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Aerospace and Electronic Systems, IEEE Transactions on

Issue 5 • Date Sept. 1974

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  • Table of contents

    Publication Year: 1974 , Page(s): c1
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  • IEEE Aerospace and Electronic Systems Society

    Publication Year: 1974 , Page(s): c2 - 752a
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  • From the Editors

    Publication Year: 1974 , Page(s): 561
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  • Satellite Broadcasting of WWV Signals

    Publication Year: 1974 , Page(s): 562 - 573
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (4335 KB)  

    An experiment concerning the broadcasting of time and frequency information from geostationary satellites is discussed. Included are discussions on satellite motion, time delay, Doppler shift, and delay calculations. Ground station requirements, time recovery techniques, and timing resolution and accuracy are also included. Delay computation aids for the user were designed to provide free space delays between the master clock and the user. Measurements made in North and South America demonstrated a timing resolution of about 10 ¿s and an accuracy of 25 ¿s. View full abstract»

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  • Modified Generalized Sign Test Processor for 2-D Radar

    Publication Year: 1974 , Page(s): 574 - 582
    Cited by:  Papers (12)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (3089 KB)  

    The modified generalized sign test processor is a nonparametric, adaptive detector for 2-D search radars. The detector ranks a sample under test with its neighboring samples and integrates (on a pulse-to-pulse basis) the ranks with a two-pole filter. A target is declared when the integrated output exceeds two thresholds. The first threshold is fixed and yields a 10-6 probability of false alarm when the neighboring samples are independent and identically distributed. The second threshold is adaptive and maintains a low false-alarm rate when the integrated neighboring samples are correlated and when there are nonhomogeneities, such as extraneous targets, in the neighboring cells. Using Monte Carlo techniques, probability of false-alarm results, probability of detection curves, and angular accuracy curves have been generated for this detector. The detector was built and PPI photographs are used to indicate the detector's performance when the radar is operated over land clutter. View full abstract»

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  • Acquisition Time of Tracking Loops Operating in the Frequency-Search Mode

    Publication Year: 1974 , Page(s): 583 - 587
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1411 KB)  

    This paper presents a theory for computing the signal acquisition time of a second-order tracing system operating in the frequency-search mode. In particular, a closed-form expression is obtained which relates the acquisition time to the relevant system parameters, to the initial loop detuning, and to the slope of the ramp that sweeps the voltage-controlled oscillator. Although the theory is only approximate and the resulting formula is exact only in the limit when the initial loop detuning ¿F goes to infinity, it has been found that it gives quite accurate results as soon as ¿F is some times greater than the equivalent noise bandwidth of the loop. View full abstract»

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  • Equalization of QPSK Data Transmission in Specular Multipath

    Publication Year: 1974 , Page(s): 588 - 594
    Cited by:  Papers (2)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1561 KB)  

    This paper gives performance results for transversal-filter equalization of quadriphase phase-shift-keyed (QPSK) signals with two-component multipath and demodulator phase error. An analytical expression for optimum, minimum mean-square-error tap weights in terms of the multipath and signal parameters is given. Probability of error results for no equalization and equalization with adaptive decision-feedback tap-weight adjustment are compared. The results show that significant improvement can be obtained with relatively simple equalizer structures. View full abstract»

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  • Aircraft Interrogation Scheduling with ASTRO-DABS

    Publication Year: 1974 , Page(s): 595 - 604
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1689 KB)  

    In the ASTRO-DABS concept for surveillance and data link, aircraft are interrogated by one of three geostationary transmitter satellites, each covering 1/3 of the contiguous United States. Interrogation scheduling involves a roll call such that aircraft responses to receiving satellites do not overlap (garble). A simple approach is developed which utilizes range ordering of aircraft with respect to transmitter satellites, but is independent of receiver satellite locations and aircraft distribution. Bounds on roll-call duration are established, showing that interrogation of 80 000 aircraft requires between 4.0 and 6.4 seconds with the ASTRO-DABS transmission format. If aircraft distribution is regionally concentrated (i.e., clustered), the roll-call duration nears the lower bound, since fewer gaps between interrogations are needed to preclude garbling. View full abstract»

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  • Insight into an Integration Algorithm

    Publication Year: 1974 , Page(s): 605 - 608
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    This paper develops, in a unique manner, a numeric algorithm for an integration and extrapolation scheme. The purpose of presenting it in this manner is to develop in the reader a complete understanding of how the algorithm is derived. It is also intended to give an insight into the limitations of the algorithm and to serve as a tool to derive additional integration schemes. View full abstract»

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  • Hard-Limiter Output Autocorrelation Function: Gaussian & Sinusoidal Input

    Publication Year: 1974 , Page(s): 609 - 614
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    An expression is derived for the autocorrelation function of the output of a hard limiter whose input is stationary Gaussian noise with zero mean plus independent random-phase sinusoidal signal. The output spectrum may then be evaluated. This spectrum is extremely useful in understanding the properties of a filter-limit-filter-detect signal processor whose signal input is an actual sinusoid, or when a sinusoid is used as a test signal. View full abstract»

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  • Statistics of Focused and Defocused Radar Maps

    Publication Year: 1974 , Page(s): 615 - 621
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    Coherent high-resolution synthetic-aperture radar systems achieve their range resolution by pulse compression and azimuth resolution by compression of naturally generated FM coding due to Doppler shifts as the aircraft flies by the target. If the data is left unprocessed, it is, in effect, a defocused map of the terrain. As such, it should exhibit less dynamic range than if the data is compressed. This paper describes an experimental study to verify the above conjecture. The results of this study indicate that if dynamic range of the data link is a problem, the radar data should be transmitted in its unprocessed form. This might very well be the case for planetary mapping by means of satellites. View full abstract»

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  • On the Optimization of MTI Clutter Rejection

    Publication Year: 1974 , Page(s): 622 - 629
    Cited by:  Papers (30)
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    In this paper is formulated the problem of optimization of the improvement factor of a nonrecursive MTI by minimization of a quadratic form. The minimum normalized clutter output (a reciprocal of the average improvement factor) is the minimum eigenvalue of this quadratic form, and the corresponding eigenvector is the optimal weight to be used in this filter. By use of classic matrix theory, some properties of this MTI improvement factor are shown, namely, that it is bounded and is a monotonic function of the clutter spectrum variance. Also discussed is the limit of an MTI system having a large number of cancellers. Finally, the problem of a staggered-PRF MTI filter is examined, for which it is shown that its improvement factor is bounded by two equivalent constant-PRF MTI systems. One of these systems has a PRF equal to the lowest PRF of the staggered-PRF system, while the other has a PRF equal to the highest PRF of the staggered system. View full abstract»

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  • Sampled-Data Control System Analysis Using the Poisson Summation Rule

    Publication Year: 1974 , Page(s): 630 - 635
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    A technique is presented which simplifies the analysis of sampled-data control systems. The use of a finite-term approximation to the Poisson summation rule, in conjunction with digital computer evaluation, is presented as a good alternative to use of the Z transform whenever frequency-domain analysis is required. The Poisson summation rule is reviewed and its application to sampled-data system analysis is discussed. The form of the computer program used in the analysis is presented, along with a design criterion to evaluate the accuracy of the technique. A detailed example of a typical application is presented. View full abstract»

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  • Velocity Computations from Radio-Range Measurements

    Publication Year: 1974 , Page(s): 636 - 642
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    A user-oriented method for generating velocity estimates based on phase measurements of radio navigation transmissions like Omega is presented. Various geometric schemes, together with numerical implementation of the algorithm, are discussed. View full abstract»

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  • Optimum Acquisition of the Idling First-Order Phase-Locked Loop

    Publication Year: 1974 , Page(s): 643 - 647
    Cited by:  Patents (1)
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    Acquisition of the idling first-order phase-locked loop (PLL) is investigated. An analytical solution for the Fokker-Planck equation is found if the noise term is neglected. Furthermore, the modulation signal that optimizes the acquisition is obtained by use of phase-plane techniques and Pontryagin's minimum principle. View full abstract»

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  • Certain Design Aspects of Single-Winding Three-Phase Inductor Alternators

    Publication Year: 1974 , Page(s): 648 - 658
    Cited by:  Papers (2)
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    Based on mathematical analysis, this paper points out that restrictions in stator/rotor slot combinations for optimum output of a conventional inductor alternator are not applicable for one with a single winding for both dc excitation and output. Design considerations for the latter are discussed, and it is demonstrated that its performance is superior to a conventional double-winding inductor alternator in all aspects. Test results on a number of experimental machines fully support the theory. View full abstract»

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  • On Finite-Lag Receivers for Fading Channels

    Publication Year: 1974 , Page(s): 659 - 669
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    This paper reports some results on the development of finite-lag receivers for reception via fading channels. The receivers are given in discrete form and clearly show the additional complexity due to introduction of delay between the instants of reception and estimation of the signal. The channel noise has been assumed to have a multiplicative component due to fading. This results in the optimal demodulators being nonlinear and unrealizable. However, the receivers proposed are suboptimal, but realizable. Simulation studies evaluating the performance of the various receivers are also discussed. View full abstract»

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  • Sensitivity Analysis of Finite-Lag Receivers

    Publication Year: 1974 , Page(s): 670 - 677
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    This paper presents the sensitivity analysis of a class of receivers called finite-lag receivers, introduced by the authors in [1] through [3]. Since these receivers are based on the use of fixed-lag smoothing techniques, algorithms for the calculation of large-scale and small-scale sensitivities of fixed-lag smoothing are derived using a state augmentation approach. Steady-state analysis of these algorithms shows that an explicit relation can be obtained between sensitivity coefficients of fixed-lag smoothing and filtering. The specific case of sensitivity to variations in the measurement (channel) noise is considered as an example. These results are applied to study the sensitivity performance of the finite-lag receivers for analog communication. It is shown, for example, that finite-lag receivers for AM signals, besides being superior in performance [1]-[3], [11], in terms of output SNR or error variance, are also much less sensitive to the additive noise power level, compared to zero-lag receivers. View full abstract»

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  • Quasi-Optimal Demodulation of Pulse-Frequency Modulation Systems

    Publication Year: 1974 , Page(s): 678 - 685
    Cited by:  Papers (2)
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    Novel demodulator structures are derived using a theory for the quasi-optimal on-line demodulation of pulse-frequency modulated (PFM) signals in the presence of white Gaussian channel noise. The basic demodulator consists of a phase-locked loop with time-varying gain elements. Furthermore, its integrators are appropriately reset as each new pulse is received. This modulator may be augmented with additional integrators and gain elements to achieve quasi-optimal demodulation with delay. The quasi-optimal demodulation approaches optimal demodulation, in the minimum mean-square-error sense, as the signal-to-noise ratio increases. The various quasi-optimal receivers are derived by application of the extended Kalman filter theory to a state-space signal model. View full abstract»

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  • Interferences in Phase-Locked Loops

    Publication Year: 1974 , Page(s): 686 - 697
    Cited by:  Papers (22)
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    An analysis of the behavior of a second-order phase-locked loop is presented when an unwanted signal is added to the useful signal. Both signals are sinusoidal and unmodulated, and the analysis is made in the absence of additive noise. When the loop remains locked on the useful signal, a parasitic signal exists at the phase detector output. This signal produces a parasitic phase modulation of the VCO and a static phase error in the loop. The parasitic signal amplitude, the parasitic phase modulation index, and the static phase error are calculated. A necessary condition for the loop to remain in lock is derived. When the loop is initially unlocked, locking can occur either on the useful signal or on the unwanted signal, depending on the amplitude ratio and the frequency difference of the two signals. A formula allowing one to compute the pull-in time is obtained. When the loop locks on the useful signal, acquisition can be slower or faster than in the absence of an unwanted signal. The same phenomenon is observed when the loop locks on the unwanted signal. View full abstract»

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  • Performance of Digital FM Systems in a Fading Environment

    Publication Year: 1974 , Page(s): 698 - 709
    Cited by:  Papers (4)
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    This paper investigates the effects of fading and predetection diversity on the error-rate performance of digital FM discriminator systems. Results are presented in graphs showing the relative improvement of the error rate for several types of diversity, and are compared with the well-known FSK systems. It is also shown that an optimum modulation index giving the minimum attainable probability of error for narrowband digital FM is not affected by the effect of fading, carrier-to-noise ratio, or the types and order of diversity. View full abstract»

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  • An All - Digital Second-Order PLL

    Publication Year: 1974 , Page(s): 710 - 712
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    A functional description with timing diagrams of two example cases is given, describing an all-digital second-order PLL, which will correct frequency as well as phase errors. Approximations yield the equivalent continuous second-order loop, so that loop parameters might easily be designed. View full abstract»

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  • The Output Pdf of a Polarity Coincidence Correlation Detector

    Publication Year: 1974 , Page(s): 712 - 715
    Cited by:  Papers (8)
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    A general expression is derived for the probability density function of the output of a cross correlator, the inputs of which are assumed to consist of clipped sine waves of similar frequency plus uncorrelated, stationary Gaussian noise. The correlator output is shown to be a piecewise linear function of the random phase difference between the two input processes; hence, the density function for the correlator output is obtained by a relatively simple transformationfrom the probability density function of the random phase difference. View full abstract»

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  • Additions and Modifications to "Word Error Rates in Cryptographic Ensembles"

    Publication Year: 1974 , Page(s): 715 - 717
    Cited by:  Papers (1)
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    First Page of the Article
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  • In this issue - Technically

    Publication Year: 1974 , Page(s): 717 - 718
    Cited by:  Papers (2)
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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