CN112558070A - Frequency domain imaging method and device of circular scanning foundation SAR - Google Patents
Frequency domain imaging method and device of circular scanning foundation SAR Download PDFInfo
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Abstract
The invention discloses a frequency domain imaging method and a frequency domain imaging device of a circular scanning foundation SAR, wherein the method comprises the following steps: carrying out distance inverse Fourier transform on the echo signals of the circular scanning foundation SAR to obtain distance compression time domain signals; resampling the distance compressed time domain signal according to a preset first distance sampling interval and a geometrical corresponding relation; carrying out distance direction Fourier transform and azimuth direction Fourier transform to obtain a distance frequency domain and azimuth direction frequency domain signal; carrying out azimuth matching filtering on the distance frequency domain azimuth frequency domain signal according to a pre-constructed matching filtering function to obtain a signal after matching filtering; performing two-dimensional inverse Fourier transform on the matched and filtered signals to obtain a focused image under a polar coordinate system; the method and the device can improve the imaging efficiency while ensuring the imaging quality and realize rapid real-time imaging.
Description
Technical Field
The invention relates to the technical field of ground SAR three-dimensional imaging, in particular to a frequency domain imaging method and a frequency domain imaging device of a circular scanning ground SAR.
Background
In recent years, a Ground-based Synthetic Aperture Radar (GBSAR) is widely applied to the fields of landslide monitoring, volcanic monitoring, glacier monitoring, open-pit mine monitoring, bridge and building monitoring, and the like. However, the conventional linear orbit (GBSAR) can only acquire two-dimensional images, has the problem of overlapping and covering in a topographic relief area, is not suitable for complex terrains, and cannot acquire three-dimensional topographic information of a monitoring scene.
The circular scanning ground SAR is a new system ground SAR with three-dimensional imaging capability. Compared with the traditional linear track ground SAR, the circular scanning ground SAR antenna forms a circular track vertical to the ground through the rotation of the cantilever, so that a two-dimensional synthetic aperture is formed, and the altitude information is acquired to realize three-dimensional imaging. Therefore, the landslide monitoring system has the advantages of being convenient and fast in system structure, fast in data acquisition and strong in landslide monitoring timeliness.
The difficulty in circular scanning ground-based SAR imaging is that the antenna motion trajectory is an arc. Due to the special motion track, the conventional frequency domain imaging method is not suitable for circular scanning ground SAR. The airborne circumferential SAR carries out imaging by transmitting signals to the inner side of the flight path; cantilever scanning (ArcSAR) is parallel to the ground and imaging is performed by transmitting signals to the outside. And the circular scanning ground SAR is vertical to the ground and transmits signals in the forward direction, which is different from the imaging mode of the signals. Although the time domain imaging method is suitable for a circular scanning ground-based SAR system and can obtain a high-precision imaging result, the time domain imaging method is large in calculation amount and low in imaging efficiency, and rapid real-time imaging is difficult to realize.
Therefore, there is a need for a frequency domain imaging scheme for circular scanning ground-based SAR that can overcome the above-mentioned problems.
Disclosure of Invention
The embodiment of the invention provides a frequency domain imaging method of a circular scanning foundation SAR, which is used for carrying out frequency domain imaging of the circular scanning foundation SAR, improving imaging efficiency while ensuring imaging quality and realizing rapid real-time imaging, and comprises the following steps:
obtaining echo signals of a circumferential scanning ground SAR;
carrying out distance inverse Fourier transform on the echo signal of the circular scanning ground SAR to obtain a distance compression time domain signal;
resampling the distance compressed time domain signal according to a preset first distance sampling interval and a geometrical corresponding relation;
performing distance direction Fourier transform and azimuth direction Fourier transform on the resampled distance compression time domain signal to obtain a distance frequency domain and azimuth direction frequency domain signal;
carrying out azimuth matching filtering on the distance frequency domain and azimuth frequency domain signals according to a pre-constructed matching filtering function to obtain matched filtered signals, wherein the matching filtering function is pre-constructed according to a conjugate algorithm;
performing two-dimensional inverse Fourier transform on the matched and filtered signals to obtain a focused image under a polar coordinate system;
performing interpolation processing on the focused image under the polar coordinate system to obtain a focused image under a rectangular coordinate system;
and performing frequency domain imaging of the circumferential scanning foundation SAR according to the focused image under the rectangular coordinate system.
The embodiment of the invention provides a frequency domain imaging device of a circular scanning foundation SAR, which is used for carrying out frequency domain imaging of the circular scanning foundation SAR, improving imaging efficiency while ensuring imaging quality and realizing rapid real-time imaging, and comprises:
the echo signal acquisition module is used for acquiring echo signals of the circumferential scanning ground SAR;
the first transformation module is used for carrying out distance inverse Fourier transformation on the echo signal of the circular scanning ground SAR to obtain a distance compression time domain signal;
the resampling module is used for resampling the distance compressed time domain signal according to a preset first distance sampling interval and a geometrical corresponding relation;
the second transformation module is used for carrying out distance direction Fourier transformation and azimuth direction Fourier transformation on the resampled distance compression time domain signal to obtain a distance frequency domain and azimuth direction frequency domain signal;
the matched filtering module is used for carrying out azimuth matched filtering on the distance frequency domain and azimuth frequency domain signals according to a pre-constructed matched filtering function to obtain matched filtered signals, and the matched filtering function is pre-constructed according to a conjugate algorithm;
the third transformation module is used for performing two-dimensional inverse Fourier transformation on the matched and filtered signals to obtain a focused image under a polar coordinate system;
the interpolation processing module is used for carrying out interpolation processing on the focused image under the polar coordinate system to obtain a focused image under a rectangular coordinate system;
and the frequency domain imaging module is used for carrying out frequency domain imaging of the circumferential scanning foundation SAR according to the focused image under the rectangular coordinate system.
The embodiment of the invention also provides computer equipment which comprises a memory, a processor and a computer program which is stored on the memory and can run on the processor, wherein the processor executes the frequency domain imaging method of the circular scanning ground-based SAR.
An embodiment of the present invention further provides a computer-readable storage medium, which stores a computer program for executing the frequency domain imaging method of the circular scanning ground-based SAR described above.
The embodiment of the invention obtains the echo signal of the circular scanning ground SAR; carrying out distance inverse Fourier transform on the echo signal of the circular scanning ground SAR to obtain a distance compression time domain signal; resampling the distance compressed time domain signal according to a preset first distance sampling interval and a geometrical corresponding relation; performing distance direction Fourier transform and azimuth direction Fourier transform on the resampled distance compression time domain signal to obtain a distance frequency domain and azimuth direction frequency domain signal; carrying out azimuth matching filtering on the distance frequency domain and azimuth frequency domain signals according to a pre-constructed matching filtering function to obtain matched filtered signals, wherein the matching filtering function is pre-constructed according to a conjugate algorithm; performing two-dimensional inverse Fourier transform on the matched and filtered signals to obtain a focused image under a polar coordinate system; performing interpolation processing on the focused image under the polar coordinate system to obtain a focused image under a rectangular coordinate system; and performing frequency domain imaging of the circumferential scanning foundation SAR according to the focused image under the rectangular coordinate system. According to the embodiment of the invention, the echo signals are converted from the inclined plane to the imaging plane through resampling, the signal data are converted, and the target is focused in the frequency domain through Fourier transform, so that the calculation efficiency is high, the imaging speed is high, and the real-time imaging is convenient, therefore, the imaging efficiency is improved while the imaging quality is ensured, and the rapid real-time imaging of the scene is realized.
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In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts. In the drawings:
FIG. 1 is a schematic diagram of a frequency domain imaging method of a circular scanning ground-based SAR according to an embodiment of the present invention;
FIG. 2 is a schematic imaging geometry diagram of a circular scanning ground-based SAR imaging mode in an embodiment of the present invention;
FIG. 3 is a schematic diagram of a geometric model of an imaging plane according to an embodiment of the present invention;
fig. 4 is a structural diagram of a frequency domain imaging device of a circular scanning ground-based SAR in an embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the embodiments of the present invention are further described in detail below with reference to the accompanying drawings. The exemplary embodiments and descriptions of the present invention are provided to explain the present invention, but not to limit the present invention.
In order to perform frequency domain imaging of a circular scanning ground based SAR, improve imaging efficiency while ensuring imaging quality, and achieve fast real-time imaging, an embodiment of the present invention provides a frequency domain imaging method of a circular scanning ground based SAR, as shown in fig. 1, the method may include:
101, obtaining an echo signal of a circular scanning ground SAR;
102, performing distance inverse Fourier transform on the echo signal of the circular scanning ground-based SAR to obtain a distance compression time domain signal;
103, resampling the distance compressed time domain signal according to a preset first distance sampling interval and a geometrical corresponding relation;
104, performing distance direction Fourier transform and azimuth direction Fourier transform on the resampled distance compressed time domain signal to obtain a distance frequency domain and azimuth direction frequency domain signal;
105, performing azimuth matching filtering on the distance frequency domain and azimuth frequency domain signal according to a pre-constructed matching filtering function to obtain a signal after matching filtering, wherein the matching filtering function is pre-constructed according to a conjugate algorithm;
106, performing two-dimensional inverse Fourier transform on the matched and filtered signal to obtain a focused image under a polar coordinate system;
and 108, performing frequency domain imaging of the circular scanning foundation SAR according to the focused image in the rectangular coordinate system.
As shown in fig. 1, the embodiment of the present invention obtains the echo signal of the circular scanning ground-based SAR; carrying out distance inverse Fourier transform on the echo signal of the circular scanning ground SAR to obtain a distance compression time domain signal; resampling the distance compressed time domain signal according to a preset first distance sampling interval and a geometrical corresponding relation; performing distance direction Fourier transform and azimuth direction Fourier transform on the resampled distance compression time domain signal to obtain a distance frequency domain and azimuth direction frequency domain signal; carrying out azimuth matching filtering on the distance frequency domain and azimuth frequency domain signals according to a pre-constructed matching filtering function to obtain matched filtered signals, wherein the matching filtering function is pre-constructed according to a conjugate algorithm; performing two-dimensional inverse Fourier transform on the matched and filtered signals to obtain a focused image under a polar coordinate system; performing interpolation processing on the focused image under the polar coordinate system to obtain a focused image under a rectangular coordinate system; and performing frequency domain imaging of the circumferential scanning foundation SAR according to the focused image under the rectangular coordinate system. According to the embodiment of the invention, the echo signals are converted from the inclined plane to the imaging plane through resampling, the signal data are converted, and the target is focused in the frequency domain through Fourier transform, so that the calculation efficiency is high, the imaging speed is high, and the real-time imaging is convenient, therefore, the imaging efficiency is improved while the imaging quality is ensured, and the rapid real-time imaging of the scene is realized.
The difficulty of imaging of the circular scanning ground-based SAR system is that the motion track of the antenna is an arc line vertical to the ground, large-scale imaging is carried out by forward scanning observation, and the imaging difficulty is increased by the special motion track. The existing imaging method is a Back Projection (BP) method, which divides an imaging area into grid points, determines a pixel value according to echo time delay of each grid point and an antenna, and performs coherent superposition on the pixel values acquired by the antenna at 360 degrees, thereby realizing imaging. Although the imaging precision is high, the calculation amount is huge, the imaging efficiency is low, and the rapid real-time imaging is difficult to realize.
Fig. 2 is an imaging geometry of a circular scanning ground-based SAR imaging mode, and fig. 3 is an imaging plane geometry model, i.e., a side view of fig. 2.aFor radar phase centre, antenna passing through cantileverOaRotate along a horizontal central axis to formOCircular scanning is carried out on the front scene for a circular motion track of a rotation center,X-Y-Zin a rectangular coordinate system, the length (i.e., the radius of the track) of the cantilever isLThe phase center is rotated by an angle of
I.e. the azimuth direction of the system.PFor a predetermined point target, in the plane as shown in FIG. 2Z p The above. The vertical distance between the plane of the point target and the motion track of the antenna isZ p . Instantaneous slope distance between point target and phase center isR n I.e. the distance direction of the system. The embodiment of the invention projects the motion track of the antenna to a two-dimensional plane where the point target is located, as shown in fig. 3. Point targets and phasesProjection of position centeraIs an instantaneous distance ofr gp Each instant slope distanceR n All corresponding to an instantaneous distance of the imaging planer gp According to the corresponding relation, the conversion of the oblique plane echo signal data and the imaging plane signal data can be completed, thereby realizing the plane where the point target is positionedZ p Two-dimensional imaging of (2). Change differentlyZ p Two-dimensional imaging of different distance planes can be completed, and therefore three-dimensional imaging of a scene is achieved.
In an embodiment, echo signals of a circumferentially scanned ground-based SAR are obtained.
In specific implementation, the spatial position coordinate of the phase center is set as (x n ，y n ，z n ) Wherein
Wherein,
is the angle by which the phase center is rotated,Lthe radius of rotation of the phase center. Point targetPHas a spatial position coordinate of (x n ，y n ，z n ) Instantaneous slope distance of point target from phase centerR n Can be expressed as:
is provided withKThe slant plane distance wavenumber can be expressed as:
whereinfIn order to be the frequency of the signal,cis the speed of light.
Circular scanningThe ground-based SAR echo signal is defined as
Expressed as:
in the embodiment, the distance inverse Fourier transform is performed on the echo signal of the circular scanning ground SAR to obtain a distance compression time domain signal.
In specific implementation, the echo signal of the circular scanning ground-based SAR is converted into a distance compression time domain signal after distance Inverse Fourier Transform (IFT), and the distance compression time domain signal is expressed as
：
Wherein,rrepresenting the distance of the point target to the radar phase center,B r is the bandwidth of the signal(s),K c is the center wave number.
In an embodiment, the distance compressed time domain signal is resampled according to a preset first distance sampling interval and a geometrical correspondence.
In this embodiment, the geometric correspondence is preset according to a projection distance from the point target to the radar on the plane, a distance from the point target to a radar phase center, and a vertical distance between the plane where the point target is located and the antenna motion track.
In specific implementation, the geometric correspondence relationship is as follows:
in this embodiment, the first distance sampling interval is preset according to a maximum wave number corresponding to a distance from the point target to a radar phase center, a maximum wave number corresponding to a projection distance from the point target to the radar on a plane, and a beam incident angle.
In specific implementation, the distance compression time domain signal is resampled, and the conversion of echo data from an inclined plane to an imaging plane is realized. The process is realized by one-dimensional interpolation, and the geometric correspondence relationship can be used for
The resampling is as follows.
Original skew distance in interpolationR n Can be rewritten as:
wherein,r g is a point target to radarz p Distance projected on a plane. Will be provided with
Multiplying by a phase shift function to shift the time domain signal to a correct position to obtain a resampled distance compressed time domain signal:
wherein,B rg for the bandwidth corresponding to the imaging plane,r gp the instantaneous distance of the point target from the phase center projection. The bandwidth corresponding to the imaging plane is:
wherein,
is the angle of beam incidenceContinuously changing with the rotation of the phase center, but due to the rotation radius of the circular scanning ground-based SARLFar shorter than the detection range of radar, the phase centre being caused at different angles of rotation
The change of (A) can be ignored, and when actual data is processed, the data will be processed
As the center of rotationOThe angle to the imaging area. As in fig. 3, the image area radius is set to
Wherein,X 1representing artificial settingsz p Radius of the imaging area on the plane, then:
then, from the above, we obtain:
wherein,K maxandK gmaxare respectively connected withrAndr g the corresponding maximum wave number.
Thus, at the interpolated grid setting, the distance sampling interval of the imaging planed rg The following formula is required:
in the embodiment, distance direction Fourier transformation and azimuth direction Fourier transformation are carried out on the re-sampled distance compressed time domain signal to obtain a distance frequency domain and azimuth direction frequency domain signal.
In specific implementation, the resampling is completed and the sampling is performed
Distance Fourier Transform (FT) is carried out to obtain distance frequency domain-azimuth time domain signals
：
Wherein,K g is prepared by reacting withr g Corresponding to the wave number of the imaging plane, the instantaneous distance of the point target from the phase center projection
。
In the embodiment, the azimuth matching filtering is performed on the distance frequency domain and azimuth frequency domain signal according to a pre-constructed matching filtering function to obtain a signal after matching filtering, and the matching filtering function is pre-constructed according to a conjugate algorithm.
In the specific implementation process, the first-stage reactor,r gp angle of rotation with phase center
There is an approximately sinusoidal fluctuation.R 0Is a point targetPTo the center of the trackOThe distance of (c). According to the cosine theorem, it can be known that:
wherein,Lin order to obtain the radius of the radar rotation track,L= R 0therefore, will be in data processingr gp The approximation is taken as:
the phase error before and after approximation cannot exceed
Corresponding to the distance error
Namely:
wherein,f c the error introduced by this term depends on the center frequencyR 0The size of the error can be known by numerical simulation analysis,R 0the larger the error, the smaller the error, thus found
Corresponding critical value
The imaging area range applicable to the method can be limitedR x Comprises the following steps:
wherein the imaging range
Is composed of
Corresponding critical value.
Imaging plane data
Can be expressed as:
the imaging plane data is subjected to an azimuth Fourier Transform (FT), and then a signal can be obtained
Definition of
Is prepared by reacting with
The corresponding azimuth wave number. The signal can be expressed as:
wherein,
is defined as
The fourier transform of the term, expressed as:
the embodiment of the invention constructs a matched filter function general formula
The item is eliminated for focusing purposes. The matched filter function is constructed according to the following formula:
wherein,
defined as a conjugate, of
And
and completing the matching filtering of the azimuth direction by multiplication:
in the embodiment, two-dimensional inverse Fourier transform is performed on the matched and filtered signals to obtain a focusing image in a polar coordinate system.
In specific implementation, the pair
Two-dimensional inverse Fourier transform is carried out to obtain a focused time domain signal,
the signal is data in polar coordinate format, and a two-dimensional focusing image of the point target in a polar coordinate system can be obtained.
In the embodiment, interpolation processing is performed on the focused image in the polar coordinate system to obtain a focused image in a rectangular coordinate system.
In specific implementation, the polar coordinate format data is converted into
Data in rectangular coordinate format
To obtain a two-dimensional focusing image of the point target in the rectangular coordinate system, i.e. to realize the given distancez p Two-dimensional imaging of a plane. This process is implemented by two-dimensional interpolation. According to the poleCorrespondence of coordinates to rectangular coordinates:
wherein,R 0is in rectangular coordinatesx，yRe-representedR 0，
To use rectangular coordinatesx，yRe-represented
。
Thus, conversion of polar coordinate data to rectangular coordinate data can be achieved using cubic spline interpolation or two-dimensional sinc interpolation.
In the embodiment, according to the focused image under the rectangular coordinate system, frequency domain imaging of the circular scanning ground SAR is carried out.
In this embodiment, performing frequency domain imaging of a circular scanning ground based SAR according to the focused image in the rectangular coordinate system includes: and carrying out chromatographic analysis on planes with equal interval distance in the scene area according to the focused image in the rectangular coordinate system and a preset second distance sampling interval.
In specific implementation, the whole scene area is subjected to equal intervalsd z The planar imaging is repeatedly carried out on the distance plane, two-dimensional imaging is realized layer by layer, and finally three-dimensional imaging of the whole scene can be completed. Sampling intervald z The sampling rule of (1) is as follows:
the distance-wise resolution in length dimension is known as:
then it is determined that,zresolution of direction
Comprises the following steps:
wherein,
thus, the sampling intervald z Should satisfy the following conditions:
based on the same inventive concept, the embodiment of the invention also provides a frequency domain imaging device for circular scanning ground-based SAR, as described in the following embodiments. Because the principles for solving the problems are similar to the frequency domain imaging method of the circular scanning ground-based SAR, the implementation of the device can refer to the implementation of the method, and repeated details are not repeated.
Fig. 4 is a structural diagram of a frequency domain imaging apparatus for circular scanning of a ground-based SAR according to an embodiment of the present invention, as shown in fig. 4, the apparatus includes:
an echo signal obtaining module 401, configured to obtain an echo signal of a circular scanning ground-based SAR;
a first transform module 402, configured to perform distance-to-inverse fourier transform on the echo signal of the circular scanning ground-based SAR to obtain a distance compressed time-domain signal;
a resampling module 403, configured to resample the distance compressed time domain signal according to a preset first distance sampling interval and a geometric correspondence;
a second transform module 404, configured to perform distance-to-fourier transform and azimuth-to-fourier transform on the resampled distance-compressed time-domain signal to obtain a distance-frequency-domain and azimuth-to-azimuth frequency-domain signal;
a matched filtering module 405, configured to perform azimuth matched filtering on the distance frequency domain and azimuth frequency domain signal according to a pre-configured matched filtering function to obtain a matched filtered signal, where the matched filtering function is pre-configured according to a conjugate algorithm;
a third transform module 406, configured to perform two-dimensional inverse fourier transform on the matched and filtered signal to obtain a focused image in a polar coordinate system;
an interpolation processing module 407, configured to perform interpolation processing on the focused image in the polar coordinate system to obtain a focused image in a rectangular coordinate system;
and the frequency domain imaging module 408 is configured to perform frequency domain imaging of the circular scanning foundation SAR according to the focused image in the rectangular coordinate system.
In one embodiment, the geometric correspondence is preset according to a projection distance from a point target to a radar on a plane, a distance from the point target to a radar phase center, and a vertical distance between the plane where the point target is located and an antenna motion track.
In one embodiment, the first distance sampling interval is preset according to a maximum wave number corresponding to a distance from the point target to a radar phase center, a maximum wave number corresponding to a projection distance from the point target to the radar on a plane, and a beam incident angle.
In one embodiment, the frequency domain imaging module 408 is further configured to: and carrying out chromatographic analysis on planes with equal interval distance in the scene area according to the focused image in the rectangular coordinate system and a preset second distance sampling interval.
In summary, the embodiment of the present invention obtains the echo signal of the circular scanning ground based SAR; carrying out distance inverse Fourier transform on the echo signal of the circular scanning ground SAR to obtain a distance compression time domain signal; resampling the distance compressed time domain signal according to a preset first distance sampling interval and a geometrical corresponding relation; performing distance direction Fourier transform and azimuth direction Fourier transform on the resampled distance compression time domain signal to obtain a distance frequency domain and azimuth direction frequency domain signal; carrying out azimuth matching filtering on the distance frequency domain and azimuth frequency domain signals according to a pre-constructed matching filtering function to obtain matched filtered signals, wherein the matching filtering function is pre-constructed according to a conjugate algorithm; performing two-dimensional inverse Fourier transform on the matched and filtered signals to obtain a focused image under a polar coordinate system; performing interpolation processing on the focused image under the polar coordinate system to obtain a focused image under a rectangular coordinate system; and performing frequency domain imaging of the circumferential scanning foundation SAR according to the focused image under the rectangular coordinate system. According to the embodiment of the invention, the echo signals are converted from the inclined plane to the imaging plane through resampling, the signal data are converted, and the target is focused in the frequency domain through Fourier transform, so that the calculation efficiency is high, the imaging speed is high, and the real-time imaging is convenient, therefore, the imaging efficiency is improved while the imaging quality is ensured, and the rapid real-time imaging of the scene is realized.
As will be appreciated by one skilled in the art, embodiments of the present invention may be provided as a method, system, or computer program product. Accordingly, the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present invention may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein.
The present invention is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each flow and/or block of the flow diagrams and/or block diagrams, and combinations of flows and/or blocks in the flow diagrams and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
Finally, it should be noted that: the above-mentioned embodiments are only specific embodiments of the present invention, which are used for illustrating the technical solutions of the present invention and not for limiting the same, and the protection scope of the present invention is not limited thereto, although the present invention is described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: any person skilled in the art can modify or easily conceive the technical solutions described in the foregoing embodiments or equivalent substitutes for some technical features within the technical scope of the present disclosure; such modifications, changes or substitutions do not depart from the spirit and scope of the embodiments of the present invention, and they should be construed as being included therein. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.
Claims (10)
1. A frequency domain imaging method of a circular scanning ground-based SAR is characterized by comprising the following steps:
obtaining echo signals of a circumferential scanning ground SAR;
carrying out distance inverse Fourier transform on the echo signal of the circular scanning ground SAR to obtain a distance compression time domain signal;
resampling the distance compressed time domain signal according to a preset first distance sampling interval and a geometrical corresponding relation;
performing distance direction Fourier transform and azimuth direction Fourier transform on the resampled distance compression time domain signal to obtain a distance frequency domain and azimuth direction frequency domain signal;
carrying out azimuth matching filtering on the distance frequency domain and azimuth frequency domain signals according to a pre-constructed matching filtering function to obtain matched filtered signals, wherein the matching filtering function is pre-constructed according to a conjugate algorithm;
performing two-dimensional inverse Fourier transform on the matched and filtered signals to obtain a focused image under a polar coordinate system;
performing interpolation processing on the focused image under the polar coordinate system to obtain a focused image under a rectangular coordinate system;
and performing frequency domain imaging of the circumferential scanning foundation SAR according to the focused image under the rectangular coordinate system.
2. The frequency-domain imaging method of the circular scanning ground-based SAR (synthetic aperture radar) according to claim 1, wherein the geometric correspondence is preset according to the projection distance of the point target to the radar on a plane, the distance between the point target and the radar phase center, and the vertical distance between the plane where the point target is located and the motion track of the antenna.
3. The frequency-domain imaging method of the circumferentially-scanned ground-based SAR of claim 1, wherein the first distance sampling interval is preset according to a maximum wave number corresponding to a distance from the point target to a radar phase center, a maximum wave number corresponding to a projection distance from the point target to the radar on a plane, and a beam incident angle.
4. The frequency-domain imaging method of the circular scanning ground-based SAR as claimed in claim 1, wherein the performing the frequency-domain imaging of the circular scanning ground-based SAR according to the focused image under the rectangular coordinate system comprises: and carrying out chromatographic analysis on planes with equal interval distance in the scene area according to the focused image in the rectangular coordinate system and a preset second distance sampling interval.
5. A frequency domain imaging device of a circular scanning ground-based SAR is characterized by comprising:
the echo signal acquisition module is used for acquiring echo signals of the circumferential scanning ground SAR;
the first transformation module is used for carrying out distance inverse Fourier transformation on the echo signal of the circular scanning ground SAR to obtain a distance compression time domain signal;
the resampling module is used for resampling the distance compressed time domain signal according to a preset first distance sampling interval and a geometrical corresponding relation;
the second transformation module is used for carrying out distance direction Fourier transformation and azimuth direction Fourier transformation on the resampled distance compression time domain signal to obtain a distance frequency domain and azimuth direction frequency domain signal;
the matched filtering module is used for carrying out azimuth matched filtering on the distance frequency domain and azimuth frequency domain signals according to a pre-constructed matched filtering function to obtain matched filtered signals, and the matched filtering function is pre-constructed according to a conjugate algorithm;
the third transformation module is used for performing two-dimensional inverse Fourier transformation on the matched and filtered signals to obtain a focused image under a polar coordinate system;
the interpolation processing module is used for carrying out interpolation processing on the focused image under the polar coordinate system to obtain a focused image under a rectangular coordinate system;
and the frequency domain imaging module is used for carrying out frequency domain imaging of the circumferential scanning foundation SAR according to the focused image under the rectangular coordinate system.
6. The frequency-domain imaging device of the circular scanning ground-based SAR (synthetic aperture radar) according to claim 5, wherein the geometric correspondence is preset according to the projection distance of the point target to the radar on a plane, the distance of the point target to the radar phase center and the vertical distance between the plane of the point target and the motion trail of the antenna.
7. The frequency-domain imaging apparatus of a circular scanning ground-based SAR of claim 5, wherein said first distance sampling interval is preset according to a maximum wave number corresponding to a distance from a point target to a radar phase center, a maximum wave number corresponding to a projection distance from the point target to the radar on a plane, and a beam incident angle.
8. The frequency-domain imaging apparatus of a swept perimeter-based SAR of claim 5, wherein the frequency-domain imaging module is further to: and carrying out chromatographic analysis on planes with equal interval distance in the scene area according to the focused image in the rectangular coordinate system and a preset second distance sampling interval.
9. A computer device comprising a memory, a processor and a computer program stored on the memory and executable on the processor, wherein the processor implements the method of any one of claims 1 to 4 when executing the computer program.
10. A computer-readable storage medium, characterized in that the computer-readable storage medium stores a computer program for executing the method of any one of claims 1 to 4.
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