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Aerospace and Electronic Systems, IEEE Transactions on

Issue 1 • Date Jan 2004

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Displaying Results 1 - 25 of 38
  • Data association for deghosting in Y-shaped passive linear array sonars

    Page(s): 103 - 113
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1026 KB) |  | HTML iconHTML  

    This paper deals with data association using three sets of passive linear array sonars (PLAS) geometrically positioned in a Y-shaped configuration, fixed in an underwater environment. The data association problem is directly transformed into a 3D assignment, which is known to be NP hard. For generic passive sensors, it can be solved using conventional algorithms, while in PLAS, it becomes a formidable task due to the presence of bearing ambiguity. Thus, the central issue of the problem in PLAS is how to eliminate the bearing ambiguity without increasing tracking error. To solve this problem, the 3D assignment algorithm used the likelihood value of only those observed bearing measurements is modified by incorporating frequency information in consecutive time-aligned scans. The region of possible ghost targets is first established by the geometrical relation of PLAS with respect to target. The ghost targets are then confirmed and eliminated by generating multiple observations in consecutive scans. Representative simulations demonstrate the effectiveness of the proposed approach. View full abstract»

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  • Robust neuro-H controller design for aircraft auto-landing

    Page(s): 158 - 167
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1062 KB) |  | HTML iconHTML  

    A robust neuro-control scheme is presented for aircraft auto-landing under severe wind conditions and partial loss of control surfaces. In the scheme, a dynamic radial basis function network (RBFN) called minimal resource allocating network (MRAN), that incorporates a growing and pruning strategy, is utilize to aid an H controller using a feedback-error-learning mechanism. The neural network uses only online learning and is not trained "a priori". Specifically, the performance of this neuro-controller for aircraft auto-landing in a microburst along with a partial loss of control effectiveness is analyzed and compared with other control schemes. Simulation studies show that the performance obtained by the neuro-H control scheme is better than the other control schemes under failure and extreme wind conditions. View full abstract»

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  • General rules for signal flow graph modeling and analysis of dc-dc converters

    Page(s): 259 - 271
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1201 KB) |  | HTML iconHTML  

    Signal flow graph (SFG) nonlinear modeling approach is well known for modeling dc-dc converters. However, all possible SFGs of a given dc-dc converter system will not yield the generalized graph. A systematic procedure and guidelines for developing unified flow graph models of the dc-dc boost converters, from which complete behavior can be determined is presented. Usefulness of the proposed method is demonstrated through examples. As an illustration a 2-cell cascade boost and interleaved boost converter systems are taken as examples. Derivation of large, small-signal and steady-state models from generalized flow graph is also demonstrated. Large-signal model is developed and programmed in TUTSIM simulator. Large-signal, responses against supply and load disturbances are obtained. Experimental observations are provided to validate the proposed algorithm. View full abstract»

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  • Linear time-varying eigenstructure assignment with flight control application

    Page(s): 145 - 157
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (589 KB) |  | HTML iconHTML  

    This work is concerned with the assignment of a desired PD-eigenstructure for linear time-varying systems. Despite its well-known limitations, gain scheduling control appeared to be a focus of the research efforts. Scheduling of frozen-time, frozen-state controllers for fast time-varying dynamics is known to be mathematically fallacious, and practically hazardous. Therefore, recent research efforts are being directed towards applying time-varying controllers. In this paper we: 1) introduce a differential algebraic eigenvalue theory for linear time-varying systems; and 2) propose a PD-eigenstructure assignment scheme via a differential Sylvester equation and a command generator tracker (CGT) for linear time-varying systems. The PD-eigenstructure assignment is utilized as a regulator. A feedforward gain for tracking control is computed by using the command generator tracker. The whole design procedures of the proposed PD-eigenstructure assignment scheme are systematic in nature. The scheme could be used to determine the stability of linear time-varying systems easily as well as to provide a new horizon of designing controllers for the linear time-varying systems. A missile flight control application is presented to validate the proposed schemes. View full abstract»

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  • Modeling of a new ZVS bi-directional dc-dc converter

    Page(s): 272 - 283
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1206 KB) |  | HTML iconHTML  

    A dual half-bridge (DHB) bidirectional dc-dc converter is a new proposed topology that has the advantages of decreased number of devices, soft-switching implementation, low cost, and high efficiency. Typical applications of this converter are the auxiliary power supply in fuel cell vehicles and battery charging and discharging systems where the power density, cost, weight, and reliability are critical factors. A switching-frequency-dependent state-space averaged model of the converter is developed here for either direction of power flow. This averaged model can be used to derive the steady-state characteristics and small signal dynamics of the proposed topology. It also provides a fast simulation tool to investigate the transient response of the converter. The simulated waveforms of the mathematical model are compared with the detailed circuit simulation to verify the accuracy of the modeling. View full abstract»

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  • Implementation of a three-phase high-power-factor rectifier with NPC topology

    Page(s): 180 - 189
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (953 KB) |  | HTML iconHTML  

    A three-phase four-wire power factor corrector based on neutral-point-clamped (NPC) topology is adopted to reduce the current harmonics and increase the input power factor. Using the NPC topology, the voltage stress of power switches can be reduced to the half of the dc-link voltage. With the dc-link voltage controller and the phase locked loop circuit, the balanced and sinusoidal line currents can be drawn from the ac supply system under the balance and unbalance mains voltages. The hysteresis current comparators are adopted in the current control loop to track the line current commands. Three voltage levels are generated on the ac terminal to the neutral point. Simulations and experiments are provided to verify the validity and the effectiveness of the proposed control scheme. View full abstract»

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  • Detection, location, and imaging of fast moving targets using multifrequency antenna array SAR

    Page(s): 345 - 355
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (850 KB) |  | HTML iconHTML  

    In this correspondence, we generalize the linear antenna array synthetic aperture radar (SAR) from transmitting single-wavelength signals to transmitting multiple-wavelength signals (called multifrequency antenna array SAR). We show that, using multifrequency antenna array SAR, not only the clutters can be suppressed but also the locations of both slow and fast moving targets can be accurately estimated: A robust Chinese remainder theorem (CRT) is developed and used for the location estimation of fast and slowly moving targets. Simulations of SAR imaging of ground moving targets are presented to show the effectiveness of the multifrequency antenna array SAR imaging algorithm. View full abstract»

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  • Ultra high resolution spaceborne SAR processing

    Page(s): 370 - 378
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1108 KB) |  | HTML iconHTML  

    The accuracy requirements of the azimuth signal for spaceborne synthetic aperture radar (SAR) processing is analysed. Degradations of simulated extended scenes and point targets are studied at high squint or if erroneous Doppler parameters are used. At a resolution less than 1 m for X-band it is shown that the azimuth signal for spaceborne SAR geometry should be used. It is found that the fourth-order extended exact transfer function (EETF4) is a good candidate for demanding SAR processing. View full abstract»

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  • Maneuver detection using the radar range rate measurement

    Page(s): 330 - 336
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (319 KB) |  | HTML iconHTML  

    Tracking maneuvering targets with radar is complicated because radar cannot directly measure target accelerations. We use the range rate measurement to calculate a new statistic that is a surrogate measurement of target acceleration under a constant rate turn model. Its distribution is found via simulation. A threshold test of the statistic turns out to be a reliable detector of a maneuver. A tracker that uses a threshold test of the new statistic of accelerations to detect maneuvers and set. the process noise in a Kalman filter tracker is developed and compared with other, common maneuvering track filters. The new method compares favorably to a two mode interacting multiple model (IMM) and a tracker that switches process noise levels based on the position measurement innovations. View full abstract»

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  • Nonlinear filtering and time varying Schrodinger equation

    Page(s): 284 - 292
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (464 KB) |  | HTML iconHTML  

    Based on our previous work we have successfully reduced the nonlinear filtering problem for Yau filtering system to the time-varying Schrodinger equation. In order to solve the nonlinear filtering problem, one needs to solve the time-varying Schrodinger equation with an arbitrary initial condition. We then solve the time-varying Schrodinger equation by constructing the fundamental solution explicitly via a system of nonlinear ODES in case the potential is quadratic in state variables. This system of nonlinear ODES is solved explicitly by the power series method. View full abstract»

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  • Automatic target classification of slow moving ground targets in clutter

    Page(s): 190 - 205
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1658 KB) |  | HTML iconHTML  

    A new approach is proposed which will allow air-to-ground target classification of slow moving vehicles in clutter. A wideband space-time adaptive (STAP) filter architecture, based on subbanding, is developed and coupled with a one dimensional template-based minimum mean squared error (MMSE) classifier. The performance of this STAP/ATC (automatic target classification) algorithm is quantified using an extensive simulation. The level of residual clutter afforded by various filter configurations and the associated incremental improvement in ATC performance is quantified, revealing the potential for realizable hardware and software implementations to achieve acceptable ATC performance. View full abstract»

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  • Design of frequency modulated waveforms via the Zak transform

    Page(s): 355 - 359
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (571 KB) |  | HTML iconHTML  

    This paper introduces a new technique for designing frequency modulated waveforms that have ambiguity functions with desirable properties, such as strong peaking at the origin and low sidelobes. The methods employed involve signal design in the Zak transform space, as well as the use of stationary phase arguments in the analysis of ambiguity functions. View full abstract»

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  • Wideband channel model for aeronautical telemetry

    Page(s): 57 - 69
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1885 KB) |  | HTML iconHTML  

    A multipath channel model for wideband aeronautical telemetry links is presented. Channel sounding data were collected at Edwards AFB, CA, at both L-band and lower S-band. Frequency domain analysis techniques were used to evaluate candidate channel models. The channel model is composed of three propagation paths: a line-of-sight direct path and two specular reflections. The first specular reflection is characterized by a relative amplitude of 70% to 96% of the line-of-sight amplitude and a delay of 10-80 ns. This path is the result of "ground bounces" off the dry lake bed at Edwards and is a typical terrain feature at DoD test ranges located in the western United States. The amplitude and delay of this path are defined completely by the flight path geometry. The second path has much lower amplitude and a longer delay. The gain of this path is well modeled as a zero-mean complex Gaussian random variable. The relative amplitude is approximately 2% to 8% of the line-of-sight amplitude. The mean excess delay is 155 ns with an rms delay spread of 74 ns. View full abstract»

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  • Airborne high-resolution ISAR imaging of ship targets at sea

    Page(s): 378 - 384
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (506 KB) |  | HTML iconHTML  

    We address the problem of airborne high resolution two-dimensional inverse synthetic aperture radar (ISAR) side-view imaging of ship targets. Using a simple model of the ship motions avoids the use of advanced joint-time frequency (JTF) transforms. A robust processing scheme including motion estimation and correction, optimal processing time and duration estimation and target shape extraction are developed. We stress the fact that the robustness of this processing leads to a single ISAR image analysis and that no merging of data from a set of radar images is necessary. View full abstract»

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  • Dynamics and radar cross section density of chaff clouds

    Page(s): 93 - 102
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (734 KB) |  | HTML iconHTML  

    A new chaff cloud model (CCM) is described which is based on fundamental principles with modifications based on laboratory observations. Excellent approximations to the exact physical model have been developed which can rapidly predict the chaff fiber density and orientation as a function of location, time and fiber characteristics. Using this information, the time varying radar cross section (RCS) density is determined for any frequency and polarization anywhere within the chaff cloud. The results are consistent with full scale observations, and the computational speed allows the model to be integrated into existing real time radar simulations. View full abstract»

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  • Design and implementation of near-field, wideband synthetic aperture beamformers

    Page(s): 206 - 220
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2350 KB) |  | HTML iconHTML  

    A coarray-based near-field, wideband synthetic aperture beamformer using stepped-frequency signal synthesis and post-data acquisition processing is presented. While coarray techniques offer significant reduction in the number of array elements for a given angular resolution, the hybrid subarray-stepped frequency realization of wideband systems simplifies implementations and offers flexibility in beamforming. Proof of concept is provided using real data collected in an anechoic chamber for several pulse shapes and array weightings. View full abstract»

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  • Detect-track-confirm filter with minimal constraints

    Page(s): 336 - 345
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (498 KB) |  | HTML iconHTML  

    We describe the theory of a detect-track-confirm filter whose role is moving target detection and clutter suppression in surveillance data. The filter has broad generality due to the minimal assumptions made in developing the theory. Track confirmation is decided on the basis of a probability measure that is fully computable from clutter properties measured from surveillance data, without needing to assume target properties such as trajectory or detectability. Experimental results on real surveillance datasets are presented. View full abstract»

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  • Blind source separation and beamforming: algebraic technique analysis

    Page(s): 221 - 235
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (926 KB) |  | HTML iconHTML  

    Blind source separation (BSS) and blind beamforming schemes attempt to separate additive source signals, collected at a sensor array, and their direction-of-arrival (DOA). To this extent, many different and powerful algorithms have been produced to accomplish these tasks. However, unlike an optimal or adaptive method, an algebraic method for BSS and blind beamforming has the relative advantage of simplicity. This paper investigates such a technique that provides closed-form, algebraic expressions for BSS and beamforming in terms of performance and reliability. We provide these results, as well as a summary of the properties, and possible uses for this technique, in contrast to more optimal, adaptive techniques. View full abstract»

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  • From the editors

    Page(s): 1
    Save to Project icon | Request Permissions | PDF file iconPDF (185 KB)  
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  • STAP for GPS receiver synchronization

    Page(s): 132 - 144
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1119 KB) |  | HTML iconHTML  

    A space-time adaptive processing (STAP) algorithm for delay tracking and acquisition of the GPS signature sequence with interference rejection capability is developed. The interference can consist of both broadband and narrowband jammers, and is mitigated in two steps. The narrowband jammers are modelled as vector autoregressive (VAR) processes and rejected by temporal whitening. The spatial ing is implicitly achieved by estimating a sample covariance matrix and feeding its inverse into the extended Kalman filter (EKF). The EKF estimates of the code delay and the fading channel are used for a t-test for acquisition detection. Computer simulations demonstrate robust performance of the algorithm in severe jamming, and also show that the algorithm outperforms the conventional delay-locked loop (DLL). View full abstract»

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  • PIV application in advanced low Reynolds number facility

    Page(s): 310 - 319
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (5285 KB) |  | HTML iconHTML  

    The advent of micro aerial vehicles (MAV) and advanced flow control methods, using microelectromechanical systems (MEMS) and micro-blowing or suction, has significantly increased the need for a better understanding of very low Reynolds number flows. Aerodynamic testing in this flow regime using conventional facilities, such as wind or water tunnels, is seriously hampered by the necessary small model sizes and low testing speeds, rendering it very difficult to diagnose the flow with adequate spatial resolution and to measure aerodynamic loads with sufficient accuracy. A proof-of-concept pilot of a novel facility specifically intended for low Reynolds number testing has been built and is briefly described. It is based on the use of a high kinematic viscosity test medium, which allows testing superscale models at the correct Reynolds number. The facility is akin to a towing tank, but does not have a free surface with its associated shortcomings. Implementation of the particle image velocimetry (PIV) technique in this type of facility is complicated by the fact that the optics, rather than being stationary as is the case in conventional aerodynamic testing facilities, move in synchronism with the model. Mistracking directly results in velocity-field errors which must be corrected. Methods to do so are described. View full abstract»

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  • An optimization technique for sum and difference array factors [radar array signal processing]

    Page(s): 360 - 370
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (444 KB) |  | HTML iconHTML  

    Modern high-resolution radars often employ planar phased array antennas. The patterns for these arrays are usually designed to have narrow mainbeams and low sidelobes. This is best achieved by minimizing the total sidelobe energy in the array factor, rather than setting a sidelobe threshold level as is usually done. A method to achieve the minimizing patterns is described here for both sum and difference array factors. We define the optimum array factor for a linear array as minimizing the total array factor energy outside of a specified angular range about the peak of the mainbeam. This optimization technique is at least as easy to apply as the older techniques and is superior for many applications. In addition, the optimization technique has far fewer restrictions on the placement of the elements and is, therefore, more general. We can easily generalize the method to include nonuniform array designs, however an initial look into the performance of nonuniform arrays gave disappointing results for the sum array factor. View full abstract»

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  • Development of three-phase switch-mode rectifier using single-phase modules

    Page(s): 70 - 79
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (757 KB) |  | HTML iconHTML  

    This paper presents a three-phase (3φ) switch-mode rectifier (SMR) consisting of three 1 φ SMRs, two center-tapped autotransformers and three changeover switches. The ac input sides of three modules are Δ-connected, and their dc output sides are connected in parallel. As any one module fault occurs, the remaining two modules becomes modified T-connected and continuously perform three-phase rectification with good line drawn power quality. When two constituted 1φ modules are faulted, the proposed 3φ SMR will be operated as 1φ SMR. The quantitative and robust voltage regulation controls for the developed SMR are made to consider the effects of changes of system parameters, operating condition, and number of connected modules. View full abstract»

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  • Novel AC line conditioner for power factor correction

    Page(s): 168 - 179
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1070 KB) |  | HTML iconHTML  

    A new ac line conditioner is presented for high input power factor and clean ac output voltages for isolating the linear or nonlinear loads. A three-phase two-leg switching mode rectifier with neutral-point-clamped topology is proposed to draw the sinusoidal line currents from the ac mains. The carrier-based current controller is used in the inner control loop to track the line current commands with unity power factor. The dc bus voltage controller is adopted in the outer control loop to regulate the dc-link voltage. A voltage compensator is used to balance the neutral point voltage on the dc tank. A three-phase two-leg inverter with neutral-point-clamped topology is adopted in the system to provide the clean ac output voltages to the critical or sensitive loads. The carrier-based current control scheme is adopted to improve the instantaneous output voltages. Experimental results show the validity and effectiveness of the proposed control strategy. View full abstract»

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  • Visual analysis in a deployable antenna experiment [satellite antenna]

    Page(s): 247 - 258
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (4688 KB) |  | HTML iconHTML  

    To establish a large deployable antenna, monitoring and collimation are essential for reliable and precise deployment. We have developed an analysis method to detect shifts in several images, in which the combination of cross-correlations between images and approximations at subpixel precision enables us to detect shifts in images with a precision of up to 0.01 pixels. The LDREX mission; which was a preliminary experiment for a large deployable antenna, ETS-VIII, was performed in December 2000. During this experiment, anomalies occurred in the antenna, and deployment was aborted. To understand the cause of the anomalies, we used our visual analysis method. Using this analysis, we detected vibrating features in the antenna, which were useful for explaining the anomalies. We outline our visual analysis method and discuss its application in monitoring the deployable antenna. 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