Measurement of RF propagation in tunnels

Radio signal propagation in tunnels exhibits significant differences from outdoor or indoor multipath environments (radio signals reflected off walls, floors, or other objects). This research measures the propagation of UHF/SHF radio signals from 455 MHz up to 5.8 GHz in frequency bands commonly used for underground wireless communications and electronic tracking. The paper focuses on the experimental methods used to collect vertically and horizontally polarized signal propagation data in tunnels as a function of separation distance between the transmitter and receiver antennas, and presents measurement results. The data show the dependence of the propagation characteristics on frequency, polarization, and tunnel dimensions.