Ellipsoidal cloak for inhomogeneous medium

In this letter, ellipsoidal cloak placed in inhomogeneous medium including layered and gradually changing medium is studied. The relative constitutive parameters of the cloak are derived based on coordinate transformation theory. The scheme to specify these parameters could also be applied to the design of a cloak in an arbitrary isotropic background. Numerical simulations are given to illustrate these properties. The simulation results validate the design formulae and show that the cloak with the proposed parameters performs well in these inhomogeneous background medium.