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Editor Work2012 Vol. 1, No. 4
Previous Issue
2012, 1(4): 329-341.
Abstract
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Bistatic SAR (BiSAR) systems have attracted the interests from global researchers and become a hotspot in the international radar community due to the progress of radar technology and rapidly increased applications nowadays. Based on the BiSAR experiments and breakthrough of the key technology, the paper summarized the general progresses of BiSAR systems, especially in European radar community, from different aspects such as system design, processing idea and topology etc. Different bistatic image formation algorithms have been analyzed and reviewed. Finally, the development trend is discussed in the paper.
Bistatic SAR (BiSAR) systems have attracted the interests from global researchers and become a hotspot in the international radar community due to the progress of radar technology and rapidly increased applications nowadays. Based on the BiSAR experiments and breakthrough of the key technology, the paper summarized the general progresses of BiSAR systems, especially in European radar community, from different aspects such as system design, processing idea and topology etc. Different bistatic image formation algorithms have been analyzed and reviewed. Finally, the development trend is discussed in the paper.
2012, 1(4): 342-352.
Based on the ocean surface microwave scattering property and its Synthetic Aperture Radar (SAR) ocean surface imaging mechanism the main research of ocean dynamical SAR detection is presented in this paper. Passing the statistical and hydrodynamical analyses of generation mechanisms of ocean internal waves and ocean bottom topographic waves as well as ship wakes their important SAR imaging features and deducing parameters are here discussed. Therefore the SAR application of oceanic observation is promoted.
Based on the ocean surface microwave scattering property and its Synthetic Aperture Radar (SAR) ocean surface imaging mechanism the main research of ocean dynamical SAR detection is presented in this paper. Passing the statistical and hydrodynamical analyses of generation mechanisms of ocean internal waves and ocean bottom topographic waves as well as ship wakes their important SAR imaging features and deducing parameters are here discussed. Therefore the SAR application of oceanic observation is promoted.
2012, 1(4): 353-360.
A brief overview on the development of Synthetic Aperture Ladar (SAL) imaging both domestically and abroad is introduced, where the quality of the obtained SAL image, the system architecture adopted and the overall progress on SAL development are reviewed. We suggest that a practical SAL should have proper imaging field of view and can be kind of adaptive to atmospheric turbulence so as to be accepted by possible end-users. We also urge that more outdoor SAL imaging experiments should be carried out and more imaging results should be published for the further development of SAL.
A brief overview on the development of Synthetic Aperture Ladar (SAL) imaging both domestically and abroad is introduced, where the quality of the obtained SAL image, the system architecture adopted and the overall progress on SAL development are reviewed. We suggest that a practical SAL should have proper imaging field of view and can be kind of adaptive to atmospheric turbulence so as to be accepted by possible end-users. We also urge that more outdoor SAL imaging experiments should be carried out and more imaging results should be published for the further development of SAL.
Micro-motion Signature Extraction Method for Wideband Radar Based on Complex Image OMP Decomposition
2012, 1(4): 361-369.
In order to extract the micro-motion signatures in condition of Migration Through Range Cells (MTRC) of micro-motional scatterers and azimuthal undersampling in wideband radar, a method based on the Orthogonal Matching Pursuit (OMP) decomposition of the complex image is proposed. By making use of the amplitude and phase information of range-slow-time image, a set of micro-Doppler signal atoms is constructed in the complex image space. The OMP algorithm in vector space is then extend to the complex image space to obtain the micro-motion parameters. Simulations demonstrate the proposed method can extract the micro-motion signatures when MTRC of micro-motional scatterers is occurred, and can also work well when the sampling rate is lower than the Nyquist sampling rate.
In order to extract the micro-motion signatures in condition of Migration Through Range Cells (MTRC) of micro-motional scatterers and azimuthal undersampling in wideband radar, a method based on the Orthogonal Matching Pursuit (OMP) decomposition of the complex image is proposed. By making use of the amplitude and phase information of range-slow-time image, a set of micro-Doppler signal atoms is constructed in the complex image space. The OMP algorithm in vector space is then extend to the complex image space to obtain the micro-motion parameters. Simulations demonstrate the proposed method can extract the micro-motion signatures when MTRC of micro-motional scatterers is occurred, and can also work well when the sampling rate is lower than the Nyquist sampling rate.
2012, 1(4): 370-379.
Based on the recently developed active-passive multifunctional all-digital HF surface wave radar hardware platform of Wuhan University, an experiment study of integrated technology for shortwave communication and Over-The-Horizon Radar (OTHR) application is carried out. Firstly, from the point of communication are demonstrated the key technologies of orthogonal frequency division multiplexing (Orthogonal Frequency Division Multiplexing, OFDM) in the short-wave communication. Secondly, from the point of radar detection are analyzed OFDM parameters design guidelines and its impact on the over-the-horizon radar detection performance. After the description of some key technologies related to communication signal demodulation and radar signal processing, the configuration parameters of hardware platform and experimental results are provided. The results show that the OFDM wave is done well in radar-communication integration systems, which is of great significance on the netted OTHR detection research.
Based on the recently developed active-passive multifunctional all-digital HF surface wave radar hardware platform of Wuhan University, an experiment study of integrated technology for shortwave communication and Over-The-Horizon Radar (OTHR) application is carried out. Firstly, from the point of communication are demonstrated the key technologies of orthogonal frequency division multiplexing (Orthogonal Frequency Division Multiplexing, OFDM) in the short-wave communication. Secondly, from the point of radar detection are analyzed OFDM parameters design guidelines and its impact on the over-the-horizon radar detection performance. After the description of some key technologies related to communication signal demodulation and radar signal processing, the configuration parameters of hardware platform and experimental results are provided. The results show that the OFDM wave is done well in radar-communication integration systems, which is of great significance on the netted OTHR detection research.
2012, 1(4): 380-386.
This paper gives the performance research on the ambiguity function and resolution of passive radar based on DVB-S (Digital Video Broadcasting-Satellite) signal. The radar system structure and signal model of DVB-S signal are firstly studied, then the ambiguity function of DVB-S signal is analyzed. At last, it has been obtained how the bistatic radar position impacts the resolution. Theoretical analyses and computer simulation show that DVB-S signal is applicable as an illuminator for passive radar.
This paper gives the performance research on the ambiguity function and resolution of passive radar based on DVB-S (Digital Video Broadcasting-Satellite) signal. The radar system structure and signal model of DVB-S signal are firstly studied, then the ambiguity function of DVB-S signal is analyzed. At last, it has been obtained how the bistatic radar position impacts the resolution. Theoretical analyses and computer simulation show that DVB-S signal is applicable as an illuminator for passive radar.
2012, 1(4): 387-392.
In modern radar systems, the clutters statistic characters are unknown. With this clutter, the capability of CFAR of parametric detection algorithms will decline. So nonparametric detection algorithms become very important. An intelligent nonparametric Generalized Sign (GS) detection algorithm Variability Index-Generalized Sign (VI-GS) based on adaptive threshold selection is proposed. The VI-GS detection algorithm comploys a composite approach based on the GS detection algorithm, the Trimmed GS detection algorithm (TGS) and the Greatest Of GS detection algorithm (GO-GS). The performance of this detection algorithm in the nonhomogenous clutter background is analyzed respectively based on simulated Gaussian distributed clutter and real radar data. These results show that it performs robustly in the homogeneous background as well as the nonhomogeneous background.
In modern radar systems, the clutters statistic characters are unknown. With this clutter, the capability of CFAR of parametric detection algorithms will decline. So nonparametric detection algorithms become very important. An intelligent nonparametric Generalized Sign (GS) detection algorithm Variability Index-Generalized Sign (VI-GS) based on adaptive threshold selection is proposed. The VI-GS detection algorithm comploys a composite approach based on the GS detection algorithm, the Trimmed GS detection algorithm (TGS) and the Greatest Of GS detection algorithm (GO-GS). The performance of this detection algorithm in the nonhomogenous clutter background is analyzed respectively based on simulated Gaussian distributed clutter and real radar data. These results show that it performs robustly in the homogeneous background as well as the nonhomogeneous background.
2012, 1(4): 393-398.
A new data association algorithm is proposed in this paper for heterogeneous sensors information fusion system, which consists of Radar and high-dynamic-range IR, based on joint usage of the nearest-neighbor (NN) and the topology similarity. The proposed algorithm can avoid the complicated system biases compensation based on topology information. Because the NN method is sensitive to the system bias while the existing topology-based algorithms need a large amount of computation, the proposed algorithm shows a lot of advantages, like high estimation accuracy and robustness as well as the improvement of success association rate. Finally, some numerical experiments are provided to demonstrate the effectiveness of the proposed method. And the estimation accuracy can be as high as 90%.
A new data association algorithm is proposed in this paper for heterogeneous sensors information fusion system, which consists of Radar and high-dynamic-range IR, based on joint usage of the nearest-neighbor (NN) and the topology similarity. The proposed algorithm can avoid the complicated system biases compensation based on topology information. Because the NN method is sensitive to the system bias while the existing topology-based algorithms need a large amount of computation, the proposed algorithm shows a lot of advantages, like high estimation accuracy and robustness as well as the improvement of success association rate. Finally, some numerical experiments are provided to demonstrate the effectiveness of the proposed method. And the estimation accuracy can be as high as 90%.
2012, 1(4): 399-405.
In the data fusion system composed of radar and infrared sensor installed in high speed of dynamic platform, the system error estimation and target correlation are dependent and are difficult very much. To solve the problem, a new target correlation algorithm based on pattern classification is proposed in the article according to the property of system errors variation. The approach realizes pattern classification by BP neural network. It neednt estimate the system error and compensate it, and has a tolerance to system error. The experiment shows that the average correct probability for target-correlation in the data fusion between the above two kind of sensors is more than 86%.
In the data fusion system composed of radar and infrared sensor installed in high speed of dynamic platform, the system error estimation and target correlation are dependent and are difficult very much. To solve the problem, a new target correlation algorithm based on pattern classification is proposed in the article according to the property of system errors variation. The approach realizes pattern classification by BP neural network. It neednt estimate the system error and compensate it, and has a tolerance to system error. The experiment shows that the average correct probability for target-correlation in the data fusion between the above two kind of sensors is more than 86%.
2012, 1(4): 406-413.
Two improved contributions have been advanced for the standard Sequential Monte Carlo Probability Hypothesis Density (SMC-PHD) filter. Firstly, a novel method is advanced for the cardinality and state estimation. A weight matrix is firstly calculated by measurements and persistent particles, and the weight sum of each row is then evaluated, the measurements indexed by row will be judged as true if its weight sum is larger than a certain threshold, and the weight sum of persistent particle states will be reported as the true target states. Secondly, an assistant variable which is used to denote the persistent age for every particle is introduced, by the help of this age variable, the overrated problem of targets number in dense clutter environment can be effectively restricted. The results of numerical simulation prove that the improved SMC-PHD filter has higher tracking performance than the standard one.
Two improved contributions have been advanced for the standard Sequential Monte Carlo Probability Hypothesis Density (SMC-PHD) filter. Firstly, a novel method is advanced for the cardinality and state estimation. A weight matrix is firstly calculated by measurements and persistent particles, and the weight sum of each row is then evaluated, the measurements indexed by row will be judged as true if its weight sum is larger than a certain threshold, and the weight sum of persistent particle states will be reported as the true target states. Secondly, an assistant variable which is used to denote the persistent age for every particle is introduced, by the help of this age variable, the overrated problem of targets number in dense clutter environment can be effectively restricted. The results of numerical simulation prove that the improved SMC-PHD filter has higher tracking performance than the standard one.
2012, 1(4): 414-419.
In order to solve the problem of the decline of accuracy when using the nonparametric methodStochastic Learning of the Cumulative (SLC) to estimate the density of High-Resolution Range Profile (HRRP) in radar target recognition under the condition that the samples are not enough, a radar target recognition approach based on the semiparametric density estimation of SLC is proposed in this paper. This method has the ability to make use of empirical knowledge which is known as the approximate Gamma distribution of amplitudes in each HRRP range cells, and the Gamma density estimate is then corrected by multiplying with SLC of a correction factor. Obviously, both advantages of parametric method and nonparametric method of SLC are merged in the semiparametric density estimation of SLC. Simulation results based on the HRRP dataset of five aircraft models demonstrate the effectiveness of the proposed approach.
In order to solve the problem of the decline of accuracy when using the nonparametric methodStochastic Learning of the Cumulative (SLC) to estimate the density of High-Resolution Range Profile (HRRP) in radar target recognition under the condition that the samples are not enough, a radar target recognition approach based on the semiparametric density estimation of SLC is proposed in this paper. This method has the ability to make use of empirical knowledge which is known as the approximate Gamma distribution of amplitudes in each HRRP range cells, and the Gamma density estimate is then corrected by multiplying with SLC of a correction factor. Obviously, both advantages of parametric method and nonparametric method of SLC are merged in the semiparametric density estimation of SLC. Simulation results based on the HRRP dataset of five aircraft models demonstrate the effectiveness of the proposed approach.
2012, 1(4): 420-425.
Shift-frequency jamming is an effective jamming to the Linear Frequency Modulation (LFM) radar. However, the feature of carrier frequency offset of the traditional shift-frequency jamming may be used to identify the jamming signal. So a new method is proposed to hide or subtract the feature of the traditional shift-frequency jamming in this paper. For the purpose of hiding or subtracting the carrier frequency offset, the pulse width of jamming signal will be truncated with a proper magnitude. Furthermore, the new method can also disturb original conversion relationship between carrier frequency offset and the frequency shifting of the jamming signal to reduce the ability of identifying false target. Compared with the traditional shift-frequency jamming, the new method has pulse width mismatch between the jamming signal and the echo. But the loss of the mismatch is acceptable. The new method is testified with the theory analysis and simulation results.
Shift-frequency jamming is an effective jamming to the Linear Frequency Modulation (LFM) radar. However, the feature of carrier frequency offset of the traditional shift-frequency jamming may be used to identify the jamming signal. So a new method is proposed to hide or subtract the feature of the traditional shift-frequency jamming in this paper. For the purpose of hiding or subtracting the carrier frequency offset, the pulse width of jamming signal will be truncated with a proper magnitude. Furthermore, the new method can also disturb original conversion relationship between carrier frequency offset and the frequency shifting of the jamming signal to reduce the ability of identifying false target. Compared with the traditional shift-frequency jamming, the new method has pulse width mismatch between the jamming signal and the echo. But the loss of the mismatch is acceptable. The new method is testified with the theory analysis and simulation results.
2012, 1(4): 426-435.
Enhanced SAR ship wake images with blur Kelvin wakes and reserved turbulent wakes are very important to the inversions of ship and motion parameters. This paper applies the Fast and Adaptive Bidimensional Empirical Mode Decomposition (FABEMD) to decompose the SAR ship wake image into Kelvin wakes, turbulent wakes and other multiscale features, which enhances the gray intensity and spectrum contrast of Kelvin wakes to other features. Based on the FABEMD, a modified Goldstein interferogram filter is developed to further enhance the Kelvin wakes. Moreover, the moment invariants are introduced to evaluate the enhancement. Therefore, the Kelvin wakes are dramatically enhanced and the turbulent wakes are reserved. Algorithm analysis, experiments, subjective and objective evaluations show the reasonable efficiency and capabilities.
Enhanced SAR ship wake images with blur Kelvin wakes and reserved turbulent wakes are very important to the inversions of ship and motion parameters. This paper applies the Fast and Adaptive Bidimensional Empirical Mode Decomposition (FABEMD) to decompose the SAR ship wake image into Kelvin wakes, turbulent wakes and other multiscale features, which enhances the gray intensity and spectrum contrast of Kelvin wakes to other features. Based on the FABEMD, a modified Goldstein interferogram filter is developed to further enhance the Kelvin wakes. Moreover, the moment invariants are introduced to evaluate the enhancement. Therefore, the Kelvin wakes are dramatically enhanced and the turbulent wakes are reserved. Algorithm analysis, experiments, subjective and objective evaluations show the reasonable efficiency and capabilities.
2012, 1(4): 436-440.
Traditional hidden surface removal algorithm based on hardware Z-Buffer technique cannot give attention to precision or efficiency at the same time when dealing with the non-uniform triangulated SAR scene model. A novel high-precision hidden surface removal approach using fast ray-tube splitting algorithm is proposed, where the SAR scene hidden surface removal problem is decomposed into two simple procedures, i.e. a Delaunay triangulator is used to generate the initial ray tubes from the projected point clouds of all incident visible vertices, then an adaptive ray-tube splitting method is adopted to carry out the complex scene shading situations and resultant visible model reconstruction. Simulation results of typical aircraft and T-72 tank show that, the new approach is feasible and effective.
Traditional hidden surface removal algorithm based on hardware Z-Buffer technique cannot give attention to precision or efficiency at the same time when dealing with the non-uniform triangulated SAR scene model. A novel high-precision hidden surface removal approach using fast ray-tube splitting algorithm is proposed, where the SAR scene hidden surface removal problem is decomposed into two simple procedures, i.e. a Delaunay triangulator is used to generate the initial ray tubes from the projected point clouds of all incident visible vertices, then an adaptive ray-tube splitting method is adopted to carry out the complex scene shading situations and resultant visible model reconstruction. Simulation results of typical aircraft and T-72 tank show that, the new approach is feasible and effective.
2012, 1(4): 441-445.
High-precision height acquisition needs to correct the interferometric parameters errors by interferometric calibration for Interferometric Synthetic Aperture Radar (InSAR) system with many Ground Control Points (GCPs). For the situation that some areas probably only have little GCPs or even no GCPs, a new high-precision calibration method for airborne InSAR based on bundle adjustment is needed, in which the Control Points (CP) selection method is a major point which has a crucial influence on the precision of InSAR calibration. A model-based CP selection method for calibration of airborne InSAR with sparse GCPs is proposed in this paper, which adopts the polynomial model fit method to choose CP based on the sensitivity characteristic of inSAR interferometric parameters. A joint calibration is made with the real InSAR data and the results confirm the
validity and rationality of the proposed method.
High-precision height acquisition needs to correct the interferometric parameters errors by interferometric calibration for Interferometric Synthetic Aperture Radar (InSAR) system with many Ground Control Points (GCPs). For the situation that some areas probably only have little GCPs or even no GCPs, a new high-precision calibration method for airborne InSAR based on bundle adjustment is needed, in which the Control Points (CP) selection method is a major point which has a crucial influence on the precision of InSAR calibration. A model-based CP selection method for calibration of airborne InSAR with sparse GCPs is proposed in this paper, which adopts the polynomial model fit method to choose CP based on the sensitivity characteristic of inSAR interferometric parameters. A joint calibration is made with the real InSAR data and the results confirm the
validity and rationality of the proposed method.
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