CN103713289B - Based on the object detection method of distributed Phased-MIMO Combined Treatment - Google Patents

Abstract

The invention discloses a kind of object detection method based on distributed Phased-MIMO Combined Treatment.The method is by being arranged in different positions in a distributed manner by multiple submatrix, the inner formation by launching beam of submatrix launches coherent signal acquisition coherent gain, between submatrix, the mutually orthogonal target diverse location that is irradiated to of signal obtains target diversity, and receiving array is formed by received beam and detects realization of goal with matched filtering.The inventive method can obtain relevant and incoherent gain, and eliminates interference, suppression reverberation, anti-target glint characteristic.In distributed object, when the beam angle of submatrix is greater than target size, detection perform is better than traditional phased array.

Description

Target detection method based on distributed phase-MIMO combined processing

Technical Field

The invention relates to an underwater target detection technology based on distributed Phased-MIMO combined processing, and belongs to the technical field of underwater sound target detection.

Background

When shallow sea target detection is performed, the dominant disturbance affecting active detection is reverberation. Both reverberation and target echo are caused by the transmitted signal, whose spectral characteristics are strongly correlated with the small doppler shift. The characteristics of reverberation are also related to propagation channels, and the reverberation has space-time variation characteristics and presents strong non-stationarity due to the influence of shallow sea underwater acoustic channels. Therefore, anti-reverberation is a difficult research point for detecting underwater targets. On the other hand, the spatial nonuniformity of the target also causes the flicker instability of the active sonar detection performance, and the interference of the emission array of the single base on the distributed target and the signal hardly ensures the stability of the detected target.

In the last decade, the research and development of Multiple Input Multiple Output (MIMO) technology in the radar field has been fast. The traditional phased array can acquire the diversity gain of the transmitting array by driving and transmitting signals, and effective focusing irradiation on a target is realized, so that the purposes of reverberation resistance and interference influence reduction are achieved. Meanwhile, the distributed MIMO system can obtain the transmitting waveform diversity and the target diversity, and is widely applied to target detection and positioning. However, due to the delay and doppler double spreading of the underwater acoustic channel, the MIMO technology develops slowly in the sonar field. In 2006, the i.bekkerman and j.tabrikaan first proposed a unified MIMO processing framework for radar and sonar. Considering the double extension of the underwater acoustic channel, and combining Phased array and MIMO technology, a distributed Phased-MIMO combined processing technology based on a broadband signal model is proposed.

Disclosure of Invention

The invention aims to provide a target detection method based on distributed Phased-MIMO combined processing, aiming at the problems of the existing single-base active sonar detection technology and considering reverberation interference and the spatial characteristics of distributed targets.

In order to achieve the purpose, the technical scheme adopted by the invention is as follows: the invention relates to a target detection method based on distributed phase-MIMO combined processing, which comprises the following steps:

1) arranging M transmitting sub-arrays at a transmitting end, wherein each transmitting sub-array comprises M_kA plurality of transmit transducer elements; each transmitting transducer array element in each transmitting subarray is connected with the output end of a power amplifier, and the input end of the power amplifier is connected with the output end of corresponding signal generating equipment; the transmitting transducer array elements in each transmitting sub-array are arranged into a uniform linear array, and the distance between the adjacent transmitting transducer array elements is smaller than or equal to the minimum value of half-wavelength of the transmitting signal of the transmitting sub-array; the spacing between each transmitting subarray meets the requirement shown in formula (1):

$d_t>\frac{R_t{\mathrm{\λ}}_{max}}{D}---\left(1\right)$

arranging N receiving sub-arrays at a receiving end, wherein each receiving sub-array comprises N_lEach hydrophone array element; the hydrophone array elements in each receiving subarray are connected with corresponding signal acquisition equipment, the hydrophone array elements in each receiving subarray are arranged into uniform linear arrays, and the distance between every two adjacent hydrophone array elements is smaller than or equal to the minimum value of half wavelength of corresponding transmitting signals; the spacing between each receiving subarray satisfies the requirement shown in formula (2):

$d_r>\frac{R_r{\mathrm{\λ}}_{max}}{D}---\left(2\right)$

wherein M is a positive integer greater than or equal to 1, M_kIs a positive integer of 1 or more andR_trepresenting the distance of the corresponding transmitting subarray of the transmitting end to the center of the target, D representing the size of the target, D_tRepresenting the spacing between adjacent transmit sub-arrays, d_rRepresenting the spacing, λ, between adjacent receiving sub-arrays_maxRepresents the maximum of the wavelengths of all the transmitted signals; n represents a positive integer of 1 or more, N_lRepresents a positive integer of 1 or more andR_rrepresenting the distance from the corresponding receiving subarray of the receiving end to the target center;

2) each of the signal generating devices generates a transmission signalWhere E represents the total energy of the transmitted signal,

m denotes the number of transmit sub-arrays,

$a_t^k({\mathrm{\θ}}_k,f_m)={\[1,e^{-i2{\mathrm{\πf}}_m\frac{d_k}{c}{\mathrm{sin\θ}}_k},\mathrm{...},e^{-i2{\mathrm{\πf}}_m\frac{d_k}{c}{\mathrm{sin\θ}}_k(M_k-1)}\]}^T,$ wherein, [ … ]]^TIs a transposed symbol, θ_kIs the angle of arrival from the target center to the transmit subarray k, k being 1,2_mIs the mth frequency of the signal transmitted by the transmitting subarray k, m is 1, 2.. L, L is the number of frequencies of the signal transmitted by each transmitting subarray, c is the propagation speed of the transmitted signal, d is the propagation speed of the transmitted signal_kIs the spacing, M, between adjacent transmit transducer elements within a transmit sub-array k_kThe number of transmitting transducer array elements contained in a transmitting subarray k, and i represents an imaginary number;

{S_k(f_m) Denotes the transmit signal of the transmit sub-array k, | S_k(f_m)||²＝1/L，j ∈ {1, 2.,. M } and j ≠ k.

Emission signal of each of the signal generating devicesThe signals are amplified by a power amplifier and then transmitted to each transmitting transducer array element in a corresponding transmitting subarray to be converted into sound wave signals to be transmitted to a water area to be detected;

3) each receiving sub-array receives the transmitting signal S of the corresponding transmitting sub-array_k(f_m) Echo R of_lk(f_m) To a corresponding signal acquisition device which processes the received echo R_lk(f_m) Performing receive beamforming as shown in equation (3):

$Y_k\left(f_m\right)={\left(b_r^l({\mathrm{\θ}}_l,f_m)\right)}^H{R}_{lk}\left(f_m\right)---\left(3\right)$

in formula (3), (…)^HIs a conjugate of the transposed symbol and,

$b_r^l({\mathrm{\θ}}_l,f_m)={\[1,e^{-i2{\mathrm{\πf}}_m\frac{d_l}{c}{\mathrm{sin\θ}}_l},\mathrm{...},e^{-i2{\mathrm{\πf}}_m\frac{d_l}{c}{\mathrm{sin\θ}}_l(M_l-1)}\]}^T,$ wherein, theta_lIs the angle of arrival from the target center to the receiving subarray l, l 1,2, N, d_lIs the spacing, N, between adjacent hydrophone elements within the receiving sub-array l_lThe number of hydrophone array elements contained in a receiving subarray l, and i represents an imaginary number;

will Y_lk(f_m) Matching is carried out according to the method shown in the formula (4):

$T=\underset{l=1}{\overset{N}{\Σ}}\underset{k=1}{\overset{M}{\Σ}}\underset{m=1}{\overset{L}{\Σ}}\left|\right|S_k^{*}\left(f_m\right)Y_{lk}\left(f_m\right)|{|}^2---\left(4\right)$

in the formula (4), ∑ represents a summation symbol, | … | | non-volatile phosphor²Indicating the modulo of a vector, S_k(f_m) Representing the transmitted signal of the transmitting subarray k, N being the number of receiving subarrays, M being the number of transmitting subarrays, and L being the number of frequencies of the signal transmitted by each transmitting subarray;

distance R from target center to all receiving sub-arrays_lThe corresponding T value is plotted as R_l-T two-dimensional images; then observe R_l-T two-dimensional image if at the center of the objectA peak exists between the receiving subarrays indicating the presence of a target.

Compared with the prior art, the invention has the beneficial effects that: the traditional phased array is combined with a distributed MIMO system, so that the target diversity information is obtained while certain resolution is obtained to inhibit reverberation interference, the target flicker resistance is achieved, and the active sonar detection performance is stabilized. Numerical simulation and experiment verification show that the phase-MIMO active target detection technology is the traditional Phased array detection technology under the conditions that the target is a distributed target and the signal-to-noise ratio is high.

Drawings

FIG. 1 is a schematic layout of a transmit array and a receive array relative to a target;

FIG. 2(a) is a graph of sound speed as a function of depth; FIG. 2(b) is an environmental schematic of one embodiment of the present invention;

FIG. 3(a) is the detection output result of the Phased-MIMO active sonar system corresponding to the emission of the PCW signal; FIG. 3(b) is the detection output result of the Phased-Array active sonar system corresponding to the emission of the PCW signal;

FIG. 4(a) is the detection output result of the Phased-MIMO active sonar system corresponding to the emission of LFM signals; fig. 4(b) is the detection output result of the Phased-Array active sonar system corresponding to the emission of the LFM signal.

Detailed Description

The method comprises the following steps:

1) m transmitting sub-arrays are arranged at a transmitting end, wherein the serial number is 1. The k (k) ═ 1, 2.., M) th transmit subarray contains M_kA transmitting transducer array, numbered 1,2_k，M_kIs a positive integer of 1 or more andR_tdenote the distance from the emitting end to the center of the target, D denotes the size of the target, one would have M × M_kThe output of the signal generating device of the circuit is connected with a circuit with M × M_kThe input end of the power amplifier of the circuit and the output end of the power amplifier are connected to M × M_kAnd a plurality of transmitting transducer elements. Spacing d between adjacent transmit transducer elements within the kth transmit sub-array_kThe minimum value of half wavelength of the transmitting signal of the kth transmitting sub-array is less than or equal to, and the distance between the adjacent transmitting sub-arrays is d_tSatisfies the requirement shown in formula (1):

$d_t>\frac{R_t{\mathrm{\λ}}_{max}}{D}---\left(1\right)$

n receiving sub-arrays are arranged at a receiving end, wherein the number is 1, and N represents a positive integer which is larger than or equal to 1. The l (l ═ 1, 2.., N) th receiving subarray includes N_lArray element of individual hydrophone, N_lRepresents a positive integer of 1 or more andR_rindicating the distance of the receiving end to the center of the target. The distance d between adjacent hydrophone array elements in the first receiving subarray_lLess than or equal to the minimum of half wavelength of the signal received by the first receiving subarray, and the spacing between adjacent receiving subarrays is d_rSatisfies the requirement expressed by the formula (2):

$d_r>\frac{R_r{\mathrm{\λ}}_{max}}{D}---\left(2\right)$

the qth (q 1, 2.., M) of the k (k 1, 2., M) transmit subarrays_k) The mth frequency point signal emitted by each emitting transducer array element isWherein, [ … ]]^TIs a transposed symbol, θ_kIs the angle of arrival from the target center to the transmit subarray k, k being 1,2_mIs the mth frequency of the signal transmitted by the transmitting subarray k, m is 1, 2.. L, L is the number of frequencies of the signal transmitted by each transmitting subarray, c is the propagation speed of the transmitted signal, d is the propagation speed of the transmitted signal_kIs the spacing between adjacent transmit transducer elements within the transmit subarray k, | S_k(f_m)||²＝1/L,m＝1,2,...L，j ∈ {1, 2.,. M } and j ≠ kWhereinFor the k-th transmitting sub-array at frequency f_mA driving vector pointing to the center of the target.

The frequency of the signal transmitted by the kth transmitting subarray and received by the pth hydrophone array element in the ith receiving subarray is f_mThe echo of (c) can be expressed as:

$r_{lk,p}\left(f_m\right)={\mathrm{\α}}_k^m{\mathrm{\ϵ}}_k^m{\mathrm{\ζ}}_l^m{M}_k\sqrt{E/M}{s}_k\left(f_m\right)e^{-i2{\mathrm{\πf}}_m\frac{d_l}{c}{\mathrm{sin\θ}}_l(p-1)}+n_{lk,p}^m---\left(5\right)$

wherein,the equivalent scattering coefficient is the m frequency point emitted by the kth emission subarray after being irradiated on a scatterer;representing the propagation loss of the transmit sub-array to the target,respectively representing the transmission loss from the transmitting subarray to the target and the propagation loss from the target to the receiving subarray; written in vector form:

$r_{lk}\left(f_m\right)={\mathrm{\α}}_k^m{\mathrm{\ϵ}}_k^m{\mathrm{\ζ}}_l^m{M}_k\sqrt{E/M}{s}_k\left(f_m\right)a_r^l({\mathrm{\θ}}_l,f_m)+n_{lk}^m---\left(6\right)$

at frequency point f for target center to the l receiving subarray_mThe response vector of (2);zero mean gaussian complex noise.

3) For each receiving subarray, the received transmission signal S of the corresponding transmitting subarray_k(f_m) Echo R of_lk(f_m) To a corresponding signal acquisition device which processes the received echo R_lk(f_m) Performing receive beamforming as shown in equation (3):

$Y_k\left(f_m\right)={\left(b_r^l({\mathrm{\θ}}_l,f_m)\right)}^H{R}_{lk}\left(f_m\right)---\left(3\right)$

in formula (3), (…)^HIs a conjugate of the transposed symbol and,

$b_r^l({\mathrm{\θ}}_l,f_m)={\[1,e^{-i2{\mathrm{\πf}}_m\frac{d_l}{c}{\mathrm{sin\θ}}_l},\mathrm{...},e^{-i2{\mathrm{\πf}}_m\frac{d_l}{c}{\mathrm{sin\θ}}_l(M_l-1)}\]}^T,$ wherein, theta_lIs the angle of arrival, l, from the center of the target to the receiving subarray l＝1,2，···，N，d_lIs the spacing, N, between adjacent hydrophone elements within the receiving sub-array l_lThe number of hydrophone array elements contained in a receiving subarray l, and i represents an imaginary number;

4) the processing data obtained in step 3) can be expressed as:

$\begin{array}{c}{Y}_k\left(f_m\right)={\left(a_r^l\right({\mathrm{\θ}}_l,f_m\left)\right)}^H\left({\mathrm{\α}}_k^m{\mathrm{\ϵ}}_k^m{\mathrm{\ζ}}_l^m{M}_k\sqrt{E/M}{s}_k\right(f_m)a_r^l({\mathrm{\θ}}_l,f_m)+n_{lk}^m)\\ {\mathrm{\α}}_k^m{\mathrm{\ϵ}}_k^m{\mathrm{\ζ}}_l^m{M}_k{N}_l\sqrt{E/M}{s}_k\left(f_m\right)v_{lk}^m\end{array}---\left(7\right)$

definition ofRepresenting the equivalent attenuation coefficient from the mth transmit sub-array to the jth receive sub-array, equation (7) can be rewritten as:

$Y_{lk}\left(f_m\right)=M_k{N}_l\sqrt{E/M}{\mathrm{\λ}}_{lk}^m{s}_k\left(f_m\right)+v_{lk}^m---\left(8\right)$

that is, the matrix form of equation (8) is as shown in equation (9):

$Y=\sqrt{E/M}Q\mathrm{\λ}+v---\left(9\right)$

wherein, MNL is multiplied by MNL dimension diagonal matrix Q is shown as formula (10):

Q＝diag[M₁N₁s₁(f₁),...,M₁N₁s₁(f_L),

M₂N₁s₂(f_L+1),...,M₂N₁s₂(f_L+L),…,

M_MN₁s_M(f_(M-1)L+1),...,M_MN₁s₂(f_ML),(10)

M₁N₂s₁(f₁),...,M₁N₂s₁(f_L),…,

M_MN₂s_M(f_(M-1)L+1),...,M_MN₂s_M(f_ML),…,

M_MN_Ns_M(f_(M-1)L+1),...,M_MN_Ns_M(f_2L)]

the MNLx 1-dimensional column vector λ is as shown in equation (11):

$\begin{array}{c}\mathrm{\λ}=\[{\mathrm{\λ}}_{11}^1,\mathrm{...},{\mathrm{\λ}}_{11}^L,{\mathrm{\λ}}_{12}^1,\mathrm{...},{\mathrm{\λ}}_{12}^L,\mathrm{...},{\mathrm{\λ}}_{1M}^1,\mathrm{...},{\mathrm{\λ}}_{1M}^L\\ {\mathrm{\λ}}_{21}^1,\mathrm{...},{\mathrm{\λ}}_{21}^L,\mathrm{...},{\mathrm{\λ}}_{2M}^1,\mathrm{...},{\mathrm{\λ}}_{2M}^L,\mathrm{...},\\ {\mathrm{\λ}}_{N2}^1,\mathrm{...},{\mathrm{\λ}}_{N2}^L,{\mathrm{\λ}}_{NM}^1,\mathrm{...},{\mathrm{\λ}}_{NM}^L{\]}^T\end{array}---\left(11\right)$

MNL × 1-dimensional column vectorTo obey CN (0, sigma)²I_MNL) Distributed complex gaussian noise.

4) Will Y_lk(f_m) Matching is carried out according to the method shown in the formula (4):

$T=\underset{l=1}{\overset{N}{\Σ}}\underset{k=1}{\overset{M}{\Σ}}\underset{m=1}{\overset{L}{\Σ}}\left|\right|S_k^{*}\left(f_m\right)Y_{lk}\left(f_m\right)|{|}^2---\left(4\right)$

in the formula (4), ∑ represents a summation symbol, | … | | non-volatile phosphor²Indicating the modulo of a vector, S_k(f_m) Representing the transmitted signal of transmit subarray k, N being the number of receive subarrays, M being the number of transmit subarrays, and L being the number of frequencies of the signal transmitted by each transmit subarray. When the received signal is judged to be present or absent, firstly, a threshold is determined, and if the received signal is matched with output energy Y²(namely the value T in the formula (4)) is greater than the threshold, judging that the target exists in the detection area; otherwise, judging that no target exists.

The MIMO detector based on NP criterion is given by the following equation (12):

$T_{MIMO}=\left|\right|Y|{|}^2\begin{array}{c}{H}_1\\ >\\ <\\ H_0\end{array}\mathrm{\&delta;}---\left(12\right)$

according to the complex Gaussian noise and the statistical characteristics of the equivalent scattering coefficient, the statistic | Y | non-calculation amount is tested²Compliance

Wherein M is₀＝M_k,k＝1,2,...,M，N₀＝N_l1, 2. Threshold according to false alarm probability P_fa(i.e., the probability of a false positive being present in the absence of a target) is selected, i.e., according to equation (14),

$P_{fa}=\mathrm{Pr}(T>\mathrm{\&delta;}|H_0)=\mathrm{Pr}(\frac{{\mathrm{\&sigma;}}_n^2}{2}{\mathrm{\&chi;}}_{2LMN}^2>\mathrm{\&delta;})=\mathrm{Pr}({\mathrm{\&chi;}}_{2LMN}^2>\frac{2\mathrm{\&delta;}}{{\mathrm{\&sigma;}}_n^2})---\left(14\right)$

to give formula (15):

$\mathrm{\&delta;}=\frac{{\mathrm{\&sigma;}}_n^2}{2}{F}_{{\mathrm{\&chi;}}_{2LMN}^2}^{-1}(1-P_{fa})---\left(15\right)$

the detection probability P that can be obtained at this time_d(i.e., the probability of correctly deciding that a target exists in the presence of a target) is as shown in equation (16):

$P_d=1-F_{{\mathrm{\&chi;}}_{2LMN}^2}\left\{\frac{{\mathrm{\&sigma;}}_n^2}{\&lsqb;\frac{E}{M}\frac{{\left(M_0{N}_0\right)}^2}{L}+{\mathrm{\&sigma;}}_n^2\&rsqb;}{F}_{{\mathrm{\&chi;}}_{2LMN}^2}^{-1}(1-P_{fa})\right\}---\left(16\right)$

the method of the present invention is specifically described below by taking the environment shown in fig. 2 as an example:

as shown in fig. 1,2 transmitting sub-arrays are arranged at the transmitting end, and are numbered as 1 and 2; each transmitting subarray comprises 3 transmitting transducer array elements which are numbered as 1,2 and 3; the distance between adjacent transmitting transducer array elements in each transmitting subarray is d_k0.075m, the spacing between the transmitting subarrays is d_t4 m. The output of an NI device with 6 channels is connected to a 6-channel power amplifier, the 6 output channels of which are connected to the inputs of 6 transmit transducer elements.

A linear target 1.5m long is located at 22m, satisfyingThe distributed condition of (2).

1 receiving subarray is arranged at a receiving end, the receiving subarray comprises 14 hydrophone array elements which are numbered as 1,2_l＝0.075m。

Signal sampling frequency f_s50kHz, the signal duration T is 10ms, i.e. the signal time T is 0, 1/fs.

Scenario 1: signal frequency of f₁8kHz and f₂In the single frequency Pulse (PCW) signal of 6kHz, 3 array elements in the transmitting sub-array 1 respectively transmit signals

3 array elements in the transmitting subarray 2 respectively transmit signals

Scenario 2: linear Frequency Modulation (LFM) signals with signal frequencies of 6-8 kHz and 8-10 kHz are transmitted, and 3 array elements in the sub-array 1 are transmitted at time t_oTransmitting signals separately

3 array elements in the transmitting subarray 2 respectively transmit signals

Wherein,representing taking the real part of the complex number, cos () being a cosine function, d₁＝0.075m,c≈1450m/s,θ₁≈15⁰I represents an imaginary number; d₂＝0.075m，θ₂≈-15⁰

The environment as shown in fig. 2 consists of three layers: a water medium layer, a sediment layer and a water bottom layer. Wherein the water depth is 21.53m, and the density is rho 1.0g/cm³The sound velocity profile is shown in fig. 2(a), and it can be seen that the sound velocity changes rapidly on the water surface, and has a relatively large negative gradient, and can be basically regarded as an equal sound velocity environment below 10m in water depth, and the energy of the transmitted signal irradiated on the target is relatively strong in the equal sound velocity environment, which is beneficial to improving the detection performance of the target. The deposited layer had a thickness of 7.343m and a density of 2.2g/cm³The speed of sound is c_s1624.3 m/s. The water bottom is a uniform half space, and the density is rho ═ 3.0g/cm³The speed of sound is c_s＝1792.4m/s。

And the 14 channels of hydrophones convert the received echoes into electric signals and transmit the electric signals to signal acquisition equipment for acquisition and storage, and the electric signals are recorded as r (t). The received signal firstly obtains the receiving array gain through the beam former, so as to obtain x (t) ═ alpha (theta) r (t), and for the stationary target (namely neglecting the Doppler effect) due to the existence of the time delay Doppler double extension in the underwater acoustic channel, a copy coherent integration detector (RCI) is adopted to comprehensively consider the target echo returned due to multipath. Namely, it is

$y\left(n\right)=\underset{j=0}{\overset{J-1}{\&Sigma;}}|\sqrt{\frac{2}{I}}\underset{i=0}{\overset{I-1}{\&Sigma;}}{s}^{*}\left(i\right)x(i+j+n){|}^2---\left(15\right)$

The presence or absence of the target is judged by comparing the output energy value of the corresponding position with the output energy value of no target around. Under the condition that the target position is unknown and the interference energy is small, the position corresponding to the maximum energy output value can be found through the technology to realize the positioning function of the target.

Conventional phased arrays, i.e., directional transmission to a target at one location and directional reception to a target at one location. Transmitting with one of 3 transmitting transducer elementsFor example, the subarray transmits 10ms of 8kHz single-frequency Pulse (PCW) signals or 10ms of 6-8 kHz Linear Frequency Modulation (LFM) signals, and the amplitude of the signals is the original amplitudeAnd (4) doubling. The receiving array is a single horizontal array with 14 paths, and the processing method is consistent with the Phased-MIMO array processing method.

As can be seen from fig. 3 and 4, two sonar systems can estimate the position of the target: the target real position is 22m, and the phase-MIMO system estimated value using the PCW signal isThe phase-Array system estimates asThe phase-MIMO system estimation value using LFM signal isThe phase-Array system estimates asUnder the condition of limited maximum instantaneous power, the pulse width of the transmitting signal is increased to improve the energy of the transmitting signal and the input signal-to-noise ratio of the receiver, thereby improving the detection performance of the receiver, and the increase of the pulse width simultaneously increases the ambiguity of distance estimation.LFM signal can better solve the contradiction, so that comparing fig. 3 and fig. 4, the matching result of LFM signal to the target position is shown to be larger than the resolution of the result of PCW signal, and simultaneously comparing the correlation matching output peak values of the two systems, the output peak value of Phased-MIMO system adopting PCW signal at the target position is shown to be 2.56 × 10⁶Greater than the output peak of the Phased-Array system at the target position (1.034 × 10)⁶) The difference is obvious because the Phased-MIMO system acquires the diversity gain of the target.

Claims (1)

1. A target detection method based on distributed phase-MIMO combined processing is characterized by comprising the following steps:

1) arranging M transmitting sub-arrays at a transmitting end, wherein each transmitting sub-array comprises M_kA plurality of transmit transducer elements; each transmitting transducer array element in each transmitting subarray is connected with the output end of a power amplifier, and the input end of the power amplifier is connected with the output end of corresponding signal generating equipment; the transmitting transducer array elements in each transmitting sub-array are arranged into a uniform linear array, and the distance between the adjacent transmitting transducer array elements is smaller than or equal to the transmitting sub-array elementsThe minimum value of half wavelength of the transmitting signal of the transmitting subarray; the spacing between each transmitting subarray meets the requirement shown in formula (1):

arranging N receiving sub-arrays at a receiving end, wherein each receiving sub-array comprises N_lEach hydrophone array element; the hydrophone array elements in each receiving subarray are connected with corresponding signal acquisition equipment, the hydrophone array elements in each receiving subarray are arranged into uniform linear arrays, and the distance between every two adjacent hydrophone array elements is smaller than or equal to the minimum value of half wavelength of corresponding transmitting signals; the spacing between each receiving subarray satisfies the requirement shown in formula (2):

wherein M is a positive integer greater than or equal to 1, M_kIs a positive integer of 1 or more andR_trepresenting the distance of the corresponding transmitting subarray of the transmitting end to the center of the target, D representing the size of the target, D_tRepresenting the spacing between adjacent transmit sub-arrays, d_rRepresenting the spacing, λ, between adjacent receiving sub-arrays_maxRepresents the maximum of the wavelengths of all the transmitted signals; n represents a positive integer of 1 or more, N_lRepresents a positive integer of 1 or more andR_rrepresenting the distance from the corresponding receiving subarray of the receiving end to the target center;

2) each of the signal generating devices generates a transmission signalWhere E represents the total energy of the transmitted signal,

m denotes the number of transmit sub-arrays,

wherein, [ … ]]^TIs a transposed symbol, θ_kIs the angle of arrival from the target center to the transmit subarray k, k being 1,2_mIs the mth frequency of the signal transmitted by the transmitting subarray k, m is 1, 2.. L, L is the number of frequencies of the signal transmitted by each transmitting subarray, c is the propagation speed of the transmitted signal, d is the propagation speed of the transmitted signal_kIs the spacing, M, between adjacent transmit transducer elements within a transmit sub-array k_kThe number of transmitting transducer array elements contained in a transmitting subarray k, and i represents an imaginary number;

{S_k(f_m) Denotes the transmit signal of the transmit sub-array k, | S_k(f_m)||²＝1/L，j ∈ {1, 2., M } with j ≠ k;

emission signal of each of the signal generating devicesThe signals are amplified by a power amplifier and then transmitted to each transmitting transducer array element in a corresponding transmitting subarray to be converted into sound wave signals to be transmitted to a water area to be detected;

3) each receiving sub-array receives the transmitting signal S of the corresponding transmitting sub-array_k(f_m) Echo R of_lk(f_m) To a corresponding signal acquisition device which processes the received echo R_lk(f_m) Performing receive beamforming as shown in equation (3):

in formula (3), (…)^HIs a conjugate of the transposed symbol and,

wherein, theta_lIs the angle of arrival from the target center to the receiving subarray l, l is 1,2, …, N, d_lIs the spacing, N, between adjacent hydrophone elements within the receiving sub-array l_lThe number of hydrophone array elements contained in a receiving subarray l, and i represents an imaginary number;

will Y_lk(f_m) Matching is carried out according to the method shown in the formula (4):

in the formula (4), ∑ represents a summation symbol, | … | | non-volatile phosphor²Indicating the modulo of a vector, S_k(f_m) Representing the transmitted signal of the transmitting subarray k, N being the number of receiving subarrays, M being the number of transmitting subarrays, and L being the number of frequencies of the signal transmitted by each transmitting subarray;

distance R from target center to all receiving sub-arrays_lThe corresponding T value is plotted as R_l-T two-dimensional images; then observe R_l-T two-dimensional image, indicating the presence of the target if there is a peak between the center of the target and the receiving subarray.