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Aerospace and Electronic Systems, IEEE Transactions on

Issue 2 • Date April 1993

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Displaying Results 1 - 25 of 35
  • Comments on "Computation of the circular error probability integral" by J.T. Gillis

    Publication Year: 1993 , Page(s): 553 - 555
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (311 KB)  

    A numerical technique for computing the circular error probability (CEP) integral using only elementary functions is presented. It is simpler and more accurate than the truncated series solution in the above-titled paper (see ibid., vol.27, p.906-10, Nov. 1991).<> View full abstract»

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  • A modified Gaussian sum approach to estimation of non-Gaussian signals

    Publication Year: 1993 , Page(s): 446 - 451
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (384 KB)  

    A Gaussian sum estimation algorithm has previously been developed to deal with noise processes that are non-Gaussian. Inherent in this algorithm is a serious growing memory problem that causes the number of terms in the Gaussian sum to increase exponentially at each iteration. A modified Gaussian sum estimation algorithm using an adaptive filter is developed that avoids the growing memory problem of the previous algorithm while providing effective state estimation. The adaptive filter is comprised of a fixed set of estimators operating in parallel with each individual estimate possessing its own corresponding weighting term. A simulation example illustrates the new non-Gaussian estimation technique View full abstract»

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  • Synchronization failure rates in master-slave synchronized phase-locked loops

    Publication Year: 1993 , Page(s): 328 - 335
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (500 KB)  

    A method for the computation of synchronization failure rates in master-slave phase-synchronized first-order phase-locked loops (PLLs) is presented. The method assumes (propagation) delay times that are long compared with tracking loop time constants and allows system optimizations of the slaved PLL in terms of improved tracking performance. Frequency turnaround ratios of phase-coherent transponders are considered, and effects of the converted transponder phase jitter on the tracking performance of the slaved PLL are discussed View full abstract»

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  • A fast method for finding the exact N-best hypotheses for multitarget tracking

    Publication Year: 1993 , Page(s): 555 - 560
    Cited by:  Papers (28)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (412 KB)  

    The necessity for multiple hypothesis tracking (MHT) is recognized throughout the SDI tracking community. However, implementations of MHT techniques have required enormous amounts of computer time and memory. An efficient method of measurement-to-target association that makes MHT practical for the first time is presented. The method finds the exact N-best feasible hypotheses directly from a sequence of linear assignment problem solutions View full abstract»

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  • Space-based tactical ballistic missile launch parameter estimation

    Publication Year: 1993 , Page(s): 412 - 424
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (816 KB)  

    The author explores the influence of a priori uncertainties in launch time and trajectory fly-out profiles, along with sensor angle measurement errors, on the estimation of missile launch location and heading angle. An error model is developed to compute the statistics of the estimation errors using a single pair of angle measurements, one from each of two satellites, or both from the same satellite platform. The measurements and estimation methods are described, followed by a derivation of the estimation errors for the hypothetical case of perfect knowledge of trajectory and launch time. Using the ideal case as a framework, the errors are generalized to include trajectory and launch time uncertainties. The results are discussed with the aid of graphics which were run parametrically to highlight important dependencies and sensitivities View full abstract»

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  • The α-β-Γ tracking filter with a noisy jerk as the maneuver model

    Publication Year: 1993 , Page(s): 578 - 580
    Cited by:  Papers (10)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (168 KB)  

    The optimal gains and covariances of an α-β-Γ filter are computed. It is assumed that the maneuver model is an uncorrelated zero mean noise jerk. Input to the tracking filter is position updates. The measurement errors are modeled as uncorrelated zero mean noise processes View full abstract»

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  • Classification of radar targets using synthetic neural networks

    Publication Year: 1993 , Page(s): 336 - 344
    Cited by:  Papers (20)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (700 KB)  

    Radar target classification performance of neural networks is evaluated. Time-domain and frequency-domain target features are considered. The sensitivity of the neural network algorithm to changes in network topology and training noise level is examined. The problem of classifying radar targets at unknown aspect angles is considered. The performance of the neural network algorithms is compared with that of decision-theoretic classifiers. Neural networks can be effectively used as radar target classification algorithms with an expected performance within 10 dB (worst case) of the optimum classifier View full abstract»

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  • Interacting multiple model tracking with target amplitude feature

    Publication Year: 1993 , Page(s): 494 - 509
    Cited by:  Papers (87)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1148 KB)  

    A recursive tracking algorithm is presented which uses the strength of target returns to improve track formation performance and track maintenance through target maneuvers in a cluttered environment. This technique combines the interacting multiple model (IMM) approach with a generalized probabilistic data association (PDA), which uses the measured return amplitude in conjunction with probabilistic models for the target and clutter returns. Key tracking decisions can be made automatically by assessing the probabilities of target models to provide rapid and accurate decisions for both true track acceptance and false track dismissal in track formation. It also provides the ability to accurately continue tracking through coordinated turn target maneuvers View full abstract»

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  • Suboptimal joint probabilistic data association

    Publication Year: 1993 , Page(s): 510 - 517
    Cited by:  Papers (24)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (596 KB)  

    A significant problem in multiple target tracking is the hit-to-track data association. A hit is a received signal from a target or background clutter which provides positional information. If an incorrect hit is associated with a track, that track could diverge and terminate. Prior methods for this data association problem include various optimal and suboptimal two-dimensional assignment algorithms which make hit-to-track associations. Another method is to assign a weight for the reasonable hits and use a weighted centroid of those hits to update the track. The method of weighting the hits is known as joint probabilistic data association (JPDA). The authors review the JPDA approach and a simple ad hoc approximation and then introduce a new suboptimal JPDA algorithm. Examples which compare an optimal two-dimensional assignment algorithm with the ad hoc and the new suboptimal JPDA formulation are given View full abstract»

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  • A multisensor-multitarget data association algorithm for heterogeneous sensors

    Publication Year: 1993 , Page(s): 560 - 568
    Cited by:  Papers (19)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (732 KB)  

    The problem of associating data from three spatially distributed heterogeneous sensors with three simultaneous detections for all three is discussed. The sensors can be active or passive. The source of a detection can be either a real target, in which case the measurement is the true observation variable of the target plus measurement noise, or a spurious one, i.e. a false alarm. The sensors may have nonunity detection probabilities. The problem is to associate the measurements from sensors to identify the real targets, and to obtain their position estimates. Mathematically this leads to a generalized 3D assignment problem, which is known to be NP-hard. An algorithm suited for estimating the positions of a large number of targets in a dense cluster, using a fast, but nearly optimal, 3D assignment algorithm, is presented. Performance results for several representative test cases with 64 targets are presented View full abstract»

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  • Dynamic compensator design in nonlinear aerospace systems

    Publication Year: 1993 , Page(s): 364 - 379
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1132 KB)  

    Based on differential algebraic results, dynamic controllers are proposed for the feedback regulation of typical aerospace systems. Fliess's generalized observability canonical form (GOCF) is used for specifying a dynamic compensator that smoothly regulates the plant dynamics. The synthesis approach used is also applicable to the design of nonlinear pulsewidth-modulation (PWM) controllers, as well as to sliding-mode control strategies. The three underlying nonlinear control techniques, explored with the aid of illustrative examples, are commonly encountered in aerospace control system design problems. Simulations are also included View full abstract»

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  • A match/merge technique for 121.5/243 MHz beacons in the COSPAS-SARSAT system

    Publication Year: 1993 , Page(s): 518 - 526
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (724 KB)  

    The COSPAS-SARSAT Mission Control Center (MCC) matches and merges estimates of position and frequency of 121.5/243 MHz distress beacons received from various ground stations and satellites. The matching and merging are done sequentially as the estimates are received, and merges are not reversed once sent out to search-and-rescue forces. A sequential, irreversible match/merge algorithm is derived based on the ratio of probabilities of the same beacon/different beacon hypotheses, and it is tested using data received at the United States MCC. The total number of mismatches based on tests for stability, correctness, and completeness was less than 0.5% when the match parameters were properly selected. The selected match parameters themselves were consistent with previously published results View full abstract»

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  • Beam overlap impact on phased-array target detection

    Publication Year: 1993 , Page(s): 404 - 411
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (540 KB)  

    The impact of beam overlap on the probability of detection during a single scan of a phased-array volumetric scan radar is examined. Rectangular and triangular beam packing arrangements are considered. Beam positions near the beam most centered on the target are allowed to contribute to the detection process. The treatment of the impact of beam overlap on target detection for a phased array is consistent with the results that would be achieved by proper use of the search radar range equation View full abstract»

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  • Frequency-hopping signal detection using partial band coverage

    Publication Year: 1993 , Page(s): 540 - 553
    Cited by:  Papers (14)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (992 KB)  

    The performance of a channelized radiometer in detecting a frequency-hopping signal is analyzed for a variable number of parallel radiometers not necessarily covering the entire hopping band. The full band may not be covered because of an attempt to avoid interfering signals, limited radiometer resources, lack of knowledge of the band frequency location, or combinations of these factors. The analysis provides for calculation of the value of the signal-to-noise ratio (SNR) required to achieve a given probability of detection for a specified false-alarm rate, assuming an observation interval equivalent to N hops using either a fixed or a moving observation window. The dependence of the probability of detection on a misalignment of the detector observation intervals with the hop transitions is also analyzed. Numerical results are presented and discussed. Applied to a typical slow-hopping VHF radio, the results imply that a 150-hop transmission can be detected by a channelized radiometer covering half the hopping band when the SNR is about 2 dB View full abstract»

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  • Spacecraft design considerations for small satellite remote sensing

    Publication Year: 1993 , Page(s): 391 - 403
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1128 KB)  

    The idea of adapting existing small satellite technology for remote sensing purposes is discussed. The major design problems and constraints influencing the design of a small low-cost remote sensing satellite bus are identified using the subsystem approach. Key design areas include the improvement of battery technology and the development of a deployable solar array, attitude control assemblies, on-board data processing/storage, and ground station data acquisition. Although the eventual satellite would also have to be somewhat larger, more powerful and, above all, more sophisticated than the previous small satellites, this is considered to be a natural progression of research in this area View full abstract»

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  • General expressions for Rician density and distribution functions

    Publication Year: 1993 , Page(s): 580 - 588
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (632 KB)  

    General expressions are derived for the density and distribution functions of the amplitude of a linear matched filter output given a nonfluctuating target in arbitrary clutter. These generalized Rician density and distribution functions are based on the density function of the clutter amplitude at the receiver output, and are easily evaluated numerically. Error bounds for the numerical calculation of the density function and several numerical examples are presented View full abstract»

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  • Sensor/actuator placement for flexible space structures

    Publication Year: 1993 , Page(s): 345 - 351
    Cited by:  Papers (10)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (576 KB)  

    A new approach for the placement of sensors and actuators in the active control of flexible space structures is developed. The approach converts the discrete nature of sensor and actuator positioning problems to a nonlinear programming optimization through approximation of the control forces and output measurements by spatially continuous functions. The locations of the sensors and actuators are optimized in order to move the transmission zeros of the system further to the left of the imaginary axis. This criterion for sensor/actuator placement can be useful for optimal regulation and tracking problems, as well as for low authority controller designs. Two performance metrics are considered for the optimization and are applied to the sensor/actuator positioning of a large-order flexible space structure View full abstract»

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  • Recursive temporal-spatial information fusion with applications to target identification

    Publication Year: 1993 , Page(s): 435 - 445
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (656 KB)  

    Centralized/distributed recursive algorithms for temporal-spatial information integration using the Dempster-Shafer technique are developed. Compared with the Bayesian approach, the Dempster-Shafer technique has the strong capability of handling information uncertainties, which are particularly desirable in many applications. In the centralized integration algorithm, all information is pooled into the central processor and integrated. In contrast, the distributed integration algorithm shares the computational burden among the local processors, which increases the computational efficiency. The developed algorithms are effectively applied to a target identification problem with three sensors: identification of friend-foe-neutral (IFFN), electronic support measurement (ESM), and infrared search and track (IRST) View full abstract»

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  • A Boolean algebra approach to multiple sensor voting fusion

    Publication Year: 1993 , Page(s): 317 - 327
    Cited by:  Papers (14)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (876 KB)  

    A technique for integrating multiple-sensor data using a voting fusion process that combines the individual sensor outputs is described. An important attribute of the method is the automatic confirmation of the target by the fusion processor without the need to explicitly determine which sensors and what level of sensor participation are involved. A three-sensor system, with multiple confidence levels in each sensor, is discussed to illustrate the approach. Boolean algebra is used to derive closed-form expressions for the multiple sensor-system detection probability and false-alarm probability. Procedures for relating confidence levels to detection and false alarm probabilities are described through an example. The hardware implementation for the sensor system fusion algorithm is discussed View full abstract»

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  • A comparison of the eigenvector weighting and Gram-Schmidt adaptive antenna techniques

    Publication Year: 1993 , Page(s): 568 - 575
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (636 KB)  

    Eigenvector and Gram-Schmidt weighting separate desired signals from interference without a priori information. For two signals and similar element patterns, eigenvector performance varies between Gram-Schmidt power inversion and perfect signal separation, depending on signal direction and array geometry. For nearly equal input powers, Gram-Schmidt always fails but eigenvector weighting often succeeds View full abstract»

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  • Stiffness enhancement of flight control actuator

    Publication Year: 1993 , Page(s): 380 - 390
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (680 KB)  

    A modification of the model reference approach, using numerical optimization is proposed for the estimation of external forces applied to control surfaces of an aircraft. This estimation provides the basis for the feedforward control of the surface position. Incorporated into the control system of a flight control actuator, this technique allows a significant enhancement of the actuator stiffness View full abstract»

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  • A method of obtaining signal components of residual carrier signal with their power content and computer simulation

    Publication Year: 1993 , Page(s): 532 - 540
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (460 KB)  

    An algorithm for obtaining all signal components of a residual carrier signal with any number of channels is presented. The phase modulation type may be NRZ-L or split phase (Manchester). The algorithm also provides an easy way of obtaining the power contents of the signal components. Steps to recognize the signal components that influence the carrier tracking loop and the data tracking loop at the receiver are given. A computer program for numerical computation is also given View full abstract»

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  • AC/DC converter topologies for the Space Station

    Publication Year: 1993 , Page(s): 425 - 434
    Cited by:  Papers (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (652 KB)  

    A new class of AC/DC converter topologies (Type-1 converters) is described, suitable for use in an advanced single-phase sine-wave voltage, high-frequency power distribution system, of the type that was proposed for a 20 kHz Space Station primary electrical power distribution system. The converter comprises a transformer, a resonant network, a current controller, a diode rectifier, and an output filter. The input AC voltage source is converted into a sinusoidal current source using the resonant network. The output of this current source is rectified by the diode rectifier and is controlled by the current controller. The controlled rectified current is then filtered by the output filter to obtain a constant voltage across the load. Three distinct converter topologies, Type-1A, Type-1B, and Type 1-C, are described, and their performance characteristics are presented. All three types have a close-to-unity rated power factor (greater than 0.98), low total harmonic distortion in input current (less than 5%), and high conversion efficiency (greater than 96%) View full abstract»

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  • A localizer design to improve missed approach guidance

    Publication Year: 1993 , Page(s): 302 - 309
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (648 KB)  

    A novel VHF localizer system has been designed, built and successfully tested to provide increased reliability and safety of commercial and general aviation air transportation. Additional benefits are more precise tracks for aircraft executing a missed approach, reduced volume of the airspace needed for missed approaches, and reduced sizes of areas affected by noise. The design uses contemporary instrument landing system (ILS) hardware to provide dual independent front and back course directional localizer operation with two carriers in the receiver passband offset 4 kHz from the nominal carrier frequency. An example is given of an application and solution to an ILS problem at Reno, NV. Relevant data are presented View full abstract»

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  • Optimum FFT-based frequency acquisition with application to COSPAS-SARSAT

    Publication Year: 1993 , Page(s): 464 - 475
    Cited by:  Papers (13)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (892 KB)  

    In the case of a single sinusoid or multiple well-separated sinusoids, a coarse estimator consisting of a windowed Fourier transform followed by a fine estimator which is an interpolator is a good approximation to an optimal frequency acquisition and measurement algorithm. The design tradeoffs are described. It is shown that for the fine-frequency estimator a good method is to fit a Gaussian function to the fast-Fourier-transform (FFT) peak and its two neighbors. This method achieves a frequency standard deviation and a bias in the order of only a few percent of a bin. In the case of short-time stationarity, for a moderate number of averages and for an adaptive threshold detector, only between 0.5 and 1 dB is lost when averaging is traded off for FFT length, in contrast to the asymptotic result of 1.5 dB. The COSPAS-SARSAT satellite system for emergency detection and localization is used to illustrate the concepts. The algorithm is analyzed theoretically, and good agreement is found with test results 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