A structure comprises an element having a cellular spacer (1) sandwiched between two films (2, 3) with an electrical conductivity gradient over their thickness. The spacer is pref. a cellular honeycomb of aramid impregnated with epoxy resin and is made electrically conducting by using conductive ink, polymer or carbon black. The films are pref. of styrene/butylacrylate resin with polypyrrole, are made conductive by doping and also have magnetic properties. At least one film is pref. bonded to the spacer by aq. polyurethane emulsion used as an adhesive. The conductivity gradient of the films may increase in the propagation direction of an incident electromagnetic wave, or where the spacer is between layers of films adjacent films may have conductivity gradients of opposite signs.
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