CN101650435B - Quick imaging method of linear array three-dimensional imaging synthetic aperture radar (SAR) based on sub-aperture approximation - Google Patents

Abstract

The invention provides a quick imaging method of a linear array three-dimensional imaging synthetic aperture radar (SAR) based on sub-aperture approximation. Aiming at the characteristic that an actual linear array three-dimensional imaging SAR echo only comprises echo signals of sparse scattering points in a three-dimensional space, the method adopts an aperture approximation technology to carry out imaging treatment on sparse targets in the three-dimensional space so as to better solve the problem of heavy computation of an imaging method of the three-dimensional imaging SAR. The invention has the advantage of realizing the linear array three-dimensional imaging SAR by utilizing smaller computation, and can be applied to the fields of SAR imaging, earth remote-sensing, and the like.

Description

Approach linear array three-dimensional imaging synthetic aperture radar fast imaging method based on sub-aperture

Technical field

The present technique invention belongs to the Radar Technology field, and it has been particularly related to the synthetic aperture radar (SAR) technical field of imaging.

Background technology

Linear-array three-dimensional imaging synthetic aperture radars (LASAR) is that linear array antenna is fixed on the platform of motion, with synthetic two-dimensional planar array, and a kind of novel polarization sensitive synthetic aperture radar system that carries out three-dimensional imaging.Linear-array three-dimensional imaging synthetic aperture radars can be realized that present single antenna synthetic-aperture radar is irrealizable three-dimensional ground is carried out to the ability of picture, become the synthetic-aperture radar hot research fields at present.The document of understanding and having delivered according to me; For example: M.Wei β; J.H.G.Ender " A 3D imaging radar for smallunmanned airplanes-ARTINO " Radar Conference; 2005.EURAD 2005.BASSEMR.MAHAFZA and MITCH SAJJADI " Three-dimensional SAR imaging using lineararray in transverse motion " IEEE transaction on aerospace and electronic system VOL32; NO.1JANUARY 1996; The linear-array three-dimensional imaging synthetic aperture radars formation method can be divided into three types: time domain three-D imaging method, frequency domain three-D imaging method and dimensionality reduction image processing method.Time domain approach arrives each antenna element distance through calculating each scattering point, and carries out coherence stack and realize the linear-array three-dimensional imaging synthetic aperture radars imaging processing; Frequency domain method is transformed to the multiply operation of frequency domain with the coherent accumulation of time domain approach, realizes the linear-array three-dimensional imaging synthetic aperture radars imaging processing; The dimensionality reduction image processing method is decomposed into several one-dimensional correlations with the higher-dimension relevant issues and handles problems, to reduce the processing operations amount.

Said method is regarded the linear-array three-dimensional imaging synthetic aperture radars imaging problem as in the three dimensions matching problem in essence.But in practical application; A lot of zones in the 3-D view space do not comprise scattering point; Or blocked by other scattering point, only comprise the echoed signal of some specific sparse scattering point in the three dimensions in the actual ghosts, therefore; The linear-array three-dimensional imaging synthetic aperture radars imaging problem can be reduced to the imaging problem of the specific scattering point in the three dimensions, thereby greatly reduces the operand of linear-array three-dimensional imaging synthetic aperture radars imaging problem.

Summary of the invention

In order to overcome the big problem of linear-array three-dimensional imaging synthetic aperture radars formation method operand; The invention provides a kind of linear array three-dimensional imaging synthetic aperture radar fast imaging method that approaches based on sub-aperture; It is to the characteristics that only comprise the echoed signal of some specific sparse scattering point in the three dimensions in the actual line array three-dimensional imaging synthetic aperture radar return; Adopt sub-aperture approximation technique; Carry out imaging processing to some sparse target in the three dimensions, thereby well solved the big problem of three-dimensional imaging synthetic aperture radar formation method operand.

Describe content of the present invention for ease, at first make following term definition:

Definition 1, linear-array three-dimensional imaging synthetic aperture radars (LASAR)

Linear-array three-dimensional imaging synthetic aperture radars (LASAR) is that linear array antenna is fixed on the platform of motion, with synthetic two-dimensional planar array, and a kind of novel polarization sensitive synthetic aperture radar system that carries out three-dimensional imaging.

Definition 2, synthetic-aperture radar gauged distance compression method

Synthetic-aperture radar gauged distance compression method is meant and utilizes the synthetic-aperture radar emission parameter, adopts following formula to generate reference signal, and the process that adopts matched filtering technique the distance of synthetic-aperture radar to be carried out filtering to signal.

$f\left(t\right)=\exp (j\&CenterDot;\mathrm{\&pi;}\&CenterDot;\frac{B}{T_p}\&CenterDot;t^2),t\&Element;[-\frac{{\mathrm{<figure-callout\; id="2"\; label="T\; p"\; filenames="H2009100595497E00032.png"\; state="\{\{state\}\}">T</figure-callout>}}_p}{2},\frac{T_p}{2}]$

Wherein, f (t) is a reference function, and B is the signal bandwidth of radar emission baseband signal, T _PBe the radar emission signal pulse width, t is an independent variable, span from

Arrive

See document " radar imagery technology " for details, protect polished grade and write, the Electronic Industry Press publishes.

Definition 3, linear-array three-dimensional imaging synthetic aperture radars image space

The linear-array three-dimensional imaging synthetic aperture radars image space is meant the scene areas that the synthetic-aperture radar wave beam shines.

Definition 4, synthetic aperture and slow time

The synthetic aperture of linear array three-dimensional synthetic aperture radar system be meant for the scattering point of mapping in the scene from get into the radar beam range of exposures to leave the radar beam range of exposures during this period of time in, the length of being passed by in the radar beam center.

The slow time of linear array three-dimensional synthetic aperture radar system is meant that transmit-receive platform flies over a needed time of synthetic aperture, because radar is with certain repetition period T _rThe emission received pulse, the slow time can be expressed as the time variable t of a discretize _s=nT _r, n=1 ... N, N are the discrete number of slow time in the synthetic aperture, T _rBe the repetition period.

The sub-aperture of definition 5, linear-array three-dimensional imaging synthetic aperture radars

The sub-aperture of linear-array three-dimensional imaging synthetic aperture radars is meant in later stage radar data processing procedure, at the core of synthetic aperture, along radar transmit-receive platform heading; Intercepting goes out one section synthetic aperture, and at the core of linear array antenna, array antenna direction along the line; Intercepting goes out one section linear array antenna; One section linear array antenna vertical placement each other that one section synthetic aperture that intercepting is gone out and intercepting go out, the two-dimensional planar array of synthesizing is the sub-aperture of linear-array three-dimensional imaging synthetic aperture radars.

Definition 6, the three-dimensional rear orientation projection of linear-array three-dimensional imaging synthetic aperture radars formation method

The three-dimensional rear orientation projection of linear-array three-dimensional imaging synthetic aperture radars formation method is the expansion of synthetic-aperture radar two dimension rear orientation projection formation method.It is historical to the distance of each array element of linear array antenna that this method is at first calculated scattering point, selects the data of respective unit, and the doppler phase of the column criterion of going forward side by side compensates and coherent accumulation, obtains the scattering coefficient of this point.This method flow diagram is seen patent accompanying drawing.See document " radar imagery technology " for details, protect polished grade and write, the Electronic Industry Press publishes.

Definition 7, traversal method

By the data ordering order, ascending, one by one data are carried out certain operation, till all data are all executed this operation.

The invention provides a kind of linear array three-dimensional imaging synthetic aperture radar fast imaging method that approaches based on sub-aperture, it comprises following step:

Step 1, initialization linear-array three-dimensional imaging synthetic aperture radars imaging system parameter:

Be initialized to as systematic parameter and comprise: the platform speed vector, note is V, platform initial position vector, note is P ⁰, the electromagnetic wave number of radar emission, note is K _c, the position at the relative platform of each array element of linear array antenna center, note is P _i, wherein i is each array element sequence number of antenna, is natural number, i=0, and 1 ..., M, M are each array element sum of linear array antenna, the signal bandwidth of radar emission baseband signal, and note is B, the radar emission signal pulse width, note is T _P, radar receives the ripple door and continues width, and note is T _o, the SF of radar receiving system, note is f _s, the pulse repetition rate of radar system, note is PRF, and the radar receiving system receives the delay of ripple door with respect to the divergent wave door that transmits, and note is T _D, linear array antenna length, note is L, the length of synthetic aperture of radar, note is l.Above-mentioned parameter is the canonical parameter of linear-array three-dimensional imaging synthetic aperture radars system, wherein, and the electromagnetic wave number K of radar emission _c, the signal bandwidth B of radar emission baseband signal, radar emission signal pulse width T _P, radar receives the ripple door and continues width T _o, the SF f of radar receiving system _s, the linear array antenna length L, the length of synthetic aperture l of radar, the pulse repetition rate PRF of radar system and receiving system receive the ripple door and confirm in linear array three-dimensional imaging synthetic aperture Radar Design process with respect to the delay of the divergent wave door that transmits; Wherein, platform speed vector V and platform initial position vector P ⁰In linear array three-dimensional imaging synthetic aperture radar observation conceptual design, confirm.According to linear-array three-dimensional imaging synthetic aperture radars system schema and linear-array three-dimensional imaging synthetic aperture radars observation program, linear array three-dimensional imaging synthetic aperture radar fast imaging method needs be initialized to be as systematic parameter known.

Step 2, linear-array three-dimensional imaging synthetic aperture radars raw data are carried out the distance compression:

Adopt synthetic-aperture radar gauged distance compression method to the synthetic aperture distance by radar to echo data D ₁Compress, obtain the linear-array three-dimensional imaging synthetic aperture radars data after distance is compressed, note is E ₁

The sub-aperture of step 3, the primary linear-array three-dimensional imaging synthetic aperture radars of intercepting:

At the core of synthetic aperture, along radar transmit-receive platform heading, intercepting goes out the part synthetic aperture that a segment length is l/d, and at the core of linear array antenna; Array antenna direction along the line, intercepting goes out the partial line array antenna that a segment length is L/d, the one section synthetic aperture that intercepting is gone out and the mutual vertical placement of one section linear array antenna of taking-up; Synthetic two-dimensional planar array, the sub-aperture of promptly synthesizing primary linear-array three-dimensional imaging synthetic aperture radars, wherein l representes the length of synthetic aperture of radar; L representes linear array antenna length, and d is a positive integer, and the value size of d is confirmed by the needs of engineering; The value of d is big more, and operand is big more, and computational solution precision is high more; The value of d is more little, and operand is more little, and computational solution precision is low more.Whether and to be provided for differentiating be the differentiation sign indicating number in the sub-aperture of linear-array three-dimensional imaging synthetic aperture radars that goes out of intercepting, and the differentiation code value of the part that intercepting is gone out is changed to 1, and the differentiation code value of remainder is changed to 0, is designated as Mask (n), and n is a positive integer, representes the slow time.

Step 4, acquisition linear-array three-dimensional imaging synthetic aperture radars image space be image in different resolution for the first time:

Adopt the three-dimensional rear orientation projection of linear-array three-dimensional imaging synthetic aperture radars formation method, k slow time, to linear-array three-dimensional imaging synthetic aperture radars image space mid point (x; Y z) is carried out to picture, wherein x; Y, z are positive integer, the three-dimensional coordinate in radar image space under the expression resolution first time; K is a positive integer, representes a slow time.

If differentiate a sign indicating number Mask (k)=1, adopt the three-dimensional rear orientation projection of linear-array three-dimensional imaging synthetic aperture radars formation method to the imaging of linear-array three-dimensional imaging synthetic aperture radars image space, obtain when k slow time; The distribution function of linear-array three-dimensional imaging synthetic aperture radars image space scattering coefficient, note is φ (k, x; Y, z), x wherein; Y, z are positive integer, the three-dimensional coordinate in radar image space under the expression resolution first time.

If differentiate sign indicating number Mask (k)=0, carry out step 5 operation.

Step 5, make k=1,2 ..., N; N is the discrete number of slow time in the synthetic aperture, to all N slow time repeating step 4, obtains distribution function φ (k, the x of the linear-array three-dimensional imaging synthetic aperture radars image space scattering coefficient of all N slow time; Y, z), x wherein; Y, z are positive integer, the three-dimensional coordinate in radar image space under the expression resolution first time.Utilize formula then Calculating resolution is ρ ₀The distribution function of linear-array three-dimensional imaging synthetic aperture radars image space scattering coefficient, note be σ (x, y, z), ρ wherein ₀Be the corresponding radar image spatial resolution in the sub-aperture of the linear-array three-dimensional imaging synthetic aperture radars of intercepting in the step 3.

Step 6, calculating linear-array three-dimensional imaging synthetic aperture radars image space scattering coefficient decision threshold:

Adopt the traversal method to seek distribution function σ (x, y, maximal value z) of linear-array three-dimensional imaging synthetic aperture radars image space scattering coefficient; Obtain the distribution function σ (x of linear-array three-dimensional imaging synthetic aperture radars image space scattering coefficient; Y, maximal value z), note is σ _MaxUtilize formula Θ=σ _Max* q calculates linear-array three-dimensional imaging synthetic aperture radars image space scattering coefficient decision threshold, and note is Θ; 0＜q＜1 wherein, the value size of q is confirmed that by the needs of engineering the value of q is more little; Operand is big more, and computational solution precision is high more, and the value of q is big more; Operand is more little, and computational solution precision is low more.

The sub-aperture of step 7, the secondary linear-array three-dimensional imaging synthetic aperture radars of intercepting:

At the core of synthetic aperture, along radar transmit-receive platform heading, intercepting goes out the part synthetic aperture that a segment length is 2 * l/d; And at the core of linear array antenna, array antenna direction along the line, intercepting goes out the partial line array antenna that a segment length is 2 * l/d; Two-dimensional planar array is synthesized in one section synthetic aperture that intercepting is gone out and one section linear array antenna vertical placements each other of taking-up, promptly synthesizes the sub-aperture of secondary linear-array three-dimensional imaging synthetic aperture radars; Wherein l representes the length of synthetic aperture of radar, and d is a positive integer, and the value size of d is confirmed by the needs of engineering; The value of d is big more, and operand is big more, and computational solution precision is high more; The value of d is more little, and operand is more little, and computational solution precision is low more.Whether and to be provided for differentiating be the differentiation sign indicating number in the sub-aperture of linear-array three-dimensional imaging synthetic aperture radars that goes out of intercepting, and the differentiation code value of the part that intercepting is gone out is changed to 1, and the differentiation code value of remainder is changed to 0, is designated as Mask ₁(n), n is a positive integer, representes the slow time.

Step 8, based on the sparse target imaging of the resolution prediction first time:

Take out linear array three-dimensional imaging synthetic aperture radar image space scattering coefficient in the step 5 distribution function σ (x, y, z), x wherein, y, z are positive integer, expression is the three-dimensional coordinate in radar image space under the resolution for the first time.The linear-array three-dimensional imaging synthetic aperture radars image resolution ratio is changed to ρ ₀/ 2, adopt the three-dimensional rear orientation projection of linear-array three-dimensional imaging synthetic aperture radars formation method, k slow time, (u, v w) are carried out to picture, wherein ρ to linear-array three-dimensional imaging synthetic aperture radars image space mid point ₀Be the corresponding radar image spatial resolution in the sub-aperture of the linear-array three-dimensional imaging synthetic aperture radars of intercepting in the step 3, k is a positive integer, represent a slow time, u, and v, w are positive integer, the three-dimensional coordinate in radar image space under the expression resolution second time.

If differentiate sign indicating number Mask ₁(k)=1 and σ (u/2, v/2, w/2)>=Θ; Adopt the three-dimensional rear orientation projection of linear-array three-dimensional imaging synthetic aperture radars formation method, to picture point (u, v; W) be carried out to picture, obtain when slow time of k picture point (u; V, linear-array three-dimensional imaging synthetic aperture radars image space scattering coefficient w), note is φ ₁(k, u, v, w);

If differentiate sign indicating number Mask ₁(k)=1 and σ (u/2, v/2, w/2)＜Θ, when being defined in k slow time, picture point (u, v, linear-array three-dimensional imaging synthetic aperture radars image space scattering coefficient φ w) ₁(k, u, v, w)=0;

If Mask ₁(k)=0, carry out step 9 operation.

Step 9, make k=1,2 ..., N, N are the discrete number of slow time in the synthetic aperture, to all N slow time repeating step 8, obtain the distribution function φ of the linear-array three-dimensional imaging synthetic aperture radars image space scattering coefficient of all N slow time ₁(k, u, v, w), and u wherein, v, w are positive integer, expression is the three-dimensional coordinate in radar image space under the resolution for the second time, utilizes formula Calculating resolution is ρ ₀The distribution function of/2 high-resolution linear-array three-dimensional imaging synthetic aperture radars image space scattering coefficient, note is σ ₁(u, v, w), ρ wherein ₀/ 2 is the corresponding radar image spatial resolution in the sub-aperture of linear-array three-dimensional imaging synthetic aperture radars of intercepting in the step 7.

Step 10, with in the step 6 the first time resolution linear-array three-dimensional imaging synthetic aperture radars image space scattering coefficient distribution function σ (z) replacing with resolution is ρ for x, y ₀Second time of/2 resolution linear-array three-dimensional imaging synthetic aperture radars image space scattering coefficient distribution function σ ₁(w), repeating step 6～9 obtains the distribution function of three-dimensional imaging synthetic aperture radar image space scattering coefficient under the resolution for the third time for u, v.

Step 11, will be for the third time the resolution comparison of resolution and linear-array three-dimensional imaging synthetic aperture radars system design, if resolution reaches the resolution of linear-array three-dimensional imaging synthetic aperture radars system design for the third time, then obtain the distribution function that the linear-array three-dimensional imaging synthetic aperture radars image space is truly differentiated scattering coefficient; The note be Ω (X, Y, Z); X wherein; Y, Z are positive integer, the three-dimensional coordinate in radar image space under the resolution of expression linear-array three-dimensional imaging synthetic aperture radars system design; If resolution does not reach the resolution of linear-array three-dimensional imaging synthetic aperture radars system design for the third time; The then operation of repeating step 10; The resolution in radar image space reaches the resolution of linear-array three-dimensional imaging synthetic aperture radars system design in step 10, finally to obtain the true distribution function of scattering coefficient down of differentiating of linear-array three-dimensional imaging synthetic aperture radars image space.

Innovative point of the present invention is to the characteristics that only comprise the echoed signal of some sparse target in the three dimensions in the actual line array three-dimensional imaging synthetic aperture radar return; Adopt sub-aperture approximation technique; Only some sparse target in the three dimensions is carried out imaging processing, thereby well solved the big problem of three-dimensional imaging synthetic aperture radar formation method operand.

The invention has the advantages that and utilize less operand to realize linear-array three-dimensional imaging synthetic aperture radars.The present invention can be applied to fields such as synthetic aperture radar image-forming, earth remote sensing.

Description of drawings:

Fig. 1 is the three-dimensional rear orientation projection of a linear-array three-dimensional imaging synthetic aperture radars formation method process flow diagram

Wherein, passage i representes the echo data of i antenna, i=1 ..., M.M representes the antenna channels sum, and PRF representes radar pulse repetition frequency, and n representes the slow time, Represent that i radar antenna is apart from scattering point

Distance, (u, v w) are the coordinate of scattering point, wherein || || ₂Represent 2 norms.Antenna phase center can be calculated by the initiation parameter of step 1 in the instructions.The linear-array three-dimensional imaging synthetic aperture radars image space that the 3-D view space is described for definition 3.Synthetic-aperture radar gauged distance compression method apart from boil down to definition 2 descriptions.Interpolation/resampling and coherent accumulation are the standard method of two-dimentional rear orientation projection formation method.

Fig. 2 is the FB(flow block) of method provided by the present invention.

The linear-array three-dimensional imaging synthetic aperture radars flight geometric relationship figure that Fig. 3 adopts for the specific embodiment of the invention.

Wherein, the PRI indicating impulse repetition period, n representes the slow time, x, and y, z representes system coordinates, p (n) expression platform track, L representes linear array antenna length, and β representes the platform heading, and γ representes linear array antenna direction, P _ωExpression scattering point position, (u, v w) are the coordinate of scattering point, 0 denotation coordination initial point, R (n, i; P _Uvw) represent that n slow moment time i radar antenna is apart from scattering point P _ωDistance.

Fig. 4 is the linear-array three-dimensional imaging synthetic aperture radars system parameter table that the invention embodiment adopts.

Fig. 5 is the radar image space of the specific embodiment of the invention to the three-dimensional point target

Wherein horizontal ordinate is for cutting the flight path direction, and ordinate is along the flight path direction, vertical coordinate be the height to, 1 is the three-dimensional point target in the radar image space.

Fig. 6 is the imaging results figure of the specific embodiment of the invention to the three-dimensional point target

Wherein horizontal ordinate is for cutting the flight path direction, and ordinate is along the flight path direction, vertical coordinate be the height to, 2 is the three-dimensional point target imaging.

Embodiment

The present invention mainly adopts the method for emulation experiment to verify, institute in steps, conclusion all correctly at VC++, the last checking of MATLAB7.0.The practical implementation step is following:

Step 1, initialization linear-array three-dimensional imaging synthetic aperture radars imaging system parameter:

The systematic parameter that this embodiment adopted sees Fig. 4 for details.

Step 2, linear-array three-dimensional imaging synthetic aperture radars raw data are carried out the distance compression:

Adopt synthetic-aperture radar gauged distance compression method to the synthetic aperture distance by radar to echo data D ₁Compress, obtain the linear-array three-dimensional imaging synthetic aperture radars data after distance is compressed, note is E ₁

The sub-aperture of step 3, the primary linear-array three-dimensional imaging synthetic aperture radars of intercepting:

At the core of synthetic aperture, along radar transmit-receive platform heading, intercepting goes out the part synthetic aperture that a segment length is l/5; And core at linear array antenna; Array antenna direction along the line, intercepting goes out the partial line array antenna that a segment length is L/5, the one section synthetic aperture that intercepting is gone out and the mutual vertical placement of one section linear array antenna of taking-up; Synthetic two-dimensional planar array; Promptly synthesize the sub-aperture of primary linear-array three-dimensional imaging synthetic aperture radars, wherein l representes the length of synthetic aperture of radar, and L representes linear array antenna length.And be provided for differentiating the differentiation sign indicating number in the sub-aperture that whether is the linear-array three-dimensional imaging synthetic aperture radars that goes out of intercepting, and the differentiation code value of the part that intercepting is gone out is changed to 1, and the differentiation code value of remainder is changed to 0; Be designated as Mask (n), n=1,2; ..., 4096, be the slow time.

Step 4, acquisition linear-array three-dimensional imaging synthetic aperture radars image space be image in different resolution for the first time:

Adopt the three-dimensional rear orientation projection of linear-array three-dimensional imaging synthetic aperture radars formation method, k slow time, to the point of linear-array three-dimensional imaging synthetic aperture radars image space (x, y z) are carried out to picture, and wherein k is a positive integer, represent a slow time, $x=\frac{\mathrm{1,2},...,128}{{\mathrm{\&rho;}}_0},$ $y=\frac{\mathrm{1,2},...,128}{{\mathrm{\&rho;}}_0},$ $z=\frac{\mathrm{1,2},...,150}{{\mathrm{\&rho;}}_0},$ The three-dimensional coordinate in radar image space under the expression resolution first time, ρ ₀=20, the corresponding radar image spatial resolution in sub-aperture of the linear-array three-dimensional imaging synthetic aperture radars of intercepting in the expression step 3.

If differentiate a sign indicating number Mask (k)=1, adopt the three-dimensional rear orientation projection of linear-array three-dimensional imaging synthetic aperture radars formation method to the imaging of linear-array three-dimensional imaging synthetic aperture radars image space, obtain when k slow time; The distribution function of linear-array three-dimensional imaging synthetic aperture radars image space scattering coefficient, note is φ (k, x; Y, z), x wherein; Y, z are positive integer, the three-dimensional coordinate in radar image space under the expression resolution first time.

If differentiate sign indicating number Mask (k)=0, carry out step 5 operation.

Step 5, make k=1,2 ..., 4096, to 4096 all slow time repeating steps 4, obtain the linear-array three-dimensional imaging synthetic aperture radars image space scattering coefficient of 4096 all slow times distribution function φ (k, x, y, z), wherein $x=\frac{\mathrm{1,2},...,128}{{\mathrm{\&rho;}}_0},$ $y=\frac{\mathrm{1,2},...,128}{{\mathrm{\&rho;}}_0},$ $z=\frac{\mathrm{1,2},...,150}{{\mathrm{\&rho;}}_0},$ The three-dimensional coordinate in radar image space under the expression resolution first time.Utilize formula then $\mathrm{\&sigma;}(x,y,z)=\underset{k=1}{\overset{N}{\mathrm{\&Sigma;}}}\mathrm{\&phi;}(k,x,y,z),$ Calculating resolution is ρ ₀The distribution function of=20 linear-array three-dimensional imaging synthetic aperture radars image space scattering coefficient, note be σ (x, y, z), ρ wherein ₀Be the corresponding radar image spatial resolution in the sub-aperture of the linear-array three-dimensional imaging synthetic aperture radars of intercepting in the step 3.

Step 6, calculating linear-array three-dimensional imaging synthetic aperture radars image space scattering coefficient decision threshold:

Adopt the traversal method to seek distribution function σ (x, y, maximal value z) of linear-array three-dimensional imaging synthetic aperture radars image space scattering coefficient; Obtain the distribution function σ (x of linear-array three-dimensional imaging synthetic aperture radars image space scattering coefficient; Y, maximal value z), note is σ _MaxUtilize formula Θ=σ _Max* 0.02, calculate linear-array three-dimensional imaging synthetic aperture radars image space scattering coefficient decision threshold, note is Θ.

The sub-aperture of step 7, the secondary linear-array three-dimensional imaging synthetic aperture radars of intercepting:

Core in synthetic aperture; Along radar transmit-receive platform heading, intercepting goes out the part synthetic aperture that a segment length is 2 * l/5, and at the core of linear array antenna; Array antenna direction along the line; Intercepting goes out the partial line array antenna that a segment length is 2 * l/5, and two-dimensional planar array is synthesized in one section synthetic aperture that intercepting is gone out and one section linear array antenna vertical placement each other of taking-up; Promptly synthesize the sub-aperture of secondary linear-array three-dimensional imaging synthetic aperture radars, wherein l representes the length of synthetic aperture of radar.Whether and to be provided for differentiating be the differentiation sign indicating number in the sub-aperture of linear-array three-dimensional imaging synthetic aperture radars that goes out of intercepting, and the differentiation code value of the part that intercepting is gone out is changed to 1, and the differentiation code value of remainder is changed to 0, is designated as Mask ₁(n), n=1,2 ..., 4096, be the slow time.

Step 8, based on the sparse target imaging of the resolution prediction first time:

Take out linear array three-dimensional imaging synthetic aperture radar image space scattering coefficient in the step 5 distribution function σ (x, y, z), x wherein, y, z are positive integer, expression is the three-dimensional coordinate in radar image space under the resolution for the first time.The linear-array three-dimensional imaging synthetic aperture radars image resolution ratio is changed to ρ ₁=ρ ₀/ 2, adopt the three-dimensional rear orientation projection of linear-array three-dimensional imaging synthetic aperture radars formation method, k slow time, to linear-array three-dimensional imaging synthetic aperture radars image space mid point (u, v w) are carried out to picture, and wherein k is a positive integer, represent a slow time, $u=\frac{\mathrm{1,2},...,128}{{\mathrm{\&rho;}}_1},$ $v=\frac{\mathrm{1,2},...,128}{{\mathrm{\&rho;}}_1},$ $w=\frac{\mathrm{1,2},...,150}{{\mathrm{\&rho;}}_1},$ The three-dimensional coordinate in radar image space under the expression resolution second time, ρ ₁=10, be the corresponding radar image spatial resolution in the sub-aperture of the linear-array three-dimensional imaging synthetic aperture radars of intercepting in the step 3.

If differentiate sign indicating number Mask ₁(k)=1 and σ (u/2, v/2, w/2)>=Θ; Adopt the three-dimensional rear orientation projection of linear-array three-dimensional imaging synthetic aperture radars formation method, to picture point (u, v; W) be carried out to picture, obtain when slow time of k picture point (u; V, linear-array three-dimensional imaging synthetic aperture radars image space scattering coefficient w), note is φ ₁(k, u, v, w);

If differentiate sign indicating number Mask ₁(k)=1 and σ (u/2, v/2, w/2)＜Θ, when being defined in k slow time, picture point (u, v, linear-array three-dimensional imaging synthetic aperture radars image space scattering coefficient φ w) ₁(k, u, v, w)=0;

If Mask ₁(k)=0, carry out step 9 operation.

Step 9, make k=1,2 ..., 4096, to 4096 all slow time repeating steps 8, obtain the distribution function φ of the linear-array three-dimensional imaging synthetic aperture radars image space scattering coefficient of 4096 all slow times ₁(k, u, v, w), wherein $u=\frac{\mathrm{1,2},...,128}{{\mathrm{\&rho;}}_1},$ $v=\frac{\mathrm{1,2},...,128}{{\mathrm{\&rho;}}_1},$ $w=\frac{\mathrm{1,2},...,150}{{\mathrm{\&rho;}}_1},$ The three-dimensional coordinate in radar image space utilizes formula under the expression resolution second time

Calculating resolution is ρ ₁The distribution function of linear array three-dimensional imaging synthetic aperture radar image space scattering coefficient under second time of=10 resolution, note is σ ₁(u, v, w), ρ wherein ₁Be the corresponding radar image spatial resolution in the sub-aperture of the linear-array three-dimensional imaging synthetic aperture radars of intercepting in the step 7.

Step 10, with in the step 6 the first time resolution linear-array three-dimensional imaging synthetic aperture radars image space scattering coefficient distribution function σ (z) replacing with resolution is ρ for x, y ₁The second time resolution linear-array three-dimensional imaging synthetic aperture radars image space scattering coefficient distribution function σ ₁(w), repeating step 6～9 obtains the distribution function of three-dimensional imaging synthetic aperture radar image space scattering coefficient under the resolution for the third time for u, v.

Step 11, will be for the third time the resolution comparison of resolution and linear-array three-dimensional imaging synthetic aperture radars system design; If resolution reaches the resolution of linear-array three-dimensional imaging synthetic aperture radars system design for the third time; Then obtain the linear-array three-dimensional imaging synthetic aperture radars image space and truly differentiate the distribution function of scattering coefficient, note is Ω (X, Y; Z), wherein $X=\frac{\mathrm{1,2},...,128}{\mathrm{\&rho;}},$ $Y=\frac{\mathrm{1,2},...,128}{\mathrm{\&rho;}},$ $Z=\frac{\mathrm{1,2},...,150}{\mathrm{\&rho;}},$ The three-dimensional coordinate in radar image space under the resolution of expression linear-array three-dimensional imaging synthetic aperture radars system design, ρ=4, the resolution of expression linear-array three-dimensional imaging synthetic aperture radars system design; If resolution does not reach the resolution of linear-array three-dimensional imaging synthetic aperture radars system design for the third time; The then operation of repeating step 10; The resolution in radar image space reaches the resolution of linear-array three-dimensional imaging synthetic aperture radars system design in step 10, finally to obtain the true distribution function of scattering coefficient down of differentiating of linear-array three-dimensional imaging synthetic aperture radars image space.

Can find out that through the specific embodiment of the invention linear-array three-dimensional imaging synthetic aperture radars formation method provided by the present invention can be realized linear-array three-dimensional imaging synthetic aperture radars imaging, and compare with three-dimensional rear orientation projection method and to have littler operand.

Claims (1)

1. the linear array three-dimensional imaging synthetic aperture radar fast imaging method that approaches based on sub-aperture is characterized in that it comprises following step:

Step 1, initialization linear-array three-dimensional imaging synthetic aperture radars imaging system parameter:

Be initialized to as systematic parameter and comprise: the platform speed vector, note is done

, platform initial position vector, note is done

, the electromagnetic wave number of radar emission, note is K _c, the position at the relative platform of each array element of linear array antenna center, note is done

, wherein i is each array element sequence number of antenna, is natural number, i=0, and 1 ..., M, M are each array element sum of linear array antenna, the signal bandwidth of radar emission baseband signal, and note is B, the radar emission signal pulse width, note is T _P, radar receives the ripple door and continues width, and note is T _o, the SF of radar receiving system, note is f _s, the pulse repetition rate of radar system, note is PRF, and the radar receiving system receives the delay of ripple door with respect to the divergent wave door that transmits, and note is T _D, linear array antenna length, note is L, the length of synthetic aperture of radar, note is l; Above-mentioned parameter is the canonical parameter of linear-array three-dimensional imaging synthetic aperture radars system, wherein, and the electromagnetic wave number K of radar emission _c, the signal bandwidth B of radar emission baseband signal, radar emission signal pulse width T _P, radar receives the ripple door and continues width T _o, the SF f of radar receiving system _s, the linear array antenna length L, the length of synthetic aperture l of radar, the pulse repetition rate PRF of radar system and receiving system receive the ripple door and confirm in linear array three-dimensional imaging synthetic aperture Radar Design process with respect to the delay of the divergent wave door that transmits; Wherein, platform speed vector

And platform initial position vector In linear array three-dimensional imaging synthetic aperture radar observation conceptual design, confirm; According to linear-array three-dimensional imaging synthetic aperture radars system schema and linear-array three-dimensional imaging synthetic aperture radars observation program, linear array three-dimensional imaging synthetic aperture radar fast imaging method needs be initialized to be as systematic parameter known;

Step 2, linear-array three-dimensional imaging synthetic aperture radars raw data are carried out the distance compression:

Adopt synthetic-aperture radar gauged distance compression method that the synthetic aperture distance by radar is compressed to echo data

; Obtain the linear-array three-dimensional imaging synthetic aperture radars data after distance is compressed, note is done

;

The sub-aperture of step 3, the primary linear-array three-dimensional imaging synthetic aperture radars of intercepting:

At the core of synthetic aperture, along radar transmit-receive platform heading, intercepting goes out the part synthetic aperture that a segment length is l/d, and at the core of linear array antenna; Array antenna direction along the line, intercepting goes out the partial line array antenna that a segment length is L/d, the one section synthetic aperture that intercepting is gone out and the mutual vertical placement of one section linear array antenna of taking-up; Synthetic two-dimensional planar array, the sub-aperture of promptly synthesizing primary linear-array three-dimensional imaging synthetic aperture radars, wherein l representes the length of synthetic aperture of radar; L representes linear array antenna length, and d is a positive integer, and the value size of d is confirmed by the needs of engineering; The value of d is big more, and operand is big more, and computational solution precision is high more; The value of d is more little, and operand is more little, and computational solution precision is low more; Whether and to be provided for differentiating be the differentiation sign indicating number in the sub-aperture of linear-array three-dimensional imaging synthetic aperture radars that goes out of intercepting, and the differentiation code value of the part that intercepting is gone out is changed to 1, and the differentiation code value of remainder is changed to 0, is designated as Mask (n), and n is a positive integer, representes the slow time;

Step 4, acquisition linear-array three-dimensional imaging synthetic aperture radars image space be image in different resolution for the first time:

Adopt the three-dimensional rear orientation projection of linear-array three-dimensional imaging synthetic aperture radars formation method, k slow time, to linear-array three-dimensional imaging synthetic aperture radars image space mid point (x; Y z) is carried out to picture, wherein x; Y, z are positive integer, the three-dimensional coordinate in radar image space under the expression resolution first time; K is a positive integer, representes a slow time;

If differentiate a sign indicating number Mask (k)=1, adopt the three-dimensional rear orientation projection of linear-array three-dimensional imaging synthetic aperture radars formation method to the imaging of linear-array three-dimensional imaging synthetic aperture radars image space, obtain when k slow time; The distribution function of linear-array three-dimensional imaging synthetic aperture radars image space scattering coefficient, note is φ (k, x; Y, z), x wherein; Y, z are positive integer, the three-dimensional coordinate in radar image space under the expression resolution first time;

If differentiate sign indicating number Mask (k)=0, carry out step 5 operation;

Step 5, make k=1,2 ..., N; N is the discrete number of slow time in the synthetic aperture, to all N slow time repeating step 4, obtains distribution function φ (k, the x of the linear-array three-dimensional imaging synthetic aperture radars image space scattering coefficient of all N slow time; Y, z), x wherein; Y, z are positive integer, the three-dimensional coordinate in radar image space under the expression resolution first time; Utilize formula then

Calculating resolution is ρ ₀The distribution function of linear-array three-dimensional imaging synthetic aperture radars image space scattering coefficient, note be σ (x, y, z), ρ wherein ₀Be the corresponding radar image spatial resolution in the sub-aperture of the linear-array three-dimensional imaging synthetic aperture radars of intercepting in the step 3;

Step 6, calculating linear-array three-dimensional imaging synthetic aperture radars image space scattering coefficient decision threshold:

Adopt the traversal method to seek distribution function σ (x, y, maximal value z) of linear-array three-dimensional imaging synthetic aperture radars image space scattering coefficient; Obtain the distribution function σ (x of linear-array three-dimensional imaging synthetic aperture radars image space scattering coefficient; Y, maximal value z), note is σ _MaxUtilize formula Θ=σ _Max* q calculates linear-array three-dimensional imaging synthetic aperture radars image space scattering coefficient decision threshold, and note is Θ; 0＜q＜1 wherein, the value size of q is confirmed that by the needs of engineering the value of q is more little; Operand is big more, and computational solution precision is high more, and the value of q is big more; Operand is more little, and computational solution precision is low more;

The sub-aperture of step 7, the secondary linear-array three-dimensional imaging synthetic aperture radars of intercepting:

At the core of synthetic aperture, along radar transmit-receive platform heading, intercepting goes out the part synthetic aperture that a segment length is 2 * l/d; And at the core of linear array antenna, array antenna direction along the line, intercepting goes out the partial line array antenna that a segment length is 2 * l/d; Two-dimensional planar array is synthesized in one section synthetic aperture that intercepting is gone out and one section linear array antenna vertical placements each other of taking-up, promptly synthesizes the sub-aperture of secondary linear-array three-dimensional imaging synthetic aperture radars; Wherein l representes the length of synthetic aperture of radar, and d is a positive integer, and the value size of d is confirmed by the needs of engineering; The value of d is big more, and operand is big more, and computational solution precision is high more; The value of d is more little, and operand is more little, and computational solution precision is low more; Whether and to be provided for differentiating be the differentiation sign indicating number in the sub-aperture of linear-array three-dimensional imaging synthetic aperture radars that goes out of intercepting, and the differentiation code value of the part that intercepting is gone out is changed to 1, and the differentiation code value of remainder is changed to 0, is designated as Mask ₁(n), n is a positive integer, representes the slow time;

Step 8, based on the sparse target imaging of the resolution prediction first time:

Take out linear array three-dimensional imaging synthetic aperture radar image space scattering coefficient in the step 5 distribution function σ (x, y, z), x wherein, y, z are positive integer, expression is the three-dimensional coordinate in radar image space under the resolution for the first time; The linear-array three-dimensional imaging synthetic aperture radars image resolution ratio is changed to ρ ₀/ 2, adopt the three-dimensional rear orientation projection of linear-array three-dimensional imaging synthetic aperture radars formation method, k slow time, (u, v w) are carried out to picture, wherein ρ to linear-array three-dimensional imaging synthetic aperture radars image space mid point ₀Be the corresponding radar image spatial resolution in the sub-aperture of the linear-array three-dimensional imaging synthetic aperture radars of intercepting in the step 3, k is a positive integer, represent a slow time, u, and v, w are positive integer, the three-dimensional coordinate in radar image space under the expression resolution second time;

If differentiate sign indicating number Mask ₁(k)=1 and σ (u/2, v/2, w/2)>=Θ; Adopt the three-dimensional rear orientation projection of linear-array three-dimensional imaging synthetic aperture radars formation method, to picture point (u, v; W) be carried out to picture, obtain when slow time of k picture point (u; V, linear-array three-dimensional imaging synthetic aperture radars image space scattering coefficient w), note is φ ₁(k, u, v, w);

If differentiate sign indicating number Mask ₁(k)=1 and σ (u/2, v/2, w/2)＜Θ, when being defined in k slow time, picture point (u, v, linear-array three-dimensional imaging synthetic aperture radars image space scattering coefficient φ w) ₁(k, u, v, w)=0;

If Mask ₁(k)=0, carry out step 9 operation;

Step 9, make k=1,2 ..., N, N are the discrete number of slow time in the synthetic aperture, to all N slow time repeating step 8, obtain the distribution function φ of the linear-array three-dimensional imaging synthetic aperture radars image space scattering coefficient of all N slow time ₁(k, u, v, w), and u wherein, v, w are positive integer, expression is the three-dimensional coordinate in radar image space under the resolution for the second time, utilizes formula

Calculating resolution is ρ ₀The distribution function of/2 high-resolution linear-array three-dimensional imaging synthetic aperture radars image space scattering coefficient, note is σ ₁(u, v, w), ρ wherein ₀/ 2 is the corresponding radar image spatial resolution in the sub-aperture of linear-array three-dimensional imaging synthetic aperture radars of intercepting in the step 7;

Step 10, with in the step 6 the first time resolution linear-array three-dimensional imaging synthetic aperture radars image space scattering coefficient distribution function σ (z) replacing with resolution is ρ for x, y ₀Second time of/2 resolution linear-array three-dimensional imaging synthetic aperture radars image space scattering coefficient distribution function σ ₁(w), repeating step 6～9 obtains the distribution function of three-dimensional imaging synthetic aperture radar image space scattering coefficient under the resolution for the third time for u, v;

Step 11, will be for the third time the resolution comparison of resolution and linear-array three-dimensional imaging synthetic aperture radars system design, if resolution reaches the resolution of linear-array three-dimensional imaging synthetic aperture radars system design for the third time, then obtain the distribution function that the linear-array three-dimensional imaging synthetic aperture radars image space is truly differentiated scattering coefficient; The note be Ω (X, Y, Z); X wherein; Y, Z are positive integer, the three-dimensional coordinate in radar image space under the resolution of expression linear-array three-dimensional imaging synthetic aperture radars system design; If resolution does not reach the resolution of linear-array three-dimensional imaging synthetic aperture radars system design for the third time; The then operation of repeating step 10; The resolution in radar image space reaches the resolution of linear-array three-dimensional imaging synthetic aperture radars system design in step 10, finally to obtain the true distribution function of scattering coefficient down of differentiating of linear-array three-dimensional imaging synthetic aperture radars image space.

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