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Aerospace and Electronic Systems, IEEE Transactions on

Issue 2 • Date March 1978

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  • Table of contents

    Publication Year: 1978 , Page(s): c1
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    Freely Available from IEEE
  • IEEE Aerospace and Electronic Systems Society

    Publication Year: 1978 , Page(s): c2 - 416a
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    Freely Available from IEEE
  • From the Editors

    Publication Year: 1978 , Page(s): 225
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  • The Measurement of Echo Direction in a Phased-Array Radar

    Publication Year: 1978 , Page(s): 226 - 236
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    For a planar-array antenna with a monopulse feed horn, this study describes a simple algorithm for the determination of the direction of target echoes. Antenna pattern measurements of the array indicate that the direction sines of a received wavefront can be independently obtained with one simple relation between a normalized difference channel output and a direction sine. This paper determines the accuracy of the algorithm. View full abstract»

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  • Performance Evaluation of Energy Detectors

    Publication Year: 1978 , Page(s): 237 - 241
    Cited by:  Papers (9)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1063 KB)  

    The prediction of energy detector performance requires a complicated calculation or a tedious manipulation of nomograms. For a large time-bandwidth product WT, however, it is commonplace to use the formula (E/No) = d¿WT to anticipate the required average input energy-to-noise spectral density ratio for a wanted signal detectability parameter d and thus avoid the computational difficulty. This paper proposes a modified formula (E/No) = ¿d¿WT that is applicable for all range of WT, where ¿ is the modification factor derived on an empirical basis. The Van Trees measure of the signal detectability parameter of the energy detector also is derived analytically and compared to the modified equation. View full abstract»

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  • Modified Savage and Modified Rank Squared Nonparametric Detectors

    Publication Year: 1978 , Page(s): 242 - 250
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1942 KB)  

    A modified form of the basic Savage statistic is considered and the performance of a modified Savage (MS) nonparametric detector using this modified statistic is derived. Also, a detector using a modified rank squared statistic (MRS) is introduced. The asymptotic relative efficiency (ARE) of the detectors is determined for chisquare, Rician, and log-normal signal fluctuations when the background noise is assumed Gaussian. The ARE performance of the generalized sign (GS) and Mann-Whitney (MW) detectors is also determined for these families of fluctuations. The ARE performance of the various detectors is then compared, and the results of a computer simulation are presented in which, for a finite number of samples, the performance of the modified detectors is compared with the performance of the GS and MW detectors. It is shown that when using a large number of reference noise samples, the ARE of the GS and MW detectors, the MRS and RS detectors, and the MS and Savage detectors are 0.75, 0.868, and 1, respectively. It is also shown that when using a finite number of reference noise samples the MS and MRS detectors can give a superior performance to that obtained with the MW detector, and that this is particularly true in the cases in which the degree of signal fluctuation is high. View full abstract»

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  • Feedback Transmission of Binary Data with Automaton Receiver

    Publication Year: 1978 , Page(s): 251 - 257
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    Feedback transmission of binary data over a discrete-time additive Gaussian white noise channel is considered. The effect of some specific finite memory structure at the receiver is investigated. The whole communication scheme is the discrete analog of the one previously analyzed by Khas'minskii. The resulting average transmission time is increased by only about 20 percent of the theoretical limit in the low signal-to-noise ratio region. Numerical results are also shown. View full abstract»

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  • On Attitude Estimation Schemes for Fine-Pointing Control

    Publication Year: 1978 , Page(s): 258 - 265
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    This paper studies single-axis equations of motion that are applicable to a spacecraft or to a space experiment pointing assembly whose motion has been perfectly isolated from the carrier vehicle. It considers four state estimators for implementation in the control loop for a stellar observation experiment. The first three estimators are very general and do not make use of input torque in their prediction models, while the proposed fourth estimator utilizes this information, It is shown via closed-loop covariance analysis that the best achievable pointing performance with the best of the first three estimators is limited to about 0.125 are-sec (rms) with the given rate-gyro and star-tracker inaccuracies. It is also shown that the fourth estimator has the capability of achieving a pointing performance far superior to the performance achievable using the first three estimators. The fourth estimator relies on the ability to accurately generate the desired control torque (i.e., low input noise). View full abstract»

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  • Area Target Response of Triangularly Frequency-Modulated Continuous-Wave Radars

    Publication Year: 1978 , Page(s): 266 - 277
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2721 KB)  

    For a postulated model of the area target returns, the variance of the signal appearing at the detector output of a frequency-modulated continuous-wave radar is analytically and graphically displayed as a function of the range and Doppler spread. The influence of important system parameters like modulation frequency, measuring time, and frequency excursion are also included in the analysis. Closedform relationships are given for sawtooth or triangular frequency modulation and a Gaussian separable scattering function. A comparison is also made between the range noise of an ideal frequency detector and a zero-crossings counter. View full abstract»

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  • Adjacent Channel Interference in a Binary Bandpass Communication System

    Publication Year: 1978 , Page(s): 278 - 283
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1260 KB)  

    The effect of adjacent channel interference on the probability of error in a binary bandpass communication system with an integrating and dumping detector is investigated. Narrowband filters are assumed in the receiver of the main signal and transmitters of both main and interfering signals. Plots of the probability of error as a function of signal to noise ratio in the main channel or as a function of carrier frequency difference between the main and interfering signals are presented, assuming that the filters are of the Butterworth type. These figures are helpful in the selection of minimal frequency spacing of adjacent channels. View full abstract»

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  • Bounds on the Probability of Error in Digitial Communications

    Publication Year: 1978 , Page(s): 284 - 291
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1641 KB)  

    A class of upper bounds and lower bounds on the probability of error in digital communications are derived. Several degrading factors like intersymbol interference, cochannel interference, inaccurate carrier synchronization, and incoherent detection can be considered in obtaining the bounds. Several examples are given and it is shown that many situations not considered so far can be put into the conceptual framework developed here. View full abstract»

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  • Sensitivity Reduction in Aircraft Control Systems

    Publication Year: 1978 , Page(s): 292 - 297
    Cited by:  Papers (7)
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    A method for reducing trajectory sensitivity to parameter perturbations for linear feedback systems is described. Application of the method to the design of aircraft control systems, with special reference to a helicopter forward flight control system, is illustrated. The response of the system based on this method is found to be better than that obtained with fixed-feedback gain controllers, although the response may not be as good as that of an adaptive control scheme. The main advantage of the method is the simplicity of its implementation relative to that of the adaptive control scheme which requires an on-board computer. View full abstract»

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  • Sensitivity Considerations in Trajectory Optimization

    Publication Year: 1978 , Page(s): 298 - 304
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1366 KB)  

    A technique by which the trajectory optimization problem can be formulated to include the trajectory sensitivity functions in the performance index is presented. It is shown that an explicit steering law, which can be derived for the upper atmospheric flight of a vehicle, is a function of the sensitivity state, adjoint vectors, and the parameters of the chosen trajectory dynamics. The new steering law is compared with the one without sensitivity considerations. A computational method is presented to implement the new steering law. View full abstract»

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  • An Upper Bound on Detection Probability for Fluctuating Signals

    Publication Year: 1978 , Page(s): 305 - 311
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2938 KB)  

    In the theory of signal detectability, the signal-to-noise ratio (SNR), defined as the quotient of the average received signal energy and the spectral density of the white Gaussian noise, is a fundamental parameter. For a signal which is exactly known, or known except for a random phase, this ratio uniquely defines the detection performance which can be achieved with a matched filter receiver. However, when the signal amplitude is a random parameter, the detection performance is changed and must be determined from the probability density function (pdf) of the amplitude. Relative to the case of a constant signal amplitude, such signal amplitude fluctuation usually degrades performance when a high probability of detection (Pd) is required, but improves performance at low values of Pd; the corresponding change in the required SNR is the so-called signal fluctuation loss Lf. Thus, since Lf in some cases represents an improvement in performance for low values of Pd, a question of at least theoretical interest is: how large might this improvement be, when the class of all signal amplitude pdf's is considered. The solution, presented here, results in a lower bound on the signal fluctuation loss Lf as a function of Pd, or equivalently an upper bound on Pd as a function of SNR. The corresponding most favorable pdf was determined using the Lagrange multiplier technique and results of a numerical maximization are included to provide insight into the general properties of the solution. View full abstract»

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  • A Technique for Measuring Fading Microwave Signals from the ATS-5 Spacecraft

    Publication Year: 1978 , Page(s): 312 - 318
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (3045 KB)  

    A description of a technique for measuring fading microwave signals from the NASA ATS-5 spacecraft is presented. A ground station was used to transmit to and receive from the ATS-5 via its L-band transponder. The experiment included an L-band transmitter, three independent L-band receiving systems, and a semiautomatic data acquisition and analysis system. Sample data are presented. View full abstract»

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  • Radio Interference in Helicopter-Borne Pulse Doppler Radars

    Publication Year: 1978 , Page(s): 319 - 328
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1589 KB)  

    Radio interference generated in a helicopter-borne pulse Doppler radar system due to rotating blades is analyzed for the case that blades are located in the far field region of the radar antenna. A first-order estimate of the blade interference power spectrum is obtained as a function of antenna depression angle and radar (helicopter) altitude and speed. Numerical calculations show that blade interference is very weak compared with the direct ground clutter. It extends, however, into the clutter-free region which causes false alarms and degrades the radar performance. View full abstract»

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  • Pull-In Time and Range of Any Order Generalized PLL

    Publication Year: 1978 , Page(s): 329 - 333
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1155 KB)  

    The general pull-in range and pull-in time expressions are derived versus the relevant system parameters and the initial detuning for any order loop with any type of phase detector by the quasistationary approach. Even though the pull-in time expression becomes more accurate as the loop's order becomes larger, it is correct also for second-and third-order loops provided that the initial detuning, supposed large, is approaching the pull-in range value. View full abstract»

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  • Some Effects of Phased-Array Dispersion on Digital Error Rates

    Publication Year: 1978 , Page(s): 334 - 342
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1815 KB)  

    Some calculations of the effect of phased-array dispersion on degrading phase-shift-keyed (PSK) error rates are presented. The results are given in the form of curves of the bit error rate versus the ratio of array "fill-time" (propagation time across the array) to signaling interval. Values of this ratio in the range 0.5 to 0.8 are required to degrade the error rate by a factor of 2. These results were obtained for both linear and square arrays, and for rectangularpulse signaling over single-pole and two-pole Butterworth equivalent low-pass channels, as well as for impulsive signaling over an idealized channel with a raised-cosine frequency response. View full abstract»

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  • Digital and Analog Subcomplementary Sequences for Pulse Compression

    Publication Year: 1978 , Page(s): 343 - 350
    Cited by:  Papers (12)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1788 KB)  

    Golay's complementary pairing has been a method to increase the utility of binary sequences, because of the temporal sidelobe suppression in the autocorrelation vector summation. Complementary sets of Tseng and Liu and of Hollis exhibit the same effect when several autocorrelations are combined. These complementary pairs and sets of sequences can be extended into long complementary chains by a simple transformation. This transformation is extended here to all pulse compression waveforms. By this method, even though analog complementary sequences cannot be formed, a new class of waveforms, called subcomplementary waveforms, can be formed. Following these rules, repetition of waveforms such as linear frequency modulation (LFM) or linear stepped frequency modulation (LSFM) in a prescribed manner is possible without creating autocorrelation grating lobes or repetitive sidelobes. This method is equally applicable to all analog or digital pulse compression waveforms. View full abstract»

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  • Minimal-Order Models for False-Alarm Calculations on Sliding Windows

    Publication Year: 1978 , Page(s): 351 - 363
    Cited by:  Papers (15)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1925 KB)  

    A procedure is developed to obtain practical numerical results in connection with the m-out-of-n sliding-window detection problem. This effort was motivated by difficulties with previous approaches involving approximation, Markov models, and Monte Carlo simulation. Generating-function methods were found to be unsatisfactory for window lengths greater than 6 due to their complexity. Instead, a Markov model is described that is then constructively reduced to the minimum number of state variables. The results are derived for binary strings with intersymbol correlation. Computational aids are discussed for obtaining design information, such as quantiles, from the minimal-order Markov models. Numerical results are given comparing the methods of the paper with a "jumping" window approximation for an 8/10 problem. View full abstract»

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  • ATS-6 Parabolic Antenna for Mounting Solar Cells

    Publication Year: 1978 , Page(s): 364 - 367
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    Calculations are made to obtain the raw electrical power that can be generated by using an ATS-6 type deployable parabolic dish as a surface for mounting solar cells without seriously interfering with its normal function as an antenna. A minimum of a few hundred watts to a maximum of a few kilowatts are generated during the apparent course of the Sun around the spacecraft. Academically, it seems that deployable solar cell panels along with their booms can be avoided. View full abstract»

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  • Suboptimal Control of Satellite Momenta in a Noisy Environment

    Publication Year: 1978 , Page(s): 368 - 371
    Cited by:  Papers (1)
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    The body rate dynamics of a spin-stabilized satellite are perturbed by white noise. We consider the optimal control of body rates and fuel consumption. The corresponding deterministic problem is solved using calculus of variation. The stochastic problem is then solved to obtain a suboptimal controller in closed form. View full abstract»

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  • Comments on "on Probability of Error in Decision Feedback Equalizer"

    Publication Year: 1978 , Page(s): 373 - 375
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    The above-mentioned paper [1] derives bounds on the error probability of a decision feedback equalizer (DFE) which are claimed to be significantly tighter than the earlier upper bound of [2]. Unfortunately, [1] makes an unsupportable assumption which reddars the conclusions incorrect. We show that valid bounds can be obtained by the methods of [1], but that for the numerical example of [2] , the resulting upper bound is never tighter than, and sometimes significantly weaker than, that derived in [2]. Similarly, a lower bound derived by the method of [1] is shown for the same numerical example to be very close to the error-free past lower bound previously known. View full abstract»

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  • The Geometry of Escaping Targets

    Publication Year: 1978 , Page(s): 375 - 379
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (681 KB)  

    The escape regions for alerted targets are analytically defined.Sets of circles which circumscribe these regions provide simplified meas of the resulting escape involutes and yield important weapon guidance and sensor search parameters. These regions permit the selection of an aimpoint which incorporates the potential of target maneuers. Applications that illustrate the improved performance of these solutions in missile deployment and lost-contact-redetect situations are included. View full abstract»

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  • Artificial Noise in Adaptive Arrays

    Publication Year: 1978 , Page(s): 380 - 384
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (782 KB)  

    "Artificial noise," or the connection of feedback paths around the the integrators, is shown to be an effective method of dealing with the problem of multiplier offsets in adaptive antennas. This probl which was analyzed by Compton [1] is particularly troubles when the covariance matrix is singular or nearly so. Like added real noise, the artificial noise improves the condition number of the underlying matrix. The artificial noise, however, avoids the obvious disadvantage of adding to the real noise level. As a result the output-signal-to-interference ratio is much less degraded. 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