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Aerospace and Electronic Systems, IEEE Transactions on

Issue 5 • Date Sept. 1986

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Displaying Results 1 - 25 of 29
  • Table of contents

    Page(s): c1
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  • IEEE Aerospace and Electronic Systems Society

    Page(s): c2
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  • From the Editors

    Page(s): 485
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  • Land Warfare - A 'classic' paper

    Page(s): 486
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  • Land Warfare

    Page(s): 487 - 512
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    The future conflicts that our nation may have to fight are more likely to be tactical than strategic. Land warfare forces, including the related elements of Tacair, play a pivotal role in our tactical combat capabilities, as evidenced by the fact that in World War II German production of virtually all critical material was still continuing to increase until Germany was on the verge of being physically overrun. Yet, our land warfare forces have been comparatively slow to embrace new technological developments, with such equipment as the tank, the rifle, and the cannon still playing major roles. Unfortunately, those instances wherein new technology has been adopted do not present a uniformly satisfying picture. One factor potentially contributing to this has been the inherent compartmentalization and fragmentation of our land warfare RDT&E efforts, with an overview of the interrelationships between aircraft and armor, rifles and rockets, and helicopters and howitzers seldom having been attempted. View full abstract»

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  • Radar Detection of Correlated Targets in Clutter

    Page(s): 513 - 532
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    This paper provides general models of radar echoes from a target. The rationale of the approach is to consider the echoes as the output of a linear dynamic system driven by white Gaussian noise (WGN). Two models can be conceived to generate N target returns: samples generated as a batch, or sequentially generated one by one. The models allow the accommodation of any correlation between pulses and nonstationary behavior of the target. The problem of deriving the optimum receiver structure is next considered. The theory of "estimator-correlator" receiver is applied to the case of a Gaussian-distributed time-correlated target embedded in clutter and thermal noise. Two equivalent detection schemes are obtained (i. e., the batch detector and the recursive detector) which are related to the above mentioned procedures of generating radar echoes. A combined analytic-numeric method has been conceived to obtain a set of original detection curves related to operational cases of interest. Finally, an adaptive implementation of the proposed processor is suggested, especially with reference to the problem of on-line estimation of the clutter covariance matrix and of the CFAR threshold. In both cases detection loss due to adaptation has been evaluated by means of a Monte Carlo simulation approach. In summary, the original contributions of the paper lie in the mathematical formulation of a powerful model for radar echoes and in the derivation of a large set of detection curves. View full abstract»

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  • A Nonlinear Tracker Using Attitude Measurements

    Page(s): 533 - 539
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    The subject of this paper involves tracking the present position of a maneuvering aircraft as well as predicting its future position. A tracking filter is developed that uses aircraft attitude angles (yaw, pitch, roll) in addition to the usual radar measurements. Computer simulation of tracker performance when tracking violently maneuvering aircraft indicates that a dramatic improvement is obtained by using attitude information. The approach taken is to develop a 12-or 15-state extended Kalman filter that models both translational and rotational degrees of freedom. By measuring and estimating attitude it is possible to approximately determine the magnitude and direction of the force system acting on the vehicle and therefore determine vehicle linear acceleration. Knowledge of acceleration is then used to improve the estimate of present and future position of the vehicle being tracked. Simulation of a T-38 aircraft performing a 5 g turn indicates that the new tracker produces maximum trajectory prediction errors that are 36 percent of the errors experienced by more conventional trackers. View full abstract»

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  • IGT/COMFET Latching Characteristics and Application to Brushless DC Motor Drive

    Page(s): 540 - 544
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    Various factors affecting the device latching current level were investigated. Results of applying the devices for driving a 340 V, 10 A brushless dc motor are presented. Recommendations to the device manufacturers, from the user's point of view, are summarized. View full abstract»

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  • A Digital Incremental Oscillator: Generation of Sinusoidal Waveform in DPCM

    Page(s): 545 - 553
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    Based on the concept of incremental computations, a digital oscillator structure is proposed which consists of two incremental integrators and one incremental multiplier. Models for these elements are developed and detailed analyses are made showing that the errors of the proposed structure are extremely low compared with the direct-form one. The proposed oscillator structure can be implemented without a hardware multiplier and can generate sinusoidal waveforms in the differential pulse code modulation representation. View full abstract»

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  • Carrier Tracking by Smoothing Filter Improves Symbol SNR

    Page(s): 554 - 558
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    The potential benefit of using a smoothing filter to estimate a carrier phase over use of phase-locked loops (PLL) is determined. Numerical results are presented for the performance of three possible configurations of an all-digital coherent demodulation receiver. These are residual carrier PLL, sideband-aided residual carrier PLL, and finally sideband aided with Kalman smoother. The average symbol SNR after losses due to carrier phase estimation is computed for different total power SNRs, symbol rates, and symbol SNRs. It is found that smoothing is most beneficial for low symbol SNRs and low symbol rates. Smoothing gains up to 0.7 dB over sideband-aided residual carrier PLL, and the combined benefit of smoothing and sideband aiding relative to residual carrier loop is often in excess of 1 dB. View full abstract»

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  • Experimental Detection of Anomalous Mode-C Reports Using Radar Data

    Page(s): 559 - 564
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    A new methodology to scan automated radar terminal system (ARTS-III) data for aircraft tracks exhibiting probable mode-C encoder/transponder faults is described. The tracks of more than 8000 climbing or descending aircraft, recorded at the Seattle-Tacoma terminal area, were analyzed using this method. Based on this sample, the probability of the previously recognized "stuck C-bit" error is estimated to be 0.44 percent (0.31-0.61 percent, 95 percent confidence). In addition, a new, more subtle error, here termed the "deficient response," was discovered which is estimated to occur with a probability of 0.77 percent (0.59-0.98 percent, 95 percent confidence). Subsequent tests found this new error to have much less impact on traffic alert and collision avoidance system (TCAS) performance than does the stuck C-bit error. View full abstract»

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  • Rotary Transformer Design with Fixed Magnetizing and/or Leakage Inductances

    Page(s): 565 - 572
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    A design algorithm is considered for transformers that must transfer electric power across a rotating interface. Among other features, this procedure allows the designer to minimize either weight or losses for either a fixed magnetizing inductance or a fixed leakage inductance. Numerical results are included to indicate the design tradeoffs between various parameters. View full abstract»

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  • Mathematical Modeling of a VSCF Aircraft Generating System

    Page(s): 573 - 582
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    DC-link converters having a variable input frequency but a constant output frequency now provide a viable alternative to the constant-speed mechanical drive as a means of providing a constant frequency power supply from an aircraft generator. The ease of replacement and repair, the reduction in servicing needs, and the ability to locate the components of the electrical system throughout the aircraft all combine to bring about a considerable reduction in the maintenance time which is required. A computationally efficient technique for the mathematical modeling of a typical electrical system, in which the overall power network is torn initially into a set of convenient subnetworks, is described. Connection matrices are employed to combine the equations computed for the various subnetworks with the equations for the overall network. Typical results are presented for the overall system. The performance detail enables many important design considerations to be investigated prior to manufacture. View full abstract»

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  • On-Line Vehicle Motion Estimation from Visual Terrain Information Part I: Recursive Image Registration

    Page(s): 583 - 587
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    This paper addresses estimation of motion from the optical flow observed by an airborne down looking electro-optical sensor. The paper is in two parts. Part I addresses the development and analysis of a velocity-to-height ratio estimation algorithm and its principal error characteristics. In part II, it is shown how the information provided by the motion estimator can be integrated with additional on-board sensors to provide a complete autonomous navigation system. Part I as presented here is a summary version of the full length paper.¿ The algorithm implements recursive registration of successive images by using the gradient of a similarity function between them to control the tracking of their relative shift. The shift estimate provides velocity/height information. Substantial saving in memory and computation as compared to conventional full frame registration is achieved by using only a single line in the TV frame. Stochastic mathematical models for the image, terrain and vehicle velocity perturbations are used in the analysis. The choice of the most appropriate similarity function in the registration algorithm is addressed. Performance analysis indicates very small error variances, as illustrated by numerical examples. View full abstract»

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  • On-line Vehicle Motion Estimation from Visual Terrain Information Part II: Ground Velocity and Position Estimation

    Page(s): 588 - 604
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    An algorithm, combining velocity/height estimates, obtained from an airborne body fixed image shift estimator with auxiliary on-board measurements and sparsely stored terrain profile information constitutes an entirely passive autonomous navigation system suitable for moderate-g flight missions. Two versions are addressed. The "naive estimator," in which altitude estimates are multiplied by velocity/height estimaters, yields ground velocity. Position, obtained by integration, diverges with time. The "extended Kalman filter" (EKF) version, in which velocity and position are defined as state space components, locks on the stored terrain profile and does not diverge with time. It degenerates into the "naive estimator" if the terrain is completely flat. Numerical examples indicate excellent performance potential of the EKF estimator. View full abstract»

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  • Damping of Generator Oscillations Using Static VAR Compensators

    Page(s): 605 - 617
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    The design of a novel static VAR compensator for the damping of electromechanical oscillation in a synchronous generator is presented. The proposed compensator, which is made up of a fixed capacitor and a thyristor-controlled inductor, is installed at the generator terminal to provide the required damping without deteriorating the voltage profile under disturbance conditions. In order to have better dynamic performance, a supplementary proportional-integral-derivative (PID) controller of which the parameters are determined by eigenvalue assignment is incorporated in the static VAR compensators. The dynamic responses of the synchronous machine subjected to a three-phase fault are given to demonstrate the effectiveness of the static VAR compensators. A comparison study of the proposed controller and a PID excitation controller is made with respect to damping enhancement and terminal voltage deviation. View full abstract»

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  • An Ultrahigh Speed CAMAC Interface for a Large Flight Simulator System

    Page(s): 618 - 627
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    The real-time simulation subsystem (RTSS) at the NASA Langley Research Center in Hampton, VA, consists of several CDC CYBER computers and over 20 flight simulation sites. This simulation network is used by the Langley Center to advance the state of aeronautics and to improve air safety. The current simulator interface system at NASA-Langley was installed in 1968 and uses centrally located analog and discrete conversion equipment. Of the alternatives studied by NASA for a replacement RTSS, only the network and input/output (I/O) system conforming to the international computer automated measurement and control (CAMAC) standards meets their requirements. The CAMAC serial highway provides a distributed I/O system with an extremely high data throughput approaching 24 000 000 information bits/per second. Fiber-optic links transmit the data over paths to 1 km. For multisite simulations, a computer-controlled electronic switch configures site highways in any combination. The CAMAC system uses analog-to-digital converters (ADCs), digital-to-analog converters (DACs), and synchro converters with 16 bits of resolution to give the needed system performance. The time to acquire data from 80 16-bit ADCs and 960 discrete inputs and transfer them to the CYBER central memory is less than 320 ¿s. Similarly, the time from CYBER central memory to the setting of 256 16-bit DACs and 960 discrete outputs is less than 650 ¿s. View full abstract»

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  • On Team Games: A Computational Structural Analysis

    Page(s): 628 - 641
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    Team games are studied here with one performance index for the team as a unit in competition with one common opponent. A structural analysis is presented with the intent to simplify the computation of optimal decision and communication processes. The minimum principle and calculus of variations are used to compute time-optimal and quadratic-optimal trajectories for certain linear "pursuit-evasion" games. A composition method is presented to compute an approximate solution to the two-versus-one problem from the solution to two one-versus-one problems. Help zones of a second pursuer to assist in the "capture" of an evader are derived. The hierarchical command and communication structure for a quadratic linear game of N pursuers and one evader is derived. An approximation is generated which has a convenient ripple or recursive structure. View full abstract»

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  • Models for Radar Scatterer Density in Terrain Images

    Page(s): 642 - 647
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    Statistical models for the density of strong scatterers detected in high resolution radar images of rural terrain are presented. The probability distribution of the density of these natural terrain detections was found to be negative binomial. The variance of the negative binomial depended strongly on the window size used to measure the density. This dependence indicates that these detections, like those of a Poisson process, are locally uncorrelated, but have a slowly varying mean density whose correlation distance is 1 km or more. Negative binomial parameters were computed using over 200 km2 of terrain image for densities measured using windows sized from 75 m × 75 m to 375 m × 375 m. Average terrain detection densities of 10-3 and 10-4 per resolution cell were evaluated on images with resolutions of 7 and 28 ft. View full abstract»

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  • An Analytical Expression for Correlation Accuracy

    Page(s): 648 - 656
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    An analytical closed-form expression for the uncertainty in aligning two images is derived as a function of image area, data fidelity, scene correlation length, limiting sensor resolution length, and degree of geometrical distortion between the two images. View full abstract»

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  • The Effect of Constant Velocity Error on SAR Focus

    Page(s): 657 - 659
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    The usual analyses of the effect of constant radar velocity error on synthetic aperture radar (SAR) focus generally yield the result that the cross-radial component of velocity error is primarily responsible for image defocusing. A simple argument is given demonstrating that image focus depends on accurately estimating radar speed, in which the along-track (AT) component of velocity error is most important. View full abstract»

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  • Ku-Band Atmospheric Attenuation Model

    Page(s): 662
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    An atmospheric attenuation model has been developed at Ku-band. This model is suitable for predicting air-to-surface radar performance over a wide range of operating conditions. View full abstract»

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  • M. Barry Cariton Award for 1985

    Page(s): 663
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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