Electromagnetic wave propagation in a rectangular metro tunnel using UWB and slot antennas.

This study investigates the propagation characteristics of electromagnetic (EM) waves radiated by Ultra-Wideband (UWB) and slot antennas inside a closed underground Cairo metro tunnel. The selected tunnel segment is rectangular, 8.85 m wide, 5.9 m high, and 4.5 km long, with reinforced concrete walls of conductivity ranging between 10⁻¹ and 10⁻² S/m. Analytical and numerical approaches are applied to solve the governing wave equations for TE and TM modes under cutoff and high-frequency conditions. Parameters such as attenuation constants, cutoff frequencies, modal field distributions, and Airy function representations in curved geometries are examined. Our results confirm the waveguide nature of tunnels and the profound impact of transverse dimensions, frequency, and polarization. This work contributes to improved antenna system designs for underground wireless communications.