Propagation prediction in rough and branched tunnels by the ADI-PE technique

The study of radiowave propagation in tunnels is important for the development of telecommunication systems. The vector Parabolic Equation (PE) and the alternate direction implicit (ADI) technique are used to study radiowave propagation in branched tunnels and in tunnels with rough walls. Previous work has shown that the ADI-PE method can accurately predict transmission loss in straight tunnels with smooth walls and with known electrical parameters. We extend the analysis of this method by including the realistic cases of branching tunnels and tunnels with rough walls. We briefly discuss the boundary conditions used in each case as well as compare our results with known numerical or analytical models. The numerical results obtained for the branched tunnel case were compared with the results produced by HFSS and the results for the rough wall case were compared with known analytical loss factors. The results show excellent agreement in both cases.