CN101718868B - Multi-split beam phase difference-based multi-beam sounding method - Google Patents

Abstract

The invention relates to the field of sonar signal processing, mainly to a multi-split beam phase difference-based multi-beam sounding method, and provides high-resolution multi-beam undersea detection technology. Various split beam dividing methods are adopted to measure a direction of arrival phase difference curve for a plurality of times, and simultaneously least square is introduced to process and estimate parameter errors so as to solve the problem that an automatic tracking gate of a conventional phase difference detection method is difficult to design. The method has the advantage of still having high detection accuracy when performing undersea detection on edge beams with relatively lower echo signal-to-noise ratio.

Description

A kind of multibeam echosounding method based on multiple spliting wave beam phase differential

Technical field

The present invention relates to the sonar signal process field, be specifically related to the Array Signal Processing field, mainly is a kind of multibeam echosounding method based on multiple spliting wave beam phase differential.

Background technology

Multibeam sounding system is a kind of efficient submarine topography mapping system that the echoed signal in each emission/reception intersection wave beam is carried out echo time of arrival (TOA, timeof arrival) and echo arrival direction (DOA, direction of arrival) estimation.Because the seabed back-scattered signal of different directions has identical frequency, along with glancing angle diminishes gradually, the echo transmission loss (TL) increases, and the echoed signal intensity that receives weakens, and obvious broadening appears in wave beam.So, can not adopt end detection method for the estimation of edge wave beam, and will adopt detection method, as dividing aperture phase difference method etc. based on phase place based on amplitude.

Yet for the pairing edge of big glancing angle wave beam, because the sound path that echo is propagated is very long and the backscattering loss is bigger, the echoed signal signal to noise ratio (S/N ratio) that receives is very low.Utilize the conventional aperture phase difference method that divides this moment, only the zero crossing of location phase differential curve is very difficult through utilizing the single curve fitting to come accurately.Therefore, wave beam Bathymetric Technology in high precision edge also is the difficult point of current multibeam echosounding signal Processing.For this reason; The multiple submatrixes treatment technology was proposed in the nineties in last century; The seabed image information is obtained in phase sequence output and least-squares estimation through measuring a plurality of submatrixs; But submatrix is handled the effective aperture reduced basic matrix, must cause wave beam to form the decline and the gain loss of resolution performance, influences the depth measurement performance with algorithm when low signal-to-noise ratio.

Summary of the invention

Technical matters to be solved by this invention provides a kind of multibeam echosounding method based on multiple spliting wave beam phase differential; Through adopting multiple split beam submatrix division methods; Formation is introduced least square simultaneously and is handled the estimated parameter error the repeatedly measurement of direction of arrival phase differential curve, has solved the problem of the automatic tracking gate difficult design of conventional phase difference detection method; Make it when the lower edge wave beam of echo signal to noise ratio (S/N ratio) being carried out the seabed detection, still have the higher detection precision.

The present invention realizes the technical scheme that purpose adopts.This multibeam echosounding method based on multiple spliting wave beam phase differential comprises that step is following:

Step 1: adopt different array element overlap modes that basic matrix is divided into two submatrixs; Be provided with M (M>=2) and plant different split beam division methods; The phase difference sequence that obtains M this wave beam is measured; Be the phase differential image on this direction, be designated as

Step 2: suppose that the wavefront that sound wave arrives is a plane wave, making echo arrive angle is θ, and two adjacent submatrix equivalent sound centers are respectively c _1iAnd c _2i, the distance between them is used d _iExpression, 1≤i≤M, the phase differential between two submatrixs is so:

Formula (1) is illustrated in the phase difference estimation of the reception signal of a given time; Wherein, F representes frequency of operation, and c is the velocity of sound, the deviation of Δ θ (n) expression echo and beam control direction; When echo was controlled direction from wave beam, was zero;

For the phase difference sequence that the different split beam division methods of synchronization obtain, must be the seabed involuting wave in same orientation, adopt least-squares estimation to handle, obtain error function e:

Wherein, k _iBe the slope of phase difference sequence, $k_i=\frac{2\mathrm{\π\; f}{d}_i}{c}$

Order $\frac{\∂e}{\∂\left(\mathrm{Sin}\mathrm{\Δ\; \θ}\left(n\right)\right)}=0,$ Obtain the estimation of Δ θ (n):

(3) formula is updated in (2), obtains an e value that shows submatrix phase function nonlinearity, be called the phase difference error function, echo in time of arrival the e value very little; When M>=2; Calculate nonlinearity size e; When e is lower than a definite thresholding;

is used to estimate that echo arrives angle (DOA) and seabed depth; The interval that this thresholding determined is a trace interval, as the preformation beam angle and time of arrival function the e value be called the phase difference error image;

Step 3: the nonzero value in the phase differential image has been represented in certain wave beam from the next echo of other direction; The phase differential image is carried out conversion; Claim that the image after the conversion is the seabed trace image; It is the function of echo arrival direction and time, and the size of each pixel point value is represented the size of seabed involuting wave possibility on a certain moment, a certain direction of arrival in the image lattice; For each pixel in the phase differential image, utilize (3) formula to calculate DOA, the value corresponding to the pixel of preset time and DOA in the image lattice of seabed will increase, and this shows seabed involuting wave possibility very big on certain direction; At first initialization, and generation seabed image B (n, α)=0, α is that n is DOA constantly; By (3) calculate Δ θ (n, β), increase B in the corresponding grid (n, α):

$B(n,\mathrm{\α})\⇐B(n,\mathrm{\α})+I(n,\mathrm{\β})---\left(4\right)$

Wherein, (n β) is increment to I, and β is the preformation field angle

I(n，β)＝1+wA(n，β)(5)

Here, constant 1 is a phase weighting, and (n is that the n moment, preformation field angle are the amplitude of the wave beam output of β β) to A, is amplitude weighting, and w is overall weighting factor;

Step 4: the wave beam of other big glancing angle is repeated above-mentioned steps one, two, three, obtain corresponding seabed trace image B (n, α);

Step 5: if the pairing employing of the bound of trace interval is respectively n constantly _lAnd n _h, combine SF to obtain corresponding time interval: t so _l=n _l* f _sAnd t _h=n _h* f _sAccording to the seabed image B under the corresponding wave beam (n, α), the amplitude weighting of time is average to calculate it in trace interval, as (TOA) estimated value echo time of arrival of this wave beam, average weighted formula is following:

$t=\underset{i=T_l}{\overset{T_h}{\mathrm{\Σ}}}{A}_i\·t_i/\underset{i=T_l}{\overset{T_h}{\mathrm{\Σ}}}{A}_i---\left(6\right)$

Estimate obtaining final degree of depth valuation by DOA-TOA at last.

The invention has the advantages that: the invention provides a kind of high-resolution multi-beam seabed detection technique; Through adopting multiple split beam division methods; Formation is introduced least square simultaneously and is handled the estimated parameter error the repeatedly measurement of direction of arrival phase differential curve, has solved the problem of the automatic tracking gate difficult design of conventional phase difference detection method; Make it when the lower edge wave beam of echo signal to noise ratio (S/N ratio) being carried out the seabed detection, still have very high accuracy of detection.

Description of drawings

Fig. 1: basic matrix synoptic diagram;

Fig. 2: Beam-former output synoptic diagram;

Fig. 3: 60 degree are the phase difference sequence synoptic diagram under 8 kinds of submatrix dividing mode during angle of releases;

Fig. 4: the phase differential image synoptic diagram that Fig. 3 phase difference sequence is corresponding;

Fig. 5: phase function error image synoptic diagram;

Fig. 6: seabed trace image synoptic diagram;

Fig. 7: the seabed detection simulation is synoptic diagram as a result;

Embodiment

Below in conjunction with accompanying drawing and embodiment invention is described further:

Basic matrix synoptic diagram of the present invention is as shown in Figure 1, specifically may further comprise the steps:

Step 1: adopt different array element overlap modes that basic matrix is divided into two submatrixs.For the preformation wave beam of θ (n) direction, these array elements are divided into two submatrix AB and CD, they have identical effective aperture.On the edge of under the wave beam; Phase difference sequence all has the liny property partial section of relative broad; Therefore the division for submatrix requires very not harsh; Can obtain M (M>=2) through the overlapping degree that changes two submatrixs and plant different split beam division methods; Thereby obtain the phase difference sequence of M this wave beam, be the phase differential image on this direction, be designated as

Step 2: like Fig. 1, suppose that the wavefront that sound wave arrives is a plane wave, making echo arrive angle is θ, and the distance at two adjacent submatrix equivalent sound centers is used d _i, 1≤i≤M representes, the phase differential between two submatrixs is so:

Formula (5) is illustrated in the phase difference estimation of the reception signal of a given time; Wherein, F representes frequency of operation, and c is the velocity of sound, the deviation of Δ θ (n) expression echo and beam control direction; When echo was controlled direction from wave beam,

was zero.

For the phase difference sequence that the different split beam division methods of synchronization obtain, must be the seabed involuting wave in same orientation, can adopt least-squares estimation to handle, have:

Wherein, k _iBe the slope of phase difference sequence, $k_i=\frac{2\mathrm{\π\; f}{d}_i}{c}.$

Order $\frac{\∂e}{\∂\left(\mathrm{Sin}\mathrm{\Δ\; \θ}\left(n\right)\right)}=0,$ Obtain the estimation of Δ θ (n):

(7) formula is updated in (6), obtains an e value that shows submatrix phase function nonlinearity, be called the phase difference error function, echo in time of arrival the e value very little.In the method; As long as M>=2; Nonlinearity size e just can calculate; Therefore when as long as e is lower than a definite thresholding,

can be used for estimating DOA and seabed depth.We claim that the interval that this thresholding determines is a trace interval, as the preformation beam angle and time of arrival function the e value be called the phase difference error image.

Step 3: the nonzero value in the phase differential image has been represented in certain wave beam from the next echo of other direction; Utilize these nonzero values to detect seabed involuting wave; Will carry out conversion to the phase differential image; Claim that the image after the conversion is the seabed trace image, it is the function of echo arrival direction and time, and the size of each pixel point value is represented the size of seabed involuting wave possibility on a certain moment, a certain direction of arrival in the image lattice.For each pixel in the phase differential image, utilize (7) formula to calculate DOA, the value corresponding to the pixel of preset time and DOA in the image lattice of seabed will increase.This shows seabed involuting wave possibility very big on certain direction.At first initialization, and generation seabed image B (n, α)=0, α is that n is DOA constantly; By (3) calculate Δ θ (n, β), increase B in the corresponding grid (n, α):

$B(n,\mathrm{\α})\⇐B(n,\mathrm{\α})+I(n,\mathrm{\β})---\left(8\right)$

Wherein, (n β) is increment to I, and β is the preformation field angle

I(n，β)＝1+wA(n，β) (9)

Here, constant 1 is a phase weighting, and (n is that the n moment, preformation field angle are the amplitude of the wave beam output of β β) to A, is amplitude weighting, and w is overall weighting factor, adjusts its size so that amplitude weighting and phase weighting have comparability.So just fully utilize amplitude and phase information after the echoed signal wave beam forms, realized the joint-detection of amplitude-phase place.

Step 4: the wave beam of other big glancing angle is repeated above-mentioned steps one, two, three, obtain corresponding seabed trace image B (n, α).

Step 5: if the pairing employing of the bound of trace interval is respectively n constantly _lAnd n _h, combine SF to obtain corresponding time interval: t so _l=n _l* f _sAnd t _h=n _h* f _sAccording to the seabed image B under the corresponding wave beam (n, α), the amplitude weighting of time is average to calculate it in trace interval, as the TOA estimated value of this wave beam, average weighted formula is following:

$t=\underset{i=T_l}{\overset{T_h}{\mathrm{\Σ}}}{A}_i\·t_i/\underset{i=T_l}{\overset{T_h}{\mathrm{\Σ}}}{A}_i---\left(10\right)$

Estimate obtaining final degree of depth valuation by DOA-TOA.

Emulation is example with the line array; Suppose that emission basic matrix and reception basic matrix all are positioned at 100 meters, the end off sea; The seabed width that covers is 8 times of Hai Shen, centre frequency 195kHz, the pulsewidth that transmits 1ms; SF through behind the base band demodulating is 20kHz, and simulation produces the flat seabed involuting wave reception of the line array data of 64 passages thus.In-70 °～70 ° scopes, form 256 preformation wave beams; For a certain preformation wave beam, array element is divided into two submatrixs, change overlapping degree; And then obtain 8 kinds of different split beam modes, it is used the above-mentioned end detection technique based on the phase differential image estimate seabed depth.

Fig. 2-Fig. 7 has provided the processing procedure based on the phase differential image detecting technique of 64 yuan of line arraies respectively; Fig. 2 is that wave beam forms output; Fig. 3 is 60 degree phase difference sequences under 8 kinds of submatrix dividing mode during angle of releases, and Fig. 4 is the corresponding phase differential image of Fig. 3 phase difference sequence, and Fig. 5 is phase function error image e; Fig. 6 is the seabed trace image, and Fig. 7 is to simulation seabed testing result.

Can see along with glancing angle diminishes gradually from the output (like Fig. 2) that wave beam forms; The sound path that echo is propagated increases, and transmission loss (TL) increases, and the echoed signal intensity that receives weakens; And obvious broadening appears in wave beam, and this has just brought difficulty to the detection of edge wave beam.And this seabed detection method is accurately confirmed trace interval through the method for least square; The output that wave beam forms is just picked out the maximum wave beam of amplitude response simply as testing result, because near the wave beam amplitude the echo direction is close, curve is " slightly "; Be unfavorable for detecting; Can obtain a series of effective DOA valuations by trace interval, the image transformation algorithm can be realized the testing result that obtains in the different beams is added up through utilizing the phase information of each submatrix; Thereby obtain the detection curve (like Fig. 6) of " carefully ", effectively improved the detection performance.

The above description of this invention does not have restricted, if those of ordinary skill in the art is enlightened by it, in the situation of the protection that does not break away from claim of the present invention, makes other malformation of the present invention and embodiment, all belongs to protection scope of the present invention.

Claims (1)

1. multibeam echosounding method based on multiple spliting wave beam phase differential, it is characterized in that: the method comprising the steps of as follows:

Step 1: adopt different array element overlap modes that basic matrix is divided into two submatrixs; Be provided with the different split beam division methods of M kind; M>=2 wherein; The phase difference sequence that obtains M this wave beam is measured; Be the phase differential image on this direction, be designated as

Step 2: suppose that the wavefront that sound wave arrives is a plane wave, making echo arrive angle is θ, and two adjacent submatrix equivalent sound centers are respectively c _1iAnd c _2i, the distance between them is used d _iExpression, 1≤i≤M, the phase differential between two submatrixs is so:

Formula (1) is illustrated in the phase difference estimation of the reception signal of a given time; Wherein, F representes frequency of operation, and c is the velocity of sound, the deviation of Δ θ (n) expression echo and beam control direction; When echo was controlled direction from wave beam,

was zero;

For the phase difference sequence that the different split beam division methods of synchronization obtain, must be the seabed involuting wave in same orientation, adopt least-squares estimation to handle, obtain the phase difference error Function e:

Wherein, k _iBe the slope of phase difference sequence,

Make to obtain the estimation of Δ θ (n):

(3) formula is updated in (2), obtains an e value that shows submatrix phase function nonlinearity, be called the phase difference error function, echo in time of arrival the e value very little; When M>=2; Calculate nonlinearity size e; When e is lower than a definite thresholding;

is used to estimate that echo arrives angle DOA and seabed depth; The interval that this thresholding determined is a trace interval, as the preformation beam angle and time of arrival function the e value be called the phase difference error function;

Step 3: the nonzero value in the phase differential image has been represented in certain wave beam from the next echo of other direction; The phase differential image is carried out conversion; Claim that the image after the conversion is the seabed trace image; It is the function of echo arrival direction and time, and the size of each pixel point value is represented the size of seabed involuting wave possibility on a certain moment, a certain direction of arrival in the image lattice; For each pixel in the phase differential image, utilize (3) formula to calculate DOA, the value corresponding to the pixel of preset time and DOA in the image lattice of seabed will increase, and this shows seabed involuting wave possibility very big on certain direction; At first initialization, and generation seabed image B (n, α)=0, α is DOA, n is constantly; By (3) calculate Δ θ (n, β), increase B in the corresponding grid (n, α):

$B(n,\mathrm{\α})\⇐B(n,\mathrm{\α})+I(n,\mathrm{\β})---\left(4\right)$

Wherein, (n β) is increment to I, and β is the preformation field angle

I(n，β)＝1+wA(n，β)(5)

Here, constant 1 is a phase weighting, and (n is that the n moment, preformation field angle are the amplitude of the wave beam output of β β) to A, is amplitude weighting, and w is overall weighting factor;

Step 4: the wave beam of other big glancing angle is repeated above-mentioned steps one, two, three, obtain corresponding seabed trace image B (n, α);

Step 5: if the pairing employing of the bound of trace interval is respectively n constantly _lAnd n _h, combine SF f so _sObtain corresponding time interval: t _l=n _l* f _sAnd t _h=n _h* f _sAccording to the seabed image B under the corresponding wave beam (n, α), the amplitude weighting of time is average to calculate it in trace interval, as the echo TOA time of arrival estimated value of this wave beam, average weighted formula is following:

$t=\underset{i=T_l}{\overset{T_h}{\mathrm{\Σ}}}{A}_i\·t_i/\underset{i=T_l}{\overset{T_h}{\mathrm{\Σ}}}{A}_i---\left(6\right)$

Estimate obtaining final degree of depth valuation by DOA-TOA at last.

Images