Wide-band maximum likelihood direction finding by using the tree-structured EM algorithm

Ankara : The Department of Electrical and Electronics Engineering and the Institute of Engineering and Sciences of Bilkent Univ., 1996.Thesis (Master's) -- Bilkent University, 1996.Includes bibliographical references leaves 38-43A thorough derivation of the Expectation Maximization (EM) algorithm, which is an iterative numerical method of Maximum Likelihood (ML) estimation, is presented for the case of estimating direction of arrivals of unknown deterministic wide-band signals incident from different directions onto a passive array. For the rec^uired signal estimation, alternative regularized least squares estimation techniques are proposed with significant improvement over the standard least squares techniques. Also, for the angle of arrival estimation of a large number of signals, a tree structured EM algorithm is proposed and compared with the conventional EM approach. Extensive simulation results are presented for comparison of the proposed algorithms with the current high-resolution methods of wide-band direction finding. In order to handle efficiently the case of available parametric prior models on the received waveforms, the required modifications are also given.Çadallı, NailM.S

A Tomographic Framework For Lidar Imaging

Detection and localization of underwater mines remains a challenging and important problem for safe operation of naval platforms. A number of new technologies exploit airborne LIDARs, which can penetrate the air-water interface and optically detect and localize underwater mines. Such systems process the received optical field generated by scattering within the water column, and have proven to be an effective technology for mine detection and localization. In this work, we consider the use of multiple looks at a single target to form a three-dimensional representation of the scatterers within the water column. To form such images, we account for the integration within the receive sensors, and formulate the problem in a tomographic framework. We will present preliminary image formation results generated from data collected at sea with a state-of-the-art Navy mine imaging system