EMF Simulation of Base Station Antennas in Real Sites using Spherical Wave Expansion and Diffracted Fields

Base station antennas for mobile communications (BTS) emit high levels of electromagnetic radiation in their vicinity. These antennas are usually located on the top of a building, and it is critical to determine the regions where the total power density surpasses the levels dictated by the regulators of the corresponding country. The power density on a given region depends not only on the total radiated power but also on the radiation pattern of the antenna and on the influence of the environment. As a result, antenna measurements become useful to perform these calculations.This paper presents a simulation tool which computes EMF exposure values of BTS antennas considering the influence of the building’s roof. The tool uses analytical calculations to obtain a fast evaluation of the fields radiated by all the antennas of a given cell site. The calculations are performed considering the radiation of the antenna as a contribution of three different propagation phenomena: a free space direct radiation component, a reflected component due to the presence of the ground and a diffracted field due to the roof’s corners. Both direct and reflected rays are computed using the Spherical Wave Expansion (SWE) of the BS antenna assuming PEC boundary. The diffracted ray are computed using ITU 526-15.