CN114252855B - Simultaneous SAR/GMT echo simulation method and system thereof - Google Patents
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Abstract
The invention discloses a simultaneous SAR/GMT echo simulation method and a system thereof, comprising the following steps: setting test parameters in an upper computer; importing test parameters, operating an SAR/GMT distributed scattering surface source parallel algorithm under a GPU architecture, obtaining independent and combined SAR/GMT one-dimensional range profile data and echo data and sending the data to a storage board; the upper computer outputs test parameters including echo types to the real-time control system; the signal processing board card selects and calls data in the storage board according to the echo type and outputs the data through the optical fiber network; and according to the echo type of the test parameter, the real-time control system controls the signal processing board card to process the one-dimensional range profile data or the echo data, then the DUC and DA conversion is carried out, and the processed data is output through the radio frequency upper variation system. The invention adopts a GPU parallel computing architecture, and can simulate SAR radar echo signals synthesized by SAR/GMT simultaneously in a single channel.
Description
Technical Field
The invention relates to the technical field of radar performance testing, in particular to a simultaneous SAR/GMT echo simulation method and a system thereof.
Background
Synthetic Aperture Radar (SAR) is a Radar system that uses pulse compression techniques and synthetic Aperture principles to obtain two-dimensional (distance and azimuth dimensions) high resolution. Compared with an optical radar system, the optical radar system is not influenced by weather and covering, can penetrate through cloud layers and vegetation to detect ground object information, and is the most important and main means of the ground object detection equipment. The method is more and more widely applied to the civil and military fields for decades and is the key research direction of radar technology and signal processing technology in various countries.
In a conventional SAR image, a Ground Moving Target (GMT) has phenomena of distance walking, defocusing, azimuth position offset and the like, and the GMT is often superimposed on a SAR image of a static scene only in a fuzzy manner. The SAR/GMT echo simulation system adopts a GPU architecture, the SAR scene and the GMT are separated, the echoes of the SAR scene and the GMT are simultaneously calculated by using a scattering surface element calculation method, and finally the SAR scene and the distributed GMT echo are synthesized to obtain the total SAR echo. Compared with a conventional SAR echo simulation system, the SAR/GMT echo simulation system has wider application scenes, reduces hardware resources compared with a multi-channel GMT echo simulation system, and greatly saves equipment cost.
Meanwhile, the SAR/GMT echo simulation system is an important device for testing the environment perception performance of the radar, and particularly has important significance for the radar with Ground Moving Target Indication (GMTI) function. The echo simulation system is mainly used for SAR/GMTI radars and is used for detecting performance tests of displaying the position of a moving target on an SAR image, detecting the number of the moving targets, measuring the speed of the moving target, positioning the moving target and the like. However, the calculated amount of SAR echo signal simulation is very large, and the calculated amount is multiplied by the echo signal simulation of a plurality of moving targets, so that the performance test requirement of the SAR/GMTI radar cannot be met.
Disclosure of Invention
The purpose of the invention is as follows: the invention aims to provide a simultaneous SAR/GMT echo simulation method and a system thereof aiming at the defects of the prior art, a GPU parallel computing architecture is adopted, SAR radar echo signals synthesized by simultaneous SAR/GMT can be simulated in a single channel, the application scene is wider, and the equipment cost is greatly saved.
The technical scheme is as follows: the invention provides a simultaneous SAR/GMT echo simulation method, which comprises the following steps:
step 1: setting test parameters in an upper computer;
step 2: importing test parameters, and operating a SAR/GMT distributed scattering surface source parallel algorithm under a GPU architecture to obtain independent and combined SAR/GMT one-dimensional range profile data and echo data;
and step 3: packing and sending the test parameters, the corresponding one-dimensional range profile data and the corresponding echo data to a storage board;
and 4, step 4: the upper computer outputs test parameters including echo types to the real-time control system, and the real-time control system controls the signal processing board card in real time according to the test parameters;
and 5: the signal processing board card selects and calls data in the storage board according to the echo type, and the selected data are packaged and then output through an optical fiber network;
step 6: if the echo type of the test parameter is direct playback, the real-time control system controls the signal processing board card to receive the radar reference signal, performs characteristic modulation on one-dimensional range profile data transmitted by the optical fiber network, performs digital up-conversion and digital analog conversion, and outputs the data after being processed by the radio frequency up-conversion system;
and 7: if the echo type of the test parameter is convolution playback, the real-time control system controls the signal processing board card to receive echo data transmitted by the optical fiber network, then digital up-conversion and digital analog conversion are carried out on the echo data, and the echo data are processed by the radio frequency up-conversion system and then output.
Further perfecting the technical scheme, the radar reference signal is generated from the outside, processed by a radio frequency down-conversion system and then input to the signal processing board card; or the real-time control system outputs waveform information to the signal processing board card according to the test parameters, and the signal processing board card calculates the baseband waveform of the waveform information in real time to generate the radar reference signal.
Further, the test parameters in the step 1 include SAR scene parameters, the number of GMTs, the initial geometric relationship between the GMTs and the SAR scene, and radar position initial information;
the SAR/GMT distributed scattering surface source parallel algorithm under the GPU architecture in the step 2 comprises the following steps:
step A: reading test parameters set by an upper computer, importing a radar GPS track analysis file, importing an SAR scene backscattering image, importing a GMT backscattering image, and designing a GMT track;
b, performing interpolation processing on the GMT backscattering image according to a preset SAR scene, a GMT track range and radar signal parameters to enable the GMT backscattering image to be fused with the pixel proportion of the SAR scene;
c, adjusting the strength and the phase of the SAR scene and the GMT backscattering coefficient to enable the signal-to-clutter ratio of the target to meet the test requirement;
d, moving the radar track file, the SAR/GMT backscattering data and the GMT track file from the CPU to a GPU video memory;
step E, setting the size of GRID according to the number of scattering surface sources of the SAR scene and the GMT, and independently and discretely distributing the GRID and the GMT to a calculation kernel of a GPU:
step F, respectively carrying out vector parallel computation on the SAR and each GMT scattering surface source simultaneously by using the parallel computation performance of the GPU, computing the amplitude phase information of all the scattering surface sources of the current pulse, and judging the distance gate where the scattering surface sources are located;
step G, accumulating the amplitude phase information of all scattering surface sources of the SAR scene of the current pulse to obtain one-dimensional range profile information of the SAR scene, simultaneously accumulating the amplitude phase information of all scattering surface sources of each GMT of the current pulse to obtain one-dimensional range profile information of each GMT, and combining the one-dimensional range profile information of the SAR/GMT of the current pulse;
step H: performing convolution processing on the one-dimensional range profile data generated in the step G according to the imported test setting, and generating and storing SAR scene echo data of the current pulse, echo data of each GMT and combined SAR/GMT echo data;
step I: and F-H are repeated until the one-dimensional range profile data and the echo data of all the pulses are calculated.
Further, the step E includes:
step E-a: calculating two-dimensional resolution according to the radar track initial position, radar beam irradiation parameters and radar signal parameters, calculating the size of the beam irradiation area, and calculating the initial resolution according to half of the resolutionDirection of beam irradiation
Number of scattering surface sources in the azimuth direction
；
Step E-b: according to
、
、
The size of the scattering plane source and the limitation of GPU computing resources, the number of threads of parallel computing is set, the computing of the scattering plane source is distributed on the computing cores of the GPU as much as possible,
representing the cumulative number of pulses for a single aperture of the synthetic aperture radar.
Further, the
、
The calculation process of (c) is as follows:
wherein, the first and the second end of the pipe are connected with each other,
representing radar arrival beamingsThe action distance of the shot center, H represents the height of the radar from the ground,
、
respectively represent the azimuth beam width and the range beam width,
is the beam down dip angle;
、
respectively representing the sizes of the azimuth direction scattering surface source and the distance scattering surface source, the calculation process is as follows
Wherein the content of the first and second substances,
and
the resolutions of the azimuth direction and the distance direction are respectively expressed, and the calculation process is as follows
Wherein, the first and the second end of the pipe are connected with each other,
is representative of the speed of flight of the radar platform,
which represents the operating frequency of the radar transmitted signal,
represents the unit of the speed of light in m/s,
represents the bandwidth of the radar emission signal;
selecting
、
As the size of the scattering surface source:
the number of accumulated pulses of a single aperture of the synthetic aperture radar in the step E-b
The calculation process is as follows:
wherein the content of the first and second substances,
representing the pulse repetition period.
Further, the step F includes:
for the SAR scattering surface source, the input parameters for SAR scene calculation include scene backscattering coefficient, radar track data, radar beam irradiation parameter and position coordinate of the scene scattering surface source, and the calculation formula is as follows:
establishing a north-east rectangular coordinate system by using the beam irradiation center at the first track position of the radar, wherein,
representing the amplitude phase information of the SAR of the p pulse north to the nth day to the a east scattering surface source;
representing the backscatter coefficients of the p pulse north to the nth day to the a east to the e scattering surface source;
represents the wavelength of the radar emission signal;
、
、
respectively representing north, sky and east positions of the p pulse moment of the radar platform;
、
、
respectively representing the position coordinates of the n th day direction, the a th east direction and the e th scattering surface source in the north direction in the SAR scene, wherein j refers to an imaginary part in complex operation;
for the GMT scattering surface source, the input parameters for GMT calculation include scene backscattering coefficient, radar track data, radar beam irradiation parameter, position coordinates of the GMT interpolated scattering surface source, and the calculation formula of each GMT track is as follows:
wherein the content of the first and second substances,
representing the source amplitude phase information of the nth north direction scattering surface of the ith pulse GMT to the e th east direction scattering surface of the ith pulse;
representing the backscatter coefficients of the nth north-oriented day of the ith pulse GMT to the (a) th east-oriented scattering surface source;
、
、
respectively representing the position coordinates of the nth north-middle direction, the eastern direction and the e-th scattering surface source of the ith GMT, and the three position information is obtained by interpolation according to the target motion trail.
Further, the one-dimensional range profile information process of the SAR/GMT of the pre-pulse combined in step G is as follows:
further, the SAR scene echo data of the current pulse in the step H
Echo data per GMT
And combined SAR/GMT echo data
Respectively as follows:
wherein, LFM is radar reference signal.
The calculation process of the step I is as follows:
the simulation system for realizing the simultaneous SAR/GMT echo simulation method comprises an upper computer, a real-time control system, a GPU acceleration simulation unit, a storage board, a radio frequency upper variational system, a radio frequency lower variational system and a signal processing board card, wherein the signal processing board card is respectively connected with the real-time control system, the radio frequency upper variational system, the radio frequency lower variational system and the storage board; the upper computer is used for setting test parameters; the GPU acceleration simulation unit is used for receiving test parameters, calling the test parameters, calculating to obtain independent and combined SAR/GMT one-dimensional range profile data and echo data and storing the data to the storage board; the real-time control system is used for receiving test parameters output by an upper computer and outputting control information to the signal processing board card;
the signal processing board card receives an external radar reference signal input by the radio frequency down-conversion system or generates a corresponding radar reference signal according to control information output by the real-time control system, reads one-dimensional range profile data and echo data of the storage card, and performs output selection according to echo types: the one-dimensional range profile data and the echo data are subjected to data packaging and then are sent to a designated terminal through an optical fiber network; the echo data are directly played back, read in real time, subjected to digital up-conversion and digital-analog conversion, processed by the radio frequency up-conversion system and then output; and (4) convolution playback, namely performing characteristic modulation on the one-dimensional range profile data, performing digital up-conversion and digital-analog conversion, and outputting the data after being processed by the radio frequency up-conversion system.
In the invention, preset test parameters are firstly placed in a data management center of an upper computer, a GPU vector parallel computation program calls an interface file to perform parallel accelerated computation on SAR scene, GMT data and track file data to obtain independent and combined SAR/GMT one-dimensional range profile data and echo data, the data are transmitted to a storage board card through an optical fiber interface/gigabit Ethernet, when a test is started, the data are transmitted to a signal processing board card through a PCIe bus, echo data are selected to perform DUC and DA processing on the data or one-dimensional range profile data are selected to perform target characteristic modulation on the echo data, then DUC and DA are performed on the echo, and finally, the SAR/GMT echo signal is generated by performing up-conversion.
Has the advantages that: compared with the prior art, the invention has the advantages that: the echo simulation system provided by the invention for the SAR/GMTI radar performance test requirement adopts the GPU parallel computing architecture, can simulate SAR radar echo signals synthesized by SAR/GMT simultaneously in a single channel, has wider application scenes, reduces hardware resources compared with a multi-channel GMT echo simulation system, and greatly saves equipment cost; the system adopts a distributed scattering surface source parallel algorithm on a GPU platform to greatly improve the speed of SAR/GMT echo simulation at the same time, separates moving target simulation from SAR scene simulation, adopts a scene target separation type processing method to calculate data in an off-line mode and then simulate echo signals in a real-time playback mode, reduces the calculation amount of parallel calculation and is beneficial to system expansion.
Considering that the possibility of switching the working modes exists at different moments of the track in the test process, the data in different modes at different moments are required to be prepared when the data are calculated off line, so that the played back data can be switched according to instructions in the test. The system adopts a GPU parallel computing architecture to compute one-dimensional range profile data/echo data of an SAR scene and GMT, adopts a real-time operating system of sysBios to carry out optical fiber communication with an upper computer, and adopts a PCIe high-speed transmission interface to carry out data transmission with a signal processing board card and a storage board card. The method is beneficial to controlling the number of moving targets, switching the radar working mode in real time and adapting to any radar transmitting signal waveform, so that the echo simulation can adapt to the SAR/GMTI radar performance test requirements, and the calculation acceleration ratio of one-dimensional range profile can reach the third power order of 10.
Drawings
FIG. 1 is a block diagram of a simultaneous SAR/GMT echo simulation system;
FIG. 2 is a GPU-based SAR/GMT distributed scattering surface source parallel algorithm computation flow chart;
FIG. 3 is a SAR scene image;
FIG. 4 is a GMT image and motion trajectory;
FIG. 5 is a simultaneous SAR/GMT composite image at a time.
Detailed Description
The technical solution of the present invention is described in detail below with reference to the accompanying drawings, but the scope of the present invention is not limited to the embodiments.
As shown in fig. 1, in the simultaneous SAR/GMT echo simulation system provided by the present invention, preset test parameters are placed in a data management center of an upper computer, a GPU vector parallel computation program calls an interface file to perform parallel accelerated computation on a SAR scene, GMT data, track file data and a scattering element, so as to obtain independent and combined SAR/GMT one-dimensional range profile data and echo data, and the several sets of data are transmitted to a storage board card through an optical fiber interface/gigabit ethernet. And when the test is started, transmitting data to the FPGA signal processing board card through the PCIe bus. The signal processing board card functions include: and performing characteristic modulation on the one-dimensional range profile data according to the radar reference signal, replaying target echo data in real time, and performing DUC and DA conversion on the echo data. The echo type output selection is set by an upper computer test, sent to a real-time control system for receiving, and then controlled to be forwarded to a signal processing board card for implementation. The radar reference signal is input externally and is not generated by the system, and when the radar reference signal is not input externally, the upper computer sets radar waveform parameters and sends the radar waveform parameters to the real-time control system to be simulated by the signal processing board card to generate an ideal radar reference signal to replace the external radar reference signal.
The signal processing board card selects echo data according to test setting, and the echo data comprises two types: 1-echo data is directly played back, and if the data is subjected to digital up-conversion and digital-to-analog conversion (DUC + DA) under the set condition, an intermediate frequency echo signal can be output; and 2-convolution playback, namely selecting one-dimensional range profile data under the setting condition to perform target characteristic modulation, then performing DUC + DA processing to output an intermediate frequency echo signal, and finally performing up-conversion to generate an SAR/GMT echo signal.
The simulation method based on the simultaneous SAR/GMT echo simulation system comprises the following steps:
step 1: setting a test initial state in an upper computer: SAR scene parameters, the number of GMTs, the initial geometric relationship between the GMT and the SAR scene, radar position initial information,
step 2: importing test parameters, operating a SAR/GMT distributed scattering surface source parallel algorithm under a GPU architecture, and generating a plurality of groups of SAR/GMT combined one-dimensional range profile data/echo data to be tested, wherein the method mainly comprises the following steps:
A. reading test parameters of an upper computer, importing a radar GPS track analysis file, importing an SAR scene backscattering image, importing a GMT backscattering image, and designing a GMT track;
B. performing interpolation processing on the GMT backscattering image according to preset SAR scene parameters, a GMT track range and radar signal parameters to enable the GMT backscattering image to be fused with the pixel proportion of the SAR scene;
C. adjusting the strength and the phase of the backscattering coefficient of the SAR scene and the GMT to enable the signal-to-noise ratio of the GMT to meet the test requirement;
D. moving the radar track file, SAR/GMT backscattering data and GMT track file from the CPU to the GPU video memory;
E. the SAR scene and the GMT are set with the size of GRID according to the number of scattering surface sources of the SAR scene and the GMT, and are independently and discretely distributed to a calculation kernel of a GPU:
F. the number of scattering surface sources of an SAR scene is 4096 multiplied by 4096, the number of GMTs is 2, the number of scattering surface sources after GMT interpolation is 32 multiplied by 32, the number of accumulative azimuth pulses is 4096, and the pulse repetition period is 1000 us. The graphics card of RTX A2000 series of NVIDIA company is selected, the CUDA core number is 3328, and the maximum number of threads running on each SM is 256.
And respectively and independently loading the scattering surface source of the SAR scene and the scattering surface source of each GMT to different GPU computing cores, and simultaneously and concurrently computing the one-dimensional range profile of all the surface sources. Theoretically, under the condition that the GPU is not limited by shared memory, the GPU can accelerate the algorithm by corresponding amount of controllable threads which are executed concurrently, but because the computation magnitude of the SAR scene is 4096 × 4096 × 4096, the threads which can be executed concurrently are obviously not enough, the computation of the scattering surface source is automatically distributed into the concurrent threads according to the distributed scattering surface source parallel algorithm, and the computation flow of the algorithm is as follows:
a. calculating two-dimensional resolution according to the radar track initial position, the radar beam irradiation parameters and the radar signal parameters, calculating the size of a beam irradiation area, and calculating the number of scattering surface sources in the distance direction and the azimuth direction of the initial beam irradiation area according to half of the resolution:
wherein
、
Respectively representing the number of azimuth and range scatter sources,
、
respectively represent the azimuth beam width and the range beam width,
、
respectively, the dimensions of the azimuthal and range scattering surface sources, in m,
representing the range of the radar to the center of beam illumination,
indicating the height of the radar from the ground,
is the beam dip angle.
In theory, it is possible to use,
wherein the content of the first and second substances,
and
resolution of the representation of the azimuth and range directions,
representing the radar platform flight speed (the radar platform flight direction is the azimuth direction),
wherein
Represents the unit of the speed of light in m/s,
which represents the operating frequency of the radar transmitted signal,
bandwidth of a radar emission signal) is represented, and in order to coordinate scene proportion and meet observation visual effect in the actual calculation process, selection is carried out
、
As the size of the scattering surface source:
b. according to
、
、
The size of (representing the number of accumulated pulses of a single aperture of the synthetic aperture radar), the limitation of GPU computing resources, the number of threads (which must be a power of 2 and is more than 128) of parallel computing is set, and the computation of the scattering plane source is distributed on the computing cores of the GPUs as many as possible;
c. And (3) respectively and simultaneously carrying out vector parallel computation on the scattering surface sources of the SAR and the GMT by utilizing the parallel computation performance of the GPU, computing the amplitude phase characteristic information of all the scattering surface sources of the current pulse, and judging the range gates where the scattering surface sources are positioned:
d. as shown in fig. 2, for the SAR scattering surface source, the input parameters for calculating the SAR scene include a scene backscattering coefficient, radar track data, radar beam irradiation parameters, and position coordinates of the scene scattering surface source, and the calculation formula is as follows:
j in the formula represents the imaginary part in the complex number, and a north-east rectangular coordinate system is established by using the beam irradiation center at the first track position of the radar, wherein,
representing the amplitude phase information of the SAR of the p pulse north to the nth day to the a east scattering surface source;
representing the backscatter coefficients of the p pulse north to the nth day to the a east to the e scattering surface source;
represents the wavelength of the radar emission signal;
、
、
respectively representing north, sky and east positions of the p pulse moment of the radar platform;
、
、
respectively representing the position coordinates of the n th day direction, the a th east direction and the e th scattering surface source in the north direction in the SAR scene;
for the GMT scattering surface source, input parameters for GMT calculation include scene backscattering coefficient, radar track data, radar beam irradiation parameters, position coordinates of the scattering surface source after target interpolation and track of each GMT, and the calculation formula is as follows:
G. accumulating the amplitude phase information of all scattering surface sources of the SAR scene of the current pulse to obtain one-dimensional range profile information of the SAR scene, and simultaneously accumulating the amplitude phase information of all scattering surface sources of all GMTs of the current pulse to obtain one-dimensional range profile information of each GMT; merging one-dimensional range profile information of SAR/GMT of the current pulse:
H. performing convolution processing on the one-dimensional range profile data generated in the last step according to the imported test setting, and generating and storing SAR scene echo data of the current pulse, echo data of each GMT and combined SAR/GMT echo data:
wherein, LFM is radar reference signal.
I. Repeating the steps F-H until the one-dimensional range profile data and the echo data of all the pulses are calculated;
and step 3: packing and sending the test parameters and the corresponding one-dimensional range profile data/echo data to a storage board;
and 4, step 4: the upper computer outputs the test parameters to the real-time control system, and the real-time control system controls the signal processing board card in real time according to the test parameters;
and 5: in a sysBios real-time control system, outputting, selecting and calling one-dimensional range profile data/echo simulation data in a storage board according to the echo type of a test parameter, and sending the data to a signal processing board card, wherein the signal processing board card packs the data and sends the data to a specified terminal through an optical fiber network;
step 6: the signal processing board card receives an externally input radar reference signal or generates a baseband waveform according to waveform information output by the real-time control system according to a real-time control command of the real-time control system, and then performs running water convolution modulation on the one-dimensional range profile data according to a working mode; or reading the echo data pulse by pulse, and finally performing DUC and DA conversion on the echo data to obtain an intermediate frequency echo signal;
and 7: the intermediate frequency echo signal is injected into the radio frequency up-conversion system, and is subjected to up-conversion, power amplification and other processing to form a simultaneous SAR/GMT radio frequency echo signal, and the simultaneous SAR/GMT radio frequency echo signal is output at a radio frequency end, as shown in FIG. 5.
The invention adopts a distributed scattering surface source parallel algorithm, greatly improves the speed of SAR/GMT echo simulation at the same time, separates moving target simulation from SAR scene simulation, reduces the calculation amount of parallel calculation and is beneficial to system expansion; the SAR echo signal synthesized by SAR/GMT can be simulated in a single channel, the application scene is wider, the hardware resource is reduced compared with a multi-channel GMT echo simulation system, and the equipment cost is greatly saved.
As noted above, while the present invention has been shown and described with reference to certain preferred embodiments, it is not to be construed as limited thereto. Various changes in form and detail may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.
Claims (9)
1. A simultaneous SAR/GMT echo simulation method is characterized by comprising the following steps:
step 1: setting test parameters in an upper computer, wherein the test parameters comprise SAR scene parameters, GMT number, initial geometric relationship between GMT and SAR scene, and radar position initial information;
step 2: importing test parameters, and operating a SAR/GMT distributed scattering surface source parallel algorithm under a GPU architecture to obtain independent and combined SAR/GMT one-dimensional range profile data and echo data;
the SAR/GMT distributed scattering surface source parallel algorithm under the GPU architecture in the step 2 comprises the following steps:
step A: reading test parameters set by an upper computer, importing a radar GPS track analysis file, importing an SAR scene backscattering image, importing a GMT backscattering image, and designing a GMT track;
b, performing interpolation processing on the GMT backscattering image according to a preset SAR scene, a GMT track range and radar signal parameters to enable the GMT backscattering image to be fused with the pixel proportion of the SAR scene;
c, adjusting the strength and the phase of the SAR scene and the GMT backscattering coefficient to enable the signal-to-clutter ratio of the target to meet the test requirement;
d, moving the radar track file, the SAR/GMT backscattering data and the GMT track file from the CPU to a GPU video memory;
step E, setting the size of GRID according to the number of scattering surface sources of the SAR scene and the GMT, and independently and discretely distributing the GRID and the GMT to a calculation kernel of a GPU:
step F, respectively carrying out vector parallel computation on the SAR and each GMT scattering surface source simultaneously by using the parallel computation performance of the GPU, computing the amplitude phase information of all the scattering surface sources of the current pulse, and judging the distance gate where the scattering surface sources are located;
step G, accumulating the amplitude phase information of all scattering surface sources of the SAR scene of the current pulse to obtain one-dimensional range profile information of the SAR scene, simultaneously accumulating the amplitude phase information of all scattering surface sources of each GMT of the current pulse to obtain one-dimensional range profile information of each GMT, and combining the one-dimensional range profile information of the SAR/GMT of the current pulse;
step H: performing convolution processing on the one-dimensional range profile data generated in the step G according to the imported test setting, and generating and storing SAR scene echo data of the current pulse, echo data of each GMT and combined SAR/GMT echo data;
step I, repeating the steps F-H until the one-dimensional range profile data and the echo data of all the pulses are calculated;
and step 3: packing and sending the test parameters, the corresponding one-dimensional range profile data and the corresponding echo data to a storage board;
and 4, step 4: the upper computer outputs test parameters including echo types to the real-time control system, and the real-time control system controls the signal processing board card in real time according to the test parameters;
and 5: the signal processing board card selects and calls data in the storage board according to the echo type, and the selected data are packaged and then output through an optical fiber network;
step 6: if the echo type of the test parameter is direct playback, the real-time control system controls the signal processing board card to receive a radar reference signal, performs characteristic modulation on one-dimensional range profile data transmitted by an optical fiber network, performs digital up-conversion and digital analog conversion, and outputs the data after being processed by the radio frequency up-conversion system;
and 7: and if the echo type of the test parameter is convolution playback, the real-time control system controls the signal processing board card to receive echo data transmitted by the optical fiber network, then digital up-conversion and digital-analog conversion are carried out on the echo data, and the echo data are processed by the radio frequency up-conversion system and then output.
2. The simultaneous SAR/GMT echo simulation method according to claim 1, characterized in that: the radar reference signal is generated from the outside, processed by a radio frequency down-conversion system and then input to the signal processing board card; or the real-time control system outputs waveform information to the signal processing board card according to the test parameters, and the signal processing board card calculates the baseband waveform of the waveform information in real time to generate the radar reference signal.
3. The simultaneous SAR/GMT echo simulation method according to claim 2, characterized in that the step E comprises:
step E-a: according to radar trackCalculating two-dimensional resolution of the initial position, radar beam irradiation parameters and radar signal parameters, calculating the size of the beam irradiation area, and calculating the distance direction of the initial beam irradiation area according to half of the resolution
Number of scattering surface sources in the azimuth direction
；
Step E-b: according to
、
、
The size of the scattering plane source and the limitation of GPU computing resources, the number of threads of parallel computing is set, the computing of the scattering plane source is distributed on the computing cores of the GPU as much as possible,
representing the cumulative number of pulses for a single aperture of the synthetic aperture radar.
4. The simultaneous SAR/GMT echo simulation method of claim 3, characterized in that the method is performed in a time-division multiple access (SAR/GMT) system
、
The calculation process of (2) is as follows:
wherein the content of the first and second substances,
denotes the range of the radar to the center of beam irradiation, H denotes the height of the radar from the ground,
、
respectively represent the azimuth beam width and the range beam width,
is the beam dip angle;
、
respectively representing the sizes of the azimuth direction scattering surface source and the distance scattering surface source, the calculation process is as follows
Wherein the content of the first and second substances,
and
respectively indicating the azimuth direction and the range directionThe resolution of (2) is calculated as follows
Wherein the content of the first and second substances,
is representative of the speed of flight of the radar platform,
which represents the operating frequency of the radar transmitted signal,
which represents the unit of the speed of light m/s,
represents the bandwidth of the radar emission signal;
selecting
、
As the size of the scattering surface source:
said step E-b of accumulating the number of pulses for a single aperture of the synthetic aperture radar
The calculation process is as follows:
wherein the content of the first and second substances,
representing the pulse repetition period.
5. The simultaneous SAR/GMT echo simulation method according to claim 4, characterized in that said step F comprises:
for the SAR scattering surface source, the input parameters for SAR scene calculation include scene backscattering coefficient, radar track data, radar beam irradiation parameter and position coordinate of the scene scattering surface source, and the calculation formula is as follows:
establishing a north-east rectangular coordinate system by using the beam irradiation center at the first track position of the radar, wherein,
representing the amplitude phase information of the SAR of the p pulse north to the nth day to the a east scattering surface source;
representing the backscatter coefficients of the p pulse north to the nth day to the a east to the e scattering surface source;
represents the wavelength of the radar emission signal;
、
、
respectively representing north, sky and east positions of the p pulse moment of the radar platform;
、
、
respectively representing the position coordinates of the n th day direction, the a th east direction and the e th scattering surface source in the north direction in the SAR scene, wherein j refers to an imaginary part in complex operation;
for the GMT scattering surface source, the calculation input parameters of the GMT include a scene backscattering coefficient, radar track data, a radar beam irradiation parameter and a position coordinate of the GMT interpolated scattering surface source, and the calculation formula of each GMT track is as follows:
wherein the content of the first and second substances,
representing the source amplitude phase information of the nth north direction scattering surface of the ith pulse GMT to the e th east direction scattering surface of the ith pulse;
representing the backscatter coefficients of the nth north-oriented day of the ith pulse GMT to the (a) th east-oriented scattering surface source;
、
、
respectively representing the position coordinates of the nth north-middle direction, the eastern direction and the e-th scattering surface source of the ith GMT, and the three position information is obtained by interpolation according to the target motion trail.
6. The simultaneous SAR/GMT echo simulation method of claim 5, wherein the one-dimensional range profile information procedure of the SAR/GMT of the merged pre-pulse in step G is as follows:
7. the simultaneous SAR/GMT echo simulation method of claim 6, characterized in that the SAR scene echo data of the current pulse in step H
Echo data per GMT
And combined SAR/GMT echo data
Respectively as follows:
wherein, LFM is radar reference signal.
8. The simultaneous SAR/GMT echo simulation method according to claim 7, characterized in that: the calculation process of the step I is as follows:
9. a simultaneous SAR/GMT echo simulation system is characterized in that: the system comprises an upper computer, a real-time control system, a GPU acceleration simulation unit, a storage board, a radio frequency upper variational system, a radio frequency lower variational system and a signal processing board card, wherein the signal processing board card is respectively connected with the real-time control system, the radio frequency upper variational system, the radio frequency lower variational system and the storage board; the upper computer is used for setting test parameters, and the test parameters comprise SAR scene parameters, GMT number, initial geometric relation between GMT and SAR scene, and radar position initial information; the GPU acceleration simulation unit is used for receiving test parameters, calling the test parameters, calculating through the following steps A to I to obtain independent and combined SAR/GMT one-dimensional range profile data and echo data, and storing the data and the echo data to the storage board;
step A: reading test parameters set by an upper computer, importing a radar GPS track analysis file, importing an SAR scene backscattering image, importing a GMT backscattering image, and designing a GMT track;
b, performing interpolation processing on the GMT backscattering image according to a preset SAR scene, a GMT track range and radar signal parameters to enable the GMT backscattering image to be fused with the pixel proportion of the SAR scene;
c, adjusting the strength and the phase of the SAR scene and the GMT backscattering coefficient to enable the signal-to-clutter ratio of the target to meet the test requirement;
d, moving the radar track file, the SAR/GMT backscattering data and the GMT track file from the CPU to a GPU video memory;
step E, setting the size of GRID according to the number of scattering surface sources of the SAR scene and the GMT, and independently and discretely distributing the GRID and the GMT to a calculation kernel of a GPU:
step F, respectively carrying out vector parallel computation on the SAR and each GMT scattering surface source simultaneously by using the parallel computation performance of the GPU, computing the amplitude phase information of all the scattering surface sources of the current pulse, and judging the distance gate where the scattering surface sources are located;
step G, accumulating the amplitude phase information of all scattering surface sources of the SAR scene of the current pulse to obtain one-dimensional range profile information of the SAR scene, simultaneously accumulating the amplitude phase information of all scattering surface sources of each GMT of the current pulse to obtain one-dimensional range profile information of each GMT, and combining the one-dimensional range profile information of the SAR/GMT of the current pulse;
step H: performing convolution processing on the one-dimensional range profile data generated in the step G according to the imported test setting, and generating and storing SAR scene echo data of the current pulse, echo data of each GMT and combined SAR/GMT echo data;
step I, repeating the steps F-H until the one-dimensional range profile data and the echo data of all the pulses are calculated;
the real-time control system is used for receiving test parameters output by the upper computer and outputting control information to the signal processing board card; the signal processing board card receives an external radar reference signal input by the radio frequency down-conversion system or generates a corresponding radar reference signal according to control information output by the real-time control system, reads one-dimensional range profile data and echo data of the storage card, and performs output selection according to echo types: the one-dimensional range profile data and the echo data are packaged and then sent to a designated terminal through an optical fiber network; the echo data are directly played back, read in real time, subjected to digital up-conversion and digital-analog conversion, processed by the radio frequency up-conversion system and then output; and (4) convolution playback, namely performing characteristic modulation on the one-dimensional range profile data, performing digital up-conversion and digital-analog conversion, and outputting the data after being processed by the radio frequency up-conversion system.
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