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Aerospace and Electronic Systems, IEEE Transactions on

Issue 2 • Date April 2011

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  • Contents

    Publication Year: 2011 , Page(s): c1
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  • [Inside front cover]

    Publication Year: 2011 , Page(s): c2
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  • From the Editor

    Publication Year: 2011 , Page(s): 769
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  • MIMO Radar Waveform Design in the Presence of Clutter

    Publication Year: 2011 , Page(s): 770 - 781
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1160 KB) |  | HTML iconHTML  

    Waveform design for target identification and classification in multiple-input multiple-output (MIMO) radar systems has been studied in several recent works. In previous works, optimal signals for an estimation algorithm are found assuming that only signal- independent noise exists. This work extends previous research by studying the case where clutter is also present. We develop a procedure to design the optimal waveform which minimizes estimation error at the output of the minimum mean squared error (MMSE) estimators in two scenarios. In the first one different transmit antennas see uncorrelated aspects of the target, and we consider the correlated target aspects in the second one. Estimation error in the first case will not zero even if the transmit power tends to infinity. This value of this error is referred to as the lower estimation error bound εOUND. It can be shown that since the MIMO radar receiver can null out the clutter subspace, εOUND is zero in the second scenario. Waveform design for MMSE estimator under the uncorrelated target aspects assumption, leads to the semi-definite programming (SDP) problem, a convex optimization problem which can be efficiently solved through numerical methods. An explicit solution is developed for this SDP problem in two cases. In the first case target and clutter covariance matrices are jointly diagonalizable, and in the second one the signal-to-noise ratio (SNR) is sufficiently high. Finding optimal transmit signals for the correlated target aspects scenario also results in an SDP problem. View full abstract»

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  • Solar Cell as a Capacitive Temperature Sensor

    Publication Year: 2011 , Page(s): 782 - 789
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2253 KB) |  | HTML iconHTML  

    Spacecrafts in geostationary Earth orbit and low Earth polar orbit experience temperatures in the range of 180°C to 80°C [1, 2] depending on the orbit. Solar cells are mounted on light weight aluminum honeycomb panels which are deployed and Sun pointed in on-orbit operation. Solar panels charge batteries and supply power to the satellite during sunlit period and batteries supply power during eclipse period. The open circuit voltage (Voc) of a silicon solar cell varies by about -2.5 mV/°C [3] and temperature can bring about a dramatic change in the solar cell characteristic, particularly with reference to operating voltage. PRT mounted on the rare of the solar panel measure the temperature of the solar panel. This introduces errors due to temperature gradients between solar cell blanket and solar panel and slow transient response of PRTs. A method of using solar cell capacitance to measure the temperature of solar cell blanket is proposed. This removes error due to location and transient response of PRT. Solar cell as a temperature sensor for measurement of temperature is demonstrated. View full abstract»

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  • Sidelobe Blanking with Expanded Models

    Publication Year: 2011 , Page(s): 790 - 805
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (3801 KB) |  | HTML iconHTML  

    Sidelobe blanking (SLB) is used in radar systems to mitigate impulsive interference that enters the radar through a sidelobe of the primary antenna. A second, auxiliary antenna and channel are employed by an SLB system to produce a second output. This latter output is compared to that of the primary antenna channel, and a decision is then made, based on the classic Maisel SLB architecture, as to whether to blank the primary channel output. This work extends previous performance results, with more realistic and versatile expanded models for targets and interference. The determination of SLB performance involves the evaluation of several probability functions. The derived probability expressions allow for an arbitrary number of integrated pulses. The SLB design and performance results can be determined with these probability functions. In this paper, examples are presented and discussed, and design results for typical SLB systems are obtained. View full abstract»

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  • New Divisible Load Distribution Methods using Pipelined Communication Techniques on Tree and Pyramid Networks

    Publication Year: 2011 , Page(s): 806 - 819
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1280 KB) |  | HTML iconHTML  

    A divisible load can be arbitrarily divided into independent small load fractions which are assigned to processors in a parallel or distributed computing system for simultaneous processing. The theory and techniques of divisible load distribution have a wide range of aerospace applications, including satellite signal and image processing, radar and infrared tracking, target identification and searching, and data reporting and aggregation and processing in wireless sensor networks. We make new progress on divisible load distribution on tree and pyramid networks. We revisit the classic method for divisible load distribution on partitionable static interconnection networks (including complete tree and pyramid networks) and derive a closed-form expression of the parallel time and speedup. We propose two new methods which employ pipelined communication techniques to distribute divisible loads on tree and pyramid networks. We derive closed-form expressions of the parallel time and speedup for both methods and show that the asymptotic speedup of both methods is bβ+1 for a complete b-ary tree network and 4β+1 for a pyramid network, where β is the ratio of the time for computing a unit load to the time for communicating a unit load. The technique of pipelined communications leads to improved performance of divisible load distribution on tree and pyramid networks. Compared with the classic method, the asymptotic speedup of our new methods is 100% faster on a complete binary tree network and 33% faster on a pyramid network for large β. View full abstract»

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  • Modeling the Dielectric Constant Distribution of Wake Vortices

    Publication Year: 2011 , Page(s): 820 - 831
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1927 KB) |  | HTML iconHTML  

    The study of scattering characteristics of a wake vortex is very important for hazard avoidance, especially near airports. Obtaining the dielectric constant distribution is one of the basic issues in the scattering study for radar detection. The present work proposes a modeling method for the dielectric constant distribution. In the method the dielectric constant variation (also the radar cross section (RCS)) due to the density variation and water vapor variation are studied. Research findings show that the density variation and water vapor variation serve as dominant factors to the RCS of a wake vortex in low frequency band and high frequency band, respectively. View full abstract»

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  • Hybrid Algorithms for Multitarget Tracking using MHT and GM-CPHD

    Publication Year: 2011 , Page(s): 832 - 847
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (3526 KB) |  | HTML iconHTML  

    The Gaussian mixture cardinalized probability hypothesis density (GM-CPHD) is a new original algorithm for multitarget tracking adapted to false alarms, nondetection and closely spaced objects. It models the target set as a random finite set (RFS) and estimates the target state as the first-order moment of a joint probability distribution. In the classical version no track assignment is implemented; this is a limit to scene understanding in a multitarget context. A technique for choosing the peak to track association is therefore proposed. With this implementation the main strength of the GM-CPHD is shown: it drastically improves the performances concerning the estimation of the number of targets and gives acceptable performances concerning the state of each individual target even if targets are close together, but it cannot rival an interacting multiple model estimator with multiple hypothesis tracking (IMM-MHT) in regards to velocity estimation, which is also the case with other multitarget tracking algorithms not equiped with IMM. However, MHT performance decreases due to poor estimation of the number of targets when targets are close together. It is worth noting that combining a probability hypothesis density (PHD) filter with a multiple-model approach should improve the velocity estimation but is unnecessary because we have developed a hybrid algorithm, combining the precision of the estimation of the number of targets given by the GM-CPHD, used in a labeled version, with the precision of the estimation of each individual state given by the MHT. These noteworthy performances can be observed for individual targets as well as for convoys. This hybrid algorithm is extended by using an IMM-MHT with road constraints. View full abstract»

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  • Performance Synthesis of UAV Trajectories in Multistatic SAR

    Publication Year: 2011 , Page(s): 848 - 863
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1836 KB) |  | HTML iconHTML  

    We develop guidelines for the design and analysis of unmanned aerial vehicle (UAV) trajectories for the purpose of high-quality image reconstructions based on a tomographic framework for a downlooking multistatic SAR imaging system. Modern matrix analysis provides several tools to generate performance bounds, which we relate to physical parameters of the synthetic aperture radar (SAR) measurement process. Both deterministic and random trajectories are considered. We apply a central result of random matrix theory to describe the system performance of random-location sampling. View full abstract»

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  • Vision-Based Navigation in Autonomous Close Proximity Operations using Neural Networks

    Publication Year: 2011 , Page(s): 864 - 883
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (5512 KB) |  | HTML iconHTML  

    Tight unmanned aerial vehicle (UAV) autonomous missions such as formation flight (FF) and aerial refueling (AR) require an active controller that works in conjunction with a precise sensor that is able to identify an in-front aircraft and to estimate its relative position and orientation. Among possible choices vision sensors are of interest because they are passive in nature and do not require the cooperation of the in-front aircraft in any way. In this paper new vision-based estimation and navigation algorithms based on neural networks is developed. The accuracy and robustness of the proposed algorithm have been validated via a detailed modeling and a complete virtual environment based on the six degrees of freedom (6-DOF) nonlinear simulation of aircraft dynamics in an autonomous aerial refueling (AAR) mission. In addition a full-state time-variant tracking controller based on the pole placement method is designed to generate required commands for aircraft control surfaces and engine during an AAR. The performance of the system in the presence of noise has also been examined. View full abstract»

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  • Application of the Dynamic Allan Variance for the Characterization of Space Clock Behavior

    Publication Year: 2011 , Page(s): 884 - 895
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (6335 KB) |  | HTML iconHTML  

    Due to their stability atomic clocks represent the core of navigation systems such as GPS and the future European Galileo system. To identify possible anomalies, it is fundamental to detect when the clock stability varies with time. The dynamic Allan variance (DAVAR) makes this monitoring process possible. We extend the DAVAR to the case of a time series with missing data, and we analyze the presence of periodic behaviors, two common phenomena in space clocks. View full abstract»

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  • Fourth-Order Buck Converter for Maximum Power Point Tracking Applications

    Publication Year: 2011 , Page(s): 896 - 911
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (3904 KB) |  | HTML iconHTML  

    Photovoltaic arrays (PVAs) need an intermediate maximum power point tracker as their v-i characteristics are nonlinear. Application of switch-mode dc-dc converters are popular in this area and the buck topology is widely used in these power tracking applications. However, the buck converter with an input L-C filter, with insufficient damping, will exhibit unwanted oscillations, or it may operate at suboptimal power points for certain solar insolations. Suitable damping must be designed otherwise the maximum power point (MPP) becomes unstable. Because of the variable impedance characteristic of PVA the design of optimal damping, suitable for all solar insolations, is a complex task. In order to eliminate these problems a fourth-order buck converter, which will track maximum power (MP) at all solar insolations, is proposed for the photovoltaic (PV) power tracking applications. Mathematical models of the proposed converter are formulated and then boundary conditions, under which the converter capable of tracking MP, are obtained. The combined PV power tracking scheme is simulated in PSIM and then power tracking performance characteristics are generated. Performance of the proposed topology is compared with the buck converter with input filter. The proposed converter effectiveness, in power tracking applications, is verified through experimental studies. Micro-controller, dsPIC30F6010, is employed in the real-time implementation of the perturb and observe (P & O) tracking algorithm. View full abstract»

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  • Theory and Application of SNR and Mutual Information Matched Illumination Waveforms

    Publication Year: 2011 , Page(s): 912 - 927
    Cited by:  Papers (18)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1557 KB) |  | HTML iconHTML  

    A comprehensive theory of matched illumination waveforms for both deterministic and stochastic extended targets is presented. Design of matched waveforms based on maximization of both signal-to-noise ratio (SNR) and mutual information (MI) is considered. In addition the problem of matched waveform design in signal-dependent interference is extensively addressed. New results include SNR-based waveform design for stochastic targets, SNR-based design for a known target in signal-dependent interference, and MI-based design in signal-dependent interference. Finally we relate MI and SNR in the context of waveform design for stochastic targets. View full abstract»

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  • M-Sequence and Secondary Code Constraints for GNSS Signal Acquisition

    Publication Year: 2011 , Page(s): 928 - 945
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (5524 KB) |  | HTML iconHTML  

    In this paper, the problem of coherently extending the integration time for the acquisition of new Global Navigation Satellite System (GNSS) signals is addressed. Unlike the acquisition of legacy GNSS signals, the presence of secondary codes allows the polarity of the transmitted signal to change each primary code period. These polarity changes have to be recovered, and symbol combinations have to be tested before extending the coherent integration time. The hierarchical structure imposed by secondary codes and the presence of data/pilot channels are exploited to improve the acquisition process. A new algorithm based on the fast m-sequence and Walsh-Hadamard (WH) transforms is developed and used for efficiently testing all the possible symbol combinations. Secondary code constraints are included to further reduce the computational complexity of enumerating all symbol combinations. The proposed algorithms are analyzed in terms of receiver operating characteristics (ROC), and an approximate expression for the probability of false alarm is derived exploiting results from extreme value theory. View full abstract»

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  • Comparison of Two Image and Inertial Sensor Fusion Techniques for Navigation in Unmapped Environments

    Publication Year: 2011 , Page(s): 946 - 958
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2278 KB) |  | HTML iconHTML  

    To enable navigation of miniature aerial vehicles (MAVs) with a low-quality inertial measurement unit (IMU), external sensors are typically fused with the information generated by the low-quality IMU. Most commercial systems for MAVs currently fuse GPS measurements with IMU information to navigate the MAV. However there are many scenarios in which an MAV might prove useful, but GPS is not available (e.g., indoors, urban terrain, etc.). Therefore several approaches have recently been introduced that couple information from an IMU with visual information (usually captured by an electro-optical camera). In general the methods for fusing visual information with an IMU utilizes one of two techniques: 1) applying rigid body constraints on where landmarks should appear in a set of two images (constraint-based fusion) or 2) simultaneously estimating the location of features that are observed by the camera (mapping) and the location of the camera (simultaneous localization and mapping-SLAM-based fusion). While each technique has some nuances associated with its implementation in a true MAV environment (i.e., computational requirements, real-time implementation, feature tracking, etc.), this paper focuses solely on answering the question "Which fusion technique (constraint- or SLAM-based) enables more accurate long-term MAV navigation?" To answer this question, specific implementations of a constraint- and SLAM-based fusion technique, with novel modifications for improved results on MAVs, are described. A basic simulation environment is used to perform a comparison of the constraint- and SLAM-based fusion methods. We demonstrate the superiority of SLAM-based techniques in specific MAV flight scenarios and discuss the relative weaknesses and strengths of each fusion approach. View full abstract»

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  • Decentralized Detection in Clustered Sensor Networks

    Publication Year: 2011 , Page(s): 959 - 973
    Cited by:  Papers (9)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2494 KB) |  | HTML iconHTML  

    We investigate decentralized detection in clustered sensor networks with hierarchical multi-level fusion. We focus on simple majority-like fusion strategies, leading to closed-form analytical performance evaluation. The sensor nodes observe a binary phenomenon and transmit their own data to an access point (AP), possibly through intermediate fusion centers (FCs). We investigate the impact of uniform and nonuniform clustering on the system performance, evaluated in terms of probability of decision error on the phenomenon status at the AP. Our results show that, under a majority-like fusion rule, uniform clustering leads to the minimum performance degradation, which depends only on the number of decision levels rather than on the specific clustered topology. We then extend our approach, taking into account the impact of spatial variations of the phenomenon, noisy communication links, and weighed fusion rules. Finally the proposed distributed detection schemes are characterized with simulation and experimental results (relative to IEEE 802.15.4-based networks), which confirm the analytical predictions. View full abstract»

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  • Efficient Waveform Design for High-Bit-Rate W-band Satellite Transmissions

    Publication Year: 2011 , Page(s): 974 - 995
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (5729 KB) |  | HTML iconHTML  

    In the EHF (extremely high frequency) domain, W-band (75-110 GHz) offers promising perspectives for future satellite communications, mainly in terms of large bandwidth availability for high-bit-rate transmission. In this work an innovative physical (PHY) layer design for broadband satellite connections operating in W-band is proposed, which is based on the prolate spheroidal wave functions (PSWFs). PSWF waveforms (originally proposed in short-range indoor ultra-wideband communications) are aimed at optimizing the tradeoff between the concentration of pulse energy in a finite time interval and in a limited bandwidth. In our paper, PSWF-based 4-ary pulse shape modulation (PSM), characterized by a nearly optimal compromise between spectral and envelope compactness, has been tested for the radio interface of a W-band geostationary (GEO) downlink connection. The effect of nonlinear distortions, introduced by power-efficient saturating amplifiers, can be drastically reduced without any power back-off and will maintain a very good spectral efficiency. Experimental results obtained by means of realistic simulations fully demonstrate the potential advantages taken by PSWF in terms of increased spectral efficiency, link availability, and net payload rate with respect to state-of-the-art pulse-shaped modulations, raised-cosine filtered quadrature amplitude modulation (QAM), and Gaussian minimum shift keying (GMSK) commonly employed in satellite communications. View full abstract»

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  • Performance Measures and MHT for Tracking Move-Stop-Move Targets with MTI Sensors

    Publication Year: 2011 , Page(s): 996 - 1025
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (4886 KB) |  | HTML iconHTML  

    We consider the problem of tracking ground-based vehicles with moving target indicator (MTI) sensors. MTI sensors can only detect a target if the magnitude of the range-rate exceeds the minimum detectable velocity, and as a result targets typically exhibit evasive move-stop-move (MSM) behavior in order to avoid detection. Further complexity is added by the fact that the environment is cluttered, resulting in both missed detections and spurious false measurements. A key problem is then to distinguish between a missed detection of a moving target and a lack of a detection due to the target stopping (or moving at low velocity). In this paper, we provide a novel framework for calculating performance measures (which are not necessarily bounds) for this problem. Our approach unifies state-of-the-art posterior Cram??????r-Rao lower bound (PCRLB) approaches for dealing with manoeuvring targets (namely, the best-fitting Gaussian approach) and cluttered environments (the measurement sequence conditioning approach). Our approach is also able to exploit the correlation between the number of measurements at each sampling time and the target motion model. Furthermore, we are able to show that established PCRLB methodologies are special cases of this unifying approach. We therefore provide a general technique for calculating performance bounds/measures for target tracking that can be applied to a broad range of problems. We also introduce a multiple hypothesis tracker (MHT) implementation for this problem. In simulations, the MHT is shown to accurately track the target, and provided that the probability of detection is close to unity, the new performance measure is an extremely accurate predictor of the localization performance of the MHT. If the probability of detection is lower, and except when employing a short scanback, the MHT performance is significantly better than the measure. In such cases the true limit of performance is the measure calculated by assuming the correct mot- - ion model, and data association hypotheses are known. The MHT filter is also shown to maintain track of the target in a high percentage of simulations, even with a scanback of just a few time steps. Therefore if track maintenance is the most important requirement, the employment of long scanbacks is not essential. We conclude that our PCRLB-like measure and MHT implementation provide effective approaches for performance prediction and target tracking, respectively, in the challenging MTI domain. View full abstract»

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  • Defending an Asset: A Linear Quadratic Game Approach

    Publication Year: 2011 , Page(s): 1026 - 1044
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2717 KB) |  | HTML iconHTML  

    Techniques based on pursuit-evasion (PE) games are often applied in military operations of autonomous vehicles (AV) in the presence of mobile targets. Recently with increasing use of AVs, new scenarios emerge such as surveillance and persistent area denial. Compared with PE games, the actual roles of the pursuer and the evader have changed. In these emerging scenarios the evader acts as an intruder striking at some asset; at the same time the pursuer tries to destroy the intruder to protect the asset. Due to the presence of an asset, the PE game model with two sets of players (pursuers and evaders) is no longer adequate. We call this new problem a game of defending an asset(s) (DA). In this paper we study DA games under the framework of a linear quadratic (LQ) formulation. Three different DA games are addressed: 1) defending a stationary asset, 2) defending a moving asset with an arbitrary trajectory, and 3) defending an escaping asset. Equilibrium game strategies of the players are derived for each case. A repetitive scheme is proposed for implementation of the LQ strategies, and we demonstrate with simulations that the LQ strategies based on the repetitive implementation can provide good control guidance laws for DA games. View full abstract»

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  • HRR Radar Signature Database Validation for ATR: An Information Theoretic Approach

    Publication Year: 2011 , Page(s): 1045 - 1059
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2822 KB) |  | HTML iconHTML  

    The ability to make radar signature databases portable for use within similar sensor systems is critical to the affordability of future airborne signature exploitation systems. The capability to hybridize measured and synthetic signature database components will maximize the impact of the investment required to build complex radar signature databases. Radar target scattering mechanisms can be modeled and the signature signal model analyzed as a random process to enable portability and hybridization. Modal mutual information is developed as a measure of similarity for future use in the comparison of measured field data to modeled synthetic data. The inherent qualities of mutual information to be used in the context of the automatic target recognition problem are demonstrated using synthetic signature sets comprised of both "similar targets" and "dissimilar targets." View full abstract»

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  • Optimization of Confirmation Time of Bistatic Tracks in Passive Radar

    Publication Year: 2011 , Page(s): 1060 - 1072
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1614 KB) |  | HTML iconHTML  

    The paper presents a method for optimizing the mean confirmation time of a bistatic track (in bistatic range, bistatic velocity coordinates) in passive radar by adjusting the processing parameters. The track confirmation method is a standard cascaded logic, or "m out of n" logic. To provide high reliability of the confirmed tracks, the expected rate of confirmed false tracks is calculated, and it is used as a constraint during the optimization process. The optimization is based on a joint analysis of several parts of the processing chain of the passive radar, including the correlator, detector, and tracker. The parameters tuned to obtain minimum confirmation time are integration time, probability of false alarm (set by detection threshold), and parameters of the initialization logic m and n. Because the results depend on the signal-to-noise ratio, a parallel processing structure is proposed with different parameters in each branch to accommodate varying echo signal strengths. As a result, one can obtain improvement in track confirmation time with assumed number of confirmed false tracks per second. The developed procedures are tested on a simulated signal as well as on real-life data recorded with the experimental passive system PaRaDe. View full abstract»

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  • Two-Dimensional Hidden Markov Model for Classification of Continuous-Valued Noisy Vector Fields

    Publication Year: 2011 , Page(s): 1073 - 1080
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2052 KB) |  | HTML iconHTML  

    In this paper we present a statistical model with a nonsymmetric half-plane (NSHP) region of support for two-dimensional continuous-valued vector fields. It has the simplicity, efficiency, and ease of use of the well-known hidden Markov model (HMM) and associated Baum-Welch algorithms for time-series and other one-dimensional problems. At the same time it is able to learn textures on a two-dimensional field. We describe a fast approximate forward procedure for computation of the joint probability density function (pdf) of the vector field as well as an approximate Baum-Welch algorithm for parameter reestimation. Radar and sonar applications include classification of two-dimensional fields such as range versus azimuth or range versus aspect angle data wherein each data point in the field consists of a multi-dimensional feature vector. We test the method using synthetic textures. View full abstract»

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  • Game Theoretic Analysis of Adaptive Radar Jamming

    Publication Year: 2011 , Page(s): 1081 - 1100
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2068 KB) |  | HTML iconHTML  

    A radar and a jammer are considered as informed opponents "playing" in a noncooperative two-player, zero-sum game. The effects of jamming on the target detection performance of a radar using constant false alarm rate (CFAR) processing are analyzed using a game theoretic approach for three cases: 1) ungated range noise (URN), 2) range-gated noise (RGN) and 3) false-target (FT) jamming. Assuming a Swerling type II target in the presence of Rayleigh-distributed clutter, utility functions are described for cell-averaging (CA) and order statistic (OS) CFAR processors and the three cases of jamming. The analyses included optimizations of these utility functions subject to certain constraints with respect to control variables (strategies) in the jammer such as jammer power and the spatial extent of jamming and control variables in the radar such as threshold parameter and reference window size. The utility functions are evaluated over the players' strategy sets, and the resulting matrix-form games are solved for the optimal or "best response" strategies of both the jammer and the radar. View full abstract»

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  • Statistical Analysis of Urban GPS Multipaths and Pseudo-Range Measurement Errors

    Publication Year: 2011 , Page(s): 1101 - 1113
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1833 KB) |  | HTML iconHTML  

    In urban environments one of the causes of pseudo-range measurement error in Global Positioning System (GPS) is short-delay multipaths due to the scatterers around the receiver. Therefore knowledge of the temporal distribution of GPS multipaths based on a statistical scatterer distribution in an urban environment is essential to estimating the positioning performance and to developing an efficient multipath mitigation technique for urban GPS applications. The work presented here introduces a scatterer distribution model for the urban environment, derives analytical expressions of the consequent time-of-arrival (TOA) probability density function (pdf) with respect to satellite elevation angles, and analyzes the effect of short-delay multipaths on the pseudo-range measurement errors. The expressions derived provide insights into the statistical properties of GPS multipaths and pseudo-range measurement errors in GPS code phase measurement functions due to the short-delay multipaths. 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