Shielding effectiveness with a twist

Traditionally Schelkunoffpsilas shielding effectiveness equation is used universally in teaching and practice throughout the EMC community as a whole. In this paper we will review the three basic classic problems of Schelkunoffpsilas found in his text book. The well-accepted definitions of near field and far field measurements and their inability to satisfy the terms in Schelkunoffpsilas expression SE = A+R+B and the popular use of the shielding expression, SE = SE(H) = SE(E) will be discussed. The results of previous papers and government sponsored reports on near and far field shielding experiments will be discussed. Through practical laboratory testing, experiments and discussion are presented in support of explaining and illustrating the case where the expression SE = SE(H) = SE(E) is not a valid axiom in the near field and how SE = SE(H) = SE(E) is valid in far field conditions in support of understanding basic shielding concepts. Then, discussion on the application of Leontovich boundary conditions, which attempts to modify Schelkunoffpsilas equations to meet near and far field conditions for shielding measurements, is included when relevant in support of basic shielding theory. No attempt however will be made to re-derive a closed mathematical expression or to provide a new comprehensive shielding theory.