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Aerospace and Electronic Systems, IEEE Transactions on

Issue 2 • Date March 1973

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Displaying Results 1 - 25 of 35
  • Table of contents

    Publication Year: 1973 , Page(s): c1
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    Freely Available from IEEE
  • IEEE Aerospace and Electronic Systems Society

    Publication Year: 1973 , Page(s): c2 - 348b
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    Freely Available from IEEE
  • From the Editors

    Publication Year: 1973 , Page(s): 129
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  • Speech Data Rate Reduction Part I: Applicability of Modern Estimation Theory

    Publication Year: 1973 , Page(s): 130 - 138
    Cited by:  Papers (10)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1335 KB)  

    Efficient coding of continuous speech signals for digital representation has attracted much interest in recent years. The underlying aim of efficient coding methods is to reduce the channel capacity required to represent a signal to meet a specific reconstruction fidelity criterion. To achieve this objective, modern speech data compression techniques rely on two very similar procedures. One procedure uses predictive deconvolution which subtracts from the current signal value that portion which can be predicted from its past and thus removes redundancy in the speech by removing sequential correlation. The signal thus requires fewer bits for equivalent quantization error. The second procedure involves identification of a complete mathematical model of the speech producing mechanism. This involves determination of the characteristics of the source that drives this transfer function. Data reduction is again achieved since the rate of change of the parameters of the speech model is much smaller than the rate of change of the speech waveform. This paper develops these data reduction procedures in terms of modern estimation theory, specifically a Kalman filter model, and illustrates the utility of this model as an analysis tool by means of an example based on a uniform tube which provides a qualitative assessment of the potential of the technique for application to real speech signals. View full abstract»

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  • Speech Data Rate Reduction Part II: Applicability of Sensitivity and Error Analysis

    Publication Year: 1973 , Page(s): 139 - 150
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2600 KB)  

    This paper deals with the application of modern estimation techniques to the problem of speech data rate reduction. It is desirable to adaptively identify and quantitize the parameters of the speech model. These paramaters cannot be identified and quantized exactly; the performance of the predictor is thereby degraded and this could prevent data reduction. In many cases it is desirable to emply a suboptimal predictor in order to simplify the algorithms, and predictor performance is again degraded. This paper develops sensitivity and error analysis as a potential method for determining quantitatively how speech data reduction system performance is degraded by imprecise parameter knowledge or suboptimal filtering. An intended use of the sensitivity and error analysis algorithms is to determine parameter identification and model structure requirements of configuration concepts for adaptive speech digitizers. First, sensitivity and error analysis algorithms are presented that form the basis for the remainder of the work. The algorithms are then used to determine how imprecise knowledge of vocal tract parameters degrades predictor performance in speech. Transversal filters have previously been proposed for this application. The sensitivity analysis algorithms are then used to determine when and by how much the transverse filter is suboptimal to the Kalman filter. In particular, the question of how effectively a higher order of all-pole model approximates a system with zeros is answered, as this question is of considerable importance in speech. Finally, the physical significance of the innovations process in speech data rate reduction is studied. View full abstract»

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  • A Semicoherent Detection and Doppler Estimation Statistic

    Publication Year: 1973 , Page(s): 151 - 165
    Cited by:  Papers (92)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (3038 KB)  

    Consider a uniform train of M coherent short pulses transmitted by a radar and received with a Doppler shift. When thermal noise is present, let the mth sample of the return at the video be represented by the complex process Zm. A novel detection and Doppler estimation criterion is analyzed which depends on the semicoherent statistic begin{equation*}{Z_{K}}^prime = sum_{m=k+1}^{M} {^{z}m^{z}m-k}^{ *}end{equation*} where the asterisk stands for complex conjugate. Its characteristics are also studied when the real and imaginary parts of Zm are digitized to one bit. View full abstract»

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  • Synthetic Aperture Processing with Limited Storage and Presumming

    Publication Year: 1973 , Page(s): 166 - 176
    Cited by:  Papers (8)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1951 KB)  

    The number of transmitted pulses associated with the Doppler histories of a side-looking radar may greatly exceed the desired azimuth compression ratio of the system. This discrepancy is taxing if the storage required for the azimuth processing is provided by cores, magnetic drums, and the like. Thus, as a practical matter, one considers presumming of the data prior to correlation in an attempt to achieve the desired performance with a minimum amount of digital storage. In this paper, the optimum (in terms of resolution) presummer is derived, along with the optimum apportionment of the available storage capacity between the presumming and correlation operations. Under the condition (or generally pessimistic approximation) that the illumination pattern of the antenna uniformly illuminates a Doppler bandwidth equal to the PRF of the radar, the optimum presumming coefficients are the first Np Fourier coefficients of a function which is one of the Doppler bandwidth to be correlated and zero on the remainder of the PRF bandwidth, where Np is the number of transmitted radar pulses over which presumming is provided. Increasing Np reduces the degradation due to presumming, but may leave inadequate storage for correlation. Hence, we optimize the apportionment between the two operations and present the obtainable resolution as a function of total storage and the number of transmitted pulses in the received Doppler history. View full abstract»

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  • Construction of Fuel and Oil Quantity Sensors for High-Performance Aircraft

    Publication Year: 1973 , Page(s): 177 - 182
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (3056 KB)  

    This paper describes the materials and methods of construction of fuel and oil quantity sensors designed to be used in the severe environments of todays high-performance aircraft. The sensors are based on the use of magnetically activated reed switches suitably compensated by resistors. In order to provide physical and electrical protection, the switches and resistors are encapsulated in a fuel and oil resistant electrical insulation formed of alternate layers of polyimide film and compatible fluorocarbon polymers. View full abstract»

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  • A Minimax Filter for Systems with Large Plant Uncertainties Using Measurements Corrupted by Colored Noise

    Publication Year: 1973 , Page(s): 183 - 186
    Cited by:  Papers (1)
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    A minimax filter is derived to estimate the state of a system, using observations corrupted by colored noise, when large uncertainties in the plant dynamics and process noise are present. View full abstract»

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  • On Signal Fluctuations in Tracking Systems

    Publication Year: 1973 , Page(s): 187 - 196
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1910 KB)  

    All tracking systems suffer, to some extent, from signal level fluctuations. The signal fluctuations are modeled by a Gaussian process and the noise performance of both linear and nonlinear first-order tracking systems is considered. In the nonlinear case, the Ito versus Stratonovich calculus difficulty arises, but it is resolved to make sense physically. Several analytical results are obtained which are useful in analyses of tracking systems. View full abstract»

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  • Unsupervised Tracking of Maneuvering Vehicles

    Publication Year: 1973 , Page(s): 197 - 207
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2259 KB)  

    The design of adaptive filters for the tracking of high-performance maneuvering targets is a fundamental problem in real-time surveillance systems. As is well known, a filter which provides heavy smoothing can not accurately track an evasive maneuver, and conversely. Consequently, one is led to the consideration of adaptive methods of filter design. This paper presents an improved self-adaptive filter algorithm for on-line solution of the above problem. Basically, this algorithm utilizes the orthogonality property of the residual time series to force the filter to automatically track the optimal gain levels in a changing environment. View full abstract»

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  • Correlated Clutter and Resultant Properties of Binary Signals

    Publication Year: 1973 , Page(s): 208 - 213
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1242 KB)  

    A simple Markov process model of binary, digitized radar clutter returns is assumed. Probability distributions for the number of hits in n observations are developed for small n with a binary parameter describing the process derived for Rayleigh distributed clutter. Tables of distributions are included, along with an example to show the effects of correlation on the false-alarm probabilities of a sliding-window detector. View full abstract»

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  • Optimum Mismatched Filters for Sidelobe Suppression

    Publication Year: 1973 , Page(s): 214 - 218
    Cited by:  Papers (95)  |  Patents (10)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1224 KB)  

    This paper discusses the application of least-mean-squares approximate inverse filtering techniques to radar range sidelobe reduction. The method is illustrated by application to the 13-element Barker code. The performance of the least-mean-square inverse filter is compared with the matched filter and with the simplified sidelobereducing filters of Rihaczek and Golden. A filter which completely suppresses the range sidelobes of a 13-element Barker sequence is only 0.2 dB worse than a matched filter in noise. View full abstract»

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  • Automatic Checkout and Monitoring in the AN TPQ-27 Radar System

    Publication Year: 1973 , Page(s): 219 - 224
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1354 KB)  

    This paper describes automatic monitoring equipment built in to a precision tracking radar system to detect and isolate faults. The purpose of the monitoring equipment is to minimize the mean time to repair faults and to exercise the overall system for pre-mission alignment and calibration. In addition, it is used to periodically check for performance degradation in key areas of the system. The paper describes the design approach used to meet the above requirements. Three types of signals are monitored: analog, digital, and switch closure. A list of each type is given and the technique used to monitor each is described. The design approach for pre-mission alignment and calibration is outlined. Tests performed are: RF alignment of the boresight axis, range tracking accuracy, angle servo calibration and accuracy, and receiver figure of merit measurements. View full abstract»

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  • Overview of the Biological Effects of Electromagnetic Radiation

    Publication Year: 1973 , Page(s): 225 - 228
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    A brief review is given of some of the problems concerning the interactions of electromagnetic radiation with biological systems. It is emphasized that we cannot continue to expand the use and power of the electromagnetic spectrum without adequate consideration of its possible biological effects. New research efforts must be started in this area, utilizing a strong and well-coordinated interdisciplinary approach. View full abstract»

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  • A Decision - Directed Adaptive Tracker

    Publication Year: 1973 , Page(s): 229 - 236
    Cited by:  Papers (51)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2055 KB)  

    In the design of a tracking filter for air traffic control (ATC) applications, a maneuvering aircraft can be modelled by a linear system with random noise accelerations. A Kalman filter tracker, designed on the basis of a variance chosen according to the distribution of the potential maneuver accelerations, will maintain track during maneuvers and provide some improvement in position accuracy. However, during those portions of the flight path where the aircraft is not maneuvering, the tracking accuracy will not be as good as if no acceleration noise had been allowed in the tracking filter. In this paper, statistical decision theory is used to derive an optimal test for detecting the aircraft maneuver; a more practical suboptimal test is then deduced from the optimal test. As long as no maneuver is declared, a simpler filter, based on a constant-velocity model, is used to track the aircraft. When a maneuver is detected, the tracker is reinitialized using stored data, up-dated to the present time, and then normal tracking is resumed as new data arrives. In essence, the tracker performs on the basis of a piecewise linear model in which the breakpoints are defined on-line using the maneuver detector. Simulation results show that there is a significant improvement in tracking capability using the decision-directed adaptive tracker. View full abstract»

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  • Theory of Adaptive Radar

    Publication Year: 1973 , Page(s): 237 - 252
    Cited by:  Papers (317)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2750 KB)  

    This paper reviews the principles of adaptive radar in which both the spatial (antenna pattern) and temporal (Doppler filter) responses of the system are controlled adaptively. An adaptive system senses the angular-Doppler distribution of the external noise field and adjusts a set of radar parameters for maximum signal-to-interference ratio and optimum detection performance. A gradient technique for control of the radar array/filter weights is described and shown to generate weights which asymptotically approach optimum values. Simulation results illustrate the convergence rate of adaptive systems and the performance improvement which can be achieved. View full abstract»

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  • High-Reliability Strapdown Platforms Using Two-Degree-of-Freedom Gyros

    Publication Year: 1973 , Page(s): 253 - 259
    Cited by:  Papers (10)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1645 KB)  

    This paper presents a new concept of high-reliability strapdown attitude sensing systems for space vehicles. Each system utilizes a set of redundant two-degree-of-freedom gyros. An optimum system configuration is obtained for maximum system reliability and the best measurement accuracy. Improved accuracy of the final data is obtained by using the least-square data reduction technique. Each system possesses a ¿sensor performance management¿ feature which is capable of failure detection, faulty gyro identification, system reconfiguration, and, possibly, sensor recalibration. Improvement in reliability, as compared to other types of strapdown systems, is demonstrated. Details of the development are described in terms of a system containing four gyros. View full abstract»

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  • Application of Adaptive Arrays to Suppress Strong Jammers in the Presence of Weak Signals

    Publication Year: 1973 , Page(s): 260 - 271
    Cited by:  Papers (57)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2088 KB)  

    The purpose of this paper is to demonstrate that an adaptive array can be used to acquire weak signals, whose direction and timing are unknown, in an environment of stronger jammers. Specifically, it is shown that in an environment of one weak signal and one strong jammer, the adaptive array output suppresses the strong jammer below the weak signal by roughly the same amount that the jammer exceeded the signal before adaptation. View full abstract»

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  • The Use of a Spinning Dissipator for Attitude Stabilization of Earth-Orbiting Satellites

    Publication Year: 1973 , Page(s): 272 - 279
    Cited by:  Papers (9)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1362 KB)  

    This paper considers a novel attitude stabilizing system which acts both as a passive nutation damper and a momentum source for an Earth-orbiting satellite. The system may be designed to use four identical wheels mounted coaxially with and at the ends of the arms of a cruciform structure. The structure may then be spun about the axis perpendicular to the arms to provide angular momentum along the spacecraft spin axis. The wheels experience torques produced by inertial forces. The necessary damping and restoring (spring) torques are provided by means of a torsional arrangement built around the center of each wheel. The performance characteristics of the proposed stabilizing unit are evaluated by considering spacecraft parameters used in one phase of development of the Communications Technology Satellite (CTS). The results obtained for a specific design of the stabilizer indicate that global stability of the desired attitude motion of the spacecraft can be guaranteed with associated damping time constant as low as one second. View full abstract»

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  • Optimal Aircraft Go - Around and Flare Maneuvers

    Publication Year: 1973 , Page(s): 280 - 289
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    This paper analyzes in detail two of the critical aircraft maneuvers associated with approach and landing: the go-around maneuver and the flare maneuver. Optimal solutions that include state and control variable constraints are obtained for both problems. Two algorithms are given for computation of the minimum and maximum altitude loss associated with the pilot-controlled go-around maneuver. A matrix operator is obtained that can be used for in-flight computation of the altitude loss on a small general-purpose digital computer. The flare optimization presented is for a cost functional that includes both the longitudinal touchdown dispersion and the normal acceleration. A closed-loop mechanization is given that approximates the optimal trajectory. A second matrix operator which can be used for prediction of the longitudinal touchdown point is obtained. Uncertainties are also obtained for the purpose of establishing a prediction confidence level. It is proposed that these prediction techniques should be incorporated into a decision making performance monitor. This monitor could provide the pilot with a continuous assessment of the approach and could generate a preflare decision on whether or not to commit the aircraft to the flare maneuver. View full abstract»

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  • Fluctuation Loss and Diversity Gain for In - Phase Systems with Post - Detection Integration

    Publication Year: 1973 , Page(s): 290 - 295
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1300 KB)  

    This paper presents a simple method for determining the losses resulting from detecting only the in-phase component of the complex signal vector returned from a Rayleigh-distributed target. A simple rule is given in terms of the fluctuation loss and integration gain of square-law-detected pulses. The integration improvement for the in-phase channel is given for both slow and fast fluctuating Rayleigh targets. The loss associated with failure to use the quadrature signal component is basic in that it accounts for only one Gaussian sample and, therefore, one degree of freedom. The loss incurred with one square-law-detected return as normally implemented in radar receivers represents two degrees of freedom. It is well known that the system performance improves, approaching that for the constant target, with increasing degrees of freedom of the received data. This paper is an extension of earlier work in that it relates previously computed data to a simple rule. View full abstract»

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  • Transmission Lines and the Environment

    Publication Year: 1973 , Page(s): 296 - 299
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1268 KB)  

    The confused and conflicting state of environmental criteria for transmission lines is discussed. The demands thrust upon electric utilities by pressure groups and legislation provide unsatisfactory guidance for environmental considerations. Environmental considerations are necessary for transmision lines, but realistic, flexible rules must be developed to balance protection of the ecology and the need for electrical energy. View full abstract»

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  • Calculation of Probability of Detection with Target Scintillation

    Publication Year: 1973 , Page(s): 300 - 305
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1556 KB)  

    This paper presents a computational method for the calculation of probability of detection using measured radar target cross-section data. The described method can also be used for probability of detection calculations when the radar target cross section follows a specified probability density function. Using the computational procedure of the paper, a number of curves are generated which can be used for probability of detection calculations with exponential and Gaussian radar target cross-section distributions. The results obtained using theoretical distributions are compared with the corresponding results using actual target cross-section measurements. The results of computer runs are compared to the corresponding values in the literature where available. View full abstract»

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  • Kalman Filter Design Considerations for Space-Stable Inertial Navigation Systems

    Publication Year: 1973 , Page(s): 306 - 319
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (3393 KB)  

    Terrestrial inertial navigation is typically performed using an instrumented platform stabilized in a ¿local-level¿ configuration for convenient generation of geographic navigation information. The local-level geographic reference must be maintained by torquing the system gyros, a requirement which may be incompatible with high-precision inertial sensors currently under development. Gyro torquing in a gimballed navigation system can be avoided by employing a ¿space-stable¿ mechanization of the platform where an inertial, rather than geographic, reference is used for navigation calculations. The software design problems associated with this concept, especially those related to the application of Kalman filtering, are the principle focus of this paper. Although the space-stable configuration has been used extensively for spacecraft navigation and guidance, it has not been widely applied to terrestrial navigation, either for air or marine applications. The chief problem in this application is to perform navigation in local-level coordinates, using system outputs generated in an inertial reference frame. It can be demonstrated that, although the navigation system error dynamics are identical for the local-level and space-stable configurations, the dynamics of the sensor errors which drive these systems are quite different. These differences in sensor error propagation characteristics impose new requirements for the design of procedures to accomplish system calibration, alignment, and reset. This paper outlines a Kalman filtering approach which is applicable to all of the above procedures, and presents numerical results to demonstrate its effectiveness. 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