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Waltham, MA, United States

Akcakaya M.,ARCON Corporation | Nehorai A.,Washington University in St. Louis
IEEE Transactions on Signal Processing | Year: 2011

We consider the effect of imperfect separability in the received signals on the detection performance of multi-input multi-output (MIMO) radar with widely separated antennas. The mutual orthogonality among the received signals is often assumed but cannot be achieved in practice for all Doppler and delay pairs. We introduce a data model considering the correlation among the data from different transmitter-receiver pairs as unknown parameters. Based on the expectation maximization algorithm, we propose a method to estimate the target, correlation, and noise parameters. We then use the estimates of these parameters to develop a statistical decision test. Employing the asymptotic statistical characteristics and the numerical performance of the test, we analyze the sensitivity of the MIMO radar with respect to changes in the cross-correlation levels of the measurements. We demonstrate the effect of the increase in the correlation among the received signals from different transmitters on the detection performance. © 2011 IEEE.

An analysis is presented of scattering of an electromagnetic linearly polarized plane wave by a multilayered sphere. The focus is on obtaining a computational form of the Mie coefficients for the scattered field. A central role is played by ratios of spherical Bessel functions that can be calculated easily, rapidly, and accurately by recurrence relations whose stabilities are demonstrated. Logarithmic derivatives are not employed. A detailed outline is given of a carefully tested computer program for implementing and validating the analysis. Numerous comparisons are given of numerical results obtained with this program with corresponding results in the literature. Important properties of the Mie coefficients and aspects of the scattered field are discussed including the loci of the Mie coefficients in the complex plane; the resonances of the Mie coefficients; the extinction, scattering, and absorption efficiencies of the scattered field; radiation pressure; the Debye series, and the complex angular momentum (CAM) method. © 2015 IEEE.

Shrestha A.,ARCON Corporation | Xing L.,University of Massachusetts Dartmouth | Coit D.W.,Rutgers University
IEEE Transactions on Reliability | Year: 2010

Multistate systems (MSS) are systems in which the system and its components are characterized by multiple states or performance levels. Component importance or sensitivity analysis facilitates the identification of vulnerabilities within the system, and aids in the quantification of criticalities of the system components. Multistate component importance analysis poses unique challenges to existing methods that are primarily based on binary-state applications. This paper presents an analytical method based on multistate multivalued decision diagrams (MMDD) for multistate component importance analysis. The contribution of this work is two-fold: 1) a novel, efficient algorithm for directly generating an MMDD model from multistate capacity network specifications without inefficient enumeration of multistate minimal path or cut vectors; and 2) an efficient, exact MMDD-based approach for evaluating MSS reliability and importance measures. The advantages of the proposed method are illustrated through a comparison with existing methods, and through detailed analyses of three case studies. © 2006 IEEE.

Akcakaya M.,ARCON Corporation | Muravchik C.H.,National University of La Plata | Nehorai A.,Washington University in St. Louis
IEEE Transactions on Signal Processing | Year: 2011

We propose to design a small-size antenna array having high direction-of-arrival (DOA) estimation performance, inspired by the Ormia ochracea's coupled ears. The female Ormia is able to locate male crickets' call accurately, for reproduction purposes, despite the small distance between its ears compared with the incoming wavelength. This phenomenon has been explained by the mechanical coupling between the Ormia's ears, modeled by a pair of differential equations. In this paper, we first solve the differential equations governing the Ormia ochracea's ear response, and convert the response to the prespecified radio frequencies. Using the converted response, we then implement the biologically inspired coupling as a multi-input multi-output filter on a uniform linear antenna array output. We derive the maximum likelihood estimates of source DOAs, and compute the corresponding Cramér-Rao bound on the DOA estimation error as a performance measure. We also consider a circular array configuration and compute the mean-square angular error bound on the three-dimensional localization accuracy. Moreover, we propose an algorithm to optimally choose the biologically inspired coupling for maximum localization performance. We use Monte Carlo numerical examples to demonstrate the advantages of the coupling effect. © 2011 IEEE.

Wu T.-J.,National Cheng Kung University | Chen P.,Syracuse University | Yan Y.,ARCON Corporation
Signal Processing | Year: 2013

We propose a consistent criterion WIC vc (vector corrected weighed average information criterion) for model order selection in multivariate linear regression models. The WIC vc is a weighted average of the asymptotically efficient criterion KIC vc (vector corrected Kullback information criterion) and the consistent criterion MBIC (multivariate Bayesian information criterion). The WIC vc behaves like KIC vc in small samples and behaves like MBIC in large samples. A numerical study comparing the performance of the proposed criterion with several available model selection criteria has been done. It shows that, over a wide range of small, moderate and large sample sizes, the WIC vc is more stable in comparison to other criteria in the study; that is, the WIC vc is either as good or comes in a strong second, whereas other criteria vary more in performance ranking. Therefore, the WIC vc is a very reliable and practical criterion. © 2012 Elsevier B.V.

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