CN113820713A - Imaging method and device of transmitter motion bistatic arc array SAR and storage medium - Google Patents

Imaging method and device of transmitter motion bistatic arc array SAR and storage medium Download PDF

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CN113820713A
CN113820713A CN202111215085.1A CN202111215085A CN113820713A CN 113820713 A CN113820713 A CN 113820713A CN 202111215085 A CN202111215085 A CN 202111215085A CN 113820713 A CN113820713 A CN 113820713A
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distance
azimuth
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CN113820713B (en
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黄平平
郝玲霞
徐伟
谭维贤
乞耀龙
韩阔业
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Inner Mongolia University of Technology
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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
    • 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
    • G01S13/9021—SAR image post-processing techniques
    • G01S13/9023—SAR image post-processing techniques combined with interferometric techniques

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Abstract

The disclosure relates to an imaging method, an imaging device and a storage medium of a transmitter moving bistatic arc array SAR, wherein distance-to-Fourier transform is carried out on the basis of the assumption that echo data are subjected to baseband demodulation processing, and distance frequency domain, azimuth and time domain echo data are obtained; generating a distance walking correction function through the decomposed double-base instantaneous slant distance to perform distance walking correction on distance frequency domain azimuth time domain echo data and then performing distance direction pulse compression; and then performing distance and azimuth decoupling processing and distance inverse Fourier transform to obtain a decoupled two-dimensional time domain signal, then performing azimuth Fourier transform and azimuth matched filtering to obtain an azimuth pulse compressed signal, and then performing azimuth inverse Fourier transform to obtain a final two-dimensional time domain focusing signal. Through the embodiments of the disclosure, the omnidirectional and high-resolution imaging is obtained through the high-order approximation of the slant range, the distance walking compensation and the Keystone transformation aiming at the double-base arc array SAR system with the moving transmitter.

Description

Imaging method and device of transmitter motion bistatic arc array SAR and storage medium
Technical Field
The disclosure relates to the technical field of radar interferometry data processing, in particular to an imaging method of a transmitter moving bistatic arc array SAR, an imaging device of the transmitter moving bistatic arc array SAR and a computer readable storage medium.
Background
In the prior art, a scholars in the past propose a back projection algorithm and a distance Doppler (RD for short) imaging algorithm based on the Keystone transform for the arc array SAR imaging processing. The back projection algorithm is a time domain algorithm, no approximate processing exists in the algorithm process, accurate images can be obtained, and the requirement of high imaging quality is met. However, the amount of calculation is too large, and the imaging processing speed is slow. The RD algorithm based on Keystone transformation utilizes Keystone transformation to carry out range migration correction in the imaging processing process, eliminates coupling between the distance and the azimuth direction, and can meet the imaging quality requirement when an aircraft flies high above the ground. However, in the imaging process of the bistatic arc array SAR in which the transmitter moves, the doppler frequency of the target changes not only with the distance position but also with the azimuth position, and the obtained data has two-dimensional space-variant property, which increases the imaging processing difficulty. On the other hand, the transmitter movement can cause serious distance walking, and the Keystone transform algorithm can not be directly used to obtain images with good focusing, so that the conventional algorithm can not be directly applied to the bistatic arc array SAR imaging of the transmitter movement.
Disclosure of Invention
The present disclosure is intended to provide an imaging method of a transmitter-moving bistatic arc array SAR, an imaging device of a transmitter-moving bistatic arc array SAR, and a computer-readable storage medium, which are capable of obtaining an omnidirectional and high-resolution image by implementing an imaging process of a system by a high-order approximation of a slant range, a distance walk compensation, and a Keystone transform for a bistatic arc array SAR system of a transmitter-moving.
According to one aspect of the disclosure, an imaging method of a transmitter motion bistatic arc array SAR is provided, which includes:
acquiring echo data of a transmitter moving bistatic arc array SAR, and performing range-to-Fourier transform on the echo data on the assumption that the echo data is subjected to baseband demodulation processing to obtain range frequency domain azimuth time domain echo data;
generating a distance walking correction function through the decomposed double-base instantaneous slant distance, and performing distance walking correction on distance frequency domain and azimuth time domain echo data by using the distance walking correction function;
distance direction pulse compression is carried out on the distance frequency domain signals after distance walk correction processing;
performing distance and azimuth decoupling processing and distance inverse Fourier transform on the distance-direction pulse compressed signal to obtain a decoupled two-dimensional time domain signal;
carrying out azimuth Fourier transform and azimuth matched filtering on the two-dimensional time domain signal to obtain an azimuth pulse compressed signal;
and performing azimuth inverse Fourier transform on the signal subjected to azimuth pulse compression to obtain a final two-dimensional time domain focusing signal.
In some embodiments, wherein a range walk correction function is generated by the decomposed two-base instantaneous slope distance, performing range walk correction on range frequency domain azimuth time domain echo data using the range walk correction function, comprises:
obtaining a first instant slope distance from a radar transmitter to a target based on an assumed arbitrary target, a receiver equivalent sampling point and coordinates of the transmitter;
approximate processing is carried out on the first instantaneous slope distance by adopting Taylor series expansion, and the first instantaneous slope distance is decomposed into two parts which are related to the speed and unrelated to the speed;
generating a distance walking correction function according to the first instant slope distance subjected to the approximate processing;
and performing range walk correction processing on the range frequency domain azimuth time domain echo data by adopting a range walk correction function to obtain range walk corrected echo data.
In some embodiments, the distance-wise pulse compressing the distance frequency domain signal after the distance walk correction process includes:
constructing a pulse compression function in a matched filtering mode;
and performing range-wise pulse compression processing on the echo signal of the range frequency domain by using the obtained pulse compression function to obtain the echo signal after range-wise pulse compression.
In some embodiments, the performing distance and orientation decoupling processing and distance inverse fourier transform on the distance-oriented pulse compressed signal to obtain a decoupled two-dimensional time-domain signal includes:
performing approximation processing on a second instantaneous slope distance from the equivalent sampling point to the target by using Taylor series expansion to obtain a second instantaneous slope distance subjected to approximation processing;
redefining a virtual azimuth sampling variable based on the obtained second instantaneous slope distance subjected to approximate processing by adopting a Keystone transformation method;
performing Keystone transformation according to the redefined virtual azimuth variable to obtain echo signals after distance and azimuth decoupling;
and performing range inverse Fourier transform on the echo signals subjected to range and azimuth decoupling to obtain two-dimensional time domain signals subjected to range and azimuth decoupling.
In some embodiments, the performing an azimuth fourier transform and an azimuth matched filter on the two-dimensional time-domain signal to obtain an azimuth pulse-compressed signal includes:
performing azimuth Fourier transform on the two-dimensional time domain signal to obtain a range-Doppler domain echo signal;
constructing an azimuth matching filter function convolution kernel, wherein the convolution kernel is a phase item related to a redefined virtual azimuth variable in a two-dimensional time domain signal;
generating an azimuth matched filtering convolution kernel according to the two-dimensional time domain signal;
carrying out azimuth Fourier transform and complex conjugate processing on the obtained convolution kernel to obtain an azimuth matched filtering function;
and performing azimuth matching filtering processing on the range-Doppler domain echo signal based on the obtained azimuth matching filtering function to obtain an azimuth pulse compressed signal.
According to one aspect of the present disclosure, an imaging apparatus for a transmitter moving bistatic arc array SAR is provided, including:
the acquisition module is configured to acquire echo data of the transmitter moving bistatic arc array SAR;
a signal processing module configured to perform distance-to-fourier transform on the echo data based on an assumption that the echo data has been subjected to baseband demodulation processing, so as to obtain distance frequency domain azimuth time domain echo data; generating a distance walking correction function through the decomposed double-base instantaneous slant distance, and performing distance walking correction on distance frequency domain and azimuth time domain echo data by using the distance walking correction function; distance direction pulse compression is carried out on the distance frequency domain signals after distance walk correction processing; performing distance and azimuth decoupling processing and distance inverse Fourier transform on the distance-direction pulse compressed signal to obtain a decoupled two-dimensional time domain signal; carrying out azimuth Fourier transform and azimuth matched filtering on the two-dimensional time domain signal to obtain an azimuth pulse compressed signal; and performing azimuth inverse Fourier transform on the signal subjected to azimuth pulse compression to obtain a final two-dimensional time domain focusing signal.
In some embodiments, wherein the signal processing module is further configured to:
generating a distance walking correction function through the decomposed double-base instantaneous slant distance, and performing distance walking correction on distance frequency domain and azimuth time domain echo data by using the distance walking correction function, wherein the distance walking correction function comprises the following steps:
obtaining a first instant slope distance from a radar transmitter to a target based on an assumed arbitrary target, a receiver equivalent sampling point and coordinates of the transmitter;
approximate processing is carried out on the first instantaneous slope distance by adopting Taylor series expansion, and the first instantaneous slope distance is decomposed into two parts which are related to the speed and unrelated to the speed;
generating a distance walking correction function according to the first instant slope distance subjected to the approximate processing;
and performing range walk correction processing on the range frequency domain azimuth time domain echo data by adopting a range walk correction function to obtain range walk corrected echo data.
In some embodiments, wherein the signal processing module is further configured to:
the distance direction pulse compression is carried out on the distance frequency domain signal after the distance walk correction processing, and the method comprises the following steps:
constructing a pulse compression function in a matched filtering mode;
and performing range-wise pulse compression processing on the echo signal of the range frequency domain by using the obtained pulse compression function to obtain the echo signal after range-wise pulse compression.
In some embodiments, wherein the signal processing module is further configured to:
the distance and direction decoupling processing and the distance inverse Fourier transform are carried out on the distance-direction pulse compressed signal to obtain a decoupled two-dimensional time domain signal, and the method comprises the following steps:
performing approximation processing on a second instantaneous slope distance from the equivalent sampling point to the target by using Taylor series expansion to obtain a second instantaneous slope distance subjected to approximation processing;
redefining a virtual azimuth sampling variable based on the obtained second instantaneous slope distance subjected to approximate processing by adopting a Keystone transformation method;
performing Keystone transformation according to the redefined virtual azimuth variable to obtain echo signals after distance and azimuth decoupling;
and performing range inverse Fourier transform on the echo signals subjected to range and azimuth decoupling to obtain two-dimensional time domain signals subjected to range and azimuth decoupling.
According to one aspect of the present disclosure, there is provided a computer-readable storage medium having stored thereon computer-executable instructions that, when executed by a processor, implement:
according to the imaging method of the transmitter motion bistatic arc array SAR.
The method for imaging the SAR, the device for imaging the SAR and the computer-readable storage medium of the SAR of the transmitter in various embodiments of the present disclosure acquire echo data of the SAR, and perform range-to-Fourier transform on the echo data based on the assumption that the echo data has been subjected to baseband demodulation processing to obtain range frequency domain azimuth time domain echo data; generating a distance walking correction function through the decomposed double-base instantaneous slant distance, and performing distance walking correction on distance frequency domain and azimuth time domain echo data by using the distance walking correction function; distance direction pulse compression is carried out on the distance frequency domain signals after distance walk correction processing; performing distance and azimuth decoupling processing and distance inverse Fourier transform on the distance-direction pulse compressed signal to obtain a decoupled two-dimensional time domain signal; carrying out azimuth Fourier transform and azimuth matched filtering on the two-dimensional time domain signal to obtain an azimuth pulse compressed signal; and performing azimuth inverse Fourier transform on the signal subjected to azimuth pulse compression to obtain a final two-dimensional time domain focusing signal. The method aims at achieving imaging processing of a double-base arc array SAR system aiming at transmitter motion through high-order approximation of slant distance, distance walking compensation and Keystone transformation, and can obtain all-dimensional and high-resolution imaging. The embodiments of the present disclosure first perform high-order approximation processing on the bistatic slant range through taylor series expansion, and decompose the slant range into two parts, one part being unrelated to the transmitter speed and the other part being related to the transmitter speed. And constructing a distance walking compensation function according to the solved slant range formula, correcting the distance walking caused by the operation of the transmitter in a distance frequency domain, and reducing the two-dimensional coupling of echo signals. On the basis, Keystone transformation is used for eliminating residual coupling between the distance and the azimuth angle. And finally, obtaining an image with good focusing through azimuth matching filtering.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the disclosure, as claimed.
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In the drawings, which are not necessarily drawn to scale, like reference numerals may designate like components in different views. Like reference numerals with letter suffixes or like reference numerals with different letter suffixes may represent different instances of like components. The drawings illustrate various embodiments generally, by way of example and not by way of limitation, and together with the description and claims, serve to explain the disclosed embodiments.
Fig. 1 shows a signal processing flow diagram of an embodiment of the imaging method of the transmitter moving bistatic arc array SAR of the present disclosure.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present disclosure more clear, the technical solutions of the embodiments of the present disclosure will be described below clearly and completely with reference to the accompanying drawings of the embodiments of the present disclosure. It is to be understood that the described embodiments are only a few embodiments of the present disclosure, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the described embodiments of the disclosure without any inventive step, are within the scope of protection of the disclosure.
Unless otherwise defined, technical or scientific terms used herein shall have the ordinary meaning as understood by one of ordinary skill in the art to which this disclosure belongs. The word "comprising" or "comprises", and the like, means that the element or item listed before the word covers the element or item listed after the word and its equivalents, but does not exclude other elements or items.
To maintain the following description of the embodiments of the present disclosure clear and concise, a detailed description of known functions and known components have been omitted from the present disclosure.
The Synthetic Aperture Radar (SAR) with the arc array is an imaging system which is newly proposed in recent years, the system arranges an antenna array along an arc in the azimuth direction, breaks through the problem that the observation visual angle of the traditional linear array SAR is single, can quickly image and sense a 360-degree scene area around an airborne platform, provides guarantee for safe flight and vertical take-off and landing of the helicopter platform, and has great application prospect in the civil and military fields. The double-base arc array SAR is characterized in that a transmitter and a receiver are placed on different platforms, and compared with a single-base arc array SAR, the double-base arc array SAR has better concealment and safety and can obtain richer target information. The bistatic arc array SAR has a flexible geometric structure due to the separation of the transceiving platforms, and different imaging modes can be set in order to meet different application requirements, for example, the bistatic arc array SAR in receiver motion, the bistatic arc array SAR in transmitter motion, and the bistatic arc array SAR in transceiving motion. In the double-base arc array SAR system with the transmitter moving, the receiver is fixed at a certain height, when the working mode of 'silence' is set, the concealment of the system can be improved, the transmitter moves over the scene, the radiation range is expanded, a plurality of receiving systems with lower cost can share the same transmitting system with high cost, the airborne safety is ensured, and the system cost is reduced. Therefore, the double-base arc array SAR is applied to the fields of airborne navigation, auxiliary landing, blind landing and the like, and has a great application prospect.
In light of the foregoing background, the present disclosure exemplifies by way of example solutions to address deficiencies in the prior art, but not as limitations to the scope of the claimed invention.
As one aspect, an embodiment of the present disclosure provides an imaging method of a transmitter moving bistatic arc array SAR, including:
acquiring echo data of a transmitter moving bistatic arc array SAR, and performing range-to-Fourier transform on the echo data on the assumption that the echo data is subjected to baseband demodulation processing to obtain range frequency domain azimuth time domain echo data;
generating a distance walking correction function through the decomposed double-base instantaneous slant distance, and performing distance walking correction on distance frequency domain and azimuth time domain echo data by using the distance walking correction function;
distance direction pulse compression is carried out on the distance frequency domain signals after distance walk correction processing;
performing distance and azimuth decoupling processing and distance inverse Fourier transform on the distance-direction pulse compressed signal to obtain a decoupled two-dimensional time domain signal;
carrying out azimuth Fourier transform and azimuth matched filtering on the two-dimensional time domain signal to obtain an azimuth pulse compressed signal;
and performing azimuth inverse Fourier transform on the signal subjected to azimuth pulse compression to obtain a final two-dimensional time domain focusing signal.
In view of the problems presented in the foregoing, embodiments of the present disclosure are directed to a method for imaging a transmitter moving bistatic arc array SAR. The method aims at a double-base arc array SAR system with a transmitter moving, imaging processing of the system is achieved through high-order approximation of the slant range, distance walking compensation and Keystone conversion, and all-dimensional and high-resolution imaging can be obtained. The algorithm firstly carries out high-order approximate processing on the double-base slant range through Taylor series expansion, and decomposes the slant range into two parts, wherein one part is irrelevant to the speed of a transmitter, and the other part is relevant to the speed of the transmitter. And constructing a distance walking compensation function according to the solved slant range formula, correcting the distance walking caused by the movement of the transmitter in a distance frequency domain, and reducing the two-dimensional coupling of echo signals. On the basis, Keystone transformation is used for eliminating residual coupling between the distance and the azimuth angle. And finally, obtaining an image with good focusing through azimuth matching filtering.
As shown in fig. 1, the specific implementation steps may include, but are not limited to, step S1 to step S6 for illustration.
The specific implementation can include:
step S1: obtaining echo data s (t) of transmitter moving bistatic arc array SARr,ta) For the echo data s (t), assuming that the data has been processed by baseband demodulationr,ta) Performing range Fourier transform, namely calculating by adopting the following formula (1) to obtain range frequency domain azimuth time domain echo data Ss(fr,ta)：
Ss(fr,ta)＝RFFT{s(tr,ta)} (1)
Wherein in the formula (1), RFFT {. cndot.) represents a distance Fourier transform, trAs a function of distance to time, taAs an azimuthal time variable, frIs the range frequency.
In some embodiments, the present disclosure may be implemented as: generating a distance walking correction function through the decomposed double-base instantaneous slant distance, and performing distance walking correction on distance frequency domain and azimuth time domain echo data by using the distance walking correction function, wherein the distance walking correction function comprises the following steps:
obtaining a first instant slope distance from a radar transmitter to a target based on an assumed arbitrary target, a receiver equivalent sampling point and coordinates of the transmitter;
approximate processing is carried out on the first instantaneous slope distance by adopting Taylor series expansion, and the first instantaneous slope distance is decomposed into two parts which are related to the speed and unrelated to the speed;
generating a distance walking correction function according to the first instant slope distance subjected to the approximate processing;
and performing range walk correction processing on the range frequency domain azimuth time domain echo data by adopting a range walk correction function to obtain range walk corrected echo data.
The specific implementation can include:
step S2: generating a distance walking correction function through the decomposed double-base instantaneous slope distance, and utilizing the function to perform distance frequency domain echo data Ss(fr,ta) The distance walk correction is performed, and the specific steps are as follows.
Step S21: let the coordinates of any target, receiver equivalent sampling point and transmitter be (theta)n,Rn,Hn)、(θr,Rr,Hr)、(θt,Rt,Ht) Then the instantaneous slant distance D of the radar transmitter to the targettCan be expressed as:
Figure BDA0003310461860000091
where v is the transmitter velocity of motion, taIs an azimuth time variable.
Step S22: using Taylor series expansion to correct the above instantaneous slope distance DtAnd (3) performing approximate processing, and decomposing into two parts which are related to the speed and unrelated to the speed:
Dt≈κ0+κ1(vta)+κ2(vta)2+κ3(vta)3+κ4(vta)4(3) wherein k is0、k1、k2、k3And k4For the solved constant coefficients, the calculation formula of each coefficient is as follows:
Figure BDA0003310461860000092
Figure BDA0003310461860000093
Figure BDA0003310461860000094
Figure BDA0003310461860000101
Figure BDA0003310461860000102
in the formula (I), the compound is shown in the specification,
Figure BDA0003310461860000103
Rt、Rnrespectively the ground distance between the transmitter and the target and the origin of coordinates, HtIs the level of the transmitter, thetatAnd thetanRespectively the azimuth angle of the transmitter and the target.
Step S23: generating a distance walking correction function according to the instantaneous slope distance obtained in the step S22, wherein the specific formula is as follows:
Figure BDA0003310461860000104
step S24: using the distance walk correction function generated in step S23Distance walk correction processing is carried out on the echo data of the distance frequency domain to obtain echo data S after distance walk corrections1(fr,ta) The specific operation is shown in formula (10):
Ss1(fr,ta)＝Ss(fr,ta)·hc(fr,ta) (10)
in the formula (10), Ss(fr,ta) As echo data in the range frequency domain, hc(fr,ta) The function is corrected for range walk.
In some embodiments, the present disclosure may be implemented as: the distance direction pulse compression is carried out on the distance frequency domain signal after the distance walk correction processing, and the method comprises the following steps:
constructing a pulse compression function in a matched filtering mode;
and performing range-wise pulse compression processing on the echo signal of the range frequency domain by using the obtained pulse compression function to obtain the echo signal after range-wise pulse compression.
The specific implementation can include:
step S3: the distance frequency domain signal S after the distance walk correction processings1(fr,ta) And (5) performing distance-direction pulse compression, wherein the specific treatment process is as follows.
Step S31: pulse compression function H constructed by adopting matched filtering moder(fr) The method comprises the following steps:
Figure BDA0003310461860000111
in the formula, KrFor adjusting the frequency, T, in the direction of the distancerFor transmitting signal pulse width, frIs the range frequency.
Step S32: using the pulse compression function H obtained in step S31r(fr) Performing range-direction pulse compression processing on the echo signal of the range frequency domain to obtain an echo signal S after range-direction pulse compressionsf_c(fr,ta)：
Ssf_c(fr,ta)＝Ss1(fr,ta)·Hr(fr) (12)
In the formula (12), Ss1(fr,ta) For distance range frequency domain signals corrected for range walk, Hr(fr) Is a function of distance-wise pulse compression.
In some embodiments, the present disclosure may be implemented as: the distance and direction decoupling processing and the distance inverse Fourier transform are carried out on the distance-direction pulse compressed signal to obtain a decoupled two-dimensional time domain signal, and the method comprises the following steps:
performing approximation processing on a second instantaneous slope distance from the equivalent sampling point to the target by using Taylor series expansion to obtain a second instantaneous slope distance subjected to approximation processing;
redefining a virtual azimuth sampling variable based on the obtained second instantaneous slope distance subjected to approximate processing by adopting a Keystone transformation method;
performing Keystone transformation according to the redefined virtual azimuth variable to obtain echo signals after distance and azimuth decoupling;
and performing range inverse Fourier transform on the echo signals subjected to range and azimuth decoupling to obtain two-dimensional time domain signals subjected to range and azimuth decoupling.
The specific implementation can include:
step S4: step S4 is to perform distance and orientation decoupling processing and distance inverse fourier transform on the signal after the distance pulse compression to obtain a decoupled two-dimensional time domain signal, and the specific processing procedure is as follows:
step S41: adopting Taylor series expansion to obtain instantaneous slope distance D from equivalent sampling point to targetrCarrying out approximation processing to obtain the approximated instantaneous slope distance DrAs shown in equation (13):
Figure BDA0003310461860000121
in the formula，HrTo equivalent sample point level, RrIs the radius of the arc array antenna, thetarIs the azimuthal angle of the equivalent sample point, betarIs inserted into the ground corner and meets the requirements
Figure BDA0003310461860000122
Step S41: instantaneous slope distance D obtained based on the above method by adopting Keystone transformation methodrRedefining a virtual azimuth sampling variable
Figure BDA0003310461860000123
Wherein
Figure BDA0003310461860000124
Sampling variable theta with azimuthrThe relationship is shown in equation (14):
Figure BDA0003310461860000125
in the formula (f)cIs a carrier frequency, frIs the distance frequency, thetanIs the azimuth angle of the target, the azimuth sampling variable thetarThe relation between the time variable and the azimuth direction is shown in the formula (15):
θr＝ωata (15)
in the formula, ωaThe switching speed of the arc array antenna unit of the receiver.
Step S42: according to the direction variable redefined in the step S41
Figure BDA0003310461860000126
Keystone transformation is carried out by adopting a formula (16) to obtain echo signals after distance and azimuth decoupling
Figure BDA0003310461860000127
Figure BDA0003310461860000128
In the formula, Ssf_c(fr,θr) I is the distance frequency domain signal after distance pulse compression, thetanIs the target azimuth angle.
Step S43: performing inverse Fourier transform on the distance frequency domain signal after Keystone transform to obtain a two-dimensional time domain signal after distance and azimuth decoupling
Figure BDA0003310461860000129
The specific calculation formula is shown as formula (17):
Figure BDA00033104618600001210
in the formula, RIFFT {. is } represents a distance inverse Fourier transform,
Figure BDA0003310461860000131
for distance frequency domain signals after Keystone transform, trAs a function of distance to time, frIs the range frequency.
In some embodiments, the present disclosure may be implemented as: carrying out azimuth Fourier transform and azimuth matched filtering on the two-dimensional time domain signal to obtain an azimuth pulse compressed signal, and the method comprises the following steps:
performing azimuth Fourier transform on the two-dimensional time domain signal to obtain a range-Doppler domain echo signal;
constructing an azimuth matching filter function convolution kernel, wherein the convolution kernel is a phase item related to a redefined virtual azimuth variable in a two-dimensional time domain signal;
generating an azimuth matched filtering convolution kernel according to the two-dimensional time domain signal;
carrying out azimuth Fourier transform and complex conjugate processing on the obtained convolution kernel to obtain an azimuth matched filtering function;
and performing azimuth matching filtering processing on the range-Doppler domain echo signal based on the obtained azimuth matching filtering function to obtain an azimuth pulse compressed signal.
The specific implementation can include:
step S5: for the obtained two-dimensional time domain signal
Figure BDA0003310461860000132
Carrying out azimuth Fourier transform and azimuth matched filtering to obtain an azimuth pulse compressed signal, and specifically comprising the following steps:
step S51: for the two-dimensional time domain signal obtained in step S43
Figure BDA0003310461860000133
Performing azimuth Fourier transform to obtain range-Doppler domain echo signal
Figure BDA0003310461860000134
The specific calculation is shown in formula (18):
Figure BDA0003310461860000135
in the formula, AFFT {. is an azimuthal Fourier transform,
Figure BDA0003310461860000136
is the two-dimensional time domain signal obtained by equation (17).
Step S52: constructing an azimuth matched filter function convolution kernel of
Figure BDA0003310461860000137
Convolution kernel as two-dimensional time-domain signal
Figure BDA0003310461860000138
Neutralization of
Figure BDA0003310461860000139
A related phase term;
step S53: generating an azimuthal matched filter convolution kernel from the two-dimensional time domain signal of equation (17)
Figure BDA00033104618600001310
The specific expression is shown as formula (19):
Figure BDA0003310461860000141
in the above formula, fcIs the carrier frequency and is,
Figure BDA0003310461860000142
the variables are virtually sampled for the azimuth redefined in step S41.
Step S54: performing azimuth Fourier transform and complex conjugate processing on the obtained convolution kernel to obtain an azimuth matched filter function
Figure BDA0003310461860000143
The specific calculation formula is as follows:
Figure BDA0003310461860000144
in the above formula, AFFT {. is an azimuthal Fourier transform, {. cndot. }*Is a complex conjugate operation.
Step S55: based on the obtained direction pulse compression function to distance Doppler signal
Figure BDA0003310461860000145
Performing azimuth matching filtering treatment, wherein the specific calculation process is shown as formula (21), and obtaining the signal after azimuth pulse compression
Figure BDA0003310461860000146
Figure BDA0003310461860000147
Step S6 may be implemented as: for the obtained range-Doppler signal
Figure BDA0003310461860000148
Performing azimuth inverse Fourier transform to obtain final two-dimensional time domain focusing signal
Figure BDA0003310461860000149
The specific calculation process is shown as the following formula:
Figure BDA00033104618600001410
as one aspect, an embodiment of the present disclosure provides an imaging apparatus for a transmitter moving bistatic arc array SAR, including:
the acquisition module is configured to acquire echo data of the transmitter moving bistatic arc array SAR;
a signal processing module configured to perform distance-to-fourier transform on the echo data based on an assumption that the echo data has been subjected to baseband demodulation processing, so as to obtain distance frequency domain azimuth time domain echo data; generating a distance walking correction function through the decomposed double-base instantaneous slant distance, and performing distance walking correction on distance frequency domain and azimuth time domain echo data by using the distance walking correction function; distance direction pulse compression is carried out on the distance frequency domain signals after distance walk correction processing; performing distance and azimuth decoupling processing and distance inverse Fourier transform on the distance-direction pulse compressed signal to obtain a decoupled two-dimensional time domain signal; carrying out azimuth Fourier transform and azimuth matched filtering on the two-dimensional time domain signal to obtain an azimuth pulse compressed signal; and performing azimuth inverse Fourier transform on the signal subjected to azimuth pulse compression to obtain a final two-dimensional time domain focusing signal.
As an embodiment, the signal processing module of the apparatus of the present disclosure may be further configured, in combination with the description of step S2, to:
generating a distance walking correction function through the decomposed double-base instantaneous slant distance, and performing distance walking correction on distance frequency domain and azimuth time domain echo data by using the distance walking correction function, wherein the distance walking correction function comprises the following steps:
obtaining a first instant slope distance from a radar transmitter to a target based on an assumed arbitrary target, a receiver equivalent sampling point and coordinates of the transmitter;
approximate processing is carried out on the first instantaneous slope distance by adopting Taylor series expansion, and the first instantaneous slope distance is decomposed into two parts which are related to the speed and unrelated to the speed;
generating a distance walking correction function according to the first instant slope distance subjected to the approximate processing;
and performing range walk correction processing on the range frequency domain azimuth time domain echo data by adopting a range walk correction function to obtain range walk corrected echo data.
As an embodiment, the signal processing module of the apparatus of the present disclosure may be further configured, in combination with the description of step S3, to:
the distance direction pulse compression is carried out on the distance frequency domain signal after the distance walk correction processing, and the method comprises the following steps:
constructing a pulse compression function in a matched filtering mode;
and performing range-wise pulse compression processing on the echo signal of the range frequency domain by using the obtained pulse compression function to obtain the echo signal after range-wise pulse compression.
As an embodiment, the signal processing module of the apparatus of the present disclosure may be further configured, in combination with the description of step S4, to:
the distance and direction decoupling processing and the distance inverse Fourier transform are carried out on the distance-direction pulse compressed signal to obtain a decoupled two-dimensional time domain signal, and the method comprises the following steps:
performing approximation processing on a second instantaneous slope distance from the equivalent sampling point to the target by using Taylor series expansion to obtain a second instantaneous slope distance subjected to approximation processing;
redefining a virtual azimuth sampling variable based on the obtained second instantaneous slope distance subjected to approximate processing by adopting a Keystone transformation method;
performing Keystone transformation according to the redefined virtual azimuth variable to obtain echo signals after distance and azimuth decoupling;
and performing range inverse Fourier transform on the echo signals subjected to range and azimuth decoupling to obtain two-dimensional time domain signals subjected to range and azimuth decoupling.
As an embodiment, the signal processing module of the apparatus of the present disclosure may be further configured, in combination with the description of step S5, to:
carrying out azimuth Fourier transform and azimuth matched filtering on the two-dimensional time domain signal to obtain an azimuth pulse compressed signal, and the method comprises the following steps:
performing azimuth Fourier transform on the two-dimensional time domain signal to obtain a range-Doppler domain echo signal;
constructing an azimuth matching filter function convolution kernel, wherein the convolution kernel is a phase item related to a redefined virtual azimuth variable in a two-dimensional time domain signal;
generating an azimuth matched filtering convolution kernel according to the two-dimensional time domain signal;
carrying out azimuth Fourier transform and complex conjugate processing on the obtained convolution kernel to obtain an azimuth matched filtering function;
and performing azimuth matching filtering processing on the range-Doppler domain echo signal based on the obtained azimuth matching filtering function to obtain an azimuth pulse compressed signal.
Specifically, one of the inventive concepts of the present disclosure is directed to obtaining echo data of a transmitter moving bistatic arc array SAR, and based on an assumption that the echo data has been subjected to baseband demodulation processing, performing range-to-fourier transform on the echo data to obtain range frequency domain azimuth time domain echo data; generating a distance walking correction function through the decomposed double-base instantaneous slant distance, and performing distance walking correction on distance frequency domain and azimuth time domain echo data by using the distance walking correction function; distance direction pulse compression is carried out on the distance frequency domain signals after distance walk correction processing; performing distance and azimuth decoupling processing and distance inverse Fourier transform on the distance-direction pulse compressed signal to obtain a decoupled two-dimensional time domain signal; carrying out azimuth Fourier transform and azimuth matched filtering on the two-dimensional time domain signal to obtain an azimuth pulse compressed signal; and performing azimuth inverse Fourier transform on the signal subjected to azimuth pulse compression to obtain a final two-dimensional time domain focusing signal. The method aims at achieving imaging processing of a double-base arc array SAR system aiming at transmitter motion through high-order approximation of slant distance, distance walking compensation and Keystone transformation, and can obtain all-dimensional and high-resolution imaging. The embodiments of the present disclosure first perform high-order approximation processing on the bistatic slant range through taylor series expansion, and decompose the slant range into two parts, one part being unrelated to the transmitter speed and the other part being related to the transmitter speed. And constructing a distance walking compensation function according to the solved slant range formula, correcting the distance walking caused by the movement of the transmitter in a distance frequency domain, and reducing the two-dimensional coupling of echo signals. On the basis, Keystone transformation is used for eliminating residual coupling between the distance and the azimuth angle. And finally, obtaining an image with good focusing through azimuth matching filtering. In various application scenes, the all-round and high-resolution observation imaging of the bistatic arc array SAR can be realized in the embodiments of the disclosure when the transmitter moves, not only the imaging characteristics of good concealment, high safety, rich target information and the like of the bistatic arc array SAR are realized, but also the imaging processing can be carried out on large scenes around the platform when the transmitter moves, and the utilization rate of the system is improved.
The present disclosure also provides a computer-readable storage medium having stored thereon computer-executable instructions that, when executed by a processor, substantially implement a method of imaging a transmitter-moving bistatic arc array SAR according to the above, comprising:
acquiring echo data of a transmitter moving bistatic arc array SAR, and performing range-to-Fourier transform on the echo data on the assumption that the echo data is subjected to baseband demodulation processing to obtain range frequency domain azimuth time domain echo data;
generating a distance walking correction function through the decomposed double-base instantaneous slant distance, and performing distance walking correction on distance frequency domain and azimuth time domain echo data by using the distance walking correction function;
distance direction pulse compression is carried out on the distance frequency domain signals after distance walk correction processing;
performing distance and azimuth decoupling processing and distance inverse Fourier transform on the distance-direction pulse compressed signal to obtain a decoupled two-dimensional time domain signal;
carrying out azimuth Fourier transform and azimuth matched filtering on the two-dimensional time domain signal to obtain an azimuth pulse compressed signal;
and performing azimuth inverse Fourier transform on the signal subjected to azimuth pulse compression to obtain a final two-dimensional time domain focusing signal.
In some embodiments, a processor executing computer-executable instructions may be a processing device including more than one general-purpose processing device, such as a microprocessor, Central Processing Unit (CPU), Graphics Processing Unit (GPU), or the like. More specifically, the processor may be a Complex Instruction Set Computing (CISC) microprocessor, Reduced Instruction Set Computing (RISC) microprocessor, Very Long Instruction Word (VLIW) microprocessor, processor running other instruction sets, or processors running a combination of instruction sets. The processor may also be one or more special-purpose processing devices such as an Application Specific Integrated Circuit (ASIC), a Field Programmable Gate Array (FPGA), a Digital Signal Processor (DSP), a system on a chip (SoC), or the like.
In some embodiments, the computer-readable storage medium may be a memory, such as a read-only memory (ROM), a random-access memory (RAM), a phase-change random-access memory (PRAM), a static random-access memory (SRAM), a dynamic random-access memory (DRAM), an electrically erasable programmable read-only memory (EEPROM), other types of random-access memory (RAM), a flash disk or other form of flash memory, a cache, a register, a static memory, a compact disc read-only memory (CD-ROM), a Digital Versatile Disc (DVD) or other optical storage, a tape cartridge or other magnetic storage device, or any other potentially non-transitory medium that may be used to store information or instructions that may be accessed by a computer device, and so forth.
In some embodiments, the computer-executable instructions may be implemented as a plurality of program modules that collectively implement the signal processing method for medical images according to any one of the present disclosure.
The present disclosure describes various operations or functions that may be implemented as or defined as software code or instructions. The display unit may be implemented as software code or modules of instructions stored on a memory, which when executed by a processor may implement the respective steps and methods.
Such content may be source code or differential code ("delta" or "patch" code) that executes directly ("object" or "executable" form). A software implementation of the embodiments described herein may be provided through an article of manufacture having code or instructions stored thereon, or through a method of operating a communication interface to transmit data through the communication interface. A machine or computer-readable storage medium may cause a machine to perform the functions or operations described, and includes any mechanism for storing information in a form accessible by a machine (e.g., a computing display device, an electronic system, etc.), such as recordable/non-recordable media (e.g., Read Only Memory (ROM), Random Access Memory (RAM), magnetic disk storage media, optical storage media, flash memory display devices, etc.). The communication interface includes any mechanism for interfacing with any of a hardwired, wireless, optical, etc. medium to communicate with other display devices, such as a memory bus interface, a processor bus interface, an internet connection, a disk controller, etc. The communication interface may be configured by providing configuration parameters and/or transmitting signals to prepare the communication interface to provide data signals describing the software content. The communication interface may be accessed by sending one or more commands or signals to the communication interface.
The computer-executable instructions of embodiments of the present disclosure may be organized into one or more computer-executable components or modules. Aspects of the disclosure may be implemented with any number and combination of such components or modules. For example, aspects of the disclosure are not limited to the specific computer-executable instructions or the specific components or modules illustrated in the figures and described herein. Other embodiments may include different computer-executable instructions or components having more or less functionality than illustrated and described herein.
The above description is intended to be illustrative and not restrictive. For example, the above-described examples (or one or more versions thereof) may be used in combination with each other. For example, other embodiments may be used by those of ordinary skill in the art upon reading the above description. In addition, in the foregoing detailed description, various features may be grouped together to streamline the disclosure. This should not be interpreted as an intention that a disclosed feature not claimed is essential to any claim. Rather, the subject matter of the present disclosure may lie in less than all features of a particular disclosed embodiment. Thus, the following claims are hereby incorporated into the detailed description as examples or embodiments, with each claim standing on its own as a separate embodiment, and it is contemplated that these embodiments may be combined with each other in various combinations or permutations. The scope of the disclosure should be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled.
The above embodiments are merely exemplary embodiments of the present disclosure, which is not intended to limit the present disclosure, and the scope of the present disclosure is defined by the claims. Various modifications and equivalents of the disclosure may occur to those skilled in the art within the spirit and scope of the disclosure, and such modifications and equivalents are considered to be within the scope of the disclosure.

Claims (10)

1. The imaging method of the transmitter motion bistatic arc array SAR comprises the following steps:
acquiring echo data of a transmitter moving bistatic arc array SAR, and performing range-to-Fourier transform on the echo data on the assumption that the echo data is subjected to baseband demodulation processing to obtain range frequency domain azimuth time domain echo data;
generating a distance walking correction function through the decomposed double-base instantaneous slant distance, and performing distance walking correction on distance frequency domain and azimuth time domain echo data by using the distance walking correction function;
distance direction pulse compression is carried out on the distance frequency domain signals after distance walk correction processing;
performing distance and azimuth decoupling processing and distance inverse Fourier transform on the distance-direction pulse compressed signal to obtain a decoupled two-dimensional time domain signal;
carrying out azimuth Fourier transform and azimuth matched filtering on the two-dimensional time domain signal to obtain an azimuth pulse compressed signal;
and performing azimuth inverse Fourier transform on the signal subjected to azimuth pulse compression to obtain a final two-dimensional time domain focusing signal.
2. The method of claim 1, wherein generating a range walk correction function from the decomposed two-base instantaneous pitches, and performing range walk correction on range frequency domain azimuth time domain echo data using the range walk correction function comprises:
obtaining a first instant slope distance from a radar transmitter to a target based on an assumed arbitrary target, a receiver equivalent sampling point and coordinates of the transmitter;
approximate processing is carried out on the first instantaneous slope distance by adopting Taylor series expansion, and the first instantaneous slope distance is decomposed into two parts which are related to the speed and unrelated to the speed;
generating a distance walking correction function according to the first instant slope distance subjected to the approximate processing;
and performing range walk correction processing on the range frequency domain azimuth time domain echo data by adopting a range walk correction function to obtain range walk corrected echo data.
3. The method of claim 2, wherein the distance-wise pulse compressing the distance frequency domain signal after the distance walk correction process comprises:
constructing a pulse compression function in a matched filtering mode;
and performing range-wise pulse compression processing on the echo signal of the range frequency domain by using the obtained pulse compression function to obtain the echo signal after range-wise pulse compression.
4. The method of claim 3, wherein performing range-azimuth decoupling processing and range-inverse Fourier transform on the range-direction pulse compressed signal to obtain a decoupled two-dimensional time-domain signal comprises:
performing approximation processing on a second instantaneous slope distance from the equivalent sampling point to the target by using Taylor series expansion to obtain a second instantaneous slope distance subjected to approximation processing;
redefining a virtual azimuth sampling variable based on the obtained second instantaneous slope distance subjected to approximate processing by adopting a Keystone transformation method;
performing Keystone transformation according to the redefined virtual azimuth variable to obtain echo signals after distance and azimuth decoupling;
and performing range inverse Fourier transform on the echo signals subjected to range and azimuth decoupling to obtain two-dimensional time domain signals subjected to range and azimuth decoupling.
5. The method of claim 4, wherein performing an azimuth Fourier transform and an azimuth matched filter on the two-dimensional time-domain signal to obtain an azimuth pulse-compressed signal comprises:
performing azimuth Fourier transform on the two-dimensional time domain signal to obtain a range-Doppler domain echo signal;
constructing an azimuth matching filter function convolution kernel, wherein the convolution kernel is a phase item related to a redefined virtual azimuth variable in a two-dimensional time domain signal;
generating an azimuth matched filtering convolution kernel according to the two-dimensional time domain signal;
carrying out azimuth Fourier transform and complex conjugate processing on the obtained convolution kernel to obtain an azimuth matched filtering function;
and performing azimuth matching filtering processing on the range-Doppler domain echo signal based on the obtained azimuth matching filtering function to obtain an azimuth pulse compressed signal.
6. An imaging device for a transmitter moving bistatic arc array SAR, comprising:
the acquisition module is configured to acquire echo data of the transmitter moving bistatic arc array SAR;
a signal processing module configured to perform distance-to-fourier transform on the echo data based on an assumption that the echo data has been subjected to baseband demodulation processing, so as to obtain distance frequency domain azimuth time domain echo data; generating a distance walking correction function through the decomposed double-base instantaneous slant distance, and performing distance walking correction on distance frequency domain and azimuth time domain echo data by using the distance walking correction function; distance direction pulse compression is carried out on the distance frequency domain signals after distance walk correction processing; performing distance and azimuth decoupling processing and distance inverse Fourier transform on the distance-direction pulse compressed signal to obtain a decoupled two-dimensional time domain signal; carrying out azimuth Fourier transform and azimuth matched filtering on the two-dimensional time domain signal to obtain an azimuth pulse compressed signal; and performing azimuth inverse Fourier transform on the signal subjected to azimuth pulse compression to obtain a final two-dimensional time domain focusing signal.
7. The apparatus of claim 6, wherein the signal processing module is further configured to:
generating a distance walking correction function through the decomposed double-base instantaneous slant distance, and performing distance walking correction on distance frequency domain and azimuth time domain echo data by using the distance walking correction function, wherein the distance walking correction function comprises the following steps:
obtaining a first instant slope distance from a radar transmitter to a target based on an assumed arbitrary target, a receiver equivalent sampling point and coordinates of the transmitter;
approximate processing is carried out on the first instantaneous slope distance by adopting Taylor series expansion, and the first instantaneous slope distance is decomposed into two parts which are related to the speed and unrelated to the speed;
generating a distance walking correction function according to the first instant slope distance subjected to the approximate processing;
and performing range walk correction processing on the range frequency domain azimuth time domain echo data by adopting a range walk correction function to obtain range walk corrected echo data.
8. The apparatus of claim 7, wherein the signal processing module is further configured to:
the distance direction pulse compression is carried out on the distance frequency domain signal after the distance walk correction processing, and the method comprises the following steps:
constructing a pulse compression function in a matched filtering mode;
and performing range-wise pulse compression processing on the echo signal of the range frequency domain by using the obtained pulse compression function to obtain the echo signal after range-wise pulse compression.
9. The apparatus of claim 8, wherein the signal processing module is further configured to:
the distance and direction decoupling processing and the distance inverse Fourier transform are carried out on the distance-direction pulse compressed signal to obtain a decoupled two-dimensional time domain signal, and the method comprises the following steps:
performing approximation processing on a second instantaneous slope distance from the equivalent sampling point to the target by using Taylor series expansion to obtain a second instantaneous slope distance subjected to approximation processing;
redefining a virtual azimuth sampling variable based on the obtained second instantaneous slope distance subjected to approximate processing by adopting a Keystone transformation method;
performing Keystone transformation according to the redefined virtual azimuth variable to obtain echo signals after distance and azimuth decoupling;
and performing range inverse Fourier transform on the echo signals subjected to range and azimuth decoupling to obtain two-dimensional time domain signals subjected to range and azimuth decoupling.
10. A computer-readable storage medium having stored thereon computer-executable instructions that, when executed by a processor, implement:
method for imaging a transmitter moving bistatic arc array SAR according to claims 1 to 5.
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王彦平: "新体制SAR三维成像技术研究进展", pages 633 - 654 *
谭维贤: "基于单特显点调频连续波阵列SAR系统幅相误差校正方法研究", pages 2672 - 2677 *
黄平平: "基于隐函数导数法的双基弧形阵列SAR二维频谱及成像算法" *

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CN117518111A (en) * 2023-09-15 2024-02-06 鹰飒科技(江苏)有限公司 Echo signal processing method and device, electronic equipment and storage medium
CN117406223A (en) * 2023-12-12 2024-01-16 中山大学 Close-range double-station foundation synthetic aperture radar imaging method and system
CN117406223B (en) * 2023-12-12 2024-03-12 中山大学 Close-range double-station foundation synthetic aperture radar imaging method and system

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