Finite-difference frequency-domain (FDFD) modelling of EMI by ESD

This paper deals with a numerical modelling of the interferences produced by electrostatic discharges that reach the surface of metallic boxes containing electronic circuits and flow toward the ground connections. The wave-form of the interfering current assumed is taken from the draft of the CENELEC ESD Standard. The distribution of the current density into the enclosure during the electrostatic discharge event is deduced by means of a scalar magnetic potential approach in the frequency domain, and by a consequent finite difference discretization. The passages from the frequency domain to the time domain and forward are made using the discrete Fourier transform. This formulation of the problem allows the simulation grid to be reduced to only the metallic enclosure, saving time either in preparation of the input data or in the numerical computation. The electromagnetic interferences radiated by the enclosure during the electrostatic discharge event are directly computed by multipole expansion of the resulting current density distribution.