Validation of simple estimates for average field strengths in complex cavities against detailed results obtained from a 3D numerical model of a car

Very simple estimates for average electric and magnetic field strengths over the passenger compartment of a car are compared with values obtained from 3D numerical simulations. The estimates are based on the power balance method, assuming that the windows are electrically large and represent the dominant loss mechanism. A method to include the effects of simple glazing in electrically large windows is also proposed and validated against numerical models. The results demonstrate that remarkably good estimates can be obtained for internal sources at frequencies in the band 1-2 GHz. This approach is expected to become more effective for larger cavities and higher frequencies. Average field estimates of this nature could be useful in the assessment of human exposure to electromagnetic fields for vehicles and other resonant environments that are not amenable to deterministic modelling because of their electrical size.