Electromagnetic field penetration through small apertures in a room

This paper presents a finite-difference time-domain (FDTD) formalism allowing one to model small apertures without discretization. This formulation is based on Bethe's small hole theory, which approximates the fields diffracted by a small aperture as equivalent to the fields radiated by an electric and a magnetic dipole. In the model, the analytical fields radiated by these two dipoles are discretized using the classical finite-difference scheme. The model is then validated by comparing it with exact FDTD. Applications and an extension of the model allowing one to consider several apertures close to each other are also presented.