CN106154250A - A kind of passive synthetic aperture method of Beam Domain - Google Patents

Abstract

The invention provides a kind of passive synthetic aperture method of Beam Domain, the method is according to number N of towed array array element and interval d, arrange and adjacent measure the fantasy sport speed v ' of array in time interval τ and the fantasy sport distance q ' d of array twice, and make it meet v ' τ=q ' d；Then the phase correction term relative to the m-1 time measurement for the m time measurement is calculated successively at Beam Domain；And carry out phase compensation with the wave beam output to the m time measurement array for front m the phase correction term；Finally at Beam Domain, relevant summation is carried out to all wave beams output after compensation phase place, to reach finally to expect the array number of extension.Using the present invention can efficiently solve tradition Beam Domain ETAM algorithm synthetic aperture needs the shortcomings such as longer measurement time, can synthesize bigger aperture within a short period of time.

Description

A kind of passive synthetic aperture method of Beam Domain

Technical field

The present invention relates to the signal transacting field of passive sonar detection, be specifically related to the passive synthesis hole of a kind of Beam Domain Routing method.

Background technology

High-resolution and high-gain are always the target that sonar field is pursued, in order to improve azimuth resolution, and conventional sound The system of receiving is to receive array number typically by increase to reach this purpose.Attenuation losses when sound wave is propagated in the seawater As the increase of frequency increases, so in actual applications, often use relatively low to improve fractal dimension Operating frequency；Under low frequency condition, increase reception array number in order to improve azimuth resolution and can cause array hole Footpath becomes huge, not only can increase the cost of system, also can bring bigger to aspects such as system design and risk controls Difficulty.In this context, passive synthetic aperture sonar technique arises at the historic moment.

By passive synthetic aperture sonar technique (Passive Synthetic Aperture Sonar, PSAS), can make The signal receiving when straight line towing motion with small-bore basic matrix, synthesis is much larger than the virtual aperture in actual physics aperture Footpath, exchanges the more unobtainable spatial gain because physical size is limited for the time gain being relatively readily available, Thus improve the azimuth discrimination performance of array, improve under the detectability of weak target signal, especially strong jamming Multi-target detection.The core of passive synthetic aperture technique is exactly the temporal coherence utilizing signal, is mended by phase place Repay, the technology such as locus compensation is by long battle array signal virtual for short battle array signal syntheses.

Passive synthetic aperture principle is as it is shown in figure 1, an equidistant horizontal drag being made up of N number of isotropism hydrophone Draging battle array, array element is spaced apart d, and basic matrix is made linear uniform motion with speed v and (with No. 1 array element to N array element direction is Speed positive direction).Carry out the L=0 time measurement when t=0, N unit basic matrix carries out spatial sampling；Enter when t=τ The L=1 time measurement of row, by selecting suitable parameter τ and q, makes v τ=qd, q represent between the time measured twice Q hydrophone position of arraymotion in τ, i.e. arraymotion distance is qd.By repeat aforesaid operations, when When carrying out the L=J time measurement during t=J τ, the array of N unit is extended to the virtual long battle array of N+Jq unit, and can use this Virtual long battle array obtains the information such as target bearing.Assume to receive from θ_sThe far field narrow band signal source in direction is s(t_i)=A exp (j2 π f₀t_i), being equal to 90 ° of normal directions with the direction of orthogonal array for θ, then No. n-th water is listened The signal that device receives can be described as:

$x_n\left(t_i\right)=\mathrm{Aexp}\left(j2\mathrm{\π}{f}_0(t_i-\frac{v{t}_i+(n-1)d}{c}\cos {\mathrm{\θ}}_s)\right)+{\mathrm{\ϵ}}_n\left(t_i\right)---\left(1\right)$

Wherein, c is the velocity of sound, n=1,2 ..., N is hydrophone number, t_i=i Δ t, i=1,2 ..., K, K are for adopting Number of samples, Δ t is the sampling interval, ε_n(t_i) it is that variance isZero-mean independent white Gaussian noise.

Through τ second (i.e. t_i+ τ the moment), v τ=qd, receipt signal expression formula is:

$\begin{array}{c}{x}_n(t_i+\mathrm{\τ})=\mathrm{Aexp}\left(j2\mathrm{\π}{f}_0(t_i+\mathrm{\τ}-\frac{v(t_i+\mathrm{\τ})+(n-1)d}{c}\cos {\mathrm{\θ}}_s)\right)+{\mathrm{\ϵ}}_n(t_i+\mathrm{\τ})\\ =\mathrm{Aexp}\left(j2\mathrm{\π}{f}_0\mathrm{\τ}\right)\exp \left(j2\mathrm{\π}{f}_0(t_i-\frac{v{t}_i+(n+q-1)d}{c}\cos {\mathrm{\θ}}_s)\right)+{\mathrm{\ϵ}}_n(t_i+\mathrm{\τ})\end{array}---\left(2\right)$

If t_iShi Keyou passage n+q, its output should be:

$x_{n+q}\left(t_i\right)=\mathrm{Aexp}\left(j2\mathrm{\π}{f}_0(t_i-\frac{v{t}_i+(n+q-1)d}{c}\cos {\mathrm{\θ}}_s)\right)+{\mathrm{\ϵ}}_n\left(t_i\right)---\left(3\right)$

, if ignoring the noise that each hydrophone receives, then there is relational expression in comparison expression (2) and formula (3):

x_n(t_i+ τ)=exp (j2 π f₀τ)*x_n+q(t_i), it can be seen that t_iThe signal x in+τ moment_n(t_i+ τ) pass through school Positive phaseT can be synthesized_iThe x in moment_n+q(t_i), array hole can be realized in this way Footpath extends.

For far field plane wave, single-frequency sound source, t_iThe battle array response in moment is:

$b_0(f_0,{\mathrm{\θ}}_s)={\mathrm{\Σ}}_{n=1}^N\left\{{\mathrm{\Σ}}_{i=1}^K{x}_n\left(t_i\right)\exp (-j2\mathrm{\π}{f}_0{t}_i)\right\}\exp \left(j2\mathrm{\π}{f}_0\frac{(n-1)d\cos {\mathrm{\θ}}_s}{c}\right)---\left(4\right)$

t_iThe response of+τ moment battle array is:

$b_{\mathrm{\τ}}(f_0,{\mathrm{\θ}}_s)={\mathrm{\Σ}}_{n=1}^N\left\{{\mathrm{\Σ}}_{i=1}^K{x}_n(t_i+\mathrm{\τ})\exp (-j2\mathrm{\π}{f}_0{t}_i)\right\}\exp \left(j2\mathrm{\π}{f}_0\frac{(n-1)d\cos {\mathrm{\θ}}_s}{c}\right)---\left(5\right)$

Can wushu (5) be reduced to by formula (2) and formula (4):

$b_{\mathrm{\τ}}(f_0,{\mathrm{\θ}}_s)=b_0(f_0,{\mathrm{\θ}}_s)\exp \left(j2\mathrm{\π}{f}_0(\mathrm{\τ}-\frac{\mathrm{v\τ}}{c}\cos {\mathrm{\θ}}_s)\right)---\left(6\right)$

Compensate the wave beam output of every time measurement by phase only pupil filter and can extend aperture:

It according to the measuring method in actual conditions, is rewritten as:

WhereinIt is referred to as phase correction term.

So, the principle of passive synthetic aperture sonar can be attributed to: estimates phase correction term, and utilizes phase place The phase of received signal of all measurements is alignd by modifying factor, thus by long battle array signal virtual for short battle array signal syntheses.

Current PSAS has three kinds of more ripe algorithms: the towed array of extension measures (ETAM) algorithm, maximum seemingly So estimating (ML) algorithm and fast Fourier synthetic aperture (FFTSA) algorithm, they are both for continuous single-frequency Signal is processed.Carry out Integrated comparative in terms of orientation estimated accuracy, robustness, amount of calculation etc., ETAM Algorithm is best.ETAM algorithm has time domain ETAM algorithm and Beam Domain ETAM algorithm.Time domain ETAM is calculated The basic thought of method is: during arraymotion, does the receipt signal of the adjacent location overlap array element of measurement space twice mutually Related average, as the phase correction term of underlapped array element receipt signal, the array element measured twice before and after making receives The phase alignment of signal, by repeating the above, reaches to extend the purpose in aperture.Time domain ETAM algorithm is not Foot is: one is under Low SNR, and the error owing to estimating phase correction term becomes very big, estimates mesh The performance in mark orientation becomes very poor；Two is to there is multiple target and the condition that wherein one or more are random targets Under, performance becomes very poor, even cannot synthetic aperture.

In order to solve the problem of time domain ETAM algorithm, Tong Poh Bee et al. proposed Beam Domain in 2006 ETAM algorithm (hereinafter referred to as " tradition Beam Domain ETAM algorithm "), the estimation to phase correction term for this algorithm It is to process at the Beam Domain that overlapping array element is formed sub-aperture, and relevant summation is also to carry out at Beam Domain Process.

Tradition Beam Domain ETAM algorithm solve time domain ETAM algorithm the multiple target of measurement (one of them or many Individual target is random targets) when degradation even cannot the problem of synthetic aperture, improve multiobject detection property Energy；Additionally, it is in sub-aperture that tradition Beam Domain ETAM algorithm carries out relevant summation to the wave beam output after phase compensation Footpath Beam Domain is carried out, and (and time domain ETAM algorithm is to be equivalent to have made each sub-aperture wave beam windowing process Make a windowing process to whole synthetic aperture), thus effectively have compressed secondary lobe, substantially improve target bearing Estimate performance.

But, when utilizing tradition Beam Domain ETAM algorithm synthetic aperture, existing cannot owing to algorithm itself limits The problem solving:

(1) the array element overlay condition v τ=qd must being fulfilled for because of tradition Beam Domain ETAM algorithm, wherein: d is Array element is spaced, and v is the speed of tow platform in water, and τ is for measuring time interval twice, and q represented between the time of measurement twice Every interior q hydrophone position of having moved；And v is generally less, to one longer battle array of synthesis, then need one section of phase When the long time.For example: when array length is 90m, and towed speed is 3m/s, the battle array synthesizing 180m array length needs 30s。

(2) the reason that because towed speed is less, the utilization rate causing data is relatively low.Such as: the data of τ second are only Q array element can be extended.

(3) due to the restriction of temporal and spatial correlations radius, when using tradition Beam Domain ETAM algorithm, if target side Position has significant change in generated time, then cannot accurately estimate, even cannot synthetic aperture.

Content of the invention

When it is an object of the invention to overcome currently with tradition Beam Domain ETAM algorithm synthetic aperture, the survey existing The shortcomings such as the amount time is longer, and condition is limited, it is proposed that a kind of passive synthetic aperture method of Beam Domain, the method energy The bigger aperture of synthesis within a short period of time, breaches the restriction of temporal and spatial correlations radius to a certain extent so that it is Angle on target change relatively fast when also can synthetic aperture, improve the utilization rate of data simultaneously.

To achieve these goals, the invention provides a kind of passive synthetic aperture method of Beam Domain, the method root According to number N and the interval d of towed array array element, the adjacent fantasy sport speed measuring array in time interval τ twice is set V ' and the fantasy sport distance q ' d of array, and make it meet v ' τ=q ' d；Then calculate successively the m time at Beam Domain Measurement is relative to the phase correction term of the m-1 time measurement；And by front m phase correction term, the m time is measured The wave beam output of array carries out phase compensation；Finally at Beam Domain, phase is carried out to all wave beams output after compensation phase place Dry summation, to reach finally to expect the array number of extension.

In technique scheme, described method farther includes:

Step 1) according to the number of towed array array element and interval, the adjacent void measuring array in time interval twice is set Intend the fantasy sport distance of movement velocity and array；

One equidistant horizontal towed array being made up of N number of isotropism hydrophone, array element is spaced apart d, selected each The array number q ' of measurement expectation extension, actual in time interval τ is unsatisfactory for (N-q ') array element weight adjacent measurement twice Folded, i.e. in the case of v τ ≠ q ' d, arrange the adjacent fantasy sport speed v ' measuring array in time interval τ twice and The fantasy sport distance q ' d of array, and make it meet v ' τ=q ' d；

Step 2) determine measurement according to the array number q ' of each measurement expectation extension and the array number of final expectation extension Number of times M+1；Take m=1；

Step 3) carry out the m time measurement when, calculate the m time and the m-1 time measure virtual overlap submatrix ripple Bundle output；

The wave beam of the virtual overlapping submatrix of the m-1 time measurement is output as:

$L_{m-1}(f_0,{\mathrm{\θ}}_s)={\mathrm{\Σ}}_{n=1}^{N-q^{\′}}{X}_{n,(m-1)}\left(f_0\right)*\exp \left(j2\mathrm{\π}\frac{f_0}{c}(n-1)d\cos {\mathrm{\θ}}_s\right);m\≥1$

In above formula, c is the velocity of sound；N=1,2 ..., N is hydrophone number；θ_sRepresent the target bearing needing scanning Angle；X_n,(m-1)(f₀) it is that the discrete Fourier transform of No. n-th hydrophone receipt signal of the m-1 time measurement is in frequency f₀ Expression；L_m-1(f₀,θ_s) when being the m-1 time measurement virtual overlapping submatrix in frequency f₀With scanning angle θ_sUnder Beamformer output；As m=1, " 0th " secondary measurement when being measured as t=0；

The wave beam of the virtual overlapping submatrix of the m time measurement is output as:

$L_m(f_0,{\mathrm{\θ}}_s)={\mathrm{\Σ}}_{n=q^{\′}+1}^N{X}_{n,m}\left(f_0\right)*\exp \left(j2\mathrm{\π}\frac{f_0}{c}(n-q^{\′}-1)d\cos {\mathrm{\θ}}_s\right);$

In formula, X_n,m(f₀) it is that the discrete Fourier transform of No. n-th hydrophone receipt signal of the m time measurement is in frequency f₀'s Expression, L_m(f₀,θ_s) when being the m time measurement virtual overlapping submatrix in frequency f₀With scanning angle θ_sUnder output wave Bundle；

Step 4) calculate the phase correction term relative to the m-1 time measurement for the m time measurement；

In above formula,It is that the m time measurement is in frequency f₀With scanning angle θ_sUnder relative to the m-1 time measurement Phase correction term；

Step 5) with front m phase correction term to the m time measurement array wave beam output carry out phase compensation；

The wave beam output b of the m time measurement array_m(f₀,θ_s) it is:

$b_m(f_0,{\mathrm{\θ}}_s)=\underset{n=1}{\overset{N}{\mathrm{\Σ}}}{X}_{n,m}\left(f_0\right)*\exp \left(j2\mathrm{\π}\frac{f_0}{c}(n-1)d\cos {\mathrm{\θ}}_s\right)$

With phase correction term to b_m(f₀,θ_s) carry out phase compensation after, the m time measurement array wave beam output b′_m(f₀,θ_s) it is:

Particularly, as m=0,

b′_m(f₀,θ_s)=b_m(f₀,θ_s)

Step 6) judge whether m is less than M, if a determination be made that certainly, make m=m+1, proceed to step 3)；Otherwise, step 7 is entered)；

Step 7) relevant summation is carried out to the wave beam output of array after M+1 phase compensation, to reach finally to expect The array number of extension.

In technique scheme, described step 7) the process that realizes be:

$B(f_0,{\mathrm{\θ}}_s)={|\underset{m=0}{\overset{M}{\mathrm{\Σ}}}{b}_m^{\′}(f_0,{\mathrm{\θ}}_s)*\exp (-j2\mathrm{\π}{f}_{0}m\frac{q^{\′}d\cos {\mathrm{\θ}}_s}{c})|}^2$

Wherein, B (f₀,θ_s) for carrying out the result of relevant summation to the wave beam output of array after M+1 phase compensation.

It is an advantage of the current invention that:

1st, the method energy of the present invention synthesizes bigger aperture within a short period of time, breaches tradition Beam Domain ETAM and calculates Method needs the bottleneck of long period due to towed speed less synthesis large aperture；

2nd, the method for the present invention breaches the restriction of temporal and spatial correlations radius in tradition Beam Domain ETAM algorithm so that it is Target bearing change remains to synthetic aperture when relatively fast.

Brief description

Fig. 1 is the principle schematic of passive synthetic aperture；

Fig. 2 is the principle schematic of tradition Beam Domain ETAM synthetic aperture method；

Fig. 3 is the principle schematic of the passive synthetic aperture of the Beam Domain of the present invention；

Fig. 4 is the flow chart of the passive synthetic aperture method of the Beam Domain of the present invention；

Fig. 5 be the present invention example 1 in the emulation of method of tradition Beam Domain ETAM synthetic aperture method and the present invention Comparison diagram；

Fig. 6 is the wave beam course figure that 64 array elements are expanded to that 128 array elements are drawn by the method for the present invention in example 2；

Fig. 7 is the wave beam course figure that 64 array elements are expanded to that 192 array elements are drawn by the method for the present invention in example 2；

Fig. 8 is the wave beam course figure that 64 array elements are expanded to that 256 array elements are drawn by the method for the present invention in example 2；

Fig. 9 is the wave beam course figure that 64 array elements are expanded to that 320 array elements are drawn by the method for the present invention in example 2；

Figure 10 is the wave beam course figure that in example 2, conventional 64 array elements are drawn.

Detailed description of the invention

In tradition Beam Domain ETAM algorithm, the n-th+q hydrophone is at t_iReception to signal can be described as:

$x_{n+q}\left(t_i\right)=\mathrm{Aexp}\left(j2\mathrm{\π}{f}_0(t_i-\frac{v{t}_i+(n+q-1)d}{c}\cos \mathrm{\θ})\right)+{\mathrm{\ϵ}}_{n+q}\left(t_i\right)---\left(9\right)$

No. n-th hydrophone is at t_i+ τ reception to signal can be described as:

$\begin{array}{c}{x}_n(t_i+\mathrm{\τ})=\mathrm{Aexp}\left(j2\mathrm{\π}{f}_0(t_i+\mathrm{\τ}-\frac{v{t}_i+\mathrm{v\τ}+(n-1)d}{c}\cos \mathrm{\θ})\right)+{\mathrm{\ϵ}}_n(t_i+\mathrm{\τ})\\ =\mathrm{Aexp}\left(j2\mathrm{\π}{f}_0(t_i-\frac{v{t}_i+\mathrm{v\τ}+(n-1)d}{c}\cos \mathrm{\θ})\right)\·\exp \left(j2\mathrm{\π}{f}_0\mathrm{\τ}\right)+{\mathrm{\ϵ}}_n(t_i+\mathrm{\τ})\end{array}---\left(10\right)$

Comparison expression (9) and formula (10) can obtain, if ignoring the noise that each hydrophone receives, then strictly meeting array element In the case of overlay condition v τ=qd, meet:

x_n+q(t_i)=exp (-j2 π f₀τ)·x_n(t_i+τ) (11)

At this moment the phase correction term that can estimate the overlapping hydrophone in locus is:

In actual application, the least square estimation of phase correction term is:

From above-mentioned derivation, tradition Beam Domain ETAM algorithm must assure that the sky of overlapping hydrophone when measuring continuously Between position identical, i.e. meet array element overlay condition v τ=qd.

The present invention relieves the tradition restriction to array element overlay condition v τ=qd for the Beam Domain ETAM algorithm.Adjacent two In secondary measurement time interval τ actual in the case of be unsatisfactory for (N-q) array element overlapping (i.e. v τ ≠ qd), can arrange One fantasy sport speed v '=v+ Δ v, and make the movement velocity v ' of this virtual setting meet the array element of v ' τ=qd Overlay condition.Thus can draw v τ=qd-τ Δ v, and certainly exist one correspondingCan make V τ=q (d-δ).In this case, No. n-th hydrophone is at t_i+ τ reception to signal can be approximately:

$\begin{array}{c}{x}_n(t_i+\mathrm{\τ})\≈\mathrm{Aexp}\left(j2\mathrm{\π}{f}_0(t_i+\mathrm{\τ}-\frac{v{t}_i+\mathrm{v\τ}+(n-1)d}{c}\cos \mathrm{\θ})\right)+{\mathrm{\ϵ}}_n(t_i+\mathrm{\τ})\\ =\mathrm{Aexp}\left(j2\mathrm{\π}{f}_0(t_i+\mathrm{\τ}-\frac{v{t}_i+q(d-\mathrm{\δ})+(n-1)d}{c}\cos \mathrm{\θ})\right)+{\mathrm{\ϵ}}_n(t_i+\mathrm{\τ})\\ =\mathrm{Aexp}\left(j2\mathrm{\π}{f}_0(t_i-\frac{v{t}_i+(n+q-1)d}{c}\cos \mathrm{\θ})\right)\·\exp \left(j2\mathrm{\π}{f}_0(\mathrm{\τ}+\frac{\mathrm{q\δ}\cos \mathrm{\θ}}{c})\right)+{\mathrm{\ϵ}}_n(t_i+\mathrm{\τ})\end{array}---\left(14\right)$

Comparison expression (9) and formula (14) can obtain, if ignoring the noise that each hydrophone receives, are then being unsatisfactory for array element weight In the case of folded condition i.e. v τ ≠ qd, meet:

$x_{n+q}\left(t_i\right)=\exp (-j2\mathrm{\π}{f}_0(\mathrm{\τ}+\frac{\mathrm{q\δ}\cos \mathrm{\θ}}{c}))\·x_n(t_i+\mathrm{\τ})---\left(15\right)$

Correspondingly, in the case of being unsatisfactory for array element overlay condition, evaluation phase modifying factor should be revised as:

In actual application, the least square estimation of phase correction term is:

From above-mentioned derivation, still can be with tradition Beam Domain in the case of being unsatisfactory for array element overlay condition i.e. v τ ≠ qd ETAM algorithm evaluation phase modifying factor synthetic aperture.

The present invention still will can use thinking and the Beam Domain ETAM algorithm of ETAM algorithm when being unsatisfactory for array element overlay condition Combining, it is proposed that a kind of passive synthetic aperture method of Beam Domain, the method first selectes measurement expectation extension every time Array number q ' (typically takeBecauseFor optimum superposing number), in water, tow platform speed v is actual discontented In the case of foot (N-q ') array element overlapping (i.e. v τ ≠ q ' d), array in adjacent time interval τ of measurement twice is set Fantasy sport speed v ' and the fantasy sport distance q ' d of array, and make it meet v ' τ=q ' d, with q ' d as parameter Synthetic aperture.

As in figure 2 it is shown, when using tradition Beam Domain ETAM algorithm synthetic aperture, due to tow platform speed in water V is less for degree, and after elapsed time τ, the move distance qd of array is less, with tradition Beam Domain ETAM algorithm extending bore During footpath, less array number can only be extended in the short period of time；If requiring the more array element of extension every time in other words Number, then need the longer time, and require target bearing during this period of time without significant change.This is using conjunction Become aperture sonar to draw during the looks of seabed sea less problematic, but be clearly difficult to be expired in passive sonar real-time detection Foot.The present invention adjacent measures the fantasy sport speed v ' of array in time interval τ and the void of array twice by arranging Intending move distance q ' d, phase is sought in the wave beam output being equivalent to take (N-q ') virtual overlapping array element in adjacent measurement twice Close as phase correction term, and the signal phase utilizing this phase correction term to measure twice before and after making aligns, After in the relevant summation of Beam Domain to extend aperture.

As it is shown on figure 3, the present invention is in the case that towed speed v is less, still can extend relatively in the short period of time How virtual array number.

The present invention is described further with instantiation below in conjunction with the accompanying drawings.

As shown in Figure 4, a kind of passive synthetic aperture method of Beam Domain, described method comprises the steps:

Step 1) according to the number of towed array array element and interval, the adjacent void measuring array in time interval twice is set Intend the fantasy sport distance of movement velocity and array；

One equidistant horizontal towed array being made up of N number of isotropism hydrophone, array element is spaced apart d, selected each The array number q ' of measurement expectation extension, actual in time interval τ is unsatisfactory for (N-q ') array element weight adjacent measurement twice Folded, i.e. in the case of v τ ≠ q ' d, arrange the adjacent fantasy sport speed v ' measuring array in time interval τ twice and The fantasy sport distance q ' d of array, and make it meet v ' τ=q ' d；

Step 2) determine measurement according to the array number q ' of each measurement expectation extension and the array number of final expectation extension Number of times M+1；Take m=1；

Step 3) carry out the m time measurement when, calculate the m time and the m-1 time measure virtual overlap submatrix ripple Bundle output；

The wave beam of the virtual overlapping submatrix of the m-1 time measurement is output as:

$L_{m-1}(f_0,{\mathrm{\θ}}_s)={\mathrm{\Σ}}_{n=1}^{N-q^{\′}}{X}_{n,(m-1)}\left(f_0\right)*\exp \left(j2\mathrm{\π}\frac{f_0}{c}(n-1)d\cos {\mathrm{\θ}}_s\right);m\≥1$

In above formula, c is the velocity of sound；N=1,2 ..., N is hydrophone number；θ_sRepresent the target bearing needing scanning Angle；X_n,(m-1)(f₀) it is that the discrete Fourier transform of No. n-th hydrophone receipt signal of the m-1 time measurement is in frequency f₀ Expression；L_m-1(f₀,θ_s) when being the m-1 time measurement virtual overlapping submatrix in frequency f₀With scanning angle θ_sUnder Beamformer output；As m=1, " 0th " secondary measurement when being measured as t=0；

The wave beam of the virtual overlapping submatrix of the m time measurement is output as:

$L_m(f_0,{\mathrm{\θ}}_s)={\mathrm{\Σ}}_{n=q^{\′}+1}^N{X}_{n,m}\left(f_0\right)*\exp \left(j2\mathrm{\π}\frac{f_0}{c}(n-q^{\′}-1)d\cos {\mathrm{\θ}}_s\right);$

In formula, X_n,m(f₀) it is that the discrete Fourier transform of No. n-th hydrophone receipt signal of the m time measurement is in frequency f₀'s Expression, L_m(f₀,θ_s) when being the m time measurement virtual overlapping submatrix in frequency f₀With scanning angle θ_sUnder output wave Bundle；

Step 4) calculate the phase correction term relative to the m-1 time measurement for the m time measurement；

In above formula,It is that the m time measurement is in frequency f₀With scanning angle θ_sUnder relative to the m-1 time measurement Phase correction term；

Step 5) with front m phase correction term to the m time measurement array wave beam output carry out phase compensation；

The wave beam output b of the m time measurement array_m(f₀,θ_s) it is:

$b_m(f_0,{\mathrm{\θ}}_s)=\underset{n=1}{\overset{N}{\mathrm{\Σ}}}{X}_{n,m}\left(f_0\right)*\exp \left(j2\mathrm{\π}\frac{f_0}{c}(n-1)d\cos {\mathrm{\θ}}_s\right)$

With phase correction term to b_m(f₀,θ_s) carry out phase compensation after, the m time measurement array wave beam output b′_m(f₀,θ_s) it is:

Particularly, as m=0,

b′_m(f₀,θ_s)=b_m(f₀,θ_s)

Step 6) judge whether m is less than M, if a determination be made that certainly, make m=m+1, proceed to step 3)；Otherwise, step 7 is entered)；

Step 7) relevant summation is carried out to the wave beam output of array after M+1 phase compensation, to reach finally to expect The array number of extension.

$B(f_0,{\mathrm{\θ}}_s)={|\underset{m=0}{\overset{M}{\mathrm{\Σ}}}{b}_m^{\′}(f_0,{\mathrm{\θ}}_s)*\exp (-j2\mathrm{\π}{f}_{0}m\frac{q^{\′}d\cos {\mathrm{\θ}}_s}{c})|}^2$

Wherein, B (f₀,θ_s) for carrying out the result of relevant summation to the wave beam output of array after M+1 phase compensation. This formula can be considered a general framework, when applying in tradition Beam Domain ETAM algorithm, makes q '=q, it is possible to Carry out the purpose that relevant summation reaches to extend aperture with this formula.

Below two examples of invention are illustrated.

Example 1:

The uniform tow line array being made up of N=18 isotropic hydrophone, the interval of adjacent two array elements D=1.5m, the frequency of corresponding receipt signal is 500Hz, and array navigates by water with the velocity linear of v=3m/s.Often In secondary measurement, single channel sample frequency is 2kHz, and sampling number is 1500.The present embodiment considers far field plane wave, And supposing that target is static during once complete measurement, definition basic matrix normal direction is 90 °.Assume There is the static sound source of two single-frequency in far field, and radiation acoustic frequency is 500Hz, two signals relative to basic matrix orientation respectively It is 120 ° and 140 °, and signal to noise ratio during each sound-source signal arrival basic matrix is equal, is 0dB

When using tradition Beam Domain ETAM algorithm synthetic aperture, one-shot measurement extendsIndividual array number, Adjacent measurement interval twice is τ=4.5s, and pendulous frequency is M=8, i.e. in 36s, 18 yuan of battle arrays is expanded to 90 Unit's battle array；When using the method for the present invention, adjacent actual interval of measuring twice is τ=1s, selected measurement expectation every time Array number q '=9 (now v τ ≠ q ' d) of extension, arrange the fantasy sport of array in adjacent measurement interval twice away from FromCorresponding fantasy sport speedPendulous frequency is M=8, i.e. by 18 yuan in 8s Battle array expands to 90 yuan of battle arrays.

Can compare from Fig. 5 and draw, the method for the present invention and tradition Beam Domain ETAM synthetic aperture method are in side In the resolution performance of position, effect is suitable, but the method for the present invention substantially reduces the measurement time required for synthetic aperture, In addition, the method for the present invention only require target bearing in this 8s without significant change, and tradition Beam Domain ETAM close Aperture approach is become to require target bearing without significant change in these 36 seconds.

Example 2:

Experimental data is marine site, the South Sea in 2014 experimental data, handled experimental data length about 14 minutes. The array receiving is the 64 passive towed arrays of array element level that array element is spaced 1.5 meters.With the method synthesis hole of the present invention During footpath, adjacent actual interval of measuring twice is τ=1s, array number q '=32 of the selected expectation extension of measurement every time, Fantasy sport speed v ' and the fantasy sport distance q ' d of array in adjacent measurement interval twice are set.

64 array elements are expanded to 128 array elements, 192 array elements, 256 array elements and 320 array elements by the method using the present invention The wave beam course figure drawn is respectively as shown in Fig. 6, Fig. 7, Fig. 8 and Fig. 9；Compared with Figure 10 it can be seen that this The method of invention is obviously improved in raising azimuth discrimination performance.

Claims (3)

1. a passive synthetic aperture method for Beam Domain, the method according to number N of towed array array element and interval d, The adjacent fantasy sport speed v ' of array in time interval τ and the fantasy sport distance q ' d of array of measuring twice is set, and It is made to meet v ' τ=q ' d；Then the phase place relative to the m-1 time measurement for the m time measurement is calculated successively at Beam Domain Modifying factor；And carry out phase compensation with the wave beam output to the m time measurement array for front m the phase correction term；? After carry out relevant summation at Beam Domain to compensating the output of all wave beams after phase place, to reach finally to expect the battle array of extension Unit's number.

2. the passive synthetic aperture method of Beam Domain according to claim 1, it is characterised in that described method Farther include:

Step 1) according to the number of towed array array element and interval, the adjacent void measuring array in time interval twice is set Intend the fantasy sport distance of movement velocity and array；

One equidistant horizontal towed array being made up of N number of isotropism hydrophone, array element is spaced apart d, selected each The array number q ' of measurement expectation extension, actual in time interval τ is unsatisfactory for (N-q ') array element weight adjacent measurement twice Folded, i.e. in the case of v τ ≠ q ' d, arrange the adjacent fantasy sport speed v ' measuring array in time interval τ twice and The fantasy sport distance q ' d of array, and make it meet v ' τ=q ' d；

Step 2) determine measurement according to the array number q ' of each measurement expectation extension and the array number of final expectation extension Number of times M+1；Take m=1；

Step 3) carry out the m time measurement when, calculate the m time and the m-1 time measure virtual overlap submatrix ripple Bundle output；

The wave beam of the virtual overlapping submatrix of the m-1 time measurement is output as:

$L_{m-1}(f_0,{\mathrm{\θ}}_s)={\mathrm{\Σ}}_{n=1}^{N-q^{\′}}{X}_{n,(m-1)}\left(f_0\right)*\exp \left(j2\mathrm{\π}\frac{f_0}{c}(n-1)d\cos {\mathrm{\θ}}_s\right);m\≥1$

In above formula, c is the velocity of sound；N=1,2 ..., N is hydrophone number；θ_sRepresent the target bearing needing scanning Angle；X_n,(m-1)(f₀) it is that the discrete Fourier transform of No. n-th hydrophone receipt signal of the m-1 time measurement is in frequency f₀ Expression；L_m-1(f₀,θ_s) when being the m-1 time measurement virtual overlapping submatrix in frequency f₀With scanning angle θ_sUnder Beamformer output；As m=1, " 0th " secondary measurement when being measured as t=0；

The wave beam of the virtual overlapping submatrix of the m time measurement is output as:

$L_m(f_0,{\mathrm{\θ}}_s)={\mathrm{\Σ}}_{n=q^{\′}+1}^N{X}_{n,m}\left(f_0\right)*\exp \left(j2\mathrm{\π}\frac{f_0}{c}(n-q^{\′}-1)d\cos {\mathrm{\θ}}_s\right);$

In formula, X_n,m(f₀) it is that the discrete Fourier transform of No. n-th hydrophone receipt signal of the m time measurement is in frequency f₀'s Expression, L_m(f₀,θ_s) when being the m time measurement virtual overlapping submatrix in frequency f₀With scanning angle θ_sUnder output wave Bundle；

Step 4) calculate the phase correction term relative to the m-1 time measurement for the m time measurement；

In above formula,It is that the m time measurement is in frequency f₀With scanning angle θ_sUnder relative to the m-1 time measurement Phase correction term；For L_m(f₀,θ_s) conjugation；

Step 5) with front m phase correction term to the m time measurement array wave beam output carry out phase compensation；

The wave beam output b of the m time measurement array_m(f₀,θ_s) it is:

$b_m(f_0,{\mathrm{\θ}}_s)=\underset{n=1}{\overset{N}{\mathrm{\Σ}}}{X}_{n,m}\left(f_0\right)*\exp \left(j2\mathrm{\π}\frac{f_0}{c}(n-1)d\cos {\mathrm{\θ}}_s\right)$

With phase correction term to b_m(f₀,θ_s) carry out phase compensation after, the m time measurement array wave beam output b′_m(f₀,θ_s) it is:

Particularly, as m=0,

b′_m(f₀,θ_s)=b_m(f₀,θ_s)

Step 6) judge whether m is less than M, if a determination be made that certainly, make m=m+1, proceed to step 3)；Otherwise, step 7 is entered)；

Step 7) relevant summation is carried out to the wave beam output of array after M+1 phase compensation.

3. the passive synthetic aperture method of Beam Domain according to claim 2, it is characterised in that described step 7) the process that realizes is:

$B(f_0,{\mathrm{\θ}}_s)={|\underset{m=0}{\overset{M}{\mathrm{\Σ}}}{b}_m^{\′}(f_0,{\mathrm{\θ}}_s)*\exp (-j2\mathrm{\π}{f}_{0}m\frac{q^{\′}d\cos {\mathrm{\θ}}_s}{c})|}^2$

Wherein, B (f₀,θ_s) for carrying out the result of relevant summation to the wave beam output of array after M+1 phase compensation.