A route to quasi-perfect invisibility cylindrical cloaks without extreme   values in the parameters
  The method of coordinate transformation offers a way to realize perfect cloaks, but provides less ability to characterize the performance of a multilayered cloak in practice. Here, we propose an analytical model to predict the performance of a multilayered cylindrical cloak, based on which, the cloak in practice can be optimized to diminish the intrinsic scatterings caused by discretization and simplification. Extremely low scattering or "quasi-perfect invisibility" can be achieved with only a few layers of anisotropic metamaterials without following the transformation method. Meanwhile, the permittivity and permeability parameters of the layers are relatively small, which is a remarkable advantage of our approach. 
Sheng Xi, Hongsheng Chen, Baile Zhang, Bae-Ian Wu, and Jin Au Kong