Parallel-planes approximation for propagation in rectangular tunnels

Channel modeling and measurements in waveguide-like structures

“…They modeled the attenuation constant associated with dominant waveguide modes in lossy tunnels by assuming the height and the width of the tunnel to be much greater than the wavelength. In 1982, the same attenuation constant was modeled for a lossy rectangular tunnel by Jacard et al [11] without any constraint on the dimensions of the tunnel. Besides the rectangular tunnels, theoretical modeling of a 'realistic waveguide' focusing on attenuation constant or received signal level along circular tunnels [12]- [14] and tunnels with arched cross-section [15] - [17] and elliptical cross-section [18] have also been done.…”