CN110673143A - Two-step processing method for sub-aperture large squint SAR (synthetic aperture radar) diving imaging - Google Patents

Two-step processing method for sub-aperture large squint SAR (synthetic aperture radar) diving imaging Download PDF

Info

Publication number
CN110673143A
CN110673143A CN201910941547.4A CN201910941547A CN110673143A CN 110673143 A CN110673143 A CN 110673143A CN 201910941547 A CN201910941547 A CN 201910941547A CN 110673143 A CN110673143 A CN 110673143A
Authority
CN
China
Prior art keywords
distance
azimuth
signal
imaging
frequency
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
CN201910941547.4A
Other languages
Chinese (zh)
Inventor
梁毅
梁宇杰
秦翰林
张罡
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Xian University of Electronic Science and Technology
Original Assignee
Xian University of Electronic Science and Technology
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Xian University of Electronic Science and Technology filed Critical Xian University of Electronic Science and Technology
Priority to CN201910941547.4A priority Critical patent/CN110673143A/en
Publication of CN110673143A publication Critical patent/CN110673143A/en
Pending legal-status Critical Current

Links

Images

Classifications

    • 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
    • G01S13/904—SAR modes
    • G01S13/9041—Squint mode
    • 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
    • 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
    • G01S13/9094—Theoretical aspects
    • 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
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/02—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00
    • G01S7/41—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00 using analysis of echo signal for target characterisation; Target signature; Target cross-section
    • G01S7/418—Theoretical aspects

Landscapes

  • Engineering & Computer Science (AREA)
  • Remote Sensing (AREA)
  • Radar, Positioning & Navigation (AREA)
  • Physics & Mathematics (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • General Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Radar Systems Or Details Thereof (AREA)

Abstract

The invention discloses a two-step processing method for sub-aperture large squint SAR (synthetic aperture radar) diving imaging, belonging to the technical field of radar signal processing; the method comprises two steps: firstly, establishing a dive equivalent level flight imaging geometric model, completing ambulation correction in a distance frequency domain, completing distance-to-pulse pressure and migration correction in a two-dimensional frequency domain, and introducing a frequency domain scaling factor into a distance Doppler domain to realize space-variant correction and complete azimuth-to-pulse pressure; and secondly, establishing a projection relation between the ground plane and the inclined plane according to the imaging processing step, and obtaining a non-deformation ground plane image by a back projection method. The invention processes the dive imaging equivalent to the level flight imaging, the imaging model satisfies the translation invariance along the direction of the resultant velocity, the uniform processing of the direction becomes possible on the premise of not increasing the computation amount, and the motion compensation becomes relatively simple.

Description

Two-step processing method for sub-aperture large squint SAR (synthetic aperture radar) diving imaging
Technical Field
The invention belongs to the technical field of radar signal processing, and particularly relates to a two-step processing method for sub-aperture large squint SAR (synthetic aperture radar) diving imaging.
Background
Synthetic Aperture Radar (SAR) is used as a microwave active sensor, can acquire two-dimensional images of observation scenes all day long, all weather long distance, and is widely applied to various radar carrier platforms. In order to ensure a certain turning maneuvering time, the SAR platform usually works in a squint imaging mode, and combines with the sub-aperture data coherent processing to realize the quick-look imaging of the region of interest, and simultaneously, the processing flow can be simplified, the complexity of motion compensation, the calculation amount and the memory amount can be reduced, and the processing efficiency can be improved. Therefore, the method has important significance for the research of large squint SAR imaging by using the sub-aperture data.
For the dive mode, due to the existence of the vertical speed, the echo signal of the SAR no longer satisfies the azimuth translation invariance in the conventional level flight mode, so that the conventional SAR imaging method cannot be directly applied to imaging processing in the dive mode. In addition, the essence of the oblique plane SAR image obtained by two-dimensional focusing is the nonlinear projection of the ground three-dimensional scene on the imaging oblique plane, which cannot reflect the features of the real ground features, and thus cannot be used for detection, identification, matching and positioning, and the oblique projection is required to obtain the real ground plane image.
Disclosure of Invention
In order to solve the above problems, the present invention aims to provide a two-step processing method for sub-aperture large squint SAR dive imaging. The azimuth processing is carried out by providing a 'dive equivalent flat flight' model and introducing a frequency domain scaling factor, so that two-dimensional accurate focusing is realized; by establishing a back projection relationship from the ground plane to the inclined plane, a fast projection geometry correction from the inclined plane image to the ground plane image is achieved.
The technical idea of the invention is as follows: the invention relates to a two-step treatment method: firstly, establishing a 'dive equivalent level flight' imaging geometric model, completing ambulation correction in a distance frequency domain, completing distance-oriented pulse pressure and migration correction in a two-dimensional frequency domain, and introducing a frequency domain scaling factor into a distance Doppler domain to realize space-variant correction and complete azimuth-oriented pulse pressure; and secondly, establishing a projection relation between the ground plane and the inclined plane according to the imaging processing step, and obtaining a non-deformation ground plane image by a back projection method.
In order to achieve the above object, the present invention adopts the following technical solutions.
A two-step processing method for sub-aperture large squint SAR (synthetic aperture radar) diving imaging comprises the following steps:
step 1, establishing a dive large squint SAR imaging geometric model to obtain a squint distance expression from a dive large squint SAR to a target in a beam coverage area, and rewriting the squint distance expression according to a dive equivalent level flight principle to obtain the dive large squint SAR squint distance expression of equivalent level flight;
step 2, constructing a fundamental frequency echo signal ss0(tr,tm；R0) For fundamental frequency echo signals ss0(tr,tm；R0) After distance Fourier transformation is carried out, a distance walking correction function H is introducedLRWC(fr,tm) Carrying out distance walk correction to obtain a distance walk corrected signal; after the azimuth Fourier transform is carried out on the distance walk corrected signal, a distance pulse pressure-distance bending correction-secondary distance pulse pressure function H is introducedRC_RCC_SRC(fr,fa) Obtaining a distance direction processed signal SS'0(fr,fa；R0)；
Step 3, comparing the signal SS 'after the distance direction processing'0(fr,fa；R0) After two-dimensional inverse Fourier transform, introducing a high-order phase compensation function Hhigh(tm；R′0) Performing high-order phase compensation to obtain a signal ss 'after high-order phase compensation'1(tr,tm；R′0)；
Step 4, for the signal ss 'after the high-order phase compensation'1(tr,tm；R′0) After the azimuth Fourier transform is carried out, a nonlinear scaling function H is introducedFNS(fa；R′0) Nonlinear scaling is carried out to obtain a signal sS 'after nonlinear scaling'2(tr,fa；R′0)；
Step 5, the signal sS 'after the nonlinear marking is carried out'2(tr,fa；R′0) After the azimuth inverse Fourier transform is carried out, an azimuth Deramp deskew function H is introducedderamp(tm；R′0) Azimuth deskew is carried out to obtain an azimuth deskewed time domain signal ss'3(tr,tm；R′0) (ii) a To the azimuth deskewed signal ss'3(tr,tm；R′0) Performing direction Fourier transform to obtain signal sS focused in range-Doppler domain4(tr,fa；R′0) Namely, the image is an oblique plane image;
step 6, a group of rectangular grid points are formed in the imaging area on the ground plane, a projection area is constructed, and the projection area is rotated in the horizontal plane along the counterclockwise directionObtaining ground grid points which are distributed along the ground distance in the direction and the distance transverse direction;
step 7, calculating the nearest distance R 'of each grid point after correction by considering the distance direction and the azimuth direction deformation for the ground grid points after rotation'BAnd azimuthal Doppler frequency f'a(ii) a And finding pixel points around each grid point on the inclined plane, and obtaining the amplitude and phase information of each grid point by adopting two-dimensional Sinc interpolation to obtain a corresponding ground plane image.
Compared with the prior art, the invention has the beneficial effects that:
(1) the method is characterized in that the dive imaging is equivalent to the flat flight imaging for processing, the imaging model meets the translation invariance along the direction of the resultant velocity, the unified processing of the direction is possible on the premise of not increasing the computation amount, and meanwhile, the motion compensation is relatively simple.
(2) In the azimuth processing process, the frequency domain phase scaling method provided by the invention compensates the space-variant part of the Doppler parameter to obtain a precisely focused two-dimensional image.
(3) In the geometric correction of the oblique projection, compared with the traditional method, the method has the advantages that fewer image pixel points are utilized during the back projection interpolation, and the parallel processing is easy, so that the conversion efficiency of the oblique projection can be greatly improved.
Drawings
The invention is described in further detail below with reference to the figures and specific embodiments.
FIG. 1 is a flow chart of an implementation of a two-step processing method of sub-aperture large squint SAR dive imaging of the present invention;
FIG. 2 is a diagram of a diving high squint SAR imaging geometric model in the invention;
FIG. 3 is a diagram of a model for geometric correction of oblique projection in accordance with the present invention;
FIG. 4 is a distribution diagram of simulation points in an imaging geometry model in an embodiment of the present invention;
FIG. 5 is an azimuth sectional view of imaging results corresponding to point 1, point 3 and point 2 in the embodiment of the present invention, where the horizontal axis is an azimuth sampling unit and the vertical axis is normalized amplitude;
FIG. 6 is a two-dimensional contour diagram of imaging results corresponding to point 1, point 3 and point 2 in the embodiment of the present invention, where the horizontal axis is an azimuth sampling unit and the vertical axis is a distance sampling unit;
FIG. 7 is a schematic view of a space-variant oblique plane in an embodiment of the present invention, in which FIG. 7(a) is a schematic view of the oblique plane as a whole, and FIGS. 7(b) and 7(c) are schematic views of two side points in a partially enlarged manner;
fig. 8 is a schematic view of a space-variant of a geometrically corrected ground plane after oblique projection in an embodiment of the present invention, where fig. 8(a) is a schematic view of the whole ground plane, and fig. 8(b) and 8(c) are schematic views of two side points in a partially enlarged manner;
Detailed Description
The embodiments and effects of the present invention will be described in further detail below with reference to the accompanying drawings.
Referring to fig. 1, the two-step processing method for sub-aperture large squint SAR dive imaging is implemented according to the following steps:
step 1, establishing a dive large squint SAR imaging geometric model to obtain a squint distance expression from a dive large squint SAR to a target in a beam coverage area, and rewriting the squint distance expression according to a dive equivalent level flight principle to obtain the dive large squint SAR squint distance expression of equivalent level flight;
firstly, a dive large strabismus SAR imaging geometric model is established, as shown in FIG. 2, due to the sub-holesThe accumulation time of the radial imaging position is short, the change of the speed and the motion direction of the platform is ignored, and the radar is considered to do uniform linear motion along the track AC. In addition, since the two-dimensional velocities in the horizontal plane can be synthesized as a new horizontal velocity, the present invention considers only the existence of the velocity v in the X directionxAnd a Z-direction velocity vzTwo-dimensional velocity of (a). The time when the SAR platform is positioned at the point B is taken as the middle time of the azimuth slow time, namely the azimuth zero time, the beam center line intersects with the ground at the point P, h is the platform height at the azimuth zero time, and R is the platform height at the azimuth zero time0Is the distance from the point B to the point P, alpha is the diving angle (the included angle between the flying direction and the X direction),is the angle between the flight direction and the beam centre line direction, thetaAThe included angle between the center line of the beam at the azimuth zero time and the projection of the beam on the YOZ plane is shown.
In the dive SAR imaging geometry model of FIG. 2, for a target P that falls at the intersection of the azimuth null-time beam centerline and the ground plane, its instantaneous slope distance can be expressed as
Figure BDA0002223033980000051
Wherein, tmThe azimuth slow time.
Because the vertical speed exists in the dive mode, the azimuth translation invariance of the traditional horizontal flying mode is not satisfied any more, and the traditional imaging algorithm is not applicable any more, so that the dive model needs to be further processed. It is easy to see that the instantaneous slope distance model can be further written as:
as can be seen from the dive SAR imaging geometry model of figure 2,
Figure BDA0002223033980000053
for the resultant velocity, i.e. the pitch velocity,
Figure BDA0002223033980000054
for the projection of horizontal and vertical velocities on the beam line of sight, i.e. the projection of the dive velocity on the beam line of sight, the variable substitution is introduced accordingly:
Figure BDA0002223033980000055
Figure BDA0002223033980000056
then the instantaneous slope distance can be rewritten as:
Figure BDA0002223033980000061
the above formula is similar to an instantaneous slope expression of the flat-flying SAR imaging, namely the expression is a dive large squint SAR slope expression of equivalent flat flying, and only the dive speed is used for replacing the flat flying speed, so that the translation invariance along the dive direction is met. The equivalent speed and squint angle are respectively:
Figure BDA0002223033980000062
Figure BDA0002223033980000063
re-analyzing the dive SAR imaging geometric model in FIG. 2, although the dive mode does not satisfy the azimuth translation invariance, the equivalent model satisfies the translation invariance in the direction of the synthesis speed. The synthesis speed direction and the beam sight line direction are expanded into a new data recording plane BCP plane, T' represents a projection point of a T point in the plane BCP under an equivalent model, and the BCP plane is a new data recording plane after equivalence due to the adoption of a dive equivalent flat flight principle, so that signals meet new translation invariance along the synthesis speed direction. In practice, the plane BT' P can be viewed as the rotation of the plane BTP along the BP axis. Through the equivalence, points in the same data recording plane in the plane flight imaging are distributed to different data recording planes, but translation invariance is met in the respective data recording planes, so that great convenience is brought to imaging algorithm research and motion compensation research.
Step 2, constructing a fundamental frequency echo signal ss0(tr,tm；R0) For fundamental frequency echo signals ss0(tr,tm；R0) After distance Fourier transformation is carried out, a distance walking correction function H is introducedLRWC(fr,tm) Carrying out distance walk correction to obtain a distance walk corrected signal; after the azimuth Fourier transform is carried out on the distance walk corrected signal, a distance pulse pressure-distance bending correction-secondary distance pulse pressure function H is introducedRC_RCC_SRC(fr,fa) Obtaining a distance direction processed signal SS'0(fr,fa；R0)；
(2.1) setting SAR radar transmission Linear Frequency Modulation (LFM) signals, and carrying out orthogonal demodulation on the received signals to obtain fundamental frequency echo signals:
Figure BDA0002223033980000071
wherein j is an imaginary unit, wr(. is a time domain form of a distance window function, wa(. is a time domain form of an orientation window function, fcIs the carrier frequency, c is the speed of light, l is the distance modulation frequency, trFor a fast time of distance, tmThe azimuth slow time.
(2.2) carrying out range-to-Fourier transform on the baseband signals to obtain signals in a range frequency domain, a direction and a time domain:
Figure BDA0002223033980000072
in the above formula, frIs a distance frequency, Wr(. cndot.) is a frequency domain version of the distance window function.
And (2.3) introducing a range walk correction function, correcting the linear component of range migration and compensating a Doppler center to reduce coupling between range and azimuth brought by strabismus imaging. Wherein the distance walk correction function:
Figure BDA0002223033980000073
(2.4) carrying out azimuth Fourier transform on the distance walk corrected signal to obtain a signal in a two-dimensional frequency domain:
Figure BDA0002223033980000074
wherein:
Figure BDA0002223033980000075
Figure BDA0002223033980000081
Figure BDA0002223033980000082
fais the azimuth frequency, Wa(. is a frequency domain form of an orientation window function, fdcIs the Doppler center frequency, and fdc＝2vsinθ0/λ，xnIs the azimuth position, [ phi ]0The term representing an azimuth frequency modulation term, phi1The term represents the distance warping term (RCC), phi2The term represents the quadratic range pulse pressure term (SRC).
(2.5) introducing a range pulse pressure-range curvature correction-quadratic range pulse pressure function HRC_RCC_SRC(fr,fa)：
Carrying out corresponding distance pulse pressure-distance bending correction-secondary distance pulse pressure on the signals in the two-dimensional frequency domain to obtain signals after distance direction processing:
Figure BDA0002223033980000084
step 3, comparing the signal SS 'after the distance direction processing'0(fr,fa；R0) After two-dimensional inverse Fourier transform, introducing a high-order phase compensation function Hhigh(tm；R′0) Performing high-order phase compensation to obtain a signal ss 'after high-order phase compensation'1(tr,tm；R′0)；
(3.1) distance-processed signals (i.e. distance-pulse-pressure and migration-corrected signals) SS'0(fr,fa；R0) Performing two-dimensional inverse Fourier transform to obtain a signal in a two-dimensional time domain:
Figure BDA0002223033980000091
where Sinc is a sine function, BrFor the distance-wise transmission of the signal bandwidth, phia(tm；R0) Is the phase in the signal in the two-dimensional time domain;
as can be seen from the above equation, the distance envelope after the distance direction processing is a Sinc function, and the distance position of the target is R0+xnsinθ0This is an azimuth dependent position xnThe amount of change means that the position of a point originally located in the same distance cell is shifted in the distance direction after the distance direction processing. For ease of analysis, variable substitutions were introduced:
R′0＝R0+xnsinθ0
the phase in the signal in the two-dimensional time domain can thus be expressed as:
Figure BDA0002223033980000092
wherein λ is carrier wavelength, KaFor adjusting the frequency of Doppler, KtIs the third order coefficient, KfFor the fourth order term coefficients, the following approximation is introduced:
Figure BDA0002223033980000093
wherein
Figure BDA0002223033980000094
Figure BDA0002223033980000095
Figure BDA0002223033980000096
(3.2) before the azimuth processing, firstly compensating the high-order non-space-variant term, and introducing a high-order phase compensation function:
the high-order phase compensation function is multiplied with the signal in the two-dimensional time domain to obtain a signal after high-order phase compensation:
Figure BDA0002223033980000102
wherein, K'tIs a space-variant part of the third-order coefficient after the higher-order phase compensation, K't＝Ktl·xn。
Step 4, for the signal ss 'after the high-order phase compensation'1(tr,tm；R′0) After the azimuth Fourier transform is carried out, a frequency domain nonlinear scaling function H is introducedFNS(fa；R′0) Nonlinear scaling is carried out to obtain a signal sS 'after nonlinear scaling'2(tr,fa；R′0)；
(4.1) Signal ss 'compensated for higher-order phase'2(tr,tm；R′0) Fourier of azimuthTransforming to obtain signals in the range-doppler domain:
Figure BDA0002223033980000103
(4.2) introducing a frequency domain nonlinear scaling function:
wherein p and q are scaling coefficients, which can be obtained by subsequent analysis.
Using frequency-domain nonlinear scaling function HFNS(fa；R′0) Multiplying the signal in the range-doppler domain to obtain a nonlinear scaled signal:
step 5, the signal sS 'after the nonlinear marking is carried out'2(tr,fa；R′0) After the azimuth inverse Fourier transform is carried out, an azimuth Deramp deskew function H is introducedderamp(tm；R′0) Azimuth deskew is carried out to obtain an azimuth deskewed time domain signal ss'3(tr,tm；R′0) (ii) a To the azimuth deskewed signal ss'3(tr,tm；R′0) Performing direction Fourier transform to obtain signal sS focused in range-Doppler domain4(tr,fa；R′0)；
For nonlinear scaled signal sS'2(tr,fa；R′0) Performing azimuth inverse Fourier transform to obtain signals in a two-dimensional time domain:
Figure BDA0002223033980000111
wherein the content of the first and second substances,represents the phase in the time domain:
Figure BDA0002223033980000113
the individual phase terms in the analytical formula:
Figure BDA0002223033980000114
for azimuthal modulation of phase, the term being related to the target azimuthal position xnIrrelevant, the unified compensation can be carried out; b (R'0,p1) Reflecting the real position of the target for the azimuth position phase coefficient; c (R'0P, q) is a first-order space-variant phase coefficient of azimuth frequency modulation rate, which is a key phase influencing the imaging focusing performance, and the space-variant thereof causes that the azimuth can not be uniformly focused; d (R'0P, q) are azimuth frequency modulation second-order space-variant phase coefficients, which affect the focusing accuracy to a certain extent; the fifth term is a constant phase, which has no effect on focus and is generally negligible.
To eliminate the space variation of the doppler parameters, let:
Figure BDA0002223033980000115
coefficients in the variable standard
Figure BDA0002223033980000121
Introducing a Deramp deskew function Hderamp(tm；R′0)：
Figure BDA0002223033980000122
Hderamp(tm；R′0) Multiplied by the two-dimensional time domain signal to obtain a deskewed signal ss'3(tr,tm；R′0)：
Figure BDA0002223033980000123
Wherein A is a constant phase having no influence on imagingTo the deskewed signal ss'3(tr,tm；R′0) Performing direction Fourier transform to obtain signal sS focused in range-Doppler domain4(tr,fa；R′0) Namely, the image is an oblique plane image;
Figure BDA0002223033980000124
wherein, BaThe corresponding doppler bandwidth for a single target sub-aperture data.
Therefore, the first step of the two-step processing method of the sub-aperture large squint SAR diving imaging is completed.
Step 6, a group of rectangular grid points are formed in the imaging area on the ground plane, a projection area is constructed, and the projection area is rotated in the horizontal plane along the counterclockwise direction
Figure BDA0002223033980000125
Obtaining ground grid points which are distributed along the ground distance in the direction and the distance transverse direction;
the method is characterized in that the diving is equivalent to the horizontal flight for imaging processing, a corresponding imaging plane rotates, and therefore large geometric distortion exists in an imaging result, the distortion is caused by projection of a time point target to the rotated imaging plane during imaging, and the imaging result cannot directly reflect real distance and azimuth position information and needs geometric correction processing. In addition, for the subsequent application of the SAR image, no matter detection identification or matching positioning, further oblique projection is required to be carried out, and a ground image of the correlation of the ground features and the landforms which accurately reflect is obtained.
The projection geometry model based on the dive equivalent fly-to-plane process of fig. 2 is shown in fig. 3, and reflects the correspondence between a certain point T in the imaging inclined plane and a certain point T' in the ground plane. In fig. 3, the resultant velocity direction and the X axis intersect at a point D, the beam center line at the time of zero intersects with the ground plane at a point P, and the imaging inclined plane after the dive equivalent flat flight processing is the BDP plane in the drawing. The "squint minimization" process of the range direction changes the imaging coordinate system from the original along and perpendicular to the flight direction to along and perpendicular to the beam gaze direction, corresponding to the R 'direction and X' direction in fig. 3, where R 'is along the beam center line BP direction and is denoted as range direction, and X' is the BDP plane perpendicular to the beam gaze direction and is denoted as range cross.
As can be seen from the two-dimensional focusing formula after the sub-aperture data is imaged, the distance position after imaging is the closest distance between a point target in an imaging plane and the vertical sight line direction, and the position is the position corresponding to the instantaneous Doppler of the target relative to the center of the sub-aperture. For the ground point target T 'in FIG. 3, the straight line connecting DT' intersects OP at point E, and plane BDE is the data recording plane for target T 'at which the instantaneous angle of observation of target T' by the aperture center can be represented as θiThen, the closest distance from the point target T' to the center of the aperture and the straight line perpendicular to the beam sight direction is:
RB＝Rcos(θi-θ0)
where R is the distance from the point target T 'to the aperture center, the instantaneous doppler frequency of the point target T' relative to the aperture center can be expressed as:
Figure BDA0002223033980000131
because the ' strabismus minimization ' process taking the scene center as a reference is introduced in the preprocessing, the Doppler center is compensated, and therefore for the target point T ', the corresponding residual Doppler center is as follows:
Figure BDA0002223033980000141
due to the introduction of the distance warping correction with reference to the center of the scene in the two-dimensional frequency domainTargets that are not scene-centered, cause a shift Δ R in distance to position, and this shift is the residual Doppler center Δ fdcFunction of (c):
ΔR＝RRCM(Δfdc)
wherein R isRCMFor the correction value of the range migration in the frequency domain, when time-frequency domain scaling is carried out, a scaling factor is introduced, so that Doppler shift is introduced:
Δfa＝f(p,q)
from the nearest distance RBAnd instantaneous Doppler frequency faThe distance position and the azimuth position of the ground target in the imaging inclined plane can be determined by simultaneously considering the space change of the distance direction and the azimuth direction introduced in the imaging processing, so that the ground plane image is obtained by completing the geometric correction through projection. In addition, since time scaling is introduced into the azimuth processing, it is necessary to take into account the change in azimuth position due to the scaling factor.
In a ground coordinate system XOY, a group of rectangular grid points are formed in a beam coverage area along the OX direction and the OY direction, namely a projection area is constructed, and all pixel points are rotated by an angle along the counterclockwise direction in a horizontal plane(where γ is the azimuth angle), the rotated grid point coordinates can be obtained:
the rotated and varied rectangular grid points are distributed laterally along the ground surface in the direction and distance corresponding to the oblique plane images distributed laterally along the direction and distance.
Step 7, calculating the nearest distance R 'of each grid point after correction by considering the distance direction and the azimuth direction deformation for the ground grid points after rotation'BAnd azimuthal Doppler frequency f'a(ii) a Finding out pixel points around each grid point on the inclined plane, and obtaining the amplitude and phase information of each grid point by adopting two-dimensional Sinc interpolation, namely obtaining the corresponding informationA planar image.
The traditional projection method is to obtain an image of an oblique plane without deformation through two-dimensional interpolation, then project each point of the oblique plane to a ground plane, because projected pixel points are distributed at unequal intervals, the two-dimensional interpolation is usually needed to obtain the image of the ground plane, and each dimension of interpolation needs to use all the pixel points of the dimension, so that the oblique conversion efficiency is seriously reduced.
The invention adopts a back projection fast geometric correction method, for a rectangular grid stretched by a ground plane, the position information (namely distance position information and azimuth Doppler position information) of each point on an inclined plane is calculated, and then the amplitude and phase information of the point is obtained through the interpolation of pixel points around the position.
The back projection fast geometry correction processing steps are as follows:
(1) for a certain ground grid point after rotation, in a data recording plane formed by the data recording plane and the synthetic speed direction, calculating the instantaneous observation angle theta of the aperture center for the pointiAnd the distance R from the point to the center of the aperture;
(2) using the instantaneous observation angle theta of the point obtained in (1)iAnd the distance R from the point to the center of the aperture, and calculating the nearest distance R of a straight line perpendicular to the sight line direction of the beam from the point to the center of the apertureBConsidering the distance deformation Δ R, the corrected closest distance is obtained:
R′B＝RB-ΔR
(3) using the instantaneous observation angle theta of the point obtained in (1)iCalculating the instantaneous Doppler frequency f of the pointaAzimuthal deformation Δ f introduced by time-frequency domain scaling considering azimuthaAnd obtaining the corrected azimuth Doppler frequency:
f′a＝fa-Δfa
(4) according to the corrected nearest distance R'BAnd corrected azimuth Doppler frequency f'aDetermining the distance position and the azimuth position of the point in the oblique distance image; taking 8 x 8 image pixel points around the point, obtaining the projection point of the ground plane by utilizing two-dimensional Sinc interpolationAmplitude and phase information, where the interpolation kernel is:
Figure BDA0002223033980000161
wherein the content of the first and second substances,
Figure BDA0002223033980000162
the distance interval between the distance direction of the oblique plane image and the distance corresponding to the distance transverse adjacent point,the doppler spacing corresponding to the distance direction and distance lateral neighbors of the oblique plane image.
(5) And (4) repeating the steps (1) to (4) until all the pixel points are calculated.
Thus, the second step of the two-step processing method of the sub-aperture large squint SAR dive imaging is completed, and a corresponding ground plane image is obtained.
Simulation experiment
The validity of the algorithm is verified by point target simulation.
The simulation parameters are shown in table 1.
TABLE 1 System simulation parameters
Parameter(s) Numerical value/Unit
Carrier frequency 16GHz
Bandwidth of 150MHz
Sampling rate 180MHz
Pulse width 10μs
Pulse repetition frequency 2kHz
Height of platform 6km
Distance of action 15km
Oblique angle 65°
Horizontal velocity 150m/s
Vertical velocity -35m/s
The simulation diagram is shown in fig. 4, and a 3 × 3 square lattice is arranged in the ground scene along the radar sight line direction and perpendicular to the radar sight line direction, and the size is 1km × 1 km. Three reference points are selected, wherein point 1 and point 2 are the edge points of the scene with the strongest space change, and point 3 is the center point of the scene with the reference. The simulation is divided into three parts: a first part: calculating equivalent parameters under a dive equivalent level flight model through the given simulation parameters; a second part: the effectiveness of the method is illustrated by an azimuth profile, a contour map and performance index parameters of the point target; and a third part: the effectiveness of the proposed geometric correction of the oblique projection is illustrated by the contrast of the oblique plane image with the ground plane image.
And (I) according to the analysis in the step 1, generating new equivalent speed and equivalent oblique angle in a dive equivalent flat flight model, and meeting the translation invariance along the direction of the synthetic speed. According to the equivalent formula, the equivalent speed and the equivalent squint angle can be calculated:
Figure BDA0002223033980000171
the imaging process will then proceed with the set of parameters.
And secondly, selecting points 1, 2 and 3 to compare to verify the focusing effect of the method, wherein an azimuth section view of the three selected points is shown in fig. 5, so that the points at the edge have similar imaging effects with the points at the center, and the main and side lobes are obviously separated, and a two-dimensional contour map of the three selected points is shown in fig. 6, so that contour maps of the three points are basically consistent. The scene edge points can be well focused, and the effectiveness of the method is verified.
In order to further evaluate the effectiveness of the method, azimuth resolution of 3 points is calculated, and peak sidelobe ratio and integral sidelobe ratio are shown in table 2, so that it can be seen that the performance index parameters obtained by the method are basically consistent with theoretical values (azimuth resolution 1m, peak sidelobe ratio-13.26 dB and integral sidelobe ratio-9.80 dB), and further the effectiveness of the method is demonstrated.
TABLE 2 Performance index parameter measurements (windowed)
Figure BDA0002223033980000181
Third, in order to verify the effectiveness of the oblique projection geometric correction method, fig. 7(a) shows an image with deformation in an oblique plane (windowed), and fig. 7(b) and 7(c) are respectively partial enlarged views of two sides, and it can be seen that the image has deformation in an inverted trapezoid shape. Fig. 8(a) shows the result of geometric deformation correction by the method of the present invention (windowed), and fig. 8(b) and 8(c) are respectively partial enlarged views of two sides, which shows that the deformation of the inclined plane disappears, and the image size matches the size of 1km × 1km set by simulation, thereby verifying the effectiveness of the inclined projection geometric correction provided herein.
The above description is only for the specific embodiments of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art can easily conceive of the changes or substitutions within the technical scope of the present invention, and all the changes or substitutions should be covered within the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the appended claims.

Claims (9)

1. A two-step processing method for sub-aperture large squint SAR (synthetic aperture radar) diving imaging is characterized by comprising the following steps of:
step 1, establishing a dive large squint SAR imaging geometric model to obtain a squint distance expression from a dive large squint SAR to a target in a beam coverage area, and rewriting the squint distance expression according to a dive equivalent level flight principle to obtain the dive large squint SAR squint distance expression of equivalent level flight;
step 2, constructing a fundamental frequency echo signal ss0(tr,tm；R0) For fundamental frequency echo signals ss0(tr,tm；R0) After distance Fourier transformation is carried out, a distance walking correction function H is introducedLRWC(fr,tm) Carrying out distance walk correction to obtain a distance walk corrected signal; after the azimuth Fourier transform is carried out on the distance walk corrected signal, a distance pulse pressure-distance bending correction-secondary distance pulse pressure function H is introducedRC_RCC_SRC(fr,fa) Obtaining a distance direction processed signal SS'0(fr,fa；R0)；
Step 3, comparing the signal SS 'after the distance direction processing'0(fr,fa；R0) After two-dimensional inverse Fourier transform, introducing a high-order phase compensation function Hhigh(tm；R′0) Performing high-order phase compensation to obtain a signal ss 'after high-order phase compensation'1(tr,tm；R′0)；
Step 4, for the signal ss 'after the high-order phase compensation'1(tr,tm；R′0) To carry outAfter the azimuth Fourier transform, a nonlinear scaling function H is introducedFNS(fa；R′0) Nonlinear scaling is carried out to obtain a signal sS 'after nonlinear scaling'2(tr,fa；R′0)；
Step 5, the signal sS 'after the nonlinear marking is carried out'2(tr,fa；R′0) After the azimuth inverse Fourier transform is carried out, an azimuth Deramp deskew function H is introducedderamp(tm；R′0) Azimuth deskew is carried out to obtain an azimuth deskewed time domain signal ss'3(tr,tm；R′0) (ii) a To the azimuth deskewed signal ss'3(tr,tm；R′0) Performing direction Fourier transform to obtain signal sS focused in range-Doppler domain4(tr,fa；R′0) Namely, the image is an oblique plane image;
step 6, a group of rectangular grid points are formed in the imaging area on the ground plane, a projection area is constructed, and the projection area is rotated in the horizontal plane along the counterclockwise direction
Figure FDA0002223033970000011
Obtaining ground grid points which are distributed along the ground distance in the direction and the distance transverse direction;
step 7, calculating the nearest distance R 'of each grid point after correction by considering the distance direction and the azimuth direction deformation for the ground grid points after rotation'BAnd azimuthal Doppler frequency f'a(ii) a And finding pixel points around each grid point on the inclined plane, and obtaining the amplitude and phase information of each grid point by adopting two-dimensional Sinc interpolation to obtain a corresponding ground plane image.
2. The two-step processing method for sub-aperture large squint SAR dive imaging according to claim 1, wherein in step 1, the expression of the slant range of the large squint SAR to the target in the beam coverage area is: for an object P that falls at the intersection of the azimuth null-time beam centerline and the ground plane, its instantaneous slope is expressed as:
Figure FDA0002223033970000021
wherein R (t)m；R0) Representing the instantaneous slant distance of the target at the intersection point of the beam center line and the ground plane at the azimuth zero moment, wherein the ground plane is an XOY plane; t is tmFor azimuthal slow time, R0Is the distance from the platform to the target at the azimuth zero time, h is the platform height at the azimuth zero time, vxThe velocity component of the platform velocity in the X direction, vzThe speed component of the platform speed in the Z direction is adopted, and the motion direction of the platform is divided into the X direction and the Z direction; thetaAThe included angle between the center line of the azimuth zero-moment wave beam and the projection of the azimuth zero-moment wave beam on a YOZ plane is formed, and the Z direction is the height direction;
because there is vertical speed in the dive mode, unsatisfied azimuth translation invariance, consequently with the above formula arrangement as:
Figure FDA0002223033970000022
wherein the content of the first and second substances,
Figure FDA0002223033970000023
for the resultant velocity, i.e. the pitch velocity,
Figure FDA0002223033970000024
the horizontal velocity and the vertical velocity are projected on the beam sight, namely the projection of the diving velocity on the beam sight;
according to a diving equivalent flat flight principle, variable substitution is introduced:
Figure FDA0002223033970000031
wherein the content of the first and second substances,
Figure FDA0002223033970000033
is the included angle between the flight direction and the beam central line direction;
then the instantaneous slope distance is rewritten as:
Figure FDA0002223033970000034
the above formula is similar to an instantaneous slope distance expression of the flat-flying SAR imaging, namely a dive large squint SAR slope distance expression of equivalent flat flying;
the speed and the oblique angle after the plane flight equivalent to dive are respectively as follows:
Figure FDA0002223033970000035
3. the two-step processing method for sub-aperture large squint SAR dive imaging according to claim 1, wherein the step 2 is implemented according to the following steps:
(2.1) setting SAR radar to transmit linear frequency modulation signals, and carrying out orthogonal demodulation on the received signals to obtain fundamental frequency echo signals:
Figure FDA0002223033970000037
wherein j is an imaginary unit, wr(. is a time domain form of a distance window function, wa(. is a time domain form of an orientation window function, fcIs the carrier frequency, c is the speed of light, l is the distance modulation frequency, trFor a fast time of distance, tmThe azimuth slow time; r (t)m；R0) Representing the instantaneous slope distance, R, for an object that falls at the intersection of the beam centerline and the ground plane at the azimuth null0The distance from the platform to the target at the azimuth zero moment;
(2.2) carrying out range-to-Fourier transform on the baseband signals to obtain signals in a range frequency domain, a direction and a time domain:
Figure FDA0002223033970000041
in the above formula, frIs a distance frequency, Wr(. h) is a frequency domain version of a distance window function;
(2.3) introducing a range walk correction function, correcting the linear component of range migration and compensating a Doppler center to reduce coupling between range and direction brought by strabismus imaging; wherein the distance walk correction function:
Figure FDA0002223033970000042
(2.4) carrying out azimuth Fourier transform on the distance walk corrected signal to obtain a signal in a two-dimensional frequency domain:
Figure FDA0002223033970000043
wherein:
Figure FDA0002223033970000044
Figure FDA0002223033970000046
fais the azimuth frequency, Wa(. is a frequency domain form of an orientation window function, fdcIs the Doppler center frequency, and fdc＝2vsinθ0λ, λ being the carrier wavelength, xnIs the azimuth position, [ phi ]0Term representation azimuth frequency modulationSystem of term, phi1The term represents a distance warping term, Φ2The term represents a quadratic range pulse pressure term;
(2.5) introducing a range pulse pressure-range curvature correction-quadratic range pulse pressure function HRC_RCC_SRC(fr,fa)：
Figure FDA0002223033970000051
Carrying out corresponding distance pulse pressure-distance bending correction-secondary distance pulse pressure on the signals in the two-dimensional frequency domain to obtain signals after distance direction processing:
4. the two-step processing method for sub-aperture large squint SAR dive imaging according to claim 1, wherein the step 3 is implemented as the following steps:
(3.1) distance-oriented processed Signal SS'0(fr,fa；R0) Performing two-dimensional inverse Fourier transform to obtain a signal in a two-dimensional time domain:
Figure FDA0002223033970000053
where Sinc is a sine function, BrFor distance to the transmission signal bandwidth, wa(. is) a time domain form of an azimuth window function, c is the speed of light, trFor a fast time of distance, tmThe azimuth slow time; r0Distance, x, from the platform to the target at azimuth zero timenIs an azimuth position phia(tm；R0) Is the phase in the signal in the two-dimensional time domain;
introducing variable substitution:
R′0＝R0+xnsinθ0
the phase in the signal in the two-dimensional time domain can thus be expressed as:
Figure FDA0002223033970000061
wherein λ is carrier wavelength, KaFor adjusting the frequency of Doppler, KtIs the third order coefficient, KfFor the fourth order term coefficients, the following approximation is introduced:
Figure FDA0002223033970000062
wherein
Figure FDA0002223033970000064
Figure FDA0002223033970000065
(3.2) before the azimuth processing, firstly compensating the high-order non-space-variant term, and introducing a high-order phase compensation function:
Figure FDA0002223033970000066
the high-order phase compensation function is multiplied with the signal in the two-dimensional time domain to obtain a signal after high-order phase compensation:
Figure FDA0002223033970000067
wherein, K'tIs a space-variant part of the third-order coefficient after the higher-order phase compensation, K't＝Ktl·xn。
5. The two-step processing method for sub-aperture large squint SAR dive imaging according to claim 4, wherein the step 4 is implemented according to the following steps:
(4.1) Signal ss 'compensated for higher-order phase'2(tr,tm；R′0) Performing azimuth Fourier transform to obtain signals in a range-Doppler domain:
Figure FDA0002223033970000071
wherein f isaIs the azimuth frequency, Wa(. h) is a frequency domain version of an azimuth window function;
(4.2) introducing a frequency domain nonlinear scaling function:
wherein, p and q are scaling coefficients and are obtained by phase analysis in a time domain;
using frequency-domain nonlinear scaling function HFNS(fa；R′0) Multiplying the signal in the range-doppler domain to obtain a nonlinear scaled signal:
Figure FDA0002223033970000073
wherein x isnIs the azimuth position.
6. The two-step processing method for sub-aperture large squint SAR dive imaging according to claim 5, wherein in step 5, the expression of the signal in the two-dimensional time domain is:
Figure FDA0002223033970000074
wherein the content of the first and second substances,
Figure FDA0002223033970000075
represents the phase in the time domain:
wherein:modulating the phase for azimuth; b (R'0,p1) Reflecting the real position of the target for the azimuth position phase coefficient; c (R'0P, q) is an azimuth frequency modulation first-order space-variant phase coefficient, which is a key phase influencing the imaging focusing performance; d (R'0P, q) is the azimuth frequency modulation second order space-variant phase coefficient; the fifth term is a constant phase, which is generally negligible;
introducing a Deramp deskew function Hderamp(tm；R′0)：
Figure FDA0002223033970000081
Hderamp(tm；R′0) Multiplied by the two-dimensional time domain signal to obtain a deskewed signal ss'3(tr,tm；R′0)：
Wherein A is a constant phase having no influence on imaging,
Figure FDA0002223033970000083
to the deskewed signal ss'3(tr,tm；R′0) Performing direction Fourier transform to obtain a signal sS focused in a range-Doppler domain4(tr,fa；R′0) Namely, the image is an oblique plane image;
Figure FDA0002223033970000084
wherein, BaThe corresponding doppler bandwidth for a single target sub-aperture data.
7. The two-step processing method for sub-aperture large squint SAR dive imaging according to claim 6, wherein the phase analysis in the time domain specifically comprises:
to eliminate phase in the time domain
Figure FDA0002223033970000085
The space variant of Doppler parameter (2) is a first order space variant phase coefficient C (R ') of azimuth frequency modulation rate'0P, q) and an azimuth modulation frequency second order space-variant phase coefficient D (R'0P, q) is 0, i.e.
Figure FDA0002223033970000086
Obtain coefficients in the scaling:
Figure FDA0002223033970000091
8. the two-step processing method for sub-aperture large squint SAR dive imaging according to claim 1, characterized in that step 6 is implemented according to the following steps:
firstly, changing an imaging coordinate system from an original flight direction and a vertical flight direction into a beam sight line direction and a vertical beam sight line direction, wherein the beam sight line direction is recorded as a distance direction along the central line direction of a beam, and the beam sight line direction is recorded as a distance transverse direction perpendicular to the beam sight line direction;
then, in a ground coordinate system XOY, a group of rectangular grid points are formed in a beam coverage area along the OX direction and the OY direction, namely a projection area is constructed, and all pixel points are rotated by an angle along the counterclockwise direction in a horizontal plane
Figure FDA0002223033970000092
Wherein gamma is an azimuth angle, and the coordinates of the rotated grid points are obtained:
Figure FDA0002223033970000093
wherein, (x, y) is the grid point coordinates before rotation;
the rotated and varied rectangular grid points are distributed laterally along the ground surface in the direction and distance corresponding to the oblique plane images distributed laterally along the direction and distance.
9. The two-step processing method for sub-aperture large squint SAR dive imaging according to claim 1, wherein step 7 specifically comprises: adopting a back projection fast geometric correction method, calculating the position information of each point on an inclined plane for a rectangular grid stretched by a ground plane, and then interpolating through pixel points around the position to obtain the amplitude and phase information of the point;
the back projection fast geometric correction is implemented according to the following steps:
(1) for a certain ground grid point after rotation, in a data recording plane formed by the data recording plane and the synthetic speed direction, calculating the instantaneous observation angle theta of the aperture center for the pointiAnd the distance R from the point to the center of the aperture;
(2) using the instantaneous observation angle theta of the point obtained in (1)iAnd the distance R from the point to the center of the aperture, and calculating the nearest distance R of a straight line perpendicular to the sight line direction of the beam from the point to the center of the apertureBConsidering the distance deformation Δ R, the corrected closest distance is obtained:
R′B＝RB-ΔR
RB＝Rcos(θi-θ0)
ΔR＝RRCM(Δfdc)
Figure FDA0002223033970000101
whereinR is the distance from the point target T' to the aperture center, RRCMIs a correction value of range migration in the frequency domain, Δ fdcIs the residual Doppler center, v is the pitch velocity, θ0The oblique angle after the plane flight equivalent to the dive is adopted, and lambda is the carrier wavelength;
(3) using the instantaneous observation angle theta of the point obtained in (1)iCalculating the instantaneous Doppler frequency f of the pointaAzimuthal deformation Δ f introduced by time-frequency domain scaling considering azimuthaAnd obtaining the corrected azimuth Doppler frequency:
f′a＝fa-Δfa
Figure FDA0002223033970000102
Δfa＝f(p,q)
wherein p and q are scaling coefficients;
(4) according to the corrected nearest distance R'BAnd corrected azimuth Doppler frequency f'aDetermining the distance position and the azimuth position of the point in the oblique distance image; taking 8 multiplied by 8 image pixel points around the point, and obtaining the amplitude and phase information of the ground plane projection point by utilizing two-dimensional Sinc interpolation, wherein the interpolation kernel is as follows:
wherein the content of the first and second substances,
Figure FDA0002223033970000113
the distance interval between the distance direction of the oblique plane image and the distance corresponding to the distance transverse adjacent point,
Figure FDA0002223033970000112
the Doppler intervals corresponding to the distance direction and the distance transverse adjacent points of the inclined plane image are set;
(5) and (4) repeating the steps (1) to (4) until all the pixel points are calculated.
CN201910941547.4A 2019-09-30 2019-09-30 Two-step processing method for sub-aperture large squint SAR (synthetic aperture radar) diving imaging Pending CN110673143A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
CN201910941547.4A CN110673143A (en) 2019-09-30 2019-09-30 Two-step processing method for sub-aperture large squint SAR (synthetic aperture radar) diving imaging

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CN201910941547.4A CN110673143A (en) 2019-09-30 2019-09-30 Two-step processing method for sub-aperture large squint SAR (synthetic aperture radar) diving imaging

Publications (1)

Publication Number Publication Date
CN110673143A true CN110673143A (en) 2020-01-10

Family

ID=69078862

Family Applications (1)

Application Number Title Priority Date Filing Date
CN201910941547.4A Pending CN110673143A (en) 2019-09-30 2019-09-30 Two-step processing method for sub-aperture large squint SAR (synthetic aperture radar) diving imaging

Country Status (1)

Country Link
CN (1) CN110673143A (en)

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN111722226A (en) * 2020-07-01 2020-09-29 成都汇蓉国科微***技术有限公司 Method and device for real-time processing bistatic forward-looking SAR echo data
CN112882029A (en) * 2021-01-12 2021-06-01 西安电子科技大学 Maneuvering track large squint beam pointing SAR imaging method based on rapid back projection
CN113341413A (en) * 2021-06-28 2021-09-03 南京航空航天大学 High-resolution squint SAR echo Doppler spectrum recovery method and system
CN113376632A (en) * 2021-05-18 2021-09-10 南京航空航天大学 Large squint airborne SAR imaging method based on pretreatment and improved PFA
CN113671497A (en) * 2021-07-06 2021-11-19 西安电子科技大学 Single-channel SAR target three-dimensional coordinate extraction method based on cylindrical symmetric model
CN115308435A (en) * 2022-09-05 2022-11-08 智驰华芯(无锡)传感科技有限公司 Two-way flow measurement side-scan Doppler radar current meter
CN115877318A (en) * 2022-12-07 2023-03-31 北京理工大学 Radiation source positioning method based on multi-aperture cross positioning
CN116840841A (en) * 2023-08-31 2023-10-03 西安电子科技大学 Large-strabismus wide-width high-resolution imaging method for diving section of maneuvering platform radar
CN116989888A (en) * 2023-09-27 2023-11-03 之江实验室 Acoustic imaging method, acoustic imaging device, computer equipment and storage medium

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN104133215A (en) * 2014-05-29 2014-11-05 西安电子科技大学 Synchronous orbit radar imaging method based on range migration fine adjustment and sub-band division
CN105974414A (en) * 2016-06-24 2016-09-28 西安电子科技大学 High resolution spotlight SAR self-focusing imaging method based on two-dimensional self-focusing
CN108490441A (en) * 2018-03-26 2018-09-04 西安电子科技大学 The big Squint SAR sub-aperture image space-variant bearing calibration of dive section based on two stage filter
CN110244300A (en) * 2019-06-24 2019-09-17 杭州电子科技大学 The flat winged section high-resolution imaging method of Missile-borne SAR based on sphere model and FENLCS algorithm

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN104133215A (en) * 2014-05-29 2014-11-05 西安电子科技大学 Synchronous orbit radar imaging method based on range migration fine adjustment and sub-band division
CN105974414A (en) * 2016-06-24 2016-09-28 西安电子科技大学 High resolution spotlight SAR self-focusing imaging method based on two-dimensional self-focusing
CN108490441A (en) * 2018-03-26 2018-09-04 西安电子科技大学 The big Squint SAR sub-aperture image space-variant bearing calibration of dive section based on two stage filter
CN110244300A (en) * 2019-06-24 2019-09-17 杭州电子科技大学 The flat winged section high-resolution imaging method of Missile-borne SAR based on sphere model and FENLCS algorithm

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
YI LIANG ET AL.: "A Two-Step Processing Method for Diving-Mode Squint SAR Imaging With Subaperture Data", 《IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING》 *
王珍等: "弹载SAR俯冲段斜视成像算法", 《数据采集与处理》 *

Cited By (16)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN111722226A (en) * 2020-07-01 2020-09-29 成都汇蓉国科微***技术有限公司 Method and device for real-time processing bistatic forward-looking SAR echo data
CN112882029A (en) * 2021-01-12 2021-06-01 西安电子科技大学 Maneuvering track large squint beam pointing SAR imaging method based on rapid back projection
CN113376632B (en) * 2021-05-18 2023-12-15 南京航空航天大学 Large strabismus airborne SAR imaging method based on pretreatment and improved PFA
CN113376632A (en) * 2021-05-18 2021-09-10 南京航空航天大学 Large squint airborne SAR imaging method based on pretreatment and improved PFA
CN113341413A (en) * 2021-06-28 2021-09-03 南京航空航天大学 High-resolution squint SAR echo Doppler spectrum recovery method and system
CN113341413B (en) * 2021-06-28 2024-04-09 南京航空航天大学 High-resolution squint SAR echo Doppler spectrum recovery method and system
CN113671497A (en) * 2021-07-06 2021-11-19 西安电子科技大学 Single-channel SAR target three-dimensional coordinate extraction method based on cylindrical symmetric model
CN113671497B (en) * 2021-07-06 2024-04-23 西安电子科技大学 Single-channel SAR target three-dimensional coordinate extraction method based on cylindrical symmetry model
CN115308435A (en) * 2022-09-05 2022-11-08 智驰华芯(无锡)传感科技有限公司 Two-way flow measurement side-scan Doppler radar current meter
CN115308435B (en) * 2022-09-05 2024-04-16 智驰华芯(无锡)传感科技有限公司 Side-scanning Doppler radar flow velocity meter capable of measuring flow in two directions
CN115877318A (en) * 2022-12-07 2023-03-31 北京理工大学 Radiation source positioning method based on multi-aperture cross positioning
CN115877318B (en) * 2022-12-07 2024-04-16 北京理工大学 Radiation source positioning method based on multi-aperture cross positioning
CN116840841A (en) * 2023-08-31 2023-10-03 西安电子科技大学 Large-strabismus wide-width high-resolution imaging method for diving section of maneuvering platform radar
CN116840841B (en) * 2023-08-31 2023-11-21 西安电子科技大学 Large-strabismus wide-width high-resolution imaging method for diving section of maneuvering platform radar
CN116989888A (en) * 2023-09-27 2023-11-03 之江实验室 Acoustic imaging method, acoustic imaging device, computer equipment and storage medium
CN116989888B (en) * 2023-09-27 2024-03-12 之江实验室 Acoustic imaging method, acoustic imaging device, computer equipment and storage medium

Similar Documents

Publication Publication Date Title
CN110673143A (en) Two-step processing method for sub-aperture large squint SAR (synthetic aperture radar) diving imaging
CN108490441B (en) Dive section large squint SAR sub-aperture imaging space-variant correction method based on two-stage filtering
CN106249237B (en) Big Squint SAR frequency domain imaging method under a kind of curvilinear path
CN109471101B (en) Missile-borne SAR image correction method
CN104597447B (en) A kind of big stravismus of sub-aperture SAR improves Omega K imaging method
CN110673144B (en) Sub-aperture large squint SAR imaging processing method based on time-varying beacon
CN107607948B (en) Motion compensation and imaging method of medium orbit satellite SAR
CN105759263A (en) High resolution satellite-borne squint SAR imaging method in large-scale scene
CN113589285B (en) SAR real-time imaging method for aircraft
CN114545411B (en) Polar coordinate format multimode high-resolution SAR imaging method based on engineering realization
CN107918124A (en) Airborne big strabismus High Resolution SAR imaging method with the correction of orientation space-variant
CN103308913A (en) Foresight SAR ambiguity resolving algorithm of double antennas carried by high-speed aircraft
CN108490439A (en) Bistatic arbitrary configuration SAR imaging methods based on equivalent oblique distance
CN110109104B (en) Array SAR (synthetic aperture radar) equidistant slice imaging geometric distortion correction method
CN108562900A (en) SAR image geometric registration method based on elevation correction
CN112558070B (en) Frequency domain imaging method and device of circular scanning foundation SAR
Li et al. Inverse-mapping filtering polar formation algorithm for high-maneuverability SAR with time-variant acceleration
CN109946682B (en) GF3 data baseline estimation method based on ICESat/GLAS
CN112859018A (en) Video SAR imaging method based on image geometric correction
CN111880179A (en) Imaging method of missile-borne arc diving high squint TOPS SAR
CN116679265A (en) SAR time domain rapid echo simulation method suitable for use in topography fluctuation scene
CN108469612B (en) Bistatic time-varying acceleration foresight SAR imaging method based on equivalent slope distance
CN113671497B (en) Single-channel SAR target three-dimensional coordinate extraction method based on cylindrical symmetry model
CN114002666B (en) Method and equipment for extracting satellite-borne ATI-SAR ocean current flow velocity under any antenna configuration
CN112578383A (en) High maneuvering platform TOPS SAR imaging method based on expanded wave number spectrum reconstruction

Legal Events

Date Code Title Description
PB01 Publication
PB01 Publication
SE01 Entry into force of request for substantive examination
SE01 Entry into force of request for substantive examination