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Aerospace and Electronic Systems, IEEE Transactions on

Issue 5 • Date Sept. 1981

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Displaying Results 1 - 25 of 33
  • Table of contents

    Publication Year: 1981 , Page(s): c1
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  • IEEE Aerospace and Electronic Systems Society

    Publication Year: 1981 , Page(s): c2 - 736-152
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  • From the Editor

    Publication Year: 1981 , Page(s): 609
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  • State-Space Models of Gravity Disturbance Gradients

    Publication Year: 1981 , Page(s): 610 - 619
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2169 KB)  

    State-space models of gravity disturbance gradients are needed to design the Kalman filters used for gradiometer-aided inertial navigation. However, the physics of the gravity field guarantee that many of the cross-spectral densities of gravity disturbance gradients are nonrational. A procedure is demonstrated for fitting gravity disturbance correlation functions with finite-dimensional state-space models. View full abstract»

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  • Detection of Coherent Light after Nonlinear Amplification

    Publication Year: 1981 , Page(s): 620 - 625
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    Numerical results on the performance of quantum amplifiers in an optical communication system show that because of the spontaneous emission, the probability of error is not improved by the introduction of such devices. It is also concluded that nonlinearity, which is known to reduce the relative fluctuations, will not help to enhance the probability of detection. View full abstract»

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  • Performance Degradation in Digitally Implemented Kalman Filters

    Publication Year: 1981 , Page(s): 626 - 634
    Cited by:  Papers (7)
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    A technique is presented for analyzing expected degradations in the performance of a fixed-point arithmetic implementation of a Kalman filter with precomputed gains. A quantitative approach is provided for comparing the relative degradations associated with different mechanizations of the same Kalman filter. The causes of divergence in digitally implemented filters are investigated. Finally, simulation studies are utilized to show how closely the analytical predictions agree with actual results. View full abstract»

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  • The Resolution Performance of Range Estimators

    Publication Year: 1981 , Page(s): 635 - 644
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    The theoretical basis and methods of implementation of a moment algorithm for the range separation estimation of two closely spaced point targets are presented. Moment estimation and noise filtering techniques introduced here result in a considerable improvement over Baum's algorithm. The error bounds are established and it is shown that the spectral moment estimator exhibits optimum (zero bias, minimum variance) performance when the target separation normalized to the standard deviation of the Gaussian pulse is 2¿1.5. Monte Carlo simulation is performed to verify the approximations made and to demonstrate the feasibility of the working models. View full abstract»

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  • Extrapolation Technique for Long Term Bit Error Rate Determination

    Publication Year: 1981 , Page(s): 645 - 650
    Cited by:  Papers (1)
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    An extrapolation method is presented for determination of characteristic curves of long term bit error rate (BER) versus signal-to-noise ratio (SNR) for digital communication equipment. The method is to obtain a single reliable data point at a BER of 10-4 or 10-5 and then to draw a theoretically shaped curve through this reference. The technique is validated by both theoretically and experimentally demonstrating that variations of the internal anomalies that contribute to bit errors in digital communications receivers cause the BER curves to shift laterally, but that the curves retain their characteristic shape. Use of this extrapolation method can reduce test time by 3 to 4 orders of magnitude. View full abstract»

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  • Minus 35kV Space-Borne Instrument Power Supply

    Publication Year: 1981 , Page(s): 651 - 655
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    A -35kV power supply has been developed for a plasma experiment on the out-of-ecliptic mission. In addition, an isolation transformer has been developed to provide low voltage power at the -35kV potential. The design features incorporated to produce a spaceflight power supply housed within a 4 × 4 × 2.5 in package are discussed. The supply is powered from an unregulated spacecraft bus and provides a regulated output of -35kV ± 5 percent with less than 0.5 percent ripple over a temperature range -20°C + 60°C. The unit serves as a bias supply with an output current less than 0.5 , ¿A. With the supply essentially operating unloaded, 5 percent regulation is achieved by sensing and regulating the first stage of a 12-stage Cockcroft/Walton multiplier. Control of the ac voltage input to the multiplier stack provides the regulation. The isolation transformer utilizes a ferrite u-core with the primary and secondary windings placed on opposite legs for separation. The transformer is encapsulated with the power supply. View full abstract»

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  • Optimum Frequencies for Aircraft Classification

    Publication Year: 1981 , Page(s): 656 - 665
    Cited by:  Papers (11)
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    The selection of the optimum features for aircraft classification from radar returns was studied. A constraint was imposed that a minimum number of simultaneous frequencies be used. The results indicate that a high reliability of classification is achievable with only two frequencies, and even a single frequency can provide over 95 percent reliability if both phase and amplitude at two orthogonal polarizations are used. The data set tested involved eight military aircraft whose sizes varied over a three-to-one range. View full abstract»

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  • Adaptive False Alarmrm Regulation in Double Threshold Radar Detection

    Publication Year: 1981 , Page(s): 666 - 675
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    In practical situations the false alarm probability in double threshold radar detection, sometimes known as binary integration with sliding window detection, is dependent on the nonstationarity and azimuthal correlation of the clutter which is present. Control of the false alarm probability can be achieved, to a certain extent, by the adjustment of the second threshold in the detection process. In this study two adaptive control techniques which are based on the statistical characteristics of the data are compared. Comparing the results for a technique based on first-order statistics with one based on second-order statistics, it is shown that the second-order, or correlation sensitive, technique can give a reduction of 30 to 45 percent in the false alarm probability with no corresponding loss in the detection probability. An interesting aspect of the results is the fact that the effects of the size of the sample area and the bias in the correlation estimator are clearly evident. View full abstract»

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  • Optimal Target t Designation Techniques

    Publication Year: 1981 , Page(s): 676 - 684
    Cited by:  Papers (2)
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    Studies of signal processing techniques are presented for achieving optimal autonomous acquisition of stationary targets located in a moderately intense nonhomogeneous radar ground clutter background. The process of target acquisition comprises three basic functions: 1) target detection, 2) target selection or designation, and 3) reacquiring the target for tracking. It is the second of these functions, i.e., autonomous designation of a target, that is the subject of this discussion. Theoretical analyses and predictions of the probability of correct target designation for two acquisition search methods are presented and compared with results achieved using real radar imagery. View full abstract»

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  • Canceler Performance Degradation Due to Estimation Noise

    Publication Year: 1981 , Page(s): 685 - 692
    Cited by:  Papers (8)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1534 KB)  

    The multiple sidelobe canceler (MSLC) configured using the gradient descent algorithm converges to an approximation to the optimum weight vector. Since the weight vector estimate is obtained from a finite data set, there is a random error that increases the steady state residue power. An exact analysis of the steady state residue power for a digital implementation is performed. The analysis predicts that as the algorithm's gain (step size) is increased, the steady state residue power tends towards infinity. The gain that causes infinite power is smaller than the gain that causes instability for the average weight vector analysis. It is shown that the steady state residue power is equal to the minimum residue power multiplied by a factor that depends upon ratios of the eigenvalues. The steady state residue power is evaluated for some special cases. It is shown that the value of the factor is greatest when the interference is due to a single jammer. View full abstract»

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  • Susceptibility of DS/FH,M, Binary DPSK to Partial and Full Band Barrage Jamming

    Publication Year: 1981 , Page(s): 693 - 700
    Cited by:  Papers (1)
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    Spread spectrum signaling schemes have been proposed to counter unfriendly, electrical jamming threats. In order to establish their effectiveness, such schemes must be analyzed. This work takes a step in this direction by developing the susceptibility equation, or equivalently, the probability of error, of a direct sequence/frequency hopped (DS/FH), binary differential phase-shift keying (DPSK) system when subjected to a barrage jamming signal. Specific system models are established for the receiving system as well as for the jamming signal and the spread spectrum techniques. Both partial and full band jamming strategies are considered. Graphical results are presented with the conclusions summarizing the spread spectrum effectiveness and the deficiencies of the FH processing gain definition. View full abstract»

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  • Radar Performance Review in Clear and Jamming Environments

    Publication Year: 1981 , Page(s): 701 - 710
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    The performance of electronically scanned radar systems is evaluated for clear and barrage jamming environments. Radar figures of merit in jamming are derived for search and track modes and are directly related to antenna pattern relative sidelobe levels. A random sidelobe model is analyzed with various numbers of independent jammers. Probability distributions of detection probability are derived to determine detection performance versus average jamming level and number of jammers. View full abstract»

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  • Approximation of Corrected Slant Range in a Radar Surveillance System

    Publication Year: 1981 , Page(s): 711 - 717
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    Consideration is given to numerical procedures for evaluating the corrected slant range in a radar surveillance system. Applications include air traffic control operations in which such calculations must be performed repeatedly in real time for a multitude of targets without overtaxing available computational resources. View full abstract»

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  • Information for authors

    Publication Year: 1981 , Page(s): 718
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    Freely Available from IEEE
  • Error Probability for Fading CPSK Signals in Gaussian and Impulsive Atmospheric Noise Environments

    Publication Year: 1981 , Page(s): 719 - 722
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (570 KB)  

    Recently the performance of digital communication systems in the presence of impulsive atmospheric noise has been evaluated assuming a noise model which is in excellent agreement with experimental results. We evaluate the bit error probability for coherent phase-shift keying (CPSK) signaling assuming the same atmospheric noise model but considering a more reasonable representation of the communication channel which accounts for the simultaneous presence of Gaussian (always present) atmospheric noise and signal fading. View full abstract»

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  • Signal-to-Noise Ratio Calculations in Pulse and Pulse Doppler Radars

    Publication Year: 1981 , Page(s): 722 - 724
    Cited by:  Papers (1)
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    In low pulse-repetition frequency (PRF) pulse radars, signal-to-noise ratio (SNR) is usually calculated on a per pulse basis and this value is then multiplied by the number of pulses integrated to obtain the SNR for a given duration of target illumination. In high PRF pulse Doppler radars, SNR is usually calculated by using the centerline power of the transmitted signal spectrum as the target return power because the centerline is kept in the receiver and returns of the PRF lines are notched out [1]. We show here that both methods of SNR calculations are entirely equivalent for matched transmit-receive radar systems. View full abstract»

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  • An Interleaved-Trace Time-Compression Radar Display

    Publication Year: 1981 , Page(s): 724 - 726
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    Detection information from conventional surveillance radars is frequently presented in the form of a display known as the plan position indicator map. In this display, new data are displayed while data from previous scans fade from the display. Target blips typically persist for several scans, making possible operator integration or correlation. However, the noise from previous scans often masks signals from small moving targets. To avoid the loss in signal-to-noise ratio caused by the addition of noise to signal plus noise, a digital signal processing display unit has been designed and is presented here. View full abstract»

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  • Comments on "The Effect of Differential Time Delays in the LMS Feedback Loop"

    Publication Year: 1981 , Page(s): 726
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  • Corrections to: "MTI Improvement Factors for Weighted DFTs"

    Publication Year: 1981 , Page(s): 726
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  • Correction to: "A New Class of Polyphase Pulse Compression Codes and Techniques"

    Publication Year: 1981 , Page(s): 726
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  • Probability of Detecting a Swerling I Targetet on Two Correlated Observations

    Publication Year: 1981 , Page(s): 727 - 730
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (579 KB)  

    Modern radars characterized by electronically steered beams, frequency agility, and range-ambiguous waveforms can use a processing technique whereby each new detection is followed by a second dwell to verify the initial detection. The second dwell is used to minimize false alarms and to resolve range and/or Doppler ambiguities. Under the assumption of a Swerling I target model, the target cross section remains constant when both dwells occur on the same scan and the same transmission frequency is used. Analytic expressions have been developed for the probability of detecting a Swerling I target on both of the correlated dwells (same target cross section). These expressions are used to calculate the probability of a second dwell detection given a first dwell detection and the probability of at least one detection on two dwells. These probabilities are compared with those of independent dwells (independent target cross sections) which result when two transmission frequencies of sufficient separation are utilized. View full abstract»

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  • Mismatched Filtering of Sonar Signals

    Publication Year: 1981 , Page(s): 730 - 734
    Cited by:  Patents (3)
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    A replica correlator (matched filter) is an optimum processor for a receiver employing a pulse of continuous wave (CW) signal in a white Gaussian noise background. In an active sonar, however, when the target of interest has low Doppler shift and is embedded in a high reverberation background, this is not so. High sidelobes of the correlator frequency response pass a significant portion of the signal contained in the mainlobe of the reverberation spectrum. In order to reduce the sidelobes of the correlator output spectrum and at the same time keep the increase in its 3 dB bandwidth to a small amount, we propose lengthening of the replica of the transmitted signal and weighting it by a Kaiser window. It is demonstrated that by extending the weighted replica by 50 percent compared with the transmitted signal, it is possible to reduce the sidelobe levels to at least 40 dB below the mainlobe peak, with the concomitant increase of the 3 dB band-width by less than 5 percent. The degradation in signal-to-noise ratio (SNR) performance for such a ¿mismatched¿ filter receiver with respect to the matched filter is less than 1.5 dB. 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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Editor-in-Chief
Lance Kaplan
Army Research Laboratory