Wide-Band Measurements and Characterization at 2.1 GHz While Entering in a Small Tunnel

Abstract

The wide-band complex transfer function and propagation characteristics in a small passageway tunnel for nonline-of-sight are studied in this paper. A two-dimensional wide-band model based on the uniform theory of diffraction (UTD) and geometric optics (GO) is implemented and a network analyzer is used to perform measurements. In order to obtain the power delay profile, a correction factor is used, which adjusts the deviation caused by the windowing and zero padding performed in frequency domain. The UTD model predicts quite well the averaged path loss, power delay profile, root-mean-square (rms) delay spread and coherence bandwidth, even when the curved tunnel is approximated to two straight lines. Furthermore, it is shown that the position of the transmitter is crucial in the performance of the system: the path loss slope and rms delay spread are increased when the inclination of the transmitter is increased. In all cases, the rms delay spread is lower than 40 ns, where the coherence bandwidth decreases to 20 MHz. This parameter is proposed to estimate the excitation zone inside a tunnel.