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Abstract
In this paper, we consider the scattering of an electromagnetic plane wave by an infinite doubly periodic array of slits in a perfectly conducting plane disposed on a grounded lossy dielectric slab. With the increasing sophistication of shielding techniques, we study cracks whose spacing is about some ten micrometers. This paper is devoted to phenomenology of the absorption phenomenon obtained with this complex structure. We show in this paper that doubly periodic cracks combined with a grounded lossy material can become an absorbing structure and ordered slits of 50 μm in a conducting plane permit field penetration. We have manufactured this kind of structure and measured it with a free space technique. We demonstrate in this paper the relevance of our mathematical model based on a Floquet development of the electromagnetic fields within the different layers of the structures and a Galerkin approximation of the surface currents. The agreement between theory and experiments is pretty good and we verify the theoretical prediction of the existence of an absorption band for such a structure.