Ship active signal time-frequency analysis method based on time-frequency parameter fine estimation

Abstract

The invention discloses a ship active signal time-frequency analysis method based on time-frequency parameter fine estimation. The method comprises the following steps: (1) obtaining a ship active signal to be processed; (2) calculating single-frequency signal energy fluctuation characteristics of the ship active signal to be processed; (3) calculating a single-frequency signal receiving time existence range based on single-frequency signal energy fluctuation characteristics; (4) calculating the frequency of receiving the single-frequency signal based on the existence range of the time of receiving the single-frequency signal; and (5) calculating the time-frequency distribution of the received frequency-modulated signal based on the frequency of the received single-frequency signal. The method is suitable for a low signal-to-noise ratio condition, can effectively calculate the time-frequency distribution of the frequency-modulated signal in the two-component ship active signal composed of the frequency-modulated signal and the single-frequency signal, and provides a basis for target feature extraction based on the ship active signal.

Description

Technical Field

[0001] This invention belongs to the field of ship signal processing, specifically relating to a time-frequency analysis method for ship active signals based on fine estimation of time-frequency parameters. Background Technology

[0002] Active ship signals include single-frequency, linear frequency modulation (FM), hyperbolic frequency modulation (HFM), and combined waveform active ship signals composed of the above three single-waveform signals. To achieve effective target detection and feature extraction, a common combination of active ship signals is a two-component form consisting of a single FM or hyperbolic frequency modulation signal and a single-frequency signal connected end-to-end. The FM signal is primarily used for target detection, while the single-frequency signal is used for feature extraction. Specifically, because the FM signal is non-stationary, time-frequency analysis can extract fine target features.

[0003] Time-frequency analysis methods are divided into two main categories: (1) Bilinear time-frequency analysis methods, mainly including Wigner-Willi distribution, etc. Although this type of method has high resolution, it has a large computational load, and there are cross terms when analyzing hyperbolic frequency modulated signals, which affects the effective extraction of features. (2) Linear time-frequency analysis methods, mainly including short-time Fourier transform, etc. This type of method has low computational complexity, but time and frequency resolution are limited, which also affects the extraction performance of target features. Summary of the Invention

[0004] Technical problem: The purpose of this invention is to provide a time-frequency analysis method for active signals from ships. This method can effectively estimate the time-frequency parameters of a received single-frequency signal when the parameters of the transmitted signal are known, and design the time-frequency distribution parameters of the frequency-modulated signal based on this, so as to obtain a time-frequency distribution of the frequency-modulated signal with better time and frequency resolution, thus providing a basis for the effective extraction of target features.

[0005] Technical solutions, such as... Figure 1 As shown, this invention proposes a time-frequency analysis method for ship active signals based on fine estimation of time-frequency parameters. The method includes the following steps:

[0006] (1) Obtain the active signal x(n) of the ship to be processed;

[0007] (2) Calculate the single-frequency signal energy fluctuation characteristics E of the active signal x(n) of the ship to be processed. CW (m CW );

[0008] (3) Based on the energy fluctuation characteristics E of single-frequency signals CW (m CW ), calculate the time range n of the received single-frequency signal. CW,recv ;

[0009] (4) Based on the time range n of the received single-frequency signal CW,recv Calculate the frequency f of the received single-frequency signal. CW,recv ;

[0010] (5) Based on the received single-frequency signal frequency f CW,recv Calculate the time-frequency distribution TF of the received FM signal. FM (m FM ,l FM ).

[0011] Furthermore, in step (1), the active signal x(n) of the ship to be processed is obtained using the following method, specifically including the following steps:

[0012] The ship's active signal x(n) to be processed is obtained from real-time data collected from N sampling points of the ship's underwater acoustic sensor, where n = 0, 1, …, N-1; or data from N sampling points is extracted from memory as the ship's active signal x(n), where n = 0, 1, …, N-1, and n is the time index of the ship's active signal x(n) to be processed, and N is the number of signal sampling points, which is N=2. κ κ is a positive integer greater than or equal to 10.

[0013] Furthermore, in step (2), the energy fluctuation characteristics E of the single-frequency signal are calculated using the following method. CW (m CW Specifically, it includes the following steps:

[0014] (2-1) Initialize the parameters for calculating the energy fluctuation characteristics of a single-frequency signal, specifically including the initialization of the following parameters:

[0015] ① Transmit single-frequency signal frequency f CW,trans Initialized to: 0 <f CW,trans <f s / 2 positive real numbers, where f s It is the sampling frequency;

[0016] ② Transmit single-frequency signal pulse width N CW,trans Initialized to: 0 <N CW,trans Positive integers ≤ N / 2;

[0017] ③ The single-frequency signal detection window length scaling parameter α is initialized to a positive real number where 0 < α ≤ 1;

[0018] ④ Single-frequency signal detection window length N CW,window Initialized to: N CW,window =max{4, round{αN CW,trans A positive integer, where max{·} represents the maximum value function and round{·} represents the rounding function;

[0019] ⑤ Single-frequency signal detection step N CW,step Initialize as: 1≤N CW,step ≤floor{N CW,window A positive integer of size 4, where floor{·} represents the floor function;

[0020] ⑥ Total number of frames M during single-frequency signal detection CW Initialized to: M CW =floor{(NN CW,window ) / N CW,step Positive integers of size -1;

[0021] ⑦ Target maximum speed v max Initialize to: 10≤v max Positive real numbers ≤ 20;

[0022] ⑧ The average underwater sound speed c0 is initialized as a positive real number where 1400 ≤ c0 ≤ 1600;

[0023] (2-2) Calculate the detection frequency range f of a single-frequency signal CW,det :

[0024]

[0025] Where, η min and η max The target maximum speed v are respectively max The corresponding minimum and maximum Doppler factors, i.e., η min =(c0-v max ) / (c0+v max ), η max =(c0+v max ) / (c0-v max );

[0026] (2-3) Calculate the starting index L of the detection frequency point of the single-frequency signal CW,start The total number of single-frequency signal detection frequency points L CW,total :

[0027]

[0028]

[0029] Among them, f CW,det (1) and f CW,det (2) f represents the detection frequency range of a single-frequency signal. CW,det The first and second elements;

[0030] (2-4) Extracting the segmented data sequence y of the single-frequency signal detection CW,0 (rCW ),y CW,1 (r CW ),…, ,…, , where the mth CW Segmented data sequence for single-frequency signal detection for:

[0031]

[0032] in, For single-frequency signal detection segmented time index, For single-frequency signal detection, the frame index is... =0,1,…,M CW -1;

[0033] (2-5) Calculate the time-frequency distribution TF of the single-frequency signal detection CW (m CW ,l CW ):

[0034]

[0035] Among them, l CW This is the frequency index for single-frequency signal detection, where j is the imaginary unit, i.e. , |·| is the modulo function;

[0036] (2-6) Calculate the energy fluctuation characteristics E of a single-frequency signal CW (m CW ):

[0037] .

[0038] Furthermore, in step (3), the time range n of the received single-frequency signal is calculated using the following method. CW,recv Specifically, it includes the following steps:

[0039] (3-1) The relative amplitude parameter β for single-frequency signal bandwidth search is initialized to a positive real number where 0 < β < 1;

[0040] (3-2) Calculate the energy fluctuation characteristics E of a single-frequency signal CW (m CW The time frame index m0 corresponding to the maximum value:

[0041]

[0042] in, E represents the energy fluctuation characteristics of a single-frequency signal. CW (m CW The time frame index corresponding to the maximum value;

[0043] (3-3) Calculate the bandwidth amplitude E of a single-frequency signal B :

[0044] ;

[0045] (3-4) Search for the energy fluctuation characteristics of a single-frequency signal E CW (m CW The maximum value to the left is less than the bandwidth amplitude E of a single-frequency signal. B Time frame index set m left :

[0046]

[0047] in, It represents all that satisfy E CW (m CW )≤E B Single-frequency signal detection time frame index m CW The set consisting of max{·} represents the function that takes the maximum value;

[0048] (3-5) Calculate the frame start index m of a single-frequency signal CW,left :

[0049]

[0050] in, Denotes the empty set, m left (end) represents the time frame index set m left The last element;

[0051] (3-6) Search for the energy fluctuation characteristics of a single-frequency signal E CW (m CW The maximum value to the right is less than the bandwidth amplitude E of a single-frequency signal. B Time frame index set m right :

[0052]

[0053] Where min{·} represents the minimum value function;

[0054] (3-7) Calculate the frame cutoff index m of a single-frequency signal CW,right :

[0055]

[0056] Where, m right (1) Represents the time frame index set m right The first element;

[0057] (3-8) Calculate the time range n of the received single-frequency signalCW,recv :

[0058]

[0059] in, Indicates search The time index n corresponding to the minimum value, Indicates search The time index n corresponding to the minimum value.

[0060] Furthermore, in step (4), the frequency f of the received single-frequency signal is calculated using the following method. CW,recv Specifically, it includes the following steps:

[0061] (4-1) Initialize the parameters for calculating the frequency of the received single-frequency signal, specifically including the initialization of the following parameters:

[0062] ① Transmit single-frequency signal period N CW,period Initialized to: N CW,period =round{f s / f CW,trans A positive integer f, where f s This is the sampling frequency, and round{·} represents the rounding function.

[0063] ② Traverse the set of frequency detectors for pulse width single-frequency signals f CW,trav Initialize to: Its length is N CW,period A vector of all zeros;

[0064] ③ Traverse the set of peak values ​​of the amplitude spectrum of the pulse width single-frequency signal A CW,trav Initialize to: Its length is N CW,period A vector of all zeros;

[0065] ④ Traverse the pulse width index d trav Initialized to: d trav =0;

[0066] (4-2) Calculate the d-th ... trav A single-frequency traversal pulse width signal :

[0067]

[0068] in, It is the dth trav A time index for traversing a single-frequency pulse width signal. It is the dth trav The number of sampling points for a single-frequency traversal pulse width signal, n CW,recv (1) and n CW,recv(2) Represent the time range n of receiving a single-frequency signal. CW,recv The first and second elements;

[0069] (4-3) Calculate the d-th ... trav A single-frequency traversal pulse width signal amplitude spectrum :

[0070]

[0071] in, It is the dth trav A frequency index for a single-frequency pulse width signal is traversed, where j is the imaginary unit, i.e. , |·| is the modulo function;

[0072] (4-4) Update the set of frequency detectors f for traversing pulse width single-frequency signals CW,trav The dth trav element f CW,trav (d trav ):

[0073]

[0074] in, Indicates the search amplitude spectrum Frequency index corresponding to the maximum value ;

[0075] (4-5) Update the set of peak values ​​of the amplitude spectrum of the pulse width single-frequency signal A. CW,trav The dth trav Element A CW,trav (d trav ):

[0076]

[0077] Where max{·} represents the function that takes the maximum value;

[0078] (4-6) Update the traversal pulse width index d trav :

[0079] ;

[0080] (4-7) Determine the pulse width index d during traversal trav Does the traversal deadline condition apply?

[0081]

[0082] If the condition is met, proceed to step (4-8); otherwise, return to step (4-2).

[0083] (4-8) Calculate the frequency f of the received single-frequency signal. CW,recv :

[0084]

[0085] Where d0 is the frequency f of the received single-frequency signal. CW,recv The corresponding traversal pulse width peak index, A CW,trav (d trav ) represents the set of peak values ​​of the amplitude spectrum of a pulse-width single-frequency signal. CW,trav The dth trav elements, f CW,trav (d0) represents the set of frequency detectors for traversing pulse width single-frequency signals f. CW,trav The d0th element.

[0086] Furthermore, in step (5), the time-frequency distribution TF of the received FM signal is calculated using the following method. FM (m FM ,l FM Specifically, it includes the following steps:

[0087] (5-1) Initialize the parameters for calculating the time-frequency distribution of the received FM signal, specifically including the initialization of the following parameters:

[0088] ① Transmit the starting frequency f of the FM signal FM,1,trans Initialized to: 0 <f FM,1,trans <f s / 2 positive real numbers, where f s It is the sampling frequency;

[0089] ② The cutoff frequency f of the transmitted frequency modulation signal FM,2,trans Initialized to: 0 <f FM,2,trans <f s Positive real numbers of 2 / 2;

[0090] ③ Transmit FM signal pulse width N FM,trans Initialized to: 0 <N FM,trans ≤NN CW,trans Positive real numbers;

[0091] ④ Time-frequency distribution frequency tolerance parameter λ f Initialize to: 0 < λ f Positive real numbers ≤ 1;

[0092] ⑤ Time-frequency distribution time tolerance parameter λ t Initialize to: 0 < λ t Positive real numbers ≤ 1;

[0093] (5-2) Calculate the frequency range f of the received FM signal. FM,recv :

[0094]

[0095] Where η0=f CW,recv / f CW,trans The target detection Doppler factor, min{·} and max{·} represent the minimum and maximum value functions, respectively;

[0096] (5-3) Calculate the time range n of the received FM signal FM,recv :

[0097]

[0098] Where, n CW,recv (1) and n CW,recv (2) Represent the time range n of receiving a single-frequency signal. CW,recv The first and second elements;

[0099] (5-4) Calculate the time-frequency distribution window length N of the received FM signal. FM,window and the time-frequency distribution step N of the received FM signal FM,step :

[0100]

[0101] Among them, f FM,recv (1) and f FM,recv (2) represent the frequency range f of the received FM signal respectively. FM,recv The first and second elements, round{·} represents the rounding function, and floor{·} represents the floor function;

[0102] (5-5) Calculate the starting index L of the received FM signal frequency point FM,start The total number of frequency points L for receiving FM signals FM,total :

[0103]

[0104] Among them, f FM,range It is the frequency tolerance range for receiving FM signals, f FM,range The first element f FM,range (1)=min{f s / 2, max{0, (1+λ f f FM,recv (1)-λ f f FM,recv (2)}},f FM,range The second element f FM,range (2)=min{f s / 2, (1+λ f f FM,recv (2)-λf f FM,recv (1)},f FM,recv (1) and f FM,recv (2) represent the frequency range f of the received FM signal respectively. FM,recv The first and second elements;

[0105] (5-6) Calculate the total number of frames M when the received FM signal time-frequency distribution is calculated. FM :

[0106]

[0107] (5-7) Extract the segmented data sequence y of the received FM signal FM,0 (r FM ), y FM,1 (r FM ), …, ,…, , where the mth FM Segmented data sequence of received FM signal for:

[0108]

[0109] Where, r FM For the time-frequency distribution segmented time index of the received FM signal, m FM For the time-frequency distribution time frame index of the received FM signal, m FM =0,1,…,M FM -1, n FM,recv (1) is the range n of the received FM signal time calculated in step (5-3). FM,recv The first element;

[0110] (5-8) Calculate and output the time-frequency distribution TF of the received FM signal. FM (m FM , l FM ):

[0111]

[0112] Among them, l FM The frequency point index for the time-frequency distribution of the received FM signal, where j is the imaginary unit, i.e. , where |·| is the modulo function.

[0113] Beneficial effects: Compared with the prior art, the technical solution of the present invention has the following beneficial technical effects:

[0114] (1) The present invention makes full use of the frequency and pulse width of the transmitted single-frequency signal and designs the energy fluctuation characteristics of the single-frequency signal, as shown in step (2). This feature contains the transmitted single-frequency signal information and can effectively reduce the impact of noise and other interference on the subsequent calculation of the time range of the received single-frequency signal.

[0115] (2) The present invention makes full use of the period of the transmitted single-frequency signal to realize the calculation of the frequency of the received single-frequency signal, as shown in step (4). This calculation process makes full use of the principle of spectrum leakage of single-frequency signal to calculate the frequency of the received single-frequency signal, which provides a basis for the design of the time-frequency distribution parameters of the subsequent frequency modulation signal.

[0116] (3) The present invention makes full use of the received single-frequency signal frequency, calculates the frequency range of the frequency modulation signal, and further designs the frequency modulation signal time-frequency distribution window length based on this, as shown in step (5). The designed frequency modulation signal time-frequency distribution window length takes into account the trade-off between time and frequency resolution. Using the obtained time-frequency distribution, parameters such as instantaneous frequency can be effectively extracted, which is beneficial for target detection and feature extraction based on ship active signals. Attached Figure Description

[0117] Figure 1 This is a flowchart illustrating the method of the present invention.

[0118] Figure 2 This is a single-frequency signal energy fluctuation characteristic diagram of Example 1.

[0119] Figure 3 This is a time-frequency distribution diagram of the received FM signal in Example 1.

[0120] Figure 4 This is a single-frequency signal energy fluctuation characteristic diagram of Example 2.

[0121] Figure 5 This is a time-frequency distribution diagram of the received FM signal in Example 2. Detailed Implementation

[0122] To better understand the purpose, structure, and function of this invention, the invention will be further described below with reference to the accompanying drawings.

[0123] In an embodiment of the present invention, the simulated received signal model x(t) is set as:

[0124]

[0125] Among them, A FM and A CW The signal amplitudes τ and τ of the frequency-modulated and single-frequency signals are respectively. 0,FM and τ 0,CW τ represents the start time of the frequency-modulated (FM) and single-frequency (SFM) signals, respectively. FM and τCW Let be the pulse widths of the frequency-modulated (FM) and single-frequency (SFM) signals, respectively, and satisfy τ. 0,FM +τ FM =τ 0,CW , τ total ω(t) is the pulse width for signal sampling; ω(t) is the signal with a mean of 0 and a variance of σ. 2 Gaussian white noise, variance σ 2 The magnitude depends on the signal-to-noise ratio (SNR): SNR = 10log 10 [(A FM +A CW ) 2 / (4σ 2 )];φ FM (t) and φ CW (t) represents the instantaneous phase of the frequency-modulated and single-frequency signals, respectively, and is expressed as:

[0126]

[0127]

[0128] Where, φ 0,FM and φ 0,CW The initial phases of the frequency-modulated and single-frequency signals are f and f, respectively. 1,FM and f 1,CW These are the starting frequencies of the frequency-modulated (FM) and single-frequency (SFM) signals, respectively; μ is the modulation frequency of the linear frequency-modulated (LFM) signal, defined as: μ = (f 2,FM -f 1,FM ) / τ FM f 2,FM k is the cutoff frequency of the FM signal; k0 is the slope of the hyperbolic FM signal period, defined as: k0=(f 2,FM -f 1,FM ) / (f 1,FM f 2,FM τ FM ).

[0129] With sampling frequency f s Discrete sampling is performed on the received signal x(t) from the above simulation to obtain the signal sampling data sequence x(n):

[0130]

[0131] Wherein, the number of signal sampling points N = round{τ total f s}; Frequency modulation signal start point N 0,FM = round{τ 0,FM f s The transmitted frequency modulation signal pulse width N FM,trans = round{τ FM fs}, Single-frequency signal starting point N 0,CW = round{τ 0,CW f s The pulse width N of the transmitted single-frequency signal CW,trans = round{τ CW f s Discrete form of instantaneous phase φ for frequency-modulated and single-frequency signals FM (n / f s ) and φ CW (n / f s ) is represented as:

[0132]

[0133] .

[0134] Example 1:

[0135] The simulation signal parameters are set as follows: the frequency modulation signal is a hyperbolic frequency modulation signal, and the signal amplitude A of the frequency modulation signal is... FM =1, the signal amplitude A of the single-frequency signal CW =1; the start time τ of the frequency modulation signal 0,FM =0.5s, the start time τ of the single-frequency signal 0,CW =1.5s; the pulse width τ of the frequency modulation signal FM =1s, the pulse width τ of a single-frequency signal CW =0.5s, signal sampling pulse width τ total =3.2768s; Signal-to-noise ratio (SNR) = -5dB; Initial phase φ of the FM signal 0,FM =0, the initial phase φ of the single-frequency signal 0,CW =0; the starting frequency f of the frequency modulation signal 1,FM =2960Hz, the cutoff frequency f of the FM signal 2,FM =3450Hz, the starting frequency f of the single-frequency signal 1,CW =3750Hz; sampling frequency f s =10000Hz.

[0136] The following calculation of the time-frequency distribution of the received FM signal is performed using the simulated signal:

[0137] According to step (1), extract the data of the number of signal sampling points N=32768 sampling points from the memory as the ship active signal x(n) to be processed;

[0138] According to step (2), set the transmission frequency f of the single-frequency signal. CW,trans =3800, transmit single-frequency signal pulse width N CW,trans=5000, single-frequency signal detection window length scaling parameter α=0.1, single-frequency signal detection window length N CW,window =500, Single-frequency signal detection step N CW,step =125, total number of frames M during single-frequency signal detection CW =257, target maximum speed v max =20, underwater average sound speed c0=1500; calculate the detection frequency range f of a single-frequency signal. CW,det =[3700,3900]; Calculate the starting index L of the single-frequency signal detection frequency point. CW,start =185, Total number of single-frequency signal detection frequency points L CW,total =11; Extract the segmented data sequence y of the single-frequency signal detection. CW,0 (r CW ), y CW,1 (r CW ), …, , …, y CW,256 (r CW ); Calculate the time-frequency distribution TF of a single-frequency signal detection CW (m CW , l CW ); Calculate the energy fluctuation characteristics E of a single-frequency signal. CW (m CW ),like Figure 2 As shown.

[0139] Based on step (3), set the relative amplitude parameter β=0.707 for the single-frequency signal bandwidth search; calculate the energy fluctuation characteristics E of the single-frequency signal. CW (m CW The index m0 corresponding to the maximum value is 126; calculate the bandwidth amplitude E of the single-frequency signal. B =1.1515; Calculate the frame start index m of a single-frequency signal. CW,left =119; Calculate the time frame cutoff index m of the single-frequency signal. CW,right =158; Calculate the time range n for receiving a single-frequency signal. CW,recv =[15125, 20000].

[0140] According to step (4), set the transmission single-frequency signal period N. CW,period =3, Traverse the pulse width single-frequency signal frequency detection set Traverse the set of peak values ​​of the amplitude spectrum of a single-frequency pulse width signal. Traverse pulse width index d trav =0; calculate the dth th trav A single-frequency traversal pulse width signal ; Calculate the dth trav A single-frequency traversal pulse width signal amplitude spectrum Update the set of frequency detectors f for traversing pulse width single-frequency signals. CW,trav The dth trav element f CW,trav (d trav Update the set of peak values ​​A of the amplitude spectrum of the pulse width single-frequency signal. CW,trav The dth trav Element A CW,trav (d trav Update the traversal pulse width index d. trav ; Calculate the received single-frequency signal frequency f CW,recv =3750.

[0141] According to step (5), set the starting frequency f of the transmitted frequency modulation signal. FM,1,trans =3000, cutoff frequency for transmitted FM signal f FM,2,trans =3500, Transmit FM signal pulse width N FM,trans =10000, time-frequency distribution frequency tolerance parameter λ f =0.15, time-frequency distribution time tolerance parameter λ t =0.15; Calculate the frequency range f of the received FM signal. FM,recv =[2960, 3450]; Calculate the time range n for receiving the FM signal. FM,recv =[5125, 15125]; Calculate the time-frequency distribution window length N of the received FM signal. FM,window =637, calculate the time-frequency distribution step N of the received FM signal. FM,step =159; Calculate the starting index L of the received FM signal frequency point. FM,start =184, calculate the total number of frequency points L for receiving FM signals. FM,total =42; Calculate the total number of time frames M for the received FM signal time-frequency distribution. FM =76; Extract the segmented data sequence y of the received FM signal. FM,0 (r FM ), y FM,1 (r FM ), …, , …, y FM,75 (r FM ); Calculate and output the time-frequency distribution TF of the received FM signal. FM (m FM , l FM ),like Figure 3 As shown.

[0142] Example 2:

[0143] The simulation signal parameters are set as follows: the frequency modulation signal is a linear frequency modulation signal, and the signal amplitude A of the frequency modulation signal is... FM =1, the signal amplitude A of the single-frequency signal CW =1; the start time τ of the frequency modulation signal0,FM =1 s, the start time τ of the single-frequency signal 0,CW =3 s; the pulse width τ of the frequency modulation signal FM =2 s, the pulse width τ of the single-frequency signal CW =1s, signal sampling pulse width τ total =5.12 s; Signal-to-noise ratio (SNR) = -3 dB; Initial phase φ of the FM signal 0,FM =0, the initial phase φ of the single-frequency signal 0,CW =0; the starting frequency f of the frequency modulation signal 1,FM =225 Hz, the cutoff frequency f of the FM signal 2,FM =421 Hz, the starting frequency f of the single-frequency signal 1,CW =490 Hz; sampling frequency f s =2000 Hz.

[0144] The following calculation of the time-frequency distribution of the received FM signal is performed using the simulated signal:

[0145] According to step (1), extract the data of N=10240 signal sampling points from the memory as the ship active signal x(n) to be processed;

[0146] According to step (2), set the transmission frequency f of the single-frequency signal. CW,trans =500, transmit single-frequency signal pulse width N CW,trans =2000, single-frequency signal detection window length scaling parameter α=0.1, single-frequency signal detection window length N CW,window =200, Single-frequency signal detection step N CW,step =50, total number of frames M during single-frequency signal detection CW =199, target maximum speed v max =20, underwater average sound speed c0=1500; calculate the detection frequency range f of a single-frequency signal. CW,det =[487, 514]; Calculate the starting index L of the detection frequency point for a single-frequency signal. CW,start =49, Total number of single-frequency signal detection frequency points L CW,total =3; Extract the segmented data sequence y of the single-frequency signal detection. CW,0 (r CW ),y CW,1 (r CW ), …, , …, y CW,198 (r CW ); Calculate the time-frequency distribution TF of a single-frequency signal detection CW (m CW , l CW ); Calculate the energy fluctuation characteristics E of a single-frequency signal. CW (m CW ),like Figure 4 As shown.

[0147] Based on step (3), set the relative amplitude parameter β=0.707 for the single-frequency signal bandwidth search; calculate the energy fluctuation characteristics E of the single-frequency signal. CW (m CW The index m0 corresponding to the maximum value is 127; calculate the bandwidth amplitude E of the single-frequency signal. B =0.5384; Calculate the frame start index m of a single-frequency signal. CW,left =121; Calculate the frame cutoff index m of the single-frequency signal. CW,right =159; Calculate the time range n for receiving a single-frequency signal. CW,recv =[6150, 8050].

[0148] According to step (4), set the transmission single-frequency signal period N. CW,period =4, Traverse the pulse width single-frequency signal frequency detection set Traverse the set of peak values ​​of the amplitude spectrum of a single-frequency pulse width signal. Traverse pulse width index d trav =0; calculate the dth th trav A single-frequency traversal pulse width signal ; Calculate the dth trav A single-frequency traversal pulse width signal amplitude spectrum Update the set of frequency detectors f for traversing pulse width single-frequency signals. CW,trav The dth trav element f CW,trav (d trav Update the set of peak values ​​A of the amplitude spectrum of the pulse width single-frequency signal. CW,trav The dth trav Element A CW,trav (d trav Update the traversal pulse width index d. trav ; Calculate the received single-frequency signal frequency f CW,recv =490.

[0149] According to step (5), set the starting frequency f of the transmitted frequency modulation signal. FM,1,trans =230, cutoff frequency for transmitted FM signal f FM,2,trans =430, Transmitted FM signal pulse width N FM,trans =4000, time-frequency distribution frequency tolerance parameter λ f =0.15, time-frequency distribution time tolerance parameter λ t =0.15; Calculate the frequency range f of the received FM signal. FM,recv =[225,421];Calculate the time range n of the received FM signal. FM,recv =[2150, 6150]; Calculate the time-frequency distribution window length N of the received FM signal.FM,window =286, calculate the time-frequency distribution step N of the received FM signal. FM,step =71; Calculate the starting index L of the received FM signal frequency point. FM,start =28, calculate the total number of frequency points L for receiving FM signals. FM,total =37; Calculate the total number of time frames M of the received FM signal time-frequency distribution. FM =68; Extract the segmented data sequence y of the received FM signal. FM,0 (r FM ), y FM,1 (r FM ), …, , …, y FM,67 (r FM ); Calculate and output the time-frequency distribution TF of the received FM signal. FM (m FM , l FM ),like Figure 5 As shown.

[0150] It is understood that the present invention has been described through some embodiments, and those skilled in the art will recognize that various changes or equivalent substitutions can be made to these features and embodiments without departing from the spirit and scope of the invention. Furthermore, under the teachings of the present invention, these features and embodiments can be modified to adapt to specific situations and materials without departing from the spirit and scope of the invention. Therefore, the present invention is not limited to the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application are within the protection scope of the present invention.

Claims

1. A time-frequency parameter based fine estimation of ship active signal time-frequency analysis method, characterized in that, The method comprises the following steps: (1) obtaining a to-be-processed ship active signal x(n); (2) calculating the single-frequency signal energy fluctuation feature E of the active signal x(n) of the ship to be processed CW (m CW ); (3) Based on the single frequency signal energy fluctuation characteristics E CW (m CW ), the received single frequency signal time exists in the range n CW,recv ; (4) Based on the received single frequency signal time existing range n CW,recv , the received single frequency signal frequency f CW,recv is calculated (5) Based on the received single frequency signal frequency f CW,recv , calculate the received frequency modulation signal time-frequency distribution TF FM (m FM , l FM ).

2. The time-frequency parameter based fine estimation of ship active signal time-frequency analysis method according to claim 1, characterized in that, In step (1), the to-be-processed ship active signal x(n) is obtained by the following method, which specifically comprises the following steps: Receive real-time acquisition data of N sampling points from a ship water acoustic sensor as a ship active signal x(n) to be processed, n = 0, 1, …, N-1, or extract N sampling points of data from a memory as a ship active signal x(n) to be processed, n = 0, 1, …, N-1, wherein n is the time index of the ship active signal x(n) to be processed, N is the number of signal sampling points, and N = 2 κ , κ is a positive integer greater than or equal to 10.

3. The method according to claim 2, wherein, In step (2), the single frequency signal energy fluctuation feature E is calculated by the following method CW (m CW ), specifically comprising the following steps: (2-1) initializing parameters for calculating single-frequency signal energy fluctuation characteristics, specifically including the initialization of the following parameters: CW,trans initialized to: 0 < f CW,trans < f s a positive real number where f s is the sampling frequency;​ (ii) transmitting a single frequency signal pulse width N CW,trans initialized to: 0 < N CW,trans a positive integer ≤ N / 2; ③ the single-frequency signal detection window length ratio parameter α is initialized as: a positive real number 0 < α ≤ 1; (4) the length N of the single-frequency signal detection window CW,window initialized to: N CW,window = max{4, round{aN CW,trans}} where max{·} denotes a maximum function and round{·} denotes a rounding function. Step N for single frequency signal detection CW,step initialized to: 1≤N CW,step ≤floor{N CW,window / 4} where floor{·} denotes the floor function; ⑥ Total number of frames M in single frequency signal detection CW initialized to: M = floor{ (N - N CW ) / N CW,window} - 1, where N is the number of samples in a frame and N CW,step is the number of samples in a period. v = 0 max initialized to a positive real number v such that 10 < v < 20 max v = 0 ⑧ the underwater average sound speed c0 is initialized as: a positive real number 1400 ≤ c0 ≤ 1600; (2-2) Calculate the single frequency signal detection frequency range f CW,det : ； Where, η min and η max The target maximum speed v are respectively max The corresponding minimum and maximum Doppler factors, i.e., η min =(c0-v max ) / (c0+v max ), η max =(c0+v max ) / (c0-v max ); (2-3) Calculate the starting index L of the single frequency signal detection frequency point CW,start and the total number of single frequency signal detection frequency points L CW,total : , ; wherein f CW,det (1) and f CW,det (2) represent the 1st and 2nd elements of a single frequency signal detection frequency range f CW,det , respectively; (2-4) Extracting the single frequency signal detection segmented data sequence y CW,0 (r CW ),y CW,1 (r CW ),…, ,…, wherein the m CW th single frequency signal detection segmented data sequence is ； wherein is a segment time index for monofrequency signal detection, is a frame index for monofrequency signal detection, = 0, 1,..., M CW - 1; (2-5) Computing a time-frequency distribution TF of the single-frequency signal detection CW (m CW ,l CW ): wherein, l CW is the single frequency signal detection frequency point index, j is the imaginary unit, i.e. |·| is the modulo function; (2-6) Calculate the single frequency signal energy fluctuation feature E CW (m CW ): 。 4. The method according to claim 3, wherein, In step (3), the receiving single-frequency signal time existing range n is calculated by the following method CW,recv and specifically includes the following steps: (3-1) the single-frequency signal bandwidth search relative amplitude parameter β is initialized as: a positive real number 0 < β < 1; (3-2) Calculate the single-frequency signal energy fluctuation feature E CW (m CW ) The time frame index m0 corresponding to the maximum value ； wherein, denotes the search single frequency signal energy fluctuation characteristic E CW (m CW ) the time frame index corresponding to the maximum value. (3-3) Calculating the single frequency signal bandwidth amplitude E B : ； (3-4) Search for the single frequency signal energy fluctuation characteristic E CW (m CW ) Maximum left side of the single frequency signal bandwidth amplitude E B of the time frame index set m left : ； in, It represents all that satisfy E CW (m CW )≤E B Single-frequency signal detection time frame index m CW The set consisting of max{·} represents the function that takes the maximum value; (3-5) Calculate the frame start index m of the single frequency signal CW,left : ； wherein denotes the empty set, m left (end) denotes the last element of the set m left of time frame indices; (3-6) Search for the single frequency signal energy fluctuation characteristic E CW (m CW ) Maximum value right side less than single frequency signal bandwidth amplitude E B of the time frame index set m right : ； Wherein, min{·} represents the minimum value function; (3-7) Calculate the frame cut-off index m for single frequency signal CW,right : ； wherein m right (1) represents the first element of the set m right of time frame indices. (3-8) Calculate the single frequency signal time receiving range n CW,recv : ； wherein, denotes the search for the time index n corresponding to the minimum value, denotes the search for the time index n corresponding to the minimum value.

5. The method according to claim 4, wherein, In step (4), the received single frequency signal frequency f is calculated using the following method CW,recv comprising the following steps: (4-1) initializing parameters for calculating received single-frequency signal frequencies, specifically including the initialization of the following parameters: N is the period of the transmitted single frequency signal CW,period N is initialized to: CW,period N = round{f s / f CW,trans} where f s is the sampling frequency and round{·} denotes the rounding function. ii. traversing the pulse width single frequency signal frequency detection set f CW,trav initialized to: which represents an all-zero vector of length N CW,period ; ③ traversing the pulse width single frequency signal amplitude spectrum peak value set A CW,trav initialized to: a full zero vector of length N CW,period ; IV. Iterating the pulse width index d trav is initialized to: d trav = 0; (4-2) calculating the d trav th traversed pulse width single frequency signal : ； wherein, is the d trav th iteration of the pulse width monopulse signal time index, is the d trav th iteration of the pulse width monopulse signal sample point number, n CW,recv (1) and n CW,recv (2) represent the 1st and 2nd elements, respectively, of the received monopulse signal time existence range n CW,recv . (4-3) calculating the amplitude spectrum of the dth trav traversed pulse-width single-frequency signal :​ wherein, is the d trav th iteration of the pulse width single frequency signal frequency index, j is the imaginary unit, i.e. , |·| is the modulo function; (4-4) update the set of frequencies f of the traversed pulse-width single-frequency signals CW,trav the d trav th element f CW,trav (d trav ) of the set ； wherein, represents a search magnitude spectrum the frequency index corresponding to the maximum value ; (4-5) updating the set A of amplitude spectrum peak values of the traversed pulse width single frequency signal CW,trav th element A trav of the d CW,trav th trav ) : ； Wherein, max{·} represents the maximum value function; (4-6) updating the traversal pulse width index d trav : ； (4-7) judging whether the traversal pulse width index d is traversed trav whether the traversal end condition is satisfied: ； Wherein, if the condition is met, step (4-8) is entered; otherwise, return to step (4-2); (4-8) Calculate the received single frequency signal frequency f CW,recv : ； where d0 is the received single frequency signal frequency f CW,recv the corresponding traversed pulse width peak index, A CW,trav (d trav ) represents the d CW,trav th element of the traversed pulse width single frequency signal amplitude spectrum peak set A trav f CW,trav (d0) represents the d0th element of the traversed pulse width single frequency signal frequency detection set f CW,trav .

6. The time-frequency parameter based fine estimation of ship active signal time-frequency analysis method according to claim 5, characterized in that, In step (5), the time-frequency distribution TF of the received frequency-modulated signal is calculated using the following method FM (m FM ,l FM ), comprising the following steps: (5-1) initializing parameters for calculating received frequency-modulated signal time-frequency distribution, specifically including the initialization of the following parameters: the starting frequency f of the transmitted frequency modulated signal FM,1,trans initialized to: 0 < f FM,1,trans < f s a positive real number smaller than f / 2, wherein f s is the sampling frequency; (ii) the transmitted frequency-modulated signal has a cut-off frequency f FM,2,trans initialized to: 0 < f FM,2,trans f s a positive real number less than 1 / 2; ③ Transmit the frequency-modulated signal pulse width N FM,trans initialized to: 0 < N FM,trans ≤ N - N CW,trans positive real number; • the frequency width limit parameter λ f initialized to: 0 < λ f a positive real number; • time-frequency distribution time width parameter λ t initialized to: 0 < λ t a positive real number; (5-2) Calculate the frequency range f of the received frequency modulation signal FM,recv : ； where η0= f CW,recv f CW,trans is the target detection Doppler factor, min{·} and max{·} denote the minimum and maximum functions, respectively; (5-3) Calculate the range n of the time of receiving the frequency-modulated signal FM,recv : ； wherein n CW,recv (1) and n CW,recv (2) represent the 1st and 2nd elements of the received single-frequency signal time existence range n CW,recv , respectively; (5-4) Calculate the window length N of the time-frequency distribution of the received frequency modulation signal FM,window and the step N of the time-frequency distribution of the received frequency modulation signal FM,step : ； where f FM,recv (1) and f FM,recv (2) represent the 1st and 2nd elements of the received frequency range f FM,recv of the frequency modulation signal, respectively, and round{·} and floor{·} represent the rounding and floor functions, respectively. (5-5) Calculate the starting index L of the frequency point of the received frequency modulation signal FM,start and the total number L of frequency points of the received frequency modulation signal FM,total : ； wherein f FM,range is the received frequency range of the frequency modulated signal, f FM,range (1) is the first element of f FM,range (1) = min{f s / 2, max{0, (1+λ f ) f FM,recv (1) - λ f f FM,recv (2)}, f FM,range (2) is the second element of f FM,range (2) = min{f s / 2, (1+λ f ) f FM,recv (2) - λ f f FM,recv (1)}, f FM,recv (1) and f FM,recv (2) are the first and second elements of the received frequency range f FM,recv , respectively; (5-6) Calculating the total number of frames M when receiving the time-frequency distribution of the frequency modulation signal FM : ； (5-7) Extracting the received frequency-modulated signal segment data sequence y FM,0 (r FM ), y FM,1 (r FM ), …, ,…, where the m FM th received frequency-modulated signal segment data sequence is wherein r FM is a time index of the segment of the time-frequency distribution of the received frequency-modulated signal, m FM is a time frame index of the time-frequency distribution of the received frequency-modulated signal, m FM = 0, 1,..., M FM - 1, n FM,recv (1) is the first element of the range n FM,recv of the time of presence of the received frequency-modulated signal calculated in step (5-3); (5-8) Calculate and output the time-frequency distribution (TF) of the received frequency-modulated signal FM (m FM , l FM ): wherein, l FM is the frequency point index of the received frequency modulation signal, j is the imaginary unit, i.e. , |·| is the modulo function.

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