CN108226929B - Detection method and detection system for front side view SAR slow speed target - Google Patents

Detection method and detection system for front side view SAR slow speed target Download PDF

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CN108226929B
CN108226929B CN201810028495.7A CN201810028495A CN108226929B CN 108226929 B CN108226929 B CN 108226929B CN 201810028495 A CN201810028495 A CN 201810028495A CN 108226929 B CN108226929 B CN 108226929B
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doppler frequency
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CN108226929A (en
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曾虹程
陈杰
杨威
王鹏波
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Beijing University of Aeronautics and Astronautics
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Beijing University of Aeronautics and Astronautics
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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
    • G01S13/9021—SAR image post-processing techniques
    • G01S13/9029—SAR image post-processing techniques specially adapted for moving target detection within a single SAR image or within multiple SAR images taken at the same time
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/02—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00
    • G01S7/41—Details 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

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

Abstract

The invention discloses a method for detecting a front side view SAR slow speed target. The detection method is a front side view SAR slow speed target detection method based on improved Radon-Fourier transformation, avoids distance interpolation operation in the traditional Radon-Fourier transformation algorithm, and effectively improves algorithm efficiency. Meanwhile, the detection method provided by the invention is carried out in a parameter search mode, and can flexibly select parameter search steps and search times by combining the detection precision requirement and the detection target type, so that the algorithm efficiency is further improved on the premise of meeting the detection requirement, the requirements of different detection precisions can be met, and the detection method has the characteristics of convenience and flexibility.

Description

Detection method and detection system for front side view SAR slow speed target
Technical Field
The invention relates to the field of signal processing, in particular to a detection method and a detection system for a front side view SAR slow-speed target.
Background
The detection of slow moving targets (such as armored vehicles, ships, unmanned planes and the like) has important significance in the application field of military and civil. When a slow-moving target exists in an SAR imaging scene, the slow movement of the target brings huge challenges to target detection. Firstly, because the SAR platform has a high motion speed, a slow target may be submerged in a Doppler frequency spectrum of clutter; secondly, the Doppler error introduced by the slow target is small, so that the defocusing phenomenon of the slow target is weak, and the slow target is inconvenient to find out from the SAR image; finally, when the target only has radial velocity, the moving target only introduces an azimuth displacement in the SAR image, so that the moving target is like a static target in the final SAR image, and the detection difficulty of the moving target is further increased.
At present, SAR moving target detection mainly aims at medium or fast moving targets to carry out research, and mainly aims at some new system SAR systems, such as azimuth multi-channel SAR, video SAR, interference SAR and the like. For slow target detection, some slow target detection methods are also proposed in succession based on special working systems such as a slow SAR platform and an interferometric SAR, but the application range of the algorithms is very limited and has no universal significance. In recent years, the proposal of Radon-Fourier transform algorithm realizes the long-time coherent accumulation of moving targets in the traditional radar, the algorithm realizes the effective detection of the targets through two-dimensional/high-dimensional joint search of target movement information (such as target distance, speed and the like), and can effectively overcome the problem that Doppler blind velocity cannot be detected. Therefore, the algorithm is widely applied to radar moving target detection.
However, the space geometric relationship, the echo signal model, the distance history and the like of the SAR system are completely different from those of the conventional radar, so that the conventional Radon-Fourier transform algorithm cannot be applied to the detection of the SAR slow-speed moving target. Therefore, how to detect the SAR slow motion target becomes a technical problem that needs to be solved urgently by those skilled in the art.
Disclosure of Invention
The invention aims to provide a detection method and a detection system for a front side view SAR slow-speed moving target, which can accurately acquire the moving parameters of the SAR slow-speed moving target.
In order to achieve the purpose, the invention provides the following scheme:
a detection method for a front side view SAR slow speed target comprises the following steps:
two-dimensional original echo simulation array S for obtaining front-side view SAR slow speed targetstartTarget detection parameter and azimuth frequency one-dimensional array ftAnd distance frequency one-dimensional array fτWherein said SstartIs Na×NrA two-dimensional complex set, the target detection parameters comprising: number of sampling points in azimuth direction NaNumber of distance sampling points NrSignal sampling rate fsOf signal bandwidth BwPulse signal repetition frequency PRF, pulse signal width τ, stage motion velocity V, reference slope distance RrefCenter frequency f of system Dopplerd0Frequency f of system Doppler modulationr0Signal propagation speed c, signal wavelengthλ；
Simulating an array S for the echostartPerforming Fourier transform to obtain a first complex set S1；
For the first plurality of groups S1Performing Fourier transform to obtain a second complex group S2；
According to the azimuth frequency one-dimensional array ftAnd distance frequency one-dimensional array fτFor the second plurality of groups S2Performing uniform compression to obtain a third complex group S3；
For the third complex number set S3Performing inverse Fourier transform to obtain a fourth complex group S4；
Searching for stepping length delta f 'according to preset Doppler frequency'dDetermining a Doppler frequency search one-dimensional array f 'with a preset Doppler frequency search time threshold N'dAnd searching for the stepping length delta f 'according to the preset Doppler modulation frequency'rDetermining a Doppler frequency modulation rate search one-dimensional array f 'according to a preset Doppler frequency modulation rate search time threshold M'r；
Obtaining the current Doppler frequency modulation rate search times m, constructing and initializing a three-dimensional complex group SresultWherein M is 1,2,.. times.m, the three-dimensional complex group SresultIs of size MxNa×NrAfter initialization, three-dimensional plural set SresultWherein each element is 0;
sampling point number N according to the azimuthaAnd pulse signal repetition frequency PRF determines azimuth moment one-dimensional array Ta；
Constructing and initializing a fifth plurality S5The fifth plurality of sets S5Is of size Na×Nr；
Obtaining the search times n of the current Doppler frequency and obtaining a one-dimensional array T according to the azimuth momentaThe signal propagation speed c, the signal wavelength lambda and the Doppler frequency search one-dimensional array f'dAnd the distance frequency one-dimensional array fτDetermining a two-dimensional distance walk-off compensation factor array Hw_rWherein N is 1, 2.., N;
according to the formula: s6(i,j)＝S5(i,j)+S4(i,j)Hw_r(i, j) determining a sixth complex set S6Wherein S is6(i, j) represents a sixth complex group S6Component of ith row and jth column, S5(i, j) represents a fifth complex group S5Component of ith row and jth column, S4(i, j) represents a fourth complex group S4Component of row i and column j, Hw_r(i, j) represents a two-dimensional distance walk compensation factor array Hw_rRow i and column j components;
judging whether the current Doppler frequency search times are equal to a preset Doppler frequency search time threshold value N or not, and obtaining a first judgment result;
if the first judgment result shows that the current Doppler frequency search times are smaller than a preset Doppler frequency search time threshold value N, updating the Doppler frequency search times N, and returning to the step ofaThe signal propagation speed c, the signal wavelength lambda and the Doppler frequency search one-dimensional array f'dAnd the distance frequency one-dimensional array fτDetermining a two-dimensional distance walk-off compensation factor array Hw_r”
If the first judgment result shows that the current Doppler frequency search times are equal to a preset Doppler frequency search time threshold N, searching a one-dimensional array f 'according to the signal wavelength lambda and the Doppler modulation frequency'rAnd the azimuth moment one-dimensional array TaDetermining a phase error compensation factor array Hc_r；
According to the formula: s7(i,j)＝S6(i,j)Hc_r(i) Determining a seventh plurality of sets S7Wherein S is7(i, j) represents a seventh complex group S7Component of row i and column j, Hc_r(i) Array H representing one-dimensional phase error compensation factorsc_rThe ith component of (a);
for the seventh complex group S7Sequentially performing inverse distance Fourier transform and Fourier azimuth transform to obtain an eighth complex group S8；
Judging whether the current Doppler frequency modulation frequency searching times M are equal to a preset Doppler frequency modulation frequency searching time threshold value M or not, and obtaining a second judgment result;
if the second judgment result shows that the current Doppler frequency modulation frequency searching times M are smaller than a preset Doppler frequency modulation frequency searching time threshold value M, updating the Doppler frequency modulation frequency searching times M, and returning to the step of sampling points N according to the azimuth directionaAnd pulse signal repetition frequency PRF determines azimuth moment one-dimensional array Ta”
If the second judgment result indicates that the current Doppler frequency modulation search times M are equal to the preset Doppler frequency modulation search time threshold value M, according to each eighth complex group S8Updating the three-dimensional complex set Sresult；
According to the three-dimensional complex number set SresultAnd determining the motion parameters of the front-side looking SAR slow target.
Optionally, the one-dimensional array f according to the azimuth frequencytAnd distance frequency one-dimensional array fτFor the second plurality of groups S2Performing uniform compression to obtain a third complex group S3The method specifically comprises the following steps:
according to the formula:determining ith row and jth column component H of consistent compression processing two-dimensional compensation complex groupc(i, j) wherein fτ(j) One-dimensional array f representing range frequencyτThe (j) th component of (a),j＝1,2,…,Nr，ft(i) one-dimensional array f representing azimuth frequencytThe (i) th component of (a),i＝1,2,…,Na；
according to the formula: s3(i,j)＝S2(i,j)Hc(i, j) determining a third complex number after the uniform compression processGroup S3Wherein S is3(i, j) represents the third complex set S3Of the ith row and the jth column, S2(i, j) represents said second complex set S2Row i and column j.
Optionally, the one-dimensional array T according to the azimuth timeaThe signal propagation speed c, the signal wavelength lambda and the Doppler frequency search one-dimensional array f'dAnd the distance frequency one-dimensional array fτDetermining a two-dimensional distance walk-off compensation factor array Hw_rThe method specifically comprises the following steps:
according to the formula: determining a two-dimensional distance walk-off compensation factor array Hw_rIth row and jth column of (1)w_r(i, j) wherein f'd(n) represents a Doppler frequency search one-dimensional array f'dN is 1,2, …, N, Ta(i) One-dimensional array T representing the azimuth timeaI-1, 2, …, Na，fτ(j) One-dimensional array f representing range frequencyτThe (j) th component of (a),
according to respective component Hw_r(i, j) generating a two-dimensional distance walk compensation factor array.
Optionally, the one-dimensional array f 'is searched according to the signal wavelength λ and the doppler modulation frequency'rAnd the azimuth moment one-dimensional array TaDetermining a phase error compensation factor array Hc_rThe method specifically comprises the following steps:
according to the formula: hc_r(i)＝exp{jπλf′r(m)Ta 2(i) Determine a one-dimensional phase error compensation factor array Hc_rOf (a) is not limited, wherein fr(m) represents a one-dimensional array f 'of Doppler modulation frequency search'rOf the m-th component, Ta(i) One-dimensional array T for representing azimuth timeaI-1, 2, …, Na，Hc_r(i) Array H representing one-dimensional phase error compensation factorsc_rThe ith component of (a); (ii) a
And generating a one-dimensional phase error compensation factor array according to the components of each one-dimensional phase error compensation factor array.
Optionally, the three-dimensional complex number group SresultDetermining the motion parameters of the front-side view SAR slow speed target specifically comprises the following steps:
in the three-dimensional complex group SresultScreening out a local maximum value;
determining the local maximum in the three-dimensional complex set SresultWhere n ', m ' and r ' respectively represent the local maximum in the three-dimensional complex set SresultCoordinates in three dimensions;
according to the formula:
determining a motion parameter (f) of the front-looking side SAR slow targetdm,frmR) wherein fdmDoppler frequency, f, representing slow objectsrmThe system Doppler modulation frequency of the slow target is shown, and r is the distance between the slow target and the SAR system.
A detection system for looking ahead at a SAR slow target, the detection system comprising:
a first data acquisition module for acquiring a two-dimensional original echo simulation array S of the front-side view SAR slow speed targetstartTarget detection parameter and azimuth frequency one-dimensional array ftAnd distance frequency one-dimensional array fτWherein said SstartIs Na×NrA two-dimensional complex set, the target detection parameters comprising: number of sampling points in azimuth direction NaNumber of distance sampling points NrSignal sampling rate fsOf signal bandwidth BwPulse signal repetition frequency PRF, pulse signal width τ, stage motion velocity V, reference slope distance RrefCenter frequency f of system Dopplerd0Frequency f of system Doppler modulationr0Signal propagation speed c, signal wavelength λ;
a first complex group obtaining module for simulating the echoArray SstartPerforming Fourier transform to obtain a first complex set S1；
A second complex group obtaining module for obtaining the first complex group S1Performing Fourier transform to obtain a second complex group S2；
A third complex group obtaining module for obtaining a one-dimensional array f according to the azimuth frequencytAnd distance frequency one-dimensional array fτFor the second plurality of groups S2Performing uniform compression to obtain a third complex group S3；
A fourth complex group obtaining module for obtaining the third complex group S3Performing inverse Fourier transform to obtain a fourth complex group S4；
A Doppler frequency search one-dimensional array determining module for searching the step length delta f 'according to the preset Doppler frequency'dDetermining a Doppler frequency search one-dimensional array f 'with a preset Doppler frequency search time threshold N'd；
A Doppler modulation frequency search one-dimensional array determining module for searching the stepping length delta f 'according to the preset Doppler modulation frequency'rDetermining a Doppler frequency modulation rate search one-dimensional array f 'according to a preset Doppler frequency modulation rate search time threshold M'r；
The Doppler frequency modulation frequency searching times acquiring module is used for acquiring the current Doppler frequency modulation frequency searching times m;
a three-dimensional complex group initialization module for constructing and initializing a three-dimensional complex group SresultWherein M is 1,2,.. times.m, the three-dimensional complex group SresultIs of size MxNa×NrAfter initialization, three-dimensional plural set SresultWherein each element is 0;
an orientation moment one-dimensional array determining module for determining the number N of sampling points according to the orientationaAnd pulse signal repetition frequency PRF determines azimuth moment one-dimensional array Ta；
A fifth complex group initializing module for constructing and initializing a fifth complex group S5Said fifth itemPlural sets S5Is of size Na×Nr；
The Doppler frequency searching times acquiring module is used for acquiring the current Doppler frequency searching times n;
a two-dimensional distance walking compensation factor array determining module for determining the one-dimensional array T according to the azimuth momentaThe signal propagation speed c, the signal wavelength lambda and the Doppler frequency search one-dimensional array f'dAnd the distance frequency one-dimensional array fτDetermining a two-dimensional distance walk-off compensation factor array Hw_rWherein N is 1, 2.., N;
a sixth complex group determination module to: s6(i,j)＝S5(i,j)+S4(i,j)Hw_r(i, j) determining a sixth complex set S6Wherein S is6(i, j) represents a sixth complex group S6Component of ith row and jth column, S5(i, j) represents a fifth complex group S5Component of ith row and jth column, S4(i, j) represents a fourth complex group S4Component of row i and column j, Hw_r(i, j) represents a two-dimensional distance walk compensation factor array Hw_rRow i and column j components;
the first judgment module is used for judging whether the current Doppler frequency search times are equal to a preset Doppler frequency search time threshold value N or not and obtaining a first judgment result;
a doppler frequency search frequency updating module, configured to update the doppler frequency search frequency N when the first determination result indicates that the current doppler frequency search frequency is smaller than a preset doppler frequency search frequency threshold N, and send the updated doppler frequency search frequency to the two-dimensional distance walking compensation factor determining module "
A phase error compensation factor array determining module, configured to search a one-dimensional array f 'according to the signal wavelength λ and the doppler modulation frequency when the first determination result indicates that the current doppler frequency search frequency is equal to a preset doppler frequency search frequency threshold N'rAnd the azimuth moment one-dimensional array TaDetermining a phase error compensation factor array Hc_r；
A seventh complex group determination module to: s7(i,j)＝S6(i,j)Hc_r(i) Determining a seventh plurality of sets S7Wherein S is7(i, j) represents a seventh complex group S7Component of row i and column j, Hc_r(i) Array H representing one-dimensional phase error compensation factorsc_rThe ith component of (a);
an eighth complex group determination module for determining the seventh complex group S7Sequentially performing inverse distance Fourier transform and Fourier azimuth transform to obtain an eighth complex group S8；
The second judgment module is used for judging whether the current Doppler frequency modulation frequency search times M are equal to a preset Doppler frequency modulation frequency search time threshold value M or not and obtaining a second judgment result;
the doppler frequency modulation frequency search frequency updating module is configured to update the doppler frequency modulation frequency search frequency M and send the updated doppler frequency modulation frequency search frequency M to the azimuth time one-dimensional array determining module when the second determination result indicates that the current doppler frequency modulation frequency search frequency M is smaller than a preset doppler frequency modulation frequency search frequency threshold M;
a three-dimensional complex group updating module, configured to, when the second determination result indicates that the current doppler frequency modulation search time M is equal to the preset doppler frequency modulation search time threshold M, update the current doppler frequency modulation search time M according to each eighth complex group S8Updating the three-dimensional complex set Sresult；
A motion parameter determination module for determining a motion parameter from the three-dimensional complex group SresultAnd determining the motion parameters of the front-side looking SAR slow target.
Optionally, the third complex group obtaining module specifically includes:
a two-dimensional compensation complex component determination unit for determining the complex component according to the formula:determining ith row and jth column component H of consistent compression processing two-dimensional compensation complex groupc(i, j) wherein fτ(j) One-dimensional array f representing range frequencyτThe (j) th component of (a),j＝1,2,…,Nr，ft(i) one-dimensional array f representing azimuth frequencytThe (i) th component of (a),i＝1,2,…,Na；
a third complex group determination unit for: s3(i,j)＝S2(i,j)Hc(i, j) determining a third complex set S after the uniform compression process3Wherein S is3(i, j) represents the third complex set S3Of the ith row and the jth column, S2(i, j) represents said second complex set S2Row i and column j.
Optionally, the two-dimensional distance walking compensation factor determining module specifically includes:
a two-dimensional distance walk compensation factor array component determination unit for, according to a formula:determining a two-dimensional distance walk-off compensation factor array Hw_rIth row and jth column of (1)w_r(i, j) wherein f'd(n) represents a Doppler frequency search one-dimensional array f'dN is 1,2, …, N, Ta(i) One-dimensional array T representing the azimuth timeaI-1, 2, …, Na，fτ(j) One-dimensional array f representing range frequencyτThe (j) th component of (a),
a two-dimensional distance walk compensation factor array generation unit for generating compensation factor arrays according to the components Hw_r(i, j) generating a two-dimensional distance walk compensation factor array.
Optionally, the phase error compensation factor determining module specifically includes:
a phase error compensation factor array component determination unit for determining a phase error compensation factor array component according to the formula:determining a one-dimensional phase error compensation factor array Hc_rOf f ', where'r(m) represents a one-dimensional array f 'of Doppler modulation frequency search'rOf the m-th component, Ta(i) One-dimensional array T for representing azimuth timeaI-1, 2, …, Na；
And the one-dimensional phase error compensation factor array generating unit is used for generating a one-dimensional phase error compensation factor array according to the components of each phase error compensation factor array.
Optionally, the motion parameter determining module specifically includes:
a screening unit for screening the three-dimensional complex group SresultScreening out a local maximum value;
a position determination unit for determining the local maximum in the three-dimensional complex group SresultWhere n ', m ' and r ' respectively represent the local maximum in the three-dimensional complex set SresultCoordinates in three dimensions;
a motion parameter determination unit for determining, according to the formula:
determining a motion parameter (f) of the front-looking side SAR slow targetdm,frmR) wherein fdmDoppler frequency, f, representing slow objectsrmThe system Doppler modulation frequency of the slow target is shown, and r is the distance between the slow target and the SAR system.
According to the specific embodiment provided by the invention, the invention discloses the following technical effects:
the detection method and the detection system provided by the invention adopt a parameter searching mode, combine the detection precision requirement and the detection target type, flexibly select the parameter searching step and the searching frequency, and can accurately determine the motion parameters of the slow motion target, thereby realizing the effective detection of the slow motion target.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without creative efforts.
Fig. 1 is a flowchart of a detection method provided in embodiment 1 of the present invention;
fig. 2 is a block diagram of a detection system according to embodiment 2 of the present invention;
fig. 3 is a flowchart of a detection method provided in embodiment 3 of the present invention;
fig. 4 is a flowchart of step 309 in the detection method provided in embodiment 3 of the present invention;
fig. 5 is a flowchart of step 310 in the detection method provided in embodiment 3 of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The invention aims to provide a detection method and a detection system for a front side view SAR slow-speed moving target, which can accurately acquire the moving parameters of the SAR slow-speed moving target.
In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in further detail below.
Example 1:
fig. 1 is a flowchart of a detection method provided in embodiment 1 of the present invention. As shown in fig. 1, a method for detecting a front side view SAR slow target includes:
step 101: two-dimensional original echo simulation array S for obtaining front-side view SAR slow speed targetstartTarget detection parameter and azimuth frequency one-dimensional array ftAnd distance frequency one-dimensional array fτWherein said SstartIs Na×NrA two-dimensional complex set, the target detection parameters comprising: number of sampling points in azimuth direction NaNumber of distance sampling points NrSignal sampling rate fsOf signal bandwidth BwPulse signal repetition frequency PRF, pulse signal width τ, stage motion velocity V, reference slope distance RrefCenter frequency f of system Dopplerd0Frequency f of system Doppler modulationr0Signal propagation speed c, signal wavelength λ;
step 102: simulating an array S for the echostartPerforming Fourier transform to obtain a first complex set S1；
Step 103: for the first plurality of groups S1Performing Fourier transform to obtain a second complex group S2；
Step 104: according to the azimuth frequency one-dimensional array ftAnd distance frequency one-dimensional array fτFor the second plurality of groups S2Performing uniform compression to obtain a third complex group S3；
Step 105: for the third complex number set S3Performing inverse Fourier transform to obtain a fourth complex group S4；
Step 106: searching for stepping length delta f 'according to preset Doppler frequency'dDetermining a Doppler frequency search one-dimensional array f 'with a preset Doppler frequency search time threshold N'dAnd searching for the stepping length delta f 'according to the preset Doppler modulation frequency'rDetermining a Doppler frequency modulation rate search one-dimensional array f 'according to a preset Doppler frequency modulation rate search time threshold M'r；
Step 107: obtaining the search times m of the current Doppler frequency modulation rate, constructing and initializingThree-dimensional plural sets SresultWherein M is 1,2,.. times.m, the three-dimensional complex group SresultIs of size MxNa×NrAfter initialization, three-dimensional plural set SresultWherein each element is 0;
step 108: sampling point number N according to the azimuthaAnd pulse signal repetition frequency PRF determines azimuth moment one-dimensional array Ta；
Step 109: constructing and initializing a fifth plurality S5The fifth plurality of sets S5Is of size Na×Nr；
Step 110: obtaining the search times n of the current Doppler frequency and obtaining a one-dimensional array T according to the azimuth momentaThe signal propagation speed c, the signal wavelength lambda and the Doppler frequency search one-dimensional array f'dAnd the distance frequency one-dimensional array fτDetermining a two-dimensional distance walk-off compensation factor array Hw_rWherein N is 1, 2.., N;
step 111: according to the formula: s6(i,j)＝S5(i,j)+S4(i,j)Hw_r(i, j) determining a sixth complex set S6Wherein S is6(i, j) represents a sixth complex group S6Component of ith row and jth column, S5(i, j) represents a fifth complex group S5Component of ith row and jth column, S4(i, j) represents a fourth complex group S4Component of row i and column j, Hw_r(i, j) represents a two-dimensional distance walk compensation factor array Hw_rRow i and column j components;
step 112: judging whether the current Doppler frequency search times are equal to a preset Doppler frequency search time threshold value N or not, and obtaining a first judgment result;
if the first judgment result indicates that the current doppler frequency search times are less than the preset doppler frequency search times threshold N, executing step 113;
if the first determination result indicates that the current doppler frequency search times are equal to the preset doppler frequency search times threshold N, go to step 114;
step 113: updating the Doppler frequency search times n, and returning to the step 110;
step 114: searching a one-dimensional array f 'according to the signal wavelength lambda and the Doppler modulation frequency'rAnd the azimuth moment one-dimensional array TaDetermining a phase error compensation factor array Hc_r；
Step 115: according to the formula: s7(i,j)＝S6(i,j)Hc_r(i) Determining a seventh plurality of sets S7Wherein S is7(i, j) represents a seventh complex group S7Component of row i and column j, Hc_r(i) Array H representing one-dimensional phase error compensation factorsc_rThe ith component of (a);
step 116: for the seventh complex group S7Sequentially performing inverse distance Fourier transform and Fourier azimuth transform to obtain an eighth complex group S8；
Step 117: judging whether the current Doppler frequency modulation frequency searching times M are equal to a preset Doppler frequency modulation frequency searching time threshold value M or not, and obtaining a second judgment result;
if the second determination result indicates that the current doppler frequency modulation frequency search time M is smaller than the preset doppler frequency modulation frequency search time threshold M, go to step 118;
if the second determination result indicates that the current doppler frequency modulation search time M is equal to the preset doppler frequency modulation search time threshold M, executing step 119;
step 118: updating the Doppler frequency modulation rate search times m and returning to the step 108;
step 119: according to the respective eighth complex group S8Updating the three-dimensional complex set Sresult；
Step 120: according to the three-dimensional complex number set SresultAnd determining the motion parameters of the front-side looking SAR slow target.
Specifically, the step 104: according to the azimuth frequency one-dimensional array ftAnd distance frequency one-dimensional array fτFor the second plurality of groups S2Performing uniform compression to obtain a third complex group S3The method specifically comprises the following steps:
step 1041: according to the formula:
determining ith row and jth column component H of consistent compression processing two-dimensional compensation complex groupc(i, j) wherein fτ(j) One-dimensional array f representing range frequencyτThe (j) th component of (a),j＝1,2,…,Nr，ft(i) one-dimensional array f representing azimuth frequencytThe (i) th component of (a),i＝1,2,…,Na；
step 1042: according to the formula: s3(i,j)＝S2(i,j)Hc(i, j) determining a third complex set S after the uniform compression process3Wherein S is3(i, j) represents the third complex set S3Of the ith row and the jth column, S2(i, j) represents said second complex set S2Row i and column j.
Specifically, in step 110: according to the azimuth moment one-dimensional array TaThe signal propagation speed c, the signal wavelength lambda and the Doppler frequency search one-dimensional array f'dAnd the distance frequency one-dimensional array fτDetermining a two-dimensional distance walk-off compensation factor array Hw_rThe method specifically comprises the following steps:
step 1101: according to the formula:determining a two-dimensional distance walk-off compensation factor array Hw_rIth row and jth column of (1)w_r(i, j) wherein f'd(n) represents a Doppler frequency search one-dimensional array f'dN is 1,2, …, N, Ta(i) One-dimensional array T representing the azimuth timeaI-1, 2, …, Na，fτ(j) One-dimensional array f representing range frequencyτThe (j) th component of (a),
step 1102: according to respective component Hw_r(i, j) generating a two-dimensional distance walk compensation factor array.
Specifically, the step 114: searching a one-dimensional array f 'according to the signal wavelength lambda and the Doppler modulation frequency'rAnd the azimuth moment one-dimensional array TaDetermining a phase error compensation factor array Hc_rThe method specifically comprises the following steps:
step 1141: according to the formula:determining a one-dimensional phase error compensation factor array Hc_rOf f ', where'r(m) represents a one-dimensional array f 'of Doppler modulation frequency search'rOf the m-th component, Ta(i) One-dimensional array T for representing azimuth timeaI-1, 2, …, Na，Hc_r(i) Array H representing one-dimensional phase error compensation factorsc_rThe ith component of (a); (ii) a
Step 1142: and generating a one-dimensional phase error compensation factor array according to the components of each one-dimensional phase error compensation factor array.
Specifically, the step 120: according to the three-dimensional complex number set SresultDetermining the motion parameters of the front-side view SAR slow speed target specifically comprises the following steps:
step 1201: in the three-dimensional complex group SresultScreening out a local maximum value;
step 1202: determining the local maximum in the three-dimensional complex set SresultWhere n ', m ' and r ' respectively represent the local maximum in the three-dimensional complex set SresultCoordinates in three dimensions;
step 1203: according to the formula:
determining a motion parameter (f) of the front-looking side SAR slow targetdm,frmR) wherein fdmDoppler frequency, f, representing slow objectsrmThe system Doppler modulation frequency of the slow target is shown, and r is the distance between the slow target and the SAR system.
Example 2:
fig. 2 is a block diagram of a detection system provided in embodiment 2 of the present invention. As shown in fig. 2, a detection system for a front side view SAR slow target, the detection system comprises:
a first data obtaining module 201, configured to obtain a two-dimensional original echo simulation array S of the front-side view SAR slow targetstartTarget detection parameter and azimuth frequency one-dimensional array ftAnd distance frequency one-dimensional array fτWherein said SstartIs Na×NrA two-dimensional complex set, the target detection parameters comprising: number of sampling points in azimuth direction NaNumber of distance sampling points NrSignal sampling rate fsOf signal bandwidth BwPulse signal repetition frequency PRF, pulse signal width τ, stage motion velocity V, reference slope distance RrefCenter frequency f of system Dopplerd0Frequency f of system Doppler modulationr0Signal propagation speed c, signal wavelength λ;
a first complex group obtaining module 202 for simulating the echo array SstartPerforming Fourier transform to obtain a first complex set S1；
A second complex group obtaining module 203 for obtaining the first complex group S1Performing Fourier transform to obtain a second complex group S2；
A third complex group obtaining module 204 for obtaining a one-dimensional array f according to the azimuth frequencytAnd distance frequency one-dimensional array fτFor the second plurality of groups S2Performing uniform compression to obtain a third complex group S3；
A fourth complex group obtaining module 205 for obtaining the third complex group S3Performing inverse Fourier transform to obtain a fourth complex group S4；
A doppler frequency search one-dimensional array determining module 206, configured to search for the step length Δ f 'according to a preset doppler frequency'dDetermining a Doppler frequency search one-dimensional array f 'with a preset Doppler frequency search time threshold N'd；
A doppler modulation frequency search one-dimensional array determining module 207, configured to search for the step length Δ f 'according to a preset doppler modulation frequency'rDetermining a Doppler frequency modulation rate search one-dimensional array f 'according to a preset Doppler frequency modulation rate search time threshold M'r；
A doppler frequency modulation frequency search frequency obtaining module 208, configured to obtain a current doppler frequency modulation frequency search frequency m;
a three-dimensional complex group initialization module 209 for constructing and initializing a three-dimensional complex group SresultWherein M is 1,2,.. times.m, the three-dimensional complex group SresultIs of size MxNa×NrAfter initialization, three-dimensional plural set SresultWherein each element is 0;
an orientation time one-dimensional array determining module 210, configured to determine the number N of sampling points according to the orientation directionaAnd pulse signal repetition frequency PRF determines azimuth moment one-dimensional array Ta；
A fifth complex group initializing module 211 for constructing and initializing a fifth complex group S5The fifth plurality of sets S5Is of size Na×Nr；
A doppler frequency search frequency obtaining module 212, configured to obtain a current doppler frequency search frequency n;
a two-dimensional distance walking compensation factor array determining module 213, configured to determine the one-dimensional array T according to the azimuth timeaThe signal propagation speed c, the signal wavelength lambda and the Doppler frequency search one-dimensional array f'dAnd the distance frequency one-dimensional array fτDetermining a two-dimensional distance walk-off compensation factor array Hw_rWherein N is 1, 2.., N;
sixth complex group determinationA module 214 for: s6(i,j)＝S5(i,j)+S4(i,j)Hw_r(i, j) determining a sixth complex set S6Wherein S is6(i, j) represents a sixth complex group S6Component of ith row and jth column, S5(i, j) represents a fifth complex group S5Component of ith row and jth column, S4(i, j) represents a fourth complex group S4Component of row i and column j, Hw_r(i, j) represents a two-dimensional distance walk compensation factor array Hw_rRow i and column j components;
a first determining module 215, configured to determine whether the current doppler frequency search time is equal to a preset doppler frequency search time threshold N, to obtain a first determination result;
a doppler frequency search frequency updating module 216, configured to update the doppler frequency search frequency N when the first determination result indicates that the current doppler frequency search frequency is smaller than a preset doppler frequency search frequency threshold N, and send the updated doppler frequency search frequency to the two-dimensional distance walking compensation factor determining module 213;
a phase error compensation factor array determining module 217, configured to search the one-dimensional array f 'according to the signal wavelength λ and the doppler modulation frequency when the first determination result indicates that the current doppler frequency search frequency is equal to a preset doppler frequency search frequency threshold N'rAnd the azimuth moment one-dimensional array TaDetermining a phase error compensation factor array Hc_r；
A seventh complex group determination module 218 configured to: s7(i,j)＝S6(i,j)Hc_r(i) Determining a seventh plurality of sets S7Wherein S is7(i, j) represents a seventh complex group S7Component of row i and column j, Hc_r(i) Array H representing one-dimensional phase error compensation factorsc_rThe ith component of (a);
an eighth complex group determining module 219 for determining the seventh complex group S7Sequentially performing inverse distance Fourier transform and Fourier azimuth transform to obtain an eighth complex group S8；
The second judging module 220 is configured to judge whether the current doppler frequency modulation search time M is equal to a preset doppler frequency modulation search time threshold M, and obtain a second judgment result;
a doppler frequency modulation frequency search frequency updating module 221, configured to update the doppler frequency modulation frequency search frequency M when the second determination result indicates that the current doppler frequency modulation frequency search frequency M is smaller than the preset doppler frequency modulation frequency search frequency threshold M, and send the updated doppler frequency modulation frequency search frequency M to the azimuth time one-dimensional array determining module 210;
a three-dimensional complex group updating module 222, configured to, when the second determination result indicates that the current doppler shift frequency search time M is equal to the preset doppler shift frequency search time threshold M, update each eighth complex group S according to the number M8Updating the three-dimensional complex set Sresult；
A motion parameter determination module 223 for determining a motion parameter based on the three-dimensional complex group SresultAnd determining the motion parameters of the front-side looking SAR slow target.
Specifically, the third complex group obtaining module 204 specifically includes:
a two-dimensional compensation complex component determining unit 2041, configured to:
determining ith row and jth column component H of consistent compression processing two-dimensional compensation complex groupc(i, j) wherein fτ(j) One-dimensional array f representing range frequencyτThe (j) th component of (a),j＝1,2,…,Nr，ft(i) one-dimensional array f representing azimuth frequencytThe (i) th component of (a),i＝1,2,…,Na；
a third complex group determination unit 2042, configured to: s3(i,j)＝S2(i,j)Hc(i, j) determining a third complex set S after the uniform compression process3Wherein S is3(i, j) represents the third complex set S3Of the ith row and the jth column, S2(i, j) represents said second complex set S2Row i and column j.
Specifically, the two-dimensional distance walking compensation factor determining module 213 specifically includes:
a two-dimensional distance walk compensation factor array component determination unit 2131, configured to:
determining a two-dimensional distance walk-off compensation factor array Hw_rIth row and jth column of (1)w_r(i, j) wherein f'd(n) represents a Doppler frequency search one-dimensional array f'dN is 1,2, …, N, Ta(i) One-dimensional array T representing the azimuth timeaI-1, 2, …, Na，fτ(j) One-dimensional array f representing range frequencyτThe (j) th component of (a),
a two-dimensional distance walk compensation factor array generation unit 2132 for generating a two-dimensional distance walk compensation factor array according to each component Hw_r(i, j) generating a two-dimensional distance walk compensation factor array.
Specifically, the phase error compensation factor array determining module 217 specifically includes:
the phase error compensation factor array component determination unit 2171 is configured to:
determining a one-dimensional phase error compensation factor array Hc_rOf f ', where'r(m) represents a one-dimensional array f 'of Doppler modulation frequency search'rOf the m-th component, Ta(i) One-dimensional array T for representing azimuth timeaThe ith component of，i＝1,2,…,Na；
A one-dimensional phase error compensation factor array generating unit 2172 for generating a one-dimensional phase error compensation factor array from the components of each phase error compensation factor array.
Specifically, the motion parameter determining module 223 specifically includes:
a screening unit 2231 for screening said three-dimensional complex groups SresultScreening out a local maximum value;
a position determination unit 2232 for determining said local maximum in said three-dimensional complex group SresultWhere n ', m ' and r ' respectively represent the local maximum in the three-dimensional complex set SresultCoordinates in three dimensions;
a motion parameter determination unit 2233 configured to:
determining a motion parameter (f) of the front-looking side SAR slow targetdm,frmR) wherein fdmDoppler frequency, f, representing slow objectsrmThe system Doppler modulation frequency of the slow target is shown, and r is the distance between the slow target and the SAR system.
Example 3:
in the method for detecting a slow-speed target of an SAR in front side view based on Radon-Fourier transform provided by this embodiment, the processed object is original echo data of the slow-speed target of the SAR in front side view, and the obtained result is the motion parameters (Doppler frequency, Doppler modulation frequency and distance) of the slow-speed moving target.
Fig. 3 is a flowchart of a detection method according to embodiment 3 of the present invention. As shown in fig. 3, the method for detecting a front side view SAR slow target based on Radon-Fourier transform includes the following steps:
step 301: read-in front-side-view SAR slow-speed target two-dimensional original echo simulation array SstartAnd corresponding target detection parameters.
Wherein S isstartIs of size Na×NrA plurality of two-dimensional groups, and the target detection parameters specifically include: number of sampling points in azimuth direction NaNumber of distance sampling points NrSignal sampling rate fsOf signal bandwidth BwPulse signal repetition frequency PRF, pulse signal width τ, stage velocity V, reference slope distance RrefCenter frequency f of system Dopplerd0Frequency f of system Doppler modulationr0Signal propagation speed c, signal wavelength λ.
Step 302: the distance direction FFT processing of the original echo signal comprises the following specific operation flows:
step 3021: constructing a one-dimensional sequence i, j, wherein i represents a row and j represents a column;
step 3021: the original echo signal S read in step 301startDistance direction FFT processing is carried out, namely FFT processing is carried out along the azimuth direction (by rows), and a plurality of two-dimensional groups S are obtained1(i,j)；
S1(i,:)＝FFT(Sstart(i,:)) (2)
Wherein S isstart(i,: represents S)startRow i of (1), S1(i,: represents S)1Line i of (2), FFT (·) represents a fast fourier transform of the one-dimensional array.
Step 303: the two-dimensional complex group S obtained in step 3021(i, j) performing direction Fourier transform, namely performing FFT along the distance direction (in columns) to obtain a two-dimensional complex group S2(i,j)：
S2(:,j)＝FFT(S1(:,j)) (3)
Wherein S is1(j) represents S1J th column of (S)2(j) represents S2Column j.
Step 304: and (3) consistent compression treatment, wherein the specific operation flow comprises the following steps:
step 3041: constructing a one-dimensional array of azimuth frequency and distance frequency:
step 3042: generating a two-dimensional compensation complex set H for uniform compression processingc(i,j)：
Step 3043: a plurality of two-dimensional groups S obtained in step 3032Each element in (i, j) is the same as HcMultiplying corresponding elements in (i, j) to obtain a two-dimensional complex group S3(i, j), completing the uniform compression processing.
S3(i,j)＝S2(i,j)Hc(i,j) (6)
Step 305: performing azimuth Fourier inverse transformation;
obtaining a plurality of two-dimensional groups S from step 3043(i, j) performing inverse Fourier transform in azimuth direction, namely performing IFFT processing along distance direction (in rows) to obtain two-dimensional complex group S4(i,j)。
S4(:,j)＝IFFT(S3(:,j)) (7)
Where IFFT (·) represents performing a fast fourier transform on the one-dimensional array.
Step 306: setting Doppler frequency search step length and number of times to be delta f 'respectively'dAnd N, setting the Doppler modulation frequency search step length and the number of times to be delta f respectively'rAnd M, and generating a Doppler frequency search one-dimensional array f'dAnd Doppler frequency modulation rate searching one-dimensional array f'rThe generation method comprises the following steps:
step 307: let m be 1, from one-dimensional array f'rF is obtained through value'r(m) and initializing a plurality of three-dimensional groups SresultArray size of MxNa×Nr：
Sresult(1:M,1:Na,1:Nr)＝0 (9)
Step 308: setting and calculating parameters: one-dimensional array T for calculating azimuth timeaArray size NaX 1, and initializing a two-dimensional complex set S5Array size Na×NrLet n be 1:
step 309: the distance walk compensation processing, the processing flow of which is shown in fig. 4, specifically includes the following steps:
step 3091: from one-dimensional array f'dF is obtained through value'd(n)；
Step 3092: is combined with f'd(n) calculating a two-dimensional distance walk compensation factor Hw_r(i,j)；
Step 3093: two-dimensional plural groups S4Distance walk compensation factor Hw_rMultiplying to obtain two-dimensional complex group and S5Adding;
S5(i,j)＝S5(i,j)+S4(i,j)Hw_r(i,j) (12)
step 3094: making N equal to N +1, and judging the sizes of N and N, if N is less than or equal to N, then returning to step 309, if N is greater than N, executing step 310;
step 310: performing secondary phase error compensation processing, distance-to-fourier inverse transformation, and azimuth-to-fourier transformation, wherein the processing flow is shown in fig. 5, and the processing method specifically comprises the following steps:
step 3101: is combined with f'r(m) calculating a quadratic phase error compensation factor Hc_r；
Step 3102: two-dimensional plural groups S5And a secondary phase error compensation factor Hc_rMultiply to obtain twoDimension complex number set S6；
S6(i,j)＝S5(i,j)Hc_r(i) (14)
Step 3103: two-dimensional plural groups S6Inverse Fourier transform is performed to obtain a two-dimensional complex group S7；
S7(i,:)＝IFFT(S6(i,:)) (15)
Step 3104: two-dimensional plural groups S7Performing direction Fourier transform to obtain a two-dimensional complex group S8；
S8(:,j)＝FFT(S7(:,j)) (16)
Step 3105: will obtain a two-dimensional plural set S8Is assigned to Sresult(m,: i.e., S)result(m,:,:)＝S8(i, j), making M equal to M +1, and determining the sizes of M and M, if M is less than or equal to M, returning to step 308 to start repeated operation, if M is greater than M, and then executing step 311;
step 311: in a plurality of three-dimensional groups SresultFinding local maximum value to obtain maximum value position (n ', m ', r '), and further obtaining moving object parameter (f)dm,frm,r)。
The method for detecting the front-side view SAR slow target based on Radon-Fourier transform provided by the embodiment is adopted to obtain the target motion parameters, and the imaging parameters related in the imaging process are shown in Table 1.
Table 1 imaging parameters for example 3
The specific implementation process is as follows:
the method comprises the following steps: read-in front-side view SAR slow speed target two-dimensional original loopWave simulation array SstartAnd corresponding target detection parameters. Wherein SstartIs a two-dimensional complex group with the size of 512 multiplied by 1024, and the imaging parameters specifically include: number of sampling points in azimuth direction NaNumber of distance sampling points NrSignal sampling rate fsOf signal bandwidth BwPulse signal repetition frequency PRF, pulse signal width τ, stage velocity V, reference slope distance RrefCenter frequency f of system Dopplerd0Frequency f of system Doppler modulationr0Signal propagation speed c, signal wavelength λ.
Step two: the distance direction FFT processing of the original echo signal comprises the following specific operation flows:
(a) constructing a one-dimensional sequence i, j, as shown in formula (1), wherein i ═ 1,2, ·,512], j ═ 1,2, ·,1024 ];
(b) reading in the original echo signal SstartDistance direction FFT processing is carried out, as shown in formula (2), a two-dimensional complex group S is obtained1(i,j)；
Step three: obtaining a plurality of two-dimensional groups S from the second step1(i, j) performing direction Fourier transform, as shown in formula (3), to obtain a two-dimensional complex set S2(i,j)；
Step four: and (3) consistent compression treatment, wherein the specific operation flow comprises the following steps:
(a) constructing a one-dimensional array of azimuth frequency and distance frequency, as shown in formula (4), and obtaining a corresponding array ft(i) And fτ(j)；
(b) Generating a two-dimensional compensation complex set H for uniform compression processingc(i, j) as shown in formula (5);
(c) the two-dimensional complex number S obtained in the step three is combined2Each element in (i, j) is the same as HcMultiplying corresponding elements in (i, j), as shown in formula (6), to obtain a two-dimensional complex group S3(i, j), completing the uniform compression processing.
Step five: obtaining a plurality of two-dimensional groups S from the step four3(i, j) performing azimuth direction inverse Fourier transform processing, as shown in formula (7), to obtain a two-dimensional complex group S4(i,j)。
S4(:,j)＝IFFT(S3(:,j)) (7)
Where IFFT (·) represents performing a fast fourier transform on the one-dimensional array.
Step six: setting the Doppler frequency search step length and the number of times respectively asAnd N ═ Na512, the doppler modulation frequency search step length and the number of times are set to Δ f'r1.0 and M200, and generates a doppler frequency search one-dimensional array f'dAnd Doppler frequency modulation rate searching one-dimensional array f'rAs shown in formula (8);
step seven: let m be 1, from one-dimensional array f'rF is obtained through value'r(m) and initializing a plurality of three-dimensional groups SresultAs shown in formula (9), the array size is 200 × 512 × 1024;
step eight: one-dimensional array T for calculating azimuth timeaThe array size is 512 x 1, and a two-dimensional complex array S is initialized5As shown in formula (10), the array size is 512 × 1024, and let n be 1; (ii) a
Step nine: distance walking compensation processing, the operation flow is as follows:
(a) from one-dimensional array f'dF is obtained through value'd(n)；
(b) Is combined with f'd(n) calculating a two-dimensional distance walk compensation factor Hw_r(i, j) as shown in formula (11);
(c) two-dimensional plural groups S4Distance walk compensation factor Hw_rMultiplying to obtain two-dimensional complex group and S5Adding, as shown in formula (12);
(d) making N equal to N +1, judging the sizes of N and N, if N is less than or equal to N, then repeating the operation from the step nine (a), and if N is more than N, then executing the step ten;
step ten: performing secondary phase error compensation processing, distance direction Fourier inverse transformation and azimuth direction Fourier transformation, wherein the operation flow is as follows:
(a) is combined with f'r(m) calculating a quadratic phase error compensation factor Hc_r(i) As shown in formula (13);
(b) two-dimensional plural groups S5And a secondary phase error compensation factor Hc_rMultiplying, as shown in equation (14), to obtain a two-dimensional complex set S6；
(c) Two-dimensional plural groups S6Inverse distance Fourier transform is performed, as shown in formula (15), to obtain a two-dimensional complex group S7；
(d) Two-dimensional plural groups S7Performing direction Fourier transform, as shown in formula (16), to obtain a two-dimensional complex group S8；
(e) Will obtain a two-dimensional plural set S8Is assigned to Sresult(m,: i.e., S)result(m,:,:)＝S8(i, j), making M equal to M +1, judging the sizes of M and M, if M is less than or equal to M, repeating the operation from the eighth step, and if M is greater than M, executing the eleventh step;
step eleven: in a plurality of three-dimensional groups SresultFinding the local maximum to obtain three local maximum positions (378,137,475), (256,100,512), (78,43,550), and combining the formula (17) to obtain the moving object parameter.
And finally, obtaining the motion parameters of the slow motion target through the processing of the steps. Table 2 shows the real motion parameters of the slow moving object and the motion parameters obtained by the method provided by the present invention. As can be seen from Table 2, the method provided by the invention can realize accurate acquisition of the motion parameters of the slow motion target, thereby realizing effective detection of slow motion.
TABLE 2 true motion parameters of slow moving object and motion parameters obtained by the method of the invention
The method for detecting the front-side view SAR slow-speed target is based on the improved Radon-Fourier transform, avoids distance interpolation operation in the traditional Radon-Fourier transform algorithm, and effectively improves the algorithm efficiency. Meanwhile, the detection method provided by the invention is carried out in a parameter search mode, and can flexibly select parameter search steps and search times by combining the detection precision requirement and the detection target type, so that the algorithm efficiency is further improved on the premise of meeting the detection requirement, the requirements of different detection precisions can be met, and the detection method has the characteristics of convenience and flexibility.
The embodiments in the present description are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments are referred to each other. For the system disclosed by the embodiment, the description is relatively simple because the system corresponds to the method disclosed by the embodiment, and the relevant points can be referred to the method part for description.
The principles and embodiments of the present invention have been described herein using specific examples, which are provided only to help understand the method and the core concept of the present invention; meanwhile, for a person skilled in the art, according to the idea of the present invention, the specific embodiments and the application range may be changed. In view of the above, the present disclosure should not be construed as limiting the invention.

Claims (10)

1. A detection method for an obverse-side-view SAR slow target is characterized by comprising the following steps:
two-dimensional original echo simulation array S for obtaining front-side view SAR slow speed targetstartTarget detection parameter and azimuth frequency one-dimensional array ftAnd distance frequency one-dimensional array fτWherein said SstartIs Na×NrA two-dimensional complex set, the target detection parameters comprising: number of sampling points in azimuth direction NaNumber of distance sampling points NrSignal sampling rate fsOf signal bandwidth BwPulse signal repetition frequency PRF, pulse signal width τ, stage motion velocity V, reference slope distance RrefCenter frequency f of system Dopplerd0Frequency f of system Doppler modulationr0Signal propagation speed c, signal wavelength λ;
simulating an array S for the echostartPerforming Fourier transform of distanceThen, a first plurality of S groups is obtained1；
For the first plurality of groups S1Performing Fourier transform to obtain a second complex group S2；
According to the azimuth frequency one-dimensional array ftAnd distance frequency one-dimensional array fτFor the second plurality of groups S2Performing uniform compression to obtain a third complex group S3；
For the third complex number set S3Performing inverse Fourier transform to obtain a fourth complex group S4；
Searching for stepping length delta f 'according to preset Doppler frequency'dDetermining a Doppler frequency search one-dimensional array f 'with a preset Doppler frequency search time threshold N'dAnd searching for the stepping length delta f 'according to the preset Doppler modulation frequency'rDetermining a Doppler frequency modulation rate search one-dimensional array f 'according to a preset Doppler frequency modulation rate search time threshold M'r；
Obtaining the current Doppler frequency modulation rate search times m, constructing and initializing a three-dimensional complex group SresultWherein M is 1,2,.. times.m, the three-dimensional complex group SresultIs of size MxNa×NrAfter initialization, three-dimensional plural set SresultWherein each element is 0;
sampling point number N according to the azimuthaAnd pulse signal repetition frequency PRF determines azimuth moment one-dimensional array Ta；
Constructing and initializing a fifth plurality S5The fifth plurality of sets S5Is of size Na×Nr；
Obtaining the search times n of the current Doppler frequency and obtaining a one-dimensional array T according to the azimuth momentaThe signal propagation speed c, the signal wavelength lambda and the Doppler frequency search one-dimensional array f'dAnd the distance frequency one-dimensional array fτDetermining a two-dimensional distance walk-off compensation factor array Hw_rWherein N is 1, 2.., N;
according to the formula: s5(i,j)＝S′5(i,j)+S4(i,j)Hw_r(i, j) updating the fifth complex group, wherein S'5(i, j) represents a fifth complex group S before update5' line ith and column jth components;
according to the formula: s6(i,j)＝S5(i,j)+S4(i,j)Hw_r(i, j) determining a sixth complex set S6Wherein S is6(i, j) represents a sixth complex group S6Component of ith row and jth column, S5(i, j) represents the updated fifth complex set S5Component of ith row and jth column, S4(i, j) represents a fourth complex group S4Component of row i and column j, Hw_r(i, j) represents a two-dimensional distance walk compensation factor array Hw_rRow i and column j components;
judging whether the current Doppler frequency search times are equal to a preset Doppler frequency search time threshold value N or not, and obtaining a first judgment result;
if the first judgment result shows that the current Doppler frequency search times are smaller than a preset Doppler frequency search time threshold value N, updating the Doppler frequency search times N, and returning to the step ofaThe signal propagation speed c, the signal wavelength lambda and the Doppler frequency search one-dimensional array f'dAnd the distance frequency one-dimensional array fτDetermining a two-dimensional distance walk-off compensation factor array Hw_r”
If the first judgment result shows that the current Doppler frequency search times are equal to a preset Doppler frequency search time threshold N, searching a one-dimensional array f 'according to the signal wavelength lambda and the Doppler modulation frequency'rAnd the azimuth moment one-dimensional array TaDetermining a phase error compensation factor array Hc_r；
According to the formula: s7(i,j)＝S6(i,j)Hc_r(i) Determining a seventh plurality of sets S7Wherein S is7(i, j) represents a seventh complex group S7Component of row i and column j, Hc_r(i) Array H representing one-dimensional phase error compensation factorsc_rThe ith component of (a);
for the seventh complex group S7In turn, theInverse distance Fourier transform and Fourier azimuth transform are performed to obtain an eighth complex group S8；
Judging whether the current Doppler frequency modulation frequency searching times M are equal to a preset Doppler frequency modulation frequency searching time threshold value M or not, and obtaining a second judgment result;
if the second judgment result shows that the current Doppler frequency modulation frequency searching times M are smaller than a preset Doppler frequency modulation frequency searching time threshold value M, updating the Doppler frequency modulation frequency searching times M, and returning to the step of sampling points N according to the azimuth directionaAnd pulse signal repetition frequency PRF determines azimuth moment one-dimensional array Ta”
If the second judgment result indicates that the current Doppler frequency modulation search times M are equal to the preset Doppler frequency modulation search time threshold value M, according to each eighth complex group S8Updating the three-dimensional complex set Sresult；
According to the three-dimensional complex number set SresultAnd determining the motion parameters of the front-side looking SAR slow target.
2. The detection method according to claim 1, wherein the one-dimensional array f is based on the azimuth frequencytAnd distance frequency one-dimensional array fτFor the second plurality of groups S2Performing uniform compression to obtain a third complex group S3The method specifically comprises the following steps:
according to the formula:
determining ith row and jth column component H of consistent compression processing two-dimensional compensation complex groupc(i, j) wherein fτ(j) One-dimensional array f representing range frequencyτThe (j) th component of (a), ft(i) One-dimensional array f representing azimuth frequencytThe (i) th component of (a),
according to the formula: s3(i,j)＝S2(i,j)Hc(i, j) determining a third complex set S after the uniform compression process3Wherein S is3(i, j) represents the third complex set S3Of the ith row and the jth column, S2(i, j) represents said second complex set S2Row i and column j.
3. The detection method according to claim 1, wherein the one-dimensional array T is determined according to the azimuth timeaThe signal propagation speed c, the signal wavelength lambda and the Doppler frequency search one-dimensional array f'dAnd the distance frequency one-dimensional array fτDetermining a two-dimensional distance walk-off compensation factor array Hw_rThe method specifically comprises the following steps:
according to the formula:determining a two-dimensional distance walk-off compensation factor array Hw_rIth row and jth column of (1)w_r(i, j) wherein f'd(n) represents a Doppler frequency search one-dimensional array f'dN is 1,2, …, N, Ta(i) One-dimensional array T representing the azimuth timeaI-1, 2, …, Na，fτ(j) One-dimensional array f representing range frequencyτThe (j) th component of (a),
according to respective component Hw_r(i, j) generating a two-dimensional distance walk compensation factor array.
4. The detection method according to claim 1, wherein said detection is performed according to said signal wavelength λ,Doppler modulation frequency search one-dimensional array f'rAnd the azimuth moment one-dimensional array TaDetermining a phase error compensation factor array Hc_rThe method specifically comprises the following steps:
according to the formula: hc_r(i)＝exp{jπλf′r(m)Ta 2(i) Determine a one-dimensional phase error compensation factor array Hc_rOf f ', where'r(m) represents a one-dimensional array f 'of Doppler modulation frequency search'rOf the m-th component, Ta(i) One-dimensional array T for representing azimuth timeaI-1, 2, …, Na，Hc_r(i) Array H representing one-dimensional phase error compensation factorsc_rThe ith component of (a);
and generating a one-dimensional phase error compensation factor array according to the components of each one-dimensional phase error compensation factor array.
5. The detection method according to claim 1, wherein said detecting is based on said three-dimensional complex set SresultDetermining the motion parameters of the front-side view SAR slow speed target specifically comprises the following steps:
in the three-dimensional complex group SresultScreening out a local maximum value;
determining the local maximum in the three-dimensional complex set SresultWhere n ', m ' and r ' respectively represent the local maximum in the three-dimensional complex set SresultCoordinates in three dimensions;
according to the formula:
determining a motion parameter (f) of the front-looking side SAR slow targetdm,frmR) wherein fdmDoppler frequency, f, representing slow objectsrmThe system Doppler modulation frequency of the slow target is shown, and r is the distance between the slow target and the SAR system.
6. A detection system for looking at a SAR slow target, the detection system comprising:
a first data acquisition module for acquiring a two-dimensional original echo simulation array S of the front-side view SAR slow speed targetstartTarget detection parameter and azimuth frequency one-dimensional array ftAnd distance frequency one-dimensional array fτWherein said SstartIs Na×NrA two-dimensional complex set, the target detection parameters comprising: number of sampling points in azimuth direction NaNumber of distance sampling points NrSignal sampling rate fsOf signal bandwidth BwPulse signal repetition frequency PRF, pulse signal width τ, stage motion velocity V, reference slope distance RrefCenter frequency f of system Dopplerd0Frequency f of system Doppler modulationr0Signal propagation speed c, signal wavelength λ;
a first complex group obtaining module for simulating the echo array SstartPerforming Fourier transform to obtain a first complex set S1；
A second complex group obtaining module for obtaining the first complex group S1Performing Fourier transform to obtain a second complex group S2；
A third complex group obtaining module for obtaining a one-dimensional array f according to the azimuth frequencytAnd distance frequency one-dimensional array fτFor the second plurality of groups S2Performing uniform compression to obtain a third complex group S3；
A fourth complex group obtaining module for obtaining the third complex group S3Performing inverse Fourier transform to obtain a fourth complex group S4；
A Doppler frequency search one-dimensional array determining module for searching the step length delta f 'according to the preset Doppler frequency'dDetermining a Doppler frequency search one-dimensional array f 'with a preset Doppler frequency search time threshold N'd；
A Doppler modulation frequency search one-dimensional array determining module for searching the stepping length delta f 'according to the preset Doppler modulation frequency'rAnd preset Doppler frequency modulationRate search frequency threshold M determines Doppler frequency modulation rate search one-dimensional array f'r；
The Doppler frequency modulation frequency searching times acquiring module is used for acquiring the current Doppler frequency modulation frequency searching times m;
a three-dimensional complex group initialization module for constructing and initializing a three-dimensional complex group SresultWherein M is 1,2,.. times.m, the three-dimensional complex group SresultIs of size MxNa×NrAfter initialization, three-dimensional plural set SresultWherein each element is 0;
an orientation moment one-dimensional array determining module for determining the number N of sampling points according to the orientationaAnd pulse signal repetition frequency PRF determines azimuth moment one-dimensional array Ta；
A fifth complex group initializing module for constructing and initializing a fifth complex group S5The fifth plurality of sets S5Is of size Na×Nr；
The Doppler frequency searching times acquiring module is used for acquiring the current Doppler frequency searching times n;
a two-dimensional distance walking compensation factor determination module for determining the one-dimensional array T according to the azimuth momentaThe signal propagation speed c, the signal wavelength lambda and the Doppler frequency search one-dimensional array f'dAnd the distance frequency one-dimensional array fτDetermining a two-dimensional distance walk-off compensation factor array Hw_rWherein N is 1, 2.., N;
a fifth complex group update module to:
S5(i,j)＝S′5(i,j)+S4(i,j)Hw_r(i, j) updating the fifth complex group, wherein S'5(i, j) represents a fifth complex group S 'before update'5The ith row and jth column component;
a sixth complex group determination module to: s6(i,j)＝S5(i,j)+S4(i,j)Hw_r(i, j) determining a sixth complex set S6Wherein S is6(i, j) represents a sixth complex group S6Component of ith row and jth column, S5(i, j) represents the updated fifth complex set S5Component of ith row and jth column, S4(i, j) represents a fourth complex group S4Component of row i and column j, Hw_r(i, j) represents a two-dimensional distance walk compensation factor array Hw_rRow i and column j components;
the first judgment module is used for judging whether the current Doppler frequency search times are equal to a preset Doppler frequency search time threshold value N or not and obtaining a first judgment result;
a doppler frequency search frequency updating module, configured to update the doppler frequency search frequency N when the first determination result indicates that the current doppler frequency search frequency is smaller than a preset doppler frequency search frequency threshold N, and send the updated doppler frequency search frequency to the two-dimensional distance walking compensation factor determining module "
A phase error compensation factor array determining module, configured to search a one-dimensional array f 'according to the signal wavelength λ and the doppler modulation frequency when the first determination result indicates that the current doppler frequency search frequency is equal to a preset doppler frequency search frequency threshold N'rAnd the azimuth moment one-dimensional array TaDetermining a phase error compensation factor array Hc_r；
A seventh complex group determination module to: s7(i,j)＝S6(i,j)Hc_r(i) Determining a seventh plurality of sets S7Wherein S is7(i, j) represents a seventh complex group S7Component of row i and column j, Hc_r(i) Array H representing one-dimensional phase error compensation factorsc_rThe ith component of (a);
an eighth complex group determination module for determining the seventh complex group S7Sequentially performing inverse distance Fourier transform and Fourier azimuth transform to obtain an eighth complex group S8；
The second judgment module is used for judging whether the current Doppler frequency modulation frequency search times M are equal to a preset Doppler frequency modulation frequency search time threshold value M or not and obtaining a second judgment result;
the doppler frequency modulation frequency search frequency updating module is configured to update the doppler frequency modulation frequency search frequency M and send the updated doppler frequency modulation frequency search frequency M to the azimuth time one-dimensional array determining module when the second determination result indicates that the current doppler frequency modulation frequency search frequency M is smaller than a preset doppler frequency modulation frequency search frequency threshold M;
a three-dimensional complex group updating module, configured to, when the second determination result indicates that the current doppler frequency modulation search time M is equal to the preset doppler frequency modulation search time threshold M, update the current doppler frequency modulation search time M according to each eighth complex group S8Updating the three-dimensional complex set Sresult；
A motion parameter determination module for determining a motion parameter from the three-dimensional complex group SresultAnd determining the motion parameters of the front-side looking SAR slow target.
7. The detection system according to claim 6, wherein the third complex group obtaining module specifically includes:
a two-dimensional compensation complex component determination unit for determining the complex component according to the formula:determining ith row and jth column component H of consistent compression processing two-dimensional compensation complex groupc(i, j) wherein fτ(j) One-dimensional array f representing range frequencyτThe (j) th component of (a), ft(i) one-dimensional array f representing azimuth frequencytThe (i) th component of (a),
a third complex group determination unit for: s3(i,j)＝S2(i,j)Hc(i, j) determining a third complex set S after the uniform compression process3Wherein S is3(i, j) tableIndicating said third complex group S3Of the ith row and the jth column, S2(i, j) represents said second complex set S2Row i and column j.
8. The detection system according to claim 6, wherein the two-dimensional distance walking compensation factor determination module specifically comprises:
a two-dimensional distance walk compensation factor array component determination unit for, according to a formula:determining a two-dimensional distance walk-off compensation factor array Hw_rIth row and jth column of (1)w_r(i, j) wherein f'd(n) represents a Doppler frequency search one-dimensional array f'dN is 1,2, …, N, Ta(i) One-dimensional array T representing the azimuth timeaI-1, 2, …, Na，fτ(j) One-dimensional array f representing range frequencyτThe (j) th component of (a),
a two-dimensional distance walk compensation factor array generation unit for generating compensation factor arrays according to the components Hw_r(i, j) generating a two-dimensional distance walk compensation factor array.
9. The detection system according to claim 6, wherein the phase error compensation factor array determination module specifically comprises:
a phase error compensation factor array component determination unit for determining a phase error compensation factor array component according to the formula: hc_r(i)＝exp{jπλf′r(m)Ta 2(i) Determine a one-dimensional phase error compensation factor array Hc_rOf f ', where'r(m) represents a one-dimensional array f 'of Doppler modulation frequency search'rOf the m-th component, Ta(i) One-dimensional array T for representing azimuth timeaI-1, 2, …, Na；
And the one-dimensional phase error compensation factor array generating unit is used for generating a one-dimensional phase error compensation factor array according to the components of each phase error compensation factor array.
10. The detection system according to claim 6, wherein the motion parameter determination module specifically includes:
a screening unit for screening the three-dimensional complex group SresultScreening out a local maximum value;
a position determination unit for determining the local maximum in the three-dimensional complex group SresultWhere n ', m ' and r ' respectively represent the local maximum in the three-dimensional complex set SresultCoordinates in three dimensions;
a motion parameter determination unit for determining, according to the formula:
determining a motion parameter (f) of the front-looking side SAR slow targetdm,frmR) wherein fdmDoppler frequency, f, representing slow objectsrmThe system Doppler modulation frequency of the slow target is shown, and r is the distance between the slow target and the SAR system.
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