An Efficient Algorithm Based on the Equivalence Principle and FDTD for Wave Propagation Prediction in Tunnels

In this paper, a hybrid technique based on the equivalence principle and parallel FDTD method is proposed for predicting the field coverage of antennas in confined spaces. The first step of the method is to decompose the whole computation domain into the antenna sub-domain and the rest environment sub-domain. The field in the antenna sub-domain is computed by FDTD with fine mesh, and then the field is coupled to the environment sub-domain by using equivalence principle on the common boundary of the two sub-domains. The radiation performance and the field coverage of a Yagi-Uda antenna in a rectangular tunnel are studied by this method at the frequency band of 900 MHz (for GSM-R system). The results show that the method is suitable for field coverage prediction of confined space, especially for the tunnel environment.