A Novel heuristic time-domain diffraction model for UWB diffraction by lossy wedges and buildings

Abstract

Diffraction is a vital propagation mechanism to predict the signal strength and to study the cell coverage in different kinds of scenarios. In this paper, a new heuristic based time-domain (TD) diffraction model is proposed for diffraction of ultra wideband (UWB) signals by lossy obstacles like wedges and buildings. The TD model is derived by using the heuristic frequency-domain (FD) diffraction coefficient that can estimate the radiowave propagation in urban scenarios. The analysis of slope diffraction is also considered to account for double diffraction or grazing incidence where amplitude diffracted field is negligible. Two dimensional (2-D) uniform theory of diffraction (UTD) approach is used for analyzing both soft and hard polarizations. The TD results are compared with the numerical inverse fast Fourier transform (IFFT) of the corresponding FD results with very good agreement between them. The TD solution is also validated by comparison with the IFFT of the Maliuzhinets’ coefficient that can be adopted as reference. Building materials with different electromagnetic properties are considered. To analyze the distortion to the input pulse, the UWB channel impulse response is also investigated. Different excitation pulse types have been employed to confirm the general behavior of the proposed TD solution. Finally the TD and IFFT-FD solutions are compared in the context of their computational time. The TD results can contribute to analyze the UWB pulse shape distortion by diffraction under frequency selective channel.