CN109856636A - Curvilinear synthetic aperture radar self-adaptation three-dimensional imaging method - Google Patents
Curvilinear synthetic aperture radar self-adaptation three-dimensional imaging method Download PDFInfo
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Abstract
The present invention proposes a kind of Curvilinear synthetic aperture radar self-adaptation three-dimensional imaging method, mainly solves the problems, such as existing BP imaging method low efficiency.Implementation step are as follows: 1) radar platform is along parabola transmitting chirp and receives echo-signal；2) pulse compression is made to echo-signal；3) interpolation processing is made to Signal for Pulse；4) search by hill climbing is made to the one-dimensional range profile after interpolation processing；5) LS-SVM sparseness is made to the one-dimensional range profile after search by hill climbing；6) gridding imaging plane is established in three-dimensional space；7) rarefaction one-dimensional range profile is made into adaptive projection to gridding imaging plane, obtains two-dimensional SAR image；8) two-dimensional SAR image is arranged in three-dimensional data block, obtains final three-dimensional imaging result.The present invention only projects the corresponding imaging grid of rarefaction one-dimensional range profile peak value in imaging process, reduces the number of projection, improves imaging efficiency, can be used for the real-time detection and imaging of high speed platform.
Description
Technical field
The invention belongs to digital signal processing technique field, in particular to it is a kind of suitable for SAR under curve aperture from
Three-D imaging method is adapted to, can be used for the real-time detection and imaging of high speed platform.
Background technique
Synthetic aperture radar SAR can with round-the-clock, it is round-the-clock, at a distance observation area is detected and is imaged, answer
It is extensive with field.Most of the SAR system that current people use works in the flat winged mode of positive side view.These SAR systems are by hair
Penetrate big Timed automata signal obtain distance to high-resolution, moved by platform and move to form big synthesis hole in orientation
Diameter is to obtain the high-resolution of orientation, but this method can only carry out two-dimensional imaging.However in many applications, such as lead
Boat, independent landing, high-precision three-dimensional mapping etc. need SAR system work to carry out in preceding side-looking mode and to observation area
Three-dimensional imaging.In addition, carrying out three-dimensional imaging to observation area has good application value for the detection for hiding target.Research
The SAR system for having three-dimensional imaging ability with development has great importance.
Curve SAR by make radar platform in azel the riding into plane, forming orientation aperture
Meanwhile in height to also progress aperture accumulation, thus has three-dimensional imaging ability.In three dimensions due to curve SAR
Data sampling is incomplete, therefore designing effectively imaging algorithm is the key that carry out high-precision three-dimensional imaging to target.It is existing
Curve SAR three-dimensional imaging algorithm be to be calculated on the basis of carrying out three-dimensional Fourier transform to echo data with RELAX mostly
Method is scattered a location estimation.However the operand of three-dimensional Fourier transform is very big, and RELAX algorithm obtain each dissipate
It requires to be updated by all scattering points of the iteration to front after exit point feature, the complexity of operation is high, and imaging efficiency is non-
It is often low.Document " Zhang Zi-shan.Research on the 3-D imaging technology of curvilinear
SAR[D].[Master dissertation],National University of Defense Technology,2009.”
For the feature of RELAX algorithm operation complexity, the RELAX algorithm of dimensionality reduction is proposed, a three-dimensional feature is extracted problem conversion
Problem is extracted at two two dimensional characters, operand is significantly reduced, reduces operation time.But this method is still base
In the thought of three-dimensional Fourier transform, operand is still very big, and imaging efficiency is low, it is difficult to meet the needs of real time imagery.
Article " Pang shou-bao, Zhang Xiao-ling.Imaging of downward-looking 3D
circle SAR by BP algorithm[J].Electronic Science and Technology,2010,23(12):
14-17. " breaches the thought of traditional three-dimensional Fourier transform, proposes to carry out three-dimensional imaging with rear orientation projection's BP algorithm, pass through
The energy accumulation to each imaging grid is realized along the integral of oblique distance course, although this method significantly reduces operand, but
BP algorithm needs project all imaging grids in practical operation, and there are a large amount of redundant operations, and operand is larger, imaging
Efficiency is still lower.
Summary of the invention
It is an object of the invention in view of the above-mentioned deficiencies in the prior art, fully take into account target in actual scene
The sparsity of distribution proposes a kind of Curvilinear synthetic aperture radar self-adaptation three-dimensional imaging method, to reduce operand, improves imaging
Efficiency.
Technical thought of the invention is: object pointer is found by search by hill climbing to one-dimensional range profile, in one-dimensional range profile
On the signal value in addition to object pointer all set 0, obtain rarefaction one-dimensional range profile；Picture is meshed into ground level foundation
Plane, and this plane is obtained into several gridding imaging planes to translating up at equal intervals along height several times；In each net
It formats in imaging plane, only grid corresponding with rarefaction one-dimensional range profile peak value is projected, remaining grid does not project；
All gridding imaging planes by projection are arranged in three dimensions to sequence from low to high by height from bottom to top
According to block, final three-dimensional imaging result is obtained.Implementing step includes the following:
(1) radar platform emits chirp along a parabolic flight with fixed pulse recurrence frequency PRF
And receives echo-signalWherein,Indicate the fast time, n indicates pulse serial number, n=1,2 ... ..., N, and N is to send out in total
The umber of pulse penetrated；
(2) to echo-signalMake process of pulse-compression, obtains Signal for Pulse
(3) to Signal for PulseThe interpolation processing for making 8 times, obtains one-dimensional range profile
(4) along the fast timeTo one-dimensional range profileMake search by hill climbing:
(4a) finds one-dimensional range profileMaximum value Vmax, initial ranging thresholding is set
(4b) is in search thresholding V0On it is rightPeak value searching is carried out, object pointer t is recordedd；
(4c) enables V0=0.5 × V0；
(4d) repeats step (4b)-(4c), until searching for thresholding V0Lower than signal noise level, this is searched for into threshold de
For noise gate V；
(5) to one-dimensional range profileMake LS-SVM sparseness:
(5a) is by one-dimensional range profileIn object pointer tdLocate corresponding signal value to remain unchanged, remaining signal value is complete
Portion sets 0, obtains rarefaction one-dimensional range profile
(5b) searches for obtained object pointer t according to (4)d, in the fast timeOn with tdCentered on shared section, to both sides
Each continuation 100 fast time sampling points, are set as region of search I for this section；
(5c) is to other one-dimensional range profilesAlong the fast timeIn region of search I,
Peak value searching is carried out on the noise gate V that (4) obtain, and keeps the signal at peak value constant, remaining signal sets 0, obtains it
Its rarefaction one-dimensional range profile
(5d) is by rarefaction one-dimensional range profile obtained in (5a)Other rarefactions obtained in (5c) it is one-dimensional away from
From pictureIt is combined into a rarefaction one-dimensional range profile set S:
(6) (A+1) a edge height is established to equally distributed gridding imaging plane g ' in three-dimensional space0,g′1,g
′2,……,g′A, wherein A indicates to be meshed into the number as plane translation:
(6a) using ground scene center as origin o, orientation is x-axis, and distance is to for y-axis, highly to for z-axis, in space
Establish three-dimensional cartesian coordinate system；
(6b) is using plane z=0 as imaging plane g0, to g centered on origin o0Grid is carried out along x-axis and y-axis respectively to draw
Point, obtain gridding imaging plane g '0, each grid corresponds to a three dimensional space coordinate (xp,yq, 0), wherein p and q points
Not Biao Shi grid row and column serial number, p=1,2 ... ..., P, q=1,2 ... ..., Q, P and Q respectively indicate the net along x-axis and y-axis
Lattice sum；
(6c) is by the gridding imaging plane g ' in (6b)0It translates up A times, obtains along z-axis certainly using δ h as interval along z-axis
Upper equally distributed (A+1) a gridding imaging plane g ' down0,g′1,……,g′a,……,g′A, wherein g 'aIt indicates a-th
Gridding imaging plane, a=0,1,2 ... ..., A, g 'aThe corresponding three dimensional space coordinate of grid of middle pth row q column is (xp,yq,a
δh)；
(7) the rarefaction one-dimensional range profile set S for utilizing (5d) to obtain is to (A+1) a gridding imaging plane in (6c)
g′0,g′1,……,g′a,……,g′AMake adaptive projection, obtains (A+1) width two-dimensional SAR image M0,M1,……,Ma,……,
MA, wherein MaIndicate rarefaction one-dimensional range profile set S in a-th of gridding imaging plane g 'aUpper imaging；
(8) (A+1) the width two-dimensional SAR image M for obtaining (7)0,M1,……,Ma,……,MABy height to from low to high
As soon as sequence line up from bottom to top size be P × Q × (A+1) three-dimensional data block Data, this three-dimensional data block Data
It is final three-dimensional imaging result.
Compared with prior art, the present invention having the advantage that
The present invention since the three-dimensional imaging of acquisition is the result is that by making LS-SVM sparseness to the one-dimensional range profile after interpolation, and
What adaptive projection was realized is made to the imaging grid in three-dimensional space using rarefaction one-dimensional range profile, avoids existing BP imaging
Traversed in method all grids projected and caused by bulk redundancy operate defect, reduce the number of projection operation, subtract
Lack calculation amount, effectively improves the efficiency of curve SAR three-dimensional imaging；Simultaneously because the present invention one-dimensional range profile is made it is dilute
When thinization processing, noise gate data below are all set 0, there is good rejection to clutter or noise.
Detailed description of the invention
Fig. 1 is implementation flow chart of the invention；
Fig. 2 is radar platform flight path schematic diagram in the present invention；
Fig. 3 is to make search by hill climbing schematic diagram to one-dimensional range profile in the present invention；
Fig. 4 is to make LS-SVM sparseness operation chart to one-dimensional range profile in the present invention；
Fig. 5 is to be meshed into three-dimensional space foundation as floor map in the present invention；
Fig. 6 is the schematic diagram adaptively projected in the present invention；
Fig. 7 is that three-dimensional data block forms schematic diagram in the present invention；
Fig. 8 is the effect contrast figure that projection imaging is carried out with the present invention and the prior art；
Fig. 9 is the result figure that three-dimensional imaging is carried out with the present invention.
Specific embodiment
In the following with reference to the drawings and specific embodiments, technical solutions and effects of the present invention is described in further detail.
Referring to Fig.1, steps are as follows for realization of the invention:
Step 1, radar emits simultaneously receives echo-signal along parabolic flight:
Radar platform is along a parabolic flight, and flight path is as shown in Fig. 2, with fixed pulse repetition rate PRF hair
Penetrate linear FM signalAnd receives echo-signal
Wherein, t indicates full-time,Indicate the fast time, T indicates pulse width, fcIndicate that carrier frequency, γ indicate signal frequency modulation
Rate, c indicate the light velocity, and n indicates pulse serial number, and n=1,2 ... ..., N, N are the umber of pulse emitted in total, RnN-th of expression slow
Moment radar range-to-go, j indicate imaginary unit, and rect () indicates rectangular window function.
Step 2, to echo-signalMake process of pulse-compression, obtains Signal for Pulse
2a) to echo-signalCarrier frequency is removed, fundamental frequency signal is obtained
2b) by fundamental frequency signalWith reference signalWhen making conjugate multiplication in frequency domain, and product of transformation being returned
Domain obtains Signal for Pulse
Wherein, BrIndicating signal bandwidth, λ indicates the wavelength of carrier wave,It indicates to make Fourier transformation in fast time-domain,
Inverse Fourier transform is made in IFFT expression, and () * indicates to take data conjugation, and rect () indicates rectangular window function, sinc ()
Indicate sinc function；Reference signalExpression formula are as follows:
Step 3, to Signal for PulseInterpolation obtains one-dimensional range profile
To Signal for PulseMake 8 times of interpolation processing, interpolation kernel is chosen the sinc function that length is 8, obtained one-dimensional
Range Profile
Step 4, along the fast timeTo one-dimensional range profileMake search by hill climbing, obtains noise gate V.
Referring to Fig. 3, this step is implemented as follows:
4a) find one-dimensional range profileMaximum value Vmax, initial ranging thresholding is set
4b) in search thresholding V0On it is rightPeak value searching is carried out, object pointer t is recordedd；
4c) enable V0=0.5 × V0；
4d) repeat step 4b) to step 4c), until searching for thresholding V0Lower than signal noise level, this search thresholding is determined
Justice is noise gate V.
Step 5, to one-dimensional range profileMake LS-SVM sparseness, obtains rarefaction one-dimensional range profile set S.
Referring to Fig. 4, this step is implemented as follows:
5a) by one-dimensional range profileIn object pointer tdLocate corresponding signal value to remain unchanged, remaining signal value is complete
Portion sets 0, obtains rarefaction one-dimensional range profile
5b) according to object pointer td, in the fast timeOn with tdCentered on shared section to each continuation in both sides 100 it is fast when
Between sampled point, this section is set as region of search I；
5c) to other one-dimensional range profilesAlong the fast timeIn region of search I,
Peak value searching is carried out on noise gate V, and keeps the signal at peak value constant, remaining signal sets 0, and it is one-dimensional to obtain other rarefactions
Range Profile
5d) by rarefaction one-dimensional range profile obtained in 5a)And 5c) obtained in other rarefaction one-dimensional distances
PictureIt is combined into a rarefaction one-dimensional range profile set S:
Step 6, (A+1) a edge height is established to equally distributed gridding imaging plane g ' in three-dimensional space0,g′1,g
′2,……,g′A。
Referring to Fig. 5, this step is implemented as follows:
6a) using ground scene center as origin o, orientation is x-axis, and distance highly to for z-axis, is built in space to for y-axis
Vertical three-dimensional cartesian coordinate system；
6b) using plane z=0 as imaging plane g0, to g centered on origin o0Grid is carried out along x-axis and y-axis respectively to draw
Point, obtain gridding imaging plane g '0, the grid interval δ y on grid interval δ x and y-axis in x-axis should meet:
Each grid corresponds to a three dimensional space coordinate (xp,yq, 0), wherein p and q respectively indicates grid row and column
Serial number, p=1,2 ... ..., P, q=1,2 ... ..., Q, P and Q respectively indicate the grid number along x-axis and y-axis, and R indicates radar position
Distance of the radar to scene center, L when synthetic aperture centerxThe equivalent projection for being curvilinear synthetic aperture in orientation is long
Degree,Indicate the pitch angle of radar when radar is located at synthetic aperture center；
6c) by the gridding imaging plane g ' in 6b)0It translates up A times, obtains along z-axis under using δ h as interval along z-axis
And upper equally distributed (A+1) a gridding imaging plane g '0,g′1,……,g′a,……,g′A, as shown in figure 5, g 'aMiddle pth
The corresponding three dimensional space coordinate of grid of row q column is (xp,yq, a δ h), the interval δ h of translation should meet:
Wherein g 'aIndicate that a-th of gridding imaging plane, a=0,1,2 ... ..., A, A indicate that gridding imaging plane is flat
The number of shifting, R indicate distance of the radar to scene center, L when radar is located at synthetic aperture centerzIndicate that curvilinear synthetic aperture exists
Highly upward equivalent projected length.
Step 7, rarefaction one-dimensional range profile set S gridding imaging plane g ' a to (A+1) is utilized0,g′1,g
′2,……,g′AMake adaptive projection.
7a) calculate a-th of gridding imaging plane g 'aIn all mesh coordinates: { (xp,yq, a δ h) | p=1,2 ...,
P, q=1,2 ..., Q } in the distance at n-th of slow moment to radar: { Ra(p, q, n) | p=1,2 ..., P, q=1,
2 ... ..., Q }, wherein a indicates the serial number of gridding imaging plane；
7b) a gridding imaging plane g 'aIn all grids correspond to n-th of rarefaction one-dimensional range profile
On, obtain g 'aIt is upper withThe corresponding grid set W of peak valuean；
7c) willTo grid set WanIn grid project, remaining grid does not project, and obtainsIn g 'a
Upper formed image g 'an, as shown in Figure 6；
7d) by each element in rarefaction one-dimensional range profile set S in g 'aOn be projected out piece image, formed with
g′aCorresponding image collection: Ga={ g 'a1,g′a2,……,g′an,……,g′aN, wherein g 'anIndicate that n-th of rarefaction is one-dimensional
Range ProfileIn a-th of gridding imaging plane g 'aUpper formed image；
7e) by image collection GaIn all elements be added, S can be obtained in g 'aUpper formed two-dimensional SAR image Ma:
Ma=g 'a1+g′a2+……+g′an+……+g′aN
7f) repeat step 7a) to step 7e) to all gridding imaging plane g '0,g′1,……,g′a,……,g′AIt holds
The identical operation of row, obtains (A+1) width two-dimensional SAR image M0,M1,……,Ma,……,MA。
Step 8, by (A+1) width two-dimensional SAR image M0,M1,……,Ma,……,MAIt is arranged in three-dimensional data block.
(A+1) width two-dimensional SAR image M that step 7 is obtained0,M1,……,Ma,……,MABy height to from low to high
It is P × Q × (A+1) three-dimensional data block Data that sequence lines up a size from bottom to top, this three-dimensional data block Data is exactly
Two-dimensional SAR image in Fig. 7 (a) as a result, as shown in fig. 7, is arranged in the three-dimensional data in Fig. 7 (b) by final three-dimensional imaging
Block completes the imaging of Curvilinear synthetic aperture radar self-adaptation three-dimensional.
Effect of the invention is further illustrated by following emulation experiment:
Experiment one:
1.1) experiment condition:
Radar signal parameter and system parameter are set, as shown in table 1:
1 experiment parameter of table
Experiment scene: SAR platform, which works in put down, flies positive side-looking mode, and the umber of pulse along azimuth accumulation is 512.On ground
Plane is provided with 5 strong scattering points, and distance is divided into 15m between, 20m is divided between orientation, and be also randomly provided on ground level
Some weak scattering points simulate clutter background.
1.2) experiment content:
It is utilized respectively existing BP and the image method of the invention above-mentioned Same Scene is imaged, experimental result such as Fig. 8 institute
Show, in which:
Fig. 8 (a) is that scattering point is distributed geometric representation,
Fig. 8 (b) is comparison diagram before and after one-dimensional range profile rarefaction,
Fig. 8 (c) is existing BP imaging results,
Fig. 8 (d) is imaging results of the present invention.
The imaging total time of two kinds of imaging methods is as shown in table 2.
The existing BP of table 2. and imaging time of the present invention compare
| Imaging method | Runing time (s) |
| Existing BP | 104.6 |
| The present invention | 66.6 |
1.3) analysis of experimental results:
From Fig. 8 (b) as can be seen that one-dimensional range profile by after LS-SVM sparseness, one-dimensional range profile will only retain mesh
The data of target data, clutter are set to 0, reduce data volume.It can be seen that from the comparison of the imaging results of Fig. 8 (c) and (d)
There is more clutter pixel in existing BP imaging, and there was only target scattering point in imaging of the present invention, image quality
It is higher.As can be seen that imaging efficiency of the invention is higher than existing BP imaging method from the comparison of the imaging time of table 2.
Experiment two:
2.1) experiment condition:
Radar signal parameter and system parameter are set, as shown in table 3:
3 experiment parameter of table
Experiment scene: SAR platform works in preceding side-looking mode, and motion profile is a parabola, in slow time integral
Umber of pulse is 2048,6 scattering points is arranged in three dimensions, the orientation interval delta x=2m of scattering point, distance is to interval
Δ y=2m, highly to interval delta z=1.5m.
2.2) experiment content:
Three-dimensional imaging is carried out to above-mentioned scene using the present invention, imaging results are as shown in Figure 9, in which:
Fig. 9 (a) indicates scattering point distribution map in scene,
Fig. 9 (b) be using the present invention to the three-dimensional imaging of Fig. 9 (a) as a result,
Fig. 9 (c) be the present invention to observation scene range-azimuth to plane projection imaging as a result,
Fig. 9 (d) be the present invention to observation scene the plane projection of height-orientation be imaged as a result,
Fig. 9 (e) be the present invention to observation scene distance-height to plane projection imaging as a result,
Fig. 9 (f) is the distance of Fig. 9 (b) to sectional view,
Fig. 9 (g) is the orientation sectional view of Fig. 9 (b),
Fig. 9 (h) is the height of Fig. 9 (b) to sectional view,
Fig. 9 (i) is the top view of three-dimensional imaging result of the present invention,
Fig. 9 (j) is the front view of three-dimensional imaging result of the present invention,
Fig. 9 (k) is the left view of three-dimensional imaging result of the present invention.
Table (4) is existing BP and the present invention compares the three-dimensional imaging time of Same Scene.
The existing BP of table 4. and three-dimensional imaging time of the present invention compare
| Imaging method | Runing time (s) |
| Existing BP | 165.4 |
| The present invention | 124.4 |
2.3) analysis of experimental results:
It is relatively several between scattering point from Fig. 9 (b) as can be seen that the present invention can carry out three-dimensional imaging to observation scene
What positional relationship is correct.From Fig. 9 (c) to Fig. 9 (e) as can be seen that the present invention carries out projection imaging on different imaging planes
It can correctly reflect the geometrical relationship of three-dimensional space scattering point.From Fig. 9 (f) and Fig. 9 (g) as can be seen that three-dimensional imaging knot
Fruit distance to in orientation have good peak sidelobe ratio, secondary lobe is below -12dB.
From Fig. 9 (h) as can be seen that due to being unevenly distributed in the upward radar sampling point of height, secondary lobe is deteriorated, about
For -10dB, but scattering point resolution can still be opened upwards in height.
From Fig. 9 (i) to Fig. 9 (k) as can be seen that the scattering point geometry site that shows of three-view diagram of three-dimensional imaging with
Fig. 9 (a) is unanimously, and consistent with two-dimensional projection's result of Fig. 9 (c) to Fig. 9 (e).
According to table 4, three-dimensional imaging efficiency of the invention is better than existing BP imaging algorithm.
To sum up, the imaging efficiency of three-D imaging method of the present invention is better than traditional BP algorithm.
Claims (6)
1. a kind of Curvilinear synthetic aperture radar self-adaptation three-dimensional imaging method, which is characterized in that include the following:
(1) radar platform with fixed pulse recurrence frequency PRF transmitting chirp and connects along a parabolic flight
Receive echo-signalWherein,Indicating the fast time, n indicates pulse serial number, n=1,2 ..., N, N emits in total
Umber of pulse；
(2) to echo-signalMake process of pulse-compression, obtains Signal for Pulse
(3) to Signal for PulseThe interpolation processing for making 8 times, obtains one-dimensional range profile
(4) along the fast timeTo one-dimensional range profileMake search by hill climbing:
(4a) finds one-dimensional range profileMaximum value Vmax, initial ranging thresholding is set
(4b) is in search thresholding V0On it is rightPeak value searching is carried out, object pointer t is recordedd；
(4c) enables V0=0.5 × V0；
(4d) repeats step (4b)-(4c), until searching for thresholding V0It is to make an uproar by this search threshold de lower than signal noise level
Glottis limits V；
(5) to one-dimensional range profileMake LS-SVM sparseness:
(5a) is by one-dimensional range profileIn object pointer tdLocate corresponding signal value to remain unchanged, remaining signal value is all set
0, obtain rarefaction one-dimensional range profile
(5b) searches for obtained object pointer t according to (4)d, in the fast timeOn with tdCentered on shared section, respectively prolong to both sides
100 fast time sampling points are opened up, this section is set as region of search I；
(5c) is to other one-dimensional range profilesAlong the fast timeIn region of search I, in (4)
Peak value searching is carried out on obtained noise gate V, and keeps the signal at peak value constant, remaining signal sets 0, obtains other sparse
Change one-dimensional range profile
(5d) is by rarefaction one-dimensional range profile obtained in (5a)Other rarefaction one-dimensional range profiles obtained in (5c)It is combined into a rarefaction one-dimensional range profile set S:
(6) (A+1) a edge height is established to equally distributed gridding imaging plane g ' in three-dimensional space0, g '1, g
′2..., g 'A, wherein A indicates to be meshed into the number as plane translation:
(6a) using ground scene center as origin o, orientation is x-axis, and distance highly to for z-axis, is established in space to for y-axis
Three-dimensional cartesian coordinate system；
(6b) is using plane z=0 as imaging plane g0, to g centered on origin o0Grid dividing is carried out along x-axis and y-axis respectively,
Obtain gridding imaging plane g '0, each grid corresponds to a three dimensional space coordinate (xp, yq, 0), wherein p and q difference
Indicate the serial number of grid row and column, p=1,2 ..., P, q=1,2 ..., Q, P and Q are respectively indicated along x-axis and y-axis
Grid sum；
(6c) is by the gridding imaging plane g ' in (6b)0Translated up A times along z-axis using δ h as interval, obtain along z-axis from lower and
Upper equally distributed (A+1) a gridding imaging plane g '0, g '1..., g 'a..., g 'A, wherein g 'aIt indicates a-th
Gridding imaging plane, a=0,1,2 ..., A, g 'aThe corresponding three dimensional space coordinate of grid of middle pth row q column is (xp,
yq, a δ h)；
(7) the rarefaction one-dimensional range profile set S for utilizing (5d) to obtain is to (A+1) a gridding imaging plane g ' in (6c)0,
g′1..., g 'a..., g 'AMake adaptive projection, obtains (A+1) width two-dimensional SAR image M0, M1...,
Ma..., MA, wherein MaIndicate rarefaction one-dimensional range profile set S in a-th of gridding imaging plane g 'aIt is upper formed
Picture；
(8) (A+1) the width two-dimensional SAR image M for obtaining (7)0, M1..., Ma..., MABy height to from low to high
It is P × Q × (A+1) three-dimensional data block Data that sequence lines up a size from bottom to top, this three-dimensional data block Data is exactly
Final three-dimensional imaging result.
2. the method according to claim 1, wherein echo-signal in (1)Expression formula are as follows:
Wherein, t indicates full-time,Indicate the fast time, T indicates pulse width, fcIndicate that carrier frequency, γ indicate signal frequency modulation rate, c table
Showing the light velocity, n indicates pulse serial number, n=1,2 ..., N, N are the umber of pulse emitted in total, RnIndicate n-th of slow moment thunder
Up to range-to-go, j indicates imaginary unit, and rect () indicates rectangular window function.
3. the method according to claim 1, wherein to echo-signal in (2)Make process of pulse-compression,
It is implemented as follows:
(2a) is to echo-signalCarrier frequency is removed, fundamental frequency signal is obtained
Wherein,Indicate the fast time, n indicates pulse serial number, and T indicates pulse width, RnIndicate that n-th of slow moment radar arrives target
Distance, c indicate that the light velocity, γ indicate signal frequency modulation rate, and j indicates imaginary unit, and λ indicates that the wavelength of carrier wave, rect () indicate square
Shape window function；
(2b) is by fundamental frequency signalWith reference signalMake conjugate multiplication in frequency domain, and product of transformation returned time domain,
Obtain Signal for Pulse
Wherein, BrIndicate signal bandwidth,It indicates to make Fourier transformation in fast time-domain, IFFT indicates that making inverse Fourier becomes
It changes, ()*It indicates to take data conjugation, sinc () indicates sinc function, reference signalExpression formula are as follows:
4. the method according to claim 1, wherein to g centered on origin o in (6b)0Respectively along x-axis and y-axis
Grid dividing is carried out, the interval δ y of grid should meet in the interval δ x of grid and y-axis in x-axis:
Wherein, λ indicates the wavelength of carrier signal, R indicate radar when being located at synthetic aperture center radar to scene center distance,
LxThe equivalent projected length for being curvilinear synthetic aperture in orientation, c indicate the light velocity, BrIndicate signal bandwidth,Indicate radar
The pitch angle of radar when positioned at synthetic aperture center.
5. the method according to claim 1, wherein by gridding imaging plane g ' in (6c)0It is put down upwards along z-axis
It moves, the interval δ h of translation should meet:
Wherein, λ indicates the wavelength of carrier signal, R indicate radar when being located at synthetic aperture center radar to scene center distance,
LzIndicate the curvilinear synthetic aperture equivalent projected length upward in height.
6. the method according to claim 1, wherein using rarefaction one-dimensional range profile set S to (A+ in (7)
1) a gridding imaging plane g '0, g '1..., g 'a..., g 'AMake adaptive projection, is by rarefaction one-dimensional distance
PictureOn nonzero value to gridding imaging plane g '0, g '1..., g 'a..., g 'AIt projects, zero is not made
Projection, is accomplished by
(7a) calculates a-th of gridding imaging plane g 'aIn all mesh coordinates: { (xp, yq, a δ h) | p=1,2 ..., P,
Q=1,2 ..., Q } in the distance at n-th of slow moment to radar: { Ra(p, q, n) | p=1,2 ..., P, q=1,
2 ..., Q }, wherein p and q respectively indicates the row serial number and column serial number of grid, and P and Q are respectively indicated along x-axis and y-axis division
Grid number, n indicates pulse serial number, n=1,2 ..., N, N be the umber of pulse emitted in total, and a expression is meshed into as putting down
The serial number in face, a=0,1,2 ..., A, A indicate to be meshed into the number as plane translation, and δ h is indicated between imaging plane
Interval；
(7b) is g 'aIn all grids correspond to n-th of rarefaction one-dimensional range profileOn, obtain g 'aIt is upper withPeak
It is worth corresponding grid set Wan；
(7c) willTo grid set WanIn grid project, remaining grid does not project, and obtainsIn g 'aUpper institute
At image g 'an；
(7d) is by each element in rarefaction one-dimensional range profile set S in g 'aOn be projected out piece image, formed and g 'aIt is right
The image collection answered: Ga={ g 'a1, g 'a2..., g 'An,..., g 'aN, wherein g 'anIndicate that n-th of rarefaction is one-dimensional
Range ProfileIn a-th of gridding imaging plane g 'aUpper formed image；
(7e) is by image collection GaIn all elements be added, S can be obtained in g 'aUpper formed two-dimensional SAR image Ma:
Ma=g 'a1+g′a2+……+g′an+……+g′aN
(7f) repeats (7a)-(7e) to all gridding imaging plane g '0, g '1..., g 'a..., g 'AIt executes identical
Operation, (A+1) width two-dimensional SAR image M can be obtained0, M1..., Ma..., MA。
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