CN107748362A - A kind of quick autohemagglutination focusing imaging methods of linear array SAR based on maximum sharpness - Google Patents
A kind of quick autohemagglutination focusing imaging methods of linear array SAR based on maximum sharpness Download PDFInfo
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
- G01S13/88—Radar or analogous systems specially adapted for specific applications
- G01S13/89—Radar or analogous systems specially adapted for specific applications for mapping or imaging
- G01S13/90—Radar or analogous systems specially adapted for specific applications for mapping or imaging using synthetic aperture techniques, e.g. synthetic aperture radar [SAR] techniques
- G01S13/9004—SAR image acquisition techniques
- G01S13/9019—Auto-focussing of the SAR signals
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- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
- G01S13/88—Radar or analogous systems specially adapted for specific applications
- G01S13/89—Radar or analogous systems specially adapted for specific applications for mapping or imaging
- G01S13/90—Radar or analogous systems specially adapted for specific applications for mapping or imaging using synthetic aperture techniques, e.g. synthetic aperture radar [SAR] techniques
- G01S13/9004—SAR image acquisition techniques
- G01S13/9017—SAR image acquisition techniques with time domain processing of the SAR signals in azimuth
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- G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
- G01S13/88—Radar or analogous systems specially adapted for specific applications
- G01S13/89—Radar or analogous systems specially adapted for specific applications for mapping or imaging
- G01S13/90—Radar or analogous systems specially adapted for specific applications for mapping or imaging using synthetic aperture techniques, e.g. synthetic aperture radar [SAR] techniques
- G01S13/904—SAR modes
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
- G01S13/88—Radar or analogous systems specially adapted for specific applications
- G01S13/89—Radar or analogous systems specially adapted for specific applications for mapping or imaging
- G01S13/90—Radar or analogous systems specially adapted for specific applications for mapping or imaging using synthetic aperture techniques, e.g. synthetic aperture radar [SAR] techniques
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Abstract
The invention provides a kind of quick autohemagglutination focusing imaging methods of the linear array SAR based on maximum sharpness, it is maximum sharpness criterion and rear orientation projection's image-forming principle based on linear array SAR 3-D views, first with the phase error estimation and phase error equation of image sharpness partial derivative construction rear orientation projection self-focusing imaging, then quick approximate solution is carried out to phase error estimation and phase error equation using conjugate gradient method, so as to realize the quick estimation of phase error in linear array SAR echoes, finally carry out phase error compensation and carry out rear orientation projection's imaging, it is achieved thereby that the quick self-focusing imaging of linear array SAR rear orientation projections.It prior information of the present invention without the distribution of known phase error, can quickly estimate the phase error of low frequency, high frequency and random distribution present in linear array SAR echo datas, be imaged suitable for the quick self-focusings of linear array SAR in the case of Comlex-locus.
Description
Technical field
The invention belongs to Radar Technology field, its more particularly to synthetic aperture radar (SAR) technical field of imaging.
Background technology
Synthetic aperture radar (SAR) has round-the-clock, round-the-clock, informative remotely sensed image technology as a kind of,
The important means of current earth observation is turned into, on terrain graph generation, target acquisition and scouting, target precision strike, territory
The national economy such as resource exploration and Natural calamity monitoring obtains more and more extensive application with military field.Because possessing three-dimensional imaging
Ability, linear array SAR (LASAR) are in recent years by a kind of new SAR imaging techniques of extensive concern.Substantially, linear array SAR is
It is a kind of to form a big virtual two-dimensional face battle array acquisition observed object two dimension resolution by controlling linear array antenna to move in space, and
The SAR imaging techniques of the third dimension resolution of target are realized with reference to pulse compression technique, referring to document, " Wei Shun armies linear array three-dimensionals close
Into aperture radar sparse imaging technique research [D] University of Electronic Science and Technology, 2013 ".It is imaged relative to conventional SAR, linear array SAR can
Work in a variety of imaging patterns, such as side view, strabismus, regard down and forward sight, breach conventional SAR imaging patterns limitation and deficiency
(conventional SAR is typically only capable to work in side view imaging pattern), refers to document and " Peng Xueming, Wang Yanping, Tan Weixian, wait to be based on across boat
Airborne to thinned array regards down MIMO 3D-SAR three-dimensional imagings algorithm [J] electronics and information journal, 2012,34 (4):943-
949”.Therefore, linear array SAR can flexibly and easily realize that complex scene (city, mountain area etc.) and special objective are (building, naval vessel, smooth
Gram etc.) high-precision three-dimensional imaging, obtained in the mapping of round-the-clock, round-the-clock dimensional topography, target positioning and identification and information etc.
There are great researching value and application prospect in national defense and military and resource management field.
At present, linear array SAR data three-dimensional imaging algorithm mainly have based on frequency domain processing distance-Doppler (RD) algorithm,
Mutative scale (CS) algorithm, and rear orientation projection (BP) algorithm based on time domain, referring to document, " Zhang Donghao linear array three-dimensionals SAR is imaged
Algorithm research and emulation [D] University of Electronic Science and Technology, 2010 ".Relative to frequency domain imaging algorithm, time domain BP algorithm due to using into
The point-to-point coherent accumulation of image field scape, it is more suitable for the reception of linear array SAR nonuniform noises and the three-dimensional imaging of irrational motion conditions
Processing.Single from traditional SAR system or double individual Antenna Operations are different, in the imaging of linear array SAR three-dimensional observations, a pulse weight
Hundreds and thousands of individual antenna phase centers (APC) are needed in multiple time array antenna while are worked.Therefore, merely with radar system
Navigation measurement system (e.g., inertial measurement system or global positioning system) data of single position are difficult to linear array SAR arrays
The accurate compensation of multiple APC kinematic errors on antenna.In order to improve linear array SAR three-dimensional imaging quality, the measurement number that navigates is being utilized
After kinematic error compensation is carried out, generally also need to combine echo data and self-focusing imaging technique realizes battle array in linear array SAR system
Arrange more APC residual motion error compensation.
So far, for the kinematic error compensation of traditional SAR imagings, related scholar has been proposed a variety of being based on different criterions
Self-focusing imaging algorithm, as maximal possibility estimation (MLE) self-focusing, minimum entropy estimate (MEE) self-focusing, maximum sharpness estimation
(MSE) the methods of self-focusing.Phase gradient autofocus (PGA) algorithm is a kind of typical case wide variety of in SAR actual imagings
MLE self-focusing imaging algorithms, refer to document " D.E.Wahl, P.H.Eichel, D.C.Ghiglia, et al. " Phase
gradient autofocus-a robust tool for high resolution SAR phase correction,”
IEEE Transactions on Aerospace and Electronic Systems,Vol.30,No.3,827-835,
1994”.But PGA imaging algorithms are on condition that observed object scene includes strong scattering point target, and requires adjacent antenna phase
The phase error variations at center are shallower, it is difficult to estimate suitable for abrupt change and random phase error.Different from PGA algorithms, MSE is certainly
For focus method mainly using SAR image maximum sharpness estimation APC phase error, it can generally realize the essence of multipoint observation target
Really focus on and recover, refer to document " Morrison, Robert L., Minh N.Do, and David C.Munson. " SAR
image autofocus by sharpness optimization:A theoretical study.”IEEE
Transactions on Image Processing,Vol.16,No.9,2309-2321,2007”.For spotlight mode SAR into
As pattern, document " Ash, Joshua N. " An autofocus method for back projection imagery in
synthetic aperture radar.”IEEE Geoscience and Remote Sensing Letters,Vol.9,
No.1,104-108,2012 " propose a kind of SAR rear orientation projections autofocus algorithm based on image maximum sharpness, using feature
Decomposition estimation phase error, but the autofocus algorithm needs construction feature matrix and feature decomposition, and it is single to utilize whole scene to differentiate
Member construction cost estimation function, the cost estimation function dimension is more when computing is big and large scene is imaged, it is difficult to practical application.Document
“Dai Y H,Kou C X.A nonlinear conjugate gradient algorithm with an optimal
property and an improved Wolfe line search[J].SIAM Journal on Optimization,
2013,23(1):A kind of SAR self-focusing imaging algorithms based on positive semidefinite relaxation and circular cone optimization are proposed in 296-320 ", it is real
Survey data result and show that this method performance under the conditions of abrupt change phase error is better than PGA algorithms and MEE self-focusing methods, but the party
Method equally needs to build the cost function of a larger dimension, the amount of calculation in linear array SAR three-dimensional imagings when large scene is imaged
Greatly and it is difficult to be applicable." Yang Ze people's fast time-domains SAR is imaged and D S AR motion compensation process research [D] Xi'an electronics document
University of Science and Technology, 2016 ", which propose a kind of quick rear orientation projection's self-focusing imagings of linear array SAR for combining multiple passage echo datas, calculates
Method, but this method does not consider higher order term, the compensation problem of random phase error.In order to overcome existing rear orientation projection's self-focusing
Imaging algorithm is realized linear array SAR quick three-dimensional Autofocus processings, also needed to after linear array SAR in the deficiency of linear array SAR three-dimensional imagings
Related improvement is carried out to projection self-focusing imaging algorithm.
The content of the invention
The present invention proposes a kind of quick autohemagglutination focusing imaging methods of the linear array SAR based on maximum sharpness, and this method is based on line
The maximum sharpness criterion and rear orientation projection's image-forming principle of battle array SAR 3-D views, constructed first with image sharpness partial derivative backward
The phase error estimation and phase error equation of self-focusing imaging is projected, then phase error estimation and phase error equation is carried out using conjugate gradient method fast
Fast approximate solution, so as to realize the quick estimation of phase error in linear array SAR echoes, finally carry out phase error compensation and carry out
Rear orientation projection is imaged, it is achieved thereby that the quick self-focusing imaging of linear array SAR rear orientation projections.The present invention has without known phase
The prior information of position error distribution, can quickly estimate low frequency present in linear array SAR echo datas, high frequency and random distribution
The features such as phase error, it is imaged suitable for the quick self-focusings of linear array SAR in the case of Comlex-locus.
In order to facilitate description present disclosure, make following term definition first：
Define 1, linear array synthetic aperture radar (LASAR)
Linear array synthetic aperture radar image-forming is that linear array antenna is fixed on loading movement platform and moved with platform
Direction is vertical, realizes array plane two-dimensional imaging to synthesize two-dimensional planar array with reference to the motion of motion platform, recycles thunder
Realized up to wave beam to echo delay apart from one-dimensional image, so as to realize a kind of synthetic aperture radar skill of observed object three-dimensional imaging
Art, refer to document " Wang Bin, Wang Yanping, Hong Wen, wait linear arrays SAR three-dimensional imagings resolution analysis [J] Computer Simulations, 2011,
28(3):282-286”。
Define 2, standard synthetic aperture radar rear orientation projection imaging algorithm
Standard synthetic aperture radar rear orientation projection imaging algorithm is the synthetic aperture radar image-forming based on matched filtering principle
Algorithm, its mainly by the calculating of SAR scene resolution cells oblique distance, range cell search, original echo Doppler phase compensation, return
Wave number realizes the focal imaging of synthetic aperture radar raw radar data according to coherent accumulation etc., and referring to document, " monarch teacher is bistatic
SAR and linear array SAR principles and imaging technique research [D] University of Electronic Science and Technology, 2009 ".
Define the 3, basic matrix of rear orientation projection's imaging algorithm
The basic matrix of rear orientation projection's imaging algorithm is by the relevant product of standard synthetic aperture radar rear orientation projection imaging algorithm
Feature accumulation function matrix obtained from tired imaging process is expressed as matrix-vector multiplication processes, it can use standard synthetic aperture
Imaging space parameter, radar system parameters and echo data are calculated radar rear orientation projection imaging algorithm, refer to text
Offer " Ash, Joshua N. " An autofocus method for back projection imagery in synthetic
aperture radar.”IEEE Geoscience and Remote Sensing Letters,Vol.9,No.1,104-
108,2012”。
Define 4, standard synthetic aperture distance by radar compression method
Standard synthetic aperture distance by radar compression method refers to the transmission signal parameters using polarization sensitive synthetic aperture radar system, raw
Into Range compress reference signal, and the mistake being filtered using matched filtering technique to the distance of synthetic aperture radar to signal
Journey, refer to document " protect polished, Xing Mengdao, Wang Tong radar imaging technology [M] Electronic Industry Presses, 2005 ".
Define 5, standard conjugate gradient method
Standard conjugate gradient method is that solve one of most useful method of large linear systems, and solution Large Scale Nonlinear is most
Optimize one of maximally effective algorithm.Standard conjugate gradient method main thought is that conjugacy is combined with steepest descending method, profit
One group of conjugate direction is constructed with the gradient at known point, and along this prescription to carrying out searching element, obtains the minimal point of object function, in detail
See document " Wang Yiju, it is magnificent non-line optimum theories and method [M] Science Presses to repair, 2015 ".
Define 6, standard synthetic aperture radar original echo emulation mode
Standard synthetic aperture radar original echo emulation mode refer to given radar system parameters, platform trajectory parameters and
Observe under the Parameter Conditions needed for scenario parameters etc., obtain believing with SAR echoes based on synthetic aperture radar image-forming principles simulation
The method of the original echoed signals of number characteristic, detailed content refers to document, and " Lan G.Cumming Frank, H Wong. are synthesized
Aperture radar imaging:Algorithm and realization [M] Electronic Industry Presses, 2012 ".
The quick autohemagglutination focusing imaging methods of linear array SAR provided by the invention based on maximum sharpness, it includes following step
Suddenly：
The systematic parameter and echo data of step 1, initialization linear array SAR：
Initialization linear array SAR system parameter includes：Position arrow of n-th of the array element l-th of slow moment in linear array SAR system
Amount, is denoted as Pn(l), wherein n is the array element sequence number of linear array antenna, and n is natural number, n=1,2 ..., battle array that N, N are linear array antenna
First sum, l are the sequence number at linear array SAR orientations slow moment, and l is natural number, l=1,2 ..., K, K be the orientation slow moment
Sum；The total length of linear array antenna, is denoted as L；The centre frequency of radar work, is denoted as fc；The carrier frequency wavelength of radar work, is denoted as
λ；The signal bandwidth of radar emission baseband signal, is denoted as Br；The pulse width of radar emission signal, is denoted as TP；Radar Receiver System
Sample frequency, be denoted as fs；The pulse recurrence frequency of radar system, is denoted as PRF；The pulse-recurrence time of radar system, it is designated as
PRI；The aerial relay speed of light, is denoted as c；Distance is designated as T, distance is designated as t to fast moment sequence to the sum at fast moment
=1,2 ..., T, wherein t are t-th distance to the fast moment；Above-mentioned parameter is the canonical parameter of linear array SAR system, its center line
The array element sum N of array antenna, linear array antenna total length L, radar center frequency fc, radar carrier frequency wavelength X, radar emission base band letter
Number signal bandwidth Br, radar emission signal pulse width TP, the sample frequency f of Radar Receiver Systems, the pulse of radar system
Repetition rate PRF has determined in linear array SAR system design process；N-th of array element is when l-th slow in linear array SAR system
The position vector P at quartern(l) had determined in linear array SAR imaging observation schemes；According to linear array SAR imaging systems scheme and sight
Survey scheme, the initialization imaging system parameters that linear array SAR imaging methods need are known；
N-th of array element of linear array SAR obtains to fast instance sample original at l-th of orientation slow moment and t-th of distance
Echo data, it is designated as s (t, l, n), t=1,2 ..., T, l=1,2 ..., K, n=1,2 ..., N；In actual linear array SAR system
In, raw radar data s (t, l, n) can be provided by linear array SAR system data receiver；In linear array SAR imaging processes are emulated,
Raw radar data s (t, l, n) can be imitated according to linear array SAR imaging system parameters using standard synthetic aperture radar original echo
True method produces to obtain；Before linear array SAR data is imaged, raw radar data s (t, l, n) is known；
Step 2, row distance is entered to pulse compression to linear array SAR original echoed signals：
Using standard synthetic aperture distance by radar compression method to the linear array SAR raw radar datas s that is obtained in step 1
(t, l, n), t=1,2 ..., T, l=1,2 ..., K, n=1,2 ..., N enter row distance to pulse compression, obtain distance to pulse
Linear array SAR echo datas after compression, are designated as sr(t, l, n), t=1,2 ..., T, l=1,2 ..., K, n=1,2 ..., N, its
Middle T is that the distance obtained in step 1 is total to the fast moment, and K is the slow moment sum of the orientation obtained in step 1, and N is step 1
In obtain linear array antenna array element sum；
The parameter of step 3, initialization linear array SAR rear orientation projections imaging space：
The parameter of linear array SAR rear orientation projections imaging space is initialized, including：With radar beam irradiation field areas ground level and
Perpendicular to the three dimensions rectangular co-ordinate that the unit vector of the Horizon upwardly is formed, the rear orientation projection as linear array SAR is imaged
Space, it is designated as Ω；Rear orientation projection imaging space Ω horizontal cross, horizontal longitudinal direction and height to length range be designated as respectively
Wx、WyAnd Wz；Rear orientation projection imaging space Ω is evenly dividing into equal-sized stereo-unit lattice, rear orientation projection's imaging space
Cell sum in Ω, is designated as M；The coordinate vector of m-th of cell, is designated as Q in rear orientation projection imaging space Ωm, m expressions
M-th of cell in rear orientation projection imaging space Ω, m are positive integer, and m=1,2 ..., M, wherein M are rear orientation projection's imaging space
Cell sum in Ω；
The basic matrix of step 4, construction linear array SAR rear orientation projections imaging algorithm：
To the distance that step 1 initialization obtained linear array SAR system parameter, step 2 obtain to the linear array after pulse compression
SAR echo datas srThe rear orientation projection imaging space Ω that the initialization of (t, l, n) and step 3 obtains, using standard synthetic aperture thunder
Up to the basic matrix of imaging algorithm construction linear array SAR rear orientation projections of rear orientation projection imaging algorithm, linear array SAR back-projection algorithms are obtained
Basic matrix, be designated as B, wherein the dimension of matrix B is M × KN, and M is the linear array SAR rear orientation projections imaging that step 3 initialization obtains
Cell sum in the Ω of space, K are the slow moment sum of orientation that step 1 initialization obtains, and N is that step 1 initialization obtains
Linear array antenna array element sum；
Step 5, the parameter for initializing maximum sharpness phase error iterative estimate：
The parameter of maximum sharpness phase error iterative estimate is initialized, including：The maximum of iterative phase error estimation procedure
Iterations, it is designated as MaxIter；K is designated as the kth time iterations of phase error iterative estimation procedure, and k is natural number, and k is initial
Value is arranged to k=0, and k span is k=0,1,2 ..., MaxIter；The decision threshold of phase error iterative estimate,
It is designated as δT；The linear array SAR phase error vectors that kth time iterative estimate obtains, are designated as φ(k), k=0,1,2 ..., MaxIter, its
Middle φ(k)For column vector and φ(k)Dimension size is (KN) × 1；The initial value for initializing linear array SAR phase error vectors is φ(0)
=0；
To the imaging results of imaging space after step 6, acquisition linear array SAR：
As the iterations k=0 of iterative phase error estimation procedure, using formula F(0)=Bexp (- j φ(0)) meter
Calculation obtains in first iterative process being designated as F to the imaging results of imaging space after linear array SAR(0), wherein F(0)For column vector and F(0)Dimension size is M × 1, and B is the basic matrix for the linear array SAR back-projection algorithms that step 4 obtains, φ(0)Initialized for step 5
Obtained linear array SAR phase error vector initial values φ(0)=0, M are in the rear orientation projection imaging space Ω that step 3 initialization obtains
Cell sum, exp () be the exponent arithmetic symbol that natural constant e is bottom, j expression imaginary parts；Vectorial F(0)In m-th
Element value, it is designated as F(0)(m), m=1,2 ..., M；
As the iterations k ＞ 0 of iterative phase error estimation procedure, using formula F(k)=Bexp (- j φ(k)) meter
Calculate and obtain in kth time iterative process being designated as F to the imaging results of imaging space after linear array SAR(k), wherein F(k)For column vector and F(k)Dimension size is M × 1, φ(k)The linear array SAR phase error vectors obtained for kth time iterative estimate；Vectorial F(k)M-th
Element value, it is designated as F(k)(m), m=1,2 ..., M；
Step 7, the partial derivative for calculating linear array SAR image acutance：
Using formulaThe linear array SAR rear orientation projections image of kth time iterative estimate is calculated
Acutance, it is designated as E(k), wherein F(k)(m) the vectorial F obtained for step 6(k)M-th of element value, F(k)The kth obtained for step 6
To the imaging results of imaging space after linear array SAR in secondary iterative process,Represent that element 1 is summed to the absolute value of element M to transport
Calculate；
Using formula ▽ E(k)=Im [| F(k)|⊙|F(k)|⊙conj(F(k))]T·B·exp(-jφ(k)) be calculated
Linear array SAR rear orientation projections image acutance E(k)To phase error vector φ(k)Partial derivative, be designated as ▽ E(k), wherein Im { }
Expression takes imaginary-part operation, and ⊙ represents vector dot computing, and conj () represents to take conjugate operation, and subscript T represents transposition computing,
| | represent the computing that takes absolute value, the basic matrix for the linear array SAR back-projection algorithms that B obtains for step 4, φ(k)For kth time repeatedly
The linear array SAR phase error vectors that generation estimation obtains；
Step 8, utilize conjugate gradient method estimating phase error vector：
Using standard conjugate gradient method to equation group ▽ E(k)=0 solves phase error vector, obtains phase error estimation and phase error
The linear array SAR phase error vectors φ of vector assignment and+1 iterative estimate of kth(k+1), wherein ▽ E(k)The line obtained for step 7
Battle array SAR rear orientation projection image acutance E(k)To phase error vector φ(k)The partial derivative of partial derivative；
To the imaging results of imaging space after step 9, renewal linear array SAR：
Using formula F(k+1)=Bexp (- j φ(k+1)) be calculated in+1 iterative process of kth after linear array SAR into
The imaging results of image space, are designated as F(k+1), wherein F(k+1)For column vector and F(k+1)Dimension size is M × 1, and B is that step 4 obtains
Linear array SAR back-projection algorithms basic matrix, φ(k+1)The linear array SAR phases of+1 iterative estimate of kth obtained for step 8
Error vector；
Step 10, maximum sharpness phase error estimation and phase error iteration ends judge：
If | | F(k+1)-F(k)||2＞ δTAnd k≤MaxIter, then k ← k+1, re-executes step 6 to step 10；If
||F(k+1)-F(k)||2≤δTOr k ＞ MaxIter, then termination phase estimation error iteration, the phase that+1 iteration of kth obtains this moment
Position error vector φ(k+1)As final linear array SAR phase error vector estimated results, the linear array SAR that+1 iteration of kth obtains
Backward imaging space imaging results F(k+1)To imaging space imaging results after as final linear array SAR, wherein k+1 represents maximum
The iterations of kth+1 during acutance phase error estimation and phase error, MaxIter are that the iterative phase for initializing to obtain in step 5 misses
The maximum iteration of poor estimation procedure, δTThe decision threshold of the phase error iterative estimate obtained for step 5 initialization, F(k)
To the imaging results of imaging space after linear array SAR in the kth time iterative process obtained for step 6, | | | |2Represent the L2 of vector
Norm oeprator, ← represent assignment operation symbol；After the linear array SAR that finally+1 iteration of kth is obtained to imaging space into
As result F(k+1)Three-dimensional matrice form is converted into, obtains the final three-dimensional imaging result of linear array SAR imaging spaces.
The innovative point of the present invention is to construct phase error estimation and phase error equation using the partial derivative of image maximum sharpness, used
Conjugate gradient method is estimated phase error in linear array SAR echo datas, there is provided fast based on the maximum linear array SAR of acutance
Fast autohemagglutination focusing imaging method, this method construct the phase error local derviation of linear array SAR image acutance using rear orientation projection's imaging algorithm
Number equation, the quick estimation of linear array SAR phase errors is realized by conjugate gradient method rapid solving phase error estimation and phase error equation.
The advantage of the invention is that maximum sharpness phase error estimation and phase error is realized using conjugate gradient method, without known phase
The prior information of error distribution, it can quickly estimate the phase of low frequency, high frequency and random distribution present in linear array SAR echo datas
Position error, it is imaged suitable for the quick self-focusings of linear array SAR in the case of Comlex-locus.
Brief description of the drawings
Fig. 1 is the handling process schematic block diagram of method provided by the present invention；
Fig. 2 is the linear array SAR system simulation parameter table that the specific embodiment of the invention uses.
Embodiment
It is of the invention mainly to be verified that all steps, conclusion are all on MATLABR2015b using the method for emulation experiment
Checking is correct.Specific implementation step is as follows：
The systematic parameter and echo data of step 1, initialization linear array SAR：
Initialization linear array SAR system parameter includes：Position arrow of n-th of the array element l-th of slow moment in linear array SAR system
Measure Pn(l)=[0.008n, 0.01l, 3000] m, wherein n are the array element sequence number of linear array antenna, and n is natural number, n=1,2 ...,
N, N are that array element the sum N=200, l of linear array antenna are the sequence number at linear array SAR orientations slow moment, and l is natural number,K is the total K=512 at orientation slow moment；Total length L=1.6m of linear array antenna；The center of radar work
Frequency fc=3 × 1010Hz；Carrier frequency wavelength X=0.01m of radar work；The signal bandwidth B of radar emission baseband signalr=5 ×
108Hz；The pulse width T of radar emission signalP=5 × 10-6s；The sample frequency f of Radar Receiver Systems=7 × 108Hz；Thunder
Up to the pulse recurrence frequency PRF=2000Hz of system；Pulse-recurrence time PRI=5 × 10 of radar system-4s；Light is in atmosphere
Relay speed c=3 × 108m/s；For distance to the total T=512 at fast moment, distance is designated as t=1 to fast moment sequence,
2 ..., T, wherein t are t-th distance to the fast moment；
Linear array SAR raw radar datas are generated using standard synthetic aperture radar original echo emulation mode, obtain linear array
The raw radar data that n-th of array element of SAR obtains at l-th of orientation slow moment and t-th of distance to fast instance sample, is designated as
S (t, l, n), t=1,2 ..., T, l=1,2 ..., K, n=1,2 ..., N；In actual linear array SAR system, original echo number
It can be provided according to s (t, l, n) by linear array SAR system data receiver；In linear array SAR imaging processes are emulated, raw radar data s
(t, l, n) can be produced according to linear array SAR imaging system parameters using standard synthetic aperture radar original echo emulation mode
Arrive；Before linear array SAR data is imaged, raw radar data s (t, l, n) is known；
Step 2, row distance is entered to pulse compression to linear array SAR original echoed signals：
Using standard synthetic aperture distance by radar compression method to the linear array SAR raw radar datas s that is obtained in step 1
(t, l, n), t=1,2 ..., T, l=1,2 ..., K, n=1,2 ..., N enter row distance to pulse compression, obtain distance to pulse
Linear array SAR echo datas after compression, are designated as sr(t, l, n), t=1,2 ..., T, l=1,2 ..., K, n=1,2 ..., N, its
Middle T is that the distance obtained in step 1 is for orientation slow moment the sum K=512, N obtained in step 1 to sum of fast moment, K
The array element sum N=200 of the linear array antenna obtained in step 1；
The parameter of step 3, initialization linear array SAR rear orientation projections imaging space：
The parameter of linear array SAR rear orientation projections imaging space is initialized, including：With radar beam irradiation field areas ground level and
Perpendicular to the three dimensions rectangular co-ordinate that the unit vector of the Horizon upwardly is formed, the rear orientation projection as linear array SAR is imaged
Space, it is designated as Ω；Rear orientation projection imaging space Ω horizontal cross, horizontal longitudinal direction and height to length range be respectively Wx=
100m、Wy=100m and Wz=100m；Rear orientation projection imaging space Ω is evenly dividing into equal-sized stereo-unit lattice, after
Cell sum M=8 × 10 into projection imaging space Ω6；The coordinate of m-th of cell in rear orientation projection imaging space Ω
Vector, it is designated as Qm, m represents m-th of cell in rear orientation projection imaging space Ω, and m is positive integer, m=1,2 ..., M；
The basic matrix of step 4, construction linear array SAR rear orientation projections imaging algorithm：
To the distance that step 1 initialization obtained linear array SAR system parameter, step 2 obtain to the linear array after pulse compression
SAR echo datas srThe rear orientation projection imaging space Ω that the initialization of (t, l, n) and step 3 obtains, using standard synthetic aperture thunder
Up to the basic matrix of imaging algorithm construction linear array SAR rear orientation projections of rear orientation projection imaging algorithm, linear array SAR back-projection algorithms are obtained
Basic matrix, be designated as B, wherein the dimension of matrix B is M × KN, and M is the linear array SAR rear orientation projections imaging that step 3 initialization obtains
Cell sum M=8 × 10 in the Ω of space6, K is that orientation slow moment the sum K=512, N that step 1 initialization obtains are
The array element sum N=200 for the linear array antenna that step 1 initialization obtains；
Step 5, the parameter for initializing maximum sharpness phase error iterative estimate：
The parameter of maximum sharpness phase error iterative estimate is initialized, including：The maximum of iterative phase error estimation procedure
Iterations MaxIter=20；K is designated as the kth time iterations of phase error iterative estimation procedure, and k is natural number, and k is initial
Value is arranged to k=0, and k span is k=0,1,2 ..., MaxIter；The decision threshold of phase error iterative estimate
δT=0.001；The linear array SAR phase error vectors that kth time iterative estimate obtains, are designated as φ(k), k=0,1,2 ...,
MaxIter, wherein φ(k)For column vector and φ(k)Dimension size is (KN) × 1；Initialize linear array SAR phase error vectors
Initial value is φ(0)=0；
To the imaging results of imaging space after step 6, acquisition linear array SAR：
As the iterations k=0 of iterative phase error estimation procedure, using formula F(0)=Bexp (- j φ(0)) meter
Calculation obtains in first iterative process being designated as F to the imaging results of imaging space after linear array SAR(0), wherein F(0)For column vector and F(0)Dimension size is M × 1, and B is the basic matrix for the linear array SAR back-projection algorithms that step 4 obtains, φ(0)Initialized for step 5
Obtained linear array SAR phase error vector initial values φ(0)=0, M are in the rear orientation projection imaging space Ω that step 3 initialization obtains
Cell sum M=8 × 106, exp () is the exponent arithmetic symbol that natural constant e is bottom, and j represents imaginary part；Vectorial F(0)
In m-th of element value, be designated as F(0)(m), m=1,2 ..., M；
As the iterations k ＞ 0 of iterative phase error estimation procedure, using formula F(k)=Bexp (- j φ(k)) meter
Calculate and obtain in kth time iterative process being designated as F to the imaging results of imaging space after linear array SAR(k), wherein F(k)For column vector and F(k)Dimension size is M × 1, φ(k)The linear array SAR phase error vectors obtained for kth time iterative estimate；Vectorial F(k)M-th
Element value, it is designated as F(k)(m), m=1,2 ..., M；
Step 7, the partial derivative for calculating linear array SAR image acutance：
Using formulaThe linear array SAR rear orientation projections image of kth time iterative estimate is calculated
Acutance, it is designated as E(k), wherein F(k)(m) the vectorial F obtained for step 6(k)M-th of element value, F(k)The kth obtained for step 6
To the imaging results of imaging space after linear array SAR in secondary iterative process,Represent that element 1 is summed to the absolute value of element M to transport
Calculate；
Using formula ▽ E(k)=Im [| F(k)|⊙|F(k)|⊙conj(F(k))]T·B·exp(-jφ(k)) be calculated
Linear array SAR rear orientation projections image acutance E(k)To phase error vector φ(k)Partial derivative, be designated as ▽ E(k), wherein Im { }
Expression takes imaginary-part operation, and ⊙ represents vector dot computing, and conj () represents to take conjugate operation, and subscript T represents transposition computing,
| | represent the computing that takes absolute value, the basic matrix for the linear array SAR back-projection algorithms that B obtains for step 4, φ(k)For kth time repeatedly
The linear array SAR phase error vectors that generation estimation obtains；
Step 8, utilize conjugate gradient method estimating phase error vector：
Using standard conjugate gradient method to equation group ▽ E(k)=0 solves phase error vector, obtains phase error estimation and phase error
The linear array SAR phase error vectors φ of vector assignment and+1 iterative estimate of kth(k+1), wherein ▽ E(k)The line obtained for step 7
Battle array SAR rear orientation projection image acutance E(k)To phase error vector φ(k)The partial derivative of partial derivative；
To the imaging results of imaging space after step 9, renewal linear array SAR：
Using formula F(k+1)=Bexp (- j φ(k+1)) be calculated in+1 iterative process of kth after linear array SAR into
The imaging results of image space, are designated as F(k+1), wherein F(k+1)For column vector and F(k+1)Dimension size is M × 1, and B is that step 4 obtains
Linear array SAR back-projection algorithms basic matrix, φ(k+1)The linear array SAR phases of+1 iterative estimate of kth obtained for step 8
Error vector；
Step 10, maximum sharpness phase error estimation and phase error iteration ends judge：
If | | F(k+1)-F(k)||2＞ δTAnd k≤MaxIter, then k ← k+1, re-executes step 6 to step 10；If
||F(k+1)-F(k)||2≤δTOr k ＞ MaxIter, then termination phase estimation error iteration, the phase that+1 iteration of kth obtains this moment
Position error vector φ(k+1)As final linear array SAR phase error vector estimated results, the linear array SAR that+1 iteration of kth obtains
Backward imaging space imaging results F(k+1)To imaging space imaging results after as final linear array SAR, wherein k+1 represents maximum
The iterations of kth+1 during acutance phase error estimation and phase error, MaxIter are that the iterative phase for initializing to obtain in step 5 misses
The maximum iteration MaxIter=20, δ of poor estimation procedureTThe phase error iterative estimate obtained for step 5 initialization is sentenced
Determine threshold value δT=0.001, F(k)To the imaging results of imaging space after linear array SAR in the kth time iterative process obtained for step 6,
||·||2The L2 norm oeprators of vector are represented, ← represent assignment operation symbol；The line that finally+1 iteration of kth is obtained
To imaging space imaging results F after battle array SAR(k+1)Three-dimensional matrice form is converted into, obtains the final three-dimensional of linear array SAR imaging spaces
Imaging results.
Claims (1)
- A kind of 1. quick autohemagglutination focusing imaging methods of linear array SAR based on maximum sharpness, it is characterized in that it includes following steps：The systematic parameter and echo data of step 1, initialization linear array SAR：Initialization linear array SAR system parameter includes：Position vector of n-th of the array element l-th of slow moment in linear array SAR system, It is denoted as Pn(l), wherein n is the array element sequence number of linear array antenna, and n is natural number, n=1,2 ..., array element that N, N are linear array antenna Sum, l are the sequence number at linear array SAR orientations slow moment, and l is natural number, l=1,2 ..., K, K be the total of orientation slow moment Number；The total length of linear array antenna, is denoted as L；The centre frequency of radar work, is denoted as fc；The carrier frequency wavelength of radar work, is denoted as λ； The signal bandwidth of radar emission baseband signal, is denoted as Br；The pulse width of radar emission signal, is denoted as TP；Radar Receiver System Sample frequency, it is denoted as fs；The pulse recurrence frequency of radar system, is denoted as PRF；The pulse-recurrence time of radar system, it is designated as PRI；The aerial relay speed of light, is denoted as c；Distance is designated as T, distance is designated as t to fast moment sequence to the sum at fast moment =1,2 ..., T, wherein t are t-th distance to the fast moment；Above-mentioned parameter is the canonical parameter of linear array SAR system, its center line The array element sum N of array antenna, linear array antenna total length L, radar center frequency fc, radar carrier frequency wavelength X, radar emission base band letter Number signal bandwidth Br, radar emission signal pulse width TP, the sample frequency f of Radar Receiver Systems, the pulse of radar system Repetition rate PRF has determined in linear array SAR system design process；N-th of array element is when l-th slow in linear array SAR system The position vector P at quartern(l) had determined in linear array SAR imaging observation schemes；According to linear array SAR imaging systems scheme and sight Survey scheme, the initialization imaging system parameters that linear array SAR imaging methods need are known；The original echo that n-th of array element of linear array SAR obtains at l-th of orientation slow moment and t-th of distance to fast instance sample Data, it is designated as s (t, l, n), t=1,2 ..., T, l=1,2 ..., K, n=1,2 ..., N；It is former in actual linear array SAR system Beginning echo data s (t, l, n) is provided by linear array SAR system data receiver；In linear array SAR imaging processes are emulated, original time Wave number according to linear array SAR imaging system parameters, is produced according to s (t, l, n) using standard synthetic aperture radar original echo emulation mode Life obtains；Before linear array SAR data is imaged, raw radar data s (t, l, n) is known；Step 2, row distance is entered to pulse compression to linear array SAR original echoed signals：Using standard synthetic aperture distance by radar compression method to obtained in step 1 linear array SAR raw radar datas s (t, l, N), t=1,2 ..., T, l=1,2 ..., K, n=1,2 ..., N enter row distance to pulse compression, obtain distance to pulse compression Linear array SAR echo datas afterwards, are designated as sr(t, l, n), t=1,2 ..., T, l=1,2 ..., K, n=1, wherein 2 ..., N, T It is the distance that is obtained in step 1 to sum of fast moment, K is the slow moment sum of the orientation obtained in step 1, and N is in step 1 The array element sum of the linear array antenna arrived；The parameter of step 3, initialization linear array SAR rear orientation projections imaging space：The parameter of linear array SAR rear orientation projections imaging space is initialized, including：With radar beam irradiation field areas ground level and vertically In the three dimensions rectangular co-ordinate that the unit vector of the Horizon upwardly is formed sky is imaged as linear array SAR rear orientation projection Between, it is designated as Ω；Rear orientation projection imaging space Ω horizontal cross, horizontal longitudinal direction and height to length range be designated as W respectivelyx、Wy And Wz；Rear orientation projection imaging space Ω is evenly dividing into equal-sized stereo-unit lattice, in rear orientation projection imaging space Ω Cell sum, be designated as M；The coordinate vector of m-th of cell, is designated as Q in rear orientation projection imaging space Ωm, m expressions are backward M-th of cell in the Ω of projection imaging space, m are positive integer, and m=1,2 ..., M, wherein M are in rear orientation projection imaging space Ω Cell sum；The basic matrix of step 4, construction linear array SAR rear orientation projections imaging algorithm：The distance that linear array SAR system parameter, the step 2 obtained to step 1 initialization obtains is returned to the linear array SAR after pulse compression Wave number is according to srThe rear orientation projection imaging space Ω that the initialization of (t, l, n) and step 3 obtains, it is backward using standard synthetic aperture radar The basic matrix of projection imaging algorithm construction linear array SAR rear orientation projections imaging algorithm, obtains the group moment of linear array SAR back-projection algorithms Battle array, B is designated as, the wherein dimension of matrix B is M × KN, and M is the linear array SAR rear orientation projections imaging space Ω that step 3 initialization obtains In cell sum, K is the slow moment sum of the obtained orientation of step 1 initialization, and N is the linear array that step 1 initialization obtains The array element sum of antenna；Step 5, the parameter for initializing maximum sharpness phase error iterative estimate：The parameter of maximum sharpness phase error iterative estimate is initialized, including：The greatest iteration of iterative phase error estimation procedure Number, it is designated as MaxIter；K is designated as the kth time iterations of phase error iterative estimation procedure, and k is natural number, and k initial values are set K=0 is set to, and k span is k=0,1,2 ..., MaxIter；The decision threshold of phase error iterative estimate, is designated as δT；The linear array SAR phase error vectors that kth time iterative estimate obtains, are designated as φ(k), k=0,1,2 ..., MaxIter, wherein φ(k)For column vector and φ(k)Dimension size is (KN) × 1；The initial value for initializing linear array SAR phase error vectors is φ(0)= 0；To the imaging results of imaging space after step 6, acquisition linear array SAR：As the iterations k=0 of iterative phase error estimation procedure, using formula F(0)=Bexp (- j φ(0)) calculate Into first iterative process F is designated as after linear array SAR to the imaging results of imaging space(0), wherein F(0)For column vector and F(0)Dimension Number sizes be M × 1, the basic matrix for the linear array SAR back-projection algorithms that B obtains for step 4, φ(0)Obtained for step 5 initialization Linear array SAR phase error vector initial values φ(0)=0, M are the list in the rear orientation projection imaging space Ω that step 3 initialization obtains First lattice sum, exp () are the exponent arithmetic symbol that natural constant e is bottom, and j represents imaginary part；Vectorial F(0)In m-th of element Value, is designated as F(0)(m), m=1,2 ..., M；As the iterations k ＞ 0 of iterative phase error estimation procedure, using formula F(k)=Bexp (- j φ(k)) calculate Into kth time iterative process F is designated as after linear array SAR to the imaging results of imaging space(k), wherein F(k)For column vector and F(k)Dimension Number size is M × 1, φ(k)The linear array SAR phase error vectors obtained for kth time iterative estimate；Vectorial F(k)M-th of element Value, is designated as F(k)(m), m=1,2 ..., M；Step 7, the partial derivative for calculating linear array SAR image acutance：Using formulaThe linear array SAR rear orientation projections image that kth time iterative estimate is calculated is sharp Degree, is designated as E(k), wherein F(k)(m) the vectorial F obtained for step 6(k)M-th of element value, F(k)The kth time obtained for step 6 To the imaging results of imaging space after linear array SAR in iterative process,Represent element 1 to the absolute value summation operation of element M；Using formulaAfter linear array SAR is calculated To projection imaging image sharpness E(k)To phase error vector φ(k)Partial derivative, be designated as ▽ E(k), wherein Im { } represent take void Portion's computing,Vector dot computing is represented, conj () represents to take conjugate operation, and subscript T represents transposition computing, | | expression takes Signed magnitude arithmetic(al), the basic matrix for the linear array SAR back-projection algorithms that B obtains for step 4, φ(k)Obtained for kth time iterative estimate Linear array SAR phase error vectors；Step 8, utilize conjugate gradient method estimating phase error vector：Using standard conjugate gradient method to equation group ▽ E(k)=0 solves phase error vector, obtains phase error estimation and phase error vector Assignment and the linear array SAR phase error vectors φ of+1 iterative estimate of kth(k+1), wherein ▽ E(k)The linear array SAR obtained for step 7 Rear orientation projection image acutance E(k)To phase error vector φ(k)The partial derivative of partial derivative；To the imaging results of imaging space after step 9, renewal linear array SAR：Using formula F(k+1)=Bexp (- j φ(k+1)) be calculated in+1 iterative process of kth after linear array SAR to imaging space Imaging results, be designated as F(k+1), wherein F(k+1)For column vector and F(k+1)Dimension size is M × 1, and B is the linear array that step 4 obtains The basic matrix of SAR back-projection algorithms, φ(k+1)The linear array SAR phase errors of+1 iterative estimate of kth obtained for step 8 to Amount；Step 10, maximum sharpness phase error estimation and phase error iteration ends judge：If | | F(k+1)-F(k)||2＞ δTAnd k≤MaxIter, then k ← k+1, re-executes step 6 to step 10；If | | F(k +1)-F(k)||2≤δTOr k ＞ MaxIter, then termination phase estimation error iteration, the phase error that+1 iteration of kth obtains this moment Vectorial φ(k+1)As final linear array SAR phase error vector estimated results, after the linear array SAR that+1 iteration of kth obtains into Image space imaging results F(k+1)After as final linear array SAR maximum sharpness phase is represented to imaging space imaging results, wherein k+1 The iterations of kth+1 in the error estimation procedure of position, MaxIter are the iterative phase error estimation for initializing to obtain in step 5 The maximum iteration of process, δTThe decision threshold of the phase error iterative estimate obtained for step 5 initialization, F(k)For step 6 To the imaging results of imaging space after linear array SAR in obtained kth time iterative process, | | | |2Represent the L2 norms fortune of vector Operator number, ← represent assignment operation symbol；To imaging space imaging results F after the linear array SAR that finally+1 iteration of kth is obtained(k+1)Three-dimensional matrice form is converted into, obtains the final three-dimensional imaging result of linear array SAR imaging spaces.
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