Subspace tracking for nested arraysSubspace tracking for nested arraysΠαρακολούθηση υποχώρου για ένθετες συστοιχίες κεραιών Διπλωματική Εργασία Diploma Work 2016-07-252016enIn radar, sonar, and mobile communications, the estimation of the directions from which multi- ple signals arrive at a point is called the direction of arrival (DoA) estimation problem and, over the past decades, has been performed often through uniform linear arrays (ULAs) in conjunc- tion with high-resolution subspace-based algorithms. Such techniques, however, have limited capability of the number of directions they can estimate; if the ULA consists of N antenna elements, then high-resolution subspace-based algorithms can estimate the directions of up to N − 1 signals. To increase this number, a novel structure that consists of N antenna elements and enables the estimation of O (N^2 ) signal directions has been developed recently. It lies on specific nonuniform-array structures which are called nested arrays. In this thesis, we first overviewed the structure and properties of nested arrays and eval- uated their performance through computer simulations. We observed that the nested arrays with conventional subspace-based signal-processing algorithms can offer high performance but require high complexity, which makes them impractical for real-time applications. Then, we developed novel subspace tracking techniques for nested arrays that have lower complexity, are proven to converge to the optimal, subspace-based estimator, and are capable of tracking changes in the directions of the arriving signals (for example, when a source is moving with respect to the array receiver).http://creativecommons.org/licenses/by/4.0/Πολυτεχνείο Κρήτης::Σχολή Ηλεκτρολόγων Μηχανικών και Μηχανικών ΥπολογιστώνFountoulakis_Emmanouil_Dip_2016.pdfChania [Greece]Library of TUC2016-07-25application/pdf665.8 kBfree Fountoulakis Emmanouil Φουντουλακης Εμμανουηλ Karystinos Georgios Καρυστινος Γεωργιος Bletsas Aggelos Μπλετσας Αγγελος Digalakis Vasilis Διγαλακης Βασιλης Πολυτεχνείο Κρήτης Technical University of Crete Signal processing