Showing papers on "Moving target indication published in 2012"

Coherent Radar Target Detection in Heavy-Tailed Compound-Gaussian Clutter

Abstract: This paper deals with the problem of detecting a radar target signal against correlated non-Gaussian clutter, which is modeled by the compound-Gaussian distribution. We prove that if the texture of compound-Gaussian clutter is modeled by an inverse-gamma distribution, the optimum detector is the optimum Gaussian matched filter detector compared to a data-dependent threshold that varies linearly with a quadratic statistic of the data. We call this optimum detector a linear-threshold detector (LTD). Then, we show that the compound-Gaussian model presented here varies parametrically from the Gaussian clutter model to a clutter model whose tails are evidently heavier than any K-distribution model. Moreover, we show that the generalized likelihood ratio test (GLRT), which is a popular suboptimum detector because of its constant false-alarm rate (CFAR) property, is an optimum detector for our clutter model in the limit as the tails get extremely heavy. The GLRT-LTD is tested against simulated high-resolution sea clutter data to investigate the dependence of its performance on the various clutter parameters.

Optimum SAR/GMTI Processing and Its Application to the Radar Satellite RADARSAT-2 for Traffic Monitoring

Abstract: This paper derives an optimum processing method for ground moving-target indication (GMTI) with a multichannel synthetic aperture radar (SAR) system. This method enables efficient detection of moving objects and accurate estimation of their parameters and does not require any knowledge of the street network. The processing is applied to data acquired with the Canadian RADARSAT-2 satellite. Results of the performed trial are compared with the expected GMTI performance of the radar in order to validate the theory.

DPCA Detection of Moving Targets in Airborne Passive Radar

Abstract: A new approach to the passive coherent location (PCL) signal processing technique dedicated for use on mobile radar platforms is presented. The main goal of the research conducted was to present different aspects of an efficient space-time ground moving target indication (GMTI) algorithm for PCL radar mounted to airborne platforms. The algorithm described, based on displacement phase center antenna (DPCA), has been successfully tested with simulated and real-life data collected with an airborne passive radar demonstrator (PaRaDe).

Fast GMTI Algorithm For Traffic Monitoring Based On A Priori Knowledge

Abstract: In this paper, a fast a priori knowledge-based ground moving target indication and parameter estimation algorithm applicable to single- as well as to multichannel synthetic aperture airborne radar data is presented. The algorithm operates directly on range-compressed data. Only the intersection points of the moving vehicle signals with the a priori known road axes, which are mapped into the range-compressed data array, are evaluated. For moving vehicle detection and parameter estimation, basically only a single 1-D fast Fourier transformation has to be performed for each considered road point. Hence, the required computational power is low, and the algorithm is well suited for real-time traffic monitoring applications. The proposed algorithm enables the estimation of the position and velocity vectors of detected moving vehicles independent of the number of channels. A single-channel synthetic aperture radar system may be sufficient in case of fast moving vehicles. The paper includes a detailed performance assessment together with experimental results that demonstrate the applicability in a real-world scenario.

Ground Moving Target Signal Analysis in Complex Image Domain for Multichannel SAR

Abstract: For along-track multichannel synthetic aperture radar, this paper proposes a novel ground moving target signal model in the high-resolution complex image domain. Based on the range-Doppler imaging of static scene, the 2-D complex response of an isolated rectilinearly moving target is derived via the stationary phase principle (SPP) approximations. It is shown that moving targets in complex domain can be divided into three types according to the 2-D motion distribution and the SPP approximation conditions. Different from the known peaklike response of a static target, different amplitude and phase modulations will appear for different types of moving targets. Moreover, a single target can be split into two targets in the image when its Doppler spectrum spreads over two ambiguous Doppler zones. All types of targets will have the same Doppler interferometric effect along multichannel images, which is decided by the target's ambiguous Doppler frequency. Furthermore, with the proposed signal model, the complex image properties can be completely described and analyzed. Finally, some numerical experiments are also provided to demonstrate the effectiveness of the proposed signal model and analysis.

Detection and Estimation With RADARSAT-2 Moving-Object Detection Experiment Modes

Abstract: This paper describes in detail several multichannel variants of the famous displaced phase center antenna (DPCA) method suitable for spaceborne multichannel synthetic aperture radar ground moving target indication (GMTI), which has become available through the RADARSAT-2 moving-object detection experiment (MODEX). A flexible signal processing architecture was developed at Defense Research and Development Canada to support R&D work in GMTI and to provide a tool for MODEX system validation. The presented multichannel DPCA method is one of the first algorithms that have been implemented and successfully tested using this architecture. The main objective is to provides a simple, yet effective and robust way to detect ground moving vehicles and to estimate their position and velocity. This work forms a baseline for further advancement in the GMTI area.

A Novel Motion Parameter Estimation Algorithm of Fast Moving Targets via Single-Antenna Airborne SAR System

Abstract: A novel parameter estimation algorithm of fast moving targets using single-antenna airborne synthetic aperture radar (SAR) databased on desampling and Radon transform (RT) is introduced in this letter. First, the dual-channel data are constructed by desampling the single-antenna airborne SAR data in the azimuth direction. Then, the clutter and the spectrum aliasing of the moving target can be cancelled by coherent subtracting. As a result, the moving target trajectory exhibits a single curve in both the range-compressed and the range-Doppler domains. Second, range cell migration correction is adopted to eliminate the range curve and parts of the range walk. Owing to the Doppler ambiguity, the moving target trajectory becomes a straight line. Third, the desampled Doppler ambiguity number and the Doppler rate of the moving target can be calculated by the slope of the line, which is measured by RT. Finally, along- and across-track velocities of the moving target are further obtained. The effectiveness of the proposed scheme is validated by the simulated and real data.

Moving Target Relative Speed Estimation and Refocusing in Synthetic Aperture Radar Images

Abstract: In this paper, a method for moving target relative speed estimation and refocusing based on synthetic aperture radar (SAR) images is derived and tested in simulation and on real data with good results. Furthermore, an approach on how to combine the estimation method with the refocusing method is introduced. The estimation is based on a chirp estimator that operates in the SAR image and the refocusing of the moving target is performed locally using subimages. Focusing of the moving target is achieved in the frequency domain by phase compensation, and therefore makes it even possible to handle large range cell migration in the SAR subimages. The proposed approach is tested in a simulation and also on real ultrawideband (UWB) SAR data with very good results. The estimation method works especially well in connection with low frequency (LF) UWB SAR, where the clutter is well focused and the phase of the smeared moving target signal becomes less distorted. The main limitation of the approach is target accelerations where the distortion increases with the integration time.

Three-channel processing for improved geo-location performance in SAR-based GMTI interferometry

Abstract: This paper describes a method for accurately geo-locating moving targets using three-channel SAR-based GMTI interferometry. The main goals in GMTI processing are moving target detection and geo-location. In a 2011 SPIE paper we showed that reliable target detection is possible using two-channel interferometry, even in the presence of main-beam clutter. Unfortunately, accurate geo-location is problematic when using two-channel interferometry, since azimuth estimation is corrupted by interfering clutter. However, we show here that by performing three-channel processing in an appropriate sequence, clutter effects can be diminished and significant improvement can be obtained in geo-location accuracy. The method described here is similar to an existing technique known as Clutter Suppression Interferometry (CSI), although there are new aspects of our implementation. The main contribution of this paper is the mathematical discussion, which explains in a straightforward manner why three-channel CSI outperforms standard two-channel interferometry when target signatures are embedded in main-beam clutter. Also, to our knowledge this paper presents the first results of CSI applied to the Gotcha Challange data set, collected using an X-band circular SAR system in an urban environment.

Ultrasonic Arrays for Localized Presence Sensing

Abstract: Advanced sensing solutions are central in the realization of energy-efficient lighting systems. This paper presents an ultrasonic array sensor for localized presence sensing in indoor environments. Localized presence sensing refers to the determination of presence and locations of occupants. Our proposed sensing solution comprises of a single transmitter and a linear array of receiving elements. In order to meet presence sensing requirements in indoor office scenarios, a pulsed sinusoid transmitter waveform and receiver processing algorithms for location estimation are designed. The signals at the receiver array are processed to obtain range and direction-of-arrival estimates. These location estimates are improved using a tracking algorithm based on occupant movement models and by mitigating multipath effects. The performance of the proposed presence sensing solution is shown in multi-occupant office environments.

Adaptive Detection of Wideband Radar Range Spread Targets with Range Walking in Clutter

Abstract: In this paper, we address detection of range spread targets with range walking in partially homogeneous clutter, which is often encountered in wideband radar. By considering the target range walking effect, a target returns model is proposed that represents the relationship between Doppler frequency and range frequency. Based on this, a generalized matched subspace detector (GMSD) and a general adaptive subspace detector (GASD) are proposed in the frequency domain. Moreover, to eliminate excess integration loss introduced by the mismatched detection window size, two improved detectors are proposed in range domain. The theoretical analysis shows that the GMSDs are of a constant false alarm rate (CFAR) with respect to both the power and the covariance matrix of the clutter but that the GASDs are of a CFAR with respect to the clutter power and an approximate CFAR with respect to the clutter covariance matrix. Simulated experiments are carried out to verify the effectiveness of the proposed detectors.

Experimental Performance Analysis of Distributed Target Coherent Radar Detectors

Abstract: In this paper a performance analysis on recorded live data of some detectors for range-spread targets is developed. To this end, real target and sea-clutter data collected by a fully coherent Ka-band radar system, featuring submeter range resolution, are used. The study is of particular interest for homeland security radar applications where a careful coastal control is necessary to prevent the arrival of nonauthorized small boats. The performance of both rank-one and subspace range-spread target detection strategies is analyzed, both in terms of constant false alarm rate (CFAR) behavior and in terms of detection capabilities. With reference to the former issue, clutter-only datafiles are used whereas, concerning the latter data containing both real target and clutter are used. The targets returns come from typical small boats (such as inflatable, wooden, and patrol boats) appearing range distributed at the resolution of the exploited radar system. Range-time detection maps are shown, assessing the capability of the analyzed processors to detect the aforementioned targets of great interest for homeland coastal security. Finally, the performance improvements achievable by over-resolving the target is quantified.

Adaptive CFAR for Space-Based Multichannel SAR–GMTI

Abstract: This paper studies the statistics of clutter data measured with a multichannel space-based synthetic aperture radar (SAR) for the purpose of ground moving target indication (GMTI) and presents an algorithm that implements an adaptive constant false-alarm rate (CFAR) detector. It discusses the differences between airborne and space-based SAR-GMTI clutter measurements and proposes how to develop the statistics of the latter from widely published results for the former. Based upon one of the differences, it proposes an adaptive CFAR detector and demonstrates detection using measured RADARSAT-2 data. The adaptive CFAR algorithm does not require a texture distribution for heterogeneous clutter.

Localization and tracking with Multipath Exploitation Radar

Abstract: This paper illustrates the exquisite localization and tracking performance that is obtainable in urban areas with Multipath Exploitation Radar (MER). First, the MER concept is described. Next, Cramer-Rao Lower Bounds of the desired localization and tracking quantities are derived and evaluated with representative parameters. Measured data is then used to demonstrate that this performance can be achieved in practice. Finally, ideas for future MER research are discussed.

Range-Dependent Clutter Suppression for Airborne Sidelooking Radar using MIMO Technique

Abstract: Range-dependent clutter suppression is an important issue in airborne bistatic radar moving target detection. Range-dependent clutter suppression using the multiple-input multiple-output (MIMO) technique is investigated. By employing the MIMO technique, the clutter ridges of all range bins are located in the same plane of the three-dimensional (3D) space. Moreover as long as the sum of the target radial velocities relative to the transmitter and the receiver is unequal to zero, the target will not be located in this plane. Thus clutter suppression can be realized by a 3D linear constrained minimum variance (LCMV) filter. In high clutter-to-noise (CNR) cases, the presented technique yields better performance than the conventional bistatic sidelooking phased-array radar. Numerical examples are given to demonstrate the effectiveness of the presented technique.

Signal model and moving target detection based on mimo synthetic aperture radar

Abstract: Recent years, a new SAR concept based on Multi-Input Multi-Output (MIMO) conflguration has demonstrated the potential advantages to simultaneously improve the performance of Synthetic Aperture Radar (SAR) imaging and ground moving target detection by utilizing multiple antennas both at transmission and reception. However, the precise signal model, as well as the efiect of ground moving target in image domain and the approaches for moving target indication based on MIMO SAR system are rarely investigated. Our paper has three main contributions. Firstly, we present a detailed signal model for stationary scene and moving target based on a colocated MIMO SAR conflguration, and analyze the motion efiect of the moving target. Secondly, we provide an algorithm of phase compensation to combine the multiple virtual channel data in order to enhance the image quality. Thirdly, an adaptive optimal approach is applied for clutter suppression, then the velocity of the moving target is estimated via Delay-and-Sum (DAS) beamforming approach. Finally, several numerical experiments are provided to illustrate the derivation and analysis in this paper.

Adaptive clutter suppression for airborne random pulse repetition interval radar based on compressed sensing

Abstract: We present an adaptive clutter suppression method for airborne random pulse repetition interval radar by using prior knowledge of clutter boundary in Doppler spectrum. In this method, by exploiting the intrinsic sparsity, compressed sensing based on iterative grid optimization (CS-IGO) is applied to directly recover the clutter spectrum with only the test range cell instead of nonhomogeneous training data from adjacent range cells. Since the sensing matrix and clutter spectrum obtained by CS-IGO are well adapted to the data, the prewhitening fllter can be efiectively obtained to cancel the mainlobe clutter. Further, the clutter residue can be suppressed by the iterative reweighted l1 minimization to enhance the target response. Simulation results show that the approach is capable of efiective suppression of clutter and precise recovery of targets' unambiguous spectrum, ofiering a high performance of output signal to clutter and noise ratio.

Non-linear automatic target tracking in clutter using dynamic Gaussian mixture

Abstract: This study presents a complete algorithm for single target tracking in clutter, which addresses simultaneously: non-linear measurements; uncertain target detections; presence of random clutter measurements; and uncertain target existence. Proposed algorithm generalises the integrated track splitting (ITS) filter by extending the ITS functionality to highly non-linear measurements. The non-linear target tracking and estimation problems may also be solved by application of particle filters, albeit incurring a significant computational expense relative to proposed solution. In an environment without data association uncertainties proposed filter becomes a non-linear estimator.

Target detection and estimation for shipborne HFSWR based on oblique projection

Abstract: It is difficult to detect the target submerged in the spread spectrum of the first-order sea clutter caused by the platform motion in shipborne high frequency surface wave radar (HFSWR). Based on oblique projection operators with steering vector, a technique for the target detection in the spread clutter spectrum is proposed in this paper, which can completely suppress interference coming from a known incident direction. The simulation and experimental results demonstrate reliable target detection and estimation in shipborne HFSWR.

GMTI from multichannel SAR images using compressed sensing

Abstract: The indication of ground moving targets (GMTI) from SAR-GMTI data is a well known problem in the processing of airborne or spaceborne radar data. A special case is the indication from several already processed synthetic aperture radar (SAR) images. In this paper we present a new approach for solving this problem based on compressed sensing - a new mathematical tool for processing sparse data. The number of simultaneously usable channels in this approach is unlimited, in contrast to most of the well established methods.

Multi-channel correcting method for ultra wide-band synthetic aperture radar

Abstract: The invention provides a multi-channel correcting method for ultra wide-band synthetic aperture radar. The method is applied to a multi-channel ultra wide-band synthetic aperture radar/ ground moving target indication (UWB SAR/ GMTI) system under an hour wide-band width product linear frequency modulation signal system. The technical scheme disclosed by the invention comprises the following stepsof: 1, constructing a matched filter system function by using a spectrum correcting technology; 2, correcting an ideal receiving channel to acquire a reference channel; 3, constructing a channel equalizer for each receiving channel; and 4, completing inconsistency correction of the channels. According to the multi-channel correcting method disclosed by the invention, by combining the spectrum correcting technology and inserting the channel equalizer into each receiving channel, frequency property mismatch is corrected, inconsistency correction of the channels is completed, and the pulse compression performance of hour wide-band width product linear frequency modulation signals is effectively improved.

Autofocus-based compensation (ABC) system and method for a hovering ground moving target indication (GMTI) sensor

Abstract: Embodiments of the present invention generally relate to motion compensation, and in particular to an autofocus-based compensation (ABC) systems and methods for a ground moving target indication platform. According to one embodiment, a method for autofocus based compensation of range data acquired from an object in motion is provided. The method may include: receiving range data; steering at least one receive beam of the range data in a desired direction; transforming the range data into the range domain; determining the width of a main clutter lobe; excluding data that is not part of the main lobe clutter response; transforming the main-lobe clutter response into the range domain; calculating a phase correction term; and applying the phase correction to the original range data.

Multipath exploitation for radar target classification

Abstract: Inclusion of multipath ghost target images, alongside direct target images, is shown to improve performance in radar target classification. When ultra wideband waveforms are employed there is sufficient range resolution that the components of the received signal relating to indirect paths appear as unique peaks. The additional returns result in a point spread function with peaks at locations other than that of the target — the ghosts. A method for localizing the ghosts is provided, and is then used to include the ghosts in target classification testing. A gain of up to 17% in classification performance is shown when the ghost targets are included. This study makes use of real radar data.

Modulation Jamming Method for High-Vivid False Uniformly-Moving Targets Against SAR-GMTI

Abstract: The modulation jamming method for high-vivid false uniformly-moving targets against SAR-GMTI is proposed by using the imaging characteristics of the uniformly-moving target.Key jamming parameters are determined,and the influence of reconnaissance errors on the jamming effects is analyzed.Besides,the countering performance of the proposed jamming method against GMTI is investigated by using the three-aperture interference cancelling technique.The experimental results indicate that the proposed method is effective to produce false uniformly-moving targets,through which certain ground uniformly-moving targets can be protected against SAR-GMTI.At the same time,the new method is efficient and flexible.

Through-the-wall moving target detection and localization using sparse regularization

Abstract: In this paper, we consider moving target detection and localization inside enclosed structures for through-the-wall radar imaging and urban sensing applications. We exploit the fact that the through-the-wall scene is sparse in the Doppler domain, on account of the presence of a few moving targets in an otherwise stationary background. The sparsity property is used to achieve efficient joint range-crossrange-Doppler estimation of moving targets inside buildings using compressive sensing. We establish an appropriate signal model that permits formulation of linear modeling with sensing matrices, so as to achieve scene reconstruction via sparse regularization. Supporting simulation results show that a sizable reduction in the data volume is achieved using the proposed approach without a degradation in system performance.

A Novel Algorithm For MIMO SAR Imaging

Abstract: A Multi-Input Multi-Output (MIMO) Synthetic Aperture Radar (SAR) system has been considered for its potential to simultaneously improve the performance of stationary scene imaging and ground moving target indication (GMTI) by utilizing multiple subarrays both at transmission and reception. To successfully exploit the potential benefits of MIMO SAR for practical imaging application, a signal model for MIMO SAR system with colocated arrays is presented in this paper, then we propose a novel procedure for imaging processing by coherently combining the returns from multiple receive subarrays. Our approach can make efficient use of the transmitted waveform power, and resulting in higher Signal-to-Noise Ratio (SNR) images. The effectiveness of model and MIMO SAR imaging method proposed in this paper are demonstrated by simulation experiments.

Maximum a Posteriori Based Approach for Target Detection in MTI Radar

Abstract: We propose a sparse recovery approach to detect moving targets in clutter. In presence of clutter, the target space is not sparse. We propose a simple way to estimate the clutter region. We then enforce sparsity by modeling the clutter as a single extended cluster of nonzero components. This done by solving a sparse signal recovery problem with partially known support within a maximum a posteriori estimation framework. The resulting algorithm is applied in angle-Doppler imaging for moving target indication in an airborne radar. Our approach has a number of advantages including improved robustness to noise and increased resolution with limited data.

Ultra wideband, multi-mode radar processing

Abstract: Recent advances in wideband digital waveform generation, analog-to-digital converters (ADC) and high speed parallel processing provide the technology to develop ultra wideband systems for simultaneous synthetic aperture radar (SAR) and ground moving target indication (GMTI) modes. A system equipped with this capability will provide uninterrupted coverage on targets entering and exiting the main-beam clutter of the Radar, typically seen in move-stop-move environments. The evolving challenge is to develop a common waveform, with emphasis on real-time signal processing, for ubiquitous target detection that employs SAR, along-track interferometry (ATI) and GMTI for advanced tracking.

Performance analysis of polarization-space- time three-domain joint processing for clutter suppression in airborne radar

Abstract: An optimum polarization-space-time joint domain pro- cessing (PST-JDP) technique is proposed for clutter suppression which adequately adopts the three-domain information including the polar- ization, space and Doppler frequency information of the radar echo. The study shows that the polarization information together with the space and Doppler frequency information are efiective to signiflcantly enhance the clutter suppression performance for airborne radar. Sev- eral new techniques, (i.e., the covariance matrix eigendecomposition, the spectral analysis and the resolution grid method), are utilized for deriving the performance of the optimum PST-JDP. The main factors which afiect on the performance of clutter rejection are the clutter degree of polarization, statistical distance of polarization between tar- get and clutter, Doppler frequency of target and input clutter-to-noise ratio. The new optimum PST-JDP method outperforms signiflcantly the traditional optimum space-time processing technology, especially in the case of the slowly or tangentially moving target. The simulation verifles the correctness and e-ciency of the model.

Detection and imaging of multiple ground moving targets using ultra-narrowband continuous-wave SAR

Abstract: We present a novel method for ground moving target detection and imaging using a SAR system transmitting ultra-narrowband continuous waveforms. We develop a new forward model that relates the velocity as well as reflectivity information at each location to a correlated received signal. We reconstruct moving target images by a filtered-backprojection method. We use the image contrast as a metric to detect moving targets and to determine their velocities. The method results in well-focused reflectivity images of moving targets and their velocity estimates regardless of the target location, speed, and velocity direction. We present numerical experiments to verify our method.