CN106886021B - High Resolution Spaceborne SAR image quality method for improving - Google Patents
High Resolution Spaceborne SAR image quality method for improving Download PDFInfo
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- CN106886021B CN106886021B CN201710055238.8A CN201710055238A CN106886021B CN 106886021 B CN106886021 B CN 106886021B CN 201710055238 A CN201710055238 A CN 201710055238A CN 106886021 B CN106886021 B CN 106886021B
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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
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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
The present invention provides a kind of High Resolution Spaceborne SAR image quality method for improving comprising following steps: step 1, and the image quality based on High Resolution SAR Images application promotes demand analysis and the combing of image quality index；Step 2 is optimized into image quality figureofmerit and decomposes and distribute；Step 3 proposes the measure for promoting image quality；Step 4, the image quality based on full link simulation promote recruitment evaluation.Method flow proposed by the invention is clear, is easily achieved, and has directive significance for satellite-borne SAR master-plan, has initiative, the image quality Study of Lifting suitable for other types of SAR satellite.
Description
Technical field
The present invention relates to a kind of aerospace system technical fields, and in particular, to a kind of High Resolution Spaceborne SAR image quality
Method for improving.
Background technique
Since U.S. NASA in 1978 emits first synthetic aperture radar (SAR) satellite, there are more than 50 thunders
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 each scientific and technological attention made the country prosperous and greatly develop.High resolution SAR satellite is always the key points and difficulties developed, 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.It can
See, high resolution SAR satellite is particularly important for high-precision targeted surveillance.Meanwhile high resolution SAR satellite is general in land resources
Look into, survey and draw, prevent and reduce natural disasters in played irreplaceable role, the assessment of the condition of a disaster is usually required better than 2m resolution ratio
SAR image.Currently, the resolution ratio overwhelming majority of typical satellite-borne SAR is in 1m~3m magnitude, such as TerraSAR of Germany in the world
Satellite and Canadian RadarSat-2 satellite highest resolution are 1m.It is widely answered as it can be seen that the promotion of resolution ratio index has
Use demand.
Meanwhile in the world in in-orbit SAR satellite image use process, it was also proposed that image quality promotion must be asked, and mainly have
The following aspects:
1, even on image under the weak background such as sea when changing region greatly to land and sea junction target dynamic and being imaged
You will appear " ghost " target, and mainly SAR fuzzy indicator is lower caused, need to promote fuzziness index.
2, the noise of certain satellite-borne SAR images is poor, the detectivity to target on image is influenced, mainly due to system
Sensitivity is not high enough, therefore, it is necessary to lifting system sensitivity index.
3, each sub radiative interband is non-uniform " scallop effect " in occurring in SCANSAR image, mainly by the attitude of satellite
Caused by error and Beam steering error influence, it is therefore desirable to be promoted to Electrodynamic radiation.
Demand is promoted from two angle analysis image quality above, is the need that external typical case promotes imaging first
It asks；Secondly the demand promoted from the problems in in-orbit SAR satellite application and deficiency analysis picture quality.At home and abroad spaceborne
The field SAR lacks always a kind of general method for High Resolution Spaceborne SAR image quality Upgrade Problem, mentions for instructing
Rise the design of Space-borne SAR Imaging quality index.
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 Spaceborne SAR image quality to mention
Lifting method, the method flow proposed is clear, is easily achieved, and has directive significance for satellite-borne SAR master-plan, has and open
Invasive, suitable for other types of SAR satellite image quality Study of Lifting.
According to an aspect of the present invention, a kind of High Resolution Spaceborne SAR image quality method for improving is provided, feature exists
In comprising following steps:
Step 1, the image quality based on High Resolution SAR Images application promote demand analysis and image quality index comb
Reason；
Step 2 is optimized into image quality figureofmerit and decomposes and distribute；
Step 3 proposes the measure for promoting image quality；
Step 4, the image quality based on full link simulation promote recruitment evaluation.
Preferably, in the step 1 specifically includes the following steps:
Step 1 11, based on the existing insufficient status of SAR satellite capacity, with considering in SAR image application typical target
High-precision identifies and confirmation demand, high-precision mapping demand, accurate the condition of a disaster evaluation requirement；Meanwhile it being used for current SAR image
In fundamental problems propose image quality index promoted require, these fundamental problems include land and sea junction region SAR figure
As ambiguity issue, signal noise ratio (snr) of image deficiency, point target secondary lobe problem, the not high problem of positioning accuracy, SCANSAR image scallop are asked
Topic；
Step 1 12 analyzes result according to demand and is combed into image quality figureofmerit system, and provides the promotion requirement of quantization；
Image quality index at least consider resolution ratio, peak sidelobe ratio, integral secondary lobe ratio, system sensitivity, azimuth ambiguity degree, apart from mould
Paste degree, positioning accuracy and Electrodynamic radiation.
Preferably, the step 2 specifically includes the following steps:
Step 2 11 is created as image quality figureofmerit formula and its relational model with influence factor；
Orientation ground resolutionWherein VgFor the ground velocity that zone position is imaged, Bp
For the doppler processing bandwidth of single target, k1Ceofficient of spread, k are weighted for orientation directional diagram2Broadening system is weighted for imaging
Number, k3For ceofficient of spread caused by Doppler parameter error, k4For ceofficient of spread caused by imaging algorithm；
Apart from resolution ratio to the groundWherein c is the light velocity, and η is incidence angle, BrFor letter
Number bandwidth, k1Ceofficient of spread, k are weighted for imaging2For ceofficient of spread caused by SAR system amplitude phase error and dispersion, k3For at
The ceofficient of spread as caused by algorithm；
Peak sidelobe ratio PSLR=PSLR0-ΔPSLR1-ΔPSLR2, wherein ΔPSLR1Draw for SAR system amplitude phase error and dispersion
The secondary lobe risen is than decline, ΔPSLR2For the secondary lobe ratio decline that imaging error introduces, PSLR0For the reason under particular procedure weighting
By peak sidelobe ratio,PsmaxFor the highest side lobe peak power of point target impulse response, PmFor a mesh
Mark the main lobe peak-peak power of impulse response；
Integrate secondary lobe ratio ISLR=ISLR0-ΔISLR1-ΔISLR2, wherein ΔISLR1Draw for SAR system amplitude phase error and dispersion
The secondary lobe risen is than decline, ΔISLR2For the secondary lobe ratio decline that imaging error introduces, ISLR0For the reason under particular procedure weighting
By integral secondary lobe ratio,H (r) is point target impulse response function, integral
It is main lobe region within domain (a, b), is secondary lobe region other than main lobe；
System sensitivityIt is worst in imaging region
NEσ0=max (NE σ0(σa,θr)), wherein TeNoise temperature is imitated for system, k is Boltzmann constant, L (σa) it is system loss,
VstFor opposite ground velocity, σaFor orientation aiming spot, R (θr) it is target to distance by radar, λ is centre carrier frequency wavelength,
For emission peak power, tpTo emit pulse time width, G2(θr) it is the gain that target is accordingly directed toward angle in directional diagram, ρrFor away from
Descriscent resolution ratio, fpTo emit pulse recurrence frequency, θrFor the downwards angle of visibility value in imaging region；
Azimuth ambiguity degreeWherein i is in orientation imaging belt
Target point serial number, K are target point quantity, i=1,2 ... K, σiFor orientation aiming spot, N is the beam scanning angle of quantization
Positional number, fn(σi) it is σiThe corresponding Doppler frequency value of n-th of scanning Angle Position of target point, n=1,2,3 ... N, Δ fdc
For Doppler center frequency error,The Doppler energy spectrum of Angle Position, f are scanned for n-thpFrequency is repeated for pulse
Rate, m are confusion region serial number；
Distance is to fuzziness RASR=max (RASR (τi)), whereinIn formulan
For confusion region serial number, theoretical maximum is the confusion region serial number when earth is tangent,For distance to transmitting-receiving round trip equivalent aerial
Directional diagram, τiFor the echo time delay of target i, fpFor pulse recurrence frequency, θiFor incidence angle, σ0For target back scattering in scene
Coefficient, 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 X1For satellite
Orientation position error caused by course made good location error, Δ X2For orientation position error caused by satellite velocities error, Δ X3
For orientation position error caused by echo data timer error, Δ R1Determine for satellite perpendicular to what the location error of track introduced
Position error, Δ R2For the position error that satellite radial position error introduces, Δ R3For oblique distance measurement error introduce position error,
ΔR4The position error introduced for target vertical error；
Electrodynamic radiation
Wherein Δ G (φ) is directional diagram error, Δ K0For scaling constant error, Δ CalinFor SAR system internal calibration error, Δ Q is amount
Change error, Δ N is influence of the noise level to Electrodynamic radiation, and Δ AASR, Δ RASR and Δ ISLR are azimuth ambiguity degree, apart from mould
The influence of paste degree and integral secondary lobe ratio error to Electrodynamic radiation, Δ LsFor the Dissipation change of electromagnetic wave in the air, Δ GimgImaging
Handle the error introduced；
Step 2 12, is created as image quality figureofmerit exploded relationship figure, and the influence factor of decomposition includes satellite orbit measurement
Precision, attitude measurement accuracy, power satellite ability, clock accuracy on star, data down transmission rate and the bit error rate, SAR system on star
Signal bandwidth, SAR system amplitude phase error, SAR antenna error dispersion, SAR system noise coefficient, system loss, SAR antenna ruler
It is very little, SAR antenna radiated power, SAR antenna efficiency, SAR antenna radiation pattern precision, imaging error, on-orbit calibration error, big
Gas and ionosphere effect, ground digital elevation model；
Step 2 13 is decomposed and is divided according to the quantization that exploded relationship figure carries out influence factor to each image quality index
Match, thus obtain each influence of satellite system, space propagation and ground system required for each image quality index is realized because
The promotion requirement of plain index；The current realization of the index value of each influence factor is horizontal to use vector Factor0It indicates, and realizes institute
The value vector Factor for needing image quality index to needMinIt indicates, the finger that each influence factor is realized after tackling problems in key technologies
Mark vector FactorPromoteIt indicates, each influence factor optimal value vector FactorOptimumIt indicates；
Step 2 14, about the distribution of image quality index or the value mode of each influence factor to realize image quality
The cost performance of index is up to criterion；Performance indicates that wherein S indicates the performance after being promoted with following formula, and i indicates imaging
Quality index number, N are expressed as image quality figureofmerit quantity, wiIndicate the weight of i-th of index, PromTimesiIndicate i-th of finger
Target promotes multiplying power；
Cost promotes bring cost summation with each influence factor and indicates, shown in following formula, wherein Cost indicates total generation
Valence, j indicate influence factor number, and M indicates influence factor quantity, uiIndicate the weight of j-th of index, cost_of_factjIt indicates
The cost that j-th of influence factor is realized；Cost performance is expressed as S/Cost as a result,；
Step 2 15 is promoted to be implemented as image quality figureofmerit, and 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
It carries 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
It is traversed, it is optimal for criterion with cost performance S/Cost, obtain optimal influence factor mix vector FactorOptimum。
Preferably, the image quality in the step 4 based on full link simulation promotes recruitment evaluation, and method is benefit
Full link semi-physical system is built with satellite-borne SAR product and radar target simulator, with FactorAchieveIt is defeated
Enter, carry out the semi-physical simulation of image quality index, imaging and index evaluation are carried out to the echo data of admission, from
And the effective evaluation that effect is promoted to image quality is obtained, if without satellite-borne SAR product and radar target simulator,
Effect is promoted to image quality using full digital trigger technique to evaluate.
Preferably, it proposes that the measure for promoting image quality proposes to promote the measure of image quality in the step 3, closes
Key is with vector FactorOptimumIn each influence factor value be input, carry out each subsystem of satellite platform, SAR load point
Tackling problems in key technologies, conceptual design and the production of system, Ground Processing System, ground calibration system, ground digital elevation model library
Product development, each influence factor finally realize index vector FactorAchieveIt indicates.
Compared with prior art, the present invention is with following the utility model has the advantages that method flow proposed by the invention is clear, easy
In realization, there is directive significance for satellite-borne SAR master-plan, there is initiative, suitable for other types of SAR satellite at
Image quality amount Study of Lifting.
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 is the flow chart of High Resolution Spaceborne SAR image quality method for improving of 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, several modifications and improvements are also made.These belong to guarantor of the invention
Protect range.
As shown in Figure 1, High Resolution Spaceborne SAR image quality method for improving of the present invention the following steps are included:
Step 1, the image quality based on High Resolution SAR Images application promote demand analysis and image quality index comb
Reason；
Step 2 is optimized into image quality figureofmerit and decomposes and distribute；
Step 3 proposes the measure for promoting image quality；
Step 4, the image quality based on full link simulation promote recruitment evaluation.
Specifically, in step 1 the following steps are included:
Step 1 11, based on the existing insufficient status of SAR satellite capacity, with considering in SAR image application typical target
High-precision identifies and confirmation demand, high-precision mapping demand, accurate the condition of a disaster evaluation requirement；Meanwhile it being used for current SAR image
In fundamental problems propose image quality index promoted require, these fundamental problems include land and sea junction region SAR figure
As ambiguity issue, signal noise ratio (snr) of image deficiency, point target secondary lobe problem, the not high problem of positioning accuracy, SCANSAR image scallop are asked
Topic；
Step 1 12 analyzes result according to demand and is combed into image quality figureofmerit system, and provides the promotion requirement of quantization；
Image quality index at least considers resolution ratio (ρ), peak sidelobe ratio (PSLR), integral secondary lobe ratio (ISLR), system sensitivity (NE
σ 0), azimuth ambiguity degree (AASR), range ambiguity (RASR), positioning accuracy (Δ P) and Electrodynamic radiation (Δ R).
Step 2 specifically includes the following steps:
Step 2 11 is created as image quality figureofmerit 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 that zone position is imaged, 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 broadening caused by Doppler parameter error
Coefficient, k4 are ceofficient of spread caused by imaging algorithm.
Apart from resolution ratio to the ground, such as following formula (2):
Wherein c is the light velocity, and η is incidence angle, BrFor signal bandwidth, k1 is that imaging weights ceofficient of spread, and k2 is SAR system
Ceofficient of spread caused by system amplitude phase error and dispersion, k3 are ceofficient of spread caused by imaging algorithm.
Peak sidelobe ratio, such as following formula (3):
PSLR=PSLR0-ΔPSLR1-ΔPSLR2 (3)
Wherein ΔPSLR1It is secondary lobe caused by SAR system amplitude phase error and dispersion than declining, ΔPSLR2For imaging error
The secondary lobe of introducing is than decline, PSLR0Theoretical peak secondary lobe ratio under being weighted for particular procedure, calculation method such as following formula (4):
PsmaxFor the highest side lobe peak power of point target impulse response, PmFor the main lobe top of point target impulse response
It is worth power.
Secondary lobe ratio is integrated, such as following formula (5):
ISLR=ISLR0-ΔISLR1-ΔISLR2 (5)
Wherein ΔISLR1It is secondary lobe caused by SAR system amplitude phase error and dispersion than declining, ΔISLR2For imaging error
The secondary lobe of introducing is than decline, ISLR0Secondary lobe ratio is integrated for the theory under particular procedure weighting, calculation method 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 other than 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, TeFor system equivalent noise temperature, k is Boltzmann constant, L (σa) it is system loss, VstFor relatively
Speed, σaFor orientation aiming spot, R (θr) it is target to distance by radar, λ is centre carrier frequency wavelength,For emission peak
Power, tpTo emit pulse time width, G2(θr) it is the gain that target is accordingly directed toward angle in directional diagram, ρrFor range resolution,
fpTo emit pulse recurrence frequency, θrFor the downwards angle of visibility value in imaging region.
Azimuth ambiguity degree, such as following formula (9):
Wherein i is target point serial number in orientation imaging belt, and K is target point quantity, i=1,2 ... K, σiFor orientation
Aiming spot, N are the beam scanning Angle Position number of quantization, fn(σi) it is σiN-th of scanning Angle Position of target point is corresponding more
General Le frequency values, n=1,2,3 ... N, Δ fdcFor Doppler center frequency error,For n-th of scanning Angle Position
Doppler energy spectrum, fpFor pulse recurrence frequency, m is confusion region serial number.
Distance is to fuzziness, such as following formula (10):
RASR=max (RASR (τi)) (10)
WhereinCalculation method such as following formula (11) and (12):
Wherein n is confusion region serial number, and theoretical maximum is the confusion region serial number when earth is tangent,It is distance to receipts
Send out round trip equivalent aerial directional diagram, τiFor the echo time delay of target i, fpFor pulse recurrence frequency, θiFor incidence angle, σ0For scene
Interior target backscattering coefficient, R (τi) it is oblique distance of the observation with interior target i, R (τi+n/fp) it is that observation is fuzzy with interior target i
The oblique distance of target.
Target location accuracy, such as following formula (13):
Wherein Δ X1For orientation position error caused by satellite course made good location error, Δ X2Draw for satellite velocities error
The orientation position error risen, Δ X3For orientation position error caused by echo data timer error, Δ R1For satellite perpendicular to
The position error that the location error of track introduces, Δ R2For the position error that satellite radial position error introduces, Δ R3For oblique distance survey
Measure the position error that error introduces, Δ R4The position error introduced for target vertical error.
Electrodynamic radiation, such as following formula (14):
Wherein Δ G (φ) is directional diagram error, Δ K0For scaling constant error, Δ CalinFor 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 integral secondary lobe ratio error to Electrodynamic radiation, Δ LsFor the Dissipation change of electromagnetic wave in the air,
ΔGimgThe error that imaging introduces.
Step 2 12, is created as image quality figureofmerit exploded relationship figure, and the influence factor of decomposition includes satellite orbit measurement
Precision, attitude measurement accuracy, power satellite ability, clock accuracy on star, data down transmission rate and the bit error rate, SAR system on star
Signal bandwidth, SAR system amplitude phase error, SAR antenna error dispersion, SAR system noise coefficient, system loss, SAR antenna ruler
It is very little, SAR antenna radiated power, SAR antenna efficiency, SAR antenna radiation pattern precision, imaging error, on-orbit calibration error, big
Gas and ionosphere effect, ground digital elevation model etc.；
Step 2 13 is decomposed and is divided according to the quantization that exploded relationship figure carries out influence factor to each image quality index
Match, thus obtain each influence of satellite system, space propagation and ground system required for each image quality index is realized because
The promotion requirement of plain index；Horizontal vector Factor can be achieved in the current of the index value of each influence factor0It indicates, and realizes
The value vector Factor that required image quality index needsMinIt indicates, each influence factor can be real after tackling problems in key technologies
Existing index vector FactorPromoteIt indicates, each influence factor optimal value vector FactorOptimumIt indicates；
Step 2 14, about the distribution of image quality index or the value mode of each influence factor to realize image quality
The cost performance of index is up to criterion；Wherein S indicates the performance after being promoted, and i is expressed as image quality figureofmerit number, and N is indicated
Image quality index quantity, wiIndicate the weight of i-th of index, PromTimesiIndicate the promotion multiplying power of i-th of index, it is as follows
Formula (15):
Cost with each influence factor promoted bring cost summation indicate, wherein Cost indicate total cost, j indicate influence because
Element number, M indicate influence factor quantity, uiIndicate the weight of j-th of index, cost_of_factjIndicate j-th of influence factor
The cost of realization；Cost performance is expressed as S/Cost as a result, such as following formula (16):
Step 2 15 is promoted to be implemented as image quality figureofmerit, and 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 and can be only achieved index, i.e. amount of orientation FactorPromoteIn corresponding factor value；It will be each
The combination of influence factor is traversed, optimal for criterion with cost performance S/Cost, obtains optimal influence factor mix vector
FactorOptimum。
The measure of promotion image quality is proposed in step 3, key is with vector FactorOptimumIn respectively influence because
Plain value is input, carry out each subsystem of satellite platform, SAR load subsystem, Ground Processing System, ground calibration system,
Tackling problems in key technologies, conceptual design and the product development in face digital elevation model library, each influence factor finally realize index with to
Measure FactorAchieveIt indicates.
Image quality in step 4 based on full link simulation promotes recruitment evaluation, and method is to produce using satellite-borne SAR
Product and radar target simulator build full link semi-physical system, with FactorAchieveFor input, carry out into image quality
The semi-physical simulation of figureofmerit carries out imaging and index evaluation to the echo data of admission, to obtain to imaging
The effective evaluation of increased quality effect.If, can also be using total without satellite-borne SAR product and radar target simulator
Word emulation promotes effect to image quality and evaluates.
The present embodiment is by taking spaceborne X-band phased array synthetic aperture radar (SAR) as an example, with reference to TerraSAR satellite parametric reduction,
Orbit altitude value about 500km, power satellite ability are about 3000W, SAR antenna size about 5m (A) × 1m (R), peak value radiation
Power about 3500W, incidence angle take 30 °, and four image quality indexs: azimuth resolution are only considered in example, and distance is to resolution
Rate, system sensitivity and positioning accuracy, the image quality index before promotion: resolution ratio is about 3m, system sensitivity about-
17dB, positioning accuracy are about 50m, the present embodiment the following steps are included:
Step 1 combs image quality and promotes demand, it is assumed that need in this example according to the different application situation of SAR image
It asks are as follows: distance resolution is promoted to 0.55m, azimuth resolution by 2.82m and is promoted to 0.6m, system sensitivity by -17dB by 3m
Be promoted to -26.75dB, positioning accuracy and 6.2m be promoted to by 41.97m, consider the promotion of 4 image quality indexs, before being promoted at
Image quality figureofmerit vector Spec0It indicates, each index value is spec_valuei(i=1,2,3,4)；Assuming that being attacked through key technology
Guan Hou, image quality index vector SpecPromoteIt indicates；Each index optimal value vector SpecOptimumIt indicates；It is defended
Index vector Spec is finally realized after star Design and DevelopmentAchieveIt indicates.
Step 2, is created as image quality figureofmerit exploded relationship figure, this example mainly considers that the influence factor decomposed includes defending
Star orbital road measurement accuracy, attitude measurement accuracy, power satellite ability, clock accuracy, SAR system signal bandwidth, SAR system on star
Amplitude phase error (being divided into amplitude and phase), SAR system noise coefficient, system loss, SAR antenna size (be divided into orientation and away from
Descriscent), SAR antenna radiated power, SAR antenna efficiency, SAR antenna radiation pattern precision (this example mainly consider beam position essence
Degree and form accuracy), imaging error (this example mainly considers adjust estimated frequency error and handle error caused by broaden),
On-orbit calibration error (this example consider oblique distance calibrated error) and ground digital elevation model error totally ten five, in consideration bracket
Subitem expansion totally ten nine, each factor value are fac_valuej(j=1,2 ... ... 19).
It decomposes and distributes according to the quantization that exploded relationship figure carries out influence factor to each image quality index.Current
Factor0Value be set as [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 tackling problems in key technologies, 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, realizing respectively influences required for the image quality index after being promoted
Factor value tolerance 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):
Become smaller for numerical value embody index promotion factor take Sgn () to take+1, otherwise take -1.It is all above to be related to logarithm
Dimension be both needed to be scaled range value after calculated again.
In order to obtain best price/performance ratio S/Cost, after excessively taking turns iterative calculation, Factor is obtainedOptimumFor [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].At this point, optimal S/Cost is 1.64.
Step 3, with vector FactorOptimumIn each influence factor value be input, propose that promoting image quality arranges
It applies, and implements in each subsystem of satellite platform, SAR load subsystem, Ground Processing System, ground calibration system, ground digital
In elevation model library, and then Spanning Star ground each scheme Design and product development, each influence factor finally realize index be to
Measure FactorAchieve。
Step 4 builds full link semi-physical system using satellite-borne SAR product and radar target simulator, with
FactorAchieveFor input, the semi-physical simulation of image quality index is carried out, the echo data of admission is carried out at imaging
Reason and index evaluation, to obtain the effective evaluation for promoting effect to image quality.If without satellite-borne SAR product and radar mesh
Echo simulator is marked, effect can also be promoted to image quality using full digital trigger technique and evaluated.
In conclusion it is clear using method flow proposed by the invention, be easily achieved, for satellite-borne SAR master-plan
With directive significance, there is initiative, the image quality Study of Lifting suitable for other types of SAR satellite.
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 Spaceborne SAR image quality method for improving, which is characterized in that itself the following steps are included:
Step 1, the image quality based on High Resolution SAR Images application promote demand analysis and the combing of image quality index；
Step 2 is optimized into image quality figureofmerit and decomposes and distribute；
Step 3 proposes the measure for promoting image quality；
Step 4, the image quality based on full link simulation promote recruitment evaluation；
In the step 1 specifically includes the following steps:
Step 1 11, it is with considering in SAR image application typical target high-precision based on the existing insufficient status of SAR satellite capacity
Degree identification and confirmation demand, high-precision mapping demand, accurate the condition of a disaster evaluation requirement；Meanwhile in current SAR image use
Fundamental problems propose that image quality index is promoted and require 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, the not high problem of positioning accuracy, SCANSAR image scallop problem；
Step 1 12 analyzes result according to demand and is combed into image quality figureofmerit system, and provides the promotion requirement of quantization；Imaging
Quality index at least considers resolution ratio, peak sidelobe ratio, integral secondary lobe ratio, system sensitivity, azimuth ambiguity degree, range ambiguity
Degree, positioning accuracy and Electrodynamic radiation；
The step 2 specifically includes the following steps:
Step 2 11 is created as image quality figureofmerit formula and its relational model with influence factor；
Orientation ground resolutionWherein VgFor the ground velocity that zone position is imaged, BpIt is single
The doppler processing bandwidth of target, k1Ceofficient of spread, k are weighted for orientation directional diagram2Ceofficient of spread, k are weighted for imaging3
For ceofficient of spread caused by Doppler parameter error, k4For ceofficient of spread caused by imaging algorithm；
Apart from resolution ratio to the groundWherein c is the light velocity, and η is incidence angle, BrFor signal band
Width, k1Ceofficient of spread, k are weighted for imaging2For ceofficient of spread caused by SAR system amplitude phase error and dispersion, k3It is calculated for imaging
Ceofficient of spread caused by method；
Peak sidelobe ratio PSLR=PSLR0-ΔPSLR1-ΔPSLR2, wherein ΔPSLR1For caused by SAR system amplitude phase error and dispersion
Secondary lobe is than decline, ΔPSLR2For the secondary lobe ratio decline that imaging error introduces, PSLR0For the theoretical peak under particular procedure weighting
It is worth secondary lobe ratio,PsmaxFor the highest side lobe peak power of point target impulse response, PmFor point target punching
Swash the main lobe peak-peak power of response；
Integrate secondary lobe ratio ISLR=ISLR0-ΔISLR1-ΔISLR2, wherein ΔISLR1For caused by SAR system amplitude phase error and dispersion
Secondary lobe is than decline, ΔISLR2For the secondary lobe ratio decline that imaging error introduces, ISLR0For 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 other than main lobe；
System sensitivityWorst NE σ in imaging region0=
max(NEσ0(σa,θr)), wherein TeNoise temperature is imitated for system, k is Boltzmann constant, L (σa) it is system loss, VstFor
Opposite ground velocity, σaFor orientation aiming spot, R (θr) it is target to distance by radar, λ is centre carrier frequency wavelength,For hair
Penetrate peak power, tpTo emit pulse time width, G2(θr) it is the gain that target is accordingly directed toward angle in directional diagram, ρrFor distance to
Resolution ratio, fpTo emit pulse recurrence frequency, θrFor the downwards angle of visibility value in imaging region；
Azimuth ambiguity degreeWherein i is target in orientation imaging belt
Point serial number, K are target point quantity, i=1,2 ... K, σiFor orientation aiming spot, N is the beam scanning Angle Position of quantization
Number, fn(σi) it is σiThe corresponding Doppler frequency value of n-th of scanning Angle Position of target point, n=1,2,3 ... N, Δ fdcIt is more
General Le centre frequency error,The Doppler energy spectrum of Angle Position, f are scanned for n-thpFor pulse recurrence frequency, m is
Confusion region serial number；
Distance is to fuzziness RASR=max (RASR (τi)), whereinIn formulan
For confusion region serial number, theoretical maximum is the confusion region serial number when earth is tangent,For distance to transmitting-receiving round trip equivalent aerial
Directional diagram, τiFor the echo time delay of target i, fpFor pulse recurrence frequency, θiFor incidence angle, σ0For target back scattering in scene
Coefficient, 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 X1For satellite course made good
Orientation position error caused by location error, Δ X2For orientation position error caused by satellite velocities error, Δ X3For echo
Orientation position error caused by data timer error, Δ R1The positioning introduced for satellite perpendicular to the location error of track misses
Difference, Δ R2For the position error that satellite radial position error introduces, Δ R3For the position error that oblique distance measurement error introduces, Δ R4
The position error introduced for target vertical error；
Electrodynamic radiationWherein Δ
G (φ) is directional diagram error, Δ K0For scaling constant error, Δ CalinFor 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
Integrate influence of the secondary lobe ratio error to Electrodynamic radiation, Δ LsFor the Dissipation change of electromagnetic wave in the air, Δ GimgImaging is drawn
The error entered；
Step 2 12, is created as image quality figureofmerit exploded relationship figure, the influence factor of decomposition include satellite orbit measurement accuracy,
Attitude measurement accuracy, power satellite ability, clock accuracy on star, data down transmission rate and the bit error rate, SAR system signal band on star
Width, SAR system amplitude phase error, SAR antenna error dispersion, SAR system noise coefficient, system loss, SAR antenna size, SAR days
Beta radiation power, SAR antenna efficiency, SAR antenna radiation pattern precision, imaging error, on-orbit calibration error, atmosphere and ionization
Layer influence, ground digital elevation model；
Step 2 13 is decomposed and is distributed according to the quantization that exploded relationship figure carries out influence factor to each image quality index,
Refer to obtain each influence factor of satellite system, space propagation and ground system required for each image quality index is realized
Target, which is promoted, to be required；The current realization of the index value of each influence factor is horizontal to use vector Factor0Indicate, and realize needed at
The value vector Factor that image quality figureofmerit needsMinIt indicates, the index that each influence factor is realized after tackling problems in key technologies is used
Vector FactorPromoteIt indicates, each influence factor optimal value vector FactorOptimumIt indicates；
Step 2 14, about the distribution of image quality index or the value mode of each influence factor to be implemented as image quality figureofmerit
Cost performance be up to criterion；Performance indicates that wherein S indicates the performance after being promoted with such as following formula, and i indicates that image quality refers to
Mark number, N are expressed as image quality figureofmerit quantity, wiIndicate the weight of i-th of index, PromTimesiIndicate mentioning for i-th of index
Rise multiplying power；
Cost promotes bring cost summation with each influence factor and indicates, is shown below, and wherein Cost indicates total cost, j table
Show that influence factor is numbered, M indicates influence factor quantity, and uj indicates the weight of j-th of index, cost_of_factjIt indicates j-th
The cost that influence factor is realized；Cost performance is expressed as S/Cost as a result,；
Step 2 15 is promoted to be implemented as image quality figureofmerit, and each influence factor value must be better than vector FactorMinIt indicates
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 for criterion with cost performance S/Cost, obtain optimal influence factor mix vector FactorOptimum；
Image quality in the step 4 based on full link simulation promotes recruitment evaluation, and method is to produce using satellite-borne SAR
Product and radar target simulator build full link semi-physical system, with FactorAchieveFor input, carry out into image quality
The semi-physical simulation of figureofmerit carries out imaging and index evaluation to the echo data of admission, to obtain to imaging
The effective evaluation of increased quality effect, if without satellite-borne SAR product and radar target simulator, also using digital imitative
Very effect is promoted to image quality to evaluate；
The measure of promotion image quality is proposed in the step 3, key is with vector FactorOptimumIn each influence factor
Value is input, proposes the measure for promoting image quality, and implement in each subsystem of satellite platform, SAR load subsystem, ground
Processing system, ground calibration system, in ground digital elevation model library, and then Spanning Star each scheme Design and product grind
System, each influence factor finally realize that index is vector FactorAchieve。
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| CN108896992B (en) * | 2018-05-09 | 2020-08-14 | 中国人民解放军国防科技大学 | Resolution estimation method suitable for circumferential synthetic aperture radar |
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| CN111881414B (en) * | 2020-07-29 | 2024-03-15 | 中南大学 | Synthetic aperture radar image quality assessment method based on decomposition theory |
| CN112115642B (en) * | 2020-09-14 | 2023-05-02 | 四川航天燎原科技有限公司 | SAR imaging parameter optimization design method for high maneuvering platform |
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