CN106886021A - High Resolution Spaceborne SAR image quality method for improving - Google Patents

High Resolution Spaceborne SAR image quality method for improving Download PDF

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CN106886021A
CN106886021A CN201710055238.8A CN201710055238A CN106886021A CN 106886021 A CN106886021 A CN 106886021A CN 201710055238 A CN201710055238 A CN 201710055238A CN 106886021 A CN106886021 A CN 106886021A
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error
sar
image quality
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target
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CN106886021B (en
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范季夏
薛伶玲
姜岩
涂上坦
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Shanghai Institute of Satellite Engineering
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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
    • G01S13/9056—Scan SAR mode
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
    • G01S13/88—Radar or analogous systems specially adapted for specific applications
    • G01S13/89—Radar or analogous systems specially adapted for specific applications for mapping or imaging
    • G01S13/90—Radar or analogous systems specially adapted for specific applications for mapping or imaging using synthetic aperture techniques, e.g. synthetic aperture radar [SAR] techniques
    • G01S13/904—SAR modes

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

Abstract

The invention provides a kind of High Resolution Spaceborne SAR image quality method for improving, it is comprised the following steps：Step one, image quality lifting demand analysis and image quality index combing based on High Resolution SAR Images application；Step 2, is optimized as quality index is decomposed and is distributed；Step 3, proposes the measure of lifting image quality；Step 4, the image quality lifting recruitment evaluation based on full link simulation.Method flow proposed by the invention is clear, be easily achieved, and has directive significance for satellite-borne SAR master-plan, with initiative, it is adaptable to the image quality Study of Lifting of other types of SAR satellites.

Description

High Resolution Spaceborne SAR image quality method for improving
Technical field
The present invention relates to a kind of aerospace system technical field, in particular it relates to a kind of High Resolution Spaceborne SAR image quality Method for improving.
Background technology
Since U.S. NASA in 1978 launches first synthetic aperture radar (SAR) satellite, there is more than 50 thunder Up to satellite launch and operation on orbit.The characteristics of Synthetic Aperture Radar satellite is with its distinctive round-the-clock, round-the-clock earth observation, obtains To it is each science and technology power attention and greatly develop.High resolution SAR satellite is always the emphasis and difficult point of development, and also radar is defended The Main way of star development.
The requirement to SAR image resolution ratio is scouted and monitored according to the U.S., battlefield target detection, resolution ratio should be better than 0.9m；Target is identified, resolution ratio should be better than 0.6m；Target is confirmed and is described, resolution ratio should be better than 0.3m.Can See, high resolution SAR satellite is particularly important for high accuracy targeted surveillance.Meanwhile, high resolution SAR satellite is general in land resources Look into, survey and draw, prevent and reduce natural disasters it is middle played irreplaceable effect, the assessment for the condition of a disaster is generally needed better than 2m resolution ratio SAR image.At present, the resolution ratio of typical satellite-borne SAR is most in 1m~3m magnitudes, such as TerraSAR of Germany in the world Satellite and Canadian RadarSat-2 satellites highest resolution are 1m.It can be seen that, the lifting of resolution ratio index has widely should Use demand.
Meanwhile, in the world during in-orbit SAR satellite images use, it was also proposed that image quality lifting must be asked, and mainly be had The following aspects：
1st, it is even on image under the weak background such as sea when the region to the change of land and sea junction target dynamic greatly is imaged You occur " ghost " target, and mainly SAR fuzzy indicators are relatively low caused, it is necessary to be lifted to fuzziness index.
2nd, the noise of some satellite-borne SAR images is poor, the detectivity to target on image is influenceed, mainly due to system Insufficient sensitivity is high, therefore, it is necessary to lifting system sensitivity index.
3rd, each sub- bar radiative interband uneven " scallop effect " in occurring in SCANSAR images, mainly by the attitude of satellite Caused by error and Beam steering error influence, it is therefore desirable to which Electrodynamic radiation is lifted.
First it is need of the external typical case's application for imaging lifting above from two angle analysis image quality lifting demands Ask；Secondly the demand of image increased quality is analyzed from the problem and shortage in in-orbit SAR satellite applications.At home and abroad spaceborne SAR fields, for High Resolution Spaceborne SAR image quality Upgrade Problem, lack a kind of general method always, for instructing to carry Rise the design of Space-borne SAR Imaging quality index.
The content of the invention
For defect of the prior art, carried it is an object of the invention to provide a kind of High Resolution Spaceborne SAR image quality Lifting method, method flow that it is proposed is clear, be easily achieved, and has directive significance for satellite-borne SAR master-plan, with opening It is invasive, it is adaptable to the image quality Study of Lifting of other types of SAR satellites.
According to an aspect of the present invention, there is provided a kind of High Resolution Spaceborne SAR image quality method for improving, its feature exists In it is comprised the following steps：
Step one, image quality lifting demand analysis and image quality index comb based on High Resolution SAR Images application Reason；
Step 2, is optimized as quality index is decomposed and is distributed；
Step 3, proposes the measure of lifting image quality；
Step 4, the image quality lifting recruitment evaluation based on full link simulation.
Preferably, following steps are specifically included in the step one：
Step one 11, based on the present situation that existing SAR satellite capacities are not enough, it is considered to typical target ground in SAR image application High accuracy recognizes and confirms demand, high accuracy mapping demand, accurate the condition of a disaster evaluation requirement；Meanwhile, used for current SAR image In fundamental problems propose that the lifting of image quality index is required, these fundamental problems include that the SAR in land and sea junction region schemes As ambiguity issue, signal noise ratio (snr) of image deficiency, point target secondary lobe problem, positioning precision problem not high, SCANSAR image scallops are asked Topic；
Step one 12, analysis result is carded to as quality index system according to demand, and provides the lifting requirement of quantization； Image quality index at least consider resolution ratio, peak sidelobe ratio, integration secondary lobe ratio, system sensitivity, azimuth ambiguity degree, apart from mould Paste degree, positioning precision and Electrodynamic radiation.
Preferably, the step 2 specifically includes following steps：
Step 2 11, is created as quality index formula and its relational model with influence factor；
Orientation ground resolutionWherein VgTo be imaged the ground velocity of zone position, Bp It is the doppler processing bandwidth of single target, k1For orientation directional diagram weights ceofficient of spread, k2It is imaging weighting broadening system Number, k3It is the ceofficient of spread that Doppler parameter error causes, k4For the ceofficient of spread that imaging algorithm causes；
Apart from earthward resolution ratioWherein c is the light velocity, and η is incidence angle, BrIt is letter Number bandwidth, k1For imaging weights ceofficient of spread, k2It is the ceofficient of spread that SAR system amplitude phase error and dispersion cause, k3It is into As the ceofficient of spread that algorithm causes；
Peak sidelobe ratio PSLR=PSLR0-ΔPSLR1-ΔPSLR2, wherein ΔPSLR1It is that SAR system amplitude phase error and dispersion are drawn The secondary lobe for rising is than decline, ΔPSLR2For the secondary lobe ratio that imaging error is introduced declines, PSLR0It is the reason under particular procedure weighting By peak sidelobe ratio,PsmaxIt is the highest side lobe peak power of point target impulse response, PmIt is a mesh Mark the main lobe peak-peak power of impulse response；
Integration secondary lobe compares ISLR=ISLR0-ΔISLR1-ΔISLR2, wherein ΔISLR1It is that SAR system amplitude phase error and dispersion are drawn The secondary lobe for rising is than decline, ΔISLR2For the secondary lobe ratio that imaging error is introduced declines, ISLR0It is the reason under particular procedure weighting By integration secondary lobe ratio,H (r) is point target impulse response function, integration It is main lobe region within domain (a, b), is secondary lobe region beyond main lobe；
System sensitivityIt is worst in imaging region NEσ0=max (NE σ0(σa,θr)), wherein, TeFor system imitates noise temperature, k is Boltzmann constant, L (σa) it is system loss, VstIt is relative ground velocity, σaIt is orientation aiming spot, R (θr) it is target to distance by radar, λ is centre carrier frequency wavelength, It is emission peak power, tpIt is transmitting pulse time width, G2(θr) the corresponding gain for pointing to angle, ρ in directional diagram for targetrBe away from Descriscent resolution ratio, fpIt is transmitting pulse recurrence frequency, θrIt is the downwards angle of visibility value in imaging region；
Azimuth ambiguity degreeWherein i is in orientation imaging belt Impact point sequence number, K is impact point quantity, i=1,2 ... K, σiIt is orientation aiming spot, N is the beam scanning angle for quantifying Positional number, fn(σi) it is σiThe corresponding Doppler frequency value of n-th scanning Angle Position of impact point, n=1,2,3 ... N, Δ fdc It is Doppler center frequency error,It is n-th Doppler energy spectrum of scanning Angle Position, fpFor pulse repeats frequency Rate, m is confusion region sequence number；
Distance is to fuzziness RASR=max (RASR (τi)), whereinIn formulaN is Confusion region sequence number, confusion region sequence number when theoretical maximum is the tangent earth,It is distance to transmitting-receiving round trip equivalent aerial side Xiang Tu, τiIt is the echo time delay of target i, fpIt is pulse recurrence frequency, θiIt is incidence angle, σ0It is target back scattering system in scene Number, R (τi) it is oblique distance of the observation with interior target i, R (τi+n/fp) it is the oblique distance for observing the fuzzy object with interior target i；
Target location accuracyWherein Δ X1It is satellite The orientation position error that course made good site error causes, Δ X2It is the orientation position error that satellite velocities error causes, Δ X3 It is the orientation position error that echo data timer error causes, Δ R1It is satellite determining perpendicular to the site error introducing of flight path Position error, Δ R2It is the position error that satellite radial position error is introduced, Δ R3It is the position error that oblique distance measurement error is introduced, ΔR4For the position error that target vertical error is introduced；
Electrodynamic radiation Wherein Δ G (φ) is directional diagram error, Δ K0It is scaling constant error, Δ CalinIt is SAR system internal calibration error, Δ Q is amount Change error, Δ N be influence of the noise level to Electrodynamic radiation, Δ AASR, Δ RASR and Δ ISLR be azimuth ambiguity degree, apart from mould The influence of paste degree and integration secondary lobe ratio error to Electrodynamic radiation, Δ LsIt is electromagnetic wave Dissipation change in the air, Δ GimgImaging Process the error for introducing；
Step 2 12, is created as quality index exploded relationship figure, and the influence factor of decomposition is measured including satellite orbit Data down transmission speed and the bit error rate, SAR system on clock accuracy, star on precision, attitude measurement accuracy, power satellite ability, star Signal bandwidth, SAR system amplitude phase error, SAR antennas error dispersion, SAR system noise coefficient, system loss, SAR antenna chis It is very little, SAR antenna radiated powers, SAR antenna efficiencies, SAR antenna radiation patterns precision, imaging error, on-orbit calibration error, big Gas and ionosphere effect, ground digital elevation model；
Step 2 13, the quantization that influence factor is carried out to each image quality index according to exploded relationship figure is decomposed and divided Match somebody with somebody, thus obtain each image quality index realize required for satellite system, space propagation and ground system each influence because The lifting requirement of plain index；The current of the index value of each influence factor realizes level vector Factor0Represent, and realize institute Need the value that image quality index needs vector FactorMinRepresent, the finger that each influence factor is realized after tackling problems in key technologies Mark vector FactorPromoteRepresent, each influence factor optimal value vector FactorOptimumRepresent；
Step 2 14, the value mode of distribution or each influence factor on image quality index is realizing image quality The cost performance of index is up to criterion；Performance represents that wherein S represents the performance after lifting with equation below, and i is expressed as picture Quality index is numbered, and N is expressed as quality index quantity, wiRepresent i-th weight of index, PromTimesiRepresent i-th finger Target lifts multiplying power；
Cost with each influence factor elevator belt come cost summation represent that shown in equation below, wherein Cost represents total generation Valency, j represents that influence factor is numbered, and M represents influence factor quantity, uiRepresent j-th weight of index, cost_of_factjRepresent J-th cost of influence factor realization；Thus, cost performance is expressed as S/Cost；
Step 2 15, to be implemented as quality index lifting, each influence factor value must be better than vector FactorMin The numerical value of expression；Some existing levels meet in each factor, amount of orientation Factor0In corresponding factor value；Some factors need Carry out tackling problems in key technologies just to touch the mark, amount of orientation FactorPromoteIn corresponding factor value；By the combination of each influence factor Traveled through, it is optimal as criterion with cost performance S/Cost, obtain optimal influence factor mix vector FactorOptimum。
Preferably, the image quality lifting recruitment evaluation based on full link simulation in the step 4, its method is profit Full link semi-physical system is built with satellite-borne SAR product and radar target simulator, with FactorAchieveFor defeated Enter, carry out the semi-physical simulation of image quality index, the echo data to enrolling carries out imaging and index evaluation, from And the effective evaluation that effect is lifted to image quality is obtained, if without satellite-borne SAR product and radar target simulator, Image quality lifting effect is evaluated using full digital trigger technique.
Preferably, propose that the measure of lifting image quality proposes the measure of lifting image quality in the step 3, its pass Key is with vectorial FactorOptimumIn each influence factor value be input, carry out each subsystem of satellite platform, SAR load point System, Ground Processing System, ground calibration system, the tackling problems in key technologies in ground digital elevation model storehouse, conceptual design and product Product are developed, and each influence factor finally realizes index vector FactorAchieveRepresent.
Compared with prior art, the present invention has following beneficial effect：Method flow proposed by the invention is clear, easy In realization, there is directive significance for satellite-borne SAR master-plan, with initiative, it is adaptable to other types of SAR satellites into As increased quality research.
Brief description of the drawings
The detailed description made to non-limiting example with reference to the following drawings by reading, further feature of the invention, Objects and advantages will become more apparent upon：
Fig. 1 is the flow chart of High Resolution Spaceborne SAR image quality method for improving of the present invention.
Specific embodiment
With reference to specific embodiment, the present invention is described in detail.Following examples will be helpful to the technology of this area Personnel further understand the present invention, but the invention is not limited in any way.It should be pointed out that to the ordinary skill of this area For personnel, without departing from the inventive concept of the premise, some deformations and improvement are also made.These belong to guarantor of the invention Shield scope.
As shown in figure 1, High Resolution Spaceborne SAR image quality method for improving of the present invention is comprised the following steps：
Step one, image quality lifting demand analysis and image quality index comb based on High Resolution SAR Images application Reason；
Step 2, is optimized as quality index is decomposed and is distributed；
Step 3, proposes the measure of lifting image quality；
Step 4, the image quality lifting recruitment evaluation based on full link simulation.
Specifically, comprised the following steps in step one：
Step one 11, based on the present situation that existing SAR satellite capacities are not enough, it is considered to typical target ground in SAR image application High accuracy recognizes and confirms demand, high accuracy mapping demand, accurate the condition of a disaster evaluation requirement；Meanwhile, used for current SAR image In fundamental problems propose that the lifting of image quality index is required, these fundamental problems include that the SAR in land and sea junction region schemes As ambiguity issue, signal noise ratio (snr) of image deficiency, point target secondary lobe problem, positioning precision problem not high, SCANSAR image scallops are asked Topic；
Step one 12, analysis result is carded to as quality index system according to demand, and provides the lifting requirement of quantization； Image quality index at least considers resolution ratio (ρ), peak sidelobe ratio (PSLR), integration secondary lobe ratio (ISLR), system sensitivity (NE σ 0), azimuth ambiguity degree (AASR), range ambiguity (RASR), positioning precision (Δ P) and Electrodynamic radiation (Δ R).
Step 2 specifically includes following steps：
Step 2 11, is created as quality index formula and its relational model with influence factor.
Orientation ground resolution, such as following formula (1)：
Its intermediate-resolution ρ, Vg are the ground velocity for being imaged zone position, and Bp is the doppler processing bandwidth of single target, and k1 is side Position weights ceofficient of spread to directional diagram, and k2 is that imaging weights ceofficient of spread, and k3 is the broadening that Doppler parameter error causes Coefficient, the ceofficient of spread that k4 causes for imaging algorithm.
Apart from earthward resolution ratio, such as following formula (2)：
Wherein c is the light velocity, and η is incidence angle, BrIt is signal bandwidth, k1 is that imaging weights ceofficient of spread, and k2 is SAR systems The ceofficient of spread that system amplitude phase error and dispersion cause, the ceofficient of spread that k3 causes for imaging algorithm.
Peak sidelobe ratio, such as following formula (3)：
PSLR=PSLR0-ΔPSLR1-ΔPSLR2 (3)
Wherein ΔPSLR1For the secondary lobe ratio that SAR system amplitude phase error and dispersion cause declines, ΔPSLR2It is imaging error The secondary lobe of introducing is than decline, PSLR0It is the theoretical peak secondary lobe ratio under particular procedure weighting, computational methods such as following formula (4)：
PsmaxIt is the highest side lobe peak power of point target impulse response, PmIt is the main lobe top of point target impulse response Value power.
Integration secondary lobe ratio, such as following formula (5)：
ISLR=ISLR0-ΔISLR1-ΔISLR2 (5)
Wherein ΔISLR1For the secondary lobe ratio that SAR system amplitude phase error and dispersion cause declines, ΔISLR2It is imaging error The secondary lobe of introducing is than decline, ISLR0Theoretical integration secondary lobe ratio under for particular procedure weighting, computational methods such as following formula (6)：
Wherein h (r) is point target impulse response function, is main lobe region within limit of integration (a, b), is secondary lobe beyond main lobe Region.
System sensitivity, such as following formula (7)：
It is worst specific such as following formula (8) in imaging region：
NEσ0=max (NE σ0(σa,θr)) (8)
Wherein, TeIt is system equivalent noise temperature, k is Boltzmann constant, L (σa) it is system loss, VstFor relatively Speed, σaIt is orientation aiming spot, R (θr) it is target to distance by radar, λ is centre carrier frequency wavelength,It is emission peak Power, tpIt is transmitting pulse time width, G2(θr) the corresponding gain for pointing to angle, ρ in directional diagram for targetrIt is range resolution, fpIt is transmitting pulse recurrence frequency, θrIt is the downwards angle of visibility value in imaging region.
Azimuth ambiguity degree, such as following formula (9)：
Wherein i is impact point sequence number in orientation imaging belt, and K is impact point quantity, i=1,2 ... K, σiIt is orientation Aiming spot, N is the beam scanning Angle Position number for quantifying, fn(σi) it is σiN-th scanning Angle Position of impact point is corresponding more General Le frequency values, n=1,2,3 ... N, Δ fdcIt is Doppler center frequency error,It is n-th scanning Angle Position Doppler energy spectrum, fpIt is pulse recurrence frequency, m is confusion region sequence number.
Distance is to fuzziness, such as following formula (10)：
RASR=max (RASR (τi)) (10)
WhereinComputational methods such as following formula (11) and (12)：
Wherein n is confusion region sequence number, and theoretical maximum is the confusion region sequence number when earth is tangent,It is distance to receipts Hair round trip equivalent aerial directional diagram, τiIt is the echo time delay of target i, fpIt is pulse recurrence frequency, θiIt is incidence angle, σ0It is scene Interior target backscattering coefficient, R (τi) it is oblique distance of the observation with interior target i, R (τi+n/fp) it is fuzzy with interior target i observation The oblique distance of target.
Target location accuracy, such as following formula (13)：
Wherein Δ X1It is the orientation position error that satellite course made good site error causes, Δ X2For satellite velocities error is drawn The orientation position error for rising, Δ X3It is the orientation position error that echo data timer error causes, Δ R1For satellite perpendicular to The position error that the site error of flight path is introduced, Δ R2It is the position error that satellite radial position error is introduced, Δ R3For oblique distance is surveyed The position error that amount error is introduced, Δ R4For the position error that target vertical error is introduced.
Electrodynamic radiation, such as following formula (14)：
Wherein Δ G (φ) is directional diagram error, Δ K0It is scaling constant error, Δ CalinIt is SAR system internal calibration error, Δ Q is quantization error, and Δ N is influence of the noise level to Electrodynamic radiation, and Δ AASR, Δ RASR and Δ ISLR are azimuth ambiguity The influence of degree, range ambiguity and integration secondary lobe ratio error to Electrodynamic radiation, Δ LsIt is electromagnetic wave Dissipation change in the air, ΔGimgThe error that imaging is introduced.
Step 2 12, is created as quality index exploded relationship figure, and the influence factor of decomposition is measured including satellite orbit Data down transmission speed and the bit error rate, SAR system on clock accuracy, star on precision, attitude measurement accuracy, power satellite ability, star Signal bandwidth, SAR system amplitude phase error, SAR antennas error dispersion, SAR system noise coefficient, system loss, SAR antenna chis It is very little, SAR antenna radiated powers, SAR antenna efficiencies, SAR antenna radiation patterns precision, imaging error, on-orbit calibration error, big Gas and ionosphere effect, ground digital elevation model etc.；
Step 2 13, the quantization that influence factor is carried out to each image quality index according to exploded relationship figure is decomposed and divided Match somebody with somebody, thus obtain each image quality index realize required for satellite system, space propagation and ground system each influence because The lifting requirement of plain index；The currently achievable level vector Factor of the index value of each influence factor0Represent, and realize The value that required image quality index needs vector FactorMinRepresent, each influence factor can be real after tackling problems in key technologies Existing index vector FactorPromoteRepresent, each influence factor optimal value vector FactorOptimumRepresent；
Step 2 14, the value mode of distribution or each influence factor on image quality index is realizing image quality The cost performance of index is up to criterion；Wherein S represents the performance after lifting, and i is expressed as quality index numbering, and N is represented Image quality index quantity, wiRepresent i-th weight of index, PromTimesiI-th lifting multiplying power of index is represented, it is as follows Formula (15)：
Cost with each influence factor elevator belt come cost summation represent that wherein Cost represents total cost, j represent influence because Element numbering, M represents influence factor quantity, uiRepresent j-th weight of index, cost_of_factjRepresent j-th influence factor The cost of realization；Thus, cost performance is expressed as S/Cost, such as following formula (16)：
Step 2 15, to be implemented as quality index lifting, each influence factor value must be better than vector FactorMin The numerical value of expression；Some existing levels can meet in each factor, i.e. amount of orientation Factor0In corresponding factor value；Have A little factors need to carry out tackling problems in key technologies to can be only achieved index, i.e. amount of orientation FactorPromoteIn corresponding factor value；Will be each The combination of influence factor is traveled through, optimal as criterion with cost performance S/Cost, obtains optimal influence factor mix vector FactorOptimum。
The measure of lifting image quality is proposed in step 3, it is critical only that with vectorial FactorOptimumIn each influence because Plain value for input, carry out each subsystem of satellite platform, SAR load subsystem, Ground Processing System, ground calibration system, The tackling problems in key technologies in face digital elevation model storehouse, conceptual design and product development, each influence factor finally realize index with to Amount FactorAchieveRepresent.
Image quality lifting recruitment evaluation based on full link simulation in step 4, its method is to be produced using satellite-borne SAR Product and radar target simulator build full link semi-physical system, with FactorAchieveIt is input, carries out imaging matter The semi-physical simulation of figureofmerit, the echo data to enrolling carries out imaging and index evaluation, so as to obtain to imaging The effective evaluation of increased quality effect.If without satellite-borne SAR product and radar target simulator, it would however also be possible to employ total Word emulation is evaluated image quality lifting effect.
The present embodiment by taking spaceborne X-band phased array synthetic aperture radar (SAR) as an example, with reference to TerraSAR satellite parametric reductions, Orbit altitude value about 500km, power satellite ability is about 3000W, SAR antenna sizes about 5m (A) × 1m (R), peak value radiation Power about 3500W, incidence angle takes 30 °, and four image quality indexs are only considered in example：Azimuth resolution, distance is to resolution Rate, system sensitivity and positioning precision, the image quality index before lifting：Resolution ratio is about 3m, and system sensitivity is about- 17dB, positioning precision is about 50m, and the present embodiment is comprised the following steps：
Step one, the different application situation according to SAR image is carded to as increased quality demand, it is assumed that needed in this example Ask for：Range resolution ratio is promoted to 0.55m, azimuth resolution and is promoted to 0.6m, system sensitivity by -17dB by 3m by 2.82m Be promoted to -26.75dB, positioning precision and 6.2m be promoted to by 41.97m, it is considered to 4 liftings of image quality index, lifting before into As quality index vector Spec0Represent, each index value is spec_valuei(i=1,2,3,4)；Assuming that being attacked through key technology Guan Hou, image quality index vector SpecPromoteRepresent；Each index optimal value vector SpecOptimumRepresent；Defended Finally index vector Spec is realized after star Design and DevelopmentAchieveRepresent.
Step 2, is created as quality index exploded relationship figure, and this example mainly considers that the influence factor decomposed includes defending Clock accuracy, SAR system signal bandwidth, SAR system on star orbital road certainty of measurement, attitude measurement accuracy, power satellite ability, star Amplitude phase error (being divided into amplitude and phase), SAR system noise coefficient, system loss, SAR antenna sizes (be divided into orientation and away from Descriscent), SAR antenna radiated powers, SAR antenna efficiencies, SAR antenna radiation patterns precision (this example mainly consider beam position essence Degree and form accuracy), imaging error (this example mainly considers to adjust estimated frequency error and the broadening that causes for the treatment of error), On-orbit calibration error (this example considers oblique distance calibrated error) and ground digital elevation model error totally ten five, it is considered in bracket Subitem launches totally ten nine, and each factor value is fac_valuej(j=1,2 ... ... 19).
The quantization that influence factor is carried out to each image quality index according to exploded relationship figure is decomposed and distributed.Current Factor0Value be set to [10m, 0.03 °, 3000W, 3ms, 100MHz, 4dB, 10 °, 5dB, 2.5dB, 5m (A), 1m (R), 3500W, 65%, 0.05 °, 0.5dB, 0.5Hz/s, 1.01,5m, 30m]；
Assuming that after through tackling problems in key technologies, the indicator vector Factor that each influence factor can be realizedPromoteFor [0.5m, 0.01 °, 10000W, 0.1ms, 500MHz, 1dB, 5 °, 3dB, 0.5dB, 5m (A), 1m (R), 15000W, 85%, 0.01 °, 0.2dB, 0.03Hz/s, 1.01,1m, 5m].Through simulation analysis, each influence required for realizing the image quality index after lifting Factor value tolerance limit is vector FactorMin, value better than [0.5m, 0.01 °, 9000W, 0.1ms, 500MHz, 1.5dB, 10 °, 3.2dB, 1dB, 5m (A), 1m (R), 10000W, 80%, 0.01 °, 0.2dB, 0.05Hz/s, 1.01,2m, 5m].
This example weighting weight wi=1/N (i=1,2 ... ... N), N=4；ui=1/M (j=1,2 ... ... M), M=19.It is right In Factor0, cost_of_factj=1 (j=1,2 ... ... M), M=19, PromTimesi=1 (i=1,2 ... ... N), root According to formula (15) and (16), S/Cost=1, for FactorOptimum, such as following formula (20) and (21)：
Diminish for numerical value and embody the factor that index lifts and take Sgn () and take+1, otherwise take -1.It is all above to be related to logarithm Being both needed to of dimension is calculated again after being scaled range value.
In order to obtain best price/performance ratio S/Cost, after excessive wheel iterative calculation, acquisition FactorOptimumFor [0.5m, 0.01 °, 11000W, 0.1ms, 500MHz, 1.5dB, 10 °, 3.5dB, 1dB, 5m (A), 1m (R), 10000W, 80%, 0.01 °, 0.2dB, 0.05Hz/s, 1.01,2m, 5m].Now, optimal S/Cost is 1.64.
Step 3, with vectorial FactorOptimumIn each influence factor value be input, propose that lifting image quality is arranged Apply, and implement in each subsystem of satellite platform, SAR load subsystem, Ground Processing System, ground calibration system, ground digital In elevation model storehouse, and then the Spanning Star each scheme Design in ground and product development, each influence factor finally realize index be to Amount FactorAchieve。
Step 4, full link semi-physical system is built using satellite-borne SAR product and radar target simulator, with FactorAchieveIt is input, carries out the semi-physical simulation of image quality index, the echo data to enrolling is carried out at imaging Reason and index evaluation, so as to obtain the effective evaluation that effect is lifted to image quality.If without satellite-borne SAR product and radar mesh Mark echo simulator, it would however also be possible to employ full digital trigger technique is evaluated image quality lifting effect.
In sum, using method flow proposed by the invention it is clear, be easily achieved, for satellite-borne SAR master-plan With directive significance, with initiative, it is adaptable to the image quality Study of Lifting of other types of SAR satellites.
Specific embodiment of the invention is described above.It is to be appreciated that the invention is not limited in above-mentioned Particular implementation, those skilled in the art can within the scope of the claims make various deformations or amendments, this not shadow Sound substance of the invention.

Claims (5)

1. a kind of High Resolution Spaceborne SAR image quality method for improving, it is characterised in that it is comprised the following steps：
Step one, image quality lifting demand analysis and image quality index combing based on High Resolution SAR Images application；
Step 2, is optimized as quality index is decomposed and is distributed；
Step 3, proposes the measure of lifting image quality；
Step 4, the image quality lifting recruitment evaluation based on full link simulation.
2. High Resolution Spaceborne SAR image quality method for improving according to claim 1, it is characterised in that the step Following steps are specifically included in one：
Step one 11, based on the present situation that existing SAR satellite capacities are not enough, it is considered to which typical target ground is high-precision in SAR image application Degree identification and confirmation demand, high accuracy mapping demand, accurate the condition of a disaster evaluation requirement；Meanwhile, in current SAR image use Fundamental problems propose that the lifting of image quality index requires that these fundamental problems include the SAR image mould in land and sea junction region Paste degree problem, signal noise ratio (snr) of image deficiency, point target secondary lobe problem, positioning precision problem not high, SCANSAR image scallop problems；
Step one 12, analysis result is carded to as quality index system according to demand, and provides the lifting requirement of quantization；Imaging Quality index at least considers resolution ratio, peak sidelobe ratio, integration secondary lobe ratio, system sensitivity, azimuth ambiguity degree, range ambiguity Degree, positioning precision and Electrodynamic radiation.
3. High Resolution Spaceborne SAR image quality method for improving according to claim 1, it is characterised in that the step Two specifically include following steps：
Step 2 11, is created as quality index formula and its relational model with influence factor；
Orientation ground resolutionWherein VgTo be imaged the ground velocity of zone position, BpFor single The doppler processing bandwidth of target, k1For orientation directional diagram weights ceofficient of spread, k2For imaging weights ceofficient of spread, k3 It is the ceofficient of spread that Doppler parameter error causes, k4For the ceofficient of spread that imaging algorithm causes；
Apart from earthward resolution ratioWherein c is the light velocity, and η is incidence angle, BrIt is signal band Width, k1For imaging weights ceofficient of spread, k2It is the ceofficient of spread that SAR system amplitude phase error and dispersion cause, k3For imaging is calculated The ceofficient of spread that method causes；
Peak sidelobe ratio PSLR=PSLR0-ΔPSLR1-ΔPSLR2, wherein ΔPSLR1For SAR system amplitude phase error and dispersion cause Secondary lobe is than decline, ΔPSLR2For the secondary lobe ratio that imaging error is introduced declines, PSLR0It is the theoretical peak under particular procedure weighting Value secondary lobe ratio,PsmaxIt is the highest side lobe peak power of point target impulse response, PmFor point target is rushed Swash the main lobe peak-peak power of response；
Integration secondary lobe compares ISLR=ISLR0-ΔISLR1-ΔISLR2, wherein ΔISLR1For SAR system amplitude phase error and dispersion cause Secondary lobe is than decline, ΔISLR2For the secondary lobe ratio that imaging error is introduced declines, ISLR0It is the theory product under particular procedure weighting Divide secondary lobe ratio,H (r) is point target impulse response function, limit of integration It is main lobe region within (a, b), is secondary lobe region beyond main lobe；
System sensitivityWorst NE σ in imaging region0= max(NEσ0(σa,θr)), wherein, TeFor system imitates noise temperature, k is Boltzmann constant, L (σa) it is system loss, VstFor With respect to ground velocity, σaIt is orientation aiming spot, R (θr) it is target to distance by radar, λ is centre carrier frequency wavelength,It is hair Penetrate peak power, tpIt is transmitting pulse time width, G2(θr) the corresponding gain for pointing to angle, ρ in directional diagram for targetrBe distance to Resolution ratio, fpIt is transmitting pulse recurrence frequency, θrIt is the downwards angle of visibility value in imaging region；
Azimuth ambiguity degreeWherein i is target in orientation imaging belt Point sequence number, K is impact point quantity, i=1,2 ... K, σiIt is orientation aiming spot, N is the beam scanning Angle Position for quantifying Number, fn(σi) it is σiThe corresponding Doppler frequency value of n-th scanning Angle Position of impact point, n=1,2,3 ... N, Δ fdcFor many General Le centre frequency error,It is n-th Doppler energy spectrum of scanning Angle Position, fpIt is pulse recurrence frequency, m is Confusion region sequence number；
Distance is to fuzziness RASR=max (RASR (τi)), whereinIn formulaN is Confusion region sequence number, confusion region sequence number when theoretical maximum is the tangent earth,It is distance to transmitting-receiving round trip equivalent aerial side Xiang Tu, τiIt is the echo time delay of target i, fpIt is pulse recurrence frequency, θiIt is incidence angle, σ0It is target back scattering system in scene Number, R (τi) it is oblique distance of the observation with interior target i, R (τi+n/fp) it is the oblique distance for observing the fuzzy object with interior target i；
Target location accuracyWherein Δ X1It is satellite course made good The orientation position error that site error causes, Δ X2It is the orientation position error that satellite velocities error causes, Δ X3It is echo The orientation position error that data timer error causes, Δ R1For satellite is missed perpendicular to the positioning that the site error of flight path is introduced Difference, Δ R2It is the position error that satellite radial position error is introduced, Δ R3It is the position error that oblique distance measurement error is introduced, Δ R4 For the position error that target vertical error is introduced；
Electrodynamic radiationWherein Δ G (φ) is directional diagram error, Δ K0It is scaling constant error, Δ CalinIt is SAR system internal calibration error, Δ Q is quantization error, Δ N be influence of the noise level to Electrodynamic radiation, Δ AASR, Δ RASR and Δ ISLR be azimuth ambiguity degree, range ambiguity and Influence of the integration secondary lobe ratio error to Electrodynamic radiation, Δ LsIt is electromagnetic wave Dissipation change in the air, Δ GimgImaging is drawn The error for entering；
Step 2 12, is created as quality index exploded relationship figure, the influence factor of decomposition include satellite orbit certainty of measurement, Data down transmission speed and the bit error rate, SAR system signal band on clock accuracy, star on attitude measurement accuracy, power satellite ability, star Width, SAR system amplitude phase error, SAR antennas error dispersion, SAR system noise coefficient, system loss, SAR antenna sizes, SAR days Beta radiation power, SAR antenna efficiencies, SAR antenna radiation patterns precision, imaging error, on-orbit calibration error, air and ionization Layer influence, ground digital elevation model；
Step 2 13, the quantization that influence factor is carried out to each image quality index according to exploded relationship figure is decomposed and distributed, So as to each influence factor for obtaining satellite system, space propagation and ground system required for each image quality index is realized refers to Target lifting is required；The current of the index value of each influence factor realizes level vector Factor0Represent, and realize needed for into As the value vector Factor that quality index needsMinRepresent, the index that each influence factor is realized after tackling problems in key technologies is used Vectorial FactorPromoteRepresent, each influence factor optimal value vector FactorOptimumRepresent；
Step 2 14, the value mode of distribution or each influence factor on image quality index is being implemented as quality index Cost performance be up to criterion；Performance represents that wherein S represents the performance after lifting with such as following formula, and i represents that image quality refers to Mark numbering, N is expressed as quality index quantity, wiRepresent i-th weight of index, PromTimesiRepresent carrying for i-th index Rise multiplying power；
S = Σ i = 1 N w i · PromTimes i
Cost with each influence factor elevator belt come cost summation represent that be shown below, wherein Cost represents total cost, j tables Show that influence factor is numbered, M represents influence factor quantity, uiRepresent j-th weight of index, cost_of_factjRepresent j-th The cost that influence factor is realized；Thus, cost performance is expressed as S/Cost；
C o s t = Σ j = 1 M u j cos t _ o f _ fact j
Step 2 15, to be implemented as quality index lifting, each influence factor value must be better than vector FactorMinRepresent Numerical value；Some existing levels meet in each factor, amount of orientation Factor0In corresponding factor value；Some factors need to carry out Tackling problems in key technologies just touches the mark, amount of orientation FactorPromoteIn corresponding factor value；The combination of each influence factor is carried out Traversal, it is optimal as criterion with cost performance S/Cost, obtain optimal influence factor mix vector FactorOptimum。
4. High Resolution Spaceborne SAR image quality method for improving according to claim 1, it is characterised in that the step Image quality lifting recruitment evaluation based on full link simulation in four, its method is using satellite-borne SAR product and radar target Echo simulator builds full link semi-physical system, with FactorAchieveIt is input, carries out half thing of image quality index Reason l-G simulation test, the echo data to enrolling carries out imaging and index evaluation, so as to obtain lift effect to image quality Effective evaluation, if without satellite-borne SAR product and radar target simulator, being also adopted by full digital trigger technique to image quality Lifting effect is evaluated.
5. High Resolution Spaceborne SAR image quality method for improving according to claim 1, it is characterised in that the step Propose that the measure of lifting image quality proposes the measure of lifting image quality in three, it is critical only that with vectorial FactorOptimum In each influence factor value be input, carry out each subsystem of satellite platform, SAR load subsystem, Ground Processing System, ground fixed Mark system, the tackling problems in key technologies in ground digital elevation model storehouse, conceptual design and product development, each influence factor are finally realized Index vector FactorAchieveRepresent.
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