CN116840841A - Large-strabismus wide-width high-resolution imaging method for diving section of maneuvering platform radar - Google Patents
Large-strabismus wide-width high-resolution imaging method for diving section of maneuvering platform radar Download PDFInfo
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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
- G01S13/9004—SAR image acquisition techniques
- G01S13/9019—Auto-focussing of the SAR signals
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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
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- 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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Abstract
The application provides a large squint wide-width high-resolution imaging method for a diving section of a maneuvering platform radar, which is characterized in that a wideband signal is sent to a large forward squint direction by utilizing the radar on the maneuvering platform, and radar echo data returned by a ground target is received; and performing distance walking correction on the radar echo data, performing bending correction and pulse pressure to obtain radar echo data subjected to distance direction processing, compensating for residual Doppler center azimuth non-space variant components, performing zero padding at two ends of a signal azimuth time domain, compensating for the radar echo data subjected to zero padding through a fourth-order phase adjustment factor and an azimuth frequency domain nonlinear scaling factor to obtain radar echo data subjected to coefficient compensation, and finally performing azimuth unified focusing to obtain a final target focusing image. According to the application, the influence caused by the oblique angle space variant is corrected in the azimuth direction, the azimuth deformation item is compensated in the azimuth focusing process, and the image distortion of the final imaging result is prevented, so that the imaging focusing quality can be improved.
Description
Technical Field
The application belongs to the technical field of radar imaging, and particularly relates to a large-squint wide-width high-resolution imaging method for a diving section of a maneuvering platform radar.
Background
The geometric model of the traditional synthetic aperture radar imaging large strabismus imaging is mostly built on the premise of uniform linear flat flight track, but the traditional uniform linear flat flight model is not established due to the high speed, maneuver and other motion characteristics of the maneuver platform, and the geometric model suitable for the diving motion track of the maneuver platform needs to be built.
Meanwhile, the traditional large squint imaging method mostly adopts a full-aperture imaging algorithm, but for the large squint imaging of a motor-driven platform radar, the size of the antenna aperture is smaller, the full-aperture imaging time is longer, the data volume is large, and the requirement of rapid imaging cannot be met due to the limitation of the platform. In addition, the azimuth resolution under the full aperture condition is far higher than the required resolution, so that the motorized platform imaging algorithm is not too complex to meet the requirement of real-time rapid imaging, and the rapid imaging can be realized by only using sub-aperture data for coherent processing on the premise of meeting the requirement of resolution, thereby reducing the operand. Meanwhile, the general imaging algorithm is designed on the premise of an ideal track, in the practical application process, the actual track deviates from the ideal track due to the fact that the motion error exists on the platform, motion compensation processing is needed, motion compensation of long-time full-aperture data is difficult, and the complexity of motion compensation can be reduced by sub-aperture data.
Aiming at large squint wide-width high-resolution imaging of a diving section of a maneuvering platform, the existing scheme reduces the problem of strong distance azimuth coupling caused by a large squint angle by introducing a linear distance walking factor, and then introduces a filtering factor to correct the space-variant problem of azimuth Doppler parameters in azimuth direction, so that the large squint imaging is realized. However, as the azimuth breadth increases, the resolution requirement increases, which will cause the squint angle space variant to affect the doppler parameter and ultimately affect the imaging quality.
Disclosure of Invention
In order to solve the problems in the prior art, the application provides a large-squint wide-width high-resolution imaging method for a diving section of a motorized platform radar. The technical problems to be solved by the application are realized by the following technical scheme:
the application provides a large squint wide-width high-resolution imaging method for a diving section of a maneuvering platform radar, which comprises the following steps:
s100, transmitting a broadband signal to the ground through a radar on a maneuvering platform, and receiving radar echo data returned by a ground target;
s200, correcting and compensating the radar echo data in a distance frequency domain to obtain compensated radar echo data;
s300, performing bending correction and pulse pressure on the compensated radar echo data in a two-dimensional frequency domain to obtain radar echo data after distance processing;
s400, compensating a non-space variant component of the Doppler center azimuth of the distance-oriented processed radar echo data to obtain radar echo data with the compensated component;
s500, carrying out two-end zero padding on the radar echo data subjected to component compensation in a signal azimuth time domain to obtain radar echo data subjected to zero padding;
s600, compensating the radar echo data subjected to zero padding through a fourth-order phase adjustment factor and an azimuth frequency domain nonlinear scaling factor to obtain radar echo data subjected to coefficient compensation;
and S700, carrying out azimuth unified focusing on the radar return wave number subjected to coefficient compensation to obtain a final target focusing image.
The application provides a large-squint wide-width high-resolution imaging method for a diving section of a maneuvering platform radar, which is characterized in that a wideband signal is sent to the ground through the radar on the maneuvering platform, and radar echo data returned by a ground target is received; correcting and compensating the radar echo data in a distance frequency domain, and performing bending correction and pulse pressure on the compensated radar echo data in a two-dimensional frequency domain to obtain radar echo data after distance processing; compensating the Doppler center azimuth non-space-variant component of the radar echo data subjected to distance direction processing to obtain radar echo data subjected to component compensation; performing two-end zero padding on the radar echo data subjected to component compensation in a signal azimuth time domain to obtain radar echo data subjected to zero padding; compensating the radar echo data after zero padding through a fourth-order phase adjustment factor and an azimuth frequency domain nonlinear scaling factor to obtain radar echo data after coefficient compensation; and carrying out azimuth unified focusing on the radar return wave number subjected to coefficient compensation to obtain a final target focusing image. According to the application, the influence caused by the oblique angle space variant is corrected in the azimuth direction, the azimuth deformation item is compensated in the azimuth focusing process, and the image distortion of the final imaging result is prevented, so that the imaging focusing quality can be improved.
The present application will be described in further detail with reference to the accompanying drawings and examples.
Drawings
FIG. 1 is a schematic flow chart of a large squint wide-width high-resolution imaging method of a diving section of a maneuvering platform radar;
FIG. 2 is a schematic illustration of a geometric model of a motorized platform linear dive provided by the present application;
FIG. 3 is a schematic diagram of the processing of radar echo data provided by the present application;
FIG. 4 is a schematic diagram of the phase error of the nose-down segment-third order approximate pitch model provided by the present application;
FIG. 5 is a schematic diagram of the phase error of the dive section-fourth order approximate pitch model provided by the present application;
FIG. 6 is a schematic diagram of a point target simulation scenario layout provided by the present application;
FIG. 7 is a center point azimuth cross-section of a reference algorithm;
FIG. 8 is an edge point azimuth cross-section of a reference algorithm;
FIG. 9 is a center point azimuthal cross-section of the imaging method of the application;
fig. 10 is an edge point azimuth cross-sectional view of the imaging method of the present application.
Detailed Description
The present application will be described in further detail with reference to specific examples, but embodiments of the present application are not limited thereto.
With reference to fig. 1 to 3, the application provides a method for forming a large squint wide-width high-resolution image of a diving section of a maneuvering platform radar, which comprises the following steps:
s100, transmitting a broadband signal to the ground through a radar on a maneuvering platform, and receiving radar echo data returned by a ground target;
referring to FIG. 2, FIG. 2 is a geometric model of a motorized platform straight dive in whichRepresenting the skew between the motorized platform and the scene center, < >>Representing the height of the motorized platform from the ground, +.>An included angle between the direction of the diving speed of the platform and the ray direction of the antenna beam is represented by +.>Representing the angle of view under the beam, < >>Representing the angle of depression of the platform>Representing the beam azimuth angle. The complementary angle of the angle between the diving speed direction of the maneuvering platform and the beam ray direction is beam center oblique angle +.>Wave, waveBeam center oblique viewing angleExpressed as:
（1）；
the instantaneous skew of the motorized platform to the target is expressed as:
（2）；
wherein ,representing the skew between the motorized platform and the scene center, < >>Representing the height of the motorized platform from the ground,an included angle between the direction of the diving speed of the platform and the ray direction of the antenna beam is represented by +.>Representing the angle of view under the beam, < >>Representing the angle of depression of the motorized platform, +.>Representing beam azimuth +.>Is the diving speed of the platform;
in practical applications, the motorized platform is curved and dived, i.e., the motorized platform has three-dimensional acceleration, rather than ideal straight dive. The general processing method is to use the idea of motion compensation, consider the influence caused by three-dimensional acceleration as motion error, and compensate the error caused by acceleration through accurate inertial navigation data. In the processing of the application, the influence of acceleration is assumed to be compensated, and the processing is designed based on a straight line dive slope distance model.
In order to ensure the precision requirement of a large squint imaging algorithm of a subsequent maneuvering platform in a dive section, an envelope and phase error are reduced by adopting a dive section-fourth-order pitch model, and an instantaneous pitch is reducedFour-order taylor expansion is performed:
（3）；
assuming that the radar-transmitted broadband signal is a linear frequency modulation signal, the returned radar echo data isIgnoring the signal amplitude only analyzes the phase, +.>Expressed as:
（4）；
wherein ,indicating distance fast time,/day>Indicating azimuth slow time, < >>Representing the frequency modulation rate of the transmitted signal,/->Indicating the speed of light +.>Representing the wavelength of the transmitted signal, ">Representing the distance of the platform from the target, < > and->Is the current time.
S200, correcting and compensating the radar echo data in a distance frequency domain to obtain compensated radar echo data;
the S200 of the present application includes:
s210, performing distance Fourier transform on the radar echo data to convert the radar echo data into a distance frequency domain, so as to obtain radar echo data of the distance frequency domain;
for radar echo dataPerforming distance fast Fourier transform to obtain:
（5）；
s220, constructing a compensation function of which the linear distance walk correction is consistent with the Doppler center;
and S230, compensating the radar echo data of the distance frequency domain by using a compensation function to obtain compensated radar echo data. The compensation function is expressed as:
（6）；
wherein ,represents distance frequency>Representing the center carrier frequency of the signal.
The application uses the distance frequency domain signalCompensation function consistent with linear distance walk correction and Doppler centre +.>And (3) dot multiplication is performed, so that the problem of strong coupling between the distance direction and the azimuth direction caused by large strabismus is eliminated. And then carrying out azimuth fast Fourier transform on the signals to obtain compensated radar echo data, wherein the radar echo data is expressed as:
（7）；
wherein ,represents azimuth frequency, ++>，/>Indicating Doppler center frequency, +.>The distance of the antenna beam rays from the target to the aperture center instant.
S300, performing bending correction and pulse pressure on the compensated radar echo data in a two-dimensional frequency domain to obtain radar echo data after distance processing;
the S300 of the present application includes:
s310, performing azimuth Fourier transform on the compensated radar echo data to convert the compensated radar echo data into a two-dimensional frequency domain;
s320, respectively constructing a correction function of distance curvature, a distance pulse pressure function and a secondary distance pulse pressure function;
the correction function is expressed as:
（8）；
the pulse pressure function is expressed as:
（9）；
s330, performing distance curvature correction on the radar echo data in the two-dimensional frequency domain by using a correction function, performing distance pulse pressure and secondary distance pulse pressure on the radar echo data after the distance curvature correction by using a pulse pressure function, and obtaining processing signal data by combining the change of the instantaneous squint angle along with a distance unit in space;
as can be seen from the geometric model of fig. 2, the temporal angle of view is expressed as a spatial variation with distance units:
（10）；
traditional methods ignore transient oblique viewing anglesInfluence of variation with distance cell, in +.>Approximately this will result in the presence of +.>The related residual phase term can have great influence on the subsequent azimuth focusing under the application scene of large strabismus and wide width and high resolution. The application considers the space variant effect of the squint angle. After finishing the distance direction treatment, let ∈ ->And ignore +.>The phase term of two or more times, and thus the processed signal data is expressed as:
（11）；
wherein ,representing an instantaneous oblique angle of view;
by two-dimensional frequency signalsRespectively with distance warp correction function->And distance pulse pressure and quadratic distance pulse pressure function +.>And performing point multiplication, performing two-dimensional fast Fourier transform, and converting back to a two-dimensional time domain, thereby finishing the distance direction processing of the signals.
S340, performing two-dimensional inverse Fourier transform on the processed signal data to convert the processed signal data into a two-dimensional time domain to obtain distance-processed radar echo data.
Signal is sent toThe azimuth fast inverse fourier transform is performed to be converted into the azimuth time domain, so the distance-processed radar echo data is expressed as:
（12）；
wherein ,，/>representing the residual doppler center corresponding to the residual linear term,indicating azimuth frequency,/->Three term coefficients representing azimuth time domain, ++>And represents the azimuth time domain cubic term coefficient.
S400, compensating a non-space variant component of the Doppler center azimuth of the distance-oriented processed radar echo data to obtain radar echo data with the compensated component;
the S400 of the present application includes:
s410, doppler coefficient of the radar echo data after distance direction processing is calculated in the following wayExpanding the position, and dividing the Doppler parameter of the two-dimensional space variant into a square space variant component and a square non-space variant component;
to simplify the subsequent processing, the Doppler coefficient is calculated byThe method is characterized in that Taylor approximate expansion is performed, the Doppler parameter of the two-dimensional space variant is divided into a square space variant component and a non-square space variant component, and the Doppler parameter of the two-dimensional space variant is expressed as:
（13）；
（14）；
（15）；
（16）；
s420, constructing a component compensation function of the azimuth non-space-variant component of the residual Doppler center;
wherein the component compensation function is expressed as:
（17）；
wherein ,non-space variant term representing residual Doppler center, < +.>A first order space variant term representing the residual Doppler center, < ->Non-space variant item representing azimuth tuning frequency, < ->A primary space-variant term representing azimuth frequency,a quadratic space variable term representing azimuth tuning frequency,/->Non-space-variant term representing the coefficient of the azimuth cubic term,/->A first order space-variant term representing a third order term coefficient of the azimuth; />And a non-space-variant term representing the four-term coefficient of the azimuth.
And S430, compensating the radar echo data subjected to the distance direction processing by using the component compensation function to obtain radar echo data subjected to the component compensation.
S500, carrying out two-end zero padding on the radar echo data subjected to component compensation in a signal azimuth time domain to obtain radar echo data subjected to zero padding;
noteworthy are: the radar echo data after the component compensation is subjected to nonlinear scaling processing in the azimuth direction, so that the spatial variability of Doppler parameters is eliminated, but a signal frequency domain phase-frequency change rate distribution line is widened along a vertical axis, and the signal frequency domain phase-frequency change rate distribution line exceeds the width of a supporting area of the original vertical axis (namely the corresponding signal time domain width), so that partial data is displayed and folded reversely, and a final imaging is caused to appear in a 'ghost'. Therefore, the application needs to widen the width of the supporting area in advance, namely zero padding is carried out at the two ends of the azimuth time domain. According to the method, azimuth two-end zero padding operation is carried out on radar echo data subjected to component compensation, a time domain supporting area is expanded, and aliasing is prevented from occurring in subsequent scaling processing.
S600, compensating the radar echo data subjected to zero padding through a fourth-order phase adjustment factor and an azimuth frequency domain nonlinear scaling factor to obtain radar echo data subjected to coefficient compensation;
the S600 of the present application includes:
s610, constructing a fourth-order phase adjustment factor and a nonlinear scaling factor of an azimuth frequency domain;
the fourth-order phase adjustment factor is used for weakening the space-variant property of the azimuth and providing enough coefficients for the subsequent nonlinear scaling treatment, and is expressed as:
（18）；
the azimuth frequency domain nonlinear scaling factor is used for eliminating the space-variant of azimuth to ensure the unified focusing of the subsequent azimuth, and the nonlinear scaling factor is expressed as:
（19）；
（20）；
（21）；
（22）；
（23）；
（24）；
s620, compensating the radar echo data after zero padding by using a fourth-order phase adjustment factor to obtain radar echo data after adjustment factor compensation;
s630, carrying out azimuth fast Fourier transform on the radar echo data compensated by the adjusting factors to obtain radar echo data of an azimuth frequency domain;
the application uses signalsAnd-> and />Dot multiplication, weakening the influence of the residual Doppler center; at this time, the signal is transformed into an azimuth frequency domain by azimuth fast Fourier transform: radar echo data in the azimuth frequency domain is expressed as:
（25）；
s640, compensating radar echo data of an azimuth frequency domain in S630 by using a nonlinear scaling factor, and performing inverse fast Fourier transform on the compensated radar echo data to obtain radar echo data with compensated coefficients; the coefficient-compensated radar echo data is expressed as:
（26）；
to simplify the signal expression, each order parameter term is composed ofTo ensure that the signal is well focused, the following set of equations is obtained: />，/>Is a constant, usually takes a value around 0.5, but +.>。
Noteworthy are: zero padding quantity is subjected to variable standard parametersThe effect of the value. In addition, parameter->The value will affect the focusing effect and also will scale the imaged scene, requiring engineering application adjustments to achieve good focusing effect. If the value is too large, the focusing effect may be poor, if the value is too small, the scene is scaled too large, and the scene may exceed the pulse repetition frequency range, at this time, zero padding is required to be performed at two ends of the azimuth frequency domain, and the pulse repetition frequency is equivalently improved to prevent the image from generating aliasing.
And S700, carrying out azimuth unified focusing on the radar return wave number subjected to coefficient compensation to obtain a final target focusing image. The S700 of the present application includes:
s710, constructing an azimuth unified focusing function; the azimuthal unifying focusing function is expressed as:
（27）；
s720, focusing the radar echo data subjected to coefficient compensation by utilizing a uniform focusing function of azimuth, and performing azimuth fast Fourier transform on the focused radar echo data to obtain a final target focusing image.
The application willAnd->And performing dot multiplication, performing fast Fourier transform on the azimuth direction to convert the azimuth direction into an azimuth frequency domain, and completing final imaging focusing to obtain a focusing image.
The technical effects of the present application are described below by simulation, and simulation parameters are shown in table 1:
table 1 simulation parameters
Radar imaging generally requires that the model residual phase error not exceedThe effect of the error can be ignored. The effect of phase error on the skew model was analyzed at 0.5m resolution and 1km distance from the edge point to the center point, with specific parameters shown in table 1, and the results shown in fig. 4 and 5 (linear phase does not affect imaging quality, but only causes image shift, so the phase error in the figure has been removed from the linear phase). It can be seen from fig. 4 that the phase error of the nose-down section-third order approximate skew model has far exceededThe imaging result is affected. While FIG. 5 shows that the phase error of the dive-fourth order approximate pitch model is less thanMeeting the requirements. Therefore, the large-squint wide-width high-resolution imaging of the diving section of the maneuvering platform can adopt a diving section-fourth-order approximate diagonal model or a diagonal model with higher precision.
To verify the effectiveness of the algorithm, first, performance evaluation is performed by performing point target simulation, and referring to fig. 6, fig. 6 is a schematic view of point target simulation scene layout. The 5 point targets of the "cross" shape were arranged with a spacing of 500m between the edge points and the center point. According to the radar beam-focusing operation mode, the parameters are shown in table 1, and imaging simulation is performed. The frequency domain phase filtering imaging algorithm is used as a reference algorithm, and compared with the frequency domain phase filtering imaging algorithm, the frequency domain phase filtering imaging algorithm is used for carrying out a comparison experiment, and the results are shown in fig. 7 to 10. FIG. 7 is a center point azimuth cross-section of a reference algorithm; FIG. 8 is an edge point azimuth cross-section of a reference algorithm; FIG. 9 is a center point azimuthal cross-section of the imaging method of the application; fig. 10 is an edge point azimuth cross-sectional view of the imaging method of the present application.
As can be seen from fig. 7 to 10, the center point imaging focusing effect of the two algorithms is good, and the distance direction and the azimuth direction are well focused. The edge point orientation of the reference algorithm is severely defocused, so that the image edge will be completely defocused when imaged over a wide range. The imaging method provided by the application has a serious azimuth focusing effect on the edge points as compared with the center point, but can still obtain a certain focusing effect, and is obviously superior to a reference algorithm.
According to the parameters of Table 1, the radar works in a beam focusing mode, the imaging method and the reference algorithm are adopted to perform imaging simulation respectively, the focusing effect of the radar focusing method is good in the center part of the scene, but the radar focusing method is seriously defocused at the edge of the scene, the image is completely invisible, and the radar focusing method can still see the outline at the edge of the scene. Therefore, the effectiveness of the algorithm of the application on large-squint wide-width high-resolution imaging of the diving section of the maneuvering platform is verified.
The application provides a large-squint wide-width high-resolution imaging method for a diving section of a maneuvering platform radar, which is characterized in that a wideband signal is sent to the ground through the radar on the maneuvering platform, and radar echo data returned by a ground target is received; correcting and compensating the radar echo data in a distance frequency domain, and performing bending correction and pulse pressure on the compensated radar echo data in a two-dimensional frequency domain to obtain radar echo data after distance processing; compensating the Doppler center azimuth non-space-variant component of the radar echo data subjected to distance direction processing to obtain radar echo data subjected to component compensation; performing two-end zero padding on the radar echo data subjected to component compensation in a signal azimuth time domain to obtain radar echo data subjected to zero padding; compensating the radar echo data after zero padding through a fourth-order phase adjustment factor and an azimuth frequency domain nonlinear scaling factor to obtain radar echo data after coefficient compensation; and carrying out azimuth unified focusing on the radar return wave number subjected to coefficient compensation to obtain a final target focusing image. According to the application, the influence caused by the oblique angle space variant is corrected in the azimuth direction, the azimuth deformation item is compensated in the azimuth focusing process, and the image distortion of the final imaging result is prevented, so that the imaging focusing quality can be improved.
Furthermore, the terms "first," "second," and the like, are used for descriptive purposes only and are not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include one or more such feature. In the description of the present application, the meaning of "a plurality" is two or more, unless explicitly defined otherwise.
Although the application is described herein in connection with various embodiments, other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed application, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the "a" or "an" does not exclude a plurality.
The foregoing is a further detailed description of the application in connection with the preferred embodiments, and it is not intended that the application be limited to the specific embodiments described. It will be apparent to those skilled in the art that several simple deductions or substitutions may be made without departing from the spirit of the application, and these should be considered to be within the scope of the application.
Claims (10)
1. The large-squint wide-width high-resolution imaging method for the diving section of the maneuvering platform radar is characterized by comprising the following steps of:
s100, transmitting a broadband signal to the ground through a radar on a maneuvering platform, and receiving radar echo data returned by a ground target;
s200, correcting and compensating the radar echo data in a distance frequency domain to obtain compensated radar echo data;
s300, performing bending correction and pulse pressure on the compensated radar echo data in a two-dimensional frequency domain to obtain radar echo data after distance processing;
s400, compensating a non-space-variant component of the Doppler center azimuth of the radar echo data after the distance direction processing to obtain radar echo data after component compensation;
s500, carrying out two-end zero padding on the radar echo data subjected to component compensation in a signal azimuth time domain to obtain radar echo data subjected to zero padding;
s600, compensating the radar echo data subjected to zero padding through a fourth-order phase adjustment factor and an azimuth frequency domain nonlinear scaling factor to obtain radar echo data subjected to coefficient compensation;
and S700, carrying out azimuth unified focusing on the radar return wave number after coefficient compensation to obtain a final target focusing image.
2. The motorized platform radar dive section large squint wide-width high-resolution imaging method according to claim 1, wherein,
s100, the complementary angle formed by the diving speed direction of the maneuvering platform and the beam ray direction is the central oblique view angle of the beamBeam center oblique view ∈>Expressed as:
（1）；
the instantaneous pitch of the motorized platform to the target in S100 is represented as:
（2）；
wherein ,representing the skew between the motorized platform and the scene center, < >>An included angle between the direction of the diving speed of the platform and the ray direction of the antenna beam is represented by +.>Representing the angle of view under the beam, < >>Representing the angle of depression of the motorized platform, +.>Representing beam azimuth +.>Is the diving speed of the platform;
the fourth-order taylor expansion of the instantaneous pitch is expressed as:
（3）；
the radar echo data in S100 is represented as:
（4）；
wherein ,indicating distance fast time,/day>Indicating azimuth slow time, < >>Representing the frequency modulation rate of the transmitted signal,/->The speed of light is indicated as being the speed of light,representing the wavelength of the transmitted signal, ">Representing the distance of the platform from the target, < > and->Is the current time.
3. The motorized platform radar dive section large squint wide-width high-resolution imaging method according to claim 2, wherein S200 comprises:
s210, performing distance Fourier transform on the radar echo data to convert the radar echo data into a distance frequency domain, so as to obtain radar echo data of the distance frequency domain;
s220, constructing a compensation function of which the linear distance walk correction is consistent with the Doppler center;
and S230, compensating the radar echo data in the distance frequency domain by using the compensation function to obtain compensated radar echo data.
4. The method for high-resolution imaging of a large squint width of a diving section of a mobile platform radar according to claim 3,
the radar echo data of the distance frequency domain in S210 is expressed as:
（5）；
the compensation function in S220 is expressed as:
（6）；
wherein ,represents distance frequency>Representing the center carrier frequency of the signal;
the compensated radar echo data in S230 is represented as:
（7）；
wherein ,represents azimuth frequency, ++>，/>Indicating Doppler center frequency, +.>The distance of the antenna beam rays from the target to the aperture center instant.
5. The motorized platform radar dive section large squint wide-width high-resolution imaging method of claim 4, wherein S300 comprises:
s310, carrying out azimuth Fourier transform on the compensated radar echo data so as to convert the compensated radar echo data into a two-dimensional frequency domain;
s320, respectively constructing a correction function of distance curvature, a distance pulse pressure function and a secondary distance pulse pressure function;
s330, performing distance curvature correction on the radar echo data in the two-dimensional frequency domain by using the correction function, performing distance pulse pressure and secondary distance pulse pressure on the radar echo data after the distance curvature correction by using the pulse pressure function, and obtaining processing signal data by combining the change of the instantaneous squint angle along with the distance unit in space;
s340, performing two-dimensional inverse Fourier transform on the processed signal data to convert the processed signal data into a two-dimensional time domain to obtain distance-processed radar echo data.
6. The motorized platform radar dive section large squint wide-width high-resolution imaging method of claim 5, wherein the correction function in S320 is expressed as:
（8）；
the pulse pressure function in S320 is expressed as:
（9）；
the instantaneous squint angle in S330 spatially varies with distance units as:
（10）；
wherein ,representing the height of the motorized platform from the ground;
the processing signal data in S330 is represented as:
（11）；
wherein ,representing an instantaneous oblique angle of view;
the distance-processed radar echo data in S340 is expressed as:
（12）；
wherein ,，/>representing the residual Doppler center corresponding to the residual linearity term, < >>Indicating azimuth frequency,/->Represents the coefficients of the cubic term in the azimuth time domain,and represents the azimuth time domain cubic term coefficient.
7. The motorized platform radar dive section large squint wide-width high-resolution imaging method of claim 6, wherein S400 comprises:
s410, doppler coefficient of the radar echo data after the distance direction processing is determined asExpanding the position, and dividing the Doppler parameter of the two-dimensional space variant into a square space variant component and a square non-space variant component;
s420, constructing a component compensation function of the azimuth non-space-variant component of the residual Doppler center;
and S430, compensating the radar echo data subjected to the distance direction processing by using the component compensation function to obtain radar echo data subjected to component compensation.
8. The motorized platform radar dive section large squint wide-width high-resolution imaging method according to claim 7,
the two-dimensional space-variant Doppler parameter in S410 is expressed as:
（13）；
（14）；
（15）；
（16）；
the component compensation function in S420 is expressed as:
（17）；
wherein ,non-space variant term representing residual Doppler center, < +.>A first order space variant term representing the residual Doppler center, < ->Non-space variant item representing azimuth tuning frequency, < ->A primary space-variant term representing azimuth frequency,a quadratic space variable term representing azimuth tuning frequency,/->Non-space-variant term representing the coefficient of the azimuth cubic term,/->A first order space-variant term representing a third order term coefficient of the azimuth;/>and a non-space-variant term representing the four-term coefficient of the azimuth.
9. The motorized platform radar dive section large squint wide-width high-resolution imaging method of claim 8, wherein S600 comprises:
s610, constructing a fourth-order phase adjustment factor and a nonlinear scaling factor of an azimuth frequency domain;
the fourth-order phase adjustment factor is expressed as:
（18）；
the nonlinear scaling factor is expressed as:
（19）；
（20）；
（21）；
（22）；
（23）；
（24）；
s620, compensating the radar echo data after zero padding by using the fourth-order phase adjustment factor to obtain radar echo data after adjustment factor compensation;
s630, carrying out azimuth fast Fourier transform on the radar echo data compensated by the adjusting factors to obtain radar echo data of an azimuth frequency domain; the radar echo data of the azimuth frequency domain is expressed as:
（25）；
s640, compensating the radar echo data of the azimuth frequency domain in S630 by using the nonlinear scaling factor, and performing inverse fast Fourier transform on the compensated radar echo data to obtain radar echo data with compensated coefficients; the radar echo data after the coefficient compensation is expressed as:
（26）；
wherein ,，/>is a constant->。
10. The motorized platform radar dive section large squint wide-width high-resolution imaging method of claim 9, wherein S700 comprises:
s710, constructing an azimuth unified focusing function; the azimuthal unified focusing function is expressed as:
（27）；
s720, focusing the radar echo data subjected to coefficient compensation by utilizing the azimuth unified focusing function, and performing azimuth fast Fourier transform on the focused radar echo data to obtain a final target focusing image.
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