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, for the efficient truncation of FDTD lattices. The proposed unsplit-field layer uses a nondiagonal symmetric tensor anisotropy and via an appropriate parameter selection achieves notable attenuation rates in the case of near-grazing angles. Hence, it can be placed much closer to large structures. Improved accuracy and lower dispersion errors are attained via higher-order FDTD schemes with regular and non-Cartesian lattices constructed by hexagonal or tetradecahedral cells. Finally, Ramahi ABC´s are invoked for the absorber´s termination. Numerical results, addressing wave attenuation at grazing incidence, prove the efficiency of the proposed PML