinsic sound rays are based on five paths: direct (DR) sound rays, surface reflection (SR) sound rays and bottom reflection (BR) sound rays, surface-bottom reflection (SBR) sound rays and bottom-surface reflection (BSR) sound rays, A j Indicates the amplitude of the sound line; τ j represents the propagation delay of the jth sound line;

[0009] S2: Active sonar radiates sound signals from the transmitting transducer, propagates to the target, and after being scattered by the target, the scattered echo propagates back to the receiver (array). The active sonar sound propagation model is a two-way propagation, including the outbound and return trips. Assuming that the transmitted pulse signal is s(t), the active target echo signal after being scattered by the target can be expressed as:

[0010]

[0011] Where h1(t) represents the outbound channel impulse response, h2(t) represents the return channel impulse response, T(θ,t) represents the target scattering function, is the convolution symbol;

[0012] A ray model is established using ocean environment information, sound source, receiving array configuration, and target location information. The outbound and return channel impulse responses h1(t) and h2(t) are calculated using the BELLHOP sound field model.

[0013] S3: Due to the influence of the time-varying, space-varying, frequency-varying characteristics of the ocean channel, the multipath effect and the ocean background interference, the transmitted signal will be distorted. It is necessary to consider the random disturbance of the ocean channel. The specific implementation method is as follows: add a random delay to each sound line path described in step S1 to simulate the random disturbance of the channel, and obtain the active target echo data under the random disturbance of the ocean channel, which is expressed as:

[0014]

[0015] Where Δτ represents the added random delay, and They represent the impulse response function of the channel under random disturbance of the ocean channel and the active target echo signal respectively.

[0016] Preferably, in step S3, the random delay added for different transmission signal frequencies is the same.

[0017] Preferably, in step S3, the random delay is Gaussian distributed with a mean of 0 ms and a standard deviation of 0.2 ms.

[0018] Preferably, the standard deviation corresponds to a path length variation setting of 30 cm.

[0019] Compared with the prior art, the present invention has the following advantages:

[0020] The present invention simulates the random disturbance of the ocean channel by adding a random time delay on each path, thereby realizing the generation of active target echo data under the random disturbance condition of the ocean channel. Description of the drawings:

[0021] Figure 1 is the simulation environment and parameters of the embodiment of the present invention;

[0022] Figure 2 is the sound velocity profile of the embodiment of the present invention.

[0023] Figure 3 It is the time domain waveform and time spectrum of the transmission signal of the embodiment of the present invention.

[0024] Figure 4 It is the five eigen-sound line structures and one-way channel response of the embodiment of the present invention.

[0025] Figure 5 These are the five eigen-sound line structures and channel responses after considering the random disturbance of the ocean channel in an embodiment of the present invention.

[0026] Figure 6 It is the active target echo signal of the embodiment of the present invention.

[0027] Figure 7 It is an active target echo signal after the random disturbance of the ocean channel is taken into consideration in the embodiment of the present invention. Specific implementation method:

[0028] The present invention will be further described below with reference to the accompanying drawings:

[0029] The present invention proposes a method for generating active target echo data based on the ray model, which takes into account the random disturbance fluctuations of the ocean channel. The sound wave starts from the sound source and reaches the target through a series of different propagation paths. The target scattered sound waves reach the receiving array through different paths after being scattered by the target. In ray acoustics, these paths are called intrinsic sound rays. They have a series of sound field information such as different amplitudes, phases, grazing angles, and propagation times. The propagation time reflects the time required for the sound wave to travel along this path, and the amplitude of the sound line reflects the attenuation of the sound wave when it propagates along this path. The active target echo is obtained by combining the propagation time of different paths and the amplitude of the sound line with the target scattering intensity. In addition, due to the influence of the time-varying, space-varying, and frequency-varying characteristics of the ocean channel, the multipath effect, and the ocean background interference, it is necessary to consider the random disturbance of the ocean channel.

[0030] Specifically, the active target echo data generation method considering the random disturbance fluctuation of the ocean channel can be implemented in the following steps:

[0031] S1: The active target echo is obtained by combining the scattering intensity with the sound line amplitude. The impulse response function of the underwater acoustic coherent multipath channel can be expressed as:

[0032]

[0033] Wherein, t is the time of sound line propagation; M is the number of eigenvalues, where the eigenvalues ​​are based on five paths: direct sound line, sea surface reflection sound line and seabed reflection sound line, sea surface-seabed reflection sound line and seabed-sea surface reflection sound line, A j Indicates the amplitude of the sound line; τ j represents the propagation delay of the jth sound line;

[0034] S2: The active sonar sound propagation model is a two-way propagation, including the outbound and return paths. Assuming that the transmitted pulse signal is s(t), the active target echo signal after target scattering can be expressed as:

[0035]

[0036] Where h1(t) represents the outbound channel impulse response, h2(t) represents the return channel impulse response, T(θ,t) represents the target scattering function, is the convolution symbol;

[0037] A ray model is established using ocean environment information, sound source, receiving array configuration, and target location information. The outbound and return channel impulse responses h1(t) and h2(t) are calculated using the BELLHOP sound field model.

[0038] S3: Considering the random disturbance of the ocean channel, the specific implementation method is as follows: add random delays in each sound line path described in step S1 to simulate the random disturbance of the channel. For different transmission signal frequencies, the added random delays are the same. These delays are Gaussian distributed with a mean of 0ms and a standard deviation of 0.2ms (corresponding to a path length change of 30cm). The active target echo data under the random disturbance of the ocean channel is expressed as:

[0039]

[0040] Where Δτ represents the added random delay, and They represent the impulse response function of the channel under random disturbance of the ocean channel and the active target echo signal respectively.

[0041] In this embodiment, Figure 1 , the simulation environment and parameters are given. The simulation conditions are as follows: the sea depth is 200m, the seabed is selected as a single-layer seabed model, the seabed sound speed is selected as 1753m / s, the density is 1.96g / cm3, and the substrate attenuation coefficient is 0.51dB / kmHz. Single array element transmission is adopted, the sound source depth is 20m, the 32-element vertical array is received, the aperture is 150m, and the first array element depth is 30m. Assume that the target depth is 50m and the distance from the vertical receiving array is 6km. The transmission signal adopts a linear frequency modulation (LFM) signal with a pulse width of 4s, a frequency range of 3000Hz~3100Hz, and a signal sampling frequency of 16kHz.

[0042] Figure 2 The sound velocity profile is given. Good hydrological conditions in shallow waters.

[0043] Figure 3 The time domain waveform and time spectrum of the transmitted signal are given, where: Figure 3 (a) is the time domain waveform, (b) is the time spectrum. The transmission signal uses a linear frequency modulation (LFM) signal with a pulse width of 4s, a frequency range of 3000Hz to 3100Hz, and a signal sampling frequency of 16kHz.

[0044] Figure 4 Five eigenwave structures and one-way channel responses are given, among which: Figure 4 (a) is the sound line structure, and (b) is the one-way channel response. Red represents the direct sound line, green represents the first sea surface reflection sound line, blue represents the first seabed reflection sound line, and black represents the sea surface-seabed reflection sound line and the seabed-sea surface reflection sound line.

[0045] Figure 5 The five eigenwave structures and channel responses after considering the random perturbation of the ocean channel are given, among which, Figure 5(a) is the sound line structure, and (b) is the one-way channel response. A random delay is added to each sound line path to simulate the random disturbance of the channel. For different transmission signal frequencies, the added random delay is the same. These delays are Gaussian distributed with a mean of 0ms and a standard deviation of 0.2ms (corresponding to a path length change of 30cm).

[0046] Figure 6 The active target echo signal is given, where Figure 6 (a) is the time domain waveform, and (b) is the time spectrum. The signal-to-noise ratio is set to 3dB, and the signal-to-noise ratio is set to the ratio of signal power to noise power in decibels within the same signal time length and bandwidth.

[0047] Figure 7 The active target echo signal after random disturbance of the ocean channel is given. Figure 7 (a) is the time domain waveform, and (b) is the time spectrum.

[0048] It can be seen that the present invention simulates the random disturbance of the ocean channel by adding a random time delay on each path, thereby realizing the generation of active target echo data under the random disturbance condition of the ocean channel.

[0049] 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 generating active target echo data taking into account random disturbance fluctuations of ocean channels, characterized in that: The following steps are included: S1: The active target echo is obtained by combining the scattering intensity with the sound line amplitude. The impulse response function of the underwater acoustic coherent multipath channel can be expressed as: Wherein, t is the time of sound line propagation; M is the number of eigenvalues, where the eigenvalues ​​are based on five paths: direct sound line, sea surface reflection sound line and seabed reflection sound line, sea surface-seabed reflection sound line and seabed-sea surface reflection sound line, A j Indicates the amplitude of the sound line; τ j represents the propagation delay of the jth sound line; S2: The active sonar sound propagation model is a two-way propagation, including the outbound and return paths. Assuming that the transmitted pulse signal is s(t), the active target echo signal after target scattering can be expressed as: Where h1(t) represents the outbound channel impulse response, h2(t) represents the return channel impulse response, T(θ,t) represents the target scattering function, is the convolution symbol; A ray model is established using ocean environment information, sound source, receiving array configuration, and target location information. The outbound and return channel impulse responses h1(t) and h2(t) are calculated using the BELLHOP sound field model. S3: Considering the random disturbance of the ocean channel, the specific implementation method is as follows: adding a random delay to each sound line path described in step S1 to simulate the random disturbance of the channel, and obtaining the active target echo data under the random disturbance of the ocean channel is expressed as: Where Δτ represents the added random delay, and They represent the impulse response function of the channel under random disturbance of the ocean channel and the active target echo signal respectively.

2. The method for generating active target echo data considering random disturbance fluctuations of ocean channels according to claim 1 is characterized in that: In step S3, for different transmission signal frequencies, the added random delay is the same.

3. The method for generating active target echo data considering random disturbance fluctuations of ocean channels according to claim 2 is characterized in that: In step S3, the random delay is Gaussian distributed with a mean of 0 ms and a standard deviation of 0.2 ms.

4. The method for generating active target echo data considering random disturbance fluctuations of ocean channels according to claim 3 is characterized in that: The standard deviation corresponds to a path length variation setting of 30 cm.

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