|M.Sc Thesis||Department of Electrical Engineering|
|Supervisor:||Prof. Leviatan Yehuda|
The FCC allocation of the 3.1 - 10.6 GHz spectrum for Ultra Wideband (UWB) radio has generated a great deal of interest in the research and design of UWB radio systems both in industry and academia. Designing of antenna that are suitable for the wide operating bandwidth of the UWB radio system presents a great challenge and constitutes the main objective of this thesis.
To ensure pulse transmission and reception with high fidelity, the antenna has to be of low VSWR and of low dispersion throughout the entire UWB bandwidth. Low dispersion antenna ensures that there is only little distortion in the received signal, which is critical for optimal SNR. Low VSWR antenna ensures that most of the power is transmitted/received and not reflected backwards, which is very important due to strict power limitations imposed by the FCC spectral mask. A compact-size antenna is another desired feature, and an omni-directional radiation pattern is preferred for communications applications. Furthermore, since in UWB communication systems, regardless of the modulation technique used, only one signal form is transmitted where the modulation varies either its magnitude, delay, or 0/1800 phase, our design procedure is aimed at achieving antenna for transmission/reception of this specific signal form with minimum distortion,.
The electromagnetic analysis of the antennas was performed by use of the commercially available Computer Simulation Technologies (CST) Microwave Studio (MWS) package, which was linked to Matlab by means of a Visual Basic Application (VBA) script. The optimization procedure was coded in Matlab. The optimization technique used in the research was a Genetic Algorithm (GA), which is a global optimization method; hence, a global optimum as a result of the optimization is ensured.
The result of this research was the design of two UWB antennas: (1) volume structure, perfectly omni-directional, and (2) printed differential antenna having a nearly omni-directional pattern. Both antennas were optimized to the transmission/reception of the Gaussian 5th derivative pulse, which is the best fit to the FCC mask single pulse. The transmission-reception relationship between pairs of such antennas was studied in a simplified, yet representative indoor communication environment containing various obstacles, which emulated multipath channel distortion.