Theory of the radio-wave propagation in railway tunnels

Research on radio-wave propagation in tunnels has important applications for mobile and personal communications. This paper first briefly reviews radio-wave propagation in empty tunnels and then concentrates on characterizing radio-wave propagation in tunnels loaded with trains. For this purpose, an oversized imperfect periodically loaded rectangular waveguide is proposed, and the surface impedance approximation is adopted to formulate the problem. The theoretical results show that HEM/sub q,mn/ and TSM/sub q,m0/ modes can propagate. Meanwhile, why TSE/sub q,m0/ modes cannot exist is also proved. The closed-form propagation constants for those important TSM/sub q,m0/ modes are obtained. The numerical results for the propagation attenuation of the dominant TSM/sub 1,10/ are presented. The influence of passengers on propagation is discussed.