December 31, 2007

Reconfigurable Wireless Communications Systems

Christofilakis Vasilios

Abstract:

Aim of this doctoral dissertation is the study and in-depth analysis of parameters and functional characteristics of Software Radio Systems with extended function Digital Beamforming. The combination of these cutting edge technologies is expected to lead to the creation of a platform that will not depend on hardware, in other words its functional characteristics will be altered via software. The doctoral dissertation is composed of four primary parts.During the accomplishment of the first part, quantitative analysis of the basic parameters concerning one of the most critical components of Software Radio system, the Analog to Digital converter, took place. The effect of these in the attribution of our system was also studied.
In the second part the research was focused in the simulation of SWR system with capabilities of DBF using a smart antenna as an RF front end. The simulation was primarily based on Graphical User Interfaces (GUIs) which were created using the Matlab programming language. Various scenarios regarding the input/output signals, the geometry, the frequency range, the space-time accuracy were tested. Emphasizing on the time critical parameters of the digital beamforming for a linear array antenna, important results were extracted.
During the third part, a new and innovative architecture of a digital time delay beamformer (DTDBF) was proposed. The specific proposal exceeds the barriers entering the minimum step angle of the main beam, due to the throughput rate and the DSP’s input/output interface, without increasing the complexity of the architecture.
The dissertation closes by examining the possibilities of reducing the electromagnetic pollution. Specifically, the reduction of the absorbed by the human head electromagnetic energy was estimated as an operation of the intelligent antennas in the future SWR handheld terminals.

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