CN104181531A - Three-dimensional correlated imaging method based on phased array radar - Google Patents

Abstract

The invention discloses a three-dimensional correlated imaging method based on phased array radar and relates to the field of radar imaging. The three-dimensional correlated imaging method based on the phased array radar comprises the steps that firstly, the antenna array surface of the phased array radar is divided, a linear frequency modulation signal is sent by a phased array radar transmitter, echo signals of target scattering points are received, and the phase shifting values of the target scattering points are set; secondly, base frequency echo signals obtained after distance pulse pressing are divided according to the distance unit; thirdly, an objective function for the scattering coefficient vectors of the target scattering points is constructed, and the objective function is solved under the sparse constraint condition, so that the estimated value of the scattering coefficient vector of the target scattering point in the u<th> distance unit is obtained; fourthly, a two-dimensional image is formed through the estimated value of the scattering coefficient vector of the target scattering point in the u<th> distance unit, and then a three-dimensional image is obtained by ranking the two-dimensional images of all the distance units in the sequence the same as that of the distance units. By the adoption of the three-dimensional correlated imaging method based on the phased array radar, high-resolution three-dimensional imaging of a target is achieved.

Description

A kind of three-dimensional relevance imaging method based on phased-array radar

Technical field

The invention belongs to radar imagery technical field, relate in particular to a kind of three-dimensional relevance imaging method based on phased-array radar.

Background technology

That microwave radar has is round-the-clock, round-the-clock, at a distance and the characteristic such as observation on a large scale, can carry out high-resolution imaging to target scene, obtains detection information, is all bringing into play crucial effect in civil and military field.As main two-dimentional microwave imaging method, developing synthetic-aperture radar (SAR) imaging and inverse synthetic aperture radar (ISAR) (ISAR) imaging the fifties in last century rapidly is to utilize the relative motion between carrier platform and target to form synthetic array manifold in space, can obtain the scatter distributions information of target in distance-Doppler plane, it is two-dimensional radar image, but there is geometric distortion and lacked one-dimension information in image, the measurement of target property is caused to very large obstacle.Therefore, high-resolution three-dimensional imaging is an important research direction in radar imagery field.

Large antenna aperture is the direct way of realizing the imaging of high-resolution microwave radar.According to wide-aperture implementation, three-dimensional microwave imaging is mainly divided into two classes, and a class is based on integrated array, and another kind of is based on the three-dimensional imaging of real aperture.The former utilizes the scanning of single antenna or linear array to form two-dimentional synthetic aperture, obtain the two-dimentional resolution characteristic of span from plane, Binding distance obtains full objective distributed image to pulse compression technique again, these class methods need the motion of platform, application scenario is limited, data acquisition real-time is poor, and signal intractability is higher; And the latter relies on the narrow beam that array antenna forms and scans in space and obtain 3-D view, its resolution depends on beam angle, it is the real physical pore size size of antenna, obtain high-definition picture, need to increase array aperture, make system complexity and cost all sharply increase, so in most of application scenarios, due to the restriction of antenna volume and cost, the method resolution is not high.

Summary of the invention

The object of the invention is to overcome the deficiency of above-mentioned prior art, a kind of three-dimensional relevance imaging method based on phased-array radar is proposed, can find out that by emulation below this formation method can break through the restriction of the bearing resolution of conventional real array of apertures radar three-dimensional imaging, thus realize distance to, orientation to pitching to high-resolution three-dimensional imaging.

For achieving the above object, the present invention is achieved by the following technical solutions.

Based on a three-dimensional relevance imaging method for phased-array radar, it is characterized in that, comprise the following steps:

Step 1, is divided into M × N submatrix by Phased Array Radar Antenna front, and each submatrix has K × L array element, always total M × N × K × L array element, array element is by rectangular uniform distribution, phased-array radar transmitter under q pulse by linear FM signal s0 _qbe transmitted in imaging scene, and receiving the echoed signal containing P target scattering point under q pulse, the phase-shift value at p target scattering point place by the array element of capable k in the submatrix of capable m that is arranged in phased-array radar front n row l row under q pulse is set as q=1,2 ..., Q, the total number of Q pulse, m=1,2,3 ..., M, M is antenna array line number, n=1,2,3 ..., N, N is antenna array columns, l=1,2,3 ..., L, the columns that L is submatrix, k=1,2,3 ..., K, the line number that K is submatrix;

Step 2, unloads f frequently to the echoed signal containing P target scattering point under q pulse _c, obtain the fundamental frequency echoed signal s1 containing P target scattering point under q pulse _q, to fundamental frequency echoed signal s1 _qcarry out apart from pulse pressure, obtain apart from the fundamental frequency echoed signal s2 after pulse pressure _q; Again from the fundamental frequency echoed signal s2 apart from pulse pressure _qin obtain in u range unit containing the echoed signal of P target scattering point u=1,2,3..., U, U represents total number of the range unit under each pulse;

Step 3, the phase-shift value at the each target scattering point place of the array element of utilizing the capable l row of k in the submatrix of the capable n row of the m of phased-array radar front under q pulse obtains the Antenna gain pattern gain matrix F of Q the target scattering point of the P under pulse, F dimension Q × P; Recycling Antenna gain pattern gain matrix F builds the echoed signal s containing P target scattering point in u range unit under Q pulse ^u; The echoed signal s containing P target scattering point in u range unit under recycling Antenna gain pattern gain matrix F and Q pulse ^ubuild the scattering coefficient vector σ of u the target scattering point of the P in range unit ^uobjective function; And under sparse constraint condition, solve objective function and obtain the scattering coefficient vector estimated value of u the target scattering point of the P in range unit

Step 4, the first vector of the scattering coefficient by P target scattering point in u range unit estimated value form two dimensional image Z _u, then by the two dimensional image Z of U range unit ₁, Z ₂... Z _u..., Z _uline up and obtain 3-D view Z=[Z according to the order of range unit ₁, Z ₂... Z _u..., Z _u].

The feature of technique scheme and further improvement are:

(1) step 1 comprises following sub-step:

1a) Phased Array Radar Antenna front is divided into M × N submatrix, each submatrix has K × L array element, always total M × N × K × L array element, and array element is divided by rectangular uniform, and phased-array radar transmitter is by the linear FM signal under q pulse be transmitted in imaging scene, and receive the echoed signal containing P target scattering point under q pulse, in formula be distance to the fast time, for distance is to window function, r is that distance is to frequency modulation rate, f _cthe carrier frequency of radar emission signal, t _q=qT _rthe slow time of q pulse, T _rthe pulse repetition time, q=1,2 ..., Q indicating impulse sequence number, Q represents total pulse number of radar emission;

1b) the phase-shift value at p target scattering point place under q pulse by the array element of capable k in the submatrix of capable m that is arranged in phased-array radar front n row l row be set as:

Wherein:

Δφ _x＝γd _xsinθ _pcosβ _p (2)

Δφ _y＝γd _ysinβ _p (3)

Δ φ in formula _xfor the space quadrature of adjacent array element on directions X, Δ φ _yfor adjacent array element space quadrature in the Y direction; d _xthe array element distance on directions X, d _ythe array element distance in Y-direction, the horizontal direction that directions X is antenna arrays of radar, the vertical direction that Y-direction is antenna arrays of radar, k is array element numbering on directions X in submatrix, k=1,2,3..., K, l is array element numbering in Y-direction in submatrix, l=1,2,3..., L, m is the submatrix at this array element place numbering on directions X, m=1,2,3..., M, n is the numbering in the Y direction of submatrix at this array element place, n=1,2,3..., N, p=1,2,3..., P, P represents total number of target scattering point in scene, θ _prepresent the position angle of p target scattering point, β _prepresent the angle of pitch of p target scattering point, γ=2 π/λ is free space wave number, and λ is radar operation wavelength, Δ φ _m,n(t _q) be the random phase shift of extra stack between submatrix, and all constant in each burst length, and interpulse be all random variation, i.e. Δ φ _m,n(t _q) be independent identically distributed a functional of a stochastic process and Δ φ _m,n(t _q) ∈ [π, π].

(2) step 2 comprises following sub-step:

2a) radar unloads f frequently to the echoed signal containing P target scattering point under q pulse _c, obtain the fundamental frequency echoed signal s1 of q the target scattering point of the P under pulse _q, that is:

${s1}_q=\underset{p=1}{\overset{P}{\mathrm{\&Sigma;}}}{\mathrm{\&sigma;}}_p{F}_q^p{a}_r(\hat{t}-\frac{{2R}_p}{c})\exp \left[\mathrm{j\&pi;r}{(\hat{t}-\frac{{2R}_p}{c})}^2\right]\exp (-j\frac{4\mathrm{\&pi;}}{\mathrm{\&lambda;}}{R}_p)---\left(4\right)$

R in formula _pthe distance of radar to p target scattering point, σ _pbe the scattering coefficient of p target scattering point, c is the light velocity, represent the Antenna gain pattern gain at p target scattering point place under q pulse, represent that p target scattering put the time delay of relative radar;

2b) use matched filtering function to the fundamental frequency echoed signal s1 of P target scattering point under q pulse _qcarry out apart from pulse pressure, obtain apart from the fundamental frequency echoed signal s2 after pulse pressure _q:

$\begin{array}{c}{s2}_q=\mathrm{IFFT}\left\{\mathrm{FFT}\right[{s1}_q\left]\mathrm{FFT}\right[s_r\left]\right\}\\ =\underset{p=1}{\overset{P}{\mathrm{\&Sigma;}}}{\mathrm{\&sigma;}}_p{F}_q^p\sin c\left[\mathrm{\&Delta;}{f}_r(\hat{t}-\frac{{2R}_p}{c})\right]\exp (-j\frac{4\mathrm{\&pi;}}{\mathrm{\&lambda;}}{R}_p)\end{array}---\left(5\right)$

Δ f in formula _rfor the bandwidth of the frequency band of radar emission linear FM signal;

2c) by the fundamental frequency echoed signal s2 apart from after pulse pressure _qafter simplification, obtain the echoed signal containing P target scattering point under q pulse echoed signal after simplifying is divided into U range unit, the echoed signal of P target scattering point in u range unit under q pulse be expressed as:

$s_q^u=\underset{p=1}{\overset{P}{\mathrm{\&Sigma;}}}{\mathrm{\&sigma;}}_p^u{F}_q^p---\left(6\right)$

In formula represent the scattering coefficient of u p target scattering point in range unit, wherein u=1,2,3..., U, U represents total number of the range unit under each pulse.

(3) step 3 comprises following sub-step:

3a) the phase-shift value at p target scattering point place under q pulse by the array element of capable k in the submatrix of capable phased-array radar front m n row l row expression formula substitution Antenna gain pattern gain function, thereby obtain the Antenna gain pattern gain of p target scattering point under q pulse

D in formula _xthe array element distance on directions X, d _ythe array element distance in Y-direction, the horizontal direction that directions X is antenna arrays of radar, the vertical direction that Y-direction is antenna arrays of radar, p=1,2,3..., P, P represents total number of target scattering point in scene, θ _prepresent the position angle of p target scattering point, β _prepresent the angle of pitch of p target scattering point, k is array element numbering on directions X in submatrix, k=1,2,3..., K, γ=2 π/λ is free space wave number, λ is radar operation wavelength, l is array element numbering in Y-direction in submatrix, l=1,2,3..., L, m is the submatrix at this array element place numbering on directions X, m=1,2,3..., M, n is the numbering in the Y direction of submatrix at this array element place, n=1,2,3..., N, Δ φ _m,n(t _q) be the random phase shift of extra stack between submatrix, and all constant in each burst length, and interpulse be all random variation, i.e. Δ φ _m,n(t _q) be independent identically distributed a functional of a stochastic process and Δ φ _m,n(t _q) ∈ [π, π];

And then obtain the Antenna gain pattern gain matrix F of Q the target scattering point of the P under pulse, that is:

By the echo vector s of P target scattering point in u range unit under Q pulse ^ube expressed as: s ^u=F σ ^u; Wherein represent the echo vector of P target scattering point in u range unit under Q pulse, represent the scattering coefficient vector of u the target scattering point of the P in range unit;

3b) utilize the echo vector s of P target scattering point in u range unit under Q pulse ^uconstruct the scattering coefficient vector σ of u the target scattering point of the P in range unit with the Antenna gain pattern gain matrix F of P target scattering point under Q pulse ^uobjective function J (σ ^u):

$J\left({\mathrm{\&sigma;}}^u\right)={\left|\right|s^u-F{\mathrm{\&sigma;}}^u\left|\right|}_2^2+\mathrm{\&mu;}{\left|\right|{\mathrm{\&sigma;}}^u\left|\right|}_1---\left(9\right)$

In formula || || ₂l ₂norm operational symbol, || || ₁l ₁norm operational symbol, μ is regularization parameter;

3c) the scattering coefficient vector σ of P target scattering point in u range unit of structure ^uobjective function J (σ ^u) at sparse constraint condition μ || σ ^u|| ₁under equation be:

$\begin{array}{c}{\min \left|\right|s^u-F{\mathrm{\&sigma;}}^u\left|\right|}_2^2+\mathrm{\&mu;}{\left|\right|{\mathrm{\&sigma;}}^u\left|\right|}_1\\ s.t.\mathrm{\&mu;}{\left|\right|{\mathrm{\&sigma;}}^u\left|\right|}_1\end{array}---\left(10\right)$

Ask at sparse constraint condition μ || σ ^u|| ₁under equation obtain the scattering coefficient vector estimated value of u the target scattering point of the P in range unit for:

${\widehat{\mathrm{\&sigma;}}}^u=\arg \min J\left({\mathrm{\&sigma;}}^u\right)={[{\widehat{\mathrm{\&sigma;}}}_1^u,{\widehat{\mathrm{\&sigma;}}}_2^u,...{\widehat{\mathrm{\&sigma;}}}_p^u...,{\widehat{\mathrm{\&sigma;}}}_P^u]}^T---\left(11\right)$

In formula, argmin is minimum operation symbol, represent the estimated value of the scattering coefficient vector of u the target scattering point of the P in range unit, represent the estimated value of the scattering coefficient of u p target scattering point in range unit.

(4) step 4 comprises following sub-step:

4a) set up taking the orientation angles of target scattering point as horizontal ordinate, coordinate system taking the luffing angle of target scattering point as ordinate, in coordinate system, the scattering coefficient estimated value of p target scattering point in u range unit of selection placement point, the horizontal ordinate of this point equals the orientation angles θ of p target scattering point _p, the ordinate of this point equals the luffing angle β of p target scattering point _p; And then obtain the scattering coefficient estimated value of u the target scattering point of the P in range unit the two dimensional image Z forming _u;

4b) make u travel through from 1 to U, repeating step 2, step 3 and step 4a), obtain the two dimensional image Z of U range unit ₁, Z ₂... Z _u..., Z _u, by the two dimensional image Z of U range unit ₁, Z ₂... Z _u..., Z _uorder according to range unit is lined up, and finally obtains the 3-D view Z=[Z of scene ₁, Z ₂... Z _u..., Z _u].

Compared with prior art, the present invention has outstanding substantive distinguishing features and significant progressive.The present invention compared with the conventional method, has the following advantages:

1, the present invention adopts two dimensional phased battle array radar, but compared with conventional scanning three-dimensional formation method, by phased array elements being fed back to phase-shift value and forming the random radiation field of space-time in space, utilize radiation profiles directional diagram with the associated sparse optimization process of scatter echo, target scattering information to be extracted, can break through the limit of real array of apertures theoretical resolution, realize distance to, orientation to pitching to high-resolution three-dimensional imaging, and only need to be than the sampling still less of scene unit number;

2, the present invention utilizes the pulse compression technique of the linear FM signal in broadband, obtain distance to high resolving power, can realize three-dimensional imaging in conjunction with association process technology, stronger than existing chromatographic technique real-time;

3, the present invention does not rely on the relative motion of radar carrier and target and the synthetic aperture that forms, can adjust neatly beam position angle and range of exposures according to application demand, realize the three-dimensional imaging under various visual angles, thereby application scenario is wider, both be applicable to motion platform, also be applicable to static platform, and data acquisition and signal intractability all lower.

Brief description of the drawings

Fig. 1 is the solution of the present invention process flow diagram;

Fig. 2 is the radar work coordinate system figure that the present invention sets up; The scene center point of getting in the drawings in scene plane is coordinate O at zero point, and X-axis is the horizontal direction of scene plane, and Y-axis is the vertical direction of scene plane, and radar normal direction is as Z axis;

Fig. 3 is bay that the present invention the adopts schematic diagram of arranging; First array element of getting in the drawings the lower left corner is coordinate O at zero point, the horizontal direction that directions X is antenna arrays of radar, the vertical direction that Y-direction is antenna arrays of radar, perpendicular to the normal direction of antenna arrays of radar as Z direction;

Fig. 4 is simulated point target profile of the present invention; In figure X-axis be the orientation of the relative target of radar to, Y-axis be the pitching of the relative target of radar to, Z axis be the relative target of radar distance to;

Fig. 5 is the two-dimensional antenna radiation directivity gain diagram that the present invention produces; In figure, horizontal ordinate represents orientation angles, and ordinate represents luffing angle;

Fig. 6 is the three-dimensional relevance imaging result figure of 625 echoes of the present invention; In figure X-axis be the orientation of the relative target of radar to, Y-axis be the pitching of the relative target of radar to, Z axis be the relative target of radar distance to;

Fig. 7 is the three-dimensional relevance imaging result figure of 80 echoes of the present invention.In figure X-axis be the orientation of the relative target of radar to, Y-axis be the pitching of the relative target of radar to, Z axis be the relative target of radar distance to.

Embodiment

With reference to the present invention's scheme process flow diagram as shown in Figure 1, a kind of three-dimensional relevance imaging method based on phased-array radar of the present invention is described.Concrete implementation step is as follows:

Step 1, is divided into M × N submatrix by Phased Array Radar Antenna front, and each submatrix has K × L array element, always total M × N × K × L array element, array element is by rectangular uniform distribution, phased-array radar transmitter under q pulse by linear FM signal s0 _qbe transmitted in imaging scene, and receiving the echoed signal containing P target scattering point under q pulse, the phase-shift value at p target scattering point place by the array element of capable k in the submatrix of capable m that is arranged in phased-array radar front n row l row under q pulse is set as

1a) as shown in Figure 3, Phased Array Radar Antenna front is divided into M × N submatrix, each submatrix has K × L array element, always total M × N × K × L array element, and array element is divided by rectangular uniform.Phased-array radar transmitter is by the linear FM signal under q pulse be transmitted in imaging scene, and receive the echoed signal containing P target scattering point under q pulse, in formula be distance to the fast time, for distance is to window function, r is that distance is to frequency modulation rate, f _cthe carrier frequency of radar emission signal, t _q=qT _rthe slow time of q pulse, T _rthe pulse repetition time, q=1,2 ..., Q indicating impulse sequence number, Q represents total pulse number of radar emission.

1b) the phase-shift value at p target scattering point place under q pulse by the array element of capable k in the submatrix of capable m that is arranged in phased-array radar front n row l row be set as:

Wherein:

Δφ _x＝γd _xsinθ _pcosβ _p (2)

Δφ _y＝γd _ysinβ _p (3)

Δ φ in formula _xfor the space quadrature of adjacent array element on directions X, Δ φ _yfor adjacent array element space quadrature in the Y direction; d _xthe array element distance on directions X, d _yit is the array element distance in Y-direction.Directions X is the horizontal direction of antenna arrays of radar, the vertical direction that Y-direction is antenna arrays of radar.P=1,2,3..., P, P represents total number of target scattering point in scene.θ _prepresent the position angle of p target scattering point, β _prepresent the angle of pitch of p target scattering point, k is array element numbering on directions X in submatrix, k=1, and 2,3..., K, γ=2 π/λ is free space wave number, and λ is radar operation wavelength, and l is array element numbering in Y-direction in submatrix, l=1,2,3..., L.M is the submatrix at this array element place numbering on directions X, m=1, and 2,3..., M, n is the numbering in the Y direction of submatrix at this array element place, n=1,2,3..., N, Δ φ _m,n(t _q) be the random phase shift of extra stack between submatrix, and all constant in each burst length, and interpulse be all random variation, i.e. Δ φ _m,n(t _q) be independent identically distributed a functional of a stochastic process and Δ φ _m,n(t _q) ∈ [π, π].

Phased-array radar transmitter is transmitted into linear FM signal in imaging scene, the scene center point of getting in scene plane is coordinate O at zero point, and using radar normal direction as Z axis, in scene plane, set up XOY axle, the radar work coordinate system of setting up as shown in Figure 2, taking the some a in scene plane as example, a spot projection is b point to X-axis, the line that phased-array radar and b are ordered and the angle of Z axis are exactly azimuth angle theta, and the angle of line that phased-array radar and a are ordered, the line of ordering with phased-array radar and b is exactly angle of pitch β.

Step 2, unloads f frequently to the echoed signal containing P target scattering point under q pulse _c, obtain the fundamental frequency echoed signal s1 of q the target scattering point of the P under pulse _q, to fundamental frequency echoed signal s1 _qcarry out apart from pulse pressure, obtain apart from the fundamental frequency echoed signal s2 after pulse pressure _q; Again from the fundamental frequency echoed signal s2 apart from pulse pressure _qin obtain in u range unit containing the echoed signal of P target scattering point

2a) radar unloads f frequently to the echoed signal containing P target scattering point under q pulse _c, obtain the fundamental frequency echoed signal s1 of q the target scattering point of the P under pulse _q, that is:

${s1}_q=\underset{p=1}{\overset{P}{\mathrm{\&Sigma;}}}{\mathrm{\&sigma;}}_p{F}_q^p{a}_r(\hat{t}-\frac{{2R}_p}{c})\exp \left[\mathrm{j\&pi;r}{(\hat{t}-\frac{{2R}_p}{c})}^2\right]\exp (-j\frac{4\mathrm{\&pi;}}{\mathrm{\&lambda;}}{R}_p)---\left(4\right)$

R in formula _pthe distance of radar to p target scattering point, σ _pbe the scattering coefficient of p target scattering point, c is the light velocity, represent the Antenna gain pattern gain at p target scattering point place under q pulse, represent that p target scattering put the time delay of relative radar.

2b) use matched filtering function to the fundamental frequency echoed signal s1 of P target scattering point under q pulse _qcarry out apart from pulse pressure, obtain apart from the fundamental frequency echoed signal s2 after pulse pressure _q.

$\begin{array}{c}{s2}_q=\mathrm{IFFT}\left\{\mathrm{FFT}\right[{s1}_q\left]\mathrm{FFT}\right[s_r\left]\right\}\\ =\underset{p=1}{\overset{P}{\mathrm{\&Sigma;}}}{\mathrm{\&sigma;}}_p{F}_q^p\sin c\left[\mathrm{\&Delta;}{f}_r(\hat{t}-\frac{{2R}_p}{c})\right]\exp (-j\frac{4\mathrm{\&pi;}}{\mathrm{\&lambda;}}{R}_p)\end{array}---\left(5\right)$

Δ f in formula _rfor the bandwidth of the frequency band of radar emission linear FM signal.

Due to the fundamental frequency echoed signal s2 containing P target scattering point under q the pulse apart from after pulse pressure _qin amplitude item distance to some scattering function, only with the signal bandwidth Δ f of radar system _rrelevant, and be all constant to fixing scattering point; And phase term also be constant term for fixing scattering point.This does not affect three-dimensional relevance imaging, therefore these two can be ignored.

2c) by the fundamental frequency echoed signal s2 apart from after pulse pressure _qafter simplification, obtain the echoed signal of q the target scattering point of the P under pulse echoed signal after simplifying is divided into U range unit, the echoed signal containing P target scattering point in u range unit under q pulse be expressed as:

$s_q^u=\underset{p=1}{\overset{P}{\mathrm{\&Sigma;}}}{\mathrm{\&sigma;}}_p^u{F}_q^p---\left(6\right)$

In formula represent the scattering coefficient of u p target scattering point in range unit.Wherein u=1,2,3..., U, U represents total number of the range unit of dividing.

Step 3, the phase-shift value at the each target scattering point place of the array element of utilizing the capable l row of k in the submatrix of the capable n row of the m of phased-array radar front under q pulse obtains the Antenna gain pattern gain matrix F of Q the target scattering point of the P under pulse; Recycling Antenna gain pattern gain matrix F builds the echoed signal s containing P target scattering point in u range unit under Q pulse ^u; The echoed signal s containing P target scattering point in u range unit under recycling Antenna gain pattern gain matrix F and Q pulse ^ubuild the scattering coefficient vector σ of u the target scattering point of the P in range unit ^uobjective function; And under sparse constraint condition, solve objective function and obtain the scattering coefficient vector estimated value of u the target scattering point of the P in range unit

3a) the phase-shift value at p target scattering point place under q pulse by the array element of capable k in the submatrix of capable phased-array radar front m n row l row expression formula substitution Antenna gain pattern gain function, thereby obtain the Antenna gain pattern gain of p target scattering point under q pulse

And then obtain the Antenna gain pattern gain matrix F of Q the target scattering point of the P under pulse, that is:

By the echo vector s of P target scattering point in u range unit under Q pulse ^ube expressed as: s ^u=F σ ^u.Wherein represent the echo vector of P target scattering point in u range unit under Q pulse, represent the scattering coefficient vector of u the target scattering point of the P in range unit.

3b) utilize the echo vector s of P target scattering point in u range unit under Q pulse ^uconstruct the scattering coefficient vector σ of u the target scattering point of the P in range unit with the Antenna gain pattern gain matrix F of P target scattering point under Q pulse ^uobjective function J (σ ^u):

$J\left({\mathrm{\&sigma;}}^u\right)={\left|\right|s^u-F{\mathrm{\&sigma;}}^u\left|\right|}_2^2+\mathrm{\&mu;}{\left|\right|{\mathrm{\&sigma;}}^u\left|\right|}_1---\left(9\right)$

In formula || || ₂l ₂norm operational symbol, || || ₁l ₁norm operational symbol, μ is regularization parameter;

In the prior art, the echo vector s to P target scattering point in u range unit under Q pulse ^ucarry out first-order linear association process, s solves an equation ^u=F σ ^uobtain the scattering coefficient vector σ of u the target scattering point of the P in range unit ^u, we wish to obtain σ ^uunique solution, but because the number of array element is limited, the Antenna gain pattern gain matrix F of P target scattering point under the Q an obtaining pulse cannot reach completely random, it is the non-full rank of matrix of coefficients F of equation, so the solution of equation is not unique, therefore adopted in the present invention the sparse characteristic of three-dimensional scenic, added sparse constraint condition μ in solution procedure || σ ^u|| ₁ask the scattering coefficient vector σ of u the target scattering point of the P in range unit ^usparse solution, can obtain σ ^uunique solution.

3c) the scattering coefficient vector σ of P target scattering point in u range unit of structure ^uobjective function J (σ ^u) at sparse constraint condition μ || σ ^u|| ₁under equation be:

$\begin{array}{c}{\min \left|\right|s^u-F{\mathrm{\&sigma;}}^u\left|\right|}_2^2+\mathrm{\&mu;}{\left|\right|{\mathrm{\&sigma;}}^u\left|\right|}_1\\ s.t.\mathrm{\&mu;}{\left|\right|{\mathrm{\&sigma;}}^u\left|\right|}_1\end{array}---\left(10\right)$

Solve the scattering coefficient vector estimated value that formula (10) can obtain u the target scattering point of the P in range unit for:

${\widehat{\mathrm{\&sigma;}}}^u=\arg \min J\left({\mathrm{\&sigma;}}^u\right)={[{\widehat{\mathrm{\&sigma;}}}_1^u,{\widehat{\mathrm{\&sigma;}}}_2^u,...{\widehat{\mathrm{\&sigma;}}}_p^u...,{\widehat{\mathrm{\&sigma;}}}_P^u]}^T---\left(11\right)$

In formula, argmin is minimum operation symbol, represent the estimated value of the scattering coefficient vector of u the target scattering point of the P in range unit. represent the estimated value of the scattering coefficient of u p target scattering point in range unit.

In the present invention, realize 3c) process can utilize matching pursuit algorithm.The IEEE paper " Signal recovery from random measurements via orthogonal matching pursuit " that the concrete steps of matching pursuit algorithm can be delivered in Dec, 2007 with reference to J.A.Tropp and A.C.Gilbert.

Step 4, the first vector of the scattering coefficient by P target scattering point in u range unit estimated value form two dimensional image Z _u, then by the two dimensional image Z of U range unit ₁, Z ₂... Z _u..., Z _uline up and obtain 3-D view Z=[Z according to the order of range unit ₁, Z ₂... Z _u..., Z _u].

4a) set up taking the orientation angles of target scattering point as horizontal ordinate, coordinate system taking the luffing angle of target scattering point as ordinate, in coordinate system, the scattering coefficient estimated value of p target scattering point in u range unit of selection placement point, the horizontal ordinate of this point equals the orientation angles θ of p target scattering point _p, the ordinate of this point equals the luffing angle β of p target scattering point _p; And then obtain the scattering coefficient estimated value of u the target scattering point of the P in range unit the two dimensional image Z forming _u;

4b) make u travel through from 1 to U, repeating step 2, step 3 and step 4a), obtain the two dimensional image Z of U range unit ₁, Z ₂... Z _u..., Z _u, by the two dimensional image Z of U range unit ₁, Z ₂... Z _u..., Z _uorder according to range unit is lined up, and finally obtains the 3-D view Z=[Z of scene ₁, Z ₂... Z _u..., Z _u].

Below in conjunction with emulation experiment, effect of the present invention is described further.

1. simulated conditions

This emulation adopts the geometric model shown in Fig. 2 to carry out simulating, verifying, and making true origin is the scene center point in scene plane, and radar phase center is apart from scene center point 1Km place, i.e. R=1000m; As shown in Figure 4, imaging region is divided into the rectangular node of 25*25*25 (apart from the * pitching of * orientation) in the distribution of target scattering point.Suppose that two dimensional surface phased-array radar array element distributes by rectangular uniform, total array element 40*40=1600, the array element distance d on directions X _x=0.004m, array element distance d in the Y direction _y=0.004m.Antenna bearingt is to aperture D _x=0.004*40=0.16m, antenna pitching is to aperture D _y=0.004*40=0.16m; The carrier frequency f of radar emission signal _c=35GHz, bandwidth B=100MHz, sample frequency F _s=200MHz.

2. emulation content and result

Make Phased Array Radar Antenna front feed back phase-shift value according to conventional sweep pattern, can form in space narrow beam antenna pattern, the width of wave beam determines the resolution of conventional sweep three-dimensional imaging; Phased Array Radar Antenna front is divided into 5*5 submatrix, each submatrix is made up of 8*8 array element, according to the phase-shift value of feeding back of the present invention, the two-dimensional antenna radiation directivity gain diagram forming as shown in Figure 5, can find out that the wavefront planar radiation field strength of two-dimensional antenna radiation directivity gain diagram representative presents the form of random fluctuation, make the width of the radiation signal that the different scattering points in same wavefront plane are subject to there is mutually the coding form of independent random, thus possess space can distinguishing characteristic.

The theoretical resolution of the real aperture three-dimensional imaging of prior art is determined by bandwidth and antenna aperture, according to the Digital Simulation parameter providing, range resolution ρ _r=C/2B=1.5m, distance is to differentiating point target; But azimuth resolution ρ _a=λ R/D _x=53.57m, pitching is to resolution ρ _p=λ R/D _y=53.57m; Orientation to pitching to resolution well beyond the space interval of point target 10m, make cannot differentiate apart from the scattering point on face in center reference.

The three-dimensional relevance imaging method based on phased-array radar that adopts the present invention to propose, in conjunction with sparse optimized algorithm, obtains the analogous diagram of target scattering point, is to utilize 625 subpulses to carry out three-dimensional imaging checking to the scattering point of scene as shown in Figure 6, range resolution ρ _r=C/2B=1.5m, azimuth resolution ρ _a=D _x/ 2=0.08m; Pitching is to resolution ρ _p=D _y/ 2=0.08m; Not only scattering point is told effectively, and obtain the high-resolution 3-D view of the scattering point of radar illumination scene, verify high-resolution three-dimensional imaging effect of the present invention, and scattering point location estimation is accurate, secondary lobe is lower, and cannot go out scattering point in district by the real aperture imaging method of the routine of prior art; Provide as shown in Figure 7 the three-dimensional relevance imaging result of only utilizing 80 subpulses, can find out that the present invention is in the case of the pulse number deficiency of sampling, still can obtain good imaging results, can greatly reduce the requirement of data acquisition storage and real time signal processing.There is very strong engineering using value.

Claims (5)

1. the three-dimensional relevance imaging method based on phased-array radar, is characterized in that, comprises the following steps:

Step 1, is divided into M × N submatrix by Phased Array Radar Antenna front, and each submatrix has K × L array element, always total M × N × K × L array element, array element is by rectangular uniform distribution, phased-array radar transmitter under q pulse by linear FM signal s0 _qbe transmitted in imaging scene, and receiving the echoed signal containing P target scattering point under q pulse, the phase-shift value at p target scattering point place by the array element of capable k in the submatrix of capable m that is arranged in phased-array radar front n row l row under q pulse is set as q=1,2 ..., Q, the total number of Q pulse, m=1,2,3 ..., M, M is antenna array line number, n=1,2,3 ..., N, N is antenna array columns, l=1,2,3 ..., L, the columns that L is submatrix, k=1,2,3 ..., K, the line number that K is submatrix;

Step 2, unloads f frequently to the echoed signal containing P target scattering point under q pulse _c, obtain the fundamental frequency echoed signal s1 containing P target scattering point under q pulse _q, to fundamental frequency echoed signal s1 _qcarry out apart from pulse pressure, obtain apart from the fundamental frequency echoed signal s2 after pulse pressure _q; Again from the fundamental frequency echoed signal s2 apart from pulse pressure _qin obtain in u range unit containing the echoed signal of P target scattering point u=1,2,3..., U, U represents total number of the range unit under each pulse;

Step 3, the phase-shift value at the each target scattering point place of the array element of utilizing the capable l row of k in the submatrix of the capable n row of the m of phased-array radar front under q pulse obtains the Antenna gain pattern gain matrix F of Q the target scattering point of the P under pulse, F dimension Q × P; Recycling Antenna gain pattern gain matrix F builds the echoed signal s containing P target scattering point in u range unit under Q pulse ^u; The echoed signal s containing P target scattering point in u range unit under recycling Antenna gain pattern gain matrix F and Q pulse ^ubuild the scattering coefficient vector σ of u the target scattering point of the P in range unit ^uobjective function; And under sparse constraint condition, solve objective function and obtain the scattering coefficient vector estimated value of u the target scattering point of the P in range unit

Step 4, the first vector of the scattering coefficient by P target scattering point in u range unit estimated value form two dimensional image Z _u, then by the two dimensional image Z of U range unit ₁, Z ₂... Z _u..., Z _uline up and obtain 3-D view Z=[Z according to the order of range unit ₁, Z ₂... Z _u..., Z _u].

2. a kind of three-dimensional relevance imaging method based on phased-array radar according to claim 1, is characterized in that, step 1 comprises following sub-step:

1a) Phased Array Radar Antenna front is divided into M × N submatrix, each submatrix has K × L array element, always total M × N × K × L array element, and array element is divided by rectangular uniform, and phased-array radar transmitter is by the linear FM signal under q pulse be transmitted in imaging scene, and receive the echoed signal containing P target scattering point under q pulse, in formula be distance to the fast time, for distance is to window function, r is that distance is to frequency modulation rate, f _cthe carrier frequency of radar emission signal, t _q=qT _rthe slow time of q pulse, T _rthe pulse repetition time, q=1,2 ..., Q indicating impulse sequence number, Q represents total pulse number of radar emission;

1b) the phase-shift value at p target scattering point place under q pulse by the array element of capable k in the submatrix of capable m that is arranged in phased-array radar front n row l row be set as:

Wherein:

Δφ _x＝γd _xsinθ _pcosβ _p (2)

Δφ _y＝γd _ysinβ _p (3)

Δ φ in formula _xfor the space quadrature of adjacent array element on directions X, Δ φ _yfor adjacent array element space quadrature in the Y direction; d _xthe array element distance on directions X, d _ythe array element distance in Y-direction, the horizontal direction that directions X is antenna arrays of radar, the vertical direction that Y-direction is antenna arrays of radar, k is array element numbering on directions X in submatrix, k=1,2,3..., K, l is array element numbering in Y-direction in submatrix, l=1,2,3..., L, m is the submatrix at this array element place numbering on directions X, m=1,2,3..., M, n is the numbering in the Y direction of submatrix at this array element place, n=1,2,3..., N, p=1,2,3..., P, P represents total number of target scattering point in scene, θ _prepresent the position angle of p target scattering point, β _prepresent the angle of pitch of p target scattering point, γ=2 π/λ is free space wave number, and λ is radar operation wavelength, Δ φ _m,n(t _q) be the random phase shift of extra stack between submatrix, and all constant in each burst length, and interpulse be all random variation, i.e. Δ φ _m,n(t _q) be independent identically distributed a functional of a stochastic process and Δ φ _m,n(t _q) ∈ [π, π].

3. a kind of three-dimensional relevance imaging method based on phased-array radar according to claim 2, is characterized in that, step 2 comprises following sub-step:

2a) radar unloads f frequently to the echoed signal containing P target scattering point under q pulse _c, obtain the fundamental frequency echoed signal s1 of q the target scattering point of the P under pulse _q, that is:

${s1}_q=\underset{p=1}{\overset{P}{\mathrm{\&Sigma;}}}{\mathrm{\&sigma;}}_p{F}_q^p{a}_r(\hat{t}-\frac{{2R}_p}{c})\exp \left[\mathrm{j\&pi;r}{(\hat{t}-\frac{{2R}_p}{c})}^2\right]\exp (-j\frac{4\mathrm{\&pi;}}{\mathrm{\&lambda;}}{R}_p)---\left(4\right)$

R in formula _pthe distance of radar to p target scattering point, σ _pbe the scattering coefficient of p target scattering point, c is the light velocity, represent the Antenna gain pattern gain at p target scattering point place under q pulse, represent that p target scattering put the time delay of relative radar;

2b) use matched filtering function to the fundamental frequency echoed signal s1 of P target scattering point under q pulse _qcarry out apart from pulse pressure, obtain apart from the fundamental frequency echoed signal s2 after pulse pressure _q:

$\begin{array}{c}{s2}_q=\mathrm{IFFT}\left\{\mathrm{FFT}\right[{s1}_q\left]\mathrm{FFT}\right[s_r\left]\right\}\\ =\underset{p=1}{\overset{P}{\mathrm{\&Sigma;}}}{\mathrm{\&sigma;}}_p{F}_q^p\sin c\left[\mathrm{\&Delta;}{f}_r(\hat{t}-\frac{{2R}_p}{c})\right]\exp (-j\frac{4\mathrm{\&pi;}}{\mathrm{\&lambda;}}{R}_p)\end{array}---\left(5\right)$

Δ f in formula _rfor the bandwidth of the frequency band of radar emission linear FM signal;

2c) by the fundamental frequency echoed signal s2 apart from after pulse pressure _qafter simplification, obtain the echoed signal containing P target scattering point under q pulse echoed signal after simplifying is divided into U range unit, the echoed signal of P target scattering point in u range unit under q pulse be expressed as:

$s_q^u=\underset{p=1}{\overset{P}{\mathrm{\&Sigma;}}}{\mathrm{\&sigma;}}_p^u{F}_q^p---\left(6\right)$

In formula represent the scattering coefficient of u p target scattering point in range unit, wherein u=1,2,3..., U, U represents total number of the range unit under each pulse.

4. a kind of three-dimensional relevance imaging method based on phased-array radar according to claim 2, is characterized in that, step 3 comprises following sub-step:

3a) the phase-shift value at p target scattering point place under q pulse by the array element of capable k in the submatrix of capable phased-array radar front m n row l row expression formula substitution Antenna gain pattern gain function, thereby obtain the Antenna gain pattern gain of p target scattering point under q pulse

D in formula _xthe array element distance on directions X, d _ythe array element distance in Y-direction, the horizontal direction that directions X is antenna arrays of radar, the vertical direction that Y-direction is antenna arrays of radar, p=1,2,3..., P, P represents total number of target scattering point in scene, θ _prepresent the position angle of p target scattering point, β _prepresent the angle of pitch of p target scattering point, k is array element numbering on directions X in submatrix, k=1,2,3..., K, γ=2 π/λ is free space wave number, λ is radar operation wavelength, l is array element numbering in Y-direction in submatrix, l=1,2,3..., L, m is the submatrix at this array element place numbering on directions X, m=1,2,3..., M, n is the numbering in the Y direction of submatrix at this array element place, n=1,2,3..., N, Δ φ _m,n(t _q) be the random phase shift of extra stack between submatrix, and all constant in each burst length, and interpulse be all random variation, i.e. Δ φ _m,n(t _q) be independent identically distributed a functional of a stochastic process and Δ φ _m,n(t _q) ∈ [π, π];

And then obtain the Antenna gain pattern gain matrix F of Q the target scattering point of the P under pulse, that is:

By the echo vector s of P target scattering point in u range unit under Q pulse ^ube expressed as: s ^u=F σ ^u; Wherein represent the echo vector of P target scattering point in u range unit under Q pulse, represent the scattering coefficient vector of u the target scattering point of the P in range unit;

3b) utilize the echo vector s of P target scattering point in u range unit under Q pulse ^uconstruct the scattering coefficient vector σ of u the target scattering point of the P in range unit with the Antenna gain pattern gain matrix F of P target scattering point under Q pulse ^uobjective function J (σ ^u):

$J\left({\mathrm{\&sigma;}}^u\right)={\left|\right|s^u-F{\mathrm{\&sigma;}}^u\left|\right|}_2^2+\mathrm{\&mu;}{\left|\right|{\mathrm{\&sigma;}}^u\left|\right|}_1---\left(9\right)$

In formula || || ₂l ₂norm operational symbol, || || ₁l ₁norm operational symbol, μ is regularization parameter;

3c) the scattering coefficient vector σ of P target scattering point in u range unit of structure ^uobjective function J (σ ^u) at sparse constraint condition μ || σ ^u|| ₁under equation be:

$\begin{array}{c}{\min \left|\right|s^u-F{\mathrm{\&sigma;}}^u\left|\right|}_2^2+\mathrm{\&mu;}{\left|\right|{\mathrm{\&sigma;}}^u\left|\right|}_1\\ s.t.\mathrm{\&mu;}{\left|\right|{\mathrm{\&sigma;}}^u\left|\right|}_1\end{array}---\left(10\right)$

Ask at sparse constraint condition μ || σ ^u|| ₁under equation obtain the scattering coefficient vector estimated value of u the target scattering point of the P in range unit for:

${\widehat{\mathrm{\&sigma;}}}^u=\arg \min J\left({\mathrm{\&sigma;}}^u\right)={[{\widehat{\mathrm{\&sigma;}}}_1^u,{\widehat{\mathrm{\&sigma;}}}_2^u,...{\widehat{\mathrm{\&sigma;}}}_p^u...,{\widehat{\mathrm{\&sigma;}}}_P^u]}^T---\left(11\right)$

In formula, argmin is minimum operation symbol, represent the estimated value of the scattering coefficient vector of u the target scattering point of the P in range unit, represent the estimated value of the scattering coefficient of u p target scattering point in range unit.

5. a kind of three-dimensional relevance imaging method based on phased-array radar according to claim 1, is characterized in that, step 4 comprises following sub-step:

4a) set up taking the orientation angles of target scattering point as horizontal ordinate, coordinate system taking the luffing angle of target scattering point as ordinate, in coordinate system, the scattering coefficient estimated value of p target scattering point in u range unit of selection placement point, the horizontal ordinate of this point equals the orientation angles θ of p target scattering point _p, the ordinate of this point equals the luffing angle β of p target scattering point _p; And then obtain the scattering coefficient estimated value of u the target scattering point of the P in range unit the two dimensional image Z forming _u;

4b) make u travel through from 1 to U, repeating step 2, step 3 and step 4a), obtain the two dimensional image Z of U range unit ₁, Z ₂... Z _u..., Z _u, by the two dimensional image Z of U range unit ₁, Z ₂... Z _u..., Z _uorder according to range unit is lined up, and finally obtains the 3-D view Z=[Z of scene ₁, Z ₂... Z _u..., Z _u].