Arbitrary Shaped Reciprocal External Cloak with Nonsingular and Homogeneous Material Parameters Using Expanding Coordinate Transformation

Arbitrary shaped reciprocal external cloak with homogeneous and nonsingular material parameters in complementary and core regions is designed by decomposing cloak geometry into several triangles. In each triangle, proposed expanding coordinate transformation is applied to cancel the space and a two-step compressing transformation is applied to restore the canceled space. The choice of transformation function is to ensure homogeneous material parameters which is the main advantage of the proposed design. Proposed design procedure is a generalized approach and can be used for any arbitrary polygonal geometries. Full-wave simulations confirm the theoretical design, and it is observed that proposed cloak shows significant invisibility effect in hiding multiple objects in the cloaked region for different cloak geometries.