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1
2014, 3(4): 383-395.
Abstract
10214KB
The sparse microwave imaging combines the sparse signal processing theory with radar imaging to obtain new theory, new system, and new methodology of microwave imaging. In this paper, a brief review of fundamental issues in applying sparse signal processing to radar imaging is provided, including sparse representation, measurement matrix construction, unambiguity reconstruction, and so on. The developments of sparse signal processing in microwave imaging are discussed, and the initial airborne experiments on the prototype Synthetic Aperture Radar (SAR) framework with sparse constraints are introduced. The results demonstrate the feasibility and effectiveness of the principle and methodology of sparse microwave imaging. Besides, we also provide an overview of sparse signal processing in various radar applications, including Tomographic SAR (TomoSAR), Inverse SAR (ISAR), Ground Penetrating Radar (GPR) as well.
The sparse microwave imaging combines the sparse signal processing theory with radar imaging to obtain new theory, new system, and new methodology of microwave imaging. In this paper, a brief review of fundamental issues in applying sparse signal processing to radar imaging is provided, including sparse representation, measurement matrix construction, unambiguity reconstruction, and so on. The developments of sparse signal processing in microwave imaging are discussed, and the initial airborne experiments on the prototype Synthetic Aperture Radar (SAR) framework with sparse constraints are introduced. The results demonstrate the feasibility and effectiveness of the principle and methodology of sparse microwave imaging. Besides, we also provide an overview of sparse signal processing in various radar applications, including Tomographic SAR (TomoSAR), Inverse SAR (ISAR), Ground Penetrating Radar (GPR) as well.
2
2014, 3(2): 129-141.
For the high-speed, high-maneuverability and stealthy target detection via modern radar in complicated electromagnetic environment, a novel radar signal processing approach called Space-Time-Frequency Focus-Before-Detection (STF-FBD) via multi-dimensional coherent integration is proposed. Based on space-timefrequency signal modeling for modern radar systems, the proposed method can effectively suppress the strong interference, such as clutter and active jamming, and overcome the problems of scaled effect of high-speed targets, aperture fill time, sparse frequency sub-band synthesis, across range units, across Doppler units and across beam units. The proposed methods improves radar signal processing performance on the steps like energy integration, target detection, parameter estimation, maneuver tracking, feature extraction and target recognition. It also outperforms the existing Track-Before-Detection (TBD) methods and establish a unified STF-FBD and STF-FBD-TBD radar signal processing frame work. The proposed method is suitable for high-speed, high-maneuverability and stealthy target, as well as for conventional targets. It is applicable for new-generation modern radar, as well as for conventional radars, and may find application to different field.
For the high-speed, high-maneuverability and stealthy target detection via modern radar in complicated electromagnetic environment, a novel radar signal processing approach called Space-Time-Frequency Focus-Before-Detection (STF-FBD) via multi-dimensional coherent integration is proposed. Based on space-timefrequency signal modeling for modern radar systems, the proposed method can effectively suppress the strong interference, such as clutter and active jamming, and overcome the problems of scaled effect of high-speed targets, aperture fill time, sparse frequency sub-band synthesis, across range units, across Doppler units and across beam units. The proposed methods improves radar signal processing performance on the steps like energy integration, target detection, parameter estimation, maneuver tracking, feature extraction and target recognition. It also outperforms the existing Track-Before-Detection (TBD) methods and establish a unified STF-FBD and STF-FBD-TBD radar signal processing frame work. The proposed method is suitable for high-speed, high-maneuverability and stealthy target, as well as for conventional targets. It is applicable for new-generation modern radar, as well as for conventional radars, and may find application to different field.
3
2014, 3(3): 339-351.
The HJ-1C satellite was successfully launched in November 19, 2012. The HJ-1C and HJ-1A/1B satellites, which were launched in September 06, 2008, constitute the 2+1 small satellite constellation for environmental and disaster monitoring. This study focuses on the analysis and evaluation of the satellite
performance with respect to environmental remote sensing, including land use interpretation, land cover classification, oil spill identification, retrieval of sea waves, and monitoring of coastal mariculture. The data used in this study cover the city of Beijing and the sea of the Fujian Province. Nine HJ-1C satellite images (level-2, S band, VV Pol, strip mode, 5 m resolution) from December 2012 to January 2013 are used. The conclusions are as follows: (1) the HJ-1C SAR images can be used to manually identify farmland, woodland, roads, rivers, urban construction, and rural residential areas; (2) the accuracy of the automatic land cover classification increased significantly when the HJ-1C SAR and HJ-1B CCD fusion images are used; (3) the HJ-1C satellite can be used to identify oil spills, to invert wave parameters, and to extract information regarding inshore aquaculture.
The HJ-1C satellite was successfully launched in November 19, 2012. The HJ-1C and HJ-1A/1B satellites, which were launched in September 06, 2008, constitute the 2+1 small satellite constellation for environmental and disaster monitoring. This study focuses on the analysis and evaluation of the satellite
performance with respect to environmental remote sensing, including land use interpretation, land cover classification, oil spill identification, retrieval of sea waves, and monitoring of coastal mariculture. The data used in this study cover the city of Beijing and the sea of the Fujian Province. Nine HJ-1C satellite images (level-2, S band, VV Pol, strip mode, 5 m resolution) from December 2012 to January 2013 are used. The conclusions are as follows: (1) the HJ-1C SAR images can be used to manually identify farmland, woodland, roads, rivers, urban construction, and rural residential areas; (2) the accuracy of the automatic land cover classification increased significantly when the HJ-1C SAR and HJ-1B CCD fusion images are used; (3) the HJ-1C satellite can be used to identify oil spills, to invert wave parameters, and to extract information regarding inshore aquaculture.
4
2014, 3(3): 249-255.
HJ-1-C is a SAR satellite owned by the Chinese Environment and Natural Disaster Monitoring constellation, and works together with the optical satellites HJ-1-A/B for monitoring environment and natural disasters. In this paper, the system design and characteristics of the first Chinese civil SAR satellite are described. In addition, the interface relation between SAR payload and platform is studied. Meanwhile, the data transmission capability, attitude, power, and temperature control that support SAR imaging are reviewed. Finally, the corresponding in-orbit verification results are presented.
HJ-1-C is a SAR satellite owned by the Chinese Environment and Natural Disaster Monitoring constellation, and works together with the optical satellites HJ-1-A/B for monitoring environment and natural disasters. In this paper, the system design and characteristics of the first Chinese civil SAR satellite are described. In addition, the interface relation between SAR payload and platform is studied. Meanwhile, the data transmission capability, attitude, power, and temperature control that support SAR imaging are reviewed. Finally, the corresponding in-orbit verification results are presented.
5
2014, 3(6): 623-631.
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.
6
2014, 3(1): 10-18.
Recently, a novel conception of Synthetic Aperture Radar (SAR) based on Multi-Input Multi-Output (MIMO) technology draws much attention for its potential advantages. MIMO-SAR could obtain much more equivalent channels than the number of the physical array elements by simultaneously utilizing multiple antennas at transmission and reception. These additional channels are demonstrated to be useful for the application of High-Resolution Wide-Swath (HRWS) imaging and slowly moving target indication. In this paper, a detailed discussion on the conception and connotation of MIMO-SAR is made firstly, and then the investigation states of MIMO-SAR, such as high range resolution SAR imaging, three-dimensional down-looking SAR imaging, HRWS imaging and Ground Moving Target Indication (GMTI), are discussed. Base on the discussion mentioned above, the advantages and disadvantages of MIMO-SAR system are analyzed, and the key technical issues in MIMO-SAR are summarized. At last, the prospects of MIMO-SAR application are pointed out.
Recently, a novel conception of Synthetic Aperture Radar (SAR) based on Multi-Input Multi-Output (MIMO) technology draws much attention for its potential advantages. MIMO-SAR could obtain much more equivalent channels than the number of the physical array elements by simultaneously utilizing multiple antennas at transmission and reception. These additional channels are demonstrated to be useful for the application of High-Resolution Wide-Swath (HRWS) imaging and slowly moving target indication. In this paper, a detailed discussion on the conception and connotation of MIMO-SAR is made firstly, and then the investigation states of MIMO-SAR, such as high range resolution SAR imaging, three-dimensional down-looking SAR imaging, HRWS imaging and Ground Moving Target Indication (GMTI), are discussed. Base on the discussion mentioned above, the advantages and disadvantages of MIMO-SAR system are analyzed, and the key technical issues in MIMO-SAR are summarized. At last, the prospects of MIMO-SAR application are pointed out.
7
2014, 3(2): 201-207.
Compared with Space-Time Adaptive Processing (STAP), Space-Time Adaptive Detection (STAD) employs the data in the cell under test and those in the training to form reasonable detection statistics and consequently decides whether the target exists or not. The STAD has concise processing procedure and flexible design. Furthermore, the detection statistics usually possess the Constant False Alarm Rate (CFAR) property, and hence it needs no additional CFAR processing. More importantly, the STAD usually exhibits improved detection performance than that of the conventional processing, which first suppresses the clutter then adopts other detection strategy. In this paper, we first summarize the key strongpoint of the STAD, then make a classification for the STAD, and finally give some future research tracks.
Compared with Space-Time Adaptive Processing (STAP), Space-Time Adaptive Detection (STAD) employs the data in the cell under test and those in the training to form reasonable detection statistics and consequently decides whether the target exists or not. The STAD has concise processing procedure and flexible design. Furthermore, the detection statistics usually possess the Constant False Alarm Rate (CFAR) property, and hence it needs no additional CFAR processing. More importantly, the STAD usually exhibits improved detection performance than that of the conventional processing, which first suppresses the clutter then adopts other detection strategy. In this paper, we first summarize the key strongpoint of the STAD, then make a classification for the STAD, and finally give some future research tracks.
8
2014, 3(2): 217-228.
This paper gives a brief review on the Sparse-Recovery (SR)-based Space-Time Adaptive Processing (STAP) technique. First, the motivation for introducing sparse recovery into STAP is presented. Next, the potential advantages and mathematical explanation of the sparse-recovery-based STAP are discussed. A major part of this paper presents the state-of-art research results in spatio-temporal spectrum-sparsity-based STAP, including the basic frame, off-grid problem, multiple measurement vector problem, and direct domain problem. The sparse-recovery-based STAP on conformal array problem is also introduced. Finally, a summary of sparse-recovery-based STAP is provided, and the problems that need to be solved and some potential research areas are discussed.
This paper gives a brief review on the Sparse-Recovery (SR)-based Space-Time Adaptive Processing (STAP) technique. First, the motivation for introducing sparse recovery into STAP is presented. Next, the potential advantages and mathematical explanation of the sparse-recovery-based STAP are discussed. A major part of this paper presents the state-of-art research results in spatio-temporal spectrum-sparsity-based STAP, including the basic frame, off-grid problem, multiple measurement vector problem, and direct domain problem. The sparse-recovery-based STAP on conformal array problem is also introduced. Finally, a summary of sparse-recovery-based STAP is provided, and the problems that need to be solved and some potential research areas are discussed.
9
2014, 3(5): 548-555.
Integration of radar and communication systems based on OFDM signals results in large Peak-to-Average Power Ratio (PAPR). Limited by the code rate, algorithm that use the Golay sequence code to restrain PAPR can only be applied under the condition of a few subcarriers. This study proposes an algorithm to restrain the PAPR of systems with a large number of subcarriers. The algorithm combines the group parallel code with the optimization of weight coefficients. First, bit streams are divided into several groups of parallel bits. Next, every group proceeds with Golay sequence coding, data symbol modulating and inverse Fourier transform. Finally, the parallel result is combined with an OFDM symbol. Before the parallel data are combined, several weight coefficients for every group are introduced; thus, the system has several candidate symbols for transmitting. Then the symbol with minimum PAPR is then selected as the transmitting signal, and the PAPR of the whole system is reduced. PAPR performance, Bit Error Radio (BER) and wideband ambiguity function of three block methods with different coding rate are also simulated. The simulations show that the PAPR of the system decreases and the BER performance improves significantly. The signal exhibits a thumbtack ambiguity function, which suggests good resolution and accuracy for distance and velocity measurements.
Integration of radar and communication systems based on OFDM signals results in large Peak-to-Average Power Ratio (PAPR). Limited by the code rate, algorithm that use the Golay sequence code to restrain PAPR can only be applied under the condition of a few subcarriers. This study proposes an algorithm to restrain the PAPR of systems with a large number of subcarriers. The algorithm combines the group parallel code with the optimization of weight coefficients. First, bit streams are divided into several groups of parallel bits. Next, every group proceeds with Golay sequence coding, data symbol modulating and inverse Fourier transform. Finally, the parallel result is combined with an OFDM symbol. Before the parallel data are combined, several weight coefficients for every group are introduced; thus, the system has several candidate symbols for transmitting. Then the symbol with minimum PAPR is then selected as the transmitting signal, and the PAPR of the whole system is reduced. PAPR performance, Bit Error Radio (BER) and wideband ambiguity function of three block methods with different coding rate are also simulated. The simulations show that the PAPR of the system decreases and the BER performance improves significantly. The signal exhibits a thumbtack ambiguity function, which suggests good resolution and accuracy for distance and velocity measurements.
10
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.
11
2014, 3(5): 533-540.
Zero Memory NonLinearity (ZMNL) and Spherically Invariant Random Process (SIRP) are two commonly used methods in K-distribution clutter simulations. An improved simulation method, which adds abranch of Gamma-distributed variable and extends the shape parameter to arbitrary positive real, is proposed to address the clutter simulation error in the conventional ZMNL method. To reduce the computation required for the conventional SIRP method, an improved method of modulation variable generation is also proposed, what avoids large computations for solving nonlinear equations and improves the simulation speed. The simulation results verify the effectiveness of the improved methods.
Zero Memory NonLinearity (ZMNL) and Spherically Invariant Random Process (SIRP) are two commonly used methods in K-distribution clutter simulations. An improved simulation method, which adds abranch of Gamma-distributed variable and extends the shape parameter to arbitrary positive real, is proposed to address the clutter simulation error in the conventional ZMNL method. To reduce the computation required for the conventional SIRP method, an improved method of modulation variable generation is also proposed, what avoids large computations for solving nonlinear equations and improves the simulation speed. The simulation results verify the effectiveness of the improved methods.
12
2014, 3(1): 85-91.
Geometrical imaging models and calculations of orientation parameters are the main factors affecting the positioning of stereo Synthetic Aperture Radar (SAR) images. For accurate positioning with squint stereo SAR images and less Ground Control Points (GCPs), a positioning algorithm with one GCP is designed. In this algorithm, the position and velocity of the radar antenna phase center are derived using orbit parameters, and the close range and Doppler centroid of the SAR images are compensated by one GCP. Thus, accurate orientation parameters are obtained and accurate positioning with stereo SAR images is completed. Airborne SAR images acquired by the Chinese Academy of Surveying and Mapping are used in experiments. The positioning errors of the checkpoints are calculated and analyzed, and it verified the accuracy and effectiveness of the proposed method.
Geometrical imaging models and calculations of orientation parameters are the main factors affecting the positioning of stereo Synthetic Aperture Radar (SAR) images. For accurate positioning with squint stereo SAR images and less Ground Control Points (GCPs), a positioning algorithm with one GCP is designed. In this algorithm, the position and velocity of the radar antenna phase center are derived using orbit parameters, and the close range and Doppler centroid of the SAR images are compensated by one GCP. Thus, accurate orientation parameters are obtained and accurate positioning with stereo SAR images is completed. Airborne SAR images acquired by the Chinese Academy of Surveying and Mapping are used in experiments. The positioning errors of the checkpoints are calculated and analyzed, and it verified the accuracy and effectiveness of the proposed method.
13
2014, 3(3): 282-287.
Expansion-driven HJ-1-C satellite components are prone to fatigue and fracture; thus, a reliability study on the optimal design is performed. According to the Failure Mode and Effects Analysis (FMEA) of the components, the main failure modes are stress relaxation and impact breakage of the torsion and scroll springs. On the basis of the failure modes, a prototype spring is tested, and the relative reliabilities are calculated. Then, reliability measures are proposed, and the design optimization of the springs is carried out. The improvements introduced by the prototype spring are indicative of the effectiveness and reliability of the design optimization process, which can help design and analyze similar antenna reflectors in the future.
Expansion-driven HJ-1-C satellite components are prone to fatigue and fracture; thus, a reliability study on the optimal design is performed. According to the Failure Mode and Effects Analysis (FMEA) of the components, the main failure modes are stress relaxation and impact breakage of the torsion and scroll springs. On the basis of the failure modes, a prototype spring is tested, and the relative reliabilities are calculated. Then, reliability measures are proposed, and the design optimization of the springs is carried out. The improvements introduced by the prototype spring are indicative of the effectiveness and reliability of the design optimization process, which can help design and analyze similar antenna reflectors in the future.
14
2014, 3(3): 266-273.
With truss deployable mesh parabolic reflector, the HJ-1-C SAR antenna has complex structure and multiple steps during the deployed processing. The design of the antenna is difficult in terms of deployed reliability and electrical performance. This paper makes intensive research on system, structure and electrical design, and the analysis of mechanical and thermal performance in the actual space conditions is also presented. The successful deploying in orbit and high image quality of the HJ-1-C satellite indicate that the mechanical, electronic, thermal and reliability design of the antenna satisfy the project requirement, and these research provides valuable experience for the design of the centralized mesh parabolic SAR antenna.
With truss deployable mesh parabolic reflector, the HJ-1-C SAR antenna has complex structure and multiple steps during the deployed processing. The design of the antenna is difficult in terms of deployed reliability and electrical performance. This paper makes intensive research on system, structure and electrical design, and the analysis of mechanical and thermal performance in the actual space conditions is also presented. The successful deploying in orbit and high image quality of the HJ-1-C satellite indicate that the mechanical, electronic, thermal and reliability design of the antenna satisfy the project requirement, and these research provides valuable experience for the design of the centralized mesh parabolic SAR antenna.
15
2014, 3(3): 256-265.
HJ-1-C is a Synthetic Aperture Radar (SAR) satellite in the Constellation of 2+1 for China environment and disaster monitoring. It works at S-band with a resolution of 5 m. SAR payload uses a reflector antenna and a high-power concentrated transmitter. Its light weight and high efficiency is very suitable for a small satellite platform. Now HJ-1-C satellite has been launched into orbit and has acquired Chinese first S-band SAR images from space, which demonstrate excellent quality and rich information about scenes imaged. This success verifies our design, testing and experiment work on the payload. With its following operation, HJ-1-C satellite is expected to make a great contribution to the applications of environment protection and disaster monitoring in China. This paper introduces the design and development of HJ-1-C SAR payload, present its main parameters and performance, describes its device details and its manufacture, testing and experiment process. Some images acquired in the orbit are showed.
HJ-1-C is a Synthetic Aperture Radar (SAR) satellite in the Constellation of 2+1 for China environment and disaster monitoring. It works at S-band with a resolution of 5 m. SAR payload uses a reflector antenna and a high-power concentrated transmitter. Its light weight and high efficiency is very suitable for a small satellite platform. Now HJ-1-C satellite has been launched into orbit and has acquired Chinese first S-band SAR images from space, which demonstrate excellent quality and rich information about scenes imaged. This success verifies our design, testing and experiment work on the payload. With its following operation, HJ-1-C satellite is expected to make a great contribution to the applications of environment protection and disaster monitoring in China. This paper introduces the design and development of HJ-1-C SAR payload, present its main parameters and performance, describes its device details and its manufacture, testing and experiment process. Some images acquired in the orbit are showed.
16
2014, 3(4): 444-449.
Target classification is particularly important in modern and future airborne radar. Nowadays, most investigations of radar target classification are based on wideband radar signals, which have higher requirements for SNR and radar systems, and are sensitive to the angles. Modern airborne radars require narrowband tracking and target classification; hence, an algorithm based on the narrowband fractal features and the amplitude modulation of a two-dimensional distribution is presented. Experimental data and Support Vector Machine (SVM) are used to verify the algorithm, and the classification results validate the proposed method, which show that jet aircrafts, propeller aircrafts, and helicopters can be classified with an average discrimination rate greater than 92%.
Target classification is particularly important in modern and future airborne radar. Nowadays, most investigations of radar target classification are based on wideband radar signals, which have higher requirements for SNR and radar systems, and are sensitive to the angles. Modern airborne radars require narrowband tracking and target classification; hence, an algorithm based on the narrowband fractal features and the amplitude modulation of a two-dimensional distribution is presented. Experimental data and Support Vector Machine (SVM) are used to verify the algorithm, and the classification results validate the proposed method, which show that jet aircrafts, propeller aircrafts, and helicopters can be classified with an average discrimination rate greater than 92%.
17
2014, 3(4): 465-473.
A novel optimal power allocation algorithm for radar network systems is proposed for Low Probability of Intercept (LPI) technology in modern electronic warfare. The algorithm is based on the LPI optimization. First, the Schleher intercept factor for a radar network is derived, and then the Schleher intercept factor is minimized by optimizing the transmission power allocation among netted radars in the network to guarantee target-tracking performance. Furthermore, the Nonlinear Programming Genetic Algorithm (NPGA) is used to solve the resulting nonconvex, nonlinear, and constrained optimization problem. Numerical simulation results show the effectiveness of the proposed algorithm.
A novel optimal power allocation algorithm for radar network systems is proposed for Low Probability of Intercept (LPI) technology in modern electronic warfare. The algorithm is based on the LPI optimization. First, the Schleher intercept factor for a radar network is derived, and then the Schleher intercept factor is minimized by optimizing the transmission power allocation among netted radars in the network to guarantee target-tracking performance. Furthermore, the Nonlinear Programming Genetic Algorithm (NPGA) is used to solve the resulting nonconvex, nonlinear, and constrained optimization problem. Numerical simulation results show the effectiveness of the proposed algorithm.
18
2014, 3(2): 241-248.
The Displaced Phase Center Antenna (DPCA) technology, a particular form of Space Time Adaptive Processing (STAP), has been widely used in Synthetic Aperture Radar Ground Moving Target Indication (SAR-GMTI). The GMTI performance depends on the capability of clutter rejection but the traditional DPCA technology operated in the complex image domain does not have the appropriate clutter rejection capability for urban areas with strong scattering stationary objects. Hence, interferometry phase is used to weight the DPCA magnitude nonlinearly, and a weighted DPCA clutter rejection approach is proposed, which reduces the interference from residual phase difference. The experimental results suggest that the new approach can improve the clutter rejection compared with the conventional DPCA.
The Displaced Phase Center Antenna (DPCA) technology, a particular form of Space Time Adaptive Processing (STAP), has been widely used in Synthetic Aperture Radar Ground Moving Target Indication (SAR-GMTI). The GMTI performance depends on the capability of clutter rejection but the traditional DPCA technology operated in the complex image domain does not have the appropriate clutter rejection capability for urban areas with strong scattering stationary objects. Hence, interferometry phase is used to weight the DPCA magnitude nonlinearly, and a weighted DPCA clutter rejection approach is proposed, which reduces the interference from residual phase difference. The experimental results suggest that the new approach can improve the clutter rejection compared with the conventional DPCA.
19
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.
20
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.
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