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Aerospace and Electronic Systems, IEEE Transactions on

Issue 5 • Date Sept. 1979

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Displaying Results 1 - 25 of 27
  • Table of contents

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

    Page(s): c2 - 752b
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    Freely Available from IEEE
  • From the Editors

    Page(s): 593
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  • Environment and Radar Operation Simulator

    Page(s): 594 - 599
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    The environment and radar operation simulator (EROS) is a hardware system whose function is to produce realistic synthetic radar backscatter, incorporating both target and clutter. The simulator is electrically connected to a subject radar and responds in real time to the radar's antenna scan angle by producing the correct composite video signal. View full abstract»

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  • Information for authors

    Page(s): 600
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  • A Distributed System Adaptive Control Strategy

    Page(s): 601 - 612
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    One attitude control device being studied for large spacecraft consists of two counter-rotating rings, each designated as an annular momentum control device (AMCD), that are attached to a spacecraft using several magnetic bearings distributed along the circumference of the rings. For large spacecraft large rings are desirable. Unfortunately, for large rings flexibility is appreciable and it becomes necessary to account for the distributed nature of the rings in the design of the magnetic bearing controllers. Also ring behavior is unpredictably sensitive to ring termperature, spin rate, manufacturing imperfections, and other variables. For that reason a distributed adaptive microcomputer-based control system is being sought for ring stabilization and maneuvering. An original adaptive-control methodology for distributed-parameter systems is detailed and application to spinning ring, i. e., AMCD, stabilization is used as an illustration. The proposed methodology, presented as a step-by-step procedure, combines a lumped-parameter expansion description of distributed parameter systems with a fundamental simultaneous identification and control strategy. Simulations are presented providing preliminary evidence of the capabilities of the proposed procedure. View full abstract»

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  • Spectrum Width Estimtes for Weather Echoes

    Page(s): 613 - 619
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    Doppler spectrum width relates to wind shear and turbulence and thus is an important parameter which characterizes severe weather phenomena. The need to scan large volumes of space quickly and to obtain real-time estimates introduces stringent requirements on the signal processing. The Fourier transform and the autocovariance methods are candidate techniques. In particular, the autocovariance estimator is attractive due to low storgage and ease of computation. Statistics of an improved and asymptotically ubiased (for Gaussian spectra) autocovariance estimator of width are presented. Spurious effects on the complex video signal such as dc offsets and imbalances are assessed. Performance of the improved estimator on weather data is shown. View full abstract»

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  • Error Analysis of an Algorithm for Magnetic Compensation of Aircraft

    Page(s): 620 - 626
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    The Tolles and Lawson equations were programmed on the IBM 370-65 computer. These equations predict the magnetic signals which are generated by the permanent moments, the induced moments and the eddy-current terms of an aircraft as it maneuvers in the Earth's magnetic field. The least mean squared (LMS) solution of these equations, which was developed for the microprocessor compensation program, was also simulated on the IBM 370 computer. By measuring the simulated figure of merit (FOM) before and after applying compensation, several types of error were studied. It was found that the error introduced by truncation effects on a 16-bit microprocessor limits the FOM to 50 milligammas. Since this figure is an order of magnitude smaller than the design goal, it is concluded that the algorithm is not limited by the microprocessor capacity. Other studies show that although the baseline model is insensitive to bearing separation, the bearing separation should be 900° ± 7.50° if 3 iterations are used in the post processor and 900° ± 15° if 5 iterations are used. Although the algorithm is robust and relatively insensitive to various types of noise, experimental evidence suggests that hysteresis can cause temporal variations in the Tolles and Lawson model. It is suggested that whitening and/or adaptive techniques could be used to minimize such variations. View full abstract»

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  • Input-Filter Design for Switching Regulators

    Page(s): 627 - 634
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    The interaction between the input filter and the control loop of switching regulators often results in detrimental effects, such as loop instability, transient response, and audio-signal-rejection rate, etc. A small-signal average model is derived to investigate these effects. Design constraints of an input-filter and switching-regulator system are formulated. An optimum low-pass and light-weight filter configuration is proposed. View full abstract»

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  • Design and Performance of an Adaptive Kalman Receiver for Synchronous Data Transmission

    Page(s): 635 - 648
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    A class of multilevel linear-modulation data-transmission systems, over unknown, slowly time-varying, and bandlimited channels is considered. It is shown how sequence estimation in the presence of Gaussian noise and intersymbol interference can be carried out by means of a discrete Kalman estimator. Moreover, the receiver can be provided with data-aided adaptive loops for performing channel identification, carrier recovery, and timing extraction. A computational method is presented to evaluate the average probability of error of the overall system in the presence of inter-symbol interference, additive noise, and phase-and sampling-synchronization errors. The method is based upon nonclassical one-and two-dimensional quadrature rules, which are outlined in the Appendix. As an example, numerical performance results related to a phase-shift-keying (PSK) system are given. The results are obtained by means of general-purpose and system-oriented computers. View full abstract»

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  • Early Shipboard Search Radars of the U. S. Navy

    Page(s): 649 - 659
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    Evolutionary charts and brief descriptive notes are presented on over one hundred types of shipboard search radars developed in the United States between 1936 and 1970. View full abstract»

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  • Error Analysis for Relay Type Satellite-Aided Search and Rescue Systems

    Page(s): 660 - 665
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    An analysis is made of the errors in the determination of the position of an emergency transmitter in a satellite-aided search and rescue system. The satellite is assumed to be at a height of 820 km in a near-circular near polar orbit. Short data spans of four minutes or less are used. The error sources considered are measurement noise, transmitter frequency drift, ionospheric effects, and error in the assumed height of the transmitter. The errors are calculated for several different transmitter positions, data rates, and data spans. The only transmitter frequency used was 406 MHz, but the result can be scaled to different frequencies. View full abstract»

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  • Preliminary Evaluation of GPS Performance for Low-Cost General Aviation

    Page(s): 666 - 672
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    Preliminary results of a simulation effort to evaluate the requirements and feasibility of the global positioning system (GPS) as a civil air navigation system are presented. Evaluation is made of GPS requirements, from operational considerations, such as application to nonprecision approaches. The conceptual low-cost GPS receiver simulated here does not correct for the ionospheric or trophospheric delay, is sequential in nature, tracks only four satellites, and is not mechanized to make independent range rate measurements based on the Doppler shift of the GPS carrier frequency. The proposed GPS system has significantly different performance characteristics from the presently used VHF omnidirectional range (VOR) solidus distance-measuring equipment (DME) system. The GPS is a low signal level system and many have a relatively slow data rate due to the low-cost sequential receiver design. The results indicate that although the conceptual low-cost GPS receiver/ navigator is potentially more accurate than a VOR, the accuracy may degrade during aircraft turns and satellite shielding periods. View full abstract»

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  • Pulse Compression Results Using Metallic Reflective Array Lines

    Page(s): 673 - 682
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    Radar pulse-compression results are presented for the first reflective-array compressor (RAC) dispersive delay lines (DDL) with both metallic reflecting arrays and phase-compensating films. The time-bandwidth product of the devices reported is approximately 400. Operation in a recirculation loop with a 37.5-dB Taylor weighting filter yielded 36-dB near-in range sidelobes. RMS phase errors less than 0.71 degrees across the band were achieved. Greater than 50-dB rejection of spurious response is achieved in the far-out range gate region. The potential for high-quality cost-effective fabrication of metallic RAC DDL for system applications is explored. View full abstract»

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  • Computer Simulation of VLF Power Amplifiers under Reactive Loading

    Page(s): 683 - 689
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    Recent efforts have been made to achieve substantially increased baud rates with the U. S. Navy's very low frequency (VLF) communication system. Because of the constraints imposed by existing transmitter and antenna structures it was necessary to reexamine the operation of every major system component. Each particular VLF transmitter was subjected to an extensive theoretical analysis followed by a detailed on-site measurement program. Following a review of three major systems, Cutler, Lualualei, and North West Cape, a sufficient body of data was available to substantiate the validity of the computer-simulated transmitter analysis presented here. With this method it is possibe to predict frequency-shift keying (FSK) and minimum shift keying (MSK) performance limitations for particular VLF transmitting systems based primarily on the 0 of the antenna at the operating frequency. View full abstract»

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  • Enhanced Power Generation of GSS4PS by Optical Solar Reflectors

    Page(s): 690 - 696
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    A novel arrangement is proposed to enhance the power generation capabilities of a gravitationally stabilized solid-state-satellite solar-power station (GSS4PS) spherical solar collector. The unilluminated portion of a GSS4PS is illuminated by employing optical solar reflectors. The different mechanisms required for implementation of this arrangement are already space proven. The detailed study of this arrangement made by the authors reveals that practical realization of this concept will enhance the power generation capability of the GSS4PS and simultaneously reduce the weight per unit power and cost per unit power in GSS4PS spherical solar collectors. View full abstract»

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  • Tradeoff between Picture Element Dimensions and Noncoherent Averaging in Side-Looking Airborne Radar

    Page(s): 697 - 708
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    An experiment was performed to determine the effect on radar image interpretation of: 1) rectangular instead of square pixels, and 2) spatial resolution in the presence of noncoherent averaging. The result is a proof of the hypothesis that interpretability of images is determined by a "spatial-gray-level (SGL) resolution volume" that is the product of the range resolution, the azimuth resolution, and a gray-level resolution. The last is defined as the ratio of the value exceeded 10 percent of the time to that exceeded 90 percent of the time for a chi-square distribution having twice as many degrees of freedom as the number of independent samples averaged. Since the area of the pixel enters, rather than explicit dependence on range or azimuth resolution, rectangular pixels are as interpretable as square pixels having the same area. The SGL accounts for the effect of reduction in fading on interpretability. The numerical interpretability assigned by experienced image interpreters asked to look for specific classes of targets was found to fall exponentially with increasing SGL volume, with a scale determined by the class of target. The experiment showed that, for most of the tasks assigned to the interpreters, the interpretability is reduced to 37 percent for a fully focussed synthetic-aperture radar (SAR) (1-look) for a 10-m (33-ft) square pixel. With an infinite number of samples averaged, the comparable square-pixel dimension is 48 m (157 ft). This is consistent with results obtained using LANDSAT images of about 60-m resolution. View full abstract»

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  • Magnetic Position and Orientation Tracking System

    Page(s): 709 - 718
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    Three-axis generation and sensing of quasi-static magneticdipole fields provide information sufficient to determine both the position and orientation of the sensor relative to the source. Linear rotation transformations based upon the previous measurements are applied to both the source excitation and sensor output vectors, yielding quantities that are linearly propotional to small changes in the position and orientation. Changes are separated using linear combinations of sensor output vectors, transformed to the desired coordinate frame, and used to update the previous measurements. Practical considerations for a head-tracking application are discussed. View full abstract»

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  • Low-Loss Almost Constant False-Alarm Rate Processors

    Page(s): 719 - 723
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    Conventional normalizing constant false-alarm rate (CFAR) circuits use the same configurations when detecting targets in interference regions and in clear regions. The CFAR penalty incurred in the clear region can be reduced by using CFAR processors that recognize the region is clear so that normalization is not necessary. An analysis of the target-detection performance for a particular modified CFAR processor, for an active-radar sensor, and for a passive infrared (IR), or sonar, sensor is given. It is shown that the decreased CFAR penalty in the clear is coupled with an increase of false-alarm rate in the clutter regions. View full abstract»

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  • Model for Spectral and Polarization Characteristics of Chaff

    Page(s): 723 - 726
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    A stochastic model which describes the spectral and polarization characteristics of radar echoes from a chaff cloud consisting of a collection of rotating dipoles, which may have either completely random or preferred orientations, is presented. View full abstract»

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  • Square-Wave Correlation Phase Detector with VLF Atmospheric Noise

    Page(s): 726 - 732
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    Correlation phase detectors often include hard limiting of both received and reference signals. The characteristics of such " square-wave" correlation detectors for both Gaussian and impluse noise are derived as functions of both phase and carrier-to-noise ratio. Decoding algorithms and accuracy are discussed. View full abstract»

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  • Some Historical Data Concerning the First Italian Naval Radar

    Page(s): 733 - 735
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    Some history is recalled about what was done in Italy following a proposal by G. Marconi for the development of the first Italian radars during the 10 years from 1933 to 1943. Italian researchers worked without any connection with the activity at that time of American, English, and German research groups because of military secrecy. The people in Italy who independently developed the first Italian naval radar can fully understand and appreciate the admirable work done by R. M. Page, winner of 1977 Pioneer Award. View full abstract»

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  • Simple Generation of One-Parameter Pseudoterrain Surfaces

    Page(s): 735 - 738
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    A simple method for generating digital terrain surfaces as a function of only the terrain standard deviation is presented. This is accomplished by fitting a postulated autocorrelation model to actual terrain data. Observed relations between model parameters are used to obtain a one-parameter model. View full abstract»

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  • The Effect of Jamming on Monopulse Accuracy

    Page(s): 738 - 741
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    An expression is applied for the probability density function (pdf) of the monopulse ratio when skin echoes from a passive target are contaminated by interference from a jammer. The analysis is valid for arbitrary signal-to-jam ratio and arbitrary locations of the target and jammer in the beam. For an on-axis skin target and a stand-off jammer at an off-axis location, the "pulling" effect of the jammer and the accuracy of the angle estimate are compared with the approximations currently employed in radar performance analysis. The pdf of the monopulse ratio for large and for small signal-to-jam ratios is presented, showing that the pdf is bimodal at small signal-to-jam ratio. View full abstract»

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  • 1979 Pioneer Award

    Page(s): 742
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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