Shielding of electromagnetic fields of current sources by spherical enclosures

Expressions for the shielding effectiveness of a conductive spherical enclosure excited by a Hertzian dipole have been derived using the dyadic Green´s function technique. This technique has the advantage that the fields inside or outside the enclosure due to arbitrary current distribution may be found by employing the same set of dyadic Green´s functions. The shielding effectiveness for plane wave incidence has been determined by considering the limiting case of the current source external to the spherical shell. Computed values of shielding effectiveness deduced in this manner have been compared with those obtained by the numerical evaluation of the expressions derived by earlier authors. The theory presented here may be useful to EMC (electromagnetic compatibility) engineers who must consider electromagnetic coupling from current sources in the vicinity of shielding enclosures