CN115356728A - Vehicle-mounted synthetic aperture radar rapid stripe imaging method and system - Google Patents
Vehicle-mounted synthetic aperture radar rapid stripe imaging method and system Download PDFInfo
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Abstract
The invention discloses a method and a system for vehicle-mounted synthetic aperture radar fast strip imaging, which comprise the following steps: obtaining echo data of a radar system, and performing range dimension pulse compression on the echo data to obtain a high-resolution range profile; estimating the speed, and calculating the Doppler center frequency to obtain the Doppler frequency of the target on the beam center line; performing azimuth dimension FFT on each frame of the high-resolution range profile, and sequentially extracting Doppler center frequency data in each frame to perform panoramic estimation to obtain a strip graph of a vehicle-mounted SAR imaging scene; uniformly correcting the coordinates of the strip chart to obtain a strip chart with uniform size; and carrying out deformation correction on the strip chart with uniform size to obtain a strip synthetic aperture radar image containing all vehicle-mounted data information. The invention greatly shortens the imaging time, obtains the strip chart containing all data information of the vehicle-mounted SAR imaging scene, and makes up the defect that the existing real-time SAR imaging algorithm cannot quickly observe all data information of the vehicle-mounted SAR.
Description
Technical Field
The invention relates to the technical field of signal processing, in particular to a method and a system for vehicle-mounted synthetic aperture radar fast strip imaging, an intelligent terminal and a storage medium.
Background
The Back Projection Algorithm (Back Projection Algorithm) is a point-by-point imaging radar Algorithm based on time domain processing, and a high-resolution Synthetic Aperture Radar (SAR) image is obtained by performing coherent accumulation on corresponding signals by calculating two-way delay, but the calculation data volume is large, and redundancy phenomenon exists, so that the calculation efficiency is low. In order to shorten the imaging time as much as possible, a transient SAR imaging algorithm which improves the operation efficiency by reducing the SAR image quality is obtained. The instantaneous SAR imaging algorithm (2D-FFT) adopts sub-aperture imaging, and is characterized in that the sub-aperture corresponding time is short enough. According to the method, the instantaneous SAR image of an imaging scene is realized by performing FFT on original echo data twice and then performing coordinate conversion to convert range Doppler data into range azimuth data. The two-time FFT is to perform FFT on the difference frequency signal to obtain distance dimension pulse compression data, and perform FFT on the azimuth dimension to obtain distance Doppler data.
The instantaneous SAR imaging algorithm has the advantages that the requirement of vehicle-mounted real-time performance is met, but in the vehicle-mounted synthetic aperture radar imaging technology in the prior art, only one sector is arranged in each imaging area, only target information in a single sector can be acquired each time, and long strip information of the whole vehicle-mounted SAR imaging scene cannot be acquired. The radar works in a front side view mode, cannot sense the road environment in advance, and severely limits the actual automatic driving application.
Thus, there is a need for improvements and enhancements in the art.
Disclosure of Invention
The technical problem to be solved by the present invention is to provide a method, a system, an intelligent terminal and a storage medium for fast strip imaging of a vehicle-mounted synthetic aperture radar, aiming at solving the technical problem that in the existing real-time SAR imaging technology, target information of each frame of SAR map is less, and long strip information of a vehicle-mounted SAR imaging scene cannot be obtained quickly.
In order to solve the above technical problem, a first aspect of the present invention provides a method for fast swath imaging for a vehicle-mounted synthetic aperture radar, where the method includes:
a method for on-board synthetic aperture radar fast swath imaging, wherein the method comprises:
obtaining echo data of a radar system, and performing range dimension pulse compression on the echo data to obtain a high-resolution range profile;
estimating the speed based on the obtained high-resolution range profile, and calculating the Doppler center frequency to obtain the Doppler frequency of the target on the beam center line;
performing azimuth dimension FFT on each frame of the high-resolution range profile, and sequentially extracting Doppler center frequency data in each frame to perform panoramic estimation to obtain a strip graph of a vehicle-mounted SAR imaging scene;
uniformly correcting the coordinates of the strip chart to obtain a strip chart with uniform size;
and carrying out deformation correction on the strip chart with uniform size to obtain a strip synthetic aperture radar image containing all vehicle-mounted data information.
The quick strip imaging method for the vehicle-mounted synthetic aperture radar is characterized in that the step of obtaining the echo data of a radar system, performing range dimension pulse compression on the echo data and obtaining a high-resolution range image comprises the following steps:
starting a radar system to acquire images, and acquiring echo data M multiplied by N of the radar system, wherein M corresponds to a distance dimensional data volume, and N corresponds to a direction dimensional data volume;
and performing distance dimension pulse compression on the echo data to obtain a high-resolution range image, wherein the distance dimension pulse compression method comprises matched filtering and de-line frequency modulation.
The rapid strip imaging method for the vehicle-mounted synthetic aperture radar comprises the following steps of estimating the speed based on the obtained high-resolution range profile, calculating the Doppler center frequency, and obtaining the Doppler frequency of a target on a beam center line:
dividing the obtained high-resolution range profile in a sub-aperture imaging mode to obtain an (N-N)/s frame synthetic aperture radar image;
measuring a current speed value through a speed sensor or a speed estimation algorithm, and taking a speed average value at every n points, namely n echoes correspond to one speed value;
calculating the Doppler frequency of the target of the beam center line according to the average velocity value v and the squint angle theta; and estimating the number of frequency deviation points on a Doppler frequency coordinate axis to obtain the Doppler center frequency under squint.
The fast strip imaging method of the vehicle-mounted synthetic aperture radar is characterized in that the step of performing azimuth dimension FFT on each frame of the high-resolution range profile, sequentially extracting Doppler center frequency data in each frame for panoramic estimation, and obtaining a strip graph of a vehicle-mounted SAR imaging scene comprises the following steps:
based on the obtained (N-N)/s frame SAR image and Doppler center frequency, performing azimuth dimension FFT on the first frame image, extracting data of the ID column as the first column of the strip chart, performing azimuth dimension FFT on the second frame image, extracting data of the ID column as the second column of the strip chart, and so on to obtain a frame of image containing all data information of the vehicle-mounted SAR imaging scene;
and when the vehicle-mounted SAR imaging scene is viewed from the front side, sequentially extracting data of the zero Doppler unit of each frame image to perform panoramic reconstruction, and obtaining a strip chart of the vehicle-mounted SAR imaging scene.
The fast banding imaging method of the vehicle-mounted synthetic aperture radar, wherein the step of uniformly correcting the coordinates of the banding graph to obtain the banding graph with uniform size comprises the following steps:
defining the time interval for processing each frame of image as t = s/PRF, and setting the corresponding speed of each frame of image as v f The distance value between two adjacent columns of data in the corrected histogram is Deltax, and the pulse repetition frequency of the corrected histogram is RPF eq Wherein PRF eq ＝PRF/s；
The distance value of two adjacent columns of data of the strip chart is tv f And carrying out horizontal coordinate conversion to obtain a coordinate-corrected strip chart, wherein the Doppler frequency interval of the strip chart is f aeq ＝[-PRF eq /2,PRF eq /2]。
The fast strip imaging method for the vehicle-mounted synthetic aperture radar is characterized in that the step of performing deformation correction on the strip image with uniform size to obtain a strip synthetic aperture radar image containing all vehicle-mounted data information specifically comprises the following steps:
performing corresponding zero filling operation on the left side and the right side of the stripmap with uniform size according to the squint angle of the target and the radar;
performing squint correction on the strip chart after zero padding in a mode of time domain translation or frequency domain compensation displacement function, and estimating the optimal number of points of each row of cyclic displacement according to the distance information of horizontal and vertical coordinates and the squint angle; calculating the shift time delay, and performing displacement compensation on the data of each distance to the moment; and obtaining a strabismus corrected strip SAR image.
An on-board synthetic aperture radar fast banding imaging system, wherein said system comprises:
the acquisition and compression processing module is used for acquiring echo data of the radar system and performing range dimension pulse compression on the echo data to obtain a high-resolution range profile;
the velocity estimation module is used for estimating the velocity based on the obtained high-resolution range profile and calculating the Doppler center frequency to obtain the Doppler frequency of the target on the beam center line;
the azimuth dimension processing and panoramic estimation module is used for performing azimuth dimension FFT on each frame of image of the high-resolution range profile, sequentially extracting Doppler center frequency data in each frame for panoramic estimation, and obtaining a strip chart of a vehicle-mounted SAR imaging scene;
the uniform correction module is used for uniformly correcting the coordinates of the strip chart to obtain the strip chart with uniform size;
and the deformation correction module is used for carrying out deformation correction on the strip chart with uniform size to obtain a strip synthetic aperture radar image containing all vehicle-mounted data information.
An intelligent terminal comprising a memory, and one or more programs, wherein the one or more programs are stored in the memory and configured to be executed by the one or more processors comprises instructions for performing any of the methods described herein.
A non-transitory computer readable storage medium, wherein instructions in the storage medium, when executed by a processor of an electronic device, enable the electronic device to perform any of the methods.
Has the advantages that: compared with the prior art, the invention provides a rapid strip imaging method for a vehicle-mounted synthetic aperture radar, which is characterized in that echo data of a radar system is obtained, and distance dimension pulse compression is carried out on the echo data to obtain a high-resolution range profile; estimating the speed based on the obtained high-resolution range profile, and calculating the Doppler center frequency to obtain the Doppler frequency of the target on the beam center line; performing azimuth dimension FFT on each frame of the high-resolution range profile, and sequentially extracting Doppler center frequency data in each frame to perform panoramic estimation to obtain a strip graph of a vehicle-mounted SAR imaging scene; uniformly correcting the coordinates of the strip chart to obtain a strip chart with uniform size; and carrying out deformation correction on the strip chart with uniform size to obtain a strip synthetic aperture radar image containing all vehicle-mounted data information. According to the method for performing panoramic reconstruction by extracting the Doppler frequency of the target of the beam center line, the optimal number of the row cyclic shift can be calculated according to the estimated distance dimension of the squint angle under a larger squint angle, the complexity of the algorithm structure is reduced, the imaging time is greatly shortened, the strip chart containing all data information of the vehicle-mounted SAR imaging scene is obtained, and the defect that the existing real-time SAR imaging algorithm cannot rapidly observe all data information of the vehicle-mounted SAR is overcome.
Drawings
Fig. 1 is a flowchart of a specific implementation of a method for fast swath imaging for a vehicle-mounted synthetic aperture radar according to an embodiment of the present invention.
Fig. 2 is a schematic flowchart of a specific implementation of a method for fast swath imaging for a vehicle-mounted synthetic aperture radar according to an embodiment of the present invention.
Fig. 3 is a schematic diagram of ultrafast SAR imaging stripes after coordinate correction of a rapid stripe imaging method for a vehicle-mounted synthetic aperture radar according to an embodiment of the present invention.
Fig. 4 is a schematic diagram of ultrafast SAR imaging strips without zero padding in an embodiment of the method for imaging fast strips of a vehicle-mounted synthetic aperture radar of the present invention.
Fig. 5 is a schematic diagram of ultrafast SAR imaging strips after zero padding of the fast strip imaging method for the vehicle-mounted synthetic aperture radar according to the embodiment of the present invention.
Fig. 6 is a schematic diagram of ultrafast SAR imaging strips after frequency shift correction of a vehicle-mounted synthetic aperture radar fast strip imaging method according to an embodiment of the present invention.
Fig. 7 is a schematic diagram of a three-dimensional model of a vehicle-mounted SAR imaging scene of the vehicle-mounted synthetic aperture radar fast banding imaging method according to the embodiment of the present invention.
Fig. 8 is a schematic diagram of ultrafast SAR imaging strips in a front side view mode of a rapid strip imaging method for a vehicle-mounted synthetic aperture radar according to an embodiment of the present invention.
Fig. 9 is a schematic diagram of a three-dimensional model of a vehicle-mounted SAR imaging scene in a front side view mode of a vehicle-mounted synthetic aperture radar fast banding imaging method according to a specific application embodiment of the present invention.
Fig. 10 is a schematic block diagram of a vehicle-mounted synthetic aperture radar fast banding imaging system according to an embodiment of the present invention.
Fig. 11 is a schematic block diagram of an internal structure of an intelligent terminal according to an embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and effects of the present invention clearer and clearer, the present invention is further described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
Synthetic Aperture Radar (SAR), an active earth observation system, can be installed on flight platforms such as airplanes, satellites, spacecraft, etc., and performs earth observation all day long and all day long, and has a certain ground surface penetration capability.
The instantaneous SAR imaging algorithm has the advantages that the requirement of vehicle-mounted real-time performance is met, but in the prior art, the vehicle-mounted synthetic aperture radar imaging technology can only see one fan-shaped distance information in each imaging, and when the radar works in a squint mode, the imaging time is long, and long strip information of a vehicle-mounted SAR imaging scene cannot be obtained; the radar in the prior art can not sense the road environment in advance when working in a front side view mode, can only reflect local information, and has the problems of low imaging efficiency, complex compensation, no real-time capability and the like of the existing strip imaging algorithm, thereby seriously limiting the actual automatic driving application.
In order to solve the problems in the prior art, the embodiment provides a method for fast imaging a stripe of a vehicle-mounted synthetic aperture radar, and when the radar works at a large squint angle, a Synthetic Aperture Radar (SAR) image which can be used for observing all data information of a vehicle-mounted SAR imaging scene is obtained fast.
Exemplary method
The method of the embodiment can be applied to an intelligent terminal, and in specific implementation, as shown in fig. 1, the method for imaging the fast strip of the vehicle-mounted synthetic aperture radar provided by the embodiment of the invention specifically comprises the following steps:
step S100: obtaining echo data of a radar system, and performing range dimension pulse compression on the echo data to obtain a high-resolution range profile;
according to the embodiment of the invention, a radar detection test signal can be sent out through a radar system, then the echo data of the radar system is received and obtained, and the distance dimension pulse compression is carried out on the echo data to obtain a High Resolution Range Profile (HRRP) under the assumption that the echo data volume of the radar system is MxN (M corresponds to a distance dimension data volume and N corresponds to an azimuth dimension data volume). Methods of distance dimensional pulse compression include matched filtering and de-line tone (Dechirp), which is suitable for use with larger bandwidth chirp signals. The greatest difference between matched filtering and the de-line tone is that the reference signal at mixing is different, and the reference signal used for mixing in matched filtering is cos (2 π f) 0 t)、sin(2πf 0 t), the reference signal used for mixing in Decirp is the transmitted signal itself, where f 0 Is the carrier frequency.
The High Resolution Range Profile (HRRP) is a vector sum of a target scattering point complex sub-echo obtained by using a broadband radar signal and projected on a radar ray, provides distribution information of the target scattering point along a distance direction, and is characterized in that a high-resolution range profile is obtained by sending a high-frequency signal with a certain wavelength and reflecting imaging time and position, has important structural characteristics of a target, and is very valuable for target identification and classification.
Step S200: estimating the speed based on the obtained high-resolution range profile, and calculating the Doppler center frequency to obtain the Doppler frequency of the target on the beam center line;
in the embodiment of the invention, the speed value in the speed estimation can be estimated through echo data, and can also be measured through inertial navigation, GPS/Beidou or other vehicle body sensors.
In the embodiment of the present invention, the step S200 specifically includes:
step S201, dividing the obtained high-resolution range profile according to sub-apertures to obtain (N-N)/S frame synthetic aperture radar images;
in the embodiment of the invention, echo data of a radar system are obtained by receiving, N is assumed to be the azimuth dimension data quantity of the echo data, N is the number of single-frame echoes, step is s, and the number of rows and columns of the all-zero space matrix are respectively M/2 and (N-N)/s. And (2) dividing the obtained high-resolution range profile (HRRP) according to the sub-apertures to obtain (N-N)/s-frame SAR (synthetic aperture radar) images by adopting a sub-aperture imaging mode based on an echo data model, wherein the abscissa represents the number of pulse emission, the ordinate represents the number of distance dimension sampling points, each sub-aperture image comprises N times of echo data, the stepping length is s times of echoes, the first frame processes 1 st to N times of echoes, the second frame processes 1+s to N + s times of echoes …, and the like until the Nth time of echoes are processed.
Step S202, a current speed value is measured through a vehicle speed sensor or a speed estimation algorithm, and a speed average value is taken at every n points, namely n echoes correspond to one speed value.
In the embodiment of the invention, a relatively accurate current speed value is measured by a vehicle speed sensor or a speed estimation algorithm and the like, and a speed average value is taken at every n points, namely n echoes correspond to one speed value.
Step S203, calculating the Doppler frequency of the target of the beam center line according to the average velocity value v and the squint angle theta; and estimating the number of frequency deviation points on a Doppler frequency coordinate axis to obtain a Doppler center frequency ID under squint.
In the embodiment of the invention, because SAR (synthetic aperture radar) pulse repetition frequency PRF can limit the maximum Doppler frequency which can be received in the azimuth, only [ -PRF/2, PRF/2 can be observed]The interval, and the Doppler center frequency in the oblique view is shifted from zero to a non-zero Doppler unit. The calculation formula of the Doppler center frequency is f a = 2v sin θ/λ, wherein f a Indicates the calculated doppler frequency, v indicates the vehicle speed, θ indicates the beam center squint angle, and λ indicates the wavelength of the radar wave.
For the pulse radar, when a target moves close to the radar in a radial direction, the Doppler frequency is positive, and the target speed is positive; when the target moves radially away from the radar, the Doppler frequency is negative, and the target speed is negative. In the invention, the Doppler frequency of the target of the beam center line is calculated according to the average velocity value v and the squint angle theta; estimating the number of frequency deviation points on a Doppler frequency coordinate axis to obtain a Doppler central frequency ID under squint, wherein the Doppler frequency of a target on a beam central line in the embodiment of the invention is the Doppler central frequency; . When the squint angle is zero, the radar works in a front side view mode, the Doppler center frequency is zero frequency, namely the ID is zero.
Step S300: and performing azimuth dimension FFT on each frame of the high-resolution range profile, and sequentially extracting Doppler center frequency data in each frame to perform panoramic estimation to obtain a strip chart of the vehicle-mounted SAR imaging scene. The vehicle-mounted SAR imaging scene is mainly used for sensing surrounding environment information in the driving process of a vehicle through a radar sensor and the like mounted on the vehicle, and the surrounding environment information comprises surrounding vehicles, pedestrians, trees, street lamps, traffic warning cones and the like.
In the embodiment of the invention, on the basis of the obtained (N-N)/s frame SAR image and Doppler central frequency, azimuth dimension FFT is carried out on each frame of high-resolution range profile, the Doppler central frequency is estimated according to the obtained minimum difference value of the Doppler frequency and a Doppler frequency axis for extraction, data of the Doppler central frequency in each frame are sequentially extracted for panoramic estimation, and a strip chart of a vehicle-mounted SAR imaging scene is obtained. The actual treatment process is as follows: and performing azimuth dimension FFT on the first frame image, extracting data of the ID column as the first column of the strip chart, performing azimuth dimension FFT on the second frame image, extracting data of the ID column as the second column … of the strip chart, and the like to obtain a frame of image containing all data information of the vehicle-mounted SAR imaging scene. When the radar works under a front side view, data of a zero Doppler unit of each frame of image are sequentially extracted for panoramic reconstruction.
Step S400: and uniformly correcting the coordinates of the strip chart to obtain the strip chart with uniform size.
In this step, the coordinates of the histogram are uniformly corrected, and the obtaining of the histogram with uniform size specifically includes: namely, the uneven abscissa of the histogram is corrected to obtain a histogram of uniform size. The time interval between two adjacent columns of data on the horizontal axis is fixed, that is, the time interval for processing each frame of image is t = s/PRF, and it is assumed that each frame of image corresponds to velocity v f The distance value between two adjacent columns of data in the corrected histogram is Deltax, and the pulse repetition frequency of the corrected histogram is RPF eq Wherein PRF eq = PRF/s. The distance value of two adjacent columns of data of the strip chart is tv f Estimating the distance abscissa of uniform size according to the minimum interval, and performing abscissa conversion to obtain a histogram after coordinate correction, wherein the Doppler frequency interval of the histogram is f aeq ＝[-PRF eq /2,PRF eq /2]。
Step S500: and carrying out deformation correction on the strip chart with uniform size to obtain a strip Synthetic Aperture Radar (SAR) image containing all vehicle-mounted data information.
Wherein, the step S500 specifically includes:
and S501, performing corresponding zero filling operation on the left side and the right side of the strip chart with the uniform size according to the squint angle of the target and the radar. And performing ordinate conversion on the strip chart with uniform size, if distance dimension FFT is performed by adopting matched filtering, converting a fast time axis into a distance direction distance axis, and if distance dimension FFT is performed by adopting a line-relief tone, converting the distance direction distance axis into the distance direction distance axis. Suppose a horizontal axisThe corrected distance coordinate is x, the distance coordinate calculated by the vertical axis is y, and the slant distance between the target and the radar is calculated according to the distance information of the horizontal and vertical coordinates
Adding optimal point number of zero padding of squint angle estimation, namely maximum oblique moment r of target and radar max . When the squint angle is zero, zero filling processing is not needed because the Doppler center frequency does not deviate, namely, the zero filling number is zero, wherein the purpose of zero filling is to avoid folding of the target in the imaging scene.
Step S502, correcting squint of the strip chart after zero padding in a mode of time domain translation or frequency domain compensation displacement function, and estimating the optimal number of points of each row of circular displacement according to the distance information of horizontal and vertical coordinates and the squint angle; calculating the shift time delay, and performing displacement compensation on the data of each distance to the moment; obtaining a strabismus corrected strip SAR image;
according to the distance information of the horizontal and vertical coordinates and the squint angle, the optimal point number of each row of cyclic shift is estimated to be x, namely x = kr sin theta, and k is the optimal shift coefficient. Calculating the shift time delay t s ＝x/PRF eq Performing displacement compensation on data of each distance to time, wherein the phase compensation amount is exp (j 2 pi f) aeq t s ). Under a larger squint angle, a scene target in the obtained strip chart inclines after being imaged, the squint correction aims to correct the squint, when the squint angle is zero, the radar works in a front side view mode, the direction of a radar antenna is vertical to the moving direction of the moving platform, the scene information of the obtained strip chart is not inclined, the squint correction is not needed, and therefore the number of points of row-column cyclic shift of each row is zero.
Therefore, the method for performing panoramic reconstruction by extracting the Doppler frequency of the target of the beam center line can perform the optimal number of points for column cyclic shift according to the estimated distance dimension of the squint angle under a larger squint angle, reduces the complexity of the algorithm structure, greatly shortens the imaging time, obtains the strip chart containing all data information of the vehicle-mounted SAR imaging scene, and overcomes the defect that the existing real-time SAR imaging algorithm cannot rapidly observe all data information of the vehicle-mounted SAR.
The effect of the present invention can be further illustrated by the following simulation experiment, wherein MATLAB software is adopted for simulation during simulation.
The parameters of the simulation data are as follows:
the radar works in an oblique viewing mode, the wave velocity center oblique viewing angle is 25 degrees, the radar carrier frequency is 22.5MHz, the frame width is 500mm, the distance sampling rate is 76GHz, the pulse repetition frequency is 5000Hz, the number of FFT-converted echoes is 400, and Step is 40.
The simulation content is as follows: wherein, the first and the second end of the pipe are connected with each other,
fig. 3 is a coordinate corrected ultra-fast SAR imaging histogram. It can be seen that the size of the histogram is uniform after coordinate correction, but some diagonal lines appear.
Fig. 4 is a strip chart of ultrafast SAR imaging with strip bands not zero padded. It can be seen that zero padding is not performed, the oblique line of the strip chart is straightened after the strabismus correction, but front and back targets are folded, and the diagonal line is obvious.
Fig. 5 is a strip chart of ultrafast SAR imaging after zero padding of the strip chart, and the simulation target is to avoid scene information coincidence in the image, that is, folding of front and rear targets. It can be seen that the circular shift in the time domain is made after the zero padding of the strip chart, and front and rear targets are not folded, but diagonal lines are obvious.
Fig. 6 is a frequency shift corrected ultrafast SAR imaging histogram. The cyclic shift is performed in the frequency domain, and the image information with most of twill being filtered can be obtained.
Fig. 8 is a histogram of ultrafast SAR imaging in front side view mode, where the squint angle is zero and the zero doppler frequency corresponds to the direction of the radar center.
Exemplary device
As shown in fig. 10, an embodiment of the present invention provides a vehicle-mounted synthetic aperture radar fast swath imaging system, comprising:
the acquisition and compression processing module 410 is configured to acquire echo data of a radar system, and perform distance dimension pulse compression on the echo data to obtain a high-resolution range profile;
a velocity estimation module 420, configured to estimate a velocity based on the obtained high-resolution range profile, and perform doppler center frequency calculation to obtain a doppler frequency of a target on a beam center line;
the azimuth dimension processing and panoramic estimation module 430 is used for performing azimuth dimension FFT on each frame of the high-resolution range profile, sequentially extracting Doppler center frequency data in each frame for panoramic estimation, and obtaining a strip chart of a vehicle-mounted SAR imaging scene;
the uniformity correction module 440 is used for performing uniformity correction on the coordinates of the strip chart to obtain a strip chart with uniform size;
and a deformation correction module 450, configured to perform deformation correction on the histogram with the uniform size to obtain a stripe synthetic aperture radar image containing all vehicle-mounted data information, as described above.
Based on the above embodiment, the present invention further provides an intelligent terminal, and a schematic block diagram thereof may be as shown in fig. 11. The intelligent terminal of the embodiment of the invention can be an intelligent multimedia device, and comprises a processor, a memory, a network interface and a display screen which are connected through a system bus. Wherein, the processor of the intelligent terminal is used for providing calculation and control capability. The memory of the intelligent terminal comprises a nonvolatile storage medium and an internal memory. The non-volatile storage medium stores an operating system and a computer program. The internal memory provides an environment for the operation of an operating system and computer programs in the non-volatile storage medium. The network interface of the intelligent terminal is used for being connected and communicated with an external terminal through a network. The computer program is executed by a processor to implement a method for on-board synthetic aperture radar fast swath imaging. The display screen of the intelligent terminal can be a liquid crystal display screen or an electronic ink display screen.
It will be understood by those skilled in the art that the block diagram of fig. 11 is only a block diagram of a part of the structure related to the solution of the present invention, and does not constitute a limitation to the intelligent terminal to which the solution of the present invention is applied, and a specific intelligent terminal may include more or less components than those shown in the figure, or combine some components, or have different arrangements of components.
In one embodiment, an intelligent terminal is provided that includes a memory, and one or more programs, wherein the one or more programs are stored in the memory and configured to be executed by the one or more processors, the one or more programs including instructions for:
obtaining echo data of a radar system, and performing range dimension pulse compression on the echo data to obtain a high-resolution range profile;
estimating the speed based on the obtained high-resolution range profile, and calculating the Doppler center frequency to obtain the Doppler frequency of the target on the beam center line;
performing azimuth dimension FFT on each frame of the high-resolution range profile, and sequentially extracting Doppler center frequency data in each frame to perform panoramic estimation to obtain a strip graph of a vehicle-mounted SAR imaging scene;
uniformly correcting the coordinates of the strip chart to obtain a strip chart with uniform size;
carrying out deformation correction on the stripmap with uniform size to obtain a stripmap synthetic aperture radar image containing all vehicle-mounted data information; as described above.
It will be understood by those skilled in the art that all or part of the processes of the methods of the embodiments described above may be implemented by hardware instructions of a computer program, which may be stored in a non-volatile computer-readable storage medium, and when executed, may include the processes of the embodiments of the methods described above. Any reference to memory, storage, databases, or other media used in embodiments provided herein may include non-volatile and/or volatile memory. Non-volatile memory can include read-only memory (ROM), programmable ROM (PROM), electrically Programmable ROM (EPROM), electrically Erasable Programmable ROM (EEPROM), or flash memory. Volatile memory can include Random Access Memory (RAM) or external cache memory. By way of illustration and not limitation, RAM is available in a variety of forms such as Static RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), double Data Rate SDRAM (DDRSDRAM), enhanced SDRAM (ESDRAM), synchronous Link DRAM (SLDRAM), rambus (Rambus) direct RAM (RDRAM), direct memory bus dynamic RAM (DRDRAM), and memory bus dynamic RAM (RDRAM).
In summary, the invention discloses a method, a system, an intelligent terminal and a storage medium for rapid strip imaging of a vehicle-mounted synthetic aperture radar, wherein the method comprises the steps of obtaining echo data of a radar system, and performing range dimension pulse compression on the echo data to obtain a high-resolution range profile; estimating the speed based on the obtained high-resolution range profile, and calculating the Doppler center frequency to obtain the Doppler frequency of the target on the beam center line; performing azimuth dimension FFT on each frame of the high-resolution range profile, and sequentially extracting Doppler center frequency data in each frame to perform panoramic estimation to obtain a strip graph of a vehicle-mounted SAR imaging scene; uniformly correcting the coordinates of the strip chart to obtain a strip chart with uniform size; and carrying out deformation correction on the strip chart with uniform size to obtain a strip synthetic aperture radar image containing all vehicle-mounted data information. According to the method for performing panoramic reconstruction by extracting the Doppler frequency of the target of the beam center line, the optimal number of the row cyclic shift can be calculated according to the estimated distance dimension of the squint angle under a larger squint angle, the complexity of the algorithm structure is reduced, the imaging time is greatly shortened, the strip chart containing all data information of the vehicle-mounted SAR imaging scene is obtained, and the defect that the existing real-time SAR imaging algorithm cannot rapidly observe all data information of the vehicle-mounted SAR is overcome.
Finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.
Claims (9)
1. A method for on-board rapid swath imaging for synthetic aperture radar, the method comprising:
obtaining echo data of a radar system, and performing range dimension pulse compression on the echo data to obtain a high-resolution range profile;
estimating the speed based on the obtained high-resolution range profile, and calculating the Doppler center frequency to obtain the Doppler frequency of the target on the beam center line;
performing azimuth dimension FFT on each frame of the high-resolution range profile, and sequentially extracting Doppler center frequency data in each frame to perform panoramic estimation to obtain a strip graph of a vehicle-mounted SAR imaging scene;
uniformly correcting the coordinates of the strip chart to obtain a strip chart with uniform size;
and carrying out deformation correction on the strip chart with uniform size to obtain a strip synthetic aperture radar image containing all vehicle-mounted data information.
2. The method according to claim 1, wherein the step of obtaining the echo data of the radar system, performing range-dimensional pulse compression on the echo data, and obtaining the high-resolution range profile comprises:
starting a radar system to acquire images, and acquiring echo data M multiplied by N of the radar system, wherein M corresponds to a distance dimensional data volume, and N corresponds to a direction dimensional data volume;
and performing distance dimension pulse compression on the echo data to obtain a high-resolution range image, wherein the distance dimension pulse compression method comprises matched filtering and de-line frequency modulation.
3. The method according to claim 1, wherein the step of estimating the velocity based on the obtained high-resolution range profile and calculating the doppler center frequency to obtain the doppler frequency of the target on the beam center line comprises:
dividing the obtained high-resolution range profile according to sub-apertures to obtain (N-N)/s frame synthetic aperture radar images;
measuring a current speed value through a speed sensor or a speed estimation algorithm, and taking a speed average value at every n points, namely n echoes correspond to one speed value;
calculating the Doppler frequency of the target of the central line of the wave beam according to the average velocity value v and the squint angle theta; and estimating the number of frequency deviation points on a Doppler frequency coordinate axis to obtain the Doppler center frequency under squint.
4. The fast banding imaging method of the vehicle-mounted synthetic aperture radar according to claim 1, wherein the step of performing an azimuth dimension FFT on each frame of the high resolution range profile, sequentially extracting Doppler center frequency data in each frame for panoramic estimation, and obtaining a banding pattern of a vehicle-mounted SAR imaging scene comprises:
based on the obtained (N-N)/s frame SAR image and Doppler center frequency, performing orientation dimension FFT on the first frame image, extracting data in the ID column as the first column of the strip chart, performing orientation dimension FFT on the second frame image, extracting data in the ID column as the second column of the strip chart, and so on to obtain one frame of image containing all data information of the vehicle-mounted SAR imaging scene;
and when the vehicle-mounted SAR imaging scene is viewed from the front side, sequentially extracting data of the zero Doppler unit of each frame image to perform panoramic reconstruction, and obtaining a strip chart of the vehicle-mounted SAR imaging scene.
5. The method according to claim 1, wherein the step of uniformly correcting the coordinates of the histogram to obtain a histogram with uniform size comprises:
defining the time interval for processing each frame of image as t = s/PRF, and setting the corresponding speed of each frame of image as v f The distance value between two adjacent columns of data in the corrected histogram is Deltax, and the pulse repetition frequency of the corrected histogram is RPF eq Wherein PRF eq ＝PRF/s；
With two adjacent columns of data in the stripmapDistance value tv f And carrying out horizontal coordinate conversion to obtain a coordinate-corrected strip chart, wherein the Doppler frequency interval of the strip chart is f aeq ＝[-PRF eq /2,PRF eq /2]。
6. The method according to claim 1, wherein the step of performing deformation correction on the histogram with uniform size to obtain the histogram of synthetic aperture radar including all data information on the vehicle specifically comprises:
according to the squint angle of the target and the radar, carrying out corresponding zero filling operation on the left side and the right side of the strip chart with uniform size;
performing squint correction on the strip chart after zero padding in a mode of time domain translation or frequency domain compensation displacement function, and estimating the optimal number of points of each row of cyclic displacement according to the distance information of horizontal and vertical coordinates and the squint angle; and calculating the shift time delay, and performing displacement compensation on the data of each distance to the moment to obtain a strabismus corrected strip SAR image.
7. An on-board synthetic aperture radar fast swath imaging system, the system comprising:
the acquisition and compression processing module is used for acquiring echo data of the radar system and performing range dimension pulse compression on the echo data to obtain a high-resolution range profile;
the velocity estimation module is used for estimating the velocity based on the obtained high-resolution range profile and calculating the Doppler center frequency to obtain the Doppler frequency of the target on the beam center line;
the azimuth dimension processing and panoramic estimation module is used for performing azimuth dimension FFT on each frame of image of the high-resolution range profile, sequentially extracting Doppler center frequency data in each frame for panoramic estimation, and obtaining a strip chart of a vehicle-mounted SAR imaging scene;
the uniform correction module is used for uniformly correcting the coordinates of the strip chart to obtain the strip chart with uniform size;
and the deformation correction module is used for carrying out deformation correction on the strip chart with uniform size to obtain a strip synthetic aperture radar image containing all vehicle-mounted data information.
8. An intelligent terminal, comprising a memory, and one or more programs, wherein the one or more programs are stored in the memory, and wherein the one or more programs being configured to be executed by the one or more processors comprises instructions for performing the method of any of claims 1-6.
9. A non-transitory computer-readable storage medium, wherein instructions in the storage medium, when executed by a processor of an electronic device, enable the electronic device to perform the method of any of claims 1-6.
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