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Aerospace and Electronic Systems, IEEE Transactions on

Issue 1 • Date Jan. 2013

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  • Contents

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  • Second-Order Markov Chain Based Multiple-Model Algorithm for Maneuvering Target Tracking

    Page(s): 3 - 19
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (4424 KB) |  | HTML iconHTML  

    A multiple-model algorithm for maneuvering target tracking is proposed. It is referred to as a second-order Markov chain (SOMC)-based interacting multiple-model (SIMM) algorithm. The target maneuver process is modeled by a SOMC to incorporate more information. SIMM adopts a merging strategy similar to that of the interacting multiple-model (IMM) algorithm, except that the one-step model transition probabilities are updated based on the SOMC. A scheme is proposed to design the transition probabilities of the SOMC for target tracking. The performance of the proposed SIMM algorithm is evaluated via several scenarios for maneuvering target tracking. Simulation results demonstrate the effectiveness of SIMM compared with IMM, the second-order IMM (IMM2) algorithm, and the likely-model set (LMS) algorithm. It is shown that SIMM performs about the same as IMM2 but requires only n filters versus n2 filters in IMM2 for n models. The effectiveness and efficiency of combining SIMM and LMS for state estimation are also demonstrated in the simulation. View full abstract»

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  • Correction of Refracted Propagation Effects for Airborne Radar Tracking

    Page(s): 20 - 41
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (9427 KB) |  | HTML iconHTML  

    This paper concerns the correction of refracted propagation effects for airborne radar tracking. An algorithm based on the Kalman filter (KF) is developed that compensates for range and elevation refraction errors, which were analytically derived using a simplified tropospheric model. In particular, the refraction error model applies to a spherically stratified troposphere and does not include the effects of azimuthal refraction errors, small-scale fluctuations, or ducting. The effectiveness of the proposed tracking algorithm is assessed in the presence of tropospheric parameter mismatch and measurement noise. Both theoretical and numerical results are described for a medium range scenario, and a quasi-ellipsoidal racetrack is chosen for the air platform that carries the radar. View full abstract»

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  • Dwell Scheduling Algorithms for Phased Array Antenna

    Page(s): 42 - 54
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (646 KB) |  | HTML iconHTML  

    In a multifunctional radar performing searching and tracking operations, the maximum number of targets that can be managed is an important measure of performance. One way a radar can maximize tracking performance is to optimize its dwell scheduling. The problem of designing efficient dwell scheduling algorithms for various tracking and searching scenarios with respect to various objective functions has been considered many times in the past and many solutions have been proposed. We consider the dwell scheduling problem for two different scenarios where the only objective is to maximize the number of dwells scheduled during a scheduling period. We formulate the problem as a distributed and a nondistributed bin packing problem and present optimal solutions using an integer programming formulation. Obtaining an optimal solution gives the limit of radar performance. We also present a more computationally friendly but less optimal solution using a greedy approach. View full abstract»

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  • Time-to-go Polynomial Guidance with Trajectory Modulation for Observability Enhancement

    Page(s): 55 - 73
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (6871 KB) |  | HTML iconHTML  

    A new impact angle control guidance law is introduced for a homing missile system equipped with a passive seeker against a stationary or slowly moving target. The proposed guidance law provides sufficient trajectory modulations, such as oscillatory trajectories, to enhance target observability from angle-only measurements. The derivation of the guidance command is based on the time-to-go polynomial guidance (TPG) law, which is one of the impact angle control laws. Closed-form solutions of the proposed law and their characteristics are investigated. The results inspired the proposed practical time-to-go calculation method and the maximum bounds of guidance gains, which are important for the practical implementation of the guidance law. Linear and nonlinear simulations with a target tracking filter are performed to investigate the performance of the proposed law. View full abstract»

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  • Polynomial Guidance Laws Considering Terminal Impact Angle and Acceleration Constraints

    Page(s): 74 - 92
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (6189 KB) |  | HTML iconHTML  

    The work presented here investigates proposed impact angle control guidance laws with terminal acceleration constraints for a stationary or slowly moving target. These laws, called time-to-go polynomial guidance (TPG), assume the guidance command as a polynomial function of time-to-go and determine the coefficients of the guidance command to satisfy the specified terminal constraints. The closed-form trajectory solutions of the guidance command and the target look angle for lag-free systems are derived and their characteristics are investigated. Based on the results we propose a systematic method to find the guidance gains that satisfy practical limits, such as the actuator's command limit and the seeker's field-of-view (FOV) limit. A time-to-go estimation method is also discussed for implementing TPG. Nonlinear and adjoint simulations are performed to investigate the performance of TPG. View full abstract»

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  • Knowledge-Aided (Potentially Cognitive) Transmit Signal and Receive Filter Design in Signal-Dependent Clutter

    Page(s): 93 - 117
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (13737 KB) |  | HTML iconHTML  

    We consider the problem of knowledge-aided (possibly cognitive) transmit signal and receive filter design for point-like targets in signal-dependent clutter. We suppose that the radar system has access to a (potentially dynamic) database containing a geographical information system (GIS), which characterizes the terrain to be illuminated, and some a priori electromagnetic reflectivity and spectral clutter models, which allow the raw prediction of the actual scattering environment. Hence, we devise an optimization procedure for the transmit signal and the receive filter which sequentially improves the signal- to-interference-plus-noise ratio (SINR). Each iteration of the algorithm, whose convergence is analytically proved, requires the solution of both a convex and a hidden convex optimization problem. The resulting computational complexity is linear with the number of iterations and polynomial with the receive filter length. At the analysis stage we assess the performance of the proposed technique in the presence of either a homogeneous ground clutter scenario or a heterogeneous mixed land and sea clutter environment. View full abstract»

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  • Kalman Filter Tracking of Limb Scan Signal using a Bank of Correlators

    Page(s): 118 - 133
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (9252 KB) |  | HTML iconHTML  

    A combined phase-locked loop/delay-locked loop (PLL/DLL) algorithm is developed for tracking Global Navigation Satellite System (GNSS) carrier phase and code phase using the output from a large number of correlators. This approach has advantages for limb-scanning applications, in which useful meteorological information, available only at the initial rising time of a GPS satellite, is desired. The technique uses a bank of correlators to span wide ranges of uncertainty in code phase and carrier Doppler shift, thereby avoiding the need for a separate acquisition and the associated loss of an initial span of data. A fusion of optimal estimation methods processes the output from these correlators. A batch optimization of a signal model's fit at a point in time to many accumulations from the correlator bank provides a Kalman filter with "measurements" of the most likely signal parameters. The Kalman filter utilizes a signal dynamics model to provide estimates that drive the PLL and DLL. The effectiveness of this algorithm is demonstrated by using a truth-model simulation of a limb scan. View full abstract»

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  • GLRT-Based CFAR Detection in Passive Bistatic Radar

    Page(s): 134 - 159
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (7188 KB) |  | HTML iconHTML  

    The work presented here addresses the problem of detecting a target in a passive bistatic radar (PBR) in the presence of interference signals, including receiver noise, direct signal, multipath/clutter echoes, and interfering targets. To this end, after outlining the model of the detection problem in the surveillance channel as a composite hypothesis test, a generalized likelihood ratio test (GLRT) is derived. Its performance is expressed in the closed forms for both the interference-alone case, the probability of false alarm, and the signal-plus-interference case, the probability of detection. A thorough performance assessment is also given, and the results show the superiority of the proposed detector in detection performance and false alarm regulation, and so the proper cancellation of the direct signal, multipath/clutter echoes, and interfering targets occur. View full abstract»

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  • 1-Bit High Accuracy Carrier Phase Discriminators

    Page(s): 160 - 174
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (11382 KB) |  | HTML iconHTML  

    Asymptotic derivation of traditional 1-bit arctangent phase discriminator (APD) is derived, even though neighboring quantized samples are dependent. The results reveal that high accuracy can be achieved by an APD in low signal-to-noise ratio (SNR) applications using sufficient samples. For high- SNR applications a novel phase discriminator called noise-balanced digital phase discriminator (NB-DPD), which has a complementary asymptotic performance of APD, is proposed to achieve high accuracy. The threshold SNR 2.6 dB that is suggested to identify either APD or NB-DPD is adopted in a specific application. Finally the sampling, quantization, and environmental noise effects on convergence of the asymptotic performance are discussed, and the simulations are provided to verify the analytical results. View full abstract»

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  • Spacecraft Electrical Power System using Lithium-Ion Capacitors

    Page(s): 175 - 188
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (6181 KB) |  | HTML iconHTML  

    The feasibility of a spacecraft power system using lithium-ion capacitors (LICs) as the energy storage source is analyzed and compared with a system that uses lithium-ion batteries (LIBs). The mass of the LIB- and LIC-based power systems, including photovoltaic (PV) arrays, are compared at various depth of discharge (DoD) levels. The LIC-based system at a deep DoD of 60-80% can be comparable with the LIB-based system at a DoD more shallow than 20% with respect to the system mass. View full abstract»

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  • The Electrical Aircraft Network—Benefits and Drawbacks of Modifications

    Page(s): 189 - 200
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (4708 KB) |  | HTML iconHTML  

    Many design objectives drive airplane development. Often aircraft weight reduction is the focus, with due consideration also given to safety, function, and performance. Aircraft weight reduction directly translates into fuel savings followed by reduced CO2 emission, and thus it supports environmental protection. A set of approaches to optimize the electrical system has been investigated for very large modern civil aircraft. Three of these approaches are presented and their benefits and drawbacks are discussed. Firstly the effects of a 230 VAC supply applied to all alternating current consumers of the electrical system are looked at. Secondly the idea of a central power center located in the middle of the aircraft is reviewed. Thirdly the consequences of a shift of allowed voltage drops from one part in the electrical system to others are considered. The investigations presented are part of the German-Spitzencluster-Wettbewerb-which is funded by the German Bundesministerium fur Bildung und Forschung (Fkz.: 03CL03A). View full abstract»

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  • Frequency Diverse MIMO Techniques for Radar

    Page(s): 201 - 222
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (30508 KB) |  | HTML iconHTML  

    It has been shown over several decades of radar research that the exploitation of diversity in a number of domains (space, frequency, time, polarization, and, recently, waveform) can provide increased agility, flexibility, robustness, and capabilities to the radar system. However this is often achieved either through efforts in system design, increased hardware complexity, or by employing additional resources. A conventional antenna array is considered with the intention of introducing, not major, but minor mismatches, in particular in the carrier frequencies and, eventually in the codes at the element level. The starting point of this analysis is the frequency diverse array (FDA), which has been demonstrated to generate a range-angle pattern. Through a reconsideration of the organization of the array, which we have termed the wavelength array (WA), a new pattern, "orthogonal" to that of the standard phased array, can be achieved. The bistatic combination of a WA and a receiver leads to the frequency diverse bistatic system (FDBS), which can be a significant application of this concept. In a second stage the analysis focuses on the effects of introducing waveform diversity in such a system. In particular, if the elements of an electronically steered array (ESA) simultaneously transmit a number of pseudonoise (PN) codes at slightly different carrier frequencies, the coherent summation of the codes gives rise to a waveform whose shape is a function of both angle and range. In fact this is the consequence of applying the multiple-input multiple-output (MIMO) technique to the FDA, which has the result of associating a waveform to each point range/angle of the space, with the possibility of recovering this information in receive after appropriate processing. View full abstract»

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  • Antenna Array Based GNSS Signal Acquisition for Interference Mitigation

    Page(s): 223 - 243
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (10736 KB) |  | HTML iconHTML  

    This work addresses the signal acquisition problem using an array of antennas in the general framework of Global Navigation Satellite Systems (GNSS) receivers. We propose a statistical approach, using the Neyman-Pearson (NP) detection theory and the generalized likelihood ratio test (GLRT), to obtain a new detector which is able to mitigate temporally uncorrelated interferences even if the array is unstructured and moderately uncalibrated. The key statistical feature is the assumption of an arbitrary and unknown covariance noise matrix, which attempts to capture the statistical behavior of the interferences and of other nondesirable signals, while exploiting the spatial dimension provided by antenna arrays. Closed-form expressions for detection and false alarm probabilities are provided. The performance and interference rejection capability are modeled and compared with their theoretical bound. Furthermore the proposed detector is analyzed under realistic conditions, which accounts for the presence of errors in the covariance matrix estimation, the residual Doppler and delay errors, and the signal quantization effects. The theoretical results are supported by Monte Carlo simulations. View full abstract»

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  • Velocity Dealiased Spectral Estimators of Range Migrating Targets using a Single Low-PRF Wideband Waveform

    Page(s): 244 - 265
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (11680 KB) |  | HTML iconHTML  

    Wideband radars are promising systems that may provide numerous advantages, like simultaneous detection of slow and fast moving targets, high range-velocity resolution classification, and electronic counter-countermeasures. Unfortunately, classical processing algorithms are challenged by the range- migration phenomenon that occurs then for fast moving targets. We propose a new approach where the range migration is used rather as an asset to retrieve information about target velocities and, subsequently, to obtain a velocity dealiased mode. More specifically three new complex spectral estimators are devised in case of a single low-PRF (pulse repetition frequency) wideband waveform. The new estimation schemes enable one to decrease the level of sidelobes that arise at ambiguous velocities and, thus, to enhance the discrimination capability of the radar. Synthetic data and experimental data are used to assess the performance of the proposed estimators. View full abstract»

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  • Doppler Shift Target Localization

    Page(s): 266 - 276
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2201 KB) |  | HTML iconHTML  

    The problem of Doppler-based target position and velocity estimation using a sensor network is outlined. The minimum number of Doppler-shift measurements at distinct generic sensor positions in order to have a finite number of solutions, and later, a unique solution for the unknown target position and velocity are stated analytically. Furthermore we study the same problem, where not only Doppler-shift measurements are collected, but also other types of measurements are available, e.g,. bearing or distance to the target from each of the sensors. Later we study the Cramer-Rao inequality associated with the Doppler-shift measurements to a target in a sensor network, and we use the Cramer-Rao bound to illustrate some results on optimal placements of the sensors when the goal is to estimate the velocity of the target. Some simulation results are presented at the end. View full abstract»

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  • Optimal Beamforming for Range-Doppler Ambiguity Minimization in Squinted SAR

    Page(s): 277 - 293
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (9948 KB) |  | HTML iconHTML  

    A method is proposed to optimize the radiation pattern of a planar array in order to maximize the signal-to-ambiguity-ratio for a squinted synthetic aperture radar (SAR) observation geometry. The optimal beamformer is the generalized eigenvector associated with a pair of matrices that depends on observation geometry and the Earth reflectivity model. The proposed approach is valid for any array configuration. This enables adaptivity to surface background and T/R module failures, thus increasing system robustness. View full abstract»

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  • A Vision-Based Automatic Safe Landing-Site Detection System

    Page(s): 294 - 311
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (17786 KB) |  | HTML iconHTML  

    An automatic safe landing-site detection system is proposed for aircraft emergency landing based on visible information acquired by aircraft-mounted cameras. Emergency landing is an unplanned event in response to emergency situations. If, as is usually the case, there is no airstrip or airfield that can be reached by the unpowered aircraft, a crash landing or ditching has to be carried out. Identifying a safe landing-site is critical to the survival of passengers and crew. Conventionally, the pilot chooses the landing-site visually by looking at the terrain through the cockpit. The success of this vital decision greatly depends on external environmental factors that can impair human vision and on the pilot's flight experience, which can vary significantly among pilots. Therefore, we propose a robust, reliable, and efficient detection system that is expected to alleviate the negative impact of these factors. We focus on the detection mechanism of the proposed system and assume that image enhancement for increased visibility and image stitching for a larger field-of-view (FOV) have already been performed on the terrain images acquired by aircraft-mounted cameras. Specifically, we first propose a hierarchical elastic horizon detection algorithm to identify the ground in the image. Then, the terrain image is divided into nonoverlapping blocks, which are clustered according to a "roughness" measure. The adjacent smooth blocks are merged to form potential landing-sites, whose dimensions are measured with principal component analysis and geometric transformations. If the dimensions of a candidate region exceed the minimum requirement for safe landing, the potential landing-site is considered a safe candidate and is highlighted on the human machine interface. At the end the pilot makes the final decision by confirming one of the candidates, and also by considering other factors such as wind speed and wind direction, etc. Preliminary experimental results show the feasibili- y of the proposed system. View full abstract»

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  • Adaptive Beamforming for Nonstationary HF Interference Cancellation in Skywave Over-the-Horizon Radar

    Page(s): 312 - 324
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (4212 KB) |  | HTML iconHTML  

    An adaptive degrees of freedom (DOFs) selection principle for notch-widening a partially adaptive beamformer is proposed. This principle indicates the relationship between the desired width of the notch and the required number of adaptive DOFs. The principle implies that a sufficient number of adaptive DOFs are required to produce a notch with the desired width at the direction of a nonstationary interference. That is to say, the number of adaptive DOFs should match the nonstationarity of the interference. The principle is validated by computer simulations that use a wide- notch beam space adaptive multiple sidelobe canceller (MSLC). According to the principle the nonstationary high-frequency (HF) interference cancellation performance is mainly affected by factors such as the number of adaptive DOFs and the nonstationarity of the interference. The effects of the number of adaptive DOFs and adaptive weights update interval on the nonstationary HF interference suppression performance are investigated by using beam space adaptive MSLC to process the experimental data collected by a trial HF over-the-horizon radar (OTHR). Experimental data processing results suggest that the principle will be very helpful in designing nonstationary interference cancellation schemes for practical implementation. View full abstract»

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  • Superresolution Doppler Estimation using UWB Random Noise Signals and MUSIC

    Page(s): 325 - 340
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (9736 KB) |  | HTML iconHTML  

    The application of the superresolution multiple signal classification (MUSIC) algorithm is extended to overcome the Doppler frequency estimation limitations due to the Fourier transform- (FT-) based techniques for ultrawideband (UWB) random noise radar signals. Simulated and experimental results are compared for single and multiple moving targets within a range bin, for narrowband (200 MHz) and UWB (1 GHz) noise radar signals. The simulated percentage error in Doppler estimation is parameterized as a function of the velocity ratio of two targets in a given range bin. View full abstract»

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  • Identification of Dynamic Parameters for a One-Axis Drag-Free Gradiometer

    Page(s): 341 - 355
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (5417 KB) |  | HTML iconHTML  

    A parametric estimation algorithm for a single-axis gradiometer is described. The most influential parameters are isolated and estimated; their bias and variance are discussed. Even though the system is closed-loop controlled, only plant parameters are estimated using an open-loop identification equation, which simplifies the identification procedure. The estimates are obtained using the method of instrumental variables (IV). The advantage of this method is that it remains bias-free even when the system states are correlated with the measurement noise. The problem is described in a one-dimensional frame, but it can be extended to the multivariate case if necessary. The estimated parameters are then used to reconstitute the closed-loop transfer function, which allows the input disturbance that caused the observed signal to be deduced. The estimation algorithm is applied to the laser interferometer space antenna (LISA) technology package, which is the scientific payload of the LISA Pathfinder spacecraft (SC), an ESA/NASA technology demonstrator to be launched in 2014. The analysis is operated on a simulated dataset produced with the mission end-to-end simulator (E2E) as well as with a simple linear simulator. The on-board software and hardware constraints are taken into account since they are important performance drivers. The results are detailed along with the experiment model. View full abstract»

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  • Performance Prediction of the Incoherent Radar Detector for Correlated Generalized Swerling-Chi Fluctuating Targets

    Page(s): 356 - 368
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (4659 KB) |  | HTML iconHTML  

    We deal with the performance prediction of the incoherent radar receiver in the presence of arbitrary correlated, possibly nonidentically-distributed target backscattered echoes. The problem is of interest in some common scenarios that account for frequency agility, and polarization, as well as for spatial diversity. We develop analytic expressions for the detection probability in terms of function series, assuming that a generalized Swerling-chi distribution models the first order probability density function (pdf) of the target amplitude. Moreover, we study the speed of convergence of the resulting series and assess the impact on the detection performance of both the correlation and the nonidentical distribution of the target returns. View full abstract»

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Aims & Scope

IEEE Transactions on Aerospace and Electronic Systems focuses on the equipment, procedures, and techniques applicable to the organization, installation, and operation of functional systems designed to meet the high performance requirements of earth and space systems.

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Meet Our Editors

Editor-in-Chief
Lance Kaplan
Army Research Laboratory