A UAPO Based Model for Predicting the Field Propagation Near a Tunnel Entrance

A propagation model is developed for predicting the field level near a tunnel entrance when considering a wireless communication system in automotive environments. The entrance has a rectangular cross section and its walls consist of a nonmagnetic lossy material, which is assumed to be nonpenetrable. The proposed approach allows one to evaluate the field at each observation point by summing the geometrical optics contributions and those due to the diffraction by the corners of the tunnel entrance. These two contributions are here determined by adopting a uniform asymptotic physical optics solution ad hoc derived. It is obtained by using a physical optics approximation of the equivalent surface currents induced by an incident field and by performing a uniform asymptotic evaluation of the resulting radiation integral. Numerical simulations are presented.