Modeling wireless propagation in a rectangular tunnel with the Compact-FDTD method

The Compact-FDTD method is optimized for modeling electrically large waveguiding structures by analyzing its dispersion relation and predicting dispersion-optimized model parameters. The resulting algorithm is used to efficiently model an electrically large earth tunnel. Using the dominant mode´s quality factor as a benchmark which is a measure of the power leakage through the tunnel walls, it is demonstrated that errors of the order of 1% could be achieved using a very coarse mesh totaling just 200 FDTD cells. This successful numerical experiment paves the way towards modeling more general and realistic tunnels with minimal computing resources.