CN104730503B - Determine methods and compensation method of the high resolution SAR reference target RCS on calibration influence - Google Patents
Determine methods and compensation method of the high resolution SAR reference target RCS on calibration influence Download PDFInfo
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01Q—ANTENNAS, i.e. RADIO AERIALS
- H01Q15/00—Devices for reflection, refraction, diffraction or polarisation of waves radiated from an antenna, e.g. quasi-optical devices
- H01Q15/14—Reflecting surfaces; Equivalent structures
- H01Q15/18—Reflecting surfaces; Equivalent structures comprising plurality of mutually inclined plane surfaces, e.g. corner reflector
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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
- 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
- G01S7/40—Means for monitoring or calibrating
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
- G01S13/88—Radar or analogous systems specially adapted for specific applications
- G01S13/89—Radar or analogous systems specially adapted for specific applications for mapping or imaging
- G01S13/90—Radar or analogous systems specially adapted for specific applications for mapping or imaging using synthetic aperture techniques, e.g. synthetic aperture radar [SAR] techniques
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
- G01S13/88—Radar or analogous systems specially adapted for specific applications
- G01S13/89—Radar or analogous systems specially adapted for specific applications for mapping or imaging
- G01S13/90—Radar or analogous systems specially adapted for specific applications for mapping or imaging using synthetic aperture techniques, e.g. synthetic aperture radar [SAR] techniques
- G01S13/9004—SAR image acquisition techniques
- G01S13/9011—SAR image acquisition techniques with frequency domain processing of the SAR signals in azimuth
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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
- 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
- G01S7/40—Means for monitoring or calibrating
- G01S7/4004—Means for monitoring or calibrating of parts of a radar system
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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
- 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
- G01S7/40—Means for monitoring or calibrating
- G01S7/4052—Means for monitoring or calibrating by simulation of echoes
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- Radar, Positioning & Navigation (AREA)
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- Computer Networks & Wireless Communication (AREA)
- General Physics & Mathematics (AREA)
- Electromagnetism (AREA)
- Signal Processing (AREA)
- Radar Systems Or Details Thereof (AREA)
Abstract
The method on calibration influence and compensation method the invention discloses a kind of determination high resolution SAR reference target RCS, based on FEKO 3 D electromagnetic simulation results, reference target RCS is obtained with frequency band or azimuthal variation data using multilevel fast multipole method, then reference target RCS is incorporated into SAR echo signal, can quantitative analysis assessment reference target RCS be comprehensively a kind of analysis method closer to actual conditions with frequency band or azimuthal variation influence on RT；Compensation method of the invention, emulated by the reference target RCS data first to the existing High Resolution SAR with different center frequency and/or frequency band range, it is then based on the result of above-mentioned calibration influence, judge whether to meet at least one more than or equal to 0.2dB in the maximum of integration energy differences in the maximum and azimuth beamwidth of the integral energy difference in the bandwidth of actually used high resolution SAR to determine whether to carrying out echo cancellation, operand can be saved while SAR detection accuracies are met.
Description
Technical field
The invention belongs to signal processing technology field, and in particular to one kind determines high resolution SAR reference target RCS to fixed
The method for marking influence.
Background technology
For arrowband and narrow azimuth beam SAR (Synthetic Aperture Radar) system, it is believed that scaled reference point
RCS (Radar Cross-Section, RCS) approximately constant in bandwidth of operation and azimuth beam of target.So
And, with the raising in remote sensing application to image resolution requirement, (frequency band range is more than to generate many high resolution SARs
The SAR of 2GHz and/or azimuth beamwidth more than 20 ° is generally considered to be high resolution SAR) system, relative bandwidth can surpass
10% even up to 100% is crossed, and orientation ranges of incidence angles can increase to tens degree even 360 ° (circular track SAR) from the several years.
In the big distance of modem high-resolution SAR system to bandwidth and wide-azimuth to wave beam the characteristics of under, at centre frequency and azimuth
RCS approximate representation reference targets backscattering characteristic, the required precision of radiation calibration, reference target RCS can not be reached
Frequency band or orientation angle dependence must take in.In the case where computer storage capacity and arithmetic speed are developed rapidly,
Also for subtly simulation of Radar System provides guarantee.
RCS traditional at present calculates many based on high-frequency approximation theoretical formula model, and based on constant more than SAR echo simulations
RCS's it is assumed that there is following deficiency in this technical method：
(1) RCS computation models are inaccurate：Theoretical formula model, obtains by multistep approximate processing, but actual RCS
Target is separated with background environment during measurement, and it is all a challenge to provide sufficient far field condition, it is impossible to preferably parsing
Formula is represented.
(2) frequency band and orientation angle dependence of RCS are ignored in SAR echo simulations：High resolution SAR system due to its it is big away from
The characteristics of descriscent bandwidth and wide-azimuth are to wave beam can additionally produce various errors, wherein just being missed including reference point target radiation characteristic
Difference.
(3) comprehensive quantitative analysis assessment is not carried out：When currently carrying out high resolution SAR system emulation, do not consider simultaneously
The influence of the frequency band and orientation angle dependence of RCS, and it is not comprehensive enough to the quality evaluation index of final result.
The content of the invention
In view of this, the invention provides a kind of method that determination high resolution SAR reference target RCS influences on calibration,
Data of the reference target RCS on calibration influence can be obtained；Meanwhile, present invention also offers one kind based on calibration influence to returning
The method of ripple compensation, can judge whether to mend echo according to the integral energy difference obtained in the method for calibration influence
Repay, thus can ensure the certain detection accuracies of high accuracy SAR.
A kind of determination high resolution SAR reference target RCS comprises the following steps on the method for calibration influence：
Step 1, for the existing High Resolution SAR with different center frequency and/or frequency band range, respectively using FEKO
The electromagnetic scattering emulation geometrical model of software building reference target, then selects multilevel fast multipole method in FEKO softwares
The corresponding reference target RCS of each High Resolution SAR is obtained respectively with frequency band and the data with azimuthal variation, each high-resolution
The corresponding data of SAR are respectively provided with two dimensions, and the first dimension is for the High Resolution SAR in beam angle internal reference target RCS with side
The data of parallactic angle change, the second dimension is the High Resolution SAR in the data changed with frequency apart from bandwidth internal reference target RCS；
Step 2, for each High Resolution SAR, original echoed signals simulation model is set up respectively, and to original echoed signals
In distance to Fourier transformation is done, obtain distance to frequency-region signal；For each High Resolution SAR, in beam angle, will return
Each sampled point of orientation time-domain signal obtains data of the reference target RCS with azimuthal variation with step 1 in ripple signal data
It is multiplied after being alignd by azimuth, acquisition introduces the orientation time-domain signal data of reference target RCS influences；Apart from band
In wide, the reference target RCS that echo signal data middle-range descriscent each sampled point of frequency-region signal and step 1 are obtained becomes with frequency
The data of change are multiplied after pressing Frequency point alignment, and acquisition introduces the distance of reference target RCS influences to frequency-domain signal data；
Step 3, for each High Resolution SAR, the distance for introducing reference target RCS influences obtained on step 2 is to frequency
Domain and orientation time domain 2-D data carry out Range compress and Azimuth Compression, and acquisition introduces the echo of reference target RCS influences
Signal SAR complex patterns；Range compress and Azimuth Compression are carried out to the original echo 2-D data, the SAR of primary signal is obtained
Complex pattern；For the echo-signal SAR complex patterns and the SAR complex patterns of primary signal that introduce reference target RCS influences, difference
Point target peak energy, integral energy, peak sidelobe ratio and integration secondary lobe ratio to the two width SAR complex patterns seek difference, obtain
Influences of the reference target RCS with frequency band and/or azimuthal correlation to image quality, thereby determines that each high score being respectively directed to
Distinguish influences of the reference target RCS of SAR with frequency band and/or azimuthal change to calibrating.
Preferably, in the step 1, the step-length that frequency bandwidth is set in FEKO softwares is 20MHz, sets azimuth beam
Angle step be 0.2 °.
Preferably, the 2-D data obtained for step 1, row interpolation is entered using cubic spline interpolation so that refer to mesh
RCS is consistent with the data point of orientation time-domain signal in the echo-signal in step 2 with the data of azimuthal variation for mark so that ginseng
Examine target RCS consistent with echo signal data middle-range descriscent frequency-domain signal data point in step 2 with the data point that frequency changes.
It is of the invention a kind of based on above-mentioned calibration compensation method of the influence to echo, step 3 find with it is actually used
The corresponding integral energy difference data of high resolution SAR, and obtain the integration energy in the bandwidth of the actually used high resolution SAR
Measure difference maximum and azimuth beamwidth in integration energy differences maximum, judge two maximums whether meet to
Rare one is more than or equal to 0.2dB, if met：Actual ghosts signal to the High Resolution SAR of the practical application is carried out
Compensation；If be unsatisfactory for, it is not necessary to which actual ghosts signal is compensated；
The compensation method is：To the actual ghosts signal in distance to Fourier transformation is done, obtain distance to frequency
Domain signal；The corresponding reference target RCS of each high accuracy SAR obtained in the step 1 are with frequency band and with azimuthal variation
2-D data in, 2-D data corresponding with the high accuracy SAR of practical application is found, by each data point of 2-D data difference
Ask reciprocal；By each sampled point of orientation time-domain signal in actual ghosts signal data with ask the reference target RCS after inverse with
The data of azimuthal variation are multiplied after being alignd by azimuth, the orientation time-domain signal data after being compensated；Will be actual
Echo signal data middle-range descriscent each sampled point of frequency-region signal and the data for asking the reference target RCS after inverse to change with frequency
It is multiplied after being alignd by Frequency point, the distance after being compensated is to frequency-domain signal data.
The present invention has the advantages that：
(1) method that a kind of determination high resolution SAR reference target RCS of the invention influences on calibration, with prior art
Compare, advantage is：Based on FEKO 3 D electromagnetic simulation results, obtained using multilevel fast multipole method (MLFMM) and referred to
Then be incorporated into reference target RCS in SAR echo signal emulation, thus by target RCS with frequency band or azimuthal variation data
Can comprehensively quantitative analysis assessment reference target RCS with frequency band or azimuthal variation influence on RT, the method with it is existing
It is a kind of analysis method closer to actual conditions that method is compared.
(2) by rationally setting the step-length and the angle step of azimuth beam of the frequency bandwidth in FEKO softwares, reduce
While the operand of FEKO, moreover it is possible to so that the data and curves variation tendency of FEKO outputs meets condition.
(3) a kind of method compensated to echo based on calibration influence of the invention, by first to existing with not
Emulated with the reference target RCS data of centre frequency and/or the High Resolution SAR of frequency band range, be then based on above-mentioned calibration
The result of influence, judges that the maximum and azimuth beam of integral energy difference in the bandwidth of actually used high resolution SAR are wide
Whether meet at least one more than or equal to 0.2dB in the maximum of integration energy differences in degree to determine whether to being returned
Ripple is compensated, and thus can save operand while the detection accuracy of SAR is met.
Brief description of the drawings
Fig. 1 is that the electromagnetic scattering in the present invention by FEKO software building reference targets emulates geometrical model figure.
Fig. 2 (a) is reference target normalization RCS surface charts in the present invention；Fig. 2 (b) is corresponding for the surface chart of Fig. 2 (a)
Section curve at centre frequency and center hold angle.
Fig. 3 is RCS with frequency band and the point target analogous diagram of azimuthal variation.
Wherein 1- is encouraged, 2- reflectors.
Specific embodiment
Develop simultaneously embodiment below in conjunction with the accompanying drawings, and the present invention will be described in detail.
It is radiation calibration theory analysis to set up target scattering characteristics with the quantitative relationship of echo-signal by radar equation
Premise, the average received signal power of High Resolution SAR Images can be expressed as：
Wherein, PtIt is transmission signal power；PnIt is noise power；G2(f, α) is round trip antenna radiation pattern；It is the visual angle of radar illumination target, θ is the angle of pitch,It is azimuth, it is right during carried SAR radiation calibration
In given reference point target, it is necessary to set the angle of pitch of corner reflector exactly according to flight track or flight path, reach
Close to preferable working condition, therefore, only RCS need to be considered with azimuthal variation characteristic；GsF () is system gain；λ (f) is
Transmission signal wavelength；R (α) is the oblique distance of radar and target；τpIt is fire pulse width；fsIt is distance to sample frequency；fPRFFor
Orientation sample frequency；V is radar platform flying speed；ρaIt is azimuth resolution；σ (f, α) is the radar cross section of point target
Product.
Have big distance to bandwidth and wide-azimuth to wave beam in view of high resolution SAR system, reference point target is preferable
Radiation characteristic no longer meets, to keep the uniformity with existing radiation calibration algorithm, it is necessary to frequency band and side to reference target RCS
Parallactic angle correlation carries out quantitative analysis, reference point target is still had flat response in system bandwidth and azimuth beam, from
And ensure actinometry difference be due to imageable target rather than reference target radiation characteristic change cause.According to system
The change of the corresponding bandwidth of mode of operation and targeting device RCS in bandwidth, by the bearing calibration in echo domain, to point target band
Mudulation effect wide is corrected, and re-imaging, to eliminate the error of the antenna pattern measurement of bandwidth introducing, for pack mould
Formula also needs to azimuth beam (response) width according to azimuth scan scope and targeting device, it is considered to azimuth beamwidth to spoke
Penetrate the influence of characteristic.
In view of this, the present invention in order to solve how accurately to obtain under the conditions of Current high resolution SAR system with frequency band or
The related reference target RCS in azimuth, and think reference target RCS in bandwidth of operation and azimuth beam during SAR system emulation
The deficiency that approximately constant is assumed, proposes a kind of side of quantitative analysis high resolution SAR reference target radiation characteristic on calibration influence
Method.The method, by FEKO 3 D electromagnetics simulation software, is obtained on the basis of the high resolution SAR radiation calibration model set up
Reference target RCS is taken with frequency band and azimuthal variation relation, with reference to high resolution SAR system emulation, quantitatively analysis reference
Influence of the frequency band or orientation angle dependence of target RCS to SAR image quality.
A kind of determination high resolution SAR reference target RCS of the invention comprises the following steps on the method for calibration influence：
Step 1, for the existing High Resolution SAR with different center frequency and/or frequency band range, respectively using FEKO
The electromagnetic scattering emulation geometrical model of software building reference target, then selects multilevel fast multipole method in FEKO softwares
(MLFMM) the corresponding reference target RCS of each High Resolution SAR is obtained respectively with frequency band and the data with azimuthal variation, often
The corresponding data of individual High Resolution SAR are respectively provided with two dimensions, and the first dimension is the High Resolution SAR in beam angle internal reference target
RCS with azimuthal variation data, the second dimension be the High Resolution SAR apart from bandwidth internal reference target RCS with frequency change
Data；MLFMM is the rapidly and efficiently numerical algorithm for studying Electrically large size object problem, and it causes to be solved on minicom
Large-scale electromagnetic scattering problems are possibly realized.In the present embodiment, under the conditions of Ku wave bands far field is irradiated, operating center frequency is
f0=16GHz, bandwidth deltaf f are 4GHz；The angle of pitch be fixed value θ=54.74 °, azimuth withCentered on, azimuth model
EncloseIt is 30 °；The size of trihedral corner reflector 2 is l=20cm, meets the λ of l ≈ 10, i.e. target scattering characteristics belongs to high frequency region.Need
To illustrate that, it is contemplated that the configuration of PC and the amount of calculation of FEKO engineerings, because the amount of calculation of FEKO can be with its parameter setting
In discrete point quantity be multiplied, it is 20MHz, angle step in azimuth beamwidth that frequency step is taken in bandwidth herein
Be 0.2 °, although the discrete points set in FEKO much smaller than the distance in SAR simulation parameters to orientation sampling number, but
Be it is discrete points can reflect plots changes in the case of, can using cubic spline interpolation process cause by
Discrete points derived from FEKO are final to be met with SAR distances to consistent with orientation sampling number, so as to avoid FEKO engineerings from advising
Mould is excessive, reduces operand, draws shown in normalization RCS curved surfaces and corresponding centre section curve such as Fig. 2 (a) and (b).
Step 2, for each High Resolution SAR, original echoed signals simulation model is set up respectively, and to original echoed signals
In distance to Fourier transformation is done, obtain distance to frequency-region signal；For each High Resolution SAR, by echo signal data
Each sampled point of orientation time-domain signal obtains reference target RCS and is carried out by azimuth with the data of azimuthal variation with step 1
It is multiplied after alignment, acquisition introduces the orientation time-domain signal data of reference target RCS influences；By distance in echo signal data
The reference target RCS obtained with step 1 to frequency-region signal each sampled point alignd by Frequency point with the data that frequency changes after phase
Multiply, acquisition introduces the distance of reference target RCS influences to frequency-domain signal data；
Step 3, for each High Resolution SAR, the distance for introducing reference target RCS influences obtained on step 2 is to frequency
Domain and orientation time domain 2-D data carry out Range compress and Azimuth Compression, and acquisition introduces the echo of reference target RCS influences
Signal SAR complex patterns；Range compress and Azimuth Compression are carried out to the original echo 2-D data, the SAR of primary signal is obtained
Complex pattern；For the echo-signal SAR complex patterns and the SAR complex patterns of primary signal that introduce reference target RCS influences, difference
Point target peak energy, integral energy, peak sidelobe ratio and integration secondary lobe ratio to the two width SAR complex patterns seek difference, obtain
Influences of the reference target RCS with frequency band and/or azimuthal correlation to image quality, thereby determines that each high score being respectively directed to
Distinguish influences of the reference target RCS of SAR with frequency band and/or azimuthal change to calibrating.
Result as shown in figure 3, in the case of four groups of bandwidth and azimuth beam parameter setting, the 1st group of parameter：Δ f=
0.5GHz,2nd group of parameter：Δ f=1GHz,3rd group of parameter：Δ f=2GHz,4th group
Parameter：Δ f=4GHz,Point target peak energy, integral energy, peak sidelobe ratio and integration secondary lobe than relative change
Change size.Wherein, Δ f represents bandwidth,Represent azimuth beamwidth.
Generally, in the distribution of whole SAR system radiation error, the error that reference target RCS changes cause, active calibration sets
Standby no more than 0.2dB, passive targeting device is no more than 0.3dB.Find that above-mentioned influence has reached by Fig. 2 and 3 simulation results
Degree is can not ignore to radiation calibration, it is necessary to which the radiation characteristic influence greatly apart from bandwidth and wide-azimuth wave beam on reference target is added
To compensate.The selection in signal transacting region is carried out in complex image domain, and then is mapped to echo domain, obtaining needs SAR to be processed to return
Ripple signal row, column is interval.
Therefore, present invention also offers a kind of benefit to actual ghosts signal influenceed on calibration based on reference target RCS
Compensation method, is compensated for before imaging algorithm to echo-signal, specially：
Integral energy difference data corresponding with actually used high resolution SAR is found in step 3, and obtains the reality
Energy differences are integrated using in the maximum and azimuth beamwidth of the integral energy difference in the bandwidth of high resolution SAR most
Big value, judges whether two maximums meet at least one more than or equal to 0.2dB, if met：Should to the reality
The actual ghosts signal of High Resolution SAR is compensated；If be unsatisfactory for, it is not necessary to which actual ghosts signal is compensated；
The compensation method is：To the actual ghosts signal in distance to Fourier transformation is done, obtain distance to frequency
Domain signal；The corresponding reference target RCS of each high accuracy SAR obtained in the step 1 are with frequency band and with azimuthal variation
2-D data in, 2-D data corresponding with the high accuracy SAR of practical application is found, by each data point of 2-D data difference
Ask reciprocal；By each sampled point of orientation time-domain signal in actual ghosts signal data with ask the reference target RCS after inverse with
The data of azimuthal variation are multiplied after being alignd by azimuth, the orientation time-domain signal data after being compensated；Will be actual
Echo signal data middle-range descriscent each sampled point of frequency-region signal and the data for asking the reference target RCS after inverse to change with frequency
It is multiplied after being alignd by Frequency point, the distance after being compensated is to frequency-domain signal data.
In sum, presently preferred embodiments of the present invention is these are only, is not intended to limit the scope of the present invention.
All any modification, equivalent substitution and improvements within the spirit and principles in the present invention, made etc., should be included in of the invention
Within protection domain.
Claims (4)
1. a kind of method that determination high resolution SAR reference target RCS influences on calibration, it is characterised in that comprise the following steps：
Step 1, for the existing High Resolution SAR with different center frequency and/or frequency band range, respectively using FEKO softwares
The electromagnetic scattering emulation geometrical model of reference target is built, multilevel fast multipole method difference is then selected in FEKO softwares
The corresponding reference target RCS of each High Resolution SAR is obtained with frequency band and the data with azimuthal variation, each High Resolution SAR
Corresponding data are respectively provided with two dimensions, and the first dimension is for the High Resolution SAR in beam angle internal reference target RCS with azimuth
The data of change, the second dimension is the High Resolution SAR in the data changed with frequency apart from bandwidth internal reference target RCS；
Step 2, for each High Resolution SAR, set up original echoed signals simulation model respectively, and to original echoed signals away from
Fourier transformation is done in descriscent, obtain distance to frequency-region signal；For each High Resolution SAR, in beam angle, echo is believed
Each sampled point of orientation time-domain signal obtains reference target RCS with the data of azimuthal variation by side with step 1 in number
Parallactic angle is multiplied after being alignd, and acquisition introduces the orientation time-domain signal data of reference target RCS influences；Apart from bandwidth
Interior, the reference target RCS that echo signal data middle-range descriscent each sampled point of frequency-region signal and step 1 are obtained changes with frequency
Data press Frequency point alignment after be multiplied, acquisition introduce reference target RCS influence distance to frequency-domain signal data；
Step 3, for each High Resolution SAR, the distance for introducing reference target RCS influences obtained on step 2 to frequency domain and
Orientation time domain 2-D data carries out Range compress and Azimuth Compression, and acquisition introduces the echo-signal of reference target RCS influences
SAR complex patterns；Range compress and Azimuth Compression are carried out to the original echo 2-D data, the SAR for obtaining primary signal schemes again
Picture；For the echo-signal SAR complex patterns and the SAR complex patterns of primary signal that introduce reference target RCS influences, respectively to this
The point target peak energy of two width SAR complex patterns, integral energy, peak sidelobe ratio and integration secondary lobe ratio seek difference, are referred to
Influences of the target RCS with frequency band and/or azimuthal correlation to image quality, thereby determines that each high-resolution being respectively directed to
Influences of the reference target RCS of SAR with frequency band and/or azimuthal change to calibrating.
2. the method that a kind of determination high resolution SAR reference target RCS as claimed in claim 1 influences on calibration, its feature
It is that in the step 1, the step-length that frequency bandwidth is set in FEKO softwares is 20MHz, sets the angle step of azimuth beam
It is 0.2 °.
3. the method that a kind of determination high resolution SAR reference target RCS as claimed in claim 2 influences on calibration, its feature
It is for the 2-D data that step 1 is obtained, row interpolation to be entered using cubic spline interpolation so that reference target RCS is with orientation
Angle change data it is consistent with the data point of orientation time-domain signal in the echo-signal in step 2 so that reference target RCS with
The data point of frequency change is consistent with echo signal data middle-range descriscent frequency-domain signal data point in step 2.
4. based on a kind of determinations high resolution SAR reference target RCS as claimed in claim 1 calibration is influenceed to echo
Compensation method, it is characterised in that：Integral energy difference data corresponding with actually used high resolution SAR is found in step 3,
And obtain integration in the maximum and azimuth beamwidth of integral energy difference in the bandwidth of the actually used high resolution SAR
The maximum of energy differences, judges whether two maximums meet at least one more than or equal to 0.2dB, if met：
Actual ghosts signal to the High Resolution SAR of the practical application is compensated；If be unsatisfactory for, it is not necessary to which actual ghosts are believed
Number compensate；
The compensation method is：To the actual ghosts signal in distance to Fourier transformation is done, obtain distance to frequency domain believe
Number；The corresponding reference target RCS of each high accuracy SAR obtained in the step 1 with frequency band and with azimuthal variation two
In dimension data, 2-D data corresponding with the high accuracy SAR of practical application is found, each data point of the 2-D data is asked down respectively
Number；By each sampled point of orientation time-domain signal in actual ghosts signal data with seek the reference target RCS after inverse with orientation
The data of angle change are multiplied after being alignd by azimuth, the orientation time-domain signal data after being compensated；By actual ghosts
Signal data middle-range descriscent each sampled point of frequency-region signal is with the data for asking the reference target RCS after inverse to change with frequency by frequency
It is multiplied after the alignment of rate point, the distance after being compensated is to frequency-domain signal data.
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| CN105301570B (en) * | 2015-10-20 | 2017-07-14 | 中国科学院电子学研究所 | A kind of outfield calibration method of airborne straight rail interference SAR system |
| CN106526547B (en) * | 2016-12-09 | 2019-02-05 | 北京环境特性研究所 | Linear scanning near field RCS based on InSAR technology tests clutter suppression method |
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