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Aerospace and Electronic Systems, IEEE Transactions on

Issue 5 • Date Sept. 1973

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Displaying Results 1 - 25 of 36
  • Table of contents

    Publication Year: 1973 , Page(s): c1 - 835-b
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    Freely Available from IEEE
  • IEEE Aerospace and Electronic Systems Society

    Publication Year: 1973 , Page(s): c2 - 835b
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    Freely Available from IEEE
  • From the Editors

    Publication Year: 1973 , Page(s): 629
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  • Radar Imagery of Oil Slicks

    Publication Year: 1973 , Page(s): 630 - 636
    Cited by:  Papers (4)
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    A joint agency controlled oil slick experiment, sponsored by the United States Coast Guard, was conducted in the Pacific Ocean in the Fall of 1970. The Naval Research Laboratory's synthetic aperature radar was used to detect and monitor the slicks at frequencies of 428, 1228, 4455, and 8910 MHz during the low sea state conditions encountered. At frequencies of 1228 MHz and higher, the slicks were depicted with sharp boundaries. At 428 MHz, the boundaries were indistinct. Approximately 400 liters of oil was detected as it was being discharged from the generating ship and larger spills were mapped from the initial thickness to equilibrium thicknesses of 1 micron or less. Thin streamers of oil and wind blown films were also imaged. Area growth rates were obtained for 2500 liter spills of API 26.1 crude oil and API 9.7 fuel oil on a calm sea. The respective rates, from approximately 1 to 4 hours after the spills, were 134 m2/s and 16 m2/s. View full abstract»

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  • On the Effective Single Trial Probability of Success

    Publication Year: 1973 , Page(s): 637 - 642
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    Define the cumulative probability Pn of occurence of some event as the probability that it occurs at least once in n trials. If the single trial probabilities are not fixed, but are drawn from a distribution of their own, or are dependent on some other nonfixed variable, then it would be convenient to have an ¿effective single trial probability (esp)¿ for use in the simple Bernoulli model which would give the same cumulative probability of occurence as actually observed. We show here that the esp can be interpreted as a kind of average, and that its value is given by 1 minus the geometric mean of 1-d(p), where d(p) is the probability density function of the single trial probabilities, the p's. We further define this geometric mean for both discrete and continuous distributions and evaluate the esp for several cases. These results are compared with earlier ones which suggest that the esp is given by the (arithmetic) average or expectation of the single trial probabilities, and we determine under what conditions this simpler result can be used. View full abstract»

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  • On the Passive Resolution of Broadcasting Targets with a Monopulse Antenna

    Publication Year: 1973 , Page(s): 643 - 648
    Cited by:  Papers (1)
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    This paper indicates a basic constraint on angular resolution of targets using monopulse measurements. The specific case at hand is the angular resolution of several broadcasting targets by a passive, standard, four-horn amplitude monopulse system. It is shown that when all broadcasting targets emit spectrally equivalent wide-sense stationary signals and the antenna and target geometry are fixed, the signals presented to the radar signal processor are equivalent to those of a canonical complex of threee broadcasting targets, one at an arbitrary angle ¿¿, one at a null of the sum channel pattern, and one at a null of the difference channel pattern. In the case of broadband flat spectral transmission, two of the three targets in the canonical complex cannot be distinguished from receiver noise. A simple method for determining the angle (or angles) at which a monopulse antenna will attempt to track a broadcasting target complex is presented. Generalizations of this theory to active and/or more complicated monopulse systems are possible. View full abstract»

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  • Angular Accuracy of a Scanning Radar Employing a Two-Pole Filter

    Publication Year: 1973 , Page(s): 649 - 653
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1160 KB)  

    A two-pole filter is proposed as a detector for a scanning radar. The optimum values of the filter coefficients are found and are approximated by a simple expression. The optimum two-pole filter requires a 0.15-dB increase in signal-to-noise ratio in order to provide the same detection capability as the optimum detector, and yields azimuth estimates whose standard deviation are within 15 percent of the Cramér-Rao lower bound. The estimator is simple to implement, avoiding the storage requirements of the moving window detector and the bias complications of the feedback integrator. View full abstract»

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  • Further Results on Multipath Angle Error Reduction Using Multiple-Target Methods

    Publication Year: 1973 , Page(s): 654 - 659
    Cited by:  Papers (2)
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    The two-target technique proposed by the author in an earlier paper [1] for reducing radar multipath angle tracking errors has been simulated on a digital computer assuming an actual closed-loop system. When tracking with noise, the technique provides angle error performance which compares quite favorably with the expected performance given in [1] Furthermore, the large bias errors usually encountered in normal monopulse systems at low elevation angles are removed. Results of typical tracks are given, both for the method of [1], and for a modified version of the method which applies primarily to shipboard radar systems. Some results on loss of lock are also presented. View full abstract»

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  • A UHF True Logarithmic IF Amplifier

    Publication Year: 1973 , Page(s): 660 - 664
    Cited by:  Papers (3)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2573 KB)  

    A UHF ¿true logarithmic IF¿ which yields a carrier output proportional in amplitude to the logarithm of the carrier input has been constructed. Although this ¿true¿ form has been known for a number of years, it appears to have been neglected in development. Good performance has been obtained over a 60-dB input signal range with rise and fall times of 2 ns per 20 dB. A high-level, detected dc coupled output without the use of any dc amplifier is obtained. Coherent signal processing of the output carrier is possible, and other important advantages to this type of logarithmic IF are described. View full abstract»

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  • Average Correlation Functions in On-Line Testing of Linear Systems

    Publication Year: 1973 , Page(s): 665 - 669
    Cited by:  Papers (1)
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    This paper is a report on new methods for on-line testing of single-input/single-output linear and time-invariant systems. No interruption of system operation is necessary, since the signals used in this test procedure are the normal operating signals. Test results indicate that detectable system errors using finite amounts of data are well within tolerance for normal operation in all but the most stringent applications. View full abstract»

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  • Stabilized Linear FM Generator

    Publication Year: 1973 , Page(s): 670 - 678
    Cited by:  Papers (8)  |  Patents (3)
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    A technique for generating high-linearity chirp (linear FM) signals is presented. It uses a delay line and mixer to sense the slope of the output of a swept oscillator, and the difference from desired slope is fed back to correct the oscillator frequency. The technique also improves the coherence of the oscillator. An analysis is performed of the amount of linearization that can be achieved for three possible loop configurations. Experimental results are presented of tests run on a backward wave oscillator (BWO) operating over a bandwidth of 240 MHz with time duration of 120 ¿s. The results indicate a linearity corresponding to a phase error (from parabolic) of 30 degrees (peak) and coherence within 5 degrees. View full abstract»

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  • Design of Optimal Radar Signals Subject to a Fixed Amplitude Constraint

    Publication Year: 1973 , Page(s): 679 - 687
    Cited by:  Papers (2)
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    The problem of designing finite-pulse-train radar signals and receivers to maximize the detectability of targets masked by thermal noise and clutter returns is considered in this paper. A practical constraint is introduced: the amplitude of each subpulse in the transmit waveform is taken to be fixed. The need for such a constraint is dictated in most radar applications, because the transmitter is most efficiently utilized by saturating its amplifying tube. An algorithm for generating optimal waveforms subject to this new constraint is presented, and the performance of the resulting waveforms is compared with those obtained using existing optimization techniques. View full abstract»

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  • Active Nutation Damping Utilizing Spacecraft Mass Properties

    Publication Year: 1973 , Page(s): 688 - 693
    Cited by:  Papers (2)
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    Active nutation damping generally requires a unique element to provide the necessary damping torques, plus a nutation-sensing system to properly monitor and control the active element by closed-loop action. This paper describes and analyzes, by computer- assisted mathematical techniques, a nutation damper for a dual-spin spacecraft which does not require an active ¿element¿. Damping is achieved through the inherent cross-axis torques generated by the spacecraft products of inertia and the existing motor controlling the relative spin rates of the two dynamic components comprising the spacecraft. View full abstract»

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  • Simplified Optimum Modulation Indices

    Publication Year: 1973 , Page(s): 694 - 700
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    The design of a narrowband, phase-modulated, multisubcarrier, phase-coherent, space-communication system requires that the subcarrier modulation indices be kept within close tolerance limits. This need arises since the modulation indices directly affect the division of power among the carrier and subcarriers. If the system is not designed in an optimum manner to handle large tolerance variation, the system performance may degrade sharply in an adverse environment. A universal graphical technique¿modulation loss contours¿is developed as a design tool for the ¿optimum¿ selection of modulation indices. The technique is novel in that it yields solutions directly from the universal curves and does not require the drawing of additional curves. Two criteria of optimization are considered, simultaneous thresholding and minimal sensitivity. The minimally sensitive case is considered as weighted simultaneous thresholding and is solved by the aid of a graphical algorithm. The technique is applicable to k subcarriers (sinusoidal and/or square wave), considering three subcarriers at a time-two subcarriers as direct variables and the third as a parameter¿all other subcarriers remaining constant. Previous techniques required trial and error methods, drawing of curves, or computerized search techniques to arrive at the proper modulation indices and maximum tolerance bands. This method allows a quick solution to the tolerance problem and optimum selection of modulation indices, facilitating the design and/or analysis of narrowband PM systems. View full abstract»

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  • Optimum Signal and Filter Design in Underwater Acoustic Echo Ranging Systems

    Publication Year: 1973 , Page(s): 701 - 713
    Cited by:  Papers (2)  |  Patents (1)
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    Optimization of the filter, the signal, and the signal and filter jointly are studied in the sonar environment under noise and reverberation limited conditions. The maximization of the receiver output signal-to-interference ratio is used as a performance criterion with unit energy constraint on both signal and filter. In the filter design problem, the optimum filter function is the solution of a linear integral equation. The kernel of the integral equation is a function of the target and medium scattering functions and the reverberation distribution. In the signal design problem, a similar type of integral equation is obtained as in the filter optimization problem. In the joint signal and filter design problem, it is shown that the optimum signal and filter functions are the solutions to a pair of linear integral equations with the largest (SIR)O. Several examples are investigated for different mediums and reverberation distributions with the finite matrix approximation method. An interative technique is used to compute the joint optimization of signal and filter. View full abstract»

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  • Elimination of Blind Velocities of MTI Radar by Modulating the Interpulse Period

    Publication Year: 1973 , Page(s): 714 - 724
    Cited by:  Papers (11)
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    The performance of a coherent MTI is determined by two sets of parameters: the interpulse periods and the weighting coefficients. The latter are expressed in terms of the former so as to maximize clutter attenuation. Interpulse periods are optimized so as to remove blind velocities. The many local optima of the interpulse periods have improvement factors that show differences of up to 6 dB for a 5-pulse canceler. A computer program has been developed that combines random search and the gradient method to produce points that combine a high value of the improvement factor with good blind speeds performance. View full abstract»

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  • Analysis of a Long-Distance System Measuring the Concentration of Atmospheric Gaseous Pollutants

    Publication Year: 1973 , Page(s): 725 - 731
    Cited by:  Papers (1)
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    A detailed inaccuracy and sensitivity analysis of a long-distance air pollution detection system, using a laser measuring the resonance absorption of polluting molecules, is introduced. The noise and the dynamic range of the radiation detectors used, the atmospheric inhomogeneities, and the atmospheric propagation losses of the electromagnetic radiation are considered. In addition, the best measuring path length as a function of a molecule density and atmospheric transparency and irregularity is discussed. View full abstract»

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  • Synthetic Aperture Radar System Design for Random Field Classification

    Publication Year: 1973 , Page(s): 732 - 740
    Cited by:  Papers (3)
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    The optimum design of synthetic aperture radar (SAR) systems intended to classify randomly reflecting areas, such as agricultural fields, characterized by a reflectivity density spectral density is studied. Assuming areas of known shape and location, the binary case, and a certain Gaussian signal field property, and ignoring interfield interference, the problem solution is given. The optimum processor includes conventional matched filter processing, but is nonlinear; a coherent optical system realization is outlined. The performance is approximated using a x2 assumption and bounded by the Cernov bound. A fundamental design problem involves the system bandwidth analogously, in a special case, as in diversity communication systems; a solution is given based on the Cernov bound. A set of summary design curves is given and exemplified by a satellite SAR system design. Also discussed is the measurement of reflectivity spectral density amplitude with imaging sidelooking (synthetic or ¿brute-force¿) radars and the maximum likelihood estimator's accuracy and realization with a coherent optical system. It is also shown that a CW modulation is useable if the random reflectivity is, effectively, isotropic. Finally, the reflectivity density spectral density amplitude, when constant over the spatial bandpass of the measuring system, is related to the scattering cross-section density commonly measured. View full abstract»

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  • Effects of Geodetic Uncertainties on a Damped Inertial Navigation System

    Publication Year: 1973 , Page(s): 741 - 752
    Cited by:  Papers (6)
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    Gravity uncertainties are an inexorable source of error in all inertial navigation systems and are particularly important in high-quality inertial navigation systems. In this paper the steady-state rms errors that are excited in a damped inertial navigation system are analytically determined for four gravity uncertainty models and two vehicle maneuver models. The statistical approach used in this paper is compared with an alternate scheme (¿direct simulation¿) that does not require statistical models for gravity uncertainties. View full abstract»

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  • Distortion Generated in Angle-Modulation Systems by Phased Arrays

    Publication Year: 1973 , Page(s): 753 - 757
    Cited by:  Papers (8)
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    The case of linear, uniformly weighted phased arrays is examined via time and frequency domain analyses. Bounds that must be placed on array length, modulation frequency, modulation index ß, and scan angle relationships if excessive distortion is to be avoided in wideband angle-modulated communication systems are established. Distortion is shown to consist of odd harmonic terms. It is also shown that, for one class of equivalent RF signals, phased arrays produce approximately three times as much distortion in frequency-modulation (FM) systems as in phase-modulation (PM) systems. Graphs of distortion plotted as functions of signal and array parameters show that, for practical array sizes, distortion is a monotonically increasing function of the product of L and sin ¿ where L is the length of the array expressed in modulation wavelengths ¿m and ¿ is the scan angle. In PM systems, distortion also increases monotonically with the modulation index ß. Plots of distortion versus L sin ¿ show that even relatively small arrays can produce intolerable distortion levels in wideband systems; e.g., an FM system having ß = 3,L = 0.35¿m, and ¿ = 60 degrees exhibits approximately 20 percent distortion. View full abstract»

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  • Effects of Navigation Errors in Maneuvering SAR

    Publication Year: 1973 , Page(s): 758 - 776
    Cited by:  Papers (11)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (3306 KB)  

    A maneuvering synthetic aperture radar in squint mode, during a loosely piloted maneuver, is simulated with presence of various navigation system errors. The error sources investigated place emphasis on short-term effects, involving platform servo transients, noise and quantization in accelerometers, interaction of angle pickoff uncertainty with the displacement from platform to radar antenna, and uncertainty in this displacement itself. Simulation results are accompained by interpretive discussion, and followed by suggested areas for further study. View full abstract»

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  • Comment on "Atomic Power: Fallacies and Facts"

    Publication Year: 1973 , Page(s): 777 - 778
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  • Choice of Burst Number for Blind-Speed Avoidance

    Publication Year: 1973 , Page(s): 778 - 781
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (877 KB)  

    A common problem in radar system design is the choice of multiple PRF's to eliminate the blind speeds associated with coherent pulse bursts with uniform pulse spacing. This correspondence describes the procedure of selecting a set of PRF's in such a manner that the unambiguous Doppler achievable with the entire set is maximized. Based on this optimization of the set of PRF's, we determine how many PRF's the set should contain in order to minimize the required beam dwell time for a specified unambiguous Doppler. View full abstract»

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  • Closed-Form Expressions for Noncoherent Radar Integration Gain and Collapsing Loss

    Publication Year: 1973 , Page(s): 781 - 783
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (556 KB)  

    Closed-form formulas allow rapid determination of noncoherent integration gain and integration loss when the single-sample IF signal-to-noise ratio (SNR) is known. In addition, if the required SNR is known for any number of integrated pulses, the required SNR for any other number is easily determined. A closed-form expression is given for radar collapsing loss, expressed in terms of the equivalent integrated signal-to-noise ratio required to produce a given combination of false-alarm and detection probabilities. Alternatively, the single-sample signal-to-noise ratio of a set of samples may be used together with the closed-form expression for integration gain to get the equivalent integrated signal-to-noise ratio. View full abstract»

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  • Steady-State Noise Reduction Factors for the Exponential Filter

    Publication Year: 1973 , Page(s): 783 - 785
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    A technique is presented using state notation for deriving the steady-state noise reduction factors for an exponential filter. The technique is carried through to derive those factors for the third-order exponential filter. 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