Fast and accurate evaluation of the shielding effectiveness of complex enclosures

We present a combined fast multilevel multipole technique combined with a singular value decomposition to evaluate the shielding effectiveness of enclosures with complex fillings up to very high frequencies and limited computer resources. Special preconditioners are proposed, adapted to the problem at hand, to reduce the number of iterations necessary. The accuracy is fully controlled and special care is taken to evaluate singular or quasi-singular contributions from the Green functions in closed form. As an example enclosures filled with a large number of boards are considered