Crosspolar levels of ring arrays in reflection at 45° incidence: influence of lattice spacing

The importance of the lattice spacing is illustrated by the performance of three arrays of simple rings arranged on square lattices with 2r/D = 0.61, 0.64 and 0.87, used as frequency selective surfaces in a 45° incidence diplexer. Peak crosspolar levels were about ¿35 dB for the closely spaced lattice, rising to ¿24 dB at the upper band edge for the widest spacing, for which the reflection band centres were not coincident for E- and H-plane incidence.