Simulation of Radiowave Propagation in Hospitals Based on FDTD and Ray-Optical Methods

This paper addresses the simulation of radiowave propagation in hospitals in the frequency range from 42.6 MHz to 5.2 GHz. Due to the special construction of the walls, wave propagation in hospitals is different from other buildings. These walls contain metallic layers within their structure, e.g., operating rooms with CrNi-steel faced walls, X-ray rooms with lead shielded walls or magnetic resonance tomography rooms with an explicit EMC shielding made of copper. Wave propagation in such rooms has not been simulated yet. This work uses a simulation tool based on the finite-difference time-domain method that allows a detailed simulation of the walls, floors and ceilings for frequencies from 42.6 to 300 MHz. For higher frequencies up to 5.2 GHz a ray-optical simulation tool must be used and the walls must be modeled homogeneously by multiple layers of different materials. In order to accurately model the walls, the electromagnetic properties of the different material layers inside the walls have to be known. The results of extensive wave propagation measurements in four different hospitals are used for the determination of these parameters. This paper presents the methods used to obtain these material parameters and their performance in a ray-optical simulation tool.