Radiofrequency (RF maxima) Propagation and Calculated Exposure Probability within Enclosures using GEV Theory

Abstract

Radiofrequency waves propagating in open space behave differently to those confined. Confined or enclosed spaces such as buildings where people reside and work can act as waveguides if propagating rf waves have wavelengths that are half wavelength multiples of the openings of these orifices. Under these conditions, waves with frequency above the cut-off frequency can propagate and set up hot spots inside.

Empirical support for the notion of wave guide propagation of rf inside large structures was investigated through the measurement of maxima electric field intensities at 54 grid points within an empty rectangular metallic cuboid of specific dimensions. These rf maxima intensities were measured for varying frequencies representing modes TE10 to TE33 at different angles of approach, AOA, of the incoming rf waves to the entrance of the confined space.  The statistics of extremes was found to best represent these measured rf electric field intensities with the Generalized Extreme Value (GEV) model giving the best fit for the distribution.

 The number of hot spots (maximum of the maxima intensities) was determined and the probability of exposure to these hot spots or more for a human within the vicinity was calculated using a Poisson distribution model.