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Aerospace and Electronic Systems, IEEE Transactions on

Issue 3 • Date July 1992

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Displaying Results 1 - 25 of 36
  • Correction to 'Lyapunov stability designs for switching regulator/low-pass filter system'

    Publication Year: 1992 , Page(s): 881 - 884
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (311 KB)  

    It is noted that the results obtained in the above-titled paper (ibid., vol.25, no.5, p.602-610, Sept. 1989) are erroneous since the Lyapunov matrix equation was not solved correctly and completely. Also, erroneous conclusions resulted because a solution to the ten simultaneous equations which result from the evaluation of that equation was not obtained. These errors are corrected and the Lyapunov simultaneous equations are solved. From the design of this fourth-order system, a comparison of the Lyapunov and Routh-Hurwitz methodologies for achieving asymptotic stability is obtained. It is shown that a design per the second method of Lyapunov simplifies the stability design calculations for this higher-order system.<> View full abstract»

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  • Comment on "Eigenstructure assignment for linear systems" by A.N. Andry, et al. [Aerospace control]

    Publication Year: 1992 , Page(s): 920 - 921
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (175 KB)  

    In the above-titled paper (see ibid., vol.AES-19, p.711-729, Sept. 1983), an achievability subspace is given and used for eigenstructure assignment of linear systems with gain output feedback. The commenter shows that the achievability subspace is not generally achievable.<> View full abstract»

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  • The effect of I,Q mismatch errors on adaptive cancellation

    Publication Year: 1992 , Page(s): 729 - 740
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (696 KB)  

    The effects of in-phase (I) and quadrature-phase (Q) amplitude errors and low-pass-filter (LPF) errors on adaptive cancellers are investigated. I,Q errors occur because of errors in the synthesis process of the mixers and LPFs designed to be identical for each input channel. These I,Q errors among the channels result in cancellation degradation. Tapped delay line transversal filters have been proposed as a way to compensate for these errors and thus improve cancellation performance. However, it is shown that if there is any LPF mismatch, then transversal filtering has a small effect on improving canceler performance. The use of individual I,Q adaptive transversal filter weighting is suggested as a means of completely eliminating the phase amplitude errors, and making the canceler performance responsive to transversal filter compensation View full abstract»

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  • Characterizing radar emissions using a robust countermeasure receiver

    Publication Year: 1992 , Page(s): 741 - 755
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1008 KB)  

    The author presents a high-sensitivity signal processing approach for detecting and estimating the angle of arrival (AOA), frequency and pulse repetition frequency (PRF) of multiple radar emitters using broadband interferometers. Two time series are generated using information embedded in the sampled cross correlation of the signals obtained from three antenna elements (i.e. two base legs). The phase and amplitude of a complex Fourier transform of these two time series with respect to the sampling clock are used to estimate the AOA and PRF of pulsed emitters View full abstract»

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  • Current distribution control for parallel connected converters. I

    Publication Year: 1992 , Page(s): 829 - 840
    Cited by:  Papers (82)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (744 KB)  

    For pt.II, see ibid., vol.28, no.3, p.841-851 (1992). A master-slave control scheme for a uniform current distribution among converter modules in a parallel connected system is presented. In this technique, inner current loops are introduced to the system to achieve output current equalization. The current distribution error is used as a criterion for judging system performance. Using this control scheme, the current distribution error can be reduced greatly even with nonidentical converters in the system. To optimize system efficiency and facilitate the fault-tolerant algorithm realization, this technique is refined so that only the necessary number of converters are activated for different load conditions View full abstract»

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  • Reduced-order multiple model adaptive controller for flexible spacestructure

    Publication Year: 1992 , Page(s): 756 - 767
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (872 KB)  

    The robustness of a moving-bank multiple model adaptive estimator/controller to order reduction in the controller design model is examined. It is shown that the adaptive mechanism and bank-moving logic are not confounded by the effects of unmodeled higher order modes of a large flexible spacestructure. Control characteristics are achieved that are essentially equivalent to those of an artificially informed benchmark controller View full abstract»

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  • Radiometric detection of spread-spectrum signals in noise of uncertain power

    Publication Year: 1992 , Page(s): 654 - 660
    Cited by:  Papers (132)  |  Patents (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (520 KB)  

    The standard analysis of the radiometric detectability of a spread-spectrum signal assumes a background of stationary, white Gaussian noise whose power spectral density can be measured very accurately. This assumption yields a fairly high probability of interception, even for signals of short duration. By explicitly considering the effect of uncertain knowledge of the noise power density, it is demonstrated that detection of these signals by a wideband radiometer can be considerably more difficult in practice than is indicated by the standard result. Worst-case performance bounds are provided as a function of input signal-to-noise ratio (SNR), time-bandwidth (TW) product and peak-to-peak noise uncertainty. The results are illustrated graphically for a number of situations of interest. It is also shown that asymptotically, as the TW product becomes large, the SNR required for detection becomes a function of noise uncertainty only and is independent of the detection parameters and the observation interval View full abstract»

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  • Convergence analysis for inexact mechanization of Kalman filtering

    Publication Year: 1992 , Page(s): 612 - 621
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (584 KB)  

    A computational aspect of real-time estimation is considered, in which the estimation algorithm to be used has the standard optimal Kalman filtering structure, but the actual inverse matrix within the Kalman gain is replaced by an expedient approximation at each instant. In real-time applications, most Kalman filtering schemes are approximate to a degree as a consequence of numerical roundoff matrix inversion. The convergence properties and error estimates of such schemes are obtained to provide a theoretical basis for gauging the utility of using the above approximations of the Kalman gain matrix at each time instant. A new exponentially convergent scheme is also suggested for approximating the inverse matrix within the Kalman gain. Conditions are determined under which online approximate matrix inversion can be eliminated as the cause of Kalman filter divergence in real-time implementations View full abstract»

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  • Interrelationships among performance characteristics, capacitance, and sequence impedances of single-phase motors

    Publication Year: 1992 , Page(s): 908 - 909
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (152 KB)  

    The author presents a clear, concise method of analysis of the performance of the single-phase induction motor with a capacitor in one winding. Using familiar symmetrical component notation, the developed equations permit rapid calculation of average electromagnetic torque, power factor, line current, and efficiency in terms of capacitance and motor sequence impedances, at any speed. The effect of varying one or more parameters can readily be determined View full abstract»

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  • A multioutput LLC-type parallel resonant converter

    Publication Year: 1992 , Page(s): 697 - 707
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (688 KB)  

    When an LLC-type parallel resonant converter (LLC-PRC) operates above resonant frequency, the switching transistors can be turned off at zero voltage. Further study reveals that the LLC-PRC possesses the advantage of lower converter voltage gain as compared with the conventional PRC. Based on the analytic results derived, a complete set of design curves from which a systematic design procedure is developed is obtained. Experimental results from a 150-W, 150-kHz, multioutput LLC-type PRC power supply are presented View full abstract»

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  • Radar receiver optimization for a continuously scanning antenna

    Publication Year: 1992 , Page(s): 861 - 868
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (552 KB)  

    The optimum coherent radar receiver configuration is derived for a continuously scanning antenna on the basis of maximizing the available energy for a given processor complexity. Included in the analysis are the length of the coherent dwell, the size of the discrete Fourier transform and the degree of weighting used for Doppler filtering, and the use of overlapped processing windows. Gaussian shapes for the processing window and antenna mainbeam are assumed in order to make the analysis tractable View full abstract»

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  • Target detection-sensitivity enhancement using high-resolution radar and 2-D and 3-D stereo target displays

    Publication Year: 1992 , Page(s): 886 - 890
    Cited by:  Papers (3)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (496 KB)  

    A 1989 experiment in detection-sensitivity enhancement of an airplane target in a background of ground clutter is reported. The experiment showed an 11 dB improvement when a high-resolution radar target was displayed as a 2-D image rather than a blip or blob (0-dimensions). A further 7 dB was observed when the target was displayed in stereo (3-D). These extraordinary observations warrant independent verification and theoretical examination View full abstract»

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  • Current distribution control for parallel connected converters. II

    Publication Year: 1992 , Page(s): 841 - 851
    Cited by:  Papers (21)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (680 KB)  

    For pt.I, see ibid., vol.28, no.3, p.829-840 (1992). In the central-limit control (CLC), the multiloop controls are employed to regulate the output voltage and track the central weighted current, thus equalizing the output current of each converter module (CM). The current distribution error (CDE) between the output current of each CM is used as a criterion in judging system performance. The prediction and simulation results of this control scheme are illustrated. When incorporated with the maximum current limit, the proposed control method can determine the number of required converters in the active state for each load condition. As a result, the efficiency of a system can be increased significantly. A comparison between the performances of the system under master-slave control (MSC) and CLC is given View full abstract»

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  • Monopulse-radar angle tracking in noise or noise jamming

    Publication Year: 1992 , Page(s): 622 - 638
    Cited by:  Papers (19)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1232 KB)  

    In many monopulse radars, feedback in the angle-tracking servo system is taken to be directly proportional to the monopulse ratio. In those radars, monopulse measurements are conditioned on simultaneous occurrences of receiver sum-channel video exceeding a detection threshold: if a detection fails to occur, the measurement is ignored, and the angle-tracking servo is made to coast. Such conditioning is shown to be necessary in order that the noise power be finite in the servo feedback. The conditional mean value and conditional variance of the monopulse ratio are derived and quantified in terms of threshold level as well as signal-to-noise ratio. The formulation permits the noise covariance between receiver difference and sum channels to be complex rather than only real-valued, so that the sources of noise jamming are not required to be positioned in the receiving-antenna mainlobe and to be copolarized with the antenna response there. Nonfluctuating and Rayleigh-fluctuating target cases are considered and compared, and fluctuation loss is quantified View full abstract»

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  • The effect of gyro nonorthogonality error on gyrocompassing

    Publication Year: 1992 , Page(s): 890 - 893
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (280 KB)  

    The effect of the gyro nonorthogonality on the two-step gyrocompassing process is analyzed. It is shown that the azimuth misalignment resulting from gyro nonorthogonality depends on the platform direction with respect to geographic frame. Gyrocompassing error is explicitly expressed in terms of gyro nonorthogonality and gyro parameters. A compensation scheme to eliminate the gyrocompassing error, which results from gyro nonorthogonality, is presented. This method can be used in cases where the gyro nonorthogonality error is beyond the standard requirements for high quality platforms. The main advantage is that it allows an increase in the tolerance of gyro nonorthogonality, and reduces the cost of inertial measurement unit manufacture View full abstract»

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  • Modification of the SAR step transform algorithm

    Publication Year: 1992 , Page(s): 666 - 674
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (640 KB)  

    When the basic step transform algorithm is used to compress synthetic-aperture radar (SAR) signals in azimuth, the linear FM rate and sampling rate must satisfy certain tight constraints. In practice, these constraints cannot be satisfied and errors are introduced into the compressed SAR image. A modification is described of the basic step transform which incorporates interpolation and resampling into the algorithm. These changes allow the removal of the constraints and make the step transform more useful for the compression of real data. An autofocusing capability is also included, without introducing much additional complexity View full abstract»

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  • Bandwidth performance of linear adaptive arrays with tapped delay-line processing

    Publication Year: 1992 , Page(s): 901 - 908
    Cited by:  Papers (26)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (648 KB)  

    The nulling bandwidth of adaptive arrays with tapped delay-line processing is examined. Linear arrays with up to 10 elements are considered. It is shown how the number of taps in the delay lines and the amount of delay between taps affect the nulling bandwidth. For each size of array, the optimal number of delay-line taps and the optimal intertap delays are determined as functions of the required nulling bandwidth View full abstract»

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  • Performance of diversely polarized antenna arrays for correlated signals

    Publication Year: 1992 , Page(s): 869 - 879
    Cited by:  Papers (14)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (776 KB)  

    The performance of direction finding systems in a correlated signal environment utilizing diversely polarized antenna arrays is investigated. The Cramer-Rao bound (CRB) is used to evaluate the accuracy of the estimated directions of arrival (DOAs). Compact closed form formulas are presented for the CRB corresponding to the joint estimation of the DOAs, signal covariance matrix, signal polarization parameters, and noise variance. The CRB is evaluated numerically for selected examples, to provide insights into the potential improvement in direction-finding accuracy due to polarization diversity View full abstract»

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  • On the connection between maximum likelihood sensitivity analysis and nuisance parameter analysis

    Publication Year: 1992 , Page(s): 884 - 886
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (256 KB)  

    Sensitivity analysis provides a mean-square-error measure of how the maximum-likelihood (ML) estimates of parameters of interest would change with changes in parameters not being estimated (i.e., nuisance parameters). This type of sensitivity analysis alone does not provide confidence intervals that include the uncertainty in nuisance parameters, whereas nuisance parameter analysis does provide such confidence intervals. The connection between these two analyses is discussed View full abstract»

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  • A persymmetric multiband GLR algorithm

    Publication Year: 1992 , Page(s): 806 - 816
    Cited by:  Papers (19)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (616 KB)  

    By exploring the covariance structure information to reduce the uncertainty in adaptive processing, a persymmetric generalized likelihood ratio algorithm (PGLR) is developed together with the closed-form expressions of probabilities of detection and false alarm. This multiband algorithm, which requires less computation, can significantly outperform the corresponding unstructured multiband GLR algorithm, especially in a severely nonstationary and/or nonhomogeneous interference environment. Simulation shows that the constant false alarm rate (CFAR) performance of the new algorithm is as insensitive as that of the unstructured multiband GLR to the departure of interference distribution from Gaussian View full abstract»

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  • An experimental investigation of three eigen DF techniques

    Publication Year: 1992 , Page(s): 852 - 860
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (664 KB)  

    The comparative direction-finding (DF) performance of multiple signal classification (MUSIC), ROOT-MUSIC, and estimation of signal parameters via rotational invariance techniques (ESPRIT) is considered. Data were collected from two target transmitters operating simultaneously. The objective of the experiment was to evaluate multipath resolution capability using measurement precision equivalent to that found in modern radio direction-finding systems View full abstract»

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  • Distributed detection by a large team of sensors in tandem

    Publication Year: 1992 , Page(s): 639 - 653
    Cited by:  Papers (36)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1024 KB)  

    The problem of decentralized binary hypothesis testing by a team consisting of N decision makers (DMs) in tandem is considered. Each DM receives an observation and transmits a binary message to its successor; the last DM has to decide which hypothesis is true. The necessary and sufficient condition for the probability of error to go asymptotically to zero as N→∞ is that the log-likelihood ratio of the observation of each DM be unbounded. The result is generalized for multiple hypotheses and multiple messages. An easily implementable suboptimal decision scheme is also considered; in this case, the necessary and sufficient condition for the probability of error to asymptotically go to zero is that the log-likelihood ratio of the observation of each DM be unbounded from both above and below. The tradeoff between the complexity of the decision rules and their performance is examined, and numerical results are presented, in order to demonstrate that the performance of both decision schemes is comparable View full abstract»

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  • Multisignal time delay detection and tracking

    Publication Year: 1992 , Page(s): 675 - 696
    Cited by:  Papers (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1456 KB)  

    An optimum solution to the time delay detection and tracking problem for a single signal is extended to the multisignal problem where the number of signals present in the observed data (if any) is unknown. The number of signals present is determined, and the time delay of each detected signal is tracked. The number of possible global, or first level, hypotheses is large because of the exponential dependence on the number of potential signals. An efficient approximate multisignal detection and tracking solution that is as near optimum as possible for the computational resources required is developed. It has the form of parallel detector-trackers (one for each potential signal) each similar to the single-signal case, with communication between them. Test results demonstrate the utility of the approach View full abstract»

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  • Optimal data fusion of correlated local decisions in multiple sensor detection systems

    Publication Year: 1992 , Page(s): 916 - 920
    Cited by:  Papers (66)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (264 KB)  

    Z. Chair and P.R. Varshney (1986) solved the data fusion problem for fixed binary local detectors with statistically independent decisions. Their solution is generalized by using the Bahadur-Lazarsfeld expansion of probability density functions. The optimal data fusion rule is developed for correlation local binary decisions, in terms of the conditional correlation coefficients of all orders. It is shown that when all these coefficients are zero, the rule coincides with the original Chair-Varshney design View full abstract»

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  • An improved multiple target angle tracking algorithm

    Publication Year: 1992 , Page(s): 797 - 805
    Cited by:  Papers (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (560 KB)  

    An improved version of a multiple-target-angle tracking algorithm using sensor array outputs is presented. While retaining all the good features of the original algorithm, the improved version greatly reduces the error propagation due to the use of recursive approximations in updating target angle estimates. The assumption of a constant signal covariance matrix is no longer necessary. The improved performance of the proposed algorithm is demonstrated by computer simulations dealing with the tracking of two moving targets 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