CN114942440A - SAR two-dimensional beam scanning method for rapidly imaging large wide area and electronic equipment - Google Patents
SAR two-dimensional beam scanning method for rapidly imaging large wide area and electronic equipment Download PDFInfo
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- 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
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- G01S13/90—Radar or analogous systems specially adapted for specific applications for mapping or imaging using synthetic aperture techniques, e.g. synthetic aperture radar [SAR] techniques
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Abstract
The invention discloses an SAR two-dimensional beam scanning method for rapidly imaging a large-size wide area, which comprises the following steps: constructing a geometric scene model; calculating the number of sub mapping bands according to the range width of the distance direction imaging scene and the pitching wave beam width of the antenna; calculating the beam center downward viewing angle of each sub-swath according to the number of the sub-swaths; calculating the distance from each sub mapping strip to the virtual rotation point corresponding to the airplane according to the antenna azimuth beam width; calculating the azimuth beam scanning rate of the antenna corresponding to each sub mapping strip according to the distance from the airplane to the virtual rotation point and the azimuth imaging scene width; controlling radar carried on the airplane to scan alternately on each sub-swath according to the downward viewing angle of the beam center, the distance from the airplane to the virtual rotation point and the antenna azimuth beam scanning rate; the improved ScanSAR scanning mode is adopted in the range direction and the TOPS scanning mode is adopted in the azimuth direction during scanning. The scanning method can realize the rapid imaging of a large-width area.
Description
Technical Field
The invention belongs to the technical field of radar emission signal processing, and particularly relates to an SAR two-dimensional beam scanning method and electronic equipment for rapidly imaging a large wide area.
Background
With the rapid development of spatial information technology, controlling and utilizing space is one of the important targets sought by the world military and the strong country. Synthetic Aperture Radar (SAR for short) can observe earth all day long, all weather, high resolution and large area due to no influence of weather and climate, and has become an important means for space-to-earth observation. The airborne SAR is an effective means for rapidly acquiring earth surface change, and has been widely applied to various fields such as homeland surveying and mapping, resource investigation, military investigation, environmental monitoring and the like with the continuous development in recent years.
High-resolution large swath imaging in the synthetic aperture radar imaging technology is a target pursued by the development of the synthetic aperture radar technology, and the solution method mainly compromises the performances of resolution, swath and the like through beam scanning. With the continuous development and deepening of the research of the application field of the synthetic aperture radar, more and more observation tasks provide more rigorous requirements for the performance indexes of the SAR, the synthetic aperture radar is required to have certain resolution and a large measuring and drawing zone, and the synthetic aperture radar is also required to realize rapid imaging, so that a new challenge is provided for the aspect of system design. In a typical airborne system, the TOPS scanning mode enables a wide range of azimuthal observations in a short time through beam azimuthal scanning, but in practice, the TOPS scanning mode no longer meets the requirements when too high azimuthal resolution is not required for the imaged scene at the same time and a larger wide swath is required. The method for improving the observation band of the synthetic aperture radar is to adopt a ScanSAR scanning mode, obtain a plurality of sub mapping bands through beam scanning, and obtain a longitudinal ultra-wide ground observation band through splicing the sub observation bands. However, although the conventional ScanSAR scanning mode can improve the range-direction observation band width, the azimuth-direction observation band width is still limited by the inherent antenna beam width and is not improved.
Therefore, a new scanning method is required to realize fast and effective imaging of a wide swath in a short time.
Disclosure of Invention
In order to solve the problems in the prior art, the invention provides an SAR two-dimensional beam scanning method and electronic equipment for rapidly imaging a large wide area. The technical problem to be solved by the invention is realized by the following technical scheme:
in a first aspect, an embodiment of the present invention provides an SAR two-dimensional beam scanning method for rapidly imaging a large wide area, including:
constructing a geometric scene model; the geometric scene model comprises a range-direction imaging scene width, an azimuth-direction imaging scene width, an antenna pitching beam width and an antenna azimuth-direction beam width;
calculating the number of sub mapping bands according to the range of the distance direction imaging scene and the pitch direction beam width of the antenna;
calculating the beam center downward view angle of each sub-swath according to the number of the sub-swaths;
calculating the distance from the airplane corresponding to each sub mapping band to the virtual rotation point according to the azimuth beam width of the antenna;
calculating the azimuth beam scanning rate of the antenna corresponding to each sub-swath according to the distance from the airplane to the virtual rotation point and the azimuth imaging scene width;
controlling a radar carried on the airplane to perform alternate scanning on each sub mapping band according to the beam center downward viewing angle of each sub mapping band, the distance from the airplane to the virtual rotation point and the antenna azimuth beam scanning rate; when each sub-swath is scanned, an improved ScanSAR scanning mode is adopted in the distance direction, and a TOPS scanning mode is adopted in the azimuth direction; during the improved ScanSAR scanning mode scanning, one emission pulse irradiates one sub mapping zone.
In one embodiment of the invention, the geometric scene model further comprises a range-direction imaging scene near-end ground distance and an aircraft flying height; calculating the number of sub mapping bands corresponding to the range direction imaging scene width and the antenna pitching direction beam width, and the method comprises the following steps:
calculating the lower view angle range of the antenna corresponding to the distance direction of the airplane according to the near-end ground distance of the distance direction imaging scene, the flight height of the airplane and the width of the distance direction imaging scene;
and calculating operator observation band number according to the antenna lower visual angle range and the antenna pitching beam width.
In an embodiment of the present invention, the calculating the beam center downward viewing angle of each sub-swath according to the number of sub-swaths includes:
calculating the beam overlapping part of each sub observation band according to the number of the sub observation bands, the lower view angle range of the antenna and the pitching beam width of the antenna;
and calculating the beam center downward viewing angle of each sub mapping band according to the near-end ground distance of the distance direction imaging scene, the flight height of the airplane, the pitching direction beam width of the antenna and the beam overlapping part of each sub mapping band.
In an embodiment of the present invention, the calculating a distance from the aircraft corresponding to each sub mapping band to the virtual rotation point according to the antenna azimuth beam width includes:
calculating the center slant distance from the airplane to each sub mapping strip;
calculating azimuth resolution in a strip mode according to the antenna azimuth beam width;
and calculating the distance from the airplane corresponding to each sub-swath to the virtual rotation point according to the ratio relation between the azimuth resolution of the TOPS scanning mode and the azimuth resolution of the strip mode and the center slant distance.
In an embodiment of the present invention, before calculating the azimuth beam scanning rate of each sub-swath according to the distance from the aircraft to the virtual rotation point and the azimuth imaging scene width, the geometric scene model further includes:
calculating the flight distance of the airplane according to the ratio relation between the azimuth resolution of the TOPS scanning mode and the azimuth resolution of the strip mode and the azimuth imaging scene width;
and calculating the scanning imaging time corresponding to each sub-swath according to the flight distance and the flight speed of the airplane.
In an embodiment of the present invention, the calculating an azimuth beam scanning rate of an antenna corresponding to each sub swath according to the distance from the aircraft to the virtual rotation point and the azimuth imaging scene width includes:
calculating the azimuth viewing angle range corresponding to each sub-swath according to the azimuth imaging scene width, the distance from the airplane to the virtual rotation point and the center slant distance;
and calculating the antenna azimuth beam scanning rate corresponding to each sub-swath according to the azimuth viewing angle range and the scanning imaging time.
In one embodiment of the present invention, further comprising:
calculating the repetition frequency of the emission pulse of each sub mapping band; wherein the transmission pulse repetition frequency is used to ensure unambiguous scanning imaging.
In one embodiment of the present invention, the calculating the transmission pulse repetition frequency of each sub-swath includes:
calculating the minimum transmitting pulse repetition frequency according to the Doppler bandwidth of the radar;
calculating the maximum transmitting pulse repetition frequency according to the center slant distance from the airplane to the farthest terminal surveying and mapping zone;
and calculating the transmission pulse repetition frequency of each sub mapping band according to the minimum transmission pulse repetition frequency and the maximum transmission pulse repetition frequency.
In a second aspect, an embodiment of the present invention provides an electronic device, including a processor, a communication interface, a memory, and a communication bus, where the processor, the communication interface, and the memory complete mutual communication through the communication bus;
the memory is used for storing a computer program;
the processor is configured to implement any of the above-described steps of the SAR two-dimensional beam scanning method for rapidly imaging a large wide area when executing the program stored in the memory.
The invention has the beneficial effects that:
the SAR two-dimensional beam scanning method for rapidly imaging the large-width area is a new scanning method, and comprises the steps of constructing a geometric scene model, designing key parameters during scanning according to the geometric scene model, wherein the key parameters comprise the number of sub mapping bands, the beam center downward viewing angle of each sub mapping band, the distance from an airplane to a virtual rotation point and the antenna azimuth beam scanning speed, controlling a radar loaded on the airplane to alternately scan on each sub mapping band through the parameters, adopting an improved ScanSAR scanning mode in the distance direction and a TOPS scanning mode in the azimuth direction during scanning of each sub mapping band, and irradiating one sub mapping band by one emission pulse during scanning of the improved ScanSAR scanning mode. Compared with the TOPS scanning mode, the scanning method provided by the invention realizes the rapid scanning imaging of the range-direction wide swath in the same time, and compared with the traditional ScanSAR scanning mode, the scanning method realizes the rapid scanning imaging of the range-direction wide swath in the same time. Therefore, within a specified distance direction and azimuth direction mapping bandwidth, the imaging time of the scanning method provided by the invention is shorter than that of a TOPS scanning mode or a traditional ScanSAR scanning mode which is adopted alone, and the rapid imaging can be realized.
The present invention will be described in further detail with reference to the accompanying drawings and examples.
Drawings
Fig. 1 is a schematic flowchart of an SAR two-dimensional beam scanning method for rapidly imaging a large wide area according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of a geometric scene model provided by an embodiment of the invention;
FIG. 3 is a schematic view of a beam center lower view of each sub swath in the geometric scene model according to the embodiment of the present invention;
fig. 4 is a schematic structural diagram of an electronic device according to an embodiment of the present invention.
Detailed Description
The present invention will be described in further detail with reference to specific examples, but the embodiments of the present invention are not limited thereto.
Example one
The inventor researches and discovers that the requirements of short imaging time and wide mapping belt width cannot be met simultaneously in both TOPS scanning mode and traditional ScanSAR scanning mode. With the more rigorous requirement of the observation task on the SAR performance index, a new scanning mode is urgently needed to be found so as to realize the rapid and effective imaging of the wide swath in a short time.
Based on the existing problems, in order to realize the rapid imaging of a large wide area, the embodiment of the invention provides an SAR two-dimensional beam scanning method for the rapid imaging of the large wide area. In the scanning process, according to the actual scene, how to design the scanning control parameters is crucial, and the unreasonable parameter design can seriously affect the scanning imaging effect. Referring to fig. 1, an embodiment of the present invention provides an SAR two-dimensional beam scanning method for fast imaging a large wide area, which reasonably designs a scanning control parameter, so that a TOPS scanning mode and an improved ScanSAR scanning mode can be effectively combined under the scanning control parameter to realize fast imaging of the large wide area, and specifically includes the following steps:
and S10, constructing a geometric scene model.
Specifically, referring to fig. 2 and 3, the geometric scene model constructed according to the embodiment of the present invention includes a distance-wise imaging scene width W g Azimuth imaging scene width W a Antenna elevation direction beam width theta f Azimuth beam width theta of antenna a Distance x towards the near end of the imaged scene 0 Airplane flying height h and airplane flying speed V s 。
S20, imaging scene width W according to distance g And antenna elevation beam width theta f And calculating the number of the sub-swaths.
Specifically, the embodiment of the invention images the scene width W according to the distance direction g And antenna elevation beam width theta f Calculating the number of sub-swaths, comprising:
s201, imaging scene near-end ground distance x according to distance 0 Airplane and airplaneFlight height h and range-wise imaging scene width W g And (3) calculating the lower view angle range of the antenna corresponding to the distance direction of the airplane, wherein the formula is as follows:
s202, according to the lower view angle range of the antenna
And antenna elevation beam width theta f Calculating the number of the sub-observation bands, and expressing the formula as follows:
wherein ceil (·) represents rounding up.
And S30, calculating the beam center downward view angle of each sub-swath according to the number N of the sub-swaths.
Specifically, the embodiment of the present invention calculates the beam center downward viewing angle of each sub swath according to the number N of the sub swaths, including:
s301, according to the number N of the sub-observation bands, the lower view angle range of the antenna
And antenna elevation beam width theta f The beam overlap of each sub-observation band is calculated. The beam overlap calculation formula for all sub-observation bands is expressed as:
the beam overlap corresponding to each sub swath is expressed as:
wherein, theta ri Indicating the beam overlap of the ith sub-swath.
S302, according to the distance, the ground distance x to the near end of the imaging scene 0 Airplane flying height h and antenna pitching beam width theta f And the beam overlap theta of each sub swath ri And calculating the lower view angle of the beam center of each sub mapping band, wherein the formula is as follows:
wherein, theta i The beam center down-view of the ith sub-swath is shown.
S40, beam width theta according to antenna direction a And calculating the distance from the airplane corresponding to each sub-swath to the virtual rotation point.
Specifically, the virtual rotation point (virtual rotation center) is an out-of-scene virtual rotation point corresponding to the TOPS scanning mode, and the embodiment of the invention provides a beam width θ according to the antenna azimuth direction a Calculating the distance from the aircraft corresponding to each sub mapping strip to the virtual rotation point, wherein the distance comprises the following steps:
s401, calculating the center slant distance from the airplane to each sub mapping strip, and recording the center slant distance as
Represents the center slope of the ith sub-swath (FIG. 2 only schematically depicts the center slope of one sub-swath); any conventional method for calculating the center skew distance may be adopted, and will not be described in detail here.
S402, beam width theta according to antenna azimuth direction a And calculating the azimuth resolution in the strip mode, wherein the formula is as follows:
where λ represents a wavelength.
S402, azimuth resolution rho according to TOPS scanning mode and azimuth resolution rho of strip mode a-strip Is related toSystem, and center pitch
And (3) calculating the distance from each sub mapping strip to the virtual rotation point corresponding to the airplane, wherein the formula is as follows:
where ρ is a-tops Which represents the azimuthal resolution of the TOPS scan pattern, here a known quantity, may take a value of e.g. 3,
and representing the distance from the plane corresponding to the ith sub-swath to the virtual rotation point.
It should be noted that the strip mode is an imaging mode commonly used for the satellite-borne SAR, and is not described in detail here. Here, only the azimuth resolution in the stripe mode is used to calculate the key scan parameters of the proposed method.
S50, according to the distance between the airplane and the virtual rotation point
And azimuth direction imaging scene width W a And calculating the scanning speed of the azimuth beam of each sub mapping band corresponding to the antenna.
Specifically, before calculating the antenna azimuth beam scanning rate corresponding to each sub-swath, the embodiment of the present invention further includes:
s501, azimuth resolution rho according to TOPS scanning mode a-tops And the azimuthal resolution of the strip mode ρ a-strip And azimuth-direction imaging scene width W a Calculating the flight distance of the airplane, and expressing the formula as follows:
s502, according to the flight distance S and the flight speed V of the airplane s And calculating the scanning imaging time corresponding to each sub-swath, wherein the formula is as follows:
therefore, the scanning imaging time T of each sub swath is the same in the embodiment of the invention.
Further, the embodiment of the invention is based on the distance from the airplane to the virtual rotation point
And azimuth direction imaging scene width W a Calculating the scanning speed of the azimuth beam of each sub mapping band corresponding to the antenna, including:
s503, imaging scene width W according to azimuth direction a Distance of aircraft to virtual rotation point
Center slant distance
And calculating the azimuth viewing angle range corresponding to each sub-swath, wherein the formula is as follows:
wherein the content of the first and second substances,
and representing the azimuth viewing angle range corresponding to the ith sub-swath.
S504, viewing angle range according to azimuth direction
And calculating the scanning speed of the antenna azimuth beam corresponding to each sub mapping band by scanning imaging time T, wherein the formula is as follows:
wherein the content of the first and second substances,
and the scanning speed of the antenna azimuth beam corresponding to the ith sub-swath is shown.
S60, according to the beam center downward angle of view theta of each sub mapping zone i Distance of the aircraft to the virtual rotation point
And antenna azimuth beam scan rate
Controlling the radar loaded on the airplane to alternately scan on each sub mapping strip; when each sub-swath is scanned, an improved ScanSAR scanning mode is adopted in the distance direction, and a TOPS scanning mode is adopted in the azimuth direction; in the improved ScanSAR scan mode, one emission pulse irradiates one sub-swath.
Specifically, through the above-mentioned S20 to S50, the number of sub swaths under the constructed geometric scene model is determined, and the view angle θ under the beam center of each sub swath is calculated i Distance of the aircraft to the virtual rotation point
And antenna azimuth beam scan rate
The radar is mounted on the airplane, and under the action of the scanning control parameters, alternate scanning is carried out on each sub-swath. In alternative scanning, an improved ScanSAR scanning mode is adopted in the distance direction and a TOPS scanning mode is adopted in the azimuth direction, and therefore the embodiment of the invention adopts different scanning modes in the distance direction and the azimuth direction, so that the effective combination of the TOPS scanning mode and the improved ScanSAR scanning mode is realized, and the scanning direction of the TOPS scanning mode is from the back directionPre-scan, the improved ScanSAR scan mode alternately illuminates sub-swaths within a synthetic aperture time, one transmit pulse illuminates a sub-swath, specifically: the first emission pulse points to the first sub-swath, the second emission pulse points to the second sub-swath, the third emission pulse points to the third sub-swath, … …, the nth emission pulse points to the nth sub-swath, the (N + 1) th emission pulse points to the first sub-swath, and so on, and the scanning of the whole imaging scene is realized by alternate irradiation.
The inventor researches and discovers that the emission pulse in the ScanSAR scanning mode improved in the embodiment of the invention has great influence on the imaging effect, and in order to ensure the imaging without the fuzzy scanning, the embodiment of the invention provides a mode for calculating the emission pulse repetition frequency of each sub mapping strip, wherein the emission pulse repetition frequency is used for ensuring the imaging without the fuzzy scanning. The selecting of the transmission pulse repetition frequency is limited by the position ambiguity and the distance ambiguity, and then the corresponding calculating of the transmission pulse repetition frequency of each sub mapping band may include:
s601, calculating the minimum transmitting pulse repetition frequency according to the Doppler bandwidth of the radar, wherein the formula is as follows:
PRF min ≥B D (12)
wherein, B D Representing the doppler bandwidth of the radar.
The minimum transmit pulse repetition frequency chosen by equation (12) avoids azimuthal ambiguity for the corresponding sub-swath.
S602, calculating the corresponding maximum emission pulse repetition frequency according to the center slope distance from the airplane to the farthest terminal mapping zone, wherein the formula is as follows:
wherein c represents the speed of light, R max Representing the center slope of the aircraft to the farthest terminal swath. R is max The calculation method is the same as that of
With the difference that, here R max And calculating the center slope distance corresponding to the measuring and drawing band of the farthest terminal.
The maximum transmit pulse repetition frequency selected by equation (13) avoids range ambiguity for the corresponding sub-swath.
S603, according to the PRF min And maximum transmit pulse repetition frequency PRF max Determining the transmit pulse repetition frequency of each sub-swath, as expressed by the formula:
wherein, PRF set Representing the PRF from the minimum transmit pulse repetition frequency min And maximum transmit pulse repetition frequency PRF max A transmit pulse repetition frequency arbitrarily selected within the determined range.
The repetition frequency of the transmission pulse transmitted to each sub-swath is calculated according to the formula (14) to ensure the effectiveness of scanning imaging.
In order to verify the effectiveness of the SAR two-dimensional beam scanning method for large-size wide-area rapid imaging provided by the embodiment of the invention, the following experiments are carried out for verification.
1. Experimental simulation parameters
The SAR system parameters in the simulation process of the embodiment of the invention are shown in Table 1.
TABLE 1SAR system simulation parameter table
| Aircraft altitude h (km) | 20 | Aircraft flight velocity V s (m/s) | 90 |
| Distance to imaging scene near-end ground distance x 0 (km) | 50 | topS azimuthal resolution ρ a-tops (m) | 3 |
| Transmission signal carrier frequency (GHz) | 8.65 | Antenna azimuth beam width theta a (°) | 2.2 |
| Imaging scene width W a ×W g (km) | 60×60 | Antenna elevation direction beam width theta f (°) | 8.9 |
2. Simulation content and result analysis
Under the simulation condition shown in the SAR system simulation parameter table, the method provided by the invention is used for calculating the relevant parameters as follows:
according to the motion of the antenna, the range of the view angle of the beam center when the antenna scans to the farthest terminal swath
Number of event test and drawing bands
Aircraft flight velocity V s Is 90m/s, the minimum transmission pulse repetition frequency PRF min 1386Hz, maximum transmit pulse repetition frequency PRF max 1606Hz, then from [1386,1606 ]]Selection of 1400Hz in the range as emission of 4 sub-swathsPulse repetition frequency PRF set At this time, for 4 sub-swaths, the pulse repetition frequency PRF of each sub-swath is 350 Hz; resolution of stripe patterns
Resolution ρ of TOPS scan mode a-tops Distance x towards the near end of the imaged scene, 3 0 Is 7.29km, so that the beam center downward viewing angle theta of the 1 st sub-swath can be obtained 1 Is 49.13 degrees, and the center slant distance
30.90km, distance of the aircraft to the virtual rotation point
5.47 km; beam center down view angle theta of the 2 nd sub swath 2 Is 56.10 degrees of center slant distance
36.18km, distance of the aircraft to the virtual rotation point
6.41 km; beam center down view angle theta of 3 rd sub swath 3 Is 63.13 DEG, center slant distance
45.38km, distance of the aircraft to the virtual rotation point
8.04 km; beam center down view angle theta of the 4 th sub-swath 4 Is 71.61 degrees, and the center slant distance
67.23km, flight distance from airplane to virtual rotary machine
11.90 km; aircraft flight distance of
So that the imaging time of each sub swath is
In order to verify the advantages of the SAR two-dimensional beam scanning method for rapid imaging of a large wide area provided by the present invention, the SAR system simulation parameters shown in table 1 are also used for simulation, and the corresponding simulation results are as follows:
when the radar imaging mode is only the traditional ScanSAR scanning mode, the scanning imaging time is as follows:
when the radar imaging mode is only the TOPS scanning mode, the scanning imaging time is as follows: t is tops 4T 401.16 s; wherein, T is the scanning imaging time of the method provided by the invention.
Therefore, the SAR two-dimensional beam scanning method for rapidly imaging the large-width area provided by the embodiment of the invention has the shortest imaging time for the same width area. On the contrary, in the same imaging time, the embodiment of the invention can realize imaging of a larger wide area. The embodiment of the invention is more suitable for the field of rapid imaging of a large-breadth area.
In summary, the SAR two-dimensional beam scanning method for rapid imaging of a large wide area, which is provided by the embodiment of the present invention, is a new scanning method, and by constructing a geometric scene model, and designing key parameters during scanning according to the geometric scene model, including the number of sub swaths, the beam center downward view angle of each sub swath, the distance from the aircraft to the virtual rotation point, and the antenna azimuth beam scanning rate, the radar mounted on the aircraft is controlled to scan alternately on each sub swath by using the parameters, an improved ScanSAR scanning mode is adopted in the distance direction and a TOPS scanning mode is adopted in the azimuth direction during scanning of each sub swath, and one emission pulse irradiates one sub swath during scanning in the improved ScanSAR scanning mode. Compared with the TOPS scanning mode, the scanning method provided by the embodiment of the invention realizes the rapid scanning imaging of the range-direction wide swath in the same time, and compared with the traditional ScanSAR scanning mode, the scanning method realizes the rapid scanning imaging of the range-direction wide swath in the same time. Therefore, within a specified distance direction and azimuth direction mapping bandwidth, the imaging time of the scanning method provided by the embodiment of the invention is shorter than that of a TOPS scanning mode or a traditional ScanSAR scanning mode which is adopted alone, and the rapid imaging can be realized.
Referring to fig. 4, an embodiment of the present invention provides an electronic device, including a processor 401, a communication interface 402, a memory 403, and a communication bus 404, where the processor 401, the communication interface 402, and the memory 403 complete mutual communication through the communication bus 404;
a memory 403 for storing a computer program;
the processor 401 is configured to implement the steps of the SAR two-dimensional beam scanning method for rapidly imaging a large wide area when executing the program stored in the memory 403.
An embodiment of the present invention provides a computer-readable storage medium, in which a computer program is stored, and when the computer program is executed by a processor, the steps of the SAR two-dimensional beam scanning method for rapidly imaging a large wide area are implemented.
For the device/electronic equipment/storage medium embodiment, since it is basically similar to the method embodiment, the description is simple, and the relevant points can be referred to the partial description of the method embodiment.
In the description of the present invention, it is to be understood that the terms "first", "second" and the like are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implying any number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of the present invention, "a plurality" means two or more unless specifically defined otherwise.
While the present application has been described in connection with various embodiments, other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed application, from a review of the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the word "a" or "an" does not exclude a plurality. A single processor or other unit may fulfill the functions of several items recited in the claims. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.
The foregoing is a more detailed description of the invention in connection with specific preferred embodiments and it is not intended that the invention be limited to these specific details. For those skilled in the art to which the invention pertains, several simple deductions or substitutions can be made without departing from the spirit of the invention, and all shall be considered as belonging to the protection scope of the invention.
Claims (9)
1. A SAR two-dimensional beam scanning method for rapidly imaging a large wide area is characterized by comprising the following steps:
constructing a geometric scene model; the geometric scene model comprises a range-direction imaging scene width, an azimuth-direction imaging scene width, an antenna pitching beam width and an antenna azimuth-direction beam width;
calculating the number of sub mapping bands according to the range width of the distance direction imaging scene and the beam width of the antenna in the pitching direction;
calculating the beam center lower view angle of each sub-swath according to the number of the sub-swaths;
calculating the distance from each sub mapping strip to the virtual rotation point corresponding to the airplane according to the antenna azimuth beam width;
calculating the azimuth beam scanning rate of the antenna corresponding to each sub-swath according to the distance from the airplane to the virtual rotation point and the azimuth imaging scene width;
controlling a radar carried on the airplane to perform alternate scanning on each sub mapping band according to the beam center downward viewing angle of each sub mapping band, the distance from the airplane to the virtual rotation point and the antenna azimuth beam scanning rate; when each sub-swath is scanned, an improved ScanSAR scanning mode is adopted in the distance direction, and a TOPS scanning mode is adopted in the azimuth direction; during the improved ScanSAR scanning mode, one emission pulse irradiates one sub mapping zone.
2. The SAR two-dimensional beam scanning method for large and wide area fast imaging according to claim 1, characterized in that the geometric scene model further comprises a range-to-imaging scene near-end ground distance and an aircraft flying height; calculating the number of sub mapping bands corresponding to the range direction imaging scene width and the antenna pitching direction beam width, and the method comprises the following steps:
calculating the lower antenna view angle range corresponding to the distance direction of the airplane according to the near-end ground distance of the distance direction imaging scene, the flight height of the airplane and the width of the distance direction imaging scene;
and calculating operator observation band number according to the antenna lower visual angle range and the antenna pitching beam width.
3. The SAR two-dimensional beam scanning method for large-size wide-area fast imaging according to claim 2, wherein said calculating the beam center down view of each sub-swath according to the number of sub-swaths comprises:
calculating the beam overlapping part of each sub observation band according to the number of the sub observation bands, the lower view angle range of the antenna and the pitching beam width of the antenna;
and calculating the beam center lower visual angle of each sub mapping band according to the distance to the near-end ground distance of the imaging scene, the flight altitude of the airplane, the antenna pitching beam width and the beam overlapping part of each sub mapping band.
4. The SAR two-dimensional beam scanning method for rapidly imaging a large wide area according to claim 1, wherein the calculating the distance from the airplane corresponding to each sub-swath to the virtual rotation point according to the antenna azimuth beam width comprises:
calculating the center slant distance from the airplane to each sub mapping strip;
calculating the azimuth resolution in a strip mode according to the azimuth beam width of the antenna;
and calculating the distance from the airplane corresponding to each sub-swath to the virtual rotation point according to the ratio relation between the azimuth resolution of the TOPS scanning mode and the azimuth resolution of the strip mode and the center slant distance.
5. The SAR two-dimensional beam scanning method for rapidly imaging a large wide area according to claim 4, wherein the geometric scene model further includes an airplane flight speed, and before calculating the antenna azimuth beam scanning rate corresponding to each sub mapping band according to the distance from the airplane to the virtual rotation point and the azimuth imaging scene width, the method further includes:
calculating the flight distance of the airplane according to the ratio relation between the azimuth resolution of the TOPS scanning mode and the azimuth resolution of the strip mode and the azimuth imaging scene width;
and calculating the scanning imaging time corresponding to each sub-swath according to the flight distance and the flight speed of the airplane.
6. The SAR two-dimensional beam scanning method for rapidly imaging a large wide area according to claim 5, wherein the calculating the azimuth beam scanning rate of the antenna corresponding to each sub mapping band according to the distance from the airplane to the virtual rotation point and the azimuth imaging scene width comprises:
calculating the azimuth viewing angle range corresponding to each sub-swath according to the azimuth imaging scene width, the distance from the airplane to the virtual rotation point and the center slant distance;
and calculating the antenna azimuth beam scanning rate corresponding to each sub-swath according to the azimuth viewing angle range and the scanning imaging time.
7. The SAR two-dimensional beam scanning method for rapidly imaging large wide areas according to claim 1, further comprising:
calculating the repetition frequency of the emission pulse of each sub mapping band; wherein the transmission pulse repetition frequency is used to ensure unambiguous scanning imaging.
8. The SAR two-dimensional beam scanning method for rapidly imaging large wide areas according to claim 7, wherein said calculating the repetition frequency of the transmission pulse of each sub-swath comprises:
calculating the minimum transmitting pulse repetition frequency according to the Doppler bandwidth of the radar;
calculating the maximum transmission pulse repetition frequency according to the center slant distance from the airplane to the farthest terminal mapping band;
and calculating the transmission pulse repetition frequency of each sub mapping band according to the minimum transmission pulse repetition frequency and the maximum transmission pulse repetition frequency.
9. An electronic device, comprising a processor, a communication interface, a memory and a communication bus, wherein the processor, the communication interface and the memory communicate with each other via the communication bus;
the memory is used for storing a computer program;
the processor is configured to implement the steps of the SAR two-dimensional beam scanning method for rapidly imaging a large wide area according to any one of claims 1 to 8 when executing the program stored in the memory.
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| CN116502476B (en) * | 2023-06-28 | 2023-09-08 | 中国科学院空天信息创新研究院 | SAR system design method based on nonlinear frequency scanning response |
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