CN103777188A - InISAR imaging method based on double-frequency conjugation processing - Google Patents

InISAR imaging method based on double-frequency conjugation processing Download PDF

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CN103777188A
CN103777188A CN201410026269.7A CN201410026269A CN103777188A CN 103777188 A CN103777188 A CN 103777188A CN 201410026269 A CN201410026269 A CN 201410026269A CN 103777188 A CN103777188 A CN 103777188A
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CN103777188B (en
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刘波
尹建凤
林晴晴
万晓云
王伟宗
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China Academy of Space Technology CAST
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
    • G01S13/88—Radar or analogous systems specially adapted for specific applications
    • G01S13/89—Radar or analogous systems specially adapted for specific applications for mapping or imaging
    • G01S13/90—Radar or analogous systems specially adapted for specific applications for mapping or imaging using synthetic aperture techniques, e.g. synthetic aperture radar [SAR] techniques
    • G01S13/9021—SAR image post-processing techniques
    • G01S13/9023—SAR image post-processing techniques combined with interferometric 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
    • G01S13/02—Systems using reflection of radio waves, e.g. primary radar systems; Analogous systems
    • G01S13/50—Systems of measurement based on relative movement of target
    • G01S13/58—Velocity or trajectory determination systems; Sense-of-movement determination systems
    • G01S13/583—Velocity or trajectory determination systems; Sense-of-movement determination systems using transmission of continuous unmodulated waves, amplitude-, frequency-, or phase-modulated waves and based upon the Doppler effect resulting from movement of targets
    • 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
    • G01S13/9021—SAR image post-processing techniques
    • G01S13/9029—SAR image post-processing techniques specially adapted for moving target detection within a single SAR image or within multiple SAR images taken at the same time
    • 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
    • G01S13/9064—Inverse SAR [ISAR]

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Abstract

The invention provides an InISAR imaging method based on double-frequency conjugation processing and discloses a method in which the double-frequency conjugation processing technique is combined with the interferometric technique to be applied to ISAR so as to achieve moving object positioning and imaging. The method comprises the steps of conducting sub-band segmentation, conducting sub-band pulse compression and double-frequency conjugation processing, conducting rough interferometric measurement on a target with composite signals, conducting original signal imaging and interferometric processing, and achieving target scattering point accurate measurement through the combination of the interference result of an original signal image and the result of rough interferometric measurement to further achieve target positioning and imaging. The method mainly solves the problem of target Doppler frequency blurring and target interferometric measurement blurring in an InISAR mode and can achieve target positioning and imaging at the same time.

Description

A kind of InISAR formation method based on the processing of double frequency conjugation
Technical field
The present invention relates to a kind of InISAR(Interferemetric Inverse Synthetic Aperture Radar based on the processing of double frequency conjugation) formation method, for obtaining true geometric size and the true spatial location of target, belong to radar imagery and Radar Signal Processing Technology field.
Background technology
Inverse synthetic aperture radar (ISAR) (Inverse Synthetic Aperture Radar, ISAR) obtain range resolution by transmitting broadband signal, utilize the relative motion between radar and target to form synthetic aperture, obtain Doppler by signal processing technology and tie up resolution, thereby obtain target image.ISAR is the main radar system to motive target imaging, and from its birth, people have recognized that ISAR is imaged on the aspects such as astronomical sight, tactical weapon, strategic defensive and has significant application value.
Along with the continuous growth of application demand, the defect of conventional single-antenna ISAR imaging technique also embodies gradually.On the one hand, it is mainly in distance-Doppler territory that ISAR obtains target image, can not obtain target in horizontal bulk information; On the other hand, single antenna ISAR image can not provide the drift angle information of target in wave beam, can not realize target orientation to location.Need to consider to use the InISAR system of many antennas to solve relevant issues for this reason.
On the basis of radar interference angle measurement technique, along with InSAR(interference synthetic aperture aperture radar) development of technology, the research work of InISAR technology has also obtained paying attention to widely.1996, Soumekh M. has proposed first a kind of InISAR method of tiny inclination angle while detecting aircraft landing for ISAR image by interference technique in Automatic aircraft landing using interferometric inverse synthetic aperture radar imaging mono-literary composition, and the various research about InISAR technology subsequently worldwide launches.Before and after 2000, the people such as the Wang Genyuan of Delaware university of the U.S. and the Victor C.Chen of Naval Research Labratory have studied and have utilized method that three slave antennas that form vertical parallax carry out three-dimensional imaging to target (referring to Wang G, Xia X-G, Chen V C.Three-dimensional ISAR imaging of maneuvering targets using three receivers[J] .Image Processing, IEEE Transactions on, 2001).Along with the development of InISAR 3 Dimension Image Technique, also progressively go deep into for the research of the practical application request such as the estimation of moving target three-dimensional motion parameter, high precision imaging, in a series of periodical meetings, report relevant progress.Referring to Publication about Document:
[1]Zhang?Q,Yeo?T?S,Du?G,et?al.Estimation?of?three-dimensional?motion?parameters?in?interferometric?ISAR?imaging[J].Geoscience?and?Remote?Sensing,IEEE?Transactions?on,2004,42(2):292-300.
[2]Zhang?Q,Yeo?T?S.Three-dimensional?SAR?imaging?of?a?ground?moving?target?using?the?InISAR?technique[J].Geoscience?and?Remote?Sensing,IEEE?Transactions?on,2004,42(9):1818-1828.
[3]Given?J?A,Schmidt?W?R.Generalized?ISAR-part?II:interferometric?techniques?for?three-dimensional?location?of?scatterers[J].Image?Processing,IEEE?Transactions?on,2005
[4] Yin Jianfeng, Li Daojing, Wu Yirong. the Space Object Detection based on spaceborne millimetre-wave radar and imaging [J]. aerospace journal, 2007,28 (6): 6.
In order to obtain the horizontal space yardstick information of target, Tsing-Hua University's CN101498788 patent discloses a kind of target rotation angle of inverse synthetic aperture radar (ISAR) and has estimated and horizontal calibrating method, the method utilizes segmentation imaging results scattering center to be optimized to velocity of rotation and the relevant corner of the relative radar of combinational estimation target, thereby determines the breadth wise dimension of image.The method advantage is not adopt principle of interference, and the few system of receiving cable is simple.Shortcoming is to target imaging under short time data, therefore echo signal to noise ratio (S/N ratio) to be had relatively high expectations; Do not solve the problem of target localization, can not determine the absolute position of target in radar beam.
Xian Electronics Science and Technology University's CN101000374 patent discloses a kind of InISAR formation method based on the aobvious point of many spies, aobvious of multiple spies that the method is not glimmered by screening carry out spy's aobvious some phase place main value unwrapping and then the aobvious point of spy are calibrated, simulate the relation of Doppler frequency and lateral separation, utilize this relation view picture ISAR to be obtained to the InISAR image of target true geometric size by pixel processing.The picture point of the method after based on ISAR imaging calibrated, and echo signal to noise ratio (S/N ratio) required lower, and in patent specification, the accompanying drawing of simulation result shows that the method can be applicable to the situation of low signal-to-noise ratio, and robustness is better.But, the method also has its significant defect: when to interferometric phase unwrapping, require according to Doppler's increasing or decreasing path integral unwrapping, but, different integration starting points may cause uncoiled result difference, the actual value of the interferometric phase that therefore, the method obtains is relatively accurate.That is to say, utilize this value to judge the distance between target scattering point, but can not obtain the absolute position of each scattering point, can not be to target localization.
Double frequency conjugation treatment technology is seen in the paper that report is Yin Jianfeng deliver in " electronic letters, vol " one piece " aerial sports target detection and the imaging of satellite-borne SAR " by name for the first time.This article has been introduced the method that subband double frequency conjugation ought to be used for moving target solution doppler ambiguity.It is a kind of difference frequency disposal route in essence that subband double frequency conjugation is processed, and the composite signal carrier frequency generating after processing is less than the bandwidth of former linear FM signal, compares former linear FM signal, and carrier frequency reduces at least one the order of magnitude, and then has reduced doppler centroid.But it is fuzzy fuzzy with doppler bandwidth that solution doppler ambiguity need to solve doppler centroid simultaneously, this article does not have multianalysis; Double frequency conjugation treatment technology can increase carrier wavelength, and this is highly beneficial to interferometric phase ambiguity solution, and this article does not deeply excavate.
Summary of the invention
Technology of the present invention is dealt with problems and is: overcome the deficiencies in the prior art, a kind of InISAR formation method based on the processing of double frequency conjugation is provided, this method solves existing motive target imaging method can not be to the problem of moving target location, optimize existing moving target size estimation method, and realize target is determined appearance and has been expanded double frequency conjugation treatment technology in the application aspect interference on the basis of location simultaneously.
Technical solution of the present invention is:
Based on an InISAR formation method for double frequency conjugation processing, comprise the imaging processing of the Moving Target Return signal of two antenna channels, step is as follows:
Step S1: the Moving Target Return signal of an antenna channels is done to Fourier transform to the fast time, full time-domain signal is transformed into m-fast frequency field when slow, and do and divide equally in fast frequency field, be divided into two subband linear FM signals;
Step S2: two subband linear FM signals in step S1 are made respectively to distance to pulse compression, then do the processing of double frequency conjugation and obtain composite signal, described double frequency conjugation is processed and is about to two distances to the subband signal conjugate multiplication after pulse compression;
Step S3: utilize ISAR imaging method to do imaging processing to the signal after synthetic, obtain the image of moving target in distance-Doppler territory, and enter step S5;
Step S4: to the signal processing in the Moving Target Return signal repeating step S1-S3 of another one antenna channels, and enter step S5;
Step S5: utilize two ranges that obtain in step S3 and S4, from the image of-Doppler domain, moving target is carried out to radial velocity without blur estimation, radial velocity is averaged and obtained target radial speed without the result of blur estimation; The image in the distance-Doppler territory of two antenna channels that obtain in step S3 and S4 done to conjugate multiplication simultaneously and then extract scattering point interferometric phase, utilizing scattering point interferometric phase realize target drift angle bigness scale amount;
Step S6: utilize ISAR imaging method to do imaging processing to the original motion target echo signal of two antenna channels, then do conjugate multiplication to processing rear image, extract scattering point interferometric phase;
Step S7: utilize the result of the target drift angle bigness scale amount of the target image interferometric phase integrating step S5 acquisition of step S6 acquisition, carry out target drift angle accurate measurement amount, and then to target scattering point location, realize InISAR imaging simultaneously.
In described step S5, the method for realize target drift angle bigness scale amount is as follows:
A, complete image registration: image after two antenna channels imagings is done respectively to interpolation processing, translation is done in picture position after one of them antenna channels interpolation, image after another one antenna channels interpolation remains unchanged, calculate simple crosscorrelation simultaneously, when simple crosscorrelation is maximum, translational movement is the required translational movement of registration, the more down-sampled interferometric phase image that obtains imaging region;
B, utilize the imaging results of the composite signal of the antenna channels that image remains unchanged after interpolation to do threshold value threshold window, utilize this window to do filtering to imaging region interferometric phase image, obtain target interferometric phase image, and utilize this target interferometric phase image realize target drift angle bigness scale amount:
Figure BDA0000459518730000041
Wherein, φ nrepresent the interferometric phase of n scattering point in target, λ drepresent effective wavelength, θ is antenna beam scanning angle, d 12it is the distance of two antenna channels phase centers.
In described step S7, target scattering point location and target imaging complete simultaneously.
The present invention's beneficial effect is compared with prior art:
(1) the present invention is lower to the requirement of Moving Target Return signal to noise ratio (S/N ratio), can under Low SNR, realize the bigness scale amount to target drift angle.
(2) the present invention can solve moving target doppler centroid and the fuzzy problem of doppler bandwidth simultaneously, can realize to target radial speed without blur estimation.
(3) the present invention adopts the method for thick smart two-stage angle measurement, true interferometric phase information initial value while utilizing the result of target drift angle bigness scale amount that accurate measurement is provided, avoid the uncoiled work of conventional I nISAR interferometric phase, can realize the orientation of target to location.
Accompanying drawing explanation
Fig. 1 is formation method process flow diagram of the present invention;
Fig. 2 is imaging geometry model schematic diagram of the present invention;
Fig. 3 is the subband signal generating principle figure of double frequency conjugation of the present invention processing;
Fig. 4 is the target ISAR imaging results that the composite signal that utilizes the processing of double frequency conjugation to obtain obtains;
Fig. 5 is target image inverting positioning result and the simulation objectives actual position comparison diagram that InISAR formation method that the present invention introduces obtains.
Embodiment
Specific embodiment below in conjunction with accompanying drawing and emulation experiment is further described in detail the specific embodiment of the present invention.
As shown in Figure 1, the concrete steps of a kind of InISAR formation method based on the processing of double frequency conjugation of the present invention are as follows:
Step S1: the Moving Target Return signal of an antenna channels is done to Fourier transform to the fast time, full time-domain signal is transformed into m-fast frequency field when slow, and do and divide equally in fast frequency field, be divided into two subband linear FM signals;
Step S2: two subband linear FM signals in step S1 are made respectively to distance to pulse compression, then do the processing of double frequency conjugation and obtain composite signal, described double frequency conjugation is processed and is about to two distances to the subband signal conjugate multiplication after pulse compression;
Step S3: utilize ISAR imaging method to do imaging processing to the signal after synthetic, obtain the image of moving target in distance-Doppler territory, and enter step S5;
Step S4: to the signal processing in the Moving Target Return signal repeating step S1-S3 of another one antenna channels, and enter step S5;
Step S5: utilize two ranges that obtain in step S3 and S4, from the image of-Doppler domain, moving target is carried out to radial velocity without blur estimation, radial velocity is averaged and obtained target radial speed without the result of blur estimation; The image in the distance-Doppler territory of two antenna channels that obtain in step S3 and S4 done to conjugate multiplication simultaneously and then extract scattering point interferometric phase, utilizing scattering point interferometric phase realize target drift angle bigness scale amount;
Step S6: utilize ISAR imaging method to do imaging processing to the original motion target echo signal of two antenna channels, then do conjugate multiplication to processing rear image, extract scattering point interferometric phase;
Step S7: utilize the result of the target drift angle bigness scale amount of the target image interferometric phase integrating step S5 acquisition of step S6 acquisition, carry out target drift angle accurate measurement amount, and then to target scattering point location, realize InISAR imaging simultaneously.
Further illustrate the course of work of the present invention below in conjunction with a specific embodiment:
Simulate signal is carrier frequency f c=35GHz, bandwidth B r=400MHz, time wide 2 μ s linear FM signal, system PRF is 4kHz, imaging geometry model as shown in Figure 2, θ=30 °, antenna beam scanning angle, the distance d of two antenna channels phase centers 12=3m, the synthetic aperture time is 0.25s, moving target radial velocity-61.6m/s, transverse velocity 78.8m/s, target forms " ten " font by 5 scattering points and distributes, lateral dimension 20m, radial dimension 10m, in the imaging moment (middle moment), target is 10km to the distance of antenna, drift angle in the wave beam of target's center's point
In described step S1, target echo is to be coupled fast time and slow time, and a slow time-sampling point obtains the echo-pulse that a fast time series represents; Moving Target Return signal is done to Fourier transform to the fast time and each echo-pulse is done to Fourier transform, full time-domain signal will be transformed into m-fast frequency field when slow.Each pulse is done and is divided equally in fast frequency field, obtain height frequency two segment signals, and in relevant position respectively zero padding do inverse Fourier transform, obtain two subband linear FM signals, as shown in Figure 3.
In described step S2, the matched filter that the two subband linear FM signals that adopt the method for matched filtering to build respectively to obtain with step S1 adapt, two subband linear FM signals are done respectively to distance to pulse compression, and two signals are done to the processing of double frequency conjugation, be about to the subband signal conjugate multiplication after two pulse pressures, obtain the signal after difference frequency:
S m _ con ( t ^ , t m ) = S 2 ( t ^ , t m ) · S 1 * ( t ^ , t m )
Wherein
Figure BDA0000459518730000072
represent low frequency sub-band,
Figure BDA0000459518730000073
represent high-frequency sub-band, " * " represents conjugation,
Figure BDA0000459518730000074
and t mrepresent respectively the speed time.
This signal by each scattering point signal in target self and the polynomial expression that forms of cross term sum.Because time difference of two subband linear FM signals is conventionally only in microsecond magnitude, the displacement of moving target is far smaller than a Range resolution unit during this period, so can think that the Range Profile of moving target is to aim in this two width image.Meanwhile, consider the character of sinc function, be greater than a Range resolution unit as long as the oblique distance of two scattering points is poor, the amplitude of its cross term be just far smaller than self, cross term just can be ignored, especially in the situation that resolution is higher.
Based on above analysis, after double frequency conjugation is processed, composite signal can be expressed as
S m ( t ^ , t m ) ≈ Σ n = 1 N sin c [ B r 2 ( t ^ - 2 R n ( t m ) C ) ] exp { - j [ 4 π C ( f c 2 - f c 1 ) R n ( t m ) + ξ n 1 - ξ n 2 ] }
In formula, C represents the light velocity, and N represents the number of target scattering point, R n(t m) represent that n scattering point is at t mtime be carved into the distance of antenna, ξ n1and ξ n2represent first phase, the centre frequency of this signal is the poor of two subband linear FM signal centre frequencies, i.e. B r/ 2, f c2represent the carrier frequency of high-frequency sub-band linear FM signal, f c1represent the carrier frequency of low frequency sub-band linear FM signal.The target doppler centroid that composite signal is corresponding is
f dc ′ = - 2 ( f c 2 - f c 1 ) C v r = - B r C v r
Target doppler bandwidth is the variation range of target Doppler frequency within the synthetic aperture time.Target radial speed is not contributed doppler bandwidth, the poor target doppler bandwidth that is of Doppler frequency that target lateral speed produced in the imaging start-stop moment.Consider maximum Doppler bandwidth, known target maximum lateral speed is v amax, the synthetic aperture time is T s, doppler bandwidth is
B Dop = 2 v a max 2 λR T s = 2 v a max 2 T s CR f c
Wherein R represents that antenna arrives the reference distance of target, and λ represents the wavelength that carrier wave is corresponding.The doppler bandwidth that double frequency conjugation is processed rear composite signal is visible, the doppler bandwidth of composite signal reduces greatly.
According to above-mentioned analysis, the parameter in conjunction with specific embodiments, target doppler centroid is reduced to 82.1Hz by 14.4kHz; Target doppler bandwidth is reduced to 0.2Hz by 37.1Hz.Visible, the processing of double frequency conjugation increases the effective wavelength of composite signal greatly, has solved the doppler ambiguity problem of general motion target.
In described step S3, composite signal carrier frequency reduces, and doppler bandwidth reduces, and corresponding target image also significantly dwindles in the scattered band of Doppler domain, and target ISAR image outline is lost, as shown in Figure 4.According to parameter in embodiment, target is reduced to 0.4Hz in the scattered band of Doppler domain by 73.5Hz, and therefore, its orientation can not identification to the position relationship between scattering point in Fig. 4 for target, and objective contour is lost.Distance is still preserved to scattering point information.
In described step S4, because composite signal effective wavelength is larger, target Doppler frequency is without fuzzy, and Doppler frequency is corresponding target radial speed
v = - C f dc ′ B r
Target Doppler frequency is 83Hz, and the target velocity that correspondence obtains is-62.25m/s, and actual value is more approaching, realized to target radial speed without blur estimation.
In described step S5, the method for realize target drift angle bigness scale amount is as follows:
A, complete image registration: image after two antenna channels imagings is done respectively to interpolation processing, translation is done in picture position after one of them antenna channels interpolation, image after another one antenna channels interpolation remains unchanged, calculate simple crosscorrelation simultaneously, when simple crosscorrelation is maximum, translational movement is the required translational movement of registration, the more down-sampled interferometric phase image that obtains imaging region;
B, utilize the imaging results of the composite signal of the antenna channels that image remains unchanged after interpolation to do threshold value threshold window, utilize this window to do filtering to imaging region interferometric phase image, obtain target interferometric phase image, and utilize this target interferometric phase image realize target drift angle bigness scale amount:
Figure BDA0000459518730000091
Wherein, φ nrepresent the interferometric phase of n scattering point in target, λ drepresent effective wavelength, θ is antenna beam scanning angle, d 12it is the distance of two antenna channels phase centers.
In conjunction with specific embodiments, the processing of double frequency conjugation increases wavelength greatly, consider θ=30 °, beam scanning angle, the not fuzzy scope of original signal angle measurement expands to 14.4775 °～48.5904 ° from 29.9055 °～30.0946 °, solved interference angle measurement fuzzy problem, the result of target drift angle bigness scale amount is the average of all target scattering points drift angle
Figure BDA0000459518730000092
Be taken as-8dB of threshold value thresholding in the present embodiment, corresponding n is 5.
In described step S6, the method for imaging and extraction interferometric phase can refer step S3 and step S5.
In described step S7, target localization and InISAR imaging need to utilize the result of target drift angle bigness scale amount true interferometric phase information initial value φ is provided,
Figure BDA0000459518730000094
corresponding true interferometric phase is known, and initial value φ is:
Figure BDA0000459518730000095
(k 1for positive integer)
Wherein, φ 0represent the main value of φ; In like manner, n scattering point drift angle in target
Figure BDA00004595187300000910
corresponding interferometric phase actual value can be expressed as
(k 2for positive integer)
φ in formula n0represent φ nmain value.
Due to target scattering point drift angle ?
Figure BDA0000459518730000098
near, when remote, can think that the difference of the two does not exceed not fuzzy scope of angle measurement.Therefore, can think that the difference of interferometric phase main value represents the poor of interferometric phase, in target, the interferometric phase actual value of n scattering point can be asked
&phi; n = &phi; + ( &phi; n 0 - &phi; 0 ) + 2 &pi; &phi; n 0 - &phi; 0 < - &pi; &phi; + ( &phi; n 0 - &phi; 0 ) - &pi; &le; &phi; n 0 - &phi; 0 < &pi; &phi; + ( &phi; n 0 - &phi; 0 ) - 2 &pi; &phi; n 0 - &phi; 0 &GreaterEqual; &pi;
And then can try to achieve the smart measurement result of target scattering point drift angle:
Obtain the drift angle of each scattering point, the range information R characterizing in conjunction with echo time delay ncan be finally inversed by target scattering point position and realize location:
Figure BDA0000459518730000102
Figure BDA0000459518730000103
The positioning instant of the each scattering point of realize target has been realized target imaging (the position of having known each point has formed target image) simultaneously, as shown in Figure 5.In figure, provided the contrast of inverting position and actual position, be less than 2m apart from location, 10km place mean square deviation, illustrated that this method imaging effect is better, target location accuracy is higher.
Above-described specific embodiment; object of the present invention, technical scheme and beneficial effect are further described; be understood that; the foregoing is only specific embodiments of the invention; be not limited to the present invention; within the spirit and principles in the present invention all, any modification of doing, be equal to replacement, improvement etc., within all should being included in protection scope of the present invention.
The content not being described in detail in instructions of the present invention belongs to those skilled in the art's known technology.

Claims (3)

1. the InISAR formation method based on the processing of double frequency conjugation, comprises and the imaging processing of the Moving Target Return signal of two antenna channels it is characterized in that step is as follows:
Step S1: the Moving Target Return signal of an antenna channels is done to Fourier transform to the fast time, full time-domain signal is transformed into m-fast frequency field when slow, and do and divide equally in fast frequency field, be divided into two subband linear FM signals;
Step S2: two subband linear FM signals in step S1 are made respectively to distance to pulse compression, then do the processing of double frequency conjugation and obtain composite signal, described double frequency conjugation is processed and is about to two distances to the subband signal conjugate multiplication after pulse compression;
Step S3: utilize ISAR imaging method to do imaging processing to the signal after synthetic, obtain the image of moving target in distance-Doppler territory, and enter step S5;
Step S4: to the signal processing in the Moving Target Return signal repeating step S1-S3 of another one antenna channels, and enter step S5;
Step S5: utilize two ranges that obtain in step S3 and S4 respectively moving target to be carried out to radial velocity without blur estimation from the image of-Doppler domain, radial velocity is averaged and obtained target radial speed without the result of blur estimation; The image in the distance-Doppler territory of two antenna channels that obtain in step S3 and S4 done to conjugate multiplication simultaneously and then extract scattering point interferometric phase, utilizing scattering point interferometric phase realize target drift angle bigness scale amount;
Step S6: utilize ISAR imaging method to do imaging processing to the original motion target echo signal of two antenna channels, then do conjugate multiplication to processing rear image, extract scattering point interferometric phase;
Step S7: utilize the result of the target drift angle bigness scale amount of the target image interferometric phase integrating step S5 acquisition of step S6 acquisition, carry out target drift angle accurate measurement amount, and then to target scattering point location, realize InISAR imaging simultaneously.
2. a kind of InISAR formation method based on the processing of double frequency conjugation according to claim 1, is characterized in that: in described step S5, the method for realize target drift angle bigness scale amount is as follows:
A, complete image registration: image after two antenna channels imagings is done respectively to interpolation processing, translation is done in picture position after one of them antenna channels interpolation, image after another one antenna channels interpolation remains unchanged, calculate simple crosscorrelation simultaneously, when simple crosscorrelation is maximum, translational movement is the required translational movement of registration, the more down-sampled interferometric phase image that obtains imaging region;
B, utilize the imaging results of the composite signal of the antenna channels that image remains unchanged after interpolation to do threshold value threshold window, utilize this window to do filtering to imaging region interferometric phase image, obtain target interferometric phase image, and utilize this target interferometric phase image realize target drift angle bigness scale amount:
Figure FDA0000459518720000021
Wherein, φ nrepresent the interferometric phase of n scattering point in target, λ drepresent effective wavelength, θ is antenna beam scanning angle, d 12it is the distance of two antenna channels phase centers.
3. a kind of InISAR formation method based on the processing of double frequency conjugation according to claim 1, is characterized in that: in described step S7, target scattering point location and target imaging complete simultaneously.
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