Broadband magnetic microwave absorbers: fundamental limitations

The question of whether the Kramers-Kronig relationships place severe limitations on the bandwidths that can be achieved in homogeneous microwave absorbing materials is addressed. An attempt is made to determine, by computer simulation, the best bandwidths theoretically achievable for homogeneous coatings of one particular class of materials, i.e., materials whose magnetic properties are defined by the Gilbert equation. The beginnings of an effort to use computer simulation to determine the maximum bandwidths achievable for multilayer absorbing structures whose constitutive parameters not only satisfy the requirements of Kramers-Kronig, but also are reasonable from an engineering standpoint, are reported