An active sonar target echo simulation method

Abstract

The present application belongs to the field of underwater acoustic signal processing, and particularly relates to a method for simulating echo of active sonar target. Firstly, the sonar transmitting signal is generated according to the sonar transmitting parameters. By setting the initial azimuth and distance of the target and the speed and course of the target and the ship, the azimuth and distance of the target relative to the ship, the attitude angle and the radial velocity at the echo time are calculated. Then, the echo intensity of the target received by the sonar is analyzed through the sonar transmitting mode, the transmitting power, the underwater acoustic propagation loss and the target type, and the echo signal amplitude is calculated according to the element sensitivity, the attenuator attenuation multiple and the DA bit number. Then, the multi-bright-point target model is established according to the target type and the azimuth, distance and attitude information of the target. The present application realizes the echo simulation of various target types of active sonar, and can effectively carry out the training and verification work of underwater target detection and target identification, and has certain practical and economic value.

Description

Technical Field

[0001] This invention belongs to the field of underwater acoustic signal processing, and specifically relates to a method for simulating the echo of an active sonar target. Background Technology

[0002] Active sonar is the primary means of long-range underwater target detection. Due to the complexity of the marine environment, the diverse types of underwater targets, and the lack of a comprehensive database for all types of targets in existing sonar systems, research on active sonar for underwater target detection and identification faces significant challenges. Therefore, it is necessary to design an active sonar target echo simulation method to conduct training and validation work for underwater target detection and identification. Summary of the Invention

[0003] To address the shortcomings of existing technologies, this invention discloses an active sonar target echo simulation method. This invention realizes echo simulation of various target types of active sonar, which can effectively carry out training and verification work for underwater target detection and target identification, and has certain practical and economic value.

[0004] This invention is achieved through the following technical solution:

[0005] A method for simulating the echo of an active sonar target includes the following:

[0006] Step 1: First, generate the sonar transmission signal based on the sonar transmission parameters;

[0007] Step 2: By setting the initial bearing and distance of the target and the speed and heading of the target and the ship, calculate the bearing, distance, attitude angle and radial velocity information of the target relative to the ship at the time of the echo.

[0008] Step 3: Then, analyze the target echo intensity received by the sonar by considering the sonar transmission method, transmission power, underwater acoustic propagation loss, and target type. Then, calculate the echo signal amplitude based on the array element sensitivity, attenuator attenuation factor, and DA bit depth.

[0009] Step 4: Then, based on the target type and the target's azimuth, distance, and attitude information, establish a multi-brightness target model to obtain the number of echo bright spots and the azimuth, distance, and amplitude values ​​of each bright spot.

[0010] Step 5: Based on the acoustic array array parameters, target position, and ship attitude information, calculate the reception delay of each bright spot echo signal relative to the reference point on each array element;

[0011] Step 6: Finally, based on all the obtained multi-brightness information, generate multi-brightness echo signals and superimpose them to synthesize the active target echo signals received by each array element.

[0012] Preferably, in step 1, the transmitted signal adopts two forms: single-frequency CW and hyperbolic frequency modulation (HFM).

[0013] in,

[0014] The single-frequency signal generates the corresponding transmission signal according to the input center frequency f0, signal pulse width T, and signal parameters, using the following formula:

[0015] s(t)=exp(j2πf0t),t∈[0,T];

[0016] The hyperbolic frequency modulated signal generates the corresponding transmitted signal according to the following formula based on the input center frequency f0, signal pulse width T, signal bandwidth B, and other signal parameters:

[0017] s(t)=exp[j2π(f0 2 -B 2 / 4)T / B·log(1+t·B / T / (f0+B / 2))],t∈[0,T].

[0018] Preferably, step 2 specifically includes the following:

[0019] Assuming that both the target and the ship are moving in uniform linear motion, the initial bearing distance of the target, the speed and heading information of the target and the ship, and the start time of each scanning range are set, and the bearing distance, attitude angle, and radial velocity information of the target relative to the ship are calculated for each range.

[0020] Taking the ship's initial position as the reference point, the formula for calculating the ship's position at the start of the i-th range is:

[0021]

[0022] In the formula:

[0023] x_ship i Let y_ship be the position of the ship on the x-axis of the Cartesian coordinate system for the i-th range; i Let v_ship be the position of the ship on the y-axis of the rectangular coordinate system during the i-th range; v_ship be the ship's speed; α_ship be the ship's speed.

[0024] The initial position of the target is:

[0025]

[0026] In the formula:

[0027] R0 is the initial distance to the target; θ0 is the initial orientation of the target; x_tag0 is the initial position of the target on the x-axis of the Cartesian coordinate system; y_tag0 is the initial position of the target on the y-axis of the Cartesian coordinate system.

[0028] The target position at the start time of the i-th range is:

[0029]

[0030] In the formula:

[0031] x_tag i Let y_tag be the position of the target in the i-th range on the x-axis of the Cartesian coordinate system. i Let v_tag be the position of the target in the i-th range on the y-axis of the Cartesian coordinate system; v_tag is the target speed; α_tag is the target heading.

[0032] Based on the positions of the ship and the target in the geographic coordinate system, the bearing and distance of the target relative to the ship at each measurement time are obtained. Then, based on the speed and heading of the target and the ship, the attitude angle and radial velocity of the target relative to the ship are calculated.

[0033]

[0034] In the formula:

[0035] R i Let θ be the distance between the i-th range target and the ship; i Let α be the bearing of the i-th range target relative to the ship; i Let v_rad be the attitude angle of the i-th range target relative to the ship. i Let be the radial velocity of the i-th range target relative to the ship.

[0036] Preferably, step 3 specifically includes the following:

[0037] The reflection intensity TS of the target is calculated based on the set target type and target attitude angle information.

[0038] The reflection intensity data of each target type at different attitude angles within a 360-degree range are pre-calculated based on the model and saved as an array for this module to read;

[0039] Then, based on the sonar source level, propagation loss, target reflection intensity, and noise level, the echo intensity at the receiving end is calculated, and the signal amplitude is calculated based on the array element sensitivity, attenuator attenuation factor, and DA bit depth.

[0040] The echo intensity at the receiving end is given by the following formula:

[0041] EL = SL - 2TL + TS - NL;

[0042] In the formula:

[0043] EL represents the receiver echo intensity; SL represents the transmitting sound source level; TL represents the propagation loss; TS represents the target reflection intensity; NL represents the noise level.

[0044] The relationship between signal voltage, echo intensity, and array element sensitivity is as follows:

[0045] M p +EL = 20logU;

[0046] Right now:

[0047]

[0048] In the formula:

[0049] U is the echo signal voltage value; M P EL represents the array element sensitivity; EL represents the echo intensity at the receiver.

[0050] Then, using a fixed gain factor and DA bit depth, the echo signal amplitude is obtained:

[0051] A = G·U·(2 N-1 -1) / V PP ;

[0052] In the formula:

[0053] A is the echo signal amplitude; U is the echo signal voltage value; G is the attenuation factor of the attenuator; N is the number of bits in the DA converter; V PP This is the maximum voltage of DA.

[0054] Preferably, step 4 specifically includes the following:

[0055] Based on different target types and the target's azimuth, distance, and attitude angle information, calculate the number of echo bright spots and the azimuth, distance, and amplitude values ​​of each bright spot;

[0056] Among them, the scale, number of bright spots, distance distribution and intensity ratio of each target type are calculated in advance according to the model and saved as an array for this module to read;

[0057] If the scale, number of bright spots, distance distribution of bright spots, and intensity ratio of each bright spot are known for the selected target type, and assuming the azimuth distances of the target echoes are respectively (θ... i ,R i The attitude angle is α. i The distance, orientation, and amplitude of each bright spot are then calculated using the following formula:

[0058]

[0059]

[0060] A i,k =a k ·A i ; i=1,…,N; k=1,…,M;

[0061] In the formula:

[0062] L represents the target scale; M represents the number of bright spots; l k The distribution of bright spots by distance; a k R represents the intensity percentage of each highlight; i Let θ be the distance between the i-th range target and the ship; i R represents the bearing of the i-th range target relative to the ship; i,k Let θ be the distance between the target at the k-th bright spot in the i-th range and the ship; i,k A represents the bearing of the target with the k-th bright spot in the i-th range relative to the ship; i,k Let be the amplitude value of the kth spot in the i-th range.

[0063] Preferably, step 5 specifically includes the following:

[0064] First, the coordinates (X, Y, F) of each element in the acoustic array are calculated in the Cartesian coordinate system based on the array configuration parameters. j ,Y j Z j ), j=1,…,N, and then, based on the ship's real-time pitch, roll, and bow angle information, calculate the actual array element coordinates (X). j ',Y j ',Z j '),j=1,…,N:

[0065]

[0066] In the formula:

[0067] φ is the real-time pitch angle; γ is the real-time roll angle; This is the real-time heading angle;

[0068] Then, based on the azimuth and elevation angle of the bright spots, calculate the receiving delay distance of each bright spot relative to the reference point on each array element:

[0069]

[0070] In the formula:

[0071] ρ i θ is the pitch angle of the i-th range; i,k Let d be the bearing of the target at the k-th bright spot in the i-th range relative to the ship; i,j,k The delay distance of the kth spot in the i-th range on the j-th array element;

[0072] Finally, by reading the real-time sound velocity, we can obtain the latency value of each bright spot on each array element:

[0073] τ i,j,k =d i,j,k / c;

[0074] In the formula:

[0075] τ i,j,k d represents the delay of the k-th spot in the i-th range on the j-th array element; i,j,k Let be the delay distance of the k-th spot in the i-th range on the j-th array element; c is the speed of sound in water.

[0076] Preferably, step 6 specifically includes the following:

[0077] Each element signal of the active target echo is composed of multiple bright spot echo signals superimposed and combined. Compared with the transmitted signal, each bright spot signal mainly differs in time delay, Doppler frequency shift and amplitude variation.

[0078] The target Doppler shift is caused by the relative motion between the target and the ship, and it is related to the target's radial velocity. The target Doppler scaling factor can be expressed as:

[0079] k_dpl i =(c-v_rad) i ) / (c+v_rad i );

[0080] In the formula:

[0081] v_rad i k_dpl represents the radial velocity of the i-th range target relative to the ship; c represents the speed of sound in water; k_dpl i The target Doppler scaling factor for the i-th range;

[0082] Assuming the transmitted signal is represented by send_sig = s(A,f0,B,T,t), then the target echo signal for each array element is represented as:

[0083]

[0084] t∈[2·R i,k / c,2·R i,k / c+T / k_dpl i ]

[0085] j = 1, ..., 48;

[0086] In the formula:

[0087] recv_sig j Let f_j be the target echo signal received by the j-th array element; A be the amplitude coefficient of the transmitted signal; f_0 be the center frequency of the transmitted signal; B be the bandwidth of the transmitted signal; T be the pulse width of the transmitted signal; k_dpl i τ is the target Doppler scaling factor for the i-th range; i,j,k A is the delay of the k-th spot in the i-th range on the j-th array element;i,k R represents the amplitude value of the k-th spot in the i-th range; i,k Let be the distance between the target at the k-th bright spot in the i-th range and the ship; c is the speed of sound in water.

[0088] The present invention has the following beneficial effects:

[0089] Based on actual needs, this invention models the echo signal generation mechanism of active sonar and designs the transmission signal according to the working parameters of the sonar platform. For different types of target characteristics, it simulates the motion state, distance and target intensity information of the target through Doppler frequency shift, echo delay and propagation loss, and realizes echo simulation of multiple target types of active sonar. It can effectively carry out training and verification work for underwater target detection and target identification, and has certain practical and economic value. Attached Figure Description

[0090] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0091] Figure 1 This is a flowchart of the target echo simulation process of the present invention.

[0092] Figure 2 This is a model diagram of the relative motion between the target of this invention and the ship.

[0093] Figure 3 This is a diagram showing the relative positions of multiple bright spots in this invention. Detailed Implementation

[0094] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0095] like Figure 1-3As shown, this invention provides an active sonar target echo simulation method. First, a sonar transmission signal is generated based on the sonar transmission parameters. By setting the initial azimuth and range of the target, as well as the target's and the ship's speed and heading, information such as the target's azimuth, range, attitude angle, and radial velocity relative to the ship at the echo time is calculated. Then, the intensity of the target echo received by the sonar is analyzed based on the sonar transmission mode, transmission power, underwater acoustic propagation loss, and target type. The echo signal amplitude is then calculated based on array element sensitivity, attenuator attenuation factor, and DA bit depth. Next, a multi-brightness target model is established based on the target type and its azimuth, range, and attitude information to obtain the number of echo bright spots and the azimuth, range, and amplitude values ​​of each bright spot. Then, based on the acoustic array configuration parameters, target position, and the ship's attitude information, the reception delay of the echo signal of each bright spot relative to the reference point at each array element is calculated. Finally, based on all the obtained multi-brightness information, a multi-brightness echo signal is generated and superimposed to synthesize the active target echo signal received by each array element.

[0096] Specifically, it includes the following:

[0097] 1) Generation of transmitted signals

[0098] This device uses two signal transmission methods: single-frequency (CW) and hyperbolic frequency modulation (HFM).

[0099] A single-frequency signal generates a corresponding transmit signal based on the input center frequency f0, signal pulse width T, and other signal parameters according to the following formula.

[0100] s(t) = exp(j2πf0t), t∈[0,T]

[0101] The hyperbolic frequency modulated signal generates the corresponding transmitted signal according to the following formula based on the input center frequency f0, signal pulse width T, signal bandwidth B, and other signal parameters.

[0102] s(t)=exp[j2π(f0 2 -B 2 / 4)T / B·log(1+t·B / T / (f0+B / 2))],t∈[0,T]

[0103] 2) Calculation of target azimuth, range, attitude, and radial velocity

[0104] Assuming that both the target and the ship are moving in uniform linear motion, by setting the initial bearing distance of the target, the speed and heading information of the target and the ship, and the start time of each scanning range, the bearing distance, attitude angle, radial velocity, and other information of the target relative to the ship can be calculated for each range.

[0105] Taking the ship's initial position as the reference point, the formula for calculating the ship's position at the start of the i-th range is:

[0106]

[0107] In the formula:

[0108] x_ship i Let be the position of the ship on the x-axis of the rectangular coordinate system during the i-th range;

[0109] y_ship i Let be the position of the ship on the y-axis of the rectangular coordinate system during the i-th range;

[0110] v_ship is the ship's speed;

[0111] α_ship represents the ship's speed.

[0112] The initial position of the target is:

[0113]

[0114] In the formula:

[0115] R0 is the initial distance to the target;

[0116] θ0 is the initial orientation of the target;

[0117] x_tag0 is the initial position of the target on the x-axis of the Cartesian coordinate system;

[0118] y_tag0 is the initial position of the target on the y-axis of the Cartesian coordinate system.

[0119] The target position at the start time of the i-th range is:

[0120]

[0121] In the formula:

[0122] x_tag i Let be the position of the target in the i-th range on the x-axis of the rectangular coordinate system;

[0123] y_tag i Let be the position of the target in the i-th range on the y-axis of the rectangular coordinate system;

[0124] v_tag represents the target speed;

[0125] α_tag represents the target heading.

[0126] Based on the positions of the ship and the target in the geographic coordinate system, the bearing and distance of the target relative to the ship at each measurement time can be obtained. Furthermore, based on the speed and heading of the target and the ship, the attitude angle and radial velocity of the target relative to the ship can be calculated.

[0127]

[0128] In the formula:

[0129] R i Let be the distance of the i-th range target relative to the ship;

[0130] θ i Let be the bearing of the i-th range target relative to the ship;

[0131] α i Let be the attitude angle of the i-th range target relative to the ship.

[0132] v_rad i Let be the radial velocity of the i-th range target relative to the ship;

[0133] 3) Calculation of echo signal amplitude

[0134] Based on the set target type (tiled submarine, untiled submarine, merchant ship, shipwreck / reef, school of fish) and target attitude angle information, calculate the target's reflection intensity TS(Ttype,α).

[0135] The reflection intensity data of different attitude angles within a 360-degree range (with an accuracy of 1 degree) for each target type are pre-calculated based on the model and saved as an array for this module to read.

[0136] Then, based on the sonar source level (transmission mode, transmission power), propagation loss, target reflection intensity, noise level, etc., the echo intensity at the receiving end is calculated, and the signal amplitude is calculated based on the array element sensitivity, attenuator attenuation factor, and DA bit depth.

[0137] The echo intensity at the receiving end is given by the following formula:

[0138] EL = SL - 2TL + TS - NL

[0139] In the formula:

[0140] EL represents the echo intensity at the receiving end;

[0141] SL represents the sound source level.

[0142] TL represents propagation loss;

[0143] TS represents the target reflection intensity;

[0144] NL represents the noise level.

[0145] The relationship between signal voltage, echo intensity, and array element sensitivity is as follows:

[0146] M p +EL=20logU

[0147] Right now:

[0148]

[0149] In the formula:

[0150] U is the echo signal voltage value;

[0151] M P For array element sensitivity;

[0152] EL represents the echo intensity at the receiving end.

[0153] Then, using a fixed gain factor and DA bit depth, the echo signal amplitude is obtained:

[0154] A = G·U·(2 N-1 -1) / V PP

[0155] In the formula:

[0156] A represents the amplitude of the echo signal;

[0157] U is the echo signal voltage value;

[0158] G is the attenuation factor of the attenuator;

[0159] N is the number of bits in DA;

[0160] V PP This is the maximum voltage of DA.

[0161] 4) Calculation of the location, distance, and amplitude of multiple bright spots

[0162] Based on different target types (tiled submarines, untiled submarines, merchant ships, shipwrecks / reefs, schools of fish), as well as the target's azimuth, distance, and attitude angle information, the number of echo bright spots and the azimuth, distance, and amplitude values ​​of each bright spot are calculated.

[0163] The scale, number of bright spots, distance distribution, and intensity ratio of each target type are pre-calculated based on the model and saved as an array for this module to read.

[0164] If the scale, number of bright spots, distance distribution of bright spots, and intensity ratio of each bright spot are known for the selected target type, and assuming the azimuth distances of the target echoes are respectively (θ... i ,R i The attitude angle is α. i The distance, orientation, and amplitude of each bright spot are then calculated using the following formula:

[0165]

[0166]

[0167] A i,k =a k ·A ii = 1, ..., N; k = 1, ..., M

[0168] In the formula:

[0169] L represents the target scale;

[0170] M represents the number of bright spots;

[0171] l k The distribution of bright spots is based on their distance.

[0172] a k The intensity percentage of each highlight;

[0173] R i Let be the distance of the i-th range target relative to the ship;

[0174] θ i Let be the bearing of the i-th range target relative to the ship.

[0175] R i,k Let be the distance between the target at the k-th bright spot in the i-th range and the ship;

[0176] θ i,k The bearing of the target at the kth bright spot in the i-th range relative to the ship;

[0177] A i,k Let be the amplitude value of the kth spot in the i-th range;

[0178] 5) Array element delay calculation

[0179] Based on the array parameters of the acoustic array, the target position, and the ship's attitude information, the reception delay of the echo signal of each bright spot relative to the reference point is calculated on each array element.

[0180] First, the coordinates (X, Y, F) of each element in the acoustic array are calculated in the Cartesian coordinate system based on the array configuration parameters. j ,Y j Z j ), j=1,…,N, and then, based on the ship's real-time pitch, roll, and bow angle information, calculate the actual array element coordinates (X). j ',Y j ',Z j '),j=1,…,N:

[0181]

[0182] In the formula:

[0183] φ is the real-time pitch angle;

[0184] γ is the real-time roll angle;

[0185] This is the real-time heading angle;

[0186] Then, based on the azimuth and elevation angle of the bright spots, calculate the receiving delay distance of each bright spot relative to the reference point on each array element:

[0187]

[0188] In the formula:

[0189] ρ i Let be the pitch angle of the i-th range;

[0190] θ i,k The bearing of the target at the kth bright spot in the i-th range relative to the ship;

[0191] d i,j,k The delay distance of the kth spot in the i-th range on the j-th array element;

[0192] Finally, by reading the real-time velocity of sound, the latency value of each bright spot on each array element can be obtained:

[0193] τ i,j,k =d i,j,k / c

[0194] In the formula:

[0195] τ i,j,k The delay of the kth spot in the i-th range on the j-th array element.

[0196] d i,j,k The delay distance of the kth spot in the i-th range on the j-th array element;

[0197] c is the speed of sound in water;

[0198] 6) Generation of multi-element array signals

[0199] Each element signal of the active target echo is composed of multiple bright spot echo signals superimposed and combined. Compared with the transmitted signal, each bright spot signal mainly differs in time delay, Doppler frequency shift and amplitude variation.

[0200] The target Doppler shift is caused by the relative motion between the target and the ship, and is related to the target's radial velocity. Let the target Doppler scaling factor be expressed as:

[0201] k_dpl i =(c-v_rad) i ) / (c+v_rad i )

[0202] In the formula:

[0203] v_rad i Let be the radial velocity of the i-th range target relative to the ship;

[0204] c is the speed of sound in water;

[0205] k_dpl i Let be the target Doppler scaling factor for the i-th range.

[0206] Assuming the transmitted signal is represented by send_sig = s(A,f0,B,T,t), the target echo signal for each array element can be expressed as:

[0207]

[0208] In the formula:

[0209] recv_sig j The target echo signal received by the j-th array element;

[0210] A is the amplitude coefficient of the transmitted signal;

[0211] f0 is the center frequency of the transmitted signal;

[0212] B represents the transmission signal bandwidth;

[0213] T is the pulse width of the transmitted signal;

[0214] k_dpl i The target Doppler scaling factor for the i-th range;

[0215] τ i,j,k The delay of the kth spot in the i-th range on the j-th array element.

[0216] A i,k Let be the amplitude value of the kth spot in the i-th range;

[0217] R i,k Let be the distance between the target at the k-th bright spot in the i-th range and the ship;

[0218] c is the speed of sound in water.

[0219] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. An active sonar target echo simulation method, characterized by, The method comprises the following steps: Step 1: first, according to the sonar emission parameters, a sonar emission signal is generated; Step 2: by setting the initial azimuth and distance of the target and the speed and heading of the target and the ship, the azimuth and distance and the attitude angle and the radial velocity information of the target relative to the ship at the echo time are calculated; Step 3: then, the target echo intensity received by the sonar is analyzed through the sonar emission mode, the emission power, the underwater sound propagation loss and the target type, and the echo signal amplitude is calculated according to the array element sensitivity, the attenuator attenuation multiple and the DA bit number; Step 4: then, according to the target type and the azimuth, distance and attitude information of the target, a multi-bright-spot target model is established to obtain the echo bright spot number and the azimuth, distance and amplitude value of each bright spot; Step 5: then, according to the sonar array pattern parameters and the target position and the attitude information of the ship, the receiving time delay of each bright spot echo signal on each array element relative to the reference point is calculated; Step 6: finally, according to all the multi-bright-spot information obtained, a multi-bright-spot echo signal is generated, and the active target echo signals received by each array element are superimposed and synthesized; The step 4 specifically comprises the following steps: According to the different target types and the azimuth, distance and attitude angle information of the target, the echo bright spot number and the azimuth, distance and amplitude value of each bright spot are calculated; Wherein, the scale of each target type, the number of bright spots and the distance distribution and intensity proportion of each bright spot are calculated in advance according to the model and saved as an array for the model to read; If the scale, the number of bright spots, the distance distribution of bright spots and the proportion of each bright spot intensity of the selected target type are known, assuming that the azimuth and range of the target echo are θ i ,R i , and the attitude angle is α i , the distance, azimuth and amplitude of each bright spot are calculated by the following formula: A i,k = a k · A i ; i = 1,..., N; k = 1,..., M; In the step 1, the form of the emission signal adopts single frequency CW and hyperbolic frequency modulation HFM; L is the target scale; M is the number of bright spots; l k is the bright spot distance distribution; a k is the proportion of each bright spot intensity; R i is the distance of the i-th range target relative to the ship; θ i is the bearing of the i-th range target relative to the ship; R i,k is the distance of the i-th range target relative to the ship; θ i,k is the bearing of the i-th range target relative to the ship; A i,k is the amplitude value of the i-th range target relative to the ship.

2. A method of active sonar target echo simulation as claimed in claim 1, characterized in that, Wherein, the single frequency signal is generated according to the input center frequency f0, signal pulse width T signal parameters, and the following formula: s(t) = exp(j2πf0t), t ∈ [0, T]; The hyperbolic frequency modulation signal is generated according to the input center frequency f0, signal pulse width T, signal bandwidth B signal parameters, and the following formula: The step 2 specifically comprises the following steps: s(t) = exp[j2π(f0 2 -B 2 / 4)T / B·log(1+t·B / T / (f0+B / 2))],t∈[0,T].

3. A method of active sonar target echo simulation as claimed in claim 2, characterized in that, Assuming that the target and the ship are moving at a uniform speed in a straight line, setting the initial azimuth and distance of the target, the speed and heading of the target and the ship and the starting time of each scanning range, the azimuth and distance and the attitude angle and the radial velocity information of the target relative to the ship in each range are calculated; Taking the initial position of the ship as the reference point, the calculation formula of the position of the ship at the starting time of the i th range is: Wherein: The initial position of the target is: x_ship i The position of the own ship on the x-axis of the rectangular coordinate system for the i-th range; y_ship i The position of the own ship on the y-axis of the rectangular coordinate system for the i-th range; v_ship The speed of the own ship; α_ship The speed of the own ship; Wherein: R0 is the initial distance of the target; θ0 is the initial azimuth of the target; x_tag0 is the initial position of the target on the x-axis of the rectangular coordinate system; y_tag0 is the initial position of the target on the y-axis of the rectangular coordinate system; Then the position of the target at the starting time of the i th range is: Wherein: According to the positions of the ship and the target in the geographical coordinate system, the azimuth and distance of the target relative to the ship at each range time are solved, and then the attitude angle and the radial velocity of the target relative to the ship are obtained according to the speed and heading of the target and the ship: x_tag i Position of the target in the x-axis of the rectangular coordinate system for the i-th range; y_tag i Position of the target in the y-axis of the rectangular coordinate system for the i-th range; v_tag is the target speed; α_tag is the target heading; Wherein: The step 3 specifically comprises the following steps: R i is the distance of the ith range target from the ship; θ i is the bearing of the ith range target from the ship; α i is the attitude angle of the ith range target from the ship, v_rad i is the radial velocity of the ith range target from the ship.

4. A method of active sonar target echo simulation as claimed in claim 3, characterized in that, According to the set target type and the target attitude angle information, the reflection intensity TS of the target is calculated; The reflection intensity data of different attitude angles in the 360-degree range of each target type is calculated in advance according to the model and saved as an array for the model to read; ​ Then according to the sonar sound source level, propagation loss, target reflection intensity, noise level, the receiving end echo intensity is calculated, and then according to the array element sensitivity, attenuator attenuation multiple, DA bit number, the signal amplitude is calculated; The receiving end echo intensity is given by the following formula: EL=SL-2TL+TS-NL; In the formula: EL is the receiving end echo intensity; SL is the transmitting sound source level; TL is the propagation loss; TS is the target reflection intensity; NL is the noise level; The relationship between the signal voltage value and the echo intensity and the array element sensitivity is as follows: M p +EL = 20 log U; That is: In the formula: U is the echo signal voltage value; M P is the array element sensitivity; EL is the received end echo intensity; Then the echo signal amplitude is obtained by the fixed gain multiple and the DA bit number: A = G - U - (2 N-1 -1) / V PP ; In the formula: A is the echo signal amplitude; U is the echo signal voltage value; G is the attenuator attenuation multiple; N is the DA bit number; V PP is the DA maximum voltage.

5. A method of active sonar target echo simulation as claimed in claim 1, wherein, The step 5 specifically includes the following: First, according to the acoustic array pattern parameters, the array element coordinates (X j ,Y j ,Z j ),j=1,…,N in the space rectangular coordinate system are solved, and then according to the real longitudinal, lateral and heading angle information of the ship, the actual array element coordinates (X j ',Y j ',Z j '),j=1,…,N are calculated. In the formula: φ is the real-time pitch angle; γ is the real-time roll angle; is the real-time heading angle; Then according to the azimuth and the elevation angle of the bright spot, the receiving delay distance of each bright spot on each array element relative to the reference point is calculated: In the formula: ρ i is the elevation angle of the i-th range; θ i,k is the target bearing relative to the ship of the k-th highlight of the i-th range; d i,j,k is the delay distance of the k-th highlight of the i-th range on the j-th array element; Finally, the real-time sound velocity is read, and the time delay value of each bright spot on each array element is obtained: τ i,j,k = d i,j,k / c; In the formula: τ i,j,k is the time delay of the ith range, kth bright spot on the jth element;d i,j,k is the delay distance of the ith range, kth bright spot on the jth element; c is the sound speed in water.

6. A method of active sonar target echo simulation as claimed in claim 5, characterized in that, The step 6 specifically includes the following: Each array element signal of the active target echo is composed of the superposition of the multi-bright spot echo signals, and each bright spot signal mainly has the differences of time delay, Doppler frequency shift and amplitude change compared with the transmitting signal; Wherein the target Doppler frequency shift is caused by the relative motion of the target and the ship, and is related to the radial velocity of the target, and the target Doppler expansion factor is expressed as: k_dpl i = (c - v_rad i ) / (c + v_rad i ); In the formula: v_rad i is the radial velocity of the i-th range target relative to the ship; c is the speed of sound in water; k_dpl i is the Doppler stretching factor of the i-th range target. Suppose that the transmitting signal is represented by send_sig=s(A,f0,B,T,t), and then the target echo signal of each array element is represented as: t e [2 · R i,k / c,2 · R i,k / c + T / k_dpl i ] j＝1,…,48； In the formula: recv_sig j received target echo signal for the jth array element; A is the amplitude coefficient of the transmitted signal; f0is the center frequency of the transmitted signal; B is the bandwidth of the transmitted signal; T is the pulse width of the transmitted signal; k_dpl i target Doppler stretching factor for the ith range; τ i,j,k delay of the kth highlight for the ith range at the jth array element; A i,k amplitude value of the kth highlight for the ith range; R i,k target relative ship distance of the kth highlight for the ith range; c is the sound speed in water.

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