Cloak for multilayered and gradually changing media

Coordinate transformation approach has previously been used for designing a cloak which can shield an interior region in a homogeneous medium. In this paper, we consider the case where the background is no longer a homogeneous medium and determine the relative constitutive parameters of the cloak according to the multilayered and gradually changing background. We propose the parameters of cylindrical cloak structures working in multilayered and gradually changing media and the scheme of specifying these parameters could also be applied to the design of a cloak in an arbitrary isotropic background. The theoretical analysis based on coordinate transformation is given and numerical simulations are performed to illustrate these properties. The simulation results show that the cloaking with the proposed parameters performs well in these inhomogeneous background medium. Potential applications are also discussed.