CN116068500A - Novel space-time interference suppression method for multichannel synthetic aperture radar - Google Patents

Novel space-time interference suppression method for multichannel synthetic aperture radar Download PDF

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CN116068500A
CN116068500A CN202310252878.3A CN202310252878A CN116068500A CN 116068500 A CN116068500 A CN 116068500A CN 202310252878 A CN202310252878 A CN 202310252878A CN 116068500 A CN116068500 A CN 116068500A
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interference
matrix
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CN116068500B (en
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黄岩
管歆宇
陈展野
杨阳
毛源
陈家乐
陈继新
洪伟
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Southeast University
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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
    • 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
    • G01S7/36Means for anti-jamming, e.g. ECCM, i.e. electronic counter-counter measures
    • 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
    • G01S13/9004SAR image acquisition techniques
    • 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
    • G01S7/41Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00 using analysis of echo signal for target characterisation; Target signature; Target cross-section

Abstract

The invention discloses a novel multichannel Synthetic Aperture Radar (SAR) space-time interference suppression method, which is based on a mathematical model of pitching dimension multichannel SAR, creatively combines a two-dimensional time domain low-rank recovery method with a airspace self-adaptive beam forming method, constructs a unified interference suppression optimization problem model, and provides an optimization problem closed solution based on an Alternating Direction Multiplier Method (ADMM) frame. Compared with the traditional interference suppression method, the SAR image result recovered by the interference suppression method has lower mean square error and higher structural similarity, namely the method has more effective interference suppression capability.

Description

Novel space-time interference suppression method for multichannel synthetic aperture radar
Technical Field
The invention belongs to the technical field of SAR interference suppression, and particularly relates to a multichannel-based SAR space-time interference suppression method.
Background
Radar, as an important military monitoring and civil detection device, is increasingly important to human production and life along with the continuous development and popularization of electronic technology, from the earliest military specialization to weather detection and topography mapping to the current vehicle-mounted radar and intelligent home. Synthetic Aperture Radar (SAR) has made a leap type progress as an all-weather, all-day and high-resolution earth observation means, has unique advantages in application in the fields of disaster monitoring, environment monitoring, marine observation, resource exploration, disaster early warning, crop estimation, forest investigation, topography mapping, battlefield reconnaissance and the like, can play the roles of other earth observation means such as visible light, infrared and the like, and is increasingly valued by the world.
The synthetic aperture radar transmits and receives electromagnetic waves at a designed pulse repetition frequency, and performs imaging processing on echo data received at different positions within a period of time by means of the motion of the platform. The technology synthesizes a series of antenna apertures by means of a motion platform to form a very large antenna aperture, and essentially utilizes time resources and space resources to obtain high resolution. The development of the array signal processing technology brings possibility for realizing a high-resolution wide-amplitude SAR imaging system, and higher scanning breadth and better resolution can be realized through a multi-channel technology.
However, a major challenge faced by current SAR systems is that rf interference, whether unintentional interference of civilian equipment or intentional interference of military equipment, has an impact on SAR systems, and thus interference suppression techniques have received increased attention. The traditional SAR interference suppression technology mainly can be divided into a non-parametric method, a parametric method and a semi-parametric method, wherein the non-parametric method is easy to realize and has relatively low computational complexity, but the optimal performance cannot be obtained because part of useful information is ignored; the parameterization method considers the amplitude information and the phase information of the signals at the same time, so that the calculation complexity is high and the performance is excellent, but certain performance is still lost during processing; the semi-parameterization method converts the interference suppression problem into a convex optimization problem, protects the real echo while suppressing the interference, and can obtain very good performance despite the very high computational complexity.
Disclosure of Invention
The invention aims to solve the problem that the current high-resolution wide-amplitude SAR imaging system is easily affected by strong radio frequency interference, and the interference suppression problem of a multichannel SAR system is solved by using the method provided by the invention. The method and the device can adaptively process the original data of the SAR system and effectively inhibit interference signals.
In order to solve the problems, the specific technical scheme of the invention is as follows: a novel multichannel synthetic aperture radar space-time interference suppression method, comprising the steps of:
step 1: inputting a multichannel SAR echo signal with interference:
step 2: constructing a space-time interference suppression convex optimization problem model;
step 3: optimizing variables in turn by using an ADMM frame;
step 4: judging whether the convergence condition is met or the maximum iteration number is reached, if yes, carrying out the step 5, and if not, repeating the step 3;
step 5: and obtaining SAR echo signals after interference suppression for subsequent imaging.
The method can adaptively inhibit interference signals from original SAR signals so as to recover real SAR imaging results, and comprises the following specific implementation steps:
step 1, an echo signal of ground scanning imaging is read by an SAR system with pitching dimension multichannel beam forming capability, wherein a transmitting signal is linear frequency modulation continuous wave, and strong radio frequency interference exists in the echo signal.
Step 2, combining a two-dimensional low-rank recovery method with a airspace self-adaptive beam forming method according to actual environment and SAR system parameters, introducing auxiliary variables at the same time, and constructing an interference suppression problem as a unified optimization problem, wherein the form is shown as follows
Figure SMS_1
Wherein:
Figure SMS_4
representing the original echo signal matrix of the input, +.>
Figure SMS_6
Representing a real echo signal matrix without interference,
Figure SMS_13
representing an interference signal matrix>
Figure SMS_2
For the introduced auxiliary variable matrix, +.>
Figure SMS_12
An operation of stacking vectors into a matrix is shown,
Figure SMS_3
weighting vectors for arrays>
Figure SMS_10
Indicating beam pointing +.>
Figure SMS_11
Array steering vector of angle, +.>
Figure SMS_16
In order to constrain the weights of the terms,
Figure SMS_5
、/>
Figure SMS_8
、/>
Figure SMS_9
respectively representing the computing kernel norms,/->
Figure SMS_15
Norms +.>
Figure SMS_14
Manipulation of norms, ++>
Figure SMS_17
As an arbitrarily small positive real number, superscript ++in the formula>
Figure SMS_7
Representing the conjugate transpose operation. The optimization objective of this optimization problem is to minimize the regularized interference signal power, minimize the error of the echo signal, and minimize the variance of the results of the array beamforming. While meeting the objective, it is also necessary to constrain the error of the sum of the interfering signal component and the echo signal component to be as small as possible with the original received signal and to ensure that the overall variance is as small as possible with the beamforming gain in the desired signal direction being a constant value. When the error of each component is optimized, each channel is processed independently, and when the beam forming problem is optimized, the data of all channels is required to be stacked and converted into a matrix form of a two-dimensional array signal through a certain operation, and the matrix form is processed. Compared with the prior art, the method has the advantages that the anti-interference performance is improved by combining the space domain beam forming constraint condition, a more effective and accurate optimization problem model is constructed, and meanwhile, the matrix data is beneficial to efficient calculation and solving.
The step 3 is specifically as follows: in order to solve the optimization problem in step 2, each variable in the optimization problem is updated in turn by using an alternate direction multiplier (ADMM) framework, the original problem is decomposed into a low rank recovery problem and an adaptive beam forming problem, and then the low rank recovery problem is converted into an augmented lagrangian function form.
And step 3, dividing the optimization problem in the step 2 into two sub-problems of time domain RPCA interference suppression optimization problem and space domain self-adaptive beam forming, constructing an augmented Lagrangian function, and introducing Lagrangian multipliers and punishment super-parameters. The augmented Lagrangian equation in step 3 is
Figure SMS_18
Wherein->
Figure SMS_19
The function is a lagrange multiplier,
Figure SMS_20
and 5, setting punishment super parameters.
And 4, optimizing the augmented Lagrangian function in the step 3 by using an ADMM frame, optimizing an interference signal matrix by using a singular value threshold method, optimizing an introduced auxiliary variable matrix by using a Lagrangian multiplier method, and optimizing a real echo signal matrix by using a soft threshold method. After that, the weight vector of the array antenna is optimized by using a linear constraint least squares (LCMV) method, and finally the remaining lagrangian multiplier and penalty parameters are optimized. And repeatedly cycling the variable optimization process until the convergence condition is met or the maximum iteration number is reached.
And 5, SAR imaging is carried out by using the real echo signals obtained in the step 4 after interference suppression and self-adaptive beam forming, so as to obtain a final output result, wherein the imaging process is similar to a coherent accumulation focusing process carried out by a conventional SAR system.
Further, the optimization problem solving sequence of the variables in the step 4 is that firstly, an interference matrix is optimized, then an auxiliary variable matrix is optimized, then a signal matrix and an array channel weighting vector are optimized, and finally, lagrangian multipliers and punishment super-parameters introduced in an augmented Lagrangian equation are optimized. And after each iteration solution is calculated through the ADMM framework, substituting the result of the iteration into the calculation formula of the next iteration for updating the variable. The singular value threshold method relaxes the non-convex optimization problem into a convex optimization problem, and the problem can be obtained by approximating a kernel norm and an F norm. The soft threshold method makes the multivariable optimization problem differentiable by constructing the monotonic function, so that the solution is convenient. The LCMV method is a traditional adaptive filtering algorithm for array signals, and reduces overall power anti-interference by limiting the gain in the desired direction to be constant.
Further, solving the variables in step 4
Figure SMS_21
The iterative closed-form solution of the optimization problem of (2) is:
Figure SMS_23
the singular value threshold function is used to assist the solution, wherein
Figure SMS_26
Representing the interference signal matrix estimation result of the next iteration, a>
Figure SMS_28
The loss function representing the current iterative calculation, the superscript of all parameters representing the iteration round, ++>
Figure SMS_24
And->
Figure SMS_25
For->
Figure SMS_29
SVT, which is a singular value decomposition matrix, represents a singular value threshold function +.>
Figure SMS_31
Wherein->
Figure SMS_22
Representing the input variable +.>
Figure SMS_27
Representing the threshold value used by the singular value threshold function, superscript ++in the formula>
Figure SMS_30
Representing the conjugate transpose operation.
Further, solving the variables in step 4
Figure SMS_32
An iterative closed-form solution to the optimization problem of +.>
Figure SMS_33
A soft threshold function is used to assist the solution, wherein +.>
Figure SMS_34
Representing the actual signal matrix estimation result of the next iteration,
Figure SMS_35
the loss function representing the current iteration calculation, the superscript of all parameters representing the iteration round, ST representing the soft threshold function +.>
Figure SMS_36
Wherein->
Figure SMS_37
Representing an input matrix +.>
Figure SMS_38
Representing the threshold used by the soft threshold function.
The novel space-time interference suppression method for the multichannel synthetic aperture radar has the following advantages:
1. the invention combines a low rank recovery method with an adaptive beam forming method;
2. the invention constructs a new space-time combined interference suppression optimization problem model;
3. the invention utilizes the ADMM framework to gradually solve the multivariable optimization problem;
4. the invention can adaptively process the input SAR original signal, output the signal after interference suppression, and effectively realize the suppression of narrowband and broadband radio frequency interference;
5. the method uses the assistance of the singular value threshold function and the soft threshold function when solving the optimization problem, improves the estimation accuracy and the anti-interference capability, reduces the root mean square error after interference suppression, and improves the structural similarity after interference suppression;
6. compared with the current method with better anti-interference capability, the method has the advantages that the performance is improved, the calculation complexity is reduced to a certain extent, and the calculation time is shortened.
Drawings
FIG. 1 is a schematic flow chart of the present invention;
FIG. 2-1 is a multi-channel SAR mathematical model (overall) of the present invention;
2-2 a multi-channel SAR mathematical model (cross-sectional view) of the present invention;
FIGS. 2-3 are multiple channel SAR mathematical models (array antennas) of the present invention;
FIG. 3 is a SAR image of a true non-interfering signal used in the present invention;
FIG. 4 is a SAR image of a real disturbance signal used in the present invention;
FIG. 5 is an SAR image after anti-interference using LCMV method;
FIG. 6 is an SAR image after anti-interference using ESP method;
fig. 7 is an SAR image after interference rejection using the method of the present invention.
Detailed Description
The present invention is further illustrated in the accompanying drawings and detailed description which are to be understood as being merely illustrative of the invention and not limiting of its scope, and various equivalent modifications to the invention will fall within the scope of the appended claims to the skilled person after reading the invention.
Example 1: a novel multichannel synthetic aperture radar space-time interference suppression method, comprising the steps of:
step 1: inputting a multichannel SAR echo signal with interference:
step 2: constructing a space-time interference suppression convex optimization problem model;
step 3: optimizing variables in turn by using an ADMM frame;
step 4: judging whether the convergence condition is met or the maximum iteration number is reached, if yes, carrying out the step 5, and if not, repeating the step 3;
step 5: and obtaining SAR echo signals after interference suppression for subsequent imaging.
The method can adaptively inhibit interference signals from original SAR signals so as to recover real SAR imaging results, and comprises the following specific implementation steps:
step 1, an echo signal of ground scanning imaging is read by an SAR system with pitching dimension multichannel beam forming capability, wherein a transmitting signal is linear frequency modulation continuous wave, and strong radio frequency interference exists in the echo signal.
Step 2, combining a two-dimensional low-rank recovery method with a airspace self-adaptive beam forming method according to actual environment and SAR system parameters, introducing auxiliary variables at the same time, and constructing an interference suppression problem as a unified optimization problem, wherein the form is shown as follows
Figure SMS_39
Wherein:
Figure SMS_45
representing the original echo signal matrix of the input, +.>
Figure SMS_41
Representing a real echo signal matrix without interference,
Figure SMS_50
representing an interference signal matrix>
Figure SMS_43
For the introduced auxiliary variable matrix, +.>
Figure SMS_46
An operation of stacking vectors into a matrix is shown,
Figure SMS_49
weighting vectors for arrays>
Figure SMS_54
Indicating beam pointing +.>
Figure SMS_52
Array steering vector of angle, +.>
Figure SMS_55
In order to constrain the weights of the terms,
Figure SMS_40
、/>
Figure SMS_47
、/>
Figure SMS_42
respectively representing the computing kernel norms,/->
Figure SMS_51
Norms +.>
Figure SMS_48
Manipulation of norms, ++>
Figure SMS_53
As an arbitrarily small positive real number, superscript ++in the formula>
Figure SMS_44
Representing the conjugate transpose operation. The optimization objective of this optimization problem is to minimize the regularized interference signal power, minimize the error of the echo signal, and minimize the variance of the results of the array beamforming. While meeting the objective, it is also necessary to constrain the error of the sum of the interfering signal component and the echo signal component to be as small as possible with the original received signal and to ensure that the overall variance is as small as possible with the beamforming gain in the desired signal direction being a constant value. When the error of each component is optimized, each channel is processed independently, and when the beam forming problem is optimized, the data of all channels is required to be stacked and converted into a matrix form of a two-dimensional array signal through a certain operation, and the matrix form is processed. Compared with the prior art, the method has the advantages that the anti-interference performance is improved by combining the space domain beam forming constraint condition, a more effective and accurate optimization problem model is constructed, and meanwhile, the matrix data is beneficial to efficient calculation and solving.
The step 3 is specifically as follows: in order to solve the optimization problem in step 2, each variable in the optimization problem is updated in turn by using an alternate direction multiplier (ADMM) framework, the original problem is decomposed into a low rank recovery problem and an adaptive beam forming problem, and then the low rank recovery problem is converted into an augmented lagrangian function form.
And step 3, dividing the optimization problem in the step 2 into two sub-problems of time domain RPCA interference suppression optimization problem and space domain self-adaptive beam forming, constructing an augmented Lagrangian function, and introducing Lagrangian multipliers and punishment super-parameters. The augmented Lagrangian equation in step 3 is
Figure SMS_56
Wherein->
Figure SMS_57
The function is a lagrange multiplier,
Figure SMS_58
and 5, setting punishment super parameters.
And 4, optimizing the augmented Lagrangian function in the step 3 by using an ADMM frame, optimizing an interference signal matrix by using a singular value threshold method, optimizing an introduced auxiliary variable matrix by using a Lagrangian multiplier method, and optimizing a real echo signal matrix by using a soft threshold method. After that, the weight vector of the array antenna is optimized by using a linear constraint least squares (LCMV) method, and finally the remaining lagrangian multiplier and penalty parameters are optimized. And repeatedly cycling the variable optimization process until the convergence condition is met or the maximum iteration number is reached.
And 5, SAR imaging is carried out by using the real echo signals obtained in the step 4 after interference suppression and self-adaptive beam forming, so as to obtain a final output result, wherein the imaging process is similar to a coherent accumulation focusing process carried out by a conventional SAR system.
Further, the optimization problem solving sequence of the variables in the step 4 is that firstly, an interference matrix is optimized, then an auxiliary variable matrix is optimized, then a signal matrix and an array channel weighting vector are optimized, and finally, lagrangian multipliers and punishment super-parameters introduced in an augmented Lagrangian equation are optimized. And after each iteration solution is calculated through the ADMM framework, substituting the result of the iteration into the calculation formula of the next iteration for updating the variable. The singular value threshold method relaxes the non-convex optimization problem into a convex optimization problem, and the problem can be obtained by approximating a kernel norm and an F norm. The soft threshold method makes the multivariable optimization problem differentiable by constructing the monotonic function, so that the solution is convenient. The LCMV method is a traditional adaptive filtering algorithm for array signals, and reduces overall power anti-interference by limiting the gain in the desired direction to be constant.
Further, solving the variables in step 4
Figure SMS_59
The iterative closed-form solution of the optimization problem of (2) is:
Figure SMS_61
the singular value thresholding function is used to assist the solution, where +.>
Figure SMS_65
Representing the interference signal matrix estimation result of the next iteration, a>
Figure SMS_68
The loss function representing the current iterative calculation, the superscript of all parameters representing the iteration round, ++>
Figure SMS_62
And->
Figure SMS_64
For->
Figure SMS_67
SVT, which is a singular value decomposition matrix, represents a singular value threshold function +.>
Figure SMS_69
Wherein->
Figure SMS_60
Representing the input variable +.>
Figure SMS_63
Representing the threshold value used by the singular value threshold function, superscript ++in the formula>
Figure SMS_66
Representing the conjugate transpose operation.
Further, solving the variables in step 4
Figure SMS_70
An iterative closed-form solution to the optimization problem of +.>
Figure SMS_71
A soft threshold function is used to assist the solution, wherein +.>
Figure SMS_72
Representing the actual signal matrix estimation result of the next iteration,
Figure SMS_73
the loss function representing the current iteration calculation, the superscript of all parameters representing the iteration round, ST representing the soft threshold function +.>
Figure SMS_74
Wherein->
Figure SMS_75
Representing an input matrix +.>
Figure SMS_76
Representing the threshold used by the soft threshold function.
Example 2: the invention discloses a novel multichannel synthetic aperture radar space-time interference suppression method, which is implemented by selecting simulated SAR image data and real SAR image data. As shown in fig. 1, the specific implementation method of the present invention is as follows:
step 1: and reading the SAR image data with real original interference by using matlab software, wherein a large amount of suppression interference exists on the original data image.
Step 2: according to the actual environment and SAR system parameters, constructing a pitching multichannel SAR system model shown in figures 2-1, 2-2 and 2-3, combining a two-dimensional low rank recovery method with a airspace self-adaptive beam forming method, introducing auxiliary variables, and constructing an interference suppression problem as a unified optimization problem, wherein the mode is as follows
Figure SMS_77
,/>
Figure SMS_78
Representing the original echo signal matrix of the input, +.>
Figure SMS_79
Matrix of real echo signals representing no interference, +.>
Figure SMS_80
Representing an interference signal matrix>
Figure SMS_81
For the introduced auxiliary variable matrix, +.>
Figure SMS_82
Representing an operation of stacking the directions as a matrix, < >>
Figure SMS_83
The vectors are weighted for the array.
Step 3: dividing the optimization problem in the step 2 into two sub-problems of time domain RPCA interference suppression optimization problem and space domain self-adaptive beam forming, constructing an augmented Lagrangian function, and introducing Lagrangian multipliers and punishment super-parameters. Its augmented Lagrangian equation can be written as
Figure SMS_84
Wherein->
Figure SMS_85
Is Lagrangian multiplier, +.>
Figure SMS_86
And 5, setting punishment super parameters.
Step 4: and (3) optimizing the augmented Lagrangian function in the step (3) by using an ADMM (adaptive modulation) framework through a programming program by using matlab software, optimizing an interference signal matrix by using a singular value threshold method, optimizing an introduced auxiliary variable matrix by using a Lagrangian multiplier method, and optimizing a real echo signal matrix by using a soft threshold method. After that, the weight vector of the array antenna is optimized by using a linear constraint least squares (LCMV) method, and finally the remaining lagrangian multiplier and penalty parameters are optimized. And repeatedly cycling the variable optimization process until the convergence condition is met or the maximum iteration number is reached. Further, the optimization problem solving sequence of the variables in the step 4 is that firstly, an interference matrix is optimized, then an auxiliary variable matrix is optimized, then a signal matrix and an array channel weighting vector are optimized, and finally, lagrangian multipliers and punishment super-parameters introduced in an augmented Lagrangian equation are optimized. And after each iteration solution is calculated through the ADMM framework, substituting the result of the iteration into the calculation formula of the next iteration for updating the variable. The singular value threshold method relaxes the non-convex optimization problem into a convex optimization problem, and the problem can be obtained by approximating a kernel norm and an F norm. The soft threshold method makes the multivariable optimization problem differentiable by constructing the monotonic function, so that the solution is convenient. The LCMV method is a traditional adaptive filtering algorithm for array signals, and reduces overall power anti-interference by limiting the gain in the desired direction to be constant.
Step 5: through the matlab program written in the step 4, echo signals of all channels after interference suppression and weighting coefficients corresponding to all channels, which are output by the method, can be obtained, and the final real echo signals for interference suppression can be obtained for imaging through weighted summation. The multichannel data are synthesized into single-channel data after being weighted by wave beam formation, and then the radar data are focused by using a conventional SAR coherent accumulation mode, so that the imaging process is completed.
In summary, in the novel multi-channel synthetic aperture radar space-time interference suppression method, imaging tests are performed on two simulated and real SAR images, the original SAR image is shown in fig. 3, and a large amount of interference exists on the interfered SAR image, as shown in fig. 4. The image processed by the method of the invention is shown in fig. 7, and the original signal is processed by the method, so that the effect of suppressing interference in the SAR system is finally realized. Fig. 5 and 6 are effects achieved by other methods, and are used for comparison with the method proposed by the present invention. The imaging effect of the method of the invention is relatively poor, and the imaging effect of the method of the invention is relatively good, so that the geomorphic features can be clearly displayed. In terms of data, the root mean square error of fig. 5 and 6 using other methods is higher than that of fig. 7 using the method of the present invention, and the structural similarity is lower than that of the method of the present invention.
The foregoing is only a preferred embodiment of the invention, it being noted that: while the invention has been described with reference to certain embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the spirit and scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.

Claims (10)

1. A novel multichannel synthetic aperture radar space-time interference suppression method, which is characterized by comprising the following steps:
step 1: a multi-channel SAR echo signal with interference is input,
step 2: constructing a space-time interference suppression convex optimization problem model,
step 3: the variables are optimized in turn by using an alternate direction multiplier method framework,
step 4: judging whether the convergence condition is met or the maximum iteration number is reached, if yes, carrying out step 5, if no, repeating step 3,
step 5: and obtaining SAR echo signals after interference suppression for subsequent imaging.
2. The method for suppressing space-time interference of a novel multi-channel synthetic aperture radar according to claim 1, wherein,
the step 1 is specifically as follows: reading an echo signal of a ground scanning imaging by an SAR system with pitching dimension multichannel beam forming capability, wherein the transmitting signal is linear frequency modulation continuous wave, and strong radio frequency interference exists in the echo signal;
the step 2 is specifically as follows: according to the actual environment and SAR system parameters, combining a two-dimensional low-rank recovery method with a airspace self-adaptive beam forming method, introducing auxiliary variables, and constructing the interference suppression problem as a unified optimization problem.
3. The method for suppressing space-time interference of a novel multi-channel synthetic aperture radar according to claim 2, wherein,
the step 3 is specifically as follows: in order to solve the optimization problem in the step 2, each variable in the optimization problem is updated in turn by using an alternate direction multiplier method framework, the original problem is decomposed into a low rank recovery problem and an adaptive beam forming problem, and then the low rank recovery problem is converted into an augmented Lagrange function form.
4. The method for suppressing space-time interference of a novel multi-channel synthetic aperture radar according to claim 3, wherein,
the step 4 is specifically as follows: optimizing the augmented Lagrangian function in the step 3 by using an alternate direction multiplier method, optimizing an interference signal matrix by using a singular value threshold method, optimizing an introduced auxiliary variable matrix by using a Lagrangian multiplier method, optimizing a real echo signal matrix by using a soft threshold method, optimizing a weight vector of an array antenna by using a linear constraint least variance method (LCMV), optimizing the rest Lagrangian multiplier and penalty parameters, and repeating the variable optimization process until convergence conditions are met or the maximum iteration times are reached.
5. The method for suppressing space-time interference of a novel multi-channel synthetic aperture radar as claimed in claim 4, wherein,
the step 5 is specifically as follows: SAR imaging is carried out by using the real echo signals obtained in the step 4, which are subjected to interference suppression and self-adaptive beam forming, so that a final imaging result is obtained, and the imaging process is similar to the coherent accumulation focusing process carried out by a conventional SAR system.
6. The method for suppressing space-time interference of a novel multi-channel synthetic aperture radar according to claim 5, wherein,
in step 2, the form is as follows:
Figure QLYQS_1
wherein:
Figure QLYQS_4
representing the original echo signal matrix of the input, +.>
Figure QLYQS_3
Matrix of real echo signals representing no interference, +.>
Figure QLYQS_9
Representing an interference signal matrix>
Figure QLYQS_5
For the introduced auxiliary variable matrix, +.>
Figure QLYQS_11
Representing an operation of stacking vectors as a matrix,/->
Figure QLYQS_13
Weighting vectors for arrays>
Figure QLYQS_16
Indicating beam pointing +.>
Figure QLYQS_12
Array steering vector of angle, +.>
Figure QLYQS_15
For the weight of the constraint term, +.>
Figure QLYQS_2
Figure QLYQS_8
、/>
Figure QLYQS_6
Respectively representing the computing kernel norms,/->
Figure QLYQS_10
Norms +.>
Figure QLYQS_14
Manipulation of norms, ++>
Figure QLYQS_17
As an arbitrarily small positive real number, superscript ++in the formula>
Figure QLYQS_7
Representing the conjugate transpose operation.
7. The method for suppressing space-time interference of a novel multi-channel synthetic aperture radar according to claim 6, wherein,
the augmented Lagrangian equation in step 3 is
Figure QLYQS_18
Wherein->
Figure QLYQS_19
Is Lagrangian multiplier, +.>
Figure QLYQS_20
And 5, setting punishment super parameters.
8. The method for suppressing space-time interference of a novel multi-channel synthetic aperture radar according to claim 7, wherein,
the optimization problem solving sequence of the variables in the step 4 is that firstly, an interference matrix is optimized, then an auxiliary variable matrix is optimized, then a signal matrix and an array channel weighting vector are optimized, finally, lagrange multiplier and punishment super-parameters introduced in an augmented Lagrange equation are optimized, after each calculation is completed through an alternate direction multiplier method frame, the result of the iteration is substituted into a calculation formula of the next iteration for updating the variables, wherein the singular value threshold method is used for solving a closed solution by loosening a non-convex optimization problem into a convex optimization problem and approximating the convex optimization problem with an F norm, the soft threshold method is used for differentiating the multi-variable optimization problem by constructing the monotonic function, the solution is convenient, the LCMV method is a traditional array signal self-adaptive filtering algorithm, and the integral power anti-interference is reduced by limiting the expected direction gain to be constant.
9. The method for suppressing space-time interference of a novel multi-channel synthetic aperture radar according to claim 8, wherein,
solving the variables in step 4
Figure QLYQS_21
The iterative closed-form solution of the optimization problem of (2) is:
Figure QLYQS_24
the singular value thresholding function is used to assist the solution, where +.>
Figure QLYQS_25
Representing the interference signal matrix estimation result of the next iteration, a>
Figure QLYQS_28
The loss function representing the current iterative calculation, the superscript of all parameters representing the iteration round, ++>
Figure QLYQS_23
And->
Figure QLYQS_27
For->
Figure QLYQS_30
SVT, which is a singular value decomposition matrix, represents a singular value threshold function +.>
Figure QLYQS_31
Wherein->
Figure QLYQS_22
Representing the input variable +.>
Figure QLYQS_26
Representing the threshold value used by the singular value threshold function, superscript ++in the formula>
Figure QLYQS_29
Representing the conjugate transpose operation.
10. The method for suppressing space-time interference of a novel multi-channel synthetic aperture radar according to claim 9, wherein,
solving the variables in step 4
Figure QLYQS_32
An iterative closed-form solution to the optimization problem of +.>
Figure QLYQS_33
A soft threshold function is used to assist the solution, wherein +.>
Figure QLYQS_34
Representing the real signal matrix estimation result of the next iteration, a>
Figure QLYQS_35
The loss function representing the current iteration calculation, the superscript of all parameters representing the iteration round, ST representing the soft threshold function +.>
Figure QLYQS_36
Wherein->
Figure QLYQS_37
Representing an input matrix +.>
Figure QLYQS_38
Representing the threshold used by the soft threshold function. />
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