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Editor Work2014 Vol. 3, No. 6
Previous Issue
2014, 3(6): 623-631.
Abstract
1017KB
The research and application of passive radar are heading from single transmitter-receiver pair to multiple transmitter-receiver pairs. As an important class of the illuminators of opportunity, most of modern digital broadcasting and television systems work on Single Frequency Network (SFN), which intrinsically determines that the passive radar based on such illuminators must be distributed and networked. In consideration of the remarkable working and processing mode of passive radar under SFN configuration, this paper proposes the concept of SFN-based Distributed Passive Radar (SDPR). The main characteristics and key problems of SDPR are first described. Then several potential solutions are discussed for part of the key technologies. The feasibility of SDPR is demonstrated by preliminary experimental results. Finally, the concept of four network convergence that includes the broadcast based passive radar network is conceived, and its application prospects are discussed.
The research and application of passive radar are heading from single transmitter-receiver pair to multiple transmitter-receiver pairs. As an important class of the illuminators of opportunity, most of modern digital broadcasting and television systems work on Single Frequency Network (SFN), which intrinsically determines that the passive radar based on such illuminators must be distributed and networked. In consideration of the remarkable working and processing mode of passive radar under SFN configuration, this paper proposes the concept of SFN-based Distributed Passive Radar (SDPR). The main characteristics and key problems of SDPR are first described. Then several potential solutions are discussed for part of the key technologies. The feasibility of SDPR is demonstrated by preliminary experimental results. Finally, the concept of four network convergence that includes the broadcast based passive radar network is conceived, and its application prospects are discussed.
2014, 3(6): 632-640.
Bistatic Synthetic Aperture Radar (BSAR) based on the Global Navigation Service System (GNSSBSAR) uses navigation satellites as radar transmitters, which are low in cost. However, GNSS-BSAR images have poor resolution and low Signal-to-Noise Ratios (SNR). In this paper, a multiangle observation and data processing strategy are presented based on BeiDou-2 navigation satellite imagery, from which twenty-six BSAR images in different configurations are obtained. A region-based fusion algorithm using region of interest segmentation is proposed, and a high-quality fusion image is obtained. The results reveal that the multiangle imaging method can extend the applications of GNSS-BSAR.
Bistatic Synthetic Aperture Radar (BSAR) based on the Global Navigation Service System (GNSSBSAR) uses navigation satellites as radar transmitters, which are low in cost. However, GNSS-BSAR images have poor resolution and low Signal-to-Noise Ratios (SNR). In this paper, a multiangle observation and data processing strategy are presented based on BeiDou-2 navigation satellite imagery, from which twenty-six BSAR images in different configurations are obtained. A region-based fusion algorithm using region of interest segmentation is proposed, and a high-quality fusion image is obtained. The results reveal that the multiangle imaging method can extend the applications of GNSS-BSAR.
2014, 3(6): 641-651.
GNSS Reflectometry (GNSS-R) is a currently developed remote sensing technology which belongs to the passive radar domain. This paper aims to deal with some issues on multi-polarization of GNSS-R technology. Four different polarization patterns of the received GNSS-R signal are discussed, including rl, rr, rv, rh. For each polarization, formulas for calculating the surface reflectivity () using dielectric constant () and satellite elevation angle () are derivated. The rationality of these formulas is validated using data from a ground-based GNSS-R soil moisture experiment. The results of this research can provide references for further GNSS-R research, including simulation, experiment design, model development and data processing.
GNSS Reflectometry (GNSS-R) is a currently developed remote sensing technology which belongs to the passive radar domain. This paper aims to deal with some issues on multi-polarization of GNSS-R technology. Four different polarization patterns of the received GNSS-R signal are discussed, including rl, rr, rv, rh. For each polarization, formulas for calculating the surface reflectivity () using dielectric constant () and satellite elevation angle () are derivated. The rationality of these formulas is validated using data from a ground-based GNSS-R soil moisture experiment. The results of this research can provide references for further GNSS-R research, including simulation, experiment design, model development and data processing.
2014, 3(6): 652-659.
To improve the estimation accuracy of the error covariance matrix in Unscented Kalman Filter (UKF). With the passive radar target tracking model, a novel Mixed Kalman Filter (MKF) is proposed, Firstly, the UKF is used to conduct a posteriori estimate for target state, and then re-establish a measurement equation, the posteriori estimated value of state by UKF is transformed into a measured value of the new measurement equation, and through linear Kalman Filter the state is best estimated secondly, improving the precision of target state estimation. Experimental results indicate that MKF algorithm significantly improves the performance of passive radar target tracking, compared with the Extended Kalman Filter (EKF) and UKF.
To improve the estimation accuracy of the error covariance matrix in Unscented Kalman Filter (UKF). With the passive radar target tracking model, a novel Mixed Kalman Filter (MKF) is proposed, Firstly, the UKF is used to conduct a posteriori estimate for target state, and then re-establish a measurement equation, the posteriori estimated value of state by UKF is transformed into a measured value of the new measurement equation, and through linear Kalman Filter the state is best estimated secondly, improving the precision of target state estimation. Experimental results indicate that MKF algorithm significantly improves the performance of passive radar target tracking, compared with the Extended Kalman Filter (EKF) and UKF.
2014, 3(6): 660-665.
A passive location method with one transmitter and one receiver using Direction Of Arrival (DOA) and Doppler measurements is proposed in this paper. The optimal trajectory analysis for the receiver is given for a moving target. The minimizing Geometrical Dilution Of Precision (GDOP) for target is used to analyze the optimal 2-D location. Unscented Kalman Filter (UKF) is used to estimate the position and velocity of the target by optimizing the receivers trajectory, and the optimal location can be obtained for every estimated moment. A computer simulation is used to illustrate the effectiveness of the proposed method.
A passive location method with one transmitter and one receiver using Direction Of Arrival (DOA) and Doppler measurements is proposed in this paper. The optimal trajectory analysis for the receiver is given for a moving target. The minimizing Geometrical Dilution Of Precision (GDOP) for target is used to analyze the optimal 2-D location. Unscented Kalman Filter (UKF) is used to estimate the position and velocity of the target by optimizing the receivers trajectory, and the optimal location can be obtained for every estimated moment. A computer simulation is used to illustrate the effectiveness of the proposed method.
2014, 3(6): 666-674.
Passive radar exploits an external illuminator signal to detect targets. It has the advantages of silence, anti-interference, and counter-stealth ability. In most cases, direct and multipath clutters should be suppressed first. Then coherent detection can be made by performing a cross-ambiguity function of the remaining target echoes and the reference signal. However, under a wide-band signal, a long-integration time, or multi-beam circumstances, a large number of computations and amount of memory is required for normal processing. This paper expresses the mathematical relationships of clutter suppression algorithms based on the Minimum Mean Square Error (MMSE) principle and coherent detection algorithms based on the cross-ambiguity function. Herein, a joint-optimize and processing method is presented. This method reduces the number of computations and amount of memory required, is easy to implement on GPU devices such as CUDA, and will be useful for engineering applications. Its high-efficiency and real-time properties are validated in the experimental results.
Passive radar exploits an external illuminator signal to detect targets. It has the advantages of silence, anti-interference, and counter-stealth ability. In most cases, direct and multipath clutters should be suppressed first. Then coherent detection can be made by performing a cross-ambiguity function of the remaining target echoes and the reference signal. However, under a wide-band signal, a long-integration time, or multi-beam circumstances, a large number of computations and amount of memory is required for normal processing. This paper expresses the mathematical relationships of clutter suppression algorithms based on the Minimum Mean Square Error (MMSE) principle and coherent detection algorithms based on the cross-ambiguity function. Herein, a joint-optimize and processing method is presented. This method reduces the number of computations and amount of memory required, is easy to implement on GPU devices such as CUDA, and will be useful for engineering applications. Its high-efficiency and real-time properties are validated in the experimental results.
2014, 3(6): 675-685.
The Normalized Least-Mean-Squares (NLMS) algorithm is widely used to cancel the direct and multiple path interferences in Passive Coherent Location (PCL) radar systems. This study proposes that the interference cancelation using the NLMS algorithm and the calculation of the radar Cross Ambiguity Function (CAF) can be modeled as a notch filter, with the notch located at zero Doppler frequency in the surface of the radar CAF. The analysis shows that the notchs width and depth are closely related to the step size of the NLMS algorithm. Subsequently, the effect of the notch in PCL radar target detection is analyzed. The results suggest that the detection performance of the PCL radar deteriorates because of the wide notch. Furthermore, the Nonuniform NLMS (NNLMS) algorithm is proposed for removing the clutter with the Doppler frequency by using notch filtering. A step-size matrix is adopted to mitigate the low Doppler frequency clutter and lower the floor of the radar CAF. With the step-size matrix, can be obtained notches of different depths and widths in different range units of the CAF, which can filter the low Doppler frequency clutter. In addition, the convergence rate of the NNLMS algorithm is better than that of the traditional NLMS algorithm. The validity of the NNLMS algorithm is verified by experimental results.
The Normalized Least-Mean-Squares (NLMS) algorithm is widely used to cancel the direct and multiple path interferences in Passive Coherent Location (PCL) radar systems. This study proposes that the interference cancelation using the NLMS algorithm and the calculation of the radar Cross Ambiguity Function (CAF) can be modeled as a notch filter, with the notch located at zero Doppler frequency in the surface of the radar CAF. The analysis shows that the notchs width and depth are closely related to the step size of the NLMS algorithm. Subsequently, the effect of the notch in PCL radar target detection is analyzed. The results suggest that the detection performance of the PCL radar deteriorates because of the wide notch. Furthermore, the Nonuniform NLMS (NNLMS) algorithm is proposed for removing the clutter with the Doppler frequency by using notch filtering. A step-size matrix is adopted to mitigate the low Doppler frequency clutter and lower the floor of the radar CAF. With the step-size matrix, can be obtained notches of different depths and widths in different range units of the CAF, which can filter the low Doppler frequency clutter. In addition, the convergence rate of the NNLMS algorithm is better than that of the traditional NLMS algorithm. The validity of the NNLMS algorithm is verified by experimental results.
Parallel Implementation of Multi-channel Time Domain Clutter Suppression Algorithm for Passive Radar
2014, 3(6): 686-693.
Cancellation of clutter and multi-path is one of the key steps in passive radar target information extraction. Extensive Cancellation Algorithm Batches (ECA-B) is an effective time-domain clutter suppression algorithm, but with high time and space complexity, and even higher with multi-channel (or multi-beam) data processing. Combining high memory throughput and tremendous computational horsepower of GPU graphics processor, this paper proposes a multi-channel ECA-B algorithm which is suitable for parallel implementation on GPUs. Firstly, the principle of multi-channel ECA-B algorithm is derived, avoiding the redundancy of processing each channel singly. Then an iterative calculation method is presented for reducing the biggest time-consuming calculation of the correlation matrix, so that time and space complexity are both reduced to 1/K (K is clutters degree of freedom) of the conventional method. Finally, the full GPU parallel implementation of the algorithm is given. The simulation and experimental results verify the accuracy and effectiveness of the proposed algorithm.
Cancellation of clutter and multi-path is one of the key steps in passive radar target information extraction. Extensive Cancellation Algorithm Batches (ECA-B) is an effective time-domain clutter suppression algorithm, but with high time and space complexity, and even higher with multi-channel (or multi-beam) data processing. Combining high memory throughput and tremendous computational horsepower of GPU graphics processor, this paper proposes a multi-channel ECA-B algorithm which is suitable for parallel implementation on GPUs. Firstly, the principle of multi-channel ECA-B algorithm is derived, avoiding the redundancy of processing each channel singly. Then an iterative calculation method is presented for reducing the biggest time-consuming calculation of the correlation matrix, so that time and space complexity are both reduced to 1/K (K is clutters degree of freedom) of the conventional method. Finally, the full GPU parallel implementation of the algorithm is given. The simulation and experimental results verify the accuracy and effectiveness of the proposed algorithm.
2014, 3(6): 694-701.
In recent years, the wireless local networks are constructed rapidly and their coverage greatly increase. The passive radar imaging of moving targets using WiFi signals is studied in this paper, which may lead to wider applications of passive radars. Firstly, the ambiguity function of WiFi signals is analyzed. The results show that the WiFi signal has good range and velocity ambiguity and can be used as an illumination source. Then, distributed apertures are used to receive target echoes and the imaging is performed using a Generalized Likelihood Ratio Test (GLRT)-based approach. The positions and velocities of the moving targets can be reconstructed. The resolution of the imaging method is also analyzed. Simulation results demonstrate the performance of the presented passive radar imaging method of moving targets using WiFi signals.
In recent years, the wireless local networks are constructed rapidly and their coverage greatly increase. The passive radar imaging of moving targets using WiFi signals is studied in this paper, which may lead to wider applications of passive radars. Firstly, the ambiguity function of WiFi signals is analyzed. The results show that the WiFi signal has good range and velocity ambiguity and can be used as an illumination source. Then, distributed apertures are used to receive target echoes and the imaging is performed using a Generalized Likelihood Ratio Test (GLRT)-based approach. The positions and velocities of the moving targets can be reconstructed. The resolution of the imaging method is also analyzed. Simulation results demonstrate the performance of the presented passive radar imaging method of moving targets using WiFi signals.
Ambiguity Function Analysis and Processing for Passive Radar Based on CDR Digital Audio Broadcasting
2014, 3(6): 702-710.
China Digital Radio (CDR) broadcasting is a new standard of digital audio broadcasting of FM frequency (87108 MHz) based on our research and development efforts. It is compatible with the frequency spectrum in analog FM radio and satisfies the requirements for smooth transition from analog to digital signal in FM broadcasting in China. This paper focuses on the signal characteristics and processing methods of radio-based passive radar. The signal characteristics and ambiguity function of a passive radar illumination source are analyzed. The adverse effects on the target detection of the side peaks owing to cyclic prefix, the Doppler ambiguity strips because of signal synchronization, and the range of side peaks resulting from the signal discontinuous spectrum are then studied. Finally, methods for suppressing these side peaks are proposed and their effectiveness is verified by simulations.
China Digital Radio (CDR) broadcasting is a new standard of digital audio broadcasting of FM frequency (87108 MHz) based on our research and development efforts. It is compatible with the frequency spectrum in analog FM radio and satisfies the requirements for smooth transition from analog to digital signal in FM broadcasting in China. This paper focuses on the signal characteristics and processing methods of radio-based passive radar. The signal characteristics and ambiguity function of a passive radar illumination source are analyzed. The adverse effects on the target detection of the side peaks owing to cyclic prefix, the Doppler ambiguity strips because of signal synchronization, and the range of side peaks resulting from the signal discontinuous spectrum are then studied. Finally, methods for suppressing these side peaks are proposed and their effectiveness is verified by simulations.
2014, 3(6): 711-719.
Space target surveillance generally uses active radars. To take full advantage of passive radars, the idea of using spaceborne illuminators of opportunity for space target detection is presented in this paper. Analysis of the detectable time and direct wave suppression shows that passive radar using spaceborne illuminators of opportunity can effectively detect a Low-Earth-Orbit (LEO) target. Meanwhile, Ku and L band bi-static radar cross section of passive radars that use spaceborne illuminators of opportunity are presented by simulation, providing the basis of choosing space target forward scatter. Finally the key parameters, mainly system gain, accumulation time and radiation source selection are studied. Results show that system size using satellite TV signals as illuminators of opportunity is relatively small. These encouraging results should stimulate the development of passive radar detection of space targets using spaceborne illuminators of opportunity.
Space target surveillance generally uses active radars. To take full advantage of passive radars, the idea of using spaceborne illuminators of opportunity for space target detection is presented in this paper. Analysis of the detectable time and direct wave suppression shows that passive radar using spaceborne illuminators of opportunity can effectively detect a Low-Earth-Orbit (LEO) target. Meanwhile, Ku and L band bi-static radar cross section of passive radars that use spaceborne illuminators of opportunity are presented by simulation, providing the basis of choosing space target forward scatter. Finally the key parameters, mainly system gain, accumulation time and radiation source selection are studied. Results show that system size using satellite TV signals as illuminators of opportunity is relatively small. These encouraging results should stimulate the development of passive radar detection of space targets using spaceborne illuminators of opportunity.
2014, 3(6): 720-726.
High Frequency (HF) passive radar is a typical bistatic radar, and the modeling and simulation of sea clutter in bistatic radar are worth researching for HF passive radar. The paper first establishes a time-domain signal model of the first-order sea clutter in bistatic radar with a detailed derivation process. Then, based on the signal model, a new simulation method for the first-order sea clutter using band-pass filter and Hilbert transform is proposed. Simulation result verifies the validity of the proposed signal model and simulation method.
High Frequency (HF) passive radar is a typical bistatic radar, and the modeling and simulation of sea clutter in bistatic radar are worth researching for HF passive radar. The paper first establishes a time-domain signal model of the first-order sea clutter in bistatic radar with a detailed derivation process. Then, based on the signal model, a new simulation method for the first-order sea clutter using band-pass filter and Hilbert transform is proposed. Simulation result verifies the validity of the proposed signal model and simulation method.
2014, 3(6): 727-731.
As one of the research hotspots, passive location system has the advantage of silent detection using civil radio illuminators. Sometimes the location information of the illuminators cant be obtained, such as the illuminators in neighboring country, which impact the use of the system. A method of unknown illuminator location is proposed, which takes use of matching multi-illuminators. The results of simulation are valuable references for tactical application of this system with simple calculation and high accuracy of positioning.
As one of the research hotspots, passive location system has the advantage of silent detection using civil radio illuminators. Sometimes the location information of the illuminators cant be obtained, such as the illuminators in neighboring country, which impact the use of the system. A method of unknown illuminator location is proposed, which takes use of matching multi-illuminators. The results of simulation are valuable references for tactical application of this system with simple calculation and high accuracy of positioning.
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