By Topic

Aerospace and Electronic Systems, IEEE Transactions on

Issue 1 • Date Jan 2002

Filter Results

Displaying Results 1 - 25 of 35
  • Detection of random signals via spectrum matching

    Publication Year: 2002 , Page(s): 301 - 307
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (655 KB) |  | HTML iconHTML  

    Using a priori knowledge of the signal power spectral density (PSD), a spectrum matching approach which effectively utilizes the available signal spectral shape is developed for random signal detection. Two spectrum matching detector (SMD) structures, which are implemented by correlogram and periodogram, respectively, are examined. Theoretical calculation of their false alarm rates is derived and confirmed by simulations. It is also demonstrated that the proposed detectors outperform the standard periodogram, Bartlett method, and energy detector under constant false alarm rate (CFAR) condition for two different random signals. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Modeling of switch-mode dc-dc cascade converters

    Publication Year: 2002 , Page(s): 295 - 299
    Cited by:  Papers (36)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (116 KB) |  | HTML iconHTML  

    Many applications of switch-mode dc-dc converters require higher conversion rates (M = Vout/E). An alternative solution to this problem is to use n-stages connected in cascade, such that the total conversion rate can be increased by an order of n. Ready-to-use nonlinear and linear models are given for n-buck and n-boost cascade converters in the continuous conduction mode using average model techniques; therefore, this work satisfies the need of having models for a class of dc-dc cascade converters. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Comments on "Receiver antenna scan rate requirements needed to implement pulse chasing in a bistatic radar receiver"

    Publication Year: 2002 , Page(s): 300 - 301
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (195 KB) |  | HTML iconHTML  

    For original paper see D.S.Purdy, ibid., vol.37, no.1, pp.285-7 (2001). It is shown that by selecting a different time variable, the approximations the author claims to be in error are indeed accurate. A reply by D.S.Purdy to these comments is included. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Author's reply [Comments on "Receiver antenna scan rate requirements needed to implement pulse chasing in a bistatic radar receiver"]

    Publication Year: 2002 , Page(s): 301
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (193 KB) |  | HTML iconHTML  

    First Page of the Article
    View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Maximum likelihood angle extractor for two closely spaced targets

    Publication Year: 2002 , Page(s): 183 - 203
    Cited by:  Papers (25)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1346 KB) |  | HTML iconHTML  

    In a scenario of closely spaced targets special attention has to be paid to radar signal processing. We present an advanced processing technique, which uses the maximum likelihood (ML) criterion to extract from a monopulse radar separate angle measurements for unresolved targets. This processing results in a significant improvement, in terms of measurement error standard deviations, over angle estimators using the monopulse ratio. Algorithms are developed for Swerling I as well as Swerling III models of radar cross section (RCS) fluctuations. The accuracy of the results is compared with the Cramer Rao lower bound (CRLB) and also to the monopulse ratio technique. A novel technique to detect the presence of two unresolved targets is also discussed. The performance of the ML estimator was evaluated in a benchmark scenario of closely spaced targets - closer than half power beamwidth of a monopulse radar. The interacting multiple model probabilistic data association (IMMPDA) track estimator was used in conjunction with the ML angle extractor View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Prescreening during image formation for ultrawideband radar

    Publication Year: 2002 , Page(s): 74 - 88
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1395 KB) |  | HTML iconHTML  

    Standard radar image formation techniques waste computational resources by full resolving all areas of the scene, even regions of benign clutter. We introduce a multiscale prescreener algorithm that runs as part of the image formation processing step for ultrawideband (UWB) synthetic aperture radar (SAR) systems. The prescreener processes intermediate radar data generated by a quadtree backprojection image former. As the quadtree algorithm iterates, it is resolving increasingly finer subpatches of the scene. After each quadtree stage, the prescreener makes an estimate of the signal-to-background ratio of each subpatch and applies a constant false alarm rate (CFAR) detector to decide which ones might contain a target of interest. Whenever the prescreener determines that a subpatch is not near a detection, it cues the image former to terminate further processing of that subpatch. Using a small database of UWB radar field data, we demonstrate that the prescreener is able to decrease the overall computational load of the image formation process. We also show that the new multiscale prescreener method produces fewer false alarms than the conventional two-parameter CFAR prescreener applied to the completely formed image View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • MHT extraction and track maintenance of a target formation

    Publication Year: 2002 , Page(s): 288 - 295
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (796 KB) |  | HTML iconHTML  

    Tracking of a group of targets temporarily operating in formation is relevant for military air-surveillance. An optimal sequential multiple hypothesis tracking (MHT) track extraction and track maintenance method for well-separated single targets embedded in clutter has been described in an earlier paper. However, applied to a group of closely spaced targets, its performance is not acceptable due to data miscorrelation. Here the approach has been generalized to include extraction and maintenance of a maneuvering formation in the presence of clutter. The unknown number of targets and imperfect detection when the group newly appears is modeled within the MHT framework. The generalized method solves the problem very well and can also track a formation after the targets separate View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Comparisons of error characteristics between TOA and TDOA positioning

    Publication Year: 2002 , Page(s): 307 - 311
    Cited by:  Papers (29)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (542 KB) |  | HTML iconHTML  

    This paper presents a comparison of error characteristics between time of arrival (TOA) and time difference of arrival (TDOA) processing of the linearized GPS pseudo-range equations. In particular, the relationship among dilutions of precision (DOPs), position estimates, and their error covariances is investigated. DOPs for TDOA are defined using the error covariance matrix resulting from TDOA processing. It is shown that the DOPs and user position estimate are the same for TDOA and TOA processing. The relationship of DOPs and position estimates for standard GPS positioning and double differenced processing are also given View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Attitude control of a bias momentum satellite using moment of inertia

    Publication Year: 2002 , Page(s): 243 - 250
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (733 KB) |  | HTML iconHTML  

    Analysis on the attitude controller based upon moment of inertia distribution for a bias momentum satellite is discussed. Spacecraft moment of inertia distribution is represented in the form of product of inertia terms in the system inertia matrix. The product of inertia between orthogonal body axes of the satellite is used to build a controller which controls the nutational motion caused by the angular momentum of the wheel. The attitude controller in the pitch axis controlling the pitch motion as well as nutational dynamics in the roll/yaw planes is analyzed in detail. Analytic expressions using linearized equations are derived providing further insight into the dynamic coupling effect among orthogonal body axes View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Regional navigation system using geosynchronous satellites and stratospheric airships

    Publication Year: 2002 , Page(s): 271 - 278
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (825 KB) |  | HTML iconHTML  

    A methodology is proposed to design a regional navigation system using geosynchronous satellites and stratospheric airships. One important factor in designing a navigation system is dilution of precision (DOP). We design a regional navigation system based on the simulations of the system's DOP. The system would consist of geosynchronous orbit satellites (GSO) and stratospheric airships for the urban areas. In the beginning stage, the system would augment the existing GPS constellation, and in the later stage with sufficient satellites and airships, we could achieve an independent alternative navigation system View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Coiflet wavelet transform applied to inspect power system disturbance-generated signals

    Publication Year: 2002 , Page(s): 204 - 210
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (716 KB) |  | HTML iconHTML  

    An application of Coiflet wavelet transform for the study of power system disturbance-generated signals is proposed. Because the wavelet transform possesses the time-frequency localization characteristics, the time and frequency information of a waveform can be integrally presented. Therefore, this approach can be more efficient in monitoring time-varying disturbances when compared with those Fourier transform-based methods. Moreover, when compared with the Morlet wavelet transform, the merits of easier implementation presented by Coiflet transform method as a discrete form further solidify the practicality for electric power quality applications. This approach has been validated through various test scenarios, including oscillatory transients, voltage sag, voltage swell, momentary interruption, and flat-top. Test results demonstrated the feasibility of the method for the applications considered View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Tripulse: A system for determining orientation and attitude of a satellite borne active phased array

    Publication Year: 2002 , Page(s): 2 - 12
    Cited by:  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1049 KB) |  | HTML iconHTML  

    Tripulse is a novel system that is designed to accurately estimate the orientation of a satellite borne phased array relative to one or more Earth stations. It has conceptual similarities to amplitude comparison monopulse systems used in tracking radars. Tripulse differs from monopulse in that it is applicable primarily to transmitting active phased arrays aboard communication satellites. The signaling structure consists of a minimum of three separate time multiplexed coherent pulses. A statistical performance analysis and a description of the methodology for converting multiple ground station orientation data to attitude estimates are presented View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Principal components, covariance matrix tapers, and the subspace leakage problem

    Publication Year: 2002 , Page(s): 152 - 162
    Cited by:  Papers (26)  |  Patents (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1143 KB) |  | HTML iconHTML  

    A new class of robust space-time adaptive beamforming techniques is introduced to address a broad range of subspace leakage phenomena that arise in many sensor array applications. When present, these leakage phenomena can significantly increase the effective rank of the dominant colored noise interference spectrum, thereby reducing the appeal of techniques that exploit low-rank dominant interference (such as principal components (PC) or diagonal loading) to reduce sample support (training) requirements. By combining the covariance matrix taper (CMT) approach with either PC or diagonal loading, the minimal sample support properties of these techniques can be preserved View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Detection of small objects in clutter using a GA-RBF neural network

    Publication Year: 2002 , Page(s): 98 - 118
    Cited by:  Papers (18)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2121 KB) |  | HTML iconHTML  

    Detection of small objects in a radar or satellite image is an important problem with many applications. Due to a recent discovery that sea clutter, the electromagnetic wave backscatter from a sea surface, is chaotic rather than purely random, computational intelligence techniques such as neural networks have been applied to reconstruct the chaotic dynamic of sea clutter. The reconstructed sea clutter dynamical system which usually takes the form of a nonlinear predictor does not only provide a model of the sea scattering phenomenon, but it can also be used to detect the existence of small targets such as fishing boats and small fragments of icebergs by observing abrupt changes in the prediction error. We applied a genetic algorithm (GA) to obtain an optimal reconstruction of sea clutter dynamic based on a radial basis function (RBF) neural network. This GA-RBF uses a hybrid approach that employes a GA to search for the optimum values of the following RBF parameters: centers, variance, and number of hidden nodes, and uses the least square method to determine the weights. It is shown here that if the functional form of an unknown nonlinear dynamical system can be represented exactly using an RBF net (i.e., no approximation error), this GA-RBF approach can reconstruct the exact dynamic from its time series measurements. In addition to the improved accuracy in modeling sea clutter dynamic, the GA-RBF is also shown to enhance the detectability of small objects embedded in the sea. Using real-life radar data that are collected in the east coast of Canada by two different radar systems: a ground-based radar and a satellite equipped with synthetic aperture radar (SAR), we show that the GA-RBF network is a reliable detector for small surface targets in various sea conditions and is practical for real-life search and rescue, navigation, and surveillance applications View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Recursive time-to-go estimation for homing guidance missiles

    Publication Year: 2002 , Page(s): 13 - 24
    Cited by:  Papers (11)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (986 KB) |  | HTML iconHTML  

    This paper addresses the problem of computing accurate time-to-go estimates, which is an important issue in implementing various optimal guidance laws developed for missiles of time-varying velocity. A recursive time-to-go computation method which updates the time-to-go in a noniterative way is presented. The recursive method includes an error compensation feature which explicitly computes the time-to-go error produced by nonzero initial heading errors. The proposed method is simple and straightforward to implement for any missile velocity profiles. Various numerical examples show that the proposed method works effectively for optimal guidance laws as well as proportional navigation and augmented proportional navigation View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Kalman filtering with state equality constraints

    Publication Year: 2002 , Page(s): 128 - 136
    Cited by:  Papers (108)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (781 KB) |  | HTML iconHTML  

    Kalman filters are commonly used to estimate the states of a dynamic system. However, in the application of Kalman filters there is often known model or signal information that is either ignored or dealt with heuristically. For instance, constraints on state values (which may be based on physical considerations) are often neglected because they do not fit easily into the structure of the Kalman filter. A rigorous analytic method of incorporating state equality constraints in the Kalman filter is developed. The constraints may be time varying. At each time step the unconstrained Kalman filter solution is projected onto the state constraint surface. This significantly improves the prediction accuracy of the filter. The use of this algorithm is demonstrated on a simple nonlinear vehicle tracking problem View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Three-phase rectifiers that apply optimal current injection

    Publication Year: 2002 , Page(s): 163 - 173
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (925 KB) |  | HTML iconHTML  

    A class of current injection based three-phase high power factor rectifiers is proposed. Low distortion of the input currents and high power factor are obtained applying near optimal current injection. The optimal current injection is discussed, and requirements it imposes to the current injection network are derived. A class of simple current injection networks that provide near optimal current injection, consisting of a transformer, two capacitors, and a number of resistors or resistance emulators is proposed. The power processed by the resistors or resistance emulators is shown to be 8.81% of the input power. Design of the current injection network is discussed, and dependence of the input current distortion on capacitance of the applied capacitors is analyzed. Volt-ampere rating of the transformer is shown to be only 0.16% of the input power. Effects caused by the output current ripple are studied, and a method for their compensation is proposed. Analytical results are experimentally verified. Switching resistance emulation is discussed and its feasibility is experimentally demonstrated View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Performance analysis of a dynamic programming track before detect algorithm

    Publication Year: 2002 , Page(s): 228 - 242
    Cited by:  Papers (47)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1140 KB) |  | HTML iconHTML  

    We analyze a dynamic programming (DP)-based track before detect (TBD) algorithm. By using extreme value theory we obtain explicit expressions for various performance measures of the algorithm such as probability of detection and false alarm. Our analysis has two advantages. First the unrealistic Gaussian and independence assumptions used in previous works are not required. Second, the probability of detection and false alarm curves obtained fit computer simulated performance results significantly more accurately than previously proposed analyses of the TBD algorithm View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Three types of distributed CFAR detection based on local test statistic

    Publication Year: 2002 , Page(s): 278 - 288
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (688 KB) |  | HTML iconHTML  

    Three types of distributed constant false-alarm rate (CFAR) detection based on local test statistic (LTS) are developed under the condition that all the samples in different sensors are independent and identically distributed (IID). They are called R (ratio), S (substract) and P (plus) types. For a two-sensor network and local order statistics CFAR (OS-CFAR) algorithm, we derive their closed-form expressions for false alarm and detection probabilities of detecting a Swerling II target in Gaussian noise. The numerical results show that ρ, the ratio between the noise power levels in two local sensors, has very strong effects on the performances of the S and P type schemes and the centralized detection. They can't hold to be CFAR when there isn't the precise prior knowledge of ρ. Compared with the centralized detection, the distributed detection scheme is more robust for the effect of ρ. Fortunately, the R type scheme is not affected by the ρ at all. It implies that the local CFAR processing can immunize the distributed detection against the ρ View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Finite-dimensional filters with nonlinear drift. XV. New direct method for construction of universal finite-dimensional filter

    Publication Year: 2002 , Page(s): 50 - 57
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (631 KB) |  | HTML iconHTML  

    We consider the explicit solution of Duncan-Mortensen-Zakai (DMZ) equation for the finite-dimensional filtering system. We show that under certain conditions, the nonlinear filtering system can be solved explicitly with an arbitrary initial condition by solving a system of ordinary differential equations and a Kolmogorov-type equation. Let n be the dimension of state space. We show that we need only n sufficient statistics in order to solve the DMZ equation View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Voltage-based maximum power point tracking control of PV system

    Publication Year: 2002 , Page(s): 262 - 270
    Cited by:  Papers (44)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (826 KB) |  | HTML iconHTML  

    Photovoltaic (PV) generators exhibit nonlinear v-i characteristics and maximum power (MP) points that vary with solar insulation. An intermediate converter can therefore increase efficiency by matching the PV system to the load and by operating the solar cell arrays (SCAs) at their maximum power point. An MP point tracking algorithm is developed using only SCA voltage information thus leading to current sensorless tracking control. The inadequacy of a boost converter for array voltage based MP point control is experimentally verified and an improved converter system is proposed. The proposed converter system results in low ripple content, which improves the array performance and hence a lower value of capacitance is sufficient on the solar array side. Simplified mathematical expressions for a PV source are derived. A signal flow graph is employed for modeling the converter system. Current sensorless peak power tracking effectiveness is demonstrated through simulation results. Experimental results are presented to validate the proposed method View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • SPRI: simulator of polarimetric radar images

    Publication Year: 2002 , Page(s): 251 - 261
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1273 KB) |  | HTML iconHTML  

    Simulator of polarimetric radar images (SPRI) consists of a suite of image processing programs for producing realistic millimeter-wave (MMW) radar images artificially on a workstation. The heart of the simulation approach is a polarimetric Rayleigh clutter simulator coupled to a clutter database. The simulator produces high resolution single-look polarimetric images. Hard targets can then be embedded into this clutter map, and the resultant image can be degraded in resolution, number of looks, polarization, etc. to match that which would be observed by a real sensor. Examples of simulated images, and comparisons of these simulations to actual images, are presented. The MMW Clutter Database is the most comprehensive to-date database of over 3500 Mueller matrices for many kinds of terrestrial clutter measured at 35 and 95 GHz, many of which are at incidence angles close to grazing. The database can be accessed via a World Wide Web flexible interface that enables data to be combined in new and unique ways specified by the user, and displayed in either tabular or graphical format. The structure and access procedure to the database are described View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Sequence CLEAN: a modified deconvolution technique for microwave images of contiguous targets

    Publication Year: 2002 , Page(s): 89 - 97
    Cited by:  Papers (40)  |  Patents (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (895 KB) |  | HTML iconHTML  

    High resolution range profiles usually suffer from range sidelobe artifacts which cause reduction in the dynamic range. The sidelobes can be greatly reduced by a deconvolution technique called Coherent CLEAN. The Coherent CLEAN algorithm is based on the assumption that the scene consists of isolated and independent targets. However, many real-life targets are contiguous. Even if we approximate the contiguous targets by very closely spaced point sources, they can hardly be assumed to radiate independently. The sidelobes and the mainlobes of these closely spaced point sources can interact constructively and destructively causing spurious peaks and peak mislocations. These problems are studied and a variation in the existing Coherent CLEAN algorithm, called Sequence CLEAN, is proposed. Sequence CLEAN is found to work well with actual targets View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Binary code imbalance and two measures of average sidelobe level

    Publication Year: 2002 , Page(s): 311 - 315
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (496 KB) |  | HTML iconHTML  

    The relationship between binary code imbalance and each of two measures of average autocorrelation sidelobe level is examined. For the first one, the arithmetic mean of signed sidelobes, an especially simple relationship is derived. It is found that the size of this average is minimized when imbalance is as dose as possible to the square root of the code length. The second is the square root of the average mean square sidelobe, where the average is taken over codes having the same imbalance. For this second measure, it is found that for any code length N ⩾ 4, there are three extreme points: a local maximum at zero imbalance and two global minima at ±U0 for some U0 > 0 that depends on N. Formulae are derived for U0 in terms of N valid for any integer N ⩾ 4. These formulae behave like (3/2)√N asymptotically as N increases View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Electronic flight progress strip prototype for en route ATC

    Publication Year: 2002 , Page(s): 119 - 127
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1073 KB) |  | HTML iconHTML  

    An electronic flight progress strip (FPS) display and a color plan view display (CPVD) as a laboratory prototype are described. The purposes of prototype development are to examine the effectiveness and problems of the electronic FPS display in comparison to the current system and to identify the controller-workstation requirements, which are necessary to decide a future planning of a production prototype development. The evaluation and additional test were conducted for a typical en route transition sector. It was found that electronic FPS was useful in the normal traffic load. Some possible improvements were identified in the heavy traffic load situations represented in the additional test View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.

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.

Full Aims & Scope

Meet Our Editors

Editor-in-Chief
Lance Kaplan
Army Research Laboratory