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Aerospace and Electronic Systems, IEEE Transactions on

Issue 4 • Date July 1975

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  • Table of contents

    Publication Year: 1975 , Page(s): c1 - 692-b
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    Freely Available from IEEE
  • IEEE Aerospace and Electronic Systems Society

    Publication Year: 1975 , Page(s): c2 - 692a
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  • From the Editors

    Publication Year: 1975 , Page(s): 429
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  • A Stochastic Algorithm for Sensitivity Analysis

    Publication Year: 1975 , Page(s): 430 - 436
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    A direct stochastic sensitivity analysis algorithm is developed for linear dynamical systems having incompletely known input statistics. The new algorithm extends previous results by applying covariance propagation concepts which utilize as a forcing function the sensitivity covariance matrix associated with the uncertainty in the elements of the system input covariance matrix itself. The developed algorithm is evaluated in the context of a generalized sensitivity analysis formulation involving nonlinear transformations on the input signals. Numerical results are provided to demonstrate the usefulness of the new algorithm. View full abstract»

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  • Modified Barker Code Approximating Huffman's Impulse-Equivalent Sequence

    Publication Year: 1975 , Page(s): 437 - 442
    Cited by:  Papers (2)
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    It is shown by use of D.A. Huffman's polynomial representation for a finite sequence of contiguous pulses in a pulse train that Barker's binary-coded sequences can be modified, by a weighting of pulse amplitudes, to a condition where time sidelobes in the pulse compressed signal are substantially reduced. In such a pulse amplitude modification there is a sacrifice in pulse train energy since each pulse does not have maximum energy. Results here are provided for Barker's sequence of length 13 only. View full abstract»

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  • An Optimal Normalization Scheme

    Publication Year: 1975 , Page(s): 443 - 446
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    An attitude normalization scheme, based on quaternion updates' of the attitude matrix in a strapdown system, is presented which is optimal in the two-norm sense. Furthermore, the algorithm requires minimal computer time and memory load. View full abstract»

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  • A Comparison of Two Approaches to Pure-Inertial and Doppler-Inertial Error Analysis

    Publication Year: 1975 , Page(s): 447 - 455
    Cited by:  Papers (27)
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    Error equations for inertial navigation systems are derived using a perturbation (or true frame) approach and a psi angle (or computer frame) approach in a manner which shows the underlying as sumptions and allows direct comparison of the two methods. The comparison is general since the analysis is not associated with any particular mechanization. Different definitions of velocity errors and misalignment angles result from the two methods of error analysis, and, consequently, have significance in testing and analysis of pure-inertial systems, Doppler-inertial systems, and inertially aided weapon delivery systems. Examples and numerical results are presented for a local-level north-pointing mechanization. View full abstract»

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  • On-Line, Real-Time Recognition System on Telegraph Codes: TETAC

    Publication Year: 1975 , Page(s): 456 - 464
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    This paper describes studies of the TETAC system (Teaching Equipment for Telegraph Technology Aided by Computer). The system has been developed for training students at the University of Electro-Communications. TETAC is an intelligent system which recognizes Morse code sent by hand and converts it to letters by means of online and real-time processing. In addition, the system evaluates the qualities of trainees' keying operations; namely, it identifies the students' faults or tendencies. Although TETAC is now in the testing stage, we are confident of the effectiveness of the training and of TETAC's usefulness in modernizing a maritime communication system. View full abstract»

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  • Detecting Instrument Malfunctions in Control Systems

    Publication Year: 1975 , Page(s): 465 - 473
    Cited by:  Papers (46)
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    A scheme for automatically detecting incipient failures in the feedback sensors (or instruments) of control systems is described. The feasibility of the scheme is investigated by applying it to a simplified version (fourth order) of the flight control system for a hydrofoil boat. A single set of inertial instruments is used to provide the feedback signals; the redundancy which is normally obtained by multiple instrument sets is obtained here, artificially, by a subsystem of multiple Luenberger observers and logic circuits. Tests indicate that scale factor errors, errors due to threshold effects, and bias errors in the instruments are detected as they occur. The tests also indicate further analytical work which should be done to explore the limitations of the basic scheme. View full abstract»

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  • The Effects of Defruiting on the ATCRBS

    Publication Year: 1975 , Page(s): 474 - 484
    Cited by:  Papers (2)
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    The defruiter that is employed in the Air Traffic Control Radar Beacon System (ATCRBS) to prefilter asynchronous replies has a complex impact on the detection, estimation and validation properties of the detection subsystem. Its positive and negative effects are quantitatively enumerated via a simulation of the beacon processing subsystem of the Automated Radar Terminal System (ARTS III). It is concluded that the disadvantages of using the present-day defruiter in the ARTS III digital processing channel outweigh the advantages when fruit rates are below several thousand per scan. As an alternative to the total elimination of the defruiter a more general class of preprocessors is defined and their input-output relationships are derived using a Markov Chain formulation. These are found to represent an improvement over the current defruiter in that the positive effects of defruiting are retained while some of the negative effects are reduced. View full abstract»

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  • ATC Beacon Interference Characteristics in the New York Area

    Publication Year: 1975 , Page(s): 485 - 494
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    An experimental program is described that had the objective of measuring the effects of the time-dependent structure of downlink (air craft to ground) interference generated by the Air Traffic Control Radar Beacon System (ATCRBS) in an active air traffic terminal area that are relevant to system and ground controller response time. The results of this program indicate a number of interesting details concerning the correlation of the level of the downlink interference with changes in the arrival and departure rates of aircraft at the local terminal sites. View full abstract»

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  • Circuit Analysis of Eddy Currents

    Publication Year: 1975 , Page(s): 495 - 498
    Cited by:  Papers (4)
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    Maxwell's equations govern the eddy-current phenomenon, and are the starting point of this analysis. It is shown that Maxwell's equations, as applied to steady-state ac conditions, can be transformed to a Fredholm-type integral equation in eddy-current density. In turn, it is demonstrated that the method of subareas can be used to solve the Fredholm equation. This approach leads to the familiar circuit-analysis concepts of resistance and inductance in finite coupled circuits. The coupledcircuit method can be utilized in cases of complex, mixed boundary conditions without difficulty, as is illustrated by an example of the eddy-current losses in a conducting disk of finite thickness and finite radius, in the presence of a current-carrying loop. Experimental data is presented which confirms the theory, for a range of disk thicknesses. References are included to previous work. View full abstract»

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  • Review of Radiation Damage to Silicon Solar Cells

    Publication Year: 1975 , Page(s): 499 - 513
    Cited by:  Papers (1)
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    This paper reviews a large number of silicon solar cell irradiation experiments performed over the last 10 years, including 1-MeV and energy spectrum electron studies, and low-(100-keV) and high-energy (up to 155-MeV) proton studies on bare and covered silicon solar cells of several types. The results of satellite flight experiments on individual solar cells are also presented, as well as data from complete solar arrays and data on the new high-efficiency solar cells. Experimental evidence indicates that the percentage of degradation is smaller in thin solar cells than in thick ones, and that cells with high resistivity (10 ¿·cm) degrade less than cells with lower resistivity (1 ¿·cm). It is shown that high-efficiency silicon solar cells produced at COMSAT Laboratories and pilot production groups of these cells retain most of their increased power output under irradiation. It is emphasized that all surfaces and edges of the solar cells must be completely shielded from the large flux protons in the space environment. Insufficiencies in the published data are noted in certain areas, and recommendations for additional research are presented. Finally, an extensive bibliography is included. View full abstract»

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  • Limiting the Impulsive Noise in a PLL

    Publication Year: 1975 , Page(s): 514 - 518
    Cited by:  Papers (2)
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    This paper analyzes the operation of a phase-locked loop (PLL) preceded by a bandpass limiter (BPL) in the presence of impulsive noise. It is shown that the effect of the limiter consists essentially in a change of the statistics of the pulse strengths of the noise, so that the behavior of a BPL + PLL can be deduced from that of a simple PLL by suitable adjustment of the noise model. It is found that the limiter greatly enhances the PLL performance by reducing both the phase-error variance in the loop and the probability of cycle slippage. Finally, the design of the filter of the BPL is discussed, resulting in the conclusion that the best results are obtained by using a singletuned RLC circuit. View full abstract»

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  • Doppler Processor Rejection of Range Ambiguous Clutter

    Publication Year: 1975 , Page(s): 519 - 522
    Cited by:  Papers (2)
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    Doppler processors are used in radar to separate target returns from clutter. When the clutter is at a range farther than the unambiguous range of the radar, the ability to reject the clutter is degraded. In this article the degradation is analyzed for an N-pulse batch processor with Dolph weighting, and the results show how degradation varies with design sidelobe level. View full abstract»

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  • The Jet Fighter Radar Cross Section

    Publication Year: 1975 , Page(s): 523 - 533
    Cited by:  Patents (1)
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    Two jet fighter models, 1/8th of original size, have been measured in the "radar range" installed in the anechoic chamber of the Armament Technology and Procurement Group in Berne. The measurements have been made at a frequency of 40 GHz (5 GHz for full scale), with an accuracy of ± 2 dB and a dynamic range of 80 dB. The statistical distribution of the radar cross section has been calculated with the help of a computer, based on the measured data. The detection probability has been calculated with the help of a correlation procedure. This procedure allows explanation of the symmetry relation between the detection probability and the cumulative distribution of the radar cross section, and of a well-known characteristic of the median value of the radar cross section. A statistical model is proposed for the distribution of the radar cross section of jet fighters, consisting of the distribution of a spheroid in which each element itself exhibits a Rayleigh fluctuation. This model presents a certain number of interesting characteristics, and there is an acceptable degree of coincidence with the measured values. View full abstract»

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  • Estimating Target Lengths Shorter Than the Radar Pulse Width

    Publication Year: 1975 , Page(s): 534 - 538
    Cited by:  Papers (2)
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    This paper discusses the performance and sensitivity of a maximum-likelihood length estimation algorithm which was originally developed to estimate the separation between unresolved point scatterers. It shows that when the two-scatterer target model is valid, the algorithm reliably estimates lengths shorter than the Rayleigh limit provided that the strength of no third interior scatterer (or its equivalent created by a few very closely spaced scatterers) is greater than the geometric mean of the strengths of the fore and aft scatterers. View full abstract»

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  • Boresight Corection Using Unlocated Targets

    Publication Year: 1975 , Page(s): 539 - 542
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    Boresight correction on detected but unlocated targets may be made if a bearing (whose error is unknown) is repeated on two seeker headings and another bearing is repeated on two seeker headings, or if bearing is repeated on three seeker headings. The assumption is made that seeker position and heading are known. The procedure is effective either with the above or with the combination of restricted seeker travel and intermittent target detection. View full abstract»

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  • Generation Schemes for Wind Power Plants

    Publication Year: 1975 , Page(s): 543 - 550
    Cited by:  Papers (2)
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    This paper reviews various electric generation schemes for wind energy conversion suitable for interconnection with a power grid. The schemes can be generally classified as constant speed constant frequency (CSCF) and variable speed constant frequency (VSCF) systems. Historically, only CSCF systems have been used for large power generation in wind power plants. However, with the advent of power electronics and the availability of solid state devices capable of handling large amounts of power, VSCF systems are becoming competitive. Various schemes under each classification are discussed and compared. It is stressed, however, that the optimum choice of the generating scheme is not decided by considering the generator alone. The optimum choice is one which minimizes the cost of energy generated by the wind power plant. View full abstract»

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  • Estimating Angular Velocity from Output of Rate-integrating Gyro

    Publication Year: 1975 , Page(s): 551 - 555
    Cited by:  Papers (2)
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    The Kalman filtering technique can be used to improve estimates of angular velocity (in a strapped-down navigation system) using angular increment (rate integral) data. A simple, second-order, constant coefficient digital filter can yield significant improvement for a very high or a very low noise-to-signal ratio·r = 4 ¿¿/¿¿T2, where ¿¿ is the rms noise in measuring angular increments, ¿¿ is the rms angular acceleration, and T is the sampling time. For r ¿ 1, the filter affords negligible performance improvement. View full abstract»

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  • Hard Limiting in Synthetic Aperture Signal Processing

    Publication Year: 1975 , Page(s): 556 - 561
    Cited by:  Papers (8)
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    In synthetic aperture radar a large linear phased array is formed from the rapid movement of a single element through each position in the array. Storage and coherent combining of the successive radar echoes are central to the array-forming process. Optical processing is the most common technique because of the efficiency with which Fourier transformation may be accomplished with simple optics. Real-time operation, however, requires all-electronic processing, which is difficult to accomplish because of the huge quantity of data to be manipulated. Dynamic range compression by hard limiting may ease the problem by reducing the number of bits per frame. The effects of hard limiting are analyzed in this paper. It is shown that large targets simultaneously illuminated by the radar antenna will produce image targets or ghosts displaced in angle. Statistically homogeneous clutter will "linearize" the hard-limited receiver and suppress the ghosts without loss in contrast, as does thermal noise if it is larger than the target echoes. Pulse compression reduces the probability of images from prominent targets. Judicious choice of the pulse-compression waveform is a powerful tool for destroying coherent buildup of images from all large targets not in the same range resolution cell. Linear FM, the most common choice, unfortunately does not exhibit this desirable property. View full abstract»

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  • Advances in Low-Frequency Radio Navigation Methods

    Publication Year: 1975 , Page(s): 562 - 574
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    Advances in the analysis and design of low-frequency radio navigation systems are presented in four sections detailing system design, propagation, receivers and processors, and error analyses. Emphasis is on the short-baseline case where radial accuracies of 114 feet are possible for non-line-of-sight operation to ranges of 50 miles from transmitters. Possibel future applications for LF include an efficient solution for commercial ground transportation management, remotely piloted vehicle navigation, and cruise missile guidance. An error budget and experimental results are included plus a countermeasures analysis. View full abstract»

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  • Optimal and Suboptimal Perfomance of a PCM/FM Communication System

    Publication Year: 1975 , Page(s): 575 - 581
    Cited by:  Papers (7)
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    Theoretical results are presented on probability of error in the detection of binary FM signals for various frequency deviations with fixed bit rate, restricted predetection filter bandwidth, ideal limiterdiscriminator reception, and integrate-and-dump postdetection filter decision. The results show that suboptimal system performance can be achieved by choosing the largest possible value of deviation index which lies approximately at 0.7 + 2n, where n = 0, 1,...,k. k is determined by the reconstructability of signal after the bandpass filter. View full abstract»

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  • Low-Level Signal Detection Using a New Transform Class

    Publication Year: 1975 , Page(s): 582 - 594
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1987 KB)  

    A system is developed to detect tracks crossing two-dimensional noise fields. This is accomplished by filtering and integration of signal power in the frequency domain of a new class of generalized transforms which include the FFT and FBT as limiting forms. If the track is essentially parallel to a transform axis and if filters are derived from hard-limited linear approximations to tracks, the FBT offers considerable hardware economy over the FFT in the mechanization algorithm. View full abstract»

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  • Phase-Locked Demodulator Threshold: A New Approach

    Publication Year: 1975 , Page(s): 595 - 599
    Cited by:  Papers (2)
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    In this paper the dependence of the threshold CNR of a simple phaselocked demodulator on the frequency deviation of an FM signal has been evaluated by the concept of quasi-stationary approximation. Experimental findings have been presented in support of the theoretical conclusion. 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