CN106291547B - Doppler ambiguity component Adaptive Suppression method based on antenna radiation pattern auxiliary - Google Patents

Doppler ambiguity component Adaptive Suppression method based on antenna radiation pattern auxiliary Download PDF

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CN106291547B
CN106291547B CN201610425179.4A CN201610425179A CN106291547B CN 106291547 B CN106291547 B CN 106291547B CN 201610425179 A CN201610425179 A CN 201610425179A CN 106291547 B CN106291547 B CN 106291547B
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doppler
component
obscuring component
lobe
main lobe
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CN106291547A (en
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杨柳
沈明威
陶震
胡佩
郑佳芝
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Hohai University HHU
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    • GPHYSICS
    • G01MEASURING; TESTING
    • G01SRADIO 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
    • G01S13/00Systems 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
    • G01S13/88Radar or analogous systems specially adapted for specific applications
    • G01S13/89Radar or analogous systems specially adapted for specific applications for mapping or imaging
    • G01S13/90Radar or analogous systems specially adapted for specific applications for mapping or imaging using synthetic aperture techniques, e.g. synthetic aperture radar [SAR] techniques
    • G01S13/904SAR modes
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01SRADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/02Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00
    • G01S7/28Details of pulse systems
    • G01S7/2813Means providing a modification of the radiation pattern for cancelling noise, clutter or interfering signals, e.g. side lobe suppression, side lobe blanking, null-steering arrays

Abstract

The invention discloses a kind of doppler ambiguity component Adaptive Suppression methods based on antenna radiation pattern auxiliary, pass through the range Doppler numeric field data after calculating Doppler ambiguity-resolution, and orientation synthetic aperture imaging is carried out to it, obtain the High Resolution SAR Images after Doppler ambiguity-resolution.It can effectively inhibit major and minor valve obscuring component, realize high resolution wide swath airborne synthetic aperture radar(SAR)Doppler ambiguity-resolution.Emulation experiment shows:Compared with not considering to inhibit secondary lobe obscuring component, point target imaging orientation peak sidelobe ratio performance improves about 9.6dB after solving doppler ambiguity using the present invention.

Description

Doppler ambiguity component Adaptive Suppression method based on antenna radiation pattern auxiliary
Technical field
The present invention relates to airborne multichannel SAR wide-scene survey fields, and in particular to one kind is assisted based on antenna radiation pattern Doppler ambiguity component Adaptive Suppression method.
Background technology
It is domestic for the contradiction for solving between wide swath and orientation high-resolution in airborne synthetic aperture radar imaging Outer scholar has mainly done many research work in terms of two, is on the one hand SAR ambiguity solution treatment technologies, is on the other hand research and development More flexible new SAR system;Usually with lower pulse recurrence frequency (PRF) to ensure wider range in usual SAR system Interior coverage rate, but bearing signal is fuzzy, therefore ambiguity solution is that SAR imagings have to solve the problems, such as.However, the algorithm is simultaneously The echo-signal that antenna side lobe receives is not considered, will also generate corresponding doppler ambiguity component, and after leading to ambiguity solution Average minor level increase.Therefore, it is high-resolution broadband mapping imaging engineering to inhibit the interference of secondary lobe doppler ambiguity component Realization has to solve the problems, such as.
Traditional frequency spectrum reconfiguration algorithm only considers that antenna main lobe receives signal, has ignored the influence of secondary lobe obscuring component, causes The performance of frequency spectrum reconfiguration algorithm declines, and orientation false target will be will produce when serious.In recent years, domestic and international scientific research personnel advocates most More methods is the interference of secondary lobe obscuring component to be eliminated using ultralow side lobe array antenna, but in antenna works application, surpass The design of low sidelobe antenna faces prodigious technical barrier with realization, and research cost is high.In addition, domestic and foreign scholars have ground The technologies such as a variety of secondary lobe interference mitigation technologies, such as secondary lobe cancellation, weighting counteracting are studied carefully, but above-mentioned technology application background all has Particularity is not particularly suited for the orientation multichannel SAR ambiguity solution.
Invention content
The technical problem to be solved by the present invention is to for defect involved in background technology, provide a kind of based on day The doppler ambiguity component Adaptive Suppression method of line directional diagram auxiliary, on the one hand solves traditional frequency spectrum reconfiguration algorithm and only considers Main lobe signal and ignore secondary lobe obscuring component problem, on the other hand effectively prevent tradition solution azimuth ambiguity when systematic error under The problem of signal cancellation and target guiding vector mismatch of the spatial domains ADBF covariance matrix.
The present invention uses following technical scheme to solve above-mentioned technical problem:
Based on the doppler ambiguity component Adaptive Suppression method of antenna radiation pattern auxiliary, include the following steps:
Step 1) respectively compresses the N number of receiving channel signal of airborne synthetic aperture radar into row distance to pulse, and according to Following formula ties up Fast Fourier Transform (FFT) into line direction, obtains the distance-Doppler numeric field data of each receiving channel:
Sn(τ, f)=FFTt[Sn(τ,t)]
Wherein t is the orientation time, and τ is distance to time, Sn(τ, t) is to believe after n-th of channel distance is compressed to pulse Number, FFTtIndicate that, about the Fourier transformation on orientation time t, f indicates orientation Doppler frequency domain, Sn(τ, f) is n-th Channel distance-Doppler domain data;
Step 2) carries out such as each range cell for each corresponding doppler cells of the range cell Lower calculating:
Step 2.1) estimates the DoA values of each secondary main lobe obscuring component using NSIE technologiesWherein Indicate the DoA values of main lobe kth time obscuring component, K is the obscuring component number of main lobe, k=1 ..., K, then each secondary main lobe obscuring component Corresponding spatial domain steering vector is E=[e1,...,ek,...,eK], wherein ekFor kth time main lobe obscuring component spatial domain guiding arrow Amount,D is array element spacing, and λ is signal wavelength, and N indicates receiving channel number, subscriptTTable Show transposition operator;
Step 2.2), it is corresponding with the relational expression of Space Angle each secondary main lobe obscuring component of calculating according to following Doppler frequency Carrier aircraft real-time speed
Wherein, fqFor the corresponding Doppler frequency value of the doppler cells, q indicates that the doppler cells are the range cell Q-th of doppler cells in corresponding doppler cells set;
Step 2.3) is averaged to the corresponding carrier aircraft real-time speed of each main lobe obscuring component obtained in step 2.2) It calculates, obtained carrier aircraft real-time speed estimated value
Step 2.4) calculates the DoA information of each secondary lobe obscuring component according to following formula, i.e., it corresponds to the sine of Space Angle Value
Wherein, fSL,mFor the corresponding Doppler frequency of the m times secondary lobe obscuring component,Due to It is the natural number more than zero that, which there are secondary lobe component, m=± 1 ..., ± M, M in main lobe both sides, and PRF is pulse recurrence frequency;
Step 2.5) calculates the corresponding steering vector of each secondary lobe obscuring component according to the DoA information of each secondary lobe obscuring component:
A=[a-M,...,am,...,aM]
Wherein, amFor the m times secondary lobe obscuring component spatial domain steering vector,m =± 1 ..., ± M;
Step 2.6), the spatial domain that the corresponding solution Doppler ambiguity-resolution of each secondary main lobe obscuring component is built according to following formula are assisted Variance matrix is:
σ in formula0For the noise power-value of load, I ∈ CN×NUnit matrix, ehIt is corresponding for the h times main lobe obscuring component Spatial domain steering vector, subscriptHIndicate conjugate transposition operator, amFor the m times obscuring component spatial domain steering vector of secondary lobe, ρmFor m The corresponding Amplitude Ration coefficient of secondary secondary lobe obscuring component, is represented by:
Wherein bmFor the corresponding antenna radiation pattern secondary lobe gain of m-th of secondary lobe obscuring component, F indicates the master of antenna radiation pattern Valve gain;
Step 2.7) extracts the Adaptive beamformer weights W of each secondary main lobe doppler ambiguity componentkFor:
Step 2.8) utilizes Adaptive beamformer weights WkExtract each main lobe obscuring component pq_kFor:
Wherein Z=[S1(i,q),...,SN(i,q)]TIndicate the vector expression of the doppler cells signal, i is indicated should The corresponding range cell of doppler cells is i-th of range cell;
Step 2.9) extracts each main lobe obscuring component signal and is denoted as P (i, k)=[p1_k,...,pNa_k], wherein pq_k For k-th of main lobe obscuring component of q-th of doppler cells extraction, Na indicates doppler cells number;
Step 3), will according to the corresponding different Doppler frequencies of each secondary main lobe obscuring component for each range cell All main lobe obscuring component signal sequence arrangements, obtain data S (i, f after each range cell Doppler ambiguity-resolutiona):
S(i,faP)=[(i, 1) ..., P (i, K)]
Wherein, faIndicate the orientation Doppler frequency after Doppler ambiguity-resolution;
Step 4) obtains the distance-Doppler numeric field data after Doppler ambiguity-resolution, and it is carried out orientation synthetic aperture at Picture obtains the High Resolution SAR Images after Doppler ambiguity-resolution.
NSIE technologies in step 2.1) are my published technology:Mingwei Shen,Liu Yang,Di Wu, Daiyin Zhu.Multichannel SAR Wide-Swath Imaging based on Adaptive Removal of Azimuth Ambiguities,Remote Sense Letters,6(8),2015.8:628-636。
The present invention has the following technical effects using above technical scheme is compared with the prior art:
According to antenna radiation pattern determine secondary lobe obscuring component amplitude coefficient its imaging after peak sidelobe ratio performance ratio not into The inhibition of row secondary lobe obscuring component is compared, and about 9.6dB or so is improved.
Description of the drawings
Fig. 1 is positive side view stripmap SAR geometrical relationship schematic diagram;
Fig. 2 is the Doppler ambiguity-resolution filter design flow diagram based on NSIT;
Fig. 3 is reception antenna direction schematic diagram;
Fig. 4 is reception diagram;
Fig. 5 is that there are the orientation sectional view azimuth ambiguity figures of point target when azimuth ambiguity;
Fig. 6 (a) is that there are the practical two-dimentional genealogical relationships of ground echo when azimuth ambiguity;
Fig. 6 (b) is that there are the two-dimentional genealogical relationships of the ideal of ground echo when azimuth ambiguity;
Fig. 7 (a) is not consider to be imaged azimuthal section after utilizing routine ADBF scheme solution azimuth ambiguities when secondary lobe obscuring component;
Fig. 7 (b) is to be imaged azimuthal section after utilizing context of methods solution azimuth ambiguity when considering secondary lobe obscuring component.
Specific implementation mode
Technical scheme of the present invention is described in further detail below in conjunction with the accompanying drawings:
The invention discloses the doppler ambiguity component Adaptive Suppression method assisted based on antenna radiation pattern, airborne radars Geometric configuration is as shown in Figure 1, carrier aircraft is flown with speed V along x-axis, and carrier aircraft flying height H, N number of even linear array is along course straight line point Cloth is, it is specified that be transmitting-receiving array element (being array element 1 in Fig. 1) along navigation direction left end array element, remaining is reception array element.Assuming that aircraft In t=0 be in coordinate origin overhead, certain one when t, the position x=Vt of aircraft, then the oblique distance in target to n-th of channel be:
Wherein R0 2=H2+y0 2, H expression aircraft altitudes, d expression array element spacing.
Then the echo model in each channel is:
K in formularRefer to the frequency modulation rate of transmitting pulse signal, τ indicates distance to the time, and t is the orientation time, and λ is wavelength.
The ground echo Doppler frequency f of carried SARdRelationship between azimuth angle theta is as shown in Figure 6, mathematical expression Formula is:
When there are the interference of secondary lobe obscuring component, since main lobe signal strength is much larger than secondary lobe signal strength, NSIE still can be with the DoA of each secondary obscuring component of main lobe.However for solving doppler ambiguity technology, all sides are completely inhibited Position obscuring component, this requires methods should be able to grasp the information of all blurred signals.Therefore fuzzy point of main lobe is utilized herein Amount DoA information inferences go out secondary lobe obscuring component DoA information, and then based on all obscuring component DoA information and main lobe and secondary lobe mould The amplitude coefficient for pasting component designs adaptive spatial filtering device, finally extracts each secondary main lobe obscuring component successively and reconstructs without fuzzy Doppler frequency spectrum.Fig. 2 gives the part signal process flow of this method.
Assuming that target point is to flight track (orientation) vertical line and flight path point of intersection orientation time t=0, now with radar The n-th channel receiving signal of array XnInto row distance dimension pulse compression for (τ, t), as:
WhereinKrTo emit the chirp rate of pulse signal;T be the orientation time, τ be away from Descriscent time, Nr are distance to sampling number, and Na is orientation sampling number, FFTτWithIt is indicated respectively about distance to τ Fourier transformation and about the inverse Fourier transform apart from frequency domain;Fast Fourier Transform (FFT), which is tieed up, by direction can get distance- Doppler domain data, by taking n-th of channel as an example:
Sn(τ, f)=FFTt[Sn(τ,t)]
S in formulan(τ, f) is n-th of channel distance-Doppler domain data, and f is orientation Doppler frequency, FFTtIt indicates to close Fourier transformation on orientation time t.
The DoA estimations of main lobe obscuring component, utilize my published technology:(Mingwei Shen,Liu Yang,Di Wu,Daiyin Zhu.Multichannel SAR Wide-Swath Imaging based on Adaptive Removal of Azimuth Ambiguities,Remote Sense Letters,6(8),2015.8:628-636.) middle using NSIE skills Art estimates the DoA values of each secondary main lobe obscuring component of i-th of range cell, by taking q-th of doppler cells as an example, it is assumed that main lobe exists K obscuring component, corresponding DoA values are respectivelyWhereinIndicate the DoA of main lobe kth time obscuring component Value, then the corresponding spatial domain steering vector of each secondary main lobe obscuring component is respectively:
E=[e1,...,ek,...,eK]
Wherein ekFor kth time main lobe obscuring component spatial domain steering vector,K= 1 ..., K, d are array element spacing, and λ is signal wavelength, and N indicates receiving channel number, subscriptTIndicate transposition operator.
Carrier aircraft real-time speed is estimated, in q-th of doppler cells, by taking kth time main lobe obscuring component as an example, according to following more The relational expression of general Le frequency and Space Angle calculates carrier aircraft real-time speed:
Wherein, fqFor the corresponding Doppler frequency value of q-th of doppler cells, all K main lobe obscuring components are estimated Carrier aircraft speed be averaged, obtained carrier aircraft real-time speed estimated value is:
Therefore, using the speed of estimation come secondary lobe obscuring component DoA values of extrapolating, in q-th of doppler cells, according to as follows Formula calculates the sine value that the m times secondary lobe obscuring component corresponds to Space Angle, i.e.,:
Wherein fSL,mFor the corresponding Doppler frequency of the m times secondary lobe obscuring component,Due to There are a secondary lobe component in main lobe both sides, m=± 1 ..., ± M, and M=5 is can use in engineer application.
The steering vector that all secondary lobe obscuring components are then calculated according to the DoA information of each secondary lobe obscuring component is:
A=[a-M,...,am,...,aM]
Wherein amFor the m times secondary lobe obscuring component spatial domain steering vector,M= ±1,…,±M。
The spatial domain steering vector that can get major and minor valve obscuring component by above description, utilizes the steering vector of acquisition Carry out Computer Aided Design Doppler ambiguity-resolution filter, by taking q-th of doppler cells extraction kth time main lobe obscuring component as an example, structure Solution Doppler ambiguity-resolution spatial domain covariance matrix be:
σ in formula0For the noise power-value of load, I ∈ CN×NUnit matrix, ehIt is corresponding for the h times main lobe obscuring component Spatial domain steering vector, subscriptHIndicate conjugate transposition operator, amFor the m times obscuring component spatial domain steering vector of secondary lobe, ρmFor m The corresponding Amplitude Ration coefficient of secondary secondary lobe obscuring component, is represented by
Wherein bmFor m-th of secondary lobe amplitude, F indicates main lobe amplitude, then extract k-th main lobe doppler ambiguity component from Adapt to Wave beam forming (ADBF) weights WkFor:
Utilize ADBF weights WkQ-th of doppler cells, k-th of main lobe obscuring component p of extractionq_kFor:
Wherein Z=[S1(i,q),...,SN(i,q)]TIndicate i-th of range cell, q-th of Doppler of N number of channel reception The vector expression of cell signal;
Last frequency spectrum reconfiguration is fuzzy by extracting k-th of main lobe respectively to each doppler cells in i-th of range cell Component signal is simultaneously denoted as P (i, k)=[p1_k,...,pNa_k], wherein pq_kFor k-th of main lobe of q-th of doppler cells extraction Obscuring component, Na indicate doppler cells number, then according to the corresponding different Doppler frequencies of each secondary main lobe obscuring component by institute There is the arrangement of main lobe obscuring component signal sequence, obtains data S (i, f after i-th of range cell Doppler ambiguity-resolutiona), i.e.,:
S(i,faP)=[(i, 1) ..., P (i, K)]
Wherein faIndicate the orientation Doppler frequency after Doppler ambiguity-resolution.
For each range cell repetitive operation above method, the distance-Doppler after Doppler ambiguity-resolution can be obtained Numeric field data, and orientation synthetic aperture imaging is carried out to it, you can obtain the High Resolution SAR Images after Doppler ambiguity-resolution.
The validity of this patent is verified below by Computer Simulation.The broadbands airborne multichannel SAR mapping system orientation battle array First number N=4, main lobe obscuring component K=3.Ground is divided into 3m drop target scattering points, target RCS along distance dimension between in emulation Meet multiple Gauss distribution.It is assumed that carrier aircraft speed presence ± 5m/s errors, i.e., when setting carrier aircraft speed V=150m/s, reality Speed V=155m/s, specific simulation parameter are as shown.
Parameter name Parameter values
Pulse recurrence frequency 210Hz
Transmitted signal bandwidth 60MHz
Distance is to sample rate 75MHz
Array element spacing 0.3m
Length of synthetic aperture 360m
Carrier aircraft flying height 4472m
Wavelength 0.03m
Reception diagram, now can by formula above as shown in figure 4, main lobe level is higher by 13.29dB than minor level Know in the Amplitude Ratio coefficient for calculating main lobe and secondary lobe, as:
I.e. principal subsidiary lobe amplitude coefficient calculated value is 0.25, the as amplitude coefficient of secondary lobe component.
Doppler's ambiguity three times is now provided as caused by orientation lack sampling, as shown in figure 5, resulting in void in orientation The appearance of decoy.
For doppler ambiguity situation, estimate that main lobe by the DoA values of lack sampling generation obscuring component, is as above schemed using NSIE Shown in 6.As Fig. 6 (a) indicates that practical carrier aircraft runs the space-time two-dimensional spectral curve of echo-signal;Fig. 6 (b) expressions pass through the derivation of equation Draw the ideal value of Space Angle.Compared to actual value, ideal value has ignored a series of error problems generated during aircraft motion, To cause steering vector mismatch problems.
This patent is the DoA information of main lobe obscuring component to be estimated by efficient NSIE, and utilize this estimated value further Derive the DoA of secondary lobe obscuring component.And then utilize the true DoA Computer Aided Designs airspace filter based on main lobe and secondary lobe obscuring component Utensil has real-time and accuracy, avoids steering vector mismatch problems.But to avoid solution doppler ambiguity in the process in The amplitude imbalance of signal and out of band signal, it is also necessary in conjunction with antenna principal subsidiary lobe Amplitude Ration coefficient.
Fig. 7 gives to be considered secondary lobe obscuring component and not to consider secondary lobe secondary lobe using peak sidelobe ratio to weigh Obscuring component inhibition.Fig. 7 (a) indicates only to consider the imaging results that Doppler frequency spectrum reconstruct obtains when main lobe obscuring component Figure;Fig. 7 (b) is after determining that secondary lobe obscuring component amplitude coefficient carries out main lobe and the inhibition of secondary lobe obscuring component based on antenna radiation pattern Imaging results figure.The simulation experiment result shows:Average peak secondary lobe ratio after the imaging of Fig. 7 (a) is 16.9dB, Fig. 7's (b) Average peak secondary lobe ratio after imaging is 26.5dB, and 9.6dB or so is improved compared to Fig. 7 (a).Therefore, context of methods can be quickly The amplitude coefficient of secondary lobe obscuring component Adaptive Suppression, and under operand, it is easy to engineering construction.
The problem that the present invention is directed to orientation doppler ambiguity and simultaneously effective inhibits secondary lobe fuzzy, it is proposed that Yi Zhongji In the doppler ambiguity component Adaptive Suppression method of antenna radiation pattern auxiliary.It is proposed in text and uses NSIE to estimate main lobe first Then the DoA values of each secondary obscuring component derive the DoA information with outer secondary lobe obscuring component, and then are based on each obscuring component DoA The amplitude coefficient of information and main lobe and secondary lobe obscuring component designs adaptive spatial filtering device, finally extracts each secondary main lobe mould successively It pastes component and reconstructs without ambiguous Doppler frequency spectrum.Simulation result shows to determine secondary lobe obscuring component amplitude according to antenna radiation pattern Peak sidelobe ratio performance ratio after its imaging of coefficient does not carry out the inhibition of secondary lobe obscuring component and compares, and improves about 9.6dB or so.This Literary grace parallel processing manner, therefore computational complexity is low, is easy to engineering construction.
Those skilled in the art of the present technique are it is understood that unless otherwise defined, all terms used herein (including skill Art term and scientific terminology) there is meaning identical with the general understanding of the those of ordinary skill in fields of the present invention.Also It should be understood that those terms such as defined in the general dictionary should be understood that with in the context of the prior art The consistent meaning of meaning, and unless defined as here, will not be explained with the meaning of idealization or too formal.
Above-described specific implementation mode has carried out further the purpose of the present invention, technical solution and advantageous effect It is described in detail, it should be understood that the foregoing is merely the specific implementation mode of the present invention, is not limited to this hair Bright, all within the spirits and principles of the present invention, any modification, equivalent substitution, improvement and etc. done should be included in the present invention Protection domain within.

Claims (1)

1. the doppler ambiguity component Adaptive Suppression method based on antenna radiation pattern auxiliary, which is characterized in that including walking as follows Suddenly:
Step 1) is respectively compressed the N number of receiving channel signal of airborne synthetic aperture radar into row distance to pulse, then progress side To dimension Fast Fourier Transform (FFT), the distance-Doppler numeric field data of each receiving channel is obtained, it is specific as follows:
Step 1.1) enables carrier aircraft fly along x-axis with speed V, and carrier aircraft flying height is H, and N number of even linear array is along course straight line point Cloth is transmitting-receiving array element along navigation direction left end array element, remaining is receives array element, and aircraft is in t=0 in coordinate origin Sky, the position x=Vt of aircraft when t, then the oblique distance in target to n-th of channel be:
Wherein, R0 2=H2+y0 2, d expression array element spacing;
Each the echo model in channel is:
In formula, KrRefer to the frequency modulation rate of transmitting pulse signal, τ indicates distance to the time, and t is the orientation time, and λ is wavelength;
Step 1.2), the ground echo Doppler frequency f of carried SARdRelationship between azimuth angle theta is as follows:
Enable target point to flight track vertical line and flight path point of intersection orientation time t=0 into row distance dimension pulse compression, then:
Wherein,KrTo emit the chirp rate of pulse signal;T be the orientation time, τ be distance to Time, Nr are distance to sampling number, and Na is orientation sampling number, FFTτAnd IFFTfrFu to τ about distance is indicated respectively In leaf transformation and about the inverse Fourier transform apart from frequency domain;
Step 1.3) ties up Fast Fourier Transform (FFT) by direction and obtains distance-Doppler numeric field data:
Sn(τ, f)=FFTt[Sn(τ,t)]
In formula, Sn(τ, f) is n-th of channel distance-Doppler domain data, and f is orientation Doppler frequency, FFTtIndicate about Fourier transformation on orientation time t;
Step 2) counts each range cell for each corresponding doppler cells of the range cell as follows It calculates:
Step 2.1) estimates the DoA values of each secondary main lobe obscuring component using NSIE technologiesWhereinIndicate master The DoA values of valve kth time obscuring component, K is the obscuring component number of main lobe, and k=1 ..., K, then each secondary main lobe obscuring component is corresponding Spatial domain steering vector is E=[e1,…,ek,…,eK], wherein ekFor kth time main lobe obscuring component spatial domain steering vector,D is array element spacing, and λ is signal wavelength, and N indicates that receiving channel number, subscript T indicate Transposition operator;
Step 2.2) calculates the corresponding carrier aircraft of each secondary main lobe obscuring component according to the relational expression of following Doppler frequency and Space Angle Real-time speed
Wherein, fqFor the corresponding Doppler frequency value of the doppler cells, q indicates that the doppler cells correspond to for the range cell Doppler cells set in q-th of doppler cells;
Step 2.3) carries out average meter to the corresponding carrier aircraft real-time speed of each main lobe obscuring component obtained in step 2.2) It calculates, obtained carrier aircraft real-time speed estimated value
Step 2.4) calculates the DoA information of each secondary lobe obscuring component according to following formula, i.e., it corresponds to the sine value of Space Angle
Wherein, fSL,mFor the corresponding Doppler frequency of the m times secondary lobe obscuring component,Due to main lobe It is the natural number more than zero that, which there are secondary lobe component, m=± 1 ..., ± M, M in both sides, and PRF is pulse recurrence frequency;
Step 2.5) calculates the corresponding steering vector of each secondary lobe obscuring component according to the DoA information of each secondary lobe obscuring component:
A=[a-M,…,am,…,aM]
Wherein, amFor the m times secondary lobe obscuring component spatial domain steering vector,M=± 1,…,±M;
Step 2.6) builds the spatial domain covariance of the corresponding solution Doppler ambiguity-resolution of each secondary main lobe obscuring component according to following formula Matrix is:
And h ≠ k, m ≠ 0
σ in formula0For the noise power-value of load, I ∈ CN×NUnit matrix, ehFor the corresponding spatial domain of the h times main lobe obscuring component Steering vector, subscriptHIndicate conjugate transposition operator, amFor the m times obscuring component spatial domain steering vector of secondary lobe, ρmFor the m times pair The corresponding Amplitude Ration coefficient of valve obscuring component, is represented by:
Wherein bmFor the corresponding antenna radiation pattern secondary lobe gain of m-th of secondary lobe obscuring component, F indicates that the main lobe of antenna radiation pattern increases Benefit;
Step 2.7) extracts the Adaptive beamformer weights W of each secondary main lobe doppler ambiguity componentkFor:
Step 2.8) utilizes Adaptive beamformer weights WkExtract each main lobe obscuring component pq_kFor:
Wherein Z=[S1(i,q),...,SN(i,q)]TIndicate that the vector expression of the doppler cells signal, i indicate that how general this is It is i-th of range cell to strangle the corresponding range cell of unit;
Step 2.9) extracts each main lobe obscuring component signal and is denoted as P (i, k)=[p1_k,...,pNa_k], wherein pq_kFor q K-th of main lobe obscuring component of a doppler cells extraction, Na indicate doppler cells number;
Step 3) will own each range cell according to the corresponding different Doppler frequencies of each secondary main lobe obscuring component Main lobe obscuring component signal sequence arranges, and obtains data S (i, f after each range cell Doppler ambiguity-resolutiona):
S(i,faP)=[(i, 1) ..., P (i, K)]
Wherein, faIndicate the orientation Doppler frequency after Doppler ambiguity-resolution;
Step 4) obtains the distance-Doppler numeric field data after Doppler ambiguity-resolution, and carries out orientation synthetic aperture imaging to it, Obtain the High Resolution SAR Images after Doppler ambiguity-resolution.
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