Advancements in Doppler cloak technology: Manipulation of Doppler Effect and invisibility for moving objects

In this contribution, we present some important advancements in Doppler cloak technology, which is based on the frequency mixing property of linear momentum-biased metamaterial, whose artificial permittivity function is modulated in space and time. The importance of such a technology is given by the possibility to manipulate the Doppler effect and restore the invisibility of cloaked object in relativistic motion. Here, we review the main characteristics of a conventional Doppler cloak, consisting of a system composed of a planar reflector covered by a spatio-temporally modulated slab. We demonstrate that such a scheme presents some drawbacks in terms of efficiency and, therefore, an enhanced version based on a momentum-biased parallel-plate medium is presented and discussed.