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Through formation flying, the distributed spaceborne SAR(synthetic aperture radar) system can increase the number of spatial degree of freedoms (DOFs) and provide flexible multi-baselines for SAR-GMTI (ground moving target indication), which improves the system performance. This paper proposes an a priori knowledge-based adaptive clutter cancellation and moving target detection technique applied to the distributed spaceborne SAR-GMTI systems. Firstly, the adaptive clutter cancellation technique is exploited to suppress the ground clutter. A priori knowledge, such as road network information, is integrated to the adaptive clutter cancellation processor to reduce any moving target steering vector mismatch. Secondly, adaptive matched filter (AMF) and adaptive beamformer orthogonal rejection test (ABORT) are exploited as adaptive detection techniques for moving target detection. Due to the dense road network, the moving target steering vector estimation may be ambiguous for the different position and orientation of the roads. The multiple hypothesis testing (MHT) technique is proposed to detect the moving targets and resolve the potential ambiguities. A scheme is exploited to detect, classify, and relocate the moving targets. Finally, simulation experiments and performance analysis have demonstrated the effectiveness and robustness of the proposed technique. [ABSTRACT FROM AUTHOR]

Synthetic aperture radar (SAR) collects signals for extended durations to generate high-resolution images. In general, SAR processing assumes stationary targets, and when moving targets are located in the scene, the processed images are defocused through blurring effects, or their locations are shifted from the true positions. Accordingly, the detection and tracking of moving targets have long been an active research topic in the SAR community. In this study, we propose a method for detecting and tracking a moving target using a single-channel spacebprem SAR system by adopting sub-aperture processing based on the spotlight mode. We show that the blurring effect of the smearing target energy is suppressed by dividing the sub-aperture intervals, thus helping identify the moving target. Accordingly, the direction and velocity of the moving target were obtained by analyzing the multi-frame target scenes. For verification, a spaceborne SAR simulator was designed for moving target tracking. The range and azimuth velocities are extracted from the multi- frame target images to compensate for the position shift and recover the true trajectory of the moving target. [ABSTRACT FROM AUTHOR]

A target-tracking method using the ground moving target indicator (GMTI) mode on active electronically scanned array (AESA) radar is proposed. The GMTI mode can operate in wide ground areas. However, the 3-dB beamwidth of the X-band radar is narrow, and a target is detected on multiple adjacent beams. To delete overlapping target plots, beam-to-beam processing considering a real-time system is proposed. In addition, a track while scan (TWS) multiple-target-tracking algorithm was constructed for the system. Through a flight test with true car mounted GPS, it was confirmed that the real-time processing ability and target-tracking performance of the GMTI algorithm were satisfactory. [ABSTRACT FROM AUTHOR]

Through formation flying, the distributed spaceborne SAR(synthetic aperture radar) system can increase the number of spatial degree of freedoms (DOFs) and provide flexible multi-baselines for SAR-GMTI (ground moving target indication), which improves the system performance. This paper proposes an a priori knowledge-based adaptive clutter cancellation and moving target detection technique applied to the distributed spaceborne SAR-GMTI systems. Firstly, the adaptive clutter cancellation technique is exploited to suppress the ground clutter. A priori knowledge, such as road network information, is integrated to the adaptive clutter cancellation processor to reduce any moving target steering vector mismatch. Secondly, adaptive matched filter (AMF) and adaptive beamformer orthogonal rejection test (ABORT) are exploited as adaptive detection techniques for moving target detection. Due to the dense road network, the moving target steering vector estimation may be ambiguous for the different position and orientation of the roads. The multiple hypothesis testing (MHT) technique is proposed to detect the moving targets and resolve the potential ambiguities. A scheme is exploited to detect, classify, and relocate the moving targets. Finally, simulation experiments and performance analysis have demonstrated the effectiveness and robustness of the proposed technique.

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Skilled at representing the chirp signal, Radon-Wigner distribution (RWD) plays an important role in parameters estimation for moving targets. By searching for the best time-frequency angle, the conventional RWD estimation method suffers from the tradeoff between the estimation accuracy and computation complexity. In this paper, an efficient RWD estimation method is proposed by exploiting the geometry information in the RWD domain, and extensive parameters searching is replaced by only two parameters computation, then the computation complexity is effectively reduced from O(MN) to O(2N). The proposed efficient RWD method is applied in moving targets velocity estimation, which is emerging issue for smart city. The non-ideal factors in real circumstance are considered, and three robust methods are proposed to improve the estimation accuracy by exploiting the geometry information in the RWD domain further. A clutter suppression RWD (CSRWD) method is proposed to cancel the clutter but preserve the moving target in the RWD domain, and a learned RWD (LRWD) method is proposed to minimize the estimation error caused by measurement error. Then, CSRWD is combined with LRWD to obtain a unified robust RWD (URRWD), which possesses the advantages of CSRWD and LRWD simultaneously. Simulation and real data processing results validate the proposed methods, and lower implementation complexity is proven under the same accuracy assumption. It can be considered as the geometry information opens a window for the searching-based estimation method to make the original bleak searching process suddenly bright. The concept can also be expanded to the other searching-based estimation methods, such as Radon transform, fractional Fourier transform and so on.

Video SAR can identify changes in the region of interest and the path of targets through continuous observation of the region of interest and targets irrespective of the weather and day or night. Recently, as the complexity of the region of interest, such as urban areas, has increased, research is being conducted to use drones as payloads for video SAR. The satellite, an existing platform, uses information through multiple antennas, and the distance between the target and the platform is sufficiently far to approximate the speed of the target to detect the moving target. However, the drones cannot approximate the target speed owing to the close distance to the target, and there is a limitation in the payload weight; hence, it is difficult to use multiple antennas. Therefore, this study investigates the process of detecting a moving target using a compressive sensing technique on a short-range platform equipped with a single antenna. Finally, through simulation and real data, it was verified that the video SAR image processing of a moving target based on compression sensing was possible. [ABSTRACT FROM AUTHOR]

This paper deals with the problem of detection and direction of arrival (DOA) estimation of slowly moving targets against clutter in multichannel mobile passive radar. A dual cancelled channel space-time adaptive processing (STAP) scheme is proposed, aiming at reducing the system computational complexity, as well as the amount of required training data, compared to a conventional full array solution. The proposed scheme is shown to yield comparable target detection capability and DOA estimation accuracy with respect to the corresponding full array solution, despite the lower computational cost required. Moreover, it offers increased robustness against adaptivity losses, operating effectively even in the presence of a limited set of training data, as often available in the highly non-homogeneous clutter scenarios experienced in bistatic passive radar. The effectiveness of the proposed scheme and its suitability for passive GMTI are demonstrated against both simulated and experimental data collected by a DVB-T-based multichannel mobile passive radar.

With the maturity of the instantaneous full-polarisation measurement, the instantaneous full-polarimetric system is becoming an important development direction of the polarimetric synthetic aperture radar (POLSAR); however, as an important research branch of the synthetic aperture radar (SAR), the along-track interferometry (ATI) technology for the ground moving target indication (GMTI) is still largely confined to be single polarimetric. In order to facilitate the study of GMTI using a full-polarimetric along-track interferometric SAR (AT-POLINSAR), this study first models the transmitting and receiving signals of AT-POLINSAR and points out its realisability in the existing technical condition of POLSAR. Then, the 6D vector interferometric model for the full-polarimetric echoes is established, where the differences of data processing with the single-polarimetric ATI are analysed. Finally, two simulation methods of the AT-POLINSAR images are given for the generation of signal-level and image-level data, where the results have shown that both the data quality of the interferometric system and its detection performance for moving targets can be improved by the introduction of full polarisation.

With the maturity of the instantaneous full-polarisation measurement, the instantaneous full-polarimetric system is becoming an important development direction of the polarimetric synthetic aperture radar (POLSAR); however, as an important research branch of the synthetic aperture radar (SAR), the along-track interferometry (ATI) technology for the ground moving target indication (GMTI) is still largely confined to be single polarimetric. In order to facilitate the study of GMTI using a full-polarimetric along-track interferometric SAR (AT-POLINSAR), this study first models the transmitting and receiving signals of AT-POLINSAR and points out its realisability in the existing technical condition of POLSAR. Then, the 6D vector interferometric model for the full-polarimetric echoes is established, where the differences of data processing with the single-polarimetric ATI are analysed. Finally, two simulation methods of the AT-POLINSAR images are given for the generation of signal-level and image-level data, where the results have shown that both the data quality of the interferometric system and its detection performance for moving targets can be improved by the introduction of full polarisation. [ABSTRACT FROM AUTHOR]

This study presents an imaging algorithm that can provide an image of a moving target in a multiple-input–multiple-output radar environment where multiple transmitting and receiving radars are fixed on the ground. The proposed algorithm, which is based on polar format processing using plane wave approximation, is shown to provide an unaliased image by using multiple transmitting radars even when the distances between the receiving radars are relatively large. We derive the conditions necessary to deploy the transmitting radars by which the resolution of the reconstructed image can be improved, while simultaneously reducing aliasing artifacts. Moreover, we offer a means of separating out each transmitting radar target echo. Finally, the performance of the proposed system is verified through a simulation. [ABSTRACT FROM AUTHOR]

Ground moving target imaging finds its main applications in both military and homeland security applications, with examples in operations of intelligence, surveillance and reconnaissance (ISR) as well as border surveillance. When such an operation is performed from the air looking down towards the ground, the clutter return may be comparable or even stronger than the target’s, making the latter hard to be detected and imaged. In order to solve this problem, multichannel radar systems are used that are able to remove the ground clutter and effectively detect and image moving targets. In this feature paper, the latest findings in the area of Ground Moving Target Imaging are revisited that see the joint application of Space-Time Adaptive Processing and Inverse Synthetic Aperture Radar Imaging. The theoretical aspects analysed in this paper are supported by practical evidence and followed by application-oriented discussions.

This paper presents a ground-to-air bistatic radar system and its implementation algorithm, which resembles an SAR(synthetic aperture radar) reconstruction algorithm. Via cooperative working between a standoff transmitting radar and an array of ground based receiving radars, it detects and images moving targets under clutter in the air. In the proposed system, the whole receiving antenna aperture is synthesized by physical ground based radars, and thus, unlike conventional SAR, it does not require long illumination time of the target area. The reconstruction algorithm uses planewave approximation based polar format processing, which alleviates the requirement of positioning the receiving radars, which can cause grating lobes if not chosen properly. We derive a reconstruction algorithm including clutter suppression and discuss implementation issues, such as the resolution of a reconstructed image and the method of compensation for the irregularity of the receiving radars' positions. A simulation that validates the proposed algorithm is also shown. [ABSTRACT FROM AUTHOR]

Using ground moving target indicators equipped with synthetic aperture radars for locating moving targets within a wide background clutter in a short time is an excellent method for monitoring traffic. Although the displaced phase center antenna (DPCA) technique and along track interferometry (ATI) are real time methods with low computational complexity, they are essential for reducing cases of false alarm that can result in poor performance. In this paper, we propose two detection methods using DPCA and ATI-the parallel fusion method and serial fusion method. Simulation results demonstrate that the proposed detection methods are characterized by low probability of false alarm along with good performance. In particular, the serial fusion method possesses high detection probability along with low probability of false alarm (1/5th of the false alarm probability of the DPCA technique). [ABSTRACT FROM AUTHOR]

Accurate and efficient moving target imaging is an important challenge for targets recognition in current synthetic aperture radar (SAR) combined with a ground moving target indication (GMTI) system. As the key but unknown parameter, the Doppler rates are estimated conventionally by searching any possible values for moving targets imaging. However, this conventional estimation method suffers from low accuracy or low efficiency due to the searching procedure. Focusing on these, we present a method to efficiently image the moving targets without the Doppler rate by Doppler delayed interferometry, and the imaged localization, which is parameterized pseudo-localization, is used to estimate the Doppler rate. In order to improve the estimation accuracy, an improved method based on the Newton method of approximation is proposed by exploiting the unused amplitude information. Compared with the conventional methods, the proposed improved method capable of high accuracy and low computation complexity simultaneously can meet the accurate and efficient requirements in the practical applications. Comparison simulations and real data processing results demonstrate the effectiveness of the proposed methods. [ABSTRACT FROM AUTHOR]

Ground moving target indicator(GMTI) using syntheticaperture radar(SAR) used for finding moving targets on wide background clutter in short time is one of good ways to monitor a traffic situation or an enemy’s threat. Although displaced phase center antenna (DPCA) is a real time method with low computational complexity, there have been few studies about its performance against various ground clutters. Thus, we need to analyze GMTI performance for various ground clutters in order to design a suitable DPCA detector. In this paper, simulation results show that the conventional DPCA detector produces different performance in terms of detection rate and false alarm rate. In particular, the false alarm rate of heterogeneous or extremely heterogeneous clutter from urban area is higher than one of homogeneous clutter from natural area. [ABSTRACT FROM AUTHOR]

An air-to-ground guidance missile aimed to hit a main battle tank(MBT) should detect a ground moving target and estimate the target position to guide. In this paper, we detect a front ground moving target by using FMCW(Frequency Modulated Continuous Wave) and estimate the position by forward-looking SAR(Synthetic Aperture Radar) via scanning certain front ground section by steering a beam with narrow beamwidth left to right mechanically. Also, by MLE(Maximum Likelihood Estimation), degree of how fast the target approach or recede from the radar can be figured out from the estimated radial velocity of the moving target. Subsequently, we generate a radar image via corrected matched filter from phase history including the radial velocity. [ABSTRACT FROM AUTHOR]

Applications of Sigma-Delta STAP, and a method of GMTI processing are presented for GMTI(Ground Moving Target Indication) mode of airborne radar with sigma, delta, and guard channels. We showed results of performance analyses of presented methods by clutter simulation with ICM(Internal Clutter Motion), signal processing simulation and MDV(Minimum Detectable Velocity). Presented methods for Sigma-Delta STAP and GMTI processing are easy to apply practically in GMTI mode of airborne radar without restriction by specific airborne radar system. [ABSTRACT FROM AUTHOR]

Recently, the SAR-GMTI mode is becoming increasingly essential in airborne radar systems. While SAR requires wideband waveforms for high resolution imaging, GMTI requires narrowband waveforms for doppler processing, which makes general LFM waveforms difficult to use for SAR-GMTI. This paper analyses the FJB(Frequency Jump Burst) waveform, which is studied for the SAR-GMTI waveform, and presents the method for the pulse compression and SAR image formation using FJB waveforms. Simulation results show that there is little difference in performances between the FJB waveform and the LFM waveform. [ABSTRACT FROM AUTHOR]

Multichannel space-based synthetic aperture radar (SAR) systems that exploit receiving antenna subarrays displaced in the along-track direction have been shown to provide the capability to detect ground moving targets and potentially estimate their radial motion velocity, thus making possible their correct relocation inside the SAR image of the background. However, the use of only two receiving channels to contain cost, mass, and data-rate, imposes limitations in terms of potentiality of joint clutter cancelation and target velocity estimation. To overcome this problem, we propose a full MIMO SAR scheme obtained by transmitting nearly orthogonal waveforms with the two subarrays achieved from a single antenna aperture and receiving with the same subarrays. A complete processing chain for the joint detection, imaging, and radial speed estimation is presented showing that by properly applying the clutter cancelation step before waveform compression, a good clutter removal performance is obtained despite the waveforms are not fully orthogonal. The performance of the proposed MIMO system is deeply investigated and compared to the performance of conventional multichannel systems to assess the relative merits and drawbacks. [ABSTRACT FROM PUBLISHER]

Abstract: The non-ideal conditions of real-world detection environments, such as beam-pattern mismatch, non-ideal sensor geometry, receiver channel imbalance and clutter heterogeneity, can preclude the performance described in much of the theoretical STAP literature. For the purpose of overcoming those problems, a new target detection and location approach with low complexity is proposed. This presented algorithm is performed in three stages, i.e. array manifold adaptive calibration, clutter rejection in Winner filter sense and target parameters estimation using modified single-snapshot multiple direction of arrival estimation method. The array manifold calibration procedure uses a power-based criterion to reject a weak clutter patch and/or target for covariance matrix estimation, meanwhile, a phase-based criterion is adopted to alleviate the strong target signal contamination problem. Once the array has been calibrated, adaptive clutter and/or jamming cancellation can be achieved in the Wiener filter sense. This step does not require angle-Doppler bin searching. The last stage is carried out at the determinate range-Doppler test cell to locate moving target by azimuth searching for that one fitting best to the moving target signal, thus the location performance would not be sacrificed in order to suppress clutter and/or interference and the high resolution radial velocity estimation can be achieved. Therefore, the proposed algorithm is computationally inexpensive and is better suited to work in real-world detection environments. A preliminary result against an airborne experimental data demonstrates the effectiveness of the proposed method. [Copyright &y& Elsevier]

We develop a theory for waveform-diverse moving-target synthetic-aperture radar in the case in which a single moving antenna is used both on transmission and on reception. We assume that the targets (scattering objects) are moving linearly, but we allow an arbitrary, known flight path for the antenna and allow it to transmit a sequence of arbitrary, known waveforms. A formula for phase-space (position and velocity) imaging is developed, and we provide a formula for the point-spread function of the corresponding imaging system. This point-spread function is expressed in terms of the ordinary radar ambiguity function. As an example, we show how the theory can be applied to the problem of estimating the errors that arise when target and antenna motion is neglected during the transit time of each pulse. [ABSTRACT FROM AUTHOR]

In this article, we study optimization of a RapidIO network and FPGA-based computation engines to address the taxing requirements of a set of real-time Ground-Moving Target Indicators (GMTI) and Synthetic Aperture Radar (SAR) kernels for Space-Based Radar (SBR). By employing a RapidIO hardware testbed and validated simulation, we determine key trade-offs in design of reconfigurable systems for GMTI and SAR in terms of processing, memory, and network throughput. In addition, we study considerations for timely delivery of latency-sensitive control traffic present in many satellite applications. Based on our results, we propose architectural modifications to further improve performance of SBR systems. [ABSTRACT FROM AUTHOR]

Abstract: Collectively moving object clusters are of particular interest in certain applications and have to be tracked as separate aggregated entities consisting of an unknown number of individuals. Group targets often will not cause as many detections since there are individual targets in the group due to limited sensor resolution capabilities. In this case, tracking and data association under the ‘one target, one detection’ assumption are no longer applicable. In this paper, ellipsoidal object extensions are modeled by random matrices, which are treated as additional state variables to be estimated. An important aspect of GMTI tracking is the incorporation of context information into the Bayesian data processing formalism. Here we consider kinematical constraints such as road maps and sensor specific characteristics such as Doppler blindness. [Copyright &y& Elsevier]

In this letter, a two-channel airborne experimental interferometric synthetic aperture radar (InSAR) designed for terrain height estimation is exploited to acquire the ability of ground moving target indication (GMTI). Due to the hybrid baseline of this system, the interferometric phase changes with the target motion as well as the terrain height. The fluctuation of the interferometric phase worsens the performance of the clutter suppression and the radial velocity estimation. In order to resolve this problem, a GMTI method with three steps is proposed. After two steps are used to eliminate the local flat-Earth phase and the cross-track interferometric phase of the scene, respectively, an adaptive filtering method is used to suppress the stationary clutter with the benefit of calibrating the sensor responses. A conventional constant false alarm rate detector is then used to indicate the moving targets. The validity of the proposed method is demonstrated with real data collected using an experimental airborne InSAR system. [ABSTRACT FROM PUBLISHER]

Abstract: For current GMTI trackers, one of the most common contextual information used is road network information. In this paper, we present our approach using the road network information in tracking ground targets and in solving some ambiguities that can arise at road intersections or following a target manoeuvre leaving the road. For this we examine the performances of an adapted algorithm for tracking manoeuvring ground targets on road and off road in a cluttered environment using the map information. [Copyright &y& Elsevier]

Abstract: With TerraSAR-X, Germany will launch its first dual-channel SAR satellite mission in the year 2006. Besides other commercial applications TerraSAR-X should also be used as a demonstrator for traffic monitoring from space. This paper revises the theoretical background of traffic monitoring with space-based SARs and applies the conclusions to a performance analysis of the TerraSAR-X Traffic monitoring system. As it is well known, an object moving with a velocity deviating from the assumptions incorporated in the focusing process of the synthetic aperture radar (SAR) principle will generally appear both displaced and blurred in the image. To study the impact of these (and related) distortions in focused SAR images, the analytic relations between an arbitrarily moving point scatterer and its conjugate in the SAR image have been reviewed and adapted to the dual-channel satellite specifications of TerraSAR-X. To be able to monitor traffic under these boundary conditions in real-life situations, a specific detection scheme is proposed. This scheme integrates complementary detection and velocity estimation algorithms with knowledge derived from external sources as, e.g., road databases. The main focus of this article lies on an extensive analytical and empirical accuracy analysis for both vehicle detection and velocity estimation. The accuracy analysis includes a theoretical accuracy evaluation and a validation with real data. [Copyright &y& Elsevier]

This paper investigates ground moving target indication using a multiaperture synthetic aperture radar. Target detectors based on an eigendecomposition of the multi-channel covariance matrix are presented. Comparisons of the proposed detectors with classical methods, such as displaced phase centre antenna, or along track interferometry, show increased capability in heterogeneous terrain. By decomposing the complex Wishart probability distribution of the sample covariance matrix into probability distributions of the eigenvalues and eigenvectors, we calculate the probability of moving target detection vs. the signal to clutter plus noise ratio for a fixed false alarm rate in homogeneous and heterogeneous terrain. The probability distributions allow implementation of a constant false alarm rate detector. The complete analysis is presented for a two-channel system. [Copyright &y& Elsevier]

This paper presents a research development of wavelets feature aided tracking, which effectively combines information from both high-resolution range (HRR) radar profiles and ground moving target indication (GMTI) radar reports. The state-of-the-art wavelets-based statistical signal processing technique: wavelets domain hidden Markov trees is used to extract robust features from HRR profiles. With the assistance of HRR wavelets features, a GMTI tracker based on a probabilistic data association logic can effectively track ground moving targets in confusing scenarios. [Copyright &y& Elsevier]

This paper deals with the problem of detection and direction of arrival (DOA) estimation of slowly moving targets against clutter in multichannel mobile passive radar. A dual cancelled channel space-time adaptive processing (STAP) scheme is proposed, aiming at reducing the system computational complexity, as well as the amount of required training data, compared to a conventional full array solution. The proposed scheme is shown to yield comparable target detection capability and DOA estimation accuracy with respect to the corresponding full array solution, despite the lower computational cost required. Moreover, it offers increased robustness against adaptivity losses, operating effectively even in the presence of a limited set of training data, as often available in the highly non-homogeneous clutter scenarios experienced in bistatic passive radar. The effectiveness of the proposed scheme and its suitability for passive GMTI are demonstrated against both simulated and experimental data collected by a DVB-T-based multichannel mobile passive radar. [ABSTRACT FROM AUTHOR]