Intrinsic properties of symmetric periodic targets

Formulation and results are presented for an investigation of the intrinsic properties of symmetric periodic targets. Attention is given to the geometry of a 1-D periodic array of 2-D strips which are lossy in the sense of the resistive boundary condition (RBC) and are arranged such that the composite periodic structure possesses a two-fold rotational symmetry. Relationships between the cross-pol transmission coefficients may be found in a manner similar to that used for the reflection coefficients. Of particular interest are those periodic targets which are both planar and periodic in a plane, for example, planar strip gratings and frequency selective screens. It is straightforward to show, using these intrinsic properties of symmetric periodic targets, that for plane wave illumination at normal incidence the cross-pol scattered fields vanish for even-fold rotational symmetries greater than two.<>