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Aerospace and Electronic Systems, IEEE Transactions on

Issue 6 • Date Nov. 1986

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Displaying Results 1 - 25 of 26
  • 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): 669
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  • A Suboptimum Rank Test for Nonparametric Radar Detection

    Page(s): 670 - 680
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    The optimum rank detector structure, in the Neyman-Pearson sense and under Gaussian noise conditions, is approximated by a suboptimum structure that depends on an adjustable parameter. This new rank detector, which operates on radar video signal, includes other well-known detectors as particular cases. The asymptotic relative efficiency (ARE) of the proposed rank detector is computed, with its maximum value the ARE of the locally optimum rank detector (LORD). The detection probability versus signal-to-noise ratio, and the effects of interfering targets are also calculated by Monte-Carlo simulations for different parameter values. View full abstract»

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  • Frequency Tracking Characteristics of Split-Loop Phase-Locked Receivers

    Page(s): 681 - 687
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    The excess time delay introduced by the incorporation of the intermediate frequency (IF) stage within the phase-locked loop (PLL) causes serious deterioration in the acquisition and tracking performance of the loop. The split-loop phase-locked system suggested by McGeehan and Sladen considerably reduces the effect of time delay on the acquisition and tracking performance of the loop. The frequency acquisition characteristics of the split-loop phase-locked receiver is investigated, and the effect of possible asymmetry in the arms of the loop on the acquisition range is examined. Closed-form approximate formulas are derived, and a comparison between split-, long-, and short-loop acquisition performance is presented. View full abstract»

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  • Effect of Initial Values of Adaptive Arrays

    Page(s): 688 - 694
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    The effect of initial weight values on the transient characteristics is investigated on three kinds of adaptive arrays under different principles, i.e., the directionally constrained minimization of power (DCMP), the least mean square (LMS), and the maximum signal-tonoise ratio (MSN). Analysis and computer simulation demonstrate how the convergence rate is affected by the initial setting. The best choice of the initial value is given. View full abstract»

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  • Staggered Costas Signals

    Page(s): 695 - 702
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    A radar signal, based on coherent processing of a train of staggered Costas bursts, is suggested and investigated. The selection of sequences of each burst is based on a minimum number of collocation of their individual ambiguity function sidelobe peaks. The resulting ambiguity function combines qualities of both "thumbtack" and "bed of nails" signals. Comparison with linear-FM, V-FM, and complementary phase coded (CPC) signals is given, as well as comparison with hybrid signals consisting of both phase and frequency coding. View full abstract»

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  • A Modified Karhunen-Loeve Model of Gravity Disturbance Vector

    Page(s): 703 - 707
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    A modified anisotropic Karhunen-Loeve (KL) model for the gravity disturbing potential is proposed. This model, unlike the previous KL model of Bose, does not vanish on the boundaries of a local region. Laplace's equation for the gravity disturbing potential and flatearth Vening-Meinesz relationships of the gravity disturbance vectorcomponents (¿,¿,¿g) when the model is isotropic, are exploited to determine the unknown parameters of the model. The resulting model, in addition to having random boundary values, has three more parameters than those found in Bose's KL model. This should provide extra flexibility in fitting the model to the noisy data available in a local finite region. View full abstract»

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  • Fast Maximnurm Likelihood Joint Estimation of Frequency and Frequency Rate

    Page(s): 708 - 715
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    A fast maximum likelihood algorithm is presented that jointly estimates the frequency and frequency rate of a sinusoid corrupted by additive Gaussian white noise. It consists of a coarse search and a fine search. First the two-dimensional frequency-frequency rate plane is subdivided into parallelograms whose size depends on the region of convergence of Newton's method used in maximizing the log-likelihood function (LLF). The size of the parallelogram is explicitly computed and is optimal for the method used. The coarse search consists of maximizing the LLF over the vertices of the parallelograms. Then starting at the vertex where the LLF attained its maximum, a two-dimensional Newton's method to find the absolute maximum of the LLF is implemented. This last step consists of the fine search. The rate of convergence of Newton's method is cubic, and is extremely fast. Furthermore Newton's method will converge after two iterations when the starting point used in the method lies within 75 percent of the distances defined by the parallelogram of convergence whose center coincides with the true values of frequency and frequency rate. In this case, the root mean square error (RMSEs) for frequency and frequency rate are practically equal to the Cramer-Rao bound at all signal-to-noise ratio (SNR)¿15 dB. The frequency-frequency rate ambiguity function is shown to be even and its periodicities are extracted. View full abstract»

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  • Two-State Feedback Loop Adaptive Arrays for Pulsed Interference Signals

    Page(s): 716 - 724
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    A two-state feedback loop is presented which increases the effectiveness of an adaptive array in the presence of pulsed interference signals. In the case of the two-state feedback loop, one state permits the maximum adpative response, consistent with the loop stability, and is activated in the presence of an interfering pulse. During the other state, which is activated when the interfering pulse is off, the weights are frozen at the values reached at the end of the last interfering pulse and are maintained until the next disturbance occurs. It is shown that an adaptive array with the proposed two-state loops steers permanent minima in the direction of the interfering signals, irrespective of their duty cycle. The performance of a communication system protected by such an adaptive array improves significantly over one protected by a conventional adaptive array. View full abstract»

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  • Design of Switching Regulator with Combined FM and On-Off Control

    Page(s): 725 - 731
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    The design and implementation of a switching regulator incorporating a high-frequency series-resonant converter and a combined FM and on-off feedback control is presented. The combined FM and on-off control results in a better conversion efficiency and a wider range of operational input voltage and output current. A 22.5 V, 50 W experimental regulator has been built to demonstrate the practicality of the circuit and its high efficiency, typically 92 to 96 percent, depending on the input and loading conditions. View full abstract»

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  • Adaptive Estimation for a System with Unknown Measu rement Bias

    Page(s): 732 - 739
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    An adaptive state estimator for passive underwater tracking of maneuvering targets is developed. The state estimator is designed specifically for a system containing unknown or randomly switching biased measurements. In modeling the stochastic system, it is assumed that the bias sequence dynamics can be modeled by a semi-Markov process. By incorporating the semi-Markovian concept into a Bayesian estimation technique, an estimator consisting of a bank of parallel, adaptively weighted, Kalman filters has been developed. Despite the large and randomly varying measurement biases, the proposed estimator, provides an accurate estimate of the system states. View full abstract»

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  • Normalized LMS Algorithm Degradation Due to Estimation Noise

    Page(s): 740 - 750
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    The steady-state weight vector derived by either the least mean square (LMS) or normalized least mean square (NLMS) algorithms has random deviations from the optimum values. These deviations increase the steady-state residue power. A previous paper derived the LMS weight noise effects for a multiple sidelobe canceller (MSLC) application. This paper describes the NLMS weight noise effects. It is shown that for a thermal noise environment, the weight noise effect for the LMS algorithm is insignificant but is quite significant for the NLMS algorithm. Calculations for example noise plus interference environments imply that the NLMS weight noise effects are always larger than that for LMS. View full abstract»

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  • Composite Bound on Arrival Time Estimation Errors

    Page(s): 751 - 756
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    Time of arrival (TOA) estimation of narrowband signals is a problem of considerable practical interest in radar and sonar applications. A new technique is presented to analyze the mean square error (MSE) performance of TOA estimation schemes, based on recently developed lower bound. We obtain a complete characterization of the MSE as a function of the signal and noise parameters. The results are given in a simple closed-form analytical expression. View full abstract»

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  • Analysis and Design of Series Resonant Converter by State-Plane Diagram

    Page(s): 757 - 763
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    Analysis based on the state-plane diagram is given for series resonant converters operating in the frequency range 0.5 ¿ fs/fo ¿ 1.0. When the voltages and currents in the converter are normalized, design parameters take on special geometric meanings in the normalized state diagram. Examples of converter design using graphical methods are given for the cases of ¿ and ¿ control. Control characteristics of the converter operating in the continuous conduction mode are derived. The concept of the energy reflection coefficient is introduced as a measure of power transfer efficiency in the converter design. View full abstract»

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  • Precision Synchronization of Satellites in Inclined Orbits

    Page(s): 764 - 780
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    Synchronization between an Earth station and a satellite in geostationary orbit can be accomplished by repeatedly transmitting sync burst signals and making small timing corrections. However, when a satellite is in an inclined nonsynchronous orbit, such as a navigation satellite, the problem is more complex due to the high relative velocity of the navigation satellite relative to the ground. One possible solution to the problem is examined by employing a satellite in geostationary orbit to communicate with the navigation satellite. It is shown that the uplink delay to the navigation satellite can be deduced to an accuracy of about 1 ns by making a single round trip transmission. View full abstract»

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  • A Selected Bibliography on Adaptive Antenna Arrays

    Page(s): 781 - 798
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    An adaptive antenna array is defined as an antenna array whose output is the weighted sum of the signals received at the antennas, with signal-dependent automatic adjustment of the weights to optimize some criterion. This open-literature bibliography of papers on the subject is intended to provide a brief overview of the field, and the authors involved, up to the end of 1985. Papers are listed both by subject area and by sole/primary/secondary author. View full abstract»

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  • Limitations on SAR Image Area Due to Motion through Resolution Cells

    Page(s): 799 - 803
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    Range-Doppler imaging systems are degraded by the motion of an object through its resolution cells during image formation. Given the range resolution dR, the cross-range (azimuth) resolution dA, and the wavelength ¿, the image's range extent DR and cross-range extent DA must be constrained by ¿DR ¿ 4d2A; ¿DA ¿ 4dAdR to avoid significant image degradation. By implication, we can image a rectangular area A ¿ DADR. We show that, in general, the acceptable image area is a parallelogram which becomes a rectangle only in the special case of unsquinted, broadside operation. Furthermore, the actual useful image area within a rectangular map of range extent DR and crossrange extent DA decreases as the squint angle measured from broadside increases. View full abstract»

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  • The Effect of the Common Process Noise on the Two-Sensor Fused-Track Covariance

    Page(s): 803 - 805
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    This note deals with the effect of the common process noise on the fusion (combination) of the state estimates of a target based on measurements obtained by two different sensors. This problem arises in a multisensor environment where each sensor has its information processing (tracking) subsystem. In the case of an ¿-ß tracking filter the effect of the process noise is that, over a wide range of its variance, the uncertainty area corresponding to the fused estimates is about 70 percent of the single-sensor uncertainty area as opposed to 50 percent obtained if the dependence is ignored. View full abstract»

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  • Information for authors

    Page(s): 806
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  • Author index

    Page(s): 807 - 809
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  • Subject index

    Page(s): 809 - 815
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  • Annual Combined Index to IEEE Publications [advertisement]

    Page(s): 816
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  • IEEE copyright form

    Page(s): 817 - 818
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  • IEEE Aerospace and Electronic Systems Society Organization

    Page(s): 818-a
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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