Showing papers on "Moving target indication published in 2003"

Multiple-input multiple-output (MIMO) radar and imaging: degrees of freedom and resolution

Abstract: In this paper, radar is discussed in the context of a multiple-input multiple-output (MIMO) system model. A comparison is made between MIMO wireless communication and MIMO radar. Examples are given showing that many traditional radar approaches can be interpreted within a MIMO context. Furthermore, exploiting this MIMO perspective, useful extensions to traditional radar can be constructed. Performance advantages in terms of degrees of freedom and resolution are discussed. Finally, a MlMO extension to space-time adaptive processing (STAP) is introduced as applied to ground moving-target indication (GMTI).

PAMIR - a wideband phased array SAR/MTI system

Abstract: Air- and spaceborne imaging radar systems in forthcoming surveillance and reconnaissance tasks have to meet increasingly severe demands. The next generation of top-level synthetic aperture radar (SAR) systems will comprise, among others, high resolution and long-range imaging capabilities, highly sensitive ground moving target indication and a multitude of sophisticated operational modes. The variety of tasks can be fulfilled only by the use of a reconfigurable phased array antenna together with a comprehensive wideband system design and a multichannel capability. At FGAN a new experimental X-band radar has been conceived, which will possess in its final upgrade an electronically steerable phased array consisting of 16 autonomous and reconfigurable subapertures, five independent receive channels, and a total signal bandwidth of about 1.8 GHz. The sensor is called PAMIR (Phased Array Multifunctional Imaging Radar). It is envisaged to demonstrate SAR imaging at a very high resolution and for a long range. The fine resolution will also be achieved with inverse SAR (ISAR) imaging of ground moving objects. Furthermore, the number of receive channels will allow ground-moving target indication (GMTI) by space-time adaptive processing and single-pass interferometric SAR (IfSAR) with a very high 3-D resolution. In its current stage of extension PAMIR is operable with one receive channel and a mechanically steerable antenna array. The system design and the intended capabilities of PAMIR are described. Ground-based and airborne experimental results concerning high-resolution SAR and ISAR imaging are also presented.

Multiple Moving Target Detection and Trajectory Estimation Using a Single

Abstract: A novel methodology is presented for determining the velocity and location of multiple moving targets using a single stripmap synthetic aperture radar (SAR) sensor. The so-called azimuth position uncertainty problem is therefore solved. The method exploits the structure of the amplitude and phase modulations of the returned echo from a moving target in the Fourier domain. A crucial step in the whole processing scheme is a matched filtering, depending on the moving target parameters, that simultaneously accounts for range migration and compresses two-dimensional signatures into one-dimensional ones without losing moving target information. A generalized likelihood ratio test approach is adopted to detect moving targets and derive their trajectory parameters. The effectiveness of the method is illustrated with synthetic and real data covering a wide range of targets velocities and signal-to-clutter ratios (SCRs). Even in the case of parallel to platform moving target motion, the most unfavorable scenario, the proposed method yields good results for, roughly, SCR > 10 dB.

Multiple moving target detection and trajectory estimation using a single SAR sensor

Abstract: A novel methodology is presented for determining the velocity and location of multiple moving targets using a single strip-map synthetic aperture radar (SAR) sensor. The so-called azimuth position uncertainty problem is therefore solved. The method exploits the structure of the amplitude and phase modulations of the returned echo from a moving target in the Fourier domain. A crucial step in the whole processing scheme is a matched filtering, depending on the moving target parameters, that simultaneously accounts for range migration and compresses two-dimensional signatures into one-dimensional ones without losing moving target information. A generalized likelihood ratio test approach is adopted to detect moving targets and derive their trajectory parameters. The effectiveness of the method is illustrated with synthetic and real data covering a wide range of targets velocities and signal-to-clutter ratios (SCRs). Even in the case of parallel to platform moving target motion, the most unfavorable scenario, the proposed method yields good results for, roughly, SCR > 10 dB.

Tracking evasive move-stop-move targets with a GMTI radar using a VS-IMM estimator

Abstract: We present the design of a variable structure interacting multiple model (VS-IMM) estimator for tracking evasive ground targets using ground moving target indicator (GMTI) reports obtained from an airborne sensor. In order to avoid detection by the GMTI sensor, the targets use a "move-stop-move" strategy, where a target deliberately stops or moves at a very low speed for some time before accelerating again. In this case, when the target's radial velocity (along the line of sight from the sensor) falls below a certain minimum detectable velocity, the target is not detected by the sensor. Under these conditions, the use of an estimator, which does not take care of this move-stop-move motion explicitly, will result in broken tracks. The tracker proposed here handles the evasive move-stop-move motion via the VS-IMM estimator, where the tracker mode set is augmented with a "stopped-target" model when the estimated speed of the target falls below a certain threshold. Using this additional stopped-target model, the target track is kept "alive" even in the absence of a measurement. A simulated scenario is used to illustrate the selection of design parameters and the operation of the tracker. Performance measures are presented to contrast the benefits of the VS-IMM estimator, which uses the stopped-target model, over a standard IMM estimator.

Computer simulation of aerial target radar scattering recognition, detection, and tracking

Abstract: Aerial Target Scattering Simulation in Decimeter and Centimeter Wave Bands - Possible Simulation Methods. Simplest Component Method. Consideration of Fast-Rotating Target Components. Consideration of Target Flight in Various Weather Conditions. Informativity of Recognition Features. Simulation of Recognition Features in the Cases of the Wide-Band and Narrow-Band Illumination. Signals - Target Range Profile Simulation by Various Wide-Band Probing Methods. Range-Polarization and Range-Frequency Target Profile Simulation. The 2-D Target Image Simulation. Simulation of Radar Cross-Sections and Polarization Parameters, Rotational Modulation Parameters and Correlation Factors of Fluctuations via Frequency Diversity in Narrow-Band Illumination. Simulation of the Aerial Target Recognition Algorithm Operation -Bayesian and Nonparametric Recognition Algorithm Variety. Direct Utilization and Wavelet Transform of Initial Data. Neural Recognition Algorithms Variety and their Use in Recognition. Simulation of the Aerial Target Detection and Tracking Algorithm Operation .- Comparison of Simulated and A Priori Fluctuation Models. Target Glint Models in Tracking. The Wideband Detection and Tracking. Peculiarity of Simulation in Ground Clutter and Ground Reflection of Narrowband and Wideband Signals.- General Principles of Simulation. Digital Terrain Maps and Peculiarities of their Use in Simulation. Recognition in the Ground Clutter and Ground Reflection. Augmented Physical Optics Utilization in Simulation. Scattering Effects for the Targets Uncovered, Partially and Completely Covered with Radar-Absorbing Materials in Bistatic and Monostatic Radar. References. Index.

Manoeuvring target detection in over-the-horizon radar using adaptive clutter rejection and adaptive chirplet transform

Abstract: In over-the-horizon radar (OTHR) systems, the signal-to-clutter ratio (SCR) used for moving target detection is very low. For slowly moving targets such as ships, the SCR is typically from 2 50 dB to 2 60 dB and their Doppler frequencies are close to that of the clutter. For manoeuvring targets, such as aircraft and missiles, the Doppler frequencies are time-varying when a long integration time is considered. When a target does not move uniformly, the Fourier transform based target detection techniques, including super-resolution spectrum techniques, may fail to work appropriately. In such situations, the Doppler signatures are time-varying and, therefore, time - frequency analysis techniques can be used for manoeuvring target detection. In addition, clutter rejection is also required for target detection due to the low SCR. The existing adaptive clutter rejection algorithms combine clutter rejection with spectrum analysis methods, which usually assume uniformly moving target (i.e. sinusoidal Doppler signature) models. An adaptive clutter reject algorithm is proposed together with the adaptive chirplet transform technique for manoeuvring target detection in a multipath environment. Simulation results using a simulated manoeuvring target signal with received raw OTHR clutter data show that targets with SCR below 2 50 dB can be detected by using the proposed algorithm.

Raw data based two-aperture SAR ground moving target indication

Abstract: This paper investigates the capability of classical two-channel SAR ground moving target indication (GMTI) techniques, such as displaced phase center antenna (DPCA) or along-track interferometry (ATI) when implemented on azimuth-uncompressed SAR data, rather than the processed SAR image. By transforming the data into the Doppler frequency domain complete target detection and parameter estimation scheme is proposed. In contrast to the conventional image based algorithms, the proposed techniques are able to detect even fast movers. The GMTI feasibility is demonstrated with measured airborne data.

PDAF with multiple clutter regions and target models

Abstract: This paper presents the theory of a new multiple model probabilistic data association filter (PDAF). The analysis is generalized for the case of multiple nonuniform clutter regions within the measurement data that updates each model of the filter. To reduce the possibility of clutter measurements forming established tracks, the solution includes a model for a visible target. That is, a target that gives sensor measurements that satisfy one of the target models. Other features included in the algorithm are the selection of a fixed number of nearest measurements and the addition of signal amplitude to the target state vector. The nonuniform clutter model developed here is applicable to tracking signal amplitude. Performance of this algorithm is illustrated using experimentally recorded over-the-horizon radar (OTHR) data.

Robust Doppler classification technique based on hidden Markov models

Abstract: A classification algorithm is presented that uses hidden Markov models (HMMs) to carry out recognition between three classes of targets: personnel, tracked vehicles and wheeled vehicles. It exploits the time-varying nature of radar Doppler data in a manner similar to techniques used in speech recognition, albeit with a modified topology, to distinguish targets with different Doppler characteristics. The algorithm was trained and tested on real radar signatures of multiple examples of moving targets from each class, and the performance was shown to be invariant to target speed and orientation and was able to be generalised with respect to variants within a class.

Comparison of nonlinear filtering algorithms in ground moving target indicator (GMTI) tracking

Abstract: Tracking using the ground moving target indicator (GMTI) sensor measurements plays an important role in situation awareness of the battlefield, surveillance, and precision tracking of ground moving targets. The GMTI sensor measurements range, azimuth, and range-rate are nonlinear functions of the target state. The extended Kalman filter (EKF) is widely used to solve the GMTI filtering problem. Since the GMTI measurement model is nonlinear, the use of an EKF is sub-optimal. The sub-optimality depends on the degree of nonlinearity of the measurement function and GMTI measurement error covariance. We can convert polar measurements range and azimuth to Cartesian measurements and approximately treat the range-rate as a linear function of the target velocity by considering the radar line-of-sight (RLOS) vector as a constant. This allows the use linear Kalman filter (KF) with linearized measurements in an approximate way. The unscented Kalman filter (UKF) and particle filter (PF) have been shown recently as robust alternate algorithms for a wide range of nonlinear estimation problems. This paper compares the performance of the KF with linearized measurements, EKF, iterated EKF (IEKF), UKF, and PF for the GMTI measurement filtering problem using a wide range of operating conditions. Estimation accuracy, statistical consistency, and computational speed and storage are used to evaluate the performance of these estimators. We use Monte-Carlo simulations and calculate the average mean square error (MSE) matrix, normalized estimation error squared (NEES), and normalized innovation squared (NIS) to analyze the accuracy and statistical consistency.© (2003) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Dual synthetic aperture radar system

Abstract: The dual synthetic aperture array system processes returns from the receiving arrays. The two identical receiving arrays employing displaced phase center antenna techniques subtract the corresponding spectrally processed data to cancel clutter. It is further processed that a moving target is detected and its velocity, angular position and range is measured, in or out of the presence of clutter. There are many techniques presented in the disclosure. These techniques are basically independent but are related based on common set of fundamental set of mathematical equations, understanding of radar principles and the implementations involved. These many techniques may be employed singly and/or in combination depending on the application and accuracy required. They are supported by a system that includes, optimization of the number of apertures, pulse repetition frequencies, DPCA techniques to cancel clutter, adaptive techniques to cancel clutter, motion compensation, weighting function for clutter and target, and controlling the system in most optimum fashion to attain the objective of the disclosure.

A moving target detection filter for an ultra-wideband radar

Abstract: A time modulated ultra-wideband (TM-UWB) through-wall impulse radar currently has been developed at Time Domain Corporation, Huntsville, AL, which detects the motion of people in range and azimuth through non-metallic walls. The radar operates in real-time with 3Hz update rate. In order to detect the motion of people moving with different velocities, a digital moving target detection (MTD) filter has been developed which is implemented in the software of the radar. The MTD filter is an IIR high-pass filter and it helps reject the stationary (time history invariant) clutter. Results on the time vs. slow-frequency (Fourier transform of slow-time response) distribution for targets moving at different velocities are presented for a given update rate. The transfer function of the MTD filter as a function of a target velocity is also presented for a given update rate.

A joint space-borne radar technology demonstration mission for NASA and the Air Force

Abstract: NASA and the Air Force are currently studying joint technology demonstration concepts for large aperture Space Based Radar (SBR) systems. The mission focuses on elements of NASA's earth science enterprise strategic plan and Air Force long term needs for global airborne and ground moving target indication (GMTI and AMTI) surveillance, and represents an unprecedented multi-agency approach to scientific and technological advancement of spaceborne radar. The preliminary design for the system specifies a low center frequency such as L-band, a large physical aperture between 50 and 150 square meters, and on-board processing capability for synthetic aperture radar (SAR) and moving target indication applications. The key technologies requiring demonstration of technical maturity and affordability are the active electronic scanned aperture (AESA) and the realtime On-Board Processing (OBP). The system concept incorporates active metrology for measurement of the shape of the aperture, and electronics and processing capability for active compensation of the aperture surface deformation. The goal of the mission is to demonstrate the ability to maintain coherence in a very large aperture in the space environment, to show scalability to larger apertures, and to demonstrate the ability to deliver fault-tolerant real-time products in space. The systems also permit characterization of spaceborne L-band phenomenology and validate adaptive processing for moving target detection. This paper describes the trades and a technology risk addressed in this study, and highlights those elements in that could be developed in concern with other SBR programs. The work is being conducted jointly by Jet Propulsion Laboratory, California Institute of Technology, and the Air Force Research Laboratory, both under contract with NASA.

Clutter effects on ground moving target velocity estimation with SAR along-track interferometry

Abstract: The SAR interferogram, defined as the product of the first channel and the complex conjugate of the second, is one way of comparing two SAR channels. When the two sub-apertures are aligned along the flight path, targets with non-zero radial velocities can be detected by exploiting the phase information of the interferogram. This paper examines the effect of clutter interference on the interferometric phase and provides a simple method for mitigating the clutter contamination by using time-frequency (TF) analysis techniques and a velocity-offset matched filter (VOMF). Both simulated and airborne results are presented.

Resolution and synthetic aperture characterization of sparse radar arrays

Abstract: The concept of radar satellite constellations, or clusters, for synthetic aperture radar (SAR), moving target indicator (MTI), and other radar modes has been proposed and is currently under research. These constellations form an array that is sparsely populated and irregularly spaced; therefore, traditional matched filtering is inadequate for dealing with the constellation's radiation pattern. To aid in the design, analysis, and signal processing of radar satellite constellations and sparse arrays in general, the characterization of the resolution and ambiguity functions of such systems is investigated. We project the radar's received phase history versus five sensor parameters: time, frequency, and three-dimensional position, into a phase history in terms of two eigensensors that can be interpreted as the dimensions of a two-dimensional synthetic aperture. Then, the synthetic aperture expression is used to derive resolution and the ambiguity function. Simulations are presented to verify the theory.

The VHF/UHF-band LORA SAR and GMTI system

Abstract: The paper describes design principles and presents first results for the airborne LORA (low-frequency radar) system. It covers operating frequencies in the VHF and UHF bands and has both synthetic-aperture radar and ground moving target indication modes. The main motivation for the system is to facilitate detection of man-made targets in a wide range of conditions, i.e. stationary or moving targets as well a targets in open terrain or in concealment under foliage or camouflage. The LORA system will operate in several configurations extending from 20 MHz to 800 MHz. Initial flight trials in 2002 were successfully conducted using the 200-400 MHz band. SAR images have been formed from the acquired data and are presented. A second band, 400-800 MHz, has also been completed but has not yet been tested in -flight. A third band, 20-90 MHz, is presently being added and will be completed during 2003. The paper also includes results from a recent experiment in northern Sweden which included an extensive target deployment to cover a broad range of operating conditions. VHF-band SAR (20-90 MHz) is compared with high-resolution Ku-band SAR. Results show the superior area-coverage rate of using VHF-compared to Ku-band for robust detection of stationary targets. The high-resolution images provided by the Ku-band SAR are, however, superior for classification and recognition purposes.© (2003) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Multiecho processing by an echolocating dolphin

Abstract: Bottlenose dolphins (Tursiops truncatus) use short, wideband pulses for echolocation. Individual waveforms have high-range resolution capability but are relatively insensitive to range rate. Signal-to-noise ratio (SNR) is not greatly improved by pulse compression because each waveform has small time–bandwidth product. The dolphin, however, often uses many pulses to interrogate a target, and could use multipulse processing to combine the resulting echoes. Multipulse processing could mitigate the small SNR improvement from pulse compression, and could greatly improve range-rate estimation, moving target indication, range tracking, and acoustic imaging. All these hypothetical capabilities depend upon the animal’s ability to combine multiple echoes for detection and/or estimation. An experiment to test multiecho processing in a dolphin measured detection of a stationary target when the number N of available target echoes was increased, using synthetic echoes. The SNR required for detection decreased as the number of available echoes increased, as expected for multiecho processing. A receiver that sums binary-quantized data samples from multiple echoes closely models the N dependence of the SNR required by the dolphin. Such a receiver has distribution-tolerant (nonparametric) properties that make it robust in environments with nonstationary and/or non-Gaussian noise, such as the pulses created by snapping shrimp.

Mutual-aided target tracking and identification

Abstract: Mutual-aided target tracking and target identification schemes are described by exploiting the couplings between the target tracking and target identification systems, which are typically implemented in a separate manner. A hybrid state space approach is formulated to deal with continuous-valued kinematics, discrete-valued target type, and discrete-valued target pose (inherently continuous but quantized). We identify and analyze ten possible mutual aiding mechanisms with different complexity in different levels. The coupled tracker design is illustrated within the context of JointSTARS using GMTI and HRRR measurements as well as digital terrain and elevation data (DTED) and road map among others. The resulting coupled tracking and identification system is expected to outperform the separately designed systems particularly during target maneuvers, for recovering from temporary data dropout, and in a dense target environment.

Improved GMTI-tracking using road-maps and topographic information

Abstract: Tracking ground targets with airborne GMTI sensor measurements proves to be a challenging task due to high target density, high clutter, and low visibility. The exploitation of non-standard background information such as road maps and terrain information is therefore highly desirable for the enhancement of track quality and track continuity. The present paper presents a Bayesian approach to incorporate such information consistently. It is particularly suited to deal with winding roads and networks of roads. Key issues are: modeling the target dynamics in quasi one-dimensional road coordinates and mapping onto ground coordinates using linear road segments. The case of several, intersecting roads with different characteristics, such as mean curvature, slope, or visibility, is treated within an Interacting Multiple Model scheme. The iterative filter equations are formulated within a framework of Gaussian sum approximations on the one hand and a numerically exact Particle Filter approach on the other hand. Simulation results for single targets taken from a realistic ground scenario show strongly reduced target location errors compared to the case of neglecting road-map information. By using a realistic GMTI sensor model, early detection of stopping targets is demonstrated.© (2003) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Metrics for SAR-GMTI based on eigen-decomposition of the sample covariance matrix

Abstract: This paper investigates different metrics for indication of ground moving targets in multi-channel SAR data (SAR-GMTI). These metrics have in common that they are all based on the eigen-decomposition of the sample covariance matrix. Their statistical properties are analytically compared and their detection capabilities, demonstrated on measured two-channel airborne data.

Development of the ultra-wideband LORA SAR operating in the VHF/UHF-band

Abstract: LORA (low-frequency radar) is a new airborne VHF/UHF-band radar which has both synthetic-aperture radar (SAR) and ground moving target indication (GMTI) modes. The main motivation for the system is to facilitate detection of man-made objects in a variety of conditions, i.e. stationary or moving, located in open terrain or in concealment under foliage. The LORA system will operate in several configurations extending from 20 MHz to 800 MHz. Initial flight trials during 2002 were successfully conducted using the 200-400 MHz band. SAR image examples are shown including both forested areas and man-made objects. A second band, 400-800 MHz, has also been completed but not yet flight tested. A third band, 20-90 MHz, is being added and will be completed during 2003.

SAR along-track interferometry with application to RADARSAT-2 ground-moving target indication

Abstract: Canada's RADARSAT-2 (R2) Synthetic Aperture Radar (SAR) satellite will be equipped with an experimental Ground Moving Target Indication (GMTI) mode, which makes use of the 'Dual-Receive' capability of the R2 antenna to provide two apertures aligned in the along-track direction. The mode allows two SAR images to be taken under identical geometry of observation, but separated by a short time lag. One of the GMTI techniques, currently being explored, is based on SAR Along-Track Interferometry (SAR-ATI), which uses the magnitude-phase information of the interferogram to extract movers from stationary clutter. In this paper, an unconventional but fully automatic detection scheme, derived using a histogram approximation to the clutter joint Probability Density Function (PDF), is proposed. The new method permits the implementation of a Constant False Alarm Rate (CFAR) detector without the need to derive a theoretical joint PDF for the clutter interferogram. A false alarm reduction technique, based on 'selective' local density calculations, is also discussed and implemented, showing striking improvement in the reduction of the number of false alarms (up to 75% reduction) over the original detector without significantly degrading its performance. The detector is shown to be robust in its ability to handle both simulated (R2) and real (airborne) data. Preliminary comparison with a conventional CFAR detector, derived using theoretical marginal PDFs of the interferogram's magnitude and phase, show the performance superiority of the new detector.

Method for reducing false alarm rate in radar images

Abstract: A method for reducing the false alarm rate, i.e. the number of alarms of fixed targets erroneously declared as moving targets in the radar images of two- or multi-channel MTI radar devices, wherein the suppression of fixed target echoes over the moving target echoes within the main antenna lobe occurs through a space time adaptive processing—STAP—filter. The method uses a comparison of the amplitude amounts or power values of the range Doppler frequency cells with a threshold that can be specified in constant terms and summary of the resulting alarms. A target function is compared with defined test functions and selection criteria are determined from suitable combined calculation methods that are applied to the test and target functions for the purpose of classifying a respective target alarm as a moving or fixed target alarm.

Target detection in sea clutter using convolutional neural networks

Abstract: A detector based on convolutional neural networks is proposed for radar detection of floating targets in highly complex and nonstationary cluttered environments. This detector is coherent and monocell, i.e. it works with the complex envelope of the echoes from the same range cell. It includes a pre-processing time-frequency block implemented by the Wigner-Ville distribution, which provides a constant false alarm rate (CFAR) behavior regarding the clutter power when normalization is utilized. Simple theoretical models for the clutter and targets were allowed to study the impact of the correlation and Doppler of both target and clutter on its performance. This detector has also been tested with real-life sea clutter with an improved performance compared to classic detectors.

Performance evaluation of two polarimetric STAP architectures

Abstract: Space-time adaptive processing (STAP) is a powerful technique for detecting slowly moving targets in strong clutter. However, STAP performance is limited when used on radars with small apertures. Past research suggests polarization's potential to effectively discriminate between targets and clutter, thereby improving detection performance. We evaluate two methods of incorporating polarization into STAP, modeled after the polarimetric matched filter (PMF) and the polarimetric whitening filter (PWF). Our analysis serves to unify various proposed approaches to combining STAP and polarization, and benchmarks the benefits of polarization to GMTI detection. Using measured clutter and target characteristics from published sources as a baseline, we found that the PMF technique offers up to 6-dB improvement over STAP. This significant advantage is realized in the center of the clutter spectrum, and the impact on minimum detectable velocity (MDV) is modest. However, the PWF offers increased performance over the entire Doppler spectrum, and can be easily implemented as a STAP post-processor.

Multi-channel signal subspace processing methods for SAR-MTI

Abstract: This paper examines coherent signal processing methods for combining the data that are collected via multi-channel airborne radar system for MTI/GMTI. We study the methods that convert multi-channel radar data into dual along-track monopulse SAR signals of the radiated scene. A 2D adaptive filtering method, that projects the data in one synthesized SAR channel into the signal subspace of the other, is used for blind calibration of the monopulse SAR signals and generation of the MTI statistic. The merits of these algorithms are studied using the data from the multi-channel airborne radar measurement (MCARM) system that has been developed by the Air Force Research Laboratory at Rome, New York.

Sharpening and bandwidth extrapolation techniques for radar micro-Doppler feature extraction

Abstract: This paper presents a time-frequency analysis sharpening technique based on bandwidth extrapolation (BWE). The method utilizes a new extremely high resolution 2D linear prediction/lattice algorithm to enhance instantaneous time and instantaneous frequency details of conventional short-time Fourier transform (STFT) time-frequency analysis (TFA). The approach preserves extreme high dynamic range (DNR), over 100 dB, in the data without introducing debilitating cross-term artifacts that severely obscure weak features in the TFA, such as those introduced by quadratic TFAs like the Wigner and Cohen TFA representations. We demonstrate the performance of the new high detail TFA for micro-Doppler feature extraction in actual X-band airborne moving target (AMTI) and ground-borne moving target (GMTI) applications. This paper illustrates the AMTI case; the GMTI will be provided at the conference.

Configuring a sparse aperture antenna for spaceborne MTI radar

Abstract: Sparse arrays provide potential for improving the minimum detectable velocity (over 3 m/s improvement for sidelooking radar) of spaceborne moving target indication radar for a given physical aperture. This paper examines the benefits and some of the challenges resulting from employing sparse arrays: grating lobes introduce ambiguities that may create Doppler blind zones; area coverage rate may reduce due to a narrower antenna main beam for coherent transmission; and intrinsic clutter motion may reduce the usable fraction of the Doppler space. We consider the application of orthogonal transmit waveforms to increase area coverage rate, as well as frequency diversity and aperiodic subarray spacings to mitigate Doppler blind zones.