CN102608609B - MIMO (multiple input multiple output) based high-resolution underwater target detection device and method - Google Patents

Abstract

The invention discloses an MIMO (multiple input multiple output) based high-resolution underwater target detection device and method. According to the invention, a potential target is actively detected through a plurality of mutually-orthogonal detection waveforms transmitted by a transmitting transducer array in a hydroacoustic environment, and a hydrophone-array received target echo is received. Through MIMO processing, a method for carrying out detection and estimation on an MIMO frame is established, and the extension of waveform diversity gains and virtual array apertures is obtained. By using the MIMO based underwater target detection method disclosed by the invention, in the process of carrying out hydroacoustic target detection, compared with conventional phase control, a higher detection resolution and higher parameter identification performance can be obtained.

Description

A kind of high-resolution Underwater Target Detection method based on MIMO

Technical field

The present invention relates to a kind of high-resolution Underwater Target Detection method based on MIMO, is a kind of signal processing new method, belongs to Underwater Acoustic Object and detects and positioning field.

Background technology

The existing Underwater Target Detection method based on level transmitting-receiving battle array structure is all the phased array structure, the emission battle array is driven same detectable signal and is emitted to a direction, mode by scanning is surveyed all interested directions, receive battle array and receive signal echo, realize target detection and location by wave beam formation to received signal and matched filtering.The target resolution of phased array detection method becomes ratio with the battle array aperture that receives battle array.Therefore can receive and dispatch the aperture of penetrating battle array by increase for the resolution that improves target and reach, but the expansion in battle array aperture needs more emitting and receiving equipment, designs more complicated sonar system, pays larger economic cost.And phased array is directive property emission same signal, an interested orientation once can only be detected, realize that omnibearing detection need to, through repeatedly comprehensive scanning, need a lot of detection times.

Summary of the invention

The objective of the invention is the problem for the existence of existing sonar technique, a kind of high-resolution Underwater Target Detection method based on MIMO is provided.

MIMO refers to multiple-input and multiple-output, many inputs refer to launches the quadrature detectable signal simultaneously, many output refers in the signal echo that receives the battle array reception and comprises the target information that different detectable signals are taken back, by wave beam, form and the matched filtering processing, distinguish the transmit virtual data vector of echo of difference, obtain the waveform diversity gain, expand virtual battle array aperture, arrive high-resolution detection and location.MIMO is non-directive emission orthogonal waveforms simultaneously, and once emission can realize the detection to all orientation, thereby can save more detection time.

For achieving the above object, the technical solution used in the present invention is: the high-resolution Underwater Target Detection device that the present invention is based on MIMO comprises:

Signal transmitter, for launching orthogonal signal;

Power amplifier, for carrying out power amplification by orthogonal signal;

The transmitting transducer battle array, be converted into acoustical signal for the orthogonal signal by after amplifying by electric signal, and acoustical signal is emitted to wish detection waters;

The receiving hydrophone battle array, for receiving the echo of the acoustical signal that described transmitting transducer paroxysm penetrates, and be converted to electric signal by the echo of described acoustical signal;

Signal receiver, the electric signal of changing for receiving and store described receiving hydrophone battle array;

Signal processor, for receiving the electric signal of receiving from signal receiver, and carry out the MIMO processing to this electric signal, obtains the MIMO beam modes; Utilize formula (1) to be estimated the MIMO beam modes, obtain the orientation of potential target, then utilize the Generalized Likelihood Ratio detecting device shown in formula (2) whether to detect on the orientation of described potential target the necessary being target:

$\widehat{\mathrm{\θ}}=\arg \underset{\mathrm{\θ},\mathrm{\α}}{\min }Q\left(\mathrm{\θ}\right)---\left(1\right)$

$Q\left(\widehat{\mathrm{\&theta;}}\right)\begin{array}{c}{H}_1\\ \&GreaterEqual;\\ <\\ {\mathrm{<figure-callout\; id="0"\; label="H"\; filenames="111219112430.png,111219112437.png"\; state="\{\{state\}\}">H</figure-callout>}}_0\end{array}\mathrm{\&delta;}---\left(2\right)$

In formula (1) and (2), Q (θ) is the MIMO beam modes, and θ is all orientation that target may exist, and α is the reflection coefficient of target,

for the orientation of the potential target that estimates, Q

for the beam modes value on the potential target orientation estimated, H ₀mean not have real target, H on the orientation of the estimated potential target gone out ₁mean to have real target, the detection threshold that δ is the Generalized Likelihood Ratio detecting device on the orientation of the estimated potential target gone out.

The method of utilizing the high-resolution Underwater Target Detection device based on MIMO of the present invention to carry out the high-resolution Underwater Target Detection comprises the steps:

(1) signal transmitter sends one group of M mutually orthogonal orthogonal signal, and described orthogonal signal are expressed as s[n]=(s ₁[n], s ₂[n] ... s _m[n]) ^t,

And described orthogonal signal meet the signal in orthogonal condition shown in formula (3):

$\frac{1}{\sqrt{L}}\underset{n=0}{\overset{L}{\mathrm{\&Sigma;}}}{s}_i\left[n\right]{s_j}^{*}\left[n\right]=\left\{\begin{array}{cc}1,& i=\mathrm{<figure-callout\; id="0"\; label="j"\; filenames="111219112430.png,111219112437.png"\; state="\{\{state\}\}">j</figure-callout>}\\ 0,& i\&NotEqual;j\end{array}\right.i,j=\mathrm{1,2}...M---\left(3\right)$

Wherein, the positive integer that M is>=1, n means n time-sampling point of described orthogonal signal, 1≤n≤L, the length that L is orthogonal signal, the computing of T representing matrix transposition, s _i[n] means described M orthogonal signal s[n] in i, s _j[n] means described M orthogonal signal s[n] in j, s _j ^*[n] means s _jthe conjugate operation of [n];

(2) the transmitting transducer battle array that comprises M unit transmitting transducer is positioned over to wish with the receiving hydrophone battle array that comprises N unit receiving hydrophone and surveys in waters, wherein, the positive integer that N is>=1; The spacing of adjacent transmitting transducer is d _t, the spacing of adjacent receiving hydrophone is d _r, the driving vector of the driving vector sum receiving hydrophone battle array of described transmitting transducer battle array is respectively suc as formula shown in (4), (5); The M that described power amplifier is launched signal transmitter orthogonal signal s[n] be sent to described transmitting transducer battle array after amplifying, described transmitting transducer battle array is converted into acoustical signal by the orthogonal signal after amplifying by electric signal, and this acoustical signal is emitted to wish detection waters; The echo of the acoustical signal that simultaneously described receiving hydrophone battle array reception transmitting transducer battle array is launched, and the echo of described acoustical signal is converted to electric signal as the formula (6):

$a_t\left(\mathrm{\&theta;}\right)=[1,e^{-\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="111219112430.png"\; state="\{\{state\}\}">j</figure-callout>}2\mathrm{\&pi;f}{d}_t\sin \mathrm{\&theta;}/c},...,e^{-\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="111219112430.png"\; state="\{\{state\}\}">j</figure-callout>}2\mathrm{\&pi;f}(M-1)d_t\sin \mathrm{\&theta;}/c}{]}^T---\left(4\right)$

$a_r\left(\mathrm{\&theta;}\right)=[1,e^{-\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="111219112430.png"\; state="\{\{state\}\}">j</figure-callout>}2\mathrm{\&pi;f}{d}_r\sin \mathrm{\&theta;}/c},...,e^{-\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="111219112430.png"\; state="\{\{state\}\}">j</figure-callout>}2\mathrm{\&pi;f}(N-1)d_r\sin \mathrm{\&theta;}/c}{]}^T---\left(5\right)$

In formula (4) and formula (5), a _t(θ) be the driving vector of transmitting transducer battle array, a _r(θ) be the driving vector of receiving hydrophone battle array, the element number of array that M is described transmitting transducer battle array, the element number of array that N is described receiving hydrophone battle array, j is complex unit, d _tfor the spacing of adjacent transmitting transducer, d _rfor the spacing of adjacent receiving hydrophone, the frequency of the orthogonal signal that f is the signal transmitter emission, the velocity of sound that c is water, θ is all orientation that target may exist, the computing of T representing matrix transposition;

r[n]=αa _r(θ)a _t ^T(θ)s[n]+w[n],1≤n≤L （6）

In formula (6), r[n] be the electric signal that the receiving hydrophone battle array receives, θ is all orientation that target may exist, the reflection coefficient that α is target, w[n] for the reception of receiving hydrophone battle array with the incoherent additive noise vector that transmits, a _t ^t(θ) mean a _t(θ) transposition;

(3) the electric signal r[n that utilizes formula (7) that the receiving hydrophone battle array is received] respectively with each orthogonal signal s _i[n] does matched filtering and processes, and obtains abundant statistical matrix as the formula (8),

${\mathrm{\&eta;}}_i={\left[\begin{array}{cccc}{\mathrm{\&eta;}}_{i1}& {\mathrm{\&eta;}}_{i2}& ...& {\mathrm{\&eta;}}_{\mathrm{iN}}\end{array}\right]}^T$

$=\frac{1}{\sqrt{L}}\underset{n=1}{\overset{L}{\mathrm{\&Sigma;}}}r\left[n\right]{s_i}^{*}\left[n\right]={\mathrm{\&alpha;a}}_r\left(\mathrm{\&theta;}\right)a_{\mathrm{ti}}\left(\mathrm{\&theta;}\right),i=\mathrm{1,2},...M$ (7)

In formula (7), s _i[n] means described M orthogonal signal s[n] in i, s _i ^*[n] means s _ithe conjugate operation of [n]; η _in(n=1,2 ... N) be the vectorial η of abundant statistics of i unit _in element, a _ti(θ) (i=1,2 ... be M) that vectorial a is driven in emission _t(θ) i element;

$E=\left[\begin{array}{cccc}{\mathrm{\&eta;}}_1& {\mathrm{\&eta;}}_2& ...& {\mathrm{\&eta;}}_M\end{array}\right]=\frac{1}{\sqrt{L}}\underset{n=1}{\overset{L}{\mathrm{\&Sigma;}}}r\left[n\right]s^H\left[n\right]---\left(8\right)$

In formula (8), E means abundant statistical matrix, s ^h[n] means s[n] do the conjugate transpose computing;

Utilize formula (9) to carry out the column vector processing described abundant statistical matrix, the vectorial η of abundant statistics as the formula (10) be expanded:

$\mathrm{\&eta;}=\mathrm{vec}\left(\begin{array}{c}\left[\begin{array}{cccc}{\mathrm{\&eta;}}_1& {\mathrm{\&eta;}}_2& ...& {\mathrm{\&eta;}}_M\end{array}\right]\end{array}\right)---\left(9\right)$

$\mathrm{\&eta;}=\mathrm{vec}\left(\frac{1}{\sqrt{L}}\underset{n=1}{\overset{L}{\mathrm{\&Sigma;}}}r\right[n\left]s^H\right[n\left]\right)$

$=\mathrm{vec}\left(\frac{1}{\sqrt{L}}\underset{n=1}{\overset{L}{\mathrm{\&Sigma;}}}\left({\mathrm{\&alpha;a}}_r\left(\mathrm{\&theta;}\right){a_t}^T\left(\mathrm{\&theta;}\right)s\right[n]+w[n\left]\right)s^H\right[N\left]\right)---\left(10\right)$

$=\mathrm{\&alpha;vec}(a_r\left(\mathrm{\&theta;}\right){a_t}^T\left(\mathrm{\&theta;}\right)+\frac{1}{\sqrt{L}}\underset{n=1}{\overset{L}{\mathrm{\&Sigma;}}}w[n\left]s^H\right[n\left]\right)$

=αd(θ)+v

In formula (9) and formula (10), the computing of vec representing matrix column vector, s ^h[n] means s[n] be conjugate transpose computing, a _t ^t(θ) mean a _t(θ) transposition, v is distributed as v～N for obeying ^c(0, σ _w ²i _nM) multiple Gaussian noise, wherein, σ _w ²noise power, I _nMthe unit matrix that order is MN, d (θ)=vec (a _r(θ) a _t ^t(θ)) be the response vector of the receiving hydrophone battle array of length M N * 1;

(4) the vectorial η of abundant statistics of the expansion obtained according to step (3), obtain MIMO beam modes figure by formula (11), and the orientation of the potential target that is obtained estimating by formula (12)

$Q\left(\mathrm{\&theta;}\right)=\frac{{\left|d^H\left(\mathrm{\&theta;}\right)\mathrm{\&eta;}\right|}^2}{{\left|\right|d\left(\mathrm{\&theta;}\right)\left|\right|}^2}=\frac{{\left|{a_r}^H\left(\mathrm{\&theta;}\right)\underset{n=1}{\overset{L}{\mathrm{\&Sigma;}}}r\right[n\left]s{\left[n\right]}^H{a_t}^{*}\left(\mathrm{\&theta;}\right)\right|}^2}{L{\left|\right|a_r\left(\mathrm{\&theta;}\right)\left|\right|}^2{\left|\right|a_t\left(\mathrm{\&theta;}\right)\left|\right|}^2}---\left(11\right)$

$\widehat{\mathrm{\&theta;}}=\arg \underset{\mathrm{\&theta;},\mathrm{\&alpha;}}{\min }Q\left(\mathrm{\&theta;}\right)---\left(12\right)$

In formula (11) and formula (12), Q (θ) is the MIMO beam modes, and θ is all orientation that target may exist, a _t(θ) be the driving vector of transmitting transducer battle array, a _r(θ) be the driving vector of receiving hydrophone battle array, || || the expression vector is asked modular arithmetic, || for asking signed magnitude arithmetic(al), L is emission orthogonal signal length, a _r ^h(θ) mean a _r(θ) be transpose conjugate computing, a _t ^*(θ) mean a _t(θ) do conjugate operation, α means the reflection coefficient of target,

the orientation of the potential target that expression estimates;

(5) orientation at the estimated potential target gone out of step (4) according to formula (13) judgement whether locate the necessary being target:

$Q\left(\widehat{\mathrm{\&theta;}}\right)\begin{array}{c}{H}_1\\ \&GreaterEqual;\\ <\\ {\mathrm{<figure-callout\; id="0"\; label="H"\; filenames="111219112430.png,111219112437.png"\; state="\{\{state\}\}">H</figure-callout>}}_0\end{array}\mathrm{\&delta;}---\left(13\right)$

In formula (13),

for the beam modes value on the potential target orientation estimated, H ₀the orientation that means the estimated potential target gone out does not exist real target, H ₁there is real target in the orientation that means the estimated potential target gone out, the detection threshold that δ is the Generalized Likelihood Ratio detecting device.

Compared with prior art, the invention has the beneficial effects as follows:

1) by MIMO, process, the gain of acquisition waveform diversity, sonar virtual battle array aperture and spatial degrees of freedom have been expanded, when the target localization wave beam forms, the narrower detection main lobe that can obtain and lower secondary lobe, improve target detection resolution and parameter recognition performance, reduced the impact that secondary lobe disturbs, improved the echo signal to noise ratio (S/N ratio).

2) detection method used in the present invention is once surveyed the detection that can realize all orientation, has avoided the process of the comprehensive scanning of phased array pattern, can save detection time.

The accompanying drawing explanation

Fig. 1 is the fundamental diagram of method in the present invention;

Fig. 2 is the schematic diagram of 7 yuan of transmitting transducer battle arrays and 6 yuan of receiving hydrophone battle arrays;

Fig. 3 is waveguide pool construction and the schematic diagram of structuring the formation;

Fig. 4 is the 7 tunnel orthogonal signal schematic diagram that the transmitting transducer paroxysm is penetrated;

Fig. 5 is the beam pattern contrast of detection method and the phased array detection of a target in the present invention.

Embodiment

Below in conjunction with accompanying drawing and instantiation, the present invention will be further described.

The present invention is based on the high-resolution Underwater Target Detection device of MIMO, comprising:

---signal transmitter, for launching orthogonal signal;

---power amplifier, for orthogonal signal are carried out to power amplification;

---the transmitting transducer battle array is converted into acoustical signal for the orthogonal signal by after amplifying by electric signal, and acoustical signal is emitted to wish detection waters;

---the receiving hydrophone battle array for receiving the echo of the acoustical signal that described transmitting transducer paroxysm penetrates, and is converted to electric signal by the echo of described acoustical signal;

---signal receiver, the electric signal of changing for receiving and store described receiving hydrophone battle array;

---signal processor, for receiving the electric signal of receiving from signal receiver, and this electric signal is carried out to the MIMO processing, obtain the MIMO beam modes; Utilize formula (1) to be estimated the MIMO beam modes, obtain the orientation of potential target, then utilize the Generalized Likelihood Ratio detecting device shown in formula (2) whether to detect on the orientation of described potential target the necessary being target:

$\widehat{\mathrm{\&theta;}}=\arg \underset{\mathrm{\&theta;},\mathrm{\&alpha;}}{\min }Q\left(\mathrm{\&theta;}\right)---\left(12\right)$

$Q\left(\widehat{\mathrm{\&theta;}}\right)\begin{array}{c}{H}_1\\ \&GreaterEqual;\\ <\\ {\mathrm{<figure-callout\; id="0"\; label="H"\; filenames="111219112430.png,111219112437.png"\; state="\{\{state\}\}">H</figure-callout>}}_0\end{array}\mathrm{\&delta;}---\left(13\right)$

In formula (1) and (2), Q (θ) is the MIMO beam modes, and θ is all orientation that target may exist, and α is the reflection coefficient of target,

for the orientation of the potential target that estimates,

for the beam modes value on the potential target orientation estimated, H ₀the orientation that means described potential target does not exist target, H ₁there is target in the orientation that means described potential target, the detection threshold that δ is the Generalized Likelihood Ratio detecting device.

Figure 1 shows that the fundamental diagram of detection method of the present invention.As shown in Figure 1, sniffer of the present invention comprises above water and underwater portion, above water comprises signal transmitter, power amplifier, signal receiver and signal processor, underwater portion comprises transmitting transducer battle array (being called for short " emission battle array ") and a receiving hydrophone battle array (being called for short " receiving battle array ") that comprises 6 yuan of receiving hydrophones of 7 yuan of transmitting transducers, now launching a burst of first number is M=7, and receiving a burst of first number is N=6.

It should be noted that, although it is example that Fig. 1 be take 7 yuan of transmitting transducers and 6 yuan of receiving hydrophones for convenience of description, but the transmitting transducer in transmitting transducer battle array of the present invention can be M unit, receiving hydrophone in the receiving hydrophone battle array can be N unit, wherein, the quantity of the mutually orthogonal orthogonal signal that the value of M sends with signal transmitter is identical, and the M positive integer that is >=1; N is the number that receives array element, and the number that receives array element is to be greater than 1 positive integer, the positive integer that N is >=1.

Emission battle array and receive battle array structure the formation schematic diagram as shown in Figure 2, the battle array spacing of emission battle array is 10cm, the battle array spacing that receives battle array is 6cm, take first emission array element is reference origin, launches so the vectorial a of driving _t(θ) drive vectorial a with receiving _r(θ) can use respectively formula (14) and formula (15) to mean,

a _t(θ)=exp(-j2πd _tfsin(θ)/c),d _t=[0102030405060] ^T/100; （14）

a _r(θ)=exp(j2πd _rfsin(θ)/c),d _r=[101622283440] ^T/100; （15）

In formula (14) and formula (15), f is emission signal frequency, the velocity of sound that c is water, and θ is all orientation that target may exist, the computing of T representing matrix transposition.

Because the pure-tone polse signal of different frequency can guarantee mutually orthogonal and meet the signal in orthogonal condition that formula (1) means, so the present invention can use the pure-tone polse signal of different frequency as transmitting.Signal transmitter shown in Fig. 1 is launched the pure-tone polse signal s[n that 7 tunnel amplitudes are 1V, the time span different frequency that is 3ms], 1≤n≤L, L is signal length.S[n] expression formula as the formula (16).

$s\left(n\right)=\left(\begin{array}{c}{s}_1\left[n\right]\\ s_2\left[n\right]\\ .\\ .\\ .\\ s_M\left[n\right]\end{array}\right)=\left(\begin{array}{c}\sin (2\mathrm{\&pi;}{f}_{1}n/f_s)\\ \sin (2\mathrm{\&pi;}{f}_{2}n/f_2)\\ .\\ .\\ .\\ \sin (2\mathrm{\&pi;}{f}_{M}n/f_s)\end{array}\right),n=\mathrm{1,2},...L---\left(16\right)$

S in formula (16) _i[n] is 7 tunnel orthogonal signal s[n of signal transmitter emission] i road signal, f=[f ₁f ₂f _m]=[6,7,8,9,10,11,12] ^tkHz, be respectively the frequency of the orthogonal signal of each road emission, f _s=50KHz is for receiving signal sampling frequency, the product that the 3ms signal length is signal sampling frequency and time, that is: L=3*10 ^-3* 50*10 ³=150.Figure 3 shows that 7 road Orthogonal injection signal (s ₁[n], s ₂[n] ... s _m[n]).

Emission battle array shown in Fig. 2 and a reception battle array level are put into to the long 8m in Zhong， pond, waveguide pond shown in Fig. 4, wide 2m, dark 1.5m, and the surrounding in pond is that the sound eliminating tile wall is used for absorbing the sound wave that arrives the pond surrounding, reduces the multipath interference, the environment of simulation free field.Transmitting transducer battle array and receiving hydrophone battle array are positioned at depth of water 0.75m place, apart from the θ of this horizontal array 5m=0 ° of direction, put a target.

7 tunnel orthogonal signal s (n) of signal transmitter emission amplify through power amplifier, be sent to the transmitting transducer battle array, the electric signal that transmitting transducer is sent out large by the power amplifier of reception is converted to acoustical signal and is emitted in water, simultaneously No. 6 receiving hydrophone battle arrays receive the echo of the acoustical signal that described transmitting transducer paroxysm penetrates, and the echo of described acoustical signal is converted to electric signal, signal receiver receives and stores the electric signal that described receiving hydrophone battle array is changed, the signal r (n) that this No. 6 receiving hydrophone battle array receives, 1≤n≤L, mean as the formula (17)

$r\left(n\right)=\left(\begin{array}{c}{r}_1\left[n\right]\\ r_2\left[n\right]\\ .\\ .\\ .\\ r_N\left[n\right]\end{array}\right),n=\mathrm{1,2},...L,N=6---\left(17\right)$

R in formula (17) _i[n] means the signal that i unit receiving hydrophone receives.

The electric signal r[n that utilizes formula (17) that the receiving hydrophone battle array is received] respectively with each orthogonal signal s _i[n] does matched filtering and processes, and obtains abundant statistical matrix as the formula (18),

${\mathrm{\&eta;}}_i={\left[\begin{array}{cccc}{\mathrm{\&eta;}}_{i1}& {\mathrm{\&eta;}}_{i2}& ...& {\mathrm{\&eta;}}_{\mathrm{iN}}\end{array}\right]}^T$

$=\frac{1}{\sqrt{L}}\underset{n=1}{\overset{L}{\mathrm{\&Sigma;}}}r\left[n\right]{s_i}^{*}\left[n\right]={\mathrm{\&alpha;a}}_r\left(\mathrm{\&theta;}\right)a_{\mathrm{ti}}\left(\mathrm{\&theta;}\right),i=\mathrm{1,2},...M$ (18)

In formula (18), η _in(n=1,2 ... N) be the vectorial η of abundant statistics of i unit _in element, a _ti(θ) (i=1,2 ... be M) that vectorial a is driven in emission _t(θ) i element;

$E=\left[\begin{array}{cccc}{\mathrm{\&eta;}}_1& {\mathrm{\&eta;}}_2& ...& {\mathrm{\&eta;}}_M\end{array}\right]=\frac{1}{\sqrt{L}}\underset{n=1}{\overset{L}{\mathrm{\&Sigma;}}}r\left[n\right]s^H\left[n\right]---\left(19\right)$

In formula (19), E is abundant statistical matrix, s ^h[n] means s[n] do the conjugate transpose computing.

Utilize formula (19) to carry out the column vector processing described abundant statistical matrix, the vectorial η of abundant statistics as the formula (20) be expanded:

η=vec([η ₁ η ₂ … η _M]) （19）

$\mathrm{\&eta;}=\mathrm{vec}\left(\frac{1}{\sqrt{L}}\underset{n=1}{\overset{L}{\mathrm{\&Sigma;}}}r\right[n\left]s^H\right[n\left]\right)$

$=\mathrm{vec}\left(\frac{1}{\sqrt{L}}\underset{n=1}{\overset{L}{\mathrm{\&Sigma;}}}\left({\mathrm{\&alpha;a}}_r\left(\mathrm{\&theta;}\right){a_t}^T\left(\mathrm{\&theta;}\right)s\right[n]+w[n\left]\right)s^H\right[n\left]\right)---\left(20\right)$

$=\mathrm{\&alpha;vec}(a_r\left(\mathrm{\&theta;}\right){a_t}^T\left(\mathrm{\&theta;}\right)+\frac{1}{\sqrt{L}}\underset{n=1}{\overset{L}{\mathrm{\&Sigma;}}}w[n\left]s^H\right[n\left]\right)$

=αd(θ)+v

In formula (19) and formula (20), the computing of vec representing matrix column vector, s ^h[n] means s[n] be conjugate transpose computing, a _t ^tθ) mean a _t(θ) do the transposition computing, v is distributed as v～N for obeying ^c(0, σ _w ²i _nM) multiple Gaussian noise, σ wherein _w ²noise power, I _nMthe unit matrix that order is MN, d (θ)=vec (a _r(θ) a _t ^t(θ)) be the battle array response vector of the receiving hydrophone battle array of length M N * 1.And the conventional phased array that the element number of array that uses the receiving hydrophone battle array is N is while surveying, the length of the battle array response vector of its receiving hydrophone battle array is N * 1, the battle array response vector length of detection method of the present invention with respect to the extended length of the battle array response vector of phased array detection mode M doubly, mean that virtual battle array aperture expanded M doubly, increase the additional space degree of freedom, thereby can improve target resolution and the parameter recognition performance of detection system.

The vectorial η of abundant statistics obtained according to formula (20), set up the maximum likelihood ratio sensor of target azimuth θ.Obtained the maximal possibility estimation of potential target orientation θ by formula (21)

$\widehat{\mathrm{\&theta;}}=\arg \underset{\mathrm{\&theta;},\mathrm{\&alpha;}}{\min }{\left|\right|\mathrm{\&eta;}-\mathrm{\&alpha;d}\left(\mathrm{\&theta;}\right)\left|\right|}^2$

$=\arg \underset{\mathrm{\&theta;},\mathrm{\&alpha;}}{\max }\frac{{\left|d^H\left(\mathrm{\&theta;}\right)\mathrm{\&eta;}\right|}^2}{{\left|\right|d\left(\mathrm{\&theta;}\right)\left|\right|}^2}$ (21)

In formula (21) || || the expression vector is asked modular arithmetic, || for asking signed magnitude arithmetic(al).Can be found out by formula (21), ask for the maximal possibility estimation in potential target orientation

be equivalent to maximize objective function

resulting θ value.

By the objective function in formula (21)

simplify and be written as Q (θ), as the formula (22):

$Q\left(\mathrm{\&theta;}\right)=\frac{{\left|d^H\left(\mathrm{\&theta;}\right)\mathrm{\&eta;}\right|}^2}{{\left|\right|d\left(\mathrm{\&theta;}\right)\left|\right|}^2}=\frac{{\left|{a_r}^H\left(\mathrm{\&theta;}\right)\underset{n=1}{\overset{L}{\mathrm{\&Sigma;}}}r\right[n\left]s^H\right[n\left]{a_t}^{*}\left(\mathrm{\&theta;}\right)\right|}^2}{L{\left|\right|a_r\left(\mathrm{\&theta;}\right)\left|\right|}^2{\left|\right|a_t\left(\mathrm{\&theta;}\right)\left|\right|}^2}---\left(22\right)$

In formula (22), a is driven in emission _t(θ) drive vectorial a with receiving _r(θ) expression formula is suc as formula shown in (14) and formula (15), the orthogonal signal s[n of emission] as the formula (16), receive the expression formula of signal as the formula (17), the length of the orthogonal signal that L=150 is the signal transmitter emission.

The expressed beam modes of use formula (22), for each-90 °≤θ≤90 °, calculate its corresponding beam modes value, obtains the beam modes figure as shown in Fig. 5 solid line.According to formula (23) and beam modes figure, search for the corresponding angle θ of maximal value of Q (θ), be the orientation of the potential target estimated

Then according to the described Generalized Likelihood Ratio detecting device of formula (24), judge the orientation of the potential target estimated

whether target necessary being.

$Q\left(\widehat{\mathrm{\&theta;}}\right)\begin{array}{c}{H}_1\\ \&GreaterEqual;\\ <\\ {\mathrm{<figure-callout\; id="0"\; label="H"\; filenames="111219112430.png,111219112437.png"\; state="\{\{state\}\}">H</figure-callout>}}_0\end{array}\mathrm{\&delta;}---\left(24\right)$

In formula (24), H ₀mean not have real target, H on the orientation of the estimated potential target gone out ₁mean to have real target on the orientation of the estimated potential target gone out, the detection threshold that δ is the Generalized Likelihood Ratio detecting device, by predefined false-alarm probability P _fdetermine.As Q (θ)>=P _fthe time think orientation, potential target place the target necessary being, otherwise think orientation, potential target place target necessary being not.

Can find out from Fig. 4 solid line the target azimuth estimated

be consistent with the realistic objective orientation, proved the correctness of inventive method.

In order to compare with the phased array situation, it is 3ms that each array element of emission battle array is launched a time span simultaneously, the frequency band that amplitude is 1V is the linear FM signal of 6Khz to 10Khz, the signal of each array element emission of now emission battle array is identical, do not meet the signal in orthogonal condition shown in formula (1), so be now phase control emission, but not MIMO emission.The reception signal that receives battle array is done to phased array beam formation and matched filtering processing, obtain the phased beam modes figure of its correspondence as shown in Fig. 5 dotted line.

According to Fig. 5, the beam modes figure that the detection method used in phased beam modes figure and invention is obtained compares, and can find out that the beam modes output of detection method of the present invention can obtain narrower detection main lobe and lower detection secondary lobe.The main lobe width of the beam modes of detection method of the present invention is conventional phased array main lobe width

the first secondary lobe is than the low 18dB of the first secondary lobe of conventional phased array, and beam modes figure has narrower main lobe can obtain higher target resolution, and lower secondary lobe can reduce the interference of other directions, improves the echo signal to noise ratio (S/N ratio), improves target detection probability.

Claims (1)

1. the high-resolution Underwater Target Detection device of a utilization based on MIMO carries out the method for high-resolution Underwater Target Detection, it is characterized in that, comprises the steps:

(1) signal transmitter sends one group of M mutually orthogonal orthogonal signal, and described orthogonal signal are expressed as s[n]=(s ₁[n], s ₂[n] ... s _m[n]) ^t,

And described orthogonal signal meet the signal in orthogonal condition shown in formula (3):

$\frac{1}{\sqrt{L}}\underset{n=0}{\overset{L}{\mathrm{\&Sigma;}}}{s}_i\left[n\right]{s_j}^{*}\left[n\right]=\left\{\begin{array}{c}1,i=j\\ 0,i\&NotEqual;j\end{array},i,j=\mathrm{1,2}...M\right.---\left(3\right)$

Wherein, the positive integer that M is>=1, n means n time-sampling point of described orthogonal signal, 1≤n≤L, the length that L is orthogonal signal, the computing of T representing matrix transposition, s _i[n] means described M orthogonal signal s[n] in i, s _j[n] means described M orthogonal signal s[n] in j, s _j ^*[n] means s _jthe conjugate operation of [n];

(2) the transmitting transducer battle array that comprises M unit transmitting transducer is positioned over to wish with the receiving hydrophone battle array that comprises N unit receiving hydrophone and surveys in waters, wherein, the positive integer that N is>=1; The spacing of adjacent transmitting transducer is d _t, the spacing of adjacent receiving hydrophone is d _r, the driving vector of the driving vector sum receiving hydrophone battle array of described transmitting transducer battle array is respectively suc as formula shown in (4), (5); The M that power amplifier is launched signal transmitter orthogonal signal s[n] be sent to described transmitting transducer battle array after amplifying, described transmitting transducer battle array is converted into acoustical signal by the orthogonal signal after amplifying by electric signal, and this acoustical signal is emitted to wish surveys waters; The echo of the acoustical signal that simultaneously described receiving hydrophone battle array reception transmitting transducer battle array is launched, and the echo of described acoustical signal is converted to electric signal as the formula (6): $a_t\left(\mathrm{\&theta;}\right)=[1,e^{-j2\mathrm{\&pi;}{\mathrm{fd}}_t\sin \mathrm{\&theta;}/c},...,e^{-j2\mathrm{\&pi;f}(M-1)d_t\sin \mathrm{\&theta;}/c}{]}^T---\left(4\right)$ $a_r\left(\mathrm{\&theta;}\right)=[1,e^{-j2\mathrm{\&pi;}{\mathrm{fd}}_r\sin \mathrm{\&theta;}/c},...,e^{-j2\mathrm{\&pi;f}(N-1)d_r\sin \mathrm{\&theta;}/c}{]}^T---\left(5\right)$

In formula (4) and formula (5), a _t(θ) be the driving vector of transmitting transducer battle array, a _r(θ) be the driving vector of receiving hydrophone battle array, the element number of array that M is described transmitting transducer battle array, the element number of array that N is described receiving hydrophone battle array, j is complex unit, d _tfor the spacing of adjacent transmitting transducer, d _rfor the spacing of adjacent receiving hydrophone, the frequency of the orthogonal signal that f is the signal transmitter emission, the velocity of sound that c is water, θ is all orientation that target may exist, the computing of T representing matrix transposition;

r[n]=αa _r(θ)a _t ^T(θ)s[n]+w[n],1≤n≤L （6）

In formula (6), r[n] electric signal that receives for the receiving hydrophone battle array, all orientation of θ for existing for target, the reflection coefficient that α is target, w[n] for the reception of receiving hydrophone battle array with transmit incoherent additive noise vector, a _t ^t(θ) mean a _t(θ) transposition;

(3) the electric signal r[n that utilizes formula (7) that the receiving hydrophone battle array is received] respectively with each orthogonal signal s _i[n] does matched filtering and processes, and obtains abundant statistical matrix as the formula (8),

${\mathrm{\&eta;}}_i=[\begin{array}{cccc}{\mathrm{\&eta;}}_{i1}& {\mathrm{\&eta;}}_{i2}& ...& {\mathrm{\&eta;}}_{\mathrm{iN}}\end{array}{]}^T$ （7）

$=\frac{1}{\sqrt{L}}\underset{n=1}{\overset{L}{\mathrm{\&Sigma;}}}r\left[n\right]{s_i}^{*}\left[n\right]={\mathrm{\&alpha;a}}_r\left(\mathrm{\&theta;}\right)a_{\mathrm{ti}}\left(\mathrm{\&theta;}\right),i=\mathrm{1,2},...M$

In formula (7), s _i[n] means described M orthogonal signal s[n] in i, s _i ^*[n] means s _ithe conjugate operation of [n]; η _in(n=1,2 ... N) be the vectorial η of abundant statistics of i unit _in element, a _ti(θ) (i=1,2 ... be M) that vectorial a is driven in emission _t(θ) i element;

$E=[\begin{array}{cccc}{\mathrm{\&eta;}}_1& {\mathrm{\&eta;}}_2& ...& {\mathrm{\&eta;}}_M\end{array}]=\frac{1}{\sqrt{L}}\underset{n=1}{\overset{L}{\mathrm{\&Sigma;}}}r[n\left]s^H\right[n]---\left(8\right)$

In formula (8), E means abundant statistical matrix, s ^h[n] means s[n] do the conjugate transpose computing;

Utilize formula (9) to carry out the column vector processing described abundant statistical matrix, the vectorial η of abundant statistics as the formula (10) be expanded:

η=vec([η ₁ η ₂…η _M]) （9）

$\mathrm{\&eta;}=\mathrm{vec}\left(\frac{1}{\sqrt{L}}\underset{n=1}{\overset{L}{\mathrm{\&Sigma;}}}r\right[n\left]s^H\right[n\left]\right)$

$=\mathrm{vec}\left(\frac{1}{\sqrt{L}}\underset{n=1}{\overset{L}{\mathrm{\&Sigma;}}}\left({\mathrm{\&alpha;a}}_r\left(\mathrm{\&theta;}\right){a_t}^T\left(\mathrm{\&theta;}\right)s\left[n\right]+w\left[n\right]\right)s^H\right[n\left]\right)---\left(10\right)$

$=\mathrm{\&alpha;vec}(a_r\left(\mathrm{\&theta;}\right){a_t}^T\left(\mathrm{\&theta;}\right)+\frac{1}{\sqrt{L}}\underset{n=1}{\overset{L}{\mathrm{\&Sigma;}}}w[n\left]s^H\right[n\left]\right)$

$=\mathrm{\&alpha;d}\left(\mathrm{\&theta;}\right)+v$

In formula (9) and formula (10), the computing of vec representing matrix column vector, s ^h[n] means s[n] be conjugate transpose computing, a _t ^t(θ) mean a _t(θ) transposition, v is distributed as v～N for obeying ^c(0, σ _w ²i _nM) multiple Gaussian noise, wherein, σ _w ²noise power, I _nMthe unit matrix that order is MN, d (θ)=vec (a _r(θ) a _t ^t(θ)) be the response vector of the receiving hydrophone battle array of length M N * 1;

(4) the vectorial η of abundant statistics of the expansion obtained according to step (3), obtain MIMO beam modes figure by formula (11), and the orientation of the potential target that is obtained estimating by formula (12)

$Q\left(\mathrm{\&theta;}\right)=\frac{{\left|d^H\left(\mathrm{\&theta;}\right)\mathrm{\&eta;}\right|}^2}{{\left|\right|d\left(\mathrm{\&theta;}\right)\left|\right|}^2}=\frac{{|{a_r}^H\left(\mathrm{\&theta;}\right)\underset{n=1}{\overset{L}{\mathrm{\&Sigma;}}}r{{\left[n\right]s\left[n\right]}^H{a}_t}^{*}\left(\mathrm{\&theta;}\right)|}^2}{L{\left|\right|a_r\left(\mathrm{\&theta;}\right)\left|\right|}^2{\left|\right|a_t\left(\mathrm{\&theta;}\right)\left|\right|}^2}---\left(11\right)$

$\widehat{\mathrm{\&theta;}}=\arg \underset{\mathrm{\&theta;},\mathrm{\&alpha;}}{\min }Q\left(\mathrm{\&theta;}\right)---\left(12\right)$

In formula (11) and formula (12), Q (θ) is the MIMO beam modes, and θ is all orientation that target may exist, a _t(θ) be the driving vector of transmitting transducer battle array, a _r(θ) be the driving vector of receiving hydrophone battle array, || || the expression vector is asked modular arithmetic, || for asking signed magnitude arithmetic(al), L is emission orthogonal signal length, a _r ^h(θ) mean a _r(θ) be transpose conjugate computing, a _t ^*(θ) mean a _t(θ) do conjugate operation, α means the reflection coefficient of target,

the orientation of the potential target that expression estimates;

(5) orientation at the estimated potential target gone out of step (4) according to formula (13) judgement

whether locate the necessary being target:

${Q\left(\widehat{\mathrm{\&theta;}}\right)}_{\underset{H_0}{<}}^{\stackrel{H_1}{\&GreaterEqual;}}\mathrm{\&delta;}---\left(13\right)$

In formula (13),

for the beam modes value on the potential target orientation estimated, H ₀the orientation that means the estimated potential target gone out does not exist real target, H ₁there is real target in the orientation that means the estimated potential target gone out, the detection threshold that δ is the Generalized Likelihood Ratio detecting device.

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