The distortion of ultra-wideband signals in the environment.

The need for higher data rates in wireless communication systems and the lack of available frequency space has led the researchers in developing new technologies, such as UWB. Ultra-wideband systems utilise signals with very short duration and very large bandwidth, from which the benefits are twofold; more information can be exchanged and coexistence with narrowband technologies is possible, as such systems perceive UWB as noise and interference is thus avoided. The increased bandwidth offers multipath resolution, which when properly treated can enhance system's performance and reliability. Signal distortion however, may prohibit system's optimum performance. It is more efficiently treated directly into the time-domain. The lack of information on the propagation of UWB signals in a complex environment, other than single reflected and diffracted waves, was tackled in this work. Easy-to-use and accurate reflection and transmission coefficients for a wave impinging on a dielectric slab were deduced. An algorithm for the prediction of a signal, which is multiply diffracted waves on an number of absorbing knife-edges and/or imperfect conducting wedges was also implemented. The algorithm accurately took into account the arisen higher-order fields, that are created in such cases, according to the Uniform Theory of Diffraction. A tool for signal prediction in a complex environment was constructed, based on the environment discretisation into tiles and segments. Its validity was initially tested for the narrowband case, by comparing its predictions with measurement, with a quite good agreement. Then, it was modified, so as to incorporate the dispersive nature of the channel. This was accomplished in the time-domain, where the TD ray-trace model not only predicts the arrival times of the multipaths but also their shape. The results were compared with measurement data collected with a VNA