Cylindrical-to-plane-wave conversion via embedded optical transformation

We investigate the conversion from cylindrical waves to plane waves in a short range through a metamaterial layer which has a circular shape in the inner outline and a square shape in the outer outline. Based on an embedded optical transformation, analytical formulas of the permittivity and permeability tensors are presented for the metamaterial layer which converts the cylindrical waves to plane waves. The designed conversion materials are validated by full-wave simulations using the finite-element method. The proposed structure can be used either as a four-beam antenna or a compact range for near-field measurement of plane waves.