Nondiagonally anisotropic PML: A generalized unsplit wide-angle absorber for the treatment of the near-grazing effect in FDTD meshes

A new generalization of the PML with wide-angle absorption is presented, fo r the efficient truncation of FDTD lattices. The proposed unsplit-field lay er uses a nondiagonal symmetric tensor anisotropy and via an appropriate pa rameter selection achieves notable attenuation rates in the case of near-gr azing angles, Hence, it can be placed much closer to large structures. Impr oved accuracy and lower dispersion errors are attained via higher-order FDT D schemes with regular and non-Cartesian lattices constructed by hexagonal or tetradecahedral cells. Finally, Ramahi ABC's are invoked for the absorbe r's termination, Numerical results, addressing wave attenuation at grazing incidence, prove the efficiency of the proposed PML.