University Librarian Centre | University of Cagliari
UniCA Eprints

Una soluzione alternativa al problema della ricostruzione olografica della superficie delle antenne a riflettore da dati in far-field o in near-field

Serra, Giampaolo (2008) Una soluzione alternativa al problema della ricostruzione olografica della superficie delle antenne a riflettore da dati in far-field o in near-field. [Doctoral Thesis]

[img]
Preview
PDF
1871Kb

Official URL: http://www.diee.unica.it/DRIEI/tesi/20_serra.pdf

Abstract

The retrieval of surface profile of a reflector antenna is an important task, mainly for radio astronomical application. Up to now the microwave holographic reconstruction technique has been applied to far field data either directly measured or extrapolated from near field measurements by using the Fourier transform inversion. The main step of this technique is the computation of the induced currents on the reflector surface. In this thesis the relation between the far field (or near field) and the current on the parabolic reflector surface is formulated as a discrete data inverse problem. Since this problem is strongly ill conditioned, an alternative technique is proposed to find a solutionin the least squares sense and to regularize it by using a Singular Value Decomposition. This technique supplies a flexible regularization scheme, able to take into account also the noise level of the data. Moreover it allows to reconstruct a surface distortions map using either far field data or the direct use of Fresnel zone field data, i.e. these data are not used to extrapolate the far field pattern, but directly used by the procedure. A comparison with the standard technique based on the FFT inversion algorithm has been made on a number of different cases, with noise free and noisy far field data generated by a commercial software. The results show that this alternative procedure is able to delect, with a very good accuracy, both the position and the amount of the distortions of the reflector surface starting from both far field and near field data.

Item Type:Doctoral Thesis
Date:28 March 2008
Tutor:Mazzarella, Giuseppe
PhD classes:Ciclo 20 > Ingegneria elettronica e informatica
Institution:Universita' degli Studi di Cagliari
Divisions:Dipartimenti (fino a dicembre 2011) > Dipartimento di Ingegneria elettrica ed elettronica
Subjects:Area 09 - Ingegneria industriale e dell'informazione > ING-INF/01 Elettronica
Uncontrolled Keywords:: Inverse problem, Singular value decomposition, Microwave Holography, Reflector Antennas, Far Field and Fresnel zone data
ID Code:59
Deposited On:28 Oct 2008 12:10

Repository Staff Only: item control page