Optimized Scheme of Antenna Diversity for Radio Wave Coverage in Tunnel Environment

To suppress the deep fading of radio waves caused by the tunnel waveguide effect, this paper presents an optimized scheme for the spatial and polarization diversities of tunnel antennas. Through the correlation coefficient analysis of path loss curves obtained by antennas placed at different positions, the two antenna positions that generate path loss curves with the lowest correlation coefficient are found, and these two antennas are defined as a diversity antenna pair. Using this scheme, the spatial diversity properties of the transmitting antenna and receiving antenna, as well as the spatial-polarization combined diversity property of the transmitting antenna, are obtained. Furthermore, the impact of antenna polarization on the spatial diversity property is investigated. The performance of the proposed scheme for spatial and polarization diversities is evaluated in terms of the intensity and uniformity of the path loss. The simulation results illustrate that the proposed diversity optimization scheme can suppress the influence of the waveguide effect and achieve more uniform and flatter radio wave coverage in a tunnel environment.