EMI potential of multiple sources within a shielded enclosure.

Abstract

An analytic model is developed for the prediction of electromagnetic emissions potential due to multiple integrated circuits (ICs) within a shielded enclosure. Detailed analysis of radiated emissions from an IC leads to dipole representations of the sources. These dipole sources are then applied in the determination of the fields and currents induced on the inside of the enclosure. The magnitude of these disturbances is taken as a metric of electromagnetic emissions potential. The power spectral density and the radiation efficiency of the ICs are investigated. ICs are represented by magnetic and electric dipoles, the magnitude and polarization of which are determined through measurement or calculation. Green's functions are derived that relate the dipole sources to the electromagnetic disturbances induced on the walls of the enclosure. Mapping matrices are proposed that relate multiple sources to multiple points on the wall. The role of source diversity in the summing problem is discussed. A stochastic analysis of the multiple source problem determines the distribution of disturbances due to known probability distributions of significant source factors. The shielding effectiveness of enclosures is determined using perturbation models of the leakage paths driven by the disturbances calculated through the application of the mapping matrices.