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CN114660600A - Method, system, medium and equipment for circular track SAR imaging based on series inversion - Google Patents

Method, system, medium and equipment for circular track SAR imaging based on series inversion Download PDF

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CN114660600A
CN114660600A CN202210225005.9A CN202210225005A CN114660600A CN 114660600 A CN114660600 A CN 114660600A CN 202210225005 A CN202210225005 A CN 202210225005A CN 114660600 A CN114660600 A CN 114660600A
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distance
imaging
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CN114660600B (en
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邢涛
胡庆荣
李军
冯亮
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Beijing Institute of Radio Measurement
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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
    • G01S13/904—SAR modes
    • G01S13/9088—Circular SAR [CSAR, C-SAR]
    • 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
    • G01S13/9011—SAR image acquisition techniques with frequency domain processing of the SAR signals in azimuth
    • 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
    • G01S13/9017—SAR image acquisition techniques with time domain processing of the SAR signals in azimuth

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Abstract

The invention relates to the field of radar imaging, in particular to a method, a system, a medium and equipment for circular track SAR imaging based on series inversion. The method comprises the following steps: the method comprises the following steps: step 1, acquiring position information of a target ground area, and establishing a circular trace imaging geometric model based on the position information; step 2, based on the circular trace imaging geometric model, carrying out distance pulse pressure processing on an oblique distance expression between the radar and a target point to obtain a first expression of a distance frequency domain and an orientation time domain signal; and 3, performing series inversion processing on the expression, and obtaining an imaging image of the circular SAR based on a processing result. The method can achieve the effect of reducing the operation amount.

Description

Method, system, medium and equipment for circular track SAR imaging based on series inversion
Technical Field
The invention relates to the field of radar imaging, in particular to a method, a system, a medium and equipment for circular track SAR imaging based on series inversion.
Background
In SAR imaging, especially in circular track SAR imaging, the Back Projection (BP) algorithm is currently used more. The BP algorithm principle is visual, the method is not limited by a flight mode, and the algorithm universality is high. Other imaging algorithms are also commonly used in the processing of circular track SAR imaging data, such as Polar Format Algorithm (PFA) and Range Migration Algorithm (RMA). Compared with BP algorithm, PFA and RMA have higher efficiency under the same hardware configuration. However, PFA needs to be interpolated from polar to rectangular coordinates, and RMA also needs to be interpolated from Stolt. The interpolation processing also requires a large amount of computation in SAR imaging.
Disclosure of Invention
The invention aims to solve the technical problem of providing a method, a system, a medium and equipment for imaging a circular track SAR based on series inversion.
The technical scheme for solving the technical problems is as follows: a circular track SAR imaging method based on series inversion comprises the following steps:
step 1, acquiring position information of a target ground area, and establishing a circular trace imaging geometric model based on the position information;
step 2, based on the circular trace imaging geometric model, carrying out distance pulse pressure processing on an oblique distance expression between the radar and a target point to obtain a first expression of a distance frequency domain and an orientation time domain signal;
and 3, performing series inversion processing on the expression, and obtaining an imaging image of the circular SAR based on a processing result.
The invention has the beneficial effects that: firstly, establishing a circular trace imaging geometric model, then performing distance expansion and distance pulse pressure on an oblique distance expression under the circular trace imaging geometric model, and performing approximate expansion on the oblique distance and performing distance pulse pressure to obtain a distance frequency domain and orientation time domain signal expression after the distance pulse pressure. And then performing series inversion to obtain a two-dimensional frequency spectrum, performing series inversion to obtain a two-dimensional frequency domain phase, performing form arrangement on the two-dimensional phase through series expansion, and obtaining the two-dimensional frequency spectrum with two-dimensional separation of distance and direction. The problem of large operation amount is solved through the scheme.
On the basis of the technical scheme, the invention can be further improved as follows.
Further, the step 1 specifically comprises:
and establishing a circular trace imaging geometric model by taking the ground scene center of the target ground area as an origin.
Further, the pitch expression is specifically:
Figure BDA0003538847650000021
wherein the cylindrical coordinate system coordinate of the target point is (phi)p，rp，zp)，φpIs an included angle, r, between the projection of the connecting line between the origin and the target point on the XOY plane and the positive direction of the X axispThe projection length of the connecting line between the origin and the target point on the XOY plane, zpProjecting point coordinates, R (t), for the target point on the OZ axism) Is the slant distance between the radar and the target point, raIs the radius of the circle, H is OOa，OaIs the center of the SAR motion trajectory phi0Is tmAnd 0, the initial azimuth angle of the radar.
Further, the first expression specifically is:
Figure BDA0003538847650000022
wherein f isrIs the distance frequency domain, tmIn the form of an azimuth time domain,
Figure BDA0003538847650000023
c is the speed of light, fcIs the carrier frequency, RcenIs the slant distance R (t)m) Zero-order term, k, after series expansion1Is the slant distance R (t)m) First order term after series expansion, k2Is the slant distance R (t)m) Second order term k after series expansion3Is the slant distance R (t)m) Cubic term, k, after series expansion4Is the slant distance R (t)m) The four terms after series expansion.
Further, the step 3 specifically includes:
performing series inversion processing on the expression to obtain a second expression, and obtaining an imaging image of the circular SAR based on the second expression;
the second expression is specifically:
Figure BDA0003538847650000031
wherein f isaIn order to realize the purpose,
Figure BDA0003538847650000032
in order to reduce the intermediate variables used by the formula,
Figure BDA0003538847650000033
in order to reduce the intermediate variables used by the formula,
Figure BDA0003538847650000034
in order to reduce the intermediate variables used by the formula,
Figure BDA0003538847650000035
in order to reduce the intermediate variables used by the formula,
Figure BDA0003538847650000036
intermediate variables for simplifying the formula.
Further, the obtaining of the imaging image of the circular track SAR based on the second expression specifically includes:
and performing bending correction on the second expression to obtain a third expression, and performing azimuth pulse pressure processing on the third expression to obtain an imaging image of the circular track SAR.
Another technical solution of the present invention for solving the above technical problems is as follows: a circular track SAR imaging system based on series inversion comprises:
the acquisition module is used for acquiring the position information of the target ground area and establishing a circular imaging geometric model based on the position information;
the processing module is used for carrying out distance pulse pressure processing on an oblique distance expression between the radar and a target point based on the circular trace imaging geometric model to obtain a first expression of a distance frequency domain and an orientation time domain signal;
and the inversion module is used for performing series inversion processing on the expression and obtaining an imaging image of the circular SAR based on a processing result.
The invention has the beneficial effects that: firstly, establishing a circular trace imaging geometric model, then performing distance expansion and distance pulse pressure on an oblique distance expression under the circular trace imaging geometric model, and performing approximate expansion on the oblique distance and performing distance pulse pressure to obtain a distance frequency domain and orientation time domain signal expression after the distance pulse pressure. And then performing series inversion to obtain a two-dimensional frequency spectrum, performing series inversion to obtain a two-dimensional frequency domain phase, performing form arrangement on the two-dimensional phase through series expansion, and obtaining the two-dimensional frequency spectrum with two-dimensional separation of distance and direction. The problem of large operation amount is solved through the scheme.
Further, the obtaining module is specifically configured to:
and establishing a circular trace imaging geometric model by taking the ground scene center of the target ground area as an origin.
Further, the pitch expression is specifically:
Figure BDA0003538847650000041
wherein the cylindrical coordinate system coordinate of the target point is (phi)p，rp，zp)，φpIs an included angle, r, between the projection of the connecting line between the origin and the target point on the XOY plane and the positive direction of the X axispThe projection length, z, of the connecting line between the origin and the target point on the XOY planepProjecting point coordinates, R (t), for the target point on the OZ axism) Is the slant distance between the radar and the target point, raIs the radius of the circle, H is OOa，OaIs the center of the SAR motion trajectory phi0Is tmAnd 0, the initial azimuth angle of the radar.
Further, the first expression specifically is:
Figure BDA0003538847650000042
wherein f isrIs the distance frequency domain, tmIn the form of an azimuth time domain,
Figure BDA0003538847650000043
c is the speed of light, fcIs the carrier frequency, RcenIs the slant distance R (t)m) Zero-order term, k, after series expansion1Is the slant distance R (t)m) First order term after series expansion, k2Is the slant distance R (t)m) Second order term k after series expansion3Is the slant distance R (t)m) Cubic term, k, after series expansion4Is the slant distance R (t)m) The four terms after series expansion.
Further, the inversion module is specifically configured to:
performing series inversion processing on the expression to obtain a second expression, and obtaining an imaging image of the circular SAR based on the second expression;
the second expression is specifically:
Figure BDA0003538847650000051
wherein f isaIn order to realize the purpose,
Figure BDA0003538847650000052
in order to reduce the intermediate variables used by the formula,
Figure BDA0003538847650000053
in order to reduce the intermediate variables used by the formula,
Figure BDA0003538847650000054
in order to reduce the intermediate variables used by the formula,
Figure BDA0003538847650000055
in order to reduce the intermediate variables used by the formula,
Figure BDA0003538847650000056
intermediate variables for simplifying the formula.
Further, the obtaining of the imaging image of the circular track SAR based on the second expression specifically includes:
and performing bending correction on the second expression to obtain a third expression, and performing azimuth pulse pressure processing on the third expression to obtain an imaging image of the circular track SAR.
Another technical solution of the present invention for solving the above technical problems is as follows: a storage medium having stored therein instructions that, when read by a computer, cause the computer to execute a method for circular track SAR imaging based on series inversion as defined in any one of the preceding claims.
The invention has the beneficial effects that: firstly, establishing a circular trace imaging geometric model, then performing distance expansion and distance pulse pressure on an oblique distance expression under the circular trace imaging geometric model, and performing approximate expansion on the oblique distance and performing distance pulse pressure to obtain a distance frequency domain and orientation time domain signal expression after the distance pulse pressure. And then performing series inversion to obtain a two-dimensional frequency spectrum, performing series inversion to obtain a two-dimensional frequency domain phase, performing form arrangement on the two-dimensional phase through series expansion, and obtaining the two-dimensional frequency spectrum with two-dimensional separation of distance and direction. The problem of large operation amount is solved through the scheme.
Another technical solution of the present invention for solving the above technical problems is as follows: an electronic device includes the storage medium and a processor executing instructions in the storage medium.
The invention has the beneficial effects that: firstly, establishing a circular trace imaging geometric model, then performing distance expansion and distance pulse pressure on an oblique distance expression under the circular trace imaging geometric model, and performing approximate expansion on the oblique distance and performing distance pulse pressure to obtain a distance frequency domain and orientation time domain signal expression after the distance pulse pressure. And then performing series inversion to obtain a two-dimensional frequency spectrum, performing series inversion to obtain a two-dimensional frequency domain phase, performing form arrangement on the two-dimensional phase through series expansion, and obtaining the two-dimensional frequency spectrum with two-dimensional separation of distance and direction. The problem of large computation amount is solved through the scheme.
Drawings
FIG. 1 is a schematic flow chart provided by an embodiment of a circular track SAR imaging method based on series inversion according to the present invention;
FIG. 2 is a structural framework diagram provided by an embodiment of a circular track SAR imaging system based on series inversion according to the present invention;
fig. 3 is a schematic diagram of a circular track imaging geometric model provided by an embodiment of the circular track SAR imaging method based on series inversion.
Detailed Description
The principles and features of this invention are described below in conjunction with examples which are set forth to illustrate, but are not to be construed to limit the scope of the invention.
As shown in fig. 1, a circular track SAR imaging method based on series inversion includes:
step 1, acquiring position information of a target ground area, and establishing a circular trace imaging geometric model based on the position information;
step 2, based on the circular trace imaging geometric model, carrying out distance pulse pressure processing on an oblique distance expression between the radar and a target point to obtain a first expression of a distance frequency domain and an orientation time domain signal;
and 3, performing series inversion processing on the expression, and obtaining an imaging image of the circular SAR based on a processing result.
In some possible implementation modes, firstly, a circle trace imaging geometric model is established, then, the slant range expression under the circle trace imaging geometric model is subjected to distance expansion and distance pulse pressure, and the distance frequency domain and orientation time domain signal expression after the distance pulse pressure is obtained by performing approximate expansion on the slant range and performing the distance pulse pressure. And then performing series inversion to obtain a two-dimensional frequency spectrum, performing series inversion to obtain a two-dimensional frequency domain phase, performing form arrangement on the two-dimensional phase through series expansion, and obtaining the two-dimensional frequency spectrum with two-dimensional separation of distance and direction. The problem of large computation amount is solved through the scheme.
It should be noted that the target ground area is: the method comprises the steps of pointing to a ground area of circular trace imaging, observing which target is on the ground, wherein the target and a peripheral range area of the target are ground scenes; the target points refer to: generally refers to a point within the imaging area of the circular trace, and if the target point P can be imaged, points at other locations within the area can also be imaged.
Step 1 and step 2 can be understood with reference to example 1.
Practice ofExample 1, the geometry of the circular trace imaging is shown in figure 3. According to fig. 3, the center of the ground scene is the point O, the coordinate system is established with the center O, XOY is on the horizontal plane, and the Z axis is vertical to the direction XOY. The point target is P, and the cylindrical coordinate system coordinate of P is (phi)p,rp,zp)，φpAn included angle between the projection of the OP connecting line on the XOY plane and the positive direction of the X axis, namely, the positive direction of the X axis rotates clockwise around the OZ axis to the angle, r, of the rotation of the OP connecting line on the XOY plane in projectionpIs the projection length of OP connecting line in XOY plane, zpThe coordinates of the projection point of the P point on the OZ axis are shown. The coordinate of P in an XYZ rectangular coordinate system is as follows:
Figure BDA0003538847650000071
wherein, OaThe point is the center of the SAR motion trail, OOaH, radius of circle ra. Let tmIs azimuth time, tmInitial azimuth angle of radar is phi when being equal to 00Radar wound around OaPoint rotation angular velocity is w, passing through tmTime, radar azimuth is: phi is aa＝φ0+wtm；tmThe coordinates of the radar at the moment in the cylindrical coordinate system are as follows: (phi)a,raH), the coordinates in XYZ coordinate system are:
Figure BDA0003538847650000072
the slant distance between the radar and the target P is as follows:
Figure BDA0003538847650000081
the above formula is a slope distance expression under the circle trace imaging model.
Step 3 can be understood with reference to example 2.
In the case of the example 2, the following examples are given,
order:
Figure BDA0003538847650000082
B＝2rarp、C＝φ0-φpobtaining:
Figure BDA0003538847650000083
to pair
Figure BDA0003538847650000084
And (3) performing series expansion to obtain a first formula:
Figure BDA0003538847650000085
order:
Figure BDA0003538847650000086
Figure BDA0003538847650000087
Figure BDA0003538847650000088
Figure BDA0003538847650000091
Figure BDA0003538847650000092
r is to becen，k1，k2，k3，k4Substituting the first equation yields:
Figure BDA0003538847650000093
let c be the speed of light and f be the carrier frequencycThe tuning frequency is gamma. Fundamental frequency echoThe signal is obtained by a second formula, which is:
Figure BDA0003538847650000094
wherein,
Figure BDA0003538847650000095
Figure BDA00035388476500000910
is distance time.
Let frFor the range frequency, the second formula performs a range FFT to obtain:
Figure BDA0003538847650000096
wherein gamma is the chirp rate.
Define the range pulse pressure function as:
Figure BDA0003538847650000097
multiplying the second formula by the defined distance pulse pressure function to obtain a third formula:
Figure BDA0003538847650000098
r (t)m) Substituting the expression into a third formula to obtain a first expression:
Figure BDA0003538847650000099
let faFor azimuth frequency, the first expression performs azimuth fourier transform to obtain a fourth formula:
Figure BDA0003538847650000101
the phase of the fourth formula is:
Figure BDA0003538847650000102
order:
Figure BDA0003538847650000103
obtaining:
Figure BDA0003538847650000104
and (5) obtaining a fifth formula:
Figure BDA0003538847650000105
and the fifth formula is different from the series inversion formula, and is deformed to obtain a sixth formula:
Figure BDA0003538847650000106
order:
Figure BDA0003538847650000107
Figure BDA0003538847650000108
Figure BDA0003538847650000109
Figure BDA00035388476500001010
substituting the four formulas into a sixth formula to obtain
Figure BDA00035388476500001011
According to a series inversion formula, obtaining a stationary phase point as follows: t is tm＝A1y+A2y2+A3y3(ii) a Wherein A is1～A3As follows:
Figure BDA0003538847650000111
Figure BDA0003538847650000112
Figure BDA0003538847650000113
neglect ratio y4And obtaining a higher order term according to a stationary phase point formula:
Figure BDA0003538847650000114
Figure BDA0003538847650000115
Figure BDA0003538847650000116
substituting the three formulas into a fourth public expression to obtain the phase:
Figure BDA0003538847650000117
two-dimensional separation of distance and direction is generally carried out in a two-dimensional frequency domain, and a single f needs to be separatedr、faAnd frAnd faItems coupled togetherThe two-dimensional spectrum after the separation of the coupling terms is:
Figure BDA0003538847650000121
order:
Figure BDA0003538847650000122
Figure BDA0003538847650000123
Figure BDA0003538847650000124
Figure BDA0003538847650000125
Figure BDA0003538847650000126
substituting the five formulas into a two-dimensional frequency spectrum to obtain:
Figure BDA0003538847650000131
wherein,
Figure BDA0003538847650000132
in order to reduce the intermediate variables used by the formula,
Figure BDA0003538847650000133
in order to reduce the intermediate variables used by the formula,
Figure BDA0003538847650000134
for simplifying formulasThe variable of the intermediate variable is changed,
Figure BDA0003538847650000135
in order to reduce the intermediate variables used by the formula,
Figure BDA0003538847650000136
intermediate variables for simplifying the formula.
In the above formula
Figure BDA0003538847650000137
Performing series expansion, and obtaining a second expression after arrangement:
Figure BDA0003538847650000138
the second expression is a two-dimensional frequency domain expression of the circular track SAR after the distance pulse pressure, and the two-dimensional separation of the distance and the direction is completed.
And performing bending correction and azimuth pulse pressure processing on a two-dimensional frequency domain expression of the circular SAR, namely a second expression, wherein the bending correction expression is as follows:
Figure BDA0003538847650000141
multiplying the expression for bend correction by the second expression yields a seventh equation:
Figure BDA0003538847650000142
performing distance IFFT on the seventh formula to obtain an eighth formula:
Figure BDA0003538847650000143
the expression of the azimuthal pulse pressure is:
Figure BDA0003538847650000144
multiplying the expression of the azimuthal pulse pressure by an eighth formula to obtain a ninth formula;
Figure BDA0003538847650000145
wherein, Δ frThe ninth formula is oriented for distance bandwidth.
Performing azimuthal IFFT on the ninth formula to obtain:
Figure BDA0003538847650000146
preferably, in any of the above embodiments, step 1 specifically is:
and establishing a circular trace imaging geometric model by taking the ground scene center of the target ground area as an origin.
Preferably, in any of the above embodiments, the pitch expression is specifically:
Figure BDA0003538847650000151
wherein the cylindrical coordinate system coordinate of the target point is (phi)p，rp，zp)，φpIs an included angle, r, between the projection of the connecting line between the origin and the target point on the XOY plane and the positive direction of the X axispThe projection length, z, of the connecting line between the origin and the target point on the XOY planepProjecting point coordinates, R (t), for the target point on the OZ axism) Is the slant distance between the radar and the target point, raIs the radius of the circle, H is OOa，OaIs the center of the SAR motion trajectory phi0Is tmAnd 0, the initial azimuth angle of the radar.
Preferably, in any embodiment described above, the first expression is specifically:
Figure BDA0003538847650000152
wherein f isrIs the distance frequency domain, tmIs the azimuth time domain, j is, c is the speed of light, fcIs represented bycenIs k is1Is k is2Is k is3Is k is4Is as follows.
Preferably, in any of the above embodiments, the step 3 specifically includes:
performing series inversion processing on the expression to obtain a second expression, and obtaining an imaging image of the circular SAR based on the second expression;
the second expression is specifically:
Figure BDA0003538847650000153
wherein f isaIn order to realize the purpose,
Figure BDA0003538847650000154
in order to reduce the intermediate variables used by the formula,
Figure BDA0003538847650000155
in order to reduce the intermediate variables used by the formula,
Figure BDA0003538847650000161
in order to reduce the intermediate variables used by the formula,
Figure BDA0003538847650000162
in order to reduce the intermediate variables used by the formula,
Figure BDA0003538847650000163
intermediate variables for simplifying the formula.
Preferably, in any embodiment described above, the obtaining of the imaging image of the circular track SAR based on the second expression specifically includes:
and performing bending correction on the second expression to obtain a third expression, and performing azimuth pulse pressure processing on the third expression to obtain an imaging image of the circular track SAR.
As shown in fig. 2, a circular track SAR imaging system based on series inversion includes:
an obtaining module 100, configured to obtain position information of a target ground area, and establish a circular imaging geometric model based on the position information;
the processing module 200 is configured to perform distance pulse pressure processing on an oblique distance expression between the radar and the target point based on the circular trace imaging geometric model to obtain a first expression of a distance frequency domain and an orientation time domain signal;
and the inversion module 300 is configured to perform series inversion processing on the expression, and obtain an imaging image of the circular track SAR based on a processing result.
In some possible implementation modes, firstly, a circle trace imaging geometric model is established, then, the slant range expression under the circle trace imaging geometric model is subjected to distance expansion and distance pulse pressure, and the distance frequency domain and orientation time domain signal expression after the distance pulse pressure is obtained by performing approximate expansion on the slant range and performing the distance pulse pressure. And then performing series inversion to obtain a two-dimensional frequency spectrum, performing series inversion to obtain a two-dimensional frequency domain phase, performing form arrangement on the two-dimensional phase through series expansion, and obtaining the two-dimensional frequency spectrum with two-dimensional separation of distance and direction. The problem of large operation amount is solved through the scheme.
Preferably, in any of the embodiments described above, the obtaining module 100 is specifically configured to:
and establishing a circular trace imaging geometric model by taking the ground scene center of the target ground area as an origin.
Preferably, in any of the above embodiments, the pitch expression is specifically:
Figure BDA0003538847650000164
wherein the cylindrical coordinate system coordinate of the target point is (phi)p，rp，zp)，φpProjecting on XOY plane for connecting the origin and the target pointThe positive direction angle of the shadow and the X-axis, rpThe projection length, z, of the connecting line between the origin and the target point on the XOY planepProjecting point coordinates, R (t), for the target point on the OZ axism) Is the slant distance between the radar and the target point, raIs the radius of the circle, H is OOa，OaIs the center of the SAR motion trajectory0Is tmAnd 0, the initial azimuth angle of the radar.
Preferably, in any of the above embodiments, the first expression is specifically:
Figure BDA0003538847650000171
wherein f isrIs the distance frequency domain, tmIs the azimuth time domain, j is the imaginary unit,
Figure BDA0003538847650000172
c is the speed of light, fcIs the carrier frequency, RcenIs the slant distance R (t)m) Zero-order term, k, after series expansion1Is the slant distance R (t)m) First order term after series expansion, k2Is the slant distance R (t)m) Second order term k after series expansion3Is the slant distance R (t)m) Cubic term after series expansion, k4Is the slant distance R (t)m) The four terms after series expansion.
Preferably, in any of the above embodiments, the inversion module 300 is specifically configured to:
performing series inversion processing on the expression to obtain a second expression, and obtaining an imaging image of the circular SAR based on the second expression;
the second expression is specifically:
Figure BDA0003538847650000173
wherein f isaIn order to realize the purpose,
Figure BDA0003538847650000174
for simplifying the disclosureThe intermediate variables used in the formula (la),
Figure BDA0003538847650000175
in order to reduce the intermediate variables used by the formula,
Figure BDA0003538847650000176
in order to reduce the intermediate variables used by the formula,
Figure BDA0003538847650000177
in order to reduce the intermediate variables used by the formula,
Figure BDA0003538847650000178
to reduce intermediate variables used by the formula.
Preferably, in any of the above embodiments, the obtaining of the imaging image of the circular track SAR based on the second expression specifically includes:
and performing bending correction on the second expression to obtain a third expression, and performing azimuth pulse pressure processing on the third expression to obtain an imaging image of the circular track SAR.
Another technical solution of the present invention for solving the above technical problems is as follows: a storage medium having stored therein instructions that, when read by a computer, cause the computer to execute a method for circular track SAR imaging based on series inversion as defined in any one of the preceding claims.
In some possible implementation modes, firstly, a circle trace imaging geometric model is established, then, the slant range expression under the circle trace imaging geometric model is subjected to distance expansion and distance pulse pressure, and the distance frequency domain and orientation time domain signal expression after the distance pulse pressure is obtained by performing approximate expansion on the slant range and performing the distance pulse pressure. And then performing series inversion to obtain a two-dimensional frequency spectrum, performing series inversion to obtain a two-dimensional frequency domain phase, performing form arrangement on the two-dimensional phase through series expansion, and obtaining the two-dimensional frequency spectrum with two-dimensional separation of distance and direction. The problem of large operation amount is solved through the scheme.
Another technical solution of the present invention for solving the above technical problems is as follows: an electronic device includes the storage medium and a processor executing instructions in the storage medium.
In some possible implementation modes, firstly, a circle trace imaging geometric model is established, then, the slant range expression under the circle trace imaging geometric model is subjected to distance expansion and distance pulse pressure, and the distance frequency domain and orientation time domain signal expression after the distance pulse pressure is obtained by performing approximate expansion on the slant range and performing the distance pulse pressure. And then performing series inversion to obtain a two-dimensional frequency spectrum, performing series inversion to obtain a two-dimensional frequency domain phase, performing form arrangement on the two-dimensional phase through series expansion, and obtaining the two-dimensional frequency spectrum with two-dimensional separation of distance and direction. The problem of large operation amount is solved through the scheme.
The reader should understand that in the description of this specification, reference to the description of the terms "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above are not necessarily intended to refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, various embodiments or examples and features of different embodiments or examples described in this specification can be combined and combined by one skilled in the art without contradiction.
In the several embodiments provided in the present application, it should be understood that the disclosed apparatus and method may be implemented in other ways. For example, the above-described method embodiments are merely illustrative, and for example, the division of steps into only one logical functional division may be implemented in practice in another way, for example, multiple steps may be combined or integrated into another step, or some features may be omitted, or not implemented.
The above method, if implemented in the form of software functional units and sold or used as a stand-alone product, may be stored in a computer readable storage medium. Based on such understanding, the technical solution of the present invention essentially or partially contributes to the prior art, or all or part of the technical solution can be embodied in the form of a software product stored in a storage medium and including instructions for causing a computer device (which may be a personal computer, a server, or a network device) to execute all or part of the steps of the method according to the embodiments of the present invention. And the aforementioned storage medium includes: various media capable of storing program codes, such as a usb disk, a removable hard disk, a Read-only memory (ROM), a Random Access Memory (RAM), a magnetic disk, or an optical disk.
While the invention has been described with reference to specific embodiments, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims (10)

1. A circular track SAR imaging method based on series inversion is characterized by comprising the following steps:
step 1, acquiring position information of a target ground area, and establishing a circular trace imaging geometric model based on the position information;
step 2, based on the circular trace imaging geometric model, carrying out distance pulse pressure processing on an oblique distance expression between the radar and a target point to obtain a first expression of a distance frequency domain and an orientation time domain signal;
and 3, performing series inversion processing on the first expression, and obtaining an imaging image of the circular SAR based on a processing result.
2. The method for circular track SAR imaging based on series inversion according to claim 1, wherein the step 1 specifically comprises:
and establishing a circular trace imaging geometric model by taking the ground scene center of the target ground area as an origin.
3. The method of claim 1, wherein the slant range expression specifically comprises:
Figure FDA0003538847640000011
wherein the cylindrical coordinate system coordinate of the target point is (phi)p，rp，zp)，φpIs an included angle, r, between the projection of the connecting line between the origin and the target point on the XOY plane and the positive direction of the X axispThe projection length of the connecting line between the origin and the target point on the XOY plane, zpProjecting point coordinates, R (t), for the target point on the OZ axism) Is the slant distance between the radar and the target point, raIs the radius of the circle, H is OOa，OaIs the center of the SAR motion trajectory phi0Is tmAnd 0, the initial azimuth angle of the radar.
4. The method according to claim 1, wherein the first expression specifically includes:
Figure FDA0003538847640000021
wherein f isrIs the distance frequency domain, tmIs the azimuth time domain, j is the imaginary unit,
Figure FDA0003538847640000022
c is the speed of light, fcIs the carrier frequency, RcenIs the slant distance R (t)m) Zero-order term, k, after series expansion1Is the slant distance R (t)m) First order term after series expansion, k2Is the slant distance R (t)m) Second order term k after series expansion3Is the slant distance R (t)m) Third degree after series expansionTerm, k4Is the slant distance R (t)m) The four terms after series expansion.
5. The method according to claim 4, wherein the step 3 specifically includes:
performing series inversion processing on the expression to obtain a second expression, and obtaining an imaging image of the circular SAR based on the second expression;
the second expression is specifically:
Figure FDA0003538847640000023
wherein, faIn order to realize the purpose,
Figure FDA0003538847640000024
in order to reduce the intermediate variables used by the formula,
Figure FDA0003538847640000025
in order to reduce the intermediate variables used by the formula,
Figure FDA0003538847640000026
in order to reduce the intermediate variables used by the formula,
Figure FDA0003538847640000027
in order to reduce the intermediate variables used by the formula,
Figure FDA0003538847640000028
intermediate variables for simplifying the formula.
6. The method according to claim 5, wherein the obtaining of the imaging image of the circular track SAR based on the second expression specifically comprises:
and performing bending correction on the second expression to obtain a third expression, and performing azimuth pulse pressure processing on the third expression to obtain an imaging image of the circular track SAR.
7. A circular track SAR imaging system based on series inversion is characterized by comprising:
the acquisition module is used for acquiring the position information of the target ground area and establishing a circular imaging geometric model based on the position information;
the processing module is used for carrying out distance pulse pressure processing on an oblique distance expression between the radar and a target point based on the circular trace imaging geometric model to obtain a first expression of a distance frequency domain and an orientation time domain signal;
and the inversion module is used for performing series inversion processing on the expression and obtaining an imaging image of the circular SAR based on a processing result.
8. The system of claim 7, wherein the acquisition module is specifically configured to:
and establishing a circular trace imaging geometric model by taking the ground scene center of the target ground area as an origin.
9. A medium having stored therein instructions which, when read by a computer, cause the computer to execute a method for circular track SAR imaging based on series inversion according to any one of claims 1 to 6.
10. A device comprising the storage medium of claim 9, a processor to execute instructions within the storage medium.
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