Analysis and optimization of anechoic chambers equipped with ferrite and hybrid absorbers using FIT-FD

The new uniform standards for EMC-testing in Europe have strengthened the specifications on electronic products to qualify for the CE-Label. A new method is shown to analyze and optimize anechoic chambers using the finite integration technique, which is based on the well-known finite difference method. A numerical algorithm is introduced for calculation of the electromagnetic fields inside anechoic chambers equipped with ferrite or hybrid absorbers. The modifications in the numerical algorithm are described and the results are verified. Further, a proper discretisation for ferrite tiles is developed and examined. Since the thickness of the ferrite tiles is small in comparison to the dimension of anechoic chambers, it is necessary to model the tiles with a fine mesh. However it is not feasible to model the whole chamber with a fine mesh, because of the computational load. The solution is to insert a step in the mesh width requiring less memory than a smooth transition between the mesh widths. It is shown that the results are accurate if some conventions are considered. The numerical results are verified by comparison with analytical solutions. It is also shown that chambers equipped with ferrite absorbers obtain better performance than those equipped with foam absorbers at frequencies lower than 500 MHz.