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Aerospace and Electronic Systems, IEEE Transactions on

Issue 1 • Date Jan 2002

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

    Page(s): 301 - 307
    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»

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  • Modeling of switch-mode dc-dc cascade converters

    Page(s): 295 - 299
    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»

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  • Comments on "Receiver antenna scan rate requirements needed to implement pulse chasing in a bistatic radar receiver"

    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»

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  • Recursive time-to-go estimation for homing guidance missiles

    Page(s): 13 - 24
    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»

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  • Measured and predicted synthetic aperture radar target comparison

    Page(s): 25 - 37
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1189 KB) |  | HTML iconHTML  

    The DARPA Image Understanding program publicly released measured and predicted synthetic aperture radar (SAR) targets were compared by means of correlation. The training set consisted of three classes (BMP-2, T-72, and BTR-70) at 17 deg depression and 233 azimuths. The test set consisting of seven different serial-numbered targets at 15 deg depression was tested at 196 azimuths. After segmentation and normalization, each test image was correlated with all the training images to generate correlation and classification statistics. Measured correlation scores were higher and more consistent for same serial number training than variant training. The average in-class (0.837) and between-class (0.734) means for measured correlations were higher than both the average in-class (0.707) and between-class (0.675) means for predicted correlations; however, the corresponding variances for in-class (0.056) and between-class (0.048) predicted correlations were higher than in-class (0.026) and between-class (0.036) measured variances. The measured training data declared the target correctly almost 100% of the time; the T-72 and BTR-70 model-predicted data declared the target correctly 80% of the time. The correlation scores varied approximately sinusoidally with aspect. Correlation plots between a single orientation target and the entire training sets showed that a target was highly correlated at both the correct aspect angle and the correct angle rotated 180 deg View full abstract»

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  • Three-phase rectifiers that apply optimal current injection

    Page(s): 163 - 173
    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»

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  • SPRI: simulator of polarimetric radar images

    Page(s): 251 - 261
    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»

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  • Aircraft flight parameter estimation using acoustical Lloyd's mirror effect

    Page(s): 137 - 151
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1721 KB) |  | HTML iconHTML  

    A model is developed for the acoustical Lloyd's mirror effect observed in the output time-frequency distribution of a microphone located near the ground during the transit of a jet aircraft. The feasibility of using this effect for flight parameter estimation is assessed by a simple Cramer-Rao lower bound analysis. The nonlinear least-squares method and the generalized Hough transform method are formulated for flight parameter estimation. The performances of both methods are evaluated and compared using real acoustic data View full abstract»

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  • Maximum likelihood angle extractor for two closely spaced targets

    Page(s): 183 - 203
    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»

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  • Voltage-based maximum power point tracking control of PV system

    Page(s): 262 - 270
    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»

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  • Principal components, covariance matrix tapers, and the subspace leakage problem

    Page(s): 152 - 162
    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»

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  • Electronic flight progress strip prototype for en route ATC

    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»

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  • Three types of distributed CFAR detection based on local test statistic

    Page(s): 278 - 288
    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»

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  • Regional navigation system using geosynchronous satellites and stratospheric airships

    Page(s): 271 - 278
    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»

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  • Attitude control of a bias momentum satellite using moment of inertia

    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»

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  • Sequence CLEAN: a modified deconvolution technique for microwave images of contiguous targets

    Page(s): 89 - 97
    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»

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  • Comparisons of error characteristics between TOA and TDOA positioning

    Page(s): 307 - 311
    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»

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  • Improved target classification using optimum polarimetric SAR signatures

    Page(s): 38 - 49
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1475 KB) |  | HTML iconHTML  

    We present a new method for automatic target/object classification by using the optimum polarimetric radar signatures of the targets/objects of interest. The state-of-the-art in radar target recognition is based mostly either on the use of single polarimetric pairs or on the four preset pairs of orthogonal polarimetric signatures. Due to these limitations, polarimetric radar processing has been fruitful only in the area of noise suppression and target detection. The use of target separability criteria for the optimal selection of radar signal state of polarizations is addressed here. The polarization scattering matrix is used for the derivation of target signatures at arbitrary transmit and receive polarization states (arbitrary polarization inclination angles and ellipticity angles). Then, an optimization criterion that minimizes the within-class distance and maximizes the between-class metrics is used for the derivation of optimum sets of polarimetric states. The results of the application of this approach on real synthetic aperture radar (SAR) data of military vehicles are obtained. The results show that noticeable improvements in target separability and consequently target classification can be achieved by the use of the optimum over nonoptimum signatures View full abstract»

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  • Spiky sea clutter at high range resolutions and very low grazing angles

    Page(s): 58 - 73
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1574 KB) |  | HTML iconHTML  

    X-band (9.5-10.0 GHz) backscatter at near grazing incidence (0.2 deg) from the sea off the coast of Kauai, Hawaii, was measured with a radar characterized by a high spatial resolution in range (0.3 m) and a high temporal resolution (2000 Hz pulse repetition frequency (PRF)). Extensive amounts (over 20 min per measurement) of vertically and horizontally polarized sea clutter data were taken with upwind (UP) and crosswind (CR) transmit geometries during the collection campaign. Specific but representative examples of the clutter were statistically and phenomenologically analyzed over time scales varying from long (200 s), to intermediate (5 s), to short (50 ms), and over range swaths varying from full (160 m), to partial (30 m), to a single range cell (0.3 m). All analyses and results presented here are noncoherent, involving only the clutter amplitudes. Each type of clutter exhibited the characteristic spiky behavior which has come to be expected from microwave sea backscatter observed at low grazing angles and high range resolutions, while showing, between themselves, marked transmit geometry and polarization dependent contrasts, with the horizontally polarized clutter, measured with an UP transmit geometry, being especially notable for its frequently occurring, significant high frequency spectral content. Within the same clutter type, differences were observed in the probability distributions of radar cross sections (RCS) of spatially and temporally extended spiking events View full abstract»

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  • Innovative estimation method with measurement likelihood for all-accelerometer type inertial navigation system

    Page(s): 339 - 346
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (682 KB) |  | HTML iconHTML  

    Presents an innovative estimation scheme to solve the initial and divergent problems for an all-accelerometer inertial navigation system (INS). The proposed system uses six accelerometers mounted diagonally on each surface of a cubic. The system proposed herein exploits additional information involving the gravity effect, allowing us to determine the angular velocity. It also provides an upper bound value to initiate the platform attitude. In addition, an estimation algorithm using the own-ship trajectory estimator providing a measurement likelihood is proposed. A simulation case for estimating position and velocity of the vehicle is investigated by this approach. Results confirm the effectiveness of this information infusing concept in obtaining a convergent INS state estimation View full abstract»

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  • High-torque density integrated electro-mechanical flight actuators

    Page(s): 174 - 182
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (736 KB) |  | HTML iconHTML  

    Electro-mechanical flight actuators (EMFAs) are core flight-critical vehicle components. Fly-by-wire or fly-by-light control of EMFAs is performed by flight management systems (flight, mission, propulsion, and integrated controls that manage any combination of specific flight, mission, and propulsion functions). Reported here are novel results in the analysis of EMFAs with permanent-magnet synchronous motors, with particular interest in the application of brushless high-torque density motors which have superior characteristics compared with other state-of-the-art motor technologies. It is shown that due to nonlinearities and bounds, new control algorithms must be developed and implemented to achieve a spectrum of performance and requirements for EMFAs. A number of important issues in control, analysis, model development, integration, and verification are studied. Tracking control algorithms are synthesized, stability studied, and novel analysis results are reported. Advanced computer-aided engineering software tools and emerging simulation-based design environments are used to guarantee high fidelity modeling and analysis within data intensive simulation. Proof-of-concept demonstration testbeds for the design of advanced EMFAs and their components are developed, and EMFA imitator performance thoroughly studied. Verification of the concepts reported are formed and documented. Precise tracking, disturbance attenuation, accuracy, stability, robustness, and excellent acceleration capabilities are reported. A demonstration is performed to substantiate the theoretical analyses to add credence to its applicability as an approach and method that the designer of future EMFAs can use to design a new class of actuators for aircraft flight control surfaces View full abstract»

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  • Tripulse: A system for determining orientation and attitude of a satellite borne active phased array

    Page(s): 2 - 12
    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»

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  • Kalman filtering with state equality constraints

    Page(s): 128 - 136
    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»

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  • Coiflet wavelet transform applied to inspect power system disturbance-generated signals

    Page(s): 204 - 210
    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»

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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