CN116224238A - SAR multi-subarea imaging radio frequency simulation method and system for periodic reconstruction of coordinate system - Google Patents

SAR multi-subarea imaging radio frequency simulation method and system for periodic reconstruction of coordinate system Download PDF

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CN116224238A
CN116224238A CN202310220599.9A CN202310220599A CN116224238A CN 116224238 A CN116224238 A CN 116224238A CN 202310220599 A CN202310220599 A CN 202310220599A CN 116224238 A CN116224238 A CN 116224238A
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sar
subarea
coordinate system
radio frequency
echo
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巩宁波
刁桂杰
王坤
张思亲
杜鑫
杨亮
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Beijing Electromechanical Engineering Research Institute
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Beijing Electromechanical Engineering Research Institute
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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
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/02—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00
    • 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
    • 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
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/02—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00
    • G01S7/40—Means for monitoring or calibrating
    • G01S7/4052—Means for monitoring or calibrating by simulation of echoes
    • 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
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/02—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00
    • G01S7/41—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00 using analysis of echo signal for target characterisation; Target signature; Target cross-section

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Abstract

The invention relates to a SAR multi-subarea imaging radio frequency simulation method and system for coordinate system periodic reconstruction, the method comprises that an SAR echo simulator receives the aircraft longitude and latitude height, speed and acceleration simulated by a simulator according to a communication period, and the aircraft longitude and latitude height of the center of a subarea to be imaged of an SAR, receives a radio frequency excitation signal, a clock signal and a radar pulse synchronous signal of the SAR through a radio frequency cable, and receives a beam pointing angle of the SAR sent by bus quick lifting equipment; the SAR echo simulator carries out SAR echo simulation of a single subarea through coordinate system reconstruction, radar beam ground center point correction, subarea on-line switching, scene transfer function calculation, SAR echo generation and periodic coordinate system withdrawal, and generates SAR echo of the single subarea in real time; by adopting the SAR echo simulation method of a single subarea, the SAR echo simulator generates the SAR echoes of all subareas in the simulation process in real time. The invention improves the accuracy and the test efficiency of the SAR scene matching guidance radio frequency semi-physical simulation of the aircraft.

Description

SAR multi-subarea imaging radio frequency simulation method and system for periodic reconstruction of coordinate system
Technical Field
The invention relates to the technical field of radio frequency simulation, in particular to a SAR multi-subarea imaging radio frequency simulation method and system for periodic reconstruction of a coordinate system.
Background
The scene matching positioning technology is an important means for improving the aircraft searching precision, under the satellite rejection condition, inertial navigation drift can cause the flight path to drift and plan the track, and at the moment, the position of the aircraft is required to be corrected through the ground point result after scene matching, so that the accurate positioning of the track is obtained, and finally, the accurate searching of a target is realized.
The working principle of aircraft SAR scene matching guidance is based on SAR imaging, according to a plurality of imaging matching points (called imaging subarea centers) planned before flight, a wide-band signal is transmitted to a designated matching point by controlling airborne SAR in the imaging process to obtain range high resolution, the azimuth high resolution is realized by Doppler caused by relative motion of an aircraft and a target in the azimuth direction, a subarea SAR image is obtained after imaging processing, registration is carried out with a reference image, and the slant range and Doppler information of characteristic points are extracted, so that auxiliary positioning correction is realized, and inertial navigation drift errors caused by time are eliminated.
In an aircraft SAR scene matching guidance radio frequency semi-physical simulation test, the traditional method needs to cut, encode and configure parameters of a reference image in advance according to planned matching points, and realizes calculation of echoes of all subareas under a fixed coordinate system. The technology has two obvious defects: firstly, a reference map is usually Gaussian plane coordinates and elevation information, the positions of the aircrafts are longitude and latitude high coordinates, for aircrafts flying at high speed, matching points are selected at a longer interval, when the aircrafts and each subarea are subjected to oblique distance calculation under the same scene coordinate system, coordinate conversion errors are introduced under the influence of the curvature of the earth, the positions of the central points of the subareas on the reference map and the oblique distances between the aircrafts and the subarea scattering points are influenced, accordingly, deviation exists between the beam irradiation range and a theory, and SAR imaging central points deviate, so that the matching positioning errors become large; secondly, the simulator has the advantages of large track configuration preparation workload, large calculation amount, fixed use mode and complex processing when different subareas are switched and beam irradiation ranges are calculated. Therefore, how to realize the on-line automatic switching of subareas and the accurate calculation of the slant ranges of pixels and aircrafts in the irradiation range of radar beams in the SAR scene matching guidance radio frequency semi-physical simulation test of aircrafts is a key problem for improving the accuracy and the test efficiency of SAR scene matching guidance radio frequency semi-physical simulation of aircrafts.
Disclosure of Invention
In view of the above analysis, the invention aims to disclose a SAR multi-subarea imaging radio frequency simulation method and system for periodic reconstruction of a coordinate system. The method solves the key problems of accuracy and test efficiency of SAR scene matching guidance radio frequency semi-physical simulation of the aircraft.
The invention discloses a SAR multi-subarea imaging radio frequency simulation method for periodically reconstructing a coordinate system, which comprises the following steps:
the SAR echo simulator receives the longitude and latitude height, the speed and the acceleration of the aircraft simulated by the simulator according to the communication period, and the longitude and latitude height of the center of the subarea to be imaged of the aircraft-carried SAR, receives the radio frequency excitation signal, the clock signal and the radar pulse synchronous signal of the SAR through the radio frequency cable, and receives the beam pointing angle of the SAR sent by the bus quick lifting device;
the SAR echo simulator carries out SAR echo simulation of a single subarea through coordinate system reconstruction, radar beam ground center point correction, subarea on-line switching, scene transfer function calculation, SAR echo generation and periodic coordinate system withdrawal, and generates SAR echo of the single subarea in real time;
by adopting the SAR echo simulation method of a single subarea, the SAR echo simulator generates the SAR echoes of all subareas in the simulation process in real time.
Further, the SAR echo simulator performing the coordinate system reconstruction described in the SAR echo simulation of the single subregion comprises:
when the radar pulse synchronous signal is detected and the coordinate reconstruction mark is invalid, performing coordinate reconstruction to establish a periodic geographic coordinate system which takes the center of the current imaging subarea as an origin and three-axis pointing as north, sky and east, and calculating the coordinate position of the aircraft in the periodic geographic coordinate system; setting the coordinate reconstruction mark to be valid; the coordinate reconstruction flag is set to be invalid in the initial state and when the coordinate system previously reconstructed is revoked.
Further, according to the longitude and latitude high coordinates of the aircraft
Figure BDA0004116459620000031
And the longitude and latitude high coordinates of the center of the subarea
Figure BDA0004116459620000032
Calculating to obtain the coordinate o of the aircraft in the periodic geographic coordinate system t1 ：
Figure BDA0004116459620000033
wherein ,
Figure BDA0004116459620000034
(X, Y, Z) is the coordinates of the aircraft in the geocentric coordinate system;
Figure BDA0004116459620000035
(X 0 ,Y 0 ,Z 0 ) Coordinates of the center point of the subarea in a geocentric coordinate system:
Figure BDA0004116459620000036
R e for the circle radius of the mortise, e is the first eccentricity of the earth.
Further, the correction of the radar beam ground center point in the SAR echo simulation of the single subarea by the SAR echo simulator comprises the following steps:
1) According to the radar beam center pitch angle alpha 1 And azimuth angle beta 1 Calculating to obtain a beam center o m1 Coordinates in a periodic geographical coordinate system
Figure BDA0004116459620000037
2) According to the subarea center o 1 Longitude and latitude of (a)
Figure BDA0004116459620000038
Longitude and latitude of scene center O>
Figure BDA00041164596200000310
Calculating to obtain a subarea center o 1 The coordinates in the fixed Gaussian coordinate system OXZ are +.>
Figure BDA0004116459620000039
3) According to the subarea center o 1 In a fixed Gaussian coordinate system, the coordinates and the beam center o m1 The beam center o after the correction of the coordinates in the periodic geographic coordinate system m1 Coordinates in a fixed Gaussian coordinate system
Figure BDA0004116459620000041
/>
Further, beam center o m1 Coordinates in a periodic geographical coordinate system
Figure BDA0004116459620000048
Figure BDA0004116459620000043
wherein ,α1 The horizontal direction is 0 DEG, the upward direction is positive, beta 1 North is 0 deg., and counterclockwise is positive.
Beam center o m1 Coordinates in a fixed Gaussian coordinate system
Figure BDA0004116459620000044
The approximate characterization is:
Figure BDA0004116459620000045
further, the SAR echo simulator performs online switching of the subareas in SAR echo simulation of the single subarea to online switching of the beam irradiation area according to the corrected radar beam ground center point to obtain reference image data of the subareas in the radar beam irradiation range; the method specifically comprises the following steps:
1) The SAR imaging echo simulator judges that the coordinate reconstruction mark is valid;
2) According to the Gaussian coordinate of the beam center
Figure BDA0004116459620000046
Reference map resolution (delta) X ,δ Z ) Index value +.>
Figure BDA0004116459620000047
3) Acquiring reference image data in the radar beam irradiation range in real time according to the index value and the number of sub-area pixels;
the reference map data includes scattering coefficients, random phases, and position coordinates of each pixel of the beam irradiation region sub-region.
Further, the calculating the scene transfer function in the SAR echo simulation of the single subarea by the SAR echo simulator comprises the following steps:
1) The simulator recursively processes the aircraft position according to the clock cycle to obtain the aircraft position;
2) Calculating the slant distance value of the pixels and the aircraft pixel by pixel;
3) Calculating a phase value introduced by the distance;
4) Carrying out phase modulation and scattering coefficient amplitude weighting on each pixel;
5) And coherently superposing pixels in the same range gate to obtain the sub-region scene transfer function.
Further, the kth pixel is inclined with the slant R of the aircraft k ：
Figure BDA0004116459620000051
t n The sub-zone scene transfer function of time:
Figure BDA0004116459620000052
m is the number of pixels falling into the range gate, A k 、R k 、t k Divide phi k Respectively representing the amplitude, distance, delay and random phase of the kth pixel echo in the range gate, T s Sampling period as system function; k (k) rw The pixel offset in the X-axis, k cl For the pixel offset in the Z-axis, H k(cl,rw) And lambda is the wavelength of the radar signal, which is the coordinate of the kth pixel on the Y axis.
Further, the SAR echo simulator performs SAR echo generation in the SAR echo simulation of the single subregion, including: after down-conversion and AD conversion of radar radio frequency excitation signals, time domain original baseband signals are generated, FFT is respectively carried out on the signals and scene transfer functions, frequency domain multiplication is carried out, IFFT is carried out, and scene echo of each radar PRT signal is obtained.
The invention also discloses a SAR multi-subarea imaging radio frequency simulation system for periodically reconstructing the coordinate system, which comprises a simulator, SAR, bus quick-lifting equipment, SAR echo simulators, an antenna array and a feed system;
the simulation machine carries out track calculation in real time, and sends the longitude and latitude height, speed and acceleration of the aircraft and the longitude and latitude height of the center of a subarea of an area to be imaged of the SAR carried by the aircraft to the SAR echo simulator according to a communication period;
the SAR injects a radio frequency excitation signal, a clock signal and a pulse synchronization signal into an SAR echo simulator through a radio frequency cable;
the bus quick-lifting device monitors communication data packets in real time and sends the beam pointing angle of SAR to the SAR echo simulator;
the echo simulator executes the SAR multi-subarea imaging radio frequency simulation method for periodically reconstructing the coordinate system to generate simulated SAR echo signals, and radiates the SAR echo signals into the microwave darkroom through the antenna array and the feed system for SAR scene matching guidance radio frequency semi-physical simulation.
The invention can realize one of the following beneficial effects:
according to the SAR multi-subarea imaging radio frequency simulation method and system for periodic reconstruction of the coordinate system, disclosed by the invention, the relative position error caused by the influence of the curvature of the earth when the traditional method is used for performing the oblique distance calculation under the fixed reference system is reduced, the accuracy of the oblique distance calculation of pixels and aircrafts in the radar beam irradiation range is improved, the processes of the SAR multi-subarea irradiation range calculation and echo signal generation of the aircrafts are simplified, meanwhile, in the radar beam irradiation range calculation process, the radar beam ground center point calculation is performed according to the actual radar position and the actual beam direction, the consistency of simulation and actual scenes is ensured, and the accuracy and the test efficiency of the SAR scene matching guidance radio frequency semi-physical simulation of the aircrafts are improved.
Drawings
The drawings are only for purposes of illustrating particular embodiments and are not to be construed as limiting the invention, like reference numerals being used to refer to like parts throughout the several views.
FIG. 1 is a flowchart of a SAR multi-subarea imaging radio frequency simulation method in an embodiment of the present invention;
FIG. 2 is a flow chart of a SAR echo simulation method for a single subregion in an embodiment of the present invention;
FIG. 3 is a diagram of a coordinate system periodic reconstruction of an aircraft SAR multi-subarea imaging radio frequency simulation method in an embodiment of the present invention;
FIG. 4 is a schematic diagram of calculating the slant distance of sub-area pixels in an embodiment of the present invention;
fig. 5 is a schematic block diagram illustrating the connection of components of a SAR multi-subarea imaging radio frequency simulation system according to an embodiment of the present invention.
Detailed Description
Preferred embodiments of the present invention are described in detail below with reference to the attached drawing figures, which form a part of the present application and, together with the embodiments of the present invention, serve to explain the principles of the invention.
One embodiment of the invention discloses a SAR multi-subarea imaging radio frequency simulation method for periodically reconstructing a coordinate system, which is shown in fig. 1 and comprises the following steps:
step S1, an SAR echo simulator receives the longitude and latitude height, the speed and the acceleration of an aircraft simulated by a simulator according to a communication period, the longitude and latitude height of the center of a subarea to be imaged of the SAR carried by the aircraft, receives a radio frequency excitation signal, a clock signal and a radar pulse synchronous signal of the SAR through a radio frequency cable, and receives a beam pointing angle of the SAR sent by a bus quick lifting device;
s2, the SAR echo simulator carries out SAR echo simulation of a single subarea through coordinate system reconstruction, radar beam ground center point correction, subarea on-line switching, scene transfer function calculation, SAR echo generation and periodic coordinate system withdrawal, and generates SAR echo of the single subarea in real time;
and S3, adopting the SAR echo simulation method of the single subarea in the step S2, and generating SAR echoes of all subareas in the simulation process in real time by the SAR echo simulator.
Specifically, the subareas are areas where imaging matching points planned before flight are located; the simulator calculates the aircraft in real time, and the longitude and latitude heights, the speed and the acceleration of the aircraft are sent to the imaging echo simulator according to the communication period of 1 ms. And the bus quick-lifting device monitors the communication data packet of the SAR radar in real time, and acquires the beam pointing angle of the SAR from the communication data packet.
As shown in fig. 2, in step S2, the SAR echo simulation method for a single subregion includes:
step S201, reconstructing a coordinate system; calculating the position of the aircraft in the periodic geographic coordinate system by re-creating the periodic geographic coordinate system;
the coordinate system reconstruction comprises:
when the SAR echo simulator detects a radar pulse synchronous signal and a coordinate reconstruction mark is invalid, coordinate reconstruction is carried out to establish a periodic geographic coordinate system which takes the center of a current imaging subarea as an origin and three-axis pointing as north, sky and east; namely, origin of coordinates O 1 Coordinate axis O for the center of the current subregion 1 X t North, coordinate axis O 1 Y t Point to the sky, coordinate axis O 1 Z t Can be determined by right hand rules;
FIG. 3 is a diagram showing a coordinate system periodic reconstruction of an aircraft SAR multi-subarea imaging radio frequency simulation method; o (O) 1 For the true flight position of the aircraft is o t1 The coordinate position of the center of the current subarea; the pitch angle alpha and the azimuth angle beta of the radar beam center are obtained by calculating the SAR of the aircraft according to the inertial navigation sensing track (with error) at the current moment and the center of the current subarea, and are the internal calculation results of the SAR, and detailed description is omitted here; o (o) m1 For the true flight position of the aircraft is o t1 And calculating the coordinate position of the obtained radar beam ground irradiation center according to the pitch angle and the azimuth angle of the radar beam center.
Calculating the coordinate position of the aircraft in a periodic geographic coordinate system; setting the coordinate reconstruction mark to be valid; the coordinate reconstruction flag is set to be invalid when the initial state and the previously reconstructed coordinate system are revoked.
More specifically, in determining the coordinates o of the aircraft in the periodic geographic coordinate system t1 In the time-course of which the first and second contact surfaces,
according to the longitude and latitude high coordinates of the aircraft
Figure BDA0004116459620000081
And the longitude and latitude height of the center of the subarea->
Figure BDA0004116459620000082
Calculating to obtain the coordinate o of the aircraft in the periodic geographic coordinate system t1 ：
Figure BDA0004116459620000083
wherein ,
Figure BDA0004116459620000084
(X, Y, Z) is the coordinates of the aircraft in the geocentric coordinate system;
Figure BDA0004116459620000085
(X 0 ,Y 0 ,Z 0 ) Coordinates of the center point of the subarea in a geocentric coordinate system:
Figure BDA0004116459620000091
R e for the circle radius of the mortise, e is the first eccentricity of the earth.
Step S202, correcting the ground center point of the radar beam; correcting a beam center point according to the pitch angle and the azimuth angle of the radar beam center and the position of the aircraft to obtain the coordinate of the beam center in a fixed Gaussian coordinate system;
more specifically, the radar beam ground center point correction includes:
1) According to the central pitch angle of radar beams α1 And azimuth angle beta 1 Calculating to obtain a beam center o m1 Coordinates in a periodic geographical coordinate system
Figure BDA0004116459620000092
Beam center o m1 Coordinates in a periodic geographical coordinate system
Figure BDA0004116459620000093
Figure BDA0004116459620000094
wherein ,α1 The horizontal direction is 0 DEG, the upward direction is positive, beta 1 North is 0 deg., and counterclockwise is positive.
2) According to the subarea center o 1 Longitude and latitude of (a)
Figure BDA0004116459620000095
Longitude and latitude of scene center O>
Figure BDA0004116459620000096
Calculating to obtain a subarea center o 1 The coordinates in the fixed Gaussian coordinate system OXZ are +.>
Figure BDA0004116459620000097
In the process of calculating the subarea center o 1 In a fixed Gaussian coordinate system OXZ as
Figure BDA0004116459620000098
In this case, the existing coordinate conversion method may be adopted, so that the protection scope of the present invention is not affected, and the specific coordinate conversion method is not described herein.
3) According to the subarea center o 1 In a fixed Gaussian coordinate system, the coordinates and the beam center o m1 The beam center o after the correction of the coordinates in the periodic geographic coordinate system m1 Coordinates in a fixed Gaussian coordinate system
Figure BDA0004116459620000099
Specifically, the beam center o m1 Coordinates in a fixed Gaussian coordinate system
Figure BDA0004116459620000101
Can be approximated as:
Figure BDA0004116459620000102
step S203, switching subareas on line; according to the corrected radar beam ground center point, the beam irradiation area is switched on line, and the datum diagram data of the subareas in the radar beam irradiation range are obtained;
specifically, the subarea online switching process includes:
1) The baseband processing unit of the SAR imaging echo simulator judges that the coordinate reconstruction mark is valid;
2) According to the Gaussian coordinate of the beam center
Figure BDA0004116459620000103
Reference map resolution (delta) X ,δ Z ) Index value +.>
Figure BDA0004116459620000104
/>
3) According to the index value
Figure BDA0004116459620000105
Acquiring reference image data in the radar beam irradiation range in real time by combining the number of pixels in the subarea;
the reference map data includes scattering coefficients, random phases, and position coordinates of each pixel of the beam irradiation region sub-region.
Wherein the scattering coefficient of the kth pixel is A k The method comprises the steps of carrying out a first treatment on the surface of the Amplitude of echo corresponding to the kth pixel; the coordinates of the kth pixel are:
Figure BDA0004116459620000106
wherein ,(krw ，k cl ) For the pixel offset of the kth pixel relative to the beam center, k rw The pixel offset in the X-axis, k cl For the pixel offset in the Z-axis, H k(cl,rw) Is the coordinate of the kth pixel on the Y-axis.
Step S204, scene transfer function calculation; extracting the datum map data and the aircraft position parameters at the current PRT moment, and calculating a sub-region scene transfer function;
specifically, the scene transfer function calculation process includes:
1) The simulator recursively processes the aircraft position according to the clock cycle to obtain the aircraft position;
the simulator recursively processes the aircraft position according to the clock period, and a recursion formula is as follows:
Figure BDA0004116459620000111
2) Calculating pixel by pixel to perform slant distance R between pixel and aircraft k And delay t k ；
Figure BDA0004116459620000112
As shown in fig. 4, a schematic diagram of calculation of the slant distance of the sub-area pixels is shown.
3) Calculating a phase value introduced by the distance;
4) Carrying out phase modulation and scattering coefficient amplitude weighting on each pixel;
5) And coherently superposing pixels in the same range gate to obtain the sub-region scene transfer function.
Specifically, t n The sub-zone scene transfer function of time:
Figure BDA0004116459620000113
m is the number of pixels falling into the range gate, A k 、R k 、t k Divide phi k Respectively representing the amplitude, distance, delay and random phase of the kth pixel echo in the range gate, T s Sampling period as system function; θ is the wavelength of the radar signal.
Step S205, SAR echo generation; performing time-frequency domain transformation according to the radar time domain original baseband signal and the sub-region scene transfer function to obtain a scene echo of each radar PRT signal;
specifically, after down-conversion and AD conversion of the radar radio frequency excitation signal, a time domain original baseband signal is generated, FFT is respectively carried out on the signal and a scene transfer function, frequency domain multiplication is carried out, IFFT is carried out, and then a scene echo of each radar PRT signal is obtained.
Step S206, the periodic coordinate system is cancelled; when the radar pulse synchronizing signal is detected to disappear, the primary imaging is finished, the coordinate reconstruction mark is set to be invalid, and the periodic coordinate system is cancelled.
In step S3, steps S201 to S206 are repeatedly performed to complete the SAR echo real-time generation of all the subregions.
Another embodiment of the invention discloses a system for simulating SAR multi-subarea imaging and radio frequency in coordinate system periodic reconstruction, which is shown in fig. 5 and comprises a simulator, SAR, bus fast lifting equipment and SAR echo simulator;
the simulation machine carries out track calculation in real time, and sends the longitude and latitude height, speed and acceleration of the aircraft to the SAR echo simulator according to the communication period, wherein the longitude and latitude height and the subarea number of the subarea center are sent to the SAR echo simulator;
the SAR injects a radio frequency excitation signal, a clock signal and a pulse synchronization signal into an SAR echo simulator through a radio frequency cable;
the bus quick-lifting device monitors communication data packets in real time and sends the beam pointing angle of SAR to the SAR echo simulator;
the echo simulator executes the SAR multi-subarea imaging radio frequency simulation method for periodically reconstructing the coordinate system in the embodiment to generate simulated SAR echo signals, and radiates the SAR echo signals into a microwave darkroom through an antenna array and a feed system for SAR scene matching guidance radio frequency semi-physical simulation.
In summary, the SAR multi-subarea imaging radio frequency simulation method and system for periodic reconstruction of the coordinate system disclosed by the embodiment of the invention reduce the relative position error caused by the influence of the curvature of the earth when the conventional method performs the slope distance calculation under the fixed reference system, greatly simplify the processes of the SAR multi-subarea irradiation range calculation and echo signal generation of an aircraft, simultaneously, perform the radar beam ground center point calculation according to the actual radar position and the actual radar beam direction in the radar beam irradiation range calculation process, ensure the consistency of simulation and actual scenes, and improve the accuracy and test efficiency of the SAR scene matching guidance radio frequency semi-physical simulation of the aircraft.
The present invention is not limited to the above-mentioned embodiments, and any changes or substitutions that can be easily understood by those skilled in the art within the technical scope of the present invention are intended to be included in the scope of the present invention.

Claims (10)

1. The SAR multi-subarea imaging radio frequency simulation method for periodically reconstructing a coordinate system is characterized by comprising the following steps of:
the SAR echo simulator receives the longitude and latitude height, the speed and the acceleration of the aircraft simulated by the simulator according to the communication period, and the longitude and latitude height of the center of the subarea to be imaged of the aircraft-carried SAR, receives the radio frequency excitation signal, the clock signal and the radar pulse synchronous signal of the SAR through the radio frequency cable, and receives the beam pointing angle of the SAR sent by the bus quick lifting device;
the SAR echo simulator carries out SAR echo simulation of a single subarea through coordinate system reconstruction, radar beam ground center point correction, subarea on-line switching, scene transfer function calculation, SAR echo generation and periodic coordinate system withdrawal, and generates SAR echo of the single subarea in real time;
by adopting the SAR echo simulation method of a single subarea, the SAR echo simulator generates the SAR echoes of all subareas in the simulation process in real time.
2. The method of simulating a multi-subarea imaging radio frequency of claim 1, wherein the coordinate system reconstruction in the SAR echo simulation of a single subarea by the SAR echo simulator comprises:
when the radar pulse synchronous signal is detected and the coordinate reconstruction mark is invalid, performing coordinate reconstruction to establish a periodic geographic coordinate system which takes the center of the current imaging subarea as an origin and three-axis pointing as north, sky and east, and calculating the coordinate position of the aircraft in the periodic geographic coordinate system; setting the coordinate reconstruction mark to be valid; the coordinate reconstruction flag is set to be invalid in the initial state and when the coordinate system previously reconstructed is revoked.
3. The SAR multi-subarea imaging radio frequency simulation method of claim 2, wherein the method is based on longitude and latitude high coordinates of an aircraft
Figure FDA0004116459610000011
And longitude and latitude high coordinates of the center of the subarea +.>
Figure FDA0004116459610000012
Calculating to obtain the coordinate o of the aircraft in the periodic geographic coordinate system t1 ：
Figure FDA0004116459610000013
wherein ,
Figure FDA0004116459610000021
(X, Y, Z) is the coordinates of the aircraft in the geocentric coordinate system;
Figure FDA0004116459610000022
(X 0 ,Y 0 ,Z 0 ) Coordinates of the center point of the subarea in a geocentric coordinate system:
Figure FDA0004116459610000023
R e for the circle radius of the mortise, e is the first eccentricity of the earth.
4. The method of simulating the rf imaging of multiple sub-areas of SAR according to claim 1, wherein said modifying the ground center point of the radar beam in the SAR echo simulation of a single sub-area by the SAR echo simulator comprises:
1) According to the radar beam center pitch angle alpha 1 And azimuth angle beta 1 Calculating to obtain a beam center o m1 Coordinates in a periodic geographical coordinate system
Figure FDA0004116459610000024
2) According to the subarea center o 1 Longitude and latitude of (a)
Figure FDA0004116459610000025
Longitude and latitude of scene center O>
Figure FDA0004116459610000026
Calculating to obtain a subarea center o 1 The coordinates in the fixed Gaussian coordinate system OXZ are +.>
Figure FDA0004116459610000027
3) According to the subarea center o 1 In a fixed Gaussian coordinate system, the coordinates and the beam center o m1 The beam center o after the correction of the coordinates in the periodic geographic coordinate system m1 Coordinates in a fixed Gaussian coordinate system
Figure FDA0004116459610000028
5. The SAR multi-subarea imaging radio frequency simulation method of claim 4, wherein,
beam center o m1 Coordinates in a periodic geographical coordinate system
Figure FDA0004116459610000029
Figure FDA0004116459610000031
wherein ,α1 The horizontal direction is 0 DEG, the upward direction is positive, beta 1 North is 0 degrees, and anticlockwise is positive;
beam center o m1 Coordinates in a fixed Gaussian coordinate system
Figure FDA0004116459610000032
The approximate characterization is:
Figure FDA0004116459610000033
6. the method for simulating the SAR multi-subarea imaging radio frequency according to claim 1, wherein the SAR echo simulator performs online switching of subareas in SAR echo simulation of a single subarea to online switch beam irradiation areas according to the corrected radar beam ground center point to obtain reference map data of subareas in a radar beam irradiation range; the method specifically comprises the following steps:
1) The SAR imaging echo simulator judges that the coordinate reconstruction mark is valid;
2) According to the Gaussian coordinate of the beam center
Figure FDA0004116459610000034
Reference map resolution (delta) X ,δ Z ) Index value +.>
Figure FDA0004116459610000035
3) Acquiring reference image data in the radar beam irradiation range in real time according to the index value and the number of sub-area pixels;
the reference map data includes scattering coefficients, random phases, and position coordinates of each pixel of the beam irradiation region sub-region.
7. The method of simulating a multi-subarea imaging radio frequency of claim 6, wherein the step of performing the scene transfer function calculation in the single subarea SAR echo simulation by the SAR echo simulator comprises:
1) The simulator recursively processes the aircraft position according to the clock cycle to obtain the aircraft position;
2) Calculating the slant distance value of the pixels and the aircraft pixel by pixel;
3) Calculating a phase value introduced by the distance;
4) Carrying out phase modulation and scattering coefficient amplitude weighting on each pixel;
5) And coherently superposing pixels in the same range gate to obtain the sub-region scene transfer function.
8. The SAR multi-subarea imaging radio frequency simulation method of claim 7, wherein,
the kth pixel and the slant distance P of the aircraft k ：
Figure FDA0004116459610000041
t n The sub-zone scene transfer function of time:
Figure FDA0004116459610000042
m is the number of pixels falling into the range gate, A k 、R k 、t k Divide phi k Respectively representing the amplitude, distance, delay and random phase of the kth pixel echo in the range gate, T s Sampling period as system function; k (k) rw The pixel offset in the X-axis, k cl For the pixel offset in the Z-axis, H k(cl,rw) And lambda is the wavelength of the radar signal, which is the coordinate of the kth pixel on the Y axis.
9. The SAR multi-subregion imaging radio frequency simulation method of claim 1, wherein the SAR echo simulator performs the SAR echo generation in the SAR echo simulation of the single subregion comprising: after down-conversion and AD conversion of radar radio frequency excitation signals, time domain original baseband signals are generated, FFT is respectively carried out on the signals and scene transfer functions, frequency domain multiplication is carried out, IFFT is carried out, and scene echo of each radar PRT signal is obtained.
10. The SAR multi-subarea imaging radio frequency simulation system for the periodic reconstruction of the coordinate system is characterized by comprising a simulator, SAR, bus quick-lifting equipment, an SAR echo simulator, an antenna array and a feed system;
the simulation machine carries out track calculation in real time, and sends the longitude and latitude height, speed and acceleration of the aircraft and the longitude and latitude height of the center of a subarea of an area to be imaged of the SAR carried by the aircraft to the SAR echo simulator according to a communication period;
the SAR injects a radio frequency excitation signal, a clock signal and a pulse synchronization signal into an SAR echo simulator through a radio frequency cable;
the bus quick-lifting device monitors communication data packets in real time and sends the beam pointing angle of SAR to the SAR echo simulator;
the echo simulator executes the SAR multi-subarea imaging radio frequency simulation method for periodically reconstructing the coordinate system according to any one of claims 1-9 to generate simulated SAR echo signals, and radiates the SAR echo signals into a microwave darkroom through an antenna array and a feed system for SAR scene matching guidance radio frequency semi-physical simulation.
CN202310220599.9A 2023-03-08 2023-03-08 SAR multi-subarea imaging radio frequency simulation method and system for periodic reconstruction of coordinate system Pending CN116224238A (en)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN116430346A (en) * 2023-06-13 2023-07-14 西安羚控电子科技有限公司 SAR image pixel point longitude and latitude calculation method and device

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN116430346A (en) * 2023-06-13 2023-07-14 西安羚控电子科技有限公司 SAR image pixel point longitude and latitude calculation method and device
CN116430346B (en) * 2023-06-13 2023-10-17 西安羚控电子科技有限公司 SAR image pixel point longitude and latitude calculation method and device

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