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Aerospace and Electronic Systems, IEEE Transactions on

Issue 5 • Date Sept. 1982

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Displaying Results 1 - 25 of 26
  • Table of contents

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

    Page(s): c2 - [708]-c
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    Freely Available from IEEE
  • From the Editors

    Page(s): 519
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  • Hard Limiter Performance as a Polarity Detector for Extremely Polluted Signals

    Page(s): 520 - 530
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    A hard limiter is a simple, yet highly efficient, RF signal sensor for VLF and LF navigation receivers. The observation reliability is used as the single quality criterion for the hard limiter if applied as a singlebit analog-to-digital converter (ADC). The effects of noise (Gaussian and atmospheric), nonsynchronous and synchronous interference, and dc offset on the observation reliability are described extensively. The single parameter determination Pobs is adequate for characterizing the polarity detector. This facilitates rank ordering of influences disturbing the signal and is a useful tool in optimizing digital tracking loops. The ¿built-in¿ noise-censoring properties of the hard limiter in the presence of atmospheric noise are excellent. Therefore, three different atmospheric noise models are used in the determination of the observation reliability Pobs. Some ways for coping with other disturbances that potentially threaten the good performance of the hard limiter are suggested. View full abstract»

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  • Simple Tracking Filters: Position and Velocity Measurements

    Page(s): 531 - 537
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    Parametric data is presented showing the effects of combining velocity measurements with the usual position measurements in a simple form of target tracking filter. Effects on steady-state performance and filter gains are shown, as well as data on time required for convergence to steady state. View full abstract»

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  • CIECA: Application to Current Programmed Switching Dc-Dc Converters

    Page(s): 538 - 544
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    Sundstrand Advanced Technology Corporation The current injection equivalent circuit approach (CIECA) to modeling switching converter power stages is extended to model the current programmed converter power stages operating in fixed frequency, continuous inductor conduction mode. To demonstrate the method, modeling is carried out for the buck, boost, and buckboost converters to obtain small-signal linear equivalent circuit models which represent both input and output properties. The results of these analyses are presented in the form of linear equivalent circuit models as well as transfer functions. Though current programmed converters exhibit single-pole response, the addition of artificial ramp changes converters to exhibit well damped two-pole response. This has been investigated for the first time using CIECA. The results of these analyses are presented in the form of linear equivalent circuit models as well as transfer functions. View full abstract»

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  • Large-Signal Transient Responses of a Switching Regulator

    Page(s): 545 - 551
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    Analytical and experimental considerations of the large-signal transient responses of the buck-type switching regulator are described. The dynamic behavior under the large-signal condition is different from the small-signal operation because of the saturation characteristics of the pulsewidth modulator feedback controller. The effect of this nonlinearity is analyzed by dividing its operation into three modes. As a result the peak values of the inrush current and output voltage are obtained analytically both for the start-up and for the step change of the load condition. View full abstract»

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  • An Adaptive MTI for Weather Clutter Suppression

    Page(s): 552 - 562
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    A digital realization of an adaptive clutter-locking loop is presented. The purpose of the loop is to estimate the mean Doppler frequency of the clutter. The clutter spectrum is then shifted toward the zero Doppler by this estimate. A fixed moving target indicator (MTI) canceler following the loop suppresses the shifted clutter. Experimental simulations illustrate the feasibility of the loop. Results indicate that the proposed canceler works significantly better than a fixed canceler, while not as well as the 10-pulse moving target detector (MTD) processor. However, the complexity of the MTD is significantly more than the relatively simple adaptive processor presented here. View full abstract»

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  • Modeling and a Correlation Algorithm for Spaceborne SAR Signals

    Page(s): 563 - 575
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    A mathematical model of a spaceborne synthetic aperture radar (SAR) response is presented. The associated SAR system performance, in terms of the resolution capability, is also discussed. The analysis of spaceborne SAR target response indicates that the SAR correlation problem is a two-dimensional one with a linear shift-variant response function. A new digital processing algorithm is proposed here in order to realize an economical digital SAR correlation system. The proposed algorithm treats the two-dimensional correlation by a combination of frequency domain fast correlation in the azimuth dimension and a time-domain convolver type of operation in the range dimension. Finally, digitally correlated SEASAT satellite SAR imagery is used in an exemplary sense to validate the SAR response model and the new digital processing technique developed. View full abstract»

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  • Implicit Adaptive Control for a Class of MIMO Systems

    Page(s): 576 - 590
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    Two implicit model reference adaptive control algorithms for multi-input multi-output systems are developed. These algorithms do not require either satisfaction of the perfect model following conditions or explicit parameter identification. The first algorithm ensures asymptotic stability of the output error provided that the output stabilized plant transfer matrix is strictly positive real. The second algorithm guarantees a bounded error under less restrictive conditions. The algorithms are applied to the lateral axis of an F-8 aircraft. View full abstract»

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  • Satellite Librational Damping Using a Quasi-Feedback Solar Controller

    Page(s): 591 - 597
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    The feasibility of developing a simple quasi-feedback solar attitude controller is explored. The case of arbitrarily-shaped satellites carrying two pairs of solar surfaces in circular orbits is considered. An approximate analytical approach is used to synthesize the suitable open-loop control relations enabling decay of the satellite librations. The quasi-feedback control scheme suggested here is found to be quite effective in damping the pitch motion. The proposed control approach appears to be particularly attractive as it requires knowledge of the librational angle and velocity only at a fixed satellite position in orbit. View full abstract»

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  • Computer Simulations of Optimum Boost and Buck-Boost Converters

    Page(s): 598 - 608
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    The development of mathematical models suitable for minimum weight boost and buck-boost converter designs are presented. The facility of an augumented Lagrangian (ALAG) multiplier-based nonlinear programming technique is demonstrated for minimum weight design optimizations of boost and buck-boost power converters. ALAG-based computer simulation results for those two minimum weight designs are discussed. Certain important features of ALAG are presented in the framework of a comprehensive design example for boost and buck-boost power converter design optimization. The study provides refreshing design insight of power converters and presents such information as weight and loss profiles of various semiconductor components and magnetics as a function of the switching frequency. View full abstract»

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  • Phase Synchronizing a Nonrigid, Distributed, Transmit-Receive Radar Antenna Array

    Page(s): 609 - 620
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    A means is described for self-organizing a nonrigid, distributed, transmit-receive antenna array for use in airborne radar. The techniques are applicable to ground-based or shipborne radar as well. Methods are described for initializing the array using various primary microwave illuninators. The description of phase conjugation techniques and means for distributing phase reference to all elements in the array are the central parts of the paper. View full abstract»

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  • Variable Dimension Filter for Maneuvering Target Tracking

    Page(s): 621 - 629
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    A novel approach to tracking a maneuvering target is developed. This approach does not rely on a statistical description of the maneuver as a random process. Instead, the state model for the target is changed by introducing extra state components when a maneuver is detected. The maneuver, modeled as an acceleration, is estimated recursively. The performance of this estimator is shown to be superior to a recent algorithm presented by Chan et al. that handles the maneuver by estimating it as an unknown input. A significant departure from the current practice of comparison of algorithms is made: a recently introduced rigorous statistical methodology is used in the comparison of these estimators. View full abstract»

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  • Gyro Motion Boundedness under Uncertain Angular Acceleration about Vehicle Output Axis

    Page(s): 630 - 636
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    An analysis of the motion of a single-axis rate gyroscope mounted in a space vehicle which has uncertain time-varying acceleration and deceleration ¿x(t) about the output axis of the gyro is presented. Using a Lyapunov function, a condition for boundedness of the gyro motion is derived. It is shown that by a proper selection of the parameters of the gyro, its motion can be forced to remain in a small neighborhood (called region of ultimate boundedness) of the origin in ¿ - ¿ plane after a certain finite interval of time for any bounded uncertain ¿x(t). Analytical relations for the selection of gyro parameters to keep the error caused in the measurement of the input rate due to ¿x within desirable limits are derived. View full abstract»

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  • Linear Frequency Modulation Derived Polyphase Pulse Compression Codes

    Page(s): 637 - 641
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    Two new polyphase pulse compression codes and efficient digital implementation techniques are presented that are very Doppler tolerant and that can provide large pulse compression ratios. One of these codes is tolerant of precompression bandwidth limitations. View full abstract»

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  • Optimization of Coverage Pattern for Regional Communications Satellite

    Page(s): 642 - 647
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    An optimization problem of an antenna coverage pattern for a regional communications satellite when an antenna-pointing error exists is discussed. A new performance measure is introduced to evaluate the coverage pattern. This measure is defined as the statistical mean of the ratio between two areas, the full service area and the part of it covered by the antenna. The optimum coverage pattern which maximizes this measure under certain constraint is obtained. The results of numerical calculations are included to demonstrate the technique. View full abstract»

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  • Upper Limits on the Performance of the Optimum Processor in Mismatched Environment

    Page(s): 648 - 654
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    In most signal detection problems, information about the observations is not precisely known beforehand. The performance of the likelihood ratio processor (LRP), designed according to a preassumed observation vector parameter, is investigated when the actual processed observations have a vector parameter that differs from the preassumed design vector parameter. An upper limit on the performance of the LRP is obtained when the actual and design vector parameters are equal. The possible need for using adaptive processors is determined by this LRP performance investigation. View full abstract»

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  • A Feedback Time Constant Concept

    Page(s): 655 - 667
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    The circuit design for a control system for tracking, pointing, and terminal conlrol which provides high static and dynamic accuracy is presented. The system is based on feedback-balanced time constant RL or RC circuits and provides fail safe operation. The system can also be used for analog to digital conversion. The concept presented is particularly for use with on-board aircraft control instrumentation based on gyro-inertial and aneroidal information sensors. The primary purposes of this paper are 1) to illustrate the circuitry design concept along with its advantages and 2) to give a basic mathematical description of the functioning in terms of dynamic resolution, stability, noise immunity, and functional options. View full abstract»

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  • Effects of Finite Wire Scatterers in the Field of VOR

    Page(s): 668 - 674
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    A computer-oriented general formula is developed to estimate the dynamic bearing errors of an airborne VOR receiver due to arbitrary bent finite wire scatterers located in the vicinity of a VOR. The current in those wires caused by the incident fields from the VOR is computed by a piecewise-sinusoidal reaction technique. The variations in the incident fields over the wire and the mutual coupling effects between close wires are taken into account. View full abstract»

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  • Estimation of Spectra from Speckled Images

    Page(s): 675 - 681
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    The effect of coherent speckling on the spectra of images and other signals is investigated. A method for estimating the spectrum of the unspeckled image is developed, and the errors inherent in such an estimate are analyzed. It is found that the error decreases when number of looks, number of averaged spectra, and contrast increase, and when spectral width decreases. View full abstract»

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  • Fast Algorithms for Time Domain Broadband Adaptive Array Processing

    Page(s): 682 - 699
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    Recursive algorithms are presented for time domain, broadband, adaptive beamforming. The algorithms are rapidly converging and can be computationally efficient for a certain range of array processor parameters. The algorithms are presented for two forms of array processor. One form is a Frost-type structure in which explicit constraints are required for defining the array-look direction and also to control the sensitivity of the array processor to implementation errors. The other form is a partitioned array processor in which constraints are built into the processor and the adaptive weight control algorithm is therefore unconstrained. The two processors presented are both element-space processors but the algorithms can be applied also to beam-space processors. View full abstract»

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  • Information for authors

    Page(s): 700
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  • Self-Noise Produced by Quadrupling of Qpsk Signals

    Page(s): 701 - 704
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    Computer simulation results of the self-noise performance of the quadrupling circuit are described. The input waveforms are assumed to admit full and half cosine roll-off spectra, and the class of nonlinearity is assumed to be memoryless vth power law. View full abstract»

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  • CTD MTI Radar Filter with Charge-Transfer Inefficiency Compensation

    Page(s): 704 - 708
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    The design and implementation of a second-order nonrecursive moving target indication (MTI) radar filter using commercially available charge-transfer devices as delay lines are described. A simple technique is included to compensate for the device charge-transfer in-efficiency and its sensitivity is analyzed. Experimental laboratory tests and results in an operating radar system are reported showing the good performance of the realized MTI radar 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