To perform the ground test of a spaceborne Synthetic Aperture Radar(SAR) system, an echo simulator with the characteristics of multimode, multi-assemblage, and real time is proposed in this paper. A hardware platform ...To perform the ground test of a spaceborne Synthetic Aperture Radar(SAR) system, an echo simulator with the characteristics of multimode, multi-assemblage, and real time is proposed in this paper. A hardware platform of the real-time echo simulator based on the VPX bus is designed. With this platform, real-time multi-point echo generation and scenario targets echo generation can be achieved by the real-time signal processing in Field Programmable Gate Array(FPGA), utilizing the parameters calculated by the industry computers. Furthermore, this platform can output different signals if it is expanded to multi-channels, making it possible for the assignment of echo generation and test in different spaceborne SAR modes. The test results with the actual SAR system show that this platform can satisfy the system requirements and is now used in practice.展开更多
This paper presents a novel method for fast calculation of radar echo in near-field regions after the equivalent source has been computed by method of moments(MoM).An easy-to-access near-field database(NFDB)is establi...This paper presents a novel method for fast calculation of radar echo in near-field regions after the equivalent source has been computed by method of moments(MoM).An easy-to-access near-field database(NFDB)is established,which is built on the auxiliary tetrahedral meshes surrounding the nearfield regions of interest.The near-fields calculation(NFC)of arbitrary observation points can be expressed explicitly via the NFDB.An efficient matrix compression scheme named random sampling-based butterfly factorization(RS-BF)is proposed to speed up the construction of NFDB.With this approach,each group of O(N)elements in the database can be calculated through one fast matrix-vector multiplication operation that has a computational complexity below O(Nlog~2 N).The proposed method can avoid time-consuming point-by-point NFC of the traditional methods.Several numerical examples are presented to demonstrate the accuracy and efficiency of this method.In particular,the echo simulation of a missile-target encounter example is presented to illustrate its capability for practical applications.展开更多
Sonar locates underwater targets by receiving reflected sound waves.However,the complex marine environment makes it difficult to set targets in appropriate locations and conditions.The sonar echo simulator has the fun...Sonar locates underwater targets by receiving reflected sound waves.However,the complex marine environment makes it difficult to set targets in appropriate locations and conditions.The sonar echo simulator has the function of simulating sonar detection target echo signals.As a cutting-edge technology,underwater backscatter has led to the emergence of array based acoustic reflection systems.The research on sonar echo simulators based on backscatter technology has promoted the solution of problems such as target echo modeling,sonar arrival direction estimation,and echo directional transmission.In response to the above problems,this paper designs an end-to-end sonar echo simulator system array phase estimation sonar echo simulation system(APE-SESS),which can independently complete highresolution real-time direction of arrival(DOA)estimation and generate directional simulation echo based on the array structure.Dual branch convolutional neural network(DB-CNN)is proposed in the system to estimate the direction of the signal array and directly obtain the phase weights containing azimuth information.Comparing DBCNN with conventional methods and classic underwater DOA network models based on classification problems,the results show that DB-CNN exhibits stability,small error,and high real-time performance under different signal-to-noise ratio(SNR).The proposed APE-SESS has end-to-end characteristics,real-time angle estimation,and azimuth simulation functions.展开更多
The lack of data is constraining research on the bistatic ballistic target(BT).In the bistatic radar system,the angle between the target axis and the radar line of sight(RLOS)is generally large,which means that the sp...The lack of data is constraining research on the bistatic ballistic target(BT).In the bistatic radar system,the angle between the target axis and the radar line of sight(RLOS)is generally large,which means that the specular scattering center(SSC)is likely to be present with the target's micro-motion.This results in a brief flash in the time-frequency representation(TFR)but has been less frequently reported.We propose a micro-motion echo simulation method with SSC by calculating its position vector and modeling its visible coefficient.Furthermore,the model with four estimated parameters is utilized to optimize the simulated TFR.The simulation results intuitively and numerically agree well with the TFR obtained by electromagnetic calculation.展开更多
Aircraft wake turbulence is an inherent outcome of aircraft flight,presenting a substan-tial challenge to air traffic control,aviation safety and operational efficiency.Building upon data obtained from coherent Dopple...Aircraft wake turbulence is an inherent outcome of aircraft flight,presenting a substan-tial challenge to air traffic control,aviation safety and operational efficiency.Building upon data obtained from coherent Doppler Lidar detection,and combining Dynamic Bayesian Networks(DBN)with Genetic Algorithm-optimized Backpropagation Neural Networks(GA-BPNN),this paper proposes a model for the inversion of wake vortex parameters.During the wake vortex flow field simulation analysis,the wind and turbulent environment were initially superimposed onto the simulated wake velocity field.Subsequently,Lidar-detected echoes of the velocity field are simulated to obtain a data set similar to the actual situation for model training.In the case study validation,real measured data underwent preprocessing and were then input into the established model.This allowed us to construct the wake vortex characteristic parameter inversion model.The final results demonstrated that our model achieved parameter inversion with only minor errors.In a practical example,our model in this paper significantly reduced the mean square error of the inverted velocity field when compared to the traditional algorithm.This study holds significant promise for real-time monitoring of wake vortices at airports,and is proved a crucial step in developing wake vortex interval standards.展开更多
This paper prcscnts a practical model of echoes for sonar engineering. Based on that the sonar systems usually use high frequency band-limited signals, the transfer function is appropriatc to characterize the target. ...This paper prcscnts a practical model of echoes for sonar engineering. Based on that the sonar systems usually use high frequency band-limited signals, the transfer function is appropriatc to characterize the target. At high frequencics, all echo components such as the specular reflected waves, the corner waves and the various clastic scattering waves can be thought of the returns from some equivalent scattering centres or highlights. The whole target is characterizcd by a group of the highlight in space.In this paper a general expression of the transfer function of the highlight is derived, which includes the amplitude factor, thc time delay and the phase jump. A determined parameter group provides a concrete target model.Simulation of the echo waveform can also be performed using the prescnted model.展开更多
文摘To perform the ground test of a spaceborne Synthetic Aperture Radar(SAR) system, an echo simulator with the characteristics of multimode, multi-assemblage, and real time is proposed in this paper. A hardware platform of the real-time echo simulator based on the VPX bus is designed. With this platform, real-time multi-point echo generation and scenario targets echo generation can be achieved by the real-time signal processing in Field Programmable Gate Array(FPGA), utilizing the parameters calculated by the industry computers. Furthermore, this platform can output different signals if it is expanded to multi-channels, making it possible for the assignment of echo generation and test in different spaceborne SAR modes. The test results with the actual SAR system show that this platform can satisfy the system requirements and is now used in practice.
基金the National Key Research and Development Program of China(2017YFB0202500)。
文摘This paper presents a novel method for fast calculation of radar echo in near-field regions after the equivalent source has been computed by method of moments(MoM).An easy-to-access near-field database(NFDB)is established,which is built on the auxiliary tetrahedral meshes surrounding the nearfield regions of interest.The near-fields calculation(NFC)of arbitrary observation points can be expressed explicitly via the NFDB.An efficient matrix compression scheme named random sampling-based butterfly factorization(RS-BF)is proposed to speed up the construction of NFDB.With this approach,each group of O(N)elements in the database can be calculated through one fast matrix-vector multiplication operation that has a computational complexity below O(Nlog~2 N).The proposed method can avoid time-consuming point-by-point NFC of the traditional methods.Several numerical examples are presented to demonstrate the accuracy and efficiency of this method.In particular,the echo simulation of a missile-target encounter example is presented to illustrate its capability for practical applications.
基金supported by the Joint Funds of the National Natural Science Foundation of China under Grant U22A2009in part by the National Key Research and Development Program under Grant 2021YFC2803000.
文摘Sonar locates underwater targets by receiving reflected sound waves.However,the complex marine environment makes it difficult to set targets in appropriate locations and conditions.The sonar echo simulator has the function of simulating sonar detection target echo signals.As a cutting-edge technology,underwater backscatter has led to the emergence of array based acoustic reflection systems.The research on sonar echo simulators based on backscatter technology has promoted the solution of problems such as target echo modeling,sonar arrival direction estimation,and echo directional transmission.In response to the above problems,this paper designs an end-to-end sonar echo simulator system array phase estimation sonar echo simulation system(APE-SESS),which can independently complete highresolution real-time direction of arrival(DOA)estimation and generate directional simulation echo based on the array structure.Dual branch convolutional neural network(DB-CNN)is proposed in the system to estimate the direction of the signal array and directly obtain the phase weights containing azimuth information.Comparing DBCNN with conventional methods and classic underwater DOA network models based on classification problems,the results show that DB-CNN exhibits stability,small error,and high real-time performance under different signal-to-noise ratio(SNR).The proposed APE-SESS has end-to-end characteristics,real-time angle estimation,and azimuth simulation functions.
基金supported by the National Natural Science Foundation of China(Nos.62071475 and 62401580).
文摘The lack of data is constraining research on the bistatic ballistic target(BT).In the bistatic radar system,the angle between the target axis and the radar line of sight(RLOS)is generally large,which means that the specular scattering center(SSC)is likely to be present with the target's micro-motion.This results in a brief flash in the time-frequency representation(TFR)but has been less frequently reported.We propose a micro-motion echo simulation method with SSC by calculating its position vector and modeling its visible coefficient.Furthermore,the model with four estimated parameters is utilized to optimize the simulated TFR.The simulation results intuitively and numerically agree well with the TFR obtained by electromagnetic calculation.
基金supported by the National Natural Science Foundation of China (No.U2133210).
文摘Aircraft wake turbulence is an inherent outcome of aircraft flight,presenting a substan-tial challenge to air traffic control,aviation safety and operational efficiency.Building upon data obtained from coherent Doppler Lidar detection,and combining Dynamic Bayesian Networks(DBN)with Genetic Algorithm-optimized Backpropagation Neural Networks(GA-BPNN),this paper proposes a model for the inversion of wake vortex parameters.During the wake vortex flow field simulation analysis,the wind and turbulent environment were initially superimposed onto the simulated wake velocity field.Subsequently,Lidar-detected echoes of the velocity field are simulated to obtain a data set similar to the actual situation for model training.In the case study validation,real measured data underwent preprocessing and were then input into the established model.This allowed us to construct the wake vortex characteristic parameter inversion model.The final results demonstrated that our model achieved parameter inversion with only minor errors.In a practical example,our model in this paper significantly reduced the mean square error of the inverted velocity field when compared to the traditional algorithm.This study holds significant promise for real-time monitoring of wake vortices at airports,and is proved a crucial step in developing wake vortex interval standards.
文摘This paper prcscnts a practical model of echoes for sonar engineering. Based on that the sonar systems usually use high frequency band-limited signals, the transfer function is appropriatc to characterize the target. At high frequencics, all echo components such as the specular reflected waves, the corner waves and the various clastic scattering waves can be thought of the returns from some equivalent scattering centres or highlights. The whole target is characterizcd by a group of the highlight in space.In this paper a general expression of the transfer function of the highlight is derived, which includes the amplitude factor, thc time delay and the phase jump. A determined parameter group provides a concrete target model.Simulation of the echo waveform can also be performed using the prescnted model.
