Edge-elements for scattering problems

It is shown that edge elements, as vectorial finite-element approximations fields like e and h, can be used to solve scattering problems. This can be done in essentially two ways, according to which of the two fields d or b one most wishes to get in divergence-free form. Apparent drawback of edge elements (due to the increased number of degrees of freedom in comparison with nodal elements) are more than compensated by economies due to greater sparsity. Moreover, they could help get rid of unwanted spurious modes when resonance frequencies of waveguides of complicated shape are computed