CN106908770B - High-resolution microwave imaging satellite star ground integrative simulation method - Google Patents
High-resolution microwave imaging satellite star ground integrative simulation method Download PDFInfo
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
- G01S13/88—Radar or analogous systems specially adapted for specific applications
- G01S13/89—Radar or analogous systems specially adapted for specific applications for mapping or imaging
- G01S13/90—Radar or analogous systems specially adapted for specific applications for mapping or imaging using synthetic aperture techniques, e.g. synthetic aperture radar [SAR] techniques
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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
- G01S7/28—Details of pulse systems
- G01S7/285—Receivers
- G01S7/292—Extracting wanted echo-signals
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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
- G01S13/904—SAR modes
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Abstract
A kind of the present invention provides high-resolution microwave imaging satellite star integrative simulation method comprising following steps：Step 1, the full link error combing in star ground；Step 2, error impact analysis and modeling；Step 3, radar target emulation；Step 4, imaging；Step 5, imaging results assessment.From the star of high-resolution microwave imaging satellite integrated index can realize angle with having combed star in detail full link error factor to the present invention, and be analyzed in terms of the Project Realization feasibility of influence factor index on-orbit calibration demand；Error impact analysis and modeling have been carried out to key influence factor；It is then based on influence factor error model and its with star contacting for integrated index proposes a set of radar target emulation mode；Echo data imaging frame and process are constructed later；Finally provide the appraisal procedure to imaging result.
Description
Technical field
The present invention relates to a kind of aerospace system technical fields, and in particular, to a kind of high-resolution microwave imaging satellite star
Ground integrative simulation method.
Background technique
The characteristics of synthetic aperture radar (SAR) satellite is with its distinctive round-the-clock, round-the-clock earth observation, obtains Liao Ge section
The attention and greatly develop that skill is made the country prosperous, SAR image all has wide application prospect in national economy and national defense construction.High score
Resolution SAR satellite is always the key points and difficulties developed, also the Main way of radar satellite development.
It is fixed that the realization of satellite-borne SAR image quality index is related to satellite platform, load, space propagation, floor treatment, ground
The complicated element in a variety of stars such as mark, geographical information library ground, therefore the also referred to as integrated index in star ground.Star integrated index mainly wrap
Include resolution ratio, imaging bandwidth, peak sidelobe ratio, integral secondary lobe ratio, positioning accuracy, Electrodynamic radiation etc..For high-resolution spaceborne
SAR system, star the influence factor that is related to of integrated index it is more, higher to the index request of each factor, some need to carry out
On-orbit calibration.Therefore, star the realization of integrated index need satellite system and ground system to work closely, conduct a research jointly
And tackling key problem.For a set of designed star integrated index needs to verify its reasonability and realizability existing
With carrying out star on the basis of product design state integrative simulation verifying and evaluation work.Need exist for, it is emphasized that star one
The design of the simulating, verifying of body index with star integrated index is an opposite process, is sure not to obscure logic.Star it is integrated
Changing emulation content mainly includes influence factor combing modeling analysis, radar target emulation and imaging.About star one
The design of body index, Beijing Institute of Aeronautics give detailed design process in pool et al.；About echo simulation, Zhang Shishan, Jin Xueming
It is proposed a kind of new time-frequency mixed algorithm, the theory and mould of analogue echoes is described in detail in Chinese Academy of Sciences electron institute high mountain straits in academic dissertation
The implementation of quasi- source hardware；About imaging, German Alberto Moreira, Josef Mittermayer and Rolf
Scheiber proposes classical ECS algorithm, and Wang Pengbo of Beijing Institute of Aeronautics et al. is proposed to be mentioned for sliding pack and TOPSAR mode
Efficient three steps imaging algorithm is gone out.But reason of certain a part in above most with the being limited to star integrative simulation of research
By research and application, with lacking the star detailed realization of the whole flow process design and each module in process of integrated index Simulation Evaluation
Scheme.
Summary of the invention
For the defects in the prior art, the object of the present invention is to provide a kind of high-resolution microwave imaging satellite star one
Body emulation mode, from the star of high-resolution microwave imaging satellite integrated index can realize angle with having combed star in detail
Full link error factor, and on-orbit calibration demand is analyzed in terms of the Project Realization feasibility of influence factor index；
Error impact analysis and modeling have been carried out to key influence factor；It is then based on influence factor error model and its with star integrated
The connection for changing index proposes a set of radar target emulation mode；Echo data imaging frame and stream are constructed later
Journey；Finally provide the appraisal procedure to imaging result.
According to an aspect of the present invention, a kind of high-resolution microwave imaging satellite star is provided integrative simulation method,
It is characterized in that, it includes the following steps：
Step 1, the full link error combing in star ground；
Step 2, error impact analysis and modeling；
Step 3, radar target emulation；
Step 4, imaging；
Step 5, imaging results assessment.
Preferably, following steps are specifically included in the step 1：
Step 1 11, the star of consideration integrated index include orientation imaging performance index, distance is to imaging performance
Index, positioning accuracy and Electrodynamic radiation；
Step 1 12, with the influencing star satellite platform of integrated index and the combing of load error factor, including when platform
Clock, attitude data, orbital data, SAR system parameter and SAR antenna parameter；
Step 1 13, with influencing star the space error factor combing of integrated index, group delay including ionosphere decline
Subtract, dispersion and flashing and the delay of atmosphere, decaying；
Step 1 14, with influencing star the ground factor combing of integrated index, dynamic range, letter including target scene
Miscellaneous ratio, height accuracy, the bit error rate of ground receiving system, imaging processing system parameter estimating error, Processing Algorithm error, direction
Chart database error, Earth Digital Elevation Model library error, the geometric calibration error of ground calibration system, radiation calibration error,
Pattern measurement error and beam position calibrated error.
Preferably, following steps are specifically included in the step 2：
Step 2 11, the factor of will affect is classified, and specifically including influences SAR system width phase of the distance to imaging performance
Error and SAR antenna error dispersion, ionosphere dispersion, imaging error, Pattern measurement error and beam position calibration miss
Difference, attitude error, orbit error, ionosphere and atmosphere delay error, DEM error, the parameter for influencing orientation imaging performance are estimated
Error, geometric calibration error, imaging error, Pattern measurement error and beam position calibrated error are counted, positioning accurate is influenced
Clocking error, orbit error, geometric calibration mistake, DEM error and the Processing Algorithm error of degree, influence the SAR system of Electrodynamic radiation
Internal calibration error, pattern data library error, parameter estimating error, Processing Algorithm error, radiation calibration error, Pattern measurement
Error and beam position calibrated error, the dynamic range of target scene, signal to noise ratio；
Step 2 12, error, which is attributed to distance to the influence principle of imaging performance, causes linear FM signal abnormal
The amplitude and phase error model of change；Range error model is shown below, and wherein H (ω) is table of the range error in frequency domain
Show, a0For constant term, m is simple harmonic quantity distortion number, amFor error coefficient, cmFor cosine period scale；
Phase error model is shown below,Expression of the phase error in frequency domain, b0For linear phase term coefficient, n
For simple harmonic quantity distortion number, bnFor error coefficient, cnFor cosine period scale；
Step 2 13, influence principle of the error for orientation imaging performance, which is attributed to, to be caused in SAR antenna phase
Oblique distance vector between the heart and ground target changes, this oblique distance include embodied in echo data true oblique distance with
And calculate measurement oblique distance used in Doppler's reference function, star oblique distance variable be shown below, wherein RsatIt (t) is satellite position
Set vector, RtIt (t) is target location vector, c is the light velocity, and Δ τ is for SAR channel time delay error remaining after geometric calibration and greatly
Gas, ionosphere delay time error, orbit error mainly influence Rsat(t), vertical error mainly influences Rt(t)；
| R (t) |=| Rsat(t)-Rt(t)|+cΔτ/2
Step 2 14, influence of the error to positioning accuracy, which mainly divides, surveys rail error, oblique distance error, vertical error and clock
The analysis of error four factors, for clocking error, is introduced primarily into echo data timer error Δ t, causes image along heading
Position error Δ x=VeΔ t, wherein VeFor velocity equivalent；
Step 2 15, influence of the error to Electrodynamic radiation are attributed to the influence of directional diagram error, space loss, imaging
Error, internal calibration and radiation calibration error；Wherein directional diagram error specifically include attitude error, SAR antenna beam error in pointing,
The influence of pattern shapes difference, space loss include atmosphere and ionospheric attenuation；Orientation directional diagram error model such as following formula institute
Show, whereinA、ω0WithRespectively azimuth beam shake amplitude, angular frequency and
Initial phase, DaIt is antenna bearingt to size, VeFor star velocity equivalent, φ are equivalent squint angle, and λ is wavelength, and R is oblique distance；
Distance is shown below to directional diagram error model, wherein θrm、ω0WithRespectively width of the distance to beam jitter
Degree, angular frequency and initial phase,DrIt is antenna distance to size, θr0To roll to wave beam
Off-axis angle.
Preferably, following steps are specifically included in the step 3：
Step 3 11, it is first determined the error model of input parameter, each parameter is determined according to step 2；
Step 3 12, establishes the satellite-Earth model model and pulse signal model of SAR imaging, comprehensive each influence because
Element, calculates original echoed signals, Doppler parameter and radar system parameters, and echo simulation data acquisition process passes through digital imitative
True test, also by semi-physical simulation；
Echo simulation result is packaged by step 3 13, forms data output file.
Preferably, following steps are specifically included in the step 4：
Step 4 11 unpacks raw radar data file, extracts radar running parameter, timing code, orbit parameter, appearance
State parameter, navigation data and SAR raw radar data carry out solution BAQ to SAR raw radar data, channel imbalance corrects in advance
Processing, is decoded radar running parameter and format is converted, and carries out interpolation, time to timing code, orbit parameter, attitude parameter
Alignment work carries out post-processing to original observed quantity of navigating to improve satellite orbit measuring precision；
Step 4 12 utilizes ephemeris parameter, in-orbit geometric calibration data, in-orbit beam position calibration result and DEM number
High-precision Doppler's parameter estimate is carried out according to progress Doppler parameter calculating, and based on raw radar data；
Step 4 13：Imaging is carried out to raw radar data using Doppler parameter and radar running parameter, is obtained
Obtain original complex pattern；
Step 4 14 utilizes scaling constant, in-orbit Pattern measurement data, ground Pattern measurement data and in-orbit several
What nominal data carries out radiant correction and geometric correction to original complex pattern, obtains SAR image secondary product.
Preferably, imaging results assessment is divided into point target assessment and scene objects assessment in the step 5, for a mesh
Marking main evaluation index includes resolution ratio, peak sidelobe ratio, integral secondary lobe ratio, peak power, peak phase, positioning accuracy, spoke
Ejaculation degree, evaluation index main for scene objects include image mean value, variance, dynamic range, equivalent number, radiation resolution
Rate.
Compared with prior art, the present invention has following beneficial effect：The present invention is from high-resolution microwave imaging satellite
Star integrated index can realize angle with having combed star in detail full link error factor, and from the engineering of influence factor index
On-orbit calibration demand is analyzed in terms of realizing feasibility；Error impact analysis has been carried out to key influence factor and has been built
Mould；It is then based on influence factor error model and its with star integrated index contacts that propose a set of radar target imitative
True method；Echo data imaging frame and process are constructed later；Finally provide the appraisal procedure to imaging result.
Detailed description of the invention
Upon reading the detailed description of non-limiting embodiments with reference to the following drawings, other feature of the invention,
Objects and advantages will become more apparent upon：
Fig. 1 be a kind of high-resolution microwave imaging satellite star of the present invention integrative simulation method flow chart.
Fig. 2 is the implementation flow chart of step 3 in the present invention.
Fig. 3 is the implementation flow chart of step 4 in the present invention.
Specific embodiment
The present invention is described in detail combined with specific embodiments below.Following embodiment will be helpful to the technology of this field
Personnel further understand the present invention, but the invention is not limited in any way.It should be pointed out that the ordinary skill of this field
For personnel, without departing from the inventive concept of the premise, various modifications and improvements can be made.These belong to the present invention
Protection scope.
As shown in Figure 1, high-resolution microwave imaging satellite star of the present invention integrative simulation method include the following steps：
Step 1, the full link error combing in star ground；
Step 2, error impact analysis and modeling；
Step 3, radar target emulation；
Step 4, imaging；
Step 5, imaging results assessment.
Following steps are specifically included in step 1：
Step 1 11, the star of consideration integrated index include orientation imaging performance index (containing azimuth resolution,
Orientation peak sidelobe ratio, orientation integrate secondary lobe ratio), distance is to imaging performance index (containing range resolution, distance to peak
Be worth secondary lobe ratio, distance to integral secondary lobe ratio), positioning accuracy and Electrodynamic radiation；
Step 1 12, with the influencing star satellite platform of integrated index and the combing of load error factor, including when platform
Clock, attitude data, orbital data, SAR system parameter and SAR antenna parameter；
Step 1 13, with influencing star the space error factor combing of integrated index, group delay including ionosphere decline
Subtract, dispersion and flashing and the delay of atmosphere, decaying；
Step 1 14, with influencing star the ground factor combing of integrated index, dynamic range, letter including target scene
Miscellaneous ratio, height accuracy, the bit error rate of ground receiving system, imaging processing system parameter estimating error, Processing Algorithm error, direction
Chart database error, Earth Digital Elevation Model library error, the geometric calibration error of ground calibration system, radiation calibration error,
Pattern measurement error and beam position calibrated error.
Following steps are specifically included in step 2：
Step 2 11, the factor of will affect is classified, and specifically including influences SAR system width phase of the distance to imaging performance
Error and SAR antenna error dispersion, ionosphere dispersion, imaging error, Pattern measurement error and beam position calibration miss
Difference, attitude error, orbit error, ionosphere and atmosphere delay error, DEM error, the parameter for influencing orientation imaging performance are estimated
Error, geometric calibration error, imaging error, Pattern measurement error and beam position calibrated error are counted, positioning accurate is influenced
Clocking error, orbit error, geometric calibration mistake, DEM error and the Processing Algorithm error of degree, influence the SAR system of Electrodynamic radiation
Internal calibration error, pattern data library error, parameter estimating error, Processing Algorithm error, radiation calibration error, Pattern measurement
Error and beam position calibrated error, the dynamic range of target scene, signal to noise ratio；
Step 2 12, error can be attributed to distance to the influence principle of imaging performance and cause linear FM signal
The amplitude and phase error model of distortion；Range error model such as following formula (1)：
Wherein H (ω) is expression of the range error in frequency domain, a0For constant term, m is simple harmonic quantity distortion number, amFor error system
Number, cmFor cosine period scale；
Phase error model such as following formula (2)：
WhereinExpression of the phase error in frequency domain, b0For linear phase term coefficient, n is simple harmonic quantity distortion number, bnFor
Error coefficient, cnFor cosine period scale；
Step 2 13, influence principle of the error for orientation imaging performance, which can be attributed to, causes SAR antenna phase
Oblique distance vector between center and ground target changes, this oblique distance include embodied in echo data true oblique distance
And measurement oblique distance used in Doppler's reference function is calculated, star ground oblique distance variable such as following formula (3)：
| R (t) |=| Rsat(t)-Rt(t)|+cΔτ/2 (3)
Wherein RsatIt (t) is satellite position vectors, RtIt (t) is target location vector, c is the light velocity, and Δ τ is after geometric calibration
Remaining SAR channel time delay error and atmosphere, ionosphere delay time error, orbit error mainly influences Rsat(t), vertical error
It is main to influence Rt(t)；
Step 2 14, influence of the error to positioning accuracy, which mainly divides, surveys rail error, oblique distance error, vertical error and clock
The analysis of error four factors, for clocking error, causes position error of the image along heading, such as following formula (4)：
Δ x=Ve·Δt (4)
Wherein Δ x is position error, VeFor velocity equivalent, echo data timer error Δ t；
Step 2 15, influence of the error to Electrodynamic radiation can be attributed to the influence of directional diagram error, space loss, at imaging
Manage error, internal calibration and radiation calibration error；Wherein directional diagram error specifically includes attitude error, SAR antenna beam is directed toward and misses
The influence of difference, pattern shapes difference, space loss includes atmosphere and ionospheric attenuation；Orientation directional diagram error model such as following formula
(5) and (6)：
Wherein Wa0For orientation directional diagram error, A, ω0WithRespectively azimuth beam shake amplitude, angular frequency and
Initial phase, DaIt is antenna bearingt to size, VeFor star velocity equivalent, φ are equivalent squint angle, and λ is wavelength, and R is oblique distance；
Distance is to directional diagram error model such as following formula (7) and (8)：
Wherein Wr0It is distance to directional diagram error, θrm、ω0WithRespectively amplitude of the distance to beam jitter, angular frequency
And initial phase, DrIt is antenna distance to size, θr0To roll to wave beam off-axis angle.
As shown in Fig. 2, specifically including following steps in step 3：
Step 3 11, it is first determined the error model of input parameter, each parameter is determined according to step 2；
Step 3 12, establishes the satellite-Earth model model and pulse signal model of SAR imaging, comprehensive each influence because
Element, calculates original echoed signals, Doppler parameter and radar system parameters, and echo simulation data acquisition process passes through digital imitative
True test, also by semi-physical simulation；
Echo simulation result is packaged by step 3 13, forms data output file.
As shown in figure 3, specifically including following steps in step 4：
Step 4 11 unpacks raw radar data file, extracts radar running parameter, timing code, orbit parameter, appearance
State parameter, navigation data and SAR raw radar data carry out solution BAQ, channel imbalance correction etc. to SAR raw radar data
Pretreatment, radar running parameter is decoded and format conversion, to timing code, orbit parameter, attitude parameter carry out interpolation, when
Between the work such as be directed at, post-processing is carried out to the original observed quantity of navigating to improve satellite orbit measuring precision；
Step 4 12 utilizes ephemeris parameter, in-orbit geometric calibration data, in-orbit beam position calibration result and DEM number
High-precision Doppler's parameter estimate is carried out according to progress Doppler parameter calculating, and based on raw radar data；
Step 4 13：Imaging is carried out to raw radar data using Doppler parameter and radar running parameter, is obtained
Obtain original complex pattern；
Step 4 14 utilizes scaling constant, in-orbit Pattern measurement data, ground Pattern measurement data and in-orbit several
What nominal data carries out radiant correction and geometric correction to original complex pattern, obtains SAR image secondary product.
Following steps are specifically included in step 5：
Imaging results assessment is divided into point target assessment and scene objects assessment.Evaluation index main for point target includes
Resolution ratio, peak sidelobe ratio, integral secondary lobe ratio, peak power, peak phase, positioning accuracy, Electrodynamic radiation；For scene objects
Main evaluation index includes image mean value, variance, dynamic range, equivalent number, radiometric resolution.
The present embodiment takes by taking spaceborne X-band phased array synthetic aperture radar (SAR) as an example with reference to TerraSAR satellite parametric reduction
Value, and certain change is done, orbit altitude value about 580km, SAR antenna size about 4m (A) × 2.4m (R), incidence angle selection
55 °, operating mode selects beam bunching mode, and signal bandwidth takes 500MHz.
Step 1, carries out full link main error factor combing, and each error value is as shown in table 1.
The full link error factor in 1 star of table ground
Step 2, to distance to the relevant range error of imaging performance, error model is assumed to be half period cosine shape, accidentally
The 5th in spread degree value reference table 1, a00, m is taken to take 1, a1Take 2, c1Take 1/ (1500Mhz)；Distance is to phase error, error
Model hypothesis is half period cosine shape, the 5th in error span value reference table 1, b00, n is taken to take 1, b110 ° are taken, c1Take 1/
(1500Mhz) handles in error reference table 1 the 10th.
Error value relevant to orientation imaging performance is referring to the 3rd, 4,8,9,10,11 value in table 1.
Error value relevant to positioning accuracy is referring to the 1st, 3,4,8,9,10,11 value in table 1.
Error value reference table 1 relevant to Electrodynamic radiation, orientation directional diagram takes form error 0.2dB, error in pointing
According to 0.02 ° of fixed value；Distance takes 0.04 ° of fixed error in pointing to directional diagram error, and space loss takes 0.35dB；Imaging
Error takes 0.5dB, internal calibration error to take 0.57dB, and radiation calibration error takes 0.5dB.
Step 3, according to the error law in table 1 in error value and step 2, and according to echo simulation shown in Fig. 2
Frame carries out the echo simulation of beam bunching mode.
Step 4 carries out imaging, processing weighting selection-to echo data using three step imaging algorithms of beam bunching mode
The simplification Taylor of 26dB weighs.
Step 5, here by taking resolution ratio, peak sidelobe ratio, integral secondary lobe ratio, positioning accuracy and Electrodynamic radiation as an example, at
As result is assessed, shown in assessment result table 2.
The assessment of 2 imaging results of table
In conclusion from the star of high-resolution microwave imaging satellite integrated index can realize that angle is combed in detail to the present invention
With having managed star full link error factor, and on-orbit calibration demand is carried out in terms of the Project Realization feasibility of influence factor index
Analysis；Error impact analysis and modeling have been carried out to key influence factor；Be then based on influence factor error model and its with
Star the connection of integrated index propose a set of radar target emulation mode；Echo data imaging frame is constructed later
Frame and process；Finally provide the appraisal procedure to imaging result.
Specific embodiments of the present invention are described above.It is to be appreciated that the invention is not limited to above-mentioned
Particular implementation, those skilled in the art can make various deformations or amendments within the scope of the claims, this not shadow
Ring substantive content of the invention.
Claims (1)
1. a kind of high-resolution microwave imaging satellite star ground integrative simulation method, which is characterized in that it includes the following steps：
Step 1, the full link error combing in star ground；
Step 2, error impact analysis and modeling；
Step 3, radar target emulation；
Step 4, imaging；
Step 5, imaging results assessment；
Following steps are specifically included in the step 1：
Step 1 11, the star of consideration integrated index include orientation imaging performance index, distance to imaging performance index,
Positioning accuracy and Electrodynamic radiation；
Step 1 12, with influencing the star satellite platform of integrated index and the combing of load error factor, including platform clock, appearance
State data, orbital data, SAR system parameter and SAR antenna parameter；
Step 1 13, with the influencing star space error factor combing of integrated index, group delay, decaying including ionosphere,
Dispersion and flashing and the delay of atmosphere, decaying；
Step 1 14, with the influencing star ground factor combing of integrated index, dynamic range, letter including target scene are miscellaneous
Than, height accuracy, the bit error rate of ground receiving system, imaging processing system parameter estimating error, Processing Algorithm error, directional diagram
Database error, Earth Digital Elevation Model library error, geometric calibration error, the radiation calibration error, side of ground calibration system
To figure test error and beam position calibrated error；
Following steps are specifically included in the step 2：
Step 2 11, the factor of will affect is classified, and specifically including influences SAR system amplitude phase error of the distance to imaging performance
With SAR antenna error dispersion, ionosphere dispersion, imaging error, Pattern measurement error and beam position calibrated error, shadow
Attitude error, orbit error, ionosphere and the atmosphere delay error, DEM error, parameter Estimation for ringing orientation imaging performance are missed
Difference, geometric calibration error, imaging error, Pattern measurement error and beam position calibrated error, influence positioning accuracy
Clocking error, orbit error, geometric calibration miss, DEM error and Processing Algorithm error, the SAR system for influencing Electrodynamic radiation are default
Mark error, pattern data library error, parameter estimating error, Processing Algorithm error, radiation calibration error, Pattern measurement error
With beam position calibrated error, the dynamic range of target scene, signal to noise ratio；
Step 2 12, error, which is attributed to distance to the influence principle of imaging performance, causes linear FM signal distortion
Amplitude and phase error model；Range error model is shown below, and wherein H (ω) is expression of the range error in frequency domain, a0
For constant term, m is simple harmonic quantity distortion number, amFor error coefficient, cmFor cosine period scale；
Phase error model is shown below,Expression of the phase error in frequency domain, b0For linear phase term coefficient, n is letter
Humorous distortion number, bnFor error coefficient, cnFor cosine period scale；
Step 2 13, influence principle of the error for orientation imaging performance be attributed to cause SAR antenna phase center with
Oblique distance vector between ground target changes, this oblique distance include embodied in echo data true oblique distance and meter
Calculate measurement oblique distance used in Doppler's reference function, star oblique distance variable be shown below, wherein Rsat(t) it is sweared for satellite position
Amount, Rt(t) be target location vector, c is the light velocity, Δ τ be SAR channel time delay error and atmosphere remaining after geometric calibration,
Ionosphere delay time error, orbit error mainly influence Rsat(t), vertical error mainly influences Rt(t)；
| R (t) |=| Rsat(t)-Rt(t)|+cΔτ/2
Step 2 14, influence of the error to positioning accuracy, which mainly divides, surveys rail error, oblique distance error, vertical error and clocking error
Four factors analysis, for clocking error, is introduced primarily into echo data timer error Δ t, image is caused to determine along heading
Position error delta x=VeΔ t, wherein VeFor velocity equivalent；
Step 2 15, influence of the error to Electrodynamic radiation are attributed to the influence of directional diagram error, space loss, imaging mistake
Difference, internal calibration and radiation calibration error；Wherein directional diagram error specifically includes attitude error, SAR antenna beam error in pointing, side
Influence to diagram shape difference, space loss include atmosphere and ionospheric attenuation；Orientation directional diagram error model is shown below,
WhereinA、ω0WithRespectively azimuth beam shake amplitude, angular frequency and just
Beginning phase, DaIt is antenna bearingt to size, VeFor star velocity equivalent, φ are equivalent squint angle, and λ is wavelength, and R is oblique distance；
Distance is shown below to directional diagram error model, wherein θrm、ω0WithRespectively amplitude from distance to beam jitter,
Angular frequency and initial phase,DrIt is antenna distance to size, θr0For roll to wave beam from
Shaft angle,
Following steps are specifically included in the step 3：
Step 3 11, it is first determined the error model of input parameter, each parameter is determined according to step 2；
Step 3 12 establishes the satellite-Earth model model and pulse signal model of SAR imaging, comprehensive each influence factor, meter
Original echoed signals, Doppler parameter and radar system parameters are calculated, echo simulation data acquisition process is tried by full digital trigger technique
It tests, also by semi-physical simulation；
Echo simulation result is packaged by step 3 13, forms data output file；
Following steps are specifically included in the step 4：
Step 4 11 unpacks raw radar data file, extracts radar running parameter, timing code, orbit parameter, posture ginseng
Number, navigation data and SAR raw radar data carry out solution BAQ, channel imbalance correction pretreatment to SAR raw radar data,
Radar running parameter is decoded and format is converted, interpolation, time alignment are carried out to timing code, orbit parameter, attitude parameter
Work carries out post-processing to original observed quantity of navigating to improve satellite orbit measuring precision；
Step 4 12, using ephemeris parameter, in-orbit geometric calibration data, in-orbit beam position calibration result and dem data into
Row Doppler parameter calculates, and carries out high-precision Doppler's parameter estimate based on raw radar data；
Step 4 13：Imaging is carried out to raw radar data using Doppler parameter and radar running parameter, is obtained former
Beginning complex pattern；
Step 4 14 utilizes scaling constant, in-orbit Pattern measurement data, ground Pattern measurement data and in-orbit geometry mark
Fixed number carries out radiant correction and geometric correction according to original complex pattern, obtains SAR image secondary product；
Imaging results assessment is divided into point target assessment and scene objects assessment in the step 5, and point target is mainly assessed and is referred to
Mark includes resolution ratio, peak sidelobe ratio, integral secondary lobe ratio, peak power, peak phase, positioning accuracy, Electrodynamic radiation, for field
The main evaluation index of scape target includes image mean value, variance, dynamic range, equivalent number, radiometric resolution.
Priority Applications (1)
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