A Simulation and Evaluation Method for the Transmitting and Receiving Co-located Time-domain and Time-frequency Distribution Characteristics of an Underwater Vehicle

Abstract

The present invention provides a simulation and evaluation method for the time-domain and time-frequency distribution characteristics of a combined transceiver of an underwater vehicle, including determining the geometric model parameters of the underwater vehicle, determining the time-domain acoustic wave information at a specific incident angle and converting it into an incident radio-frequency domain signal, determining the coordinates of the incident point and the receiving point, evaluating the reflection coefficient and transmission coefficient of the underwater vehicle's outer shell at different frequencies under this incident angle and a specified receiving angle, and establishing a model according to the shell form of the underwater vehicle to calculate the target frequency-domain transfer function; processing the target frequency-domain transfer function and the incident radio-frequency domain signal to obtain the time-frequency distribution characteristics of the combined transceiver of the underwater vehicle, and comparing with the index requirements to obtain an evaluation conclusion. The present invention takes the geometric model, material parameters and incident signal of the underwater vehicle as inputs, and realizes the evaluation of the time-frequency distribution characteristic index of the combined transceiver of the underwater vehicle.

Description

Technical Field

[0001] The present invention relates to the technical field of underwater vehicle acoustic stealth demonstration and evaluation, and particularly relates to a method for evaluating the time-frequency distribution characteristics of underwater vehicles when transmitting and receiving are combined at the same location. Background Art

[0002] At present, there is no analysis method based on quantitative calculation or simulation for evaluating the time-frequency distribution characteristics of underwater vehicles when transmitting and receiving are combined at the same location at home and abroad. In the overall scheme design stage of underwater vehicles, the overall design results of underwater vehicles include documents and drawings such as the overall scheme design specification, basic structure design specification, hull form drawing, basic structure drawing, general arrangement drawing, appendage structure drawing, etc. The form, size, shell thickness and other parameter information of the inner and outer shell structures, base structures and interspace structures of underwater vehicles related to the overall scheme of underwater vehicles have been initially determined. Therefore, an evaluation of the time-frequency distribution characteristics of underwater vehicles when transmitting and receiving are combined at the same location is established with these parameters and incident signals as inputs, so as to realize the risk quantitative evaluation of the time-frequency distribution characteristic indexes of underwater vehicles, which has important practical application value for the acoustic stealth of underwater vehicles. Summary of the Invention

[0003] Object of the Invention: In the overall scheme design stage, according to the overall design scheme of the underwater vehicle, using the Kirchhoff approximation, with the target characteristic data of transmitting and receiving combined at a certain angle and the incident signal as inputs, the time-frequency distribution characteristics are evaluated and compared with the index requirements to realize the risk assessment of the reachability of the time-frequency distribution characteristic indexes.

[0004] Technical Solution: A simulation evaluation method for the time-domain time-frequency distribution characteristics of underwater vehicles when transmitting and receiving are combined at the same location, comprising the following steps:

[0005] Step 1. Analyze the overall design results of the underwater vehicle and sort out the structural modeling parameters to establish a geometric simulation model;

[0006] Analyze the overall design results of the underwater vehicle, including documents and drawings such as the overall scheme design specification, basic structure design specification, hull form drawing, basic structure drawing, general arrangement drawing, etc., and the form, size, shell thickness and other parameters of the inner and outer shell structures of the underwater vehicle related to the overall scheme of the underwater vehicle; according to the relevant data parameters, use three-dimensional modeling methods to establish a full-scale geometric simulation model of the underwater vehicle structure. This geometric simulation model includes the form, structure, size, etc. of the inner and outer shells; this geometric simulation model does not need to be established as a solid model with thickness parameters, but only needs to be established as a shell model, and preferably the coordinate origin is adjusted to the geometric acoustic center of the geometric simulation model.

[0007] Step 2. Determine the time-domain acoustic wave information at the incident angle and convert the incident time-domain acoustic wave information into an incident radio-frequency domain acoustic wave signal;

[0008] The incident time-domain acoustic wave information includes: setting the type, frequency, pulse width, sampling frequency, and transmission interval of the incident time-domain pulse signal to obtain the incident time-domain acoustic wave signal. For the determined time-domain acoustic wave information incident signal x(t) at this angle, it is transformed into a frequency-domain signal X(f) through Fourier transform;

[0009] Step 3. Establish a coordinate system to determine the coordinates of the incident / receiving angle and describe it using the horizontal azimuth angle and the distance between the incident / receiving point and the equivalent geometric acoustic center of the underwater vehicle;

[0010] In coordinate form, establish a coordinate system with the equivalent geometric center of the underwater vehicle as the origin, and represent the coordinates of the incident point and the receiving point on the horizontal plane using the horizontal azimuth angle; The transmitting / receiving point must simultaneously satisfy the far-field condition, that is, the distance r from the observation point to the equivalent geometric acoustic center of the underwater vehicle is not less than the ratio of the square of the total length L of the underwater vehicle to the acoustic wavelength λ; The incident acoustic wave is a point source, and under the far-field condition, it is approximately a plane wave when it reaches the target position; The scattered acoustic wave is regarded as the secondary radiation of the underwater vehicle's hull.

[0011] Step 4. Evaluate the reflection coefficient and transmission coefficient of the underwater vehicle's hull at different frequencies according to the hull wall thickness and material of the underwater vehicle;

[0012] Generally, the structure of an underwater vehicle is mostly a single-hull or double-hull structure. Its reflection coefficient and transmission coefficient can be attributed to the acoustic propagation theory of layered elastic media. For any layer of medium, the acoustic wave potential function can be defined in the form of the longitudinal wave potential function and the flexural wave potential function for the acoustic pressure of adjacent two layers of media, and then the acoustic reflection and transmission coefficients are derived;

[0013] Step 5. According to the hull form of the underwater vehicle, that is, two forms of single-hull structure or double-hull structure, and the hull reflection coefficient and transmission coefficient, establish an overall evaluation model of the target frequency-domain transfer function and calculate the target frequency-domain transfer function;

[0014] Step 5.1 Establish an evaluation model for the structural plate elements of the underwater vehicle; Triangulate the inner and outer hulls of the actual-scale geometric model of the underwater vehicle's structure, and export the topological information and node information of the triangular surface mesh, and save them separately;

[0015] Step 5.2 Read the node information and the triangular surface mesh file, draw the mesh models of the inner and outer hulls of the underwater vehicle respectively. After setting the initial incident / receiving point, check the normal direction of the triangular surface mesh to ensure that the normal direction of the triangular surface mesh faces the outside of the underwater vehicle;

[0016] Step 5.3 Establish an acoustic scattering model for the underwater vehicle's hull and express it in the form of a summation of surface elements. For a double-hull structure, consider the outer hull of the underwater vehicle as a thin steel elastic shell, taking into account the reflection and transmission of sound waves. At the same time, the sound waves transmitted through the outer hull to the inner hull are further transmitted and then pass through the outer hull again, and together with the first reflection of the outer hull, they are received by the receiving point. Finally, calculate the sum of the scattering contributions of all surface elements within the incident radio frequency domain signal frequency band at this angle, that is, the target frequency domain transfer function at this angle.

[0017] Step 6. Process the target frequency domain transfer function and the incident radio frequency domain signal to obtain the time-frequency distribution characteristics of the underwater vehicle when the transceiver is co-located.

[0018] Multiply the target frequency domain transfer function and the incident radio frequency domain signal point by point to obtain the echo in the frequency domain. Finally, perform an inverse Fourier transform on the echo in the frequency domain to obtain the time-frequency distribution characteristics of the underwater vehicle when the transceiver is co-located. Use the sound pressure amplitude curve at a certain moment as the evaluation index for the time-frequency distribution characteristics of the underwater vehicle when the transceiver is co-located.

[0019] Step 7. Compare the time-frequency distribution characteristics of the transceiver co-location obtained in Step 6 with the index requirements to obtain the evaluation conclusion of the time-frequency distribution characteristics index of the underwater vehicle when the transceiver is co-located.

[0020] According to the requirements of the evaluation index system, calculate the time-frequency distribution characteristics of the underwater vehicle when the transceiver is co-located at a certain angle according to the evaluation focus frequencies such as 500 Hz, 1 kHz, 3 kHz, 5 kHz, 10 kHz, etc. Compare and analyze the sound pressure amplitude curve at a certain moment with the design index to judge the risk of reachability of the index.

[0021] The present invention provides a simulation evaluation method for the time-frequency distribution characteristics of an underwater vehicle when the transceiver is co-located in the scheme design stage. According to the overall design scheme of the underwater vehicle and using the Kirchhoff approximation, the present invention takes the geometric model, material parameters, and incident signal of the underwater vehicle as inputs to evaluate the time-frequency distribution characteristics of the transceiver co-location at a certain angle and compare with the index requirements to realize a method for risk assessment of the time-frequency distribution characteristics index of the overall scheme when the transceiver is co-located. This evaluation method mainly includes six steps: analyzing the overall scheme design results of the underwater vehicle and sorting out the structural modeling parameters to establish a geometric simulation model, determining the incident radio frequency domain acoustic signal, establishing a coordinate system to determine the coordinates of the incident / receiving angle, evaluating the reflection coefficient and transmission coefficient of the underwater vehicle's outer hull at different frequencies, establishing an overall evaluation model of the target frequency domain transfer function and calculating the target frequency domain transfer function, and processing the target frequency domain transfer function and the incident radio frequency domain signal to obtain the time-frequency distribution characteristics of the underwater vehicle when the transceiver is co-located. This method can calculate the time-frequency distribution characteristics of the transceiver co-location, has the advantages of fast calculation speed and reliable evaluation results, and can be widely applied to the evaluation and design fields of underwater weapons targets such as underwater vehicles, underwater unmanned submersibles, and torpedoes.

[0022] Beneficial effects: The method of the present invention is reasonable and feasible, overcomes the uncertainty in the evaluation of the time-frequency distribution characteristics of the transceiver co-location of underwater vehicles at present, can realize the quantitative simulation calculation of the time-frequency distribution characteristics of the transceiver co-location of single-hull and double-hull underwater vehicles, and obtains an evaluation conclusion on the risk level of the time-frequency distribution characteristics index of the transceiver co-location by comparing with the index requirements. Compared with the current evaluation method of the time-frequency distribution characteristics of the transceiver co-location, it can greatly improve the rationality and accuracy of the evaluation results of the time-frequency distribution characteristics of the transceiver co-location of underwater vehicles.

[0023] The evaluation method of the time-frequency distribution characteristics of the transceiver co-location applicable to the overall design stage of underwater vehicles of the present invention can, according to the overall design scheme of underwater vehicles, use the geometric model, material parameters and incident signals of underwater vehicles as inputs to evaluate the time-frequency distribution characteristics of the transceiver co-location, and compare with the index requirements of the time-frequency distribution characteristics of the transceiver co-location to realize the evaluation of the risk level of the time-frequency distribution characteristics index of the transceiver co-location. Description of the Drawings

[0024] Figure 1 is a schematic diagram of the geometric model of the Benchmark underwater vehicle in a preferred embodiment of the present invention;

[0025] Figure 2 is Figure 1 the schematic diagram of the outer shell mesh of the Benchmark underwater vehicle in the illustrated embodiment;

[0026] Figure 3 is Figure 1 the schematic diagram of the inner shell mesh of the Benchmark underwater vehicle in the illustrated embodiment;

[0027] Figure 4 is Figure 1 the schematic diagram of the normal line of the outer shell mesh of the Benchmark underwater vehicle in the illustrated embodiment;

[0028] Figure 5 is Figure 1 the schematic diagram of the normal line of the inner shell mesh of the Benchmark underwater vehicle in the illustrated embodiment;

[0029] Figure 6 Figure 1 The schematic diagram of the incident signal of the Benchmark underwater vehicle in the illustrated embodiment, which is a single-frequency signal with a frequency of 10000 Hz and a pulse width of 1 ms;

[0030] Figure 7 is Figure 1 the sound pressure amplitude curve of the Benchmark underwater vehicle in the illustrated embodiment when the incident signal is a single-frequency signal with a frequency of 10 kHz and a pulse width of 1 ms and the detection distance is 1000 m at 0-degree incidence;

[0031] Figure 8 is Figure 1 In the illustrated embodiment, the incident signal of the Benchmark underwater vehicle is a single-frequency signal with a frequency of 10 kHz and a pulse width of 1 ms, and the sound pressure amplitude curve at a detection distance of 1000 m at 90-degree incidence;

[0032] Figure 9 is Figure 1 In the illustrated embodiment, the incident signal of the Benchmark underwater vehicle is a single-frequency signal with a frequency of 10 kHz and a pulse width of 1 ms, and the sound pressure amplitude curve at a detection distance of 1000 m at 180-degree incidence; Detailed implementation manners

[0033] The present invention will be further described below in conjunction with the accompanying drawings and specific implementation manners.

[0034] The simulation evaluation method for the time-frequency distribution characteristics of the underwater vehicle with combined transceiver in this embodiment performs the following steps:

[0035] Step 1. Analyze the overall design results of the underwater vehicle and sort out the structural modeling parameters to establish a geometric simulation model;

[0036] Analyze the overall design results of the underwater vehicle, including the overall design specification, basic structure design specification, body plan, basic structure drawing, general arrangement drawing and other documents and drawing materials, and the form, size, shell thickness and other parameters of the inner and outer shell structures of the underwater vehicle related to the overall plan of the underwater vehicle; according to the relevant data parameters, use the three-dimensional modeling method to establish a full-scale geometric simulation model of the underwater vehicle structure. This geometric simulation model includes the form, structure, size, etc. of the inner and outer shells; this geometric simulation model does not need to be established as a solid model with thickness parameters, but only needs to be established as a shell model, and preferably adjust the coordinate origin to the geometric acoustic center of the geometric simulation model.

[0037] Step 2. Determine the time-domain acoustic wave information at a certain incident angle and convert the incident time-domain acoustic wave information into an incident frequency-domain acoustic wave signal;

[0038] Determining the incident time-domain acoustic wave information includes setting the type of incident time-domain pulse signal, such as typical single frequencies of 500 Hz, 1 kHz, 3 kHz, 5 kHz, 10 kHz, etc., setting the pulse width to 1 ms, 5 ms, etc., and the sampling frequency is generally more than 2.5 times the transmission frequency. For the determined time-domain acoustic wave information incident signal x(t) at this angle, it is transformed into a frequency-domain signal X(f) through Fourier transform;

[0039] Step 3. Establish a coordinate system to determine the coordinates of the incident / receiving angle and describe it using the horizontal azimuth angle and the distance between the incident / receiving point and the equivalent geometric acoustic center of the underwater vehicle;

[0040] A coordinate system is established with the equivalent geometric center of the underwater vehicle as the origin, and the coordinates of the incident point and the receiving point are represented on the horizontal plane by the horizontal azimuth angle; the transmitting / receiving point must simultaneously satisfy the far-field condition, that is, the distance r from the observation point to the equivalent geometric acoustic center of the underwater vehicle is not less than the ratio of the square of the total length L of the underwater vehicle to the acoustic wavelength λ; the incident sound wave is a point source, and under the far-field condition, it is approximately a plane wave when it reaches the target position; the scattered sound wave is regarded as the secondary radiation of the underwater vehicle's shell.

[0041] Step 4. Evaluate the reflection coefficient and transmission coefficient of the underwater vehicle's shell at different frequencies according to the shell wall thickness and material of the underwater vehicle.

[0042] For the theoretical model calculation of the acoustic scattering problem of any multi-layer, for any layer l, the following acoustic wave potential functions are defined:

[0043] φ l =[A l exp(iα l z)+B l exp(-ia l z)]exp[i(σx - ωt)](1)

[0044] ψ t =[C t exp(iβ t z)+D t exp(-iβ t z)]exp[i(σx - ωt](2)

[0045] Where φ l is the longitudinal wave potential function, and ψ t is the flexural wave potential function.

[0046] B l and D t are the amplitudes of the incident waves; A l and C t are the amplitudes of the reflected waves, and there are:

[0047]

[0048]

[0049] σ l =k t sinθ l (5)

[0050] Where k l and K t are the wave numbers of the longitudinal wave and the flexural wave.

[0051] Through a series of derivation processes, the expression of the acoustic reflection coefficient can be finally obtained as follows:

[0052]

[0053] Among them,

[0054] C ij = F IJ - F 4J * F i1 / F 41 (7)

[0055] Z0 = ρ0c0 / cosθ0 (8)

[0056] Z n+1 = ρ n+1 c n+1 / cosθ n+1 (9)

[0057] According to the condition that the sum of the squares of the reflection coefficient and the transmission coefficient is 1 under the condition of neglecting losses, the transmission coefficient can be deduced from the above reflection coefficient;

[0058] Step 5. According to the hull form of the underwater vehicle, namely, the single-hull structure or the double-hull structure, and the outer hull reflection coefficient and transmission coefficient, establish an overall evaluation model of the target frequency-domain transfer function and calculate the target frequency-domain transfer function;

[0059] Step 5.1 Establish an evaluation model of the structural plate element of the underwater vehicle; triangulate the inner and outer hulls of the actual-scale geometric model of the underwater vehicle structure, and export the topological information and node information of the triangular surface mesh, and save them separately;

[0060] Step 5.2 Read the node information and the triangular surface mesh file, and draw the mesh models of the inner and outer hulls of the underwater vehicle respectively. After setting the initial incident / receiving points, check the normal direction of the triangular surface mesh to ensure that the normal direction of the triangular surface mesh faces the outside of the underwater vehicle;

[0061] Step 5.3 Establish an acoustic scattering model of the underwater vehicle hull and express it in the form of summation of surface elements. For the double-hull structure, regard the outer hull of the underwater vehicle as a thin steel elastic shell, and consider the reflection and transmission of sound waves; at the same time, the sound waves transmitted through the outer hull to the inner hull are transmitted again, pass through the outer hull, and are received by the receiving point together with the first reflection of the outer hull. Finally, calculate the sum of the scattering contributions of all surface elements within the incident frequency-domain signal frequency band, that is, the target frequency-domain transfer function;

[0062] Step 5.4 Calculate the acoustic scattering model of a single-hull underwater vehicle using the Kirchhoff approximation. That is, express the integral form of the Kirchhoff approximation method as a form of surface element summation. Consider the surface of the underwater vehicle target as absolutely rigid, without considering the transmission of sound waves, and obtain the total scattered sound pressure using surface element summation;

[0063] The Kirchhoff formula gives the scattering sound field:

[0064]

[0065] In Equation (10), φ s is the scattered sound pressure, r2 is the radius vector of the scattering point, n is the outer normal of the surface, and S is the surface of the scatterer. For high-frequency cases, it is usually assumed that:

[0066] a) The contribution of the geometric shadow region to the sound field can be ignored; the actual integration area is the part of the surface that is in the illuminated region when viewed from the emission point and the reception point.

[0067] b) The surface of the scatterer satisfies the rigid boundary condition.

[0068] Further simplification gives the scattered sound pressure for the co-located transmitter and receiver:

[0069]

[0070] The integral term in Equation (11) can be reduced to an operation of surface element coordinates.

[0071] Step 5.5 Establish an acoustic scattering model of a double-hull underwater vehicle using the Kirchhoff approximation. Its basic principle is also to express the integral form of the Kirchhoff approximation method as a form of surface element summation. However, different from Step 5.4, the total acoustic scattering characteristic I of the underwater vehicle is equal to the echo intensity I out of the outer shell plus the inner shell, that is, the echo intensity I in of the inner shell. Among them, the echo intensity I out of the outer shell is generated by the plate with water on both sides, and the echo intensity I in of the inner shell is generated by the pure inner shell (outer shell) echo intensity I in,0 when it is assumed that the outer shell (outer shell) does not exist and only the inner shell (inner shell) exists plus the two transmission losses of the outer shell (outer shell). Define the reflection coefficient of the target at the azimuth angle φ as V(f, φ) , and the transmission coefficient as T(f, φ) . Use TS out and TS in,0 to represent the acoustic scattering characteristics of the outer shell (outer shell) and the pure inner shell (inner shell) respectively, and obtain the total echo intensity reduced to a distance of 1 m

[0072]

[0073] In Equation (12), I i is the incident sound intensity; thus, the total sound scattering characteristics are obtained as

[0074]

[0075] Step 6. Process the target frequency-domain transfer function and the incident frequency-domain signal to obtain the time-frequency distribution characteristics of the underwater vehicle with co-located transceiver;

[0076] Multiply the target frequency-domain transfer function and the incident frequency-domain signal point by point to obtain the echo in the frequency domain. Finally, perform an inverse Fourier transform on the echo in the frequency domain to obtain the time-frequency distribution characteristics of the underwater vehicle with co-located transceiver; use the sound pressure amplitude curve as the evaluation index for the time-frequency distribution characteristics of the underwater vehicle with co-located transceiver

[0077] Step 7. Compare the time-frequency distribution characteristics of the co-located transceiver obtained by evaluating and calculating in Step 6 with the index requirements to obtain the evaluation conclusion of the time-frequency distribution characteristics index of the underwater vehicle with co-located transceiver.

[0078] According to the requirements of the evaluation index system, evaluate the time-frequency distribution characteristics results of the corresponding underwater vehicle with co-located transceiver at the evaluation focus frequencies such as 500 Hz, 1 kHz, 3 kHz, 5 kHz, and 10 kHz, compare and analyze them with the design indexes, and judge the risk of index reachability.

[0079] Figure 7 、 Figure 8 and Figure 9 are the sound pressure amplitude curves of the corresponding Benchmark underwater vehicle when the sound wave is incident at 0 degrees, 90 degrees, and 180 degrees respectively at a frequency of 10000 Hz, a pulse width of 1 ms, and a detection distance of 1000 m;

[0080] The abscissa represents the echo time, and the ordinate represents the echo sound pressure amplitude; taking the incident at the 0-degree azimuth angle of Figure 8 as an example, the earliest echo time is around 1.3 s. This is because the detection distance is set to 1000 m, plus the geometric length of the model itself. Using the round-trip distance of detection and the propagation speed of sound waves underwater, the echo time of the sound wave that reaches the head first is obtained. Around 1.31 s later, the echo generated by the two bow rudders is obtained. The subsequent echoes represent the conning tower and stern rudder and other structures in turn. The structural characteristics of the underwater vehicle can be intuitively seen from the echo sound pressure amplitude.

[0081] It can be seen that this method can evaluate the risk of the time-frequency distribution characteristics index of the underwater vehicle.

Claims

1. A simulation and evaluation method for the time-domain and time-frequency distribution characteristics of a combined transceiver of an underwater vehicle, characterized in that It includes the following steps: Step 1. Determine the total length, shell form, shell wall thickness, material parameters of the geometric model of the underwater vehicle, and the coordinate origin of the geometric model of the underwater vehicle according to the overall design results of the underwater vehicle and the structural modeling parameters, and define this coordinate origin as the equivalent geometric acoustic center of the underwater vehicle; Step 2. Determine the time-domain acoustic wave information at a specific incident angle and transform it into an incident radio-frequency domain signal through Fourier transform; Step 3. Determine the coordinates of the incident / receiving angle and describe it using the horizontal azimuth angle and the distance between the incident / receiving point and the equivalent geometric acoustic center of the underwater vehicle; Step 4. Evaluate the reflection coefficient and transmission coefficient of the outer shell of the underwater vehicle at this angle at different frequencies according to the wall thickness and material of the outer shell of the underwater vehicle; Step 5. According to the shell form of the underwater vehicle, that is, two forms of single-shell structure or double-shell structure, and the outer shell reflection coefficient and transmission coefficient, establish an overall evaluation model of the target frequency-domain transfer function at this incident / receiving angle, and calculate the target frequency-domain transfer function; Step 6. Multiply the target frequency-domain transfer function at this angle by the incident radio-frequency domain signal point by point to obtain the echo in the frequency domain. Finally, through the inverse Fourier transform of the echo in the frequency domain, obtain the time-frequency distribution characteristics of the underwater vehicle when the transceiver is combined; Step 7. Compare the time-frequency distribution characteristics of the combined transceiver evaluated and calculated in Step 6 with the index requirements to obtain the evaluation conclusion of the time-frequency distribution characteristics index of the underwater vehicle when the transceiver is combined.

2. The simulation and evaluation method for the time domain and time-frequency distribution characteristics of a combined transceiver of an underwater vehicle according to claim 1, characterized in that, The overall design results of the underwater vehicle and the structural modeling parameters in Step 1 include the overall design specification, basic structure design specification, hull form drawing, basic structure drawing, general arrangement drawing, and the form, size, and shell thickness parameters of the inner and outer shell structures of the underwater vehicle related to the overall design of the underwater vehicle; for structures without clear thickness parameters, refer to the relevant parameter values of the standard underwater vehicle.

3. The simulation and evaluation method for the transceiver-integrated time-domain and time-frequency distribution characteristics of an underwater vehicle according to claim 1, characterized in that The set incident time-domain acoustic wave information in Step 2 includes: setting the type, frequency, pulse width, and sampling frequency of the incident time-domain pulse signal, and converting it into an incident radio-frequency domain acoustic wave signal through Fourier transform.

4. The simulation and evaluation method for the time-domain and time-frequency distribution characteristics of a combined transceiver of an underwater vehicle according to claim 1, characterized in that The transmitting / receiving point in Step 3 must simultaneously satisfy the far-field condition: the distance r from the observation point to the equivalent geometric acoustic center of the underwater vehicle is not less than the ratio of the square of the total length L of the underwater vehicle to the acoustic wavelength λ.

5. A simulation and evaluation method for the time-domain and time-frequency distribution characteristics of a combined transceiver of an underwater vehicle, according to claim 1, wherein The incident acoustic wave in Step 3 is a point source, and under the far-field condition, it is approximately a plane wave when it reaches the target position; the scattered acoustic wave is regarded as the secondary radiation of the underwater vehicle shell.

6. The simulation and evaluation method for the time-domain and time-frequency distribution characteristics of a combined transceiver of an underwater vehicle according to claim 1, wherein Step 5 also includes: Step 5.1 Establish an evaluation model of the structural plate element of the underwater vehicle; respectively divide the inner and outer shells of the geometric model of the actual scale of the underwater vehicle structure into triangular surface meshes, and export the topological information and node information of the triangular surface meshes and save them separately; Step 5.2 Read the node information and the triangular surface mesh file, respectively draw the mesh models of the inner and outer shells of the underwater vehicle, and after setting the initial incident / receiving point, check the normal direction of the triangular surface mesh to ensure that the normal direction of the triangular surface mesh faces the outside of the underwater vehicle; Step 5.3: Establish an acoustic scattering model for the underwater vehicle's hull and express it in the form of summing surface elements. For a double-layer hull structure, consider the outer shell of the underwater vehicle as a thin steel elastic shell, taking into account the reflection and transmission of sound waves. At the same time, the sound waves transmitted through the outer shell to the inner shell are further transmitted, pass through the outer shell, and are received at the receiving point together with the first reflection of the outer shell. Finally, calculate the sum of the scattering contributions of all surface elements within the input radio frequency domain signal frequency band, which is the target frequency domain transfer function at the calculated angle.

7. The simulation evaluation method for the transmit-receive co-located time-domain and time-frequency distribution characteristics of an underwater vehicle according to claim 1, wherein In Step 7, use the sound pressure amplitude curve at a certain moment as the evaluation index for the time-frequency distribution characteristics of the underwater vehicle when the transceiver is co-located.

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