CN103529441B - Method and system for detecting and distinguishing passive synthetic aperture target signal - Google Patents

Abstract

The present invention provides a method and a system for detecting and distinguishing a passive synthetic aperture target signal, wherein the method comprises the following steps: step 101) constructing a motion doppler receiving model for a target signal under motion of a towed array sonar; step 102) respectively performing cross correlation averaging on target signals which are received by a hydrophone at an overlapping part on spatial position according to a passive synthetic aperture sonar algorithm when the array performs two successive motions in a fixed time interval, and then performing frequency domain wave beam forming treatment on the target signals which are received by array elements at different time periods; step 103) performing energy integration on the output sub-frequency-bands after forming of the frequency domain wave beam for obtaining wave beam output of each time interval; step 104) performing phase estimation on time delay and spatial position movement according to the doppler receiving model, and acquiring a phase correction factor according to the phase estimation; and step 105) compensating the wave beam output through each phase correction factor of time interval, and performing cross combined accumulation on the compensated wave beam output and realizing detection on the target through a time orientation process map.

Description

A kind of passive synthetic aperture target echo detection and resolving method and system

Technical field

The present invention relates to underwater sound Passive Sonar Signal detection method and drag linear array passive synthetic aperture sonar (Passive Synthetic Aperture Sonar, PSAS) technology is used for the algorithm of target echo detection and resolution, particularly relates to the non-overlapped aperture of a kind of motion and drags linear array passive synthetic aperture signal detecting method and system.

Background technology

In recent years, the detection of passive sonar systems to low noise target becomes more and more important, and more and more difficult, and its detectability is subject to serious challenge along with the appearance of calm type target and fast development.Make a general survey of sonar development history, high-resolution and high-gain are the targets that sonar field is pursued always, for improving fractal dimension, its working frequency range is more and more lower, and improve bearing resolution under low frequency condition and mean longer hydrophone array, but due to the restriction of the stability in towing process and maneuverability, it is unpractical that basic matrix length is increased to too large magnitude, passive synthetic aperture algorithm is a kind of important means of head it off, it obtains the synthetic aperture array more much bigger than effective aperture by towing line array motion synthesis, rely on the restriction of the motor-driven breakthrough array aperture of short battle array, obtain the bearing resolution of higher gain and Geng Gao.Learning that the blade cutting seawater of screw propeller produces the line spectrum compositions such as simple signal component according to target characteristics analysis such as naval vessels is under water that synthesis one effective aperture more much bigger than physical pore size provides possibility, passive synthetic aperture sonar technique implementation method is when array moves for twice in succession, cross-correlation is done to the nautical receiving set Received signal strength of lap on locus average, as the phase correction term of this underlapped nautical receiving set Received signal strength rear, what the coherent combination that the wave beam of this phase correction term in gust sequential positions of moving exports can be expanded drags linear array equivalent length.Due to the array movement deviation that medium and path disturbance under actual underwater complex environment cause, the compensation of conventional passive synthetic aperture sonar algorithm phase only pupil filter is on two continuous positions fixed interval time, array element not exclusively overlaps before and after aperture, the phase estimation factor is made to occur error even mistake, namely PSAS algorithm drags linear dimension algorithm to carry out having overlapping element position restricted problem in array extension as expansion, causes effectively detecting and differentiating Underwater Target Signal.Overlapping array element (aperture) passive synthetic aperture sonar algorithm is generally used for detection and the resolution of ideally echo signal, consider the effect of complicate factors such as underwater acoustic channel, when dragging linear array to maintain constant speed to ensure continuous coverage in practical application, locus identical being difficult to of overlap nautical receiving set meets, not there is feasibility, versatility and practicality, the detection of passive synthetic aperture sonar normal signal and resolving method rationally can not be applied in engineering.

Summary of the invention

The object of the invention is to, the shorter basic matrix of passive sonar towing line array application obtains gain and the resolving power of the actual physics aperture battle array of several times to tens times, realize the effective detection to weak signal target signal under water, and make passive synthetic aperture technique effectively be applied in engineering reality, namely the invention provides a kind of passive synthetic aperture target echo detection and resolving method and system.

To achieve these goals, the invention provides a kind of passive synthetic aperture target echo detection and resolving method, the method application passive synthetic aperture technique realizes effectively detecting weak signal target signal under water, and described method comprises:

Step 101) be configured in and drag linear array to move the lower motion Doppler to echo signal reception model;

Step 102) according to passive synthetic aperture sonar algorithm utilize drag linear array array twice motion in succession occur at interval at a fixed time time, it is average that the echo signal received the nautical receiving set of lap on locus respectively does cross-correlation, the echo signal being about to receive carries out time segment process, analyze the Received signal strength of often adjacent twice time period, then frequency-domain beamforming process is carried out to the echo signal that each array element of different time sections receives;

Step 103) energy integral is carried out to the output frequency division band after frequency-domain beamforming obtain each time period wave beam and export;

Step 104) receive model by the Doppler dragging linear array to move lower structure, respectively line phase is moved forward into time delay and locus and estimate, and obtain phase correction term according to the phase estimation obtained;

Step 105) each for time segment time phase correction term is used for compensation process 103) wave beam export, wave beam output coherent combination after compensating is added up and then obtains course figure time aziniuth, read orientation, target place, its azimuth recording is carried out processing and differentiating, realizes the detection to target.

In technique scheme, the concrete overlapping number of the nautical receiving set of described lap is the half of dragging the total number of linear array array element.

In technique scheme, described phase correction term be that time delay estimadon and locus travel(l)ing phase are estimated and.

In technique scheme, described step 102) comprise following sub-step further:

Step 102-1) according to passive synthetic aperture sonar algorithm utilize drag linear array array twice motion in succession occur at interval at a fixed time time, respectively cross-correlation is done to the nautical receiving set Received signal strength of lap on locus average, carry out time segment process by Received signal strength, analyze the Received signal strength of often adjacent twice time period;

Wherein, this step also comprises the useful signal in the echo signal adopting the detection of line-spectrum detection strategy to receive;

Step 102-2) then frequency-domain beamforming process is carried out to each array element Received signal strength of different time sections.

In technique scheme, described step 105) comprise following sub-step further:

Step 105-1) according to step 104) " the phase estimation acquisition phase correction term " and the step 103 that obtain) and in " each time period wave beam exports ", time segment process, the phase correction term of each time period is exported with corresponding time period wave beam and carries out process such as being multiplied, namely complete to " time segment each phase correction term be used for compensation process 103) wave beam export ";

Step 105-2) signal of above-mentioned each time period is superposed, namely coherent combination is carried out to the wave beam output after compensation and add up and then obtain course figure time aziniuth;

Step 105-3) course figure wave beam time aziniuth is exported detect again, obtain the corresponding orientation of object beam, be specially: detection orientation corresponding for different frequency bands internal object wave beam is carried out record, quadratic fit is carried out in the orientation stored in each frequency band, according to result of calculation computer azimuth estimation variance, the detection variance thresholding of the orientation estimation variance of calculating and setting is compared, if be less than thresholding, the underwater acoustic target signal result then detected is true, receive Underwater Target Signal really containing underwater acoustic target signal, otherwise testing result is false-alarm, not containing echo signal in the signal received, combine the detection and positioning of echo signal.

The invention provides a kind of passive synthetic aperture target echo detection and resolution system based on said method, this system application passive synthetic aperture technique realizes effectively detecting weak signal target signal under water, and described system comprises:

Acceptance Model sets up module, drags linear array to move the lower motion Doppler to echo signal reception model for being configured in;

First processing module, when dragging linear array array for utilizing according to passive synthetic aperture sonar algorithm twice motion in succession occur at interval at a fixed time, respectively cross-correlation is done to the nautical receiving set Received signal strength of lap on locus average, time segment process is carried out by Received signal strength, analyze the Received signal strength of often adjacent twice time period, then frequency-domain beamforming process is carried out to each array element Received signal strength of different time sections;

Second processing module, obtains each time period wave beam output for carrying out energy integral to the output frequency division band after frequency-domain beamforming;

Space-time phase correction term acquisition module, for receiving model by the Doppler dragging linear array to move lower structure, moving forward into line phase to time delay and locus respectively and estimating, and obtaining phase correction term according to the phase estimation obtained; With

Motion phase error compensation and testing result output module, export for each for time segment time phase correction term being used for compensate described wave beam, carry out coherent combination to the wave beam output after compensation add up and then obtain course figure time aziniuth, obtain the corresponding orientation of object beam by its time bearing history figure again, complete the detection and positioning of echo signal.

In technique scheme, the concrete overlapping number of the nautical receiving set of described lap is the half of dragging the total number of linear array array element.

In technique scheme, described phase correction term be that time delay estimadon and locus travel(l)ing phase are estimated and.

In technique scheme, described first processing module comprises following submodule further:

Time segment process submodule, when dragging linear array array for utilizing according to passive synthetic aperture sonar algorithm twice motion in succession occur at interval at a fixed time, respectively cross-correlation is done to the nautical receiving set Received signal strength of lap on locus average, carry out time segment process by Received signal strength, analyze the Received signal strength of often adjacent twice time period; With

Frequency-domain beamforming submodule, for carrying out frequency-domain beamforming process to each array element Received signal strength of different time sections.

In technique scheme, described motion phase error compensation and testing result output module comprise following submodule further:

Motion phase error compensation submodule, exports for each for time segment phase correction term is compensated wave beam;

Coherent combination process submodule, adds up for carrying out coherent combination to the wave beam output after compensation; With

Testing result output sub-module, for being obtained the corresponding orientation of object beam by course figure time aziniuth, completes the detection and positioning of echo signal.

Wherein, in technique scheme time aziniuth course figure observation be common method in UNDERWATER ACOUSTIC SIGNAL DETECTION, without the need to repeating, be briefly described below: time aziniuth, course figure was formed by carrying out Short Time Fourier Transform to continuous print sampled data, the sample sequence of original signal is carried out sub-frame processing and (as be divided into 100 frames, every frame 2000 points), interframe overlapped 50%, respectively Wave beam forming process is carried out to each frame signal, obtain the corresponding target azimuth of each frame, namely the temporal joint of each frame is obtained course figure time aziniuth.In a word, adopt one time aziniuth course figure can read orientation, target place, follow-up process of fitting treatment and threshold discrimination are carried out in its azimuth recording, the effective detection to target can be realized.

In sum, the invention provides a kind of proposition and a kind ofly drag detection and the resolving method of linear array passive synthetic aperture echo signal based on the non-overlapped aperture of motion, the method is avoided due to complicated Underwater Acoustic Environment impact and makes tow line array be difficult to maintain constant speed, then can not ensure that the locus of overlapping nautical receiving set during continuous coverage is identical, the non-overlapped aperture PSAS algorithm proposed moves front and back array element for twice at adjacent time inter and need not overlap completely, and utilizing time delay and locus to move equiphase modifying factor respectively can fine compensation motion phase error.Described scheme comprises the specificity analysis of the target radiated noise such as naval vessel under water and drags linear array to move the structure of lower motion Doppler Received signal strength model, consider that echo signal can utilize line-spectrum detection technology for detection to useful signal, described method can utilize frequency-domain beamforming to be processed, usually analyze for broadband signal, extract signal in this frequency range, then obtain wave beam to export, simultaneously because target frequency when arraymotion receives Doppler shift can occur, the error that during concrete consideration linear array Received signal strength, Doppler frequency domain is brought, the non-overlapped aperture of described motion is dragged linear array passive synthetic aperture signal detecting method can be directly used in phase delay and is compensated, need not consider that array element is mutually completely overlapping.

Compared with prior art, proposed by the inventionly a kind ofly the detection of linear array passive synthetic aperture echo signal and resolving method is dragged to have the following advantages based on the non-overlapped aperture of motion:

On the one hand, the method is without the need to knowing the position angle of signal source, definite frequency and towed array speed accurately, the reception data of nautical receiving set can be synthesized by phase estimation compensating approach, without the need to guaranteeing that element position must overlap completely, moved by time delay and locus and can obtain phase only pupil filter compensating factor, passive synthetic aperture algorithm application not by the constrained of aperture location, replaces it in Element space enterprising line phase correction at Beam Domain in input, is directly used in phase only pupil filter and compensates;

On the other hand, in conjunction with to the analysis of the target radiated noise characteristic such as naval vessel under water and drag linear array to move the structure of lower motion Doppler Received signal strength model, wherein analyze ship noise characteristic not to be only the passive synthetic aperture technique that underwater propeller cutting forms line spectrum signal and to lay the foundation, and provide theoretical reference for follow-up signal detects to technology such as towing ship noise counteractings; Doppler's Received signal strength model construction of array movement makes clear understanding to signal formation, array element mobile reception etc., and definitely the integrated array Received signal strength of passive synthetic aperture is formed and phase only pupil filter compensation method;

Secondly, in this embodiment containing the error that Doppler frequency domain during linear array Received signal strength is brought, consider its time delay, locus is moved, the phase place that the factors of influence such as Doppler shift bring is inconsistent, as long as move due to time delay and locus and ensure that adjacent time inter moves twice, front and back array and has the aperture length exceeding array length half to overlap and can do correction-compensation to it, refinement need not consider that array moves overlapping positions, more overlap completely without requiring array aperture, avoid the detection signal target azimuth out of true caused because element position movement deviation aperture does not overlap completely, linear array is dragged to move the process of middle Received signal strength time segment, the each array element Received signal strength of linear array basic matrix is dragged to carry out frequency-domain beamforming process to different time sections, and to the output frequency division band after frequency-domain beamforming carry out energy integral can obtain wave beam export,

Finally, drag linear array passive synthetic aperture signal detecting method can be directly used in phase delay due to the non-overlapped motion in aperture to compensate, need not consider that array element is mutually completely overlapping, apply gain and resolving power that shorter basic matrix obtains the actual physics aperture battle array of several times to tens times, excellent to the detectability of weak signal target signal under water, speed, it has certain engineering practicability.

Accompanying drawing explanation

Fig. 1 is that the present invention utilizes horizontal line array to carry out the sketch of walkaway to the radiated noise of submarine target;

Fig. 2 of the present inventionly drags linear array array element to move overlap (aperture completely overlapping) passive synthetic aperture schematic diagram based on motion;

Fig. 3 is that linear array passive synthetic aperture input and resolving method process flow diagram are dragged in the non-overlapped aperture of motion

Embodiment

Below in conjunction with the drawings and specific embodiments, elaborate the method completely overlapping in aperture time phase place correction-compensation workflow.

The present invention proposes a kind of detection and the resolving method that drag linear array passive synthetic aperture echo signal based on the non-overlapped aperture of motion, avoid due to complicated Underwater Acoustic Environment impact and make tow line array be difficult to maintain constant speed, then can not ensure that the locus of overlapping nautical receiving set during continuous coverage is identical, namely the non-overlapped aperture PSAS algorithm proposed moves front and back array element for twice without requiring adjacent time inter and overlaps completely, and space-time unite phase only pupil filter can fine compensation motion phase error to utilize time delay and locus to move respectively etc.The invention provides a kind of passive synthetic aperture algorithm can be directly used in phase delay and compensate, need not consider that array element is mutually completely overlapping, excellent to the detectability of weak signal target signal under water, speed, it has certain engineering practicability.

To achieve these goals, the invention provides the non-overlapped aperture of a kind of motion and drag linear array passive synthetic aperture target echo detection and resolving method, it is characterized in that considering in the complicated Underwater Acoustic Environment of the actual underwater sound that to drag linear array to move irregular when causing array element aperture not exclusively overlapping, effectively can detect weak signal target signal under water, described method comprises following steps:

Step (1) constructs signal dragging linear array to move lower motion Doppler and receives model based on the target radiated noise specificity analysises such as naval vessel under water;

Step (2), on the basis building Signal reception model, considers that linear array will be dragged to move middle actual Received signal strength carries out time segment process, drag each array element Received signal strength of linear array basic matrix to carry out frequency-domain beamforming process to different time sections;

Step (3) is carried out energy integral to the output frequency division band after step (2) frequency-domain beamforming and is obtained wave beam output;

Step (4) is estimated to the time delay caused due to time segment process in step (2) and step (3) and because locus moves forward into line phase respectively;

Each phase correction term of time segment in step (4) is used for step (3) wave beam and exports compensation by step (5), and coherent combination exports and obtains the corresponding orientation of object beam, realizes the effective detection to echo signal.

In technique scheme, the error that when described step (2) and step (3) also consider linear array Received signal strength, Doppler frequency domain is brought, consider time delay, locus is moved, the phase place that the factors of influence such as Doppler shift bring is inconsistent, as long as move due to time delay and locus and ensure that adjacent time inter moves twice, front and back array and has the aperture length exceeding array length half to overlap and can do correction-compensation to it, refinement need not consider that array moves overlapping positions, more overlap completely without requiring array aperture, avoid the detection signal target azimuth out of true caused because element position movement deviation aperture does not overlap completely.

In technique scheme, described step (1) comprises the analysis of ship noise under water further and drags linear array to move the structure of lower motion Doppler Received signal strength model: wherein analyze ship noise characteristic and be not only the passive synthetic aperture technique that underwater propeller cutting forms line spectrum signal and lay the foundation, and provide theoretical reference for follow-up signal detects to technology such as towing ship noise counteractings; Doppler's Received signal strength model construction of array movement makes clear understanding to signal formation, array element mobile reception etc., for the integrated array Received signal strength analysis of passive synthetic aperture and phase compensation indicate thinking.

The mechanical noise of hull, propeller noise and hydrodynamic noise are three kinds of main sources of naval vessel ship noise, and wherein mechanical noise and propeller noise are the main sound source of ship noise.Mechanical noise be navigation or industry naval vessel on various mechanical vibration, by the noise that hull is formed to radiation in water, due to the difference of various mechanical motion form, its underwater radiation noise character produced is also just different, and this noise can regard the superposition of strong line spectrum and weakly continuous spectrum as; Propeller noise is by the noise of the screw propeller institute radiation be rotating, and comprises Propeller Cavitation Noise and propeller blade vibrates the noise produced, the major part of ship-radiated noise high band often; Hydrodynamic noise is flow through motion marine surfaces by ocean current that is irregular, that rise and fall and is formed, and is the result that flow dynamic acts on naval vessel, in intensity generally by mechanical noise and propeller noise cover.

Warship radiated noise spectral property and frequency, the speed of a ship or plane, the degree of depth are relevant under water, and the low frequency end composed during the low speed of a ship or plane is mainly mechanical noise and propeller blade speed spectral line, and along with frequency increases, this spectral line reduces brokenly; When the speed of a ship or plane is higher, the continuous spectrum of Propeller Cavitation Noise is even more important, masks a lot of line spectrum.Total power spectrum of ships radiated noise signal can be write as broadband continuous spectrum and line spectrum and:

G(t,f)=G _s(f)+G _L(f)+2m(t)m(f)G _s(f)

G in formula _sf () represents stable and continuous power spectrum, G _lf () represents line spectrum part, 2m (t) m (f) G _sf () represents non-stationary time varying spectrum, m (t) and m (f) is respectively modulating function and depth of modulation spectrum.For ship-radiated noise, under the given speed of a ship or plane and the degree of depth, the principal ingredient of spectrum is relevant with threshold frequency, common naval vessel threshold frequency is between 100 ~ 1000Hz, during lower than this frequency, the machinery of ship and the line spectrum of screw propeller during the principal ingredient of composing, during higher than this frequency, the principal ingredient of spectrum is then the continuing noise spectrum of propeller cavitation.Show according to research, the frequency domain characteristic of ship-radiated noise is the superposition of broadband continuous spectrum and arrowband line spectrum, and arrowband spectral line mainly concentrates on below 1kHz, and broadband continuous spectrum then covers multiple octave.

Because echo signal and Receiving Array Hydrophone move mutually in actual measurement, there is Doppler signal Receiver Problem.Fig. 1 (illustrating see accompanying drawing) for utilizing horizontal line array to carry out the sketch of walkaway to the radiated noise of submarine target, through horizontal line array, sample to noise signal, completes the detection to noise source by naval vessel or measured target.For the linear array that N number of primitive forms, because the existence of towed speed is moved mutually, make the signal that receives and radiation sound source there is the inconsistent situation of frequency, and relative sound source motion receive frequency uprise, and deviates from sound source motion receive frequency step-down.

Can be expressed as radiated noise signals s (t) complex envelope

$s\left(t\right)=\mathrm{Re}\left[\stackrel{\·}{s}\left(t\right)e^{j2\mathrm{\π}{f}_{c}t}\right]$

Signal arrives receiving hydrophone through certain time-delay, and N number of array element superposition forms f (t)

$f\left(t\right)=\underset{n=1}{\overset{N}{\mathrm{\Σ}}}{a}_n\left(t\right)s(t-\frac{x_n}{c})$

$=\mathrm{Re}\left[\underset{n=1}{\overset{N}{\mathrm{\Σ}}}{a}_n\left(t\right)\stackrel{\·}{s}(t-\mathrm{\τ}\left(n\right))e^{j2\mathrm{\π}{f}_c(t-\mathrm{\τ}\left(n\right))}\right]$

When receiving battle array and moving with speed v, each run duration is △ t, and angle is a _n, corresponding path changes in time

△x _n=v△tcosa _n

Receiving signal is

$f\left(t\right)=\mathrm{Re}\left[\underset{n=1}{\overset{N}{\mathrm{\Σ}}}{a}_n\left(t\right)\stackrel{\·}{s}(t-\frac{x_n-{\mathrm{\Δx}}_n}{c})e^{j2\mathrm{\π}{f}_c(t-\frac{x_n-{\mathrm{\Δx}}_n}{c})}\right]$

$=\mathrm{Re}\left[\underset{n=1}{\overset{N}{\mathrm{\Σ}}}{a}_n\left(t\right)\stackrel{\·}{s}(t-\frac{x_n}{c}+\frac{\mathrm{v\Δ}t\cos {\mathrm{\α}}_n}{c})e^{j2\mathrm{\π}{f}_c(t-\frac{x_n}{c}+\frac{\mathrm{v\Δ}t\cos {\mathrm{\α}}_n}{c})}\right]$

Consider drag linear array to echo signal motion receive, due to sampling time interval sequence variation, can cause receive frequency and echo signal frequency inconsistent.

Step (2) and step (3) will drag linear array to move the process of middle Received signal strength time segment, drag each array element Received signal strength of linear array basic matrix to carry out frequency-domain beamforming process to different time sections, and to the output frequency division band after frequency-domain beamforming carry out energy integral obtain wave beam export.The object that sonar wave beams is formed is that the linear array that forms multiple primitive obtains directive property in a predetermined direction through suitable process, echo signal can utilize line-spectrum detection technology for detection to useful signal, utilize frequency-domain beamforming to be processed further, be usually directed to target zone f _min~ f _maxbroadband signal can be analyzed the signal of frequency range, extract signal in this frequency range, then obtain wave beam to export, because when arraymotion receives, target frequency Doppler shift can occur, namely receive frequency and echo signal inconsistent, so the error that when specifically should consider linear array Received signal strength, Doppler frequency domain is brought.

Drag linear array for passive synthetic aperture principle schematic as Fig. 2 (illustrating see accompanying drawing), be applied to passive synthetic aperture normal signal detection algorithm, array number is the towed array array element distance of N is d, and movement velocity is v.In the t=0 moment, N unit basic matrix carries out spatial sampling to sound field, after τ second, basic matrix displacement is v τ, selects rational parameter v, makes basic matrix in mobile q primitive position time interval τ second, after motion J τ, expand to (N+Jq) individual array element and namely can be considered a virtual array.For the linear array being at equal intervals spaced apart d that is made up of N number of nautical receiving set, drag forward with speed v, consider single-point sound source under water, consider Doppler contribution, Received signal strength sample frequency is f _s, sampling time interval is T _s=1/f _s, actual signal sampling time interval is t _i, the time samples of each nautical receiving set can be expressed as:

x _n(t _i)=Aexp[j2πf(t _i-τ _n)]+ξ _n,j

N=1 in formula, 2 ... N, array element; A-amplitude; F-frequency; t _i-the i-th sampling time, τ _nbe No. n-th nautical receiving set relative to No. 1 nautical receiving set time delay, as shown in Figure 1,

τ _n=(R _n-R ₁)/c

Wherein ξ _n,jit is independent, zero-mean gaussian random noise.

Linear array will be dragged to move the process of middle Received signal strength time segment, and single nautical receiving set seasonal effect in time series Fourier transform is

$X_n\left(f\right)=\underset{i=1}{\overset{J}{\mathrm{\Σ}}}{x}_n\left(t_i\right)\exp (-j2\mathrm{\π}{\mathrm{ft}}_i)$

The each array element Received signal strength of linear array basic matrix is dragged to carry out frequency-domain beamforming process, at moment t to different time sections ₀wave beam export be:

$b{(f_0,{\mathrm{\θ}}_s)}_{t_0}=\underset{n=1}{\overset{N}{\mathrm{\Σ}}}{X}_n\left(f_0\right)\exp \left[j2\mathrm{\π}{f}_0\frac{d(n-1)\sin {\mathrm{\θ}}_s}{c}\right]$

θ in formula _sthe angle of change.At t=t _iin+τ the moment, battle array response is:

$b{(f_0,{\mathrm{\θ}}_s)}_t=\underset{n=1}{\overset{N}{\mathrm{\Σ}}}\left\{\underset{i=2}{\overset{J}{\mathrm{\Σ}}}{x}_n(t_i+\mathrm{\τ})\exp (-j2\mathrm{\π}{f}_0{t}_i)\right\}\exp \left[j2\mathrm{\π}{f}_0\frac{d(n-1)\sin {\mathrm{\θ}}_s}{c}\right]$

Can draw:

$b{(f_0,{\mathrm{\θ}}_s)}_t=b{(f_0,{\mathrm{\θ}}_s)}_{t_0}\exp \left[j2\mathrm{\π}{f}_0(\mathrm{\τ}-\frac{\mathrm{v\τ}\sin \mathrm{\θ}}{c})\right]$

After J τ second, arraymotion distance is vJ τ, therefore at moment t _i+ l τ expression formula is:

$B{(f_0,{\mathrm{\θ}}_s)}_{\mathrm{J\τ}}=\underset{i=1}{\overset{J}{\mathrm{\Σ}}}b{(f_0,{\mathrm{\θ}}_s)}_{\mathrm{i\τ}}\exp [-j{\mathrm{\Φ}}_i]$

In formula: i-beamlet produces synthetic aperture wave beam and exports after J phase compensation also relevant summation, i=1 ..., J, Φ _i-phase correction term, ${\mathrm{\Φ}}_i=2\mathrm{\π}{f}_0(1\±\frac{v\sin {\mathrm{\θ}}_s}{c})\mathrm{i\τ}.$

Motion drags overlapping array element number in linear array passive synthetic aperture method directly to determine the estimated result of phase correction term, it is average that conventional passive synthetic aperture algorithm requires that array does cross-correlation to the nautical receiving set Received signal strength of lap on locus when in succession moving for twice, array element should be completely overlapping using the accurate phase correction term as Received signal strength on rear underlapped nautical receiving set, and optimum superposing array element number is N/2.Actual basic matrix due to the impact of the disturbance by underwater complex surrounding medium and path, can not make array in succession accurately reach coincidence before and after twice motion when moving.The one proposed non-overlapped aperture of moving drags linear array passive synthetic aperture signal detecting method can be directly used in phase delay to compensate, need not consider that array element is mutually completely overlapping, replace it in the enterprising line phase correction of Element space at Beam Domain.

T=0 moment n array element receives signal x _n(t _i), make M point FFT to it, corresponding kth array element is X ₀(k, K), K=1 ..., M, after making frequency-domain beamforming further, each array element exports cumulative, and each array element being exported does to add up is converted to Beam Domain by it by Element space:

$S_0=\underset{k=1}{\overset{N}{\mathrm{\Σ}}}{X}_0(k,K)\exp [-j2\mathrm{\π}(K-1)\frac{\mathrm{fs}}{M}(k-1)\mathrm{\Δ\τ}]$

F in formula _s-sample frequency, equally by the signal x after motion τ second _n(t _i+ τ), make M point FFT to it, corresponding kth array element is X ₁(k, K), K=1 ..., M, integrating step (2), (3) after making frequency-domain beamforming further each array element export cumulative, have:

$S_1=\underset{k=1}{\overset{N}{\mathrm{\Σ}}}{X}_1(k,K)\exp [-j2\mathrm{\π}(K-1)\frac{\mathrm{fs}}{M}(k-1)\mathrm{\Δ\τ}]$

In technical scheme, step (4) moves forward into line phase to time delay and locus respectively and estimates, for keeping phase place consistent, to move respectively and time delay variation is paid attention to locus, to S after motion τ second ₁compensate, space motion compensation, move distance is v τ, can be the non-integral multiple of each array element distance d at this v τ,

$P_1=S_1\·\exp [-j2\mathrm{\π}(K-1)\frac{\mathrm{fs}}{M}\frac{\mathrm{v\τ}}{d}\mathrm{\Δ\τ}]$

Consider time delay equalization, move τ second, have:

$P_2=S_1\·\exp [-j2\mathrm{\π}(K-1)\frac{\mathrm{fs}}{M}\mathrm{\τ}]$

Combine and consider space and time upper change, i.e. time delay and locus travel(l)ing phase correction, by P ₁and P ₂be added, obtain array and move the total phase only pupil filter compensation in front and back:

P ₀=P ₁+P ₂

Described protocol step (5) considers that each for time segment time phase correction term being used for wave beam exports compensation, and coherent combination exports and obtains the corresponding orientation of object beam, realizes the effective detection to echo signal.Total phase only pupil filter compensates and cumulatively obtains corresponding synthesis and export relevant with angle, and Virtual array length is v τ, and namely after expansion, array element total length is Nd+v τ, and with this after the J τ second of moving, N array element basic matrix expands to the linear array that length is Nd+vJ τ.The cumulative output of coherent combination is the non-overlapped aperture of motion and drags linear array passive synthetic aperture detection method thus, because passive synthetic aperture algorithm need not consider that array element is mutually completely overlapping before and after mobile, directly can carry out phase only pupil filter compensation, thus realize the effective detection to echo signal.

In technique scheme, linear array passive synthetic aperture input and resolving method process flow diagram is dragged (to illustrate see accompanying drawing) as shown in Figure 3 for non-overlapped aperture of moving, successively ship-radiated noise characteristic is analyzed and build signal drag linear array move lower motion Doppler receive model, and receive an array element Received signal strength time segment process in linear array being dragged to move on this Signal reception model basis, the each array element Received signal strength of linear array basic matrix is dragged to carry out frequency-domain beamforming process to different time sections, consider the factor impacts such as Doppler shift, energy integral is carried out for the output frequency division band after frequency-domain beamforming and obtains wave beam output further, tectonic model is received in conjunction with the signal movement built, move forward into line phase to time delay and locus respectively to estimate, last just time segment each phase correction term is used for the phase compensation correction that wave beam exports, namely the coherent combination output that adds up obtain the corresponding orientation of object beam, thus the effective detection realized echo signal.

In such scheme, comprise the analysis of the target radiated noise such as naval vessel under water and drag linear array to move the structure of lower motion Doppler Received signal strength model, wherein analyze ship noise characteristic not to be only the passive synthetic aperture technique that underwater propeller cutting forms line spectrum signal and to lay the foundation, Doppler's Received signal strength model construction of linear array array movement makes clear understanding to signal formation, array element mobile reception etc., and definitely the integrated array Received signal strength of passive synthetic aperture is formed and phase only pupil filter compensation method.For the error that Doppler frequency domain during linear array Received signal strength is brought, consider time delay, phase place that the factor of influence such as locus is moved, Doppler shift brings is inconsistent.

As shown in Figure 1, this figure is that the present invention utilizes horizontal line array to carry out the sketch of walkaway to the radiated noise of submarine target, when naval vessel or measured target are under water through horizontal line array, towing line array is sampled to noise signal, the motion of nautical receiving set array element finishes receiving the detection to noise source, each nautical receiving set numbering is respectively No. 1 nautical receiving set, No. 2 nautical receiving sets, (N-1) number nautical receiving set, N nautical receiving set, the regular hour is had to postpone between each nautical receiving set Received signal strength when not moving, namely Received signal strength form is identical, phase place is different, consider underwater ambient noise, analyze the target radiated noise characteristic such as naval vessel under water, build linear array and be in resting state Received signal strength model.

The present invention proposes the non-overlapped aperture of a kind of motion and drags linear array passive synthetic aperture target echo detection and resolving method, when consider in the complicated Underwater Acoustic Environment of the actual underwater sound drag linear array move irregular cause array element aperture not exclusively overlapping, application passive synthetic aperture technique realizes effectively detecting weak signal target signal under water, on the basis building linear array resting state Received signal strength model, carry out subsequent treatment as follows:

Step (1) is configured in drags linear array to move the lower motion Doppler to echo signal reception model;

During twice motion in succession that step (2) utilizes array to determine in the time interval according to passive synthetic aperture sonar algorithm, cross-correlation is done to the nautical receiving set Received signal strength of lap on locus average, time segment process is carried out by Received signal strength, analyze the Received signal strength of often adjacent twice time period, and frequency-domain beamforming process is carried out to each array element Received signal strength of different time sections;

Step (3) is carried out energy integral to the output frequency division band after frequency-domain beamforming and is obtained each time period wave beam output;

Step (4) receives model by the Doppler dragging linear array to move lower structure, moves forward into line phase respectively estimate time delay and locus;

Each for time segment time phase correction term is used for wave beam and exports compensation by step (5), and cumulative output of coherent combination obtains the corresponding orientation of object beam by its time bearing history figure.

Motion Doppler frequency displacement is there is when step (1) considers linear array Received signal strength in such scheme, linear array passive synthetic aperture algorithm is built by each time of reception section Received signal strength as shown in Figure 2 when wherein array element moves, the t=0 moment, N unit basic matrix carries out spatial sampling to sound field, after τ second, mobile q primitive position (aperture can be not exclusively overlapping), after motion J τ, expands to (N+Jq) individual array element and namely can be considered a virtual array.Step (2), (3) error that during consideration linear array Received signal strength, Doppler frequency domain is brought, as long as move due to time delay and locus when linear array motion Received signal strength and ensure that adjacent time inter moves twice, front and back array and has the aperture length exceeding array length half to overlap and can do correction-compensation to it, combine and consider space and time upper change, i.e. time delay and locus travel(l)ing phase correction, time delay and locus travel(l)ing phase correction-compensation are added, obtain array and move the total phase only pupil filter compensation in front and back, then each for time segment time phase correction term is used for wave beam and exports compensation, coherent accumulation array output obtains the corresponding orientation of object beam, realize the effective detection to echo signal.

As shown in Figure 3, this figure is that linear array passive synthetic aperture input and resolving method process flow diagram are dragged in the non-overlapped aperture of motion, in conjunction with to dragging linear array to move the irregular situation passive synthetic aperture causing array element aperture not exclusively overlapping for signal detecting method in the complicated Underwater Acoustic Environment of the actual underwater sounds of the analysis integrated consideration of target radiated noise such as naval vessel under water, move lower motion Doppler to dragging linear array and receive model construction, split-band, time segment wave beam export, time delay and locus travel(l)ing phase are estimated, phase only pupil filter compensates and does concrete elaboration for the synthesis of steps such as outputs.

In a word, core of the present invention is: first, utilizes ship-radiated noise specificity analysis, completes the structure to dragging linear array to move the lower motion Doppler to signal reception model; Secondly, when considering Doppler shift, time segment carries out frequency-domain beamforming process to each array element Received signal strength, and split-band is carried out energy integral and obtained each time period wave beam output; Then, when utilizing linear array Signal reception motion Doppler model to consider that array element aperture is not exclusively overlapping, as long as move due to time delay and locus and ensure that adjacent time inter moves twice, front and back array and has the aperture length exceeding array length half to overlap and can do correction-compensation to it, further illustrate and need not overlap completely by refinement requirement array aperture, meet underwater complex Underwater Acoustic Environment situation on drag linear array move along a straight line produce impact, realistic service condition; Finally, Doppler frequency deviation and ship noise radiation characteristic is under water considered in passive synthetic aperture signal detecting method based on the non-overlapped aperture of motion, be beneficial to the reasonable employment of the methods such as motor message detection and towing ship noise counteracting, there is certain engineering practicability.

Embodiment

As shown in Figure 1, naval vessel or measured target are through horizontal line array under water, and each array element is sampled to noise signal, because the existence of towed speed is moved mutually, make the signal that receives and radiation sound source there is the inconsistent situation of frequency.Composition graphs 2 linear array basic matrix does rectilinear motion, for N number of be equidistantly the isotropy linear array of d, speed is v, receives ships radiated noise signal for normative reference with t=0 moment the 1st array element, 2nd array element is △ τ relative to the 1st array element propagation delay, then the n-th array element receives signal and is

x _n(t _i)=Aexp[j2πf(t _i-τ _n)]+ξ _n(t _i)

A-amplitude in formula; F-frequency; t _i-the i-th sampling time, τ _nbe that No. n-th nautical receiving set array element is relative to the 1st array element propagation delay

τ _n=(R _n-R ₁)/c

ξ _n(t _i) represent independent zero-mean ambient sea noise.

With after speed v motion τ second, the n-th array element receives signal and is

x _n(t _i+τ)=Aexp[j2πf(t _i+τ-τ _n(t _i+τ))]+ξ _n(t _i+τ)

Consider the t=0 moment, linear array will be dragged to move the process of middle Received signal strength time segment, for each nautical receiving set seasonal effect in time series Fourier transform be

$X_n\left(f\right)=\underset{i=1}{\overset{J}{\mathrm{\Σ}}}{x}_n\left(t_i\right)\exp (-j2\mathrm{\π}{\mathrm{ft}}_i)$

The each array element Received signal strength of linear array basic matrix is dragged to carry out frequency-domain beamforming process, at moment t to different time sections ₀wave beam export be:

$b{(f_0,{\mathrm{\θ}}_s)}_{t_0}=\underset{n=1}{\overset{N}{\mathrm{\Σ}}}{X}_n\left(f_0\right)\exp \left[j2\mathrm{\π}{f}_0\frac{d(n-1)\sin {\mathrm{\θ}}_s}{c}\right]$

θ in formula _sthe angle of change.At t=t _iin+τ the moment, battle array response is:

$b{(f_0,{\mathrm{\θ}}_s)}_t=\underset{n=1}{\overset{N}{\mathrm{\Σ}}}\left\{\underset{i=2}{\overset{J}{\mathrm{\Σ}}}{x}_n(t_i+\mathrm{\τ})\exp (-j2\mathrm{\π}{f}_0{t}_i)\right\}\exp \left[j2\mathrm{\π}{f}_0\frac{d(n-1)\sin {\mathrm{\θ}}_s}{c}\right]$

When towboat continues, by speed v motion, continuously spatial information to be synthesized Virtual array, when phase correction term is estimated accurate, the virtual synthetic aperture obtained can be equivalent to the physical pore size that actual array element is formed.Consider the impact due to the disturbance by underwater complex surrounding medium and path when moving of actual basic matrix, array accurately can not reach coincidence before and after twice motion in succession.When considering that array element is mutually completely overlapping, replace it in the enterprising line phase correction of Element space at Beam Domain.T=0 moment n array element receives signal x _n(t _i), make M point FFT to it, corresponding kth array element is X ₀(k, K), after different time sections being dragged linear array basic matrix each array element Received signal strength to carry out frequency-domain beamforming process, each array element exports cumulative, and each array element being exported does to add up is converted to Beam Domain by it by Element space:

$S_0=\underset{k=1}{\overset{N}{\mathrm{\Σ}}}{X}_0(k,K)\exp [-j2\mathrm{\π}(K-1)\frac{\mathrm{fs}}{M}(k-1)\mathrm{\Δ\τ}]$

F _s-sample frequency, equally by the signal x after motion τ second _n(t _i+ τ), make M point FFT to it, corresponding kth array element is X ₁(k, K), K=1 ..., M, after different time sections being dragged linear array basic matrix each array element Received signal strength to make frequency-domain beamforming equally, each array element exports cumulative:

$S_1=\underset{k=1}{\overset{N}{\mathrm{\Σ}}}{X}_1(k,K)\exp [-j2\mathrm{\π}(K-1)\frac{\mathrm{fs}}{M}(k-1)\mathrm{\Δ\τ}]$

Move forward into line phase to time delay and locus respectively to estimate, keeping on the consistent basis of phase place, respectively locus to be moved and time delay variation is paid attention to, to S after motion τ second ₁compensate, space motion compensation, move distance is v τ, can be the non-integral multiple of each array element distance d at this v τ,

$P_1=S_1\·\exp [-j2\mathrm{\π}(K-1)\frac{\mathrm{fs}}{M}\frac{\mathrm{v\τ}}{d}\mathrm{\Δ\τ}]$

Time delay equalization, move τ second, have:

$P_2=S_1\·\exp [-j2\mathrm{\π}(K-1)\frac{\mathrm{fs}}{M}\mathrm{\τ}]$

Combine and consider space and time upper change, i.e. time delay and locus travel(l)ing phase correction, by P ₁and P ₂be added, obtain array and move the total phase only pupil filter compensation in front and back:

P ₀=P ₁+P ₂

Each phase correction term is used for wave beam and exports compensation, associating time, space phase correction-compensation, the coherent combination output that adds up obtains the corresponding orientation of object beam, total phase only pupil filter compensates and cumulatively obtains corresponding synthesis and export relevant with angle, Virtual array length is v τ, namely after expansion, array element total length is Nd+v τ, and with this after motion J τ second, N array element basic matrix expands to the linear array that length is Nd+vJ τ.The cumulative output of coherent combination is the non-overlapped aperture of motion and drags linear array passive synthetic aperture detection method thus, because passive synthetic aperture algorithm need not consider that array element is mutually completely overlapping before and after mobile, directly can carry out phase only pupil filter compensation, thus realize the effective detection to echo signal.

In a word, the invention discloses a kind of detection and the resolving method that drag linear array passive synthetic aperture echo signal based on the non-overlapped aperture of motion, utilize the target radiated noise specificity analysis such as naval vessel under water, complete the structure to dragging linear array to move the lower motion Doppler to signal reception model, avoid due to complicated Underwater Acoustic Environment impact and make tow line array be difficult to maintain constant speed, then can not ensure that the locus of overlapping nautical receiving set during continuous coverage is identical, the non-overlapped aperture passive synthetic aperture algorithm adjacent time inter proposed moves front and back array element for twice and need not overlap completely, utilizing time delay and locus to move equiphase modifying factor respectively can fine compensation motion phase error.As long as move due to time delay and locus and ensure that adjacent time inter moves twice, front and back array and has the aperture length exceeding array length half to overlap and can do correction-compensation to it, meet underwater complex Underwater Acoustic Environment situation on drag linear array move along a straight line produce impact, the testing conditions of the echo signals such as realistic naval vessel under water, is beneficial to and effectively detects calm type weak signal target signal under water and differentiate.

Other guide in specification documents, for the those of ordinary skill in this professional domain, all can carry out technology realization, repeat no more here.It should be noted last that, above embodiment is only in order to illustrate technical scheme of the present invention and unrestricted.Although with reference to embodiment to invention has been detailed description, those of ordinary skill in the art is to be understood that, modify to technical scheme of the present invention or equivalent replacement, do not depart from the spirit and scope of technical solution of the present invention, it all should be encompassed in the middle of right of the present invention.

Claims (10)

1. passive synthetic aperture target echo detection and a resolving method, the method application passive synthetic aperture technique realizes effectively detecting weak signal target signal under water, and described method comprises:

Step 101) be configured in and drag linear array to move the lower motion Doppler to echo signal reception model;

Step 102) according to passive synthetic aperture sonar algorithm utilize drag linear array array twice motion in succession occur at interval at a fixed time time, it is average that the echo signal received the nautical receiving set of lap on locus respectively does cross-correlation, the echo signal being about to receive carries out time segment process, analyze the Received signal strength of often adjacent twice time period, then frequency-domain beamforming process is carried out to the echo signal that each array element of different time sections receives;

Step 103) energy integral is carried out to the output frequency division band after frequency-domain beamforming obtain each time period wave beam and export;

Step 104) receive model by the Doppler dragging linear array to move lower structure, respectively line phase is moved forward into time delay and locus and estimate, and obtain phase correction term according to the phase estimation obtained;

Step 105) each for time segment time phase correction term is used for compensation process 103) wave beam export, wave beam output coherent combination after compensating is added up and then obtains course figure time aziniuth, read orientation, target place, its azimuth recording is carried out processing and differentiating, realizes the detection to target.

2. passive synthetic aperture target echo detection according to claim 1 and resolving method, it is characterized in that, the concrete overlapping number of the nautical receiving set of described lap is the half of dragging the total number of linear array array element, and when can effectively avoid ensureing continuous coverage owing to dragging linear array to be difficult to maintain constant speed, the locus of nautical receiving set is completely overlapping.

3. passive synthetic aperture target echo detection according to claim 1 and resolving method, is characterized in that, described phase correction term be that time delay estimadon and locus travel(l)ing phase are estimated and.

4. passive synthetic aperture target echo detection according to claim 1 and resolving method, is characterized in that, described step 102) comprise following sub-step further:

Step 102-1) according to passive synthetic aperture sonar algorithm utilize drag linear array array twice motion in succession occur at interval at a fixed time time, respectively cross-correlation is done to the nautical receiving set Received signal strength of lap on locus average, carry out time segment process by Received signal strength, analyze the Received signal strength of often adjacent twice time period;

Wherein, this step also comprises the useful signal in the echo signal adopting the detection of line-spectrum detection strategy to receive;

Step 102-2) then frequency-domain beamforming process is carried out to each array element Received signal strength of different time sections.

5. passive synthetic aperture target echo detection according to claim 1 and resolving method, is characterized in that, described step 105) comprise following sub-step further:

Step 105-1) according to step 104) " the phase estimation acquisition phase correction term " and the step 103 that obtain) and in " each time period wave beam exports ", time segment process, the phase correction term of each time period and corresponding time period wave beam are exported to carry out being multiplied and process, namely complete to " time segment each phase correction term be used for compensation process 103) wave beam export ";

Step 105-2) signal of above-mentioned each time period is superposed, namely coherent combination is carried out to the wave beam output after compensation and add up and then obtain course figure time aziniuth;

Step 105-3) course figure wave beam time aziniuth is exported detect again, obtain the corresponding orientation of object beam, be specially: detection orientation corresponding for different frequency bands internal object wave beam is carried out record, quadratic fit is carried out in the orientation stored in each frequency band, according to result of calculation computer azimuth estimation variance, the detection variance thresholding of the orientation estimation variance of calculating and setting is compared, if be less than thresholding, the underwater acoustic target signal result then detected is true, receive Underwater Target Signal really containing underwater acoustic target signal, otherwise testing result is false-alarm, not containing echo signal in the signal received, combine the detection and positioning of echo signal.

6. drag linear array to move the passive synthetic aperture target echo detection in non-overlapped aperture and a resolution system, this system application passive synthetic aperture technique realizes effectively detecting weak signal target signal under water, and described system comprises:

Acceptance Model sets up module, drags linear array to move the lower motion Doppler to echo signal reception model for being configured in;

First processing module, when dragging linear array array for utilizing according to passive synthetic aperture sonar algorithm twice motion in succession occur at interval at a fixed time, respectively cross-correlation is done to the nautical receiving set Received signal strength of lap on locus average, time segment process is carried out by Received signal strength, analyze the Received signal strength of often adjacent twice time period, then frequency-domain beamforming process is carried out to each array element Received signal strength of different time sections;

Second processing module, obtains each time period wave beam output for carrying out energy integral to the output frequency division band after frequency-domain beamforming;

Space-time phase correction term acquisition module, for receiving model by the Doppler dragging linear array to move lower structure, moving forward into line phase to time delay and locus respectively and estimating, and obtaining phase correction term according to the phase estimation obtained; With

Motion phase error compensation and testing result output module, export for each for time segment time phase correction term being used for compensate described wave beam, carry out coherent combination to the wave beam output after compensation add up and then obtain course figure time aziniuth, obtain the corresponding orientation of object beam by its time bearing history figure again, complete the detection and positioning of echo signal.

7. passive synthetic aperture target echo detection according to claim 6 and the system of resolution, it is characterized in that, the concrete overlapping number of the nautical receiving set of described lap is the half of dragging the total number of linear array array element.

8. passive synthetic aperture target echo detection according to claim 6 and the system of resolution, is characterized in that, described phase correction term be that time delay estimadon and locus travel(l)ing phase are estimated and.

9. passive synthetic aperture target echo detection according to claim 6 and the system of resolution, it is characterized in that, described first processing module comprises following submodule further:

Time segment process submodule, when dragging linear array array for utilizing according to passive synthetic aperture sonar algorithm twice motion in succession occur at interval at a fixed time, respectively cross-correlation is done to the nautical receiving set Received signal strength of lap on locus average, carry out time segment process by Received signal strength, analyze the Received signal strength of often adjacent twice time period; With

Frequency-domain beamforming submodule, for carrying out frequency-domain beamforming process to each array element Received signal strength of different time sections.

10. passive synthetic aperture target echo detection according to claim 6 and the system of resolution, it is characterized in that, described motion phase error compensation and testing result output module comprise following submodule further:

Motion phase error compensation submodule, exports for each for time segment phase correction term is compensated wave beam;

Coherent combination process submodule, adds up for carrying out coherent combination to the wave beam output after compensation; With

Testing result output sub-module, for being obtained the corresponding orientation of object beam by course figure time aziniuth, completes the detection and positioning of echo signal.